This device has a number of potential applications. It may be used in a direct view mode as a thermal night sight. It may be integrated with a fiber-optic faceplate visible charge-couple device (CCD) and then used as a TV-type thermal imager. Alignment of the sensor to the CCD is not very critical. In a slightly modified version, the output image may be a spatial light modulator serving as input to an optical processor. Examples of the above implementations are given. The converter can be tailored to accept either the 3 to 5 micrometers or the 8 to 14 micrometers infrared bands. The quantum efficiency is on the order of 30, but the low noise performance and starting mode of operation readily offset this. The unique design greatly reduces the impact of structural defects. Pixel-to-pixel uniformity of the device is very good. The simple design offers a potential for high-resolution large-area imagers. The paper discusses the supporting theory and device design. The manufacturing process, the results to date, and the performance are also discussed.
The solar spectral response of a Schottky-barrier infrared detector (PtSi) is compared to a photovoltaic detector (InSb) of comparable average over the region of interest. The effect of sunlight on a Schottky-barrier detector is found to be even more pronounced than that of a photovoltaic detector of equivalent sensitivity. To reduce this exaggerated effect, a spectral model has been developed for the selection of the optimum filter for use on a PtSi focal-plane array. The model makes it possible to reduce the effect of solar irradiance while not significantly impacting the performance of the detector against a thermal target. The spectral ratio of solar irradiance to a 290-K target for a Schottky-barrier detector is discussed. The solar-to-target contrast ratio is plotted against the integrated 3-5-micron spectral sensitivity to help the user select an optimum cut-off wavelength.