JP2011135537A - Imaging apparatus and control method of the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To eliminate image quality deterioration caused by image blur during an exposure time of an imaging element, even if blur to be applied to an imaging apparatus is increased such as when an image is captured during walking. <P>SOLUTION: An imaging apparatus includes: an imaging means for photoelectrically converting a subject image formed on an imaging plane by an imaging optical system and outputting an image signal; an exposure time setting means for setting an exposure time during which the imaging means produces the image signal; a shake detecting means for detecting shake of the apparatus; a blur correcting means having a plurality of correction modes for correcting image blur caused by apparatus shake; a blur correction control means for controlling the blur correcting means by calculating a blur correction control signal based on detection output from the blur detecting means; and a blur correction mode setting means for setting a correction mode for correcting image blur caused by apparatus shake from among the plurality of blur correction mode of the blur correcting means. The blur correction control signal is calculated so as to attenuate blur correction gain output as an amplitude applied to the apparatus becomes larger. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an imaging apparatus and a method for controlling the imaging apparatus, and more particularly to a technique suitable for use in performing blur correction of a captured image caused by camera shake caused by camera shake of a photographer.

  In moving images taken by an imaging device such as a video camera, there is a problem that blurring occurs in the image particularly when the lens is zoomed to the telephoto side. In order to correct such image blurring, an imaging apparatus equipped with a camera shake correction apparatus that detects camera shake of a photographer applied to the imaging apparatus and corrects the shake based on the detected camera shake component is proposed and put into practical use. Has been.

  As the camera shake correction method, an optical method is known in which a part of the photographing lens is made movable and the optical axis is decentered in a direction to cancel the detected camera shake. In addition, there is an electronic method in which an effective pixel area that can move within the effective pixel area of the image sensor is set, and the effective pixel area is moved within the effective pixel area in a direction that cancels the detected camera shake. The latter electronic method is advantageous in size and weight and optically from the viewpoint of cost. However, because of the limitations of the system, it cannot be used for blur correction during the exposure time of the image sensor, so Deterioration of image feeling occurs. The following proposal has been made as a measure for improving the phenomenon in which the sense of resolution of a photographed image deteriorates (for example, see Patent Document 1).

  In Patent Document 1, an electronic system is adopted for the shake correction device, and a photographed image in which the sense of resolution changes depending on the difference between the case where the shake correction effect of camera shake occurring during the exposure time of the image sensor is high and the case where it is low. This is to improve the degradation of resolution.

  Specifically, the limiter characteristics are changed based on the detected vibration amplitude, frequency, and shutter speed. In the case of camera shake with a small amplitude, an appropriate shake correction is performed. Degradation of resolution is reduced by obtaining a captured image with little change in resolution due to.

JP 2002-148670 A

  However, in the shake correction apparatus described in Patent Document 1, the shake correction effect is intentionally reduced when the amplitude of camera shake applied to the imaging apparatus is large. For example, there has been a problem that a blur correction effect cannot be obtained sufficiently when a blur correction mode for correcting a large blur such as during walking shooting is set.

  In addition, if a large amount of blur occurs during the exposure time of the image sensor, such as when shooting while walking, the difference between the case where the blur correction effect by the blur correction mode for correcting the large blur is high and the case where it is low becomes larger. There is also a problem that a change in feeling appears remarkably and a captured image with a deteriorated feeling of resolution is obtained.

  SUMMARY OF THE INVENTION In view of the above-described problems, an object of the present invention is to improve image quality deterioration due to image blurring during an exposure time of an image sensor even when blurring applied to an imaging apparatus becomes large as during shooting while walking. .

  An image pickup apparatus according to the present invention includes an image pickup unit that photoelectrically converts a subject image formed on an image pickup surface by an image pickup optical system and outputs an image signal, and an exposure that sets an exposure time for the image pickup unit to generate the image signal. A time setting unit, a blur detection unit for detecting a blur of the device, a blur correction unit having a plurality of correction modes for correcting a blur of an image caused by the blur of the device, and a correction of an image blur caused by the blur of the device As a correction mode for performing the correction, at least the first shake correction mode and the shake correction mode setting means capable of setting the second shake correction mode having a correction range narrower than that of the first shake correction mode and the shake detection means A shake correction control signal that calculates a shake correction control signal based on the detected output and drives and controls the shake correction means in accordance with the correction mode; and a plurality of shake correction means A blur correction mode setting unit that sets a correction mode for correcting a blur of an image caused by the blur of the device from among the blur correction modes, and the blur correction control unit includes a first correction mode among the correction modes. In the case of the first blur correction mode, when the exposure time of the exposure time setting means exceeds a predetermined time, the blur correction control signal is calculated so as to attenuate the output amplitude. In the case of the second blur correction mode, the blur correction control signal is calculated at a lower rate of attenuation of the output amplitude than in the first blur correction mode.

According to the present invention, the correction gain is set in the shake correction control signal for the shutter speed based on the setting of the camera shake correction mode. As a result, even when blurring applied to the imaging apparatus becomes large as during walking shooting, it is possible to improve image quality degradation due to image blurring during the exposure time of the imaging device.
According to another feature of the present invention, the correction gain is set in the shake correction control signal for the focal length based on the setting of the shake correction mode. As a result, even when blurring applied to the imaging apparatus becomes large as during walking shooting, it is possible to improve image quality degradation due to image blurring during the exposure time of the imaging device.

It is a block diagram which shows the structural example of the imaging device concerning 1st Embodiment. It is a block diagram which shows the example of an internal structure of a system control part. It is a block diagram which shows the structural example of a vector detection circuit. It is a figure which shows the selection setting screen of camera shake correction mode. (A) is the figure which showed the cut-out area | region, (b) It is a figure explaining the blurring correction angle. It is a flowchart which shows an example of the process performed by a system control part. It is a flowchart which shows the subroutine of the process in a system control part. It is the figure which showed the attenuation characteristic with respect to the shutter speed of the blurring correction control signal. It is a flowchart which shows the subroutine of the process performed in 2nd Embodiment. It is the figure which showed the attenuation characteristic with respect to the focal distance of a blurring correction control signal. It is the figure which showed the blurring remaining amount of the blurring applied to an imaging device.

First, the remaining blur amount of blur applied to the imaging apparatus will be described with reference to FIG.
FIG. 11 is a diagram illustrating the remaining blur amount between fields when the blur frequency applied to the imaging apparatus is 7.5 Hz.

  In FIG. 11, an upper stage shows a shake waveform applied to the imaging apparatus, where 1101 indicates a small amplitude and 1102 indicates a large amplitude. The middle and lower sections show the parts of the shake waveform applied to the imaging device, extracted for each shutter speed, and show the remaining blur amount at shutter speed 1/60 seconds and the remaining blur amount at shutter speed 1/120 seconds, respectively. Yes. The horizontal axis is the time axis.

As can be seen from FIG. 11, the greater the blur amplitude, the greater the remaining blur amount. As described above, when the blur amplitude is large, the entire captured image has the effect of blur correction, but the scene with a high blur correction effect with a small image flow and the blur correction effect with a large image flow are low. The scenes will be displayed alternately. When viewing this captured image, it may appear that the focus repeats focusing or non-focusing, or the blur correction effect appears to intermittently increase or decrease. The image feeling changes and the resolution is deteriorated.
Hereinafter, embodiments of the present invention will be described with reference to the drawings.

<First Embodiment>
FIG. 1 is a block diagram illustrating a configuration example of an imaging apparatus equipped with the camera shake correction apparatus according to the present embodiment, and illustrates an electrical configuration of the imaging apparatus.
In FIG. 1, 11 is an image pickup optical system comprising a lens and a diaphragm, and 12 is an image pickup element comprising a CCD or CMOS sensor.

  The lens driving circuit 21 drives a zoom lens, a focus lens, a diaphragm, etc. (all not shown) in the imaging optical system 11. The position detection sensor 22 detects the positions of the zoom lens, focus lens, diaphragm, and the like inside the imaging optical system 11. The image sensor drive circuit 23 drives the image sensor 12. The camera signal processing circuit 13 performs signal processing necessary for the captured image data.

  The motion vector detection circuit 14 detects a motion vector from the image data signal-processed by the camera signal processing circuit 13. The memory read control circuit 15 controls a range of image data to be recorded or displayed by a control signal calculated by the system control unit 25 from a motion vector that is a detection output of the motion vector detection circuit 14.

  The image memory 16 stores the image data signal-processed by the camera signal processing circuit 13. The recording medium 18 includes a memory card, a hard disk, and the like. The recording signal processing circuit 17 records the signal-processed image data on the recording medium 18. The display device 20 displays the signal processed image data. The display circuit 19 displays an image on the display device 20. The operation unit 24 instructs to operate the imaging apparatus. The system control unit 25 controls the entire imaging apparatus.

Next, the structure of each control part comprised in the above-mentioned system control part 25 is demonstrated using FIG.
FIG. 2 is a block diagram illustrating an internal configuration of the system control unit 25 of the imaging apparatus. The camera function control unit 27 outputs a control signal for driving the image sensor 12 from the output of the camera signal processing circuit 13 to the image sensor drive circuit 23. The lens drive control unit 28 outputs a control signal to the lens drive circuit 21 that drives the lens of the imaging optical system 11 based on the outputs of the lens and diaphragm position detection sensors. The operation setting / shooting operation instruction control unit 29 outputs a control signal for controlling operation settings and operation instructions related to shooting of the imaging apparatus based on the input operation of the operation switch of the operation unit 24. The display control unit 30 controls the display device 20 to display a photographed image and a display related to photographing. The recording signal processing control unit 31 records the captured image output from the image memory 16 on the recording medium 18.

Hereinafter, a photographing operation in the imaging apparatus of the present embodiment configured as described above will be described.
First, the lens drive circuit 21 drives the aperture, zoom lens, and focus lens in the imaging optical system 11 based on the lens drive control signal from the lens drive control unit 28 in the system control unit 25 to display the subject image. An image is formed on the image sensor 12. The position detection signals of the driven diaphragm, zoom lens, and focus lens actuators are input to the lens drive control unit 28 in the system control unit 25 via the position detection sensor 22 and used for focal length detection. In addition, an aperture position detection signal is input to the camera function control unit 27 and is used for setting an exposure time such as setting an exposure time (shutter speed) of the image sensor 12.

  The image pickup device 12 is driven by a drive pulse generated by the image pickup device drive circuit 23 based on a control signal output from the camera function control unit 27 in the system control unit 25, and photoelectrically converts a subject image into an electric signal. Then, an analog image signal is generated and output. The analog image signal output from the image sensor 12 is converted into a digital image signal by an A / D converter (not shown) disposed in the camera signal processing circuit 13.

  Next, on the basis of the control signal output from the camera function control unit 27 in the system control unit 25, the camera signal processing circuit 13 performs color conversion, white balance correction, gamma correction, etc. on the digital image signal. Image processing, resolution conversion processing, image compression processing, and the like are performed. The image memory 16 is used for temporarily storing a digital image signal being subjected to signal processing in the camera signal processing circuit 13 and storing image data which is a digital image signal subjected to signal processing.

  The motion vector detection circuit 14 performs motion vector detection for detecting a motion vector from the image data (image signal) signal-processed by the camera signal processing circuit 13. Details of the vector detection will be described later. The memory read control circuit 15 performs control for determining a range of image data to be recorded or displayed so that image blur is corrected. This control is performed by a control signal calculated by the shake correction control unit 26 in the system control unit 25 based on the motion vector information detected by the motion vector detection circuit 14.

  The image data signal-processed by the camera signal processing circuit 13 and the image data stored in the image memory 16 are given to the recording signal processing circuit 17. Then, the data is converted into data suitable for recording on the recording medium 18 (for example, file system data having a hierarchical structure) and recorded on the recording medium 18.

  In addition, after the resolution conversion processing is performed by the camera signal processing circuit 13, the display circuit 19 converts the signal into a signal suitable for the display device 20 (for example, an NTSC analog signal or the like) and displays it on the display device 20. The imaging apparatus is configured to perform various settings and operations related to shooting by operating various switches of the operation unit 24, thereby enabling shooting.

Next, vector detection by the motion vector detection circuit 14 for performing blur detection of the imaging apparatus will be described.
As a method for detecting a motion vector of an image, a correlation method based on a correlation calculation, a block matching method, or the like is known. In the block matching method, an input image signal is divided into a plurality of block areas (for example, 8 pixels × 8 lines) having an appropriate size. Then, the difference between the previous field (or frame) and a certain range of pixels is calculated in units of blocks, and the block of the previous field (or frame) that minimizes the sum of the absolute values of the differences is searched. And the relative shift | offset | difference between screens shall show the motion vector of the block.

  For matching operations, Morio Onoe et al., Information Processing Vol. 17, no. 7, p. 634-P. Since it is discussed in detail in 640 July 1976, detailed description thereof is omitted here.

Next, an example of a motion vector detection method using the block matching method will be described with reference to FIG. FIG. 3 is a schematic block diagram of the motion vector detection method.
First, an image signal (field or frame) that is a motion vector detection target is input to a filter 301 that extracts a spatial frequency component. The image signal input to the filter 301 is also input to the image memory 16 of FIG. The filter 301 extracts a spatial frequency component useful for motion vector detection from the image signal. That is, the low spatial frequency component and the high spatial frequency component of the image signal are removed.

  The image signal that has passed through the filter 301 is input to the binarization circuit 302. The binarization circuit 302 binarizes the input image signal with reference to the zero level. Specifically, the sign bit of the output signal is output. The binarized image signal is input to the correlation calculation circuit 303 and the memory 304 as one field period delay means. The correlation operation circuit 303 further receives the image signal of the previous field from the memory 304.

  The correlation calculation circuit 303 divides the image area into block areas of an appropriate size as described above according to the block matching method, performs correlation calculation between the current field and the previous field in units of blocks, and moves the correlation value as a result. Input to the vector detection circuit 305. The motion vector detection circuit 305 detects a motion vector in units of blocks from the calculated correlation value. Specifically, the block of the previous field that minimizes the correlation value is searched, and the relative shift is used as the motion vector.

  This block-based motion vector is input to the system control unit 25. The system control unit 25 determines the entire motion vector from the motion vector in units of blocks by the internal shake correction control unit 26. Specifically, the median value or average value of motion vectors in units of blocks is used as the motion vector of the entire image (hereinafter, representative vector).

  The shake correction control unit 26 calculates a memory read position so as to correct the shake of the image due to the shake of the apparatus based on the input motion vector based on the representative vector, and sends a control signal to the memory read control circuit 15. Is output. The memory read control circuit 15 controls the read position (read address) of the image memory 16 in which the captured image is stored based on the control signal calculated by the blur correction control unit 26. In this way, the image memory 16 in which the reading position is controlled outputs an image signal in which the image blur due to the blur of the apparatus is corrected.

Next, a camera shake correction mode that can be switched by the imaging apparatus of the present embodiment will be described with reference to FIG.
FIG. 4 is a diagram illustrating an example of a mode selection screen displayed on the display device 20 of the imaging apparatus, and the mode to be set relates to camera shake correction.
In FIG. 4, 401 displayed on the display device 20 is a mode item to be set. Reference numerals 402 to 404 are options in the mode 401 to be set, and in this embodiment, there are a plurality of correction modes for correcting image blur. Reference numeral 402 denotes a first shake correction mode, 403 denotes a second shake correction mode, and 404 denotes a shake correction off mode. The mode selection screen is displayed by operating a switch such as a menu provided in the operation unit 24, and can be switched by the photographer intentionally selecting from the above-described three camera shake correction modes displayed.

Next, options for the camera shake correction mode will be described.
First, the first blur correction mode will be described. The first blur correction mode is a mode for performing blur correction when the blur applied to the imaging apparatus is large. Specifically, it is a camera shake correction mode setting that assumes a greater shake correction than general hand-held shooting, such as when a photographer walks while shooting. Shooting while walking is shooting with a lot of blur, and it can be said that it is suitable for shooting with a wide focal length so that the photographer can easily capture the subject image within the angle of view.

Next, the second blur correction mode will be described. The second shake correction mode is a camera shake correction mode setting mainly used for general hand-held shooting, although it is not suitable for correcting a large shake such as when walking. The second blur correction mode has a smaller correction range than the first blur correction mode. For this reason, it is possible to perform camera shake correction that assumes greater camera shake correction than general hand-held shooting, such as a photographer shooting while walking. Depending on the focal length, the correction range in the first blur correction mode and the correction range in the second blur correction mode may be the same, particularly on the telephoto side.
Finally, the blur correction off mode will be described. This mode is a mode in which so-called blur correction is not performed, and is a mode in which blur correction is not set to malfunction when shooting with the imaging device fixed to a tripod. Therefore, since it is not selected in handheld shooting, the subsequent description is omitted.

Next, the difference in blur correction angles at which blur correction can be performed in the first blur correction mode and the second blur correction mode will be described with reference to FIGS. 5 (a) and 5 (b). FIG. 5A is a diagram illustrating the entire imageable area of the image sensor 12.
In FIG. 5A, reference numeral 501 denotes an effective pixel area that is a cutout area that can be imaged by the image sensor 12, and reference numeral 502 denotes an execution pixel area that is a cutout area smaller than the effective pixel area 501.

  The execution pixel area 502 can freely move in the effective pixel area 501 by controlling the reading position of the image sensor 12. As can be seen from FIG. 5A, there are four directions in which the execution pixel area 502 can be moved, but the description is represented by one direction (ΔY) for simplification of description.

In the case of shooting with an imaging device equipped with the imaging device 12 described above, ΔY in FIG. 5A can be converted into a correction angle for blur correction. For example, the focal length of the lens is 2.6 [mm] to 96.2 [mm]. The effective pixel area 501 of the image sensor 12 is 1152 (H) × 864 (V). The execution pixel area 502 is 992 (H) × 558 (V). When the cell size is 2.10 [um], since the surplus pixel ΔY is 153 pixels, the tele-end correction angle is approximately 0.19 [deg] according to the following equation 1.
Blur correction angle Θ = tan −1 ((ΔYx cell size) / focal length) Formula 1
Similarly, at the wide end, it is about 7.0 [deg].

FIG. 5B shows the blur correction angle obtained by the above calculation.
In FIG. 5B, the horizontal axis represents the focal length, the vertical axis represents the moving area on the imaging surface, Θt represents the blur correction angle at the tele end, and Θw represents the blur correction angle at the wide end. The camera shake correction mode in which the camera shake correction angle can be varied in the range of Θt to Θw based on the focal length is the first camera shake correction mode. The blur correction mode is the second blur correction mode. As can be seen from FIG. 5B, even when the number of surplus pixels is the same, a larger blur component can be corrected because the blur correction angle is larger on the wide focal length side.

  Next, the blur correction control signal calculation process processed by the blur correction control unit 26 in the system control unit 25 will be described with reference to the flowchart of FIG. FIG. 6 is a routine that is processed for each vertical synchronization cycle in the overall processing of the system control unit 25.

When the process is started, first, the motion vector of each block detected by the motion vector detection circuit 14 is fetched in S601, and the process proceeds to S602.
Next, in S602, a representative vector that is a motion vector of the entire image is calculated from the motion vector of each block captured in S601, and the process proceeds to S603.

Next, in S603, a shake correction control signal for correcting shake is calculated from the representative vector calculated in S602, and the process proceeds to S604. Details of S603 will be described later.
In step S604, the blur correction control signal calculated in step S603 is output to the memory read control circuit 15, and the process ends.

  As described above, the blur correction control unit 26 in the system control unit 25 performs a process of calculating the blur correction control signal from the motion vector detected by the motion vector detection circuit 14 and outputting the motion correction control signal to the memory read control circuit 15. Is done. Then, the memory read control circuit 15 to which the shake correction control signal output from the shake correction control unit 26 in the system control unit 25 is input controls the read position of the image memory 16 so that the image subjected to the shake correction is performed. A signal can be output.

  Next, calculation of the blur correction control signal for correcting blur from the representative vector described in the flowchart of the blur correction control signal calculation process of FIG. 6 described above (S603 described above) will be described.

FIG. 7 is a flowchart for calculating the shake correction control signal.
In FIG. 7, in step S701, the camera shake correction mode setting of the imaging apparatus is determined. Specifically, it is determined which of the above-described three camera shake correction modes is supported by the bit setting output from the operation mode setting / operation instruction control unit in the system control unit 25. For example, it is determined which of the first blur correction mode (bit 0), the second blur correction mode (bit 1), and the blur correction mode off (bit 2) is set.

  As a result of the determination in S701, if the first shake correction mode (bit 0) is selected, the process proceeds to S702. If the second shake correction mode (bit 1) is set, the process proceeds to S705 and the shake correction mode is turned off (bit 2). In this case, the process proceeds to S708.

First, the case where the process proceeds to the first blur correction mode of S702 will be described.
In S702, it is determined whether or not the shutter speed of the imaging apparatus is equal to or higher than a predetermined value. This is because the longer the exposure time of the image sensor 12, the larger the image blur of the captured image with respect to the blur. In the first blur correction mode aiming at blur correction with a large amplitude, the fastest possible shutter speed is desirable. In the present embodiment, 1/180 seconds is applied as the threshold value of the shutter speed. What is necessary is just to set the optimal value as the threshold value of the shutter speed used here as a threshold value by examination. If the shutter speed is equal to or higher than the predetermined value, the process proceeds to S703. If the shutter speed is equal to or lower than the predetermined value, the process proceeds to S704.

  Next, in S703, since the determination of the shutter speed in S702 is equal to or greater than a predetermined value, a 100% correction gain is set in the shake correction control signal for the calculated representative vector size. That is, the blur correction effect is maximized. When the predetermined correction gain setting is completed for the shake correction control signal, the process proceeds to the next step (S604 described above).

  On the other hand, when the process proceeds to S704, since the determination of the shutter speed in S702 is equal to or less than a predetermined value, a predetermined ratio of correction gain is set in the shake correction control signal for the calculated representative vector size.

  For example, the correction gain for the shutter speed is set by table data, and the shutter speed of 1/180 seconds or less lowers the amplitude of the shake correction control signal at a predetermined attenuation rate. That is, the blur correction effect is reduced. This is because the exposure time of the image sensor 12 is long, and if a large blur occurs during the exposure time, the shot image is blurred, and the effect of blur correction is high when this shot image is recorded and played back. This is because the resolution seems to be deteriorated due to the difference between the low and low cases. In order to reduce such degradation in resolution, calculation is performed so as to limit the output amplitude of the shake correction control signal, and the correction effect of shake correction is reduced. When the predetermined correction gain setting is completed for the shake correction control signal, the process proceeds to the next step (S604 described above).

Next, the case of S705 that has proceeded to the second blur correction mode will be described.
In S705, it is determined whether or not the shutter speed of the imaging apparatus is equal to or higher than a predetermined value. Since this is the same as S702, description thereof is omitted. In the present embodiment, 1/120 second is applied as the threshold value of the shutter speed.

  The reason why the shutter speed serving as the threshold is different from that in the first blur correction mode is that the second blur correction mode does not assume a large-amplitude blur correction as in walking. The shutter speed threshold value may be set to an optimum value by examination, and there is no problem even if the same setting as that in the first blur correction mode is set. If the shutter speed is equal to or higher than the predetermined value, the process proceeds to S706. If the shutter speed is equal to or lower than the predetermined value, the process proceeds to S707.

  Next, in S706, since the determination of the shutter speed in S705 is equal to or greater than a predetermined value, the blur correction control signal for the calculated representative vector size is 100% as in the case of the first blur correction mode setting. Set the correction gain to maximize the blur correction effect. When the predetermined correction gain setting is completed for the shake correction control signal, the process proceeds to the next step (S604 described above).

  On the other hand, if the process proceeds to S707, since the determination of the shutter speed in S705 is equal to or less than a predetermined value, the blur correction control signal corresponding to the calculated representative vector size is displayed as in the first blur correction mode setting. A predetermined ratio of correction gain is set to reduce the blur correction effect. The correction gain setting here is set to a lower attenuation rate than in the first blur correction mode.

  The reason for making the correction gain different from that in the first blur correction mode is that the second blur correction mode does not assume a large-amplitude blur correction at the time of shooting while walking, and gives priority to normal blur correction. Is to increase Further, since the targeted effect is the same as that in the first blur correction mode setting, the description thereof is omitted. When the predetermined correction gain setting is completed for the shake correction control signal, the process proceeds to the next step (S604 described above).

Finally, the case of S708 which has proceeded to the blur correction mode off will be described.
In S708, since setting is made not to perform blur correction, a correction gain of 0% is set to the blur correction control signal for the calculated representative vector size. Therefore, no blur correction is performed. When the predetermined correction gain setting is completed for the shake correction control signal, the process proceeds to the next step (S604 described above).

Next, FIG. 8 shows a change in the shake correction control signal in which the above-described correction gain setting is performed.
In FIG. 8, the horizontal axis represents the shutter speed, the vertical axis represents the gain ratio, 801 is the attenuation characteristic of the blur correction control signal in the first blur correction mode, and 802 is the attenuation characteristic of the second blur correction control signal. It is.

  Since the blur correction control signal below the shutter speed threshold set in both the first blur correction mode and the second blur correction mode is attenuated, the blur correction effect is reduced. During the exposure time of the image sensor 12, when the shutter speed is slow, the blur correction effect is reduced, thereby reducing the degradation of the sense of resolution of the captured image. In particular, since the reduction in the blur correction effect is larger in the first blur correction mode, the image quality deterioration is reduced even when there is a large blur such as during walking shooting.

  As described above, in the present embodiment, when the camera shake correction mode setting by the camera shake correction mode setting unit is set to the first camera shake correction mode, and the exposure time of the image sensor 12 is equal to or longer than the predetermined exposure time. The output amplitude of the shake correction control signal is attenuated. Thereby, even when the camera shake correction mode of the imaging apparatus is set to the first camera shake correction mode, it is possible to reduce degradation of the resolution of the captured image during the exposure time of the image sensor.

<Second Embodiment>
Next, this embodiment will be described.
In the first embodiment described above, based on the camera shake correction mode setting by the camera shake correction mode setting means, the output amplitude of the camera shake correction control signal is set to a predetermined ratio of the correction gain when the image sensor has exceeded a predetermined exposure time. Set to attenuate. Then, it has been explained that the reduction in image quality due to the deterioration of the resolution of the captured image is reduced.

  On the other hand, in the present embodiment, based on the camera shake correction mode setting, the attenuation factor of the correction gain of the output amplitude of the shake correction control signal is lowered as the focal length becomes the tele side, thereby reducing image quality deterioration on the wide side. In addition, the focal length improves the blur correction effect on the tele side. Since the configuration according to this embodiment is the same as that of the first embodiment, the description thereof is omitted.

  Next, on the basis of the camera shake correction mode setting, the shake correction control unit 26 executes in order to change the shake correction effect by lowering the attenuation factor of the correction gain of the output amplitude of the camera shake correction control signal as the focal length becomes the tele side. The process to be performed will be described with reference to the flowchart of FIG.

  FIG. 9 is a flowchart illustrating in detail the blur correction control signal calculation process (S603 described above) for correcting blur from the representative vector described in the flowchart of the blur correction control signal calculation process of FIG. 6 described above.

  In FIG. 9, in step S901, the camera shake correction mode setting of the imaging apparatus is determined. The specific determination of the mode setting is the same as that in the first embodiment, and a description thereof will be omitted. If the determination result of the camera shake correction mode setting is the first camera shake correction mode (bit 0), the process proceeds to S902. If the camera shake correction mode setting is the second camera shake correction mode (bit 1), the process proceeds to S905, and the camera shake correction mode is turned off (bit 2). ), The process proceeds to S908.

First, a description will be given from the case of S902 that has advanced to the first blur correction mode.
In S902, it is determined whether or not the focal length of the imaging apparatus is equal to or greater than a predetermined focal length (predetermined value). This is because the image blur of the captured image with respect to the blur becomes larger as the focal length of the image pickup device is telephoto side. When the focal length is equal to or greater than a predetermined focal length, the blur correction is prioritized.

  Further, in the case of shooting at the telephoto end with the focal length, it is difficult for the photographer to put the subject image within the shooting angle of view, and thus shooting while walking is not generally performed. Therefore, it is desirable to improve the blur correction effect at the telephoto focal length even in the first blur correction mode intended for large amplitude blur correction.

  In the present embodiment, the tele-end focal length is applied as a threshold value. The focal length serving as a threshold here may be set to an optimum value by examination, or may be a focal length that is equal to or greater than a predetermined value near the telephoto end. As a result of the determination in S902, if the focal length is at the tele end, the process proceeds to S903, and if the focal distance is wider than the tele end, the process proceeds to S904.

  Next, in S903, since the determination of the focal length in S902 is the tele end, a correction gain of 100% is set in the shake correction control signal for the calculated representative vector size. That is, the blur correction effect is maximized. In this embodiment, a correction gain based on the focal length is set, and the effect of blur correction is reduced as the focal length changes to the wide side. When the predetermined correction gain setting is completed for the shake correction control signal, the process proceeds to the next step (S604 described above).

  In S904, since the determination of the focal length in S902 is on the wide side from the telephoto end, a predetermined ratio of correction gain is set in the shake correction control signal for the calculated representative vector size. For example, the correction gain for the focal length is given as table data, and the blur correction control signal is lowered at a predetermined attenuation rate for the focal length on the wide side from the telephoto end.

  That is, the blur correction effect is reduced. This is because blurring becomes harder to understand even if the effect of blurring correction decreases as the focal length becomes wider, and it becomes easier for the photographer to capture the subject image within the shooting angle of view as the focal length becomes wider. This is because blurring applied to the imaging device may increase when shooting is performed. As described above, as the blur applied to the apparatus increases, the image blur of the photographed image starts to stand out and the resolution is deteriorated as described above. Therefore, in order to reduce resolution degradation, the correction effect of blur correction is reduced. When the predetermined correction gain setting is completed for the shake correction control signal, the process proceeds to the next step (S604 described above).

Next, the case of S905 that has proceeded to the second blur correction mode will be described.
In S905, it is determined whether or not the focal length of the imaging apparatus is equal to or greater than a predetermined focal length (predetermined value). Since this determination has the same meaning as in S902, detailed description thereof is omitted. If the determined focal length is at the tele end, the process proceeds to S906. If the focal distance is wider than the tele end, the process proceeds to S907.

  In S906, since the determination of the focal length in S905 is the tele end, a correction gain of 100% is set in the shake correction control signal for the calculated representative vector size. That is, the blur correction effect is maximized. In the present embodiment, a correction gain based on the focal length is applied to reduce the effect of blur correction as the focal length changes to the wide side. When the predetermined correction gain setting is completed for the shake correction control signal, the process proceeds to the next step (S604 described above).

  In S907, since the determination of the focal length in S905 is on the wide side from the telephoto end, a predetermined ratio of correction gain is set in the shake correction control signal for the calculated representative vector size. For example, the correction gain for the focal length is given as table data, and the blur correction control signal is lowered at a predetermined attenuation rate for the focal length on the wide side from the telephoto end.

  That is, the blur correction effect is reduced. The correction gain setting here is set to a lower attenuation rate than in the first blur correction mode. The reason for making the correction gain different from that in the first blur correction mode is that the second blur correction mode does not assume a large-amplitude blur correction at the time of shooting while walking, and gives priority to normal blur correction. Is to increase Further, since the setting of the correction gain has the same meaning as in S904, detailed description thereof is omitted. When the predetermined correction gain setting is completed for the shake correction control signal, the process proceeds to the next step (S604 described above).

  Finally, the case of S908 that has proceeded to the blur correction mode off will be described. In S908, since the setting for not performing the blur correction is made, a correction gain of 0% is set to the blur correction control signal for the calculated representative vector size. Therefore, no blur correction is performed. When a predetermined gain setting is completed for the shake correction control signal, the process proceeds to the next step (S604 described above).

Next, FIG. 10A shows a change in the gain setting for the above-described blur correction.
In FIG. 10A, the horizontal axis represents the focal length, the vertical axis represents the gain, 1001 represents the attenuation characteristic of the blur correction control signal in the first blur correction mode, and 1002 represents the second blur correction control signal. Attenuation characteristics. It can be seen that the blur correction effect is reduced because the blur correction control signal equal to or less than the tele-end focal length set as the threshold value in both the first blur correction mode and the second blur correction mode is attenuated. In the present embodiment, the focal length threshold is the tele end focal length, but the focal length near the tele end may be set as the threshold.

  FIG. 10B shows the attenuation characteristics when the focal length in the vicinity of the telephoto end is used as a threshold value for setting the correction gain of the shake correction control signal. 1003 is an attenuation characteristic of the shake correction control signal when the focal length is 30 times, and 1004 is an attenuation characteristic of the shake correction control signal when the focal length is 25 times. In the characteristic of FIG. 10B, it can be seen that the blur correction effect at the focal length near the telephoto end is improved.

  As described above, when the camera shake correction mode setting by the camera shake correction mode setting unit is set to the first camera shake correction mode and the focal length is equal to or less than the predetermined focal length, the output amplitude of the camera shake correction control signal is attenuated. I tried to do it. As a result, even when the camera shake correction mode of the apparatus is set to the first camera shake correction mode, it is possible to reduce degradation of the resolution of the captured image as the focal length becomes wider. In addition, the blur correction effect at the tele end can be improved.

  Although the present invention has been described in detail based on preferred embodiments thereof, the present invention is not limited to these specific embodiments, and various forms within the scope of the present invention are also included in the present invention. included. You may combine the above-mentioned embodiment suitably.

(Other examples)
The present invention can also be realized by executing the following processing. That is, software (computer program) that realizes the functions of the above-described embodiments is supplied to a system or apparatus via a network or various computer-readable storage media. Then, the computer (or CPU, MPU, etc.) of the system or apparatus reads out and executes the program.

DESCRIPTION OF SYMBOLS 11 Imaging optical system, 12 Image sensor, 13 Camera signal processing circuit, 14 Motion vector detection circuit, 15 Memory read-out control circuit, 16 Image memory, 24 Operation part, 25 System control part, 26 Shake correction control part, 27 Camera function control 28, lens drive control unit, 29 operation setting / operation instruction control unit, 30 display control unit, 31 recording signal processing control unit

Claims (6)

Imaging means for converting a subject image formed on an imaging surface by an imaging optical system and outputting an image signal;
Exposure time setting means for setting an exposure time for the imaging means to generate the image signal;
Blur detection means for detecting the blur of the device;
Blur correction means for correcting image blur caused by the blur of the apparatus;
At least a first blur correction mode and a second blur correction mode having a narrower correction range than the first blur correction mode are set as correction modes for correcting the blur of an image caused by the blur of the device. A shake correction mode setting means capable of calculating a shake correction control signal based on a detection output of the shake detection means, and a shake correction control means for driving the shake correction means according to the correction mode;
Have
In the first blur correction mode of the correction modes, the blur correction control means is configured to attenuate the output amplitude so that the output amplitude is attenuated when the exposure time of the exposure time setting means exceeds a predetermined time. A correction control signal is calculated, and in the case of the second blur correction mode among the correction modes, the blur correction control signal is calculated at a lower rate of attenuation of the output amplitude than in the first blur correction mode. An imaging apparatus characterized by the above. Imaging means for converting a subject image formed on an imaging surface by an imaging optical system and outputting an image signal;
A focal length detection means for detecting a focal length of the imaging optical system;
Blur detection means for detecting the blur of the device;
Blur correction means for correcting image blur caused by the blur of the apparatus;
At least a first blur correction mode and a second blur correction mode having a narrower correction range than the first blur correction mode are set as correction modes for correcting the blur of an image caused by the blur of the device. A shake correction mode setting means capable of calculating a shake correction control signal based on a detection output of the shake detection means, and a shake correction control means for driving the shake correction means according to the correction mode;
Have
In the first shake correction mode among the correction modes, the shake correction control means sets the output amplitude of the shake correction control signal when the output of the focal length detection means is equal to or less than a predetermined focal length. In the case of the second blur correction mode among the correction modes, if the output of the focal length detection means is equal to or less than a predetermined focal length, the output is greater than that in the first blur correction mode. An image pickup apparatus, wherein the blur correction control signal is calculated by reducing a rate at which the amplitude is attenuated.   The imaging apparatus according to claim 1, wherein the blur detection unit is a motion vector detection unit that detects a motion vector from an image signal output from the imaging unit.   The imaging apparatus according to claim 1, wherein the blur correction unit stores a photographed image in an image memory, and corrects the blur by controlling an address of the image memory. A method for controlling an imaging apparatus having imaging means for converting a subject image formed on an imaging surface by an imaging optical system and outputting an image signal,
An exposure time setting step for setting an exposure time for the imaging means to generate the image signal;
A shake detection step for detecting a shake of the device;
A blur correction step for correcting the blur of the image due to the blur of the device;
At least a first blur correction mode and a second blur correction mode having a narrower correction range than the first blur correction mode are set as correction modes for correcting the blur of an image caused by the blur of the device. A blur correction mode setting step that calculates the blur correction control signal based on the detection output of the blur detection step, and a blur correction control step that drives and controls the blur correction step according to the correction mode;
Have
In the blur correction control step, in the first blur correction mode among the correction modes, the blur correction control step attenuates the output amplitude when the exposure time in the exposure time setting step exceeds a predetermined time. A correction control signal is calculated, and in the case of the second blur correction mode among the correction modes, the blur correction control signal is calculated at a lower rate of attenuation of the output amplitude than in the first blur correction mode. A method for controlling an image pickup apparatus. A method for controlling an imaging apparatus having imaging means for converting a subject image formed on an imaging surface by an imaging optical system and outputting an image signal,
A focal length detection step for detecting a focal length of the imaging optical system;
A shake detection step for detecting a shake of the device;
A blur correction step for correcting the blur of the image due to the blur of the device;
At least a first blur correction mode and a second blur correction mode having a narrower correction range than the first blur correction mode are set as correction modes for correcting the blur of an image caused by the blur of the device. A blur correction mode setting step that calculates the blur correction control signal based on the detection output of the blur detection step, and a blur correction control step that drives and controls the blur correction step according to the correction mode;
Have
In the blur correction control step, in the first blur correction mode of the correction modes, the output amplitude of the blur correction control signal is set when the output of the focal length detection step is equal to or less than a predetermined focal length. In the second blur correction mode among the correction modes, when the output of the focal length detection step is equal to or less than a predetermined focal length, the output is greater than that in the first blur correction mode. A method for controlling an imaging apparatus, wherein the blur correction control signal is calculated by reducing a rate at which the amplitude is attenuated.

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