US 4,234,837 A · Digital center tracking system

Abstract

A digital servo system for maintaining a detection device, such as a reading beam, as nearly as possible centered with respect to an information track, such as an optical track on a video recording disc. In each of the embodiments disclosed, circuitry is provided to process a signal obtained from the reading beam, to obtain timing signals indicative of transitions of the beam across noncentral switching lines parallel with the track. In one embodiment, a constant-magnitude acceleration signal is applied to a beam position transducer, and is reversed in polarity each time a switching line is crossed after first crossing the centerline. In another embodiment, the polarity of the constant-magnitude acceleration signal is reversed after crossing a switching line a second time and after applying an additional acceleration impulse of relatively short duration. In a third embodiment, an acceleration impulse is initiated when the beam reaches a switching line, and the beam moves at essentially constant velocity when not subject to an acceleration pulse.

Claims17

Dependent claims

A digital servo control system for controlling the position of a detection means with respect to an information track, said system comprising:

first transducer means for moving the detection means transversely with respect to the information track;
second transducer means for deriving an information signal from the detection means;
means for filtering the information signal to obtain an error signal indicative of the position of the detection means with respect to the track centerline;
signal processing means, for processing the error signal to obtain a timing signal indicative of transitions of the detection means through non-central parallel switching lines located at preselected distances from the track centerline;
and
control means, responsive to the timing signal, for controlling the polarity and duration of an acceleration signal applied to said first transducer means to accelerate the detection means toward a corrected position, whereby the detection means is accelerated in alternating directions and oscillates about the track centerline.

3 more elements

A digital servo control system for controlling the position of a reading beam used to derive information from a recording track on a disc, said system comprising:

beam position transducer means for moving the beam transversely with respect to the information track;
detection transducer means for deriving an information signal from the beam;
means for filtering the information signal to obtain an error signal indicative of the beam position with respect to the track centerline;
signal processing means, for processing the error signal to obtain a timing signal indicative of transitions of the beam through non-central parallel switching lines located at preselected distances from the track centerline;
and
control means, responsive to the timing signal, for controlling the polarity and duration of an acceleration signal applied to said beam position transducer means to accelerate the beam toward a corrected position, whereby the beam is accelerated in alternating directions and oscillates about the track centerline.

3 more elements

A method for controlling the position of a detection means with respect to an information track, said method comprising the steps of:

deriving an information signal from the detection means;
filtering the information signal to obtain an error signal indicative of the position of the detection means with respect to the track centerline;
processing the error signal to obtain a timing signal indicative of transitions of the detection means through non-central parallel switching lines located at preselected distances from the track centerline;
generating an acceleration signal for application to the detection means, said generating step including the step of controlling the polarity and duration of the acceleration signal in accordance with the timing signal;
and
applying the resulting acceleration signal to the detection means, to move it in an oscillatory fashion about the track centerline.

3 more elements

Dependencies are inferred from the claim text.

Digital center tracking system

Life of this patent

Digital center tracking system

Life of this patent

Abstract

Claims17