JPH05314505A - Focus control circuit device for optical information read/ write device - Google Patents

Abstract

(57) [Summary] [Object] To provide a focus control circuit device of an optical information reading / writing device capable of maintaining good focusing of a laser beam on a disk by always maintaining an offset voltage in a focus error signal appropriately. To do. A wobble signal demodulating means 4 for performing a demodulation operation of a wobble signal included in a tracking error signal and counting demodulation accuracy in the demodulation operation, and a focus error when a count value of the demodulation accuracy exceeds a predetermined value. Adjusting offset voltage generating means 5 for outputting an adjusting offset voltage for correcting the offset voltage in the signal, and offset voltage correction for correcting the offset voltage with the adjusting offset voltage output by the adjusting offset voltage generating means. Means 7 and are provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a focus control circuit device of an optical information reading / writing device for reading / writing information using an optical pickup.

[0002]

2. Description of the Related Art When reading or writing optical information from or to a disc which is a recording medium, it is necessary to perform a focusing operation for aligning the focus of, for example, laser light emitted from an optical pickup with the surface of the disc. As a signal for performing this focusing operation, a focus error generated based on a light receiving signal sent by a light receiving element that receives the laser light reflected on the disk surface (hereinafter,
The signal may be used as FE). However, there is a problem in that the focus error signal causes an offset voltage as shown in FIG. 7 due to pit distortion, noise, and the like, and the focus of the laser light does not match the disk surface due to the offset voltage. Therefore, in the conventional circuit for correcting the offset voltage, the offset voltage in the focus error signal sent from the focus error signal amplifier 1 and the correction voltage output from the offset voltage adjusting volume 50 are different from each other in the circuit shown in FIG. The method of synthesizing by the dynamic amplifier 20 is adopted. As a method of adjusting the output voltage of the offset adjusting volume 50, a standard disc is reproduced, and a high frequency (hereinafter referred to as RF) signal sent from the pickup at that time is displayed on an oscilloscope and the eye indicated by the waveform is displayed. The volume is adjusted so that the pattern opens best.

As a method of adjusting the offset voltage, there is also a method of using a tracking error signal in a circuit as shown in FIG. That is, as is well known, the output side of the light receiving elements A to D respectively arranged in the four regions, which receive the laser light reflected on the disk surface of the recording medium, is separated from these light receiving elements A to D. A focus error signal created based on the obtained light receiving signal is supplied and connected to one input terminal of the differential amplifier 20 via the focus error signal amplifier 1 for amplifying the focus error signal.

The output side of the light receiving elements A to D is
Through the tracking error signal amplifier 2 that amplifies the tracking error signal generated by the light receiving signal transmitted by the light receiving elements A to D, the positive / negative peak holding the maximum value of the positive and negative amplitude values in the tracking error signal. It is connected to the hold circuit 21. The output side of the positive / negative peak hold circuit 21 is connected to the system controller 23 via an AD converter 22 that converts the maximum value into a digital value.

The system controller 23 compares the maximum value a supplied last time from the AD converter 22 with the maximum value a supplied this time, and when the maximum value a is larger than the maximum value a, the system When the controller 23 is sending a value larger than the value sent last time to the DA converter 24 of the next stage, the system controller 23 sends a value larger than the value sent last time to the DA converter 24, and vice versa. When a value smaller than the value transmitted last time is transmitted, the system controller 23 transmits a value smaller than the value transmitted last time to the DA converter 24. On the other hand, when the maximum value A is smaller than the maximum value A, the system controller 23
Is sending a value larger than the value sent last time to the DA converter 24 at the next stage, the system controller 23 sends a value smaller than the value sent last time to the DA converter 24, and vice versa. When a value smaller than the previously transmitted value is transmitted, the system controller 23 transmits a value larger than the previously transmitted value to the DA converter 24. In this way, the system controller 23 determines that the maximum value of the tracking error signal is D
It operates so as to be sent to the A converter 24.

The output side of the DA converter 24 is connected to the other input terminal of the differential amplifier 20, and the DA converter 2
As described above, the offset voltage corresponding to the maximum amplitude value of the tracking error signal is applied from the DA converter 24 to the differential amplifier 20. Therefore, the differential amplifier 20 corrects the offset voltage in the focus error signal with the voltage applied from the DA converter 24, and sends the focus error signal having an appropriate offset voltage.

[0007]

However, adjusting the volume is a labor-intensive operation, and the dispersion of the reflected light amount of the laser light on the disk surface, the laser diode emitting the laser light and the reflected laser light are received. Since the offset voltage changes depending on the temperature characteristic of the light receiving element and the like, the volume correction described above cannot follow the change in the offset voltage, and the problem of defocusing still occurs.

Further, the correction of the offset voltage in the focus error signal is performed so that the eye pattern of the high frequency signal is opened to the maximum extent as described above.
As described above, it is not enough to solve the problem by adjusting the offset voltage in the focus error signal only with the maximum value of the amplitude value of the tracking error signal, and thus there is a problem that the focusing of the laser light on the disk cannot be maintained well. is there. The present invention has been made in order to solve such a problem, and an optical information for maintaining good focusing of a laser beam on a disk by always maintaining an offset voltage in a focus error signal at an appropriate value. An object of the present invention is to provide a focus control circuit device for a read / write device.

[0009]

The present invention relates to a focus control circuit device of an optical information reading / writing device for reading / writing optical information from / to a disc, which is an information recording medium, via an optical pickup. A wobble signal demodulating means for performing a demodulation operation of a wobble signal included in a tracking error signal generated based on a light reception signal transmitted by an optical pickup and expressing a demodulation accuracy in the demodulation operation by a count value, and a demodulation accuracy meter. First adjusting offset voltage generating means for outputting an adjusting offset voltage for correcting the offset voltage in the focus error signal generated based on the light receiving signal transmitted by the optical pickup when the numerical value becomes equal to or more than a predetermined value. And the offset voltage in the focus error signal A first offset voltage correction means is use the offset voltage generating means for correcting at adjusting the offset voltage to be output, characterized by comprising a.

With this configuration, the first adjusting offset voltage generating means is for adjusting the offset voltage of the focus error signal when the count value of the demodulation accuracy in the wobble signal demodulating means becomes a predetermined value or more. The offset voltage is sent to the first offset voltage correction means. The first offset voltage correction means corrects the offset voltage in the focus error signal supplied to the first offset voltage correction means based on the adjustment offset voltage. Therefore, the wobble signal demodulation means, the first adjustment offset voltage generation means, and the first offset voltage correction means
It works so that the offset voltage in the focus error signal is always maintained properly.

Further, according to the present invention, there is provided a focus control circuit device of an optical information reading / writing device for reading / writing optical information from / on a disc which is an information recording medium via an optical pickup. Second adjusting offset voltage generating means for correcting the offset voltage in the focus error signal generated based on the light receiving signal sent by the optical pickup by the control signal sent by the arithmetic processing unit, and the offset voltage in the focus error signal. And a second offset voltage correction means for correcting the above with the adjustment offset voltage output from the second adjustment offset voltage generation means.

With this configuration, the second adjusting offset voltage generating means sends the adjusting offset voltage of an appropriate value to the second offset voltage correcting means based on the control signal sent by the central processing unit. .. The second offset voltage correction means corrects the offset voltage in the focus error signal supplied to the second offset voltage correction means based on the adjustment offset voltage. Therefore,
The second adjusting offset voltage generating means and the second offset voltage correcting means operate so that the offset voltage in the focus error signal is always maintained properly.

The control signal may be a read signal and a write signal sent to the optical pickup or a write signal or a read signal.

Further, according to the present invention, a tracking error signal generating means for generating a tracking error signal based on a light receiving signal sent from an optical pickup for reading / writing information from / to a disc which is an information recording medium, and the tracking generated as described above. TE peak holding means for holding the maximum positive and negative amplitudes of the error signal, focus error signal generating means for generating a focus error signal based on the received light signal sent by the optical pickup, and focus from the focus error signal generating means. Focus control of an optical information reading / writing apparatus, which is provided with an error signal and which corrects an offset voltage value in the focus error signal based on the maximum positive and negative amplitude values sent by the peak hold means. Circuit equipment In the above, the RF peak hold means for holding the maximum value of the positive and negative amplitudes in the high frequency signal generated based on the received light signal, and the first offset correction voltage based on the maximum value of the positive and negative amplitudes sent by the TE peak hold means. A control means for generating the second offset correction voltage based on the maximum value of the positive and negative amplitudes sent by the RF peak hold means, and an offset of the focus error signal based on the first and second offset correction voltages. And a correction unit that corrects the voltage.

With this configuration, the control means creates the offset correction voltage based not only on the maximum value of the positive and negative amplitudes in the tracking error signal but also on the maximum value of the positive and negative amplitudes in the high frequency signal. Compared to the conventional method, which adjusts the offset voltage in the focus error signal only with the maximum amplitude value of the tracking error signal, the offset voltage can always be maintained at an appropriate value and the focusing of the laser light on the disk can be maintained well. To act like.

[0016]

【Example】

First Embodiment: An embodiment of the focus control circuit device of the present invention will be described below with reference to FIG. As is well known, the output sides of the light receiving elements A to D, which receive the laser light reflected by the disk surface of the recording medium and are respectively arranged in the four regions, are obtained from these light receiving elements A to D. A focus error signal generated based on the received light signal is supplied and is connected to a synthesizing circuit 7 described later via a focus error signal amplifier 1 that amplifies the focus error signal. Further, the output side of the tracking error signal amplifier 2 which is supplied with the tracking error signal generated based on the above received light signal and amplifies the tracking error signal is
It is connected to a demodulation circuit 4 via a wobble signal amplifier 3 which amplifies a wobble signal obtained from the tracking error signal.

As shown in FIG. 3, the demodulation circuit 4 has an FSK (Freq) to which the output side of the wobble signal amplifier 3 is connected.
uency Shift Keying) demodulator 4a,
A bi-phase demodulator 4b connected to the output side of the FSK demodulator 4a, a data demodulator 4c connected to the output side of the bi-phase demodulator 4b, and a CRC (Cyclic Redundancy) connected to the output side of the data demodulator 4c.
Code) error detector 4d, which is connected to the output side of the CRC error detector 4d and comprises a CRC error counter 4e for counting the number of detected errors.

The demodulation circuit 4 demodulates the data representing the address of the disk contained in the wobble signal and counts the demodulation accuracy, that is, the error rate of the data for one second, for example, and the counted value is predetermined. When it exceeds the value, a switching signal is sent.

The output side of the demodulation circuit 4 is connected to the injection ratio switching circuit 5 for FE offset adjustment, and the output side of the injection ratio switching circuit 5 for FE offset adjustment is connected to the synthesis circuit 7.
The injection ratio switching circuit 5 for FE offset adjustment has a configuration as shown in FIG. 2, for example, and in order to correct the offset voltage in the focus error signal, the power supply 5c is provided through the resistors 5a and 5b set to a predetermined resistance value. Has contact terminals 5d and 5e to which a predetermined voltage value is applied, and these contact terminals 5d and the like and the injection ratio switching circuit 5 for FE offset adjustment.
Switching the electrical connection with the output terminal 5f of the demodulator circuit 4
Is switched by the above switching signal sent by. Note that FIG. 2 shows a case where two resistors for generating a correction voltage are provided, and normally, the output terminal 5f of the injection ratio switching circuit 5 for FE offset adjustment is electrically connected to the contact terminal 5d and switched. When the signal is supplied, the output terminal 5f switches to the contact terminal 5e, and when the count value falls below a predetermined value, the output terminal 5f returns to the connection with the contact terminal 5d. Further, the number of resistors for generating the correction voltage is not limited to two, and three or more resistors may be provided. In such a case, the restoration circuit 4 needs to send out a plurality of switching signals according to the count value, and
The offset adjustment injection ratio switching circuit 5 switches the contact terminals to be connected according to the plurality of switching signals.

The operation of the focus control circuit device thus configured will be described. The focus error signal generated by the light receiving signal sent from the light receiving element is supplied to the combining circuit 7. On the other hand, a wobble signal obtained from the tracking error signal generated from the light receiving signal is supplied to the demodulation circuit 4, and the demodulation circuit 4 sends the switching signal to the injection ratio switching circuit 5 for FE offset adjustment. The output terminal 5f of the injection ratio switching circuit 5 for FE offset adjustment has a contact terminal 5d when a switching signal is not supplied from the demodulation circuit 4.
The output terminal 5f is switched to the contact terminal 5e when the switching signal is supplied from the demodulation circuit 4, and
When the count value falls below a predetermined value, the output terminal 5
f returns to the connection with the contact terminal 5d. Therefore, the compensating circuit 7 is appropriately supplied with an appropriate correction offset voltage in order to compensate the offset voltage in the focus error signal, so that the offset voltage does not occur in the focus error signal, or it is determined that the offset voltage has occurred. Also, the value can be reduced, and the focus of the laser light on the disk surface can be matched.

In the above embodiment, the switching signal supplied to the injection ratio switching circuit 5 for FE offset adjustment is created based on the wobble signal. However, as shown in FIG. A switching signal may be a write signal for writing information to the disc or a read signal for reading information from the disc, which is sent by the central processing unit (CPU) 6 provided in the focus control circuit device. In FIG. 4, the same components as those shown in FIG. 1 are designated by the same reference numerals.

By switching the correction offset voltage in accordance with the write / read signal as described above, the laser light intensity is completely different when writing and reading information, but an appropriate correction offset voltage is supplied in each case. Therefore, in the focus error signal, the offset voltage does not occur, or even if it does occur, its value can be reduced, and the focus of the laser light on the disk surface can be matched.

Also, as shown in FIG. 5, a switching signal is injected from the central processing unit 6 for FE offset adjustment in accordance with the writing intensity value in the laser beam, which is sent out by the central processing unit 6 when writing information. It may be sent to the ratio switching circuit 5. In FIG. 5, the same components as those in FIGS. 1 and 4 are designated by the same reference numerals.

By transmitting the switching signal according to the write intensity value in this manner, a more appropriate correction offset voltage can be supplied at the time of writing information, so that an offset voltage is generated in the focus error signal. If not, or even if it occurs, its value can be made small, and the focus of the laser light on the disk surface can be matched.

Second Embodiment: Another embodiment of the focus control circuit device of the present invention will be described below with reference to FIG.
In FIG. 6, the same components as those shown in FIG. 9 are designated by the same reference numerals and the description thereof will be omitted. The circuit shown in this embodiment has a configuration obtained by adding the following configuration to the circuit shown in FIG. That is, the output sides of the light receiving elements A to D are connected via the high frequency signal amplifier 30 for amplifying the high frequency signal to the positive / negative peak hold circuit 31 for holding the maximum values in the positive and negative amplitudes of the high frequency signal, and the positive / negative peak hold circuit 31. The output side of the peak hold circuit 31 is connected via the AD converter 32 to the system controller 2 described in FIG.
3 is connected.

The system controller 23 processes the tracking error signal as described above and also processes the high frequency signal in the same manner as the tracking error signal. Such a system controller 2
The output side of 3 is connected to the other input terminal of the differential amplifier 20 via the DA converter 24 and the DA converter 33 as described above.

With respect to the operation of the focus control circuit device configured as described above, the same processing as the processing relating to the tracking error signal described with reference to FIG. Since the offset voltage for adjustment corresponding to the maximum value of the amplitude of the tracking error signal and the maximum value of the amplitude of the high frequency signal is supplied to the other input terminal of the differential amplifier 20, adjustment of the offset voltage in the focus error signal is performed. Can be sufficiently performed, and the quality of the high frequency signal can be maintained.

When the positive maximum value sent by the positive and negative peak hold circuit 31 in the high frequency signal is RFH and the negative maximum value is RFL, the system controller 23 determines that A
The RFH and RFL supplied from the D converter 32
Based on the signal corresponding to, the symmetry (asymmetry) in the high frequency signal is calculated, and this value is calculated by the DA converter 3
Alternatively, the data may be sent to the No. 3 station. The above symmetry is
It is calculated by (RFH-RFL) / (RFH + RFL).

[0029]

As described above in detail, according to the present invention, when the count value of the demodulation accuracy in the demodulation operation of the wobble signal exceeds the predetermined value, the adjustment offset voltage for correcting the offset voltage of the focus error signal is set. By sending out, the offset voltage in the focus error signal can always be maintained at an appropriate value, and the focusing of the laser light on the disk can be favorably maintained.

Further, according to the present invention, by transmitting the adjustment offset voltage for correcting the offset voltage of the focus error signal by the control signal transmitted by the central processing unit provided in the focus control circuit device, the focus error signal The offset voltage can always be maintained at an appropriate value, and the focusing of the laser light on the disk can be favorably maintained.

Further, according to the present invention, not only the maximum value of the positive / negative amplitude in the tracking error signal but also the adjustment offset voltage for correcting the offset voltage of the focus error signal is sent based on the maximum value of the positive / negative amplitude in the high frequency signal. By doing so, the offset voltage in the focus error signal can always be maintained at an appropriate value, and the focusing of the laser light on the disk can be favorably maintained.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of a focus control circuit device of an optical information reading / writing device of the present invention.

FIG. 2 is a diagram showing a configuration example of an injection ratio switching circuit for FE offset adjustment shown in FIG.

FIG. 3 is a block diagram showing a configuration example of a demodulation circuit shown in FIG.

FIG. 4 is a block diagram showing an example of a configuration of a focus control circuit device when a write / read signal is used as a switching signal supplied to an injection ratio switching circuit for FE offset adjustment.

FIG. 5 is a block diagram showing an example of a configuration of a focus control circuit device when a write intensity signal is used as a switching signal supplied to an injection ratio switching circuit for FE offset adjustment.

FIG. 6 is a block diagram showing the configuration of another embodiment of the focus control circuit device of the optical information reading / writing device of the present invention.

FIG. 7 is a diagram showing an offset voltage in a focus error signal.

FIG. 8 is a diagram showing a conventional circuit configuration example for correcting an offset voltage in a focus error signal.

FIG. 9 is a diagram showing a conventional circuit configuration example using a tracking error signal to correct an offset voltage in a focus error signal.

[Explanation of symbols]

4 ... Demodulation circuit, 5 ... FE offset adjustment injection ratio switching circuit, 6 ... Central processing unit, 7 ... Synthesis circuit, 20 ... Differential amplifier, 31 ... Positive / negative peak hold circuit.

Claims (5)

[Claims] 1. A focus control circuit device of an optical information reading / writing device for reading / writing optical information from / on a disc, which is an information recording medium, via an optical pickup, the focus control circuit device being generated based on a light reception signal sent from the optical pickup. Wobble signal demodulation means for performing a demodulation operation of the wobble signal included in the tracking error signal and expressing the demodulation accuracy in the demodulation operation by a count value, and when the count value of the demodulation accuracy is equal to or more than a predetermined value, The first adjustment offset voltage generating means for outputting an adjustment offset voltage for correcting the offset voltage in the focus error signal generated based on the light reception signal transmitted by the optical pickup; and the offset voltage in the focus error signal as described above. The first adjustment offset voltage generating means outputs A focus control circuit device for an optical information reading / writing device, comprising: a first offset voltage correcting means for correcting with an adjusting offset voltage. 2. A focus control circuit device of an optical information reading / writing device for reading / writing optical information from / on a disc as an information recording medium via an optical pickup, wherein a central processing unit provided in the focus control circuit device is provided. Second adjusting offset voltage generating means for correcting the offset voltage in the focus error signal generated based on the received light signal sent by the optical pickup by the control signal sent out, and the offset voltage in the focus error signal as the second A focus control circuit device for an optical information reading / writing device, comprising: a second offset voltage correcting means for correcting the adjusting offset voltage outputted by the adjusting offset voltage generating means. 3. A focus control circuit device for an optical information reading / writing device according to claim 1, comprising the focus control circuit device for an optical information reading / writing device according to claim 2. 4. A tracking error signal generating means for generating a tracking error signal based on a light receiving signal sent from an optical pickup for reading and writing information from and on a disc which is an information recording medium, and the tracking error signal A TE peak hold means for holding the maximum value of positive and negative amplitudes, a focus error signal generation means for generating a focus error signal based on a light reception signal sent from the optical pickup, and a focus error signal from the focus error signal generation means. A focus control circuit device for an optical information reading / writing apparatus, comprising: an offset voltage correcting means for correcting an offset voltage value in the supplied focus error signal based on a maximum value of positive and negative amplitudes sent by the peak holding means. , the above An RF peak hold means for holding the maximum value of positive and negative amplitudes in a high frequency signal generated based on the received light signal, and a first offset correction voltage based on the maximum value of positive and negative amplitudes sent by the TE peak hold means. Control means for creating a second offset correction voltage based on the maximum value of the positive and negative amplitudes sent by the RF peak hold means, and correction of the offset voltage of the focus error signal based on the first and second offset correction voltages. A focus control circuit device for an optical information reading / writing device, comprising: 5. The optical information reading document according to claim 4, wherein the control means calculates the symmetry based on the maximum value of the positive and negative amplitudes sent by the RF peak hold means and creates the second offset correction voltage. Focus control circuit device for embedded device.