JP2000020973A - Servo signal processing device and optical disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a servo signal processing device and an optical disk device, permitting to set an optimal TPP coefficient for each disk and to improve tracking servo accuracy. SOLUTION: The operation of a servo signal processing device 1 is controlled by a system controller 100. When the system controller 100 receives a push-pull amplitude(PPA) signal from a tracking error detecting part 30, it generates from a size of this PPA signal, a control signal CONT for determining a TPP coefficient which is used at the time of detecting a tracking error signal TE by a tracking error detecting part 30. The tracking error detecting part 30 determines the TPP coefficient according to the control signal CONT, and multiplies a peak level of an optically detected signal obtained from the returned light from a track by the coefficient.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a servo signal processing device used to accurately follow a light beam of one spot on a track of a disk-shaped recording medium, and an optical disk device provided with the servo signal processing device.

[0002]

2. Description of the Related Art Recording / recording on a so-called optical disk such as a compact disk (CD) or a mini disk (MD).
In a recording / reproducing apparatus for performing reproduction, a three-spot method is mainly used as a tracking servo method for appropriately following a track, in which the amounts of reflected light from two sub-beams arranged with a main beam interposed therebetween are compared. ing. But,
From the viewpoints of simplification, miniaturization and reliability of the apparatus, a push-pull method capable of detecting a tracking error in one spot has attracted attention. The push-pull method utilizes the fact that the intensity distribution of light that is diffracted and reflected by the pits and grooves and re-enters the objective lens changes depending on the relative position between the pits and grooves and the spot. This is a method in which light is received by a plurality of divided photodetectors, and a tracking error is obtained based on the difference in the amount of light received by each photodetector.

In the push-pull method, when the objective lens fluctuates, the spot moves on the photodetector, and a DC offset may occur in the tracking error signal. This DC offset occurs when a pickup having a configuration in which only the objective lens moves is used, or when the disk surface is shifted from the optical axis of the beam by 90 degrees due to disk skew. Therefore, when using the push-pull method, it is necessary to cancel this DC offset. As a method for canceling the DC offset and appropriately detecting the tracking error, for example, the following method is available.

With respect to lens drive and disk skew as described above, the fact that the envelope of the RF signal is slightly modulated is used to detect, in particular, a change in the peak value of the envelope, and the change is determined as a predetermined value. There is a method in which a DC offset is obtained by multiplying by the coefficient of

[0005] This tracking error detection method uses a top hold push-pull (hereinafter referred to as T).
It is called PP. ), Which is a method usually used in a CD reproducing apparatus.

In the above-mentioned TPP method, the offset included in the tracking error signal is obtained by multiplying the top level of the ± 1st-order diffracted light detected by the photodetector from the reflected light of the disk by the coefficient Kt and subtracting it from the original RF signal. Has been canceled.

[0007]

By the way, the above coefficient K
Although t has an optimum value depending on the parameters of the disk originally used, in the above-mentioned conventional TPP method, one coefficient Kt corresponds to all disks, and the offset cannot be completely canceled depending on the disk. Was. For this reason, the conventional TPP method may cause detracking and reduce the accuracy of tracking servo.

The present invention has been made in view of the above problems, and has as its object to provide a servo signal processing device and an optical disk device that can set an optimum coefficient for each disk and improve the accuracy of tracking servo. And

[0009]

In order to solve the above-mentioned problems, a servo signal processing apparatus according to the present invention uses a coefficient for multiplying a peak level of a light detection signal obtained from light returned from a track by a disc-shaped recording medium. A tracking error detecting means for switching according to the push-pull amplitude level obtained from the above, multiplying the peak level, and detecting a tracking error signal from which an offset component caused by relative fluctuation of the objective lens is removed; Servo processing means for performing tracking servo processing based on the tracking error signal from the detection means.

According to another aspect of the present invention, there is provided an optical disk apparatus that irradiates a disk-shaped recording medium with a beam of one spot and receives return light from the disk-shaped recording medium with a split sensor. An optical pickup means for outputting a light detection signal based on the amount of received light, and the disc-shaped recording at the peak level of the light detection signal from the optical pickup means when tracking a track formed by pits. A tracking error detection unit that multiplies a coefficient corresponding to a push-pull amplitude level of a medium to detect a tracking error signal in which an offset component is canceled, and performs tracking servo processing based on the tracking error signal from the tracking error detection unit Servo processing means.

Therefore, according to the present invention, an optimum tracking error signal can be detected for each disk, and an optimum tracking servo can be realized using the tracking error signal.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a servo signal processing device according to the present invention will be described with reference to the drawings. This embodiment is a servo signal processing device 1 as shown in FIG. 1, and is applied when reproducing an optical disc having tracks by pits.

The servo signal processing device 1 calculates the respective light detection signals output by the first photodetector PD1 from the reflected light of the light beam of one spot applied to the optical disk.
A signal combining section 20 for generating a desired signal suitable for input to a tracking error detecting section 30 described later, and a tracking error detecting section for detecting a tracking error signal using the desired signal generated by the signal combining section 20 30
A focusing error detection unit 80 that detects a focusing error signal using each detection signal output by the second photodetector PD2, performs tracking servo processing based on the tracking error signal, and performs focusing based on the focusing error signal. And a servo processing circuit 90 for performing servo processing.

The operation of the servo signal processing device 1 is controlled by a system controller 100. The tracking error detector 30 sends a push-pull amplitude (PPA) signal to the system controller 100.
), A tracking signal detecting section 30 generates a control signal CONT for determining a TPP coefficient used when detecting the tracking error signal TE from the magnitude of the PPA signal.

Here, the tracking error detecting section 30
Is a circuit for detecting the tracking error signal by the push-pull method, and detects the tracking error signal TE based on the signal input via the signal synthesis unit 20. Specifically, the tracking error detection unit 30
A Top Hold Push-Pull (hereinafter, referred to as TPP) method is applied.

The tracking error detecting section 30 receives the first photodetector PD1 from the return light of the light beam of one spot irradiated on the track formed by the pits.
Is detected, and the level of the peak value of the combined light detection signals L and R obtained by combining the signal
The tracking error signal TE in which the offset component is canceled is detected by multiplying by a coefficient switched by the system controller 100 according to the signal.

In FIG. 1, a first photodetector P
D1 is provided in an optical pickup for irradiating the optical disc with one spot of light beam, and diffracted by the optical disc.
The reflected light is detected, and a signal corresponding to the amount of light is output. This first photodetector PD1 has four detectors PD1-A, PD1-B, PD1-C and PD1-D arranged as shown in the figure. Four detectors PD1-A, PD1-
B, two detection units PD among PD1-C and PD1-D
1-A and PD1-B detect the first-order diffracted light reflected on the left side of the data track, and the remaining two detectors PD1-C and PD1-
D detects the -1st-order diffracted light reflected on the right side of the data track. Specifically, the two detectors PD1-A and PD1-B
Are added by the adder 21 in the signal synthesizing section 20 to become a synthesized light detection signal L. Also, 2
The light detection signals C and D detected by the detection units PD1-C and PD1-D are added by an adder 22 in the signal synthesis unit 20 to become a combined light detection signal R.

The principle of the TPP method performed by the tracking error detector 30 will be described with reference to FIG.
FIG. 2 is an RF envelope waveform of the combined light detection signal L corresponding to the amount of all first-order diffracted lights.

In FIG. 2, a waveform P is a peak of a signal L, and a signal S is an LPF (low-pass filter) which indicates an RF envelope used when performing tracking by a push-pull method.
The signal Q after passing through is a waveform indicating a change in the offset of the signal S. In order to cancel the offset due to the lens shift or the disk skew, the offset change q may be subtracted from the signal S. That is, q = Kt ×
If a constant Kt (Kt <1) is determined to be p, the signal from which the offset has been canceled can be represented by S−Kt × p. Therefore, if the peak change p is obtained, the offset value can also be obtained.

In the TPP method, the tracking error signal TE is calculated by performing the calculation shown in the following equation (1).
Cancels the offset component of.

TE = (E−Kt × Etop) − (F−Kt × Ftop) (1) In the equation (1), E and F are transimpedance amplifiers and are output from the signal synthesis unit 20. The composite light detection signal L and the composite light detection signal R are converted into voltage signals. Etop and Ftop are the top levels of E and F. Kt is a TPP coefficient.

The optimum value for the TPP coefficient Kt in the above equation (1) is determined by the conditions of the optical system including the optical disk and the optical pickup. Among these, it is known that the optimum value of Kt varies depending on the condition of the optical disk, particularly due to the difference in the PPA. The PPA is defined as a parameter proportional to the push-pull signal level standardized by the total amount of returned light. The relationship so far is PPA (EF) / (E + F) (2). That is, if the PPA of a certain disk is known, the optimum TPP coefficient Kt for that disk can be predicted.

Therefore, in the tracking error detecting section 30 shown in FIG. 3, two coefficients Kt such as Kt1 and Kt2 are prepared and switched according to the PPA detected by the PPA detecting section. The signal TE is detected.

The tracking error detector 3 shown in FIG.
The portion surrounded by the solid line of 0 or the portion including the dotted line is R
It is configured in an integrated circuit for F signal processing.

A transimpedance amplifier 31 and a transimpedance amplifier 32 for converting the combined light detection signal L and the combined light detection signal R into a voltage signal E and a voltage signal F are provided in the dotted line portion.

The solid line indicates a peak hold circuit 41 for holding the peak value Etop of the voltage signal E, a peak hold circuit 42 for holding the peak value Ftop of the voltage signal F, and a non-inverting input of the peak value Etop. A subtractor 43 that inputs the peak value Ftop to an inverting input terminal and outputs a subtraction result (Etop-Ftop), and Kt1 multiplies the subtraction result (Etop-Ftop) by a first TPP coefficient Kt1. An amplifier 44; a Kt2 amplifier 45 for multiplying the subtraction result (Etop-Ftop) by a second TPP coefficient Kt2;
The result of the subtraction multiplied by Kt1 by the amplifier 44 (Etop-Fto
p) and the subtraction result (Et) multiplied by Kt2 by the Kt2 amplifier 45
op-Ftop) according to a control signal CONT from the system controller 100.
6 and a subtractor 47 for supplying the switching output from the changeover switch 46 to the inverting input terminal and for supplying (EF) described later to the non-inverting input terminal to output the tracking error signal TE. .

The solid line portion is a subtractor 48 for inputting the voltage signal E to a non-inverting input terminal, inputting the voltage signal F to an inverting input terminal and outputting (EF), An adder 49 that adds E to the voltage signal F and outputs (E + F); and a subtraction output (E−F) from a subtractor 48.
Is input to the numerator input terminal, and the addition output (E
+ F) is input to the denominator input terminal, and the division result ((E−F)
/ (E + F)), a peak hold circuit 51 for holding the peak value of the division force, and a bottom hold circuit 52 for holding the bottom value of the division force.
And the peak value from the peak hold circuit 51 ((E−
F) / (E + F)) top is input to the non-inverting input terminal, and the bottom value ((E−F) / (E)
+ F)) There is provided a subtractor 53 for inputting bot to the inverting input terminal and outputting the PPA as a subtraction result. Here, the subtraction output (E-F) from the subtractor 48 is also supplied to the non-inverting input terminal of the subtractor 47. Further, the subtracter 48, the adder 49, the divider 50, the peak hold circuit 51, the bottom hold circuit 52, and the subtractor 53 constitute the PPA detection section.

For example, a servo processing operation performed on a certain optical disk by the servo signal processing device 1 will be described.

The peak hold circuit 41 holds the peak value Etop of the voltage signal E of the combined light detection signal L corresponding to the input light amount of all the first-order diffracted lights. The peak hold circuit 42 holds the peak value Ftop of the voltage signal F of the combined light detection signal R corresponding to the amount of the input all-first order diffracted light. The subtracter 43 subtracts the peak value Ftop from the peak value Etop, and supplies the subtraction result (Etop−Ftop) to the Kt1 amplifier 44 and the Kt2 amplifier 45. The selection terminals of the changeover switch 46 include a Kt1 amplifier 44 and a Kt2 amplifier 45.
Multiplied outputs Kt1 (Etop-Ftop) and Kt2 (Etop
-Ftop).

On the other hand, the divider 50 divides the subtraction output (E−F) of the subtractor 48 by the addition output (E + F) of the adder 49 ((E−F) / (E + F)) to obtain a peak hold circuit 51. And to the bottom hold circuit 52. Subtractor 5
3 is the hold output of the peak hold circuit 51 ((E−
The hold output ((E−F) / (E + F)) bot of the bottom hold circuit 52 is subtracted from F) / (E + F)) top, and the above PPA is calculated as PPA = ((E−F) / (E + F)) top − ((E−F) / (E + F)) bot (3) is output.

The PPA signal obtained by the above equation (3) is supplied to the system controller 100 shown in FIG. That is, the system controller 100 first turns on the focus servo processing by the servo processing circuit 90, and then uses the PPA signal supplied from the tracking error detection unit 30 to generate the TPP coefficient Kt1 or Kt2.
The control signal CONT for switching the changeover switch 46 is supplied to the tracking error detection unit 30. Then, the changeover switch 46
Selects (Etop-Ftop) multiplied by Kt1 or Kt2 and supplies it to the subtractor 47.

For example, if the use of the coefficient Kt1 is determined by the system controller 100, Kt1 (Etop-Ftop)
Is supplied to the inverting input terminal of the subtractor 47, and the result of subtraction from (EF) supplied to the non-inverting input terminal is output as the tracking error signal TE shown in the following equation (4).

TE = (E−F) −Kt 1 (Etop−Ftop) (4) Also, for example, when it is determined that Kt2 is to be used, the subtracter 47 shows the subtraction result in the following equation (5). Output as tracking error signal TE.

TE = (E−F) −Kt 2 (Etop−Ftop) (5) The above is the description of the tracking error detection unit 30. However, in the servo signal processing device 1, the focusing error detection unit 80 Have. In the following description,
The conversion process to the voltage signal by the transimpedance amplifier is omitted.

The focusing error detecting section 80 has the second
Of the photodetector PD2 from the detector PD2-X1 and the detector PD2-Y based on the combined detection signal X from the detector PD2-X2.
Subtracter 81 for subtracting the detection signal Y from the above, and an operational amplifier 82 for calculating (A + D)-(B + C) using the above-mentioned light detection signal A, light detection signal B, light detection signal C and light detection signal D.
And a subtracter 83 for subtracting the output result of the operational amplifier 81 from the output result of the operational amplifier 82, and finally outputs a focus error signal FE represented by the following equation (6).

FE = {(A + D) − (B + C)} − (XY) (6) Further, the servo processing circuit 90 includes the A / D converter 91 and the DS
And a focus servo processing signal and a tracking servo processing signal based on the focusing error signal FE, the tracking error signal TE, and the synthesized light detection signal Ig.

Therefore, the servo signal processing device 1
Can set the optimum TPP coefficient for each optical disc in accordance with the PPA, thereby improving the accuracy of the tracking servo.

Next, a modification of the above embodiment will be described. This modification is a servo signal processing device in which the tracking error detection unit 30 shown in FIG. 3 in the servo signal processing device 1 shown in FIG. 1 is replaced with the tracking error detection unit 30 shown in FIG.

The tracking error detector 30 shown in FIG. 3 uses two fixed gain amplifiers, ie, a Kt1 amplifier 44 and a Kt2 amplifier 45, and switches the output with a changeover switch 46. It uses one variable gain amplifier, namely a variable Kt amplifier 55, instead of two fixed gain amplifiers as shown in FIG. By using the variable Kt amplifier 55, any number of coefficients can be set without being fixed to two types.

The P-type P having the same configuration as that of the PPA detector of FIG.
When the PPA signal of the disk detected by the PA detection unit is sent to the system controller 100, the system controller 1
00 is a gain control signal CO according to the PPA signal.
NT is generated, and the variable gain of the variable Kt amplifier 55 is set.

Specifically, the system controller 100
First, the focus servo processing by the servo processing circuit 90 is turned on, and then the tracking error detection unit 30 is turned on.
A gain control signal CONT for the TPP coefficient Kt is generated by using the PPA signal supplied from the controller, and the variable gain of the variable Kt amplifier 55 is set. Then, the subtractor 47 outputs Kt (Etop-Ftop) as a tracking error signal.

Therefore, the servo signal processing device 1 of this modification can set the optimum TPP coefficient Kt for each disk, and can improve the accuracy of the tracking servo.

Note that the above two servo signal processing devices are:
Although it has been described that the voltage signals E and F are configured in an integrated circuit for RF processing, the above operations may be entirely performed by digital signal processing (DSP). By converting all TPP operations to DSP, the number of analog circuits is greatly reduced, and the cost and power consumption of the entire disc reproducing system can be reduced.

Further, the shape, arrangement, and the like of each detection unit of the first photodetector PD1 are not limited to the above-described four divisions, but may be a division sensor having an arbitrary configuration. The same applies to the second photodetector PD2.

Next, another embodiment of the servo signal processing device according to the present invention will be described with reference to the drawings.

Another embodiment is a servo signal processing device 60 shown in FIG. 5, which includes a read-only optical disk having a pit track and a wobble-like track in which the boundary between a pre-groove and a land is wobbled. Can be applied to both recording / reproducing type optical discs partially having

This servo signal processing device 60 differs from the servo signal processing device 1 in that the RF signal processing circuit 6
1 is a configuration of a tracking error detection unit 62 inside.

As shown in FIG. 6, the tracking error detecting section 62 includes three tracking error detecting circuits, that is, a TPP section 105, a wobble push-pull (Wobble P
ush-Pull, hereafter referred to as WPP. ) WPP section 110, track-on section 125, and their changeover switch 65
And 66.

The TPP section 105 has the same configuration as the tracking error detection section 30 shown in FIG. In addition,
Here, the conversion process to the voltage signal by the transimpedance amplifier is omitted.

In a servo signal processing device that applies tracking servo to both a read-only optical disk and a recording / reproducing optical disk, the TPP unit 105 is used to apply a light beam to pit tracks formed in at least both lead-in areas. It is necessary to apply a tracking servo so as to follow

However, in the lead-in area of the read-only optical disk and the lead-in area of the recording / reproducing optical disk, the reflectance and the shape of the pit generally differ. Therefore, the above PPA is also different. If the PPA is different, the above T
It is appropriate to change the PP coefficient.

Therefore, in the TPP section 105, the coefficient K
Two t's are prepared, such as Kt1 and Kt2, and are switched according to the type of PPA of the disc to be used.

The detailed operation will be described below. For example, when a read-only optical disk is set or when a read / write optical disk is set and the lead-in area is reproduced first, the TPP unit 105 is controlled based on a track identification signal GR / PIT described later. Becomes substantially effective.

Here, the TPP coefficient Kt1 is an optimal coefficient for the above-mentioned read-only optical disk, and the TPP coefficient Kt2 is an optimal coefficient for the above-mentioned recording / reproducing optical disk. In the lead-in area, information signals are recorded by pits. However, the read-only optical disc and the recording / reproducing optical disc have different PPA because the read-in area has a different reflectance and pit shape. , This P
Two previously prepared coefficients Kt1 and Kt2 are switched according to the PA.

The multiplied output Kt1 (Etop−
Ftop) and the multiplied output Kt2 of the Kt2 amplifier 45 (Etop-F
top) is switched by the switch 46 in accordance with the switching control signal CONT generated by the system controller 100 based on the PPA signal. The switching output of the changeover switch 46 is supplied to the inverting input terminal of the subtractor 47.

For example, when a read-only optical disk is loaded and the system controller 100 determines the use of Kt1 based on the PPA signal from the PPA detection unit, Kt1
(Etop-Ftop) is supplied to the inverting input terminal of the subtractor 47, and the result of subtraction from (EF) supplied to the non-inverting input terminal is output as the tracking error signal TE shown in the above equation (4). .

Further, for example, when the recording / reproducing type optical disk is mounted and the use of Kt2 is determined from the PPA signal, the subtracter 47 outputs the subtraction result as the tracking error signal TET shown in the above equation (5). .

Therefore, the TPP unit 105 can set the optimum TPP coefficient for each of the read-only optical disk and the recording / reproducing optical disk in accordance with the PPA, and set the optimum tracking error signal depending on the type of the disk. TET can be output. As a result, the servo signal processing device 60 can improve the accuracy of tracking servo.

The tracking error signal TET is supplied to the selected terminal b of the changeover switch 66. The changeover switch 66 is switched in accordance with the track to be processed according to the track identification signal GR / PIT.
When the track to be processed is the lead-in area of the reproduction type optical disc and the recording / reproduction type optical disc, the terminal b is selected, and the tracking error signal TET from the TPP section 100 is sent to the tracking error detection section 62.
Output TE.

The tracking error signal TET output from the tracking error detection section 62 is
Is converted into a digital signal by an A / D converter 91,
Servo processing is performed by a digital signal processing unit (DSP) 92. Then, the servo processing circuit 90 can track the lead-in area of the read-only optical disk or the read / write optical disk with high accuracy according to the disk type.

The servo signal processor 60 performs the following wobble push-pull (hereinafter referred to as WP) when tracking servo is performed on the wobbled data area of the recording / reproducing optical disk.
It is called P. ) The tracking error signal TEW or the tracking error signal TER obtained by the section 110 or the track-on section 125 is used.

Here, a tracking error detection method performed by WPP section 110 will be described. When tracking servo is applied to an area where a wobble is formed on a track as shown in FIG. 7, it is used that the amplitude of the wobble frequency component included in the output signal of the photodetector changes depending on the position of the objective lens. Then, there is a method of detecting the amplitude of the wobble frequency component, finding the position of the objective lens, and canceling the offset value generated in the tracking error. This tracking error detection method is called a WPP method. It is used during tracking servo in the U-TOC area and the program area of the recording / reproducing small-diameter optical disc. In FIG. 7,
The disk substrate 130 has a pre-groove 13 corresponding to the groove.
1 and a land 132 corresponding to a land portion.
The edges meander at a predetermined cycle. Pregroove 1
Recording / reproducing of data is performed while the spot 133 follows the spot 31.

The WPP section 110 is a tracking error detection circuit that processes the wobble-like track shown in FIG. 7 and is substantially effective when the tracking state is the on-track state.

As shown in FIG. 6, the WPP unit 110 includes wobble amplitude detectors 111, 112 and 115, a subtractor 1
13 and 114, a divider 116, a coefficient multiplier 117, a DC offset value detection circuit, a subtractor 118,
It comprises a push-pull signal detection circuit composed of a divider 119, and a DC offset cancel circuit composed of a changeover switch 120 and a subtractor 121.

The WPP unit 110 includes a light detection signal A of the detection unit PD 1 -A, a light detection signal D of the detection unit PD 1 -D, the combined light detection signal L, the combined light detection signal R, and a signal combining unit. The synthesized light detection signal Ig from the adder 23 of FIG.
A + B + C + D is input.

First, the configuration of the DC offset value detection circuit will be described. The first wobble amplitude detection unit 111
The wobble amplitude signal Aw is detected from the light detection signal A.

This first wobble amplitude detection section 111
As shown in FIG. 8, it includes a band-pass filter 135, a full-wave rectifier 136, and a low-pass filter 137. The first wobble amplitude detection unit 111 limits the band of the input photodetection signal A with a band-pass filter 135, shapes the signal with a full-wave rectifier 136, passes the low-pass filter 137, and modulates the wobble amplitude of the signal A. Signal AW
Is detected.

The second wobble amplitude detection section 112 detects the wobble amplitude signal Dw of the light detection signal D, similarly to the first wobble amplitude detection section 111. This second
The configuration and operation of the wobble amplitude detector 112 of the first wobble amplitude detector 111 described with reference to FIG.
The configuration and operation are the same.

The subtractor 113 calculates the amplitude component Aw of the left wobble detected by the first wobble amplitude detector 111,
The meandering difference Aw-Dw from the right wobble amplitude component Dw detected by the second wobble amplitude detector 112 is obtained, and the difference is output to the divider 116.

The difference between the photodetection signal A and the photodetection signal D is obtained in the subtractor 114, and the difference (A−D) is output to the third wobble amplitude detection section 115.

The third wobble amplitude detector 115 detects a wobble amplitude signal (AD) w in the input push-pull signal (AD) and outputs it to the divider 116. The configuration and operation of the third wobble amplitude detector 115 are the same as the configuration of the first wobble amplitude detector 111 described above.

The divider 116 uses the signal Aw-Dw input from the subtractor 113 as a dividend and the signal (AD) w input from the third wobble amplitude detector 115 as a divisor.
The division shown in the following equation (7) is performed, and the result is output to the coefficient multiplier 117.

(Aw−Dw) / (A−D) w (7) Then, in the coefficient multiplier 117, as shown in the following equation (8), the division result in the divider 116 is determined in advance. The DC offset cancellation value of the tracking error signal is obtained by multiplying the predetermined coefficient Kw.

Kw × (Aw−Dw) / (AD) w (8) The DC cancel value obtained in the coefficient multiplier 117 is supplied to the subtractor 121 via the changeover switch 120. .

Next, the configuration of the push-pull signal detection circuit will be described.

The subtracter 118 calculates the difference between the combined light detection signal L and the combined light detection signal R, and obtains the result L−
R is output to the divider 119.

The divider 119 divides the result L-R of the subtractor 118 as a dividend and the output signal Ig corresponding to the total amount of light supplied from the adder 23 as a divisor, and performs a push operation normalized by the total amount of light. A pull signal (LR) / Ig is obtained.

In the subtractor 121 constituting the DC offset cancel circuit, the cancel value Kw × (Aw−Dw) / (A−D) is obtained from the push-pull signal (LR) / Ig obtained by the divider 119. ) Subtract w. As a result, a signal TWw, which is a push-pull signal with the offset canceled and corresponding to the tracking error of WPP, is obtained as shown in the following equation (9).

TEw = {(LR) / Ig} − {Kw × (Aw−Dw) / (AD) w} (9) Note that the changeover switch 120 is a DC offset in the WPP unit 105. This is a switch for turning ON / OFF the cancellation of the value. WPP unit 110 is valid,
When the DC offset cancellation value obtained by the first wobble amplitude detector 111 to the coefficient multiplier 117 is subtracted from the push-pull signal, the switch 120 selects the terminal a. Also, a track-on unit 125 described later.
Is enabled, the changeover switch 120 is connected to the terminal b
Is selected, the subtraction value in the subtractor 121 is set to 0, and the result of the divider 119 is output as it is. The output of the WPP unit 110 is supplied to the track-on unit 125 and the switch 6.
5 is output to the terminal a.

The track-on section 125 includes the WPP section 110
Is a tracking error detection circuit for interpolating the operation of (1). That is, when a recording medium having a wobble in a data track is to be processed as in the case of the WPP unit 110 and the tracking state is off-track, a tracking error is output instead of the WPP unit 110. Circuit.

The track-on section 125 includes a peak hold section 126, a bottom hold section 127, and an intermediate value calculation section 12.
8 and a subtractor 129.

A signal for controlling ON / OFF of a tracking servo (not shown) is input to the track-on section 125, and operation is performed based on this signal.

The peak hold unit 126 and the bottom hold unit 127 hold the peak value and the bottom value immediately after the track jump, for example, at the moment when the tracking servo is turned on.

The intermediate value calculator 128 calculates an intermediate value between the peak value held in the peak hold unit 126 and the bottom value held in the bottom hold unit 127, and supplies the calculated value to the subtractor 129.

Then, in the subtracter 129, the intermediate value from the intermediate value calculation unit 128 is subtracted from the tracking error signal TEW output from the WPP unit 110. As a result, a signal TER corresponding to the tracking error is obtained. The output of the track-on section 125 is output to the terminal b of the changeover switch 65.

The changeover switch 65 is switched based on a signal OFFTRK indicating whether or not the tracking servo is effective. In the on-track state, the terminal a is selected and the tracking error signal TEW detected by the WPP unit 110 is selected. In the off-track state, the terminal b is selected and the tracking error signal TER detected by the track-on section 110 is output.

The off-track state refers to a state during which the tracking servo is off due to a track jump or the like, and a period from when the tracking servo is turned on until a brake pulse is generated and converges to the on-track state. It is.

The switch 120 of the WPP unit 110 is also switched in synchronization with the switch 65. Specifically, the changeover switch 65 is connected to the terminal a
Is selected and the tracking error signal TEW from the WPP unit 110 is selected, the changeover switch 12
0 also selects the terminal a to enable the offset cancel circuit of the WPP unit 110, and the changeover switch 65 sets the terminal b
Is selected to select the tracking error signal from the track-on section 125, the changeover switch 12
0 selects the terminal b, and a signal without offset cancellation is output from the WPP unit 110 to the track-on unit 12.
5 to be input.

As described above, the changeover switch 66 is switched in accordance with the recording medium to be processed, based on the track identification signal GR / PIT indicating the form of the track to be tracked. When the processing target is a wobble-like track, the changeover switch 66 selects the terminal a, and the WPP
The tracking error signal TEW or TER from the unit 110 or the track-on unit 125 is output.

When the processing target is a pit track, the terminal b is selected so that the tracking error signal TET is output from the TPP unit 105.

Therefore, the servo signal processing device 60
Is a TP for a pit track in the lead-in area of a read-only optical disk and a read-only optical disk.
An optimum tracking servo can be applied in accordance with the PPA based on the type of the disc by using the P section 105, and the WPP section 110 or the track-on section 125 is used for the wobble-shaped track of the recording / reproducing optical disc. To apply tracking servo. Further, a focusing servo can be applied by the focusing error detection unit 80.

The tracking error detecting section 30 of the servo signal processing device 60 may use the tracking error detecting section 30 shown in FIG. Although a detailed description is omitted, one variable gain amplifier, that is, the variable Kt amplifier 55 is used instead of the two fixed gain amplifiers, so that any number of coefficients can be set without being fixed to two types. .

That is, when the PPA signal of the disk detected by the PPA detecting section having the same configuration as the PPA detecting section of FIG. 6 is sent to the system controller 100, the system controller 100 generates the gain control signal CONT according to the PPA signal. Then, the variable gain of the variable Kt amplifier 55 is set. Then, the subtractor 47 outputs the variable gain Kt.
(Etop−Ftop) is output as a tracking error signal.

Therefore, the servo signal processing device 60
The optimum TPP coefficient Kt can be set for each disk, and the accuracy of tracking servo can be improved.

Next, an embodiment of the optical disk device according to the present invention will be described with reference to FIG. This embodiment is an optical disc device 140 using the servo signal processing device 60.

The optical disk device 140 irradiates an optical disk 138 with a light beam of one spot and receives a reflected light from the optical disk 138, and includes an optical pickup 3 having a first photodetector PD1 and a second photodetector PD2; A servo signal processing device 60 including the RF signal processing circuit 61 and the servo processing circuit 90 is provided.

The servo signal processing device 60 eliminates the deterioration of the precision of the focusing servo and the tracking servo of the objective lens of the optical pickup 3. The servo signal processing device 60 also performs thread servo of the optical pickup 3 without deteriorating accuracy. Further, the servo signal processing device 60 also performs servo of the spindle motor 141.

In particular, the optical disk device 140 reproduces a read-only optical disk using a pit track and enables recording / reproduction on a recording / reproducing optical disk using a wobble-like track.

First, the reproduction system PB of the optical disk device 140 will be described. The RF signal processing circuit 61 converts the combined light detection signal Ig from the signal
To supply. The decoder 150 outputs the combined light detection signal I
Then, processing such as deinterleaving processing, decoding processing for error correction, and EFM demodulation processing is performed, and the reproduced data is supplied to the memory 151.

In the memory 151, data writing and reading are controlled by the system controller 149.
Reproduction data is written from the decoder 150. Also,
The reproduction data is continuously read from the memory 151 at a constant bit rate.

The reproduced data continuously read from the memory 151 is supplied to the decoder 152. When the reproduced data is compressed data, the decoder 152 expands the data by, for example, four times. The digital data from the decoder 152 is supplied to a D / A converter 153, converted into an analog signal, and derived from an output terminal 154 to the outside.

Next, the recording system REC of the optical disk device 140 will be described. The analog signal supplied from the input terminal 142 is converted into a digital signal by the A / D converter 143. This digital signal is so-called straight PCM data that has not been subjected to compression processing. As a specific example, the sampling frequency is 44.1 KH, similar to a standard compact disk format.
z is PCM data having a quantization bit number of 16 bits. The 16-bit PCM data is supplied to an encoder 144 for high-efficiency encoding processing such as AD (adaptive difference) PCM.

The encoder 144 performs a high-efficiency bit compression process on the PCM data and supplies it to the memory 145.

The memory 145 has a buffer for storing and compressing the bit-compressed data supplied from the encoder 144, temporarily storing the bit-compressed data supplied from the encoder 144 under the control of the system controller 149. Used as a memory.

The compressed data read from the memory 145 is subjected to an interleave process, an error correction coding process, an EFM
It is supplied to an encoder 146 for performing a modulation process or the like. Here, in the data string supplied from the memory 145 to the encoder 146, one cluster consisting of a predetermined sector is a unit that is continuously recorded in one recording.
When this is encoded, the data amount is obtained by adding several sectors for cluster connection to the data amount for one cluster. This cluster connection sector is the encoder 1
The length is set to be longer than the interleave length at 46, so that interleaving does not affect the data of other clusters.

The encoder 146 performs coding processing for error correction (parity addition and interleaving processing), EFM coding processing, and the like on the recording data supplied in bursts from the memory 145 as described above. The recording data that has been subjected to the encoding process by the encoder 146 is supplied to the magnetic head drive circuit 147. The magnetic head drive circuit 147 is connected to a magnetic head 148, and drives the magnetic head 148 so as to apply a modulation magnetic field corresponding to the recording data to the optical disk 138.

When reading out the TOC information recorded by the pit track from the lead-in area of the read-only optical disk or the read / write optical disk, the optical disk device 140 uses the TPP section 105 shown in FIG. Since the tracking servo can be applied by selecting an optimum coefficient according to the PPA, the TOC information can be accurately read.

[0108]

According to the present invention, the coefficient by which the peak level of the light detection signal obtained from the return light from the track of the disk-shaped recording medium is multiplied according to the push-pull amplitude level obtained from the disk-shaped recording medium. By switching and multiplying the peak level, it is possible to detect a tracking error signal from which an offset component caused by relative fluctuation of the objective lens has been removed. Further, if the tracking error signal is used, an optimal tracking servo can be realized.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a servo signal processing device according to an embodiment of the present invention.

FIG. 2 is a characteristic diagram for explaining the principle of a TPP unit.

FIG. 3 is a block diagram showing a configuration of a tracking error detection unit which is a main part of the servo signal processing device.

FIG. 4 is a block diagram illustrating a configuration of a tracking error detection unit that is a main part of a modified example of the servo signal processing device.

FIG. 5 is a block diagram showing a configuration of a servo signal processing device according to another embodiment of the present invention.

FIG. 6 is a block diagram showing a configuration of a tracking error detection unit which is a main part of the servo signal processing device shown in FIG. 5;

FIG. 7 is a diagram showing a part of an optical disk on which wobble-like tracks are formed.

FIG. 8 is a block diagram illustrating a detailed configuration of a wobble amplitude detection unit used in a WPP unit included in the tracking error detection unit illustrated in FIG. 6;

FIG. 9 is a block diagram showing a configuration of an embodiment of an optical disk device according to the present invention.

[Explanation of symbols]

1 servo signal processing device, 2 RF signal processing device, 30
Tracking error detector, 100 system controller

Claims (10)

[Claims] 1. A servo signal processing device for irradiating a track formed by pits on a disk-shaped recording medium with a beam of one spot, detecting a tracking error and performing tracking servo. The coefficient multiplied by the peak level of the detected photodetection signal is switched according to the push-pull amplitude level obtained from the disk-shaped recording medium, and the peak level is multiplied to remove the offset component caused by the relative fluctuation of the objective lens. A servo signal processing device comprising: a tracking error detection unit that detects a tracking error signal obtained by the above-described method; and a servo processing unit that performs tracking servo processing based on the tracking error signal from the tracking error detection unit. 2. The method according to claim 1, wherein the tracking error detecting means switches at least two types of the coefficients according to the push-pull amplitude levels obtained from the same type of different disk-shaped recording media, and multiplies the peak level. The servo signal processing device according to claim 1, wherein 3. The tracking error detecting means switches at least two types of coefficients according to the push-pull amplitude levels obtained from different types of disk-shaped recording media, and multiplies the peak level. The servo signal processing device according to claim 1. 4. The tracking error detecting means according to claim 1, wherein the coefficient is made variable according to the push-pull amplitude level obtained from the same type of different disk-shaped recording medium, and multiplies the peak level. The servo signal processing device according to the above. 5. The tracking error detecting means according to claim 1, wherein the coefficient is made variable in accordance with the push-pull amplitude level obtained from different types of disc-shaped recording media, and multiplied by the peak level. Servo signal processing device. 6. An optical pickup means for irradiating a disk-shaped recording medium with one spot beam, receiving return light from the disk-shaped recording medium by a split sensor, and outputting a light detection signal based on the amount of received light. When tracking a track formed by pits, the peak level of the light detection signal from the optical pickup means is multiplied by a coefficient corresponding to the push-pull amplitude level of the disk-shaped recording medium, and an offset component An optical disc apparatus comprising: a tracking error detection unit that detects a canceled tracking error signal; and a servo processing unit that performs tracking servo processing based on the tracking error signal from the tracking error detection unit. 7. The tracking error detecting means switches at least two types of coefficients according to the push-pull amplitude levels obtained from the same type of different disk-shaped recording media, and multiplies the peak level. 7. The optical disk device according to claim 6, wherein: 8. The tracking error detecting means switches at least two types of coefficients according to the push-pull amplitude levels obtained from different types of disk-shaped recording media, and multiplies the peak level. The optical disk device according to claim 6, wherein 9. The tracking error detecting means according to claim 6, wherein the coefficient is made variable according to the push-pull amplitude level obtained from the same kind of different disk-shaped recording media, and multiplied by the peak level. An optical disk device as described in the above. 10. The tracking error detecting means,
7. The optical disk device according to claim 6, wherein a coefficient is made variable according to the push-pull amplitude level obtained from different types of disk-shaped recording media, and the coefficient is multiplied by the peak level.