Bobier W R, Campbell M C, McCreary C R, Power A M, Yang K C
Appl Opt. 1992 Jul 1;31(19):3601-15. doi: 10.1364/AO.31.003601.
We provide a novel geometrical optical analysis of two coaxial photorefractive methods (isotropic and orthogonal). The size of the photorefractive pattern is defined in terms of the critical optical parameters without reference to specific camera parameters. A set of equations is derived that defines the following: a working range where the photorefractive pattern increases linearly with refractive error and pupil size, a dead zone where changes in refractive error do not influence pattern size, and critical values where vignetting by the camera lens becomes important. From this analysis optical parameters can be systematically adjusted to vary a photorefractor's working range. Small discrepancies found between measurements taken with model eyes indicated threshold and blooming effects that require calibration.
我们对两种同轴光折变方法（各向同性和正交）进行了新颖的几何光学分析。光折变图案的大小是根据关键光学参数定义的，而无需参考特定的相机参数。推导了一组方程，这些方程定义了以下内容：一个工作范围，其中光折变图案随屈光不正和瞳孔大小线性增加；一个死区，其中屈光不正的变化不影响图案大小；以及临界值，此时相机镜头的渐晕变得很重要。通过这种分析，可以系统地调整光学参数以改变验光仪的工作范围。在使用模型眼进行测量时发现的小差异表明存在需要校准的阈值和光晕效应。
