| 摘要 |
PROBLEM TO BE SOLVED: To easily constitute an objective lens capable of recording and reproducing optical recording media different in thickness by one lens by noticing the characteristic of the bonded surface of a lens and obtaining the existence of the design parameter of the lens that the change directions of spherical aberration are opposite to each other in accordance with the user conditions of the respective optical recording media having the different thickness. SOLUTION: The bonded surface is made convex to a light source side, the refractive index of the lens 2 on the light source side of the bonded surface to light having wavelength λ1 is made larger than that of the lens 1 on the optical recording medium side, and the refractive index of the lens 2 on the light source side of the bonded surface to light having wavelength λ2 is made smaller than that of the lens 1 on the optical recording medium side, thus the bonded surface has negative refractive power to the light having the wavelength λ1 and positive refractive power to the light of the wavelength λ2, respectively. Then, the bonded surface becomes the one having the design parameter of the lens that the change directions of the spherical aberration are opposite to each other between the use conditions of a thick disk and a thin disk. |
