Search

What we believe to be a method for recording speckle interference fringe with electrically addressed liquid crystal display (EALCD) and CCD is presented. The speckle patterns are obtained by image plane speckle method. Two patterns of speckle interference field before and after displacement are recorded by CCD camera and stored in computer. After subtracting and taking the absolute value, the correlative fringe pattern including object's displacement information is acquired. In this paper, methods that subtract optical noise are analyzed to enhance the signal-to-noise ratio of secondary speckle fringes using double-exposure measurements on rough surfaces. The speckle pattern is processed in spatial domain and frequency domain and the obvious results are given. Compared with the results, synthesized filter is proposed in the paper. The contrast of interference pattern is increased and high SNR of the speckle fringe pattern is realized. Experimental pictures are provided in the article. The experimental result shows that the application of the method, synthesized filtering of spatial domain with frequency domain, can be used to improve the fringe contrast. The results of the experimental studies proved that the synthesized filtering is the most effective way.

Real-time test is one of the important parts in digital holographic interferometry researches. In this paper, taking advantage of electrically addressed liquid crystal display(EALCD) features of real-timely writing in and reading out images, the digital holographic interferometry system for real-time measurement of displacement is designed. In order to raise the contrast of the holographic hologram, the image enhancement based on the Laplacian operator has been used to process holograms. Based many advantages of CCD and EALCD, the holographic interferogram with high contrast can be obtained quickly, which can realize the precise measurement of small deformation and displacement of objects. Moreover, the measurement efficiency and precision is raised greatly.

Based on the appearance of infrared dual-band device and the technical parameters of infrared seeker, a new-type Cassegrain optical system is designed. The main advantages of the system are large field-of-view, infrared dual-band common path and compact structure. In the Cassegrain optical system, the working wavelengths are 3.7m~4.8m and 8m~12m, the field-of-view 4° and the aperture 240mm. The paraboloidal primary mirror and hyperboloidal secondary mirror are all replaced by spherical surfaces. So the problems of high machining accuracy and alignment become much easier. In order to balance the aberrations, two compensating lenses are used in the system. The amounts of compensating lenses are much less than other optical systems. So the new optical system becomes much more economy, light and compact. The total length of system is 170mm. The ratio of total length to focal length is 0.62. So it can meet the operating requirement of seeker in limited space. Moreover, the system has a good performance of athermalization between negative 40°c and positive 50°c. The design results of the system show that the MTF value of each field is greater than 0.7 when the cut-off frequency is 11 lp / mm. Wavefront aberration is less than 0.038.

Low light level target detection has received more attentions in varieties of domains in recent years. In this paper we use hybrid optoelectronic joint transform correlator(HOJTC) for detecting and recognizing low light level target. It is thought to be one of the most effective methods in target detection. But because of the cluttered backgrounds and strong noises of the low light level target, it always can not be detected successfully. In order to solve this problem efficiently, firstly we choose sym4 wavelet function to achieve the purpose of wavelet de-noising. After that edge extraction processing is used to distinguish the useful target from the cluttered backgrounds with Sobel operator. At last processed targets can be put into HOJTC to obtain a pair of correlation peaks clearly. To prove this method, many experiments of low light level targets have been implemented with computer simulation method and optical experiment method. As an example a low light level image "deer" is presented. The results show that the low light level target can be detected from the cluttered backgrounds and strong noises with wavelet de-noising and Sobel operator successfully.