JP2003067939A - Optical information-storage medium and recording-and- reproducing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical information-storage medium which can stably make recording and reproduction with a narrow track pitch. SOLUTION: The optical information-storage medium is provided with a substrate 31 and a recording layer 34 of at least one layer. The substrate is provided with guiding tracks 32 which are separated at a prescribed guiding pitch to extend without intersecting to each other and recording marks whose reflectivity or transmissivity are changed and whose recording intervals are narrower than the guiding pitches, arranged in parallel to the guiding tracks. The recording or reproduction of information can be made by the change in reflectivity or transmissivity of the recording layer caused by a light beam converged on the recording layer 34. The light beams separated from each other at the recording interval are radiated, a tracking error signal is generated based on the returned light from the guiding tracks 32 radiated by one of the light beams, the spot of the light beam is followed on the guiding track, the recording is made with another spot of the light beams, and a reading signal is generated by the returned light from at least one of the spots of the light beams.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information recording medium such as an optical disc and an optical card, and a recording / reproducing method for irradiating an optical information recording medium with a light beam to record or reproduce information.

[0002]

2. Description of the Related Art Recently, DVDs (Digita
2. Description of the Related Art A high recording density and large capacity information recording medium called a "Versatile Disc" and a recording / reproducing system using the same are widely known. In a DVD, information is recorded and reproduced as a change in reflectance, but different optical disk structures and systems such as DVD-ROM, DVD-RAM, DVD-RW, and D
VD-R and the like exist. For example, as shown in FIG.
In the structure of a read-only optical disc (DVD-ROM), a row of embossed pits P having irregularities is formed as recording information on the reflective recording surface of the transparent substrate 1. As shown in FIG. 2, a transparent substrate 1 is used for DVD-RW, DVD-R, etc.
The recording layer RL made of the dye or the phase change material is provided with a groove G having irregularities, and has a structure of a groove recording system in which a row of pits (recording marks) RM having a changed reflectance is formed as recording information. There is. Further, as shown in FIG. 3, a land / groove in which a land L and a groove G having irregularities are provided in the phase change material recording layer RL of the transparent substrate 1 and a pit row RM is similarly formed in the recording layer on the land and the groove. There is also a recording type optical disc structure.

Generally, in recording / reproducing of these optical disks, a land or groove is used as a guide track, and a light beam is made to follow this to be condensed to form a spot, which is recorded on the land or groove as the guide track.
Further, the return light reflected and returned from the spot on the land or groove is detected, and the demodulation signal and various error signals are generated based on the output thereof.

Therefore, conventionally, a tracking servo is used which uses the light intensity distribution of the reflected light on the photodetector in order to make the light beam follow the land or groove guide track. In a recordable optical disc, for example, a so-called push-pull tracking error signal is obtained by calculating the difference detection output of the reflected light intensity distribution on the photodetector divided into two in the direction along the track, which becomes zero. By controlling the position of the light beam as described above, the tracking servo in which the light beam follows the groove is executed.

Further, as one of the push-pull methods of tracking servo, the track on which data is to be recorded is irradiated,
In addition to the main beam that is focused for detection, side beams are focused near the tracks on both sides of the main beam, and a photodetector is provided for each return beam of the three beam spots, and radial push is performed from each side beam. Detect the pull signal,
A so-called differential push-pull method is known in which the differential signal is used as a tracking error signal to detect an error from the track. In order to obtain three light beams, it is general to diffract the light beams by a diffraction grating and use the 0th order diffracted light of the main beam and the ± 1st order diffracted light of the side beams generated. Furthermore, in order to suppress so-called crosstalk in which the signals of adjacent tracks leak during reproduction, the main beam of the 0th-order diffracted light is set to ± 1 on one target track.
By collecting both side beams of the second-order diffracted light on adjacent tracks on both sides, the signals of the adjacent tracks are read out at the same time, and the signals are subtracted from the read signal by the main beam in the center to cancel the crosstalk (hereinafter, crosstalk canceller). That) has been realized.

[0006]

In order to increase the density of optical discs, in addition to shortening the pit length in the track direction, the track pitch in the direction perpendicular to the track direction is also shortened. ing. When the track pitch is shortened, it becomes possible to remove the crosstalk by electrical signal processing like the above-mentioned crosstalk canceller, so the crosstalk generation amount can be reduced when the track pitch is narrowed. Is no longer the main determinant of.

A factor limiting the narrowing of the track pitch is the tracking servo itself. When the track pitch is narrowed, the output of the tracking error signal, especially the radial push-pull signal, becomes small, and there is the problem that sufficient tracking cannot be executed even though the signal can be reproduced by the crosstalk canceller. Was. If the track pitch is narrowed, tracking can be performed if there is no scratch or vibration on the cover surface of the optical disk, but in actual use, tracking becomes unstable and correct writing cannot be performed.

The present invention has been made to solve the above problems of the conventional tracking method, and an object of the present invention is to provide an optical information recording medium capable of stable recording or reproduction at a narrow track pitch, and a recording medium. It is to provide a reproduction method.

[0009]

The optical information recording medium of the present invention comprises a substrate and at least one recording layer, and changes the reflectance or the transmittance of the focused light beam to the recording layer. An optical information recording medium capable of recording or reproducing information, comprising a plurality of guide tracks formed on the substrate and extending at a predetermined guide pitch without intersecting each other, and recording in a direction orthogonal to the guide tracks. A plurality of recording marks each having an interval smaller than the guide pitch and arranged in parallel on the guide track and having a changed reflectance or transmittance.

In the optical information recording medium of the present invention,
The guide layer on which the guide track is arranged and the recording layer on which the recording mark is arranged are laminated at a predetermined interval via a spacer layer. In the optical information recording medium of the present invention, at least two recording layers and spacer layers are alternately laminated.

In the optical information recording medium of the present invention,
The recording mark is formed on a recording layer disposed between the guide tracks. In the optical information recording medium of the present invention, the guide track is spirally formed on the substrate, and the guide track is composed of a plurality of cut spiral arcs.

In the optical information recording medium of the present invention,
The guide track is characterized by having an intermittent guide track formed such that a space between adjacent guide tracks is larger than a radius change amount per one circumference of the spiral. In the optical information recording medium of the present invention, the distance between adjacent guide tracks in the guide track is n times the radius change amount per revolution of the spiral (where n is a natural number of 2 or more).
It is characterized by having an intermittent guide track characterized by being formed.

In the optical information recording medium of the present invention,
The guide tracks are formed in parallel on the substrate. In the optical information recording medium of the present invention, the recording layer is made of a phase change material. An optical information recording medium recording / reproducing method of the present invention comprises a substrate and at least one recording layer, and a plurality of guide tracks formed on the substrate and extending at a predetermined guide pitch without extending and intersecting each other. A plurality of recording marks having a recording interval in a direction orthogonal to the guide track smaller than the guide pitch and arranged in parallel to the guide track and having a changed reflectance or transmittance, and to the recording layer A recording / reproducing method of an optical information recording medium capable of recording or reproducing information by changing the reflectance or the transmittance of the recording layer by the condensed light beam of a plurality of light beams separated from each other at the recording interval. Irradiating a beam to generate a tracking error signal based on the reflected return light from the guide track irradiated with at least one of the light beams, A spot of the light beam is made to follow on the guide track based on a locking error signal, and the recording mark is recorded by one of the spots of the light beam, or from at least one of the spots of the light beam. It is characterized in that a read signal is generated based on the modulated return light.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the accompanying drawings. <First Embodiment> FIG. 4 shows a two-layer optical disc structure of an optical disc according to the first embodiment of the present invention.
In the figure, 31 is a disk-shaped substrate, 32 is a guide groove GG as a guide track formed on this substrate.
A guide layer having a reflective film for supporting the light guide layer 33, a light-transmitting spacer layer, and 34, a flat recording in which a plurality of pits (recording marks) RM, which are areas in which the reflectance changes, are arranged in parallel with the guide groove GG. Layer 35 is a transparent cover layer. The guide groove GG (which may be a guide land as a guide track) is formed without substantially intersecting along the tangential direction of the optical disc, and extends in a radial direction at a predetermined guide pitch so that the disc-shaped substrate is formed. It is spirally formed in the center and consists of multiple cut spiral arcs. The plurality of recording marks have a recording interval, that is, a track pitch in a direction (radial direction) orthogonal to the guide groove GG smaller than the guide groove GG pitch and are arranged in parallel with the guide groove GG. The two-layer optical disc has a two-layer structure including a recording layer 34 below the cover layer 35 and a second guide layer 32 in the back when viewed from the reading side (irradiation side). As shown in FIG. 4, the recording layer 34 is a translucent film so that the reading light can be transmitted and the guide groove GG of the guide layer 32 can be read. The spacer layer 33 separates the recording layer 34 and the guide layer 32 with a constant thickness.

In addition to the two-layer optical disc structure of FIG. 4, as shown in FIG. 5, the optical disc has a guide layer 32 on a substrate 31.
And the deepest recording layer 341 are laminated at a predetermined interval via the spacer layer 33, and at least two or more spacer layers 33 and recording layers 342 are alternately laminated to form a multilayer structure. . Thus, according to the present invention, as shown in FIGS.
A plurality of guide grooves GG that are formed on the guide groove and extend at a predetermined guide pitch GD without separating and intersecting each other, and the track pitch in the direction orthogonal to the guide groove GG, that is, the recording interval RD is smaller than the guide pitch GD and the guide groove GD. A plurality of recording marks RM arranged in parallel with the GG and having a changed reflectance.

This optical disk recording / reproducing method irradiates a plurality of light beams separated from each other with a track pitch smaller than the guide pitch, and reflects from the guide groove GG irradiated with at least one of the light beam spots. A tracking error signal is generated based on the return light, tracking servo control of the light beam is performed based on this tracking error signal, and one of the spots of the light beam
A recording mark is recorded, or a read signal is generated based on reflected return light from at least one of the spots of the light beam.

For example, as shown in FIG. 6, three diffracted lights from one light source light (main beam 0th order light and its side beams ± 1st order light) are used for tracking servo control, and are placed at positions overlapping the 0th order light. It is possible to record / reproduce on / from the optical disk by using the spots RS of the light beams of different wavelengths for recording / reproduction that are irradiated. In an optical disc for recording / reproducing using spots of four light beams, there is a guide groove used when recording or reproducing information by forming a spiral track on the center of a disc-shaped substrate, and the guide groove is It is composed of a plurality of cut spiral arcs, and the interval between the guide groove and the adjacent guide groove is set to be larger than the radius change amount per one turn of the spiral. The guide groove is an intermittent guide track.

FIG. 7 shows an optical disk having an intermittent guide track. The optical disc has a guide groove 1 carved on a substrate, and is irradiated with spots of a main beam 3 and side beams 2 and 4 that follow the guide groove 1. In the figure, the dotted line 5 is a blank track or a recorded track. The light source used for forming the light spot on the substrate is, for example, a laser having a wavelength of 400 nm, which is narrowed down by using, for example, an objective lens having a numerical aperture of 0.85. At this time, a spot having a light beam diameter of about 0.28 μm can be obtained on the substrate. The guide groove 1 carved on the substrate is formed in a spiral shape, and satisfies the condition of the radial position r of the guide groove shown by the following formula (1).

[0019]

## EQU1 ## r = r0 + a.theta ./ (2.pi.) (1) where r0 is the radius of the innermost circumference of the guide groove 1 and is, for example, 20 mm. a is the amount of increase in the radius per round, and is set to 0.28 μm here. θ represents the rotation angle from the innermost circumference in radians, and does not return to 0 even after one rotation, but is integrated and counted. Note that the guide group is formed only when the integer part of θ / (2π) is an even number because it is intermittent.

Next, the operation of the optical disc having the intermittent guide track will be described. As shown in FIG. 7, the main beam 3
Is on an even number of revolutions, guide groove 1
Tracking servo is applied so that the main beam 3 is above. Specifically, the push-pull tracking error signal is extracted from the difference between the photodetection outputs obtained by dividing the reflected light of the main beam 3 in the direction along the guide groove 1, and the radial position of the light beam is controlled so as to be zero. Then, recording is performed on the guide groove 1. At this time, since the distance between the adjacent tracks is 0.56 μm, it is possible to obtain a push-pull tracking error signal having a sufficient size.

As shown in FIG. 8, when the optical disk enters an odd number of turns, this time, push-pull tracking error signals are extracted from both the side beams 2 and 4. As a result, the main beam 3 is controlled to a central position 5 (blank track) between the respective guide grooves, and information is recorded by the main beam 3. Switching between the even-numbered and odd-numbered turns in the optical disk can be performed by monitoring the output of the push-pull signal obtained from each light beam reflected light, as in the above embodiment. Alternatively, it is possible to record in advance a change in the shape of the groove for notifying the pre-recorded guide groove before it is interrupted, and detect the change to switch the tracking servo control.

Further, as shown in FIG. 9, the three beams 2 of FIG.
It is also possible to use the spots of the five light beams in which the side beams 2a and 4a are arranged further outside of 3 and 4, and to obtain the tracking error signal by the outside side beams 2a and 4a in the even number of turns. is there. Alternatively, it is possible to set the side beam interval to be slightly narrower or wider than the guide groove interval. With this setting, if the difference signal between the push-pull signals is used for tracking, it is possible to cancel the offset generated in the push-pull signal due to various factors. A so-called differential push-pull signal can be obtained.

In the above-described embodiment, the guide louves are arranged at every 1 guide pitch to be recorded. However, in this arrangement, for example, the guide grooves are arranged at every 2 tracks to further widen the gap between the guide grooves. Is also possible. An example of such a configuration is shown in FIG. In FIG. 10, diffracted light emitted from each pickup, 23 is a main beam for recording or reproducing a signal,
Reference numerals 21, 22, 24 and 25 are side beams. Solid line 2
Reference numeral 6 indicates a guide groove formed on the substrate, and dotted line 27 indicates a blank track or a recorded track on the substrate. In this case, the groove is recorded on the substrate under the following conditions. That is, the guide groove 2 carved on the substrate
6 is formed in a spiral shape and satisfies the condition of the radial position r of the guide groove, which is expressed by the following equation (2).

[0024]

## EQU2 ## r = r0 + a.theta ./ (2.pi.) (2) where r0 is the radius of the innermost circumference of the guide groove 1 and is, for example, 20 mm. a is the amount of increase in the radius per round, and is set to 0.28 μm here. θ represents the rotation angle from the innermost circumference in radians, and does not return to 0 even after one rotation, but is integrated and counted. It should be noted that since it is intermittent every two tracks, the integer part of θ / π m = int
The guide groove is formed only when (θ / π) is a multiple of 3. When the integer part m = int (θ / π) is 3 and the main beam 23 is on the guide groove 26, the push-pull signal for tracking is the reflected light of the main beam 23. Get from Then, when the optical disk makes a half turn and the integer part m = 4, this time, tracking error signals are obtained from the reflected lights of the side beams 21 and 24, respectively, and tracking is continued. By doing so, a recording track having a guide pitch of "a" is continuously formed from the track recorded with the integer part m = 3. At this time, since the push-pull signal due to the guide groove is not generated from the tracks other than the side beams 21 and 24, tracking can be continuously applied by adding the generated push-pull signals.

Although the above embodiment describes the method of generating the tracking error signal using 5 beams, it is also possible to perform tracking with 3 spots without using the beams 21 and 25. In this case, 2 when m = 3
3 to 24 for m = 4, 22 for m = 5, and the lid 23 for m = 6. The push-pull signal is generated from one of the guide grooves. It can be used for tracking.

The above-described embodiment can be similarly configured by widening the guide groove interval, and n is a natural number, and the integer part int (nθ / (2
Expansion is possible based on the rule that the guide groove is formed only when (π)) is a multiple of n + 1. At this time, the tracking error signal can be similarly detected using 2n-1 light beams.

FIG. 11 shows an outline of an optical pickup optical system of an optical disc information recording / reproducing apparatus according to the present invention when recording / reproducing an optical disc by the spots of four light beams of the first embodiment. The optical pickup of the information recording / reproducing apparatus includes a first light source 11 for information recording / reproducing, a second light source 12 for emitting light having a wavelength longer than that of the first light source for reading tracking information of the guide layer, first and second light sources. 2 light sources 1
Multiplexing prism 1 for coaxially combining the light emitted from 1 and 12
3 and a grating 12a for generating diffracted light between the second light source 12 and the combining prism 13.

Further, the optical pickup includes aperture limiting means 11 such as a beam splitter 14, a collimator lens 15, and an aperture stop that acts to stop the wavelengths of the second light source 12.
7 and an objective lens 16 such as a second group objective lens unit including two lenses. With the above-mentioned light irradiation optical system, the divergent light beam from the light source passes through the beam splitter 14 and collimator lens 15
Is converted into a nearly parallel light beam, and is condensed by the objective lens 16 toward the optical disk 30. In the case of the 3-beam type grating 12a, spots of a plurality of light beams (main beam 0th order light and its side beams ± 1st order light) are generated on the guide layer of the optical disk, and the light spots are formed on the respective layers of the optical disk 30. Form.

At this time, as the aperture limiting means 117, an aperture stop having a diaphragm action including a dichroic mirror portion that transmits the wavelength of the first light source 11 and blocks only the light of the second light source 12 is used. The numerical aperture at which the long wavelength light beam is narrowed down by limiting the circumference of the cross section of the long wavelength light beam from the second light source 12 to the aperture stop of the aperture limiting means 117 in an annular manner,
It can be selected to be smaller than the numerical aperture for the light of the first light source 11.

The distance from the collimator lens 15 to the first and second light sources 11 and 12 on the optical axis is set so that the second light source 12 is closer to the first light source 11.
The light beam of the first light source 11 is generated near the recording layer 34 at the same time,
The light beams (main beam and both side beams) of the second light source 12 are set on the guide layer 32 at positions where they are focused respectively. Although the second group objective lens 16 is used as the objective lens, the objective lens is the aperture limiting means 11
Lens (or lens group) between the optical disc 7 and the optical disc 30
It includes all, and may be a single lens or multiple lenses. Since the predetermined focal length is determined by all the lenses between the aperture stop and the optical disc, the position of the aperture stop is determined based on the focal length of the objective lens.

In addition to the above light irradiation optical system, the optical pickup further has a light detection optical system such as a detection lens, and the objective lens 16 and the beam splitter 14 are also used in the light detection optical system. The photodetection optical system includes a first photodetector 113 for reading a reproduction signal from the first light source to detect a focus error signal, and a second photodetector 114 for detecting a tracking error signal from the second light source.
And a dividing means for dividing the light of the first and second light sources such as the dichroic mirror 112.

By the light detection optical system, the reflected light from the optical disk 30 is collected by the objective lens 16 and directed by the beam splitter 14 to the detection condenser lens 111 of a predetermined magnification and converged. The convergent light condensed by the condenser lens 111 is directed to the dichroic mirror 112. In the dichroic mirror 112, the reflected light from the spot of the short-wavelength light (first light source) on the recording layer 34 is given astigmatism by passing through the transparent parallel plate portion of the dichroic mirror 112, and the first photodetector is detected. The light is condensed near the center of the light receiving surface of 113. An astigmatism generating element (not shown) such as a cylindrical lens or a multi-lens may be used instead of the parallel plate to form a light spot near the center of the light receiving surface of the photodetector.

Reflected light from the three spots of long-wavelength light (second light source) on the guide layer 32 is reflected by the dichroic mirror 112 and condensed near the center of the light receiving surface of the second photodetector 114. Therefore, the second light source having the reflected light of the first light source from the information recording surface of the recording layer 34 detected by the first photodetector 113 and the groove information of the guide layer 32 detected by the second photodetector 114. The reflected light from the first and second light sources 11 and 12 is separated by the dichroic mirror 112 and independently detected by the first and second photodetectors 113 and 114.

The first photodetector 113 is connected to a focus error detection circuit (not shown), and this circuit includes an actuator 115 for focus servo control of the objective lens 16.
Is connected to a drive circuit for driving. The focus actuator 115 drives the objective lens 16 in the irradiation optical axis according to the supplied signal. Specifically, when recording or reproducing, the reflected light from the recording layer 34 is detected by the first photodetector 113, and the dichroic mirror 112 is detected.
By using the astigmatism added by, the difference in diagonal components is detected by the four-division detector to obtain a focus error signal by the so-called astigmatism method.

On the other hand, as shown in FIG. 12, the second photodetector 114 has light receiving portions (B1, B2) divided along the radial direction and arranged at the focal point of the reflected light of the first light source light. And a light receiving element 400 for the 0th-order diffracted light and light receiving portions (A1, A2) (C1, C) divided along the radial direction, respectively.
The light receiving portions of the light receiving elements 401 and 402 for ± 1st-order diffracted light of 2) are provided. Each light receiving portion of the second photodetector 114 is connected to a tracking error detection circuit (not shown), and a predetermined calculation is performed based on each signal output by photoelectric conversion of the light receiving portion to generate a tracking error signal. . For example, in this circuit, when the sign of the light receiving element 400 for the 0th order diffracted light and the light receiving portions of the ± 1st order diffracted light for light receiving elements 401 and 402 is shown as its output, the tracking error signal TE expressed by the following equation (3) is obtained. To generate.

[0036]

[Equation 3] TE = (B1-B2) + G × {(A1-A2) + (C1-C2)} ... (3) However, in the above formula, G represents a correction coefficient.

The tracking error detection circuit is an actuator 11 for controlling the tracking servo of the objective lens 16.
6 is connected to a drive circuit. The actuator 116 drives the objective lens 16 in the radial direction of the optical disc according to the signal supplied. Thus, the light receiving elements 400, 401, 402 for the 0th and ± 1st order diffracted lights
Then, a radial push-pull signal is detected, and a tracking error signal is generated from the differential signal. Based on the obtained tracking error signal, the tracking actuator 116 is driven to perform tracking servo control.

Further, the tracking error detection circuit can be provided with a track switching means. The track switching means is, for example, as shown in FIG. 12, a light receiving element 400 for 0th order diffracted light and a light receiving element 40 for ± 1st order diffracted light.
When the signs of the light receiving units 1 and 402 are shown as the output, the tracking error signals TE1 and TE2 represented by the following equations (4) and (5) are switched and generated according to the track position state.

[0039]

[Equation 4] TE1 = G × {(A1-A2) + (C1-C2)} ... (4) TE2 = B1-B2 (5) However, in the above formula, G represents a correction coefficient.

When the tracking error signal TE1 is generated, as shown in FIG. 6 and FIG.
When the spot of the 0th-order light of the main beam of the two diffracted lights is between the guide grooves GG, the ± 1st-order light beams on both sides of the ± 1st-order diffracted light receiving elements 401 and 402 shown in FIG. The push-pull signal is extracted from both of the return light of and the tracking servo is applied. When generating the tracking error signal TE2, as shown in FIGS.
As shown in FIG. 3, when the spot of the main beam 0th order light is on the guide groove GG, the light receiving element 400 for the 0th order diffracted light shown in FIG. And take out the tracking servo. At this time, since the interval between the adjacent guide grooves is larger than the track pitch, that is, the recording interval RD, it is possible to obtain a push-pull tracking error signal having a sufficient size.

The track switching means can control the switching timing by monitoring the output of the push-pull signal obtained from the respective reflected light beams. Alternatively, the pre-recorded guide groove G
It is also possible to record a change in the shape of the groove for notifying G before it is interrupted and to detect the change in the tracking servo control.

In FIG. 6, the recording marks RM are recorded at a recording interval RD that is 1/2 of the guide pitch GD, but as shown in FIG. 14, a short wavelength light beam is used for reading the recording layer 34 and long wavelength light is used. The 0 diffracted light, the ± 1st diffracted light, and the ± 2nd diffracted light of the beam may be used for tracking servo control by the guide layer 32 to form an optical disc on which recording marks RM are recorded at a recording interval RD that is ¼ of the guide pitch GD. it can.

According to the optical disc of the first embodiment, FIG.
As shown in FIG. 7, the surface (recording layer 34) on which the recording material is applied can be made flat, so that it becomes easy to form a recording layer under uniform conditions over the entire recording surface. Further, a flat recording surface can be secured even when several such recording layers are laminated. By doing so, it is possible to perform recording by irradiating light without passing through the groove of the track on the conventional recording surface, so that the recording performance is improved and the interval (spacer layer) between adjacent recording layers can be shortened. .

As described above, when the recording layer is arranged at a position apart from the guide layer, the focus of the light beam can be operated so as to be focused on the recording surface. This is because, according to the present invention, a tracking error signal having a small amount of track progress per turn can be obtained by the guide groove GG having a substantially wide pitch interval, so that a light beam having a spot diameter increased from the recording layer can be used. This is because the tracking error signal can also be obtained.

Further, according to the optical disc of the present invention, another light source having a wavelength longer than that of the recording light source is prepared for tracking detection, and a tracking error signal is obtained by using a long wavelength light beam. be able to. Depending on the conventional configuration, for example, the track pitch is 0.3 μm
The tracking error signal for recording on the track could not be obtained without using a short wavelength blue laser, but according to the present invention, the actual guide pitch is 0.6 μm.
With a guide groove GG of 0.9 μm or 0.9 μm.
Since a tracking error signal for recording at a track pitch of 3 μm can be obtained, it is possible to use a laser with a wavelength of red 650 nm or near infrared 780 nm as a light source for tracking detection. These light sources integrated with a detector are easily available.

When two light beams having different wavelengths are used as described above, the guide groove GG has only to have a high sensitivity to the wavelength for tracking detection. That is, when the recording layer is recorded or reproduced at the first wavelength and the guide layer is irradiated at the second wavelength, the guide layer is made of a material whose signal modulation degree obtained by the guide layer is larger than that of the recording layer. Has been formed. For example, when the optical depth of the groove is set to 200 nm, which is a half of the recording / reproducing laser wavelength of 400 nm, the phase difference given by reflection becomes exactly 1 wavelength with respect to this wavelength. Don't give. On the other hand, if the light source wavelength for tracking detection is set to 780 nm, for example, a sufficient amount of push-pull signal signal can be obtained. By doing so, the adverse effect of the groove on the reproduction signal can be eliminated, and when the recording layer is provided separately from the guide layer, the reflective film characteristic of the recording layer is completely reflected at the wavelength of 400 nm and becomes 780 nm. Since it is possible to design so as to transmit almost at the wavelength of, it is possible to increase the amount of each signal. <Second Embodiment> In the first embodiment, an example in which a spacer layer is formed on a guide layer and a recording material is applied on the spacer layer to form a recording layer has been described. Apply the recording material directly to the surface where the groove GG is provided,
A configuration in which recording is performed on this surface is also possible.

In the optical disc of the second embodiment, instead of the guide layer 32, the spacer layer 33 and the recording layer 34, a row of recording marks RM is arranged between a pair of adjacent guide tracks GG as shown in FIG. Recording layer 32
4 has the same structure as that of the first embodiment except that the fourth structure is formed. Also, an optical disc structure in which two or more recording layers 324 are laminated can be used.

Also in the second embodiment of the present invention, there is a guide groove used when recording or reproducing information by spirally forming a track on the center of the disk-shaped substrate, and the guide groove has a plurality of guide grooves. An interval between the guide groove and a guide groove adjacent to the guide groove is set to be larger than the radius change amount per revolution of the spiral. The guide groove is an intermittent guide track.

In the above-described embodiment, the method of generating the tracking error signal by push-pull has been described as an example. However, this method simply subtracts the outputs of the light-receiving portions of the side beams symmetrically located with respect to the main beam.
Various conventionally known tracking error signal generation methods can be used, such as a beam method or a wobble method in which a signal component that changes with time is wobbled in a groove to wobble and capture this signal.

In the above embodiment, the description has been made focusing on the operation at the time of recording, but in the case of reading as well, a tracking error signal can be similarly obtained from the guide groove to follow the recorded track. It is also possible to obtain the tracking error signal by the phase difference method directly from the recorded track. Further, it is possible to simultaneously reproduce a plurality of tracks at the time of reproduction, and the information read from the plurality of tracks can be directly demodulated and reproduced, or the crosstalk canceller described above can be used to cross the signals from each other. It is also possible to remove talk and demodulate and reproduce.

In the above embodiment, the actual spacing between the plurality of light beams is not particularly limited, but if the distance measured in the direction perpendicular to the track satisfies the necessary condition, the actual spacing on the light receiving portion will be. It can be selected as the design of the pickup system, such as selecting the light beam spots so that they do not overlap each other. In addition, this method of generating a multi-light beam is achieved by combining a plurality of laser diodes with each other by combining a plurality of light beams using a diffraction grating or by using a laser array having a plurality of light emitting regions as a light source. May be arranged so as to have a common optical axis,
Whichever method is used, a system for operating the present invention can be configured if a plurality of light beams are obtained. When a laser array or multiple laser diodes are used, each laser can be independently modulated, so recording on multiple tracks at the same time,
It can be configured to increase the recording speed.

The present invention is applicable to various recording methods such as a recording layer using a phase change medium and a recording film using a dye, and a recording film using a change in transmittance instead of a change in reflectance as a recording mark. It is possible to apply. In the above-described embodiment, the case where the spiral track is formed on the disc-shaped optical disk has been described. However, as in the above-described embodiment, the guide grooves are spaced apart from each other and a plurality of light beams having a narrower track direction spacing are used. It is not limited to the spiral track on the disk to record information with a track pitch narrower than the guide pitch of the guide groove, for example, in the case of an optical card, it is necessary to form parallel guide grooves. Is also possible. The structure of such an optical card is shown in FIG. In FIG. 16, reference numerals 41, 46, 411 denote guide grooves, 42, 4
3, 44, 45, 47, 48, 49, 410 are blank tracks or recorded tracks, 421, 422, 4
24 and 425 are side beams for tracking, 42
Reference numerals 3 respectively denote main beams for signal recording. When a signal is recorded in the guide groove 46, the light beam 423
Tracking is performed by itself, and when recording a signal on the track 47, tracking servo control is performed so that the side beam 422 follows the guide groove 46. Recording can be performed on each track as in the above embodiment. The configuration of another optical card is shown in FIG.
In this optical card, instead of parallel guide grooves,
It is configured by forming a spiral intermittent guide track every two tracks shown in FIG. 10.

[0053]

As described above, in the present invention, the guide groove is provided separately from the recording portion such as existing as a separate layer or intermittently, and tracking is performed by following this with a plurality of light beams. Since it is configured to perform, a tracking error signal of a sufficient size is obtained by a guide pitch of a guide pitch in addition to a narrow track pitch where a stable tracking error signal cannot be obtained, and information is recorded at high density. It will be possible.

Further, by stacking the recording surfaces, it becomes possible to perform recording on a flat recording surface and improve the quality of the recording signal. In addition, since the guide pitch is wide, a sufficiently large tracking error signal can be obtained without accurately focusing on the guide groove. Therefore, in a medium having multiple recording layers, the focus always performs high-density recording on the recording surface. It is possible.

Further, it is also possible to adopt a structure in which a laser of a long wavelength is used for detecting the tracking error signal, and in such a case, the influence of the groove on the recording signal can be reduced, so that the recording density is further improved. It can be performed.

[Brief description of drawings]

FIG. 1 is a schematic partial perspective view showing a ROM optical disc structure.

FIG. 2 is a schematic partial perspective view showing a groove recording optical disc structure.

FIG. 3 is a schematic partial perspective view showing a land-groove recording optical disc structure.

FIG. 4 is a schematic partial perspective view showing a two-layer optical disc structure according to an embodiment of the present invention.

FIG. 5 is a schematic cross-sectional view showing a multilayer optical disc structure according to another embodiment of the present invention.

FIG. 6 is a schematic partial plan view showing a dual-layer optical disc structure according to another embodiment of the present invention.

FIG. 7 is a schematic partial plan view showing a track structure of an optical disc according to another embodiment of the present invention.

FIG. 8 is a schematic partial plan view showing a track structure of an optical disc according to another embodiment of the present invention.

FIG. 9 is a schematic partial plan view showing a track structure of an optical disc according to another embodiment of the present invention.

FIG. 10 is a schematic partial plan view showing a track structure of an optical disc according to another embodiment of the present invention.

FIG. 11 is a configuration diagram showing an outline of an optical pickup for recording and reproducing from a double-layer optical disc according to another embodiment of the present invention.

FIG. 12 is a plan view showing a second photodetector of an optical pickup for recording / reproducing on / from a double-layer optical disc according to another embodiment of the present invention.

FIG. 13 is a schematic partial plan view showing a double-layer optical disc structure according to another embodiment of the present invention.

FIG. 14 is a schematic partial perspective view showing a double-layer optical disc structure according to another embodiment of the present invention.

FIG. 15 is a schematic partial perspective view showing an optical disc structure of another embodiment according to the present invention.

FIG. 16 is a schematic plan view showing a track structure of an optical card according to another embodiment of the present invention.

FIG. 17 is a schematic plan view showing a track structure of an optical card according to another embodiment of the present invention.

[Explanation of symbols]

1, 26, 41, 46, 411 Guide groove 2, 4, 21, 22, 24, 25 Side beam 2a, 4a Outer side beam 3,23 Main beam 5, 27, 42, 43, 44, 45, 47, 48 Four
9, 410 Blank track or recorded track 11 First light source 12 Second light source 13 Multiplexing prism 14 Beam splitter 15 Collimator lens 16 Objective lens 30 Optical disc 32 Guide layer 33 Spacer layers 34, 324, 342 Recording layer 111 Condensing lens 112 dichroic mirror 113 1st photodetector 114 2nd photodetector 115 focus actuator 116 tracking actuator 117 aperture limiting means 421, 422, 424, 425 tracking side beam 423 signal recording main beam

Continued front page    F term (reference) 5D029 JB14 JB33 KB03 WA11 WA27                       WB11 WC09 WC10 WD10 WD12                       WD21                 5D090 AA01 BB05 BB12 CC14 FF02                       FF16 GG02 GG05 GG22 KK11                       KK13 KK15

Claims (10)

[Claims] 1. An optical information recording medium comprising a substrate and at least one recording layer and capable of recording or reproducing information by changing the reflectance or the transmittance of the focused light beam to the recording layer. A plurality of guide tracks formed on the substrate and extending at a predetermined guide pitch without extending apart from each other, and a recording interval in a direction orthogonal to the guide track is smaller than the guide pitch and An optical information recording medium, comprising a plurality of recording marks arranged in parallel and having varying reflectance or transmittance. 2. The guide layer on which the guide track is arranged and the recording layer on which the recording mark is arranged are laminated at a predetermined interval via a spacer layer. Optical information recording medium. 3. The optical information recording medium according to claim 2, wherein at least two or more recording layers and spacer layers are alternately laminated. 4. The optical information recording medium according to claim 1, wherein the recording mark is formed on a recording layer disposed between the guide tracks. 5. The optical system according to claim 1, wherein the guide track is spirally formed on the substrate, and the guide track is composed of a plurality of cut spiral arcs. Information recording medium. 6. The intermittent guide track is characterized in that the guide track is formed such that a space between adjacent guide tracks is larger than a radius change amount per one circumference of the spiral. The optical information recording medium according to claim 5. 7. The guide track is formed such that a distance between adjacent guide tracks is n times a radius change amount per one turn of the spiral (where n is a natural number of 2 or more). 7. The optical information recording medium according to claim 5, further comprising an intermittent guide track characterized by being provided. 8. The optical information recording medium according to claim 1, wherein the guide tracks are formed in parallel on the substrate. 9. The optical information recording medium according to claim 1, wherein the recording layer is made of a phase change material. 10. A plurality of guide tracks each of which comprises a substrate and at least one recording layer, which are formed on the substrate and extend at a predetermined guide pitch so as to be spaced apart and not intersect with each other.
A plurality of recording marks having a recording interval in a direction orthogonal to the guide track smaller than the guide pitch and arranged in parallel to the guide track and having a changed reflectance or transmittance, and to the recording layer Is a recording / reproducing method of an optical information recording medium capable of recording or reproducing information by changing the reflectance or the transmittance of the recording layer by the focused light beam of a plurality of light beams separated from each other at the recording interval. Irradiating a beam to generate a tracking error signal based on the reflected return light from the guide track irradiated with at least one of the light beams, and based on the tracking error signal, the light on the guide track. The spot of the beam is made to follow, and the recording mark is recorded with one of the spots of the light beam, or the spot of the light beam is reduced. A recording / reproducing method characterized in that a read signal is generated based on at least one modulated return light.