JP7175704B2 - Imaging device and its control method - Google Patents

Description

The present invention relates to an imaging apparatus that performs focus detection using a dedicated focus detection sensor and an imaging element.

In a single-lens reflex digital camera, when light from an interchangeable lens is reflected to an optical viewfinder by a mirror to allow the user to observe the subject image, the light transmitted through the half-mirror portion of the mirror is sent to a focus detection sensor (AF sensor). lead to Focus detection by the phase difference detection method by the AF sensor and drive of the focus lens based on the detection result, that is, AF are performed. Further, when the mirror is retracted from the optical path from the interchangeable lens, focus detection can be performed by the imaging plane phase difference detection method using the focus detection pixels provided in the imaging element.

If the subject or camera moves between AF using the AF sensor and imaging, the imaging will result in an out-of-focus image. By performing focus detection using the image sensor during imaging, it is possible to confirm whether the output image is a focused image or an out-of-focus image when the image is output after imaging. Japanese Unexamined Patent Application Publication No. 2002-200000 discloses an imaging apparatus that enables a user to variably set a threshold value for in-focus/out-of-focus determination by focus detection using an imaging device.

JP 2011-209450 A

However, it is actually difficult for the user to determine the above threshold. If the threshold is too high, an image obtained by imaging will be determined as an out-of-focus image even if the subject or camera hardly moves. On the other hand, if the threshold is too low, even clearly out-of-focus images will be judged as in-focus images.

SUMMARY OF THE INVENTION The present invention provides an imaging apparatus that can easily set a threshold for evaluating the degree of focus of an output image after imaging.

An imaging device as one aspect of the present invention includes an imaging device that captures an image of a subject, image generating means that generates an output image having a resolution different from that of the imaging device from an imaging signal output from the imaging device, an imaging plane focus detection means for obtaining a pair of focus detection signals used for focus detection by an imaging plane phase difference detection method from an imaging element and calculating a phase difference between the pair of focus detection signals; and a phase difference and a threshold. and evaluation means for comparing and evaluating the degree of focus of the output image. The evaluation means is characterized by changing the threshold according to the resolution of the output image.

Further, a control method as another aspect of the present invention is applied to an imaging apparatus having an imaging device that captures an image of a subject. The control method includes steps of generating an output image having a resolution different from that of the imaging device from an imaging signal output from the imaging device; It has a step of acquiring focus detection signals and calculating a phase difference between the pair of focus detection signals, and an evaluation step of comparing the phase difference with a threshold to evaluate the degree of focus of the output image. In the evaluation step, the threshold is changed according to the resolution of the output image.

A computer program that causes a computer of the imaging apparatus to execute processing according to the above control method also constitutes another aspect of the present invention.

According to the present invention, it is possible to easily set a threshold for evaluating the degree of focus of an output image after imaging.

1 is a block diagram showing the configuration of a camera system that is Embodiment 1 of the present invention. FIG. FIG. 4 is a diagram showing a pixel array of an image sensor in Example 1; 4 is a flowchart showing imaging processing according to the first embodiment; 4 is a flowchart showing still image capturing processing according to the first embodiment; 7 is a graph showing an example of calculation of an image shift amount in Example 1; 4A and 4B are diagrams showing focus detection areas according to the first embodiment; FIG. 4A and 4B are views showing display examples according to the first embodiment; FIG. 9 is a flow chart showing moving image capturing processing in Embodiment 2 of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows an interchangeable lens system comprising a single-lens reflex digital camera (hereinafter simply referred to as a camera) 20 as an image pickup apparatus and an interchangeable lens 10 detachably attached to the camera 20, which is Embodiment 1 of the present invention. 1 shows the configuration of a model camera system. The camera control unit 212 mounted on the camera 20 and the lens control unit 106 mounted on the interchangeable lens 10 can communicate with each other.

The interchangeable lens 10 has an imaging optical system including a fixed lens 101, a diaphragm 102, and a focus lens 103 arranged in order from the object side. The interchangeable lens 10 also has an aperture drive unit 104, a focus lens drive unit 105, and the lens control unit 106 and lens operation unit 107 described above.

A diaphragm 102 is driven by a diaphragm drive unit 104 to control the amount of light incident on an image sensor 201, which will be described later. The focus lens 103 is driven in the optical axis direction of the imaging optical system by a focus lens drive unit 105 to perform focus adjustment. The lens control unit 106 drives the diaphragm 102 and the focus lens 103 by controlling the diaphragm driving unit 104 and the focus lens driving unit 105 according to the drive command received from the camera control unit 212 .

The lens operation unit 107 includes operation members such as switches and dials operated by the user. The lens control unit 106 performs various controls on the interchangeable lens 10 according to user operations on the lens operation unit 107 . The lens control unit 106 also transmits lens information such as identification (ID) information of the interchangeable lens 10 and optical information of the imaging optical system to the camera control unit 212 .

On the other hand, the camera 20 has a quick return mirror 252 that can move in and out of the optical path from the imaging optical system. A quick return mirror 252 placed in the optical path reflects part of the light flux from the imaging optical system and reaches the user's eye via an optical viewfinder composed of a pentaprism 251 and an eyepiece lens 256 . This allows the user to observe the subject image (finder image) through the optical viewfinder. A central portion of the quick return mirror 252 is formed as a half mirror portion. A light beam transmitted through the half mirror portion in the optical path is reflected by a sub-mirror 253 arranged behind the quick return mirror 252 and guided to an AF sensor 254 as a focus detection sensor (sensor dedicated to focus detection). The AF sensor 254 can perform focus detection in a plurality of (for example, 11) focus detection areas 701 in a photographing screen (finder image) 700, as shown in FIG. 6(a).

The AF sensor 254 has a plurality of pairs of line sensors each including a plurality of photodiodes, and acquires a pair of focus detection signals as its output signal from each pair of line sensors. The focus detection circuit 255 performs correlation calculation on the pair of focus detection signals, calculates the phase difference (image shift amount) between the pair of focus detection signals, and outputs the image shift amount to the camera control unit 212 .

When the quick return mirror 252 is withdrawn from the optical path, the luminous flux from the imaging optical system passes through the optical filter 259 having infrared cut and low-pass actions and the focal plane shutter 258 in the open state to capture the subject image on the imaging device 201 . Form. The imaging element 201 is a photoelectric conversion element such as a CMOS sensor, and captures (photoelectrically converts) a subject image. A focal plane shutter 258 opens and closes to control the amount of exposure of the image sensor 201 .

A plurality of imaging pixels are two-dimensionally arranged on the imaging surface, which is the light receiving surface of the imaging element 201 . each imaging pixel. It generates and accumulates electric charges according to the amount of incident light. The charge accumulated in each imaging pixel is read out as a voltage signal corresponding to the amount of charge in response to a drive pulse supplied from the timing generator 215 in response to a command from the camera control section 212 .

FIG. 2 shows the arrangement of imaging pixels in the imaging device 201 . A large number of pixel units are two-dimensionally arrayed on the imaging surface, with four imaging pixels of 2 pixel rows×2 pixel columns serving as pixel units. Two of the four imaging pixels in the pixel unit are G pixels with green (G) color filters, and the other two are R pixels with red (R) color filters and blue (B) pixels. B pixels with color filters.

Furthermore, in the image pickup device 201, each image pickup pixel has one microlens 293 and two (pairs) of photodiodes (focus detection pixels) 291, 291, 291, 291, 291, 291, 291, 291, 291, 291, 291, and 291, respectively. 292. A light flux from the imaging optical system is separated by a microlens 293 and received and photoelectrically converted by a pair of photodiodes 291 and 292 , thereby obtaining a pair of focus detection signals from the pair of photodiodes 291 and 292 .

FIG. 6B shows a plurality (for example, 31) of focus detection areas 711 capable of performing focus detection by the imaging plane phase difference detection method on the image pickup element 201 (image pickup screen 710). A pair of focus detection signals is obtained by synthesizing output signals from a plurality of pairs of focus detection pixels in each focus detection area 711 . A plurality of focus detection areas 711 are superimposed and displayed on the subject image on the display unit (display means) 206 . Although the number of focus detection areas 711 (31) is different from the number of focus detection areas 701 (11) of the AF sensor 254, 11 of the 31 focus detection areas 711 overlap the focus detection areas 701. ing.

By performing a correlation calculation for obtaining a correlation value for the pair of focus detection signals obtained from the image sensor 201 in this way, an image shift amount as a phase difference between the pair of focus detection signals can be obtained. , the defocus amount can be calculated (detected) from the image shift amount. An imaging signal is obtained by adding the output signals from the pair of photodiodes 291 and 292 for each imaging pixel and synthesizing the added output signals from all the imaging pixels.

A pair of focus detection signal and imaging signal read out from the imaging element 201 are respectively input to the CDS/AGC/AD converter 202 . A CDS/AGC/AD converter 202 performs correlated double sampling for removing reset noise, gain adjustment, and A/D conversion on the paired focus detection signal and imaging signal, and converts the paired focus detection signal as a digital signal. Generating signals and imaging signals. A pair of focus detection signal and imaging signal output from the CDS/AGC/AD converter 202 is input to an image processing unit 203 as image generation means. The image processing unit 203 performs various types of image processing such as γ conversion and color interpolation processing on the imaging signal to generate an image signal (image data), which is stored in the SDRAM 209 . Also, the image processing unit 203 outputs a pair of focus detection signals to the AF signal processing unit 204 .

The image data stored in the SDRAM 209 is input to the display control unit 205 via the bus 21, and the display control unit 205 displays the image data on the display unit 206. FIG. When image data is to be recorded, the image data is recorded on the recording medium 208 by the recording medium control unit 207 . The ROM 210 stores computer programs executed by the camera control unit 212 connected via the bus 21 and various data required for control. The flash ROM 211 stores various setting information regarding the operation of the camera 20 such as setting values set by the user.

An AF signal processing unit 204 serving as imaging plane focus detection means performs pixel addition processing on the pair of focus detection signals, and further performs correlation calculation on the pair of focus detection signals after the pixel addition processing to determine the distance between the pair of focus detection signals. The amount of image shift, which is the phase difference of , is calculated. The AF signal processing unit 204 also calculates the reliability (matching degree, steepness degree, contrast, etc.) of the pair of focus detection signals. The AF signal processing unit 204 outputs the calculated image shift amount and reliability to the camera control unit 212 .

The camera control unit 212 notifies the AF signal processing unit 204 of changes in the conditions for calculating the image shift amount and the reliability in accordance with the image shift amount and the reliability. For example, when the amount of image shift is large, the area for correlation calculation is widened, or the type of bandpass filter is changed according to the contrast. Details of the correlation calculation will be described later.

Note that, in this embodiment, a pair of focus detection signal and imaging signal is obtained from the imaging device 201 . However, one of the pair of focus detection signals and the imaging signal may be obtained from the image sensor 201, and the other focus detection signal may be obtained by subtracting the one focus detection signal from the imaging signal by the image processing unit 203. good.

The camera control unit 212 controls the entire camera 20, and turns on/off the power, changes various settings, and starts capturing (recording) still images/moving images in response to inputs (user operations) from the camera operation unit 214. and stop, execution of AF, generation and display of an output image, and various other operations. The output image is an image generated from an imaging signal and is finally saved in the recording medium 208 or displayed on the display unit 206 .

Further, the camera control unit 212 acquires lens information from the lens control unit 106 through communication, and transmits various drive commands to the lens control unit 106 as described above. Further, the camera control unit 212 performs image rating processing, which will be described later, as evaluation means.

The flowchart in FIG. 3 shows imaging processing executed by the camera control unit 212 according to a computer program. In the following description, "S" indicates a step.

First, in S<b>301 , the camera control unit 212 performs initialization processing of the camera 20 . Next, in S<b>302 , the camera control unit 212 determines whether or not the user has selected (instructed) the still image capturing mode in the camera operation unit 214 . If the still image capturing mode is selected, the process proceeds to S303; otherwise, the process proceeds to S304.

In S303, the camera control unit 212 performs still image capturing processing. After that, the process returns to S302. Details of the still image capturing process will be described later.

In S<b>304 , the camera control unit 212 determines whether or not the user has selected (instructed) the moving image imaging mode in the camera operation unit 214 . If the moving image capturing mode is selected, the process proceeds to S305; otherwise, the process proceeds to S306.

In S305, the camera control unit 212 performs moving image capturing processing. After that, the process returns to S302. Details of the moving image capturing process will be described in a fourth embodiment later.

In S<b>306 , the camera control unit 212 determines whether or not the user has selected (instructed) the image viewing mode in the camera operation unit 214 . If the image viewing mode has been selected, the process proceeds to S307; otherwise, the process proceeds to S308.

In S307, the camera control unit 212 performs image browsing processing. After that, the process returns to S302. Image viewing processing will be described later.

In S<b>308 , the camera control unit 212 determines whether or not the user has instructed to turn off the power through the camera operation unit 214 . If power-off has been instructed, this process is terminated; otherwise, the process returns to S302.

The flowchart in FIG. 4 shows the still image capturing process performed in S304 in FIG. In S<b>401 , the camera control unit 212 determines whether or not the user has performed a half-press operation (SW1 ON) of the shutter switch in the camera operation unit 214 . The determination of S401 is repeated until SW1 is turned on, and when SW1 is turned on, the process proceeds to S402.

In S402, the camera control unit 212 performs photometry. Specifically, the camera control unit 212 causes a photometric sensor (not shown) to measure the light flux that has passed through the pentaprism 251 from the imaging optical system via the quick return mirror 252, and acquires the result. The camera control unit 212 sets an aperture value at which proper exposure is obtained according to the result of photometry.

Next, in S403, the camera control unit 212 causes the AF sensor 254 and the focus detection circuit 255, which receive the light flux reflected by the sub-mirror 253, to perform focus detection. The camera control unit 212 acquires the detected (calculated) image shift amount from the focus detection circuit 255 .

Next, in S404, the camera control unit 212 uses the image shift amount obtained from the focus detection circuit 255 to calculate the defocus amount of the imaging optical system as the focus detection result, and obtains the in-focus state according to the defocus amount. A drive amount (focus drive amount) of the focus lens 103 for the purpose is calculated. The camera control unit 212 then transmits the focus drive amount to the lens control unit 106 . The lens control unit 106 drives the focus lens 103 via the focus lens driving unit 105 according to the received focus driving amount. In this manner, the camera control unit 212 performs phase difference detection AF (focus detection and focus control) using the AF sensor 254 as focus control means before the imaging device 201 takes an image.

Next, in S<b>405 , the camera control unit 212 determines whether or not the user has fully pressed the shutter switch (SW2 ON) in the camera operation unit 214 . The determination of S405 is repeated until SW2 is turned on, and when SW2 is turned on, the process proceeds to S406.

In S406, the camera control unit 212 retracts the quick return mirror 252 and the sub-mirror 253 out of the optical path through a mirror driving circuit (not shown).

Next, in S<b>407 , the camera control unit 212 transmits to the lens control unit 106 an aperture drive command including the aperture value set in S<b>402 . The lens control unit 106 narrows down the aperture 102 to the set aperture value through the aperture drive unit 104 according to the received aperture drive command.

Next, in S408, the camera control unit 212 opens the focal plane shutter 258 through a shutter driving circuit (not shown). Then, the camera control unit 212 closes the focal plane shutter 258 through the shutter drive circuit in S409 according to the lapse of the predetermined shutter time. Furthermore, the camera control unit 212 causes the focal plane shutter 258 to perform a charging operation through the shutter driving circuit in preparation for the next opening operation.

Next, in S<b>410 , the camera control unit 212 causes the image processing unit 203 to acquire an A image signal and a B image signal as a pair of focus detection signals from the image sensor 201 .

Next, in S<b>411 , the camera control unit 212 causes the image processing unit 203 to acquire an imaging signal from the imaging element 201 .

Next, in S412, the camera control unit 212 instructs the lens control unit 106 to open the diaphragm 102. FIG. The lens control unit 106 opens the diaphragm 102 via the diaphragm driving unit 104 according to the open instruction.

Next, in S413, the camera control unit 212 moves the mirror 252 into the optical path through the mirror driving circuit.

Next, in S414, the camera control unit 212 causes the AF signal processing unit 204 to calculate the image shift amount, which is the phase difference between the A image signal and the B image signal acquired by the image processing unit 203 in S410. As a result, focus detection is performed by the imaging plane phase difference detection method using the imaging device 201 . A method of calculating the amount of image shift between the A image and B image signals will be described later.

Next, in S415, the camera control unit 212 calculates the allowable amount of blur using the resolution of the image sensor 201 and the currently set output resolution, which is the resolution of the output image (still image). The allowable amount of blur and its calculation method will be described later.

Next, in S416 (evaluation step), the camera control unit 212 performs image rating processing for evaluating the degree of focus of the output image. Specifically, the camera control unit 212 compares the image shift amount calculated in S414 with the allowable blur amount as a threshold calculated in S415, and determines whether or not the image shift amount is smaller than the allowable blur amount. . If the amount of image shift is smaller than the allowable amount of blurring, the rate is set to 1 on the assumption that the output image will be a focused image with a high degree of focus. On the other hand, if the amount of image shift is equal to or greater than the allowable amount of blurring, the output image is assumed to be an out-of-focus image with a low degree of focus, and the rate is set to 0.

Next, in S417, the camera control unit 212 causes the image processing unit 203 to perform addition/reduction processing for converting the resolution of the imaging signal acquired in S411 to the currently set output resolution, thereby outputting an output image. generate. Further, the camera control unit 212 causes the image processing unit 203 to perform compression processing on the output image, and causes the recording medium control unit 207 to output the compressed output image. At this time, the camera control unit 212 outputs the rate as a result of evaluating the output image in S416 to the recording medium control unit 207. FIG. The recording medium control unit 207 associates the compressed output image with the rate and records them in the storage medium 208 .

Calculation of the image shift amount performed in S414 of FIG. 4 will be described with reference to FIGS. The upper part of FIG. 5A shows a subject image 500 formed on the imaging surface of the imaging device 201 in a focused state. A white circle in this subject image 500 is on one imaging pixel in an imaging pixel group (one square frame indicates one imaging pixel) 501 in the imaging device 201, as shown in the middle of FIG. is formed in Each imaging pixel includes one microlens and a pair of photodiodes as shown in FIG. Output signals from one photodiode in the imaging pixel group are combined to generate an A image signal, and output signals from the other photodiode are combined to generate a B image signal.

The lower part of FIG. 5A shows an A image signal 504 and a B image signal 505 obtained from an imaging pixel in the imaging pixel group 501 through which an arrow 503 passes. Since FIG. 5A shows the in-focus state, the A image signal 504 and the B image signal 505 actually overlap (the amount of image shift is 0). shown shifted.

The upper part of FIG. 5B shows a blurred subject image 510 formed on the imaging surface of the imaging device 201 in an out-of-focus (defocus) state. White circles in the blurred subject image 510 extend over six imaging pixels in the imaging pixel group 511 in the imaging device 201, as shown in the middle part of FIG. 5B. The lower part of FIG. 5B shows an A image signal 514 and a B image signal 515 obtained from two imaging pixels in the imaging pixel group 511 through which an arrow 513 passes. Since it is out of focus, the A image signal 514 and the B image signal 515 have an image shift amount d.

FIGS. 5(c) and 5(d) show graphs of the image shift amounts shown in FIGS. 5(a) and 5(b), respectively. Specifically, the A image signal (504, 514) and the B image signal (505, 515) are obtained by relatively shifting the A image signal (504, 514) and the B image signal (505, 515) by one pixel, and the A image signal and the hatched A image signal in FIG. The graph shows the change in the difference XOR of the B image signal. In FIGS. 5C and 5D, the horizontal axis indicates the amount of shift (the number of pixels), and the vertical axis indicates the XOR.

In the in-focus state shown in FIG. 5(a), XOR becomes minimum (=0) at a shift amount of 0 as shown in FIG. 5(c). A shift amount of 0 at this time indicates an image shift amount of 0. On the other hand, as shown in FIG. 5(b), in the out-of-focus state where the object image of one pixel size is blurred to two pixels, XOR is performed with a shift amount of 1 or −1 as shown in FIG. 5(d). is the minimum. A shift amount of -1 or 1 at this time indicates an image shift amount of -1 or 1.

FIG. 5(f) shows the shift amount interpolation processing. As shown in FIG. 5(b), this interpolation processing is performed when the amount of blurring that is not just an integer pixel is generated. For example, as shown in FIG. 5(f), when four XOR values are obtained at shift amounts of −1, 0, 1, and 2, an approximate curve 520 passing through these four points is obtained, and the approximate curve 520 shows A shift amount s that minimizes XOR is obtained. Also, as shown in the figure, the shift amount corresponding to the intersection 522 of two straight lines connecting two of the above four points may be obtained as s. As a result, the amount of shift, that is, the amount of image deviation can be obtained even if the amount of blur does not correspond to an integral number of pixels.

Next, the method of calculating the allowable amount of blur performed in S415 of FIG. 4 will be described. For example, when the image sensor 201 has 7680×4320=32M imaging pixels capable of outputting an 8K moving image, the image output mode of the camera 20 is set by the user to output (record) a still image as an output image of 3840×2160=8M pixels. ) mode. At this time, the still image of 32M pixels obtained as an imaged image by the imaging device 201 is added and reduced by 1/2 in both vertical and horizontal directions to generate a still image of 8M pixels as an output image. Therefore, even if a subject image having a size of one pixel is blurred by two pixels, the output still image is a focused image. Therefore, in this image output mode, a blur amount of two pixels is allowed. That is, the allowable amount of blur is two pixels. The allowable amount of blur is the amount of blur on the image pickup device that allows the output image to be determined as a focused image at the resolution of the output image.

Assume that a still image (32M pixels) acquired as a captured image and a still image (8M pixels) as an output image have the same aspect ratio. In this case, when the horizontal resolution (the number of pixels in the horizontal direction) of the image sensor 201 is the imaging resolution, and the horizontal resolution (the number of pixels in the horizontal direction) of the output image is the output resolution, the allowable amount of blur is expressed by the following formula: (1) is calculated as follows.
Permissible blur amount = imaging resolution / output resolution (1)
FIG. 7A shows a display example on the display unit 206 by the image viewing process performed in S307 of FIG. Two still images 801 and 802 that are output images are displayed on the display unit 206 . Underneath each still image, the shooting date is displayed, and under one still image 802, one star mark 803 is displayed. No star mark is displayed below the still image 801 . A star mark is an index indicating a rating as a result of the image rating processing performed in S416 of FIG. The presence of the star mark indicates that the rating is 1, and the absence of the star mark indicates that the rating is 0. It should be noted that other indicators such as numbers and symbols other than the star mark may be used instead of the star mark.

A still image 801 is an out-of-focus image in which the image shift amount calculated in S414 exceeds the allowable shift amount calculated in S415 (equation (1)). Therefore, the star mark is not displayed. On the other hand, the still image 802 is a focused image in which the image shift amount calculated in S414 is equal to or less than the allowable shift amount calculated in S415 at the currently set output resolution. Therefore, a star mark 803 is displayed. The user can easily determine whether each still image is in focus or out of focus from the presence or absence of the star mark 803 without looking closely at the small still images 801 and 802 displayed and confirming their focus states. can judge.

According to this embodiment, the user can easily confirm the degree of focus of the output image (whether it is a focused image or an unfocused image) after imaging. Also, if the user specifies the output resolution of the camera, a threshold (permissible amount of deviation) for evaluating the degree of focus of the output image is automatically set.

Next, Example 2 of the present invention will be described. This embodiment performs the same configuration and control as those of the first embodiment, except for the calculation of the allowable deviation amount.

In the first embodiment, a case has been described in which the allowable blur amount is automatically calculated and set according to the output resolution set by the user using the equation (1) in S415 of FIG. However, the allowable amount of blur corresponding to the set image output mode may differ from the allowable amount of blur intended by the user. On the other hand, as described above, it is difficult for the user to set the allowable amount of blur, which is a specific threshold. For this reason, in the second embodiment, the user selects the allowable blur amount to be used from among a plurality of allowable blur amounts corresponding to each of a plurality of image output modes that can be set in the camera 20. ).

In the present embodiment, the case where the image pickup device 201 has 7680×4320=32M image pickup pixels capable of outputting an 8K moving image will also be described as an example. Also, the image output modes that can be set in the camera 20 and the permissible amount of blur corresponding to these are
Mode H: 7680×4320=32M pixels Allowable blur amount=1 pixel Mode M: 3840×2160=8M pixels Allowable blur amount=2 pixels Mode L: 1920×1080=2M pixels Allowable blur amount=4 pixels will be explained.

FIG. 7B shows a display example of a user interface (“Rating setting”) that allows the user to select one of the three allowable blur amounts. The user interface indicates ON/OFF of the image rating process and the allowable amount of blur selected by the user (arrows indicate the allowable amount of blur corresponding to modes H, M, and L).

According to this embodiment, the user can easily confirm the degree of focus (whether the image is in focus or out of focus) of the output image after imaging, and the user can set the allowable amount of blur regardless of the output resolution. Can be selected arbitrarily.

Next, Example 3 of the present invention will be described. This embodiment performs the same configuration and control as those of the first embodiment, except for the calculation of the allowable deviation amount.

It may be inconvenient if the evaluation of the focus degree of the output image is determined by the allowable blur amount set according to the image output mode as in the first embodiment or the allowable blur amount selected by the user as in the second embodiment. . Specifically, the resolution of the output image to be finally saved can be determined later, such as by developing the RAW image later, or by extracting a still image from a moving image as described later in the examples. It may be preferable to

In this embodiment, as in the second embodiment, the image sensor 201 has 7680×4320=32M imaging pixels capable of outputting 8K moving images, and the three image output modes described in the second embodiment and the corresponding allowable blur amount is set.

In this embodiment, the rate is set to any one of 0 to 3 from the lowest in accordance with the amount of image shift in the image rating process of S416 of FIG. Specifically, the relationship between the amount of blur in the captured image that is the source of the output image (that is, the amount of blur on the image sensor 201) and the number of star marks indicating rates 0 to 3 of the output image is as follows. be.
When blur amount = 1 pixel: 3 star marks (★★★)
When blur amount = 2 pixels: 2 star marks (★★)
When blur amount = 4 pixels: 1 star mark (★)
When blur amount>4 pixels: no star mark FIG. 7C shows a display example of image rating processing in this embodiment. The two still images 812, 813 are the output images generated in mode L. One star mark 810 is displayed on the still image 812 on the left side, and two star marks 811 are displayed on the still image 813 on the right side where the amount of blur of the original captured image is smaller than that of the still image 812 . This indicates that the still image 813 can be output as a focused image even in a higher resolution image output mode (mode M).

According to this embodiment, the user can easily confirm not only the degree of focus of the output image after imaging (whether it is a focused image or an unfocused image), but also the resolution of the output image that can be output as a focused image. can be done.

Next, Example 4 of the present invention will be described. In this embodiment, a moving image is captured with the same configuration as that of the first embodiment, and a still image can be cut out from the moving image. The flowchart of FIG. 8 shows the moving image capturing process in this embodiment.

In S<b>901 , the camera control unit 212 retracts the quick return mirror 252 out of the optical path through the mirror control circuit in response to the user selecting the moving image imaging mode on the camera operation unit 214 .

Next, in S902, the camera control unit 212 opens the focal plane shutter 258 through the shutter driving circuit. As a result, the luminous flux from the imaging optical system always reaches the imaging device 201 .

Next, in S<b>903 , the camera control unit 212 determines whether or not the user has instructed the camera operation unit 214 to start moving image recording. The determination in step S903 is repeated until the start of moving image recording is instructed, and when the start of moving image recording is instructed, the process advances to step S904.

In S<b>904 , the camera control unit 212 causes the image processing unit 203 to generate an image signal (moving image data) from the imaging signal from the image sensor 201 and output the moving image data to the display control unit 205 . The display control unit 205 causes the display unit 206 to display the moving image corresponding to the moving image data.

Next, in S<b>905 , the camera control unit 212 causes the AF signal processing unit 204 to acquire from the image processing unit 203 an A image signal and a B image signal as a pair of focus detection signals from the image sensor 201 .

Next, in S906, the camera control unit 212 causes the AF signal processing unit 204 to calculate the image shift amount between the A image signal and the B image signal.

Further, in S907, the camera control unit 212 calculates a defocus amount using the calculated image shift amount, and calculates a focus drive amount for obtaining an in-focus state from the calculated defocus amount. The camera control unit 212 transmits the focus drive amount to the lens control unit 106 . The lens control unit 106 drives the focus lens 103 via the focus lens driving unit 105 according to the received focus driving amount. As a result, AF is performed by the imaging plane phase difference detection method.

Next, in S<b>908 , the camera control unit 212 records the moving image data on the recording medium 208 via the recording medium control unit 207 . At this time, the camera control unit 212 records the image shift amount calculated in S906 for each frame of the moving image data.

Next, in S<b>909 , the camera control unit 212 determines whether or not the user has instructed to stop recording the moving image. Until an instruction to stop moving image recording is given, the determination in step S909 is repeated to continue moving image shooting.

In S<b>910 , the camera control unit 212 ends the moving image capturing and closes the focal plane shutter 258 . Then, in S911, the camera control unit 212 moves the quick return mirror 252 into the optical path, and ends this processing.

FIG. 7D shows a display example on the display unit 206 by the image viewing process performed in S307 of FIG. 3 when a still image is cut out from a moving image. The display unit 206 has a touch panel function. The display unit 206 displays a video playback button 821, a pause button 820, a fast-forward button 825, and a fast-reverse button 826 together with the video to be played.

When the user touches the play button 821, fast-forward button 825, or fast-reverse button 826, the moving image is played, fast-forwarded, or fast-reversed. When the user touches the pause button 820 at any one frame, the moving image reproduction is stopped at that one frame and the frame image 823 of the one frame is displayed on the display unit 206 . In this state, when the user fully presses the shutter switch in the camera operation unit 214, the displayed frame image 823 is recorded in the recording medium 208 as a still image as an output image.

The camera control unit 212 performs image rating processing on the displayed frame image 823 in response to the pause instruction by the pause button 820, as in S416 of FIG. As a result, if the image shift amount is smaller than the allowable blur amount, a star mark 822 is displayed on the display unit 206 as shown in FIG. 7D, and if the image shift amount is greater than or equal to the allowable blur amount, no star mark is displayed. .

According to the present embodiment, when still images (frame images) are cut out from a moving image after capturing a moving image, the user can easily check the degree of focus (whether it is a focused image or an unfocused image) for each frame image. can.

In each of the above-described embodiments, the case where only one threshold value is used to evaluate whether the output image is focused or not is evaluated as the degree of focus of the output image. However, multiple thresholds may be used to evaluate the degree of focus (for example, just in focus or approximately in focus) or the degree of out-of-focus (for example, small blur or large blur) of the output image.

In each of the above-described embodiments, a lens-interchangeable single-lens reflex camera having an interchangeable lens (imaging optical system) and having a mirror has been described. However, the embodiments of the present invention include interchangeable-lens mirrorless cameras with interchangeable lenses and no mirrors, and integrated-lens cameras with integrated lenses.

Further, in each of the above embodiments, the case of performing AF by driving the focus lens 103 in the direction of the optical axis has been described. good too.
(Other examples)
The present invention supplies a program that implements one or more functions of the above-described embodiments to a system or device via a network or a storage medium, and one or more processors in the computer of the system or device reads and executes the program. It can also be realized by processing to It can also be implemented by a circuit (for example, ASIC) that implements one or more functions.

Each embodiment described above is merely a representative example, and various modifications and changes can be made to each embodiment in carrying out the present invention.

20 camera 103 focus lens 201 imaging device 204 AF signal processing unit 212 camera control unit 254 AF sensor

Claims (10)

an imaging device that captures an image of a subject;
image generating means for generating an output image having a resolution different from that of the imaging device from an imaging signal output from the imaging device;
imaging plane focus detection means for acquiring a pair of focus detection signals used for focus detection by an imaging plane phase difference detection method from the imaging element and calculating a phase difference between the pair of focus detection signals;
Evaluating means for evaluating the degree of focus of the output image by comparing the phase difference and a threshold;
The imaging apparatus, wherein the evaluation means changes the threshold according to the resolution of the output image. It has display means for displaying the output image,
2. The imaging apparatus according to claim 1, wherein said evaluation means displays an index indicating said focus degree on said display means together with said output image. 3. The imaging apparatus according to claim 1, wherein the evaluation means evaluates whether the output image is a focused image or an unfocused image as the degree of focus of the output image. 4. The imaging apparatus according to any one of claims 1 to 3, wherein the threshold value is an amount of blur on the imaging device that allows the output image to be determined as a focused image at the resolution of the output image. . The conversion means changes the resolution of the output image according to a user operation,
5. The imaging apparatus according to any one of claims 1 to 4, wherein the evaluation means changes the threshold according to the changed resolution of the output image. The evaluation means changes the threshold so that the threshold is selected by a user from a plurality of thresholds corresponding to each of a plurality of resolutions that can be set as the resolution of the output image , regardless of the resolution of the output image. The imaging device according to any one of claims 1 to 5, characterized in that: 3. The image pickup apparatus according to claim 2, wherein said evaluation means displays an index indicating an amount of blur on said image pickup device together with said output image on said display means. a focus detection sensor that is provided separately from the imaging element and generates a pair of focus detection signals used for phase difference detection type focus detection;
and focus control means for calculating a phase difference between the pair of focus detection signals generated by the focus detection sensor before imaging by the image sensor and performing focus control according to the phase difference. The imaging device according to any one of claims 1 to 7. A control method for an imaging device having an imaging element for imaging a subject,
generating an output image having a resolution different from that of the imaging device from the imaging signal output from the imaging device;
a step of acquiring a pair of focus detection signals used for focus detection by an imaging plane phase difference detection method from the imaging element and calculating a phase difference between the pair of focus detection signals;
an evaluation step of comparing the phase difference and a threshold to evaluate the degree of focus of the output image;
A control method for an imaging apparatus, wherein in the evaluation step, the threshold value is changed according to the resolution of the output image. A computer program for causing a computer of an imaging device having an imaging element for imaging a subject image to execute processing according to the control method according to claim 9 .

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