Aberration-free linear holographic scanner and its application to a diode-laser printer

Multifunctional binary diffractive optical elements for structured light projectors

A set of diffractive optical elements for multiple-stripe structured illumination was designed, fabricated and characterized. Each of these elements with a single layer of binary surface relief combines functions of a diffractive lens, Gaussian-to-tophat beam shaper, and Dammann beam splitter. The optical investigations of laser light patterns at 20° fanout angle reveal up to 88% diffraction efficiency, high contrast, and nearly diffraction limited resolution. The developed technology has the potential for reducing complexity, number of optical components, power consumption and costs of structured light projectors in mobile and stationary 3D sensors.

Holographic optical scanning elements with minimum aberrations

An analytical method to design holographic optical elements for focusing laser scanners, especially disk scanners, with minimum aberrations and optimum scan line definition is reported. The results reveal that the focused spot constraint to a straight line is always astigmatic. However, by accepting small deviations from the straight line, the astigmatism can be eliminated. The second-order analytical solutions are examined with the help of geometrical ray tracing and compared with experimental results. By extending the method to higher-order approximations, it was found that the correction of the aberrations is essentially limited to the direction perpendicular to the scan line.

Analysis of a low-aberration holographic scanner

Low-aberration holographic scanners that eliminate the need tor lenses or mirrors promise to greatly reduce the cost of laser printers and image scanners. This paper describes how the spot profile of such a scanner can be predicted using the Fresnel-Kirchhoff diffraction integral, and the diffraction efficiency of the scanner can be predicted using Kogelnik's coupled-wave theory. Experimental results verity the accuracy of these design methods. For a prototype scanner used in a high-resolution He-Ne laser printer, the measured linearity error was under +/- 100 microm, and the spot size (half-intensity beamwidth) was under 60 microm for a span (scan width) of 280 mm.