JPH03201268A - Data reproducing clock signal generator and data reproducing device - Google Patents

Abstract

PURPOSE:To obtain an external clock signal suitable for reproducing data by correcting a phase of the external clock signal based on a regenerative signal of a reference clock signal at the time of reproducing the data. CONSTITUTION:One segment Sg is composed of a servo area 1 and a data area 2, and in the servo area 1, one pair of wobble pits for obtaining the so- called tracking error signal and clock pits for the purpose of synchronizing a clock are provided in advance, while in the data area 2, a data is recorded or reproduced by utilizing the magneto-optical effect. Then, in order to dissolve a problem caused by a phase shift, a reference clock signal and a constant level signal are recorded, for instance, in the data area 2 of the 2nd segment. A regenerative signal of the reference clock signal recoded to a recording medium in this way is sampled by using the external clock signal having a different phase from each other, and the external clock signal having such a phase that a difference from this sample value is a max. is selected. By this way, the external clock signal suitable for reproducing data can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION C. Industrial Field of Application The present invention relates to a clock signal generator for data reproduction and a data reproduction device, and in particular to a clock signal generating device for data reproduction and a data reproduction device, in particular a method for generating an external clock signal using a reference clock signal recorded on a recording medium. The present invention relates to a clock signal generation device for data reproduction, and a data reproduction device that reproduces data using the external clock signal.

[Summary of the invention]

A clock signal generator for data reproduction according to the present invention samples a reference clock signal actually recorded on a recording medium using a plurality of external clock signals having mutually different phases, and generates a sample value by each external clock signal. By determining the maximum value of the difference and using the external clock signal corresponding to this maximum value as the data reproduction clock signal, an external clock signal with a high window margin and suitable for data reproduction is obtained.

Further, the data reproducing device according to the present invention samples the reference clock signal actually recorded on the recording medium using a plurality of external clock signals having mutually different phases, and calculates the difference between the sample values due to each external clock signal. Find the maximum value, use the external clock signal corresponding to this maximum value as the clock signal for data reproduction, sample the reproduction signal from which data is reproduced using this external clock signal, and calculate the difference between this sample value and the above Data is reproduced by comparing approximately 1/2 of the maximum difference between the sample values of the reproduced signal of the reference clock signal, thereby making it possible to reproduce data with a high noise margin.

[Conventional technology]

As shown in FIG. 4, magneto-optical recording records data by magnetizing a portion of a disk that has reached its Curie temperature through laser irradiation in the direction of an externally applied magnetic field. In other words, for example, a laser diode is driven in pulses to emit light, an external magnetic field is modulated with recorded data, and pits (portions magnetized by the external magnetic field) corresponding to the spot size of the laser beam are formed on the recording surface in a time-division manner. By doing so, data is recorded.

By the way, in order to increase the recording density, if the interval between the pulses that drive the laser light source is made smaller than the laser beam spot size, part of the laser beam spot overlaps with a part of the previously formed pit, causing magnetization to occur first. Some of the pits that have been created will be overwritten (overwritten) by pits that will be formed later.In other words, the pits will be formed one by one in a time-division manner, and as the recording density is increased, overlapping will occur. As a result, so-called edge recording occurs in which the points of change (edges) in the direction of magnetization contain information.

Further, a magneto-optical recording medium, such as a magneto-optical disk, is rotated by a spindle motor at a constant linear velocity (CLV) or a constant angular velocity (CAV), so that the pits are formed in a spiral or concentric pit row. It has become.

By the way, in the case of constant angular velocity (CAV) driving, the distance (length) that the recording head advances per unit time is smaller on the inner circumference than on the outer circumference. Therefore, as shown in FIG. is larger than the amount of overlap in .

When data is reproduced from the pits recorded in this way, as shown in Figure 6, the signals reproduced from the inner pits are temporally advanced (shifted) than the signals reproduced from the outer pits. It takes shape.

Therefore, in the so-called external clock method, for example, the bits on the inner circumference are reproduced using the same external clock signal as the synchronized clock signal (hereinafter referred to as external clock signal) obtained from the magneto-optical disk for reproducing the pits on the outer circumference. In this case, the position of the above-mentioned change point, that is, the edge, cannot be detected accurately. In other words, the so-called detection window width becomes narrower, and when the modulation method of the external magnetic field is so-called NRZI modulation, the noise margin for the threshold value for determining the presence or absence of an edge during reproduction becomes smaller.

[Problem to be solved by the invention]

As a way to solve the above problem, it is possible to form a pi-node by making a correction in advance during recording based on the radius information and surrounding environment (temperature, laser light source power, etc.), but since the correction It is difficult to obtain detailed recording conditions. Furthermore, due to differences in the characteristics of magneto-optical disks (individual differences) and differences between data recording devices and data reproducing devices, correction during recording alone is not sufficient to solve the above-mentioned problems. Therefore, in order to achieve high-density recording, it is necessary to correct, for example, the phase of the external clock signal based on the waveform of the signal reproduced during data reproduction (reproduced signal waveform).

In addition, a clock signal is superimposed on a data signal recorded on a magneto-optical disk, and this recorded clock signal is extracted during playback, and this clock signal is used as a clock signal for playback. There is a clock method, but this method requires the use of a dedicated modulation method and also requires a lock pull-in area to allow sufficient clock extraction.

The present invention is described above! This was developed in view of the above-mentioned problems, and is used when playing magneto-optical disks that are driven at constant angular velocity (CAV) using an external clock method, especially when playing magneto-optical disks that are recorded at high density. The purpose of the present invention is to provide a clock signal generator for data reproduction that forms an external clock signal that can prevent data errors caused by a phase shift between the reproduced waveforms between the inner and outer circumferences of a disk, and furthermore, An object of the present invention is to provide a clock signal generation device for data reproduction that can freely select a modulation method without being affected by differences (individual differences), environments at the time of recording, and differences in data recording devices and data reproducing devices.

Another object of the present invention is to provide a data reproducing device that reproduces data using an external clock signal from the data reproducing clock signal generator, and furthermore,
The purpose of the present invention is to provide a data reproducing device that is not affected by differences in the recording environment (individual differences), recording environments, and data recording devices and data reproducing devices.

[Means for solving yA problem]

A clock signal generation device for data reproduction according to the present invention is a clock signal generation device for data reproduction that uses a recording medium on which a reference clock signal is recorded, and the external clock signal generates a plurality of external clock signals having mutually different phases. forming means, sampling means for sampling a reproduced signal of the reference clock signal using each external clock signal formed by the external clock signal forming means, and corresponding to each of the external clock signals from the sampling means. maximum value detection means for detecting the maximum value of the difference between sample values; and an external clock signal for selecting and outputting an external clock signal from the external clock signal forming means corresponding to the maximum value detected by the maximum value detection means. The above problem is solved by having a selection means.

Further, the data reproducing device according to the present invention is a data reproducing device that uses a recording medium on which a reference clock signal having a frequency equal to the highest recording frequency of data is recorded, and forms a plurality of external clock signals having mutually different phases. an external clock signal forming means, a sampling means for sampling a reproduced signal reproduced from the recording medium using an external clock signal formed by the external clock signal forming means, and a sample value of the reproduced signal from the sampling means. and maximum value detection means for detecting the maximum value of the difference between sample values corresponding to each of the external clock signals of the reproduced signal of the reference clock signal based on the calculation output from the calculation means. , external clock signal selection means for selecting and outputting an external clock signal from the external clock signal forming means corresponding to the maximum value detected by the maximum value detection means; data reproducing means for reproducing data by comparing the difference between the sample values of the reproduced signal from the arithmetic means using a clock signal and a value of about 1/2 of the maximum value from the maximum value detecting means; This solves the above problem.

[For production]

A clock signal generator for data reproduction according to the present invention samples a reproduced signal of a reference clock signal recorded on a recording medium using external clock signals having mutually different phases, and selects a phase that maximizes the difference between the sample values. By selecting an external clock signal, an external clock signal suitable for data reproduction is generated.

Further, the data reproducing device according to the present invention can detect a difference between sample values obtained by sampling a data reproducing signal using an external clock signal from the data reproducing clock signal generator and a reproducing signal of the reference clock signal. The data is reproduced by comparing the data with a value that is approximately 1/2 of the difference between the maximum sample values when sampled using the external clock signal.

〔Example〕

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

FIG. 1 is a block circuit diagram of a data reproducing device using a clock signal generating device for data reproducing according to the present invention.

FIG. 2 is a diagram showing an integrated recording format of a magneto-optical disk used in this data reproducing apparatus.

First, the recording format of this magneto-optical disk will be explained.

In FIG. 2, one sector (or block) serving as an information recording unit is composed of a predetermined number of segments (or frames). One segment is composed of a servo area 1 and a data wI area 2 (in the first segment of the sector, a header area 3 in which information such as an address is recorded). In the servo area 1, a pair of rounded so-called wobble bits for obtaining a so-called tracking error signal and a clock pit for synchronizing the clock are provided in advance.

Data (information) is recorded or reproduced in the data area 2 using the magneto-optic effect. In order to solve the problem caused by the phase shift of the data reproduction signal between the inner and outer circumferences of the magneto-optical disk, for example, a reference clock signal and a constant level signal are added to the data area 2 of the second segment. is recorded. That is, as shown in FIG. 3, for example, the amplitude and frequency of the reproduced signal when data area 2 of the second segment is reproduced are equal to the maximum amplitude and highest frequency of the data reproduced signal. A reference clock signal is recorded in the first half of the data area 2 of the segment.

Further, in the remaining portion of the data area 2 of the second segment, a signal is recorded such that the reproduced signal when reproduced has a constant level.

When reproducing a recording medium having the above-mentioned recording format, for example, a magneto-optical disk, a synchronized clock signal (hereinafter referred to as an external clock signal) formed from the above-mentioned clock pits is used as a clock signal for data reproduction. It will be done.

In the present invention, the phase of this external clock signal is corrected using the reference clock signal, as will be described later. Thus, in this embodiment, a magneto-optical disk having the recording format as described above is used as a recording medium on which a reference clock signal is recorded.

Next, a data reproduction clock signal generation device will be explained.

In FIG. 1, a terminal 10 is connected to an RF (high frequency) signal reproduced from a magneto-optical disk which is rotated at a constant angular velocity (CAV) by a spindle motor, and a reproduced signal (MO signal) is transmitted through an amplifier, etc. It is supplied as. Further, the terminal 11 is supplied with a signal obtained by reproducing the clock pit in the servo area 1 of the magneto-optical disk.

The external clock generation circuit 12 is composed of a circuit such as a PLL, for example, and forms an external clock signal CK from a signal reproduced from the clock pit. This external clock signal CK is delayed in, for example, three delay circuits 13, 14, and 15 connected in series. Thus, a plurality of external clock signals C having mutually different phases
The external clock signal forming means for forming K, CK+, CKz, and CKs is the external clock generating circuit 12,
It is composed of delay circuits 13-15.

The selector 16 is controlled by the control signal from the counter 17.
For example, one external clock signal is sequentially selected from the external clock signals CK, -CK and supplied to the A/D converter 18. The A/D converter 18 also has the terminal I
The above-mentioned reproduction signal is supplied via O, and the A/
The D converter 18 receives the external clock signal CK from the selector 16.

~CK3 is used to sample the reproduced signal of the reference clock signal, for example as shown in FIG. 3, and convert the sampled value into a digital sample value S.

This sample value S is supplied to the register 19 and the arithmetic circuit 20. Thus, in this embodiment, the A/D converter 18 is used as a sampling means for sampling the reproduced signal of the reference clock signal using each of the external clock signals CK o to CK 3.

The register 19 delays the sample value S by one sampling time, and transfers the delayed sample value S to the arithmetic circuit 2.
Supply to 0. The arithmetic circuit 2o calculates the absolute value of the difference between the sample values SN (N represents the number of the external clock signal) corresponding to each external clock signal CK, ~CK, as shown in FIG. 3, for example. As shown, the absolute value of the difference between the sample values SN corresponding to each external clock signal CK, ~CK, respectively, is expressed as DH=S□-3° (N represents the number of the external clock signal) It can be found from Eq. The absolute value DH of the difference between the sample values corresponding to each external clock signal CK, ~CK, is supplied to the register 21 and the comparator 22. The register 21 delays the absolute value of the sample value difference 4a DN by, for example, one sample time, and supplies the delayed absolute value of the sample value difference to the comparator 21. The comparator 21 compares the absolute value of the difference between the delayed sample values and the absolute value DN of the difference between the current sample values from the arithmetic circuit 20, and supplies the comparison result to the controller 30, for example. As shown in FIG. 3, when the absolute value D2 of the difference between the current sample values is greater than the absolute value Dz of the delayed sample values, the controller 30 calculates the absolute value Dz of the difference between the current sample values. The register 21 is controlled so as to store in the register 21. That is, the register 21 stores the maximum value of the absolute value of the difference between the sample values when the reproduced signal of the reference clock signal recorded on the magneto-optical disk is sampled using each external clock signal CK, ~CK. is now memorized.

On the other hand, the register 31 receives a control signal from the counter 17 that controls the selector 16, and stores the latest control signal each time the register 21 is updated with a larger value as described above. . That is, register 3
1 finally stores the control signal when the selector 16 selects the external clock signal that maximizes the absolute value of the difference between the sample values of the reproduced signal and the reference clock signal.

The controller 3o receives this control signal stored in the register 31, controls the counter 17 so that the selector 16 selects the external clock signal as an external clock signal for data reproduction, which will be described later, and outputs the external clock signal. For example, in the specific example shown in FIG.
K is determined as a data reproduction clock signal and output.

The controller 30 also controls the maximum value of the sample value difference (S□anyHI) stored in the register 21 at this time.
N) is stored in the register 23. Thus, in this embodiment, each external clock'; one signal CK@~C
The maximum difference between sample values corresponding to K (SNAII
5HIN ) is composed of the selector 16, counter 17, register 19.21, arithmetic circuit 20, comparator 22, and controller 30,
The maximum value detected by the maximum value detection means (SMAX
External clock signal selection means for selecting and outputting an external clock signal from the external clock signal forming means corresponding to 5HIN) is comprised of the selector 16, counter 17, controller 30, and register 31.

As described above, in the clock signal generation device for data reproduction according to the present invention, the phase of the external clock signal is corrected based on the reproduced signal of the reference clock signal actually recorded on the magneto-optical disk. A data playback clock that enables data playback that is not affected by differences in pit density between the outer and inner sides of the disk, environmental conditions during recording, differences in characteristics between recording and playback devices, individual disc differences, etc. It becomes possible to obtain a signal. Further, by using a reference clock signal, that is, a repeating pattern, the code amount interference between each pattern becomes uniform, and no shift of the external clock signal occurs.

Furthermore, even if there is a defect in a part of the area where the reference clock signal is recorded and the level of the reproduced signal in this part decreases, the above-mentioned operation to detect the maximum difference between sample values is performed multiple times. By doing so, it is possible to accurately detect the maximum value of the difference between sample values. In other words, in the segment where the reference clock signal is recorded, there is no need to detect a disc defect, and this defect will not adversely affect data reproduction.

Next, the operation of the data reproducing device will be explained.

As described above, in the data reproducing clock signal generator, the data area 2 of the second segment shown in FIG.
An external clock signal whose phase has been corrected using the reference clock signal recorded in , when the maximum value of the difference between the sample values of the reproduced signal of the reference clock signal described above is calculated from the reproduced signal obtained by regenerating the signal of a partial level following the reference clock signal of the data area 2 of the second segment described above. Find the maximum amplitude of the noise using the same operation as above.

Specifically, as shown in FIG. 2, for example, the controller 30 uses the external clock signal CKz that maximizes the difference between the sample values of the reproduced signal of the reference clock signal described above to adjust the signal at the constant level. The reproduced signal is sampled, and the maximum value of the difference between these sample values is stored in the register 21. That is, the register 21 stores the maximum amplitude of noise (Nnaw N□8) when a signal of a certain level following the reference clock signal is reproduced.The controller 30 stores the maximum amplitude of this noise (NMAX NMIN).
is stored in the register 24.

The arithmetic circuit 25 calculates the maximum amplitude of the reproduction signal of the reference clock signal from the register 23 (SMAX 5HIN) and the maximum amplitude of the noise from the register 24 (NMAX-N□N).
For example, a threshold value TH for determining the presence or absence of an edge necessary for reproducing data recorded using the so-called NRZI modulation method.
is calculated and supplied to the comparator 26. Specifically, the threshold value TH for edge detection is determined by the formula expressed as TH""(SMAX 5HIN 1N) IAIIN□Nl)/2 and is supplied to the comparator 26.

The comparator 2''6 calculates the difference between the sample values of the data reproduction signal recorded in the data area 2 of the third and subsequent segments of the selector from the arithmetic circuit 20 and the threshold value TH.
The presence or absence of edges is detected by comparing them. For example, when the difference between the sample values of the data reproduction signal is larger than the threshold TH, it is determined that there is an edge, and when it is smaller than the threshold TH, it is determined that there is no edge. The signal indicating the presence or absence of this edge is from terminal 2.
7.

Thus, in this embodiment, the external clock signal forming means for forming a plurality of external clock signals CKo to CK having mutually different phases is composed of the external clock generation circuit 12 and the delay circuits 13 to 15, and D converter 18
The reproduction signal reproduced from the recording medium is converted into an external clock signal CK, which is formed by an external clock signal forming means.
The registers 19,
Maximum value detection means, which is composed of an arithmetic circuit 20 and detects the maximum value of the difference between the sample values corresponding to each of the external clock signals CKo to CK3 of the reproduced signal of the reference clock signal based on the arithmetic output from the arithmetic means, External clock signal selection means is composed of the register 21, comparator 22, and controller 30, and selects and outputs an external clock signal from the external clock signal forming means corresponding to the maximum value detected by the maximum value detection means. It is composed of the selector 16, counter 17, controller 30, and register 31, and is composed of the difference between the sample value of the reproduced signal from the calculation means using the external clock signal selected by the external clock signal selection means and the maximum value detection means. A data reproducing means for reproducing data by comparing it with the maximum value of about 172 is comprised of registers 23 and 24, an arithmetic circuit 25, a comparator 26, and a controller 30.

As described above, the data reproducing device according to the present invention uses an external clock signal whose phase is corrected based on the reproduced signal of the reference clock signal actually recorded on the magneto-optical disc. It is possible to perform edge detection, that is, data reproduction, without being affected by differences in pit density between the outer and inner peripheries, environmental conditions during recording, differences in characteristics between data recording devices and data reproducing devices, and individual differences between disks. can. In addition, since the threshold value for edge detection is determined based on the reproduction signal of the reference clock signal actually recorded on the magneto-optical disk, it is possible to Data can be reproduced without being affected by individual differences. Furthermore, it is possible to further increase the noise margin by including the maximum value of the noise obtained from the reproduced signal of a certain level of the signal recorded on the magneto-optical disk into the dark value used for edge detection. Become.

Note that the present invention is not limited to the above embodiments,
For example, the frequency of the reference clock signal recorded on the magneto-optical disk may be set to a frequency other than the highest data recording frequency.

Furthermore, in consideration of the case where the external clock signal cannot be reproduced within one selector due to a defect in the reference clock signal recorded on the magneto-optical disk, for example, it is possible to reproduce the external clock signal using the reference clock signals of multiple selectors. The operation for forming the signal may be performed multiple times.

Furthermore, for example, the darkness value TH used for edge detection of the reproduced signal of the NRZI modulation method is expressed as T H= l SMAX
It may be set to 5HINl/2.

Further, in the above embodiment, an external clock signal whose phase has been corrected is used for edge detection. The presence or absence of a mark may be determined from a direct reproduction signal in synchronization with an external clock signal from a signal generator.

As is clear from the above description, according to the present invention, a reference clock signal for detecting phase information is recorded at the beginning of recorded data, and when data is reproduced, this reference clock signal is reproduced and referenced. By correcting the phase of the external clock signal based on the clock signal, it is possible to obtain an external clock signal with a large window margin, that is, suitable for data reproduction. In addition, even if data is recorded at high density on a magneto-optical disk that is rotated at a constant angular velocity (CAV), and the formed pits overlap, data can be reproduced using the external clock signal, which is faster than conventional disks. It is possible to perform data reproduction with a higher noise margin compared to the conventional method.

In addition, by correcting the phase of the external clock signal based on the reproduction signal of the reference clock signal actually recorded on the magneto-optical disk, it is possible to compensate for differences in the environmental conditions during recording, the characteristics of the recording device and the reproduction device, This makes it possible to reproduce data without being affected by individual differences. Furthermore, since an external clock method can be used, the modulation method can be freely selected.

〔Effect of the invention〕

According to the clock signal generator for data reproduction according to the present invention, a reference clock signal for detecting phase information is recorded at the beginning of recorded data, and a reproduction signal of this reference clock signal is also used during data reproduction. By correcting the phase of the external clock signal, it is possible to obtain an external clock signal with a large window margin, that is, suitable for data reproduction. Furthermore, it is possible to record data at high density on a magneto-optical disk that is rotated at a constant angular velocity (CAV), and to obtain an external clock signal that enables accurate data reproduction even when the formed pits overlap. I can do it. In addition, by correcting the phase of the external clock signal based on the reproduction signal of the reference clock signal actually recorded on the magneto-optical disk, it is possible to compensate for differences in the environmental conditions during recording, the characteristics of the recording device and the reproduction device, It is possible to obtain an external clock signal that enables data reproduction that is not affected by individual differences in data. Furthermore, since an external clock method can be used, the modulation method can be freely selected.

Further, according to the data reproducing device according to the present invention, a reference clock signal for detecting phase information is recorded at the beginning of recorded data, and when reproducing data, a reference clock signal is used based on the reproduced signal of this reference clock signal. By using an external clock signal whose phase has been corrected and determining the dark value for edge detection based on the maximum amplitude of the reproduced signal of this reference clock signal, a magneto-optical device that is rotationally driven at a constant angular velocity (CAV) is used. Even when data is recorded on a disk at high density and overlap occurs in the formed pits, data can be reproduced accurately. In addition, by correcting the phase of the external clock signal based on the reproduction signal of the reference clock signal actually recorded on the magneto-optical disk, it is possible to compensate for differences in the environmental conditions during recording, the characteristics of the recording device and the reproduction device, This makes it possible to reproduce data without being affected by individual differences.

[Brief explanation of drawings]

FIG. 1 is a block circuit diagram of a data reproducing device using a clock signal generator for data reproducing according to the present invention.
FIG. 2 is a diagram showing the recording format of a magneto-optical disk used in the data reproducing device, and FIG. 3 is a diagram showing the relationship between a reference clock signal, a reproduction signal of a constant level signal, and an external clock signal. FIG. 4 is a diagram for explaining the recording principle of a magneto-optical recording medium, FIG. 5 is a diagram showing pits formed on a magneto-optical disk using a constant angular velocity (CAV) drive method, and FIG. 6 is a diagram representing the pit shown in FIG. 5 on a time axis. FIG. 12...External clock generation circuits 13-15...Delay circuit 16...Selector 17...Counter 18...A/D converter 19.21.23.24.31...Register 20. 2
5...Arithmetic circuit 22.26...Comparator 30...Controller

Claims (2)

[Claims] (1) A clock signal generation device for data reproduction using a recording medium on which a reference clock signal is recorded, comprising an external clock signal forming means for forming a plurality of external clock signals having mutually different phases; and the external clock signal forming means. sampling means for sampling a reproduced signal of the reference clock signal using each external clock signal formed by the above, and a maximum value for detecting the maximum value of the difference between sample values corresponding to each of the external clock signals from the sampling means. A data reproducing device comprising: a detection means; and an external clock signal selection means for selecting and outputting an external clock signal from the external clock signal forming means corresponding to the maximum value detected by the maximum value detection means. clock signal generator. (2) A data reproducing device using a recording medium on which a reference clock signal having a frequency equal to the highest recording frequency of data is recorded, an external clock signal forming means for forming a plurality of external clock signals having mutually different phases; sampling means for sampling a reproduced signal reproduced from a recording medium using an external clock signal formed by the external clock signal forming means; and a calculating means for calculating a difference between sample values of the reproduced signal from the sampling means. , maximum value detection means for detecting the maximum value of the difference between sample values corresponding to each of the external clock signals of the reproduced signal of the reference clock signal based on the calculation output from the calculation means; an external clock signal selection means for selecting and outputting an external clock signal from the external clock signal forming means corresponding to the maximum value determined by the external clock signal; and an arithmetic operation means using the external clock signal selected by the external clock signal selection means. a data reproducing device for reproducing data by comparing the difference between the sample values of the reproduced signal from the maximum value detecting means and a value that is about 1/2 of the maximum value from the maximum value detecting means. .