Comparison between a new holographically generated complex filter and the binary phase filter for depth-of-field extension

Abstract

To improve the depth of field in imaging systems, we propose a new method for designing pupil filters with the classical approach used for computer-generated holograms. This method allows us to calculate a complex amplitude/phase filter in order to obtain a desired distribution of intensity along the optical axis, and thus the desired depth of field.We will compare our complex filter with binary-phase filters, which are one of the different methods already investigated to improve the depth of field in imaging applications. This study will reveal that the complex filter is an interesting alternative for applications where very low fluctuations of the amplitude distribution along the optical axis are required. It is indeed as energy-efficient as a pure phase filter even with a non negligible absorption. It also ensures to precisely tailor the shape of the focal line of an imaging lens, as the decrease of intensity is sharper outside the regions of interest than with the binary-phase filter. Moreover, it also benefits from lower sidelobes. With these characteristics, this new complex filter will be suitable particularly for 3D imaging applications.