JP2015025852A - Imaging apparatus, control method thereof, and control program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To focus on a main subject without additional image processing, and to simultaneously blur subjects located in front and back to obtain a natural image.SOLUTION: An imaging apparatus includes an optical part 101 having a focus lens. In capturing an image of a composition including a plurality of subjects located from front to rear, at least one of the subjects is imaged as a main subject, while blurring subjects other than the main subject. A CPU 1004 controls a DSP 1007 to detect a distance between the main subject and the imaging apparatus, obtains distance information, and determines a focal point of the focus lens so that the main subject falls within a depth of field, according to the distance information. The CPU move-controls the focal point of the focus lens along an optical axis of the optical part during an exposure period for capturing a composition in a range so that the main subject falls within the depth of field.

Description

  The present invention relates to an imaging apparatus, a control method thereof, and a control program, and more particularly, to blurring of an image obtained as a result of imaging by the imaging apparatus.

  In general, in photography, an expression technique is known in which a part of an image is intentionally blurred by the effect of a photographing lens. This expression technique is called a blur expression technique, and when this technique is used, it is possible to highlight and emphasize a portion (for example, a main subject) to be noticed.

  By the way, the above-described blur expression method includes a so-called back blur method that enhances the main subject (main role) by blurring the background, a so-called front blur method that blurs an object (subject) located in front of the main subject, There is a so-called back-and-forth blur method for blurring an object positioned in the front-rear direction.

  FIG. 9 is a diagram for explaining the relationship between the distance from the imaging device and the image blur. FIG. 9A is a diagram showing a composition to be photographed, and FIG. 9B and FIG. 9C are diagrams showing a focal point and a focusing range with respect to the distance from the imaging device, respectively.

  Now, assume that the user holds the imaging device 9000 as shown in FIG. 9A and determines the composition to be photographed. Here, in FIGS. 9B and 9C, the distance from the optical unit (for example, focus lens) 9005 provided in the imaging device 9000 to the focal point is defined as W (M).

  In addition, the distance from the optical unit 9005 to the near end of the depth of field in the range focused on the subject is L1 (M), and the distance from the optical unit 9005 to the far end of the depth of field Is L2 (M). Note that the distance from the front end to the back end is called the depth of field.

  In the graphs shown in FIG. 9B and FIG. 9C, the solid line indicates the change in the circle of confusion circle σ according to the distance from the imaging device 9000 (that is, the optical unit 9005), and the broken line indicates the distance from the imaging device 9000. The change of the degree of focus according to distance is shown. Here, the degree of focus is inversely proportional to the circle of confusion circle σ and the amount of blur. The circle of confusion diameter σ is a diameter indicating the spread of an image on the light receiving surface of the image sensor 9004 when a subject represented by a point is photographed.

  The circle of confusion σ is treated as a physical quantity proportional to the amount of blur, but the details are known and will not be described. Further, δ represents the allowable confusion circle diameter in the image pickup apparatus 9000, and the amount of blur is minimum in the range where the confusion circle diameter σ reaches the allowable confusion circle diameter δ.

  Further, in the graph shown in FIG. 9B, as indicated by a broken line, the degree of focusing becomes higher as it gets closer to the focal point, and becomes maximum within the depth of field. The permissible circle of confusion δ is determined by image processing or the like in addition to the pixel pitch of the image sensor 9004. Generally, when the pitch (interval) between the pixels of the image sensor 9004 is d, the permissible circle of confusion is δ = Kd.

  Here, k is a constant specific to the imaging device 9000 and is determined by the amount of decrease in resolution caused by the optical low-pass filter and image processing.

  9B, the distance from the optical unit 9005 to the main subject 9001 is W, the aperture diameter of the diaphragm included in the optical unit 9005 is D, the focal length of the optical unit 9005 is f, The F number (aperture value) of the zoom lens provided in the optical unit 9005 is F = f / D.

At this time, the depth of field is from the distance L1 (M) to the distance L2 (M). That means
Depth of field = L2 (M) −L1 (M). The distances L1 (M) and L2 (M) are expressed by the following expressions (1) and (2), respectively.

L1 (M) = W (M) × F ² × (f ² −k × F × d × (W (M) −f)) (1)
L2 (M) = W (M) × F ² × (f ² + k × F × d × (W (M) −f)) (2)
By the way, in an imaging device having a small light receiving surface size of an image sensor such as a compact digital camera, the depth of field is relatively deeper than a so-called single-lens camera having a large light receiving surface size. For this reason, it is difficult for an imaging device with a small light receiving surface size to capture a subject image other than the main subject with a large blur.

  In order to improve such a point, for example, when there is a subject whose distance in the depth direction is different from that of the main subject, a subject other than the main subject has a depth of field (between L1 (M) and L2 (M)). There is known an imaging apparatus that performs imaging at a focal point that does not fall within (see Patent Document 1).

  In the imaging apparatus described in Patent Document 1, the sense of distance between the main subject 9001 and the main subject 9001 and the subjects 9002 and 9003 having different distances in the depth direction is emphasized by using the front blur method and the rear blur method. Emphasizes the existence and makes it stand out.

JP 2003-125281 A

  However, in the imaging apparatus described in Patent Document 1, for example, when shooting with the composition shown in FIG. 9A, as shown in FIG. 9C, the main subject 9001 and other subjects 9002 in the depth direction and When sandwiched between 9003, the following inconvenience occurs.

  Assume that the in-focus point is set on the back side of the main subject 9001. In this case, the distance from the optical unit 9005 to the focal point is defined as W (T). A subject 9003 located on the near side of the main subject 9001 is located on the near side with respect to the near end (the distance from the optical unit 9005 is L1 (T)) in the depth of field. Therefore, the degree of focus with respect to the subject 9003 decreases, and the subject 9033 can be blurred and photographed (pre-blurred state).

  On the other hand, the subject 9002 located on the far side of the main subject 9001 is located on the near side of the far side end (the distance from the optical unit 9005 is L2 (T)) in the depth of field. As a result, the degree of focus on the subject 9002 is improved and the subject 9002 is in focus.

  As described above, in the imaging device described in Patent Document 1, when the subject 9003 exists on the front side with the main subject 9001 sandwiched therebetween and further the subject 9002 exists on the back side, one of the main subjects 9001 is sandwiched therebetween. When trying to blur the subject, the other subject may fall within the depth of field. In such a case, the degree of focus of the subject that falls within the depth of field becomes high in the same way as the main subject, and it becomes difficult to emphasize and emphasize only the presence of the main subject.

  Accordingly, an object of the present invention is to obtain a natural image with a simple configuration that does not require additional image processing, focusing on the main subject, and simultaneously blurring the subject existing on the back side and the near side. An imaging device capable of performing the same, a control method thereof, and a control program are provided.

  In order to achieve the above object, an imaging apparatus according to the present invention includes an imaging optical system having a focus lens, and when shooting a composition in which a plurality of subjects are positioned from the near side to the back side, An imaging apparatus that blurs and shoots a subject other than the main subject with at least one as a main subject, the distance detecting means for obtaining distance information by detecting the distance between the main subject and the imaging device, and the distance information And a focus calculation means for obtaining a focal point of the focus lens so that the main subject falls within the depth of field, and the focus during the exposure period for photographing the composition within a range where the main subject falls within the depth of field. Control means for controlling movement of the focal point of the lens along the optical axis of the imaging optical system.

  The control method according to the present invention includes an imaging optical system having a focus lens, and when photographing a composition in which a plurality of subjects are located from the front side to the back side, at least one of the plurality of subjects is used as a main subject. A method for controlling an imaging apparatus that shoots a subject other than a main subject while blurring, wherein a distance detection step of obtaining a distance information by detecting a distance between the main subject and the imaging apparatus, and the main information according to the distance information A focal point calculating step for obtaining a focal point of the focus lens in which the subject is within the depth of field; and a focal point of the focus lens during an exposure period in which the composition is photographed in a range where the main subject is within the depth of field. And a control step for controlling movement along the optical axis of the imaging optical system.

  The control program according to the present invention includes an imaging optical system having a focus lens, and when photographing a composition in which a plurality of subjects are located from the front side to the back side, at least one of the plurality of subjects as a main subject. A distance detection step for obtaining distance information by detecting a distance between the main subject and the imaging apparatus in a computer provided in the imaging apparatus, which is a control program used to blur and photograph a subject other than the main subject And a focal point calculating step for obtaining a focal point of the focus lens in which the main subject is within the depth of field according to the distance information, and an exposure for photographing the composition in a range where the main subject is within the depth of field. And a control step for controlling movement of the focal point of the focus lens along the optical axis of the imaging optical system during the period. The features.

  According to the present invention, the focal point of the focus lens at which the main subject falls within the depth of field is obtained according to the distance information indicating the distance between the main subject and the imaging device, and the main subject falls within the depth of field. Since the focus of the focus lens is controlled to move along the optical axis of the imaging optical system during the exposure period for photographing the composition, no additional image processing is required and the main subject is focused and It is possible to blur a subject existing on the side and the near side at the same time and obtain a natural image.

1 is a block diagram illustrating a configuration of an example of an imaging apparatus according to a first embodiment of the present invention. It is a figure which shows the example about the structure of the optical part and imaging device which are shown in FIG. 2A and 2B are diagrams for explaining a blur process performed by the camera shown in FIG. 1, in which FIG. 1A is a diagram for explaining a focal point, a depth of field, and a degree of focus, and FIG. The figure which shows the relationship between the distance from a camera when it shakes to the back side from the position close | similar to 3 and the diameter of a circle of confusion, FIG. These are the figures which show the relationship between the distance from a camera, and exposure time. 3 is a flowchart for explaining a photographing operation in the camera shown in FIG. 1. 2 is a timing chart for explaining a photographing operation in the camera shown in FIG. 1. It is a figure which shows an example of the composition image | photographed with the camera by the 2nd Embodiment of this invention. It is a flowchart for demonstrating the imaging | photography operation | movement in the camera by the 2nd Embodiment of this invention. It is a timing chart for demonstrating imaging | photography operation | movement in the camera by the 2nd Embodiment of this invention. It is a figure for demonstrating the relationship between the distance from an imaging device, and an image blur, (a) is a figure which shows the composition which image | photographs, (b) and (c) are the in-focus and focusing with respect to the distance from an imaging device, respectively. It is a figure which shows the range of the distance to focus.

  Hereinafter, an example of an imaging apparatus according to an embodiment of the present invention will be described with reference to the drawings.

[First Embodiment]
FIG. 1 is a block diagram showing the configuration of an example of an imaging apparatus according to the first embodiment of the present invention.

  The illustrated imaging apparatus is, for example, a digital compact camera (hereinafter simply referred to as a camera), and includes an optical unit (imaging optical system) 1001. The optical unit 1001 includes a lens barrel and a zoom lens, a focus lens, and a diaphragm mechanism arranged in the lens barrel, and forms a subject image (also referred to as an optical image) on the light receiving unit of the image sensor 102. Let The optical unit 1001 is driven and controlled by the CPU 1004 to perform autofocus and the like.

  The image sensor 1002 converts the optical image formed by the optical unit 1001 into an electrical signal (analog signal). The image sensor 1002 performs an OB (optical black) clamp process and an A / D conversion process on the analog signal, generates a digital image signal, and sends the digital image signal to the DSP (digital signal processor) 1007. Output.

  The CPU 1004 controls the entire camera. In controlling the camera, the CPU 1004 controls the camera using the ROM 1005 and the RAM 1006. The ROM 1005 stores a program such as firmware for driving and controlling the camera. The RAM 1006 temporarily stores control information related to the camera, and the RAM 1006 is used as a work area for the CPU 1004.

  The DSP 1007 receives a digital image signal from the image sensor 1002, performs various signal processing on the digital image signal, and generates a still image or moving image video signal (image data: for example, a YUV signal) in a predetermined format. Generate. Further, the DSP 1007 performs exposure control, detection of the main subject, and detection of the distance from the camera to the main subject under the control of the CPU 1004 in accordance with the digital image signal received from the image sensor 1002 during live view driving. .

  The external interface 1008 includes various encoders and D / A converters, and various control signals and data (image data) with external elements (for example, the display 1012, the memory medium controller 1010, and the operation panel 1011). Send and receive. As a result, an image obtained as a result of imaging is displayed on the display 1012. The display 1012 also displays an image in live view driving.

  Although the illustrated display 102 is incorporated in the camera, image data may be transmitted to a display device outside the camera, and an image corresponding to the image data may be displayed on the display device.

  As shown in the figure, a memory medium controller 1010 is connected to the external interface 1008, and the memory medium 1009 is detachably inserted into the memory medium controller 1010. The memory medium 1009 is, for example, a memory card, and image data obtained as a result of imaging is stored in the memory medium 1009. In addition to the memory card, for example, a disk medium using magnetism or light may be used as the memory medium 1009.

  The operation panel 1011 is operated by a user, and the user inputs various instructions using the operation panel 1011. The CPU 1004 monitors instructions by operating the operation panel 1011 and controls the camera according to the instructions.

  FIG. 2 is a diagram illustrating an example of the configuration of the optical unit 1001 and the image sensor 1002 illustrated in FIG.

  As shown in the figure, an image sensor 1002 is arranged at the subsequent stage of the optical unit 1001. The optical unit 1001 includes a zoom lens unit (hereinafter simply referred to as a zoom lens) 2001, a focus lens unit (hereinafter simply referred to as a focus lens) 2002, and a diaphragm 2003.

  The zoom lens 2001 is a lens for changing the zoom magnification. A focus lens 2002 is a lens for changing the focal point. The stop 2003 is for controlling the amount of light incident on the image sensor 1002. The diaphragm 2003 increases the amount of incident light by widening the aperture diameter, and reduces the amount of incident light by narrowing the aperture diameter.

  The zoom lens 2001 is driven along the optical axis by a zoom motor 2101 to change its zoom magnification. Similarly, the focus lens 2002 is driven along the optical axis by the focus motor 2102 to change the focal point. The diaphragm 2002 is driven by a diaphragm motor 2103 to change its opening diameter. The diaphragm 2002 is provided in the zoom lens 2001.

  The zoom motor 2101, the focus motor 2102, and the aperture motor 2103 described above are driven by the drive circuit 2004 under the control of the CPU 1004.

  FIG. 3 is a diagram for explaining a blur process (blur effect) performed by the camera shown in FIG. 3A is a diagram for explaining the focal point, the depth of field, and the degree of focusing, and FIG. 3B is a diagram when the focal point is moved from a position close to the camera to the back side. It is a figure which shows the relationship between the distance from the camera, and a confusion circle diameter. FIG. 3C is a diagram showing the blur effect when the focal point is moved during the exposure period, and FIG. 3D is a diagram showing the relationship between the distance from the camera and the exposure time.

  FIG. 3A shows a state in which a main subject 3001 that is a distance W (C) away from the camera, that is, the optical unit 1001, is in focus. That is, the main subject 3001 has a focal point, and the distance between the optical unit 1001 and the focal point is W (C). Here, the distance L1 (C) indicates the distance between the optical unit 1001 and the near end of the depth of field, and the distance L2 (C) indicates the distance between the optical unit 1001 and the far end of the depth of field. Indicates.

  In the graph shown in FIG. 3A, the solid line indicates a change in the degree of focus. Here, the degree of focus is reduced in almost all regions of the depth of field (from the front side end to the back side end) excluding the focal point. Decreasing the degree of focus increases the amount of blur. When a high resolution is obtained only for the main subject 3001 located at the focal point, the subjects 3002 and 3003 existing on the back side and the front side of the main subject 3001 are simultaneously blurred (front and back blur), and a natural image is obtained. Can do.

  Here, with reference to FIG. 3B and FIG. 3C, image blurring by the camera shown in FIG. 1 will be described.

  As described above, L1 (C) represents the distance to the near end of the depth of field when the distance to the focal point is W (C), and L2 (C) represents the distance to the focal point. Indicates the distance to the far end of the depth of field when is W (C).

  Further, L1 (S) and L2 (S) are the distance to the near end of the depth of field and the far end of the depth of field when the distance to the focal point is W (S), respectively. Indicates the distance. Similarly, L1 (E) and L2 (E) are the distance to the near end of the depth of field and the far end of the depth of field when the distance to the focal point is W (E), respectively. Indicates the distance to.

  In the following description, the distances W (C), W (S), and W (E) may be referred to as in-focus points W (C), W (S), and W (E), respectively. Further, the distances L1 (C), L1 (S), and L1 (E) are referred to as front end portions L1 (C), L1 (S), and L1 (E), respectively, and the distances L2 (C), L2 ( S) and L2 (E) may be referred to as back side end portions L2 (C), L2 (S), and L2 (E), respectively.

  In the graph shown in FIG. 3B, the solid line indicates the relationship between the distance from the camera and the circle of confusion σ when exposure is performed when the distance to the focal point is W (C). In a region where the circle of confusion σ is smaller than the permissible circle of confusion δ (from the front end L1 (C) to the back end L2 (C)), a focused state is obtained.

  Similarly, in the graph shown in FIG. 3B, the dotted line indicates the distance from the camera when exposure is performed when the distance to the focal point is the distance W (S) on the near side of W (C). And the circle of confusion circle σ. In a region where the circle of confusion σ is smaller than the allowable circle of confusion δ (from the front side end L1 (S) to the back side end L2 (S)), a focused state is obtained.

  Note that the relationship between the focal point W (S), the front side end L1 (S), and the back side end L2 (S) is as follows: the focal point W (C), the front side end L1 (C), and the back side end This is the same as the relationship with the part L2 (C).

  In the graph shown in FIG. 3B, the alternate long and short dash line indicates the distance and confusion from the camera when the exposure is performed when the distance to the focal point is the distance W (E) which is the back side of W (C). The relationship with the circle diameter σ is shown. In a region where the circle of confusion circle σ is smaller than the allowable circle of confusion circle δ (from the front side end L1 (E) to the back side end L2 (E)), a focused state is obtained.

  The relationship between the focal point W (E), the front side end L1 (E), and the back side end L2 (E) is as follows: the focal point W (C), the front side end L1 (C), and the back side end This is the same as the relationship with the part L2 (C).

  As described above, the depth of field changes according to the distance from the camera to the focal point. Here, for convenience of explanation, the circle of confusion σ is assumed to be equal to the allowable circle of confusion δ near the focal point. This is because the permissible circle of confusion δ and the amount of blur are treated as proportional physical quantities, and even if the circle of confusion circle σ is smaller than the permissible circle of confusion δ, the amount of blur remains the same as when σ = δ. It depends.

  In addition, both the back side end L2 (S) of the depth of field at the focal point W (S) and the near side end L1 (E) of the depth of field at the focal point W (E) are both from the camera. It is assumed that it is equal to the distance W (C). That is, W (C) = L2 (S) = L1 (E). This condition is a condition for obtaining the maximum effect in the present embodiment, assuming that the main subject 3001 moves from the near-side edge of the depth of field to the far-side edge of the depth of field.

  The distances L2 (S) and L1 (E) are expressed by the following formulas (3) and (4), respectively.

L2 (S) = W (S) × F ² × (f ² −k × F × d × (W (S) −f)) (3)
L1 (E) = W (E) × F ² × (f ² + k × F × d × (W (E) −f)) (4)
As described above, since W (S) = L2 (S) = L1 (E), Expression (3) and Expression (4) can be transformed into Expression (5) and Expression (6), respectively.

k × F × d × W (S) ² − (f ² + k × F × d × f) × W (S) + W (C) / F ² = 0 (5)
^{k × F × d × W (} E) 2 + (f 2 -k × F × d × f) × W (E) -W (S) / F 2 = 0 (6)
In Equation (5) and Equation (6), when the solution of the quadratic equation is obtained for W (S) and W (E), W (S) and W (E) are expressed by Equation (7) and Equation (8), respectively. Represented by

W (S) = (− (f ² + k × F × d × f) + ((f ² + k × F × d × f) ² −4 × k × d × W (C) / F) ^1/2 ) / (2 × k × F × d) (7)
W (E) = ((f ² + k × F × d × f) − ((f ² + k × F × d × f) ² + 4 × k × d × W (C) / F) ^1/2 ) / ( 2 × k × F × d) (8)
Note that there is one solution for each of W (S) and W (E). For W (S), W (C) is the far end of the depth of field, and for W (E) This is because W (C) is the front end of the depth of field.

  Next, with reference to FIG. 3C, the blur effect when the focal point is moved during the exposure period will be described. Here, a case will be described in which an image with a shallow depth of field in which only the main subject 3001 located at the distance W (C) is focused is captured.

  In FIG. 3C, the horizontal axis indicates the distance from the camera, and the vertical axis indicates the time average value of the circle of confusion diameter σ. In general, the amount of blur of the subject is proportional to the circle of confusion diameter σ, but if the focus lens 2002 is moved during the exposure period, the amount of blur is the time average within the exposure period of the circle of confusion diameter σ at that point (that is, the focus position). Proportional to value.

  In the graph shown in FIG. 3C, a dotted line indicates a blur effect when the focus lens 2002 is fixed at a position where the focus lens 2002 is in focus. On the other hand, in the graph shown in FIG. 3C, the solid line indicates the end portion on the far side of the depth of field from the focal point W (S) where the main subject 3001 is on the near side end portion of the depth of field during the exposure period. 3 shows the time average value of the circle of confusion diameter δ for each distance from the camera when the focus lens 2002 is moved at a predetermined speed when moving to the in-focus point W (E).

  When the focus lens 2002 is moved during the exposure period, the time average value during the exposure period with respect to the confusion circle diameter σ is set to be larger than the allowable confusion circle diameter δ for another subject 3002 or 3003 whose distance from the camera is different from the main subject 3001. Can be bigger. As a result, the subjects 3003 and 3002 positioned at the front end L1 (C) and the back end L2 (C) can be blurred by one shooting.

  Here, the conditions for obtaining the maximum effect (that is, W (S) and W (E) satisfying W (C) = L2 (S) = L1 (E)) have been described as an example. When S) and W (E) are set to positions closer to W (C) than the states shown in equations (7) and (8), the amount of blur around the main subject gradually becomes smaller. (C) = W (S) = W (E), the amount of blur around the main subject is minimized. When W (C) = W (S) = W (E), the moving distance of the focus lens is 0, which is equivalent to the conventional imaging method described above.

  In FIG. 3D, the hatched portion indicates the depth of field for each exposure time, and the degree of focus when the focus is changed during the exposure period is the sum of the depth of field in the time direction. It will be expressed as a value.

  FIG. 4 is a flowchart for explaining a photographing operation (photographing process) in the camera shown in FIG. 4 is performed under the control of the CPU 1004.

  FIG. 5 is a timing chart for explaining a photographing operation (photographing process) in the camera shown in FIG.

  Referring to FIGS. 4 and 5, it is assumed that the user presses the power button at time t1. The camera is activated by pressing the power button, and the CPU 1004 displays a live view on the display 1012 (step S4001).

  During the live view period from time t1 to time t2, the DSP 1007 performs main subject detection processing for detecting the main subject with respect to a digital image pickup signal (hereinafter also simply referred to as an image) output from the image pickup device 1002 under the control of the CPU 1004. Do.

  When detecting the main subject, for example, face detection for detecting a face area is used. Furthermore, the main subject detection process may be performed on the assumption that the main subject exists in an angle of view area set in advance in the camera. In any case, since the method for detecting the main subject is known, the description is omitted here.

  Subsequently, at time t2, the CPU 1004 determines whether or not the shutter button (SW) has been pressed (step S4002). If the shutter button is not pressed (NO in step S4002), CPU 1004 returns to the process in step S4001 and performs live view display.

  When the shutter button is pressed (YES in step S4002), CPU 1004 controls DSP 1007 to perform exposure measurement (detection of exposure conditions) (step S4003), and sets an appropriate exposure amount for the main subject according to the exposure detection result. Ask. The DSP 1007 obtains the aperture value, shutter speed, and ISO sensitivity according to the appropriate exposure amount under the control of the CPU 1004.

  The exposure control (that is, exposure measurement) performed in step S4003 is known and will not be described in detail. However, the DSP 1007 measures the subject brightness in accordance with the output of the image sensor 1002, and selects the image selected by the user. The aperture value, shutter speed, and ISO sensitivity are determined according to the mode (for example, aperture priority, shutter speed priority, etc.).

  Subsequently, at times t3 to t4, the DSP 1007 measures the distance W (C) to the main subject 3001 under the control of the CPU 1004 (step S4004). Here, distance information is obtained by performing distance measurement using a known contrast AF method, but other methods such as a phase difference AF method may be used.

  At time t4, under the control of the CPU 1004, the DSP 1007 calculates the in-focus distances (W (S) and W (E)) at which the distance W (C) to the main subject 3001 is the end of the depth of field. In this way, it is obtained (step S4005). Further, the DSP 1007 calculates the moving speed (that is, the moving speed of the focal point) V of the focus lens 2002 when moving from the distance W (S) to the distance W (E) within the exposure time (step S4006).

  Here, the moving speed V of the focal point by the focus lens 2002 = (W (E) −W (S) (that is, the moving distance of the focal point by the focus lens 2002)) ÷ exposure time.

  At times t5 to t6, the CPU 1004 focuses so as to focus on the focal point W (S) at which the position of the main subject 3001 becomes the front end (L2 (S)) that is one end of the depth of field. The focal point in the focus lens 2002 is moved (step S4007). Then, from time t7 to t8, the CPU 1004 performs exposure and movement of the focal point of the focus lens 2002.

  Then, the CPU 1004 performs exposure for a predetermined time obtained by the exposure measurement shown in step S4003, and is positioned at the back end (L1 (E)) that is the other end of the depth of field. The focal point in the focus lens 2002 is controlled to move to the focal point W (E) (step S4008).

  When the exposure is completed, the CPU 1002 outputs a digital image signal from the image sensor 1002 to the DSP 1007 (image signal reading), and performs image processing by the DSP 1007 (step S4009). Thereafter, the CPU 1004 determines whether or not the power is turned off by the power button (step S4010). When the power is turned off (YES in step S4010), CPU 1004 ends the shooting operation.

  On the other hand, if the power is not turned off (NO in step S4010), CPU 1004 returns to the process in step S4001 and performs live view display.

  In the example illustrated in FIG. 5, at time t8 to t9, the display returns to the live view display, and the CPU 1004 moves the focal point of the focus lens 2002 to the focal point W (C) so as to focus on the main subject 3001. At time t10, live view display is performed again.

  As described above, in the first embodiment of the present invention, the position of the focus lens at the time of exposure is focused on the focal point W (S) that is the front end (L2 (S)) of the depth of field. As described above, the focal point of the focus lens 2002 is moved.

  Thereafter, exposure is performed for a predetermined time, and the focal point of the focus lens 2002 is moved to the focal point W (E) located at the far side end (L1 (E)) of the depth of field. As a result, with a simple configuration that does not require additional image processing, it is possible to focus on the main subject and blur the subject existing on the back side and the near side at the same time, and obtain a natural image.

[Second Embodiment]
Next, an example of a camera according to the second embodiment of the present invention will be described. The configuration of the camera according to the second embodiment is the same as that of the camera described with reference to FIGS.

  In the second embodiment, a method for obtaining a blur effect similar to that in the first embodiment when continuous shooting is performed for a plurality of subjects having different distances from the camera. explain.

  FIG. 6 is a diagram showing an example of a composition photographed by the camera according to the second embodiment of the present invention.

  In the illustrated example, there are subjects 6001 to 6003. Here, it is assumed that there is one main subject in one exposure, and different subjects are photographed as main subjects for each exposure. Furthermore, it is assumed that the subject is positioned in the order of the subject 6001, the subject 6002, and the subject 6003 from the optical unit 1001 side, and the focal point of the focus lens 2002 with respect to the subjects 6001, 6002, and 6003 (that is, the distance from the optical unit 1001). Are W (C, 6001), W (C, 6002), and W (C, 6003), respectively.

  In the example shown in FIG. 6, the number of subjects is three, but it is sufficient that at least three subjects exist.

  FIG. 7 is a flowchart for explaining a photographing operation (photographing process) in the camera according to the second embodiment of the present invention. 7 is performed under the control of the CPU 1004. Further, in FIG. 7, the same steps as those in the flowchart shown in FIG.

  FIG. 8 is a timing chart for explaining a photographing operation (photographing process) in the camera according to the second embodiment of the present invention.

  After the process of step S4001 described above is performed at time t1, the processes of steps S4002 and S4003 are performed at time t2.

  Subsequently, at time t3 to t4, under the control of the CPU 1004, the DSP 1007 measures the distance to each of the subjects 6001 to 6003 shown in FIG. 6 (step S7004). Here, distance measurement is performed using a known contrast AF method, but other methods such as a phase difference AF method may be used.

  In step S7004, the distance to each of the subjects 6001 to 6003 is measured by one distance measurement. This makes it possible to shorten the total shooting time compared to the case where distance measurement is performed for each exposure.

  At time t4, the DSP 1007 measures the positions of the subjects 6001 to 6003 under the control of the CPU 1004. Here, the DSP 1007 has a distance W (C, 6001) from the camera to the nearest subject 6001, a distance W (C, 6002) to the next nearest subject 6002, and a distance W (C, 6003) to the third subject 6003. ).

  Further, the DSP 1007 has a focus point (W (S, 6001), W (E, 6001), W (S, 6002), W (E, 6002), W) of the focus lens 2002 that is an end of the depth of field. (S, 6003), W (E, 6003)) are obtained as described above (step S7005).

  The DSP 1007 sets the number of each of the subjects 6001 to 6003 to N, and sets the moving speed V (N) of the focus lens 2002 when moving from the focal point W (S, N) to W (E, N) within the exposure time. Obtained (step S7006). Here, the moving speed is V (N) = (W (E, N) −W (S, N)) ÷ accumulation time.

  For example, the moving speed V (6001) of the in-focus point of the focus lens 2002 when shooting the foremost subject 6001 is V (6001) = (W (E, 6001) −W (S, 6001)) ÷ accumulation time. It becomes.

  At times t5 to t6, the CPU 1004 moves the focal point of the focus lens 2002 to the position W (S, 6001) that is the end (front end) of the depth of field (step S7007). Then, from time t7 to t8, the CPU 1004 performs exposure for a predetermined time obtained by the exposure measurement shown in step S4003, and at the same time, the focus lens up to the back end W (E, 6001) of the depth of field. The focal point 2002 is moved (step S7008).

  Here, the moving direction of the focus lens 2002 during exposure is from the end W (S, 6001) to the end W (E, 6001), but immediately after the distance measurement, immediately before the focal lens 2002 is moved, the focus lens 2002 is moved. When the end W (E, 6001) is closer to the in-focus point, the shutter time lag is shorter when the focus lens 2002 is moved from the end W (E, 6001) to the end W (S, 6001). Become.

  When the exposure is completed, the CPU 1002 proceeds to the process of step S4009 described above and performs image processing by the DSP 1007. Subsequently, the CPU 1004 determines whether or not shooting of all the sheets set in the continuous shooting mode is completed (step S7010). If shooting of all the sheets is not completed (NO in step S7010), step 1007 is performed. The process returns to S7007.

  In the example shown in FIG. 8, from time t8 to time t9, the CPU 1004 returns to the process of step S7007 and moves the focus lens 2002 to the initial position for the next shooting. At this time, the CPU 1004 compares the end portion W (S, 6002) and the end portion W (E, 6002), and moves the focal point of the focus lens 2002 using the one closer to the current position as the initial position.

  Subsequently, from time t9 to t10, in step S7008, the CPU 1004 performs exposure and movement of the focal point of the focus lens 2002 for the subject 6002 closest to the camera in the same procedure as that for the closest subject.

  Under this condition, the end W (E, 6002) is closer to the end W (E, 6001) than the end W (S, 6002), so the moving direction of the focus lens 2002 in the second shooting is From the back side to the near side direction.

  In this way, the CPU 1004 repeats the processing of steps S7007 to S7009 until shooting of all subjects is completed (that is, until shooting of all the sheets is completed).

  Here, since the three subjects are each photographed as the main subject, the moving direction and moving range of the in-focus point in the focus lens 2002 are changed from time t10 to t12 in the same manner as the time t8 to t10. The same processing is performed.

  When all the images have been shot (YES in step S7010), CPU 1004 proceeds to the process in step S4010 and determines whether the power is turned off. Then, as described above, when the power is turned off, the CPU 1004 ends the photographing operation. On the other hand, if the power is not turned off, the CPU 1004 returns to the process of step S4001 and performs live view display.

  In the example shown in FIG. 8, at time t13, the CPU 1004 starts moving the focus lens 2002 to return the focus point of the focus lens 2002 to the focus point W (C, 6001). At time t14, the CPU 1004 performs live view display again.

  In the second embodiment, the focus lens 2002 is alternately moved from the near side to the far side and from the far side to the near side every time exposure is performed. As a result, with respect to the position of the focal point of the focus lens 2002 at the time of completion of the previous exposure, the next exposure starts exposure from the end closer to the start of the next exposure in continuous shooting. Time has been shortened.

  As described above, in the second embodiment of the present invention, a simple configuration that does not require additional image processing even when performing continuous shooting with a plurality of subjects as main subjects sequentially and blurring subjects other than the main subject. Thus, while focusing on the main subject, the subject existing on the back side and the near side of the main subject can be blurred simultaneously and a natural photographed image can be obtained.

  As is clear from the above description, in the example shown in FIG. 1, the CPU 1004 and the DSP 1007 function as distance detection means and in-focus calculation means, and the CPU 1004 functions as control means. The CPU 1004 and the DSP 1007 function as an exposure detection unit and an exposure calculation unit.

  As mentioned above, although this invention was demonstrated based on embodiment, this invention is not limited to these embodiment, Various forms of the range which does not deviate from the summary of this invention are also contained in this invention. .

  For example, the function of the above embodiment may be used as a control method, and this control method may be executed by the imaging apparatus. Further, a program having the functions of the above-described embodiments may be used as a control program, and the control program may be executed by a computer included in the imaging apparatus. The control program is recorded on a computer-readable recording medium, for example.

  Each of the above control method and control program has at least a distance detection step, a focal point calculation step, and a control step.

  The present invention can also be realized by executing the following processing. That is, software (program) that realizes the functions of the above-described embodiments is supplied to a system or apparatus via a network or various recording media, and the computer (or CPU, MPU, etc.) of the system or apparatus reads the program. To be executed.

1001 Optical unit 1002 Imaging element 1004 CPU
1005 ROM
1006 RAM
1007 DSP
1008 External interface 1010 Memory medium controller 1011 Operation panel 1012 Display

Claims (7)

An imaging optical system having a focus lens is provided, and when shooting a composition in which a plurality of subjects are located from the front side to the back side, at least one of the plurality of subjects is used as a main subject and subjects other than the main subject are blurred. An imaging device for shooting
Distance detection means for detecting distance between the main subject and the imaging device to obtain distance information;
A focal point calculation means for obtaining a focal point of the focus lens in which the main subject falls within the depth of field according to the distance information;
Control means for moving and controlling the focal point of the focus lens along the optical axis of the imaging optical system during an exposure period for photographing the composition within a range in which the main subject is within the depth of field;
An imaging device comprising: Exposure detection means for detecting an exposure condition for the main subject and obtaining an exposure detection result;
Exposure calculation means for obtaining an exposure period based on the exposure detection result,
The control means performs exposure in the exposure period obtained by the exposure calculation means, and moves the focus lens during the exposure period in a range of the depth of field and the movement distance of the focus lens. The imaging apparatus according to claim 1, wherein calculation is performed according to an exposure period.   The imaging apparatus according to claim 2, wherein the control unit performs exposure while moving a focal point of a focus lens at the moving speed. In continuous shooting in which the plurality of subjects are sequentially photographed as a main subject, the distance detection unit detects the distance from the imaging device for each of the plurality of subjects to obtain the distance information;
The in-focus calculation means obtains the in-focus point of the focus lens at which the subject falls within the depth of field for each of the plurality of subjects based on the distance information;
The control means controls the movement of the focal point of the focus lens within a range of the depth of field determined by the focal point every time the plurality of subjects are sequentially exposed as main subjects in the continuous shooting. The imaging device according to claim 1.   When the control unit moves the focal point of the focus lens, the control unit moves the focal point of the focus lens from one end of the depth of field closer to the other end immediately before the movement. The imaging apparatus according to claim 4, wherein movement control of a focal point of the focus lens is performed. An imaging optical system having a focus lens is provided, and when shooting a composition in which a plurality of subjects are located from the front side to the back side, at least one of the plurality of subjects is used as a main subject and subjects other than the main subject are blurred. A method of controlling an imaging device for photographing,
A distance detection step of detecting distance between the main subject and the imaging device to obtain distance information;
A focal point calculating step for obtaining a focal point of the focus lens in which the main subject falls within the depth of field according to the distance information;
A control step of moving and controlling the focal point of the focus lens along the optical axis of the imaging optical system during an exposure period for photographing the composition within a range in which a main subject falls within the depth of field;
A control method characterized by comprising: An imaging optical system having a focus lens is provided, and when shooting a composition in which a plurality of subjects are located from the front side to the back side, at least one of the plurality of subjects is used as a main subject and subjects other than the main subject are blurred. A control program used in an imaging device for photographing,
In the computer provided in the imaging device,
A distance detection step of detecting distance between the main subject and the imaging device to obtain distance information;
A focal point calculating step for obtaining a focal point of the focus lens in which the main subject falls within the depth of field according to the distance information;
A control step of moving and controlling the focal point of the focus lens along the optical axis of the imaging optical system during an exposure period for photographing the composition within a range in which a main subject falls within the depth of field;
A control program characterized by causing

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