Rotational velocity controlling system for information recording medium

Abstract

A control information generating circuit uses linear velocity information at a recording/reproduction position on an optical disc, which is obtained from an information recording medium by a synchronous signal cycle counter, and revolution number information, which is obtained from a rotation mechanism by a cycle counter of a frequency generator, to generate a piece of rotation control information, and the resultant information is supplied to a motor driving circuit. A variation detecting circuit generates a linear velocity abnormality detecting signal based on an abnormality detection result obtained by a division circuit, thereby preventing an abnormal operation of a spindle motor. With such a structure, switching of the control mode between CAV control mode and CLV control mode in a continuous recording/reproduction operation on an optical disc, or the like, is smoothly performed using one pierce of rotation control information. Furthermore, the disturbance in CLV control, which may occur due to a flaw on an information recording medium, or the like, is reduced.

Dependencies are inferred from the claim text.