Proceedings PaperImprovement in a volume hologram characteristic for application to a laser scanner
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A volume hologram has an advantage in regard to productivity and diffraction efficiency for a holographic optical element (HOE). However, reconstruction beam characteristics for the hologram are influenced by product process conditions, and they deteriorate when keep illuminating by high power light and held in a high temperature ambient. For this reason, the volume hologram has not been used for the HOE practically. This paper report the causes of these probrems and their countermeasures. First, a reconstructed beam angle from the hologram was measured very accurately by a newly designed instrument. From this measurement result, it was found that there was a difference between diffraction angle value, estimated from Kogelnik's theory, and the measured value in an off-Bragg's incident beam angle condition. Next, a variation between hologram characteristics was assumed to be caused by recording emulsion deformation in a development process. The deformation was measured, using a spectrometer and a scanning tunneling microscope (STM) . To improve the efficiency deterioration, haloid gas was permeated into the emulsion, and the emulsion was sealed between glass plates. Finaly, the authors attempted to make a laser scanner with the volume hologram. Due to the improvements, beam spot size became below 200,urn through a 200mm scanning range.