JPH04219633A - Tracking device - Google Patents

Abstract

PURPOSE:To conduct a stable control even when a tracking error signal is changed around non-zero as a center when both relative movements are controlled such that the light irradiating to an information track tracks the information track. CONSTITUTION:Reflected light is converted to plural electric signals with plural photoelectric transducers 16 and the deference signal is found with a substractor 24 and the mean value of the difference signal is derived with a first means 27. The mean value found with the first means 27, the differential signal and the differential signal from an oscillator 29 are applied to a driving means 10. Besides by leading out the synchronization component of the reflected light varied while is synchronizes with a fluctuating signal, the prescribed mean value is corrected based on the synchronization component. Then since the mean value of the deference signal is applied on the driving means 10 together with the difference signal, the control work can start even when the difference signal is non-synmetric and when the mean value is varied, the value is corrected.

Description

[Detailed description of the invention]

0001

FIELD OF INDUSTRIAL APPLICATION The present invention relates to a tracking device, and particularly to a recording medium on which a guide groove is formed or an information track is recorded. The present invention relates to a tracking device that performs control to track a groove or an information track.

0002

[Background Art] A push-pull method is one of the tracking methods for controlling the relative positional relationship between the information track and the light irradiated onto the recording medium of a reproducing device that optically reproduces information from a recording medium having an information track. It has been known. For example, Television Society Journal Vol42 No11
An example of such a push-pull method is given in 1988, pages 100-109. In this push-pull method, a recording medium having an information track is irradiated with light, and the reflected light from the information track is received by usually four photoelectric converters.
Tracking control is performed by amplifying the difference in current obtained from this.

[0003] That is, when the irradiation light is irradiated perpendicularly to the recording medium, the reflected light changes symmetrically with respect to the center of the four photoelectric converters according to the positional deviation between the information track and the irradiation light. do. Therefore, the above current difference (i.e. tracking error signal) when the illumination light crosses the information track
appears as positive and negative centered around zero, so tracking control is performed using this characteristic. .

0004

[Problems to be Solved by the Invention] However, when the irradiation light is irradiated perpendicularly to the recording medium, as described above, it is difficult to prevent the irradiation from occurring due to unevenness on the plane of the disk-shaped recording medium, inclination of the recording medium disk, etc. When the irradiation light is not perpendicularly irradiated, the reflected light changes depending on the positional deviation between the information track and the irradiation light around a point shifted from the center of the four photoelectric converters. Therefore, the tracking error signal changes around non-zero when the irradiation light traverses the information track. If the deviation of the light irradiated onto the recording medium from the perpendicular direction is large, the tracking error signal will not become zero in any case. When performing tracking control by amplifying such a tracking error signal, the maximum electrical signal is applied to an actuator (drive device) that mechanically changes the relative positional relationship between the irradiation light and the information track. There was a problem in that it could become uncontrollable.

The present invention has been made to solve the above-mentioned problems, and its object is to provide a tracking device that can perform stable control even when the tracking error signal changes around non-zero. .

[0006]

[Means for Solving the Problems] In order to achieve the above object, a tracking device according to a first aspect of the present invention converts reflected light into a plurality of electrical signals by a plurality of photoelectric converters, and converts reflected light into a plurality of electrical signals. first means for determining the average value of the difference signal of the electrical signals;
a second means for applying a difference signal between the average value obtained by the first means and the electric signal and a uniquely fluctuating fluctuation signal to the driving means for causing the relative movement; The present invention is characterized by comprising a third means for deriving a synchronous component of reflected light that changes synchronously and correcting the average value based on this synchronous component.

Furthermore, in the tracking device according to the second invention, in the tracking device according to the first invention, when the tracking device shifts to a tracking operation of an information track different from the information track being tracked,
When the tracking control operation being executed is ended, the correction operation by the third means is controlled to be stopped, and after the tracking control operation for a different information track is started, the correction operation is restarted. It is characterized by comprising the means of 4.

[0008]

[Operation] Therefore, according to the tracking device of the first aspect of the present invention, the average value of the difference signal of the electric signals from the photoelectric converter is applied to the driving means by the second means together with the difference signal of the electric signals. Therefore, the control operation can be started even when the difference signal of the electric signal is asymmetric between positive and negative, and even if the above-mentioned average value fluctuates by the third means, the value is corrected, so stable control can always be performed. It becomes like this.

Furthermore, according to the tracking device of the second invention,
In the case of transitioning to a tracking operation of an information track different from the information track being tracked, in order to terminate the tracking control operation in progress, the correction operation by the third means is stopped by the fourth means, and, After that, the correction operation is resumed after starting the tracking control operation for a different information track, so that stable control can be performed even in playback operations that involve so-called track jumps, such as song selection operations.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of a tracking device of the present invention. Further, FIG. 2 is a block diagram of the optical pickup (10) shown in FIG. 1.

First, in FIG. 2, an optical pickup (1
0) is a semiconductor laser diode (
11), a collimator lens (12) that converts the diverging light from the semiconductor laser diode (11) into parallel light, an objective lens (13) that focuses the parallel light from the collimator lens (12), and an objective lens (13). When the laser beam focused by the disk (20) is irradiated, the laser beam is reflected and becomes reflected light, and the reflected light is reflected by the objective lens (1
3), the light is again focused into parallel light, and a semi-reflecting mirror (16) changes the direction of the parallel light toward the photoelectric converter (16).
4), a cylindrical lens (15) that focuses the reflected light whose direction has been changed by the semi-reflective mirror (14) from parallel light onto the photoelectric converter (16), and the reflected light focused by the cylindrical lens (15). A photoelectric converter (16) consisting of elements A, B, C, and D that converts the signal into an electric signal and an objective lens (13) are moved in the radial direction of the disk (20) to irradiate the disk (20) with light. and a coil (17) that moves the disk (20) in the radial direction.

[0012] The optical pickup (10) constructed as described above is arranged at the position shown in FIG. 1 in the tracking device of the present invention. That is, in FIG. 1, the tracking device of the present invention is a recording medium having a spiral information track, and includes an objective lens (13) in an optical pickup (10).
A disk (20
) and a motor (21) that rotates the disk (20).
) and a photoelectric converter (16) in the optical pickup (10)
an adder (22) that adds electrical signals from elements A and B that constitute the , and elements C and D of the photoelectric converter (16).
an adder (23) that adds electrical signals from the adder (23);
22) and the adder (23) to output a tracking error signal TE1 indicating the relative positional deviation between the information track and the irradiation light based on the principle of the so-called push-pull method. 24), a peak hold circuit (25) that outputs the maximum value of the tracking error signal TE1, a bottom hold circuit (26) that outputs the minimum value of the tracking error signal TE1, and a peak hold circuit (25). An adder (27) inputs the maximum value of the tracking error signal TE1 and the minimum value of the tracking error signal TE1 output from the bottom hold circuit (26) and outputs the average value;
2) and the output signals from the adder (23) to form the total incident light on the photoelectric converter (16), that is, the disk (20).
an adder (28) that outputs an electric signal HF approximately equivalent to the total reflection light from the oscillator (29) that outputs a constant frequency signal W0, and an adder (28) that outputs an electric signal HF that is approximately equivalent to the total reflected light from A periodic detection circuit (30) that performs periodic detection by holding or the like and outputs a detected signal TE2, an amplifier (31) that amplifies the detected signal TE2, and an amplifier (3).
A coil (32) that moves the optical pickup (10) in the radial direction of the disk (20) based on the output of 1), a resistor (33), a capacitor (34), and a subtracter (24).
A subtracter (35) inputs the tracking error signal TE1 outputted from the subtracter (35) and the voltage of the capacitor (34) and outputs the difference signal TE3, and the output signal TE of the subtracter (35).
an adder (36) that superimposes a constant frequency signal W0 from an oscillator (29) on 3, and switches (37), (38),
(39).

Next, the operation of the tracking device of the present invention constructed as described above will be explained using FIGS. 3 and 4. In addition,
3 and 4 are waveform diagrams showing signal waveforms of operation signals of each part of the tracking device of the present invention. In the tracking device of the present invention, when the switches (37), (38), and (39) are opened and the disk (20) is rotating, the tracking error signal TE1 and the electric signal HF are respectively shown in FIG. 3(b). ，
The signal waveform is as shown in (c). That is, when the laser beam irradiated from the optical pickup (10) to the disk (20) is vertically irradiated, the tracking error signal TE1 is centered around the TE1="0" line as shown in FIG. 3(a). The signal has vertically symmetrical amplitude. However, if the laser beam is slightly tilted from the vertical, the tracking error signal T
As shown in FIG. 3(b), E1 becomes a signal whose amplitude is vertically symmetrical around a position shifted from the TE1="0" line.

In addition, in FIG. 3(c) showing the signal waveform of the electrical signal HF output from the adder (28), point A where the electrical signal HF has the maximum amplitude is located on the information track of the optical pickup (10). This indicates the location where the irradiation light is irradiated, and this location is the control center point at which tracking should be performed. In conventional tracking devices, although the control center point to be tracked is point A, the tracking error signal TE1 at point A is not "0", so the tracking error signal TE1 becomes "0" and deviates slightly. Tracking control was performed centering on point B.

However, the tracking device of the present invention operates as follows. In other words, the tracking error signal TE1 is not directly used for tracking control, but is
First, the peak hold circuit (25) detects and holds the maximum value Vp of the tracking error signal TE1 shown in FIG. 3(b), and the bottom hold circuit (26) detects and holds the minimum value Vb. The adder (27) has the above Vp,
Vb is input, and the tracking error signal TE in this state is
The average value Va=1/2 (Vp+Vb) of 1 is output. Therefore, by closing the switch (37) in this state, the average value Va of the tracking error signal TE1 and the tracking error signal TE1 are input to the subtracter (35), so the output signal TE3 of the subtracter (35) is The tracking error signal is obtained by omitting the asymmetric component Va from the tracking error signal TE1.

On the other hand, the constant frequency signal W0 from the oscillator (29) is applied to the output signal TE3 of the subtracter (35).
36) and the output signal T of the adder (36)
E4 closes the switch (38) to close the coil (
17), and functions to perform tracking control so that the maximum amplitude of the electric signal HF is obtained.

The objective lens (13) receives a constant frequency signal W0.
minute vibrations in the radial direction of the disk (20) in synchronization with
Accordingly, the light irradiated onto the disk (20) also slightly vibrates in the direction across the information track. Figure 4(b),(c)
) shows the signal waveform of the electric signal HF in response to W0 in FIG. 4(a), which shows the signal waveform of the constant frequency signal W0, and the information track is captured by the light irradiated onto the disk (20). The signal waveform of the electrical signal HF in this case is shown in Fig. 4(b).
If there is a slight deviation, the signal waveform of the electrical signal HF will be as shown in FIG. 4(c).

Here, if a multiplier is used as the period detection circuit (30) and the optical pickup (10) moved by the coil (32) is constructed so as to hardly respond to the frequency of the constant frequency signal W0, the period Detection circuit (30)
The detected signal TE2 output from the detector has a signal waveform as shown in FIGS. 4(d) and (e). Specifically, the signal waveform of the detection signal TE2 in FIG. 4(d) is the same as the electric signal HF shown in FIG. 4(b) when the information track and the irradiation light match.
This corresponds to (a), and the detected signal T in FIG. 4(e)
The signal waveform of E2 is generated when the information track and the irradiation light are slightly shifted, that is, the electric signal HF (b
).

On the other hand, the optical pickup (10) is configured to respond to the low frequency (sufficiently lower than the frequency of the constant frequency signal W0) component of the detected signal TE2.
) is "0", so the optical pickup (10) does not move. In addition, the detection signal TE
2 is applied to the capacitor (34) via the resistor (33). When the switch (37) is opened in this state, the voltage of the capacitor (34) is set to the average value Va of the tracking error signal TE1, which is the output of the adder (27), as an initial value, and the voltage of the capacitor (34) is changed to the capacitor (34) via the resistor (33). 34) is corrected by the low frequency component of the detection signal TE2 applied to the detection signal TE2. When the information track and the irradiation light are slightly misaligned, that is, in FIG. 4(e), the average voltage Vte2 of the detection signal TE2 becomes negative, and as the optical pickup (10) is moved in the radial direction of the disk (20), Lower the voltage of the capacitor (34).

Assuming that the disc (20) is curved, if the playback is continued continuously, the disc (20) will be curved.
20) moves in the radial direction, and due to the curvature, the irradiation angle of the irradiation light onto the disk (20) changes with time, and the average value Va of the tracking error signal TE1 which is the output of the adder (27) The value of changes. On the other hand, the average voltage Vte2 of the detection signal TE2 becomes "0" when the information track and the irradiation light match, almost regardless of the irradiation angle of the irradiation light. The detection signal TE2 is transmitted through a resistor (33) as a low frequency component of the tracking error signal.
, is used as a signal to drive the objective lens (13) via a condenser (34), and is used as a tracking error signal TE.
1 is a subtracter (
35) is used as a signal to drive the objective lens (13).

Next, a reproduction operation involving a so-called track jump, such as a music selection operation, will be explained. When performing a track jump operation, the tracking control described above is temporarily stopped by opening the switches (38) and (39), and is performed by applying a rapid movement voltage to the coils (17) and (32). During this period, the movement of the objective lens (13) becomes unrelated to the constant frequency signal W0, and the electric signal HF
is also unrelated to the constant frequency signal W0, and the detected signal T
E2 becomes a meaningless signal. Therefore, in order to prevent the voltage of the capacitor (34) from changing due to the detection signal TE2, which is a meaningless signal, the switch (39) is opened during the track jump operation, and is closed after the track jump operation is completed to restart the operation. controlled to do so.

In the above embodiment, the detection signal TE2 is used as the signal for driving the optical pickup (10), but the output signal TE3 of the subtracter (35) may also be used. In addition, a method has been shown in which the constant frequency signal W0 is added to the output signal TE3 of the subtracter (35) that changes the irradiation light in synchronization with the constant frequency signal W0, and the resultant signal is applied to the coil (17). A similar effect can be obtained by using a method of moving the objective lens (13) in the radial direction using a ceramic resonator or the like independently of the output signal TE3 in (35).

[0023]

As explained above, according to the tracking device of the first invention, reflected light is converted into a plurality of electrical signals by a plurality of photoelectric converters, and the average value of the difference signal of the plurality of electrical signals is calculated. a first means for determining the relative motion; and a second means for applying a difference signal between the average value determined by the first means and the electric signal and a fluctuation signal that uniquely varies to the drive means for causing the relative motion. and a third means for deriving a synchronous component of the reflected light that changes in synchronization with the fluctuation signal and correcting the average value based on this synchronous component,
Since the average value of the electrical signal difference signal from the photoelectric converter is applied to the driving means together with the electrical signal difference signal by the second means, the control operation is started even when the electrical signal difference signal is asymmetric between positive and negative. Even if the average value fluctuates by the third means, the value is corrected, so stable control can always be performed, and even if the tracking error signal changes around non-zero, it can be stabilized. This has the effect of allowing control.

Furthermore, according to the tracking device of the second invention,
When transitioning to a tracking operation of an information track different from the information track being tracked, control is performed to stop the correction operation by the third means when the tracking control operation in progress is terminated, and after that, a different information track is tracked. Since the present invention is configured to include a fifth means for controlling to restart the correction operation after starting the tracking control operation, stable control can be performed even in playback operations that involve so-called track jumps such as song selection operations. There is an effect.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a tracking device showing one embodiment of the present invention.

2 is a block diagram of an optical pickup (10) of the tracking device of the present invention shown in FIG. 1. FIG.

FIG. 3 is a signal waveform showing the relationship between the tracking error signal TE1, the electrical signal HF, and the output signal TE3 of the subtracter (35) of the tracking device of the present invention shown in FIG.

4 shows the relationship between the electrical signal HF and the detection signal TE2 in the tracking device of the present invention shown in FIG. 1, when the information track and the irradiation light match and when the information track and the irradiation light are slightly deviated; This is the signal waveform shown.

[Explanation of symbols]

(10) Optical pickup (11) Semiconductor laser diode (12) Collimator lens (13) Objective lens (14) Semi-reflective mirror (15) Cylindrical lens (16) Photoelectric converter (17), (32) Coil (20) Disk (21) Motor (22), (23), (27), (28), (36)
Adder (24), (35) Subtractor (25) Peak hold circuit (26) Bottom hold circuit (29) Oscillator (30) Periodic detection circuit (31) Amplifier (33) Resistor (34) Capacitor

Claims (2)

[Claims] 1. A recording medium having an information track is irradiated with light almost perpendicularly, and the irradiated light tracks the information track by changes in reflected light caused by relative movement between the irradiated light and the information track. A tracking device for controlling the relative movement, wherein the reflected light is converted into a plurality of electrical signals by a plurality of photoelectric converters, and a first means for calculating an average value of a difference signal of the plurality of electrical signals. and a second means for applying a difference signal between the average value obtained by the first means and the electric signal and a fluctuation signal that uniquely fluctuates to the drive means for causing the relative movement, and the fluctuation signal. A tracking device comprising: third means for deriving a synchronous component of reflected light that changes in synchronization with the signal and correcting the average value based on this synchronous component. 2. In the tracking device according to claim 1, when moving to a tracking operation of an information track different from the information track being tracked, the correction operation by the third means is stopped, and the correction operation is then changed to a different information track. A tracking device comprising: fourth means for controlling the correction operation to be restarted after starting the tracking control operation.