JPH0368457B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an optical disk and a method for recording and reproducing various information by irradiating the optical disk with a laser. This invention relates to an optical disc and a method for reproducing its addresses.

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 is formed on the surface of the optical disk with a V-shaped cross section in the disk radial direction, and the slope of the V groove is used as a track to record and reproduce signals. proposed a method to do this. (Special request 1982)
(No.-175259) Figure 2 shows a radial cross section of an optical disk with a V-groove. Two adjacent slopes, such as A and B or C and D in FIG. 2, are irradiated with two laser spots 1 and 2 as shown in FIG. 3.
By driving these lasers independently of each other, independent signals can be recorded using the two slopes as tracks. The recording thin film 3 is, for example,
Using TeOx (x1.1), 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, by optimizing the shape of the V-groove, it is possible to receive mainly the ±1st-order diffracted light of the reflected light from the disk, and thereby It is possible to sufficiently suppress the crosstalk between the tracks and reproduce the signals of one track.

Further, in order to search for a target track on the disk, an address is recorded on the track in advance. The address signal is recorded by forming pits 4 with varying groove depths, as shown in FIG. Discs with V-grooves are created by cutting the metal master disc with a V-shaped cutting needle.
A stamper is taken from this metal master disk, and the base resin is molded with the stamper. The address pit is created by vibrating the cutting needle in accordance with the pit position when cutting the metal master disc.

The address signal can be reproduced by utilizing the fact that the intensity of the diffracted light reflected from the disk changes as the depth of the V-groove due to the pit changes.

Problems to be Solved by the Invention In the conventional address recording system as described above, as shown in FIG.
Even if address pits are recorded on D, crosstalk occurs in the reproduced signals of tracks B and E because the mountain ridgelines α and β shared with adjacent tracks B and E, respectively, are modulated.

A cross section of the V-groove disk is shown in FIG. The track pitch is Pt, the depth of the V groove is d, and the angle of the V groove is θ.
shall be. The following shape is used as an example of the V-groove shape.

{Pt=λ (λ: laser wavelength) d=λ/4n (n: refractive index of the base material) At this time, tan (θ/2)=Pt/d=4n Here, due to the address pit, the depth of the V groove If the track width changes by ΔPt when the width changes by Δd, then from the above equation, ΔPt=1/2Δd tan(θ/2)=2n·Δd (1). When the refractive index of the base material is n=1.5, from equation (1), the track width changes three times as much as the change in pit depth Δd, and the ridge line changes twice as much as ΔPt. For example, when Δd=0.02μm, 2・ΔPt=0.12μm, and the track pitch Pt
is approximately 1 μm, so variations in this edge line are a major cause of crosstalk. In particular, when addresses overlap in adjacent V-grooves as shown in FIG. 6, there is a high possibility that the address signals will be misread due to the influence of the adjacent address signals.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an optical disk and an address recording/reproducing method that can eliminate crosstalk between address signals and reproduce address signals without error.

Means for Solving the Problems In order to solve the above problems, the present invention records address signals by modulating the depth of every other V-groove on an optical disk. To reproduce the address signal of this optical disc, two laser spots are irradiated on adjacent tracks on the V-groove, respectively.
The reflected light from the optical disk is received by two photodetectors, and interpolation is performed using address signals reproduced by each photodetector.

Function The optical disc according to the present invention has the following features:
Since address signals are recorded in the grooves between books,
No crosstalk occurs between address signals.

In addition, when reproducing the address signal of this optical disk, when reproducing a V-groove track in which an address is recorded, the two photodetectors each reproduce an address signal with the same address value, and do not record an address. When reproducing a track of a V-groove, each photodetector can reproduce the address signal of an adjacent V-groove by crosstalk, and the address values of the V-grooves on both sides are determined from the output of each photodetector. By interpolating from these address values, the address value of the corresponding V groove can be obtained.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

FIG. 7 shows the format of the disk in this embodiment. In FIG. 7, 5 represents the outermost circumference of the disk, 6 the innermost circumference of the disk, and 7 the center hole. The part surrounded by the outermost periphery 5 and the innermost periphery 6 (a in the figure)
A V-groove is formed in a concentric or spiral shape in the range indicated by . Further, part b represents an address area. In the address area, V
Address signals are recorded by modulating the depth of every other groove. 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.

FIG. 1 shows an enlarged view of the address area of the optical disk as described above. In Figure 1, V groove A (tracks A, B) and V groove C (tracks E, F) are shown.
The address signal is recorded using an address pit Pi with a deep V-groove. No address signals are recorded in the V grooves (tracks C and D).

First, the case of reproducing the address signal of V groove A will be explained. Assume that laser spot 1 is irradiating track A and laser spot 2 is irradiating track B. The reflected light from each laser spot is received by photodetectors D1 and D2 (shown in FIG. 8). The reflected light from the disk is diffracted by address pits on the track. Therefore, the intensity of the reflected light received by the photodetector changes depending on the presence or absence of the address pit. The address signal can be reproduced by this intensity change. In this case, the address signals reproduced from the two photodetectors D1 and D2 have the same address value. The same method can be used to reproduce the address signal of V-groove C.

Next, the case of reproducing the address signal of the V-groove will be explained. As shown in Figure 1, track C
Laser spot 1 is irradiated on track D, and laser spot 2 is irradiated on track D. As shown in Fig. 1, the track C is aligned with the ridgeline α by the V-groove address pit.
is removed, and the track width becomes narrower. The change in track width (track pitch Pt) is larger than the address pit depth Δd, as shown in equation (1). Therefore, if the depth Δd of this address pit is increased to a certain extent, laser spot 1 on track C can sufficiently detect the address pit in the adjacent V-groove A. Similarly, the address pit of the V-groove C can be detected using the laser spot 2 on the track D. In this case, in the photodetector D1, the address signal of the V groove A is transmitted to the photodetector D1.
In No. 2, the address signals of the V-groove C are respectively reproduced, and the address values reproduced by the two photodetectors do not match. The address value of V-groove B can be determined by interpolation using the reproduced address value of V-groove A and the address value of V-groove C.

FIG. 8 shows a block diagram of the address signal reproducing circuit in this embodiment. In Figure 8, 10
is photodetector D1, 15 is photodetector D2, 11, 1
6 is a preamplifier, 12 and 17 are address area detection circuits, 13 and 18 are address demodulation circuits, 14 is an interpolation circuit, and 19 is an output terminal. As explained in FIG. 1, the photodetector D1 has a laser spot 1.
reflected light is incident. The photodetector D1 converts the reflected light into an electrical signal and outputs it. Preamplifier 1
1 amplifies the output signal of the photodetector D1 to obtain a reproduced signal p. The address area detection circuit 12 detects an address mark signal in the address signal from the reproduced signal p, and detects an address gate signal q indicating the address area.
Send out. The address demodulation circuit 13 detects an address code signal and an error correction code from the reproduced signal p in accordance with the address gate signal q, detects and corrects errors in the address code, and reproduces the address value r of the corresponding track. Similarly to the above, for the laser spot 2, the photodetector D2 receives the reflected light, the preamplifier 16 obtains the reproduced signal s, and the address area detection circuit 17 generates the address gate signal t from the reproduced signal s. Using this signal, the address demodulation circuit 18 reproduces the address value u of the corresponding track. The interpolation circuit 14 is
It is determined whether the input address value r and address value u match. If they match, the value is the V irradiated by the two laser beams 1 and 2.
It is sent from the output end 19 as the groove address value v. If they do not match, the address value v of the corresponding V groove is determined from the address value r and the address value u according to a predetermined interpolation method, and this is sent from the output terminal 19.

In FIG. 8, the reproduced signal p and the reproduced signal s of the two tracks are sent to a signal reproducing circuit (not shown) in order to be used not only for reproducing the address signal but also for reproducing the recorded data signal.

Next, the address interpolation method will be explained. The interpolation method depends on how address values are recorded on disk. As an example, assume that an address value is sequentially assigned to each V-groove of the disk. At this time, in FIG. 1, if the address value of V groove A is set to address n (n: integer), the address value of V groove C is set to address n+2, and is increased or decreased by each address. An embodiment of the interpolation circuit in this case is shown in FIG. In FIG. 9, 13 and 18 are address demodulation circuits, 14 is an interpolation circuit, and 19 is an output terminal.
These are the same circuits as explained in FIG. 20 is an adder circuit, and 21 is a divider circuit. As explained in FIG. 8, the address demodulation circuit 13
reproduces the address value r of the track irradiated by the laser spot 1, and the address demodulation circuit 18
The address value u of the track irradiated by the laser spot 2 is reproduced. Adder circuit 20 adds address value r and address value u. Division circuit 21
divides this addition result by 2 and calculates the value V
It is sent from the output terminal 19 as the groove address value v. Generally, these operations are performed in binary code, so the division circuit 21 divides the addition result into one bit.
Just shift to the LSB side. When this interpolation circuit reproduces the address signal of V groove A, both the address value r and the address value u become address n. Therefore, the address value v after the interpolation process also becomes address n. Similarly, when reproducing the V groove C, the address value v becomes address n+2. Next, when reproducing the V groove bottom, the address value r becomes address n, and the address value u becomes address n+2. In the interpolation circuit 14,
By taking the average of these address values, the address value v of the V-groove can be determined as address n+1.

The method of recording address values varies depending on the disk format. FIG. 10 shows another example of the disk format. In FIG. 10, 5 is the outermost circumference of the disk, 6 is the innermost circumference of the disk, and 7 is the center hole, which are the same as shown in FIG. As shown in Figure 10, the disk is K
(K=8 in the figure) sectors.
Ci is the i-th sector separator. It is convenient to manage each sector for recording, reproducing, searching, etc. of data signals. Therefore, an address is assigned to each sector. In this case, the address values of adjacent V grooves within one sector separator change by k addresses. At this time, if address signals are recorded in the V-groove for recording address signals every 2k addresses, that is, the next address after n is address n+2k, the interpolation circuit shown in FIG. Address values can be determined in a similar manner.

Furthermore, if the address values of each V-groove do not form an arithmetic progression as described above, the interpolation circuit shown in FIG. 9 cannot be used. Generally, the interpolation circuit 14 in FIG. 8 can be constructed from a ROM. A predetermined address value is written into this ROM. When reproducing the address, the reproduced address value r and address value u may be used as ROM addresses, the written data may be read out, and this may be used as the address value v of the V groove to be determined.

Effects of the Invention As described above, according to the present invention, by recording address signals in every other V-groove, interference of address signals between V-grooves can be eliminated. Further, when reproducing address signals, by actively utilizing the crosstalk of address signals from adjacent tracks, it is possible to obtain address values of V-grooves in which no address signals are recorded by interpolation. By using such an optical disc and address reproducing method, it becomes possible to reproduce the address value of each groove more accurately, which is extremely useful in practice.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an address area of an optical disc in an embodiment of the present invention, FIG. 2 is a diagram showing a cross section of an optical disc with a V-groove, and FIG. 3 is a method of irradiating a laser spot onto a V-groove disc. Figure 4 showing
6 and 6 are diagrams showing the address area of a conventional optical disk, FIG. 5 is a diagram showing a cross section of a V-groove, and FIG.
8 is a block diagram showing an address reproducing circuit in an embodiment of the present invention. FIG.
This figure is a block diagram showing an address interpolation circuit in one embodiment of the invention, and FIG. 10 is a diagram showing the format of an optical disk in another embodiment of the invention. A, B, C...V groove, A, B, C, D, E, F
...Truck, Pi...Address pit, 1, 2...
...laser spot, 10,15...photodetector,
13, 18... Address demodulation circuit, 14... Interpolation circuit, 20... Addition circuit, 21... Division circuit.

Claims (1)

[Claims] 1. The disc has a V-groove whose cross section in the radial direction is V-shaped, and information is recorded using the slope of the V-groove as a track, and the depth is modulated in every other V-groove. Adjacent V where address is recorded and address is not recorded
An optical disk characterized in that the track width of the groove is width-modulated by the depth modulation. 2. The optical disc according to claim 1, wherein the address value recorded in the V-groove of the optical disc is changed by even numbered addresses. 3. Using an optical disk that has a V-groove with a V-shaped cross section in the disk radial direction and on which information is recorded using the slope of the V-groove as a track, the depth is modulated in every other V-groove during the recording operation. At the same time, the track width of the adjacent V-groove where no address is recorded is width-modulated by the depth modulation described above, and in the reproduction operation, a laser spot is irradiated on each opposing track of the V-groove, and the reflected light is emitted. The light receiver receives the light separately for each track and reproduces a signal corresponding to the information.In addition, in the V groove where the address is recorded by depth modulation, the address is reproduced from the change in the amount of received light due to the change in depth, and the address is reproduced. For V-grooves in which V-groove is not recorded by depth modulation, the address of the V-groove adjacent to that track is detected from the change in the amount of light received due to the track width change in each of the opposing tracks, and the detected two adjacent address values are interpolated. An address recording and reproducing method for an optical disc, characterized in that an address value on a corresponding V-groove is obtained by performing the following steps. 4. The optical disc according to claim 3, wherein the address value of each V-groove is detected by adding the respective address values detected by two photodetectors and dividing by 2. Address recording and playback method.