| 摘要 |
PURPOSE:To contrive to stabilize focusing and tracking control at write and reproduction by providing an ultrasonic optical polarizer onto an optical axis of a reflected laser beam on an optical disk so as to adjust the luminous quantity of the diffracted light by means of the acoustooptic effect. CONSTITUTION:A laser beam radiated from a semiconductor laser 1 is led to the optical disk 9 by the optical disk 9 by the optical system and the information is recorded by the change in the beam quantity. The reflected beam of the disk 9 is added with a pulse power corresponding to the beam incremented luminous quantity of a modulation drive pulse of the laser 1 by the ultrasonic wave optical polarizer 14 and the result is a diffracted light with reduced luminous quantity. The diffracted light is collected by a condenser lens 16, made incident in a photodetector 12 and an information reproducing signal and a focusing and tracking error signal are detected. Thus, the stable focusing and tracking control is applied not only at reproduction but also at write. |
