JP2001202630A - Data recording medium and data recording reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform movement between a plurality of recording layers at high speed, obtaining a sufficient light quantity for a servo control, even when the reflectivity of the recording layer is low and the recording layer itself cannot apply the servo. SOLUTION: The first groove of a first track guide layer is recorded in a spiral shape as shown in the recording direction 50 to the forward spiral direction which goes from the inner periphery to the outer periphery, and the second groove of a second track guide layer is recorded in a spiral shape as shown in the recording direction 51 to the reverse spiral direction which goes from the outer periphery to the inner periphery. A code track is recorded on a recording layer having an odd number in the forward spiral direction as shown to the recording direction 50, in the direction which goes from a leader 52 to a termination 53. A code track is recorded on a recording layer having an even number in the reverse spiral direction as shown in the recording direction 51, in the direction which goes from a leader 54 to a termination 55.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data recording medium and a data recording / reproducing apparatus, and more particularly, to a data recording medium and a data recording / reproducing apparatus characterized by a track control portion in a multilayer recording layer using tracks formed in a spiral shape. About.

[0002]

2. Description of the Related Art In recent years, memories such as optical disks have been required to have a large capacity. On the other hand, by providing multiple recording layers on the disc and controlling the focus of the optical pickup, each layer can be selectively reproduced,
Alternatively, an apparatus for recording and reproducing has been devised.

For example, Japanese Patent Application Laid-Open No. Hei 8-212561 discloses such a multilayer recording disk and a recording / reproducing apparatus therefor.

[0004] However, the disclosure of the multilayer recording disk described in the above-mentioned literature does not sufficiently consider the tracking means.

When there are a large number of recording layers, it is necessary to provide track guides, which are fixed information, in all of the layers, which increases the manufacturing cost.

In the case of single-layer recording, as a tracking means, the intensity of the reflected light of the recording layer is read and followed, but in the case of a multi-layer disc, the transmittance of the recording layer must be increased. And the amount of light sufficient for tracking cannot be obtained.

In order to solve such a problem, it has been proposed to provide a track guide layer. For example, Japanese Patent No. 2835074 discloses a multilayer recording disk having a track guide layer.

[0008]

However, in the disclosure of the multilayer recording disk described in the above-mentioned prior art document, there is no consideration for spiral recording.

When a track guide layer is provided, an information track is formed on the recording layer along a track guide recorded on the track guide layer.

Considering that the information track is spirally recorded from the inner circumference to the outer circumference, recording is to be performed on the next layer when the information track reaches the outermost circumference which is the end of the information track. The recorded track guide is spiral, so you have to jump to the innermost circumference or reverse the disk. In particular, when continuity is required as in the case of audio or image data, the time for reversely rotating the disk becomes a major problem. Also, when the rotation speed of the disk is different between the inner circumference and the outer circumference as in CLV recording, it is necessary to stabilize the rotation of the disk by jumping from the outermost circumference to the innermost circumference, and the time required for this is fatal. Become.

That is, if the spiral of the track guide recorded on the track guide layer is in only one direction, it is difficult to move the recording layer, and high-speed continuous access becomes impossible.

The present invention has been made in view of the above circumstances, and even in a case where the recording layer has a low reflectivity and servo cannot be applied by the recording layer itself, it is possible to obtain a sufficient amount of light for the servo. It is an object of the present invention to provide a data recording medium and a data recording / reproducing apparatus which can move at high speed between a plurality of recording layers.

[0013]

According to the present invention, there is provided a data recording medium comprising: a first recording layer in which a data recording direction is defined in a first recording direction spirally extending from the inner periphery to the outer periphery of a disk; A second recording layer defined in a second recording direction in which the data recording direction spirals from the outer periphery to the inner periphery of the disc; and a first track guide recorded along the first recording direction. And a second track guide recorded along the second recording direction.

[0014] The data recording / reproducing apparatus of the present invention comprises: a first recording layer in which a data recording direction is defined in a first recording direction spirally extending from the inner periphery to the outer periphery of the disc;
A second recording layer defined in a second recording direction in which the data recording direction spirals from the outer periphery to the inner periphery of the disc; and a first track guide recorded along the first recording direction. And a single track guide layer having a second track guide recorded along the second recording direction, and a data recording medium that performs recording and reproduction of data, As a track control operation in the first track guide and the second track guide, a track control mechanism for alternately switching operation / non-operation is provided.

[0015]

Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) FIGS. 1 and 2 relate to a first embodiment of the present invention. FIG. 1 is a diagram showing a cross section of a multilayer recording disk and a configuration of a recording / reproducing apparatus. FIG.
FIG. 4 is an explanatory diagram for explaining a first groove of a first track guide layer and a second groove of a second track guide layer.

As shown in FIG. 1, a multilayer recording disk 10 according to the present embodiment has a first track guide layer 12 having a first groove 11 corresponding to a track guide and serving as a reflection surface, Second track guide layer 1 having group 13 and having higher transmittance than first track guide layer 12
4, a medium 15 such as a photopolymer, a photorefractive crystal, or a photochromic material provided below the second track guide layer 14, and provided on both surfaces of the first track guide layer 12 and on a lower surface of the medium 15. And a plurality of recording layers 17 to 22 in which information is recorded by changing the refractive index and the light absorption rate, respectively, at different depth positions in the medium 15. . Here, the number of recording layers is six, but may be any number.

FIG. 2 shows a recording direction of information when the multilayer recording disk 10 is viewed from above in FIG. The first groove 11 of the first track guide layer 12 is spirally recorded in the forward spiral direction from the inner periphery to the outer periphery as shown in the recording direction 50 (FIG. 2A), and the second groove 11 is formed. The second grooves 13 of the track guide layer 14 are spirally recorded in a reverse spiral direction from the outer periphery to the inner periphery as shown in the recording direction 51 (FIG. 2B). The directions of the information tracks recorded on the recording layers 17 to 22 alternately coincide with the directions of the first groove 11 and the second groove 13, and the odd-numbered recording layers have the order shown in the recording direction 50. An information track is recorded in the spiral direction from the start end 52 to the end 53, and an information track is recorded on the even-numbered recording layer in a reverse spiral direction as shown in the recording direction 51 from the start end 54 to the end 55. Be recorded.

As described above, the reflectivity of the second track guide layer 14 is lower than the reflectivity of the first track guide layer 12. For example, the reflectivity is set to about 38%.

Assuming an ideal state, the transmittance of the recording layers 17 to 22 is 100%, the reflectance of the first track guide layer 12 is 100%, and the absorptance of the second track guide layer 14 is 0%. Then, the servo laser light that passes through the second track guide layer 14 and reaches the first track guide layer 12 is 100-28 = 62%, and the reflected light of the first track guide layer 12 is the second laser light. Is 0.62 × 0.62 = 0.38, which is 38%, which is approximately equal to the reflected light of the second track guide layer 14, and symmetry is obtained.

If the reflectivity is about 38%, the servo can be operated stably.

Returning to FIG. 1, a method for recording / reproducing information with respect to each recording layer of the multilayer recording disk 10 of this embodiment is as follows.
0 and a servo laser beam 40 for performing focus control and tracking control are irradiated to perform recording / reproduction on a desired recording layer. The wavelength of the recording / reproducing laser beam 30 is shorter than the wavelength of the servo laser beam 40.

The recording / reproducing laser light 30 is emitted from the semiconductor laser 31, converted into parallel light by a collimator lens 32, and made to enter a polarization beam splitter 33 as P-polarized light. 1/4
The laser beam is made incident on a dichroic prism 35 via a wave plate 34 and reflected by the dichroic prism 35, and the laser light reflected by the dichroic prism 35 is collected on an information track of a desired recording layer of the multilayer recording disk 10 by an objective lens 36. Light up. The objective lens 36 is mounted on the multilayer recording disk 1 by a biaxial actuator (not shown).
The driving direction is configured in the focus direction and the tracking direction with respect to 0.

The recording / reproducing laser beam 30 reflected by the multi-layer recording disk 10 follows a path reverse to the outward path, passes through an objective lens 36, a dichroic prism 35, and a quarter-wave plate 34, and a polarization beam splitter. 33. Here, the reflected light from the multilayer recording disk 10 that enters the polarization beam splitter 33 passes through the quarter-wave plate 34 on the outward path and the return path, and becomes S-polarized light, and is reflected by the polarization beam splitter 33. The laser beam reflected by the polarization beam splitter 33 is transmitted to a detection lens 37
Then, the light is received by the photodiode 38 at the light-converging point, and a desired recording layer of the multilayer recording disk 10 is recorded / reproduced based on the output.

On the other hand, the servo laser light 40 is emitted from the light source unit 41. In this light source unit 41,
A semiconductor laser, a photodetector 43, and a hologram 44 are provided, and a servo laser beam 40 having a wavelength different from that of the recording / reproducing laser beam 30 is emitted from the semiconductor laser 42 via the hologram 44. The laser light 40 for servo from the light source unit 41 is converted into parallel light by a collimator lens 45, then passes through a dichroic prism 35, and is passed by an objective lens 36 to a first track guide layer 12 or a second track guide layer of the multilayer recording disk 10. 2 track guide layers 1
Focus on 4 The collimator lens 45 is configured to be drivable in the focus direction by a one-axis actuator (not shown).

The servo laser light 40 reflected by the multi-layer recording disk 10 follows a path reverse to the outward path, passes through the objective lens 36, the dichroic prism 35, and the collimator lens 45 to the hologram 44 of the light source unit 41. Inject and diffract, detect the focus error signal by the known beam size method or Foucault method,
A tracking error signal is detected by a push-pull method.

In the embodiment described above, for example, when reading information recorded on the recording layer 17 of FIG. 1, the objective lens 36 and the collimator lens 45 are arranged so that the recording / reproducing laser beam is focused on the recording layer 17. It is driven in the focus direction, and the objective lens 36 is driven in the focus direction and the tracking direction based on the focus error signal and the tracking error signal, so that the recording / reproducing laser beam 30 is condensed on the recording layer 17 and is used for servo. Laser light 4
0 is the first groove 11 of the first track guide layer 12
The light is condensed on the top and controlled to follow a desired information track. When information recorded on the recording layer 18 is read, similarly, a desired information track is followed by tracking the second groove 13 of the second track guide layer 14.

When moving the layer to be read from the recording layer 17 to the recording layer 18, since the recording direction is reversed, the track direction is changed from the forward spiral direction (inner circumference → outer circumference) to the reverse spiral direction (outer circumference → inner circumference). Need to switch to.

For this purpose, first, the spot of the servo laser beam focused on the first track guide layer 12 is changed to the second spot.
To the track guide layer 14. As a moving procedure, the collimator lens 45 is locked, the servo on the first groove 11 is released, the objective lens 36 is moved in the focusing direction, and the laser light for servo is focused on the second track guide layer 14. Illuminate the second groove 13
Tracking to

Then, in order to move the recording layer, the recording / reproducing laser beam is focused on the recording layer 18 by interlocking the objective lens 36 and the collimator lens 45. As an interlocking operation, for example, when it is desired to move the focus of the recording / reproducing laser beam downward in the drawing, the collimator lens 45 is moved downward, and the objective lens 36 is moved to the second track guide layer 1.
When the objective lens 36 moves downward so as to focus on the focal point 4, the focus of the recording / reproducing laser beam also moves downward.

By configuring as in the present embodiment, in a multi-layer recording disk having a recording direction in the spiral direction, the servo is reliably applied even when the recording layer has a low reflectance and the servo cannot be applied. It is possible,
In addition, movement between layers can be performed at high speed.

This embodiment can also be applied to multilayer CLV recording. In CLV recording, the linear density of information is substantially the same at the inner circumference and the outer circumference. Therefore, it is necessary to change the rotation speed of the disk between the inner circumference and the outer circumference. If the recording / reproducing device is moved from the outer periphery to the inner periphery when moving between a plurality of recording layers, not only the moving time of the recording / reproducing device but also the time required to change and stabilize the rotational speed of the disk is required.
In the present embodiment, since the recording layer is moved on either the inner circumference or the outer circumference, it is possible to save the moving time of the recording / reproducing device and the time for changing and stabilizing the rotation speed of the disk. .

In this embodiment, a plurality of recording layers are formed below the first track guide layer 12 and the second track guide layer 14. However, the first track guide layer 12 and the second track The guide layer 14 is an intermediate layer,
An even number of recording layers are provided on the upper layer and the lower layer of the intermediate layer, and the recording directions between the even number of recording layers provided on the upper layer and the lower layer are alternately changed to different spiral shapes (see FIG. 2: forward spiral, reverse spiral). Is also good.

(Second Embodiment) FIGS. 3 to 9 relate to a second embodiment of the present invention, FIG. 3 is a first explanatory diagram for explaining a multilayer recording disk, and FIG. FIG. 5 is a second explanatory diagram illustrating the multilayer recording disk, FIG. 5 is a third explanatory diagram illustrating the multilayer recording disk of FIG. 3, and FIG. 6 illustrates a configuration of a control circuit that performs track control of the multilayer recording disk of FIG. FIG. 7 is a waveform diagram showing the waveforms of the sum signal and the difference signal of FIG. 6, FIG. 8 is a configuration diagram showing the configuration of the area discriminating groove detecting unit and the judging unit of FIG. 6, and FIG. 9 is the control circuit of FIG. 3 is a flowchart showing a flow of track control of a multilayer recording disk in FIG.

Since the second embodiment is almost the same as the first embodiment, only different points will be described, and the same components will be denoted by the same reference numerals and description thereof will be omitted.

When the first embodiment is to be realized, there is a problem that the servo becomes complicated. This is because, when moving the track guide layer, it is necessary to once remove the focus control of the servo laser beam and re-execute the focus control on another layer again, resulting in a time loss.

In the second embodiment, in consideration of such a situation, grooves in the forward spiral direction and the reverse spiral direction are provided on the same track guide layer.

Normally, when the forward spiral and the reverse spiral are overlapped with each other, two intersecting places are formed during one round of the disk as shown in FIG. If the track guide is a groove, interference of a track error signal occurs at the intersection.

In order to avoid this, in the present embodiment,
An area 60 where grooves in the forward spiral direction are recorded as shown in FIG. 4A and an area 61 where grooves in the reverse spiral direction are recorded as shown in FIG. To distribute.

At the boundary between the regions 60 and 61, region discriminating grooves 62 and 63 are provided radially with respect to the disk. The region discriminating groove has a reflectivity lower than that of the groove, and is formed of a single groove. The discriminating grooves 62 and the area discriminating grooves 63 composed of two grooves are alternately arranged, and the area discriminating grooves 62 are used for discriminating the area 60, and the area discriminating grooves 63 are used for discriminating the area 61.

While the servo laser beam spot can be tracked in the groove while it is present in the area 60, the track actuator is fixed when it enters the area 61 in which the groove in the reverse spiral direction is recorded. , Tracking is likely to come off. Especially the area 60
When the track actuator is fixed for a long time, the correct track cannot be pulled in when the next area 60 is entered. Therefore,
The regions 60 and 61 are required to be finely divided.

That is, in FIG.
Although the area is divided into regions, taking into account the band of tracking control, the requirement can be satisfied by dividing into approximately 100 regions. That is, the band required for tracking is generally referred to as 3 to 4 kHz, and 6 to 8 kHz is required in consideration of the sampling theorem.
Assuming that the disk rotation speed is 3600 rpm, 6
Since the frequency is 0 Hz, the number of track guide areas required for tracking control per disk rotation is 6000、6.
0 = 100.

FIG. 5 is an enlarged view of the disk to show the positional relationship between the groove and the area discriminating groove. Area 60 in which groove 70 in the forward spiral direction is recorded
There is an area 61 in which a groove 72 in the reverse spiral direction is recorded, and one area discriminating groove 62 is provided at the boundary where the spot 76 of the servo laser light switches from the area 61 to the area 60 when the disk is rotated. In the boundary where the region 60 is switched to the region 61, two region determination grooves 63 are provided, and the spot 76 of the servo laser beam moves along the groove when viewed from the disk. Be sure to cross the discrimination groove 63.

For example, the operation of tracking in the forward spiral direction will be described with reference to the block diagram of FIG. For tracking, a push-pull method is used. The servo laser beam reflected by the disk is received by the two-divided PD 80, and the subtractor 81
The difference signal 87 is calculated / amplified, the track controller 82 calculates the amount of deviation from the groove, and drives the track actuator 83 so that the spot of the servo laser beam follows the groove. At the same time, the sum signal 88 (see FIG. 7) of the two-divided PD 80 is calculated and amplified by the adder 84, and when the area discriminating groove detecting section 85 crosses the area discriminating groove, the sum signal 88 becomes a predetermined area detecting threshold value 89 ( (See FIG. 7), the discrimination section 86 judges that one area discrimination groove has been detected if the sum signal has decreased once, and the track control section 82 immediately pulls the track. If an instruction is issued and the sum signal drops twice, it is determined that two area discriminating grooves have been detected, and the spot of the servo laser beam enters the area where the groove in the reverse spiral direction has been recorded. An instruction is issued to the section to fix the track actuator 83.

The area discriminating groove detecting section 85 detects the area discriminating groove by utilizing the difference in the reflectance between the groove and the area discriminating groove. That is, as shown in FIG. 8, since the reflectivity of the region discriminating groove is lower than that of the groove, when the spot of the servo laser beam enters the region discriminating groove, the sum signal of the two-divided PD decreases. It is detected when the value falls below the detection threshold value 89, and the number of times the value falls below the detection threshold value 89 is counted by the counter 92.

The determination section 86 uses the count number output from the area determination groove detection section 85 as a track control flag.
The XOR 96 controls the track control unit 82 by taking an exclusive OR with the flag indicating the tracking direction from the CPU 95. When the count number is 1, the number of the region determination grooves is one, and the region
Is determined, the flag for track control is set to 1 so that the track control unit performs tracking. When the count number is 2, there are two area determination grooves. By making a decision, the track control flag is set to 0, and the track control unit is fixed.

FIG. 9 is a flow chart showing a series of operations of the judgment section 86.
Shown in It is configured to have two types of flags, SF as a flag indicating the direction of tracking from the CPU 95 and TF as a flag indicating an area where the servo laser beam is currently incident. In step S1, the direction to be tracked is determined from the address of the data to be accessed. In the case of the forward spiral direction, SF = 1 is set in step S2, and in the case of the reverse spiral direction, SF = 0 is set in step S3. Then, in step S4, the area where the servo laser beam is currently incident is determined from the output of the area discriminating groove detecting section 85, and if it is determined that the area is in the area 60 where the groove in the forward spiral direction is recorded, step S4 is performed. TF = 1 in S5,
Area 61 in which grooves in the reverse spiral direction are recorded
If it is determined that TF = 0, TF = 0 is set in step S6.

In step S7, the SF takes the exclusive OR with the TF. When the exclusive OR is 0, if the SF is 1 and the TF is 1 in step S8, it is necessary to perform tracking in the forward spiral direction. In addition, since the current position of the servo laser beam is also an area where grooves in the forward spiral direction are recorded, a command is given to the track control unit to operate the track actuator. Similarly, when SF is 0 and TF is 0, tracking is performed in the reverse spiral direction.

When the exclusive OR is 1, in step S9, SF is 1 and TF is 0, or SF is 0 and TF is 0.
Is 1, the tracking direction does not match the direction of the groove recorded in the current area.
A command is given to the track control unit to fix the track actuator.

That is, if the exclusive OR of SF and TF is obtained and the value is 0, the track actuator is turned on.
In the case of 1, the track actuator is fixed.

The operation for tracking in the forward spiral direction has been described above. When switching the tracking in the reverse spiral direction, the track is pulled in when two discriminating grooves are detected by the discriminating section 86 in FIG. When one is detected, control may be performed so that the track actuator is fixed.

With the structure as in the present embodiment, in addition to the effect of the first embodiment, the groove in the forward spiral direction and the groove in the reverse spiral direction are recorded on the same track guide layer, so that the recording surface is improved. Since it is not necessary to remove the focus control of the servo laser beam when moving the laser beam and switching the tracking direction, the control can be performed easily and at high speed. Further, by using one track guide layer, the manufacturing cost can be reduced.

Note that, as in the first embodiment, the area 6
A track guide layer provided with 0 and 61 is an intermediate layer, and an even number of recording layers are provided on an upper layer and a lower layer of the intermediate layer, and the recording directions between the even number of recording layers provided on the upper layer or the lower layer are alternately different from each other. (See FIG. 2: forward spiral,
(Reverse spiral).

[0054]

As described above, according to the present invention, even when the reflectivity of the recording layer is low and servo cannot be applied by the recording layer itself, a plurality of servos can be obtained while obtaining a sufficient light amount for the servo. There is an effect that the movement between the recording layers can be performed at high speed.

[Brief description of the drawings]

FIG. 1 is a diagram showing a cross section of a multilayer recording disk and a configuration of a recording / reproducing apparatus according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram illustrating a first groove of a first track guide layer and a second groove of a second track guide layer in FIG. 1;

FIG. 3 is a first explanatory view illustrating a multilayer recording disk according to a second embodiment of the present invention;

FIG. 4 is a second explanatory diagram illustrating the multilayer recording disk of FIG. 3;

FIG. 5 is a third explanatory view illustrating the multilayer recording disk of FIG. 3;

FIG. 6 is a configuration diagram showing a configuration of a control circuit that performs track control of the multilayer recording disk of FIG. 4;

FIG. 7 is a waveform chart showing waveforms of a sum signal and a difference signal of FIG. 6;

FIG. 8 is a configuration diagram showing a configuration of an area determination groove detection unit and a determination unit in FIG. 6;

FIG. 9 is a flowchart showing a flow of track control of the multilayer recording disk in the control circuit of FIG. 6;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Multi-layer recording disk 11 ... 1st groove 12 ... 1st track guide layer 13 ... 2nd group 14 ... 2nd track guide layer 15 ... Medium 16 ... Protective layer 17-22 ... Recording layer 30 ... Information reading Laser light for use 31 Semiconductor laser 32 Collimator lens 33 Polarizing beam splitter 34 Quarter-wave plate 35 Dichroic prism 36 Objective lens 37 Detection lens 38 Photodiode 40 Servo laser light 41 Light source unit 42 ... semiconductor laser 43 ... photodetector 44 ... hologram

Claims (7)

[Claims] 1. A first recording layer in which a data recording direction is defined as a first recording direction spirally moving from an inner periphery to an outer periphery of a disk, and a data recording direction is defined from an outer periphery of the disk to an inner periphery. A second recording layer defined in a second recording direction heading spirally, and a first track guide recorded along the first recording direction and recorded along the second recording direction. And a track guide layer having a second track guide. 2. The track guide layer includes a first track guide layer and a second track guide layer, the first track guide is recorded on the second track guide layer, and the second track The data recording medium according to claim 1, wherein a guide is recorded on the second track guide layer. 3. The single track guide layer, wherein the first track guide and the second track guide are recorded on the single track guide layer. Item 2. The data recording medium according to Item 1. 4. The recording medium according to claim 1, wherein the recording density of the first recording layer and the recording density of the second recording layer are substantially the same on the inner circumference and the outer circumference, respectively. The data recording medium according to one of the above. 5. The data recording medium according to claim 1, wherein a recording layer having a pair of the first recording layer and the second recording layer is provided on an upper layer and a lower layer of the track guide layer. . 6. A first recording layer whose data recording direction is defined as a first recording direction spirally moving from the inner circumference to the outer circumference of the disc, and a data recording direction from the outer circumference to the inner circumference of the disc. A second recording layer defined in a second recording direction heading spirally, a first track guide recorded along the first recording direction and recorded along the second recording direction. A data recording / reproducing apparatus for recording / reproducing data on / from a data recording medium having a single track guide layer having a second track guide and the first track guide and the second track A data recording / reproducing apparatus having a track control mechanism for alternately switching operation / non-operation as a track control operation in a guide. 7. The data recording / reproducing apparatus according to claim 6, wherein the track control mechanism has an operation / non-operation switching cycle of about 10 kHz.