JPH0248982B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an optical disk and a method for reproducing addresses when recording and reproducing signals by irradiating the optical disk with focused laser light.

Conventional Structures and Their Problems In recent years, optical disk memories have been actively developed with the aim of achieving large capacities and high transfer rates.
Among these, a method has been proposed in which a V-shaped groove is formed on the surface of an optical disk, and the opposing slopes are used as a set of signal surfaces to record and reproduce signals, thereby doubling the capacity and transfer rate. (Special Application No. 147133,
(Special Application No. 175259/1982). In this method, as shown in Fig. 1, a first laser spot 1 and a first laser are placed on two adjacent slopes, such as slopes A and B, or C and D, as shown in Fig. 2. is a second motor that can be driven independently.
Signals are recorded and reproduced by focusing and irradiating the laser spot 2. Signal recording is performed using a recording medium thin film (for example, TeOx, X<2)
This is done by changing the reflectance of the laser beam by irradiating it with laser power. To reproduce the signal, two adjacent slopes (for example, C and D) are read out simultaneously. Regarding this regeneration method, as detailed in the specification of the above-mentioned patent application, if the shape of the V-shaped groove is optimized,
By receiving mainly the ±1st-order light among the reflected light from the disk, the signals of each slope can be reproduced. The signal address pit Pi is created by varying the depth of the disk when cutting a V-shaped groove, as shown in Figure 3.
In FIG. 3, VC represents a cutter for cutting the V-groove, and Pi represents an address bit that is cut by vibrating this cutter in the depth direction in accordance with the address bit. Although the actual address pit is cut more gently than shown in FIG. 3, it is shown schematically here. Addresses can be read using a reproduction light-receiving element by taking advantage of the fact that the intensity of the diffracted light changes with this change in depth. However, as shown in Figure 4, if the addresses cut on the slopes A and B and the addresses cut on C and D overlap in the radial direction of the disk in adjacent V-shaped grooves, then the slopes B and Since the shared peak is modulated by both addresses, it is possible to misread the address. This point will be explained below. FIG. 5 shows a cross-sectional view of the V-groove disk. For example, θ=161°, PT=800nm,
Assuming that d=134 nm, when a change of ε=200 Å is applied in the depth direction for address cutting, the peak 5 of the V groove changes in the radial direction 11 by γ=1200 Å. Therefore, if a case occurs where addresses N and M overlap in the radial direction in adjacent V grooves as shown in Figure 6, the peak 5 shared by slopes B and C of the V grooves will overlap address N and address M. As shown in FIG. 7, the laser spot 2 for reproducing the address N cut into the V-groove 3 is affected by the address M cut into the V-groove 4. There was a risk of misreading N.

Purpose of the Invention As stated above, when recording and reproducing signals on a V-groove disk, if the addresses of adjacent V-grooves on the disk overlap in the radial direction, an error in reading the address will occur. It is an object of the present invention to provide an optical disc that solves the conventional problems, and to provide a method for accurately reproducing addresses on this optical disc.

Structure of the Invention The present invention provides an optical disk in which diffracted light has a V-shaped cross section in the radial direction. This is an optical disk that is cut so that addresses do not overlap in the radial direction.

Further, in the present invention, when the address of the disk is reproduced, when two laser beams focused on both slopes of the V-groove detect the same address, the address is reproduced as a true address, and the address is reproduced as a true address. This makes it possible to accurately reproduce addresses on an optical disk having a V-shaped groove.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings.

Figure 8a shows constant angular velocity drive (hereinafter abbreviated as CAV)
This figure shows the state in which addresses are cut on the V-groove disk when recording and reproducing signals on the V-groove disk. In this way, when recording and reproducing signals with CAV, the address areas are arranged in the radial direction of the disk. Each set of A and B, C and D, and E and F represents the two slopes of the V groove, as shown in Figure 8b. 8 in FIG. 8b indicates an address area. If L is the number of address bits including the signal address length, address mark indicating the start of the address, error check code for monitoring address errors, etc., this address area 8 cuts at least 2L bits of information. We have ensured the physical length possible.

In FIG. 9a, this address area 8 is 3, 4,
By dividing the area into two equal parts as shown by 6 and 7, and cutting the addresses alternately in the areas 3 and 7 using radially adjacent V grooves as shown in Figure 8b, the addresses do not overlap. Since the address can be read out using the reproduction beams 1 and 2, it is possible to read the address using the reproduction beams 1 and 2. This point will be explained below. Now, attention is paid to two sets of adjacent grooves A and B and C and D. As shown in FIG. 9a, the address areas of a pair of V grooves A and B are divided into two halves, and are designated as 3 and 6. Similarly, a set of address areas consisting of C and D is set to 2.
Let the equally divided parts be 4 and 7. FIG. 9a shows how addresses are cut in parts 3 and 7. FIG. 9b is a front view of FIG. 9a and shows changes in the track width PT of the V groove when the address is cut in the depth direction. In tracks C and D adjacent to tracks A and B, addresses are cut into address areas of 7 instead of 4. By doing this, the mountain 5 at the boundary between tracks B and C changes independently depending on the address N and the address M, so that the address N and the address M can be accurately reproduced by the laser spots 1 and 2.

Next, a method for reproducing addresses will be described. The signal can be reproduced by using the reflected light from the two spots 1 and 2 focused on the disk in the same manner as described in the conventional example. Two laser spots 1,
The reflected lights 9 and 10 (Fig. 10) of 2 contain the signals of the slopes A and B, respectively, and are received by the two photodetectors D ₁ and D ₂ shown in Fig. 10 a and b, and the signals are reproduced. It is done. Address regeneration can basically be performed in the same way as signal regeneration, and the photodetector D ₁ ,
Just read the address when the same address is detected in D ₂ . For example, in Figure 11, playback spot 1
1 and 12 pass through the address area 6, the photodetector
D ₁ detects the address P by the reflected light 9 of the laser spot 11, but the photodetector D ₂ detects the address Q by the reflection groove 10 of the laser spot 12 and does not read it, but the reproduction spots 11 and 12 are in the address area. 4, the photodetector D ₁ ,
D ₂ is the reflected light 9, 1 of the laser spots 11, 12
Since the same address M is detected by 0, it can be reproduced as an address. FIG. 12 shows the configuration of the address reproducing circuit. In Figure 12,
D ₁ and D ₂ are photodetectors, 13 and 14 are address signal amplifiers, 15 and 16 are signal amplifiers, and 17 and 1
8 is an address demodulator, 19 is an address match detection circuit, and 20 is an address buffer that outputs an address when the match detection circuit detects address match. In Figure 12, reflected lights 9 and 10 are photodetectors.
The signals are detected by D ₁ and D ₂ , amplified by amplifiers 13 to 16, and in the case of an address, passed through address demodulation circuits 17 and 18 that demodulate the modulated address on the disk, and then sent to a coincidence detection circuit 19. is input. The coincidence detection circuit 19 detects whether or not the addresses that have entered the photodetectors D ₁ and D ₂ are the same. If they are the same, the addresses are taken into the controller from the address buffer 20. By reading the same address at two spots in this way, it becomes possible to read the address accurately. Note that the laser spots 11 and 12 on the V-groove disk need not be aligned in the radial direction of the disk as shown in FIG. 11, but may be offset by S in the track direction as shown in FIG. In this case, laser spot 12' reads address N before laser spot 11'. In this case, the first
As shown in FIG. 4, a delay circuit DL may be inserted to compensate for the delay in the address reading time of the laser spot 11'.

Other embodiments of the present invention will be described below with reference to the drawings.

FIG. 15 shows an embodiment of the present invention in which a V-groove optical disk is driven at constant linear velocity (hereinafter abbreviated as CLV). In FIG. 15, the hatched area represents the address area, and 21 to 24 represent V grooves, respectively.
In this case, assuming that the basic unit of signal access is 1 byte, the physical length of the record occupied by this 1 byte is constant regardless of the outer or inner circumference of the optical disk. Let this length be RL, and this RL shall include the address of the signal. Although the addresses are not all arranged in the radial direction as in the case of the CAV shown in the previous embodiment, there are also cases in which the address areas shown in FIG. 16 overlap in the radial direction. It is an integer multiple of RL, but the center of the optical disk
2π _times (π
is pi). In other words, N・RL
= 2πγ (N: integer). Adjacent grooves as shown in Figure 16
Pay attention to V ₀ , V ₁ , and V ₂ . At this time, if the distance between one V groove and the adjacent V groove is 2P, then the difference δ in the circumference between the groove V ₁ we are currently focusing on and the groove V ₂ one groove outside or the groove V ₀ one groove inside is approximately There are 2π and 2P. Now 2P=1.6 (μm)
Then, it becomes δ10 (μm). Address 26 in V ₁ and address 25 in V ₀ or address 27 in V ₂ will overlap in the radial direction if the address length AR is longer than δ, for the same reason as described in the previous embodiment. So, address 25, 26, 2
It becomes difficult to read 7 accurately. In order to solve this difficulty, in this embodiment, as shown in FIG. 17, the length of the address area is twice the physical length required for cutting (2・AR) plus δ. Areas for cutting addresses are provided at both ends of the address area 9, and an area 8 for not cutting addresses is provided near the center of the address area.

Within this area, as shown in Figure 17, the address area 9
Addresses 28, 29, and 30 are placed in the adjacent V grooves in the first half, second half, and first half of the address cutting area.
Cut so that they do not overlap in the radial direction. Addresses 28, 29, and 30 in this case are not necessarily a series of addresses, but once the basic unit of access l and address format are determined, and the bit length required for address cutting is determined, the address area and the cutting in that area are determined. The address to be cut and the area to be cut can be uniquely determined in advance. Regeneration of addresses can be performed in the same manner as described in the previous embodiment. By cutting the addresses as described above, it becomes possible to more accurately read the addresses cut by CLV on the V-groove optical disk.

Effects of the Invention As described above, the present invention provides a V-groove optical disk in which, when forming a V-groove, the address area is at least twice as long as the length required for address cutting, and signal addresses are adjacent to each other. By deciding where to cut the addresses within the address area so that they do not overlap in the radial direction of the V-grooves, it is possible to more accurately read the signals on the V-groove optical disc, and this makes it practical. The effects are huge.

Further, according to the present invention, when the addresses reproduced by two lasers match each other, it is regarded as a true address, thereby making it possible to read the address accurately.

[Brief explanation of drawings]

Figure 1 is a partial cross-sectional view of a V-groove optical disc, Figure 2 is a diagram showing a laser spot irradiated onto the V-groove optical disc, and Figure 3 is a diagram showing addresses cut in the depth direction of the V-groove optical disc. Figure 4 shows a pit and the cutter used to cut the pit. Figure 4 shows a case where addresses overlap in adjacent V grooves. Figure 5 shows changes in the V groove when addresses are cut in the depth direction. Figure 6 is a diagram showing the case where the addresses of the V-groove disks overlap in the radial direction, Figure 7 is a front view showing the V-groove addresses and their reproduction in the conventional example, and Figure 8a is the CAV
FIG. 8b is a diagram showing addresses on a disk in an embodiment of the present invention when a signal is reproduced in an embodiment of the present invention, FIG.
Figure 9a is a perspective view showing an address pit in an embodiment of the present invention, Figure 9b is a front view showing addresses on a disk in an embodiment of the invention, and Figure 10 is a perspective view showing an address pit in an embodiment of the present invention.
The figure shows a photodetector and reflected laser beam for signal reproduction of a V-groove disk, FIG. 11 shows how addresses are recorded in the address area of the disk in the present invention, and FIG. 12 shows the present invention. A circuit diagram showing a circuit configuration for address and signal reproduction in one embodiment. FIG. 13 is a diagram showing a case where two laser spots are separated in the disk rotation direction. FIG. 14 is a diagram showing a case where two laser spots are separated from each other in the disk rotation direction. A circuit diagram showing an address reproducing circuit when they are separated in the rotational direction. FIG. 15 is a diagram showing addresses on a disk in an embodiment of the present invention when recording and reproducing signals by constant linear velocity drive (CLV). , 16th
The figure shows the overlap of addresses when recording and reproducing signals using CLV in the conventional example, and FIG. 17 is a diagram showing how address areas and addresses are cut in the present invention. 1, 2, 11, 12...Laser spot, 3,
4, 6, 7...Address cutting area, 8
... Address area, 5 ... V-groove peak, 9, 10 ...
...Reflected laser spot, 17, 18... Address demodulation circuit, 19... Coincidence detection circuit, Pi...
Address pit, VC...V groove and address cutter, PT...Width of V groove signal track, M, N, P,
Q...Address signal, _D1 , _D2 ...Photodetector, S
...Distance between two spots.

Claims (1)

[Claims] 1. A groove having a V-shaped cross section in the radial direction;
The address area of the address cut in the depth direction along the V-shaped groove has a length at least twice the cutting length of the address along the V-shaped groove, and An optical disk characterized in that addresses are cut within an address area so that the cut addresses do not overlap in the radial direction. 2. The address area is equally divided into a first half region and a second half region along the V-shaped groove, and so that the first half or the second half region does not overlap in the radial direction of the adjacent V-shaped groove, 2. The optical disc according to claim 1, wherein the optical disc is recorded or reproduced by cutting addresses alternately and driving at a constant angular velocity. 3. A patent in which the address area has a length that is at least twice the cutting length of the address plus 2π times the width of the V-shaped groove, and is recorded or reproduced by being driven at a constant linear speed. An optical disc according to claim 1. 4. A groove having a V-shaped cross section in the radial direction, and the V
The address area of the address cut in the depth direction along the V-shaped groove has a length at least twice the cutting length of the address along the V-shaped groove, and Two lasers that can be driven independently are focused and irradiated onto the two adjacent slopes of the optical disk where the addresses are cut within the address area so that the cut addresses do not overlap in the radial direction. 1. A method for reproducing an address for an optical disk, characterized in that when addresses reproduced by the two lasers match each other when a signal is independently recorded or reproduced on the disc, the address is determined to be a true address.