Wavefront coding (WFC) is used to extend the field depth of an incoherent optical system by employing a phase mask on the pupil. We uses a Fisher information (FI) metric based optimization method to design a phase mask by taking the modulation transfer function (MTF) of the practical optical system into consideration. This method can modulate the wavefront so that the point spread function and optical transfer function are insensitive to the object distance. The simulation results show that the optimized phase mask based on the proposed method can further improve the defocusing image quality while maintaining the focusing image quality.

采用三次相位板进行景深延拓的波前编码系统得到非对称的点扩展函数。为了获得最终清晰的彩色图像，研究了一种基于广义极小残差法(GMRES)的迭代算法，结合Tikhonov规整化方法，并利用多通道处理过程对中间图像进行去卷积恢复。为了消除恢复图像边界的振铃效应，推导了新的光学成像过程数学模型，该模型采用反镜像边界条件并利用直积近似对卷积核进行处理。模拟数据的分析表明，采用多通道处理过程对彩色图片进行恢复时，新的算法在给出精确的反卷积结果的同时能有效地抑制噪声的放大;实验结果显示，较之经典的维纳滤波恢复结果，新算法能够更好的消除边界的振铃和图像边缘的振动波纹。

Optical systems are analyzed with three kinds of rotational symmetric pupil masks: annular Gaussian ring mask, supergaussian ring mask, and quartic phase mask. In these masks, the quartic phase mask is found to be the best one to extend focal depth. Point spread function (PSF) and Strehl ratio (SR) are used to evaluate the imaging quality of the system with different defocus parameters. Without decoding needed, the focal depth of the system with quartic phase mask is four times as deep as aberration-free system. Different from the others, it suffers no obvious loss in the light throughput and lateral resolution. With twice focal depth extension, supergaussian ring mask suffers less loss in light throughput and lateral resolution than annular Gaussian ring mask.

By applying the wavefront coding technique to an optical system, the depth of focus can be greatly increased. Several complicated methods have already been taken to optimize for the best pupil phase mask in ideal condition. Here a simple Strehl ratio based method with only the standard deviation method used to evaluate the Strehl ratio stability over the depth of focus is applied to optimize for the best coefficients of pupil phase mask in practical optical systems. Results of imaging simulations for optical systems with and without pupil phase mask are presented, and the sharpness of image is calculated for comparison. The optimized pupil phase mask shows good results in extending the depth of focus.