Hitachi Maxell, Limited

Hitachi, Ltd.

Other

Hitachi Maxwell, Ltd.

Yasuyuki Sugi

Takesuke Maruyama

Mitsuhiro Miyauchi

Yukio Fukui

Koichiro Wakabayashi

Yutaka Makino

Yoshiaki Minakawa

Masayuki Inoue

Shigeru Nakamura

Takeshi Shimano

Kunikazu Ohnishi

Shinji Fujita

Hidenori Shinohara

Toshio Sugiyama

Nobuo Imada

Mitsuhiko Ota

Keiko Hirao

Yoshikazu Mitsui

Mitsuru Ito

Yoshiaki Tachibana

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

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.

Optical pickup system, optical head, optical disk apparatus, and objective lens

When the DVD provided with the DVD substratehaving thickness tof 0.6 mm is installed in the optical disc apparatus, the light beamhaving wavelength &#x3bb;=655 nm is used as luminous flux of numerical aperture NA=0.63 to be condensed on the information surfaceon the DVD substrate. When the CD provided with the CD substratehaving thickness tof 1.2 mm is installed in the optical disc apparatus, the light beamhaving wavelength &#x3bb;=790 nm is effectively used as luminous flux of approximate numerical aperture NA=0.45 to be condensed on the information surfaceon the DVD substrate. The wavefront aberration caused by a thickness difference between the DVD substrateand CD substrateis canceled out by the chromatic aberration caused by a wavelength difference between the light beamsand. Therefore, in spite of the difference in the transparent substrates, the light beams are suitably condensed respectively on the information surfaceand

Objective lens design method, lens, and optical system, optical head, and optical disc apparatus using the same

An imaging lens unit comprising, in order from the object side, a first lens having a meniscus shape with its convex surface on the object side, an aperture stop and a second lens having a meniscus shape with its convex surface on the image side. A maximal value of a tangent angle within a range of a lens surface effective diameter of the surface on the object side of the first lens is 70 to 90 degrees. A maximal value of a tangent angle within a range of a lens surface effective diameter of the surface on the image side of the second lens is 70 to 90 degrees.

Imaging lens unit

An objective lens of this embodiment is used in an optical head in which a distance between a DVD laser and a CD laser is fixed. The objective lens focuses a laser beam emitted from the DVD laser on a DVD by a numerical aperture of 0.60, and focuses a laser beam emitted from the CD laser on a CD by an numerical aperture of 0.47. The wavefront aberration in design for CD is set greater than the wavefront aberration in design for DVD.

Objective lens, optical head, optical system, and design method for objective lens

When the DVD provided with the DVD substratehaving thickness tof 0.6 mm is installed in the optical disc apparatus, the light beamhaving wavelength &#x3bb;=655 nm is used as luminous flux of numerical aperture NA=0.63 to be condensed on the information surfaceon the DVD substrateWhen the CD provided with the CD substratehaving thickness tof 1.2 mm is installed in the optical disc apparatus, the light beamhaving wavelength &#x3bb;=790 nm is effectively used as luminous flux of approximate numerical aperture NA=0.45 to be condensed on the information surfaceon the DVD substrateThe wavefront aberration caused by a thickness difference between the DVD substrateand CD substrateis canceled out by the chromatic aberration caused by a wavelength difference between the light beamsandTherefore, in spite of the difference in the transparent substrates, the light beams are suitably condensed respectively on the information surfaceand

The multi-wavelength lens for condensing a plurality of kinds of monochromatic light by refraction is disclosed. The lens comprises a common use area for all monochromatic light on at least one lens surface, the area sectioned into a plurality of aspherical zones each of which having a different refractive power; and step portions, each of which formed between adjacent aspherical zones of the plurality of aspherical zones and having a step height Dj (j=1,2,3,4, and so on, in order of closeness to a lens optical axis) in a direction parallel to the lens optical axis. At least half of the step portions satisfy a following formula when a minimum value and a maximum value of Aij for each wavelength &#x3bb;i are MIN(Aij) and MAX(Aij), respectively:MAX()/MIN()&#x3c;3where, Aij=absolute(Bij&#x2212;mij),Bij=(absolute(Dj))*(ni&#x2212;1)/&#x3bb;i&#x2212;C, ni is a refractive index of a lens for a wavelength &#x3bb;i, mij is an integral number closest to Bij, and C is a corrective term.

Multi-wavelength lens, and optical system, optical head and optical disc apparatus using the lens

When the DVD provided with the DVD substrate having thickness t of 0.6 mm is installed in the optical disc apparatus, the light beam having wavelength &lgr; &equals;655 nm is used as luminous flux of numerical aperture NA&equals;0.63 to be condensed on the information surface on the DVD substrate . When the CD provided with the CD substrate having thickness t of 1.2 mm is installed in the optical disc apparatus, the light beam having wavelength &lgr; &equals;790 nm is effectively used as luminous flux of approximate numerical aperture NA&equals;0.45 to be condensed on the information surface on the DVD substrate . The wavefront aberration caused by a thickness difference between the DVD substrate and CD substrate is canceled out by the chromatic aberration caused by a wavelength difference between the light beams and . Therefore, in spite of the difference in the transparent substrates, the light beams are suitably condensed respectively on the information surface and

An optical detector for detecting at least three optical beams reflected by an optical information recording medium and outputting an electric signal, the optical detector having three light receiving areas each of which receives a respective one of the three optical beams and each of which has four light receiving surfaces, twelve signal lines to transmit an electric signal obtained on respective ones of the four light receiving surfaces of the three light receiving areas, selected ones of the twelve signal lines connected to the four light receiving surfaces of different ones of the three light receiving areas being joined together within the optical detector, and less than nine signal output lines formed by joining the selected ones of the twelve signal lines extend from the optical detector to a signal processing circuit.

Growing community of inventors

Ibaraki, Japan

Yasuyuki Sugi