Apparatus for reading a disk-shaped record carrier with track jumping for charging motion effects
AssigneeU.S. Philips Corporation
InventorHermanus Antonius Kappert
Life of this patent
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Abstract
An apparatus for optically reading a record carrier on which information is contained in tangentially extending tracks includes a directing system for making the scanning spot cooperate with the desired track. In order to enable a jump-wise displacement of the scanning spot from a track being followed to an adjacent track, a switching device is provided for supplying a suitable control signal to the directing system. The control signal is automatically adapted to varying track distances, so that a correct jump-wise displacement of the scanning spot is guaranteed.
Claims8
Apparatus for reading a disk-shaped record carrier on which information is recorded in optically coded form in tangentially extending tracks, which apparatus is of the type comprising a radiation source means for producing a read beam of radiation, a directing system means for making a scanning spot produced by said read beam of radiation on the record carrier cooperate with a desired track, a read detector means for converting the information contained in said read beam after cooperation with the record carrier into an electrical signal, a measuring detector means for measuring the radial position of the scanning spot relative to the desired track, and for supplying a corresponding control signal to the directing system, and a switching device means for causing the scanning spot to effect a jump-wise displacement from a track being followed to an adjacent track in response to a start signal, which switching device comprises a signal source means for supplying a control signal which is suitable for causing said jump-wise displacement to the directing system, which control signal consists of two consecutive signal periods of mutually substantially the same duration and substantially the same shape, but of opposite polarity, the improvement wherein the switching device includes a detection circuit means for detecting the instant at which the scanning spot is displaced half-way between two adjacent tracks during the jump-wise displacement and for at that instant supplying a detection signal to the signal source, and wherein said signal source means comprises means for supplying a control signal whose two signal periods have a duration which automatically substantially equals the time interval between the start signal and the detection signal.
Apparatus for reading a disc shaped record carrier on which information is recorded in optically coded form in tangentially extending tracks, said apparatus comprising a radiation source means for producing radiation, directing system means for focussing said radiation as a spot on a desired track, whereby the information in the track modulates the radiation, read detector means for converting the modulated radiation from the track into an electrical signal corresponding to said information, measuring detector means for measuring the radial position of the scanning spot relative to the desired track and for providing a corresponding radial control signal to the directing system means, switching device means responsive to a start signal for replacing the radial control signal with a track-jump control signal of an amplitude sufficient to cause the directing means to move the focussed radiation spot radially off the desired track towards an adjacent track, detection circuit means for detecting the instant that the radiaton spot is disposed halfway between the desired track and the adjacent track and for providing at that instant a detection signal to said switching device means, said switching device means further comprising means responsive to said detection signal for reversing the polarity of said track-jump signal, timing means for measuring the time period between said start signal and said detection signal and for providing a radial control restoring signal to said switching means at a time delayed from said start signal by substantially twice the period of time between said start signal and said detection signal, said switching means operating in response to said radial control restoring signal for substituting the radial control signal for said reverse polarity track-jump control signal.
Dependencies are inferred from the claim text.