Optical pickup device

Abstract

Abstract PURPOSE:To realize a stable servo operation with a simple constitution by irradiating the reflected beams sent from a disk to a detector which is divided into two parts in the direction corresponding at least to the radius direction and irradiating only a prescribed range at the center part of the reflected beam to the detector. CONSTITUTION:A mask 5C is provided at the peripheral parts of photodetecting parts 5A and 5B of an optical detector 5. The reflected beams are divided right and left by diffraction. When the parts 5A and 5B are reduced, the necessary detection signals are also reduced. In this connection, the diameter ratio between parts 5A and 5B is reduced to the reflected beam in order to reduce relatively the level fluctuation. However, the degree of improvement is saturated at a certain level (about <=0.6) or less. Therefore the diameters of parts 5A and 5B is set by the mask 5C at about <=0.6 of the diameter of the reflected beam and at a value large enough to detect the reflected beam. As a result, the unbalanced detection output due to a shift of an objective lens can be avoided. Then this balanced detection output is used to ensure a stable servo operation.

Inventors

• 👤 Mikio Sugiki
• 👤 美喜雄 杉木

Bibliographic Details