Studies On The Characteristics And Applications Of The Annular Imaging System With High Resolving Power

The annular lens imaging system, which is one kind of panoramic imaging systems, has broad application future in the areas of inspection, security, robot's vision, and et al. The panoramic imaging system are generally understood as a system, which can project the 360°surrounding objects into a two dimensional image plane. The annular lens imaging system has unique characteristics as it is using the Flat Cylinder Perspective (FCP) instead of traditional Central Point Perspective (CPP).The critical element of an annular lens imaging system is the annular lens. This thesis has detailed the characteristics of the annular lens and the object-image relation; proposed the pupil abberation theory and the dual-lens stereoscopic vision theory of the annular lens. According to that theories, we have designed manufactured, fabricated and tested an annular lens with high resolving power and large field of view, which is exceeding the horizontal line, based on the liquid crystal shutter (LCS) technique. This thesis has discussed the LCS both qualitatively and quantitatively; proposed the dual-layer structure LCS, and fixed the LCS inside the annular lens. We have built two types of annular lenses, one of which is equipped with a LCS and the other is not, and the results of resolving power and MTF tests shows the image degradation effect of the adding LCS is neglectable in our system.This thesis detailed the smears problems in the image plane caused by that the LCS cannot block the incident light to 100%, and also proposed the shading mechanical method to solve the direct sun shine problem and the image processing method to compensate the smears. For the annular image exceeding the horizontal line, we proposed the base line for the image transformation to keep the magnification ratio of tangential and sagittal directions. The detailed research contents are listed as follow.ChapterⅠintroduced the research background, pointed out that the annular lens technique can fulfil the requirement of realtime omnidirectional inspection. We compared the existing un-staring and staring panoramic imaging techniques, and determined the research aims.ChapterⅡanalyzed the optical characteristics of the PAL lens in detail, pointed out that the illumination on the image plane is more uniform than the other panoramic lenses. The sphere abberation of the entrance pupil of the annular lens was studied thoroughly, and the mathematic model of the PAL lens was made. A fast ray tracing method using polynomial abberation prediction was proposed.ChapterⅢanalyzed four image height expressions with not-resemble imaging characteristics, discussed their magnifying ratios and distortions. We proposed the dual-lens stereoscopic vision method using the annular lens using the f-θrelationship. When applied that method to the endoscopy of the pipes and bores, we proposed the method to measure the distance of the objects, i.e. the radius of the pipes, using the frames taken by a single annular lens. An bore endoscopy experiment system using the annular lens was made and the caused error was discussed.ChapterⅣproposed a design of an annular lens with high resolving power based on the LCS as the optical shutter. In order to find the image degradation caused by the LCS, we designed and fabricated two super hemisphere annular lens with high resolving power, one of which is equipped with a LCS and the other is not. We pretreated the readout images, and the methods to compensate the smears on the image plane caused by the LCS was discussed emphatically. Combining the object-image relation discussed in ChapterⅢ, we discussed the characteristics of annular image transformation, pointed out that in order to keep the tangential and sagittal magnifying ratios same, one should use the circle image corresponding to the field of angle of 90°as the base line. A corresponding experiment was given.ChapterⅤdiscussed the twisted nematic LCS both qualitatively and quantitatively. The results should guide the design of LCS. We designed a double-layer LCS, and tested the transmission of the LCS.ChapterⅥdiscussed the annular lens testing methods, including the resolving power and MTF tests. We tested the two types of lenses and compared the results, analyzed the effects of the auxiliary equipment, especially the CCD discrete sampling period. It shows that the built in LCS has no evident image quality degradation. Both testing results were fulfill our design aims.The last chapter summarized the full thesis and proposed the future plan.