JP2003234948A - Shaking image preventing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a shaking image preventing device which is possible to easily change the operation characteristics, by realizing an integrating function of signals outputted from a shaking detection sensor with an IIR (Infinite Impulse Response) filter of digital signal processing theory in a shaking image preventing device of an optical correction system. <P>SOLUTION: An angular speed signal outputted from an angular speed sensor 16 is sent to an A/D converter 24 through a high pass filter 18, and input to a CPU 22 after conversion to a digital signal. The CPU 22 functions as the IIR filter which processes integration of a sensor signal, and at the same time functions as an arithmetic means to calculate an access value (correction value) of a correction lens based on an integral result. Various filter characteristics are realized by appropriately setting a parameter corresponding to a filter coefficient (multiplication coefficient) by a program (software). Furthermore, the function of the IIR filter is possible to realize by hardware such as a digital signal processing processor (DSP). <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image shake prevention device, and more particularly to a technique for controlling a correction optical system for optically correcting an image shake caused by vibration applied to a photographing device such as a television camera.

[0002]

2. Description of the Related Art A movable lens (correction lens) for image shake correction is arranged in a photographing optical system of a TV camera, and the correction lens is moved by an actuator so as to cancel the image shake due to vibration applied to the camera to suppress the image shake. A device is known (Japanese Patent No. 3186219). In such an optical correction type image blur prevention device, vibration is detected by an angular velocity sensor or the like provided in the camera, and the sensor output signal is integrated and used for controlling the correction lens.

[0003]

As disclosed in the above publication, conventionally, the function of integrating an angular velocity signal from an angular velocity sensor has been realized by an analog electric circuit composed of an operational amplifier, a resistor and a capacitor. The integration characteristics (cutoff frequency, gain, phase characteristics, etc.) are determined by the frequency components of the target vibration, and various "fluctuations" occur.
In order to respond to, it is required to dynamically change the circuit constant,
Corresponding quantities of resistors, capacitors and analog switches are required. In addition, recently, in addition to the function of eliminating vibration, unnatural operation countermeasures at the time of pan / tilt operation are required, and it is desired to realize more various circuit constants.
More circuit components are needed.

The present invention has been made in view of such circumstances, and realizes various integral characteristics with a simple structure.
It is an object of the present invention to provide an image blur prevention device whose operation characteristics can be easily changed.

[0005]

In order to achieve the above-mentioned object, an image shake preventing apparatus according to the present invention comprises a vibration detecting means for detecting a vibration applied to a photographing device, and an image detecting device arranged on an optical path of the photographing device. A correction optical member that corrects an image shake caused by vibration, a driving unit that displaces the correction optical member, a high-pass filter that passes a high-frequency component of a detection signal output from the vibration detection unit, and a high-pass filter that passed the high-pass filter. An A / D converter that converts a detection signal into a digital signal, an IIR filter that realizes a function of integrating a signal output from the A / D converter, and a signal obtained by performing an integration process by the IIR filter Calculation processing means for obtaining a correction amount for displacing the correction optical member so as to suppress the image shake, and controlling the driving means according to the obtained correction amount. It is characterized a control means, further comprising a that.

A lens, a prism or the like can be used as the correction optical member. According to the present invention, when vibration is applied to the image capturing apparatus, the vibration detecting means detects this and the electric signal (detection signal) corresponding to the vibration is output from the vibration detecting means. The offset signal (DC component) and the low frequency component of the detection signal are cut off via the high pass filter, and only the high frequency component of a predetermined frequency or higher is output. The signal that has passed through the high-pass filter is converted into a digital signal by the A / D converter and then input to the IIR filter (infinite impulse response filter).

The IIR filter is a digital filter which can realize a desired filter characteristic by appropriately setting a parameter corresponding to a filter coefficient, and is used as a means for performing an integration process in the present invention. The signal output from the IIR filter is sent to the arithmetic processing means, and the arithmetic processing means obtains a correction amount for displacing the correction optical member in a direction of canceling the image shake due to the vibration. The image shake is suppressed by controlling the driving unit according to the correction amount thus obtained and displacing the correction optical member from the reference position in optical design. The reference position of the correction optical member corresponds to the center position which is the origin of correction, and is, for example, the position where the optical axis of the photographing optical system and the optical axis of the correction lens coincide.

According to the present invention, since the IIR filter based on the theory of digital signal processing is used to realize the integration function of the detection signal from the vibration detecting means, various integration characteristics can be easily realized by changing the parameters. it can. Further, in the conventional configuration using the analog electric circuit, the accuracy variation due to the circuit components is a problem, but since the IIR filter of the present invention is a process by numerical operation, there is a problem that the accuracy variation due to the circuit components. There is an advantage that it does not occur.

The arithmetic processing means and control means in the present invention can be realized by a central processing unit (CPU), and the IIR filter can be realized by a program (software) executed by the CPU. Of course II
The function of the R filter is the digital signal processor (DS
It may be realized by hardware such as P). If a dedicated DSP is used, it becomes possible to perform processing at a higher speed than arithmetic processing by software.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of an image shake preventing apparatus according to the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a block diagram of an image shake prevention apparatus according to an embodiment of the present invention. The image shake preventing device 10 is mounted on, for example, a lens device for a television camera, a movie camera, a still camera, or the like, or is configured as a detachable anti-vibration adapter. The correction lens 12 shown in the figure moves up and down (vertical direction) and left and right (horizontal direction) within a plane perpendicular to the optical axis of the photographing optical system in a photographing device or the like in which the image shake prevention device 10 is mounted. Arranged freely.

When vibration occurs in the photographing device (photographing optical system), the motor 14 is controlled according to the vibration, and the power of the motor 14 causes the correction lens 12 to prevent the image shake (vibration is canceled). Position). In addition,
Although the correction lens 12 is driven in the up-down direction and the left-right direction, it is driven by the same drive mechanism in any direction. Therefore, in the present embodiment, in order to simplify the description, image shake in the up-down direction is prevented. The configuration will be described.

The angular velocity sensor 16 is used as a vibration detecting means for detecting the vibration of the photographing device. As the angular velocity sensor 16, for example, a gyro sensor is applied. Further, in place of the angular velocity sensor 16, a known unit such as a velocity sensor or an acceleration sensor may be used. The angular velocity sensor 16 is installed at an appropriate place of the image pickup apparatus (for example, the upper surface of the lens barrel) and outputs an electric signal (voltage signal) according to the detected vibration.

The high-pass filter (HPF) 18 is an angular velocity signal (sensor signal) output from the angular velocity sensor 16.
Is a filter that passes the high frequency component of the sensor output, and blocks the DC component and low frequency component of the sensor output. The high-pass filter 18 is composed of a capacitor C1 and resistors R11 and R12, and its resistance value can be changed by a control switch 20. In this example, the CP that functions as a control unit
The resistance value is changed by switching the state of the control switch 20 by the control signal from the U22, and the characteristics (cutoff frequency, etc.) of the high-pass filter 18 are switched. Specifically, the cutoff frequency is 0.5H
It is possible to switch between two types, z and 10 Hz. Note that the filter characteristic is not limited to the configuration in which the resistance value is changed as in FIG. 1, and the filter characteristic may be switched by switching the capacitance of the capacitor.

The output signal from the angular velocity sensor 16 is sent to the A / D converter 24 through the high pass filter 18,
After being converted into a digital signal, it is input to the CPU 22. The data input to the CPU 22 via the A / D converter 24 is used for drive control of the correction lens 12. The signal line of the path for inputting the output of the A / D converter 24 to the CPU 22 can be connected to the ground (GND) via the control switch 26 as shown in FIG. The connection state of the control switch 26 is switched by a control signal from the CPU 22, and by closing the control switch 26, the input signal (angular velocity signal) to the CPU 22 can be forcibly set to "0".

The output of the angular velocity sensor 16 does not pass through the high-pass filter 18 but is A / D by another route.
It is input to the CPU 22 via the converter 28. CP
The U22 determines the pan / tilt operation and detects the speed of the pan / tilt operation based on the sensor signal acquired via the A / D converter 28. However, in the actual circuit design, a multi-channel A / D converter in which the functions of the A / D converters 24 and 28 are integrated can be used.

The CPU 22 has a ROM 30 and a RAM 32, and performs various arithmetic processes and control processes according to programs stored in the ROM 30. That is, CP
U22 functions as an IIR filter that integrates the sensor signal, and also functions as a calculation unit that calculates the drive amount (correction amount) of the correction lens 12 based on the integration result. When calculating the correction amount, lens information of the photographing optical system (for example, zoom position information and extender magnification information) is also taken into consideration.

The CPU 22 also functions as means for determining the pan / tilt operation and detecting the speed of the pan / tilt operation based on the signal input via the A / D converter 28. The RAM 32 is used as a work area for storing data and the like necessary for the calculation of the CPU 22.

The CPU 22 performs integration processing or the like on the angular velocity signal acquired through the A / D converter 24 to correct the image shake, that is, the position of the correction lens 12, that is, the displacement of the correction lens 12 with respect to the center of shake. Calculate the amount (correction amount to correct the image shake) and set the control signal required for the movement to D
And outputs to the / A converter 34. The control signal converted into the analog signal by the D / A converter 34 is the motor drive circuit 3
Added to 6. The position of the correction lens 12 is a position sensor (for example, position detecting means such as a potentiometer) 38.
The detection signal is sent to the motor drive circuit 36.

The motor drive circuit 36 detects the position of the correction lens 12 by the position sensor 38, and the CPU 2
The motor 14 is driven on the basis of the position command signal given from 2, and the correction lens 12 is moved to the position instructed by the position command signal. As means for adjusting the moving speed of the correction lens 12, speed detecting means (not shown) such as a speed generator may be added.

Next, the operation of the image shake prevention device 10 configured as described above will be described.

FIG. 2 is a flow chart showing a calculation procedure of the CPU 22 for realizing the function of the IIR filter. As is well known, the IIR filter is a digital filter that can realize various filter characteristics by appropriately setting a filter coefficient (multiplication coefficient). In this example,
The second-order IIR filter is realized by software, and the parameters (PA1, PA2, PA3, PB) corresponding to the multiplication coefficient are realized.
By changing (1, PB2) as needed, a desired filter characteristic is instantly realized.

As shown in FIG. 2, when the arithmetic process is started, first, variables R1, R2 and R3 are all set to "0" as an initial setting (step S110). Next, the latest input data is fetched into the variable R1 (step S11
2), calculation is performed according to the calculation formula shown in step S114, the calculation result is fetched into the variable R1, and the data of the variable R1 is updated.

After that, calculation is performed according to the calculation formula shown in step S116, and the obtained result (OUT) is output as output data (step S118). Then the variable R
The data of 3 is replaced with the data of variable R2 (step S120), and the data of the variable R2 is replaced with data of the variable R1 (step S1).
22) and returns to step S112.

By repeating the steps S112 to S122, the latest input data is fetched into the variable R1, the calculation is performed by the calculation formula of step S114, and the data obtained by this calculation is R2 → R3. Are shifted in this order and used in the arithmetic expressions of step S114 and step S115.

By repeating the above calculation, an IIR filter based on the theory of digital signal processing can be realized.
For example, when realizing a low-pass filter with a cutoff frequency fc = 0.5 Hz, PA1 = 0.00216
8, PA2 = 0.002168, PA3 = 0, PB1 =
A coefficient of 0.998891, PB2 = 0 is used.

Conventionally, the function of integrating the angular velocity signal from the angular velocity sensor has been realized by an analog electric circuit composed of an operational amplifier, a resistor and a capacitor, but in this embodiment, the IIR filter is realized by software. . Since only a few floating point constants determine the characteristics of the filter, virtually unlimited characteristics can be provided and the integral characteristics can be changed easily. According to the present embodiment, even with a lens device that has already been shipped, the operating characteristics can be changed by changing the software, so that the trouble of replacing parts is unnecessary.

Further, in the conventional structure using the analog electric circuit, there is a problem that the precision of the circuit parts varies. In particular, it is difficult to manufacture a capacitor with high precision. In this respect, the IIR filter of this example has a merit that it does not cause a problem of accuracy variation due to circuit components because the IIR filter is a processing by numerical calculation.

By the way, the processing equivalent to the flowchart shown in FIG. 2 is performed by a digital signal processor (DSP).
It is also possible to realize by. FIG. 3 shows a processing flowchart of the DSP. It is possible to perform high-speed processing using the registers in the hardware shown in FIG.
The characteristics of the filter are determined by the CPU to the DSP.
Since only the parameters (multiplication coefficients) given by the above are used, virtually infinite characteristics can be provided as in the case of using the software described in FIG. In addition, the DSP shown in FIG.
Even if the lens device has already been shipped,
Since the operation characteristics can be changed by changing the software on the PU side, there is no need to replace parts and the like, and there is an advantage that accuracy does not vary depending on the parts of the circuit. Therefore, the software explained in FIG. 2 is used. The same effect as the case can be obtained.

FIG. 4 is a flow chart showing the flow of operation control of the image shake prevention apparatus 10. When the image shake preventing apparatus 10 is powered on and the image shake preventing function is turned on (step S210), the CPU 22 causes the angular velocity sensor 16 to operate.
The sensor signal from is read (step S212), and it is determined whether or not the pan / tilt operation is intentionally performed on the photographing apparatus based on the acquired signal (step S214). As a method of determining the pan / tilt operation,
For example, the frequency, amplitude, and duration of the sensor signal are detected, and it is determined that the detection result is compared with a predetermined criterion.

If the pan / tilt operation is not detected in step S214, the process proceeds to step S216.
An image shake correction process of moving the correction lens 12 in a direction in which the image shake caused by vibration is canceled is executed. Step S216
After that, the process returns to step S212.

On the other hand, when the pan / tilt operation is detected in step S214, the process proceeds to step S220, and the image shake prevention function is stopped. Subsequently, processing for detecting the speed of the pan / tilt operation is performed (step S2
22), depending on the detected pan / tilt operation speed,
The speed at which the correction lens 12 is returned to the center of the photographing optical axis is determined (step S224). When the pan / tilt operation speed is fast (during quick operation), the speed at which the correction lens is returned to the optical axis is also increased, and when the pan / tilt operation is slow (during slow operation), the correction lens 12 is returned to the optical axis. Set a slow speed. When determining the return speed, a look-up table prepared in advance may be used, or a predetermined arithmetic expression may be used for the calculation.

Thereafter, the process proceeds to step S226, and the correction lens 1 is set at the speed set in step S224.
2 is moved to the optical axis (step S22)
6). If the speed at which the correction lens 12 is returned to the optical axis is constant, the movement due to the return movement of the correction lens 12 becomes unnatural during slow motion, and the correction lens 12 still emits light at the end of the operation during quick operation. There is a problem that a situation where the axis is not completely returned to the axis causes unnatural movement even after the pan / tilt operation is stopped. In order to eliminate such a problem, in the present embodiment, the returning speed of the correction lens 12 to the optical axis is controlled according to the pan / tilt operation speed.

In step S226, the correction lens 12
After performing the process of returning to the optical axis, it is determined in step S230 whether the pan / tilt operation is stopped, and after the pan / tilt operation is stopped, the image shake prevention function is restarted (step S240). After step S240, the process returns to step S212, and the above-described processing is repeated.

According to the control method shown in FIG. 4, when the pan / tilt operation is detected, the image shake prevention function is stopped, so that unnatural movement during the pan / tilt operation can be prevented. it can. Further, according to this example, the correction lens 12 is returned to the optical axis at a speed determined by the pan / tilt operation speed to prepare for the restart of the image shake prevention function after the stop. There is an advantage that unnatural movement does not occur at the start of the image shake prevention function during operation and after the operation is stopped.

When the correction lens 12 is moved to the optical axis in preparation for the restart of the image shake prevention function after the stop of the pan / tilt operation, the position servo is executed in order to perform the processing of moving the correction lens 12 at an appropriate speed. It must also be used to set the speed control.

However, since such processing is complicated, it is preferable to use the integration processing to obtain the same result without using the position and velocity servo, as described below. FIG. 5 shows the control flow. As shown in the figure, when the image shake prevention device 10 is powered on and the image shake prevention function is turned on (step S310), the CPU
22 reads the sensor signal from the angular velocity sensor 16 (step S312), and based on the acquired signal, determines whether or not the pan / tilt operation has been intentionally performed on the photographing apparatus (step S314).

If no pan / tilt operation is detected in step S314, the flow advances to step S316.
An image shake correction process of moving the correction lens 12 in a direction in which the image shake caused by vibration is canceled is executed. In this case,
The parameters of the IIR filter that performs the integration process are set to predetermined values. After step S316, the process returns to step S312.

On the other hand, when the pan / tilt operation is detected in step S314, the process proceeds to step S320 to stop the image shake prevention function. Subsequently, processing for forcibly setting the input data of the integration processing to "0" is performed (step S322). Specifically, the control switch 26 described in FIG. 1 is closed, and the input signal to the CPU 22 is set to 0v.
As a result, the correction lens 12 is controlled to return to the optical axis. Also, to set the speed during this return operation,
In step S324 of FIG. 5, the parameters of the IIR filter are changed. Step S322 and step S3
By the processing of 24, the correction lens 12 returns to the optical axis at an appropriate speed.

Then, in step S330, bread /
It is determined whether or not the tilt operation has stopped. When the pan / tilt operation is stopped, the parameters of the IIR filter are returned to the original values (step S332), and the input data of the integration process is returned to the original sensor signal (step S33).
4). That is, the control switch 26 described in FIG. 1 is opened and the sensor signal from the angular velocity sensor 16 is set to CP.
Input to U22.

In this way, after returning to the original state, the image shake prevention function is restarted (step S34).
0). After step S340, the process returns to step S312 and the above-described processing is repeated.

As described above, according to the control method shown in FIG. 5, during the pan / tilt operation, the input data of the integration process is forcibly set to "0" and the integration process is performed by the IIR.
Since the parameter of the filter is changed to obtain the predetermined speed at which the correction lens 12 moves to the optical axis, the correction lens 12 can be returned to the optical axis without using the position / speed servo.

As described above, the vibration applied to the photographing device is detected by the angular velocity sensor 16, and the sensor signal is integrated and used for controlling the correction lens 12. If the signal output from the angular velocity sensor 16 (angular velocity signal) has an offset voltage, the integrated output diverges during integration processing,
It is widely known that there is actually a problem that the maximum signal is positive or negative. Therefore, a high-pass filter that removes the offset is arranged before the integration process to prevent the above divergence phenomenon. The cut-off frequency (fc) of this high-pass filter must be below the frequency range in which the image stabilization function (image shake correction function) operates, and is therefore usually set below 1 Hz (for example, 0.5 Hz).

However, when the pan / tilt operation is performed, an undesired signal is output (the signal trails) for several seconds due to the influence of the high-pass filter after the pan / tilt operation is stopped. There is a problem that the image stabilization function does not work effectively. For reference, FIG. 8 shows an example of the above-mentioned tail-drawing phenomenon. FIG. 8 is a waveform diagram of the angular velocity signal that has passed through the high pass filter, and is a signal waveform measured at the position corresponding to point A in FIG.

In order to solve such a problem, in the present embodiment, when the pan / tilt operation is detected, the cutoff frequency of the high pass filter is changed to a frequency higher than the corresponding frequency of the pan / tilt operation, and the pan / tilt operation is performed. After the tilt operation is stopped, the control to return to the original cutoff frequency is performed to prevent the phenomenon of the tail pulling. The cutoff frequency is changed by switching the state of the control switch 20, as described with reference to FIG.

FIG. 6 shows the control flow. When the image blur prevention device 10 is powered on and the image blur prevention function is turned on (step S410), the CPU 22 sets the cutoff frequency of the high-pass filter 18 to a predetermined frequency (for example, 0.5 Hz) at which the image blur correction function operates. The control signal is output to the control switch 20 so as to be set to () (step S411). After that, the CPU 22 sets the angular velocity sensor 1
The sensor signal from 6 is read (step S412),
The pan / tilt operation is detected based on the acquired signal (step S414).

If the pan / tilt operation is not detected in step S414, the flow advances to step S416.
An image shake correction process of moving the correction lens 12 in a direction in which the image shake caused by vibration is canceled is executed. Step S416
After that, the process returns to step S412.

On the other hand, when the pan / tilt operation is detected in step S414, the process proceeds to step S420 to stop the image shake prevention function. Subsequently, processing for switching the cutoff frequency of the high-pass filter 18 to a frequency higher than the frequency corresponding to the pan / tilt operation is performed (step S422). The cutoff frequency set at this time is higher than a predetermined frequency at which the image shake correction function operates.

Then, in step S430, the bread /
It is determined whether or not the tilt operation has stopped. When the pan / tilt operation is stopped, the cutoff frequency of the high pass filter 18 is restored (step S432),
The image shake prevention function is restarted (step S44).
0). After step S440, the process returns to step S412 to repeat the above process.

FIG. 7 shows a waveform diagram when the control method shown in FIG. 6 is applied. FIG. 7 is a waveform diagram of the angular velocity signal that has passed through the high pass filter 18, which is a signal waveform measured at the position corresponding to the point A in FIG. As is clear from a comparison between the waveforms in FIG. 7 and the waveforms in FIG. 8, in FIG. 7, the phenomenon of tailing after the pan / tilt operation is stopped does not occur. As shown in FIG. 7, a discontinuous signal is output when the cutoff frequency is switched, but the image shake prevention function is stopped before and after the cutoff frequency switching timing. It doesn't matter. As a result, the image shake prevention function is immediately activated for the vibration after the pan / tilt operation is stopped.

In the above embodiment, an example in which a correction lens is used as the correction optical member has been described, but the applicable range of the present invention is not limited to this, and a mode in which the variable apex angle prism is drive-controlled is also possible.

[0052]

As described above, according to the image shake preventing apparatus of the present invention, the integration function of the detection signal output from the vibration detecting means is realized by using the IIR filter based on the digital signal processing theory. Therefore, various integral characteristics can be easily realized by changing the parameters. This makes it possible to equip with virtually unlimited characteristics and save time and effort such as replacement of parts.

Further, since the IIR filter of the present invention is a processing by numerical calculation, there is no problem of accuracy variation due to circuit parts.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an image shake prevention apparatus according to an embodiment of the present invention.

FIG. 2 is a CPU for realizing the function of the IIR filter.
Flowchart showing the calculation procedure of

FIG. 3 is a block diagram showing the configuration of a digital signal processor that realizes the function of an IIR filter.

FIG. 4 is a flowchart showing a control procedure of the image shake prevention apparatus according to the present embodiment.

FIG. 5 is a flowchart showing a control procedure of the image shake prevention apparatus according to the present embodiment.

FIG. 6 is a flowchart showing a control procedure of the image shake prevention apparatus according to the present embodiment.

FIG. 7 is a diagram showing an output waveform example of a high-pass filter when the control procedure shown in FIG. 6 is performed.

FIG. 8 is a waveform diagram showing a phenomenon in which an unnecessary signal is output (the signal is trailing) for several seconds due to the influence of the high-pass filter after the pan / tilt operation is stopped.

[Explanation of symbols]

10 ... Image shake prevention device, 12 ... Correction lens, 14 ... Motor, 16 ... Angular velocity sensor, 18 ... High pass filter, 2
2 ... CPU, 24, 28 ... A / D converter, 34 ... D / A
Converter, 36 ... Motor drive circuit

Claims (3)

[Claims] 1. A vibration detecting means for detecting a vibration applied to an image pickup apparatus, a correction optical member arranged on an optical path of the image pickup apparatus for correcting an image shake caused by the vibration, and a drive for displacing the correction optical member. Means, a high-pass filter that passes a high-frequency component of the detection signal output from the vibration detection means, an A / D converter that converts the detection signal that has passed the high-pass filter into a digital signal, and the A / D converter An IIR filter that realizes a function of integrating the signal output from the image pickup device, and a correction amount that displaces the correction optical member so as to suppress the image shake based on the signal obtained by the integration process of the IIR filter. An image shake prevention apparatus comprising: an arithmetic processing unit to be obtained; and a control unit to control the driving unit according to the obtained correction amount. 2. A central processing unit (CPU) that functions as the arithmetic processing means and the control means,
The image shake prevention device according to claim 1, wherein the IR filter is realized by a program executed by the CPU. 3. The image blur prevention device according to claim 1, further comprising a digital signal processor functioning as the IIR filter.