JP2565233B2 - Optical disk device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described in the following order.

A Industrial Field B Outline of Invention C Prior Art D Problems to be Solved by the Invention (FIGS. 6 to 8) E Means for Solving Problems (FIG. 1) F Action (FIG. 1) G Example (FIGS. 1 to 5) H Effect of the invention A Industrial field of application The present invention relates to an optical disk device, and more particularly to a magneto-optical disk device using an optical disk having a pull group formed therein. It is suitable for application to an optical disk device.

B. SUMMARY OF THE INVENTION The present invention prevents occurrence of a focus error in an optical disk device by controlling a dead zone circuit for removing the leak signal based on the signal level of the leak signal mixed in the focus error signal. Can be prevented.

C Conventional Technology Conventionally, in this type of magneto-optical disk device, it is possible to reliably record and reproduce information by tracking control and focus control of an optical head.

That is, the tracking error signal is obtained based on the reflected light obtained from the pre-group formed in advance between the recording tracks of the optical disk, and the optical head is drive-controlled based on the tracking error signal, so that the just track track is generated. Get the King state.

Furthermore, based on the reflected light obtained from the recording track,
By obtaining a focus error signal and driving and controlling the optical head based on the focus error signal, the state of the just focus is obtained.

On the other hand, at the time of seek, the optical head is driven and controlled in the radial direction of the optical disk based on a predetermined drive signal instead of the tracking error signal, thereby moving the optical head with respect to a desired recording track. It is done like this.

D. The problem to be solved by the invention. However, in this type of magneto-optical disk device, if the optical head moves in the radial direction of the optical disk during seek, a focus error occurs each time the optical spot crosses the pre-groove and the recording track. A phenomenon occurs in which the amount of reflected light used for signal detection changes.

Therefore, as shown in FIG. 6, the focus error signal S
_{In the FE} , the signal level changes as the amount of reflected light changes, and as a result, a high-frequency signal component (that is, a signal modulated by pregroove, referred to as a leak signal below) is mixed into the focus error signal. There is a problem (Fig. 6 (A)).

As shown in FIG. 7, the focus servo circuit 1 is actually used.
In order to improve the response characteristics, the phase compensation circuit 2
Is used to emphasize the high frequency signal component of the focus error signal S _FE , and then the focus output actuator S 4 is driven by the drive output signal S _FD of the drive circuit 3.

Therefore, such a leak signal is a focus error signal S.
_When mixed into _FE , the leakage signal is emphasized in the focus servo loop configured by the focus servo circuit 1, and finally the peak is saturated and waveform drive distortion occurs in the drive output signal S _FD (Fig. 6). (B)) It will be output.

When the waveform distortion occurs in the drive output signal S _FD in this way, there is a problem that the DC level of the drive output signal S _FD changes correspondingly and a focus error occurs.

As one method for solving this problem, as shown in FIG. 8, a method of inputting the focus error signal S _FE to the phase compensation circuit 2 (FIG. 7) via the leakage signal removal circuit 10 has been proposed. (Japanese Patent Application No. 62-69053).

That is, the operational amplifier circuit of the voltage follower circuit configuration
The focus error signal S _{FE is applied} to the dead zone circuit 12 via 11 and the output signal of the dead zone circuit 12 is supplied to the resistor 13 and the capacitor 14.
And a phase compensating circuit 2 through a hold circuit 16 composed of an operational amplifier circuit 15 having a voltage follower circuit configuration.

The dead band circuit 12 is a diode connected in parallel with opposite polarity.
The leakage signal mixed in the focus error signal S _FE is removed by using the potential difference between the rising voltages of the two diodes 17 and 18.

That is, with respect to the hold voltage V _H held at the non-inverting input terminal of the operational amplifier circuit 15, the input voltage V
_{When FE} (that is, the voltage of the focus error signal mixed with the leak signal) fluctuates, this voltage fluctuation width (that is, the potential difference V _H −V _FE ) causes the rising voltage V _D1 or V of the diode 17 or 18. When it is smaller than _D2 , both the diodes 17 and 18 maintain the off state, and as a result, the hold voltage V _H held in the hold circuit 16 is
It is directly output to the phase compensation circuit 2 (FIG. 6).

On the other hand, the voltage fluctuation range V _H −V _FE is
When it becomes larger than the rising voltage V _D1 or V _{D2 of} 8, the diode 17 or 18 is turned on, and the difference voltage obtained by subtracting the rising voltage V _D1 or V _D2 of the diode 17 or 18 from the changed voltage V _H −V _FE . The hold voltage V _H changes by that amount.

Against sub connexion hold voltage V _H, also the input voltage V _FE is varied in signal level in the range of threshold voltage V _D1 and V _D2 of the diode 17 and 18, the holding voltage V _H is not changed region (hereinafter deadband ) Can be obtained, and thus the leak signal mixed in the focus error signal S _FE can be removed by using the dead zone.

However, in the leakage signal elimination circuit 10 having the configuration shown in FIG. 8, the dead band width is the rising voltage of the diodes 17 and 18.
Since it is obtained by V _D1 and V _D2, there is a problem that it is difficult to efficiently remove only the leak signal.

That is, if a leak signal that changes with a potential difference larger than the rising voltages V _D1 and V _D2 is mixed, the leak signal may be output without being completely removed from the focus error signal F _FE. May occur.

On the contrary, when a leak signal that changes with a potential difference smaller than the rising voltage is mixed as a whole, not only the leak signal but also the signal level of the focus error signal is lowered more than necessary. Therefore, the focus error correction characteristic of the entire focus loop is degraded by that amount,
A focus error could occur.

Further, in practice, the rising voltage is the diodes 17 and 18
There is a problem in that the width of the dead zone becomes narrower as the temperature rises.

The present invention has been made in consideration of the above points, and proposes an optical disk device that efficiently and stably removes a leak signal mixed in a focus error signal to prevent the occurrence of a focus error. It is what

E Means for Solving the Problems In order to solve the problems, according to the present invention, an optical disk device configured to use an optical disk having a pregroup is provided with a hold circuit for holding an input voltage V _H. , The focus error signal S _FE is received, and the signal level V _FE of the focus error signal S _FE is held by the hold circuit 16
Predetermined range based on the hold voltage V _H held at
The dead-zone circuit 23 that suppresses only V _F1 and V _{F2 and} outputs it as the input voltage V _H of the hold circuit 16 and the focus error signal S _FE1 obtained through the hold circuit 16 cause the leakage modulated by the pre-groove. The leak signal detection circuits 32, 33, 40, 43 for detecting the signal level V _C of the signal S _M1 and the dead band circuit 23 based on the detection results V _C of the leak signal detection circuits 32, 33, 40, 43.
A dead band width control circuit 25, 26, 48, 57 for controlling the signal level range V _F1 , V _F2 suppressed by the hold circuit 16 is provided.
The focus control is performed based on the focus error signal S _FE1 obtained via.

F action Detects the signal level V _C of the leak signal S _M1 from the focus error signal S _FE1, and detects the dead zone circuit based on the detection result.
By controlling the signal levels V _F1 and V _F2 suppressed by 23, the leakage signal S _M1 mixed in the focus error signal S _FE
Can be removed efficiently and stably.

G Embodiment One embodiment of the present invention will be described in detail below with reference to the drawings.

In FIG. 1 in which parts corresponding to those in FIG. 8 are designated by the same reference numerals, reference numeral 20 denotes a leakage signal removing circuit as a whole, and resistors 21 and 22 having a resistance value R ₁ connected in series to diodes 17 and 18, respectively. The dead band circuit 23 is configured by.

Further diode 17 and resistor 21, to the connection point of the diodes 18 and the resistor 22, the current I ₁ and connected current sources 25 and 26 of the I ₂ is, thus the current I ₁ and by the I ₂ connexion resistors 21 and 22 Of the voltage drop V _R1 and V _R2 that occurs in the diode 17 and the offset voltage (that is, the voltage V _FE −V _R1 and V _FE + V _R2 ) compared with the input voltage V _FE of the dead zone circuit 23.
It is designed to be applied to 18.

Therefore, in the diodes 17 and 18, the applied voltage V _FE −V _R1 and V _FE + V _R2 are respectively compared with the hold voltage V _H by the following formula V _D1 <(V _FE −V _R1 ) −V _H ...... (1) When V _D2 <V _H − (V _FE + V _R2 ) ... (2), it turns on, and thus the formulas (1) and (2) are modified to obtain the following formula V _D1 + V _R1 <V _FE −V It is possible to obtain the relational expression of _H …… (3)-(V _D2 + V _R2 )> V _FE −V _H …… (4).

That is, when the fluctuation width of the input voltage V _FE with respect to the hold voltage V _H exceeds the voltages V _D1 + V _R1 and − (V _D2 + V _R2 ) respectively, the diodes 17 and 18 are turned on and the hold voltage V _H
You can see that changes.

Therefore, when the voltage fluctuation of the input voltage V _FE with respect to the hold voltage V _H is in the range of the voltage V _D1 + V _R1 to the voltage − (V _D2 + V _R2 ), the dead band of the dead band circuit 23 can be obtained, and the current sources 25 and 26 can be obtained. The width of the dead zone can be set to a desired value by controlling the currents I ₁ and I ₂ of.

Therefore, depending on the signal level of the leakage signal, the current I ₁ and
By controlling I ₂ , the dead zone width can be controlled according to the signal level of the leak signal, and the signal level of the focus error signal S _FE is lowered more than necessary, and conversely the leak signal is completely eliminated. It is possible to prevent from being output without being removed.

That is, the high-pass filter circuit 32 including the capacitor 30 and the resistor 31 receives the focus error signal S _FE1 output from the hold circuit 16, extracts the leak signal S _M1, and supplies it to the absolute value circuit 33.

As a result, as shown in FIG.
20, the focus error signal S _FE mixed with the leak signal S _M2
When (Fig. 2 (A)) is input, the leakage signal
If the dead band width is narrower than the signal level of S _M2 , the leak signal S _M1 (FIG. 2 (B)) corresponding to the signal level exceeding the dead band is extracted via the high-pass filter circuit 32, and the absolute value is extracted. Input to the circuit 33.

The absolute value circuit 33 is composed of an input resistance 34, a feedback resistance 35, and an operational amplifier circuit 37 having a rectifying diode 36 at the output end so that the resistance values of the feedback resistance 35 and the input resistance 34 are equal to each other. It has been selected.

As a result, a double-wave rectified output signal S _MA (FIG. 2 (C)) is obtained via the absolute value circuit 33, and this is output via the operational amplifier circuit 40 of the voltage follower circuit to the resistor 41 and the capacitor 42. It is input to the envelope detection circuit 43 of the low-pass filter circuit configuration constituted by.

As a result, an envelope signal S _E (FIG. 2 (D)) whose signal level changes according to the signal level of the leak signal S _M1 extracted by the high-pass filter circuit 32 can be obtained via the envelope detection circuit 43. .

Thus, the high-pass filter circuit 32, the absolute value circuit 33, the operational amplifier circuit 40, and the low-pass filter circuit 43 constitute a leak signal detection circuit that detects the signal level of the leak signal mixed in the focus error signal S _SE1 .

The inverting amplifier circuit 48 is composed of an operational amplifier circuit 47 having an input resistor 45 and a feedback resistor 46, receives the envelope signal S _E and outputs its inverted output signal to the current sources 25 and 26.

Here, in the inverting amplifier circuit 48, when the resistance values of the feedback resistor 46 and the input resistor 45 are set to the same value, and the signal level of the leakage signal S _M1 extracted by the high-pass filter circuit 32 is set to the voltage V _C , -V _C envelope signal is output.

The current source 25 has a feedback resistor between the non-inverting input terminal and the output terminal.
It has an operational amplifier circuit 53 in which a feedback resistor 52 is connected to an inverting input end from an output end via an output resistance 51 while connecting 50,
The non-inverting input terminal receives the reference voltage V _D3 obtained from the reference power source 57 composed of the resistor 55 and the temperature compensating diode 56, and the envelope signal output from the inverting amplifier circuit 48 is received by the resistor 58. Received through the inverting input terminal.

Further, the current source 25 outputs a current to the resistor 21 via the output resistor 51.
I ₁ is given and the resistance value of the output resistor 51 becomes equal to the resistance value R _{1 of the} resistor 21.

Further the input resistor 54 and 58 and the feedback resistor 52 and 50, the resistance value is selected to be equal to the resistance value R ₂ together, in its result resistor 51, the input voltage V _C and V _D3 of the current source 25 For the output current I ₁ and the output current I ₁ , the following relational expression I ₁ R ₁ = V _C −V _D3 (5) can be obtained.

On the other hand, the voltage drop V _R1 of the resistor 21 due to the flow of the current I ₁ becomes the value expressed by the relational expression of the following expression V _R1 = R ₁ I ₁ (6), and the result (5 From equations (6) and (6), the relational expression of V _R1 = V _C −V _D3 (7) can be obtained.

As a result, the dead band voltage V _F1 determined by the resistor 21 and the diode 17 can be expressed by the following equation V _F1 −V _D1 + V _R1 = V _D1 + V _C −V _D3 (8), where For diodes 17, 18 and 56, if diodes having the same rising voltages V _D1 , V _D2 and V _D3 are used, the relational expression of V _F1 = V _C (9) Obtainable.

Thus, the diode 17 of the dead band of the dead band circuit 23 is
The dead band width V _F1 determined by the resistor 21 can be controlled in proportion to the output voltage V _C of the envelope detection circuit 43.

On the other hand, the current source 26 has an operational amplifier circuit 64 in which the inverting input terminal and the output terminal are connected by the feedback resistor 62 and the feedback resistor 60 is connected from the output terminal to the non-inverting input terminal via the output resistor 61.
And receives the reference voltage V _D3 and the output voltage −V _C of the inverting amplifier circuit 48 at the non-inverting input terminal and the inverting input terminal via the input resistors 65 and 66, respectively.

Further, in the current source 26, the resistance value of the output resistance 61 is set to a value equal to the resistance value R ₁ of the output resistance 51 and the resistance 22 of the current source 25, and the feedback resistances 60 and 62 and the input resistances 65 and 66 are further set.
Are of a resistance R ₂ equal to the corresponding resistances 50, 52, 54 and 58 of the current source 25.

Therefore, in the current source 26, in the output resistor 61, a current whose magnitude is equal to that of the current I _{1 in the} opposite direction to that of the current source 25.
I ₂ is obtained and the current I ₂ is supplied to the resistor 22.

Therefore, as in the case of the resistor 21 and the diode 17, the resistor 22 and the diode 18 are opposite to the diode 17 and the resistor 21 expressed by the relational expression of the following equation V _F2 = V _C = V _F1 (10). The dead zone of the direction can be obtained, and the envelope detection circuit 43
The width V _F2 of the dead zone can be controlled in proportion to the output voltage V _C.

As a result, the leak signal S _M1 mixed in the focus error signal S _FE1 output from the hold circuit 16 is extracted, and the dead band widths V _F1 and V are proportional to the signal level of the leak signal S _M1.
By controlling _F2 , the dead band widths V _F1 and V _F2 are controlled so that the signal level of the leak signal S _M1 mixed in the focus error signal S _FE1 becomes 0 level as a whole, and thus the leak signal is efficiently generated. A well-removed focus error signal S _FE1 (FIG. 2 (E)) can be obtained.

That is, as shown in FIG. 3, the dead zone circuit 23, input-output potential difference (i.e. the difference between the input voltage V _FE for holding voltage V _H) changes ΔV proportional to hold voltage V _H in proportionality constant 1 against _For the input / output characteristics (shown by the broken line) in which _H changes, 0 at the voltage of the input / output potential difference V _H −V _FE
It is possible to obtain the input / output characteristic in which the dead band widths V _F1 and V _F2 change depending on the signal level of the leak signal centering on [V].

As a result, as shown in FIG. 4, the input / output characteristic in which the hold voltage V _H changes in proportion to the input voltage V _FE (shown by the broken line).
Against the hold voltage V _H held in the hold circuit 16.
It is possible to obtain input / output characteristics in which the dead band widths V _F1 and V _F2 change around the center.

Thus, as shown in FIG. 5, dead band widths V _F1 and V _F2
By controlling the width V _F1 and V _F2 of the dead zone in response to the signal level of the leakage signal S _M1 with a set to each other equal, Fuo Kas error signal leakage signal S _M1 is mixed S _FE
When is input, the focus error signal S _{FE1 in} which the leak signal S _M1 is efficiently removed can be obtained, and as a result, the focus error can be prevented from occurring.

Thus, the current sources 25 and 26, the inverting amplifier circuit 48, and the power supply circuit 57 change the dead band width of the dead band circuit 23 into an envelope signal.
A dead band width control circuit is controlled based on S _E.

Further, by using diodes having the same characteristics as the diode 56 for temperature characteristic compensation of the power supply circuit 57 and the diodes 17 and 18 of the dead zone circuit 23, the leak signal elimination circuit as a whole has a closed loop circuit configuration for controlling the width of the dead zone. The temperature characteristics of the diodes 17 and 18 can be sufficiently compensated for practical use, and the leak signal can be removed stably and efficiently.

Further, in practice, the focus control circuit is designed to adjust the gain of the focus control circuit so that a loop gain is practically obtained in a range where the focus servo circuit does not oscillate. If a leakage signal removing circuit is added to, the width of the dead zone can be widened immediately before the focus servo completely falls into the oscillation state, and the oscillation state can be avoided in advance.

Therefore, the work of adjusting the gain of the focus control circuit can be further simplified accordingly.

In the above configuration, the focus error signal S _FE is
The signal is input to the dead band circuit 23 via the operational amplifier circuit 11, and the output signal of the dead band circuit 23 is output to the phase compensation circuit 2 (FIG. 7) via the hold circuit 16.

At this time, after the leak signal S _M1 mixed in the focus error signal S _FE1 output from the hold circuit 16 is extracted by the high-pass filter circuit 32, the absolute value circuit 33, the operational amplifier circuit 40, and the envelope detection circuit 43 are operated. The signal level of the leak signal S _M1 is detected via this.

The envelope signal S _E that is the detection result is output to the current sources 25 and 26 as a control signal of the currents I ₁ and I ₂ that control the dead band widths V _F1 and V _F2 of the dead band circuit 23, and thus the leakage signal removal circuit. The dead band widths V _F1 and V _F2 of the dead band circuit 23 are controlled and mixed into the focus error signal S _FE1 so that the signal level of the leak signal S _M1 obtained through the high-pass filter circuit 32 becomes 0 level as a whole. Leak signal S
_M1 can be removed efficiently.

According to the above configuration, by detecting the signal level of the leak signal and controlling the dead band width of the dead band circuit based on the detection result, the leak signal mixed into the focus error signal is stable and efficient as a whole. Can be removed.

In the above embodiment, the case where the resistors 21 and 22 of the dead zone circuit and the resistors 51 and 61 of the current source are set to the same resistance value so that the currents flowing through the respective resistors are equal has been described. Is not limited to this, and the resistance value may be set to a different value, or different currents may flow between the resistors 21 and 22 as necessary.

Further, in the above-described embodiments, the case where the present invention is applied to the magneto-optical disk device has been described, but the present invention is not limited to this, and is widely applied to an optical disk device configured to use an optical disk in which a pregroup is formed. Can be applied.

As described above, according to the present invention, the width of the dead zone is controlled according to the signal level of the leak signal to remove the leak signal, so that the leak signal can be removed stably and efficiently. It is possible to prevent the occurrence of a scrap error.

[Brief description of drawings]

FIG. 1 is a connection diagram showing an embodiment of a leakage signal removal circuit according to the present invention, FIG. 2 is a signal waveform diagram used for explaining the operation thereof, and FIGS. 3 and 4 are characteristic curves showing its input / output characteristics. FIG. 5 and FIG. 5 are signal waveform diagrams for explaining the operation, and FIG.
FIG. 7 is a signal waveform diagram used to explain a leak signal, FIG. 7 is a block diagram showing the structure of a focus servo circuit, and FIG. 8 is a connection diagram showing a conventional leak signal removing circuit. 1 ... Focus servo circuit, 10, 20 ... Leakage signal elimination circuit, 11, 15, 37, 40, 47, 53, 64 ... Operational amplifier circuit,
12, 23 ... Dead band circuit, 16 ... Hold circuit, 17, 18,
36, 56 ...... Diode, 25, 26 ...... Current source, 32 ...... High pass filter circuit, 33 ...... Absolute value circuit, 43 ...... Envelope detection circuit, 48 ...... Inverting amplification circuit, 57 ...... Power supply circuit.

Claims (1)

(57) [Claims] 1. An optical disk device configured to use an optical disk in which a pregroup is formed, a hold circuit for holding an input voltage, a focus error signal, and a signal level of the focus error signal, Based on the hold voltage held in the hold circuit, the dead band circuit that suppresses only a predetermined range and outputs as the input voltage of the hold circuit, and the focus error signal obtained through the hold circuit, A leak signal detection circuit that detects the signal level of the leak signal that is modulated by this, and a dead band width control circuit that controls the range of the signal level suppressed by the dead band circuit based on the detection result of the leak signal detection circuit. The focus control is based on the focus error signal obtained through the hold circuit. Optical disc system being characterized in that the.