EP0460368A2 Expired / Lapsed EP ⏱️ 0.0 years remaining

Optical pickup head

Assignee: Panasonic Holdings Corp

•

Filing: 1991-03-26

•

Granted: —

•

Expires: 2011-03-26

📄 Original PDF 🌐 Google Patents 🔄 Sync Now

Abstract

Abstract A light source emits a light beam which is focused on an optical recording medium. The light beam is reflected and diffracted by the optical recording medium. A holographic optical element has divided regions formed with different holographic patterns. The divided regions of the holographic optical element diffract the light beam reflected and diffracted by the optical recording medium, and thereby generate diffraction light beams respectively. The divided regions of the holographic optical element lie in quadrants of an imaginary X-Y coordinate system respectively. An X axis of the coordinate system extends in a direction corresponding to a direction of a pit sequence on the optical recording medium, that is, a tangential direction of the optical recording medium. A Y axis of the coordinate system extends in a direction corresponding to a direction perpendicular to the direction of the pit sequence, that is, a radial direction of the optical recording medium. Photodetectors receive the diffraction light beams generated by the divided regions of the holographic optical element, and convert the received diffraction light beams into corresponding electric signals. Phases of the electric signals are compared, and a tracking error signal is generated on the basis of a result of the phase comparison.

Inventors

👤 Shinichi Kadowaki
👤 Yoshiaki Komma
👤 Naoyasu Miyagawa

Bibliographic Details

Application Number —

Jurisdiction EP

Data Source google_patents

Last Synchronized 2026-10-24 17:18

CPC Classifications

G; G11; G11B; G11B7/00; G11B7/12; G11B7/125; G11B7/127; G11B7/123; G11B7/13; G11B7/131; G11B7/135; G11B7/1353

Claims Analysis

Total Claims: 4

Claim 1

Independent Claim 251 words

An optical pickup head operating on an optical recording medium having a pit sequence, wherein a direction of the pit sequence is defined as a tangential direction of the optical recording medium and a direction perpendicular to the direction of the pit sequence is defined as a radial direction of the optical recording medium, the optical pickup head comprising: a light source emitting a light beam; means for focusing the light beam emitted from the light source on the optical recording medium, wherein the light beam is reflected and diffracted by the optical recording medium; a holographic optical element having divided regions formed with different holographic patterns, wherein the divided regions diffract the light beam reflected and diffracted by the optical recording medium, and generate diffraction light beams from the light beam reflected and diffracted by the optical recording medium respectively, wherein the divided regions lie in quadrants of an imaginary X-Y coordinate system respectively, and an X axis of the coordinate system extends in a direction corresponding to the tangential direction of the optical recording medium and a Y axis of the coordinate system extends in a direction corresponding to the radial direction of the optical recording medium; photodetectors receiving the diffraction light beams generated by the divided regions of the holographic optical element, and converting the received diffraction light beams into corresponding electric signals; and means for comparing phases of the electric signals and generating a tracking error signal on the basis of a result of said phase comparing.

Claim 2

Dependent Claim 67 words

The optical pickup head of claim 1 wherein the holographic optical element has a region formed with a predetermined pattern for generating two focus-error-detecting diffraction light beams of different focal points from the light beam reflected and diffracted by the optical recording medium, and further comprising means for generating a focus error signal by use of the focus-error-detecting diffraction light beams in a spot size detection method.

Claim 3

Dependent Claim 63 words

The optical pickup head of claim 1 wherein the holographic optical element has a region formed with a predetermined pattern for generating two focus-error-detecting diffraction light beams from the light beam reflected and diffracted by the optical recording medium, and further comprising means for generating a focus error signal by use of the focus-error-detecting diffraction light beams in a double knife edge method.

Claim 4

Dependent Claim 170 words

An optical pickup head operating on an optical recording medium having a track, comprising: a light source emitting a light beam; means for focusing the light beam emitted from the light source on the optical recording medium, wherein the light beam is reflected and diffracted by the optical recording medium; a holographic optical element having divided regions formed with different holographic patterns, wherein the divided regions diffract the light beam reflected and diffracted by the optical recording medium, and generate diffraction light beams from the light beam reflected and diffracted by the optical recording medium respectively, wherein the divided regions are in a configuration predetermined with respect to a direction of the track of the optical recording medium; photodetectors receiving the diffraction light beams generated by the divided regions of the holographic optical element, and converting the received diffraction light beams into corresponding electric signals; and means for comparing phases of the electric signals and generating a tracking error signal on the basis of a result of said phase comparing.

References Cited (Backward Citations)

No citation records indexed.

USPTO Annuity & Maintenance Windows

Maintenance schedule is calculated for granted US utility patents.

Assigned Categories & Tags

No categories assigned to this patent yet.

Assign Category Tag

Select Category

Notes (Optional)