为了解决采用细平行光照明测量大像差人眼时测量精度下降的问题,设计了一种自动可调照明系统。照明光路中加入了一个位置可以自动调整的准直透镜,调整这个透镜的位置可以准确地改变照明光的光屈度,精密电控平移台可以对准直透镜的位置进行快速准确扫描定位。实验测量了模拟眼的像差,对细平行光照明系统和自动可调照明系统的实验结果进行了对比。结果显示,使用自动可调照明使传感器获得图像的峰值信噪比(PSNR)由5.72 dB提高到19.89 dB,对-5 m-1模拟眼测量的平均离焦也由-(4.285±0.208) m-1提高到-(5.041±0.157) m-1,表明使用自动可调照明系统提高了Hartmann-Shack传感器图像的信噪比,使测量结果更加准确。

A kind of automatic and adjustable illumination system was designed to improve the poor precision in the measurement of strong ocular aberration of human by a narrow parallel beam illumination.By adding a position adjustable collimation lens in the light path,the diopter of illumination light source could be precisely controlled by adjusting the lens,and the position of collimation lens could be exactly and rapidly scanned and located by a motorized stage. Moreover,the aberrations of a model eye are measured by the narrow parallel beam illumination system and by the adjustable illumination system in this experiment respectively. The obtained results show that the Peak Signals to Noise Ratio(PSNR) of the image got by the sensor in the automatic and adjustable illumination system are improved from 5.72 dB to 19.89 dB,and the average defocuses of a -5 m-1 model eye is changed from -(4.285±0.208) m-1 to -(5.041±0.157) m-1 as compared with that of the narrow parallel beam illumination. These data show that the PSNR of the image for Hartmann-Shack sensor has been obviously improved by the automatic and adjustable illumination system,which makes the measurement result more accurate.