6533b839fe1ef96bd12a62e7

RESEARCH PRODUCT

Dynamic wavefront sensing and correction with low-cost twisted nematic spatial light modulators

subject

description

Off-the-shelf spatial light modulators (SLMs), like twisted nematic liquid crystal displays (TNLCDs) used in projection systems, show some interesting features such as high spatial resolution, easy handling, wide availability, and low cost. We describe a compact adaptive optical system using just one TNLCD to measure and compensate optical aberrations. The current system operates at a frame rate of the order of 10 Hz with a four-level codification scheme. Wavefront estimation is performed through conventional Hartmann–Shack sensing architecture. The system has proved to work properly with a maximum rms aberration of 0. 76 μm and wavefront gradient of 50 rad/mm at a wavelength of 514 nm. These values correspond to typical aberrations found in human eyes. The key point of our approach is careful characterization and optimization of the TNLCD for phase-only modulation. For this purpose, we exploit the so-called retarder–rotator approach for twisted nematic liquid crystal cells. The optimization process has been successfully applied to SLMs working either in transmissive or in reflective mode, even when light depolarization effects are observed.