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Diffraction grating, optical pickup device, and optical disk apparatus

A technology of optical pickups and diffraction gratings, which is applied in beam guiding devices, optical detectors, instruments, etc., and can solve problems such as tracking error signal amplitude fluctuations and narrowing of objective lens displacement.

Inactive Publication Date: 2006-09-06
HITACHI MEDIA ELECTORONICS CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Therefore, if the position of the center of the passing beam and the dividing line of the diffraction grating are misaligned when the objective lens is shifted, and the amount of objective lens shift increases, the amplitude of the SPP occurs, and there is a problem that the amplitude of the tracking error signal fluctuates. Narrow objective lens shift amount such limitation

Method used

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  • Diffraction grating, optical pickup device, and optical disk apparatus
  • Diffraction grating, optical pickup device, and optical disk apparatus
  • Diffraction grating, optical pickup device, and optical disk apparatus

Examples

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Embodiment 1

[0039] Embodiment 1 of the present invention will be described in detail with reference to the drawings. Here, an optical pickup for recording or reproducing (generating tracking error signals) corresponding to a DVD-R with a guide groove pitch of 0.74 μm will be described. Of course, the present invention is not limited to DVD-R, and can be applied to all recording type optical discs having guide grooves.

[0040] FIG. 1 is a diagram showing an optical pickup, an optical disc, and an arrangement of light spots on the optical disc in Embodiment 1. As shown in FIG. A is a schematic arrangement diagram of an optical disc and an optical pickup, and B is an arrangement of light spots on the optical disc.

[0041]First, A will be explained. The optical disk 001 has a small hole in the center, and in a general optical disk device, it is fixed to the spindle 002 through the small hole of the optical disk 001 as shown in the figure. The spindle 002 has a function of rotating around...

Embodiment 2

[0074] In the second embodiment, the optical pickup for generating a tracking error signal according to the first embodiment will be described. An optical pickup for DVD-R recording and reproduction will be described as an example. Of course, the present invention is not limited to DVD-R, and can be applied to all recording type optical discs having guide grooves.

[0075] Figure 8 is a diagram showing a schematic configuration of the optical pickup 100 . The dotted line in the figure represents the optical path of the light beam. A dotted line 003 is an axis that passes through the center of the optical disc 100 and is parallel to the radial direction of the optical disc.

[0076] Generally, a semiconductor laser with a wavelength of 660 nm is used for recording or reproducing DVD discs. Therefore, a light beam having a wavelength of approximately 660 nm is emitted from the semiconductor laser 102 as divergent light. The beam emitted from the semiconductor laser 102 is ...

Embodiment 3

[0085] In the third embodiment, different embodiments of the branch element 200 of the second embodiment are described. Since it is the same as that of Embodiment 2 except that the branch element 201 is used, repeated description is omitted.

[0086] The branching element 201 for branching the beam into five beams will be described with reference to FIG. 10 . A is a diagram showing a schematic configuration of the branch element 201 . The figure is a view seen from the beam splitter side. The branching element 201 is a diffraction grating for diffracting light beams, and the regions 221 forming grating grooves at an angle θ1 and the regions 220 forming grating grooves at an angle θ2 different from the angle θ1 are alternately arranged in the z direction on the beam exit surface. By dividing perpendicularly to the y-direction as shown in the figure, there is an effect that there is no difference in the intensity distribution caused by the shift of the objective lens.

[0087...

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Abstract

An optical pickup device is provided which reduces variations in amplitude of a tracking error signal in a seek operation due to an installation error of the optical pickup device onto an optical disk apparatus, thereby generating the tracking error signal with high accuracy without any influence from stray lights, and which is high in productivity and low cost. Two sub-light beams are focused on at least one of forward and backward sides in a rotational direction of the disk with respect to a main light beam focused on the disk. When n is an integer number, and t is a distance between guide grooves of the disk, the two sub-light beams focused are spaced apart from each other by a distance of tx(n+0.5) in the radial direction of the optical disk. As splitting means for splitting the light beams into a plurality of beams, a diffraction grating is used which has grid grooves spaced apart at equal intervals, but having different angles at the upper and lower parts of an exiting surface of the light beam.

Description

technical field [0001] The present invention relates to tracking technology of an optical pickup mounted on an optical disc device. Background technique [0002] In recent years, optical disc devices capable of recording and reproducing information, such as CD-R / RW and DVD-R / RW, have become widespread. Recently, optical disk devices such as 'Blu-ray' and HD-DVD have been developed as optical disks that require higher density than DVD. This optical disc device has a structure in which a built-in optical pickup irradiates a light beam to an optical disc to record information, and detects a reflected light beam from the optical disc to read information. [0003] In recording and reproducing information by an optical pickup, it is necessary to accurately track a light beam along a guide groove in an optical disc in order to perform stable recording and reproducing processing. This technology of tracking the light beam along the guide groove is called tracking technology. In a...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G11B7/135
CPCG11B7/08505G11B7/0903G11B7/131G11B2007/0006G11B7/1353
Inventor 川村友人泉克彦大西邦一嶋田坚一
Owner HITACHI MEDIA ELECTORONICS CO LTD