Santa Barbara Research Center

Russell D Granneman

William O McKeag

William H Wellman

A focal plane array (10) of radiation detectors (10b) has all features inclined with respect to an illuminating beam of radiation. That is, all features that would be orthogonally disposed with respect to an incoming wavefront are instead inclined to the incoming wavefront, an arrangement referred to as compound tipping. The disclosed embodiments of the invention create a compound tipping of the focal plane array such that there are no features of the array, such as mesa edges and sidewalls, that lie in the plane of the incoming wavefront. As a result, only a small amount of scattered light is observed, and the optical signature is significantly reduced. The invention substantially eliminates the optical signature by simultaneously tipping the focal plane features (optically and/or mechanically) in both major array axes, without degrading the imaging performance of the detective assembly.

Compound optically tipped detectors

A radiation detector includes a photovoltaic diode mesa structure (16) having of a plurality of sub-mesa structures (16a, 16b). Each of said sub-mesa structures includes a first layer (14a) of semiconductor material having a first type of electrical conductivity and a second layer (14b) having a second type of electrical conductivity such that a p-n junction is formed between the first and the second layers. Metalization (24) is disposed within a trench (30a) that runs between the sub-mesas and includes a tab portion (24a) that extends upwardly over a sidewall of each of said sub-mesa structures so as to electrically contact the second layer contained within each. As a result, each of said sub-mesa structures are electrically connected in parallel. The trench is disposed parallel to a radiation scan axis of the radiation detector and orthogonal to a radiation cross-scan axis of the radiation detector for reducing a width of surface features across the scan axis, thereby reducing a light signature of the detector.

Remote indium bump corrugated PV diodes

An IR detector array (10) wherein a metal contact pad (20) makes contact to an underlying radiation detector through one or more thin, electrically conductive stripes (20a). The striped pad contact shape is used in conjunction with a highly absorptive and opaque coating (18) that is interposed between a bottom surface of the contact pad and a top surface of the radiation detector. The highly absorptive coating serves to mask the bottom surface of the metal contact pad from any radiation that would impinge thereon and be reflected. As a result, stray or unabsorbed radiation reaching to a region of the contact pad encounters only the relatively small target presented by the edge of the one or more thin electrically conductive stripes. Furthermore, the one or more thin stripes are aligned with respect to a radiation scan axis and/or rotation axis so as to further minimize the width of the contact edge presented to the unabsorbed radiation, thereby further reducing the probability of an unwanted reflection occurring.

Striped contact IR detector

A radiation shield 40 is mounted to an uncooled portion, such as an outer case 14, of an IR detector assembly 10 such that it surrounds a thermoelectric cooler 16 and a radiation detector 18. The shield 40 has a curved reflective upper surface 42 having the shape of a toric segment and cylindrical or rectangular reflective sidewalls 44 for imaging the detector 18 and the upper cooler stage upon the tops and sides of lower and slightly warmer cooler stages, which absorb and eliminate radiative energy. This beneficially reduces the heat load upon the coldest stage by excluding hotter surfaces from its view, and by inhibiting reflective couplings of unwanted energy admitted by aperture 46. An aperture 46 defines the effective coldstop for the detector 18.

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Goleta, CA, United States of America

Russell D Granneman