Title: Optical reader for information discs equipped with means for automatic access to the information

Abstract: The optical reader, for information discs of which the items of information are locatable by addresses previously recorded on each of the grooves forming the track, comprises a device for counting the number of grooves traversed during search phases which simultaneously uses the envelope of the reading signal and the signal representing the radial error in the position of the head relative to the nearest track, for algebraically counting the number of tracks traversed. After comparison with the number of grooves to be traversed, the counting device controls the deceleration of the radial advance when the spot is at a predetermined distance from the groove to be reached and also its total stoppage and the closure of the radial servocontrol loop when the groove is reached.

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Inventors: Lehureau, Jean-Claude (Paris, FR)
Oprandi, Pierre (Paris, FR)

Application Number: 919552
Filing Date: 1978-06-27
Publication_date: 1979-02-06
Assignee: Thomson-Brandt (Paris, FR)
Primary Class(es): 369/44.28 360/78.14, 365/215, 365/234, 369/30.13, 369/41.01, 369/44.25, 369/44.29
Other Classes:
US Patent Ref:

3962688	Jun, 1976	Westerberg	365/234.
4059841	Nov, 1977	Bricot et al.	358/128.
4063287	Dec, 1977	Van Rosmalen	358/128.
4067044	Jan, 1978	Maeda et al.	358/128.
4074312	Feb, 1978	Van Rosmalen	358/128.
4093832	Jun, 1978	Isaacson et al.	274/15.
4094010	Jun, 1978	Pepperl et al.	365/215.
4094013	Jun, 1978	Hill et al.	365/215.

Other Refs:
Primary Examiner: Boudreau, Leo H.
Assistant Examiner:
Attorney: Cushman, Darby & Cushman