Image matching method between the SLM and the CCD in a adaptive beam shaping system

Liquid-crystal spatial light modulator (SLM) is a widely-used adaptive device for beam shaping to achieve high quality nearfield measured by CCD camera in high power lasers. Precise image matching between the SLM and CCD is the key issue in this shaping system. We demonstrate an image matching method by using a four-blocker pattern written in the SLM and the output nearfield image measured by the CCD after long-distance spatial propagation. The size and edge-softening factor of the locating blocker in the SLM pattern is designed by using numerical simulation method. Experimental results show that when the locating blocker size is 1 mm and the edge-softening factor is 23%, a perfect CCD image can be achieved for matching with the SLM.