JPH11275448A - Image pickup device and storage medium readable by computer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the device from slipping out of the still mode due to even a small shock when the device is set to a mode where a shake correction band is limited (still mode) to prevent an image pattern from being shaken due to a noise of a shake sensor while the video camera is fixed on a tripod. SOLUTION: When the video camera is fixed on a tripod, a shake signal sensed by a shake sensor is given to an HPF 210 via an HPF 202 and a detector 211 detects the frequency (f). A discrimination device 212 compares the frequency (f) with threshold frequencies fg, fb (fb>fg). In the case of f<=fg, a higher cut-off frequency of the HPF 210 is selected and the still mode is set to the device. In the case of f<=fb, the still mode is released, a lower cut-off frequency is selected and the usual shake correction mode is selected. Through the selection of fb>fg, the device is easily entered to the still mode and is hardly slipped out of the still mode.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image pickup apparatus and a computer-readable storage medium which are used in a video camera or the like and have a function of correcting a shake such as a hand shake.

[0002]

2. Description of the Related Art A video camera or the like employs a high-magnification zoom lens, and a zoom ratio of 10 times or more has become common in the field of consumer use. If the focal length on the long focal length side becomes a large numerical value with the enlargement of the zoom ratio, the camera shake due to camera shake or the like on the long focal length side has a large effect on the captured image, and the main subject is not moved. It moves unsightly on the screen. Therefore, in the field of video cameras and the like, a shake correction function for removing the influence of camera shake and the like has been put to practical use.

The shake correction function includes at least shake detection means for detecting a shake component, and shake correction means for correcting a shake according to the detection result of the detection means. Of these, the shake detection means is used between continuous fields,
Alternatively, an electronic detection method of detecting an image motion by comparing images between frames, or a method of directly measuring a camera motion using an angular velocity sensor, an angular acceleration sensor, or the like may be used.

On the other hand, in addition to the optical vibration correcting means for optically adjusting the angle of the photographing optical axis in a direction in which the camera shake is removed, the vibration correcting means actually records or outputs the image from the obtained image. There is a so-called electronic correction means for electronically selecting a range (cutout range) to be performed.

When a camera equipped with such a shake correction function is mounted on a tripod for shooting, a noise component from the shake detection means causes the image which should be stopped to fluctuate. Sometimes. Therefore, the camera has a shake determination unit for determining whether or not the camera is fixed and installed in a stable place such as a tripod.If the determination unit determines that the camera is fixed, the band of the shake correction is limited, and the noise is reduced. There has been proposed a method of removing image shaking.

The shake determining means makes a determination based on the magnitude and frequency component of the shake signal detected by the shake detecting means. First, when the frequency of the shake is lower than the predetermined threshold value A and the level of the shake signal is lower than the predetermined threshold value B during the normal shake correction for a predetermined time, the band is limited for the shake correction, and unnecessary. To cut off the movement. This state is called a stationary mode. Conversely, when the shake frequency is higher than the predetermined threshold value A and the level of the shake signal is higher than the predetermined threshold value B in the stationary mode, the process returns to the normal correction.

[0007]

However, in the above conventional example, if the camera is shaken lightly with a finger in the stationary mode fixed to a tripod or the like, the camera easily exits the stationary mode and stops again. Until the mode is entered, there is a problem that the image shakes swayingly and gives a sense of incongruity.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to prevent the user from inadvertently exiting the still mode during the still mode.

[0009]

In an image pickup apparatus according to the present invention, an image pickup means for picking up a subject image and outputting an image signal; a shake detection means for detecting a shake of the image pickup means;
Correction means for correcting the shake of the image signal based on the shake signal detected by the shake detection means; shake frequency detection means for detecting the frequency of the shake signal; And control means for restricting the correction by the shake correction means when the vibration frequency is smaller than the threshold value and releasing the restriction when the shake frequency is higher than the second threshold value.

In the storage medium according to the present invention, an image pickup process for picking up a subject image and outputting an image signal, a shake detection process for detecting a shake of the image pickup means, and a shake signal detected in the shake detection process are performed. A correction process for correcting a shake of the image signal, a shake frequency detection process for detecting a frequency of the shake signal, and limiting the correction by the shake correction process when the detected shake frequency is smaller than a first threshold value. And a control process for canceling the restriction when the shake frequency is larger than the second threshold value.

[0011]

FIG. 1 is a block diagram showing an embodiment of an imaging apparatus according to the present invention. In FIG. 1, reference numeral 101 denotes a first lens group, which is a fixed lens group for condensing light. Reference numeral 102 denotes a second lens group which is movable in the optical axis direction for zooming. 103 is the aperture,
Reference numeral 104 denotes a third lens group, which is a fixed lens group.
Reference numeral 105 denotes a fourth lens group, which is a correction lens group having both a function of correcting an imaging position moved by the movement of the variable power lens group 102 and a function of performing focus adjustment, and is also movable in the optical axis direction. Has become. With the lens unit composed of these lens groups, finally the CC as an image sensor
A variable magnification subject image is formed on the imaging surface of D111.

Reference numeral 121 denotes a motor, and 126 denotes a motor driver. The motor driver 126 drives the motor 121 to move the zoom lens group 102. Similarly, regarding the correction lens group 105, 125 motors,
It is moved by a 128 motor driver. 123 is I
The G meter 127 is an IG driver. In the present embodiment, the motors 121 and 125 are assumed to be stepping motors, and detect the absolute position by counting the number of pulses from the reference position. When other actuators are used, a position detection sensor is required as needed.

Reference numeral 111 denotes a CCD (charge cup).
and converts light into electric charge.
Here, the CCD 111 has a larger number of pixels (number of photoelectric conversion elements) than a standard CCD required in a broadcast system (for example, the NTSC system). 116 is a CCD
The driving circuit drives the CCD 111. The CCD driving circuit 116 is designed so that it can select from which line the area to be finally output is cut out in the V direction according to a control command from a microcomputer 117 described later.

In FIG. 3, reference numeral 301 denotes an example of the total image size I _s of the CCD, and 302, 303, and 304 are examples of the standard image size I _N according to the broadcasting system. For example, when validating from a line y1 + 1 below the Δy1 line from the uppermost line, the Δy1 line can be read at a high speed, and the vertical synchronizing signal can be read from y1 + 1 at the same timing as when a standard-size CCD is used.

In FIG. 1, reference numeral 112 denotes an analog signal processing unit which performs predetermined processing on a signal obtained by the CCD 111 to generate an analog image signal. For example, a CDS circuit (correlated double sample)
ng correlated double sampling circuit), an AGC circuit and the like. An A / D converter 113 converts an analog image signal into a digital image signal. Reference numeral 114 denotes a memory which can store a digital image signal for at least one line, and further has a predetermined position (address).
Can be read. A digital signal processing unit 115 generates a final output image signal.

Note that the digital image signal stored in the memory 114 has a larger number of pixels than the standard image size. The digital signal processing unit 115 responds to a control command from a microcomputer 117 described later, and
The first pixel to be read out from the memory 14 can be selected, and the device is designed to read out only the standard image size.

Reference numeral 117 denotes a microcomputer which controls the entire camera system. For example, it controls the motor drivers 126 and 128. Also, the number of driven pulses is constantly monitored, and variable-magnification lens position data and correction lens position data representing the absolute position from the reference position are generated.
For example, if it is assumed that the entire stroke can be moved by 1280 pulses, the stroke is equally divided every 10 pulses to generate 128-stage position data. Reference numeral 140 denotes a zoom key which is operated by the user when changing the focal length. The microcomputer 117 reads the signal of the zoom key 140 and controls the zoom lens 103 accordingly.

An angular velocity sensor 131 detects an angular velocity component in one direction of camera shake (shake of the CCD 111). 132 is an HPF (high-pass filter), 133 is an amplifier, 134 is an LPF (low-pass filter),
Thus, a predetermined frequency limitation and amplification are performed on the output signal of the angular velocity sensor detected by the angular velocity sensor 131 to generate an angular velocity signal.

An angular velocity sensor 135 also detects an angular velocity component of the camera shake in the other direction. 136 is H
PF (high-pass filter), 137 is an amplifier, 138 is an LPF (low-pass filter).
4 has the same function as each part. However, both are CCD1
The components are arranged so as to detect components orthogonal to each other on the 11 imaging surfaces. Specifically, one is in the vertical (V) direction,
The other detects the horizontal (H) direction.

The microcomputer 117 has a built-in A / D converter, and the angular velocity signals in two directions are converted into digital signals by the built-in A / D converter to become angular velocity data. Further, predetermined signal processing is performed on the angular velocity data to generate vertical and horizontal shake correction signals. The microcomputer 117 converts the vertical shake correction signal to CC.
The lateral shake correction signal is transmitted to the D drive circuit 116 to the digital signal processing unit 115, respectively. As described above, the CCD drive circuit 116 and the digital signal processing unit 115 each change the cutout position in accordance with the shake correction signal.

[0021] The series of operations described above, the total image size I _s 301 as shown in FIG. 3, for example 302,3
04 in can be cut by shifting the standard image size I _N from the center as it is possible to correct the shake due to the result camera shake or the like.

143 is a storage medium according to the present invention for storing the microcomputer control program. The control program includes a program for executing processing shown in FIGS. This storage medium 143
For example, a semiconductor memory, an optical disk, a magneto-optical disk, a magnetic medium, or the like may be used. In addition, ROM,
The present invention may be applied to a RAM, a CD-ROM, a memory card, a floppy disk, a magnetic tape, a magnetic card, or the like.

Next, signal processing for converting angular velocity data in the microcomputer 117 into a shake correction signal will be described with reference to FIG. Since the same processing is performed in the vertical direction and the horizontal direction, only one direction will be described here. First, angular velocity data is fetched by processing 201. The process 202 is an HPF (High Pass Filter),
DC component is mainly cut off from angular velocity data. Therefore, the cutoff frequency is sufficiently low. The process 210 is an HPF (high-pass filter), and 213 is a cutoff frequency table. The HPF 210 sets the cutoff frequency in the cutoff frequency table 2
13 can be selected.

A process 203 is an integrator, and outputs an angular displacement signal by integrating the HPF output. Process 204
Multiplies the zoom gain and outputs a correction amount. When the camera is shaken by an angular displacement θ, the focal length 1 and the object movement amount Δx on the imaging surface are expressed as Δx = 1 × tan θ (1). Multiply here. Reference numeral 205 denotes focal length data. As described above, actually, the position of the variable power lens is limited to a finite number (for example, 0).
To 128).

Reference numeral 207 denotes a zoom gain table, in which focal length data and zoom gain are associated with each other and stored in the ROM area. The zoom gain 204 reads the gain of the focal length data 205 from the zoom gain table 207. The process 206 is a limiter, and the zoom gain 2
04 is restricted, and the correction amount is output. 208
Is a limiter table in which focal length data and limiter values (the number of pixels to be shifted) are associated with each other and stored in the ROM area. The limiter 206 has the focal length data 205
Is read from the limiter table 207, the output of the zoom gain 204 is compared with the limiter value, and if the output value is larger than the limiter value, the limiter value is output as a correction amount.

Reference numeral 211 denotes a shake frequency detector, which is an HPF.
A shake frequency component is detected from the output signal of 202. The shake frequency detector 211 outputs the largest detected frequency data. Reference numeral 212 denotes a shake state discriminator, which is an HPF.
A shake state is determined from the output signal of the shake filter 202 and the shake frequency data from the shake frequency detector 211, and the HPF 21
Control the zero cutoff frequency. In the present embodiment, the mode is switched between the correction mode and the stationary mode by the shake determiner. The correction mode is a mode for performing normal shake correction, and the stationary mode is a mode in which the image which should have been stopped originally shakes due to noise of a shake detection system when installed in a stable place such as a tripod. This is a mode in which the band of the shake correction is limited in order to prevent the fluctuation, and the shake of the image due to noise is removed.

In the stationary mode, the cutoff frequency of the HPF 210 is changed in order to limit the band of the shake correction. Specifically, in the normal mode, the cutoff frequency of the HPF 210 is set sufficiently low, and in the stationary mode, the cutoff frequency is set to a value necessary for removing noise. Each of the cutoff frequencies is set in advance to a predetermined value.

Next, the operation of the shake state discriminator 212 will be described with reference to FIG. Note that the process of FIG. 4 is repeatedly executed at a predetermined cycle. Steps 403 to 406 are executed independently in the horizontal and vertical directions. In step 402, it is determined whether the current mode is the stationary mode. If it is determined in the process 402 that the mode is the correction mode, the process proceeds to a process 408.

[0029] In process 408 P, velocity S of Y are both determined whether is smaller than a predetermined threshold value S _e. Here, P (pitch) means the vertical direction, and Y (yaw) means the horizontal direction. In the process 409, it is determined whether or not both the shake frequencies f of P and Y are equal to or lower than a predetermined threshold value fg. If both are determined to be fg or less in the process 409, the process proceeds to a process 410. In process 409, 1 is added to the value of the memory Count and stored. In the process 411, it is determined whether or not the value of the memory Count is equal to the predetermined value ch. If it is determined in step 411 that they are equal, the process proceeds to step 412. If they are not equal, the process ends in step 407.

In the process 412, the mode shifts to the stationary mode.
Specifically, the cutoff frequency of the HPF 210 is changed to a value to be set in the stationary mode. When the conditions are not satisfied in the processes 408 and 409, and after the process 412 is executed, the process proceeds to the process 413. In step 413, the memory Count0 is stored and initialized.

If it is determined in step 402 that the mode is the stationary mode, the process proceeds to step 403. In step 403, it is determined whether or not the angular velocity S is smaller than a predetermined threshold value Sa. Process 40
If it is determined to be large in step 8, the process proceeds to step 404. In the process 404, it is determined whether or not the shake frequency f is smaller than a predetermined threshold value fb. If it is determined in step 404 that it is equal to or higher than fb, the process proceeds to step 406. In step 406, the mode shifts to the correction mode. Specifically, the cutoff frequency of the HPF 210 is changed to a value to be set in the correction mode.

The present embodiment is characterized in that the threshold values fb and fg are different. This means that if you shake the camera lightly with your finger while in the still mode, you can easily exit the still mode and enter the still mode again.
This is again to prevent the image from swaying and giving a sense of incongruity. In other words, by setting the threshold value fb to a value larger than the threshold value fg, it is easy to enter the still mode, and it is difficult to leave the mode.

In the present embodiment, the cutoff frequency of the HPF 210 is made variable, but the characteristics of the integrator 203 may be made variable, or the characteristics of both the HPF and the integrator may be made variable. Also, in the present embodiment, an electronic shake correction system by cutting out from the CCD 111 has been described as an example. However, a system that performs shake correction by shifting some of the lenses in the lens group, or a high refractive index It is apparent that the present invention is also effective in the case of optical shake correction means such as a system for correcting shake by changing the apex angle of a prism (variable apex prism (VAP)) in which a liquid is sealed.

[0034]

As described above, according to the present invention,
It is easy to enter a mode that limits correction such as a stationary mode fixed to a tripod, etc., and it is possible to make it difficult to pull out, so if you shake the camera lightly with your finger during this mode, it will be easier as before Until the camera exits the still mode and enters the still mode again, it is possible to effectively prevent the image from swaying and giving an uncomfortable feeling, and it is possible to realize good shake correction.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an embodiment of an imaging device according to the present invention.

FIG. 2 is a block diagram illustrating signal processing for converting angular velocity data into a shake correction signal.

FIG. 3 is a configuration diagram illustrating an imaging surface of a CCD.

FIG. 4 is a flowchart showing the operation of a shake state discriminator.

[Explanation of symbols]

 102 Second lens group (magnification lens group) 111 CCD 115 Digital signal processing section 116 CCD drive circuit 117 Microcomputer 131, 135 Angular velocity sensor 143 Storage medium 132, 136 HPF 301 Total image size 302 to 304 Standard image size

Claims (11)

[Claims] An image pickup means for picking up a subject image and outputting an image signal; a shake detection means for detecting a shake of the image pickup means; and a shake of the image signal based on the shake signal detected by the shake detection means. Correction means for correcting, shake frequency detection means for detecting the frequency of the shake signal, and limiting the correction by the shake correction means when the detected shake frequency is smaller than a first threshold value, wherein the shake frequency Control means for canceling the restriction when the value is larger than a threshold value of 2. 2. The imaging device according to claim 1, wherein the second threshold is larger than the first threshold. 3. The image pickup means has a configuration in which the number of photoelectric conversion elements arranged in the horizontal direction and the vertical direction of the image pickup surface is larger than the image size (the number of pixels) required in a compliant broadcasting system. 2. The image pickup apparatus according to claim 1, wherein the shake correcting means performs the correction by selecting an image size required in the compliant broadcasting system from pixels within the effective image circle diameter. 4. The imaging apparatus according to claim 1, wherein said shake correcting means performs said correction by optically bending an optical axis. 5. A zooming means for zooming a subject image formed on an imaging surface of the imaging means, wherein the shake correcting means comprises:
The image pickup apparatus according to claim 4, wherein the image pickup apparatus is arranged between the image pickup means and the magnification changing means. 6. The image pickup apparatus according to claim 4, wherein said shake correcting means is a variable apex prism. 7. The imaging apparatus according to claim 4, wherein said shake correction means is a shift lens. 8. The imaging apparatus according to claim 1, wherein the restriction of the correction by the control means is to limit a band of the shake correction. 9. An image pickup process for picking up a subject image and outputting an image signal, a shake detection process for detecting a shake of an image pickup means, and correcting the shake of the image signal based on the shake signal detected in the shake detection process Correction processing, a vibration frequency detection processing for detecting the frequency of the vibration signal, and limiting the correction by the vibration correction processing when the detected vibration frequency is smaller than a first threshold, so that the vibration frequency becomes the second. A computer-readable storage medium storing a program for executing a control process for canceling the restriction when the threshold value is larger than the threshold value. 10. The computer-readable storage medium according to claim 9, wherein said second threshold value is larger than said first threshold value. 11. The computer-readable storage medium according to claim 9, wherein the limitation of the correction by the control processing is to limit a band of the shake correction.