Servomechanism for disc player

Servo apparatus for use in positioning a magnetic playback head from a first generally circular information-bearing track of a rotatable magnetic disc to a second generally circular information-bearing track thereof, said tracks being susceptible to undesirable eccentricity therein, comprising

• (a) means for isolating and storing the approximately smallest signal amplitude produced by said magnetic head during each successive rotation of said disc, thereby to provide playback signals that are essentially immune to the effects of track eccentricity,
• (b) means for establishing a threshold signal amplitude,
• (c) first signal comparing means for comparing each said isolated signal amplitude with said threshold signal amplitude,
• (d) means responsive to the output of said first signal comparing means for moving said head in a given direction from said first track toward said second track when the output of said first signal comparing means is of a first sense, thereby to cause the output of said first signal comparing means eventually to be of a second sense, and for thereafter moving said head in that same given direction towards said second track when the output of said first signal comparing means has said second sense, and
• (e) second signal comparing means cooperative with said means for isolating for comparing successive isolated signal amplitudes,
• said means responsive to the output of said first signal comparing means being further responsive to the output of said second signal comparing means for further moving said head in said given direction when the output of said second signal comparing means has a first sense and for interrupting the positioning of said head when the output of said second signal comparing means is of a second sense.

Servo apparatus for use in positioning a magnetic playback head from a first generally circular track of a rotatable magnetic disc to either a more inwardly or a more outwardly disposed second track of said disc, said tracks being susceptible to undesired eccentricity therein, comprising

• (a) means for producing a control signal for signifying whether said head is to be positioned from said first track to said more inwardly or said more outwardly disposed second track,
• (b) means for isolating and storing the smallest signal amplitude produced by said magnetic head during each successive rotation of said disc, thereby to provide playback signals that are immune to the effects of track eccentricity,
• (c) means for establishing a threshold signal amplitude,
• (d) first signal comparing means for comparing each said isolated signal amplitude with said threshold signal amplitude,
• (e) means for receiving said control signal and the output of said first signal comparing means for moving, under directional control of said control signal, said head in a given direction from said first track toward said second track when the output of said first signal comparing means is of a first sense, and for thereafter moving said head in that same given direction toward said second track when the output of said first signal comparing means has a second sense, and
• (f) second signal comparing means cooperative with said means for isolating for comparing successive isolated signal amplitudes,
• said means for receiving said control signal and the output of said first signal comparing means further receiving the output of said second signal comparing means for further moving said head in said given direction when the output of said second signal comparing means is of a first sense and for interrupting the positioning of said head when the output of said second signal comparing means is of a second sense.