Patent Publication Number: US-8537261-B2

Title: Image-capturing apparatus and computer-readable computer program product containing image analysis computer program

Description:
INCORPORATION BY REFERENCE 
     The disclosure of the following priority application is herein incorporated by reference: Japanese Patent Application No. 2009-246881 filed Oct. 27, 2009. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an image-capturing apparatus and a computer-readable computer program product containing an image analysis computer program. 
     2. Description of Related Art 
     An image-capturing apparatus known in the related art may be capable of synthesizing an image achieving focus on a given image plane by using data obtained through a single photographing operation. The image-capturing apparatus disclosed in Japanese Laid Open Patent Publication No. 2007-4471 generates image data based upon the values output from pixels that receive light entering the centers of micro-lenses after passing through a photographic optical system. 
     SUMMARY OF THE INVENTION 
     However, a high level of accuracy cannot be assured with image data synthesis processing executed based upon design values by assuming that they each indicate the exact position of a specific pixel to receive a light beam that enters the center of the corresponding micro-lens after passing through the photographic optical systems as described above and an image obtained through such image data synthesis processing may not be in focus. This issue arises from a production-related difficulty in achieving precise alignment of the micro-lens array where the micro-lenses are disposed with respect to the image sensor where the pixels are disposed. In other words, there is an issue yet to be effectively addressed in that the position of a pixel to receive a light beam that enters the center of the corresponding micro-lens after passing through the photographic optical system cannot be determined accurately. 
     According to the 1st aspect of the present invention, an image-capturing apparatus comprises: a micro-lens array that includes a plurality of micro-lenses arrayed therein; an image sensor that includes arrayed therein a plurality of pixels that capture a plurality of pupil projection images, each corresponding to a pupil of an optical system projected via one of the plurality of micro-lenses as a light flux from the optical system passes through the micro-lens array; a photographic image generation unit that generates, based upon an output from the image sensor, a photographic image including a partial image corresponding to each of the plurality of pupil projection images; and an arithmetic operation unit that executes position calculation to determine a center position of the partial image by scanning the photographic image in reference to a reference image corresponding to the partial image. 
     According to the 2nd aspect of the present invention, in the image-capturing apparatus according to the 1st aspect, it is preferred that the plurality of micro-lenses includes a first micro-lens and a second micro-lens different from the first micro-lens; the plurality of pupil projection images includes a first projection image corresponding to the first micro-lens and a second projection image corresponding to the second micro-lens; and the arithmetic operation unit determines through the position calculation a first center position of the partial image corresponding to the first projection image and calculates a second center position of the partial image corresponding to the second projection image based upon the first center position and an array arrangement assumed for the plurality of micro-lenses. 
     According to the 3rd aspect of the present invention, in the image-capturing apparatus according to the 1st aspect, it is preferred that the image-capturing apparatus further comprises: a selecting unit that selects the reference image based upon attribute information indicating attributes of the optical system. 
     According to the 4th aspect of the present invention, in the image-capturing apparatus according to the 1st aspect, it is preferred that the image-capturing apparatus further comprises a storage unit in which the center position, calculated by the arithmetic operation unit when a pupil position of the pupil of the optical system takes a predetermined value, is stored as a reference position. When the pupil position is altered to assume a value other than the predetermined value, the arithmetic operation unit calculates the center position by using the reference position. 
     According to the 5th aspect of the present invention, in the image-capturing apparatus according to the 4th aspect, it is preferred that, when the pupil position is altered to assume the value other than the predetermined value, the arithmetic operation unit calculates the center position based upon the value other than the predetermined value as well as the predetermined value. 
     According to the 6th aspect of the present invention, in the image-capturing apparatus according to the 1st aspect, it is preferred that the image-capturing apparatus further comprises: a image synthesis unit that selects pixels among the plurality of pixels based upon the center position determined through the position calculation and synthesizes a subject image by using outputs from the selected pixels. 
     According to the 7th aspect of the present invention, in the image-capturing apparatus according to the 1st aspect, it is preferred that the image-capturing apparatus further comprises: a focus detection unit that selects from the plurality of pixels a pair of pixels corresponding to each of the plurality of micro-lenses, at which a pair of images are formed with a pair of light fluxes passing through a pair of pupils of the optical system different from each other, based upon the center position determined through the position calculation, and detects a focusing condition for the optical system based upon outputs from the pair of pixels. 
     According to the 8th aspect of the present invention, in the image-capturing apparatus according to the 1st aspect, it is preferred that the image-capturing apparatus further comprises: a reference image generation unit that updates, based upon a correlation of the reference image and the photographic image manifesting when a pupil diameter in each of the plurality of pupil projection images corresponding to the attribute information is represented by a provisional value, the pupil diameter with an update value, and generates the reference image in correspondence to the pupil diameter assuming the update value. 
     According to the 9th aspect of the present invention, a computer-readable computer program product containing an image analysis computer program that enables, in an image-capturing apparatus comprising an optical system, a micro-lens array with a plurality of micro-lenses arrayed therein, and an image sensor with a plurality of pixels arrayed therein, image analysis to be executed in conjunction with image-capturing data generated based upon output from the image sensor, the image analysis computer program comprises: a generation instruction for generating, based upon the image-capturing data, a photographic image including a partial image corresponding to each of a plurality of pupil projection images each corresponding to a pupil of the optical system; and a first arithmetic operation instruction for determining a center position of the partial image by scanning the photographic image in reference to a reference image corresponding to the partial image. 
     According to the 10th aspect of the present invention, in the computer-readable computer program product according to the 9th aspect, wherein the image analysis computer program further comprises: a second arithmetic operation instruction for calculating, after a first center position of the partial image corresponding to one pupil projection image among the plurality of pupil projection images is determined in response to the first arithmetic operation instruction, a second center position of the partial image corresponding to another pupil projection image among the plurality of pupil projection images based upon the first center position and an array arrangement assumed for the plurality of micro-lenses. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates the structure of the camera achieved in a first embodiment. 
         FIGS. 2A and 2B  each present a detailed flowchart of an operation executed by the main control unit. 
         FIG. 3  is a front view of the image sensor onto which a subject image is projected. 
         FIG. 4  is an enlarged view of a partial area constituting part of the image sensor. 
         FIG. 5  shows the results that may be obtained by executing edge extraction processing for the image data from the partial area shown in  FIG. 4 . 
         FIGS. 6A ,  6 B and  6 C each show a template image that may be used in pattern matching when calculating pupil projection center positions in  FIG. 5 . 
         FIG. 7  presents a detailed flowchart of the processing executed by the main control unit in step S 210  in  FIG. 2A  and  FIG. 2B  in order to determine the pupil projection center positions. 
         FIG. 8  shows points indicating the pupil projection center positions calculated for the individual sets of sampling data plotted on a plane in a coordinate system defined by an x-axis and an i-axis, and the regression line drawn based upon the plotted points. 
         FIG. 9  presents a detailed flowchart of the processing executed by the main control unit in step S 210  in  FIG. 2A  and  FIG. 2B , in order to determine the pupil projection center positions in a second embodiment. 
         FIG. 10  presents a detailed flowchart of the processing executed by the main control unit in step S 210  in  FIG. 2A  or  2 B, in order to determine the pupil projection center positions in a third embodiment. 
         FIG. 11  shows a connection structure adopted in a fourth embodiment to connect the camera with a PC. 
         FIG. 12  presents a detailed flowchart of the processing executed by the PC based upon an image analysis computer program in order to determine the pupil center projection in the fourth embodiment. 
     
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     First Embodiment 
     In reference to  FIGS. 1 through 10 , the first embodiment achieved by adopting the image-capturing apparatus according to the present invention in a camera is described.  FIG. 1  illustrates the structure of a camera  1  achieved in the embodiment. The camera  1  in  FIG. 1 , which includes a camera body  10  and a lens barrel  15 , has either a focus detection function or an image synthesis function, or both of these functions. A photographic lens control unit  150 , a photographic lens  160  and a lens barrel memory  170  are located at the lens barrel  15 . A main control unit  100 , an image sensor  110 , a micro-lens array  120 , an internal memory  130  and a memory card  140  are located at the camera body  10 . The photographic lens  160  includes a photographic optical system constituted with a focusing lens, a zooming lens, an aperture and the like. 
     At the lens barrel  15 , the photographic lens control unit  150  executes focus adjustment for the photographic lens  160  by driving the photographic lens  160  and the aperture (not shown) in response to instructions issued by the main control unit  100  in the camera body  10 . Design values related to the photographic lens  160 , such as the focal length, the maximum aperture number of the photographic lens  160  or the like, are recorded in the lens barrel memory  170 . 
     At the camera body  10 , the main control unit  100  executes focus detection for the photographic lens  160 , controls the focus adjustment executed by the photographic lens control unit  150  for the photographic lens  160  based upon the focus detection results, generates a photographic image based upon an image sensor output obtained as the image sensor  110  captures an image of a subject, and records the image data expressing the photographic image thus generated into the memory card  140 . In addition, it obtains photographic lens attribute information from the photographic lens control unit  150 , determines pupil projection center positions through the processing to be described in detail later and records the pupil projection center positions thus determined into the internal memory  130 . 
     In  FIG. 1 , a distance h between the photographic lens  160  and the micro-lens array  120 , i.e., a pupil position h, a pitch d with which the individual micro-lenses constituting the micro-lens array  120  are set side-by-side, and the focal length f of the micro-lenses, are indicated. The focal length f of the micro-lenses is equal to the distance between the micro-lens array  120  and the image sensor  110 . Assuming that an x-axis defines the direction along which the longitudinal side or the lateral side of the image sensor extends, a position x 0  and a position x i  in  FIG. 1  are respectively the position of a pixel that receives a light beam entering the center of a 0th micro-lens closest to the optical axis of the photographic lens  160  and the position of a pixel that receives a light beam entering the center of an ith micro-lens located at the ith position counted from the 0th micro-lens along the x-axis. 
       FIGS. 2A and 2B  each present a detailed flowchart of an operation that may be executed by the main control unit  100 . The main control unit  100  executing the operation shown in  FIG. 2A  determines pupil projection center positions in step S 210 . It then executes focus detection for the photographic lens  160  based upon the pupil projection center positions having been determined and controls the focus adjustment executed by the photographic lens control unit  150  for the photographic lens  160  accordingly. The focus detection for the photographic lens  160  and control of the focus adjustment for the photographic lens  160  may be executed by adopting, for instance, the split-pupil phase detection method disclosed in Japanese Laid Open Patent Publication No. H1-216306. In step S 230 , the main control unit  100  selects a pair of pixels at which a pair of images are formed with a pair of light fluxes passing through two different pupils of the photographic lens  160 , among a plurality of pixels on the image sensor  110 , in correspondence to each micro-lens based upon the pupil projection center positions having been determined in step S 210  and detects the focusing condition for the photographic lens  160  by using the outputs from the pair of pixels thus selected. It is preferable that the pupil projection center positions be immediately determined in step S 210 , as soon as the user turns on the power to the camera  1  and that the main control unit wait in standby, ready to start the focus detection and the focus adjustment control for the photographic lens  160  in step S 220  in response to a user operation. 
     In the operation in the flowchart presented in  FIG. 2B , the main control unit  100  determines the pupil projection center positions in step S 210  and then synthesizes an image in step S 230  based upon the pupil projection center positions having been determined. An image may be synthetically generated in step S 230  by adopting, for instance, the art disclosed in Japanese Laid Open Patent Publication No. 2007-4471. In step S 230 , the main control unit  100  selects pixels that correspond to the subject image forming position, among the plurality of pixels disposed on the image sensor  110 , each in correspondence to a given micro-lens, based upon the pupil projection center positions having been determined in step S 210 , and synthetically generates a subject image by using the outputs from these selected pixels. It is preferable that the pupil projection center positions be determined in step S 210  repeatedly over fixed intervals while a live-view image display is up at a monitor (not shown) of the camera  1  as the main control unit waits in standby, ready to start synthesizing an image in step S 230 . The following is a detailed description of the pupil projection center position determining processing. 
       FIG. 3  is a front view of the image sensor  110 , onto which a subject image  310  of a plant, chosen as an image-capturing target subject, is projected. The figure does not illustrate the individual pixels. A further description is provided by focusing on a partial area  300  of the image sensor  110 , which contains an image  350  of part of a leaf of the plant. 
       FIG. 4  is an enlarged view of the partial area  300  of the image sensor  110 , in which the image  350  of part of the leaf of the plant, i.e., the photographic subject in  FIG. 3 , is formed. Square image-capturing pixels  115  are disposed next to one another over the area  300  at the image sensor  110 . In addition, each unfilled circular area is a projection image  125  of a pupil of the photographic lens  160 , projected onto the light receiving surface of the image sensor  110  with a light flux entering a micro-lens after passing through the photographic lens  160 . A pupil projection center position  425  is taken at the center of each pupil projection image. The pupil projection images  125  in the area outside the image  350  of part of the leaf, which is hatched in  FIG. 4 , assume high intensity values and are thus clear. However, the pupil projection images  125  in the area inside the image  350  of part of the leaf assume lower intensity values compared to the intensity values in the pupil projection images  125  in the area outside the image  350  of part of the leaf. An even lower intensity value is indicated in a leaf vein image  410 . The following is a description of a method that may be adopted when calculating pupil projection center positions  425  through pattern matching for the partial area  300  in  FIG. 4 . 
       FIG. 5  shows the results that may be obtained by executing edge extraction processing for image data generated based upon the output data corresponding to the partial area  300  in  FIG. 4 , which are included in an image sensor output provided by the image sensor  110 . Such edge extraction processing may be achieved through, for instance, a differential filter processing like Laplacian differential filter processing. An edge extraction image  305  in  FIG. 5 , which is obtained through Laplacian differential filter processing, contains outlines  1250  of the pupil projection images  125  extracted as faint lines. An outline  3500  of the image  350  of part of the leaf, with a lesser extent of variance in the intensity level, is extracted as a slightly darker line. The outline  3500  is indicated with a slightly narrower unfilled line in  FIG. 5 . No edge is extracted in the area within the image  350  of part of the leaf, except for a line  4100  representing the leaf vein image. This means that the pupil projection images  125  within the subject image area cannot be detected readily. 
       FIG. 6  shows template images that may be used for purposes of pattern matching when calculating the pupil projection center positions in  FIG. 5 .  FIGS. 6A ,  6 B and  6 C respectively show template images of a large circle, a medium-sized circle and a small circle. In template image-based pattern matching, the partial area  300  in  FIG. 5 , is scanned in reference to the template image in  FIG. 6A ,  FIG. 6B  or  FIG. 6C  set over the partial area, and a specific pupil projection image  125  matching the template image within the partial area  300  is determined. In more specific terms, the template image is shifted by one pixel position at a time until all the pixel positions within the area  300  are covered, and a correlation value indicating a match factor is calculated at each pixel position. A threshold correlation value is set in advance and whenever a changeover point at which the correlation value having increased to a value large enough to exceed the threshold value starts to decrease, is detected, it is judged that an outline  1250  of a pupil projection image  125  has been detected. Under these circumstances, the pupil projection center position  425  of the particular pupil projection image  125  can be calculated as the position of the center of the circle expressed by the template image aligned with the detected outline  1250 . As an alternative, since the outline of a pupil projection image  125  is estimated to be present at the position indicating the highest correlation value, the pupil projection center position  425  in the particular pupil projection image  125  can be calculated based upon the position data indicating the position. 
     The template images in  FIGS. 6A ,  6 B and  6 C are recorded in advance in the internal memory  130 , and the specific template image to be used is selected based upon the photographic lens attribute information such as the F number of the photographic lens  160 , since the size of the pupil projection images  125 , i.e., the pupil diameter, is determined in correspondence to the aperture diameter and the focal length of the photographic lens  160 . The photographic lens attribute information is obtained by the main control unit  100  from the photographic lens control unit  150 . The correlation value should be calculated through pattern matching processing by adopting, for instance, the technology described as the prior art in Japanese Laid Open Patent Publication No. H9-102039. 
     The pupil projection center positions  425  must be determined only in correspondence to a predetermined number of sets of sampling data through the pattern matching processing described above, since all the remaining pupil projection center positions  425  can be determined by identifying a specific optimal arithmetic operation expression that will allow the remaining pupil projection center positions to be estimated based upon the pupil projection center positions  425  having been determined in correspondence to the predetermined number of sets of sampling data, as detailed later. In the example presented in  FIG. 5 , after executing the edge extraction processing, pupil projection center positions  425  may be determined for the predetermined number of sets of sampling data indicating highest correlation values. Such sampling data are highly likely to have been obtained by executing the pattern matching processing described above on data with complete outlines  1250  of pupil projection images  125  extracted without any portions of the outlines missing, and are thus likely to allow pupil projection center positions  425  to be accurately calculated. 
     As described earlier, the outline  3500  of the image  350  of part of the leaf is extracted as a slightly darker line in  FIG. 5 . Accordingly, the pattern matching processing described earlier may be executed after exclusively extracting the outlines  1250  of the pupil projection images  125  through, for instance, binarization processing so as to improve the accuracy of the pattern matching processing. 
       FIG. 7  presents a detailed flowchart of the processing executed by the main control unit  100  in step S 210  in the flowcharts in  FIGS. 2A and 2B  in order to determine the pupil projection center positions. In step S 710 , an image of the subject is captured by controlling the image sensor  100 . In step S 715 , a photographic image is generated based upon the image sensor output. In step S 720 , the edge extraction processing described earlier is executed for the photographic image. In step S 730 , the photographic lens attribute information including the F number of the photographic lens  160  is obtained from the photographic lens control unit  150 . This step may be executed before step S 710 . 
     In step S 740 , the optimal template image is selected based upon the photographic lens attribute information, the pattern matching processing is executed in step S 750 , and then a pupil projection center position  425  is calculated in step S 760  based upon the pattern matching results. Until it is decided in step S 770  that pupil projection center positions  425  for the predetermined number of sets of sampling data have been obtained, the correlation value is calculated by shifting the template image by, for instance, one pixel position at a time and the processing in step S 750  and step S 760  is repeatedly executed. 
     Once the pupil projection center positions  425  are obtained for the predetermined number of sets of sampling data, a specific arithmetic operation expression to be used to calculate pupil projection center positions  425 , as described later, is determined in step S 780 . Then, all the pupil projection center positions  425  are determined by using the determined arithmetic operation expression and the pupil projection center positions having been determined are recorded into the internal memory  130  in step S 790  before the main control unit  100  returns to the processing in  FIG. 2A  or  FIG. 2B . 
     The specific arithmetic operation expression identified in step S 780  in  FIG. 7  to be used to calculate pupil projection center positions  425  is described. The position x i  of the pixel that receives the light beam entering the center of the ith micro-lens, the position x 0  of the pixel that receives the light beam entering the center of the micro-lens located closest to the optical axis of the photographic lens  160 , the pupil position h, the micro-lens pitch d and the focal length f of the micro-lenses in  FIG. 1  achieve a relationship expressed in (1) below. 
     
       
         
           
             
               
                 
                   
                     
                       
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     Expression (1) can be modified to expression (2) 
     
       
         
           
             
               
                 
                   
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     The pupil projection center positions  425  having been obtained as described above in conjunction with the predetermined number of sets of sampling data are each equivalent to the position x i , and a graph drawn by plotting the pupil projection center positions x i  having been obtained on a plane in the coordinate system defined by the x-axis and the i-axis should regress to the straight line defined by expression (2).  FIG. 8  shows dots  810 , indicating the pupil projection center positions x i  calculated in conjunction with the predetermined number of sets of sampling data plotted on the plane in the x-axis/i-axis coordinate system and a dotted line representing a regression line  820  defined in expression (2). The slope d(1+f/h) of the straight line defined in expression (2) can be determined through the method of least squares in expression (3), based upon the differences between the pupil projection center positions x i  having been obtained as described earlier in conjunction with the predetermined number of sets of sampling data and their average and the differences between the ordinal numbers i each indicating the ordinal assigned to a specific micro-lens and the average of the ordinal numbers. 
     
       
         
           
             
               
                 
                   
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     Based upon expressions (2) and (3), the x intercept x 0 (1+f/h) of the regression line defined in expression (2) can be determined as expressed in (4) below. 
     
       
         
           
             
               
                 
                   
                     
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     Since the micro-lens pitch d and the micro-lens focal length f are known design values, the pupil position h can be calculated based upon expression (3). The position x o  can then be determined based upon expression (4). Expression (2), with the constants d, f, h and x 0  incorporated therein for substitution, expresses the relationship between a given pupil projection center position x i  and the corresponding ordinal number i. The specific arithmetic operation expression to be used to determine pupil projection center positions  425 , is determined in step S 780  in  FIG. 7  by assuming the known values for the constants d, f, h and x 0  for substitution in expression (2). 
     The camera  1  achieved in the first embodiment described above adopts a structure that allows the pupil projection center positions x i  for the predetermined number of sets of sampling data to be ascertained through pattern matching and all the pupil projection center positions  425  to be calculated as defined in a specific arithmetic operation expression determined as the arithmetic operation expression to be used to calculate the pupil projection center positions by assuming the known values for the constants d, f, h and x 0  for substitution in expression (2) based upon the pattern matching results. As a result, the positions of the pixels that receive light beams entering the centers of the individual micro-lenses after passing through the photographic lens can be determined with a high level of precision, leading to an advantage in that the focus detection and the focus adjustment, as well as the synthetic image generation can be executed with better accuracy. 
     Second Embodiment 
     In the first embodiment achieved by adopting the image-capturing apparatus according to the present invention in a camera, an optimal template image corresponding to the pupil diameter, among the template images in  FIGS. 6A ,  6 B and  6 C recorded in advance in the internal memory  130 , is selected in step S 740  in  FIG. 7 . However, it may not be possible to provide any template image options for use in conjunction with the camera. Or, it may not be possible to obtain the photographic lens attribute information in step S 730  if a lens barrel  15  without a photographic lens control unit  150  mounted. Under either of these circumstances, an optimal template image corresponding to the pupil diameter will have to be generated in step S 740 . The second embodiment achieved by adopting the image-capturing apparatus according to the present invention in the camera  1  when no photographic lens attribute information can be obtained in step S 730  is now described in reference to  FIG. 9 . 
       FIG. 9  presents a detailed flowchart of processing that may be executed by the main control unit  100  in step S 210  in the  FIGS. 2A and 2B  in order to determine pupil projection center positions. The same step numbers are assigned to steps identical to those in  FIG. 7 . The following explanation focuses on the processing executed in steps assigned with different step numbers. 
     Since no photographic lens attribute information has been obtained and an optimal template image corresponding to the pupil diameter cannot be generated, a temporary template is generated in step S 910  based upon a predetermined provisional pupil diameter value. In step S 920 , pattern matching processing similar to that executed in step S 750  is executed and the correlation value is calculated in step S 930 . It can be deemed that an outline  1250  of a pupil projection image  125  has been detected upon detecting, for instance, a changeover point at which the correlation value taking on a value large enough to exceed the threshold value then starts to decrease, and a provisional pupil projection center position in the particular pupil projection image  125  can be thus calculated. Next, a temporary template is generated by adjusting the pupil diameter centered on the provisional pupil projection center position and a correlation value is calculated again. It can be deemed that an outline  1250  of the pupil projection image  125  has been detected upon detecting a changeover point at which the correlation value taking on a value large enough to exceed the threshold value then starts to decrease, and a provisional pupil diameter in the particular pupil projection image  125  can be thus. The processing described above is repeatedly executed until it is decided in step S 940  that the correlation value exceeds the predetermined threshold value, before the most likely pupil diameter and pupil projection center position  425  can be determined. In step S 950 , an optimal template image corresponding to the pupil diameter is generated. 
     With the camera  1  in the second embodiment as described above, advantages similar to those of the camera  1  in the first embodiment can be achieved even when the photographic lens attribute information cannot be output from the lens barrel  15 . 
     Third Embodiment 
     In the first embodiment achieved by adopting the image-capturing apparatus according to the present invention in the camera  1 , the pupil projection center positions  425  are recorded into the internal memory  130  in step S 790  in  FIG. 7 . Based upon the pupil projection center position data recorded as described above, a pupil projection center position correction quantity may be calculated so as to enable calculation of all the pupil projection center positions  425  even when the pupil position h has changed due to, for example, focus adjustment executed for the photographic lens  160  or due to replacement of the lens barrel  15 . In reference to  FIG. 10 , the third embodiment achieved by adopting the image-capturing apparatus according to the present invention in the camera  1  is described. 
       FIG. 10  presents a detailed flowchart of the processing executed by the main control unit  100  in step S 210  in the  FIGS. 2A and 2B  in order to determine pupil projection center positions. The same step numbers are assigned to steps identical to those in  FIG. 7 . The following explanation focuses on the processing executed in steps assigned with different step numbers. 
     In step S 1010 , a specific arithmetic operation expression to be used to calculate a pupil projection center position quantity as described later, is determined. In step S 1020 , the reference position that is a pupil projection center position assumed when the pupil position h recorded in the internal memory  130  is equal to h 0 , is ascertained. In step S 1030 , all the pupil projection center positions  425  are determined through an arithmetic operation to be detailed later, executed based upon the specific arithmetic operation expression and the reference position, and the pupil projection center positions thus determined are recorded into the internal memory  130 . 
     The specific arithmetic operation expression identified in step S 1010  in  FIG. 10 , which is used to calculate the pupil projection center position correction quantity, is now described. When the pupil projection center position x i  corresponding to the pupil position h in expression (1) is notated as x i {h}, pupil projection center position x i =x i {h 0 } is true if pupil position h=h 0 . The pupil projection center position x i {h 0 } is the reference position recorded in the internal memory  130  as explained earlier. In consideration of expression (1), the pupil projection center position correction quantity Δx i  can be expressed as in (5) below by using the pupil projection center position x i {h} and the reference position x i {h 0 }. 
     
       
         
           
             
               
                 
                   
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     Accordingly, expression (6) can be designated as the specific arithmetic operation expression to be used in step S 1030  in  FIG. 10  to calculate all the pupil projection center positions  425 . 
     
       
         
           
             
               
                 
                   
                       
                   
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     The camera  1  in the third embodiment described above, which does not require pattern matching processing, still achieves advantages similar to those of the camera  1  in the first embodiment, while succeeding in minimizing the volume of arithmetic operation. 
     Fourth Embodiment 
     In the first through third embodiments, each achieved by adopting the image-capturing apparatus according to the present invention in the camera  1 , the main control unit  100 , located in the camera body  10  of the camera  1 , which executes focus detection and focus adjustment for the photographic lens  160  or image synthesis, also determines the pupil projection center positions. As an alternative, a PC (personal computer) engaged in operation based upon, for instance, an image analysis computer program, may be assigned to generate the synthetic image and determine the pupil projection center positions by taking in necessary information from the camera  1 . In reference to  FIGS. 11 and 12 , the fourth embodiment achieved by installing the image analysis computer program according to the present invention in a PC is described. 
       FIG. 11  shows a connection structure that may be adopted to achieve a connection for a PC  2  and a camera  1  in the embodiment. The PC  2  and the camera  1  are connected with each other through communication. The mode of connection in this case may be either a wireless connection or a wired connection. The image analysis computer program according to the present invention is installed in the PC  2  via a recording medium  3  such as a CD-ROM. Namely, the image analysis computer program according to the present invention, which enables the PC  2  to execute image analysis including pupil projection center position determination and synthetic image generation, is distributed as a computer program product containing the computer program recorded in the recording medium  3 . 
     The PC  2  in the embodiment determines the pupil projection center positions  425  in step S 210  in  FIG. 2B  in accordance with the image analysis computer program and generates a synthetic image in step S 230  based upon the pupil projection center positions determined.  FIG. 12  presents a detailed flowchart of the processing executed by the PC  2  in the embodiment in accordance with the image analysis computer program, in order to determine the pupil projection center positions. The same step numbers are assigned to steps identical to those in  FIG. 7 . The following explanation focuses on the processing executed in steps assigned with different step numbers. 
     In step S 1210 , image-capturing data generated in the camera  1  are input through communication and, based upon the image-capturing data thus input, a photographic image is generated in step S 715 . Following the edge extraction executed in step S 720 , the photographic lens attribute information in the camera  1  is input through communication in step S 1230 . Subsequently, processing similar to that in  FIG. 7  is executed. 
     In the camera  1  in the fourth embodiment described above, advantages similar to those of the camera  1  in the first embodiment are achieved without diminishing the arithmetic processing performance capability of the main control unit  100  in the camera  1 . Furthermore, an even higher level of user convenience is assured since the PC  2  will be capable of more advanced image manipulation processing. 
     —Variations— 
     In the first embodiment of the present invention described earlier, the edge extraction processing is achieved through differential filter processing such as Laplacian differential filter processing. When such edge extraction processing is executed using image-capturing data containing a significant high-frequency component, e.g., image-capturing data expressing an image with a finely patterned subject, low pass filter preprocessing may be executed as preprocessing prior to the edge extraction processing. 
     The computer program product enabling the image analysis including the pupil projection center position determination and the synthetic image generation in the fourth embodiment of the present invention may be provided as a data signal transmitted through a communication network  4  such as the Internet instead of via the recording medium  3 , as illustrated in  FIG. 11 . In order to avail itself of such a computer program product, the PC  2  must be capable of connecting with the communication network  4 . A server  5  is a computer that provides the image analysis computer program according to the present invention stored in a storage device such as a hard disk. The server  5  provides the image analysis computer program read out from the storage device as a data signal on a carrier wave, which is then transferred to the PC  2  via the communication network  4 . It is preferable that the image analysis computer program according to the present invention be distributed as a computer program product that may assume any of various modes such as the recording medium  3  and the data signal transmitted via the communication network  4 . 
     The embodiments and variations described above may be adopted in any combination. In addition, as long as the functions characterizing the present invention are not compromised, the present invention is in no way limited to any of the specific device structures described in reference to the above embodiments. 
     The above described embodiments are examples, and various modifications can be made without departing from the scope of the invention.