Optimization of Virtual Shack-Hartmann Wavefront Sensing.

Xian Yue,Hao Dai,Chao Geng,Yaliang Yang,Yudong Zhang,Fei Xiao

doi:10.3390/s21144698

Abstract

Virtual Shack–Hartmann wavefront sensing (vSHWS) can flexibly adjust parameters to meet different requirements without changing the system, and it is a promising means for aberration measurement. However, how to optimize its parameters to achieve the best performance is rarely discussed. In this work, the data processing procedure and methods of vSHWS were demonstrated by using a set of normal human ocular aberrations as an example. The shapes (round and square) of a virtual lenslet, the zero-padding of the sub-aperture electric field, sub-aperture number, as well as the sequences (before and after diffraction calculation), algorithms, and interval of data interpolation, were analyzed to find the optimal configuration. The effect of the above optimizations on its anti-noise performance was also studied. The Zernike coefficient errors and the root mean square of the wavefront error between the reconstructed and preset wavefronts were used for performance evaluation. The performance of the optimized vSHWS could be significantly improved compared to that of a non-optimized one, which was also verified with 20 sets of clinical human ocular aberrations. This work makes the vSHWS’s implementation clearer, and the optimization methods and the obtained results are of great significance for its applications.

Highlights

Shack–Hartmann wavefront sensing (SHWS) [1] is currently the main means of wavefront aberration measurements in astronomy [2], high-energy laser [3], retinal imaging [4], optical communication [5], and optical testing [6] due to its simple principle
The performance of Virtual Shack–Hartmann wavefront sensing (vSHWS) when using the round lenslets is significantly better than when using the square lenslets, which is contrary to the expectation that the latter with a higher fill factor should have a better performance
The working process of vSHWS was described in detail, and some optimization methods were used to improve the performance

Summary

Introduction

Shack–Hartmann wavefront sensing (SHWS) [1] is currently the main means of wavefront aberration measurements in astronomy [2], high-energy laser [3], retinal imaging [4], optical communication [5], and optical testing [6] due to its simple principle. Due to the low numerical aperture of the lenslets, SHWS is not sensitive to the aberration change along the depth, and it cannot resist the stray reflections from the interfaces of optics and specimen [10] in the case of biomedical imaging. Phase singularities occur at the points where the amplitudes of interference signals go to zero, decreasing the phase unwrapping accuracy [13]. Both conventional and advanced phase unwrapping algorithms are not satisfactory for the wrapped phase with a strong noise and a lot of singularities [14]

Methods

Results

Discussion

Conclusion