Very efficient speckle contrast reduction realized by moving diffuser device

Speckle noise reduction is best tested on a precise speckle contrast measurement bench, which should be able to measure 100% contrast in fully developed speckle as well as the smallest contrast (for example, less than 10%) after its reduction. On such a test bench, we have measured very efficient speckle contrast reduction by temporal averaging using a moving diffuser on a tuning fork, which vibrates at 100 Hz over 60 microm in amplitude, a distance that is three times the surface roughness correlation length of the diffuser.