JPH10269617A - Optical disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To precisely generate a state detection signal by performing automatic gain control for preventing an erroneous read of a signal and simultaneously keeping an envelope of an output waveform required for performing state detection of an optical pickup. SOLUTION: When an output of a variable gain amplifier 24 exceeds a first reference voltage 36, the gain of the variable gain amplifier 24 is lowered at a first response speed. When the output doesn't arrive at the first reference voltage 36, the gain of the variable gain amplifier 24 is increased at a second response speed in the direction charging a capacitor 30. Further, when the output of the variable gain amplifier 24 doesn't arrive at a second reference voltage 37 lower than the first reference voltage 36, a unistable multivibrator 34 is operated, and a switch 32 is turned on only for a prescribed time, and the charging of the capacitor 30 is delayed by making a part of a current flowing out from an amplifier 29 flow into a current source 31, and the envelope of the output waveform of the variable gain amplifier 24 is kept by reducing the second response speed and increasing a gain.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generates an optical pickup state detection signal by amplifying an information signal reproduced from an optical pickup by a variable gain amplifier and detecting an envelope of a peak value of the output. ,
The present invention relates to an optical disk device that performs accurate optical pickup control.

[0002]

2. Description of the Related Art In recent years, an optical disk device such as a mini disk (MD) which performs only recording / reproduction or reproduction of a digital signal using a magneto-optical recording / reproduction technique or the like has been put to practical use.

Hereinafter, an example of a conventional optical disk device will be described with reference to the drawings. FIG. 5 is a block diagram showing a configuration of a conventional optical disk device.

In FIG. 5, an optical pickup (PU) is shown.
2, a circuit composed of a reproducing circuit 3 and a variable gain amplifier 4 is a circuit for generating a reproduced signal 5 from an information signal recorded on the optical disc 1, a detecting circuit 6, and a state detecting means 7.
Is a circuit that generates a signal 8 for detecting the state of the optical pickup 2 (hereinafter abbreviated as a state detection signal 8) using the output signal of the reproduction circuit 3.

Next, the operation will be described. FIG.
5A and 5B are waveforms of respective parts for explaining the operation of the optical disk apparatus shown in FIG. 5, and waveforms (a) and (b) in FIG. 5 show waveforms of an input signal of the variable gain amplifier 4 and an output signal of the variable gain amplifier 4 in FIG. Each is shown. First, an information signal recorded on the optical disc 1 is photoelectrically converted by the optical pickup 2 and output as an electric signal. In the reproducing circuit 3, processing corresponding to the type of the disc, for example, generation of a sum signal of two types of signals output from the optical pickup 2 at the time of reproduction of the reproduction-only area, and difference signal of the two types of signals at the time of reproduction of the reproduction recording area Is generated, and signal amplification and equalization are performed.

[0006] Thus, the output from the reproduction circuit 3 is
A signal (for example, waveform (a)) input to the variable gain amplifier 4 has a variation in signal amplitude caused by a variation in the optical disk 1 and the optical pickup 2. A signal, for example, a waveform (b), which is gain-amplified by the variable gain amplifier 4 so that the signal amplitude becomes a constant reference value, is output.
A reproduction signal 5 is generated. Suppress variations in signal amplitude,
By making the signal amplitude constant, a signal reading error can be prevented. During the reproduction of the reproduction recording area, it is necessary to read the intermittently recorded information signal and to instantaneously detect the presence of the information signal.
Requires the fastest possible response speed.

Next, the operation when the state detection signal 8 is generated will be described. By inputting the output signal of the reproduction circuit 3 to the detection circuit 6, the envelope of the output waveform is detected.
The state detection means 7 compares the amplitude of the envelope with a reference value determined according to the amplitude of the envelope to generate a state detection signal 8. The state detection signal 8 is a signal used to know the positional relationship of the optical pickup 2 with respect to the optical disc 1, for example, a signal for detecting that tracking is off. This signal is used for

[0008]

However, in the above-mentioned conventional optical disk apparatus, the state detection signal 8 is generated using the output signal of the reproduction circuit 3, so that the amplitude of the input signal of the detection circuit 6 is reduced. When the signal amplitude is small, the signal reading error occurs due to the deterioration of the S / N when the signal amplitude is small, or the output is saturated in the detection circuit 6 or the state detection means 7 when the signal level is large. As a result, an accurate state detection signal 8 could not be obtained, and as a result, the optical pickup 2 could not be controlled. At this time, the optical pickup 2 becomes uncontrollable, and a serious error occurs in reading the information signal recorded on the optical disk 1.

As a means for solving the above problem, it is conceivable to generate the state detection signal 8 using the output signal of the variable gain amplifier 4, but the output signal is, for example, as shown in FIG.
Since the envelope is smoothed by the variable gain amplifier 4 as shown in the waveform (b), the detection of the envelope by the detection circuit 6 is impossible, and the state detection signal 8 with high accuracy cannot be generated. Therefore, also in this case, the optical pickup 2 becomes uncontrollable, and a serious error occurs in reading the information signal recorded on the optical disc 1.

SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional problems. It is possible to prevent signal reading errors by correcting variations in signal amplitude, and to generate a highly accurate optical pickup state detection signal. It is an object to provide an optical disk device.

[0011]

In order to solve the above-mentioned problems, the present invention is to generate a state detection signal of an optical pickup using a signal output from a variable gain amplifier. When the state detection signal is generated, the envelope of the output waveform is preserved by switching the time constant so that the response speed becomes slow.

Thus, the variation in the signal amplitude caused by the optical disk or the optical pickup is suppressed by using the variable gain amplifier, the signal amplitude is kept constant, the reading error of the signal is prevented, and the time constant of the variable gain amplifier is switched. This saves the envelope of the output waveform necessary for generating the state detection signal of the optical pickup, so that a highly accurate state detection signal can be obtained.

[0013]

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a variable gain amplifier for amplifying and outputting an information signal reproduced from an optical disk using an optical pickup in accordance with a gain control signal, and a peak value of the output of the variable gain amplifier. When the envelope value exceeds a first reference value, the gain of the variable gain amplifier is decreased at a first response speed, and when the envelope value is less than the first reference value, the gain is reduced.
A gain control circuit that outputs the gain control signal so as to increase the gain of the variable gain amplifier at a response speed of, and a peak value of the output of the variable gain amplifier or an envelope value of the peak value is lower than the first reference value. A time constant circuit for lowering the second response speed for a predetermined time when the value does not reach the set second reference value, and detecting the envelope of the output waveform of the variable gain amplifier to detect the state of the optical pickup; Is what you do.

Thus, variations in signal amplitude caused by an optical disk or an optical pickup are suppressed by using a variable gain amplifier, a signal reading error is prevented by keeping the signal amplitude constant, and a time constant of the variable gain amplifier is switched. Thus, the envelope of the output waveform required for generating the state detection signal of the optical pickup is stored.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. (Embodiment 1) FIG. 1 is a block diagram showing a configuration of an optical disk device according to Embodiment 1 of the present invention. In FIG. 1, a circuit composed of an optical pickup (PU) 22, a reproducing circuit 23, and a variable gain amplifier 24 is a circuit for generating a reproduced signal 25 from an information signal recorded on the optical disk 21, and a detection circuit 26, a state detection The circuit constituted by the means 27 is a circuit for generating a signal 28 (hereinafter abbreviated as a state detection signal 28) for detecting the state of the optical pickup 22 using the output signal of the variable gain amplifier 24.

The gain control circuit 39 includes the variable gain amplifier 24
Output when the output amplitude is smaller than the first reference value voltage 36, the amplifier 29, the capacitor 30, and the output amplitude of the variable gain amplifier 24, into which the current flows when the output amplitude is larger than the first reference value voltage 36, are equal to the second reference value. A comparator 33 that outputs a high level when the voltage is smaller than a value voltage 37; a monostable multivibrator 34 that operates when the comparator 33 outputs a high level; a switch 32 that is turned on by a switch circuit 35; A part of the current flowing out of the capacitor 29 flows into the capacitor 3
It comprises a time constant circuit composed of a current source 31 for delaying the charging rate of 0. The first reference voltage 36 is higher than the second reference voltage 37, and the current flowing through the current source 31 is always smaller than the current flowing out of the amplifier 29.

The output of the gain control circuit 39 is the gain control signal 4
0, and the variable gain amplifier 2
4 is performed.

Next, the operation of this embodiment will be described. FIG. 2 shows waveforms at various parts for explaining the operation of the optical disk device shown in FIG. 1, and waveforms (c), (d),
(E) shows the input signal of the variable gain amplifier 24, the output signal of the monostable multivibrator 34, and the variable gain amplifier 2 of FIG.
4 shows the waveforms of the output signals. First, the information signal recorded on the optical disk 21 is
And is output as an electrical signal. In the reproduction circuit 23, processing according to the type of the disc, for example, generation of a sum signal of two types of signals output from the optical pickup 22 at the time of reproduction of the reproduction-only area, and difference signal of the two types of signals at the time of reproduction of the reproduction recording area Is generated, and signal amplification and equalization are performed. The signal output from the reproducing circuit 23 and input to the variable gain amplifier 24, for example, the signal as shown in the waveform (c) has a variation in signal amplitude caused by a variation in the optical disk 21 and the optical pickup 22. The signal is amplified in the variable gain amplifier 24 according to the gain control signal 40.

When the peak value or the envelope value of the peak value exceeds the first reference value voltage 36, the amplifier 29 supplies a current in a direction of discharging the capacitor 30 and outputs the current of the variable gain amplifier 24 at a first response speed. When the gain is lowered and the voltage is less than the first reference voltage 36, the current flows out in the direction of charging the capacitor 30, and the variable gain amplifier 2 is turned on at the second response speed.
The gain control signal 40 is generated so as to increase the gain of No. 4. The comparator 33 compares the peak value envelope value with a second reference value voltage 37 set lower than the first reference value voltage 36. When the envelope value is less than the second reference value voltage 37, the monostable multivibrator 34 is activated. After the operation, the monostable multivibrator 34 outputs, for example, a waveform as shown in waveform (d). Switch circuit 3
In 5, the switch 32 is switched according to the output of the monostable multivibrator 34. For example, the switch 32 is turned on when the output is “1”, and a part of the current flowing out of the amplifier 29 flows into the current source 31. The gain control signal 40 is generated so as to delay the charging of the capacitor 30 and decrease the second response speed (the response speed in the gain increasing direction).

When the amplitude is less than the second reference voltage 37, the time constant of the variable gain amplifier 24 is switched for a predetermined time by using the gain control signal 40 output from the gain control circuit 39, and the second response speed , The envelope of the output waveform of the variable gain amplifier 24 is preserved, for example, as shown in waveform (e).

Next, the operation when the state detection signal 28 is generated will be described. The output signal of the variable gain amplifier 24 is detected by a detection circuit 2
6, the envelope of the output waveform is detected. A state detection signal 28 is generated by the state detection means 27 using the envelope. The state detection signal 28 is transmitted to the optical pickup 2 with respect to the optical disc 21.
The signal is used to know the positional relationship of No. 2, for example, a signal for detecting that the tracking is turned off. This signal is used for controlling the optical pickup 22 at the time of reproducing the reproduction-only area.

Therefore, the variation in signal amplitude caused by the optical disk 21 or the optical pickup 22 is suppressed by using the variable gain amplifier 24 to prevent a signal reading error, and the variable gain is controlled by using the gain control signal 40 as described above. By storing the envelope of the output signal of the amplifier 24, for example, as shown in a waveform (e), an accurate state detection signal 28 can be generated. Since the intermittent signal needs to be read at the time of reproduction in the reproduction recording area, the variable gain amplifier 24 is required to have a response speed as fast as possible.
Therefore, the first response speed and the second response speed cannot be reduced in advance.

(Embodiment 2) FIG. 3 is a block diagram showing a configuration of an optical disk apparatus according to Embodiment 2 of the present invention. In FIG. 3, a circuit composed of an optical pickup (PU) 42, a reproducing circuit 43, and a variable gain amplifier 44 converts an information signal recorded on the optical disc 41 into a reproduced signal 4
5 is a circuit configured by the detection circuit 46 and the state detection means 47. The circuit 48 detects the state of the optical pickup 42 using the output signal of the variable gain amplifier 44 (hereinafter, the state detection signal 48 (Abbreviation).

The gain control circuit 59 includes a variable gain amplifier 44
The amplifier 49, the capacitor 50, and the area of the optical disk 41 that is playing out the current when the output amplitude is smaller than the reference value voltage 56, and the current flows out when the output amplitude is smaller than the reference value voltage 56. , An area detection circuit 58 for outputting a reproduction area detection signal and a switch 52 turned on by a switch circuit 55;
Current source 5 which injects a part of the current flowing out of the amplifier 49 when the
1 is a time constant circuit. The current flowing into the current source 51 is always smaller than the current flowing out of the amplifier 49.

The output of the gain control circuit 59 is the gain control signal 6
0, and the variable gain amplifier 4
4 is performed.

Next, the operation of this embodiment will be described. FIG. 4 shows waveforms at various parts for explaining the operation of the optical disk device shown in FIG. 3, and waveforms (f), (g), and
(H) shows the waveforms of the input signal of the variable gain amplifier 44, the output signal of the area detection circuit 58, and the output signal of the variable gain amplifier 44 in FIG. First, the information signal recorded on the optical disk 41 is photoelectrically converted by the optical pickup 42 and output from the reproduction circuit 43 as an electric signal. In the reproducing circuit 43, when processing according to the type of the disc, for example, when reproducing the reproduction-only area, the optical pickup 4
2 and a difference signal between the two signals is generated during reproduction of a reproduction recording area.
Signal amplification and equalization are performed. Thus, the reproduction circuit 4
3, the signal input to the variable gain amplifier 44, for example, the signal as shown in the waveform (f) has a variation in signal amplitude caused by a variation in the optical disk 41 and the optical pickup 42, and the variable gain amplifier At 44, it is amplified according to the gain control signal 60.

When the peak value or the envelope value of the peak value exceeds the reference value voltage 56, the amplifier 49 flows a current in a direction of discharging the capacitor 50 and increases the gain of the variable gain amplifier 44 at the first response speed. When the voltage drops below the reference value voltage 56, a gain control signal 60 is generated so that current flows out in the direction of charging the capacitor 50 and the gain of the variable gain amplifier 44 is increased at the second response speed. Further, the area detection circuit 58 uses, for example, a reproduction signal level to
It detects that the area being reproduced is a reproduction-only area and outputs a reproduction area detection signal, for example, a waveform (g). The switch circuit 55 switches the switch 52 according to the output of the area detection circuit 58. For example, when the output is “1”, the switch 5
2 is turned on, a part of the current flowing out of the amplifier 49 flows into the current source 51, thereby delaying the charging of the capacitor 50 and lowering the second response speed (response speed in the gain increasing direction). A gain control signal 60 is generated.

The time constant of the variable gain amplifier 44 is switched using the gain control signal 60, which is the output signal of the gain control circuit 59, when the area of the optical disk 41 being reproduced is a reproduction-only area. , The envelope of the output waveform of the variable gain amplifier 44 is preserved, for example, as shown in waveform (h).

Next, the operation when the state detection signal 48 is generated will be described. The output signal of the variable gain amplifier 44 is detected by a detection circuit 4
6, the envelope of the output waveform is detected. The state detection means 47 generates a state detection signal 48 using the envelope. The state detection signal 48 is transmitted to the optical pickup 4 with respect to the optical disc 41.
The signal is used to know the positional relationship of No. 2, for example, a signal for detecting that tracking is off, and this signal is used to control the optical pickup 42 during reproduction of the reproduction-only area.

Therefore, by suppressing the variation of the signal amplitude caused by the optical disk 41 and the optical pickup 42 by using the variable gain amplifier 44, it is possible to prevent a signal reading error and to use the gain control signal 60 to control the variable gain as described above. By storing the envelope of the output signal of the amplifier 44 as, for example, a waveform (h), an accurate state detection signal 48 can be generated. Since the intermittent signal needs to be read during reproduction of the reproduction recording area, the variable gain amplifier 44 is required to have a response speed as fast as possible.
Therefore, the first response speed and the second response speed cannot be reduced in advance.

[0031]

As described above, according to the optical disk apparatus of the present invention, it is possible to prevent signal reading errors by correcting signal amplitude variations, and to preserve the signal envelope necessary for generating a state detection signal. Therefore, a state detection signal of the optical pickup can be generated with high accuracy, and as a result, the control of the optical pickup can be performed accurately.

[Brief description of the drawings]

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

FIG. 2 is a waveform chart of each part for explaining the operation of the optical disc device.

FIG. 3 is a block diagram illustrating a configuration of an optical disc device according to a second embodiment of the present invention;

FIG. 4 is a waveform chart of each part for explaining the operation of the optical disc device.

FIG. 5 is a block diagram showing a configuration of a conventional optical disk device.

FIG. 6 is a waveform chart of each part for explaining the operation of the optical disk device according to the conventional technique.

[Explanation of symbols]

 Reference Signs List 21 optical disk 22 optical pickup 23 reproducing circuit 24 variable gain amplifier 26 detecting circuit 27 state detecting means 29 amplifier 30 capacitor 31 current source 32 switch 33 comparator 34 monostable multivibrator 35 switch circuit 36 first reference voltage 37 second reference voltage 39 Gain control circuit

Claims (2)

[Claims] 1. A variable gain amplifier for amplifying and outputting an information signal reproduced from an optical disk using an optical pickup according to a gain control signal, and wherein the envelope value of the peak value of the output of the variable gain amplifier is a first value. When exceeding a reference value, the gain of the variable gain amplifier is decreased at a first response speed, and when less than the first reference value, the gain of the variable gain amplifier is increased at a second response speed. A gain control circuit that outputs the gain control signal to the variable gain amplifier, and when the peak value or the envelope value of the peak value of the output of the variable gain amplifier is less than a second reference value set lower than the first reference value, An optical disc device comprising: a time constant circuit for lowering the second response speed for a predetermined time; and detecting a state of the optical pickup by detecting an envelope of an output waveform of the variable gain amplifier. 2. A variable gain amplifier for amplifying and outputting an information signal reproduced from an optical disk using an optical pickup in accordance with a gain control signal, and wherein an envelope value of a peak value of an output of the variable gain amplifier is a first value. When exceeding a reference value, the gain of the variable gain amplifier is decreased at a first response speed, and when less than the first reference value, the gain of the variable gain amplifier is increased at a second response speed. A gain control circuit that outputs the gain control signal to the optical disc; an area detection circuit that detects that the area of the optical disc being reproduced is a read-only area, and outputs a reproduction area detection signal; An optical disk device comprising: a switch circuit for lowering the second response speed; and detecting a state of the optical pickup by detecting an envelope of a waveform of an output of the variable gain amplifier. .