Apodized grating cell to display 3D images

A novel design of the diffraction grating cell used as a pixel on a 3D display is proposed. When illuminating the display, we can observe parallax images from corresponding directions through the diffractive function of each grating cell. Because the small grating cell is designed usually as a binary grating filling a small rectangle area, the first order diffracted light from each pixel has a broadened diffraction intensity distribution. The diffracted light which exists outside the geometrically projected area is so-called 'feet' of the diffraction pattern. The feet result in crosstalks in the 3D display between the images from adjacent pixels corresponding to the other viewing angles. It is better for the diffracted light from each cell to have a flat distribution in a desired area on an observation plane, and zeros in the surroundings. We introduce a spherical wavefront generation and an apodization in the grating cell design to realize arbitrary extent of the diffracted light with diminishing feet. As a result, a 3D display consisting of the grating cells designed in this manner can reconstruct 3D images with less crosstalks than that of the binary case.