Koji SUZUKI, Tatsuo FUKUI, Shigeo KUBOTA, and Yasunori FURUKAWA

Oxide-Kubota Laboratory, Oxide Corporation, Yokohama 223-0052, Japan

(Received May 28, 2013; Accepted October 1, 2013)

The speckle contrasts of two types of laser projectors were measured at various observation distances and observation lens pinhole diameters using a quantitative measurement technique. We found that the speckle contrast as a function of the observation numerical aperture varies with the projection architecture. In a full-frame projector, it is proportional to the numerical aperture, but it is proportional to its square root in a raster-scanned projector. The difference in speckle contrast as a function of the numerical aperture was analyzed based on Goodman's speckle theory. The obtained results were found to be very useful and applicable for speckle evaluation and display qualifications in an arbitrary observer's position.

Key words: speckle contrast, laser display, full-frame projection, raster-scanned projection