| 摘要 |
PROBLEM TO BE SOLVED: To improve the accuracy of recording and reproducing by simultaneously executing the change of numerical aperture and the correction of aberrations of an objective lens with an aperture varying means and an aberration correcting means. SOLUTION: The light from a semiconductor laser 2 is made incident on the objective lens 10 via an aperture and aberration variable element 3 capable of changing the aperture and aberration as the aperture varying means and the aberration correcting means, by which the writing and reading out of the information signals at the points irradiated and converged with the laser beam on an optical disk 1a or 1b are executed. The return light from the recording surface heads toward a photodetector 11. The element 3 has piezoelectric elements 6a to 6d and an annular elastic supporting body 7 between a transparent plate 4 and a thin glass sheet 5. A housing part 7a is filled with an electrolyte prepd. by melting AgBr. A toric transparent electrode 8 precipitates Ag atop the electrode 8 by current supply. The region shields the light and electrochemically changes the numerical aperture. |
