JPH08194983A - Optical disc drive, data transmitter and dc level measuring circuit - Google Patents

Abstract

PURPOSE: To obtain an optical disc drive, a data transmitter and a DC level measuring circuit in which a readback signal can be binarized correctly even when a modulation system including DC component is selected. CONSTITUTION: Upper and lower envelopes EU, EL of an input signal MO are detected and threshold values B0-B6 having signal levels, which follow up the signal levels of the upper and lower envelopes EU, EL, are set. Signal level of the threshold value B0-B6 is then switched and the comparison results of switched threshold value and an input signal MO is counted.

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, a data transmission device and a DC level measuring circuit, and can be applied to, for example, a magneto-optical disk device.

[0002]

2. Description of the Related Art Conventionally, a magneto-optical disk device which is a data transmission device effectively avoids intersymbol interference between consecutive data and selects a recording condition to keep a direct current level of a reproduced signal constant. The value is held so that the recorded data is surely reproduced.

That is, in this type of magneto-optical disk device, the magneto-optical disk has an information recording surface formed by forming a perpendicularly magnetized film made of a magnetic film on a predetermined disk-shaped substrate by applying a method such as sputtering. Is formed, and a protective film is further arranged on this information recording surface.

At the time of recording, the magneto-optical disk apparatus irradiates the information recording surface of the magneto-optical disk by intermittently raising the light quantity of the laser beam to the magneto-optical disk, and the laser beam irradiation position is predetermined. The modulation magnetic field of is applied. As a result, the magneto-optical disk device records desired data by applying the thermomagnetic recording method.

On the other hand, at the time of 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 returned light.
A reproduced signal whose signal level changes according to the change of the plane of polarization is detected, and the recorded data is reproduced by binarizing the reproduced signal with a predetermined threshold value. As a result, the magneto-optical disk device utilizes the magnetic Kerr effect to reproduce the data recorded on the magneto-optical disk.

Therefore, in the magneto-optical disk apparatus, if the direct current level of the reproduced signal fluctuates, it becomes difficult to properly binarize the reproduced signal, and eventually it becomes difficult to correctly reproduce the recorded data.

Therefore, in the magneto-optical disk device, the write data is modulated by a predetermined modulation method at the time of recording and recorded, and the decoding processing corresponding to this modulation method is executed at the time of reproduction. That is, this modulation processing is performed by adding an error correction code or the like to write data input from a host computer or the like, and then performing modulation so that the logical "H" level period is equal to the logical "L" level period. In order to set the DC level to 0 level in the subsequent data string, write data is written, for example, EFM (Eight to Fourteen Modulat).
ion) is executed after being modulated.

As a result, the magneto-optical disk device keeps the direct current level of the reproduced signal at a constant value during reproduction when the recorded data is recorded under the correct condition.

Further, in the magneto-optical disk device, the DC level of the reproduction signal is constant even if the data length of the recorded data is changed by performing the trial writing using the trial writing area previously formed on the magneto-optical disk. The light intensity of the laser beam is adjusted so that the value is maintained.

That is, in the magneto-optical disk device, by irradiating a laser beam, the temperature at the laser beam irradiation position is raised to above the Curie temperature of the perpendicular magnetization film, and then the perpendicular magnetization film locally heated during cooling. Is magnetized to the polarity of the modulation magnetic field to form continuous pits with the polarity of the recording data to record the recording data.

Therefore, in this type of magneto-optical disk device, 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) In addition, the size of the pits formed varies depending on the amount of laser beam writing light, the ambient temperature, and the like.

That is, when a laser beam is applied,
If the ambient temperature is high or the sensitivity of the magneto-optical disk is high, the temperature of the laser beam irradiation position quickly rises to the Curie temperature, which causes a large pit to be formed compared with the period when the light intensity of the laser beam was raised. It On the contrary, when the ambient temperature is low, the temperature of the laser beam irradiation position rises slowly, and a small pit is formed as compared with the period when the light amount of the laser beam is raised.

When the size of the pit thus formed changes, even if the DC level of the recorded data is held at 0 level, the DC level of the reproduced signal changes according to the data length of the recorded data. Like Therefore, in the magneto-optical disk device, the optimum recording condition is detected based on the reproduction result of the test-written data, and the laser beam is irradiated under this recording condition.

As a result, in the conventional magneto-optical disk device, the reproduced signal is binarized with a constant threshold value, and the recorded data can be surely reproduced.

[0015]

By the way, if a modulation system that positively utilizes inter-code interference is applied as this modulation system, for example, a 1-16 modulation system which is one of variable length coding systems, It is considered that the recordable frequency band of the spectroscopic magnetic disk can be fully utilized and the recording density of the magneto-optical disk can be improved.

However, in the case where the recordable frequency band of the magneto-optical disk is fully utilized by positively utilizing the inter-code interference in this way, in the transmission system of the magneto-optical disk device, the frequency characteristics other than the band where the frequency characteristic is constant are used. Recording and reproduction are also performed using the band, and the DC level of the reproduction signal changes according to the data length of the recorded data. In this case, in the conventional magneto-optical disk device, it is difficult to properly binarize the reproduced signal by binarizing the reproduced signal whose DC level changes with a constant threshold value.

The present invention has been made in consideration of the above points, and an optical disk device, a data transmission device and a data transmission device which can properly binarize a reproduction signal even when a modulation method including a DC component is selected. It is intended to propose a DC level measuring circuit.

[0018]

In order to solve such a problem, according to the present invention, an envelope detection circuit for envelope-detecting an input signal input through a transmission system and detecting an upper envelope and a lower envelope of the input signal. And a threshold setting circuit that sets a threshold value at which the signal level of the upper envelope and the lower envelope changes according to the signal levels of the upper envelope and the lower envelope, and this threshold value. It is equipped with a comparison circuit that outputs the comparison result with the input signal and a counter that counts the comparison result and outputs the count result, and this transmission system is controlled by the count result obtained by switching the signal level of this threshold value. Measure the DC level of the input signal input via.

Further, in the second invention, an envelope detection circuit for envelope-detecting an input signal inputted through the transmission system to detect an upper envelope and a lower envelope of the input signal, and an upper envelope and a lower envelope. A threshold setting circuit that sets a threshold value at which the signal level changes in accordance with the signal levels of the upper envelope and the lower envelope, and outputs the comparison result of this threshold value and the input signal. A comparison circuit and a counter for counting the comparison result and outputting the count result are provided, and the transmission system is optimized by the count result obtained by switching the threshold signal level.

In the third invention, an envelope detection circuit for envelope-detecting an input signal input via the transmission system and detecting an upper envelope and a lower envelope of the input signal, and an upper envelope and a lower envelope. Threshold value setting circuit that sets the threshold value that changes the signal level of the upper envelope and the lower envelope signal level based on the envelope, and outputs the comparison result of this threshold value and the input signal Comprising a comparison circuit, a counter that counts this comparison result and outputs the count result, and a signal processing circuit that converts the input signal into serial data, depending on the count result obtained by switching the signal level of the threshold value, Optimize the signal processing circuit.

Further, in a fourth aspect of the present invention, an optical disc apparatus for sequentially recording desired recording data on a disc-shaped recording medium and reproducing the recorded data on the disc-shaped recording medium is obtained by reproducing the disc-shaped recording medium. For the reproduced signal that is reproduced, the envelope detection circuit that detects the envelope of the reproduced signal and detects the upper and lower envelopes of the reproduced signal, and the signal level of the upper and lower envelopes with reference to the upper and lower envelopes. A threshold value setting circuit that sets a threshold value at which the signal level changes in accordance with
It comprises a comparison circuit for outputting the comparison result of the threshold value and the reproduction signal, and a counter for counting the comparison result and outputting the count result, and the reproduction signal can be obtained by switching the threshold signal level. Measure the DC level of.

In particular, based on the measurement result of the DC level,
The recording / reproducing system of the disk-shaped recording medium is optimized by correcting the light amount and / or irradiation time of the light beam applied to the disk-shaped recording medium.

A filter circuit for correcting the frequency characteristic of the reproduced signal and a signal processing circuit for converting the reproduced signal into serial data by obtaining a comparison result between the reproduced signal and a predetermined binarization level are provided. The frequency characteristic and / or the binarization level of the filter circuit are corrected based on the measurement result of the DC level.

[0024]

The upper envelope and the lower envelope of the input signal are detected, and the threshold value at which the signal level changes according to the signal levels of the upper envelope and the lower envelope is set. By counting the comparison result between the threshold value obtained by switching and the input signal, even if the DC level of the input signal fluctuates depending on the data length of the input signal, the threshold signal level is optimal for the input signal. When held at, the count result with the highest rise of the count value can be obtained, whereby the DC level can be easily measured from the count result with the highest rise of the count value.

Therefore, the same configuration can be applied to the data transmission device to optimize the transmission system of the data transmission device.

The signal processing circuit for converting an input signal into serial data can also be optimized 1.

Further, it can be applied to an optical disk device to measure the DC level of a reproduced signal.

Therefore, in the optical disc apparatus, the recording / reproducing system can be optimized by correcting the light quantity and / or irradiation time of the light beam.

Further, the filter circuit for correcting the frequency characteristic of the reproduction signal and the signal processing circuit for converting the reproduction signal into serial data by obtaining the comparison result between the reproduction signal and a predetermined binarization level are also provided. The frequency characteristic and / or the binarization level of the filter circuit can be corrected and optimized.

[0030]

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

(1) First Embodiment In FIG. 2, reference numeral 1 denotes a magneto-optical disk device as a whole, in which data DATA inputted from an external device such as a computer is recorded on a magneto-optical disk 2, and the optical data is further recorded. The data DATA recorded on the magnetic disk 2 is read and output to an external device.

Here, the magneto-optical disk 2 is formed by forming a perpendicular magnetic film on a predetermined disk-shaped substrate and then further disposing a plastic protective film. Further, in this magneto-optical disk 2, a so-called pre-groove, which is a groove for guiding a laser beam, is formed in a spiral shape so that tracking control can be performed by the pre-groove, and the meandering of the pre-groove is detected to control the spindle. Further, the position information of the laser beam irradiation position can be detected.

That is, in the magneto-optical disk device 1,
The optical pickup 3 condenses the laser beam emitted from the laser diode on the information recording surface of the magneto-optical disc 2 by the built-in objective lens 4, and further returns light obtained from the magneto-optical disc 2 to the objective lens 4. The light is collected by and is received by the built-in photo detector. Here, in this photodetector, the light receiving surface is, for example, the magneto-optical disk 2
Are formed by being divided in the radial direction and the circumferential direction, and output signals of the respective divided light receiving surfaces are output.

The preprocessing circuit 5 performs current-voltage conversion processing on the output signal of each light-receiving surface, and then performs addition / subtraction processing, whereby the tracking error signal TE and the focus error signal F are obtained.
E and the like are generated, and further, the change of the polarization plane of the return light is detected to generate the reproduction signal MO. Further, the preprocessing circuit 5 corrects the frequency characteristic of the reproduction signal MO and outputs it by filtering the reproduction signal MO.

The servo circuit 6 receives the focus error signal F
Based on E and the tracking error signal TE, the objective lens 4 is moved up and down and to the left and right to perform tracking control and focus control, and at the same time, the spindle motor 7 is driven to rotate the magneto-optical disk 2 under a constant linear velocity condition. To drive.

When a write command is input from the host computer while the tracking control, focus control and spindle control are performed in this way, the magneto-optical disk device 1 causes the optical pickup 3 to magneto-optically move before recording data. Move to the trial writing area of disk 2,
In this test writing area, the light quantity of the laser beam is intermittently raised from the light quantity at the time of reading to a predetermined light quantity, and a predetermined modulation magnetic field is applied, whereby predetermined data is recorded in the test writing area under a predetermined condition. To do.

Subsequently, the magneto-optical disk device 1 shifts to the reproducing operation and detects a change in the signal level of the reproducing signal MO to detect the optimum writing condition. A series of these processes are executed by controlling the entire operation by the system control circuit, and the system control circuit selects the optimum write light amount and the like based on the measurement result of the DC level measurement circuit 14 described later. Executed by.

When the writing condition is selected in the trial writing area in this manner, the magneto-optical disk device 1 records the subsequently input data DATA on the magneto-optical disk 2. That is, in this magneto-optical disk device 1, the input / output circuit 10 forms an interface circuit with an external device and a data buffer circuit, and inputs / outputs commands such as write, read, and interrupt with the external device. Further, the written data DATA and the read data DATA are input / output.

The recording data processing circuit 11
After adding an error correction code to the data DATA output from the input / output circuit 10 in a predetermined block unit, the data DATA is converted into recording data by the 1-16 modulation system which is one of the variable length coding systems. Further, data such as sync, resync, and address are added to this recording data and output.

The drive circuit 12 drives the laser diode of the optical pickup 3 according to the serial data D2 output from the recording data processing circuit 11, and the laser beam is emitted during the period when the logic level of the serial data D2 rises. The amount of light is raised from the amount of light for reading to the amount of writing. As a result, in the magneto-optical disk device 1, pits are sequentially formed in the magneto-optical disk 2 according to the serial data D2, and the data DATA input from the external device is recorded on the magneto-optical disk 2.

On the other hand, when a read command is input from an external device, the magneto-optical disk device 1 reads the data designated by this command from the magneto-optical disk 2 and outputs it. That is, in the magneto-optical disk device 1, the comparison circuit 13 inputs the reproduction signal MO to the non-inverting input terminal, inputs the threshold SL set by the system control circuit to the inverting input terminal, and uses the threshold SL. The reproduction signal MO is converted into binary data D3 and output.

The reproduction data processing circuit 15 decodes the data DATA from the binarized data D3 to input / output the circuit 10.
Output to. At this time, the reproduction data processing circuit 15 detects the sync and resync of the binarized data D3, performs processing such as error correction in block units, and decodes the data, thereby validating bit errors and the like in the read data DATA. To avoid. Further, the reproduction data processing circuit 15 has a built-in FIFO (First
In First Out) The binarized data D3 is temporarily stored in the memory circuit, processed, and output to the input / output circuit 10 at a timing synchronized with a predetermined internal clock.

Thus, in the magneto-optical disk device 1, since the 1-16 modulation system is applied, the frequency band of the magneto-optical disk 2 can be effectively used by positively utilizing the intersymbol interference. The recording density can be improved as compared with the conventional magneto-optical disk device.

Here, the DC level measuring circuit 14 is formed as shown in FIG. In FIG. 1, the magneto-optical disk device 1 is understood as a data transmission device, the signal processing circuit from the input / output circuit 10 to the drive circuit 12 is represented by a data generation source 21, and the modulation coil and the optical pickup 3 are connected to the front. A recording / reproducing system including a recording medium up to the processing circuit 5 is represented by a transmission system 20.

In this type of data transmission system, the serial data D2 generated by the data generation source 21 is transmitted by the transmission system 20.
, The signal waveform of the serial data D2 to be transmitted is changed by the transfer characteristic of the transmission system 20, and is input to the receiving side as a reproduction signal MO.

In such a data transmission system, for example, as shown in FIG.
When the serial data D2 whose logical level is inverted at T, 2T, and 8T is repeatedly transmitted, the periods 8T and 2T
When the transmission system 20 has the same amplitude characteristic with respect to the data length of, that is, when the frequency band of the transmission system 20 is sufficient for the frequency band having the periods 8T and 2T as basic periods. , A reproduction signal MO as shown in FIG.
Can be obtained.

Here, this reproduction signal MO is the reproduction signal MO.
When the amplitude is observed with reference to the signal level L1 which is ½ of the maximum amplitude of
The signal level a1 from this signal level L1 to the maximum value
And the signal level b1 from the signal level L1 to the minimum value b1 is held at the same signal level. Cycle 2
In the data length portion of T, the signal level a2 from the signal level L1 to the maximum value and the signal level L1
To the minimum value are held at the same signal level.

Thus, when the frequency band of the transmission system 20 is sufficient, the reproduction signal MO is binarized by setting the signal level L1 of 1/2 of the maximum amplitude as the threshold value.
The transmitted serial data D2 can be correctly binarized.

On the other hand, as shown in FIG. 5, when the amplitude characteristics of the transmission system 20 are different with respect to the data lengths of the periods 8T and 2T, that is, the frequencies having the periods 8T and 2T as the basic periods. When the frequency characteristic changes in the band, a reproduction signal MO whose DC level changes according to the data length is obtained as shown in FIG. That is, in this case, since the amplitude characteristic of the data length of the cycle 2T is deteriorated as compared with the data length of the cycle 8T, the signal level of the reproduction signal MO rises to the maximum amplitude in the portion of the cycle 8T.
The fall of the signal level becomes small in the part of the cycle 2T, and the signal level rises to the maximum amplitude in the part of the following cycle 2T.

As a result, the intermediate value level L2 between the maximum value and the minimum value in the portion of the cycle 8T (that is, the signal level at which the signal levels a3 and b3 are equal in FIG. 6) and the maximum value and the minimum value in the portion of the cycle 2T are obtained. Intermediate value level L3 (that is, signal level a in FIG. 6)
4 and b4 have the same signal level), and eventually, the reproduction signal MO is binarized by setting the above-mentioned signal level L1 as a threshold value. The data D2 cannot be reproduced correctly.

As shown in FIG. 7, the signal levels A and B between the signal levels L2 and L3 and the minimum value of the reproduction signal MO are expressed by the following equations.

[Equation 1] The value AS represented by the relational expression is referred to as asymmetry, and hereinafter, the degree to which the DC level changes depending on the data length is represented by this asymmetry AS. Therefore, when the DC level does not change depending on the data length, the asymmetry AS is 50%.

Therefore, the DC level measuring circuit 14 inputs the reproduction signal MO to the envelope detection circuit 22 and envelope-detects the reproduction signal MO. That is, the envelope detection circuit 22 obtains the upper envelope detection result EU and the lower envelope detection result EL of the reproduction signal MO as shown in FIG. 8, and generates the upper envelope detection result EU and the lower envelope detection result EL as reference levels. Output to the circuit 23.

Here, the reference level generating circuit 23 is formed by connecting eight resistors having the same resistance value in series in this embodiment, and the upper envelope detection result EU and the lower envelope detection result EU are respectively formed at both ends of this series circuit. The result EL is input and the connection midpoint of each resistor is connected to each contact of the selection circuit 24. As a result, the DC level measuring circuit 14 causes the upper envelope detection result EU and the lower envelope detection result E to be detected.
The signal level determined by L is divided by eight resistors, and the resulting divided voltages B0 to B6 are output to the selection circuit 24.

The selection circuit 24 uses the divided voltages B0 to B6.
Are sequentially selected at a predetermined cycle, and the selected output is compared circuit 25.
Output to the non-inverting input terminal of. The comparison circuit 25 has a hysteresis characteristic and is adapted to input the reproduction signal MO to the inverting input terminal. As a result, the comparison circuit 25
A reproduction signal M based on the selected divided voltages B0 to B6
The O is binarized and the binarized result is output to the counter 26.

The counter 26 has a gate signal generating circuit 27.
After being reset by the reset signal RT output from, the rising edge of the signal level of the output signal of the comparison circuit 25 is counted with the gate signal GT as a reference, and this count value CT is output.

In the magneto-optical disk device 1 according to this series of processing, the specified serial data D is written in the trial writing area.
2 is repeatedly recorded, and the reset signal RT and the gate signal GT are further output from the gate signal generation circuit 27 in a cycle synchronized with the repeating cycle of the serial data D2, whereby the counter 26 reproduces the trial writing in the writing area. This counting operation is repeated in the repetition cycle of the signal MO, and the selection circuit 24 sequentially switches the contacts in synchronization with this repetition cycle.

In this case, as shown in FIG.
In the case where the divided voltage B1 is selected and the divided voltage B2
When the divided voltage B2 is selected, since the signal level of the reproduction signal MO crosses the signal level of the divided voltage B2 more often than when the divided voltage B2 is selected. The count value CT is larger in this case. Further, in this case, as the threshold value for binarizing the reproduction signal MO, the divided voltage B2 having the larger count value CT can be judged to be more appropriate.

As a result, as shown in FIG. 9, the counter 2
When the asymmetry AS of the reproduction signal MO is 50 [%], the count value CT obtained via 6 is the divided voltage B3 which is a signal level intermediate between the upper envelope detection result EU and the lower envelope detection result EL. When selected, the count value CT becomes the largest, and when the comparison reference of the comparison circuit 25 moves away from the divided voltage B3, that value also becomes smaller.

Further, when the asymmetry AS of the reproduction signal MO is deviated from 50%, when the divided voltage displaced from the divided voltage B3 is selected, the count value CT becomes the largest, and this divided voltage is When the comparison standard moves away from, the value becomes smaller accordingly. Therefore, it is possible to detect the divided voltage at which the count value CT becomes the largest and detect the asymmetry AS of the reproduction signal MO.

Therefore, in this type of data transmission device,
Based on the detected asymmetry AS, the optimum transmission condition is selected by adjusting the condition of the data source, the condition of the transmission system 20, the threshold value at the time of reproduction, etc. Even when is selected, the reproduced signal can be correctly binarized.

Therefore, in the magneto-optical disk device 1,
The system control circuit uses the count value C of the counter 26.
After sequentially taking in T, the divided voltages B0 to B6 at which the count value CT rises most are detected. At this time, the system control circuit detects the maximum value by performing a curve approximation of the count value CT described above with reference to FIG. 9, and thereby the asymmetry A with high accuracy with respect to the discrete divided voltage B0 to B6.
Detect S.

Further, the system control circuit calculates the amount of light for writing and the period for which the laser beam is raised to the amount of light for writing based on the asymmetry AS detected in the writing area, and the asymmetry A
The write condition for S to be 50 [%] is calculated. Subsequently, the system control circuit sends a control command to the recording data processing circuit 11 and the drive circuit 12, and at the time of subsequent data recording, the serial data D2 is recorded on the magneto-optical disk 2 according to the calculated condition.

As a result, in the magneto-optical disk device 1, even when the serial data D2 is reproduced via the transmission system in which the DC level varies according to the data length, the serial data is kept under the condition that the DC level is optimally maintained. D2 can be recorded, and even when a modulation method including a DC component is selected, the recording / reproducing system can be optimized and the reproduced signal can be correctly binarized.

On the other hand, during reproduction, similarly, in the magneto-optical disk device 1, prior to the reproduction of data, the DC level measuring circuit 14 detects the asymmetry AS using the data to be reproduced. Further, in the magneto-optical disk device 1, the system control circuit issues a control command to the preprocessing circuit 5 based on the detection result of the asymmetry AS, and the asymmetry AS becomes 50 [%].
The filtering characteristic is switched so as to approach to, and the threshold value of the comparison circuit 13 is optimized.

That is, in this type of magneto-optical disk device, the magneto-optical disk 2 may be replaced, and the 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 optimized based on the measurement result of the DC level measuring circuit 14 as in this embodiment, the transmission characteristics of the entire recording / reproducing system are optimized even when reproducing by another magneto-optical disk device. The reproduced signal MO can be binarized correctly.

On the contrary, the magneto-optical disk 2 recorded by another magneto-optical disk apparatus may be reproduced by the magneto-optical disk apparatus 1 according to this embodiment. In this case, as in this embodiment, Filtering characteristics and threshold SL
By setting, the transmission characteristics of the entire recording / reproducing system can be optimized and the reproduced signal MO can be correctly binarized.

As a result, the magneto-optical disk device 1 not only records and reproduces data with the magneto-optical disk device 1, but also reproduces the magneto-optical disk 2 recorded with another magneto-optical disk device. Even when the magneto-optical disk 2 recorded by the magneto-optical disk apparatus 1 is reproduced by another magneto-optical disk apparatus, the transmission system is optimized so that the recorded data can be surely reproduced.

In the above configuration, when a write command is input from an external device, the magneto-optical disk device 1
Causes the optical pickup 3 to move to the test writing area and perform test writing, whereby the writing light amount is set. At this time, the magneto-optical disk device 1 repeatedly records the specified data under the specified condition, reproduces the recorded data, selects the writing condition based on the reproduction result, and optimizes the recording / reproducing system.

That is, in the reproduced signal MO, the DC level measuring circuit 14 detects the upper envelope and the lower envelope, and the reference level generating circuit 23 divides the divided voltage between the upper envelope detection result EU and the lower envelope detection result EL. B0 to B6 are generated. Further, the result of comparison between the divided voltages B0 to B6 and the reproduction signal MO is counted by the counter 26, and the asymmetry AS is detected by the count result.

Further, this asymmetry AS corrects the writing light amount and the period during which the laser beam is raised to the writing light amount so that the asymmetry AS becomes 50%, and the recording / reproducing system is set to the optimum writing condition. Is optimized.

On the other hand, the data DATA input from the external device via the input / output circuit 10 is subjected to 1-16 modulation after the error correction code is added in a predetermined block unit in the recording data processing circuit 11. Received data, sync data, resync data, etc. are added and converted into serial data D2. The serial data D2 is output to the drive circuit 12, whereby the light quantity of the laser beam is changed from the light quantity at the time of reading to the light quantity for writing set by the test writing according to the logic level of the serial data D2. Switching is performed intermittently in units of the set rising period, and pits corresponding to recording data are sequentially formed on the magneto-optical disk 2.

On the other hand, when a read command is input from the external device, the reproduction signal MO output from the optical pickup 3 is applied to the threshold value SL in the comparison circuit 13.
Is used as a reference to generate binarized data D3, and this binarized data D3 is reproduced data processing circuit 15
In, the data is decoded, error-corrected, and output to an external device via the input / output circuit 10.

In the binarization, the reproduced signal MO is detected by the DC level measuring circuit 14 in the same manner as the asymmetry AS, and the asymmetry AS is 50 [%].
Therefore, the filtering characteristic is set so that the threshold value SL for binarization is set.

According to the above configuration, the reference level generating circuit 2 is based on the upper envelope and the lower envelope.
And the reproduction signal M
By counting the result of comparison with O with the counter 26 and detecting the asymmetry AS based on the count result, the asymmetry AS can be detected even when the DC level changes depending on the data length.

Thus, this detected asymmetry A
By optimizing the recording system and the reproduction system with S as a reference, the reproduction signal MO can be correctly converted into binary data. As a result, the recording density can be improved as compared with the conventional case by effectively utilizing the frequency band of the recording / reproducing system.

(2) Other Embodiments In the above-described embodiment, the contacts of the selection circuit 24 are sequentially switched to obtain the count result, so that the threshold signal level is sequentially switched with respect to the reproduction signal MO. I described the case of detecting the obtained count result,
The present invention is not limited to this, but a plurality of systems of comparator circuits and counters are arranged corresponding to the divided voltages B0 to B6, and even if the count result obtained by switching the signal level of the threshold value is detected at the same time. Good.

By doing so, since the asymmetry can be detected in real time, the filtering characteristic and the threshold for binarization can be switched in real time based on the result of the asymmetry detection, and the reproduction can be performed more accurately. The signal MO can be binarized.

In the above embodiments, the case where the 1-16 modulation method is applied has been described, but the present invention is not limited to this and can be widely applied when various modulation methods are selected. Can also be applied when a modulation method that does not involve a DC component is selected.

Further, in the above-mentioned embodiment, the case where the present invention is applied to the magneto-optical disk device has been described.
The present invention is not limited to this, and can be widely applied to various optical disk devices such as a write-once type optical disk device, and further to a magnetic recording / reproducing device such as a hard disk device and a data transmission device such as an optical communication device using an optical fiber. You can

That is, as shown in FIG. 10, in a magnetic recording / reproducing apparatus such as a hard disk device, like the magneto-optical disk device of this type, the write data is modulated and converted into the recording data REC (FIG. 10 (A)). Then, a recording current is supplied to the magnetic head according to the recording data REC. As a result, in the magnetic recording / reproducing apparatus, a magnetized area that is continuous in the direction of the scanning locus is formed on the scanning locus of the magnetic head (FIG. 10B), and the write data is recorded on the magnetic recording medium such as a hard disk.

On the other hand, at the time of reproducing, the magnetic recording / reproducing apparatus traces the scanning locus of this magnetic head with the reproducing head, whereby the reproducing signal PB in which the signal level rises positively and negatively at the boundary of the magnetized region. Is detected (Fig. 10
(C)) The reproduction signal PB is binarized by judging the reproduction signal PB as 1, 0, −1 with reference to two threshold values sandwiching the 0 level therebetween. Therefore, in FIG. 11, the state in which the reproduction signal is held at 0 level represents the logic 0, and the state in which the reproduction signal changes to 1 or -1 represents the logic 1.

Therefore, also in the magnetic recording / reproducing apparatus, if the recording density is improved and the inter-code interference occurs, the signal level of the reproduced signal PB to be held at the logic 1 eventually changes according to the data length. become. As a result, the DC level measuring circuit described above with reference to FIG. 1 is applied to this type of magnetic recording / reproducing apparatus to detect asymmetry, and the recording / reproducing system is optimized based on the result of the asymmetry detection so that the reproduction signal PB is correctly binary. Can be converted.
Specifically, based on the asymmetry detection result, the recording current is corrected, the frequency characteristic of the reproduction signal PB is corrected, and the threshold value for binarizing the reproduction signal PB is corrected to obtain the reproduction signal PB. Can be correctly binarized.

On the other hand, in the optical communication device using the optical fiber, as shown in FIG. 11, similarly, the write data is modulated to generate the transmission data D4 (FIG. 11A), and the transmission data D4 is generated. The laser diode is driven according to D4 to emit a laser beam. As a result, in the optical communication device, when the transmission distance is maintained at a sufficiently appropriate distance, a laser beam that rises from a light amount of almost 0 level corresponding to the logical level of the transmission data D4 (FIG. 11B). Can be received, and the received data can be binarized to reproduce the transmission data D4.

However, when a laser beam is transmitted by an optical fiber, it is difficult to avoid the dispersion of light. Therefore, when the transmission distance becomes long, the rise and fall of the light quantity becomes gentle (FIG. 11C), and finally. The eye pattern has a small aperture in both the amplitude direction and the phase direction. That is, in this case, the amplitude margin and the phase margin are reduced according to the transmission distance (FIG. 11).
(D)).

In the optical communication device having such characteristics, when intersymbol interference occurs by improving the transmission rate, the light quantity of the laser beam, which should be held at the logic 0, for example, is eventually transmitted according to the data length. It will change on the target side. Thus, in this type of optical communication device, the DC level measuring circuit described above with reference to FIG. 1 is applied to detect asymmetry, and the transmission system is optimized based on the asymmetry detection result to correctly reproduce transmitted data. You can Specifically, the light quantity of the laser beam is corrected based on the asymmetry detection result, the irradiation period of the laser beam is also corrected, and further the frequency characteristic of the light reception result and the threshold value for binarizing the light reception result are corrected. Then, it can be correctly binarized.

[0086]

As described above, according to the present invention, even if the DC level changes according to the data length, this DC level can be detected, and the recording / reproducing system can be optimized based on this detection result. The data transmitted can be reproduced correctly.

[Brief description of drawings]

FIG. 1 is a block diagram showing a DC level measuring circuit of a magneto-optical disk device according to an 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 magneto-optical disk device of FIG.

FIG. 4 is a signal waveform diagram showing a reproduced signal in the magneto-optical disk device of FIG. 2 when the frequency band of the recording / reproducing system is sufficient.

5 is a characteristic curve diagram showing an actual frequency characteristic of the magneto-optical disk device of FIG.

6 is a signal waveform diagram showing an actual reproduction signal of the magneto-optical disk device of FIG.

FIG. 7 is a signal waveform diagram for explaining asymmetry.

FIG. 8 is a signal waveform diagram for explaining the operation of the DC level measuring circuit of FIG.

9 is a characteristic curve diagram showing a measurement result of the DC level measuring circuit of FIG.

FIG. 10 is a signal waveform diagram for explaining an embodiment in which the present invention is applied to a magnetic recording / reproducing apparatus.

FIG. 11 is a signal waveform diagram for explaining an embodiment in which the present invention is applied to an optical communication device.

[Explanation of symbols]

 1 Magneto-optical disk device 2 Magneto-optical disk 3 Optical pickup 13 and 24 Comparison circuit 14 DC level measurement circuit 20 Transmission system 21 Data generation source 22 Envelope detection circuit 23 Reference level generation circuit 26 Counter

Claims (6)

[Claims] 1. An envelope detection circuit for detecting an upper envelope and a lower envelope of the input signal by performing envelope detection on an input signal input via a transmission system, and using the upper envelope and the lower envelope as a reference. A threshold value setting circuit that sets a threshold value at which the signal level changes in accordance with the signal levels of the upper envelope and the lower envelope, and a comparison that outputs a comparison result of the threshold value and the input signal. A circuit and a counter that counts the comparison result and outputs the count result, wherein the count result obtained by switching the signal level of the threshold value causes the input signal to be input via the transmission system. A DC level measuring circuit characterized by measuring a DC level. 2. An envelope detection circuit that detects an upper envelope and a lower envelope of the input signal by performing envelope detection on an input signal input through a transmission system, and the upper envelope and the lower envelope as a reference. A threshold value setting circuit that sets a threshold value at which the signal level changes in accordance with the signal levels of the upper envelope and the lower envelope, and a comparison that outputs a comparison result of the threshold value and the input signal. A circuit and a counter that counts the comparison result and outputs a count result, and optimizes the transmission system according to the count result obtained by switching the signal level of the threshold value. Transmission equipment. 3. An envelope detection circuit for detecting an upper envelope and a lower envelope of the input signal by performing envelope detection of an input signal input via a transmission system, and using the upper envelope and the lower envelope as a reference. A threshold value setting circuit that sets a threshold value at which the signal level changes in accordance with the signal levels of the upper envelope and the lower envelope, and a comparison that outputs a comparison result of the threshold value and the input signal. A circuit, a counter that counts the comparison result and outputs a count result, and a signal processing circuit that converts the input signal into serial data, and according to the count result obtained by switching the signal level of the threshold value. A data transmission device characterized by optimizing the signal processing circuit. 4. A reproduction signal obtained by reproducing the disk-shaped recording medium in an optical disk device for sequentially recording desired recording data on the disk-shaped recording medium and reproducing the data recorded on the disk-shaped recording medium. An envelope detection circuit that detects the upper envelope and the lower envelope of the reproduced signal by envelope-detecting the reproduced signal, and a signal of the upper envelope and the lower envelope with reference to the upper envelope and the lower envelope. A threshold setting circuit that sets a threshold value at which the signal level changes in accordance with the level, a comparison circuit that outputs a comparison result between the threshold value and the reproduction signal, and a count result that counts the comparison result. A counter for outputting the result, which is obtained by switching the signal level of the threshold value. An optical disk device, wherein the DC level of the reproduction signal is measured based on the counted result. 5. The recording / reproducing system of the disk-shaped recording medium is optimized by correcting the light quantity and / or irradiation time of the light beam with which the disk-shaped recording medium is irradiated, based on the measurement result of the DC level. The optical disk device according to claim 4, wherein: 6. A filter circuit for correcting the frequency characteristic of the reproduction signal, and a signal processing for converting the reproduction signal into serial data by obtaining a comparison result between the reproduction signal and a predetermined binarization level. 6. The optical disk device according to claim 4, further comprising a circuit, and correcting the frequency characteristic and / or the binarization level of the filter circuit based on the measurement result of the DC level.