Extended depth of field through wave-front coding

TLDR

The system builds on standard incoherent optics by adding a phase mask and digital processing. The study designs an optical‑digital system to achieve near‑diffraction‑limited imaging with an extended depth of field. The system uses a phase mask that codes the incoherent wavefront to keep the PSF and OTF stable with defocus, combined with focus‑independent digital filtering of the intermediate image, and the masks are designed via the ambiguity function and stationary‑phase method. High‑resolution extended depth of field is achieved, but it requires an increased dynamic range.

Abstract

We designed an optical-digital system that delivers near-diffraction-limited imaging performance with a large depth of field. This system is the standard incoherent optical system modified by a phase mask with digital processing of the resulting intermediate image. The phase mask alters or codes the received incoherent wave front in such a way that the point-spread function and the optical transfer function do not change appreciably as a function of misfocus. Focus-independent digital filtering of the intermediate image is used to produce a combined optical-digital system that has a nearly diffraction limited point-spread function. This high-resolution extended depth of field is obtained through the expense of an increased dynamic range of the incoherent system. We use both the ambiguity function and the stationary-phase method to design these phase masks.