JP3556629B2 - Optical recording / reproducing method and optical recording / reproducing apparatus - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an optical recording medium and an optical recording / reproducing apparatus, and more particularly to an optical recording / reproducing method and an optical recording / reproducing apparatus for an optical recording medium having a multilayer recording layer.
[0002]
[Prior art]
In an optical recording medium, for example, a DVD-RAM, which is a phase-change rewritable optical disk, information is recorded by changing the intensity of light to be focused and irradiated on the disk to form a phase-change mark array. On the other hand, information reproduction is performed by irradiating the disk with light of a constant intensity lower than that in the case of recording, and detecting the phase change mark array from the amount of reflected light.
[0003]
As a method for improving the recording capacity of one RAM-type optical disk, a single-sided, two-layer structure in which two recording films are stacked is considered. This is based on the single-sided, two-layer technique employed in DVD-ROMs, which are read-only optical discs. Irradiation light is applied to a disc manufactured with two recording layers separated by a transparent layer. Light is condensed from the same side, and recording and reproduction are performed on either of the recording layers. For example, when recording / reproducing information on a recording layer on the back side (hereinafter, referred to as a second recording layer) when viewed from the light incident direction, a recording layer on the near side with respect to the light incident surface (hereinafter, referred to as a second recording layer). , The first recording layer), the transmittance of the first recording layer changes in an area irradiated with the recording / reproducing light beam depending on the recorded / unrecorded state. Accordingly, when the state of the first recording layer irradiated with the light beam of the recording / reproducing light changes from the recorded state to the unrecorded state or from the unrecorded state to the recorded state, the second recording layer , The amount of light that arrives at the device rapidly changes, so that information recording and reproduction cannot be performed stably.
[0004]
When information is reproduced from the second recording layer, the reflected light from the second recording layer is superimposed on the reflected light from the first recording layer. The reflectivity of the first recording layer changes depending on the recorded / unrecorded state of the area of the first recording layer. Thereby, when the state of the first recording layer irradiated with the light beam of the recording / reproducing light changes from the recorded state to the unrecorded state, or from the unrecorded state to the recorded state, the state of the second recording layer is changed. The intensity of the reflected light, that is, the intensity of the reproduced signal changes, and information cannot be reproduced stably.
[0005]
By the way, the track centers of the first recording layer and the second recording layer are aligned with the mechanical precision, but include a slight deviation. Therefore, when the optical disc rotates during recording / reproducing of information, eccentricity occurs, and the track irradiated with the light beam of the recording / reproducing light is shifted between the first recording layer and the second recording layer. For example, when information is recorded / reproduced on a certain track of the second recording layer, the luminous flux of the recording / reproducing light applied to the first recording layer changes from a recorded state to an unrecorded state due to eccentricity. Alternatively, there is a possibility that the state changes from an unrecorded state to a recorded state. Then, the transmittance changes when the recording / reproducing light applied to the second recording layer passes through the first recording layer, and the amount of light reaching the second recording layer changes rapidly, and Recording cannot be performed stably. Further, when the reproduction light reflected from the second recording layer passes through the first recording layer, the reproduction light is superimposed on the reflection light from the first recording layer, and the reproduction signal intensity changes, so that information can be stably recorded. become unable.
[0006]
Furthermore, although the case where information is recorded / reproduced on a track having the second recording layer has been described here, the present invention is not limited to this, and information is reproduced on a track having the first recording layer. The same is the case. That is, since the reflectance of the second recording layer irradiated with the light beam of the recording / reproducing light changes according to the recorded / unrecorded state, the reflected light from the first recording layer is reflected by the second recording layer. The intensity of the reproduced signal is greatly changed by being superimposed on the reflected light from the optical disk, thereby deteriorating the stability of reproduction on the optical disk.
[0007]
[Problems to be solved by the invention]
As described above, in the related art, the tracks on the first recording layer and the tracks on the second recording layer irradiated with the light beam of the recording / reproducing light are irradiated in a state where they are deviated due to eccentricity. Therefore, for example, when information is recorded / reproduced on a certain track of the second recording layer, the track on the first recording layer irradiated with the light beam of the recording / reproducing light changes from a recorded state to an unrecorded state, Alternatively, the state changes from an unrecorded state to a recorded state, and the transmittance of the first recording layer changes. As a result, the amount of recording / reproducing light applied to the second recording layer suddenly changes before passing through the first recording layer and arriving at the second recording layer. Cannot be performed stably.
[0008]
In addition, when the reproduction light reflected from the second recording layer passes through the first recording layer, the reproduction light is superimposed on the reflection light from the first recording layer, and the reproduction signal intensity is changed. There was a problem that could not be done.
[0009]
Furthermore, when information is reproduced from a track on the first recording layer, the reflectivity of the second recording layer irradiated with the light beam of the reproduction light changes according to whether the information is recorded or unrecorded. The reflected light from the first recording layer is superimposed on the reflected light from the second recording layer, causing a large change in the intensity of the reproduced signal, and the stability of reproduction on the optical disc is impaired.
[0010]
The present invention has been made to solve such a problem, and the reflectance / transmittance of an optical disc having two or more recording layers has a reflectance / transmittance at a boundary between the recorded area and the unrecorded area. It is an object of the present invention to realize an optical recording / reproducing method and an optical recording / reproducing apparatus for recording a boundary area having an intermediate value between area values.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, the present invention irradiates a laser beam from one side of an optical recording medium having a plurality of stacked recording layers, and records information on a selected recording layer, In the optical recording / reproducing method of reproducing the information by obtaining the reflected light reflected from the recording layer, a method may be used in which a recorded area where the information is recorded on the recording layer and an unrecorded area where the information is not recorded yet. Is divided into n areas, and for each of the divided areas, the information is recorded every N1, N2,..., Nn (1 <N1 <N2 <,..., <Nn) tracks. And
[0012]
With the above configuration, even when recording / reproducing is performed on another information recording layer, the degree of interference due to a change in reflectance and transmittance in the information recording layer in which a recorded area and an unrecorded area are present suddenly changes. And information can be stably recorded / reproduced.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0014]
FIG. 1 is a block diagram showing the overall configuration of an optical recording / reproducing apparatus according to an embodiment of the present invention.
In FIG. 1, an optical disc 1, which is an information recording medium, has a single-sided, two-layer structure in which two recording layers of the same phase change type as a DVD-RAM are laminated. A transparent layer 4 is interposed between the lower first recording layer 2 and the upper second recording layer 3. That is, the first and second recording layers 2 and 3 are laminated with the transparent layer 4 interposed therebetween. The optical disk 1 is driven to rotate at a predetermined speed by a spindle motor 5.
[0015]
The optical pickup 7 irradiates the optical disc 1 with a laser beam from below, focuses the laser beam on one of the first and second recording layers selected by the objective lens 9, and focuses only on the selected recording layer. Is recorded and reproduced.
[0016]
The objective lens 9 is driven to be moved closer to or farther from the optical disc 1 by a focus actuator 11 having a magnet (not shown) and a moving coil cooperating with the magnet. Further, similarly to the focus actuator 5, the objective lens 9 can be moved in the radial direction of the optical disc 1 by a tracking actuator 13 having a magnet and a moving coil (not shown). The laser light emitted by the semiconductor laser provided in the optical pickup 7 is condensed on the recording layer of the optical disc 1 via the objective lens 9, reflected by the presence or absence of pits on the optical disc 1, and reflected. Not received by the photodetector.
[0017]
The RF amplifier 14 includes, for example, an adder and a subtractor, and generates and outputs a focus error signal, a tracking error signal, and a reproduction signal from the information signal received by the photodetector.
[0018]
The servo processing circuit 15 generates, based on the generated focus error signal and tracking error signal, a focus control signal and a tracking control signal for ensuring that the laser beam converges on the pit row to be tracked, and 11, supply to the tracking actuator 13. As a result, a servo loop is formed and servo control is performed.
[0019]
The signal processing circuit 17 converts the reproduced signal generated by the RF amplifier 14 into an electric signal.
[0020]
The decoding circuit 19 performs a decoding process such as an 8-16 demodulation and an error correction process on the electric signal converted by the signal processing circuit 17. The decoded signal is transmitted to an external device (not shown), for example, a host computer via an interface.
[0021]
The recording information storage memory 21 stores the recording information transmitted from the host computer via the interface, and also stores the boundary recording information necessary for forming the boundary area. This boundary region is a region between a recorded region and an unrecorded region, which gradually changes from the average transmittance and reflectance in the recorded region to the average transmittance and reflectance in the unrecorded region. This is an area provided so that after the recording information is recorded, boundary recording information described later is recorded to form a boundary area. Note that the average transmittance and reflectance in the recorded area refer to the transmittance and reflectance felt by the defocused beam. That is, in the information recording (recorded area), the area ratio between the recording mark and the space (the part where no recording mark is formed) is 1: 1 on average in a wide range. , The average of the transmittance and the reflectance of the space. The average transmittance and reflectance in the unrecorded area mean the transmittance / reflectance of the space since the entire unrecorded area can be interpreted as a space.
[0022]
The encoding circuit 23 performs an encoding process such as 8-16 demodulation and an error correction process on the recording information stored in the recording information storage memory 21.
[0023]
The recording waveform generation circuit 25 generates a recording pulse signal for recording on the optical disc 1 from the recording information encoded by the encoding circuit 23.
[0024]
The LD drive control circuit 27 controls the semiconductor laser provided in the optical pickup 7 based on the recording pulse signal generated by the recording waveform generation circuit 25.
[0025]
All these device operations are performed under the control of the controller 29.
[0026]
FIG. 2A is a diagram showing an optical disc in which a boundary area is provided between a recorded area and an unrecorded area, in which a first recording layer and a second recording layer have a center deviation. It is. FIGS. 2B and 2C are cross-sectional views of the optical disk shown in FIG. 2A in a state where laser light is applied to the positions X and Y of the recording / reproducing tracks.
[0027]
In FIG. 2A, the optical disc 1 has two phase-change recording type information recording layers laminated on one side. The first recording layer is disposed on the near side with respect to the light incident surface, and the second recording layer is disposed on the far side with respect to the light incident surface. In the first recording layer, information is recorded such that the transmittance and the reflectance of the recorded area where the information is recorded from the inner peripheral side by the optical pickup 7 and the transmittance and the reflectance of the unrecorded area from the recorded area change stepwise. A boundary area and an unrecorded area that has not yet been recorded are formed. In this state, it is assumed that the optical pickup 7 performs recording / reproducing from a track having a second recording layer, that is, from a position Y to a position X of a recording / reproducing track shown in the drawing.
[0028]
Now, assuming that the recording / reproducing light emitted from the optical pickup 7 is converging at the position Y of the recording / reproducing track on the second recording layer, the luminous flux of the recording / reproducing light on the first recording layer is already present. The recording area is irradiated (see FIG. 2C). Also, when the recording / reproducing light is converging on the position X of the recording / reproducing track on the second recording layer, it can be seen that the light flux of the recording / reproducing light on the first recording layer irradiates the boundary area. (See FIG. 2 (b)). This is because there is a limit in the accuracy of aligning the centers of a plurality of recording layers when manufacturing the optical disc 1 having multiple recording layers.
[0029]
If there is this center deviation, eccentricity occurs when the optical disc 1 rotates, and the first recording and reproducing light when the recording / reproducing light is condensed at the positions Y and X of the recording / reproducing tracks on the second recording layer. The region irradiated with the light beam of the recording / reproducing light in the layer changes. Then, the transmittance / reflectance changes between the recorded area and the unrecorded area in the first recording layer, and the amount of recording / reproducing light reaching the second recording layer or the second recording layer The intensity of the reflected light (reproduced signal) from the device changes rapidly. Therefore, by forming the boundary area according to the present invention after the already-recorded area, the amount of recording / reproducing light and the intensity of the reproduced signal can be prevented from abruptly changing.
[0030]
In order to form this boundary area, it is necessary to calculate the deviation due to the eccentricity of the first recording layer and the second recording layer to determine the range of the boundary area. That is, when recording / reproducing on / from the second recording layer, the number of tracks on which the light flux of the recording / reproducing light on the first recording layer can be irradiated is calculated to determine the range of the boundary area. Assuming that the number of tracks that can be irradiated is δ, the eccentricity of the optical disc 1 is R, the radius of the first recording layer irradiated with the light beam is R, and the track pitch is Tp.
(2R + δ) / Tp [track] (1)
It becomes.
[0031]
However, the range to be processed as the boundary area only needs to have a track corresponding to the radius of the area where the light beam irradiates the first recording layer.
(R + δ) / Tp [track] (2)
It becomes.
[0032]
Therefore, the boundary areas are provided by the determined number of tracks. Actually, the controller 29 calculates the number of tracks by using the equation (2), and controls the number of tracks to provide a boundary area following the completion of the recording of the recording information. The eccentricity information refers to eccentricity information recorded in advance on the optical disc, and determines a range to be processed as a boundary area. When the information of the eccentricity is not recorded in advance on the optical disc, the range to be processed as the boundary area may be determined by using the maximum value of the eccentricity determined by the optical disc standard.
[0033]
The recording process of the boundary area will be described with reference to the flowchart of FIG.
[0034]
It is assumed that both the first and second recording layers are unrecorded areas. When information is recorded on the first or second recording layer, the LD drive control circuit 27 emits light from a semiconductor laser provided in the optical pickup based on the record information stored in the record information storage memory 21. Control the laser light. The controlled laser light is condensed from the optical pickup 7 onto the first or second recording layer, and recording information is recorded (step S1). Then, the controller 29 calculates the deviation due to the eccentricity using the above equation (2), and determines the range of the boundary area (steps S3 and S5). Further, the controller 29 controls the encoding circuit 23, the recording waveform generation circuit 25, and the LD drive control circuit 27 to read the boundary recording information stored in the recording information storage memory 21 (Step S7). With this control, the boundary recording information stored in the recording information storage memory 21 is read, and the LD drive control circuit 27 causes the semiconductor laser to record the boundary recording information following the recording information recorded in step S1. Control is performed (step S9). Therefore, after the already recorded area where the recording information is recorded on the first or second recording layer of the optical disc 1, the boundary recording information is recorded only within the calculated boundary area.
[0035]
Next, the boundary record information recorded in the boundary area in step S9 will be described with reference to FIGS.
[0036]
In FIG. 4, in the boundary area, every few tracks, for example, every two tracks, such that the average transmittance / reflectance in the recorded area gradually changes from the average transmittance / reflectance in the unrecorded area. The boundary record information is recorded in the. By performing recording in this way, for example, when recording / reproducing is performed on the second recording layer, the first recording layer irradiated with the optical path focused on the second recording layer has already been irradiated. It can have an intermediate transmittance / reflectance between the average transmittance / reflectance in the recording area and the average transmittance / reflectivity in the unrecorded area. That is, in the first recording layer, the luminous flux of the recording / reproducing light to be irradiated is considerably wide because it is in a defocused state. In this state, when the entire boundary area recorded every two tracks is viewed, an average is obtained. Transmittance / reflectance can be obtained.
[0037]
In FIG. 5, boundary recording information is recorded every few tracks in the boundary area of FIG. 4, but here, it is divided into two areas such as a first boundary area and a second boundary area. The interval between tracks recorded in the boundary area is changed. At the time of division, the controller 29 calculates and determines a region to be divided from the number of tracks calculated using the above equation (2). The first boundary area is provided adjacent to the recorded area, and the second boundary area is provided adjacent to the first boundary area, and the other is provided adjacent to the unrecorded area. In the first boundary area, information is recorded every M tracks, and in the second boundary area, information is recorded every N tracks. That is, when the boundary recording information is recorded in the first and second boundary regions so that the relationship of M <N holds, the average transmission is performed from the recorded region to the unrecorded region, that is, in the boundary region. The reflectivity and reflectivity are changed in three steps from the value of the recorded area to the value of the unrecorded area. Therefore, the conversion between the transmittance and the reflectance can be made more gradual than in the boundary region in FIG. Here, the case where the boundary region is divided into two has been described, but the same effect can be expected even when the boundary region is generalized and divided into K.
[0038]
Further, in FIG. 6, in FIGS. 4 and 5, information is recorded at least every two tracks in a boundary area between a recorded area and an unrecorded area. However, it is assumed that information is recorded on continuous tracks. That is, recording is performed by changing the ratio of recording marks and spaces to be recorded in order to change the average transmittance and reflectance.
[0039]
Assuming that the transmittance / reflectivity of the recording mark is Tm, Rm and the transmittance / reflectivity of the space is Ts, Rs, when the appearance ratio of the recording mark and the space is 50:50, the average transmittance T, The reflectance R is
T = (１ ／) × Tm + (１ ／) × Ts (3)
R = (１ ／) × Rm + (１ ／) × Rs (4)
It becomes.
[0040]
Next, when the appearance ratio of recording marks and spaces is a: b,
T = (a / (a + b)) × Tm + (b / (a + b)) × Ts (5)
R = (a / (a + b)) × Rm + (b / (a + b)) × Rs (6)
It becomes. All unrecorded areas are considered as spaces.
[0041]
In order to change the average transmittance / reflectance in the boundary area from the value of the recorded area to the unrecorded area, the appearance ratio of the recording mark and the space may be changed from 50:50 to 0: 100. I understand. When the appearance ratio of the recording mark and the space to be recorded in the boundary area is, for example, 25:75, it can be easily realized by recording the repetition signal of the 2T recording mark and the 6T space. Note that the boundary area may be divided as in FIG. 5 to change the appearance ratio of the recording mark and the space. In this case, assuming that the appearance ratio of the recording mark and the space is a1: 1 in the first boundary region and a2: 1 in the second boundary region, 1>a1> a2 may be satisfied.
[0042]
Therefore, information is recorded on a certain recording layer of an optical disc having a plurality of recording layers, and when a boundary between a recorded area and an unrecorded area occurs in this recording layer, a boundary area is provided, and the information is transmitted stepwise in this boundary area. The rate and reflectivity are varied. For this purpose, boundary recording information is recorded every few tracks, or divided into two regions such as a first and a second boundary region to change the interval between tracks to be recorded in each boundary region. Recording is performed by changing the appearance frequency of recording marks and spaces.
[0043]
The boundary record information to be recorded in the boundary area may record information (user information) that the user wants to record. In this case, when the user information is stored in the recording information storage memory 21 via, for example, the host computer, the controller 29 detects the recording information end signal indicating that the user information is nearing the end, and detects the detection. The recording process of the boundary area is started by the recording information end signal. The recording information end signal is added to the boundary recording information in advance by the host computer.
[0044]
Further, the boundary record information to be recorded in the boundary area may be information different from the information that the user wants to record. In this case, the dummy information stored in the recording information storage memory 21 in advance is recorded.
[0045]
As described above, in the present invention, when a recorded area and an unrecorded area exist in the first recording layer, stability is impaired even when information is recorded / reproduced on / from the second recording layer. Although such a configuration has been described, the effect of the present invention can be expected by performing the same processing even when the first recording layer and the second recording layer have the opposite relationship. Although the present invention has been described in connection with the case where the number of the recording layers is two, the effect of the present invention is not impaired even when the number of the recording layers is three or more. Further, in the present invention, it is not necessary to specify the order of recording information on the first recording layer and the second recording layer, and it is only necessary to record a boundary area when recording on a certain recording layer, which is convenient. Further improve.
[0046]
【The invention's effect】
As described above, even when recording / reproducing is performed on another recording layer, the degree of interference due to a change in the transmittance and the reflectance in the recording layer in which the recorded area and the unrecorded area exist suddenly changes. And information can be stably recorded / reproduced. This is because the amount of light transmitted through the first recording layer is abrupt, regardless of whether information is recorded / reproduced on / from the second recording layer or reproduced / reproduced from the first recording layer. And the intensity of the reflected light (reproduced signal) reflected from the first and second recording layers does not change significantly, so that information can be recorded / reproduced stably.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an overall configuration of an optical recording / reproducing apparatus according to an embodiment of the present invention.
FIG. 2 is a diagram showing an optical disc in which a boundary area is provided between a recorded area and an unrecorded area, in which a first recording layer and a second recording layer are shifted.
FIG. 3 is a flowchart of a boundary area recording process.
FIG. 4 is a diagram showing a boundary area recorded every two tracks.
FIG. 5 is a diagram showing a boundary area divided into two areas.
FIG. 6 is a diagram showing a boundary area recorded by changing the appearance ratio of a recording mark and a space.
[Explanation of symbols]
Reference Signs List 1 optical disk 2 first recording layer 3 second recording layer 4 transparent layer 5 spindle motor 7 optical pickup 9 objective lens 11 focus actuator 13 tracking actuator 14 RF amplifier 15 servo processing circuit 17 signal processing circuit 19 decoding circuit 21 recording Information storage memory 23 Encoding circuit 25 Recording waveform generation circuit 27 LD drive control circuit

Claims (4)

By irradiating laser light from one side of the optical recording medium having a plurality of stacked recording layers, information is recorded on the selected recording layer, and reflected light reflected from the recording layer is obtained. In the optical recording / reproducing method for reproducing the information,
An area between a recorded area in which the information is recorded on the recording layer and an unrecorded area that has not been recorded is divided into n areas, and the information is divided into N1 and N2 for each of the divided areas. ,..., Nn (1 <N1 <N2 <,..., <Nn) . 2. The optical recording / reproducing method according to claim 1, wherein the information recorded in the area is user data. By irradiating laser light from one side of the optical recording medium having a plurality of stacked recording layers, information is recorded on the selected recording layer, and reflected light reflected from the recording layer is obtained. In an optical recording and reproducing apparatus for reproducing the information,
Irradiation means for irradiating the recording layer with the laser light,
A first recording unit that records the information on the recording layer based on the laser light irradiated by the irradiation unit;
Dividing means for dividing an area between a recorded area in which the information is recorded by the first recording means and an unrecorded area not yet recorded into n areas;
A second recording means for recording the information at every N1, N2,..., Nn (1 <N1 <N2 <,..., <Nn) tracks for each area divided by the division means. An optical recording / reproducing apparatus characterized by the above-mentioned. The optical recording / reproducing apparatus according to claim 3, wherein the information recorded in the area is user data.

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