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Hemispheric Array Detector for Imaging (HARDI)
Program Manager: Dr. Devanand Shenoy
State-of-the-art cameras, on UAVs for example, are a trade-off between field of view and weight. In addition they have insufficient spectral range and non-uniform illumination over the focal plane for a large field of view. This is due to their need for multiple lenses to correct for spherical and other optical aberrations due in part to relying on a flat focal plane detector. A simple curved focal plane (analogous to the human eye, where the retina acts as the curved focal plane) would allow for a very wide field-of-view without the aberrations encountered in the flat focal plane.
The objective of the HARDI program is to exploit the optical, electrical, and mechanical properties of both organic and hybrid organic/inorganic semiconductor materials along with innovative processing methods to create a curved focal plane array that will allow the use of fewer optical elements and eliminate the need for image post processing.
Curved focal planes have been previously demonstrated with a radius of curvature ≥ 5 meters while this program seeks to develop curved focal planes with a radius of curvature down to 1 cm. A significant challenge to be addressed in this program is to develop materials and processes that will allow the fabrication of a pixelated photodetector array with a high detectivity, D* on a hemispherical surface. The figure of merit D* was chosen because it is a normalized metric that is independent of unit area and bandwidth. In addition, these new materials will allow for detection from 400-1900 nm which will expand the useful optical bands for the eventual camera. The detectivity of such a curved focal plane array will be comparable to the performance of inorganic semiconductor planar arrays currently demonstrated in the NIR spectral region (using detectivity, D*, as the relevant metric.) but with a field of view of 120° that far exceeds those of current systems.
The improved functionality will be highly beneficial to many military applications by replacing the need for multiple detectors or gimbals thus lessening the mechanical and optical complexity of the system normally required to achieve a wide field of view.