JP2011090196A - Focus detecting device, and imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress a situation in which a high-contrast subject existing outside a focus detection area is brought into focus without increasing the focus detection area. <P>SOLUTION: The focus detecting device includes: a detection part configured to detect a focus evaluated value obtained by integrating output equal to or more than prescribed frequency of an imaging signal obtained by picking up an image in the prescribed area on an image surface of an optical system and a position where a maximum value of the output equal to or more than the prescribed frequency in the prescribed area is obtained according to a focus adjustment state of the optical system; and a determination part configured to determine the focus adjustment state in which the focus evaluated value is a peak as false focusing when the position where the maximum value of the output corresponding to the focus adjustment state in which the focus evaluated value is the peak is obtained is on a circumferential part in the prescribed area. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a focus detection technique.

  A subject image is imaged while moving the focus adjustment lens in the optical axis direction, a focus evaluation value is calculated based on an imaging signal in a predetermined area (focus detection area), and a focus adjustment state in which the focus evaluation value reaches a peak is obtained. There is a focus detection technique for detecting the in-focus state. In such a focus detection technique, the range of the subject included in the focus detection area is changed by a change in image magnification accompanying the movement of the focus adjustment lens. In this case, if a high-contrast subject enters the focus detection area, the focus evaluation value is affected, and accurate focus adjustment cannot be performed.

  As a technique for solving such a problem, a technique for obtaining a focus evaluation value history in each of a focus area (focus detection area) and a true / false determination area has been proposed (see Patent Document 1). In this technique, the authenticity determination area completely includes the focus area and is wider than the focus area. The camera determines whether the maximum position of the focus evaluation value history by the focus area matches the maximum position of the focus evaluation value history by the authenticity determination area, and calculates the focus lens position if they match. In this case, the focus lens position is not calculated.

JP-A-2005-208274

However, the technique disclosed in Patent Document 1 has a problem in that it is necessary to increase the focus detection area, resulting in an increase in cost.
In view of the above circumstances, the present invention provides a focus detection device and an imaging device that can suppress focusing on a high-contrast subject outside the focus detection region without increasing the focus detection region. It is an object.

  One aspect of the present invention is a focus detection apparatus, in which a focus evaluation value obtained by integrating outputs of an imaging signal that is obtained by capturing an image in a predetermined area on an image plane of an optical system, and the predetermined area Detecting the position where the maximum value of the output above the predetermined frequency is obtained in association with the focus adjustment state of the optical system, and corresponding to the focus adjustment state where the focus evaluation value reaches a peak And a determination unit that determines that the focus adjustment state in which the focus evaluation value reaches a peak is false in-focus when the position where the maximum output value is obtained is the peripheral portion in the predetermined region.

  One aspect of the present invention is the above-described focus detection device, wherein the determination unit is a case where a position where the maximum value of the output is obtained is not a peripheral portion in the predetermined region and the focus is the peak. When the adjustment state is at the closest end of the focus adjustment range of the optical system, the focus adjustment state at the peak is determined to be false in-focus.

  One aspect of the present invention is the focus detection apparatus described above, wherein the focus adjustment direction of the optical system is determined based on a change in the focus evaluation value corresponding to the change in the focus adjustment state, and the output of the output is determined. A direction determining unit that prohibits determination of a focus adjustment direction based on a change in the focus evaluation value corresponding to a change in the focus adjustment state when the position where the maximum value is obtained is a peripheral portion in the predetermined region; It is characterized by providing.

  One aspect of the present invention is the focus detection apparatus described above, wherein the detection unit is configured to output the focus evaluation value and the output for each of the plurality of predetermined regions set at a plurality of positions in an image plane of the optical system. And a position where the maximum value is obtained.

  One aspect of the present invention is the focus detection apparatus described above, and when there are a plurality of the focus adjustment states that are not determined to be falsely focused by the determination unit, the closest focus side of the focus adjustment range of the optical system corresponds to And a selection unit that selects a focus adjustment state to be performed.

  One aspect of the present invention is the above-described focus detection device, wherein the determination unit changes at least one of a position and a size of the predetermined region on the image plane of the optical system when the determination unit determines that the focus is false. Then, the determination is performed again.

  One embodiment of the present invention is an imaging apparatus including the above-described focus detection apparatus and an imaging unit that captures an image by the optical system.

  According to the present invention, it is possible to suppress focusing on a high-contrast subject outside the focus detection area without increasing the focus detection area.

It is a schematic block diagram showing the function structure of an imaging device. It is a schematic block diagram showing the structure of 1st embodiment of a contrast AF apparatus. It is a figure showing the outline of the detection method of the focus evaluation value by a detection part. It is a figure showing the outline of a focus evaluation value table. It is a flowchart showing operation | movement of an imaging device provided with 1st embodiment of a contrast AF apparatus. It is a figure which shows the example in case a focus state is detected correctly. It is a figure which shows the example in case false detection is detected. It is a figure which shows the transition of a focus evaluation value in case a focusing state and a false focusing are each detected. It is a figure showing the movement of the focus adjustment lens in the case of FIG. It is a schematic block diagram showing the structure of 2nd embodiment of a contrast AF apparatus. It is a figure showing the outline of the focus detection area | region in 2nd embodiment of a contrast AF apparatus. It is a figure which shows the transition of the focus evaluation value detected in each focus detection area | region of FIG. It is a flowchart showing operation | movement of an imaging device provided with 2nd embodiment of a contrast AF apparatus. It is a schematic block diagram showing the structure of 3rd embodiment of a contrast AF apparatus. It is a flowchart showing the operation | movement of the direction determination process in 3rd embodiment of a contrast AF apparatus. It is a flowchart showing operation | movement of an imaging device provided with 4th embodiment of a contrast AF apparatus.

  FIG. 1 is a schematic block diagram illustrating a functional configuration of the imaging apparatus 1. FIG. 1 illustrates a functional configuration when the imaging device 1 is configured as a single-lens reflex digital still camera. However, the imaging device 1 may be configured as various imaging devices such as a compact digital camera or a video camera. It does not matter whether the lens is interchangeable.

  The imaging apparatus 1 includes a photographing optical system 101, a quick return mirror 102, a finder screen 103, a pentaprism 104, an eyepiece lens 105, a photometric lens 106, a photometric sensor 107, an image sensor 109, an operation unit 110, a phase difference AF device 111, A contrast AF device 112, a lens driving motor 113, a lens driving control unit 114, and an image recording unit 115 are provided.

  The photographing optical system 101 (optical systems 101 a to 101 c) forms a subject image to be imaged on the imaging surface of the image sensor 109. The optical system 101a and the optical system 101c are fixedly installed in the lens barrel. The optical system 101 b is a focus adjustment lens that can move in the optical axis direction by the power of the lens driving motor 113. Such a configuration of the photographing optical system 101 is merely an example, and the photographing optical system 101 may be configured in any other manner as long as it can be adjusted in focus.

  The quick return mirror 102 blocks incident light to the image sensor 109 and reflects light to the pentaprism 104 before exposure as shown in the figure. On the other hand, the quick return mirror 102 moves to the lower side of the finder screen 103 by moving upward during exposure, and introduces the light that has passed through the photographing optical system 101 into the image sensor 109.

The viewfinder screen 103 forms a subject image by light from the subject reflected by the quick return mirror 102.
The pentaprism 104 reflects the luminous flux of the subject image formed on the finder screen 103 to the eyepiece lens 105 and the photometric lens 106.

  The eyepiece 105 transmits the light of the subject image on the finder screen 103 reflected by the pentaprism 104. The imager can visually recognize the subject image formed on the finder screen 103 via the pentaprism 104 by looking into the eyepiece lens 105.

The photometric lens 106 focuses the light of the subject image on the finder screen 103 reflected by the pentaprism 104 on the photometric sensor 107.
The photometric sensor 107 is composed of a plurality of light receiving elements such as a CMOS sensor (Complementary Metal Oxide Semiconductor) and a CCD (Charge Coupled Device). The photometric sensor 107 receives the light transmitted through the photometric lens 106 and converts it into an electrical signal. Then, an imaging signal of the same subject image as the subject imaged by the imaging element 109 is generated. The photometric sensor 107 outputs the captured image signal to the contrast AF device 112.

The sub mirror 108 reflects the light transmitted through the half mirror part of the photographing optical system 101 and the quick return mirror 102 to the phase difference AF device 111.
The image sensor 109 is configured by arranging light receiving elements such as a CMOS sensor and a CCD, receives light from a subject transmitted through the photographing optical system 101, converts it into an electric signal, and images it. The image sensor 109 may include an infrared cut filter for cutting infrared light on the front surface of the image pickup surface, an optical low-pass filter for preventing image aliasing noise, and the like.

  The operation unit 110 selects a switch for selecting an autofocus area (focus detection area) corresponding to a subject to be focused, and sets the autofocus mode to either a phase difference autofocus mode or a contrast autofocus mode. AF setting button, a mode selection switch for selecting an imaging mode, a release button for inputting an imaging instruction, and the like.

  The phase difference AF device 111 is installed on the bottom side of the body of the imaging device 1 and performs autofocus processing based on a phase difference detection method. Specifically, the phase difference AF device 111 is configured using a so-called autofocus module including a mask, a separator lens, a CCD sensor unit, and the like. The phase difference AF device 111 calculates a defocus amount in each of a plurality of focus detection areas based on a light reception signal obtained by receiving a pair of light beams traveling straight through the photographing optical system 101. Then, the phase difference AF device 111 determines a defocus amount (lens drive defocus amount) used for lens driving based on the calculated defocus amount, and the determined lens drive defocus amount is determined by the lens. Notify the drive controller 114.

The contrast AF device 112 calculates a focus evaluation value according to the imaging signal, and detects a focus adjustment state where the focus evaluation value reaches a peak as a focused state. The contrast AF device 112 mounted on the imaging device 1 has a plurality of modes, for example, a first embodiment to a third embodiment described later.
The lens driving motor 113 is an actuator for driving the focus adjustment lens of the photographing optical system 101 in the optical axis direction, and is driven according to control by the lens drive control unit 114.

The lens drive control unit 114 sets the lens drive motor 113 based on the defocus amount calculated by the phase difference AF device 111 or the focus adjustment state detected as the in-focus state by the contrast AF device 112. Control.
Hereinafter, the first to third embodiments of the contrast AF device 112 will be described.

[First embodiment]
FIG. 2 is a schematic block diagram showing the configuration of the first embodiment of the contrast AF device 112. The contrast AF device 112 includes a detection unit 201, a focus evaluation value storage unit 202, a focus detection unit 203, and a determination unit 204. The contrast AF device 112 operates when the autofocus mode is set to the contrast autofocus mode in the operation unit 110. When the autofocus mode is set to the phase difference autofocus mode, the phase difference AF device 111 operates.

  While the focus adjustment lens is moving on the optical axis, the detection unit 201 detects a focus evaluation value obtained by integrating outputs of a predetermined frequency or more of the imaging signal in a plurality of different focus adjustment states. For example, the detection unit 201 detects a plurality of different focus evaluation values while the focus adjustment lens is moving from the infinite end to the close end.

FIG. 3 is a diagram illustrating an outline of a focus evaluation value detection method by the detection unit 201. In FIG. 3, P (x−1), P (x), and P (x + 1) represent the values of the imaging signals at the respective pixels x−1, x, and x + 1 arranged side by side. For example, the detection unit 201 obtains the unit evaluation value f (x) at the pixel x by the following equation 1.

f (x) = | C0 · P (x-1)
+ C1 · P (x) + C2 · P (x + 1) |

  In Equation 1, the values of C0, C1, and C2 are parameters and are values set in advance in the contrast AF device 112. In this case, the unit evaluation value f (x) is a value representing the contrast of the imaging signal, and is calculated by a process of detecting an edge (a predetermined frequency component or more) from the imaging signal for three pixels in the horizontal direction. The detecting unit 201 calculates a unit evaluation value f (x) for all pixels in a predetermined region (focus detection region) on the imaging surface, and detects a focus evaluation value by integrating all the calculated unit evaluation values. To do. At this time, the detection unit 201 detects the position of the pixel (hereinafter referred to as “maximum unit evaluation pixel”) for which the maximum unit evaluation value (hereinafter referred to as “maximum unit evaluation value”) has been calculated. Then, the detection unit 201 associates and writes the focus evaluation value, the position of the maximum unit evaluation pixel, and the focus adjustment state in the focus evaluation value storage unit 202.

  The focus evaluation value storage unit 202 is configured using a storage device such as a magnetic hard disk device or a semiconductor storage device, and stores a focus evaluation value table. FIG. 4 is a diagram illustrating an outline of the focus evaluation value table. The focus evaluation value table has a focus evaluation value, a position of the maximum unit evaluation pixel, and a focus adjustment state in association with each other.

  Based on the focus evaluation value detected by the detection unit 201, the focus detection unit 203 detects a focus adjustment state in which the focus evaluation value reaches a peak as a focused state. For example, the focus detection unit 203 detects a focus adjustment state in which the focus evaluation value reaches a peak by performing an interpolation process based on a plurality of focus evaluation values.

  The determination unit 204 refers to the data stored in the focus evaluation value storage unit 202 and determines whether or not the focus state detected by the focus detection unit 203 is false focus. Specifically, in the determination unit 204, the position of the maximum unit evaluation pixel stored in the focus evaluation value storage unit 202 in association with the focus adjustment state detected as the in-focus state is the peripheral portion of the focus detection region. It is determined whether or not. If the position of the maximum unit evaluation pixel is the peripheral portion, the determination unit 204 determines that the focus adjustment state is false in-focus. The peripheral edge portion of the focus detection area is an inner portion near the boundary line of the focus detection area, and the range is set in advance by a designer or a user. Further, as the range of the peripheral portion used for the determination of the false focus, one of a plurality of ranges may be dynamically selected according to the configuration of the photographing optical system 101, the zoom position, and the aperture control.

  Next, the operation of the imaging apparatus 1 including the first embodiment of the contrast AF device 112 will be described. FIG. 5 is a flowchart illustrating the operation of the imaging apparatus 1 including the first embodiment of the contrast AF device 112. First, the detection unit 201 and the focus detection unit 203 of the contrast AF device 112 execute a hill-climbing AF search (step S101), and detect a focus adjustment state that is in a focused state (step S102). If the focus adjustment state that is in the in-focus state cannot be detected (NO in step S102), the focus detection unit 203 indicates that the focus adjustment state that is in the in-focus state cannot be detected. Output to one function unit. Then, the imaging apparatus 1 executes a detection impossible process (step S107). Existing technology is applied to the undetectable process. For example, the display unit of the imaging apparatus 1 (not shown) notifies the photographer that the focus adjustment state that is the in-focus state cannot be detected. In addition, the lens drive control unit 114 moves the focus adjustment lens to adjust the focus adjustment state to a predetermined state (for example, a hyperfocal distance state).

  In step S102, when the focus adjustment state in the in-focus state can be detected (step S102-YES), the determination unit 204 refers to the focus evaluation value storage unit 202 and stores it in association with the focus adjustment state. The position of the maximum unit evaluation pixel is read (step S103). Then, the determination unit 204 determines whether or not the position of the maximum unit evaluation pixel is the peripheral portion of the focus detection region in the focus adjustment state detected as the in-focus state (step S104). When the position of the pixel is the peripheral edge of the focus detection area (step S104—YES), the determination unit 204 determines that it is in a false in-focus state, and the determination result is a functional unit of the imaging device 1 such as the lens drive control unit 114. Output for. Then, the image capturing apparatus 1 executes the non-detectable process similarly to step S107 (step S105).

  On the other hand, when the pixel position is not the peripheral edge of the focus detection region (NO in step S104), the determination unit 204 determines that the focus detection state is not false, and the focus adjustment state detected as the focus state by the focus detection unit 203. Is output to the functional unit of the imaging apparatus 1 such as the lens drive control unit 114. Then, the imaging device 1 executes a focusing process (step S106). Existing technology is applied to the focusing process. For example, the display unit of the imaging device 1 (not shown) notifies the photographer that the focus adjustment state that is in a focused state has been detected. The lens drive control unit 114 moves the focus adjustment lens to adjust the focus adjustment state to the in-focus state. Thereafter, when the photographer presses the release button of the operation unit 110, the image sensor 109 captures an image, and the image recording unit 109 stores the captured image data.

  Next, the effect which 1st embodiment of the contrast AF apparatus 112 has is demonstrated. Generally, in the contrast AF method, as described above, the focus adjustment lens is moved on the optical axis, and focus evaluation values are calculated in a plurality of focus adjustment states to detect the in-focus state. At this time, the focal length changes as the position of the focus adjustment lens moves on the optical axis. For this reason, an object that was not initially in the focus detection area may enter the focus detection area in response to a change in focal length, and an in-focus state in which the object is in focus may be erroneously detected. . Such an in-focus state is called false in-focus.

  FIG. 6 is a diagram illustrating an example when the in-focus state is correctly detected. FIG. 7 is a diagram illustrating an example when false in-focus is detected. In FIG. 6, images of tree branches and leaves are included in the entire focus detection area A1 in advance, and even if the focal length changes, the tree branch and leaf images exist in the focus detection area A1. In such a case, the in-focus state is correctly detected so that the tree branches and leaves are in focus. In contrast, in FIG. 7A, no image of a tree branch or leaf is included in the focus detection area A1, but in accordance with the change in focal length, a tree branch or leaf in the focus detection area A1 in FIG. 7B. Contains leaf images. In this case, an image of a tree branch or leaf has a higher frequency component than an image of a mountainside that occupies the focus detection area A1 from the beginning. Therefore, the focus evaluation is performed in the focus adjustment state in FIG. 7B, although the focus state should be the focus state on the image of the mountainside that normally occupies the focus detection region A1 in advance. The value becomes a peak.

  FIG. 8 is a diagram illustrating the transition of the focus evaluation value when the in-focus state and the false in-focus are detected. FIG. 9 is a diagram illustrating movement of the focus adjustment lens in the case of FIG. In FIG. 8, the vertical axis represents the focus evaluation value, the horizontal axis represents the focus adjustment state, the left side of the horizontal axis represents the infinite end, and the right side of the horizontal axis represents the closest end. In FIG. 9, the vertical axis represents the focus adjustment state, and the horizontal axis represents time.

  In the case of FIG. 6, since the image of a tree branch or leaf is in the focus detection area A1 in any focus adjustment state, the focus evaluation value in the focus adjustment state where the image of the tree branch or leaf is in focus. Becomes a peak, and the in-focus state is correctly detected.

  On the other hand, in the case of FIG. 7, the image of the mountainside is initially in the focus detection area A1. However, since the image of the mountainside has a low frequency component, the focus evaluation value remains low even if the image is in focus. Thereafter, the focus evaluation value reaches a peak in the focus adjustment state Perr when an image of a tree branch or leaf enters the focus detection area A1. At this time, the focus adjustment state is not a state in which an image of a tree branch or leaf is in focus. Nevertheless, because the frequency components of the tree branches and leaves are high in the first place, the focus evaluation value of the image of the blurred tree branches and leaves is the image of the mountainside in focus. Higher than. Therefore, in the case of FIG. 7, the peak of the focus evaluation value appears at a position shifted to the closest end side compared to the case of FIG. 6, and the focus evaluation value that becomes the peak is smaller than that in the case of FIG. 6. In such a false focus state of FIG. 7, both the image of the mountainside in the focus detection area A1 and the image of the tree branch or leaf that caused the false focus are both included. The image is out of focus, and an image that is out of focus as a whole is captured. The above is the problem of the conventional false focusing.

  For such a problem, in the first embodiment of the contrast AF device 112, even if the focus detection unit 203 detects the in-focus state, the position of the maximum unit evaluation pixel at that time is the peripheral part of the focus detection region. In some cases, it is determined that the focus is false, and the focus adjustment state is adjusted to a predetermined state different from the false focus by executing the detection impossible process. Therefore, it is possible to prevent imaging in a false focus state without increasing the number of focus detection areas.

<Modification>
The detection unit 201 determines whether or not the largest unit evaluation value in the focus detection area exceeds a predetermined threshold (hereinafter referred to as “unit evaluation threshold”). The evaluation value, the position of the maximum unit evaluation pixel, and the focus adjustment state may be written in the focus evaluation value storage unit 202.

  Here, the unit evaluation threshold will be described. At the time of FIG. 6A, since the focus detection area A1 does not include an image having a high-frequency component, the unit evaluation value is a very low value for the entire focus detection area. However, if a noise component is rarely included in the focus detection region, the unit evaluation value may take a higher value than other portions due to the noise component, and may become the maximum unit evaluation value. If the maximum unit evaluation value and the position of the maximum unit evaluation pixel resulting from the noise component are stored in the focus evaluation value storage unit 202 in this way, the processing accuracy in the determination unit 204 may be reduced. On the other hand, by performing the processing as described above using the unit evaluation threshold value, it is possible to prevent the maximum unit evaluation value caused by the noise component from being stored and the processing accuracy of the determination unit 204 from being reduced. .

  Note that the unit evaluation threshold value is a value that depends on the specification of the imaging apparatus 1, such as the value of a parameter used to calculate the unit evaluation value, the output characteristics of the image sensor 109, the exposure control amount, and the characteristics of the imaging optical system 101. Yes, it is set appropriately according to these characteristics. For example, the unit evaluation threshold value may be set so as to change according to the control sensitivity value SV value (sensitivity during autofocus) of the image sensor 109 when the unit evaluation value is acquired. In this case, the unit evaluation threshold is set to be higher as the SV value is higher. More specifically, the unit evaluation threshold value may be selected according to the SV value by storing a table in which the unit evaluation threshold value and the SV value are associated in advance, or an evaluation formula using the SV value as a variable. , The unit evaluation threshold value may be calculated according to the SV value.

  The determination unit 204 may be configured to determine that it is false in-focus when the focus adjustment state detected as the in-focus state is closer to the end than the predetermined state. In general, in the hill-climbing AF search, the focus adjustment state transitions from the infinite end side to the closest end side. At this time, a subject outside the focus detection region is more likely to enter the focus detection region when the focus adjustment state is at the closest end than when the focus adjustment state is at the infinite end. Therefore, by performing the determination of false focusing as described above, it is possible to increase the accuracy of the determination of false focusing. For example, when the focus adjustment state detected as the in-focus state is a state closer to the near end than half of the focus adjustment range driven by the focus adjustment lens in the hill-climbing AF search, the determination unit 204 is false in-focus. Is configured to determine.

[Second Embodiment]
FIG. 10 is a schematic block diagram showing the configuration of the second embodiment of the contrast AF device 112. The second embodiment of the contrast AF device 112 is different from the first embodiment in that the selection unit 205 is further provided, and other configurations are the same as those of the first embodiment. Hereinafter, regarding the second embodiment of the contrast AF device 112, differences from the first embodiment will be described.

  FIG. 11 is a diagram illustrating an outline of a focus detection area in the second embodiment of the contrast AF device 112. The second embodiment of the contrast AF device 112 corresponds to a plurality of focus detection areas (A11, A12, A13 in FIG. 11), detects a focus adjustment state that is in focus for each focus detection area, and detects each focus. It is determined whether the area is falsely focused. That is, the detection unit 201 detects a focus evaluation value for each focus detection region, and associates the focus evaluation value, the position of the maximum unit evaluation pixel, and the focus adjustment state in the focus evaluation value storage unit 202 for each focus detection region. Write. The focus evaluation value storage unit 202 stores the focus evaluation value, the position of the maximum unit evaluation pixel, and the focus adjustment state in association with each other for each focus detection region. The focus detection unit 203 detects, as an in-focus state, a focus adjustment state where the focus evaluation value reaches a peak for each focus detection region. The determination unit 204 determines whether or not false focus is achieved for each focus detection area.

  The selection unit 205 selects one optimum focus detection region as the focus state from among a plurality of focus detection regions determined by the determination unit 204 to be in a correct focus state that is not false focus. For example, when the focus state is detected in a plurality of focus detection areas, the selection unit 205 selects the focus adjustment corresponding to the closest end side of the focus adjustment range among the focus adjustment states detected as the focus state. Select a state. Note that the selection unit 205 selects the focus adjustment state detected in the focus detection region when there is one focus detection region in which the focus state is detected.

  FIG. 12 is a diagram showing a transition of focus evaluation values detected in each focus detection region of FIG. In FIG. 12, the vertical axis represents the focus evaluation value, the horizontal axis represents the focus adjustment state, the left side of the horizontal axis represents the infinite end, and the right side of the horizontal axis represents the closest end. In this case, in the focus detection area A12, false focusing is caused by an image of a tree branch or leaf immediately outside the focus detection area. On the other hand, no false focusing occurs in the focus detection areas A11 and A13. In this case, the selection unit 205 selects one focus detection area from the focus detection areas A11 and A13 where no false focusing occurs. For example, when the selection unit 205 is configured to select the focus adjustment state corresponding to the closest end of the focus adjustment range as described above, the focus detection area A13 is selected from the focus detection areas A11 and A13. select.

  FIG. 13 is a flowchart illustrating the operation of the imaging apparatus 1 including the second embodiment of the contrast AF device 112. In FIG. 13, the same operations as those of the imaging apparatus 1 including the first embodiment are denoted by the same reference numerals as those in FIG.

  First, the process of step S101-step S104 is performed for every focus detection area. At this time, when the focus adjustment state in which focus is achieved cannot be detected in step S102 (step S102-NO), the focus detection unit 203 determines that focusing is impossible (step S201). If the pixel position is the peripheral edge of the focus detection area in step S104 (step S104-YES), the determination unit 204 determines that the focus state is false (step S202). On the other hand, when the position of the pixel is not the peripheral edge of the focus detection area (step S104—NO), the determination unit 204 determines that it is not a false in-focus state (step S203). The detection unit 201, the focus detection unit 203, and the determination unit 204 execute the above processing for all focus detection regions (step S204). When the above processing is completed for all focus detection areas (YES in step S204), the selection unit 205 selects an optimum focus detection area (step S205). Then, the imaging device 1 executes a focusing process based on the focusing state of the focus detection area selected in step S205 (step S106).

  In the second embodiment of the contrast AF device 112 configured as described above, an optimum focus detection region is selected from a plurality of focus detection regions, and a focus adjustment state is adjusted. It becomes possible.

[Third embodiment]
FIG. 14 is a schematic block diagram showing the configuration of the third embodiment of the contrast AF device 112. The third embodiment of the contrast AF device 112 is different from the first embodiment in that it further includes a direction determination unit 206, and other configurations are the same as those of the first embodiment. Hereinafter, regarding the third embodiment of the contrast AF device 112, differences from the first embodiment will be described.

  The direction determination unit 206 controls the lens drive control unit 114 to move the focus adjustment lens back and forth along the optical axis to execute a wobbling search. Then, the direction determination unit 206 sets a search direction. The search direction is a direction in which the focus adjustment lens should be moved when the detection unit 201 and the focus detection unit 203 perform a hill-climbing AF search.

  FIG. 15 is a flowchart showing the operation of the direction determination process in the third embodiment of the contrast AF device 112. First, the direction determination unit 206 executes a wobbling search by controlling the lens drive control unit 114 (step S301). At this time, the direction determination unit 206 moves the focus adjustment lens back and forth along the optical axis, and the detection unit 201 detects focus evaluation values in a plurality of focus adjustment states. Then, the direction determination unit 206 determines that the direction with the higher focus evaluation value is the search direction. At this time, the detection unit 201 writes the focus evaluation value, the position of the maximum unit evaluation pixel, and the focus adjustment state in the focus evaluation value storage unit 202 in association with each focus adjustment state.

  When the search direction is not found by the process of step S301 (step S302-NO), the direction determination unit 206 performs a detection impossible process (step S307). Existing technology is applied to the undetectable process. For example, the direction determination unit 206 notifies the detection unit 201 that the search direction has not been found, and the detection unit 201 performs a hill-climbing AF search after moving the focusing lens to one of the infinite end or the closest end. .

  On the other hand, when the search direction is determined by the processing in step S301, the direction determination unit 206 determines that the position of the maximum unit evaluation pixel in the focus adjustment state where the focus evaluation value reaches a peak in the wobbling search is the peripheral portion of the focus detection region. Whether or not (step S303). If the position of the maximum unit evaluation pixel is the peripheral edge of the focus detection area (step S304—YES), it is determined that the determination result of the search direction is an erroneous determination (step S305), and the detection impossible process similar to step S307 is performed. Do.

  On the other hand, when the position of the maximum unit evaluation pixel is not the peripheral portion of the focus detection region (NO in step S304), it is determined that the determination of the search direction is an accurate determination, and the search direction is notified to the detection unit 201. In this case, the detection unit 201 performs a hill-climbing AF search in the notified search direction.

  In the third embodiment of the contrast AF device 112 configured as described above, the direction determination unit 206 determines the search direction in the wobbling search. At that time, the direction determination unit 206 performs false focusing based on whether or not the position of the maximum unit evaluation pixel is the peripheral portion of the focus detection region with respect to the peak of the focus evaluation value that is the reference for determining the search direction. As in the case of, it is determined whether or not it is an erroneous peak. Therefore, in the wobbling search, it is possible to detect the search direction more accurately and to prevent the hill-climbing AF search from being executed in the wrong direction.

[Fourth embodiment]
Next, a fourth embodiment of the contrast AF device 112 will be described. Since the functional configuration of the fourth embodiment of the contrast AF device 112 is the same as that of the first embodiment, a schematic block diagram is omitted. The fourth embodiment of the contrast AF device 112 is the first embodiment in that when the position of the maximum unit evaluation pixel is the peripheral portion of the focus detection area, the focus detection area is changed and the hill-climbing AF search process is performed again. And different.

  FIG. 16 is a flowchart illustrating the operation of the imaging apparatus 1 including the fourth embodiment of the contrast AF device 112. In FIG. 16, the same operations as those of the imaging apparatus 1 including the first embodiment are denoted by the same reference numerals as those in FIG.

  In step S104, when the pixel position is the peripheral edge of the focus detection area (step S104-YES), the determination unit 204 determines that the focus is false and changes at least one of the position and size of the focus detection area. (Step S401). At this time, when changing the size of the focus detection area, the determination unit 204 changes the area so that the area becomes larger. Further, when changing the position of the focus detection area, the determination unit 204 changes the position so that the position of the maximum unit evaluation pixel does not become the peripheral portion. For example, the determination unit 204 moves the focus detection region so that the position of the maximum unit evaluation pixel is at the center. The determination unit 204 may change the size and position of the focus detection area.

  Then, the detection unit 201 and the focus detection unit 203 execute a hill-climbing AF search based on the newly set focus detection region (step S402), and detect a focus adjustment state that is in a focused state (step S403).

  If the focus adjustment state that is in the in-focus state cannot be detected (NO in step S403), the imaging device such as the lens drive control unit 114 indicates that the focus detection unit 203 has not been able to detect the focus adjustment state that is in the in-focus state. Output to one function unit. Then, the imaging apparatus 1 executes a detection impossible process (step S107). On the other hand, when the focus adjustment state that is in the in-focus state is detected (step S403-YES), the determination unit 204 performs the false in-focus determination process (S104) based on the position of the maximum unit evaluation pixel. The detected focus adjustment state is output to the functional unit of the imaging apparatus 1 such as the lens drive control unit 114. Then, the imaging device 1 executes a focusing process (step S106).

In the fourth embodiment of the contrast AF device 112 configured as described above, when it is determined to be false in-focus, the size or position of the focus detection area is changed, and hill-climbing AF is performed based on the new focus detection area. The search is performed again. Therefore, even if it is false in-focus, the in-focus state that does not become false in-focus is detected again by the hill-climbing AF search again.
The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and includes designs and the like that do not depart from the gist of the present invention.

DESCRIPTION OF SYMBOLS 1 ... Imaging device, 101 ... Imaging optical system, 111 ... Phase difference AF device, 112 ... Contrast AF device, 201 ... Detection part, 202 ... Focus evaluation value memory | storage part, 203 ... Focus detection part, 204 ... Determination part, 205 ... Selection unit, 206 ... direction determination unit

Claims (7)

A focus evaluation value obtained by integrating the output of the imaging signal obtained by capturing an image in a predetermined area on the image plane of the optical system and the maximum value of the output exceeding the predetermined frequency in the predetermined area are obtained. A detection unit that detects a position in association with a focus adjustment state of the optical system;
When the position where the maximum value of the output corresponding to the focus adjustment state at which the focus evaluation value reaches a peak is a peripheral portion within the predetermined region, the focus adjustment state at which the focus evaluation value reaches a peak is falsely identified. A determination unit for determining that the image is in focus;
A focus detection apparatus. The focus detection apparatus according to claim 1,
The determination unit is a case where the position where the maximum value of the output is obtained is not a peripheral portion in the predetermined region, and the focus adjustment state that becomes the peak is at the closest end of the focus adjustment range of the optical system In some cases, the focus adjustment state at the peak is determined to be false in-focus. The focus detection device according to claim 1 or 2,
Based on the change in the focus evaluation value corresponding to the change in the focus adjustment state, the focus adjustment direction of the optical system is determined, and the position where the maximum value of the output is obtained is the peripheral portion in the predetermined region. In this case, the apparatus further includes a direction determination unit that prohibits determination of the focus adjustment direction based on the change in the focus evaluation value corresponding to the change in the focus adjustment state. The focus detection apparatus according to claim 1,
The detection unit detects the focus evaluation value and the position where the maximum value of the output is obtained for each of the plurality of predetermined areas set at a plurality of positions in an image plane of the optical system. . The focus detection device according to any one of claims 1 to 4,
When there are a plurality of focus adjustment states that are not determined to be false in-focus by the determination unit, the selection unit further includes a selection unit that selects a focus adjustment state corresponding to the closest end side of the focus adjustment range of the optical system. To do. It is a focus detection apparatus in any one of Claims 1-5,
The determination unit may perform the determination again by changing at least one of a position and a size of the predetermined area on the image plane of the optical system when determining that the focus is false. A focus detection apparatus according to any one of claims 1 to 6;
An imaging unit that captures an image by the optical system;
An imaging apparatus comprising:

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