| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a chromatic aberration correction coupling lens available at two or more wavelengths and having high light use efficiency. <P>SOLUTION: This coupling lens for chromatic aberration correction arranged on the light source side of an objective lens for converging luminous fluxes having a plurality of wavelengths on the information recording surface of an optical recording medium, and provided with a plurality of rings constituted of concentric steps around an optical axis in the surface of the objective lens side, has a wavelength of λ<SB>1</SB>=380 to 430 nm, a size d of the step satisfying λ<SB>1</SB>d=m<SB>1</SB>λ<SB>1</SB>/(n<SB>1</SB>-1) (m<SB>1</SB>is a real number, and n<SB>1</SB>is a refractive index of the coupling lens at wavelength λ1), and 9.9≤m<SB>1</SB>≤10.1 are established. <P>COPYRIGHT: (C)2008,JPO&INPIT |
