Calculation of the contribution of the non-uniformity of the scene projector to the non-uniformity of the output image of a test article

The inherent non-uniformity of a Wideband Infrared Scene Projector (WISP) necessitates an analytical prediction of the contribution of the scene projector's non-uniformity to a test article's output image non-uniformity. A mathematical model has been developed to calculate this non-uniformity based upon a number of input parameters. The output image non-uniformity is dependent on both the non-uniformity of the scene projector and the test article, as well as a weighting factor that results from the relative contribution of the different emitters to the individual detector elements. It is through this weighting factor that parameters such as the sampling ratio, the optical blur of the emitters on the detector's focal plane array, the fill factor of the detector array, and the alignment of the emitters with respect to the detector elements affect the non-uniformity of the output image. Using this model, a theoretical limit for the maximum output image non-uniformity can be calculated for particular values of the scene projector's non-uniformity and the test article's non-uniformity. Realistic situations likely to be encountered during simulation testing were all found to be below the maximum. In order to make this model a useful tool for the laboratory environment, a computer program has been written that calculates the output image non-uniformity based on a given set of input parameters and a numerical approximation of the weighting factor.