JPH01130144A - Vibration detector - Google Patents

Abstract

PURPOSE:To obtain the earlier stability of integrated output by controlling such that the time constant of an integrator is changed. CONSTITUTION:A time constant modification control circuit integrates angular velocity signals from the integrator 6 into angular signals with the aid of an integrator 10. An absolute value circuit 9 issues output in response to absolute values of the angular signals, and a comparator 7 compares the output from the absolute value circuit 9 with that from a chopping wave oscillator 8. On/off pulse signals of prescribed duty ratio imparted in such a way are input to the integrator 6 from a signal line 22, and they are regarded as on/off signals for a switch 20 to modify the time constant. Ultimately control is performed to modify the output characteristics of the integrator 6. Thus, the integrator can detect vibration speedily and precisely at all times.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a vibration detection device used to detect vibrations of equipment that is subject to vibrations at frequencies as low as 1Hz to 30Hz. Detect the shake,
The present invention relates to a vibration detection device that is suitably used to construct an image blur prevention device that keeps an image apparently stationary based on this detection information.

(Prior Art) To explain how to detect low-frequency vibrations using a system that prevents image deterioration (image blur) due to camera shake during shooting as an example, various methods have been used for this image blur prevention system. Vibration detection methods and devices have been proposed.

One such image blur prevention system uses an acceleration detection device to detect camera shake that occurs in the camera, and uses this detection signal to vibrate the correction optical system to correct the image blur on the image plane. There is a device that apparently stops the vibration of the image and prevents the image from tilting. Japanese Patent Publication No. 62-47013
The proposal in JP-A No. 62-47012 is to vibrate the correction optical system for image pre-correction using a velocity signal (or a second-order integrated displacement signal) obtained by integrating the detected acceleration signal. This is what I did.

In addition, in such an image blur prevention system, if a signal such as an acceleration component (DC component, etc.) not derived from camera shake is included in the signal of the acceleration detection device during vibration detection, the accuracy of the velocity signal or displacement signal after integration may be affected. is extremely low, so some proposals have been made to provide a bypass filter to remove signals such as these DC components from the input signal of the integrator, thereby increasing the accuracy of the integral output.

Furthermore, a camera equipped with such an image pre-prevention device has a unique problem when using the device, namely, after pointing the camera at a first subject and taking a picture, pointing the camera at a second subject. When shooting with a so-called panning operation, it takes a long time to wait for the output to stabilize before the error in the integrator output due to clipping of the output signal of the acceleration detector that occurs during the adjustment is eliminated. There is a problem that it is necessary. This is because, as mentioned above, the vibrations targeted by the camera's image pre-prevention system have fairly low frequencies (1 to 1).
(approximately 30 Hz), therefore, in order to improve the accuracy of the bypass filter, the time constant must be set to a large value, and as a result, it takes time to stabilize the output of the integrating device including the bypass filter. The problems associated with setting such a large time constant also exist in the integrator itself. It is known that the phenomenon in which the integrator becomes saturated is likely to occur when the panning operation described above, that is, the operation of changing the direction of the camera when taking continuous photographs or panoramic photographs, is performed.

Therefore, proposals have been made to solve the problem of long-time stabilization of the integrator. For example, the present applicant has made the time constant of the integrator variable in Japanese Patent Application No. 121494/1983, and ) A method in which the time constant of the integrator is changed by detecting a velocity signal or a displacement (angle) signal, thereby quickly recovering the integrator from saturation and quickly reducing the offset error caused by it. is proposed.

Figure 9 shows an example of such an integrator with a variable time constant. indicates a CdS photocoupler, which constitutes an integrator 25.

Reference numeral 21 indicates an input terminal of the integrator 25, and when an acceleration signal is input from this terminal, a speed signal is output from the output terminal 23. Furthermore, 24 indicates an input terminal for a control signal for changing the time constant.

The cut-off frequency of the integrator 25 configured as described above is determined by the following equation, where R is the combined resistance of the capacitor C1 resistor 17 of the capacitor 18 and the output resistance of the CdS fort coupler whose resistance decreases in inverse proportion to the input current. It can be expressed as

Here, since the integrator 25 has the above-mentioned configuration so that its characteristics change continuously according to the value of the input current from the signal line 24, the resistance value of the CdS photocoupler 27 is high (signal line When the resistance value of the CdS photocoupler is low (when the input current is large), the cutoff frequency is higher than when the input current from 24 is small (when the input current from 24 is small). changes, so rapid stabilization of the integrator output can be achieved.

(Problems to be Solved by the Invention) However, since the integrator 25 shown in FIG. 9 uses the CdS photocoupler 27 to change its time constant,
There may be a problem of deterioration of characteristics over time, and the change curve of the cutoff frequency of the integrator 25 with respect to the signal input from the signal line 24 depends on the characteristics of the CdS photocoupler, resulting in changes in the time constant. There is a problem in that there are limits to accurately controlling the curve or changing the shape of the curve.

(Means for Solving the Problems) In view of the above problems, the present invention eliminates the adverse effects when using an integrator with a large time constant as an integrator used in a vibration detection device that detects low frequency vibrations, It is an object of the present invention to provide a vibration detection device in which the time constant of the integrator is made variable so that early stabilization of the integrated output can be obtained.

Another object of the present invention is to provide a vibration detection device that can perform stable control over time with minimal deterioration of circuit components over time.

Still another object of the present invention is to provide a vibration detection device that is suitable for RC conversion and is effective in realizing a low-cost device.

The vibration detection device according to the present invention, which has been made to achieve the above object, is characterized in that the vibration detection device includes an integrator that integrates and outputs a low-frequency vibration input signal, and includes a switch means that is operated intermittently. a lower limit frequency changing circuit of the integrable frequency band of the integrator, the time constant of which is variable according to the ratio of the on/off; The device has a switch driving means for outputting an intermittent operation signal, and a pulse width modulating means for varying the duty ratio of the pulse signal outputted by the switch driving means depending on the output signal value from the integrator. It is in.

As the above-mentioned time constant setting circuit, for example, a circuit including a resistor and a capacitor provided with a switch means can be exemplified.

(Function) By having the above-described configuration, the present invention can quickly recover the integrator from the saturated state by performing control to vary the time constant even if the integrator falls into the saturated state, At the same time, offset errors can also be quickly reduced.

Therefore, even if an input signal that saturates the integrator enters the integrator, it is possible to quickly obtain an accurate vibration detection signal without requiring a long stabilization wait time.

(Example) The present invention will be described below based on embodiments shown in the drawings.

1 to 3 show an example of the configuration of an image blur prevention device for a camera configured by applying the vibration detection device of the present invention, and in FIG. It forms a group of focal lenses. Reference numeral 2 indicates a lens group of a correction optical system that drives an image on the image plane F by converging a parallel light beam and shifting it in the radial direction.

In this example, the shift amount of the correction optical system 2 and the shift of the image formed on the image plane are set to be 1:1.

3 is an actuator provided in conjunction with the correction optical system 2, which includes movable magnets 3a, 3a' and coils 3b, 3b.
' and a position sensor 3c that detects the lens position. Note that the lens group constituting the correction optical system is supported by a plate spring (not shown) so as to be held at the center position in the radial direction when not energized.

Reference numeral 4 denotes an angular acceleration sensor provided in the lens barrel 2, which detects the angular velocity of the rotational movement of the lens within the same plane as the paper surface. 5 is a bypass filter that removes the DC offset component of the output signal of the angular acceleration sensor 4.

The output signal of this bypass filter 5 is inputted from a signal line 21 to an integrator 6 with a variable time constant, which is a characteristic component of this example, and the input angular acceleration signal is converted into an angular velocity signal. The angular velocity signal is output from 23.

The output signal of this integrator 6 is branched, one of which is transmitted to a drive control circuit of a correction optical system which will be described later, and the other is transmitted to an integrator 10 which is a means for changing the time constant of the integrator 6. ．． Absolute value circuit 9. The signal is transmitted to a time constant change control circuit consisting of a converter tough and a triangular wave oscillator 8. This time constant change control circuit of this example includes a switch driving means for outputting a high frequency pulse signal for turning on/off a switch 20 provided in the integrator 6, which will be described later, and a pulse signal for changing the duty ratio of this pulse signal. It is formed in combination with width modulation means.

This time constant change control circuit in this example integrates the angular velocity signal from the integrator 6 into an angle signal by the integrator lO,
An output corresponding to the absolute value of this angle signal is outputted from a known absolute value circuit 9, and the output from this absolute value circuit 9 and the output of the triangular wave oscillator 8 are compared by a comparator 7, and a predetermined value given thereby is output. An on/off pulse signal with a duty ratio of is inputted to the integrator 6 from the signal line 22, and is used as an on/off operation signal for the switch 20 for changing the time constant.

Note that it is desirable that the oscillation frequency of the triangular wave oscillator 8 is sufficiently higher than the frequency band to be integrated by the integrator 6 of this example.

On the other hand, the drive control circuit for the correction optical system of this example is configured as follows.

That is, the position filter 11 that receives the signal from the integrator 6 simultaneously receives the signal from the position sensor 3c that detects the radial position of the correction optical system 2, and by these signals, the correction optical system 2 can move six times in the radial direction. The angular velocity from the integrator 6 can be transmitted to the actuator only when the actuator is in the correct state (that is, when corrective movement is possible). In other words, for this reason, the gain characteristic of the position filter 11 is, as shown in FIG. 3, when the correction optical system is within the limit position in the radial direction, the gain is 1; The gain is set to 0.

12 is a differential amplifier that constitutes a feedback loop for moving the correction optical system 2 under speed control; 13 is a differentiator that converts the position signal of the correction optical system detected by the position sensor 3c into a speed signal; Speed servo is applied by magnet sensors 3a, 3a', coils 3b, 3b', position sensor 3c, differentiator 13, and differential amplifier 12 to control the movement of the correction optical system.

Reference numeral 14 designates a differential amplifier that constitutes a weak position feedback that outputs a weak velocity signal in the negative direction to the correction optical system 2 so that the position of the correction optical system 2 is at the center position in the radial direction.

FIG. 2 is a diagram showing a specific configuration of the integrator 6. In this figure, numerals 15, 16, and 17 are resistors, 18 is a capacitor, and 19 is an operational amplifier. Reference numeral 20 denotes an analog switch which is a characteristic component of this embodiment, and is connected to the comparator 7 and turned on/off by a signal from a signal line 22.

The above explanation of the configuration describes a system for preventing image blur related to vibrations in the vertical direction of the figure for a camera having the lens system shown in Figure 1, but this also applies in the direction perpendicular to the plane of the figure. are configured similarly.

Next, the operation of the image blur prevention device having the above structure will be explained.

When the above circuit is energized and normal photographing operations are performed, and considering that the photographer is holding the camera against a stationary target, the camera generally has a small An accelerated motion is occurring. At this time, the angle between the target direction and the center line of the lens changes due to camera shake (however, the angular velocity and angular acceleration due to camera shake are zero on average). .

The angular acceleration signal detected by the angular acceleration sensor 4 has its offset components etc. removed by the bypass filter 5, and then
It is converted into an angular velocity signal by an integrator 6, and based on this angular velocity signal, the correction optical system 2 is vibrated by an actuator to prevent image distortion. This effect is as described above.

Note that during this normal time, the analog switch 20 of the time integrator 6
is in an off state, which will be discussed further later.

The differential movement of the image pre-prevention device in the normal shooting condition is explained as above, but from this normal shooting condition (the state where the camera is held facing the first still subject) to the next shooting point Next, a case will be described in which the direction of the camera is changed (the camera is held toward a second still subject) and the panning operation is performed to perform the next photographing.

In this case, the present example is characterized in that the function of the integrator 6 whose time constant is configured to be changeable in the following manner is effectively exhibited.

That is, the angular velocity signal from the integrator 6 is input to an integrator 10 constituting a time constant change control circuit, further converted into an angle signal, and this angle signal is input to the absolute value circuit 9. This absolute value circuit 9 outputs an absolute value signal of a predetermined level proportional to the value of the input angle signal.

The time constant change control circuit of this example compares this absolute value signal with the signal from the triangular wave oscillator 8 using the comparator 7, thereby adjusting the duty ratio according to the magnitude of the absolute value signal from the absolute value circuit 9. The determined on/off pulse signal is output as the output signal of the comparator, and this is given to the analog switch 20 of the integrator 6 as an operating signal for turning on/off the switch through the signal line 22, turning the analog switch 20 on/off. Control off.

In the configuration of the time constant change control circuit of this example configured as described above, the output of the converter tough is explained in relation to the output from the absolute value circuit 9 as shown in FIG.

That is, the output waveform of the triangular wave oscillator 8 of this example is shown in FIG.
), the output from the absolute value circuit 9 (signal on the signal line 24) is now between the maximum value H and the minimum value of the output waveform of the triangular wave oscillator 8. Considering the case where it is and the case where it is, the absolute value circuit 9
When the output of is relatively small (■), the output of the converter tough is on in the range where the output of the absolute value circuit 9 exceeds the triangular wave, and on the contrary, it is off in the range where it is below the triangular wave, and the waveform is as shown in Figure 6 ( On the other hand, when the output of the absolute value circuit 9 is relatively large (2), the output of the comparator 7 becomes as shown in FIG. 6(C). In other words, the duty ratio of the pulse signal output from the converter tough is determined by the level at which the output signal of the absolute value circuit 9 cuts the predetermined triangular wave output from the triangular wave generator 8. , this duty ratio varies from 0% to 100% between the maximum value H and the minimum value of the triangular wave output depending on the magnitude of the output signal of the absolute value circuit (therefore, the magnitude of the output signal from the integrator 6). Continuously changing.

The analog switch 20 of the integrator 6 is turned on/off by inputting such an on/off pulse signal with a changed duty ratio.

Next, we will explain the operation of the integrator 6 when the output signal from the absolute value circuit 9 is below L and when it is above H. In the former case (when the output signal is below L), 6th
As can be seen from the figure, the output of the converter tough is always off, so the analog switch 20 continues to be off. At this time, the characteristics of the amplification factor A with respect to the frequency of the integrator 6 are as shown in (■) in Fig. 4, and the cutoff frequency f1 at this time is given as follows, and the integral operation is performed more than the cutoff frequency f1. This is done for input signals in high frequency bands.

On the other hand, in the latter case (when the output signal is H or lower), as can also be seen from FIG. 6, the output of the converter tough is always on, and therefore the analog switch 20 continues to be on. At this time, the characteristic of the integrator 6 against the frequency and the amplification factor is as shown in ■ in Figure 4, and the cutoff frequency fz at this time is different from the case of f1 above, and is given as follows, and the integration operation is performed for an input signal in a frequency band higher than the cutoff frequency f2.

In between these, as shown in FIG. 7, the time constant of the integrator changes substantially continuously according to the ratio given from the relationship between the magnitude of the output of the absolute value circuit 9 and the duty ratio of the pulse signal. do. Some of the intermediate duty ratios (on/off) of the pulse signal are 0:2.
0,1:19,2=18,4:16,10:10,19
:1, 20:0, the cutoff frequency characteristics in each of these cases are shown in Figure 4, as shown in Figure 4.
It can be seen that the value changes substantially continuously between .

As explained above, according to the vibration detection device of the present example having an integrator whose time constant can be changed by controlling the duty ratio of the pulse signal, the integral output may be saturated or the like depending on the output state of the integrator 6. When the time average value of the output becomes large, the output of the integrator lO also becomes large,
A pulse signal with a duty ratio selected to a predetermined value based on the characteristics of the absolute value circuit 9 and the converter tough is input to the integrator 6 as an operation signal for turning on/off the analog switch 20. The time constant of is small, so the cut-off frequency becomes large, and in a normal shooting state with a 4-point target, the integrator 6 changes from an abnormal state where the time average value of its output is large to 0.
There is a tendency to quickly recover to a normal state close to that of normal. Along with this, as the output value of the absolute value circuit 9 connected to the integrator 1o becomes smaller, the characteristics of the integrator gradually shift from the ■ side to the ■ side in Fig. 5, resulting in a smooth transition to the normal state. can do.

Control for varying the output characteristics of such an integrator is performed by controlling the integrator 20 depending on the output value from the absolute value circuit.
Since this method is performed by changing the duty ratio of the pulse signal that determines the intermittent ratio of the , the circuit elements also have excellent stability over time.

It goes without saying that the present invention is not limited to the above embodiments. For example, a circuit that outputs a pulse signal for intermittent on/off operation of an analog switch of an integrator is, of course, not limited to the above-mentioned triangular wave oscillator, and the waveform of this oscillator may be different. This makes it possible to provide various ways of changing the time constant.

FIG. 8(a) shows an example of an oscillator having an oscillation output with another waveform, and this output waveform is used as an intermittent operation signal for an analog switch depending on the output of the absolute value circuit. The pulse duty ratio in this case is shown in Figure 8 (
b) The cutoff frequency of the integrator will also show a change similar to this.

(Effects of the Invention) As described above, according to the vibration detection device according to the present invention, the characteristics of the CR resonant circuit that determines the cutoff frequency of the integrator can be changed depending on the pulse signal whose duty ratio can be changed. A resistor in parallel with the CR resonance circuit is operated intermittently to vary the characteristics, thereby making it possible to substantially continuously vary the cutoff frequency of the integrator, thereby preventing the integrator from falling into a saturated state for a long time. This has the advantage that vibration detection can always be performed quickly and accurately. Therefore, it is possible to suitably configure a camera image blur prevention device due to camera shake.

Further, the vibration detection device of the present invention has the advantage that it can be easily integrated into an IC, can be manufactured at a low cost, and is less affected by aging than a similar device using a CdS photocoupler.

[Brief explanation of the drawing]

Figure 1 is a diagram showing an example of the configuration of an image blur prevention device for a camera to which the vibration detection device according to the present invention is applied, Figure 2 is a schematic diagram of the configuration of an integrator, and Figure 3 is a diagram showing an example of the configuration of an integrator. Figure 4 is a diagram to explain the amplification characteristics of the correction signal input to the actuator of the correction optical system, Figure 4 is a diagram to explain the characteristics of the cutoff frequency of the integrator in Figure 2, and Figure 5 is the pulse A diagram for explaining the relationship between the degree of width modulation and the cutoff frequency characteristics of the integrator, Figure 6 (a) is a diagram showing the relationship of the human input signal to the comparator, Figure 6 (b), (
c) is a diagram showing the waveform of a pulse width modulated pulse signal, Figure 5 is a diagram showing the relationship between the absolute value circuit and the duty ratio of the pulse signal, and Figure 8 (a) is the output waveform of another oscillator. FIG. 8(b) is a diagram showing the relationship between the absolute value circuit and the duty ratio of the pulse signal, and FIG. 9 is a diagram showing an outline of the configuration of an integrator of a comparative example. 2: Correction optical system 3: Actuator 3a: Possible! II magnet 3b: Coil 3C: Position sensor 4: Acceleration sensor
5: Bypass filter 6: Integrator 7: Comparator 8: Triangular wave oscillator 9: Absolute value circuit 10: Integrator 11: Position filter 12
: Differential amplifier 13 : Differentiator 14 : Differential amplifier is, 16, 17 : Resistor 18
: Capacitor 19: Ober amplifier 20: Analog switch 22: Signal line 25: CdS photocoupler Fig. 1 Fig. 5 Fig. 1o9f Fig. 6 Fig. 7 Fig. 1 Co) Output Te? of Pashi-97? Tee ratio □ Figure 8

Claims (1)

[Claims] In a vibration detection device equipped with an integrator that integrates and outputs a low-frequency vibration input signal, a frequency band in which the integrator can integrate is provided, the time constant of which is variable according to the ratio of the intermittence of the switching means that is intermittently operated. a lower limit frequency change circuit,
switch driving means for outputting a pulse signal with a higher frequency than the frequency to be integrated by the integrator as an intermittent operation signal of the switch means; and a duty ratio of the pulse signal outputted by the switch driving means as an output signal from the integrator. 1. A vibration detection device comprising: pulse width modulation means for varying the pulse width depending on the value.