JP7422466B2 - Image stabilization control device, imaging device, and control method thereof - Google Patents

Description

The present invention relates to an image blur correction control device, an imaging device, and a control method thereof.

A digital camera has an image sensor in which a focus detection pixel for performing focus detection is arranged on an imaging surface, as shown in Patent Document 1, and two images are captured from different areas of the exit pupil of a photographing optical system. An imaging device that performs focus detection based on the phase difference of signals has been disclosed.

Further, Patent Document 2 discloses a camera that corrects image blur by driving a part of an image sensor and a photographing optical system through allocation control.

JP 2016-57474 Publication Patent No. 4567313

By applying the image stabilization function of the camera disclosed in Patent Document 2 and keeping the subject that the photographer wants to focus on within the focus detection frame within the shooting screen, it is possible to accurately assist the photographer in framing. Conceivable. However, as in this camera, driving the image sensor as an image stabilization means and a part of the photographic optical system essentially changes the positional relationship between the optical axis of the photographic optical system and the center of the image sensor. Equivalent to. Therefore, when the image blur correction means is driven, the state of vignetting that occurs in the light flux passing through the photographing optical system changes in the same way as the image height of the focus detection frame is changed. As a result, the light intensity balance of the two imaging signals used to calculate the phase difference changes, reducing the accuracy of focus detection, resulting in images that are out of focus even if the photographer's framing is accurately assisted. I ended up taking a picture of it. An object of the present invention is to provide an image blur correction control device that can suppress the influence of vignetting during focus detection.

An image stabilization control device as one aspect of the present invention provides focus detection that performs focus detection based on the phase difference between a pair of image signals obtained by an image sensor that captures a light flux that has passed through different pupil regions of a photographic optical system. means, an image shake correction control means for controlling a first image shake correction means for moving the image sensor with respect to the photographing optical system based on an image shake correction amount, and a focal length of the photographing optical system is set to a predetermined value. and determining means for determining whether or not the aperture value of the photographing optical system is in a first state where the aperture value is longer than the focal length of the imaging optical system and the aperture value of the photographing optical system is greater than a predetermined aperture value, the image blur correction control means , if the determining means does not determine that the first state is present, a first distance is defined as a distance over which the image sensor can move in a first direction perpendicular to the optical axis of the photographing optical system; When the determining means determines that the image sensor is in the first state, a distance over which the image sensor can move in the first direction is set as a second distance shorter than the first distance.

Other aspects of the present invention will be made clear in the embodiments described below.

According to the present invention, it is possible to provide an image blur correction control device that can suppress the influence of vignetting during focus detection.

1 is a diagram showing a configuration example of an imaging device according to Examples 1 and 2. FIG. This is an example of a pixel array of an image sensor. FIG. 2 is a diagram illustrating an example of the configuration of pixels of an image sensor. FIG. 3 is a diagram illustrating the correspondence between the pixel structure of an image sensor and pupil divisions. FIG. 3 is a diagram illustrating the correspondence between an image sensor and pupil division. FIG. 3 is a diagram illustrating the relationship between the amount of defocus and the amount of image shift. 3 is a flowchart illustrating an example of focus detection processing. FIG. 3 is a diagram illustrating a relationship between a pupil partial region at a peripheral image height of an image sensor and an exit pupil of a photographing optical system. FIG. 3 is a diagram illustrating an example of a passband for filter processing. FIG. 6 is a diagram showing an example of a state of pupil separation on an exit pupil plane. FIG. 2 is a flow diagram illustrating an imaging operation in the imaging device of Example 1. FIG. FIG. 3 is a flowchart illustrating an imaging operation in the imaging device of Example 2. FIG.

Hereinafter, preferred embodiments of the present invention will be described in detail based on the accompanying drawings. In addition, in each figure, the same reference number is attached|subjected about the same member, and the overlapping description is abbreviate|omitted.

FIG. 1 is a diagram showing an example of the configuration of an imaging device according to this embodiment. The imaging system 1000 is a lens-interchangeable digital camera that includes an imaging device (camera body) 12 and an interchangeable lens 12 that is detachable from a mounting portion (mount) of the imaging device. In the imaging system 1000, a photographing optical system 101 is disposed within an attached interchangeable lens 11, and an optical path for a photographing light beam is formed. The light beam transmitted through this optical path reaches an image sensor 102 disposed in the image sensor 12, and is photoelectrically converted by photodiodes in pixels arranged in a plane perpendicular to the optical axis of the image sensor 102. The image processing means performs gamma processing, noise processing, etc. on the signal obtained by photoelectric conversion to generate image data, and then writes the image data into a nonvolatile memory, thereby completing the photographing process for one image.

The imaging system 1000 performs focus detection according to instructions from a photographer, so that an image with a desired subject in focus can be captured. A pixel arranged in the image sensor 102 also serves as a focus detection pixel, and a focus detection means 103 detects the focus state of the subject based on the output of the focus detection pixel. Specifically, the focus detection unit 103 performs focus detection based on the phase difference between a pair of image signals (focus detection signals) obtained by photoelectric conversion of light fluxes passing through different pupil regions of the photographing optical system. The focus detection means 103 calculates the amount of movement of the focus adjustment optical system 108 in the optical axis direction based on the detection result of the focus state. Then, the focus adjustment control means (not shown) included in the lens unit moves the focus adjustment optical system 108 by the amount of movement in the optical axis direction. Details of focus detection will be described later.

Further, the imaging system 1000 includes a plurality of image blur correction units that suppress unnecessary vibrations such as camera shake that occur when a photographer performs handheld shooting. The first image blur correction means is a sensor shift type image blur correction means 105 that holds the image sensor 102 movably in a plane perpendicular to the optical axis and performs image blur correction by moving the image sensor 102. .

The second image blur correction means is a lens shift type image blur correction means 104 having an image blur correction optical system 109 that is a part of the photographing optical system 101 disposed within the interchangeable lens 11. The image blur correction optical system 109 is a concave lens disposed closer to the image plane than the aperture 111.

The image shake correction control means 107 controls the sensor shift type image shake correction means 105 and the lens shift type image shake correction means 104 based on the image shake correction amount, and controls the image sensor 102 and the image shake correction optical system 109. is shifted in a plane perpendicular to the optical axis. Thereby, sensor shift type image blur correction and lens shift type image blur correction can be performed. The image blur correction amount is the amount of movement of the image sensor 102 and the image blur correction optical system 109 for correcting image blur due to the amount of movement of the imaging system 1000, and is the amount of movement of the image sensor 102 and the image blur correction optical system 109, and is based on the output of the angular velocity sensor, the output of the acceleration sensor, the motion vector, etc. Based on. Although the second image blur correction means of this embodiment executes image blur correction by lens shift, the method of image blur correction is not limited to lens shift. Image blur correction may be performed by swinging the entire photographic optical system 101, or may be performed by changing the prism angle of a variable prism that is a part of the photographic optical system 101.

The image blur correction control means 107 further controls the state in which the focal length of the photographing optical system 101 is longer than a predetermined focal length, and the aperture value of the photographing optical system is larger than the predetermined aperture value (hereinafter simply referred to as the first aperture value). (sometimes referred to as a state). This determination is made based on lens information acquired from the lens unit. If it is determined that the first state is present, the movable distance of the image sensor 102 during sensor shift image stabilization is limited to a shorter distance than when it is not determined that the first state is the first state. . Details of this control will be described later.

In this embodiment, by using two image shake correction means, the area where image shake can be corrected is expanded, and the captured image is stabilized. The holding frame 110 is a mechanical structure of a lens barrel that holds the final group of the photographing optical system 101. In a high image height region away from the optical axis of the image sensor, the photographing light beam is blocked by a mechanical structure such as the holding frame 110, resulting in so-called "vignetting", which affects focus detection. Therefore, during focus detection, the imaging system 1000 uses the information regarding vignetting stored in the storage unit 106 to control the image blur correction unit. Vignetting will be described later.

Note that the focus detection means 103 and the image blur correction control means 107 are functional blocks, and may be realized by hardware such as an ASIC or a programmable logic array (PLA). Alternatively, it may be realized by a programmable processor such as a CPU or MPU executing software. Alternatively, it may be realized by a combination of software and hardware. Therefore, in the following description, even when different functional blocks are described as operating entities, the same hardware can be implemented as operating entities. Furthermore, the storage means 106 can be configured with a memory, and when the focus detection means 103 and the image blur correction control means 107 are configured with a processor, it is possible to store software executed by the processor.

(Imaging surface phase difference focus detection system)
Next, focus detection performed by the imaging device 12 will be described using FIGS. 2 to 9. FIG. 2 is a diagram showing the pixel array of the image sensor 102 of the imaging device 12 in a range of 4 columns x 4 rows, and the focus detection pixel array in a range of 8 columns x 4 rows.

In the pixel group 200 of 2 columns×2 rows shown in FIG. 2, a pixel 200R having a spectral sensitivity of R (red) is arranged at the upper left position. Further, a pixel 200G having a spectral sensitivity of G (green) is arranged at the upper right and lower left. Further, a pixel 200B having a spectral sensitivity of B (blue) is arranged at the lower right. Further, each pixel includes a first focus detection pixel 201 and a second focus detection pixel 202 arranged in two columns and one row.

By arranging a large number of 4 columns x 4 rows of pixels (8 columns x 4 rows of focus detection pixels) shown in FIG. 2 on a surface, it is possible to acquire a captured image (focus detection signal). In this example, the pixel period P is 4 μm, the number of pixels N is 5575 horizontal columns × 3725 vertical rows = approximately 20.75 million pixels, the column direction period PAF of focus detection pixels is 2 μm, and the number of focus detection pixels NAF is 11150 horizontal columns × The explanation will be given assuming that the image sensor has 3725 vertical lines = approximately 41.5 million pixels.

FIG. 3 is a diagram illustrating an example of the configuration of pixels of an image sensor. FIG. 3A shows a plan view of the pixel 200G of the image sensor 102 shown in FIG. A cross-sectional view seen from the y side is shown in FIG. 3(b). Note that the "optical axis" shown in FIG. 3(b) indicates the optical axis of the microlens 305.

As shown in FIG. 3, in the pixel 200G, a microlens 305 is formed to collect the incident light on the light receiving side of each pixel, and the microlens 305 is divided into _NH (divided into 2) in the x direction and divided into _NV (divided into 2) in the y direction. A photoelectric conversion section 301 and a photoelectric conversion section 302 (divided into one) are formed. A photoelectric conversion unit 301 and a photoelectric conversion unit 302 correspond to the first focus detection pixel 201 and the second focus detection pixel 202, respectively. The photoelectric conversion unit 301 and the photoelectric conversion unit 302 may be a pin structure photodiode in which an intrinsic layer is sandwiched between a p-type layer and an n-type layer, or if necessary, the intrinsic layer may be omitted and a pn junction It can also be used as a photodiode.

In each pixel, a color filter 306 is formed between the microlens 305 and the photoelectric conversion section 301 and the photoelectric conversion section 302. Further, if necessary, the spectral transmittance of the color filter may be changed for each pixel, or the color filter may be omitted. The light incident on the pixel 200G is collected by the microlens 305, separated by the color filter 306, and then received by the photoelectric conversion unit 301 and the photoelectric conversion unit 302.

In the photoelectric conversion unit 301 and the photoelectric conversion unit 302, pairs of electrons and holes are generated depending on the amount of light received, and after being separated by a depletion layer, negatively charged electrons are accumulated in an n-type layer (not shown). Holes are discharged to the outside of the image sensor through a p-type layer connected to a constant voltage source (not shown). Electrons accumulated in the n-type layers (not shown) of the photoelectric conversion section 301 and the photoelectric conversion section 302 are transferred to a capacitance section (FD) via a transfer gate and converted into a voltage signal.

FIG. 4 is a diagram illustrating the correspondence between the pixel structure of the image sensor and pupil division. FIG. 4 shows a cross section of the aa cross section of the pixel structure shown in FIG. 3A viewed from the +y side and the exit pupil plane of the photographing optical system 101. In order to correspond to the coordinate axes of the exit pupil plane, the x-axis and y-axis of the cross-sectional view are reversed with respect to FIG. 3. The first pupil partial region 501 of the first focus detection pixel 201 has a generally conjugate relationship with the light receiving surface of the photoelectric conversion unit 301 whose center of gravity is eccentric in the -x direction and the microlens 305, It represents the pupil area where the focus detection pixel 201 can receive light. The first pupil partial region 501 of the first focus detection pixel 201 has a center of gravity eccentric to the +X side on the pupil plane.

The second pupil partial region 502 of the second focus detection pixel 202 has a generally conjugate relationship with the light receiving surface of the photoelectric conversion unit 302 whose center of gravity is decentered in the +x direction and the microlens 305, and is in a conjugate relationship with the microlens 305. It represents the pupil area where the detection pixel 202 can receive light. The center of gravity of the second pupil partial region 502 of the second focus detection pixel 202 is eccentric to the −X side on the pupil plane.

The exit pupil 400 is formed by the aperture of the photographing optical system 101, and the light flux inside the area of the exit pupil 400 reaches the image sensor 102. Further, the pupil region 500 is a pupil region in which light can be received by the entire pixel 200G including the photoelectric conversion unit 301 and the photoelectric conversion unit 302 (the first focus detection pixel 201 and the second focus detection pixel 202). FIG. 5 is a diagram illustrating the correspondence between the image sensor and the pupil divisions. The light flux that has passed through different pupil partial areas, the first pupil partial area 501 and the second pupil partial area 502, enters each pixel of the image sensor 102 at a different angle, and the first focus detection pixel is divided into 2×1. The light is received by the second focus detection pixel 201 and the second focus detection pixel 202 . In this embodiment, the pupil area is divided into two in the horizontal direction. Note that pupil division may be performed in the vertical direction if necessary. The image sensor 102 includes a first focus detection pixel 201 that receives a light flux passing through a first pupil partial area of the photographing optical system 101, and a second pupil partial area of the photographing optical system 101 that is different from the first pupil partial area. A plurality of second focus detection pixels 202 that receive a light beam are arranged. In addition, the image sensor 102 has a plurality of arrayed imaging pixels that receive a light flux that passes through a pupil area that is a combination of the first pupil partial area and the second pupil partial area of the photographic optical system 101 . In this embodiment, each imaging pixel is composed of a first focus detection pixel and a second focus detection pixel.

The imaging device 12 collects the light reception signals of the first focus detection pixels 201 of each pixel of the image sensor 102 to generate a first focus signal that is an image signal. Further, the imaging device 12 collects the light reception signals of the second focus detection pixels 202 of each pixel to generate a second focus signal that is an image signal. The imaging device 12 then performs focus detection based on the first focus signal and the second focus signal. Furthermore, the imaging device 12 generates an imaging signal with a resolution of the effective number of pixels N by adding the signals of the first focus detection pixel 201 and the second focus detection pixel 202 for each pixel of the imaging element 102.

The relationship between the defocus amount and the image shift amount of the first focus detection signal and the second focus detection signal obtained from the image sensor 102 of the imaging device 12 will be described below.

FIG. 6 is a diagram illustrating the relationship between the defocus amount of the first focus detection signal and the second focus detection signal and the image shift amount between the first focus detection signal and the second focus detection signal.

An imaging element 102 (not shown) of the imaging device 12 is arranged on the imaging surface 800, and the exit pupil of the imaging optical system 101 is arranged in the first pupil partial area 501 and the second pupil partial area 502, as in FIGS. 4 and 5. It is divided into two parts.

The defocus amount d is defined as the distance from the subject's imaging position to the imaging plane as size |d|, and the front focus state where the subject's imaging position is closer to the subject than the imaging plane is defined as a negative sign (d<0). defined. Further, the defocus amount d is defined as a positive sign (d>0) for a rear focus state in which the imaging position of the subject is on the opposite side of the subject from the imaging plane.

In a focused state where the imaging position of the subject is on the imaging plane (focus position), d=0. In FIG. 6, a subject 801 is in focus (d=0). The subject 802 is in a front-focus state (d<0). The front focus state (d<0) and the back focus state (d>0) are defocus states (|d|>0). In the front focus state (d<0), among the light fluxes from the subject 802, the light fluxes that have passed through the first pupil partial area 501 (second pupil partial area 502) are once condensed and then moved to the center of gravity G1 of the light beams. (G2) as the center and spreads to a width Γ1 (Γ2), resulting in a blurred image on the imaging surface 800. The blurred image is received by the first focus detection pixel 201 (second focus detection pixel 202) that constitutes each pixel arranged in the image sensor 102, and a first focus detection signal (second focus detection signal) is generated. Ru. Therefore, the first focus detection signal (second focus detection signal) is recorded as a subject image in which the subject 802 is blurred to a width Γ1 (Γ2) at the center of gravity position G1 (G2) on the imaging surface 800. The blur width Γ1 (Γ2) of the subject image generally increases in proportion as the magnitude |d| of the defocus amount d increases. Similarly, the magnitude |p| of the image shift amount p of the subject image between the first focus detection signal and the second focus detection signal (=difference G1-G2 in the gravity center position of the luminous flux) also depends on the magnitude of the defocus amount d. As |d| increases, it generally increases in proportion. The same is true in the rear focus state (d>0), although the direction of image shift of the subject image between the first focus detection signal and the second focus detection signal is opposite to that in the front focus state. Therefore, as the magnitude of the defocus amount of the first focus detection signal and the second focus detection signal or the imaging signal obtained by adding the first focus detection signal and the second focus detection signal increases, the first focus detection signal increases. The amount of image shift between the signal and the second focus detection signal increases.

The imaging apparatus of this embodiment performs phase difference focus detection using the relationship between the defocus amount and the image shift amount of the first focus detection signal and the second focus detection signal. Specifically, the focus detection means 103 calculates a correlation amount representing the degree of coincidence of the signals by relatively shifting the first focus detection signal and the second focus detection signal, and calculates the image shift from the shift amount that improves the correlation. Detect amount. The focus detection means 103 detects image shift based on the relationship that the amount of image shift between the first focus detection signal and the second focus detection signal increases as the amount of defocus of the imaging signal increases. Focus detection is performed by converting the amount into a detected defocus amount.

FIG. 7 is a flowchart illustrating an example of focus detection processing.

When the image sensor 102 performs imaging for focus detection, a first focus detection signal is acquired based on the result of photoelectric conversion by the photoelectric conversion unit 301, and a second focus detection signal is acquired based on the result of photoelectric conversion by the photoelectric conversion unit 302. A focus detection signal is obtained. The first focus detection signal and the second focus detection signal are a pair of image signals used for focus detection. Once the first focus detection signal and the second focus detection signal are acquired, step S110 starts.

In step S110, the focus detection means 103 performs 3-pixel addition processing in the column direction for each of the first focus detection signal and the second focus detection signal in order to suppress the amount of signal data. Further, the focus detection means 103 performs Bayer (RGB) addition processing to convert the RGB signals into luminance Y signals. Further, the focus detection means 103 performs a vertical thinning process in which one line is read out every three lines. In this embodiment, the horizontal addition and vertical thinning processes are performed after reading out from the image sensor 102, but the horizontal addition and vertical thinning processes may be performed in advance within the image sensor 102. In step S120, the focus detection unit 103 sets a focus detection area to be subjected to focus adjustment from among the effective pixel areas of the image sensor 102. The focus detection means 103 generates a first focus detection signal from the light reception signal of the first focus detection pixel in the focus detection area, and generates a second focus detection signal from the light reception signal of the second focus detection pixel in the focus detection area. Next, in S130, the focus detection means 103 performs shading correction processing on each of the first focus detection signal and the second focus detection signal. Shading due to pupil shift between the first focus detection signal and the second focus detection signal will be described below.

FIG. 8 is a diagram illustrating the relationship between the pupil partial region at the peripheral image height of the image sensor and the exit pupil of the photographing optical system. In FIG. 8, the first pupil partial area 501 of the first focus detection pixel 201, the second pupil partial area 502 of the second focus detection pixel 202, and the exit pupil 400 of the photographing optical system 101 at the peripheral image height of the image sensor 102 are shown. Let's take the relationship as an example. FIG. 8A shows a state in which the exit pupil distance Dl of the photographing optical system 101 and the set pupil distance Ds of the image sensor 102 are the same. In this state, the exit pupil 400 of the photographing optical system 101 is divided almost equally by the first pupil partial area 501 and the second pupil partial area 502. FIG. 8B shows a state in which the exit pupil distance Dl of the photographing optical system 101 is shorter than the set pupil distance Ds of the image sensor 102. In this state, at the peripheral image height of the image sensor 102, a pupil misalignment occurs between the exit pupil 400 and the entrance pupil of the image sensor 102, and the exit pupil 400 is divided unevenly. FIG. 8C shows a state in which the exit pupil distance Dl of the photographing optical system 101 is longer than the set pupil distance Ds of the image sensor 102. In this state, at the peripheral image height of the image sensor 102, a pupil misalignment occurs between the exit pupil 400 and the entrance pupil of the image sensor 102, and the exit pupil 400 is divided unevenly. As the pupil division becomes non-uniform at the peripheral image height, the intensities of the first focus detection signal and the second focus detection signal also become non-uniform. Shading occurs where one intensity becomes larger and the other intensity becomes smaller. As will be described later, the limitation on the amount of movement of the sensor shift type image stabilization means 105 that performs image stabilization is due to the long focal length of the photographing optical system 101, when the state shown in FIG. 8(c) occurs. to be done.

Returning to the explanation of FIG. 7. In step S130, the focus detection means 103 generates a first shading correction coefficient for the first focus detection signal and a second shading correction coefficient for the second focus detection signal. The focus detection means 103 determines a first shading correction coefficient and a second shading correction coefficient according to the image height of the focus detection area, the F value (aperture value) of the photographing optical system 101, the exit pupil distance, and the vignetting state of the exit pupil light flux. generate. The focus detection means 103 multiplies the first focus detection signal by a first shading correction coefficient, and multiplies the second focus detection signal by a second shading correction coefficient, thereby shading the first focus detection signal and the second focus detection signal. Perform correction processing. In focus detection using a phase difference method, a detected defocus amount is detected based on the correlation between a first focus detection signal and a second focus detection signal. When shading occurs due to pupil shift, the correlation between the first focus detection signal and the second focus detection signal may decrease. Therefore, in phase difference method focus detection, shading correction processing (optical correction processing ) is desirable.

Although not shown in FIG. 8, in addition to the aperture that constitutes the exit pupil 400, there are also mechanical members that hold each optical system and mechanical members within the imaging device from the last group of the interchangeable lens 11 to the image sensor 102. exist. Depending on the aperture value, image height, etc., the light beam passing through the photographing optical system may be blocked by these mechanical members, and this is generally referred to as "vignetting" of the light beam.

Shading between the first focus detection signal and the second focus detection signal also occurs due to vignetting, and under conditions where vignetting is known, shading correction that also takes vignetting into consideration can be performed to prevent a decrease in focus detection accuracy. Can be done. The imaging device 12 stores the shading correction coefficient SHD in the storage unit 106 as a table corresponding to the image height of the focus detection area, the F value (aperture value) of the photographing optical system 101, the exit pupil distance, and the vignetting state. . The shading correction coefficient SHD corresponds to the intensity ratio of a plurality of image signals obtained from mutually different regions of the exit pupil of the photographing optical system. Since the exit pupil distance is a different value for each interchangeable lens (for each zoom state in the case of a zoom lens), tables are provided for each. Furthermore, since the vignetting state changes depending on the position of the image blur correction optical system 109, it is expressed by providing a shading correction coefficient SHD for each stroke amount (movement amount) of the image blur correction optical system 109. The imaging device 12 retains vignetting information by having a table of shading correction coefficients SHD that differ for each stroke amount of the lens shift type image blur correction means 104. The position of the image sensor 102 to which the sensor shift type image blur correction means 105 moves can be understood as a simple change in the image height of the focus detection area. Therefore, the imaging device 12 does not maintain a shading correction coefficient table for each position of the imaging element 102, and the amount of shading correction accompanying movement of the imaging element 102 is determined based on a table of shading correction coefficients SHD for each image height. get. The imaging device 12 holds, for example, the relative positional relationship that can be achieved by the movement of the lens shift type image shake correction means 104 and the sensor shift type image shake correction means 105 as the stroke amount of the image shake correction optical system 109 described above.

In step S140 of FIG. 7, the focus detection means 103 performs filter processing on the first focus detection signal and the second focus detection signal. FIG. 9 is a diagram illustrating an example of a pass band of the filter processing.

The solid line in FIG. 9 indicates the passband of filter processing. In this embodiment, since focus detection is performed in a large defocus state by phase difference method focus detection, the passband of filter processing is configured to include a low frequency band. When performing focus adjustment from a large defocus state to a small defocus state, the passband of the filter processing during focus detection is adjusted to a higher frequency band according to the defocus state, as shown by the dashed line in Figure 9. You may do so.

Next, in step S150 in FIG. 7, the focus detection means 103 performs a shift process to relatively shift the filtered first focus detection signal and second focus detection signal in the pupil division direction, and Calculate the amount of correlation representing . Let A(k) be the k-th first focus detection signal after filter processing, B(k) be the second focus detection signal, and W be the range of number k corresponding to the focus detection area. The correlation amount COR is calculated by the following formula, where the shift amount due to the shift process is s1, and the shift range of the shift amount s1 is Γ1.

焦点検出手段１０３は、シフト量ｓ１の第１シフト処理により、ｋ番目の第１焦点検出信号Ａ（ｋ）とｋ－ｓ１番目の第２焦点検出信号Ｂ（ｋ－ｓ１）を対応させ減算し、シフト減算信号を生成する。焦点検出手段１０３は、生成されたシフト減算信号の絶対値を計算し、焦点検出領域に対応する範囲Ｗ内で番号ｋの和を取り、相関量（第１評価値）ＣＯＲ（ｓ１）を算出する。必要に応じて、各行毎に算出された相関量（第１評価値）を、シフト量毎に、複数行に渡って加算しても良い。

The focus detection means 103 associates and subtracts the k-th first focus detection signal A (k) and the k-s1 second focus detection signal B (ks1) by a first shift process with a shift amount s1. , generate a shift subtraction signal. The focus detection means 103 calculates the absolute value of the generated shift subtraction signal, takes the sum of the numbers k within the range W corresponding to the focus detection area, and calculates the correlation amount (first evaluation value) COR (s1). do. If necessary, the correlation amount (first evaluation value) calculated for each row may be added for each shift amount over multiple rows.

In step S160, the focus detection means 103 uses sub-pixel calculations from the correlation amount to calculate a real-valued shift amount that minimizes the correlation amount, and sets it as the image shift amount p1. The focus detection means 103 multiplies the image shift amount p1 by the image height of the focus detection area, the F value of the photographing optical system 101, the exit pupil distance, and the conversion coefficient K corresponding to the vignetting information to obtain the detected defocus amount (Def ) is detected. That is, the phase difference between the plurality of image signals is converted into a defocus amount using the conversion coefficient K. The conversion coefficient K exists as table data stored in the storage means 106 included in the imaging device 12. Similar to the table of shading correction coefficients SHD, the table of conversion coefficients K is provided as a table corresponding to the exit pupil distance of each interchangeable lens. Similarly, regarding the vignetting state, a conversion coefficient K is described for each stroke amount of the image blur correction optical system 109. The imaging device 12 retains vignetting information by having a table of conversion coefficients K that differ for each stroke amount of the image blur correction optical system 109. The focus detection means 103 determines the amount of movement of the focus adjustment optical system 108 by multiplying the detected defocus amount by the focus sensitivity.

In the still image shooting mode, the process explained with reference to FIG. Implemented. Further, this process is executed every frame in the video shooting mode. The image height of the focus detection area is predicted and determined from the history of tracking (automatic selection of focus detection frames) and the history of the movement positions of the two image blur correction means in a plurality of past frames. Although details will be described later, in this embodiment, the image blur correction means performs movement control based on the position of the focus detection frame indicating the focus detection area, with the movement center being at a position where the effect of vignetting is less than a predetermined value.

In this embodiment, the shading correction coefficient SHD and the conversion coefficient K are stored in the storage means 106 in the form of a table, but the vignetting information is stored as a two-dimensional frame shape on the pupil plane, and this vignetting information is used as the source. Alternatively, the coefficients may be calculated within the camera. The two-dimensional frame shape described above corresponds to the shape of the light flux on the exit pupil plane of the photographing optical system depending on the state of vignetting. Further, although this embodiment does not specifically describe the location of the storage means 106, the storage means 106 may be provided on the imaging device 12 side, or may be separated between the interchangeable lens 11 and the imaging device 12. You can have it.

Next, the relationship between the movement of the lens shift type image shake correction means 104 and the sensor shift type image shake correction means 105, which are the image shake correction means of the imaging system 1000, and focus detection will be described using FIG.

In FIG. 10 ((a) to (c)), the photographing optical system 101 is a so-called super-telephoto lens with a long focal length, and has a large aperture value (=small aperture diameter); in other words, the photographing optical system shows the state in the first state. In FIG. 10, the exit pupil distance Dl of the photographing optical system 101 is longer than the set pupil distance Ds of the image sensor 102, as in FIG. 8(c). Generally, when the focal length of the photographic optical system is long, the exit pupil distance Dl is longer than when the focal length is short.

FIG. 10A shows how pixels near the central image height of the image sensor 102 are divided into pupils, and FIG. 10B shows how pixels at the peripheral image height of the image sensor 102 are divided into pupils. 10A and 10B show a state in which the sensor shift type image blur correction means 105 is not operating and the center of the image sensor 102 is aligned with the optical axis of the photographing optical system 101. In particular, when the image height of the area where focus detection is performed (area where image signals are acquired; AF area) is high as shown in FIG. Focus detection is performed with a reduced S/N ratio. FIG. 10(c) shows how the sensor shift type image blur correction means 105 has moved to the left in the figure from the state shown in FIG. 10(b). As the sensor shift type image blur correction means 105 moves, the photoelectric conversion section 301 and the photoelectric conversion section 302 also move to the left in the figure. As a result, the amount of signal acquired from the first pupil partial region 501 is further reduced than in FIG. 10(b), and there is a concern that the S/N may be reduced.

On the other hand, since the photographing optical system 101 has a long focal length, the effect of image blur correction (relative movement amount between the subject image and the imaging surface) is smaller than when the focal length is short. Therefore, when the focal length is long, even if the sensor shift type image stabilization means 105 moves significantly, the effect of image stabilization is not large, and if the image stabilization is performed during focus detection, the obtained image stabilization effect will be affected. On the other hand, there are cases where the accuracy of focus detection is significantly reduced. Therefore, in this embodiment, in a situation where the photographing optical system is in the first state, by setting a limit on the stroke amount of the sensor shift type image blur correction means 105, the decrease in focus detection accuracy is reduced. do.

How to limit the stroke amount will be explained using FIG. 11. FIG. 11 is a flowchart of the imaging operation performed by the image blur correction control means 107 of the imaging device 12. FIG. 11 shows a flowchart of an example in which the image blur correction control means 107 determines whether the photographing optical system is in the first state based on the focal length information and the aperture value (F number) of the photographing optical system 101. shows.

The flow in FIG. 11 starts when the power is turned on or the release button is pressed halfway (SW1), which is an instruction to prepare for photographing. Further, in this embodiment, it is assumed that the image blur correction operation by the sensor shift type image blur correction means 105 is performed before or at the same time as the start of the main flow. In other words, when this flow is executed, the sensor shift type image blur correction means 105 is being driven even before the imaging process. Since image blur correction only needs to be effective during exposure of a still image, it is not necessary to drive the sensor shift type image blur correction means 105 before exposure. However, if the interchangeable lens 11 does not have the lens shift type image shake correction means 104, or for framing in continuous shooting mode, the sensor shift type image shake correction means 105 may be driven before exposure. , this embodiment is also assumed to be driven before exposure.

In step S1001, the image blur correction control unit 107 determines whether the focal length f of the photographing optical system 101 is longer than a predetermined focal length fth. The predetermined focal length fth is predetermined based on the degree of decrease in the S/N of the focus detection described above, and a relatively large value such as 500 mm is adopted, for example, and is stored in the storage means 106. As mentioned above, as the focal length f becomes larger, the lens exit pupil distance becomes larger, so the S/N ratio decreases. Note that although the focal length itself is used for determination here, the present invention is not limited thereto, and any value corresponding to the focal length can be used for determination. For example, when the lens shift type image shake correction means 104 and the sensor shift type image shake correction means 105 share and correct the image shake correction angle in a ratio based on the focal length, the sensor shift type image shake correction means The determination may be made based on the ratio of the correction amount of the shake correction means 105. For example, if the control ratio of the lens shift type image stabilization means 104 is overwhelmingly high, it is presumed that the optical system exceeds a predetermined focal length, so the determination in this step is made based on this. You can. If it is determined that the focal length is longer than the predetermined focal length fth, the process advances to step S1002. If it is determined that the length is not long (less than fth), the process advances to step S1004.

In step S1002, the image blur correction control unit 107 determines whether the current aperture value (Fno.) of the photographing optical system 101 is a predetermined aperture value Fno. It is determined whether the value is larger than th. Predetermined aperture value Fno. th is predetermined based on the degree of decrease in S/N of focus detection described above, and is set based on the optical characteristics of the image sensor 102 and the photographing optical system 101. For example, a relatively large value such as 8 is adopted and stored in the storage means 106. Fno. is the predetermined aperture value Fno. If it is determined that the aperture value is larger than th, it is determined that the photographing optical system is in the first state where the focal length is long and the aperture value is large, and the process advances to step S1003. Fno. is the predetermined aperture value Fno. If it is determined that the value is not larger than th (less than or equal to Fno.th), the process advances to step S1004. In this embodiment, the aperture value (Fno.) was used for the determination, but the aperture size may be used instead of the aperture value for the actual determination.

In step S1003, since the focal length f of the photographing optical system 101 is long and the aperture value (Fno.) is large, the image blur correction control means 107 uses a sensor that limits the amount of movement of the sensor shift type image blur correction means 105. Activates shift amount limiting operation. As a result, the amount of movement of the sensor shift type image blur correction means 105 is determined by the amount of movement of the sensor shift type image blur correction unit 105 when the focal length f is less than or equal to a predetermined value or the aperture value is less than or equal to a predetermined value (when it is determined that it is not in the first state). This can be suppressed to a range smaller than the amount of movement of the shake correction means 105. Thereby, the S/N ratio of the focus detection signal used for focus detection by the focus detection means 103 can be ensured without falling into the situation as shown in FIG. 10(c). The sensor shift amount may be limited so that the image sensor 102 can only move a shorter distance after step S1003 than when it does not. Specifically, if the movable distance of the image sensor 102 in the first direction (X direction) perpendicular to the optical axis of the photographic optical system 101 is set to the first distance, in this step, the first distance is set. A movable distance of the image sensor 102 in this direction is defined as a second distance shorter than the first distance. Note that the first direction is preferably the arrangement direction of the first focus detection pixels 201 and the second focus detection pixels 202 (the phase difference detection direction, in this embodiment, the X direction). The second distance may be a distance stored in advance in the storage means 106, or may be obtained by multiplying the first distance by a coefficient less than 1 or subtracting a predetermined value from the first distance. You can. Alternatively, information regarding the second distance may be acquired from the lens unit, and the second distance may be determined based on the acquired information. Alternatively, the second distance may be set to zero. In this case, the imaging device is designed to allow the sensor shift image stabilization function to be turned ON/OFF (valid/invalid) by the user's operation, and even if the user has set it to ON, the image stabilization function using the sensor shift method cannot be used. Stops the image stabilization function.

When the second distance is set in step S1003, sensor shift type image blur correction is performed in which the second distance is the maximum value of the moving distance (that is, the movable range) until step S1006, which will be described later. .

In step S1004, the focus detection unit 103 performs the focus detection process shown in FIG. 7, and the focus adjustment control unit performs focus adjustment drive based on the acquired focus detection result. When the focus adjustment drive is completed, the process advances to step S1005. Note that sensor shift type image blur correction is also performed during the exposure period for acquiring the first focus detection signal and the second focus detection signal. At this time, the movable distance of the image sensor 102 in the first direction is limited to the second distance after passing through step S1003, and when proceeding from step S1001 or S1002 to step S1004 without passing through step S1003. This is the first distance.

In step S1005, it is determined whether the release button has been fully pressed (SW2), which is an instruction to start the imaging operation. If SW2 is not detected, the process returns to step S1001, and steps S1001 to S1004 are repeated until SW2 is detected. Note that in this embodiment, like so-called servo AF, the focus adjustment operation on the subject is repeated until SW2 is detected, so the process returns to step S1001, but the present invention is not limited to this. For example, when the focus adjustment drive in step S1004 is completed, the process may wait in step S1005 until SW2 is detected. If SW2 is detected, the process advances to step S1006.

In step S1006, in order to start the imaging operation, the sensor shift amount limiting operation activated in step S1003 is stopped, and the movable distance of the image sensor 102 in the first direction is set to the first distance. As a result, regardless of the focal length or aperture value, the sensor shift type image blur correction is switched to normal image blur correction driving that corrects the shake applied to the imaging device 12 as much as possible. In this embodiment, the movable distance during focus detection and the movable distance during imaging when no restrictions are applied are both set as the first distance, but the movable distance during imaging is set as the third distance. You can also use it as In this case, the third distance is preferably greater than or equal to the first distance. Thereafter, in step S1007, imaging processing is performed by the image sensor 102, and the process advances to step S1008.

In step S1008, it is determined whether SW2 continues to be instructed (whether the release button continues to be fully pressed). If it is determined that SW2 has transitioned to a state where it is not instructed, the process advances to step S1009. If it is determined that the SW2 instruction continues, the process returns to step S1007. In step S1009, it is determined whether SW1 is instructed (whether the release button is pressed halfway). If SW1 is not instructed, this flow ends. If SW1 is instructed, the process returns to S1001. This return destination may be a return to step S1005, as described in step S1005.

According to this embodiment, by setting a limit on the amount of sensor shift during focus detection, it is possible to provide an imaging device that secures the S/N ratio of the focus detection signal.

In this embodiment, the image stabilization control means 107 uses the photographic optical system 101 based on the identification information indicating the lens type of the interchangeable lens 11, which is related to the focal length information and aperture value (F number) of the photographic optical system 101. An example of determining whether or not is in the first state will be explained. Since the only difference from the first embodiment is the flow of the imaging operation, explanations of the configurations of the interchangeable lens 11 and the imaging device 12 will be omitted.

FIG. 12 is a flowchart of the imaging operation performed by the image blur correction control means 107 of the imaging device 12. The difference from the flow in FIG. 11 is that in step S2001, it is determined whether the interchangeable lens 11 is in the first state based on individual identification information (lens ID) that includes lens information indicating the lens type (model number). This is the point.

For example, in the case of a single focal length lens, the focal length and open aperture value of the photographing optical system 101 are fixed values from the stage of designing the interchangeable lens 11. If it is known at the design stage that the focal length and maximum aperture value are greater than a predetermined value, the photographic optical system can only take the first state, so depending on the lens type, the above-mentioned sensor It becomes possible to switch whether or not to perform the shift amount limiting operation. Further, even if the lens is a zoom lens and the focal length is movable, the same applies when the minimum value of the focal length is equal to or greater than a predetermined value (fth). Therefore, a lens type that cannot take a focal length less than a predetermined focal length and cannot take a predetermined aperture value (that is, can take only the first state) is registered in advance in the storage means of the imaging device. I'll keep it. Then, in step S2001, the photographing optical system is in the first state by determining whether the attached interchangeable lens 11 is a registered type of lens based on the acquired lens ID. It is possible to determine whether or not (only the first state can be taken). Note that the lens ID is transmitted from the interchangeable lens 11 to the imaging device 12 when the interchangeable lens 11 is attached to the imaging device 12. In this way, it is possible to determine whether or not the image stabilization control means is in the first state without using the focal length or aperture value itself. It is assumed that a determination is being made as to whether or not the aperture value is larger than a predetermined aperture value.

Steps S2004 to S2009 correspond to steps S1004 to S1009 in FIG. 11, respectively, so their explanation will be omitted. However, in this flow, if it is determined in step S2005 that SW2 is not instructed, the return position is step S2005, and the flow waits in step S2005 until SW2 is input. Note that, as in the first embodiment, the focus adjustment operation on the subject may be repeated until SW2 is detected, and if the determination is No in step S2005, the process may return to step S2004. Furthermore, in this flow, when it is determined in step S2009 that the SW1 instruction has been input, the return position is step S2005, and the flow waits in step S2005 until SW2 is input.

According to this embodiment, by setting a limit on the amount of sensor shift during focus detection, it is possible to provide an imaging device that secures the S/N ratio of the focus detection signal.

[Modified example]
In the above embodiment, one pixel has two photoelectric conversion units 301 and 302, and the first focus detection pixel 201 and the second focus detection pixel 202 are arranged adjacently. The focus detection method using the plane phase difference method was explained. However, the configuration of the image sensor is not limited to this. For example, an image sensor may be used to capture an image using an image sensor in which a pixel having only a photoelectric conversion unit 301 and a pixel having only a photoelectric conversion unit 302 are arranged, or an image sensor in which pixels having two photoelectric conversion units are scattered. Focus detection using a plane phase difference method may also be performed.

Further, in step S1003 and step S2003, the movable distance of the image sensor 102 is uniformly set to the second distance, but the second distance may be set based on the focal length or the aperture value. For example, when the same lens unit is attached, the second distance set in step S1003 when the focal length is 700 mm is shorter than the second distance set in step S1003 when the focal length is 500 mm. You can.

In addition, an imaging system that moves the image sensor in accordance with the position of the optical axis of the photographic optical system of the attached interchangeable lens to bring the center of the effective area of the image sensor closer to or match the optical axis. There is. In this case, even if the sensor shift amount limiting operation is performed, the amount of movement of the image sensor according to the position of the optical axis is not limited, and if the movement is based on the amount of change in the position of the optical axis, the amount of movement of the image sensor is not limited. It is good also as a form which moves more than a 2nd distance.

Further, the focus detection signal is generally an image signal of a part of the imaging range (AF region). The amount of S/N reduction in the focus detection signal due to movement of the image sensor differs depending on the distance (image height) of the AF area from the optical axis. Therefore, in addition to the focal length and aperture value, it may be determined whether or not to limit the movable distance of the image sensor based on the image height of the AF area. Furthermore, the movable distance (second distance) in the case of restriction may be obtained based on the image height of the AF area. In this case, the lower the image height, the longer the movable distance.

Further, in step S1006, the sensor shift amount limiting operation is ended and the movable distance of the image sensor in the first direction is set as the first distance, but if the movable distance in step S1007 is longer than the second distance, It is not limited to the first distance. For example, when SW2 is detected, the movable distance of the image sensor in the first direction may be set to a third distance that is longer than the first distance. Even if the focal length and aperture value are below predetermined values, depending on the image height, the S/N may decrease significantly due to movement of the image sensor. By setting the movable distance after SW2 to the third distance, it is possible to reduce the decrease in the S/N of the focus detection signal and also to reduce the decrease in the image blur correction effect of the sensor shift method during exposure in image pickup processing. Can be done. Note that exposure in the imaging process is exposure for capturing an image to be stored in the storage unit 106 or a removable storage unit such as an SD card.

Furthermore, in the above-described embodiments, the image capturing apparatus includes the image blur correction control means, but the present invention is not limited thereto. For example, the interchangeable lens 11 determines whether or not the photographing optical system is in the first state, and if it is determined that the photographing optical system is in the first state, the image pickup device is configured to limit the movable distance of the image sensor. The sensor shift type image blur correction means may be controlled. Further, a control device wirelessly connected to the imaging system 1000, not the imaging device 12 or the interchangeable lens 11, includes an image blur correction control means, and the control device controls the sensor shift type image blur correction means in the imaging device 12. You can.

Although preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications and changes can be made within the scope of the gist thereof.

102 Image sensor 103 Focus detection means 104 Lens shift type image shake correction means 105 Sensor shift type image shake correction means 106 Storage means 107 Image shake correction control means 108 Focus adjustment optical system

Claims (12)

a focus detection unit that performs focus detection based on a phase difference between a pair of image signals obtained by an image sensor that captures images of light fluxes that have passed through different pupil regions of the photographic optical system;
Image shake correction control means that controls a first image shake correction means for moving the image sensor with respect to the photographing optical system based on an image shake correction amount;
determining means for determining whether the focal length of the photographing optical system is longer than a predetermined focal length and the aperture value of the photographing optical system is in a first state larger than the predetermined aperture value;
Equipped with
The image blur correction control means includes:
If the determining means does not determine that the first state is present,
A first distance is a distance that the image sensor can move in a first direction perpendicular to the optical axis of the photographic optical system,
When the determining means determines that the first state is present,
An image blur correction control device characterized in that a distance over which the image sensor can move in the first direction is a second distance shorter than the first distance. The lens unit including the photographing optical system is removably attachable to the imaging device including the image sensor,
The determining means is
The image stabilization control device according to claim 1, wherein the image stabilization control device determines whether or not the first state is based on lens information acquired from the lens unit. The image stabilization control device according to claim 2, wherein the lens information is identification information of the lens unit. The image blur correction control device according to any one of claims 1 to 3, wherein the second distance is a predetermined distance. the second distance is 0;
When the determining means determines that the first state is present,
5. The image blur correction control device according to claim 4, wherein the image blur correction control means stops the image blur correction function of the first image blur correction means. Further comprising a setting means for setting whether or not to enable an image blur correction function by the first image blur correction means based on a user's input,
The image blur correction control means includes:
5. When the determination means determines that the first state is present, the image blur correction function of the first image blur correction means is stopped, regardless of the settings made by the setting means. The image stabilization control device described in . The image blur correction control means includes:
The image stabilization control device according to claim 2 or 3, wherein the second distance is determined based on lens information acquired from the lens unit. The focus detection means performs the focus detection based on a phase difference between the pair of image signals acquired from a partial area of the image sensor,
When the determining means determines that the first state is present,
The image blur correction control means determines whether the distance over which the image sensor can move is the first distance or the second distance based on the position of the area where the pair of image signals is acquired. The image stabilization control device according to any one of claims 1 to 3, characterized in that: The focus detection means performs the focus detection based on a phase difference between the pair of image signals acquired from a partial area of the image sensor,
8. The image stabilization control device according to claim 1, wherein the second distance is determined based on the position of the area. The image blur correction control means controls the first image blur correction means to move the image sensor based on the amount of change in the position of the optical axis of the photographing optical system,
Even if the determination means determines that the first state is present,
10. A movable distance of the image sensor in the first direction based on an amount of change in the position of the optical axis is not limited to the second distance. The image stabilization control device described above. A mounting section on which a lens unit including the image sensor, the first image blur correction means, the image blur correction control device according to any one of claims 1 to 10, and the photographic optical system can be mounted. An imaging device having: a focus detection means that performs focus detection based on a phase difference between a pair of image signals obtained by an image sensor that images light fluxes that have passed through different pupil regions of a photographing optical system; A method for controlling an imaging device comprising: a first image blur correction means that is moved relative to an optical system;
a determination step of determining whether the focal length of the photographing optical system is longer than a predetermined focal length and the aperture value of the photographing optical system is in a first state larger than the predetermined aperture value;
an image blur correction control step of controlling the first image blur correction means based on an image blur correction amount;
In the determination step, if it is not determined that the first state is present,
In the image blur correction control step,
A first distance is a distance that the image sensor can move in a first direction perpendicular to the optical axis of the photographic optical system,
In the determination step, if it is determined that the first state is present,
In the image blur correction control step,
A method for controlling an imaging device, characterized in that a distance over which the imaging device can move in the first direction is a second distance that is shorter than the first distance.

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