POSITIONING METHOD OF OPTICAL DISC

PURPOSE:To extend the continuous track following-up range of an optical beam after positioning by setting always an extent of movement of a head in the circumferential outward direction to a position in the outside of a target position to position always the head to a target track in the circumferential inward direction with the optical axis tip control. CONSTITUTION:The current position of an optical head mechanism part is track number 1, and the movement target position is track number 100. In this case, a subtracting circuit 7 outputs difference ''99'' and a moving signal, which indicates the movement direction of the mechanism part in accordance with the sign of this difference, on a basis of both positions. Number ''99'' of traversed track pitches (a) and a number (n) of track pitches (a) are inputted to an adding circuit 8 and a subtracting circuit 9 simultaneously to obtain 99+n and 99-n. An MPX 11 takes out number 99+n(99+a') of traversed pitches in the circumferential outward direction in accordance with the movement direction signal by said data and the subtracting circuit 7 and stores it in a register 11. An actuator control part takes out this data to move an actuator. At this time, an object lens is in the neutral state. After this movement, the mechanism part moves the object lens for a minute length a' in the circumferential inward direction to place it in the target position.