JP4305723B2 - Image blur correction device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image shake correction apparatus, and more particularly to an image shake correction apparatus that corrects (prevents) image shake of a camera due to vibration.
[0002]
[Prior art]
For example, as an image blur correction device for a television camera, when an anti-vibration lens is arranged in a photographing optical system so as to be movable within a plane perpendicular to the optical axis, and vibration is applied to the camera (camera photographing optical system), the vibration is reduced. There is known a lens in which an image stabilizing lens is corrected by driving an anti-vibration lens with an actuator in a direction to cancel. In such an image shake correction apparatus, vibration applied to the camera is detected by a shake detection sensor (such as an angular velocity sensor or an acceleration sensor), and the image shake is corrected based on the shake signal output from the shake detection sensor. The amount of displacement of the anti-vibration lens is required (for example, see Patent Document 1).
[0003]
By the way, in the shake signal output from the shake detection sensor, in addition to the signal caused by the vibration to be corrected such as camera shake, the signal caused by the intentional camera operation of the photographer such as the pan operation or the tilt operation. Etc. are also included. Accordingly, when the image stabilizing lens is driven simply based on the shake signal, image shake correction is performed even during pan / tilt operation. However, if image blur correction is performed at the time of pan / tilt operation, image blur (shake back) occurs after the pan / tilt operation is completed, which causes an uncomfortable feeling in camera operation or video.
[0004]
Therefore, conventionally, it is automatically determined whether or not the shake signal output from the shake detection sensor is due to pan / tilt operation. If it is determined to be due to pan / tilt operation, image blur correction is stopped and image stabilization is stopped. There has been proposed shakeback correction in which the lens is returned to the center of the movable range (a reference position where the amount of displacement is 0) and stopped (see, for example, Patent Document 2).
[0005]
[Patent Document 1]
Japanese Patent Laid-Open No. 2002-229089
[Patent Document 2]
Japanese Patent Laid-Open No. 5-142624 [0007]
[Problems to be solved by the invention]
However, when shake back correction is performed as described above, the image blur correction performance in a stationary state in which no pan / tilt operation is performed is deteriorated as compared with the case where shake correction is not performed. was there.
[0008]
The present invention has been made in view of such circumstances, and an object thereof is to provide an image blur correction apparatus that can exhibit appropriate correction performance in consideration of the frequency of pan / tilt operations.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, the invention according to claim 1 is an image blur detection unit that detects an image blur of an image formed by an optical system and outputs a blur signal indicating the image blur, and the image Whether or not the pan / tilt operation of the optical system is performed at predetermined time intervals in an image blur correction device including an image blur correction unit that corrects an image blur based on a shake signal output by the shake detection unit Pan / tilt operation frequency acquisition means for acquiring the number of times that the pan / tilt operation has been performed during a predetermined time, and the number of times acquired by the pan / tilt operation frequency acquisition means. And a target frequency band changing unit that changes a frequency band that is a target of image blur correction with respect to a shake signal.
[0010]
According to a second aspect of the present invention, in the first aspect of the invention, the pan / tilt operation frequency acquisition means has a shake signal value output by the image shake detection means exceeding a predetermined value. In this case, it is determined that a pan / tilt operation is being performed.
[0011]
The invention according to claim 3 is the invention according to claim 1 or claim 2, wherein the target frequency band changing means has the number of times obtained by the pan / tilt operation frequency obtaining means being greater than a predetermined value. In some cases, the cut-off frequency on the lower side of the frequency band targeted for image blur correction is increased as compared with a case where the frequency is smaller than a predetermined value.
[0012]
According to the present invention, the number of pan / tilt operations is detected, and the frequency band of a shake signal to be subjected to image blur correction is changed according to the number of pan / tilt operations. Image blur correction performance is exhibited.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
A preferred embodiment of an image blur correction apparatus according to the present invention will be described below in detail with reference to the accompanying drawings.
[0014]
FIG. 1 is a configuration diagram showing an embodiment of an image blur correction apparatus according to the present invention. The image blur correction device is mounted, for example, on a television camera lens device (photographing lens), a movie camera, a still camera, or the like. The image stabilization lens 10 shown in FIG. In the photographing optical system of the camera, the camera is arranged so as to be movable up and down (vertical direction) and left and right (horizontal direction) in a plane perpendicular to the optical axis. The anti-vibration lens 10 is driven up and down or left and right by a motor 12, and when the camera (shooting optical system) vibrates, the motor 12 prevents image blur. It moves to the position (position to cancel the vibration). Note that when the anti-vibration lens 10 is moved vertically and horizontally, the photographing range of the photographing optical system is displaced vertically and horizontally. In addition, since the anti-vibration lens 10 is similarly driven based on vibration generated in each direction in both the vertical direction and the horizontal direction, in the present embodiment, an image in one direction (hereinafter, the horizontal direction) is displayed. Only the configuration for performing shake correction will be described, and the configuration is the same for other directions.
[0015]
An angular velocity sensor 14 shown in the figure is a gyro sensor, for example, and is used as a shake detection sensor for detecting camera vibration. The angular velocity sensor 14 is installed, for example, on the upper surface of the lens barrel, detects the angular velocity of vibration in the left-right direction of the lens barrel, and outputs an electric signal having a voltage corresponding to the detected angular velocity. A signal output from the angular velocity sensor 14 is hereinafter referred to as an angular velocity signal.
[0016]
The angular velocity signal output from the angular velocity sensor 14 is branched into two lines, and one of them is converted into a digital signal by the A / D converter 16 after low frequency noise is removed by the high pass filter 15. And it is given to CPU24. On the other hand, the angular velocity signal output from the angular velocity sensor 14 is directly converted into a digital signal by the A / D converter 18 and supplied to the CPU 24.
[0017]
In addition, the photographic lens in the present embodiment can change the zoom magnification (focal length), and a detection signal of a voltage corresponding to the set position (zoom position) is output from the zoom position detector 20, and A / After being converted into a digital signal by the D converter 22, it is given to the CPU 24.
[0018]
The processing contents of the CPU 24 will be described later. From the CPU 24, a position command signal indicating the displacement of the image stabilizing lens 10 as a target, that is, a displacement amount with respect to the reference position of the image stabilizing lens 10 is output to the D / A converter 26. It has come to be. The position command signal output to the D / A converter 26 is input to the adder 30 after being converted into an analog voltage signal. The reference position of the anti-vibration lens 10 is, for example, the center of the movable range (center of shake), and the signal value indicating the position at that time is zero. However, the reference position may not be the center of deflection.
[0019]
The adder 30 is supplied with a voltage signal from a potentiometer 28 that detects the rotational position of the motor 12 as a position signal indicating the current position of the image stabilizing lens 10, and receives a position command signal from the CPU 24 and a position from the potentiometer 28. A voltage signal indicating a difference from the signal is generated. The voltage signal is supplied to an amplifier (servo amplifier) 32.
[0020]
The amplifier 32 amplifies the voltage signal supplied from the adder 30 with a predetermined gain and applies the amplified signal to the motor 12. As a result, the motor 12 is driven so that the voltage signal supplied from the adder 30 becomes zero, and the image stabilizing lens 10 moves to the position commanded by the position command signal from the CPU 24.
[0021]
Next, processing of the CPU 24 will be described. The block of the CPU 24 in FIG. 1 shows functional blocks corresponding to each process performed by the CPU 24, and the process of the CPU 24 will be described as the process of each functional block.
[0022]
In the CPU 24, only the low frequency component is extracted from the angular velocity signal given from the A / D converter 16 by the low pass filter 34. This process corresponds to the process of integrating the angular velocity signal.
[0023]
The low-pass filter 34 can change filter characteristics (frequency characteristics) by changing parameters, and the filter characteristics can be changed by characteristic control of a pan / tilt detector 38 described later. For example, the cut-off frequency fc of the low-pass filter 34 is switched between about 1 Hz and about 3 Hz. Hereinafter, it is assumed that the cut-off frequency fc of the low-pass filter 34 is switched between 1 Hz and 3 Hz.
[0024]
Here, the frequency characteristics of the low-pass filter 34 and the angular velocity sensor 14 will be described. When the cut-off frequency fc of the low-pass filter 34 is 1 Hz and 3 Hz, the frequency characteristic of the low-pass filter 34 is represented by a frequency response (gain characteristic) as shown in FIG. Note that the gain characteristics in the figure show the relationship between the frequency of the sine wave input signal having a constant amplitude and the amplitude of the sine wave output signal.
[0025]
On the other hand, the frequency characteristic of the angular velocity sensor 14 is represented by a frequency response (gain characteristic) as shown in FIG. Note that the gain characteristics in the figure show the relationship between the frequency of a sine wave input signal (angular velocity changing sinusoidally) having a constant amplitude and the amplitude of a sine wave output signal (angular velocity signal changing sinusoidally).
[0026]
Therefore, the frequency characteristic considering both the low-pass filter 34 and the angular velocity sensor 14, that is, the characteristic (integration characteristic) relating to the integration of the angular velocity of the vibration generated in the camera is the sum of the gain characteristics shown in FIGS. The gain characteristics as shown in FIG. 4 are obtained when the cutoff frequency of the low-pass filter 34 is 1 Hz and 3 Hz.
According to this, when the cut-off frequency of the low-pass filter 34 is 1 Hz, the frequency characteristics of a high-pass filter with 1 Hz as the cut-off frequency are shown in the entire frequency range of the vibration subject to image blur correction. When the cut-off frequency of the filter 34 is 3 Hz, frequency characteristics like a high-pass filter having a cut-off frequency of 3 Hz are shown. Thereby, when the cut-off frequency of the low-pass filter 34 is 1 Hz, image blur correction is executed for vibration having a frequency higher than 1 Hz. When the cut-off frequency of the low-pass filter 34 is 3 Hz, the image blur correction is performed from 3 Hz. Image blur correction is performed for vibrations having a large frequency.
[0027]
As described above, the signal that has passed through the low-pass filter 34 is amplified by the gain unit 36 with a predetermined gain, and the signal is output to the D / A converter 26 as the position command signal. The gain in the gain unit 36 is set to a value corresponding to the zoom position obtained from the zoom position detector 20.
[0028]
The position of the vibration-proof lens 10 for correcting (preventing) image shake with respect to vibration applied to the camera based on the angular velocity signal given from the A / D converter 16 by the processing of the CPU 24 as described above. That is, a position command signal indicating the amount of displacement with respect to the shake center of the image stabilizing lens 10 is obtained and output to the D / A converter 26.
[0029]
On the other hand, the angular velocity signal given from the A / D converter 18 is read by the pan / tilt detector 38. The pan / tilt detector 38 that has read the angular velocity signal detects the frequency of the pan / tilt operation based on the angular velocity signal.
[0030]
For example, as shown in FIG. 5, when the value of the angular velocity signal obtained from the A / D converter 18 is larger than a predetermined threshold value V _S , the angular velocity signal is due to pan / tilt operation, that is, pan / tilt. It is determined that the operation has been performed. The same applies when the value of the angular velocity signal becomes smaller than the threshold value −V _S. Such a determination is performed at predetermined time intervals while a fixed time elapses, and the number of times it is determined that the pan / tilt operation has been performed is measured.
[0031]
When the number of pan / tilt operations counted as described above is less than a predetermined number, it is determined that the frequency of pan / tilt operations is low, and the cut-off frequency fc of the low-pass filter 34 is set to 1 Hz. As a result, image blur correction is performed for vibrations having a frequency greater than 1 Hz, and optimal image blur correction performance is exhibited when the camera is stationary.
[0032]
On the other hand, when the number of pan / tilt operations is equal to or greater than the predetermined number, it is determined that the frequency of pan / tilt operations is high, and the cut-off frequency fc of the low-pass filter 34 is set to 3 Hz. As a result, image blur correction is performed only for vibrations having a frequency greater than 3 Hz, and image blur correction is not performed for vibrations smaller than 3 Hz that may be caused by pan / tilt operations. For this reason, shake back does not occur when the camera is performing the pan / tilt operation.
[0033]
By controlling the characteristics of the low-pass filter 34 as described above, an optimum integration characteristic is set according to the frequency of the pan / tilt operation, and appropriate image blur correction is performed.
[0034]
Although omitted in the present embodiment, the angular velocity signals in the horizontal direction and the vertical direction are obtained from separate angular velocity sensors, and the horizontal angular velocity signal is used for the panning operation from the horizontal angular velocity signal. Is used to detect the number and frequency of tilt operations. In addition, integration processing by a low-pass filter and the like are separately performed on the angular velocity signals in the horizontal direction and the vertical direction. Therefore, the characteristic (integration characteristic) of the low-pass filter is also changed by the frequency of the pan operation for the angular velocity signal in the horizontal direction, and is changed by the frequency of the tilt operation for the angular velocity signal in the vertical direction. However, in consideration of the overall frequency of the pan operation and the tilt operation, both the horizontal direction and the vertical direction may be set and changed to the same integral characteristic.
[0035]
FIG. 6 is a flowchart showing the processing procedure of the CPU 24 for setting the filter characteristic (integration characteristic) of the low-pass filter 34. First, the CPU 24 clears the timer (step S10). Then, an angular velocity signal is acquired from the angular velocity sensor 14 via the A / D converter 18, and it is determined whether a pan / tilt operation is being performed based on the angular velocity signal (step S12). If the determination is YES, the pan / tilt count value is increased by 1 (step S14). Note that the initial value of the count value of the number of pan / tilt is zero. On the other hand, if NO is determined in step S12, the count value of the number of pan / tilt times is not increased.
[0036]
Subsequently, the CPU 24 determines whether or not the measurement time of the timer indicates that a certain time has elapsed (step S16). When it determines with NO, the process from step S12 is repeated. On the other hand, if YES is determined, it is determined whether or not the pan / tilt count value shown in step S14 is smaller than a predetermined value n (step S18). If it is determined YES, that is, if it is determined that the frequency of the pan / tilt operation is low, the cutoff frequency fc of the low-pass filter 34 is lowered (set to 1 Hz) (step S20). On the other hand, when it is determined NO, that is, when it is determined that the frequency of the pan / tilt operation is high, the cutoff frequency fc of the low-pass filter 34 is increased (set to 3 Hz) (step S22). With the above processing, an appropriate integration characteristic is set according to the frequency of the pan / tilt operation.
[0037]
As described above, in the above-described embodiment, the case where the image blur is prevented by the anti-vibration lens that is displaced in the plane perpendicular to the optical axis of the photographing optical system has been described. However, the present invention is applicable to an image blur correction apparatus using another method. Applicable. For example, the present invention can be applied to an image blur correction apparatus that uses an electronic method that corrects image blur by shifting the range in which a video signal is cut out from an image sensor.
[0038]
In the above embodiment, it is determined whether or not the pan / tilt operation is performed based on whether or not the angular velocity signal exceeds a predetermined value. However, other methods may be used.
[0039]
The present invention can also be applied to image blur correction other than a television camera.
[0040]
【The invention's effect】
As described above, according to the image shake correction apparatus of the present invention, the number of pan / tilt operations is detected, and the frequency band of the shake signal targeted for image shake correction is changed according to the number of times. Thus, an appropriate image blur correction performance is exhibited according to the frequency of the pan / tilt operation.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing an embodiment of an image blur correction apparatus according to the present invention.
FIG. 2 is a diagram illustrating filter characteristics of a low-pass filter.
FIG. 3 is a diagram illustrating frequency characteristics of an angular velocity sensor.
FIG. 4 is a diagram illustrating frequency characteristics in consideration of both a low-pass filter and an angular velocity sensor.
FIG. 5 is a diagram illustrating an example of an angular velocity signal output from an angular velocity sensor.
FIG. 6 is a flowchart illustrating a processing procedure of a CPU for setting a filter characteristic (frequency characteristic) of a low-pass filter.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Anti-vibration lens, 12 ... Motor, 14 ... Angular velocity sensor, 15 ... High pass filter, 16, 18, 22 ... A / D converter, 20 ... Zoom position detector, 24 ... CPU, 26 ... D / A converter 28 ... Potentiometer, 30 ... Adder, 32 ... Amplifier, 34 ... Low-pass filter, 36 ... Gain section, 38 ... Pan / tilt detection section

Claims (3)

An image blur detecting unit that detects an image blur of an image formed by the optical system and outputs a blur signal indicating the image blur, and an image blur is corrected based on the blur signal output by the image blur detecting unit. In an image blur correction apparatus including an image blur correction unit,
The number of pan / tilt operations that determines whether or not the pan / tilt operation of the optical system is performed at a predetermined time interval, and obtains the number of times that the pan / tilt operation is performed during the predetermined time Acquisition means;
Target frequency band changing means for changing a frequency band to be subjected to image blur correction with respect to a shake signal based on the number of times acquired by the pan / tilt operation frequency acquiring means;
An image blur correction apparatus comprising: The pan / tilt operation frequency acquisition unit determines that a pan / tilt operation is being performed when a value of a shake signal output by the image shake detection unit exceeds a predetermined value. Item 1. The image blur correction device according to Item 1. The target frequency band changing unit has a lower frequency band to be subjected to the image blur correction when the number of times acquired by the pan / tilt operation frequency acquisition unit is larger than a predetermined value compared to a case where the number is less than the predetermined value. 3. The image blur correction apparatus according to claim 1, wherein a cutoff frequency on the band side is increased.

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