| 摘要 |
PROBLEM TO BE SOLVED: To perform high density recording by moving an objective lens having a specified numerical aperture and a beam spot of a light beam converged with the objective lens, making the beam spot arrive at a prescribed position of an optical disk and detecting a reflection beam obtained from the optical disk. SOLUTION: The numerical aperture of the objective lens converging the light beam is made 0.45-0.55. A laser beam is converted to a parallel beam, and transmits through a beam splitter having a polarization property, and is converted from linear polarization to circular polarization to be made incident on the objective lens 43. The laser beam is led to the objective lens, and is converged to be emitted to the optical disk D, and the reflection beam from the optical disk D runs oppositely on this optical path, and is converted again to the linear polarization in an optical part 22 to arrive at the beam splitter. A part of the reflection beam is led to a prescribed photosensitive part, and is photoelectric converted, and an information signal is obtained, and it controls so that deviation in the radial direction between the beam spot converged by the objective lens 43 and a track center on the optical disk D is reduced. |
