JP2003099948A - Optical recording medium, method for reproducing optical recording medium, and optical recording medium reproducing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical recording medium reproducing apparatus capable of efficiently preventing a reproduction deterioration phenomenon, in which the reproduction can be performed while rotating an optical recording medium at a constant linear velocity. SOLUTION: In the optical recording medium reproducing apparatus capable of reproducing the optical recording medium while rotating it at a constant linear velocity, the irradiation intensity of a laser beam is set at a first power when the reproduction is performed at a first linear velocity, and the irradiation intensity of the laser beam is set at a second power less than the first power when the reproduction is performed at a second linear velocity slower than the first linear velocity. Thus, the reproduction deterioration phenomenon is efficiently prevented, because the thermal energy per unit time from the laser beam which is received by the optical recording medium is leveled with respect to the reproducing linear velocity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording medium, and more particularly to an optical recording medium capable of reproduction by rotation control using the CLV system. The present invention also relates to a method of reproducing an optical recording medium, and more particularly to a method of reproducing an optical recording medium by rotation control using the CLV method. Furthermore, the present invention relates to an optical recording medium reproducing apparatus, and more specifically, a CL
The present invention relates to an optical recording medium reproducing device capable of reproduction by rotation control using the V method.

[0002]

2. Description of the Related Art Conventionally, optical recording media represented by CD and DVD have been widely used as recording media for recording digital data. The rotation control method of the optical recording medium at the time of recording / reproducing on such an optical recording medium is roughly classified into a method of rotating at a constant linear velocity (CLV method) and a method of rotating at a constant angular velocity (CAV method). be able to.

According to the rotation control using the CLV method, the data transfer rate becomes constant regardless of whether the recording / reproducing position is the inner peripheral portion or the outer peripheral portion of the optical recording medium. However, it is necessary to change the rotation speed of the optical recording medium according to the recording / reproducing position, but the control of the motor is complicated, and the random access speed is slow. have. On the other hand, the rotation control using the CAV method has an advantage that the random access speed is fast because the motor control is simple, but has a drawback that the data transfer rate is low. Although such a drawback can be solved to some extent by increasing the clock frequency as the recording position advances to the outer periphery of the optical recording medium, even in this case, the data transfer rate at the inner peripheral portion of the optical recording medium decreases. Is inevitable.

Recording / recording of currently used optical recording media
Most of the reproduction methods adopt the CLV method, which is a result of focusing on the advantage that the data transfer rate can be maximized.

Therefore, in order to obtain a high data transfer rate with a simple recording strategy, it is effective to adopt the CLV method.

[0006]

[Problems to be Solved by the Invention] However, CLV
When reproducing an optical recording medium on which data is recorded using the method, the reproduction linear velocity differs depending on the drive used, and reproduction is not always performed under the same conditions.

According to the research conducted by the present inventors, when the CLV system is adopted in a recordable optical recording medium using a phase change film or the like in the recording layer, the slower the reproducing linear velocity, the more the recording layer is accompanied with the reproduction of data. That the signal recorded in
It was found that a so-called "regeneration deterioration phenomenon" is likely to occur. This phenomenon is considered to be due to the fact that the thermal energy per unit time received by the laser beam becomes higher as the reproduction is performed at a slower linear velocity, and in order to enable high-speed recording, the recording layer is crystallized. It becomes more remarkable as the speed of the optical recording medium is increased.

Therefore, an object of the present invention is to provide an improved optical recording medium which can be reproduced using the CLV system.

Another object of the present invention is to provide an improved optical recording medium reproducing method using the CLV system.

Still another object of the present invention is CLV.
It is an object of the present invention to provide an improved optical recording medium reproducing apparatus capable of reproducing using the method.

Still another object of the present invention is to provide an optical recording medium, a reproducing method of the optical recording medium and an optical recording medium reproducing apparatus which can effectively suppress the reproduction deterioration phenomenon.

[0012]

The present invention is based on the technical knowledge that when the CLV system is adopted in a recordable optical recording medium, the reproduction deterioration phenomenon is more likely to occur as the reproduction linear velocity is set lower. In an optical recording medium capable of reproducing data by rotating at a constant linear velocity, when reproducing at a first linear velocity, the irradiation intensity of the laser beam is set to a first power, When reproduction is performed at a second linear velocity lower than the first linear velocity, the irradiation intensity of the laser beam is set to a second intensity lower than the first power.
It is achieved by an optical recording medium characterized in that it has the information necessary to set the power of.

According to the present invention, the thermal energy per unit time received from the laser beam is leveled with respect to the reproducing linear velocity, so that the reproducing deterioration phenomenon is effectively suppressed.

In a preferred embodiment of the present invention, the information is information necessary for setting the intensity of the laser beam stepwise lower when reproducing at a slower linear velocity.

According to the preferred embodiment of the present invention, the thermal energy per unit time received by the laser beam is more leveled with respect to the linear velocity of reproduction, so that the deterioration phenomenon of reproduction is more effectively suppressed.

[0016] In another preferred embodiment of the present invention, the information is information necessary for continuously setting the intensity of the laser beam to be lower when reproducing at a slower linear velocity.

According to another preferred embodiment of the invention,
Since the thermal energy per unit time received by the laser beam is further leveled with respect to the reproducing linear velocity, the reproducing deterioration phenomenon is suppressed more effectively.

The above object of the present invention is also a method of reproducing an optical recording medium which rotates at a constant linear velocity, wherein a laser beam is applied to the recording surface of the optical recording medium when reproducing at a first linear velocity. Is irradiated with a first power and reproduction is performed at a second linear velocity lower than the first linear velocity, the laser beam is applied to the recording surface of the optical recording medium above the first power. This is achieved by a reproducing method for an optical recording medium, which is characterized in that irradiation is performed with a low second power.

The above object of the present invention is also an optical recording medium reproducing apparatus capable of reproducing an optical recording medium while rotating at a constant linear velocity, and irradiating a laser beam when reproducing at a first linear velocity. When the intensity is set to the first power and the reproduction is performed at the second linear velocity slower than the first linear velocity, the irradiation intensity of the laser beam is set to the second power lower than the first power. Is achieved by an optical recording medium reproducing apparatus.

[0020]

DETAILED DESCRIPTION OF THE INVENTION Referring to the accompanying drawings,
A preferred embodiment of the present invention will be described in detail.

FIG. 1 is a diagram schematically showing a main part of an optical recording medium recording / reproducing apparatus according to a preferred embodiment of the present invention.

The optical recording medium recording / reproducing apparatus according to this embodiment is an optical recording medium recording / reproducing apparatus capable of reproducing data by rotation control using at least the CLV system, and as shown in FIG. A spindle motor 2 for rotating the optical recording medium 1, and a head 3 for irradiating the optical recording medium 1 with a laser beam and receiving reflected light thereof.
A controller 4 for controlling the operations of the spindle motor 2 and the head 3, a laser drive circuit 5 for supplying a laser drive signal to the head 3, and a lens drive circuit 6 for supplying a lens drive signal to the head 3. .

Further, as shown in FIG. 1, the controller 4 includes a focus servo follow-up circuit 7, a tracking servo follow-up circuit 8 and a laser control circuit 9. When the focus servo follow-up circuit 7 is activated, the recording surface of the rotating optical recording medium 1 is focused, and when the tracking servo follow-up circuit 8 is activated, the eccentric signal of the optical recording medium 1 is output. The spot of the laser beam automatically follows the track. The focus servo follow-up circuit 7 and the tracking servo follow-up circuit 8 are respectively provided with an automatic gain control function for automatically adjusting the focus gain and an automatic gain control function for automatically adjusting the tracking gain. The laser control circuit 9 is a circuit for generating a laser drive signal supplied from the laser drive circuit 5, and generates an appropriate laser drive signal based on the reproduction condition setting information recorded on the optical recording medium 1. I do. Here, the reproduction condition setting information refers to various conditions necessary for reproducing data on the optical recording medium 1. In the present embodiment, the relationship between the reproduction linear velocity and the laser beam power during reproduction. Contains at least the information needed to determine. The reproduction condition setting information may be recorded as wobbles or pre-pits, or may be recorded at the time of recording the information, and not only concretely indicate each condition necessary for reproducing the data,
The reproduction condition may be specified by designating any one of various conditions stored in advance in the optical recording medium reproducing device.

The focus servo follow-up circuit 7,
The tracking servo follow-up circuit 8 and the laser control circuit 9 do not need to be circuits incorporated in the controller 4, and may be components separate from the controller 4. Furthermore, these do not have to be physical circuits and may be software executed in the controller 4.

Next, the structure of the optical recording medium 1 according to this embodiment will be described.

FIG. 2 shows an optical recording medium 1 according to this embodiment.
It is sectional drawing which shows the structure of.

As shown in FIG. 2, the optical recording medium 1 comprises:
The substrate 11 having a thickness of about 1.1 mm and the thickness of about 10 to 30
The reflective layer 12 having a thickness of 0 nm and the second layer having a thickness of approximately 10 to 50 nm
Dielectric layer 13 and recording layer 14 having a thickness of about 5 to 30 nm
And a first dielectric layer 15 having a thickness of about 30 to 300 nm.
And a light transmission layer 16 having a thickness of about 50 to 150 μm. In addition, a hole 17 is formed in the central portion of the optical recording medium 1.
Is provided. In recording / reproducing data on / from the optical recording medium having such a structure, the distance (working distance) between the objective lens, which is a part of the head 3 and focuses the laser beam, and the surface of the optical recording medium 1 is The beam spot diameter is set to be extremely narrow (for example, about 80 to 150 μm), and thus a beam spot diameter extremely smaller than that of the conventional one is realized. In addition, the optical recording medium 1 includes
The above-mentioned reproduction condition setting information is recorded. The optical recording medium 1 having such a structure can realize a large capacity and a high data transfer rate, and it is effective to adopt the CLV system in order to maximize this advantage.

The recording layer 14 of the optical recording medium 1 is composed of a phase change film, and data is recorded by utilizing the fact that the reflectance in the crystalline state is different from the reflectance in the amorphous state. Be seen. Specifically, the state of the recording layer 14 in the unrecorded area is a crystalline state, and therefore the reflectance thereof is, for example, 20%. When recording some data in such an unrecorded area, according to the data to be recorded, a predetermined portion of the recording layer 14 is heated to a temperature exceeding the melting point and then rapidly cooled to change to an amorphous state. The reflectance in the portion in the amorphous state is, for example, 7%, whereby the predetermined data is recorded. Then, when overwriting the recorded data, the recording layer 14 in the portion where the data to be overwritten is recorded is heated to a temperature equal to or higher than the crystallization temperature or the melting point according to the data to be recorded, and the crystalline state is set. Alternatively, it is changed to an amorphous state.

In this case, the power Pw of the laser beam applied when melting the recording layer 14, the power Pb of the laser beam applied when cooling the recording layer 14, and the crystallizing of the recording layer 14. The relation with the power Pe of the laser beam with which the laser beam is irradiated is Pw>Pe> Pb. Therefore, when recording data on the optical recording medium 1, the controller 4 controls the laser drive circuit 5 via the laser control circuit 9 so that the power of the laser beam at the time of recording becomes Pw, Pe, or Pb, and then the data is recorded. Based on this, the laser drive circuit 5 controls the power of the laser drive signal. In such an optical recording medium 1, data is generally recorded from the inner peripheral portion toward the outer peripheral portion.

Next, a method of reproducing an optical recording medium using the optical recording medium recording / reproducing apparatus according to this embodiment will be described.

First, when an optical recording medium is inserted into the optical recording medium recording / reproducing apparatus, the controller 4 drives the spindle motor 2 to rotate the optical recording medium 1 at a predetermined speed, and the laser driving circuit 5 causes the head to move. By driving 3 to irradiate the recording surface of the optical recording medium 1 with a laser beam for reproduction, the reproduction condition setting information recorded in the optical recording medium 1 is read. As described above, the reproduction condition setting information recorded on the optical recording medium 1 includes information necessary for determining the relationship between the reproduction linear velocity and the laser beam power during reproduction. Based on this, the medium recording / reproducing apparatus determines the power of the laser beam at the time of reproduction according to the actual reproduction linear velocity.

In the present embodiment, based on the above information, when the reproduction linear velocity is set to a predetermined value or higher and reproduction is performed, the laser beam power during reproduction is set to the first power P.
When the reproduction linear velocity is set to r1 and the reproduction linear velocity is set to be less than the above-mentioned predetermined value, the laser beam power during reproduction is set to the second power Pr2 (<Pr1). In this case, the first power Pr1 and the second power Pr2 are suppressed to sufficiently low values so that the recording layer 14 of the optical recording medium 1 does not reach the crystallization temperature, and in relation to the laser beam during recording, for example, , Pw>Pe>Pr1>Pr2> Pb. As an example, the laser beam powers Pw, Pe and Pb at the time of recording are 6.0 mW,
When set to 2.8 mW and 0.1 mW, the first power Pr1 and the second power Pr2 of the laser beam at the time of reproduction may be set to about 0.4 mW and 0.3 mW.

As described above, when reproducing an optical recording medium by the CLV system, the linear velocity is constant regardless of the reproducing position of the optical recording medium 1, but the linear velocity of the optical recording medium recording / reproducing apparatus is less than a predetermined value. In the case of reproducing by the method, since the intensity of the laser beam is set to be weaker than the intensity of the laser beam used in reproducing at a linear velocity of a predetermined value or more, the unit that the recording layer 14 receives by the laser beam is The thermal energy per hour is leveled with respect to the linear velocity of reproduction. As a result, in the present embodiment, the reproduction deterioration phenomenon that conventionally occurs when the reproduction linear velocity is low is effectively suppressed.

As described above, according to the present embodiment, since the thermal energy per unit time that the optical recording medium 1 receives from the laser beam during reproduction is leveled with respect to the reproduction linear velocity, the reproduction linear velocity is slow. It is possible to effectively suppress the reproduction deterioration phenomenon that occurs in some cases. Moreover, when the linear velocity is set to be high, since reproduction is performed with a strong reproduction laser beam, high reproduction quality is ensured.

Information necessary for determining the relationship between the reproduction linear velocity and the power of the laser beam at the time of reproduction is stored in the optical recording medium 1 as reproduction condition setting information. Even when reproducing data using a device different from the recording / reproducing device shown in the optical recording medium,
The reproduction deterioration phenomenon can be suppressed by adjusting the power of the laser beam.

Here, a reproduction linear velocity at which the intensity of the laser beam at the time of reproduction is set to the first power Pr1 and reproduction is performed, and a reproduction linear velocity at which the intensity is set to the second power Pr2 and reproduction is performed. The boundary setting is not particularly limited, but the recording layer 1
It is preferable to determine it based on the crystallization rate of the phase change material used in No.

[0037]

EXAMPLE First, having the structure shown in FIG. 2, the substrate 11 had a thickness of 1.1 mm, and the reflective layer 12 had a thickness of 100 n.
m, the thickness of the second dielectric layer 13 is 30 nm, the thickness of the recording layer 14 is 20 nm, the thickness of the first dielectric layer 15 is 130 nm, and the thickness of the light transmitting layer 16 is 100 μm. Optical recording media 1-1 and 1-2 were prepared.

For such optical recording media 1-1 and 1-2, the laser wavelength is 405 nm and the NA (numerical aperture) is 0.
An optical recording medium recording / reproducing apparatus No. 85 was used to set a bit length of 0.13 μm / bit and record data by rotation control using the CLV method. Table 1 shows the recording conditions
Shown in.

[0039]

[Table 1] Next, the optical recording medium 1 on which data is recorded in this way
Data was reproduced for -1 and 1-2 by rotation control using the CLV method. Table 2 shows the reproduction conditions.
As is clear from Table 2, the reproduction power for the optical recording medium 1-2 is lower than the reproduction power for the optical recording medium 1-1.

[0040]

[Table 2] Next, the jitter after reproducing 10 times and the jitter after 1 million times were measured. Jitter is measured by Yokogawa Denki Time I
The interval Analyzer (TA-520) was used. This jitter is clock jitter, and σ
/ T (T is the cycle of the clock). Table 3 shows the measurement results.

[0041]

[Table 3] As shown in Table 3, in each of the optical recording media 1-1 and 1-2, the jitter after the reproduction was performed 10 times, even though the data was reproduced at the different linear velocities, No difference appeared in the jitter after reproduction was performed 1,000,000 times.

Next, an optical disk 1-3 having the same structure as the optical recording media 1-1 and 1-2 was prepared, and data recording was performed under the conditions shown in Table 1 by rotation control using the CLV system. I went.

Next, the optical recording medium 1-3 on which the data was recorded in this way was reproduced by the rotation control using the CLV system. Table 4 shows the reproduction conditions. As is clear from Table 4, the reproduction power for the optical recording medium 1-3 is equal to the reproduction power for the optical recording medium 1-1.

[0044]

[Table 4] Next, the jitter after reproducing 10 times and the jitter after 1 million times were measured. The measuring method is as described above. Table 5 shows the measurement results.

[0045]

[Table 5] As shown in Table 5, under the reproduction condition shown in Table 4, even though the linear velocity is the same as that of the optical recording medium 1-2, reproduction is performed at 1
It was confirmed that the jitter was significantly deteriorated after the operation was performed, 000,000 times.

The present invention is not limited to the above embodiments, and various modifications can be made within the scope of the invention described in the claims, and these are also included in the scope of the present invention. It goes without saying that it is a thing.

For example, in the above embodiment, the intensity of the laser beam at the time of reproduction is set in two stages based on the linear velocity of reproduction, but the present invention thus sets the intensity of the laser beam at the time of reproduction to 2 levels. It is not essential to set the number of stages, and the intensity of the laser beam may be gradually reduced as the reproduction linear velocity becomes slower, and the number of stages may be set to three or more. Further, the intensity of the laser beam at the time of reproduction may not be changed stepwise as described above, but the intensity of the laser beam may be continuously decreased as the reproduction linear velocity becomes slower.

In the above embodiment, the power of the laser beam at the time of reproduction is adjusted according to the reproduction linear velocity based on the reproduction condition setting information stored in the optical recording medium 1. The setting information does not need to use the reproduction linear velocity as a parameter, and other parameters related to the determination of the reproduction linear velocity, such as the data transfer rate, are used as parameters, and the power of the laser beam during reproduction is adjusted accordingly. Do not mind.

The optical recording medium 1 shown in FIG. 2 is given as an example of the optical recording medium to which the reproducing method of the optical recording medium according to the preferred embodiment of the present invention is preferably applied. The application of the method is not limited to such an optical recording medium, and can be applied to any optical recording medium as long as it is a recordable optical recording medium.

Further, although the optical recording medium recording / reproducing apparatus according to the above-mentioned embodiment is configured to record not only data but also data, the optical recording medium recording / reproducing apparatus according to the present invention can record and reproduce data. It is not necessary that both reproduction be possible, and at least reproduction of the optical recording medium by the CLV method is sufficient.

In the above embodiment, both the first power Pr1 and the second power Pr2 are set higher than the power Pb of the laser beam during recording.
These may be set lower than the power Pb of the laser beam at the time of recording. Further, the powers Pb and Pe of the laser beam during recording may be at the same level.

[0052]

As described above, according to the present invention,
Since the intensity of the laser beam at the time of reproduction is set based on the reproduction linear velocity, it is possible to effectively suppress the reproduction deterioration phenomenon when reproducing the optical recording medium by the CLV method.

Therefore, the present invention is particularly effective in a recording / reproducing system for an optical recording medium in which a reproduction deterioration phenomenon is likely to occur. As a recording / reproducing system for an optical recording medium in which a reproduction deterioration phenomenon easily occurs, a high NA lens (for example, NA
= 0.8 or more) or a laser beam having a short wavelength (for example, wavelength λ = 380 to 450 nm), a recording / reproducing system of a type in which the beam spot can be narrowed down to a very small value. Further, as a recording / reproducing system for another optical recording medium in which a reproduction deterioration phenomenon is likely to occur, a material having a high recording linear velocity (for example, 70 Mbps or more) and therefore a material having a very high crystallization rate is used as a material for the recording layer. A type of recording / playback system may be mentioned.

[Brief description of drawings]

FIG. 1 is a diagram schematically showing a main part of an optical recording medium recording / reproducing apparatus according to a preferred embodiment of the present invention.

FIG. 2 is a sectional view schematically showing the structure of an optical recording medium 1 according to a preferred embodiment of the present invention.

[Explanation of symbols]

1 Optical recording medium 2 spindle motor 3 heads 4 controller 5 Laser drive circuit 6 lens drive circuit 7 Focus servo tracking circuit 8 Tracking servo tracking circuit 9 Laser control circuit 11 board 12 Reflective layer 13 Second dielectric layer 14 Recording layer 15 First Dielectric Layer 16 Light transmission layer 17 holes

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hideki Hirata             1-13-1, Nihonbashi, Chuo-ku, Tokyo             -In DC Inc. F-term (reference) 5D029 PA03                 5D090 AA01 BB05 CC04 FF09 GG33                       KK03                 5D119 AA31 BA01 BB04 DA05 HA20                       HA54                 5D789 AA31 BA01 BB04 DA05 HA20                       HA54

Claims (5)

[Claims] 1. An optical recording medium capable of reproducing data by rotating at a constant linear velocity, wherein when reproducing at a first linear velocity, the irradiation intensity of a laser beam is set to a first power. However, when reproduction is performed at a second linear velocity lower than the first linear velocity, information necessary for setting the irradiation intensity of the laser beam to a second power lower than the first power. An optical recording medium having: 2. The information is required to set the intensity of the laser beam stepwise lower when reproducing at a slower linear velocity.
The optical recording medium according to 1. 3. The information is information necessary for continuously setting the intensity of the laser beam to be lower when reproducing at a slower linear velocity.
The optical recording medium according to 1. 4. A reproducing method for an optical recording medium rotating at a constant linear velocity, wherein a laser beam is applied to a recording surface of the optical recording medium at a first power when reproducing at a first linear velocity. When irradiating and reproducing at a second linear velocity lower than the first linear velocity, the laser beam is applied to the recording surface of the optical recording medium at a second power lower than the first power. A method for reproducing an optical recording medium, which comprises irradiating. 5. An optical recording medium reproducing apparatus capable of reproducing an optical recording medium while rotating at a constant linear velocity, wherein the laser beam irradiation intensity is first when reproducing at a first linear velocity.
Power, and when reproducing at a second linear velocity slower than the first linear velocity, set the irradiation intensity of the laser beam to a second power lower than the first power. An optical recording medium reproducing device characterized by.