JP2001236664A - Optical disk drive - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To enable highly reliable information reading in an optical disc device in which reading speed is improved by simultaneously reading information recorded on a plurality of tracks using a multi-laser beam. An optical disk device is provided. A TE signal operation circuit includes a quadrant photodetector.
Is used to calculate the tracking error signal TE. The error detection circuits 33 to 37 output the number of read errors of each track. The addition circuit 46 adds the output of the TE signal and the output of the variable DC signal 45. The control circuit 44 adjusts the output of the variable DC signal 45 so that the difference between the maximum value and the minimum value of the outputs of the error detection circuits 33 to 37 is minimized, and corrects the operating point of the TE signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk device, and more particularly to an optical disk device in which information recorded on a plurality of tracks is read at the same time by using a multi-laser beam to improve the reading speed. The present invention relates to an optical disk device capable of reading information.

[0002]

2. Description of the Related Art In an optical disk apparatus, a disk on which information is optically recorded (hereinafter referred to as an optical disk) is irradiated with a laser beam to read the recorded information from the difference in the amount of reflected light from the optical disk. There has been proposed an optical disk device in which the reading speed is improved by reading information from the tracks at the same time.

FIG. 2 is a block diagram of a conventional optical disk drive for reading a plurality of tracks simultaneously. In FIG. 2, 1 is a semiconductor laser, 2 is a collimator lens, 3 is a diffraction grating, 4 is a beam splitter, 5 is an objective lens, 6
Is an optical disk, 7 is a cylindrical lens, 8 is an aperture lens, 9 is a multi-beam photodetector, 10 to 14 are photodetectors, 15 is an addition circuit, 16 is a focus error signal (hereinafter referred to as FE signal) calculation circuit, 17 Is a tracking error signal (hereinafter referred to as TE signal) calculation circuit, 18 to 22 are binarization circuits, 23 to 27 are data strobe circuits, 28 to 32 are demodulation circuits, 33 to 37 are error detection circuits, and 38 is a focus servo. Control circuit, 39 is a tracking servo control circuit, 40 is a focus drive circuit, 4
1 is a tracking drive circuit, 42 is a focus actuator, and 43 is a tracking actuator.

[0004] Each component will be described below.

[0005] The semiconductor laser 1 emits a laser beam having a predetermined wavelength.

The collimator lens 2 includes a semiconductor laser 1
The laser beam emitted from is shaped into parallel light.

The diffraction grating 3 diffracts the collimated laser beam into 0th to ± nth order light beams. The optical disk device shown in FIG. 2 is a five-beam optical disk device using diffracted lights up to ± 2 orders.

[0008] The beam splitter 4 is a semiconductor laser 1
The laser beam from the optical disk 6 is transmitted and the laser beam from the optical disk 6 is reflected.

The objective lens 5 focuses the laser beam to focus on the recording layer of the optical disk 6.

On the optical disk 6, information is digitally recorded due to unevenness of the recording layer or difference in reflectance.

The cylindrical lens 7 shapes a laser beam in order to generate an FE signal by an astigmatism method.

The aperture lens 8 has a multi-beam photodetector 9
The laser beam reflected from the optical disk is focused on the photodetector arranged above.

The photodetectors 10 to 14 are arranged linearly on the multi-beam photodetector, and output an electric signal corresponding to the light amount of each laser beam. The photodetector 12 arranged at the center of the five photodetectors is the photodetector 1
The output of the photodetectors 12-1 to 12-4 is a four-divided photodetector consisting of 2-1 to 12-4.
It is supplied to the E signal operation circuit 16 and the TE signal operation circuit 17. The other photodetectors 10, 11, 13, 14 are respectively
It is supplied to the binarization circuits 18, 19, 21 and 22.

The adder circuit 15 is connected to the photodetectors 12-1 to 12-1.
2-4 are added, and the added signal is converted to a binarization circuit 2
0 is supplied.

The FE signal operation circuit 16 includes a photodetector 12-
Using the signals supplied from 1 to 12-4, an FE signal is calculated by, for example, a known astigmatism method and supplied to the focus servo control circuit 38.

The TE signal operation circuit 17 includes a photodetector 12-
Using the signals supplied from 1 to 12-4, a TE signal is calculated by, for example, a push-pull method and supplied to the tracking servo control circuit 39.

The binarizing circuits 18 to 22 convert the input signal into Hi or Low square wave pulses based on a predetermined threshold and supply the same to the data strobe circuits 23 to 27.

The data strobe circuits 23 to 27 oscillate a clock synchronized with the input square wave pulse, measure the width of the square wave pulse by using the clock, take in the digital data as digital data, and send it to the demodulation circuits 28 to 32. input.

The demodulation circuits 28 to 32 return the input digital data to a data format before being recorded on the optical disk 6 according to a predetermined conversion method.

The error detection circuits 33 to 37 output the number of data errors of the reproduced data.

The focus servo control circuit 38 compensates for the gain and phase necessary for focus control on the FE signal, and inputs the output to a focus drive circuit 40.

The tracking servo control circuit 39 has a TE
The gain and phase necessary for tracking control are compensated for the signal, and the output is input to the tracking drive circuit 41.

The focus drive circuit 40 outputs a signal for driving the focus actuator 42 according to the input signal.

The tracking drive circuit 41 outputs a signal for driving the tracking actuator 43 according to the input signal.

The focus actuator 42 moves the objective lens 5 substantially in the optical axis direction of the laser according to the output of the focus drive circuit 40.

The objective lens 5 is moved in a substantially radial direction of the optical disk 6 according to the outputs of the tracking actuator 43 and the tracking drive circuit 41.

With the above configuration, the multi-beam emitted from the diffraction grating 3 can follow a plurality of tracks on the optical disk 6, so that information can be read from a plurality of tracks at the same time.

In order to realize the above optical disk apparatus, for example, Japanese Patent Application Laid-Open No. 57-141032 discloses that a laser beam is separated into diffracted light using a diffraction grating to form a beam spot corresponding to a plurality of tracks on the optical disk surface. By doing so, information on a plurality of tracks can be read simultaneously.

[0029]

However, when the above-mentioned diffraction grating is used, the interval between the laser spots of the respective diffracted lights on the optical disk surface is reduced due to an incident angle error of the laser beam with respect to the diffraction grating, an installation position error of the optical component, and the like. May not be constant. In the case of the conventional optical disk device shown in FIG. 2, tracking control is performed using one laser spot among a plurality of laser spots. In addition,
The reason why tracking control is performed using only one laser spot is that an increase in circuit scale can be prevented by using a tracking control circuit for a single beam. On the other hand, other laser spots are linked to the laser spot used for tracking. Therefore, a residual error occurs between a laser spot not used for tracking control and a track corresponding to the laser spot. Therefore, the number of data errors in the data read from each track may differ from track to track. Problems in this case are described below.

In FIG. 2, the reflected light of the laser beam condensed on tracks n-2, n-1, n, n + 1, n + 2 on the optical disk 6 is reflected by photodetectors 10, 11, 1 respectively.
Light is condensed on 2, 13, and 14. FIG. 3 shows an example of the maximum value of the number of data errors in the reproduction data of each track at this time. In the optical disk device of FIG. 2, since tracking control is performed using the photodetector 12 that detects reflected light from the track n, the track n has a smaller residual deviation than other tracks. Therefore, the number of data errors on track n is small. On the other hand, since tracking control is performed so that the laser spot for the track n follows the track n, a tracking residual error occurs between the other laser spots and the track for them. for that reason,
The number of data errors in other tracks is larger than that in track n. In FIG. 2, it is assumed that the number of data errors on track n-2 is larger than the number of data errors on other tracks. Here, if the data error number of the track n-2 is smaller than the allowable data error number, all the error data can be corrected, so that the read data of all the tracks read at the same time is highly reliable. On the other hand, if the number of erroneous data is larger than the allowable number of data errors, all the erroneous data cannot be corrected, so that the reliability of the reproduction data of the track n-2 is impaired. That is, the reproduced signal from the track n-2 cannot be used as read data due to deterioration in quality.

The present invention has been made in consideration of the above problems, and has been described in an optical disk device in which information recorded on a plurality of tracks is simultaneously read using a multi-laser beam to improve the reading speed. An object of the present invention is to provide an optical disk device capable of reading high information.

[0032]

SUMMARY OF THE INVENTION In an optical disk apparatus in which the spot position of a multi-laser beam applied to an optical disk changes in conjunction with the optical disk, the multi-laser beam including an objective lens is focused on a plurality of tracks of the optical disk. Multi-laser irradiating means, light detecting means for converting each reflected light from the plurality of tracks into electric signals corresponding to the respective intensities and outputting the electric signals, and calculating the output of the light detecting means to obtain the objective lens for the optical disk Error signal calculating means for calculating a lens position error signal indicating a position error of the digital camera, digital converting means for converting the output of the light detecting means into a digital signal, and controlling the position of the objective lens using the lens position error signal Control means for correcting the control target of the control means; Quality detection means for detecting the quality of the reproduction signal from each track using the output of the above, the correction value of the correction means to reduce the quality difference of the reproduction signal from each track output by the quality detection means It is configured to be adjusted.

Further, the quality detecting means includes an error detecting means for detecting the number of read error data using the output of the digital converting means, and detects the quality of the reproduced signal based on the output of the error detecting means. .

Alternatively, the digital conversion means includes a binarization means for binarizing an output of the light detection means with a reference value, and the quality detection means is synchronized with an output signal of the binarization means. Clock generating means for generating a converted clock, and phase difference measuring means for measuring a phase difference between the output signal of the binarizing means and the clock, and the quality of a reproduced signal based on the output of the phase difference measuring means. Is detected.

The error signal calculating means calculates a focus error signal indicating a position error of the objective lens with respect to a focus direction of the optical disk.

Alternatively, the error signal calculating means is configured to calculate a tracking error signal indicating a position error of the objective lens with respect to a tracking direction of the optical disk.

Further, the optical disc apparatus may further comprise a reproducing signal from a track other than the defective track when there is a defective track whose reproduction signal from each track is equal to or less than a predetermined quality even after adjusting the correction value of the correction means. The correction means adjusts the correction value so that the quality difference of
A reproduction signal from a track other than the defective track is used as a reproduction signal.

[0038]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first embodiment of the optical disk device according to the present invention will be described.

FIG. 1 is a block diagram showing a first embodiment of the present invention.

This embodiment differs from the conventional embodiment of FIG. 2 in that a control circuit 44, a variable DC signal source 45, and an addition circuit 46 are provided.
Are included in the configuration, and the input signal to the tracking servo control circuit 39 is supplied from the adder circuit 46. Parts corresponding to those in FIG. Omitted.

The control circuit 44 controls the error detection circuits 33 to 3
The number of data errors output from 7 is supplied, and the output of the variable DC signal source 45 is adjusted according to the number. The adjustment method will be described later.

The variable DC signal source 45 supplies the DC signal whose output value has been adjusted by the control circuit 44 to the adding circuit 46.

The addition circuit 46 adds the output of the TE signal operation circuit 17 and the output of the variable DC signal source 45 and supplies the result to the tracking servo control circuit 39.

In the above configuration, first, the optical disk 6 is set so that the zero-order light of the laser beam becomes the center of the track n.
Is reproduced, and the maximum value of the number of data errors in each track output from the error detection circuits 33 to 37 is determined by the control circuit 4.
4 memorizes.

Thereafter, the control circuit 44 controls the variable DC signal source 4
5 is changed by a predetermined ΔV to shift the control center of the tracking control from the center of the track n.
The maximum value of the number of data errors in each track is stored again.

The above adjustment is performed by setting ΔV in a plurality of ways, and the setting of ΔV that minimizes the difference between the maximum values of the number of data errors in each track is the final adjustment value. FIG.
Shows the number of data errors before adjustment by a solid line, and the number of data errors after adjustment by a dotted line. The data error number of the track n-2 was larger than the allowable data error number before the adjustment, but was smaller than the allowable data error number after the adjustment. Although this adjustment may cause the number of data errors of tracks other than the track n-2 to be larger than that before the adjustment of the variable DC signal source 45, the number of data errors of all tracks read at the same time is smaller than the allowable number of data errors. If there is no system problem.

If there is a track on which the number of data errors is larger than the allowable error number even if the output value of the variable DC signal 45 is adjusted, data read from that track is not treated as read data. As a result, although the overall reading speed is reduced, the reliability of the read data is not impaired, so that highly reliable reading is possible.

According to the first embodiment described above, the control center of the tracking control is corrected so that the difference in the number of errors in the data reproduced from each track is reduced using the number of data errors as the quality evaluation parameter of the reproduced signal. By doing so, the quality difference of the reproduction signal from each track is reduced, and highly reliable reading is enabled.

Next, a second embodiment of the present invention will be described.

FIG. 5 is a block diagram showing a second embodiment of the present invention.

In FIG. 5, the configuration of the second embodiment differs from the configuration of the first embodiment in that an input signal to the control circuit 44 is supplied from the data strobe circuit 23 to 27.

The data strobe circuits 23 to 27 output the output signals (a) of the binarization circuits 18 to 22 as shown in FIG.
It is assumed that the frequency of the reproduction clock is controlled so that the transition point of the reproduction clock and the falling edge of the reproduction clock (b) are synchronized.
Here, the reason for synchronizing the transition point of the binarization circuit output signal (a) and the falling edge of the reproduction clock (b) is that the transition point of the binarization circuit output signal (a) and the reproduction clock (b) By increasing the phase margin between rising edges,
This is to avoid the influence of noise at the changing point of the binarization circuit output signal (a) and to correctly latch the binarization circuit output signal (a) at the rising edge of the reproduction clock (b).

FIG. 7 shows an example of the data strobe circuits 23 to 37.

The latch circuit 47 supplies the signal A obtained by latching the binarized circuit output signal with the reproduced clock to the EXOR circuit 48 and the counter circuit 51.

The EXOR circuit 48 calculates the exclusive OR of the binarized circuit output signal and the signal A, and supplies the result to the compensator 49. The output signal of the EXOR circuit 48 is a signal indicating a phase shift between the output signal of the binarization circuit and the reproduced clock, and is hereinafter referred to as a phase comparison signal.

The compensator 49 smoothes the phase comparison signal to compensate for the operating point, and converts the signal into a VCO (Voltage Control) signal.
(Ocillator) circuit 50 and the control circuit 44 of FIG.

The VCO circuit 50 oscillates a clock having a frequency corresponding to the output voltage of the compensator 49 and supplies the clock to the clock terminal of the latch circuit 47.

The counter circuit 51 supplies the digital signal obtained by counting the pulse width of the signal A output from the latch circuit 47 with the reproduced clock to the demodulation circuits 28 to 32 in FIG.

FIG. 8 shows each signal waveform of the data strobe circuit having the above configuration. The left diagram in FIG. 8 shows a case where the phase of the binarized circuit output (a) and the phase of the reproduced clock (b) are synchronized, and the output voltage of the compensator 49 is V0. Similarly, the middle diagram shows a case where the phase of the reproduced clock (b) is advanced with respect to the binarization circuit output signal (a), and the voltage V1 of the compensator output (e) is reduced to the voltage V0 in the case of the same phase. Higher than. Similarly, the right diagram shows the case where the phase of the reproduced clock (b) is delayed with respect to the output signal (a) of the binarization circuit, and the voltage V2 of the output (e) of the compensator is compared with V0 when the phase is the same. Low. For this reason,
The oscillation frequency of the VCO circuit 50 changes according to the compensator output (e), and control is performed so that the change point of the binarization circuit output signal (a) and the phase of the falling edge of the reproduction clock (b) match.

Here, the data strobe circuits 23-2
There is no problem if the phase relationship between the binarized circuit output signal (a) and the reproduced clock (b) in FIG. 7 is as shown in the left diagram of FIG. However, in a certain data strobe circuit, as shown in the middle diagram of FIG. 8, and in a certain data strobe circuit, as shown in the right diagram of FIG. 8, the change point of the binarization circuit output signal (a) and the reproduction clock (b)
Since the phase margin of the rising edge of
It becomes more susceptible to noise at the changing point of the output signal (a).

Accordingly, the control circuit 44 adjusts the output voltage of the variable DC voltage source 45 so that the difference between the output voltages supplied from the compensators of the data strobe circuits 23 to 27 is minimized. Here, the reason why the output voltage of each compensator changes is that the control voltage of the tracking control is changed by changing the output voltage of the variable DC voltage source 45, that is, the focal point of the laser beam is shifted to a position slightly shifted from the track center. This is because the pulse width of the signal supplied to the binarization circuits 18 to 22 changes due to the adjustment.

By the adjustment described above, the voltage V1 in the middle diagram of FIG. 8 approaches the voltage V0, and the voltage V2 also becomes the voltage V0.
Approach. In other words, the phase margin between the change point of the binarization circuit output signal (a) and the rising edge of the reproduced clock (b) increases, thereby reducing the influence of noise at the change point of the binarization circuit output signal (a). Can be avoided.

Since the voltage V0 in the left diagram of FIG. 8 is higher or lower than this state, the phase margin between the change point of the binarization circuit output signal (a) and the rising edge of the reproduction clock (b) is obtained. Is smaller, but the binarization circuit output signal
There is no problem because the noise is not affected by the noise of (a).

According to the second embodiment described above, 2
Using the phase difference between the output signal of the digitizing circuit and the reproduced clock as a quality evaluation parameter of the reproduced signal, the control center of the tracking control is corrected so that the difference between the phase difference between the binarized signal of the reproduced signal and the reproduced clock in each track is reduced. This makes it possible to reduce the difference in quality of the reproduction signal from each track, thereby enabling highly reliable reading.

Although the first and second embodiments described above have described the tracking adjustment method, these embodiments may be applied to the focus adjustment method. FIG. 9 shows an example in which FIG. 1 showing the first embodiment is applied to focus. Similarly, FIG. 10 shows an example in which FIG. 5 showing the second embodiment is applied to focus. The difference between FIG. 1 and FIG. 9 and the difference between FIG. 5 and FIG. 10 is that the output of the TE signal calculation circuit 17 is supplied to the tracking servo control circuit 39, the output of the FE signal calculation circuit 16 is The outputs of the signal sources 45 are respectively supplied to the addition circuits 46,
The point is that the addition signal is supplied to the focus control circuit 38. By using these configurations and the adjusting method of the variable DC signal source 45 described in the first and second embodiments, the focus control center is corrected so that the difference in the quality of reproduction signals from a plurality of tracks is reduced. You. Therefore, data recorded on each track can be read with high reliability. The correction of the control center of focus and tracking may be used together.

[0066]

According to the present invention, in an optical disc apparatus in which information recorded on a plurality of tracks is simultaneously read by using a multi-laser beam to improve the reading speed, the number of data errors in each track can be reduced by an allowable data. It is possible to provide an optical disk device that can reduce the number of errors and can read information with high reliability.

[Brief description of the drawings]

FIG. 1 is a block diagram of an embodiment of the present invention.

FIG. 2 is a block diagram of a conventional example.

FIG. 3 is a schematic diagram of the number of data errors in each track in the conventional example.

FIG. 4 is a schematic diagram of the number of data errors in each track according to the present invention.

FIG. 5 is a block diagram of another embodiment of the present invention.

FIG. 6 is a schematic diagram of a binarization circuit output signal and a reproduction clock.

FIG. 7 is a schematic diagram of a data strobe circuit.

FIG. 8 is a schematic diagram of a waveform of each signal of the data strobe circuit.

FIG. 9 is a block diagram of another embodiment of the present invention.

FIG. 10 is a block diagram of another embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Semiconductor laser, 2 ... Collimator lens, 3 ... Diffraction grating, 4 ... Beam splitter, 5 ... Objective lens, 6 ... Optical disk, 7 ... Cylindrical lens, 8 ... Aperture lens, 9 ... Multi-beam photodetector, 10, 11 .., Photodetector, 12... 4-split photodetector, 12-1 to 12-4... Photodetector, 13, 14... Photodetector, 15.
FE signal operation circuit, 17 ... TE signal operation circuit, 18-2
2 ... binarization circuit, 23 to 27 ... data strobe circuit,
28 to 32: demodulation circuit, 33 to 37: error detection circuit, 3
8 focus servo control circuit 39 tracking servo control circuit 40 focus drive circuit 41 tracking drive circuit 42 focus actuator
43: tracking actuator, 44: control circuit,
45 variable DC signal source, 46 addition circuit, 47 latch circuit, 48 EXOR circuit, 49 compensator, 50 VC
O circuit, 51 ... counter circuit.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5D118 AA13 BA01 BB01 BD02 BF02 CA13 CB05 CC12 CD02 CD03 CD11 CF06 CG05 CG14 CG36

Claims (6)

[Claims] 1. An optical disk apparatus in which a spot position of a multi-laser beam applied to an optical disk changes in conjunction therewith, a multi-laser irradiating means including an objective lens and condensing the multi-laser beam corresponding to a plurality of tracks of the optical disk. A light detecting unit that converts each reflected light from the plurality of tracks into an electric signal corresponding to each intensity and outputs the electric signal; and calculates an output of the light detecting unit to calculate a position error of the objective lens with respect to an optical disc. Error signal calculation means for calculating a lens position error signal shown, digital conversion means for converting the output of the light detection means into a digital signal, and control means for controlling the position of the objective lens using the lens position error signal. Using the correction means for correcting the control target of the control means and the output of the digital conversion means. Quality detecting means for detecting the quality of the reproduced signal from each track, and adjusting the correction value of the correcting means so that the quality difference of the reproduced signal from each track outputted by the quality detecting means becomes small. Optical disk device. 2. The quality detection means according to claim 1, further comprising: an error detection means for detecting the number of read error data using an output of said digital conversion means, wherein a quality of a reproduced signal is determined based on an output of said error detection means. An optical disk device characterized by detecting the following. 3. The digital conversion means according to claim 1, further comprising a binarization means for binarizing an output of said light detection means with a reference value, wherein said quality detection means comprises a binarization means. Clock generating means for generating a clock synchronized with an output signal of the means, and phase difference measuring means for measuring a phase difference between the output signal of the binarizing means and the clock, wherein an output of the phase difference measuring means is provided. An optical disc device for detecting the quality of a reproduction signal based on the information. 4. The optical disc apparatus according to claim 1, wherein the error signal calculating means calculates a focus error signal indicating a position error of the objective lens with respect to a focus direction of the optical disc. 5. The optical disk apparatus according to claim 1, wherein the error signal calculating means calculates a tracking error signal indicating a position error of the objective lens with respect to a tracking direction of the optical disk. 6. The optical disk device according to claim 1, wherein, even if the correction value of said correction means is adjusted, if there is a defective track whose reproduction signal from each track is equal to or less than a predetermined quality, the defective track other than said defective track is provided. An optical disk device, wherein the correction means adjusts the correction value so as to reduce the quality difference of the reproduced signal from the track, and uses the reproduced signal from a track other than the defective track as the reproduced signal.