JP3896015B2 - Image pickup device with shake correction function - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image pickup apparatus with a shake correction function. More specifically, an image of a subject is formed on a light receiving surface of an image pickup element by a photographing optical system, converted into an electric signal, and taken into the acquired electric signal. The present invention relates to an image pickup apparatus with a shake correction function that automatically adjusts the focus lens to a focus position determined based on the image and corrects image shake on a light receiving surface due to camera shake caused by camera shake during shooting, for example. Is.
[0002]
[Prior art]
Conventionally, this type of image pickup apparatus is known as a video camera or a digital still camera. For example, in the case of a digital still camera, due to the limit of sensitivity at the time of exposure of an image pickup device composed of a CCD (charge coupled device), Such a short shutter time is difficult to realize, and blurs such as “image flow” tend to occur in an image captured by camera shake.
[0003]
Shake correction is to prevent blurring of the image due to camera shake during exposure, and usually detects angular velocities about two fixed axes orthogonal to the optical axis of the camera, and the camera “ Find the “tilt angle due to shake” and move the correction lens included in the photographic optical system, adjust the direction of the optical axis, or move the image sensor so that the image shake corresponding to this tilt angle is corrected. Thus, the elements of the driven system such as the correction lens have a mechanism that moves in two axial directions.
[0004]
In general, a mechanism for correcting image blur includes a correction member that independently corrects image blur that occurs when the imaging position on the light receiving surface moves in two different directions orthogonal to the optical axis of the camera, A central processing unit (CPU) of a microcomputer (hereinafter referred to as a microcomputer) detects a shake amount in two directions based on an output of a shake detection sensor such as an angular velocity sensor, and cancels the image shake based on the detected shake amount. In addition, the image forming position on the light receiving surface is displaced in two directions by the correction member.
[0005]
More specifically, in order to detect the amount of shake in two directions based on the detection output of the shake detection sensor, the microcomputer digitally converts an analog electrical signal, which is the sensor output, at a predetermined sampling period, and imports the acquired digital signal. The shake amount is detected by the value. Next, a displacement amount corresponding to the detected shake amount in each direction is calculated, and driving for driving the actuator constituting the correction member so as to displace the imaging position on the light receiving surface by an amount corresponding to the displacement amount. By outputting a signal to the actuator, image blur that may occur in each direction due to camera shake is eliminated.
[0006]
The member that is actually actuated by the actuator to correct the image blur is a correction lens in a lens optical system that is a photographing optical system that determines the image formation position of the image, or an image is formed in an electronic camera. Any CCD image sensor can be used as long as it can change the image formation position. Then, the above-described correction operation from taking in the sensor output to driving the correction member is performed in the same manner with respect to the shake in any direction.
[0007]
This type of camera is generally provided with a shake correction ON / OFF mode, and the camera user can operate and stop the shake correction function by arbitrarily switching and selecting the mode. When the shake correction mode is in the operating state, each angular velocity sensor always detects camera shake, calculates the amount of displacement for shake correction based on the detected shake, and drives the correction means. It is done with a microcomputer.
[0008]
Also, in this type of imaging apparatus, prior to actual shooting, an image is formed on the light-receiving surface of the image sensor by the shooting optical system and converted into an electrical signal before the actual shooting. Some have an additional function of autofocus that determines the focal position and automatically adjusts the focal point to the determined focal position.
[0009]
[Problems to be solved by the invention]
By the way, the correction operation of the correction member must be performed as faithfully as possible to the output change of the sensor that detects the shake and with good followability. For this purpose, the microcomputer captures the sensor output by shortening the sampling cycle as much as possible, and the microcomputer outputs to the actuator that constitutes the correction member and changes the drive signal that determines the displacement amount for shake correction with the smallest possible gradation. In order to achieve more accurate shake correction, the microcomputer is required to have high-speed processing capability.
[0010]
In particular, in an image pickup apparatus having an autofocus function, a microcomputer mounted on the image pickup apparatus generally has to perform an autofocus process in addition to the above-described image blur correction process. For this reason, the burden on the microcomputer becomes heavier, and in order to perform shooting as quickly as possible, a microcomputer capable of high-speed processing is required, which has been a major factor in increasing the cost.
[0011]
By the way, when determining the in-focus position based on the image of the subject imaged on the light receiving surface of the image sensor, it is determined that the subject image is in focus when the contrast in the pixel unit of the subject image is maximum. In such a case, when blurring occurs due to image blur, the contrast is lowered and it is difficult to accurately obtain the in-focus position. Therefore, although it is necessary to perform shake correction even during autofocus, in order to determine the position of the maximum contrast, the direction of viewing the contrast in pixel units is not necessarily equal in all directions, and the direction of shake correction The direction used to determine the in-focus position does not match. For this reason, the shake correction in the non-matching direction can be said to be a useless correction in a sense when determining the focus position.
[0012]
Therefore, in view of the above-described points, the present invention changes the ratio of the period of shake correction corresponding to the direction of shake when detecting the in-focus position for autofocus, to reduce the cost. An object of the present invention is to provide an imaging apparatus with a shake correction function that can appropriately perform autofocus without increasing the speed.
[0013]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the invention according to claim 1 of the present invention forms an image of a subject on a light receiving surface of an image pickup device by a photographing optical system having a focus lens, converts it into an electric signal, takes it in, and takes it in This is an image pickup apparatus with a shake correction function that automatically adjusts the focus lens to the in-focus position determined based on the electrical signal and corrects the image shake on the light receiving surface due to the shake. A shake detecting means for detecting a shake in two directions orthogonal to the optical axis of the photographing optical system and outputting a detection signal corresponding to the magnitude of the detected shake in the two directions; A shake correction means for independently displacing the image formation position on the light receiving surface, and a detection signal output from the shake detection means, and the image formation position on the light reception surface is determined based on the acquired detection signal. Drive control means for drivingly controlling the shake correction means so as to correct image shake due to shake by being displaced in two directions, and the drive control means is configured such that the shake correction means is an image forming position on the light receiving surface. An image pickup apparatus with a shake correction function, wherein a ratio of a period for correcting a shake by displacing the lens in each of the two directions is temporarily different from a ratio of a period at the time of shooting when determining the in-focus position. Exist.
[0014]
According to the above-described configuration of the first aspect, the shake detection unit detects the shake in two directions orthogonal to the optical axis of the photographing optical system having the focus lens and the detected two-way shake. A corresponding detection signal is output. The drive control means captures the detection signal output from the shake detection means, drives and controls the shake correction means based on the captured detection signal, and shifts the imaging position on the light receiving surface of the image sensor in two directions. Corrects image blur caused by. The drive control means automatically adjusts the focus lens prior to actual shooting based on the electric signal obtained by converting the image of the subject imaged on the light receiving surface of the image sensor by the imaging optical system. When determining the in-focus position, the shake correction means temporarily shifts the imaging position in two directions to change the shake correction period ratio so as to be different from the period ratio at the time of shooting.
[0015]
In this way, when determining the in-focus position for autofocus, the pre-shooting operation for determining the in-focus position is performed by temporarily changing the ratio of the period for shake correction from the period ratio at the time of shooting. The period of shake correction in a direction that is not always necessary can be lengthened, with a cycle ratio corresponding to the directionality required for shake correction when determining the shake correction focus position and shake correction during shooting. Since shake correction can be performed, waste is eliminated and both shake corrections can be appropriately performed without increasing the burden.
[0016]
According to a second aspect of the present invention, in the imaging apparatus with a shake correction function according to the first aspect, the determination of the in-focus position is performed by comparing the captured electric signal in units of pixels adjacent in one direction of the two directions. When the pixel comparison method is used, the ratio of the periods is changed so that the period in the other direction is longer than the period for correcting the shake by displacing the imaging position on the light receiving surface in the one direction. It exists in the imaging device with a shake correction function that is characteristic.
[0017]
According to the configuration of claim 2, when the in-focus position is determined by a pixel comparison method in which the captured electric signal is compared in units of adjacent pixels in one direction in two directions, the light receiving surface in this one direction. The ratio of the period is changed so that the period in the other direction becomes longer than the period of shake correction by displacing the upper imaging position, so the focus position can be determined while reducing the burden by increasing the period. Can be done appropriately.
[0018]
According to a third aspect of the present invention, in the imaging apparatus with a shake correction function according to the first aspect, a pixel comparison method for comparing the taken-in electric signal in units of adjacent pixels in the two directions in determining the in-focus position. The period in the other direction is longer than the period of correcting the shake by displacing the imaging position on the light receiving surface in the weighted direction when determining the in-focus position. The present invention resides in an image pickup apparatus with a shake correction function, characterized in that the ratio is changed.
[0019]
According to the configuration of the third aspect, when the focus position is determined by a pixel comparison method in which the captured electric signal is compared in units of adjacent pixels in two directions, it is important to determine the focus position. The ratio of the period is changed so that the period in the other direction becomes longer than the period for correcting the shake by displacing the imaging position on the light receiving surface in the selected direction, reducing the burden by increasing the period. It is possible to appropriately determine the in-focus position while satisfying the direction of shake correction when determining the in-focus position.
[0020]
According to a fourth aspect of the present invention, in the imaging apparatus with a shake correction function according to any one of the first to third aspects, the changed period is acquired until the image signal for determining the in-focus position is captured. The imaging apparatus with a shake correction function is characterized in that it is held and then returned to the ratio of the period before the change.
[0021]
According to the configuration of the fourth aspect, since the changed cycle is held until the image signal for determining the in-focus position is captured and then returned to the ratio of the cycle before the change, the shake for actual shooting is performed. Correction can be started early.
[0022]
The invention according to claim 5 of the present application is the imaging device with shake correction function according to any one of claims 1 to 4, wherein the shake correction function is activated by operating the shake correction unit and the drive control unit. Or further comprising selection means for selecting one of the off states in which the shake correction function does not work by stopping the operation of the shake correction means and the drive control means. Even when the off-state is selected, when determining the in-focus position, the shake correction unit and the drive control unit are activated, and the shake ratio is different from that at the time of shooting. The present invention resides in an imaging apparatus with a shake correction function, wherein the correction means is driven and controlled.
[0023]
According to the configuration of the fifth aspect, even when the selection unit selects the off state in which the shake correction function does not work by stopping the operation of the shake correction unit and the drive control unit, Is determined, the shake correction unit and the drive control unit are activated, and the shake correction unit is driven and controlled with a ratio of a period different from that at the time of shooting, so even if the shake correction is not performed at the time of shooting, The focus position for autofocus can be accurately determined with a minimum increase in burden.
[0024]
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing an embodiment of an imaging apparatus according to the present invention, and schematically shows a schematic configuration of a digital still camera with a shake correction function.
[0025]
In FIG. 1, a digital still camera with a shake correction function forms an image of a subject on a light receiving surface 13a of an image pickup means 13 that is also built in the camera body by a photographing optical system 11 built in the camera body. The image is converted into a signal and captured, and image blur caused by camera shake at the time of shooting is corrected, so that the influence of shooting on shooting is minimized.
[0026]
Specifically, the photographing optical system 11 includes a zoom lens 11A and a focus lens 11B as imaging lenses, and an imaging unit 13 is disposed on the optical axis 11C. The image of the subject formed on the light receiving surface 13a of the image pickup means 13 by the photographing optical system 11 is converted into an electric signal and taken into a microcomputer (microcomputer) 15 built in the camera body.
[0027]
The microcomputer 15 includes a memory for storing programs and data, a central processing unit (microcomputer) that operates according to the program stored in the memory, an analog-digital (AD) converter, and the like.
[0028]
The digital still camera also detects the angular velocities around two axes x and y orthogonal to the optical axis 11C and orthogonal to each other, and outputs a detection signal corresponding to the detected angular velocity. An angular velocity sensor 17ax and a y-axis angular velocity sensor 17ay, and an x-axis sensor amplifier 17bx and a y-axis sensor amplifier 17by that amplify detection signals output from the respective angular velocity sensors to a predetermined level, are built in the camera body. .
[0029]
The x-axis angular velocity sensor 17ax and the x-axis sensor amplifier 17bx detect the x-axis angular velocity detection means 17x that detects the angular velocity around the axis x, and the y-axis angular velocity sensor 17ay and the y-axis sensor amplifier 17by detect the angular velocity around the axis y. Each of the y-axis angular velocity detection means 17y is configured to detect, as a whole, an optical axis of the photographing optical system and two directions of vibration that are orthogonal to each other, and outputs a detection signal corresponding to the magnitude of the detected two-way vibration. The shake detection means is configured.
[0030]
The microcomputer 15 digitally converts detection signals corresponding to the detected angular velocities output by the x-axis angular velocity detection means 17x and the y-axis angular velocity detection means 17y at a predetermined sampling period, and integrates the acquired detection signals. Thus, the “tilt angle due to shake” of the camera for each axis is calculated. Subsequently, the microcomputer 15 determines, based on the calculated inclination angle, a movement amount of the image formed on the light receiving surface 13a of the imaging unit 13 in the axis x direction and the axis y direction on the light receiving surface 13a. Based on the angular velocities detected by the x-axis angular velocity detecting means 17x and the y-axis angular velocity detecting means 17y, the displacement amounts for respectively displacing the imaging positions on the light receiving surface in two directions by the calculated movement amounts are obtained. calculate. In this way, the microcomputer 15 drives the shake correction means to determine the amount of displacement for displacing the imaging position on the light receiving surface in two directions, respectively, based on the detection signal.
[0031]
The calculation of the displacement amount by the microcomputer 15 is the amount of movement of the image on the light receiving surface 13a caused by the inclination of the camera by the inclination angle calculated for each axis, that is, the axis x of the image forming position on the light receiving surface 13a. It is obtained by calculating the amount of movement in the direction and the axis y direction.
[0032]
The digital still camera also moves the light receiving surface 13a of the image pickup means 13 independently in the axis x direction and the axis y direction based on the calculated displacement amount in the axis x direction and the axis y direction. The x-direction correction actuator 19ax and the y-direction correction actuator 19ay that return the image forming position that has moved to the original position, and the x-direction correction drive circuit 19bx and the y-direction correction drive circuit that drive the x-direction correction actuator 19ax and the y-direction correction actuator 19ay, respectively. 19by, and these are built in the camera body. The x-direction correction actuator 19ax and the x-direction correction drive circuit 19bx constitute an x-direction shake correction means 19x, and the y-direction correction actuator 19ay and the y-direction correction drive circuit 19by constitute a y-direction shake correction means 19y, respectively. A shake correcting means for independently displacing the imaging position on the light receiving surface in two directions orthogonal to the optical axis of the system is constructed.
[0033]
The microcomputer 15 also operates the x-direction shake correction unit 19x and the y-direction shake correction unit 19y based on the calculated displacement amount for shake correction, and the imaging position moved on the light receiving surface 13a due to the shake is restored. The correction driving operation for returning to the position is controlled. Therefore, the microcomputer 15 takes in the detection signal output from the shake detection means, and based on the acquired detection signal, the shake correction is performed so as to correct the image shake due to the shake by displacing the imaging position on the light receiving surface in two directions. Acts as drive control means for driving and controlling the means.
[0034]
The digital still camera further includes a switch (not shown) that is turned on and off by an operation of a shake correction button 21 provided on the outside of the camera body as selection means for selecting whether to operate or stop the shake correction function. A zoom control unit 23A and a focus control unit 23B that control the zoom and focus by driving the zoom lens 11A and the focus lens 11B as imaging lenses are included in the camera body.
[0035]
The microcomputer 15 also has a zoom operation button 25A and a release operation button 25B provided outside the camera body, in addition to a process for shake correction performed based on a signal of a switch (not shown) that is turned on / off by the operation of the shake correction button 21. Based on the above operation, other processes such as zoom driving and focus driving of the zoom lens 11A and the focus lens 11B of the photographing optical system 11 are performed via the zoom control unit 23A and the focus control unit 23B, respectively.
[0036]
In particular, when the release operation button 25B is operated, the autofocus control unit 23B automatically adjusts the focus lens to the in-focus position under the control of the microcomputer 15 at an initial stage before shooting. To work.
[0037]
First, when the microcomputer 15 is in the ON state in which the shake correction function is activated by the operation of the shake correction button 21, the imaging unit 13 formed of a CCD is used by the photographing optical system 11 having the focus lens 11 </ b> B according to the operation of the release operation button 25 </ b> B. The image of the subject is formed on the light receiving surface 13a and converted into an electric signal, and the in-focus position is determined based on the acquired electric signal.
[0038]
For this purpose, on the light receiving surface 13a of the image pickup means 13, as shown in FIG. 2, an autofocus determination region R is defined at the center of the light receiving surface 13a. An in-focus position is determined using image information of an image of a subject that is captured after being converted into a signal. Further, the microcomputer 15 converts the image portion of the subject imaged in the determination region R into an electric signal for each movement while moving the focus lens 11B along the optical axis 11C by a predetermined amount within the movable range. take in. Then, based on the image information of the captured image portion of the subject, the microcomputer 15 obtains the charge amount ai in comparison with the adjacent pixel ai + 1 in the CCD pixel unit as shown in FIG. Based on the evaluation value, it is searched where the in-focus position is in the movable range of the focus lens 11B.
[0039]
Specifically, for each predetermined amount of movement, the charge amount ai (i = 1, 2,... N) of each pixel in the determination region R is compared with the charge amount ai + 1 of a pixel adjacent in the region R in the horizontal direction. As a result, for example, the absolute value | (ai−ai + 1) | of the charge amount subtraction is obtained, and the absolute value which is the comparison result is added in the same region R to sequentially create the evaluation value Σ | (ai−ai + 1) | To do. When an evaluation value within the movable range is created, a position where the evaluation value is maximized is searched for, and this position is regarded as a focus position. This is based on the fact that when the light is not in focus, the light beam spreads to surrounding pixels, so that the difference in charge amount between each pixel and the adjacent pixel is smaller than that when the light is in focus.
[0040]
The evaluation value can be obtained by using a horizontal pixel comparison method that determines the in-focus position using the charge amount difference between adjacent pixels in the horizontal direction, and a vertical pixel that uses the charge amount difference between adjacent pixels in the vertical direction. Although there is a comparison method and a method that uses both methods together, the charge amount difference is smaller than when there is no shake because it mixes with the light rays that enter around when the imaging device is shaken, Shake correction needs to be performed.
[0041]
In the present invention, when determining the in-focus position for auto-focusing before the shooting, the shake correction at the time of shooting does not have to be the same, and at least the shake that satisfies the determination of the in-focus position. Paying attention to the correction, the shake correction means temporarily shifts the imaging position on the light receiving surface in two directions to correct the shake, and temporarily determines the focus position when determining the in-focus position. It is different from the ratio of the period when shooting.
[0042]
Specifically, for example, when the ratio of the correction period at the time of shooting is 1: 1 (vertical: horizontal) in two directions, the horizontal pixel comparison method corresponds to horizontal, for example, 3: 1. The shake correction cycle in the vertical direction corresponding to the vertical direction is lengthened without changing the shake correction cycle in the horizontal direction. In this way, by increasing the shake correction period in a direction in which shake does not cause a problem in determining the in-focus position, the amount of processing increases when determining the in-focus position for performing autofocus. The burden on the microcomputer can be reduced by extending the shake correction cycle.
[0043]
In addition, paying attention to the directionality of image shake, in order to reduce the burden on the microcomputer, the shake correction period in the direction in which shake is unlikely to occur is increased in advance, for example, the shake correction cycle ratio at the time of shooting is 1: 3. There are cases like this. In such a case, the burden on the microcomputer will not be reduced, but by temporarily reversing the shake correction cycle ratio to 3: 1 in determining the in-focus position, and making it different from the cycle ratio at the time of shooting, The in-focus position can be appropriately determined without increasing the burden on the microcomputer.
[0044]
Further, for example, the ratio of correction periods at the time of shooting is 1: 1 (vertical: horizontal) in two directions, and the vertical pixel comparison method is, for example, 1: 3 in contrast to the horizontal direction pixel comparison method. As described above, the shake correction cycle in the horizontal direction corresponding to the horizontal is lengthened without changing the shake correction cycle in the vertical direction corresponding to the vertical. Furthermore, in the bi-directional pixel comparison method for comparing pixels in both vertical and horizontal directions, if the comparison is made with emphasis on one direction, the period in the other direction is lengthened, and the correction corresponding to the weighting ratio is made. By changing to the cycle ratio, the burden on the microcomputer can be reduced by increasing the cycle.
[0045]
Thus, by increasing the shake correction period in a direction in which shake does not cause a problem in determining the focus position, the microcomputer increases the processing amount when determining the focus position for autofocusing. Can be reduced by extending the shake correction period.
[0046]
In the above configuration, in the normal shake correction when the shake correction function is activated by turning on the shake correction button 21, the microcomputer 15 and the optical axis 11 </ b> C of the photographing optical system 11 with respect to the imaging means 13 and 2 orthogonal to each other. When vibration occurs around one axis x and y, the x-axis angular velocity sensor 17ax and the x-axis angular velocity detector 17x including the x-axis sensor amplifier 17bx, and the y-axis including the y-axis angular velocity sensor 17ay and the y-axis sensor amplifier 17by. Detection signals corresponding to the angular velocities generated by the angular velocity detection means 17y are digitally converted and captured at a first predetermined sampling period. Then, the microcomputer 15 detects the tilt angle based on the acquired detection signal, and calculates the shake amount and the displacement amount for correcting the shake based on the tilt angle.
[0047]
Further, the microcomputer 15 outputs a drive signal to the correction drive circuits 19bx and 19by of the shake correction means 19x and 19y based on the calculated displacement amount for shake correction and drives the correction actuators 19ax and 19ay. Let The driven correction actuators 19ax and 19ay move the imaging unit 13 in a plane orthogonal to the optical axis 11C to perform shake correction operations in the horizontal direction that is the x-axis direction and the vertical direction that is the y-axis direction.
[0048]
In addition, when the release operation button 25B is turned ON, the microcomputer 15 performing the shake correction operation performs a control signal for performing an autofocus operation for automatically adjusting the focus lens 11B to an appropriate focal position prior to photographing. Is output to the focus control unit 23B, and the ratio of the period for correcting the shake by displacing the imaging position on the light receiving surface in two directions is temporarily made different from the ratio of the period at the time of photographing. While changing the ratio of the shake correction period, the microcomputer 15 moves the focus lens 11B along the optical axis 11C by a predetermined amount within the movable range, and subjects the image formed in the determination region R for each movement. The image portion of the image is converted into an electrical signal and captured, and an evaluation value for determining the in-focus position is obtained based on the image information of the captured image portion of the subject, and the focus lens is determined based on the obtained evaluation value. It is searched where the in-focus position is in the movable range of 11B.
[0049]
For example, the microcomputer 15 always performs normal processing of angular velocity detection, shake amount calculation, displacement amount calculation for shake correction, and shake correction drive until the release operation button 25B is turned on. The sampling period for taking in the detected detection signal can be set individually for each direction. When the method for obtaining the evaluation value for determining the in-focus position based on the image information of the image portion of the subject is the horizontal pixel comparison method, when the release operation button 25B is turned on, From the first predetermined sampling period, the detection signal from the x-axis angular speed detection means 17x that has been digitally converted and captured at the same first predetermined sampling period as the detection signal corresponding to the angular speed generated by the y-axis angular speed detection means 17y. Is changed so as to be digitally converted and captured at a second predetermined predetermined sampling cycle.
[0050]
As a result, the microcomputer 15 performs all of the shake correction processing including normal velocity detection, horizontal shake amount calculation, displacement amount calculation for shake correction, and shake correction drive. As a result, the shake correction means 19x and 19y receive the light receiving surface when determining the in-focus position for autofocus performed in response to the ON operation of the release operation button 25B. The ratio of the period for displacing the upper imaging position in two directions is different from that at the time of photographing. Specifically, the horizontal and vertical shake correction operations that have been performed with the same cycle of 1: 1 are changed, and the cycle ratio is changed to, for example, 1: 3.
[0051]
As described above, the change in the ratio of the correction period changed by the ON operation of the release operation button 25B is at least the image information of the image portion of the subject necessary for obtaining the evaluation value for determining the in-focus position. It can be done until it is captured and then restored until the actual shooting is performed, but when considering the stability of the correction operation after restoring, immediately after obtaining the necessary image information It is preferable to restore it.
[0052]
Note that the shake correction function 21 may not be turned on by operating the shake correction button 21 in some cases. In such a case, if the shake correction is not performed at the time of determining the focus position for autofocus performed according to the operation of the release operation button 25B, an appropriate focus position cannot be determined by camera shake. Therefore, in the present invention, even when an off state in which the shake correction function does not work is selected, the shake correction operation is performed only when the in-focus position is determined, and the correction cycle is different from that at the time of shooting. The shake correction operation is performed with the ratio.
[0053]
The outline of the digital still camera with a shake correction function has been described above. The details will be described below with reference to the flowchart of FIG.
[0054]
The microcomputer 15 starts the operation when the power is turned on, and when the shake correction button 21 is turned on (when step S1 is Y), the correction cycle ratio during the shake correction operation is set to the normal cycle ratio and the shake correction is performed. When the shake correction operation is performed even when the button 21 is OFF, the shake correction F (flag) for indicating the state is cleared (step S2). This shake correction F is formed in a flag area in the memory. Then, the shake correction process (step S3) is repeatedly executed at the set normal cycle ratio until the release operation button 25B is turned on (until step S4 is Y). In this shake correction process, both the cycles Txs and Tys for sampling the detection signals corresponding to the angular velocities generated by the x-axis angular velocity detector 17x and the y-axis angular velocity detector 17y are set to the first cycle T1, respectively. The drive control process is performed at one sampling period T1.
[0055]
When the release operation button 25B is turned on in the course of performing the shake correction process (when step S4 is Y), a cycle ratio to be changed is set in order to determine a focus position for autofocus. At the same time, a change F (flag) indicating that the shake correction operation is performed at the changed period ratio is set (step S6), and until the capture of the image information for determining the in-focus position is completed (step S7). Until Y becomes Y), the shake correction process is performed with the set change cycle ratio (step S3).
[0056]
In the shake correction processing with this change cycle ratio, the detection signal corresponding to the angular velocity generated by the x-axis angular velocity detection means 17x is left as it is, while the cycle Tys for sampling the detection signal corresponding to the angular velocity generated by the y-axis angular velocity detection means 17y is left as it is. The sampling period Txs is changed to the second period T2 longer than the first period T1, and the inclination angle is detected based on the detection signal corresponding to the angular velocity generated by the x-axis angular velocity detection means 17x. Based on the amount of shake and the amount of displacement for correcting shake, the vertical direction is to correct the shake in the vertical direction of the imaging position on the light-receiving surface. The vertical direction is the direction in which the pixels are compared when determining the in-focus position. Since the degree of importance is extremely low compared with the horizontal shake as described above, there is no problem in the accuracy of determining the in-focus position even if the sampling period is long.
[0057]
When capturing of image information consisting of an image of a subject for determining the in-focus position is completed (when step S7 is Y), the shake correction cycle is restored and information necessary for determining the in-focus position is acquired. In-focus F (flag) is set to indicate that has ended (step S8).
[0058]
Although not shown in the flowchart, the microcomputer 15 determines an in-focus position based on the captured image information, and performs a process for autofocus control that automatically adjusts the focus lens 11B to the determined position. Separately.
[0059]
The change F set in step S6 is for setting the cycle ratio to be changed when the release operation button 25B is operated (step S5). The focus F set in step S8 is the image F. This is for returning the cycle ratio to the original normal cycle ratio when the information has been captured (step S9).
[0060]
When the in-focus F is set, the shake correction button 21 is turned off (step S1 becomes N), which is impossible in practice, or until the shooting operation is finished and the release operation button 25B is turned off (step S1). Until S4 becomes N), the shake correction process is performed with the normal cycle ratio restored (Step S3). Then, when shooting is finished and the release operation button 25B is turned off (when step S4 is N), the above-described settings of shake correction F, change F and focus F are cleared (step S11), and then The same process is repeated until the shake correction button 21 is turned off (whether step S1 is N) or the release operation button 25B is turned on (step S4 is Y).
[0061]
When the shake correction button 21 is off (when the step S1 is N) and the release operation button 25B is turned on (when the step S12 is Y), an unusual cycle ratio is set and the cycle ratio is set. After the change F indicating the change is set (step S6), shake correction processing is performed in the set change correction cycle (step S3). In performing the shake correction process, a shake correction F indicating that the process is not a correction performed when the shake correction button 21 is turned on is set (step S13).
[0062]
When the shake correction F is set (steps S10 and S14 are Y), the microcomputer 15 captures image information for determining the in-focus position (when step S9 is Y). Thereafter, the shake correction process in step S3 is not performed. That is, when the shake correction button 21 is off, the shake correction operation is performed only during the period of taking in image information for determining the in-focus position, and the period ratio of the shake correction operation at that time is different from the normal cycle ratio. This is done with the changed period ratio. Then, when shooting is finished and the release operation button 25B is turned off (when step S12 is N), the above-described settings of shake correction F, change F, and focus F are cleared (step S11). The shake correction process is not performed until the correction button 21 is turned on (whether step S1 becomes Y) or the release operation button 25B is turned on (step S12 becomes Y).
[0063]
In order to make the correction cycle ratio different, the sampling frequency of the detection signal for the shake in the direction that is not important for determining the in-focus position is lengthened, so that the frequency of sampling by sampling of the angular velocity is reduced. By finally reducing the number of times of calculating the amount of displacement based on the angular velocity and correcting the image blur due to the shake by displacing the imaging position on the light receiving surface in two directions based on the calculated amount of displacement. A method of extending the drive control period of the shake correction means is conceivable. In this way, by increasing one of the sampling periods, the period ratio at which the shake correction unit displaces the image forming position on the light receiving surface in two directions is set to the period at the time of photographing temporarily when determining the in-focus position. Therefore, the microcomputer 15 can have a margin, and the in-focus position can be determined with high accuracy without increasing the cost.
[0064]
Another method is to drive control the shake correction means by reducing the frequency of displacement calculation by thinning out one detection signal sampled and captured without changing the sampling period. It is also conceivable to lengthen the period to do.
[0065]
By the way, shake correction is to prevent blurring of the image due to camera shake at the time of exposure, but when camera shake is analyzed, the camera shape and form, for example, large in the case of camera shake due to the release operation, are analyzed. Now, with different cameras such as weight, release button position, operation feeling, etc., we have come to recognize that there is a direction in how easy it is to get up. For example, it has been found that hand shake is likely to occur in the pushing direction of the release button, but shake is less likely to occur in the direction orthogonal to the pushing direction, and the amount of shake is small even if it occurs.
[0066]
For this reason, if the camera shake has directionality, it is not always necessary to perform the same correction operation in any direction, so the shake correction cycle in the direction with a small shake amount is lengthened. However, there is no problem even if the control accuracy is once lowered. Rather, in one direction, when the shake correction operation cycle is temporarily increased, the processing load on the microcomputer 15 can be reduced. Therefore, it is conceivable to change the correction operation according to the directionality of the shake.
[0067]
In the case where such shake correction is performed, the direction of shake correction and the direction important in determining the in-focus position may be completely reversed. In such a case, it is necessary not only to lengthen one sampling period but also to shorten the other sampling period to temporarily make the period ratio different from the period ratio at the time of photographing.
[0068]
In short, if there is a discrepancy between the directionality of shake correction and the directionality when determining the in-focus position, by changing the period ratio of the shake correction so as to match the directionality when determining the in-focus position, Since the processing load on the microcomputer is reduced, the autofocus can be appropriately performed without increasing the cost.
[0069]
【The invention's effect】
As described above, according to the first aspect of the present invention, when determining the focus position for autofocus, the ratio of the period for shake correction is temporarily made different from the period ratio at the time of shooting. It is possible to lengthen the period of shake correction in the direction that is not always necessary in the pre-shooting operation to determine the focus position, and to correct shake when correcting the focus position and shake correction during shooting The shake correction can be performed at a cycle ratio corresponding to the directionality required for the required shake correction, and unnecessary focus correction can be omitted, and the autofocus can be appropriately performed without increasing the cost.
[0070]
According to the second aspect of the present invention, the period ratio is changed temporarily so that the period of shake correction in one direction becomes longer in accordance with the pixel comparison method for determining the focus position for autofocus. As a result, the autofocus can be appropriately performed while reducing the burden by increasing the period.
[0071]
According to the third aspect of the present invention, the period of the one-way shake correction is temporarily increased in accordance with the weighting with respect to the direction of the pixel comparison method for determining the focus position for autofocus. Since the ratio is changed, it is possible to appropriately perform autofocus while reducing the burden by increasing the period.
[0072]
According to the fourth aspect of the present invention, the changed cycle is held until an electric signal for determining the in-focus position is captured, and then returned to the ratio of the cycle before the change, so that the actual shooting can be performed. Since the shake correction can be started at an early stage, the cycle ratio can be changed without affecting the shake correction at the time of shooting.
[0073]
According to the fifth aspect of the present invention, even when shake correction is not performed at the time of shooting, the in-focus position for autofocus can be accurately determined with a minimum increase in burden, and autofocus. Can be done appropriately.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a schematic configuration of a camera body in an embodiment of an imaging apparatus with a shake correction function according to the present invention.
FIG. 2 is a diagram illustrating an autofocus determination area provided on a light receiving surface of an imaging unit.
FIG. 3 is a diagram illustrating an autofocus determination area in FIG. 2 in units of pixels.
4 is a flowchart showing processing performed by the microcomputer in FIG. 1 in the embodiment of the imaging apparatus with a shake correction function according to the present invention.
[Explanation of symbols]
11 Shooting optical system
11B Focus lens
11C optical axis
13 Imaging means
13a Photosensitive surface
15 Microcomputer (drive control means)
17x, 17y Angular velocity detection means (shake detection means)
19x, 19y shake correction means
21 Shake correction button
25B Release operation button
x, y axis

Claims (5)

An image of a subject is formed on a light receiving surface of an image sensor by a photographing optical system having a focus lens, converted into an electric signal and captured, and the focus lens is automatically set at a focus position determined based on the captured electric signal. An image pickup apparatus with a shake correction function that adjusts the image and corrects the image shake on the light receiving surface due to the shake to perform shooting,
A shake detection unit that detects shakes in two directions orthogonal to the optical axis of the photographing optical system and outputs detection signals corresponding to the magnitudes of the detected shakes in the two directions;
Shake correcting means for independently displacing the imaging position on the light receiving surface in the two directions;
The shake correction unit captures a detection signal output from the shake detection unit and, based on the acquired detection signal, displaces an image forming position on the light receiving surface in the two directions to correct image blur due to the shake. Drive control means for controlling the drive,
The drive control unit temporarily captures a ratio of periods in which the shake correction unit displaces the image forming position on the light receiving surface in the two directions to correct the shake when determining the in-focus position. An imaging apparatus with a shake correction function, wherein the imaging apparatus is different from a period ratio of time. The imaging apparatus with a shake correction function according to claim 1,
When the determination of the in-focus position is performed by a pixel comparison method in which the captured electric signal is compared in units of adjacent pixels in one direction of the two directions, the imaging position on the light receiving surface is set in the one direction. An imaging apparatus with a shake correction function, wherein the ratio of the cycles is changed so that a cycle in another direction is longer than a cycle in which shake is corrected by displacement. The imaging apparatus with a shake correction function according to claim 1,
In the case where the determination of the in-focus position is performed by a pixel comparison method in which the captured electric signal is compared in units of adjacent pixels in the two directions, the light-receiving surface is placed in a direction that places importance on the determination of the in-focus position. An imaging apparatus with a shake correction function, characterized in that the period ratio is changed so that the period in the other direction is longer than the period in which the upper imaging position is displaced and shake correction is performed. In the imaging device with a shake correction function according to any one of claims 1 to 3,
An imaging apparatus with a shake correction function, wherein the changed period is held until the electric signal for determining the in-focus position is captured, and then returned to the ratio of the period before the change. In the imaging device with a shake correction function according to any one of claims 1 to 4,
An on state in which the shake correction function is activated by operating the shake correction unit and the drive control unit, or an off state in which the operation of the shake correction unit and the drive control unit is deactivated and the shake correction function is not activated. A selection means for selecting one of
The drive control means, even when the selection means is selecting the off state, when determining the in-focus position, to put the shake correction means and the drive control means into operation, An imaging apparatus with a shake correction function, wherein the shake correction means is driven and controlled at a ratio of the period different from that at the time of shooting.

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