Studies of the spectral "crosstalk" in two-color IR projection systems

In some of its infrared projection systems, the Kinetic Kill Vehicle Hardware-In-the-Loop Simulator (KHILS) facility uses two 512 x 512 Wideband Infrared Scene Projector (WISP) resistor arrays to stimulate two different camera wavebands at the same time. The images from the two arrays are combined with a dichroic beam combiner, allowing the two camera bands to be independently stimulated. In early tests it was observed that the projector bands were not completely independent. When one array was projecting, the projected pattern could be seen in the opposite camera band. This effect is caused by spectral "crosstalk" in the camera/projector system. The purpose of this study was to build a mathematical model of the crosstalk, validate the model with measurements of a 2-color projection system, and then use the model as a tool to determine the spectral characteristics of filters that would reduce the crosstalk. Measurements of the crosstalk were made in the KHILS 2-color projector with two different 2-color cameras. The KHILS Quantum Well Infrared Photodetector (QWIP) Mid-Wave (MW)/Long-Wave (LW) camera and the Army Research Laboratory HgCdTe (HCT) MW/LW camera were used in the tests. The model was used to analyze the measurements, thus validating the model at the same time. The model was then used to describe conceptual designs of new 2-color projection configurations, enabling a prediction of crosstalk in the system, and selection of filters that would eliminate the crosstalk.