Binary code DOE optimization for speckle suppression in a laser display

Using a laser light source in imaging devices provides a wide color gamut, high brightness, resolution, and efficiency. At the same time, it creates a speckle pattern that deteriorates the image quality. This paper is related to the application of the moving binary code diffractive optical element (DOE) for speckle suppression in a laser display. Analytical optimization of DOE parameters is made in this paper. The optimal DOE pitch is found analytically. Limitation of the DOE code length is shown, and the highest possible code length is estimated. Application of the compound Barker code for the DOE design is suggested. As an alternative, the M-sequence and minimum peak side-lobe codes are considered. The expected residual speckle contrast ratio after application of those codes is estimated for the number of codes. A comparison of the different codes is done, and recommendations for speckle suppression DOE design are provided.