JPS62239324A - Address reproducing circuit for optical disk - Google Patents

Abstract

PURPOSE:To attain the application of an optical disk whether the tracking center between both laser beams is set at the top or bottom part of a V-shaped groove, by using such an optical disk where the address signals are arranges so that they have no mutual superposition at the V-shaped grooves adjacent to each other and reproducing the reference signal of the track address value, etc. with use of just a single laser beam. CONSTITUTION:No interference is produced between address signals since these address signals have no mutual superposition at a V-shaped grooves adjacent to each other. Therefore the use of just one of two laser beams is enough for reproduction of address signals in case both beams are made incident on tracks B and C centering on a top 25 of the groove. For instance, a spot 17 of an optical disk is used and this spot 17 moves on the track B. When the reflected light sent from the spot 17 is made incident on a photodetector 40, the detector 40 converts its incident light into electric signals and delivers them. These electric signals are amplified by a preamplifier 41 and the reproduction signal P is obtained. Then the spot 17 detects an address signal 38 and reproduces the address value r38. Furthermore the spot 17 moves to detect an address signal 3 and reproduces the address value r35.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an optical disc and an optical disc device for recording and reproducing various information by irradiating the optical disc with a laser, and particularly to an address reproducing circuit.

2. Description of the Related Art In recent years, many optical disk memories have been proposed in which various types of information are recorded and reproduced on a disk using laser light. Among these, as a recording and reproducing method to improve the recording density and transfer rate, a groove with a V-shaped cross section in the radial direction of the disk is formed on the surface of the optical disk, and the slope of the V groove is used as a track to record and reproduce signals. I proposed a way to do it. (Japanese Unexamined Patent Publication No. 69-36338) FIG. 2 shows a perspective view of a radial cross section of an optical disc having a V-groove. Two adjacent slopes, such as M and B or C and D in FIG. 2, are irradiated with two laser beams 1 and 2 as shown in FIG. By driving these lasers independently of each other, independent signals can be recorded using the two slopes as tracks. Recording thin film 3
For example, using TeOx (x':: 1.1),
Signals are recorded by changing the reflectance as the laser power changes.

When reproducing a signal recorded as described above, two adjacent slopes are irradiated with a laser as the reproducing power in the same manner as during recording, and the signals of two tracks are simultaneously reproduced. Regarding this reproduction method, as detailed in the above patent application, if the shape of the V-groove is optimized, the ±1st-order diffracted light of the reflected light from the disc will be received as the center of the light.
Crosstalk from adjacent slopes can be sufficiently suppressed, and signals from one track can be reproduced individually. The photodetector is shown in FIG. 3 of this prior application.

Next, an example of a method for manufacturing an optical disc having a V-groove will be briefly described. Figure 3 shows a cross section of the metal master disc during cutting. As shown in FIG. 3, the metal master 6 is cut with a V-shaped cutting needle 6. Generally, the width of the cutting needle 6 is larger than the pitch of the V-groove, so
As shown in the figure, overlapping cutting is performed. In this specification, the portion cut by the tip 7 of the cutting needle 6 will be referred to as a valley, and the portion formed by overlapping cutting will be referred to as a peak. In Fig. 3, 8 and 9 are valleys, and 10° and 11 are mountains.

Next, this metal master is plated with nickel or the like to form a stamper, and the base resin is molded using a stamper.

In general, in addition to the grooves forming the recording tracks, reference signals are recorded on an optical disc at the time of manufacturing the optical disc in order to display various information about the optical disc.

Examples of reference signals include address signals for searching for a target track, sector signals for dividing a disk into sectors, and code signals representing various identification signals.

In this specification, an address signal will be described as an example of a reference signal.

The address signal consists of a code signal with an address value indicating each V-groove, an address mark signal indicating the start point of the address area, an error correction code for detecting and correcting errors that occur when reproducing the code signal, a clock synchronization signal, etc. do.

The address signal is recorded by forming pits tLp with varying depths of V-grooves, as shown in FIG. This pit &p is made by moving the cutting needle 6 shown in FIG.
It is created by vibrating in accordance with the position of the pit when cutting the groove. A cross-sectional view taken along the ridgeline γ of the valley in FIG. 4 is shown in FIG. Figure 6 shows an example of the change in the depth of the V-groove due to pitch) & p).
The change in the depth of the V groove due to &p becomes gradual as shown in FIG. Figure 4 shows the beep)! LP is schematically shown.

Further, the address signal can be reproduced by detecting the change in the intensity of the diffracted light reflected from the disk due to the change in the depth of the V-groove caused by the pit.

However, in such an address recording method, as shown in FIG. 4, even if pits are recorded in tracks C and D on one V-groove, the ridgelines α and β of the mountain shared with tracks B and E, respectively, are is also modulated, and crosstalk occurs in the reproduced signal of track B, IC. Particularly, as shown in FIG. 6, when address signal pits overlap in adjacent V-grooves, there is a high possibility that the address signal will be misread due to the influence of the adjacent pits.

Therefore, we proposed an address recording and reproducing method that eliminates the effects of crosstalk between adjacent address signal grooves. (Japanese Patent Application No. 59-181752) Next, the application filed in Japanese Patent Application No. 59-181752 will be briefly explained.

In this application, when recording an address signal by modulating the depth of a V-groove, the address signals are arranged so that they do not overlap in adjacent V-grooves. When reproducing address signals,
Two laser beams are irradiated onto two tracks (tracks C and D in the example shown in FIG. 4) sandwiching the valley of the V groove, and the reflected light from the optical disc is received by a photodetector, thereby detecting the V groove. The signals on the two slopes of the groove are independently reproduced, and when the two address signals reproduced from the photodetector match, they are used as the address signal of the corresponding V-groove.

Problems to be Solved by the Invention When actually cutting a V-groove as shown in FIG. 3, the angle of the tip 7 of the canting needle 6 tends to be rounded, and the angle of the valley of the V-groove also tends to be rounded. There is. This example is shown in the 7th
As shown in the figure. FIG. 7 represents a cross section of the disk. 12,1
3.14 indicates a valley and 15.16 indicates a peak. As explained in the conventional example, when laser beams 1 and 2 are irradiated from the direction of the arrow in the figure to tracks C and D, respectively, if the valley 130 corner between the two tracks is rounded, the diffracted light reflected from the disk will be distribution changes, and crosstalk components from adjacent slopes increase.

Therefore, as shown in Fig. 8, two laser beams 1
, 2 on the track sandwiching the peak of the V groove (for example, track B
A possible method is to irradiate the light onto the light source and C). As shown in FIG. 3, since the peaks of the V-groove are formed by overlapping cutting with a cutting needle, the angle thereof is kept constant, and crosstalk components from adjacent slopes do not increase.

However, if tracking control is performed centered on the peak of this V-groove, the two laser beams will straddle the two V-grooves, and the conventional address signal reproduction method will not be able to reproduce the correct address signal. It is not possible.

FIG. 9 is a perspective view of the disk shown in FIG. 8. For example, assume that a bit &P is formed on a V-groove having valleys 13. In the case of FIG. 8, laser beams 1 and 2 create spots 17 and 18 on tracks B and C, respectively. The ridge line α changes as shown in the figure due to the bit hp, and the bit is detected at both spots 17 and 18. At this time, in the conventional address signal reproducing method, it is determined that the bit is the correct bit on the track. Furthermore, when the laser beams 1 and 2 are irradiated onto the track D,
17' spot on that track.

18'. The edge line β also changes due to the bit ap, and the bit is detected at both spots 1/ and 1a/.

Therefore, in this case as well, the bit is determined to be correct. In this way, when performing tracking control centered on the peak of the groove, the conventional address signal reproduction method
Since crosstalk components cannot be separated, a correct address signal cannot be reproduced.

The present invention has been made in view of this point, and when two tracks sandwiching the peak of a V-groove are used as a set, crosstalk between address signals can be eliminated and address signals can be reproduced without error. The purpose of this invention is to provide a method for reproducing address signals.

Means for Solving the Problems In order to solve the above problems, the present invention provides
An optical disk is used in which an address signal is recorded by modulating the depth of the groove, and the address signals are arranged so that they do not overlap in adjacent V-grooves. To reproduce the address signal on the optical disc, two laser beams are irradiated onto adjacent tracks centered on the peak of the V-groove, and a photodetector receives the light reflected from the optical disc by at least one of the laser beams. A plurality of address signals on adjacent V-grooves are detected from the signals, and a determination circuit determines the address value of the target track from these address signals.

Operation In the optical disc used in the present invention, address signals do not overlap in adjacent V-grooves, so no interference occurs between address signals.

Also, when reproducing the address signal of this optical disc,
Since the ridgeline of the V-groove varies depending on the pits recorded on both tracks, one laser spot can reproduce address signals on both tracks. In other words, since the address signals on the two V grooves that are in contact with each other at the ridge line can be reproduced with one laser spot, two
Regardless of whether the tracking position of one laser spot is on the peak or valley of the V-groove, the address value of the corresponding track can be determined from these address signals by a predetermined determination method.

EXAMPLE An example of the present invention will be described below with reference to the drawings. Also in this embodiment, an address signal will be explained as an example of a reference signal.

FIG. 10 shows the format of the disc in this embodiment. In FIG. 10, 20 is the outermost circumference of the disk, 2
1 represents the innermost circumference of the disk, and 22 represents the center hole. A V-groove is formed in a concentric or spiral shape in a portion surrounded by the outermost periphery 20 and the innermost periphery 21. Further, 23 represents a header area. In the header area 23, address signals for each V-groove are recorded by modulating the depth of the groove.

Next, FIG. 11 shows an enlarged view of the header area.

In FIG. 11, M~J are tracks, 24~29 are V
The groove peaks 30 to 34 indicate the valleys of the V groove. The ridgelines of the V-grooves are still shown as solid lines, and the ridgelines of the valleys are shown as broken lines.

The shaded area 36 represents the address signal recorded on the V-groove having the valley 3o. The address signal indicates the presence or absence of the bit shown in Fig. 4, for example, as a binary code "0" or '1'.
Record in accordance with. Similarly, address signals 36 to 39 are recorded in each groove. For example, track C,
Since the address signal 38 on D changes the ridge lines of the peaks 25 and 26 and changes the depth of some of the grooves in tracks B and E, the address signal 38 is also transmitted from these tracks.
8 can be played.

Next, a method for reproducing the address signal will be explained.

For example, a case will be described in which two laser beams sandwich the peak 26 of the V-groove and are incident on tracks B and C. 17 and 18 each represent a spot created by a laser beam. FIG. 1 shows a block diagram of an address signal reproducing circuit in this embodiment. In Figure 1,
4o is a photodetector, 41 is a preamplifier, 42 is a control circuit,
43 is a demodulation circuit, 44 is a buffer memory, 46 is a determination circuit, and 46 is an output terminal. Furthermore, in the method for reproducing address signals in this embodiment, it is sufficient to use only one of the two laser beams. For example, using spot 17 in FIG. 11, assume that spot 17 is moving upward on track B (in the direction of address signal 36).

The reflected light from the spot 17 on the optical disc is detected by the photodetector 4o.
incident on . The photodetector 4o converts the incident light into an electrical signal and outputs it. The preamplifier 41 amplifies the output signal of the photodetector 4o to obtain a reproduced signal P. The control circuit 42 detects an address mark signal in the address signal from the reproduced signal P, and sends out an address gate signal q indicating the address area. According to the address gate signal q, the demodulation circuit 43
Detects the address code signal and error correction code from the reproduced signal P, and detects errors in the address code.

The address value r of the corresponding track is then corrected and reproduced.

If spot 17 moves in the above direction, spot 1
7 detects the address signal 38 and reproduces the address value r38. At this time, the control circuit 42 sends out a control signal S indicating that the first address signal has been reproduced. Buffer memory 44 writes address value r3B in response to control signal S. Furthermore, the spot 17 moves and the address signal 3
6 is detected and the address value r35 is reproduced. Control circuit 4
2 indicates that the second address signal has been reproduced using the control signal S. The backup memory 44 reads out the stored address value r38 in response to this control signal S. The determination circuit 46 determines two address values r according to the control signal S.
35 and r38, and determines the address value R of track B according to a predetermined determination method, and sends this out from the output terminal 46.

Next, a method of determining an address value will be explained. This determination method depends on the method of recording address values on the disk. - As an example, assume that address values are sequentially assigned to each V-groove of the disk, starting from the first position. At this time, in FIG. 11, the address value of the address signal 36 is determined to be an address n, the address value of the address signal 38 is determined to be an address (n+1), and the address value of the address signal 3'6 is determined to be an address (n+2). An embodiment of the determination circuit in this case is shown in FIG. 1st
In FIG. 2, 47 is a comparison circuit, and 4B is a switching circuit. Let address value r1 be the value of the first address signal read from the backup memory, and let address value r2 be the value of the second address signal. The comparison circuit compares the magnitude of the two address values r++r2 and sends the determination signal C to the switching circuit 48.
Send to. The switching circuit 48 always outputs the smaller address value from the output terminal 46 according to the determination signal C. In the example of FIG. 11, when spot 17 reproduces track B, the address values to be reproduced are addresses n and (n+1). At this time, the address value output from the determination circuit 46 becomes the address R/dn. Next spot 17 is track D
When playing, (n-)-1) address, (n+2
) plays the address value of the address.

In this case, the address value R after determination becomes address (n+1). Hereafter, the address values of the tracks of spot 17 can be sequentially reproduced in this manner. Furthermore, the switching circuit can be configured to always select the larger address value based on the determination signal C.

More generally, the determination circuit can be constructed using a ROM as shown in FIG. A correspondence table of address values R of corresponding tracks corresponding to a plurality of address values reproduced from the same track is written in the ROM in advance. When reproducing an address, the reproduced address value r
1*The address generation circuit 49 generates a ROM address from r2, and the corresponding address value R is generated from the ROM 50.
Read out. In this embodiment, the track address values are written in the ROM, but the present invention is not limited to this. For example, reference signals such as code signals representing various identification signals may be written in the ROM.

Effects of the Invention As described above, according to the present invention, by using an optical disc in which address signals are arranged so that they do not overlap in adjacent V-grooves, and by using only one laser beam, the track to be reproduced can be recorded. Since reference signals such as address values can be regenerated, it is possible to provide an address regeneration circuit that can be used regardless of whether the tracking center of the two laser beams is at the peak or valley of the V-groove. Extremely useful.

Further, the address reproducing circuit according to the present invention can also be used in a one-channel optical disc device that uses one laser beam on one side of the V-groove.

[Brief explanation of drawings]

Fig. 1 is a block diagram of an address reproducing circuit according to an embodiment of the present invention, Fig. 2 is a perspective view of a cross section of an optical disc having a V-groove, Fig. 3 is a cross-sectional view of a metal master disc, and Fig. 4 is a bit on the V-groove. FIG. 6 is a cross-sectional view of the bit on the V-groove, FIG. 6 is a perspective view showing the overlapping of the bits on the V-groove, FIGS. 7 and 8 are cross-sectional views showing the tracking position of the laser beam, Figure M9 is a perspective view of Figure 8, Figure 10 is a format diagram of the optical disc, Figure 11 is a plan view showing the header area of the optical disc, Figure 12 is a block diagram of the determination circuit in an embodiment of the present invention. FIG. 13 is a block diagram of a determination circuit in another embodiment of the present invention. A, B, C, D, IC, F...Track, 1,
2... Laser beam, 40... Photodetector, 44... Buffer memory, 46...
...Judgment circuit, 47... Comparison circuit, 48...
...Switching circuit, 6o...ROM. Name of agent: Patent attorney Toshio Nakao and 1 other person Compilation 2
Figure 4 Truck Truck Truck Truck Track B
CDE Fig. 5 Pitge P Fig. 6 Fig. 7 Fig. 8 Fig. 9 Fig. 10 α) To -

Claims (3)

[Claims] (1) The disk has a V-groove with a V-shaped cross section in the radial direction, and an address signal is recorded in advance by modulating the depth of the V-groove.
By using an optical disc in which these address signals are arranged so that they do not overlap in adjacent V grooves,
This is a circuit for reproducing an address signal in an optical disc device that uses the slope of a groove as a track, irradiates a laser beam onto the track, and receives the reflected light from the optical disc with a photodetector to obtain a reproduction signal. An address for an optical disc characterized by having a buffer memory that temporarily stores one or more of two or more address signals reproduced from a track, and a determination circuit that determines the address value of a corresponding track from these address signals. regeneration circuit. (2) It has a determination circuit consisting of a comparison circuit that compares the magnitude of address values of a plurality of address signals reproduced from the same track, and a switching circuit that selects the minimum or maximum address value from the comparison results. An address reproducing circuit for an optical disc according to claim 1, characterized in that: (3) It has a ROM in which a correspondence table between the address values included in a plurality of address signals and the address values of the corresponding tracks is written in advance. 2. An address reproducing circuit for an optical disc according to claim 1, further comprising a determination circuit for reading out an address value of a corresponding track.