DISC DRIVE

摘要

A disc drive in which a disc recording medium having specified marks formed on the track at every specified distance is rotated by means of a spindle motor and the track is irradiated with laser light by means of a semiconductor laser. A signal detecting means detects a signal related to the specified mark based on the reflected light from the track, period of that signal is detected and power of the semiconductor laser is turned off if the difference between the detected period and a reference period is larger than a specified value. In a recorder/reproducer subjected to CLV control, a decision is made quickly whether rotational control of a disc is performed correctly or not regardless of the radial position of a pickup in order to protect data under an emergency state where the line speed of the disc is low.