JP2007249000A - Imaging apparatus, imaging method, and imaging program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To take a photograph with high focusing performance in accordance with a photographing condition such as a focal value, a zoom value and a subject distance. <P>SOLUTION: A control part 20 detects the stop position, the focal distance, the F value of a zoom lens in a lens unit 11, and the position of a focus lens when taking the photograph by using contrast AF. Then, the depth of field on a front side and the depth of field on a rear side are obtained from the stop position, the focal distance, the F value of the zoom lens, and the position of the focus lens. Furthermore, the size of a focus area which can be changed stepwise in accordance with the photographing condition is decided according to the depth of field on the front side and the depth of field on the rear side. An image acquiring part 10 performs imaging by autofocusing in the focus area. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an imaging apparatus, an imaging method, and an imaging program.

  In a digital camera, generally, when performing contrast autofocus, a part of an image is sampled (cut out) and scanned to detect a high frequency component (= contrast). In the case of a relatively distant subject, sampling may be performed in a region having a relatively large area. On the other hand, at a distance where a shallow depth of field appears remarkably as in macro photography, a sample point with a very small area enables more accurate autofocus. That is, if sampling is performed over a wide area, a portion with clear contrast and a portion with blur are mixed in the region, and it is difficult to determine where to focus.

In view of this, a technique has been proposed in which the size of a sampling region is variably controlled between an AF (autofocus) mode and a macro mode in which a difference in shallow / deep depth of field is significant (for example, Patent Documents). 1). In the prior art, when the macro mode is selected, the AF area is automatically switched to a wide range to improve the AF focusability in the macro mode.
JP 2004-20773 A

  By the way, in a digital camera, generally, the depth of field is deep when the optical zoom is at the wide angle side, and the depth of field is shallow at the telephoto side (the range in focus is narrow). Further, in the case of having multistage aperture blades, the deeper the aperture, the deeper the depth of field, and the wider the aperture, the shallower the depth of field.

  However, in the above-described conventional technology, the AF area is simply switched according to the shooting mode, and the depth of field that varies depending on the shooting conditions such as the focus value, the zoom value, and the subject distance is not considered. Therefore, in the conventional technology, the focus is indefinite at a sample point of a small area, and one point is surely sharp focus (generally the closest point in the focus area), while the “overall image” There was a problem that the image tends to be blurred.

  Therefore, the present invention provides an imaging apparatus, an imaging method, and an imaging program capable of imaging with high focus according to imaging conditions such as an aperture value, a focus value, a zoom value, and a subject distance. Objective.

  In order to achieve the above object, the inventions according to claims 1, 13, and 15 detect a shooting condition including at least an aperture value, a zoom lens position, and a subject distance, and acquire a depth of field based on the shooting condition. Determine the autofocus area size based on the depth of field, detect contrast from the signal sampled at the autofocus area size, and then execute autofocus to focus on the subject based on the contrast It is characterized by doing.

  Further, as a preferred aspect, for example, as in claim 2, in the imaging apparatus according to claim 1, the autofocus area size is prepared for each of a plurality of change patterns that change at different ratios according to the depth of field. The autofocus area size determining means may select an autofocus area according to any one of the plurality of change patterns. Therefore, the rate of change of the size of the autofocus area can be changed according to the subject, and shooting is performed with higher focus according to shooting conditions such as aperture value, focus value, zoom value, subject distance, etc. can do.

  Further, as a preferable aspect, for example, as in claim 3, in the imaging apparatus according to claim 2, it is possible to select which change pattern auto-focus area is to be used by the user operation among the plurality of change patterns. You may make it comprise a selection means. Therefore, the change rate of the size of the autofocus area can be changed by the user according to the subject, and higher focusability can be obtained according to shooting conditions such as aperture value, focus value, zoom value, subject distance, etc. You can shoot with

  Further, as a preferred aspect, for example, as in claim 4, in the imaging device according to claim 1, prior to detecting contrast in a focus area of an autofocus area size determined by the autofocus area size determining means, Preliminary contrast detecting means for detecting preliminary contrast from a signal sampled in a focus area having a predetermined focus area size, and subject distance calculating means for calculating the subject distance based on the preliminary contrast detected by the preliminary contrast detecting means You may make it comprise. Therefore, the subject distance can be calculated without using any special means, and it is possible to photograph with high focusability according to photographing conditions such as an aperture value, a focus value, a zoom value, and a subject distance. .

  Moreover, as a preferable aspect, for example, as in claim 5, in the imaging device according to any one of claims 1 to 4, an imaging unit for imaging an imaging target and an imaging target imaged by the imaging unit are displayed. Display means for displaying, and display control means for causing the display means to display an autofocus area of the autofocus area size determined by the autofocus area size determining means. Therefore, it is possible to easily identify whether the autofocus area size matches the user's request, and high focusability according to shooting conditions such as aperture value, focus value, zoom value, subject distance, etc. You can shoot with

  Further, as a preferred aspect, for example, as in claim 6, in the imaging apparatus according to claim 5, the image change apparatus includes a size changing unit that can change a size of an autofocus area displayed on the display unit by a user operation. You may make it do. Therefore, even if the autofocus area size does not match the user's request, it can be easily changed by user operation, and shooting conditions such as aperture value, focus value, zoom value, subject distance, etc. Depending on the situation, it is possible to shoot with higher focusability.

  Further, as a preferred aspect, for example, as in claim 7, in the imaging device according to claim 5 or 6, the position changing means that allows the position of the autofocus area displayed on the display means to be changed by a user operation. You may make it comprise. Therefore, even if the autofocus area size does not match the user's request, it can be easily changed by user operation, and shooting conditions such as aperture value, focus value, zoom value, subject distance, etc. Depending on the situation, it is possible to shoot with higher focusability.

  In order to achieve the above object, the inventions according to claims 8, 14 and 16 recognize a subject to be photographed, identify the type of the subject, and determine the autofocus area size based on the type of the subject. Then, after performing contrast detection from a signal sampled with the autofocus area size, autofocus for focusing on the subject based on the contrast is executed. Therefore, in addition to the photographing conditions such as the aperture value, the focus value, the zoom value, the subject distance, etc., it is possible to photograph with high focusability according to the type of the subject.

  Further, as a preferred aspect, for example, as in claim 9, in the imaging device according to claim 8, the occupied area detection means for detecting an occupied area on the angle of view of the subject recognized by the recognition means, and the occupation A size correction unit that corrects the autofocus area size determined by the autofocus area size determination unit based on the area occupied by the subject detected by the area detection unit, and the contrast detection unit includes the size correction unit. Contrast detection may be performed from a signal sampled with the autofocus area size corrected by the means. Therefore, a more optimal autofocus area size can be determined according to the occupied area of the subject type, and a higher accuracy can be obtained according to shooting conditions such as an aperture value, a focus value, a zoom value, and a subject distance. You can shoot with charity.

  Further, as a preferred aspect, for example, as in claim 10, in the imaging apparatus according to claim 8 or 9, an imaging unit that captures an imaging target, and a display unit that displays the imaging target captured by the imaging unit And a display control means for displaying on the display means an autofocus area having the autofocus area size determined by the autofocus area size determining means. Therefore, it is possible to easily identify whether the autofocus area size matches the user's request, and high focusability according to shooting conditions such as aperture value, focus value, zoom value, subject distance, etc. You can shoot with

  Further, as a preferable aspect, for example, as in claim 11, in the imaging apparatus according to claim 10, the image change apparatus includes a size changing unit that allows a user operation to change the size of the autofocus area displayed on the display unit. You may make it do. Therefore, even if the autofocus area size does not match the user's request, it can be easily changed by user operation, and shooting conditions such as aperture value, focus value, zoom value, subject distance, etc. Depending on the situation, it is possible to shoot with higher focusability.

  Further, as a preferred aspect, for example, as in claim 12, in the imaging device according to claim 10 or 11, the position changing means that allows the position of the autofocus area displayed on the display means to be changed by a user operation. You may make it comprise. Therefore, even when the position of the autofocus area does not match the user's request, it can be easily changed by the user's operation, and shooting such as aperture value, focus value, zoom value, subject distance, etc. It is possible to take a picture with higher focus according to conditions.

  According to the present invention, a shooting condition including at least an aperture value, a zoom lens position, and a subject distance is detected, a depth of field is acquired based on the shooting condition, and an autofocus area is determined based on the depth of field. After determining the size and performing contrast detection from the signal sampled at the autofocus area size, autofocus is performed to focus on the subject based on the contrast. In addition, there is an advantage that it is possible to shoot with high focus according to shooting conditions such as a zoom value and subject distance.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

A. First embodiment A-1. Configuration of First Embodiment FIG. 1 is a block diagram showing a configuration of a digital camera according to a first embodiment of the present invention. In the figure, the image acquisition unit 10 includes a lens unit 11, a shutter 12, and an LPF 13. The lens unit 11 includes a lens group including a zoom lens, a focus lens, and the like, in which aspherical lenses are stacked, and includes a DC motor for driving the zoom lens and the focus lens. The shutter 12 is a so-called mechanical shutter that is operated by a motor driver 14-1 driven by the control unit 20 when a shutter button is operated. The LPF 13 is a crystal low-pass filter and is mounted to prevent the occurrence of moire. The motor driver 14-1 controls the driving of the DC motor of the lens unit 11 under the control of the control unit (CPU) 20 to move the zoom lens, move the focus lens, and the like. The driver 14-2 drives the image sensor 16.

  Next, the analog signal processing unit 15 includes an image sensor (CCD, CMOS) 16, a sampling / signal amplification processing unit 17, and an A / D converter 18. The imaging sensor 16 forms a subject image (image), and converts the intensity of light of each color of RGB into a current value. The sampling / signal amplification processing unit 17 performs correlated double sampling processing and signal amplification processing for suppressing noise and color unevenness. The A / D converter 18 is also called an analog front end, and converts the sampled / amplified analog signal into a digital signal (converts each color of RGB and CMYG into 12-bit data and outputs it to the bus line).

  Next, the control unit (CPU) 20 controls the entire digital camera 1 (imaging device) according to a program stored in a program memory described later. In particular, in the first embodiment, the control unit (CPU) 20 detects the stop position of the zoom lens in the lens unit 11, the focal length, the F value, the position of the focus lens, and the like, and the above-described depth of field table. 35-1, the front depth of field and the rear subject depth are obtained from the stop position of the zoom lens, the focal length, the F value, and the position of the focus lens, and the focus area size table 35-2 is obtained. With reference, a focus area of an appropriate size is determined from the front depth of field and the rear subject depth, and autofocusing is performed according to the focus area. The depth of field table 35-1 and the focus area size table 35-2 will be described later.

  The preview engine 22 is stored in the image buffer 26 immediately after detection of digital data input via the image acquisition unit 10 and the analog signal processing unit 15 in the recording mode (also referred to as recording mode or photographing mode) or shutter operation detection. Thinning processing is performed in order to display the digital data and the digital data stored in the image memory 31 on the display unit 25. The D / A converter 23 converts the digital data thinned out by the preview engine 22 and outputs it to the driver 24 at the subsequent stage. The driver 24 includes a buffer area for temporarily storing digital data displayed on the display unit 25 at the subsequent stage, and drives the display unit 25 based on a control signal input via the key operation unit 27 and the control unit 20. The display unit 25 includes a color TFT liquid crystal, an STN liquid crystal, or the like, and displays a preview image, image data after shooting, a setting menu, and the like.

  The image buffer 26 temporarily stores digital data immediately after photographing until it is input via the analog signal processing unit 15 or the digital signal processing unit 28 and passed to the digital signal processing unit 28. The key operation unit 27 includes a shutter button, a recording / playback mode selection slide switch, a menu button, a cross key (determined by pressing the center), and the like.

  The digital signal processing unit 28 performs white balance processing, color processing, gradation processing, contour emphasis, conversion from RGB format to YUV format, YUV format for digital data input via the analog signal processing unit 15. To JPEG format. The digital signal processing unit 28 also generates an image file according to the Exif standard from the image data captured by the image acquisition unit 10 and the analog signal processing unit 15. The image compression / decompression processing unit 29 compresses and encodes the digital data input via the digital signal processing unit 28 into the JPEG format, or decompresses the JPEG format file in the reproduction mode. The program memory 30 stores various programs loaded on the control unit 20, EV values in the best shot function, color correction information, and the like.

  The image memory 31 stores image data temporarily held in the image buffer 26 and digital data converted into various file formats. The card I / F 32 controls data exchange between the external recording medium 33 and the imaging apparatus main body. The external recording medium 33 is a detachable recording medium composed of a compact flash (registered trademark), a memory stick, an SD card, or the like. The external connection I / F 34 includes a USB connector slot and the like, is connected to a personal computer or the like, and is used for transferring photographed image data. The RAM 35 stores various setting data, data necessary for the operation of the control unit 20, the above-described depth of field table 35-1, the focus area size table 35-2, and the like.

  FIG. 2 is a conceptual diagram showing a data structure of the depth-of-field table 35-1. The depth-of-field table 35-1 holds a focus lens step (position), a moving amount of the focus lens group, and a front depth of field and a rear subject depth for each aperture (F value). . In the illustrated example, zoom lens steps are Z0 to Z16 for the aperture (F value) “3.3” to “7.4”, and focus lens steps are 0 to 555 (wide) for each zoom lens step. There are 556 steps at the end but 247 steps at the tele end), the focus group movement amount is 0 to 4.1625 mm (0 to 1.845 mm on the tele end side), and the object distance is −14462669.225 to 0.20006692 m (tele end) -14426689.25 to 0.010007479m) on the side, 61.85793572-0.199240379m (61.879573572-0.009811648m on the tele end side), and the rear depth of field (-61. 87779572 to 0.2008997778 m (−61.877793572 on the tele end side) It has become a 0.010206671m).

  In the depth-of-field table 35-1, detailed data when aperture = F3.3 and zoom lens step = Z0 are shown in FIG. The control unit 20 first specifies the aperture (F value) at the time of shooting, and then specifies the zoom lens step, the focus lens step, the focus group movement amount, and the subject distance, so that the front-side subject at that time is specified. The depth of field and the rear depth of field are obtained, and the focus area size is determined from the depth of field coefficient (= front depth of field / rear depth of field).

  A small depth-of-field coefficient, that is, a shallow depth of field, means that the focus is only on the pinpoint in terms of the distance of the subject. It is desirable to make the size a small area. Therefore, the optimum focus area is continuously variably calculated from the depth-of-field coefficient (= front depth of field / rear depth of field) obtained from the depth-of-field table 35-1, The shallower the depth of field, the smaller the focus area size, thereby obtaining a captured image with a very sharp focus.

  Therefore, in the first embodiment, a focus area size table 35-2 for obtaining an optimum focus area from the depth of field coefficient (= front side depth of field / rear side depth of field) is provided. FIG. 4 is a conceptual diagram showing a data configuration of the focus area size table 35-2 according to the first embodiment. The focus area size table 35-2 stores a focus area size pattern A and a focus area size pattern B for each depth of field coefficient (= front side depth of field / rear side depth of field). For example, if the depth-of-field coefficient (= front side depth of field / rear side depth of field) is 10 or more, the focus area size pattern A is 20% of the specified size, and the focus area size pattern B is the specified size. If the depth of field coefficient (= front side depth of field / rear side depth of field) is 4, the focus area size pattern A is 8% of the specified size, and the focus area size pattern B Is 11% of the specified size, and if the depth of field coefficient (= front depth of field / rear depth of field) is 1.05 or less, the focus area size pattern A is 1 of the specified size. %, The focus area size pattern B is set to be 8% of the specified size.

  In the focus area size pattern A, as shown in FIG. 5, the size is changed at the same ratio. The smaller the depth of field coefficient, that is, the smaller the depth of field, the smaller the ratio. It is supposed to be. On the other hand, in the focus area size pattern B, as shown in FIG. 6, the ratio is changed stepwise, and the smaller the depth of field coefficient, that is, the shallower the depth of field. It is designed to be reduced step by step.

  By the way, as shown in FIG. 7, for example, when the focus area size is relatively large, the focus is in the middle between the flower and the insect that stops on the flower. On the other hand, as shown in FIG. 8, when the focus area size is relatively small, only the insects that have stopped on the flower are in focus and the insects are imaged very sharply. In this case, the flowers will be slightly blurred. The depth of field changes in accordance with the zoom lens step, the aperture, and the subject distance (= focus lens step) in a single digital camera. Naturally, it is unique to the lens and depends on the target CCD size.

  As described above, when the focus area size is reduced, the insects are in focus but the flowers are blurred. Replacing this with a human face, for example, can be a photo that focuses on the nose but is not in focus on the eyes. It can be seen that there are cases where it is better not to use the pin focus area just because the depth of field is shallow. Therefore, as described above, the focus area size pattern B is prepared in which the focus area size is gradually reduced as the depth of field coefficient is decreased, that is, as the depth of field is decreased. When the focus area size pattern B is used, in the above-described example, it is possible to relatively focus only on the insect. However, which of the focus area size patterns A and B is used depends on the preference of picture creation, and it is preferable that the user can select it.

A-2. Operation of First Embodiment Next, the operation of the first embodiment described above will be described. Here, FIGS. 9 and 10 are flowcharts for explaining the operation of the mobile phone 1 according to the first embodiment. First, it is determined whether or not the shutter is half-pressed (AF operation) (step S10). When the shutter is half-pressed, a predetermined focus area is selected (step S12) and pre-AF is performed (step S14). .

  Next, the equivalent subject distance is calculated from the stop lens position by pre-AF (step S16), referring to the depth-of-field table 35-1, and the aperture, zoom lens position (zoom lens step), and focus lens position during AF. (Focus lens step) The front depth of field and the rear depth of field are acquired from the subject distance (step S18). Next, with reference to the focus area size table 35-2, an optimum focus area size (pattern A or pattern B) is determined from the depth of field coefficient (= front side depth of field / rear side depth of field). (Step S20).

  Next, the focus area is arranged in the imaging area with the determined focus area size (step S22), and actual autofocus is performed within the focus area (step S24). Next, it is determined whether or not the shutter is fully pressed (step S26). If the shutter is not fully pressed, it is determined whether or not the shutter is released (step S26). If the shutter is released, the process returns to step S10 and the above-described processing is repeated from the beginning.

  On the other hand, if the shutter is not released and the shutter is fully pressed, shooting is performed by the image acquisition unit 10 and the analog signal processing unit 15 under the shooting conditions at that time (step S30), and the shot image data is stored in the image memory 31. (Step S32), the process returns to step S10, and the above-described processing is repeated from the beginning.

  In the first embodiment described above, when shooting using contrast AF, focusing is performed on the subject in a focus area where the size can be changed stepwise according to shooting conditions, thereby achieving higher focusability. You can shoot.

B. Second Embodiment Next, a second embodiment of the present invention will be described.

B-1. Configuration of Second Embodiment FIG. 11 is a block diagram showing a configuration of a digital camera according to the second embodiment. In addition, the same code | symbol is attached | subjected to the part corresponding to FIG. 1 mentioned above, and description is abbreviate | omitted. In the figure, an image recognizing unit 40 recognizes a subject from hue, area, modeling and the like using the image data processed by the digital signal processing unit 28, and the subject is “(person) face”, “ Whether it is “landscape” or “flower (plant)” is recognized. The control unit 20 specifies a focus area size that is optimal for the shooting conditions according to the recognition result of the image recognition unit 40.

  More specifically, when the subject is recognized as “(person) face”, the focus area is set to a medium size. When the subject is recognized as “landscape”, the focus area is a large area. Further, when the subject is recognized as “flower (plant)”, the focus area is set to a small area. Furthermore, for the focus area specified above, the focus area size correction coefficient is calculated from the recognized subject area, and the final focus area is determined by calculating “focus area” × “focus area size correction coefficient”. It is supposed to be.

  In order to perform the above processing, the RAM 35 stores a focus area table 35-3 shown in FIG. 12 and a focus area size correction coefficient table 35-4 shown in FIG. The focus area table 35-3 stores the type of the subject and the size of the focus area to be selected when the subject is the subject. In the focus area size correction coefficient table 35-4, for each type of subject, the focus corresponding to the subject areas S1-0 to S1-n, S2-0 to S2-n, and S3-0 to S3-n. Area size correction coefficients K1-0 to K1-n, K2-0 to K2-n, and K3-0 to K3-n are stored.

B-2. Operation of the Second Embodiment Next, the operation of the second embodiment described above will be described. Here, FIG. 14 to FIG. 16 are flowcharts for explaining the operation of the mobile phone 1 according to the second embodiment. First, it is determined whether or not the shutter is half-pressed (AF operation) (step S40). When the shutter is half-pressed, a predetermined focus area is selected (step S42) and pre-AF is performed (step S44). .

  Next, the image recognizing unit 40 recognizes the subject from the hue, area, and modeling (step S46), and determines whether the subject is a human face (step S48). When the subject is recognized as a human face, an intermediate focus area is selected from the focus area table 35-3 (step S50). Next, the area of the subject (face) is calculated (step S52), and referring to the focus area size correction coefficient table 35-4, any one of the focus area size correction coefficients K1-0 to K1-n is calculated from the area of the subject. Is specified (step S54).

  Next, the selected focus area is multiplied by one of the focus area size correction coefficients K1-0 to K1-n to determine the final focus area size (step S56), and the focus of the determined focus area size is determined. The area is arranged in the imaging area (step S58), and actual autofocus is performed within the focus area (step S84). Next, it is determined whether or not the shutter has been fully pressed (step S86). If the shutter has not been fully pressed, it is determined whether or not the shutter has been released (step S88). If the shutter is released, the process returns to step S40, and the above-described processing is repeated from the beginning.

  On the other hand, when the shutter is not released and the shutter is fully pressed, shooting is performed by the image acquisition unit 10 and the analog signal processing unit 15 under the shooting conditions at that time (step S90), and the shot image data is stored in the image memory 31. (Step S92), the process returns to step S40, and the above-described processing is repeated from the beginning.

  On the other hand, if the subject is not a human face, it is determined whether or not the subject is a landscape (step S60). When the subject is recognized as a landscape, a large focus area is selected from the focus area table 35-3 (step S62). Next, the area of the subject (landscape) is calculated (step S64), and any one of the focus area size correction coefficients K2-0 to K2-n is determined from the area of the subject with reference to the focus area size correction coefficient table 35-4. Is identified (step S66).

  Next, the selected focus area is multiplied by one of the focus area size correction coefficients K2-0 to K2-n to determine the final focus area size (step S66), and the focus of the determined focus area size is determined. The area is arranged in the imaging area (step S58). Similarly, the actual autofocus is performed in the focus area (step S84). When the shutter is fully pressed, an image is acquired with the shooting conditions at that time. The image capturing is performed by the unit 10 and the analog signal processing unit 15 (step S90), and the captured image data is stored in the image memory 31 (step S92).

  If the subject is neither a human face nor a landscape, it is determined whether or not the subject is a flower (step S72). When the subject is recognized as a flower, a small area is selected from the focus area table 35-3 (step S74). Next, the area of the subject (flower) is calculated (step S76), and referring to the focus area size correction coefficient table 35-4, any one of the focus area size correction coefficients K3-0 to K3-n is determined from the area of the subject. Is identified (step S78).

  Next, the selected focus area is multiplied by one of the focus area size correction coefficients K3-0 to K3-n to determine the final focus area size (step S80), and the focus of the determined focus area size is determined. The area is arranged in the imaging area (step S82), and thereafter, in the same manner, the actual autofocus is performed in the focus area (step S84). When the shutter is fully pressed, the image is acquired with the shooting conditions at that time. The image capturing is performed by the unit 10 and the analog signal processing unit 15 (step S90), and the captured image data is stored in the image memory 31 (step S92).

  FIG. 17 shows a case where the subject is a human face. When it is recognized that the subject is a human face, a moderate focus area is selected as shown in FIG. 17A. However, the focus area is corrected according to the occupied area of the human face, and finally As shown in FIG. 17B, the size is corrected so that only the face portion is included in the focus area. Therefore, the image is taken so that the face of the person who is the subject is in focus.

  FIG. 18 shows the case where the subject is a landscape. When it is recognized that the subject is a landscape, a large focus area is selected as shown in FIG. 18A. However, the focus area is corrected according to the occupation area of the landscape. As shown in FIG. 18B, the size is corrected so that only the important part of the landscape (the mountain part in front of the background) enters the focus area. Therefore, the subject is photographed so that it is in focus.

  FIG. 19 shows the case where the subject is a flower. When it is recognized that the subject is a flower, a small focus area is selected as shown in FIG. 19A. However, the focus area is corrected according to the area occupied by the flower, and finally, As shown in FIG. 19B, the size is corrected so that the center portion of the flower enters the focus area. Therefore, the image is taken so that the center of the subject flower is in focus.

  In the second embodiment described above, when shooting using contrast AF, the type of subject, which is one of the shooting conditions, is image-recognized, a focus area of a different size is specified according to the subject, and the subject The area occupied by the screen is calculated, corrected so that the size of the focus area changes stepwise according to the area of the subject, and the subject is focused in the focus area, thereby shooting with higher focusability. Can do.

C. Modified Example Next, a modified example of the present invention will be described. In the present modification, as described in the first or second embodiment, after the focus area size is once determined, the focus area size can be manually changed by the user. That is, even if the focus area size is determined according to the shooting conditions, it does not necessarily match the user's request. Therefore, as shown in FIG. 20, the focus area displayed on the display unit 25 can be changed by the control unit 20 in accordance with an instruction from the key operation unit 27.

  At this time, not only the focus area size can be changed, but also the position of the focus area can be moved. Further, when the user changes the size and position of the focus area, AF is performed again in accordance with the focus area, and the display unit 25 displays the in-focus state. It may be possible to variably operate the size and position of the.

  In the above-described embodiment, the focus area size is changed stepwise with reference to various tables. However, the present invention is not limited to this, and calculation may be performed using an arithmetic expression to prevent an increase in memory capacity. Good. In the above-described embodiment, only the digital camera has been described. However, the present invention is not limited to this, and a mobile phone or the like may be used as long as the device has a shooting function.

It is a block diagram which shows the structure of the digital camera by 1st Embodiment of this invention. It is a conceptual diagram which shows the data structure of the depth-of-field table 35-1 by this 1st Embodiment. In the depth-of-field table 35-1, it is a conceptual diagram showing detailed data when aperture = F3.3 and zoom lens step = Z0. It is a conceptual diagram which shows the data structure of the focus area size table 35-2 by this 1st Embodiment. It is a schematic diagram for demonstrating the focus area size pattern A. FIG. It is a schematic diagram for demonstrating the focus area size pattern B. FIG. It is a schematic diagram for demonstrating the focus condition by the difference in the size of a focus area. It is a schematic diagram for demonstrating the focus condition by the difference in the size of a focus area. 4 is a flowchart for explaining the operation of the mobile phone 1 according to the first embodiment. 4 is a flowchart for explaining the operation of the mobile phone 1 according to the first embodiment. It is a block diagram which shows the structure of the digital camera by this 2nd Embodiment. It is a conceptual diagram which shows the data structure of the focus area table 35-3 by this 2nd Embodiment. It is a conceptual diagram which shows the data structure of the focus area size correction coefficient table 35-4 by this 2nd Embodiment. 7 is a flowchart for explaining the operation of the mobile phone 1 according to the second embodiment. 7 is a flowchart for explaining the operation of the mobile phone 1 according to the second embodiment. 7 is a flowchart for explaining the operation of the mobile phone 1 according to the second embodiment. In this 2nd Embodiment, it is a schematic diagram which shows the focus area size when a to-be-photographed object is a person's face. In this 2nd Embodiment, it is a schematic diagram which shows the focus area size when a to-be-photographed object is a landscape. In this 2nd Embodiment, it is a schematic diagram which shows the focus area size when a to-be-photographed object is a flower. It is a schematic diagram for demonstrating manual operation of the focus area size by the modification of this invention.

Explanation of symbols

10 Image acquisition unit (autofocus means, photographing means)
11 Lens unit 12 Shutter 13 LPF
14-1 Driver 14-2 Driver 15 Analog Signal Processing Unit 16 Imaging Sensor 17 Sampling / Signal Amplification Processing Unit 18 A / D Converter 20 Control Unit (Shooting Condition Detection Unit, Depth of Field Obtaining Unit, Autofocus Area Size Determination Unit Auto focus means, subject distance calculation means, display control means, occupied area detection means, size correction means)
22 Preview Engine 23 D / A Converter 24 Driver 25 Display Unit (Display Unit)
26 Image buffer 27 Key operation unit (selection means, size change means, position change means)
28 Digital signal processing unit (contrast detection means, preliminary contrast detection means)
29 Image compression / decompression processing unit 30 Program memory 30-1 Tracking table 31 Image memory 32 Card I / F
33 External recording medium 34 External connection I / F
35 Memory 35-1 Depth of Field Table 35-2 Focus Area Size Table 35-3 Focus Area Table 35-4 Focus Area Size Correction Coefficient Table 40 Image Recognition Unit (Recognition Unit, Subject Type Identification Unit)

Claims (16)

An imaging device that detects the contrast of a captured image and performs autofocus,
Shooting condition detection means for detecting shooting conditions including at least an aperture value, a zoom lens position, and a subject distance;
A depth of field acquisition means for acquiring a depth of field based on the shooting conditions;
Auto focus area size determining means for determining an auto focus area size based on the depth of field acquired by the depth of field acquiring means;
Contrast detection means for performing contrast detection from a signal sampled at the autofocus area size determined by the autofocus area size determination means;
An image pickup apparatus comprising: autofocus means for executing autofocus for focusing on a subject based on the contrast detected by the contrast detection means. The autofocus area size is prepared for each of a plurality of change patterns that change at different ratios according to the depth of field,
The imaging apparatus according to claim 1, wherein the autofocus area size determining unit selects an autofocus area according to any one of the plurality of change patterns.   The imaging apparatus according to claim 2, further comprising a selection unit that allows a user operation to select which of the plurality of change patterns is used as an autofocus area. Prior contrast detection means for performing preliminary contrast detection from a signal sampled in a focus area having a predetermined focus area size prior to contrast detection in a focus area having an autofocus area size determined by the autofocus area size determining means. When,
The imaging apparatus according to claim 1, further comprising: a subject distance calculating unit that calculates the subject distance based on the preliminary contrast detected by the preliminary contrast detecting unit. A photographing means for photographing the photographing object;
Display means for displaying a subject to be photographed by the photographing means;
5. The imaging according to claim 1, further comprising: a display control unit that causes the display unit to display an autofocus area having an autofocus area size determined by the autofocus area size determination unit. apparatus.   6. The imaging apparatus according to claim 5, further comprising a size changing unit that allows a user operation to change a size of an autofocus area displayed on the display unit.   7. The image pickup apparatus according to claim 5, further comprising position changing means for changing the position of the autofocus area displayed on the display means by a user operation. An imaging device that detects the contrast of a captured image and performs autofocus,
A recognition means for recognizing the subject to be photographed,
Subject type identification means for identifying the type of subject recognized by the recognition means;
Auto focus area size determining means for determining an auto focus area size based on the type of subject identified by the subject type identifying means;
Contrast detection means for performing contrast detection from a signal sampled at the autofocus area size determined by the autofocus area size determination means;
An image pickup apparatus comprising: autofocus means for executing autofocus for focusing on a subject based on the contrast detected by the contrast detection means. Occupied area detecting means for detecting the occupied area on the angle of view of the subject recognized by the recognizing means;
Size correcting means for correcting the autofocus area size determined by the autofocus area size determining means based on the occupied area of the subject detected by the occupied area detecting means,
9. The imaging apparatus according to claim 8, wherein the contrast detection unit performs contrast detection from a signal sampled with an autofocus area size corrected by the size correction unit. A photographing means for photographing the photographing object;
Display means for displaying a subject to be photographed by the photographing means;
The imaging apparatus according to claim 8, further comprising: a display control unit that causes the display unit to display an autofocus area having an autofocus area size determined by the autofocus area size determination unit.   The imaging apparatus according to claim 10, further comprising a size changing unit that allows a user operation to change a size of an autofocus area displayed on the display unit.   12. The image pickup apparatus according to claim 10, further comprising position changing means for changing the position of the autofocus area displayed on the display means by a user operation. An imaging method for performing autofocus by detecting the contrast of a captured image,
Detecting a shooting condition including at least an aperture value, a zoom lens position, and a subject distance;
Obtaining a depth of field based on the shooting conditions;
Determining an autofocus area size based on the acquired depth of field;
Performing contrast detection from a signal sampled at the determined autofocus area size;
And an auto-focusing step of focusing on a subject based on the detected contrast. An imaging method for performing autofocus by detecting the contrast of a captured image,
Recognizing a subject to be photographed;
Identifying the recognized subject type;
Determining an autofocus area size based on the identified subject type;
Performing contrast detection from a signal sampled at the determined autofocus area size;
And an auto-focusing step of focusing on a subject based on the detected contrast. An imaging program that detects the contrast of a captured image and performs autofocus,
On the computer,
A shooting condition detection function for detecting shooting conditions including at least an aperture value, a zoom lens position, and a subject distance;
A depth of field acquisition function for acquiring a depth of field based on the shooting conditions;
An autofocus area size determination function for determining an autofocus area size based on the acquired depth of field;
A contrast detection function for performing contrast detection from a signal sampled at the determined autofocus area size;
An imaging program for realizing an autofocus function for executing autofocus for focusing on a subject based on the detected contrast. An imaging program that detects the contrast of a captured image and performs autofocus,
On the computer,
A cognitive function that recognizes the subject being shot,
A subject type identification function for identifying the recognized subject type;
An autofocus area size determination function for determining an autofocus area size based on the type of the identified subject;
A contrast detection function for performing contrast detection from a signal sampled at the determined autofocus area size;
An imaging program for realizing an autofocus function for executing autofocus for focusing on a subject based on the detected contrast.

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