SPINDLE SERVO MECHANISM HAVING FIXED LINEAR VELOCITY

摘要

PURPOSE:To obtain required response characteristics over the inner and outer peripheries of a track and to reduce the unevenness of a linear velocity by compensating the transmission function of a servo in accordance with the revolving radius position of the track read out at a fixed linear velocity on a recording medium. CONSTITUTION:Sound signals on a track which are successively read out by a pickup P are applied to an error detecting circuit 4 through a clock extracting circuit 1 and a signal obtained by multiplying the error signal SE by a turning radius signal Sr is applied to a driving circuit 6. The signal Sr is obtained by converting the number of pulses from a motor M by a counter circuit 11 and the driving circuit 6 controls the motor M at its revolution. Consequently, the gain or phase is compensated in accordance with the turning radius direction of a disc D, servo stability and required response characteristics are obtained over the inner and outer peripheries of the track and the performance having a fixed linear velocity free from linear velocity unevenness due to the eccentricity or warp from the recording medium can be attained.