JPH1091242A - Displacement controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the need for higher accuracy of all related parts elements by driving with control a displacement-controlled object so as to be amplified and offset each other by plural error signal amplifier means where the displacement error signals have different amplification characteristics. SOLUTION: The displacement error of a displacement-controlled object 100 is detected by a displacement error detection means 101, and an error signal is generated. This error signal is sent to plural error signal amplifier means 102 which have different amplification characteristics and amplify each error signal. The amplification characteristics of the means 102 are set so as to secure the desired amplification characteristic through their mutual superimposition. Thus, plural drive control means 103 drive with control the object 100 so as to receive the amplification signals corresponding to the means 102 and to offset the displacement error signals with each other. In such a way, the amplification characteristic that is totally needed is distributed to plural means 102 and also the parts accuracy can be distributed to plural means 103. As a result, the high stability is secured at low cost.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a displacement control device, and more particularly to a displacement control device for an optical disk, a multi-beam copying machine, or the like.

[0002]

2. Description of the Related Art FIG. 19 shows an example of a block diagram of a positioning control system. The displacement error of the displacement-controlled body is detected by the sensor 111 and an error signal is generated. The error signal is adjusted in phase advance and the like by the control filter 112, and the signal is amplified by the power amplifier 113. Mechanism 114
Receives the amplified signal amplified by the power amplifier 113 and drives and controls the displacement control body so as to cancel the displacement error. FIG.
0 shows the amplitude amplification characteristic (a) and the phase amplification characteristic (b) of the power amplifier 113, and FIG. 21 shows the amplitude amplification characteristic (a) and the phase amplification characteristic (b) of the control filter 112. FIG.
As shown in FIG. 21, usually, a frequency moderately lower than the secondary resonance frequency is selected as the control band frequency, and the system is stabilized using phase lead compensation as shown in FIG. A positioning control system having open loop characteristics is constructed.

[0003] The suppression rate of displacement disturbance or displacement error to the positioning control system depends on the gain of the open loop characteristic. Therefore, in order to drive-control the object to be displaced with desired positioning accuracy, the open-loop characteristics must be set so that each frequency has a gain exceeding the ratio between the displacement disturbance assumed for each frequency and the required positioning accuracy. Must be designed. For example, at 10 Hz 2
If a displacement disturbance of 0 mm (pp) is assumed and the required positioning accuracy is 10 μm (pp), then 20
High gain of 00 times, that is, about 66 dB or more, at 10 Hz
It is necessary in. High gain is required at other frequencies in the desired frequency band.

[0004]

In such a control system, it is necessary to use, for example, a component element that satisfies the accuracy of 2000 times as all the related components such as the power amplifier 113 shown in the block diagram of FIG. It will be necessary. Such a high precision or high gain component element has a problem in that the displacement control device is expensive because of its high price. In particular, it is necessary to pay attention to noise removal in the analog circuit section. In this case, when all the related component elements are used with high accuracy, there is a problem that, for example, an oscillation phenomenon occurs due to noise and it is difficult to construct a highly stable displacement control device. .

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art, and to provide a displacement controller which is inexpensive and has a high stability without the necessity of making all the related components highly accurate. .

[0006]

In order to achieve the above object, a displacement control device according to the present invention comprises a displacement error detecting means for detecting a displacement error of an object to be displaced and generating an error signal; A plurality of error signal amplifying means for amplifying the error signal, and driving and controlling the displacement controlled body so as to cancel the displacement error by receiving the respective amplified signals generated by the plurality of error signal amplifying means. And a plurality of drive control means.

[0007] Preferably, the amplification characteristics of each of the plurality of error signal amplifying means are set such that a desired amplification characteristic is formed when they are superimposed on each other.

Further, one of the plurality of error signal amplifying units has a high frequency amplification characteristic for amplifying a high frequency component in the error signal, and the other one of the plurality of error signal amplifying units includes the error signal amplifying unit. It has low-frequency amplification characteristics for amplifying low-frequency components in a signal.

The high-frequency amplification characteristic is formed by subtracting the low-frequency amplification characteristic from the overall frequency amplification characteristic of the plurality of error signal amplifiers.

The low frequency amplification characteristic is formed by subtracting the high frequency amplification characteristic from the entire frequency amplification characteristic of the plurality of error signal amplifiers.

Further, the high-frequency amplification characteristic has a maximum amplification factor difference that is at least twice as large as the low-frequency amplification characteristic, or the low-frequency amplification characteristic has a difference with respect to the high-frequency amplification characteristic.

Further, the displacement error is a displacement error of a light beam irradiation position in the optical disk device.

The displacement error is a displacement error of a light beam irradiation position in a multi-beam copying machine.

In the above-mentioned invention, since a plurality of error signal amplifying means having amplification characteristics different from each other and amplifying the error signal are provided, the required amplification characteristic as a whole is distributed to the plurality of error signal amplifying means. It becomes possible. As a result, it is not necessary for each error signal amplifying means itself to overload the amplification characteristics required as a whole, and it is possible to configure the error signal amplifying means at low cost using highly versatile component elements. Will be possible. Further, since the amplification characteristics of each error signal amplifying means can be set conservatively, it is possible to suppress an oscillation phenomenon or the like due to noise or the like, and it is possible to configure a highly stable displacement control device.

In addition, a plurality of drive control means are provided corresponding to the plurality of error signal amplifying means and drive-control the displacement-controlled body so as to cancel the displacement error by receiving the respective amplified signals. The component accuracy required as a whole can be distributed to a plurality of drive control means. As a result, the entire drive control means can be configured at low cost and with high stability as compared with the case where the component characteristics are borne alone.

Since the amplification characteristics of each of the plurality of error signal amplifying means are set so that desired amplification characteristics are formed when they are superimposed on each other, even when a plurality of error signal amplifying means are used, a desired amplification characteristic is obtained. The error signal can be amplified by the characteristic.

The plurality of error signal amplifying means can be simply constituted by the error signal amplifying means having the high frequency amplifying characteristic and the error signal amplifying means having the low frequency amplifying characteristic.

This high frequency amplification characteristic can be easily formed by subtracting the low frequency amplification characteristic from the entire frequency amplification characteristic of the plurality of error signal amplification means. Further, the low frequency amplification characteristic can be easily formed by subtracting the high frequency amplification characteristic from the entire frequency amplification characteristic of the plurality of error signal amplifiers.

Further, by making the high-frequency amplification characteristic and the low-frequency amplification characteristic have a difference of the maximum amplification rate which is twice or more, digital processing can be performed significantly.

[0020]

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

First, a basic configuration of a displacement control device according to the present invention will be described with reference to FIG. In FIG. 1, a displacement control device includes a displacement error detecting unit 101 that detects a displacement error of a displacement controlled body 100 and generates an error signal;
A plurality of error signal amplifiers 102 having different amplification characteristics and amplifying the error signal; and a plurality of error signal amplifiers 1
A plurality of drive control means 103 are provided to receive the respective amplified signals generated in step 02 and drive-control the displacement-controlled body so as to cancel the displacement error.

Next, as a first embodiment of the displacement control device of the present invention, an example in which the displacement control device of the present invention is applied to a tracking control device in an optical disk device will be described.

Tracking control in an optical disk device requires high-precision positioning in a large dynamic range.

FIG. 2 shows a tracking control system of an optical disk device using the driving device and the control device of the present invention. On the surface of an optical disc (optical recording medium) 1, recording tracks (grooves) are formed in a spiral or concentric manner, and the rotation of the optical disc 1 is controlled by a spindle motor 2. Recording and reproduction of information on the optical disk 1 are performed by an optical head 3 provided below the optical disk 1. Although the optical disc 1 uses a recording film that forms pits with holes, a recording layer utilizing a phase change or a multi-phase recording film may be used. Further, a magneto-optical disk may be used, and in this case, the configuration of the optical head and the like is appropriately changed.

An objective lens is supported on the optical head 3 by a wire, a leaf spring, or the like (not shown). The objective lens is moved in a focusing direction (an optical axis direction of the lens) by a focus drive coil (not shown). The entire optical head 3 is moved by a linear motor 4 in a tracking direction (a direction perpendicular to the optical axis of the lens and orthogonal to the track). Laser light is
The light is radiated onto the optical disk 1 via an optical head 3 including a collimator lens, a half prism, an objective lens, and the like, and the reflected light from the optical disk 1 is again guided to the photodetector 5 via the optical system 3. The output of the photodetector 5 is sent to the signal amplifier 6 for processing.

The state of this processing will be described with reference to FIG.
The light detector 5 includes four light detection cells 5a, 5b, 5c, 5
d, and the amplifier 6a,..., 6d and the adder / subtractors 6e to 6l constitute the signal amplifier 6.

The output signal of the photodetector cell 5a of the photodetector 5 is supplied to one end of adders 6e and 6g via the amplifier 6a, and the output signal of the photodetector cell 5b is supplied to the adder 6f via the amplifier 6b. , 6h and supplied to one end of the light detection cell 5c.
Is supplied to the other ends of the adders 6f and 6g via the amplifier 6c, and the output signal of the photodetection cell 5d is supplied to the other ends of the adders 6e and 6h via the amplifier 6d. The output signals of the light detection cells 5a, 5b, 5c, 5d of the light detector 5 are supplied to the high-speed adder 6i via the amplifiers 6a, 6b, 6c, 6d, respectively. High-speed adder 6i
Outputs a signal for reproduction. The output signal of the adder 6e is supplied to the inverting input terminal of the differential amplifier 6j, and the output signal of the adder 6f is supplied to the non-inverting input terminal. Thus, the differential amplifier 6j supplies a tracking error signal to the tracking control circuit 7 according to the difference between the adders 6e and 6f. The output signals of the adders 6e and 6f are supplied to the adder 6k. Thus, the adder 6k supplies the sum signal to a seek control unit (not shown), a focusing control circuit (not shown), and a tracking control circuit 7. The output signal of the adder 6g is supplied to the inverting input terminal of the differential amplifier 61, and the output signal of the adder 6h is supplied to the non-inverting input terminal. Thus, the differential amplifier 61 supplies a signal relating to the focus point to a focusing control circuit (not shown) according to the difference between the adders 6g and 6h. The output signal of the focusing control circuit is supplied to a focus drive coil (not shown), and the laser light is controlled so as to be always just focused on the optical disc 1. This is called focus control. The tracking control circuit 7 generates a tracking control signal from the tracking error signal and the sum signal. A current is supplied to the linear motor 4 in accordance with the tracking control signal, and a tracking operation is performed to control the laser beam to be irradiated on the track. This is called tracking control or position control. This will be described in detail later.

As described above, the sum of the outputs of the photodetector cells 5a to 5d of the photodetector 5 in the state where the focusing and tracking control is performed, that is, the output signal (reproduction signal) from the high-speed adder 6i is The change in the reflectance from the bits (recording information) formed on the track is reflected. This signal is supplied to a signal processing circuit (not shown),
The recorded information and address information (track number, sector number, etc.) are reproduced.

The reproduction information reproduced by the signal processing circuit passes through a controller 8 and is connected to an external personal computer 9.
Etc. The controller 8 receives information to be recorded from an external personal computer or the like, and records the information on an optical disk.

Next, the tracking operation will be described in detail.

First, the specifications required for the tracking control system of the optical disk device will be described.

In the optical disk device, since the removable disk is rotated at a frequency of several tens of Hz, the eccentric component at the rotation frequency becomes the largest as a displacement disturbance. It is required for the tracking control system to suppress the disturbance displacement component to several thousandths. In this case, several tens of Hz
In the following low frequency range, a disturbance displacement having a constant amplitude is assumed. At frequencies higher than the rotation frequency, the mechanical specifications of the disk indicate that there is a disturbance displacement that changes with time in a sinusoidal manner at a normal acceleration. In this case, the slope in the graph shown in FIG. Is represented by a straight line.

FIG. 4 shows such a disturbance characteristic. In FIG. 4, the frequency (logarithm) of the disturbance displacement is plotted on the horizontal axis, and the amplitude (logarithm) of the disturbance displacement is plotted on the vertical axis, and the characteristic of the disturbance displacement is shown by the relationship between the two.

Taking concrete figures using an SD disk (120 mm diameter) as an example, the amount of eccentricity is 100 μm, and the maximum value of the eccentric frequency is about 22 Hz. This is ± 0.02 μm
It is required to perform tracking control with the accuracy of (1). 0.
When the logarithmic axis is represented by 02 μm as zero dB, the eccentricity is 10
0 μm is 74 dB (5000 times).

In FIG. 4, a disturbance displacement having a constant acceleration is represented by a straight line having a slope of -40 dB / dec. Assuming that the acceleration at the maximum value of the eccentric frequency exists as it is up to the high frequency, as shown in FIG.
It becomes a straight line of 40 dB / dec. The curve drawn in this manner is called a disturbance curve.

It is necessary to design a control system having a gain larger than the disturbance curve at all frequencies. As a result, disturbance can be suppressed to the required tracking accuracy (± 0.02 μm). Such a control system also has a gain (74
A very high dynamic range is also required for the frequency (about 4 KHz).

In the embodiment of the present invention, such a high dynamic range is made possible by a plurality of error signal amplifying means 102 and a plurality of drive control means 103.
This will be described in detail below.

FIG. 5 is a diagram showing a mechanism system of the displacement control device according to the present embodiment in a simplified model. The coil A21 and the coil B22 are coils constituting two drive control units 23 and 24 having different drive sensitivities (drive force with respect to an applied voltage). These drive control means 23 and 24 are, for example, electromagnetic actuators. The drive control units 23 and 24 having different drive sensitivities can be obtained by changing the number of turns of the coils A21 and B22, the coil resistance, the strength of the magnetic field, and the like. Although the drive control means 23 and 24 are electromagnetic actuators here, the drive sensitivity of actuators of other types such as an electrostatic type may be changed and used, or actuators of different types may be used in combination. Absent. In any case, the optical head 3 as one displacement-controlled body is configured to be drive-controlled by two drive control units 23 and 24 having different drive sensitivities (driving force with respect to applied voltage).

FIG. 6 shows an example of the frequency characteristic of the mechanical system obtained by combining the drive control means 23 and 24.

Next, FIG. 7 shows a control diagram in this embodiment. Here, a high frequency pass filter 28, an amplifier 29, a low frequency pass filter 31, and an amplifier 30 are provided as a plurality of error signal amplifying means 102. Also,
The drive control means 23 and the drive control means 24 are provided as the plurality of drive control means 103. Further, a sensor 26 is provided as the displacement error detecting means 101.

In FIG. 7, a tracking error signal in the tracking direction of the optical head 3 is detected by a sensor 26, compared with a reference signal by a subtracter 26a, and two signals are set based on the tracking error signal so that the signal becomes zero. A current is caused to flow through the coils A21 and B22. The tracking error signal first enters the phase compensation filter 27. The reason is that the phase of the mechanical system is about -180 degrees near the control band (the frequency at which the open loop gain becomes 0 dB), so that it is necessary to stabilize the system by the phase compensation filter 27. .

Next, the error signal is transmitted to the high-frequency pass filter 2.
8, the high frequency component passes, and the power amplifier 29
Then, the drive control means 23 having low drive sensitivity is energized via the coil A23.

Here, as an example of the high frequency pass filter 28, there is a filter having a frequency characteristic as shown in FIG. 8A, the lower one is set as the main resonance frequency of the mechanical system, and the higher one is used as the drive control means 23 with low drive sensitivity and the drive control means 24 with high drive sensitivity. The switching frequency of the main assigned frequency may be used.

The low-pass filter 31 is formed by subtracting the output of the high-pass filter 28 from the output of the phase compensation filter 27 with a subtractor. It should be noted that the low frequency pass filter may be one that passes only low frequency components from the output of the phase compensation filter 27. The signal that has passed through the low-frequency pass filter 31 is passed through the power amplifier 30 and through the coil B22 to drive the drive control unit 24 with high drive sensitivity.

The gains of the two control filters 28 and 31 are appropriately set in accordance with the drive sensitivity of the coils 21 and 22, that is, in accordance with the drive force with respect to the applied voltage.
For example, if the ratio of the sensitivity of the drive control unit 24 of high drive sensitivity to the drive control unit 23 of low drive sensitivity is a: b, the ratio of the gain of the control filter 31 to the control filter 28 is set to b: a. You.

By setting as described above, of the disturbance displacement components to be canceled out, components having a large amplitude and a low frequency are assigned to the drive control means 24 having a high drive sensitivity, while components having a small amplitude are used for the drive sensitivity. Low drive control means 23
Can be assigned to.

The output signals 35 of the drive control means 23 and 24,
36 is superimposed by an adder 37 and sent to an actuator 40 such as the linear motor 4.

FIG. 9 shows drive control means 23 and 24 and adder 3.
7 is shown in the Bode diagram. In FIG. 9, the drive control means 2
The frequency characteristic of the amplitude and phase at the output port 35
The amplitude and phase frequency characteristics at the output port 36 of the drive control means 24 are denoted by 36a and 36b, and the amplitude and phase frequency characteristics at the output port 38 of the adder 37 are denoted by 38a and 38b. As can be seen from FIG. 9, the drive control device 24 with high sensitivity is in charge of low frequency components, and the drive control unit 23 with low sensitivity is mainly in charge of high frequency components. Further, although the gain is large at a low frequency, the drive control means 23 having a low drive sensitivity has a gain of 1/3 of the gain.
It can be seen that it has about 0, and enables driving with high resolution.

As a result, each power amplifier 29,
30, the two drive control means 23, 24
, It is possible to perform high-precision driving as a whole.

Next, FIG. 10 shows a modification of the configuration shown in FIG. 7, in which a digital arithmetic element such as a DSP is used as a control filter. In FIG. 10, the subtractor 26a
An A / D converter 42 is provided between the high frequency filter 28 and the low frequency filter 31, and D / A converters 29 and 30 such as a DSP are provided after the high frequency filter 28 and the low frequency filter 31.

Also in this modified example, by driving the actuator 40 simultaneously by the two drive control means 23 and 24, the number of bits of the D / A converter after the DSP calculation by the D / A converters 29 and 30 is small. Even
Driving can be performed with the same high accuracy as when an A / D converter having a higher number of bits is used. Here, it is assumed that the influence of the phase delay due to sampling can be ignored.

FIG. 13A shows a simulation result when the control system shown in FIG. 10 is used. For comparison,
FIG. 11 shows the results when a control system is used in which the same driven member is driven by one drive control means 45 using a D / A converter having the same bit number (both are 8 bits) and the actuator 40 is driven. Show. Figure 1 shows the simulation results
This is shown in FIG.

FIG. 12 is a Bode diagram of an open loop when digital control of the control system shown in FIG. 10 is used.
The frequency characteristics of amplitude and phase in the Bode diagram of the open loop shown in FIG. 12 are apparently the same as 38a and 38b shown in FIG.

FIGS. 13A and 13B show characteristics with respect to a 10 Hz sinusoidal disturbance 50. FIG. 13A shows drive control means 23 and 24 for canceling disturbance 50.
5 shows the waveforms of the drive signals A and B output from the controller 40 and the tracking error 55 which is the output signal of the actuator 40. FIG. 13B shows a drive signal 45 a output from the drive control unit 45 and a tracking error 56 which is an output signal of the actuator 40.

As can be seen by comparing FIGS. 13 (a) and 13 (b), in the case of the method of the present invention shown in FIG. 13 (a), the two drive control means 23 and 24 operate cooperatively. As a result, an accurate following error 55 is obtained. On the other hand, in the case of the conventional method shown in FIG.
Since the number of bits of the A converter 43 is insufficient, it cannot be followed, and it can be recognized that only the tracking error 56 with low accuracy can be obtained.

As described above, according to the embodiment of the present invention, the high frequency pass filter 28, the amplifier 29, the low frequency pass filter 31, and the amplifier 30 are provided as the plurality of error signal amplifying means 102, Control means 103
Since the drive control means 23 and the drive control means 24 are provided, it becomes possible to distribute the amplification characteristics required as a whole to a plurality of error signal amplification means. As a result, the high frequency pass filter 28, the amplifier 29, the low frequency pass filter 31, and the amplifier 30 do not need to overload the required amplification characteristics as a whole, and use component elements having high versatility. Thus, the displacement control device can be configured at low cost.

Further, each high frequency pass filter 28,
Since the amplification characteristics of the amplifier 29, the low-frequency pass filter 31, and the amplifier 30 can be set conservatively, it is possible to suppress an oscillation phenomenon due to noise or the like, and to configure a highly stable displacement control device. Can be.

Also, a plurality of drive control means 23, 2 which receive the respective amplified signals corresponding to the plurality of error signal amplifying means and drive control the displacement controlled body so as to cancel the displacement error.
Since the number 4 is provided, it is possible to distribute the component accuracy required for the entire drive control means to the plurality of drive control means 23 and 24. As a result, the displacement control device can be configured at low cost and with high stability as compared with a case where the component characteristics are borne alone.

Next, as a second embodiment of the displacement control device of the present invention, an example applied to light beam position control in a multi-beam copying machine will be described.

FIG. 14 is a simplified configuration diagram of a so-called multi-beam copying machine in which a plurality of scanning lines are drawn on one surface of a polygon mirror 70 using two or more laser beams. The multi-beam copier includes a plurality of laser light sources 71 and 72 for generating laser light, and a plurality of laser lights generated from the plurality of laser light sources 71 and 72 to a recording medium 73.
First deflecting element 7 for scanning over in a first scanning direction
6, a second deflecting element 77 for scanning the laser beam in a second scanning direction substantially orthogonal to the first scanning direction, and a sensor 79 for measuring the interval between the positions of the plurality of laser beams on the recording medium 73. The second deflecting element 77 or the first deflecting element 76 is controlled based on the output signal of the sensor 79 so that the positions of the plurality of laser beams on the recording medium 73 are at predetermined intervals.

The intervals between the positions of the plurality of laser beams on the recording medium 73 need to be constant in order to make the line intervals uniform. As the change component of the position interval, there is a change component having a large amplitude that changes gradually with time due to a change in the thermal environment of the entire device, in addition to a minute change component that is always present and has a short time change, Therefore, the position interval component has a high frequency minute amplitude component and a low frequency large amplitude component.

In the optical system of the multi-beam copying machine,
The mounting position and angle slightly change due to the effects of aging and thermal expansion. For this reason, the laser beams from the two light sources 71 and 72 are displaced on the photosensitive drum surface 73.
In order to correct the beam pitch shift, the lens 75 and the like are moved to change the image forming position of the beam, thereby performing alignment.

The multi-beam copying machine is described in, for example, Japanese Patent Publication No. 6-94215.

The displacement caused on the image plane by the movement of the optical system is about 1 mm. On the other hand, the precision required for the positioning control is about 1 micron, which requires a gain of 1000 times or more. Therefore, the driving units 76 and 77 for moving the lenses 74 and 75 need to move a wide range with high accuracy, and it has conventionally been necessary to use expensive elements with high resolution for the driving circuit.

FIG. 15 is a diagram showing, in a simplified model, the mechanism system of the displacement control device of the present embodiment. Each of the drive units 76 and 77 for moving the lenses 74 and 75 is constituted by two drive control units 83 and 84 having different drive sensitivities for each lens.

The control system has substantially the same configuration as that shown in FIG. 7 or FIG. FIG. 16 shows an example of the frequency characteristic of the lens driving system. In this example, the primary resonance frequency is higher than the control band. For such characteristics,
The control filter adds a first-order integration characteristic. FIG. 17 shows characteristics obtained by adding a filter to the mechanical system characteristics. In the control band, the phase is -90 deg. No phase compensation was performed because of the delay. After the control filter, there is a high frequency pass filter, through which high frequency components pass and which passes through the power amplifier to energize the coil of the drive control means with low drive sensitivity.

FIG. 1 shows an example of a high frequency pass filter.
8 having the characteristics shown in FIG. The output signal of the high frequency pass filter is amplified by the power amplifier and drives the actuator via the coil of the drive control means having high drive sensitivity. On the other hand, the low-frequency pass filter is formed so as to output a value obtained by subtracting the output of the high-frequency pass filter from the output of the control filter, and the output signal passes through the power amplifier and is provided by the drive control means having high drive sensitivity. The actuator is driven via the coil.

The gains of the high frequency filter and the low frequency filter are appropriately set according to the drive sensitivity of the drive control means 83, 84. For example, if the ratio of the sensitivity of the drive control unit of high drive sensitivity to the drive control unit of low drive sensitivity is a: b, the ratio of the gain of the filter is b: a. In the above manner, among the signal components to be driven, those having a large amplitude and a low frequency are handled by the drive control unit having a high drive sensitivity, and those having a small amplitude are handled by the drive control unit having a low drive sensitivity. Will be.

In this embodiment, the beam position is adjusted by moving the lens. However, the position is adjusted by changing the angle of the parallel plate in the optical path or the angle of the reflection mirror. The present invention can be similarly applied to such a case.

The mechanical characteristics of the control drive device have been described with respect to the configuration in which the primary resonance frequency is higher than the control band. However, the primary resonance frequency is higher than the control band as in the example of the optical disk positioning control system. It may be something. In this case, similar to the case of the optical disk device (although the frequency is different)
An accurate positioning control system can be configured by using the above filters and the like.

According to the configuration of the present embodiment, as in the example of the first embodiment, accurate positioning can be performed even if an element having a circuit with insufficient resolution is used.

[0072]

As described above, according to the structure of the present invention, since a plurality of error signal amplifying means having different amplification characteristics are provided, the required amplification characteristics as a whole can be reduced by a plurality of error signal amplifying means. It becomes possible to distribute to the means. As a result, it is not necessary for each error signal amplifying means itself to overload the amplification characteristics required as a whole, and it is possible to configure the error signal amplifying means at low cost using highly versatile component elements. Will be possible. Further, since the amplification characteristics of each error signal amplifying means can be set conservatively, it is possible to suppress an oscillation phenomenon or the like due to noise or the like, and it is possible to configure a highly stable displacement control device. Also, since a plurality of drive control means are provided corresponding to the plurality of error signal amplifying means, the component accuracy required as a whole of the drive control means can be distributed to the plurality of drive control means, and the component characteristics can be reduced to a single unit. Thus, a displacement control device which is inexpensive and has high stability can be provided as compared with the case where the control device is used.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a schematic configuration of a displacement control device according to the present invention.

FIG. 2 is a diagram showing a tracking control system of the optical disk device to which the present invention is applied.

FIG. 3 is a diagram showing a control signal generation unit of the optical disk device.

FIG. 4 is a diagram showing frequency characteristics of a disturbance component of the optical disk device.

FIG. 5 is a diagram showing a driving device of the present invention in a simplified model.

FIG. 6 is a diagram illustrating an example of frequency characteristics of amplitude (a) and phase (b) of a mechanical system used in the optical disc device.

FIG. 7 is a block diagram showing an example of a control system according to the present invention.

FIG. 8 is a diagram showing an example of frequency characteristics of the amplitude (a) and the phase (b) of the high frequency pass filter used in the control system of the present invention.

FIG. 9 is a diagram illustrating an example of a frequency characteristic of a control system according to the present invention, illustrating a frequency characteristic of each output of a plurality of drive control means and a frequency characteristic of a superposition of the frequency characteristics.

FIG. 10 is a block diagram when a digital operation element is used as a control element in the control system of the present invention.

FIG. 11 is a control block diagram of a conventional control system having one drive unit.

FIG. 12 is a diagram showing frequency characteristics of an embodiment using digital control of a control system.

13 shows a disturbance response simulation result (a) of the embodiment using digital control of the control system, and a disturbance response simulation result (b) of using the control system shown in FIG. 11;
FIG.

FIG. 14 is a diagram showing a schematic configuration of a multi-beam copying machine.

FIG. 15 is a diagram showing an embodiment in which the displacement control device of the present invention is applied to a multi-beam copying machine.

FIG. 16 is a diagram illustrating an example of frequency characteristics of a driving device of a multi-beam copying machine.

FIG. 17 is a diagram illustrating an example of a frequency characteristic of a control system of the multi-beam copying machine.

FIG. 18 is a diagram illustrating an example of a high-frequency filter used for controlling a multi-beam copying machine.

FIG. 19 is a block diagram showing a conventional positioning control system.

FIG. 20 is a diagram illustrating an example of a frequency characteristic of a mechanism used in a conventional positioning control system.

FIG. 21 is a diagram showing an example of a position advance circuit used in a conventional positioning control system.

FIG. 22 is a diagram showing an example of a frequency characteristic of a conventional positioning control system.

[Explanation of symbols]

 3 Optical Head (Displacement Controlled Object) 23 Drive Control Means 24 Drive Control Means 26 Sensor (Displacement Error Detection Means) 27 Phase Compensation Filter 28 High Frequency Filter 29 Power Amplifier 30 Power Amplifier 31 Low Frequency Filter 40 Actuator 74, 75 Control body 100 Displacement controlled body 101 Displacement error detecting means 102 Error signal amplifying means 103 Drive control means 103

Claims (8)

[Claims] 1. A displacement error detecting means for detecting a displacement error of a displacement controlled object and generating an error signal; a plurality of error signal amplifying means having amplification characteristics different from each other and amplifying the error signal; A displacement control device, comprising: a plurality of drive control means for receiving the respective amplified signals generated by the error signal amplifying means and controlling the drive of the displacement controlled body so as to cancel the displacement error. 2. The variable control means according to claim 1, wherein the amplification characteristics of each of said plurality of error signal amplification means are set such that a desired amplification characteristic is formed when they are superimposed on each other. . 3. One of the plurality of error signal amplifying means has a high frequency amplification characteristic for amplifying a high frequency component in the error signal. The displacement control device according to claim 1, wherein the displacement control device has a low-frequency amplification characteristic for amplifying a low-frequency component in the signal. 4. The displacement control device according to claim 3, wherein said high-frequency amplification characteristic is formed by subtracting said low-frequency amplification characteristic from the entire frequency amplification characteristic of said plurality of error signal amplifying means. 5. The displacement control device according to claim 3, wherein said low frequency amplification characteristic is formed by subtracting said high frequency amplification characteristic from the entire frequency amplification characteristic of said plurality of error signal amplification means. 6. The high-frequency amplification characteristic has a maximum amplification factor difference of at least twice as large as the low-frequency amplification characteristic or the low-frequency amplification characteristic has a difference with respect to the high-frequency amplification characteristic. The displacement control device according to claim 3. 7. The displacement control device according to claim 3, wherein the displacement error is a displacement error of a light beam irradiation position in the optical disc device. 8. The displacement control device according to claim 3, wherein the displacement error is a displacement error of a light beam irradiation position in a multi-beam copying machine.