Full speckle suppression in laser projectors using two Barker code-type diffractive optical elements

The mathematical model of a speckle-suppression method based on two Barker code-type diffractive optical elements (DOEs) moving in orthogonal directions is developed. The analytic formulae for speckle suppression efficiency are obtained. The model indicates that the one pair of DOEs can be used for laser beams of different colors. The speckle contrast is not dependent on the distance from the viewer to the screen until the distance decreases below the distance where the spatial resolution of the eye on the screen is less than the length of the image of the DOE structure period on the screen. The analysis of the simulated results demonstrates that the method can decrease the speckle contrast to less than 5%, which is below human eye sensitivity, with an optical efficiency greater than 90%.