Screening the surface defect image of steel plate is a crucial link in the steel inspection system. In order to improve the detection efficiency, a defect image screening algorithm based on regional gradient projection is proposed. After the gradient map of the original image is obtained by an operator, it is divided into several equal-size regions which are projected horizontally and vertically, that can calculate the normalized standard deviation of each area in both directions, and then arrange in descending order among which the top 45% standard deviation is selected to the mean value to compare with the threshold to complete the defect image screening. The experimental results demonstrate that compared with the traditional gradient method, the accuracy of this method is improved by 8.95%, the missed detection rate is reduced by 5.33%, and the false detection rate is reduced by 3.62%. Therefore, the algorithm is simple, efficient and robust, which can meet the requirements of enterprise defect image screening
Strip flatness is an important indicator of steel quality, and its detection technology has always been the focus of research at home and abroad. This paper proposes a non-contact online real-time measurement scheme for hot rolled strip steel. Our research is based on the laser triangulation method, which transforms the flatness detection into the strip surface height detection. In order to prevent errors caused by jitter during strip transportation, we have added a three-point measurement method. The flatness measurement system has carried out the system hardware design with FPGA and linear CCD as the core and the system software design with the laser spot positioning as the core. The basic technology realization process is based on FPGA as the main control and processing chip, collecting the laser reflection light signal of the measured strip steel surface through the optical system through the linear array CCD to obtain the strip surface height information. The collected signals are subjected to photoelectric conversion, filtering and amplification, and A/D conversion, and are transmitted through a network port based on UDP protocol. Finally, the spot center is positioned by comparing the selected threshold method to obtain important data for calculating the flatness information. In this study, a semiconductor laser with a wavelength of 450nm, a TCD1304AP linear CCD and an FPGA chip of the XC7A35T model produced by Xilinx were selected. In the range of 4 mm above and below the reference position, the measurement accuracy of the system can reach 10μm, which meets the measurement requirements of the measured strip elongation accuracy of 1% (when the elongation is 10~200 I) or 1 I (when the elongation is less than 1 I).
Seeker technology is the core of laser semi-active guidance. At present, laser semi-active guidance weapons are mainly used for large caliber ammunition such as shells, bombs and missiles, while small caliber ammunition is rarely used. It is an important development direction of laser semi-active guidance weapons. In this paper, a miniaturized high-precision laser azimuth detection system for laser semi-active guidance seeker is designed. On the basis of existing laser plate active guidance seeker technology, the working principle of quadrant detector is analyzed. A quadrant detector with photosensitive diameter of 3.04mm and photosensitive area product of 2.52mm2 is selected to design a high-precision calculation based on FPGA which is different from sum difference algorithm Law. According to the actual needs, the design index of the optical system is summarized. An optical system with an entrance pupil diameter of 8mm is designed. The optical system is evaluated and analyzed. The propagation characteristics of the laser in the atmosphere are analyzed. A variable gain amplifier circuit with a gain adjustment range of 24dB is designed. In order to improve the signal-to- noise ratio and anti-interference ability, the relevant detection circuit is designed. The experimental results show that the average absolute error of the system is 0.09° which meets the design requirements.
China’s LAMOST telescope is the most powerful spectroscopic measurement telescope for studying large field of view and large sample astronomy. It combines the world’s leading splicing mirror technology with thin mirror technology for the first time, breaking through the inability of previous astronomical instruments to combine large clear apertures and wide The bottleneck of the field of view. In order to more accurately detect the movement between the sub-mirrors of large-aperture telescopes, it is necessary to install a precise sensor at the edge of the sub-mirror to detect the movement between the sub-mirrors, and then adjust the mirror displacement in time through the force actuator under the mirror to obtain more Good image quality. Due to the particularity of the mirror surface, there are strict requirements on the displacement measurement accuracy of the sensor. Its research focuses on the acquisition and filtering of sensor displacement signals. In order to extract useful digital signals from strong noises and improve the signal-to-noise ratio (SNR) of the digital signals output by the detection system, this paper proposes a dual-channel digital filtering algorithm combining improved four-entry wavelet and adaptive filtering. By improving the four-entry wavelet algorithm, the algorithm improves the reconstruction capability and linearity while taking into account the multi-resolution characteristics of the traditional wavelet transform algorithm, and ensures the continuity of the wavelet coefficients at the threshold; and the second channel collects the high The frequency characteristic noise signal is processed again through adaptive filtering, and finally a sensor displacement signal with a higher signal-to-noise ratio (SNR) is obtained. After the front-end algorithm development is completed, the displacement signal acquisition and processing system is realized through the ZYNQ-7000 development platform, including AD conversion, digital filtering, signal transmission and LCD screen display, etc., and the Gui interface program is written using Matlab to convert the displacement signal Real-time display and save records on the PC side. The entire experiment of the displacement sensor was carried out at the Nanjing Institute of Astronomical Optics Technology, Chinese Academy of Sciences. The results show that the digital signal-to-noise ratio (SNR) processed by the algorithm is 20.7% higher than that of the traditional wavelet algorithm. The root mean square error (RMSE) of the fitted displacement curve is reduced by 19.8% on average, and the running time was reduced by 50%. It shows that the algorithm is accurate and fast, and its entire signal processing system has important application significance for the research of displacement sensors between splicing mirrors of large astronomical telescopes.
When performing Three-dimension (3D) measurements with phase-shifting method, usually a digital projector, or a translation stage is used to generate phase-shifted fringe patterns. However, in these cases, errors like gamma distortion, lens distortion and random errors caused by mechanisms are inevitable. In order to reduce the effect caused by system errors, simplify calibration procedures as well as further minimizing, in this paper, phase-shifted fringes are generated by linear LED arrays and a Ronchi grating. Phase-shifting will be performed by switching one linear LED array to another. The advanced iteration algorithm which do not require the phase-shifting amount to be known and unified is employed to minimize the calculation error caused by un-unified phase-shifting amount, since the phase-shifting amount produced by this method depends on the distance to the grating plane, which could not be exact 2π/3. Experiment results suggest that the system has a measurement error less than 0.05mm at the working distance of 130mm.
Checking of the micro-displacement between the segmented mirrors of the large aperture telescope is the foundation of the Active Optical System to adjust the system to gain the optimum observing effect. In this paper, the signal processing system of a new type of area-alterable differential capacitive micro-displacement sensor used in the active optical system was designed, including both the hardware and software of it. The hardware consists of the high performance instrument amplifier, the lock-in demodulator, Analog to Digital converter, FPGA and the microprocessor. The software includes the MCU codes and FPGA-based modules such as the excitation pulse generation, system control and implementation of the signal processing algorithms. On the basis of the EDA simulation and test of the circuit modules, the schematic and PCB layout were designed and the experimental setup was assembled. Then the codes of FPGA and Microprocessor were designed and debugged. In the end, the system was tested on the platform of the micro-displacement experiment. Results showed that the general design scheme is feasible although the precision of the system is needed to be improved.
KEYWORDS: Field programmable gate arrays, Sensors, Active optics, Analog electronics, Clocks, Mirrors, Active sensors, Data transmission, Interfaces, Data conversion
Active optics is a wave surface correction technology, which is used to eliminate deformation caused by gravity and temperature. The measurement of the micro displacement between sub-mirrors of large astronomical telescope is the key to automatic adjustment of the active optical system. In this paper, for a differential capacitive micro displacement sensor, the functions of each main module are realized through the designing of the software of FPGA and network microcontroller, which includes the modules of the capacitive-driving signal generation based on FPGA, the controlling module of demodulator ADA2200, A/D conversion module of analog signal, data transmission module via Ethernet based on MCU W7100A. The actual debugging shows that these modules achieved the expected function and lay a good foundation for the operation of the micro displacement sensor system.
In the Active Optical System, the precise measurement of the micro-displacement is the important evidence for the adjustment of the segmented mirrors and has great influence upon the full playing of the system’s optical performance. In this paper, both the median and adaptive filters are designed and simulated based on MatLab platform to remove the noises in the received signal of the micro-displacement sensor which has the features of low frequency, small amplitude and being susceptible to interference. The algorithms are also verified in the real micro-displacement measuring system. The results show that both of these two algorithms are effective and contribute to improve the system’s performance.
KEYWORDS: Wavelets, Filtering (signal processing), Electronic filtering, Digital filtering, Linear filtering, Interference (communication), Signal processing, Sensors, Digital signal processing, Wavelet transforms
Active optical technology used in large-caliber astronomical telescope depends on micro displacement sensors capable of real-time data processing. Proposed for a kind of differential capacitance micro-displacement sensor, a multi-channel digital filter based on a wavelet transform is designed in this paper to remove noise and gain a clean output signal. This algorithm includes: 1. From the multi-channel wavelets and refinement equation, a multi-channel filter bank is established and thus a down-sampling of M can be made to improve the real-time performance of the filter. 2. Based on the above, filter coefficients are truncated to integers by the way of wavelet lifting scheme. 3. An efficient iterative method is adopted to improve the wavelet decomposition process and simplify the algorithm itself. Through combining the above three methods, the computation amount of the multiplication and rms in the entire filtering process is reduced greatly, which leads to saving of the hardware resource and reducing of the computation time and benefits the designing of the real-time filter on FPGA platform in future. Verified by Matlab, the algorithm described in this paper achieves good noise processing capability.
KEYWORDS: Signal processing, Signal detection, Field programmable gate arrays, Laser systems engineering, Data processing, Photodiodes, Laser scanners, Laser processing, Digital signal processing, Digital filtering
Microfabrication technology places very high demands on the accurate measurement of filament diameters. The application of non-contact photoelectric measurement methods based on FPGA to the measurement of filament diameter is very significant for obtaining the diameter of the filament to be measured quickly and accurately to improve the quality and production efficiency of the filament. In this paper, the advantages and disadvantages of the laser scanning method and the diffraction method are firstly compared and analyzed. Based on this, a high-precision measurement method of filament diameter based on laser scanning and FPGA signal processing technology is proposed. Then, the system’s working principle, configuration of the hardware, and the algorithm of the signal processing based on FPGA were discussed. The factors affecting the accuracy of the measuring system are also analyzed and the corresponding solutions are given. At the same time, a program based on MATLAB GUI was also designed for the measurement results can be further processed and displayed in the host computer.
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