Patent ID: 7715084

Claim:
A method of reducing speckle in a laser illumination system comprising: inserting a despeckle device in a beam of light, the beam of light including light emitted from a coherent laser in the laser illumination system, the despeckle device including an optical retarder for providing an odd integer multiple of substantially half-wave retardation for the light emitted from the coherent laser, the optical retarder having a substantially constant retardance and a spatially varied slow axis, the spatially varied slow axis for imposing a phase mask on the beam of light, the phase mask for providing sub-resolution optical phase modulation to a resolution spot on a detector; and actuating the optical retarder such that the sub-resolution optical phase modulation is varied within an integration time of the detector and such that an intensity non-uniformity of one detected resolution spot to another is reduced.