Laser speckle reduction by multimode optical fiber bundle with combined temporal, spatial, and angular diversity

Abstract

We report significant speckle reduction in a laser illumination system using a vibrating multimode optical fiber bundle. The optical fiber bundle was illuminated by two independent lasers simultaneously. The beams from both lasers were first expanded and collimated and were further divided into multiple beams to illuminate the fiber optic bundle with normal and oblique incidence. Static diffusers were also placed at the input and output faces of the fiber bundle, thus introducing the spatial as well as angular diversity of illumination. Experiments were carried out both in free space and in imaging geometry configuration. Standard deviation, speckle contrast and signal-to-noise ratio of the images were computed, and the results were compared with those of white light illumination. Speckle contrast close to that of white light was obtained using a vibrating fiber bundle with combined temporal, spatial, and angular diversities of the illumination.

54‐1: Laser Speckle Reduction using Nanoparticle‐Embedded Liquid Crystals

“…There are several solutions proposed to reduce laser speckles based on the decorrelation at the perspectives of wavelength, spatial, angular, and polarization. The majority of the proposed solutions are introducing optical components such as diffuser, microlens-array beam shaper, phase matrix and optical fibers with mechanical motion such as rotation or vibration in the system to reduce the coherence of light source [4][5][6][7][8]. Motionless optical components for speckle reductions are demonstrated such as polymer dynamic diffraction gratings, deformable mirrors, scattering from colloidal suspension, spatial light modulator, and ferroelectric liquid crystal cell [9][10][11][12][13].…”

Experimental evaluation of speckle suppression efficiency using a moving 2D Barker code DOE

“…One of the most effective methods of speckle suppression is the speckle averaging mechanism that is based on a vibrating random diffuser or a regular diffractive optical element (DOE) [9][10][11][12][13][14][15][16]. In our previous publication, we proposed a method of a speckle suppression based on Barker code and M-sequence DOEs and worked out its mathematical model [17][18][19][20].…”

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

“…Several groups have reported on the use of a multimode fiber to reduce speckle contrast in laser projectors [29][30][31][32]. The theory behind this method was developed by Manni and Goodman [33].…”