JP2001325748A - Multilayered optical recording medium, its recording/ reproducing device and manufacturing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multilayered optical recording medium in which a wobbled mark is formed with superior positional precision using a hologram and to provide its manufacturing device. SOLUTION: Four laser beams E1, E2, E'1, E'2, which are generated by dividing a laser beam from a light source 1 with a first to a third beam splitters 3, 6, 10 are shaped into slit-shaped convergent light beams with a cylindrical lens 13 or the like, and are emitted to the nearly same plane from both sides in the medium thickness direction of the recording area 12c of a disk, which is made of a recording material having light transmissivity, to form two holograms. In the meantime, the two laser beams E1, E'2 are phase-controlled synchronously by respective first and second phase shifters 15, 21 under the control of a controller 26, and simultaneously, the disk 12 is rotated while the laser light source 1 is turned on and off. As a result, wobbled marks for tracking and focusing are formed on each of the multilayered recording layers in the recording area 12c all together.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-layer optical recording medium in which wobbled marks for tracking and focusing are arranged on each of a plurality of recording layers formed in a recording area in the thickness direction of the medium. The present invention relates to a recording / reproducing apparatus and a manufacturing apparatus for a multilayer optical recording medium.

[0002]

2. Description of the Related Art When information is recorded / reproduced on / from a multilayer optical recording medium having a plurality of recording layers formed in a recording area on a substrate in the thickness direction of the medium, focusing on a desired recording layer and recording / reproducing of the information are performed. It is necessary to perform servo control including tracking to a desired track, and in order to perform this servo control reliably, it is necessary for each of the plurality of recording layers to have a servo area. A multi-layer optical recording medium having such a servo area provided in the recording area is disclosed in, for example,
No. 01398 is disclosed.

In general, in a multilayer optical recording medium, a preformat flag is previously formed on a substrate of the multilayer optical recording medium by a stamper or the like, and the preformat flag is used as a guide to determine a corresponding position of a recording layer. The servo marks (wobble marks for tracking and focusing, clock marks) are written one by one using the change in the refractive index induced by light. On the other hand, Japanese Unexamined Patent Publication No.
In a multilayer optical recording medium described in JP-A-101398 (hereinafter, referred to as a conventional example), a guide pit for tracking and a prepit such as a layer address indicating a layer position are provided in each of a plurality of recording layers. In this case, information can be recorded / reproduced by applying servo with guide tracks provided on each of the plurality of recording layers.

[0004]

When servo marks having an arrangement as shown in FIG. 7 are formed on a normal optical disk having only one recording layer, the position where the servo marks are formed is located on a single plane. Therefore, it can be easily formed by a stamper or the like. However, when a servo mark is formed on a multilayer optical recording medium having the above-mentioned preformat flag, since the position where the servo mark is formed is in a three-dimensional space, the servo mark is formed on the recording layer using the preformat flag in the substrate as a guide. Is performed for each recording layer, it takes a lot of time to create servo marks. Further, a method of simultaneously writing a servo mark at a position corresponding to a preformat flag of a plurality of recording layers by using a plurality of lasers has also been proposed, but using a plurality of lasers is not practical,
Even if a plurality of N lasers are used, the servo mark creation time of the entire medium is only 1 / N, and the servo mark creation time is still too long.

In the multilayer optical recording medium having the preformat flag, the wobbled marks for tracking are arranged so as to be shifted left and right by a predetermined interval with respect to the track. It is necessary to precisely control the irradiation position of the laser beam on the track so that the above arrangement is obtained, but the wobbled track on the adjacent track or the same track due to mechanical position fluctuation caused by this position control. The relative position of the mark will fluctuate. Therefore, when tracking servo is performed using a wobbled mark including the relative position variation, a problem may occur in which accurate tracking servo cannot be performed.

Further, in the above-mentioned conventional multilayer optical recording medium, a guide track for tracking and a pre-pit such as a layer address indicating the position of the layer are provided in each of the plurality of recording layers, so that the medium preparation process is complicated. It is extremely difficult to realize.

In order to solve the above-mentioned problem of difficulty in producing a conventional multilayer optical medium, a guide track for tracking is provided only on a substrate, and a servo light source is provided in a recording / reproducing apparatus for a multilayer optical recording medium. And a light source for recording / reproducing is provided. Servo is applied to the guide track by the light source for servo, and recording / reproducing is performed on a plurality of recording layers by the light source for recording / reproducing so as to follow the servo operation. A recording / reproducing apparatus for performing this is proposed in Japanese Patent Application Laid-Open No. Hei 4-301226. However, this recording / reproducing apparatus has a problem that the configuration becomes complicated because it has two light sources, and that the alignment of the optical components for superimposing the light beams from the two light sources becomes complicated.

A first object of the present invention is to provide a multilayer optical recording medium in which wobbled marks are formed with high positional accuracy by using a hologram. The present invention
It is a second object of the present invention to provide a recording / reproducing apparatus having a simple configuration for recording / reproducing information on / from a multilayer optical recording medium on which a wobbled mark is formed with high positional accuracy by using a hologram. A third object of the present invention is to provide a manufacturing apparatus for efficiently manufacturing a multilayer optical recording medium on which a wobbled mark is formed with high positional accuracy by using a hologram.

[0009]

In order to achieve the first object, a first invention according to claim 1 comprises a substrate and a recording area made of a recording material having optical transparency. Is a multilayer optical recording medium having a plurality of recording layers formed in the thickness direction of the medium and wobbled marks for tracking and focusing arranged in each of the recording layers, wherein the recording material is a photoreactive material Wherein the wobbled mark is a hologram formed.

According to a second aspect of the present invention, in the multilayer optical recording medium according to the first aspect, the wobbled marks are formed so as to be arranged so that the layer interval is larger than the track interval. Features.

According to a third aspect of the present invention, there is provided a wobbled wobble, wherein a guide track is formed at a specific position on the substrate according to the first or second invention, and the hologram is formed in the recording area based on the guide track. It is characterized by comprising a plurality of recording layers having marks.

[0012] In order to achieve the second object, a fourth aspect is provided.
According to a fourth aspect of the present invention, there is provided a recording / reproducing apparatus for recording / reproducing information on / from the multilayer optical recording medium according to the first, second, or third aspect of the present invention, comprising: a laser light source; It is characterized by comprising an objective lens for condensing light on a multilayer recording medium, and a photodetector for detecting light reflected from the multilayer recording medium.

[0013] In order to achieve the third object, a fifth aspect is provided.
According to a fifth aspect of the present invention, there is provided a laser light source, a first beam splitter for splitting a laser beam from the laser light source into two, and a second beam splitter for splitting one of the laser beams split by the first beam splitter into two. A third beam splitter for splitting the other of the laser beams split by the first beam splitter into two, a first phase shifter for controlling the phase of one of the laser beams split by the second beam splitter; A second phase shifter that performs phase control of one of the laser beams split by the three-beam splitter in synchronization with the first phase shifter, and control means that controls operations of the laser light source and the first and second phase shifters. And irradiating laser light for forming a hologram from both sides in the medium thickness direction of a recording area made of a recording material having optical transparency formed on the substrate. Accordingly, characterized in that so as to arrange the wobbled de marks for tracking and focusing each of the plurality of layers formed by the recording layer in the medium thickness direction in the recording area.

According to the first aspect of the present invention, a plurality of tracking and focusing walkers arranged in a plurality of recording layers formed in the thickness direction of the medium in a recording region made of a photoreactive recording material of a multilayer recording medium. Since the bull mark is formed by forming a hologram (for example, the hologram can be used in a manner such that a hologram is formed by irradiating a laser beam for forming a hologram from both sides in the medium thickness direction of the recording region to form a periodic pattern in the recording region. With the electric field intensity distribution formed,
The method of forming the wobbled mark can be used by controlling the phase of the laser beam in synchronization with the rotation control of the multilayer optical recording medium. In this method, the laser beam with respect to the track when the wobbled mark is created can be used. The position control of the irradiation position is replaced by the laser light phase control), and the relative position accuracy of wobbled marks on adjacent tracks or on the same track is guaranteed. Therefore, a multilayer optical recording medium in which wobbled marks are formed with high positional accuracy by using a hologram is obtained.

The wobbled marks of the first invention are formed on a multilayer optical recording medium by arranging the wobbled marks so that the layer spacing is larger than the track spacing, as described in the second invention. Further, as described in the third invention, a guide track is formed at a specific position on the substrate in the first or second invention, and the hologram is formed in the recording area based on the guide track. A plurality of recording layers having bull marks are formed.

According to the fourth invention, the laser light source, the objective lens for condensing the laser light from the laser light source on the multilayer recording medium, and the photodetector for detecting the reflected light from the multilayer recording medium are provided. The recording / reproducing apparatus is configured to record / reproduce information on / from a multilayer optical recording medium on which a wobbled mark is formed with high positional accuracy by using the hologram of the first, second or third invention. Recording / reproducing apparatus that performs Further, since this recording / reproducing apparatus uses only one laser light source, the recording / reproducing apparatus has a simple configuration.

According to the fifth aspect, the laser light source, the first beam splitter for splitting the laser light from the laser light source into two, and the second beam splitter for splitting one of the laser light split by the first beam splitter into two. A beam splitter, a third beam splitter that splits the other of the laser light split by the first beam splitter into two, a first phase shifter that controls the phase of one of the laser light split by the second beam splitter, A second phase shifter for phase-controlling one of the laser beams split by the third beam splitter in synchronization with the first phase shifter, and a control for controlling operations of the laser light source and the first and second phase shifters Means for manufacturing a multilayer optical recording medium, the manufacturing apparatus includes a medium in a recording area made of a recording material having optical transparency formed on a substrate. By irradiating a laser beam for forming a hologram from both sides in the vertical direction and controlling the phase of each laser beam, tracking and tracking are performed on each of a plurality of recording layers formed in the recording region in the medium thickness direction in the recording area. Since the wobbled marks for focusing are arranged, the wobbled marks can be formed on a plurality of recording layers and a plurality of tracks at the same time. Is a manufacturing apparatus capable of efficiently manufacturing a multilayer optical recording medium on which is formed.

[0018]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a diagram showing a configuration of a multilayer optical recording medium manufacturing apparatus according to the first embodiment of the present invention. The apparatus for manufacturing a multilayer optical recording medium according to the present embodiment includes a laser light source 1, a shutter 2 that passes or blocks laser light emitted from the laser light source 1, and a first beam splitter that splits the laser light emitted from the shutter 2 into two. A second beam splitter 6 that splits one of the laser beams split by the first beam splitter 3 through a first frequency shifter (AOM) 4 and a beam expander 5 to split the laser beam into two;
The other of the laser beams split by the beam splitter 3 is input via a mirror 7, a second frequency shifter (AOM) 8 and a beam expander 9 and split into two by a third beam splitter 10 and a second beam splitter 6. One of the split laser beams is transmitted through a mirror 11 to a multilayer optical recording medium (hereinafter, referred to as a multilayer optical recording medium).
A cylindrical lens 13 for irradiating one end face in the thickness direction of a recording area of a disc 12, and a mirror 14 for applying the other of the laser beams split by the second beam splitter 6 to a mirror 14.
Phase shifter 15 which controls the phase by entering through the
A cylindrical lens 17 for irradiating the laser beam emitted from the first phase shifter 15 to the one end face of the recording area of the disk 12 via a mirror 16, and one of the laser beams split by the third beam splitter 10. Mirror 1
8. A cylindrical lens 20 for irradiating the other end face in the thickness direction of the recording area of the disk 12 via the mirror 19
A second phase shifter 21 that receives the other of the laser beams split by the third beam splitter 10 and controls the phase in synchronization with the first phase shifter 15; and mirrors the laser beam emitted from the second phase shifter 21. A cylindrical lens 23 for irradiating the other end surface of the recording area of the disk 12 via the optical disk 22, a moving mechanism 24 for moving the disk 12 in the radial direction, and a guide light 12 formed on a guide track 12 b formed on the substrate 12 a of the disk 12. Guide light source 2 for irradiating light
5, the laser light source 1, the shutter 2, the first frequency shifter 4, the second frequency shifter 8, the first phase shifter 15, the second
It comprises a controller 26 for controlling the operation of the phase shifter 21, the moving mechanism 24 and the guide light source 25. Note that the shutter 2 can be replaced by frequency shifters 4 and 8, in which case the modulation of both is synchronized and lenses are installed before and after the frequency shifters 4 and 8, as necessary. .

FIGS. 2A to 2E show guide tracks formed in advance on the substrate of the multilayer optical recording medium on which a wobbled mark is to be formed by the multilayer optical recording medium manufacturing apparatus of the first embodiment. FIG. As shown in FIGS. 2A to 2C, the position where the guide track 12b is formed may be any one of the outermost circumference, the innermost circumference, and a plurality of locations between the inner and outer circumferences in the radial direction of the substrate 12a. As the guide track 12b, a concentric guide track having a width of about several tracks as shown in FIG. 2D is used, but a spiral shape of about 2 to 3 turns as shown in FIG. May be used. The number of the guide tracks 12b is preferably three or more to facilitate position detection. The guide track 12b emits guide light from a laser light source (not shown) of the positioning guide light source 25 shown in FIG. 1 and detects reflected light with a photodetector (not shown) to form a wobbled mark ( Used for tracking and focusing during formatting.

FIGS. 3A to 3C are diagrams schematically showing the wobbled mark arrangement after formatting of the multilayer optical recording medium of the first embodiment. As shown in the perspective view of FIG. 3A in which a part of the multilayer optical recording medium is cut away to expose a radial cross section, the disk 12 is composed of a substrate 12a and a light-reactive recording material having optical transparency. (For example, a material whose refractive index changes when irradiated with light having a light amount equal to or larger than a threshold value). As the recording material, for example, a photopolymer can be used. A large number of wobbled marks 27 for tracking and focusing are periodically formed on each of a plurality of recording layers formed in the recording area 12c in the medium thickness direction. In this case, in the radial section, as shown in FIG. 3B, the wobbled marks 27 arranged at equal intervals on the n-th recording layer are adjacent to the (n + 1) -th layer and the (n + 1) -th layer.
-1) A honeycomb-like arrangement in which wobbled marks 27 arranged at equal intervals on the first recording layer are shifted by a half pitch. On the other hand, in the cross section in the direction along the track, as shown in FIG. 3C, servo marks composed of five wobbled marks 27 that are continuous with the track are arranged along the track in common for each layer. And three wobbled marks 27 and two wobbled marks 27 which are arranged at predetermined intervals above and below the track.

FIGS. 4A and 4B show FIGS. 3A to 3C.
FIG. 3 is a diagram showing the wobbled mark arrangement of FIG. That is, in the cross section in the direction along the track,
As shown in FIG. 4A, of the servo marks composed of five wobbled marks 27 continuous with the track,
The three wobbled marks on the left side of the figure arranged on the track constitute wobbled marks for tracking, and the wobbled mark at the center thereof is a clock mark. Also, of the servo marks composed of five wobbled marks 27 continuous with the track, two wobbled marks on the right side of the figure arranged vertically (1/4) layer apart from each other with respect to the track. It constitutes a wobbled mark for focusing. These wobbled marks for tracking and wobbled marks for focusing are respectively views of the wobbled marks in the recording layer as viewed from above, and as shown in FIG. The center wobbled marks are arranged on a track to form a clock mark, and the left and right wobbled marks are respectively displaced vertically (1/4) from the track. On the other hand, the two wobbled marks on the right side of the figure are arranged along the track. To summarize the above, only the wobbled marks serving as clock marks are completely arranged on the track, and the remaining four wobbled marks are arranged shifted from the track in any cross section. Will be. 3 (a) to 3 (c) and FIG.
The servo mark arrangements (a) and (b) are merely examples, and it goes without saying that different servo mark arrangements may be used.

Next, using the manufacturing apparatus of the present embodiment shown in FIG. 1, the unformatted disk 12 shown in FIG. 2 is inserted into the unformatted disk 12 shown in FIGS. 3 (a) to 3 (c) and FIGS. 4 (a) and 4 (b). A format operation for creating a wobbled mark having the arrangement shown will be described.

In the manufacturing apparatus shown in FIG. 1, when a YAG laser (wavelength 450 nm) equipped with, for example, an SHG (second harmonic optical element) is used as the laser light source 1, When the shutter 2 is controlled to open and close as shown in the control sequence of FIG.
While the laser beam is open, the laser beam is emitted from the first beam splitter 3.
And split into two. Each of the two divided laser beams is shifted in frequency by several tens to several hundreds MHz by the first frequency shifter 4 and the second frequency shifter 8 in order to avoid interference between two holograms to be described later. , 9 after the beam width has been expanded
The beam splitter 6 and the third beam splitter 10 enter and split into two, and the four laser beams E ₁ , E ₂ ,
E _'1, E' ₂ become.

Two laser beams E ₂ and E ′ ₁ of the above four laser beams are supplied to a mirror and a cylindrical lens (for example, a mirror 11 and a cylindrical lens 13).
, And the remaining two laser beams E ₁ and E ′ ₂ are respectively phase-modulated by the first phase shifter 15 and the second phase shifter 21 and then mirror and cylindrical lenses (for example, mirror 16). And enters the disk 12 via a cylindrical lens 17). Each of the four laser beams is incident on the disk 12 by a cylindrical lens.
Is formed into slit-shaped convergent light that extends in the radial direction of.
These slit convergent lights are incident on substantially the same plane of the disk 12. At this time, the laser beams E ₁ , E ₂ and E ′ ₁ , E ′ ₂ each form one hologram, and these two holograms are incident on the recording area 12 c of the disk 12 from both sides in the medium thickness direction. At this time, in order to prevent scattering and diffraction of the laser light, the position where the two holograms are incident is set so as to remove the guide track 12b formed on the portion of the substrate 12a near the outer periphery of the disk.

When the two holograms are made incident on the disk 12 as described above, a periodic electric field intensity distribution can be formed in a spatial region, and a photoreaction (in this case, refraction in this case) occurs on the disk at a portion where the electric field intensity is strong. Rate change), wobbled marks can be collectively formed in the disk 12 using this photoreaction. For example, laser light source 1
Is 532 nm, E ₁ , E ₂ , E ′ ₁ , E ′ ₂
Angle of incidence (angle formed with the vertical axis of the incident point of disk 12)
Are 24.6 degrees, 15.7 degrees, 24.6 degrees, 1
If it is 5.7 degrees, the track interval is 1.6 μm and the layer interval is 5
A μm honeycomb lattice is formed. In this case, it is assumed that there is no interference between the holograms.

The laser light source 1 is turned on and off while rotating the disk 12 in the four laser light irradiation states.
When F is performed, the honeycomb lattice as shown in FIG. For example, turning on the laser light source 1
Assuming that the OFF modulation frequency is about 100 KHz, the disk rotation speed is 1 rpm, and the effective irradiation range of the two holograms is about 1/10 of the recording area 12c of the disk 12, the effective irradiation of the disk space takes about 1 second. Lattice points serving as wobbled marks are formed in a range corresponding to the region. Therefore, by moving the disk 12 at predetermined time intervals by the moving mechanism 24, a wobbled mark is formed in the entire disk space in a short time. In this case, grid points are formed concentrically on each recording layer as if tracks were formed over the entire circumference of the disk. When the guide track is formed in a spiral shape, lattice points are formed in a spiral shape.

Therefore, if the phase of each laser beam is modulated as shown in FIGS. 5A and 5B in synchronization with the ON-OFF operation of the laser light source 1, the laser beam is separated from the track by a predetermined distance in the horizontal direction. A grid point can be moved to a point vertically or vertically separated from a point or track by a predetermined distance. That is, when the liquid crystal modulator or the electro-optic modulator is used as the EOM 15 and the EOM 21 and the phase modulation is performed at a modulation speed of several tens KHz to several MHz, the “E
When both OM15 and EOM21 are not phase-modulated, the grid points are arranged on the track to become clock marks shown in FIGS. 4A and 4B, and when "phase-modulated by + π / 2 for both EOM15 and EOM21". Indicates that grid points are arranged on the right side of the track, and that "Eπ15 and EOM21 are both -π / 2
In the case where only phase modulation is performed, grid points are arranged on the left side of the track, and "EOM 15 is phase-modulated by -π / 2 and EOM
In the case where "21 is phase-modulated by + π / 2", lattice points are arranged above the track, and in the case where "EOM15 is phase-modulated by + π / 2 and EOM21 is phase-modulated by -π / 2", The lattice points are arranged below. In this way, wobbled marks having the arrangement shown in FIGS. 4A and 4B can be created.

Note that the wobbled mark appears before the data area, and usually requires a servo area of about 2 bytes for a data area of about 8 bytes. is necessary. In order to create such a large number of wobbled marks, it is necessary to repeat the sequence of FIG. 5A 1,000 times or more, whereby wobbled marks can be formed over the entire circumference of the disk.

According to the present embodiment, the disk 12 on which the wobbled mark 27 has been formed by the above-described apparatus for manufacturing a multilayer optical recording medium has a laser beam E ₁ for forming a hologram from both sides of the recording area 12c in the medium thickness direction. , E ₂
In the state where a periodic electric field intensity distribution is formed in the recording area 12c by irradiating E ′ ₁ and E ′ ₂ , the phase control of the laser beam is performed in synchronization with the rotation control of the disk 12 for recording. Since the wobbled marks 27 for tracking and focusing are formed on the recording layers formed in the area 12c in the thickness direction of the medium, the wobbled marks 27 on adjacent tracks or on the same track are formed. Is guaranteed relative positional accuracy. Therefore, the disk 1 on which the wobbled mark is formed with high positional accuracy by using the hologram is used.
It becomes 2.

According to the disk 12 of the present embodiment, instead of forming a preformat flag on the entire area of the disk substrate as in the above-described multilayer optical recording medium,
Since several guide tracks for positioning at the time of hologram irradiation are provided at positions deviated from the guide light, there is no problem that laser light is scattered or diffracted and hinders the format operation. In the above configuration, the first beam splitter 3 splits the laser light from the laser light source into two.
However, the first beam splitter 3 can be omitted by using two laser light sources having the same wavelength.

According to the apparatus for manufacturing a multilayer optical recording medium of the present embodiment, the recording area 12c made of a recording material having optical transparency formed on the substrate 12a of the disk 12 is viewed from both sides in the medium thickness direction. The wobbled marks 27 for tracking and focusing are arranged on each of the plurality of recording layers in the recording area 12c by irradiating the four laser lights for forming the holograms and controlling the phases of the respective laser lights. Because it was configured
The wobbled marks 27 can be simultaneously formed on a plurality of recording layers and a plurality of tracks. Therefore, the disadvantage that the relative position of the wobbled mark on the adjacent track or the same track fluctuates due to the mechanical position fluctuation of the irradiation position of the laser beam with respect to the track as in the multilayer optical recording medium having the preformat flag described above. Since this does not occur and the relative position between the recording layers and between the tracks is guaranteed, the disk 12 on which the wobbled marks 27 are formed with high positional accuracy can be efficiently manufactured by using the hologram. Further, compared to the case of manufacturing a multilayer optical recording medium having the preformat flag and the case of manufacturing a disk in which recording layers in which the preformat flag is formed by a stamper or the like are manufactured, a disk can be manufactured extremely easily. .

According to the apparatus for manufacturing a multilayer optical recording medium of the present embodiment, as described in JP-A-10-143933, a disk in which a servo mark in which a track is deformed into a waveform with respect to a track is formed. Even in the case of (1), servo marks can be collectively formed in a multilayered recording area only by controlling the phase of each laser beam without turning on / off the laser light source 1.

FIG. 6 is a diagram showing a configuration of a recording / reproducing apparatus for a multilayer optical recording medium according to the first embodiment of the present invention. As shown in FIG. 6, the recording / reproducing apparatus according to the present embodiment includes a laser light source 31, a collimator lens 32 that converts the laser light from the laser light source 31 into parallel light, A first polarizing beam splitter 33 to be
A λ / 2 plate 34 for converting the laser light emitted from the first polarization beam splitter 33 into linearly polarized light, a second polarization beam splitter 35 for receiving and reflecting the laser light that has been linearly polarized light, and a second polarization beam An objective lens 36a in an objective lens actuator 36 that focuses the laser light emitted from the splitter 35 on the disk 12, a lens 37,
It comprises a photodetector 38 and the like. The reflected light from the disk 12 is converted into parallel light by the objective lens actuator 36 and then reflected by the second polarizing beam splitter 35,
After the deflection direction is rotated by 90 degrees by the λ / 2 plate 34, the light is incident on the first polarization beam splitter 33, where the direction is rotated by 90 degrees and is incident on the lens 37. , Where a track error signal and a focus error signal are detected, and information is recorded and reproduced.

According to the recording / reproducing apparatus for a multilayer optical recording medium of the present embodiment, a wobbled mark formed on each recording layer of the recording area 12c of the disk 12 of the present embodiment with high positional accuracy using a hologram is used. Thus, information can be recorded / reproduced while performing a servo operation, so that a stable servo operation is guaranteed. Further, since only one laser light source 31 is used, the recording / reproducing apparatus has a significantly simpler configuration than the recording / reproducing apparatus described in Japanese Patent Application Laid-Open No. Hei 4-301226, which requires two light sources. . Further, since the servo operation and the information recording / reproducing operation are performed together, it is possible to reliably perform information recording / reproduction on a desired recording layer and data track.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an apparatus for manufacturing a multilayer optical recording medium according to a first embodiment of the present invention.

FIGS. 2A to 2E are diagrams showing id tracks formed in advance on a substrate of a multilayer optical recording medium on which a wobbled mark is to be formed by the multilayer optical recording medium manufacturing apparatus according to the first embodiment; It is.

FIGS. 3A to 3C are diagrams schematically showing a wobbled mark array after formatting of the multilayer optical recording medium of the first embodiment.

FIGS. 4A and 4B are diagrams showing the wobbled mark arrangement of FIGS. 3A to 3C in more detail.

FIGS. 5A and 5B are diagrams showing a control sequence of laser light phase control in the multilayer optical recording medium manufacturing apparatus according to the first embodiment.

FIG. 6 is a diagram showing a configuration of a recording / reproducing apparatus for a multilayer optical recording medium according to the first embodiment of the present invention.

FIG. 7 is a diagram illustrating a servo mark array in a single-layer optical recording medium.

[Explanation of symbols]

 Reference Signs List 1 laser light source 2 shutter 3 first beam splitter 4 first frequency shifter (AOM) 5, 9 beam expander 6 second beam splitter 7, 11, 14, 16, 18, 19, 22 mirror 8 second frequency shifter (AOM) 10) Third beam splitter 12 Multilayer optical recording medium (disk) 12a Substrate 12b Guide track 12c Recording area 13, 17, 20, 23 Cylindrical lens 15 First phase shifter 21 Second phase shifter 24 Moving mechanism 25 Guide light source 26 Controller ( Control means) 31 Laser light source 32 Collimator lens 33 First polarizing beam splitter 34 λ / 2 plate 35 Second polarizing beam splitter 36 Objective lens actuator 36a Objective lens 37 Lens 38 Photodetector

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) G11B 7/09 G11B 7/09 BC 7/135 7/135 Z 7/26 7/26 F term (reference) 5D029 JB13 KB03 VA08 WA36 WD12 5D090 AA01 BB04 BB12 BB17 CC01 CC04 CC12 CC14 DD01 DD05 GG22 GG25 GG26 HH03 KK09 KK13 KK14 LL02 5D118 BA01 BB08 BC03 BC13 BC14 BF02 BF03 CC12 CD02 CD03 DC03 5D119 AA50 BA01 DA01 AA50 BA01 EA03 5D121 AA09 GG28

Claims (5)

[Claims] 1. A recording medium comprising: a substrate; and a recording area made of a recording material having optical transparency. The recording area includes a plurality of recording layers formed in a thickness direction of a medium and a tracking layer arranged on each of the recording layers. And a wobbled mark for focusing, wherein the recording material is a photoreactive material, and the wobbled mark is a hologram formed. 2. The multilayer optical recording medium according to claim 1, wherein the wobbled marks are formed on the multilayer optical recording medium by arranging the wobbled marks so that the layer intervals are larger than the track intervals. 3. A guide track is formed at a specific position on the substrate, and a plurality of recording layers having the wobbled marks formed with the holograms are formed in the recording area based on the guide tracks. The multilayer optical recording medium according to claim 1, wherein 4. A recording / reproducing apparatus for recording / reproducing information on / from a multilayer optical recording medium according to claim 1, wherein the laser light source and the laser light from the laser light source are transmitted to the multilayer optical recording medium. A recording / reproducing apparatus for a multilayer optical recording medium, comprising: an objective lens for converging light on a recording medium; and a photodetector for detecting light reflected from the multilayer recording medium. 5. A laser light source, a first beam splitter for splitting a laser beam from the laser light source into two, a second beam splitter for splitting one of the laser beams split by the first beam splitter into two, A third beam splitter for splitting the other of the laser beams split by the first beam splitter into two, a first phase shifter for controlling the phase of one of the laser beams split by the second beam splitter;
A second phase shifter that performs phase control of one of the laser beams split by the beam splitter in synchronization with the first phase shifter, and a control unit that controls operations of the laser light source and the first and second phase shifters. By irradiating a laser beam for forming a hologram from both sides in the medium thickness direction of a recording area made of a recording material having optical transparency formed on a substrate, the recording area is formed in the medium thickness direction in the recording area. An apparatus for manufacturing a multilayer optical recording medium, wherein wobbled marks for tracking and focusing are arranged on each of a plurality of recording layers.