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Method and apparatus for recovering information from a videodisc

  • US 4,536,863 A
  • Filed: 04/15/1982
  • Issued: 08/20/1985
  • Est. Priority Date: 04/15/1982
  • Status: Expired due to Term
First Claim
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1. A method for manipulating a track reader for recovering information from a selected target track of a plurality of spiralling and substantially circular information tracks or concentric circular information tracks on a record disc, each said track containing at least in part a unique track identifying code, said method comprising the steps of:

  • (a) generating a target track identifying code that matches the track identifying code of said target track;

    (b) rotating the disc in a prescribed fashion;

    (c) scanning the disc with the track reader at a prescribed radial velocity relative to the disc, toward the target track to recover information recorded thereon including track identifying codes;

    (d) comparing recovered track identifying codes with said target track identifying code and detecting the difference therebetween;

    (e) scanning continuously toward said target track until said comparing and detecting step indicates that the recovered track identifying code is within a fixed range of the target track identified code;

    (f) thereafter moving the track reader incrementally within said range relative to said disc across a prescribed number of tracks during each revolution of the disc, toward the target track;

    (g) upon passing the target track by detection in said comparing and detection step, that the difference between the recovered track identifying code and the target track identifying code is increasing, reversing the radial scanning direction;

    (h) continuing said incremental scanning while continuing to detect the difference between the recovered track identifying code and the target track identifying code, and continuing to reverse the radial direction of movement upon each detection of an increasing difference between the recovered track identifying code and the target track identifying code until a match is made therebetween, and in the absence of a match in a first prescribed period of time, incrementing the target track identifying code by a fixed value;

    (i) continuing said incremental scanning toward said target track until a match between the recovered track identifying code and the incremented target track identifying code is found; and

    (j) after a match is found, ceasing the relative radial movement across the disc and recovering the information from the arrived at track.

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