JPH1079171A - Optical disk apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an optical disk apparatus by which high-density recorded data is reproduced surely by a method wherein a low-frequency noise is removed from a reproduced signal, a lost low-frequency component is reproduced, a slice level or a DC level is made variable and binarized in such a way that a duty ratio becomes a prescribed value. SOLUTION: An HPF 12 removes a low-frequency noise from a reproduced signal RF. A comparison circuit 13 receives the output signal RF1 of the HPF 12 via an addition circuit 14 so as to binariezethe signal RF1. An LPF 15 suppresses a high-frequency component from the output signal of the circuit 13 so as to be fed back to the circuit 14. The circuit 14 adds the signal LPF1 to the signal RF1 so as to reproduce the low-frequency component of the spoiled signal RF. A comparison circuit 17 binarizes a reproduced signal RF2 from the circuit 14 so as to generate reproduced data D2 from the signal RF2. A duty-ratio detection circuit 18 changes an output signal level according to the duty ratio of the data D2 so as to be output as the slice level of the circuit 17. Thereby, even when the DC level of the signal RF is shifted, the edge of the data D2 is held at a correct timing.

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 can be applied to, for example, a write-once optical disk device. The present invention removes low-frequency noise from a reproduced signal using a high-pass filter, corrects a lost low-frequency component, and subsequently corrects a slice level or a DC level to generate reproduced data. The present invention effectively avoids the influence of area noise, and ensures that high-density recorded data can be reliably reproduced even when the DC level of a reproduction signal is displaced due to a change in laser power.

[0002]

2. Description of the Related Art Conventionally, in an optical disk apparatus of a write-once type or the like, a laser signal is controlled and a noise component is removed to binarize a reproduction signal, thereby reproducing data recorded at high density on an optical disk. Has been made.

That is, this type of optical disc apparatus encodes recording data using a modulation code such as an RLL (1, 7) code (Run Length Limited), and then encodes the resulting encoded data onto an optical disc. By recording, desired data is recorded at high density by applying a so-called edge recording technique.

At the time of this data recording, the optical disk device
By irradiating a laser beam to locally heat the information recording surface of the optical disk, pits are sequentially formed in accordance with the recording data, and thereby desired data is recorded. Therefore, in the optical disk device, when the laser power changes with respect to the optical disk, the size of the pit changes, and the DC level of the reproduced signal changes.

For this reason, the optical disk apparatus corrects the laser power at the time of recording according to the ambient temperature and the result of the trial writing in the trial writing area, and when the sensitivity of the recording medium is different, the ambient temperature becomes lower. Even if it changes, the laser power is controlled so that a pit of a predetermined shape can always be formed.

However, in the optical disk apparatus, the DC level of the reproduction signal fluctuates not only due to fluctuations in the reflectance and sensitivity of the recording medium, but also due to residual errors during focus control and tracking control. Observed as low frequency noise. For this reason, in the optical disk device, low-frequency noise mixed in the reproduced signal is removed by a high-pass filter, and then binarized by a predetermined slice level to generate reproduced data.

[0007] Through these processes, the optical disk device causes the logical level to be switched at the correct timing (ie, at the timing corresponding to the coded data at the time of recording) in the generated reproduced data, so that the bit error of the reproduced data is obtained. Has been made to effectively avoid.

[0008]

However, even when the laser power is controlled based on the results of trial writing, it is difficult to completely maintain the laser power at an optimum value, and the DC level may be displaced from the optimum value. . In this case, the DC level of the reproduced signal is displaced, the timing of the edge of the reproduced data is displaced, and a bit error may occur.

The present invention has been made in view of the above points, and aims to propose an optical disk apparatus capable of reliably reproducing data recorded at high density even when the laser power is displaced from an optimum value. It is.

[0010]

According to the present invention, there is provided a high-pass filter for suppressing a low-frequency component of a reproduction signal, an addition circuit for adding an output signal of the high-pass filter and a correction signal, A first comparison circuit for binarizing the output signal of the adder circuit, and a frequency characteristic complementary to that of the above-mentioned high-pass filter; And a low-pass filter that generates In addition to the above configurations, a second comparison circuit for binarizing the output signal of the addition circuit and outputting reproduction data, and a second comparison circuit for setting a duty ratio of the reproduction data to a predetermined value. And a control circuit for varying the DC level of the output signal of the adder circuit or the slice level of the control signal.

Alternatively, a first high-pass filter for suppressing a low-frequency component of a reproduced signal, an adding circuit for adding an output signal of the first high-pass filter and a correction signal, and an output of the adding circuit A first comparison circuit for binarizing the signal; and a frequency characteristic complementary to that of the first high-pass filter. And a low-pass filter to be generated. In addition to these configurations, a second high-pass filter that removes and outputs a DC component from the output signal of the above-described addition circuit and a second high-pass filter that binarizes the output signal of the second high-pass filter and outputs reproduced data 2 comparison circuits.

In the high-pass filter, if low-frequency components of the reproduced signal are suppressed, low-frequency noise of the reproduced signal can be removed. Further, the output signal of the high-pass filter and the correction signal are added by an adder circuit, and the output signal of the adder circuit is binarized. Then, the output signal of the high-pass filter is corrected by a low-pass filter having a frequency characteristic complementary to that of the previous high-pass filter. By generating a signal, it is possible to reproduce the low-frequency component lost when removing the low-frequency noise. Subsequently, the output signal of the adder circuit is binarized to output reproduced data, and the control circuit changes the slice level or the DC level of the output signal of the adder circuit so that the duty ratio of the reproduced data becomes a predetermined value. For example, the slice level or the DC level can be controlled according to the DC level of the reproduction signal that changes according to the light beam light amount at the time of recording, and the edge change in the reproduction data can be effectively avoided.

Similarly, if the low-frequency component of the reproduced signal is removed by the first high-pass filter and the lost low-frequency component is reproduced, only the DC component can be removed by the second high-pass filter. it can. Therefore, by generating the reproduced data by binarizing the second high-pass filter, the effect of the low-frequency component of the modulation code can be effectively avoided, and the DC level of the DC level that changes according to the light beam light amount at the time of recording can be effectively avoided. The change can be effectively avoided, and the reproduced signal can be binarized, whereby the change of the edge in the reproduced data can be effectively avoided.

[0014]

Embodiments of the present invention will be described below in detail with reference to the drawings.

(1) First Embodiment FIG. 2 is a block diagram showing an optical disk drive according to a first embodiment of the present invention. The optical disk drive 1 switches operations under the control of an external device, records input data input from the external device on the optical disk 2, and reproduces and outputs data recorded on the optical disk 2.

The optical disk 2 is a so-called phase-change type optical disk, in which pre-pits are formed in advance by a formatter and pre-formatted. As a result, the optical disc 2 can perform tracking control by applying a so-called sample format technique, and can be driven to rotate. In addition, the recording / reproducing position is confirmed, and desired data can be recorded / reproduced in sector units. .

The spindle motor 3 is used for the optical disk 2
Is held by chucking, and the optical disk 2 is rotationally driven at a predetermined rotational speed. The spindle servo circuit 4
The drive speed of the spindle motor 3 is controlled by the drive controller 5 based on the reproduction result of prepits obtained by irradiating the optical disk 2 with a laser beam.

The thread servo circuit 6 is controlled by the drive controller 5, drives a thread motor (not shown) to move the optical pickup 7 in the radial direction of the optical disk 2, and performs a tracking control process together with the tracking control mechanism of the optical pickup 7. I do.

The optical pickup 7 emits a laser beam L from a built-in laser diode, and irradiates the optical disk 2 with the laser beam L via an objective lens.
Further, the optical pickup 7 receives the return light of the laser beam L by a light receiving element via an objective lens, and performs an arithmetic processing of the received light by an arithmetic processing circuit (not shown).

As a result, the optical pickup 7 reproduces the reproduced signal R whose signal level changes following the change in the amount of return light.
F, which generates and outputs a focus error signal FE whose signal level changes according to the defocus amount of the laser beam L and a tracking error signal TE whose signal level changes according to the detrack amount of the laser beam L.

When irradiating the laser beam in this manner, the optical pickup 7 is controlled by a built-in automatic light amount control circuit to change the laser power in the user data area of each sector from the light amount at the time of reproduction at the time of recording. The light is intermittently started at the writing light amount, whereby pits are sequentially formed on the optical disk 2 corresponding to the encoded data input from the signal processing circuit, and the encoded data is recorded on the optical disk 2.

At this time, the optical pickup 7 controls the light quantity of this writing based on the ambient temperature as a result of the trial writing in the trial writing area, thereby changing the sensitivity of the optical disk 2 or changing the ambient temperature. However, pits having a fixed shape are sequentially formed.

The pickup servo circuit 8 moves the objective lens of the optical pickup 7 left and right and up and down in response to the tracking error signal TE and the focus error signal FE input via the signal processing circuit 9, thereby performing tracking control. And focus control. In the optical disk drive 1, the tracking error signal TE
The tracking control is also performed by driving the sled motor in accordance with the low-frequency component.

The drive controller 5 is formed of a microcomputer for controlling the operation of the entire optical disk drive 1. The drive controller 5 responds to a control command input from an external device, and supplies a recording / reproduction supplied via a signal processing circuit 9. The operation of the thread servo circuit 6 and the like is controlled based on the position information. Thus, the optical disk drive 1 can access the optical disk 2 in response to a request from an external device while the optical disk 2 is driven to rotate.

The signal processing circuit 9 binarizes the reproduction signal RF output from the optical pickup 7 to generate reproduction data, and then generates a reproduction clock from the reproduction data.
Further, the signal processing circuit 9 decodes and reproduces the reproduced data with reference to the reproduced clock, thereby reproducing and outputting the data D1 recorded on the optical disk 2.

At this time, the signal processing circuit 9 detects the preformatted address data from the reproduced data and outputs it to the drive controller 5, whereby the optical disk drive 1 checks the recording / reproducing position and accesses the desired sector. It is formed so that it can be done. The signal processing circuit 9 amplifies the tracking error signal TE and the focus error signal FE and outputs the amplified signal to the pickup servo circuit 8.

FIG. 1 is a block diagram showing a reproduced signal processing circuit in the signal processing circuit 9. Signal processing circuit 9
In the reproduction signal processing circuit 10, the reproduction signal RF
After correcting the signal level of the reproduced data D2
Is generated, and processing such as decoding and error correction is performed by the subsequent digital signal processing circuit to output data D1.

In the reproduction signal processing circuit 10, a high-pass filter (HPF) 12 suppresses and outputs a low frequency band of the reproduction signal RF, thereby removing low-frequency noise from the reproduction signal RF. The comparison circuit (COM) 13 includes the addition circuit 1
4, the output signal RF of the high-pass filter 12
1, the output signal RF1 is binarized and output.

The low-pass filter (LPF) 15 has a frequency characteristic set to a characteristic complementary to that of the high-pass filter 12, suppresses high-frequency components from the output signal COM 1 of the comparison circuit 13, and feeds it back to the addition circuit 14. The adding circuit 14 adds the output signal LPF1 of the low-pass filter 15 to the output signal RF1 of the high-pass filter 12 and outputs the result. Thereby, the comparison circuit 13, the addition circuit 14, and the low-pass filter 1
5 reproduces the low-frequency component of the reproduction signal RF damaged by the high-pass filter 12.

The comparison circuit 17 binarizes the reproduction signal RF2 output from the addition circuit 14, thereby generating and outputting reproduction data D2 from the reproduction signal RF2. The duty ratio detection circuit 18 changes the signal level of the output signal according to the duty ratio of the reproduced data D2,
This output signal is output as a slice level of the comparison circuit 17. Accordingly, the comparison circuit 17 and the duty ratio detection circuit 18 switch the slice level so that the reproduction signal RF2 is binarized so that the duty ratio of the reproduction data D2 becomes a predetermined duty ratio, and the laser power at the time of recording is optimized. Even if the DC level of the reproduction signal RF shifts due to a further displacement, the edge of the reproduction data D2 is held at the correct timing.

Specifically, the reproduction signal processing circuit 10
It is formed as shown in FIG. That is, the reproduction signal processing circuit 1
0 receives the reproduction signal RF in the addition circuit 14 via the capacitor 20, and inputs the output signal RF2 of the addition circuit 14 to the non-inverting input terminal of the comparison circuit 13. This comparison circuit 13
Sets the slice level to 0 level by grounding the inverting input terminal, and binarizes the reproduction signal RF2 by this slice level. The comparison circuit 13 outputs an output signal obtained by binarization to the addition circuit 14 via the resistor 21.

As a result, the capacitor 20 and the resistor 21
Forms a high-pass filter 12 (FIG. 1) when viewed from the input end side of the reproduction signal processing circuit 10;
When viewed from the output end of the high-pass filter 12, as shown in FIG.
A low-pass filter 15 (FIG. 2) having 5A is formed. The cut-off frequencies f of the high-pass filter 12 and the low-pass filter 15 are as follows: the capacitance of the capacitor 20 is C, and the resistance of the resistor 21 is R
And expressed by 1 / 2πRC.

Thus, the reproduction signal processing circuit 10 removes the low-frequency noise LN from the reproduction signal RF (FIG. 5A) by the high-pass filter 12 of the capacitor 20 and the resistor 21, and reproduces the reproduction signal by the low-frequency noise LN. RF pulsation is suppressed (FIG. 5B). Further, a reproduction signal processing circuit 1
0 binarizes the output signal RF1 of the high-pass filter 12 input via the addition circuit 14 (see FIG. 5).
(C)), by feeding back the binarized output signal through the low-pass filter 15, a low-frequency component of the reproduction signal RF1 is extracted by a time constant determined by the constants of the capacitor 20 and the resistor 21 (FIG. D)), high-pass filter 1
2 reproduces the low-frequency components lost. At this time, by setting the frequency characteristics of the high-pass filter 12 and the low-pass filter 15 to complementary frequency characteristics, the reproduction signal processing circuit 10 reliably reproduces the low-frequency components lost in the high-pass filter 12 by the low-pass filter 15. .

When pits are successively formed by modulating the laser beam L with a recording signal S1 (FIG. 6A) having a duty ratio of 50%, when the laser power is held at an optimum value, the optical disk In No. 2, pits and lands are formed to have the same length in the track direction.
Thus, in the reproduced signal RF2 obtained by reproducing the lost low-frequency component, the DC level is maintained at 0 level (FIG. 6B), and the 0 level is set to the slice level SL. The original recording signal waveform can be reproduced.

On the other hand, when the laser power is smaller than the optimum value (FIG. 6 (C)), the pit length is correspondingly shorter, and the DC level is reduced. Therefore, in this case, the slice level SL
1 and reduce the duty ratio to 50.
The recording signal waveform of [%] can be reproduced, and the timing of the edge of the reproduction data D2 can be set to the correct timing.

On the contrary, when the laser power is larger than the optimum value (FIG. 6D), the length of the pit is formed longer and the DC level rises. Therefore, in this case, the signal level of the slice level SL2 is increased and the duty ratio 50
The recording signal waveform of [%] can be reproduced, and the timing of the edge of the reproduction data D2 can be set to the correct timing.

That is, when the DC level is reproduced in this manner, the edge level of the reproduction data D2 can be set to the correct timing by changing the slice level in response to the DC level of the reproduction signal. By effectively utilizing this relationship, the reproduction signal processing circuit 10 detects the duty ratio of the reproduction signal RF2 at the timing at which the reproduction signal RF having the duty ratio of 50% is obtained,
The slice level of the comparison circuit 17 is set based on the detection result, and the slice level is controlled in response to the DC level of the reproduction signal RF which changes according to the displacement from the optimum value.

That is, the comparison circuit 17 (FIG. 3) receives the reproduction signal RF2 at the non-inverting input terminal, and inputs the output signal SL of the duty ratio detecting circuit 18 to the non-inverting input terminal.

The duty ratio detection circuit 18 receives the reproduction data D2 from the current drive type operational amplifier circuit 23, and according to the logic level of the reproduction data D2, the integration capacitor 24.
, And discharges the discharge current from the integrating capacitor 24 in the opposite direction. Accordingly, the duty ratio detection circuit 18 varies the terminal voltage of the integration capacitor 24 according to the duty ratio of the reproduction data D2.

At this time, in the duty ratio detecting circuit 18, the operational amplifier circuit 23 is controlled by the gate signal GT output from the timing generator to execute the above-described charging / discharging process, whereby the reference signal recorded on the optical disk 2 is obtained. The duty ratio of the reproduction signal RF2 is detected at the timing of the signal.

Here, on the optical disk 2, a reference signal VFO is recorded at a fixed period by preformatting. When data is recorded in the user data area, the same reference signal VFO is repeatedly recorded a predetermined number of times. Necessary data is recorded. As the reference signal VFO, a reference signal having a duty ratio of 50 [%] at which the signal level switches at a period of 2T with respect to the reference period T of the pit formation period of the optical disk 2 (FIG. 7)
(A)) In the optical disc drive 1, a reproduction clock is generated by a PLL circuit based on the reproduction result of the reference signal VFO.

The gate signal GT is generated by the timing generator so that the signal level rises at the timing of the reference signal VFO recorded at the head of the preformat section (FIG. 7B). Thus, the operational amplifier circuit 23 detects the DC level displacement of the reproduction signal RF2 based on the reproduction data D2 of the reference signal VFO.

That is, the duty ratio detection circuit 18
The terminal voltage of the integrating capacitor 24 is compared with the voltage of the comparing circuit 1 via the operational amplifier circuit 25 having a voltage follower circuit configuration.
7, thereby varying the slice level of the comparison circuit 17 according to the duty ratio detection result.

For example, when reproducing data recorded with an amount of light lower than the optimum value, the reproduction signal RF (FIG. 8A) containing low-frequency noise is removed by the high-pass filter 12 while the low-frequency noise is removed. The low-frequency component is lost (FIG. 8B), and the output signal LP of the low-pass filter 15 is output.
By adding F1 (FIG. 8C), the lost low-frequency component is reproduced (FIG. 8D).

Further, in the reproduction signal RF2, the slice level SL is variably controlled in accordance with the reproduced DC level, and reproduction data D2 (FIG. 8E) is generated based on the slice level SL. In other words, even when the laser power during recording is displaced from the optimum value, the slice level SL is corrected and binarized according to the DC level that changes according to the displacement, and the original recording signal waveform is correctly reproduced. Will be done.

As a result, the optical disk drive 1 can generate a reproduction clock from the reproduction data D2 of the reference signal VFO and generate the reproduction clock at the correct timing. Further, by processing other reproduction data D2 based on this reproduction clock, bit errors can be effectively avoided and the reproduction data D2 can be processed, thereby reliably reproducing data recorded at high density. Can be.

In the above configuration, the optical disk 2 is irradiated with the laser beam L from the optical pickup 7 while being rotated and driven by the spindle motor 3, and the return light of the laser beam L is received by the optical pickup 7, A reproduction signal RF, a tracking error signal TE, a focus error signal FE, and the like are generated.

The reproduced signal RF is transmitted to the signal processing circuit 9.
After the data is binarized and reproduced data D2 is generated, the reproduced data D2 undergoes a predetermined process to reproduce the data D1 recorded on the optical disk 2.

In the signal processing circuit 9, the reproduced signal R
F is input to the capacitor 20 of the reproduction signal processing circuit 10 (FIGS. 1 and 3), and the capacitor 20 and the resistor 21
The low-pass noise is removed by the high-pass filter 12 and the low-pass component is lost. The reproduction signal RF1 is input to the comparison circuit 13 via the addition circuit 14, where the reproduction signal RF1 is binarized based on the 0 level, and then has a complementary characteristic with the high-pass filter 12 formed by the resistor 21 and the capacitor 20. The low-frequency component is reproduced by the low-pass filter 15, and the reproduced low-frequency component is added by the adding circuit 14.

As a result, in the reproduction signal RF2, only the low-frequency noise is removed while maintaining the low-frequency component, and
, Where the data is binarized by the slice level SL to generate reproduction data D2. At this time, the reproduction signal R
F2 is a reference signal VFO having a duty ratio of 50%.
At the timing of FIG. 7, the charge / discharge current is supplied from the operational amplifier circuit 23 to the integration capacitor 24 in accordance with the logic level of the reproduced data D2, so that the duty ratio of the reference signal VFO having the duty ratio 50 [%] is reduced. The displacement of the ratio is detected, and the slice level S
L is controlled.

As a result, the reproduction signal RF2 has the slice level S so as to correct the displacement of the laser power during recording.
In a state where L is controlled, the data is binarized and converted into reproduction data D2, and even when the laser power is displaced from the optimum value, the edge of the reproduction data D2 can be held at a correct timing.

In the above arrangement, after the low-pass noise is removed from the reproduced signal by the high-pass filter, the low-pass component lost when the low-pass noise is removed is reproduced by the low-pass filter having a complementary frequency characteristic. Subsequently, by controlling the slice level and binarizing the signal so that the duty ratio becomes a predetermined value, the edge of the reproduction data D2 can be held at the correct timing even when the laser power is displaced from the optimum value. Thus, data recorded at high density can be reproduced by effectively avoiding bit errors.

(2) Second Embodiment FIG. 9 is a block diagram showing a reproduced signal processing circuit according to a second embodiment of the present invention. In this embodiment, reproduction data D2 is generated from a reproduction signal RF by using a reproduction signal processing circuit 30 instead of the reproduction signal processing circuit 10 according to the first embodiment. Note that FIG. 10 following FIG.
In the configuration shown in FIG. 5, the same components as those in FIGS. 1 and 3 described above are denoted by the same reference numerals, and redundant description will be omitted.

That is, the reproduced signal processing circuit 30 removes low-frequency noise from the reproduced signal RF by the high-pass filter 12, and reproduces the low-frequency component by the adding circuit 14, the comparing circuit 13, and the low-pass filter 15. Further, the reproduction signal processing circuit 30 inputs the output signal RF2 of the addition circuit 14 to the high-pass filter 31, and removes a DC level generated when the laser power is displaced from an optimum value.
The subsequent comparison circuit 32 generates reproduced data D2.

More specifically, as shown in FIG. 10, the reproduction signal processing circuit 30 inputs the reproduction signal RF2 output from the addition circuit 14 to a high-pass filter of a capacitor 33 and a resistor 34, and outputs the high-pass filter. Signal HPF
2 is input to the non-inverting input terminal of the comparison circuit 32. The comparison circuit 32 is configured such that the slice level is set to 0 level by grounding the inverting input terminal.

Here, the high-pass filter including the capacitor 33 and the resistor 34 has a cutoff frequency of the first
Is selected so as to have a frequency sufficiently lower than that of the high-pass filter 12, thereby effectively avoiding the waveform deterioration of the output signal HPF2 and removing only the DC component of the reproduction signal RF. Thereby, in the reproduction signal processing circuit 30,
From the reproduction signal RF2 obtained by reproducing the DC component, a component in a lower frequency range (including a DC component) is further removed as compared with the low frequency component removed by the first high-pass filter 12. As a result, the reproduction signal processing circuit 30 removes the change in the DC level that changes according to the laser power at the time of recording, and binarizes the reproduction signal.

That is, in the reproduced signal RF (FIG. 11A) input to the reproduced signal processing circuit 30, low-pass noise is removed by the high-pass filter 12 (FIG. 11B), and the low-frequency component of the signal is also added. Is lost. Thereby, the addition circuit 1
4, the output signal RF1 of the high-pass filter 12 is replaced by the output signal LPF1 of the low-pass filter 15 (FIG. 11).
(C)), and the reproduction signal RF2 is obtained as shown in FIG.
(D)), the low-frequency component from which the signal has been lost is reproduced, and the DC component is removed (the DC level is set to 0 level) in the subsequent high-pass filter 31 (FIG. 11).
(E)).

Thus, in the comparison circuit 32, the output signal HPF2 of the high-pass filter 31 is binarized on the basis of the 0-level slice level SL, and the influence of the low-frequency component of the modulation code and the influence of the laser power displacement. Can be effectively prevented, and the reproduced data D2 can be generated with a signal waveform equal to the recording signal waveform (FIG. 11F).

According to the configuration shown in FIG. 9, after the low-pass noise is removed from the reproduced signal by the high-pass filter, the lost low-pass component is reproduced, and then the DC component is removed and binarized. Even when the laser power is displaced from the optimum value, the edge of the reproduction data D2 can be held at the correct timing, thereby effectively preventing bit errors and reproducing data recorded at high density.

(3) Other Embodiments In the first embodiment described above, the case where the slice level of the comparison circuit is controlled based on the duty ratio detection result has been described. However, the present invention is not limited to this. Instead of the slice level, the DC level of the output signal output from the adding circuit 14 may be controlled. In this case, for example, the output signal of the adder circuit 14 is clamped by a clamp circuit, and the clamp level can be controlled and executed based on the duty ratio detection result.

In this case, for example, when the DC level of the reference signal VFO is 0, the DC level of the reproduced signal RF of the reference signal VFO is clamped to the 0 level, so that the slice of the 0 level is obtained. Reproduced data with a duty ratio of 50% can be obtained at the level. As a result, the DC level of the reproduction signal RF2 is clamped at the timing of the reference signal VFO so as to be 0 level, and the output signal of the addition circuit is
The DC level can be corrected to have a predetermined duty ratio with a simple configuration.

Further, in the first embodiment, the case where the duty ratio is detected by the integration circuit has been described. However, the present invention is not limited to this. For example, the duty ratio may be determined based on the result of phase comparison with a reproduced clock or the like. The ratio may be detected.

In the above-described embodiment, the case where desired data is recorded / reproduced using a phase change type optical disk has been described. Can be widely applied to the case of recording / reproducing, and the case of reproducing desired data using a read-only optical disk.

[0064]

As described above, according to the present invention, after removing the low-frequency noise from the reproduction signal, the lost low-frequency component is reproduced, and then the slice level is adjusted so that the duty ratio becomes a predetermined value. Or by varying the DC level and binarizing, or by removing the DC component and binarizing,
The effect of noise can be effectively avoided, and even when the DC level of a reproduction signal is displaced due to a change in laser power, data recorded at high density can be reliably reproduced.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a reproduction signal processing circuit of an optical disk drive according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing an overall configuration of the optical disk drive of FIG.

FIG. 3 is a connection diagram showing a specific configuration of a reproduction signal processing circuit of FIG. 1;

FIG. 4 is a characteristic curve diagram showing characteristics of a high-pass filter and a low-pass filter of the reproduction signal processing circuit of FIG.

FIG. 5 is a signal waveform diagram for explaining reproduction of a DC component in the reproduction signal processing circuit of FIG. 1;

FIG. 6 is a signal waveform diagram showing a relationship between laser power and a slice level during recording.

FIG. 7 is a signal waveform diagram for explaining an operation of a duty ratio detection circuit in the reproduction signal processing circuit of FIG. 3;

FIG. 8 is a signal waveform diagram for explaining generation of reproduction data D2.

FIG. 9 is a block diagram showing a reproduction signal processing circuit of the optical disk drive according to the second embodiment of the present invention.

FIG. 10 is a connection diagram showing a specific configuration of the reproduction signal processing circuit of FIG. 9;

11 is a signal waveform chart for explaining the operation of the reproduction signal processing circuit of FIG. 10;

[Explanation of symbols]

1 ... optical disk drive, 2 ... optical disk, 10,
Reference numeral 30: reproduction signal processing circuit, 12, 31, high-pass filter, 13, 17, 32, comparison circuit, 14, addition circuit, 15, low-pass filter, 18: duty ratio detection circuit

Claims (2)

[Claims] 1. A method for irradiating a disk-shaped recording medium with a light beam,
An optical disc apparatus for reproducing data recorded on the disc-shaped recording medium based on a reproduction signal obtained by receiving the return light of the light beam, wherein a high-pass filter for suppressing and outputting a low-frequency component of the reproduction signal An addition circuit that adds and outputs the output signal of the high-pass filter and the correction signal; a first comparison circuit that binarizes and outputs the output signal of the addition circuit; and a frequency that is complementary to the high-pass filter. A low-pass filter having characteristics and suppressing the high band of the output signal of the comparison circuit to generate the correction signal; and binarizing the output signal of the addition circuit with reference to a slice level to output reproduced data. A second comparison circuit, the slice level or the DC level of the output signal of the addition circuit being set so that the duty ratio of the reproduction data becomes a predetermined value. Optical disk apparatus characterized by comprising a control circuit for. 2. A disk-shaped recording medium is irradiated with a light beam,
An optical disc device for reproducing data recorded on the disc-shaped recording medium based on a reproduction signal obtained by receiving the return light of the light beam, wherein a first component for suppressing and outputting a low-frequency component of the reproduction signal is provided. A high-pass filter, an addition circuit that adds and outputs an output signal of the first high-pass filter and a correction signal, a first comparison circuit that binarizes and outputs an output signal of the addition circuit, A low-pass filter having a frequency characteristic complementary to the high-pass filter of No. 1 and suppressing the high frequency of the output signal of the comparison circuit to generate the correction signal; and removing a DC component from the output signal of the addition circuit. A second high-pass filter for outputting, and a second comparison circuit for binarizing an output signal of the second high-pass filter with reference to a slice level and outputting reproduced data. Optical disc apparatus according to claim Rukoto.