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15 July 1997 Managing projector aliasing for tactical infrared imaging systems
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Resistor arrays are the leading technology for testing tactical imaging infrared sensors with a real-time Dynamic Infrared Scene Projector (DIRSP) system. The fundamental goal of a DIRSP system is to project `in-band' infrared imagery to a level of detail such that a Unit Under Test (UUT) perceives and responds to the synthesized scenes just as it would to the real world scenes. In the real world, these tactical scenes are continuous functions that contain both low and high spatial frequencies. Unfortunately, resistor arrays have a discrete number of elements requiring a sampled version of the scenario. The output of the DIRSP is a stepwise continuous radiance distribution that is projected through the DIRSP optics, the UUT optics, and onto the UUT detector array. In many sensors, the UUT detector array produces a sampled version of the irradiance. This continuous to digital to continuous to digital system requires careful analysis regarding the aliasing that may result. Results of such an analysis are presented here. Specifically, the aliasing issues are addressed with results obtained for the typical case of a slightly undersampled sensor (regarded in testing as `natural' aliasing). The analysis indicates the scene projector's spatial frequency limit (i.e., its folding frequency) should exceed the average of the UUT sensor' cutoff spatial frequency and the spatial frequency cutoff of the scene pre-filter (or scene band limit if pre-filtering is not used). This constraint does not eliminate aliasing. Rather is provides for the natural aliasing present in the sensor while avoiding spurious effects from unnatural aliasing in the creation and projection of the synthetic tactical scenes. The scene projector requirement developed in this work is applicable for tactical imagers and imaging missile seekers.
© (1997) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Ronald G. Driggers, Mark August Manzardo, Eddie Burroughs Jr., Carl E. Halford, and Richard H. Vollmerhausen "Managing projector aliasing for tactical infrared imaging systems", Proc. SPIE 3084, Technologies for Synthetic Environments: Hardware-in-the-Loop Testing II, (15 July 1997);

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