Search operation control apparatus in an optical disc reader

Abstract

A search operation control apparatus in an optical disc reader searches a desired position on an optical disc which is controllably rotated at a constant linear velocity and has its information pits arranged in a segmental spiral, in response to a search command which includes information of the desired position. The apparatus has an optical pickup, an optical-pickup moving controller, and an optical-disc driving controller. The optical-pickup moving controller controllably moves the optical pickup from a current position to a desired position at high speed when it receives a search command. The optical-disc driving controller controllably drives the optical disc during an acceleration/deceleration control timing, and a free-run or constant-run time. During the high-speed translation of the optical pickup, spindle servocontrol to the optical disc is not executed, but the acceleration/deceleration control process and the free-run or constant-run control process are executed. The acceleration/deceleration control process is carried out during the interval which is required to change the rotation speed of the optical disc from that of the current position of the optical pickup to that of the desired position. After the acceleration/deceleration control process, the free-run or constant-run control process is carried out during the interval which is calculated by substracting the acceleration/deceleration control timing from the total translation time of the optical pickup.