Theory and experiments based on tracked moving flexible DOE loops for speckle suppression in compact laser projection

Abstract

This paper describes a speckle suppression method using flexible diffractive optical elements (DOEs) based on binary random sequences with tracked motion. The DOE loops consist of 1D random-sequence diffractive structures with similar but different inclination angles. A mathematical approach for determining the optimal inclination angles and DOE speed for speckle suppression is developed, and a model for calculating the speckle suppression efficiency is constructed. Theoretical and experimental results show that the proposed method decreases the speckle contrast to below the sensitivity of the human eye, making it suitable for compact laser projections. The experimental results also indicate that current DOE production technology should be improved to avoid limiting the image quality.