JPH09274725A - Automatic tracking servo gain control circuit and its method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable the gain control by setting a tracking error signal into a servo even when the level of its initial signal is low. SOLUTION: First of all, before the tracking servo is turned on, an amplitude (e) of the tracking error signal obtained via an optical pickup 10, an RF processing circuit 20 and an A/D converter 31 is measured by an amplitude measuring part 32. Based on this amplitude (e), a 1st gain K of a coefft. multiplier 33 is adjusted by a microcomputer 50 in order to enable its tracking error signal to have a level at least to an extent for setting the servo. Then, the tracking servo is turned on, and under the tracking servo state, disturbance is impressed upon a head from a disturbance impressing part 36 to move the head, and for a tracking error signal attending upon this movement a gain is measured by a gain measuring part 34, and based on this measured gain, a suitable gain is set in a gain control amplifier 35.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tracking servo gain automatic adjustment circuit for tracking servo applied to an optical disk device for recording / reproducing a compact disk (CD) and a method thereof.

[0002]

2. Description of the Related Art In an optical disc apparatus for recording / reproducing a so-called optical disc such as a compact disc (CD) or a mini disc (MD), it is based on the distribution of reflected light of the light irradiated on the disc-shaped recording medium. To generate a tracking error signal and apply tracking servo. The tracking error signal can be generated by a three-spot method in which the amounts of reflected light from two sub-beams sandwiching the main beam are compared, or by irradiating one spot of light and distributing the intensity of the reflected light. The push-pull method that uses is used. In order to properly perform such tracking servo, it is necessary to generate an appropriate servo signal by applying an appropriate gain to the tracking error signal. However, the level of the detected tracking error signal changes depending on various conditions such as the set optical disk and the state of the set, so it is necessary to adjust the gain of the tracking servo according to the change.

A conventional tracking servo gain automatic adjustment circuit for automatically performing this adjustment will be described with reference to FIG. In the circuit shown in FIG. 5, when the power of the optical disk device is turned on or immediately after the optical disk is replaced,
The tracking servo is turned on, and the disturbance is applied to the servo signal from the disturbance applying unit 36 via the adder 37 while the tracking servo is being applied. As a result, the optical pickup 10 is moved by the tracking coil drive driver 40 by this signal. Next, the gain measuring unit 34 measures the gain of the tracking error signal detected by the RF processing circuit 20 by this movement, and the gain of the gain adjusting amplifier 35 is adjusted based on the measured gain. The tracking error signal obtained by the RF processing circuit 20 is converted into a digital signal by the A / D converter 31, and the subsequent processing is performed by the digital servo circuit 3.
Digitally processed within 0.

[0004]

By the way, in order to perform the above-described automatic gain adjustment, it is necessary to turn on the tracking servo to bring it into an on-track state. However, the gain before adjustment may be low and the servo may not be pulled in due to variations in the disc or variations in the optical system. In such a case, there arises a problem that not only the automatic gain adjustment described above cannot be performed but also tracking servo cannot be applied in the first place. Further, if the output from the RF amplifier is set to a large value in order to avoid such a state, a problem such as exceeding the input range of the A / D converter in the digital servo circuit may occur. It is not possible to make various settings.

Therefore, an object of the present invention is to provide a tracking servo gain automatic adjustment circuit capable of appropriately adjusting the gain so that the tracking servo can be appropriately applied even when the initial value of the signal level is largely different. Especially. Another object of the present invention is to provide such a tracking servo gain automatic adjustment method.

[0006]

In order to solve the above-mentioned problems, the rough gain setting, that is, the rough adjustment is first performed based on the amplitude of the tracking error signal before the tracking servo is turned on. After the servo is applied, the gain is finely adjusted by the disturbance injection as before.

Therefore, the tracking servo gain automatic adjustment circuit of the present invention comprises an amplitude measuring means for measuring the amplitude of the tracking error signal before the tracking servo is turned on, and a first gain determining means based on the amplitude. No. 1 gain determining means, first amplifying means for amplifying the tracking error signal with the determined first gain, and the tracking error signal amplified with the first gain are used to turn on the tracking servo. In this state, the gain of the tracking servo is measured, and the gain adjusting means for determining the second gain so that the gain becomes a desired gain, and the determined second gain with the first gain Second amplification means for further amplifying the amplified tracking error signal.

Preferably, the gain adjusting means uses a disturbance applying means for applying a predetermined disturbance signal to the tracking error signal and a tracking error signal obtained as a result of tracking servo by the tracking error signal to which the disturbance is applied. Gain measuring means for measuring the gain based on the measured gain, and second gain determining means for determining the second gain based on the measured gain so that the tracking servo has a desired gain.

Specifically, the first amplifying means and the second amplifying means are the same amplifying means, and in the amplifying means, the first gain determined by the first gain determining means. Is set as an initial value, the initial value is corrected by the second gain determined by the second gain determining means, and the input tracking error signal is amplified by the corrected gain.

Further, the tracking servo gain automatic adjustment method of the present invention measures the amplitude of the tracking error signal before the tracking servo is turned on, and based on the measured amplitude of the tracking error signal, the tracking error signal is adjusted. Further, a gain is determined so that a signal having a level that can be at least pulled into the tracking servo is generated, the input tracking error signal is amplified by the determined gain, and based on the amplified tracking error signal Turn on the tracking servo, apply a predetermined disturbance signal to the tracking servo circuit while the tracking servo is applied, and measure the gain of the tracking servo circuit from the tracking error signal obtained by applying the disturbance signal. , The measured gay Based on, the tracking servo circuit for adjusting the gain to have a desired gain.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION First Embodiment First Embodiment of Tracking Servo Gain Automatic Adjustment Circuit of the Present Invention
An embodiment will be described with reference to FIGS. 1 and 2. FIG. 1 is a diagram showing a circuit related to a tracking servo gain automatic adjustment circuit of a tracking servo circuit applied to an optical disk device for recording / reproducing on / from an optical disk.
It has an RF processing circuit 20, a tracking servo gain automatic adjustment circuit 1 and a tracking coil drive driver 40. In addition, the tracking servo gain automatic adjustment circuit 1
Is an A / D converter 31, an amplitude measuring unit 32, a coefficient multiplier 3
3, a gain measuring unit 34, a gain adjusting amplifier 35, a disturbance applying unit 36, an adder 37, and a microcomputer 50. The components other than the microcomputer 50 of the tracking servo gain automatic adjustment circuit 1 are configured as circuits in the digital servo circuit 30.

First, the configuration of each part of the circuit shown in FIG. 1 will be described. The optical pickup 10 has a laser diode (LD), an objective lens (OL), a photodetector (PD), and the like. The PD is divided into a predetermined shape, detects the light emitted from the LD onto the optical disc and diffracted / reflected by the optical disc, and outputs a signal corresponding to the amount of light. The RF processing circuit 20 performs a predetermined process on the light detection signal from the optical pickup 10, detects a tracking error signal TE, and inputs the tracking error signal TE to the tracking servo gain automatic adjustment circuit 1.

Tracking servo gain automatic adjustment circuit 1
First, in the A / D converter 31, first, the tracking error signal TE input from the RF processing circuit 20 is input.
To a digital signal. The converted signal is output to the amplitude measuring unit 32 and the coefficient multiplier 33. The amplitude measuring unit 32 detects the amplitude e of the tracking error signal TE converted into the digital signal input from the A / D converter 31. The detected amplitude e can be appropriately read by the microcomputer 50.

Based on the amplitude e of the tracking error signal TE detected by the amplitude measuring section 32, the microcomputer 50
The first gain K is determined so that the tracking error signal TE 'for performing the tracking servo can be obtained at a substantially appropriate level. This first gain K is
It is determined that the amplified tracking error signal K × TE has a level that can be pulled into the servo.

Regarding the operation of the microcomputer 50, the flow of FIG.
This will be described with reference to a chart. First, when turning on the power
Gain of tracking error signal when disc is exchanged, etc.
Is newly determined (step S0), the amplitude measuring unit
The amplitude e detected from 32 is read (step S
1). A first threshold value THL that predetermines the amplitude e_LAnd ratio
Comparison (step S2), e ≧ THL_LIf was the first
1 gain K is a small gain K_S(Step
S3). In step S2, e <THL_LIs
In case of the above, the second threshold value T which further predetermines the amplitude e
HL_S(Step S4), e ≦ THL_Swas
If the first gain K is a large gain K_LToss
(Step S6). In step S4, e> TH
L_SIf so, the first gain K is a normal gain
A certain K_MAnd In addition, THL _S<THL_LIt is. S
The gain K determined in steps S3, S5 and S6 is related to
It is set in the number multiplier 33 (step S7), and the microcomputer 50
Ends the process (step S8).

The coefficient multiplier 33 is a tracking error signal TE converted into a digital signal by the A / D converter 31.
Is amplified by using the first gain K set by the microcomputer 50 as a multiplier and converted into a substantially appropriate tracking error signal of a level at least retractable to the servo.

When the tracking servo is turned on, the gain measuring unit 34 is servo-controlled based on the signal to which the disturbance signal output from the disturbance applying unit 36 is applied during the tracking servo gain adjusting operation described later. The gain of the tracking error signal in the digital servo circuit 30 is measured based on the obtained tracking error signal. The measured gain is the digital servo circuit 3
It is output to a control unit (not shown) within 0. In the control unit in the digital servo circuit 30 (not shown), the gain detected by the gain measurement unit 34 during the tracking servo gain adjustment operation is performed so that the tracking error signal TE is input to the tracking coil drive driver 40 at an appropriate level. The gain of the gain adjusting amplifier 35 is adjusted based on

The gain adjusting amplifier 35 is a coefficient multiplier 33.
The input tracking error signal is amplified by the adjusted gain and converted into a signal of a desired level.
The disturbance applying unit 36 generates a signal as a disturbance to be applied to the tracking error signal in order to check the level of the tracking error signal during the tracking servo gain adjustment operation. In the present embodiment, the disturbance applying unit 36 outputs a 1 kHz sine wave. The adder 37 adds the tracking error signal TE output from the gain adjusting amplifier 35 and the disturbance signal generated by the disturbance applying unit 36. The added signals are output to the tracking coil drive driver 40. Since the disturbance applying unit 36 does not substantially operate during the normal operation, the disturbance applying unit 3 does not operate.
There is no signal input from 6, and the adder 37 outputs the output of the gain adjustment amplifier 35 to the tracking coil drive driver 40 as it is.

The tracking coil drive driver 40 is
The tracking coil is driven based on the tracking error signal output from the tracking servo gain automatic adjustment circuit 1 to perform tracking of the optical pickup 10.

Next, the operation of the tracking servo gain automatic adjustment circuit 1 will be described. When the power of the optical disk device is turned on, immediately after exchanging the optical disk, and before the tracking servo is further turned on, coarse adjustment of the tracking error signal is first performed. The amplitude measuring unit 32 measures the amplitude e of the tracking error signal obtained via the optical pickup 10, the RF processing circuit 20, and the A / D converter 31, and based on the amplitude e, the tracking error signal is at least servo controlled. The microcomputer 50 adjusts the first gain K of the coefficient multiplier 33 so that the microcomputer 50 has a level that can be pulled in.

After the rough adjustment of the gain of the tracking error signal is performed as described above, the fine adjustment is then performed. The tracking servo is turned on, and a disturbance is applied from the disturbance applying unit 36 while the tracking servo is being applied to cause a tracking error. Then, the gain measuring unit 34 measures the gain of the tracking error signal accompanying it, and sets an appropriate gain for the gain adjusting amplifier 35 based on the measured gain.

As described above, in the tracking servo gain automatic adjustment circuit 1 of the first embodiment, first, the gain is roughly adjusted based on the amplitude of the tracking error signal in the state where the tracking servo is not applied,
Tracking servo is applied by using the signal whose gain is roughly adjusted, and the gain is finely adjusted by the disturbance injection. Therefore, even when a signal that cannot be pulled into the tracking servo is initially input, such as when a significantly low-level push-pull signal is input, the gain can be appropriately adjusted.

Second Embodiment Second Embodiment of the tracking servo gain automatic adjustment circuit of the present invention
The embodiment will be described with reference to FIG. The circuit shown in FIG. 3 is almost the same as the circuit of the first embodiment shown in FIG. 1, but the coefficient multiplier provided in the tracking servo gain automatic adjustment circuit 1 of the first embodiment. 33
However, it is deleted in the tracking servo gain automatic adjustment circuit 1b of the second embodiment.

That is, in the tracking servo gain automatic adjustment circuit 1b of the second embodiment, first, the microcomputer 50 performs tracking servo based on the amplitude e of the tracking error signal TE detected by the amplitude measuring section 32. The first gain K for obtaining the tracking error signal TE ′ to be obtained at an almost appropriate level is determined, and this gain K is set in the gain adjustment amplifier 35b as an initial value of the gain adjustment amplifier 35b. Then, at the time of fine gain adjustment by the disturbance injection using the disturbance applying unit 36, the initial gain K set in the gain adjusting amplifier 35b is adjusted based on the gain measured by the gain measuring unit 34 to obtain a desired value. Change the gain so that a signal of a level that enables the servo of can be obtained.

As described above, in the tracking servo gain automatic adjustment circuit 1b of the second embodiment, the tracking servo gain automatic adjustment circuit 1 of the first embodiment is used.
It is possible to simplify the configuration while having substantially the same operation and function. The tracking servo gain automatic adjustment circuit 1 may have such a configuration according to the configuration of other circuits of the digital servo circuit 30.

Third Embodiment Third Embodiment of the Tracking Servo Gain Automatic Adjustment Circuit of the Present Invention
The embodiment will be described with reference to FIG. The tracking servo gain automatic adjustment circuit 1c of the third embodiment shown in FIG. 3 uses the analog tracking error signal before A / D conversion in the A / D converter 31 to perform coarse gain adjustment. It is the one.

That is, in the tracking servo gain automatic adjustment circuit 1c of the third embodiment, first, R
The amplitude e of the tracking error signal TE input from the F processing circuit 20 is detected by the amplitude measuring unit 32c, and the first gain K is calculated in the microcomputer 50 based on the amplitude e.
To determine. Then, the gain K is set in the analog multiplier 33c to amplify the analog tracking error signal TE by K times. The A / D converter 31 performs A / D conversion on the signal whose level has already been roughly adjusted, and converts it into a digital signal. Finely adjust the gain by disturbance injection.

As described above, the coarse gain adjustment according to the present invention can be similarly performed on an analog signal, and such a configuration may be employed. Of course, in the tracking servo gain automatic adjustment circuit 1c of the third embodiment, the first
Also, as in the second embodiment, appropriate gain adjustment can be performed.

The present invention is not limited to these first to third embodiments, and various modifications can be made. For example, the determination of the gain K in the microcomputer 50 is determined by the process shown in the flowchart of FIG. 2 in the above-described embodiment. But,
For example, the relationship between the amplitude e and the gain K may be determined by an arbitrary method such as referring to a predetermined table. In addition, the configuration of each unit may be changed as desired.

[0030]

According to the present invention, there is provided a tracking servo gain automatic adjustment circuit and a method therefor capable of appropriately adjusting the gain even when the initial value of the signal level becomes large. I was able to. As a result, it is possible to provide a tracking servo circuit that can appropriately perform tracking servo and an optical disk device that can perform accurate tracking.

[Brief description of drawings]

FIG. 1 is a first embodiment of the present invention, showing a circuit related to a tracking servo gain automatic adjustment circuit of the present invention of a tracking servo circuit applied to an optical disk device for recording / reproducing on / from an optical disk. FIG.

FIG. 2 is a flowchart showing processing performed by a microcomputer of the circuit shown in FIG.

FIG. 3 is a diagram showing a tracking servo gain automatic adjustment circuit according to a second embodiment of the present invention.

FIG. 4 is a diagram showing a tracking servo gain automatic adjustment circuit according to a third embodiment of the present invention.

FIG. 5 is a diagram showing a conventional tracking servo gain automatic adjustment circuit.

[Explanation of symbols]

1 ... Tracking servo gain automatic adjustment circuit, 10 ... Optical pickup, 20 ... RF processing circuit, 30 ...
Digital servo circuit, 31 ... A / D converter, 32 ... Amplitude measuring section, 33 ... Coefficient multiplier, 34 ... Gain measuring section, 35
... Gain adjustment amplifier, 36 ... Disturbance applying section, 37 ... Adder, 40 ... Tracking coil drive driver, 50 ... Microcomputer

Claims (4)

[Claims] 1. A circuit for adjusting the gain of a tracking servo circuit, comprising: amplitude measuring means for measuring the amplitude of a tracking error signal before the tracking servo is turned on; and an amplitude measuring means based on the measured amplitude of the tracking error signal. And a first gain deciding means for deciding a first gain so as to generate a signal of a level that can be at least pulled into the tracking servo from the tracking error signal, and the tracking with the decided first gain. A first amplifying means for amplifying the error signal, and a state where the tracking servo is turned on based on the tracking error signal amplified by the first gain,
Gain adjusting means for measuring a gain of the tracking servo and determining a second gain so that the gain becomes a desired gain; and tracking amplified by the first gain with the determined second gain. A tracking servo gain automatic adjustment circuit having a second amplification means for further amplifying an error signal. 2. The gain adjusting means is based on a disturbance applying means for applying a predetermined disturbance signal to the tracking error signal, and a tracking error signal obtained as a result of tracking servo by the tracking error signal to which the disturbance is applied. And a second gain determining unit configured to determine a second gain so that the tracking servo has a desired gain based on the measured gain. Tracking servo gain automatic adjustment circuit described. 3. The first amplifying means and the second amplifying means are the same amplifying means, and in the amplifying means, the first gain determined by the first gain determining means is an initial value. The tracking according to claim 2, wherein the initial value is corrected by a second gain determined by the second gain determining means, and the input tracking error signal is amplified by the corrected gain. Servo gain automatic adjustment circuit. 4. The amplitude of the tracking error signal before the tracking servo is turned on is measured, and based on the measured amplitude of the tracking error signal, a level of at least a level at which the tracking error signal can be pulled into the tracking servo is measured. A gain for generating a signal is determined, the input tracking error signal is amplified by the determined gain, a tracking servo is turned on based on the amplified tracking error signal, and the tracking servo is applied. Applying a predetermined disturbance signal to the tracking servo circuit in the state, from the tracking error signal obtained by applying the disturbance signal, to measure the gain of the tracking servo circuit, based on the measured gain, The tracking servo circuit is Tracking servo automatic gain adjustment method for adjusting the gain to have a down.