Optimization of a spatial light modulator for beam steering and tracking applications


  • Stigwall Johan

Publish date: 2002-01-01

Report number: FOI-R--0552--SE

Pages: 58

Written in: English


Spatial light modulators (SLMs) based on liquid crystal technology are devices where the refractive index and the phase of the light can be controlled in every pixel over a surface by an electric field. By applying a sawtooth refractive index pattern corresponding to a linear phase shift the direction of a reflected laser beam can be changed. The steering direction can be set exactly, but due to diffraction effects light will also scatter into unwanted directions. This study contains an optical characterization of a liquid crystal SLM and the development of an appropriate simulation model that describe its performance. Using the results from the characterization and the simulations four methods that compensate for the unwanted diffraction effects were developed, as well as two methods that increase the switching speed. Employing compensation methods the usable steering range of the examined device was extended to about +- 2° and the switching speed was roughly doubled. In addition, some tracking algorithms were developed and evaluated in a laboratory set-up.