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 TM) laser projection system using the Hadamard diffuser has resulted in a suppression to 8% residual speckle contrast.