A holographic scanner includes a rotating glass disk (10) carrying a plurality of scan line generating holograms, a laser light source (14) and means (16) for detecting reflected optical energy. The scanner is improved by adding a plurality of relatively small position-indicating holograms (38) in alternation with the scan line generating holograms (36). The position-indicating holograms (38) redirect the laser beam along desired paths on the same side of the disk (10) as the laser (14). The redirected laser beam may be detected by the system photodetector (16) or an auxiliary photodetector to provide signals indicating the current disk position. The position information can be used by a system processor (34) to optimize scanner parameters as a function of the characteristics of the next active scan-line generating hologram (36).
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