Automatic tracking method and apparatus for rotary scan tape transport

Claim 1

An automatic tracking control circuit for a transverse scan tape transport which includes a capstan drive for longitudinal translation of magnetic tape and a rotary magnetic head rotating in a path angulated with respect to said tape for reading tracks of prerecorded video information and said transport being equipped with an audio head for reading a prerecorded longitudinal audio track on said tape, wherein said circuit comprises; an electrical signal source issuing a periodically varying electrical signal of a frequency substantially less than a lower frequency limit of said prerecorded video information and being equal to or less than low frequency limit of the audio track bandwidth, said source being connected to said capstan drive for periodically varying the translation speed of said tape; comparator means having inputs coupled to said source and said rotary magnetic head for detecting frequency and phase correspondence of signals issued therefrom; an amplitude detector and filter serially connected between and coupling said rotary magnetic head to an input of said comparator means, said amplitude detector having a frequency sensitivity below said lower frequency limit of said video information and said filter passing signals at the frequency of said source signal such that the signal received at said comparator from said magnetic head represents certain frequency components of the envelope of prerecorded information as modulated by the varying translation of said tape; and feedback circuit means connected between said comparator means and said capstan drive and being responsive to the frequency and phase correspondence of the signals from said source and comparator means to issue control signals to said capstan drive for adjusting the translation of said tape to maintain optimum registration between said head assembly and said prerecorded video information tracks.

Claim 4

A method of maintaining optimum playback tracking between the rotary magnetic head of a rotary transverse scan tape transport and the prerecorded transverse tracks on the tape wherein the information on said prerecorded transverse tracks has a known frequency range, and said transport includes a stationary magnetic head for reproducing a longitudinal audio frequency track on said tape, comprising: moving the tape at a desired average translation speed and varying such speed at a frequency substantially below said known frequency range of said prerecorded transverse track information and at a frequency at or below the low frequency limit of the audio frequency and at an amplitude such that the rotary head vacilates about a center line of said transverse tracks; detecting an amplitude modulation of the playback signal from said rotary head caused by the varying tape speed; comparing the frequency, amplitude, and phase relationship between a signal drive from said detecting step and signal representing the varying tape speed; and adjusting the tape translation in an amount and direction dictated by said amplitude and phase relationship as provided by said comparing step to bring said tracks into optimum tracking registration with said rotary head.

Claim 5

A method of maintaining optimum playback tracking between the rotary magnetic head of a rotary transverse scan tape transport and the prerecorded transverse tracks on the tape wherein the information on said prerecorded transverse tracks has a known frequency range, and said transport includes a stationary magnetic head for reproducing a longitudinal audio frequency track on said tape, comprising: moving the tape at a desired average translation speed and varying such speed at a frequency substantially below said known frequency range of said prerecorded transverse track information and at a frequency at or below the low frequency limit of the audio frequency and at an amplitude such that the rotary head vacilates about a center line of said transverse tracks; detecting an amplitude modulation of the playback signal from said rotary head caused by the varying tape speed; comparing the frequency, amplitude, and phase relationship between a signal drive from said detecting step and signal representing the varying tape speed; and adjusting the tape translation in an amount and direction dictated by said amplitude and phase relationship as provided by said comparing step to bring said tracks into optimum tracking registration with said rotary head.