Dynamic head position tracking control for a magnetic tape playback system

Details

Inventors: Oldershaw, Reginald W.; Hutson, John;
Assignee: Ampex Corporation (Redwood City, CA)
Primary Examiner: Faber; Alan
Assistant Examiner: Robertson; David L.
Attorney, Agent or Firm: LaBarre; James A., Almeida; George B., Lange; Richard P.

A dynamic head position tracking control for a magnetic tape playback system employs a detected dither signal to determine the elevational position of a pair of magnetic transducing heads relative to tracks of recorded information being scanned by the heads. This detection is carried out at several locations along the lengths of the tracks being scanned, and a value is stored for each of the locations. Based upon the stored information, an estimation is made of a position value for the first location along the length of the tracks. This estimation is determined from a weighted extrapolation of the following two samples taken during the scan of the track. The elevational position of the heads is then dynamically controlled in accordance with the actual and estimated head position values.

DETAILED DESCRIPTION What is claimed is: 1.
In a magnetic tape reproduction machine of the type in which information is stored on the tape in tracks and a magnetic transducing head is scanned along the length of each track to reproduce the stored information, apparatus for aligning the head with respect to the track, comprising: head elevation positioning means for moving the head in a direction that is transverse to the direction of a scanning movement; means for detecting the elevational position of the head relative to a track being scanned at plural locations along the length of the track, and storing a position value for at least some of said locations; means for estimating a position value for one of said locations on the basis of the stored position values for at least two locations adjacent said one location in the direction of scan of the tracks; and means for controlling said head elevation positioning means in response to said estimated value and said stored values during the scanning of a track to thereby position said head in accordance with a predicted shape for the track being scanned.
2.
The apparatus of claim 1 wherein said detecting and storing means includes means for generating a signal indicative of the elevational position of the head relative to a track of stored information, and plural sample and hold devices for sampling the value of said signal at respective times during the scan of a track and storing the sampled values.
3.
The apparatus of claim 2 wherein said estimating means includes means for generating an estimation signal having a value that is an extrapolation of the stored values for at least the two locations immediately adjacent said one location.
4.
The apparatus of claim 3 wherein said one location is the first sampled location along the length of a track and said two adjacent locations are the second and third locations along the length of the track.
5.
The apparatus of claim 3 wherein said estimation signal generating means includes a weighting function such that the stored value for the first location immediately adjacent said one location has a greater influence on said extrapolated value than the stored value for the next location adjacent said one location

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