JP5531607B2 - Focus detection apparatus and imaging apparatus - Google Patents

Description

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

  Conventionally, based on the defocus amount obtained for the focus detection area, the plurality of focus detection areas are divided into a plurality of groups, a group corresponding to the main subject is selected from the plurality of groups, and the selected group There is known a technique for determining a focus detection area to be used for focus adjustment from among a plurality of focus detection areas belonging to (Patent Document 1).

JP 2008-65206 A

  However, in the prior art, in order to appropriately detect the focus state with respect to the subject, only the focus detection area with high reliability of the defocus amount is targeted for grouping, and when the luminance of the subject is low, It is difficult to obtain a highly reliable defocus amount, and many focus detection areas are excluded from the grouping target. As a result, focus detection accuracy for the subject may be insufficient.

  The problem to be solved by the present invention is to provide a focus detection device that can accurately detect a focus even when the luminance of a subject is low.

  The present invention solves the above problems by the following means. In addition, although the code | symbol corresponding to drawing which shows embodiment of this invention is attached | subjected and demonstrated, this code | symbol is only for making an understanding of invention easy, and is not the meaning which limits invention.

[1] A focus detection apparatus according to the present invention includes a light receiving unit (161d) that receives light beams corresponding to a plurality of focus detection positions set at a plurality of positions in an image plane by an optical system and outputs a light reception signal; Focus detection means (163) for detecting the focus state of the optical system based on the light reception signal, irradiation means (140) for irradiating a subject with illumination light, and when the illumination light is irradiated by the irradiation means First classification means (170) for classifying the plurality of focus detection positions into a plurality of first groups based on a difference between the obtained light reception signal and a light reception signal when the illumination light is not irradiated ; Second classification means (170) for classifying the focus detection positions included in the first group into a plurality of second groups based on the focus state with respect to the focus detection positions included in the first group. Features and That.

[2] In the invention according to the focus detecting device, before Symbol second classification means (170), out of the plurality of first group, the focus detection position belonging to the first group the difference is large, the second group It can be configured to be a target of classification.

[3] In the invention relating to the focus detection apparatus, the first classification unit (170) may further include the plurality of focus detection positions in a plurality of groups based on the focus state of the focus detection position in addition to the difference. Can be configured to classify.

  [4] In the invention related to the focus detection apparatus, the first determination criterion is used to determine the reliability of the focus state detected by the focus detection unit (163), and from the first determination criterion. Determination means (170) for determining the reliability of the focus state with respect to the focus detection position that is the object of classification by the second classification means (170) using the second determination criterion that is easily determined to be reliable. It can comprise.

  [5] In the invention relating to the focus detection apparatus, the determination unit (170) may be configured to change the second determination criterion according to the type of the illumination light.

  [6] In the invention relating to the focus detection apparatus, the determination unit (170) may be configured such that when the light is light having a uniform intensity, the light is light including contrast. The second determination criterion can be configured so as to be easily determined to be reliable.

  [7] In the invention relating to the focus detection apparatus, the focus detection unit (163) may be configured to redetect the focus state according to the classification result by the first classification unit (170). .

  [8] In the invention relating to the focus detection apparatus, an extraction unit (170) for extracting a first position having a predetermined brightness or more from the plurality of focus detection positions, and a first position excluding the first position. Determining means (162) for determining the accumulation condition of the light receiving means (161d) based on the light reception signal of the light receiving means corresponding to the position of 2, the focus detection means (163) is the determination means The re-detection process can be performed based on the received light signal stored under the storage condition determined in (1).

  [9] An imaging apparatus according to the present invention includes the focus detection apparatus.

  According to the present invention, focus detection can be performed with high accuracy even when the luminance of a subject is low.

FIG. 1 is a block diagram showing a camera 1 according to the present embodiment. FIG. 2 is a diagram illustrating a configuration example of the focus detection module 161. FIG. 3 is a diagram illustrating an arrangement example of a plurality of focus detection areas set in the imaging screen of the imaging optical system. FIG. 4 is a diagram for explaining a correspondence relationship between a plurality of focus detection areas set in the imaging screen of the imaging optical system and the line sensor 161d of the focus detection module 161. FIG. 5 is a flowchart showing the operation of the camera 1 according to the first embodiment. FIG. 6 is a diagram illustrating an example of a scene of a subject imaged on the imaging screen of the imaging optical system. FIG. 7 is a diagram illustrating an example of a correspondence relationship between a subject imaged in the imaging screen of the imaging optical system illustrated in FIG. 6 and a plurality of focus detection areas set in the imaging screen of the imaging optical system. FIG. 8 is a flowchart showing defocus amount calculation processing according to the first embodiment. FIG. 9 is a flowchart showing automatic selection AF processing according to the first embodiment. FIG. 10 is a flowchart showing the operation of the camera 1 according to the second embodiment. FIG. 11 is a flowchart showing a re-accumulation determination process according to the second embodiment.

  In the following, an embodiment in which the present invention is applied to a single-lens reflex digital camera will be described with reference to the drawings. However, the present invention can also be applied to other imaging devices such as a silver salt film camera.

<< First Embodiment >>
FIG. 1 is a block diagram showing a single-lens reflex digital camera 1 according to the present embodiment. The illustration and description of a general configuration of the camera other than the configuration related to the focus detection apparatus and the imaging apparatus of the present invention are partially omitted. To do.

  As shown in FIG. 1, the single-lens reflex digital camera 1 (hereinafter simply referred to as camera 1) of the present embodiment includes a camera body 100 and a lens barrel 200, and the camera body 100 and the lens barrel 200 are detachable. Combined as possible.

  The lens barrel 200 incorporates a photographing optical system including lenses 211, 212, 213 and a diaphragm 220.

  The focus lens 212 is provided so as to be movable along the optical axis L1 of the lens barrel 200, and its position is adjusted by the lens driving motor 230 while its position is detected by the encoder 260.

  The specific configuration of the moving mechanism along the optical axis L1 of the focus lens 212 is not particularly limited. For example, a rotating cylinder is rotatably inserted into a fixed cylinder fixed to the lens barrel 200, a helicoid groove (spiral groove) is formed on the inner peripheral surface of the rotating cylinder, and the focus lens 212 is fixed. The end of the lens frame is fitted into the helicoid groove. Then, by rotating the rotating cylinder by the lens driving motor 230, the focus lens 212 fixed to the lens frame moves linearly along the optical axis L1. The lens barrel 200 is provided with lenses 211 and 213 other than the focus lens 212. Here, the embodiment will be described by taking the focus lens 212 as an example.

  As described above, the focus lens 212 fixed to the lens frame by rotating the rotating barrel with respect to the lens barrel 200 moves straight in the direction of the optical axis L1, but the lens drive motor 230 as its drive source is operated by the lens mirror. The tube 200 is provided. The lens driving motor 230 and the rotating cylinder are connected by a transmission composed of a plurality of gears, for example, and when the driving shaft of the lens driving motor 230 is driven to rotate in any one direction, it is transmitted to the rotating cylinder at a predetermined gear ratio, and When the rotating cylinder rotates in any one direction, the focus lens 212 fixed to the lens frame moves straight in any direction of the optical axis L1. When the drive shaft of the lens drive motor 230 is rotated in the reverse direction, the plurality of gears constituting the transmission also rotate in the reverse direction, and the focus lens 212 moves straight in the reverse direction of the optical axis L1.

  The position of the focus lens 212 is detected by the encoder 260. As described above, the position of the focus lens 212 in the direction of the optical axis L1 correlates with the rotation angle of the rotating cylinder. Therefore, for example, if the relative rotation angle of the rotating cylinder with respect to the lens barrel 200 is detected, the position is obtained. Can do.

  As the encoder 260 of the present embodiment, an encoder that detects the rotation of a rotating disk coupled to the rotational drive of the rotating cylinder with an optical sensor such as a photo interrupter and outputs a pulse signal corresponding to the number of rotations, or a fixed cylinder And the contact point of the brush on the surface of the flexible printed wiring board provided on either one of the rotating cylinders, and the brush contact provided on the other, the amount of movement of the rotating cylinder (in either the rotational direction or the optical axis direction) A device that detects a change in the contact position according to the detection circuit using a detection circuit can be used.

  The aperture 220 has an aperture diameter centered on the optical axis L1 in order to limit the amount of light flux that passes through the imaging optical system and reaches the image sensor 110 provided in the camera body 100 and adjusts the amount of blur. It is configured to be adjustable. Adjustment of the aperture diameter by the aperture 220 is performed by transmitting an appropriate aperture diameter calculated in the automatic exposure mode from the camera control unit 170 to the aperture drive unit 240 via the lens control unit 250, for example. In addition, the adjustment of the aperture diameter is performed by a manual operation via the operation unit 150 provided in the camera body 100, and the set aperture diameter is transmitted from the camera control unit 170 to the aperture drive unit 240 via the lens control unit 250. Is also done. The aperture diameter of the aperture 220 is detected by an aperture aperture sensor (not shown), and the lens controller 250 recognizes the current aperture diameter.

  On the other hand, the camera body 100 includes a mirror system 120 for guiding the light flux from the subject to the image sensor 110, the finder 135, the photometric sensor 137, and the focus detection module 161. The mirror system 120 includes a quick return mirror 121 that rotates by a predetermined angle between the observation position and the imaging position of the subject around the rotation axis 123, and the quick return mirror 121 that is pivotally supported by the quick return mirror 121. And a sub mirror 122 that rotates in accordance with the rotation. In FIG. 1, a state where the mirror system 120 is at the observation position of the subject is indicated by a solid line, and a state where the mirror system 120 is at the imaging position of the subject is indicated by a two-dot chain line.

  The mirror system 120 is inserted on the optical path of the optical axis L1 in the state where the subject is at the observation position of the subject, while rotating so as to retract from the optical path of the optical axis L1 in the state where the subject is in the imaging position.

  The quick return mirror 121 is composed of a half mirror, and in a state where the subject is at the observation position, the quick return mirror 121 reflects a part of the light flux (optical axes L2 and L3) from the subject (optical axis L1). Then, the light is guided to the finder 135 and the photometric sensor 137, and a part of the light beam (optical axis L4) is transmitted to the sub mirror 122. On the other hand, the sub mirror 122 is configured by a total reflection mirror, and guides the light beam (optical axis L4) transmitted through the quick return mirror 121 to the focus detection module 161.

  Therefore, when the mirror system 120 is at the observation position, the light flux (optical axis L1) from the subject is guided to the finder 135, the photometric sensor 137, and the focus detection module 161, and the subject is observed by the photographer and exposure calculation is performed. And the focus adjustment state of the focus lens 212 is detected. Then, when the photographer fully presses the release button, the mirror system 120 rotates to the photographing position, and all the luminous flux (optical axis L1) from the subject is guided to the image sensor 110, and the photographed image data is stored in a memory (not shown). To do.

  The light flux (optical axis L2) from the subject reflected by the quick return mirror 121 forms an image on a focusing screen 131 disposed on a surface optically equivalent to the image sensor 110, and forms a pentaprism 133 and an eyepiece lens 134. It is possible to observe through. At this time, the transmissive liquid crystal display 132 superimposes and displays a focus detection area mark on the subject image on the focusing screen 131 and relates to shooting such as the shutter speed, aperture value, and number of shots in an area outside the subject image. Display information. As a result, the photographer can observe the subject, its background, and photographing related information through the finder 135 in the photographing preparation state.

  The photometric sensor 137 is composed of a two-dimensional color CCD image sensor or the like, and divides the photographing screen into a plurality of regions and outputs a photometric signal corresponding to the luminance of each region in order to calculate an exposure value at the time of photographing. A signal detected by the photometric sensor 137 is output to the camera control unit 170 and used for automatic exposure control.

  The AF illumination light emitting unit 140 is controlled by a control signal from the camera control unit 170 based on the output of the photometric sensor 137. The illumination light irradiated by the AF illumination light emitting unit 140 may be, for example, illumination light having a uniform intensity as a whole, or illumination light having a predetermined contrast pattern, and the type thereof is particularly It is not limited.

  The operation unit 150 includes, for example, a shutter release button, a mode setting switch for setting various operation modes of the camera 1, and the operation unit 150 is used to switch between an autofocus mode / manual focus mode and an autofocus. An automatic selection AF mode for automatically selecting a focus detection area to be used for focus adjustment among the modes can be selected. The shutter release button switch 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.

  The focus detection module 161 is a focus detection element for executing automatic focusing control by a phase difference detection method using subject light, and the imaging surface of the imaging element 110 of the light beam (optical axis L4) reflected by the sub-mirror 122. It is fixed at an optically equivalent position.

  FIG. 2 is a diagram illustrating a configuration example of the focus detection module 161 illustrated in FIG. The focus detection module 161 of this embodiment includes a condenser lens 161a, a diaphragm mask 161b in which a pair of openings are formed, a pair of re-imaging lenses 161c, and a pair of line sensors 161d. Although not shown, the line sensor 161d of the present embodiment includes a pixel having a microlens disposed in the vicinity of a planned focal plane of the imaging optical system and a photoelectric conversion element disposed with respect to the microlens. A plurality of pixel columns are provided. A pair of image signals can be acquired by receiving a pair of light fluxes passing through a pair of regions having different exit pupils of the focus lens 212 by each pixel arranged in the pair of line sensors 161d. The focus adjustment state can be detected by obtaining the phase shift between the pair of image signals acquired by the pair of line sensors 161d by a well-known correlation calculation described later.

  For example, as shown in FIG. 2, when the subject P is imaged on the equivalent plane (planned imaging plane) 161e of the image sensor 110, the focused state is achieved, but the focus lens 212 moves in the direction of the optical axis L1, If the imaging point deviates from the equivalent surface 161e toward the subject (referred to as the front pin) or deviates toward the camera body (referred to as the rear pin), the focus is shifted.

  When the imaging point of the subject P is shifted from the equivalent surface 161e toward the subject, the interval W between the pair of image signals detected by the pair of line sensors 161d becomes shorter than the interval W in the focused state, and vice versa. If the imaging point of the subject P is shifted to the camera body 100 side, the interval W between the pair of image signals detected by the pair of line sensors 161d becomes longer than the interval W in the focused state.

  That is, the image signal detected by the pair of line sensors 161d overlaps with the center of each line sensor 161d in the in-focus state, but the image signal deviates with respect to the center of the line sensor 161d in the out-of-focus state, That is, since a phase difference occurs, it is possible to focus by moving the focus lens 212 by an amount corresponding to this phase difference (deviation amount).

  Here, FIG. 3 shows an arrangement example of a plurality of focus detection areas set in the photographing screen 50 of the photographing optical system. As shown in FIG. 3, a plurality of focus detection areas AFP are set in the shooting screen 50 of the shooting optical system. In the present embodiment, the focus detection module 161 corresponds to each focus detection area AFP. As will be described later, a plurality of a pair of line sensors 161d are provided, so that an image signal in each focus detection area AFP can be acquired. In the present embodiment, as indicated by AFP 1 to 51 in FIG. 3, 51 focus detection areas AFP are provided, and each position corresponds to a predetermined position in the imaging range of the image sensor 110. The number and arrangement of the focus detection areas AFP are not limited to the mode shown in FIG.

FIG. 4 shows the correspondence between a plurality of focus detection areas set in the shooting screen 50 of the shooting optical system and the line sensor 161d of the focus detection module 161. As shown in FIG. 4, in the present embodiment, a total of 11 line sensors 161 d _{1 to} 161 d ₁₁ are provided, the line sensor 161 d ₁ is provided corresponding to the AFPs ₁ to 5, and the line sensor 161 d ₂ Are provided corresponding to the AFPs 6 to 10, and similarly, the line sensors 161d _{3 to} 161d ₁₁ are provided corresponding to the AFPs ₁₁ to 51, respectively. Each of the line sensors 161d _{1 to} 161d ₁₁ is composed of a pair (two) of line sensors. In FIG. 4, _{one of} the pair of line sensors constituting the line sensors 161d _{1 to} 161d ₁₁ is _one of them. Only the line sensor is shown. Furthermore, as shown in FIG. 4, each region _161d 10a _{~161d 10c} of the line sensor 161d ₁₀ corresponds to the focus detection area AFP46～48, by receiving the light beam in the region _{161d 10a} of the line sensor 161d ₁₀ obtained image signal which is the output as an image signal corresponding to AFP47, image signals obtained by receiving the light beam in the region _{161d 10b} of the line sensor 161d ₁₀ is outputted as an image signal corresponding to AFP46, the line sensor 161d ₁₀ An image signal obtained by receiving the light beam in the region 161d _10c is output as an image signal corresponding to the AFP48. Similarly, each region (not shown) in each of the pair of line sensors 161d _{1 to} 161d ₉ and 161d ₁₁ also corresponds to the focus detection areas AFP 1 to 45 and 49 to 51, respectively, and each of the pair of line sensors 161d ₃ to 161d ₃ image signal received in each region of 161d ₁₁ is output as an image signal corresponding to each focus detection area AFP1～45,49～51.

  Returning to FIG. 1, the AF-CCD control unit 162 controls accumulation conditions such as the gain and accumulation time of the line sensor 161 d of the focus detection module 161 in the autofocus mode, and is provided in the focus detection module 161. The image signals detected by the plurality of pairs of line sensors 161d are read in correspondence with the respective focus detection areas, and the read image signals are output to the camera control unit 170 and the defocus calculation unit 163.

Here, as described above, the pair of line sensors 161d of the focus detection module 161 are provided so as to correspond to the plurality of focus detection areas AFP, respectively, and the AF-CCD control unit 162 includes each pair of line sensors. The accumulation conditions such as gain and accumulation time are controlled every 161d. That is, a plurality of image signals corresponding to a plurality of focus detection areas corresponding to the same pair of line sensors 161d can be obtained under the same accumulation condition. For example, in the example shown in FIG. 4, since AFP46~48 corresponds to the same pair of line sensors 161d _10, AF-CCD controller 162, by controlling the accumulation conditions of the pair of line sensors 161d _10, Image signals corresponding to the AFPs 46 to 48 are obtained under the same accumulation conditions. A method of controlling the accumulation conditions such as the gain and the accumulation time is not particularly limited, for example, in the example shown in FIG. 4, AF-CCD controller 162, from the region _161d 10a _{~161d 10c} of the line sensor 161d ₁₀ Based on the obtained image signal, the luminance of the image signal corresponding to each of the AFPs 46 to 48 is determined, and the line sensor 161d ₁₀ is selected according to the luminance of the highest image signal among the luminances of the image signals respectively corresponding to the AFPs 46 to 48. And a method for controlling the gain and the accumulation time.

  The defocus calculation unit 163 converts a shift amount of a pair of image signals corresponding to each focus detection area sent from the AF-CCD control unit 162 into a defocus amount, and outputs this to the lens drive amount calculation unit 164. To do.

  Based on the defocus amount sent from the defocus calculation unit 163, the lens drive amount calculation unit 164 calculates a lens drive amount Δd corresponding to the defocus amount, and outputs this to the lens drive control unit 165. .

  The lens drive controller 165 drives the lens drive motor 230 based on the lens drive amount Δd sent from the lens drive amount calculator 164 and adjusts the position of the focus lens 212.

  The image sensor 110 is provided on the planned focal plane of the photographing optical system including the lenses 211, 212, and 213 on the optical axis L1 of the light beam from the subject of the camera body 100, and a shutter 111 is provided on the front surface thereof. ing. The image sensor 110 is a device in which a plurality of photoelectric conversion elements are two-dimensionally arranged, and can be composed of a device such as a two-dimensional CCD image sensor, MOS sensor, or CID. The image signal photoelectrically converted by the image sensor 110 is subjected to image processing by the camera control unit 170 and then stored in a memory (not shown). Note that the memory for storing the photographed image can be constituted by a built-in memory or a card-type memory.

  The camera control unit 170 is composed of peripheral components such as a microprocessor and a memory, reads an image signal from the image sensor 110, performs predetermined information processing as necessary, and outputs it to a memory (not shown). In addition, the camera control unit 170 controls the entire camera 1 such as correction of captured image information, detection of the focus adjustment state of the lens barrel 200, and detection of the aperture adjustment state.

  Further, in the present embodiment, the camera control unit 170 controls irradiation of illumination light for focus detection by the AF illumination light emitting unit 140 based on the output from the photometric sensor 137. Further, as will be described later, the camera control unit 170 calculates the luminance of the image signal in a state where the illumination light for focus detection is irradiated and the luminance of the image signal in a state where the illumination light for focus detection is not irradiated. Grouping of focus detection areas based on the difference (first stage grouping) and grouping of focus detection areas based on the defocus amount of the focus detection area (second stage grouping) are performed.

  Next, an operation example of the camera 1 according to the present embodiment will be described with reference to FIG. FIG. 5 is a flowchart showing the operation of the camera 1 according to this embodiment. In the following, a case will be described as an example in which the automatic selection AF mode for automatically selecting a focus detection area for use in focus adjustment is selected from among the autofocus modes.

First, in step S101, the camera control unit 170 confirms that the power is on and the automatic selection AF mode is selected from among the autofocus modes. Then, the process proceeds to step S102, and the focus detection module. Charge storage by 161 line sensor 161d is performed. The signal information stored in the line sensor 161d is read out by the AF-CCD control unit 162 corresponding to each focus detection area set in the shooting screen 50 of the imaging optical system, and is output to the camera control unit 170. The In the present embodiment, the storage conditions are controlled for each pair of line sensors 161d _{1 to} 161d ₁₁ by the AF-CCD control unit 162. That is, according to the luminance of the highest image signal among the luminances of the plurality of image signals obtained corresponding to the plurality of focus detection areas corresponding to the respective pairs of line sensors 161d _{1 to} 161d ₁₁ , the line sensor The accumulation condition of 161d is controlled.

  In step S103, the camera control unit 170 determines whether the shutter release button is half-pressed (the first switch SW1 is turned on). If it is determined that the first switch SW1 is on, the process proceeds to step S104. If it is determined that the first switch SW1 is not on, the process returns to step S101, and focus detection is performed until the first switch SW1 is turned on. Power storage by the line sensor 161d of the module 161 and output of the accumulated signal information are repeatedly performed.

  In step S104, the camera control unit 170 determines whether the luminance value of the subject is less than a predetermined value based on the output from the photometric sensor 137. If it is determined that the luminance value of the subject is less than the predetermined value, it is determined that the luminance of the subject is not sufficient for detecting the focus state, and the process proceeds to step S105 to irradiate the illumination light for focus detection. On the other hand, if it is determined that the luminance of the subject is equal to or higher than the predetermined value, the process proceeds to step S111.

  In step S105, since it is determined that the luminance of the subject is not sufficient for detecting the focus state, the camera control unit 170 controls the AF illumination light emitting unit 140 to emit illumination light for focus detection. A signal is transmitted, and irradiation of illumination light for focus detection is started by the AF illumination light emitting unit 140. In the subsequent step S106, electric charge is stored by the line sensor 161d of the focus detection module 161 in a state where illumination light for focus detection is emitted from the AF illumination light emitter 140. The signal information stored in the line sensor 161d is read out by the AF-CCD control unit 162 corresponding to each focus detection area AFP set in the shooting screen 50 of the imaging optical system. The data is output to the focus calculation unit 163. Then, the process proceeds to step S107, and irradiation of illumination light for focus detection by the AF illumination light emitting unit 140 is terminated. In step S106, accumulation conditions such as gain and accumulation time are controlled by the AF-CCD control unit 162 based on the output of the photometric sensor 137 obtained in a state where illumination light for focus detection is irradiated. The

  In step S108, as will be described later, the brightness of the image signal obtained when the illumination light for focus detection is emitted and the illumination light for focus detection are not emitted by the camera control unit 170 in step S108. The luminance of the obtained image signal is compared. In subsequent step S109, based on the comparison result in step S108, the plurality of focus detection areas set in the imaging screen of the imaging optical system are classified into subject area group SG and background area group BG (1). Step grouping). Here, in step S109, among the plurality of focus detection areas set in the imaging screen of the imaging optical system, the focus detection area corresponding to the subject existing in the irradiation range of the illumination light for focus detection is the subject area group. A region where the subject is not present in the irradiation range of the illumination light for focus detection, that is, a focus detection area corresponding to the background is classified into the background region group BG.

  Specifically, in step S108, the image signal corresponding to the focus detection area obtained in the state where the illumination light for focus detection is not irradiated in step S102 (when illumination light is not irradiated) and the focus detection in step S106. Brightness of the image signal corresponding to the focus detection area when the illumination light is not irradiated, based on the image signal corresponding to the focus detection area obtained when the illumination light is irradiated (when the illumination light is irradiated) It is determined whether or not the difference from the luminance of the image signal corresponding to the focus detection area at the time of illumination light irradiation is a predetermined value S or more. In step S109, the focus detection in which the difference between the luminance of the image signal corresponding to the focus detection area when illumination light is not irradiated and the luminance of the image signal corresponding to the focus detection area when illumination light is irradiated is equal to or greater than a predetermined value S. The area is determined to be a focus detection area corresponding to a subject existing in the irradiation range of the illumination light for focus detection, and is classified into the subject region group SG. On the other hand, the focus detection area in which the difference between the brightness of the image signal corresponding to the focus detection area when illumination light is not irradiated and the brightness of the image signal corresponding to the focus detection area when illumination light is irradiated is less than a predetermined value S The subject is not present in the irradiation range of the illumination light for detection, and is determined to be a focus detection area corresponding to the background, and is classified into the background region group BG.

  Here, FIG. 6 is a diagram illustrating an example of a scene of a subject imaged in the imaging screen 50 of the imaging optical system, and FIG. 7 is an image captured in the imaging screen 50 of the imaging optical system illustrated in FIG. It is a figure which shows an example of the correspondence of a to-be-photographed object and the some focus detection area set in the imaging | photography screen 50 of an imaging optical system. 6 and 7 exemplify scenes in which the first subject (person) and the second subject (tree) are imaged in the imaging screen 50 of the imaging optical system. For example, in the example shown in FIGS. 6 and 7, when the first subject and the second subject shown in FIG. 6 exist in the illumination range of the focus detection illumination light, the focus detection illumination light is irradiated in step S105. Is started, the first subject and the second subject shown in FIG. 6 are irradiated with the irradiation light. Therefore, as shown in FIG. 7, focus detection areas AFP1, 3, 5, 6, 8, and 10 corresponding to the first subject, and focus detection areas AFP4, 12, 14, 21 to 25 corresponding to the second subject, 32, 34, and 44 correspond to the brightness of the image signal corresponding to the focus detection area AFP at the time of non-illumination illumination obtained in step S102 and the focus detection area AFP at the time of illumination light illumination obtained in step S106. The difference between the brightness of the image signal to be detected is determined to be equal to or greater than the predetermined value S, and the image signal is classified into the subject area group SG. On the other hand, for areas other than the first subject and the second subject, that is, focus detection areas AFP2, 7, 9, 11, 13, 15-20, 26-31, 33, 35-43, 45-51 corresponding to the background. Since the subject does not exist in the region where the irradiation light can be irradiated and the irradiation of the irradiation light for focus detection is started in step S105, the luminance of the obtained image signal does not change before and after the irradiation light irradiation starts. The difference between the luminance of the image signal corresponding to the focus detection area AFP at the time of non-illumination illumination obtained in step S102 and the luminance of the image signal corresponding to the focus detection area AFP at the time of illumination light irradiation obtained in step S106. Is determined to be less than the predetermined value S, and is classified into the background region group BG.

  Next, in step S110, defocus amount calculation processing for calculating the defocus amount of the focus detection area is performed for each group classified in step S109. Hereinafter, the defocus amount calculation processing in step S110 will be described with reference to FIG. FIG. 8 is a flowchart showing a defocus amount calculation process according to the present embodiment.

  First, in step S201, the defocus calculation unit 163 calculates an image shift amount by the phase difference detection method based on a pair of image signals detected corresponding to each focus detection area belonging to the subject region group SG. The defocus amount of each focus detection area belonging to the subject area group SG is calculated.

  Here, an example of the defocus amount calculation process (correlation calculation process) will be briefly described.

A pair of line sensors 161d corresponding to each focus detection area is composed of a plurality of photoelectric conversion pixels, and a plurality of output signal sequences a [1],. . . , A [n], b [1],. . . b [n] is output. Then, the correlation calculation is performed while the data in a predetermined range of the pair of output signal sequences is relatively shifted by k by predetermined data.
C (k) = Σ | a (n + k) −b (n) | (1)
In the above equation (1), the Σ operation indicates a cumulative operation (phase sum operation) for n, and is limited to a range in which data of a (n + k) and b (n) exist according to the image shift amount k. The The image shift amount k is an integer, and is a shift amount in units of the pixel interval of the pixel column arranged in the line sensor 161d. In the calculation result of the above formula (1), the correlation amount C (k) becomes minimal (the smaller the correlation is, the higher the correlation is) in the shift amount k where the correlation between the pair of data is high.

Next, a shift amount x that gives a minimum value C (x) with respect to a continuous correlation amount is obtained using a three-point interpolation method shown in the following formulas (2) to (5). Note that C (kj) shown in the following equation is the smallest value among the correlation amounts C (k) obtained in the above equation (1).
D = {C (kj−1) −C (kj + 1)} / 2 (2)
C (x) = C (kj) − | D | (3)
x = kj + D / SLOP (4)
SLOP = MAX {C (kj + 1) -C (kj), C (kj-1) -C (kj)} (5)

The defocus amount df is calculated from the shift amount x by the following equation.
df = Kf · x (6)
In the above equation (6), Kf is a constant determined by the pitch width of the photoelectric conversion pixels of the line sensor 161d.

The defocus amount obtained in this way is output to the camera control unit 170, and the camera control unit 170 determines whether or not there is reliability. The reliability of the defocus amount is determined based on whether or not the conditions shown in the following formulas (7) to (9) are satisfied.
C (x) <C1 (7)
SLOP> E1 (8)
C (x) / SLOP <G1 (9)
In the above formulas (7) to (9), C1, E1, and G1 are determination reference values for determining the reliability of the defocus amount. When the degree of correlation between the pair of image signals is low, the value of the interpolated minimum amount C (x) of the correlation amount increases. Therefore, when the minimum value C (x) is less than the predetermined determination reference value C1, it is determined that the reliability of the calculated defocus amount is high. Since SLOP is a value proportional to the contrast, if SLOP is larger than a predetermined determination reference value E1, it is determined that the subject has high contrast and the calculated defocus amount is highly reliable. . Further, in order to normalize C (x) with the contrast of the image signal, when the value obtained by dividing C (x) by SLOP which is a value proportional to the contrast is less than a predetermined determination reference value G1, the calculated data It is determined that the reliability of the focus amount is high.

  If the correlation between the pair of image signals is low and the correlation amount C (k) does not drop in the shift range, the minimum value C (x) cannot be obtained. In such a case, the focus detection is impossible. Determined.

  Thus, in step S201, the defocus amount of each focus detection area belonging to the subject region group SG is calculated, and the reliability of the calculated defocus amount is determined. As will be described later, the focus detection area corresponding to the defocus amount determined to be reliable is classified into a plurality of defocus amounts when reclassifying the focus detection area in step S205, or in step S301. It is used when classifying into groups (grouping in the second stage).

  In subsequent step S202, the camera control unit 170 determines whether or not the defocus amount has been calculated for all focus detection areas belonging to the subject region group SG. If it is determined that the defocus amount has been calculated for all focus detection areas belonging to the subject region group SG, the process proceeds to step S203, while the defocus amount is calculated for all focus detection areas belonging to the subject region group SG. If it is determined that the defocus amount is not calculated, the calculation of the defocus amount is repeated until the defocus amount is calculated for all focus detection areas belonging to the subject region group SG.

  Next, in step S203, the camera control unit 170 calculates the defocus amount for each focus detection area belonging to the background region group BG, as in step S201, and determines the reliability of the calculated defocus amount. Then, the defocus amount determined to be reliable is output to the camera control unit 170. In step S204, as in step S202, it is determined whether the defocus amount has been calculated for all focus detection areas belonging to the background region group BG. If it is determined that the defocus amount has been calculated for all focus detection areas belonging to the background region group BG, the process proceeds to step S205, while the defocus amount is determined for all focus detection areas belonging to the background region group BG. If it is determined that the defocus amount has not been calculated, the calculation of the defocus amount is repeated until the defocus amount is calculated for all focus detection areas belonging to the background region group BG. Note that step S201 and step S203 may be performed in parallel, or step S203 may be performed prior to step S201.

  In step S205, the focus detection area is reclassified into the subject region group SG or the background region group BG based on the defocus amount of each focus detection area calculated in steps S201 and S203. A method for reclassifying the focus detection area into the subject region group SG and the background region group BG based on the defocus amount of the focus detection area is not particularly limited. For example, the subject region group SG (or the background region group BG) An average value of the defocus amounts of the plurality of focus detection areas classified into the subject region group SG (or the background region group BG) and the defocus amount of the focus detection area to be sold belonging to the subject region group SG (or the background region group BG) The focus detection area may be reclassified from the subject area group SG (or background area group BG) to the background area group BG (or subject area group SG) when the difference from the average value is a predetermined value or more. Good.

  Thereby, for example, an image signal corresponding to the same focus detection area due to camera shake caused by a photographer is obtained when the illumination light is not irradiated in step S102 and an image obtained when the illumination light is irradiated in step S106. When the signal corresponds to a different subject, the brightness of the image signal corresponding to the focus detection area when illumination light is not illuminated and the brightness of the image signal corresponding to the focus detection area when illumination light is illuminated Even if the focus detection area cannot be properly classified only by the difference, the focus detection area is reclassified into the subject area group SG or the background area group BG based on the defocus amount of each focus detection area. Each focus detection area can be appropriately classified into the subject area group SG and the background area group BG.

  Returning to FIG. 5, in step S112, an automatic selection AF process for selecting a focus detection area to be used for focus adjustment is performed. Hereinafter, the automatic selection AF process in step S112 will be described with reference to FIG. FIG. 9 is a flowchart showing automatic selection AF processing according to the present embodiment.

  First, in step S301, the camera control unit 170 further classifies the plurality of focus detection areas corresponding to the subject region group SG into a plurality of defocus amount groups based on the defocus amounts of these focus detection areas ( Second grouping). In the present embodiment, in order to appropriately classify the focus detection area into the defocus amount group, the defocus determined to be reliable based on a predetermined determination reference value for determining the reliability of the defocus amount. Only the focus detection area corresponding to the amount is classified into the defocus amount group. Hereinafter, a specific method for classifying a plurality of focus detection areas into a plurality of defocus amount groups based on the defocus amounts of the focus detection area will be described.

That is, first, the camera control unit 170 determines the variance v of the set of defocus amounts from the defocus amount Xi (i = 1 to N) of each focus detection area belonging to the subject region group SG according to the following equation (10). calculate.
v = Σ (Xi−X _ave ) ² / N (10)
In the above formula (10), X _ave is the average value of N defocus amounts, and Σ represents the sum of i = 1 to N. In addition, the defocus amount is not necessarily detected in all 51 focus detection areas AFP in the shooting screen 50. If there is a focus detection area where the focus state cannot be detected, or the defocus amount is obtained. However, as a result of the reliability determination, there may be cases where reliability is not considered. Therefore, in the present embodiment, the variance v of the set of defocus amounts is calculated according to the above equation (10) based on the defocus amounts of the N focus detection areas AFP excluding these.

Next, a standard deviation σ as a quantity representing the degree of variation in the set of N defocus amounts is calculated according to the following equation (11).
σ = √ (v) (11)

A defocus width H for grouping the N defocus amounts Xi (i = 1 to N) is determined by the following formula (12) using the standard deviation σ representing the variation degree of the set.
H = α · σ (12)
In the above formula (12), α is a coefficient, and usually about 0.4 to 0.6 is appropriate.

  Next, grouping of defocus amounts is performed by the following procedure using the defocus width H for grouping obtained above. First, the defocus amounts Xi (i = 1 to N) of the N focus detection areas AFP in which the defocus amounts are detected are arranged in ascending order of values, that is, in order from the closest defocus amount. For the defocus amounts arranged in order, when the difference between the defocus amounts before and after each other is equal to or smaller than the defocus width H for grouping, the defocus amounts that follow each other belong to the same defocus amount group. On the other hand, if the difference between the defocus amounts before and after each other is larger than the defocus width H for grouping, it is determined that the defocus amounts following each other belong to different defocus amount groups. .

  For example, in the example shown in FIGS. 6 and 7, when the shooting distance to the first subject (person) is short and the shooting distance to the second subject (tree) is long, each focus detection area belonging to the subject area group SG When the defocus amounts are arranged, the defocus amount of the focus detection area AFP (AFP1, 3, 5, 6, 8, 10) corresponding to the first subject, and then the focus detection area AFP (AFP4, AFP4 corresponding to the second subject). 12, 14, 21 to 25, 32, 34, 44). In this case, the defocus amount of the focus detection area AFP (AFP 1, 3, 5, 6, 8, 10) corresponding to the first subject and the focus detection area AFP (AFP 4, 12, 14,. 21 to 25, 32, 34, 44) is larger than the defocusing width H for grouping, and the focus detection areas (AFP1, 3, 5, 6) corresponding to the first subject. , 8, 10) and the focus detection areas (AFP4, 12, 14, 21 to 25, 32, 34, 44) corresponding to the second subject are classified into different defocus amount groups.

  Next, in step S302, the camera control unit 170 selects a defocus amount group from the plurality of defocus amount groups grouped in step S301. The selection method of the defocus amount group is not particularly limited, and a known method can be applied, but a method of selecting a defocus amount group that is likely to capture the main subject is preferable, For example, a method of selecting the closest defocus amount group, a method of selecting a defocus amount group including the focus detection area AFP located in the center portion in the photographing screen 50, and the like can be given.

  For example, in the example shown in FIGS. 6 and 7, when the shooting distance to the first subject (person) is short and the shooting distance to the second subject (tree) is long, the defocus amount group corresponding to the first subject and Of the defocus amount groups corresponding to the second subject, the defocus amount group corresponding to the first subject which is the closest defocus amount group is likely to capture the main subject. Selected as.

  In step S303, the camera control unit 170 selects a focus detection area to be used for focus adjustment from the focus detection areas belonging to the defocus amount group selected in step S302. A method for selecting a focus detection area for use in focus adjustment is not particularly limited, but the closest focus detection area is selected from among a plurality of focus detection areas belonging to the selected defocus amount group. Examples thereof include a method and a method of selecting a focus detection area located at the center portion in the shooting screen 50 among a plurality of focus detection areas belonging to the selected defocus amount group.

  For example, in the examples shown in FIGS. 6 and 7, the focus detection areas AFP1, 3, 5, 6, 8, and 10 belonging to the defocus amount group corresponding to the first subject are located at the center of the captured image 50. The AFP 1 is determined as a focus detection area for use in focus adjustment.

  In step S304, it is determined in step S303 whether or not a focus detection area to be used for focus adjustment has been determined from among a plurality of focus detection areas belonging to the subject region group SG. If the focus detection area to be used for focus adjustment is determined, the automatic selection AF process shown in FIG. 9 is terminated, and the process proceeds to step S113 shown in FIG. On the other hand, if a focus detection area for use in focus adjustment has not been determined, a step for determining a focus detection area for use in focus adjustment from among a plurality of focus detection areas belonging to the background region group BG is performed. The process proceeds to S305. In addition, as a case where the focus detection area to be used for focus adjustment is not determined, for example, when the focus state cannot be detected for all focus detection areas belonging to the subject region group SG, or the defocus amount is Even when the obtained focus detection area is present, there are cases where the reliability is determined to be unreliable as a result of the reliability determination.

  In step S305, based on the defocus amounts of the focus detection areas belonging to the background region group BG, the camera control unit 170 further converts the plurality of focus detection areas belonging to the background region group BG into a plurality of defocus amount groups. Classification (second grouping). Note that the method of classifying the plurality of focus detection areas belonging to the background region group BG into a plurality of defocus amount groups based on the defocus amount in step S305 is a plurality of focus detection belonging to the subject region group SG in step S301. The area can be performed by a method similar to the method of classifying the areas into a plurality of defocus amount groups based on the defocus amount.

  In steps S306 and S307, a defocus amount group is selected for the focus detection area corresponding to the background region group BG, as in steps S302 and S303 (step S306), and the focus detection area is used for focus adjustment. Is selected (step S307). As a result, the automatic selection AF process shown in FIG. 9 is terminated, and the process proceeds to step S113 shown in FIG.

  In step S113, it is determined whether or not a focus detection area to be used for focus adjustment in the automatic selection AF process in step S112 has been determined. That is, when a focus detection area to be used for focus adjustment among the plurality of focus detection areas belonging to the subject region group SG is determined in step S303 shown in FIG. 9, or a plurality of focus detection areas belonging to the background region group BG is determined in step S307. It is determined whether or not a focus detection area for use in focus adjustment in the focus detection area has been determined. If it is determined that a focus detection area for use in focus adjustment has been determined, the process proceeds to step S114. On the other hand, if it is determined that a focus detection area for use in focus adjustment has not been determined, the process proceeds to step S116.

  In step S <b> 114, the lens drive amount calculation unit 164 calculates a lens drive amount Δd corresponding to the defocus amount of the focus detection area used for focus adjustment, and the calculated lens drive amount Δd is sent to the lens drive control unit 165. Is output.

  In step S115, the lens drive control unit 165 sends a drive command to the focus lens drive motor 230 via the lens control unit 250 based on the lens drive amount Δd calculated in step S114. Is driven.

  On the other hand, if it is determined in step S113 that the focus detection area to be used for focus adjustment has not been determined, the process proceeds to step S116, and a scanning operation is performed. Specifically, the lens drive control unit 250 sends a lens drive signal to the focus lens drive motor 230, thereby driving the focus lens 212 in a predetermined direction and setting the defocus amount for each focus detection area. By performing the calculation, the focus state is searched. When the scanning operation in step S116 is completed, the process proceeds to step S117, and in-focus determination is performed.

  In step S117, the camera control unit 170 performs in-focus determination. For example, in the present embodiment, when the defocus amount in the focus detection area for focus adjustment is equal to or less than a predetermined value, it is determined to be in focus. If it is determined to be in focus, the process proceeds to step S118. On the other hand, if it is not determined to be in focus, the process returns to step S103, and the above-described processing is repeated until focus is achieved.

  In step S118, the camera control unit 170 determines whether or not the shutter release button has been fully pressed (the second switch SW2 is turned on). If it is determined that the second switch SW2 is on, the process proceeds to step S119, and an image is captured by the image sensor 110. Thereby, an image focused on the main subject is captured, and the captured image is transmitted to the camera control unit 170 and subjected to predetermined processing, and then stored as image data in a memory (not shown). On the other hand, if it is determined in step S118 that the second switch SW2 is off, the process returns to step S103, and the above-described processing is repeated until the second switch SW2 is turned on.

In the present embodiment, when the luminance of the subject is low and it is determined in step S104 that the luminance value of the subject is less than a predetermined value (step S104 = YES), the camera 1 operates as described above.
On the other hand, when the brightness of the subject is high and the brightness value of the subject is determined to be greater than or equal to a predetermined value in step S104 (step S104 = NO), the focus detection area is classified based on the brightness of the image signal corresponding to the focus detection area. (First grouping) is not performed, and the process proceeds to step S111. In step S111, the defocus amount is calculated for all focus detection areas by the same method as the defocus amount calculation method in step S201 described above, and the reliability of the defocus amount is determined. In step S112, the focus detection areas corresponding to the defocus amounts determined to be reliable among all the focus detection areas are classified into a plurality of defocus amount groups based on the calculated defocus amounts. The In the first embodiment, when determining the reliability of the defocus amount obtained in the state where the illumination light for focus detection is irradiated (steps S201 and S203), the illumination light for focus detection is used. In the case where the reliability of the defocus amount obtained in the state of no irradiation is determined (step S111), the reliability of the defocus amount is determined using the same determination reference value.

  As described above, in the present embodiment, the luminance of the image signal with respect to the focus detection area obtained in a state where the illumination light for focus detection is not irradiated and the illumination light for focus detection are obtained. Whether each focus detection area is an area corresponding to a subject existing in the irradiation range of the irradiation light for focus detection based on the difference between the brightness of the image signal with respect to the selected focus detection area, or for focus detection It is determined whether there is no subject in the irradiation light irradiation range, that is, an area corresponding to the background, and each focus detection area is a subject region including a focus detection area corresponding to a subject existing in the irradiation light irradiation range. The group is classified into a group SG and a background region group BG including a focus detection area corresponding to the background (first-stage grouping). Furthermore, in this embodiment, for each group of the subject region group SG and the background region group BG, the plurality of focus detection areas are further divided into a plurality of defocus amount groups based on the defocus amounts of these focus detection areas. (Second grouping). In particular, a plurality of focus detection areas belonging to the subject area group SG are divided into a plurality of defocus amount groups (second-stage grouping), and the main subjects are likely to be supplemented from the plurality of defocus groups. By selecting a focus amount group and determining a focus detection area to be used for focus adjustment from this group, the focus detection area corresponding to the subject is appropriately classified into the defocus amount group (second grouping). ). Accordingly, a plurality of focus detection areas can be appropriately classified into a plurality of defocus amount groups, and a defocus amount group corresponding to a main subject can be appropriately selected. The focus detection area can be appropriately determined. As a result, it is possible to appropriately detect the focus state with respect to the subject.

<< Second Embodiment >>
Next, 2nd Embodiment of this invention is described based on drawing. In the second embodiment, the camera 1 shown in FIG. 1 is the same as the first embodiment except that a re-accumulation determination process is performed in steps S411 and S412 as shown in FIG. Hereinafter, the re-accumulation determination process according to the second embodiment will be described with reference to FIGS. 10 and 11. FIG. 10 is a flowchart showing the operation of the camera 1 according to the second embodiment, and FIG. 11 is a flowchart showing the re-accumulation determination process according to the second embodiment.

  In steps S401 to S410, similarly to steps S101 to S110 of the first embodiment, the luminance of the image signal corresponding to the focus detection area when illumination light is not irradiated and the focus detection area when illumination light is irradiated are corresponded. Based on the difference from the luminance of the image signal, each focus detection area is classified into a subject area group SG and a background area group BG (first stage group), and a defocus amount is calculated for these focus detection areas. . Then, after the defocus amount calculation process is performed in step S410, the process proceeds to step S411. In step S411, a re-accumulation determination process is performed to determine whether to accumulate the image signal again by changing the accumulation condition of the line sensor 161d. Hereinafter, the re-accumulation determination process in step S411 will be described with reference to FIG.

  First, in step S501, it is determined whether this re-accumulation determination process has been performed even once. If it is determined that the re-accumulation determination process has been performed even once, the process proceeds to step S506, and after it is determined that the re-accumulation is not necessary, the re-accumulation determination process illustrated in FIG. On the other hand, if it is determined that the re-accumulation determination process has never been performed, the process proceeds to step S502.

  In step S502, the camera control unit 170 determines whether at least one focus detection area is classified into the subject region group SG. If it is determined that at least one focus detection area is classified in the subject area group SG, the process proceeds to step S506, and after it is determined that re-accumulation is not necessary, the re-accumulation determination process in FIG. The process proceeds to step S412 shown in FIG. On the other hand, if it is determined that the focus detection area is not classified into the subject region group SG, the process proceeds to step S503 in order to store the image signal by changing the storage condition of the line sensor 161d.

  In step S503, the AF irradiation light emitting unit 140 starts irradiation of illumination light for focus detection. In step S504, the AF-CCD control unit 162 changes the accumulation condition of the line sensor 161d. Hereinafter, an example of changing the accumulation condition of the line sensor 161d will be described.

  For example, for each focus detection area, the brightness of the image signal corresponding to the focus detection area obtained in step S402 and the illumination light non-irradiation obtained in step S406 is determined by the AF-CCD control unit 162. It is determined whether or not the luminance of the image signal corresponding to the current focus detection area is greater than or equal to a predetermined value L. When the brightness of the image signal corresponding to the focus detection area when illumination light is not irradiated and the brightness of the image signal corresponding to the focus detection area when illumination light is not irradiated are both equal to or greater than a predetermined value L, the focus detection area is It is determined that the focus detection area corresponds to a high-luminance subject such as a light source, and is excluded from the focus detection area that is the target of the accumulation condition. That is, the accumulation condition is determined based on the luminance of the image signal corresponding to the remaining focus detection areas other than the focus detection area.

For example, in the example shown in FIG. 4, the AFP 47 corresponds to a high-luminance subject such as a light source among the focus detection areas AFP 46 to 48 corresponding to the pair of line sensors 161d ₁₀ , and the illumination light non-obtained obtained in step S <b> 402 is not used. When the brightness of the image signal corresponding to the AFP 47 at the time of irradiation and the brightness of the AFP 47 at the time of non-irradiation of the illumination light obtained in step S406 are both equal to or greater than a predetermined value L, the accumulation condition of the line sensor 161d ₁₀ corresponds to the AFP 47. The storage condition according to the brightness of the image signal to be changed is changed to the storage condition according to the brightness of the highest image signal among the brightnesses of the image signals corresponding to the AFP 46 and AFP 48 excluding the AFP 47. Note that the accumulation conditions of the other line sensors 161d _{1 to} 161d ₉ and 161d ₁₁ other than the line sensor 161d ₁₀ are changed in the same manner.

  After the accumulation condition is changed in step S504, the process proceeds to step S505. After it is determined that re-accumulation is necessary, the re-accumulation process in FIG. 11 is terminated, and the process proceeds to step S412 shown in FIG.

  In step S412, the camera control unit 170 determines whether to perform re-accumulation based on the determination result of the re-accumulation determination process in step S411. If it is determined that re-accumulation is necessary, the process returns to step S406, and image signals are re-accumulated according to the changed accumulation condition. On the other hand, if it is determined that re-accumulation is not necessary, the process proceeds to step S414, and automatic selection AF processing is performed as in the first embodiment. If it is determined in step S412 that re-accumulation is necessary and the image signal is re-accumulated, if the focus detection area is not classified in the subject area group SG, the automatic selection AF process is not performed in step S414. In step S418, a scan operation may be performed.

  As described above, in the second embodiment, when the focus detection area is not classified into the subject region group SG, the luminance of the image signal corresponding to the focus detection area when illumination light is not irradiated and when illumination light is not irradiated. The accumulation condition of the line sensor 161d is changed based on the luminance of the image signal corresponding to the remaining focus detection area, except for the focus detection area where the luminance of the image signal corresponding to the focus detection area is equal to or greater than the predetermined value L. Image signals are re-accumulated under the changed accumulation conditions. Here, as shown in FIG. 4, each pair of line sensors 161d corresponds to a plurality of focus detection areas, respectively, and the AF-CCD control unit 162 includes a plurality of focus detection areas corresponding to the pair of line sensors 161d. The accumulation condition of the line sensor 161d is controlled according to the luminance of the highest image signal among the luminances of the image signals corresponding to. Therefore, when there is a focus detection area corresponding to a high-luminance subject such as a light source, the accumulation condition of the line sensor 161d corresponding to this focus detection area is controlled according to the luminance of the image signal such as the light source. Thus, image signals in other focus detection areas may not be detected properly. Even in such a case, according to the second embodiment, by controlling the accumulation condition of the line sensor 161d except for the focus detection area corresponding to a high-luminance subject such as a light source, the focus detection area is changed to the subject region group SG. And the background region group BG, and as a result, the focus state with respect to the subject can be detected appropriately.

«Third embodiment»
Next, a third embodiment of the present invention will be described. In the third embodiment, in the camera 1 shown in FIG. 1, when the reliability of the defocus amount is determined in step S201 shown in FIG. 8, the determination reference value for determining the reliability of the defocus amount is changed. Except this, it is the same as the first embodiment. Hereinafter, a specific method for determining the reliability of the defocus amount in the third embodiment will be described.

That is, as described above, in the first embodiment, when determining the reliability of the defocus amount (steps S201, S203, and S111), C (which is the minimum value of the interpolated correlation amount is uniformly set. x) and SLOP, which is a value proportional to contrast, have a defocus amount that satisfies the conditions of the following formulas (7) to (9) in relation to the determination reference values C1, E1, and G1 that are predetermined values. It is determined that there is.
C (x) <C1 (7)
SLOP> E1 (8)
C (x) / SLOP <G1 (9)

  On the other hand, in the third embodiment, in step S201, the reliability of the defocus amount of the focus detection area belonging to the subject region group SG obtained in the state where the illumination light for focus detection is irradiated is determined. In this case, the determination reference value for determining the reliability of the defocus amount is changed to a value that is easily determined to be reliable, and the reliability of the defocus amount is determined.

Specifically, as shown in the following formulas (13) to (15), the judgment reference value C1 in the above formula (7) is changed to a judgment reference value C2 that is more easily determined to be more reliable than the judgment reference value C1. The determination reference value E1 of the above equation (8) is changed to a determination reference value E2 that is more easily determined to be more reliable than the determination reference value E1, and the determination reference value G1 of the above equation (9) is changed from the determination reference value G1. The determination reference value G2 is easily changed to be determined to be reliable. Then, C (x) and SLOP determine that the defocus amount satisfying the conditions of the following formulas (13) to (15) is reliable in relation to these determination reference values C2, E2, and G2.
C (x) <C2 (where C1 <C2) (13)
SLOP> E2 (where E1> E2) (14)
C (x) / SLOP <G2 (where G1 <G2) (15)

  Note that predetermined values may be used as the determination reference values C2, E2, and G2 for determining the reliability of the defocus amount shown in the above formulas (13) to (15), or the focal point The determination reference values C2, E2, and G2 may be determined according to the type of illumination light for detection. As a configuration for determining the determination reference values C2, E2, and G2 according to the type of illumination light for focus detection, for example, when the illumination light for focus detection has a predetermined contrast pattern, a predetermined contrast is applied to the subject. Is generated, and it becomes easier to detect the defocus amount. Therefore, as compared with the case where the illumination light for focus detection has a uniform intensity, determination reference values C2, E2, and C2, for determining the reliability of the defocus amount. G2 may be configured to be changed to a value that is easily determined to be reliable.

  In addition to step S201, when determining the reliability of the defocus amount corresponding to the focus detection area belonging to the background region group BG in step S203, the determination reference value for determining the reliability of the defocus amount is changed. It is good also as composition to do. In this case, for example, the determination reference values C3, E3, and G3 for determining the reliability of the defocus amount in step S203 are the defocus obtained in the state in which the illumination light for focus detection is not irradiated in step S111. The reliability of the defocus amount of the focus detection area corresponding to the subject region group SG in step S201 is determined more easily than the determination reference values C1, E1, and G1 for determining the reliability of the amount. The determination reference values C2, E2, and G2 for determination may be changed to values that are less likely to be determined to be reliable.

  As described above, in this embodiment, the defocus amount of the focus detection area belonging to the subject region group SG obtained in the state where the AF illumination light emitting unit 140 irradiates the focus detection illumination light in step S201. Is more reliable than the case of determining the reliability of the defocus amount obtained when the AF illumination light emitting unit 140 is not irradiated with illumination light for focus detection. Is used to determine the reliability of the defocus amount. Here, the defocus amount obtained in a state where the illumination light for focus detection is irradiated, in particular, the defocus amount of the focus detection area belonging to the subject region group SG corresponding to the subject existing in the illumination light irradiation range, Compared to the defocus amount obtained when the illumination light for focus detection is not irradiated, the influence of noise is low, so the reliability of the defocus amount is determined using a criterion value that is easily determined to be reliable. By determining, while ensuring the reliability of the defocus amount targeted for defocus amount group classification, more focus detection areas can be targeted for defocus amount group classification. The focus state with respect to the subject can be detected appropriately.

  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.

DESCRIPTION OF SYMBOLS 1 ... Camera 100 ... Camera body 110 ... Image pick-up element 140 ... AF illumination light emission part 161 ... Focus detection module 162 ... AF-CCD control part 163 ... Defocus calculating part 164 ... Lens drive amount calculating part 165 ... Lens drive control part 170 ... Camera control unit 200 ... Lens barrel 212 ... Focus lens 230 ... Lens drive motor 250 ... Lens control unit

Claims (9)

A light receiving means for receiving a light beam corresponding to a plurality of focus detection positions set at a plurality of positions in an image plane by an optical system and outputting a light reception signal;
A focus detection means for detecting a focus state of the optical system based on the light reception signal;
An irradiation means for irradiating the subject with illumination light;
The plurality of focus detection positions are classified into a plurality of first groups based on a difference between the light reception signal obtained when the illumination light is irradiated by the irradiation unit and a light reception signal when the illumination light is not irradiated. First classification means for
Second classification means for classifying the focus detection positions included in the first group into a plurality of second groups based on the focus state with respect to the focus detection positions included in the predetermined first group. Focus detection device. The focus detection apparatus according to claim 1 ,
Before Stories second classification means, among the plurality of first group, the focus detection position belonging to the first group the difference is large, the focus detection device, characterized in that the target of the classification of the second group. The focus detection apparatus according to claim 1 or 2,
The first classification unit classifies the plurality of focus detection positions into a plurality of first groups based on a focus state of the focus detection position in addition to the difference . The focus detection apparatus according to any one of claims 1 to 3,
The first determination criterion is used to determine the reliability of the focus state detected by the focus detection unit, and the second determination criterion that is more easily determined to be more reliable than the first determination criterion is used. A focus detection apparatus comprising: a determination unit configured to determine reliability of a focus state with respect to a focus detection position that is a classification target by the second classification unit. The focus detection apparatus according to claim 4,
The determination unit changes the second determination reference according to the type of the illumination light. The focus detection apparatus according to claim 5,
In the case where the light is light having a uniform intensity, the determination means sets the second determination criterion to be easily determined to be reliable as compared to the case where the light is light including contrast. A focus detection device. The focus detection apparatus according to any one of claims 1 to 6,
The focus detection device, wherein the focus detection unit redetects the focus state in accordance with the classification result by the first classification unit. The focus detection apparatus according to claim 7,
An extracting means for extracting a first position having a predetermined brightness or more among the plurality of focus detection positions;
Determining means for determining an accumulation condition of the light receiving means based on a light reception signal of the light receiving means corresponding to a second position excluding the first position;
The focus detection apparatus, wherein the focus detection unit performs the re-detection process based on a light reception signal stored under the storage condition determined by the determination unit. The imaging device provided with the focus detection apparatus of any one of Claims 1-8.

Images