JPH1091981A - Tracking error signal calculation circuit for optical disk drive - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To remove an offset included in a tracking error signal in an optical disk device, add frequency dependency, and calculate a tracking error signal according to a tracking state. SOLUTION: A top hold / coefficient multiplying circuit 22, 24 is provided.
Detects the peaks of the detection signals E and F in the left and right regions of the photodiode and multiplies the result by a coefficient K. The subtraction circuits 24 and 28 subtract the multiplication results of the circuits 22 and 24 from the detection signals E and F. The alignment signal AL (= EF) is added to the signal E or F through the low-pass filter circuit 64 in order to change the coefficient K according to the frequency band. The transistor 62 is turned on / off by a mirror signal whose level changes on / off in detrack or on track, and the circuit 24 or
The signal AL is added to or not added to any of the 28 outputs. The subtraction circuit 30 performs a push-pull operation on these operation results to calculate a tracking error signal TPP (TE).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a compact disk drive (CD), a CD-ROM, a mini disk drive (M
D: a registered trademark of Sony Corporation). The present invention also relates to a tracking error signal calculation circuit used for an optical disk device.

[0002]

2. Description of the Related Art An optical pickup is used to record data along a track (guide groove) of a disk recording medium of an optical disk device and to read the recorded data.
The optical pickup includes a semiconductor laser, a photodiode (PD), and optical members such as a prism and an objective lens. When recording or reading data on a disk recording medium,
Focusing servo control and track servo control are performed in order to eliminate the effects of track runout, tilt of the turntable of the disk drive, surface runout due to scouring motion, and track runout.

Focusing servo control focuses (just-focuses) laser convergent light emitted from an objective lens on the recording surface of a disk recording medium.
The objective lens is positioned toward the surface of the disk recording medium. The tracking servo control positions the optical pickup in the radial direction of the disk recording medium such that the laser convergent light emitted from the objective lens is located on a desired track (on-track) of the disk recording medium. A focusing error signal is used for focusing servo control, and a tracking error signal is used for tracking servo control. Usually, a tracking error signal is calculated by calculating signals detected by two photodiodes by a push-pull method.

An offset appears in the tracking error signal by the push-pull method. Even if the tracking error signal indicates 0 when there is an offset, if the tracking servo control is performed using the tracking error signal, the control beam will not be controlled properly when performing the tracking control because the light beam of the semiconductor laser is off the center of the track. The problem is that it happens. The causes of the offset appearing in the tracking error signal include the optical axis deviation of the objective lens,
There are radial inclination of the disk recording medium, imbalance in the groove shape of the disk recording medium, and the like. Various measures have been taken to reduce the offset caused by the above-described factors. For example, "Optical Disc Technology", supervised by Morio Onoe, Radio Engineering, pages 91-98,
reference.

[0005]

However, the inventor of the present application has found that the above-described measures for reducing the offset are not sufficient and that the tracking error signal still has an offset. Therefore, when the tracking error signal calculated by the conventional push-pull method is used, there is a problem that an accurate and stable tracking servo control cannot be performed in the optical disk device. Further, when it is desired to operate the optical disk device at high speed, for example, when operating at 4 × speed in a CD-ROM, the tracking speed needs to be reduced in the detrack state. And the tracking speed is not increased even in the detrack state.

SUMMARY OF THE INVENTION An object of the present invention is to provide a tracking error signal calculation circuit and method for an optical disk device that can accurately calculate a tracking error signal used in an optical disk device. Another object of the present invention is to provide a tracking error signal calculation circuit and method for an optical disk device that can calculate an optimum tracking error signal according to a tracking state.

[0007]

According to the present invention, an optical disk having light receiving means for outputting first and second light receiving detection signals from regions located on both sides of a track center of a disk recording medium, respectively. A tracking error signal calculation circuit of the device, wherein a peak of the first light reception detection signal is detected from a first light reception detection signal (E) from the light receiving means, and a first coefficient (K) is assigned to the peak. The second light reception detection is performed based on a first calculation circuit that calculates a first calculation signal (TPP (E)) by subtracting the multiplied signal and a second light reception detection signal (F) from the light receiving unit. A second arithmetic circuit for detecting a signal peak and subtracting the signal obtained by multiplying the peak by a second coefficient (K) to calculate a second arithmetic signal (TPP (F)); The difference between the detection signal and the second light reception detection signal (E-F A filter circuit (64) for passing a predetermined frequency component of the third signal (alignment signal AL) is, the predetermined frequency component signal of said third signal,
Selective signal addition for adding to the first operation signal and / or the second operation signal in accordance with the level of a mirror signal having an on / off level defined according to the on-track or de-track state A tracking circuit for an optical disc device, comprising: a circuit (62); and a third arithmetic circuit for calculating the tracking error signal by subtracting the second arithmetic signal from the first arithmetic signal from the selective signal adding circuit. An error signal calculation circuit is provided.

When the result of multiplying the peak of the light reception detection signal by a predetermined coefficient is subtracted from the light reception detection signals (E and F, respectively), the offset included in each light reception detection signal is canceled. The first and second operation signals (TPP (E) and TPP (E),
By performing a push-pull operation on PP (F)), a tracking error signal having no offset can be calculated. push·
Before calculating the tracking error signal by the pull method, the difference between the first light reception detection signal and the second light reception detection signal (E−
F) (the alignment signal A
When L) is added to the first operation signal (TPP (E)), a result equivalent to reducing the coefficient is obtained. Further, the third signal is converted to the second operation signal (TPP (F)).
, A result equivalent to increasing the above coefficient is obtained. Further, when the third signal is added to the first operation signal or the second operation signal obtained by extracting the signal of the predetermined frequency band through the filter circuit (64), the value of the coefficient substantially depends on the frequency band. Can be changed.
Further, in the selective signal adding circuit (62), the signal obtained by passing the third operation signal through the filter circuit is detracked or on-tracked so that the value of the coefficient becomes substantially large at the time of detracking. May or may not be added to the first operation signal or the second operation signal depending on the state of (1).

According to the present invention, a tracking error signal of an optical disk device having light receiving means for outputting first and second light receiving detection signals from regions located on both sides of a track center of a disk recording medium, respectively. A calculation method, comprising: detecting a peak of the first light reception detection signal from the first light reception detection signal and subtracting a signal obtained by multiplying the peak by a first coefficient to calculate a first operation signal; Detecting a peak of the second light reception detection signal from the second light reception detection signal and subtracting a signal obtained by multiplying the peak by a second coefficient;
Calculating a second operation signal; calculating a difference between the first light reception detection signal and the second light reception detection signal; extracting a predetermined frequency component of the difference signal as a third signal; 3 is selectively added to the first operation signal and / or the second operation signal according to the on-track or detrack state, and the selectively added first operation is performed. There is provided a tracking error signal calculation method for an optical disk device that calculates a tracking error signal by subtracting the second operation signal from a signal.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As an embodiment of the present invention, as an optical disk device, for example, a mini disk device, C
D, CD-ROM, etc., and a circuit for calculating a tracking error signal used for tracking servo control, such as a mini disk device, as the tracking error signal calculation circuit of the present invention. First, in order to make the understanding of the present invention clearer, for example, a mini disk device,
The basics of a tracking error signal used in an optical disk device such as a CD and a CD-ROM will be described.

[0011] the laser coupler LC Figure 1 is a diagram showing the cross section of the laser coupler LC mounted on the optical pickup, the ray trajectories of the disk recording medium (not shown) located thereon. The laser coupler LC includes a semiconductor laser LD, two photodiodes PD1 and PD2, and a microprism 1. The micro prism 1 is a semiconductor laser L
45 ° inclined surface 1a on which light from D enters, and upper surface 1b
And a lower surface 1c and a back surface 1d. A half mirror 1f is provided on the 45-degree inclined surface 1a, a total reflection mirror 1g is provided on the upper surface 1b, an AR coat 1h is provided on the lower surface 1c, and an entire surface absorbing film 1i is provided on the back surface 1d. Further, a half mirror 1j is provided above the arrangement of the photodiodes PD1 on the lower surface of the microprism 1. The two photodiodes PD1 and PD2 are provided on the lower surface of the micro prism 1,
They are arranged at predetermined intervals so that signals can be detected with a predetermined phase difference. Light emitted from the semiconductor laser LD is reflected by the half mirror 1f on the inclined surface 1a of the microprism 1 toward the upper disk recording medium (not shown), and return light reflected by the disk recording medium is reflected by the inclined surface of the microprism 1. Half mirror 1 on 1a
f into the microprism 1 and the photodiode P
D1 (front PD), the light reflected therefrom is reflected on the upper surface of the microprism 1 and the photodiode P
D2 (rear PD) is incident.

[0012] tracking error signal diagram 2 of 3 division scheme is a plan view of a three-part photodiodes used as the photodiodes PD1, PD2 as shown in FIG. Each of the photodiodes PD1 and PD2 has three regions:
It is divided into RA, RB, RC and RA ', RB', RC '. The region is divided in a direction orthogonal to the direction in which track shake (detrack) occurs. The central regions RB and RB 'have the same area,
The external regions RA and RA 'have the same area, the regions RC and RC' have the same area, and the regions RA and RC, R
A 'and RC' have the same area. Further, during on-track, the amount of light received in the region RB (RB ') is
The areas of these regions are defined so as to be equal to the sum of the amounts of light received by A and RC.

The tracking error signal TE of the three division system
Detects that the center region RB corresponds to the track center and detracks either above or below this region RB. Therefore, similarly to the two-segment photodiode, the difference between the detection signals of the outer regions RA and RC is detected. , (A-C), that is, as a push-pull signal.

[0014] 4 division tracking error signals Figure 3 is a plan view of a quadrant photodiode is used as the photodiode PD1, PD2 as shown in FIG. Regarding the photodiode PD1 (front PD), the central region RB and the region RC have the same area, and the outer region RA and the region RD have the same area. At the time of just focus, the amount of light received in the regions RB and RC is defined to be the same as the amount of light received in the regions RA and RD. Signals A1, A3, A4, and A2 are detected from the areas RA, RB, RC, and RD of the front PD. Similarly, for the photodiode PD2 (rear PD), the central region RB 'and the region RC' have the same area.
The outer area RA 'and the area RD' have the same area. At the time of just focus, the amount of light received in the regions RB ′ and RC ′ is defined in the same manner as the light received in the regions RA ′ and RD ′. Areas RA ', RB', R of rear PD
Signals B1, B3, B4, and B2 are detected from C 'and RD'.

FIG. 4 shows a four-division photodiode PD1, P
FIG. 9 is a diagram illustrating an operation of detecting a tracking error signal TE when D2 is used. 4A shows a state in which the track is detracked to the (+) side, FIG. 4B shows an on-track state,
FIG. 4C shows a state where the track is detracked to the (-) side. Whether the track is detracked or on-track is determined by dividing each of the photodiodes PD1 and PD2 into left and right regions at the center, and determining the intensity distribution of the first-order diffracted light on the photodiodes PD1 and PD2. During on-track, the centers of the divided areas of the photodiodes PD1 and PD2 are located at the center of the track. The photodiodes PD1 and PD2 are arranged such that detection signals from the same divided region have a reverse phase relationship with respect to return light. Therefore, the tracking error signal TE when the two photodiodes PD1 and PD2 are used calculates the first sum signal E by adding (A2 + A4) and (B1 + B3), which are signals having the same phase relationship, and calculates the same. A second sum signal F is calculated by adding (A1 + A3) and (B2 + B4) which are in the in-phase relationship, and the sum signal is calculated by performing a push-pull process. As described above, the signals having the common-mode relationship are added together because of the common-mode noise removal ratio (Common Mode).
This is to increase the Noise Rejection Ratio).

E = A2 + A4 + B1 + B3 (1) F = A1 + A3 + B2 + B4 (2) PP = EF = (A2 + A4 + B1 + B3)-(A1 + A3 + B2 + B4) (3)

The differential amplifier circuit 19 has a push
The tracking error signal TE by the pull method is calculated. As shown in FIG. 4 (B), when on-track, 2
Since the intensity distributions of the two first-order diffracted lights become equal, the tracking error signal TE, which is the difference between them, becomes zero. FIG.
As shown in FIG. 4A or FIG. 4C, the tracking error signal TE at the time of detracking has no (+) or (−) primary diffracted light in the radial direction. Or (-).

Disadvantages of Push-Pull Method The problems (disadvantages) of the push-pull method will be described below. First Problem: Offset of Tracking Error Signal Due to Shift of Objective Lens in Radial Direction (Tracking Direction) FIG. 5 is a diagram illustrating a push-pull signal when the objective lens 5 is displaced in the radial direction (tracking direction). . When the objective lens 5 shifts in the radial direction with respect to the disk recording medium 3, the photodiodes PD1, P
The return light on D2 is shifted, and the intensity distributions of the respective photodiodes PD1 and PD2 become unbalanced, causing a DC offset in the push-pull signal. As a result, if tracking servo control is performed using this push-pull signal, tracking control cannot be performed correctly.

Second Problem: Offset of Tracking Error Signal Due to Radial Skew FIG. 6 is a diagram showing a state in which the spot of the return light on the photodiodes PD1 and PD2 shifts due to the radial skew of the disk recording medium 3. Disk recording medium 3
Skews in the radial direction, the photodiode P
The intensity distribution of the return light incident on D1 and PD2 becomes unbalanced, and a DC offset occurs in the tracking error signal TE. As a result, if the tracking error signal TE in this state is used, accurate tracking servo control cannot be performed. In the actual laser coupler LC, it is rotated 45 degrees with respect to the pit. As a result, even if the disk recording medium 3 skews in the tangential direction, a DC offset occurs in the tracking error signal TE.
The offset amount is 1 / 1.41 in both the radial and tangential directions because the laser coupler LC is rotated by 45 degrees. Regarding the skew of the disk recording medium 3 described above, even when the objective lens 5 is skewed with respect to the disk recording medium 3, a DC offset occurs in the tracking error signal TE in the same manner as described above.

The principle of the present invention: top hold push
Pull method The principle of the present invention for canceling the offset caused by the movement of the field of view of the objective lens described above will be described. As the optical disk device of the present invention, for example, a mini disk device, a CD, and a CD-RM are exemplified. As a tracking error signal calculation circuit of the present invention, a circuit for calculating a tracking error signal used for tracking servo control in these optical disk devices will be exemplified.

FIG. 7 shows the R of the first sum signal E (= A2 + A4 + B1 + B3) shown in FIGS.
5 is a graph showing a waveform of an F envelope signal. Curve C
V1 indicates a peak change of the RF envelope of the first sum signal E due to a shift or skew of the objective lens. The peak width is shown as a. A curve CV2 is a waveform of a signal obtained when low-pass filtering is applied to a tracking error signal TE used for applying a tracking servo in the push-pull method. The curve CV3 shows the change in the offset of the tracking error signal actually used. The signal is denoted by A, and the width is denoted by b. In order to cancel the DC offset caused by the shift of the objective lens 5 or the skew of the disk recording medium 3, the value shown by the curve CV2 may be subtracted by the offset width b shown by the curve CV3. The offset removal has been described above for the first sum signal E, but the same applies to the second sum signal F. The present invention provides a first sum signal E
After subtracting the respective offsets from the RF envelope of the second sum signal F and the RF envelope of the second sum signal F, a push-pull signal is calculated. As a result, the offset is removed from the tracking error signal.

First Embodiment: Basic Operation and Basic Circuit Hereinafter, a basic circuit and an operation thereof according to a first embodiment of the present invention will be described in detail. Under the conditions described above, the offset b is a product of the coefficient K and the peak a, that is, b = K
The constant K is determined so as to be × a. However, K <1. Then, the signal that canceled the offset is
It can be expressed as (A-Ka). A indicates the first sum signal E or the second sum signal F. In the present invention,
(A-Ka) is used as the corrected first sum signal or the corrected second sum signal for calculating the tracking error signal TE. FIG. 8 is a diagram showing a basic circuit 20 (a circuit as a first embodiment) for calculating a tracking error (TE) signal after the above-described offset correction of the present invention. First
It is assumed that the sum signal E and the second sum signal F are calculated by a circuit including the arithmetic circuit 19 illustrated in FIG. The top hold push-pull (TPP) signal calculation circuit 20 shown in FIG. 8 replaces the arithmetic circuit 19 shown in FIGS. The top hold / push / pull (tracking error) signal calculation circuit 20 detects and holds the peak a of the first sum signal E, and multiplies the result by a constant K, and a top hold / constant multiplication circuit 22; −K × a), and a top hold / constant multiplication circuit 26 that detects and holds the peak a ′ of the first sum signal F and multiplies it by a constant K.
And a differential amplifier circuit 28 for calculating (F−K × a ′);
A differential amplifier circuit 30 for performing a push-pull operation on these calculated signals. A tracking error signal is output from the differential amplifier circuit 30. In the tracking error signal calculating circuit 20, a peak hold / constant multiplying circuit 2 is used to detect a change in peak and multiply by a coefficient K.
Using (2, 26), (E−K × a) and (F−K × a ′) are calculated. (E−K × a) is the first sum signal after the top hold processing (abbreviated to “top hold / first sum signal”)
TPP (E), (F−K × a ′) is referred to as a second sum signal after the top hold processing (abbreviated as top hold / second sum signal) TPP (F), and the constant K is referred to as TPP (F). The tracking error signal calculated by the circuit 30 is called a calculation coefficient, and the top hold tracking error signal TPP
(TE). The offset of the top hold tracking error signal TPP (TE) is removed according to the above-described principle.

More preferably, a low-pass filter circuit 32 provided at a stage subsequent to the circuit 30 is provided, and the top-hold tracking error signal TPP (TE) from the circuit 30 is provided.
, A top hold tracking error signal TPP (TE) ′ that has passed the low frequency component of

In the subtraction circuit 36 shown in FIG. 8, the alignment signal AL obtained by subtracting the second sum signal F from the first sum signal E is used.
Can be calculated. Use of the alignment signal AL will be described later.

Embodiment 2 Circuit FIG. 9 shows a top hold / first sum signal TPP (E) and a top hold F signal TPP (F) obtained by the top hold / push / pull signal calculation circuit 20 shown in FIG. )
From the top hold push-pull signal, that is, the top hold tracking error signal TPP
FIG. 9 is a diagram illustrating a circuit configuration of a second embodiment for calculating (TE). The circuit configuration illustrated in FIG. 9 makes it possible to output a basic signal from the laser coupler LC as much as possible while taking into account that there are limits to the components housed in the laser coupler LC from the viewpoint of mounting. It is designed to facilitate easy adjustment of a tracking error (TE) signal. The laser coupler LC includes the laser LD and the photodiodes PD1 and PD shown in FIG.
2 and a microprism 1. Further, the laser coupler LC includes the objective lens 5 to the amplification circuit 19 illustrated in FIG. 4 and the top hold / constant multiplication circuits 22 and 26 and the amplification circuits 24 and 28 illustrated in FIG.
An arithmetic circuit 30, an LPF 32, and a calculation circuit 36 for calculating an alignment signal AL are housed therein. That is, in the laser coupler LC, the top hold / first sum signal TPP (E) and the top hold / second sum signal TP
P (F) is calculated, and (E signal−F signal) is calculated as the alignment signal AL. These signals T
PP (E), TPP (F) and AL are basic output signals as the laser coupler LC.

TPP (E) = K × E _TP −E (5) TPP (F) = K × F _TP −F (6) AL = E−F (7) E _TP is the peak holding value of the E signal, and F _TP is F
This is the peak holding value of the signal, and K is the TPP calculation coefficient (K <1).

In calculating the final tracking error (TE) signal, there is a high possibility that the gain is adjusted. Therefore, the resistors 42 and 44 having the resistance value R1 and the high-frequency integrated circuit RFIC are provided outside the laser coupler LC.
Is provided. In a high frequency integrated circuit RFIC, a differential amplifier circuit 50, its negative feedback resistor 46, a positive feedback resistor 4
8 are provided. The resistance values of the negative feedback resistor 46 and the positive feedback resistor 48 are each R2. The top hold tracking error signal TPP (TE) is represented by the following equation.

TPP (TE) = (R2 / R1) × [(K × _FTP- F) − (K × _ETP- E)] = (R2 / R1) × [(EF) −K ( _ETP− F _TP )] ・ ・ ・ (8)

In the circuit shown in FIG. 9, the gain can be changed by appropriately adjusting the resistance values R1 and R2 outside the laser coupler LC, and the top hold tracking error signal TPP (TE) with the gain adjusted appropriately can be provided.

Practical signal processing of laser coupler LC
Sense circuit diagram 10 is a practical circuit diagram of a signal processing circuit in the laser coupler LC. Front PD and rear P
The detection signal from D is amplified to a predetermined signal level by a current / voltage conversion / amplification circuit I-VAMP containing a current / voltage (I / V) conversion circuit and an amplification circuit (AMP), respectively. The above-mentioned signals, SPD1, SPD2, E, and F, are calculated by the operational amplifier circuit SUMMINGAMP.
Furthermore, the operational amplifier AMP (AL) uses the alignment signal AL, and the operational amplifier AMP (E) controls the top hold signal.
First sum signal TPP (E), operational amplifier circuit AMP (F)
Calculates the top hold / second sum signal TPP (F). In the sum operation amplification circuit SUMTING AMP, a bias is applied from the bias circuit BIAS.

Embodiment 3 Circuit FIG. 11 shows a top hold / first sum signal TPP (E), top hold / second sum obtained by the top hold / push / pull signal calculation circuit 20 shown in FIG. Signal T
FIG. 11 is a diagram illustrating a circuit configuration of a third embodiment for calculating a top hold tracking error (TPP (TE)) signal from PP (F). The circuit of FIG. 11 is a circuit that substantially changes the TPP calculation coefficient in the circuit illustrated in FIG. From the laser coupler LC shown in FIG. 1, as shown in FIGS. 8 and 11, the top hold / first sum signal TPP (E) and the top hold / second sum signal TP
P (F), and outputs an alignment signal AL. In order to calculate the top hold tracking error signal TPP (TE), the resistors 42 and 44 having a resistance value R1, the resistors 45 having a resistance value R3, and the high frequency integrated circuit RFIC are provided outside the laser coupler LC. . A differential amplifier circuit 50, a negative feedback resistor 46 thereof, and a positive feedback resistor 48 are provided in the high frequency integrated circuit RFIC. The resistance values of the negative feedback resistor 46 and the positive feedback resistor 48 are R2
It is. The circuit illustrated in FIG. 11 includes, in addition to the circuit illustrated in FIG. 9, a resistor that adds the alignment signal AL to the top hold / first sum signal TPP (E) and applies the signal to the inverting terminal (−) of the amplifier circuit 50. A resistor 45 with value R3 is added. Top hold tracking error signal TPP
(TE) is represented by the following equation.

[0032] TPP (TE) = (R2 / R1) × _{[(EF) -K (E TP -F} TP) ] - (R2 / R3) (EF ) = (R2 / R1) × [(EF) - ( R2 / R3) (EF)] - (R2 / R1) [K (E _TP -F _TP)] = [(R2 (R3-R2 )) / (R1R3)] · (EF) -K 1 '(E TP -F _TP )] (9) where K ₁ ′ = (R3 / (R3-R2) × K.

The circuit illustrated in FIG. 11 has a constant K ₁ ′ = (R3 / (R3-R2) × K, as compared with the circuit illustrated in FIG.
Since the (coefficient) is multiplied by (E _TP -F _TP ), there is an advantage that the TPP calculation coefficient K can be increased. The optimum value of the TPP calculation coefficient K differs depending on the optical disk device in accordance with the variation in the characteristics of the optical disk device. However, since the TPP calculation coefficient is set constant in the laser coupler LC, it is usually fixed for all the optical disk devices of the same model. So in the adjustment stage,
When it is desired to change to the optimum TPP calculation coefficient K (in the case of this embodiment, to increase the coefficient K), the circuit configuration shown in FIG. 11 has an advantage that the change can be performed outside the laser coupler LC. There is. The external resistors 42, 44, and 45 of the laser coupler LC and the high-frequency integrated circuit RFIC are used as variable resistors, and their resistance values are adjusted to adjust the TPP calculation coefficient K, in other words, the top hold / first sum. The gain of signal TPP (E) can be adjusted as appropriate. FIG. 11 shows a high frequency integrated circuit RFI.
Resistors 46 and 48 illustrated inside C can also be provided externally. The resistors 46 and 48 are connected to a high frequency integrated circuit RFI.
The provision outside the capacitor C not only increases the flexibility of gain adjustment by making the gain adjustment resistor variable, but also incorporates resistors 46 and 48 having large resistance values in the high-frequency integrated circuit RFIC as an IC circuit. This is because it may not be preferable to do so.

Embodiment 4 Circuit FIG. 12 shows a top hold / first sum signal TPP (E), top hold / second sum obtained by the top hold / push / pull signal calculation circuit 20 shown in FIG. Signal T
FIG. 14 is a diagram illustrating a configuration of a circuit of a fourth embodiment that calculates a top hold tracking error (TPP (TE)) signal from PP (F). The circuit in FIG. 12 is a circuit in which the TPP calculation coefficient in the circuit illustrated in FIG. 9 can be reduced. The optimum TPP calculation coefficient K differs depending on the optical disk device according to the variation in the characteristics of the optical disk device. However, since the TPP calculation coefficient is set constant in the laser coupler LC, it is usually fixed for all the optical disk devices of the same model. Therefore, when it is desired to change to the optimum TPP calculation coefficient in the adjustment stage (in the case of this embodiment, to increase the coefficient), the circuit configuration shown in FIG. 12 is used. Laser coupler L
From C, the top hold / first sum signal TPP
(E), the top hold / second sum signal TPP (F),
Outputs alignment signal AL. In order to calculate the top hold tracking error signal TPP (TE), resistors 42 and 44 having a resistance value R1, a resistor 47 having a resistance value R3, and a high frequency integrated circuit RFIC are provided outside the laser coupler LC. . High frequency integrated circuit RFI
In C, a differential amplifier circuit 50, a negative feedback resistor 46 thereof, and a positive feedback resistor 48 are provided. The resistance values of the negative feedback resistor 46 and the positive feedback resistor 48 are each R2.
The circuit illustrated in FIG. 12 is different from the circuit illustrated in FIG. 9 in that the alignment signal AL is top-held and the second sum signal T
Non-inverting terminal (+) of amplifier circuit 50 by adding to PP (F)
, A resistor 46 having a resistance value R3 to be applied to the power supply is added.
Top hold tracking error signal TPP (T
E) is represented by the following equation.

[0035] TPP (TE) = (R2 / R1) × [(EF) -K (E TP -F TP)] + [R2 / (R3 + R2) (1 + R2 / R1) (EF) = [( R2 / R1) (R1 + 2R2 + R3) / (R2 + R3)] × [(EF) −K ₂ ′ (E _TP −F _TP )] (10) where K ₂ ′ = [(R2 + R3) / (R1 + 2R2 + R3)] × K.

The circuit illustrated in FIG. 12 is different from the circuit illustrated in FIG. 9 in that K ₂ ′ = [(R2 + R3) / (R1 + 2R2 + R3)] × K
Since (E _TP -F _TP ) is multiplied by a constant (coefficient)
The TPP calculation coefficient K can be reduced. External resistor 4 for laser coupler LC and high frequency integrated circuit RFIC
The gain of the second sum signal TPP (F) can be appropriately adjusted by adjusting the resistance values of the variable resistors 2, 44 and 47 as variable resistors. Thus, the resistors 42, 44, 4
7 is a laser coupler LC and a high frequency integrated circuit RF
Providing the IC outside the IC facilitates gain adjustment. The resistors 46 and 48 illustrated in FIG. 12 inside the high-frequency integrated circuit RFIC can also be provided outside as described with reference to FIG. That is, the resistor 4
Providing 6,48 outside the high frequency integrated circuit RFIC not only increases the flexibility of gain adjustment by making the gain adjustment resistor variable, but also has a large resistance value for the high frequency integrated circuit RFIC as an IC circuit. This is because it may not be preferable to incorporate the resistors 46 and 48.

Second Embodiment to Fourth Circuit The second embodiment shown in FIG. 9 is a basic circuit for calculating the top hold tracking error signal TPP (TE). The circuit of the third embodiment shown in FIG. 11 can be used when the TPP calculation coefficient K is increased from outside the laser coupler LC and the RFIC. The circuit of the fourth embodiment shown in FIG. 12 can be used when the TPP calculation coefficient K is reduced from outside the laser coupler LC and the RFIC. In addition, laser coupler L
To enable the TPP calculation coefficient K to be increased or decreased from outside the C and the RFIC, the resistor 42 and / or the resistor 44 may be replaced by a variable resistor and the RFIC
To change the amplification factor of the differential amplifier circuit 50 inside.

Fifth Embodiment Circuit: Considering Tracking State
The circuit diagram 13 that the RF signal is a graph showing the mirror signal MIRR indicating whether detrack from on-track by the value of the RF signal. The mirror signal MIRR is at a low level during on-track and at a high level during detrack. In short, the mirror signal MIRR indicates whether the track is on-track or de-tracked. FIG. 14 shows a circuit in which an inverter 60 and a transistor 61 are added to the tracking error signal calculation circuit shown in FIG. As described above, the tracking error signal calculation circuit illustrated in FIG. 11 is different from the circuit illustrated in FIG.
This is a circuit that adds L to the first sum signal TPP (E) to reduce the value of the TPP calculation coefficient. At the time of off-track, since the mirror signal MIRR is at a high level, the inverter 6
The transistor 62 is turned off by the mirror signal inverted by 1 and the alignment signal AL becomes the first sum signal T
PP (E) is added. As a result, the value of the TPP calculation coefficient decreases. This state is the same state as the circuit illustrated in FIG. When on-track, the mirror signal MIR
Since R is at a low level, the transistor 62 is turned on by the mirror signal inverted by the inverter 61, and the alignment signal AL is not added to the first sum signal TPP (E). As a result, the value of the TPP calculation coefficient does not change. This state is the same state as the circuit illustrated in FIG. If the TPP calculation coefficient K = 0.80 for on-track and the TPP calculation coefficient K = 0.68 for on-track, the TPP for off-track may be considered.
The calculation coefficient is set to 0.68, and 0.8 for on-track.
If it is set to be larger than 0, it can be considered that the tracking speed can be reduced when on-track than when off-track. In particular, for example, in a CD-ROM or the like that operates at a quadruple speed, the tracking can be pulled in quickly.

Modification of Fifth Embodiment As shown by the broken line in FIG. 14, the transistor 62 is turned on / off by the mirror signal MIRR without passing through the inverter 60, and the alignment signal AL is changed to the second sum signal TPP ( If the circuit configuration is determined as to whether or not it is added to F),
The circuit state illustrated in FIG. 9 and the circuit state illustrated in FIG. 12 can be obtained. In this case, contrary to the state described above,
At the time of detracking, the alignment signal AL is not added to the second sum signal TPP (F), and the value of the TPP calculation coefficient is maintained. At the time of the on-track, the alignment signal AL is added to the second sum signal TPP (F), and the value of the TPP calculation coefficient becomes practically large. Also in this case, the TPP calculation coefficient K is set to 0.80 for on-track and the TPP calculation coefficient K is set to 0.68 for detrack.

[0040]Sixth embodiment circuit: TPP calculation coefficient frequency
Circuit with added dependencies FIG. 15 is a graph illustrating the relationship between the frequency and the TPP calculation coefficient.
It is rough. In the circuit illustrated in FIG. 11 or FIG.
Pass the alignment signal AL through a low-pass filter
And the top hold first sum signal TPP (E) or
To add to the top hold second sum signal (F)
Thus, the TPP calculation coefficient K can be changed according to the frequency band.
You. For example, 60H_ZIn the above, the TPP calculation coefficient K =
0.68, 60H_ZBelow is TP
P calculation coefficient K is increased to 0.72. Thus, the frequency
By changing the TPP calculation coefficient according to the band,
The tracking operation can be performed depending on the frequency.
You. In the above example, 60H _ZTP in the following low frequency band
Since the value of the P calculation coefficient increases, the tracking operation
60H_ZIt will be faster when above. In the sixth embodiment
Even if the TPP calculation coefficient is outside the laser coupler LC
There is an advantage that it can be adjusted with. Sixth Embodiment Circuit Configuration
It will be described later with reference to FIG. The detailed circuit is shown in FIG.
7 will be described.

Seventh Embodiment Circuit: Fifth and Sixth Embodiments
FIG. 16 is a circuit diagram of a seventh embodiment of the tracking error signal calculation circuit of the optical disk device according to the present invention. The tracking error signal calculation circuit of FIG. 16 is a circuit obtained by adding a part of the low-pass filter circuit 64 of the sixth embodiment to the circuit of FIG. 14 exemplified as the fifth embodiment. The low frequency component AL ′ is extracted from the alignment signal AL in the low pass filter circuit 64. When the low-frequency component AL ′ is applied to the top-hold first sum signal TPP (E) or the top-hold second sum signal TPP (F), the low-frequency component AL ′ of the sixth embodiment described with reference to FIG. Thus, the TPP calculation coefficient is changed according to the frequency band. Further, there is provided an alignment signal addition selection transistor 61 which is turned on / off in accordance with the level of the mirror signal MIRR to permit or prohibit the addition of the alignment signal AL 'of the low frequency component passed through the low-pass filter circuit 64. Have been. Therefore, if the frequency band is, for example, 6
Against TPP calculation coefficient 0.72 at 0H _Z or less, further, it is possible to change the value in either on-track or detrack. Similarly, for TPP calculation coefficient 0.68 60H _Z above, further, it is possible to change the value in either on-track or detrack. As a result, when on-tracking, the tracking time can be shortened by increasing the TPP detection coefficient optimally set in a certain frequency band.

[0042] The specific circuit diagram 17 illustrates a related circuit and a tracking error calculation circuit 60 as a specific circuit of the seventh embodiment described above. In the tracking error calculation circuit 60, the resistors 46 and 48 are provided outside the integrated circuit chip 50A corresponding to the RFIC in FIG. 20, and the differential amplifier circuit in the RFIC shown in FIG. 50 and its peripheral circuits. Thus, the resistor 4
By disposing the resistors 6, 48 outside the integrated circuit chip 50A, it is possible to avoid difficulty in mounting a resistor having a large resistance value on the semiconductor integrated circuit, and to replace the resistors 46, 48 in the same manner as the resistors 42, 44. As well as facilitating mounting as an external resistor, its change is also facilitated.

A circuit corresponding to the circuit of the seventh embodiment will be described. The tracking error calculation circuit 60 includes:
A transistor 62 for switching the level of the mirror signal MIRR, that is, the TPP calculation coefficient substantially substantially at the time of on-track, is provided downstream of the resistor 47. The inverter 61 is connected to the base of the transistor 62. Further, the tracking error calculation circuit 60 is provided with a low-pass filter circuit 64 that passes a low-frequency component of the alignment signal AL. The low-pass filter circuit 64 includes a resistor 641, a capacitor 642, and a resistor 642. In particular, capacitors 642
Functions as a circuit for extracting a low-frequency signal component. The tracking error calculation circuit 60 is further provided with a series circuit of a variable resistor 67 and a resistor 65 in parallel with a series circuit of the resistor 47 and the low-pass filter circuit 64. At the time of on-track, the transistor 62 is turned on and the alignment signal AL is not added to the top hold / first sum signal TPP (E). Therefore, the value of the TPP calculation coefficient does not change. On the other hand, in the case of the detrack, the transistor 62 is turned off, and the alignment signal AL becomes the top hold / first sum signal TP
It is added to P (E). Therefore, the value of the TPP calculation coefficient specified in the frequency band at that time becomes substantially small. This operation will be additionally described. Considering the change in the TPP calculation coefficient, if the value is set to a specified value in the case of detrack, the result is substantially the same as a value larger than the specified value in the case of on-track. As described above, in the tracking error calculation circuit 60,
A low-pass filter circuit 64 including a capacitor 642 is provided so that the TPP calculation coefficient K can be changed according to the frequency band. In addition, the transistor 62 can change the TPP calculation coefficient according to the tracking state. As a result, an accurate tracking error signal can be obtained in accordance with the frequency characteristics, and a tracking operation can be quickly performed, for example, in quadruple-speed reproduction on a CD-ROM.

Modification In the circuit configuration of FIG. 17, the inverter 61 is removed,
The circuit may be configured to add the output of the low-pass filter circuit 64 to the top hold / second sum signal TPP (F).

In FIG. 17, the top hold tracking error signal TPP (TE) is changed to SL shown in FIG.
The phase is compensated in a phase compensation track jump circuit 80 for generating a signal for causing the ED to perform a track jump operation, and the tracking coil 120 is driven via the switch circuit 100 and applied to the tracking driver circuit 110. Since the phase compensation track jump operation itself is not directly related to the present invention, its details will not be described. The inverted ENABLE signal is output from a CP of a microcomputer or the like that performs tracking servo control.
This signal is provided from U and determines the operation timing.

The top hold tracking error signal TPP calculated by the tracking error calculation circuit 60
(TE) is applied to the midpoint servo control circuit 120 for controlling the optical pickup to the midpoint position of the track when performing coarse control (Coarse Control) for moving the optical pickup to the vicinity of the track, and the center signal together with the alignment signal AL. Used to generate the point servo control signal CE. FIG. 19 shows the operation of the midpoint servo, but it is not directly related to the present invention, and thus details thereof will not be described.

As described above, a mini-disc device, a CD, and the like are exemplified as the optical recording device of the present invention.
Although the signal processing of E) has been described, the present invention is not limited to a mini-disc device, a CD, and the like, and can be applied to other optical recording devices using a tracking error signal.

[0048]

Since the top hold tracking error signal TPP (TE) according to the present invention contains almost no offset, the tracking servo control in the optical recording apparatus can be accurately performed. Particularly, in the present invention, in addition to optimizing the top hold coefficient in accordance with the frequency characteristics, an optimum value is selected according to the tracking state, so that a tracking error signal that enables the best tracking control is provided. it can.

[Brief description of the drawings]

FIG. 1 is a diagram showing a cross section of a laser coupler and a ray trajectory of a disk recording medium (not shown) located above the laser coupler.

FIG. 2 is a plan view of a three-division photodiode of the two photodiodes (front PD and rear PD) shown in FIG.

FIG. 3 is a plan view of a four-division photodiode among the photodiodes (front PD and rear PD) shown in FIG.

FIG. 4 is a diagram illustrating an operation of detecting a tracking error signal when the four-division photodiode shown in FIG. 3 is used, and FIG. 4 (A) shows a state where the track is detracked to the (+) side; , FIG. 4B shows an on-track state, and FIG.
Indicates a state where the track is detracked to the (-) side.

FIG. 5 is a diagram illustrating a push-pull signal when the objective lens is displaced in a radial direction (tracking direction).

FIG. 6 is a diagram showing a state in which a spot of return light on a photodiode shifts due to radial skew of a disk recording medium.

FIG. 7 is a graph showing various waveforms of the signals shown in FIGS. 4 (A) to 4 (C).

FIG. 8 is a diagram showing a circuit of a first embodiment for calculating a tracking error signal according to the present invention.

FIG. 9 is a diagram showing a circuit of a second embodiment for calculating a tracking error signal according to the present invention.

FIG. 10 is a practical circuit configuration diagram of a signal processing circuit in the laser coupler LC.

FIG. 11 is a diagram showing a circuit for calculating a tracking error signal according to a third embodiment of the present invention.

FIG. 12 is a diagram showing a circuit for calculating a tracking error signal according to a fourth embodiment of the present invention.

FIG. 13 is a graph showing an RF signal and a mirror signal.

FIG. 14 is a diagram showing a fifth embodiment circuit for calculating a tracking error signal according to the present invention.

FIG. 15 is a graph illustrating frequency dependency of a TPP calculation coefficient according to a sixth embodiment of the tracking error signal calculation circuit of the present invention.

FIG. 16 is a diagram showing a circuit for calculating a tracking error signal according to a seventh embodiment of the present invention.

FIG. 17 is a diagram showing a detailed circuit of a seventh embodiment for calculating a tracking error signal according to the present invention and a detailed circuit of a related portion.

FIG. 18 is an operation timing chart for causing the SLED to perform a track jump operation.

FIG. 19 is a timing chart showing the operation of the midpoint servo.

[Explanation of symbols]

 1. Micro prism 3. Disk recording medium 5. Objective lens LD Laser PD1, PD2 Photodiode LC Laser coupler 20 Top hold push-pull signal calculation circuit 60 Tracking error calculation Circuit 62: Transistor for alignment signal addition selection 64: Low-pass filter circuit

Claims (2)

[Claims] 1. A tracking error signal calculation circuit for an optical disk device having light receiving means for outputting first and second light reception detection signals from regions located on both sides of a track center of a disk recording medium, respectively. Detecting a peak of the first light receiving detection signal from the first light receiving detection signal from the light receiving means and subtracting a signal obtained by multiplying the peak by a first coefficient to calculate a first operation signal; A second arithmetic circuit comprising: detecting a peak of the second light reception detection signal from the second light reception detection signal from the light receiving means and subtracting a signal obtained by multiplying the peak by a second coefficient; A second arithmetic circuit for calculating a signal; a filter circuit for passing a predetermined frequency component of a third signal which is a difference between the first light reception detection signal and the second light reception detection signal; Signal of predetermined frequency component And adding the signal to the first operation signal and / or the second operation signal according to the level of the mirror signal having an on / off level defined according to the on-track or detrack state. Tracking of an optical disk device, comprising: a target signal addition circuit; and a third calculation circuit for calculating the tracking error signal by subtracting the second calculation signal from the first calculation signal from the selective signal addition circuit. Error signal calculation circuit. 2. A tracking error signal calculation method for an optical disk device having light receiving means for outputting first and second light reception detection signals from regions located on both sides of a track center of a disk recording medium, respectively. Detecting a peak of the first light reception detection signal from the first light reception detection signal and subtracting a signal obtained by multiplying the peak by a first coefficient to calculate a first operation signal; From the light reception detection signal, a peak of the second light reception detection signal is detected, and a signal obtained by multiplying the peak by a second coefficient is subtracted to calculate a second operation signal. Calculating a difference from the second light reception detection signal, extracting a predetermined frequency component of the difference signal as a third signal, and converting the third signal into the first signal according to the on-track or de-track state. An operation signal and the second operation signal Tracking error signal calculation of an optical disk device for calculating a tracking error signal by subtracting the second calculation signal from the selectively added first calculation signal. Method.