大景深成像系统中目标离焦量的测定

Measurement of the Object Defocus with Extended Depth-of-field Imaging System

以三次相位板为例,基于菲涅尔积分法建立了相位板横向偏移量与成像系统离焦量之间的函数关系.由于解码图像中伪影现象的产生是由编码点扩散函数和解码点扩散函数的不一致引起的,可将伪影现象作为成像系统离焦量的评判标准.结合相位板横向偏移量与离焦量的关系和产生伪影现象的物理内涵,提出了大景深成像系统中物体离焦量的测定方法.该方法可同时获取目标的离焦像差图和大景深、无伪影的解码图像,并对所提出的方法进行了实验验证.此外,本文所提出的方法同样适用于其他奇对称型相位板,这进一步拓展了奇对称型相位板景深延拓成像系统在实际应用中的范围.

The relationship between defocus and the lateral shifts of cubic phase mask has been built based on the Fresnel integral.Based on the fact that the artifacts appeared in the decoded images are resulted from the differences between the coding and decoding point spread function,the artifacts can be treated as indicators of defocus.Finally,we combined the built relationship previously and the reason producing artifacts in the decoded images to propose an imaging way to obtain defocus map and artifacts-free images with laterally shifted cubic phase mask,which subsequently verified by experiments with our designed imaging system.The proposed method avoids errors introduced by shifting the ideal imaging plane deliberately.Moreover,although the idea we developed only was analyzed and illustrated with cubic phase mask,it also can be generalized to other types of odd-symmetric phase masks,which further widen the application range of odd-symmetric phase mask imaging system.