JP3042069B2 - recoding media - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording medium suitable for application to a magneto-optical disk on which digital data is recorded.

[0002]

2. Description of the Related Art An optical disk is irradiated with a laser beam,
An optical disc apparatus that reads data recorded on an optical disc based on the intensity of the return light, phase change, and the like, performs high-density recording on the optical disc, and performs bit rate (minimum bit) of data recorded on each track of the optical disc. The spatial frequency) increases, and the reproduction margin in the data detection circuit of the reproduction system, that is, the phase margin (detection window margin)
Becomes narrower.

In particular, in the disc of CAV (constant angular velocity control) the rotational speed at the time of recording and reproducing is constant, the track T _in the inner circumferential side of the track T _out of the outer peripheral side of the disc D as shown in FIG. 6 The bit rate of the data recorded on the disc increases with the radii r ₁ and r ₂ of the disc, and the inter-symbol interference of the reproduced data increases toward the inner circumference of the disc.

Therefore, as shown in FIGS. 7A, 7B, and 7C, the eye pattern of the reproduced RF signal becomes narrower as the track moves from the outer track to the inner track, and is detected from this eye pattern. The error rate of data tends to decrease.

[0005] FIG. 8 shows an NRZ sequence (Non-Non-Zero) that allows relatively high-density recording on an optical disk having a fixed rotation angle.
(Return to Zero) data is recorded on the recording surface of the disk at the same clock rate, and the trend of the phase margin (detection window margin) when the reproduced RF signal is digitized by the binary detection circuit to detect the data is shown by a solid line. A, the horizontal axis represents the recording density in _terms of the pit length λ (μm) of the minimum bit P _min , and the vertical axis represents R with the center of the eye pattern as the threshold level.
FIG. 14 shows a change in a phase margin of a clock when binary data is detected from the F signal. FIG. Here, the phase margin indicates a margin for a data phase shift. For example, a phase margin of 0.4 can accurately detect data even if the phase of reproduced data is shifted by 0.4 bits (in this example, a data error). Rate 1
× 10 ⁻⁵ or less).

As can be seen from this figure, in the outer track where the minimum data bit interval is about 1 μm, the eye pattern of the reproduced RF signal is A in FIG. 7, and the phase margin for detection is about 0. 8, when the minimum bit interval approaches 0.5 μm on the inner peripheral side of the optical disk, the eye pattern of the reproduced RF signal becomes as shown in FIG. 7C, and the phase margin for detection is obtained. Rapidly decreases to 0.5 or less. The phase margin indicates an allowable range of the phase of the detection window so that the error rate (error rate) of the data at the time of reproduction becomes equal to or less than a predetermined value.

[0007]

Therefore, the detection circuit for detecting the reproduced data from the disk at a constant angular velocity rotation as described above performs signal reproduction so that the data error rate becomes, for example, 1 × 10 ^-5 or less. To do so, the phase margin on the inner circumference side of the disk becomes extremely strict, which leads to quality control of the optical disk, an increase in the cost of the reproducing circuit, and the like.

Further, since the recording capacity of the entire optical disc is limited by the recording density on the inner peripheral side, the data capacity recorded on one optical disc is limited by the recording surface density on the inner peripheral side. It couldn't be higher.

In order to solve this problem, the present applicant has previously disclosed in Japanese Patent Application No. 2-320768 a circuit for detecting reproduced data by binary detection, and a ternary circuit utilizing intersymbol interference due to a partial response. A reproduction method has been proposed in which a circuit for detecting reproduction data by detection is switched between an outer peripheral side and an inner peripheral side of a disk for reproduction. According to this reproducing method, reproduced data is detected by binary detection for an outer track having a relatively low recording density, and reproduced data is detected by ternary detection for an inner track having a relatively high recording density. Even in the case where the density recording is performed, the reproduction data can be favorably detected from the outer periphery to the inner periphery. That is,
FIG. 8 shows the change in the phase margin in the case where the ternary detection by the partial response is performed, as indicated by a broken line B. At a certain bit interval or less, the phase margin is secured as compared with the ordinary binary detection, and the change in the recording density is higher. In the track on the peripheral side, the phase margin is secured by the ternary detection based on the partial response. Therefore, by switching between binary detection and ternary detection, data detection with a good phase margin becomes possible.

[0010] However, the reproducing apparatus which can cope with the two kinds of reproducing methods has a problem that the configuration becomes complicated. That is, it is necessary to prepare both data detection circuits, a circuit for detecting the reproduced data by binary detection and a circuit for detecting the reproduced data by ternary detection by the partial response, and the circuit scale of the reproducing apparatus becomes large. Would.

In view of the foregoing, it is an object of the present invention to provide a recording medium of this kind which can reproduce data recorded at high density with a simple structure.

[0012]

According to the present invention, for example, as shown in FIG. 1, a predetermined number of zones A, B # are divided in a radial direction, and at least a rotation is performed at a constant speed in each zone to reproduce the data. At the same time, in a disk-shaped recording medium for recording digital data having a different clock rate for each zone, a reproduced signal is compared with two different threshold levels to detect two series of digital data. In this case, the vicinity of a portion where the reproduction margin becomes equal to or less than a predetermined value when performing ternary detection for detecting the reproduction data from is set at the boundary of each zone.

[0013]

According to the present invention, the data recording state in all the zones is set by setting the boundary of each zone near a point where the reproduction state in the data detection by the ternary detection becomes a predetermined value or less. , It can be set so that it can be satisfactorily reproduced only by data detection by ternary detection, and data recorded at high density can be satisfactorily reproduced by a single reproduction method.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS.

First, the configuration of the disk of this embodiment will be described. In this example, the present invention is applied to a magneto-optical disk on which data is recorded and reproduced by the magneto-optical effect, and the zoning recording is performed on this magneto-optical disk.

That is, as shown in FIG. 1, a plurality of tracks are formed concentrically on one magneto-optical disk, and the plurality of tracks are divided into a zone A and a zone B. In this case, zone A is near the center. The range of each zone is set based on a data detection state described later.
Here, according to this setting, for example, when the size of the magneto-optical disk is 32 mm in radius, the range of zone A is 16 to 22 mm in radius, and the range of zone B is 22 mm to 30 mm in radius. In each zone, data recording / reproducing (ie, CA) is performed at a constant rotation speed.
In this example, zoning recording in which the recording density is changed by changing the clock rate of the recording data for each zone is performed.

In each of the annular tracks arranged in the zones A and B, one track is divided into predetermined segments (the number of segments in one track is the same in all zones), and several tens of segments are defined as one unit. A sector is configured. That is, several tens of sectors are arranged in one track, and several tens of segments are arranged in each unit sector. And
When recording data, data is recorded in units of this sector.

Each unit segment is composed of a servo area and a data area. The servo area of each segment is a so-called pre-pit in which data is previously recorded in pits on the disk.
At the time of reproduction, sample servo control for tracking is performed by the data of the pre-pits. Also, a track address and a sector address are recorded as data based on the pre-pits, and are used at the time of search. Then, predetermined bytes of data are recorded in the data area following the servo area by the magneto-optical effect. In this case, the recording capacity of the data area of each segment differs for each zone. This difference in recording capacity for each zone is caused by a difference in recording clock rate in each zone. That is, the zoning recording sets the linear recording density of the innermost track of each zone to be almost the same, and the recording capacity of the data area of each segment changes for each zone by such setting.

The modulation method of data recorded in the data area of each zone is NRZ suitable for high-density recording.
(Non Return to Zero) is pre-encoded as NRZI (NRZ Inverted).

Here, zones 2 and 2 are assigned to zones A and B in this manner.
The setting of the boundary between the two zones in the case of division will be described. The data recording density of the innermost track in each zone is made substantially equal as described above. At this time, the data recording density of the innermost track of each zone is set to have a constant phase margin when the recording data is detected by the ternary detection of the partial response class 1. That is, when the data is reproduced by the ternary detection of the partial response (PR), as shown by the curve B in FIG. 8 described above, the peak margin decreases around the certain value before and after the certain value. Becomes Here, in this example, the phase margin in the ternary detection is set to be equal to or more than a certain value. As shown in FIG. 2, the phase margin of the innermost track of zone A and the outermost track of zone A The phase margins of the tracks are made equal, and the phase margin of the innermost track in zone B is also made equal to these phase margins. Accordingly, the phase margin between the innermost track and the outermost track in each zone is the worst, and the track in the substantially middle portion of each zone has the phase margin. Then, the value in the state where the phase margin is the worst is set to such an extent that normal data reproduction can be performed (the reference level indicated by a broken line in FIG. 2: a value slightly exceeding the phase margin 0.4). However, in the case of data detection by the ternary detection of the partial response class 1, the change in the phase margin is small, and in fact, the change amount of the phase margin due to the difference in the track is small. Although not shown, when the recorded data of each track in each zone is reproduced by normal binary detection, the phase margin is equal to or lower than the reference level. In other words, the data recording state in each zone is high-density recording such that data cannot be properly reproduced by ordinary binary detection.

The phase margin described here changes according to the error rate (error rate) of the reproduced data.
The change in the phase margin and the change in the error rate are in a certain proportional relationship. Therefore, it is the same as determining the configuration of each zone so that the error rate of the reproduction data is equal to or less than a certain value.

Next, the configuration of the reproducing apparatus of the present embodiment for reproducing data using the magneto-optical disk configured as described above will be described with reference to FIG.

In FIG. 3, reference numeral 1 denotes a magneto-optical disk driven by a spindle motor 2 so that the rotation angle is constant, and 3 denotes a laser light source for irradiating the magneto-optical disk 1 with a laser light output and a laser light source of the laser light. The optical head includes an optical system element for reading recorded data from reflected light. The magneto-optical disk 1 here is divided into two zones A and B to perform zoning recording, as shown in FIG. 1 described above.

The RF reproduced from the optical head 3
After the signal is output through the RF signal amplifier 4, the signal is supplied to the equalizer 5 where the signal is shaped.

The reproduced RF output from the equalizer 5
The signal is supplied to a data detection circuit 10 to be described later and binary digital data is reproduced. A part of the signal is supplied to a clock detection circuit 7 to detect a clock signal of a recording data string, The detected clock signal is supplied to the spindle servo circuit 8, and controls the rotation of the spindle motor 2.

In this case, in the present embodiment, since the above-described zoning recording is performed on the magneto-optical disk 1, a clock having a different frequency is formed in each zone. That is, since the recording clock rate for the data area of each zone is different, a clock corresponding to the recording clock rate of each zone is generated. The generation of the clock by the clock detection circuit 7 is performed by converting the detection data of the servo area into a frequency signal of a predetermined multiple by a PLL circuit (phase locked loop circuit).

Returning again to the description of the reproduction system circuit with reference to FIG. 3, tracking control and focus control for the optical head 3 are also performed by detecting sample servo pits formed together with the above-mentioned clock pits and tracking error. This is performed by an output signal of the servo circuit 6 which forms a signal and a focus error signal.

As a detection circuit for extracting data from the RF signal reproduced from the track on the disk 1, the reproduced RF signal is extracted from two digital signals binarized by comparing with two different threshold levels. A partial response ternary detection circuit 10 (hereinafter referred to as a PR ternary detection circuit) for forming detection data from a series of pulse trains is provided. Then, the PR3 value detection circuit 10
The detection data detected in step (1) is supplied to a subsequent circuit (not shown) such as an error correction circuit via a terminal 9.

Here, a specific configuration of the PR ternary value detection circuit 10 is shown in FIG.

In FIG. 4, comparators 11 and 12 each use a first threshold signal E _th A and a second threshold signal E _th B as comparison values, 13 a NOR circuit,
Reference numerals 14, 15, and 16 denote D-flip-flop circuits.

The operation of the PR tri-state detection circuit 10 is shown in FIG.
The data recorded in the NRZI code is MTF (Mo) on the inner circumference side of the disk.
Duration Transfer Function
With the decrease in n), the peak value of the single pulse reproduction waveform RF _(in) decreases as shown in the figure, and the edge of the reproduction RF signal expands. Therefore, "1", but increases the peak level P ₂ of the portion to be continuous, that "0" data contained in the successive "1" is not reduced to the foot of a single "1" data Become.

In such a reproduced RF signal, the central eye pattern is reduced as shown in FIG. 7C.

In the PR ternary value detection circuit 10 of the present embodiment, such a reproduced RF signal RF _(out) has two comparators using the first threshold signal E _th A and the second threshold signal E _th B as comparison voltages. It is supplied to the 11 and 12 outputs a pulse P _a and P _B of two series by being sliced by the comparative voltage.

Further, from the two pulse trains P _A and P _B ,
By taking the logical sum by the NOR circuit 33, a composite pulse train P _{A + B} is obtained.

The synthesized pulse train P _{A + B} is extracted by the D-flip-flop 14 to which the inverted clock CLKI in which the phase of the clock signal CLK is shifted by 90 ° is supplied, and becomes data D ₁ . Further, the data D ₁
It is D- In the flip-flop 15, is a 1-bit delayed data D _2, the detection data D _out obtained by being extracted again by the clock CLK.

Since the PR tri-level detection circuit 10 slices the reproduced RF signal in which intersymbol interference has occurred by setting the two threshold levels E _th A and E _th B as described above, It becomes easy to detect an eye pattern that is difficult to remove by ordinary binary detection based on the threshold level of the threshold level, and the phase margin is also determined by setting the threshold levels (E _th A, E _th B) at appropriate positions. Can be wider.

In this embodiment, as described above, the phase margin when the data adjacent to the boundary of each zone of the magneto-optical disk 1 is reproduced by the ternary detection is as follows.
Since the reference level is set to be constant, the data is detected by the ternary detection of the partial response in each zone, so that a sufficient phase margin is secured and good data can be detected. Therefore, the partial response 3
Good data detection becomes possible only by value detection, and it is not necessary for the reproducing apparatus to include a binary detection circuit. In this case, 3
Since the recording density at which a good phase margin can be secured when data is detected by value detection is higher than the recording density at which a good phase margin can be secured when ordinary binary data is detected, data recording in each zone is performed. The density can be increased, and high-density recording can be performed.

The PR ternary detection circuit described in the above embodiment is also called a partial response class 1 or a duobinary detection circuit. However, the present invention is not limited to the above embodiment, and the ternary detection using intersymbol interference can be performed. As long as the detection is performed, a detection circuit using another partial response may be used.

In the above embodiment, the zoning recording is divided into two zones. However, the present invention can be applied to the zoning recording divided into two or more zones.

The specific numerical value of the radius of the boundary between the zones is only an example in the above-described embodiment, and varies depending on the actual data recording state such as the recording density. By determining the phase margin in the case of ternary detection as described above, a specific numerical value at the boundary of each zone is determined. In this case, even if the boundary of each zone is slightly shifted from the position of the reference level, there is almost no problem in actual reproduction, and there is no problem.

Further, in the above-described embodiment, the phase margin is obtained and the boundary of each zone is set. However, the boundary may be set based on another reproduction condition (reproduction margin). For example, a portion where the error rate of the reproduction data exceeds a certain reference level may be set as the boundary of each zone.

Further, the recording medium to which the present invention is applied is not limited to an optical disk or a magneto-optical disk, but can be applied to various types of rotating recording media whose linear velocity changes relatively.

[0043]

According to the present invention, the boundary of each zone is
Since the reproduction state in the data detection by the ternary detection is set in the vicinity of a portion where the reproduction state is equal to or less than the predetermined value, the recorded data in all the zones can be reproduced well only by the data detection by the ternary detection. For this reason, the reproducing apparatus for reproducing the recording medium of the present invention reproduces the recording medium on which high-density recording is performed, but only has to perform data detection by ternary detection, and the configuration is simplified. can do.

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating a zoning recording state according to an embodiment of the present invention.

FIG. 2 is a characteristic diagram showing a data detection state according to one embodiment.

FIG. 3 is a configuration diagram showing a recording medium reproducing apparatus according to an embodiment.

FIG. 4 is a configuration diagram showing a main part of the playback device shown in FIG. 3;

FIG. 5 is a timing chart showing a ternary detection state according to one embodiment;

FIG. 6 is a configuration diagram showing a track formation state of an optical disc.

FIG. 7 is an explanatory diagram showing an eye pattern of a reproduction signal.

FIG. 8 is a characteristic diagram illustrating a change in a phase margin depending on a detection state.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Magneto-optical disk 3 Optical head 7 Clock detection circuit 10 Partial response ternary detection circuit

Continuation of the front page (56) References JP-A-2-18969 (JP, A) JP-A-3-19172 (JP, A) JP-A-59-178628 (JP, A) JP-A-5-54386 (JP) (A) JP-A-4-192161 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G11B ^7/ 00-7/013 G11B 11/10 586 G11B 20/10 321

Claims (1)

(57) [Claims] 1. A disk-shaped recording medium which is divided into a predetermined number of zones in a radial direction, is rotated at least in each zone at a constant speed, is reproduced, and records digital data having a different clock rate for each zone. The reproduced signal is compared with two different threshold levels, two series of digital data are detected, and the reproduction margin for performing ternary detection of detecting the reproduced data from the two series of digital data is equal to or less than a predetermined value. A recording medium in which the vicinity of a location is set at the boundary of each zone.