Wide-angle achromatic prism beam steering for infrared countermeasure applications

The design and analysis of achromatic doublet prisms for use in laser beam steering is presented. The geometric relationships describing the maximum steering angle are given, as are discussions of first- and second-order dispersion reduction. Infrared (IR) material alternatives and optimum IR material characteristics for wide-angle achromatic prism beam steering are also investigated. Sixteen materials in 120 different combinations have been examined to date. For midwave IR applications it is shown that the minimum dispersion currently achievable across the full 2 to 5 mum spectrum is 1.7816 mrad at an average maximum steering angle of 45 deg. This is accomplished using LiF/ZnS doublet prisms. Several issues related to the azimuth and elevation angles into which light is steered as a function of prism rotation angles are also presented. (C) 2003 Society of Photo-Optical Instrumentation Engineers.