JP2003077135A - Rf signal amplitude controller for optical disk - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably and accurately output an RF signal amplitude even at multiple speed reproduction. SOLUTION: The RF signals obtained from a quadripartite photodetector 11 converging a reflected light from a laser emitted to an optical disk medium are added and amplified after the current-voltage conversion, and the amplified signals are logically added after binarized by comparators 15a, 15b having both positive and negative polarities, then the logically added signals are amplified by two amplifiers 17a, 17b having the relation of gain ratio 10:1. An output signal of the amplifier 17a is integrated, and also an output signal of the amplifier 17b is inverted and integrated, and from these output voltages, a difference voltage is obtained by a voltage-current converter 19 and converted further into the current. By adopting such a constitution, the generation of an accurate error signal of RF amplitude becomes possible, then such a RF signal amplitude controller is obtained that the stable RF amplitude is controllable at multiple speed reproduction such as 16-fold speed or faster.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an RF of an optical disk.
The present invention relates to a signal amplitude control device.

[0002]

2. Description of the Related Art In recent years, an RF signal amplitude control device for an optical disk not only generates a reproduction signal by extracting data and a clock from the signal, but also detects a scratch on the surface of the disk and detects whether the track is on a track at the time of track jump. It detects whether it is between tracks. Since the signal is used for processing the servo signal, an error occurs in the detection timing when a constant amplitude level does not always appear. Therefore,
Along with the increase in the speed of optical disk devices, there is a demand for a device capable of stable RF amplitude control even during high speed reproduction.

A conventional RF signal amplitude control device for an optical disc will be described below.

FIG. 3 shows an example of a conventional RF signal amplitude control device for an optical disk. FIG. 4 is a timing diagram related to an example of the conventional RF signal amplitude control apparatus for an optical disc in FIG.

In FIG. 3, 11 is a four-division light receiving element, 1
2a, 12b, 12c, 12d are current-voltage converters, 13
Is an adder, 14 is a variable gain amplifier capable of changing the gain according to the control voltage, 15a and 15b are comparators, and 16 is an OR circuit. Reference numeral 20 is a charge pump circuit having a current ratio of the charging current and the discharging current of 10: 1, and its output current corresponds to the amplitude error signal. C is a capacity charged and discharged by the charge pump circuit 20,
The terminal voltage is given to the variable gain amplifier 14 as a control voltage.

The charge pump circuit 20 described above generally has two sets of constant current sources 20b, 20c and 2 as shown in FIG.
It is composed of a pair of switch circuits 20d and 20e and an inverter 20a for inverting the output signal E of the OR circuit 16. The switch circuits 20d and 20e are turned on and off respectively by the output signal E of the OR circuit 16,
As a result, the capacitance C is charged / discharged by the current 10i and the current i, whereby the current is converted into a voltage.

A conventional RF signal amplitude control device for an optical disc uses an RF (high frequency) from a four-division light receiving element 11 which collects and detects reflected light when an optical disc medium (not shown) is irradiated with convergent laser light. ) The signal is output as a current. The four outputs from the four-division light receiving element 11 are converted into voltages by the current-voltage converters 12a, 12b, 12c and 12d, respectively. Each current-voltage converter 12a, 1
The output voltages of 2b, 12c, and 12d are added by the adder 13, and the output of the adder 13 is the variable gain amplifier 14
And is output as an RF signal from the variable gain amplifier 14.

The output voltage R of the variable gain amplifier 14
The F signal is binarized by the comparators 15a and 15b by using predetermined levels of both positive and negative polarities as threshold values. The output of each comparator 15a, 15b is the OR circuit 1
6 is logically added, and the output of the OR circuit 16 is integrated by the charge pump circuit 20 and the capacitor C and converted into a voltage. The terminal voltage of the capacitor C is given to the variable gain amplifier 14 as a control voltage, so that the level of the RF signal output from the variable gain amplifier 14 is controlled to be constant.

RF of the optical disk constructed as described above
The operation of the signal amplitude control device will be described below with reference to FIG.

FIG. 4 shows that when a converged laser beam is irradiated onto an optical disk medium, the reflected light from the optical disk medium is a signal due to variations in laser elements, the reflectance of the medium (optical disk medium), and fingerprints and scratches on the disk surface. 9 shows a timing chart when the amplitude is controlled when an RF signal whose reflected light is larger than the target amplitude is input.

The reflected light is converted into a current by the four-division light receiving element 11, and current / voltage converters 12a, 12b, 12c, 1 are converted.
Converted to voltage in 2d. Current-voltage converters 12a, 12
The outputs of b, 12c and 12d are added by the adder 13 to obtain the waveform A of FIG. The signal of the waveform A in FIG. 4 is amplified by the variable gain amplifier 14 and becomes the waveform B in FIG. The signal of this waveform B is the comparator 15
a and 15b. The comparator 15a has a threshold value V that defines the signal of waveform B and a positive target amplitude level.
And binarize. Further, the comparator 15b compares the signal of the waveform B with a threshold value V that defines a negative target amplitude level, and binarizes the signal. In the waveforms A and B of FIG. 4, the central broken line indicates the reference potential ref, and the upper and lower broken lines indicate the target amplitude level.

The outputs of the comparators 15a and 15b are like the waveforms C and D of FIG. 4, respectively.
The signal of the waveform C which is the output of a becomes a high level when the signal of the waveform B has a signal level higher than the target amplitude level,
It goes low at all other times. On the other hand, the signal of the waveform D output from the comparator 15b has a high level when the signal of the waveform B has a signal level lower than the target signal level, and has a low level otherwise.

The signals of the waveforms C and D, which are the outputs of the comparators 15a and 15b, are logically added by the OR circuit 16, and the output of the OR circuit 16 becomes the waveform E of FIG.
The signal of the waveform E causes the charge pump circuit 20 to operate, whereby the integration operation by the capacitor C is performed. That is, the charge pump circuit 20 is controlled so that the charge current flows through the capacitor C when the input to the charge pump circuit 20 is at the high level and the discharge current flows through the capacitor C when the input is at the low level. Since the current ratio at this time is 10: 1, the operation is as shown by the waveform J in FIG.
The equilibrium state is reached when the output of 4 has the target amplitude. The broken line in the waveform J of FIG. 4 indicates the control voltage level corresponding to the target amplitude level. The same applies to the waveform J ′ described later.

Here, the gain of the variable gain amplifier 14 is varied by the control voltage of the waveform J, but the gain is controlled so as to decrease when the voltage of the waveform J is high,
When the duty of the signal of the waveform E becomes 10: 1, the signal J is maintained in the equilibrium state. Therefore, the amplitude of the output signal of the variable gain amplifier 14 is controlled to the target level like the signal of the waveform B.

[0015]

However, in the above-mentioned conventional configuration, for example, when the reproduction speed of the DVD-ROM exceeds 16 times,
The maximum frequency of the signal is 72 MHz or higher, and the waveform E
The pulse width of the output signal is narrowed. On the other hand, the switch circuits 20d and 20e generally have a low operation speed, and a delay occurs due to the on / off operation speed of the charge pump circuit 20 being delayed, which is controlled by the output signal E of the OR circuit of FIG. The signal of the waveform J becomes like the waveform J ′ and is not controlled by the amplitude of the target level. The signal of the waveform E in FIG. 4 becomes like the waveform E ′ in FIG. 4, and the duty is 10: 1. The equilibrium state is not reached and
The signal of the waveform B has a value larger than the target level as the waveform B ′. In the waveform J ′ of FIG. 4, the portion indicated by the symbol X indicates the occurrence of delay due to the on / off speed of the charge pump circuit 20. Further, the symbol Y indicates a deviation from the control voltage level corresponding to the target level. The delay of the switch circuits 20d and 20e is caused by the slow operation speed of the transistors that form the switch.

FIG. 5 shows a graph of a reproduction speed and an RF signal amplitude in a conventional optical disk RF signal amplitude control device. As shown in this graph, when the reproduction speed becomes high speed, it deviates from the target amplitude, and it becomes impossible to output the RF signal amplitude stably and accurately.

The present invention solves the above-mentioned conventional problems and stably detects an output error signal having an RF signal amplitude even when the reproduction speed of an optical disk becomes a high speed such as over 16 times. , R of an optical disk capable of controlling stable and accurate signal amplitude in high speed double speed reproduction
An object is to provide an F signal amplitude control device.

[0018]

In order to achieve this object, an RF signal amplitude control apparatus for an optical disc according to claim 1 of the present invention has a variable gain depending on a control voltage, and a focusing laser on an optical disc medium. A variable gain amplifier that amplifies a high-frequency signal extracted from a light receiving element by detecting reflected light when light is emitted, and an output voltage of the variable gain amplifier is set to a predetermined level of both positive and negative polarities as threshold values. Of the first and second comparators that are binarized, the logical sum circuit that adds the outputs of the first and second comparators, the first amplifier that amplifies the output signal of the logical sum circuit, and the first amplifier A second amplifier having a gain ratio set to a predetermined value and inverting and amplifying the output signal of the logical sum circuit, and first and second products for integrating the output voltages of the first and second amplifiers, respectively. And a voltage-current converter that converts the difference voltage between the first and second integrators into a current, and the control voltage is increased or decreased by the output current of the voltage-current converter to change the output voltage of the variable gain amplifier. It is controlled to be constant. In the above, the gain ratio of the first and second amplifiers is set to 10: 1, for example. Further, the voltage-current converter preferably changes the conversion ratio, that is, the conductance value, and changes the conversion ratio in proportion to the linear velocity of the track of the optical disk medium.

According to this structure, the output signal of the logical sum circuit is amplified and inverted by the first and second amplifiers whose gain ratio is set to a predetermined value, for example, 10: 1. The output voltage of the second amplifier is integrated by the first and second integrators, respectively, and the difference voltage between the output voltages of the first and second integrators is converted into a current by the voltage-current converter, whereby the RF signal amplitude of Since the output error signal is obtained, the output error signal of the RF signal amplitude can be stably detected without causing the delay problem of the charge pump circuit even during the high-speed reproduction, and the high-speed reproduction is possible. During reproduction, the output amplitude of the RF signal can be controlled stably and accurately.

Further, if the conversion ratio of the voltage-current converter, that is, the conductance value is made variable and the conversion ratio is changed in proportion to the linear velocity of the track of the optical disk medium, the response speed changes in accordance with the reproduction speed. Therefore, stable RF amplitude control can be performed at an optimum response speed during high-speed reproduction such as reproduction at 16 × speed or more on an optical disc medium such as a DVD-ROM.

RF of the optical disk according to claim 2 of the present invention
The signal amplitude control device detects the reflected light when the converged laser beam is irradiated onto the optical disk medium and extracts the high-frequency signal as a current, and the four-division light-receiving element converts the output current of the four-division light-receiving element into voltage. Current-voltage converter, an adder that adds the output voltages of the four current-voltage converters, a variable gain amplifier that can arbitrarily change the gain according to the control voltage, and that amplifies the output voltage of the adder, A first and second comparator for binarizing the output voltage of the gain amplifier using predetermined levels of both positive and negative polarities as threshold values, an OR circuit for adding the outputs of the first and second comparators, and a logic A second amplifier for amplifying the output signal of the OR circuit and a second amplifier for inverting and amplifying the output signal of the OR circuit by setting a gain ratio between the first amplifier and the first amplifier to a predetermined value.
Amplifier, first and second integrators that integrate the output voltages of the first and second amplifiers, respectively, and a voltage-current converter that converts the voltage difference between the first and second integrators into a current. The output voltage of the variable gain amplifier is controlled to be constant by increasing or decreasing the control voltage with the output current of the voltage-current converter. In the above, the gain ratio of the first and second amplifiers is set to 10: 1, for example.
Further, the voltage-current converter preferably changes the conversion ratio, that is, the conductance value, and changes the conversion ratio in proportion to the linear velocity of the track of the optical disk medium.

According to this structure, the output signal of the OR circuit is amplified and inverted by the first and second amplifiers whose gain ratio is set to a predetermined value, for example, 10: 1. The output voltage of the second amplifier is integrated by the first and second integrators, respectively, and the difference voltage between the output voltages of the first and second integrators is converted into a current by the voltage-current converter, whereby the RF signal amplitude of Since the output error signal is obtained, the output error signal of the RF signal amplitude can be stably detected without causing the delay problem of the charge pump circuit even during the high-speed reproduction, and the high-speed reproduction is possible. During reproduction, the output amplitude of the RF signal can be controlled stably and accurately.

If the conversion ratio of the voltage-current converter, that is, the conductance value is made variable and the conversion ratio is changed in proportion to the linear velocity of the track of the optical disk medium, the response speed changes in accordance with the reproduction speed. Therefore, stable RF amplitude control can be performed at an optimum response speed during high-speed reproduction such as reproduction at 16 × speed or more on an optical disc medium such as a DVD-ROM.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a configuration of an RF signal amplitude control device for an optical disc according to an embodiment of the present invention, and FIG. 2 is a timing diagram relating to the RF signal amplitude control device for an optical disc in FIG. Is.

In FIG. 1, 11 is a four-division light receiving element, 1
2a, 12b, 12c, 12d are current-voltage converters, 13
Is an adder, 14 is a variable gain amplifier capable of changing the gain according to the control voltage, 15a and 15b are comparators, and 16 is an OR (logical sum) circuit. C is the capacity. These are the same as the configuration of the conventional example.

The output of the OR circuit 16 has a different gain (for example, a charge pump circuit as in the conventional example) (for example,
10: 1) connected to the amplifiers 17a and 17b, and the amplifier 1
The outputs of 7a and 17b are connected to integrators 18a and 18b, respectively, and the outputs of the integrators 18a and 18b are connected to the non-inverting input and the inverting input of the voltage-current converter 19, respectively. The amplifier 17a amplifies and outputs the input signal 10 times without reversing the polarity, and the amplifier 17b reverses the polarity of the input signal and outputs the reversed signal. The above voltage-current converter 1
The output current of 9 becomes the output error signal of the RF signal amplitude.

The operation of the RF signal amplitude control apparatus for an optical disc of the present embodiment having the above-described configuration will be described below.

FIG. 2 shows that when the converged laser beam is irradiated onto the optical disc medium, the reflected light from the optical disc medium is a signal due to variations in laser elements, the reflectance of the medium (optical disc medium), and fingerprints and scratches on the disc surface. 9 shows a timing chart when the amplitude is controlled when an RF signal whose reflected light is larger than the target amplitude is input.

The reflected light is converted into a current by the four-division light receiving element 11, and current-voltage converters 12a, 12b, 12c, 1
Converted to voltage in 2d. Current-voltage converters 12a, 12
The outputs of b, 12c and 12d are added by the adder 13 to obtain the waveform A in FIG. The signal of the waveform A in FIG. 2 is amplified by the variable gain amplifier 14 and becomes the waveform B in FIG. The signal of this waveform B is the comparator 15
a and 15b. The comparator 15a has a threshold value V that defines the signal of waveform B and a positive target amplitude level.
And binarize. Further, the comparator 15b compares the signal of the waveform B with a threshold value V that defines a negative target amplitude level, and binarizes the signal. In the waveforms A and B of FIG. 2, the central broken line indicates the reference potential ref, and the upper and lower broken lines indicate the target amplitude level.

The outputs of the comparators 15a and 15b have the waveforms C and D shown in FIG. 2, respectively.
The signal of waveform C, which is the output of a, becomes high level when the signal of waveform B is higher than the target amplitude level, and becomes low level at other times. On the other hand, comparator 1
The signal of waveform D, which is the output of 5b, becomes high level when the signal of waveform B has a signal level lower than the target signal level, and becomes low level at other times.

The signals of the waveforms C and D, which are the outputs of the comparators 15a and 15b, are logically added by the OR circuit 16, and the output of the OR circuit 16 becomes the waveform E of FIG.
The signal of the waveform E is amplified by the amplifiers 17a and 17b, respectively. The amplifier 17a amplifies the waveform E signal with the same polarity, while the amplifier 17b inverts and amplifies the waveform E signal. Further, since the amplifier 17a makes its amplification factor 10 times that of the amplifier 17b, its output is as shown in FIG.
Waveform F. Further, the amplifier 17b inverts the signal E and amplifies it with a gain of 1 time, and its output becomes as shown by the waveform G in FIG.

The signals of the waveforms F and G are integrated by the integrators (low-pass filters) 18a and 18b and converted into a voltage, and become the signals of the waveforms H and I of FIG. 2, respectively.

Here, in the signals of the waveforms H and I, the amplitude signal represents the output error signal with respect to the target amplitude level by the voltage-current converter 19, and the capacitance C produces the waveform J as shown in FIG. It is detected as a voltage value, controls the variable gain amplifier 14, and enters a balanced state when the target amplitude level is reached.

Here, the reason why the error signal can be accurately obtained without using the delay problem of the charge pump circuit when two amplifiers, two integrators and two current-voltage converters are used will be described. To do. When a charge pump circuit is used as in the conventional example, if there is a circuit delay, the duty of the pulse shifts and an accurate error signal cannot be obtained, but in the case of the configuration of the present invention, the amplifier and the integrator are Even if a delay occurs, no error occurs in the integrated value, so that an accurate error signal can be obtained.

As described above, according to the present embodiment, the output pulse duty of the OR circuit 16 can be converted into the DC voltage component by providing the amplifiers 17a and 17b and the integrators 18a and 18b. That is, the output signal of the OR circuit 16 is amplified and inverted / amplified by the amplifiers 17a and 17b whose gain ratio is set to a predetermined value, for example, 10: 1, and the output voltages of the amplifiers 17a and 17b are integrated.
The output pulse duty of the OR circuit 16 is converted into a DC voltage component by integrating with a and 18b, respectively, and the difference voltage between the output voltages of the integrators 18a and 18b is converted into a voltage-current converter 1.
Since the output error signal of the RF signal amplitude is obtained by converting into the current at 9, the problem of delay like the charge pump circuit does not occur even at the high speed reproduction, and the output error of the RF signal amplitude is not generated. The signal can be stably detected, and the output amplitude of the RF signal can be stably and accurately controlled during high-speed reproduction.

As described above, by adding the above circuit in place of the charge pump circuit which causes the most circuit delay, the output error signal of the RF signal amplitude can be detected stably and accurately during high speed reproduction. Therefore, the RF signal amplitude can be controlled.

The voltage-current converter 19 preferably changes the conversion ratio, that is, the conductance value, and changes the conversion ratio in proportion to the linear velocity of the track of the optical disk medium. In this case, by changing the conversion ratio in proportion to the linear velocity of the track, it is possible to match the response speed of the AGC circuit to the reproduction speed, and it is stable even for a defective disk such as a missing RF signal. Therefore, the RF signal amplitude can be controlled.

Although the gain ratio of the two amplifiers is set to 10: 1 in the above embodiment, this gain ratio affects the performance when reproducing a defective disc or the like. For example, 7: It is considered that up to about 3 can be set.

[0040]

As described above, according to the present invention, the predetermined
For example, two sets of amplifiers having a gain ratio of 10: 1 and an integrator are provided after the output of the OR circuit, and an error between the RF signal amplitude and the target amplitude is converted into a DC voltage, thereby operating speed of a charge pump circuit or the like. The present invention realizes an excellent RF signal amplitude control device for an optical disc, which is capable of accurately and stably controlling the RF amplitude during high-speed reproduction of the optical disc without being limited to the above.

[Brief description of drawings]

FIG. 1 is an RF of an optical disc according to an embodiment of the present invention.
It is a block diagram which shows the structure of a signal amplitude control apparatus.

FIG. 2 is an RF of an optical disc according to the embodiment of the present invention.
It is a timing diagram which shows the signal of each part of a signal amplitude control apparatus.

FIG. 3 is a circuit diagram showing a configuration of a conventional RF signal amplitude control device for an optical disc.

FIG. 4 is a timing chart showing signals of respective parts of the RF signal amplitude control device for the optical disc in the conventional example.

FIG. 5 is a graph of a reproduction speed and an RF signal amplitude in a conventional RF signal amplitude control device for an optical disc.

FIG. 6 is a circuit diagram showing a configuration of a charge pump circuit.

[Explanation of symbols]

11 4-division photo detector 12a to 12d current-voltage converter 13 adder 14 Variable gain amplifier 15a, 15b comparator 16 OR circuit 17a, 17b amplifier 18a, 18b integrator 19 Voltage-current converter 20 Charge pump circuit

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Masayuki Kosasa             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. F-term (reference) 5D044 BC03 BC04 EF06 FG05                 5D090 AA01 BB02 CC04 CC16 DD03                       EE11 FF21 LL09

Claims (4)

[Claims] 1. A variable gain amplifier for amplifying a high frequency signal extracted from a light receiving element by detecting reflected light when a converged laser beam is applied to an optical disk medium, the gain of which is arbitrarily variable according to a control voltage. First and second comparators that binarize the output voltage of the variable gain amplifier using predetermined levels of both positive and negative polarities as threshold values, and an OR circuit that adds the outputs of the first and second comparators A first amplifier for amplifying the output signal of the OR circuit, and a second amplifier for inverting and amplifying the output signal of the OR circuit with a gain ratio between the first amplifier and the first amplifier set to a predetermined value. A first and second integrator for integrating the output voltages of the first and second amplifiers, respectively, and a voltage-current converter for converting a difference voltage between the first and second integrators into a current And an RF signal amplitude control device for an optical disc, wherein the output voltage of the variable gain amplifier is controlled to be constant by increasing or decreasing the control voltage with the output current of the voltage-current converter. 2. A four-division light-receiving element for extracting a high-frequency signal as a current by detecting reflected light when an optical disc medium is irradiated with convergent laser light, and four pieces for respectively converting the output currents of the four-division light-receiving element into voltage. A current-voltage converter, an adder for adding the output voltages of the four current-voltage converters, and a variable gain amplifier for amplifying the output voltage of the adder, the gain of which is arbitrarily variable according to the control voltage. , A first and second comparator for binarizing the output voltage of the variable gain amplifier using predetermined levels of both positive and negative polarities as threshold values, and a logical sum for adding the outputs of the first and second comparators Circuit, a first amplifier that amplifies the output signal of the logical sum circuit, and a gain ratio between the first amplifier and the first amplifier are set to a predetermined value to reverse the output signal of the logical sum circuit. A second amplifier for amplifying; first and second integrators for integrating output voltages of the first and second amplifiers respectively; and a differential voltage of the first and second integrators for converting into a current. An RF signal amplitude control device for an optical disk, comprising: a voltage-current converter, wherein the output voltage of the variable gain amplifier is controlled to be constant by increasing or decreasing the control voltage with the output current of the voltage-current converter. 3. The gain ratio of the first and second amplifiers is 1.
The RF signal amplitude control device for an optical disc according to claim 1, wherein the RF signal amplitude control device is set to 0: 1. 4. The RF signal amplitude control of an optical disk according to claim 1, wherein the voltage-current converter is configured to change the conversion ratio so as to change the conversion ratio in proportion to the linear velocity of the track of the optical disk medium. apparatus.