| 摘要 |
PROBLEM TO BE SOLVED: To prevent a variation in the diameter of a beam which is made incident to an objective lens even when a relay lens is moved in order to compensate the spherical aberration occurred due to the error in the thickness of an optical disk base plate. SOLUTION: The optical disk device is provided with a laser source which emits a light beam, an optical disk which has a recording and reproducing face and a transparent base plate on the surface, an objective lens which condenses the light beam on the optical disk, a relay lens system composed of one or more lenses inserted between the laser source and the objective lens, a means which moves one or more lenses among the relay lens system in the optical axis direction in order to compensate the spherical aberration according to the thickness of the transparent base plate of the optical disk and a means which keeps the diameter of incident light to the objective lens when one or more lenses of the relay lens move. |
