TITLE:
Speckle Reduction in Imaging Projection Systems
AUTHORS:
Weston Thomas, Christopher Middlebrook
KEYWORDS:
Diffractive Diffusers; Speckle Contrast Reduction; Laser Pico-Projectors
JOURNAL NAME:
Optics and Photonics Journal,
Vol.2 No.4,
December
31,
2012
ABSTRACT: Diffractive diffusers (phase gratings) are routinely
used for homogenizing and beam shaping for laser beam applications. Another use
for diffractive diffusers is in the reduction of speckle for pico-projection
systems. While diffusers are unable to completely eliminate speckle they can be
utilized to decrease the resultant contrast to provide a more visually
acceptable image. Research has been conducted to quantify and measure the
diffusers overall ability in speckle reduction. A theoretical Fourier optics
model is used to provide the diffuser’s stationary and in-motion performance in
terms of the resultant contrast level. Contrast measurements of two diffractive
diffusers are calculated theoretically and compared with experimental results.
Having a working theoretical model to accurately predict the performance of the
diffractive diffuser allows for the verification of new diffuser designs
specifically for pico-projection system applications.