JPH1166579A - Tracking control apparatus and method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tracking control apparatus and method based on a 1-beam method which enables adaptively setting of the optimum servo coefficient for each optical disc. SOLUTION: A difference (E-F) between signals E and F and a sum (E+F) thereof from terminals 11 and 12 are found by an subtraction amplifier 13 and an addition amplifier 14 to find a standardized push/pull signal NPP =(E-≠)/(E+F) with a division circuit 20. The amplitude of the signal is detected by a signal amplitude detection circuit 30 and sent to a coefficient calculation circuit 50 through an A/D conversion circuit 40 to set a tracking servo coefficient K according to the amplitude of the NPP signal. A moving value signal CSL of an objective lens generated by top hold circuits 65 and 66 and a subtraction amplifier 70 is multiplied by the coefficient K using a multiplication amplifier 80 to make a cancel signal, which is subtracted from a pushpull signal PP by a subtraction amplifier 99. Thus, the offset of the signal PP is cancelled to obtain the optimum tracking error.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to tracking control of a light beam applied to an optical disk, and more particularly to a tracking control device for canceling an offset generated in a tracking error signal generated by using a push-pull method in a one-beam method. It relates to a tracking control method.

[0002]

2. Description of the Related Art An optical disk apparatus for reproducing a signal recorded on an optical disk focuses a light beam, irradiates the signal surface of the optical disk, receives the returned light, and receives a reproduced signal and a servo error signal. Is provided with an optical pickup for outputting the same.

An optical disk mounted on a spindle of an optical disk drive and driven to rotate always has radial deflection due to eccentricity of a center hole or eccentricity generated during chucking, and optical axis direction deflection due to warpage or uneven thickness. Has occurred. For this reason, the optical pickup performs control so that the focal point of the light beam always irradiates the track on the signal surface, following the deflection of the optical disk due to the rotation drive.

For example, a compact disc (CD) is
The track pitch is set to 1.6 μm, and the tracking control is performed so that the focal point of the light beam is in a range of about ± 0.1 μm from the track. Also,
The deflection width in the optical axis direction of the signal surface is allowed up to about ± 0.5 mm, while the focus point is ± 1 μm from the signal surface.
Focus control is performed so as to be in the range of about.

[0005] The control of the irradiation position of the light beam is as follows.
This is performed by, for example, finely moving a part of the optical system of the optical pickup with an actuator according to a control signal. This control signal is a tracking error signal or a focus error signal obtained from the return light from the optical disc,
The above control is performed by supplying these to the servo system.

As a typical method for obtaining the above-mentioned tracking error signal, a three-beam method and a one-beam method are used.

In the three-beam method, a diffraction grating (grating) is arranged on the outward path of a light beam applied to an optical disk, and a main beam (zero-order light) and two sub-beams (± first-order light) are provided.
In this method, three light beams are generated, and two sub beams are used for detecting a tracking error. In this method, on both sides of the light receiving element for detecting the main beam,
A light receiving element for detecting two sub-beams is arranged, and a change in the return light of the sub-beam generated according to the shift amount of the focal point of the main beam applied to the track of the optical disc from the track position. To obtain a tracking error signal.

On the other hand, the one-beam method is a method of irradiating an optical disk with one beam and obtaining a tracking error signal from the returned light. In the optical system using the one-beam method, an optical element such as a grating required when using the three-beam method can be omitted.

FIG. 15 shows an example of an optical system of an optical pickup in which a tracking error signal is obtained by a one-beam method.

The light emitting and receiving element 21 formed on the substrate 217
The light from the laser diode 211, which is the light emitting element unit of No. 0, is reflected by the inclined surface 212a of the prism 212, is condensed by the beam splitter 222 and the objective lens 223, and is irradiated on the optical disc 200. The focused light spot 224 is subjected to focus control so as to be located on the signal surface 200a of the optical disc 200.

The return light from the optical disk 200 passes through the objective lens 223 again, and is separated by the beam splitter 222 into an optical path toward the photodetector 225 and an optical path toward the prism 212 of the light receiving / emitting element 210.

The light-receiving element portion of the light-receiving / emitting element 210 includes photodetectors 213 and 215 each having a four-divided light-receiving surface.
The return light incident from the light source 213a enters the photodetector 213 and is further reflected and reflected by the upper surface 212 of the prism 212.
The focus 214 is focused at b, and is also incident on the photodetector 215.

In this optical system, the focus error signal FE is obtained by the light receiving element of the light receiving / emitting element 210. Here, the focus error signal FE is
It is obtained by the calculation of the following equation (1). However, (1)
In the equation, signals a to d are light detection signals from the respective light receiving areas a to d of the light receiving surface divided into four parts of the photodetector 213, and similarly, signals e to g are four parts of the light detector 215. It is assumed that the signal is a light detection signal from each of the light receiving areas e to g on the light receiving surface.

FE = {(a + d) − (b + c)} − {(e + h) − (f + g)} (1) On the other hand, in this optical system, the tracking error signal TE is
The above photodetectors 213, 215 and 225
Can be obtained.

For example, when obtaining the tracking error signal TE from the photodetector 225, the difference between the photodetection signal (i + j) from the left light receiving area of the light receiving surface and the light detection signal (k + 1) from the right light receiving area is obtained. {(I + j)-(k + 1)}
Is extracted as a push-pull signal PP. In addition,
Hereinafter, a case where the tracking error signal TE is obtained from the photodetector 225 will be described as an example.

FIG. 16 shows the configuration of the light receiving surfaces of the photodetectors 213, 215, and 225 of the optical pickup using the one-beam method illustrated in FIG.

The light receiving surface of each of these photodetectors is generally divided into two or more in the track direction of the optical disk 200, and here, an example is shown in which the light receiving surface is divided into four.
For example, in the photodetector 225, the light receiving surfaces thereof are a light receiving region i, a light receiving region j, a light receiving region k, and a light receiving region 1 in order from one end.

Then, E used for tracking control
The signal is the sum of the signal from the two light receiving areas i on the left side of the four divided light receiving surfaces and the signal from the light receiving area j (i +
j). Similarly, the F signal used for tracking control is obtained as the sum (k + 1) of the signal from the light receiving region k, which is the two light receiving regions on the right side of the four divided light receiving surfaces, and the signal from the light receiving region l. . Normally, a differential signal (E-F) between the E signal and the F signal is used as a push-pull signal PP for tracking control.

By the way, when the tracking control is performed by the one-beam method using the optical system as described above, if only the objective lens 223 is moved, the center of the photodetector whose light receiving surface is divided and the center of the return light are shifted. Do not coincide with each other, the incident position of the spot on the light receiving surface of the photodetector moves as shown by the dotted line in FIG.
An offset occurs in E. For this reason, the positional relationship between the track and the light beam cannot be controlled correctly, and the RF reproduced from the optical disc may be deteriorated.

Therefore, the offset is canceled by using a movement amount signal corresponding to the movement amount of the objective lens 223 or the movement amount of the light spot 224 on the optical disk 200.

For example, let the above-mentioned movement amount signal be CSL,
Assuming that the coefficient of the servo system for tracking control is K by the one-beam method, the photodetector 225 obtains the tracking error signal TE by the following equation (2).

TE = {(i + j) − (k + 1)} − K × CSL (2)

[0023]

However, in the conventional tracking servo system, the servo coefficient K is a fixed value. However, since the characteristics of the optical disc and the optical pickup vary, the above K value cannot be optimized for all the optical discs.

Therefore, the optical pickup using the one-beam method has a problem that it is difficult to improve the accuracy and reliability of the tracking servo.

The present invention has been made to solve such a problem, and it is possible to set a servo coefficient for each optical disk having different characteristics, thereby improving the accuracy and reliability of a servo system. It is an object of the present invention to provide a tracking control device and a tracking control method that use a one-beam method.

[0026]

According to a tracking control device of the present invention proposed to solve the above-mentioned problems, a correction coefficient is multiplied by a push-pull signal obtained from a return light of a light beam applied to an optical disk. In the tracking control device for canceling the offset of the tracking error signal generated in accordance with the movement of the objective lens or the movement of the irradiation position of the light beam on the optical disk by subtracting the cancel signal, the moving amount of the objective lens or the optical disk Moving amount signal detecting means for detecting a moving amount signal generated in accordance with the moving amount of the irradiation position of the light beam, and a correction for setting a correction coefficient multiplied by the moving amount signal in accordance with the amplitude of the push-pull signal A coefficient setting means for multiplying the offset component by the set correction coefficient to cancel the signal And cancellation signal generation means for generating, the cancellation signal is characterized in that and a tracking error signal generating means for generating a tracking error signal is subtracted from the push-pull signal.

Further, a tracking control device of the present invention proposed to solve the above-mentioned problem provides a cancel signal multiplied by a correction coefficient from a push-pull signal obtained from return light of a light beam applied to an optical disk. In the tracking control device for canceling the offset of the tracking error signal generated in accordance with the movement of the objective lens or the irradiation position of the light beam on the optical disk by subtracting, the amount of movement of the objective lens or the light beam on the optical disk Moving amount signal detecting means for detecting a moving amount signal generated in accordance with the moving amount of the irradiation position; correction coefficient setting means for setting a correction coefficient by which the offset component is multiplied in accordance with the amplitude of the track wobble signal; A cancellation signal is generated by multiplying the movement amount signal by the correction coefficient set above. And cancellation signal generation means, characterized in that and a tracking error signal generating means for generating a tracking error signal by subtracting the canceling signal from the push-pull signal.

Further, the tracking control method of the present invention proposed to solve the above-mentioned problem provides a tracking control method of the present invention in which a push-pull signal obtained from a return light of a light beam applied to an optical disc is used to convert a cancel signal multiplied by a correction coefficient. In the tracking control method for canceling the offset of the tracking error signal generated by the movement of the objective lens or the irradiation position of the light beam on the optical disk by subtracting, the amount of movement of the objective lens or the light beam on the optical disk A movement amount signal detection step of detecting a movement amount signal generated according to the movement amount of the irradiation position, and a correction coefficient setting step of setting a correction coefficient multiplied by the offset component according to the amplitude of the push-pull signal, The offset signal is multiplied by the correction coefficient set above to generate a cancel signal. And cancellation signal generation step of, is characterized in that it has a tracking error signal generating step of generating a tracking error signal by subtracting the canceling signal from the normalized push-pull signal.

Further, the tracking control method according to the present invention proposed to solve the above-mentioned problem provides a cancel signal multiplied by a correction coefficient from a push-pull signal obtained from return light of a light beam applied to an optical disk. In the tracking control method for canceling the offset of the tracking error signal generated by the movement of the objective lens or the irradiation position of the light beam on the optical disk by subtracting, the amount of movement of the objective lens or the light beam on the optical disk A movement amount signal detection step of detecting a movement amount signal generated according to the movement amount of the irradiation position, and a correction coefficient setting step of setting a correction coefficient multiplied by the movement amount signal in accordance with the amplitude of the track wobble signal, The offset signal is multiplied by the set correction coefficient to generate a cancel signal. And cancellation signal generation step, is characterized in that it has a tracking error signal generating step of generating a tracking error signal by subtracting the canceling signal from the push-pull signal.

According to the present invention described above, it is possible to provide a tracking control device and a tracking control method capable of improving the reliability of tracking servo with respect to variation in characteristics of an optical disk.

[0031]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a tracking control device and a tracking control method according to the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a configuration example of a main part of a tracking control device according to an embodiment of the present invention.

This tracking control device performs a tracking control by extracting a push-pull signal from the return light from the optical disk.

The input terminals 11 and 12 receive the E signal and the F signal from the optical pickup. Then, the difference signal (E−F) is generated by the subtraction amplifier 13, and the sum signal (E + F) is generated by the addition amplifier 14.

Then, the division circuit 20 outputs the signal (EF)
Is divided by the signal (E + F), and the resulting signal (E−
F) / (E + F) is sent to the signal amplitude detection circuit 30.

Here, the above signal (EF) is a signal corresponding to the push-pull signal PP obtained by differentially detecting the return light from the optical disk by the light receiving element having the divided light receiving surface. , A signal obtained by dividing this by a sum signal (E + F)
(E−F) / (E + F) corresponds to the standardized push-pull signal NPP.

The signal amplitude detection circuit 30 detects the amplitude of the standardized push-pull signal NPP from the division circuit 20. A specific circuit example for this will be described later. The amplitude detection signal (amplitude value) from the signal amplitude detection circuit 30 is converted into a digital signal by the A / D conversion circuit 40 and sent to the coefficient calculation circuit 50.

The coefficient calculation circuit 50 is for setting a coefficient (gain) K of the tracking servo system in accordance with the amplitude of the standardized push-pull signal NPP. Send control information.
The coefficient calculation circuit 50 is configured by a microcomputer or the like.

On the other hand, as described above, in the tracking control using the push-pull signal PP, the offset component generated in the push-pull signal PP is canceled according to the movement amount of the objective lens of the optical pickup or the movement amount of the light spot on the optical disk. Otherwise, there is a problem that tracking control cannot be performed correctly.

For this reason, a moving amount signal corresponding to the moving amount of the objective lens or the moving amount of the light spot on the optical disk is represented by:
A signal for canceling the offset by multiplying by an appropriate correction coefficient (hereinafter, simply referred to as a cancel signal).
Needs to be generated.

The top hold circuits 65 and 66 and the subtraction amplifier 70 are parts that generate this movement amount signal.

The peak level of the E signal input from the input terminal 11 is held by the top hold circuit 65.
Similarly, the peak level of the F signal input from the input terminal 12 is held by the top hold circuit 66. Then, the top hold value of the E signal and the top hold value of the F signal are subtracted by the subtraction amplifier 70 to obtain a movement amount signal CSL for generating a cancel signal. It should be noted that the movement amount signal CSL does not indicate the deviation itself between the track and the light spot on the optical disk.

The multiplication amplifier 80 multiplies the movement amount signal CSL by the servo coefficient K set by the coefficient value calculation circuit 50 and sends the multiplied signal to the subtraction amplifier 90.

On the other hand, the subtraction amplifier 71 subtracts the E signal and the F signal to generate a signal (EF) corresponding to the push-pull signal PP.

Then, the displacement signal CSL multiplied by the servo coefficient K is subtracted from the push-pull signal PP by the subtraction amplifier 90, and is output as a so-called top hold push-pull (TPP) signal.

FIG. 2 schematically shows the top hold push-pull signal TPP. That is, the E signal and the F signal are signals in which the peak level is held constant. When the optical disk is, for example, a compact disk (CD), the intensity of the return light from the mirror surface on which no recording pit is formed becomes maximum, giving a top level.

FIG. 3 shows a standardized push-pull signal N
1 shows an example of a signal amplitude detection circuit 30 for detecting the amplitude of PP.

In this signal amplitude detection circuit, the push-pull signal PP from the optical pickup = {(i + j)-(k + 1)}
And the sum signal (i + j + k + 1). As described above, the push-pull signal PP corresponds to the signal (E−F), and the sum signal corresponds to the signal (E + F).

In the division circuit 20, the signal {(i + j)-(k + 1)} from the subtraction amplifier 13 is divided by the signal (i + j + k + 1) from the addition amplifier 14, and the standardized push-pull signal NPP = {(I + j)-(k + 1)} / (i + j +
k + 1) is sent to the top hold circuit 32 and the bottom hold circuit 33.

Then, the top value held by the top hold circuit 32 and the bottom value held by the bottom hold circuit 33 are subtracted by the subtraction amplifier 34 to obtain D
The signal is sent to the C level detection circuit 35.

The DC level detection circuit 35 detects a DC level corresponding to the amplitude of the standardized push-pull signal NPP from the difference signal between the top hold value and the bottom hold value of the NPP signal from the subtraction amplifier 34. Is done. Note that this DC level detection circuit is configured by an analog / digital conversion circuit or the like, and the measured value is temporarily stored in a semiconductor memory or the like.

The signal amplitude detection circuit 30 as described above
Alternatively, the standardized push-pull signal NPP may be converted from analog to digital to measure the difference between the average value of the peak value and the bottom value of the signal.

FIG. 4 shows a top hold circuit 32 and a bottom hold circuit 33 in the signal amplitude detection circuit of FIG.
Is shown.

FIG. 4A shows an example of a top hold circuit. Standardized push-pull signal NPP
Is input from the terminal 38 and charges the capacitor C1 via the resistor R1 and the diode D1 arranged in the forward direction.
At this time, the capacitance C1 is the maximum (peak) of the NPP signal PP.
The NPP signal is charged to the voltage, and the voltage between both ends is held at the peak value of the amplitude of the NPP signal.

By inputting the voltage between both ends of the capacitor C 1 to the operational amplifier 45, N
An output corresponding to the maximum amplitude of the PP signal is obtained from the terminal 39.

Here, the diode D1 viewed from the capacitance C1
And the input impedance of the operational amplifier 45 are both sufficiently large, the electric charge held in the capacitor C1 is discharged via the resistor R2 connected in parallel with the capacitor C1. Therefore, the resistance R1 and the capacitance C1
The time constant given as the product C1 · R2 of the resistance R2 and
It is determined to be appropriate for the frequency of the input NPP signal.

FIG. 4B shows an example of a bottom hold circuit. This configuration is similar to the configuration of the top hold circuit described above, but the direction of the diode D2 is opposite to that of the top hold circuit.

That is, the terminal 3 to which the NPP signal is input
8, a capacitor C2 is connected via a resistor R3 and a diode D2 arranged in the opposite direction. When the voltage of the push-pull signal PP input to the terminal 38 is lower than the voltage across the capacitor C2, Capacitance C2 is diode D2
And discharge through the resistor R3. Therefore, the voltage across the capacitor C2 is held at the bottom value of the amplitude of the NPP signal. By inputting the voltage between both ends of the capacitor C2 to the operational amplifier 46, an output corresponding to the minimum amplitude of the push-pull signal PP input from the terminal 38 is obtained from the terminal 41.

The top hold characteristic and the bottom hold characteristic of the above circuit are selected so as to be optimal for detecting the amplitude of the push-pull signal or the track wobble signal obtained by each optical disk and each optical pickup.

Next, the standardized push-pull signal NP
Another configuration example of the signal amplitude detection circuit 30 for detecting the amplitude of P will be described.

FIG. 5 shows a standardized push-pull signal N
10 shows another configuration example of the signal amplitude detection circuit 30 for detecting the amplitude of PP.

In this circuit, the DC component of the push-pull signal NPP standardized by the division circuit 20 is removed by the DC removal circuit 36. And the top hold circuit 33
Is doubled by the operational amplifier 37 to obtain an amplitude value by the DC level detection circuit 35.

As described above, without using the top hold circuit and the bottom hold circuit, the top hold value 2
The amplitude of the NPP signal may be obtained by multiplication.

FIG. 6 shows a configuration example of the DC removing circuit 36 used in the signal amplitude detecting circuit described above.

The standardized push-pull signal NPP is
The DC component is input from the terminal 42 and blocked by the capacitor C3. Then, the voltage at one end is input to the operational amplifier 47 via the resistor R5. As a result, a standardized push-pull signal NPP from which the DC component has been removed and multiplied by a predetermined gain is output from the terminal 43.

The characteristics of the DC component removing circuit are selected so as to be optimal for detecting the amplitude of the push-pull signal or the track wobble signal obtained by each optical disk and each optical pickup.

Although the DC removing circuit constituting the high-pass filter is illustrated here, a band-pass type having a characteristic of passing a push-pull signal PP or a track wobble signal component TW described later is also used. Filters can also be used.

Next, another embodiment of the tracking device of the present invention will be described.

FIG. 7 is a block diagram showing another example of the configuration of the main part of the tracking control device as one embodiment of the present invention.

This tracking control device detects a push-pull signal PP from return light from an optical disk having a guide groove formed in a meandering shape on the optical disk, removes the offset of the push-pull signal PP, and generates a tracking error signal. It was made to get.

The input terminals 111 and 112 receive an E signal and an F signal from an optical pickup.
Then, the difference signal (E−
F) is generated, and the sum signal (E + F) is generated in the addition amplifier 114.

The dividing circuit 120 outputs the signal (E-
F) is divided by the signal (E + F), and the resulting signal is a standardized push-pull signal (EF) / (E +
F) to the signal amplitude detection circuit 130. Here, the signal obtained by differentially detecting the track wobble signal TW is:
This corresponds to a push-pull signal.

The signal amplitude detection circuit 130 includes the division circuit 12
The amplitude of the track wobble signal TW from 0 is detected.
As the signal amplitude detection circuit 130, a circuit similar to that shown as a specific example of the signal amplitude circuit 30 described above can be used. The amplitude value from the signal amplitude detection circuit 130 is converted into a digital signal by the A / D conversion circuit 140 and sent to the coefficient calculation circuit 150.

The coefficient calculation circuit 150 is for controlling the coefficient Kw of the tracking servo system according to the amplitude of the track wobble signal TW, and sends coefficient (gain) control information to a gain control amplifier 180 described later. The coefficient calculation circuit 150 is configured by a microcomputer or the like.

On the other hand, as described above, in the tracking control based on the push-pull method in the one-beam method, the push-pull method is performed by using a movement amount signal corresponding to the movement amount of the objective lens 123 or the light spot 224 on the optical disk 200. It is necessary to cancel the offset of the pull signal.

The band pass filters 163 and 164,
Top hold circuits 165 and 166, subtraction amplifier 1
Reference numeral 70 denotes a portion for generating the movement amount signal.

The signal a input from the input terminal 161 is
The signal is sent to the top hold circuit 165 via the band pass filter 163, and the peak level is held. Similarly, the d signal input from the input terminal 162 is sent to the top hold circuit 166 via the band pass filter 164, and is held at the peak level. Then, the top hold values from the top hold circuits 165 and 166 are subtracted by the subtraction amplifier 170 to obtain a movement amount signal CSL for generating a cancel signal. The signals a and d are track wobble signals from the light receiving area a and the light receiving area d at both ends of the photodetector whose light receiving surface is divided into four, and are signals from the optical disc on which the wobble track of the optical disc is formed. This is a signal obtained by differentially detecting the return light.

Further, the above-described band-pass filter 163,
The center frequency of the pass band 164 is set to about 22 kHz, which is the wobbling frequency of the track of the optical disc.

Then, the a signal top-held from the top hold circuit 165 by the subtracting amplifier 170 and
The top-held d signal from the top hold circuit 166 is subtracted from the top-held d signal to generate a movement amount signal CSL. Note that, as described above, the movement amount signal CSL
Does not represent the deviation itself between the track and the light spot on the optical disk.

The gain control amplifier 180 multiplies the movement amount signal CSL by the servo coefficient Kw set by the coefficient value calculation circuit 150 and sends the result to the subtraction amplifier 190.

Then, the displacement signal CSL multiplied by the servo coefficient Kw is subtracted from the push-pull signal by the subtraction amplifier 190, and is output as a push-pull signal WPP corresponding to the wobble amplitude of the track.

FIG. 8 schematically shows the shape of a wobble track formed on an optical disk.

The track (wobble track) 3 of the optical disc 300 formed by meandering (wobble) the guide groove.
The push-pull signal PP can be obtained by modulating the intensity of the return light of the light spot 224 irradiated on 01 according to the wobble.

Such a wobble track is, for example,
Used for recordable magneto-optical disks. As a specific example, there is a magneto-optical disk having a diameter of 64 mm and a wobble frequency of 22 kHz, a track pitch of 1.6 μm and a wobble amplitude of 0.03 μm as described above. By forming this wobble track,
An address of a signal to be recorded / reproduced can be formed on an optical disk.

FIG. 9 shows an example of the amplitude detection circuit 130 for detecting the amplitude of the track wobble signal TW.

The amplitude detection circuit 130 is the same as the amplitude detection circuit 30 described above, except that the track wobble signal T obtained by differentially detecting the return light from the wobble track is used.
The difference is that a push-pull signal is obtained as W.

The signal amplitude detection circuit 130 has a push-pull signal {(i + j)-(k + 1)} from the optical pickup.
And the sum signal (i + j + k + 1). This push-pull signal corresponds to the signal (E−F), and the sum signal corresponds to the signal (E + F).

In the division circuit 120, the signal {(i + j) − (k + 1)} from the subtraction amplifier 113 is divided by the signal (i + j + k + 1) from the addition amplifier 114, and the resulting ｛(i + j)
− (K + 1)｝ / (i + j + k + 1) is the top hold circuit 13
2 and the bottom hold circuit 133.

Then, the top value held by the top hold circuit 132 and the bottom value held by the bottom hold circuit 133 are subtracted by the subtraction amplifier 134.

Then, the track wobble signal TW
Is sent to a DC level detection circuit 135, and a DC level corresponding to the amplitude is detected.

FIG. 10 shows another example of the signal amplitude detection circuit 130 for detecting the amplitude of the track wobble signal TW.

In this circuit, the DC of the push-pull signal from the wobble track standardized by the division circuit 120 is
The components are removed by the DC removal circuit 136. And
The value held by the top hold circuit 133 is
The amplitude value is obtained by the DC level detection circuit 135 by doubling it by the operational amplifier 137. As described above, the amplitude of the track wobble signal TW may be obtained by doubling the top hold value without using the top hold circuit and the bottom hold circuit.

Next, an embodiment of the tracking control method of the present invention will be described.

In the above-described tracking control device according to the present invention, the servo coefficient K set so as to be optimal for each optical disk is, for example, a push-pull signal NPP standardized by the total amount of light incident on the photodetector 225. Is a function of the amplitude value.

This standardized push-pull signal NPP
Is given by the following equation (3).

NPP = {(i + j) + (k + 1)} / (i + j + k + 1) (3) The optimum tracking error signal TE is given by the following equation (4) or (5).

TE = (i + j) + (k + 1)｝ − K (NPP) × CSL (4) TE = (i + j) + (k + 1)｝ / (i + j + k + 1) −K (NPP) × CSL (5) That is, the optical disk In order to obtain the best tracking error signal TE every time, the NPP value should be obtained for each optical disk.

As described above, the detection of the amplitude value of the standardized push-pull signal NPP is performed by comparing the top level and the bottom level of the standardized push-pull signal NPP with no tracking servo applied. It can be obtained as a differential value of the held signal or from a value obtained by holding the top level of the signal after removing the DC component from the standardized push-pull signal NPP.

On the other hand, in an optical disk on which a wobble track is formed, the tracking servo coefficient Kw can be obtained with the tracking servo applied.

The wobble track signal TW is given by the following equation (6).

Tw = {(i + j) + (k + 1)} / (i + j + k + 1) (6) Further, since the coefficient Kw of the best tracking servo for each optical disc is a function value of the wobble track signal TW,
Best tracking error signal TE for optical disc
Is calculated by the following equation (7) or (8).

TE = {(i + j) + (k + 1)} − TW (Tw) × CSL (7) TE = {(i + j) + (k + 1)} / (i + j + k + 1) −TW (Tw) × CSL (8) FIG. FIG. 11 is a functional block diagram showing a main signal flow when performing tracking control by the above-described tracking control method according to the present invention.

First, the amplitude of the push-pull signal PP or the amplitude of the wobble track signal TW obtained from the optical disk is obtained by the signal amplitude detecting means 230.

The amplitude values are converted into digital signals by analog / digital (A / D) conversion means 240,
It is taken into the microcomputer 250.

This microcomputer 250 is a means for calculating the coefficient K or Kw of the tracking servo, and calculates the amplitude value of the push-pull signal PP or the wobble track signal TW input through the A / D conversion means 240. In accordance with the amplitude value, a multiplier 280 described later is controlled by the gain control signal. The above amplitude value and the coefficient value K (Kw) of the tracking servo calculated by the microcomputer 250 are values obtained for each optical disk, and are stored in the memory 255 at least until the optical disk is replaced. Will be retained. Note that the servo coefficient obtained here may be held by a level hold circuit, and an instruction may be issued to the servo circuit. The value of the held servo coefficient is not changed or updated unless instructed by a microcomputer or the like.

Note that K is a function for calculating the best servo coefficient K for tracking by the one-beam method.
Since (NPP) or Kw (Tw) exists for each type of optical disc and for each time of reproduction / recording, a plurality of functions are configured by an electric circuit or software.

The multiplier 280 is provided by the microcomputer 2
The CSL signal is multiplied by a servo coefficient value K (NPP) or Kw (TW) in accordance with the gain control signal from F.50. As described above, the CSL signal is a signal corresponding to the amount of movement of the objective lens of the optical pickup or the amount of movement of the light spot on the optical disk.

Then, the CSL obtained by multiplying the push-pull signal PP by the value of the servo coefficient is subtracted by the subtractor 290.
The signal is subtracted and output as a tracking error signal 290.

FIG. 12 is an example of a function representing a change in the Kw value with respect to the amplitude value of the standardized push-pull signal NPP.

As described above, the value of the servo coefficient K changes according to the amplitude value of the standardized push-pull signal NPP.

FIG. 13 is a flowchart showing a basic processing procedure for controlling the servo coefficient K using the standardized push-pull signal NPP by the tracking control method according to the present invention.

First, in step S1, the focus servo is turned on, and the light beam irradiated on the optical disk is
It is made to focus on the signal surface of the optical disc. At this time, the tracking servo is not turned on, and the light spot whose focus is controlled on the optical disk does not yet follow the track.

Next, in step S2, the amplitude of the standardized push-pull signal NPP is detected. Here, as described above, a method of A / D converting a level hold signal using a level hold circuit such as a top hold circuit or a bottom hold circuit and then binarizing the signal, or a method of converting a standardized push-pull signal NPP to an A / D signal. For example, a method of detecting from the binarized signal value after the / D conversion is used.

Next, in step S3, a servo coefficient K for obtaining an optimum tracking signal TE is calculated from the detected amplitude value of the standardized push-pull signal NPP. Here, the optimal tracking signal TE has the smallest track deviation with respect to the difference between the optical pickup, the optical disk, the tracking control method, and the environment in which the signal is recorded / reproduced on or from another optical disk. This is a tracking error signal. Then, the servo coefficient K is obtained by performing an operation by a microcomputer, an arithmetic processor, or the like using the previously obtained function as described above. Note that the above function is
The optimum coefficient value for the amplitude value of the standardized push-pull signal NPP can be obtained in advance by measurement, simulation of an optical system, or the like.

Next, in step S4, the calculated servo coefficient value K is multiplied by the CSL signal. As described above, the CSL signal is a signal corresponding to the amount of movement of the objective lens of the optical pickup or the amount of movement of the light spot on the optical disk. This multiplication is performed by passing the CSL signal through an operational amplifier and controlling the amplifier gain corresponding to the value of the servo coefficient from a microcomputer or the like.

In step S5, the CSL signal multiplied (multiplied by K) by the value K of the servo coefficient is subtracted from the push-pull signal PP, and is normalized to obtain the optimum tracking error signal TE. Push-pull signal N
A PP is generated. Here, the polarity of the K-folded CSL signal is the push-pull signal PP when the objective lens is moved.
, And cancels the offset of the push-pull signal PP when the objective lens is moved.

With the above procedure, the process of setting the tracking servo coefficient by using the amplitude level of the push-pull signal NPP standardized by the total amount of return light from the optical disk is completed.

Next, a basic processing procedure for controlling the servo coefficient Kw using the amplitude of the wobble track signal by the tracking control method according to the present invention will be described.

FIG. 14 is a flowchart showing a basic processing procedure for controlling the servo coefficient Kw using the wobble track signal TW by the tracking control method according to the present invention.

First, in step S11, the focus servo is turned on, so that the light beam irradiated on the optical disk is focused on the signal surface of the optical disk. At this time, the tracking servo is not turned on, and the light spot whose focus is controlled on the optical disk does not yet follow the track.

Next, in step S12, the tracking servo is turned on, and the light spot on the optical disc, which is under focus control, is controlled so as to follow the track. At this time, the tracking servo is applied using the push-pull signal PP or the WPP signal or the TPP signal in which the value of the temporary servo coefficient is set.

Next, in step S13, the amplitude of the wobble track signal WT is detected by a push-pull signal operation in a state where tracking control is performed. Here, as described above, a method of A / D converting a level hold signal using a level hold circuit such as a top hold circuit or a bottom hold circuit and then binarizing the signal, or a method of converting a standardized push-pull signal NPP to an A / D signal. A method is used in which detection is performed from the binarized signal value after the / D conversion.

Next, in step S14, a servo coefficient Kw for obtaining an optimal tracking signal TE is calculated from the detected amplitude value of the wobble track signal TW. Here, the optimum tracking signal TE has the smallest track deviation with respect to the difference between the optical pickup, the optical disk, the tracking control method, and the like, and the environment in which the signal is recorded / reproduced on another optical disk. This is a tracking error signal. The servo coefficient Kw is obtained by performing an operation by a microcomputer, an arithmetic processor, or the like using a function obtained in advance. Note that the above function can be obtained by measuring the optimum coefficient value for the amplitude value of the wobble track signal TW in advance, or simulating an optical system.

Next, in step S15, the calculated servo coefficient value Kw is multiplied by the CSL signal. This CSL
As described above, the signal is a signal corresponding to the movement amount of the objective lens of the optical pickup or the movement amount of the light spot on the optical disk. This multiplication is performed by passing the CSL signal through an operational amplifier and controlling the amplifier gain corresponding to the value of the servo coefficient from a microcomputer or the like.

Then, in step S16, the CSL signal multiplied (multiplied by Kw) by the servo coefficient value Kw is subtracted from the push-pull signal PP, and the push-pull signal WPP for obtaining the optimum tracking error signal TE is obtained. Is generated. Here, the polarity of the CSL signal multiplied by Kw is the same as the polarity of the offset of the push-pull signal when the objective lens is moved, and the offset of the push-pull signal when the objective lens is moved is cancelled.

With the above procedure, the process of setting the tracking servo coefficient using the amplitude level of the wobble track signal ends.

In the embodiment of the present invention described above, the case where tracking control is performed using the photodetector 225 in the optical system illustrated in FIG. 16 has been described. A similar effect can be obtained by using a light receiving means in which a photodetector is arranged so as to divide a once-diffracted light distribution of a light spot reflected by an optical disc into two, like the photodetectors 213 and 215. Can also. It should be noted that the angle formed by the direction of division of the light receiving surfaces of these photodetectors and the tracks on the optical disk is not necessarily parallel, and it operates sufficiently from parallel to an angle of about 45 degrees.

[0128]

According to the present invention, the value of the servo coefficient to be multiplied as the correction coefficient by the cancellation signal for canceling the offset component of the push-pull signal is changed to the normalized amplitude of the push-pull signal NPP or the wobble track signal. Is set adaptively in accordance with the amplitude of the data, it is possible to improve the accuracy and reliability of the servo with respect to the characteristic variation of each optical disc in the one-beam method, and to simplify the setting of the tracking servo coefficient. A tracking control device and a tracking control method that can be provided.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration example of a tracking control device according to the present invention.

FIG. 2 is a diagram illustrating a TPP signal.

FIG. 3 is a diagram illustrating an example of a signal amplitude detection circuit for detecting the amplitude of a standardized push-pull signal NPP.

FIG. 4 is a diagram illustrating an example of a top hold circuit and a bottom hold circuit used in the signal amplitude detection circuit.

FIG. 5 is a diagram showing another configuration example of a signal amplitude detection circuit for detecting the amplitude of a standardized push-pull signal NPP.

FIG. 6 is a diagram illustrating an example of a DC removal circuit of the signal detection circuit.

FIG. 7 is a block diagram illustrating another configuration example of the tracking control device according to the present invention.

FIG. 8 is a diagram for explaining a wobble track.

FIG. 9 is a diagram showing an example of an amplitude detection circuit for detecting the amplitude of a wobble track signal.

FIG. 10 is a diagram showing another example of the signal amplitude detection circuit for detecting the amplitude of the wobble track signal TW.

FIG. 11 is a functional block diagram of a tracking control device to which the tracking control method according to the present invention is applied.

FIG. 12 is a diagram illustrating an example of a function representing a change in a value of a servo coefficient K with respect to an amplitude value of a standardized push-pull signal NPP.

FIG. 13 shows a tracking control method according to the present invention;
9 is a flowchart illustrating a basic processing procedure for controlling the value of a servo coefficient K using a standardized push-pull signal NPP.

FIG. 14 shows a tracking control method according to the present invention.
9 is a flowchart illustrating a basic processing procedure for controlling the value of a servo coefficient K using a wobble track signal TW.

FIG. 15 is a diagram showing an example of an optical system of an optical pickup in which a tracking error signal is obtained by a one-beam method.

FIG. 16 is a diagram for describing a configuration of a light receiving surface of a photodetector used in the above optical system.

[Explanation of symbols]

11, 12 input terminals, 13 subtraction amplifier, 14
Addition amplifier, 20 division circuit, 30 signal amplitude detection circuit, 40 A / D conversion circuit, 50 count value calculation circuit, 65, 66 top hold circuit, 70, 71
Subtraction amplifier, 80 multiplication amplifier, 90 subtraction amplifier,
99 output terminal

Claims (17)

[Claims] 1. A method of moving an objective lens or an irradiation position of a light beam on an optical disc by subtracting a cancel signal multiplied by a correction coefficient from a push-pull signal obtained from return light of a light beam applied to the optical disc. In a tracking control device for canceling an offset of a tracking error signal generated in accordance with the movement of the optical disk, a movement amount for detecting a movement amount signal generated in accordance with a movement amount of the objective lens or a light beam irradiation position on the optical disk. Signal detection means, a correction coefficient setting means for setting a correction coefficient to be multiplied by the movement amount signal in accordance with the amplitude of the push-pull signal, and a cancellation signal by multiplying the offset component by the correction coefficient to be set. Cancel signal generating means for generating, and the push-pull signal for the cancel signal Tracking control apparatus characterized by comprising a tracking error signal generating means for generating a tracking error signal by subtracting al. 2. A push-pull signal normalizing means for normalizing the push-pull signal by dividing the push-pull signal by a total signal according to the total amount of light incident on the photodetector for detecting the return light, and setting the correction coefficient 2. The tracking control device according to claim 1, wherein the means sets the correction coefficient in accordance with the amplitude of the standardized push-pull signal. 3. The tracking control device according to claim 2, wherein the correction coefficient setting means sets the correction coefficient as a function value having the amplitude of the standardized push-pull signal as a variable. 4. The push-pull signal normalizing means according to claim 1, wherein the change in the amount of return light generated when the irradiated light beam crosses a track on the optical disk is divided into two or more light receiving surfaces in the track direction. 3. The tracking control according to claim 2, wherein the standardized push-pull signal is obtained by dividing a push-pull signal obtained by detection by a photodetector having the following by a sum signal from the photodetector. apparatus. 5. The push-pull signal normalizing means according to claim 1, wherein the change in the amount of return light generated when the irradiated light beam crosses a track on the optical disk is divided into two or more light receiving surfaces in the track direction. The push-pull signal obtained by differential detection by the photodetector having the above is divided by the sum signal of the return light from the mirror surface of the optical disc held in advance from the detector and standardized by dividing the push-pull signal. 3. The tracking control device according to claim 2, wherein a simplified push-pull signal is obtained. 6. The tracking control device according to claim 1, wherein the correction coefficient setting means includes signal amplitude detection means for detecting the amplitude of the push-pull signal by top-holding and bottom-holding the push-pull signal. . 7. The correction coefficient setting means detects the amplitude of the push-pull signal from the average value of the peak value and the average value of the bottom value of the signal after analog-digital conversion of the push-pull signal. The tracking control device according to claim 1, wherein: 8. A movement of an objective lens or an irradiation position of a light beam on an optical disk by subtracting a cancel signal multiplied by a correction coefficient from a push-pull signal obtained from return light of a light beam applied to the optical disk. In a tracking control device for canceling an offset of a tracking error signal generated in accordance with the movement of the optical disk, a movement amount for detecting a movement amount signal generated in accordance with a movement amount of the objective lens or a light beam irradiation position on the optical disk. Signal detection means; correction coefficient setting means for setting a correction coefficient to be multiplied by the offset component according to the amplitude of the track wobble signal; and a cancel signal is generated by multiplying the movement amount signal by the correction coefficient to be set. Cancel signal generating means for executing the cancel signal from the push-pull signal. Tracking control apparatus characterized by comprising a tracking error signal generating means for generating a tracking error signal by subtracting the. 9. The tracking control device according to claim 8, wherein the correction coefficient setting means sets the correction coefficient as a function value having the amplitude of the track wobble signal as a variable. 10. The track wobble signal is detected in a state where focus control is performed so that the irradiated light beam is focused on an optical disk and tracking control is performed. The tracking control device according to the above. 11. The tracking control device according to claim 8, wherein said correction coefficient setting means includes signal amplitude detection means for detecting the amplitude of said track wobble signal by top-hold and bottom-hold. . 12. The correction coefficient setting means detects an amplitude of the track wobble signal from an average value of a peak value and an average value of a bottom value of the signal after analog / digital conversion of the track wobble signal. 9. The tracking control device according to claim 8, wherein: 13. A movement of an objective lens or an irradiation position of a light beam on an optical disc by subtracting a cancel signal multiplied by a correction coefficient from a push-pull signal obtained from return light of a light beam applied to the optical disc. In a tracking control method for canceling an offset of a tracking error signal generated according to the movement of the optical disk, a movement amount for detecting a movement amount signal generated according to a movement amount of the objective lens or a light beam irradiation position on the optical disk. A signal detection step, a correction coefficient setting step of setting a correction coefficient to be multiplied by the offset component according to the amplitude of the push-pull signal, and a cancellation signal is generated by multiplying the offset component by the set correction coefficient. Cancel signal generation process to be performed and whether the standardized push-pull signal Tracking control method characterized by comprising a tracking error signal generating step of generating a tracking error signal by subtracting the canceling signal. 14. A push-pull signal normalizing step of dividing the push-pull signal by a total signal according to the total amount of light incident on a photodetector for detecting the return light and normalizing the push-pull signal; 14. The tracking control method according to claim 13, wherein the correction coefficient is set according to the amplitude of the standardized push-pull signal in the setting step. 15. The tracking control method according to claim 13, wherein the correction coefficient is set as a function value having the amplitude of the standardized push-pull signal as a variable. 16. A movement of an objective lens or an irradiation position of a light beam on an optical disc by subtracting a cancel signal multiplied by a correction coefficient from a push-pull signal obtained from return light of a light beam applied to the optical disc. In a tracking control method for canceling an offset of a tracking error signal generated according to the movement of the optical disk, a movement amount for detecting a movement amount signal generated according to a movement amount of the objective lens or a light beam irradiation position on the optical disk. A signal detection step, a correction coefficient setting step of setting a correction coefficient to be multiplied by the movement amount signal in accordance with the amplitude of the track wobble signal, and a cancellation signal is generated by multiplying the offset component by the correction coefficient to be set. A cancel signal generating step for canceling, and the above-described canceling from the push-pull signal. Tracking control method characterized by comprising a tracking error signal generating step of generating a tracking error signal by subtracting the issue. 17. The tracking control method according to claim 16, wherein the correction coefficient is set as a function value having the amplitude of the track wobble signal as a variable.