| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a small and light-weight objective lens for optical disk which is satisfactorily achromatized over a wide wavelength range. <P>SOLUTION: The objective lens (PL) for optical disk includes a diffraction optical element including a positive lens (Lp) having a numerical aperture of 0.4 or more and having a first diffractive optical surface and a negative lens (Ln) having a second diffractive optical surface. One of the positive lens and the negative lens is formed of an optical material having a relatively high refractive index and low dispersion, and the other is formed of an optical material having a relatively low refractive index and high dispersion. The first diffractive optical surface and the second diffractive optical surface are arranged to face each other. <P>COPYRIGHT: (C)2009,JPO&INPIT |
