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Optical disc unit

A technology of optical discs and light beams, applied in the field of optical disc units, can solve problems such as difficulty in distinguishing the surface of the optical disc from the information surface, difficulty in ensuring focus on the information surface, increased collision rate between the objective lens and the surface of the optical disc, etc.

Inactive Publication Date: 2009-01-21
PANASONIC CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0005] However, this conventional method has a problem that when the working distance of the objective lens (the distance between the objective lens and the surface of the disc) is smaller than the wobble of the disc, the collision rate between the objective lens and the disc surface increases
Thus, depending on the amount of total internal reflection, it is difficult to distinguish between the disc surface and the information surface
This means that if focusing is performed in a manner similar to conventional methods, it is difficult to secure focus on the information surface

Method used

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  • Optical disc unit
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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0073] figure 1 An exemplary structure of the optical disc unit 1001 according to Embodiment 1 of the present invention is shown.

[0074] The optical disc unit 1001 records information on an optical disc 1100 and reproduces information recorded on the optical disc unit 1100 . The optical disc 1100 has an information recording layer 1120 and a protection layer 1110 formed on the information recording layer 1120 .

[0075] The optical disc unit 1001 includes an optical head 1002 for irradiating a converging laser beam on the information recording layer 1120 .

[0076] The optical head 1002 includes a laser source 1201 , a light receiving device 1202 , an objective lens actuator 1204 and an objective lens 1203 .

[0077] The laser source 1201 outputs a laser beam. A laser beam output from this laser source 1201 is focused by an objective lens 1203 . As a result, the optical disc 1100 is irradiated with the converging laser beam. The converging laser beam reflected off the o...

Embodiment 2

[0116] FIG. 4 shows an exemplary structure of an optical disc unit 2002 according to Embodiment 2 of the present invention.

[0117] In this embodiment, a photodetector 2113 and a TE signal generating circuit 2102 (described later) are used as tracking error detecting means. The tracking error detecting device detects a misalignment between a light beam applied to an optical disc 2100 having an information surface on which a plurality of tracks is formed and a corresponding one of the tracks, and outputs a tracking error indicating the misalignment Signal.

[0118] A photodetector 2113, an FE signal generation circuit 2115, a phase compensation circuit 2116, a power amplifier 2118, and an actuator 2104 serve as focus adjustment means. The focus adjustment means performs focus adjustment so that the distance between the focus of the light beam and the information surface of the optical disc 2100 is within a predetermined error limit.

[0119] A microcomputer 2122 is used as c...

Embodiment 3

[0154] FIG. 10 shows an exemplary structure of an optical disc unit 2003 of Embodiment 3. As shown in FIG. In FIG. 10, elements similar to those in the above-described embodiment are denoted by the same reference numerals, and descriptions thereof are omitted.

[0155] Figure 11 A plurality of tracks formed on the information surface of an optical disc 2150 are shown. Each track is corrugated. exist Figure 11 In the exemplary structure shown, each track is slightly oscillated at a predetermined period W in its radial direction. These slight wobbles can be detected by the TE signal as misalignment between the beam 2106 and the tracks. The optical disc 2150 may be a single-layer disc, or a multi-layer disc, including a dual-layer disc.

[0156] Figure 12 Waveforms of these signals when the focus adjustment is performed and the beam 2106 traverses the tracks are shown, where (a) schematically represents the tracks, waveform (b) represents the TE signal, and waveform (c) ...

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Abstract

An optical disc unit 2001 comprises: reflective surface detection means 1010 for detecting a reflective surface; focus control means (1202, 1003, 1009, 1008, 1003, 1012, 1005 and 1204) for performing focus control to a reflective surface so that the distance between the focal point of an optical beam applied to an optical disc 2100 and the reflective surface is within a predetermined error limit; shift means 1007 for shifting the focal point of the optical beam in a direction perpendicular to the optical disc; and control means 1006 for controlling the focus control means and the shift means.

Description

technical field [0001] The present invention relates to an optical disc unit for recording information such as digital video information on an optical disc at high density and for reproducing information recorded on an optical disc, and more particularly, to an optical disc unit capable of recording information such as digital video information on an optical disc The information surface performs precise focus control. Background technique [0002] Recently, an optical disc has been attracting attention as a replaceable medium having a high capacity and it is expected that an optical disc unit will be more widely used as a video recorder in the future. One of the reasons is that an optical disc is a high-capacity interchangeable medium that allows recording / reproduction to be performed without touching the medium. In other words, a laser beam is focused and irradiates an information recording layer of an optical disc with its focal point, and thus recording and reproduction ...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G11B7/095
Inventor 石桥广通渡边克也藤亩健司山田真一久世雄一
Owner PANASONIC CORP