JP2009086030A - Imaging apparatus, method and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To acquire an image in a focused state intended by a photographer even if the focused results by automatic focusing is not proper. <P>SOLUTION: A focusing position detection part 150 finds a focusing curve showing relationship between respective lens positions and a focusing evaluated value based on a calculated focusing evaluated value. A peak position detection part 2 detects the position of a maximal point (peak) of the focusing curve. A number-of-peaks detection part 1 counts the number of peaks and determines whether a plurality of peaks exist. When the plurality of peaks exist, a condition for focus bracket photographing is set according to the state of the peak. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a photographing apparatus having an automatic focusing function.

  In Patent Document 1, a focus position information measuring unit capable of measuring a plurality of moving positions of a lens group or an imaging surface of a CCD in order to focus a plurality of subjects existing in a shooting range a plurality of times is measured by the measuring unit. An AF motor for sequentially moving the lens group or the CCD image pickup surface to each focus position, and a photographing means for photographing each time the lens group or the CCD image pickup surface moves to each focus position.

In Patent Document 2, in a camera provided with a multipoint distance measuring means, an automatic focus adjusting means, and a continuous photographing means, two or more of the plurality of distance measurement data measured by the multipoint distance measuring means. There is provided a bracket control means for executing bracket photographing by driving the automatic focus adjusting means and the continuous photographing means based on the distance measurement data.
JP 2001-116979 A JP 7-318785 A

  In an imaging device equipped with an automatic focusing function, such as a digital camera, when shooting a subject, if there are multiple subjects in the image area to be evaluated for focusing, the main subject that the photographer wants to focus on It may be difficult to focus. Thus, when shooting in a scene where autofocus is difficult to operate as intended by the photographer, the obtained image is not in the proper focus state, and the photographer may feel uncomfortable. It was.

  In this regard, in the invention of Patent Document 1, it is assumed that an in-focus image intended by the photographer can be obtained by focusing on each of a plurality of subjects and shooting at each focus position. However, in a situation where multiple subjects are present in the image area where focus is evaluated, the high-frequency components of each subject affect each other, so the focus position obtained as a result of automatic focusing is not necessarily optimal. Not necessarily.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to obtain an image in a focused state intended by a photographer even when a focusing result by automatic focusing is not appropriate.

  An imaging apparatus according to the present invention forms an image on an imaging plane, an imaging optical system that forms a subject image on a predetermined imaging plane, a drive unit that drives the imaging optical system to change a focal position, and An imaging unit that photoelectrically converts a subject image and outputs an image signal; a generation unit that generates image data based on the output image signal; and a drive unit that determines a focal position of the imaging optical system according to a shooting preparation operation A focus evaluation value calculation unit that calculates a focus evaluation value from image data generated each time the position is changed to a position, and a maximum value detection that detects a maximum value from the focus evaluation value calculated by the focus evaluation value calculation unit Image data while controlling the focus position of the imaging optical system by controlling the driving position and the imaging unit in accordance with the shooting operation. Focus bracket shooting is repeated The imaging control unit, the peak number detection unit for detecting the number of maximum values detected by the maximum value detection unit, and the peak number detection unit when detecting a plurality of maximum values, depending on the distribution state of the plurality of maximum values A condition setting unit for setting a focus bracket shooting execution condition, and the imaging control unit performs focus bracket shooting at least near the focus position of the main subject according to the focus bracket shooting execution condition set by the condition setting unit .

  According to the present invention, when there are a plurality of maximum values of the focus evaluation value, it is assumed that the maximum point indicating the focus position of the main subject is deviated from the original focus position due to the presence of a plurality of subjects. Therefore, in this case, the present invention performs focus bracket photographing at least near the focus position of the main subject. As a result, it is possible to obtain an image in an optimally focused state in which the main subject is not out of focus.

  You may further provide the peak position detection part which detects the peak position which is a focus position of the imaging optical system corresponding to local maximum.

  It further includes a peak-to-peak distance calculation unit that calculates a distance between the focus position of the main subject and a peak position other than the focus position of the main subject, and the condition setting unit is responsive to the distance calculated by the peak-to-peak distance calculation unit. The focus bracket shooting execution condition may be set.

  As the distance between the focus position of the main subject and the other peak positions is short, the local maximum point indicating the focus position of the main subject is assumed to deviate from the original focus position. Therefore, an appropriate focus bracket shooting execution condition is set according to the distance. As a result, it is possible to obtain an image in an optimally focused state in which the main subject is not out of focus.

  The condition setting unit may set at least one of the driving range of the focal position of the imaging optical system and the number of image data output from the generation unit according to the distance.

  The condition setting unit may set only the focus position of the main subject as the driving range of the imaging optical system when the distance exceeds a predetermined threshold.

  In other words, if the distance is long, the shift of the focus position of the main subject from the original focus position is small, and even if imaging is performed only at the focus position of the main subject, an image without blur is obtained. Prevent unnecessary focus bracket shooting.

  The condition setting unit further includes a peak relative position detection unit that detects a relative positional relationship between a focus position of the main subject and a peak position other than the focus position of the main subject, and the relative detection detected by the peak relative position detection unit The focus bracket shooting execution condition may be set according to the positional relationship.

  If the focus position of the main subject is closer to the peak position than the focus position of the main subject, the condition setting unit sets the drive range of the focal position of the imaging optical system closer to the focus position of the main subject. Set to the side.

  If the focus position of the main subject is closer to the peak position than the focus position of the main subject, the focus position of the main subject is assumed to be shifted from the original focus position to the infinity side. The Therefore, the present invention sets the drive range of focus bracket shooting closer to the focus position of the main subject. As a result, it is possible to obtain an image in an optimally focused state in which the main subject is not out of focus. In addition, an appropriate focus bracket condition can be set to prevent an unnecessary increase in the number of shootings.

  When the focus position of the main subject is on the infinity side of the peak position other than the focus position of the main subject, the condition setting unit sets the drive range of the focal position of the imaging optical system to be greater than the focus position of the main subject. It should be set to infinity.

    When the focus position of the main subject is on the infinity side of the peak position other than the focus position of the main subject, it is assumed that the focus position of the main subject is shifted from the original focus position to the closest side. The Therefore, the present invention sets the drive range of focus bracket shooting to the infinity side with respect to the focus position of the main subject. As a result, it is possible to obtain an image in an optimally focused state in which the main subject is not out of focus. In addition, an appropriate focus bracket condition can be set to prevent an unnecessary increase in the number of shootings.

  It further includes a peak width calculation unit that calculates the width of the focus curve near the peak position other than the focus position of the main subject, and the condition setting unit sets the focus bracket shooting execution condition according to the width calculated by the peak width calculation unit. It is good to set.

  If the width of the focus curve near the peak position other than the focus position of the main subject is large, the influence on the shift of the focus position of the main subject is large. Therefore, the present invention sets the focus bracket shooting execution condition according to the width. As a result, it is possible to obtain an image in an optimally focused state in which the main subject is not out of focus. In addition, an appropriate focus bracket condition can be set to prevent an unnecessary increase in the number of shootings.

  The condition setting unit sets at least one of the driving range of the focal position of the imaging optical system and the number of image data output from the generation unit according to the width.

  A depth-of-field calculating unit that calculates the depth of field may be further provided, and the condition setting unit may set the focus bracket shooting execution condition according to the depth of field calculated by the depth-of-field calculating unit.

  That is, when the depth of field is shallow, the number of times of photographing and the image processing time can be reduced by narrowing the drive range of focus bracket photographing.

  The imaging method according to the present invention forms an image on the imaging surface every time the focus position of the imaging optical system that forms the subject image on the predetermined imaging surface is changed to a predetermined position in accordance with the shooting preparation operation. A step of photoelectrically converting the image of the subject image and outputting an image signal; a step of generating image data based on the output image signal; a step of calculating a focus evaluation value from the image data; and a focus evaluation value Detecting the local maximum from the step, detecting the focus position of the main subject according to the local maximum, detecting the number of detected local maximums, and if a plurality of local maximums are detected, Steps for setting focus bracket shooting conditions according to the distribution of local maximum values, and at least near the focus position of the main subject according to the focus bracket shooting conditions set according to the shooting operation Comprising a step of performing the focus bracketing, and.

  An imaging program for causing a computer to execute the above imaging method is also included in the present invention.

  When there are a plurality of local maximum evaluation values, it is assumed that the local maximum point indicating the focus position of the main subject is deviated from the original focus position due to the presence of a plurality of subjects. Therefore, according to the present invention, in this case, focus bracket shooting is performed at least near the focus position of the main subject. As a result, it is possible to obtain an image in an optimally focused state in which the main subject is not out of focus.

<First Embodiment>
FIG. 1 is a block diagram showing the configuration of a digital camera. The digital camera 10 includes a lens 12, an aperture 13, a CCD image pickup device 14, an analog front end (AFE) 16, a vertical drive circuit (V driver) 136, a digital signal processing unit 20, a main memory 22, and a CPU 100. The CPU 100 controls the entire camera 10.

 The analog image signal of the subject output from the CCD image sensor 14 is sent to an analog front end (AFE) 16. The AFE 16 is a signal processing unit that performs preprocessing for converting the output signal of the CCD image pickup device 14 into a signal format suitable for processing in the subsequent digital signal processing unit 20, and includes correlated double sampling (CDS) processing and color separation. In addition to performing gain adjustment and the like, the analog image signal is converted into a digital signal and output to the digital signal processing unit 20.

  Although the detailed structure of the CCD image sensor 14 is not shown, the CCD image sensor 14 has a two-dimensional array of a large number of photodiodes (photoelectric conversion elements) that accumulate signal charges having a charge amount corresponding to the amount of incident light. A vertical transfer CCD (V-CCD) for transferring the signal charges accumulated in each photodiode in the vertical direction, and a horizontal transfer CCD (H for transferring the signal charges transferred by the vertical transfer CCD for each line in the horizontal direction. -CCD). Also, red (R), green (G), and blue (B) primary color filters are arranged in a predetermined arrangement structure (Bayer, G stripe, etc.) corresponding to each photodiode.

  The vertical drive circuit 136 outputs a drive signal including a vertical synchronization signal VD for driving the CCD 14 and a high-speed sweep pulse P. A control signal from the CPU 100 is input to the vertical drive circuit 136 and is driven according to the control signal.

  An infrared cut filter 18 is disposed between the lens 12 and the CCD 14. The infrared cut filter 18 blocks infrared rays from entering the CCD 14.

  Further, an optical low-pass filter 19 for removing high-frequency components of light is disposed behind the infrared cut filter 18 in order to prevent the occurrence of moire.

  The lens 12 is driven by a lens driving circuit 111 that performs zooming and focus adjustment. The aperture 13 is driven to open and close by an aperture drive circuit 112 that performs aperture adjustment.

  When the release button of the camera operation unit 104 is half-pressed, the integrating unit 151 determines the brightness of the subject based on image data (through image) periodically (every 1/30 second to 1/60 second) obtained by the CCD 14. Then, photometry (calculation of EV value) is performed.

  That is, the integrating unit 151 integrates the R, G, and B image data output from the digital signal processing unit 20 and provides the integrated value to the CPU 100. The CPU 100 detects the average brightness (subject luminance) of the subject based on the integrated value input from the integrating unit 151, and calculates an exposure value (EV value) suitable for photographing.

  Then, the CPU 100 determines an exposure value including an aperture value (F value) of the aperture 13 and an electronic shutter (shutter speed) of the CCD 14 based on the obtained EV value according to a predetermined program diagram.

  When the release button is fully pressed, acquisition of image data for recording is started. The CPU 100 drives the aperture 131 based on the determined aperture value, controls the aperture diameter of the aperture 131, and controls the charge accumulation time in the CCD 14 via the vertical drive circuit 136 based on the determined shutter speed. (AE operation). Note that the CPU 100 causes the light emitting unit 101 for flash emission to emit light as necessary.

  The AE operation includes an aperture priority AE, a shutter speed priority AE, a program AE, etc. In any case, the subject brightness is measured, and an exposure value determined based on the photometric value of the subject brightness, that is, an aperture value and a shutter. By taking a picture in combination with the speed, control is performed so that an image is taken with an appropriate exposure amount, and it is possible to save troublesome determination of exposure.

  The focus position detection unit 150 extracts image data corresponding to the detection range selected by the CPU 100 from the image data of the digital signal processing unit 20 in response to the release button being pressed halfway. The method of detecting the focal position is performed using the feature that the high frequency component of the image data has the maximum amplitude at the in-focus position. The focus position detection unit 150 calculates the amplitude value by integrating the high-frequency component of the extracted image data for one field period. The in-focus position detection unit 150 causes the CPU 100 to drive and control the lens driving unit 111 to move the lens 12 within the movable range, that is, from the end point on the infinity side (INF point) to the end point on the closest side (NEAR point). During this time, the calculation of the amplitude value is executed sequentially, and the detected value is transmitted to the CPU 100 when the maximum amplitude is detected.

  The CPU 100 acquires this detection value and issues a command to the lens driving unit 111 to move the lens 12 to the corresponding in-focus position. The lens driving unit 111 moves the focus lens included in the lens 12 to the in-focus position according to a command from the CPU 100 (AF operation).

  The CPU 100 is connected to the release button of the camera operation unit 104, and the in-focus position is detected when the release button is half-pressed by the user. The lens driving unit 111 is connected to the CPU 100, and the lens driving unit 111 is driven when a zoom command from the user in the TELE direction or the WIDE direction is acquired by the zoom switch of the camera operation unit 104. Thus, the zoom lens included in the lens 12 is moved between the WIDE end and the TELE end.

  The compression / decompression processing unit 143 reads and compresses the image data stored in the main memory 22 via the bus line 142 in response to the full release button being pressed, and outputs the compressed image data to the recording medium of the external recording unit 24. The compression / decompression processing unit 143 reads out and decompresses the image data stored in the recording medium of the external recording unit 24 and stores it in the main memory 22.

  The display unit 147 converts the color video signal YC generated by the digital signal processing unit 20 based on the image signal periodically obtained from the CCD 14 into an RGB signal of three colors and outputs it to a monitor (not shown). In this way, the through image is displayed on the monitor.

  Processing of the peak number counting unit 1 and the peak position detecting unit 2 will be described later.

  FIG. 2 shows a flow of photographing processing executed by the camera 10. This process is controlled by the CPU 100. This process may be executed only when a specific mode is set from the camera operation unit 104. A program that defines this processing is stored in the main memory 22.

  In S1, it is determined whether or not the release button of the camera operation unit 104 is half-pressed. If it is determined that the release button has been pressed halfway, the process proceeds to S2.

  In S2, the lens driving unit 111 is controlled to move the position of the focus lens included in the lens 12 to the initial position.

  In S3, a through image is acquired and a focus evaluation value is calculated. For example, in the contrast AF method, the focus evaluation value is calculated by a predetermined unit (for example, infinite from the closest side) by step driving within the operating range for focusing the lens 12 (for example, from the close side to the infinity side). The operation range to the far side is moved by one unit when equally divided into 50 stages, and image data is acquired every time the unit is step-driven by a predetermined unit, and a predetermined area (for example, a screen) of the acquired image data A focus evaluation value indicating the sharpness of the subject image is calculated based on image data of a rectangular region near the center or a face detection region.

  In S4, it is determined whether or not focus evaluation values have been calculated at all focus lens positions. If it is determined that focus evaluation values have not been calculated at all focus lens positions, the process proceeds to S5. When it is determined that the focus evaluation values have been calculated at all the focus lens positions, the process proceeds to S6.

  In S5, the position of the focus lens is moved to a position where a focus evaluation value has not yet been calculated. Then, returning to S3, a focus evaluation value is calculated.

  In S6, the focus position detection unit 150 obtains a focus curve representing the relationship between each lens position and the focus evaluation value based on the calculated focus evaluation value. The peak position detection unit 2 detects the position of the maximum point (peak) of the focusing curve. Then, the peak number counting unit 1 counts the number of peaks and determines whether there are a plurality of peaks. If there are a plurality of peaks, the process proceeds to S7, and if there are not a plurality of peaks, the process proceeds to S10.

  In S7, a subroutine for setting bracket shooting conditions is executed. In focus bracket shooting, the focus position of the focus lens that is moved by the lens driving unit 11 is set to a position that is moved back and forth by a predetermined step a unit by s steps (s is an integer of 1 or more) around the maximum peak. And repeat the shooting. The bracket shooting conditions are the width of the predetermined step a, the number of moving steps s, and the like, and are set according to the peak state. Details of the bracket shooting condition setting subroutine will be described later.

  In S8, it is determined whether or not the release button of the camera operation unit 104 has been fully pressed. If it is fully pressed, the process proceeds to S9.

  In S9, focus bracket shooting is performed according to the conditions set in S7. Focus bracket imaging is performed for at least one of the plurality of peaks. For example, focus bracket photography is performed for the peak that is on the widest angle side (closest side) of the peaks, or for each peak that is up to a predetermined number (two or three, etc.) from the closest side, or for all peaks. Do.

  In S10, the focus lens is moved to the lens position corresponding to the peak of the focusing curve.

  In S11, it is determined whether or not the release button of the camera operation unit 104 has been fully pressed. If it is fully pressed, the process proceeds to S12.

  In S12, shooting is performed.

  FIG. 3 shows an example of a subject to be photographed by this processing, and FIG. 4 shows an example of a focusing curve corresponding to each subject.

  In FIG. 3A, in the focus evaluation value calculation area Z, there are two subjects, a person who is a main subject that the photographer wants to focus on and a tree. In FIG. 3B, a person's subject exists in the focus evaluation value calculation area Z. In FIG. 3C, a tree subject exists in the focus evaluation value calculation area Z.

  As shown in FIG. 4, when there are two subjects of a person and a tree, the focusing curve A is obtained by adding the focusing curve B of the person subject and the focusing curve C of the subject of the tree. There is a peak PA · PC. The focus curve B for a person only subject has one peak PB, and the focus curve C for a subject only tree has one peak PC.

  The peak PA of the focusing curve A is shifted from the peak PB indicating the focusing position of the original human subject due to the influence of the focusing curve B. Therefore, even when shooting is performed with the focus lens position set to the peak PA, the person who is the main subject is not in focus and the photographer may feel uncomfortable.

  Therefore, in the above processing, the peak of the focusing curve A is counted, and if there are a plurality of peaks, it is considered that the peak has shifted, and the focus is set near the peak PA corresponding to the focusing position of the main subject. Perform bracket shooting. If it does so, imaging | photography will be carried out in the focus position close | similar to the original peak PB, and the image of the suitable focus state with respect to a main to-be-photographed object can be obtained.

Second Embodiment
FIG. 5 shows a main configuration of a digital camera according to the second embodiment.

  A switch 4 is provided between the data transfer lines connecting the peak position detection unit 2 and the CPU 100, and a peak-to-peak distance calculation unit 3 is disposed on the downstream side. The on / off of the switch 4 is controlled by the peak number counting unit 1.

  The peak-to-peak distance calculation unit 3 calculates a distance Lp between a plurality of peaks existing in the focusing curve.

  Further, as functions of a program executed by the CPU 100, there are a photographing focus lens position setting unit 100a and a focus lens control unit 100b. The peak number counting unit 1, the peak position detecting unit 2, the inter-peak distance calculating unit 3, the photographing focus lens position setting unit 100a, and the focus lens control unit 100b may be configured by a one-chip microcomputer or the like.

  The photographing focus lens position setting unit 100a sets the position of the focus lens in the focus lens control unit 100b according to the distance Lp calculated by the inter-peak distance calculation unit 3. The focus lens control unit 100b controls the lens driving unit 111 to move the focus lens to a set position.

  FIG. 6 shows details of a bracket condition setting subroutine (S7) executed by the camera 10 of the present embodiment. In carrying out this processing, the peak number detection unit 1 turns on the switch 4 in response to the peak position detection unit 2 detecting a plurality of peaks, and the peak position detected by the peak position detection unit 2 is changed between peaks. It is transmitted to the distance calculation unit 3.

  In S21, the peak of the focusing curve corresponding to the focusing position of the main subject and the peak of the focusing curve corresponding to the focusing position of other subjects are identified among the plurality of peaks. Hereinafter, the former is called a main peak and the latter is called a sub peak. The discrimination between the main peak and the sub peak is arbitrary. For example, the peak first detected by the hill-climbing method in contrast AF is set as the main peak. Alternatively, when the main subject is a human subject, a peak corresponding to the in-focus position of the face obtained by using various face detection AF techniques (for example, Japanese Patent Application Laid-Open No. 2007-226141 by the present applicant) is a main peak. And Alternatively, when a predetermined shooting mode such as a person shooting mode is set and the main subject can be considered to be present at the closest position, the closest peak is identified as the main peak.

  In S22, the peak-to-peak distance calculation unit 3 calculates the distance Lp between the main peak and the sub peak. When there are a plurality of sub-peaks, the distance between the sub-peak closest to the main peak and the main peak is Lp. This is because the sub peak closest to the main peak is considered to most affect the deviation of the original peak of the main subject. In addition, if there are multiple sub-peaks closest to the main peak (when the main subject is sandwiched between the foreground and the background, and the sub-peak is on both the near side and the infinity side of the main peak), which distance Is also Lp.

  In S23, it is determined whether or not the distance Lp is equal to or greater than a predetermined threshold L1 (for example, 30 steps in the lens driving unit when calculating the focus evaluation value). If Lp> L1, S24, Lp ≦ L1 In this case, the process proceeds to S25.

  In S24, the photographing focus lens position setting unit 100a sets the movement position of the focus lens only to the main peak position.

  In S25, the photographing focus lens position setting unit 100a sets a bracket condition according to Lp. For example, as shown in FIG. 7, when Lp> L1, the driving range is only the lens position “10”, and L1 ≧ Lp> L2 (L2 is a threshold value. For example, lens driving at the time of calculating the focus evaluation value In the case of 20 steps), three images are taken at a lens position of “9” to “11” in the driving range, and when L2 ≧ Lp, the driving range is at the lens position of “7” to “13”. Seven pictures are taken. In other words, the shorter the peak-to-peak distance, the larger the original peak deviation amount, and the larger the driving range and the number of shots.

  8 and 9 show the relationship between the main peak and sub peak distance Lp of the focusing curve A and the original peak position. In FIG. 8, since a person and a tree exist in the focus evaluation value calculation region (FIG. 3), two peaks PA · PC appear in the focus curve A, and their distance Lp is relatively short.

  When the distance Lp between the peaks is short, the contrast components of a plurality of subjects interfere with each other, and the shift of the original in-focus position increases. Therefore, in this case, focus bracket shooting is performed.

  In FIG. 9, a person and a tree exist in the focus evaluation value calculation area, and two peaks PA · PC appear on the focus curve A, but the distance Lp between them is long. The longer the distance Lp between peaks, the smaller the interference of contrast components of a plurality of subjects, and the smaller the deviation of the original peak. Therefore, in this case, focus bracket shooting is not performed. In this way, bracket shooting can be performed without waste, and the shooting time can be shortened.

<Third Embodiment>
FIG. 10 shows a main configuration of a digital camera according to the third embodiment.

  A switch 4 is provided between the data transfer lines connecting the peak position detection unit 2 and the CPU 100, and a peak relative position calculation unit 5 is disposed downstream thereof. The on / off of the switch 4 is controlled by the peak number counting unit 1. The peak relative position calculation unit 5 may be composed of a one-chip microcomputer or the like.

  FIG. 11 shows details of a bracket condition setting subroutine (S7) executed by the camera 10 of the present embodiment. In performing this process, the peak number counting unit 1 turns on the switch 4 in response to the peak position detecting unit 2 detecting a plurality of peaks, and the peak position detected by the peak position detecting unit 2 is the peak relative value. It is transmitted to the position calculation unit 5.

  In S31, the peak relative position calculation unit 5 identifies the main peak and the sub peak.

  In S32, the peak relative position calculation unit 5 calculates the relative position of the main peak and the sub peak. That is, it is determined whether the main peak is closer to the infinity side than the sub peak.

  In S33, it is determined whether or not the main peak position is closer to the sub-peak position. When the main peak position is closer to the sub peak position, the process proceeds to S34, and when the main peak position is closer to the infinity side than the sub peak position, the process proceeds to S35.

  In S34, the photographing focus lens position setting unit 100a sets the lens driving range in the bracket condition closer to the main peak position.

  In S35, the photographing focus lens position setting unit 100a sets the lens driving range in the bracket condition to the infinity side from the main peak position.

  Although illustration is omitted, there are a plurality of sub-peaks closest to the main peak (when the main subject is sandwiched between the foreground and the background, and the sub-peak is on both the near side and the infinity side of the main peak) If it is not determined that the main peak position is closer to the infinity side or the infinity side than the sub peak position, the lens drive range may be set to both the infinity side and the near side centered on the main peak position. Good.

  FIG. 12 shows the relationship between the relative positions of the main peak and the sub peak of the focusing curve A and the original peak position. The fact that the main peak is closer to the sub-peak means that the subject at the focal length of the sub-peak is farther than the main subject of the main peak, and as a result, the main peak of the focusing curve where both are mixed Is shifted to the infinity side from the peak of the focusing curve of only the main subject. Therefore, in the above processing, the lens drive range for focus bracket shooting is set toward the close side opposite to the direction of the shift (toward the original peak).

  On the other hand, although illustration is omitted, the fact that the main peak is on the infinity side of the sub peak means that the subject at the focal length of the sub peak is closer to the main subject of the main peak. The main peak of the in-focus curve is shifted closer to the focus curve peak of only the main subject. Therefore, in the above processing, the lens drive range for focus bracket shooting is set toward the infinity side opposite to the direction of the shift (toward the original peak).

  Thus, by setting the lens drive range for focus bracket shooting in the direction in which the original peak is shifted, bracket shooting can be performed without waste, and the shooting time can be shortened.

<Fourth embodiment>
FIG. 13 shows a main configuration of a digital camera according to the fourth embodiment.

  A switch 4 is provided between the data transfer lines connecting the peak position detection unit 2 and the CPU 100, and a peak width calculation unit 6 is disposed downstream thereof. The on / off of the switch 4 is controlled by the peak number counting unit 1. The peak width calculation unit 6 may be composed of a one-chip microcomputer or the like.

  FIG. 14 shows details of a bracket condition setting subroutine (S7) executed by the camera 10 of the present embodiment. In performing this process, the peak number counting unit 1 turns on the switch 4 in response to the peak position detecting unit 2 detecting a plurality of peaks, and the peak position detected by the peak position detecting unit 2 is the peak width. It is transmitted to the calculation unit 6.

  In S41, the peak width calculation unit 6 identifies a main peak and a sub peak.

  In S <b> 42, the peak width calculation unit 6 calculates the width (peak width) of the focusing curve near the sub peak where the sub peak is the maximum value. For example, the half-width at half maximum of the focusing curve near the sub-peak, 80% of the full width at half maximum, and the like are obtained and set as the peak width PW. Alternatively, the peak may be approximated by a function, the peak sharpness may be determined by the differential coefficient of the function, and the peak sharpness may be used instead of the peak width. If the peak is abrupt, the peak width is short. If the peak is gentle, the peak width is long. Alternatively, the kurtosis is obtained by approximating a curve near the sub-peak with a normal distribution. When the kurtosis is large, the spread of the skirt is large and the peak width is long.

  In S43, the photographing focus lens position setting unit 100a sets the bracket condition according to the peak width PW. For example, as shown in FIG. 15, when PW1 ≦ PW <PW2, the driving range is “10” to “11”, and the number of shots is two at the positions “10” and “11”. In the case of PW2 ≦ PW <PW3, the drive range is “8” to “12”, and the number of shots is five, “8”, “9”, “10”, and “11”. When PW3 ≦ PW, the driving range is “7” to “15”, and the number of shots is “7” “8” “9” “10” “11” “12” “13” “14” “15”. Nine. That is, the wider the peak width, the larger the driving range and the number of shots.

  Here, PW1, PW2, and PW3 are threshold values. For example, PW1 = 10 steps in the lens driving unit when the focus evaluation value is calculated, PW2 = 15 steps, and PW3 = 20 steps.

  16 and 17 show the relationship between the peak width and the drive range in this process.

  As shown in FIG. 16, when the peak width near the sub-peak is wide, the influence on the shift of the peak position indicating the focus position of the main subject is large. Therefore, in this process, the drive range for focus bracket shooting is widened.

  On the other hand, as shown in FIG. 17, when the peak width near the sub-peak is narrow, the influence on the shift of the peak position indicating the focus position of the main subject is small. Therefore, in this process, the drive range for focus bracket shooting is narrowed.

  In this way, when setting the bracket condition, it is not necessary to estimate the deviation of the main peak position by considering the peak width of the sub peak and set the appropriate focus lens drive position or the number of bracket shots. Bracketing can be performed without shortening the shooting time.

<Fifth Embodiment>
In the first to fourth embodiments, the lens driving range and the number of brackets may be set according to the depth of field.

  FIG. 18 shows a main configuration of a digital camera according to the fifth embodiment.

  A switch 4 is provided between the data transfer lines connecting the peak position detection unit 2 and the CPU 100, and a zoom position / aperture value acquisition unit 7 is disposed downstream thereof. The on / off of the switch 4 is controlled by the peak number counting unit 1. The zoom position / aperture value acquisition unit 7 may be composed of a one-chip microcomputer or the like.

  FIG. 19 shows details of a bracket condition setting subroutine (S7) executed by the camera 10 of the present embodiment. This process can be incorporated into a part of the bracket condition setting subroutine of the first to fourth embodiments.

  In S51, the zoom position / aperture value acquisition unit 7 acquires the current position (focal length) f of the zoom lens.

  In S <b> 52, the zoom position / aperture value acquisition unit 7 acquires the current aperture value F set for the aperture 13.

  In S53, the photographing focus lens position setting unit 100a calculates the depth of field from the focal length f and the aperture value F. Then, bracket conditions are set according to the depth of field.

  For example, as shown in FIG. 20, when the depth of field is shallow, the lens driving range is “9” to “11”, and the number of shots is as small as three. When the depth of field is deep, the lens drive range is “7” to “11”, and the number of shots is as large as five. For example, when the lens driving range is set on the close side as in S34 of the third embodiment, the driving range and the number of brackets are further limited.

  21 and 22 show the relationship between the depth of field and the driving range in this process.

  As shown in FIG. 21, when the depth of field is deep, the background tree is not out of focus. In this case, as shown in FIG. 23, the influence of the contrast component of the tree on the shift of the peak position indicating the focus position of the person who is the main subject is large. Therefore, in this processing, when the depth of field is deep, the lens driving range is widened. Note that the drive range may be expanded by increasing the step width. This is because, when the depth of field is deep, the influence on the focus is small even if the step width is somewhat wide.

  On the other hand, as shown in FIG. 22, when the depth of field is shallow, the tree that is the background causes blurring. In this case, as shown in FIG. 24, the influence of the focusing curve by the contrast component of the tree on the shift of the peak position indicating the focusing position of the person who is the main subject is small. Therefore, in this process, when the depth of field is shallow, the lens drive range is narrowed and the number of shots is reduced.

  In this way, when setting the bracket conditions, considering the depth of field, the appropriate focus lens drive position or the number of bracket shots are set, so bracket shooting can be done without waste and the shooting time can be shortened. It becomes possible.

Block diagram showing the electrical configuration of the digital camera Flowchart of photographing process according to the first embodiment A figure showing an example of a subject image The figure which shows an example of the focusing curve according to a to-be-photographed object image The figure which shows the principal part structure of the digital camera which concerns on 2nd Embodiment. Flowchart of bracket condition setting subroutine according to the second embodiment Diagram showing setting example of distance between peaks and bracket condition Figure illustrating the distance between the peaks of the focusing curve (short) A diagram illustrating the distance (length) between the peaks of the focusing curve The figure which shows the principal part structure of the digital camera which concerns on 3rd Embodiment. Flowchart of bracket condition setting subroutine according to the third embodiment Diagram illustrating the shift of the peak of the focusing curve The figure which shows the principal part structure of the digital camera which concerns on 4th Embodiment. Flowchart of bracket condition setting subroutine according to the fourth embodiment Diagram showing setting example of peak width and bracket condition Diagram illustrating the relationship between the peak width (large) and the peak shift of the in-focus curve Figure illustrating the relationship between the peak width (small) and the peak shift of the in-focus curve The figure which shows the principal part structure of the digital camera which concerns on 5th Embodiment. Flowchart of bracket condition setting subroutine according to the fifth embodiment Diagram showing setting example of depth of field and bracket condition The figure which shows an example of a to-be-photographed object when the depth of field is deep The figure which shows an example of a to-be-photographed object when a depth of field is shallow The figure which shows an example of the focusing curve when the depth of field is deep The figure which shows an example of the focusing curve when the depth of field is shallow

Explanation of symbols

1: peak number detection unit, 2: peak position detection unit, 3: peak distance calculation unit, 5: peak relative position calculation unit, 6: peak width calculation unit, 7: zoom position / aperture value acquisition unit, 10: digital Camera, 12: Lens, 13: Aperture, 14: CCD

Claims (13)

An imaging optical system that forms an image of a subject on a predetermined imaging plane;
A drive unit for driving the imaging optical system to change a focal position;
An imaging unit that photoelectrically converts the subject image formed on the imaging surface and outputs an image signal;
A generating unit that generates image data based on the output image signal;
A focus evaluation value calculation unit that calculates a focus evaluation value from image data generated each time the drive unit changes the focal position of the imaging optical system to a predetermined position according to a shooting preparation operation;
A maximum value detection unit for detecting a maximum value from the focus evaluation value calculated by the focus evaluation value calculation unit;
An in-focus position detector that detects an in-focus position of the main subject in accordance with the maximum value;
An imaging control unit that controls the drive unit and the imaging unit in accordance with a shooting operation, and performs focus bracket shooting that repeats generation of image data while changing a focal position of the imaging optical system;
A peak number detection unit for detecting the number of maximum values detected by the maximum value detection unit;
When the peak number detection unit detects a plurality of maximum values, a condition setting unit that sets a focus bracket shooting execution condition according to the distribution status of the plurality of maximum values,
The imaging apparatus, wherein the imaging control unit performs the focus bracket imaging at least in the vicinity of the focus position of the main subject according to the focus bracket imaging execution condition set by the condition setting unit.   The imaging apparatus according to claim 1, further comprising a peak position detection unit that detects a peak position that is a focal position of the imaging optical system corresponding to the maximum value. A peak-to-peak distance calculation unit that calculates a distance between the focus position of the main subject and a peak position other than the focus position of the main subject;
The imaging apparatus according to claim 2, wherein the condition setting unit sets the focus bracket shooting execution condition according to the distance calculated by the peak-to-peak distance calculation unit.   The imaging apparatus according to claim 3, wherein the condition setting unit sets at least one of a driving range of a focal position of the imaging optical system and the number of image data output from the generation unit according to the distance.   The imaging apparatus according to claim 4, wherein the condition setting unit sets only a focus position of the main subject as a driving range of the imaging optical system when the distance exceeds a predetermined threshold. The condition setting unit further includes a peak relative position detection unit that detects a relative positional relationship between an in-focus position of the main subject and a peak position other than the in-focus position of the main subject,
The imaging apparatus according to claim 2, wherein the focus bracket photographing execution condition is set according to a relative positional relationship detected by the peak relative position detection unit.   When the focus position of the main subject is closer to the peak position than the focus position of the main subject, the condition setting unit sets the drive range of the focus position of the imaging optical system to the focus range of the main subject. The imaging apparatus according to claim 6, wherein the imaging apparatus is set closer to the focal position.   When the focus position of the main subject is on the infinity side with respect to a peak position other than the focus position of the main subject, the condition setting unit sets the drive range of the focus position of the imaging optical system of the main subject. The imaging apparatus according to claim 6, wherein the imaging apparatus is set on the infinity side with respect to the focus position. A peak width calculation unit for calculating a width of a focusing curve near a peak position other than the focusing position of the main subject;
The imaging apparatus according to claim 2, wherein the condition setting unit sets the focus bracket shooting execution condition according to a width calculated by the peak width calculation unit.   The imaging apparatus according to claim 9, wherein the condition setting unit sets at least one of a driving range of a focal position of the imaging optical system and the number of image data output from the generation unit according to the width. A depth of field calculation unit for calculating the depth of field;
The imaging apparatus according to claim 1, wherein the condition setting unit sets the focus bracket shooting execution condition according to the depth of field calculated by the depth of field calculation unit. Each time the focus position of the imaging optical system that forms a subject image on a predetermined imaging surface is changed to a predetermined position according to the shooting preparation operation, the subject image formed on the imaging surface is photoelectrically converted. And outputting an image signal,
Generating image data based on the output image signal;
Calculating a focus evaluation value from the image data;
Detecting a local maximum value from the focus evaluation value;
Detecting a focus position of a main subject according to the maximum value;
Detecting the number of detected maximum values;
When a plurality of local maximum values are detected, setting focus bracket shooting execution conditions according to the distribution state of the local maximum values;
Performing the focus bracket shooting at least in the vicinity of the focus position of the main subject in accordance with the shooting operation according to the set focus bracket shooting execution condition;
An imaging method including:   An imaging program for causing a computer to execute the imaging method according to claim 12.

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