倾斜入射的波前编码系统的点扩散函数扩大效应分析

通过对坐标系统进行旋转，计算得到了三次型波前编码系统的倾斜入射的光瞳函数，并给出了近似表达式. 分析表明倾斜入射会产生三次相位扩大效应和离焦扩大效应，它们和入射角的正负无关，且随着入射角绝对值的增大而增大. 这表现在点扩散函数(point spread function, PSF)上会扩展PSF包络的两条直角边，表现在调制传递函数(modulation transfer function, MTF)上会降低MTF值. 子午面倾斜入射时，子午方向的三次相位扩大效应和离焦放大效应大于弧矢方向，从而导致子午方向

The extension effect of point spread function in wavefront coding system due to off-axis illumination

The off-axis illumination pupil function of the wavefront coding system with cubic phase mask is analyzed by coordinate-rotation for the first time. The approximate expression of the pupil function shows that off-axis illumination brings about the extension effect of cubic phase and defocusing. The extension effect is independent of the sign of the incident angle; however, the extension effect will get larger as the absolute value of the angle increases. This causes a decrease in modulation transfer function (MTF) and the extension effects on both sides of the point spread function (PSF) envelope. When the off-axis illumination is in the tangential plane, the extension effects of cubic phase and defocusing in y direction is larger than that in x direction, which results in larger extension of PSF and lower MTF in the y direction. When off-axis illumination is in the sagittal plane, the extension effects of cubic phase and defocusing in x direction is larger than that in the y direction, which results in larger extension of PSF and lower MTF in x direction.