JP2009192774A - Focus adjustment device and imaging device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a focus adjustment device and an imaging device for detecting a focal point optimal for a subject. <P>SOLUTION: The focus adjustment device comprises: an imaging means for imaging a subject image formed by an imaging optical system; a recognition means for recognizing parts of the subject based on the subject image (S204); a focus detection means for detecting the focus adjustment state of the imaging optical system based on a focus detection signal according to the image of the imaging optical system concerning a focus detection position set on a screen by the imaging optical system; and a detection direction determination means for determining a direction for detecting the focus detection signal in the focus detection position according to the recognized parts of the subject (S207). <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

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

  There is known an imaging apparatus that detects the position of a person's eyes and adjusts the focus of a photographing lens in a focus detection area corresponding to the position of the eyes (for example, see Patent Document 1).

Prior art documents related to the invention of this application include the following.
JP 2005-128156 A

  However, depending on the size and orientation of the person's face in the shooting screen, it is not always best to focus on the eyes. In the cross-shaped focus detection area, the vertical area and the horizontal direction are It is necessary to select which of the areas is used for focus adjustment.

(1) The invention of claim 1 is set in an image capturing unit that captures a subject image formed by the photographing optical system, a recognition unit that recognizes a part of the subject based on the subject image, and a screen formed by the photographing optical system. Focus detection means for detecting the focus adjustment state of the imaging optical system based on a focus detection signal corresponding to the image of the imaging optical system related to the focus detection position, and focus detection at the focus detection position according to the recognized subject part Detection direction determining means for determining the detection direction of the signal.
(2) The invention of claim 2 is the focus detection apparatus according to claim 1, wherein a plurality of focus detection areas having different detection directions of the focus detection signal intersect at the focus detection position, The priority order is set for each of the plurality of focus detection areas according to the recognized part of the subject.
(3) A third aspect of the present invention is the focus detection apparatus according to the first or second aspect, wherein a plurality of focus detection positions are set in the screen, and a magnification detection means for detecting a photographing magnification of the subject; Selecting means for selecting a focus detection position in accordance with the photographing magnification among the focus detection positions corresponding to the recognized part of the subject;
(4) According to a fourth aspect of the present invention, in the focus detection apparatus according to the third aspect of the present invention, the focus detection device includes a direction detection unit that detects the direction of the subject based on the subject image, and the selection unit detects the focus detection position according to the direction of the subject. Select.
(5) According to a fifth aspect of the present invention, in the focus detection apparatus according to the third or fourth aspect, the selection means selects the focus detection position according to the photographing magnification when the photographing magnification is smaller than the predetermined magnification. Is prohibited.
(6) According to a sixth aspect of the present invention, the focus detection apparatus according to any one of the first to fifth aspects and the focus adjustment of the photographing optical system based on the focus adjustment state detected by the focus detection means with respect to the detection direction. And a focus adjusting means.
(7) According to a seventh aspect of the present invention, in the focus adjustment apparatus according to the sixth aspect, the focus detection means detects a focus evaluation value related to the contrast of the subject image by the photographing optical system as a focus adjustment state, and the focus adjustment means The photographing optical system is positioned with the position where the focus evaluation value is maximized as the in-focus position.
(8) The invention according to an eighth aspect is an imaging apparatus including the focus detection apparatus according to any one of the first to fifth aspects.
(9) The invention according to claim 9 is the imaging apparatus according to claim 8, further comprising second imaging means for imaging a subject image by the imaging optical system, wherein the imaging means is arranged at a position different from the second imaging means. This is a photometric means for measuring the brightness of the subject.
(10) According to the tenth aspect of the present invention, an image pickup means for picking up a subject image formed by the photographing optical system, a recognition means for recognizing a part of the subject based on the subject image, and a screen set by the photographing optical system are set. A focus detection unit that detects a focus adjustment state of the imaging optical system with respect to the detected focus detection position, a magnification detection unit that detects a shooting magnification of a subject, and a focus detection position corresponding to a recognized subject part. Selection means for selecting a focus detection position accordingly.
(11) According to an eleventh aspect of the present invention, in the focus detection apparatus according to the tenth aspect, the apparatus includes a direction detection unit that detects the direction of the subject based on the subject image, and the selection unit detects the focus according to the direction of the subject. Select a position.
(12) According to a twelfth aspect of the present invention, the focus adjustment of the photographing optical system is performed based on the focus detection state of the focus detection device according to the tenth or eleventh aspect and the focus detection position selected by the selection means. And a focus adjustment unit that performs the focusing operation.

  According to the present invention, it is possible to perform optimum focus detection according to the subject.

  An embodiment in which the focus adjustment device and the imaging device of the present invention are applied to a single-lens reflex digital camera will be described. The present invention is not limited to a single-lens reflex camera, and can be applied to many cameras such as a compact camera.

  FIG. 1 shows a configuration of a single-lens reflex digital camera according to an embodiment. The photographing lens 1 includes a focusing lens, a zooming lens, a diaphragm, and the like, and forms a subject image on the imaging surface. The quick return mirror 2 is a mirror that selectively guides a light beam from a subject to an image sensor or a viewfinder, and a central portion is a half mirror. Before photographing, the quick return mirror 2 is set in the photographing optical path as shown, the subject light is reflected and guided to the finder, and a part of the subject light transmitted through the half mirror part is focused through the sub mirror 7. Guided to the detector. On the other hand, at the time of shooting, the quick return mirror 2 is retracted from the shooting optical path, and the subject light is guided to the imaging unit.

  A subject image is formed on the finder screen 3 by the photographing lens 1 and is visually recognized by the photographer through the pentaprism 4 and the eyepiece lens 5. The image sensor 6 is composed of a CCD or a CMOS, and converts the subject image formed on the light receiving surface by the photographing lens 1 into an image signal and outputs it. Note that an infrared cut filter for cutting infrared light and an optical low-pass filter for preventing image aliasing noise are arranged on the front surface of the image sensor 6, but these are not shown in FIG. . The sub mirror 7 reflects the subject light transmitted through the central half mirror part of the quick return mirror 2 before photographing and guides it to the focus detection part. At the time of shooting, the sub mirror 7 is retracted from the shooting optical path together with the quick return mirror 2.

  The phase difference AF (Auto Focus) detection element 8 separates the subject light for focus detection into a pair of light beams by a mask (not shown), and re-forms a pair of images on the pair of line sensors. The shift amount of the pair of images indicating the focus adjustment state is detected. The AF-CCD control unit 9 controls an appropriate gain and accumulation time of an AF CCD sensor (not shown, hereinafter referred to as an AF sensor) set corresponding to a plurality of AF areas in the shooting screen, and each AF The charge signal accumulated for each area is read out. The defocus calculation unit 10 calculates a defocus amount indicating the focus adjustment state of the photographing lens 1 based on the charge signal for each AF area read by the AF-CCD control unit 9.

  The lens drive amount calculation unit 11 calculates the drive amount of the focusing lens to the target position where the defocus amount becomes 0 based on the defocus amount calculated by the defocus calculation unit 10. The lens drive control unit 12 drives and controls the actuator 13 that drives the focusing lens, and adjusts the focus of the focusing lens according to the target drive amount. Part of the subject light guided to the viewfinder 4 is guided to the photometric sensor 15 via the photometric lens 14 and the brightness of the subject is measured. The operation member 16 includes various switches for operating the camera, such as an AF area selection switch, a shooting mode selection switch, a shutter button half-press switch, and a full-press switch.

  The control device 17 includes peripheral components such as a microcomputer, an A / D converter, and a memory, and performs sequence control of the camera and various calculations.

  FIG. 2 is a diagram in which an AF area 20 (shown by a thick square frame in the drawing) 20 that is visually recognized from the viewfinder and AF sensors 21 and 22 corresponding to each AF area 20 are overlapped. . In this embodiment, an example in which 47 AF areas are arranged in the shooting screen is shown. The 45 AF areas 20 in the center are formed by crossing the vertical and horizontal areas in a cross shape, and the vertical and horizontal areas have separate AF sensors 21 and 22, respectively. Focus detection can be performed. Note that the left and right AF areas 20 are composed of only vertical areas, and a vertical AF sensor 21 is disposed.

  FIG. 3 shows a finder image when a person's face is captured on the entire shooting screen. The magnification of the subject (face) is large, and a plurality of AF areas 20 correspond to the face portion. On the other hand, FIG. 4 shows a viewfinder image when a small person's face is captured in the shooting screen. The magnification of the subject (face) is small, and a small AF area 20 corresponds to the face portion as compared with FIG.

  As described above, depending on the size and orientation of the person's face in the shooting screen, it is not always best to focus on the eyes. In the cross-shaped AF area (cross area), It is necessary to select which of the vertical area and the horizontal area is used for focus adjustment.

Therefore, in this embodiment, in the cross area, whether the vertical area or the horizontal area is captured, or the average of the focus detection results of both areas is adopted, or the closest side of the focus detection result or high contrast As shown in Table 1, it is determined in advance for each part of the face such as eyes, nose, ears, mouth, contour, and other parts of the face. When the cross areas correspond to these parts, the AF area is selected according to Table 1 for each part.

  In Table 1, when the cross area corresponds to the eye part, the vertical area is selected, and focus detection is performed based on the output of the AF sensor in the vertical area. Since the human eye has a higher probability that the contrast in the vertical direction is clearer than that in the horizontal direction, focus detection can be reliably performed. If the cross area corresponds to the human nose, there is little difference in contrast between the vertical and horizontal areas. In this case, the closest focus detection result in the vertical and horizontal areas is obtained. Select the area that will be displayed. Even if the cross area corresponds to the part of the ear, it is considered that there is little difference in contrast between the vertical area and the horizontal area, so in this case, select the high contrast area of the vertical area and the horizontal area, Or the average of the focus detection results of both areas is adopted.

  When the cross area corresponds to the mouth area, the vertical area is selected because the contrast in the vertical direction is more likely to be clear than in the horizontal direction. When the cross area corresponds to the contour of the face, it is considered that there is a high probability that the contrast in the horizontal direction becomes clearer than that in the vertical direction, so the horizontal area is selected. On the other hand, when the cross area corresponds to the inside of the other face, a high contrast area is selected from the vertical area and the horizontal area, or the average of the focus detection results of both areas is adopted.

  Next, as shown in FIG. 3, when a person's face is captured on the entire shooting screen, the face parts other than the eyes correspond to different AF areas, but the eyes are not necessarily focused. In this embodiment, the AF area corresponding to each part of the face is determined according to the size of the face of the person in the shooting screen, that is, the magnification of the face and the orientation of the face. Set which one to preferentially select.

Table 2 shows the priority order of adoption of the AF area for the face part, which is set according to the face magnification and the face direction.

  When the magnification of the face is large and the face is facing the front with respect to the camera, the priority order of the AF area corresponding to the nose part is set to the highest, and the following is shown in Table 2 and FIG. 5A. Employment priorities are as follows. As a result, it is possible to obtain a picture of the best focus of the entire face rather than focusing on the eye part. When the magnification of the face is small and the face is facing the front of the camera, the priority order of the AF area corresponding to the eye part is set to the highest, and the following is shown in Table 2 and FIG. 5B. Employment priorities are as follows.

  When the magnification of the face is large and the face is facing sideways with respect to the camera, the priority of the AF area corresponding to the ear part is set highest, and as shown in Table 2 and FIG. Hiring priority. When the magnification of the face is small and the face is facing sideways with respect to the camera, the priority order of the AF area corresponding to the eye part is set to the highest, and as shown in Table 2 and FIG. Hiring priority.

  FIG. 6 is a flowchart showing the focus adjustment operation of the embodiment. In step 101, the microcomputer of the control device 17 (see FIG. 1) starts the focus adjustment operation when the release button half-press switch of the operation member 16 is turned on. In step 102, the subroutine shown in FIG. 7 is executed to perform face detection processing. This face detection process will be described later. In the subsequent step 103, an area selection processing subroutine shown in FIGS. 8 and 9 is executed to select an AF area for focus adjustment. This area selection process will be described later.

  In step 104, the lens drive amount from the current lens position to the target lens position is calculated based on the defocus amount detected in the area selected as the AF area for focus adjustment. In step 105, the focusing lens of the photographic lens 1 (see FIG. 1) is driven and driven to the target lens position.

  FIG. 7 is a flowchart illustrating a face detection processing subroutine according to one embodiment. In step 201, the skin color portion and the skin hue area of the person are extracted. In the next step 202, the face width is calculated based on the extracted person information. The lens information is obtained from the photographing lens 1, the magnification of the subject image is calculated based on the subject distance and the focal length included in the lens information, and the face width is estimated. In step 203, the area of the person's face is calculated based on the information obtained in steps 201 and 202. At this point, the outline of the person's face is recognized.

  In step 204, position information of each part of the face, that is, eyes, nose, mouth, ears, etc., is extracted based on information such as the outline of the face. In the next step 205, a confidence value of the extracted face information is calculated. If the face area information is sized in accordance with the size of the person's face and information on each part of the face is obtained, the reliability of the person's face information is assumed to be high. In step 206, an AF area corresponding to the person's face information is extracted.

  If the AF area corresponding to each part of the face is a cross area based on the face information of the person in step 207, the vertical area, the horizontal area, the area showing high contrast, both areas according to the selection table shown in Table 1 A focus adjustment area in the cross area, such as an average of the focus detection results of the two or an area indicating the closest focus detection result, is selected.

  8 and 9 are flowcharts illustrating an area selection processing subroutine according to one embodiment. In step 301, it is confirmed whether or not an AF area corresponding to the face position exists in the face detection process shown in FIG. If there is an AF area corresponding to the face position, the process proceeds to step 302, and it is determined whether the face information is reliable based on the reliability of the face information of the person calculated by the face detection process shown in FIG. To do.

  If there is an AF area corresponding to the face position and the face information is reliable, the process proceeds to step 303, where CCD accumulation is performed to optimize the sensor gain and charge accumulation time of the AF area corresponding to the human face. Take control. In step 304, charge accumulation data is read from the AF sensor corresponding to the face position, and the defocus amount is calculated based on the charge accumulation data read in step 305. In step 306, it is checked whether or not the reading of the charge accumulation data and the defocus amount calculation have been completed in all AF areas corresponding to the face position. If not completed, the process returns to step 304 to return the remaining corresponding to the face position. The above-described processing is performed in the AF area.

  When the defocus amount is calculated in all the AF areas corresponding to the face position, the process proceeds to step 307 to determine in which direction the person is facing the camera. In this embodiment, an example of determining whether the camera is facing the front or the side is shown. However, the orientation of the face with respect to the camera is not limited to the front and the side. May be added.

  Next, in steps 308 to 314 in FIG. 9, according to the magnification of the face of the person and the orientation of the face, the adoption priority order adopted for the AF area that performs focus adjustment from among the AF areas corresponding to each part of the face. Set. When the magnification of the face is large and the face is facing the front with respect to the camera, the adoption priority order shown in Table 2 and FIG.

  If the magnification of the face is large and the face is facing sideways with respect to the camera, the adoption priority order shown in Table 2 and FIG. When the magnification of the face is small and the face is facing the front with respect to the camera, the priority order of adoption shown in Table 2 and FIG. When the magnification of the face is small and the face is facing sideways with respect to the camera, the adoption priority order shown in Table 2 and FIG.

  In step 315 after setting the adoption priority order according to the magnification and orientation of the face, it is confirmed whether or not a reliable defocus amount is obtained from the AF area with the higher adoption priority order. In subsequent step 316, it is confirmed whether or not a reliable defocus amount is obtained in any of the AF areas corresponding to the face parts of the adoption priority order, and the adoption area can be determined.

  At this time, a reliable defocus amount is not always obtained in the AF area of the part having the highest adoption priority, but it is finally reliable in the AF area of the second, third or lower order. Defocus amount may be obtained. In any case, if a reliable defocus amount is obtained in any one of the AF areas corresponding to the facial part, the area is selected as an adoption area for performing focus adjustment regardless of the adoption priority. The process ends. If a reliable defocus amount cannot be obtained in all AF areas corresponding to each part of the face and the adopted area cannot be determined, the process proceeds to step 317, and the process is terminated as no adopted area.

  If there is no AF area corresponding to the face position in step 301, or if it is determined in step 302 that the face information is not reliable, the process proceeds to step 318, where the current AF mode is determined by the camera according to a predetermined algorithm. It is confirmed whether or not the automatic selection AF mode for automatically selecting any AF area is selected. If the automatic selection AF mode is set, the process proceeds to step 319, and the normal automatic selection AF mode processing is executed. The automatic selection AF mode processing is not directly related to the present invention and will not be described. On the other hand, if it is not the automatic selection AF mode, the process proceeds to step 320, and the AF area selected by the photographer with the area selection switch of the operation member 16 assuming that the manual selection AF mode is set is set as the adopted area for focus adjustment.

  In the above-described embodiment, the pupil division type phase difference detection method AF has been described as an example. However, this is based on a focus detection element independent of the image sensor, and for focus detection in the imaging pixel array. Focus detection may be performed by an image sensor in which the pixels are mixed. A signal indicating the sharpness of the image, for example, high-frequency component and contrast of the image, is extracted from the image signal of the image sensor while moving the focusing lens, and the sharpness is obtained by processing such as a high-pass filter, band-pass filter, or Fourier transform. The present invention can also be applied to contrast AF which detects a position where the maximum is detected and adjusts the focusing lens to that position. In the case of this contrast AF, the sharpness detection direction in the captured image may be changed in accordance with the magnification and direction of the person's face.

The figure which shows the structure of the single-lens reflex digital camera of one embodiment. The figure which shows arrangement | positioning of AF area in the imaging | photography screen of one Embodiment Figure showing the viewfinder image when a person's face is captured on the full shooting screen The figure which shows the finder image when the face of a small person is captured in the shooting screen The figure which shows the adoption priority of AF area according to the magnification and direction of the face The flowchart which shows the focus adjustment operation | movement of one Embodiment The flowchart which shows the face detection processing subroutine of one embodiment The flowchart which shows the area selection processing subroutine of one embodiment FIG. 8 is a flowchart illustrating an area selection processing subroutine according to the embodiment, following FIG.

Explanation of symbols

6; Image sensor, 8; Phase difference AF detection element, 10; Defocus calculation unit, 11; Lens drive amount calculation unit, 12; Lens drive control unit, 15; Photometric sensor, 17;

Claims (12)

Imaging means for imaging a subject image formed by the imaging optical system;
Recognizing means for recognizing a part of the subject based on the subject image;
Focus detection means for detecting a focus adjustment state of the photographing optical system based on a focus detection signal corresponding to an image of the photographing optical system related to a focus detection position set in a screen by the photographing optical system;
A focus detection apparatus comprising: a detection direction determination unit that determines a detection direction of the focus detection signal at the focus detection position in accordance with the recognized subject part. The focus detection apparatus according to claim 1,
The focus detection position intersects a plurality of focus detection areas with different detection directions of the focus detection signal,
The focus detection apparatus, wherein the detection direction determination means sets a priority order for each of the plurality of focus detection areas according to the recognized part of the subject. The focus detection apparatus according to claim 1 or 2,
A plurality of the focus detection positions are set in the screen,
A magnification detecting means for detecting a photographing magnification of the subject;
A focus detection apparatus comprising: a selection unit configured to select the focus detection position according to the photographing magnification among the focus detection positions corresponding to the recognized subject part. The focus detection apparatus according to claim 3,
Direction detecting means for detecting the direction of the subject based on the subject image;
The focus detection apparatus, wherein the selection means selects the focus detection position according to the direction of the subject. In the focus detection apparatus according to claim 3 or 4,
The focus detection apparatus, wherein the selection unit prohibits selection of the focus detection position according to the shooting magnification when the shooting magnification is smaller than a predetermined magnification. The focus detection apparatus according to any one of claims 1 to 5,
A focus adjustment apparatus comprising: a focus adjustment unit that performs focus adjustment of the photographing optical system based on a focus adjustment state detected by the focus detection unit with respect to the detection direction. The focusing apparatus according to claim 6, wherein
The focus detection unit detects a focus evaluation value related to a contrast of a subject image by the photographing optical system as the focus adjustment state,
The focus adjustment device, wherein the focus adjustment unit positions the photographing optical system with a position where the focus evaluation value is maximized as a focus position.   An imaging apparatus comprising the focus detection apparatus according to claim 1. The imaging device according to claim 8,
Second imaging means for imaging a subject image by the imaging optical system;
The imaging apparatus, wherein the imaging unit is a photometric unit that is arranged at a position different from the second imaging unit and measures the brightness of the subject. Imaging means for imaging a subject image formed by the imaging optical system;
Recognizing means for recognizing a part of the subject based on the subject image;
Focus detection means for detecting a focus adjustment state of the photographing optical system related to a focus detection position set in a screen by the photographing optical system;
A magnification detecting means for detecting a photographing magnification of the subject;
A focus detection apparatus comprising: a selection unit configured to select the focus detection position according to the photographing magnification among the focus detection positions corresponding to the recognized subject part. The focus detection apparatus according to claim 10, wherein
Direction detecting means for detecting the direction of the subject based on the subject image;
The focus detection apparatus, wherein the selection means selects the focus detection position according to the direction of the subject. The focus detection apparatus according to claim 10 or 11,
A focus adjustment device comprising: a focus adjustment unit configured to adjust a focus of the photographing optical system based on a focus adjustment state detected at a focus detection position selected by the selection unit.

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