Control of Laser Speckle Noise Using Liquid Crystals

Laser speckle noise occurs owing to the strong interference that originates in the high coherency of laser light and the surface topography of the screen. The suppression of the speckle noise is necessary for laser displays such as in an image projection system. In order to reduce speckle noise, we try to control the speckle pattern by using liquid crystals that have electrically controllable optical characteristics. The modulation of polarized light using the birefringence of liquid crystals is very effective. However, the ratio of noise reduction does not exceed 30%. This is because the polarized light transmitted through the liquid crystal medium is formed by only two optical eigenmodes. The wedge-type liquid crystal cell can control the position of the laser spot on the screen. The incident-angle modulation of laser light is also effective for noise reduction. (C) 2011 The Japan Society of Applied Physics