JP2809043B2 - optical disk - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a write-once optical disk and a rewritable optical disk, and more particularly to a high-density optical disk having a guide groove.

[0002]

2. Description of the Related Art In a read-only optical disk such as a compact disk (hereinafter referred to as a CD), a spiral information track having a track pitch of about 1.6 μm is provided on the optical disk, and a width of about 0 μm is provided on the information track. Information pits of 0.5 μm are recorded as a change in the shape of unevenness. In a write-once type or rewritable optical disk, a guide groove for tracking control (hereinafter, also simply referred to as a groove) is formed spirally at a track pitch of, for example, about 1.6 μm. Tracks are formed. Hereinafter, a space between the guide grooves is also referred to as a land or an inter-groove portion.

[0003] Recently, with the trend of miniaturization of devices and the trend of high quality of reproduced images, it is desired to improve the recording density of optical discs. To improve this recording density,
Studies have been made on shortening the wavelength of a laser beam used for recording or reproduction and increasing the NA of a lens (NA indicates the numerical aperture of a lens). However, realization of a short-wavelength laser (for example, a blue laser) is quite difficult, and when a high NA lens is used, an extremely high-precision disk is required.

Therefore, as another means for increasing the density of an optical disk, it has been studied to increase the track density by reducing the track pitch of information tracks. However, in this case, there are the following two problems. a. Crosstalk between adjacent tracks b. Tracking control for guiding the laser beam spot on the center line of the information track cannot be performed.

[0005] Of the above two problems, measures against crosstalk between adjacent tracks a are disclosed in
As described in Japanese Patent Publication No. 18, a method of reducing crosstalk between adjacent tracks by performing reproduction using a multi-beam has been proposed, and further introduced in 1992 / Autumn Society of Applied Physics 18a-T-3. As described above, when the depth of the guide groove is set to about λ / 5 (λ indicates the wavelength of the laser beam for reproduction), information is transmitted to both the guide groove for tracking formed on the transparent substrate and the space between the guide grooves. It is said that crosstalk from adjacent tracks is reduced even when recording is performed.

Of the above two problems a and b, the problem of the tracking control of b is that the resolution of the optical pickup is limited, so that a good tracking error signal cannot be obtained using the tracking guide groove. For this reason, the stability of the tracking control deteriorates. To solve this problem, the following means have been proposed to substantially increase the track density while keeping the pitch of the guide grooves relatively large. That is, as described in JP-A-59-139147, a method for recording information in both the tracking guide groove and the space between the guide grooves has been proposed. Japanese Patent Application Laid-Open No. Hei 3-165114 discloses that a guide groove for tracking and a shape change of pits (pits) between the guide grooves are provided.
A method for recording information is described as
No. 4021 describes a method of changing the groove depth of adjacent guide grooves.

Each of these optical disks has a guide groove, and the guide groove may be partially discontinuous in order to record a preformat signal or the like in the guide groove. It is provided continuously. FIG. 2 shows an example of a conventional high-density optical disk. In FIG. 2, an optical disk 2 is a recording / reproducing optical disk, in which spiral (spiral) guide grooves G are provided at a groove pitch 2P as shown by a solid line. Groove information track is formed.

An inter-groove information track indicated by a dotted line is provided on the center line of the inter-groove (land) L, and information is recorded in the same manner. Therefore, the track pitch of the information track is P
It is. The width of the guide groove G is substantially P, but only the center line of the guide groove is shown by a solid line in the figure. When recording and reproducing continuous information such as an audio signal and a video signal on the optical disk, for example, when recording is started from the outermost peripheral portion C1 on the groove information track, it is necessary to record continuously on the guide groove. When recording is performed up to the innermost peripheral portion D of the guide groove, the optical head is moved to the outermost peripheral portion E1 of the land, and is continuously recorded on the inter-groove information track toward the innermost peripheral portion F of the land. .

In this case, after the recording in the guide groove is completed at the innermost circumference, the optical head is moved from the innermost circumference to the outermost circumference, and it is necessary to perform the tracking control again. However, there is a problem that recording and reproduction cannot be performed continuously without interruption. As one means for solving this problem, it is conceivable to alternately record and reproduce data in the groove portion and the groove portion every other turn. In this case, in FIG. 2, recording is first performed for one round from C1 to C2 of the guide groove, and then a track jump is performed to irradiate a laser beam spot on an adjacent track, and E1 to E2 in the inter-groove portion. It is recorded for one round up to.

[0010] Thereafter, a track jump is further performed, and a laser beam spot is irradiated on an adjacent track, and is recorded in one turn from C2 to C3 of the guide groove. In the same manner, the data is gradually recorded toward the innermost circumference. At the time of reproduction, they are reproduced in the recording order described above. In the case of the recording or reproduction,
Each time a jump to an adjacent track is performed, the laser beam spot must be guided on the center line of the guide groove G or on the center line of the inter-groove (land) L by tracking control. There is a problem that recording or reproduction cannot be performed until the time is stabilized, and the recording capacity of the optical disk is substantially reduced.

[0011]

When recording on the conventional optical disc shown in FIG. 2, for example, recording is started from C1 and then recorded on the guide groove G and the inter-groove (land) L as follows. The street is conceivable. a. Recording is performed from the outermost peripheral portion C1 of the guide groove G to the innermost peripheral portion D of the guide groove, and then from the outermost peripheral portion E1 between the grooves to the innermost peripheral portion F between the grooves. b.
The outermost peripheral portions C1 to C2 of the guide groove G are recorded, the track jump is performed, and the outermost peripheral portions E1 to E2 of the gap L are recorded.
Record from 2 to C3. Similarly, recording is performed up to the innermost peripheral portion.

In the case of a, when reproducing the continuous information recorded in the guide groove and the land, the optical head is moved from the innermost circumference to the outermost circumference of the optical disk 2 or from the outermost circumference to the innermost circumference. It is necessary to move, and information cannot be read continuously. Therefore, in order to output continuous information, it is necessary to store the information read by the optical head in a large-capacity buffer in advance, and to read the information from the buffer during the moving time of the optical head.

In case b, the optical disk 2 is 1
Since the optical head executes a track jump every time it rotates, it takes time for the track jump and tracking control after the jump, during which information cannot be recorded or reproduced, and the recording area of the optical disk is substantially reduced, thereby reducing the recording capacity. Is substantially reduced. In addition, there is a problem that a relatively large-capacity buffer is required for reproducing continuous information. The optical disk of the present invention has been made in view of the above problems, and has as its object to provide an optical disk having a large recording capacity and capable of performing stable tracking control.

[0014]

The optical disk of the present invention comprises:
A recording capacity which makes the pitch of the guide groove for tracking control relatively large to facilitate the tracking control, and continuously records information in both the guide groove and the guide groove without performing a track jump. It is a large optical disk. That is, in an optical disc in which information is optically recorded on a spiral information track and the recorded information is optically reproduced, the spiral information track is formed in a groove portion provided in a tracking guide groove. An information track and an inter-groove information track provided between the guide grooves are provided, and approximately one round of the groove information track and approximately one round of the inter-groove information track are alternately provided in the information track direction. An optical disc having tracking switching information for inverting the polarity of a tracking error signal formed at a boundary between the groove information track and the inter-groove information track. Further, the optical disc of the present invention is an optical disc in which the tracking switching information is formed by pits having irregular shapes.

[0015]

In the spiral information track, a groove information track provided in approximately one guide groove and an inter-groove information track provided between substantially one guide groove (land) correspond to the information track. Because it is arranged alternately in the direction,
The pitch of the tracking control guide groove is larger than the track pitch, and tracking control can be stably performed. Further, even if a track jump is not performed, information is continuously recorded and reproduced, so that the area where recording cannot be performed is reduced.
During the recording and reproduction of the optical disc, the tracking switching information formed at the boundary between the groove information track and the inter-groove information track is reproduced, and the polarity of the tracking error signal is switched by the reproduced tracking switching information. In addition, tracking control is favorably performed on both the groove information track and the inter-groove information track.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the optical disk of the present invention, the pitch of the guide grooves is made relatively large to secure the stability of tracking control, and information tracks are provided between the guide grooves to substantially reduce the track density. Double the recording capacity,
The reproduction light spot does not need to be moved discontinuously between the case where reproduction is performed from the guide groove and the case where reproduction is performed between the guide grooves. Although the structure of the optical disc of the present invention is basically based on a recording layer provided on a transparent substrate and a reflective layer provided on the recording layer, the principle of optically recording or reproducing is a general one. Therefore, here, the guide groove for tracking and the information track, which are features of the present invention, will be described.

An embodiment of the optical disk according to the present invention will be described below with reference to FIG. FIG. 1 is a diagram showing an embodiment of the optical disk of the present invention, which is a recording / reproducing optical disk. In FIG. 1, a guide groove G indicated by a solid line is spirally formed on a transparent substrate such as polycarbonate, and has a groove pitch of 2P and a groove width of P. An information track is also provided between the guide grooves, that is, on the center line of the land L. As a whole, the information track T is composed of one round of the groove information track provided in the guide groove G and the land L.
Are arranged alternately in the information track direction. Therefore, the track pitch of the information track T is P.

That is, the guide groove G is located at the outermost periphery A1 shown in FIG.
To B1 are formed spirally for one rotation of the optical disc 1, and a groove information track is provided in this guide groove. One rotation from B1 to A2 is a spiral land L, and this land L is provided with an inter-groove information track. Similarly, on the inner peripheral side from A2, substantially one round groove portion and substantially one round groove portion are alternately arranged in the guide groove direction, and information tracks are provided on both of them. The width of the guide groove G is substantially P, but FIG. 1 shows only the center line of the guide groove by a solid line.

In the information track T, at the boundary between the guide groove G and the land L, tracking switching information for inverting the polarity of the tracking error signal is formed in advance by pits having irregularities. The information track T is divided into a number of sectors as necessary, and sector information, synchronization information, and the like are recorded in advance in the form of irregularities. It should be noted that the tracking switching information is not provided independently at the boundary between the guide groove G and the land L, but may be a method using the displacement of the guide groove in the groove width direction. In the same manner as the conventional guide groove forming method, the guide groove G is formed by, for example, irradiating a glass disk coated with a photoresist with a laser beam with a laser cutting machine, and developing, plating, and pressing. In this case, the irradiation of the laser beam is performed every other turn of the optical disk by turning on / off the optical modulator or the like.

The recording of information is performed on the groove information tracks and the inter-groove information tracks. At the time of recording, for example, the information is recorded in the guide grooves from A1 to B1 of the optical disc 1, and then recorded on the lands from B1 to A2.
Further, it is recorded in the guide grooves from A2 to B2. Thereafter, recording is similarly performed up to the innermost circumference. The information recorded on the information track composed of the guide groove and the land is reproduced by the reproducing device shown in FIG. FIG.
FIG. 1 is a diagram illustrating an example of an optical disc reproducing device according to the present invention. As shown in FIG. 3, the laser beam emitted from the optical head 10 becomes a light spot on the information track of the optical disc 1 of the present invention, and the optical spot 1
Is reflected on the four-divided photodiode 8.

In the optical head 10, the laser light emitted from the laser light source 3 is collimated by the collimator lens 4, condensed by the objective lens 6 via the beam splitter 5, and irradiated on the optical disc 1. The reflected light from the optical disk 1 is incident on a condenser lens 7 via an objective lens 6 and a beam splitter 5. The laser light that has passed through the condenser lens 7 enters the four-division photodiode 8. The position of the objective lens 6 is controlled by a lens actuator 9. That is, the objective lens 6
With this movement, tracking control for guiding the laser light on the center line of the information track on the optical disc 1 and focus control for forming a light spot of the laser light on the recording layer of the optical disc 1 are performed.

In FIG. 3, four outputs of the four-division photodiode 8 are applied to a demodulation circuit 11 and an error detection circuit 12. In the demodulation circuit 11, an information reproduction signal is generated from the RF signal and output to the terminal 14, and a track type signal indicating whether the information track is in the guide groove or the information track provided between the guide grooves is detected. Output to the terminal 15 and the error detection circuit 1
2 is applied. The track type signal is set to 1 when the laser beam spot is scanning the guide groove of the optical disk, and is set to 0 when scanning the land. In the case where the light spot moves from the guide groove G to the land L along the information track T and from the land L to the guide groove G, tracking switching information is recorded at the boundary between the guide groove and the land. Therefore, tracking switching information is detected at the boundary portion, and the track type signal is output according to the detected tracking switching information. In the error detection circuit 12, a tracking error signal and a focus error signal are detected, and an actuator control circuit 1 for controlling the lens actuator 9 is provided.
3 is applied.

FIG. 4 is a diagram showing the relationship between the optical disk of the present invention and a tracking error signal. In FIG. 4, the optical disk of the present invention is shown on the upper side, but the illustration of the guide groove G and the land L is schematically shown without illustration of the transparent substrate, the reflection film and the like. During recording or reproduction, a laser beam is applied to the optical disc in the direction of the arrow. Here, the left side of the optical disk is the inner side and the right side is the outer side.
In the tracking error signal TE shown in FIG. 4, a signal g is a signal output from the error detection circuit 12 when the laser light spot scans the guide groove G, and a signal n is a signal between the guide grooves (land). 3) A signal output from the error detection circuit 12 when scanning L. Here, the tracking error signal TE is obtained by a known method of calculating the four outputs of the four-division photodiode, and the signal g and the signal n have the same amplitude and only the polarity is inverted.

The switching between the signals g and n is performed by the demodulation circuit 1
1 is performed by the error detection circuit 12 in accordance with the track type signal output from the control signal 1. For example, when the light spot scans the guide groove G, the light spot is
If the signal g is shifted to the outer peripheral side from C, the signal g becomes a positive output, and the light spot is moved to the inner peripheral side. Conversely, if the light spot is shifted to the inner peripheral side from the center line GC of the guide groove G, the signal g becomes a negative output, and the light spot is moved to the outer peripheral side.

On the other hand, the light spot is located between the guide grooves (lands) L.
When scanning is performed, if the light spot deviates from the center line LC of the land L to the outer peripheral side, the signal n becomes a positive output, and the light spot is moved to the inner peripheral side. Conversely, if the light spot is shifted inward from the center line LC of the land L, n becomes a negative output, and the light spot moves to the outer circumference. By the tracking control described above, the laser beam spot irradiated on the optical disk is always guided on the center line of the guide groove or on the center line between the guide grooves.

At the time of reproduction, information is read from the information tracks in the recorded order. In the above-described example, since recording is performed from the outer periphery to the inner periphery, reproduction is also performed from the outer periphery to the inner periphery. If the recording is performed from the inner circumference to the outer circumference, the reproduction is also performed from the inner circumference to the outer circumference. In the optical disc 1 shown in FIG. 1, for example, at the boundary between the guide groove G and the land L indicated by B1, the center line of the information track in the guide groove G and the center line of the information track in the land L are substantially equal. Since the tracking error signal TE is on a straight line and the tracking error signal TE is substantially zero, even if the polarity of the tracking error signal TE is switched near the boundary B1,
There is no adverse effect on tracking control, and there is no dead time for track jump as described in the conventional example. Further, the switching of the tracking signal is only required to provide the tracking switching information at the boundary portion on the information track of the optical disk 1, so that the recording capacity of the optical disk 1 is hardly reduced.

[0027]

According to the optical disk of the present invention, it is possible to record continuously between the guide grooves without a track jump, or to continuously reproduce the recorded information. However, the recording capacity of the optical disk becomes large. Further, since the pitch of the tracking guide groove is larger than the track pitch, the tracking control is performed stably.

[Brief description of the drawings]

FIG. 1 is a diagram showing one embodiment of an optical disk of the present invention.

FIG. 2 is a diagram showing an example of a conventional optical disk.

FIG. 3 is a diagram showing an example of an optical disk reproducing device according to the present invention.

FIG. 4 is a diagram showing a relationship between the optical disc of the present invention and a tracking error signal.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Optical disk 3 Laser light source 4 Collimating lens 5 Beam splitter 6 Objective lens 7 Condensing lens 8 Quadrant photodiode 9 Lens actuator 10 Optical head 11 Demodulation circuit 12 Error detection circuit

Claims (2)

(57) [Claims] 1. An optical disk in which information is optically recorded on a spiral information track and the recorded information is reproduced optically, the spiral information track is provided in a tracking guide groove. The groove information track provided between the guide grooves and the groove information track provided between the guide grooves.
The circumferential groove information tracks and the substantially one round of the inter-groove information tracks are alternately provided in the information track direction. An optical disc characterized by forming tracking switching information for reversing the direction. 2. The optical disk according to claim 1, wherein the tracking switching information is formed by pits having a concave-convex shape.