Today diffractive elements are routinely designed and fabricated that diffract laser beams into hundreds of spots with diffraction efficiencies in excess of 90%. Thus it is easy to imagine that an electrically addressed phase-only spatial light modulator (SLM) could be used for the simultaneous and independent scanning of multiple spots in arbitrary directions. As opposed to single spot scanning, each spot would be present for the entire frame time of the modulator, thereby increasing dwell time over raster-based scanners. Key to actually achieving arbitrary scanning operations at real-time rates is the issue of specifying the electrical control values to the SLM. The control values are not obvious because arbitrary complex modulation is needed to produce arbitrary diffraction patterns. Calculation of the control values using global optimization (as is used to design diffractive optics) is too slow. Group oriented encoding procedures are fast but the use of groups to represent individual complex values reduces the resolution of the scanner correspondingly. The recently developed method referred to as pseudorandom encoding can be computed in real- time and does not sacrifice resolution. This statistically based encoding procedure is reviewed with emphasis on its performance and suitability for applications requiring multispot beam steering.

Date Published: 7 July 1997
PDF: 11 pages
Proc. SPIE 3131, Optical Scanning Systems: Design and Applications, (7 July 1997); doi: 10.1117/12.277743

Published in SPIE Proceedings Vol. 3131:
Optical Scanning Systems: Design and Applications
Leo Beiser; Stephen F. Sagan, Editor(s)