WO2003030156A1

WO2003030156A1 - Optical recording medium, optical recording medium reproduction method, and optical recording medium reproduction apparatus

Info

Publication number: WO2003030156A1
Application number: PCT/JP2002/009737
Authority: WO
Inventors: Tatsuya Kato; Hiroshi Shingai; Hideki Hirata
Original assignee: Tdk Corporation
Priority date: 2001-09-27
Filing date: 2002-09-20
Publication date: 2003-04-10
Also published as: JP2003099948A

Abstract

An optical recording medium reproduction apparatus reproduces information while rotating an optical recording medium at a constant linear velocity and can efficiently suppress deterioration of reproduction. When performing reproduction at a first linear speed, the radiation intensity of the laser beam is set to a first power. When performing reproduction at a second linear velocity slower than the first linear velocity, the radiation intensity of the laser beam is set to a second power lower than the first power. Thus, thermal energy received by the optical recording medium from the laser beam per unit time is averaged with respect to the reproduction linear velocity and accordingly, it is possible to efficiently suppress deterioration of reproduction.

Description

Technical Field Optical recording medium, optical recording medium reproducing method, and optical recording medium reproducing apparatus

The present invention relates to an optical recording medium, and more particularly, to an optical recording medium capable of reproducing by rotation control using a CLV system. Further, the present invention relates to a method for reproducing an optical recording medium, and more particularly, to a method for reproducing an optical recording medium by rotation control using a CLV system. Further, the present invention relates to an optical recording medium reproducing apparatus, and more particularly, to an optical recording medium reproducing apparatus capable of reproducing by rotation control using a CLV system. Conventional technology

Conventionally, optical recording media such as CD and DVD have been widely used as recording media for recording digital data. The method of controlling the rotation of the optical recording medium when recording and reproducing 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). can do.

According to the rotation control using the CLV method, the data transfer rate is constant irrespective of whether the recording Z playback position is on the inner or outer peripheral portion of the optical recording medium, and thus the data transfer rate is reduced. Although it has the advantage of being able to take full advantage, the control of the motor is complicated because the rotation speed of the optical recording medium must be changed according to the recording / reproducing position, and the random access speed is low. Has disadvantages. On the other hand, rotation control using the CAV method has the advantage that the random access speed is high because the motor control is simple, but has the disadvantage that the data transfer rate is low. Such disadvantages can be alleviated to some extent by increasing the click frequency as the recording position advances to the outer periphery of the optical recording medium. It is inevitable that the data transfer rate in the inner circumference of the recording medium will decrease. Many of the recording / reproducing methods for optical recording media that are currently in practical use adopt the CLV method, but this is a result of focusing on the advantage that the data transfer rate can be maximized. is there.

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

However, when reproducing an optical recording medium on which data is recorded using the CLV method, the reproduction linear velocity differs depending on the drive used, and the reproduction is not always performed under the same conditions. Disclosure of the invention

According to the study of the present inventors, when the CLV method is employed in a recordable optical recording medium using a phase change film or the like for the recording layer, the lower the reproduction linear velocity, the more the data is reproduced. It was found that the so-called “reproduction degradation phenomenon”, which is the deterioration of the signal being reproduced, easily occurs. This phenomenon is thought to be due to the fact that the lower the linear velocity, the higher the thermal energy per unit time received from the laser beam. It becomes more remarkable in an optical recording medium with an increased conversion speed.

Therefore, an object of the present invention is to provide an improved optical recording medium capable of reproducing using the CLV system.

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

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

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

The present invention relates to a case where the CLV method is adopted in a recordable optical recording medium. In this case, it is based on the technical knowledge that as the reproduction linear velocity is set lower, the reproduction deterioration phenomenon is more likely to occur, and it is an optical recording medium that can reproduce data by rotating at a constant linear velocity. When performing reproduction at the linear velocity of 1, the irradiation intensity of the laser beam is set to the first power, and when performing reproduction at the second linear velocity lower than the above-mentioned first linear velocity, the laser beam irradiation is performed. This is achieved by an optical recording medium having information necessary for setting the irradiation intensity of the beam to a second power lower than the first power.

According to the present invention, the thermal energy per unit time received from the laser beam is leveled with respect to the reproduction linear velocity, so that the reproduction 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 as the reproduction is performed at a lower linear velocity.

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

In another preferred embodiment of the present invention, the information is information necessary for setting the intensity of the laser beam continuously lower as the reproduction is performed at a lower linear velocity.

According to another preferred embodiment of the present invention, since the thermal energy per unit time received from the laser beam is further leveled with respect to the reproduction linear velocity, the reproduction deterioration phenomenon is more effectively suppressed. You.

The object of the present invention is also a method for reproducing an optical recording medium rotating at a constant linear velocity, wherein when reproducing at a first linear velocity, a first laser beam is applied to a recording surface of the optical recording medium. When the laser beam is irradiated at a second linear velocity lower than the first linear velocity, the laser beam is applied to a recording surface of an optical recording medium at a second linear velocity lower than the first power. Power of This is achieved by a method for reproducing an optical recording medium, characterized by irradiating with an optical recording medium.

The 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, wherein when reproducing at a first linear velocity, the irradiation intensity of a laser beam is reduced. When the power is set to the first power and the reproduction is performed at the second linear velocity lower than the first linear velocity, the irradiation intensity of the laser beam is set to the second power lower than the first power. This is achieved by an optical recording medium reproducing apparatus. BRIEF DESCRIPTION OF THE FIGURES

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 the optical recording medium 1 according to a preferred embodiment of the present invention.

FIG. 3 is a flowchart showing a method for determining the reproduction power of the laser beam. Embodiment of the Invention

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

An optical recording medium recording / reproducing apparatus according to the present embodiment is an optical recording medium recording / reproducing apparatus capable of reproducing data by at least rotation control using the CLV method. As shown in FIG. A spindle motor 2 for rotating the medium 1; a head 3 for irradiating the optical recording medium 1 with a laser beam and receiving the reflected light; and a controller for controlling the operations of the spindle motors 2 and 3 Controller 4, a laser drive circuit 5 that supplies a laser drive signal to the head 3, and a lens drive signal to the head 3. Lens driving circuit 6 for supplying

Further, as shown in FIG. 1, the controller 4 includes a focus servo tracking circuit 7, a tracking servo tracking circuit 8, and a laser control circuit 9. When the focus servo tracking circuit 7 is activated, the recording surface of the rotating optical recording medium 1 is in focus, and when the tracking servo tracking circuit 8 is activated, the optical recording medium 1 is decentered. The spot of the laser beam automatically follows the current signal track. The focus servo tracking circuit 7 and the tracker servo tracking circuit 8 are provided with an auto gain control function for automatically adjusting the focus gain and an auto gain control function for automatically adjusting the tracking gain. Further, the laser control circuit 9 is a circuit for generating a laser drive signal supplied by the laser drive circuit 5, and based on reproduction condition setting information recorded on the optical recording medium 1, an appropriate laser drive signal is generated. Generate. Here, the reproduction condition setting information refers to various conditions necessary for reproducing data from the optical recording medium 1. In the present embodiment, the relation between the reproduction linear velocity and the power of the laser beam at the time of reproduction is described. It contains at least the information needed to determine The reproduction condition setting information may be recorded as a record or a pre-pit, or may be recorded at the time of recording the information, and may not only specifically indicate each condition required for data reproduction but also optical recording. The reproduction condition may be specified by specifying any of various conditions stored in the medium reproduction device in advance.

The focus servo tracking circuit 7, tracking servo tracking circuit 8, and laser control circuit 9 need not be circuits incorporated in the controller 4, but may be separate components from the controller 4. . Further, these need not be physical circuits, but may be software executed in the controller 4. Next, the structure of the optical recording medium 1 according to the present embodiment will be described. FIG. 2 is a sectional view schematically showing the structure of the optical recording medium 1 according to the present embodiment.

As shown in FIG. 2, the optical recording medium 1 has a substrate 11 having a thickness of about 1.1 mm, a reflective layer 12 having a thickness of about 10 to 300 nm, and a thickness of about 10 to 300 nm. A second dielectric layer 13 having a thickness of about 10 to 50 nm; a recording layer 14 having a thickness of about 5 to 30 nm; and a first dielectric layer having a thickness of about 30 to 300 nm. It is composed of a body layer 15 and a light transmitting layer 16 having a thickness of about 50 to 150 m. In addition, a hole 17 is provided in the center of the optical recording medium 1. In recording / reproducing data to / from an optical recording medium having such a structure, the distance (working distance) between the objective lens for converging a laser beam, which is a part of the head 3, and the surface of the optical recording medium 1 ) Is set to be very narrow (for example, about 80 to 150111), thereby achieving an extremely small beam spot diameter as compared to the past. In addition, the above-described reproduction condition setting information is recorded on the optical recording medium 1. The optical recording medium 1 having such a structure can realize a large capacity and a high data transfer rate, and in order to maximize this advantage, it is effective to adopt the CLV method.

The recording layer 14 of the optical recording medium 1 is composed of a phase change film, and data is recorded by utilizing the difference between the reflectivity in a crystalline state and the reflectivity in an amorphous state. Will be Specifically, the state of the recording layer 14 in the unrecorded area is in a crystalline state, and the reflectance is, for example, 20%. When any data is recorded in such an unrecorded area, a predetermined portion of the recording layer 14 is heated to a temperature exceeding the melting point and then rapidly cooled to an amorphous state according to the data to be recorded. Change. The reflectance in the amorphous state portion is, for example, 7%, whereby the predetermined data is recorded. When overwriting the data once recorded, the recording layer 14 where the data to be overwritten is recorded is heated to a temperature higher than the crystallization temperature or higher than the melting point according to the data to be recorded. Heat to change to crystalline or amorphous state.

In this case, the power Pw of the laser beam irradiated when melting the recording layer 14, the power Pb of the laser beam irradiated when cooling the recording layer 14, and the recording layer 14 No. of the laser beam irradiated during crystallization. The relationship with Pe

P w> P e> P b

It is. Therefore, when data is recorded on the optical recording medium 1, the controller 4 is controlled by the laser drive circuit via the laser control circuit 9 so that the power of the laser beam at the time of recording becomes Pw, Pe or Pb. 5 and the laser drive circuit 5 controls the power of the laser drive signal based on this. Generally, data is recorded on such an optical recording medium 1 from the inner peripheral portion to the outer peripheral portion.

Next, a method for reproducing an optical recording medium using the optical recording medium recording / reproducing apparatus according to the present embodiment will be described with reference to FIG.

First, when the 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 head is driven by the laser driving circuit 5. By driving the laser beam 3 to irradiate the recording surface of the optical recording medium 1 with a laser beam for reproduction, the reproduction condition setting information recorded on the optical recording medium 1 is read (step S 1). 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 power of the laser beam during reproduction. Based on this, the medium recording / reproducing apparatus determines the laser beam power at the time of reproduction according to the actual reproduction linear velocity.

In the present embodiment, when the reproduction is performed by setting the reproduction linear velocity to a predetermined value or more based on the above information, the power of the laser beam at the time of reproduction is set to the first power Pr1, and the reproduction is performed. When the reproduction is performed with the linear velocity set to be less than the predetermined value, the power of the laser beam at the time of reproduction is set to the second power—Pr 2 (<Pr 1). That is, the controller 4 compares the reproduction linear velocity specified by the user or the like with the predetermined reproduction linear velocity included in the reproduction condition setting information obtained in step S1 (step S2). If the instructed reproduction linear velocity is equal to or higher than the predetermined reproduction linear velocity included in the reproduction condition setting information (step S2: YES), the reproduction power of the laser beam is set to Pr 1 according to the reproduction condition setting information. (Step S3) If the reproduction linear velocity specified by the user or the like is lower than the predetermined reproduction linear velocity included in the reproduction condition setting information (Step S2: NO), the laser beam is reproduced according to the reproduction condition setting information. Set the power to Pr 2 (step S4).

In this case, the first power Pr 1 and the second power Pr 2 are suppressed to sufficiently low values so that the recording layer 14 of the optical recording medium 1 does not reach the crystallization temperature. In relation to, for example,

Pw> Pe> Pr1> Pr2> Pb

Is set to be As an example, if the powers Pw, Pe, and Pb of the laser beam at the time of recording are set to 6.0 mW, 2.8 mW, and 0.1 mW, respectively, The first power Pr 1 and the second power Pr 2 may be set to about 0.4 mW and about 0.3 mW. When the setting of the reproducing power of the laser beam is completed, the laser beam whose reproducing power is set to Pr 1 or Pr 2 is irradiated on the recording layer 14 of the optical recording medium 1, and the data is actually reproduced. It is started (step S5).

As described above, in the reproduction of the optical recording medium by the CLV method, the linear velocity is constant irrespective of the reproduction position of the optical recording medium 1, but the optical recording medium recording / reproducing apparatus operates at a linear velocity less than a predetermined value. When performing reproduction, the recording layer 14 receives the laser beam because the intensity of the laser beam is set to be lower than the intensity of the laser beam used when reproducing at a linear velocity equal to or higher than a predetermined value. Thermal energy per unit time is averaged to the regeneration linear velocity. As a result, in the present embodiment, the reproduction degradation 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 received by the optical recording medium 1 from the laser beam during reproduction is leveled with respect to the reproduction linear velocity, it occurs when the reproduction linear velocity is low. It is possible to effectively suppress the phenomenon of reproduction deterioration. In addition, when the linear velocity is set to be high, the reproduction sensitivity is increased because the reproduction is performed by the laser beam having a high intensity, and particularly, in the case of the short wavelength (λ = 380 ηη! ~ 450 nm). Since laser noise, which is a problem in semiconductor lasers, is reduced, high reproduction quality is ensured.

The information necessary for determining the relationship between the reproducing 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 data is reproduced using a device different from the recording medium recording Z reproducing device, the reproduction degradation phenomenon can be suppressed by adjusting the power of the laser beam. Here, the reproduction linear velocity at which the reproduction is performed by setting the intensity of the laser beam at the time of reproduction to the first power Pr1, and the reproduction linear velocity at which the reproduction is performed by setting the intensity to the second power Pr2 Although the setting of the boundary with is not particularly limited, it is preferably determined based on the crystallization speed of the phase change material used for the recording layer 14.

The present invention is not limited to the above embodiments, and various changes 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. Needless to say, there is.

For example, in the above embodiment, the intensity of the laser beam at the time of reproduction is set in two steps based on the reproduction linear velocity. However, the present invention thus sets the intensity of the laser beam at the time of reproduction in two steps. The setting is not essential, and may be set in three or more steps so that the intensity of the laser beam gradually decreases as the reproduction linear velocity decreases. Instead of changing the intensity of the laser beam at the time of reproduction in a stepwise manner as described above, the intensity of the laser beam may be set to decrease continuously as the reproduction linear velocity decreases. 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. It is not necessary to use the playback linear velocity as a parameter, but other parameters related to the determination of the playback linear velocity, for example, the data transfer rate as a parameter, and accordingly, the power of the laser beam during playback. Adjustments may be made.

In addition, the optical recording medium 1 shown in FIG. 2 has been described as an optical recording medium to which the method for reproducing an optical recording medium according to a preferred embodiment of the present invention is suitably applied. The application of the present invention 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.

Furthermore, the optical recording medium recording and reproducing apparatus according to the above embodiment is configured to be capable of not only reproducing data but also recording data. However, the optical recording medium recording and reproducing apparatus according to the present invention can perform both recording and reproducing. It is not necessary to be able to read from an optical recording medium by at least the CLV method.

In the above embodiment, the first power Pr 1 and the second power Pr 2 are both set higher than the power Pb of the laser beam at the time of recording. It may be set lower than the power Pb of the laser beam. Further, the powers Pb and Pe of the laser beam at the time of recording may be the same level.

As described above, according to the present invention, the intensity of the laser beam at the time of reproduction is set based on the reproduction linear velocity. Therefore, in the reproduction of the optical recording medium by the CLV method, the reproduction deterioration phenomenon is effectively performed. It is possible to control

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 Z-playback system for recording on an optical recording medium that is susceptible to playback degradation, a high NA lens (for example, By using a laser beam with a short wavelength (for example, wavelength λ = 380 to 450 ηηι), the type of recording / reproducing can be narrowed down to a very small beam spot. System. In addition, as a recording / reproducing system for other optical recording media in which reproduction deterioration phenomenon is liable to occur, the recording linear velocity is high (for example, 7 OM bps or more). One example is a type of recording / reproducing system that uses very fast materials. Example

First, having the structure shown in FIG. 2, the thickness of the substrate 11 is 1.1 mm, the thickness of the reflective layer 12 is 100 nm, and the thickness of the second dielectric layer 13 is 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 10 nm. Optical recording media 111 and 112 having a size of 0 μm were prepared.

For such an optical recording medium 1-1 and 1-2, an optical recording medium recording / reproducing apparatus having a laser wavelength of 405 nm and an NA (numerical aperture) of 0.85 has a bit length of 0. Data was recorded by rotation control using the CLV method by setting lS / m / bit. Table 1 shows the recording conditions.

table 1

Quack frequency 262.5MHz

Dock JS period (1Τ) 3.8nsec

Linear velocity 22.8msec

Modified ffl method (1,7) RL

Data transfer rate 175Mbps

Format efficiency 80%

Data ft transmission rate 140Mbps

(Considering efficiency)

Channel bit length 0.13 // mbit

Numerical aperture <NA) 0.85

Laser wavelength 405nm

Pw 4.0mW -10.0mW

Pe 2.8mW

Pb 0.5 mW Next, data was reproduced from the optical recording media 1-1 and 112 on which the data was recorded in this manner by rotation control using the CLV method. Table 2 shows the regeneration conditions. As is apparent from Table 2, the reproducing power for the optical recording media 1-2 is lower than the reproducing power for the optical recording media 111.

Table 2

Next, the jitter after 10 times of reproduction under the above conditions and the jitter after 100,000 times of reproduction were measured. The jitter was measured using a Time Internaval Analyzer (TA-1520) manufactured by Yokogawa Electric Corporation. This jitter is clock jitter, and is defined by _σ / Τ (Τ is the period of the clock). Table 3 shows the measurement results.

Table 3 jitter

Views

Optical recording medium 1-1 Optical recording medium 1-2

10 times 9.2% 9.2%

1,000,000 times 9.2% 9.2% As shown in Table 3, despite the data being reproduced at different linear velocities, the reproduction was performed 10 times on both the optical recording media 111 and 112. There was no difference between the jitter after the operation was performed and the jitter after the reproduction was performed 100,000 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 was recorded by rotation control using the CLV method under the conditions shown in Table 1. .

Next, data was reproduced from the optical recording medium 13 on which the data was recorded in this manner by rotation control using the CLV method. Table 4 shows the conditions for regeneration. As is clear from Table 4, the reproduction power for the optical recording medium 113 is equal to the reproduction power for the optical recording medium 111.

Table 4

Next, the jitter after 10 times of reproduction under such conditions and the jitter after 100,000 times of reproduction were measured. The measuring method is as described above. Table 5 shows the measurement results.

Table 5

As shown in Table 5, the reproduction conditions shown in Table 4 Despite the same linear velocity as above, a significant deterioration in jitter after 100,000 reproductions was confirmed.

Claims

The scope of the claims

1. An optical recording medium from which data can be reproduced by rotating at a constant linear velocity. When reproducing at a first linear velocity, the irradiation intensity of the laser beam is set to the first power, When performing reproduction 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 is stored. An optical recording medium characterized in that:

2. The optical recording according to claim 1, wherein the information is information necessary for setting the intensity of the laser beam stepwise lower as the reproduction is performed at a lower linear velocity. Medium.

3. The optical recording according to claim 1, wherein the information is information necessary for setting the intensity of the laser beam continuously lower as the reproduction is performed at a lower linear velocity. Medium.

4. A method for reproducing an optical recording medium that rotates at a constant linear velocity, wherein when reproducing at a first linear velocity, a recording surface of the optical recording medium is irradiated with a laser beam at a first power, When reproduction is performed at a second linear velocity lower than the first linear velocity, the recording surface of the optical recording medium is irradiated with the laser beam at a second power lower than the first power. A method for reproducing an optical recording medium, characterized in that:

5. The reproducing method for an optical recording medium according to claim 4, wherein the intensity of the laser beam is set stepwise lower as the reproduction is performed at a lower linear velocity.

6. The intensity of the laser beam increases as the playback speed decreases. 5. The method for reproducing an optical recording medium according to claim 4, wherein the value is set continuously low.

7. An optical recording medium reproducing device that can reproduce an optical recording medium while rotating it at a constant linear velocity. When reproducing at a first linear velocity, the irradiation intensity of the laser beam is set to the first power. When performing reproduction at a second linear velocity lower than the first linear velocity, the irradiation intensity of the laser beam is set to a second power lower than the first power. Recording medium playback device.

8. The optical recording medium reproducing apparatus according to claim 7, wherein the intensity of the laser beam is set stepwise lower as the reproduction is performed at a lower linear velocity.

9. The optical recording medium reproducing apparatus according to claim 7, wherein the intensity of the laser beam is set continuously lower as the reproduction is performed at a lower linear velocity.