Optical EngineeringIncidence angle reducer for holgraphic optical elements used to improve laser detection systems
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How special reflective devices reduce the angle of incidence of a laser beam irradiating a surface with the ability to decrease the incidence angle over a wide range of angles is described. To optimize the diffraction efficiency of a focusing holographic optical element (HOE), spread of the angle of incidence of an incoming laser beam about a preferred angle should be small. There is a constraint with thick HOEs in which a Bragg effect condition must be satisfied to achieve high diffraction efficiency. Angle reduction and applications of military interest are discussed. Ways to couple a reflection angle reducer component and an HOE to a photographic or TV camera are suggested.