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Optical pick-up

A photodetector, beam technology, applied in instruments, optical recording heads, beam guides, etc., can solve the problems of DPP signal instability and amplitude reduction

Inactive Publication Date: 2007-12-26
SHARP KK
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

As a result, it was found that the DPP signal obtained from the light spots of MB and SB1 and 2 on the optical disc converged by the second objective lens was unstable, resulting in a decrease in amplitude
[0024] This problem is not limited to the structure having two objective lenses, but all optical pickups having an objective lens whose center is deviated from the center line extending from the central axis of the optical disc to the feeding axis of the optical pickup cause this problem.

Method used

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Examples

Experimental program
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Embodiment approach 1

[0069] The optical pickup of this embodiment (referred to as this optical pickup) is built into a device capable of writing information or reading information by irradiating light beams to multiple optical discs (optical recording media) such as BD (Blu-ray Disc), DVD, and CD. An optical pickup of an optical information recording and reproducing device. Specifically, it is an optical pickup capable of precise tracking control among optical pickups having a plurality of objective lenses and a plurality of light sources.

[0070] An embodiment of the present invention will be described with reference to FIGS. 1 to 7 . 1 is a plan view showing a schematic configuration of an optical information recording device (hereinafter referred to as the present optical information recording and reproducing device) incorporating the optical pickup of the present embodiment (hereinafter referred to as the present optical pickup).

[0071] As shown in FIG. 1, this optical information recordin...

Embodiment approach 2

[0112] Another embodiment of the present invention will be described below with reference to FIGS. 8 to 10 . FIG. 8 is a system diagram showing the optical path of the optical pickup of this embodiment (hereinafter referred to as the present optical pickup). For convenience of description, members having the same functions as those shown in the drawings of Embodiment 1 are denoted by the same reference numerals, and their descriptions are omitted. In the present embodiment, the positional relationship between the second objective lens and the first objective lens is the same as that in FIG. 1 of the above-mentioned first embodiment, and therefore description thereof will be omitted.

[0113] As shown in FIG. 8, this optical pickup has a structure in which the second optical system 2' is used instead of the second optical system of the optical pickup according to Embodiment 1, thereby achieving stable tracking control. That is, this optical pickup is different from Embodiment ...

Embodiment approach 3

[0131] Another embodiment of the present invention will be described with reference to FIG. 11 as follows. FIG. 11 is a schematic configuration diagram showing the optical pickup of this embodiment (hereinafter referred to as the present optical pickup). For convenience of description, members having the same functions as those shown in the drawings of Embodiment 1 are denoted by the same reference numerals, and their descriptions are omitted.

[0132] This optical pickup is different from Embodiment 1 in that it further includes a third optical system 3 in the optical path to the second optical system and the common optical system 10'. The third optical system is a system for converging light beams onto the third optical disc by the second objective lens 35 . In this optical pickup, as in the second optical system, the second objective lens 35 converges the light beam on the second optical disc. That is, in this optical pickup, the second objective lens 35 is provided as a ...

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Abstract

It is an object of the present invention to realize stable tracking control even in a structure including an objective lens whose center is offset from a central line extending from the central axis of an optical disk in the direction of the axis along which an optical pick-up is moved. An optical pick-up of the present invention includes a second optical system having a light source for emitting a beam, a second diffraction grating for splitting, into three beams MB, SB1, SB2 and SB3, the beam emitted from the light source, a second objective lens for converging the three beams on an optical disk, and a photodetector for detecting a push-pull signal from reflected light obtained by reflecting the three beams. The second objective lens is placed in an offset position offset from a central line. The second diffraction grating has a lattice structure plane that gives a phase difference to a light beam passing through the second diffraction grating, and the lattice structure plane is designed so that the amplitude of a push-pull signal detected from reflected light obtained by reflecting SB1 and SB2 is substantially 0.

Description

technical field [0001] The present invention relates to optical pickups. Specifically, the present invention relates to an optical pickup for optically recording or reproducing information on an optical recording medium such as an optical disk. Background technique [0002] In recent years, optical discs have been used in many fields such as audio, video, and computers because they can record a large amount of information signals at a high density. Recently, there are recording and reproducing devices that record and reproduce information on a plurality of optical discs such as BD (Blue-ray Disc), DVD, and CD. [0003] In this recording and reproducing device, since the device itself is large, a BD-compatible optical pickup and a DVD / CD-compatible optical pickup are separately constructed in the device to realize recording and reproducing information on multiple optical discs. [0004] On the other hand, when incorporating into electronic devices such as notebook personal ...

Claims

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Application Information

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IPC IPC(8): G11B7/135G11B7/08G11B7/09G11B7/1353G11B7/1374G11B7/1392
Inventor 堀山真
Owner SHARP KK