| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an objective lens for optical recording medium and an optical device using the objective lens in which different numerical apertures and converging functions corresponding to 2 optical recording media of different standard are provided despite that the device is compact and inexpensive without complicating the structure of the optical pickup device. <P>SOLUTION: The surface 16 of the objective lens 8 facing to a light source is aspherical and a diffractive optics face is formed thereon and a zone 14 for adjustment of the numerical aperture is provided. The diffractive optics face so functions that substantially parallel light is converged on the prescribed positions on both of the 2 optical recording media which use 2 different wavelength bands in a condition that aberration is excellently corrected. Further, the zone 14 is formed in a concave form with respect to the central part 15 of the objective lens, the light quantity of luminous flux at the outer circumferential part is apparently cancelled out for one of the wavelengths of light by an interference effect and the light quantity for the other wavelength of light is preserved, thus the numerical apertures are available corresponding to 2 optical recording media, respectively. <P>COPYRIGHT: (C)2004,JPO |
