JPS6234334A - Optical disk and reference signal reproducing method - Google Patents

Abstract

PURPOSE:To record and reproduce a reference signal shown by an (n) value code signal by modulating the depth of a groove for constituting a recording track by (N+1) kinds of frequencies selected so that the frequencies are not overlapped to each other even if the revolving speed of a disk is varied within a prescribed range. CONSTITUTION:A V-groove for constituting recording tracks (i), (i)+1,... is formed on a disk 22, and address areas 6, 7,... are provided on the track (i). An address signal is constituted of an address mark signal for showing the start point of the areas 6,..., and binary code signals (1 and 0) for showing an address value. The address signal uses three kinds of frequencies f0, f1 and f2, and it is recorded by a fact that the frequencies are selected so that they are not overlapped to each other even if the revolving speed of the disk is varied within a prescribed range and the V-groove is modulated. In this case, said signal becomes the frequency f0 for the address mark signal from an input terminal 25, and becomes frequencies f1, f2 by code signals '0', '1' from an input terminal 16. In this way, a recorded signal is detected by a photodetector, and the address signal can be demodulated stably.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an optical disc on which reference signals such as address signals are recorded, and a method for reproducing the reference signals by irradiating the optical disc with a laser.

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. That-
An example is an optical disc on which information signals can be recorded. This recordable optical disc has grooves formed on the disc to perform tracking control during recording. An example is shown in which a groove having a V-shaped cross section in the radial direction of the disk is formed, and signals are recorded and reproduced using the troughs of the V groove as tracks. FIG. 2 is a schematic diagram showing a cross section of an optical disc having a V-groove. In FIG. 2, reference numeral 1 denotes a disk base material, which has a large number of V-grooves 2 on its upper surface, and has a recording thin film 3.
is provided. Further, 4 is a laser spot, which irradiates the valley of the groove. By modulating the power of this laser, the optical characteristics of the recording thin film 3 are changed and signals are recorded. For example, Te0x (
When using X21j), the reflectance changes as the laser power changes.

When reproducing a signal recorded as described above, the power of the laser spot 4 is set to a constant reproduction power, and the laser spot 4 is irradiated onto the valley of the groove. The intensity of the reflected light from the optical disk changes according to changes in the reflectance of the recording thin film 3. A signal can be reproduced by receiving this reflected light with a photodetector.

Additionally, optical discs contain, for example, address signals for track search and disc attributes (write-once type).

A reference signal such as a code signal indicating the type (e.g. erasure type) is recorded in advance. FIG. 3 shows a reference signal recording section. As shown in FIG. 3, the reference signal is recorded by forming a pit 5 with a deeper groove. For example, a disk having a groove is made by cutting a metal master with a cutting needle having a 7-shaped shape, removing a stamper from the metal master, and molding a base resin with the stamper. The bit 5 representing the reference signal is created by vibrating a cutting needle in accordance with the bit position when cutting a metal master. Therefore, although FIG. 3 schematically shows that the edge of the pit changes sharply, the actual change in the depth of the bit tends to be gradual. A cross section taken along the V-groove X-X/ in FIG. 3 is shown in FIG. 4 (,). When this V-groove is irradiated with a laser, the intensity of the reflected light changes according to the depth of the V-groove, and by receiving this reflected light with a photodetector, a reference signal as shown in Figure 4 0)) is generated. Reproduce. If this reproduced reference signal is judged using the threshold value vth, a binary code as shown in FIG. 4(c) will be obtained. By sampling this binary code using the reference clock signal shown in FIG. 4(d) and converting it into a code signal, the information of the reference signal can be reproduced as shown in FIG. 4(e).

Problems to be Solved by the Invention In general, optical discs use constant linear velocity driving (hereinafter referred to as CLV) to improve recording density. in this case,
The rotational speed of the disk is controlled so that the linear velocity remains constant even if the radius of the track changes. If the radius of the track on the disk is R1 and the rotational speed at this time is Ti, then the linear velocity is V. is expressed as follows.

vo=2πui,'ri・
......■ Usually, the response time of such rotation speed control is designed to reduce the influence of noise and to be suitable for tracing along a track. Therefore, when jumping from one track to another, the response of this control cannot follow.

For example, from track 1 with radius R to track 2 with radius R2
If the rotational speed remains unchanged at T1, the linear velocity v2 at track 2 is expressed as follows.

For example, in an optical disc with a diameter of 30α, the radius Rmin of the innermost track is 50jff, and the radius Rmax of the outermost track is 145. If fJ is the linear velocity vi0 of the outermost circumference when jumping from the innermost circumference to the outermost circumference, and the linear velocity V of the innermost circumference when jumping from the outermost circumference to the innermost circumference. l
The equations are as follows:0 ■・=0.34V0 From the above, for an optical disk with a diameter of 3oc7n, the linear velocity immediately after a jump changes by about 10 times.On the other hand, among the reference signals, especially Since the address signal is used to search for a track, it must be read while the linear velocity is changing immediately after the jump.

In the reproduction method using a reference clock signal as explained in FIG. 4, the frequency of this reference clock signal must be changed in accordance with the linear velocity.

Generally, the reference clock signal is a regenerated binary code (fourth
Figure (C)) is controlled to achieve phase synchronization, but as mentioned above, it is synchronized over a frequency range of about 10 times, and the synchronization pull-in is controlled at high speed in response to sudden frequency fluctuations such as immediately after a jump. It is difficult to do.

The present invention has been made in view of the above points, and is an optical disc and a reference signal reproducing method that can stably reproduce reference signals such as address signals even when the linear velocity changes rapidly such as during a jump. is intended to provide.

Means for Solving the Problems The present invention solves the above problems by using an n-value code signal (
The reference signal is recorded by modulating the depth of the track on the disk at (n+1) types of frequencies fk (k=◯-n), where n is a positive integer. Each frequency is selected so that it does not overlap even if the number of rotations of the disk changes within a predetermined range.

When recording a reference signal, corresponding frequencies are sequentially selected from (n+1) types of recording frequencies fk according to the n-value code signal. When reproducing the reference signal, frequency components of each recording frequency fk are extracted from the reproduced signal obtained by receiving the reflected light from the disk with a photodetector (n
+1) The recording frequency is determined using a type of band pass filter (hereinafter abbreviated as BPF). According to this change in recording frequency, the n-value code signal is reproduced.

Function In the present invention, the recording frequency fk (k=0 to
n) is selected so that the ranges of variation of each recording frequency fk do not overlap even when the linear velocity of the disk changes the most.

Therefore, even when the linear velocity changes suddenly, such as during a jump, the frequency of the reproduced signal can be changed to the original recording frequency f.
k can be determined immediately.

EXAMPLE An example of the present invention will be described below with reference to the drawings.

The reference signal includes many types of signals, but in this embodiment, an address signal will be explained as an example. FIG. 5 shows a schematic diagram of the formant of the disc in this embodiment. In FIG. 5, i represents the track i on the V groove,
6,7. The shaded area indicated by B is the address area. The address area and the following area with a certain recording capacity are collectively called a sector. In the case of a CLV disk, the physical length RL of this sector is constant on any track.

Address signals are recorded in the address area. The address signal is composed of an address mark signal indicating the starting point of the address area and a binary code signal (1 and 0) indicating the address value of each sector.

In the present invention, the binary code signal has three frequencies fo, f
1. Expressed using f2. These recording frequencies are selected so that even if the linear velocity changes during reproduction, for example, as shown in equation (2), the variation ranges of the reproduced frequencies do not overlap.

For example, if the selection is made as shown in Table 1 below, the frequencies of the reproduced signals will not overlap within the variation range shown by equation (2).

Table 1 Next, the correspondence between the binary code signal and three types of recording frequencies will be explained. The previous recording frequency is fk (k=0.1.2)
Then, when the code signal is "0", the recording frequency is f
k+1, and when the code signal is "1", the recording frequency is fk+2. Since fo=f3, the frequency f
k+2 is equal to frequency fk-1. In other words, if three types of recording frequencies are arranged as shown in Figure 6, the frequency will change clockwise for the code signal "0", and the frequency will change clockwise for the code signal "1". It will change counterclockwise.

An example of the configuration of a modulation circuit that performs such modulation is shown in FIG. In FIG. 7, 10, 11.

12 is an oscillator, 13, 14.15 is a switching circuit, 16 is an input terminal, 17 is a shift register, 18 is a high voltage amplifier, j
9 is a piezoelectric element, 20 is a turntable, 21 is a motor,
22 is a metal master disk, 23 is a cutting needle, and 24 is a feeding device. Oscillators 10, 11 and 12 each have a recording frequency f. , Jl, f2 are oscillated. In order to record an address signal in the address area, first, an address mark signal is input to the input terminal 25. The shift register 17 is set to an initial value by an address mark signal. The initial value is
Three output signals S. , Sl, and S2, only one is at H level, and two are at L level. In FIG. 7, the output signal S. becomes H level. The shift register 17 is a ring type register, and when the code signal inputted from the input terminal 16 is 10'', the shift register 17 shifts to the right, and the output signal S1 becomes H level. ”, the shift register 17 shifts to the left and the output signal S2 becomes H level.Hereafter, the 11th order left/right shift is performed according to the code value of the input signal.The switching circuits 13, 14, and 15 , shift register output signal S., 511S2 becomes conductive when it becomes H level, and supplies the corresponding recording frequency fk to the high voltage amplifier 18. In this case, the address mark signal has the frequency f0 and the first code. If the signal is “0” 1
changes to the frequency f1, and when the code signal is "1#", the frequency becomes f2.The high voltage amplifier 18 vibrates the piezoelectric element 19 at the input recording frequency fk.

A metal master disk 22 is rotated by a motor 21 on a turntable 20 . The cutting needle 23 is attached to the piezoelectric element 19 and further attached to the feeding device 10, moves in the radial direction in synchronization with the rotation of the turntable 2o, and cuts a spiral groove in the metal master disk 22. . At this time, if the piezoelectric element 19 is vibrated at the recording frequency fk, the cutting needle 23 is displaced in the vertical direction of the metal master disk 22, and the depth of the cut groove can be modulated, thereby recording the address signal. I can do it.

FIG. 1 shows the address signal recorded as described above. FIG. 1 shows track (i-1), i.

Of (1+1), 026 representing the case where an address signal is recorded on track i is an address area, and each recording frequency fk is recorded for a period of length L. Lo,
L1 and L2 indicate the areas of each bit. The head of the 0 address area is an address mark signal, and a frequency of 10 is recorded. The beginning of the address value of track 1 is O,
According to the modulation method shown in FIG. 6, frequency f1 is recorded, the second address value is 1, and similarly frequency f0
is recorded next.

A method for reproducing address signals from an optical disc on which address signals have been recorded as described above will be explained.

When the linear velocity during reproduction changes, the frequency of the reproduced address signal also changes. This relationship is shown in FIG. When the groove axis in Fig. 8 is expressed by the logarithm of the frequency, in the case of linear velocity v0,
The reproduced recording frequency fη=0.1.2) can be expressed as a solid line. The linear velocity during playback is V. In the case of i, each reproduced frequency fk' is represented by the broken line in FIG. It can be expressed as a dashed dotted line in i9. In this way, even if the linear velocity changes, each reproduced frequency does not overlap, so each frequency /k can be separated using a BPF having the characteristics shown in 27, 28, and 29 in Figure 8. .

FIG. 9 shows an example of an address signal reproducing circuit in this embodiment. In FIG. 9, 30 is a photodetector, 31 is a preamplifier, 32.33.34 is a BPF, and 35.36.3
7 is a comparison circuit, 38 is an address demodulation circuit, and 39 is an output terminal. For example, assume that a laser spot is irradiated onto track i in FIG. A photodetector 30 receives reflected light from the disk. The photodetector 3o converts the reflected light into an electrical signal, which is amplified by the preamplifier 31 to obtain a reproduced signal p. BPF32, 33.34 are bandpass filters whose passband center frequencies are recording frequencies fo and f11f2, respectively, and are similar to 27.28.2 in Fig. 8.
It has the characteristics shown in 9. The comparison circuits 35, 36, and 37 respectively compare the reference voltage and the output voltage of the BPF. For example, the recording frequency of the address area is f. When a portion of
fO', the output of the BPF 32 is not thick, and the output F of the comparator circuit 36. becomes H level. Similarly, when the frequency of the reproduced signal p is f1/~f1'', the output F1 of the comparator circuit 36 becomes H level, and when the frequency of the reproduced signal p is f2'~f2'', the output F2 of the comparator circuit 37 becomes H level. The address demodulation circuit 38 demodulates the code value of the address according to the order of change in the output of each comparison circuit in accordance with FIG. 6, and outputs it to the output terminal 39.

Next, an example of an address demodulation circuit is shown in FIG. 1o. In FIG. 10, the input terminals 40, 41 and 42 have a ninth
Outputs F0. from comparison circuits 35, 36, 3 in the figure. F1. F2
Enter. For example, if the frequency of the reproduced signal is fo, the output is F. becomes H level. Flip-flops (hereinafter abbreviated as F and F) 43 are set, and AND gates 51 and 53 serve as ovens. Next output F1
Suppose that becomes H level, the output of AND gate 51 becomes H level, and output F through OR gate 65.
Set F57 and set the output signal to L level at output terminal 3.
9 and demodulates the code value "0". Still, depending on the level of output F1, F is output through OR gate 46.48.
- Reset F, as and F-F45 respectively.

Since F-F44 is set, Antogame) 49
．． 54 is open. Next, if the output F0 becomes H level, the output of the AND gate 49 becomes H level, the output F-F57 is reset through the OR gate 66, the output signal is set to H level, and the code value is "1".
demodulate.

Similarly, the output F0 of the comparator circuits 35, 36, 37
．． F1. Code values "0" and "1" can be demodulated from the change in F2.

Note that in this embodiment, reference signals such as address signals are
Although a method has been described in which the code signal is expressed as a value code signal and modulated using three types of recording frequencies, the present invention is not limited to this method.
'n+1) types of recording frequencies can be used for modulation. For example, the previous recording frequency is fkc k =0
, 1 , ... n), then for the value m of the n-value code signal, the recording frequency is fk+m (however, fn+, = f0)
All you have to do is switch to .

Also, the recording frequency f is recorded in the address mark signal. However, the present invention is not limited to this, and may be omitted if another signal is used. In this case, modulation may be started from frequency f for the first code value l of the address value.

In addition, in this embodiment, the method of (1) recording and reproducing signals on the valleys of the grooves has been described, but the present invention is not limited to this method. This method can also be applied when the cross-sectional shape of the groove is trapezoidal or U-shaped.

Furthermore, in this embodiment, a case has been described in which the grooves and the reference signal are recorded by mechanical cutting, but the recording method is not limited to this method. A reference signal can be recorded.

Effects of the Invention According to the present invention, (n+1) types of recording frequencies are selected so that even when the linear velocity of the disk changes over a wide range, the variation ranges of the respective recording frequencies do not overlap. Therefore, even when the linear velocity changes suddenly, such as during a jump, the recording frequency can be determined with a simple circuit configuration using a BPF.

Also, the reference signal is expressed as an n-value code signal, (n+1)
Because it is a method that modulates by switching between different recording frequencies,
As for the reproduction method, the n-value code signal can be reproduced by changing the recording frequency determined at the time of reproduction. Since the reproduction method according to the present invention does not require the use of a clock signal, the reference signal can be reproduced stably even if the linear velocity changes, and there is no need to wait for a response from the disk rotation control system. , it becomes possible to shorten the search time, which is extremely useful in practice.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram showing the address area of an optical disc in an embodiment of the present invention, Fig. 2 is a radial cross-sectional view of an optical disc with a V-groove, and Fig. 3 is a schematic diagram showing the address area of an optical disc in a conventional example. FIG. 4 is a waveform diagram showing a conventional reference signal reproduction method, FIG. 5 is a schematic diagram showing the format of an optical disc in an embodiment of the present invention, and FIG.
The figure is a state transition diagram showing the modulation/demodulation method in one embodiment of the present invention, FIG. 7 is a block diagram showing the configuration of a modulation circuit in one embodiment of the present invention, and FIG. 8 is a reproduced signal in one embodiment of the present invention. FIG. 9 is a block diagram showing the configuration of a reproducing circuit in an embodiment of the present invention.
FIG. 0 is a circuit diagram showing an address demodulation circuit in one embodiment of the present invention. 26...Address area L LQ, Ll, I,
2.--... Each person's area. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Figure 3 Figure 4 (e) / 0 0 0 / / 0
/ / /Figure 5 vJGFigure 8 Figure

Claims (3)

[Claims] (1) Grooves constituting recording tracks are formed on the disk, and a recording layer for optical recording is provided on the grooves, and the frequencies do not overlap even if the rotational speed of the disk is changed within a predetermined range. An optical disc characterized in that a reference signal expressed as an n-value code signal is recorded by modulating the depth of the groove with (n+1) types of frequencies selected as follows. (2) From (n+1) types of frequencies f_k (k=0, 1, 2...n) selected so that the frequencies do not overlap even if the rotational speed of the disk is changed within a predetermined range, 2. The optical disc according to claim 1, wherein the frequency for modulating the groove depth is switched from frequency f_k to frequency f_k_+_m with respect to value m of the n-value code signal. (3) Grooves constituting recording tracks are formed on the disk, and a recording layer for optical recording is provided on the grooves, and even if the rotational speed of the disk is changed within a predetermined range, the frequencies do not overlap with each other. By modulating the depth of the groove with (n+1) frequencies selected as follows, a laser beam is focused on the track using an optical disc on which a reference signal expressed as an N-value code signal is recorded. irradiates the optical disk, and a photodetector receives the reflected light from the optical disc.
When reproducing the reference signal on the track, extract frequency components corresponding to the (n+1) types of frequencies from the reproduced signal, and reproduce the value of the n-value code signal of the reference signal by changing the frequency components. A reference signal reproduction method characterized by: