Interactive servo control system for use with a rotating-head magnetic tape player

In a servo control apparatus for use with a magnetic tape recorder of the type in which a magnetic tape having slant recorded tracks thereon is moved past a rotating playback head for reproduction of an information signal therefrom,

• a. position sensing means overlapping first and second adjacent magnetic tracks for reproducing first and second signals from said first and second magnetic tracks respectively, said first and second signals having amplitudes corresponding to the amount of overlap between said position sensing means and said first and second adjacent tracks respectively;
• b. means cooperatively associating said position sensing means with said playback head for providing that said first and second signals have predetermined respective amplitudes when said playback head overlies a playback track in an aligned tracking position, said cooperatively associating means further adapted for providing that said position sensing means have a plurality of different positions overlapping said first and second adjacent tracks in correspondence with a plurality of different non-aligned tracking positions of said playback head with respect to said playback track, each said overlapping position providing first and second signals having respective amplitudes that uniquely correspond to each said non-aligned tracking position;
• and
• c. means responsive to changes in the amplitudes of said first and second signals for adjusting the movement of the tape whereby said playback head maintains said aligned tracking position, the improvement comprising:
• 1. means for separating a varying time base parameter from the information signal;
• 2. means for detecting the departure of said varying time base parameter from a reference time base and for providing a control signal indicative thereof;
• 3. means responsive to said control signal for altering the speed of rotation of the playback head and thereby altering both the time base of the information signal reproduced therefrom and the tracking position of the playback head, whereby the time base of the reproduced information signal approximates the time base of said reference;
• and
• 4. means interacting said responsive means and said position sensing means for readjusting the movement of the tape in response to a changed tracking position of the playback head, whereby said playback head maintains said aligned tracking position.

In a magnetic video tape player having a capstan servo for controlling the speed of a magnetic tape in accordance with a control signal obtained from the video information,

• a. a plurality of adjacent slanted recording tracks on said tape, separated by a guard band, and having synchronization information recorded thereon in accordance with a reference time base;
• b. a playback head mounted for rotation on a head wheel;
• c. sensing means also mounted for rotation on said head wheel for straddling adjacent slanted tracks whenever said playback head is substantially overlying a slanted playback track and for increasingly straddling one or the other said adjacent track when said playback head slips off said slanted playback track in one or the other direction, said sensing means adapted to reproduce a train of signals including a composite synchronizing component from said synchronizing information in each of said adjacent tracks, said component having a pair of amplitude parameters relatively determined by the degree of overlap between said sensing means and each of said adjacent tracks;
• and
• d. means responsive to said amplitude parameters of said composite synchronizing component for providing said control signal to said capstan servo.
• whereby the speed of the magnetic tape is so controlled that the playback head overlies each slanted recording track, the improvement comprising:
• 1. means connected to said playback head for detecting the time base of the reproduced video information and departures thereof from the reference time base;
• 2. head servo control means for regulating the speed of said head wheel;
• and
• 3. means responsive to said detecting means for providing a control signal to said head servo control means for regulating the speed of said head wheel,
• whereby the speed of the head wheel is so controlled that (1) the reproduced video information duplicates the reference time base, and (2) the resulting adjustment in head speed has a cooperative, interactive effect on said sensing means thereby causing the speed of the magnetic tape to be modified such that the playback head continues to overlie the slanted recording track.