SERVOMECHANISM FOR RECORDING AND/OR REPRODUCING APPARATUS USING A ROTATABLE RECORDING CARRIER

In a recording and/or reproducing apparatus having a rotated record carrier, for example, in the form of a disc, adapted to have video or other signals optically recorded in successive turns of a spiral track on a surface of the record disc, a recording and/or reproducing transducer or head assembly with an optical system including a movable lens for focusing a light beam at the disc surface and/or a movable mirror for deflecting the light beam so as to cause the latter to scan the track, and a servo system for detecting deviations from the proper focused and/or scanned conditions, for example, due to fluctuations of the rotated record disc in directions normal to, or in the plane of rotation thereof, and for correspondingly displacing the lens and/or mirror, respectively, so as to maintain the proper focused and scanned conditions; such servo system is provided with a gain-frequency characteristic having peaks at a fundamental frequency corresponding to the rotational speed of the record disc and at least at one harmonic of such fundamental frequency so as to improve the accuracy with which the servo system responds to fluctuations of the record disc for maintaining the proper focused and/or scanned condition.