Wide-angle achromatic prism beam steering for infrared countermeasure applications

Abstract

The design and analysis of achromatic doublet prisms for use in laser beam steering is presented. The geometric relationships describ- ing the maximum steering angle are given, as are discussions of first- and second-order dispersion reduction. Infrared (IR) material alterna- tives and optimum IR material characteristics for wide-angle achromatic prism beam steering are also investigated. Sixteen materials in 120 dif- ferent combinations have been examined to date. For midwave IR appli- cations it is shown that the minimum dispersion currently achievable across the full 2 to 5 mm spectrum is 1.7816 mrad at an average maxi- mum steering angle of 45 deg. This is accomplished using LiF/ZnS dou- blet 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. © 2003 Society of Photo-Optical Instrumentation Engineers.