23 September 2015 2×2-array pixelated optical interference filters
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The need for imaging systems for onboard scientific applications (e.g. for planetology) is becoming of prime interest. Today’s CCD scientific cameras do not provide spectral information of the observed scene. Multi-spectral imaging therefore requires the usage of filters wheels which allow achieving the required optical performances but are a heavy and bulky solution that make them non-adapted for space missions. The goal of this work consisted in developing pixelated filters that could be directly integrated in front of an onboard CCD camera in order to provide with the required spectral information without significantly changing the volume and the weight of the whole system. In this paper, we show the first demonstration of 2×2-array pixelated optical filters with 30 × 30 μm2 pixel size. Four bandpass filters centered at 550, 700, 770 and 840 nm, about 40 nm bandwidth and rejecting in a broadband from 500 to 900 nm were designed. These filters were then fabricated by a masking technique using lift-off processes with two photoresists in order to secure sharp edges for each pixel and ion assisted deposition. Local mapping of the transmission of each pixelated filter was finally carried out with a dedicated system. Comparative measurements between witness samples and filters prototypes show that the pixelated filters have performances comparable to the witness 25 mm aperture filters. This new technology therefore paves a way to the fabrication of multispectral imagers with versatile spectral specifications.
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Michel Lequime, Michel Lequime, Laetitia Abel-Tiberini, Laetitia Abel-Tiberini, Karine Mathieu, Karine Mathieu, Jacques Berthon, Jacques Berthon, Julien Lumeau, Julien Lumeau, } "2×2-array pixelated optical interference filters", Proc. SPIE 9627, Optical Systems Design 2015: Advances in Optical Thin Films V, 96270V (23 September 2015); doi: 10.1117/12.2191210; https://doi.org/10.1117/12.2191210

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