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14 October 2005 Evaluation of contrast loss introduced by scattering effects at optical mounts: field dependence in the IR region
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The reduction of contrast due to scattering by optical mounts and buffers was studied, especially for the systems that must work in the infrared region. When a particular optical system is optimized [1,2] up a specified field value the scattering effects introduced by optical mounts and buffers must be taken into account. The scattering effect plays an important role in the IR region where the influence of off-field effects is important. The contrast reduction due to scattering effects is not uniform with the object position, in other words the influence of scattering effects has field dependence. The scattering model used is based on the classical point of view of the scattering electromagnetic wave and it is adapted for optical evaluation using ray-tracing techniques. In order to test the validity of our scattering model we calculated the distribution of illumination produced for a laser beam in a plane-parallel plate with perfect scattering properties at the back surface. The comparison between the results obtained form our model and the analytical models permit us to extrapolate the use of our model in systems that involve more complex geometry. The model was applied in a four element IR objective with germanium and silicon lenses. In all the situations the contrast as a function of the field value was calculated, with and without the scattering effects. By contemplating the contrast loss, a better choice of materials, geometries and buffer positions can be made possible.
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C. Pizarro, P. Blanco, J. Arasa, and A. F. Cifuentes "Evaluation of contrast loss introduced by scattering effects at optical mounts: field dependence in the IR region", Proc. SPIE 5962, Optical Design and Engineering II, 59622U (14 October 2005);

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