Coded aperture systems as non-conventional lensless imagers for the visible and infrared

Coded aperture imaging (CAI) has been used extensively at gamma- and X-ray wavelengths, where conventional refractive and reflective techniques are impractical. CAI works by coding optical wavefronts from a scene using a patterned aperture, detecting the resulting intensity distribution, then using inverse digital signal processing to reconstruct an image. This paper will consider application of CAI to the visible and IR bands. Doing so has a number of potential advantages over existing imaging approaches at these longer wavelengths, including low mass, low volume, zero aberrations and distortions and graceful failure modes. Adaptive coded aperture (ACAI), facilitated by the use of a reconfigurable mask in a CAI configuration, adds further merits, an example being the ability to implement agile imaging modes with no macroscopic moving parts. However, diffraction effects must be considered and photon flux reductions can have adverse consequences on the image quality achievable. An analysis of these benefits and limitations is described, along with a description of a novel micro optical electro mechanical (MOEMS) microshutter technology for use in thermal band infrared ACAI systems. Preliminary experimental results are also presented.