| 摘要 |
PURPOSE:To accurately detect reflected light from an optical recording medium by making a means varying the diameter of the aperture of an objective lens and the objective lens an integrated type and constituting to move them simultaneously by an objective lens actuator. CONSTITUTION:A laser power control signal corrected in accordance with the transmission efficiency of a light beam decided by the magnitude of the aperture of a means 4 changing the diameter of the aperture of the objective lens is inputted to a laser driving circuit 18 from a laser power control part 17. Thus, since the optical power of a light source 7 is changed in accordance with the transmission efficiency of the light beam decided by the magnitude of the aperture of the means 4 changing the diameter of the aperture of the objective lens, the optical power irradiating the optical recording medium 2 is made constant when the various kinds of the optical recording medium 1 with different recording density are recorded and reproduced by changing the diameter of the aperture of the objective lens. |
