Hoya Corporation

Pentax Corporation

Asahi Kogaku Kogyo Kabushiki Kaisha

Other

Hitachi, Ltd.

Pioneer Corporation

Shuichi Takeuchi

Daisuke Koreeda

Koichi Maruyama

Satoshi Inoue

Naoki Yamagata

Yoshiyuki Tashiro

Yutaka Takakubo

Takeshi Shimano

Takashi Iizuka

Kazuo Shigematsu

Junji Kamikubo

Katsuhiro Koike

Naohito Sasaki

Tetsuo Ariyoshi

Kenzo Yamanaka

An objective optical system for information recording/reproducing, at least one of optical surfaces of the objective optical system comprising a diffraction surface including a first region contributing to converging first, second and third beams and including a diffraction structure formed such that use diffraction orders for the first, second and third beams are 1st-orders and a condition 0.03&#x3c;(&#x3bb;B&#x2212;&#x3bb;1)/&#x3bb;1&#x3c;0.40 is satisfied; a second region contributing to converging only the first and second beams and including a diffraction structure formed such that the use diffraction orders are 1st-orders and a condition: &#x2212;0.35&#x3c;(&#x3bb;B&#x2212;&#x3bb;B)/&#x3bb;1&#x3c;0.35 is satisfied; and a third region contributing to converging only the first beam and including a diffraction structure formed such that the use diffraction order for the first beam is an odd order and a condition: &#x2212;0.23&#x3c;m((&#x3bb;B&#x2212;&#x3bb;1)/&#x3bb;1)&#x3c;0.23 is satisfied.

Optical information recording/reproducing apparatus and objective optical system for the same

A method for adjusting a tilt angle of an objective lens with respect to one of a multilayer optical disc having a plurality of recording layers and an optical axis of an optical information recording/reproducing apparatus, wherein a use wavelength &#x3bb; and a numerical aperture NA are defined by conditions: 390&#x3c;&#x3bb;&#x3c;420 and 0.75&#x3c;NA&#x3c;0.90. The method includes determining the tilt angle of the objective lens such that a spot quality defined through a predetermined transparent parallel flat plate matches a predetermined standard, and tilting the objective lens to have the determined tilt angle. When t1 represents a thickness of the predetermined transparent parallel flat plate and t2 represents a design protective layer thickness at which a coma caused when off-axis light is incident on the objective lens becomes smallest, t1 and t2 satisfy: &#x2212;0.015&#x3c;t1&#x2212;t2&#x3c;0.005.

Tilt angle adjustment method for objective lens and optical information recording/reproducing apparatus

An objective optical system for information recording/reproducing, at least one of optical surfaces of the objective optical system comprising a diffraction surface including a first region contributing to converging first, second and third beams and including a diffraction structure formed such that use diffraction orders for the first, second and third beams are 1st-orders and a condition 0.03&#x3c;(&#x3bb;B)/&#x3bb;&#x3c;0.40 is satisfied; a second region contributing to converging only the first and second beams and including a diffraction structure formed such that the use diffraction orders are 1st-orders and a condition: &#x2212;0.35&#x3c;(&#x3bb;B&#x2212;&#x3bb;B)/&#x3bb;&#x3c;0.35 is satisfied; and a third region contributing to converging only the first beam and including a diffraction structure formed such that the use diffraction order for the first beam is an odd order and a condition: &#x2212;0.23&#x3c;m&#xd7;((&#x3bb;B)/&#x3bb;)&#x3c;0.23 is satisfied.

An objective optical system for an optical information recording/reproducing apparatus, at least one surface of the objective optical system being configured to be a phase shift surface having a phase shift structure, wherein: the phase shift surface has a first area contributing to converging first, second and third light beams onto recording surfaces of first, second and third optical discs, respectively; in the first area, the phase shift surface has at least two types of phase shift structures including a first phase shift structure having first steps and a second phase shift structure having second steps; the phase shift surface has a plurality of combinations of annular zones which satisfy a condition:0.95&#x3c;1/2&#x3c;1.05&#x2003;&#x2003;(1), andthe phase shift surface satisfies a following condition:&#x2212;3.00&#x3c;&#x394;&#x3c6;1/&#x394;&#x3c6;2&#x3c;&#x2212;0.10&#x2003;&#x2003;(2).

An optical information recording/reproducing apparatus for an optical disc using a light beam having a wavelength of &#x3bb; including: an objective lens that converges the light beam onto a recording surface of the optical disc and satisfies a condition: 

Objective lens and optical information recording/reproducing apparatus

There is provided an objective lens for information recording/reproducing for three types of optical discs, which includes a first area contributing to converging a third light beam onto a record surface of a third optical disc. The first area includes a phase shift structure having refractive surface zones concentrically formed about a predetermined axis. The phase shift structure includes first and second step groups. The first step group is configured such that an optical path length difference &#x394;OPD(nm) given by each step of the first step group to a first light beam satisfies a condition: 2N+1.10&#x3c;|&#x394;OPD/&#x3bb;1|&#x3c;2N+1.40, where Nis an integer or zero, and the second step group is configured such that an optical path length difference &#x394;OPD(nm) given by each step of the second step group to the first light beam satisfies a condition: 2N&#x2212;0.10&#x3c;|&#x394;OPD/&#x3bb;1|&#x3c;2N+0.10, where Nis an integer.

Objective lens and optical information recording/reproducing device having the same

An objective lens for an optical information recording/reproducing apparatus, at least one of optical surfaces of the objective lens comprising a diffraction surface having a diffraction structure defined by an optical path difference function, and wherein: the diffraction surface has a first region contributing to converging first and second light beams and having a diffraction structure configured such that diffraction orders at which the diffraction efficiencies are maximized for the first and second light beams are 1order; the diffraction surface has a second region located outside the first region, and the second region is configured to contribute to converging the first light beam and not to contribute to convergence of the second light beam; and the objective lens satisfies a condition:35&#x3c;2&#xd7;2&#x3c;200 &#x2003;&#x2003;(1).

Optical information recording/reproducing apparatus and objective lens for the same

There is provided an optical disc drive, which includes a light source emitting a light beam, a beam dividing element that divides the light beam into main and sub-beams, an objective lens, an astigmatism producing unit that gives astigmatism to the main and sub-beams, a signal generation unit that has sensors for the beams and generates a focus error signal based on output signals of the sensors; and an optical element that has a function of adjusting intensity distribution of the main beam such that the main beam incident on the optical disc has a predetermined intensity distribution where a maximum intensity level is positioned at a predetermined height within a range of 70% of a pupil diameter, the predetermined height is not equal to an optical axis, and an intensity of the main beam decreases gradually from the predetermined height to a peripheral portion of the pupil.

Optical disc drive having a mechanism to reduce the noise level of a focus error signal

There is provided an objective lens for an optical pick-up. The objective lens is formed to be a single-element plastic lens having a first surface and a second surface. The first surface is configured to have, within an effective diameter, an inflection point at which a second derivative of a sag of the first surface takes a value of 0. Further, the objective lens having a numerical aperture larger than or equal to 0.75.

Objective lens for optical pick-up

An objective optical system for an optical information recording/reproducing apparatus for recording/reproducing for first, second and third optical discs by selectively using three types of substantially collimated light beams including first, second and third light beams respectively having first, second and third wavelengths, wherein at least one of optical surfaces of the objective optical system comprises a diffraction surface having a diffraction structure, the diffraction surface includes a first region defined by first and second optical path difference functions, a second region defined by at least one type of optical path difference function, and a third region defined by at least one type of optical path difference function, the first region satisfies a condition:&#x2212;0.15&#x3c;1/&#x3c;&#x2212;0.03&#x2003;&#x2003;(1),

An objective lens including: a first region to respectively converge first and second light beams onto recording surfaces of first and second optical discs; and a second region located outside of the first region and configured to converge the first light beam onto the recording surface of the first optical disc and not to converge the second light beam onto the recording surface of each of the first and second optical discs, and wherein the first region is divided into a plurality of refractive surface zones concentrically formed about an optical axis and has a first step, a diffraction order at which a diffraction efficiency is maximized for each of the first and second light beams passing through the first step in the first region is a first order, and the objective lens satisfies a condition:0.80&#x3c;((out&#x2212;)/out)/&#x3b7;in&#x3c;1.45&#x2003;&#x2003;(1).

There is provided an objective lens for an optical pick-up. The objective lens includes a first surface on a light source side, and a second surface on an optical disc side. The first surface has a convex shape. The objective lens is formed to be a single-element lens having a numerical aperture of 0.75 or more. In this configuration, the objective lens satisfies a condition:0.95&#x3c;(&#x2212;1)&#xb7;tan &#x3b8;&#x3c;1.50&#x2003;&#x2003;(1)

An optical system of an optical pick-up including a resin coupling lens and a resin objective lens with NA larger than 0.8, wherein, magnification &#x3b2; satisfies a condition: &#x2212;0.13&#x3c;&#x3b2;&#x3c;&#x2212;0.08, a focal length f of the objective lens satisfies a condition: 1.15&#x3c;f&#x3c;1.50, the objective lens has an annular zone structure on at least one surface of the objective lens, and the annular zone structure has a plurality of annular zones and has steps each of which extends in a direction of an optical axis of the objective lens and is formed at a boundary between adjacent ones of the plurality of annular zones to cause a predetermined optical path length difference between a light beam passing inside the boundary and a light beam passing outside the boundary, and the optical system of an optical pick-up satisfies a condition: 

Optical system of optical pick-up and optical information recording/reproducing apparatus

There is provided an objective lens used for a plurality of types of optical discs having a front surface and a rear surface, each of which includes an inner region and an outer region. The outer region has a surface shape which suppresses a coma caused when a beam used for a first optical disc is incident thereon obliquely with respect to an optical axis of the objective lens. The inner region is configured such that, at a boundary position between the inner region and the outer region, the coma caused when a beam used for a second optical disc is incident on the inner region obliquely at a first angle with respect to the optical axis is less than the coma caused when the beam used for the second optical disc is incident on the outer region obliquely at the first angle with respect to the optical axis. Further, an inclination &#x3b8;of the inner region and an inclination &#x3b8;of the outer region of the rear surface satisfy a condition: &#x2212;2.5&#x3c;&#x3b8;&#x2212;&#x3b8;&#x3c;0.0 . . . (1).

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Saitama, Japan

Shuichi Takeuchi