JPH0765404A - Optical recording medium and its recording and/or reproducing device - Google Patents

Abstract

PURPOSE:To provide an optical disk capable of well applying focusing and tracking servo even if an optical disk is provided with a light transmittance variable medium for a high-density recording. CONSTITUTION:The optical disk 1 has a mask layer 3 for reducing the effective spot diameter of a laser beam and is provided with a servo region 15 capable of applying the light quantity sufficient for applying the focusing servo to a photodetector in a part of a lead-in signal region 16. The servo region 15 is reproduced first and the focusing servo is applied to the optical disk 1 at the time of reproducing the optical disk. The information signal region 15 subjected to the high-density recording is reproduced in the state of maintaining the servo state. The focusing servo is applied to the optical disk by irradiating the predetermined position on the optical disk with a laser beam of the intensity higher than the intensity at the time of information signal reproducing in the case of the optical disk not provided with the servo region 15.

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 in which information is recorded at a high density and / or information is recorded at a high density and a recording and / or reproducing apparatus therefor, and in particular, irradiation light intensity and temperature. An optical recording medium for recording and / or reproducing information at a high density on an optical recording medium by reducing the effective spot diameter of an irradiation spot by a mask layer made of a light transmittance variable medium whose transmittance changes according to changes and the like. The present invention relates to a recording and / or reproducing device.

[0002]

2. Description of the Related Art In recent years, a large capacity optical disc has been studied,
Various proposals have been made. An optical disc can form a recording mark smaller than the light spot diameter by controlling the laser light power at the time of recording, and therefore there is no limit in principle to the improvement of the density at the time of recording. However, the diameter of the light spot when the laser light is narrowed down by a lens has a limit value that cannot be narrowed down to a certain value or less, and the densification of an optical disk depends on how to reduce the reproduction laser spot. The repetition wavelength (recording wavelength) of the recording mark at the reproduction limit is given by λ / 2NA. Here, λ is the wavelength of light and NA is the numerical aperture of the lens.

It is understood that in order to identify and reproduce a recording mark having a shorter recording wavelength, it is sufficient to reproduce with a light having a short wavelength λ or use a lens having a large numerical aperture NA. However, it is technically difficult to shorten the wavelength of a semiconductor laser used for reproduction, and it is not easy to incorporate a lens having a large numerical aperture NA into an optical disk device.

Therefore, a substance having a high light transmittance due to temperature rise due to light irradiation is provided in a layered form in the optical disk, and only the central portion of the light irradiated portion is made light transmissive when recording or reproducing information on the optical disk. A method of recording information on an optical disc with high density or reproducing information recorded on the optical disc with high density has been conventionally known.

As one of the high density recording techniques for such an optical disc, a light transmittance variable medium layer having temperature dependence is used.
Japanese Laid-Open Patent Publication No. 5-12673 discloses a technique for reducing the apparent diameter of the light spot, which is provided on the information recording layer and utilizes the high temperature of the rear portion of the light spot on the optical disc in the light spot traveling direction. Are disclosed by Reflection from the disk in the optical head by utilizing the fact that the reflectance of the low light transmittance part of the temperature-dependent light transmittance variable medium is sufficiently lower than the reflectance of the high light transmittance part. By controlling the output laser power so that the amount of light received by the photodetector that monitors the light is always constant, the area ratio of the portion with high light transmittance in the total area of the light spot is always controlled to be constant. You can

[0006]

However, based on the above-mentioned conventional technique, it has been found that the effect of reducing the spot system is not produced until the servo is applied during repeated experiments of high density recording / reproducing on the optical disk. This is because the variable light transmittance medium is set so that the light transmittance becomes high at the light intensity of the central portion of the spot near the focal depth of the focused laser beam. Generally, in order to mount an optical disc on a recording / reproducing apparatus and apply focus servo, it is necessary that the reflected light or transmitted light from the optical disc has a certain amount of light. However, the variable light transmittance medium has the characteristics shown in FIG. 4, and absorbs light or heat thereof to transmit light in a portion reaching saturation intensity or in a high temperature within the light spot. It is a substance whose rate changes. Therefore, if the light intensity of the irradiation laser beam for applying the servo is weak, the light transmittance of the variable light transmittance medium will not be high, and the irradiation light will be absorbed by the variable light transmittance medium and will be absorbed by the light receiver. It becomes impossible to receive a sufficient amount of light. However, immediately after the optical disc is loaded, the light spot is out of focus,
The variable light transmittance medium is not irradiated with light that reaches the saturation intensity. Therefore, the emitted light is absorbed,
This means that a sufficient amount of light necessary to apply the servo cannot be received. As a result, the focus servo cannot be applied. Also, if the focus servo cannot be applied,
The tracking servo cannot be applied. By thus providing the variable light transmittance medium on the information recording layer, the light radiated onto the optical disk is absorbed by the variable light transmittance medium, and it is not possible to obtain a sufficient amount of received light. It has become clear that it is difficult to apply focus and tracking servo for recording / reproducing of the recording medium.

Therefore, the present invention has been made by paying attention to the above points, and an optical disk which can perform focus and tracking servo satisfactorily even if an optical transmittance variable medium for high density recording is provided on the optical disk. It is intended to provide.

[0008]

Means for Solving the Problems As a means for achieving the above object, the present invention provides a row of light-readable minute pits formed on a light-transmissive substrate or laminated on a light-transmissive substrate. The information recording layer capable of optical recording and reproduction and the fact that the light transmittance reversibly changes by absorbing light of a specific wavelength or heat of light reversibly utilizes the device side on the pit row or the information recording layer. A mask layer for reducing the effective spot diameter of the laser beam emitted from the optical recording medium for recording and / or reproducing information at a high density by the laser beam, within a scannable range of the laser beam. Even if the irradiation intensity of the laser beam is weak at a predetermined position, it is possible to return the light having the light amount necessary for performing the focus servo of the laser beam to the device side. The are intended to provide an optical recording medium characterized by comprising.

The present invention also provides, as means for achieving the above object, a row of minute pits capable of reading out light formed on a light transmissive substrate, or an optical recording / reproducing layer stacked on the light transmissive substrate. Irradiation from the device side onto the pit row or the information recording layer by utilizing the possible information recording layer and the fact that the light transmittance reversibly changes by absorbing light of a specific wavelength or heat of light. A recording and / or reproducing apparatus for an optical recording medium, which has a mask layer for reducing an effective spot diameter of a laser beam, and records and / or reproduces information at a high density by the laser beam. After that, a laser beam having an intensity higher than the irradiation intensity of the laser beam applied at the time of recording and / or reproducing the information is applied to a predetermined position on the optical recording medium to perform the focus servo. It is intended to provide a recording and / or reproducing apparatus for an optical recording medium characterized Rukoto.

Further, according to the present invention, as a means for achieving the above object, a row of minute pits capable of reading out light formed on a light transmissive substrate, or an optical recording / reproducing layer laminated on the light transmissive substrate. Irradiation from the device side onto the pit row or the information recording layer by utilizing the possible information recording layer and the fact that the light transmittance reversibly changes by absorbing light of a specific wavelength or heat of light. And a mask layer for reducing the effective spot diameter of the laser beam, and at a predetermined position within the scannable range of the laser beam, even when the irradiation intensity of the laser beam is weak, A recording and / or reproducing apparatus for an optical recording medium provided with a servo area capable of returning light having a light amount necessary for applying a focus servo to the device side, after the optical recording medium is mounted, Serial in which by irradiating a laser beam to the servo area and to provide a recording and / or reproducing apparatus for an optical recording medium characterized by applying a focus servo.

[0011]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a configuration diagram of an optical disc according to an embodiment of the present invention. The optical disc 1 shown in the figure is a read-only or recordable type optical disc, in which a lead-in signal area 16 is provided in the innermost peripheral portion and a lead-out signal area 13 is provided in the outermost peripheral portion. Further, in the area sandwiched between the lead-in signal area 16 and the lead-out signal area 13, an information signal area 14 in which information signals are recorded at high density is provided.

The information signal area 14 is of a read-only type or a recordable type and has a structure as shown in FIG. Here, the respective structures of the read-only optical disc and the recordable optical disc will be described. 2A and 2B are views showing a part of the longitudinal section of the optical disc in FIG. 1, where FIG. 2A shows a read-only optical disc 11 and FIG. 2B shows a recordable optical disc 12. In FIG. 1A, a read-only optical disc 11 includes a mask layer 3, a mask layer 3,
And a reflective layer 4, and a signal modulated in advance is recorded as pits 5 on the substrate 2. Also, in FIG. 1B, a recordable optical disc 12 has a mask layer 3, an optical recording / reproducing recording layer 6, and a reflecting layer 4 on a light-transmissive substrate 2, and guides in advance. The groove 7 is provided in a spiral shape or a concentric shape.

As the light-transmitting substrate 2, various materials can be used as is well known, and any of glass, epoxy resin, polycarbonate resin, polymethacrylate ester resin, amorphous polyolefin resin and the like can be used. In the case of, it can be used if it has good transparency. The mask layer 3 is formed, for example, in Japanese Patent Application No. 4-33.
It is possible to use a light-dependent variable light transmittance medium such as that disclosed in Japanese Patent No. 1049, or a temperature-dependent variable light transmittance medium such as spiropyran, lactone, or fluoran dye. Since these substances have absorption in a specific wavelength region at room temperature and the absorption wavelength varies with the temperature rise, an appropriate substance may be selected according to the laser light wavelength used for recording and reproduction. In addition, this mask layer 3
Is formed by, for example, a vacuum vapor deposition method or, if it is soluble in a solvent, it is dissolved in a suitable solvent and used by a spin coating method. The reflective film 4 is provided on the mask layer 3 by means such as vacuum deposition or sputtering. That is, the optical discs 11 and 12 are reflection type optical discs, and are easily compatible with the existing optical disc system.

Here, in the read-only optical disc 11, the method of recording signals in the lead-in signal area 16 and the information signal area 14 on the substrate 2 is not particularly limited, but on a polished glass master. A method of applying a photoresist, recording a signal with a recording laser, developing, and then forming a stamper by providing a conductive film and then obtaining a substrate by injection molding, a method by etching, a so-called 2P method called ultraviolet ray Any method such as an embossing method using a cured resin can be used. Further, in the signal of the lead-in signal area 16, address information, content information and the like are recorded as in the conventional read-only recording medium.

When the recordable optical disk 12 is manufactured, it is necessary to provide the recording layer 5 between the mask layer 3 and the reflective layer 4. The recording layer 6 can be appropriately selected and selected from conventionally known optical recordable materials, and there is no particular limitation on the production thereof.

Further, in FIG. 1, a servo area 15 is provided in a part of the lead-in signal area 16 so that a sufficient amount of light for applying focus servo can be given to the photodetector, and the servo area 15 is excluded. In the lead-in signal area 16, the information signal area 14, and the lead-out signal area 13, the mask layer 3 which is the above-mentioned light transmittance variable medium is used.
Is formed, and the irradiation spot diameter is reduced by the mask layer 3. In addition, the servo area 15
Is formed by making the mask layer 3 thinner than the information signal region 14, reducing the coloring amount of the mask layer 3, or not forming the mask layer 3 for applying a servo. It is possible to reduce the amount of the irradiation light absorbed by the mask layer 3 or prevent the irradiation light from being absorbed so that the light receiver can receive a sufficient amount of light for applying servo.

The servo area 15 may be provided at any place in the optical disk 1 in consideration of the recording / reproducing method and the recording / reproducing apparatus, but the present optical disk is widely used as a compact disk or the like. In the system, the lead-in signal area 1 provided at the innermost circumference
Since 6 is reproduced first, in consideration of upward compatibility with the current system in the future, the lead-in signal area 1
6, in particular, in the position where the optical disc 1 is first traced, that is, in the case of the current system in which tracing is started from the inner peripheral portion of the optical disc 1, it is preferable to be provided in the innermost peripheral portion as described above. Further, if the system starts tracing from the outer circumference, it may be provided in the outermost circumference.

Although the optical disks 11 and 12 have been described as being of the reflected light detection type, it goes without saying that they may be of the transmitted light detection type.

Next, the reproducing apparatus for the optical disc 1 will be described. FIG. 3 is a schematic configuration diagram showing an example of a main part of the optical disc reproducing apparatus according to the embodiment of the present invention. In the figure, a reproducing device 21 includes an optical disk 1 and an optical head 2 described above.
3 and a light receiver 24 that receives the reflected light reflected by the optical disc 1 and outputs an output signal according to the detection result.
And a focus control circuit 25 for generating a focus servo signal for causing the irradiation light spot to follow the surface wobbling of the optical disc 1 based on the output signal from the light receiver 24.
And a tracking control circuit 26 for generating a tracking servo signal for scanning the irradiation light spot on a track on the optical disc 1 based on an output signal from the light receiver 24, and a focus control circuit 25 and a tracking control circuit 26. And a system control circuit 27 for generating a head drive signal 28 and a lens drive signal 29 based on the respective servo signals.

The optical head 23 is used for the optical disc 1
A semiconductor laser 30 for generating irradiation light for servo or signal reproduction, a condenser lens 31 for condensing irradiation light emitted from the semiconductor laser 30, and a condenser lens 31 for driving the lens drive signal 29. Based on the above, the actuator 32 for driving in the direction perpendicular to the information signal recording surface of the optical disc 1 and the reflected light reflected on the optical disc 1 and incident on the condenser lens 31 are received by the light receiver 2
The polarization prism 33 is divided into four parts.

Next, the operation of the reproducing apparatus 21 will be described. When the optical disc 1 is loaded into the playback device 21,
The system control circuit 27 outputs a head drive signal 28 for driving the optical head 23 to the servo area 15 in the lead-in signal area 16. Here, the system control circuit 27 stores position information of the servo area 15 at a predetermined position on the optical disc 1 in advance, and the system control circuit 27 outputs a head drive signal 29 based on this position information. . Further, if the servo area 15 is located at the innermost peripheral portion of the lead-in signal area 16, it is also the place where the trace is first made on the optical disc 1, so that the position information in that case need not be stored.

The servo area 15 in the lead-in signal area 16 is irradiated with a laser beam, and focus servo is first applied by using the focus control circuit 25. As described above, in the servo area 15, for example, even when the focus is deviated, the reflected light having a sufficient light amount necessary for applying the servo is supplied to the light receiver 24. Stable in the servo area. Once the servo is applied in the servo area 15, the medium configuration is within the depth of focus, so that the tracking is easy, the effect of reducing the spot diameter is exhibited, and the tracking servo can be applied stably. Therefore, the lead-in area 16 and the information signal area 15 which are recorded at high density are reproduced with the servo state maintained. In the reproduction of the information signal area 15, since the servo is applied in the servo area 15, the effect of reducing the effective spot diameter by the mask layer 3 is effectively exhibited, and the information signal recorded at high density is stably reproduced. Will be done.

Similarly, in the recording apparatus capable of recording information on the recordable optical disk 12, if servo is applied in the servo area 15 and then information is recorded in the information signal area 14, the mask layer 3 is used. The effect of reducing the effective spot diameter is satisfactorily exhibited, and high-density recording can be stably performed.

By the way, since the reproducing device 21 is for reproducing the optical disc 1 having the servo area 15, it cannot be used for an optical disc having no servo area 15. Therefore, when reproducing an optical disc in which the servo area 15 is not provided, a laser beam having an irradiation intensity higher than the irradiation intensity of the irradiation laser beam at the time of information reproduction is applied to a predetermined position (for example, a lead-in area) of the optical disc. The innermost peripheral portion) of the information recording medium is irradiated and the focus servo is applied, and then the irradiation intensity is set to the normal intensity (the irradiation intensity capable of high density reproduction) to reproduce the information signal area. Since the optical disc may be damaged if the laser beam is condensed while the light intensity of the laser beam is high, the light beam of the laser beam output from the semiconductor laser 30 is detected while detecting the light intensity of the light received by the light receiver 24. The intensity may be controlled. The recording apparatus also performs the same operation before the recording operation to apply the focus servo.

[0025]

As described above, according to the optical recording medium of the present invention, the fact that the light transmittance is reversibly changed by absorbing the light of the specific wavelength or the heat of the light is utilized from the device side. In an optical recording medium having a mask layer that reduces the effective spot diameter of the irradiated laser beam, even if the irradiation intensity of the laser beam is weak at a predetermined position within a range in which the laser beam can be scanned, Since the servo area that can return the light having the light quantity necessary for applying the focus servo of the laser beam to the device side is provided, if this servo area is used, the optical recording medium having the mask layer is provided. Also makes it easier to apply focus servo.

Further, according to the recording and / or reproducing apparatus of the optical recording medium of the present invention, the optical recording having the mask layer whose light transmittance is reversibly changed by absorbing the light of the specific wavelength or the heat of the light. After the medium is mounted, the servo area is irradiated with a laser beam, or a predetermined position on the optical recording medium is irradiated with a laser beam having a light intensity higher than the reproduction light intensity, so that focus servo is applied. Even if it has the mask layer, it is possible to apply servo quickly and stably, the effect of reducing the irradiation spot diameter by the mask layer is exhibited, and high density recording and / or reproduction of information can be stably performed. There are effects such as being able to.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an optical disc according to an embodiment of the present invention.

FIG. 2 is a diagram showing a part of a vertical cross section of the optical disc in FIG.

FIG. 3 is a schematic configuration diagram showing an example of a main part of an optical disc reproducing apparatus according to an embodiment of the present invention.

FIG. 4 is a diagram showing light transmittance characteristics of a variable light transmittance medium.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 optical disk 2 substrate 3 mask layer 4 reflective layer 5 pit 6 recording layer 7 guide groove 11 read-only type optical disk 12 recordable optical disk 14 information signal area 15 servo area 16 lead-in area 21 reproducing device 23 optical head 24 photoreceiver 25 Focus control circuit 26 Tracking control circuit 27 System control circuit 28 Head drive signal 29 Lens drive signal 30 Semiconductor laser 31 Condenser lens 32 Actuator 33 Polarizing prism

Claims (5)

[Claims] 1. A light-readable minute pit array formed on a light-transmitting substrate, or an information recording / reproducing information recording layer laminated on the light-transmitting substrate, and light having a specific wavelength or light A mask layer that reduces the effective spot diameter of the laser beam irradiated from the device side on the pit row or the information recording layer by utilizing the fact that the light transmittance reversibly changes by absorbing heat is provided. However, in the optical recording medium that records and / or reproduces information with high density by the laser beam, even if the irradiation intensity of the laser beam is weak at a predetermined position within a scannable range of the laser beam,
An optical recording medium provided with a servo area capable of returning light having an amount of light necessary for performing focus servo of the laser beam to the device side. 2. The optical recording medium according to claim 1, wherein the servo area is an area in which a mask layer having a light transmittance higher than that of the mask layer formed on the pit row or the information recording layer is formed. An optical recording medium characterized by: 3. The optical recording medium according to claim 1, wherein the servo area is an area in which the mask layer is not formed within a range in which the laser beam can be scanned on the optical recording medium. And an optical recording medium. 4. An optically readable row of minute pits formed on a light transmissive substrate, or an optical recording / reproducing information recording layer laminated on the light transmissive substrate, and light having a specific wavelength or A mask layer that reduces the effective spot diameter of the laser beam irradiated from the device side on the pit row or the information recording layer by utilizing the fact that the light transmittance reversibly changes by absorbing heat is provided. In the recording and / or reproducing apparatus of the optical recording medium for recording and / or reproducing the information with high density by the laser beam, the recording and / or the recording of the information after the optical recording medium is mounted.
Alternatively, recording of an optical recording medium characterized by irradiating a predetermined position on the optical recording medium with a laser beam having an intensity higher than the irradiation intensity of the laser beam applied during reproduction to perform focus servo, and And / or a playback device. 5. A row of light-readable minute pits formed on a light-transmitting substrate, or an information recording / reproducing information recording layer laminated on the light-transmitting substrate, and light having a specific wavelength or light A mask layer that reduces the effective spot diameter of the laser beam irradiated from the device side on the pit row or the information recording layer by utilizing the fact that the light transmittance reversibly changes by absorbing heat is provided. In addition, even if the irradiation intensity of the laser beam is weak at a predetermined position within a scannable range of the laser beam, a device that emits light having a light amount necessary to apply focus servo of the laser beam is provided. A recording and / or reproducing apparatus for an optical recording medium provided with a servo area that can be returned to the side, wherein the servo area is irradiated with a laser beam after the optical recording medium is mounted. A recording and / or reproducing apparatus for an optical recording medium, characterized by applying a servo.