Variable Focus SLM using Electric-field-driven LC Lens for CGHs

초록

In this paper we suggest a variable focus SLM(Spatial Light Modulator) combining a LC(Liquid Crystal) SLM and an ELC(Electric-field-driven Liquid Crystal) Fresnel lens for CGHs(Computer Generated Hologram). We first calculated phase retardation according to an applied voltage, and then calculated the applied voltage distribution throughout the variable focus SLM from the phase of the Fourier transformed image as an input data for the SLM considering a 3-demensional OPD(Optical Path Difference). The input image for reconstruction of the CGH is created from the point cloud datasets. The 3-demensional OPD used for the simulation, represented in Figure 1. (a),was designed to have an OPD as close as possible to that of an ideal Fresnel lens. We finally reconstructed the image using the Fourier transformation. The simulation was carried out for the variable focus SLM of an ECB(Electrically Controlled Birefringence) mode LCD. The size and the resolution of the SLM are 1cm ?1cm and 1000?1000, respectively. The discontinuities in the phase distribution between neighboring pixels shown in Figure 1. (a), caused by the pixelated variable focus SLM, generate the noise in the reconstructed image as shown in Figure 1. (c). The noise of the present result can be reduced by adopting an additional filtering and correcting the aberration of the lens.