Hitachi Maxell, Limited

Hitachi Maxwell, Ltd.

Mitsuhiro Miyauchi

Yasuyuki Sugi

Koichiro Wakabayashi

Yutaka Makino

Yoshikazu Mitsui

Keiko Hirao

Mitsuru Ito

Koji Maezawa

Yoshiaki Minakawa

Aya Morishima

Naofumi Ueda

An object of the invention is to provide a plastic objective lens having a good lens tilt property in both thicknesses of a two-layer disc in a used temperature range even in the plastic objective lens in which a numerical aperture (NA) is equal to or higher than 0.81, while dissolving the problem mentioned above. The objective lens includes a point at which a third order comma aberration amount generated at a time of a lens tilt of the objective lens becomes equal to a third order comma aberration amount generated at a time when a disc is tilted at the same angle amount as the lens tilt angle, in a transparent board thickness which is thicker than a larger thickness of the two-layer transparent board under a room temperature (25&#xb1;3&#xb0; C.).

Objective lens

A pickup lens with a phase compensator is composed of a condenser lens and a phase compensator. At least one surface of the condenser lens has a step-like annular zone structure to compensate wavefront aberration generated when recording and reproducing data on an information recording medium having a substrate thickness of twith a laser beam having a wavelength &#x3bb;and wavefront aberration generated when recording and reproducing data on an information recording medium having a substrate thickness of twith a laser beam having a wavelength &#x3bb;. The phase compensator compensates wavefront aberration generated when recording and reproducing data on an information recording medium having a substrate thickness of twith a laser beam having a wavelength &#x3bb;

Pickup lens with phase compensator and optical pickup apparatus using the same

A coupling lens for chromatic aberration correction is placed between a light source and an objective lens for focusing light beams with a plurality of wavelengths on an information recording surface of an optical recording medium, and at least one surface of the coupling lens includes a plurality of annular zones having a step concentric with an optical axis. The coupling lens is designed so that when a wavelength &#x3bb;=380 to 430 nm and a height of the step is d=m&#x3bb;/(n&#x2212;1) where mis an actual number and nis a refractive index of the coupling lens at the wavelength &#x3bb;, 9.9&#x2266;m&#x2266;10.1 is satisfied.

Coupling lens and optical pickup device

An optical pickup lens focuses laser beams having different wavelengths &#x3bb;and &#x3bb;on at least three kinds of optical discs. At least one side of the optical pickup lens has a concentric loop zonal structure for compensating wavefront aberration occurring when recording or reproducing an optical disc having a substrate thickness tby the laser beam having the wavelength &#x3bb;and wavefront aberration occurring when recording or reproducing an optical disc having a substrate thickness tby the laser beam having the wavelength &#x3bb;. When recording or reproducing an optical disc having a substrate thickness tby the laser beam having the wavelength &#x3bb;, a phase difference given to the laser beam having the wavelength &#x3bb;due to the concentric loop zonal structure is about 0.15&#x3bb; or smaller.

Optical pickup lens and optical pickup apparatus

An optical pickup system for reading information of three kinds of optical recording media. The optical pickup system has a wavelength selective filter that includes an outer area for shielding one light beam of light beams having three kinds of wavelengths and an inner area for allowing all the light beams to pass through. The optical pickup system also has an objective lens that focuses each light beam having passed through the wavelength selective filter on each light recording medium. An optical head and an optical disk apparatus have the optical pickup system.

Growing community of inventors

Ibaraki, Japan

Mitsuhiro Miyauchi