Research On Wavefront Reconstruction Technology Of Retinal Cells Microscope System

High resolution retinal imaging potentially offers a powerful adjunct for early diagnosis of various retina related diseases, better treatment of diseases, and for scientific research on human vision. However, as an optical system, human eye has high and low level aberrations inside, which makes it the imaging of the retina not reach the diffracting limitation level. So the retina images with high DPI are not available by the common technology. But the adaptive optical technology, which have had been significantly developed in recent years, makes it possible to get the retina images in the cell level. In this paper, aberration reconstruction, one of the most important technologies in the imaging of retina cells, is studied in the background of the development of retina cell microscope. The main contributions of the study work are:1) The basic structure of the human eye, retinal imaging features together with the definition and causes of wavefront aberration are discussed, meanwhile theoretical model of wavefront aberrations based on orthogonal normalized Zernike polynomials is established.2) The principle of measuring aberration making use of Hartmann-Shack wavefront sensor has been studied. A method based on Hex-point theorem to determine Sub-spot is proposed on the basis of spot image preprocessing, thereby, the accurate positioning of the sub-spots and the centroids is achieved.3) Reconstruction algorithm based on Zernike mode of wavefront is mainly studied which include arithmetic based on normal equation method based on Least Squares, Gram-Schmidt orthogonal transformation, Householder transformation, singular value decomposition. Theoretical analysis and reconstruction experiments show that four kinds of algorithm are all quite accurate, and be able to meet the accuracy requirements of wavefront reconstruction but the algorithm of singular value decomposition performances better because of simple theory, less calculation steps and easy programming and so on.4) Error of wavefront reconstruction based on Zernike polynomial model is analyzed. The optimal number of Zernike polynomials is chosen by discussing the relationship between truncation error, confusion error together with coupling coefficient and the item number of reconstruction. The module of wavefront aberration measurement and reconstruction is developed based on the study mentioned above, and it achieves accurate measurement and reconstruction of human eye aberrations that provide aberration data for the follow-up cycle of correcting the aberration. The practical application shows that this module is able to meet the imaging requirement of retinal cells on microscope imaging.