| 摘要 |
<p>An optical pickup has a light source for generating a laser light, an objective lens for condensing the laser light to form a light spot so as to irradiate an optical disk formed of a substrate and having a pair of major surfaces spaced from each other by a thickness of the substrate and a recording face interposed between the major surfaces, and an actuator for moving the objective lens in a direction of the thickness of the optical disk within a total movable range so as to focus the light spot on either one of the recording face and the major surface. The total movable range of the objective lens is set to be equal to or more than a sum of an allowance range and an additional range. The allowance range is set to allow the objective lens to keep a constant distance between the objective lens and the recording face even when a level of the optical disk varies in the direction of the thickness. The additional range is set by dividing a gap between the major surface and the recording face of the optical disk by an absolute refraction index of the substrate of the optical disk. <IMAGE></p> |
