The influence of phase mask position upon wavefront coded system: doublet imaging system

Abstract

Cubic phase wavefront coding technique is applied to an imaging system with the aim of extending the depth of field (DOF). The design is based on the wavefront coding method proposed by Dowski and Cathey 1. The method employs a cubic phase mask (CPM) to modify the point spread function (PSF) of the imaging system under incoherent illumination such that the PSF of the system is formed as an isosceles right triangle, which makes the PSF insensitive to defocus. Researchers have found the optimized values of cubic phase coefficient and the exit pupil distance for the given specifications for solving wavefront coded task-based imaging problem 2. The extended DOF design is usually based on placing a phase mask exactly in the pupil plane of the imaging system. However, this is not always practical because the complex design of the imaging system leads to a limited practical advantage of this kind of arrangement. In this work, the influence of phase mask position upon wavefront coding technique in the doublet imaging system is studied. The main goal is to find the position where to place the CPM in the imaging system, which type of arrangement can effectively improve the modulation transfer function. Finally, we compare two system configurations, front aperture stop and rear aperture stop in designing the doublet wavefront coded system.