JP5338197B2 - Focus detection apparatus and imaging apparatus - Google Patents

Description

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

  There is known an autofocus device that detects a person's face from a captured image signal and sets an area in a predetermined range centered on the detected face as an AF area (for example, Patent Document 1).

2007-65290

  However, with the conventional autofocus device, there is a possibility that the focus cannot be accurately adjusted according to the condition of the subject.

The focus detection apparatus according to the first aspect of the present invention detects a face area including a human face from an image obtained by capturing an image by an optical system, and a first signal corresponding to the position of the eye of the face; A detection unit that outputs a second signal corresponding to the size of the face; a setting unit that sets a focus evaluation value calculation region at a position based on the first signal corresponding to the eye position; and a light beam from the optical system A light receiving unit that receives the light and generates a light reception signal, a calculation unit that calculates a focus evaluation value in the focus evaluation value calculation region using the light reception signal, and a control unit that performs focus adjustment control using the focus evaluation value The setting unit sets the size of the focus evaluation value calculation region so that only one eye is included based on the second signal corresponding to the size of the face, and the second signal Face size corresponding to the first predetermined value and the first The focus evaluation value calculation region is set between a maximum size and a minimum size according to the face size when the second signal is smaller than a second predetermined value smaller than the second predetermined value. When the face size corresponding to is greater than or equal to the first predetermined value, the size of the focus evaluation value calculation area is set to the maximum size, and the face size corresponding to the second signal is set to the second predetermined value. When the value is equal to or smaller than the value, the size of the focus evaluation value calculation area is set to the minimum size .

  According to the present invention, it is possible to focus on the face of the subject with high accuracy.

  FIG. 1 is a block diagram illustrating a configuration of an embodiment of a camera according to the present embodiment. The camera 100 includes an operation member 101, a lens 102, an image sensor 103, a control device 104, a memory card slot 105, and a monitor 106. The operation member 101 includes various operation buttons operated by the user. For example, the operation member 101 includes a power button, a release button, a zoom button, a cross button, an enter button, a play button, a delete button, and the like.

  The lens 102 is composed of a plurality of optical lenses, but is representatively represented by one lens in FIG. The lenses constituting the lens 102 include an AF lens for AF (Auto Focus / automatic focus adjustment) described later. The image sensor 103 is an image sensor such as a CCD or a CMOS, for example, and receives a light beam from the lens 102 to generate a light reception signal. Then, the generated light reception signal (image signal) is output to the control device 104.

  The control device 104 generates image data in a predetermined image format, for example, JPEG format (hereinafter referred to as “main image data”) based on the image signal input from the image sensor 103. Further, the control device 104 generates display image data, for example, thumbnail image data, based on the generated image data. The control device 104 generates an image file that includes the generated main image data and thumbnail image data, and further includes header information, and outputs the image file to the memory card slot 105. In the present embodiment, image file generation processing by the control device and recording processing of the generated image file on a memory card are referred to as photographing processing.

  The memory card slot 105 is a slot for inserting a memory card as a storage medium, and the image file output from the control device 104 is written and recorded on the memory card. The memory card slot 105 reads an image file stored in the memory card based on an instruction from the control device 104.

  The monitor 106 is a liquid crystal monitor (rear monitor) mounted on the back surface of the camera 100, and the monitor 106 displays an image stored in a memory card, a setting menu for setting the camera 100, and the like. . Further, when the operation member 101 is operated by the user and the start of live view is instructed by the user, the control device 104 outputs image data for display of images acquired in time series from the image sensor 103 to the monitor 106. As a result, a through image is displayed on the monitor 106.

  The control device 104 includes a CPU, a memory, and other peripheral circuits, and controls the camera 100. Note that the memory constituting the control device 104 includes SDRAM and flash memory. The SDRAM is a volatile memory, and is used as a work memory for the CPU to develop a program when the program is executed or as a buffer memory for temporarily recording data. The flash memory is a non-volatile memory in which data of a program executed by the control device 104, various parameters read during program execution, and the like are recorded.

  The camera 100 according to the present embodiment has a face recognition AF function that recognizes a human face on a through image and optimizes AF for the human face during shooting. For this purpose, the control device 104 executes a known face recognition process for each frame of the through image to recognize a human face. Then, the control device 104 performs focus adjustment using a known contrast detection method based on the recognized human face. In the present embodiment, a focus evaluation value calculation region for calculating a focus evaluation value is set at the position of the person's eyes, considering that it is desirable that the person's eyes are in focus.

  Specifically, when the face area is specified by the face recognition process, the control device 104 specifies the eye position based on the face area, and calculates a focus evaluation value for the eye position in the shooting screen. A focus evaluation value calculation area is set. For example, the control device 104 identifies an eye position by detecting an eye image from the image data. Alternatively, since the position of the eyes in the entire face is not greatly different even if there are some individual differences, an estimated position of the eyes with respect to the face area is set in advance. Then, when detecting the face area from the frame, the control device 104 specifies the position of the eye by estimating that there is an eye at a preset estimated position in the detected face area, and shooting the face area. A focus evaluation value calculation area is set at the position of the eye in the screen.

  At this time, as shown in FIG. 2A, the control device 104 sets the focus evaluation value calculation area 2b at the position of one of the left and right eyes included in the face area 2a. If two focus evaluation value calculation areas 2b are set for each eye, the distance from the camera 100 to the left and right eyes is different when the face is facing obliquely sideways (not facing the front). In other words, there is a possibility that the eye is in the middle of both eyes or in the farther distance from the camera 100. In order to avoid this, for example, the control device 104 sets a focus evaluation value calculation region at the position of the eye closer to the peripheral edge of the image.

  Further, when setting the focus evaluation value calculation area at the position of the person's eyes, the control device 104, as shown in FIG. 2A, the length of one side of the face area recognized by the face recognition process (face recognition). Based on (area length) 2c, the length (evaluation value calculation range length) 2d of one side of the focus evaluation value calculation area set in the photographing screen is determined. Specifically, in principle, the control device 104 makes the evaluation value calculation range length 2d proportional to the face recognition area length 2c. For example, as shown in FIG. 2C, the control device 104 sets the focus evaluation value calculation area so that the evaluation value calculation range length 2d is ½ of the face recognition area length 2c in principle.

  Further, the maximum value and the minimum value of the evaluation value calculation range length 2d are set in advance, and the control device 104 sets the evaluation value calculation range length 2d in proportion to the face recognition area length 2c. When 2d is equal to or greater than the maximum value, the evaluation value calculation range length 2d is fixed to the maximum value. For example, when the evaluation value calculation range length 2d is ½ of the face recognition area length 2c, the control device 104 has one side of the set focus evaluation value calculation area equal to or greater than the maximum value of the evaluation value calculation range length 2d. In other words, if the face recognition area length 2c is equal to or greater than twice the maximum value of the evaluation value calculation range length 2d, the evaluation value calculation range length 2d is set in advance as shown in FIG. It is set to the maximum value of the set evaluation value calculation range length 2d.

  On the other hand, as a result of making the evaluation value calculation range length 2d proportional to the face recognition area length 2c, the evaluation value calculation range length 2d is fixed to the minimum value when the evaluation value calculation range length 2d is equal to or smaller than the minimum value. To do. For example, if the evaluation value calculation range length 2d is ½ of the face recognition area length 2c, the control device 104 has one side of the set focus evaluation value calculation area equal to or smaller than the minimum value of the evaluation value calculation range length 2d. In other words, when the face recognition area length 2c is not longer than twice the minimum value of the evaluation value calculation range length 2d, the evaluation value calculation range length 2d is set in advance as shown in FIG. It is set to the minimum value of the set evaluation value calculation range length 2d.

  When the release button included in the operation member 101 is half-pressed by the user, the control device 104 uses the contrast detection method focus based on the received light signal from the image sensor 102 within the set focus evaluation value calculation area. A focus evaluation value necessary for adjustment is calculated, and focusing is performed based on the calculated focus evaluation value.

  In this way, by setting the focus evaluation value calculation region at the position of the person's eyes and performing focus adjustment, it is possible to prevent the eyes from blurring due to focusing on parts other than the eyes, such as hair. And focus on the subject's face with high accuracy. In addition, since the focus evaluation value calculation area is set at the position of one of the left and right eyes, it is possible to focus on the eyes with high accuracy even when the face is oriented obliquely.

  FIG. 3 is a flowchart showing processing of the camera 100 in the present embodiment. The processing shown in FIG. 3 is performed by the control device 104 as a program that is started when a live image is displayed on the monitor 106 when the operation member 101 is operated by the user to start live view. Executed.

  In step S10, the control device 104 temporarily sets the focus evaluation value calculation area at a predetermined position on the shooting screen, for example, the center of the shooting screen, and proceeds to step S20. At this time, the size of the focus evaluation value calculation area is set to a predetermined size. In step S20, the control device 104 recognizes the face of a person existing in the through image by executing a known face recognition process. Thereafter, the process proceeds to step S30, and the control device 104 determines whether or not a person's face has been recognized by the face recognition process. If a positive determination is made in step S30, the process proceeds to step S40.

  In step S40, the control device 104 acquires the size of the face area (face size) recognized by the face recognition process and the position of the face area (face position) in the through image, and proceeds to step S50. In step S50, the control device 104 displays a face area, for example, by displaying a frame indicating the face area on the through image, and proceeds to step S60.

  In step S60, the control device 104 determines whether or not the face size acquired in step S40 is greater than or equal to a predetermined value. For example, as described above with reference to FIG. 2, the face recognition area length 2c is the maximum of the evaluation value calculation range length 2d. It is determined whether or not the length is twice or more the value. If an affirmative determination is made in step S60, the process proceeds to step S70, and the control device 104 sets the size of the focus evaluation value calculation area to a preset maximum value. For example, as shown in FIG. 2A, the evaluation value calculation range length 2d is set to the maximum value of the preset evaluation value calculation range length 2d. Then, it progresses to step S110.

  On the other hand, if a negative determination is made in step S60, the process proceeds to step S80, and the control device 104 determines whether or not the face size acquired in step S40 is equal to or smaller than a predetermined value, for example, as described above with reference to FIG. It is determined whether the recognition area length 2c is less than or equal to twice the minimum value of the evaluation value calculation range length 2d. When an affirmative determination is made in step S80, the process proceeds to step S90, and the control device 104 sets the size of the focus evaluation value calculation area to a preset minimum value. For example, as shown in FIG. 2B, the evaluation value calculation range length 2d is set to the minimum value of the preset evaluation value calculation range length 2d. Then, it progresses to step S110.

  On the other hand, when a negative determination is made in step S80, the process proceeds to step S100, and the control device 104 makes the size of the focus evaluation value calculation area proportional to the size of the face area. For example, as illustrated in FIG. 2C, the control device 104 sets the focus evaluation value calculation region so that the evaluation value calculation range length 2d is ½ of the face recognition area length 2c. Then, it progresses to step S110.

  The control device 104 identifies the position of the eyes based on the face area, temporarily sets the center of the shooting screen in step S10, and sets the focus evaluation value calculation area whose size is set in step S70, S90, or S100 to the step In S110, the position is shifted to the eye position in the shooting screen. Then, it progresses to step S150 mentioned later.

  On the other hand, if a negative determination is made in step S30, the process proceeds to step S120. In step S120, the control device 104 determines whether or not a face has been detected by face recognition processing in a past frame acquired within a predetermined time from the current frame.

  When an affirmative determination is made in step S120, the process proceeds to step S130, and the control device 104 moves to a position on the shooting screen set based on the face area detected in the latest frame among the past frames in which the face has been detected. A focus evaluation value calculation area having the same size as that at that time is set, and the process proceeds to step S150. On the other hand, if a negative determination is made in step S120, the process proceeds to step S140, and the control device 104 sets the focus evaluation value calculation region to a predetermined position on the shooting screen, for example, the center of the shooting screen, and then step Proceed to S150. At this time, the size of the focus evaluation value calculation area is set to a predetermined size.

  In step S150, the control device 104 determines whether or not the release button included in the operation member 101 has been half-pressed by the user. If a negative determination is made in step S150, the process proceeds to step S190 described later. On the other hand, when an affirmative determination is made in step S150, the process proceeds to step S160, and the control device 104 determines the contrast based on the light reception signal from the image sensor 102 in the focus evaluation value calculation region set in the above-described processing. A focus evaluation value necessary for focus adjustment of the detection method is calculated, and focusing is performed based on the calculated focus evaluation value. Thereafter, the process proceeds to step S170.

  In step S170, the control device 104 determines whether or not the release button included in the operation member 101 has been fully pressed by the user. If a negative determination is made in step S170, the process proceeds to step S190 described later. On the other hand, when an affirmative determination is made in step S170, the process proceeds to step S180, and the control device 104 executes the above-described photographing process and proceeds to step S190.

  In step S190, the control device 104 determines whether or not the end of the live view is instructed by operating the operation member 101 by the user. If a negative determination is made in step S190, the process returns to step S20 to execute each process described above for the next frame. On the other hand, when an affirmative determination is made in step S190, the process ends.

According to the present embodiment described above, the following operational effects can be obtained.
(1) The control device 104 executes face recognition processing for each frame of the through image to detect the face area including the face of the person and the position of the human eye in the face area, and the size of the detected face area The focus evaluation value calculation area is set based on the eye position. As a result, the AF process can be performed so that the eyes of the person are in focus, and the face of the subject can be accurately focused.

(2) The control device 104 makes the size of the focus evaluation value calculation area proportional to the size of the face area. Accordingly, it is possible to set a focus evaluation value calculation area having an optimum size according to the size of the face area.

(3) The control device 104 fixes the size of the focus evaluation value calculation area to the maximum value when the size of the face area exceeds a predetermined size. Accordingly, it is possible to suppress a decrease in the processing speed of the control device 104 due to an increase in the size of the focus evaluation value calculation area.

(4) The control device 104 fixes the size of the focus evaluation value calculation area to the minimum value when the size of the face area is equal to or smaller than a predetermined size. As a result, the size of the focus evaluation value calculation area can be prevented from becoming unnecessarily small, and a reduction in focusing performance can be prevented.

(5) The control device 104 sets the focus evaluation value calculation region at the position of the eye closer to the peripheral edge of the image among the left and right eyes of the person. Thus, even when the distance from the camera 100 to the left and right eyes is different because the face is directed obliquely to the side, it is possible to reliably focus on one eye.

(6) If the face area cannot be detected even after performing the face recognition process, the control device 104 sets the focus evaluation value calculation area at a predetermined position on the shooting screen, for example, at the center of the shooting screen. . As a result, the AF process can be executed even when the face area cannot be detected. Even when shooting a scene without a person, for example, a landscape, with face recognition AF turned on, AF is performed in the center, so the photographer does not bother to change face recognition AF off. Can be recognized in advance.

(7) The control device 104 detects the face by the face recognition process in the past frame acquired within a predetermined time from the current frame even if the face area cannot be detected by performing the face recognition process. If it is, the focus evaluation value calculation area of the same size as that at that time is set at the position on the shooting screen set based on the face area detected in the latest frame among the past frames in which the face was detected. Was set. As a result, even when the face area cannot be detected for a moment, the AF process can be executed using the focus evaluation value calculation area in the past frame. Therefore, AF is not performed in the center area when half-pressed.

-Modification-
The camera according to the above-described embodiment can be modified as follows.
(1) In the above-described embodiment, the control device 104 has been described with respect to an example of performing focus adjustment using a known contrast detection method for a focus evaluation value calculation region set in the shooting screen. However, the present invention can also be applied to the case where the focus adjustment of a known phase difference method is performed for the focus evaluation value calculation region set in the shooting screen.

(2) In the above-described embodiment, the control device 104 has described the example in which the focus evaluation value calculation region is set at the position of the eye closer to the peripheral edge of the image among the left and right eyes of the person. However, the control device 104 temporarily sets focus evaluation value calculation areas at the positions of the left and right eyes, and a focus adjustment state detected based on a light reception signal from the image sensor 102 in these focus evaluation value calculation areas Among them, AF may be performed using the focus evaluation value calculated in the focus evaluation value calculation area set at the position of the eye indicating the closest.

(3) In the embodiment described above, the control device 104 has described an example in which the focus evaluation value calculation area is set so that the evaluation value calculation range length 2d is ½ of the face recognition area length 2c in principle. . However, the present invention is not limited to this, and the control device 104 may set the evaluation value calculation range length 2d to be a length between 2/5 and 3/5 of the face recognition area length 2c, for example.

  Note that the present invention is not limited to the configurations in the above-described embodiments as long as the characteristic functions of the present invention are not impaired. Moreover, it is good also as a structure which combined the above-mentioned embodiment and a some modification.

1 is a block diagram illustrating a configuration of an embodiment of a camera 100. FIG. It is a figure which shows the example of a setting of a focus evaluation value calculation area | region. FIG. 6 is a flowchart showing processing of the camera 100.

Explanation of symbols

100 Camera, 101 Operation member, 102 Lens, 103 Image sensor, 104 Control device, 105 Memory card slot, 106 Monitor

Claims (6)

A face region including a human face is detected from an image obtained by capturing an image by an optical system, and a first signal corresponding to the eye position of the face and a second signal corresponding to the size of the face are detected. A detector to output;
A setting unit that sets a focus evaluation value calculation region at a position based on a first signal corresponding to the eye position;
A light receiving unit that receives a light beam from the optical system and generates a light reception signal;
A calculation unit that calculates a focus evaluation value in the focus evaluation value calculation region using the received light signal;
A control unit that performs focus adjustment control using the focus evaluation value,
The setting unit, together with the eye on the basis of a second signal corresponding to the size of the face to set the size of the focus evaluation value calculation region to include only one face the second signal corresponding When the size is between a first predetermined value and a second predetermined value smaller than the first predetermined value, the size of the focus evaluation value calculation area is set between the maximum size and the minimum size. When the face size corresponding to the second signal is equal to or larger than the first predetermined value, the size of the focus evaluation value calculation area is set to the maximum size, and the second signal is set. When the face size corresponding to is less than or equal to the second predetermined value, the size of the focus evaluation value calculation region is set to the minimum size . The focus detection apparatus according to claim 1,
The focus detection device, wherein the detection unit specifies the position of the eye by estimating that the eye has an eye at a preset estimated position in the face area. The focus detection apparatus according to claim 1 or 2 ,
The setting unit uses a position on the light receiving unit corresponding to the position of the eye indicating the closest position among the focus adjustment states detected based on the light receiving signals corresponding to the left and right eyes of the person. The focus detection apparatus is characterized in that the range is set. In the focus detection apparatus as described in any one of Claims 1-3 ,
The focus detection device, wherein the setting unit sets the range with respect to a predetermined position on the light receiving unit when the face region is not detected by the detection unit. In the focus detection apparatus according to any one of claims 1 to 4 ,
The detection unit detects the face region from the repeatedly obtained image,
The focus detection apparatus according to claim 1, wherein when the detection unit does not detect the face area, the setting unit determines a range in the light receiving unit based on a past detection result of the face area. Imaging apparatus characterized by comprising a focus detecting device according to any one of claims 1-5.

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