Design and implementation of passive speckle reduction in laser projector with refractive optical element and lenslet integrator

A refractive optical element (ROE), together with a lenslet integrator (LI), is designed for passive speckle reduction in laser projection displays. ROE cells create optical path differences among laser sub-beams, and consequently destroy laser temporal and spatial coherences when the partially correlated laser sub-beams are superposed by the LI. By using the ROE and the LI, objective and subjective speckle contrasts are reduced to 0.18 and 0.2, respectively. The demonstrated passive speckle reduction technique does not require the use of motors, which shows superiorities over other speckle reduction methods by changing diffuser etc.