JP3551480B2 - Optical disk device and waveform shaping circuit - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to an optical disk device and a waveform shaping circuit, and can be applied to, for example, a magneto-optical disk device.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, a magneto-optical disk device records desired data by applying a thermomagnetic recording technique, and reproduces data recorded on a magneto-optical disk by using the Kerr effect.
[0003]
That is, in this type of magneto-optical disk device, the magneto-optical disk has an information recording surface formed by forming a perpendicular magnetic film made of a magnetic film on a predetermined disk-shaped substrate by applying a technique such as sputtering. Further, a protective film for protecting the information recording surface is disposed and formed.
[0004]
For this magneto-optical disk, the magneto-optical disk device intermittently starts up the amount of the laser beam from the amount of light for reading to the amount of light for writing during recording, and applies this laser beam to the information recording surface of the magneto-optical disk. Irradiation. As a result, the magneto-optical disk device raises the temperature of the laser beam irradiation position to a temperature equal to or higher than the Curie temperature of the magnetic material forming the perpendicular magnetization film. Further, the magneto-optical disk device applies a predetermined modulating magnetic field to the laser beam irradiation position, and switches the polarity of the modulating magnetic field according to data to be recorded.
[0005]
As a result, when the magneto-optical disk is cooled at the laser beam irradiation position where the temperature has risen above the Curie temperature, the perpendicular magnetization film is locally magnetized to have the polarity of the modulation magnetic field when cooled, whereby the size is determined by the laser beam irradiation period. A pit train (that is, a size in the circumferential direction of the disk) is formed, and a data train determined by the modulation magnetic field is recorded.
[0006]
Further, at this time, the magneto-optical disk device applies a modulating magnetic field so that the magnetic field lines cross the perpendicular magnetization film perpendicularly, thereby applying a perpendicular magnetic recording technique to perform high-density recording.
[0007]
On the other hand, during reproduction, the magneto-optical disk device irradiates the magneto-optical disk with a linearly polarized laser beam and detects a change in the plane of polarization of the return light. As a result, the magneto-optical disk device reproduces data recorded on the magneto-optical disk using the magnetic Kerr effect. That is, at the time of this data reproduction, the magneto-optical disk device obtains a reproduction signal whose signal level changes in accordance with the change in the polarization plane of the return light, and converts this reproduction signal into a binary signal with a predetermined binarization threshold. After converting the reproduced signal into serial data, the serial data is decoded, error correction processing, etc., and the recorded data is reproduced.
[0008]
Therefore, in this type of magneto-optical disk drive, the Curie temperature of the magnetic material forming the perpendicular magnetization film, the thermal conductivity of the components of the magneto-optical disk, etc. (that is, the sensitivity of the magneto-optical disk) The size of the pits to be formed varies depending on the amount of writing light, the ambient temperature, and the like.
[0009]
In other words, when the laser beam is irradiated, if the ambient temperature is high, if the sensitivity of the magneto-optical disk is high, the temperature of the laser beam irradiation position quickly rises to the Curie temperature, thereby raising the light amount of the laser beam. Large pits are formed as compared with. Conversely, when the ambient temperature is low or the like, the temperature rise at the laser beam irradiation position is delayed, and pits smaller than the period during which the light amount of the laser beam is raised are formed.
[0010]
This phenomenon occurs due to local variations in the sensitivity of the magneto-optical disk, and also due to runout of the magneto-optical disk itself.
[0011]
In this case, as shown in FIG. 5, even when the laser beam light amount is switched to the writing light amount during the period in which the logical level of the drive signal S1 (FIG. 5A) rises, the laser beam is irradiated. When the light amount of the laser beam is large compared to the sensitivity of the magneto-optical disk, the ambient temperature, and the like (FIG. 5B), a large pit is formed, and the reproduced signal MO obtained by receiving the return light is: The period during which the signal level rises becomes longer.
[0012]
When the reproduction signal MO is binarized, if the threshold value is fixed to an intermediate signal level, a binarization result in which the rising edge and the falling edge are respectively changed back and forth is obtained. The symmetry is degraded. Therefore, in this case, the threshold value SL1 for binarizing the reproduction signal MO is set by shifting from the intermediate level SL3 (FIG. 5D) by the rise of the signal level of the reproduction signal MO as a whole. Therefore, a binarized waveform having good symmetry can be obtained.
[0013]
Conversely, when the light intensity of the laser beam is large compared to the sensitivity of the magneto-optical disk, the ambient temperature, and the like (FIG. 5C), a small pit is formed, so that the reproduced signal MO becomes a signal. The period during which the level rises becomes short. In this case, if the threshold value is fixed to an intermediate signal level, a binarized result in which the falling edge and the rising edge are respectively changed before and after is obtained. Therefore, in this case, the threshold value SL2 needs to be set by shifting from the intermediate level SL3 by an amount corresponding to the fall of the signal level as a whole.
[0014]
In accordance with this correction principle, the magneto-optical disk device forms a feedback loop so that the DC level of the binarized data obtained by binarizing the reproduction signal MO with the threshold becomes zero. The threshold value is set in such a manner that binary data D1 (FIG. 5E) with good symmetry is obtained, so that bit errors and the like can be effectively avoided.
[0015]
[Problems to be solved by the invention]
By the way, the drive signal S1 serving as a reference for pit generation is formed by modulating data to be recorded by a predetermined modulation method. In the conventional magneto-optical disk device, the DC level of the binarized data is reduced to 0 level by applying, for example, an EFM (Eight to Fourteen Modulation) system in which the drive signal S1 does not include a DC component as the modulation system. A feedback loop is formed so as to generate binarized data D1 with good symmetry.
[0016]
If a modulation method in which a DC component is included in the drive signal S1 after modulation, such as a 1-7 modulation method, which is one of variable length coding methods, is applied as the modulation method, for example, It is considered that the recording density can be improved by effectively using the recordable frequency band. However, when a modulation method that includes a DC component in the drive signal S1 is applied, there is a problem that it is difficult to generate binarized data D1 having good symmetry.
[0017]
That is, when a modulation method that includes a DC component is applied, the DC level of the reproduction signal MO naturally fluctuates irrespective of the effect of the magneto-optical disk or the like. If the threshold value is set according to the DC level of the signal MO, the symmetry of the binarized data will be degraded.
[0018]
As a method for solving this problem, for example, as shown in FIG. 6, a method of setting a threshold value SL4 in a certain area, holding the threshold value SL4, and binarizing the reproduction signal MO is considered. In this case, the fixed area may be, for example, a repetition part (that is, a VFO area) of the highest frequency for pulling in a PLL (Phase Locked Loop) added to the head of each data to generate a clock.
[0019]
However, even in this case, if the reproduced signal MO swells due to uneven sensitivity of the magneto-optical disk or a local change in the birefringence, the threshold value SL4 cannot be corrected correspondingly. There is a problem that it is difficult to obtain good binary data.
[0020]
As shown in FIG. 7, a method is also conceivable in which the upper and lower envelopes ENVU and ENVU of the reproduction signal MO are detected, and a threshold value is set at an intermediate level between the two envelopes ENVU and ENVU. Since the frequency components included in the signal MO change momentarily in a wide band, there is a problem that the envelopes ENVU and ENVU are accurately detected, and there is also a problem that they are liable to malfunction due to noise.
[0021]
A method of removing the DC component from the reproduction signal MO in advance and binarizing it is also conceivable. This method can avoid the influence of waveform undulation due to uneven sensitivity or the like, but the reproduction signal MO inherently has By removing the DC component, the waveform distortion increases and the error rate deteriorates.
[0022]
Further, a method combining these methods with the conventional method is also conceivable. However, in the end, a change in the DC level caused by unevenness in sensitivity or the like cannot be completely distinguished from the DC level inherent in the reproduced signal MO itself. Therefore, there is a feature that the threshold value cannot be completely corrected.
[0023]
The present invention has been made in consideration of the above points, and has a good symmetry even when a modulation method including a DC component is selected when a reproduced signal is converted into binary data using a threshold value. An optical disk device capable of obtaining binarized data and a waveform shaping circuit applied to this type of device are proposed.
[0024]
[Means for Solving the Problems]
To solve such issuesFirstThe present invention relates to an optical disc device that receives return light obtained from an optical disc by a light receiving element and reproduces data recorded on the optical disc from an output signal of the light receiving element.
A binarization circuit that binarizes an output signal and outputs binarized data based on a predetermined threshold value;
Rising edge of binary dataHas an edge synchronized withA first reference signal generation circuit for generating a first reference signal;
Falling edge of binary dataHas an edge synchronized withA second reference signal generation circuit for generating a second reference signal;
A first synchronization detection circuit that detects a synchronization signal of the binary data based on the first reference signal and outputs a first synchronization signal detection signal;
A second synchronization detection circuit that detects a synchronization signal of the binarized data based on the second reference signal and outputs a second synchronization signal detection signal;
First synchronization signal detection signalReset byA first frequency divider for dividing the first reference signal and outputting a first frequency-divided signal;
Second synchronization signal detection signalReset byA second frequency divider for dividing the second reference signal and outputting a second frequency-divided signal;
FirstAnd the divided signal ofSecond divided signalWhenPhase comparisonAccording to the phase difference between the first frequency-divided signal and the second frequency-divided signal, the phase difference is equal to or less than a predetermined value.A phase comparison circuit that corrects the signal level of the thresholdWithAn optical disc device characterized by the above-mentioned.
[0025]
Further, the second inventionIs to set the amount of light for writing and / or the period during which the light beam rises based on the phase difference so that the phase difference is equal to or less than a predetermined value.
[0026]
Further third inventionIs to set the frequency division ratio so that the phase difference between the first frequency-divided signal and the second frequency-divided signal does not exceed the period of the binarized data.
[0027]
The fourth inventionIsA binarization circuit that binarizes an output signal and outputs binarized data based on a predetermined threshold value;
Rising edge of binary dataHas an edge synchronized withA first reference signal generation circuit for generating a first reference signal;
Falling edge of binary dataHas an edge synchronized withA second reference signal generation circuit for generating a second reference signal;
A first synchronization detection circuit that detects a synchronization signal of the binary data based on the first reference signal and outputs a first synchronization signal detection signal;
A second synchronization detection circuit that detects a synchronization signal of the binarized data based on the second reference signal and outputs a second synchronization signal detection signal;
First synchronization signal detection signalReset byA first frequency divider for dividing the first reference signal and outputting a first frequency-divided signal;
Second synchronization signal detection signalReset byA second frequency divider for dividing the second reference signal and outputting a second frequency-divided signal;
FirstAnd the divided signal ofSecond divided signalWhenPhase comparisonAccording to the phase difference between the first frequency-divided signal and the second frequency-divided signal, the phase difference is equal to or less than a predetermined value.A phase comparison circuit that corrects the signal level of the thresholdWithA waveform shaping circuit characterized in that:
[0028]
The fifth inventionIs to set the frequency division ratio so that the phase difference between the first frequency-divided signal and the second frequency-divided signal does not exceed the period of the binarized data.
[0029]
[Action]
When the output signal MO is binarized based on a predetermined threshold SL to generate binarized data D3, the binarized data D3 is binarized based on the rising edge and the falling edge of the binarized data D3. By generating the first and second reference signals CK1 and CK2 of the digitized data D3, when the rising edge and the falling edge of the binarized data D3 are held at correct timing, the first and second signals having no phase difference Second reference signals CK1 and CK2 can be obtained. As a result, the first and second synchronization signal detection signals DET1 and DET2 of the binary data D3 are obtained with reference to the first and second reference signals CK1 and CK2, respectively. If the phase comparison results are obtained in the first and second frequency-divided signals SB1 and SB2 obtained by dividing the first and second reference signals CK1 and CK2 with reference to the detection signals DET1 and DET2, respectively, It is possible to detect a difference in timing between the edge and the falling edge. Therefore, if the signal level of the threshold value SL is corrected based on the result of the phase comparison, the threshold value SL can be set so that the rising edge and the falling edge of the binary data D3 are held at the correct timing.
[0030]
Thus, based on the result of the phase comparison, it is possible to set the light amount for writing and / or the period for raising the light beam to the light amount for writing, and perform recording under the optimum writing condition.
[0031]
At this time, even if the rising edge and / or the falling edge of the binary data D3 change in the first and second frequency dividing circuits 24 and 25, the phase difference between the first and second frequency-divided signals SB1 and SB2. If the frequency division ratio is selected so that θ does not exceed the cycle of the binarized data D3, the threshold value SL can be correctly corrected even when the edge greatly changes.
[0032]
【Example】
Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.
[0033]
In FIG. 2, reference numeral 1 denotes a magneto-optical disk device as a whole, which records data DATA input from an external device such as a computer on the magneto-optical disk 2 and reads data DATA recorded on the magneto-optical disk 2 to read the data DATA from the external device. Output to device.
[0034]
Here, the magneto-optical disk 2 is formed by forming a perpendicular magnetic film on a predetermined disk-shaped substrate and further arranging a plastic protective film. Further, on the magneto-optical disk 2, a so-called pre-groove formed of a groove for guiding a laser beam is formed in a helical shape so that tracking control can be performed by the pre-groove, and spindle control is performed by detecting meandering of the pre-groove. In addition, the position information of the laser beam irradiation position can be detected.
[0035]
That is, in the magneto-optical disk device 1, the optical pickup 3 focuses the laser beam emitted from the laser diode on the information recording surface of the magneto-optical disk 2 by the built-in objective lens 4, and further obtains the laser beam from the magneto-optical disk 2. The returned light is collected by the objective lens 4 and received by a built-in photodetector. Here, the photodetector is formed by dividing the light receiving surface in, for example, the radial direction and the circumferential direction of the magneto-optical disk 2, and outputs an output signal of each divided light receiving surface.
[0036]
The preprocessing circuit 5 performs a current-voltage conversion process on the output signal of each light receiving surface, performs an addition / subtraction process, thereby generating a tracking error signal TE, a focus error signal FE, and the like, and further detects a change in the polarization plane of the return light. Upon detection, a reproduction signal MO is generated.
[0037]
The servo circuit 6 moves the objective lens 4 up, down, left and right based on the focus error signal FE and the tracking error signal TE, thereby performing tracking control and focus control.Do, And spinned togetherLeMoTa7 is driven to rotate the magneto-optical disk 2 under the condition of a constant angular velocity.
[0038]
When a write command is input from the host computer in the state where the tracking control, the focus control, and the spindle control are performed in this manner, the magneto-optical disk device 1 causes the optical pickup 3 to move the optical pickup 3 to the magneto-optical disk 2 prior to recording data. The laser beam is moved to the test writing area, and the light quantity of the laser beam is intermittently increased from the reading light quantity to the writing light quantity in the test writing area. At this time, the magneto-optical disk device 1 sequentially switches the light amount of the writing in a stepwise manner, and then proceeds to a reproducing operation to detect a change in the signal level of the reproduced signal MO. These series of processes are executed by controlling the entire operation by the system control circuit, and the system control circuit selects the optimum light amount for writing based on the measurement result of the threshold setting circuit 14 described later.
[0039]
When the light quantity at the time of writing is selected in the test writing area in this way, the magneto-optical disk device 1 records the subsequently input data DATA on the magneto-optical disk 2. That is, in the magneto-optical disk device 1, the input / output circuit 10 forms an interface circuit and a data buffer circuit with an external device, and inputs and outputs commands such as writing, reading, and interruption with the external device. , And further inputs and outputs data DATA to be written and data DATA to be read.
[0040]
At the time of writing, the recording data processing circuit 11 adds an error correction code to the data DATA output from the input / output circuit 10 in a predetermined block unit, and then performs a 1-7 modulation method which is one of variable length coding methods. This data DATA is converted into recording data, and data such as sync, resync, address and the like are added to the recording data and output. In this embodiment, a sync of 4 bits and a resync of 2 bits are added to the 30-bit data modulated by adding the error correction code.
[0041]
The drive circuit 12 drives the laser diode of the optical pickup 3 according to the output data D2 of the recording data processing circuit 11, and during the period when the logic level of the output data D2 rises, the light amount of the laser beam is read. Start up from the light quantity to the writing light quantity. Thus, in the magneto-optical disk device 1, pits are sequentially formed on the magneto-optical disk 2 in accordance with the output data D2 of the recording data processing circuit 11, and data DATA input from an external device is recorded on the magneto-optical disk 2.
[0042]
On the other hand, when a read command is input from an external device, the magneto-optical disk device 1 reads data specified by the command from the magneto-optical disk 2 and outputs the data. That is, in the magneto-optical disk device 1, the comparison circuit 13 inputs the reproduction signal MO to the non-inverting input terminal, and inputs the threshold value SL set by the threshold value setting circuit 14 to the inverting input terminal. The reproduction signal MO is converted into binary data D3 by the value SL and output.
[0043]
The reproduction data processing circuit 15 decodes the data DATA from the binary data D3 and outputs the data to the input / output circuit 10. At this time, the reproduction data processing circuit 15 detects the sync and resync of the binarized data D3 and executes processing such as error correction in block units, thereby effectively avoiding bit errors and the like of the read data DATA. . Further, when executing the processing such as error correction, the reproduction data processing circuit 15 temporarily stores the binary data D3 in a built-in FIFO (First In First Out) memory circuit, processes the binary data D3, and synchronizes with the predetermined internal clock. It outputs to the input / output circuit 10 at the set timing. Thus, in the magneto-optical disk device 1, the frequency band of the magneto-optical disk 2 can be effectively used by applying the 1-7 modulation method, and the recording density is correspondingly higher than that of the conventional magneto-optical disk device. Has been made to be able to improve.
[0044]
Here, in this embodiment, the magneto-optical disk device 1 applies a threshold value setting circuit shown in FIG. 1 to a reproduced signal MO that includes a DC component as a result of applying the 1-7 modulation method as described above. By setting the threshold at 14, the waveform deterioration of the binarized data D3 is effectively avoided.
[0045]
That is, in FIG. 1, the threshold value setting circuit 14 converts the binary data D3 output from the comparison circuit 13 into a rising edge PLL (Phase Locked Loop) circuit 20, a falling edge PLL circuit 21, a rising synchronization detection circuit 22, The signal is input to the falling synchronization detection circuit 23.
[0046]
Here, as shown in FIG. 3, in the case of this embodiment, for example, the output data D2 of the recording data processing circuit 11 whose logic levels are continuous at "1, 0, 0, 1,..." (FIG. 3A) Accordingly, during the period in which the logical level of the output data D2 rises, the light amount of the laser beam rises from the light amount at the time of reproduction to the light amount at the time of writing to form a pit, thereby forming a reproduction signal MO (FIG. In B)), the signal level changes following the change in the logic level of the output data D2. Further, the binarized data D3 (FIG. 3C) is maintained at the logical "H" level during a period in which the signal level of the reproduction signal MO rises above the threshold SL.
[0047]
The rising edge PLL circuit 20 operates based on the rising edge of the binarized data D3 to output the reproduction clock CK1 of the reproduction signal MO whose signal level falls at the timing of the rising edge (FIG. 3 ( D)). On the contrary, the falling edge PLL circuit 21 operates on the basis of the falling edge of the binary data D3, and thereby the reproduction clock of the reproduction signal MO whose signal level falls at the timing of the falling edge. CK2 is output (FIG. 3E).
[0048]
Accordingly, the threshold setting circuit 14 sets the logical level of the binary data D3 in the rising edge PLL circuit 21 and the falling edge PLL circuit 22 based on the rising edge and the falling edge of the binary data D3, respectively. Are inverted at the correct timing, the first and second reproduced clocks CK1 and CK2 whose signal levels are switched in synchronization with each other are generated.
[0049]
The rising synchronization detection circuit 22 operates with reference to the recovered clock CK1 generated by the rising edge PLL circuit 20, and thereby the rising of the binary data D3 based on the timing at which the signal level of the recovered clock CK1 falls. Detect edges. Further, the rising synchronization detection circuit 22 detects a sync and a resync from the binary data D3 by comparing the detection result of the rising edge with a preset reference pattern. The logic level of the signal DET1 rises (FIG. 3 (F)).
[0050]
On the other hand, the falling synchronization detection circuit 23 operates based on the recovered clock CK2 generated by the falling edge PLL circuit 21 to thereby perform the binary operation based on the timing at which the signal level of the recovered clock CK2 falls. The falling edge of the coded data D3 is detected. Further, the rising synchronization detecting circuit 23 detects a sync and a resync from the binary data D3 by comparing the detection result of the falling edge with a preset reference pattern. The logic level of the output signal DET2 rises (FIG. 3 (G)).
[0051]
Thus, in this embodiment, the sync and resync added at the time of writing can be performed using any one of the reproduction clocks CK1 and CK2 generated based on the rising edge and the falling edge, respectively, as a reference. The pattern is selected so that it can be reliably detected.
[0052]
That is, when the data D2 having the pattern shown in FIG. 4 (FIG. 4A) is applied, the data D2 is generated by the reproduced clock CK1 (FIG. 4B) generated based on the rising edge of the data D2. When the rising edge is detected, the logic level first rises for one clock cycle, and then a detection result D4 in which the logic level rises with a delay of four clock cycles can be obtained (FIG. 4C). On the other hand, when the falling edge of the data D2 is detected by the reproduced clock CK2 (FIG. 4E) generated based on the falling edge of the data D2, the detection result D5 different from the detection result D4 by the rising edge is obtained. Is obtained (FIG. 4D). Thus, even in such a case, it is necessary to select a pattern so that sync and resync can be correctly detected.
[0053]
The frequency divider 24 is formed of a frequency divider that outputs a quarter frequency-divided signal SB1 (FIG. 3 (H)) of the reproduced clock CK1, and is reset by an output signal DET1 of the rising synchronization detecting circuit 22. ing. As a result, the frequency divider 24 outputs a frequency-divided signal SB1 whose logical level is set based on the timing of the sync and resync, and which is synchronized with the rising edge of the binary data D3.
[0054]
The frequency divider 25 is formed of a frequency dividing circuit that outputs a quarter frequency dividing signal SB2 (FIG. 3I) of the reproduced clock CK2, and is reset by an output signal DET2 of the rising synchronization detecting circuit 23. ing. As a result, the frequency divider 25 outputs a frequency-divided signal SB2 whose logical level is set based on the timing of the sync and resync, and which is synchronized with the falling edge of the binary data D3.
[0055]
The phase comparator 26 obtains a phase comparison result between the frequency-divided signal SB1 synchronized with the rising edge and the frequency-divided signal SB2 synchronized with the falling edge, and compares the phase comparison result via the loop filter 27 with a threshold value. Output as SL. Thereby, the threshold setting circuit 14 forms a feedback loop as a whole so that the phase comparison result becomes 0 level, that is, the phase difference θ between the frequency-divided signals SB1 and SB2 shown in FIG. , The signal level of the threshold value SL is corrected.
[0056]
That is, in the threshold value setting circuit 14, the frequency-divided signal SB1 and the frequency-divided signal SB2 whose phases are compared are switched in phase with each other when the logical level of the binary data D3 is inverted at the correct timing. Since the first and second reproduced clocks CK1 and CK2 are divided and generated, the signal level of the threshold SL is set so that the phase comparison result of the divided signal SB1 and the divided signal SB2 becomes 0 level. Is corrected, the binary data D3 whose logic level switches at the correct timing can be obtained even when the DC level of the reproduction signal MO fluctuates.
[0057]
Therefore, when correcting the threshold value SL in this manner, the threshold value SL is adjusted to the optimum value even when the DC level is changed by the magneto-optical disk 2 when the reproduction signal MO itself includes a DC component. And binary data D3 with good symmetry can be obtained. Further, even when jitter occurs in the reproduction signal MO, it can be removed, and the influence of noise or the like can be effectively avoided. Therefore, the reliability of the entire magneto-optical disk device 1 can be improved.
[0058]
At this time, the threshold value setting circuit 14 determines that the rising edge and / or the falling edge of the binary data DATA is obtained by dividing the reproduced clocks CK1 and CK2 by １ ／ in the frequency dividing circuits 24 and 25, respectively. Even when the frequency greatly changes to exceed the period of CK1 and CK2, the correct phase relationship can be determined in the frequency-divided signals SB1 and SB2 for phase comparison. Therefore, the signal level of the threshold value SL can be surely corrected and binary data with good symmetry can be obtained.
[0059]
In the threshold setting circuit 14, a fixed reference level (for example, a signal level half the peak value of the reproduction signal MO) is used instead of the threshold SL output from the loop filter 27. If the signal is input to the inverting input terminal and the output signal of the phase comparator 26 is observed, the phase difference between the recovered clocks CK1 and CK2 based on the rising edge and the falling edge can be observed. As a result of this observation, if the phase difference between the reproduction clocks CK1 and CK2 is 0, the duty ratio is maintained in the correct relation in the binarized reproduction data D3. In this case, the fixed reference level This means that the reproduced signal MO held at the correct amplitude with respect to the threshold value is input.
[0060]
That is, in this case, data is recorded on the magneto-optical disk 2 under the optimum conditions for the reproducing system. Accordingly, by setting the light amount for writing, and furthermore, the period during which the laser beam is raised to the light amount for writing, so that the phase comparison result of the phase comparator 26 becomes 0 level, desired data can be obtained under optimum conditions. Can be recorded. Thus, when reproducing the test-written area after the test writing, the magneto-optical disk device 1 uses the fixed reference level instead of the threshold value SL output from the loop filter 27 as the inverted input of the comparison circuit 13. By inputting the signal to the end and observing the output signal of the phase comparator 26, the optimum write condition is detected, and data sequentially input under the detected condition is recorded.
[0061]
Actually, in this type of magneto-optical disk device, the magneto-optical disk 2 may be replaced, and data recorded by the magneto-optical disk device 1 may be reproduced by another magneto-optical disk device. In this case, if the write condition is set based on the result of the phase comparison in the threshold value setting circuit as in this embodiment, the binary data having good symmetry can be reproduced even when the data is reproduced by another magneto-optical disk device. Obtainable.
[0062]
Conversely, data recorded by another magneto-optical disk device may be reproduced by the magneto-optical disk device 1 according to this embodiment. In addition to the case of recording and reproducing by the magneto-optical disk device 1, In this case, a threshold value is set as in this embodiment, and binary data with good symmetry can be obtained.
[0063]
In the above configuration, when a write command is input from an external device, the magneto-optical disk drive 1 moves the optical pickup 3 to a test writing area and performs test writing, thereby setting the amount of writing light. At this time, the magneto-optical disk device 1 records the predetermined data by switching the write light amount stepwise, and then reproduces the recorded data. The reproduced result is obtained based on the phase comparison result obtained in the threshold value setting circuit 14. Detected, thereby selecting the optimum writing condition.
[0064]
On the other hand, data DATA input from an external device via the input / output circuit 10 is subjected to 1-7 modulation after an error correction code is added in a predetermined block unit in the recording data processing circuit 11, and is subjected to sync. , Resync, etc., and converted into recording data D2. The recording data D2 is output to the drive circuit 12, whereby the light quantity of the laser beam is intermittently switched from the reading light quantity to the writing light quantity according to the logical level of the recording data D2. Pits corresponding to the recording data are sequentially formed.
[0065]
On the other hand, when a read command is input from an external device, the reproduction signal output from the optical pickup 3 is binarized by the comparison circuit 13 with reference to the threshold value SL to generate binarized data D3. Is generated, and the reproduced data processing circuit 15 decodes the binary data D3, performs error correction processing on the decoded data D3, and outputs the result to an external device via the input / output circuit 10.
[0066]
In this binarization, the rising edge PLL circuit 20 and the falling edge PLL circuit 22 generate reproduction clocks CK1 and CK2 of the binary data D3 on the basis of the rising edge and the falling edge, respectively. In the detection circuit 22 and the falling synchronization detection circuit 23, sync and resync are detected based on the reproduction clocks CK1 and CK2, respectively.
[0067]
The reproduced clocks CK1 and CK2 are frequency-divided by 1/4 in frequency dividing circuits 24 and 25 which are reset by the sync and resync detection results of the rising synchronization detecting circuit 22 and falling synchronization detecting circuit 23, respectively. Therefore, even if the edge of the binary data D3 greatly changes to about the period of the reproduction clocks CK1 and CK2, the change of the frequency-divided signals SB1 and SB2 exceeds 1/4 period. Is kept as not.
[0068]
The frequency-divided signals SB1 and SB2 are compared in phase by the phase comparator 26, and the signal level of the threshold SL is corrected so that the result of the phase comparison becomes 0, whereby the binary data D3 rises. The signal level of the threshold SL is corrected so that the edge and the falling edge have the correct timing.
[0069]
When setting the write condition, a reference level whose signal level is 1/2 with respect to the peak value of the reproduction signal MO is input to the comparison circuit 13 instead of the output signal of the loop filter 27. By monitoring the output signal of the comparator 26, an optimum writing condition is detected.
[0070]
According to the above configuration, sync and resync are detected based on the recovered clocks CK1 and CK2 generated based on the rising edge and the falling edge of the binarized data D3, and based on the detection results of the sync and resync. The reproduced clocks CK1 and CK2 are frequency-divided, respectively, to generate frequency-divided signals SB1 and SB2, and a threshold value SL as a reference for generating the binary data D3 is corrected based on the phase comparison result of the frequency-divided signals SB1 and SB2. Thus, the threshold value SL can be corrected so that the rising edge and the falling edge of the binary data D3 have the correct timing, and thus, even when the reproduced signal includes the DC level, Can obtain binarized data D3 with good symmetry even when the DC level fluctuates.
[0071]
Even when jitter occurs during writing and reading, binarized data can be generated by effectively avoiding the effect of this jitter, and the effect of noise can also be effectively avoided. Thus, a highly reliable, high-density recording magneto-optical disk device can be obtained.
[0072]
Further, the threshold setting circuit is used to detect the optimum write condition based on the phase comparison result of the threshold setting circuit 14 so that the magneto-optical disk recorded by this magneto-optical disk device can be used for other purposes. In the case of reproducing with the above-mentioned device, binary data D3 with good symmetry can be obtained.
[0073]
In the above embodiment, the case where the rising edge PLL circuit 20 and the falling edge PLL circuit 22 generate the reproduction clocks CK1 and CK2 on the basis of the rising edge and the falling edge, respectively, has been described. The present invention is not limited to this, and a reference signal having a frequency that is an integral multiple of the clock of the binary data D3 may be generated. However, in this case, it is necessary to increase the frequency division ratio in the frequency dividers 24 and 25.
[0074]
In the above-described embodiment, the rising and falling edges of the binary data D3 are detected in the sync and resync detection results of the rising and falling synchronization detection circuits 22 and 23 to detect the sync and resync, respectively. However, the present invention is not limited to this. For example, the inversion and non-inversion of the logic level based on the first and second reproduced clocks CK1 and CK2, respectively, may be performed in accordance with the modulation method to be applied. May be detected to detect sync and resync.
[0075]
Further, in the above embodiment, the case where the 1-7 modulation method is applied has been described. However, the present invention is not limited to this, and can be widely applied when various modulation methods are selected. Also, the present invention can be applied to a case where a modulation method not accompanied by
[0076]
Further, in the above-described embodiment, the case where the present invention is applied to a magneto-optical disk device has been described. However, the present invention is not limited to this, and various optical disk devices such as a light-wind type optical disk device and a direct current The present invention can be widely applied to binarization and decoding of data transmitted by a modulation scheme involving components.
[0077]
【The invention's effect】
As described above, according to the present invention, even when data is transmitted by a modulation method involving a DC component or when data is recorded / reproduced on an optical disk, the transmitted signal and the fluctuation of the DC level of the reproduced signal are effectively avoided to achieve symmetrical operation. It is possible to obtain binarized data having good characteristics, to secure a sufficient margin for jitter, and to reduce the influence of noise.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a threshold value setting circuit of a magneto-optical disk drive according to one embodiment of the present invention.
FIG. 2 is a block diagram showing the magneto-optical disk device of FIG.
FIG. 3 is a signal waveform diagram for explaining the operation of the threshold circuit of FIG. 1;
FIG. 4 is a signal waveform diagram for explaining sync and resync.
FIG. 5 is a signal waveform diagram for explaining a threshold value setting in a conventional magneto-optical disk device.
FIG. 6 is a signal waveform diagram for explaining a case where a modulation method involving a DC component is selected in the conventional method.
FIG. 7 is a signal waveform diagram for explaining a conventional method considered as a method of responding to a change in the DC level.
[Explanation of symbols]
1 Magneto-optical disk drive
2 Magneto-optical disk
3 Optical pickup
13 Comparison circuit
14 Threshold value setting circuit
20 Rising edge PLL circuit
21 Falling Edge PLL Circuit
22 Rising synchronization detection circuit
23 Fall synchronization detection circuit
24, 25 frequency divider
26 phase comparator
27 Loop filter

Claims (5)

In an optical disc apparatus for receiving return light obtained from an optical disc by a light receiving element and reproducing data recorded on the optical disc from an output signal of the light receiving element,
A binarization circuit that binarizes the output signal and outputs binarized data based on a predetermined threshold value;
A first reference signal generation circuit that generates a first reference signal having an edge synchronized with a rising edge of the binary data;
A second reference signal generation circuit that generates a second reference signal having an edge synchronized with a falling edge of the binarized data;
A first synchronization detection circuit that detects a synchronization signal of the binarized data based on the first reference signal and outputs a first synchronization signal detection signal;
A second synchronization detection circuit that detects a synchronization signal of the binarized data based on the second reference signal and outputs a second synchronization signal detection signal;
A first frequency divider circuit that is reset by the first synchronization signal detection signal , frequency- divides the first reference signal, and outputs a first frequency-divided signal;
A second frequency divider circuit that is reset by the second synchronization signal detection signal , frequency- divides the second reference signal, and outputs a second frequency-divided signal;
The first frequency-divided signal and the second frequency-divided signal are compared in phase, and the first frequency-divided signal and the second frequency-divided signal are compared so that the phase difference is equal to or less than a predetermined value. optical disk apparatus characterized by comprising a phase comparator circuit for correcting the signal level of the threshold according to the phase difference. 2. The optical disk device according to claim 1, wherein a light amount for writing and / or a rising period of a light beam are set based on the phase difference so that the phase difference is equal to or less than a predetermined value . 2. The optical disc according to claim 1, wherein a frequency division ratio is set so that a phase difference between the first frequency-divided signal and the second frequency-divided signal does not exceed a period of the binarized data. apparatus. A binarization circuit that binarizes the output signal and outputs binarized data based on a predetermined threshold value;
A first reference signal generation circuit that generates a first reference signal having an edge synchronized with a rising edge of the binary data;
A second reference signal generation circuit that generates a second reference signal having an edge synchronized with a falling edge of the binarized data;
A first synchronization detection circuit that detects a synchronization signal of the binarized data based on the first reference signal and outputs a first synchronization signal detection signal;
A second synchronization detection circuit that detects a synchronization signal of the binarized data based on the second reference signal and outputs a second synchronization signal detection signal;
A first frequency divider circuit that is reset by the first synchronization signal detection signal , frequency- divides the first reference signal, and outputs a first frequency-divided signal;
A second frequency divider circuit that is reset by the second synchronization signal detection signal , frequency- divides the second reference signal, and outputs a second frequency-divided signal;
The first frequency-divided signal and the second frequency-divided signal are compared in phase, and the first frequency-divided signal and the second frequency-divided signal are compared so that the phase difference is equal to or less than a predetermined value. waveform shaping circuit, characterized in that a phase comparator circuit for correcting the signal level of the threshold according to the phase difference. The waveform according to claim 4, wherein the frequency division ratio is set such that the phase difference between the first frequency-divided signal and the second frequency-divided signal does not exceed the cycle of the binarized data. Molding circuit.

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