Theoretical calculation and experimental investigation of speckle reduction by multiple wavelength lasers in laser projector with different angular diversities


Hirotaka Yamada1,2, Kengo Moriyasu1, Hiroto Sato1, Hidekazu Hatanaka3 and Kazuhisa Yamamoto2

1 Ushio Inc., 1194 Sazuchi, Bessho-cho, Himeji, Hyogo 671-0024, Japan
2 Institute of Laser Engineering, Osaka University, 2-6 Yamadaoka, Suita, Osaka 565-0871, Japan
3 Ushio Inc., Marunouchi Kitaguchi Bldg., 1-6-5 Marunouchi Chiyoda-ku, Tokyo 100-8150, Japan


 Speckle is one of the most important issues to develop laser projectors. In order to reduce speckle noise, wavelength diversity and angular diversity are widely used. Conventionally, these two methods were treated independently. 

In this paper, the dependency between wavelength and angular diversity is investigated theoretically and experimentally. It is shown that the effects of these two methods are not independent on some screens. The dependency is negligible for screen with high surface roughness, but not negligible for screens with low surface roughness. 

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