JPH0411470A - Image pickup device - Google Patents

Abstract

PURPOSE:To attain stable pickup by providing a means detecting the vibration of a camera, means correcting the vibration and a means applying drive control to the correction means so as to form a closed loop frequency characteristic to be a notch filter type. CONSTITUTION:A movement detector 103 detects the movement of a picture of a television camera 102 to drive a variable apex angle prism 101 via a control unit 106 and an actuator 107. The tilt of the optical axis of the prism 101 is controlled by packing a silicon group liquid between two parallel galas plates and varying the angle between the parallel glass plates thereby correcting the movement of the picture due to a blur of a camera. Taking the vibration frequency due to a hand blurring given to a camera concentrated in a range of 0.1-3Hz into account in general, the center frequency of a BPF 104 in the unit 106 is selected to be 0.5-2.0Hz, a high frequency cut-off frequency to be 3Hz or over and a low cut-off frequency to be 0.5Hz. Thus, an output picture stable at all times against the blurring of the camera is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an imaging optical device having an image stabilizing function and a subject tracking function for use in television cameras, electronic still cameras, industrial image measuring instruments, and the like.

(Prior art) In recent years, the development of video equipment including the above-mentioned television cameras, electronic still cameras, industrial image measurement equipment, etc. has been remarkable, and efforts have been made to increase multi-function and high performance. Camera shake is a very serious problem when using video equipment. Camera shake not only degrades the quality of the image, but also causes many problems, such as significantly lowering resolution and causing control systems such as automatic focusing devices to malfunction, so camera shake can be corrected by taking pictures. This is an extremely important function.

Methods for correcting camera shake include a method in which camera vibration is physically detected using an external sensor such as an angular velocity sensor, and a method in which the movement of the image corresponding to camera shake is detected from the image signal and the optical system is corrected. , there are various things,
Since the latter method can detect the photographing state from the image signal and does not require a special sensor, it is considered to be a method that will be widely used in the future.

An example of an optical imaging device that detects camera shake from an image signal and optically corrects the camera shake based on the signal is, for example, Japanese Patent Application Laid-Open No. 61-269572, ``Imaging Optical Apparatus J.''

A schematic diagram of an example of the configuration of this device is shown in FIG.

In the figure, 101 is a variable apex angle prism, and 102 is a television camera, which serves as image input means that is movable with respect to the camera housing of the "imaging optical device."

103 is a motion detection device, 106 is a controller, 107
is an actuator (eg, motor, voice coil, etc.).

In this imaging optical device, when the entire device vibrates, the incident angle θ of the object changes.

Since the television camera 102 captures the object image as a video, the object position within the screen changes.

Next, the motion detection device outputs the difference in object position between the previous screen and the current screen, and this signal is sent to the control unit 106 to calculate predetermined control information, and the actuator 107 controls the variable apex angle. Since the prism 101 is driven in a direction that compensates for the movement of the image, the monitor output provides a stable image with no vibrations.

In addition, with the vibration detection method using a sensor, "Video camera image stabilization prevention technology j (National Te
Chnical Report vol, 34. No,
6Dec, 1988). In this system, the lens barrel is rotated freely by the camera body and the gimbal structure, and two small gyros attached to this lens barrel detect the angular velocity of the lens barrel and control the relative angle with the camera body. Therefore, the lens barrel always maintains a fixed direction, and stable images without shake can be obtained.

(Problems to be Solved by the Invention) However, the above-described conventional device causes the following problems regarding the control system.

First, let us discuss the first problem.

We evaluate the frequency characteristics of the vibration suppression ratio, which determines how to stabilize the output image against camera shake. Figure 3 shows its frequency characteristics.

In the former conventional example, the characteristic is upward-sloping to the right as shown in 301 in the figure, and in the latter case, as is clear from the contents of the literature, the characteristic is downward-sloping to the right as shown in 302.

In general, camera vibration caused by camera shake or walking has many frequency components due to human breathing and walking (therefore, shake correction requires suppressing the amplitude at this frequency. However, in conventional cases, the vibration at the target frequency is The vibration suppression ratio is small and inefficient compared to other frequencies.

The second problem is that sensor motion detection devices generally have detection errors and nonlinearity, so conventional examples include an integral element or a circuit with a large time constant in the feedback circuit to stabilize the system. However, these detection errors are also integrated, resulting in drift (a phenomenon in which the output fluctuates even when there is no input change).

The third problem is that if there is a step-like vibration and there is no further vibration, the expensive image stabilization means (variable apex prism and lens barrel) will remain deviated from the neutral position and will continue to consume power. That's true.

The fourth problem is that optical image blur correction means has a limit on the correction angle, so when this limit is reached during anti-vibration operation, the previously stable image suddenly shakes, resulting in an unpleasant image. It is.

(Means for Solving the Problems) The present invention has been made for the purpose of solving the above-mentioned problems, and its features include a detection means for detecting vibration of the camera, and a detection means for shifting the image. The imaging apparatus includes a control system comprising a correction means for correcting the vibration by using the detection means, and a control means for driving and controlling the correction means in accordance with the output of the detection means, and has a closed-loop frequency characteristic configured in a Sotchi filter type.

Other features of the present invention include a detection means for detecting vibrations of an imaging device, a correction means for shifting an image to correct the vibrations, and control for driving and controlling the correction means in accordance with an output of the detection means. an imaging device comprising: a closed-loop control system comprising means, wherein the control means sets a frequency characteristic in the closed-loop control system such that the control amount of the correction means differs depending on the frequency of the vibration. It is in.

(Function) As a result, vibration correction can be performed so that the suppression operation has a large effect on the frequency of vibration caused by camera shake, and stable imaging operation can be performed.

(Embodiment) Hereinafter, an embodiment of the imaging apparatus according to the present invention will be described in detail with reference to each drawing.

FIG. 1 is a block diagram showing the configuration when the imaging device according to the present invention is applied to an anti-shake camera.

In the same figure, reference numeral 101 is a variable apex angle prism, for example, a silicone liquid is filled between two parallel glass plates and the periphery is sealed, and the optical axis can be changed by changing the angle between the parallel glass plates. The system controls the tilt of the image and corrects image movement caused by camera shake.

102 is a television camera, 103 is a motion detection device that detects the movement of an image, 106 is a control unit that comprehensively controls the device of the present invention, and 107 is a variable apex angle prism 10.
This is an actuator that drives 1.

Here, the control unit 106 is divided into a bandpass filter 104 and another filter section 105.

Next, the operation of this device will be explained using the concept of control theory.

First, when considering the response of a digital system, we use a system transfer function.

The transfer function in this device is expressed as G (
z), it can be expressed as G (z) = E (z) /U (z). However, IJ (z) is the Z transformation of the sample value of the input signal u (t), and E (z) is the output signal e (t).
This is a two-transformation of the sample value of .

In this device, camera angle information is discretely input to the television camera 102, and this information is input to the object position u (
t), and the on-screen object position e (t) on the monitor and VTR is output. This device is a regulator system that maintains e (t) at O even if u (t) is manually applied.

In addition, the sampling frequency is 60H in the case of the NTSC standard.
z or 30Hz.

Here, the feature of this device is that the transfer function G (z) has frequency characteristics of a notch filter. In order to realize this characteristic, this device includes a BPF 104 in the control unit 106.

The value of the passing frequency of BPF104 and the transfer function G of this device
The relationship (z) will be explained using FIG.

FIG. 4 is a further model of the block diagram of FIG. 1, and each block shows its transfer function.

401 is a sampler which means the television camera 102. 402 is a motion detection device 103. 403 is a calculation unit of the control unit 106, 404 is a zero-order hold (A/D converter 110), and 405 is a variable apex angle prism 1.
01 and actuator 107.

Here, the denominator R(z) of block 403 is separated into two, and R(z) = R, (z) · R, (z).

Here, 1/R+(z) is BPF104, S(z)/
R2(z) becomes the transfer function of the filter circuit 105.

In addition, the sampler 401, the holder 402, and the block 403
are combined into one block, and the transfer function H(z) of the entire anti-shake camera is as follows.

Transfer function 1/R of BPF104, (zl is R+ (z
) l −2γC03(ωCT)Z−′+ Y 2
It may also be derived from an analog filter using Z-2 or bi-dimensional transformation.

Note that γ is a coefficient (γ×1), ωC is a central angular frequency, and T is a sampling interval.

After designing the BPF 104, the poles of the denominator of G(z) are arranged. This stabilizes the system.

Due to the influence of R,(z) of the molecule, the inverse characteristics of BPF 104 (ie, notch filter) are obtained.

Here, it is assumed that the center frequency fe of the BPF 104, the high-frequency cutoff frequency fH1, and the low-frequency cutoff frequency f.

Generally, the vibration frequency of camera shake is 0.1 to 3.
Considering that the frequency is concentrated in Hz, it is desirable that fe = 0.5 to 2.0 Hz fH = 3.0 Hz or more and fL = 0.5 H2 or less.

That is, f is set to make the zero cross frequency as high as possible, fc is set to solve the first problem that the present invention is trying to solve, and fL is set to solve the second problem. Third. This solves the fourth problem.

FIG. 5 shows the image stabilization suppression ratio of the image stabilization television camera designed by the method described above.

As is clear from the figure, the maximum suppression ratio is in the frequency band of 0.5 to 2.0 Hz, where vibrations such as camera shake occur the most.

FIG. 6 shows a block diagram of an anti-vibration television camera in a second embodiment. The difference in configuration from the block diagram in FIG. 1 is that BPFIO4 is 104-1, 104-
2, 104-3, and the configurations and functions of the other blocks are the same. Here, each B P F 104-1, 104-2, 104-3
Let the center frequencies of fc, , fc2 . Let it be fcg.

The purpose of the apparatus of this embodiment is to increase the vibration suppression ratio compared to the configuration shown in FIG. 1 and to obtain a wider frequency band or a plurality of frequency bands.

In order to show this action and effect, each BP-
The frequency characteristics of F are shown.

In the same figure, B P F 104-1, 104-2
, 104-3 center frequency f el+ f c2+ f
c and 3 are different, and the purpose of each is: f e+: Preventing vibrations caused by human breathing: 0.5 to 1
．． 0Hz f C2: Prevent vibrations caused by walking: 1, C) ~ 3.0Hz f C3: Prevent vibrations caused by button operations, etc.: 4
．． It is OHz.

FIG. 7(b) shows the vibration suppression ratio of the anti-vibration television camera. It is shown that vibrations are effectively suppressed at the frequency corresponding to f Cl 1 f e2+ f ci.

Next, a third embodiment of the present invention will be described.

In this embodiment, a case will be described in which the present invention is applied to a camera shake prevention device in "image shake prevention technology for video cameras" as described in the description of the prior art.

FIG. 8 shows a block diagram of the apparatus of this embodiment. In the figure, 802 is a lens barrel, 804 is an angular velocity sensor such as a vibrating gyro, 806 is a BPF, 808 is a filter circuit, and 810 is an actuator. Here, the BPF 806 and the filter circuit 808 constitute a control unit.

The difference from the conventional example is that the control unit has B
PF806 is provided.

Next, the operation and effect of the apparatus of this embodiment will be explained. Since the angle sensor 804 detects the differential value θn of the lens barrel angle On, an integrator is used for feedback.

However, in this case, as described above, detection errors of the sensor accumulate, resulting in characteristics such as drift. However, if the feedback gain is set low for this purpose, a problem arises in that a sufficient vibration suppression ratio cannot be obtained.

Therefore, the BPF 806 is used to feed back only the frequencies that cause a lot of vibration with a high gain, thereby obtaining an efficient (high vibration damping effect).

This embodiment differs from the first embodiment in that it is a continuous control system rather than a discrete control system, and that the inertia of the lens barrel 802 is large and has a vibration suppressing effect itself. It is.

FIG. 9 shows the vibration suppression ratio of the vibration-proof imaging device according to the present invention. The frequency characteristic obtained with this device is in the form 904, which is significantly improved compared to the vibration isolation characteristic 302 published in the above-mentioned literature.

(Effects of the Invention) As explained above, according to the imaging device of the present invention, by configuring at least one or more stages of BPF in the feedback loop of an anti-shake control system such as an anti-shake TV camera, It has the effect of effectively damping vibration frequencies.

Furthermore, there is no drift, the power consumption is low, and sudden screen shake at the correction limit angle can be reduced, making it possible to realize a natural and stable image stabilization device.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing a first embodiment of the imaging device according to the present invention, Fig. 2 is a block diagram showing a conventional configuration, and Fig. 3 is the same.
FIG. 4 is a block diagram showing the control system of the first embodiment using a transfer function; FIG. 5 is a diagram showing the frequency characteristics of the control system in FIG. 4; The figure is a block diagram showing a second embodiment of the imaging device according to the present invention, FIG. 7 is a diagram showing frequency characteristics in the control system of the second embodiment of FIG. 6, and FIG. 8 is a diagram showing the imaging device according to the present invention. FIG. 9 is a diagram showing frequency characteristics in the control system of the second embodiment of FIG. 8.

Claims (7)

[Claims] (1) A control system consisting of a detection means for detecting camera vibration, a correction means for shifting an image to correct the vibration, and a control means for driving and controlling the correction means according to the output of the detection means. An imaging device characterized in that the closed-loop frequency characteristic is configured as a notch filter type. (2) In claim (1), the control means includes a bandpass filter in a control loop that controls the correction means according to the output of the detection means, and the bandpass filter is configured by software. Alternatively, an imaging device characterized in that it is configured by hardware. (3) The imaging device according to claim (2), wherein the correction means is constituted by a deflection means for optically shifting an image. (4) The imaging device according to claim (1), wherein a blocking frequency of the notch filter is set to approximately 0.2 Hz to 10 Hz. (5) The imaging device according to claim (2), wherein the pass frequency of the bandpass filter is set to about 0.2 Hz to 10 Hz. (6) Closed-loop control consisting of a detection means for detecting vibrations of the imaging device, a correction means for correcting the vibrations by shifting an image, and a control means for driving and controlling the correction means according to the output of the detection means. An imaging apparatus, comprising: a control unit configured to set a frequency characteristic in the closed-loop control system such that a control amount of the correction unit differs depending on a frequency of the vibration. (7) In claim (6), the control means controls the correction means according to the output of the detection means to suppress the vibration, so that the suppression ratio is maximized with respect to vibrations caused by camera shake, etc. An imaging device characterized in that it is set so that