JP2013104921A - Image pickup apparatus, image pickup system, and control method of image pickup apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To appropriately control whether to enable or disable image blur correction according to a focal length and a subject distance (photographic magnification) when a subject image is displayed on a display device as a moving image.SOLUTION: The image pickup apparatus including an imaging optical system capable of changing a focal length includes: a correction unit for correcting image blur due to shake of the image pickup apparatus; an angular shake detecting unit for detecting angular shake of the image pickup apparatus; a display unit for displaying a photographed image; a correction amount calculation unit that calculates a correction amount of the image blur on the basis of the angular shake, the focal length of the imaging optical system, and the photographic magnification calculated from the focal length of the imaging optical system and the subject distance; and a control unit that, when the display unit displays the photographed image as a through-the-lens image, sets a suppression rate of the image blur according to the focal distance and the photographic magnification.

Description

  The present invention relates to a technique for correcting image blurring (deterioration of an image) caused by camera shake such as camera shake.

  In recent years, interchangeable lenses, digital cameras, and digital video cameras having an image stabilization control device (consisting of an image blur correction unit, a drive unit, a vibration detection unit, and the like) that prevent image blur caused by camera shake or the like have been commercialized. An angular velocity meter is used as a shake detection device for correcting image blur. However, in photographing at a close distance (photographing conditions with a high photographing magnification), image degradation caused by a shake in a direction parallel or perpendicular to the optical axis of the camera, which is a so-called parallel shake, which cannot be detected only by an angular velocity meter cannot be ignored.

  On the other hand, a digital camera can display a moving image on a screen such as an LCD. At this time, even if there is an effect on an image captured as a still image, the user may not recognize image blurring in an image that is simply displayed as a through image (moving image), for example, when capturing on the wide-angle side.

  Therefore, for example, Patent Document 1 discloses the following technique. That is, it is determined whether or not the amount of displacement of the display subject image due to camera shake exceeds the pixel pitch of the display screen while moving images are displayed on the wide-angle side where the focal length is small. Then, in the case of camera shake that does not cause image blur in the display subject image, the angular velocity sensor and the image blur correction mechanism are brought into an operation stop state. Further, in the case of camera shake that causes image blur in the display subject image, the control unit is caused to function so as to operate the angular velocity sensor and the image blur correction mechanism.

JP 2006-325060 A

  However, the angle shake amount and the parallel shake amount increase as the shooting magnification increases when the subject such as macro photography is at a close distance. However, in the conventional technique disclosed in Patent Document 1 described above, this increase in shake amount is considered. It has not been. For this reason, there is a problem in that the image blur correction mechanism is stopped while the moving image display is in a state of being easily blurred at a close distance on the wide angle side.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to perform image blur correction according to a focal length and a subject distance (shooting magnification) when a subject image is displayed as a moving image on a display device. Proper control of operation and stopping.

  An image pickup apparatus according to the present invention is an image pickup apparatus having an image pickup optical system in which a focal length can be changed, and a correction unit that corrects image blur due to shake of the image pickup apparatus, and an angle at which angular shake of the image pickup apparatus is detected. Based on shake detection means, display means for displaying the captured image, the angular shake, the focal length of the imaging optical system, and the imaging magnification calculated from the focal length and subject distance of the imaging optical system Correction amount calculation means for calculating an image blur correction amount, and when the display means displays the captured image as a through image, the image blur suppression according to the focal length and the shooting magnification. And a control means for setting the rate.

  According to the present invention, when a subject image is displayed on a display device as a moving image, it is possible to appropriately control the operation and stop of image blur correction according to the focal length and the subject distance (shooting magnification). .

1 is a block diagram of an imaging apparatus according to a first embodiment of the present invention. FIG. 3 is a plan view of a camera equipped with the image blur correction system according to the first embodiment. 1 is a side view of a camera equipped with an image blur correction system according to a first embodiment. The block diagram explaining the internal structure of the image stabilization control part which performs angle shake correction in 1st Embodiment. The figure showing the focal distance and the suppression effect in 1st Embodiment. The top view of the camera carrying the image blurring correction system in 2nd Embodiment. The side view of the camera carrying the image blurring correction system in 2nd Embodiment. The block diagram explaining the internal structure of the image stabilization control part which correct | amends an angular shake and a parallel shake in 2nd Embodiment. The figure showing the focal distance by the object distance in 2nd Embodiment, and the suppression effect.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(First embodiment)
FIG. 1 is a block diagram showing a configuration of an imaging apparatus according to the first embodiment of the present invention. This imaging device is a digital camera mainly for taking still images and moving images.

  In FIG. 1, a zoom unit 101 includes a zoom lens that performs a zooming operation of a photographing optical system (the focal length can be changed by moving a zoom position). The zoom drive control unit 102 drives and controls the zoom unit 101. The correction lens (shift lens) 103 can change its position in a direction orthogonal to the optical axis, and corrects image blur. The image stabilization control unit 104 controls driving of the correction lens 103.

  The aperture / shutter unit 105 controls the amount of incident light. The aperture / shutter drive control unit 106 controls the drive of the aperture / shutter unit 105. The focus unit 107 includes a lens that performs focus adjustment. The focus drive control unit 108 controls the drive of the focus unit 107. The zoom unit 101, the correction lens 103, the aperture / shutter unit 105, and the focus unit 107 are disposed in a photographing lens that forms a subject image.

  The imaging unit 109 converts the optical image that has passed through each lens group into an electrical signal. The imaging signal processing unit 110 converts the electrical signal output from the imaging unit 109 into a video signal. The video signal processing unit 111 processes the video signal output from the imaging signal processing unit 110 according to the application. The display unit 112 performs image display as necessary based on the signal output from the video signal processing unit 111. The power supply unit 113 supplies power to the entire system according to the application. The external input / output terminal unit 114 inputs and outputs communication signals and video signals with the outside. The operation unit 115 is used for operating the system. The storage unit 116 stores various data such as video information. The posture information control unit 117 determines the posture of the imaging apparatus and provides posture information. The camera system control unit 118 controls the entire system.

  Next, a schematic operation of the imaging apparatus having the above configuration will be described.

  The operation unit 115 includes an image stabilization switch that enables selection of an image blur correction (image stabilization) mode. When the shake correction mode is selected by the image stabilization switch, the camera system control unit 118 instructs the image stabilization control unit 104 to perform the image blur correction operation, and the image stabilization control unit 104 that receives the instruction instructs the image stabilization correction off. The image blur correction operation is performed until it is done. In addition, the operation unit 115 includes a shooting mode selection switch that allows one of a still image shooting mode and a moving image shooting mode to be selected, and changes the operating condition of each actuator in each shooting mode. Can do.

  The operation unit 115 includes a shutter release button configured such that the first switch (SW1) and the second switch (SW2) are sequentially turned on according to the amount of pressing. The switch SW1 is turned on when the shutter release button is depressed approximately half, and the switch SW2 is turned on when the shutter release button is depressed to the end. When the switch SW1 is turned on, the focus drive control unit 108 drives the focus unit 107 to perform focus adjustment, and the aperture / shutter drive control unit 106 drives the aperture / shutter unit 105 to set an appropriate exposure amount. To do. When the switch SW2 is turned on, image data obtained from the light image exposed to the imaging unit 109 is stored in the storage unit 116.

  The operation unit 115 includes a moving image recording switch. Movie recording starts after the switch is pressed, and recording is ended when the switch is pressed again during recording. The operation unit 115 also includes a playback mode selection switch that can select a playback mode, and stops the image blur correction operation in the playback mode.

  Further, the operation unit 115 includes a zooming switch for instructing zoom zooming. When an instruction for zooming magnification is given by the zooming switch, the zoom drive control unit 102 that has received the instruction via the camera system control unit 118 drives the zoom unit 101 to move the zoom unit 101 to the instructed zoom position. Let At the same time, based on the image information sent from the imaging unit 109 and processed by each signal processing unit (110, 111), the focus drive control unit 108 drives the focus unit 107 to perform focus adjustment.

  2 and 3 are a plan view and a side view showing a camera provided with an image stabilization control device. The image blur correction system mounted on this camera performs image blur correction on shakes (hereinafter referred to as angle shakes) indicated by arrows 203p and 203y with respect to the optical axis 202.

  In the camera 201, 204 is a release button (included in the operation unit 115), and 205 is a camera CPU (included in the camera system control unit 118). Reference numerals 207p and 207y denote angular velocity detectors (hereinafter referred to as angular velocity meters) that detect angular fluctuations around the arrows 207pa and 207ya, respectively. The lens driving unit 208 is provided in the image stabilization control unit 104, and drives the correction lens 103 freely in the directions of arrows 208p and 208y in FIGS. 2 and 3 to correct image blur due to angular shake. Here, the outputs of the angular velocity meters 207p and 207y are input to the camera CPU 205. Then, the image blur correction is performed by the drive unit 208 according to the relationship between these outputs. In the present invention, a compact digital camera will be described as an example. On the other hand, in the case of an imaging system comprising an interchangeable lens as an optical device having an imaging optical system and a main body side (imaging device side) as in the case of a digital single lens reflex camera, the optical system and its driving means are on the interchangeable lens side. The image sensor, the display unit, and the release button 204 are on the main body side. The camera CPU 205 and angular velocity meters 207p and 207y that perform angular shake correction are generally on the optical device side, but the correction amount may be communicated to the interchangeable lens side on the main body side.

  FIG. 4 is a block diagram of the camera CPU 205 (correction amount calculation unit) that performs angular shake correction. The AD converter 301 converts the signal from the angular velocity meter (gyro) 207 into a digital signal. A high-pass filter (hereinafter HPF) and a low-pass filter (hereinafter integration filter) 302 cut a DC component and convert an angular velocity signal into an angle signal. The cutoff switching unit 303 switches the cutoff frequency of HPF and LPF. A gyro gain unit 304 is connected to the HPF / integration filter 302.

  The sensitivity correction unit 305 corrects the sensitivity using the zoom and focus information 306. The output correction unit 307 multiplies the shake correction value calculated up to the sensitivity correction unit 305 by an output correction coefficient from 1 to 0. When the output correction value is 1, the calculated shake amount is output as it is. On the other hand, when the output correction value is 0, the shake correction amount is 0 and image blur correction is not performed. The angular velocity signal input to the camera CPU 206 is calculated as an angular shake correction amount by performing these series of processes.

  Next, the image blur amount δ (image blur amount) due to the shake angle θ of the imaging optical system will be considered. From the shake angle θ, the focal length f of the imaging optical system, and the imaging magnification β, the blur amount δ of the image generated on the imaging surface can be obtained by the following equation (1).

δ = (1 + β) × f × tan θ (1)
Here, f is a focal length, β is a photographing magnification obtained by zooming / focusing of the imaging optical system, and a shake angle θ is obtained from an integration result of the angular velocity meter 207p. Here, when the deflection angle θ is small, tan θ [rad] ≈θ [rad], and when the photographing magnification is small, the following is expressed.

δ ≒ f × θ [rad] (2)
Thus, when the focal length (detected by the focal length detection means) is a predetermined value at a certain zoom position, the angular shake correction is performed by correcting the shake amount δ obtained by the above-described equation. be able to.

  Consider the case where the subject image is displayed on the LCD. The number of pixels of the LCD is considerably smaller than the number of pixels of the image sensor (for example, the number of vertical pixels of the LCD is 240 compared to the number of vertical pixels 3000 of the image sensor). Therefore, when a still image or moving image is not recorded and a through image is displayed on the LCD, if the amount of image blur is equal to or less than the pixel pitch of the LCD, the user does not notice the blur on the screen.

Here, for example, if the number of vertical pixels of the image sensor is 240 and the vertical width is 24 mm (35 mm equivalent), the blur amount δ ′ that can be recognized by the user is
δ ′ = 24 [mm] / 240 = 100 [μm]
When the focal length f (35 mm equivalent) is 24 mm, the shake angle that the user can recognize on the screen from equation (2) is
θ = δ ′ / f = 100 [μm] / 24 [mm] = 0.416 [rad]
= 0.24 [degree]
It becomes. Since human hand shake is about 0.2-0.3 degrees, most users cannot recognize image blur on the screen when holding firmly at this focal length, and the shake angle is larger than this. Even if there is a shake of about one pixel in the through image, it does not matter so much.

  As described above, when a through image is displayed on the LCD instead of being recorded, the image blur correction is performed at a focal length where the user cannot recognize the shake on the screen in a normal hand-held state or the shake is not much noticeable. There is no problem to stop. As an effect, since the image blur correction can be started from the movable center of the correction lens 103 at the start of photographing, the entire movable range can be used, and power can be saved because the correction lens 103 can be fixed during a through image.

  FIG. 5 shows the relationship between the zoom position and image blur correction. The horizontal axis represents the zoom position (from the Wide end to the Tele end), and the vertical axis represents the suppression effect (suppression rate). When the vibration suppression effect is 0%, the image blur correction OFF state is indicated, and the correction lens 103 is in the center fixed state. A suppression effect of 100% indicates that optimum image blur correction is performed in accordance with the shake amount.

  Here, it is assumed that the focal length in terms of 35 mm in which the user is worried about the blur on the through image when the image blur correction is off in the handheld state is f1. At this time, as shown by a solid line in the figure, the vibration suppression effect may be 0% when the focal position is equal to or smaller than the zoom position of the focal length f1, and the vibration suppression effect may be 100% otherwise. Further, at the Wide end, the vibration suppression effect may be raised to a zoom position of a certain focal length with the vibration suppression effect being 0%. In addition, various methods such as increasing the suppression effect from the focal length f1 can be considered. Even when the suppression effect is gradually increased, the driving amount of the shift lens is suppressed, so that there is at least an effect in securing a movable range and power saving.

  Next, a method for setting the suppression effect will be described. For example, in the output correction unit 307 of FIG. 4, the output correction coefficient is set to 1 when the suppression effect is 100%, and is set to 0 when the suppression effect is 0%. There is a way to decide. Other methods such as changing the value of the gyro gain unit 304 in accordance with the suppression effect, or changing the value of the cutoff switching unit 303 to set the suppression effect by panning control are also conceivable.

  As described above, when a through image is displayed on the LCD instead of during recording, the correction lens movable range is secured at the start of shooting and recording by suppressing the effect of suppression at the zoom position where the user cannot recognize image blur. And can save power.

(Second Embodiment)
Next, an imaging apparatus according to the second embodiment of the present invention will be described. The block configuration of the imaging apparatus according to the second embodiment is assumed to be almost the same as that of the first embodiment, and only the parts different from the first embodiment will be described.

  6 and 7 are a plan view and a side view showing the camera of the second embodiment provided with the image stabilization control device. The image blur correction system mounted on this camera is adapted to shakes indicated by arrows 211p and 211y (hereinafter referred to as parallel shakes) in addition to shakes indicated by arrows 203p and 203y with respect to the optical axis 202 (hereinafter referred to as angular shakes). Perform image blur correction.

  Further, the acceleration detectors (hereinafter referred to as accelerometers) 212p and 212y detect parallel shakes indicated by arrows 212pa and 212ya, respectively. The lens driving unit 208 in the image stabilization control unit 104 drives the correction lens 103 freely in the directions of the arrows 208p and 208y, and performs image blur correction in consideration of both angular shake and parallel shake.

  Here, the outputs of the angular velocity meters 207p and 207y and the accelerometers 212p and 212y are input to the camera CPU 205. Then, the image blur correction is performed by the drive unit 208 according to the relationship between these outputs.

  FIG. 8 is a block diagram of the camera CPU 205 that performs both angular shake correction and parallel shake correction. The AD converter 401 converts the signal from the accelerometer into a digital signal. A high-pass filter (hereinafter referred to as HPF) and an integration filter 402 cut DC components and convert acceleration signals into parallel shift amounts.

  The angular shake correction amount is calculated from the output from the angular velocity sensor, while the parallel shake correction amount is calculated from the output from the accelerometer. The output correction amount is determined by adding both the shake amounts (307), and both the angular shake correction and the parallel shake correction are performed.

  Here, the blur amount δ of the image generated on the imaging surface from the parallel shake Y at the principal point position of the imaging optical system, the shake angle θ of the imaging optical system, the focal length f of the imaging optical system, and the imaging magnification β is expressed by the following equation (3) ).

δ = (1 + β) × f × θ + β × Y (3)
The first term on the right side is the above-described angular shake correction amount, and the second term on the right side is the parallel shake correction amount obtained from the second-order integral value Y of the accelerometer 212p, zoom and focus, and the imaging magnification β obtained thereby. It is. Image blur correction is performed on the added blur amount δ.

  The shooting magnification β is determined from the focal length f and the subject distance (detected by the subject distance detecting means). For example, even when the focal length f is equal to 24 mm (35 mm equivalent), the shooting magnification β is 0.02 when the subject distance is 2 m, and 0.5 when the subject distance is 10 cm. to differ greatly. As a result, as shown in the expression (3), the shake amount δ obtained by adding the angular shake amount and the parallel shake amount is greatly changed, and the influence of the parallel shake is particularly large at a close distance. Therefore, the blur amount δ may be twice or more as compared with the case of only the angular deflection.

  As described above, when stopping the image blur correction depending on the zoom position when a through image is displayed on the LCD instead of at the time of recording, the shooting magnification β depending on the subject distance is not considered in addition to the focal length f. must not. This is shown in FIG. FIG. 9A shows the case where the subject distance is 2 m and the shooting magnification β = 0.02. In this case, there is almost no influence of parallel shake, which is almost the same as considering only angular shake. On the other hand, FIG. 9B shows the case where the subject distance is 10 cm and the photographing magnification β = 0.5. At this time, the influence of the parallel shake is large, and the blur amount δ on the screen becomes large even at the same focal length, so it is necessary to improve the suppression effect with a smaller focal length.

  In this way, by setting the image blur correction effect of the shift lens in consideration of not only the focal length but also the shooting magnification depending on the subject distance, a more optimal image blur correction setting can be performed for a through image on the LCD. .

  In the above embodiment, it has been shown that by changing the image blur correction effect according to the focal length and the subject distance, it is possible to set an optimal image blur correction state in consideration of power saving and securing a movable range during exposure. In addition, since the amount of blurring is more noticeable in enlarged display and electronic zoom display than in normal display, it is preferable to set the image blur correction effect so as not to decrease regardless of the focal length and subject distance.

  Here, in the above-described embodiment, so-called optical image blur correction in which the correction lens is moved in a plane perpendicular to the optical axis based on the calculated correction amount is used as the image blur correction unit. However, the correction method based on the correction amount may be a method in which image blur correction is performed by moving the image sensor in a plane perpendicular to the optical axis. Furthermore, it is a method using electronic image blur correction that reduces the effect of shake by changing the cutout position of each shooting frame output by the image sensor, or by performing image blur correction by combining them. The object of the present invention can be achieved.

Claims (9)

An imaging apparatus having an imaging optical system capable of changing a focal length,
Correction means for correcting image blur due to shake of the imaging device;
Angular shake detecting means for detecting angular shake of the imaging device;
Display means for displaying the captured image;
Correction amount calculation means for calculating a correction amount of image blur based on the angular shake, the focal length of the imaging optical system, and the photographing magnification calculated from the focal length of the imaging optical system and the subject distance;
Control means for setting the image blur suppression rate according to the focal length and the shooting magnification when the display means displays the captured image as a through image;
An imaging apparatus comprising:   It further comprises parallel shake detection means for detecting parallel shake in a direction orthogonal to the optical axis of the imaging optical system, and the correction amount calculation means includes the angular shake, the focal length of the imaging optical system, and the imaging magnification. The image pickup apparatus according to claim 1, wherein an image blur correction amount is calculated based on the parallel shake detected by the parallel shake detection unit.   The imaging apparatus according to claim 1, wherein the control unit decreases the vibration suppression rate as the focal length is shorter.   4. The control unit according to claim 1, wherein when the display unit is performing an enlarged display or an electronic zoom display, the control unit sets the vibration suppression rate so as not to decrease. 5. Imaging device. An imaging system comprising an optical device having an imaging optical system capable of changing a focal length, and an imaging device having an imaging unit that captures an image formed by the imaging optical system,
The imaging device
A display means for displaying the captured image;
The optical instrument is:
A focal length detection means for detecting a focal length of the imaging optical system;
Subject distance detection means for detecting the subject distance to the subject;
Correction means for correcting image blur due to device shake;
Angular shake detection means for detecting the angular shake of the device;
Correction amount calculating means for calculating a correction amount of image blur based on the angular shake, the focal length, and a photographing magnification calculated from the focal length and the subject distance;
Control means for setting the image blur suppression rate according to the focal length and the shooting magnification when the display means displays the captured image as a through image;
An imaging system comprising: The optical apparatus further includes parallel shake detection means for detecting parallel shake in a direction orthogonal to the optical axis of the imaging optical system,
The correction amount calculation unit calculates an image blur correction amount based on the angular shake, the focal length of the imaging optical system, the photographing magnification, and the parallel shake detected by the parallel shake detection unit. The imaging system according to claim 5.   The imaging system according to claim 5, wherein the control unit decreases the suppression rate as the focal length is shorter.   8. The control unit according to claim 5, wherein when the display unit is performing an enlarged display or an electronic zoom display, the control unit sets the vibration suppression rate so as not to decrease. Imaging system. An imaging apparatus control method comprising: an imaging optical system capable of changing a focal length; a correction unit that corrects image blur due to shake of the apparatus; and a display unit that displays a captured image.
An angular shake detection step for detecting angular shake of the imaging device;
A correction amount calculating step of calculating an image blur correction amount based on the angular shake, the focal length of the imaging optical system, and the photographing magnification calculated from the focal length of the imaging optical system and the subject distance;
And a control step of setting the image blur suppression rate according to the focal length and the photographing magnification when the display unit displays the captured image as a through image. Control method of imaging apparatus.

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