JP2015087705A - Focus control device, and control method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve focusing quality and achieve stable focusing in moving image photographing using an image plane phase detection AF system.SOLUTION: In an imaging apparatus, an image plane phase detection AF system is used, a plurality of range-finding areas are arranged, one defocus amount is calculated from range-finding results obtained from respective range-finding areas, lenses are driven, and focusing is performed. In the imaging apparatus, at least two range-finding areas of sizes having different ratios with respect to an image plane are arranged as a first range-finding area arrangement. Then, the range-finding areas are arranged such that the range-finding areas with smaller ratios with respect to the image plane are larger in the number compared to the range-finding areas with larger ratios. Further, when range-finding results are not obtained in the first range-finding area arrangement, range-finding results are obtained in a second range-finding area arrangement in which range-finding areas with greater ratios with respect to the image plane than those of the first range-finding areas are arranged.

Description

  The present invention relates to focus control of an imaging apparatus or the like.

  As a focus control method of the imaging apparatus, for example, there are a phase difference detection method and a contrast detection method (see Patent Document 1 and Patent Document 2). There is also an imaging surface phase difference detection method that takes into account an LV (live view) mode in which an image is captured while displaying a captured image on a rear monitor or the like (see Patent Document 3).

Japanese Patent Laid-Open No. 09-054242 JP 2001-004914 A JP 2001-083407 A

  However, even in the imaging surface phase difference detection method in consideration of the live view mode, it is necessary to perform focus control that is more stable than the conventional one, which is suitable for the live view mode and moving image shooting. In particular, if the focus state is changed carelessly as the number of pixels increases, a moving image may be uncomfortable for an observer.

  Accordingly, in order to solve the above-described problem, the invention described in claim 1 of the present application includes a first focus information output unit that outputs focus information (defocus amount / correlation value) corresponding to the first region, and a second focus information output unit. A second focus information output means for outputting focus information (defocus amount / correlation value) corresponding to the area of the first area, and the first area and the second area are all within one area in the captured image. Each of the plurality of output focus information is used to acquire one defocus information corresponding to the area, and control means for performing focus control based on the acquired defocus information. The first area in the area is shorter than the second area in the area.

  As described above, according to the invention described in claim 1 of the present application, it is possible to provide focus control capable of performing stable focus control so as to be more suitable for live view mode and moving image shooting.

It is a block diagram which shows the structure of the imaging device and lens apparatus as a focus control apparatus. It is a figure which shows the partial area | region of an image sensor. It is a flowchart which shows AF control processing. It is a flowchart which shows a lens drive process. It is a flowchart which shows the setting process of the detection area which detects a defocus amount. It is a figure which shows the example of arrangement | positioning of the detection area which detects a defocus amount. It is a figure which shows the image signal obtained from the detection area which detects a defocus amount. It is a figure which shows a correlation amount waveform, a correlation change amount waveform, and a focus shift | offset | difference amount. It is a figure which shows the method of calculating 2 image coincidence degree. It is a flowchart of a phase difference AF process. 10 is a flowchart for calculating a defocus amount. It is a figure which shows the image signal example in an imaging surface phase difference detection system.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The embodiment described below is an example as means for realizing the present invention, and should be appropriately modified or changed depending on the configuration and various conditions of the apparatus to which the present invention is applied. It is not limited to the embodiment.

<Configuration of imaging device>
An imaging apparatus as an example of a focus control apparatus according to an embodiment of the present invention will be described. In the present embodiment, the imaging device to which the lens device can be attached will be described, or another imaging device such as a digital camera with a lens attached may be used.

  FIG. 1 is a block diagram illustrating a configuration of main parts of the lens device and the imaging device according to the present embodiment.

  As shown in FIG. 1, the present embodiment includes a lens device 10 and an imaging device 20, and a lens control unit 106 that controls the overall operation of the lens device, and a camera control unit that controls the overall operation of the imaging device. 207 is communicating information.

  First, the configuration of the lens device 10 will be described. The lens device 10 includes a fixed lens 101, an aperture 102, a focus lens 103, an aperture drive unit 104, a focus lens drive unit 105, a lens drive 106, and a lens operation unit 107. The photographing optical system represents a fixed first group lens 101, a diaphragm 102, and a focus lens 103.

  The diaphragm 102 is driven by the diaphragm controller 104 and controls the amount of light incident on the image sensor 201 described later. The focus lens 103 is driven by a focus lens driving unit 105 and adjusts a focus that forms an image on an image sensor 201 described later. The aperture driving unit 104 and the focus lens driving unit 105 are controlled by the lens control unit 106 to determine the aperture amount of the aperture 102 and the position of the focus lens 103. When there is a user operation through the lens operation unit 107, the lens control unit 106 performs control according to the user operation. The lens control unit 106 controls the aperture driving unit 104 and the focus lens driving unit 105 in accordance with a control command / control information received from a camera control unit 207, which will be described later, and transmits lens control information to the camera control unit 207. To do.

  Next, the configuration of the imaging device 20 will be described. The imaging device 20 can acquire an imaging signal from a light beam that has passed through the imaging optical system of the lens device 10. An image sensor 201, a CDS / AGC circuit 202, a camera signal processing unit 203, an AF signal processing unit 204, a display unit 205, a recording unit 206, a camera control unit 207, and a camera operation unit 208 are provided. The image sensor 201 is a member as an image sensor, and includes a CCD, a CMOS sensor, or the like. The light flux that has passed through the photographing optical system on the lens device side is imaged on the light receiving surface of the image sensor 201 and converted into a signal charge corresponding to the amount of incident light by the photodiode. The signal charge accumulated in each photodiode is sequentially read out from the image sensor 201 as a voltage signal corresponding to the signal charge based on a drive pulse supplied from the timing generator 209 in accordance with a command from the camera control unit 207.

  The video signal and AF signal read from the image sensor 201 are input to the CDS / AGC circuit 202 that samples and adjusts the gain, and the video signal is input to the camera signal processing unit 203 and the signal for the imaging plane phase difference AF is input. Each is output to the AF signal processing unit 204.

  The camera signal processing unit 203 performs various kinds of image processing on the signal output from the CDS / AGC circuit 202 to generate a video signal.

  A display device 205 configured by an LCD or the like displays the video signal output from the camera signal processing unit 203 as a captured image.

  The recording unit 206 records the video signal from the camera signal processing unit 203 on a recording medium such as a magnetic tape, an optical disk, or a semiconductor memory.

  The AF signal processing unit 204 performs a correlation calculation based on the two image signals for AF output from the CDS / AGC circuit 202, and performs defocus amount, reliability information (two-image coincidence, two-image steepness, contrast Information, saturation information, scratch information, etc.). The calculated defocus amount and reliability information are output to the camera control unit 207. Further, the camera control unit 207 notifies the AF signal processing unit 204 of changes in settings for calculating these based on the acquired defocus amount and reliability information. Details of the correlation calculation will be described later with reference to FIGS.

  The camera control unit 207 performs control by exchanging information with the entire camera 20. In response to input from the camera operation unit 208 as well as processing within the camera 20, the user has performed operations such as turning the power on / off, changing settings, starting recording, starting AF control, and checking recorded video. Perform various camera functions. Further, as described above, information is exchanged with the lens control unit 106 in the lens apparatus 10, lens control commands / control information are sent, and information in the lens is acquired.

<Image sensor>
FIG. 2 shows a part of the light receiving surface of an image sensor 201 as an image sensor. In order to enable imaging surface phase difference AF, the imaging element 201 has a pixel portion that holds two photodiodes as light receiving portions as photoelectric conversion means for one microlens arranged in an array. Thereby, each pixel unit can receive a light beam obtained by dividing the exit pupil of the lens device 10.

  FIG. 2A is a schematic diagram of a part of the image sensor surface of an example of Bayer arrangement of red (R), blue (B), and green (Gb, Gr) for reference. FIG. 2B shows an example of a pixel portion in which two photodiodes as photoelectric conversion means are held for one microlens corresponding to the arrangement of the color filters in FIG.

  The image sensor having such a configuration can output two signals for phase difference AF (hereinafter also referred to as A image signal and B image signal) from each pixel unit. Further, an image recording signal (A image signal + B image signal) obtained by adding the signals of the two photodiodes can be output. In the case of this added signal, a signal equivalent to the output of the image sensor of the Bayer array example schematically described in FIG.

  By using an output signal from the image sensor 201 as such an image sensor, an AF signal processing unit 204 (to be described later) performs a correlation operation between the two image signals, and calculates information such as a defocus amount and various reliability.

  In the present embodiment, a total of three signals, that is, two signals for imaging and two signals for phase difference AF are output from the imaging element 201. This point is not limited to such a method. For example, a total of two signals out of two signals of an imaging signal and an image signal for phase difference AF may be output. In this case, after output, the other one of the two signals of the image signal for phase difference AF is calculated using the two output signals from the image sensor 201.

  FIG. 2 shows an example in which pixel portions holding two photodiodes as photoelectric conversion means are arranged in an array for one microlens. In this regard, pixel portions holding three or more photodiodes as photoelectric conversion means may be arranged in an array for one microlens. Moreover, you may make it have two or more pixel parts from which the opening position of a light-receiving part differs with respect to a micro lens. That is, it is sufficient if two signals for phase difference AF capable of detecting the phase difference, such as an A image signal and a B image signal, can be obtained as a result.

<AF control processing>
Next, AF control processing executed by the camera control unit 207 will be described.

  FIG. 3 is a flowchart showing an AF control process executed by the camera control unit 207 in FIG. This process is executed according to a computer program stored in the camera control unit 207. For example, it is executed in the readout cycle (every vertical synchronization period) of the imaging signal from the imaging device 201 for generating one field image (hereinafter also referred to as one frame and one screen). In this regard, it may be repeated a plurality of times within the vertical synchronization period (V rate).

  In FIG. 3, first, it is confirmed whether or not the AF signal is updated in the AF signal processing unit 204 (Step 301), and if updated, the result is acquired from the AF signal processing unit 204 (Step 302).

  Next, it is determined whether or not the defocus amount indicating the amount of out-of-focus in the acquired result is within a predetermined depth and the reliability level of the defocus amount is higher than the predetermined level and is reliable. (Step 303). When the defocus amount is within the depth and the reliability level of the defocus amount is higher than the predetermined level, the focus stop flag is turned on (Step 304), and in the opposite case, the focus stop flag is turned off (Step 305). ). The state where the focus stop flag is ON is a flag indicating that the focus is controlled at the focus position and the focus control should be stopped.

  Here, the reliability level of the defocus amount is a defocus that indicates the direction in which the focus position will exist, assuming that the reliability level is high when it can be determined that the accuracy of the calculated defocus amount is certain. When the direction is certain, it is determined as “medium”. For example, when the reliability level of the defocus amount is high, the contrast between the A image signal and the B image signal is high, and the shapes of the A image signal and the B image signal are similar (the two image coincidence level is high). In other words, the main subject image is already in focus. In this case, the driving is performed with reliability of the defocus amount.

  When the reliability level of the defocus amount is “medium”, the two image coincidence level calculated by the AF signal processing unit 204 is lower than a predetermined value, but the A image signal and the B image signal are relatively shifted. There is a certain tendency in the correlation obtained by this, and the defocus direction is reliable. For example, the determination is often made in a state where the main subject is slightly blurred. Further, when the defocus amount and the defocus direction are not reliable, it is determined that the reliability level is low. For example, the contrast of the A image signal and the B image signal is low and the image matching level is low. This is often the case when the subject is greatly blurred, and it is difficult to calculate the defocus amount.

When the defocus amount is within the predetermined depth and the reliability level of the defocus amount is high, the lens drive for controlling the focus is stopped (Step 307), and the process proceeds to Step 308.
On the other hand, when the focus stop flag is turned off (Step 305), the lens drive setting described later is performed (Step 306), the process proceeds to the area arrangement setting process (Step 308), and the process ends.

<Lens drive processing>
FIG. 4 is a flowchart showing details of the AF control process (Step 306) of FIG.

  First, in step 401, the camera control unit 207 determines whether the defocus amount is obtained and the reliability level is high. When the defocus amount is obtained and the reliability level is high (YES in Step 401), the drive amount and the drive direction are determined based on the defocus amount (Step 402).

  Then, the error count and end count are cleared (Step 403), and the process is terminated. If the defocus amount is not obtained or the reliability level is not high (No in Step 401), it is determined whether or not the error count exceeds the first count (Step 404). Here, although not shown, the first count may be a value that is stored and determined in advance in a nonvolatile memory. For example, what is necessary is just to set the value more than twice the below-mentioned 2nd count.

  If the error count is smaller than the first count (No in Step 404), the error count is incremented (Step 405), and the process is terminated. If the error count is larger than the first count (Yes in Step 404), it is determined whether the search drive flag is ON (Step 406).

  If the search drive flag is OFF in Step 406 (No in Step 406), the search operation is not yet started, or the search is not in progress. Therefore, the search drive flag is turned on (Step 407), and it is determined whether or not the defocus reliability level is “medium” (Step 408).

  When the reliability is “medium”, the drive direction is set using the defocus direction (Step 409), and a predetermined drive amount is set (Step 411). At this time, search driving is performed to drive the focus in the defocus direction obtained by a predetermined amount without driving based on the absolute value of the defocus amount itself.

  When the reliability is not “medium” (No in Step 408), the driving direction is set in a direction far from the lens end (Step 410), and a predetermined driving amount is set (Step 411).

  As the predetermined drive amount of Step 411, a value determined in advance in a nonvolatile memory may be used. For example, the driving amount is a distance several times the focal depth. Further, it may be variable according to the focal length. For example, the longer the focal length, the greater the driving amount. Note that the search drive direction at this time is, for example, a direction in which the lens end is far from the current focus position.

  If the search drive flag is ON (Yes in Step 406), the search drive has already been executed. Therefore, the previous focus control is continued and executed. Then, it is determined whether or not the lens is at the lens driving limit position during focus control (Step 412). If the lens is hit (Yes in Step 412), the end count is incremented (Step 413). .

  If the end count exceeds the predetermined value (Yes in Step 414), it indicates that a defocus amount cannot be obtained even if the focus lens is operated from the closest end to the infinite end. Therefore, it is determined that there is no subject that can be brought into focus, the search drive flag is turned off (Step 415), and the lens drive is stopped (Step 416). Then, the error count and end count are cleared (Step 417), and the process is terminated.

  If the end count does not exceed the predetermined value (No in Step 414), the lens driving direction associated with the focus control is set to the driving direction opposite to the current driving direction (Step 418), and the predetermined driving amount is set ( Step 411).

<Area setting process>
FIG. 5 is a flowchart showing details of the area setting process (Step 308) of FIG.

  First, it is determined whether the defocus amount is obtained and the reliability level is high (Step 501). If the defocus amount is obtained and the reliability level is high (YES in Step 501), it is determined whether or not the area arrangement in the captured image that is currently set is the first area arrangement (Step 504). If it is the first area arrangement (Yes in Step 504), the setting state of the first area arrangement is maintained as it is. If it is not the first area layout (No in Step 504), it is determined in Step 506 whether the focus stop flag is ON. If the focus stop flag is ON (Yes in Step 506), the first area layout is determined. (Step 505). This results in a relatively narrow area arrangement after focusing. If the focus stop flag is OFF (No in Step 506), the process can be changed and the setting can be changed by setting the second area arrangement wider than the first area arrangement (Step 507).

  Here, when the focus stop flag is ON (Step 506), the reason for shifting to the first area arrangement is that the captured subject images may be different between the second area arrangement and the first area arrangement. It is. For this reason, in the second area arrangement, when the focus stop flag is turned ON and the lens drive as the focus control is stopped in a focused state, the first area arrangement is shifted to a relatively narrow area. This is because in the case of moving image shooting, the main subject is often in the center of the screen. Therefore, by setting the first area arrangement to be relatively narrow, it is possible to increase the probability that the finally aimed subject image will be in focus.

  Note that the subject is not necessarily a subject whose defocus amount can be detected when the first area arrangement is relatively narrow. Therefore, when the camera control unit 207 returns to the relatively narrow first area arrangement, the camera control unit 207 obtains information that is significantly different from the information related to the defocus amount at the time of the relatively wide second area arrangement. In such a case, it may be returned to the second area arrangement again.

  Next, when the defocus amount cannot be obtained and the reliability is not high (No in Step 501), it is determined whether or not the NG count exceeds the second count (Step 502). If the NG count does not exceed the second count (No in Step 502), the NG count is counted up (Step 503). Then, the camera control unit 207 determines whether or not it is the first area arrangement (Step 504).

  On the other hand, when the NG count exceeds the second count (Yes in Step 502), the NG count is cleared (Step 508), and the camera control unit 207 determines whether or not search driving is being performed (Step 509). If the search is being driven (Yes in Step 509), the first area arrangement is set (Step 512). If the search is not being driven (No in Step 509), it is determined whether or not it is the first area arrangement (Step 510). If it is currently the first area arrangement (Yes in Step 510), the second area arrangement is set to be relatively wide (Step 511). If it is not the second area arrangement (No in Step 510), the comparison is made. Therefore, the first area arrangement is set to be narrow (Step 512).

  As described above, whether or not the search drive is being performed is determined (Step 509) by performing an operation of first switching the first area and the second area before executing the search drive. This is because search drive is executed when the area arrangement is NG.

  If a defocus amount with a high reliability level can be acquired during search driving, search driving is stopped and focus control is performed according to the acquisition result. Therefore, if the second area is relatively large during search driving, a subject image that is not an appropriate subject image may be captured. Therefore, the first area is set.

<Area arrangement (1)>
The area arrangement will be described more specifically with reference to FIG. FIG. 6A is a diagram showing a first area arrangement. Seven areas 601 to 607 exist in the area. Two areas 601 and 607 are arranged in the second length area where the horizontal ratio to the screen is β%. Further, an area having a first length shorter than the second length by α% is arranged in five areas 602 to 606 in the center of the photographing screen. In this way, a plurality of regions having different lengths are arranged in the area, and the number of short regions is larger than the number of long regions.

  Then, using a combination of defocus amounts obtained from the seven regions, one effective defocus amount and effective defocus direction, which will be described later, are acquired. Using this effective defocus amount and effective defocus direction, the lens is driven for focus control to perform focusing. Hereinafter, the effective defocus amount is also described as a concept meaning one defocus amount corresponding to the area arrangement. In addition, the effective defocus direction is also described as a concept meaning one defocus direction corresponding to the area arrangement.

  By arranging not only a relatively short first length area but also a relatively long second length area, the quality of moving image shooting and live view images is ensured. That is, there is a high possibility that the main subject image cannot be captured or the main subject image moves out of the area only with the relatively short first-length region aggregate. In this case, the output from the image sensor corresponding to the relatively short first length region may cause the focus to fluctuate. Therefore, a relatively long second length region is arranged in the area so that the main subject image can be maintained while being captured. In the example of FIG. 6A described above, the number of short regions is larger than the number of long regions. Even if this is reversed, a certain effect can be obtained by providing areas of different lengths in the area. However, as illustrated, the user's intention is to eliminate the perspective conflict by arranging the number of relatively short regions with a small ratio to the shooting screen more than the number of long regions. It becomes possible to focus on the subject image. Furthermore, in the example of FIG. 6A described above, as shown in FIG. 6A, the relatively long second region is disposed outside the relatively short first region. Yes. In this regard, a certain effect can be obtained even if the relatively long second length region is arranged inside the relatively short first region. However, as shown in FIG. 6A, the following effect can be obtained by disposing the relatively long second region outside the relatively short first region. In other words, in the case of moving image shooting, this is an effect considering that the main subject image intended by the user is relatively central. The short area occupies the center of the area so that the center of the subject image captured by the area arrangement is focused. This is because, in moving image shooting and live view images, there are many scenes for shooting moving subject images. Therefore, it is considered that the user often shoots so that the main subject image is located at the center of the shooting screen so that the subject image intended for focusing does not deviate from the shooting screen. In the first area arrangement of FIG. 6A, when the area is at the center of the screen, the number of regions having the same length as the region located at the center of the screen is larger than the number of other regions. It is arranged. In this regard, when the area is at the center of the screen, a certain effect can be obtained even if the number of regions having the same length as the region located at the center of the screen is less than the number of other regions. However, in moving image shooting, as described above, considering that the main subject image is often located at the center of the screen, when the area is at the center of the screen, the area located at the center of the screen The number of regions having the same length as the number of regions is arranged more than the number of other regions. Set the size of the center area of the shooting screen so that the user can properly focus on the subject image targeted by the user, and set the number of the size of the area to be the largest. Yes. In addition, even if the temporarily aimed subject falls out of the relatively short first length region, the stable focus is obtained in order to capture the subject image in the relatively long second length region. Control can be performed.

  As these comprehensive actions, the stability of focus control can be dramatically improved.

  FIG. 6B shows the second area arrangement, but the area arrangement is wider than the first area arrangement of FIG. 6A. The ratio of the horizontal direction with respect to the shooting screen is β ′%, the relatively long fourth length area is two areas (611, 617), and the relatively short third length area is α ′%. Has 5 areas (612-616). In FIG. 6, the first length is twice the second length and is the same as the third length, and the fourth length is twice the third length. . In this regard, the magnification is not limited to these. However, in the case of such an exemplary magnification relationship, circuit design and program configuration may be simplified.

  The reason why the relatively wide second area arrangement is provided in addition to the relatively narrow first area arrangement will be described with reference to FIG.

  For example, when a subject image as shown in FIG. 12A is photographed, an image having two mountain shapes appears in the area in the vicinity of the focus (FIG. 12B). Here, for example, assume that 1501 is an A image and 1502 is a B image, the phase difference detection method is applied, and the defocus amount is calculated by calculating the shift amount of these two images. However, in the case of a large blur (a state that is largely blurred), the shape of the two mountain images themselves collapses, resulting in a single mountain shape. Further, in the shape of the mountain, the mountain has a mountain shape in which the base of the mountain can be seen. That is, the shape of the subject image to be captured differs greatly depending on the focus state (whether it is in a large blur state or a state close to focusing) (FIG. 12C).

  In this regard, even when there is a high possibility that the defocus amount cannot be obtained in a state where the image is largely blurred, it is possible to improve the focusing stability by using the relatively large second area arrangement. In other words, the frequency with which the defocus amount and the defocus direction can be obtained can be improved by having a relatively wide second area.

<Area arrangement (2)>
6A and 6B, the length in the horizontal direction is described. This is a technical idea that can be applied even when a region (so-called vertical eye) is arranged in the vertical direction.

  Furthermore, the area setting process of FIG. 5 is illustrated by the flow for switching between the first area arrangement and the second area arrangement shown in FIGS. In this regard, if the arithmetic circuit scale and the program scale allow, for example, as shown in FIG. 6C, an arrangement corresponding to the number of areas corresponding to the shooting screen is arranged in advance so as to include both the first area and the second area. It may be selected and used. That is, as shown in FIG. 6C, the regions 621 to 634 are arranged in the area, and the regions 601 to 607 in FIG. 6A are changed to the regions 621 to 627 in FIG. The areas 611 to 617 in FIG. 6B are the area areas 628 to 634 in FIG. According to this, in the case of the first area arrangement described in FIG. 5, the areas 621 to 627 are used, and in the case of the second area arrangement, the areas 628 to 634 are selected and used.

  In addition, until now, the first area and the second area are arranged in the center of the shooting screen. In view of this, the fourth area arrangement may be installed in consideration of the scene where the subject image to be photographed by the photographer who is the user is not located at the center of the photographing screen in consideration of the composition of the photographing (see FIG. 6 (D)). This is not shown, but it is possible to focus on the detected image using a function that identifies a predetermined subject image, such as a face detection function, or on the shooting screen by a user instruction such as a touch operation. This can also be applied when it is desired to focus on a desired subject. Like the areas 641 to 647 in FIG. 6D, the camera control unit 207 is not located at the center of the screen, or the area arrangement can be moved and the position where the face is detected or the position designated by the user is Set the area arrangement as described above.

  Thus, improving the degree of freedom of various area arrangements is compatible with the imaging surface phase difference AF method.

<About correlation calculation>
Next, although the calculation of the effective defocus amount described above will be exemplified, the calculation of the effective defocus amount is illustrated after explaining the correlation calculation, the correlation amount waveform, and the like as the correlation information.

  FIG. 7D illustrates a region from which an image signal is acquired, and is a conceptual diagram on the pixel array of the image sensor 201 as an image sensor. For a pixel array 701 in which pixel parts (not shown) are arranged in an array, a region to be calculated described below is a region 702. A combination of the shift area 703 and the area 702 necessary for the correlation calculation when calculating the defocus amount of the area 702 is a shift area 704 necessary for performing the correlation calculation.

  7, 8, and 9, p, q, s, and t represent coordinates in the x-axis direction, respectively, p to q represent a shift region 704, and s to t represent a region 702.

  7A, 7B, and 7C are image signals acquired from the shift region 704 set in FIG. 7D. s to t correspond to the region 702, and p to q are image signals corresponding to the shift region 704 in the range necessary for the calculation for calculating the defocus amount based on the shift amount. FIG. 7A is a diagram conceptually showing waveforms of the A image signal and the B image signal before the shift for correlation calculation. A solid line 801 is the A image signal A, and a broken line 802 is the B image signal. FIG. 7B is a conceptual diagram when the image waveforms before the shift in FIG. 7A are shifted in the plus direction, and FIG. 7C is in the minus direction with respect to the image waveform before the shift in FIG. It is a conceptual diagram at the time of shifting mutually. When calculating the correlation amount, which is the degree of correlation between the two images, for example, the A image signal 801 and the B image signal 802 are shifted bit by bit in the directions of the arrows, respectively.

  Next, a method for calculating the correlation amount COR will be described. First, as shown in FIGS. 7B and 7C, for example, the image signal A and the image signal B are shifted bit by bit, and the absolute value of the difference between the A image signal and the B image signal in each state is calculated. Calculate the sum. At this time, the shift amount is represented by i, the minimum shift number is ps in FIG. 8, and the maximum shift number is qt in FIG. X is the start coordinate of the distance measurement area, and y is the end coordinate of the distance measurement area. Using these, it can be calculated by the following equation (1).

  FIG. 8A is a conceptual diagram showing the amount of correlation in a waveform graph. The horizontal axis of the graph indicates the shift amount, and the vertical axis indicates the correlation amount. The correlation amount waveform 901 is an example having extreme values 902 and 903. Among these, the smaller the correlation amount, the higher the coincidence between the A image and the B image.

  Next, a method for calculating the correlation change amount ΔCOR will be described. First, from the conceptual diagram of the correlation amount waveform in FIG. 8A, for example, the correlation change amount is calculated from the difference in the correlation amount after skipping one shift. At this time, the shift amount is represented by i, the minimum shift number is ps in FIG. 8D, and the maximum shift number is qt in FIG. 8D. Using these, it can be calculated by the following equation (2).

  FIG. 8B is a conceptual diagram illustrating the correlation change amount ΔCOR with a waveform graph. The horizontal axis of the graph indicates the shift amount, and the vertical axis indicates the correlation change amount. The correlation change amount waveform 1001 has points 1002 and 1003 at which the correlation change amount becomes positive to negative. The state in which the correlation change amount is 0 from this point 1002 is the shift amount between the A image signal and the B image signal that have a relatively high degree of coincidence between the A image and the B image. The shift amount at that time corresponds to the defocus amount.

  FIG. 9A is an enlarged view of the point 1002 in FIG. 8B, and a waveform 1101 is a partial waveform of the correlation change amount waveform 1001. With reference to FIG. 9A, an example of a method of calculating the focus shift amount PRD corresponding to the defocus amount will be described. The concept of the focus shift amount is divided into an integer part β and a decimal part α. The decimal part α can be calculated by the following equation (3) from the similar relationship between the triangle ABC and the triangle ADE in the figure.

Subsequently, the decimal part β can be calculated by the following formula (4) from FIG.
β = k−1 (4)

  As described above, the focus shift amount PRD can be calculated from the sum of α and β.

  In addition, when there are a plurality of zero crosses as shown in FIG. 8B, the first zero cross is a point where the steepness maxder (hereinafter referred to as steepness) of the correlation amount change at the zero cross is large. This steepness is an index indicating the ease of AF. The larger the value, the easier it is to perform AF. The steepness can be calculated by the following equation (5).

  As described above, when there are a plurality of zero crosses, the first zero cross is determined based on steepness.

  Next, an example of a method for calculating the reliability level of the focus deviation amount will be described. This corresponds to the reliability of the defocus amount, but the following explanation is an example, and the reliability level may be calculated by another known method. The reliability can be defined by the steepness described above and the degree of coincidence fnclvl (hereinafter referred to as the degree of coincidence of two images) of the two images of the A image signal and the B image signal. The degree of coincidence between the two images is an index representing the accuracy of the amount of focus deviation. FIG. 9B is an enlarged view of the vicinity of the extreme value 902 in FIG. 8A, and is a waveform 1201 that is a partial waveform of the correlation amount waveform 901. From this, the calculation method of the steepness and the degree of coincidence of two images will be exemplified. The degree of coincidence between two images can be calculated by the following equation (6).

  As described above, the degree of coincidence of two images is calculated.

<Defocus amount calculation>
FIG. 10 is a flowchart showing the process up to the defocus amount calculation. In the following explanation of examples, the amount of focus deviation and the amount of defocus are distinguished and exemplified. In this regard, the defocus amount in the technical idea of the present application may be conceptualized by an absolute distance from the in-focus position or the number of pulses, or may be a concept with a different concept, dimension, unit, or a relative concept. This is a concept indicating how far it can be determined that it is away from the in-focus state and how much focus control can be performed to determine that it can shift to the in-focus state. Acquisition of defocus information as such a concept will be described as acquisition of focus information.

  In Step 1301, the image signals A and B are acquired from the pixels at the positions of the image sensor 201 corresponding to the respective areas set as exemplified above. Next, a correlation amount is calculated from the acquired image signal (Step 1302). Subsequently, a correlation change amount is calculated from the calculated correlation amount (Step 1303). Then, the focus shift amount is calculated from the calculated correlation change amount (Step 1304). Also, a reliability level representing how reliable the calculated focus deviation amount is calculated (Step 1305). These processes are performed according to the number of areas in the area.

  Then, the amount of focus shift is converted into a defocus amount for each region in the area (Step 1306). Further, an effective defocus amount and an effective defocus direction are calculated (Step 1307, Step 1308).

<Calculation of effective defocus amount>
FIG. 11 is a flowchart of the process of calculating one defocus amount corresponding to the area arrangement as the effective defocus amount shown in Step 1307 described above. The correlation calculation performed by the AF signal processing unit 204 will be described with reference to FIGS.

  As for the effective defocus amount, first, among the plurality of regions in the area arrangement, a region where the defocus amount is obtained and the reliability level is high is searched. The average value of the defocus amounts of the areas that satisfy the search condition is calculated (Step 1401).

  Next, the difference between the defocus amount of each region and the average value calculated in Step 1401 is calculated (Step 1402). Then, it is determined whether the maximum value among the calculated differences between the areas is equal to or greater than a predetermined difference. That is, it is determined whether the defocus amount has a large deviation among the defocus amounts of the plurality of regions in the area arrangement. If the maximum value of the calculated differences between the regions is less than the predetermined difference (No in Step 1403), the average value calculated in Step 1401 is set as the effective defocus amount (Step 1404). On the contrary, when the maximum value among the calculated differences between the areas is equal to or larger than the predetermined difference (Yes in Step 1403), the defocus amount of the area that has become the maximum difference is excluded from the calculation target when calculating the average value (Step 1405). . Of the defocus amounts of the plurality of regions in the area arrangement, the defocus amount having a large deviation is excluded from the calculation target.

  It is determined whether or not there is a defocus amount in the remaining area (in Step 1406). If there is a defocus amount in the remaining area (No in Step 1406), the process proceeds to Step 1401 again, and the process is repeated. When the defocus amount of the remaining area becomes 1 (Yes in Step 1406), it is determined that the effective defocus amount has not been obtained, and is set to none (Step 1407).

  The effective defocus direction is the same as the effective defocus amount. Further, for example, in the effective defocus direction, a search is made for a region where the defocus amount is obtained and the reliability level is high or the defocus amount reliability level is “medium” from among a plurality of regions. Then, the most common direction is set as the effective defocus direction.

  In the above example, the defocus amount in the region having the largest difference is exemplified as a defocus amount having a large deviation and excluded from the calculation target when calculating the average value (Step 1405). In this respect, even if the defocus amount having a large deviation is not excluded from the calculation, reducing the weighting has a certain effect. In this case, however, there is a possibility that the main subject image is defocused by the weight.

  The reason why the defocus amount having a large deviation among the defocus amounts of the plurality of regions in the area arrangement is not used is as follows. That is, for the convenience of calculating one defocus amount with respect to the area arrangement from the defocus amounts of a plurality of areas, the possibility of so-called perspective conflict is relatively high because of the size of the area arrangement. .

<Closest priority>
Here, FIG. 11 exemplifies a process of giving priority to the near side direction over the far side direction when calculating the effective defocus amount. This is because the subject image that the photographer as the user intends to focus on is assumed to be close to the background. That is, the photographer often focuses on the subject image on the close side, and the subject image on the close side is more likely to be the subject image intended by the photographer. Therefore, for example, when calculating the difference between the defocus amount of a certain area in the area arrangement and the average value of the area arrangement (Step 1402), when the defocus amount accompanies the closest defocus direction, this defocus amount is calculated. The difference between the focus amount and the average value is multiplied by a value smaller than 1. As another example, the value of the predetermined difference in Step 1403 is increased. As a result, the defocus amount with the closest defocus direction is less likely to be relative to the defocus amount having the maximum value among the calculated differences between the regions. As a result, it is possible to increase the probability of using the defocus amount of the output area when there is a subject image on the close side among a plurality of areas in the area arrangement, and achieve so-called close priority priority focus control. Is something that can be done. However, the method of giving priority to the near side is not limited to this, and the defocus amount with the defocus direction on the near side is excluded from the target that takes the difference from the average defocus amount over the average defocus amount. May be.

  In the above description, the averaging process is exemplified as a method for acquiring one piece of defocus information corresponding to the area using each of the plurality of focus information output in the area arrangement. In this regard, instead of the average, for example, the defocus amount may be calculated with a certain weight. Thus, the significance of acquiring one defocus information corresponding to the area using each of the plurality of output focus information is as follows. That is, if one defocus amount is selected from the defocus amounts of each area in the area arrangement, the subject image is captured by “line” or “point”, and “line” or “point” with respect to the subject image is captured. The focus control is performed even with respect to the difference in defocus amount for each area captured in step 1, and there is a high possibility that it is not appropriate as a live view image or a moving image. In this regard, according to the technical idea of averaging the defocus amount of each area, the subject image is captured by “surface”, so the defocus amount for each area captured by “line” or “point” While reducing the adverse effects caused by the focus control due to the difference, the accuracy of focusing on the subject image intended by the user is also ensured as exemplified above. The same applies if one piece of defocus information corresponding to the area is acquired using each of a plurality of pieces of focus information output with weighting instead of averaging processing.

  In this way, by averaging the multiple defocus amounts in the area arrangement for the subject image to be captured as a single unit, the variation in the defocus amount for each area in the area arrangement is suppressed and stable focus control is performed. Can be achieved.

<Others>
Although the present invention has been described in detail based on preferred embodiments thereof, the present invention is not limited to these specific embodiments, and various forms within the scope of the present invention are also included in the present invention. included. A part of the above-described embodiments may be appropriately combined.

  Also, when a software program that realizes the functions of the above-described embodiments is supplied from a recording medium directly to a system or apparatus having a computer that can execute the program using wired / wireless communication, and the program is executed Are also included in the present invention.

  Accordingly, the program code itself supplied and installed in the computer in order to implement the functional processing of the present invention by the computer also realizes the present invention. That is, the computer program itself for realizing the functional processing of the present invention is also included in the present invention.

  In this case, the program may be in any form as long as it has a program function, such as an object code, a program executed by an interpreter, or script data supplied to the OS.

  As a recording medium for supplying the program, for example, a magnetic recording medium such as a hard disk or a magnetic tape, an optical / magneto-optical storage medium, or a nonvolatile semiconductor memory may be used.

  As a program supply method, a computer program that forms the present invention is stored in a server on a computer network, and a connected client computer downloads and programs the computer program.

DESCRIPTION OF SYMBOLS 10 Lens 20 Camera 101 Fixed lens 102 Aperture 103 Focus lens 104 Aperture drive part 105 Focus lens drive part 106 Lens control part 107 Lens operation part 201 Image pick-up element 202 CDS / AGC circuit 203 Camera signal processing part 204 AF signal processing part 205 Display part 206 Recording unit 207 Camera control unit 208 Camera operation unit 209 Timing generator

Claims (18)

First focus information output means for outputting focus information corresponding to the first region;
Second focus information output means for outputting focus information corresponding to the second area;
Each of the first area and the second area is in one area in the captured image, and one defocus information corresponding to the area is used by using each of the plurality of output focus information. And a control means for performing focus control based on the acquired defocus information,
The focus control apparatus according to claim 1, wherein the first area in the area is shorter than the second area in the area.   2. The focus control apparatus according to claim 1, wherein the second area in the area is at least two or more than the first area.   The focus control apparatus according to claim 1, wherein the shortest area is the largest among the plurality of areas in the area.   4. The focus control apparatus according to claim 1, wherein the first area is located outside the second area in the area. 5.   The focus control apparatus according to claim 1, wherein the control unit is capable of moving the area in the captured image.   The focus control apparatus according to claim 1, wherein the control unit is capable of changing a size of the area in the captured image.   The focus control apparatus according to claim 6, wherein the control unit reduces the area after focusing.   The focus control apparatus according to claim 6, wherein the control unit switches the size of the area before search driving.   9. The focus control apparatus according to claim 6, wherein the control unit is a small area among the plurality of size areas during search driving. 10.   10. The focus control apparatus according to claim 6, wherein the lengths of the first region and the second region also change with a change in the size of the area. 11.   11. The focus control according to claim 1, wherein when outputting the one defocus information, the weighting of the near-side focus information is made larger than the weighting of the far-side focus information. apparatus.   A pair of images is output from positions of image sensors corresponding to the first region and the second region, and the focus information is defocus information based on a phase difference between the pair of images. Item 12. The focus control device according to Items 1 to 11.   The focus control apparatus according to claim 12, wherein the length is a direction in which the phase difference is detected.   The focus control apparatus according to claim 12, wherein the focus information is correlation information of two images.   15. The focus control apparatus according to claim 1, further comprising an image sensor having a plurality of microlenses, and a plurality of light receiving portions corresponding to the microlenses.   The focus control device according to claim 1, further comprising: an image sensor having a plurality of microlenses, and a pixel portion having a different opening position of a light receiving portion corresponding to the microlens.   The control means corresponds to the area using the average value of the plurality of output focus information, wherein the first area and the second area are both in one area in the captured image. The focus control apparatus according to claim 1, wherein one piece of defocus information is acquired. A control method of a focus control device,
An output step of first focus information for outputting focus information corresponding to the first region;
An output step of second focus information for outputting focus information corresponding to the second region;
Each of the first area and the second area is in one area in the captured image, and one defocus information corresponding to the area is used by using each of the plurality of output focus information. And a control step for controlling focus based on the acquired defocus information,
The control method of the focus control apparatus, wherein the first area in the area is shorter than the second area in the area.

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