A direct comparison between a MEMS deformable mirror and a liquid crystal spatial light modulator in signal-based wavefront sensing

A R Jewel,B Vohnsen,V Akondi

doi:10.2971/jeos.2013.13073

Abstract

Aberrations degrade the performance of optical systems in terms of resolution and signal-to-noise ratio. This work explores the feasibility of a signal-based wavefront sensor, which employs a search algorithm to estimate Zernike coefficients of given aberrations. The search algorithm was supported by Gaussian interpolation. The performance of two different reflective wavefront correctors, a deformable mirror and a spatial light modulator in signal-based wavefront sensing, was compared under identical conditions. The aberrations were introduced by using another identical high resolution reflecting spatial light modulator. The performance was quantified using the Strehl ratio, which was estimated from simultaneously acquired Hartmann-Shack measurements of Zernike coefficients. We find that the spatial light modulator can be a good alternative to the deformable mirror in terms of dynamic range and sensitivity, when speed is not a limiting factor. Distinct advantages of the spatial light modulator are high number of pixels and a larger active area.

Highlights

Conventional wide-field microscopes and confocal microscopes can produce images with a resolution down to sub-micrometer scale
HS measured Zernike coefficients before correction of astigmatism (Z22), trefoil (Z3−3) and randomly-generated aberrations, introduced by SLM1 are shown in Figure 5(a), 6(a) and 7(a) respectively
Similar to the deformable mirror (DM) wavefront correction system, SLM1 was employed to induce aberrations and SLM2 was used for correction

Summary

Introduction

Conventional wide-field microscopes and confocal microscopes can produce images with a resolution down to sub-micrometer scale. Fluorescence based microscopy methods provide functional information of cellular processes and chemical specificity [1, 2]. New methods of nanoscopy that combine optical and photophysical phenomena can resolve details of a specimen in tens-of-nanometer scale [3]. The specimen generally has inhomogeneous optical properties and exhibits a spatially varying refractive index and absorption that reduce the resolution and imaging efficiency [4, 5]. The intensity of the fluorescent emission decreases due to aberrations of the excitation light. Using higher intensities to compensate this effect can cause photo-bleaching and photo-toxicity [6]

Methods

Results

Conclusion