JPH10302398A - Recorded signal reproducing method and optical disk device using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To read out correctly a recorded signal by preventing the influence of dispersion of a characteristic of a disk, dust, and the like. SOLUTION: A reproduced signal SMOB of an optical disk outputted from an amplifier 301 is supplied to a peak-hold 303 and a bottom-hold 305, a signal Sv indicating a level between an amplifier 306 and an envelope is obtained, and supplied to comparators 310, 311. A range is set by signals Vref, Vdb so that the signal Sv is in the prescribed level range even if the signal Sv is varied based on a signal of a disk. When a level of the signal Sv is varied by dust and the like and it is larger than a level range, down-count is performed using a signal CLK by a counter 314, when it is smaller, up-count is performed. Gain of the amplifier 301 is adjusted by a signal GC based on a counted value and a level of the signal SMOB is controlled. An average value signal Savg is obtained by an average value calculating circuit 307. A signal SMOC excluding offset variation and level variation is obtained from the amplifier 320 based on the signals SMOB, Savg.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording signal reproducing method and an optical disk device using the same. More specifically, for example, the envelope of a reproduction signal obtained by reproducing an optical disk is detected, the amplitude level of the reproduction signal is obtained based on the envelope, and the fluctuation of the amplitude level of the reproduction signal is based on the signal recorded on the recording medium. In some cases, the level range is set so that the amplitude level falls within a predetermined level range, and when the amplitude level of the reproduction signal fluctuates due to dust or the like and exceeds the predetermined level range, the amplitude level of the reproduction signal becomes a predetermined level. By controlling the signal level of the reproduction signal so as to be within the level range, only the variation in the amplitude level of the reproduction signal that is not based on the signal recorded on the recording medium is corrected. By performing processing such as waveform equalization, a digital signal recorded on a recording medium can be correctly read.

[0002]

2. Description of the Related Art In a conventional optical disk apparatus, the signal level of a reproduction signal of an optical disk fluctuates due to the influence of dust or the like adhering to the surface of the optical disk or the change in the amount of return light due to the change in the amount of laser light, or the reflection of the optical disk. It is known that the offset level of the reproduction signal of the optical disk is fluctuated due to the variation of the index and the birefringence, and for example, a clamp circuit is used to remove the influence of the fluctuation of the signal level of the reproduction signal and the fluctuation of the offset level. I have.

This clamp circuit, as shown in FIG.
A reproduction signal SMO obtained by reproducing the optical disk is supplied to a non-inverting input terminal of an operational amplifier 71 and a sample and hold circuit 72.
Supplied to Further, a clamp signal CL is supplied to the sample hold circuit 72. This clamp signal C
L is a signal indicating that the signal is a region (hereinafter, referred to as a “clamping region”) in which a signal for clamping operation (for example, “0”) provided in sector units or segment units is recorded.

In the sample hold circuit 72, the signal level of the reproduced signal SMO when the clamp area is reproduced based on the clamp signal CL is held and supplied to the inverting input terminal of the operational amplifier 71 as the clamp level signal SCL. For this reason, the operational amplifier 71 outputs the reproduced signal SMOC from which the influence of the fluctuation of the signal level and the fluctuation of the offset level has been removed by the clamp processing.

[0005]

In such a clamp circuit, if the cycle of the clamp signal CL is not short with respect to the cycle of the offset level fluctuation, for example, as shown in FIG. The effects cannot be fully eliminated.

In FIG. 7, FIG. 7A shows a reproduced signal SMO, and FIG. 7B shows a clamp signal CL. In the sample hold circuit 72, when the clamp signal CL is set to the high level "H", the signal level of the reproduction signal SMO is held, and the clamp level signal SCL shown in FIG. 7C is generated. The clamp level signal SCL and the reproduction signal S
Based on the MO, as shown in FIG. 7D, the operational amplifier 71 outputs the reproduced signal S affected by the fluctuation of the offset level.
MOA is output.

[0007] Further, the fluctuation of the signal level caused by dust or the like must be corrected in real time, but as shown in FIG. 8, the frequency band of the fluctuation of the signal level of the reproduced signal caused by the dust or the like is recorded. Since the frequency band of the fluctuation of the signal level based on the signal is close, if it is assumed that the gain of the amplifier is controlled to prevent the fluctuation of the signal level by removing the influence of the fluctuation of the amplitude level caused by dust or the like, MTF (Modulation Transfer Functio
Even when the signal level of the reproduced signal fluctuates due to n) or the like, the signal level of the reproduced signal is varied. here,
PRML (Partial R) used to increase the recording density
Using a signal processing method called "esponse maximum likelihood", for example, a reproduced signal is converted into a ternary signal, a ternary signal is converted into binary data, and a waveform equalization process is performed. If it is assumed that an error in data detection by Viterbi decoding is prevented and a correct signal is obtained, the signal level of the reproduced signal is varied to cause signal distortion, resulting in a different ternary signal, and correct signal reproduction. May not be possible.

In view of the above, the present invention provides a recording signal reproducing method capable of correctly reading recorded signals while preventing the effects of variations in disk characteristics and dust and the like, and an optical disk apparatus using the same. .

[0009]

A recording signal reproducing method according to the present invention is provided only when the amplitude level of a reproduced signal obtained by reproducing a recording medium on which a digital signal is recorded is not within a predetermined level range. Controlling the amplitude level of the reproduction signal to be within a predetermined level range and processing the reproduction signal having the amplitude level within the predetermined level range to obtain a digital signal recorded on a recording medium. .

[0010] Also, an optical disk device according to the present invention is a disk drive.
An optical disk reproducing means for reproducing the optical disk to obtain a reproduced signal; a level varying means for varying and outputting the signal level of the reproduced signal obtained by the optical disk reproducing means; and an amplitude level of the reproduced signal outputted from the level varying means. Level detecting means for detecting, determining means for determining whether the amplitude level detected by the level detecting means is greater than or less than a predetermined level range, and reproduction output from the level varying means based on the determination result of the determining means Level change control means for controlling the level variable means so that the amplitude level of the signal is within a predetermined level range, and range setting means for setting the predetermined level range, and the reproduction signal output from the level variable means This is to obtain a signal recorded on the optical disk by processing.

The level detecting means includes a peak hold circuit for sequentially holding a peak value of the reproduced signal output from the level varying means to obtain an envelope on a peak side of the reproduced signal, and a reproducing signal outputted from the level varying means. , A bottom hold circuit for sequentially holding the bottom values of the signals to obtain an envelope on the bottom side of the reproduced signal, and an amplitude detector for detecting an amplitude level from the envelope obtained by the peak hold circuit and the bottom hold circuit.

Also, an average value calculating means for obtaining an average signal level of the reproduced signal output from the level variable means using the envelopes obtained by the peak hold circuit and the bottom hold circuit, and an output signal from the level variable means. Offset correction means for subtracting the average level obtained by the average value calculation means from the reproduction signal to remove offset fluctuations of the reproduction signal output from the level variable means.

Further, the level fluctuation control means includes a counter and a clock signal generating circuit for generating a clock signal serving as a reference for the counter operation of the counter. The counter has a predetermined amplitude level based on the result of the determination by the determination means. When the level is larger or smaller than the level range, a count-up or count-down operation is performed using the clock signal generated by the clock signal generation circuit, and the amplitude of the reproduced signal output from the level varying means is calculated using the count value of the counter. The level varying means is controlled so that the level falls within a predetermined level range.

In the present invention, for example, an envelope is detected from a reproduced signal obtained by reproducing an optical disk, and the amplitude level of the reproduced signal is obtained from the envelope. Here, when the fluctuation of the amplitude level of the reproduction signal is based on the signal recorded on the recording medium, the predetermined level range is set so as to be within the predetermined level range. When the amplitude level of the reproduced signal fluctuates due to dust or the like and the discriminating means determines that the amplitude level is larger or smaller than a predetermined level range, the counter counts up or down based on the clock signal according to the discrimination result. A count is made. The level varying means is controlled based on the count value, and when the amplitude level is larger than a predetermined level range, the amplitude level of the reproduced signal is reduced. When the amplitude level is smaller than the predetermined level range, the amplitude level of the reproduced signal is reduced. Is controlled to be within a predetermined level range. Further, a new reproduced signal from which the amplitude level and the offset fluctuation are removed is generated by subtracting the average level of the signal level of the reproduced signal from the reproduced signal whose amplitude level is within a predetermined level range.

[0015]

Next, an embodiment of an optical disk according to the present invention will be described. In FIG. 1, for example, a magneto-optical disk 10 of a sample servo system is rotated at a predetermined speed by a spindle motor 55. In order to record a signal or read a signal recorded on the magneto-optical disk 10, a laser beam is applied to the magneto-optical disk 10 by an optical pickup 2 constituting a disk reproducing unit.
Irradiated from 1. The output of the laser light is controlled based on a laser control signal LC from the laser control unit 51. The disk reproducing means includes an optical pickup 21 and an IV conversion matrix section 22, which will be described later.

In the optical pickup 21, the reflected light shifted from the magneto-optical disk 10 is incident on, for example, a Wollaston prism (not shown), which is a kind of birefringent prism, and a P component wave and an S component wave are obtained. And the P component wave and the S component wave are respectively guided to a photodetector (not shown),
A current signal corresponding to each component wave is generated by photoelectric conversion. This current signal is supplied to the IV conversion matrix unit 2
2 is supplied.

In the IV conversion matrix section 22, after the current signal supplied from the optical pickup 21 is converted into a voltage signal, a voltage signal based on the P component wave and the S component wave is added to generate a signal SA. At the same time, the voltage signal is subtracted to generate a signal SMO. The signal SA is supplied to an A / D converter 23, where the signal SA is converted into a digital signal DTA based on a clock signal CKS, which will be described later, and then a PLL is applied.
(Phase Locked Loop) unit 24 and tracking error signal generation unit 26. The signal SMO is supplied to the signal correction unit 30 as a reproduction signal. Further, in the IV conversion matrix unit 22, a focus error signal FE indicating a focus error is generated, and the servo control unit 52
Supplied to

In the PLL section 24, a clock signal CKS synchronized with the sample servo mark of the magneto-optical disk 10 is generated from the signal DTA and supplied to the A / D conversion section 23 and the timing signal generation section 25. In the PLL section 24, a data read clock signal CKD is generated and supplied to the timing signal generation section 25 and an A / D conversion section 31 described later.

The timing signal generator 25 generates a data synchronizing signal DSY as a reference for correctly reading a data signal recorded on the magneto-optical disk based on the clock signals CKS and CKD, and supplies the data synchronizing signal DSY to the data detector 32. . Further, a position signal ST indicating the timing of the sample servo mark for correctly irradiating the laser light on the track is generated and supplied to the tracking error detection unit 26. Further, the timing signal generation unit 25 generates a timing signal WT indicating a data recording area when recording data, and supplies the timing signal WT to the encoder unit 60.

In the tracking error detecting section 26, based on the position signal ST from the timing signal generating section 25,
A tracking error signal TE indicating a tracking error from the amplitude difference between the sampled servo marks.
Is generated. This tracking error signal TE is supplied to the servo control unit 52.

The servo control unit 52 converts the focus error signal FE and the tracking error signal TE into the focus drive signal FD and the tracking drive signal T.
D is generated and supplied to an actuator (not shown) of the optical pickup 21 so that the laser beam is correctly irradiated on the track and the laser beam is
The servo operation is performed so that the light is focused on the recording surface of.

The signal correction section 30 to which the reproduction signal SMO is supplied from the IV conversion matrix section 22 has the configuration shown in FIG.

In FIG. 2, a reproduced signal SMO is supplied to a gain control amplifier 301 which is a level varying means. In the gain control amplifier 301, the signal level of the reproduction signal SMO is adjusted based on a control signal GC described later. The reproduction signal SMO whose signal level has been adjusted is supplied to the peak hold circuit 303 via the buffer 302 as the reproduction signal SMOB, and is also supplied to the bottom hold circuit 305 via the buffer 304. Also,
It is supplied to the non-inverting input terminal of the operational amplifier 320.

The peak hold circuit 303 constituting the level detecting means sequentially detects the peak value of the signal waveform of the reproduction signal SMOB, and generates a peak hold signal PH indicating the envelope of the peak of the signal waveform. The peak hold signal PH is supplied to the non-inverting input terminal of the operational amplifier 306 and to the average value calculation circuit 307. The level detecting means includes a peak hold circuit 303, a bottom hold circuit 305, and an operational amplifier 306 as an amplitude detector.

In the bottom hold circuit 305, the reproduced signal S
The bottom value of the MOB signal waveform is sequentially detected, and the bottom hold signal BH indicating the bottom envelope of the signal waveform
Is generated. The bottom hold signal BH is supplied to the operational amplifier 3
The signal is supplied to the inversion input terminal 06 and to the average value calculation circuit 307.

The peak hold circuit 303 and the bottom hold circuit 305 are supplied with a control signal HAC from a system control unit 50 described later, and the control signal HAC generates the peak hold signal PH and the bottom hold signal BH. Is controlled.

The operational amplifier 306 obtains the difference between the signal levels of the peak hold signal PH and the bottom hold signal BH, and generates an amplitude signal Sv indicating the amplitude level of the reproduction signal SMOB. It is supplied to the non-inverting input terminal and the inverting input terminal of the comparator 311. The determination means is a comparator 310,
311, an adder 312 and a subtractor 313.

The average value calculating circuit 307 adds the peak hold signal PH and the bottom hold signal BH and then multiplies the signal level by (１ ／) to calculate the average value of the peak hold signal PH and the bottom hold signal BH. The average signal Savg shown is generated. This average signal Savg is supplied to the inverting input terminal of the operational amplifier 320.

The signal correction section 30 has a reference signal Vref indicating the most desirable amplitude level of the reproduction signal SMO and a level width (hereinafter referred to as "dead range") which does not need to adjust the amplitude level of the reproduction signal SMO. The dead range setting signal Vdb to be set is generated by the system control unit 50 as the range setting means and supplied to the adder 312 and the subtractor 313. In the adder 312, the reference signal Vref and the dead range setting signal Vdb are added, and the upper limit level V indicating the upper limit value of the amplitude level of the reproduction signal SMO that does not need to be adjusted.
UL is set and supplied to the inverting input terminal of the comparator 310. In the subtractor 313, the dead range setting signal Vdb is subtracted from the reference signal Vref, and the lower limit level VLL indicating the lower limit value of the amplitude level of the reproduction signal SMO that does not need to be adjusted is set. 31
1 inverting input terminal.

In the comparator 310, the amplitude signal Sv is compared with the upper limit level VUL, and a discrimination signal JH indicating whether the amplitude signal Sv is higher than the upper limit level VUL is supplied to a counter 314 constituting a level variation control means. You.
The comparator 311 compares the amplitude signal Sv with the lower limit level VLL, and supplies a determination signal JL indicating whether the amplitude signal Sv is lower than the lower limit level VLL to the counter 314. The level fluctuation control means is a counter 31
4 and a clock signal generation circuit 315 and a D / A converter 316 to be described later.

A clock signal generating circuit 315 is connected to the counter 314, and receives a clock signal CLK. In this counter 314, as shown in FIG.
When it is determined that it is larger than L, the clock signal CL
Down counting is performed in synchronization with K, and when it is determined based on the determination signal JL that the amplitude signal Sv is smaller than the lower limit level VLL, up counting is performed in synchronization with the clock signal CLK. Further, when the amplitude signal Sv is set in the dead range that is within the range between the upper limit level VUL and the lower limit level VLL, the counting operation is stopped and the count value is held.

A digital signal DCT indicating the count value of the counter 314 is supplied to a D / A converter 316 and converted into an analog control signal GC. This control signal GC is supplied to the gain control amplifier 301.

In the gain control amplifier 301, when the count value of the counter 314 is large based on the control signal GC, the gain is large, and when the count value is small, the gain is small.

Therefore, the gain control amplifier 30
The gain of 1 is varied with a hysteresis characteristic with respect to the signal level of the amplitude signal Sv by the comparators 310 and 311 and the counter 314, and the reproduced signal SMOB is obtained.
Is adjusted so that the amplitude level is within the insensitive range.

Further, in the operational amplifier 320, the average value signal Savg obtained by the average value calculation circuit 307 is subtracted from the reproduced signal SMOB whose signal level has been adjusted by the gain control amplifier 301, whereby the offset of the reproduced signal SMO is reduced. Fluctuations and fluctuations in the DC component caused by the gain being varied by the gain control amplifier 301 are eliminated. Therefore, the operational amplifier 320 outputs a signal from which the influence of the change in the gain of the gain control amplifier 301 has been removed along with the signal level fluctuation caused by the offset fluctuation of the reproduction signal SMO or dust. The signal output from the operational amplifier 320 is a reproduction signal SMO
C is supplied to the A / D converter 31 shown in FIG.

In the A / D converter 31, the reproduced signal SMOC supplied from the signal corrector 30 is converted into a digital reproduced data signal DMOC based on the data clock signal CKD, and the waveform is equalized by digital equalization or the like. . For example, a ternary signal DP obtained by performing the waveform equalization processing is supplied to the data detection unit 32 and the threshold value detection unit 33.

The threshold value detecting section 33 calculates the threshold value Vth by reproducing a pattern having a specific amplitude width for setting the threshold value, for example, recorded at the head of each sector of the magneto-optical disk 10. Is done. This threshold value Vth is supplied to the data detection unit 32.

The data detector 32 includes a threshold detector 3
The ternary signal DP is converted to 3 using the threshold value Vth calculated in step 3.
The data is converted into value data, and binarized data is generated from the ternary data. By processing the binary data by, for example, Viterbi decoding or the like, a correct reproduced data signal DOU can be obtained.
You can get T. The reproduced data signal DOUT is output to an external computer device or the like (not shown) via the controller 41.

When the recording data signal DIN is supplied from an external computer or the like, the controller 4
1 to the encoder unit 60.

In the encoder section 60, the data input signal D
IN is modulated to be a recording signal WA. Here, for example, in the case of the magnetic field modulation recording method, the recording signal WA is supplied to the magnetic head driving unit 61 based on the timing signal WT from the timing signal generation unit 25. In the magnetic head driving section 61, a magnetic head driving signal HA is generated based on the recording signal WA and supplied to the magnetic head 62. The magnetic head 62 applies a magnetic field to the magneto-optical disk 10, and generates a magnetic field based on a magnetic head drive signal HA. The output of the laser beam at this time is set to the output level for signal recording, and a signal is recorded on the magneto-optical disk 10 based on the magnetic field from the magnetic head 62.

The system control unit 50 records a signal on the magneto-optical disk 10 or
A laser control signal LC for controlling the output of the laser light used to read the signal recorded in the laser controller is generated, and the laser control signal LC is supplied to the laser control unit 41. The laser controller 41 controls the output of the laser light by generating the laser drive signal LDA based on the laser control signal LC.

The system control unit 50 also includes a reference signal Vref for setting the dead range described above, a dead range setting signal Vdb, a control signal HAC for controlling the hold operation of the peak hold circuit 303 and the bottom hold circuit 305, and the like. Is also generated.

Next, the operation of the signal correction unit 30 will be described. FIG. 4 shows a case where the offset fluctuation is removed from the reproduction signal SMO. FIG. 4A shows a reproduced signal SMOB when the gain is set to be constant (for example, the gain value “G1”) by the gain control amplifier 301, and a peak hold signal PH and a bottom hold signal BH of the reproduced signal SMOB. For example, the amplitude level of the reproduction signal SMOB is set to be small in the period from the time point t1 to the time point t5. Here, in the operational amplifier 306 of the signal correction unit 30 shown in FIG. 2, when the gain is fixed by the gain control amplifier 301, as shown in FIG. 4B, the difference between the signal levels of the peak hold signal PH and the bottom hold signal BH is obtained. Is generated and the comparators 310 and 31
1 is supplied.

The comparator 310 is supplied with the upper limit voltage VUL obtained by adding the dead zone setting voltage Vdb to the reference voltage Vref, and the comparator 311 is supplied with the reference voltage Vref.
Is supplied with the lower limit voltage VLL obtained by subtracting the dead zone setting voltage Vdb from.

Here, when the signal level of the amplitude signal Sv is smaller than the lower limit voltage VLL at time t2,
The counter 314 counts up based on the discrimination signal JL from the comparator 311 to increase the count value. Therefore, the gain of the gain control amplifier 301 is increased from the gain value “G1” as shown in FIG. 4C based on the control signal GC.

As described above, when the signal level of the amplitude signal Sv is smaller than the lower limit voltage VLL, the gain of the gain control amplifier 301 is set to be large. SMOB is controlled to have a level substantially equal to the amplitude level at time t2 as shown in FIG. 4E.
FIG. 4D shows the amplitude signal Sv when the gain of the gain control amplifier 301 is changed.

When the amplitude level of the reproduced signal SMO decreases most at the time point t3 and then increases, the signal level of the amplitude signal Sv becomes larger than the lower limit level VLL, so that the counter 314 determines from the comparators 310 and 311. The up-count is stopped based on the signals JH and JL, and the gain of the gain control
It is held in the state of the gain value “G3” at 3.

At time t3, the gain of the gain control amplifier 301 is set to the gain value "G3", and the signal level of the reproduced signal SMO is controlled. For this reason, the signal level of the reproduced signal SMOB is set to be higher than the case where the gain of the gain control amplifier 301 is in the state of the gain value "G1", and the signal level of the amplitude signal Sv exceeds the upper limit level VUL at time t4. Is done.

When the signal level of the amplitude signal Sv exceeds the upper limit level VUL at time t4, the counter 314 counts down based on the discrimination signal JH from the comparator 310, the count value decreases, and the gain of the gain control amplifier 301 increases. Is reduced. Therefore, the reproduction signal SMO
B is controlled to have an amplitude level substantially equal to the signal level at time t4.

At time t5, when the amplitude level of the reproduced signal SMO is returned to the original level, the counter 314 stops counting down based on the discrimination signals JH and JL from the comparators 310 and 311.
The gain of 01 is held in the state of the gain value “G2” at time t5.

As described above, even if the amplitude level of the reproduced signal SMO greatly changes due to dust or the like, the gain of the gain control amplifier 301 is varied, and the reproduced signal is controlled so that the amplitude level falls within a desired range. SMOB can be obtained. Further, in the case of a variation caused by an MTF whose variation is smaller than the variation of the amplitude level caused by dust or the like, the signal level of the amplitude signal Sv is in the insensitive range, so that the gain of the gain control amplifier 301 is fixed. No distortion occurs in the waveform of the reproduced signal.

FIG. 4 shows a case where the offset fluctuation is removed from the reproduced signal SMO.
Will be described with reference to FIG.

The reproduced signal SMOB output from the gain control amplifier 301 is controlled so that the amplitude level falls within a desired range, and is supplied to the operational amplifier 320. This reproduced signal SMOB is shown in FIG. 5A. In the average value calculation circuit 307, an average value signal Savg indicating the average value of the reproduction signal SMOB is generated from the reproduction signal SMOB as shown in FIG. 5B and supplied to the operational amplifier 320. Therefore, the reproduction signal SMOC output from the operational amplifier 320 is free from the influence of the offset fluctuation of the reproduction signal SMOB as shown in FIG. 5C.

Also, by changing the frequency of the clock signal CLK generated by the clock signal generation circuit 315, the response characteristic of the gain of the gain control amplifier 301 to the fluctuation of the amplitude signal Sv, ie, the gain control loop Since the band can be changed, for example, the recording area is divided into a plurality of areas from the inner circumference to the outer circumference, and the recording / reproducing frequency is sequentially increased for each area from the inner circumference to the outer circumference. Even in an optical disk of the zone CAV system, it is possible to prevent the influence of the fluctuation of the amplitude level of the reproduction signal SMO according to each region only by changing the frequency of the clock signal CLK.

Further, if the above-described processing for eliminating the influence of the fluctuation of the amplitude level and the offset fluctuation of the reproduction signal SMO is performed during the reproduction period of the data area of the magneto-optical disk 10 in which the signal indicating the information is recorded. Thus, a signal indicating information correctly can be obtained without affecting signals in other areas.

As described above, according to the above-described embodiment,
With respect to the fluctuation in the amplitude level of the reproduction signal due to dust or the like, the signal level of the reproduction signal is controlled by controlling the gain of the gain control amplifier 301, and the fluctuation in the signal level is compared with the fluctuation in the amplitude level of the reproduction signal due to the dust or the like. MTF with small volume
With respect to the fluctuation of the amplitude level of the reproduction signal due to the above, the insensitive range is set so that the gain of the gain control amplifier 301 is maintained at a constant value, and the offset fluctuation is removed using the average value of the reproduction signal. As a result, recorded signals can be correctly read out while preventing the effects of variations in the characteristics of the magneto-optical disk and dust.

In the above-described embodiment, the optical disk apparatus using the magneto-optical disk has been described. However, it is needless to say that the present invention is not limited to the magneto-optical disk but may be another optical disk.

[0058]

According to the present invention, for example, an envelope is detected from a reproduced signal obtained by reproducing an optical disk, and the amplitude level of the reproduced signal is obtained from the envelope. Here, when the fluctuation of the amplitude level of the reproduction signal is based on the signal recorded on the optical disk, the control of the amplitude level is not performed. It is controlled to be within the level range. Furthermore, the average level of the signal level of the reproduced signal is subtracted from the reproduced signal whose amplitude level is within a predetermined level range, thereby removing the offset fluctuation of the reproduced signal. For this reason, the recorded signal can be correctly read out while preventing the variation of the characteristics of the optical disc and the influence of dust and the like. Further, when the amplitude level of the reproduction signal fluctuates and exceeds a predetermined level range, the counter means is used. Up-counting or down-counting is performed, and the signal level of the reproduced signal is controlled using the count value of the counter means so that the amplitude level of the reproduced signal falls within a predetermined level range. For this reason, by controlling the frequency of the clock signal which is the reference for the counting operation in the counter means, the band of the control loop of the amplitude level of the reproduction signal can be easily changed.

[Brief description of the drawings]

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

FIG. 2 is a diagram illustrating a configuration of a signal correction unit.

FIG. 3 is a diagram for explaining the operation of a counter.

FIG. 4 is a diagram for explaining an operation of a signal correction unit.

FIG. 5 is a diagram for explaining the operation of the signal correction unit.

FIG. 6 is a diagram showing a configuration of a conventional clamp circuit.

FIG. 7 is a diagram for explaining the operation of the clamp circuit.

FIG. 8 is a diagram illustrating a relationship between a signal level fluctuation amount and a frequency.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Magneto-optical disk, 22 ... IV conversion matrix part, 30 ... Signal correction part, 301 ... Gain control amplifier, 303 ... Peak hold circuit, 305 ... Bottom hold circuit , 306,320
... Operational amplifier, 307 ... Average value calculation circuit, 31
0, 311 ··· comparator, 312 ··· adder,
313: subtractor, 314: counter, 315
..Clock signal generation circuits, 316... D / A converters

Claims (9)

[Claims] 1. An amplitude level of a reproduction signal within a predetermined level range only when an amplitude level of the reproduction signal obtained by reproducing a recording medium on which a digital signal is recorded is not within a predetermined level range. A recording signal reproducing method comprising: controlling a reproduction signal having an amplitude level within the predetermined level range to obtain a digital signal recorded on the recording medium. 2. The method according to claim 1, wherein when the amplitude level of a reproduction signal obtained by reproducing the recording medium is based on a digital signal recorded on the recording medium, the predetermined level range causes the fluctuation. 2. The recording signal reproducing method according to claim 1, wherein the amplitude level is set so as to fall within the predetermined level range. 3. The recording signal reproduction according to claim 1, wherein an envelope of a reproduction signal obtained by reproducing the recording medium is detected, and an amplitude level of the reproduction signal is obtained by using the detected envelope. Method. 4. A new reproduced signal is generated by subtracting the average level of the signal level of the reproduced signal from the reproduced signal whose amplitude level is within the predetermined level range, and processing the new reproduced signal. 2. The recorded signal reproducing method according to claim 1, wherein a digital signal recorded on the recording medium is obtained. 5. An optical disk reproducing means for reproducing an optical disk to obtain a reproduced signal, a level varying means for varying and outputting a signal level of a reproduced signal obtained by the optical disk reproducing means, and an output signal from the level varying means. Level detecting means for detecting an amplitude level of the reproduced signal, a determining means for determining whether the amplitude level detected by the level detecting means is larger or smaller than a predetermined level range, and a determining result of the determining means. Level variation control means for controlling the level varying means so that the amplitude level of the reproduction signal output from the level varying means is within the predetermined level range, and range setting means for setting the predetermined level range. Processing the reproduced signal output from the level varying means to obtain a signal recorded on the optical disc. Optical disk device. 6. The range setting means, wherein when the amplitude level of a reproduction signal obtained by reproducing the optical disk is based on a signal recorded on the optical disk, the amplitude level at which the fluctuation occurs is determined by the predetermined level. 6. The level range is set so as to fall within the level range of (5).
An optical disk device as described in the above. 7. The level detecting means includes: a peak hold circuit for sequentially holding a peak value of the reproduced signal output from the level varying means to obtain an envelope on a peak side of the reproduced signal; A bottom hold circuit that sequentially holds the bottom value of the reproduced signal to obtain an envelope on the bottom side of the reproduced signal, and an amplitude detector that detects an amplitude level from the envelope obtained by the peak hold circuit and the bottom hold circuit. 6. The optical disk device according to claim 5, wherein: 8. An average value calculating means for obtaining an average signal level of a reproduced signal output from the level varying means using an envelope obtained by the peak hold circuit and the bottom hold circuit; and the level varying means. And an offset correcting means for subtracting an average level obtained by said average value calculating means from the reproduced signal output from said means to remove an offset variation of said reproduced signal output from said level varying means. 8. The optical disc device according to 7. 9. The level fluctuation control means includes a counter, and a clock signal generation circuit for generating a clock signal serving as a reference for the counter operation of the counter. The counter, based on a determination result of the determination means,
When the amplitude level is larger or smaller than a predetermined level range, a count-up or count-down operation is performed using the clock signal generated by the clock signal generation circuit, and the level variable unit uses the count value of the counter to perform the count-up or count-down operation. 6. The optical disk device according to claim 5, wherein said level varying means is controlled so that the amplitude level of the output reproduction signal falls within the predetermined level range.