JP2013120273A - Digital camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce consumption power.SOLUTION: A digital camera comprises: automatic photographing means 15 for automatically performing a photographing operation when a determination is made that a distance between a first focusing position relating to a first principle subject and a second focusing position related to a second principle subject is within a predetermined determination threshold; stopping means 15 for stopping a search operation of contrast type focus detecting means when the distance is determined to be out of the determination threshold; size detecting means 15 for detecting a change in the size of an image of at least one of the first and second principle subjects when the distance is determined to be out of the determination threshold; approach determining means 15 for determining based on the detected change in size that whether the first and second principle subjects have approached to each other; and exerting means 15 for cancelling the stop of a search operation when a determination is made that the first and second principle subjects have approached to each other, and exerting the search operation again.

Description

  The present invention relates to a digital camera.

  The following automatic imaging apparatus is known. The automatic imaging apparatus measures the distance from the automatic imaging apparatus to the first subject, sets a predetermined range including the measured distance as a range where photography is permitted, and then the range set by the second subject. When entering, the image is automatically taken (see Patent Document 1).

JP 2010-193423 A

  In the prior art, in order to monitor whether the second subject is within the set range, it is necessary to always perform a focusing operation to measure the distance from the automatic imaging device to the second subject, and to reduce power consumption. There was a problem that became larger.

  A digital camera according to the present invention periodically detects at least a first main subject and a second main subject from an image pickup unit that picks up a subject image by a photographing optical system and outputs a subject image signal, and the subject image signal. A subject recognizing unit that performs the search and a focus lens of the photographing optical system in the optical axis direction to detect a first in-focus position relating to the first main subject and a second in-focus position relating to the second main subject, respectively. Contrast-type focus detection means, focus adjustment means for performing focus adjustment based on at least one of the first focus position and the second focus position, and the first focus position and the second focus position. A distance determination unit that determines whether or not the distance is within a predetermined determination threshold, and automatic shooting that automatically performs a shooting operation when the distance determination unit determines that the distance is within the determination threshold And the distance determining means determine that the distance is outside the determination threshold, and the distance determining means determines that the distance is outside the determination threshold. The size detection means for detecting a change in the size of at least one of the first main subject and the second main subject, and the first main subject based on the size change detected by the size detection means. When it is determined that the first main subject and the second main subject are approaching each other by the approach determination unit that determines whether or not the second main subject is close to each other, And executing means for releasing the stop of the search operation by the stop means and re-executing the search operation.

  According to the present invention, power consumption can be reduced.

It is a block diagram explaining the structural example of the digital camera by one embodiment of this invention. It is a flowchart explaining an automatic imaging | photography mode process. It is a flowchart explaining a 1st AF process. It is a figure explaining the 1st AF processing. It is a figure explaining the relationship between the image size of a main subject, and a focus position. It is a figure explaining the relationship between the image size of a main subject, and a focus position. It is a flowchart explaining a 2nd AF process. It is a figure explaining the search range in the 2nd AF processing.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. FIG. 1 is a block diagram illustrating a configuration example of a digital camera according to an embodiment of the present invention. The digital camera includes a photographing optical system 11, an image sensor 12, a lens drive control circuit 13, an image signal processing circuit 14, a CPU 15, a display unit 16, and an operation member 17.

  The photographing optical system 11 includes a plurality of lens groups including a zoom lens and a focusing lens, and forms a subject image on the light receiving surface of the image sensor 12. In order to simplify FIG. 1, the photographing optical system 11 is shown as a single lens. The lens drive control circuit 13 drives an optical system drive mechanism (not shown) in response to an instruction from the CPU 15. A focusing lens driving member included in the optical system driving mechanism drives the focusing lens of the photographing optical system 11 to advance and retreat in the optical axis direction, and a zoom lens driving member included in the optical system driving mechanism drives the zoom lens of the photographing optical system 11 to the optical axis. Drive forward and backward in the direction.

  The imaging element 12 is configured by a CMOS image sensor or the like in which photodiodes of light receiving elements constituting pixels are two-dimensionally arranged on the light receiving surface. The image sensor 12 photoelectrically converts an image of a light beam that has passed through the photographing optical system 11 and outputs an image signal.

  The image signal output from the image sensor 12 is converted into digital image data by an A / D conversion circuit (not shown) and then input to the image signal processing circuit 14. The image signal processing circuit 14 performs various types of image processing (color interpolation processing, gradation conversion processing, contour enhancement processing, white balance adjustment processing, etc.) on the digital image data.

  The CPU 15 inputs a signal output from each block in the digital camera, performs a predetermined calculation, and outputs a control signal based on the calculation result to each block. The display unit 16 is configured by a liquid crystal panel or the like. The display unit 16 displays an image, an operation icon, a menu screen, and the like according to an instruction from the CPU 15.

  The operation member 17 includes various input members operated by the user, for example, a power button, a release button, a photographing mode button, and the like, and outputs a signal corresponding to the operation of each button to the CPU 15. The shooting mode button is a button for switching between normal shooting mode / automatic shooting mode (described later).

<Focus adjustment>
The CPU 15 performs focus adjustment (contrast AF) by a contrast detection method based on data from pixels corresponding to the AF area among the pixels of the image sensor 12. In contrast AF, the focus lens is moved within a predetermined search range (for example, the range from the closest end to the infinite end), and the lens position where the contrast is maximized is searched, and the focus lens is moved to the lens position. To adjust the focus of the digital camera.

  Specifically, filter processing is performed so as to remove low-frequency components, particularly DC components, of the image data corresponding to the AF area, and the image data after the filter processing is integrated. In the integration process, the absolute values of the image data are integrated in order to integrate the differences due to the high frequency components.

  The CPU 15 obtains a focus evaluation value (contrast value) using the integrated value. The lens position corresponding to the peak of the contrast value is the focus position of the focus lens. When detecting the peak of the contrast value, the CPU 15 sends an instruction to the lens drive control circuit 13 to move the focus lens to a lens position corresponding to the peak of the contrast value.

<Automatic shooting mode processing>
In addition to the normal shooting mode in which the digital camera of this embodiment acquires an image in response to the release button full-press operation and records it in a recording unit (not shown), the image is automatically acquired regardless of the release button full-press operation. And an automatic photographing mode for recording in the recording unit. Since the digital camera has a feature in processing in this automatic shooting mode, the following description will be focused on automatic shooting processing in this mode.

  FIG. 2 is a flowchart for explaining the flow of automatic shooting mode processing executed by the CPU 15. In response to a signal from the shooting mode switch, the CPU 15 switches the shooting mode from the normal shooting mode to the automatic shooting mode, and starts a program for performing the processing of FIG. Alternatively, the automatic photographing process may be started by operating the operation member 17 after switching to the automatic photographing mode. This program is stored in a ROM (not shown) in the CPU 15.

  In step S10, the CPU 15 determines whether or not a main subject has been detected by subject recognition processing. The subject recognition processing is processing for periodically detecting the main subject image from the through image signal, and is executed in parallel with the automatic shooting mode processing. In the subject recognition process, for example, adults, children, pets, etc. are distinguished and recognized. As such subject recognition processing, a known subject recognition technique can be used. Note that the through image signal is a signal that is repeatedly imaged at predetermined time intervals by the image sensor 12 and output before the recording image is acquired (that is, imaged). Based on this signal, the monitor image is sequentially displayed on the display unit 16.

  The automatic shooting mode of the present embodiment is a mode specialized for so-called two-shot shooting in which two main subjects are shot. In the digital camera, a combination of two main subjects in the automatic shooting mode in advance by the user via a selection button of the operation member 17 (for example, one combination among people & pets, adults & children, people & people, etc.) Is selected. In the subject recognition process, the position and size of each main subject image in the through image are detected for the two selected main subjects and stored in a memory (not shown).

  If both of the two main subjects are detected by the subject recognition process, the CPU 15 makes a positive determination in step S10 and proceeds to step S20. When both of the two main subjects are not detected by the subject recognition process, or when only one of the two main subjects is detected, the CPU 15 makes a negative determination in step S10 and performs the determination process. repeat.

  In step S20, the CPU 15 executes a first AF process. Details of the first AF process will be described with reference to FIG. In step S201, the CPU 15 sets the photographing permission flag to OFF, which is an initial value, and proceeds to step S202. The photographing permission flag is a flag indicating whether or not automatic photographing is performed.

  In step S202, the CPU 15 sets a range from the closest end to the infinite end as a search range in contrast AF, and proceeds to step S203.

  In step S203, as shown in FIG. 4A, the CPU 15 has regions (for example, each of the main subject images G1 and the second main subject image G2) detected by the subject recognition process (for example, each main subject image G2). Each area surrounding the image is set as an AF area (first subject AF area A1 and second subject AF area A2), and the process proceeds to step S204.

  In step S204, the CPU 15 sends an instruction to the lens drive control circuit 13, drives the focus lens to an initial position (search start position, for example, the closest end), and proceeds to step S205.

  In step S205, the CPU 15 obtains a contrast value in association with the focus lens position for the first subject AF area A1 and the second subject AF area A2 at the initial position, and proceeds to step S206.

  In step S206, the CPU 15 sends an instruction to the lens drive control circuit 13 to start search drive in a predetermined speed and a predetermined direction (for example, a direction from the closest end to the infinite end) of the focus lens, and then proceeds to step S207. move on.

  In step S207, the CPU 15 obtains a contrast value in association with the focus lens position for each of the first subject AF area A1 and the second subject AF area A2 at predetermined time intervals, and determines a contrast value peak. To go to step S208. FIG. 4B is a diagram illustrating an example of the relationship (contrast curve) between the focus lens position and the contrast value. In FIG. 4B, the horizontal axis represents the focus lens position, and the vertical axis represents the contrast value. The upper row shows the contrast curve of the second subject AF area A2, and the lower row shows the contrast curve of the first subject AF area A1.

  In step S208, the CPU 15 determines whether or not a contrast value peak has been detected in both the first subject AF area A1 and the second subject AF area A2. When the peak of the contrast value is detected in both of these, the CPU 15 makes an affirmative decision in step S208 and proceeds to step S210. On the other hand, if only one of the contrast value peaks is detected, or if no contrast value peak is detected for both, a negative determination is made in step S208 and the process proceeds to step S209.

  In step S209, the CPU 15 determines whether or not the position of the focus lens is a search end position (for example, an infinite end). If it is the search end position, the CPU 15 makes an affirmative determination in step S209 and proceeds to step S210. If it is not the search end position, the CPU 15 makes a negative determination in step S209 and returns to step S207. When returning to step S207, the above-described processing is repeated.

  In step S210, the CPU 15 sends an instruction to the lens drive control circuit 13, stops the search driving of the focus lens, and proceeds to step S211.

  In step S211, the CPU 15 determines whether or not a contrast value peak is detected in the first subject AF area A1. If the peak is detected, the CPU 15 makes an affirmative determination in step S211 and proceeds to step S212. If the peak is not detected, the CPU 15 makes a negative determination in step S211 and proceeds to step S218.

  In step S212, the CPU 15 determines the position of the focus lens (that is, the focus position of the first main subject) P1 corresponding to the contrast value peak of the first subject AF area, and the first main subject image G1 obtained by subject recognition processing. Are combined and stored in a memory (not shown), and the process proceeds to step S213.

  In step S213, the CPU 15 determines whether or not a contrast value peak is detected in the second subject AF area A2. If the peak is detected, the CPU 15 makes an affirmative determination in step S213 and proceeds to step S214. If the peak is not detected, the CPU 15 makes a negative determination in step S213 and proceeds to step S220.

  In step S214, the CPU 15 determines the position of the focus lens (that is, the focus position of the second main subject) P2 corresponding to the contrast value peak of the second subject AF area A2, and the second main subject image obtained by the subject recognition process. The size of G2 is combined and stored in a memory (not shown), and the process proceeds to step S215.

  In step S 215, the CPU 15 sends an instruction to the lens drive control circuit 13, and the in-focus position P 1 of the first main subject and the in-focus position P 2 of the second main subject are in focus (in FIG. 4B, in-focus). The focus lens is driven to position P2), and the process proceeds to step S216. As a result, of the first main subject and the second main subject, the main subject having the shorter shooting distance (that is, closer to the digital camera) is focused. Of the first main subject and the second main subject, the main subject with the longer shooting distance may be focused. Alternatively, the main subject to be focused may be selected by the user via the operation member 17.

  In step S216, the CPU 15 determines whether or not the distance between the focus position P1 of the first main subject and the focus position P2 of the second main subject is within a predetermined determination threshold Th. The determination threshold Th is, for example, for determining whether or not both the first main subject and the second main subject are in focus when the position of the focus lens is aligned with either the in-focus position P1 or P2. Which is determined by the depth of focus of the photographic optical system 11. Therefore, the fact that the distance between the in-focus positions (P1 to P2) of the first main subject and the second main subject is within the determination threshold Th is, for example, that when the first main subject is focused, Is also in focus (that is, both the first main subject and the second main subject are within the depth of field of the photographing optical system 11). On the other hand, the distance between the in-focus positions (P1 to P2) of the first main subject and the second main subject is outside the determination threshold Th, for example, when the second main subject is focused on the first main subject. Is out of focus (that is, the second main subject is outside the depth of field of the photographing optical system 11).

  Therefore, if the distance is outside the determination threshold Th, the CPU 15 makes a negative determination in step S216, and ends the process of FIG. 3 while setting the photographing permission flag to OFF. On the other hand, if the distance is within the determination threshold Th, an affirmative determination is made in step S216 and the process proceeds to step S217. In step S217, the CPU 15 sets the photographing permission flag to ON and ends the processing in FIG.

  In step S218, which proceeds after making a negative determination in step S211, the CPU 15 determines whether or not a contrast value peak has been detected in the second subject AF area A2, as in step S213. If the peak is detected, the CPU 15 makes an affirmative decision in step S218 and proceeds to step S219. If the peak is not detected, the CPU 15 makes a negative decision in step S218 and proceeds to step S221.

  In step S219, the CPU 15 determines the focus lens position P2 (that is, the focus position of the second main subject) corresponding to the peak contrast value of the second subject AF area A2, and the second main subject image obtained by subject recognition processing. The size of G2 is combined and stored in a memory (not shown), and the process proceeds to step S220.

  When the process proceeds to step S220, the in-focus position of either the first main subject or the second main subject is detected. Therefore, in step S220, the CPU 15 sends an instruction to the lens drive control circuit 13, drives the focus lens to the detected focus position (P1 or P2), and ends the process of FIG.

  On the other hand, when the process proceeds to step S221, neither in-focus position of the first main subject or the second main subject is detected. Therefore, in step S221, the CPU 15 sends an instruction to the lens drive control circuit 13, drives the focus lens to a predetermined lens position, and ends the process of FIG. Here, the predetermined lens position is a position where the main subject can be easily detected, for example, a position where the subject at the shooting distance of 2 m is focused. The predetermined lens position may be changed according to the focal length and zoom ratio of the photographing optical system 11.

  When the CPU 15 ends the first AF process in this way, the process proceeds to step S30 (FIG. 2). In step S30, the CPU 15 determines whether or not the photographing permission flag is ON. If the photographing permission flag is ON, the process proceeds to step S40.

  In step S40, the CPU 15 executes a photographing process. That is, the image sensor 12 performs photoelectric conversion for recording, and the subject image data based on the image signal output from the image sensor 12 is recorded in a recording unit (not shown). Thereafter, the processing according to FIG. As a result, an image focused on both the first main subject and the second main subject can be taken.

  On the other hand, if the photographing permission flag is not ON (that is, is OFF) in step S30, the CPU 15 proceeds to step S50. In step S50, the CPU 15 determines whether one or both of the first main subject image G1 and the second main subject image G2 have disappeared from the through image signal based on the result of the latest subject recognition process. . In the subject recognition process, if either one or both of the first main subject image G1 and the second main subject image G2 are not detected, the CPU 15 makes an affirmative decision in step S50 and returns to step S10. On the other hand, if both are detected, a negative determination is made in step S50, and the process proceeds to step S60.

  In step S60, the CPU 15 acquires the sizes of the first main subject image G1 and the second main subject image G2 most recently detected by the subject recognition process, and proceeds to step S70.

  In step S <b> 70, the CPU 15 determines whether or not the first main subject and the second main subject are close to each other in the optical axis direction of the photographing optical system 11. Specifically, the CPU 15 stores the in-focus position P1 of the first main subject and the first main subject image stored in the memory in the most recent AF processing (the first AF processing or the second AF processing described later). The size of G1, the focus position P2 of the second main subject and the size of the second main subject image G2 are read out. The CPU 15 compares the read focus positions P1 and P2, and recognizes which is the closest side and which is the infinite side. Further, the CPU 15 reads the size of the first main subject image G1 and the size of the second main subject image G2, and the sizes of the first main subject image G1 and the second main subject image G2 detected by the latest subject recognition process. Are compared.

  For example, as shown in FIG. 5A, a case where the focus position P2 of the second main subject is on the infinite side with respect to the focus position P1 of the first main subject will be described. Here, FIG. 5B shows a through image including the first main subject image G1 and the second main subject image G2 in the case where the position of the focus lens is the focus position P1 of the first main subject.

  When the state shown in FIG. 5B is changed to the state shown in FIG. 5D, that is, when the size of the second main subject image G2 having the in-focus position P2 on the infinite side is increased. As shown in FIG. 5C, this means that the focus position P2 of the second main subject has approached the focus position P1 of the first main subject. That is, it means that the second main subject has approached the first main subject in the optical axis direction of the photographing optical system 11.

  Further, as shown in FIG. 6A, a case will be described in which the in-focus position P2 of the second main subject is closer to the in-focus side than the in-focus position P1 of the first main subject. Here, FIG. 6B shows a through image including the first main subject image G1 and the second main subject image G2 when the position of the focus lens is the in-focus position P1 of the first main subject.

  When the state shown in FIG. 6B is changed to the state shown in FIG. 6D, that is, when the size of the second main subject image G2 having the in-focus position P2 on the close side is reduced, As shown in FIG. 6C, it means that the focus position P2 of the second main subject has approached the focus position P1 of the first main subject. That is, it means that the second main subject has approached the first main subject in the optical axis direction of the photographing optical system 11.

  Therefore, the CPU 15 compares the image size of the main subject whose focus position is on the infinity side (hereinafter also referred to as the infinity side subject) with the size (hereinafter also referred to as memory size) stored in the memory in the most recent AF process. When the image size of the main subject whose focus position is closer and closer (hereinafter also referred to as the closest subject) is smaller than the memory size, the two main subjects are moved closer to each other. Recognizing that it has moved, affirmative determination is made in step S70. Further, the CPU 15 also moves the two main subjects closer to each other even when the image size of the closest subject does not substantially change from the memory size and the image size of the infinite subject is larger than the memory size. It is recognized that it has moved to step S70, and an affirmative decision is made in step S70. Furthermore, the CPU 15 also moves the two main subjects closer to each other even when the image size of the infinite subject is almost unchanged from the memory size and the image size of the closest subject is smaller than the memory size. It is recognized that it has moved to step S70, and an affirmative decision is made in step S70. If the CPU 15 makes a positive determination in step S70, it proceeds to step S80.

  On the other hand, when the image size of the infinite subject is smaller than the memory size and the image size of the closest subject is larger than the memory size, the CPU 15 moves the two main subjects away from each other. It is recognized that it has moved to step S70, and a negative determination is made in step S70. In addition, the CPU 15 determines that the two main subjects are separated from each other even when the image size of the near subject does not substantially change from the memory size and the image size of the infinite subject is smaller than the memory size. It is recognized that it has moved to step S70, and a negative determination is made in step S70. Furthermore, even when the image size of the infinite subject does not substantially change compared to the memory size and the image size of the closest subject increases compared to the memory size, the two main subjects are separated from each other. It is recognized that the movement has been made, and a negative determination is made in step S70. Note that the CPU 15 also makes a negative determination in step S70 when both of the image sizes of the two main subjects are not substantially changed from the memory size, that is, when both of the two main subjects are stationary. The CPU 15 also determines that the image size of the infinite subject is larger than the memory size and the image size of the closest subject is also larger than the memory size, that is, the two main subjects are both closer to the near side. Also when it moves, negative determination is made at step S70. In the opposite case, that is, when both of the two main subjects have moved to the infinite side, a negative determination is also made in step S70. If the CPU 15 makes a negative determination in step S70, it returns to step S30 and repeats the above-described processing.

  In step S80, the CPU 15 executes a second AF process. Details of the second AF processing will be described with reference to FIG. Note that the second AF process will be described only in parts different from the first AF process, and description of parts common to the first AF process will be omitted.

  In step S <b> 801, the CPU 15 detects the focus position P <b> 1 of the first main subject and the focus position of the second main subject, which are detected and stored in the memory in the most recent AF process (first AF process or second AF process). Read P2. Then, the CPU 15 sets a predetermined range including a range from the read focus position P1 to the focus position P2 as a contrast AF search range. For example, as shown in FIG. 8, when the in-focus position P1 is on the near side and the in-focus position P2 is on the infinite side, the in-focus position P2 from the position P3 closer to the predetermined distance ΔL than the in-focus position P1. A range up to a position P4 on the infinite side of the predetermined distance ΔL is set as a contrast AF search range.

  The reason for setting the search range in this way is as follows. As described above, the second AF process is performed when two main subjects approach each other. Therefore, the in-focus positions of the first main subject and the second main subject at the time when the second AF processing is executed are determined from the in-focus position P1 of the first main subject detected in the most recent AF processing. There is a high possibility of being in the range up to the in-focus position P2. Therefore, even if the range from the closest end to the infinite end is not set as the search range, the in-focus positions of the first main subject and the second main subject can be detected by setting the search range as described above. . By doing so, the search time can be shortened and the power consumption can be reduced compared to the case where the range from the closest end to the infinite end is set as the search range. Furthermore, the peak value of the contrast value can be detected more accurately by expanding the search range by a predetermined distance ΔL closer to the focus position P1 and closer to the infinite side than the focus position P2.

  When the CPU 15 sets the contrast AF search range as described above, the process proceeds to step S802.

  In step S802, the CPU 15 performs the same process as in step S203 of the first AF process. In step S803, the CPU 15 sends an instruction to the lens drive control circuit 13 to drive the focus lens to an initial position (search start position, for example, the closest search end point (position P3)), and the process proceeds to step S804.

  In steps S804 to S807, the CPU 15 performs processes similar to those in steps S205 to S208 of the first AF process, respectively. In step S808, the CPU 15 determines whether or not the position of the focus lens is a search end position (for example, an infinite search end point (position P4)). If it is the search end position, the CPU 15 makes a positive determination in step S808 and proceeds to step S809. If it is not the search end position, the CPU 15 makes a negative determination in step S808 and returns to step S806.

  In steps S809 to S820, the CPU 15 performs processes similar to those in steps S210 to S221 of the first AF process, respectively.

  When the second AF process is thus executed, the CPU 15 returns to step S30 (FIG. 2) and repeats the above-described process.

  As described above, after executing the first AF process, the CPU 15 monitors the image sizes of the two main subjects to determine whether the two main subjects are close to each other, and determines that they are close to each other. Then, the second AF process is executed. In other words, the CPU 15 stops the contrast AF when the distance between the main subjects is long and the automatic shooting is not performed at the time when the first AF processing is executed, and then the two main subjects approach each other. If it is determined that the contrast AF is stopped, the stop of the contrast AF is canceled and the contrast AF is executed again.

  Unlike the present embodiment, if contrast AF is always executed periodically, the two main subjects approach each other while the search operation started when the two main subjects are not approaching each other. Even if the distance that allows automatic shooting is reached, it is not determined that automatic shooting is possible until the next search operation is executed, and the shooting timing may be missed.

  However, in this embodiment, the search operation is not performed when the two main subjects are not close to each other, and the search operation is executed only when it is determined that they are close to each other. When the shooting distance is reached, it is possible to determine whether automatic shooting is possible without missing the timing. Therefore, the AF time lag can be shortened and photographing can be performed at an appropriate timing. Further, in this embodiment, since the number of times that the search operation is executed is smaller than in the case where the contrast AF is always executed periodically, the power consumption can be reduced.

According to the embodiment described above, the following operational effects can be obtained.
(1) The digital camera periodically captures an image sensor 12 that captures a subject image by the photographing optical system 11 and outputs a subject image signal, and at least a first main subject image G1 and a second main subject image G2 from the subject image signal. Each of the CPU 15 for detecting the lens and the focus lens of the photographing optical system 11 in the optical axis direction to detect the focusing position P1 of the first main subject and the focusing position P2 of the second main subject, respectively. The control circuit 13 and the CPU 15, the lens drive control circuit 13 and the CPU 15 that perform focus adjustment based on at least one of the focusing position P1 of the first main subject and the focusing position P2 of the second main subject, and the alignment of the first main subject. CPU 15 for determining whether the distance between the focus position P1 and the focus position P2 of the second main subject is within a predetermined determination threshold, and the distance When it is determined that the distance is within the determination threshold, the CPU 15 automatically executes the photographing operation; when the distance is determined to be outside the determination threshold, the CPU 15 stops the contrast AF search operation; and When it is determined that the distance is outside the determination threshold, the CPU 15 that detects a change in the size of the first main subject image G1 and the second main subject image G2, and the first main subject based on the detected size change When the CPU 15 determines whether or not the second main subject is close to each other, and when it is determined that the first main subject and the second main subject are close to each other, the search operation is stopped and the search is stopped. Since the CPU 15 that re-executes the operation is provided, the power consumption can be reduced as compared with the case where the search operation is always executed.

(2) In the digital camera of (1) above, in the search operation (search operation in the second AF process) that is re-executed when it is determined that the first main subject and the second main subject are close to each other The focus lens is configured to search between the focus lens position P3 corresponding to the focus position P1 of the first main subject and the focus lens position P4 corresponding to the focus position P2 of the second main subject. Compared with the case where the search range is from the near end to the infinite end, the time required for the search operation can be shortened. Therefore, shooting can be performed without delay in timing, and power consumption can be reduced.

(3) In the digital camera of (1) or (2), the focus adjustment is performed based on the closest focus position among the focus position P1 of the first main subject and the focus position P2 of the second main subject. Since it is configured to do so, it is possible to focus on the subject with the shorter shooting distance.

(4) In the digital cameras of the above (1) to (3), the determination threshold is configured to be a value determined by the depth of focus of the photographic optical system 11, and therefore both of the two main subjects are in focus. You can take an image.

(Modification 1)
In the above-described embodiment, an example has been described in which when the in-focus position of two main subjects is detected, the focus lens is driven to the in-focus position, and the main subject with a shorter shooting distance is focused. However, the focus lens may be driven to an in-focus position with respect to the main subject with less movement so that the main subject with less movement is focused.

  For example, when the selected combination of main subjects is an adult and a child, the main subject that is recognized as an adult by the subject recognition process is focused. When the selected combination of main subjects is a person & pet, the main subject recognized as a pet by the subject recognition process is focused. When the selected combination of main subjects is person & person, the main subject having the larger image size is focused.

  It should be noted that the main subject with the smaller image size change of the two main subjects may be specified as the main subject with less movement, and the specified main subject may be focused.

  By focusing on the main subject with less movement in this way, the focus is unlikely to shift when the two main subjects approach each other, and the photographing operation can be started quickly.

(Modification 2)
If the time during which it is not determined in step S70 that the two main subjects are close to each other continues for a predetermined time or longer, the search operation stop in contrast AF is canceled, and the process returns to step S20 to return to the search operation (first step). 1 AF processing) may be re-executed. The predetermined time is, for example, 3 to 5 seconds, and is longer than the subject recognition processing execution interval. By doing so, it is possible to periodically detect the in-focus position of the two main subjects and focus on one of the main subjects.

(Modification 3)
In the above-described embodiment, an example in which a combination of main subjects (such as a person & pet) is selected by a user in advance and the selected main subject is detected has been described. However, the digital camera may automatically detect the subject estimated as the main subject. When the CPU 15 of Modification 3 automatically detects two subjects estimated to be main subjects, it detects the in-focus positions of the two main subjects detected, and the distance between these in-focus positions is determined as described above. When the value falls within the threshold, the photographing operation is automatically executed.

(Modification 4)
In the above-described embodiment, an example has been described in which when the in-focus position of two main subjects is detected, the focus lens is driven to the in-focus position, and the main subject with a shorter shooting distance is focused. However, the center position between the in-focus positions of the two main subjects may be calculated, and the focus lens may be driven to the center position.

(Modification 5)
In the above-described embodiment, the example in which the change in the image size of the two main subject images is detected has been described. However, a change in the image size of one of the two main subject images may be detected. It is preferable that the main subject for detecting a change in the image size is a main subject that moves much more than the other main subject. When the CPU 15 of the modification 5 detects a change in the main subject image whose in-focus position is on the closest side, the image size is smaller than the image size stored in the memory in the most recent AF process. It is determined that two main subjects are close to each other. In addition, when detecting a change in the main subject image whose in-focus position is on the infinite side, two main subjects are used when the image size is larger than the image size stored in the memory in the most recent AF process. Are determined to be close to each other.

(Modification 6)
In the above-described embodiment, in the second AF process, a range including the focus position P1 of the first main subject to the focus position P2 of the second main subject and a predetermined distance before and after the focus position P1 (position P3 to position P4). ) Has been described as an example of setting the search range. However, a range from the focus position P1 of the first main subject to the focus position P2 of the second main subject may be set as the search range of the second AF process. Further, a range from the closest end to the infinite end may be set as the search range for the second AF process.

(Modification 7)
In the above-described embodiment, an example in which images of two main subjects are detected has been described. However, three or more main subject images may be detected. For example, when images of three main subjects are detected, in-focus positions of any two main subjects among the three main subjects are detected, and the distance between these in-focus positions is equal to or greater than a predetermined determination threshold. In some cases, the photographing operation may be automatically executed. Alternatively, the in-focus positions of all three main subjects may be detected, and the photographing operation may be automatically executed when the distance between these in-focus positions exceeds a predetermined determination threshold.

  The above description is merely an example, and is not limited to the configuration of the above embodiment. Moreover, you may combine the structure of each modification suitably with the said embodiment.

DESCRIPTION OF SYMBOLS 11 ... Shooting optical system 12 ... Imaging element 13 ... Lens drive control circuit 14 ... Image signal processing circuit 15 ... CPU

Claims (6)

Imaging means for imaging a subject image by a photographing optical system and outputting a subject image signal;
Subject recognition means for periodically detecting at least a first main subject and a second main subject from the subject image signal;
A contrast type for searching the focus lens of the photographing optical system in the optical axis direction to detect a first in-focus position with respect to the first main subject and a second in-focus position with respect to the second main subject. A focus detection means;
Focus adjusting means for performing focus adjustment based on at least one of the first focus position and the second focus position;
Distance determining means for determining whether a distance between the first in-focus position and the second in-focus position is within a predetermined determination threshold;
An automatic photographing unit that automatically performs a photographing operation when the distance determining unit determines that the distance is within the determination threshold;
Stop means for stopping the search operation of the contrast-type focus detection means when the distance determination means determines that the distance is outside the determination threshold;
Size detection means for detecting a change in the size of at least one of the first main subject and the second main subject when the distance determination means determines that the distance is outside the determination threshold; ,
An approach determining means for determining whether or not the first main subject and the second main subject are close to each other based on the size change detected by the size detecting means;
When the approach determining unit determines that the first main subject and the second main subject are close to each other, the stop of the search operation by the stop unit is canceled and the search operation is re-executed. Execution means
A digital camera comprising: The digital camera according to claim 1, wherein
The contrast-type focus detection unit performs the focus lens in a search operation that is re-executed when the approach determination unit determines that the first main subject and the second main subject are close to each other. A digital camera that performs the search operation between a focus lens position corresponding to the first focus position and a focus lens position corresponding to the second focus position. The digital camera according to claim 1 or 2,
The digital camera according to claim 1, wherein the focus adjustment unit performs focus adjustment based on a focus position on a closest side among the first focus position and the second focus position. The digital camera according to claim 1 or 2,
The digital camera according to claim 1, wherein the focus adjustment unit performs focus adjustment based on a focus position related to a main subject with less movement among the first main subject and the second main subject. In the digital camera according to any one of claims 1 to 4,
The execution means performs the search operation by the stop means when a time during which the first main subject and the second main subject are not determined to be close to each other continues for a predetermined time or longer by the approach determination means. A digital camera, wherein the search operation is released and the search operation is re-executed. The digital camera according to claim 1,
The digital camera according to claim 1, wherein the determination threshold is a value determined by a depth of focus of the photographing optical system.

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