JP7034585B2 - Focus control device, image pickup device, focus control method and focus control program - Google Patents

Description

The present invention relates to a technique for performing focus control (AF) by a phase difference detection method.

There is an imaging surface phase difference detection method as an AF method capable of performing focusing at high speed and with high accuracy when still image imaging is performed while viewing a live view image generated by moving image imaging. In the image pickup surface phase difference detection method, for example, two light receiving elements and one microlens are provided in each pixel of the image pickup element, and light from different regions of the exit pupil of the image pickup optical system is provided by the two light receiving elements through the microlens. The pupil is divided by receiving light. Then, the defocus amount is obtained by calculating the deviation amount (phase difference) of the pair of phase difference image signals generated by the outputs from each of the one and the other light receiving elements in the plurality of pixels, and the defocus amount is used as the defocus amount. The in-focus state is obtained by controlling the position of the focus lens based on this. Such an imaging surface phase difference detection method is disclosed in Patent Document 1.

On the other hand, as a case where it is difficult to obtain an in-focus state by AF, there is a case where a so-called perspective conflict occurs in which a plurality of subjects having different subject distances are included in the focus detection region in the image pickup screen. When AF is performed in a state where perspective conflict occurs in a phase difference detection method including an imaging surface phase difference detection method, as shown in FIGS. 12 (a) and 12 (b), a near-side subject and a far-side subject AF may be completed without being in focus on any of the above. In Patent Document 2, when it is determined that perspective competition has occurred based on the calculation result of the phase difference in the focus detection region, the region where the perspective competition has occurred (hereinafter referred to as the perspective competition region) is excluded. A method of resetting the focus detection region and recalculating the phase difference is disclosed.

Japanese Unexamined Patent Publication No. 2001-083407 Japanese Unexamined Patent Publication No. 2011-242677

However, in the method disclosed in Patent Document 2, in order to recalculate the phase difference in the reconfigured focus detection region when it is determined from the calculation result of the phase difference in the focus detection region that perspective competition has occurred. , The time required to complete AF becomes longer. Further, when an image of a moving subject is taken, the focus detection region reset so as not to include the perspective competition region may change to include the perspective competition region at the time of recalculating the phase difference. In this case, AF completion may be further delayed or AF may not be executed.

INDUSTRIAL APPLICABILITY The present invention provides a focus control device and the like capable of performing good AF by suppressing the occurrence of perspective conflict even when imaging a moving subject in AF using a phase difference detection method.

The focus control device as one aspect of the present invention includes a focus detection means for detecting the focus state of the image pickup optical system by a phase difference detection method, a control means for performing focus control according to the focus state, and a focus state in the image pickup screen. It has a setting means for setting a focus detection area for detecting. Then, the setting means detects the subject included in the image pickup screen by using the image pickup signal generated by the image pickup, detects the movement amount of the subject, and determines the focus detection region whose position is different according to the movement amount. If the movement amount is smaller than the predetermined movement amount, the focus detection area corresponding to the detection position of the subject in the image pickup screen is set, and if the movement amount is larger than the predetermined movement amount, the image pickup screen is set. It is characterized in that a focus detection region shifted from the detection position in the above to the movement direction of the subject is set , and the size of the focus detection region is made smaller than when the movement amount is smaller than the predetermined movement amount . Further, the setting means detects the position of the subject included in the image pickup screen by using the image pickup signal generated by the image pickup, and also detects the movement amount of the subject, and the focus detection region based on the position and the movement amount. The feature is that the size of the focus detection region set when the movement amount is equal to or more than the predetermined movement amount is set to be smaller than the size set when the movement amount is smaller than the predetermined movement amount. do.

An image pickup device having an image pickup element for capturing a subject image formed by an image pickup optical system and the focus control device also constitutes another aspect of the present invention.

Further, the focus control method as another aspect of the present invention includes a step of detecting the focus state of the image pickup optical system by a phase difference detection method, a step of performing focus control according to the focus state, and a focus in the image pickup screen. It has a setting step for setting a focus detection area for detecting a state. Then, in the setting step, the subject included in the image pickup screen is detected using the image pickup signal generated by the image pickup, the movement amount of the subject is detected, and the focus detection area having a different position is set according to the movement amount. If the movement amount is smaller than the predetermined movement amount, a focus detection area corresponding to the detection position of the subject in the image pickup screen is set, and if the movement amount is larger than the predetermined movement amount, the detection in the image pickup screen is performed. It is characterized in that a focus detection area shifted from a position to a moving direction of a subject is set , and the size of the focus detection area is smaller than when the movement amount is smaller than a predetermined movement amount . Further, in the setting step, the position of the subject included in the image pickup screen is detected using the image pickup signal generated by the image pickup, the movement amount of the subject is detected, and the focus detection area is based on the position and the movement amount. The size of the focus detection region to be set when the movement amount is equal to or larger than the predetermined movement amount is set to be smaller than the size set when the movement amount is smaller than the predetermined movement amount.

Further, a focus control program, which is a computer program for causing a computer of an image pickup apparatus to execute a focus control process according to the focus control method, also constitutes another aspect of the present invention.

According to the present invention, in focus control (AF) using a phase difference detection method, even when a moving subject is imaged, it is possible to suppress the occurrence of perspective conflict and perform good AF.

The block diagram which shows the structure of the interchangeable lens type camera system which is Example 1 of this invention. The figure which shows the pixel array which does not correspond to the image pickup surface phase difference AF, and the pixel array which corresponds to the image pickup surface phase difference AF. The flowchart which shows the image pickup processing in Example 1 (and Examples 2-4 of this invention). The flowchart which shows the still image image pickup processing in Example 1 (and Examples 2-4). The flowchart which shows the focus detection process in Example 1 and Example 2. The flowchart which shows the AF area setting process in Example 1. FIG. The figure which shows the AF area used in the focus detection process. The figure which shows the phase difference image signal obtained from the AF region shown in FIG. 7. The figure which shows the relationship between the shift amount and the correlation amount of the phase difference image signal shown in FIG. The figure which shows the relationship between the shift amount of the phase difference image signal shown in FIG. 8 and the correlation change amount. The flowchart which shows the AF processing in Example 1, Example 3 and Example 4. The figure which shows the example of the false focusing state which occurs in a perspective conflict. A diagram showing an example in which the AF area deviates from the main subject of the current frame when the main subject is moving, and a diagram showing an example of the AF area set when the amount of movement of the subject in Examples 1 and 2 is large. .. The flowchart which shows the AF area setting process in Example 2. The flowchart which shows the AF process in Example 2. The flowchart which shows the focus detection process in Example 3 and Example 4. The flowchart which shows the AF area setting process in Example 3 and Example 4. The figure which shows the example of the 1st AF area and the 2nd AF area in Example 3 and Example 4. FIG. The flowchart which shows the use AF area selection process in Example 3. FIG. The flowchart which shows the use AF area selection process in Example 4. FIG.

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

FIG. 1 shows the configuration of an interchangeable lens camera system as an image pickup apparatus according to a first embodiment of the present invention. The camera system of this embodiment includes a camera body 20 and a lens unit 10 that is detachably (replaceable) attached to the camera body 20. The lens unit 10 is provided with a lens control unit 106 that controls the entire operation of the lens unit 10. Further, the camera body 20 is provided with a camera control unit 212 that controls the entire operation of the camera system including the lens unit 10. The camera control unit 212 and the lens control unit 106 can communicate with each other via a communication terminal provided on a mount that mechanically and electrically connects the two.

First, the configuration of the lens unit 10 will be described. The lens unit 10 has an imaging optical system including a fixed lens 101, an aperture 102, and a focus lens 103. The diaphragm 102 is driven by the diaphragm driving unit 104 and controls the amount of light incident on the image pickup device 201, which will be described later. The focus lens 103 is driven by the focus lens driving unit 105, and adjusts the focus of the imaging optical system according to the position thereof. The aperture drive unit 104 and the focus lens drive unit 105 are controlled by the lens control unit 106.

The lens operation unit 107 is an input for the user to make settings related to the operation of the lens unit 10, such as switching between AF (autofocus) / MF (manual focus) modes, adjusting the position of the focus lens by MF, and setting the image stabilization mode. Includes devices. In response to the operation of the lens operation unit 107, the lens control unit 106 performs control corresponding to the operation.

The lens control unit 106 controls the aperture drive unit 104 and the focus lens drive unit 105 according to the control command and control information received from the camera control unit 212, and also transmits the lens control information to the camera control unit 212.

Next, the configuration of the camera body 20 will be described. The camera body 20 has an image pickup device 201 that captures (photoelectrically converts) a subject image formed by an image pickup optical system. The image sensor 201 is composed of a CCD sensor and a CMOS sensor. The image pickup device 201 has a plurality of pixels, and a photodiode (light receiving element) provided in each pixel converts incident light into an electric charge according to the amount of light and stores the incident light. The electric charge accumulated in each photodiode is sequentially read out from the image pickup element 201 as a voltage signal according to the amount of electric charge from the drive pulse output by the timing generator 215 in response to a command from the camera control unit 212.

Each pixel of the image pickup device 201 used in this embodiment is composed of two (pair) photodiodes A and B and one microlens provided for the pair of photodiodes A and B. .. Each pixel divides the incident light with a microlens to form a pair of optical images on the pair of photodiodes A and B, and the pair of photodiodes A and B are used as a pair of AF signals to be described later. Output signals (A signal and B signal). Further, by adding the signals from the pair of photodiodes A and B, a pixel signal for imaging (A + B signal) can be obtained.

By synthesizing a plurality of A signals and a plurality of B signals output from a plurality of pixels, an AF signal (in other words, an imaging surface phase difference AF) used for AF by an imaging surface phase difference detection method (hereinafter referred to as an imaging surface phase difference AF). , A pair of phase difference image signals as a focus detection signal). The AF signal processing unit 204, which will be described later, performs a correlation operation on the pair of phase difference image signals to calculate the phase difference (hereinafter referred to as the image shift amount) which is the amount of deviation of the pair of phase difference image signals. Then, the defocus amount (and the defocus direction) indicating the focal state of the imaging optical system is calculated (detected) from the image shift amount.

FIG. 2A shows a pixel configuration that does not correspond to the image pickup surface phase difference AF, and FIG. 2B shows a pixel configuration that corresponds to the image pickup surface phase difference AF. In each of the figures, the Bayer arrangement is used, where R indicates a red color filter, B indicates a blue color filter, and Gr and Gb indicate a green color filter. The pixel configuration shown in FIG. 2B corresponding to the imaging surface phase difference AF corresponds to one pixel (shown by a solid line) in the pixel configuration not corresponding to the imaging surface phase AF shown in FIG. 2A. Two photodiodes A and B divided into two in the horizontal direction in the figure are provided in the pixel. The pixel division method shown in FIG. 2B is merely an example, and may be divided in the vertical direction of the figure or divided into two in the horizontal and vertical directions (four divisions in total). Further, a plurality of types of pixels divided by different division methods may be included in the same image pickup device.

The CDS / AGC / AD converter 202 refers to an image pickup signal formed by a pair of phase difference image signals output from a plurality of pixels of the image pickup device 201 and an image pickup pixel signal output from each of the plurality of pixels. Performs correlated double sampling, gain adjustment and AD conversion. The converter 202 outputs the image pickup signal (video signal) and the pair of phase difference image signals that have undergone these processes to the image input controller 203 and the AF signal processing unit 204, respectively.

The image input controller 203 stores the image pickup signal output from the converter 202 in the SDRAM 209 via the bus 21. The image pickup signal stored in the SDRAM 209 is read out by the display control unit 205 via the bus 21 and displayed on the display unit 206. Further, in the recording mode for video recording, the image pickup signal stored in the SDRAM 209 is recorded on a recording medium 208 such as a semiconductor memory by the recording medium control unit 207.

The ROM 210 stores a control program and a processing program executed by the camera control unit 212, various data necessary for their execution, and the like. The flash ROM 211 stores various setting information and the like related to the operation of the camera 20 set by the user.

The subject detection / tracking processing unit 216 detects a specific subject included in the image pickup screen using the image pickup signal input from the image input controller 203, and conveys the position of the specific subject in the image pickup screen to the camera control unit 212. .. Further, the subject detection / tracking processing unit 216 continuously receives an image pickup signal from the image input controller 203, and determines the position of the movement destination when the detected specific subject changes (that is, the specific subject moves). To inform the camera control unit 212. This makes it possible to follow the position of a moving specific subject (moving subject).

The specific subject is, for example, a subject existing at a position designated by the user in the image pickup screen through the face or the camera operation unit 214. As will be described later, the information regarding the position and size of the detected specific subject is mainly used for setting the AF area (focus detection area) which is the area for performing AF.

The AF signal processing unit 204 performs a correlation operation on a pair of phase difference image signals which are AF signals output from the converter 202, and calculates an image shift amount and reliability of the pair of phase difference image signals. The reliability is calculated using the two-image coincidence, which will be described later, and the steepness of the correlation change amount. Further, the AF signal processing unit 204 sets the position and size of the AF region for focusing detection and AF in the image pickup screen. Further, the AF signal processing unit 204 outputs the image shift amount (detection amount) and reliability information calculated in the AF region to the camera control unit 212. The AF signal processing unit 204 functions as a focus detection means.

The camera control unit 212 changes the settings for the AF signal processing unit 204 as necessary based on the image shift amount, reliability, and information indicating the states of the lens unit 10 and the camera body 20 obtained by the AF signal processing unit 204. do. For example, when the image shift amount is a predetermined amount or more, the AF region is widened, or the type of the bandpass filter is changed according to the contrast of the pair of phase difference image signals. Further, the camera control unit 212 has the position and size of the AF region based on the information of the specific subject detected by the subject detection / tracking processing unit 216 and the position designated by the user in the image pickup screen by the camera operation unit 214. To set. The camera control unit 212 functions as a setting means together with the subject detection / tracking processing unit 216.

In this embodiment, a total of three signals, a pixel signal for imaging and a pair of phase difference image signals which are AF signals, are acquired from the image sensor 201. However, in consideration of the load of the image sensor 201, for example, a total of two signals, an image pickup pixel signal and one AF signal, are taken out, and the difference between the taken out image pickup pixel signal and the AF image signal is used for another AF. It may be used as a signal.

The camera control unit 212 controls these while exchanging information with each unit in the camera body 20. Further, the camera control unit 212 can be used for user operations such as power ON / OFF, change of various settings, imaging processing, AF processing, and recording image reproduction processing in response to input from the camera operation unit 214 based on user operation. Perform the corresponding various processes. Further, the camera control unit 212 transmits control commands to the lens unit 10 (lens control unit 106) and information on the camera body 20 to the lens control unit 106, and acquires information on the lens unit 10 from the lens control unit 106. do. The camera control unit 212 is configured by a microcomputer and controls the entire camera system including the interchangeable lens 10 by executing a computer program stored in the ROM 210.

The camera control unit 212 controls the drive of the focus lens 103 through the lens control unit 106 based on the defocus amount calculated by the AF signal processing unit 204. That is, AF is performed as focus control. The camera control unit 212 functions as a control means.

Further, the camera control unit 212 has a subject movement determination unit 213. When the subject movement determination unit 213 detects the subject by the subject detection / tracking processing unit 216, whether or not the subject has a large movement amount in the image pickup signal (that is, in the image pickup screen), that is, It is determined whether or not the movement of the subject captured in the image pickup screen is large. The camera control unit 212 changes the position and size of the AF area set for the AF signal processing unit 204 according to the determination result of the subject movement determination unit 213. This process suppresses perspective conflict that occurs when the AF area includes other subjects that exist at a different distance and position from the main subject that the user wants to capture, and the AF area is more accurate with respect to the main subject. To set.

The AF signal processing unit 204, the camera control unit 212 (subject movement determination unit 213), and the subject detection / tracking processing unit 216 constitute a focus control device.

The perspective competition of the subject will be described with reference to FIGS. 12 (a) and 12 (b). In phase-difference AF, when perspective conflict occurs in the captured subject, it is in the focused state even though neither the near subject nor the far side subject is in focus. AF may be completed by erroneously determining that there is. This is not the amount of correlation that corresponds to either the distance between the near and far subjects, but the amount of correlation that corresponds to the distance between them (hereinafter referred to as the intermediate distance) when performing the correlation calculation. This is to become. Furthermore, when the focus lens is located at a position corresponding to the intermediate distance, the correlation amount is balanced and the defocus amount is increased by the presence of subjects having different defocus directions on the near side and the far side of the intermediate distance. This is because it becomes smaller and is erroneously determined to be in focus.

As one of the cases where perspective competition is likely to occur, there is a case where the movement of the detected subject is particularly large. As shown in FIG. 13A, when the movement of the main subject is large, the moving distance of the main subject between the frames that generate the image pickup signal and the pair of phase difference image signals is large. At this time, the position of the main subject detected by the subject detection / tracking processing unit 216 is notified to the AF signal processing unit 204 via the camera control unit 212, but while this processing is being performed, the image sensor 201 is already next. The signal of the frame is output. Therefore, the AF signal processing unit 204 reflects the detected position of the main subject in the AF signal in the frame after the frame in which the position is detected by the subject detection / tracking processing unit 216. That is, the larger the moving distance of the main subject, the larger the deviation between the actual main subject position and the position of the AF region, and the more likely the perspective conflict is to occur.

In order to solve this problem, in this embodiment, the subject movement determination unit 213 described above determines whether or not the amount of movement of the main subject in the image pickup signal is large. When the amount of movement of the main subject is large, the position and size of the AF area are corrected to correspond to the movement of the main subject to prevent the occurrence of perspective conflict, and the detected main subject is better captured. And set an appropriate AF area. This process prevents the focus lens from being driven in the wrong direction or erroneously determined to be in focus at the wrong position when AF is performed, and focuses on the main subject at higher speed and with higher accuracy. Can be matched. Details of the processing performed by the subject movement determination unit 213 and the AF signal processing unit 204 will be described later.

Next, the processing performed by the camera control unit 212 will be described with reference to the flowchart shown in FIG. The camera control unit 212 performs this processing according to an image pickup processing program which is a computer program. S means a step.

In S301, the camera control unit 212 performs initialization processing of various settings and proceeds to S302.

In S302, the camera control unit 212 determines whether the image pickup mode of the camera body 20 is the moving image imaging mode or the still image imaging mode, and proceeds to S303 in the case of the moving image imaging mode and S304 in the case of the still image imaging mode. ..

In S303, the camera control unit 212 performs a moving image imaging process and proceeds to S305. Further, in S304, the camera control unit 212 performs a still image imaging process and proceeds to S305. The AF area setting process corresponding to the moving subject can be performed in either the moving image imaging mode or the still image imaging mode, but in this embodiment, the AF area setting process corresponding to the moving subject in the still image imaging mode will be described. do. Further, in this embodiment, the description of the moving image imaging process will be omitted.

In S305, the camera control unit 212 determines whether or not the still image or moving image imaging process has been stopped, proceeds to S306 if it has not been stopped, and ends the imaging process if it is stopped. The image pickup process is stopped when the user turns off the power of the camera body 20 through the camera operation unit 214, performs operations for various settings, or instructs a reproduction process for confirming the captured image. ..

In S306, the camera control unit 212 determines whether or not the imaging mode has been changed. When the imaging mode is changed, the camera control unit 212 returns to S301, performs initialization processing, and then performs imaging processing in the changed imaging mode. On the other hand, if the image pickup mode has not been changed, the camera control unit 212 returns to S302 and continues the process in the current image pickup mode.

Next, the still image imaging process performed in S304 in FIG. 3 will be described in detail with reference to the flowchart of FIG.

In S401, the camera control unit 212 causes the AF signal processing unit 204 to perform focus detection processing based on the subject detection result by the subject detection / tracking processing unit 216 and the processing content by the subject movement determination unit 213. The focus detection process is a process for acquiring information on the amount of defocus and reliability for performing image plane phase difference AF. Further, in the focus detection process, the camera control unit 212 also sets an area (focus detection area: hereinafter referred to as an AF area) in the image pickup screen for acquiring information related to AF according to the state of the camera body 20. Details will be described later.

Next, in S402, the camera control unit 212 determines whether or not an AF processing start instruction (hereinafter referred to as an AF instruction) has been input from the camera operation unit 214. The AF instruction is output from the camera operation unit 214 in response to the user pressing the shutter button halfway or pressing the AFON button for executing AF. The camera control unit 212 proceeds to S403 when the AF instruction is input, and proceeds to S404 when the AF instruction is not input.

In S403, the camera control unit 212 performs AF processing (focus control processing). This AF process will be described later.

In S404, the camera control unit 212 determines whether or not a start instruction for imaging processing (hereinafter referred to as an imaging instruction) has been input from the camera operation unit 214. The image pickup instruction is output from the camera operation unit 214 in response to the user pressing the shutter button fully. The camera control unit 212 proceeds to S405 when an imaging instruction is input, and proceeds to S407 when an imaging instruction is not input.

In S405, the camera control unit 212 determines whether or not the AF process in S403 is currently in the in-focus stop state. The in-focus stopped state is a state in which the imaging optical system is in the in-focus state and the focus lens 103 is stopped. If it is not in the in-focus stop state, the camera control unit 212 proceeds to S403 and obtains the in-focus state by starting or continuing the AF process. When the focus is stopped, the camera control unit 212 proceeds to S406, performs an image pickup process, stores the captured image (recorded image) in the recording medium 208 via the recording medium control unit 207, and proceeds to S407.

In S407, the camera control unit 212 releases the in-focus stop state and ends the still image imaging process.

Next, using the flowchart of FIG. 5, the focus detection process performed by the camera control unit 212, the subject movement determination unit 213, and the AF signal processing unit 204 in S401 of FIG. 4 will be described. The AF signal processing unit 204 is configured by a microcomputer and performs focus detection processing according to a focus control program (which may be a part of an imaging processing program) as a computer program.

First, in S501, the camera control unit 212 sets an AF region for performing AF on the image pickup screen (that is, the image pickup element 201). The AF area is set based on an instruction by the user through the camera operation unit 214 and a subject detection state by the subject detection / tracking processing unit 216. When the subject detection / tracking processing unit 216 detects the subject, the AF area is further set according to the subject movement information from the subject movement determination unit 213. This AF area setting process will be described in detail later.

The camera control unit 212 that has set the AF area in S501 sends AF area information to the AF signal processing unit 204, and the AF signal processing unit 204 that receives the information performs focus detection processing in the steps after S502. conduct.

Next, in S502, the AF signal processing unit 204 acquires a pair of phase difference image signals as AF signals from a plurality of pixels included in the AF region of the image sensor 201.

Next, in S503, the AF signal processing unit 204 calculates the correlation amount of the pair of phase difference image signals while relatively shifting the acquired pair of phase difference image signals by one pixel (1 bit). The correlation amount is calculated as described later in each of the plurality of pixel lines (hereinafter referred to as scanning lines) provided in the AF region. In this embodiment, when the correlation amount of each scanning line is calculated, each correlation amount is added and averaged to calculate one correlation amount. Further, in this embodiment, the pair of phase difference image signals are relatively shifted one pixel at a time in the calculation of the correlation amount, but may be shifted in units of more pixels such as two pixels at a time. Further, in this embodiment, one correlation amount is calculated by adding and averaging the correlation amounts of each scanning line. For example, the addition averaging is performed on a pair of phase difference image signals of each scanning line, and then the addition is performed. The amount of correlation may be calculated for a pair of averaged retardation image signals.

Next, in S504, the AF signal processing unit 204 obtains the correlation change amount from the correlation amount calculated in S503. The method of calculating the amount of correlation change will also be described later.

Then, in S505, the AF signal processing unit 204 calculates the image shift amount (phase difference) using the correlation change amount calculated in S504. The method of calculating the amount of image shift will be described later.

Further, in S506, the AF signal processing unit 204 calculates the reliability of the image shift amount calculated in S505. The reliability calculation method will also be described later.

Next, in S507, the AF signal processing unit 204 calculates the defocus amount in the AF region using the image shift amount calculated in S505, and ends the focus detection process.

Next, the focus detection process will be described in detail. FIG. 7 shows an example of the AF region 702 set on the pixel array 701 in the image sensor 201 in the focus detection process. The shift regions 703 on both sides of the AF region 702 are regions necessary for the correlation calculation. Therefore, the region 704, which is the sum of the AF region 702 and the shift region 703, is the pixel region required for the correlation calculation. In the figure, p, q, s, and t represent the coordinates in the horizontal direction (x-axis direction), respectively, p and q represent the x-coordinates of the start point and the end point of the pixel region 704, respectively, and s and t represent the AF region, respectively. The x-coordinates of the start point and the end point of 702 are shown.

FIG. 8A shows an example of a pair of phase difference image signals for AF acquired from a plurality of pixels included in the AF region 702 shown in FIG. 7. The solid line 801 is one phase difference image signal A (hereinafter referred to as A image signal), and the broken line 802 is the other phase difference image signal B (hereinafter referred to as B image signal). FIG. 8A shows the A image signal 801 and the B image signal 802 before the shift. 8 (b) and 8 (c) show the states in which the A image and the B image signals 801, 802 are shifted from the state of FIG. 8 (a) in the plus direction and the minus direction, respectively. When calculating the correlation amount of the A image and the B image signals 801, 802, both the A image and the B image signals 801, 802 are shifted by 1 bit in the direction of the arrow.

Next, a method of calculating the correlation amount will be described. First, as shown in FIGS. 8 (b) and 8 (c), the A image and the B image signals 801, 802 are shifted by 1 bit each, and the sum of the absolute values of the differences between the A image and the B image signals 801, 802 is calculated. calculate. When the shift amount is i, the minimum shift amount is ps, the maximum shift amount is qt, x is the start coordinate of the AF region 702, and y is the end coordinate of the AF region 702, the correlation amount COR is It can be calculated by the following equation (1).

FIG. 9A shows an example of the relationship between the shift amount and the correlation amount COR. The horizontal axis shows the shift amount, and the vertical axis shows the correlation amount COR. Of the extreme values near the extreme values 902 and 903 in the correlation amount 901 that changes with the shift amount, the degree of coincidence between the A image and the B image signal is the highest in the shift amount corresponding to the smaller correlation amount.

Next, a method of calculating the amount of correlation change will be described. The difference in the correlation amount every other shift in the waveform of the correlation amount 901 shown in FIG. 9A is calculated as the correlation change amount. Assuming that the shift amount is i, the minimum shift amount is ps, and the maximum shift amount is qt, the correlation change amount ΔCOR can be calculated by the following equation (2).

FIG. 10A shows an example of the relationship between the shift amount and the correlation change amount ΔCOR. The horizontal axis shows the shift amount, and the vertical axis shows the correlation change amount ΔCOR. The correlation change amount 1001 that changes with the shift amount changes from plus to minus in the portion of 1002, 1003. The state in which the amount of correlation change is 0 is called zero cross, and the degree of coincidence between the A image and B image signals is the highest. Therefore, the shift amount that gives zero cross is the image shift amount.

10 (b) shows an enlarged portion of the portion shown by 1002 in FIG. 10 (a). 1004 is a part of the correlation change amount 1001. A method of calculating the image shift amount PRD will be described with reference to FIG. 10 (b).

The shift amount (k-1 + α) that gives a zero cross is divided into an integer part β (= k-1) and a decimal part α. The fractional part α can be calculated by the following equation (3) from the similarity relationship between the triangle ABC and the triangle ADE in the figure.

The integer part β can be calculated from FIG. 10 (b) by the following equation (4).

Then, the image shift amount PRD can be calculated from the sum of α and β.

When there are a plurality of zero crosses of the correlation change amount ΔCOR as shown in FIG. 10 (a), the one having a larger change in the correlation change amount ΔCOR in the vicinity thereof is defined as the first zero cross. This steepness is an index showing the ease of performing AF, and the larger the value, the easier it is to perform accurate AF. The steepness maxder can be calculated by the following equation (5).

As described above, in this embodiment, when there are a plurality of zero crosses of the correlation change amount, the first zero cross is determined by the steepness thereof, and the shift amount giving the first zero cross is defined as the image shift amount.

Next, a method of calculating the reliability of the image shift amount will be described. The reliability of the amount of image shift can be defined by the degree of coincidence between the A image and the B image signals (hereinafter referred to as the degree of coincidence between two images) fnclvl and the steepness of the above-mentioned amount of correlation change. The degree of coincidence between two images is an index showing the accuracy of the amount of image shift, and in the correlation calculation method in this embodiment, the smaller the value, the better the accuracy.

In FIG. 9B, the portion shown by 902 in FIG. 9A is enlarged, and 904 is a part of the correlation amount 901. The two-image matching degree fnclvl can be calculated by the following equation (6).

Next, using the flowchart of FIG. 6, the AF area setting process performed by the camera control unit 212 (subject movement determination unit 213) in S501 of FIG. 5 will be described. The camera control unit 212 executes this process according to the focus control program described above.

In S601, the camera control unit 212 determines whether or not the subject detection / tracking processing unit 216 has detected the subject (in the subject detection state). The camera control unit 212 proceeds to S601 if it is in the subject detection state, and proceeds to S608 if it is not in the subject detection state. In the subject detection state, the detected subject movement determination unit 213 determines whether or not the movement of the detected subject (hereinafter referred to as the detected subject) in the image pickup screen is large by the following processing.

First, in S602, the detected subject movement determination unit 213 determines whether or not the subject detection state is continued for two frames or more. When the subject detection state continues for two or more frames, the movement of the detected subject is performed using the difference in the position of the detected subject (hereinafter referred to as the subject detection position) between the previous frame and the current frame, which are the two frames. Calculate the amount. If the subject detection state continues for two or more frames, the process proceeds to S603, and if the subject detection state is one frame, the process proceeds to S606.

In S603, the subject movement determination unit 213 determines whether or not the difference in the subject detection position between the previous frame and the current frame is larger than a predetermined value (threshold value), in other words, the amount of movement of the detected subject between the previous frame and the current frame. It is determined whether or not the movement amount is larger than the predetermined movement amount. When the difference between the subject detection positions is larger than a predetermined value, the detected subject and the AF area may deviate from each other because the amount of movement of the detected subject in the image pickup screen is large as shown in FIG. 13 (a). As a result, there is a possibility that the AF accuracy may be lowered due to a perspective conflict in which the detected subject and the subject having a different distance from the detected subject are included in the AF region. The subject movement determination unit 213 proceeds to S604 if the difference in the subject detection positions is larger than a predetermined value, and proceeds to S606 otherwise.

When the subject detection state is continued for two frames or more in S602 and the difference in the subject detection positions is larger than the predetermined value in S603, the subject movement determination unit 213 determines that the amount of movement of the detected subject is large, and determines the determination result. Notify the camera control unit 212. In other cases, the subject movement determination unit 213 determines that the amount of movement of the detected subject is not large, and notifies the camera control unit 212 of the determination result.

The threshold value for the difference in the subject detection positions is set from the viewpoint of whether or not the size of the range in which the AF region deviates from the detection subject due to the movement of the detected subject becomes wider than a predetermined amount. It is desirable that there is no range where the AF area deviates from the detected subject, but it may be difficult depending on the size of the detectable subject, so it is a threshold value that allows the AF area to deviate slightly from the detected subject. May be set to. It is desirable to change this threshold value according to the subject detection performance of the subject detection / tracking processing unit 216 of the camera body 20.

In S604, the camera control unit 212 sets the position of the center (or the center of gravity) of the AF region according to the difference between the subject detection position of the current frame and the subject detection position between the previous and current frames. Specifically, the moving direction of the detected subject in the imaging screen is calculated from the difference in the subject detection position between the previous frame and the current frame, and the position shifted from the subject detection position of the current frame to the movement direction of the detected subject is the center. Set a new AF area. If the AF area is simply set around the subject detection position, the AF area may include subjects other than the detected subject due to the movement of the detected subject. Therefore, by setting (the center of) the AF area to a position shifted from the subject detection position of the detected subject to the position shifted in the moving direction of the detected subject, the AF area is set to include only the detected subject as much as possible. As a result, it is possible to suppress the occurrence of perspective competition in which a plurality of subjects having different distances from each other exist in the AF region, and to perform AF with higher accuracy on the detected subject.

The amount of shift of the AF area from the subject detection position to the movement direction of the detected subject may be a preset fixed value, or may be variably set according to the difference in the subject detection position between the previous and current frames. You may. The shift amount may be set so that the center of the AF area is brought closer to the center of the original detected subject.

In S605, the camera control unit 212 sets the width of the AF area to α and ends the AF area setting process. The width α is set to a value smaller than the width β set in S607 and S609 described later.

On the other hand, in S606, the camera control unit 212 sets the AF area centered on the subject detection position of the frame this time. That is, when the subject movement determination unit 213 determines that the amount of movement of the detected subject is not large, the AF area is set with respect to the subject detection position of the frame this time. Then, the process proceeds to S607.

In S607, the camera control unit 212 sets the width of the AF area to β and ends the AF area setting process.

As described above, when the subject movement determination unit 213 determines that the movement amount of the detected subject is large, the width of the AF area is set to α in S605, and when it is determined that the movement amount of the detected subject is not large, S607. Set the width of the AF area to β with. α and β have the following relationship.
α <β
When the amount of movement of the detected subject is not large, the AF region having a wider width β is controlled so as to be able to perform AF with high accuracy including the contrast portion as much as possible with respect to the detected subject. However, if the width of the AF region is set to β when the amount of movement of the detected subject is large, there is a high possibility that the AF region will protrude from the detected subject and perspective competition will occur. Therefore, when the amount of movement of the subject is large, an AF region having a width α narrower than the width β is set to reduce the possibility of perspective competition.

An example of the processing of S604 and S605 is shown in FIG. 13 (b). When the amount of movement of the detected subject is large, the position of the AF area is shifted from the subject detection position to the direction of movement of the detected subject when the amount of movement of the detected subject is not large as shown in FIG. 13 (a). , Set the width of the AF area to α, which is narrower than β. If the center of the AF area is shifted in the moving direction of the detected subject, it is considered that the position of the AF area is shifted in the moving direction of the detected subject. Therefore, for example, even when the left half of the AF area shown in FIG. 13B when the detection subject movement determination is not taken is set as the AF area, it is considered that the position of the AF area is shifted in the moving direction.

Further, in this embodiment, the width of the AF region (width in the focus detection direction) is set to α <β, but if the position of the AF region is shifted in the moving direction of the detection subject, the size of the AF region does not change. You may. Further, even if the size of the AF area (width in the focus detection direction) is reduced without shifting the position of the AF area, it is difficult for other subjects to be included in the AF area, so that the effect of suppressing perspective competition can be achieved. Obtainable.

On the other hand, in S608, the camera control unit 212 sets the AF area around the position arbitrarily set by the user in the image pickup screen, and proceeds to S609.

In S609, the camera control unit 212 sets the width of the AF area to β and ends the AF area setting process.

In this embodiment, the width of the AF area set in S607 when the amount of movement of the detected subject is not large and the width set in S609 when the subject is not detected are set to the same β, but these are the same β. It may be different. Further, in this embodiment, the AF area is set so that the subject detection position or the position set by the user is the center, but the AF area is set so that the subject detection position or the position set by the user is other than the center, for example, the upper left. May be set.

Next, using the flowchart of FIG. 11, the AF process performed by the camera control unit 212 in S403 of FIG. 4 will be described. The camera control unit 212 executes this process according to the focus control program described above.

In S1101, the camera control unit 212 determines whether or not AF is currently completed and is in the in-focus stop state, proceeds to S1102 if it is not in the in-focus stop state, and proceeds to S1109 in the case of the in-focus stop state.

In S1102, the camera control unit 212 determines whether or not the reliability of the defocus amount calculated in S401 of FIG. 4 (S507 of FIG. 5) is higher than the predetermined reliability. The reliability referred to here is determined by the steepness of the two-image coincidence and the image shift amount described above, and the maximum value of the reliability range in which not only the calculated defocus amount but also the defocus direction is unreliable is determined. It is desirable to set it as reliability. The reliability may be obtained by using both the degree of coincidence between the two images and the steepness of the amount of image shift, or may be obtained by using only one of them. Further, other indexes such as the signal level of two images may be used. If the defocus amount is higher than the predetermined reliability, the process proceeds to S1103, and if not, the process proceeds to S1107.

In S1103, since the camera control unit 212 performs AF using a highly reliable defocus amount, it first determines whether or not the defocus amount is within the depth of focus, and if it is within the depth of focus, proceeds to S1104. If it is not within the depth of focus, the process proceeds to S1105.

In S1104, the camera control unit 212 considers that the defocus amount is in the in-focus state within the depth of focus, shifts to the in-focus stop state, and ends the AF process.

On the other hand, in S1105, the camera control unit 212 considers that the in-focus state has not been obtained yet, sets the lens drive for driving the focus lens 103 based on the defocus amount, and proceeds to S1106. The lens drive setting is a setting such as a drive speed of the focus lens 103 and a gain applied to the defocus amount in consideration of an error in the defocus amount.

In S1106, the camera control unit 212 transmits a control command for the focus lens 103 to the lens control unit 106 based on the defocus amount and the information of the lens drive setting set in S1105. That is, focus control is performed. This ends the AF process.

On the other hand, in S1107, the defocus amount calculated in S507 cannot be used. Therefore, the camera control unit 212 is a search drive that calculates the defocus amount while moving the focus lens 103 toward the movable end in order to detect the position of the focus lens 103 that can obtain a highly reliable defocus amount. I do. Specifically, the camera control unit 212 first sets the lens drive for search drive. The lens drive setting for search drive is a setting such as the drive speed of the focus lens 103 and the direction in which the drive is started.

Subsequently, in S1108, the camera control unit 212 transmits a control command for the focus lens 103 to the lens control unit 106 based on the lens drive setting for search drive set in S1107. Then, the AF process is terminated.

In this embodiment, the camera body 20 that can perform only the image pickup surface phase difference AF using the output signal of the image sensor 201 has been described. However, when contrast AF can be performed using the output signal of the image sensor 201, contrast AF may be performed when it is determined in S1102 that the reliability of the defocus amount is low.

In S1109, the camera control unit 212 keeps the in-focus stop state and ends the AF process.

As described above, in the present embodiment, when the movement amount of the detected subject is large, the AF area narrower than the case where the movement amount is not large is set at the position shifted from the subject detection position to the movement direction of the detected subject. Set. With such control, even if the amount of movement of the detected subject is large, it is possible to suppress the occurrence of perspective conflict due to the AF area being displaced with respect to the detected subject and including other subjects. AF can be performed with high accuracy.

In this embodiment, the case where the correlation calculation is performed in the horizontal direction as shown in FIG. 2B has been described, but the correlation calculation may be performed in the vertical direction or the diagonal direction.

Next, Example 2 of the present invention will be described. In this embodiment, in the AF area setting process described in the first embodiment, the AF area setting method is further changed according to the reliability of the detected defocus amount, the state of the aperture, and the detection state of camera shake. The configurations of the camera body and the lens unit in this embodiment are the same as those in the first embodiment, and the common components are designated by the same reference numerals as those in the first embodiment. Further, the image pickup process, the still image image pickup process, and the focus detection process performed on the camera body 20 are the same as the processes described with reference to FIGS. 3, 4, and 5 in Example 1.

The AF area setting process performed by the camera control unit 212 and the subject movement determination unit 213 in S501 of FIG. 5 will be described with reference to the flowchart of FIG. The processing from S1501 to S1503 in FIG. 14 is the same as the processing from S601 to S603 in FIG. Further, the processing from S1506 to S1511 in FIG. 14 is the same as the processing from S604 to S609 in FIG.

In S1504, the subject movement determination unit 213 determines whether or not the reliability of the defocus amount detected in the previous frame is higher than the predetermined reliability. If the reliability is higher than the predetermined reliability, the process proceeds to S1505, and if the reliability is lower than the predetermined reliability, the process proceeds to S1508. As described in Example 1, the reliability referred to here is also obtained by the steepness of the two-image coincidence and the image shift amount, and not only the calculated defocus amount but also the defocus direction is unreliable. It is desirable to set the highest value of the sex range as the predetermined reliability.

The case where the reliability of the defocus amount detected in the previous frame is lower than the predetermined reliability is the case where the AF area does not include a subject with contrast because the width of the AF area is set to α narrower than β in S1507. And so on. More specifically, it is a case where the AF region includes only a portion having low contrast such as the cheek of the face detected. By narrowing the AF area, it is possible to suppress the occurrence of perspective conflict, but conversely, by narrowing the AF area, there is a high possibility that high-contrast subjects that can easily detect the amount of image shift will not be included, and defocusing will occur. The reliability of the quantity may decrease. Therefore, if the reliability of the defocus amount detected in the previous frame is low, the image shift amount is temporarily detected by setting the width to β in S1509 instead of setting the width of the AF area to α. Prioritize ease.

In S1505, the subject movement determination unit 213 determines whether or not the aperture is opened from the predetermined aperture value, and if the aperture is opened from the predetermined aperture value, the process proceeds to S1506, and if not, the process proceeds to S1508. The AF of the imaging surface phase difference detection method has a characteristic that the conversion coefficient for calculating the defocus amount from the image shift amount increases as the aperture is stopped down, and the AF accuracy becomes difficult to obtain. The aperture threshold value set here is, for example, based on the AF accuracy standard, and the aperture is set so that the AF accuracy is improved to some extent.

As described above, in the imaging surface phase-difference AF, the conversion coefficient for calculating the defocus amount from the image shift amount increases as the aperture is stopped down, and it becomes difficult to improve the AF accuracy. Therefore, when the AF region does not include a subject with high contrast that makes it easy to detect the amount of image shift, the amount of defocus varies widely, and the focus lens 103 moves near the position where the in-focus state can be obtained. There is a risk of continuing to do so. Further, when the depth of field is deepened by narrowing the aperture, even if perspective competition occurs, each tends to be in focus, so that blurring due to perspective competition is less likely to occur. For these reasons, in a situation where the AF accuracy tends to decrease because the aperture is narrowed down from the predetermined aperture value, the AF area is widened rather than the suppression of perspective competition by narrowing the AF area, and a subject with high contrast is created. It is easy to be included in the AF area.

Next, the AF process performed by the camera control unit 212 in S403 of FIG. 4 will be described with reference to the flowchart of FIG. The processing from S1601 to S1606 in FIG. 15 is the same as the processing from S1101 to S1106 in FIG. Further, the processing from S1608 to S1610 in FIG. 15 is the same as the processing from S1107 to S1109 in FIG.

In S1607, the camera control unit 212 determines whether or not the reliability of the defocus amount detected in the previous frame is higher than the predetermined reliability. If the reliability of the defocus amount is higher than the predetermined reliability, the AF process is terminated, and if it is lower than the predetermined reliability, the process proceeds to S1608. The reliability referred to here is also the same as that described in S1504.

In Example 1, when the reliability of the defocus amount was low in S1102, the lens drive processing by search drive was performed in S1107 and S1108. On the other hand, in this embodiment, if the reliability of the defocus amount is lower than the predetermined reliability in S1602, and if the reliability of the defocus amount of the previous frame is lower than the predetermined reliability, the search is performed in S1608 and S1609. The lens drive process by drive is not performed. This is because the inadvertent search drive is not performed when the reliability is lowered because the width α of the narrower AF region is set in S1507 according to the determination result of S1504 in FIG.

As described above, also in this embodiment, when the movement amount of the detected subject is large, the AF area is set at the position shifted from the subject detection position to the movement direction of the detected subject, which is narrower than that when the movement amount is not large. In this embodiment, the reliability of the defocus amount and the aperture information are taken into consideration. That is, when the reliability of the defocus amount is lowered because the AF area having a narrow width is set, the AF area having a wide width is set. When the aperture is stopped down, a wide AF area is set in consideration of AF accuracy and depth of field. With such control, it is possible to avoid a decrease in AF accuracy while suppressing perspective competition.

Next, Example 3 of the present invention will be described. In this embodiment, in the AF area setting process described in the first embodiment, when the movement amount of the detected subject is further large, a narrow width AF area and a wide width AF area are set. Then, which AF region is used for AF processing is selected according to the reliability of the defocus amount calculated in each AF region. The configurations of the camera body and the lens unit in this embodiment are the same as those in the first embodiment, and the common components are designated by the same reference numerals as those in the first embodiment. Further, the image pickup process, the still image image pickup process, and the AF process performed by the camera body 20 are the same as the processes described with reference to FIGS. 3, 4, and 11.

The focus detection process performed by the camera control unit 212, the subject movement determination unit 213, and the AF signal processing unit 204 in S401 of FIG. 4 will be described with reference to the flowchart of FIG. The processing from S1702 to S1707 in FIG. 16 is the same as the processing from S502 to S507 in FIG. However, as will be described later, the processes from S1703 to S1707 are executed for each of the plurality of AF areas when a plurality of AF areas are set in the process of S1701.

In S1701, the camera control unit 212 sets an AF region for performing AF on the image pickup screen (that is, the image pickup element 201). The AF area is set based on an instruction by the user through the camera operation unit 214 and a subject detection state by the subject detection / tracking processing unit 216. When the subject detection / tracking processing unit 216 detects the subject, the AF area is further set according to the subject movement information from the subject movement determination unit 213. Further, in this embodiment, a plurality of AF areas may be set as described later.

In S1708, the camera control unit 212 selects which AF region among the plurality of AF regions set in S1701 is used for the AF processing performed in S403 of FIG. 4, and ends the focus detection processing.

Next, using the flowchart of FIG. 17, the AF area setting process performed by the camera control unit 212 and the subject movement determination unit 213 in S1701 of FIG. 16 will be described. The processing of S1801 in FIG. 17 is the same as the processing of S601 in FIG. Further, the processing of S1804 and S1805 in FIG. 17 is the same as the processing of S602 and S603 in FIG.

In S1802, the camera control unit 212 sets a first AF area (first focus detection area) centered on the subject detection position, and proceeds to S1803.

In S1803, the camera control unit 212 sets the width of the first AF region to β, and proceeds to S1804. As described above, in this embodiment, when it is determined in S1801 that the subject is in the subject detection state, the first AF region having the width β around the subject detection position is always set.

In S1806, the camera control unit 212 sets the center of the second AF area (second focus detection area) according to the difference between the subject detection position of the current frame and the subject detection position between the previous and current frames. do. Specifically, the moving direction of the detected subject in the imaging screen is calculated from the difference in the subject detection position between the previous frame and the current frame, and the moving direction of the detected subject from the subject detection position of the current frame will be described in Example 1. The position shifted by the shift amount is set at the center of the second AF region.

In S1807, the camera control unit 212 sets the width of the second AF region to α, and proceeds to S1808.

In S1808, the camera control unit 212 resets the position of the center of the first AF region to the same position as the center of the second AF region. The center of the first AF area was set in S1802, but if the subject movement determination unit 213 determines that the amount of movement of the detected subject is large, the shift amount from the subject detection position of the frame to the direction of movement of the detected subject this time. Reset it so that it is centered on the shifted position. However, the width of the first AF region is left as β set in S1803, and is wider than the width α of the second AF region. Then, the AF area setting process is terminated. An example of the first AF region and the second AF region is shown in FIG.

In the first embodiment, the position of the AF area to be set is changed according to the determination result of the subject movement determination unit 213, but in the present embodiment, when it is determined that the movement amount of the detected subject is large, the first and second Set the AF area (that is, multiple AF areas). Thereby, the AF area having a more appropriate position and size can be set as compared with the first embodiment by the AF area selection process described later. On the other hand, in S1809, the camera control unit 212 sets the first AF region centered on a position arbitrarily set by the user in the image pickup screen, and proceeds to S1810.

In S1810, the camera control unit 212 sets the width of the first AF region to β and ends the AF region setting process.

The AF area selection process performed by the camera control unit 212 in S1708 of FIG. 16 will be described with reference to the flowchart of FIG. In S1901, the camera control unit 212 determines whether or not there are two or more AF areas set in the AF area setting process of S1701, and if there are two or more set AF areas, the process proceeds to S1902. If there is one, proceed to S1904. In S1902, the camera control unit 212 determines whether or not the reliability of the defocus amount calculated in the second AF region is higher than the predetermined reliability, and if the reliability is higher than the predetermined reliability, proceeds to S1903. If the reliability is lower than the predetermined reliability, the process proceeds to S1904. The reliability and predetermined reliability referred to here are the same as those described in Examples 1 and 2. In S1903, the camera control unit 212 selects the second AF area as the used AF area, and ends the used AF area selection process. In S1904, the camera control unit 212 selects the first AF area as the used AF area, and ends the used AF area selection process.

In this embodiment, when the first and second AF regions are set and the defocus amount obtained in the second AF region is highly reliable, the second AF region is used for AF processing. However, when the reliability is low, the first AF region is used for AF processing. In Example 2 described above, when the reliability of the defocus amount obtained in the set AF area is low, the position and size of the AF area are determined according to the determination result of the reliability of the defocus amount detected in the previous frame. Changed the width. Since it is not necessary to hold data for a plurality of AF areas in the second embodiment, there is an advantage that the used capacity of the ROM 210 is reduced. However, in Example 2, an extra time is required for one frame. On the other hand, in this embodiment, the capacity of the ROM 210 is increased, but the AF area can be changed within the same frame, so that the time required for AF can be shortened.

As described above, in this embodiment, when the amount of movement of the detected subject is large, the first AF region and the second AF are located at the subject detection position and the position shifted from the subject detection position in the movement direction of the detected subject, respectively. Set the area. Then, this second AF region is used for AF processing only when the reliability of the defocus amount obtained in the second AF region is high. With such control, even if the amount of movement of the detected subject is large, it is possible to suppress the occurrence of perspective conflict due to the AF region being displaced from the detected subject and including another subject. As a result, more accurate AF can be performed on the moving detected subject.

Further, in this embodiment, when the reliability of the defocus amount is low because the second AF area set to include the detected subject more accurately includes only the low-contrast subject area, the size is wider. The first AF area having a contrast is reset within the same frame. As a result, even if a highly reliable defocus amount cannot be calculated in the second AF region, AF can be performed with high accuracy and high speed.

Next, Example 4 of the present invention will be described. In this embodiment, in addition to the AF area setting process and the used AF area selection process described in the third embodiment, the AF area to be used is changed according to the state of the aperture. The configurations of the camera body and the lens unit in this embodiment are the same as those in the first embodiment, and the common components are designated by the same reference numerals as those in the first embodiment. Further, the image pickup process, the still image image pickup process, and the AF process performed on the camera body 20 are the same as the processes described with reference to FIGS. 3, 4, and 11 in the first embodiment. Further, the focus detection process and the AF area setting process in this embodiment are the same as the processes described with reference to FIGS. 16 and 17 in Example 3.

The AF area selection process performed by the camera control unit 212 in S1708 of FIG. 16 will be described with reference to the flowchart of FIG. The processing of S2101, S2102, S2104 and S2105 in FIG. 20 is the same as the processing of S1901, S190, S1903 and S1904 in FIG.

In S2103, the camera control unit 212 determines whether or not the aperture is opened from a predetermined aperture value. If the aperture is opened from the predetermined aperture value, the process proceeds to S2104, and if the aperture is stopped from the predetermined aperture value, the process proceeds to S2105. Since the reason for changing the AF area to be used according to the state of the aperture is the same as the process described in S1505 of FIG. 14 in the second embodiment, the description thereof will be omitted.

Also in this embodiment, as in the third embodiment, when the amount of movement of the detected subject is large, the first AF region is set in each of the subject detection position and the position shifted from the subject detection position to the movement direction of the detected subject. Set the second AF area. Then, the second AF region is used for the AF process only when the reliability of the defocus amount obtained in the second AF region is high and the aperture is opened from the predetermined aperture value. In a situation where the AF accuracy is likely to decrease due to the aperture being stopped down by such control, the AF area is widened rather than suppressing perspective competition by narrowing the AF area, and the subject with high contrast is the AF area. The stability of AF can be improved by making it easy to include in.
(Other examples)
The present invention supplies a program that realizes one or more functions of the above-described embodiment to a system or device via a network or 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 the processing to be performed. It can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

Each of the above-described embodiments is only a representative example, and various modifications and changes can be made to each embodiment when the present invention is implemented.

10 Lens unit 20 Camera body 103 Focus lens 201 Image sensor 204 AF signal processing unit 212 Camera control unit 213 Subject movement determination unit 216 Subject detection / tracking processing unit

Claims (12)

Focus detection means for detecting the focal state of the imaging optical system by the phase difference detection method,
A control means for performing focus control according to the focus state, and
It has a setting means for setting a focus detection area for detecting the focus state in the image pickup screen.
The setting means is
Using the imaging signal generated by imaging, the subject included in the imaging screen is detected, the movement amount of the subject is detected, and the focus detection region whose position is different according to the movement amount is set.
When the movement amount is smaller than the predetermined movement amount, the focus detection area corresponding to the detection position of the subject in the image pickup screen is set.
When the movement amount is larger than the predetermined movement amount, the focus detection area shifted from the detection position in the image pickup screen to the movement direction of the subject is set , and the movement amount is smaller than the predetermined movement amount. Also, a focus control device characterized in that the size of the focus detection region is reduced . The focus control device according to claim 1, wherein the setting means sets the focus detection region so that the detection position or a position shifted from the detection position in the moving direction becomes the center or the center of gravity. The setting means has a case where the movement amount is larger than the predetermined movement amount, and when the reliability of the detected focal state is higher than the predetermined reliability, the movement amount is smaller than the predetermined movement amount. The focus control device according to claim 1 or 2 , wherein the size of the focus detection region is reduced. In the setting means, when the movement amount is larger than the predetermined movement amount, when the aperture included in the imaging optical system is opened from the predetermined aperture value, the movement amount is smaller than the predetermined movement amount. The focus control device according to any one of claims 1 to 3, wherein the size of the focus detection region is reduced. When the movement amount is larger than the predetermined movement amount, the setting means sets a plurality of the focus detection regions having different sizes from each other, and uses any one of the plurality of focus detection regions for the focus control. The focus control device according to any one of claims 1 to 4 , wherein the focus detection region is selected. The plurality of focus detection regions include a first focus detection region and a second focus detection region having a size smaller than that of the first focus detection region.
The setting means selects the first focus detection region as the focus detection region used for the focus control when the reliability of the focus state detected in the second focus detection region is lower than the predetermined reliability. The focus control device according to claim 5 . The plurality of focus detection regions include a first focus detection region and a second focus detection region having a size smaller than that of the first focus detection region.
The setting means is
When the aperture included in the image pickup optical system is narrowed down from a predetermined aperture value, the first focus detection region is selected as the focus detection region used for the focus control.
The focus control device according to claim 5 or 6 , wherein when the aperture is opened from the predetermined aperture value, the second focus detection area is selected as the focus detection area used for the focus control. Focus detection means for detecting the focal state of the imaging optical system by the phase difference detection method,
A control means for performing focus control according to the focus state, and
It has a setting means for setting a focus detection area for detecting the focus state in the image pickup screen.
The setting means is
Using the imaging signal generated by imaging, the position of the subject included in the imaging screen is detected, the movement amount of the subject is detected, and the focus detection area is set based on the position and the movement amount.
Focus control characterized in that the size of the focus detection region set when the movement amount is equal to or larger than the predetermined movement amount is smaller than the size set when the movement amount is smaller than the predetermined movement amount. Device. The step of detecting the focal state of the imaging optical system by the phase difference detection method,
The step of performing focus control according to the focus state and
It has a setting step for setting a focus detection area for detecting the focus state in the image pickup screen.
In the setting step, the subject included in the image pickup screen is detected by using the image pickup signal generated by the image pickup, the movement amount of the subject is detected, and the focus detection region whose position is different according to the movement amount is detected. Set,
When the movement amount is smaller than the predetermined movement amount, the focus detection area corresponding to the detection position of the subject in the image pickup screen is set.
When the movement amount is larger than the predetermined movement amount, the focus detection area shifted from the detection position in the image pickup screen to the movement direction of the subject is set , and the movement amount is smaller than the predetermined movement amount. Also, a focus control method characterized in that the size of the focus detection region is reduced . The step of detecting the focal state of the imaging optical system by the phase difference detection method,
The step of performing focus control according to the focus state and
It has a setting step for setting a focus detection area for detecting the focus state in the image pickup screen.
In the setting step
Using the imaging signal generated by imaging, the position of the subject included in the imaging screen is detected, the movement amount of the subject is detected, and the focus detection area is set based on the position and the movement amount.
A focus control method characterized in that the size of the focus detection region set when the movement amount is equal to or greater than the predetermined movement amount is smaller than the size set when the movement amount is smaller than the predetermined movement amount. .. A computer program that causes the computer of the image pickup device to execute focus control processing.
The focus control process includes a process of detecting the focus state of the imaging optical system by a phase difference detection method and a process of detecting the focus state.
The process of performing focus control according to the focus state and
It includes a setting process for setting a focus detection area for detecting the focus state in the image pickup screen.
In the setting process, the computer
Using the image pickup signal generated by the image pickup, the subject included in the image pickup screen is detected and the movement amount of the subject is detected, and the focus detection area whose position is different according to the movement amount is set.
When the movement amount is smaller than the predetermined movement amount, the focus detection area corresponding to the detection position of the subject in the image pickup screen is set.
When the movement amount is larger than the predetermined movement amount, the focus detection area shifted from the detection position in the image pickup screen to the movement direction of the subject is set , and the movement amount is smaller than the predetermined movement amount. Also, a focus control program characterized in that the size of the focus detection area is reduced . A computer program that causes the computer of the image pickup device to execute focus control processing.
The focus control process is
A process of detecting the focal state of the imaging optical system by a phase difference detection method, a process of performing focus control according to the focal state, and a process of performing focus control.
It includes a setting process for setting a focus detection area for detecting the focus state in the image pickup screen.
In the setting process, the computer
Using the imaging signal generated by imaging, the position of the subject included in the imaging screen is detected, the movement amount of the subject is detected, and the focus detection area is set based on the position and the movement amount.
A focus control program characterized in that the size of the focus detection region set when the movement amount is equal to or greater than the predetermined movement amount is made smaller than the size set when the movement amount is smaller than the predetermined movement amount. ..

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