In this paper, a micro-projection display with telecentric beam path in image space is designed. The device consists of a 0.26-inch liquid crystal on silicon (LCOS), a polarizing beam splitting cube and a hybrid refractive-diffractive eyepiece. The refractive-diffractive eyepiece has a focal length of 9.16 mm, a full field of view of 40° and a spectral bandwidth of 422~632 nm. The eyepiece is optimized by the wide-angle eyepiece, which consists of four optical lenses. The designed hybrid refractive-diffractive micro-projection display system has good projection effect while using a small number of lenses in a simple structure. This provides a reference for the future development of lightweight micro-projection systems.
The parallel wire fine line control system is mainly used for the adjustment of the distance between the two electrode wires and the parallel control during the fabrication of the miniature thermocouple. It mainly adopts precision electronic control and computer vision precision micro-measurement technology to ensure the adjustment and stability of the two-electrode wire spacing parameters during thermoforming. Hanging 17μm-60μm wire on the device, tightening the suspension wire by controlling the two-phase stepping motor, adjusting the five-phase stepping motor to adjust the parallel wire spacing, collecting the wire image in real time, automatically interpreting the wire spacing parameter by using a fast algorithm, and interpreting the wire The result output is displayed.
At present, micro lens arrays have been widely used in the fields of infrared detection, light gathering, portable solar battery and so on. The focusing and imaging properties of micro lens arrays are closely related to the performance parameters such as point diffusion function, diffraction efficiency and optical intercept. In order to better evaluate the quality of micro lens, this paper introduces a method for accurately measuring the optical intercept of micro lens arrays, which is more precise and has less deviation than interferometry, CCD direct imaging and so on. This experiment is based on the principle of CCD imaging and image processing, and a set of testing system is established. The system is mainly composed of a laser light source, a collimation system, samples and a camera. After many experiments, The optical post intercept detection device can obtain test accuracy below 5μm
In order to study the spatial wavelength division diffraction effect, the Chirped Volume Bragg Gratings (CVBG) based on the Photo-thermo-refractive glass on the oblique incident light was analyzed by the fundamental matrix method. When diffracted by grating, the complex beam would be separated into multiple beams in space by wavelength. The diffraction efficiency of the separated optical wave can reach up to 90%. Furthermore, the diffraction efficiency, increases as the refractive index modulation depth increases and decreases as the chirp rate increases. The diffraction spectrum has the characteristics of flat-top band pass. To increase the spatial separation distance, multiple schemes of CVBGs in parallel combination are designed. By combining a self-focusing lens array, the proposed system can realize wavelength division multiplexing with bandwidth less than 0.4nm.
In order to meet the increasing demand for the diagnosis of household medical eye fundus, the design of a new fundus camera is proposed. The entire structure includes the imaging system and the lighting system. The optical imaging system, modeled on the Kepler telescope, matches the exit pupil of the human eye and the entrance pupil of the mobile phone camera. Thus, this system uses a mobile camera lens that owns more than 5 million pixels to take a picture of a clear fundus. A new type of fundus camera is designed with the field of 40°, the working distance of 30mm and the full length of 138 mm. The value of MTF outweighs 0.5 at the central field of view. The lighting system takes advantage of the Kohler illumination. The stray light of the reflection of corneal is effectively suppressed by adding an annular aperture on the optical path. The inner diameter of the annular light spot formed at the cornea was larger than 4mm, the outer diameter was less than 6mm, and the diameter of the evenly illuminated fundus area was 12mm.
In this paper, the radial refractive index change of the grin lens is measured based on the principle of Mach-Zehnder interference. Using an image sensor to obtain experimentally detected images, the computer-derived interference pattern is subjected to grayscale stretching and filtering, and then the center position of the interference ring and the distance between the interference rings are determined to obtain the refraction of the grin lens. The rate changes. Through experiments, the actual samples of different thicknesses were tested, and the measurement accuracy can reach 10-4.
An experimental method is used to measure the optical parameters of a GRIN lens. The intrinsic properties of the lens are well characterized by measuring the intercept values of the different GRIN lenses. Firstly, the intercept equation is derived from the transmission matrix of the GRIN lens, and the measurement method is described in detail. Secondly, we design and make the optical path measuring system. Finally, the error analysis of the experimental results is presented, which shows the feasibility of the working principle and the experiment operation. The principle and equipment of this measuring method are relatively effective, which affords great practical significance for the measurement of the GRIN lens.
A new light field spectrometry microscope imaging system, which was composed by microscope objective, microlens array and spectrometry system was designed in this paper. 5-D information (4-D light field and 1-D spectrometer) of the sample could be captured by the snapshot system in only one exposure, avoiding the motion blur and aberration caused by the scanning imaging process of the traditional imaging spectrometry. Microscope objective had been used as the former group while microlens array used as the posterior group. The optical design of the system was simulated by Zemax, the parameter matching condition between microscope objective and microlens array was discussed significantly during the simulation process. The result simulated in the image plane was analyzed and discussed.
As the light travels through the wavefront coding (WFC) system, the modulation transfer function(MTF) of the WFC system was very low, consequently the intermediate blurred image has been received by the detector. However, there is no zero point in the passband of the MTF of the WFC imaging system, and the target information cannot be saved very well. An appropriate filter can be used to restore the sampled intermediate image. The noise of the system is enlarged in the restoration process where the signal be amplified by the filter, and the signal to noise ratio(SNR) of the image is reduced. In order to solve the above issues, an improved algorithm has been proposed in this paper. The noise is controlled by the wavelet in the reconstruction process, and the intermediate blurred image is restored by the wiener filter algorithm with a prior knowledge of the degradation function. Thus, the wavelet de-noising and wiener filter algorithm are combined to restore the middle blurred image of the WFC system. Finally, the restoration image with the diffraction limit level is acquired in image detail restoration and noise control.
Light field microscope (LFM) can be built by inserting microlens array into a traditional microscope. Different perspective image of the sample could be obtained by reconstruction algorithm dealing with the four dimensional light field information captured by the detector. Since light field microscope has been always studied in laboratory, the reconstructed image quality which depends on the microlens array is still not too high. The pixels between every two sub image of microlens array is waste when circle aperture of objective is used. In this article, rectangular aperture has been used in this paper to improve the utilization of the CCD, which is favorable to reconstruction algorithm. Progress has been made in reconstruction algorithm which can improve the reconstruction image quality, wave optic theory has been used to calculate the PSF of the whole imaging system due to the short object distance, subpixel interpolation algorithm has been combined with the reconstruction algorithm of LFM to improve the image quality, good imaging quality has been obtained through the improved algorithm.
Non-rotational symmetric aspheric surface has many significant advantages, but it still can not be widely used because the limiting that there is no method can tests it precisely. At present, the coordinate contour measuring machine is the main testing method for the aspheric surface with non-rotational symmetric, but the measurement accuracy of this method is not high. In this paper, the method of diffraction compensator (computed graphic holograph) has been adopted to test the combined aspheric surface, which can compensate the phase caused by tested lens. The sample surface is the combined aspheric surface with diameter of 33.84mm, and the process from optical software simulation design, the fabrication of the computed graphic holograph (CGH) to experimental platform built is given in detail after testing via the CGH technology. The simulation results show that the root mean square (RMS) of remnant wave-front error is 0.004 λ, and the peak to valley (PV) is 0.0245 λ. The free-from surface has been tested by Zygo interferometer, and the experimental results show that the RMS is 0.49 λ, the PV is 4.69 λ. The accuracy of the result is higher than that of coordinate contour measuring machine. The system error caused by optical elements analysed is 0.1149λ. The accurate result means that the CGH technology for testing the combined aspheric surface is realized.
Benefit from the attractive features such as compact volume, thin and lightweight, the imaging systems based on
microlens array have become an active area of research. However, current imaging systems based on microlens array have
insufficient imaging quality so that it cannot meet the practical requirements in most applications. As a result, the
post-digital image processing for image reconstruction from the low-resolution sub-image sequence becomes particularly
important. In general, the post-digital image processing mainly includes two parts: the accurate estimation of the motion
parameters between the sub-image sequence and the reconstruction of high resolution image. In this paper, given the fact
that the preprocessing of the unit image can make the edge of the reconstructed high-resolution image clearer, the
low-resolution images are preprocessed before the post-digital image processing. Then, after the processing of the pixel
rearrange method, a high-resolution image is obtained. From the result, we find that the edge of the reconstructed
high-resolution image is clearer than that without preprocessing.
Compressive Sensing (CS) indicates that when the signal of interest is sparse or compressible (i.e., sparse after mathematical transformation), one can take a small number of linear projection measurements from the signal, and reconstruct the signal almost perfectly through proper algorithm. The feature of the CS has great potential applications in that high-resolution imaging is highly desirable while large size detector array is unavailable, such as those in ultraviolet or infrared wavelength region or that in aircrafts and satellites working condition when the data transmission is a key issue.
However, CS technique still faces challenges in the signal sampling and reconstruction. Firstly, detector measurements must be nonnegative in linear optical system which is different from digital image processing. Secondly, blurring caused by practical optical system should be considered, which will destroy the effect of reconstruction.
In this paper, we discuss some kinds of phase encoding which could be used in practice imaging system. We make a compensation to solve the non-negative problem when CS applied in the practical optical system, use a small size detector to receive a general image degrading model, and reconstructed image from the single, low-solution and noisy observation through a fast and feasible non-linear algorithm, the result proves our system is robust and feasible.
Wavefront coding enables conventional optical imaging systems to operate over an extended depth of field/focus by modifying the light field using a specially designed phase mask. Different phase masks can be used to alter the transmitted wavefront of the optical system which may result in different performances in terms of the capability of the depth-of-focus extension, aberration suppression and the process of imaging acquirement. In this paper, we present a comparative study on the performances of two major different categories of the phase mask, i.e., rotational symmetric and asymmetric type phase masks. Three different types of phase masks that are of cubic, quartic, and logarithmic phase profile are investigated. Fabrication and metrology of a cubic mask is conducted and a full cycle of imaging process including the image coding and decoding is performed.