Extending the depth of field of incoherent imaging system through wave-front coding by using composite phase masks

摘要

Since 1995 when wave-front coding was first proposed by Dowski and Cathey, this technique has become a powerful tool to extend the DOF (depth of field) of incoherent imaging systems. By introducing a phase mask to the aperture plane, the optical transfer function (OTF) can be made insensitive to defocus and thus the key to this technique lies in the design of suitable phase masks. So far, many phase masks have been proposed to achieve the goal of DOF extension. In this paper, a new kind of phase mask, called composite phase mask, is designed by combining existing phase masks. With the optimized parameters, the composite phase mask can be made even less sensitive to defocus than any single mask. At the same time, as the number of phase masks used to generate one composite phase mask increases, the DOF extension effect can also be changed. Both the simulations and experiments demonstrate the effectiveness of the composite phase masks and the work reported also enriches the phase mask family used to realize the large DOF effect.