JP2003185911A - Optical system control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology for focussing the objects of a close view and of a distant view even when the contrast of the object of the close view is low. <P>SOLUTION: A large edge LE including a far and near boundary is detected by using a luminance difference between the adjacent pixels of an image. Based on the means of a Hough transformation, etc., a vertical edge A on the left-hand side of a first image region P1 is detected from the direction of the line segment of the large edge LE and the change of the direction. A first evaluation region F1 including a part of large edge LE and including a first image region P1 more than a second image region P2, and a second evaluation region F2 including the second image regions P2 more than the first image region P1 are set up at the position. Evaluation values regarding the focussing state of the photographic lens 11 is determined about the first and second evaluation regions F1 and F2. The far and near boundary is detected on the basis of the evaluation values, and the focussing operation of the photographic lens is carried out on the basis of the evaluation value of one evaluation region to the far and near boundary. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital camera, and more particularly to automatic focusing (hereinafter
Also referred to as "autofocus" or "AF". ) Technology.

[0002]

2. Description of the Related Art Conventionally, as an autofocus device used in a digital camera or the like, while the photographing lens is driven in the optical axis direction, the combination of the photographing lens with respect to a specific evaluation area of an image acquired at each lens position is used. In general, an evaluation value relating to a focus state is obtained, and based on the evaluation value, an autofocus operation by a contrast method for performing a focusing operation of a photographing lens is performed. Further, the evaluation value mentioned here is obtained by calculating the contrast value by comparing the pixel value of each pixel with the pixel value of the adjacent pixel, and adding the contrast value for a plurality of pixels in a predetermined area. That is, the evaluation value is obtained as the sum of contrast values between adjacent pixels in the evaluation area.

FIG. 17 shows a curve CL representing the relationship between the evaluation value and the position x of the taking lens in the optical axis direction. As shown in FIG. 17, when the taking lens is in the in-focus position (x = xv), the evaluation value is the largest. Then, the contrast autofocus operation is performed by comparing the evaluation values of at least two picked-up images picked up at different positions x in the optical axis direction of the taking lens. Specifically, the evaluation values of the two images are compared, and the taking lens is driven in the direction in which the evaluation value becomes larger. Then, by repeating such an operation and driving the taking lens, the taking lens can be driven to the in-focus position.

[0004]

However, in the case where the near-field subject (near-view subject) and the distant-view subject (distant-view subject) are mixed in the image in the evaluation area, the image shown in FIG.
As shown in 8, the curve CL indicated by the solid line is calculated as the evaluation value. Here, the evaluation value is the dashed-dotted curve C
The evaluation value (near view evaluation value) for the near view subject and the evaluation value (distant view evaluation value) for the distant view subject, which are respectively indicated by Ln and CLf, are calculated as a combined value. Therefore, in such a case, it is impossible to focus on either the near view object or the distant view object at the position (x = xv) of the taking lens where the evaluation value is the largest.

Further, when the contrast of the near view subject is low, specifically, as shown in FIG.
When P is a flag and pole with low contrast and the distant view subject FP is a building with high contrast, the evaluation value for the evaluation area FA is the evaluation shown by the solid line CL, as shown in FIG. It is calculated as a value. Also here, the evaluation values are the dashed line curves CLn and CL.
It is calculated as a value obtained by combining the near view evaluation value and the distant view evaluation value respectively indicated by f. Since the distant view evaluation value has a significantly larger peak than the near view evaluation value, the photographing lens position (x = xv) at which the evaluation value is maximized is the image at which the distant view evaluation value is maximized. Since the position is close to the position of the lens (x = xvf), even if the position of the shooting lens is driven to the position of the shooting lens (x = xv) where the evaluation value is maximum, it is not possible to focus on the near-field subject. Further, here, if the evaluation area is set only for the near-view subject, the contrast of the near-view subject is low, and therefore the evaluation value does not have a peak above a certain level. The amount of change in the evaluation value is small. The overall level of evaluation value is low. It is determined by the digital camera that all three conditions are satisfied, and that the contrast in the evaluation area FA is not higher than a certain level, and the position of the taking lens that focuses the near-field subject cannot be obtained.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a technique capable of easily focusing on a near-distance subject or a distant-distance subject even when the contrast of the near-distance subject is low. .

[0007]

In order to solve the above-mentioned problems, the invention of claim 1 is an optical system control device for inputting an image composed of a plurality of pixels to control the focusing of a photographing lens. A detection area setting means for setting a predetermined boundary detection area in the image, an edge detection means for detecting an edge including a boundary between a near view object and a distant view object from the boundary detection area, and a part of the edge The first and second image areas which are areas on both sides of the edge and which include the first image area more than the second image area, and the first evaluation area. The second from the image area of
Evaluation area setting means for setting a second evaluation area including a large number of image areas, and evaluation value calculation means for calculating an evaluation value regarding the focus state of the photographing lens for the first and second evaluation areas, Control means for determining a focus position of the taking lens based on the evaluation value calculated by the evaluation value calculating means and controlling driving of the taking lens to the focus position.

According to a second aspect of the present invention, in the optical system control device according to the first aspect, the edge detecting means recognizes an edge as an edge when a brightness difference between adjacent pixels is a predetermined value or more. It is characterized in that it includes an edge recognizing means for performing.

The invention according to claim 3 is the optical system control device according to claim 1 or 2.
The detection area setting means sets the entire image as a boundary detection area.

The invention according to claim 4 is the optical system control device according to claim 1 or 2.
The detection area setting means sets a boundary detection area having a constant width in the horizontal direction with respect to the image.

Further, the invention of claim 5 is the optical system control device according to any one of claims 1 to 4, wherein the first and second evaluation regions are respectively separated by the edge. The area of one area is 2 of the area of the other area.
It is characterized by being more than double.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

<Main Structure of Digital Camera> FIG. 1 is a perspective view showing a digital camera 1 according to an embodiment of the present invention. 2 is a rear view of the digital camera 1.

As shown in FIG. 1, a taking lens 11 and a finder window 2 are provided on the front side of the digital camera 1. A CCD image pickup device 30 is provided inside the photographing lens 11 as an image generation unit for photoelectrically converting a subject image incident through the photographing lens 11 to generate an image signal (a signal including an array of pixel data for each pixel). It is provided.

The photographic lens 11 includes a lens system that can be driven along the optical axis direction. By driving the lens system in the optical axis direction, a subject image formed on the CCD image pickup device 30 is formed. It is configured so that a focused state can be realized. Further, the taking lens 11 is provided with an aperture that can change the depth of field, and the aperture can be increased to increase the depth of field.

A shutter button 8, a zoom key 10, a camera status display section 13, and a photographing mode setting button 14 are arranged on the upper surface of the digital camera 1. The shutter button 8 is a button that the user presses to photograph the subject and gives a photographing instruction to the digital camera 1. Here, the shutter button 8 is half-pressed (S1) to perform an autofocus operation described later, and the fully-pressed state (S2) is to perform a main shooting described later. The zoom key 10 is pressed by the user to take the photographing lens 1.
1 is driven to perform zooming. Camera status display 1
Reference numeral 3 is composed of, for example, a segment display type liquid crystal monitor, and is provided to show the user the present setting contents and the like in the digital camera 1. Further, the shooting mode setting button 14 is one of a plurality of shooting modes such as a portrait mode, a landscape mode, a near-view mode and a distant-view mode, which will be described later, depending on a subject. It is a button for selecting and setting the shooting mode by manual operation.

A mounting portion 15 for mounting a memory card 9 for recording image data obtained in a main photographing operation in response to a user's operation of pressing the shutter button 8 is formed on a side surface portion of the digital camera 1. A removable memory card 9 can be attached. further,
A card take-out button 7 that is pressed when taking out the memory card 9 from the wearing section 15 is arranged.
The memory card 9 can be taken out from.

Further, as shown in FIG. 2, a rear view of the digital camera 1 is provided with a liquid crystal display unit 16 for displaying a live view image, a photographed image, etc., and various setting states of the digital camera 1. An operation button 17 and a finder window 2 are provided. Further, a quad switch 25 is provided, and by pressing the quad switch 25 variously, it is possible to change the detection area described later. In addition, in FIG. 2, a Cartesian coordinate system is attached to clarify the directional relationship, and when the same Cartesian coordinate system is attached in the following drawings, the same directional relationship is shown. Be present.

<Functional Block of Digital Camera> FIG. 3 is a block diagram showing the internal structure of the digital camera 1.
As shown in FIG. 3, the digital camera 1 includes a photographing function unit 3 for processing an image signal, an optical system control unit 150 for realizing autofocus control, and a lens driving unit 1.
10 and a camera control unit 100 that integrally controls each unit provided in the digital camera 1.

CCD image pickup device 3 via the taking lens 11
The subject image formed at 0 is converted into an electric image having a plurality of pixels, that is, an image signal in the CCD image pickup device 30, and is guided to the A / D converter 40.

The A / D converter 40 converts the image signal output from the CCD image pickup device 30 into, for example, a digital signal of 10 bits per pixel. The image signal output from the A / D converter 40 is guided to the image processing unit 50.

The image processing unit 50 performs image processing such as white balance adjustment, γ correction and color correction on the image signal. At the time of displaying the live view image, the image processing unit 50 outputs the image signal subjected to the image processing to the live view image creation unit 6
Give to 0. Further, when performing the autofocus control, the image processing unit 50 gives an image signal to the image memory 70. Further, during the shooting operation (main shooting) performed in response to the pressing operation of the shutter button 8, the image processing unit 50 provides the image compression unit 80 with the image signal subjected to the image processing.

When the live view image is displayed, the live view image creating section 60 generates an image signal suitable for the liquid crystal display section 16 and supplies it to the liquid crystal display section 16. Therefore, at the time of displaying the live view image, image display is performed on the liquid crystal display unit 16 based on the image signal obtained by successive photoelectric conversion in the CCD image pickup device 30.

The image memory 70 is for temporarily storing an image signal for performing autofocus control. In the image memory 70, the optical system control unit 150 drives the lens position of the taking lens 11 in a stepwise manner, and the image signal taken at each lens position of the taking lens 11 is stored under the control of the camera control unit 100. .

The timing at which the image signal is stored in the image memory 70 from the image processing section 50 is the timing at which the autofocus control is performed. For this reason, when it is desired to display a focused live view image on the liquid crystal display unit 16 during live view image display, an image signal may be stored in the image memory 70 during the live view image display. good.

Further, when the shutter button 8 is pressed, it is necessary to perform autofocus control before the photographing operation of the main photographing. Therefore, before performing the main photographing operation, the image signals photographed at the respective lens positions are stored in the image memory 70 while driving the lens positions of the photographing lens 11 in stages. The optical system controller 150 is configured to acquire an image signal stored in the image memory 70 and perform a contrast autofocus operation.
Then, after the photographic lens 11 is driven to the in-focus position by performing the autofocus control by the optical system control unit 150, the photographing operation of the main photographing is performed, and the image signal obtained by the main photographing is given to the image compressing unit 80. To be

The image compression section 80 is configured to perform an image compression process by a predetermined compression method on the image signal obtained by the actual photographing, and the image signal subjected to the image compression is output from the image compression section 80. And is stored in the memory card 9.

The camera control unit 100 is realized by the CPU executing a predetermined program, and the shutter button 8, the user presses various buttons including the photographing mode setting button 14, the operation button 17, and the quad switch 25. In this case, each unit of the photographing function unit 3 and the optical system control unit 150 are configured to be controlled according to the operation content. Further, the camera control unit 100 includes the optical system control unit 15
When the optical system controller 150 drives the lens position of the photographing lens 11 stepwise in autofocus control, the photographing operation of the CCD image pickup device 30 is controlled at each lens position and the photographing is performed. It controls so as to store the generated image signal in the image memory 70.

The lens driving unit 110 includes an optical system control unit 15
It is a drive unit for driving the taking lens 11 along the optical axis in response to a command from 0, and changes the focus state of the subject image formed on the CCD image pickup device 30. Further, the lens driving unit 110 includes an optical system control unit 150.
And the photographing lens 1 under the control of the camera control unit 100.
The diaphragm provided in 1 is driven.

<Regarding Optical System Control Unit 150> FIG. 4 is a block diagram showing the internal structure of the optical system control unit 150.
As shown in FIG. 4, the optical system control unit 150 includes an image acquisition unit 151, a detection area setting unit 152, an edge detection unit 153,
It comprises an evaluation area setting unit 154, an evaluation value calculation unit 155, a boundary detection unit 156, an evaluation area selection unit 157, and a drive control unit 158, acquires the image signal stored in the image memory 70, and uses the contrast method. Performs auto focus control. In other words, the photographing lens 11 operates so as to guide the subject image formed on the CCD image pickup device 30 to the in-focus position.

The function of the optical system controller 150 in the autofocus control differs depending on the photographing mode set by the operation of the photographing mode setting button 14. Here, the features of the digital camera 1 according to the present invention are described. The function of each part of the optical system control unit 150 in the near view mode and the distant view mode selected when the contrast of a certain near view subject is low, etc. will be described, and when other portrait mode, landscape mode, etc. are set, The description is omitted because it is similar to the autofocus control by the conventional contrast method.

The image acquisition unit 151 acquires the image signal input to the image memory 70 from the image memory 70.

The edge detecting section 153 detects an edge including a boundary between the near view object and the distant view object (a perspective boundary) from a predetermined boundary detection area set in the image acquired from the image memory 70. Specifically, first, the image memory 7
From the image signal stored in 0, a portion in which a group of adjacent pixels whose luminance difference between adjacent pixels is a predetermined value or more is continuous for a predetermined threshold length or more is recognized as an edge. When the edge detection unit 153 recognizes an edge, it is preferable to set the aperture of the digital camera 1 to the most narrowed state so that the edge can be easily recognized regardless of the distance of the subject.

As described above, the edge detecting section 153 can recognize the edges, but if the distant view subject has many portions with a large luminance difference, many edges will be recognized. Therefore, here, by utilizing the fact that many of the edges in the distant object are relatively fine, the relatively fine edges are excluded as the portion where the luminance difference of the distant object is severe.
For example, this can be achieved by setting the threshold length in the above edge detection 153 to be relatively large. In this way, it is possible to detect a relatively large edge in the distant view subject and a large edge composed of the perspective boundary.

The boundary detection area is a unit area for detecting an edge including a perspective boundary from the image, and is set for the image stored in the image memory 70 by the detection area setting unit 152. FIG. 5 is a diagram showing an example of the boundary detection area. As illustrated, the detection area setting unit 152 sets a boundary detection area EA1 composed of three areas having a certain width in the horizontal direction with respect to the image G10 stored in the image memory 70. When the edge detection unit 153 cannot detect a large edge in the boundary detection area EA1, or when the boundary detection unit 156 described later cannot selectively detect a perspective boundary in the boundary detection area EA1, detection is performed. The area setting unit 152
Switch the boundary detection area. Specifically, as shown in FIG. 6, it is set as a boundary detection area EA2 composed of three areas having a constant width in the vertical direction with respect to the image G10 stored in the image memory 70. The "horizontal direction" and the "vertical direction" in these are the direction in which the CCD scanning line runs in the angle of view of the digital camera 1 (DX direction in FIG. 2),
Each is defined as a direction perpendicular to it (the DY direction in FIG. 2). From the original purpose of distinguishing a distant view from a near view, it is preferable to correspond to the horizon (horizontal line) direction and the vertical direction respectively, but the digital camera 1 is often used with its bottom face facing downward. , The CCD scanning line direction can be defined as a reference to cover many cases. In addition, even when the digital camera 1 is tilted to take an image, the edge detection and the boundary detection of this embodiment are not impossible. Therefore, the horizontal direction and the vertical direction are defined as described above. However, there is no practical problem.

FIG. 7 is a schematic diagram showing an example in which the boundary detection area EA1 is set for the image G10 stored in the image memory 70, in which the contrast of the foreground subject is low and the contrast of the background subject in the background is high. Is. Here, the near view subject NP is a flag and a pole with low contrast, and the distant view subject FP is a building with high contrast. Here, for convenience of description, the image G10 and the boundary detection area EA stored in the image memory 70 are illustrated for convenience.
1 is also shown together with the frame indicating No. 1, but the frame indicating the boundary detection area EA1 is not actually included in the image G10. As shown in FIG. 7, since the boundary between the foreground object NP and the distant object FP exists in the boundary detection area EA1,
The edge detection unit 153 detects a large edge, and the boundary detection unit 1
56 can selectively detect the perspective boundary.

FIG. 8 shows an image G10 in which the foreground subject has a low contrast and the background distant subject has a high contrast.
It is a schematic diagram which shows an example in which the boundary detection area EA1 is set with respect to. Here, as in FIG. 7, the near-view subject NP is a flag and a pole with low contrast, and the distant-view subject FP is a building with high contrast. Here, as in FIG. 7, for convenience of explanation, the image G10 and the boundary detection area EA1 stored in the image memory 70 are also illustrated for convenience of explanation.
The frame indicating the boundary detection area EA1 is not actually included in the image G10. As shown in FIG. 8, in the boundary detection area EA1, since there is no place where the brightness difference between adjacent pixels is large, the edge detection unit 153 cannot detect a large edge. In such a case, the detection area setting unit 152
The boundary detection area is switched from the boundary detection area EA1 to the boundary detection area EA2 as shown in FIG.

FIG. 9 shows that after switching the boundary detection area,
It is a schematic diagram which shows an example in which the boundary detection area EA2 is set with respect to the image G10. In the image here, as in FIG. 8, the near-view subject NP is a flag and a pole with low contrast, and the distant-view subject FP is a building with high contrast. Here, for convenience of description, the image G10 and the boundary detection area EA stored in the image memory 70 are illustrated for convenience.
2 is also shown together with the frame indicating the area 2, but the frame indicating the boundary detection area EA2 is not actually included in the image G10. As shown in FIG. 9, since the boundary between the foreground object NP and the distant object FP exists in the boundary detection area EA2,
The edge detection unit 153 detects a large edge, and the boundary detection unit 1
56 can selectively detect the perspective boundary.

The evaluation area setting unit 154 includes the edge detection unit 1
Based on the large edge detected by 53, an evaluation area for obtaining an evaluation value regarding the focus state of the taking lens 11 is set for the image stored in the image memory 70. 10 and 11 are schematic diagrams illustrating setting of the evaluation area. FIG. 10 is a diagram illustrating setting of an evaluation area when a vertical edge described below is detected in the boundary detection area EA1 by the edge detection unit 153, and FIG. FIG. 6 is a diagram illustrating setting of an evaluation area when a horizontal edge described below is detected or when a horizontal edge is detected by the edge detection unit 153 in the boundary detection area EA2.

When a large edge is detected in the boundary detection area EA1 by the edge detection unit 153, the evaluation area setting unit 154 uses a method such as Hough transformation to determine a portion in which the line segment of the large edge is oriented vertically (vertically). Edge), and as shown in FIG. 10, the first image area P1 and the second image area P1 that include a part of the large edge LE at the position of the vertical edge A and are areas on both sides of the large edge LE. Second about P2
Of the first evaluation area F1 including the first image area P1 more than the first image area P2 and a part of the large edge LE, and more second image area P2 than the first image area P1. The second evaluation area F2 including the area is set. Note that FIG.
Then, although there are two vertical edges A and B, in such a case, for example, from the change in the direction of the line segment of the large edge LE found by a method such as Hough transform, the first image region P1 The left vertical edge (portion A) is automatically selected.

Here, regarding the areas in which the first evaluation area F1 and the second evaluation area F2 are each separated by the large edge LE, in consideration of the accuracy of focusing by the autofocus operation described later, the areas are separated by the large edge LE. It is preferable that the area of one of the two regions is at least twice the area of the other region. Specifically, referring to FIG. 10 as an example, regarding the first evaluation area F1, the area occupied by the first image area P1 is twice or more the area occupied by the second image area P2. It is in a state. Further, in order to perform focusing by the autofocus operation with higher accuracy, it is preferable that the area of one region divided by the large edge LE is four times or more the area of the other region. In addition,
Here, when the vertical edge cannot be found, the horizontal edge is found and a part of the large edge LE is included at that position, as described later in FIG.
A first evaluation area F1 including a larger number of first image areas P1 than the second image area P2 and a second evaluation area F2 including a larger number of second image areas P2 than the first image area P1. .

When the edge detecting section 153 detects a lateral edge described later in the boundary detecting area EA1,
Alternatively, the edge detection unit 153 causes the boundary detection area EA to be detected.
When a large edge is detected in No. 2, the evaluation area setting unit 154 uses the Hough transform or the like to determine the large edge LE that is the boundary between the first image area P1 and the second image area P2.
Finds a portion (horizontal edge) in which the line segment of FIG. 11 is oriented in the horizontal direction, and includes a part of the large edge LE at that position, and the first image rather than the second image region P2 A first evaluation region F1 including a large amount of the region P1 and a second evaluation region F2 including a larger amount of the second image region P2 than the first image region P1 are set. In FIG. 11, there are two horizontal edges C and D, but in such a case,
For example, a large edge LE obtained by a method such as Hough transform
The horizontal edge (C portion) on the upper side of the first image region P1 is automatically selected from the change in the direction of the line segment.

Here, regarding the area where the first evaluation area F1 and the second evaluation area F2 are separated by the large edge LE, as described with reference to FIG. 10, the accuracy of focusing by the autofocus operation described later is taken into consideration. Then, the area of one region divided by the large edge is preferably twice or more the area of the other region. Further, in order to perform focusing by the autofocus operation with higher accuracy, it is preferable that the area of one region divided by the large edge is four times or more the area of the other region. When setting the evaluation area for the large edge detected in the boundary detection area EA2, the horizontal edge is found from the beginning and the evaluation area is set, but this is the large edge in the boundary detection area EA1. This is because when is not detected and a large edge is detected in the boundary detection area EA2, the line segment of the detected large edge is generally in the horizontal direction.

The evaluation value calculation unit 155 includes an evaluation area setting unit 1
The first evaluation area F1 and the second evaluation area F1 set by 54
With respect to the evaluation area F2, the evaluation value regarding the in-focus state of the taking lens 11 is obtained. This evaluation value is normally obtained as the sum of contrast values between adjacent pixels in the evaluation area, as in the case of being performed in the contrast autofocus operation.

As described above, the large edge is composed of the relatively large edge of the distant view subject and the perspective boundary, and FIGS. 12 and 13 show the first and second evaluation areas F1 and F2, respectively. FIG. 6 is a schematic diagram showing an example of curves CL1 and CL2 representing the relationship between the obtained evaluation values (first and second evaluation values) and the position x of the taking lens 11 in the optical axis direction. FIG. 12 shows the evaluation values for the first and second evaluation areas set for the perspective boundary, and FIG. 13 shows the first and second evaluation areas set for the relatively large edge of the distant view subject. The evaluation value is shown.

As shown in FIG. 12, the curve CL1 is the first evaluation value, the curve CL2 is the second evaluation value, and the taking lens 11 is in the in-focus position with respect to the first evaluation area. In the case (x = x1) and when the taking lens 11 is in the in-focus position with respect to the second evaluation area (x = x2),
The above evaluation values are the largest. Here, the first
Even if most of the evaluation area F1 of the first evaluation area F1 is occupied by a near-field subject having a low contrast, the first evaluation area F1 includes a perspective boundary, and thus the first evaluation value is mainly based on the contrast of the perspective boundary. It has a peak above a certain level. Then, since the first and second image areas are mainly occupied by the near-view subject and the distant-view subject, respectively, the lens positions x = x1 and x = x2 have different values of a certain value or more. Also, as shown in FIG.
When both the first and second image areas are distant objects, the lens positions x = x1 and x = x2 have almost the same value.

The boundary detecting section 156 has an evaluation value calculating section 155.
The perspective boundary is detected by specifying the first and second evaluation regions set for the perspective boundary based on the evaluation value calculated by. Specifically, when the lens positions x = x1 and x = x2, which have the maximum evaluation values for the first and second evaluation areas, show different values of a certain value or more, they are set for the perspective boundary. It is possible to specify the first and second evaluation areas.

The in-focus area selection section is operated by the user to depress various operation buttons 17 before shooting to selectively set the near view mode or the distant view mode, so that either the near view object or the distant view object is in focus. The first evaluation area F1 and the second evaluation area F1 set for the detected perspective boundary are selected based on the selected result regarding whether to focus.
One of the evaluation areas F2 is selected as the focus area for bringing the taking lens 11 into the focus state.
It should be noted that here, two evaluation regions are used to determine which one of the two evaluation regions is the evaluation region containing many near-view subjects (near-view evaluation region) or the evaluation region containing many distant-view subjects (distant view evaluation region). Can be discriminated from the lens position (x = x1, x2) where the evaluation value of is maximum.

The drive control means obtains the in-focus position of the taking lens 11 based on the evaluation value calculated for the in-focus area selected by the in-focus area selecting section, and drives the taking lens 11 to the in-focus position. Control. Specifically, when the near view mode is selected, the focusing position of the taking lens 11 is obtained based on the evaluation value of the near view evaluation area, and the driving of the taking lens 11 to the focusing position is controlled. When the distant view mode is selected, the focus position of the taking lens 11 is obtained based on the evaluation value of the distant view evaluation area, and the driving of the taking lens 11 to the focus position is controlled.

<Operation of Digital Camera 1> Next, the operation of the digital camera 1 will be described. 14 to 16
3 is a flowchart showing a focusing operation in the digital camera 1, and shows an example of performing autofocus control when the user selects the near view mode or the distant view mode in advance.

First, as shown in FIG. 14, when the user sets the near-field mode or the distant-view mode by operating the photographing mode setting button 14, when the digital camera 1 enters the photographing standby state, the process proceeds to step S1.

In step S1, the camera control unit 100 of the digital camera 1 determines whether or not the user has pressed the shutter button 8 halfway (S1) to input an instruction to start the autofocus operation. Then, when the user inputs an instruction of an autofocus operation, the autofocus control for bringing the subject image formed on the CCD image pickup device 30 into the in-focus state in the digital camera 1 is started, and step S2 Proceed to.

In step S2, the detection area setting unit 152
Thus, the boundary detection area is set for the image stored in the image memory 70, and the process proceeds to step S3. Specifically, the boundary detection area EA1 shown in FIG. 5 is set.

In step S3, the edge detection section 153 recognizes an edge in the boundary detection area EA1 and the process proceeds to step S4.

In step S4, the edge detecting section 153 excludes the relatively fine edges among the edges recognized in step S3 as a portion where the luminance difference of the distant view subject is large, and proceeds to step S5. Here, by excluding relatively fine edges, it is possible to detect only the relatively large edges in the distant view subject and the large edges including the perspective boundary.

The data processing in subsequent steps S5 to S9 is executed by the evaluation area setting unit 154. Hereinafter, steps S5 to S9 will be described.

In step S5, for the large edge detected in step S4, a vertical edge is found from the change in the direction of the line segment of the large edge by a method such as Hough transform.
Go to step S6.

In step S6, it is determined whether or not the vertical edge could be detected in step S5. Here, if the vertical edge can be detected, the process proceeds to step S9, and if the vertical edge cannot be detected, the process proceeds to step S7.

In step S7, with respect to the large edge detected in step S4, a horizontal edge is found from the change in the direction of the line segment of the large edge by a method such as Hough transform.
Go to step S8.

In step S8, it is determined whether or not the horizontal edge could be detected in step S7. Here, if the horizontal edge can be detected, the process proceeds to step S9, and if the horizontal edge cannot be detected, the process returns to step S1.

In step S9, first and second evaluation areas F1 and F2 for obtaining an evaluation value relating to the focus state of the taking lens 11 are set, and the flow advances to step S10. Specifically, when the process proceeds from step S6 to step S9, as shown in FIG. 10, it includes a part of the large edge LE at the position of the vertical edge A, and is larger than the second image region P2. A first evaluation area F1 including a large amount of the first image area P1
And a part of the large edge LE at the position of the vertical edge A,
In addition, the second evaluation area F2 including the second image area P2 more than the first image area P1 is set. Further, when the process proceeds from step S8 to step S9, as shown in FIG. 11, it includes a portion of the large edge LE at the position of the lateral edge C and is located at a position that is larger than that of the second image region P2. The first evaluation area F1 including many image areas P1 and the large edge LE
And a second evaluation area F2 including a part of the first image area P1 and a larger number of the second image area P2 than the first image area P1.

In step S10, the evaluation value calculation section 155 obtains an evaluation value regarding the in-focus state of the taking lens 11 for the first and second evaluation areas F1 and F2, and proceeds to step S11.

In step S11, the boundary detection unit 156
However, the perspective boundary is detected from the evaluation value obtained in step S10, and the process proceeds to step S12. Specifically, FIG.
As shown in FIG. 2, the first and second evaluation areas F1 and F1
When the lens position at which the evaluation value for 2 shows the maximum value differs by a certain amount or more, the first and second evaluation areas F1,
The large edge for which F2 is set is detected as the perspective boundary.

In step S12, based on the result of detecting the perspective boundary in step S11, the boundary detection unit 1
It is determined by 56 whether or not the near-far boundary can be detected. When the perspective boundary can be detected, the process proceeds to step S20, and when the perspective boundary cannot be detected, the process proceeds to step S13.

In step S13, the detection area setting unit 15
2, the boundary detection area for the image stored in the image memory 70 is switched, and the process proceeds to step S14.
Specifically, from the boundary detection area EA1 shown in FIG.
The boundary detection area EA2 shown in FIG.

In step S14, as in step S3, the edge detection unit 153 causes the boundary detection area EA2 to be detected.
The inner edge is recognized, and the process proceeds to step S15.

In step S15, as in step S4, among the edges recognized in step S14,
The relatively fine edge is excluded as a portion having a large brightness difference in the distant view subject, and the process proceeds to step S15. Here, by excluding relatively fine edges, it is possible to detect a large edge including a relatively large edge in the distant view subject and a perspective boundary.

In step S16, the evaluation area setting unit 15
The first evaluation area F1 and the second evaluation area F2 for obtaining the evaluation value regarding the focus state of the taking lens 11 are set by 4, and the process proceeds to step S17. In particular,
As shown in FIG. 11, with respect to the large edge LE detected in step S15, a horizontal edge is found from the change in the direction of the line segment of the large edge LE found by a method such as Hough transform, and the large edge LE is located at the position of the horizontal edge. Of the first image area P1 including a part of the first image area P1 and a larger number of the first image area P1 than the second image area P2, and a part of the large edge LE, and the first image area P1. A second evaluation area F2 including a larger number of second image areas P2 than that is set.

In step S17, the evaluation value calculation section 155 obtains an evaluation value relating to the in-focus state of the taking lens 11 for the first and second evaluation areas F1 and F2, and proceeds to step S18.

In step S18, as in step S11, the boundary detecting section 156 detects the perspective boundary based on the evaluation value obtained in step S17, and then in step S18.
Proceed to 19.

In step S19, based on the result of detecting the perspective boundary in step S18, the boundary detection unit 1
It is determined by 56 whether or not the near-far boundary can be detected. Then, when the perspective boundary can be detected, the process proceeds to step S20, and when the perspective boundary cannot be detected, the process returns to step S1.

In step S20, of the first evaluation area F1 and the second evaluation area F2 set for the perspective boundary by the focus area selection unit according to the shooting mode set by the user before shooting. One of the evaluation areas is selected as the focus area for bringing the taking lens 11 into the focus state. Here, when the near view mode is selected, the near view evaluation area is selected as the focus area, and the process proceeds to step S21. When the near view mode is not selected, that is, when the distant view mode is selected, , The distant view evaluation area is selected as the focus area, and the process proceeds to step S22.

In step S21, if the process proceeds from step S12 to step S20, the lens position for bringing the photographing lens 11 into the in-focus state based on the evaluation value calculated by the evaluation value calculation section 155 for the near view evaluation area in step S10. From step S19 to step S2
When the process proceeds to 0, the evaluation value calculation unit 155 calculates the lens position that brings the taking lens 11 into the in-focus state based on the evaluation value calculated for the near view evaluation region in step S17, and the process proceeds to step S23.

In step S22, if the process proceeds from step S12 to step S20, the lens position for bringing the photographing lens 11 into the in-focus state based on the evaluation value calculated by the evaluation value calculation unit 155 for the distant view evaluation area in step S10. From step S19 to step S2
When the process proceeds to 0, the evaluation value calculation unit 155 calculates the lens position that brings the taking lens 11 into the in-focus state based on the evaluation value calculated for the distant view evaluation region in step S17, and the process proceeds to step S23.

In step S23, based on the lens position of the taking lens 11 calculated in step S21 or step S22, the taking lens 11 with respect to the subject is taken.
The drive control unit 1 drives the taking lens 11 so that
It is driven under the control of 58 and the process proceeds to step S24.

In step S24, the shutter button 8
When is pressed, the camera control unit 1 determines whether or not the full-pressed state (S2) is given and an instruction to perform the main photographing is given.
00 judges. Here, if there is an instruction to perform the main photographing, the process proceeds to step S25, and if there is no instruction to perform the main photographing, the determination in step S24 is repeated. Although illustration is omitted here, if there is no instruction to carry out the main photographing for a certain period of time, the process returns to step S1.

In step S25, the main photographing is performed, the image signal is transmitted from the image processing section 50 to the image compressing section 80, and the image compressing section 80 applies a predetermined compression method to the image obtained by the main photographing. Image compression processing is performed, and the image signal subjected to the image compression is output from the image compression unit 80 and stored in the memory card 9. Then, it returns to step S1.

As described above, the edge including the perspective boundary is detected from the predetermined boundary detection area set in the image, and the first and second image areas including a part of the edge and on both sides of the edge are detected. , The focusing of the photographing lens for the first evaluation area including the first image area more than the second image area and the second evaluation area including the second image area more than the first image area By calculating an evaluation value for the state, obtaining the in-focus position of the taking lens based on the calculated evaluation value, and driving the taking lens to the in-focus position, even if the contrast of the near-field subject is low, It can focus on both subjects and distant subjects.

<Modification> The embodiment of the present invention has been described above, but the present invention is not limited to the above description.

For example, regarding the above-described autofocus control, the function of the optical system control unit 150 described above is
Since it can be realized by U executing predetermined software, the optical system control unit 150 is not always necessary.
It is not necessary that the respective parts in are configured separately.

Further, in the above-described embodiment, the boundary detection area is, as shown in FIG. 5, the image G10 stored in the image memory 70 at the start of the autofocus operation.
However, the present invention is not limited to this, and the position of the boundary detection area EA1 is not limited to this, and the position of the boundary detection area may be changed by the user operating the operation button 17 and the quad switch 25 before photographing. The size may be variously changed.

Further, in the above-described embodiment, the boundary detection area is composed of three areas having a constant width in the horizontal direction or the vertical direction, but the invention is not limited to this, and the boundary detection area is not limited to this. , One region having a constant width in the horizontal direction or the vertical direction, or two regions or four or more regions may be configured.

In the above-described embodiment, the boundary detection area is a partial area of the entire area of the image G10 stored in the image memory 70, as shown in FIGS. However, the invention is not limited to this, and the boundary detection area may be the entire area of the image G10 stored in the image memory 70.

Further, in the above-described embodiment, the boundary detection unit 156 selectively detects the perspective boundary and then sets one of the near view evaluation area and the distant view evaluation area as the focus area. However, the present invention is not limited to this. Not
In the near view mode, the lens position with the maximum evaluation value is calculated for the evaluation areas set for all large edges, and even if the lens position that focuses on the closest object is automatically selected, good. In the distant view mode, the lens position with the maximum evaluation value is calculated for the evaluation areas set for all large edges, and the lens position that focuses on the farthest object is automatically selected. May be.

Further, in the above-described embodiment, the near view mode or the distant view mode can be selected, but the present invention is not limited to this, and only the near view mode can be selected by the focusing area selection unit in the near view evaluation area or the distant view mode. A foreground evaluation area of the evaluation areas may be automatically selected as the focus area. The specific embodiments described above include inventions having the following configurations.

(1) In the optical system controller according to claim 4, the detection area setting means, when the perspective boundary cannot be detected in the boundary detection area having a constant width in the horizontal direction, An optical system control device comprising area switching means for vertically switching the boundary detection area to an area having a constant width.

With this configuration, when the perspective boundary cannot be detected in the boundary detection area having a constant width in the horizontal direction, such as when the line segment of the perspective boundary in the image is the horizontal direction, the boundary detection area is detected. By switching to a region with a constant width in the vertical direction, it is possible to improve the probability of detecting the perspective boundary even when the direction of the line segment is in any direction.

(2) The optical system control device according to any one of claims 1 to 5 or (1), wherein the control means automatically performs the first and second evaluation areas. An optical system control device, wherein a focusing position of the photographing lens is obtained based on an evaluation value of an evaluation region including a large number of near-view subjects, and driving of the photographing lens to the focusing position is controlled.

With this configuration, since the focusing operation is automatically performed on the near-view subject, the user can easily focus on the near-view subject having a low contrast.

[0090]

As described above, according to the invention of claim 1, an edge including a perspective boundary is detected from a predetermined boundary detection area set in an image, and a part of the edge is included, and Regarding the first and second image areas on both sides of the edge, a first evaluation area including a larger number of the first image area than the second image area and a second image area than the first image area are provided. By calculating an evaluation value relating to the in-focus state of the taking lens with respect to the second evaluation area including a large amount, obtaining the in-focus position of the taking lens based on the calculated evaluation value, and driving the taking lens to the in-focus position Even if the contrast of the near view subject is low, it is possible to focus on the near view subject and the distant view subject.

According to the second aspect of the invention, the edge including the perspective boundary can be detected by recognizing the position where the brightness difference between the adjacent pixels in the image is a predetermined value or more as the edge.

According to the third aspect of the present invention, by detecting the edge in the entire image, it is possible to detect the edge including the perspective boundary regardless of the position of the near view subject in the image.

Further, according to the invention of claim 4, by detecting the edge in the boundary detection area having a constant width in the horizontal direction, the edge is detected in a smaller area than in the case where the edge is detected in the entire image. It is possible to improve the processing speed for detecting an edge including a perspective boundary.

Further, in the fifth aspect of the present invention, in the first and second evaluation areas, the area of one of the areas divided by the edge is set to be twice or more the area of the other area, so that the near-view subject is photographed. Even when the contrast is low, it is possible to accurately focus on a near-field subject and a distant-view subject.

[Brief description of drawings]

FIG. 1 is a perspective view showing a digital camera according to an embodiment of the present invention.

FIG. 2 is a rear view of the digital camera shown in FIG.

FIG. 3 is a block diagram showing an internal configuration of a digital camera.

FIG. 4 is a block diagram showing an internal configuration of an optical system controller.

FIG. 5 is a diagram showing an example of a boundary detection area set for an image.

FIG. 6 is a diagram showing a boundary detection area after switching.

FIG. 7 is a schematic diagram showing an example in which a boundary detection area is set for an image.

FIG. 8 is a schematic diagram showing an example in which a boundary detection area is set for an image.

FIG. 9 is a schematic diagram showing an example in which a boundary detection area after switching is set for an image.

FIG. 10 is a schematic diagram illustrating setting of an evaluation area for an image.

FIG. 11 is a schematic diagram illustrating setting of an evaluation area for an image.

FIG. 12 is a schematic diagram showing an example of a relationship between an evaluation value and a lens position of a photographing lens.

FIG. 13 is a schematic diagram showing an example of the relationship between the evaluation value and the lens position of the taking lens.

FIG. 14 is a flowchart showing a focusing operation.

FIG. 15 is a flowchart showing a focusing operation.

FIG. 16 is a flowchart showing a focusing operation.

FIG. 17 is a schematic diagram showing an example of the relationship between the evaluation value and the lens position of the taking lens.

FIG. 18 is a schematic diagram illustrating an example of the relationship between the evaluation value and the lens position of the photographing lens for an image in which a near-field subject and a distant-view subject are mixed.

FIG. 19 is a schematic diagram showing an example in which an evaluation area is set for an image in which a near-field subject has low contrast and a distant-view subject has high contrast.

FIG. 20 is a schematic diagram showing an example of the relationship between the evaluation value and the lens position of the photographing lens for an image in which the contrast of the near-field subject is low and the contrast of the distant-view subject is high.

[Explanation of symbols]

1 digital camera 8 shutter button 11 Shooting lens 70 image memory 100 camera controller 110 lens drive 150 Optical system controller 152 detection area setting unit 153 Edge detector 154 Evaluation area setting section 155 Evaluation value calculation unit 158 Drive control unit A, B vertical edge C, D horizontal edge LE large edge EA1, EA2 boundary detection area F1 First evaluation area F2 Second evaluation area P1 First image area P2 Second image area

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Keiji Tamai             2-3-3 Azuchi-cho, Chuo-ku, Osaka-shi, Osaka Prefecture               Osaka International Building Minolta Co., Ltd. (72) Inventor Motohiro Nakanishi             2-3-3 Azuchi-cho, Chuo-ku, Osaka-shi, Osaka Prefecture               Osaka International Building Minolta Co., Ltd. F term (reference) 2H011 AA03 BA31 BB02 BB04                 2H051 AA00 BA47 CE14 CE16 DA19                       DA23 DA26 DB01 DD10 DD17                 5C022 AA13 AB29 AB30 AB66 AC02                       AC03 AC32 AC42 AC74

Claims (5)

[Claims] 1. An optical system control device for inputting an image composed of a plurality of pixels to control focusing of a photographing lens, comprising: detection area setting means for setting a predetermined boundary detection area in the image. Edge detection means for detecting an edge including a boundary between a near view object and a distant view object from the boundary detection area, and first and second images including a part of the edge and being areas on both sides of the edge Regarding a region, a first evaluation region including more of the first image region than the second image region, and a second evaluation region including more of the second image region than the first image region. An evaluation area setting means for setting the evaluation value, an evaluation value calculation means for calculating an evaluation value relating to a focus state of the photographing lens for the first and second evaluation areas, and an evaluation value calculated by the evaluation value calculation means. Based on the shooting Determined focus position of the lens, the optical system control apparatus characterized by comprising a control means for controlling driving of the photographic lens to the focus position. 2. The optical system control device according to claim 1, wherein the edge detecting means includes edge recognizing means for recognizing an edge when a difference in brightness between adjacent pixels is a predetermined value or more. An optical system controller characterized by. 3. The optical system control device according to claim 1, wherein the detection area setting means sets the entire image as a boundary detection area. System controller. 4. The optical system control device according to claim 1, wherein the detection area setting means sets a boundary detection area having a constant width in the horizontal direction with respect to the image. An optical system control device characterized by the above. 5. The optical system control device according to claim 1, wherein the first and second evaluation regions have an area of one region divided by the edge, respectively. The optical system control device is characterized in that it is at least twice as large as the area of the region.