JP5124929B2 - Focus adjustment device and digital camera - Google Patents

Description

  The present invention relates to a focus detection device and a digital camera including the focus detection device.

  In an automatic focus adjustment apparatus using a contrast method, a focus adjustment operation is performed using an AF evaluation value calculated from an imaging signal in an AF area (see, for example, Patent Document 1).

JP 2004-325619 A

  Incidentally, even in a lens-integrated digital camera, there is a case where the magnification is increased and the chief ray angle in the peripheral area on the screen is increased. In such a case, there is a problem in that the subject is displaced in the radial direction at the periphery of the screen during the focusing operation, which affects the focusing operation.

According to a first aspect of the present invention, there is provided a focus adjusting apparatus comprising: an imaging element that outputs an imaging signal; an AF area setting unit that sets a peripheral AF area at least around the imaging range of the imaging element; and a photographing lens in an optical axis direction thereof. The contrast information of the imaging signal in the peripheral AF area set by the AF area setting means at each of the plurality of movement positions of the photographing lens is detected and detected for each of the plurality of movement positions. A focus detection unit that calculates a focus position based on a plurality of contrast information; and a focus adjustment unit that adjusts the focus to the focus position calculated by the focus detection unit. The AF area setting unit includes the photographing lens. when imaging state of the imaging lens is moved in a direction in which the front focus state, the peripheral position of the peripheral AF area from the center of the imaging range Heading change along the radial direction, when the photographing lens in a direction imaging state of the imaging lens is a rear focus state moves, radially toward the center position of the peripheral AF area from the periphery of the imaging range It is characterized by changing along .
According to a seventh aspect of the present invention, there is provided a digital camera comprising: a photographic lens that forms a subject image on a planned imaging plane; and the focus adjustment device according to any one of the first to sixth aspects. To do. According to a tenth aspect of the present invention, there is provided a focus adjustment apparatus including: an AF area setting unit that sets a peripheral AF area at least around an imaging range of an image sensor; and a photographing lens that is moved to a plurality of positions in an optical axis direction. A focus detection unit that detects a focus position using a contrast of an imaging signal in the AF area at each position, and a control unit that controls movement of the photographing lens in the optical axis direction, in accordance with the moving direction of the exit pupil position by moving in the optical axis direction of the photographing lens for detecting the focus position, away the position of the peripheral AF area from the radial direction or center toward the center of the imaging range Control is performed so as to move in the radial direction .
Digital camera according to the invention of claim 14 is characterized in that it comprises a focusing device according to any one of claims 10 to 13.

  According to the present invention, since the position or position and size of the AF area in the imaging range is changed in accordance with the focusing operation of the photographing lens, the subject in the vicinity of the AF area is caused to be affected by the focusing operation. It is possible to avoid entering the area or moving the target subject out of the AF area.

  Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings. FIG. 1 is a block diagram for explaining an embodiment of a digital camera according to the present invention. The digital camera shown in FIG. 1 is an interchangeable lens camera, and an interchangeable lens 2 having a photographing lens 3 is detachably attached to a camera body 1.

  The photographing lens 3 is a zoom lens having a variable focal length, and includes a focus lens (not shown) for performing focus adjustment. In the lens barrel of the interchangeable lens 2, a lens driving unit 9 for driving the focus lens and the zoom lens, and a ROM 4 in which lens information relating to the zoom lens, the focus lens, and the like are stored in advance are provided. The camera body 1 is provided with an image sensor 5 that captures a subject image formed by a photographing lens. As the image sensor 5, a CCD image sensor, a MOS type image sensor, or the like is used.

  The imaging signal output from the imaging element 5 is converted into a digital signal by the A / D converter 6 and then stored in the memory 7. The imaging data stored in the memory 7 is read into the image processing circuit 10 where various image processing is performed. Image data obtained by image processing is stored in the memory 7 and recorded in the external storage medium 8. Further, the image processing circuit 10 generates a display image from the image data, and the image is displayed on the LCD display device 11.

  The CPU 12 comprehensively manages control of the entire camera, and AF control, exposure control, and the like are performed according to commands from the connected release operation unit 13. Only the functions related to the present embodiment will be described below. The AF calculation unit 121 reads an imaging signal in the AF area from the memory 7 and calculates an AF evaluation value by a known contrast method. The AF evaluation value is obtained, for example, by taking out data in the horizontal direction or the vertical direction in a predetermined AF area, performing a filtering process, calculating a difference with an adjacent pixel, and accumulating the differences. . And it is judged that it is so high that this AF evaluation value is large.

  The AF area described above designates which area of the imaging range is used to calculate the AF evaluation value. For example, the AF areas 21A to 21E of rectangular areas as shown in FIG. 20 is set. Conventionally, the sizes and positions of the AF areas 21 </ b> A to 21 </ b> E have been fixed, but in the present embodiment, the positions and sizes are changed according to the focusing operation as described later. The AF area setting unit 122 sets the size and position of the AF areas 21A to 21E based on the lens information stored in the focus lens and the driving amount ROM 4.

<Description of focusing operation>
In the digital camera of this embodiment, focusing is performed using the contrast AF method. The CPU 12 controls the lens drive 9 based on the AF evaluation value calculated by the AF calculation unit 121 and causes the photographing lens 3 to perform a focusing operation. In the focusing operation using the AF evaluation value, when the subject is in focus, the captured image includes the most high-frequency components, and the higher the distance from the in-focus position, the lower the high-frequency components included in the image. Using the increase in the ratio of frequency components, AF is performed by a method called “mountain climbing AF”.

  FIG. 3 is a diagram showing the relationship between the lens position of the focus lens and the AF evaluation value, and the curve L represents the AF evaluation value with respect to the focus lens position. This curve L is based on the imaging signal of any one of the AF areas 21A to 21E shown in FIG. Since the subject area captured for each AF area 21A to 21E is different, the shape of the curve L is different for each AF area 21A to 21E. In the following description, the curve L1 is related to the AF area 21B.

  In hill-climbing AF, the magnitude of the AF evaluation value before and after the movement is compared each time the focus lens is moved by a predetermined amount, and the AF evaluation value is maximized by repeatedly moving in the direction in which the AF evaluation value increases based on the comparison result. The focus lens is moved to the lens position D0. The focusing operation is started when the release button provided in the release operation unit 13 of FIG. 1 is half-pressed.

  For example, when the lens position at the start of the focusing operation is D1 in FIG. 3, the focus lens is moved to the ∞ side until it passes the peak of the AF evaluation value as indicated by D2 and D3. If the peak is passed, the lens position D0 is estimated from the AF evaluation values at the lens positions D1 to D3, and the focus lens is moved to the estimated lens position D0, thereby completing the focusing operation.

<< Explanation of subject movement on the imaging surface >>
Next, subject movement on the imaging surface will be described. FIG. 4 is a diagram for explaining the relationship between the exit pupil position of the photographic lens 3 during the focusing operation and the position of the subject image on the imaging surface. In FIG. 4, (a) shows a state when focus is achieved, (b) shows a front pin state, and (c) shows a rear pin state.

  As shown in FIG. 4A, the principal ray 40 at each imaging plane position of the subject light incident on the imaging surface 5a of the imaging element 5 is emitted from the center 41 of the exit pupil at a principal ray angle γ. Usually, since the distance PO1 from the imaging surface 5a to the exit pupil (hereinafter referred to as the exit pupil position) is finite, the principal ray angle γ is not zero at positions other than on the optical axis J of the imaging surface 5a. When the focus lens is moved during the focusing operation, the principal ray angle γ hardly changes, but the exit pupil position changes.

  In the in-focus state shown in FIG. 4A, the subject image is formed on the imaging surface 5a, and the focused subject image is captured. At this time, the incident position of the principal ray 40 on the imaging surface 5a is a position a distance a from the optical axis J. In the front pin state of FIG. 4B, the imaging position is on the photographing lens side (the left side in the figure) with respect to the imaging surface 5a, and the principal ray incident position at this time is a position b from the optical axis J. On the other hand, in the rear pin state shown in FIG. 4C, the imaging position is on the rear side of the camera (right side in the figure) with respect to the imaging surface 5a, and the principal ray incident position at this time is at a distance c from the optical axis J. . The distances a, b, and c are b> a> c as can be seen from FIG.

  When the focus lens moves in the order of D1, D2, and D3 in FIG. 3 during the focusing operation, the state changes from the state of FIG. 4C to the order of (a) and (b). As a result, the position of the subject on the imaging surface 5a moves radially from the center of the screen, which is the position of the optical axis J, to the peripheral direction as shown by the arrow in FIG. In FIG. 2, 22a, 22b, and 22c represent subjects having the same principal ray angle γ, and moved by the same distance in the radial direction. Reference numeral 23 denotes a subject having a larger principal ray angle γ, and the moving distance in the radial direction is larger.

  For example, when focusing on the AF area 21B before and after the movement, the subject 22b outside the area before the movement enters the area, and conversely, the subject 23 inside the area before the movement goes out of the area. Yes. Here, a case is considered where the relationship between the focus lens lens position and the AF evaluation value regarding the subjects 22b and 23 is as indicated by the curves L1 and L2 in FIG. D10 and D11 indicate the focus lens positions before and after the movement.

  Since the AF area 21B captures the subject 23 at the lens position D10, the focus lens is moved to the closest lens position D11 so that hill-climbing AF is performed according to the curve L1. When the lens position D11 is moved, the subject 23 comes out of the AF area 21B and the subject 22b enters the area as described above. As a result, the AF evaluation value changes from C1 on the curve L1 to C2 on the curve L2. After that, hill-climbing AF is performed according to the curve L2 related to the subject 22b. Therefore, the focus lens is moved to the ∞ side and focused on the peak P2 of the curve L2, and the subject 23 that the user wanted to focus on is It will be out of focus.

<Explanation of AF area change>
In the present invention, in order to avoid such an inconvenience, the position and size of the AF area are changed according to the focusing operation. FIG. 6 is a diagram showing an AF area changing mode, and (a) and (b) show different modes. In FIG. 6A, the four AF areas 21B to 21E except the AF area 21A at the center of the screen are moved in the radial direction in conjunction with the focus operation. The broken line indicates the AF area after movement.

  The amount of movement (size and direction) of the AF area 21B in the radial direction can be calculated from the amount of change in the exit pupil position (size and direction in the optical axis direction) and the principal ray angle γ. FIG. 7A shows the relationship between the change amount ΔPO of the exit pupil position during the focusing operation and the amount of movement of the subject. PO1 indicates the exit pupil position of the photographic lens 3. The exit pupil position PO1 is stored in advance in a ROM 4 provided in the lens barrel. The CPU 21 reads this position PO1 from the ROM 4, calculates the principal ray angle γ1 for each of the AF areas 21B to 21E, and stores it in the memory 7. Here, the principal ray angle γ1 is assumed to be a principal ray angle with respect to the center position of the AF areas 21B to 21E.

  When the focus operation is performed, for example, the exit pupil position changes within a range sandwiched between broken lines. Here, if the exit pupil position is moved by ΔPO in the direction of the taking lens from PO1 by the focus operation, the movement amount Δx1 of the subject at the center of the AF area 21B is given by Δx1 = ΔPO · tanγ1. Here, this movement amount Δx1 is set as the movement amount of the AF area 21B.

  The movement amount ΔPO of the exit pupil position is determined according to the movement amount of the focus lens, and the correlation between the movement amount of the exit pupil position and the movement amount of the focus lens is stored in the ROM 4 in advance. The CPU 21 calculates the exit pupil position movement amount ΔPO based on the correlation and the lens driving amount actually driven.

  When the photographing lens 3 is a zoom lens, the exit pupil position is changed by the zoom operation. FIG. 7B is a diagram for explaining the case of the zoom lens, where PO1 is the exit pupil position at the zoom position 1 and PO2 is the exit pupil position at the zoom position 2. FIG. In the case of the zoom position 1, the AF area movement amount is Δx1 with respect to the exit pupil position movement amount ΔPO as in the case of FIG. On the other hand, at the zoom position 2, the chief ray angle is γ2 (<γ1), and the AF area movement amount Δx2 with respect to the same exit pupil position movement amount ΔPO is smaller than the AF area movement amount Δx1 at the zoom position 1.

  Each time the zoom operation is performed, the CPU 21 reads the exit pupil position at the zoom position from the ROM 4, calculates the principal ray angle γ, stores it in the memory 7, and calculates the AF area movement amount using the principal ray angle γ. To do. In other words, the AF area is moved to an appropriate position according to the subject movement amount by adjusting the movement amount of the exit pupil position according to the zoom operation.

  On the other hand, in the AF area changing mode shown in FIG. 6B, the AF area is moved in the radial direction and the area of the AF area is enlarged as in the case of FIG. As can be seen from (b) and (c) of FIG. When deviating from the focus position, the subject image on the imaging surface 5a is blurred and spreads around the principal ray incident position. For this reason, even if the AF area is moved in the radial direction, a blurred part may come out of the area. In this case, subject information is reduced and the evaluation value changes. Therefore, by increasing the AF area area according to the focus operation, it is possible to reduce the change in the information amount of the target subject.

  As described above, in the present embodiment, the AF area is moved in the radial direction of the screen in accordance with the focus operation, so that a subject around the AF area enters the area or the target subject is It will not come out of the area. As a result, it is possible to avoid false focusing and the like in which the focus is different from the original focus position.

  The AF areas 21A to 21E shown in FIGS. 2 and 6 are displayed on the LCD display device 11 together with the subject image. However, the AF areas on the LCD display device 11 are interlocked with the change of the AF areas 21A to 21E described above. Change the position and size of the display. The AF areas 21A to 21E are always changed during the focusing operation, but if the photographing operation is performed, the settings of the AF areas 21A to 21E are reset to the default state (initial position, initial size). Is done.

  Note that the present invention is not limited to the above embodiment as long as the characteristics of the present invention are not impaired. For example, the present invention can be applied to not only an interchangeable lens type digital camera but also a lens-integrated digital camera.

It is a block diagram explaining one Embodiment of the digital camera by this invention. It is a figure which shows AF areas 21A-21E set on the imaging | photography screen 20. FIG. It is a figure which shows the relationship between the lens position of a focus lens, and AF evaluation value. It is a figure explaining the relationship between the exit pupil position at the time of a focus operation | movement, and the position of a to-be-photographed image, (a) is a state when it is focusing, (b) is a front-focus state, (c) is back. Each pin state is shown. It is a figure explaining false focusing. It is a figure which shows AF area change form, (a) shows a 1st form, (b) shows a 2nd form, respectively. It is a figure which shows the relationship between the variation | change_quantity of the exit pupil position at the time of focus operation | movement, and the moving amount | distance of a to-be-photographed object, (a) shows the case of a non-zoom lens, (b) shows the case of a zoom lens, respectively.

Explanation of symbols

1: Camera body 2: Interchangeable lens 3: Shooting lens 4: ROM
5: Image sensor 7: Memory 10: Image processing circuit 11: LDC display device 12: CPU 121: AF operation unit 122: AF area setting unit

Claims (14)

An image sensor that outputs an image signal;
AF area setting means for setting a peripheral AF area at least around the imaging range of the image sensor;
The imaging lens is moved in the optical axis direction, and contrast information of the imaging signal in the peripheral AF area set by the AF area setting means is detected at each of a plurality of movement positions of the imaging lens, Focus detection means for calculating a focus position based on a plurality of contrast information detected for each movement position;
Focus adjusting means for adjusting the focus to the in-focus position calculated by the focus detecting means,
The AF area setting means moves the position of the peripheral AF area along a radial direction from the center of the imaging range toward the periphery when the imaging lens moves in a direction in which the imaging state of the imaging lens becomes a front pin state. Change the position of the peripheral AF area along the radial direction from the periphery to the center of the imaging range when the imaging lens moves in a direction in which the imaging state of the imaging lens is in the rear pin state. A focusing device characterized by that. The focus adjustment apparatus according to claim 1,
The focus adjustment apparatus, wherein the AF area setting means changes the size of the AF area in addition to the change of the position of the peripheral AF area according to a plurality of movement positions of the photographing lens. The focusing apparatus according to claim 2, wherein
The focus is characterized in that the AF area setting means changes the size of the peripheral AF area to be larger as the position of the peripheral AF area is changed away from the center of the imaging range in the radial direction. Adjusting device. In the focus adjustment apparatus according to any one of claims 1 to 3,
The photographing lens is a zoom lens capable of changing a focal length,
The focus adjustment apparatus, wherein the AF area setting means changes the position of the peripheral AF area according to a plurality of movement positions of the photographing lens and a focal length of the zoom lens. In the focus adjustment apparatus according to any one of claims 1 to 4,
The AF area setting means can set a central AF area near the center of the imaging range in addition to the peripheral AF area,
The focus adjustment apparatus, wherein the AF area setting means does not change the position of the central AF area according to a plurality of movement positions of the photographing lens. In the focus adjustment apparatus according to any one of claims 1 to 5,
A display device;
The display device displays the AF area set by the AF area setting means and also displays the AF area changed by the AF area setting means. A photographic lens that forms a subject image on a planned imaging plane;
A digital camera comprising: the focus adjustment device according to claim 1. The digital camera according to claim 7, wherein
The AF area setting means sets the position of the peripheral AF area as a default if a shooting operation is performed by the image sensor after changing the position of the peripheral AF area according to a plurality of movement positions of the shooting lens. A digital camera characterized by returning to the state of. The digital camera according to claim 7 or 8,
A digital camera, wherein the photographing lens is an interchangeable lens that is detachably attached to a camera body. An AF area setting unit that sets a peripheral AF area at least around the imaging range of the imaging device;
A focus detection unit that moves the photographic lens to a plurality of positions in the optical axis direction and detects a focus position using the contrast of the imaging signal in the AF area at each of the plurality of positions;
A control unit that controls movement of the photographing lens in the optical axis direction;
Wherein, in accordance with the moving direction of the exit pupil position by moving in the optical axis direction of the photographing lens for detecting the focus position toward the position of the peripheral AF area at the center of the imaging range radiation A focus adjustment device that controls to move in a radial direction away from the direction or center . The focus adjustment apparatus according to claim 10.
The taking lens is a zoom lens,
The focus adjustment apparatus, wherein the control unit changes a change amount of the position of the AF area linked to the movement of the photographing lens according to the magnification of the zoom lens. The focusing apparatus according to claim 10 or 11,
A central AF area set near the center of the imaging range, and a peripheral AF area set around the central AF area;
The controller is configured to change the position of the peripheral AF area in conjunction with the movement of the photographing lens, and does not change the position of the central AF area. In the focus adjustment apparatus according to any one of claims 10 to 12,
The focus adjustment apparatus, wherein the control unit changes the position and size of the AF area in conjunction with movement of the photographing lens.   A digital camera comprising the focus adjustment device according to claim 10.

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