To correct wave front distortion, a phased only Liquid Crystal Spatial Light Modulator (LCSLM) is used. LCSLM can modulate the phase of the incident beam by changing the electric field applied to the transparent electrodes of a liquid crystal cell. The voltage change causes the refractive index of the liquid crystal change, so a phase shift produces. The distortion of a wave front can be measured by using a wave front interferometer. Since each pixel of SLM may be addressed and controlled independently, so proper voltage is supplied to each pixel to compensate the phase corresponding to the distortion. Before wave front correction, the LCSLM is tested and corrected by employing a Twyman-Green interferometer, which shows the relationship between the applied voltage and the phase value of each pixel. Experiment result shows that after error compensation of LCSLM, the wave front distortion correction accuracy reaches 0.06 λ.
Phase-Only Optically Addressable Spatial-Light Modulator and On-Line Phase-Modulation Detection System