JPH10124891A - Servo signal processor and optical disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a servo signal processor and an optical disk device capable of performing tracking servo operation to an optical disk having a different kind with high accuracy. SOLUTION: TPT part 40 (top hold pushpull) multiplys the peak values Lp and Rp of synthesized optical detecting signals L and R, detected by a first photodetector from the returned light beam of one spot projected on a track formed by pits and obtained by synthesizing a signal in a signal synthesizing part, by a coefficient Kt1 or a coefficient Kt2 complied with the characteristic of an optical disk and a tracking error signal TET whose offset component is canceled is detected.

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 In recent years, a small-diameter long-time recording optical disk (hereinafter, referred to as a small-diameter optical disk) having a diameter of about 64 mm, for example, having a storage capacity capable of recording a tone signal for 74 minutes or more is widely known. Is now available. This small-diameter optical disc includes a read-only type small-diameter optical disc in which data is recorded by pits, and magneto-optical recording (MO).
There are roughly two types of recording / reproducing small-diameter optical discs on which data is recorded and which can be reproduced according to the method.

[0003] In a read-only type small-diameter optical disc, the format on the disc is a lead-in area, a program area, and a lead-out area from the inner peripheral side. In each of these areas, data is recorded by the pits.

[0004] On the other hand, a lead-in area, a user management information (User Table Of Contents, U-TOC) area, a program area, and a lead-out area are formed on the recording / reproducing small-diameter optical disc from the inner peripheral side. However, data is recorded by pits only in the lead-in area, and data is recorded by MO in the U-TOC area, program area, and lead-out area.

As described above, data is recorded in the lead-in area of both types of small-diameter optical discs by using pits. Specifically, the TOC is pre-recorded when the disc is manufactured. For example, the start and end addresses corresponding to a maximum of 255 songs are recorded in the TOC of a read-only small-diameter optical disc. On the other hand, in a TOC of a recording / reproducing small-diameter optical disc, a laser power, a recordable area, a UTOC address, and the like necessary for recording are recorded in advance.

[0006] It should be noted that the recording / reproducing small-diameter optical disk U-
The TOC area and the program area meander (wobble) at regular intervals in the radial direction of the disc when the disc is formed.
A groove called a groove G in which cluster address and sector address information to be recorded is recorded is formed in advance.
The address information recorded in the groove G is ADI
This signal is called a P (ADdress In Pregroove) signal, and is used for spindle motor rotation control (CLV servo) and head positioning (tracking servo). Further, it is used for controlling an access operation at the time of data recording and reproduction, and can perform high-speed and stable random access.

In tracking servo processing of an optical disk device that performs recording / reproduction on both types of small-diameter optical disks, a tracking error is detected at one spot in terms of simplification, miniaturization, and reliability of the device. A push-pull method that can be used is adopted. 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 a pickup having a structure in which only the objective lens moves is used,
When the objective lens fluctuates, such as when the disk surface is deviated from the optical axis of the beam by 90 ° due to disk skew, the spot moves on the photodetector, causing a DC offset in the tracking error signal. Would. 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, the change in the peak value of the envelope, and the change is determined as a predetermined value. There is a method in which the DC offset is obtained by multiplying by the coefficient of

This tracking error detection method uses a top hold push-pull (hereinafter referred to as T).
It is called PP. ), Which is used for tracking servo in all areas of a small-diameter read-only optical disc on which data is recorded by pits.

When a tracking servo is applied to an area where a wobble is formed on a track as shown in FIG. 9, the amplitude of the wobble frequency component included in the output signal of the photodetector changes depending on the position of the objective lens. Utilizing this, 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 Wobble Push-Pull (hereinafter, referred to as WPP), and is a U-TOC of the recording / reproducing small-diameter optical disc.
Used for tracking servo in area and program area. In FIG. 9, the disk substrate 1
Numeral 30 is composed of a pre-groove 131 corresponding to a groove and a land 132 corresponding to a land, the edge of which is meandering at a predetermined cycle. Data recording / reproducing is performed with the spot 133 following the pre-groove 131.

[0012]

By the way, from the lead-in area of the small-diameter optical disks of both types, the TOC is required.
When information is read, tracking servo is applied by the above-described TPP method. However, the reflectance and the pit shape are different between the read-in area of the read-only small-diameter optical disc and the read-in area of the recording / reproducing small-diameter optical disc.

For this reason, when reading out the TOC information from the lead-in area in an optical disk apparatus that records / reproduces data on the small-diameter optical disks of both types, the change in the peak value of the envelope is determined by the TPP method. If only one predetermined coefficient is multiplied, an offset cancellation error (remaining) may occur depending on the disk, which may cause detracking and reduce the accuracy of the tracking servo.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a servo signal processing device and an optical disk device capable of performing tracking servo for different types of optical disks with high accuracy.

[0015]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, a servo signal processing apparatus and an optical disk apparatus according to the present invention provide disk-shaped recording at a peak level of a light detection signal obtained from light returned from a pit track. A tracking error detection unit is used that detects a tracking error signal from which an offset component caused by a relative change of the objective lens is removed by multiplying by a coefficient that changes according to the characteristics of the medium.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a servo signal processing device according to the present invention will be described below.

This embodiment is a servo signal processing apparatus 1 as shown in FIG. 1, which can reproduce a read-only optical disk having pit tracks and a wobble-like track in which the boundary between a pre-groove and a land is wobbled. The present invention can be applied to both recording / reproducing optical disks.

The servo signal processing device 1 inputs each of the light detection signals output by the _first photodetector PD1 from the reflected light of the light beam of one spot irradiated on the optical disk to a tracking error detection unit 30 described later. a signal synthesizing unit 20 to generate the desired signal suitable for a tracking error detection unit 30 for detecting a tracking error signal with the desired signal generated by the signal synthesizing portion 20, the second photodetector PD ₂ is output A focusing error detection unit 80 that detects a focusing error signal using each of the detected signals, a servo processing circuit 90 that performs tracking servo processing based on the tracking error signal, and performs focusing servo processing based on the focusing error signal. Is provided.

Here, the tracking error detector 30
Is a circuit for detecting a tracking error signal by a push-pull method. Tracking error detector 3
0 detects the tracking error signal TE based on the signal input via the signal synthesis unit 20.

As shown in FIG. 2, the tracking error detecting section 30 includes three tracking error detecting circuits, namely, a top hold push-pull.
l, hereinafter referred to as TPP. ) TPP unit 40, Wobble Push-Pull (hereinafter referred to as WPP) W
It has a PP section 50, a track-on section 70, and switching circuits 31 and 32 thereof.

The TPP section 40 detects the combined light detected by the first photodetector PD ₁ from the return light of the light beam of one spot applied to the track formed by the pits and combined by the signal combining section 2. The level of the peak value of the signals L and R is multiplied by a coefficient corresponding to the characteristics of the optical disk, and the tracking error signal T in which the offset component is canceled
To detect the E _T.

Here, the first photodetector PD
_{Numeral 1} is provided in an optical pickup for irradiating the optical disk with one spot of light beam, detects light diffracted and reflected by the optical disk, and outputs a signal corresponding to the amount of light. Photodetector PD ₁ of the first, the four detector PD ₁ -A, PD ₁ -B, are arranged as shown in the drawing the PD ₁ -C, and PD ₁ -D. Four detectors PD ₁ -A, PD _1-
B, two detection units PD among PD ₁ -C and PD ₁ -D
₁ -A and PD ₁ -B detect first-order diffracted light reflected to the left side of the data track, and the remaining two detectors PD ₁ -C and PD _1-
D detects -1 diffracted light reflected off the right side of the data track. Specifically, the light detection signals A and B detected by the two detection units PD ₁ -A and PD ₁ -B are added by an adder 21 in the signal synthesis unit 20 to become a synthesized light detection signal L. Further, the light detection signals C detected by the two detectors PD ₁ -C and PD ₁ -D,
D is added by an adder 22 in the signal combining unit 20 to become a combined light detection signal R.

First, the principle of the TPP method performed by the TPP section 40 will be described with reference to FIG.

FIG. 3 shows an RF envelope waveform of the combined light detection signal L corresponding to the amount of all first-order diffracted lights. In FIG. 3, a waveform P is a peak of the signal L, a signal S is a signal obtained by passing an RF envelope used for performing tracking by a push-pull method through an LPF (low-pass filter),
The signal Q has 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, if a constant K _t (K _t <1) that satisfies q = K _t × p is determined, the signal from which the offset has been canceled can be expressed by S−K _t × p. Therefore, if the peak change p is obtained, the offset value can also be obtained.

By the way, as in this embodiment, in a servo signal processing device that applies tracking servo to both a read-only optical disk and a recording / reproducing optical disk, the T
It is necessary to apply a tracking servo so that the light beam follows the pit tracks formed in at least both the lead-in areas using the PP unit 40.

However, in the lead-in area of the read-only optical disc and the lead-in area of the recording / reproducing optical disc, the reflectivity and the pit shape are generally different.

Therefore, in the TPP section 40, the coefficient K _t
Are prepared as K _t1 and K _t2 , and the peak value of the signal L and the peak value of the signal R are multiplied, respectively, and the multiplied output is switched depending on whether it is a reproduction-only type or a recording / reproduction type. ing.

More specifically, the TPP section 40 includes a peak hold circuit 41 for holding the peak value L _p of the combined light detection signal L, and a peak value L from the peak hold circuit 41.
a coefficient multiplier 42a for multiplying _p by the coefficient K _t1 and a coefficient multiplier 42 for multiplying the peak value L _p by the coefficient K _t2
b and the multiplied output from the coefficient multiplier 42a
And a switching circuit 43 for supplying a multiplied output from a coefficient multiplier 42b to a selected terminal b and selecting one of the selected pieces by a selection piece, and synthesizing the one multiplied output selected by the switching circuit 43. multiplying the operational amplifier 44 to subtract from the light detection signal L, and the peak hold circuit 45 for holding the peak value R _p of the combined optical detection signal R, the coefficient K _t1 to the peak value R _p from the peak hold circuit 45 a coefficient multiplier 46a for a coefficient multiplier 46b for multiplying the coefficient K _t2 to the peak value R _p, the multiplication output from the coefficient multiplier 46a is supplied to the fixed terminal a, a coefficient multiplier 46b
A switching circuit 47 which supplies the multiplied output from the switch to the selected terminal b and selects any one of them by a selection piece;
7, an operational amplifier 48 for subtracting one multiplied output selected from the composite light detection signal R from the composite light detection signal R, and a subtraction output of the operational amplifier 48 further subtracted from the subtracted output of the operational amplifier 44 to cancel a tracking error in which an offset component is canceled. comprising an arithmetic amplifier 49 for outputting a signal TE _T.
The tracking error signal TE _T is supplied to the fixed terminal b of the switching circuit 32.

For example, when a read-only optical disk is set, or when a recording / reproducing optical disk is set and the lead-in area is reproduced first, a lead-in area is reproduced based on a track identification signal GR / PIT described later. TPP
The part 40 becomes substantially effective.

The peak hold circuit 41 holds the peak value L _p of the combined light detection signal L corresponding to the amount of entered all first-order diffracted light. Coefficient multiplier 42a and coefficient multiplier 4
2b multiplies the peak value _Lp by a coefficient _Kt1 and a coefficient _Kt2 .

Here, the coefficient K _t1 is an optimal coefficient for the above-mentioned read-only optical disk, and the coefficient K _t2 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 disk and the recording / reproducing optical disk have different reflectivity and pit shape in the lead-in area. , Two coefficients K _t1 and K _t2 are prepared in advance.

The multiplication output K _t1 of the coefficient multiplier 42a
Any one of L _p and the multiplied output K _t2 · L _p of the coefficient multiplier 42b is selected by the switching circuit 43 and input to the inverting input terminal of the operational amplifier 44. The switching circuit 43 switches based on a gain control signal GAIN CNT output in response to a signal that detects whether the optical disk of the reproduction-only type or the optical disk of the recording / reproduction type is mounted on the device. Can be

For example, when a read-only optical disk and a recording / reproducing optical disk are of a type housed in a disk cartridge, a disk type detection unit (not shown) is inserted through a type identification hole formed in each disk cartridge. Is an optical disk. Then, the gain control section generates the gain control signal GAINCNT according to the detection result from the disc type detection section.

[0034] For example, the reproduction-only optical disc is mounted, the switching circuit 43 selects the multiplication output K _t1 · L _p from the coefficient multiplier 42a, is inputted to the inverting input terminal of the operational amplifier 44 . The combined light detection signal L is input to a non-inverting input terminal of the operational amplifier 44. Thus, the operational amplifier 44 outputs a calculation result that L-K _t1 · L _p to the non-inverting input terminal of the operational amplifier 49.

On the other hand, the peak hold circuit 45 outputs the combined light detection signal R corresponding to the amount of the inputted all-first order diffracted light.
Hold the peak value R _p of Coefficient multiplier 46a and the coefficient multiplier 46b multiplies the coefficient K _t1 and the coefficient K _t2 to the peak value R _p.

The product output K _t1 of the coefficient multiplier 46a is obtained.
Any one of R _p and the multiplied output K _t2 · R _p of the coefficient multiplier 46b is selected by the switching circuit 47 and input to the inverting input terminal of the operational amplifier 48. The switching circuit 47 is also switched based on a gain control signal GAIN CNT output in response to a signal that detects whether the optical disk of the reproduction-only type or the optical disk of the recording / reproduction type is mounted on the device. .

[0037] For example, the reproduction-only optical disc is mounted, the switching circuit 47 selects the multiplication output K _t1 · R _p from the coefficient multiplier 46a, is inputted to the inverting input terminal of the operational amplifier 48 . The composite light detection signal R is input to a non-inverting input terminal of the operational amplifier 48. Thus, the operational amplifier 48 outputs a calculation result that R-K _t1 · R _p to the inverting input terminal of the operational amplifier 49.

The operational amplifier 49, the calculation result R-K _t1 · R _p from the operational amplifier 48 from the calculation result L-K _t1 · L _p from the operational amplifier 44 is subtracted by the following formula (1) outputs a tracking error signal TE _T shown.

TE _T = (L−K _t1 · L _p ) − (R−K _t1 · R _p ) (1) Here, for example, if a recording / reproducing type optical disc is mounted, the switching circuit is used. 43 and a switching circuit 47 provide a multiplication output K _t2 · L _p from the coefficient multiplier 42b and the coefficient multiplier 46b.
And the multiplication output K _t2 · R _p are selected.
9 is a tracking error signal T expressed by the following equation (2).
And outputs the E _T.

TE _T = (L−K _t2 · L _p ) − (R−K _t2 · R _p ) (2) As described above, the TPP unit 40 determines the coefficient according to the type of the optical disk. K _t1 and the coefficient K _t2 are prepared, and the multiplied output is selected according to the type of the disk. Therefore, the optimum tracking error signal T depends on the type of the disk.
It is possible to output the E _T.

[0041] The tracking error signal TE _T is supplied to the fixed terminal b of the switching circuit 32. The switching circuit 32 is switched according to the track to be processed based on 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 TE from the TPP section 40 is selected.
_{Let T be} the output TE of the tracking error detector 30.

The tracking error signal TE output from the tracking error detector 30 is converted into a digital signal by an A / D converter 91 constituting a servo processing circuit 90, and is subjected to servo processing by a digital signal processor (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.

When the servo signal processing apparatus 1 performs tracking servo on the wobbled data area of the recording / reproducing optical disk, the servo signal processing apparatus 1 obtains the tracking servo data by the following WPP unit 50 or track-on unit 70. It was used tracking error signal TE _W or the tracking error signal TE _R.

First, the WPP section 50 processes a wobble-like track as shown in FIG. 9 above, and more particularly, a tracking error detecting circuit which is substantially effective when the tracking state is the on-track state. is there.

The WPP unit 50 includes a wobble amplitude detection unit 5
1, 52 and 55, operational amplifiers 53 and 54, a divider 56, a coefficient multiplier 57, a DC offset value detecting circuit, an operational amplifier 58, a push-pull signal detecting circuit composed of a divider 59, And a DC offset canceling circuit composed of a device 60 and an operational amplifier 61.

The WPP unit 50 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. Synthesized light detection signal I _g = A from adder 23 of combining section 20
+ B + C + D is input.

First, the configuration of the DC offset value detection circuit will be described. The first wobble amplitude detecting unit 51, from the light detection signal A, it detects the amplitude signal A _w of the wobble.

The first wobble amplitude detector 51 includes a band-pass filter 65, a full-wave rectifier 66 and a low-pass filter 67, as shown in FIG. The first wobble amplitude detection section 51 limits the band of the input photodetection signal A with a band-pass filter 65, shapes the signal with a full-wave rectifier 66, passes the low-pass filter 67, and modulates the wobble amplitude of the signal A. The signal A _W is detected.

The second wobble amplitude detecting unit 52, similarly to the first wobble amplitude detecting unit 51 detects the amplitude signal D _w of the wobble of the optical detection signal D. The configuration and operation of the second wobble amplitude detector 52 are the same as the configuration and operation of the first wobble amplitude detector 51 described above with reference to FIG.

The operational amplifier 53 includes an amplitude component A _w of the left wobble detected by the first wobble amplitude detection section 51,
The meandering difference A _w -D _w from the right wobble amplitude component D _w detected by the second wobble amplitude detector 52 is obtained, and the difference is output to the divider 56.

In the operational amplifier 54, the difference between the light detection signal A and the light detection signal D is obtained, and the difference (A−D) is output to the third wobble amplitude detector 55.

The third wobble amplitude detector 55 detects a wobble amplitude signal (AD) _w in the input push-pull signal (AD) and outputs the same to the divider 56. The configuration and operation of the third wobble amplitude detector 55 are the same as the configuration of the first wobble amplitude detector 51 described above.

The divider 56 uses the signal A _w -D _w input from the operational amplifier 53 as a dividend and the signal (AD) _w input from the third wobble amplitude detector 55 as a divisor.
The division shown in the following equation (3) is performed, and the result is output to the coefficient multiplier 57.

(A _w −D _w ) / (A−D) _w (3) In the coefficient multiplier 57, as shown in the following equation (4), the division result in the divider 56 is multiplied by a predetermined coefficient _Kw to obtain the tracking error signal. Obtain the DC offset cancellation value.

K _w × (A _w −D _w ) / (A−D) _w (4) The DC cancellation value obtained in the coefficient multiplier 57 is supplied to the operational amplifier 61 via the switch 60. Supplied.

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

The operational amplifier 58 outputs the synthesized light detection signal L
And the difference between the combined light detection signal R and the result L
-R is output to the divider 59.

[0058] The divider 59, a subtraction result L-R of the operational amplifier 58 dividend, performs division of the output signal I _g corresponding to all light amount supplied from the adder 23 as a divisor, which is normalized by the total light The push-pull signal (LR) / _Ig is obtained.

Then, in the operational amplifier 61 constituting the DC offset cancel circuit, the cancel value K _w × (A _w −D _w ) / is obtained from the push-pull signal (LR) / I _g obtained by the divider 59. (AD) Reduce _w . As a result, as shown in the following equation (5), a push-pull signal is canceled offset, signal TW _w is obtained which corresponds to the WPP tracking error.

TE _w = {(LR) / I _g } − {K _w × (A _w −D _w ) / (A−D) _w } (5) The switch 60 is a WPP A switch for turning ON / OFF the cancellation of the DC offset value in the unit 50. When the WPP unit 50 is effective and the DC offset cancellation value obtained by the first wobble amplitude detection unit 51 to the coefficient multiplier 57 is subtracted from the push-pull signal, the switch 60 selects the terminal a. When the track-on unit 70 described later is made effective, the switch 60 selects the terminal b, sets the subtraction value in the operational amplifier 61 to 0, and outputs the result of the divider 59 as it is. The output of the WPP unit 50 is output to the track-on unit 70 and the terminal a of the switching circuit 31.

The track-on section 70 is a tracking error detection circuit for interpolating the operation of the WPP section 50. That is, similarly to the WPP unit 50, when a recording medium in which a wobble is provided in a data track is to be processed and the tracking state is an off-track state, a tracking error is output instead of the WPP unit 50. Circuit.

The track-on section 70 has a peak hold section 71, a bottom hold section 72, an intermediate value calculation section 73, and an operation amplifier 74.

A signal for controlling ON / OFF of a tracking servo (not shown) is input to the track-on section 70, and the track-on section 70 operates based on this signal.

The peak hold section 71 and the bottom hold section 72 are, for example, immediately after a track jump,
The peak value and the bottom value at the moment when the tracking servo is turned on are held.

The intermediate value calculation section 73 includes a peak hold section 7
1 and the bottom hold unit 72
Is calculated and supplied to the operational amplifier 74.

Then, in the operational amplifier 74, WPP
The intermediate value from the intermediate value calculation unit 73 is subtracted from the tracking error signal TE _W output from the unit 50. As a result, the signal TE _R is obtained which corresponds to the tracking error. The output of the track-on section 70 is output to the terminal b of the switching circuit 31.

The switching circuit 31 is switched based on a signal OFFTRK indicating whether the tracking servo is valid or not.
And outputs the detected tracking error signal TE _W in Part 50, turned off when the track state, outputs a tracking error signal TE _R detected by the track-on unit 70 selects the terminal b.

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

In synchronization with this switching circuit 31, WP
The switch 60 of the P section 50 is also switched. In particular,
When the switching circuit 31 selects the terminal a to select the tracking error signal TE _W from the WPP unit 50, the switching unit 60 also selects the terminal a to enable the offset canceling circuit of the WPP unit 50, and the switching circuit When the terminal 31 selects the terminal b and selects the tracking error signal from the track-on section 70, the switch 60 selects the terminal b and the signal from the WPP section 50 on which the offset cancellation has not been performed is track-on. The input is made to the unit 70.

As described above, the switching circuit 32 outputs the track identification signal GR indicating the form of the track to be tracked.
Switching is performed according to the recording medium to be processed based on / PIT. When processed is a wobble-shaped tracks, the switching circuit 32 selects the terminal a, the tracking error signal TE _W or TE _R from WPP unit 50 or the track-on unit 70 is to be outputted.

[0071] Further, the processing target is, when the pit track, selects the terminal b, so that the tracking error signal TE _T from TPP section 40 is outputted.

The above is the description of the tracking error detection section 30. The servo signal processing device 1 also includes the focusing error detection section 80.

The focusing error detection section 80
Detector PD ₂ -Y from joint detection signal X of the detector PD ₂ -X ₁ of photodetector PD ₂ between the detector PD ₂ -X ₂
An operational amplifier 81 that subtracts the detection signal Y from the optical detection signals A, B, C, and D
And (A + D)-(B + C), and an operational amplifier 81 based on the output result of the operational amplifier 82.
And an operational amplifier 83 for subtracting the output result of
Finally, the focus error signal FE shown in the following equation (6)
Is output.

FE = {(A + D) − (B + C)} − (XY) (6) As described above, with reference to FIGS. 1 to 4, the tracking error detection unit 30 configuring the servo signal processing device 1 And the focusing error detection unit 80, the detection unit and the signal synthesis unit 20 constitute the RF signal processing circuit 2 as shown in FIG.

[0075] The servo processing circuit 90, becomes an A / D converter 91 and DSP 92, on the basis of the above focusing error signal FE and the tracking error signal TE and the synthesized light detection signal I _g, Focus Generate a servo processing signal and a tracking servo processing signal.

Therefore, the servo signal processor 1
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 according to the type of the disc can be applied by using the P section 40, and the WPP section 5 can be applied to a wobble-like track of a recording / reproducing optical disc.
The tracking servo can be applied by using 0 or the track-on unit 70. 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 apparatus 1 includes a TPP section 85, a TPP section 90, and a TPP section 100 as shown in FIGS.
May be used in place of the TPP section 40.

First, the TPP unit 85 shown in FIG. 5 uses a variable coefficient multiplier 86 and a variable coefficient
Different from the PP unit 40. Coefficient K _t for multiplying the peak value of the combined light detection signal L held by the peak hold circuit 41
When, it is made variable in the coefficient K _t to be multiplied by the peak value of the synthesized light detection signal R peak hold circuit 45 is held.

That is, the TPP unit 85 uses one variable coefficient multiplier instead of two coefficient multipliers, so that any number of coefficients can be set without fixing them to two types. Therefore, variations in the characteristics of the lead-in area, by using a constantly optimum coefficient K _t in response to the variation of the optical pickup or the like, it is possible to further improve the offset canceling precision of the tracking error signal. The variable coefficient K _t is may be set, for example, an external resistor on the basis of the gain control signal GAIN CNT, may be controlled by a command from the microcomputer.

[0080] Further, TPP section 90 shown in FIG. 6, the peak value R of the synthesized light detection signal R held by the peak hold circuit 93 from the peak value L _p of the combined optical detection signal L held by the peak hold circuit 92 subtracting the _p an operational amplifier 94, the subtraction result L _p -R two coefficients K _t1 and the coefficient K _t2 after multiplying with the coefficient multiplier 95a and the coefficient multiplier 95b to _p, the multiplication output K _t1 The switching circuit 96 switches between (L _p -R _p ) and the multiplied output K _t2 · (L _p -R _p ) based on the gain control signal GAIN CNT.

Then, the LR obtained by the operational amplifier 91 is obtained.
The switching output of the switching circuit 96 from the subtraction output by subtracting an operational amplifier 97, seeking tracking error signal TE _T.

[0082] For example, if the read-only optical disk apparatus is mounted, the switching circuit 96, K _t1 · (L _p -
R _p ) is input to the inverting input terminal of the operational amplifier 97. Therefore, the TPP section 90 outputs the tracking error signal TE _T shown in the following equation (7).

TE _T = (LR) − {K _t1 · (L _p −R _p )} (7) For example, when a recording / reproducing optical disk is mounted on the apparatus, the switching circuit is used. 96 inputs K _t2 · (L _p −R _p ) to the inverting input terminal of the operational amplifier 97. Then, the TPP section 90 outputs the tracking error signal TE _T shown in the following equation (8).

TE_T= (LR)-｛K_t2・ (L_p-R_p)｝ ・ ・ ・ (8)  The TPP unit 100 shown in FIG.
The variable coefficient multiplier 101 adds the subtraction output of_tTo
The point of multiplication is different from the TPP unit 90. That is,
By using the variable coefficient multiplier 101, two kinds of coefficients can be used.
You can set as many as you want, without fixing it to any kind.

Next, an embodiment of the optical disk device according to the present invention will be described. This embodiment is an optical disk device 110 using the servo signal processing device 1 described above.

The optical disk drive 110 irradiates the optical disk 105 with a light beam of one spot and receives a reflected light from the optical disk 105 with a first photodetector PD ₁ and a second photodetector PD _2. Signal processing device 1 including the RF signal processing circuit 2 and the servo processing circuit 90
have.

The servo signal processing device 1 eliminates the deterioration of the precision of the focusing servo and tracking servo of the objective lens of the optical pickup 3. Further, the servo signal processing device 1 also performs thread servo of the optical pickup 3 without deteriorating accuracy. Further, the servo signal processing device 1
Also performs the servo of the spindle motor 111.

In particular, the optical disk device 110 reproduces a read-only optical disk using a pit track and enables recording / reproduction on a recording / reproduction optical disk using a wobble-like track.

[0089] First, a description will be given reproducing system P _B of the optical disk apparatus 110. RF signal processing circuit 2 supplies the combined beam detection signal I _g from the signal synthesizing unit 20 to the decoder 120. The decoder 120 performs processing such as deinterleaving processing, decoding processing for error correction, and EFM demodulation processing on the combined light detection signal I, and stores the reproduced data in the memory 1.
21.

In the memory 121, data writing and reading are controlled by the system controller 119.
Reproduction data is written from the decoder 120. Also,
The reproduction data is continuously read from the memory 121 at a constant bit rate.

The reproduced data continuously read from the memory 121 is supplied to the decoder 122. When the reproduced data is compressed data, the decoder 122 expands the data by, for example, four times. The digital data from the decoder 122 is supplied to a D / A converter 123, converted into an analog signal, and led out of the output terminal 124.

Next, a description will be given of a recording system R _EC of the optical disk apparatus 110. The analog signal supplied from the input terminal 112 is converted into a digital signal by the A / D converter 113. 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 114 for high-efficiency encoding processing such as AD (adaptive difference) PCM.

The encoder 114 performs a high-efficiency bit compression process on the PCM data and supplies it to the memory 115.

The memory 115 is a buffer for controlling the writing and reading of data by the system controller 119 to temporarily store the bit-compressed data supplied from the encoder 114 and to record it on the disk as needed. Used as a memory.

The compressed data read from the memory 115 is subjected to an interleaving process, an error correction coding process, an EFM
It is supplied to an encoder 116 for performing modulation processing and the like. Here, in the data string supplied from the memory 115 to the encoder 116, one cluster consisting of a predetermined sector is a unit that is continuously recorded in one recording.
When this is encoded, the data amount becomes a data amount 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 16 so that interleaving does not affect the data of other clusters.

The encoder 116 performs coding processing (parity addition and interleaving processing) for error correction, EFM coding processing, and the like on the recording data supplied in bursts from the memory 115 as described above. The recording data that has been subjected to the encoding process by the encoder 116 is supplied to the magnetic head drive circuit 117. A magnetic head 118 is connected to the magnetic head driving circuit 117, and drives the magnetic head 118 so as to apply a modulation magnetic field according to the recording data to the optical disk 105.

When the optical disk device 110 reads the TOC information recorded in the pit track from the lead-in area of the read-only optical disk or the read / write optical disk, as described above, the TPP unit 40 and the TPP unit 8
5. Since the tracking servo can be applied by selecting the optimum coefficient for the disc characteristics using the TPP unit 90 or the TPP unit 100, the TOC information can be read accurately.

Further, the shape, arrangement, etc. of each detection section of the first photodetector PD ₁ are not limited to the above-mentioned four divisions, but may be a division sensor having an arbitrary configuration. The same applies to the second photodetector PD _2.

[0099]

The servo signal processing apparatus according to the present invention multiplies the peak level of the light detection signal obtained from the return light from the pit track by a coefficient that changes according to the characteristics of the disk-shaped recording medium, and provides an objective lens. Since the tracking error detecting means for detecting the tracking error signal from which the offset component generated by the relative fluctuation of the optical disk is removed is used, the tracking servo for the different types of optical disks can be performed with high accuracy.

Further, since the optical disk device according to the present invention uses the above-mentioned servo signal processing device, high-quality recording and / or reproduction of an information signal can be realized.

[Brief description of the drawings]

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

FIG. 2 is a circuit diagram showing a configuration of a tracking error detection unit which is a main part of the embodiment.

FIG. 3 is a TP constituting the tracking error detection unit.
FIG. 4 is a characteristic diagram for explaining the principle of a P section.

FIG. 4 is a diagram illustrating a WP constituting the tracking error detection unit.
FIG. 3 is a circuit diagram for explaining a wobble amplitude detection unit used in a P unit.

FIG. 5 is a block diagram showing another specific example replacing the TPP unit.

FIG. 6 is a block diagram showing another specific example different from FIG. 5 in place of the TPP unit.

FIG. 7 is a block diagram showing another specific example different from FIG. 6 in place of the TPP unit.

FIG. 8 is a block diagram of an embodiment of an optical disk device according to the present invention.

FIG. 9 is a diagram showing a part of an optical disk on which wobble-like tracks are formed.

[Explanation of symbols]

30 tracking error detection section, 40 TPP section, 4
1 peak hold circuit, 42a coefficient multiplier, 42b
Coefficient multiplier, 43 switching circuit

Claims (6)

[Claims] 1. A servo signal processing device for irradiating a disk-shaped recording medium with a beam of one spot, detecting a tracking error and performing tracking servo, detecting light obtained from return light from a track formed by pits. Tracking error detection means for multiplying the peak level of the signal by a coefficient that varies according to the characteristics of the disk-shaped recording medium, and detecting a tracking error signal from which an offset component caused by relative fluctuation of the objective lens has been removed, A servo signal processing device for performing tracking servo processing based on the tracking error signal from the tracking error detection means. 2. The apparatus according to claim 1, wherein the tracking error detecting means switches the coefficient according to the type of the plurality of types of disk-shaped recording media having different characteristics and multiplies the peak level of a light detection signal from the optical pickup by an offset component. 2. The servo signal processing device according to claim 1, wherein the tracking error signal having been canceled is detected. 3. The servo signal processing device according to claim 1, wherein the characteristics of the disk-shaped recording medium are different depending on a difference between a disk reflectance and a pit shape. 4. An optical pickup means for irradiating a disc-shaped recording medium with one spot beam, receiving return light from the disc-shaped recording medium by a split sensor, and outputting a light detection signal based on the received light amount. When tracking the track formed by the pits, the peak level of the light detection signal from the optical pickup means is multiplied by a coefficient corresponding to the characteristics of the disk-shaped recording medium to cancel the offset component. An optical disc device comprising: a tracking error detection unit that detects a tracking error signal obtained by the tracking error detection unit; and a servo processing unit that performs tracking servo processing based on the tracking error signal from the tracking error detection unit. 5. The tracking error detecting means switches the coefficient according to the type of a plurality of types of disk-shaped recording media having different characteristics and multiplies the peak level of a light detection signal from the optical pickup by an offset component. 5. The optical disk device according to claim 4, wherein the tracking error signal having been canceled is detected. 6. The optical disk device according to claim 5, wherein the characteristics of the disk-shaped recording medium are different depending on a difference between a disk reflectance and a pit shape.