JP2008245054A - Photographing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photographing apparatus that shortens photographing time when generating an image in which a main subject is in focus and a background subject is blurred.
An AF evaluation value representing the degree of focusing at each focus position is obtained by a field distance distribution measuring means, and a main subject area is determined based on the obtained AF evaluation value for each area and for each focus position. The background separation area 35 separates the background subject area from the background subject area, and the out-of-focus position detection means 36 determines the focus position at which the AF evaluation value is equal to or less than a predetermined evaluation threshold and the background subject area has the lowest AF evaluation value. The background image is generated by shooting at the focus position, and the subject image is generated by shooting at the focus position focused on the main subject, and these images are synthesized by the image synthesis means 37. Then, an image in which the main subject is focused and the background subject is blurred is generated.
[Selection] Figure 3

Description

  The present invention relates to a photographing apparatus that forms an image by forming a subject on an image sensor with a photographing optical system and reading the subject image with the image sensor.

  2. Description of the Related Art In recent years, there has been a demand for higher functionality in digital cameras, which are one type of photographing apparatus, and information terminals with cameras such as mobile phones and PDAs (Personal Digital Assistants) in which the functions of the digital cameras are incorporated. Here, the digital camera has a shorter actual focal length than a silver halide camera that takes a photograph on a roll-shaped 35 mm photographic film, so that the depth of focus is deep and it is far from a short-distance subject in one image. All subjects up to the distance subject fall within the depth, and therefore there is a problem that it is difficult to obtain a blurred image of the background subject with a digital camera. However, as one of the increasingly sophisticated functions of a digital camera, There is a demand for a function for obtaining a high-quality image with a three-dimensional effect and a depth feeling by generating an image in which a background subject is blurred while focusing.

  Therefore, for example, in Patent Document 1, an image to be photographed is divided into a plurality of areas (areas), and the foreground or background of the main subject is photographed while being shifted from the focal position corresponding to the distance of the area. A technique has been proposed in which an image of each shot area is individually extracted and combined with a main subject to shoot an image with a desired amount of blur.

  Further, Patent Document 2 receives image information of two images having different focus conditions, detects a main part and a background of these two images, and determines image information of the two images according to the detection result. For at least one of these, a technique for performing different image processing between the main part and the background has been proposed.

  Furthermore, in Patent Document 3, a subject is extracted from an image acquired by the first shooting, a partial image is cut out, and the second shooting is performed with the partial image displayed as a foreground on the shooting screen. A technique for synthesizing the foreground and the image acquired by the second shooting has been proposed.

Also, in Patent Document 4, the most focused part is extracted from each image information from a plurality of still images taken with different focal lengths (focus), and as many parts as possible are focused. A technique for synthesizing a single still image has been proposed.
JP 2003-209727 A Japanese Patent Laid-Open No. 10-233919 JP 2006-128754 A JP-A-8-32858

  However, in the technique proposed in Patent Document 1, for each of a plurality of regions that are foregrounds or backgrounds (hereinafter collectively referred to as background subjects) other than the main subject, focus positions (focus points) corresponding to the distances of the plurality of regions are used. It is necessary to take a plurality of images by shifting from the position. Therefore, there is a problem that it takes a long time to shoot and time is also required for image composition processing.

  The technique proposed in Patent Document 2 has a problem that it takes a long time for image processing because it is necessary to perform different image processing for the main part and the background.

  Further, Patent Document 3 proposes a technique for synthesizing a foreground that is a partial image of an image acquired by the first shooting and an image acquired by the second shooting. No technique has been proposed for generating an image with a blurred background subject.

  Patent Document 4 proposes a technique for synthesizing a still image that is in focus as the entire image data, but it also proposes a technique for generating an image in which the main subject is in focus and the background subject is blurred. It has not been.

  SUMMARY OF THE INVENTION In view of the above circumstances, an object of the present invention is to provide a photographing apparatus that shortens the photographing time when generating an image in which a main subject is in focus and a background subject is blurred.

The first photographing device of the photographing device of the present invention that achieves the above object is a photographing device that forms an image by forming a subject on an image pickup device with a photographing optical system and reading the subject image with the image pickup device.
This indicates the degree of focus at each focus position when the focus position of the photographing optical system is moved for each area when the object field shown on the image sensor is divided into a plurality of areas in a two-dimensional manner. A field distance distribution measuring means for obtaining an evaluation value;
A region separating unit that separates each region into a region belonging to the main subject and a region belonging to the background subject based on the evaluation value for each region and for each focus position determined by the field distance distribution measuring unit;
The evaluation value is the lowest when all the regions belonging to the background subject are regarded as one region within a range satisfying the first condition that the evaluation value is equal to or less than a predetermined evaluation threshold for all the regions belonging to the background subject. A blur focus position detecting means for obtaining a focus position satisfying the second condition;
Photographing means for photographing at a focus position obtained by the blur focus position detecting means to generate a first image, and photographing at a focus position focused on the main subject to generate a second image;
Image synthesizing means for synthesizing the first image and the second image to focus on the main subject and generate an image in which the background subject is blurred is provided.

  The first imaging apparatus of the present invention belongs to the background subject within a range that satisfies the first condition that the evaluation value for each region and for each focus position is equal to or less than a predetermined evaluation threshold for all the regions belonging to the background subject. A focus position that satisfies the second condition that minimizes the evaluation value when all areas are regarded as one area is obtained, a background subject is photographed using the focus position as a blur focus position, and a main subject is photographed. It is. By doing so, for example, as shown in the embodiment, it is possible to reduce the lens shift amount for photographing the background subject after photographing the main subject. For this reason, the amount of lens shift between the lens position for photographing the background subject and the lens position for photographing the main subject can be kept small, and an image in which the background subject is surely blurred can be obtained with a small number of shots. Can do. Accordingly, it is possible to reduce the shooting time when generating an image in which the main subject is in focus and the background subject is blurred.

Here, when it is impossible to detect the focus position satisfying the first condition and the second condition by the blur focus position detection unit, the photographing unit generates the second image, and Generating a plurality of third images in which the evaluation values of the respective areas belonging to the background subject are each equal to or less than the evaluation threshold value,
The image synthesizing unit preferably synthesizes the second image and the plurality of third images to generate an image in which the main subject is focused and the background subject is blurred.

  In this way, even if the focus position that satisfies the first condition and the second condition cannot be detected, a blurred image representing the background subject can be generated reliably.

A second imaging device of the imaging device of the present invention that achieves the above object is an imaging device that forms an image by forming an object on an image sensor with an imaging optical system and reading the object image with the image sensor. In
This indicates the degree of focus at each focus position when the focus position of the photographing optical system is moved for each area when the object field shown on the image sensor is divided into a plurality of areas in a two-dimensional manner. A field distance distribution measuring means for obtaining an evaluation value;
A region separating unit that separates each region into a region belonging to the main subject and a region belonging to the background subject based on the evaluation value for each region and for each focus position determined by the field distance distribution measuring unit;
Prior to the movement of the focus position of the photographing optical system for the field distance distribution measurement by the field distance distribution measuring means, a first image is generated and focused on the main subject. Photographing means for photographing at a focus position to generate a second image;
Image synthesizing means for synthesizing the first image and the second image to focus on the main subject and generate an image in which the background subject is blurred is provided.

  The second photographing apparatus of the present invention performs photographing at the lens position at the time when the shutter button is pressed halfway and receives a photographing start instruction to generate a first image representing the background subject, and then moves the lens position. Then, an evaluation value representing the degree of focus at each focus position is obtained, and a second image is generated by photographing at the focus position focused on the main subject separated based on the evaluation value, and the first image And the second image are combined to generate an image in which the main subject is focused and the background subject is blurred. For this reason, it is not necessary to move the photographic lens when photographing the background subject. Therefore, it is possible to generate an image in which the background subject is in focus and the background subject is surely blurred with a small number of photographs, and the photographing time is shortened. be able to.

Here, when the first image is obtained by dividing the first image into a plurality of regions in a two-dimensional manner, the evaluation value is a predetermined evaluation threshold value for all the regions belonging to the background subject among the regions. A background blur determining means for determining whether or not
If the first image is not an image satisfying the condition that the evaluation value is equal to or less than a predetermined evaluation threshold for all the regions belonging to the background subject by the background blur determination unit, the photographing unit further includes: And generating a plurality of third images in which the evaluation values of the respective areas belonging to the background subject are each equal to or less than the evaluation threshold value,
The image synthesizing unit preferably synthesizes the second image and the plurality of third images to generate an image in which the main subject is focused and the background subject is blurred.

  In this way, even if the image does not satisfy the condition that the evaluation value is equal to or less than a predetermined evaluation threshold for all the regions belonging to the background subject, a blurred image representing the background subject is generated reliably. be able to.

Furthermore, a third imaging device of the imaging device of the present invention that achieves the above object is an imaging device that forms an image by forming an object on an image sensor with an imaging optical system and reading the object image with the image sensor. In
This indicates the degree of focus at each focus position when the focus position of the photographing optical system is moved for each area when the object field shown on the image sensor is divided into a plurality of areas in a two-dimensional manner. A field distance distribution measuring means for obtaining an evaluation value;
A region separating unit that separates each region into a region belonging to the main subject and a region belonging to the background subject based on the evaluation value for each region and for each focus position determined by the field distance distribution measuring unit;
A defocus position detection unit that detects a focus position that is a predetermined distance threshold away from all the in-focus positions of each of the regions belonging to the background subject;
Photographing means for photographing at a focus position obtained by the blur focus position detecting means to generate a first image, and photographing at a focus position focused on the main subject to generate a second image;
Image synthesizing means for synthesizing the first image and the second image to focus on the main subject and generate an image in which the background subject is blurred is provided.

  The third image capturing apparatus of the present invention detects a focus position that is a predetermined distance threshold away from all in-focus positions of each region belonging to the background subject, and captures the background subject using the focus position as a blurred focus position. . For this reason, in photographing the background subject, the lens shift position may be set to a position shifted by a predetermined distance threshold from all the focus positions of the respective regions belonging to the background subject. By doing so, it is possible to reduce the amount of lens shift in photographing the background subject, and to obtain an image in which the background subject is surely blurred with a small number of photographs. Accordingly, it is possible to reduce the shooting time when generating an image in which the main subject is in focus and the background subject is blurred.

Here, when the focus position that is a predetermined distance threshold away from all the focus positions of the respective areas belonging to the background subject cannot be detected by the blur focus position detection means, the photographing means Generating an image and generating a plurality of third images in which the evaluation value of each region belonging to the background subject is equal to or less than the evaluation threshold value,
The image synthesizing unit preferably synthesizes the second image and the plurality of third images to generate an image in which the main subject is focused and the background subject is blurred.

  This ensures that a blurred image representing the background subject is generated even when it is impossible to detect a focus position that is a predetermined distance threshold away from all the in-focus positions of the respective regions belonging to the background subject. can do.

  According to the present invention, it is possible to provide an imaging device that can reduce the imaging time when generating an image in which the main subject is in focus and the background subject is blurred.

  Embodiments of the present invention will be described below.

  FIG. 1 is an external perspective view of a digital camera according to a first embodiment of the photographing apparatus of the present invention as viewed from the front obliquely above, and FIG. 2 is an external perspective view of the digital camera shown in FIG. .

  The digital camera 1 shown in FIGS. 1 and 2 forms a subject image on a CCD image sensor (hereinafter referred to as CCD), which is one of the image sensors in the photographing optical system, and reads the subject image with the CCD. An imaging device for generating an image.

  As shown in FIG. 1, the digital camera 1 includes a photographic lens 11 constituting a photographic optical system in the center of the front surface of the camera body 1a. Further, an optical viewfinder objective window 12 and an auxiliary light emitting unit 13 are provided on the upper front of the digital camera 1.

  A shutter button 14 and a slide type power switch 15 are provided on the upper surface of the digital camera 1.

  Further, as shown in FIG. 2, an optical viewfinder eyepiece window 16, a menu switch 17, an execution / screen changeover switch 18, and an image monitor 19 are provided on the back of the digital camera 1.

  FIG. 3 is a block diagram showing a circuit configuration of the digital camera shown in FIG.

  The digital camera 1 includes a photographing lens 11 and a CCD 22 which are also shown in FIG. Subject light incident through the taking lens 11 is formed on the CCD 22 as a subject image.

  The digital camera 1 also includes an analog signal processing unit 23, an A / D unit 24, a digital signal processing unit 25, a temporary memory 26, a compression / decompression unit 27, and a built-in memory (or memory card) 28. 2 is provided with an image monitor 19 and a drive circuit 29 which are also shown in FIG. The CCD 22 is driven at a timing generated by a timing generation circuit (not shown) in the drive circuit 29, and outputs an analog image signal representing a subject image. The drive circuit 29 also includes a drive unit that drives the photographic lens 11. The analog image signal output from the CCD 22 is subjected to analog signal processing by the analog signal processing unit 23, A / D converted by the A / D unit 24, and digital signal processed by the digital signal processing unit 25. Data representing the digital signal processed signal is temporarily stored in the temporary memory 26. The data stored in the temporary memory 26 is compressed by the compression / decompression unit 27 and recorded in the built-in memory (or memory card) 28. Depending on the shooting mode, the compression process may be omitted and the recording may be performed directly in the built-in memory 28. Data stored in the temporary memory 26 is read out to the image monitor 19, whereby an image of the subject is displayed on the image monitor 19.

  Further, the digital camera 1 includes a CPU 30 for controlling the entire digital camera 1, an operation switch unit 31 including the menu switch 17 and the execution / screen changeover switch 18 described above, and a shutter button also shown in FIGS. 14 are provided.

  Further, the digital camera 1 includes an auxiliary light emitting unit 13 also shown in FIG. 1, an AF detection circuit 32 that detects image focus information, and an AE & AWB detection unit 33 that detects image brightness information and white balance information. It has been. Specifically, the AF detection circuit 32 measures the subject distance by AF (Automatic Focusing) control based on a so-called “mountain climbing method” that performs AF control by measuring the subject distance of the image based on the image signal generated by the CCD 22. . That is, a focus lens (not shown) constituting the photographic lens 11 is slightly moved back and forth along the optical axis, and the focus lens is gradually moved to the maximum point of the evaluation value while checking the increase / decrease direction of the focus evaluation value. The in-focus position is determined by moving it. The above configuration corresponds to the photographing means referred to in the present invention.

  Further, the digital camera 1 is provided with a field distance distribution measuring unit 34 and a region separating unit 35. These will be described with reference to FIG.

  FIG. 4 is a diagram showing each area when the object scene captured on the CCD is two-dimensionally divided into a plurality of areas.

  FIG. 4 shows an area belonging to a background subject composed of areas indicated by background area numbers 1, 2, 3, 4,..., N when the object field on the CCD 22 is two-dimensionally divided into a plurality of areas. A part A, an area part B belonging to the main subject, and an area part C located at the boundary between the area part A and the area part B are shown.

  The field distance distribution measuring means 34 is shown in FIG. 4 for each region (regions A, B, and C) when the object field projected on the CCD 22 is two-dimensionally divided into a plurality of regions. An AF evaluation value (corresponding to an example of the evaluation value in the present invention) representing the degree of focus at each focus position when the focus position of the photographic lens 11 is moved is obtained.

  The area separating unit 35 divides each area into an area belonging to the main subject and an area belonging to the background subject based on the AF evaluation value for each area and for each focus position obtained by the field distance distribution measuring means 34. To separate. Thereby, the area A and the area B are determined. Each region belonging to the region portion C is included in one of the region portions A and B. Specifically, when many of the regions belonging to the region portion C belong to the region portion A, they are included on the region portion A side, and when many of the regions belonging to the region portion C belong to the region portion B, they are included on the region portion B side. Will be included.

  Further, the digital camera 1 is provided with a blur focus position detecting means 36. The blur focus position detection means 36 will be described with reference to FIG.

  FIG. 5 is a graph for explaining the out-of-focus position detecting means.

  The horizontal axis of the central graph in FIG. 5 indicates the focus position X (focal length, lens position, etc.). The vertical axis represents the average of the AF evaluation values of the entire background area.

  The blur focus position detection unit 36 regards all the regions belonging to the background subject as one region within the range that satisfies the first condition that the AF evaluation value is equal to or less than the predetermined evaluation threshold K for all the regions belonging to the background subject. The focus position satisfying the second condition that provides the lowest AF evaluation value is obtained. That is, as shown in the upper left graph of FIG. 5 and the left circle of the central graph, the AF evaluation value of the partial area is evaluated even if the average of all the areas indicated by the background area number is the minimum. When the threshold value K is exceeded, it is assumed that the range does not satisfy the first condition. On the other hand, as shown in the upper right graph of FIG. 5 and the right circle of the central graph, the AF evaluation value of the entire area is not required even if the average of the entire area indicated by the background area number is not minimum. Is equal to or less than the evaluation threshold K, the range satisfies the first condition. A focus position that satisfies the second condition that minimizes the AF evaluation value when all the areas belonging to the background subject are regarded as one area within the range satisfying the first condition is obtained. In this way, the optimum background photographing lens position shown in FIG. 5 is obtained.

  The description will be continued with reference to FIG. 3 again. In this digital camera 1, the above-described photographing means performs photographing at a focus position focused on the main subject to generate a main subject image (corresponding to the second image in the present invention), and then the blur focus position detection means 36. The background image (corresponding to the first image referred to in the present invention) is generated by taking a picture at the focus position obtained in the above. Here, an example is described in which a main subject image is generated by shooting at a focus position focused on the main subject, and then a background image is generated by shooting at the focus position obtained by the blur focus position detection unit 36. However, the present invention is not limited to this, and a background image is generated by shooting at the focus position obtained by the blur focus position detection means 36, and then the main subject image is shot at the focus position focused on the main subject. May be generated.

  Further, the digital camera 1 is provided with an image composition unit 37 that synthesizes the main subject image and the background image to focus on the main subject and generate an image in which the background subject is blurred.

  When the focus position detection unit 36 cannot detect the focus position satisfying the first condition and the second condition, an image of the main subject is generated and each region belonging to the background subject is detected. A plurality of background images (corresponding to the third image in the present invention) each having an AF evaluation value equal to or less than the evaluation threshold K are generated. The image composition means 37 composes the main subject image and a plurality of background images to generate an image in which the main subject is in focus and the background subject is blurred.

  FIG. 6 is a diagram illustrating a flow of an image composition processing routine for generating an image in which the main subject is focused and the background subject is blurred in the digital camera of the first embodiment.

  This image composition processing routine is activated when the shutter button 14 is half-pressed (S1 accepted). First, in step S1, the lens position is moved to X. Next, in step S2, AF evaluation is performed on the entire region. Specifically, the AF evaluation representing the degree of focusing at each focus position when the focus position is moved for each area when the object field captured on the CCD 22 is two-dimensionally divided into a plurality of areas. A value (focus area AF evaluation value) is obtained. In step S3, the in-focus area number and the in-focus area AF evaluation value are temporarily recorded.

  Next, in step S4, it is determined whether or not the in-focus positions of all areas have been acquired. If it is determined that the in-focus position of the entire area has been acquired, the process proceeds to step S7 described later. On the other hand, if it is determined that the in-focus position of the entire area has not been acquired, the process proceeds to step S5. In step S5, it is determined whether or not X = Y (Y indicates the focal position at the end of the AF search). If it is determined that X = Y is not satisfied, X is incremented (X = X + 1) in step S6, and the process returns to step S1. On the other hand, if it is determined that X = Y, the focus position is the end of the AF search, so the process proceeds to step S7.

  In step S7, a subject area (main subject area) and a background area are discriminated. That is, based on the AF evaluation value for each region and for each focus position, each region is separated into a region belonging to the main subject and a region belonging to the background subject.

  Next, the lens is moved to the subject in-focus position in step S8, the subject is photographed in step S9, and the subject is extracted and recorded temporarily in step S10.

  In step S11, AF evaluation values for all focal positions of all background areas are read out. Next, in step S12, the average of the AF evaluation values of all the areas at all the focal positions is calculated. Further, in step S13, numbers (background region numbers) are assigned in order of increasing AF evaluation value average.

  In step S14, it is determined whether or not the AF evaluation value of all the regions at the background region number Z-th focal position is equal to or less than the evaluation threshold value K (AF evaluation value ≦ K). When it is determined that the AF evaluation value is equal to or less than the evaluation threshold value K, the process proceeds to step S17 described later. On the other hand, if it is determined that the AF evaluation value exceeds the evaluation threshold K, the process proceeds to step S15. In step S15, it is determined whether Z = N (N indicates the background area number shown in FIG. 4). If it is determined that Z = N is not satisfied, Z is incremented (Z = Z + 1) in step S16, and the process returns to step S13. On the other hand, if it is determined that Z = N, the process proceeds to step S20 described later.

  In step S17, the lens is moved to the optimum background photographing position. Next, in step S18, the background is photographed, and the process proceeds to step S19. In step S19, the subject and background images are combined and the routine is terminated.

  If it is determined in step S15 that Z = N and the process proceeds to step S20, the background is photographed at a plurality of positions by shifting the lens position from the focus position of each region in step S20. Further, in step S19, the image of the subject and the background photographed at a plurality of places are combined and this routine is terminated.

  As described above, in the digital camera 1 according to the first embodiment, after the main subject is photographed, the AF evaluation value for each region and for each focus position is equal to or less than a predetermined evaluation threshold for all the regions belonging to the background subject. The focus position satisfying the second condition that minimizes the AF evaluation value when all the areas belonging to the background subject are regarded as one area within the range satisfying the first condition is obtained, and the focus position is set as the blur focus position. A background subject is photographed. By doing so, it is possible to suppress the lens shift amount for photographing the background subject after photographing the main subject. For this reason, the amount of lens shift between the lens position for photographing the background subject and the lens position for photographing the main subject can be kept small, and an image in which the background subject is surely blurred can be obtained with a small number of shots. Can do. Accordingly, it is possible to reduce the shooting time when generating an image in which the main subject is in focus and the background subject is blurred.

  FIG. 7 is a block diagram showing a circuit configuration of a digital camera according to the second embodiment of the photographing apparatus of the present invention.

  The external view of the digital camera 2 shown in FIG. 7 is the same as the external view of the digital camera shown in FIGS. Also, the same components as those in the digital camera 1 shown in FIG.

  In the digital camera 2 shown in FIG. 7, a background image is generated by photographing before the movement of the focus position of the photographing lens 11 for the field distance distribution measurement by the field distance distribution measuring unit 34, and The main subject image is generated by shooting at the focus position focused on the subject.

  Further, the digital camera 2 has an AF evaluation value for a predetermined evaluation value for each of the regions belonging to the background subject of the regions when the background image is two-dimensionally divided into a plurality of regions. Background blur determination means 41 for determining whether or not the threshold value is not more than the threshold value is provided.

  Further, in the digital camera 2, when the background image is not an image satisfying the condition that the AF evaluation value is equal to or less than the predetermined evaluation threshold value K for all the regions belonging to the background subject by the background blur determination unit 41. Further, a plurality of background images in which the AF evaluation value of each area belonging to the background subject is equal to or less than the evaluation threshold value K are generated. In addition, the image composition unit 37 composes the main subject image and a plurality of background images, and generates an image in which the main subject is focused and the background subject is blurred.

  FIG. 8 is a diagram illustrating a flow of an image composition processing routine for generating an image in which the main subject is in focus and the background subject is blurred in the digital camera of the second embodiment.

  This image composition processing routine is activated when the shutter button 14 is half-pressed (S1 accepted). First, in step S31, the initial focus position (lens position at the time of receiving an imaging start instruction) is temporarily recorded. Next, photographing is performed in step S32. Further, in step S33, a background image (image candidate: a candidate image that may eventually become a background image) is temporarily recorded.

  In step S34, the outline of the subject (main subject) is extracted after AF control by a known technique, and then in step S35, the subject is extracted and recorded temporarily. In step S36, both (1) the subject photographing focal position and (2) the initial focal position are read out.

  In step S37, it is determined whether | (1) − (2) | ≧ L (L is the lens shift amount). That is, it is determined whether or not the difference between the AF focus position and the focus position at the time of initial shooting is equal to or greater than the planned lens shift amount. Specifically, it is determined whether or not the focal length difference is greater than or equal to the subject depth. If it is determined that | (1) − (2) | ≧ L, the process proceeds to step S38. In step S35, the subject image and the candidate background image are combined and the routine is terminated. On the other hand, if it is determined that | (1) − (2) | ≧ L, the process proceeds to step S39. In step S39, the background is photographed at a plurality of positions by shifting the lens position from the focus position of each region. Further, in step S38, images of the subject and the background photographed at a plurality of places are combined and this routine is terminated.

  As described above, the digital camera 2 according to the second embodiment shoots at the lens position at the time when the shutter button 14 is half-pressed and receives a shooting start instruction, generates an image of the background subject, and then sets the lens position. An AF evaluation value representing the degree of focus at each focus position is obtained by moving, and shooting is performed at the focus position focused on the main subject separated based on the AF evaluation value to generate a subject image. The image is synthesized with the image of the background subject to focus on the main subject and generate an image in which the background subject is blurred. For this reason, it is not necessary to move the taking lens 11 when shooting the background subject. Therefore, an image in which the background subject is in focus and the background subject is surely blurred can be generated with a small number of shots, and the shooting time is shortened. can do.

  FIG. 9 is a diagram showing a flow of a first automatic blur control routine for combining the focused subject image and the background image subjected to signal processing.

  The first automatic blur control routine is started when the shutter button 14 is half-pressed (S1 accepted). First, in step S41, AF control is performed. Next, in step S42, the spatial frequency referenced at the time of subject extraction is temporarily recorded.

  In step S43, shooting is performed and a subject is extracted by a known technique. Next, in step S44, the subject and the background other than the subject are temporarily recorded. Further, in step S45, the spatial frequency referred to for subject extraction (frequency such as 1 MHz or 300 kHz for focusing determination during AF control) is read out.

  In step S46, the cut-off frequency of the low-pass filter for performing image processing on the background image is set to be equal to or lower than the spatial frequency referenced for subject extraction. In step S47, the background image is subjected to image processing at the cut-off frequency. Further, in step S48, the temporarily saved subject image and the background image after image processing are combined. In this way, the blurring of the background image may be automatically adjusted according to the spatial frequency of the subject. By doing so, the background image can be blurred at an optimum level even when the subject image itself has a low spatial frequency. Therefore, the image quality of the synthesized image can be improved.

  FIG. 10 is a diagram illustrating a flow of a second automatic blur control routine for combining the focused subject image and the background image subjected to signal processing.

  The second automatic blur control routine is started when the shutter button 14 is half-pressed (S1 accepted). First, in step S51, in-focus positions of all areas (all divided areas) in the screen are inspected within a predetermined lens movable range by a known technique. Next, in step S52, the subject is extracted.

  In step S53, the subject and the background other than the subject are temporarily recorded. Further, in step S54, the in-focus position of the entire background area is read out. Next, in step S55, the subject relative position of the entire area is calculated. That is, the subject relative distance of each area is calculated from the focus position of the divided area in the screen and the subject focus position (unit: focal position, lens feed pulse, etc.).

  Next, in step S56, the cut-off frequency of each region for performing image processing on the background image is set. In step S57, image processing is performed on the background image at the cutoff frequency. In step S58, the subject image temporarily stored and the background image after image processing are combined.

  FIG. 11 is a diagram showing an example of the cutoff frequency set in step S56 shown in FIG.

  The horizontal axis in FIG. 11 indicates the in-focus position X (focal length, lens position, etc.). The vertical axis indicates the cutoff frequency level. As shown in FIG. 8, the subject position is at the peak of the cutoff frequency. Here, the background is slightly blurred when shifted to the left from the peak position of the cutoff frequency, and the background is considerably blurred when the subject is shifted to the right from the peak position of the cutoff frequency. In this way, the image quality of the synthesized image may be improved by automatically adjusting the blur of the background image according to the position relative to the subject (synonymous with the distance from the digital camera).

  FIG. 12 is a diagram showing a flow of a third automatic blur control routine for synthesizing the focused subject image and the background image subjected to signal processing.

  The third automatic blur control routine is started when the shutter button 14 is half-pressed (S1 accepted). First, in step S61, after shooting with AF control, the contour of the subject is extracted by a known technique. Next, in step S62, the subject and the background other than the subject are temporarily recorded. Furthermore, in step S63, the distance (unit is a pixel etc.) from the to-be-photographed object of each area | region is calculated.

  Next, in step S64, a cut-off frequency for each region for performing image processing on the background image is set. In step S65, the background image is subjected to image processing at the cutoff frequency. Further, in step S66, the subject image temporarily stored and the background image after image processing are combined.

  FIG. 13 is a diagram illustrating an example of the cutoff frequency set in step S64 illustrated in FIG. 12, and a diagram illustrating an image processing image processed at the cutoff frequency.

  FIG. 13A shows the relationship between the distance from the subject (in the screen) and the cutoff frequency. In FIG. 13A, the horizontal axis indicates the distance from the subject (focal length, lens position, etc.), and the vertical axis indicates the level of the cutoff frequency.

  As shown in FIG. 13A, the subject position is at the peak of the cutoff frequency. Here, at a position A slightly deviated from the peak position of the cutoff frequency, the background is slightly blurred as shown in FIG. Further, at a position B that is shifted to some extent from the peak position of the cutoff frequency, the background is also blurred to some extent as shown in FIG. Further, at a position C that is significantly deviated from the position of the peak of the cutoff frequency and a position D that is further deviated, the background is considerably blurred as shown in FIG.

In this way, the blur of the background image may be automatically adjusted according to the position with respect to the subject (distance from the subject in the screen). By doing this, even if the subject extraction accuracy is poor, blurring can be weakened around the subject, and blurring can be strengthened in a region away from the subject. Therefore, an unnatural contour due to the extraction accuracy of the subject can be made inconspicuous, and thus the image quality can be improved. FIG. 14 shows a digital camera according to the third embodiment of the photographing apparatus of the present invention. It is a block diagram which shows a circuit structure.

  The external view of the digital camera 3 shown in FIG. 14 is the same as the external view of the digital camera shown in FIGS. Also, the same components as those in the digital camera 1 shown in FIG.

  The digital camera 3 shown in FIG. 14 includes a blur focus position detection unit 51 that detects a focus position that is a predetermined distance threshold away from all the focus positions of the respective regions belonging to the background subject. Further, when it is impossible to detect the focus position that is a predetermined distance threshold away from all the focus positions of the respective regions belonging to the background subject by the blur focus position detection unit 51, a main subject image is generated, and A plurality of background images in which the evaluation value of each region belonging to the background subject is equal to or less than the evaluation threshold value are generated.

  FIG. 15 is a diagram illustrating a flow of an image composition processing routine for generating an image in which the main subject is focused and the background subject is blurred in the digital camera of the third embodiment.

  This image composition processing routine is activated when the shutter button 14 is half-pressed (S1 accepted). First, in step S71, the lens position is moved to X. Next, in step S72, AF evaluation is performed on the entire area. Further, in step S73, it is determined whether or not there is an AF in-focus area. If it is determined that there is an AF in-focus area, the process proceeds to step S76 described later. On the other hand, if it is determined that there is no AF focus area, the process proceeds to step S74. In step S74, it is determined whether or not X = Y (Y indicates the focus position at the end of the AF search). If it is determined that X = Y is not satisfied, X is incremented (X = X + 1) in step S75, and the process returns to step S71. On the other hand, if it is determined that X = Y, the focus position is the end of the AF search, and the process proceeds to step S78 described later.

  In step S73, the focus area number and the focus position are temporarily recorded. Furthermore, in step S77, it is determined whether or not the in-focus positions of all areas have been acquired. If it is determined that the in-focus position of the entire area has not been acquired, the process returns to step S73. On the other hand, if it is determined that the in-focus position of the entire area has been acquired, the process proceeds to step S78.

  In step S78, a subject area (main subject area) and a background area are discriminated. Next, the lens is moved to the subject in-focus position in step S79, and the subject is photographed in step S80, and the subject is extracted and temporarily recorded in step S81.

  In step S82, the in-focus position of the entire background area is read out. Next, in step S83, the in-focus area at the focal position X ± L (L is the lens shift amount) is searched. Further, in step S84, it is determined whether or not there is an area to be focused at X ± L. If it is determined that there is no region to be in focus at X ± L, the process proceeds to step S87 described later. On the other hand, if it is determined that there is a region to be focused at X ± L, the process proceeds to step S85. In step S85, it is determined whether X = Y. If it is determined that X = Y is not satisfied, X is incremented (X = X + 1) in step S86, and the process returns to step S83. On the other hand, if it is determined that X = Y, the process proceeds to step S90 described later.

  In step S87, the lens is moved to the optimum background photographing position. In other words, the lens is moved to the focus position that is a predetermined distance threshold away from all the focus positions of the respective areas belonging to the background subject. Next, the background is photographed in step S88, and the process proceeds to step S89. In step S89, the subject and background images are combined and the routine is terminated.

  If it is determined in step S85 that X = Y, and the process proceeds to step S90, the background is photographed at a plurality of positions by shifting the lens position from the focus position of each region in step S90. Further, in step S89, the images of the subject and the background photographed at a plurality of places are combined and this routine is terminated.

  FIG. 16 is a diagram illustrating the optimum background photographing lens position that has been determined to have no background area to be focused and moved.

  The horizontal axis in FIG. 16 indicates the in-focus position X (focal length, lens position, etc.), and the vertical axis indicates the number of in-focus areas.

  In FIG. 16, in step S83 shown in FIG. 15, the in-focus area at all focal positions X ± L is searched, and then in step S84, it is determined that there is no in-focus area at X ± L. The optimum background photographing lens position when the lens is moved to the background photographing position is shown.

  A portion in the two lens shift amounts L with the optimum background photographing lens position shown in FIG. 16 represents a predetermined margin leading to the occurrence of the in-focus area. The background is photographed at the optimum background photographing lens position, and an image of the subject (main subject) and the background is synthesized to generate an image in which the main subject is in focus and the background subject is blurred.

  As described above, the digital camera 3 according to the third embodiment detects a focus position that is a predetermined distance threshold away from all the focus positions of the respective areas belonging to the background subject after photographing the main subject, and the focus position. The background subject is photographed with the bokeh focus position. For this reason, when photographing the background subject, the lens shift position may be set to a position shifted by a predetermined distance threshold from all the focus positions of the respective regions belonging to the background subject. By doing so, it is possible to suppress the amount of lens shift in photographing the background subject, and to obtain an image in which the background subject is surely blurred with a small number of photographs. Accordingly, it is possible to reduce the shooting time when generating an image in which the main subject is in focus and the background subject is blurred. Here, it is not necessary to record the AF evaluation value, so that the processing time can be shortened.

  In the above-described embodiment, the digital camera is described as an example of the photographing apparatus according to the present invention. However, the present invention is not limited to this, and the photographing apparatus according to the present invention is mounted on a mobile phone or a PDA. It may be a camera or a video camera.

It is the external appearance perspective view which looked at the digital camera of 1st Embodiment of the imaging device of this invention from the front diagonally upward. It is the external appearance perspective view which looked at the digital camera shown in FIG. 1 from back diagonally upward. It is a block diagram which shows the circuit structure of the digital camera shown in FIG. It is a figure which shows each area | region when the to-be-photographed field reflected on CCD is divided | segmented into several area | regions two-dimensionally. It is a graph for demonstrating a bokeh focus position detection means. In the digital camera of 1st Embodiment, it is a figure which shows the flow of the image-synthesis process routine which produces | generates the image which focused on the main to-be-photographed object and the background subject was blurred. It is a block diagram which shows the circuit structure of the digital camera of 2nd Embodiment of the imaging device of this invention. In the digital camera of 2nd Embodiment, it is a figure which shows the flow of the image-synthesis process routine which produces | generates the image which focused on the main subject and the background subject was blurred. It is a figure which shows the flow of the 1st automatic blurring control routine which synthesize | combines the focused subject image and the background image which performed the signal processing. It is a figure which shows the flow of the 2nd automatic blurring control routine which synthesize | combines the focused subject image and the background image which performed the signal processing. It is a figure which shows an example of the cutoff frequency set by step S56 shown in FIG. It is a figure which shows the flow of the 3rd automatic blurring control routine which synthesize | combines the focused subject image and the background image which performed the signal processing. It is a figure which shows an example of the cutoff frequency set by step S64 shown in FIG. 12, and a figure which shows the image processing image processed with the cutoff frequency. It is a block diagram which shows the circuit structure of the digital camera of 3rd Embodiment of the imaging device of this invention. In the digital camera of 3rd Embodiment, it is a figure which shows the flow of the image synthetic | combination processing routine which produces | generates the image which focused on the main subject and the background subject was blurred. It is a figure which shows the optimal background photographing lens position which was determined that there was no background area to focus and was moved.

Explanation of symbols

1, 2, 3 Digital camera 1a Camera body 11 Shooting lens 12 Optical viewfinder objective window 13 Auxiliary light emitting unit 14 Shutter button 15 Power switch 16 Optical viewfinder eyepiece window 17 Menu switch 18 Execution / screen changeover switch 19 Image monitor 22 CCD
23 Analog signal processing unit 24 A / D unit 25 Digital signal processing unit 26 Temporary memory 27 Compression / decompression unit 28 Built-in memory 29 Drive circuit 30 CPU
Reference Signs List 31 Operation switch group 32 AF detection circuit 33 AE & AWB detection circuit 34 Subject distance distribution measurement means 35 Area separation means 36 Bokeh focus position detection means 37 Image composition means 41 Background blur determination means 51 Bokeh focus position detection means

Claims (6)

In a photographing apparatus that forms an image by forming an image of a subject on an image sensor with a photographing optical system and reading the subject image with the image sensor,
It represents the degree of focus at each focus position when the focus position of the photographing optical system is moved for each area when the object field captured on the image pickup device is two-dimensionally divided into a plurality of areas. A field distance distribution measuring means for obtaining an evaluation value;
A region separating unit that separates each region into a region belonging to the main subject and a region belonging to the background subject based on the evaluation value for each region and for each focus position determined by the field distance distribution measuring unit;
The evaluation value is the lowest when all the regions belonging to the background subject are regarded as one region within the range satisfying the first condition that the evaluation value is equal to or less than a predetermined evaluation threshold for all the regions belonging to the background subject. A blur focus position detecting means for obtaining a focus position satisfying the second condition;
Photographing means for photographing at a focus position determined by the blur focus position detecting means to generate a first image, and photographing at a focus position focused on a main subject to generate a second image;
An image pickup apparatus comprising: an image composition unit that combines the first image and the second image to focus on a main subject and generate an image in which a background subject is blurred. When it is impossible to detect the focus position satisfying the first condition and the second condition by the blur focus position detection unit, the photographing unit generates the second image and sets it as a background subject. A plurality of third images in which the evaluation values of the respective regions belonging to the respective regions are equal to or less than the evaluation threshold value,
The image synthesizing unit synthesizes the second image and the plurality of third images to generate an image in which a background subject is blurred while focusing on a main subject. The imaging device according to claim 1. In a photographing apparatus that forms an image by forming an image of a subject on an image sensor with a photographing optical system and reading the subject image with the image sensor,
It represents the degree of focus at each focus position when the focus position of the photographing optical system is moved for each area when the object field captured on the image pickup device is two-dimensionally divided into a plurality of areas. A field distance distribution measuring means for obtaining an evaluation value;
A region separating unit that separates each region into a region belonging to the main subject and a region belonging to the background subject based on the evaluation value for each region and for each focus position determined by the field distance distribution measuring unit;
Prior to the movement of the focus position of the photographing optical system for the field distance distribution measurement by the field distance distribution measuring means, the first image is generated by taking a picture and the main subject is focused. Photographing means for photographing at a focus position to generate a second image;
An image pickup apparatus comprising: an image composition unit that combines the first image and the second image to focus on a main subject and generate an image in which a background subject is blurred. When the first image is obtained by dividing the first image into a plurality of areas in a two-dimensional manner, the evaluation value is equal to or less than a predetermined evaluation threshold for all the areas belonging to the background subject among the areas. A background blur judging means for judging whether or not,
When the first image is not an image satisfying the condition that the evaluation value is equal to or less than a predetermined evaluation threshold for all the regions belonging to the background subject by the background blur determination unit, the photographing unit further includes: And generating a plurality of third images in which the evaluation values of the respective areas belonging to the background subject are each equal to or less than the evaluation threshold value,
The image synthesizing unit synthesizes the second image and the plurality of third images to generate an image in which a background subject is blurred while focusing on a main subject. The imaging device according to claim 3. In a photographing apparatus that forms an image by forming an image of a subject on an image sensor with a photographing optical system and reading the subject image with the image sensor,
It represents the degree of focus at each focus position when the focus position of the photographing optical system is moved for each area when the object field captured on the image pickup device is two-dimensionally divided into a plurality of areas. A field distance distribution measuring means for obtaining an evaluation value;
A region separating unit that separates each region into a region belonging to the main subject and a region belonging to the background subject based on the evaluation value for each region and for each focus position determined by the field distance distribution measuring unit;
A defocus position detection unit that detects a focus position that is a predetermined distance threshold away from all the in-focus positions of each of the regions belonging to the background subject;
Photographing means for photographing at a focus position determined by the blur focus position detecting means to generate a first image, and photographing at a focus position focused on a main subject to generate a second image;
An image pickup apparatus comprising: an image composition unit that combines the first image and the second image to focus on a main subject and generate an image in which a background subject is blurred. When it is impossible to detect a focus position that is a predetermined distance threshold away from all in-focus positions of each region belonging to the background subject by the blur focus position detection unit, the photographing unit generates the second image. And generating a plurality of third images in which the evaluation values of the respective regions belonging to the background subject are each equal to or less than the evaluation threshold value,
The image synthesizing unit synthesizes the second image and the plurality of third images to generate an image in which a background subject is blurred while focusing on a main subject. The imaging device according to claim 5.

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