JP2020064208A - Imaging apparatus and control method thereof - Google Patents

Abstract

To easily set a threshold for evaluating the focus degree of an output image after imaging.SOLUTION: An imaging apparatus 20 generates an output image having resolution different from the resolution of an image element 201 from an imaging signal output from the imaging element for imaging a subject image. The image apparatus includes the steps of: acquiring a pair of focus detection signals used for focus detection of the image plane phase difference detection method from the imaging element; calculating phase difference between the pair of focus detection signals; and evaluating the focus degree of the output image by comparing the phase difference with a threshold. In the evaluation, the threshold is changed in accordance with the resolution of the output image.SELECTED DRAWING: Figure 1

Description

The present invention relates to an image pickup apparatus that performs focus detection using a sensor for focus detection and an image sensor.

  In a single-lens reflex digital camera, when a light from an interchangeable lens is reflected by an optical finder by a mirror to allow a user to observe a subject image, the light transmitted through a half mirror portion of the mirror is a focus detection sensor (AF sensor). Lead to. Then, focus detection by the phase difference detection method by the AF sensor and driving of the focus lens based on the result, that is, AF is performed. Further, during image pickup in which the mirror is retracted from the optical path from the interchangeable lens, focus detection can be performed by the image pickup surface phase difference detection method using the focus detection pixels provided in the image pickup element.

  If the subject or the camera moves between AF using the AF sensor and imaging, a non-focused image is obtained by imaging. By performing focus detection using the image sensor at the time of image capturing, it is possible to confirm whether the output image is a focused image or a non-focused image at the time of outputting the image after the image capturing. Patent Document 1 discloses an image pickup apparatus in which a user can variably set a threshold value for focus / non-focus determination by focus detection using an image sensor.

JP, 2011-209450, A

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

  The present invention provides an image pickup apparatus capable of easily setting a threshold value for evaluating the focus degree of an output image after image pickup.

  An image pickup device as one aspect of the present invention includes an image pickup device that picks up a subject image, and an image generation unit that generates an output image having a resolution different from that of the image pickup device from an image pickup signal output from the image pickup device. An image pickup surface focus detection unit that obtains a pair of focus detection signals used for focus detection of an image pickup surface phase difference detection method from an image pickup element and calculates a phase difference between the pair of focus detection signals, and a phase difference and a threshold value. And an evaluation unit that evaluates the in-focus degree of the output image by comparison. The evaluation means is characterized in that the threshold value is changed according to the resolution of the output image.

  The control method according to another aspect of the present invention is applied to an image pickup apparatus having an image pickup element that picks up a subject image. The control method includes a step of generating an output image having a resolution different from that of the image pickup element from an image pickup signal output from the image pickup element, and a pair of steps used for focus detection of the image pickup surface phase difference detection method from the image pickup element. The method includes a step of acquiring a focus detection signal and calculating a phase difference between the pair of focus detection signals, and an evaluation step of comparing the phase difference with a threshold value to evaluate the focus degree of the output image. In the evaluation step, the threshold value is changed according to the resolution of the output image.

  A computer program that causes a computer of the image pickup 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 value for evaluating the focus degree 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. 3 is a diagram showing a pixel array of the image sensor in the first embodiment. 6 is a flowchart showing an image pickup process in the first embodiment. 6 is a flowchart showing still image capturing processing according to the first embodiment. 6 is a graph showing an example of calculating the image shift amount in the first embodiment. FIG. 3 is a diagram showing a focus detection area in the first embodiment. FIG. 6 is a diagram showing a display example in the first embodiment. 9 is a flowchart showing a moving image capturing process according to the second embodiment of the present invention.

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

  FIG. 1 is a lens exchange including a single-lens reflex digital camera (hereinafter, simply referred to as a camera) 20 as an image pickup apparatus that is Embodiment 1 of the present invention, and an interchangeable lens 10 detachably attached to the camera 20. 1 shows the configuration of a type 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 subject side. The interchangeable lens 10 also includes an aperture drive unit 104, a focus lens drive unit 105, the above-described lens control unit 106, and lens operation unit 107.

  The diaphragm 102 is driven by the diaphragm driving unit 104, and controls the amount of light incident on the 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 the focus lens driving unit 105 to perform focus adjustment. The lens control unit 106 controls the diaphragm driving unit 104 and the focus lens driving unit 105 according to the driving command received from the camera control unit 212 to drive the diaphragm 102 and the focus lens 103.

  The lens operating unit 107 includes operating 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 a user operation 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 image pickup optical system to the camera control unit 212.

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

  The AF sensor 254 has a plurality of pairs of line sensors each including a plurality of photodiodes, and obtains a pair of focus detection signals as its output signal from each pair of line sensors. The focus detection circuit 255 performs a correlation calculation on the pair of focus detection signals to calculate a 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 retreats out of the optical path, the light flux from the image pickup optical system passes through the optical filter 259 having the infrared cut and lowpass action and the open focal plane shutter 258 to form a subject image on the image pickup element 201. Form. The image pickup element 201 is a photoelectric conversion element such as a CMOS sensor and picks up (photoelectrically converts) a subject image. The focal plane shutter 258 opens and closes to control the exposure amount of the image sensor 201.

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

  FIG. 2 shows an array of image pickup pixels in the image pickup device 201. Four image pickup pixels of 2 pixel rows × 2 pixel columns are used as a pixel unit, and a large number of pixel units are two-dimensionally arranged on the image pickup surface. Two of the four image pickup pixels of the pixel unit are G pixels having a green (G) color filter, and the other two are R pixels having a red (R) color filter and blue (B). It is a B pixel with a color filter.

  Further, in the image pickup device 201, each image pickup pixel has one microlens 293 and two (pair) photodiodes (focus detection pixels) 291, so that focus detection can be performed by the image pickup surface phase difference detection method. Have 292. The light flux from the image pickup optical system is separated by the microlens 293, and the pair of photodiodes 291 and 292 receive and photoelectrically convert the pair of focus detection signals.

  FIG. 6B shows a plurality of (for example, 31) focus detection areas 711 capable of performing focus detection by the imaging surface phase difference detection method on the imaging element 201 (imaging screen 710). By combining output signals from a plurality of pairs of focus detection pixels in each focus detection area 711, a pair of focus detection signals can be obtained. The plurality of focus detection areas 711 are displayed on the display unit (display unit) 206 so as to be superimposed on the subject image. Although the number of focus detection areas 711 (31) is different from the number of focus detection areas 701 of the AF sensor 254 (11), 11 out of 31 focus detection areas 711 overlap with the focus detection areas 701. ing.

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

  The pair of focus detection signals and image pickup signals read from the image pickup device 201 are input to the CDS / AGC / AD converter 202, respectively. The CDS / AGC / AD converter 202 performs correlated double sampling for removing reset noise, gain adjustment, and A / D conversion for a pair of focus detection signals and an image pickup signal, and detects a pair of focus as a digital signal. Generate a signal and an imaging signal. The pair of focus detection signals and image pickup signals output from the CDS / AGC / AD converter 202 are input to the image processing unit 203 as an image generating unit. The image processing unit 203 performs various image processing such as γ conversion and color interpolation processing on the image pickup signal to generate an image signal (image data), and stores the image signal in the SDRAM 209. The image processing unit 203 also 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. When recording image data, 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 necessary 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.

  The AF signal processing unit 204 as the imaging plane focus detection means performs pixel addition processing on the pair of focus detection signals, and further performs a correlation calculation on the pair of focus detection signals after the pixel addition processing to detect 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 (coincidence, steepness, 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, according to the image shift amount and the reliability. For example, when the image shift amount is large, the area in which the correlation calculation is performed is expanded, or the type of bandpass filter is changed according to the contrast. Details of the correlation calculation will be described later.

  In this embodiment, a pair of focus detection signals and image pickup signals are acquired from the image pickup element 201. However, even if one of the pair of focus detection signals and the image pickup signal are obtained from the image pickup element 201, and the other focus detection signal is obtained by subtracting the one focus detection signal from the image pickup signal by the image processing unit 203. Good.

  The camera control unit 212 controls the entire camera 20, and turns on / off the power supply, changes various settings, and starts still image / moving image capturing (recording) according to an input (user operation) from the camera operating unit 214. Controls various operations such as stop and stop, execution of AF, generation and display of an output image. The output image is an image generated from the image pickup signal and is finally stored in the recording medium 208 or displayed on the display unit 206.

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

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

  First, in S301, the camera control unit 212 performs initialization processing of the camera 20. Next, in S302, the camera control unit 212 determines whether or not the user has selected (instructed) the still image capturing mode on the camera operation unit 214. If the still image capturing mode is selected, the process proceeds to S303, and if not, the process proceeds to S304.

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

  In S304, the camera control unit 212 determines whether or not the user has selected (instructed) the moving image capturing mode on the camera operation unit 214. If the moving image capturing mode is selected, the process proceeds to S305, and if not, the process proceeds to S306.

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

  In S306, the camera control unit 212 determines whether or not the user has selected (instructed) the image browsing mode on the camera operation unit 214. If the image browsing mode is selected, the process proceeds to S307, and if not, the process proceeds to S308.

  In S307, the camera control unit 212 performs an image browsing process. Then, the process returns to S302. The image browsing process will be described later.

  In step S308, the camera control unit 212 determines whether the user has instructed to turn off the power in the camera operation unit 214. If the power-off is instructed, this process ends, otherwise, the process returns to S302.

  The flowchart of FIG. 4 illustrates the still image capturing process performed in S304 of FIG. In S401, the camera control unit 212 determines whether or not the user has half-pressed the shutter switch (SW1 ON) in the camera operation unit 214. The determination in S401 is repeated until the SW1 is turned on, and when the 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 penta prism 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 that provides a proper exposure according to the result of photometry.

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

  Next, in step S404, the camera control unit 212 calculates the defocus amount of the imaging optical system as the focus detection result using the image shift amount acquired from the focus detection circuit 255, and obtains the in-focus state according to the defocus amount. The drive amount (focus drive amount) of the focus lens 103 for calculating Then, 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 drive unit 105 according to the received focus drive amount. In this way, the camera control unit 212 performs AF (focus detection and focus control) of the phase difference detection method using the AF sensor 254 as the focus control unit before the image pickup by the image pickup element 201.

  Next, in step S405, 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 in S405 is repeated until the SW2 is turned on, and when the 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 drive circuit (not shown).

  Next, in step S407, the camera control unit 212 transmits an aperture driving command including the aperture value set in step S402 to the lens control unit 106. The lens control unit 106 narrows the diaphragm 102 to the set diaphragm value through the diaphragm driving unit 104 according to the received diaphragm driving command.

  Next, in step S408, the camera control unit 212 opens the focal plane shutter 258 through a shutter drive 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 a predetermined shutter time. Further, the camera control unit 212 causes the focal plane shutter 258 to perform the charging operation through the shutter drive circuit in preparation for the next opening operation.

  Next, in step S410, the camera control unit 212 causes the image processing unit 203 to acquire the A image signal and the B image signal as a pair of focus detection signals from the image sensor 201.

  Next, in S411, the camera control unit 212 causes the image processing unit 203 to acquire an image pickup signal from the image pickup element 201.

  Next, in step S412, the camera control unit 212 instructs the lens control unit 106 to open the diaphragm 102. The lens controller 106 opens the diaphragm 102 via the diaphragm driver 104 in response to the opening instruction.

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

  Next, in S414, the camera control unit 212 causes the AF signal processing unit 204 to calculate the image shift amount that 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 image pickup surface phase difference detection method using the image pickup element 201. A method of calculating the image shift amount between the A image signal and the B image signal will be described later.

  Next, in step S415, the camera control unit 212 calculates the allowable blur amount using the resolution of the image sensor 201 and the output resolution that is the currently set resolution of the output image (still image). The allowable blur amount 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 focus degree of the output image. Specifically, the camera control unit 212 compares the image shift amount calculated in S414 with the allowable blur amount calculated as the threshold value in S415 to determine whether the image shift amount is smaller than the allowable blur amount. . If the image shift amount is smaller than the allowable blur amount, the output image is a focused image with a high degree of focusing, and the rate is set to 1. On the other hand, if the image shift amount is equal to or more than the allowable blur amount, the output image is a non-focused image with a low focus degree, and the rate is set to 0.

  Next, in step S <b> 417, the camera control unit 212 causes the image processing unit 203 to perform addition / reduction processing of converting the resolution of the image pickup signal acquired in step S <b> 411 into the currently set output resolution, and output the output image. To generate. Further, the camera control unit 212 causes the image processing unit 203 to perform compression processing on the output image and outputs the compressed output image to the recording medium control unit 207. 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. The recording medium control unit 207 records the compressed output image and the rate in the storage medium 208 in association with each other.

  The 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 image sensor 201 in the focused state. A white circle in the subject image 500 is on one image pickup pixel of the image pickup pixel group (one square frame indicates one image pickup pixel) 501 in the image pickup element 201, as shown in the middle part 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 image pickup 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.

  In the lower part of FIG. 5A, the A image signal 504 and the B image signal 505 obtained from the image pickup pixels through the arrow 503 in the image pickup pixel group 501 are shown. Note that, since FIG. 5A shows the in-focus state, the A image signal 504 and the B image signal 505 actually overlap (the image shift amount is 0), but they are slightly shown in the figure for easy viewing. The figures are shifted and shown.

  A blurred subject image 510 formed on the imaging surface of the image sensor 201 in the out-of-focus state (defocused state) is shown in the upper part of FIG. White circles in the blurred subject image 510 spread over six image pickup pixels of the image pickup pixel group 511 in the image pickup element 201, as shown in the middle part of FIG. 5B. In the lower part of FIG. 5B, an A image signal 514 and a B image signal 515 obtained from the two image pickup pixels passing through the arrow 513 in the image pickup pixel group 511 are shown. Since it is out of focus, the A image signal 514 and the B image signal 515 have an image shift amount d.

  5C and 5D show graphs of the image shift amounts shown in FIGS. 5A and 5B, respectively. Specifically, an A image signal indicated by hatching in FIG. 5E is obtained by relatively shifting the A image signal (504, 514) and the B image signal (505, 515) by one pixel. The change in the difference XOR of the B image signal is shown in the graph. 5C and 5D, the horizontal axis represents the shift amount (number of pixels) and the vertical axis represents the XOR.

  In the in-focus state shown in FIG. 5A, the XOR becomes minimum (= 0) when the shift amount is 0 as shown in FIG. 5C. The shift amount 0 at this time indicates the image shift amount 0. On the other hand, as shown in FIG. 5B, in a non-focused state in which a subject image having a size of one pixel is blurred in two pixels, XOR is performed with a shift amount of 1 or -1 as shown in FIG. 5D. Is the smallest. The shift amount -1 or 1 at this time indicates the image shift amount -1 or 1.

  FIG. 5F shows the interpolation processing of the shift amount. As shown in FIG. 5B, this interpolation processing is performed when a blur having a blur amount that is not exactly an integer pixel has occurred. For example, as shown in FIG. 5F, when four XOR values at shift amounts -1, 0, 1 and 2 are obtained, an approximate curve 520 passing through these four points is obtained, and the approximate curve 520 shows The shift amount s that minimizes XOR is calculated. Further, as shown in the figure, the shift amount corresponding to the intersection 522 of two straight lines connecting two points of the above four points may be obtained as s. As a result, the shift amount, that is, the image shift amount can be obtained even if the blur amount is not an integer pixel.

  Next, a method of calculating the allowable blur amount performed in S415 of FIG. 4 will be described. For example, when the image sensor 201 has 7680 × 4320 = 32M image pickup pixels capable of outputting an 8K moving image, the user outputs a still image as an output image of 3840 × 2160 = 8M pixels in the image output mode of the camera 20 (recording). ) Mode. At this time, a 32 M pixel still image obtained as a captured image by the image sensor 201 is added / reduced to 1/2 in both vertical and horizontal directions to generate an 8 M pixel still image as an output image. Therefore, even if the 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 blur amount is 2 pixels. The permissible blur amount is the blur amount on the image sensor at which the output image can be determined as the focused image at the resolution of the output image.

It is assumed that the still image (32M pixels) acquired as a captured image and the output image still image (8M pixels) 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 of the output image (the number of pixels in the horizontal direction) is the output resolution, the allowable blur amount is the following formula. It is calculated as (1).
Allowable blur amount = Imaging resolution / Output resolution (1)
FIG. 7A shows a display example on the display unit 206 by the image browsing processing performed in S307 of FIG. The display unit 206 displays two still images 801, 802 that are output images. The shooting date is displayed below each still image, and one star mark 803 is displayed below one still image 802. No star mark is displayed below the still image 801. The star mark is an index indicating the rate as a result of the image rating process performed in S416 of FIG. A star mark indicates that the rate is 1, and no star mark indicates that the rate is 0. Instead of the star mark, other indexes such as numbers and symbols other than the star mark may be used.

  The 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, the star mark 803 is displayed. The user can easily determine whether each still image is a focused image or a non-focused image based on the presence / absence of the star mark 803 without having to check the displayed small still images 801 and 802 in detail and check their focus states. You can judge.

  According to the present embodiment, the user can easily confirm the focus degree (focused image or non-focused image) of the output image after capturing. Further, if the user specifies the output resolution of the camera, a threshold value (allowable shift amount) for evaluating the focus degree of the output image is automatically set.

  Next, a second embodiment of the present invention will be described. The present embodiment has the same configuration and control as the first embodiment except the calculation of the allowable deviation amount.

  In the first embodiment, the case where the allowable blur amount is automatically calculated and set according to the output resolution set by the user by the expression (1) in S415 of FIG. 4 has been described. However, the allowable blur amount corresponding to the set image output mode may differ from the allowable blur amount intended by the user. On the other hand, as described above, it is difficult for the user to set the allowable blur amount, which is a specific threshold value. Therefore, in the second embodiment, the user sets the allowable blur amount to be used from the plural allowable blur amounts corresponding to the plural image output modes that can be set in the camera 20, to the current image output mode (that is, the output resolution). ) Regardless of the choice.

Also in this embodiment, the case where the image sensor 201 has 7680 × 4320 = 32M image pickup pixels capable of outputting an 8K moving image will be described as an example. Further, the image output modes that can be set in the camera 20 and the allowable blur amount 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 described.

  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 permissible blur amount selected by the user (the arrows indicate the permissible blur amounts corresponding to the modes H, M, and L).

  According to the present embodiment, the user can easily confirm the focus degree (focused image or non-focused image) of the output image after capturing, and the user can set the allowable blur amount regardless of the output resolution. It can be arbitrarily selected.

  Next, a third embodiment of the present invention will be described. The present embodiment has the same configuration and control as the first embodiment except 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, it is possible to later decide the resolution of the output image to be finally saved, such as developing the RAW image later or cutting out a still image from a moving image as described in the examples below. In some cases it may be preferable.

  Also in the present embodiment, as in the second embodiment, the image sensor 201 has 7680 × 4320 = 32M image pickup pixels capable of outputting an 8K moving image, and the three image output modes described in the second embodiment and the permissible blur corresponding thereto It is assumed that the amount has been set.

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

  According to the present embodiment, the user can easily confirm not only the focus degree (whether the focused image or the out-of-focus image) of the output image after imaging but also the resolution of the output image that can be output as the focused image. You can

  Next, a fourth embodiment of the present invention will be described. In the present 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 in FIG. 8 shows the moving image capturing process in this embodiment.

  In step S901, the camera control unit 212 retracts the quick return mirror 252 to the outside of the optical path through the mirror control circuit in response to the user selecting the moving image capturing mode on the camera operation unit 214.

  Next, in step S902, the camera control unit 212 opens the focal plane shutter 258 through the shutter drive circuit. As a result, the light flux from the image pickup optical system always reaches the image pickup element 201.

  Next, in step S903, 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 S903 is repeated until the start of moving image recording is instructed, and when the start of moving image recording is instructed, the process proceeds to S904.

  In step S904, the camera control unit 212 causes the image processing unit 203 to generate an image signal (moving image data) from the image pickup signal from the image pickup device 201, and causes the display control unit 205 to output the moving image data. The display control unit 205 causes the display unit 206 to display a moving image corresponding to the moving image data.

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

  Next, in step 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 step S907, the camera control unit 212 calculates the defocus amount using the calculated image shift amount, and calculates the focus drive amount for obtaining the 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 drive unit 105 according to the received focus drive amount. As a result, AF is performed by the imaging plane phase difference detection method.

  Next, in step 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 step S <b> 909, the camera control unit 212 determines whether the user has instructed to stop moving image recording. Until the stop of the moving image recording is instructed, the moving image capturing is continued while repeating the determination of S909, and when the stop of the moving image recording is instructed, the process proceeds to S910.

  In step S910, the camera control unit 212 ends moving image capturing and closes the focal plane shutter 258. Then, in step 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 browsing processing 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. On the display unit 206, a moving image playback button 821, a pause button 820, a fast-forward button 825, and a fast-rewind button 826 are displayed along with the moving image to be played back.

  When the user touches the play button 821, the fast-forward button 825 or the fast-reverse button 826, the moving image is played, fast-forward or fast-reverse. When the user touches the pause button 820 in any one frame, the moving image reproduction stops in that one frame and the frame image 823 of the one frame is displayed on the display unit 206. Then, when the user fully presses the shutter switch in the camera operation unit 214 in that state, 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 the image rating process on the displayed frame image 823 in the same manner as S416 of FIG. 4 in response to the temporary stop instruction by the pause button 820. Accordingly, if the image shift amount is smaller than the allowable blur amount, the star mark 822 is displayed on the display unit 206 as shown in FIG. 7D, and if the image shift amount is the allowable blur amount or more, the star mark is not displayed. .

  According to the present embodiment, when cutting out a still image (frame image) from a moving image after capturing the moving image, the user can easily confirm the focus degree (focused image or out-of-focus image) for each frame image. it can.

  It should be noted that in each of the above-described embodiments, the case where only one of the focused image and the out-of-focus image is evaluated as the focusing degree of the output image using one threshold value has been described. However, a plurality of thresholds may be used to evaluate the degree of focus of the output image (for example, just focus or almost in-focus) or the degree of non-focus (for example, small blur or large blur).

  In each of the above embodiments, the lens (imaging optical system) is interchangeable and the lens interchangeable single-lens reflex camera having the mirror is described. However, a lens-interchangeable mirrorless camera having interchangeable lenses and no mirror, and a lens-integrated camera having an integrated lens are also included in the embodiments of the present invention.

Further, in each of the above-described embodiments, the case where the focus lens 103 is driven in the optical axis direction to perform AF has been described. However, the image pickup element 201 is used as a focus element, and AF is performed by driving this in the optical axis direction. Good.
(Other embodiments)
The present invention supplies a program that realizes one or more functions of the above-described embodiments to a system or apparatus via a network or a storage medium, and one or more processors in a computer of the system or apparatus read and execute the program. It can also be realized by the processing. It can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

  The embodiments described above are merely representative examples, and various modifications and changes can be made to the embodiments when implementing the present invention.

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

Claims (10)

An image sensor for capturing a subject image,
Image generation means for generating an output image having a resolution different from the resolution of the image sensor from the image signal output from the image sensor;
An image pickup surface focus detection unit that obtains a pair of focus detection signals used for focus detection of an image pickup surface phase difference detection method from the image pickup element and calculates a phase difference between the pair of focus detection signals,
Comparing the phase difference and the threshold value, and having an evaluation means for evaluating the focus degree of the output image,
The evaluation device changes the threshold according to the resolution of the output image. It has a display means for displaying the output image,
The image pickup apparatus according to claim 1, wherein the evaluation unit displays an index indicating the degree of focus on the display unit together with the output image.   The imaging apparatus according to claim 1, wherein the evaluation unit evaluates whether the output image is a focused image or a non-focused image as a focus degree of the output image.   4. The image pickup apparatus according to claim 1, wherein the threshold value is a blur amount on the image pickup element that allows the output image to be determined to be 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,
The image pickup apparatus according to claim 1, wherein the evaluation unit changes the threshold according to the changed resolution of the output image.   The imaging device according to claim 1, wherein the evaluation unit changes the threshold value according to a user operation regardless of the resolution of the output image.   The image pickup apparatus according to claim 2, wherein the evaluation unit displays, on the display unit, an index indicating a blur amount on the image pickup device together with the output image. A focus detection sensor that is provided separately from the image sensor and that generates a pair of focus detection signals used for focus detection of a phase difference detection method,
A focus control unit that calculates a phase difference between the pair of focus detection signals generated by the focus detection sensor and performs focus control according to the phase difference before image capturing by the image sensor. The image pickup apparatus according to claim 1. A method of controlling an image pickup apparatus having an image pickup element for picking up a subject image, comprising:
Generating an output image having a resolution different from that of the image sensor from an image signal output from the image sensor;
Acquiring a pair of focus detection signals used for focus detection of an imaging plane phase difference detection method from the image sensor, and calculating a phase difference between the focus detection signals of the pair,
Comparing the phase difference and a threshold value, and having an evaluation step of evaluating the focus degree of the output image,
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 image pickup apparatus having an image pickup element for picking up a subject image to execute processing according to the control method according to claim 9.