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Zichun Le, A. Lapchuk, I. Gorbov, Zhiyi Lu, Songlong Yao, I. Kosyak, T. Kliuieva,Yanyu Guo, O. Prygun. Theory and experiments based on tracked moving flexible DOE loops for speckle suppression in compact laser projection // Optics and Lasers in Engineering 124 (2020) 105845

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.

ANATOLY LAPCHUK,  ZICHUN LE,  YANYU GUO,  YANXIN DAI,  ZONGSHEN LIU,  QIYONG XU,  ZHIYI LU,  ANDRIY KRYUCHYN  AND IVAN GORBOV.Investigation of speckle suppression beyond human eye sensitivity by using a passive multimode fiber and a multimode fiber bundle //Optics express Vol. 28, No. 5 / 2 March 2020. P. 6820-6834.

Abstract

A method of speckle suppression without any active device is expected for picoprojectors. The effectiveness of the passive method of speckle reduction using a single multimode fiber and a multimode fiber bundle was actually measured and theoretically analyzed. The dependences of the speckle contrast and speckle suppression coefficient on the parameters of multimode fiber and projection systems were investigated. Our results shown that the efficiency of speckle suppression was limited because only the radial direction of the objective lens aperture was used. An improvement using both of the radial and azimuthal directions of the objective lens aperture is required.
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