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为获得高分辨率视网膜血管图像,在自适应成像系统中,采用双光源照明模式。由于人眼存在色差,采用双光源照明模式会导致探测到的波前与实际需校正波前不一致。采用36项Zernike多项式拟合人眼波前,利用Liou&Brenann、Navarro模型眼和真实人眼分析了人眼色差对夏克-哈特曼波前探测器的影响:对于Liou&Brenann和Navarro模型眼,561 nm和785 nm光的波前色差均方根值(RMS)分别为0.09λ和1.44λ,去除离焦项后的波前色差RMS值分别为0.0025λ和0.01λ;对于真实人眼,两光源的波前色差RMS值为1.92λ,去除离焦项后的波前色差RMS值为0.04λ。根据Maréchal判据,除离焦项外,色差对其他波前像差的影响均方根值小于衍射极限(1/14λ),故波前像差的影响可忽略。由色差造成的离焦量可通过移动成像相机进行补偿。从结果可以看出采用双光源照明的视网膜血管自适应光学成像方案是可行的。
In order to obtain high-resolution retinal blood vessel images, a dual light source illumination mode is employed in the adaptive imaging system. Due to the existence of human eye color, the use of dual-light illumination mode will lead to the detection of the wavefront and the actual need to be corrected wavefront inconsistencies. Using 36 Zernike polynomials to fit the human wavefront, the effect of human eye color on the Shack-Hartmann wavefront detector was analyzed using the Liou & Brenann, Navarro model and real human eyes. For the Liou & Brenann and Navarro model eyes, the 561 nm and The root mean square error (RMS) of wavefront aberrations of 785 nm light is 0.09λ and 1.44λ respectively, and the RMS values of wavefront aberrations after defocusing are 0.0025λ and 0.01λ, respectively. For real human eyes, the wave of two light sources The RMS value of the front color difference is 1.92λ, and the RMS value of the wavefront color difference after the defocus item is removed is 0.04λ. According to the Maréchal criterion, the effect of color aberration on the other wavefront aberrations is less than the diffraction limit (1 / 14λ) except for the defocused term, so the effect of wavefront aberration is negligible. The amount of defocus caused by chromatic aberration can be compensated by moving the imaging camera. It can be seen from the results that a dual-light source retinal vascular adaptive optical imaging solution is feasible.