JPH08293126A - Tilt controller - Google Patents

Abstract

PURPOSE: To always control vertically an orthogonal relation between an information surface of an optical disk and an optical axis of a light beam by changing a control target value of a tilt control means based on a pulse width fluctuation signal according to the fluctuation in a pulse width of an information reproducing signal. CONSTITUTION: A pulse width fluctuation detector 5 detects deviation in an edge between an RF pulse signal PRF and a reproduction reference clock, and outputs the pulse width fluctuation signal PD according to the deviation amount. A target value variable circuit 6 outputs a correction signal for changing a target value of a tilt servo to a tilt control circuit 9 according to the values of the signal PD and an orthogonal deviation signal TLE. A tilt sensor 7 outputs the deviation in the orthogonal relation between an optical disk 1 and the optical axis of the light beam 3 to output it to the circuit 9 through an orthogonal deviation detector 8. A slope mechanism 10 is controlled by the signal TLE and the correction signal from the circuit 9, and maintains the orthogonal relation between the disk 1 and the optical axis of the beam 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording / reproducing apparatus for optically recording or reproducing a signal on a recording medium by using a light source such as a laser. The present invention relates to a tilt control device having a tilt servo system that maintains an orthogonal relationship between an optical axis of a recording / reproducing light beam and a recording surface of a recording medium (disk).

[0002]

2. Description of the Related Art As an example of a conventional tilt control device, for example, as shown in Japanese Patent Laid-Open No. 61-51630 (optical head device), a deviation of the orthogonal relationship between a disk and an optical axis of a light beam on the disk is detected. Dedicated sensor (tilt sensor)
It is known that the control is performed so as to maintain the orthogonal relationship according to the detected orthogonal shift signal.

A conventional tilt control device will be described below.

FIG. 41 is a block diagram showing a schematic configuration of a conventional tilt control device. In FIG. 41, 101 is an optical disk, which is mounted on the rotation shaft of a spindle motor 111. An optical pickup 102 has a laser light emitting element, an objective lens, and an objective lens actuator, and irradiates the optical disc 101 with a focused light beam. The optical pickup 102 is further provided with a light receiving element, which detects an information reproduction signal and a servo signal of a focus error signal or a tracking error signal. The signal corresponding to the recorded information, that is, the information reproduction signal (RF) is a signal obtained by converting the light reflected from the optical disc 101 into an electric signal. The focus error signal (FE) is an electric signal corresponding to the distance between the focal position of the focused light beam and the information recording surface of the optical disc 101. This focus error signal is fed back to the objective lens actuator of the optical pickup 102 via a focus control circuit (not shown), and as a result, FE is controlled to be substantially zero.

When tracking control (illustration omitted) in which the optical pickup 102 is controlled so as to follow a track on the optical disc 101 is performed in the state where the above-mentioned focus control is performed, on the optical disc 101 from the reproduced RF signal. You will be able to read the information recorded in.

However, the optical disc 101 and the optical disc 1
When the deviation of the orthogonal relationship with the optical axis of the light beam 103 radiated on 01 occurs, the frequency of identification error of the reproduced RF signal increases. So, disc 101 and disc 1
01, a tilt servo controlled so as to maintain an orthogonal relationship with the optical axis of the light beam 103 radiated on 01 is required.

The tilt servo will be described below.

The optical disc 1 is placed on the optical pickup 102.
01 and a tilt sensor 107 for detecting the orthogonal relationship between the optical beam 103 applied to the optical disc 101 are mounted. The tilt sensor 107 includes a light source such as a light emitting diode that emits light toward the optical disc 101 and the optical disc 10.
It is composed of a light receiving element that receives the reflected light from the light source 1. The signal from the tilt sensor 107 is the orthogonal shift detector 1
08, and an orthogonal shift signal is generated. An optical pickup is mounted on the tilt mechanism 110, and the tilt control circuit 109 drives the optical disk 101 based on the orthogonal shift signal.
The tilt of the light beam applied to the optical disc 101 with respect to is changed so that the deviation of the orthogonal relationship becomes zero.

[0009]

However, the above-mentioned prior art has the following problems. That is, when performing tilt servo using the tilt sensor 107, if there are variations in characteristics due to individual differences in the tilt sensor 107, assembly errors in the device, etc., the optical disk 101 and the optical disk 101 will be recorded even if the tilt servo is operating. A shift occurs in the orthogonal relationship with the optical axis of the irradiated light beam.

That is, even if the quadrature shift signal is zero, the normal quadrature relationship cannot be maintained because the offset occurs. The offset of the orthogonal shift signal has to be adjusted to a predetermined value or less for each device in the assembly process, which causes a problem of high production cost.

Further, when the sensor output changes due to a change with time or temperature characteristics of the tilt sensor 107, an offset occurs in the orthogonal shift signal, and the optical disc 101 and the optical disc 101 are irradiated despite the tilt servo. A shift occurs in the orthogonal relationship with the optical axis of the light beam 103. When the deviation of the orthogonal relationship occurs, the frequency of identification error of the reproduced RF signal increases as described above, and there is a problem that recording or reproduction cannot be performed in an optimum state.

The present invention has been made to solve the above problems, and its object is to provide an information surface of an optical disk and an optical axis of an information recording / reproducing light beam convergently irradiated on the optical disk. By correcting the orthogonal relationship and the deviation of the orthogonal relationship detected by the tilt sensor, control is performed so that the actual orthogonal relationship is always vertical.

[0013]

A tilt control device of the present invention is a tilt control device for controlling so that a deviation of an orthogonal relationship between an optical disc and an optical axis of a light beam applied to the optical disc is minimized. , An optical pickup for irradiating the optical beam onto the optical disc to reproduce the information recorded on the optical disc, and an orthogonal shift signal according to a shift in the orthogonal relationship between the optical disc and the optical axis are output. An orthogonal deviation detecting means, an inclination means for inclining the optical axis, and a tilt control means for driving the inclination means according to the orthogonal deviation signal so as to control the optical disk and the optical axis to intersect each other vertically. A pulse width variation detecting means for outputting a pulse width variation signal according to a variation in the pulse width of an information reproduction signal obtained from the optical pickup, and a control of the tilt control means based on the pulse width variation signal. A target value changing means for changing the target value comprises a, the object is achieved.

In one embodiment, the target value changing means is
The value of the orthogonal shift signal when the pulse width fluctuation signal has the minimum value is output to the tilt control means as the control target value.

In one embodiment, the target value varying means is
The control target value is set at least once after the device is activated.

In one embodiment, the target value changing means is
The control target value is set during signal recording or reproduction.

In one embodiment, the target value changing means is
The control target value is set when the pulse width variation signal exceeds a predetermined value during recording or reproduction of the signal.

In one embodiment, a timing generating means for generating a timing signal at the center level of the AC component of the orthogonal shift signal and a sampling means for sampling the pulse width variation signal based on the timing signal are further provided. Therefore, the target value varying means controls the target value of the tilt controlling means so that the value of the sampled pulse width fluctuation signal is minimized.

In one embodiment, the timing generating means has a high pass filter for passing a high frequency component of the orthogonal shift signal, and a binarization circuit for binarizing an output signal of the high pass filter. .

In one embodiment, the target value varying means is
The target value varying means has a function approximating means for approximating the relationship between the orthogonal shift signal and the pulse width variation signal by a function by tilting the optical axis with respect to the optical disc by the tilting means. , The control target value corresponding to the pulse width variation signal is changed using the function obtained by the function approximating means.

In one embodiment, the target value changing means is
It has a correction signal detecting means for outputting a correction signal corresponding to the direction and amount of the deviation of the orthogonal relationship from the orthogonal deviation signal and the pulse width variation signal.

In one embodiment, a disturbance signal generating means for generating a disturbance signal for driving the inclining means in a predetermined cycle is further provided, and the target value varying means includes the disturbance signal and the pulse width variation. It has a correction signal detecting means for outputting a correction signal corresponding to the direction and amount of the deviation of the orthogonal relationship from the signal.

In one embodiment, there is provided a tilt control device for controlling the deviation of the orthogonal relationship between the optical disc and the optical axis of the light beam applied to the optical disc to be minimized, and the light beam is directed onto the optical disc. An optical pickup for irradiating and reproducing the information recorded on the optical disc;
Inclination means for inclining the optical axis, reproduction error detection means for outputting a bit error rate signal corresponding to the bit error rate of the information reproduction signal obtained from the optical pickup, and for driving the inclination means in a predetermined cycle The disturbance signal generating means for generating the disturbance signal and the target value varying means for changing the control target of the inclining means according to the bit error rate signal and the disturbance signal.

The tilt control device of the present invention is a tilt control device for controlling such that the deviation of the orthogonal relationship between the optical disc and the optical axis of the light beam applied to the optical disc is minimized. An optical pickup for irradiating an optical disc and reproducing information recorded on the optical disc, and an orthogonal shift detecting means for outputting an orthogonal shift signal according to a shift in the orthogonal relationship between the optical disc and the optical axis. An inclination means for inclining the optical axis, a tilt control means for controlling the inclination means by driving the inclination means according to the orthogonal shift signal so that the optical disk and the optical axis intersect perpendicularly, Reproduction error detection means for outputting a bit error rate signal corresponding to the bit error rate of the reproduced information reproduction signal, and control of the tilt control means based on the bit error rate signal A target value changing means for changing the target,
The above-mentioned object is achieved thereby.

In one embodiment, the target value varying means is
The value of the orthogonal shift signal when the bit error rate takes the minimum value is output to the tilt control means as the control target value.

The tilt control device of the present invention is a tilt control device for controlling such that the deviation of the orthogonal relationship between the optical disc and the optical axis of the light beam applied to the optical disc is minimized. An optical pickup for irradiating the optical disc to reproduce information recorded on the optical disc, an inclining means for inclining the optical axis, and a pulse width variation of an information reproduction signal obtained from the optical pickup. Pulse width variation detecting means for outputting the pulse width variation signal, disturbance signal generating means for generating a disturbance signal for driving the tilting means in a predetermined cycle, and the pulse width variation signal and the disturbance signal according to the disturbance signal. Tilt control means for driving the tilting means to control the optical disc so that the optical axis and the optical axis intersect perpendicularly, and the tilt control based on the pulse width variation signal and the disturbance signal. A target value changing means for changing a control target value of the stage comprises a said object is achieved.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A tilt control device according to the present invention will be described with reference to the drawings. The same reference numerals are
The same components are shown.

(Embodiment 1) FIG. 1 is a block diagram of a tilt control device according to a first embodiment of the present invention. The optical disc 1 is mounted on the rotation shaft of a spindle motor 11. The optical pickup 2 has a laser light emitting element, an objective lens, and an actuator, and irradiates the optical disc 1 with a focused light beam 3. The actuator drives the objective lens in the optical axis direction of the light beam 3.
The optical pickup 2 further has a light receiving element, which outputs an information reproduction signal RF and a servo signal including a focus error signal and a tracking error signal. The light receiving element of the optical pickup 2 receives the light beam reflected on the information recording surface of the optical disc 1 and incident on the light receiving element, and outputs an information reproduction signal RF corresponding to the information recorded on the optical disc 1.

The information signal detector 4 receives the information reproduction signal RF output from the optical pickup 2 and binarizes the input information reproduction signal RF with an appropriate threshold value. The information signal detector 4 uses the binarized information reproduction signal R
Pulse width fluctuation detector 5 with F as RF pulse signal PRF
Output to.

The pulse width fluctuation detector 5 compares the phase of the RF pulse signal PRF with the phase of the clock serving as a reference for reproduction, so that the phases of these signals have a predetermined relationship (that is, a synchronized state). Phase lock control is performed so that As a result, the pulse width fluctuation detector 5 is
The deviation of the edge between the pulse signal PRF and the reproduction reference clock is detected. In other words, the pulse width variation detector 5 detects whether the pulse width of the RF pulse signal PRF is wider or narrower than the pulse width of the RF pulse signal having the ideal pulse width, and determines the amount of edge shift. The corresponding electric signal, that is, the pulse width variation signal PD is output.

The target value varying circuit 6 has a pulse width variation signal P.
A correction signal ΔTLE for changing the target value of the tilt servo according to the value of D and the orthogonal shift signal TLE described later.
Is output to the tilt control circuit 9 described later. Tilt sensor 7
Outputs a signal corresponding to the amount of deviation from the state where the optical disc 1 and the optical axis of the light beam irradiated on the optical disc 1 intersect perpendicularly (hereinafter, simply referred to as “orthogonal relation deviation”). The orthogonal shift detector 8 receives the signal output from the tilt sensor 7 and outputs the orthogonal shift signal TLE to the tilt control circuit 9. Here, the “orthogonal shift” means an error from a state where the surface of the optical disc 1 and the light beam 3 intersect perpendicularly.

FIG. 2 is a diagram showing the internal structure of the tilt sensor 7 and the orthogonal shift detector 8. The tilt sensor 7 is
It has two photodetectors 701 and 702 and an LED (light emitting diode) 703. The light emitted from the LED 703 is reflected on the surface of the optical disc 1 and enters the photodetectors 701 and 702. The photodetectors 701 and 702 output a signal having a voltage corresponding to the intensity of incident light. The quadrature shift detector 8 has a differential amplifier 802. The differential amplifier 802 has a photodetector 701 at its non-inverting input terminal and its inverting input terminal, respectively.
And 702, and outputs a signal having a voltage difference between the signals from the output terminal to the orthogonal shift signal T.
Output as LE. Optical axis of light beam 3 and optical disc 1
Ideally, the voltages of the signals output from the photodetectors 701 and 702 become equal, and as a result, the orthogonal shift signal TLE becomes zero level. If they do not intersect vertically, for example, if the optical pickup 2 is tilted with respect to the optical disc 1 so that the light incident on the photodetector 701 is stronger than the light incident on the photodetector 702, the orthogonal shift signal TLE is
It has a positive voltage. When the optical pickup 2 is tilted in the opposite direction, the orthogonal shift signal TLE has a negative voltage.

The tilting mechanism 10 changes the tilt between the optical disk 1 and the optical axis of the light beam 3 irradiated on the optical disk 1. In the following embodiments, the tilt in the radial direction of the optical disc 1 (so-called radial tilt) is changed by the tilting mechanism 10. The tilt control circuit 9 controls the tilting mechanism 10 according to the orthogonal shift signal TLE and the correction signal ΔTLE to control the optical disc 1 and the light beam 3 irradiated on the optical disc 1.
Maintains an orthogonal relationship with the optical axis of.

FIG. 3 is a diagram for explaining the operations of the tilt control circuit 9 and the tilt mechanism 10. The tilt control circuit 9 receives the orthogonal shift signal TLE, and the signal V = K2
(K1 · TLE-CS) (K1: gain adjustment circuit 901
, Gain of K2: gain of drive circuit 903). The tilt mechanism 10 includes a DC motor 1010 and a worm gear 1020. The DC motor 1010 drives the worm gear 1020 at an angular velocity ω (ω = K3 · V, K3: constant) according to the signal V. Worm gear 1020
Tilts the optical pickup 2 by θ (θ = K4 · ω, K4: constant).

The operation of the first embodiment will be described below. First,
Focus error signal FE output by the optical pickup 2
Is fed back to the objective lens actuator of the optical pickup 2 via a focus control circuit (not shown). As a result, the distance between the focal point of the light beam 3 emitted through the objective lens and the optical disk information recording surface is kept substantially constant.

When the tracking control (not shown) for controlling the light beam 3 to follow the track on the optical disc 1 is also performed in the state where the above focus control is performed,
The information recorded on the optical disc 1 can be reproduced based on the information reproduction signal RF.

If a shift occurs in the orthogonal relationship, the tilt control circuit 9 drives the tilt mechanism 10 by an amount corresponding to the orthogonal shift signal TLE output from the orthogonal shift detector 8. As a result, the inclination between the information surface of the optical disc 1 and the optical axis of the light beam 3 with which the optical disc 1 is irradiated changes, and feedback control is performed so that the orthogonal shift signal TLE finally becomes zero.

However, as described above, even if the orthogonal deviation signal TLE is controlled to be zero when there is an assembly error of the apparatus, a characteristic change of the tilt sensor 7 with time, or a temperature change, the optical disc is controlled. 1 and the optical axis of the light beam emitted onto the optical disc 1 do not intersect perpendicularly.

Therefore, the tilt control device of the present invention searches for the optimum point of the control target value of the tilt servo when the device is started up or during recording / reproduction.

FIG. 4 shows the reproduction signal RF with respect to the orthogonal shift amount.
3A and 3B are diagrams showing the waveform of FIG. 4 and the waveform of the RF pulse signal PRF. Focused light beam 3 of optical pickup 2 is optical disc 1
When an information pit formed on the recording surface of the optical disc is scanned, the reproduction signal RF shown in FIG.
Is reproduced, and the potential Vt is further detected by the information signal detector 4.
RF pulse signal PRF binarized with h as a threshold
Is generated. At this time, the pulse width of the RF pulse signal PRF becomes a predetermined length T if there is no deviation of the above-mentioned orthogonal relationship. This T generally corresponds to an integral multiple of the cycle of the reference clock signal of the information recorded on the optical disc 1.
If a shift in the orthogonal relationship occurs here, the waveform of the RF signal changes as shown in FIG. This is because the deviation of the orthogonal relationship causes a change in the shape of the reflected light from the disc 1 which is incident on the photodetector (not shown) for detecting the servo signal and the reproduction signal on the optical pickup 2 and the reproduction signal. R
This is because the signal quality of the F signal is deteriorated, and the servo signal such as the focus error signal and the tracking error signal is offset to deteriorate the signal quality of the reproduction signal RF. As the quadrature shift increases, the signal quality of the reproduction signal RF further deteriorates, and as a result, the pulse width of the RF pulse signal PRF further changes (in this case, the pulse width becomes larger as shown in FIG. 4C). Change to become smaller)
To do. Therefore, if you measure this change in pulse width,
The amount corresponding to the orthogonal shift can be detected.

Next, in the pulse width fluctuation detector 5, R
A method of measuring the pulse width of the F pulse signal PRF will be described.

FIG. 5 shows the pulse width fluctuation detector 5 of the first embodiment.
It is a block diagram of. The phase comparison circuit 501 detects the phase shift of the RF pulse signal PRF with respect to the clock signal CLK output from the VCO (voltage controlled oscillator) 504. Specifically, a pulse having a pulse width corresponding to the phase shift is output from the output terminals UP and DN according to whether the phase of the RF pulse signal PRF leads or lags the phase of the clock signal CLK. . Differential circuit 5
02 calculates the difference between the pulse signals UP and DN output from the phase comparison circuit 501, and outputs the difference to the integration circuit 503. The integrating circuit 503 integrates the difference between these signals to obtain V
Output to CO504. The VCO 504 is an integrating circuit 50.
The clock signal CLK having a frequency corresponding to the output of No. 3 is output to the phase comparison circuit 501. The adder circuit 505 outputs the pulse signals UP and D output from the phase comparison circuit 501.
Calculate the sum of N and LPF (low pass filter) 506
Output to. The LPF 506 outputs the low frequency component of the input signal as the pulse width variation signal PD.

The operation of the pulse width fluctuation detector 5 will be described below with reference to FIG. FIG. 6 shows the RF pulse signal PR
F, clock signal CLK and pulse signals UP and D
It is a figure which shows the timing of N. In practice, for example, EF
In the case of M (eight to four teen modulation), it is general that the shortest pulse of the RF pulse signal PRF has three pulses of the clock signal CLK output from the VCO 504. In the explanation using FIG. 6,
For simplicity, it is assumed that the pulse widths of the RF pulse signal PRF and the clock signal CLK are equal.

The phase comparison circuit 501, the differential circuit 502, the integration circuit 503, and the VCO 504 are PLL (phase locked).
loop). First, the phase comparison circuit 501
The pulse signals UP and DN corresponding to the phase difference between the F pulse signal PRF and the clock signal CLK are output as shown in FIG. That is, when the RF pulse signal PRF leads the clock signal CLK at the rising edge and the falling edge, the pulse signal UP having a width corresponding to the leading is output (A in FIG. 6). On the other hand, when there is a delay, a pulse signal DN having a width corresponding to the delay is output (B in FIG. 6). The phase advance or delay becomes a positive / negative pulse signal by the differential circuit 502, and further becomes a signal that is cumulatively added by the integration circuit 503. The VCO 504 generates a clock signal CLK having a frequency corresponding to the voltage of the added signal and feeds it back to the phase comparison circuit 501. As a result, the clock signal CLK becomes
The average of the phase difference is controlled to be zero.

If there is no fluctuation in the pulse width, as a result of the feedback, the pulse signals UP and DN have no pulse corresponding to the phase difference (that is, remain at zero level). Here, it is assumed that the RF pulse signal PRF has a narrower pulse width than the clock signal CLK (C in FIG. 6).
At this time, the pulse signal DN is generated at the rising edge of the clock signal CLK, and the pulse signal UP is generated at the falling edge of the RF pulse signal PRF.
On the contrary, it is assumed that the RF pulse signal PRF has a wider pulse width than the clock signal CLK (D in FIG. 6). At this time,
The pulse signal UP is generated at the rising edge of the RF pulse signal PRF, and the pulse signal DN is generated at the falling edge of the clock signal CLK.

As described above, the frequency and phase of the clock signal CLK are controlled by the PLL so that the average of the phase differences between the inputs U and V of the phase comparison circuit 501 becomes zero. Therefore, when the pulse width of the RF pulse signal PRF fluctuates, pulses having the same width are output as the pulse signals UP and DN. As a result, the adder circuit 50
5 outputs only the fluctuation component of the pulse width. LPF50
6 smoothes the fluctuation component of the pulse width, and outputs a DC voltage converted signal as the pulse width fluctuation signal PD.

FIG. 7 is a diagram showing the internal configuration of the phase comparison circuit 501. The rising edge and the falling edge of the RF pulse signal PRF are respectively detected by monomulti. These edge signal and clock signal C
Among the edges with LK, there is a circuit that sets the flip-flop at the earlier signal edge and resets it at the later signal edge. As a result, a circuit having a differential output and an addition output of the pulse signals UP and DN, that is, (UP
It may be a circuit including -DN) and (UP + DN) as output terminals. If only (UP + DN),
For example, it can be directly realized by an exclusive OR. However, with a relatively simple configuration (U
In order to obtain (P-DN) and (UP + DN), a circuit that can output the pulse signals UP and DN independently is preferable. The internal configuration of the phase comparison circuit 501 only needs to have the above-mentioned function, and can be realized by other circuit configurations.

Next, an apparatus and method for searching the tilt servo target value so that the relationship between the optical disk and the optical axis of the light beam irradiated on the optical disk becomes vertical will be described.

FIG. 8 is a diagram showing the relationship between the orthogonal shift signal TLE and the pulse width variation signal PD when searching for the tilt servo target value. In FIG. 8, the orthogonal shift signal T
When LE has a value of offset ΔTLE, the optical disk and the optical axis of the light beam irradiated on the optical disk intersect perpendicularly. In general, the orthogonal shift signal TLE periodically changes as shown in FIGS. 8A to 8C in accordance with the rotation of the optical disc and the “warpage” of the optical disc itself. Actually, even if the tilt servo is operated with the correction signal CS output from the target value variable circuit 6 being zero, the orthogonal deviation signal TLE has an AC (alternating current) having a high frequency component that the tilt servo cannot follow. The tilt component remains. At this time, the orthogonal shift signal TLE is controlled so that the average value of periodic fluctuations becomes zero.

When the offset ΔTLE is larger than the amplitude of the AC tilt component (case (A) of FIG. 8), the pulse width fluctuation signal PD takes the minimum value at one of the two peaks of the orthogonal shift signal TLE. . P of the target value variable circuit 6
The Dmin timing detector 610 uses the pulse width fluctuation signal P
A sampling pulse is generated at the timing when D takes the minimum value. As shown in FIG. 8A, a sampling pulse is generated at time t1 and output to the correction signal generator 620. The correction signal generator 620 samples the orthogonal shift signal TLE at the timing of the sampling pulse output from the PDmin timing detector 610.
In FIG. 8A, ΔTLE1 at time t1
The orthogonal shift signal TLE having a value of is sampled. The correction signal generator 620 outputs the correction signal CS having a value of ΔTLE1 to the tilt control circuit 9.

Gain adjusting circuit 901 of tilt control circuit 9
Receives the orthogonal shift signal TLE, amplifies the orthogonal shift signal TLE as much as necessary for feedback control, and then outputs it to the adder 902. Here, for simplicity, the gain of the gain adjusting circuit 901 is 1 (that is, the levels of the input signal and the output signal of the gain adjusting circuit 901 are equal).
And The adder 902 adds the correction signal CS and the signal from the gain adjustment circuit 901 and outputs the result to the drive circuit 903. The drive circuit 903 drives the tilting mechanism 10. Δ
The correction signal CS having a value of TLE1 is the orthogonal shift signal T
As a result of being added to LE, as shown in FIG. 8B, the average value of the orthogonal shift signal TLE becomes ΔTLE1,
The feedback loop is controlled. When the optical disc and the optical axis of the light beam intersect perpendicularly (when the deviation of the orthogonal relationship is zero), the value that the orthogonal deviation signal TLE may take, the offset ΔTLE, and the orthogonal deviation signal TLE in FIG. 8B. The difference from the center of fluctuation is ΔTLE2 (= ΔTL
E-ΔTLE1).

As shown in FIG. 8B, if the offset ΔTLE is located within the amplitude of the AC tilt component of the orthogonal shift signal TLE (that is, between the two peak values),
The pulse width variation signal PD has a minimum value when the information recording surface of the optical disc 1 and the optical axis of the light beam 3 are vertical (for example, time t2). In the vicinity of this time t2, the graph of the pulse width variation signal PD changes so as to turn back.

Again, PDmin timing detector 610
A sampling pulse is generated at the timing when the pulse width variation signal PD takes the minimum value. As shown in FIG. 8B, a sampling pulse is generated at time t2 and output to the correction signal generator 620. The correction signal generator 620 causes the orthogonal shift signal TLE (= ΔTLE1 +) at the time t2.
Sample ΔTLE2). Correction signal generator 62
0 is a correction signal CS having a value of offset ΔTLE
Is output to the tilt control circuit 9.

As a result of adding the sampled offset ΔTLE to the orthogonal shift signal TLE, as shown in FIG. 8C, the optical disc 1 and the light beam 3 are located at the center position of the periodic shift of the orthogonal shift signal TLE. The orthogonal relationship with the optical axis of is satisfied.

In the above description, the offset ΔTLE is
This can be canceled by sampling the orthogonal shift signal TLE twice at the timing when the pulse width variation signal PD takes the minimum value. Orthogonal shift signal TL
The larger the difference between the amplitude of the AC tilt component of E and the offset ΔTLE, the greater the number of times of sampling required.

During the operation of the recording / reproducing apparatus, the mathematical expression (1) is always applied.
If the correction shown in (1) is executed, the deviation of the orthogonal relationship can be reduced to zero even if there is a sensor error due to a temperature change of the tilt sensor that occurs after the device is activated and a sensor error due to a change over time.

ΔTLEi = ΔTLEi−1 + ΔTLEx (1) Here, ΔTLEi−1 and ΔTLEi are (i−1), respectively.
It is a correction offset amount in the process of the previous time (previous) and i-th time (this time), and ΔTLEx is the correction offset amount newly added in the process of this time. For example, in FIG. 8B, ΔTLEi is ΔTLE, ΔTLEi-1 is ΔTLE1,
ΔTLEx corresponds to ΔTLE2, respectively.

In the above description, the target position for tilt control is set by adding the offset ΔTLE to the tilt control circuit 9 of the first embodiment. Below is the offset ΔT
The operation when the LE is supplied to the control loop at different points will be described.

FIG. 9 is a diagram showing a configuration in which the target value of tilt control is changed by changing the gain balance of the orthogonal shift detector 801 for the correction signal in the first embodiment. The difference from the configuration of FIG. 1 is that the orthogonal shift detector 801 receives the correction signal CS output from the target value varying circuit 6.

FIG. 10 is a diagram showing the internal structure of the tilt sensor 7 and the orthogonal shift detector 801. The quadrature shift detector 801 has a differential amplifier 802 and a variable amplifier 803 connected to its non-inverting input terminal. The variable amplifier 803 receives the output signal of the photodetector 701 at its input terminal, and receives the correction signal CS output from the target value varying circuit 6 at its gain control terminal. The variable amplifier 803 amplifies the signal input by the gain according to the level of the correction signal CS input from the gain control terminal, and outputs the amplified signal to the non-inverting input terminal of the differential amplifier 802. As a result, according to the correction signal CS, the tilt sensor 7
The gain balance of the signals output from the photodetectors 701 and 702 can be changed. With the above configuration,
The quadrature shift detector 801 changes the target value of tilt control by changing the gain balance when differentially amplifying the output signal of the tilt sensor 7.

Referring again to FIG. Tilt control circuit 9A
Drives the tilting mechanism 10 according to the orthogonal shift signal TLE whose control target value has been corrected by the correction signal CS. As a result, as in the case shown in FIG. 1, it is possible to perform control so that the deviation of the orthogonal relationship becomes zero.

Although the tilt control for changing the target value has been described above, it suffices that the offset ΔTLE that is constantly present can be given to the feedback loop, and the position where the correction signal CS is added to the loop is not limited to the above example. .

According to the first embodiment, the orthogonal position can be searched with high accuracy by detecting the orthogonal deviation with high sensitivity and further correcting it.

Next, another example of the pulse width fluctuation detector 5 will be described with reference to FIG. FIG. 11 is a state transition diagram of the phase comparison circuit of the pulse width variation detector 5. A phase comparison circuit that realizes the state transition diagram of FIG. 11 is a phase comparison circuit 50 that is a constituent element of the pulse width variation detector 5 shown in FIG.
It operates in the same manner as 1. In FIG. 11, a, b, c, d,
e and f are nodes that represent states. In FIG. 11, the numerical values are written in the order of “U, V / UP, DN”. For example, "11/00" means U = 1, V = 1, UP
= 0 and DN = 0. Here, "0" represents a low level (L) and "1" represents a high level (H).
The operation of this state transition diagram will be described by taking the section A of FIG. 6 as an example. State a is a state in which both inputs U and V are (L). At this time, nothing is output. Input U (P
When RF) rises earlier, the output UP becomes (H) (U: V / UP: DN = 10/10), and the state changes to state b. Next, when V (CLK) rises, UP becomes 0 (U: V / UP: DN = 11/00), and the state changes to state d. The output UP becomes (H) during the state b, which means that the phase advance pulse is generated at the rising edge. The state c means a phase-delayed pulse, and the states e and f respectively lead the phase at the falling edge,
This means outputting a delayed pulse.

The operation of FIG. 11 can be realized by designing a logic circuit that realizes the above state transition diagram. 12
11 state 3 a to 3 f (S1: S2: S).
It is a figure shown by 3). The circuit can be simplified by setting the lower 2 bits (S2: S3) to match the outputs UP and DN as shown below. From FIG. 12, the logical formulas for realizing the above state transitions are as shown in Formula (2), Formula (3), and Formula (4).

S1 = U · S1 + V · S1 + U · V ·! S1 (2) S2 = U! V! S1 +! U ・ V ・ S1 (3) S3 =! U ・ V ・! S1 + U! V · S1 (4) Here, “! V” represents NOT of V.
"! U" represents NOT of U. "! S" is N of S
It represents OT. At this time, the output UP can be set as shown in Expression (5), and the output DN can be set as shown in Expression (6).

UP = S2 (5) DN = S3 (6) The characteristic of the phase comparison circuit with the above configuration is that it does not require the rising / falling edge detection using monomulti as shown in FIG. It is to be realized with a simple circuit configuration of only a logic circuit.

Next, still another example of the pulse width fluctuation detector will be described with reference to FIG. FIG. 13 is a block diagram showing still another example of the pulse width fluctuation detector. Differential circuit 502, integrating circuit 503, adding circuit 505 and L
The PF (low pass filter) 506 operates in the same manner as in FIG. The clock extraction circuit 510 uses the RF pulse signal P
The clock signal CLK is extracted from RF. The D flip-flop (latch) 512 latches the rising edge and the falling edge of the RF pulse signal PRF at the timing of the edge of the clock signal CLK. The variable delay circuit 513 delays the RF pulse signal PRF according to the output voltage of the integrating circuit 503. The phase comparison circuit 514 operates similarly to that shown in FIG.

The operation of the pulse width fluctuation detector having the above configuration will be described. First, since the phase comparison circuit for realizing the state transition diagram shown in FIG. 11 compares the edges of two input signals, P
During the LL operation, the cycles of these two input signals must be exactly the same. However, in general, the RF pulse signal PRF
Is modulated with information (that is, digital data) and includes a cycle that is an integral multiple of the cycle (basic cycle) of the clock signal CLK. In such a case, the clock signal CLK can be synchronized with the fundamental period component of the RF pulse signal PRF by using a PLL normally equipped with an exclusive OR type phase comparison circuit. However, this type of phase comparison circuit does not essentially detect rising / falling edges, and can separate and output the lead and lag of the phase into two outputs like the phase comparison circuit of FIG. Can not. Therefore, the pulse width fluctuation cannot be detected. Therefore, in the example described here, means for extracting the clock signal CLK from the PRF signal as described above,
That is, the clock signal extraction by the PLL and the pulse width variation detection by the phase comparison circuit of FIG. 11 are separated.

The clock extraction circuit 510 is composed of a PLL equipped with an exclusive OR type phase comparison circuit, an integration circuit, and a VCO, and is V for the RF pulse signal PRF.
The CO output is synchronized and is output as the clock signal CLK. Since the rising and falling edges of the RF pulse signal PRF that have passed through the D flip-flop 512 are all given by the clock signal CLK, they serve as reference signals with no pulse width fluctuation. However, since the phase is delayed by about half a clock with respect to the signal before input, it is necessary to delay the PRF signal to align the phases of both. It is possible to use a fixed delay line as a means for this delay, but the RF pulse signal P is affected by the fluctuation of the rotation of the optical disk.
When the RF cycle changes subtly, a phase error may occur between the output signal of the D flip-flop 512 and the output signal of the delay line, and this may be erroneously detected as a pulse width fluctuation. Therefore, in this example, this phase error is detected by the phase comparison circuit 514 and is fed back to the variable delay circuit 513 via the integration circuit 503 to cancel.
FIG. 14 is a diagram showing a waveform of each part of the pulse width variation detector shown in FIG. The hatched portion of the waveform in FIG. 14 shows the pulse width variation of the RF pulse signal PRF and the variation of other signals caused thereby.

According to the pulse width fluctuation detector shown in FIG. 13, the pulse width fluctuation amount can be detected from the modulated RF pulse signal PRF by using a simple phase comparison circuit. In this example, the case where the phase difference between the RF pulse signal PRF and the latch signal thereof is automatically corrected has been described, but as described above, the fixed delay line may be used instead of the variable delay circuit. In this case, the phase comparison circuit 514-2
Of the two outputs, only (UP + DN) is required, so
An exclusive OR circuit can be used instead of the phase comparison circuit 514 and the addition circuit 505 of FIG.
The circuit is simplified. Although a specific example of the pulse width fluctuation detector has been described above, the present invention is not limited to the pulse width fluctuation detector described above.

In Example 1, forcibly AC (alternating current)
By adding the disturbance signal to the tilt servo loop,
Orthogonal deviation search can also be performed. FIG. 15 is a diagram showing a configuration including a disturbance generator for applying an AC disturbance signal to the tilt servo loop. The disturbance generator 950 is an AC
A disturbance signal having a component is generated and output to the adder 902. With the configuration shown in FIG. 15, it is possible to perform a more accurate orthogonal shift search. The disturbance generator 950 preferably adds an AC disturbance signal as an AC tilt component to the feedback loop when the AC tilt component generated by the disc rotation is too small. In addition, the AC tilt component originally generated by the rotation of the disk,
The sum with the AC disturbance signal applied by the disturbance generator 950 needs to be limited to a level that does not cause an abnormality in the operation of the recording / reproducing apparatus. In order to effectively search the offset amount, it is preferable that the AC disturbance signal applied to the feedback loop is synchronized with the AC tilt component generated by the disk rotation. In FIG. 15, the disturbance generator 950 receives the quadrature shift signal TLE, detects the period of the AC fluctuation component of the quadrature shift signal TLE, and outputs the AC disturbance signal synchronized with the period and the phase to the tilt control circuit 9. .

(Embodiment 2) A second embodiment will be described in which the quadrature target value search is performed while keeping the variation amount of the quadrature target value constant regardless of the magnitude of the AC tilt.

FIG. 16 is a block diagram of the second embodiment.
The timing circuit 12 includes an HPF (high pass filter) 1
It has 201 and a binarization circuit 1202. HPF12
01 receives the orthogonal shift signal TLE and blocks the low frequency component of the orthogonal shift signal TLE to output a high frequency component corresponding to the rotation frequency of the disk to the binarization circuit 1202. The binarization circuit 1202 converts the input signal into 2
By digitizing, the timing signal TS indicating the timing at which the waveform having the AC tilt component of the orthogonal shift signal TLE (in particular, the AC tilt component corresponding to the rotation frequency of the disk) crosses the center of the periodic fluctuation is output.

The target value varying circuit 6B has a sampling circuit 6B1, a controller 6B2 and a memory 6B3. The sampling circuit 6B1 is the timing circuit 1
The pulse width fluctuation signal PD is sampled at the rising edge and the falling edge of the timing signal TS outputted from the signal No. 2. The controller 6B2 stores the data representing the level of the sampled pulse width variation signal PD in the memory 6B3 or extracts the data stored in the memory 6B3. Further, the controller 6B2 is
A predetermined step amount is added to or subtracted from the correction signal CS according to the increase / decrease of the pulse width fluctuation signal PD, and is output to the adder 90. The adder 90 receives the orthogonal shift signal TLE and the correction signal CS, and outputs a signal obtained by adding these signals to the tilt mechanism 10.

The operation of the tilt control device having the above configuration will be described. FIG. 17 is a diagram of the orthogonal shift signal TLE and the pulse width variation signal PD for explaining the second embodiment. In the servo operating state, the offset ΔT described in the first embodiment
Due to the presence of LE, as shown in FIG. 17A, the output of the quadrature shift detector 8 has an AC tilt component (sinusoidal variation in FIG. 17) superimposed on a DC (direct current) tilt servo component (ATLE1). The orthogonal shift signal TLE is output.
The orthogonal shift signal TLE is the HPF1 of the timing circuit 12.
It is input to 201. The timing circuit 12 outputs a timing signal TS for sampling the pulse width variation signal PD to the timing input terminal of the sampling circuit 6B1. The sampling circuit 6B1 samples the pulse width variation signal PD output from the pulse width variation detector 5 in accordance with the timing signal TS output from the timing circuit 12. The target value varying circuit 6B outputs a correction signal CS such that PD becomes a minimum value or a predetermined value or less, and outputs the correction signal CS to the adder 90.

The specific operation will be described with reference to FIG. In FIG. 17A, the center of variation of the AC tilt component (ATLE1) and the offset ΔTLE are different. Generally, the TLE signal is a signal obtained by superimposing an AC tilt on a DC tilt, and periodically changes at the rotation frequency of the disc. On the other hand, when the PD signal has a relatively large orthogonal shift ((A) in FIG. 17), it has a waveform corresponding to the AC component (AC tilt) of TLE which periodically changes at the rotation frequency of the disk. When the orthogonal shift becomes relatively small ((B) and (C) in FIG. 17), the waveform does not necessarily correspond to the AC tilt. In FIG. 17B, the pulse width fluctuation signal PD is a signal having two minimum values as a result of being folded back at the minimum value. Therefore, the AC component of the pulse width variation signal PD does not have a symmetrical waveform. Further, in FIG. 17C, PD has a minimum value when the AC component of the orthogonal shift signal crosses ATLE3.

In the initial state, it is assumed that the target value varying circuit 6B does not apply DC disturbance to the tilt servo loop. That is, the correction signal C output by the controller 6B2
S has a zero level. Therefore, the output of the adder 90 is the same signal as the orthogonal shift signal TLE. The center of the AC tilt fluctuation at this time is ATLE1. The output timing signal TS of the timing circuit 12 has a rising edge and a falling edge at the timing when the AC component of tilt crosses ATLE1. The sampling circuit 6B1 samples the pulse width variation signal PD at the rising edge and the falling edge of the timing signal TS. In FIG. 17A,
The pulse width variation signal PD sampled at the time t1 has the level PD1. The controller 6B2 is
Data representing the size of the level PD1 is stored in the memory 6B3.
To be stored.

Next, the controller 6B2 adds a new correction signal CS (having a level ΔTLE1) obtained by adding ΔTLE1 to the current correction signal CS having a zero level to the adder 9
Output to 0. As a result, the orthogonal shift signal TLE becomes
It periodically changes with LE2 (= ATLE1 + ΔTLE1) as the center. The timing circuit 12 outputs to the sampling circuit 6B1 a timing signal TS that represents the timing at which the AC component of tilt crosses the center ATLE2 of fluctuation. The sampling circuit 6B1 samples the pulse width variation signal PD at time t2. As shown in FIG. 17B, the sampled value is PD2.
With a level of.

The controller 6B2 compares the PD1 stored in the memory here with the PD2. If PD1>
If PD2, the polarity of ΔTLE1 (ΔTLE1 = ATL
E2-ATLE1> 0), the same processing is repeated as appropriate. During the repeated processing, the pulse width fluctuation signal PD is sampled at the timing when the AC tilt component crosses the center of fluctuation, and it is determined whether the sampled value is equal to or less than a predetermined value.

In FIG. 17C, the correction signal CS
By adding ΔTLE1 to, the pulse width variation signal PD decreases from PD1 to PD2. Therefore, ΔTLE2 is added to the correction signal CS. as a result,
As shown in FIG. 17C, at time t3 when the orthogonal shift signal TLE crosses the center of fluctuation (that is, ATLE3), the pulse width fluctuation signal PD takes the minimum value PDmin (here, zero level). Here, further, ΔTLE1
And a signal having the same polarity (positive) as ΔTLE2 are added to the correction signal CS, the pulse width fluctuation signal PD at the timing when the orthogonal shift signal TLE crosses the center of fluctuation.
On the contrary, the value of increases.

On the contrary, if PD1 <PD2, it can be seen that ΔTLE1 having the opposite polarity (that is, negative) should be added to the correction signal CS. At this time the controller 6
B2 adds −ΔTLE1 to the correction signal CS and repeats the same processing again.

Actually, the pulse width fluctuation signal P at the timing when the orthogonal shift signal TLE crosses the center of fluctuation.
When the value of D falls within a predetermined range (PDmin to PDth in FIG. 17), it is preferable to end the repeating process. This can prevent the value of the pulse width variation signal PD from vibrating near PDmin.

In FIG. 17, ΔTLE1 and ΔTLE2 which are the step widths of the signals added to the correction signal CS.
Are equal, but not limited to. For example, as the difference between the center of fluctuation of the pulse width fluctuation signal PD and the zero level becomes smaller, this step width is made smaller,
The target value search can be performed more precisely.

The variation of the orthogonal shift signal TLE when the control target of the tilt servo is changed by the correction signal CS from the target value varying circuit 6B will be described below. The maximum value (offset) of the DC orthogonal shift variation amount in the second embodiment is ΔTLE. The minimum gap width of the variation amount of the orthogonal shift at the time of searching the orthogonal position is ΔTLE1 (= ΔTLE2). After starting the orthogonal position search, ΔTLE1 is added to the correction signal CS in the first search. When the pulse width variation signal PD is rather increased by the addition of ΔTLE1, the orthogonal shift is the largest. Here, the pulse width fluctuation signal PD before the orthogonal position search is PD1, and ΔTLE at the time of the orthogonal position search.
The change in the pulse width fluctuation signal PD when 1 is added is ΔP
It is preferable to satisfy the relationship shown in Expression (7), where Dmp is the maximum allowable value of the pulse width fluctuation signal PD.

PD1 + ΔPD ≦ PDmp (7) That is, the pulse width detection signal PD immediately before the start of the orthogonal position search.
In contrast to 1, even if the pulse width variation increases by ΔPD by further applying the offset of ΔTLE1 to the tilt control circuit, it is preferable not to exceed the maximum allowable value PDmp of the pulse width variation signal PD. Therefore ΔTL
E1 is preferably determined so as to satisfy the mathematical expression (7).

PDmp is the maximum jitter amount that can satisfy the bit error rate required for the system,
In the case of a CLV (constant linear velocity) disk, the value is determined by the stability of rotation control.

In the second embodiment, the gain crossover frequency of the tilt servo is set to the disk 1
If the frequency is set lower than the rotation frequency of, the tilt servo loop does not follow the AC tilt component generated by the rotation of the disk even in the servo operating state. Therefore, AC
The tilt component remains as a servo residual in the orthogonal shift signal.

As described above, the orthogonal shift signal is A
By controlling the pulse width fluctuation signal PD at the time of crossing the center of fluctuation of the C tilt component to be the minimum value or a predetermined value or less, the information recording surface of the disc 1 is set to be the optimum pulse width fluctuation signal PD. The orthogonal relationship with the optical axis of the light beam 3 can be maintained.

According to the second embodiment, the quadrature target value search can be performed while changing the quadrature target value by a constant step amount regardless of the magnitude of the AC tilt component.

(Embodiment 3) FIG. 18 shows a block diagram of a third embodiment. The third embodiment is a target value variable circuit 6C.
The configuration is the same as that of the first embodiment except for the configuration. The target value variable circuit 6C has a function approximation circuit 6C1 and an offset generator 6C2. The offset generator 6C2 generates an offset ΔV based on the control signal output from the controller 6C3, and outputs it to the function approximation circuit 6C1 and the adder 902 of the tilt control circuit 9. Function approximation circuit 6C1
Receives the offset ΔV and the pulse width fluctuation signal PD, and based on the control signal from the controller 6C3,
A function that determines the relationship between the orthogonal shift signal TLE and the pulse width variation signal PD is obtained (that is, function approximation processing is performed). After the function is obtained by the function approximation processing, the function approximation circuit 6C1 sends to the tilt control circuit 9 the offset ΔTLE that minimizes the pulse width fluctuation signal PD as the correction signal CS, based on the control signal output from the controller 6C3. Output.

Offset Δ added to orthogonal shift signal TLE
If the graph is plotted with V being the horizontal axis and the pulse width fluctuation signal PD being the vertical axis, it will be close to a quadratic function. The function approximation circuit 6C1 converts this quadratic function into PD = a · (ΔV−ΔV
0) ² + b (where a, b and ΔV0 are constants), the constants a, b and ΔV0 are obtained.

FIG. 19 is a flowchart of the function approximation processing for obtaining the function constant. In step 190, the offset generator 6C2 changes the value of the offset ΔV by a predetermined step width, and sets the offset ΔV when the pulse width fluctuation signal PD has the minimum value PDmin to ΔV0 in the above-described quadratic function. In step 191,
Let the minimum value PDmin be the constant b of the above-mentioned quadratic function.

In step 192, the offset generator 6C2 calculates (ΔV0 + ΔV1) from the function approximation circuit 6C1.
Output to. In step 193, the function approximation circuit 6
C1 obtains the constant a1 from the pulse width variation signals PD1, ΔV1 and constant b when (ΔV0 + ΔV1) is supplied.

In step 194, the offset generator 6C2 calculates (ΔV0-ΔV1) from the function approximation circuit 6C1.
Output to. In step 195, the function approximation circuit 6
C1 obtains a constant a2 from the pulse width variation signals PD2, ΔV1 and constant b when (ΔV0−ΔV1) is supplied.

In step 196, the function approximation circuit 6
C1 determines an equation for approximating the pulse width fluctuation signal PD as a quadratic function of the offset ΔV. Here, there are two expressions representing the pulse width variation signal PD in order to approximate different curves in the left and right regions with the apex of the parabola as the center. In other words, this is to improve the accuracy of approximation when the constant a1 in the region where the offset is larger than ΔV0 and the constant a2 in the region where the offset is smaller than ΔV0 are different. Therefore, if the constants a1 and a2 in these two regions are sufficiently close,
One approximation formula may be used by using either constant.

FIG. 20 is a flowchart of the processing for searching for the offset ΔTLE. In step 201, the function approximation process described with reference to FIG. 19 is performed. The function approximation process is performed at least once after the device is activated. In step 202, the pulse width variation signal PD
ΔTLE is obtained from When the pulse width variation signal PD changes, for example, in FIG. 20, the pulse width variation signal P
Consider when D takes PDx. By the function obtained by the function approximation, from the value PDx, conversely (ΔV0 + Δ
TLE) and (ΔV0−ΔTLE) are obtained. Here, in order to reduce the pulse width fluctuation signal PD from the value PDx to the value PDmin, the correction signal CS is either + ΔTLE or −ΔTLE. As described above, the pulse width fluctuation signal PD is approximated by a quadratic function. for that reason,
Even if it is known that the pulse width variation signal PD takes the value PDx, it is not possible to determine whether the current state is the point P or the point Q. That is, the value to be applied to the adder 902 of the tilt control circuit 9 as the correction signal CS cannot be uniquely obtained from the value PDmin.

At step 203, the polarity for applying ΔTLE is obtained. In other words, in step 203, it is determined which of + ΔTLE and −ΔTLE described above is to be applied. As a determination method, for example, the offset is changed to such an extent that the operation state of the device is not hindered, and the pulse width fluctuation signal PD at this time is changed.
It is possible to determine whether the current state is the point P or the point Q by the change of the value of. Specifically, a positive value is output to the tilt control circuit 9 as the correction signal CS, and the pulse width variation signal PD
Is increased, the current state is point P (apply −ΔTLE), and conversely, if PD is decreased, the current state is point Q.
(Apply + ΔTLE).

The value of ΔTLE must be within a range that does not hinder the operating state of the device even if the pulse width fluctuation signal PD has a minimum value and is applied with a polarity opposite to that which should be applied. If step 203 is omitted, ΔTLE is actually
May be applied, and the polarity to be applied may be determined depending on whether the pulse width variation signal PD decreases. That is, it is understood that if the pulse width variation signal PD is increased by applying ΔTLE, −ΔTLE may be applied. In step 204, ΔTLE obtained in step 202 is output to the tilt control circuit 9 with the polarity obtained in step 203.

According to the third embodiment, the function approximation is performed in advance, and the correction signal CS is generated based on the approximated function during the operation of the apparatus. Therefore, it is not necessary to search for the target value. As a result, there is an effect that highly accurate correction can be performed in a short time.

(Embodiment 4) The polarity and the magnitude of the orthogonal relationship deviation are detected from the pulse width fluctuation value PD and the orthogonal deviation signal TLE, and the pulse width fluctuation value PD is minimized based on the detected deviation of the orthogonal relationship. A fourth embodiment will be described in which the tilt control target value is searched so as to achieve the above. FIG. 21 is a block diagram of the fourth embodiment. The target value varying circuit 6D uses the orthogonal shift signal TLE output from the orthogonal shift detector 8 and the pulse width variation signal PD to determine the orthogonal relationship between the optical disc 1 and the optical axis of the light beam 3 corresponding to the pulse width variation signal PD. The deviation amount and the polarity thereof are detected as a voltage, and the tilt control target value is output to the tilt control circuit 9 according to the detected deviation amount and the polarity of the orthogonal relationship.

The tilt control circuit 9 uses the orthogonal shift signal TLE.
The tilting mechanism 10 is controlled on the basis of the correction signal CS and the optical disc 1 so that the optical axis of the light beam 3 irradiated on the optical disc 1 intersects perpendicularly. The internal configuration of the tilt control circuit 9 is as shown in FIG.

FIG. 22 is a block diagram showing the structure of the target value varying circuit 6D. The target value detector 6D01 detects the target value signal TS from the orthogonal shift signal TLE and the pulse width fluctuation signal PD and sends it to the target value generation circuit 6D02 described later.
The target value generation circuit 6D02 receives the target value signal TS, amplifies the target value signal TS by a predetermined gain, and then outputs it to the tilt control circuit 9 as a correction signal CS for changing the target value for tilt control.

An HPF (high-pass filter) 601 extracts the AC component of the orthogonal deviation signal TLE from the orthogonal deviation detector 8. The pulse shaping circuit 602 compares the AC component of the orthogonal shift signal from the HPF 601 with its center level to generate a high level signal when the level is higher than the center level and a low level signal when the level is lower than the center level. To occur. The inverting circuit 603 outputs a signal obtained by inverting the signal of the pulse shaping circuit 602. sample&
The hold (S / H) circuit 604 is a pulse shaping circuit 60.
The pulse width fluctuation signal PD is output from the pulse width fluctuation detector 5 when the pulse signal output from 2 is high level, and is held when it is low level. S / H circuit 60
5 outputs the pulse width fluctuation signal PD from the pulse width fluctuation detector 5 when the pulse signal output from the inverting circuit 603 is at the high level, and holds it when the pulse signal is at the low level. The differential operation circuit 606 performs a difference operation between the output of the S / H circuit 604 and the output of the S / H circuit 605. An LPF (low pass filter) 607 extracts the low frequency component of the output of the differential operation circuit 606.

In the fourth embodiment, the target value detector 6D01
Is the AC of the orthogonal deviation signal TLE from the orthogonal deviation detector 8.
The polarities of orthogonal shifts are detected from the components. Further, the target value signal TS in which the polarity and the magnitude of the pulse width variation value PD from the pulse width variation detector 5 corresponding to the detected polarity of the orthogonal shift is detected is output. The target value generation circuit 6D02 amplifies the target value signal TS from the target value detector 6D01 and outputs it as a correction signal CS.

Next, the specific operation of the target value detector 6D01 will be described. FIG. 23 shows the deviation of the orthogonal relationship and the pulse width variation value PD for explaining the operation of the target value detector 6D01.
It is a figure which shows the relationship with. FIG. 24 is a diagram showing the relationship between the deviation of the orthogonal relationship and the output voltage TS of the target value detector 6D01. FIG. 25 is a diagram for explaining the operation of the target value detector 6D01 when the deviation of the orthogonal relationship occurs by + ΔTLE. FIG. 26 is a diagram for explaining the operation of the target value detector 6D01 when the deviation of the orthogonal relationship occurs by −ΔTLE.
FIG. 27 shows the target value detector 6D0 when the orthogonal shift is zero.
It is a figure explaining operation | movement of 1.

As shown in FIG. 23, the pulse width variation value PD with respect to the deviation of the orthogonal relationship becomes the minimum value when the deviation of the orthogonal relationship is zero, and when the deviation of the orthogonal relationship is + ΔTLE.
When ΔTLE, the polarities are opposite to each other. The operation of the target value detector 6D01 when the deviation of the orthogonal relationship is + ΔTLE and the AC component of the orthogonal deviation signal is TLE (1) at point A in FIG. 23 will be described with reference to FIG. 25. FIG. 25A shows HP
This is the output of F601. FIG. 25B shows the output of the pulse shaping circuit 602. FIG. 25C shows the output of the inverting circuit 603. 25D is the pulse width variation value PD. FIG. 25E shows the output of the S / H circuit 604. FIG. 25F shows the output of the S / H circuit 605. FIG. 25G shows the output of the differential operation circuit 606. FIG. 25H shows the output of the LPF 607. (A) to (H) of FIG. 25 correspond to (A) to (H) of FIG.
The waveform of the signal in (H) is shown. FIG. 25B shows
The signal in FIG. 25A (TLE (1) in FIG. 23) is + Δ
It is a signal that becomes high level when it is larger than TLE. The signal in (C) of FIG. 25 is an inverted signal of (B) in FIG. 25E is the pulse width variation signal PD sampled and held in FIG. 25B, and is sampled when the signal in FIG. 25B is at the high level, and the signal is at the low level. Sometimes held. 25F is the pulse width variation value PD sampled and held in FIG. 25C,
The signal shown in FIG. 25C is sampled when it is at high level and held when it is at low level. 25G is a signal obtained by subtracting the signals of FIGS. 25E and 25F by the differential operation circuit 606. 25 (H)
Is a signal obtained by extracting the DC component (DC component) of the output of the differential operation circuit 606 by the LPF 607, and the polarity and the magnitude of the deviation of the orthogonal relationship based on the pulse width fluctuation signal PD at point A in FIG. Is detected and is output as a positive voltage value.

The deviation of the orthogonal relationship at the point a in FIG. 23 is -ΔTL.
E, the operation of the target value detector 6D01 when the AC component of the orthogonal shift signal is TLE (2) will be described with reference to FIG. 26 (A) to (H) correspond to FIG. 25 (A) to (H).
Similar to (H), the waveforms of the signals in (A) to (H) of FIG. 22 are shown. Note that description that overlaps with FIG. 25 will be omitted. FIG. 26
26, the differential operation circuit 606 receives the signals of (E) and (F) of FIG. 26, takes the difference between these signals,
The signal is output as the signal shown in FIG. 26 (H) is a signal obtained by extracting the DC component (DC component) of the output of the differential operation circuit 606 by the LPF 607, and FIG.
The polarity and the magnitude of the deviation of the orthogonal relationship based on the pulse width variation value PD of point A are detected and output as a negative voltage value.

The operation of the target value detector 6D01 when the deviation of the orthogonal relationship is zero at the point c in FIG. 23 and the AC component of the orthogonal deviation signal is TLE (3) will be described with reference to FIG.
(A) to (H) of FIG. 27 show the waveforms of the signals of (A) to (H) of FIG. 22 similarly to (A) to (H) of FIG. Note that description that overlaps with FIG. 25 will be omitted. In FIG. 27, the differential operation circuit 606 receives the signals (E) and (F), takes the difference between these signals, and outputs it as (G). (H) of FIG. 27 is a signal obtained by extracting the DC component (DC component) of the output of the differential operation circuit 606 by the LPF 607, and the deviation of the orthogonal relationship based on the pulse width variation value PD of point c in FIG. 23. The polarity and the size of
At this time, the output negative voltage value becomes zero.

The points a of FIG.
The operation of the target value detector 6D01 has been described with respect to a and c. FIG. 24 shows the relationship between the deviation of the orthogonal relationship and the pulse width variation value PD as shown in FIG. 23 as the relationship between the deviation of the orthogonal relationship and the output voltage TS of the target value detector 6D01.

As described above, the target value varying circuit 6D according to the fourth embodiment uses the pulse width variation value PD from the pulse width variation detector 5 and the orthogonal shift signal TLE from the orthogonal shift detector 8 to determine the pulse width variation. When the value PD is the minimum, the target value signal TS in which the deviation of the orthogonal relationship becomes zero is detected, and the target value signal TS is detected.
The correction signal CS is output based on Therefore, the tilt control device of the present invention changes the control target value of the tilt control circuit 9 according to the correction signal CS from the target value varying circuit 6D so that the pulse width variation value PD from the pulse width variation detector 5 is minimized. To work. According to the present invention, it is possible to detect the polarity and magnitude of the shift of the orthogonal relationship from the AC component of the orthogonal shift signal TLE and the pulse width variation value PD, so that the change over time of the tilt sensor 7 and the temperature characteristic. Even if the deviation of the orthogonal relationship due to occurs, it can be corrected in real time so that it is always zero.

(Fifth Embodiment) In the fifth embodiment, when the AC component of the quadrature deviation signal is small, the polarity of the quadrature relationship deviation and its magnitude are detected from the pulse width variation value PD and the disturbance signal D. Then, the tilt control target value is searched based on the detected deviation of the orthogonal relationship so that the pulse width variation value PD is minimized.

FIG. 28 is a block diagram of the fifth embodiment.
The target value varying circuit 6E calculates the deviation amount of the orthogonal relationship between the optical axis of the optical disc 1 and the optical axis of the light beam 3 corresponding to the pulse width variation signal from the disturbance signal D from the disturbance generator 13 and the pulse width variation signal PD described later. The polarity is detected as a voltage, and a tilt control target value is output to the tilt control circuit 9 according to the detected shift amount of the orthogonal relationship and the polarity.

The tilt control circuit 9 uses the orthogonal shift signal TLE.
Accordingly, the tilting mechanism 10 is controlled via an adding circuit 14 described later so that the optical disc 1 and the optical axis of the light beam 3 irradiated on the optical disc 1 intersect perpendicularly. The internal configuration of the tilt control circuit 9 is as shown in FIG. The disturbance generator 13 outputs a disturbance signal to one input terminal of an adding circuit 14, which will be described later, to drive the tilting mechanism 10 in a constant cycle. The adder circuit 14 adds the disturbance signal from the disturbance generator 13 and the output from the tilt control circuit 9.

FIG. 29 is a block diagram showing the structure of the target value variable circuit 6E. In FIG. 29, 6E01 is a target value detector and 6E02 is a target value generating circuit. Similar to the target value generation circuit 6D02, the target value generation circuit 6E0
2 receives the target value signal TS, amplifies the target value signal TS by a predetermined gain, and then outputs it to the tilt control circuit 9 as a correction signal CS that changes the target value for tilt control. The configuration of FIG. 29 is the same as that of FIG. 22 except that the disturbance signal D from the disturbance generator 13 is input to the HPF 601.
The configuration is the same as that of. The HPF 601 is the disturbance generator 13
The AC component of the disturbance signal D from is extracted.

In this embodiment, the target value detector 6E01
Detects the polarity of the disturbance signal from the AC component of the disturbance signal D from the disturbance generator 13. Further, the disturbance signal D from the disturbance generator 13 is input to the tilting mechanism 10 via the adding circuit 14 to drive the tilting mechanism 10 at a constant cycle. When the tilting mechanism 10 is driven by the disturbance signal D via the adder circuit 14, the target value varying circuit 6E has the polarity and magnitude of the pulse width variation signal PD from the pulse width variation detector 5 corresponding to the polarity of the disturbance signal. A target value signal TS that detects S and S is output.
The target value generation circuit 6E02 amplifies the target value signal TS from the target value detector 6E01 and outputs it as a correction signal CS.

FIG. 30 shows the target value detector 6E0 of the fifth embodiment.
FIG. 3 is a diagram showing a relationship between a deviation of an orthogonal relationship and a pulse width variation value PD for explaining the operation of No. 1; FIG. 31 is a diagram showing the relationship between the deviation of the orthogonal relationship and the output voltage TS of the target value detector 6E01. FIG. 32 is a diagram for explaining the operation of the target value detector 6E01 when the deviation of the orthogonal relationship occurs by + ΔTLE. FIG. 33 is a diagram for explaining the operation of the target value detector 6E01 when the deviation of the orthogonal relationship is −ΔTLE. FIG. 34 shows the target value detector 6 when the orthogonal shift is zero.
It is a figure explaining operation | movement of E01.

As shown in FIG. 30, the pulse width variation value PD with respect to the deviation of the orthogonal relationship has the minimum value when the deviation of the orthogonal relationship is zero, and is − when the deviation of the orthogonal relationship is + ΔTLE.
When ΔTLE, the polarities are opposite to each other. At point a in FIG. 30, the deviation of the orthogonal relationship is + ΔTLE, and the AC component of the disturbance signal D is D.
The operation of the target value detector 6E01 in the case of (1) will be described with reference to FIG. Note that the description overlapping with the description of FIG. 25 will be omitted. FIGS. 32A to 32H are diagrams showing the waveforms of the signals in FIGS. 29A to 29H. FIG. 32A shows the AC component of the disturbance signal D. FIG.
32B is the signal of FIG. 32A (D of FIG. 29).
This is a signal that becomes high level when (1)) is larger than + ΔTLE. As in the case of FIG. 25, the differential operation circuit 6
The signal 06 receives the signals of (E) and (F) of FIG. 32, takes the difference between these signals, and outputs it as the signal shown in (G) of FIG. 32 (H) is a signal in which the DC component is extracted by the LPF 607, and detects the polarity and magnitude of the shift in the orthogonal relationship based on the pulse width variation value PD at point A in FIG. It is output as a positive voltage value.

The deviation of the orthogonal relationship at the point a in FIG. 30 is -ΔTL.
E, the operation of the target value detector 6E01 when the AC component of the disturbance signal D is D (2) will be described with reference to FIG.
Descriptions that overlap with those of FIGS. 25, 28, and 32 will be omitted. (A) to (H) of FIG. 33 correspond to (A) to (H) of FIG.
Similar to (H), it corresponds to (A) to (H) in FIG. In FIG. 33, (G) is a signal obtained by subtracting the signals of (E) and (F), and has a waveform similar to that of FIG. 33 (H) is a signal in which the DC component is extracted by the LPF 607, and the polarity and the magnitude of the deviation of the orthogonal relationship based on the pulse width variation value PD of point a in FIG. 30 are detected, It is output as a negative voltage value.

The operation of the target value detector 6E01 when the deviation of the orthogonal relationship is zero at point c in FIG. 30 and the AC component of the disturbance signal D is D (3) will be described with reference to FIG. 34. Note that the description overlapping with the description of FIGS. 25, 27, and 32 will be omitted. 34 (A) to (H) are similar to FIG. 32 (A) to (H).
Similar to (H), it corresponds to (A) to (H) in FIG. In FIG. 34, (G) is a signal obtained by taking the difference between the signals of (E) and (F), and has a waveform similar to that of FIG. 34 (H) is a signal in which the DC component is extracted by the LPF 607, and is the pulse width variation value PD at point c in FIG.
The polarity and the magnitude of the deviation of the orthogonal relationship based on are detected, and the output negative voltage value at this time becomes zero.

The operation of the target value detector 6E01 has been described above with reference to FIGS. FIG. 31 is a diagram showing the relationship between the deviation of the orthogonal relationship and the pulse width variation value PD shown in FIG. 30 as the relationship between the deviation of the orthogonal relationship and the output voltage TS of the target value detector 6E01.

As described above, the target value variable circuit 6E of the present invention determines the pulse width variation value PD from the pulse width variation value PD from the pulse width variation detector 5 and the disturbance signal D from the disturbance generator 13. The target value signal TS having the zero deviation of the orthogonal relationship at the minimum is detected, and the correction signal CS is output based on the target value signal TS. Therefore, in the fifth embodiment, the control target value of the tilt control circuit 9 is changed according to the correction signal CS from the target value changing circuit 6E, and the pulse width fluctuation value PD from the pulse width fluctuation detector 5 is minimized. Works like. According to the fifth embodiment, A of the orthogonal shift signal TLE
Even if the C component is small, it is possible to detect the polarity and the magnitude of the deviation of the orthogonal relationship from the AC component of the disturbance signal D from the disturbance generator 13 and the pulse width variation value PD, so that the tilt sensor 7 can be used over time. It is possible to perform correction in real time so that it is always zero even if the orthogonal relationship shifts due to changes in temperature or temperature characteristics.

(Sixth Embodiment) In the sixth embodiment, the polarity of the orthogonal relationship deviation and its magnitude are detected and detected from the pulse width fluctuation signal PD and the disturbance signal D without using the tilt sensor. Tilt control is performed based on the deviation of the orthogonal relationship. FIG. 35 is a block diagram of the sixth embodiment. The target value detector 6E01 has a disturbance signal D from a disturbance generator 13 and a pulse width fluctuation signal PD from the pulse width fluctuation detector 5 which will be described later.
From that, the optical disc 1 corresponding to the pulse width variation signal PD
And a signal for detecting a deviation amount of the orthogonal relationship between the light beam 3 and the optical axis of the light beam 3 and its polarity as a voltage, and changing a target value of tilt control according to the detected deviation amount of the orthogonal relationship and the polarity thereof. That is, the target value signal TS is generated and output to the tilt control circuit 9A.

The tilt control circuit 9A has a target value detector 6E.
The optical disc 1 is controlled by controlling the tilting mechanism 10 via an adding circuit 14 described later in accordance with the target value signal TS output from the optical disc 1.
And the optical axis of the light beam 3 irradiated on the optical disk 1 are controlled to intersect perpendicularly. The tilt control circuit 9A is as shown in FIG. 9, except that it receives the correction signal CS instead of the orthogonal shift signal TLE. The disturbance generator 13 outputs a disturbance signal D to one input terminal of an adding circuit 14 to be described later, and drives the tilting mechanism 10 in a constant cycle. The adder circuit 14 adds the disturbance signal D from the disturbance generator 13 and the output signal from the tilt control circuit 9A.

FIG. 35 shows the operation of the tilt control device having the above configuration.
Will be described with reference to. It should be noted that the description of the same parts as those in the fifth embodiment will be omitted.

The target value detector 6E01 shown in FIG.
Of the target value detector 6E01
The input signals to are the disturbance signal D from the disturbance generator 13 and the pulse width fluctuation signal PD from the pulse width fluctuation detector 5. The tilt control circuit 9A in FIG. 35 has the same configuration as the tilt control circuit 9A in FIG. In Figure 9,
The input of the tilt control circuit 9A was the orthogonal shift signal TLE from the orthogonal shift detector 801, but in FIG. 35, the correction signal CS from the target value detector 6E01 is input instead of the orthogonal shift signal TLE. The target value detector 6E01 is shown in FIG.
The same operation as the target value variable circuit 6E of 8 is performed to detect the correction signal CS from the disturbance signal D from the disturbance generator 13 and the pulse width variation value PD from the pulse width variation detector 5. That is, in the sixth embodiment, the polarity and the magnitude of the deviation of the orthogonal relationship from the disturbance signal D and the pulse width variation value PD when the tilting mechanism 10 is moved at a constant cycle based on the disturbance signal D from the disturbance generator 13. Is detected as a correction signal CS by the target value detector 6E01, and based on the detected correction signal CS,
The tilt mechanism 10 is controlled by a signal from the tilt control circuit 9A via the adder circuit 14 to operate so that the correction signal CS becomes zero.

Therefore, according to the sixth embodiment, when the pulse width fluctuation value PD is minimum due to the pulse width fluctuation value PD from the pulse width fluctuation detector 5 and the disturbance signal D from the disturbance generator 13, an orthogonal relationship is obtained. Since it is possible to detect the polarity and the magnitude of the deviation of the orthogonal relationship such that the deviation becomes zero, it is possible to perform control so that the deviation of the orthogonal relationship becomes zero without using the tilt sensor 7.

(Embodiment 7) In the seventh embodiment, tilt control is performed so that the bit error rate of the reproduced signal is minimized. FIG. 36 is a block diagram of the seventh embodiment.
The bit error rate measuring circuit 15 detects the bit error rate of the reproduction signal and outputs the voltage signal BER corresponding to the bit error rate. FIG. 37 is a block diagram showing the internal configuration of the bit error rate measuring circuit 15. The bit error rate measuring circuit 15 has a parity error detector 1501, a bit error detector 1502 and a cycle counter 1503. The parity error detector 1501 receives the RF pulse signal PRF and outputs a parity error signal PE. A parity bit is added to the data recorded on the optical disc 1 for each symbol data. Parity error detector 150
1 sets the parity error signal PE to a high level when a parity error occurs from this parity bit and the data reproduced from the RF pulse signal PRF. The cycle counter 1503 periodically outputs a pulse signal to the bit error detector 1502. Bit error detector 1
Reference numeral 502 counts the number of times the parity error signal PE becomes high during one cycle of the pulse signal output from the cycle counter 1503, and outputs a signal B indicating a bit error rate.
Output as ER.

The target value detector 6F is the disturbance generator 1 described later.
From the disturbance signal D output from the optical disc 3 and the signal BER output from the bit error rate measuring circuit 15, the deviation amount of the orthogonal relationship between the optical axis of the optical disc 1 and the optical axis of the light beam 3 corresponding to the signal BER and the polarity thereof Then, a signal for changing the target value for tilt control, that is, a correction signal CS, is generated according to the detected deviation amount of the orthogonal relationship and its polarity, and is output to the tilt control circuit 9A. The tilt control circuit 9A uses the correction signal C output from the target value detector 6F.
According to S, the tilting mechanism 10 is controlled via an adding circuit 14 described later so that the optical disk 1 and the optical axis of the light beam 3 irradiated on the optical disk 1 intersect perpendicularly. The tilt control circuit 9A is as shown in FIG. 9, except that it receives the correction signal CS instead of the orthogonal shift signal TLE. The disturbance generator 13 outputs a disturbance signal D to one input terminal of an adding circuit 14 to be described later, and drives the tilting mechanism 10 in a constant cycle. The adder circuit 14 adds the disturbance signal D output from the disturbance generator 13 and the output from the tilt control circuit 9A, and outputs the added signal to the tilt mechanism 10.

FIG. 36 shows the operation of the tilt control device having the above configuration.
And 38. It should be noted that the description of the same parts as those in the above-described embodiment will be omitted.

FIG. 38 is a block diagram of the target value detector 6F. The components of FIG. 38 are the same as those of FIG. 29, and the target value detector 6F expresses the disturbance signal D from the disturbance generator 13 as an input signal and the bit error rate as a voltage level signal. The difference is that it receives the signal BER output from the error rate measuring circuit 15. The tilt control circuit 9A in FIG. 36 has the same configuration as the tilt control circuit 9A in FIGS. 9 and 35. In FIG. 9, the input of the tilt control circuit 9A is the orthogonal shift signal TLE from the orthogonal shift detector 801, and in FIG.
36, the correction signal CS from the target value detector 6E01 was input, but in FIG. 36, instead of the orthogonal shift signal TLE or the correction signal CS, the correction signal CS based on the bit error rate from the target value variable circuit 6F is input. It has been entered. The target value detector 6F performs the same operation as that of FIG. 28 or FIG. 35, and the disturbance signal D from the disturbance generator 13 and the signal BE output from the error rate measuring circuit 15 are output.
R and are received, and the correction signal CS is output. That is,
In the seventh embodiment, the disturbance signal D from the disturbance generator 13
Based on the disturbance signal D when the tilting mechanism 10 is moved at a constant cycle and the BER from the bit error rate measuring circuit 15, the polarity and the magnitude of the deviation of the orthogonal relationship are detected by the target value detector 6F as the correction signal CS. Then, based on the detected correction signal CS, the tilt mechanism 10 is controlled by the signal from the tilt control circuit 9A via the addition circuit 14 to obtain the correction signal C.
It operates so that S becomes zero.

Therefore, according to the seventh embodiment, the BER from the bit error rate measuring circuit 15 and the disturbance generator 13 are provided.
It is possible to detect the polarity and the magnitude of the deviation of the orthogonal relationship such that the deviation of the orthogonal relationship becomes zero when the bit error rate (BER) is minimum from the disturbance signal from. As a result, it is possible to control the deviation of the orthogonal relationship to zero without using the tilt sensor 7.

(Embodiment 8) In the eighth embodiment, the tilt control target value is changed so that the bit error rate of the reproduced signal is minimized in the tilt servo using the tilt sensor. FIG. 39 is a block diagram of the eighth embodiment. In the first embodiment, the target value for tilt control is changed based on the pulse width fluctuation signal, whereas in the present embodiment, the target value for tilt control is changed based on the error rate. There is. The error rate measuring circuit 15 detects the bit error rate of the reproduction signal and outputs the voltage signal BER corresponding to the bit error rate, as described in the seventh embodiment with reference to FIG. The target value variable circuit 6G includes an error rate measuring circuit 15
A correction signal CS for changing the target value of the tilt control is generated based on the signal BER from, and is output to the tilt control circuit 9. The target value varying circuit 6G is the same as the first embodiment except that it receives the signal BER corresponding to the bit error rate.
Functions as described above. The tilt control circuit 9 changes the target value for tilt control according to the correction signal CS from the target value varying circuit 6G so that the optical disc 1 and the optical axis of the light beam 3 irradiated on the optical disc 1 intersect perpendicularly. To control. Further, the orthogonal shift signal TLE from the orthogonal shift detector 8 is input to the tilt control circuit 9, and as described in the first embodiment, the tilt control circuit 9 is already input.
Performs tilt control based on the orthogonal deviation signal TLE from the orthogonal deviation detector 8.

FIG. 39 shows the operation of the tilt control device having the above configuration.
And 40. It should be noted that the description of the part overlapping with that of the first embodiment is omitted, and the tilt servo target value is searched so that the orthogonal relationship between the optical disc in the eighth embodiment and the optical axis of the light beam irradiated on the optical disc is vertical. How to do is described.

FIG. 40 shows the orthogonal shift signal TLE and the bit error rate B when the tilt servo target value is searched.
It is a figure which shows the relationship of ER. In FIG. 40, when the orthogonal shift signal TLE has a value of offset ΔTLE,
The optical disk and the optical axis of the light beam irradiated on the optical disk intersect perpendicularly. Generally, the orthogonal shift signal TLE is generated by the rotation of the optical disc or the "warpage" of the optical disc itself.
As shown in (A) to (C) of FIG. 40, it changes periodically. Actually, even if the tilt servo is operated with the correction signal CS output from the target value varying circuit 6G being zero,
An AC (alternating current) tilt component having a high frequency component that cannot be followed by the tilt servo remains in the orthogonal shift signal TLE. At this time, the orthogonal shift signal TLE is controlled so that the average value of periodic fluctuations becomes zero.

When the offset ΔTLE is larger than the amplitude of the AC tilt component (case of FIG. 40A), the bit error rate BER takes the minimum value at one of the two peaks of the orthogonal shift signal TLE. The BERmin timing detector 6G10 of the target value varying circuit 6G generates a sampling pulse at the timing when the bit error rate BER takes the minimum value. As shown in (A) of FIG. 40, a sampling pulse is generated at time t1 and output to the correction signal generator 620. The correction signal generator 620 is
At the timing of the sampling pulse output from the ERmin timing detector 6G10, the orthogonal shift signal T
Sample LE. In FIG. 40 (A),
At time t1, the orthogonal shift signal TLE having a value of ΔTLE1 is sampled. Correction signal generator 620
Outputs a correction signal CS having a value of ΔTLE1 to the tilt control circuit 9.

Gain adjusting circuit 901 of tilt control circuit 9
Receives the orthogonal shift signal TLE, amplifies the orthogonal shift signal TLE as much as necessary for feedback control, and then outputs it to the adder 902. Here, for simplicity, the gain of the gain adjusting circuit 901 is 1 (that is, the levels of the input signal and the output signal of the gain adjusting circuit 901 are equal).
And The adder 902 adds the correction signal CS and the signal from the gain adjustment circuit 901 and outputs the result to the drive circuit 903. The drive circuit 903 drives the tilting mechanism 10. Δ
The correction signal CS having a value of TLE1 is the orthogonal shift signal T
As a result of being added to LE, as shown in FIG.
The feedback loop is controlled so that the average value of the quadrature shift signal TLE becomes ΔTLE1. When the optical disc and the optical axis of the light beam intersect perpendicularly (when the deviation of the orthogonal relationship is zero), the value that the orthogonal deviation signal TLE may take, the offset ΔTLE, and the orthogonal deviation signal TLE in FIG. The difference from the center of fluctuation of ΔTLE2
(= ΔTLE−ΔTLE1).

As shown in FIG. 40B, if the offset ΔTLE is located within the amplitude of the AC tilt component of the orthogonal shift signal TLE (that is, between the two peak values), the bit error rate BER is , Takes the minimum value when the information recording surface of the optical disc 1 and the optical axis of the light beam 3 become vertical (for example, time t2). In the vicinity of this time t2, the graph of the bit error rate BER changes so as to turn back.

BERmin timing detector 6G10 again
Generates a sampling pulse at the timing when the bit error rate BER takes the minimum value. As shown in FIG. 40B, a sampling pulse is generated at time t2,
Output to the correction signal generator 620. Correction signal generator 62
0 is the orthogonal shift signal TLE (= ΔT at time t2).
LE1 + ΔTLE2) is sampled. The correction signal generator 620 outputs a correction signal CS having a value of offset ΔTLE to the tilt control circuit 9.

As a result of adding the sampled offset ΔTLE to the orthogonal shift signal TLE, FIG.
As shown in, the orthogonal relationship between the optical disc 1 and the optical axis of the light beam 3 is satisfied at the center position of the periodic fluctuation of the orthogonal shift signal TLE.

In the above description, the offset ΔTLE is
The sampling of the orthogonal shift signal TLE at the timing when the bit error rate BER takes the minimum value
It can be canceled by performing it twice. The larger the difference between the amplitude of the AC tilt component of the orthogonal shift signal TLE and the offset ΔTLE, the greater the number of times of sampling required.

During operation of the recording / reproducing apparatus, the formula (8) is always satisfied.
If the correction shown in (1) is executed, the deviation of the orthogonal relationship can be reduced to zero even if there is a sensor error due to a temperature change of the tilt sensor that occurs after the device is activated and a sensor error due to a change over time.

ΔTLEi = ΔTLEi-1 + ΔTLEx (8) Here, ΔTLEi-1 and ΔTLEi are (i-1), respectively.
It is a correction offset amount in the process of the previous time (previous) and i-th time (this time), and ΔTLEx is the correction offset amount newly added in the process of this time. For example, FIG. 40 (B)
Then, ΔTLEi is ΔTLE and ΔTLEi-1 is ΔTLE.
1 and ΔTLEx correspond to ΔTLE2, respectively.

As described above, according to the eighth embodiment, the orthogonal deviation is detected from the bit error rate BER with high sensitivity,
By correcting the control target value of tilt control, the orthogonal position can be searched with high accuracy. Further, in the eighth embodiment, the orthogonal shift search may be performed by adding the disturbance signal to the tilt servo loop as described with reference to FIG.

The target value detectors of the fourth, fifth and sixth embodiments described above show the pulse width variation value and the polarity and magnitude of the deviation of the orthogonal relationship from the orthogonal deviation signal or the disturbance signal. The configuration is not limited to the configuration of the target value detector of this embodiment as long as it operates so as to detect.

The target value detector of the seventh embodiment described above is the same as the target value detector of the present embodiment as long as it operates to detect the deviation and the magnitude of the orthogonal relationship from the bit error rate and the disturbance signal. The configuration is not limited to the target value detector.

Although the bit error rate measuring circuit of the seventh embodiment described above is configured to generate a signal corresponding to the bit error rate, it generates a signal corresponding to the reproduction error amount at every predetermined time. However, the configuration is not limited to the bit error rate.

The same effect can be obtained by replacing the bit error rate of the seventh embodiment described above with the pulse width variation values of the second to fifth embodiments.

Further, in the fifth, sixth or seventh embodiment described above, the disturbance signal from the disturbance generator 13 has a deviation in the orthogonal relationship which is increased by the amount of movement of the tilting mechanism by the disturbance signal. It is preferable to use a disturbance signal that does not hinder the signal reproduction state.

Next, the timing of the control target value searching operation of the highly accurate tilt control device using the pulse width variation detector 5 or the bit error rate measuring circuit 15 described above will be described.

The target value searching operation of the tilt control of the present invention is as follows.
Since it is performed according to the pulse width fluctuation signal of the reproduction signal or the bit error rate as described above, after starting the device,
This is performed in a state where each control system such as focus control, tracking control, and tilt control is in an operating state and a reproduction signal from the optical disc can be obtained. Then, by performing the control target value search operation at least once immediately after the device is activated,
The deviation of the orthogonal relationship between the recording surface of the optical disc and the optical axis of the light beam irradiated on the optical disc in the tilt servo operation state due to the variation of the characteristics due to the sensor individual difference, the assembly error of the device, and the aging of the device is corrected.

Further, the target value searching operation of the tilt control of the present invention is always performed while the control system is in operation and reproducing information from the recording disk or recording information on the optical disk after the apparatus is activated. The deviation of the orthogonal relationship in the tilt servo operation state due to the temporal change of the device after the control target value searching operation immediately after the start-up and the temperature characteristic is corrected.

Alternatively, in the tilt control target value searching operation of the present invention, after the apparatus is started, the pulse width variation detector is further operated in a state where the reproduction signal from the recording disk can be obtained while each control system is operating. By performing when the pulse width fluctuation signal detected by or the bit error rate measured by the bit error rate measuring circuit increases beyond a predetermined value,
Compared with the case of always performing the control target value searching operation, the control system can be provided with a margin by performing the control target value searching operation to the necessary minimum.

Although the radial tilt control of the optical disk has been described above as the embodiment of the present invention, the present invention also relates to the tilt (tangential tilt) control of the optical disk in the circumferential direction. It is applicable by changing the direction and the mounting direction of the tilt sensor.

[0155]

According to the present invention, the orthogonal relationship between the information surface of the optical disk and the optical axis of the light beam irradiated on the optical disk is perpendicular even if there are variations in characteristics due to individual differences in the sensor, assembly errors in the apparatus, and the like. Thus, it is possible to record or reproduce in an optimum state.

Even if the tilt sensor changes with time or the sensor output changes due to temperature characteristics after the apparatus is activated, the orthogonal relationship between the information surface of the optical disk and the optical axis of the light beam irradiated on the optical disk is kept vertical, and is always maintained. It is possible to perform highly accurate tilt servo, and it is possible to perform recording or reproduction in an optimum state.

[Brief description of drawings]

FIG. 1 is a block diagram of a first embodiment of a tilt control device according to the present invention.

FIG. 2 is a diagram showing an internal configuration of a tilt sensor 7 and an orthogonal shift detector 8.

FIG. 3 is a diagram for explaining operations of a tilt control circuit 9 and a tilt mechanism 10.

FIG. 4 is a diagram showing a waveform of a reproduction signal RF and a waveform of an RF pulse signal PRF with respect to an orthogonal shift amount.

FIG. 5 is a block diagram of a pulse width variation detector 5 according to the first embodiment.

FIG. 6 is a diagram showing timings of an RF pulse signal PRF, a clock signal CLK, and pulse signals UP and DN.

7 is a diagram showing an internal configuration of a phase comparison circuit 501. FIG.

FIG. 8 is a diagram showing a relationship between an orthogonal deviation signal TLE and a pulse width variation signal PD when searching for a tilt servo target value.

FIG. 9 is a diagram showing a configuration in which a target value for tilt control is changed by changing a gain balance of a quadrature shift detector 801 for a correction signal in the first embodiment.

FIG. 10: Tilt sensor 7 and orthogonal shift detector 801
It is a figure which shows the internal structure of.

11 is a state transition diagram of the phase comparison circuit of the pulse width variation detector 5. FIG.

FIG. 12 shows the states a to f of FIG. 11 in 3 bits (S1: S).
2: It is a figure shown by S3).

FIG. 13 is a block diagram showing still another example of the pulse width fluctuation detector.

14 is a diagram showing a waveform of each part of the pulse width variation detector shown in FIG.

FIG. 15 is a diagram showing a configuration including a disturbance generator for applying an AC disturbance signal to a tilt servo loop.

FIG. 16 is a block diagram of a second embodiment of the tilt control device according to the present invention.

FIG. 17 is an orthogonal shift signal TL for explaining the second embodiment.
It is a figure of E and the pulse width fluctuation signal PD.

FIG. 18 shows a block diagram of a third embodiment of the tilt control device according to the present invention.

FIG. 19 is a flowchart of a function approximation process for obtaining a function constant.

FIG. 20 is a flowchart of a process for searching for an offset ΔTLE.

FIG. 21 is a block diagram of a fourth embodiment of the tilt control device according to the present invention.

FIG. 22 is a block diagram showing the configuration of a target value variable circuit 6D.

FIG. 23 is a diagram showing the relationship between the deviation of the orthogonal relationship and the pulse width variation value PD for explaining the operation of the target value detector 6D01.

FIG. 24 is a diagram showing the relationship between the deviation of the orthogonal relationship and the output voltage TS of the target value detector 6D01.

FIG. 25 is a graph showing a deviation of the orthogonal relationship + ΔTLE,
It is a figure explaining operation of target value detector 6D01.

FIG. 26 is a graph when a deviation of the orthogonal relationship occurs by −ΔTLE,
It is a figure explaining operation of target value detector 6D01.

FIG. 27 is a target value detector 6D0 when the orthogonal shift is zero.
It is a figure explaining operation | movement of 1.

FIG. 28 is a block diagram of a fifth embodiment of the tilt control device according to the present invention.

FIG. 29 is a block diagram showing a configuration of a target value variable circuit 6E.

FIG. 30 is a diagram showing the relationship between the deviation of the orthogonal relationship and the pulse width variation value PD for explaining the operation of the target value detector 6E01 of the fifth embodiment.

FIG. 31 is a diagram showing the relationship between the deviation of the orthogonal relationship and the output voltage TS of the target value detector 6E01.

FIG. 32 is a graph showing a deviation of the orthogonal relationship + ΔTLE,
It is a figure explaining operation | movement of the target value detector 6E01.

FIG. 33 is a graph showing a deviation of the orthogonal relationship of −ΔTLE,
It is a figure explaining operation | movement of the target value detector 6E01.

FIG. 34 is a target value detector 6E0 when the orthogonal shift is zero.
It is a figure explaining operation | movement of 1.

FIG. 35 is a block diagram of a sixth embodiment of the tilt control device according to the present invention.

FIG. 36 is a block diagram of a tilt control device according to a seventh embodiment of the present invention.

FIG. 37 is a block diagram showing an internal configuration of a bit error rate measuring circuit 15.

FIG. 38 is a block diagram of a target value detector 6F.

FIG. 39 is a block diagram of an eighth embodiment of the tilt control device according to the present invention.

FIG. 40 is a diagram showing a relationship between the orthogonal deviation signal TLE and the bit error rate BER when searching for a tilt servo target value.

FIG. 41 is a block diagram showing a schematic configuration of a conventional tilt control device.

[Explanation of symbols]

 1 Optical Disc 2 Optical Pickup 3 Optical Beam 4 Information Signal Detector 5 Pulse Width Fluctuation Detector 6 Target Value Variable Circuit 7 Tilt Sensor 8 Orthogonal Deviation Detector 9 Tilt Control Circuit 10 Tilt Mechanism 11 Spindle Motor 610 PDmin Timing Detector 620 Correction Signal Generator 901 Gain adjustment circuit 902 Adder 903 Drive circuit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Mitsuro Moriya 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (29)

[Claims] 1. A tilt control device for controlling a deviation of an orthogonal relationship between an optical disc and an optical axis of a light beam applied to the optical disc to be minimum, and irradiating the optical beam onto the optical disc. An optical pickup for reproducing information recorded on the optical disc, an orthogonal shift detection means for outputting an orthogonal shift signal according to a shift in the orthogonal relationship between the optical disc and the optical axis, and an inclination of the optical axis. Tilting means, tilt control means for driving the tilting means according to the orthogonal shift signal so as to control the optical disc and the optical axis to intersect perpendicularly, and a pulse of an information reproduction signal obtained from the optical pickup. Pulse width variation detecting means for outputting a pulse width variation signal according to the variation of the width, target value varying means for varying the control target value of the tilt control means based on the pulse width variation signal, Tilt control device. 2. The tilt according to claim 1, wherein the target value changing means outputs the value of the orthogonal shift signal when the pulse width fluctuation signal has a minimum value to the tilt control means as the control target value. Control device. 3. The tilt control device according to claim 1, wherein the target value changing means sets the control target value at least once after the device is activated. 4. The tilt control device according to claim 1, wherein the target value varying means sets the control target value during recording or reproduction of a signal. 5. The tilt control device according to claim 1, wherein the target value varying means sets the control target value when the pulse width variation signal exceeds a predetermined value during recording or reproduction of the signal. 6. Further comprising: timing generating means for generating a timing signal at the center level of the AC component of the orthogonal shift signal; and sampling means for sampling the pulse width variation signal based on the timing signal, The tilt control device according to claim 1, wherein the target value changing means controls the target value of the tilt control means so that a value of the sampled pulse width variation signal is minimized. 7. The high-pass filter for passing the high-frequency component of the orthogonal shift signal, the timing generating means,
The tilt control device according to claim 6, further comprising a binarization circuit that binarizes an output signal of the high-pass filter. 8. The tilt control device according to claim 6, wherein the target value varying means sets the control target value at least once after the device is activated. 9. The tilt control device according to claim 6, wherein the target value varying means sets the control target value during recording or reproduction of a signal. 10. The tilt control device according to claim 6, wherein the target value varying means sets the control target value when the pulse width fluctuation signal exceeds a predetermined value during recording or reproduction of the signal. 11. The function approximating means for approximating the relationship between the orthogonal shift signal and the pulse width fluctuation signal by a function by tilting the optical axis with respect to the optical disk by the tilting means. The tilt control device according to claim 1, wherein the target value varying means changes the control target value corresponding to the pulse width variation signal by using the function obtained by the function approximating means. . 12. The target value varying means sets the control target value at least once after the apparatus is activated.
The tilt control device according to. 13. The tilt control device according to claim 11, wherein the target value varying means sets the control target value during recording or reproduction of a signal. 14. The tilt control device according to claim 11, wherein the target value varying means sets the control target value when the pulse width variation signal exceeds a predetermined value during recording or reproduction of the signal. 15. The target value varying means has a correction signal detecting means for outputting a correction signal corresponding to a direction and an amount of deviation of the orthogonal relationship from the orthogonal deviation signal and the pulse width fluctuation signal. The tilt control device according to claim 1. 16. The target value varying means sets the control target value at least once after the apparatus is activated.
The tilt control device according to. 17. The tilt control device according to claim 15, wherein the target value varying means sets the control target value during recording or reproduction of a signal. 18. The tilt control device according to claim 15, wherein the target value varying means sets the control target value when the pulse width fluctuation signal exceeds a predetermined value during recording or reproduction of the signal. 19. The apparatus further comprises a disturbance signal generating means for generating a disturbance signal for driving the inclining means in a predetermined cycle, wherein the target value varying means uses the disturbance signal and the pulse width variation signal to generate the disturbance signal. The tilt control device according to claim 1, further comprising a correction signal detection unit that outputs a correction signal corresponding to a direction and an amount of deviation of the orthogonal relationship. 20. The target value varying means sets the control target value at least once after the apparatus is activated.
The tilt control device according to. 21. The tilt control device according to claim 19, wherein the target value varying means sets the control target value during recording or reproduction of a signal. 22. The tilt control device according to claim 19, wherein the target value varying means sets the control target value when the pulse width variation signal exceeds a predetermined value during recording or reproduction of the signal. 23. A tilt control device for controlling a deviation of an orthogonal relationship between an optical disc and an optical axis of a light beam applied to the optical disc to a minimum, wherein the light beam is applied to the optical disc. An optical pickup for reproducing information recorded on the optical disc, an inclination means for inclining the optical axis, and a bit error rate signal corresponding to a bit error rate of an information reproduction signal obtained from the optical pickup. Reproduction error detecting means, disturbance signal generating means for generating a disturbance signal for driving the inclining means in a predetermined cycle, and a control target of the inclining means according to the bit error rate signal and the disturbance signal. A tilt control device comprising: 24. A tilt control device for controlling such that a deviation of an orthogonal relationship between an optical disc and an optical axis of a light beam applied to the optical disc is minimized, the light control device irradiating the optical beam onto the optical disc. An optical pickup for reproducing information recorded on the optical disc, an orthogonal shift detection means for outputting an orthogonal shift signal according to a shift in the orthogonal relationship between the optical disc and the optical axis, and an inclination of the optical axis. Tilting means, tilt control means for driving the tilting means according to the orthogonal shift signal so as to control the optical disc and the optical axis to intersect perpendicularly, and a bit of an information reproduction signal obtained from the optical pickup. Reproduction error detection means for outputting a bit error rate signal according to the error rate, and a target for changing the control target of the tilt control means based on the bit error rate signal A tilt control device comprising a value varying means. 25. The tilt control according to claim 24, wherein the target value varying means outputs the value of the orthogonal shift signal when the bit error rate has a minimum value to the tilt control means as the control target value. apparatus. 26. The target value varying means sets the control target value at least once after the apparatus is activated.
The tilt control device according to. 27. The tilt control device according to claim 24, wherein the target value varying means sets the control target value during recording or reproduction of a signal. 28. The tilt control device according to claim 24, wherein the target value varying means sets the control target value when the pulse width variation signal exceeds a predetermined value during recording or reproduction of the signal. 29. A tilt control device for controlling a deviation of an orthogonal relationship between an optical disc and an optical axis of a light beam applied to the optical disc to be minimized, wherein the light beam is applied to the optical disc. An optical pickup for reproducing the information recorded on the optical disc, an inclining means for inclining the optical axis, and a pulse width variation signal corresponding to the variation of the pulse width of the information reproduction signal obtained from the optical pickup. A pulse width variation detecting means for outputting, a disturbance signal generating means for generating a disturbance signal for driving the tilting means at a predetermined cycle, and a tilting means for driving the tilting means according to the pulse width fluctuation signal and the disturbance signal. Tilt control means for controlling the optical disc and the optical axis to intersect perpendicularly, and a control target value of the tilt control means is changed based on the pulse width fluctuation signal and the disturbance signal. And a target value varying means for changing the target value.