Photon counting arrays for AO wavefront sensors

John Vallerga; Anton Tremsin; Jason McPhate; Bettina Mikulec; Allan Clark; Oswald Siegmund

doi:10.1117/12.620295

25 August 2005 Photon counting arrays for AO wavefront sensors

John Vallerga, Anton Tremsin, Jason McPhate, Bettina Mikulec, Allan Clark, Oswald Siegmund

Proceedings Volume 5903, Astronomical Adaptive Optics Systems and Applications II; 59030M (2005) https://doi.org/10.1117/12.620295
Event: Optics and Photonics 2005, 2005, San Diego, California, United States

Abstract

Future wavefront sensors for AO on large telescopes will require a large number of pixels and must operate at high frame rates. Unfortunately for CCDs, there is a readout noise penalty for operating faster, and this noise can add up rather quickly when considering the number of pixels required for the extended shape of a sodium laser guide star observed with a large telescope. Imaging photon counting detectors have zero readout noise and many pixels, but have suffered in the past with low QE at the longer wavelengths (> 500 nm). Recent developments in GaAs photocathode technology, CMOS ASIC readouts and FPGA processing electronics have resulted in noiseless WFS detector designs that are competitive with silicon array detectors, though at ~ 40% the QE of CCDs. We review noiseless array detectors and compare their centroiding performance with CCDs using the best available characteristics of each. We show that for sub-aperture binning of 6x6 and greater that noiseless detectors have a smaller centroid error at fluences of 60 photons or less, though the specific number is dependent on seeing conditions and the centroid algorithm used. We then present the status of a 256x256 noiseless MCP/Medipix2 hybrid detector being developed for AO.

Citation Download Citation

John Vallerga, Anton Tremsin, Jason McPhate, Bettina Mikulec, Allan Clark, and Oswald Siegmund "Photon counting arrays for AO wavefront sensors", Proc. SPIE 5903, Astronomical Adaptive Optics Systems and Applications II, 59030M (25 August 2005); https://doi.org/10.1117/12.620295

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