JP3511657B2 - Optical disk reproducing apparatus and optical disk reproducing method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk reproducing apparatus, a recording medium, and an optical disk reproducing apparatus for reproducing data by reading a reproduction signal from a magneto-optical disk having a magnetic film whose properties change in response to temperature changes. Regarding the method.

[0002]

2. Description of the Related Art For an optical disc on which data is recorded and reproduced by magneto-optical interaction, a wavelength higher than an optical limit determined by the wavelength of a laser beam used for recording and reproducing data on the optical disc and the characteristics of an objective lens. As an optical disk reproducing method (super-resolution reproducing method) capable of density recording and reproducing, for example, Japanese Patent Application Laid-Open No. HEI 1
-143042, JP-A-3-97140,
The one disclosed in Japanese Patent Laid-Open No. 3-88156 is known. These optical disc reproducing methods control the size of recording magnetic domains (pits or marks) formed in the magnetic film or the direction of the magnetic field by changing the temperature of the magnetic film of the optical disc, and A reproduction signal is obtained by irradiating a laser beam on the surface of the object and by magneto-optical interaction.

Further, for example, the phase pit type optical disk reproducing method disclosed in Japanese Patent Laid-Open No. 3-292632 is a method used for an optical disk for reproduction only,
Irregularities are formed on the light-reflecting layer of the optical disk, and the irregularities are irradiated with a laser beam to obtain a reproduction signal from the reflected light. Similar to the method of controlling the size of the recording magnetic domain by changing the temperature of the magnetic film as described above, also in the phase pit method, a material whose reflectance is changed by temperature in the light reflecting layer of the optical disk, or a photon amount of which exceeds a certain level By using a material having a dye that is decolorized when it becomes unfavorable, it is possible to perform high-density recording and reproduction exceeding the optical limit even in the phase pit system.

[0004]

However, there is an asymmetry between the rising waveform and the falling waveform of the reproduction signal obtained from the optical disk. The asymmetry of the reproduced signal waveform is mainly due to the size of the spot of the reproducing laser beam on the magnetic film of the optical disk reproducing device. Moreover, the size of the laser beam spot on the magnetic film changes depending on various conditions such as the output of the laser beam, the characteristics of the magnetic film of the optical disk, and the temperature change of the optical disk due to the change of the ambient temperature. As described above, when the reproduced signal has asymmetry, there is a problem that the reliability of the reproduced data obtained by identifying the reproduced signal decreases, and it becomes difficult to improve the storage density of the optical disc. Also,
As described above, since the asymmetry of the reproduction signal changes depending on various conditions, there is a problem that it is difficult to perform the equalization process for removing this asymmetry.

The optical disk reproducing apparatus of the present invention has been made in view of the above-mentioned problems of the prior art, and compensates the asymmetry of the reproduced signal by an appropriate equalization process to improve the reliability of the reproduced data. Is possible, and in addition,
To improve the storage density of an optical disk and an object thereof is to provide an optical disk reproducing apparatus and method capable. It is another object of the present invention to provide an optical disk reproducing apparatus and method capable of adaptively equalizing a reproduced signal and appropriately compensating for the asymmetry of the reproduced signal.

[0006]

According to a first aspect of the present invention, by changing the temperature of a magnetic film of a recording medium in which a recording magnetic domain having a predetermined pattern is formed in advance, the magnetic property is improved. the size of the recording magnetic domain formed in the film, or to control the direction of the magnetic field, a reproduction signal generating means for generating a reproduction signal from the recording magnetic domain by using the magneto-optical interaction in the recording magnetic domain, at least the Adjust the amplitude of the playback signal waveform
Transfer function with a coefficient that adjusts the phase linearity
In equalization characteristic which is defined by the number, the wave of the reproduced signal
Waveform equalization means for performing shape equalization processing, the reproduced signal
The reproduction detected based on the clock signal extracted from
At the rising and falling transition points of the signal
Asymmetrical detection means for comparing the amount of change in the reproduction signal ,
A recording domain corresponding to a predetermined recording magnetic domain of the recording medium is reproduced.
At least the predetermined pattern based on the waveform of the raw signal
It corresponds to the reproduction signal from the recording magnetic domain corresponding to the recording magnetic domain.
The equalization characteristic of the waveform equalizing means is determined by the asymmetry detecting means.
Based on the comparison result of the change amount of the reproduction signal calculated in
A function for adjusting the amplitude of the waveform of the reproduction signal of the transfer function
Equalization to change the number and coefficient to adjust the phase linearity
And a characteristic changing means comprises a waveform equalizing means,
An optical disk reproducing device is provided.

[0007]

According to a second aspect of the present invention, the size of the recording magnetic domain formed in the magnetic film is changed by changing the temperature of the magnetic film of the recording medium in which the recording magnetic domain having a predetermined pattern is formed in advance. Alternatively, a reproduction signal generating step of generating a reproduction signal from the recording magnetic domain by using the magneto-optical interaction in the recording magnetic domain by controlling the direction of the magnetic field, and a coefficient for adjusting at least the amplitude of the waveform of the reproduction signal. And a waveform equalization step of performing a waveform equalization process of the reproduction signal with an equalization characteristic defined by a transfer function having a coefficient for adjusting phase linearity, based on a clock signal extracted from the reproduction signal. Asymmetry detecting step of comparing the change amounts of the reproduction signal at the rising change point and the falling change point of the reproduction signal detected by Comparison of the amount of change in the reproduction signal calculated in the asymmetry detection step, based on the waveform of the reproduction signal corresponding to the magnetic domain, of the equalization characteristic with respect to the reproduction signal from the recording magnetic domain corresponding to the recording magnetic domain of at least the predetermined pattern. An optical disc having a waveform equalization step, which comprises a coefficient for adjusting an amplitude of a waveform of the reproduction signal of the transfer function and an equalization characteristic changing step for changing a coefficient for adjusting the phase linearity based on the result. A playback method is provided.

[0009]

The reproducing signal generating means controls the temperature of the magnetic film of the optical disk in which the recording magnetic zone formed on the magnetic film expands and contracts according to the temperature of the magnetic film, optically reads this optical disk, and further, the optical disk. The optical signal read from the device is converted into an electrical reproduction signal. The waveform equalizing means equalizes the reproduction signal with equalization characteristics adapted to the waveform of the reproduction signal. By these means, the reproduction signal asymmetry is adaptively performed with the optimum equalization characteristic in order to eliminate the asymmetry of the reproduction signal that varies depending on the location or the factors such as the variation of the optical disc. Eliminates the adverse effects that will have on the restoration of reproduced data.

The above-mentioned waveform equalizing means has an equalizing characteristic changing means for always performing equalizing of the reproduced signal with an equalizing characteristic optimum for removing the asymmetry of the reproduced signal. The means detects the asymmetry of the reproduced signal by comparing the amount of change of the reproduced signal at the rising point and the falling point,
The equalization characteristic of the waveform equalizer is changed based on the detected asymmetry of the reproduced signal.

In the above-mentioned recording medium (optical disk), the recording magnetic domain formed in the magnetic film expands or contracts depending on the temperature of the magnetic film, and in order to obtain a reproduction signal waveform for detecting the asymmetry of the reproduction signal. Of recording magnetic domains of a predetermined pattern. The optical disk reproducing device for reproducing this recording medium equalizes the reproduced signal by the equalization characteristic adapted to the waveform of the reproduced signal corresponding to the predetermined pattern.

[0012]

[Embodiment 1] The configuration and operation of an optical disk reproducing apparatus 1 of the present invention will be described below with reference to FIGS. 1 to 6 as a first embodiment. FIG. 1 is a diagram showing the configuration of an optical disk reproducing apparatus 1 of the present invention in the first embodiment. FIG. 2 is an equalizing circuit 1 of the optical disc reproducing apparatus 1 of the present invention shown in FIG.
It is a figure which shows the structure of 6. FIG. 3 shows frequency characteristics of equalized output amplitude (reproduction signal input amplitude) of the pulse slimmer 160 shown in FIG. FIG. 4 shows the pulse slimmer 1 shown in FIG.
The frequency characteristic of the equalization output phase (reproduction signal input phase) of 60 is shown.

FIG. 5 shows a case in which the mark is read by raising the temperature of the rear portion of the reproduction spot (FAD; Front Ap).
(A) shows the waveform of a reproduction signal obtained in the (Aurture Detection), where (A) shows the relationship between the temperature rising part of the reproduction spot, the traveling direction of the optical disc, and the mark, and (B) shows (A). The waveform of the reproduction signal obtained from the indicated mark is shown. FIG. 6 shows a case where the temperature of the front portion of the reproduction spot is raised to read the mark (RAD;
(A) shows a waveform of a reproduction signal obtained in r Aperture Detection), where (A) shows a temperature rise portion of a reproduction spot, a traveling direction of an optical disc, and a relationship with a mark, and (B) shows (A). The waveform of the reproduction signal obtained from the mark shown in FIG.

First, the configuration of the optical disk reproducing apparatus 1 will be described with reference to FIG. Since the optical disc reproducing apparatus of the present invention described below relates to the reproduction of data, the portion related to data recording in the optical disc reproducing apparatus 1 is omitted. The optical disc reproducing device 1 is a device for reading the optical disc 10 in which data is recorded at a recording density equal to or higher than the optical limit and restoring reproduced data. The optical disc 10 records data by magneto-optical interaction,
Also, in an optical disc to be reproduced, the recording magnetic domain formed in the magnetic film can be expanded and contracted, or the direction of the magnetic field can be reversed by changing the temperature of the magnetic film of the optical disc. However, in each of the following embodiments, the case where the recording magnetic domain can be expanded and contracted will be described as an example. The optical disc reproducing apparatus 1 controls the output of the laser beam applied to the optical disc 10 and the position of the spot on the optical disc 10 to control the properties of the recording magnetic domains as described above, and optically writes and reads data. As a result, it is possible to record and reproduce data at a recording density higher than the optical limit of the recording density determined by the wavelength of the laser beam used in the optical disc 10 and the characteristics of the objective lens.

The photodetector (PD) 12 is, for example, a 4-division type photodetector composed of a photodiode or the like, and the laser beam applied to the optical disk 10 causes magneto-optical interaction in the recording magnetic domain of the optical disk 10. Optical signal (reproduced optical signal) generated by being reflected by the
Of the preamplifier circuit 14 as an electrical reproduction signal
To enter. The preamplifier circuit 14 amplifies the reproduction signal input from the photodetector 12, and further, a sum signal (RF signal) used to restore the reproduction data from the reproduction signal.
And a servo signal used for tracking servo, and the RF signal of these signals is input to the equalization circuit 16.

The equalization circuit 16 performs equalization processing on the waveform of the RF signal and inputs the equalized RF signal to the comparison circuit 18. The equalization processing in the equalization circuit 16 will be described below. The recording magnetic area of the optical disc 10 is long (long mark)
In this case, the amplitude of the RF signal becomes large, and when it is short (short mark), the amplitude of the RF signal becomes relatively small. The equalizing circuit 16 increases the amplitude of the RF signal corresponding to the short recording magnetic domain so that the RF signal corresponds to the amplitude of the RF signal corresponding to the long recording magnetic domain, and is reproduced by the equalizing circuit 16 and thereafter regardless of the length of the recording magnetic domain. Keep data error rates low. The operation of the equalization circuit 16 is called boost. The equalization circuit 1
The configuration and operation of 6 will be described later with reference to FIG.

The comparison circuit 18 compares the voltage of the RF signal after the waveform equalization processing with the voltage of a predetermined threshold value, discriminates it into a binary value, and outputs the data sample circuit 20 as a digital RF signal in a digital format. , To the clock extraction circuit 22. That is, the logical value 1 is output when the voltage of the RF signal is higher than the threshold value, and the logical value 0 is output when the voltage is low. The clock extraction circuit 22 generates a clock signal used to restore the reproduction data synchronized with the digital RF signal. The data sampling circuit 20 is a digital RF
The signal is sampled in synchronism with the clock signal to restore the reproduced data and output as output data, for example, to a data decompressor (not shown) provided after the optical disc reproducing apparatus 1.

The structure of the equalizing circuit 16 will be described below with reference to FIG. As shown in FIG. 2, the equalization circuit 16 includes a pulse slimmer circuit 160 and a low pass filter (LP).
F) 162. Pulse slimmer circuit 160
Has a characteristic represented by a transfer function F (s) expressed by the following equation, and performs the above-described boosting process on an input RF signal to generate an RF signal corresponding to a short mark and a long mark on the optical disc 10. Low pass filter 162 with the same amplitude
To enter.

[0019]   F (s) = (1 + s / Kl) (1-s / Kt) (1)

Specifically, as the one used for the pulse slimmer circuit 160, for example, IMP42C4 manufactured by IMP Co., Ltd.
55 etc. can be mentioned. Low pass filter 162
Of the RF signal, which is boosted by the pulse slimmer circuit 160, passes only a signal component having a frequency equal to or lower than a predetermined frequency and is input to the comparison circuit 18.

The characteristics of the equalizing circuit 16 will be described below with reference to FIGS. 3 and 4. R after equalization by the equalization circuit 16
As for the amplitude characteristic of the F signal output, as shown in FIG. 3, the frequency characteristic of the amplitude of the output signal of the equalization circuit 16 (equalized output amplitude) becomes large in a predetermined frequency region a. That is, the equalization circuit 16 emphasizes the high frequency band of the RF signal. The frequency characteristic of the amplitude of the output signal of the equalization circuit 16 is determined by the parameter (coefficient) of Expression 1. That is, the parameter K
When either or both of l and Kt become large, the swelling in the frequency domain a becomes high. That is, in this case, the enhancement of the high frequency band of the RF signal by the equalization circuit 16 becomes weak. Conversely, when either or both of the values of the parameters Kl and Kt become small, the frequency domain a
The swell in is small. That is, in this case, the enhancement of the high frequency band of the RF signal by the equalization circuit 16 becomes weak.

Further, as shown in FIG.
The phase of the F signal is corrected. Here, the phase characteristic of the RF signal output after the equalization by the equalization circuit 16 is also determined by the parameters Kl and Kt of the equation 1 as shown in FIG. That is, when the relationship between the parameters Kl and Kt is Kl> Kt, the equalization circuit 1 is used in the high frequency region as shown by the curve a.
The phase (equalization output phase) delay of the output signal of 6 becomes blunt and K
When l = Kt, the phase delay of the output signal of the equalization circuit 16 increases proportionally in the entire frequency region as shown by the curve b, and when Kl <Kt, the frequency increases as shown by the curve c. In the area, the phase delay of the output signal of the equalization circuit 16 becomes larger. Therefore, by appropriately setting the values of the parameters Kl and Kt for the equalization circuit 16, the boost amount for the RF signal and the phase linearity of the RF signal can be adjusted. Therefore, it is possible to adjust the asymmetry of the waveform of the RF signal shown in FIGS. 5 and 6 and described later.

The waveform of the RF signal input to the equalizing circuit 16 will be described below with reference to FIGS. 5 and 6. First, the waveform of the RF signal in the case of FAD will be described with reference to FIG. In the case of FAD, as shown in FIG. 5A, the recording magnetic domain a, the low temperature portion b of the laser spot d, and
The temperature raising part c is located. That is, the optical disc 10 is shown in FIG.
Since it rotates in the direction shown by the arrow in (A), FIG.
With respect to the recording magnetic domain (mark) a shown in FIG. 5A, the temperature rising portion c of the laser spot d shown as a shaded portion in FIG. 5A is located rearward, and the low temperature portion b is located forward. Here, since the recording magnetic domain of the magnetic film of the optical disk 10 shrinks when the temperature is high and expands when the temperature is low, it is possible to obtain the RF signal corresponding to the mark in the low temperature part b.
Therefore, as shown in FIG. 5B, the waveform of the RF signal corresponding to the recording magnetic domain a has a gentle rising portion e and a steep falling portion f.

Next, the waveform of the RF signal in the case of RAD will be described with reference to FIG. In the case of RAD, as shown in FIG. 6A, the recording magnetic domain a and the laser spot d
The low temperature part b and the temperature rising part c are located. That is, since the optical disc 10 rotates in the direction shown by the arrow in FIG. 6A, the laser spot shown as a shaded area in FIG. 6A is recorded with respect to the recording magnetic domain (mark) a shown in FIG. 6A. d
The temperature raising part c is located in the front and the low temperature part b is located in the rear. Here, as described above, the recording magnetic domain of the magnetic film of the optical disc 10 is contracted when the temperature is high and expanded when the temperature is low, so that the RF signal corresponding to the mark can be obtained at the low temperature portion b. Therefore, as shown in FIG. 6B, in contrast to the case of FAD, R corresponding to the recording magnetic domain a.
In the waveform of the F signal, the falling portion f is gentle and the rising portion e is steep. The difference between the rising and falling points of the RF signal (reproduction signal) as described above is called RF signal asymmetry.

The operation of the optical disc reproducing apparatus 1 will be described below. The reproduction optical signal obtained from the optical disk 10 is converted into an electric reproduction signal by the photodetector 12 and input to the preamplifier circuit 14. The preamplifier circuit 14 separates the RF signal (sum signal) and the servo signal from the reproduction signal, and inputs only the RF signal to the equalization circuit 16. The equalization circuit 16 aligns (equalizes) the amplitude of the waveform corresponding to the short mark and the amplitude of the waveform corresponding to the long mark of the RF signal.
Input to the comparison circuit 18. The comparison circuit 18 is equalized R
The voltage of the F signal is compared with a predetermined threshold value, binarized and inputted to the data sampling circuit 20 and the clock extraction circuit 22 as a digital reproduction signal. The data sampling circuit 20 samples the output signal of the comparison circuit 18 based on the clock signal generated by the clock extraction circuit 22, restores the reproduced data, and outputs the reproduced data as output data.

As shown in FIGS. 5 and 6, in the super-resolution reproducing system using the optical disk 10 in which the size of the recording magnetic domain is controlled by the temperature, the RF signal (reproducing signal) is asymmetrical. Will be generated. When the reproduction data is reproduced from the RF signal that has the asymmetry, problems such as increase in intersymbol interference and decrease in clock phase margin occur. Equalization circuit 1
6, the high frequency characteristic is emphasized with respect to the RF signal having asymmetry, and the phase linearity is adjusted to equalize the RF signal and improve its symmetry.

Since the optical disc reproducing apparatus 1 equalizes the RF signal to improve the symmetry and restores the reproduced data, intersymbol interference caused by the asymmetry of the RF signal in the super-resolution reproducing system, and , The phase margin of the clock signal reproduced from the RF signal can be improved.
Therefore, the reliability of the reproduction data reproduced from the optical disc 10 by the optical disc reproducing device 1 is improved. Although the above-mentioned optical disk reproducing apparatus 1 reproduces an optical disk for controlling the size of the recording magnetic domain, the optical disk reproducing apparatus 1 is also applied to an optical disk reproducing apparatus of the type that controls the direction of the magnetic field of the recording magnetic domain to read the reproduction signal. Of course you can
It can also be applied to a phase pit type optical disc reproducing apparatus by appropriate modification.

[0028]

Second Embodiment Hereinafter, as a second embodiment, FIGS.
The configuration and operation of the optical disc reproducing apparatus 3 of the present invention will be described with reference to FIG. By the way, in the optical disc reproducing apparatus 1 shown in the first embodiment, the asymmetry of the RF signal (reproducing signal) is mainly determined by the size of the mask formed in the temperature rising portion of the laser beam spot of the optical disc 10.
The size of this mask is determined by the output of the laser beam applied to the optical disc 10 to obtain the reproduction optical signal, the size of the spot of the laser beam on the optical disc 10, the characteristics of the magnetic film of the optical disc 10 due to variations in manufacturing, Also, it varies depending on the temperature of the optical disk 10 and the like which change depending on the temperature of the outside air and the like.

In the optical disc reproducing apparatus 1 of the present invention in the first embodiment, the asymmetry of the reproduced signal is different depending on various conditions as described above, whereas the transfer function F (s) shown in the equation 1 is used. Since the parameters K1 and Kt are fixed, there is a problem in that it is not possible to avoid problems such as an increase in intersymbol interference and a decrease in clock phase margin when the above-mentioned conditions are different. The optical disk reproducing apparatus 3 of the present invention in the second embodiment is an apparatus which reproduces data from an optical disk by the super-resolution reproducing system similarly to the optical disk reproducing apparatus 1, and the coefficient of the transfer function of the equalization circuit, that is, the expression Parameters Kl and Kt shown in 1
Is adaptively changed according to the waveform of the RF signal (reproduction signal) so that good equalization processing can always be performed on the RF signal.

The configuration of the optical disk reproducing apparatus 3 of the present invention will be described below with reference to FIGS. 7 and 8. FIG. 7 shows the second
It is a figure which shows the structure of the optical disk reproducing apparatus 3 of this invention in the Example of. FIG. 8 is a diagram showing a configuration of the asymmetry detection circuit 30 shown in FIG. Each component of the optical disc reproducing device 3 not described below is the same as each component of the optical disc reproducing device 1 shown in FIG.

In FIG. 7, the equalizing circuit 36 is different from the equalizing circuit 16 of the optical disc reproducing apparatus 1 shown in the first embodiment in that the values of the parameters Kl and Kt can be changed from the outside. , The RF signal is equalized by the transfer function F (s) of Expression 1 in which the values of the set parameters Kl and Kt are substituted. The asymmetry detection circuit 30 compares the change amounts of the rising point and the falling point of the input RF signal based on the gate signal input from the gate circuit 34, detects the asymmetry of the RF signal, and asymmetrically detects the asymmetry. It is input to the parameter reference table 32 as a signal. The configuration of the asymmetry detection circuit 30 will be described later with reference to FIG.

The parameter reference table 32 stores optimum parameters Kl and Kt for each value of the asymmetric signal detected by the asymmetry detection circuit 30, and corresponds to the value of the asymmetry signal input from the asymmetry detection circuit 30. The parameters Kl and Kt are set in the equalization circuit 36. The gate circuit 34 is synchronized with the falling point and the rising point of the RF signal based on the digital reproduction signal input from the comparison circuit 18 and the clock signal input from the clock extraction circuit 22, and has a predetermined pulse width. The generated gate signal is generated and input to the asymmetry detection circuit 30.
The timing of the gate signal with respect to the RF signal and the method of generating the gate signal will be described later with reference to FIG. The control circuit 38 controls the optical system and the tracking system of the optical disc reproducing apparatus 3 so that the reproduction optical signal of the optical disc 40 is read by FAD or RAD.

The configuration and operation of the asymmetry detection circuit 30 will be described below with reference to FIGS. 8 and 9. The buffer amplifier 300 buffers the input RF signal and inputs it to the gate circuit 302. The comparison circuit 312 compares the voltage of the input RF signal with a predetermined threshold voltage V _th, and sets the output signal to a logical value 1 when the voltage of the RF signal is higher than the threshold voltage V _th. If the output signal is low, the output signal is set to a logical value of 0 and the change point detection circuit 314 is binarized RF.
Input as a signal.

The change point detection circuit 314 comprises a comparison circuit 312.
The rising point and the falling point of the binarized RF signal input from are detected, and these are input to the logic circuit 316 as the rising point signal and the falling point signal. The logic circuit 316 calculates a logical sum signal of the falling point signal and the falling point signal of the binarized RF signal, and
The calculation result of the logical product of the gate signals is input to the gate circuit 302 as a sampling signal.

The gate circuit 302 allows the RF signal to pass when the input sampling signal has a logical value of 1,
When the logical value is 0, the RF signal is cut off. The capacitor (C1) 304 is the R input from the gate circuit 302.
The voltage value of the F signal is temporarily held as electric charge. The buffer amplifier 306 buffers the voltage value corresponding to the difference between the falling point and the change amount of the falling point of the RF signal held by the capacitor 304, and inputs the voltage value to the analog / digital conversion circuit (A / D) 308. To do. That is, the gate circuit 302, the capacitor 304, and the buffer amplifier 306 are a kind of sample and hold (S / S).
H) constitutes the circuit 310. The S / H circuit 31
The operation of 0 will be described later with reference to FIG. The analog / digital conversion circuit 308 converts the voltage value of the reproduction signal output from the S / H circuit 310 into a digital format signal, and inputs it to the parameter reference table 32 as an asymmetrical signal.

The operation of the asymmetry detection circuit 30 will be described below with reference to FIGS. 9 to 11 by taking the case of FAD as an example. Figure 9
FIG. 9 is a diagram showing signal waveforms and the like in each part of the asymmetry detection circuit 30 shown in FIG. 8. In addition, (B) of FIG.
The waveforms shown in (G) are the waveforms of the signals of the respective portions of the asymmetry detection circuit 30 shown in B to G of FIG. Figure 10
9 by using the sampling signal shown in FIG. 9G by the asymmetry detection circuit 30 shown in FIGS. 7 and 8.
It is a figure explaining the method of detecting the amount of change of the rising point and falling point of the RF signal shown in (B). Figure 11
FIG. 9 is a diagram showing an output voltage of the buffer amplifier 306 of the asymmetry detection circuit 30 shown in FIG.

In the optical disc 40 applied to the optical disc reproducing apparatus 3, in order to correct the parameters of the transfer function F (s) as shown in FIG. 9A at a predetermined position, for example, the frontmost position of the sector. That is, a unique correction pattern (marks a, d to k) provided to detect the asymmetry of the RF signal and generate the asymmetric signal is formed.
An optical disc 40 having a correction pattern is shown in FIG.
Since it rotates in the direction of, the correction pattern is the mark h,
The temperature rising part c shown in FIG. 9A is read by the FAD located behind the low temperature part b in the order of g, ..., D, a.
The RF signals (reproduction signals) corresponding to the marks a and d to h of these correction patterns have the waveforms shown in FIG. 9 (B).
This correction pattern is provided, for example, at the beginning of the sector of the optical disc 40, and the reproduction signal in the corresponding sector is equalized by the equalization characteristic corrected by this correction pattern.

Of the correction patterns, the optical disk reproducing apparatus 1 does not directly use the RF signal corresponding to the short mark portion to generate the asymmetric signal. R corresponding to the short mark
The F signal is used by the optical disc reproducing apparatus 1 to simply detect that the pattern is a correction pattern. The RF signal corresponding to the long mark is actually used to generate the asymmetric signal. The reason is that the width of the waveform of the RF signal corresponding to the long mark is wide, so that it is easy to detect the amount of change in the rising point and the falling point.
This is because the width of the waveform of the RF signal corresponding to the short mark is narrow and it is difficult to detect the amount of change.

The RF signal corresponding to the correction pattern is compared with the threshold voltage V _th by the comparison circuit 312 and binarized to be a binarized RF signal shown in FIG. 9C. The change point detection circuit 314 delays the input binarized RF signal by a predetermined time, for example, a few n seconds, and inverts the logical values of the binarized RF signal and the delayed binarized RF signal. Is ANDed to generate a rising point signal of the binarized RF signal shown in FIG. On the other hand, the change point detection circuit 314 performs an AND operation on the signal in which the logical value of the binarized RF signal is inverted and the delayed RF signal, and
The falling point signal shown in (E) is generated.

The logic circuit 316 receives the signal obtained as a result of the OR operation of the rising point signal and the falling point signal shown in FIGS. 9C and 9D, and FIG. 9F input from the gate circuit 34. 9) is performed with the gate signal shown in FIG. 9A to generate a sampling signal shown in FIG. Here, the gate signal is generated by the gate circuit 34 as follows, for example. The gate circuit 34 uses the reproduction data output from the data sampling circuit 20 as shown in FIG.
When the correction pattern shown in FIG. 9 is detected, the clock signal is counted for a predetermined period after detecting the reproduction data corresponding to the mark d in FIG. ), The gate signal shown in FIG.

The S / H circuit 310 will be described below with reference to FIG.
The operation of will be described. As shown in FIG. 10, the gate circuit 302 allows the RF signal buffered by the buffer amplifier 300 to pass while the logical value of the sampling signal is 1. First, the change amount of the voltage of the RF signal in the portion where the logical value of the sampling signal is 1 or more, that is, the threshold voltage V _{th of the} RF signal shown in FIG. 10, that is, the shaded portion attached to the rising point a. Is stored in the capacitor 304. Next, the change in the voltage of the RF signal shown in FIG. 10 which is equal to or lower than the threshold voltage V _{th of the} RF signal and in which the logical value of the sampling signal is 1, that is, the shaded portion attached to the rising point b. A charge corresponding to the quantity is discharged from the capacitor 304.

As a result of the above operation, the capacitor 304 is charged with a charge corresponding to the difference between the amount of change in the RF signal in the shaded area at the rising point a and the amount of change in the RF signal in the shaded area at the falling point b shown in FIG. Stored and capacitor 304
Indicates the terminal voltage corresponding to this charge. Capacitor 30
The terminal voltage of No. 4 is input to the analog / digital conversion circuit 308 via the buffer amplifier 306, and is input to the parameter reference table 32 as a digital change point signal. That is, the voltage value of the output signal of the buffer amplifier 306 becomes a positive value when the amount of change at the rising point is large, as shown in the range a of FIG. 11, and conversely, when the amount of change at the falling point is large. Becomes a negative value as shown in the range b of FIG. This buffer amplifier 30
Since the output signal of 6 is input to the analog / digital conversion circuit 308, the analog / digital conversion circuit 308
Outputs a numerical value corresponding to the output voltage of the buffer amplifier 306 as an asymmetrical signal. The above FA
The tracking control of the optical disc reproducing apparatus 3 and the control of the optical system when the reproduction optical signal is read by D are performed by the control circuit 38.
It is possible to read the reproduction optical signal by RAD as well as FAD. The operation of the asymmetry detection circuit 30 described above is common to the case of RAD.

Hereinafter, the overall operation of the optical disc reproducing apparatus 3 of the present invention will be described with reference to FIG. 7 again. The optical system and the tracking system of the optical disc reproducing apparatus 3 are the control circuit 3
It is controlled by 8. The reproduction optical signal obtained from the optical disc 40 is converted into an electric reproduction signal by the photodetector 12, and the preamplifier circuit 14 converts the reproduction signal into an RF signal.
The signals are separated and the equalization circuit 36 and the asymmetry detection circuit 3 are separated.
Input to 0. The asymmetric detection circuit 30 generates the asymmetric signal as described above and inputs it to the parameter reference table 32, and the parameter reference table 32 sets the parameters Kl and Kt corresponding to the values of the asymmetric signal in the equalization circuit 36. The equalization circuit 36 equalizes the RF signal with a characteristic defined by a function obtained by substituting the parameters Kl and Kt set from the parameter reference table 32 into the transfer function F (s) shown in Expression 1, and then the equalization circuit 36 outputs the equalized signal to the comparison circuit 18. input. The comparison circuit 18 is R
The F signal is binarized and input to the data sampling circuit 20 and the clock extraction circuit 22. Clock extraction circuit 22
Generates a clock signal in synchronization with the binarized RF signal, and the data sampling circuit 20 samples the binarized RF signal in synchronization with this clock signal to produce reproduction data, which is output data. Output.

Of the respective parts of the optical disk reproducing apparatus 3 described above, the control circuit 38, the photodetector 12, and the preamplifier circuit 14 correspond to the reproducing signal generating means according to the present invention.
The equalization circuit 36, the asymmetry detection circuit 30, the parameter reference table 32, and the gate circuit 34 correspond to the waveform equalization means according to the present invention, and the asymmetry detection circuit 30, the parameter reference table 32, and the gate circuit 34 are the same. Corresponding to the conversion characteristic changing means, the parameter reference table 32 corresponds to the coefficient changing means according to the present invention, the optical disc 40 corresponds to the recording medium according to the present invention, and the correction pattern provided on the optical disc 40 corresponds to the present invention. It corresponds to the predetermined pattern.

According to the optical disc reproducing apparatus 3 of the present invention described in the second embodiment, when the optical disc is reproduced by the super-resolution reproducing system, the ambient temperature at that time, the individuality of the optical disc, or the like. It is possible to adaptively compensate for the asymmetry of the reproduction signal determined by, and thus improve the reliability of the reproduction data. Further, FAD and RAD can be switched and used at an arbitrary time as a method of reading the reproduction optical signal. That is, since the asymmetry detection circuit 30 of the optical disc reproducing device 3 constantly monitors the asymmetry of the reproduction signals, the equalization characteristic of the equalization circuit 36 is adaptively changed when the reading method of these reproduction optical signals is switched. It is possible to switch and always equalize the reproduction signal with the optimum equalization characteristic.

Further, according to the optical disc reproducing apparatus 3 of the present invention, the tolerance of the optical disc reproducing apparatus to the variation of the optical disc can be increased, so that the tolerance range of the precision of the optical disc as the object of data reproduction can be widened. . Therefore, it is possible to reduce the manufacturing cost of the optical disc. Similarly, since the tolerance range of the accuracy of the optical system and the mechanical system of the optical disc reproducing apparatus 3 itself can be widened, the manufacturing cost of the optical disc reproducing apparatus 3 itself can be reduced. In addition, the optical disk reproducing device 3
Since the internal temperature, that is, the operating temperature range of the optical disk can be widened, the device can be downsized.
Further, if the precision of the optical disc and the optical disc reproducing device is kept the same, the optical disc reproducing device 3 of the present invention can record and reproduce higher density data than before.

The logical values of the signals of the respective parts of the optical disk reproducing apparatuses 1 and 3 in the above-mentioned respective embodiments are examples. Further, the equalization method used in the optical disk reproducing apparatus 3 is a method in which the size of the recording magnetic domain is controlled by the temperature of the magnetic film of the optical disk to generate a reproduction signal, and the direction of the magnetic field of the recording magnetic domain is reversed. Alternatively, it can be applied to a case where a reproduction signal is generated by the phase pit method. In the asymmetry detection circuit 30, a plurality of long marks of the correction pattern on the optical disc 40 are provided and the asymmetry signal is generated based on the average asymmetry of the reproduction signal corresponding to each of these marks, or the parameter K is used.
A modification such as a configuration in which the selection of l and Kt is performed by feedback processing is conceivable. Further, the equalization circuit 36 may be configured to use a multi-tap transversal filter. The correction pattern described above is provided for each sector of the optical disc and is used to correct the equalization characteristics of the sector. For example, the correction pattern is provided not for each sector but for each track of the optical disc to reproduce the optical disc. The apparatus may be configured to correct the equalization characteristic on a track-by-track basis. Further, in the optical disc reproducing apparatus 3, the width of the sampling signal for the gate circuit 302 is constant, but the frequency of the clock signal used for reproducing the data changes for each part on the optical disc ZCA.
In order to support the V system, the signal width may be variable. The optical disc reproducing apparatus of the present invention is not limited to those shown in each of the above-described embodiments, but may have various configurations, for example, as shown in each of the above-described modifications.

[0048]

As described above, according to the optical disk reproducing apparatus of the present invention, it is possible to compensate the asymmetry of the reproduced signal by an appropriate equalization process and improve the reliability of the reproduced data. It is possible to improve the storage density of the optical disc. Further, it is possible to adaptively equalize the reproduced signal and appropriately compensate for the asymmetry of the reproduced signal.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an optical disc reproducing apparatus of the present invention in a first embodiment.

FIG. 2 is a diagram showing a configuration of an equalizing circuit of the optical disc reproducing apparatus of the present invention shown in FIG.

3 shows frequency characteristics of equalized output amplitude (reproduction signal input amplitude) of the pulse slimmer shown in FIG.

4 shows a frequency characteristic of an equalized output phase (reproduction signal input phase) of the pulse slimmer shown in FIG.

FIG. 5 is a diagram showing a waveform of a reproduction signal obtained when a mark is read out by raising the temperature of the rear portion of the reproduction spot (FAD), in which (A) is a temperature rising portion of the reproduction spot, the traveling direction of the optical disc. , And the relationship with the mark,
(B) shows the waveform of the reproduction signal obtained from the mark shown in (A).

FIG. 6 is a diagram showing a waveform of a reproduction signal obtained when a mark is read out by raising the temperature of the front portion of the reproduction spot (RAD), where (A) is a temperature rising portion of the reproduction spot, the traveling direction of the optical disc. , And the relationship with the mark,
(B) shows the waveform of the reproduction signal obtained from the mark shown in (A).

FIG. 7 is a diagram showing a configuration of an optical disc reproducing apparatus of the present invention in a second embodiment.

8 is a diagram showing a configuration of the asymmetry detection circuit shown in FIG.

9 is a diagram showing signal waveforms and the like in respective portions of the asymmetric detection circuit shown in FIG. 8, in which each waveform shown in (B) to (G) is an asymmetric detection circuit shown in BG in FIG. The waveform of the signal of each part of is shown.

FIG. 10 is a diagram illustrating a case where the asymmetry detection circuit shown in FIGS. 7 and 8 is used and the sampling signal shown in FIG.
It is a figure explaining the method of detecting the amount of change of the rising point and falling point of the RF signal shown in (B).

11 is a diagram showing an output voltage of a buffer amplifier of the asymmetric detection circuit shown in FIG.

[Explanation of symbols]

1, 3 ... Optical disk reproducing device, 10, 40 ... Optical disk, 12 ... Photodetector, 14 ... Preamplifier circuit, 16 ... Equalization circuit, 18 ... Comparison circuit, 20 ... Data sampling circuit,
22 ... Clock extraction circuit, 30 ... Asymmetry detection circuit, 32
... Parameter reference table, 34 ... Gate circuit, 300
... buffer amplifier, 302 ... gate circuit, 304 ... capacitor, 306 ... buffer amplifier, 308 ... analog /
Digital conversion circuit, 312 ... Comparison circuit, 314 ... Change point detection circuit, 316 ... Logic circuit, 34 ... Gate circuit, 3
6 ... Equalization circuit, 38 ... Control circuit

Continuation of the front page (56) Reference JP-A-5-89551 (JP, A) JP-A-1-143042 (JP, A) JP-A-3-97140 (JP, A) JP-A-3-88156 (JP , A) JP 3-292632 (JP, A) JP 5-120798 (JP, A) JP 5-67374 (JP, A) JP 64-8513 (JP, A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) G11B 11/10-11/105 G11B 7/00-7/007 G11B 20/10-20/12

Claims (2)

(57) [Claims] 1. A recording magnetic domain having a predetermined pattern is formed in advance.
The size of the recording magnetic domains formed in the magnetic film by changing the temperature of the magnetic film of which a recording medium, or,
Reproduction signal generating means for controlling the direction of the magnetic field and generating a reproduction signal from the recording magnetic domain by using magneto-optical interaction in the recording magnetic domain, and at least a coefficient for adjusting the amplitude of the waveform of the reproduction signal.
And a transfer function with a coefficient to adjust the phase linearity
Waveform equalization processing of the reproduction signal with specified equalization characteristics
A waveform equalizing means for processing, which is detected based on the clock signal extracted from the reproduction signal.
Rising change point and falling edge of the reproduced signal
Asymmetry comparing the amount of change of the reproduction signal at the change point
A detecting means and a reproducing unit corresponding to a recording magnetic domain of a predetermined pattern of the recording medium.
At least the predetermined pattern based on the waveform of the raw signal
It corresponds to the reproduction signal from the recording magnetic domain corresponding to the recording magnetic domain.
The equalization characteristic of the waveform equalizing means is determined by the asymmetry detecting means.
Based on the comparison result of the change amount of the reproduction signal calculated in
A function for adjusting the amplitude of the waveform of the reproduction signal of the transfer function
Equalization to change the number and coefficient to adjust the phase linearity
And a characteristic changing means comprises a waveform equalizing means,
Optical disc playback device. 2. The size of the recording magnetic domain formed on the magnetic film by changing the temperature of the magnetic film of the recording medium on which the recording magnetic domain having a predetermined pattern is formed in advance, or
A reproduction signal generating step of controlling a direction of a magnetic field and generating a reproduction signal from the recording magnetic domain by using magneto-optical interaction in the recording magnetic domain; and a coefficient and a phase linearity for adjusting at least an amplitude of a waveform of the reproduction signal. A waveform equalization step of performing a waveform equalization process of the reproduction signal with an equalization characteristic defined by a transfer function having a coefficient for adjusting the detected signal based on a clock signal extracted from the reproduction signal. An asymmetry detection step of comparing the amount of change of the reproduction signal at the rising change point and the falling change point of the reproduction signal; and at least the predetermined amount based on the waveform of the reproduction signal corresponding to the recording magnetic domain of the predetermined pattern of the recording medium. The reproduction signal calculated in the asymmetry detecting step is the equalization characteristic for the reproduction signal from the recording magnetic domain corresponding to the recording magnetic domain of the pattern. An equalization characteristic changing step of changing the coefficient for adjusting the amplitude of the waveform of the reproduction signal of the transfer function and the coefficient for adjusting the phase linearity based on the comparison result of the change amount of the waveform equalization step, An optical disk reproducing method comprising: