Research On Image Mosaic Technology Based On Curved Optical System With Large Field Of View

The eyes of creatures in nature can be roughly divided into two categories:human monocular and insect compound eye.As a main visual optical system,the eye selects an optical system with a larger field angle as much as possible when observing the target,so that more image information can be obtained at the same time.Large-field imaging optical system can adopt single-aperture structure and compound-eye optical system structure in structural design.The single eye of humans can correspond to a single aperture optical system in geometric optics.According to the basic laws of geometric optics,the larger the field angle of the single aperture optical system,the smaller the focal length of the corresponding system,and the greater the distortion of the edge optical system,the worse the image quality.Therefore,when designing an optical system with a large field of view,if an optical engineer uses a single-aperture optical system,it usually needs to perform distortion correction processing on the image.The single-aperture optical system is usually limited by the volume and diffraction limit of the system,it is difficult to put it into normal use in some places that require large field of view imaging.Later,biologists found that insect compound eyes have the characteristics of small size,large field of view,and high sensitivity,so he started to study compound eyes.At present,domestic and foreign researchers mainly focus on the process and structure of compound eyes.Although some research results have been put into practical use,the bionic compound eye theory and optical processing still have major problems.In this paper,the structural design of the compound eye optical system and the image stitching technology are researched accordingly.Compared with the single-aperture large-field optical system,the curved compound-eye structure not only improves the resolution of the system,but also makes it easier to obtain the spatial information of the image.In this paper,a single-aperture optical system and a curved compound-eye structure are used to design a set of optical systems.When designing a single-aperture optical system,the structure in the known patent is used to zoom the focal length,a single-aperture optical system with an 80-degree field of view is obtained.In the design of the curved compound eye optical system,the structural model of the bionic compound eye system was obtained by studying the biological and optical characteristics of the insect compound eye.And through the bionic compound eye theory formulacombined with the critical conditions of the field of view stitching,under the condition of satisfying the 80 degree field of view angle,a set of compound eye optical system including a three-ring lens group was designed.After the theoretical analysis is completed,the optical design software ZEMAX is used to perform ray tracing on the above two optical systems,the design system is optimized using the software's own evaluation function,the image quality is evaluated by the spot diagram and the modulation transfer function(MTF).The evaluation results show that the optical system designed in this paper meets the needs of visual imaging optical system.After the design is completed,the planar compound eye optical system and the curved compound eye optical system are simulated by the corresponding structure and industrial camera.Respectively,the planar compound eye image and the curved compound eye image are obtained,which lays the foundation for the next image stitching.After the simulation experiment is completed,the feature points of the image are extracted by the Scale-invariant feature transform(SIFT)algorithm,and the range of the overlapping area of the field of view is obtained according to the feature area determined by the feature points.Finally the overlapped area is fused,with one image as a template,and the other image taken corresponding.After the transformation and the spatial overlap fusion,the two images have completed the image stitching.Then we repeat the above steps to complete the stitching of multiple images.The results show that the bionic compound eye theory is feasible,and the stitched field of view has no blind spots.