JP6476539B2 - Focus detection apparatus and imaging apparatus - Google Patents

Description

  The present invention relates to a focus detection apparatus and an imaging apparatus.

  Conventionally, when photographing a subject including a point light source such as an outdoor light at night, the image signal of the pixel corresponding to the point light source is saturated, and the focus state of the optical system cannot be detected based on the image signal. was there. On the other hand, when a point light source is present, the more focused the point light source is, the smaller the image of the point light source, and the corresponding number of pixels corresponding to the point light source is reduced. The integrated value of the image signal in the area becomes small. Therefore, when the image signal is saturated by the point light source, the image signal within the predetermined image area including the point light source is integrated, and the lens position where the integrated value of the image signal is minimum is detected as the in-focus position. Is known (see, for example, Patent Document 1).

JP 2004-246013 A

  However, the conventional technique detects a lens position of a focusing lens that is focused on a point light source as a focus position. For example, when photographing a face of a person wearing glasses at night, When the illumination light is reflected by the spectacles, the point light source such as an external light or illumination is in focus, and it may not be possible to take an image in focus on the human face.

  The present invention solves the above problems by the following means.

[1] A focus detection apparatus according to the present invention includes an acquisition unit that acquires an image signal corresponding to an image by an optical system including a focus adjustment lens, and a face area included in the image based on the image signal as a specific subject. A specifying unit for specifying, a setting unit for setting, as a detection target region, the focus detection region corresponding to the specific subject among a plurality of focus detection regions set on the image plane by the optical system, and a luminance of a predetermined value or more A detection unit that detects a subject as a high-luminance subject, an extraction unit that extracts a frequency signal corresponding to a specific frequency component from the image signal, and a plurality of the frequencies extracted in a plurality of image regions in the detection target region It outputs the first cumulative value output unit for outputting as a first integration value by integrating the signal, as the second cumulative value by integrating the image signals in a plurality of image areas within the detection target area And 2 integrated value output section, the maximum of the maximum value output section and said first integration value or the frequency signal to output a maximum value of a plurality of said frequency signal extracted in a plurality of image areas within the detection target area A focus detection unit that detects a focus state of the optical system using a value, and the focus detection unit specifies the face region by the specification unit, and the detection unit detects the face region by the detection unit. If the high luminance object is detected, prior SL using the maximum value to detect the focus state of the optical system, the said face region according to a particular unit is identified, and, by the detecting unit in the detection target area When the high brightness subject is not detected, the focus state of the optical system is detected using the first integrated value, the face area is not specified by the specifying unit, and the high brightness subject is not set by the detecting unit. But If issued, to detect the focus state of the optical system using the second integrated value.
[2] In the invention relating to the focus detection device, the first integrated value output unit outputs an integrated value of the frequency signal for each predetermined lens position of the focus adjustment lens, and the maximum value output unit includes: The maximum value of the frequency signal is output for each predetermined lens position of the focus adjustment lens, and the focus detection unit detects the high-frequency object in the detection target region when the high-luminance subject is detected. The lens position with the largest maximum value is detected as the in-focus position, and if the high-luminance subject is not detected in the detection target area, the lens position with the largest first integrated value is detected as the in-focus position. be able to.
[3] In the invention according to the focus detection apparatus, the detection unit may have an average value of the overall luminance of the image corresponding to the image that is equal to or less than a predetermined value, and the maximum of the image signal while driving the optical system. By detecting the position of the focusing lens whose value is the output upper limit value of the imaging pixel, the high-luminance subject can be detected.
[4] In the invention according to the focus detection apparatus, the focus detection unit includes a determination unit that determines whether or not illumination light for illuminating the subject is emitted, and the focus detection unit emits the illumination light by the determination unit. When the high brightness subject is detected by the detection unit in the detection target area, the focus state of the optical system can be detected using the maximum value of the frequency signal.
[5] In the invention according to the focus detection device, the focus detection unit uses the first integrated value to determine the focus state of the optical system when the determination unit determines that the illumination light is not emitted. Can be detected.
[ 6 ] In the invention relating to the focus detection apparatus, the focus detection device may be configured to include a selection unit that allows the user to select one of the plurality of focus detection areas.
[ 7 ] In the invention related to the focus detection apparatus, when the one focus detection area is selected by the selection unit, the specifying unit determines that the one focus detection area and the focus detection area corresponding to the specific subject are If they match, the detection target area can be set.
[ 8 ] An imaging apparatus according to the present invention includes the focus detection apparatus.

  According to the present invention, it is possible to appropriately detect the focus state of the optical system.

FIG. 1 is a configuration diagram illustrating a camera according to the first embodiment. FIG. 2 is a block diagram illustrating a configuration of the camera control unit. FIG. 3 is a flowchart showing the operation of the camera according to the first embodiment. FIG. 4 is a diagram illustrating an example of the focus evaluation value when the image signal is saturated by the point light source and the focus evaluation value when the image signal is not saturated. FIG. 5 is a diagram illustrating an example of the focus evaluation value and the point light source evaluation value when the image signal is saturated by the point light source. FIG. 6 is a diagram illustrating an example of a positional relationship among a camera, a subject (person), and a point light source. FIG. 7 is a diagram illustrating an example of the focus evaluation value and the point light source evaluation value when the point light source is reflected by the glasses. FIG. 8 is a block diagram showing a camera according to the second embodiment. FIG. 9 is a flowchart showing the operation of the camera according to the second embodiment. FIG. 10 is a flowchart showing the operation of the camera according to the third embodiment.

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

<< First Embodiment >>
FIG. 1 is a block diagram showing a digital camera 1 according to the first embodiment of the present invention. A digital camera 1 according to the first embodiment (hereinafter simply referred to as a camera 1) includes a camera body 2 and a lens barrel 3. The camera body 2 and the lens barrel 3 are detachably coupled by a mount unit 4. ing.

  The lens barrel 3 is an interchangeable lens that can be attached to and detached from the camera body 2. As shown in FIG. 1, the lens barrel 3 contains an optical system including lenses 31, 32, 33 and a diaphragm 34.

  The lens 32 is a focus lens, and the focal length of the optical system can be adjusted by moving in the direction of the optical axis L1. The focus lens 32 is provided so as to be movable along the optical axis L1 of the lens barrel 3, and its position is adjusted by the focus lens drive motor 36 while its position is detected by the encoder 35.

  Information on the current position of the focus lens 32 detected by the encoder 35 is sent to the camera control unit 21 to be described later via the lens control unit 37, and the focus lens driving motor 36 calculates the focus lens 32 calculated based on this information. Is driven by being sent from the camera control unit 21 via the lens control unit 37.

  The diaphragm 34 is configured such that the aperture diameter around the optical axis L1 can be adjusted in order to limit the amount of light beam that passes through the optical system and reaches the image sensor 22 and to adjust the amount of blur. The adjustment of the aperture diameter by the diaphragm 34 is performed, for example, by sending an appropriate aperture diameter calculated in the automatic exposure mode from the camera control unit 21 via the lens control unit 37. Further, the set aperture diameter is input from the camera control unit 21 to the lens control unit 37 by a manual operation by the operation unit 28 provided in the camera body 2. The aperture diameter of the aperture 34 is detected by an aperture sensor (not shown), and the lens controller 37 recognizes the current aperture diameter.

  On the other hand, the camera body 2 is provided with an image sensor 22 for receiving the light beam L1 from the optical system on the planned focal plane of the optical system, and a shutter 23 is provided on the front surface thereof. The image sensor 22 is composed of a device such as a CCD or CMOS, converts the received optical signal into an electrical signal, and sends it to the camera control unit 21. The image information sent to the camera control unit 21 is sequentially sent to the liquid crystal drive circuit 25 and displayed on the electronic viewfinder (EVF) 26 of the observation optical system, and a release button (unavailable) provided on the operation unit 28. When (shown) is fully pressed, the image information is recorded in the camera memory 24 which is a recording medium. The camera memory 24 can be either a removable card type memory or a built-in memory.

  The camera body 2 is provided with an observation optical system for observing an image picked up by the image pickup device 22. The observation optical system of the present embodiment includes an electronic viewfinder (EVF) 26 composed of a liquid crystal display element, a liquid crystal driving circuit 25 that drives the electronic viewfinder (EVF) 26, and an eyepiece lens 27. The liquid crystal drive circuit 25 reads the captured image information captured by the image sensor 22 and sent to the camera control unit 21, and drives the electronic viewfinder 26 based on the read image information. Thereby, the user can observe the current captured image through the eyepiece lens 27. Note that, instead of or in addition to the observation optical system using the optical axis L2, a liquid crystal display may be provided on the back surface of the camera body 2, and a photographed image may be displayed on the liquid crystal display.

  A camera control unit 21 is provided in the camera body 2. The camera control unit 21 is electrically connected to the lens control unit 37 through an electric signal contact unit 41 provided in the mount unit 4, receives lens information from the lens control unit 37, and defocuses to the lens control unit 37. Send information such as volume and aperture diameter. The camera control unit 21 reads out the pixel output from the image sensor 22 as described above, generates image information by performing predetermined information processing on the read out pixel output as necessary, and generates the generated image information. Is output to the liquid crystal driving circuit 25 and the memory 24 of the electronic viewfinder 26. The camera control unit 21 controls the entire camera 1 such as correction of image information from the image sensor 22 and detection of an aperture adjustment state of the lens barrel 3.

  Furthermore, in addition to the above, the camera control unit 21 also detects the focus state of the optical system. Here, FIG. 2 is a block diagram illustrating the configuration of the camera control unit 21, and illustrates the configuration related to the detection of the focus state of the optical system among the configurations of the camera control unit 21. In order to detect the focus state of the optical system, as shown in FIG. 2, the camera control unit 21 performs a high-pass filter (HPF) 211, a first integration circuit 212, a first maximum value circuit 213, and a second integration. A circuit 214, a second maximum value circuit 215, and a focus detection unit 216 are provided.

  In the present embodiment, as shown in FIG. 2, the imaging element 22 has a plurality of imaging pixels 221 arranged in a two-dimensional manner on a light receiving surface that receives a light beam L <b> 1 and includes a focus lens 32. The imaging pixel 221 receives the light beam L1 that has passed through the optical system. Each imaging pixel 221 outputs an image signal corresponding to the intensity of received light to the camera control unit 21. The plurality of image signals output from the plurality of imaging pixels 221 are input to the high-pass filter 211, the second integration circuit 214, and the second maximum value circuit 215, as shown in FIG.

  The high pass filter 211 is a detection filter such as an FIR digital filter. The high-pass filter 211 acquires a plurality of high-frequency signals from the plurality of imaging pixels 221 by extracting a high-frequency signal corresponding to a high-frequency component from the image signal output from each imaging pixel 221.

  For example, when the imaging pixels 221A to 221E are continuously arranged on the imaging element 22, the high-pass filter 211 has a high-frequency image signal of the central imaging pixel 221C among the five consecutive imaging pixels 221A to 221E. When extracting a component as a high frequency signal, a predetermined filter process is performed on each of the image signals of the five consecutive imaging pixels 221A to 221E, so that the high frequency component of the image signal of the imaging pixel 221C is used as a high frequency signal. Can be extracted. Then, the plurality of high frequency signals extracted by the high pass filter 211 are sent to the first integration circuit 212 and the first maximum value circuit 213.

  The first integration circuit 212 acquires a plurality of high-frequency signals extracted by the high-pass filter 211, and calculates an integrated value of the acquired plurality of high-frequency signals as a focus evaluation value. In this embodiment, a plurality of focus detection areas AFP are set in the shooting screen of the shooting optical system, and the first integration circuit 212 performs focus evaluation for each focus detection area AFP set in the shooting screen. Calculate the value. That is, the first integration circuit 212 calculates the integrated value of the high-frequency signal for each focus detection area AFP as the focus evaluation value by integrating the high-frequency signals of the plurality of imaging pixels 221 for each focus detection area AFP. Then, the focus evaluation value calculated by the first integration circuit 212 is sent to the focus detection unit 216.

  Note that the number of the imaging pixels 221 corresponding to the focus detection area AFP is not particularly limited. For example, the focus detection area AFP may be set as an area corresponding to the imaging pixels 221 for 10,000 pixels of 100 × 100. it can. In this case, the focus evaluation value is calculated as an integrated value of the high-frequency signal of the imaging pixels 221 for 10,000 pixels.

  The first maximum value circuit 213 acquires a plurality of high-frequency signals extracted by the high-pass filter 211, and calculates the maximum value among the acquired plurality of high-frequency signals as a high-frequency maximum value. In the present embodiment, the first maximum value circuit 213 calculates the high frequency maximum value for each focus detection area AFP. That is, the first maximum value circuit 213 calculates the maximum value among the high-frequency signals of the plurality of imaging pixels 221 corresponding to the focus detection area AFP as the high-frequency maximum value, so that the high-frequency signal for each focus detection area AFP is calculated. The maximum value is calculated as the high frequency maximum value. For example, when the number of imaging pixels 221 corresponding to the focus detection area AFP is 10,000 pixels, the first maximum value circuit 213 has the highest value among the high-frequency signals output from the 10,000 imaging pixels 221. The value of the high frequency signal of one large imaging pixel 221 is calculated as the maximum high frequency value. The high frequency maximum value calculated by the first maximum value circuit 213 is sent to the focus detection unit 216.

  The second integration circuit 214 acquires a plurality of image signals output from the plurality of imaging pixels 221 and calculates an integrated value of the acquired plurality of image signals as a point light source evaluation value for evaluating a point light source. As described above, the second integration circuit 214 calculates the point light source evaluation value by integrating the image signal output from the imaging pixel 221 without passing through the high-pass filter 211. In the present embodiment, the second integrating circuit 214 calculates a point light source evaluation value for each focus detection area AFP. That is, the second integration circuit 214 calculates the integrated value of the image signal for each focus detection area AFP as the point light source evaluation value by integrating the image signals of the plurality of imaging pixels 221 for each focus detection area AFP. Then, the point light source evaluation value calculated by the second integration circuit 214 is sent to the focus detection unit 216.

  The second maximum value circuit 215 acquires a plurality of image signals output from the plurality of imaging pixels 221 and calculates the maximum value among the acquired plurality of image signals as the image signal maximum value. The second maximum value circuit 215 calculates the image signal maximum value by using the image signal output from the imaging pixel 221 as it is without passing through the high-pass filter 211, as in the second integration circuit 214. Further, in the present embodiment, the second maximum value circuit 215 calculates the image signal maximum value for each focus detection area AFP. In other words, the second maximum value circuit 215 calculates the maximum value among the image signals of the plurality of imaging pixels 221 corresponding to the focus detection area AFP as the image signal maximum value, so that the image signal for each focus detection area AFP. Is calculated as the image signal maximum value. Then, the image signal maximum value calculated by the second maximum value circuit 215 is sent to the focus detection unit 216.

  The focus detection unit 216 includes a focus evaluation value transmitted from the first integration circuit 212, a high-frequency maximum value transmitted from the first maximum value circuit 213, a point light source evaluation value transmitted from the second integration circuit 214, Based on the maximum value of the image signal transmitted from the second maximum value circuit 215, the focus state of the optical system is detected. A focus detection method by the focus detection unit 216 will be described later.

  Returning to FIG. 1, the operation unit 28 is an input switch for a photographer to set various operation modes of the camera 1 such as a shutter release button, and can switch between an autofocus mode and a manual focus mode. . Various modes set by the operation unit 28 are sent to the camera control unit 21, and the operation of the entire camera 1 is controlled by the camera control unit 21. The shutter release button includes a first switch SW1 that is turned on when the button is half-pressed and a second switch SW2 that is turned on when the button is fully pressed.

  Next, an operation example of the camera 1 according to the first embodiment will be described. FIG. 3 is a flowchart showing the operation of the camera 1 according to the first embodiment.

  First, in step S101, the camera control unit 21 starts calculation of the focus evaluation value, the high frequency maximum value, the point light source evaluation value, and the image signal maximum value. Specifically, the camera control unit 21 first sends a drive start command for the focus lens 32 to the lens control unit 37, and moves the focus lens 32 to the focus lens drive motor 36 via the lens control unit 37. Drive along L1. The focus lens 32 may be driven from the infinity end to the close end, or from the close end to the infinity end.

  Then, the camera control unit 21 reads out the plurality of image signals from the plurality of imaging pixels 221 at predetermined intervals while driving the focus lens 32, and the read-out plurality of image signals as shown in FIG. 211, the second integration circuit 214, and the second maximum value circuit 215.

  The high pass filter 211 extracts a plurality of high frequency signals from the image signals of the plurality of imaging pixels 221 and sends the extracted plurality of high frequency signals to the first integration circuit 212 and the first maximum value circuit 213. As a result, the integrated value of the plurality of high frequency signals is calculated for each focus lens position as the focus evaluation value in the first integrating circuit 212, and the maximum value among the plurality of high frequency signals is calculated in the first maximum value circuit 213. The high frequency maximum value is calculated for each focus lens position.

  The second integration circuit 214 acquires a plurality of image signals from the plurality of imaging pixels 221 without using the high-pass filter 211, and the integrated value of the acquired plurality of image signals is used as a point light source evaluation value as a focus light source evaluation value. Calculated for each lens position. Further, the second maximum value circuit 215 acquires a plurality of image signals from the plurality of imaging pixels 221 without passing through the high-pass filter 211, and the maximum value among the acquired plurality of image signals is the image signal maximum value. Is calculated for each focus lens position.

  Further, in the present embodiment, a plurality of focus detection areas AFP are set in the shooting screen, and the camera control unit 21 sets the focus evaluation value, the high frequency maximum value, the point light source evaluation value, for each focus detection area AFP. And the maximum value of the image signal is calculated. In other words, in the present embodiment, the first integration circuit 212 calculates the focus evaluation value for each focus detection area AFP by integrating the high-frequency signals of the plurality of imaging pixels 221 for each focus detection area AFP. The 1 maximum value circuit 213 calculates the maximum value among the high-frequency signals of the plurality of imaging pixels 221 corresponding to the focus detection area AFP for each focus detection area AFP, thereby calculating the maximum high-frequency value for each focus detection area AFP. To do. Similarly, the second integration circuit 214 calculates the point light source evaluation value for each focus detection area AFP by integrating the image signals of the plurality of imaging pixels 221 for each focus detection area AFP, and the second maximum value circuit 215. Calculates the maximum value of the image signal for each focus detection area AFP by calculating the maximum value of the image signals of the plurality of imaging pixels 221 corresponding to the focus detection area AFP for each focus detection area AFP.

  As described above, the camera control unit 21 calculates the focus evaluation value, the high frequency maximum value, the point light source evaluation value, and the image signal maximum value for each focus detection area AFP and for each focus lens position. In step S101 and subsequent steps, the camera control unit 21 repeatedly calculates the focus evaluation value, the high frequency maximum value, the point light source evaluation value, and the image signal maximum value while driving the focus lens 32.

  In step S <b> 102, the camera control unit 21 detects a human face area from the captured image captured by the image sensor 22. For example, the camera control unit 21 detects the face area of the person from the captured image by comparing the template image data (reference image data) of the person's face stored in advance with the captured image. can do. In step S103, the camera control unit 21 determines whether or not the face area of the person has been detected in step S102. If the face area of the person can be detected, the process proceeds to step S108. If the face area of the person cannot be detected, the process proceeds to step S104.

  In step S104, the camera control unit 21 determines whether the image signal is saturated by the point light source. Here, when the shooting screen is entirely dark, such as during night scene shooting, image signals are amplified in order to adjust exposure. In this case, when a high brightness subject such as a point light source exists, an image signal corresponding to the high brightness subject is also amplified, and the image signal corresponding to the high brightness subject may be saturated. Therefore, in step S104, for example, the camera control unit 21 calculates the maximum value of the image signal while driving the focus lens 32 in step S101 while the average value of the luminance of the entire image is equal to or less than a predetermined value. When the lens position where the maximum value of the image signal is the upper limit value (output upper limit value) of the image signal that can be output by the imaging pixel 221 can be detected, it is determined that the image signal is saturated by the point light source. it can. If it is determined that the image signal is saturated by the point light source, the process proceeds to step S107. On the other hand, if it is determined that the image signal is not saturated by the point light source, the process proceeds to step S105.

  In step S104, when the focus detection area AFP for performing focus detection is set, the image signal is saturated by the point light source in the focus detection area AFP set for performing focus detection. Judge whether or not. On the other hand, if the focus detection area AFP for performing focus detection is not set, whether or not the image signal is saturated by the point light source in all the focus detection areas AFP set in the shooting screen. Judgment can be made.

  If it is determined in step S104 that the image signal is not saturated by the point light source, in step S105, the camera control unit 21 detects the lens position where the focus evaluation value is maximized as the in-focus position. The

  Here, FIG. 4 is a diagram illustrating an example of the focus evaluation value when the image signal is saturated by the point light source and the focus evaluation value when the image signal is not saturated. For example, when image signals of a plurality of continuous imaging pixels 221 are saturated by a point light source, the image signals of the plurality of continuous imaging pixels 221 become a constant value (output upper limit value) due to saturation. For this reason, the high frequency component (contrast) of the subject cannot be detected based on the image signal of the imaging pixel 221 as described above, and as shown in FIG. The focus evaluation value, which is the integrated value of the signal, may decrease. On the other hand, due to the influence of the flare of the point light source, the focus evaluation value is calculated to be larger at the infinity side than the subject position and closer to the subject position. As a result, as shown in FIG. In some cases, the peak of the focus evaluation value is detected at the infinity side and the lens position closer to the subject position. In such a case, if the peak position of the focus evaluation value is detected as the in-focus position, the subject cannot be focused.

  On the other hand, when the image signal is not saturated, the image signals of the plurality of adjacent imaging pixels 221 do not become a constant value (output upper limit value) due to saturation, and the contour of the subject at the subject position does not occur. The corresponding high frequency component (contrast) can be detected appropriately. Therefore, as shown in FIG. 4, when the image signal is not saturated, only one peak of the focus evaluation value can be appropriately detected at the subject position. Therefore, in this embodiment, when the image signal is not saturated, the peak position of the focus evaluation value is detected as the in-focus position. The camera control unit 21 performs calculations such as a three-point interpolation method using these focus evaluation values when the focus evaluation value rises twice and then moves down twice. Thus, the peak position of the focus evaluation value can be detected.

  In step S106, the camera control unit 21 performs focus driving for driving the focus lens 32 to the focus position (the peak position of the focus evaluation value) detected in step S105. Specifically, the camera control unit 21 calculates a lens drive amount necessary for driving the focus lens 32 to the in-focus position, and the calculated lens drive amount is sent to the lens drive motor 36 via the lens control unit 37. To send. Then, the lens driving motor 36 drives the focus lens 32 to the in-focus position based on the received lens driving amount.

  On the other hand, if it is determined in step S104 that the image signal is saturated by the point light source, the process proceeds to step S107. In step S107, the lens position where the point light source evaluation value is minimized is determined by the camera control unit 21. It is detected as the in-focus position. Here, in a scene where a point light source is detected, such as a scene where illumination is shot during night scene shooting, there are many cases where it is preferable to focus on the point light source, so the camera control unit 21 applies to a high-luminance subject that is a point light source. The in-focus lens position is detected as the in-focus position.

  Here, the more focused a high-luminance subject that is a point light source, the smaller the image of the point light source, and the corresponding number of image pickup pixels 221 that are saturated by the point light source. Therefore, when a point light source exists in the focus detection area AFP, the point light source evaluation value obtained by integrating the image signals in the focus detection area AFP tends to decrease as the point light source is focused. Therefore, the camera control unit 21 detects the lens position at which the point light source evaluation value is minimum as the lens position that focuses on the high-luminance subject that is the point light source, that is, the point light source position.

  FIG. 5 is a diagram illustrating an example of the focus evaluation value and the point light source evaluation value when the image signal is saturated by the point light source. For example, if the subject is a point light source and the image signal of the imaging pixel 221 is saturated by the point light source, such as when shooting illumination at night, as shown in FIG. 5, the subject (point light source) is in focus. In some cases, the focus evaluation value decreases at a lens position (subject position) that matches, and the peak of the focus evaluation value cannot be detected at the subject position. On the other hand, the point light source evaluation value is the smallest value at the lens position (subject position) that focuses on the high-brightness subject that is the point light source, and thus the lens position where the point light source evaluation value is the minimum is focused. By detecting the position, it is possible to focus on the subject (point light source). Then, the process proceeds to step S106, and in-focus driving is performed to drive the focus lens 32 to the in-focus position detected in step S107 (the lens position where the point light source evaluation value is minimum).

  If it is determined in step S103 that the face area of the person has been detected, the process proceeds to step S108. In step S108, the camera control unit 21 specifies a focus detection area AFP including a human face area as a detection target area AFP for performing focus detection. In step S109, as in step S104, it is determined whether the image signal is saturated by the point light source.

  If it is determined in step S109 that the image signal is not saturated by the point light source, the process proceeds to step S110. In step S110, as in step S105, the focus lens position where the focus evaluation value is maximum is in focus. It is detected as a position. On the other hand, if it is determined in step S109 that the image signal is saturated by the point light source, the process proceeds to step S111.

  In step S111, the camera control unit 21 detects the lens position at which the maximum high-frequency value is maximum in the detection target area AFP as the focus position. Here, when photographing a specific subject (person's face) wearing glasses during night photography, for example, the camera 1, the specific subject (person's face), and the point light source are in the positional relationship shown in FIG. 6. In such a case, the point light source may be reflected by the glasses, and in such a case, if the lens position where the point light source evaluation value is minimum is detected as the in-focus position, the point light source is focused. May be unable to focus on the person's face. That is, as shown in FIG. 6, the distance D2 in the optical axis direction from the specific subject (human face) to the image sensor 22 and the optical axis direction from the point light source to the specific subject (human face) to the image sensor 22. Since the distance D1 + D2 is different, if the point light source is focused, it may not be possible to focus on the human face. FIG. 6 is a diagram illustrating an example of a positional relationship among the camera 1, a specific subject (human face), and a point light source.

  FIG. 7 is a diagram illustrating an example of a focus evaluation value, a point light source evaluation value, and a high frequency maximum value in a scene where the point light source is reflected by glasses. In a scene where the point light source is reflected on the glasses, as shown in FIG. 6, the distance D2 from the image sensor 22 to the subject is different from the distance D1 + D2 from the image sensor 22 to the point light source. Therefore, as shown in FIG. 7, the point light source evaluation value is minimum at the point light source position where the point light source is focused, and when the focus lens 32 is driven to the lens position where the point light source evaluation value is minimum, The point light source is in focus, and it is not possible to shoot an image in which the specific subject (human face) is in focus.

  On the other hand, the high frequency maximum value is a value corresponding to the high frequency component (contrast) of the subject, and the lens position where the maximum high frequency value is the maximum can be said to be the lens position where the high frequency component (contrast) of the subject is the largest. . Therefore, by detecting the lens position where the maximum high-frequency value is maximum as the in-focus position, it is possible to appropriately capture an image focused on a specific subject (human face).

  In addition, when the image signal is saturated by the point light source, the focus evaluation value obtained by integrating the high frequency signals of the plurality of imaging pixels 221 is greatly affected by the saturation by the point light source, but the maximum high frequency value is a plurality of values. Since it is the value of the high-frequency signal of one imaging pixel 221 having the largest value among the imaging pixels 221, the influence of saturation by the point light source can be reduced. Therefore, by detecting the lens position where the high frequency component is maximum as the in-focus position, the in-focus position corresponding to the specific subject (human face) can be detected even when the image signal is saturated by the point light source. Is possible. In step S106, focus drive is performed to drive the focus lens 32 to a focus position (a lens position where the maximum high-frequency value is maximum).

  As described above, in the present embodiment, when a human face region is specified in the focus detection area AFP when the image signal is saturated by the point light source, the lens position where the maximum high-frequency value is maximized is determined. It is detected as the in-focus position. Accordingly, as shown in FIG. 6, the distance D1 from the image sensor 22 to the specific subject (human face) is different from the distance D1 + D2 from the image sensor 22 to the specific subject (human face) to the point light source. If the high-luminance subject that is a point light source is in focus, the point light source is in focus, and even if the human face cannot be in focus, the maximum high-frequency value is maximum as shown in FIG. By detecting the lens position as the in-focus position, it is possible to appropriately capture an image focused on a specific subject (human face).

  In particular, in this embodiment, since the image signal is saturated by the point light source, the focus evaluation value obtained by integrating the high-frequency signals of the plurality of imaging pixels 221 focuses on the subject due to the influence of the saturation of the image signal by the point light source. Even when it is not possible to appropriately detect the lens position (in-focus position) that matches, the high-frequency maximum value that is the value of the high-frequency signal of one imaging pixel 221 having the largest value among the plurality of imaging pixels 221 is used. Since the influence of saturation by the point light source can be reduced, even when the image signal is saturated by the point light source, the lens position in focus on the target subject (human face) is appropriately detected as the in-focus position. be able to.

  Furthermore, in this embodiment, when the image signal is not saturated by the point light source, the lens position where the focus evaluation value is maximized is detected as the in-focus position. Thereby, in this embodiment, since a focus position can be detected based on the high frequency signal of the some imaging pixel 221, it can detect a focus position appropriately. Further, in the present embodiment, when the image signal is saturated by the point light source and the face area of the person is not detected, the lens position where the point light source evaluation value is minimum is determined as the in-focus position. Detect as. Also in this case, since the focus position can be appropriately detected based on the image signals of the plurality of imaging pixels 221, the focus position can be detected appropriately. As described above, in the present embodiment, it is possible to perform focus detection with higher accuracy by selectively using data for detecting the focus state of the optical system according to the shooting environment.

<< Second Embodiment >>
Next, the camera 1a according to the second embodiment will be described. As shown in FIG. 8, the camera 1 a according to the second embodiment includes an AF auxiliary light emitting unit 29 in addition to the configuration of the camera 1 according to the first embodiment. FIG. 8 is a configuration diagram showing a camera 1a according to the second embodiment.

  The AF auxiliary light emitting unit 29 emits AF auxiliary light under the control of the camera control unit 21. Specifically, the camera control unit 21 outputs a control signal for emitting AF auxiliary light when the subject is determined to have low brightness or the contrast of the subject is low. Send to the light emitting unit 29. Then, the AF auxiliary light emitting unit 29 performs AF auxiliary light emission driving based on this control signal.

  Next, the operation of the camera 1a according to the second embodiment will be described. FIG. 9 is a flowchart showing the operation of the camera 1a according to the second embodiment.

  In step S201, as in step S101 of the first embodiment, calculation of the focus evaluation value, the high frequency maximum value, the point light source evaluation value, and the image signal maximum value is started while driving the focus lens 32. In step S202, the camera control unit 21 determines whether the AF auxiliary light emitting unit 29 is emitting AF auxiliary light. For example, the camera control unit 21 outputs a control signal for emitting the AF auxiliary light when the subject is determined to have low brightness or the subject has a low contrast. When this control signal is sent to the AF auxiliary light emitting unit 29, it can be determined that the AF auxiliary light emitting unit 29 is emitting AF auxiliary light. If it is determined that the AF auxiliary light emitting unit 29 is emitting AF auxiliary light, the process proceeds to step S205, and the AF auxiliary light emitting unit 29 is emitting AF auxiliary light. If it is determined that there is not, the process proceeds to step S203.

  In step S203, as in step S105 of the first embodiment, the lens position at which the focus evaluation value is maximized is detected as the focus position. Then, in step S204, the focus lens 32 is moved to the focus position (focus evaluation value is Focusing driving is performed to drive the lens position to the maximum).

  If it is determined in step S202 that the AF auxiliary light emitting unit 29 is emitting AF auxiliary light, the process proceeds to step S205. In steps S205 to S212, the same processes as in steps S102 to S104 and S107 to S111 of the first embodiment are performed.

  That is, when the human face area is detected (step S205) and the human face area cannot be detected (step S206 = No), it is determined that the image signal is not saturated by the point light source (AF auxiliary light). If this is the case (step S207 = No), the lens position with the maximum focus evaluation value is detected as the in-focus position (step S203), and it is determined that the image signal is saturated by the point light source (AF auxiliary light). If it is detected (step S207 = Yes), the lens position with the smallest point light source evaluation value is detected as the in-focus position (step S208).

  When the face area of the person can be detected (step S206 = Yes), after the focus detection area AFP including the face area of the person is specified as the detection target area AFP (step S209), the detection target area AFP Then, it is determined whether or not the image signal is saturated by the point light source (AF auxiliary light) (step S210). If it is determined that the image signal is not saturated by the point light source (AF auxiliary light) (step S210 = No), the lens position where the focus evaluation value is maximum is detected as the focus position (step S211). ) When it is determined that the image signal is saturated by the point light source (AF auxiliary light) (step S210 = Yes), the lens position at which the maximum high-frequency value is maximum is detected as the in-focus position (step S210). S212).

  As described above, in the second embodiment, it is determined whether or not AF auxiliary light is emitted. When the AF auxiliary light is emitted, the image signal is saturated by the point light source (AF auxiliary light). When the face area of the person can be detected, the lens position where the maximum high frequency value is maximized is detected as the in-focus position. Thus, in the present embodiment, when AF auxiliary light is irradiated, even when the AF auxiliary light is reflected on the glasses of the person who is the target subject, it is possible to appropriately capture an image focused on the person's face. it can.

<< Third Embodiment >>
Next, the camera 1a according to the third embodiment will be described. As shown in FIG. 8, the camera 1 a according to the third embodiment has the same configuration as the camera 1 a according to the second embodiment, and operates according to the second embodiment except that it operates as described below. It operates similarly to the camera 1a.

  In the third embodiment, the photographer can select a focus detection area AFP for performing focus detection via the operation unit 28 of the camera 1a. When the focus detection area AFP is selected by the photographer via the operation unit 28, the camera control unit 21 sets the selected focus detection area AFP as the detection target area AFP.

  Next, the operation of the camera 1a according to the third embodiment will be described. FIG. 10 is a flowchart showing the operation of the camera 1a according to the third embodiment.

  In step S301, as in step S101 of the first embodiment, calculation of the focus evaluation value, the high frequency maximum value, the point light source evaluation value, and the image signal maximum value is started while driving the focus lens 32. In step S302, as in step S202 of the second embodiment, it is determined whether or not the AF auxiliary light emitting unit 29 is emitting AF auxiliary light. When the AF auxiliary light is not emitted, the process proceeds to step S303, and in step S303, the lens position at which the focus evaluation value is maximized is detected as the in-focus position, and then in step S304, the in-focus position is obtained. Focusing driving for driving the focus lens 32 is performed. On the other hand, if it is determined that AF auxiliary light is emitted, the process proceeds to step S305.

  In step S <b> 305, the camera control unit 21 determines whether the photographer has selected the detection target area AFP via the operation unit 28. If the photographer has selected the detection target area AFP via the operation unit 28, the process proceeds to step S306, and in step S307, the camera control unit 21 detects a human face area in the detection target area AFP. Is done. On the other hand, if the photographer has not selected the detection target area via the operation unit 28, the process proceeds to step S307, and the camera control unit 21 detects the human face area in all the focus detection areas AFP. .

  In step S308, the camera control unit 21 determines whether or not a human face area has been detected by detecting the face area in step S306 or step S307. If no human face area is detected, the process proceeds to step S309. In step S309, it is determined whether the image signal is saturated by the point light source (AF auxiliary light). If the image signal is not saturated by the point light source (AF auxiliary light), the focus evaluation value is determined. When the maximum lens position is detected as the in-focus position (step S303) and the image signal is saturated with the point light source (AF auxiliary light), the lens position with the minimum point light source evaluation value is the in-focus position. (Step S310).

  On the other hand, if a human face area is detected in step S308, the process proceeds to step S311. In step S311, it is determined whether the image signal is saturated by the point light source (AF auxiliary light). If the image signal is not saturated by the point light source (AF auxiliary light), the focus evaluation value is determined. When the maximum lens position is detected as the in-focus position (step S312) and the image signal is saturated by the point light source (AF auxiliary light), the lens position with the maximum high-frequency value is set as the in-focus position. It is detected (step S313).

  As described above, in the third embodiment, when the target detection area AFP selected by the photographer is selected via the operation unit 28, the face area of the person is selected in the selected target detection area AFP. Detection is performed. Then, in the target detection area AFP, when a human face is detected and it is determined that the image signal is saturated, the lens position where the maximum high-frequency value is maximum is detected as the in-focus position. As a result, in the present embodiment, in the scene where the focus detection area AFP including the specific subject (human face) is selected as the target detection area AFP by the photographer via the operation unit 28, the point light source is the spectacle of the target subject. Even when the light is reflected, it is possible to appropriately capture an image in which the face of the person is in focus.

  The embodiment described above is described for facilitating the understanding of the present invention, and is not described for limiting the present invention. Therefore, each element disclosed in the above embodiment is intended to include all design changes and equivalents belonging to the technical scope of the present invention.

  For example, in the above-described embodiment, the configuration in which the integrated value of the image signal is calculated as the point light source evaluation value is exemplified. However, the configuration is not limited to this configuration, and for example, the difference value between the integrated value of the image signal and the focus evaluation value May be calculated as a point light source evaluation value. Further, a difference value between a value obtained by multiplying the integrated value of the image signal by a predetermined coefficient and the focus evaluation value may be calculated as the point light source evaluation value. Also in these cases, since the point light source evaluation value is the smallest at the lens position corresponding to the point light source, the lens position where the point light source evaluation value is minimum can be detected as the point light source position.

  Further, in the above-described embodiment, when the maximum high frequency value in the detection target area AFP is calculated, high frequency signals are extracted from the image signals of all the imaging pixels 221 corresponding to the detection target area AFP, and the detection target area AFP is extracted. Although the configuration in which the maximum value among the high-frequency signals of all the corresponding imaging pixels 221 is calculated as the maximum high-frequency value is exemplified, the present invention is not limited to this configuration. For example, a predetermined number of imaging pixels corresponding to the detection target area AFP A configuration may be adopted in which a high-frequency signal is extracted from only 221 and the maximum value among the predetermined number of high-frequency signals is calculated as the maximum high-frequency value. Alternatively, the high-frequency signals of the imaging pixels 221 in the detection target area AFP may be integrated for each predetermined number of imaging pixels 221 and the maximum value among the integrated values of the plurality of high-frequency signals may be calculated as the maximum high-frequency value. . The same can be done when calculating the maximum value of the image signal.

  Furthermore, in the above-described embodiment, when the image signal is saturated by the point light source and the face area of the person is specified, a configuration in which the lens position where the maximum high-frequency value is maximum is detected as the in-focus position. Although illustrated, it is not limited to this configuration. For example, when it is determined whether a person is wearing glasses based on a captured image and it can be determined that the person is wearing glasses, the maximum value of the high frequency is The maximum lens position may be detected as the in-focus position.

  Further, in the above-described embodiment, the configuration in which the high-pass filter 211 is provided and a high-frequency signal is extracted from the image signal of the imaging pixel 221 by the high-pass filter 211 is illustrated. However, the present invention is not limited to this configuration. The frequency signal corresponding to a specific frequency component may be extracted from the image signal of the imaging pixel 221 using a band pass filter.

  The camera 1 of the embodiment described above is not particularly limited, and the present invention may be applied to other optical devices such as a digital video camera, a lens-integrated digital camera, and a camera for a mobile phone.

DESCRIPTION OF SYMBOLS 1 ... Digital camera 2 ... Camera body 21 ... Camera control part 211 ... High pass filter 212 ... 1st integration circuit 213 ... 1st maximum value circuit 214 ... 2nd integration circuit 215 ... 2nd maximum value circuit 22 ... Image pick-up element 221 ... Imaging Pixel 29 ... AF auxiliary light emitting unit 3 ... Lens barrel 32 ... Focus lens 36 ... Focus lens drive motor 37 ... Lens control unit

Claims (8)

An acquisition unit for acquiring an image signal corresponding to an image by an optical system including a focusing lens;
A specifying unit that specifies a face area included in the image as a specific subject based on the image signal;
A setting unit that sets, as a detection target region, the focus detection region corresponding to the specific subject among a plurality of focus detection regions set on an image plane by the optical system;
A detection unit for detecting a subject having a luminance of a predetermined value or higher as a high-luminance subject;
An extraction unit for extracting a frequency signal corresponding to a specific frequency component from the image signal;
A first integration value output unit for outputting as a first integration value by integrating a plurality of said frequency signal extracted in a plurality of image areas within the detection target area,
A second integrated value output unit that integrates the image signals in a plurality of image regions within the detection target region and outputs the result as a second integrated value;
And the maximum value output unit for outputting a maximum value of a plurality of said frequency signal extracted in a plurality of image areas within the detection target area,
Using the first cumulative value or previous Symbol maximum value, and a focus detection unit which detects a focus state of said optical system,
The focus detection unit
Wherein the face region by the identification unit is specified, and the high when the luminance subject is detected, prior SL using the maximum value to detect the focus state of the optical system by the detection unit in the detection target area,
When the face region by the specifying unit is specified and the high-luminance subject is not detected by the detection unit in the detection target region, the focus state of the optical system is detected using the first integrated value ,
The focus state of the optical system is detected using the second integrated value when the face area is not specified by the specifying unit and the high-luminance subject is detected by the detecting unit. Focus detection device. The focus detection apparatus according to claim 1,
The first integrated value output unit outputs an integrated value of the frequency signal for each predetermined lens position of the focus adjustment lens,
The maximum value output unit outputs the maximum value of the frequency signal for each predetermined lens position of the focus adjustment lens,
When the high-intensity subject is detected in the detection target area, the focus detection unit detects a lens position having the largest maximum value of the frequency signal as an in-focus position, and the high-frequency subject is detected in the detection target area. A focus detection apparatus that detects a lens position having the largest first integrated value as an in-focus position when a luminance subject is not detected. The focus detection apparatus according to claim 1 or 2,
The focus is such that the average value of the overall luminance of the image corresponding to the image is not more than a predetermined value, and the maximum value of the image signal while driving the optical system is the output upper limit value of the imaging pixel. A focus detection apparatus that detects the high-luminance subject by detecting a position of an adjustment lens. The focus detection apparatus according to claim 1,
A determination unit for determining whether or not the illumination light for illuminating the subject is emitted;
The focus detection unit determines the maximum value of the frequency signal when the determination unit determines that the illumination light is emitted and the detection unit detects the high-intensity subject in the detection target region. A focus detection apparatus that detects a focus state of the optical system. The focus detection apparatus according to claim 4,
The focus detection device, wherein the focus detection unit detects a focus state of the optical system using the first integrated value when the determination unit determines that the illumination light is not emitted. It is a focus detection apparatus in any one of Claims 1-5 ,
A focus detection apparatus comprising: a selection unit that allows a user to select one of the plurality of focus detection areas. It is a focus detection apparatus of Claim 6, Comprising:
When the one focus detection region is selected by the selection unit, the specifying unit sets the detection target region when the one focus detection region matches the focus detection region corresponding to the specific subject. A focus detection apparatus.   An imaging device comprising the focus detection device according to claim 1.

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