IMAGING PERFORMANCE OF CRYSTALLINE AND POLYCRYSTALLINE OXIDES

Knowledge of the scatter characteristics of candidate infrared sensor dome materials is necessary for the evaluation of image quality and su sceptibility to bright off-axis sources. For polycrystalline materials in particular, the scattering levels are high enough to warrant conce rn. To evaluate the effects of scatter on image quality, estimates of the window point spread function or its transform, the optical transfe r function, are required. In addition, estimates of the material scatt er cross section per unit volume are essential for determining flare s usceptibility. Experimental procedures and models used at the Applied Physics Laboratory allow the determination of each. Measurement result s are provided for samples of sapphire (ordinary ray), pure yttria, la nthanum-doped yttria, spinel, and ALON. Applications of these results are illustrated for planar windows having arbitrary orientations with respect to the optical axis.