| 摘要 |
PROBLEM TO BE SOLVED: To prevent the focusing control of an objective lens from becoming complication when an optical signal is recorded/reproduced by utilizing an evanescent wave. SOLUTION: When recording of an optical disk, etc., in the closest field is performed by using an objective lens 1 and an almost spherical lens 2 capable of generating an evanescent wave, a meniscus lens 3 is provided between the objective lens 1 and the almost spherical lens 2 and the relative position between the meniscus lens 3 and the almost spherical lens 2 is kept constant by a holding member 4. Consequently, since a numerical aperture of light made incident on the almost spherical lens 2 becomes larger than a numerical aperture when the meniscus lens is absent, an objective lens having a small numerical aperture is easily used. Thus, even when the relative position between a combined lens composed of the meniscus lens 3 and the almost spherical lens 2 and the objective lens 1 is changed, the wavefront aberration is not increased much and the focusing control of objective lens becomes easy. |
