  The phase characteristics of reflecting and transmitting type twisted nematic
liquid crystal based Spatial Light Modulators (SLMs) were measured using
interferometry. Device parameters like contrast, brightness, input and output
polarizer angles have been optimized and SLM phase nonlinearity was reduced by
higher order polynomial interpolation. Higher order aberration production
ability of SLMs was tested by measuring the shift in the spots of a Shack
Hartmann Sensor.
