Variation around a Pyramid theme: optical recombination and optimal use of photons

TL;DR

This paper introduces the Flattened Pyramid-WFS, a new wave front sensor that improves sensitivity and linearity over existing sensors, especially for high-contrast applications, by overlapping pupil images into a single intensity map.

Contribution

The paper presents the FPWFS, a novel wave front sensor with a reduced pyramid angle that enhances sensitivity and linearity compared to traditional WFSs.

Findings

FPWFS is more linear than modulated pyramid for high-spatial order aberrations.

FPWFS offers improved sensitivity over non-modulated pyramid.

Pixel arrangement in FPWFS is more efficient, suitable for high-contrast applications.

Abstract

We propose a new type of Wave Front Sensor (WFS) derived from the Pyramid WFS (PWFS). This new WFS, called the Flattened Pyramid-WFS (FPWFS), has a reduced Pyramid angle in order to optically overlap the four pupil images into an unique intensity. This map is then used to derive the phase information. In this letter this new WFS is compared to three existing WFSs, namely the PWFS, the Modulated PWFS (MPWFS) and the Zernike WFS (ZWFS) following tests about sensitivity, linearity range and low photon flux behavior. The FPWFS turns out to be more linear than a modulated pyramid for the high-spatial order aberrations but it provides an improved sensitivity compared to the non-modulated pyramid. The noise propagation may even be as low as the ZWFS for some given radial orders. Furthermore, the pixel arrangement being more efficient than for the PWFS, the FPWFS seems particularly well suited for high-contrast applications.