An investigation of the potential for the use of a high resolution adaptive coded aperture system in the mid-wave infrared

Abstract

Previous applications of coded aperture imaging (CAI) have been mainly in the energetic parts of the electro-magnetic spectrum, such as gamma ray astronomy, where few viable imaging alternatives exist. In addition, resolution requirements have typically been low (~ mrad). This paper investigates the prospects for and advantages of using CAI at longer wavelengths (visible, infrared) and at higher resolutions, and also considers the benefits of adaptive CAI techniques. The latter enable CAI to achieve reconfigurable modes of imaging, as well as improving system performance in other ways, such as enhanced image quality. It is shown that adaptive CAI has several potential advantages over more traditional optical systems for some applications in these wavebands. The merits include low mass, volume and moments of inertia, potentially lower costs, graceful failure modes, steerable fields of regard with no macroscopic moving parts and inherently encrypted data streams.Among the challenges associated with this new imaging approach are the effects of diffraction, interference, photon absorption at the mask and the low scene contrasts in the infrared wavebands. The paper analyzes some of these and presents the results of some of the tradeoffs in optical performance, using radiometric calculations to illustrate the consequences in a mid-infrared application. A CAI system requires a decoding algorithm in order to form an image and the paper discusses novel approaches, tailored to longer wavelength operation. The paper concludes by presenting initial experimental results.

Liquid Crystal Tunable Metamaterial Absorber

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Challenges in the evolution of advanced imaging systems

“…By varying the aperture pattern, other benefits can be realized, which open the pathway for improved imaging quality, variable field of view and steerable field of regard [24]. In a sense, some of these follow-on from the initial suggestion of Grindley and Hong [20], who found that up to two orders of magnitude improvement in signal to background ratio could be obtained in X-ray imaging by scanning the field of view over the telescope.…”

A model of PSF estimation for coded mask infrared imaging

“…Diffraction effects were analyzed at the beginning of their system design stage. The diffraction leads to energy dispersion of the information, which means there is a tradeoff between the convenience of measurement with more sensing cells and the algorithmic complexity for imaging reconstruction with high quality [15]. Their following works were mainly focused on PSF control (including mask pattern design [16] and microshutter array technology [17]) and the imaging reconstruction based on PSF calibration [18,19].…”