Simultaneous spectral differential imaging with a focal plane holographic diffuser

David Lafrenière; René Doyon; Étienne Artigau; Christian Marois; Mathilde Beaulieu; Daniel Nadeau; René Racine

doi:10.1117/12.671968

30 June 2006 Simultaneous spectral differential imaging with a focal plane holographic diffuser

David Lafrenière, René Doyon, Étienne Artigau, Christian Marois, Mathilde Beaulieu, Daniel Nadeau, René Racine

Proceedings Volume 6269, Ground-based and Airborne Instrumentation for Astronomy; 62692H (2006) https://doi.org/10.1117/12.671968
Event: SPIE Astronomical Telescopes + Instrumentation, 2006, Orlando, Florida , United States

Abstract

Direct exoplanet detections are limited by the speckle noise of the point spread function (PSF). This noise can be reduced by subtracting PSF images obtained simultaneously in adjacent narrow spectral bands using a multichannel camera (MCC). Experiments have shown that speckle attenuation performances are severely degraded by differential optical aberrations between channels that decorrelate the PSFs of the different spectral bands. We present a new technique which can greatly alleviate this problem: the introduction of a holographic diffuser at the focal plane of the MCC. The holographic diffuser converts the PSF image into an incoherent illumination scene that is then re-imaged with the MCC. This imaging process is equivalent to a convolution of the scene with the PSF of each channel of the MCC. The optical aberrations in the MCC then affect only the convolution kernel of each channel and not the PSF globally, resulting in more correlated images. We report laboratory measurements with a dual channel prototype (1.575 μm and 1.625 μm) to validate this approach. We achieved a speckle noise suppression factor of 12-14, which is ~4-6 times better than what has been achieved by existing MCCs.

Citation Download Citation

David Lafrenière, René Doyon, Étienne Artigau, Christian Marois, Mathilde Beaulieu, Daniel Nadeau, and René Racine "Simultaneous spectral differential imaging with a focal plane holographic diffuser", Proc. SPIE 6269, Ground-based and Airborne Instrumentation for Astronomy, 62692H (30 June 2006); https://doi.org/10.1117/12.671968

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