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Sen Han,1 Jonathan D. Ellis,2 Junpeng Guo,3 Yongcai Guo4
1Univ. of Shanghai for Science and Technology (China) 2Univ. of Rochester (United States) 3The Univ. of Alabama in Huntsville (United States) 4Chongqing Univ. (China)
This PDF file contains the front matter associated with SPIE Proceedings Volume 9677, including the Title Page, Copyright information, Table of Contents, Invited Panel Discussion, and Conference Committee listing.
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Optical Test, Measurement Technology, and Equipment
There are a lot of shortcomings with traditional optical adjustment in interferometry, such as low accuracy, time-consuming, labor-intensive, uncontrollability, and bad repetitiveness, so we treat the problem by using wireless remote control system. Comparing to the traditional method, the effect of vibration and air turbulence will be avoided. In addition the system has some peculiarities of low cost, high reliability and easy operation etc. Furthermore, the switching between two charge coupled devices (CCDs) can be easily achieved with this wireless remote control system, which is used to collect different images. The wireless transmission is achieved by using Radio Frequency (RF) module and programming the controller, pulse width modulation (PWM) of direct current (DC) motor, real-time switching of relay and high-accuracy displacement control of FAULHABER motor are available. The results of verification test show that the control system has good stability with less than 5% packet loss rate, high control accuracy and millisecond response speed.
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With the rapid development of the optical remote sensor technology, it puts forward higher requirements to the sensor’s index. For space camera with large field of view, long focal distance, the image quality and the focal length of the various parameters of the optical system puts forward higher requirements. Therefore how to meet the control index of the sensors put forward new problems for the alignment. The present reports on focal length mainly around the focal length calculation and accurate measurement, but there is no report about how to accurately control the focal length. This article proposed a method for combinatorial optimization based on the focal length and image quality evaluation, geometrical parameter error of the iterative optimization to obtain the best mirror distance compensation combination, that establish mirror-distance compensation control curve to guide the camera alignment process. The focus control precision is less than 1%, the field of view system surface shape is better than 0.08 λ.
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A non-matching algorithm displacement measurement based on gray scale is proposed in this paper in order to realize the measurement of displacement of MEMS micro structures with high precision. In this method, Against the clear sequences of moving image are obtained by imaging technology of strobe lighting. First, the region of interest(ROI) are selected from still images and stroboscopic images and use bilinear interpolation in the two regions. Moreover, characteristic curve of gray value are generated along a single direction after interpolated. Finally, the difference between the two characteristic curves of gray value in ROI are calculated. At the same time, the error caused by image contrast and brightness is compensated and optimized the detection results. The experimental results indicate that with this method, the precision of the measurement of MEMS micro structures in-plane displacement can reach sub-pixel level, which can obtain the displacement of MEMS in real time with high precision.
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Test sieves with dense grid structure are widely used in many fields, accurate gird size calibration is rather critical for success of grading analysis and test sieving. But traditional calibration methods suffer from the disadvantages of low measurement efficiency and shortage of sampling number of grids which could lead to quality judgment risk. Here, a fast and precise test sieve inspection method is presented. Firstly, a coaxial imaging system with low and high optical magnification probe is designed to capture the grid images of the test sieve. Then, a scaling ratio between low and high magnification probes can be obtained by the corresponding grids in captured images. With this, all grid dimensions in low magnification image can be obtained by measuring few corresponding grids in high magnification image with high accuracy. Finally, by scanning the stage of the tri-axis platform of the measuring apparatus, whole surface of the test sieve can be quickly inspected. Experiment results show that the proposed method can measure the test sieves with higher efficiency compare to traditional methods, which can measure 0.15 million grids (gird size 0.1mm) within only 60 seconds, and it can measure grid size range from 20μm to 5mm precisely. In a word, the presented method can calibrate the grid size of test sieve automatically with high efficiency and accuracy. By which, surface evaluation based on statistical method can be effectively implemented, and the quality judgment will be more reasonable.
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According to the larger error when reversing in photoelectric tracking control system, the improved cascade Active Disturbance Rejection Controller (ADRC) is put forward to improve the system position tracking performance and tracking precision. First of all, this essay analyses the controlled object model and system control strategy; Then, it gives design method of the improved cascade ADRC; Finally, in order to analyses the improved cascade’s better control performance, in the condition of the same input signal ,the improved cascade ADRC, conventional ADRC-ADRC and traditional PI-PI controller are used in photoelectric tracking control system to do comparative experiment. The experiment results show that the improved cascade ADRC's performance is better than other two algorithms, the tracking error and the steady state mean square error are significantly reduced, tracking accuracy is significantly improved. The improved cascade ADRC is an appealing solution in dealing with industrial control system problems where uncertainties and interference abound.
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Nowadays, Photovoltaic module contains more high-performance components in smaller space. It is also demanded to work in severe temperature condition for special use, such as aerospace. As temperature rises, the failure rate will increase exponentially which makes reliability significantly reduce. In order to improve thermal adaptability of photovoltaic module, this paper makes a research on reinforcement technologies. Thermoelectric cooler is widely used in aerospace which has harsh working environment. So, theoretical formulas for computing refrigerating efficiency, refrigerating capacity and temperature difference are described in detail. The optimum operating current of three classical working condition is obtained which can be used to guide the design of driven circuit. Taken some equipment enclosure for example, we use thermoelectric cooler to reinforce its thermal adaptability. By building physical model and thermal model with the aid of physical dimension and constraint condition, the model is simulated by Flotherm. The temperature field cloud is shown to verify the effectiveness of reinforcement.
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An infrared scene projector is described in this paper which based on light down conversion. The film transducer is the key device of the projector which is a free standing substrate and coated on one side with an absorbing optical black. The optical black coating absorbs the visible light and emits the infrared light. The emission spectrum is similar with the blackbody. The single pixel which is 25×25μm in sizes and 35um at intervals in a film transducer is realized by MEMS technology. The array size of the film transducer is more than 1024×1024 in a transducer of 76.2mm (3 inch) diameter. Illuminated by a visible light projector with different intensities, the gray scale is more than 200 and the equivalent black body temperature of the transducer could be varied in the range of 293K to 573K.
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Experimental program is designed to analyze the radiation and absorption characteristic of the sky background at near-infrared Oxygen A absorption band of passive ranging based on Oxygen spectral absorption; an acousto-optic tunable hyper spectral imaging spectrometer is used as the measuring device. Under the condition of sunny, cloudy, and snowy weather, the sky background spectral distribution is collected using the acousto-optic tunable hyper spectral imaging spectrometer. Then the Oxygen absorption rate is calculated according to the principle of Oxygen spectrum absorption passive ranging. The measurement result shows: absorption lines exist in the sky background spectral distribution at the Oxygen A absorption band, and the absorption rates are different at different weather conditions. The Oxygen absorption rates are the biggest under snowy weather, bigger under cloudy weather, and the smallest under sunny weather. The general change pattern of Oxygen absorption rate under different weather conditions is obtained and the result has laid solid foundation for suppressing the interference of the background and extracting target spectral accurately in subsequent passive ranging researching.
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When Opto-Electronic Tracking system operates in complex environments, every subsystem must operate efficiently and stably. As a important part of Opto-Electronic Tracking system, the performance of PMSM(Permanent Magnet Synchronous Motor) servo system affects the Opto-Electronic Tracking system’s accuracy and speed greatly[1][2]. This paper applied embedded real-time operating system μC/OS to the control of PMSM servo system, implemented SVPWM(Space Vector Pulse Width Modulation) algorithm in PMSM servo system, optimized the stability of PMSM servo system. Pointing on the characteristics of the Opto-Electronic Tracking system, this paper expanded μC/OS with software redundancy processes, remote debugging and upgrading. As a result, the Opto- Electronic Tracking system performs efficiently and stably.
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Rayleigh backscattering noise, which is one of the reasons that limit the sensitivity, has been deemed as noise in traditional resonant optic gyroscopes. However Rayleigh backscattering noise is one of the incentives of mode splitting phenomenon in high-Q resonators. Regarding the change of the resonance frequency of the resonator caused by the scattering signal as a measurement, we can use mode splitting to measure temperature, size of nanoparticle, etc. Light is confined by total internal reflection in whispering gallery mode (WGM) optical resonators, which is characterized by high-Q factors and small mode volumes. With regards to this, we propose a sensing mechanism based on mode splitting in high-Q WGM optical resonators. It is possible for us to measure the angular velocity of carrier according to the changes in the resonant frequencies of the two splitting modes. We propose the Miniature resonant optic gyroscope based on mode splitting (MROG-MS) with WGM resonators in the paper. Considering the Sagnac effect, mode splitting in high quality optical micro-resonators, and the rotation-induced impact on backscattering process, we modify the equations of motion that describe mode splitting, derive the explicit expression of angular rate versus the splitting amount, and verify the sensing mechanism by the simulation based on COMSOL. Furthermore, after monitoring the transmission spectra at different number of scattering particles, the simulation shows that mode splitting phenomenon resulted by single particle is more suitable for angular velocity measurement.
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Micro motor, a typical equipment to adjust the zoom lens, together with a position feedback sensor constitute the closed position loop, which is the key factor to perform successfully accurate lens focusing. Traditionally, the incremental grating ruler tends to be adopted as the position sensor, which continues counting the number of grating pitches on a dynamic one-dimensional moving platform. Instead of incremental counting, this paper proposes a dual-frequency-moiré based absolute position sensing method for reading immediate position at static environment. According to the relative positions of two kind of moiré, the absolute position of the measurement point can be retrieve at nano-meters level through look-up table. By the way, the measurement range can be expanded to millimeters level satisfying the demands of lens focusing, and furthermore the measurement efficiency is improved greatly without dynamic moving. In order to verify the performances of proposed method, a model of dual-frequency-moiré is built, and theological principles are deduced. Finally, the simulation results indicate that, with established configurations, dual-frequency-moiré could measure position within 0~5000μm. At the same time, the measurement accuracy achieves nano-meters level.
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For the consideration of the special application environment of the electronic products used in aerospace and to further more improve the human-computer interaction of the manned aerospace area. The research is based on the design and implementation way of the high resolution spaceborne infrared touch screen on the basis of FPGA and DSP frame structure. Beside the introduction of the whole structure for the high resolution spaceborne infrared touch screen system, this essay also gives the detail information about design of hardware for the high resolution spaceborne infrared touch screen system, FPGA design, GUI design and DSP algorithm design based on Lagrange interpolation. What is more, the easy makes a comprehensive research of the reliability design for the high resolution spaceborne infrared touch screen for the special purpose of it. Besides, the system test is done after installation of spaceborne infrared touch screen. The test result shows that the system is simple and reliable enough, which has a stable running environment and high resolution, which certainly can meet the special requirement of the manned aerospace instrument products.
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A detection system of energy fluctuation has been designed using C8051F120 mirco-controller chip as the central processor. The detection system is based on the principle that the current output increases linearly with the growth of the input laser power under the condition of adding anti-biased voltage into PIN photo diode. Real-time monitoring output fluctuation has been achieved by measuring the output voltage of optical-electrical conversion which is related to the peak output of nanosecond laser.
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As to the inspection of small and medium workpieces with complex surfaces such as blades, a non-contact optical measuring system is built up in the paper. With the system, the measurement task of such parts can be accomplished in a rapid, precise and efficient manner. Based on the laser displacement sensor, probe head and the mechanical framework of CMM etc, the system combines the advantages of optical sensor and CMM together to cope with the measurement of sculptured surfaces. In the system, the unit direction vector of measuring beam can be obtained through calibration method, which is based on solving of a series of overdetermined nonlinear equations. After that, the one-dimensional length of the laser beam can be transformed to the three-dimensional coordinates of the points on the surface. At the same time, the coordinates of measuring points can be converted to the same world coordinate system to complete the construction of point clouds through coordinate system transformation. Finally, a standard gauging block is measured by the system at 10 different orientations. Compared with the real value, the errors of the 10 measuring results are all smaller than 0.05mm, which manifests the practicability and validity of the system.
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A convenient method to study the influence of error sources in Fizeau is to build a ray-tracing model to simulate the error sources. In this paper an interferometer model is presented; an extension program is called to simulate the interference; and a preliminary research of several error sources is conducted. These examples demonstrate error analysis based on interferometer models is feasible and provide some guidance for optimizing our interferometer design.
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Fringe projection profilometry (FPP) is a rapidly developing technique which is widely used for industrial manufacture, heritage conservation, and medicine etc. because of its high speed, high precision, non-contact operation, full-field acquisition, and easy information processing. Among the various FFP methods, the squared binary defocused projection method (SBM) has been promptly expanding with several advantages: (1) high projection speed because of 1-bit grayscale fringe; (2) eliminating nonlinear gamma of the projector for the defocusing effect. Nevertheless, the method is not trouble-free. When the fringe stripe is wide, it brings down the fringe contrast and is difficult to control the defocused degree, resulting in a low measurement accuracy. In order to further improve high-speed and high-precision three-dimensional shape measurement, this paper presents a new three-dimensional shape measurement method based on double-frequency fringes projection. This new method needs to project two sets of 1-bit grayscale fringe patterns (low-frequency fringe and high-frequency fringe) onto the object surface under slightly defocused projection mode. The method has the following advantages: (1) high projection speed because of 1-bit grayscale fringe; (2) high measurement precision for selectively removing undesired harmonics. Low-frequency fringe is produced by error-diffusion dithering (Dithering) technique and high-frequency fringe is generated by optimal pulse-width modulation (OPWM) technique. The two kinds of fringe patterns have each superiorities and flaws. The low-frequency fringe has a low measurement accuracy, but the continue phase can be easily retrieved. However, the property of high-frequency fringe and low-frequency fringe is the opposite. The general idea of this method proposed is as follows: Because the both fringes test the same object, the height is the same. The low-frequency fringe can be used to assist the high frequency fringe to retrieve continue phase map, then the three-dimensional shape information of the object can be obtained. Theory analyzes the mathematical principle of error-diffusion dithering technique, optimal pulse-width modulation technique and three-dimensional reconstructed algorithm based on double-frequency fringes projection. A second-hand mouse was used to test the proposed method. The experiment results show that the three-dimensional shape measurement method combining OPWM technique and Dithering technique can achieve fast-speed and high-precision three-dimensional shape measurement.
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Hg2+ ions are one of the most toxic heavy metal ion pollutants, and are caustic and carcinogenic materials with high cellular toxicity. The Hg2+ ions can accumulate in the human body through the food chain and cause serious and permanent damage to the brain with both acute and chronic toxicity. According to the US Environment Protection Agency (EPA) guidelines, Hg2+ ions must be at concentrations below 1 ng/ml (10 nM) in drinking water. If the Hg2+ ions are higher than 2.5 ng/ml in serum, that will bring mercury poisoning. The traditional testing for Hg2+ ions includes atomic absorption, atomic fluorescence, and inductively coupled plasma mass spectrometry. These methods are usually coupled with gas chromatography, high-performance liquid chromatography, and capillary electrophoresis. However, these instrument-based techniques are rather complicated, time-consuming, costly, and unsuitable for online and portable use. An ultrasensitive and selective detection of mercury (II) in serum was investigated using a laser scanning confocal imaging-surface plasmon resonance system (LSCI-SPR). The detection limit was as low as 0.01 ng/ml for Hg2+ ions in fetal calf serum and that is lower than that was required Hg2+ ions must be at concentrations below 1 ng/ml by the US Environment Protection Agency (EPA) guidelines. This sensor was designed on a T-rich, single-stranded DNA (ssDNA)-modified gold film, which can be individually manipulated using specific T–Hg2+–T complex formation. The quenching intensity of the fluorescence images for rhodamine-labeled ssDNA fitted well with the changes in SPR. The changes varied with the Hg2+ ion concentration, which is unaffected by the presence of other metal ions. A good liner relation was got with the coefficients of 0.9116 in 30% fetal calf serums with the linear part over a range of 0.01 ng/ml to10 ng/ml.
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The charge-coupled device (CCD) array spectrometers are increasingly being used in wide variety of scientific researches and industrial applications. However, all CCD detectors suffer some amount of non-linear behavior on response to light, and the accuracy of the CCD array spectrometer measurement will be influenced from the non-linear behavior, the detectable error is presented. Therefore, the non-linearity correction method is important to obtain the accurate results of spectrometers based on the CCD. Here, we proposed a convenient experiment and calculation method to solve the problem of non-linearity. With the combined values of all the pixels across the detector, a 7th order polynomial is fitted in the relation between the normalized counts per second and counts, and the correction coefficients were generated by this polynomial for the pixels. The method to apply the correction is dividing the original response by the calculated correction coefficients for all the pixels. Finally, the CCD detector response is linear to >99.5% after correcting for the non-linearity of spectrometers, experimental results show that the proposed method is reasonable and efficient.
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Because of the substrate back reflectance phenomena, the reflectance of optical thin film stack on a transparent substrate is totally different from that of on an opaque substrate. In this paper, a method for the measurement of low reflectance optical film thickness that has substrate back reflectance is proposed for the first time. Through the analysis of the actual substrate back reflectance, a compensation model is introduced to reduce the influence of substrate back reflectance. The experimental results show good fitting precision and proves that this model can be used directly for the measurement of the optical film thickness with substrate back reflectance, and no extra process is needed.
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This paper has proposed a non-contact vibration sensor based on fiber Bragg grating sensing, and applied to detect vibration of steam turbine rotor dynamic balance experimental platform. The principle of the sensor has been introduced, as well as the experimental analysis; performance of non-contact FBG vibration sensor has been analyzed in the experiment; in addition, turbine rotor dynamic vibration detection system based on eddy current displacement sensor and non-contact FBG vibration sensor have built; finally, compared with results of signals under analysis of the time domain and frequency domain. The analysis of experimental data contrast shows that: the vibration signal analysis of non-contact FBG vibration sensor is basically the same as the result of eddy current displacement sensor; it verified that the sensor can be used for non-contact measurement of steam turbine rotor dynamic balance vibration.
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The wavefront of the laser beam was tested by a point-diffraction interferometer with bidirectional phase-shifting. The phase-shifting is obtained by the bidirectional modulated of the electro-optic effect lithium niobate crystal combining with a pinhole filter in half-wave film. The wavefront aberration of incoming beam is directly measured by analyzing five frames phase-shifted interferograms captured by a CCD camera.
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Although mist is similar to smoke in morphology, their compositions are very different. Therefore there is a significant difference between mist and smoke when detected by electromagnetic wave. This paper puts forward a kind of feasible solution based on Ansoft HFSS software about how to determine the forest fire by distinguishing mist and smoke above the forest. The experiments simulate the difference between mist and smoke model when detected by electromagnetic wave in different wavelengths. We find the mist and smoke model cannot absorb or reflect electromagnetic wave efficiently in Megahertz band. While in Gigahertz band, mist model began to absorb and reflect electromagnetic wave above 650 Gigahertz band, but no change in smoke model. And the biggest difference appears in Terahertz band.
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A simple method has been set up to quickly test the emissivity with an infrared thermal imaging system within a small distance according to the theory of measuring temperature by infrared system, which is based on the Planck radiation law and Lambert-beer law. The object’s temperature is promoted and held on by a heater while a temperature difference has been formed between the target and environment. The emissivity of human skin, galvanized iron plate, black rubber and liquid water has been tested under the condition that the emissivity is set in 1.0 and the testing distance is 1m. According to the invariance of human’s body temperature, a testing curve is established to describe that the thermal imaging temperatures various with the emissivity which is set in from 0.9 to 1.0. As a result, the method has been verified. The testing results show that the emissivity of human skin is 0.95. The emissivity of galvanized iron plate, black rubber and liquid water decreases with the increase of object’s temperature. The emissivity of galvanized iron plate is far smaller than the one of human skin, black rubber or water. The emissivity of water slowly linearly decreases with the increase of its temperature. By the study, within a small distance and clean atmosphere, the infrared emissivity of objects may be expediently tested with an infrared thermal imaging system according to the method, which is promoting the object’s temperature to make it different from the environment temperature, then simultaneously measures the environmental temperature, the real temperature and thermal imaging temperature of the object when the emissivity is set in 1.0 and the testing distance is 1.0m.
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The specifications accuracy of ultraviolet, visible, near-infrared (UV-VIS-NIR) spectrometer may change after used for a period of time, due to optoelectronic devices inside and environment. It directly affects the accuracy of scientific research and product quality measurement. Therefore this requires that the instrument should be checked after working a period of time. How various specifications are checked? What is chosen as a standard to check? Which method is more reasonable? If we choose unreasonable standard and checking method, the instrument will lose its accuracy. All of these are described in this paper in detail.
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With the continuous development of technology, the ranging accuracy of pulsed laser range finder (LRF) is higher and higher, so the maintenance demand of LRF is also rising. According to the dominant ideology of "time analog spatial distance" in simulated test for pulsed range finder, the key of distance simulation precision lies in the adjustable time delay. By analyzing and comparing the advantages and disadvantages of fiber and circuit delay, a method was proposed to improve the accuracy of the circuit delay without increasing the count frequency of the circuit. A high precision controllable delay circuit was designed by combining the internal delay circuit and external delay circuit which could compensate the delay error in real time. And then the circuit delay accuracy could be increased. The accuracy of the novel circuit delay methods proposed in this paper was actually measured by a high sampling rate oscilloscope actual measurement. The measurement result shows that the accuracy of the distance simulated by the circuit delay is increased from ± 0.75m up to ± 0.15m. The accuracy of the simulated distance is greatly improved in simulated test for high precision pulsed range finder.
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Mie scattering theory was shown in this paper to be suitable for analyzing the forward scattered light intensity distribution of micro-sized air bubble defects in glass, shining by a monochrome laser with a wavelength of 532um. The scattered light was measured by a high definition CCD camera. The scattering process can be classified as uncorrelated single scattering according to the properties of optical media. After calculating and smoothing the gray value of split rings of picture, Chahine algorithm was applied to reverse the size of defects. This technique was accurate to within 5% for defects with radii of <50um.
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As a noncontact, fast, robust, high-sensitive and area-averaging technique, the light scattering containing the structural information of optical surfaces has been used to measure surface roughness for many years, and the high resolution makes it feasible to measure the surface imperfection of silicon substrates. In this paper, using the total scattering (TS) instrument at 633nm, the total scattering was measured by scanning the entire surface of silicon substrates in different surface finish levels and sizes. Then, the root-mean-square (RMS) roughness of silicon substrates was calculated according to the measured TS-values and compared to the measured results with atomic force microscope (AFM) or optical profiler, indicating the validity of the method of light scattering for estimating the RMS roughness of optical components. In addition, the silicon substrates of different surface finish levels were scanned, and the results reveal that the higher the finish level is, the larger the total scattering is. Finally, the scatter maps of silicon substrates were plotted based on the measured TS-values, and the surface defects of silicon substrates were observed and compared to the results observed with an optical microscope, indicating that the spots with larger scattering correspond to the surface defects. It can be shown from our results that measuring light scattering is an effective method to investigate the surface quality of optical components.
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In order to precisely measure dynamic angle of sight for hardware-in-the-loop simulation, a dynamic measurement methodology was established and a set of measurement system was built. The errors and drifts, such as synchronization delay, CCD measurement error and drift, laser spot error on diffuse reflection plane and optics axis drift of laser, were measured and analyzed. First, by analyzing and measuring synchronization time between laser and time of controlling data, an error control method was devised and lowered synchronization delay to 21μs. Then, the relationship between CCD device and laser spot position was calibrated precisely and fitted by two-dimension surface fitting. CCD measurement error and drift were controlled below 0.26mrad. Next, angular resolution was calculated, and laser spot error on diffuse reflection plane was estimated to be 0.065mrad. Finally, optics axis drift of laser was analyzed and measured which did not exceed 0.06mrad. The measurement results indicate that the maximum of errors and drifts of the measurement methodology is less than 0.275mrad. The methodology can satisfy the measurement on dynamic angle of sight of higher precision and lager scale.
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To ensure the functionality, safe reliability and amenity of contact lens, the center thickness tc , diameter φt and base curves r0 are three key parameters to be measured. For purpose of measuring the parameters tc , φt and r0 of contact lens in a single compact instrument with high accuracy and efficiency, a new method based on digital image processing is proposed and examined. Firstly, aim at establishing appropriate measurement environment and obtaining the measuring images properly, the instrument structure is designed and implemented according to the characteristics of contact lenses. Several main environmental factors affects the accuracy has been considered, such as measuring medium and temperature. Secondly, the procedure of the geometric features location and coordinate conversion is analyzed and demonstrated. Thanks to the Canny-Zernike edge detection, the feature points in the image can be effectively positioned at sub-pixel level without increasing the hardware costs. In order to map the feature points’ pixel coordinates to world coordinates, the homography between the measuring plane and the imaging plane is estimated based on the pinhole imaging model. Lastly, with the specific obtained feature world coordinates, the distance formula and least squares curve fitting are used to calculate the object parameters. The instrument prototype and experimental analysis show that the proposed technique has advantages in terms of accuracy, volume reduction and efficiency over existing optical-mechanical techniques.
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In this paper pose measurement refers to flying pose measurement of rigid body including the pitch angle, yaw angel and roll angle. Pose measurement is of vital importance for such items as weapons settings, fault analysis and optimation design. Pose measurement based on optical images has many merits such as intuitive and non-contacted, which is a main method to measure pose currently. According to the parameters used and principle of the algorithms, the existing methods of pose measurement based on optical images are classified systematically and comprehensively for the first time as following: the methods of one station un-using camera’s inner parameters are divided into the feature length ratio method and the direct linear transformation(DLT )method, otherwise they are divided into the perspective n points(PNP)problem and the optical and radar integration method, the axes from planes intersection using two stations extensible to multistation, and model matching applied to one or more stations, and then they are comparatively analyzed .At last combined with practical applications such as one or more stations, have or no model and inner parameters used or unused, some selection and improvement of key points are given practically.
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Space deployable mechanisms are widely used, important and multi-purpose components in aerospace fields. In order to ensure the mechanism in normal situation after unfolded, detecting the deformation caused by huge temperature difference in real-time is necessary. This paper designed a deployable mechanism setup, completed its distributed deformation measurement by means of fiber Bragg grating (FBG) sensors and BP neural network, proved the mechanism distributed strain takes place sequence and FBG sensor is capable for space deployable mechanisms deformation measuring.
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In this paper, robotic reposition error measurement method based on laser interference remote positioning is presented, the geometric error is analyzed in the polishing system based on robot and the mathematical model of the tilt error is presented. Studies show that less than 1 mm error is mainly caused by the tilt error with small incident angle. Marking spot position with interference fringe enhances greatly the error measurement precision, the measurement precision of tilt error can reach 5 um. Measurement results show that reposition error of the polishing system is mainly from the tilt error caused by the motor A, repositioning precision is greatly increased after polishing system improvement. The measurement method has important applications in the actual error measurement with low cost, simple operation.
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The present scanning system consists of an industrial robot and a line-structured laser sensor which uses the industrial robot as a position instrument to guarantee the accuracy. However, the absolute accuracy of an industrial robot is relatively poor compared with the good repeatability in the manufacturing industry. This paper proposes a novel method using the workspace measurement and positioning system (wMPS) to remedy the lack of accuracy of the industrial robot. In order to guarantee the positioning accuracy of the system, the wMPS which is a laser-based measurement technology designed for large-volume metrology applications is brought in. Benefitting from the wMPS, this system can measure different cell-areas by the line-structured laser sensor and fuse the measurement data of different cell-areas by using the wMPS accurately. The system calibration which is the procedure to acquire and optimize the structure parameters of the scanning system is also stated in detail in this paper. In order to verify the feasibility of the system for scanning the large free-form surface, an experiment is designed to scan the internal surface of the door of a car-body in white. The final results show that the measurement data of the whole measuring areas have been jointed perfectly and there is no mismatch in the figure especially in the hole measuring areas. This experiment has verified the rationality of the system scheme, the correctness and effectiveness of the relevant methods.
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In this paper, the short dead time detection probability is introduced to the linear SNR model of fixed frequency multipulse accumulation detection system. Monte Carlo simulation is consistent with the theory simulation, which proves that with the increased laser power, the SNR first gets larger quickly and then becomes stable. Then the range standard deviation model is settled and firstly shows that larger dead time brings better range precision, which is consistent with the B. I. Cantor’s research. Secondly, Monte Carlo simulation and theory simulation both indicate that with the increased laser power, range precision first enhances and then becomes stable. Experimental results show that based on 500000c/s high background noise, the maximum of SNR can be obtained with emitting laser power at about 400uw at 50ms integrated time. Range precision reaches the optimal level at 6mm. The experimental data show a precision which is always worse than the Monte Carlo simulated results. This arises from the fact that the histograms’ jitter is not taking into account and introduced during simulation, whereas the experimental system has approximately 500ps' jitter. The system jitter causes larger time stamp value fluctuation, leading to worse range precision. To sum up, theory and experiment all prove that the optimal performance receiving of SNR and precision is achieved on this multi-pulse accumulation detection system.
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Multiangle dynamic light scattering (MDLS) compensates for the low information in a single-angle dynamic light scattering (DLS) measurement by combining the light intensity autocorrelation functions from a number of measurement angles. Reliable estimation of PSD from MDLS measurements requires accurate determination of the weighting coefficients and an appropriate inversion method. We propose the Recursion Nonnegative Phillips-Twomey (RNNPT) algorithm, which is insensitive to the noise of correlation function data, for PSD reconstruction from MDLS measurements. The procedure includes two main steps: 1) the calculation of the weighting coefficients by the recursion method, and 2) the PSD estimation through the RNNPT algorithm. And we obtained suitable regularization parameters for the algorithm by using MR-L-curve since the overall computational cost of this method is sensibly less than that of the L-curve for large problems. Furthermore, convergence behavior of the MR-L-curve method is in general superior to that of the L-curve method and the error of MR-L-curve method is monotone decreasing. First, the method was evaluated on simulated unimodal lognormal PSDs and multimodal lognormal PSDs. For comparison, reconstruction results got by a classical regularization method were included. Then, to further study the stability and sensitivity of the proposed method, all examples were analyzed using correlation function data with different levels of noise. The simulated results proved that RNNPT method yields more accurate results in the determination of PSDs from MDLS than those obtained with the classical regulation method for both unimodal and multimodal PSDs.
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Star simulator acts ground calibration equipment of the star sensor, It testes the related parameters and performance of the star sensor. At present, when the dynamic star simulator based on LCOS splicing is identified by the star sensor, there is a major problem which is the poor LCOS contrast. In this paper, we analysis the cause of LC OS stray light , which is the relation between the incident angle of light and contrast ratio and set up the function relationship between the angle and the irradiance of the stray light. According to this relationship, we propose a scheme that we control the incident angle . It is a popular method to use the compound parabolic concentrator (CPC), although it can control any angle what we want in theory, in fact, we usually use it above ±15° because of the length and the manufacturing cost. Then I set a telescopic system in front of the CPC , that principle is the same as the laser beam expander. We simulate the CPC with the Tracepro, it simulate the exit surface irradiance. The telescopic system should be designed by the ZEMAX because of the chromatic aberration correction. As a result, we get a collimating light source which the viewing angle is less than ±5° and the area of uniform irradiation surface is greater than 20mm×20mm.
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Background sunlight effect the technical performance of laser detection system significantly. Analyses and experiments were done to find the degree and regularity of effects of background sunlight on laser detection system. At first, we established the theoretical model of laser detection probability curve. We emulated and analysed the effects on probability curve under different sunlight intensity by the model. Moreover, we got the variation regularity of parameter in probability curve. Secondly, we proposed a prediction method of probability curve, which deduced the detecting parameter from measured data. The method can not only get the probability curve in arbitrary background sunlight by a measured probability curve in typical background sunlight, but also calculate the sensitivity of laser detection systems by probability curve at the specified probability. Thirdly, we measured the probability curves under three types of background sunlight. The illumination conditions in experiments included fine, overcast and night. These three curves can be used as reference to deduce other curves. Using model, method, and measured data mentioned above, we finally finished the analyses and appraisal of the effects of background sunlight on typical laser detection system. The research findings can provide the theoretical reference and technical support for adaptability evaluation of typical laser detection systems in different background sunlight.
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A reference goniophotometer and primary standards for specular gloss established at the SIMT have been described, as well as the theory and measurement equations relevant to the measurements. The instrumentation, standards, and measurement techniques used to measure specular gloss have been described, including the illuminator, goniometer, receiver, sample-holding system and the characterization of the instrument. The new primary specular gloss standard and its characterization are presented.
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The Hardware-in-the-loop simulation can establish the target/interference physical radiation and interception of product flight process in the testing room. In particular, the simulation of environment is more difficult for high radiation energy and complicated interference model. Here the development in IR scene generation produced by a fiber array imaging transducer with circumferential lamp spot sources is introduced. The IR simulation capability includes effective simulation of aircraft signatures and point-source IR countermeasures. Two point-sources as interference can move in two-dimension random directions. For simulation the process of interference release, the radiation and motion characteristic is tested. Through the zero calibration for optical axis of simulator, the radiation can be well projected to the product detector. The test and calibration results show the new type compound simulator can be used in the hardware-in-the-loop simulation trial.
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As a new type of light dispersion device, Acousto-Optic Tunable Filter (AOTF) based on the acousto-optic interaction principle which can achieve diffractive spectral, has rapidly developed and been widely used in the technical fields of spectral analysis and remote sensing detection since it launched. The precise measurement of AOTF’s optical performance parameter is the precondition to ensure spectral radiometric calibration and data inversion in the process of quantitation for spectrometer based on AOTF. In this paper, a kind of AOTF performance analysis system in 450~3200nm wide spectrum was introduced, including the fundamental principle of the basic system and the test method of the key optical parameters of AOTF. The error sources and the influence of the magnitude of the error in the whole test system were analyzed and verified emphatically. The numerical simulation of the noise in detecting circuit and the instability of light source was carried out, and based on the simulation result, the method for improving the measuring accuracy of the system were proposed such as improving light source parameters, correcting and changing test method by using dual light path detecting, etc. Experimental results indicate that: the relative error can be reduced by 20%, and the stability of the test signal is better than 98%. Finally, this error analysis model and the potential applicability in other optoelectronic measuring system were also discussed in the paper.
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In order to reduce the frequency of researchers routing in and out of the testing site and ensure the fluency of the testing we design a new filter system applied to the streak cameras. This system promotes streak cameras’ abilities on spatial discrimination and time resolution. This paper focuses on the instruction of the piezoelectric motor’s principle based on field-effect tubes. Filter wheel is driven by piezoelectric motor. It can effectively avoid the influences of high field produced by streak tube. Finally we achieve auto regulation at different gears and promote the efficiency of operations and guarantee the safety of researchers. CD4046 introduces the driven clock of this system and we use an inverter to get two synchronous inverted signals. These signals are amplified by field-effect tubes to more than 300V. The amplified ones are integrated at the output terminals to generate sinusoidal signal. The test shows that in this filter system piezoelectric motor operates at its resonance frequency under a control signal of 62.5 KHz. Its working current is 1.9A and driving power is almost 10W. By adjusting the gears, the filter wheel costs less than 2 seconds to calibrate. We accomplish the test in respected results.
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Periodic systematic error caused by erroneous reference phase adjustments and instabilities of interferometer has a great influence on precision of measurement micro-profile using white light phase-stepping interferometry. This paper presents a five-frame algorithm that is insensitive to periodic systematic error. This algorithm attempts to eliminate the periodic systematic error when calculating the phase. Both theoretical and experimental results show that the proposed algorithm has good immunity to periodic systematic error and is able to accurately recover the 3D profile of a sample.
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Volatile Organic Compounds (VOCs) emitted from chemical, petrochemical, and other industries are the most common air pollutants leading to various environmental hazards. Regulations to control the VOCs emissions have been more and more important in China, which requires specific VOCs measurement systems to take measures. Multi-components analysis system, with an infrared spectrometer, a gas handling module and a multi-pass gas cell, is one of the most effective air pollution monitoring facilities. In the VOCs analysis system, the optical multi-pass cell is required to heat to higher than 150 degree Celsius to prevent the condensation of the component gas. Besides that, the gas cell needs to be designed to have an optical path length that matches the detection sensitivity requirement with a compact geometry. In this article, a multi-pass White cell was designed for the high temperature absorption measurements in a specified geometry requirement. The Aberration theory is used to establish the model to accurately calculate the astigmatism for the reflector system. In consideration of getting the optimum output energy, the dimensions of cell geometry, object mirrors and field mirror are optimized by the ray-tracing visible simulation. Then finite element analysis was used to calculate the thermal analysis for the structure of the external and internal elements for high stability. According to the simulation, the cell designed in this paper has an optical path length of 10 meters with an internal volume of 3 liters, and has good stability between room temperature to 227 degree Celsius.
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Optical fiber power is an important physical quantity for optical fiber communication measurement. Currently, the absolute optical fiber power is traceable to absolute radiometer, such as electrically calibrated radiometer, and cryogenic radiometer. For optical fiber power transfer, the primary standard of NIM is the cryogenic radiometer that has an uncertainty of 2 parts in 104. Because most cryogenic radiometers are designed to be used with collimated beams rather than divergent beams from an optical fiber; therefore transfer standards should be well designed for optical power measurement using the beam geometry correction.
We designed a trap detector using for optical fiber power transfer. One can omit the beam geometry correction from an optical fiber using his design. We present a fiber power measurement using a planar detector compared with this trap detector, which are traceable to the primary standard (cryogenic radiometer). The difference between the comparison shows that the trap detector is suitable for absolute fiber power measurement, meanwhile optical fiber power transfer using planar detectors should be corrected when transferred from cryogenic radiometer.
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Electrooptic sampling has been shown to be a very powerful technique for making time-domain measurements of fast electronic devices and circuits, such as oscilloscope. In this paper, we review the principles of electrooptic sampling technique for electronic waveform probing with applications to characterizing 100GHz photodetector pulse response.
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In this work, we use the liquid-prism SPR sensing configuration to determine the chromatic dispersion of different liquids, since the condition of SPR is sensitive to the refractive index of the liquid prism. We use the glass slide coated with 50 nm Au film as the sensing chip, and use AvaLight - HAL (360 nm - 2500 nm) light source as the broaden band light source in our experiments. We adopt the deionized water as the standard sample to determine the chromatic dispersion of different liquid samples (ethanol and n-hexane), and we implement the experiment through the SPR sensing configuration in angular and spectral interrogations. According to the experimental data, the chromatic dispersions of ethanol and n-hexane are obtained. The proposed technique provides a new high sensitive method for the determination of chromatic dispersion of liquids.
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A method for measuring the focal length of the lens and the radius of curvature of the spherical surface using wavefront difference method is proposed. Based on Fizeau interferometer, an experimental system for focal length measurements is set up to verify the principle. Based on the point diffraction interferometer, an experimental system for radius of curvature measurements is proposed to verify the proposed method. With the focal length testing system, both the positive and negative lens experimental results indicate that the measurement accuracy is less than 0.16%under normal experimental environment. With the radius of curvature testing system, the radius of curvature of spherical mirrors and the surface figure can be measured in a higher precision simultaneously. The experimental results indicate that the measurement accuracy is in the order of 10-4 .
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Digital projector is frequently applied to generate fringe pattern in phase calculation-based three dimensional (3D) imaging systems. Digital projector often works with camera in this kind of systems so the intensity response of a projector should be linear in order to ensure the measurement precision especially in Phase-Measuring Profilometry (PMP). Some correction methods are often applied to cope with the non-linear intensity response of the digital projector. These methods usually rely on camera and gamma function is often applied to compensate the non-linear response so the correction performance is restricted by the dynamic range of camera. In addition, the gamma function is not suitable to compensate the nonmonotonicity intensity response. This paper propose a gamma correction method by the precisely detecting the optical energy instead of using a plate and camera. A photodiode with high dynamic range and linear response is used to directly capture the light optical from the digital projector. After obtaining the real gamma curve precisely by photodiode, a gray level look-up table (LUT) is generated to correct the image to be projected. Finally, this proposed method is verified experimentally.
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A 15× double-group linkage zoom lens was presented based on the 640×512 cooled FPA. Having two alternate components linked and moved together, double-group zoom structure has smoother cam curve, so the displacement of all components are smaller and the total length is shorter. The focal length rang is 30~450mm and wavelength is 3.7~4.8μm, F number is 4. This lens was placed at cold shield and 100% cold shield efficiency had reached. Moreover, detailed design and image quality were given by CODE V® optical software. After analysis, MTF approaches diffraction limit. The results show that this optical system has large zoom ratio, and excellent image quality.
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In order to ensure the imaging resolution of aerial camera and compensating defocusing caused by the changing of atmospheric temperature, pressure, oblique photographing distance and other environmental factor [1,2], and to meeting the overall design requirements of the camera for the lower mass and smaller size , the linear focusing mechanism is designed. Through the target surface support, the target surface component is connected with focusing driving mechanism. Make use of precision ball screws, focusing mechanism transforms the input rotary motion of motor into linear motion of the focal plane assembly. Then combined with the form of linear guide restraint movement, the magnetic encoder is adopted to detect the response of displacement. And the closed loop control is adopted to realize accurate focusing. This paper illustrated the design scheme for a focusing mechanism and analyzed its error sources. It has the advantages of light friction and simple transmission chain and reducing the transmission error effectively. And this paper also analyses the target surface by finite element analysis and lightweight design. Proving that the precision of focusing mechanism can achieve higher than 3um, and the focusing range is ±2mm.
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Based on a 384×288 uncooled long-wavelength IR detector, a dual-FOV zooming optical system has been designed. To match the requirement of lightweight and flexible optoelectronic system, the zoom lens has been designed demountable. To evaluate the image quality, the MTF and RMS have been mainly considered. Also, the temperature analysis has been done to get the focusing solution. The result showed that the image quality was well and matched the requirement well.
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Bolometer is mainly used for measuring thermal radiation in the field of public places, labor hygiene, heating and ventilation and building energy conservation. The working principle of bolometer is under the exposure of thermal radiation, temperature of black absorbing layer of detector rise after absorption of thermal radiation, which makes the electromotive force produced by thermoelectric. The white light reflective layer of detector does not absorb thermal radiation, so the electromotive force produced by thermoelectric is almost zero. A comparison of electromotive force produced by thermoelectric of black absorbing layer and white reflective layer can eliminate the influence of electric potential produced by the basal background temperature change. After the electromotive force which produced by thermal radiation is processed by the signal processing unit, the indication displays through the indication display unit. The measurement unit of thermal radiation intensity is usually W/m2 or kW/m2. Its accurate and reliable value has important significance for high temperature operation, labor safety and hygiene grading management. Bolometer calibration device is mainly composed of absolute radiometer, the reference light source, electric measuring instrument. Absolute radiometer is a self-calibration type radiometer. Its working principle is using the electric power which can be accurately measured replaces radiation power to absolutely measure the radiation power. Absolute radiometer is the standard apparatus of laser low power standard device, the measurement traceability is guaranteed. Using the calibration method of comparison, the absolute radiometer and bolometer measure the reference light source in the same position alternately which can get correction factor of irradiance indication. This paper is mainly about the design and calibration method of the bolometer calibration device. The uncertainty of the calibration result is also evaluated.
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A new laser differential reflection-confocal lens thickness measurement (DRCTM) method is proposed for the high-accuracy measurement of the lens thickness. DRCTM uses the test beam reflected from the lens first and last surface to determine the vertex positions of the two surfaces. Differential confocal technology is used to precisely identify the lens vertexes of the lens first and last surfaces, thereby enabling the precise measurement of the lens thickness. Compared with the existing measurement methods, DRCTM has high accuracy and strong anti-interference capability. Theoretical analysis and experimental results indicate that the DRCTM measurement error can be limited to 0.0015%.
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The non-linearity of the phase shifting mechanism in white light interferometry system can seriously affect the measuring accuracy of the system. In this paper, the correcting method is to combine the displacement feedback control technology with the fuzzy PID control technology. Displacement feedback control mechanism and fuzzy PID controller are designed and then try to figure it out through Matlab simulation and experiment.. The result shows that combining the displacement feedback control technology with the fuzzy PID control technology can fulfill decent overall non-linear correction in the white light interferometry measuring system. Meanwhile, the accuracy of the correction is high and the non-linearity drop from 2% to 0.1%.
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Multi-beam interference will exist in the cavity of Fizeau interferometer due to the high reflectivity of test optics. The random phase shift error will be generated by some factors such as the environmental vibration, air turbulence, etc. Both these will cause phase retrieving error. We proposed a non-iterative approach called Carrier Squeezing Multi-beam Interferometry (CSMI) algorithm, which is based on the Carrier squeezing interferometry (CSI) technique to retrieve the phase distribution from multiple-beam interferograms with random phase shift errors. The intensity of multiple-beam interference was decomposed into fundamental wave and high-order harmonics, by using the Fourier series expansion. Multi-beam phase shifting interferograms with linear carrier were rearranged by row or column, to fuse one frame of spatial-temporal fringes. The lobe of the fundamental component related to the phase and the lobes of high-order harmonics and phase shift errors were separated in the frequency domain, so the correct phase was extracted by filtering out the fundamental component. Suppression of the influence from high-order harmonic components, as well as random phase shift error is validated by numerical simulations. Experiments were also executed by using the proposed CSMI algorithm for mirror with high reflection coefficient, showing its advantage comparing with normal phase retrieving algorithms.
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High resolution and simple device ranging technology has prospects of broad application and attractive. Laser frequency scanning interferometer has capability of high-resolution, low-noise ratio measurement. The tuning nonlinearity is a main factor limited to the ranging resolution which needs to be corrected. When using hardware to correct laser tuning nonlinearity, it would increases the complexity of the instrument structure. For the purpose of making structure of the instrument much simple, we proposed a method that using fiber reference channel to compensate the nonlinearity of measurement path beat frequency, which can achieve high resolution measurement. The method require obtaining the reference and measurement path beat signal simultaneously, then extracting the phase of the reference channel signal which is formed by fiber end face to compensate the nonlinearity of measurement signal. Hilbert transform is used to calculate the phase of signal, and empirical mode decomposition (EMD) method is used to reduce the noise of reference signal. The laser frequency scanning interferometer is demonstrated by experiment, we show that this performance enables 132μm for 10nm tuning bandwidth over several meter range. The method does not need to estimate the tuning nonlinearity function, so it could reduce the complexity of algorithm.
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New method for reconstructing rotationally asymmetric surface deviation with pixel-level spatial resolution is proposed. It is based on basic iterative scheme and accelerates the Gauss-Seidel method by introducing an acceleration parameter. This modified Successive Over-relaxation (SOR) is effective for solving the rotationally asymmetric components with pixel-level spatial resolution, without the usage of a fitting procedure. Compared to the Jacobi and Gauss-Seidel method, the modified SOR method with an optimal relaxation factor converges much faster and saves more computational costs and memory space without reducing accuracy. It has been proved by real experimental results.
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Bubbles in the sea are important to the research of geography, chemical engineering, biology etc. This paper presented an underwater laser imaging system for micro-bubbles, including the design, construction and performance. The system using a series 532-nm laser for lighting, and transform a piece-source. The piece-source illumination and image an area of bubbles by a high resolution CCD. It is impossible to achievement imaging the bubbles with diameters from 10µm to 500µm at the same time, we use three different focus apertures to adapt the requirements of resolution and receiver field of view. We can change the adaptive aperture for bubbles with different diameters. The imaging capability of the system is tested in the laboratory. The solid targets of specified size have been imaged in the sink, and obtained the clear images of the target with 500µm and 10µm for three magnifications. In order to verify the reliability of the system, experiments were carried out in the marine to obtain the bubble distribution in the offshore area. The results of bubbles distribution characteristics showed that the distribution is basically according with index law.
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A visible, MWIR, long focal, oblique view and focusing optical system of aerial camera is described, and in this paper we design an innovative optical system with common optical path and catadioptics configuration. The focal length of this optical system is 1.45m in the visible waveband (0.7~0.9μm,) and 0.61m in MWIR waveband (3.7~4.8μm), and the oblique view scanning range is within 20km~100km. To meet the requirements for the sharp imaging quality under the circumstances of high altitude environment and real time variable range, this aerial camera is focused by making back cutoff length longer to add a mirror, then MTF of optical system is all above 0.4 in Nyquest frequency.
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The continuous wavelet transform (CWT) introduces an expandable spatial and frequency window which can overcome the inferiority of localization characteristic in Fourier transform and windowed Fourier transform. The CWT method is widely applied in the non-stationary signal analysis field including optical 3D shape reconstruction with remarkable performance. In optical 3D surface measurement, the performance of CWT for optical fringe pattern phase reconstruction usually depends on the choice of wavelet function. A large kind of wavelet functions of CWT, such as Mexican Hat wavelet, Morlet wavelet, DOG wavelet, Gabor wavelet and so on, can be generated from Gauss wavelet function. However, so far, application of the Gauss wavelet transform (GWT) method (i.e. CWT with Gauss wavelet function) in optical profilometry is few reported. In this paper, the method using GWT for optical fringe pattern phase reconstruction is presented first and the comparisons between real and complex GWT methods are discussed in detail. The examples of numerical simulations are also given and analyzed. The results show that both the real GWT method along with a Hilbert transform and the complex GWT method can realize three-dimensional surface reconstruction; and the performance of reconstruction generally depends on the frequency domain appearance of Gauss wavelet functions. For the case of optical fringe pattern of large phase variation with position, the performance of real GWT is better than that of complex one due to complex Gauss series wavelets existing frequency sidelobes. Finally, the experiments are carried out and the experimental results agree well with our theoretical analysis.
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A white-light microscopy interferometer was developed for measurement of the 3D profile and roughness.10X, 20X and 50X Mirau interference microscope objectives with the numerical aperture of 0.3, 0.4 and 0.55 were designed, manufactured and then provided as the accessories. Thickness deviation between beam splitter plate and reference mirror plate as well as the numerical aperture will both affect the contrast of interference fringe, according to optical modeling and image evaluation. The former would generate dispersion and then decrease the fringe contrast, while the latter would not produce dispersion separately but impact the amount of dispersion when thickness deviation exists, and their influence on fringe contrast was based on the expression of white-light interference intensity. Simulations for interference fringes from Mirau interference microscope objectives with different NA and thickness deviation were implemented, demonstrated that the fringe contrast will be falling with NA and thickness deviation increasing. A standard step with the nominal step value of 110 nm was used to calibrate the white-light microscopy interferometer, showing that less than1nm deviation can be reached.
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In the three-dimensional angle measurement, yaw and pitch angle can be detected easily by several convention optical devices. While the roll angle is difficult to measure since its rotation axis is parallel to the incident plane. This work is based on the application of the Talbot effect with a Ronchi grating. The period of Moiré fringes which generated by two gratings will be changed with small rotation. The roll angle can be calculated by the width change of fringes.
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A device and procedure for measuring the asymmetry of backscattering coupling coefficients in square passive resonant cavity are described in this article. The asymmetry means that the two backscattering (BS) coupling coefficients r1 (in CW direction) and r2 (in CCW direction) are unequal, where CW and CCW correspond to clockwise and counter-clockwise directions respectively. It has been proved theoretically that a laser gyro will have a smaller lock-in threshold when the asymmetry of backscattering coupling coefficient is lower. The relative difference of BS coupling parameters for oppositely directed waves in ring cavity (RC) used in experiments is measured with high accuracy in measuring each BS coupling parameter. The system contributes to forecast the lock-in threshold of the laser gyro when assembling its square resonant cavity. Those research results are important for high precision laser gyro.
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The future naval battle will take place in a complex electromagnetic environment. Therefore, seizing the electromagnetic superiority has become the major actions of the navy. Radar reconnaissance equipment is an important part of the system to obtain and master battlefield electromagnetic radiation source information. Azimuth measurement function is one of the main function radar reconnaissance equipments. Whether the accuracy of direction finding meets the requirements, determines the vessels successful or not active jamming, passive jamming, guided missile attack and other combat missions, having a direct bearing on the vessels combat capabilities . How to test the performance of radar reconnaissance equipment, while affecting the task as little as possible is a problem. This paper, based on radar signal simulator and GPS positioning equipment, researches and experiments on one new method, which povides the azimuth benchmark required by the direction-finding precision test anytime anywhere, for the ships at jetty to test radar reconnaissance equipment performance in direction-finding. It provides a powerful means for the naval radar reconnaissance equipments daily maintenance and repair work[1].
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Cavity ring-down spectroscopy is a new type of high sensitive spectroscopy emerging in recent years. It can be subdivided into straight cavity, folding cavity and ring cavity ring-down spectroscopy by the structure of the optical resonator. In folded cavity ring-down spectrometer, the folded mirror surface may be polluted for various reasons. Different from straight cavity mirror, ring cavity mirror and folded cavity end mirror, there are two symmetrical beams incidence on the surface of folded mirror. So the performance of folded cavity in this case appears new characteristics, the most concerned one is that the scattering fields will produce an interference effect when two beams irradiate on the particulate. Embarking from the scattering theory and combining with the analysis of the light field in the resonator, this paper qualitatively analyzes the influence of the particulate loss on the performance of folded cavity ring-down spectrometer. These works have a guiding significance for the study of folded cavity ring-down spectroscopy and can improve its system performance.
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Pyranometer is an instrument used to measure the solar radiation, according to pyranometer differs as installation state, can be respectively measured total solar radiation, reflected radiation, or with the help of shading device for measuring scattering radiation. Pyranometer uses the principle of thermoelectric effect, inductive element adopts winding plating type multi junction thermopile, its surface is coated with black coating with high absorption rate. Hot junction in the induction surface, while the cold junction is located in the body, the cold and hot junction produce thermoelectric potential. In the linear range, the output signal is proportional to the solar irradiance. Traceability to national meteorological station, as the unit of the national legal metrology organizations, the responsibility is to transfer value of the sun and the earth radiation value about the national meteorological industry. Using the method of comparison, with indoor calibration of solar simulator, at the same location, standard pyranometer and measured pyranometer were alternately measured radiation irradiance, depending on the irradiation sensitivity standard pyranometer were calculated the radiation sensitivity of measured pyranometer. This paper is mainly about the design and calibration method of the pyranometer indoor device. The uncertainty of the calibration result is also evaluated.
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The magnetic field is one of the main causes of zero drift in a Ring Laser Gyroscope (RLG), which should be avoided by adopting a magnetic shielding system. The Gauss Meter is usually used to measure the magnetic shielding effectiveness. Generally, the traditional Gauss Meter has advantages of high measure range and high reliability, however, its drawbacks such as complex structure, high price and the PC client software cannot be customized at will, are also obvious. In this paper, aiming at a type of experimental magnetic shielding box of RLG, we design a new portable three-axis magnetic field measurement system. This system has both high modularity degree and reliability, with measuring range at ±48Gs, max resolution at 1.5mGs and can measure the magnetic field in x, y and z direction simultaneously. Besides, its PC client software can be easily customized to achieve the automatic DAQ, analysis, plotting and storage functions. The experiment shows that, this system can meet the measuring requirements of certain type of experimental magnetic shielding box for RLG, meanwhile, for the measurement of some other magnetic shielding effectiveness, this system is also applicable.
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The polarization imaging detection technology increased the polarization information on the basis of the intensity imaging, which is extensive application in the military and civil and other fields, the research on the polarization characteristics of target is particularly important. The research of the polarization reflection model was introduced in this paper, which describes the scattering vector light energy distribution in reflecting hemisphere polarization characteristics, the target polarization characteristics test system solutions was put forward, by the irradiation light source, measuring turntable and camera, etc, which illuminate light source shall direct light source, with laser light sources and xenon lamp light source, light source can be replaced according to the test need; Hemispherical structure is used in measuring circumarotate placed near its base material sample, equipped with azimuth and pitching rotation mechanism, the manual in order to adjust the azimuth Angle and high Angle observation; Measuring camera pump works, through the different in the way of motor control polaroid polarization test, to ensure the accuracy of measurement and imaging resolution. The test platform has set up by existing laboratory equipment, the laser is 532 nm, line polaroid camera, at the same time also set the sending and receiving optical system. According to the different materials such as wood, metal, plastic, azimuth Angle and zenith Angle in different observation conditions, measurement of target in the polarization scattering properties of different exposure conditions, implementation of hemisphere space pBRDF measurement.
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Flatness of the optical flat measurement mainly has two methord: first is laser plane interferometer, second is the Phase-shifting Laser Interferometer. The two methods were compared by analysis. For the detection of high precision optical flat, expounds the principle and method of Phase-shifting Laser Interferometer. Uncertainty analysis was carried out to validate the approach, meet the flat verification regulation. The method is feasible.
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Multi-task and real-time measurement of relative displacement is widely needed in the present industrial field. Existing measuring methods require complex preparation and data processing, or are unable meet the requirement of automation, multi-task and real-time. The instruments used to measure absolute coordinates are inefficiency because of the measured target is relative displacement. A new single-station wMPS (Workspace Measuring Position System) measurement method combined distance measurement is presented in this paper. It learns from measuring principle of total station, measures angle based on rotating scanning laser plane measuring method, and measures distance based on optoelectronic scanning multi-angle intersection location principle, uses the angle-length resection measuring method, builds a new mathematical model to measure the relative displacement of the target. The result of experiment proves that it increases measuring efficiency and achieves multi-task and real-time measurement of relative displacement.
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Cone parts are widely used in advanced manufacturing and precision mechanics, providing air proof, torque transmission and so on. The straightness of generatrix is one of the important parameters, and the required accuracy can be up to submicrometers. In order to realize the rapid and high precision generatrix measurement of smooth surface cone, a laser interferometric method is proposed based on the structure of typical Fizeau interferometer. The high precision optical flat is used for reference standard, and the surface of cone is the measured object. Two cylindrical lenses with different focal lengths realize unidirectional expansion of parallel beam, solving the problem of CCD camera fringe resolution. The interference fringes are curved because of the cone angle, and the peak is the basis for accurate determination of the generatrix. Two fringe processing techniques are described in detail, which are single-frame and phase-shifting methods. Single-frame method includes two steps, i.e. the calculation of integral part and decimal part. The advantage of this method is the simple measurement structure. Phase-shifting method needs piezoelectric transducer (PZT) to generate several steps for phase calculation, with the advantage of high accuracy. The experimental results show that the straightness measurement accuracy can be better than 0.2 μm.
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In this manuscript, we establish a model and theoretically investigate the novel structure of AFTP designed by ourselves. We analyze each sub-structure of the new type of AFTP and firstly use the software of ANSYS to simulate the deformation of the flexible hinge under the external force. The result shows that the deformation of the flexible hinge is mainly from and almost linear to the middle part. Further, after considering the influence of the levers and piezoelectric actuators, we setup the theoretical model in which the displacement is only relative to the ratio of the lever R. With the optimal value of R, we can get the relative largest displacement of the end cap when the other parameters are confirmed. As the maximal voltage applied on the piezoelectric stacks actuators (PSA) is finite, the largest displacement of the end cap is restricted. Neglecting the influence of the effective friction force (Ff) of inner-system, the relationship between the largest displacement of the end cap and the ratio (R) is derived numerically. From the calculated results, we get the largest displacement is about 67 μm with R of 6.9. This work provides a reference for structure optimization of AFTP based on flexible hinges and levers.
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To perform the in-orbit test, verification and surveillance task, the laser simulation and test station must be constructed. Cooperated with the fixed laser communication ground station, we can not only test the main specifications of the laser communication terminals, but also test the performances of the laser backbone link.
In this paper, we first give the basic theory of the in-orbit test. Then designed the laser simulation and test station, which consists of laser transmitter module, laser receiver module, and general test module. In the GEO-to-LEO laser communication terminal test progress, the laser simulation and test station responsible for the simulation of the LEO laser communication terminal. In the LEO-GEO-Ground laser link performance test progress, the laser simulation and test station simulate the LEO satellite, which transfer high date rate data flow to GEO satellite, then the GEO satellite route the data flow to the GEO-to-Ground laser communication terminal through optical router, finally GEO satellite transfer the LEO data down to fixed laser receiver on ground.
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The objectives of this tutorial are to introduce an optical method of measuring atmospheric turbulent outer scale. The method utilizes the ratio between the correlation functions of the wandering in two perpendicular planes. A simple relationship to obtain the outer scale from the measured correlation functions is established for a particular model of turbulence, the modified Von Karman model. Base on the rational conclusion, an implementary project of measuring atmospheric turbulent outer scale with optical method is designed. At the same time, the plan of the experiment system is given. By predigesting the model, the calculating program of the measurement is written also.
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AA2198 alloy is one of the third generation Al-Li alloys which have low density, high elastic modulus, high specific strength and specific stiffness. Compared With the previous two generation Al-Li alloys, the third generation alloys have much improved in alloys strength, corrosion resistance and weldable characteristic. For these advantages, the third generation Al-Li alloys are used as aircraft structures, such as C919 aviation airplane manufactured by China and Russia next generation aviation airplane--MS-21. As we know, the aircraft structures are usually subjected to more than 108 cycles fatigue life during 20-30 years of service, however, there is few reported paper about the third generation Al-Li alloys’ very high cycle fatigue(VHCF) which is more than 108 cycles fatigue. The VHCF experiment of AA2198 have been carried out. The two different initiation mechanisms of fatigue fracture have been found in VHCF. The cracks can initiate from the interior of the testing material with lower stress amplitude and more than 108 cycles fatigue life, or from the surface or subsurface of material which is the dominant reason of fatigue failures. During the experiment, the infrared technology is used to monitor the VHCF thermal effect. With the increase of the stress, the temperature of sample is also rising up, increasing about 15 °C for every 10Mpa. The theoretical thermal analysis is also carried out.
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A moving target should be missing from a photoelectric theodolite tracker, when the clouds and other special conditions encountered in the course of a theodolite tracking a moving object, and this condition should cause the interruption of tracking process. In view of this problem, an algorithm based on the frame of parameter identification and rolling prediction to trajectory was presented to predicting the target trajectory when it missing. Firstly, the article makes a specification of photoelectric theodolite and it operating mechanism detailed. The reasons of flying target imaging disappear from the field of theodolite telescope and the traditional solution to this problem, the least square curve fitting of trajectory quadratic function of time, were narrated secondly. The algorithm based on recursive least square with forget factor, identify the parameters of target motion using the data of position from single theodolite, then the forecasting trajectory of moving targets was presented afterwards ,in the filtering approach of past data rolling smooth with the weight of last procedure. By simulation with tracking moving targets synthetic corner from a real tracking routine of photoelectric theodolite, the algorithm was testified, and the simulation of curve fitting a quadratic function of time was compared at the last part.
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Coating curing curve is one of the most important methods to reflect the coating curing properties. It is of great significance for the coating curing properties. In this paper, by using the reflective Terahertz (THz) time-domain spectroscope technique, the curing properties of coating with different thicknesses are studied. Three different parameters used for studying the properties of coating curing curve are proposed in this paper. They are respectively the differential time of flight, power spectrum and amplitude for reflective THz time-domain waveform. In this paper, two kinds of coating (with different thicknesses) curing properties curves are established and the relative errors from three parameter analysis methods are compared respectively. This study shows that the study on coating curing properties curves by using the power spectrum of reflective THz time-domain waveform is superior to the amplitude parameter method. But for the thick coating, the differential time of flight for the reflective THz time-domain waveform can also better reflect the coating curing properties.
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The existence of Gravitational Wave (GW) is one of the greatest predictions of Einstein’s relative theory. It has played an important part in the radiation theory, black hole theory, space explore and so on. The GW detection has been an important aspect of modern physics. With the research proceeding further, there are still a lot of challenges existing in the interferometer which is the key instrument in GW detection especially the measurement of the super large radius optics. To solve this problem, one solution , Fizeau interference, for measuring the super large radius has been presented. We change the tradition that curved surface must be measured with a standard curved surface. We use a flat mirror as a reference flat and it can lower both the cost and the test requirement a lot. We select a concave mirror with the radius of 1600mm as a sample. After the precision measurement and analysis, the experimental results show that the relative error of radius is better than 3%, and it can fully meet the requirements of the measurement of super large radius optics. When calculating each pixel with standard cylinder, the edges are not sharp because of diffraction or some other reasons, we detect the edge and calculate the diameter of the cylinder automatically, and it can improve the precision a lot. In general, this method is simple, fast, non-traumatic, and highly precision, it can also provide us a new though in the measurement of super large radius optics.
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This article described the rotation angle system of the bidirectional reflectance distribution function (BRDF) measurement device. A high-precision multidimensional angle platform device is built. The rotation angle system uses two scanning rotational mechanical arms and a two-dimensional coaxial turntable mechanical structure, each rotational axis are driven by high-power motor and completed closed-loop control with high-precision encoder. Rotation of the motors can be automatically measured in accordance with point by the control software. The detecting arm can be rotated to measure any point in hemisphere space, the rotary range of light arm is ± 90 °, the rotary range of sample stage is 360 ° and the angular resolution is 0.01°. The rotation angle system meets the absolute positioning hemisphere space requirements of BRDF device. The experimental result shows that the rotation angle system met the high-precision positioning requirements for the BRDF absolute measurement.
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With the development of laser technology, the laser wavelength has been the primary standard of length measurement. The measurement of laser wavelength is studied widely in the world. In fact, the accuracy is different when measured in the air and vacuum. The measurement accuracy of laser wavelength is high when measured in vacuum, such as beat frequency method, its precision can meet 10-15 order of magnitude. However, most of length measurement are taken place in air which influenced by environmental factors such as temperature, pressure, humidity and air ingredient. The research of how to enhance the measurement precision in air is meaningful. There are many general methods for measurement of laser wavelength include Edlen empirical formula method, the extraction method (the refractive index interferometer), F-P etalon method, and grating diffraction method, etc. By comparing and analyzing these methods, among them the Edlen formula method is the most simple and practical, the measurement result and analysis demonstrate the measurement method can achieve the precision of 3× 10-8.
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The bidirectional reflectance distribution function (BRDF) diffuse plate as the standard of value transfer and carrier for BRDF, plays an important role in the study of radiometric calibration and scattering properties of. The space spectral characteristics of developed BRDF diffuse standard plate were measured by BRDF standard device. The standard BRDF values were given under more wavelengths and more geometric conditions in the visible to the infrared spectral bands, and the uncertainty is 1%. By comparison, the developed BRDF diffuse standard plate in visible and infrared bands reached the similar international standards plate level.
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Because of the huge advantage of RAID technology in storage, it has been widely used. However, the question associated with this technology is that the hard disk based on the RAID card can not be queried by Operating System. Therefore how to read the self-information and log data of hard disk has been a problem, while this data is necessary for reliability test of hard disk. In traditional way, this information can be read just suitable for SATA hard disk, but not for SAS hard disk. In this paper, we provide a method by using LSI RAID card’s Application Program Interface, communicating with RAID card and analyzing the feedback data to solve the problem. Then we will get the necessary information to assess the SAS hard disk.
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The Space point measurement repeatability is a prerequisite for achieving high-precision measurements to tracker, so it is important to Spatial positioning accuracy. Different measurement object means different error propagation model. In this paper, we research on the tracker measure a fixed point in a manner such single point, which according to model arrangement, under controlled conditions. Experimental measurements from three different perspectives just as different distances, different horizontal and different Vertical angle. From the integrated angle error, the repeat single point measurement accuracy is given. Then establish of a single point evaluate model that combine with algorithm.
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Aiming at the problem of the resolution reduction in a miniaturized grating spectrometer, we presented a method to improve its spectral resolution by inserting a tunable Fabry-Perot filter into its optical path before the grating. The Fabry-Perot filter was designed to filter out a partial spectrogram and separate the original undistinguishable spectral lines so as to make their actual wavelengths can be detected. The different cavity length of the Fabry-Perot filter is corresponding to the different separated partial spectrogram. Combining all the separated partial spectrograms, an entire spectrogram with improved resolution can be achieved. Experimentally, the spectral resolution of a grating dispersive system was improved from 2 nm to 1.2nm in a broad spectral range by insetting a homemade tunable Fabry-Perot filter, which demonstrated the feasibility of this scheme. The tunable Fabry-Perot filter is fit for miniaturization by using MEMS technology and is able to work as an independent module. The method proposed provides a potential way to improve the spectral resolution without reducing the spectral range of the existing miniaturized grating spectrometers.
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This paper proposes a novel optical three-dimensional (3D) measurement method using the traditional space-time stereo system. In the proposed method, the projector not only shoots fringe pattern onto the measurement object to achieve precise matching, but also plays a vital role in the 3D information calculation. With the combination of two cameras and a projector, two digital fringe projection (DFP) measurement systems and one traditional space-time stereo measurement system can be obtained. In another word, the measurand will be measured three times simultaneously, which results in three independent point clouds of the same region of the object to be measured. So it is necessary to register these three sets of points for obtaining one final data set. The iterative closest points (ICP) method, which is known as the most popular registration approach, is sensitive to the initial estimation of the transformation between the two sets of points to be matched. Thus, a robust rough registration, which is introduced from Natasha, is useful for ICP to realize accurate registration. After registration, a scattered point set with redundant and errors, which are caused by overlapping, is obtained. Then some local surfaces are constructed for those overlapping regions using the moving least squares (MLS) method, and the points extracted from those surfaces are used to replace the points of the overlapping regions. Finally, a simplified, precise point cloud can be obtained.
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Absolute distance measurement systems are of significant interest in the field of metrology, which could improve the manufacturing efficiency and accuracy of large assemblies in fields such as aircraft construction, automotive engineering, and the production of modern windmill blades. Frequency scanning interferometry demonstrates noticeable advantages as an absolute distance measurement system which has a high precision and doesn’t depend on a cooperative target. In this paper , the influence of inevitable vibration in the frequency scanning interferometry based absolute distance measurement system is analyzed. The distance spectrum is broadened as the existence of Doppler effect caused by vibration, which will bring in a measurement error more than 103 times bigger than the changes of optical path difference. In order to decrease the influence of vibration, the changes of the optical path difference are monitored by a frequency stabilized laser, which runs parallel to the frequency scanning interferometry. The experiment has verified the effectiveness of this method.
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We present a design for a spin-exchange optical pumping system to produce large quantities of highly polarized 129Xe and 131Xe. Low xenon concentrations in the flowing gas mixture which allow the laser to maintain high Cs polarization. The large spin-exchange rate between Cs and Xe through the long-lived van der Waals molecules at low pressure, combined with a high flow rate, results in large production rates of hyperpolarized xenon. The fast rates make it possible to obtain large nuclear polarizations after several minutes of optical pumping with a laser.At high Xe pressures. According to the theory, the longitudinal spin-elaxation rate 1T1 of Xe in a high-pressure sample containing only Xe and Cs vapor has the simple form is the velocity averaged binary spin-exchange cross section, It is the relaxation rate due to wall collisions and perhaps magnetic field inhomogeneities. Our results complement earlier studies performed at 129Xe pressures of about 20 Torr and 131Xe pressures of about 20 Torr and N2 pressures of 600 Torr . This work is useful for predicting spin-exchange rates between polarized Cs atoms and Xe nuclei.
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Spore is an important part of bioaerosols. The optical characteristics of spore is a crucial parameter for study on bioaerosols. The reflection within the waveband of 2.5 to15μm were measured by squash method. Based on the measured data, Complex refractive index of Aspergillus oryzae spores within the waveband of 3 to 5μm and 8 to 14 μm were calculated by using Krames-Kronig (K-K) relationship. Then,the mass extinction coefficient of Aspergillus oryzae spores within the waveband of 3 to 5μm and 8 to 14μm were obtained by utilizing Mie scattering theory, and the results were analyzed and discussed. The average mass extinction coefficient of Aspergillus oryzae spores is 0.51 m2/g in the range of 3 to 5μm,and 0.48m2/g in the range of 8 to 14μm. Compared with common inorganic compounds, Aspergillus oryzae spores possesses a good extinction performance in infrared band.
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Based on our previous work in liquid-crystal microlens arrays (LCMAs), a new kind of arrayed optical switches (AOSs) based on LCMAs with a key dual-mode function including beam convergence and divergence, is proposed and simulated in this paper. Different with our previous LCMAs, the developed LCMAs leading to AOSs have two layers of control electrodes deposited directly over the surface of the top glass substrate. One is the patterned electrode, which is designed into basic circular holes with suitable diameter, and the other is the planar electrode. Both layered electrodes are effectively separated by a thin SiO2 film with a typical thickness of about several micrometers, and then driven by electrical signals with different root mean square (rms) voltage amplitude. The experiment results show that the AOSs can work well through applying proper voltage signals over the device. Compared with other AOS structures, our AOSs have a greater integration level and lower cost.
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Quantum Sensors like Quantum Radar and Lidar based on the interference of non-classical states can achieve super-sensitivity beyond the Standard Quantum Limit (SQL). But as the photons transporting in atmosphere, the environmental interaction causes quantum de-coherence and results in the reduction of super-sensitivity range of the quantum sensors. The most significant effect of atmospheric transmission is photon loss along with phase fluctuation. In this letter, we introduce both the photon loss and phase fluctuation by adding a fictitious beam splitter in the signal arm of Mach- Zehnder interferometer (MZI). The density matrix with N00N and M&M' entangled states being the input states under the condition of photon loss and phase fluctuation is given respectively. Then as the optimal detection schemes parity operator is used as the detector and the formula of the sensitivity is derived. The super-sensitivity range of M&M’ and N00N states with de-coherence are simulated. As a consequence, with high photon loss M&M’ states shows the better phase sensitivity than N00N states but the N00N state is better when the loss is smaller than 20%. And with pure phase fluctuations N00N states get the longer range. M&M’ states is sensitive to the transmittance difference between two arms of the interferometer.
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Gimbals and Fast steering mirrors (FSMs) are commonly used to stabilize the line-of-sight (LOS) of the electro-optical tracking system mounted on moving platforms .The gimbal is used to restrain the vibration of low frequencies, and the FSM is used to restrain the vibration of high frequencies. The restraining performance of the Electro-Optical tracking system is equal to the multiplication of the restraining performance of the gimbal and the FSM. The vibration of high frequencies is mainly restrained by the FSM, and so the performance of the FSM is very important to the Electro-Optical tracking system. There are two ways to improve the stabilization accuracy and bandwidth of the FSM, one way is to improve the accuracy and bandwidth of inertial sensors, and the other way is to use low weight inertial sensors to reduce the load of FSM and increase the mechanical resonance frequency. And so the inertial sensors of high accuracy, high bandwidth and low weight are the key to improve the stabilization accuracy and bandwidth of the FSM.
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3D micro profiles are often needed for measurement in many fields, e.g., binary optics, electronic industry, mechanical manufacturing, aeronautic and space industry, etc. In the case where height difference between two neighboring points of a test profile is equal to or greater than λ / 4, microscopic interferometry based on laser source will no longer be applicable because of the uncertainty in phase unwrapping. As white light possesses the characteristic of interference length approximate to zero, applying it for micro profilometry can avoid the trouble and can yield accurate results. Using self-developed Mirau-type scanning interference microscope, a step-like sample was tested twice, with 128 scanning interferograms recorded for each test. To process each set of the interferograms, the method of spatial frequency domain analysis was adopted. That is, for each point, by use of Furrier transform, white-light interference intensities were decomposed in spatial frequency domain, thus obtaining phase values corresponding to different wavenumbers; by using least square fitting on phases and wave numbers, a group-velocity OPD was gained for the very point; and finally in terms of the relation between relative height and the group-velocity OPD, the profile of the test sample was obtained. Two tests yielded same profile result for the sample, and step heights obtained were 50.88 nm and 50.94 nm, respectively. Meantime, the sample was also measured with a Zygo Newview 7200 topography instrument, with same profile result obtained and step height differing by 0.9 nm. In addition, data processing results indicate that chromatic dispersion equal to and higher than 2nd order is negligible when applying spatial frequency domain analysis method.
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An apparatus for determining the spectral response of large area solar cells based on filter method has been introduced. The spectral response of a solar cell is measured by irradiating it by means of a narrow-bandwidth light source at a series of different wavelengths covering its response range, and measuring the short-circuit current density and irradiance at each of these wavelengths. Experiments have been performed to analyze the factors which can affect the spectral response measurements such as the full width at half maximum (FWHM) of filters, the non-uniformity of monochromatic light. The results indicate that less FWHM of filters, more uniformity of monochromatic light will lead to a more accurate measurement.
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A solar simulator is a device that provides illumination approximating natural sunlight. Solar simulators are classified as A, B or C for each of the three categories based on criteria of spectral distribution, irradiance non-uniformity on the test plane and temporal instability of irradiance. In this paper, we find that spectral match may change during the pulse of a pulsed solar simulator. In our experiments, a second PV device, which is placed at a fixed position outside the test area, has been used for monitoring the irradiance during the pulse and correcting the measurement results. We focus on the temporal instability measurements of pulsed solar simulators, especially for those whose irradiance changes rapidly during the time of data acquisition, and make a conclusion.
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Importance of ultraviolet calibration is growing fast as ultraviolet payloads are wildly used in national space plan. Calibration device for UV radiation celestial body simulator is established especially for the calibration of instantaneous radiation parameters and high-sensitivity radiation parameters. Parameters such as spectral radiance, spectral irradiance can be calibrated from 200 nm to 400 nm. The uncertainty of spectral radiance is 15% (k=2)and the uncertainty of spectral irradiance is 20% (k=2).The calibration device is perspective for its application in national defense system.
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The spectrum not-matching of a calibration source with target source can affect star sensor measurement precision in the calibration of star sensor. Quantitatively analysis the different colour temperature light source due to the spectral mismatch to the focus light source at 0 magnitude. The results show that the star sensor calibration error caused by spectrum mismatch is up to 0.323 magnitude. Put forward a kind of spectrally tunable light source, which can simulate any spectral distribution of stars and applied to the star sensor calibration. The experimental results show that calibration accuracy can be enhanced within 0.62%.
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In order to solve the weakness of traditional vertical target coordinate measurement, such as complex structure, inconvenient debugging and difficult to form a large area target, a method based on intersection laser screens was proposed. The effective area of was constituted by the intersection of two fan-shaped laser screens. Photodiode (PD) array was used to measure the intensity of laser light. When the projectile passes through the laser screens, the corresponding PDs receive signal. After signal processing and adaptive threshold comparator circuit processing, the signal is transmitted to PC to calculate the projectile target coordinate. The calculation method of feature point and the calculation process of coordinate were described in detail. Error distribution in effective area was analyzed. Experiment was carried out by using simulating projectile and the principle prototype whose effective target area is 1m×1m. The result shows that the precision of location measurement is up to 2mm. The method has the advantages of simple structure, convenient debugging. It is easy to construct a larger area target, and the maximum effective area can reach to 6m×6m.
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This paper describes the design and realization of a refocusing system for a space TDICCD camera of 2.2-meter focal length, which, features a three mirror anastigmatic(TMA) optical system along with 8 TDICCDs assemble at the focal plane, is high resolution and wide field of view. TDICCDs assemble is a kind of major method of acquiring wide field of view for space camera. In this way, the swath width reach 60km. First, the design of TMA optical system and its advantage of this space TDICCD camera was introduced; Then, the refocusing system as well as the technique of mechanical interleaving assemble for TDICCDs focal plane of this space camera was discussed in detail, At last, the refocusing system was measured. Experimental results indicated that the precision of the refocusing system is ± 3.12μm(3σ), which satisfy the refocusing control system requirements of higher precision and stabilization.
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As a key technology to improve the imaging quality of remote multispectral CCD camera, the performance of a focusing system for multispectral CCD camera was presented in detail in this paper. Firstly, the focusing precision required was calculated in the optical system. The method of direct adjusting multispectral CCD focal plane was proposed, which was suitable for this multispectral CCD camera optical system. Secondly, we developed a focusing system which has the advantages of lower constructional complexity, easier hardware implementation and high focusing sensitivity. Finally, experimental test was constructed to evaluate the focusing precision performance of the focusing system. The result of focusing precision test is 3.62μm(3σ) in a focusing range of ±2.5mm. The experimental result shows that the focusing system we proposed is reasonable, and reliability as well as stable, which meet the focusing precision requirements for multispectral CCD camera.
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In order to obtain the far-field distribution of high dynamic range laser focal spot, the mathematical model of schlieren method to measure the far-field focal spot was proposed, and the traditional schlieren reconstructed algorithm was optimized in many aspects in this paper. First of all, the mathematical model which used to measure the far-field focal spot was created, the amplificatory coefficient K of the main lobe intensity and amplificatory coefficient b of the laser spot area were selected ; Secondly, the two important parameters were calibrated and the accurate main lobe spot and side lobe spot were captured by the integrated diagnostic beam fast automatic alignment system; Finally, the schlieren reconstructed algorithm was optimized by circle fitting method to calculate side lobe image center and weighted average method to fuse the joint image edge, and the error of traditional schlieren reconstruction method for side lobe center was reduced and the obvious joint mark of reconstructed image was eliminated completely. The method had been applied in a certain laser driver parameter measurement integrated diagnostic system to measure far-field laser focal spot. The experimental results show that the method can measure the far-field distribution of high dynamic range laser focal spot exactly on the condition that the parameter of mathematical model is calibrated accurately and the reconstructed algorithm of schlieren measure is optimized excellently.
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At present, the conversion efficiency of high concentrated photovoltaic modules is about 30%, most of the solar energy is converted into heat, which will result in solar cell temperature rise and subsequent module efficiency decrease. For existing module with large solar cell, the heat source is concentrated and additional cooling fins must be used, resulting in high system complexity and cost rise. In order to lower the cost of photovoltaic, we developed distributed cooling type module with simple structure. This paper depicts a distributed cooling design for high concentrated photovoltaic module, as well as the thermal simulation of this design with analysis software. Module prototype was also made to test the actual effect. The final outdoor results showed high consistency with the simulation results. The chip temperature can be lower than 45℃ and the module outdoor working efficiency is higher than 26% ,and lower temperature provide a guarantee of long-term reliability to module packaging material.
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