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A 244X190-element monolithic interline transfer CCD infrared imager (the 2441) has been developed which combines PtSi Schottky barrier photodiode technology with proven CCD imager technology that has been used successfully for years in the production of visible imagers. The unit cell of this device is 36um high and 60um wide. The diagonal of the television format array is 14.4mm. Each Schottky barrier photodiode (SBPD) has an active area of 430um2. Assuming quantum efficiency of 1% at 4um and given f/2.5 optics, this device should passively image a 300°K scene with a noise equivalent blackbody temperature difference of approximately 0.08°C. This sensitivity makes this television sensor useful for such applications as general passive night viewing at moderate to high scene temperatures (50°F) and dynamic thermal data acquisition from scenes. The pixel count provides approximately half the resolution of standard television in both vertical and horizontal direc-tions. The 14.4mm diagonal is relatively small for IR imagers, allowing use of smaller and light-weight lenses than those required by imagers with larger pixels. The wafer fab process and the design rules used to make this device are almost entirely the same as those used to manufacture the Fairchild-Weston 488X380-element visible imager. The primary differences are the addition of the PtSi steps and low-temperature processes for subsequent processing. The processing employs 3-level poly-Si, buried channels and an ultra-high-vacuum process for forming a thin PtSi layer. The design employs 4-phase vertical registers, a 2-phase output register and a resettable-gate preamplifier. The evaluation camera incorporates a 12-bit video digitizer, a 16-frame-averaging reference frame memory and a real-time reference frame subtractor. It functions as a one-point offset uniformity correction. Performance tests to date, using an f/1.8 lens, have given MRTs as low as approximately 0.1°C and NEDTs as low as approximately 0.2°C or better. In general the imagers tested to date show excellent uniformity and few cosmetic defects.
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