| 摘要 |
PURPOSE:To simplify the moving structure of an objective lens by pressing the objective lens radially so as to change the curvature of the surfaced so as to change the focal length thereby controlling the system so as to bring the focus on a recording medium. CONSTITUTION:A lens holder 19 has a cylindrical lens holder main body 19a and a lens pressing member 19 having a thick tours shape with a piezoelectric element whose outer periphery is fixed to the inner periphery of the lens holder main body 19a and whose inner periphery is fixed to the outer periphery of the objective lens 18. A lens pressing means 15 presses the objective lens 18 radially in response to the focusing error signal to change the curvature of the surface of the objective lens 18 thereby changing the focal length of the objective lens 18 and bringing the focus onto a recording medium. Thus, the focusing control structure is simplified and the constitution of the objective lens actuator 15 is made simple and the number of components is decreased to attain small size, cheapness and the improvement of the reliability. |
