JP2006092667A - High density recording optical disk - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high recording density optical disk wherein recording layers are provided at a land part and a groove part without necessitating complicated control for performing high density recording and reproduction. <P>SOLUTION: In the optical disk wherein information is recorded to and reproduced from a spiral recording track, nearly projectingly shaped land parts and groove parts between the land parts are formed, dichroic beam splitters 303 reflecting a laser incident beam having a wavelength shorter than a specified wavelength and transmitting a laser incident beam having a wavelength longer than the specified wavelength are provided between the adjacent land parts and the recording layers are constituted of a land part recording layer 301 having an inner peripheral wall surface of the land part by incident beam reflection of the dichroic beam splitter as a recording layer and a groove part recording layer 302 having the groove part by incident beam transmission of the dichroic beam splitter as a recording layer. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical disc, and relates to a structure of an optical disc for performing high-density recording and simplifying a recording method and a reproducing method accompanying high-density recording.

  It has a spiral recording track with respect to the center of the disk-shaped recording medium surface, and this track is irradiated with laser light to record on an optical disk, or reflected light from laser light irradiation is detected and recorded. In an optical disc that reproduces information recorded on a track, in order to perform high-density recording, recording and reproduction are performed on the land portion recording layer 401 and the groove portion recording layer 402 as shown in FIG. 7, or as shown in FIG. As described above, recording layers 501 and 502 for recording / reproducing by changing the shape such as the size, width, and depth of the recording groove have been proposed. Here, FIG. 7 is a diagram showing a land / groove system of an optical disc related to the prior art, and FIG. 8 is a diagram showing a configuration example corresponding to a high recording density of the optical disc related to the prior art.

In addition, as a conventional technology for optical disks that perform high-density recording and high-speed reproduction, a spiral recording track is formed in an inverted V shape having a pair of inclined surfaces of 45 degrees and reflected by light irradiation. There has been proposed one in which a recording film having a variable rate is formed on each inclined surface (see, for example, Patent Document 1).
Japanese Patent Laid-Open No. 11-16215

  However, there is an optical path difference between the optical path by the land recording portion (land portion recording layer 401 shown in FIG. 7) provided for high density recording and the optical path by the groove recording portion (groove portion recording layer 402 shown in FIG. 7). Occurs (see FIG. 7). Therefore, in order to focus when recording and reproducing the groove portion from when recording and reproducing the land portion information, or when recording and reproducing the land portion information from recording and reproducing the groove portion, a pickup is used. Focus control is performed by operating the actuator and the objective lens. For this reason, the subject that the operating range of an actuator and an objective lens becomes narrow by the part of the level | step difference between a land part and a groove part arises.

  Further, in the configuration example shown in FIG. 8 and the technique of the above-mentioned Patent Document 1, the recording groove shape is devised, and recording is performed from the time when information on the recording layer 1 (501 in FIG. 8) is recorded and reproduced. When recording and reproducing information on the layer 2 (502 in FIG. 8) or recording and reproducing information on the recording layer 2 (502 in FIG. 8), information on the recording layer 1 (501 in FIG. 8) is recorded and reproduced. When reproducing, control for switching to different recording layers is required. For this reason, the subject that the detection apparatus of a laser beam becomes complicated for high-density recording arises.

  An object of the present invention is to provide a high recording density optical disc in which recording layers are provided in a land portion and a groove portion without requiring complicated control for performing high density recording and reproduction.

In order to solve the above problems, the present invention mainly adopts the following configuration.
In an optical disc that records information by irradiating a spiral recording track with laser light, or detects information reflected by the laser light irradiation and reproduces information recorded on the recording track.
The optical disc is formed with a substantially convex land portion and a groove portion between the land portions,
A dichroic beam splitter that reflects laser incident light having a shorter wavelength than a specific wavelength and transmits laser incident light having a longer wavelength is provided between the adjacent land portions.
The recording layer irradiated with the laser light includes a land recording layer having a recording layer with a wall surface facing the inner or outer periphery of the land by reflection of incident light by the dichroic beam splitter, and a recording layer formed by the dichroic beam splitter. And a groove portion recording layer having the groove portion as a recording layer by transmitting incident light.

  By using the optical disk of the present invention, the operating range of the actuator and the objective lens during focus control can be expanded. Further, since there is no change in the shape of the recording layer for high density recording, it becomes possible to simplify the control mechanism for recording / reproducing of the optical disc apparatus.

  Further, by providing a recording layer not only on the land portion wall surface but also on the groove portion, a high recording density optical disc having a recording density nearly doubled can be obtained.

  An optical disc according to an embodiment of the present invention will be described in detail below with reference to FIGS. FIG. 1 is an external view of an optical disc according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of the optical disc of this embodiment. FIG. 3 is a view showing details of a cross section of the optical disk of the present embodiment and a path of a light beam. FIG. 4 is a diagram showing a manufacturing process in the optical disc of this embodiment. FIG. 5 is a diagram showing a manufacturing result in the optical disc of the present embodiment. FIG. 6 is a diagram showing a configuration example of a pickup optical system applied to the optical disc of the present embodiment.

  Here, 101 is an optical disc, 201 is a land portion, 202 is a groove portion, 203, 303, 601, and 701 are dichroic beam splitters, 301, 602, and 702 are land portion recording layers, and 302, 603, and 703 are grooves. Partial recording layer, 304 is incident light, 305 is reflected light, 306 is transmitted light, 704 is a protective layer, 801 is a laser light emitting element, 802 is a beam splitter, 803 is a condensing lens, 804 is a quarter wavelength plate, 805 Denotes an objective lens, 806 denotes an optical disk, 807 denotes an optical disk pit, 808 denotes a photodetector, 810 denotes a recording optical path, and 811 denotes a reproduction optical path.

  The optical disc according to the embodiment of the present invention has a spiral recording track (cross-sectional view) as shown in FIG. 2 with respect to the center hole of the surface portion 101 of the disc-like recording medium as shown in FIG. The track pitch configuration is constant in the radial direction. Further, as shown in FIG. 3, the recording layer is composed of a wall surface 301 of the land portion (a sidewall surface 301 instead of an upper surface of the land portion) and a groove recording layer 302.

  In the present embodiment, the dichroic beam splitter 303 is installed between adjacent land portions. The light beam 304 emitted from the objective lens by the dichroic beam splitter 303 is as follows. The dichroic beam splitter 303 reflects a short wavelength with a certain wavelength as a boundary and transmits a long wavelength. Therefore, a wavelength shorter than a certain wavelength is reflected to the recording layer 301 on the side wall surface of the land portion. Further, a wavelength longer than a specific wavelength is transmitted and irradiated to the recording layer 302 in the groove portion. In FIG. 3, the light is reflected in the left direction of the drawing. However, the land portion recording layer may naturally be irradiated by installing a dichroic beam splitter 303 that directs the reflected light to the reverse (right) side.

  In other words, the present embodiment has a spiral recording track with respect to the center of the surface of the disk-shaped recording medium, and this recording track is irradiated with a laser beam to be recorded on an optical disc, or the laser beam is irradiated. In an optical disk that reproduces information recorded on a recording track by detecting reflected light from a recording layer, a recording layer to be irradiated with laser light is used as a wall facing the inner circumference of a land portion of a disk-shaped recording medium or a land of a disk-shaped recording medium. And a recording layer is also provided in the groove portion. In this embodiment, a dichroic beam splitter that reflects the incident light of the laser beam between the land recording layer and the land recording layer, reflects a short wavelength with a certain wavelength as a boundary, and transmits a long wavelength. Provide. The optical disc according to the present embodiment includes a recording layer having only a land portion.

  In the prior art for high density recording, as shown in FIG. 7, there are steps in the land recording layer 401 and the groove recording layer 402, and when switching between the land and groove, the actuator and objective The focus direction is adjusted by driving the lens, and a load is applied to the actuator and the objective lens. In addition, the operating range of the actuator and the objective lens is narrowed by the level difference due to the level difference between the land part and the groove part. Also, as shown in FIG. 8, when performing high density recording by changing the shape, width, depth, etc. of the recording groove, control for switching between the recording layer 501 and the recording layer 502 is required. The device was to become complicated.

  Here, the principle of recording and reproduction in the optical disc apparatus to which the optical disc according to the present embodiment is applied will be described with reference to FIG. The optical system for recording and reproduction includes a laser light emitting element 801 such as a semiconductor laser that generates laser light to be applied to the optical disk 806, a beam splitter 802 for changing the optical path of reflected light from the optical disk, and a laser light emitting element. A condensing lens 803 that collimates the laser light emitted in 801, a quarter-wave plate 804 for bending the optical path of reflected light from the optical disk at a right angle, and a spot-like shape on the surface of the optical disk An objective lens 805 for forming laser light and a photodetector 808 for detecting the intensity of reflected light from the beam splitter 802 are included.

  The light beam 810 emitted from the semiconductor laser 801 passes through the beam splitter 802, becomes circularly polarized light by the quarter wavelength plate 804, is condensed by the objective lens 805, and is applied to the pit 807 of the optical disk 806. The reflected light again passes through the quarter-wave plate 804 and becomes linearly polarized light, so that the light beam 811 reflected by the beam splitter 802 is guided to the photodetector 808.

  The optical disc according to the present embodiment is provided with a recording layer 601 on the wall surface (so-called side wall surface) of the land portion as shown in FIG. 4, and also provided with a recording layer 603 on the groove portion, and a groove between adjacent land portions. After the dichroic beam splitter 601 is installed in the part, the recording layer is covered with a protective layer 704 as shown in FIG.

  In the optical system as shown in FIG. 6, the spot-like laser beam formed by the objective lens 805 is reflected by the dichroic beam splitter 701 on the optical disk of this embodiment when the wavelength is shorter than a specific wavelength. Then, a wavelength longer than a specific wavelength is transmitted to the recording layer 702 on the wall surface of the land portion and irradiated to the recording layer 703 in the groove portion.

  As described above, the embodiments of the present invention are characterized by having the following configurations, functions, and actions. That is, the recording layer is provided on the land wall surface (side wall surface) perpendicular to the incident direction of the laser beam, and the recording layer is also provided on the groove portion, and the incident light of the laser beam is provided between the recording layer and the recording layer. By installing a dichroic beam splitter for reflection and transmission, the optical path length does not change from the innermost to the outermost circumference of the disk radius, and the shape of the recording layer changes for high density recording. Therefore, recording / playback is possible without requiring control for switching.

  Further, since the recording layer is provided on the wall surface of the land portion, the pitch between the grooves can be shortened, and thereby the recording capacity can be increased.

1 is an external view of an optical disc according to an embodiment of the present invention. It is sectional drawing of the optical disc of this embodiment. It is a figure which shows the cross-sectional detail of the optical disc of this embodiment, and shows the path | route of a light beam. It is a figure which shows the manufacturing process in the optical disc of this embodiment. It is a figure which shows the manufacture result in the optical disc of this embodiment. It is a figure which shows the structural example of the pick-up optical system applied to the optical disc of this embodiment. It is a figure which shows the land-groove system of the optical disc regarding a prior art. It is a figure which shows the structural example corresponding to the high recording density of the optical disc regarding a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Optical disc 201 Land part 202 Groove part 203,303,601,701 Dichroic beam splitter 301,401,602,702 Land part recording layer 302,402,603,703 Groove part recording layer 304 Incident light 305 Reflected light 306 Transmitted light 501 Recording layer 1
502 Recording layer 2
704 Protective layer 801 Laser light emitting element 802 Beam splitter 803 Condensing lens 804 1/4 wavelength plate 805 Objective lens 806 Optical disk 807 Optical disk pit 808 Photo detector 810 Optical path during recording 811 Optical path during reproduction

Claims (6)

In an optical disc that records information by irradiating a spiral recording track with laser light, or detects information reflected by the laser light irradiation and reproduces information recorded on the recording track.
The optical disc is formed with a substantially convex land portion and a groove portion between the land portions,
The recording layer irradiated with the laser beam is composed of a land portion recording layer having a recording layer as a wall surface facing the inner circumference of the land portion, and a groove portion recording layer having the groove portion as a recording layer. A featured optical disc. In claim 1,
The land recording layer has an outer peripheral wall surface of the land portion as a recording layer instead of the inner peripheral wall surface of the land portion. In claim 1 or 2,
A dichroic beam splitter that reflects a laser incident light having a shorter wavelength than a specific wavelength and transmits a laser incident light having a longer wavelength is provided between the adjacent land portions. In an optical disc that records information by irradiating a spiral recording track with laser light, or detects information reflected by the laser light irradiation and reproduces information recorded on the recording track.
The optical disc is formed with a substantially convex land portion and a groove portion between the land portions,
A dichroic beam splitter that reflects laser incident light having a shorter wavelength than a specific wavelength and transmits laser incident light having a longer wavelength is provided between the adjacent land portions.
The recording layer irradiated with the laser light includes a land portion recording layer having a recording layer on the inner circumferential surface of the land portion by reflection of incident light at the dichroic beam splitter, and incident light at the dichroic beam splitter. An optical disc comprising: a groove portion recording layer having the groove portion as a recording layer by transmission. In an optical disc that records information by irradiating a spiral recording track with laser light, or detects information reflected by the laser light irradiation and reproduces information recorded on the recording track.
The optical disc is formed with a substantially convex land portion and a groove portion between the land portions,
A dichroic beam splitter that reflects laser incident light having a shorter wavelength than a specific wavelength and transmits laser incident light having a longer wavelength is provided between the adjacent land portions.
The recording layer irradiated with the laser beam includes a land portion recording layer having a recording layer with a wall surface facing the outer periphery of the land portion by reflection of incident light at the dichroic beam splitter, and incident light transmission at the dichroic beam splitter. And a groove portion recording layer having the groove portion as a recording layer. In Claims 3, 4, and 5,
An optical disc comprising a protective layer covering the dichroic beam splitter and the land portion.

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