| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an optical head device in which a high NA objective lens having large chromatic aberration is used, converging capability to an information recording surface of an optical disk is improved even though wavelength fluctuation of a light source is generated and the size and the weight are reduced. <P>SOLUTION: In a collimator lens 1 which is to be arranged for the optical head device, the shape of the cross section that goes through the optical axis of the lens 1 has a Fresnel lens shape, a dome shaped convex lens 14 is formed at the center region and a tooth-shaped diffraction grating 13 is formed in a concentric circular shape manner in the peripheral region surrounding the center region. The depth d of the tooth is set so that optical path length difference of air with respect to incident light beams becomes a integer multiple of the wavelength and the lens 1 is arranged in the optical path between the light source and the objective lens. <P>COPYRIGHT: (C)2004,JPO |
