Nonsequential Speckle Reduction Method by Generating Uncorrelated Laser Subbeams With Equivalent Intensity Using a Reflective Spatial Light Modulator

摘要

Speckle must be suppressed in laser displays. Here, we proposed and demonstrated a non-sequential speckle reduction method by dividing one laser beam as uncorrelated laser sub-beams (LSBs), where light intensities of the LSBs were made as equivalent by programming a reflective spatial light modulator. The proposed method has no requirement of the modulators speed; thus, it has obvious merit comparing with the sequential speckle reduction methods, especially when slow liquid crystals are used.Sequential speckle reduction methods demand the usage of fast modulators due to the short integration period of human eyes. Here, a nonsequential speckle reduction method by splitting one laser beam with short coherence length into uncorrelated laser subbeams (LSBs) is reported. In order to realize the most efficient speckle reduction, with the help of a polarization beam splitter, we have programmed a reflective spatial light modulator to make the LSBs intensities equivalent. Three uncorrelated LSBs with equivalent light intensity are designed to demonstrate this idea; the speckle contrast ratio is reduced to 0.55, which closes to the expected value of 0.58. This nonsequential speckle reduction method has no requirement of the modulators speed; thus, it has obvious merit comparing with the sequential speckle reduction methods.