Non-uniformity Correction And Image Masaic Of Bionic Compound Eye System Based On Micro-surface Fiber Faceplate

With the development of society,people’s demand for miniaturized large-field-of-view optical systems is increasing day by day.Due to the limitation of diffraction effects,it is difficult to balance the resolution and the angle of view while reducing the volume for traditional optical systems.Therefore,new optical systems need to be studied.With advantages of small size,compact structure,large field of vision,etc.,the bionic compound eye imaging system has great potential for applications in both military fields and civilian fields.This study was conducted on the basis of a nine-eye bionic compound eye experimental system in our laboratory.The system is a multi-aperture overlapping compound eye system based on a multi-face fiber panel,its large-field-of view imaging needs not only an effective field-of-view splicing algorithm to synthesize a panoramic image,but also require uniform system response.So,this paper focuses on the non-uniformity correction method and image splicing algorithm.Because the overall field of view of the system is too large(about 74.3?),the existing integrating sphere can not provide uniform input of illumination for all the sub eyes at the same time.Therefore,a three-dimensional electric displacement table is used to build a nonuniformity detection system,which each time provides uniform lighting for a single sub eye.The response output image under uniform light input is synthesized through image cropping and splicing method.The effective pixels are determined by the threshold segmentation method to calculate the non-uniformity.On the basis of confirming the linear relationship between system output and input,a non-uniformity correction method based on least squares and color channels processing separately is proposed.The experimental results show that the method can effectively improve the system non-uniformity and reduce the color cast,the nonuniformity of each color channel before calibration was more than 50%,and the nonuniformity of R,G,and B channels after calibration was reduced to 9%,5.5%,and 3%,respectively.The traditional SIFT/SURF algorithm has a wide range of applications,but its efficiency is low.In the paper,an image stitching algorithm based on the image overlap degree prior is proposed for the bionic compound eye imaging system after analyzing system requirements and its imaging characteristics.Firstly,the two images to be spliced together are both divided into overlapping regions and non-overlapping regions.Then,Feature points in overlapping regions are extracted using SURF detector and described by BRIEF descriptor.The initial matching of the feature points is made with the hamming distance matching.RANSAC and angular consistency of the pairing feature points are used to further purify the feature point pairs.Finally,the weighted mean method is used on the images after registration to get the blended image.The sub-eye images are spliced in each layer and then the spliced images of each layer are stitched together successively to get the final panoramic image.Experimental results showed that the splicing speed of the proposed algorithm is 2 to 3 times higher than that of SIFT algorithm.Compared with SURF algorithm,the splicing speed also increased by about 50%.In addition,more correct matching can be remained,so that the results of image registration and splicing can be more reliable.The research results of this paper can provide technical support for further developments of relevant work,and have substantial help in promoting the practical application of bionic compound eye imaging system.