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Optical Engineering

Reconfigurable Shack-Hartmann wavefront sensor
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Paper Abstract

The conventional Shack-Hartmann wavefront sensor (SH-WFS) has a fixed subaperture area that is determined by consideration of several parameters such as the average atmospheric coherence diameter r0 at the telescope site. Its SNR can be severely degraded due to low-light conditions caused by increasing turbulence, strong atmospheric scintillation, or simply viewing a faint object. Typically, the integration time of the sensor is increased to improve the SNR. Unfortunately, a decrease in bandwidth causes an increase in residual wavefront error that reduces image quality. We show that an increase in subaperture area produces a smaller residual wavefront error than an equivalent increase in integration time. Furthermore, we show that the ability to reconfigure the subaperture area, in combination with control bandwidth adjustment, provides superior performance over a system with fixed subaperture area when r0 is different than the design point. We present a reconfigurable Shack-Hartmann wavefront sensor (RSH-WFS) with adjustable subaperture area implemented using a phase-modulated liquid crystal device (LCD). Experimental results demonstrate that the RSH-WFS increases system dynamic range by increasing the subaperture diameter whenever the Hartmann spot irradiance falls below the threshold of operation of the conventional SH-WFS.

Paper Details

Date Published: 1 January 2004
PDF: 6 pages
Opt. Eng. 43(1) doi: 10.1117/1.1625950
Published in: Optical Engineering Volume 43, Issue 1
Show Author Affiliations
Jungtae Rha, New Mexico State Univ. (United States)
David G. Voelz, New Mexico State Univ. (United States)
Michael K. Giles, New Mexico State Univ. (United States)

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