An adaptive coded aperture imager: building, testing and trialing a super-resolving terrestrial demonstrator

Abstract

There is an increasingly important requirement for day and night, wide field of view imaging and tracking for both imaging and sensing applications. Applications include military, security and remote sensing. We describe the development of a proof of concept demonstrator of an adaptive coded-aperture imager operating in the mid-wave infrared to address these requirements. This consists of a coded-aperture mask, a set of optics and a 4k x 4k focal plane array (FPA). This system can produce images with a resolution better than that achieved by the detector pixel itself (i.e. superresolution) by combining multiple frames of data recorded with different coded-aperture mask patterns. This superresolution capability has been demonstrated both in the laboratory and in imaging of real-world scenes, the highest resolution achieved being ½ the FPA pixel pitch. The resolution for this configuration is currently limited by vibration and theoretically ¼ pixel pitch should be possible. Comparisons have been made between conventional and ACAI solutions to these requirements and show significant advantages in size, weight and cost for the ACAI approach.

Novel EO/IR sensor technologies

“…QinetiQ's project aiming at a polarimetric camera exploiting coded aperture imaging techniques [30] (figure 4) was a project that levered separate investment by DARPA, but ultimately demonstrated some of the challenges associated with applying the technique for discriminative imaging. The DARPA-supported activity separately addressed the design and build of a MWIR coded aperture camera addressing requirements for high altitude persistent surveillance, working towards a TRL 4 demonstrator [31]. Polarimetric coded aperture image A technique was developed by Thales for the adaptive, scene-based non-uniformity correction of IR FPAs [32].…”

Systems for persistent surveillance

“…In contrast DARPA's LACOSTE programme [48] takes a different approach by exploiting coded aperture techniques, which enabled a much smaller number of FPAs to be used (albeit each with 8 Mpixels), to provide an optical beam-forming system for simultaneous tracking of multiple targets within a wide field of regard, with capability for arbitrary foveation and super-resolution. As such it is an optical analogue of a SAR-GMTI system, avoiding shortfalls in the latter systems when required for providing persistence over large urban areas.…”