COACH-based Shack-Hartmann wavefront sensor with an array of phase coded masks.

Nitin Dubey,Ravi Kumar,Joseph Rosen

doi:10.1364/oe.438379

Abstract

Shack-Hartmann wavefront sensors (SHWS) are generally used to measure the wavefront shape of light beams. Measurement accuracy and the sensitivity of these sensors are important factors for better wavefront sensing. In this paper, we demonstrate a new type of SHWS with better measurement accuracy than the regular SHWS. The lenslet array in the regular SHWS is replaced with an array of coded phase masks, and the principle of coded aperture correlation holography (COACH) is used for wavefront reconstruction. Sharper correlation peaks achieved by COACH improve the accuracy of the estimated local slopes of the measured wavefront and consequently improve the reconstruction accuracy of the overall wavefront. Experimental results confirm that the proposed method provides a lower mean square wavefront error by one order of magnitude in comparison to the regular SHWS.

Highlights

Shack-Hartmann wavefront sensor (SHWS) was developed for optical metrology purposes [1] and later has been used in various other fields, such as adaptive optics [2], microscopy [3], retinal imaging [4], and high-power laser systems [5]
We present a new technique of COACHbased SHWS that increases the accuracy of wavefront sensing
Based on several recently published studies [9,10,11] about interferenceless coded aperture correlation holography (COACH), we conclude that using a certain coded phase mask (CPM) can yield at the end of the process a spot that is narrower than the focused spot of the regular SHWS

Summary

Introduction

Shack-Hartmann wavefront sensor (SHWS) was developed for optical metrology purposes [1] and later has been used in various other fields, such as adaptive optics [2], microscopy [3], retinal imaging [4], and high-power laser systems [5]. The ensemble of dots obtained from the measured wavefront are cross-correlated with a reference dot pattern created by illuminating a single CPM with a plane wave. As in conventional SHWS, in front of each CPM, the local wavefront emitted from the phase object is approximated to a tilted plane wave.

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Conclusion