Differential Imaging with a Multicolor Detector Assembly: A New Exoplanet Finder Concept

Simultaneous spectral differential imaging is a high-contrast technique by which subtraction of simultaneous images reduces noise from atmospheric speckles and optical aberrations. Small non-common-wave-front errors between channels can seriously degrade its performance. We present a new concept, a multicolor detector assembly, which can eliminate this problem. The device consists of an infrared detector and a microlens array onto the flat side of which a checkerboard pattern of narrowband microfilters is deposited, each microfilter coinciding with a microlens. Practical considerations for successful implementation of the technique are mentioned. Numerical simulations predict a noise attenuation of 10-3 at 0.″5 for a 105 s integration on a mH = 5 star of Strehl ratio 0.9 taken with an 8 m telescope. This reaches a contrast of 10-7 at an angular distance of 0.″5 from the center of the star image.