JPH06274896A - Optical disk - Google Patents

Abstract

PURPOSE:To increase recording density by densifying track density and to enable stable tracking control. CONSTITUTION:In an optical disk for optically reproducing information recorded on a spiral information track T, the spiral information track T is composed of a grooved part provided on a groove G having almost the same width as the track pitch P of the information track T and an non-grooved part provided between the groove L and about one round of the grooved part and about one round of the non-grooved part are alternately provided in the direction of the information track. Consequently, the pitch 2P of a guide groove for tracking is larger compared with the track pitch P, the tracking control is stably performed and the recording areas are not decreased since a track jumping is not necessary.

Description

Detailed Description of the Invention

[0001]

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

[0002]

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

By the way, recently, with the trend toward miniaturization of devices and the trend toward higher image quality of reproduced images, it is desired to improve the recording density of optical discs. To improve this recording density,
Studies have been conducted on shortening the wavelength of laser light used for recording or reproduction and increasing the NA of the lens (NA indicates the numerical aperture of the lens). However, it is quite difficult to realize a short-wavelength laser (for example, a blue laser), and when a high NA lens is used, an extremely high-precision disk is required.

Therefore, as another means for increasing the density of the optical disc, it has been considered to reduce the track pitch of the information tracks to increase the track density, but in this case, there are the following two problems. a. Crosstalk between adjacent tracks b. Tracking control for guiding the laser light spot to the center line of the information track cannot be performed.

Of the above two problems, as a measure against crosstalk between adjacent tracks of a, Japanese Patent Laid-Open No. 3-2321
As described in Bulletin No. 18, a method of reproducing by using multi-beam to reduce crosstalk between adjacent tracks 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 (where λ indicates the wavelength of the reproduction laser beam), the tracking guide groove (recess) formed between the transparent substrate and the guide groove (convex portion) is formed. It is said that the crosstalk from the adjacent tracks is reduced even when the information is recorded on both of them.

Of the above two problems a and b, the problem of 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 tracking control deteriorates. Therefore, as a solution to this problem, the following means have been proposed for substantially increasing the track density while keeping the pitch of the guide grooves relatively large. That is, as described in JP-A-59-139147, a method has been proposed in which information is recorded both in the tracking guide groove (recess) and between the guide grooves (convex). Further, Japanese Patent Application Laid-Open No. 3-165114 describes a method of recording information as a shape change of unevenness between a guide groove for tracking and a guide groove.
No. 04021 describes a method of changing the groove depth of adjacent guide grooves.

Each of these optical discs 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 substantially continuously. Figure 2
FIG. 4 is a diagram showing an example of a conventional high density optical disc. In FIG. 2, the optical disc 2 is a read / write type optical disc, and as shown by the solid line, spiral guide grooves G (grooves) are provided at a groove pitch 2P, and information is provided in the guide grooves G. An information track for recording is formed.

Between the guide groove and the guide groove, that is, the land L
An information track indicated by a dotted line is provided on the center line of the (convex portion), and information is recorded similarly. Therefore, the track pitch of the information track is P. Although the width of the guide groove G is substantially P, 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 audio signals and video signals on this optical disc, for example, when recording is started from the outermost peripheral portion C1 in the guide groove (recess), it is necessary to continue recording in the guide groove. . When the innermost peripheral portion D of the concave portion is recorded, the optical head is moved to the outermost peripheral portion E of the convex portion, and recording is continuously performed on the convex portion toward the innermost peripheral portion F of the convex portion.

In this case, after the recording in the recess is completed at the innermost circumference, the optical head needs to be moved from the innermost circumference to the outermost circumference and the tracking control needs to be performed again.
There is a problem that recording and reproduction cannot be performed continuously without interruption in time. As one means for solving this problem, it is conceivable to alternately record and reproduce the concave portions and the convex portions every other round. In this case, in FIG. 2, first, one round of recording from C1 to C2 of the recess is recorded.
Next, a track jump is performed to irradiate a laser beam spot on an adjacent track and recording is performed on one round from E1 to E2 of the convex portion.

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

[0011]

In the case of recording on the optical disc of the conventional example shown in FIG. 2, for example, as a method of starting recording from C1 and recording on the guide groove G and the groove L, the following two methods are available.
You can think of the street. 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, a track jump is performed, and the outermost peripheral portions E1 to E2 of the inter-groove L are recorded.
Is recorded, and a track jump is performed again to guide groove G
Record from C2 to C3. Similarly, the innermost peripheral portion is recorded.

In the case of the above 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 or from the outermost circumference to the innermost circumference of the optical disk 2. It is necessary to move, and information cannot be read continuously. Therefore, in order to output continuous information, it is necessary that the information read by the optical head is stored in a large capacity buffer in advance and the information is read from the buffer during the moving time of the optical head.

In the case of b, the optical disc 2 is 1
Since the optical head executes a track jump each time it rotates, it takes time to perform 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, resulting in a recording capacity. However, there is a problem that it will decrease substantially. There is also a problem that a buffer having a relatively large capacity is required for reproducing the continuous information. The optical disk of the present invention is made in view of the above problems, and an object thereof is to provide an optical disk having a large recording capacity and capable of stable tracking control.

[0014]

The optical disc of the present invention comprises:
Recording capacity for facilitating tracking control by making the pitch of the guide groove for tracking control relatively large, and continuously recording information on both the guide groove and between the guide grooves without performing track jump. It is a large optical disc. That is, in an optical disc in which information recorded on a spiral information track is optically reproduced, the spiral information track is provided in a groove having a width substantially the same as the track pitch of the information track. An optical disc comprising a grooved portion and a grooveless portion provided between the grooves, wherein the grooved portion having approximately one turn and the grooveless portion having approximately one turn are alternately provided in the direction of the information track. is there.

[0015]

In the spiral information track, the information track provided in the guide groove of about one turn and the information track provided between the guide grooves (land) of about one turn are alternately arranged in the direction of the information track. Since they are arranged, the pitch of the guide grooves for tracking control is larger than the track pitch, and the tracking control can be stabilized. Further, since the information is continuously recorded and reproduced without performing the track jump, the unrecordable area is reduced.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The optical disc of the present invention has a relatively large pitch between the guide grooves to ensure stability of tracking control, and an information track is provided between the guide grooves to substantially improve the track density. Double the recording capacity and
The reproduction light spot does not have to be discontinuously moved between the case of reproducing from the guide groove and the case of reproducing from between the guide grooves. The structure of the optical disk 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, but the principle of optically recording or reproducing is general. Therefore, the guide groove for tracking and the information track, which are the features of the present invention, will be described here.

An embodiment of the optical disc of the present invention will be described below with reference to FIG. FIG. 1 is a diagram showing an embodiment of an optical disc of the present invention, which is a recording / reproducing optical disc. In FIG. 1, the guide groove G (groove) shown 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 configured such that one round of the information track provided in the guide groove G and one round of the information track provided in the land L are alternately arranged in the track direction. Therefore, the track pitch of the information track T is P.

That is, the guide groove G is the outermost circumference A1 shown in FIG.
From B1 to B1 are formed in a spiral shape for one rotation of the optical disc 1, and an information track is provided in this guide groove. B1
One rotation from A to A2 is a spiral land L, and the land L is also provided with an information track. The A
Similarly, from 2 to the inner circumference side, the information track has guide grooves of approximately one turn and lands of about one turn which are alternately arranged in the track direction, and the information tracks are provided on both of them. In the following description, the information track provided in the guide groove G may be referred to as a grooved portion, and the information track provided in the land L may be referred to as a grooveless portion. Although the width of the guide groove G is substantially P, only the center line of the guide groove is shown by a solid line in FIG.

In the information track T, tracking switching information for reversing the polarity of the tracking control signal is preliminarily formed at the boundary between the guide groove G and the land L by concave and convex pits. Further, the information track T is divided into a large number of sectors as required, and sector information, synchronization information, etc. are recorded in advance in the shape of concavities and convexities. Incidentally, the tracking switching information is not provided independently at the boundary between the guide groove G and the land L, but
There is also a method of utilizing the displacement of the guide groove in the groove width direction. The method for forming the guide groove G is similar to the conventional guide groove forming method, in which a glass disk coated with a photoresist is irradiated with laser light by a laser cutting machine, and is formed through development, plating, and pressing steps. In this case, the irradiation of the laser light is performed every other round of the optical disk by turning on / off the light modulator.

Information is recorded in both the information track (grooved portion) provided in the guide groove G and the information track (non-grooved portion) provided in the land L. At the time of recording, for example, it is recorded in the guide groove from A1 to B1 of the optical disc 1 and then in the land from B1 to A2.
Furthermore, it is recorded in the guide groove from A2 to B2. After that, it is recorded in the same way 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 apparatus shown in FIG. Figure 3
It is a figure which shows an example of the optical disk reproducing apparatus concerning this invention. As shown in FIG. 3, the laser light 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 disc 1 formed by this light spot.
The reflected light from is incident on the four-division photodiode 8.

In the optical head 10, the laser light emitted from the laser light source 3 is collimated by the collimator lens 4, collimated by the objective lens 6 through the beam splitter 5, and irradiated onto the optical disc 1. The reflected light from the optical disc 1 enters the condenser lens 7 through the objective lens 6 and the beam splitter 5. The laser light passing through the condenser lens 7 is incident on 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
By the movement of, the tracking control for guiding the laser beam onto the center line of the information track of the optical disc 1, the focus control for forming the light spot of the laser beam on the recording layer of the optical disc 1, and the like are performed.

In FIG. 3, the four outputs of the four-division photodiode 8 are applied to the demodulation circuit 11 and the error detection circuit 12. In the demodulation circuit 11, an information reproduction signal is generated from the RF signal and is output to the terminal 14, and at the same time, a track type signal indicating an information track in the guide groove or an information track provided between the grooves is detected. It is output to the terminal 15 and applied to the error detection circuit 12. 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. The light spot extends from the guide groove G along the information track T to the land L.
Since the tracking switching information is recorded at the boundary portion between the guide groove and the land when moving to the land and from the land L to the guide groove G, the tracking switching information is detected at the boundary portion. The track type signal is output according to the detected tracking switching information. The error detection circuit 12 detects a tracking error signal and a focus error signal, and controls the lens actuator 9 by an actuator control circuit 13
Applied to.

FIG. 4 is a diagram showing the relationship between the optical disc of the present invention and the tracking error signal. In FIG. 4, reference numeral 1 is an optical disk of the present invention, in which the description of the transparent substrate, the reflective film, etc. is omitted, and the guide groove G and the land L are shown in a schematic view. At the time of recording or reproducing, the laser light is applied to the optical disc 1 in the direction of the arrow. Here, the left side of the optical disk 1 is the inner circumference side and the right side of the figure is the outer circumference 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 land between the laser light spot and the guide groove. This is 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 are obtained.
In and, the amplitude is the same and only the polarity is inverted.

The switching between the signals g and n is performed by the demodulation circuit 1
The error detection circuit 12 performs the operation in accordance with the track type signal output from the No. 1. For example, the light spot is groove G
If the light spot is shifted from the center line GC of the groove G to the outer peripheral side during scanning, the signal g becomes a positive output and the light spot is moved to the inner peripheral side. On the contrary, if the light spot is displaced from the center line GC of the groove G to the inner circumference side, the signal g becomes a negative output and the light spot is moved to the outer circumference side.

On the other hand, when the light spot is scanning the land L between the guide grooves, the light spot is the center line L of the land L.
If it is deviated to the outer peripheral side from C, the signal n becomes a positive output and the light spot is moved to the inner peripheral side. On the contrary, if the light spot deviates from the center line LC of the land L to the inner circumference side, the above n becomes a negative output, and the light spot is moved to the outer circumference side. By the tracking control as described above, the laser light spot applied to the optical disc 1 is always guided to the center line of the guide groove or the center line between the guide grooves.

During reproduction, information is read from the information tracks in the order in which they were recorded. In the above example, since recording is performed from the outer circumference to the inner circumference, reproduction is also performed from the outer circumference to the inner circumference. 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, 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 at the boundary between the guide groove G and the land L indicated by B1, for example. Since they are 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 jumping as described in the conventional example. Further, since the tracking signal can be switched only by providing the tracking switching information at the boundary portion on the information track of the optical disc 1, the recording capacity of the optical disc 1 is hardly reduced.

[0027]

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

[Brief description of drawings]

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

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

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

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

[Explanation of symbols]

1 Optical Disc 3 Laser Light Source 4 Collimating Lens 5 Beam Splitter 6 Objective Lens 7 Condensing Lens 8 4-Division Photodiode 9 Lens Actuator 10 Optical Head

Claims (1)

[Claims] 1. An optical disc in which information recorded on a spiral information track is optically reproduced, wherein the spiral information track is formed into a groove having a width substantially the same as the track pitch of the information track. It is composed of a grooved portion provided and a grooveless portion provided between the grooves, and the grooved portion of approximately one turn and the grooveless portion of approximately one turn are alternately provided in the information track direction. optical disk.