JPH07210873A - Optical disk medium and its clock forming device - Google Patents

Abstract

PURPOSE:To make the crosstalks from adjacent tracks uniform and to record information at a specified recording density by setting the meandering periods of the track grooves at a specified angle viewed from a central point regardless of positions where the track grooves are formed. CONSTITUTION:All of the track grooves 1 of an optical disk medium are so formed as to meander at the equal interval periods thetak and, therefore, the unification of all the meandering periods to the same phase is possible. Then, the influence of the crosstalks from the adjacent tracks is made constant and eventually, the meandering of the tracks is stably detected even if the track pitch is narrowed. However, the meandering periods are longer nearer the outer periphery and, therefore, the number of equal division is made larger nearer the outer periphery in such a case. Consequently, the execution of recording at the equal density for the inside and the outside is possible.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disc medium for recording information by CLV, and a clock generation device for generating a clock signal necessary for recording information on the optical disc medium.

[0002]

2. Description of the Related Art In recent years, the density of optical disc media has been increasing. An example of a conventional optical disc medium will be described below with reference to the drawings.

FIG. 9 is a partial block diagram of a conventional optical disk medium. In FIG. 9, reference numeral 100 denotes a track center line, and track grooves 101 are provided along the track center line 100 in a meandering manner with a period of a constant length K or a period of an integral multiple thereof. The track center line 100 is a part of a virtual one that is spirally defined on a disk-shaped disk substrate.

The operation of the optical disk medium having the above structure will be described below. Track groove 1
01 is formed along the continuous spiral line from the inner circumference to the outer circumference of the disk substrate, and information is recorded in the track groove 101.
Continuously recorded on. At this time, the meandering is used to keep the recording density constant on the inner and outer circumferences of the disk substrate. That is, regardless of the inner and outer circumferences of the disc, the meandering formed in a cycle of a constant length K is first detected, a clock that equally divides the cycle K is generated, and information is recorded in synchronization with this. Further, by forming the meandering with a combination of cycles K, 2K, 3K, ..., This can be used as address information. (For example, US Pat. No. 5,185.
732 specification)

[0005]

However, in the structure of the optical disc medium as described above, the narrower the track pitch, the more difficult it becomes to detect the meandering, and therefore, there is a problem that it is not suitable for high density recording. Was there. That is, when the track groove 101 is formed from the inner circumference to the outer circumference, the track length per disk circumference gradually increases. Here, since the meandering period is K, which is constant, the number of meandering per track is increased toward the outer peripheral side. Therefore,
The meandering between adjacent tracks may not be synchronized and may happen to be in phase with each other or may happen to be formed in opposite phase as shown in FIG. As a result, the meandering of the adjacent tracks may cause crosstalk to affect the central track, and the period K may not be detected correctly.

In view of the above problems, the present invention provides an optical disk medium capable of stably detecting a meander even if the track pitch is narrowed and capable of high density recording at a constant density on the inner and outer circumferences.

[0007]

In order to solve the above problems, the optical disk medium of the present invention has a constant meandering period of the track groove from the center of the optical disk regardless of the position where the track groove is formed. In addition, a plurality of address mark groups are formed at equal distances in the track groove, and information about the clock wave number for the meandering period is recorded in the address mark group.

[0008]

According to the present invention, the crosstalk from the adjacent tracks can be made uniform by the above-mentioned structure, and as a result,
Even if the track pitch is narrowed, it is possible to correctly detect the meandering period of the track groove. Further, by multiplying the track groove period by the wave number ratio extracted from the address mark to generate the clock, it is possible to record information at a constant recording density regardless of the inner and outer circumferences.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An optical disk medium according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a top view of an optical disk medium according to a first embodiment of the present invention, and FIG. 2 is a schematic view of its essential part. In FIG. 1, 10 is a track center line, which is a virtual one defined in a spiral shape from the inner circumference to the outer circumference of the disk substrate, as in the conventional example. The track grooves 1 meander around the track center line 10 and are formed in a cycle of an equal angle θk when viewed from the disk substrate center O. Address marks 2 and 3 are shown in FIG.
As shown in FIG. 3, the track groove 1 is formed by partially cutting it off. Further, the address marks 2 and 3 are formed at a constant length L regardless of the inner and outer circumferences of the disc.

The operation of the optical disc medium configured as described above will be described. Since all the track grooves 1 are formed so as to meander at the equiangular interval period θk,
The meandering synchronization can be all in phase, as shown in FIG. Therefore, the influence of crosstalk from adjacent tracks can be made constant, and as a result, track meandering can be detected stably even if the track pitch is narrowed.

However, since the meandering period becomes longer toward the outer circumference, if the clock is generated by equally dividing the meandering cycle as in the conventional example, the recording density becomes lower toward the outer circumference. Therefore, in the present embodiment, the information obtained from the address marks 2 and 3 formed at equal intervals L is used to increase the equifraction number toward the outer circumference, and as a result, uniform density recording can be performed on the inner and outer circumferences. The specific method will be described in the next embodiment.

As described above, according to the present embodiment, since the track groove 1 is provided to meander at an equal angle, it is possible to stably detect the meander even under a narrow track pitch. A second embodiment of the present invention will be described below with reference to the drawings.

FIG. 3 shows a second embodiment of the present invention, and FIG.
3 is a block diagram of a clock signal generation device using the optical disc medium of FIG. In FIG. 3, 11 is a light receiving element as a constituent element, and is composed of elements 11a and 11b. Reference numerals 12 and 13 are a differential amplifier and an addition amplifier, respectively. Reference numeral 14 is a binarization circuit, which generates a pulse signal C from the output of the differential amplifier 12. An address mark identification circuit 15 detects the address mark 2 from the output of the addition amplifier 13. Reference numeral 16 denotes a multiplication ratio determination circuit, which determines the multiplication ratio N corresponding to the address mark detection signal.
A variable multiplication circuit 17 multiplies the pulse signal C by the multiplication ratio N and outputs a clock signal CLK.

FIG. 4 shows the relationship between the respective constituent elements and the operation of the clock generation circuit composed of the above respective constituent elements.
Will be explained. First, the meandering of the track groove 1 is detected as a signal T by the light receiving element 11 and the differential amplifier 12. Further, the signal T becomes the pulse signal C by the binarization circuit 14. Further, this pulse signal C is a variable multiplier 1
It is divided into N equal parts by 7 and becomes the clock signal CLK. Here, the multiplication ratio N is determined by the multiplication ratio determination circuit 16 from the information obtained by the address mark identification circuit 15. That is, the address mark 2 is detected from the signals obtained by the light receiving element 11 and the addition amplifier 13, and the multiplication ratio N is determined based on this. Therefore, as shown in FIG. 4, it is possible to change the number of clocks for one meandering on the inner and outer circumferences of the disc, and as a result, it is possible to record information at the same recording density on the inner and outer circumferences. As a method of determining the multiplication ratio N, the following methods can be considered. (1) The interval between the address marks 2 and 3 is measured, and the multiplication ratio N is set so as to be proportional to this. The mark interval can be measured by counting the number of meanders of the track groove 1. (2) Information relating to the multiplication ratio N (for example, radial position) is recorded in advance in the address mark 2, and the multiplication ratio N is determined from this. (3) A reference clock is recorded in advance on the address mark 2, and the reference clock and the clock signal CLK are recorded.
The multiplication ratio N is determined so that Of the above, the one described in (3) will be described in detail in the next embodiment.

The third embodiment of the present invention will be described below. FIG. 5 is a block diagram of the clock generator of the third embodiment. In FIG. 5, a summing amplifier 12 and a differential amplifier 1
3, the binarization circuit 14 and the variable multiplication circuit 17 are the same as those shown in FIG. The present embodiment is characterized in that a binarization circuit 151, a synchronous clock detection circuit 152, a frequency comparison circuit 153, and an up / down counter 154 are provided in place of the address mark identification circuit 15 and the multiplication ratio determination circuit 16.

The operation of the clock generator configured as shown in FIG. 5 will be described below with reference to FIG. First,
The synchronous clock detection circuit 152 extracts the reference clock W from the binarized address mark reproduction signal A. The frequency comparison circuit 153 compares the frequencies of the reference clock W and the clock signal CLK. That is, if the clock signal CLK is faster than the reference clock, the P output is pulsed, and if it is later, the Q output is pulsed. The up / down counter 154 is P for the current multiplication ratio N.
Output is up-counted and Q output is down-counted. Since the frequency of the clock signal CLK is determined by the multiplication ratio N, the frequency comparison circuit 153, the up / down counter 154, and the variable multiplication circuit 17 eventually form a feedback loop, and the multiplication ratio N balances this loop. It is decided to be in a state. In other words, ideally, when neither P output nor Q output has a pulse,
In other words, the steady state is achieved when the frequencies of the reference clock W and the clock signal CLK are completely equal.

As described above, according to this embodiment, the multiplication ratio N can be determined from the clock included in the address mark.
The fourth embodiment of the present invention will be described below. FIG. 7 is a partial configuration diagram of an optical disk medium of a fourth embodiment of the present invention. In FIG. 7, 1 is a track groove, which is the same as that shown in FIG. 2 differs from FIG. 2 in that instead of the address mark 2 formed by intermittently forming the track groove 1, an address mark 20 formed by changing the width of the track groove 1 is provided.

By doing so, the address mark 20
Not only can it suppress the influence of the data on the adjacent tracks, but it is also possible to overwrite the information on the address. That is, when the address mark is provided by changing the track groove width, the reproduced maximum amplitude becomes smaller than that when the address mark is provided by the intermittent track groove. As a result, the influence on adjacent tracks is reduced. However, there is concern that the amplitude of the address mark reproduction signal decreases and the S / N decreases, making it impossible to correctly identify the address mark. However, as described below, the recording density of the address mark 20 is sufficiently reduced. Therefore, it is possible to suppress a decrease in S / N.

That is, by providing the address mark 20 as shown in FIG. 7, it is possible to form the track groove 1 without interruption, so that information can be recorded on the address mark 20. Further, if a magneto-optical recording film is used as the recording material, the address mark (change in amplitude) and the recorded information (change in polarization angle) can be reproduced separately from each other without affecting each other. If the address mark and the record information can be overwritten in this way, the overhead due to the address mark is eliminated, and therefore the recording density of the address mark is sufficiently lowered, and even if the address mark recording area is increased, the total recording capacity of the optical disc medium is reduced. It does not decrease.

The fifth embodiment of the present invention will be described below. FIG. 8 is a schematic view of the essential parts of the optical recording medium of the fifth embodiment. In FIG. 8, reference numeral 5 is a track groove that is periodically meandered. The difference from the track groove 1 in FIG. 1 is that the track groove 1 meanders in the same phase as the adjacent track, whereas the track groove 5 of this embodiment meanders in the opposite phase to the adjacent track. Is provided.
With this, the track groove meander is added to the amplifier 12.
(Fig. 3) It can be obtained from the output. That is, as shown in FIG. 8, the density of the tracks appears remarkably, so that the variation of the reflected light amount is superimposed on the meandering detection signal, resulting in a larger amplitude than that shown in FIG. The meander is detected at.

[0022]

As is apparent from the above description of each embodiment, the present invention forms the meandering period of the track groove at a constant angle as viewed from the center point of the disk, regardless of the inner and outer circumferences of the disk. Further, a plurality of address mark groups are formed in the track groove so that the formation cycle thereof is a constant distance along the track groove, and moreover, information of the number of clocks with respect to the meandering cycle of the track groove is written in the address mark group. As a result, the crosstalk due to the meandering of the adjacent tracks can be made uniform, and as a result, the track pitch can be made narrower than that of the conventional one, and information can be recorded at a constant recording density regardless of the inner and outer circumferences. Can be recorded.

[Brief description of drawings]

FIG. 1 is a top view of an optical disc medium according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram of a main part of the optical disc medium of the same embodiment.

FIG. 3 is a block diagram of a clock generation device according to a second embodiment of the present invention.

FIG. 4 is a timing chart showing the operation of the clock generation device according to the embodiment.

FIG. 5 is a block diagram of a clock generation device according to a third embodiment of the present invention.

FIG. 6 is a timing chart showing the operation of the clock generation device according to the embodiment.

FIG. 7 is a configuration diagram of main parts of an optical disc medium according to a fourth embodiment of the present invention.

FIG. 8 is a configuration diagram of essential parts of an optical disc medium according to a fifth embodiment of the present invention.

FIG. 9 is a schematic view of a conventional optical disc medium.

[Explanation of symbols]

 1 track groove 2 address mark 3 address mark 10 track center line 11 light receiving element 15 address mark identification circuit 16 multiplication ratio determination circuit 17 variable multiplier 152 synchronous clock detection circuit 153 frequency comparison circuit

Claims (10)

[Claims] 1. An optical disk medium in which track grooves are formed that meander on the inner and outer circumference sides of a spirally defined track centerline centered around the center of a disk-shaped disk substrate. The optical disk medium, wherein the meandering period of the track groove is a constant angle when viewed from the center point regardless of the position where the track groove is formed. 2. The optical disk medium according to claim 1, wherein a plurality of address mark groups are formed in the track groove, and the formation cycle of the address mark group is a constant distance along the track groove. 3. The optical disk medium according to claim 2, wherein the address mark is formed by changing the width of the track groove. 4. The optical disk medium according to claim 2, wherein the clock is generated by dividing the meandering period of the track, and the information about the division ratio at this time is recorded in the address mark group. . 5. The optical disk medium according to claim 4, wherein a signal having a period that equally divides an interval in which the address mark group is formed is formed in each address mark. 6. The optical disk medium according to claim 1, wherein adjacent track grooves are formed in a meandering manner in mutually opposite phases. 7. A clock generation device for converting the reflected light of the laser beam applied to the optical disc medium according to claim 1 into an electric signal by a light receiving element, and generating a clock signal from the electric signal, wherein the light receiving element is at least It is divided into two in parallel with the track mapping, and is provided with a multiplication means for frequency-multiplying the difference signal of each output of the divided light-receiving element by an arbitrary multiplication number to obtain a clock signal, the multiplication number being closer to the outer circumference of the optical disc medium. A clock generation device characterized by being set large. 8. A clock generation device for converting the reflected light of the laser beam applied to the optical disc medium according to claim 2 into an electric signal by a light receiving element, and generating a clock signal from the electric signal, the output of the divided light receiving element. 8. The clock generation device according to claim 7, wherein a division ratio is extracted from the address mark group reproduction information detected from the signal, and the divided light receiving element differential signal is multiplied by the division ratio to form a clock signal. 9. A synchronous clock detecting means for detecting a synchronous clock from an address mark formed on the optical disk medium according to claim 5, a frequency difference between the synchronous clock and the clock signal is detected, and a multiplication factor is calculated from the frequency difference. 9. The clock generation device according to claim 8, further comprising a feedback loop for setting. 10. The clock generation device according to claim 8, wherein the division ratio is extracted so that the interval at which the address mark group is sequentially detected is divided into substantially equal parts.