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 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.
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.
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