Speckle contrast reduction in laser projection displays

Speckle arises when coherent light scattered from a rough surface is detected by an intensity detector that has a finite aperture, such as an observer. In a laser projection display, the presence of speckle tends to mask the image information and therefore its reduction is highly desirable. Speckle contrast reduction is based on averaging a number of speckle configurations within the spatio-temporal resolution of the detector through diversification of the light parameters – angle, polarization, and wavelength. The maximum speckle contrast reduction for a given system will be derived, and two novel approaches to achieve the maximum reduction will be introduced. Application to the Grating Light Valve (GLV ) laser projection system using the Hadamard diffuser has resulted in a suppression to 8% residual speckle contrast.