Automatic scan tracking servo system

In a magnetic tape recording and/or reproducing apparatus of the type which has a tape guide drum around which tape is wrapped, at least one rotatable transducing head mounted to an element that is movable along a path generally transverse to the longitudinal orientation of tracks of video information recorded on the tape, a servo system for controlling the movement of the element to accurately follow a track during reproducing and to selectively reposition the element to reproduce a desired track subsequently upon completion of the reproducing of a track, said system comprising:

• drive means for controlling the movement of the element along said path;
• means operatively connected to said drive means for causing the same to impart oscillatory dither movement to the element;
• means for receiving a video signal reproduced by the reproducing head and for detecting the amplitude of a component of the reproduced signal related to the oscillatory movement;
• a microprocessor;
• and
• means for generating interrupt pulses to cause said microprocessor to sample the detected amplitude component at a predetermined number of locations relative to each track and to generate error correcting signals in response to the samples for application to said drive means, said microprocessor controlling the phase of the oscillatory movement causing means to thereby synchronize the sampling and the oscillatory movement to one another.