Automatically compensated movable head servo circuit and method

Abstract

In an apparatus for automatically maintaining a transducing head assembly on the proper track, which is particularly adapted for a helical scan recording and/or reproducing apparatus capable of providing special motion effects, an automatically compensated movable head servo is disclosed. The apparatus is of the type which utilizes transverse positioning of the transducing head assembly to accurately follow a track during reproducing and, at the completion of the reproduction from the track, to properly position the head in position to either reproduce the next adjacent successive track, reproduce the same track or reproduce another track so that the appropriate special motion effect is achieved. Proper tracking is maintained by applying a small oscillatory motion to the head to cause it to vibrate laterally of the track, examining the resulting modulation of the reproduced signal's envelope to generate a tracking error correction signal and applying the error correction signal to the head assembly. The reference signal employed in the generation of the tracking error correction signal is automatically phase synchronized in response to the head vibrations to correct errors introduced to the tracking error signal as a result of phase changes introduced to the modulation of the reproduced signal's envelope by effects other than mistracking by the head.