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Imaging Systems

Sinusoidal rotating grating for speckle reduction in laser projectors: feasibility study

[+] Author Affiliations
Sigbjørn Vindenes Egge

Norwegian University of Science and Technology, Department of Electronics and Telecommunications, 7491 Trondheim, Norway

M. Nadeem Akram

Vestfold University College, Institute for Microsystems Technology, P.O. Box 2243, 3103 Tønsberg, Norway

Vladimir Kartashov

poLight AS, P.O. Box 163, 3192 Horten, Norway

Kristine Welde

Norwegian University of Science and Technology, Department of Electronics and Telecommunications, 7491 Trondheim, Norway

Zhaomin Tong

Vestfold University College, Institute for Microsystems Technology, P.O. Box 2243, 3103 Tønsberg, Norway

Ulf Österberg

Norwegian University of Science and Technology, Department of Electronics and Telecommunications, 7491 Trondheim, Norway

Astrid Aksnes

Norwegian University of Science and Technology, Department of Electronics and Telecommunications, 7491 Trondheim, Norway

Opt. Eng. 50(8), 083202 (April 29, 2011June 27, 2011June 28, 2011August 04, 2011August 31, 2011August 04, 2011). doi:10.1117/1.3613937
History: Received April 29, 2011; Revised June 27, 2011; Accepted June 28, 2011; Published August 04, 2011; August 31, 2011; Online August 04, 2011
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This paper describes a novel idea for reduction of speckle contrast in laser display projectors using the rotation of a diffraction pattern whose zeroth order has been canceled out without losing power. The feasibility of the proposed method was investigated by illuminating gratings with a sinusoidal phase on two spatial light modulators (SLMs) in series for minimal intensity modulation, where the phase grating pattern was rotated with respect to the previous one on both SLMs. Two series of measurements were done with different periods of the sinusoidal grating. For each series, an image of the speckle pattern was recorded at discrete rotation angles of the phase grating, and then an average image was calculated. Experimental results were compared with a new theoretical model for speckle contrast of N partially correlated speckle patterns. The experimental measurement results compare well with the theoretical predictions resulting in a minimum speckle contrast of 0.36, with further reduction possible. Parameters necessary to achieve target contrast (0.08 or less) are discussed.

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© 2011 Society of Photo-Optical Instrumentation Engineers (SPIE)

Citation

Sigbjørn Vindenes Egge ; M. Nadeem Akram ; Vladimir Kartashov ; Kristine Welde ; Zhaomin Tong, et al.
"Sinusoidal rotating grating for speckle reduction in laser projectors: feasibility study", Opt. Eng. 50(8), 083202 (April 29, 2011June 27, 2011June 28, 2011August 04, 2011August 31, 2011August 04, 2011). ; http://dx.doi.org/10.1117/1.3613937


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