JP2014095915A - Focus adjustment device and imaging device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform an appropriate focus adjustment control even when a composition is changed during locking in-focus.SOLUTION: The focus adjustment device comprises: focus adjustment means 19 that performs a focus adjustment of an optical system 8 on the basis of a focus adjustment state of the optical system 8; prohibition means 19 that prohibits the focus adjustment of the optical system 8 from being performed by the focus adjustment means 19; reference image setting means 19 that sets an image of a subject intended for the focus adjustment of the optical system 8 as a reference image; recognition means 19 that repeatedly recognizes a position of an image corresponding to the reference image within a screen by the optical system 8; and control means 19 that, when the position of the image recognized by the recognition means 19 is changed at a time the focus adjustment of the optical system 8 is prohibited by the prohibition means 19, cancels the prohibition of the focus adjustment of the optical system 8 by the prohibition means 19 and causes the focus adjustment means 19 to resume the focus adjustment of the optical system 8 on the basis of a focus adjustment state corresponding to the changed position of the image.

Description

  The present invention relates to a focus adjustment device and an imaging apparatus including the focus adjustment device.

  2. Description of the Related Art Conventionally, there is an automatic focus adjustment device that performs focus lock by prohibiting driving of a focus adjustment lens included in an optical system when it is detected that the optical system is in focus. In such an automatic focus adjustment device, when a rear pin state is detected during focusing lock, it is determined that the subject is a moving object, the focusing lock is released, and focus adjustment is resumed. (See Patent Document 1).

JP 2000-66086 A

  In the conventional automatic focus adjustment device disclosed in Patent Document 1, even when the composition is changed during the focus lock, the focus lock is inadvertently released, and appropriate focus adjustment control cannot be performed.

A focus adjustment apparatus according to the present invention includes a focus adjustment unit that performs focus adjustment of an optical system based on a focus adjustment state of the optical system, a prohibition unit that prohibits focus adjustment of the optical system by the focus adjustment unit, and a focus adjustment of the optical system. The reference image setting means for setting the image of the subject to be used as the reference image, the recognition means for recognizing the position of the image corresponding to the reference image in the screen by the optical system, and the focus adjustment of the optical system by the prohibit means When the position of the image recognized by the recognizing means changes when it is prohibited, the prohibition of the focus adjustment of the optical system by the prohibiting means is canceled and based on the focus adjustment state corresponding to the changed image position. And a control means for causing the focus adjustment means to resume focus adjustment of the optical system.
An imaging apparatus according to the present invention includes a focus adjustment device and an imaging unit that captures an image by an optical system.

  According to the present invention, appropriate focus adjustment control can be performed even when the composition is changed during focusing lock.

It is a figure which shows the structure of the imaging device provided with the focus adjustment apparatus of one Embodiment. It is a figure which shows the detailed structure of a body drive control apparatus. It is a front view which shows the detailed structure of a 2nd image pick-up element. It is a detail drawing of the pixel of the 2nd image sensor. It is a figure which shows arrangement | positioning of the focus detection area in an imaging | photography screen. It is a figure explaining the subject tracking method of one embodiment. It is a figure explaining the subject tracking method of one embodiment. It is a flowchart of the process which a body drive control apparatus performs at the time of focus adjustment operation | movement. It is a flowchart of a focusing lock process. It is a flowchart of a tracking initial process. It is a flowchart of a tracking calculation process. It is a flowchart of a refocusing process.

  A focus adjustment apparatus according to an embodiment of the present invention will be described below. This focus adjustment device is provided in an imaging device such as a single-lens reflex digital still camera, and performs automatic focus adjustment (AF) with a focus lock function. That is, in a plurality of focus detection areas set in the shooting screen of the imaging device, the focus adjustment state (defocus amount in this embodiment) of the shooting lens is detected, and based on the defocus amount of any area. To drive the focusing lens. When it is detected that the taking lens is in focus, the driving of the taking lens is prohibited and focusing lock is performed. Further, the focus adjustment device has a function of releasing the focus lock when changing the composition. That is, when a change in composition is detected during the focus lock, the focus lock is released and the focus adjustment can be resumed.

  FIG. 1 shows a configuration of an imaging apparatus (single-lens reflex digital still camera) 1 provided with a focus adjustment apparatus. In FIG. 1, illustration and description of camera devices and circuits not directly related to the present invention are omitted. In the imaging apparatus 1, an interchangeable lens 3 is attached to a camera body 2 in a replaceable manner. The camera body 2 is provided with a first image sensor 4 for capturing a subject image and recording the image. The first image sensor 4 can be constituted by a CCD, a CMOS, or the like. At the time of photographing, the quick return mirror 5 and the sub mirror 6 are retracted to a position outside the photographing optical path indicated by a solid line, the shutter 7 is opened, and a subject image is formed on the light receiving surface of the first image sensor 4 by the photographing lens 8.

  At the bottom of the camera body 2, a focus detection optical system 9 and a distance measuring element 10 for detecting the focus adjustment state of the photographing lens 8 are provided. Here, an example in which a focus detection method based on a pupil division type phase difference detection method is adopted is shown. The focus detection optical system 9 guides the pair of focus detection light fluxes that have passed through the photographing lens 8 to the light receiving surface of the distance measuring element 10 and forms a pair of optical images. The distance measuring element 10 includes, for example, a pair of CCD line sensors, and outputs a focus detection signal corresponding to the pair of optical images. Before shooting, the quick return mirror 5 and the sub mirror 6 are set at positions in the shooting optical path as indicated by broken lines. Thereby, the pair of focus detection light beams from the photographing lens 8 are transmitted through the half mirror portion of the quick return mirror 5, reflected by the sub mirror 6, and guided to the focus detection optical system 9 and the distance measuring element 10.

  A finder optical system is provided on the upper part of the camera body 2. Prior to photographing, the quick return mirror 5 and the sub mirror 6 are in positions indicated by broken lines. Thereby, the subject light from the photographing lens 8 is reflected by the quick return mirror 5 and guided to the focusing screen 11, and a subject image is formed on the focusing screen 11. The liquid crystal display element 12 superimposes and displays information such as a focus detection area mark on the subject image formed on the focusing screen 11 and displays various photographing information such as an exposure value at a position outside the subject image. The subject image on the focusing screen 11 is guided to the eyepiece window 15 via the penta roof prism 13 and the eyepiece lens 14 so that the photographer can visually recognize the subject image.

  The finder optical system at the top of the camera body 2 is provided with a second image sensor 16 that captures a subject image for subject tracking and photometry. The subject image formed on the focusing screen 11 before photographing is guided to the second image sensor 16 via the penta roof prism 13, the prism 17 and the imaging lens 18, and the subject image is formed on the light receiving surface of the second image sensor 16. Is re-imaged. The second image sensor 16 outputs an image signal corresponding to the subject image. As will be described in detail later, tracking control and exposure calculation are performed based on the subject image captured by the second image sensor 16.

  The camera body 2 is also provided with a body drive control device 19 and an operation member 20. The body drive control device 19 includes a microcomputer, a memory, and an A / D converter, which will be described in detail later. The body drive control device 19 performs various controls and calculations of the imaging device 1. The operation member 20 includes switches and selectors for operating the imaging apparatus 1 such as a release button, a focus detection area selection switch, and a shooting mode selection switch.

  The interchangeable lens 3 is provided with a zooming lens 8a, a focusing lens 8b, a diaphragm 21, a lens drive control device 22, and the like. Here, the photographing lens 8 is representatively represented by a zooming lens 8a, a focusing lens 8b, and a diaphragm 21, but the configuration of the photographing lens 8 is not limited to the configuration shown in FIG. The lens drive control device 22 includes a microcomputer (not shown) and peripheral components such as a memory, a drive circuit, and an actuator, and performs drive control of the lenses 8a and 8b and the diaphragm 21 and detection of their set positions. Information such as a focal length and an open aperture value of the interchangeable lens 3 is stored in a memory built in the lens drive control device 22.

  The body drive control device 19 and the lens drive control device 22 communicate via the contact 23 of the lens mount unit. For example, information such as a lens drive amount and an aperture value is transmitted from the body drive control device 19 to the lens drive control device 22, and lens information and aperture information are transmitted from the lens drive control device 22 to the body drive control device 19.

  FIG. 2 shows a detailed configuration of the body drive control device 19. Note that illustration and description of control functions not directly related to the present invention are omitted. The body drive control device 19 includes an element control circuit 19a, an A / D converter 19b, a microcomputer 19c, a memory 19d, and the like. The element control circuit 19 a controls charge accumulation and reading of the second image sensor 16. The A / D converter 19b converts the analog image signal output from the second image sensor 16 into a digital image signal. The microcomputer 19c constitutes a tracking control unit 19e, an exposure control unit 19f, a focus detection calculation unit 19g, a lens drive amount calculation unit 19h, and a mode setting unit 19i depending on the software form. The memory 19d stores information such as a template image for image tracking and a defocus amount, or lens information such as a focal length, an open F value, an aperture value, and a conversion coefficient from an image shift amount to a defocus amount. To do.

  The tracking control unit 19e generates a template image (reference image) of the subject image captured by the second image sensor 16 and corresponding to the tracking target position manually specified by the photographer or the tracking target position automatically set by the camera 1. Image) is stored in the memory 19d. Further, the target position is recognized by searching for an image region that matches or is similar to the template image from images repeatedly photographed thereafter. The exposure calculation unit 19f calculates an exposure value based on the image signal captured by the second image sensor 16.

  The focus detection calculation unit 19g detects the focus adjustment state of the photographing lens 8, here the defocus amount, based on the focus detection signal corresponding to the pair of optical images output from the distance measuring element 10. Although details will be described later, a plurality of focus detection positions (focus detection areas) are set in the shooting screen of the shooting lens 8, and the distance measuring element 10 responds to a pair of optical images for each focus detection area. The focus detection signal is output. The focus detection calculation unit 19g detects a defocus amount for each focus detection area based on a focus detection signal corresponding to a pair of light images output from the distance measuring element 10 for each focus detection area. The lens driving amount calculation unit 19h converts the detected defocus amount into a lens driving amount.

  The mode setting unit 19i can select one of two types of AF modes for the imaging apparatus 1 (focus adjustment apparatus). One of the two types of AF modes selected by the mode setting unit 19i is called a single AF mode. When the single AF mode is selected, the focus of the photographic lens 8 is adjusted based on the defocus amount detected by the imaging device 1, and the focus is locked when the in-focus state is reached, and the focus adjustment of the photographic lens 8 is prohibited. The If a change in composition is detected during the focus lock, the focus lock is released and focus adjustment is resumed. The composition change detection method will be described in detail later. The other of the two types of AF modes selected by the mode setting unit 19i is called a continuous AF mode. When the continuous AF mode is selected, the focus adjustment of the photographing lens 8 based on the defocus amount detected by the imaging device 1 is repeatedly performed. In the continuous AF mode, the focus lock is not performed even when the focus is achieved.

  FIG. 3 is a front view showing a detailed configuration of the second image sensor 16. The second imaging element 16 includes a plurality of pixels (photoelectric conversion elements) 26 (here, horizontal 16 × vertical 12 = 192) arranged in a matrix. As shown in FIG. 4, each pixel 26 is divided into three portions 26a, 26b, and 26c, and primary color filters of red R, green G, and blue B are provided in these portions 26a, 26b, and 26c, respectively. . Thereby, the RGB signal of the subject image can be output for each pixel 26.

  Next, the focus adjustment operation in the imaging device 1 (focus adjustment device) will be described. 5 to 7 are diagrams for explaining the focus adjustment operation. 8 to 12 are flowcharts showing processing executed by the body drive control device 19 during the focus adjustment operation. The focus adjustment operation will be described below with reference to these drawings.

  Note that the quick return mirror 5 is set in the photographing optical path shown by the broken line in FIG. 1 except when the photographer fully presses the release button to photograph, and the subject light incident from the photographing lens 8 is the focusing plate. 11 is imaged. The subject image on the focusing screen 11 is guided to the second image sensor 16 via the penta roof prism 13, the prism 17 and the imaging lens 18, and the subject image signal is repeatedly output from the second image sensor 16.

  A plurality of focus detection areas are set in the photographing screen by the photographing lens 8. The liquid crystal display element 12 superimposes and displays an area mark indicating each focus detection area on the subject image on the focusing screen 11, and presents the position of each focus detection area to the photographer. Here, as shown in FIG. 5, an example is shown in which focus detection areas 45a to 45k are set at 11 locations in the shooting screen. When an arbitrary area is selected by the focus detection area selection switch of the operation member 20, the mark of the area is lit up.

  The process shown in the flowchart of FIG. 8 is executed when the photographer selects one of the focus detection areas with the focus detection area selection switch of the operation member 20 and half-presses the release button of the operation member 20 in this state. . In step S1, the body drive control device 19 determines whether the AF mode set by the mode setting unit 19i is the single AF mode or the continuous AF mode. If the single AF mode is set, the process proceeds to step S2, and if the continuous AF mode is set, the process proceeds to step S11.

  In step S2, the body drive control device 19 determines the focus detection area that was selected when the photographer pressed the release button halfway as the initial area. Information on this initial area is stored in the memory 19d. As a result, the subject corresponding to the initial area is designated as the subject to be tracked in the tracking initial process performed in step S5. In this example, the photographer selects the first area and manually specifies the subject to be tracked. However, for example, in a camera having a function of automatically recognizing a subject, the first area is determined based on the subject recognition result. In addition, a tracking target subject may be set.

  In step S3, the body drive control device 19 executes a focus lock process shown in FIG. In step S31 of FIG. 9, the body drive control device 19 performs focus detection on the initial area determined in step S2. Here, the defocus amount for the initial area is detected by the focus detection calculation unit 19g based on the focus detection signal output from the distance measuring element 10.

  In step S32, the body drive control device 19 determines whether or not the photographing lens 8 is in focus based on the defocus amount detected in step S31. If the defocus amount is within the predetermined range, it is determined that the in-focus state is achieved, and the process proceeds to step S33. Otherwise, it is determined that the in-focus state is not achieved, and the process proceeds to step S34.

  In step S33, the body drive control device 19 performs focusing lock. Here, the focus adjustment of the photographing lens 8 is prohibited by restricting the driving of the focusing lens 8b by the lens drive control device 22. After executing Step S33, the body drive control device 19 ends the focus lock process of FIG. 9, and proceeds to Step S4 of FIG.

  In step S34, the body drive control device 19 drives the taking lens 8 to the in-focus position. Here, the lens drive amount calculation unit 19h converts the defocus amount detected in step S31 into a lens drive amount and outputs it to the lens drive control device 22. Accordingly, the focusing lens 8b is driven by the lens driving amount by the lens driving control device 22, and the focus of the photographing lens 8 is adjusted. After executing Step S34, the body drive control device 19 returns to Step S31.

  By performing the focus lock process described above, the focus adjustment of the photographing lens 8 is repeatedly performed until the focus state is achieved. In addition, after the in-focus state is achieved, the focus lock is performed, and the focus adjustment of the photographing lens 8 is prohibited.

In step S4 of FIG. 8, the body drive control device 19 acquires a tracking initial image (an image acquired first after starting the image tracking process) based on the image signal output from the second image sensor 16. This initial tracking image is represented by RGB values for each pixel as shown in the following equation (1). In Equation (1), x and y are coordinate values representing pixel positions.
R [x, y], G [x, y], B [x, y] (1)

Based on the RGB value for each pixel represented by the above equation (1), the color information RG and BG and the luminance information L of each pixel are calculated as in the following equation (2). In Expression (2), T and Gain are exposure time and gain when an image is acquired, and Kr, Kg, and Kb are predetermined color composition coefficients.
RG [x, y] = Log ₂ (R [x, y]) − Log ₂ (G [x, y]),
BG [x, y] = Log ₂ (B [x, y]) − Log ₂ (G [x, y]),
L [x, y] = Log ₂ (Kr × R [x, y] + Kg × G [x, y] + Kb × B [x, y]) − Log ₂ (T) −Log ₂ (Gain) (2)

  In step S5, the body drive control device 19 executes a tracking initial process shown in FIG. In step S51 in FIG. 10, the body drive control device 19 determines an initial subject area corresponding to an area where the subject to be tracked first exists. Here, in the initial tracking image acquired in step S4, a predetermined range area around the initial area determined in step S2, for example, a 3 × 3 pixel area, is determined as the initial subject area. Thereby, for example, when the focus detection area 45f is set as the initial area, a subject region 47 as shown in FIG. 6 is set in the tracking initial image.

In step S52, the body drive control device 19 sets the image in the initial subject area determined in step S51 among the tracking initial images as a template image (reference image) used for the image tracking process. For example, a template image 48 is set for the initial subject area 47 shown in FIG. If the starting point position at this time is (x, y) = (8, 6), the color information of the template image 48 is expressed as follows.
RGref [rx, ry] = RG [x, y],
BGref [rx, ry] = BG [x, y],
Lref [rx, ry] = L [x, y] (rx, ry = 1 to 3, x = 8 to 10, y = 6 to 8) (3)

  By executing step S52, an image of the subject to be subjected to focus adjustment of the photographing lens 8 is set as a template image, that is, a reference image. The set template image is stored in the memory 19d.

  In step S53, the body drive control device 19 determines a search area at the time of subject tracking around the initial subject area determined in step S51. For example, an area that is enlarged by 3 pixels each in front, rear, left, and right with the initial subject area as the center is determined as the search area. Thereby, for example, a search area 49 is set for the subject area 47 shown in FIG. After step S53 is executed, the body drive control device 19 ends the tracking initial process in FIG. 10, and proceeds to step S6 in FIG.

  In step S <b> 6, the body drive control device 19 determines whether the photographer has fully pressed the release button of the operation member 20. When the release button is fully pressed, the body drive control device 19 proceeds to step S22 and performs photographing control. At this time, a subject image by the photographing lens 8 is picked up by the first image pickup device 4, and a picked-up image is acquired. The acquired captured image is recorded on a recording medium (not shown). After step S22 is executed, the body drive control device 19 ends the process of FIG.

  On the other hand, if it is determined in step S6 that the release button has not been fully pressed, the body drive control device 19 proceeds to step S7. In step S <b> 7, the body drive control device 19 acquires a tracking next image based on the image signal output from the second image sensor 16. At this time, the color information RG [x, y], BG [x, y] and luminance information L [x, y] of each pixel in the following tracking image is calculated and stored in the memory 19d as in the process of step S4. The

  In step S8, the body drive control device 19 executes a tracking calculation process shown in FIG. In step S81 of FIG. 11, the body drive control device 19 sequentially selects images having the same size as the template image from the images in the search area determined in the latest step S53 or S83 among the following tracking images acquired in step S7. cut. Then, a color information difference Diff is calculated for each pixel corresponding to the cut-out image and the template image.

Assuming that the starting point position of the search area 49 is (scx, scy) = (5, 3) as shown in FIG. 7, the difference Diff is calculated as follows.
Diff [dx, dy] = ΣΣ {ABS (RG [scx + dx−1 + rx, scy + dy−1 + r
y] -RGref [rx, ry]) + ABS (BG [scx + dx-1 + rx, scy + dy-1 + ry] -BGref [rx, ry]) + ABS (L [scx + dx-1 + rx, scy + dy-1 + ry] -Lref [rx, ry]) } (4)

  In the equation (4), dx, dy = 1 to 7, rx, ry = 1 to 3, scx = 5, scy = 3, and ΣΣ is a sum operation of rx = 1 to 3 and ry = 1 to 3.

  Next, among all the differences Diff calculated by the equation (4), the difference having the smallest value is set as the minimum difference MinDiff. In the example shown in FIG. 7, the position (minx, miny) at which the minimum difference MinDiff is (11, 3). The smaller the value of the minimum difference MinDiff, the higher the similarity with the template image.

  In step S82, the body drive control device 19 determines a new subject area in the following tracking image based on the difference Diff calculated in step S81. Here, the cut-out area indicating the minimum difference MinDiff among the differences Diff is determined as the new subject area. As a result, for example, a subject area 47 as shown in FIG. 7 is set in the following tracking image. By determining the new subject area in this way, the position of the image corresponding to the reference image in the screen by the photographing lens 8 is recognized.

  In step S83, the body drive control device 19 determines a search area for the next subject tracking around the new subject area determined in step S82. For example, as in step S53, an area that is enlarged by three pixels in the front, rear, left, and right sides around the new subject area is determined as the search area. After executing Step S83, the body drive control device 19 ends the tracking calculation process of FIG. 11, and proceeds to Step S9 of FIG.

  In step S9, the body drive control device 19 determines whether or not the composition has been changed based on the result of the tracking calculation process in step S8. Here, it is determined whether or not the composition has been changed based on whether or not the position of the subject area determined by the most recent tracking calculation process has changed from the previous position. That is, it is determined that the composition has been changed when the position of the image corresponding to the reference image recognized by the repeated tracking calculation process is changed, and it is determined that the composition has not been changed when it has not changed. If it is determined that the composition has been changed, the body drive control device 19 proceeds to step S10. On the other hand, if it is determined that the composition has not been changed, the body drive control device 19 returns to step S6, and repeats the processing after step S6 as described above.

  In the composition change determination performed in step S9, it is determined that the image position has changed only when the image position after the change is continuously maintained or when the image position is maintained for a predetermined time or longer, and the composition change is performed. You may make it make determination. That is, when the position of the image corresponding to the reference image recognized by the repeated tracking calculation process is moved and the position after the movement is continuously maintained, for example, the position after the movement is maintained three times or more. In this case, it is determined that the image position has changed. Alternatively, it is determined that the image position has changed when the position after movement is maintained for a predetermined time or longer, for example, 1 second or longer. In this way, it is possible to avoid erroneously determining that the composition has been changed, such as when camera shake occurs or when a moving subject is shot.

  In step S10, the body drive control device 19 performs the refocusing process shown in FIG. In step S101 of FIG. 12, the body drive control device 19 performs focus detection on the focus detection area corresponding to the new subject area determined in step S82, that is, the focus detection area corresponding to the changed image position. . Here, the focus detection calculation unit 19g detects the defocus amount for the focus detection area existing in the new subject area based on the focus detection signal output from the distance measuring element 10. Thereby, for example, in FIG. 7, the defocus amount is detected with respect to the focus detection area 45c.

  Alternatively, in step S101, the body drive control device 19 can detect the defocus amounts for a plurality of focus detection areas corresponding to the changed image positions. For example, when there are a plurality of focus detection areas in the new subject area, the defocus amount is detected for each focus detection area. Alternatively, the defocus amount is detected for each of the focus detection area existing in the new subject area and the focus detection area existing around the focus detection area.

  In step S102, the body drive control device 19 determines whether or not to refocus the taking lens 8 based on the defocus amount detected in step S101. Here, the defocus amount detected in step S101 (or step S31) executed last time, that is, the defocus amount detected for the focus detection area corresponding to the image position before change (hereinafter referred to as defocus before change). The defocus amount detected in step S101 executed this time, that is, the defocus amount detected for the focus detection area corresponding to the image position after the change (hereinafter referred to as the post-change defocus amount). ) To determine whether to refocus. When it is determined to refocus, that is, when it is determined to resume the focus adjustment of the photographing lens 8, the body drive control device 19 proceeds to step S103. On the other hand, when it is determined that refocusing is not performed, that is, when it is determined that focus adjustment of the photographing lens 8 is not resumed, the body drive control device 19 ends the refocusing process of FIG. 12, and proceeds to step S6 of FIG. Return. In this case, since refocusing is not performed, the focus lock of the photographing lens 8 is not released, and the focus adjustment of the photographing lens 8 is not resumed.

  In step S102, for example, when the difference between the pre-change defocus amount and the post-change defocus amount is less than a predetermined threshold value (for example, about 900 μm), it is determined that refocusing is performed. That is, when the difference between the focus adjustment state for the image position before the change and the focus adjustment state for the image position after the change is small, the photographing lens 8 is refocused. On the other hand, when the difference between the pre-change defocus amount and the post-change defocus amount is greater than or equal to the threshold value, that is, the difference between the focus adjustment state with respect to the image position before change and the focus adjustment state with respect to the image position after change is large. In this case, the refocusing of the taking lens 8 is not performed. Thereby, when the subject image is recognized at the wrong position, it is possible to avoid the refocusing of the photographing lens 8 according to the focus adjustment state at the wrong position.

  When defocus amounts are detected for a plurality of focus detection areas as described above in step S101, the body drive control device 19 in step S102 determines that the plurality of post-change defocus amounts and pre-change defocus amounts. Based on the above, it may be determined whether to refocus. For example, if the difference between the pre-change defocus amount and any at least one post-change defocus amount is less than the threshold value, it is determined that refocusing is performed, and the pre-change defocus amount and all post-change defocus amounts. If the difference is greater than or equal to the threshold value, it is determined that refocusing is not performed. In this way, it is possible to further improve the refocusing determination accuracy in step S102.

  In step S103, the body drive control device 19 releases the focus lock performed in step S33. Thereby, the prohibition of the focus adjustment of the photographing lens 8 is released.

  In step S104, the body drive control device 19 determines a refocusing area. Here, the focus detection area where the defocus amount is detected in step S101 is determined as the refocusing area. Thereby, for example, in FIG. 7, the focus detection area 45c is set as the refocusing area.

  If the defocus amount is detected for each of the plurality of focus detection areas in step S101 as described above, the body drive control device 19 selects and restarts the plurality of focus detection areas in step S104. The focus area. For example, the focus detection area where the defocus amount after change having the smallest difference from the defocus amount before change is detected is selected, and this is set as the refocusing area.

  In step S105, the body drive control device 19 drives the photographing lens 8 to the in-focus position based on the defocus amount detected for the refocusing area determined in step S104. Here, as in step S34, the lens drive amount calculation unit 19h converts the defocus amount detected in step S101 into a lens drive amount and outputs it to the lens drive control device 22. As a result, the focusing lens 8b is driven by the lens drive amount by the lens drive control device 22, and the focus adjustment of the photographing lens 8 is resumed.

  In step S106, the body drive control device 19 executes the focus lock process of FIG. That is, the focus adjustment is repeated until the photographing lens 8 is in focus, and when it is in focus, the focus is locked and the focus adjustment of the photographing lens 8 is prohibited. After executing the focus lock process, the body drive control device 19 returns to step S6, and repeats the processes after step S6 as described above. When the single AF mode is set, the body drive control device 19 executes the processing as described above.

  On the other hand, when it is determined in step S1 that the continuous AF mode is set, in step S11, the body drive control device 19 performs an initial area determination process similar to step S2. In the next step S12, the body drive control device 19 performs a focus detection process similar to that in step S31. That is, the defocus amount for the initial area determined in step S11 is detected. In step S13, the body drive control device 19 drives the taking lens 8 based on the defocus amount detected in step S12. Thereby, the focus of the photographic lens 8 is adjusted.

  In step S14, the body drive control device 19 acquires a tracking initial image in the same manner as in step S4. In step S15, the body drive control device 19 executes a tracking initial process shown in FIG. Thereby, an initial subject area is determined, a template image is set, and a search area is determined.

  In step S <b> 16, the body drive control device 19 determines whether or not the photographer has fully pressed the release button of the operation member 20. When the release button is fully pressed, the body drive control device 19 proceeds to step S22 and performs shooting control to acquire a captured image. After step S22 is executed, the body drive control device 19 ends the process of FIG.

  On the other hand, if it is determined in step S16 that the release button has not been fully pressed, the body drive control device 19 proceeds to step S17. In step S <b> 17, the body drive control device 19 acquires a tracking next image in the same manner as in step S <b> 7. In the next step S18, the body drive control device 19 executes the tracking calculation process shown in FIG. As a result, a new subject area and search area are determined for the following tracking image.

  In step S19, the body drive control device 19 performs focus detection on the focus detection area corresponding to the new subject area determined in step S82, that is, the focus detection area corresponding to the changed image position, and the defocus amount. Is detected. At this time, similarly to step S101, the defocus amount may be detected for each of a plurality of focus detection areas. In the next step S20, the body drive control device 19 determines an in-focus area. Here, when the defocus amounts are detected for each of the plurality of focus detection areas in step S19, one of the focus detection areas is determined as the focus area based on the plurality of defocus amounts. For example, the focus detection area in which the defocus amount with the smallest difference from the previously detected defocus amount detected last time is detected is determined as the focus area. If focus detection has been performed for only one focus detection area in step S19, that focus detection area is set as the focus area.

  In step S21, the body drive control device 19 drives the photographing lens 8 to the in-focus position based on the defocus amount detected for the in-focus area determined in step S20. Accordingly, the focusing lens 8b is driven by the lens driving amount by the lens driving control device 22, and the focus of the photographing lens 8 is adjusted.

  After executing Step S21, the body drive control device 19 returns to Step S16, and repeatedly executes the processes after Step S16. Thereby, when the continuous AF mode is set, the focus adjustment of the photographing lens 8 is repeatedly performed based on the defocus amount of the focus detection area corresponding to the image position after the change.

  If the continuous AF mode is set, a process for updating the template image using the image information of the new subject area may be added after performing the tracking calculation process in step S18. In this case, for example, the template image is updated by adding 20% of the image information of the new subject area to 80% of the image information of the original template image. In this way, the latest image information is updated little by little with respect to the image information of the template image, and it becomes easier to follow changes in the tracking subject.

For example, the update calculation is performed on the subject region 47 shown in FIG. 7 as follows.
RGref [rx, ry] = 0.8 × RGref [rx, ry] + 0.2 × RG [x, y],
BGref [rx, ry] = 0.8 × BGref [rx, ry] + 0.2 × BG [x, y],
Lref [rx, ry] = 0.8 × Lref [rx, ry] + 0.2 × L [x, y],
(Rx, ry = 1 to 3, x = 11 to 13, y = 3 to 5) (5)

  Note that the ratio between the image information in the template image so far and the image information in the subject area 47 when the template image 48 is updated may be a fixed value as described above, or may be variable according to the minimum difference MinDiff. Good.

  On the other hand, when the single AF mode is set, it is preferable not to limit the template image update as described above. This is because when the single AF mode is set, it is considered that the movement of the subject image is relatively small, so that it is not necessary to update the template image. Alternatively, the photographer may be able to select whether to update the template image regardless of the AF mode setting.

According to the embodiment described above, the following operational effects are obtained.
(1) The body drive control device 19 provided in the imaging device 1 adjusts the focus of the photographic lens 8 based on the focus adjustment state of the photographic lens 8 (step S34), and focuses when it is in focus. Locking is performed to prohibit the focus adjustment of the taking lens 8 (step S33). Further, an image of a subject to be focused on the photographing lens 8 is set as a reference image (step S52), and a tracking calculation process is performed thereafter, whereby an image corresponding to the reference image in the screen by the photographing lens 8 is obtained. The position is recognized repeatedly (step S82). Further, when the focus adjustment of the photographing lens 8 is prohibited by the focus lock, when the position of the image recognized by the tracking calculation process is changed, it is determined that the composition has been changed, and the refocus process is performed. (Steps S9 and S10). Thereby, the prohibition of the focus adjustment of the photographing lens 8 is canceled (step S103), and the focus adjustment of the photographing lens 8 is resumed (step S105). Since it did in this way, when a composition is changed during focus lock, focus lock can be released and focus adjustment can be resumed.

(2) In step S9, the body drive control device 19 moves the position of the image recognized by the tracking calculation process when the focus adjustment of the photographing lens 8 is prohibited by the focus lock, and repeats after the movement. When the position of the recognized image is continuously maintained, it can be determined that the position of the image has changed, and a composition change determination can be made. In this way, it is possible to avoid erroneously determining that the composition has been changed, such as when camera shake occurs or when a moving subject is shot.

(3) Alternatively, in step S9, the body drive control device 19 moves the position of the image recognized by the tracking calculation process when the focus adjustment of the photographing lens 8 is prohibited by the focus lock, and further after the movement. When the position of the image that is repeatedly recognized is maintained for a predetermined time or longer, it can be determined that the position of the image has changed, and a composition change determination can be made. Even in this way, similarly to the above, it is possible to avoid erroneously determining that the composition has been changed when camera shake occurs or when a moving subject is shot.

(4) The body drive control device 19 detects a defocus amount indicating the focus adjustment state of the photographing lens 8 for a plurality of focus detection areas set in the screen by the photographing lens 8 (steps S31 and S101). . Further, the body drive control device 19 has a pre-change defocus amount detected with respect to the focus detection area corresponding to the image position before the change when the position of the image recognized by the tracking calculation process changes, Based on the post-change defocus amount detected with respect to the focus detection area corresponding to the changed image position, it is determined whether or not the focus adjustment of the photographing lens 8 is resumed (step S102). As a result, when the subject image is recognized at the wrong position by subject tracking, it is possible to avoid refocusing of the photographing lens 8 according to the focus adjustment state at the wrong position. .

(5) In step S102, the body drive control device 19 determines to resume the focus adjustment of the photographing lens 8 when the difference between the pre-change defocus amount and the post-change defocus amount is less than a predetermined threshold value. can do. In this way, it is possible to easily and reliably determine whether or not to resume the focus adjustment of the photographing lens 8 based on the pre-change defocus amount and the post-change defocus amount.

(6) A plurality of post-change defocus amounts may be detected for a plurality of focus detection areas corresponding to the position of the image after the change. In this way, the accuracy of determination in step S102 can be further improved.

(7) When a plurality of post-change defocus amounts are detected for a plurality of focus detection areas as described above, the body drive control device 19 determines in step S105 the pre-change defocus amount among the plurality of post-change defocus amounts. It is preferable to resume the focus adjustment of the taking lens 8 based on the smallest difference from the focus amount. In this way, the photographing lens 8 can be brought into a more appropriate focus adjustment state when the composition is changed.

(8) The body drive control device 19 uses the mode setting unit 19i to repeat the focus adjustment of the photographing lens 8 based on the detected defocus amount, and the photographing lens based on the detected defocus amount. It is possible to set a single AF mode in which after the focus adjustment of 8 is performed, the focus is locked and the focus adjustment of the taking lens 8 is prohibited. Further, when the single AF mode is set and the focus adjustment of the photographic lens 8 is prohibited, the body drive control device 19 performs composition change determination and refocusing processing, and performs a reference in the screen by the photographic lens 8. The prohibition of the focus adjustment of the photographing lens 8 is canceled according to the change in the position of the image corresponding to the image. Since this is done, focus adjustment control can be performed so as to eliminate the focus shift caused by the cosine error caused by the composition change even in the single AF mode in which focus adjustment is normally prohibited after focusing.

(9) When the continuous AF mode is set, the body drive control device 19 performs the tracking calculation process in step S18, and then uses the image information of the new subject area determined in step S82 as a reference image. May be updated. On the other hand, when the single AF mode is set, it is preferable to limit such update of the reference image. In this way, in the continuous AF mode, it becomes easy to follow the change of the subject in the tracking calculation process, while unnecessary update of the reference image can be avoided in the single AF mode.

  In the above embodiment, the focus adjustment state of the photographing lens 8 is detected by the focus detection optical system 9 and the distance measuring element 10 independent of the first image sensor 4. You may detect a focus based on the output of what mixedly provided the pixel for focus detection in the pixel arrangement | sequence. That is, the first image sensor 4 receives an image pixel that receives light via the photographing lens 8 and outputs an image signal, and a focus detection pixel that receives light via the photographing lens 8 and outputs a focus detection signal. A plurality of pixels. Then, the body drive control device 19 detects the defocus amount based on the focus detection signal output from the focus detection pixel. You may do this. In this case, the focus detection pixel of the first image sensor 4 includes, for example, a microlens and one or a plurality of photoelectric conversion units, and is configured to receive a pair of light beams that have passed through different areas of the pupil of the photographing lens 8. Has been. The pupil division type focus detection is performed based on the light receiving signals of the pair of light beams.

4 First imaging device 8 Shooting lens 10 Distance measuring device 16 Second imaging device 19 Body drive control device 22 Lens drive control device

The focus adjustment apparatus according to the present invention includes a recognition unit that recognizes whether or not the position of the tracking target has changed using reference information including information on the tracking target and image information repeatedly acquired by the imaging unit; A focus detection unit for detecting a focus state of an optical system including a focus optical system, a selection unit capable of selecting at least one of a first mode and a second mode, and the focus when the first mode is selected. The focus drive is limited after focus drive is performed to drive the focus optical system to a focus position using the output of the detection unit, and the recognition unit recognizes that the position of the tracking target has changed. And a control unit that performs control for canceling the restriction of the focusing drive, and performs control that does not limit the focusing drive after the focus driving is performed when the second mode is selected. .
An imaging apparatus according to the present invention includes the focus adjustment apparatus according to any one of claims 1 to 8.

Claims (10)

Focus adjusting means for adjusting the focus of the optical system based on the focus adjustment state of the optical system;
Prohibiting means for prohibiting focus adjustment of the optical system by the focus adjusting means;
A reference image setting means for setting, as a reference image, an image of a subject as a focus adjustment target of the optical system;
Recognizing means for repeatedly recognizing the position of the image corresponding to the reference image in the screen by the optical system;
When the position of the image recognized by the recognition unit changes when the focus adjustment of the optical system is prohibited by the prohibition unit, the prohibition of the focus adjustment of the optical system by the prohibition unit is canceled. And a control means for causing the focus adjustment means to resume focus adjustment of the optical system based on the focus adjustment state corresponding to the changed position of the image. The focus adjustment apparatus according to claim 1,
A focus detection unit that detects a focus adjustment state of the optical system with respect to a plurality of focus detection positions set in a screen by the optical system;
When the position of the image recognized by the recognition means changes, the control means detects the optical system detected by the focus detection means with respect to the focus detection position corresponding to the position of the image before the change. And the second focus adjustment state of the optical system detected by the focus detection unit with respect to the focus detection position corresponding to the position of the image after the change. A focus adjustment device for determining whether or not to resume focus adjustment of an optical system. The focusing apparatus according to claim 1 or 2,
The control means moves the position of the image recognized by the recognition means when the focus adjustment of the optical system is prohibited by the prohibiting means, and further recognizes the position of the image repeatedly recognized after the movement. The focus adjustment apparatus determines that the position of the image has changed when the image is continuously maintained. The focusing apparatus according to claim 1 or 2,
The control means moves the position of the image recognized by the recognition means when the focus adjustment of the optical system is prohibited by the prohibiting means, and further recognizes the position of the image repeatedly recognized after the movement. The focus adjustment apparatus determines that the position of the image has changed when is maintained for a predetermined time or longer. The focusing apparatus according to claim 2, wherein
The control means determines that the focus adjustment of the optical system is resumed when a difference between the first focus adjustment state and the second focus adjustment state is less than a predetermined threshold value. Focusing device. The focusing apparatus according to claim 5, wherein
The second focus adjustment state includes a plurality of detections with respect to a plurality of focus detection positions corresponding to the positions of the image after the change. The focusing apparatus according to claim 6, wherein
The control means causes the focus adjustment means to resume the focus adjustment of the optical system based on a difference between the plurality of second focus adjustment states and the first focus adjustment state being the smallest. Focus adjustment device characterized. In the focus adjustment apparatus according to any one of claims 1 to 7,
A first focus adjustment mode in which focus adjustment of the optical system is repeatedly performed based on the focus adjustment state; and focus adjustment of the optical system by the prohibiting unit after performing focus adjustment of the optical system based on the focus adjustment state. Further comprising mode setting means capable of setting any of the second focus adjustment mode for prohibiting
When the second focus adjustment mode is set by the mode setting means and the focus adjustment of the optical system by the prohibiting means is prohibited, the control means adjusts the focus according to the change in the position of the image. A focus adjustment device which cancels the prohibition. The focus adjustment device according to claim 8.
The reference image is updated when the first focus adjustment mode is set by the mode setting means, and the reference image is updated when the second focus adjustment mode is set by the mode setting means. And a reference image update means for restricting the focus. A focus adjustment device according to any one of claims 1 to 9,
An imaging apparatus comprising: an imaging unit that captures an image by the optical system.

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