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

•Describing an enhanced speckle suppression method based on the tracked motion of flexible diffractive optical element (DOE) loops. The DOE loops consist of 1D random-sequence DOEs with similar but different inclination angles.•Developing a theory and corresponding formula for determining the optimal inclination angles and DOE speed for speckle suppression as well as a model for calculating the speckle suppression efficiency.•Verifying the proposed method decreases the speckle contrast to below the sensitivity of the human eye with compact size and very low power consumption by theoretical and experimental results. 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.