$Holographic scanner control based on monitored diffraction efficiency$

Holographic scanner control based on monitored diffraction efficiency

Operating parameters for a multiple facet holographic disc scanner are adjusted on real time basis as a function of the actual diffraction efficiency of the facet region aligned with the impinging laser beam. The operating parameters are adjusted to achieve optimum signal levels independent of facet...

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Bibliographische Detailangaben
Hauptverfasser:	DICKSON, LEROY D, STOKES, JR., OLEN L, CATO, ROBERT T
Format:	Patent
Sprache:	eng
Schlagworte:	CALCULATING COMPUTING COUNTING ELECTRIC COMMUNICATION TECHNIQUE ELECTRICITY HANDLING RECORD CARRIERS OPTICAL ELEMENTS, SYSTEMS, OR APPARATUS OPTICS PHYSICS PICTORIAL COMMUNICATION, e.g. TELEVISION PRESENTATION OF DATA RECOGNITION OF DATA RECORD CARRIERS
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Beschreibung
Zusammenfassung:	Operating parameters for a multiple facet holographic disc scanner are adjusted on real time basis as a function of the actual diffraction efficiency of the facet region aligned with the impinging laser beam. The operating parameters are adjusted to achieve optimum signal levels independent of facet characteristics. Diffraction efficiency is inversely related to zero order beam power for a given level of input beam power. A photodetector measures the zero order beam power. The output of this photodetector is used to control video amplifier gain and/or semiconductor laser current.