JPH09161290A - Optical disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the adverse effect of jitter increase in a reproduced signal caused by a tangential skew with simple constitution. SOLUTION: A signal recorded on an optical disk medium 10 is reproduced by an optical pickup 11 to be sent to a waveform equalizer circuit 12 in which a waveform equalization characteristic is varied by a control signal supplied to a control terminal 13. A characteristic control circuit 14 sends the control signal for variable controlling the waveform equalization characteristic of the waveform equalizer circuit 12 to the control terminal 13 according to a skew detection signal from a skew detection element 15 provided in opposition to the recording surface of the optical disk recording medium 10. The regenerative signal waveform equalization processed by the waveform equalizer circuit 12 is taken out from an output terminal 16. In the waveform equalizer circuit 12, plural kinds of waveform equalization characteristics are awaited to be switch selected according to a skew angle.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disc apparatus for reproducing a signal recorded on an optical disc recording medium, performing waveform equalization processing, and outputting the signal, and more particularly to a tangential direction which is a track tangential direction of the optical disc. The present invention relates to an optical disc device that corrects a skew error of a reproduction signal due to the inclination of the optical disc.

[0002]

2. Description of the Related Art There is known a disk device using an optical pickup for recording and reproducing information on an optical recording medium such as an optical disk.

In such an optical disk device, coma may occur due to the tilt of the optical disk medium, so-called disk skew, and the original reading performance may not be exhibited, and a reading error may occur.

For example, when a disc skew in the tangential direction which is the tangential direction of the track of the optical disc, that is, a tangential skew, occurs, intersymbol interference increases in the digital signal due to the asymmetry of the spot, and it is necessary to sufficiently extract the signal. Will be difficult. Further, in the analog signal, C / N (carrier-to-noise ratio) decreases due to an increase in tangential skew, and a group delay occurs. Especially, in a video disc or the like, color unevenness appears on the screen.

[0005]

By the way, in recent years, the density of optical discs has been increased, and as the density of optical discs has been increased, the skew margin, which is the allowable range of skew, has decreased.

In particular, the tangential skew is
Since it includes a disk fluctuation component, if mechanical correction is to be performed using, for example, an actuator, it is necessary to drive the actuator at a high speed, which is extremely difficult to realize.

The present invention has been made in view of the above-mentioned circumstances, and the signal quality can be improved by equalizing a high-frequency reproduction signal obtained by reading an optical disc, that is, an RF signal, and a simple skew detecting mechanism is used. It is an object of the present invention to provide an optical disk device capable of correcting a skew error of a signal and expanding a skew margin.

[0008]

In order to solve the above-mentioned problems, the present invention reproduces a signal recorded on an optical disk recording medium to perform waveform equalization processing, and the waveform equalization characteristic at this time is It is characterized in that it is variably controlled according to a skew detection signal obtained by detecting the inclination of the optical disk recording medium.

Here, using a waveform equalizer capable of switching and selecting any one of a plurality of waveform equalization characteristics, the controller equalizes the waveform equalizer according to the skew detection signal from the skew detector. It is possible to switch and control the waveform equalization characteristics of.

According to the detected skew angle, waveform equalization characteristics for skew correction are switched and selected, and skew correction is performed.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram schematically showing an example of the configuration of an optical disk device according to an embodiment of the present invention.

The optical disc apparatus shown in FIG. 1 uses an optical pickup 11 to output a signal recorded on an optical disc recording medium 10.
It is reproduced by and is sent to the waveform equalization circuit 12. The waveform equalization circuit 12 has a waveform equalization characteristic changed by a control signal supplied to the control terminal 13. Further, a skew detecting element 15, which is a so-called skew sensor, is provided so as to face the recording surface of the optical disk recording medium 10 and detect an inclination of the recording surface. This skew detecting element 15
Is sent to the characteristic control circuit 14, and the characteristic control circuit 14 sends a control signal for variably controlling the waveform equalization characteristic of the waveform equalization circuit 12 in accordance with the skew signal. I am sending it to. Waveform equalization circuit 1
The reproduction signal subjected to waveform equalization processing by 2 is output to the output terminal 16
Taken out.

Here, as an example, the skew detecting element 1
Reference numeral 5 is arranged so as to detect an inclination in a so-called tangential direction which is a tangential direction of a recording track of the optical disc recording medium 10. In addition, the waveform equalization circuit 12
The characteristic control circuit 14 has a configuration capable of switching selection to one of two or more fixed waveform equalization characteristics, and the characteristic control circuit 14 divides the skew detection signal from the skew detection element 15 into predetermined skew angle ranges. The waveform equalization characteristics are selectively switched and controlled for each skew angle range.

For example, as the waveform equalizing circuit 12, two waveform equalizing characteristics can be switched depending on whether the tangential skew is a + (positive) side inclination or a − (negative) side inclination. The characteristic control circuit 14 discriminates the skew detection signal between the + side and the − side, and switches the waveform equalization characteristic of the waveform equalization circuit 12. Further, the waveform equalization circuit 12 has three types of positive side correction and negative side correction including a state without correction.
The types of waveform equalization characteristics are switchable, and the characteristic control circuit 14 controls the tangential skew angle to a predetermined angle ± α.
Is a threshold value, the skew detection angle is + α or more, −α to +
An example is also possible in which one of the three ranges of α and −α or less is discriminated and the above three types of waveform equalization characteristics are selectively switched.

FIG. 2 is a block circuit diagram showing a concrete example of the waveform equalization circuit 12 and the characteristic control circuit 14.

In FIG. 2, the reproduction signal from the optical pickup 11 shown in FIG. 1 is supplied to the input terminal 21 of the waveform equalization circuit 12. The reproduced signal from the input terminal 21 is sent to the cascade connection circuit of the delay elements 22a to 22d. The reproduction signal from the input terminal 21 and the output signals from the delay elements 22a to 22d are sent to the coefficient multipliers 23a and 23b to 23e, respectively. The output signals from the coefficient multipliers 23b to 23d are sent to the adder 24, and one of the output signals from the coefficient multipliers 23a and 23e is selected by the change-over switch 25 and sent to the adder 24. The output signal from the adder 24 is taken out from the output terminal 16 as a waveform-equalized signal.

As for the changeover control signal to the changeover switch 25, the skew angle of the skew detection signal from the skew detecting element 15 is set to 0 by the comparator 27 provided in the characteristic control circuit 14.
Is obtained by being compared with the skew 0 signal corresponding to and is supplied via the control terminal 13.

Here, the delay time of each of the delay elements 22a to 22d is one sample time for each of the delay elements 22b and 22c and several sample time for each of the delay elements 22a and 22d. The multiplication coefficient of the coefficient multipliers 23a to 23e is 1, the coefficient multiplier 23c is 1,
b and 23d are k ₁ , and coefficient multipliers 23a and 23e are k ₂ . These delay times are determined by the wavelength λ of the signal reproducing system of the optical disk device, the numerical aperture NA of the objective lens, and the disk linear velocity v, and are the sum of the delay times of the delay elements 22a and 22b or the delay elements 22c and 22d. It is preferable to set the sum of delay times to be approximately 1.64λ / (2NA · v).

Next, FIG. 3 shows a concrete example of a waveform equalizing circuit as an essential part of an optical disk device according to another embodiment of the present invention. The waveform equalizer circuit shown in FIG.
Since it can be used as the waveform equalizing circuit 12 and other configurations are the same as those in FIG. 1, illustration and description thereof are omitted.

In FIG. 3, the input terminal 31 is supplied with the reproduction signal from the optical pickup 11 shown in FIG. The reproduced signal from the input terminal 31 is sent to the cascade connection circuit of the delay elements 32a to 32f. In addition, the reproduced signal from the input terminal 31, each delay element 32a ...
The output signals from 32b and 32d to 32f are respectively supplied to coefficient multipliers 33a, 33b to 33c and 33d to 33.
sent to f. The output signals from the coefficient multipliers 33b to 33e and the output signal from the delay element 32c are added by the adder 3
4, the output signals from the coefficient multipliers 33a and 33f are switched and selected by the changeover switch 35 and sent to the adder 36. This adder 36 has an adder 3
The output signal from 4 is also sent. The output signal from the adder 36 is output to the output terminal 16 as a signal subjected to waveform equalization processing.
Taken out.

The change-over switch 35 has a selected terminal a to which the output signal from the coefficient multiplier 33a is supplied, a selected terminal b to which an output signal from the coefficient multiplier 33f is supplied, and 0
This is a three-terminal changeover switch with a selected terminal c corresponding to input or 0 addition, and one of these terminals a, b, c is selected and connected by a three-value changeover control signal from the control terminal 13. , Its output signal is sent to the adder 36. This three-value switching control signal is generated by the characteristic control circuit 14 of FIG. 1 with the skew detection angle of + α or more and −α to + α, −α or less, with the predetermined value ± α of the tangential skew angle as a threshold. It is obtained by determining which of the two ranges.

FIG. 4 shows a specific example of the relationship between the skew angle of the tangential skew and the amount of jitter of the waveform equalized output signal when using such a configuration. In the example of FIG. 4, the angle α that is the threshold value is 0.2 degrees.

In FIG. 4, when the skew angle of the tangential skew is within a range of ± 0.2 degrees around 0 degree, the changeover switch 35 of FIG. The jitter component (%) in the signal obtained from is as shown by the curve c in FIG. When the skew angle is 0.2 degrees or more, the changeover switch 35 of FIG. 3 is switchably connected to the selected terminal a, and the jitter becomes as shown by the curve a of FIG. Further, the skew angle is 0.
When it is 2 degrees or less, the changeover switch 35 of FIG. 3 is changeably connected to the selected terminal b, and the jitter becomes as shown by the curve b of FIG.

Therefore, the characteristic control circuit 14 shown in FIG.
With the threshold of ± 0.2 degrees of the angle of the tangential skew detected by the skew detection element 15, +0.2
Each angle range from 0.degree. To -0.2.degree. To + 0.2.degree., And -0.2.degree. Or less is discriminated, and the selected terminals a, c, b of the changeover switch 35 shown in FIG. By controlling the switching and connection, the jitter of the waveform equalized reproduction signal from the output terminal 16 becomes as shown by the thick line in FIG.

As is apparent from FIG. 4, when the correction according to the tangential skew angle is not performed,
As shown by the curve c in FIG. 4, the jitter exceeds 15% when the tangential skew angle is out of the angle range of ± 0.45 degrees, but it depends on the tangential skew angle as in the present embodiment. By making corrections
The jitter can be suppressed within 15% up to the angle range of ± 0.50 degrees, and the skew margin can be expanded.

In determining the waveform equalization characteristic for performing skew correction as shown by the curves a and b in the optical disc apparatus according to the embodiment of the present invention, when designing a circuit, for example, By simulation, the multiplication coefficient of the waveform equalization circuit 12, so-called equalization coefficient, is changed so as to perform correction according to the skew angle to obtain the jitter during waveform equalization output, and the optimum equalization that minimizes this jitter is obtained. It suffices to perform a process for determining the coefficient. These waveform equalization characteristic curves a and b have a skew angle ± α that suppresses jitter more than the waveform equalization curve c without correction, and in the example of FIG. 4, ± 0.2 degrees is used as a threshold value.
The equalization coefficient is switched so that each characteristic can be switched. There is no problem even if this threshold is rough to some extent. Therefore, high accuracy is not required for skew detection. This is because, as a comparative example, when the waveform equalization characteristic is changed linearly or in analog according to the skew detection signal, accuracy is required for skew detection,
When considering that a good correction result cannot be obtained because it is difficult to correct the skew by the optimum equalization coefficient in real time due to the variation of the tangential skew, according to the above-described embodiment, the accuracy is not required and is simple. Skew detection may be performed, and the skew correction of the reproduced signal can be effectively performed by a simple process of discriminating the skew signal with a predetermined threshold value and switching the equalization coefficient, thereby improving the signal quality. Further, since the structure is simple, skew correction can be realized at low cost.

The present invention is not limited to the examples of the above-described embodiment, and for example, an optical disk reproducing apparatus for reading recorded information has been described.
It can be easily applied to a recording / reproducing device and the like. In addition to the optical skew sensor, various skew detections such as skew detection using an RF signal from the photodetector can be performed for skew detection.

[0029]

According to the present invention, a signal recorded on an optical disc recording medium is reproduced to perform waveform equalization processing, and the waveform equalization characteristic at this time is obtained by detecting the inclination of the optical disc recording medium. Since the variable control is performed according to the skew detection signal, the tangential skew correction including the disk fluctuation component can be effectively performed.

Further, since one of a plurality of waveform equalization characteristics which can be switched and selected by the waveform equalizing means is switched and selected and controlled according to the skew detection signal, it is optimum for a predetermined skew angle in advance. By setting some waveform equalization characteristics that can perform skew correction, discriminating the skew angle with a threshold value, and switching and selecting between these waveform equalization characteristics, effective skew correction can be easily realized and the reproduced signal The quality of can be improved. Moreover, since the accuracy of skew detection is not required, a simple skew detecting means can be used.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of an embodiment of an optical disc device according to the present invention.

FIG. 2 is a block circuit diagram showing a specific example of a waveform equalization circuit and its peripheral circuits used in the optical disk device of FIG.

FIG. 3 is a block circuit diagram showing a specific example of a waveform equalization circuit as a main part of another embodiment of the optical disc apparatus according to the present invention.

FIG. 4 is a diagram showing a specific example of jitter with respect to a skew angle.

[Explanation of symbols]

 10 Optical Disc Recording Medium 11 Optical Pickup 12 Waveform Equalization Circuit 14 Characteristic Control Circuit 15 Skew Detection Element

Claims (3)

[Claims] 1. An optical pickup means for reproducing a signal recorded on an optical disk recording medium, and a waveform equalization process for a reproduced signal from the optical pickup means, the waveform equalizing characteristic being controlled by an external control signal. Changing waveform equalizing means, skew detecting means for detecting the inclination of the optical disk recording medium, and control means for variably controlling the waveform equalizing characteristic of the waveform equalizing means according to a skew detection signal from the skew detecting means. An optical disk device comprising: 2. The waveform equalizing means has a plurality of waveform equalizing characteristics to be switched and selected, and the control means controls a plurality of the waveform equalizing means according to a skew detection signal from the skew detecting means. 2. The optical disc apparatus according to claim 1, wherein the waveform equalization characteristics of the above are selectively controlled. 3. The optical disk device according to claim 2, wherein the waveform equalizing means has a waveform equalizing characteristic without skew correction and a waveform equalizing characteristic for performing positive and negative skew correction.