In coded aperture imaging, adaptive masks provide significant benefit, notably for their role in supporting the image recovery process. Each discrete mask pattern produces a unique point spread function on the detector array, which can be used to enhance the resolution of imagery and indeed to enable tracking on a sub-pixel basis. The choice of adaptive mask technology is very dependent on both the spectral region of interest and the configuration of the coded aperture camera. Transmissive masks can be based on liquid crystal, micro-machined air-spaced Fabry-Perot cavities or even phase-change materials, whilst reflective masks can be based on liquid crystal on silicon (LCOS) or MEMS tip-tilt mirrors. Such components can also provide the basis for discriminative imaging. This paper provides a review of the various technologies and assesses performance levels in relation to different applications.
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