Patent Publication Number: US-8534836-B2

Title: Fundus camera

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a Continuation of U.S. patent application Ser. No. 12/870,506 filed Aug. 27, 2010 Now U.S. Pat. No. 8,147,064 B2, which claims priority to Japanese Patent Application No. 2009-201291 filed Sep. 1, 2009, both of which are hereby incorporated by reference in their entireties. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a fundus camera to take an image of a fundus of a subject&#39;s eye for use, for example, in ophthalmic hospitals and mass medical examination. 
     2. Description of the Related Art 
     It is well known that to facilitate focusing on a fundus of a subject&#39;s eye, images of indexes are projected to the fundus, and a positional relation of index images is observed through a focusing lens of an observing and photographing system, to thereby obtain a clear image of the fundus. 
     Japanese Patent Application Laid-Open No. 5-95907 discusses a fundus camera, in which two focus split index images projected onto the fundus are captured and a focus state is detected based on positions of the focus split index images while attenuating the brightness of the index images. 
     Japanese Patent Application Laid-Open No. 8-275921 discusses an ophthalmic apparatus, in which focus index images are projected onto the fundus, the focus index images are captured by a photographing optical system, and a focus state is detected. 
     Japanese Patent Application Laid-Open No. 1-178237 discloses a modified embodiment of an apparatus for automatic focusing (AF) by capturing an electronic image during observation and detecting contrast between captured images. In other words, when first and second ranges are brought into focus by using high frequency components of fundus images to perform focusing, and a distance in a light axis direction is obtained from the focusing lens positions. 
     However, a conventional fundus camera divides incident light into a fundus illumination light flux, a focus split index light flux, and an observation photographing light flux in regions near the pupil of the examined eye in order to remove reflected light from the cornea. Therefore, when there are personal differences in aberration in the examined eye&#39;s optical system, if an image is captured only based on the focus split index image positions which are predetermined, there is a possibility that errors may occur in focusing for some examined eyes, resulting in a blurred fundus image. 
     As a solution to this problem, an apparatus is known, in which electronic image sensing is performed even during observation, and automatic focusing (AF) is carried out by detecting contrast among captured images. 
     In an apparatus as described above, the drawback that a focusing error may occur for some examined eyes, which will result in an out-of-focus image can be solved. However, because regions where a focus is detected are fixed in some portions of the imaging system, there is another problem yet to be solved. 
     In a conventional method of AF detection, in which, as to some regions of the fundus, fundus images are formed at different distances in the depth direction; therefore, the focus detection ranges have to be fixed, it is necessary to guide the line of sight of the examined eye in such a manner that the regions to be focused may match a focus detection range. 
     Like general AF single-lens reflex cameras, even if the focus detection range is movable, it must still be moved manually, and further the AF detection position changes with the movement of the eyeball. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to providing a fundus camera capable of easy alignment. 
     According to an aspect of the present invention, a fundus camera includes a fundus illuminating optical system configured to illuminate a fundus of a subject&#39;s eye, a fundus photographing optical system including a focusing lens driven to bring the fundus into focus, a focusing lens drive unit configured to drive the focusing lens, a fundus image capturing unit arranged in a conjugate relationship with the fundus in the fundus photographing optical system, a display monitor configured to display a fundus image captured by the fundus image capturing unit, a focus state detecting unit configured to detect an AF evaluation value representing a degree of a focus state based on an output signal from the fundus image capturing unit, and a lens drive control unit configured to drive the focusing lens based on the AF evaluation value detected by the focus state detecting unit. The focus state detecting unit includes a fundus position detecting unit configured to detect a specific region of the fundus image by using a regional pattern inherent in a fundus region based on output from the fundus image capturing unit, and a focus detection range determining unit configured to determine a focus detection range based on output of the fundus position detecting unit. Furthermore, the focus state detecting unit calculates the AF evaluation value in the focus detection range determined by the focus detection range determining unit. 
     Further features and aspects of the present invention will become apparent from the following detailed description of exemplary embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate exemplary embodiments, features, and aspects of the invention and, together with the description, serve to explain the principles of the invention. 
         FIG. 1  is a block diagram of a fundus camera according to a first exemplary embodiment of the present invention. 
         FIG. 2  is a structure diagram of a focus state detecting unit. 
         FIG. 3  is a structure diagram of a fundus position detecting unit. 
         FIG. 4  is a structure diagram of a focus detection range determining unit. 
         FIG. 5  is a flowchart of a method for controlling the fundus camera. 
         FIG. 6  is a diagram illustrating a principle of contrast detection. 
         FIG. 7  is a diagram illustrating a fundus image displayed on a display monitor. 
         FIG. 8  is a diagram illustrating a method for calculating AF evaluation values. 
         FIG. 9  is a structure diagram of a focus detection range determining unit according to a third exemplary embodiment of the present invention. 
         FIG. 10  is a structure diagram of a focus detection range determining unit according to a third exemplary embodiment of the present invention. 
         FIG. 11  is an external view of the fundus camera. 
         FIG. 12  is a structure diagram of a left/right eye detecting unit. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     Various exemplary embodiments, features, and aspects of the invention will be described in detail below with reference to the drawings. 
     A first exemplary embodiment of the present invention will be described.  FIG. 1  is a block diagram of a fundus camera. In a fundus illumination optical system, an observation light source  1 , a photographic light source  2 , a lens  3 , and a mirror  4  are arranged on a light axis L 1 , and also relay lenses  5 ,  6 , and a pierced mirror  7  with a hole in the center are arranged on a light axis L 2  in a reflection direction of the mirror  4  in series. Furthermore, an objective lens  8  is arranged facing the examined eye E on a light axis L 3  in a reflection direction of the mirror  7 . The observation light source  1  for illuminating the fundus comprises, for example, a halogen lamp that emits a stationary light, and the photographic light source  2  comprises, for example, a stroboscopic tube that emits visible light. 
     On the other hand, a fundus photographing optical system is formed by successively arranging, behind a pierced mirror  7  on the light axis L 3 , a focusing lens  9  configured to adjust a focus by moving the focusing lens  9  along a light axis, a photographic lens  10 , and a fundus image sensing unit  11  placed at a position in a conjugate relation with the fundus Er. 
     Output of a fundus image sensing unit  11  is coupled to a focus state detecting unit  21 . Output of the focus state detecting unit  21  is coupled to a focusing lens  9  via a lens drive control unit  22  and a focusing lens drive unit  23 , and further coupled through an illuminating light quantity control unit  24  to an observation light source  1  and to a display monitor  25 . The display monitor  25  is provided with a focus detection range display  25   a.    
     While observing a fundus image on the display monitor  25 , and using the observation light source  1 , the examiner fine-tunes positioning of the examined eye E relative to a housing provided with the optical system, then adjusts the focus, and captures an image with the photographic light source. 
     The present exemplary embodiment provides an AF function to automatically adjust the focus. A focus detection range is shown to the examiner, on a window in a focus detection range display  25   a , which is superposed onto a fundus image captured by a fundus image sensing unit  11 . Because the focus detection range is presented to the examiner in a visual form, the AF operability is improved. 
     In a fundus camera configured as described, a focus is detected by detecting contrast of a fundus image formed by a photographing light flux. Therefore, in contrast to a conventional apparatus which projects a focus index through a front eye region outside of the photographing light flux, this fundus camera can perform automatic focusing not based on chromatic aberration of the examined eye optical system. 
     As illustrated in  FIG. 2 , the focus state detecting unit  21  includes a fundus position detecting unit  21   a  configured to detect a specific position of the fundus Er, and a focus detection range determining unit  21   b  configured to determine a focus detection range based on a signal from the fundus position detecting unit  21   a . The focus state detecting unit  21  further includes an AF evaluation value memory unit  21   c  configured to store an AF evaluation value and a position of the focusing lens  9  when an AF evaluation value is detected. 
     As illustrated in  FIG. 3 , the fundus position detecting unit  21   a  also includes a fundus image pattern memory  21   d  to store a fundus image pattern as a regional pattern based on a standard image of a specific region in a fundus image. This fundus image pattern is used to extract a specific region from the fundus image. Positional information about a specific region is obtained by pattern matching between regional patterns stored in the fundus image pattern memory  21   d  and an output signal from the fundus image sensing unit  11 . The focus detection range determining unit  21   b  determines a range where a focus is to be adjusted based on output of fundus image&#39;s specific region extracted by the fundus position detecting unit  21   a . However, as illustrated in  FIG. 4 , to enable the examiner to correct the size of the focus detection range, the focus detection range determining unit  21   b  preferably includes a focus detection range correcting unit  21   e  configured to correct the range by performing a cursor operation on the image of the display monitor  25 . 
     The focus state detecting unit  21  calculates an AF evaluation value of a focus detection range determined by the focus detection range determining unit  21   b , and also stores information about the position of the focusing lens  9  at this time. 
       FIG. 5  is a flowchart of an AF control method. When an instruction to start AF operation is issued by an AF start switch (not illustrated), in step S 1 , a recognition process of a fundus image pattern is started. In step S 2 , the fundus position detecting unit  21   a  calculates, for example, a correlation function between output of the fundus image sensing unit  11  and a regional pattern of a fundus image&#39;s specific region stored in the fundus image pattern memory  21   d . It is determined whether a range has a correlation value equal to or larger than a threshold value and can be used as a focus detection range. Then, it is determined whether pattern recognition can be performed in this focus detection range. 
     When automatic focusing is started, if the focusing lens  9  is displaced widely from a position at a focusing time and pattern recognition is disabled, the processing proceeds to step S 3 , where pattern recognition is performed repeatedly by driving the focusing lens  9  little by little until pattern recognition becomes possible. 
     In step S 2 , if it is determined that pattern recognition is possible, in step S 4 , the focus detection range determining unit  21   b  determines a focus detection range based on output of the fundus position detecting unit  21   a . When a focus detection range is determined, in step S 5 , the focus state detecting unit  21  calculates an AF evaluation value representing a degree of focus state in the focus detection range. A method for calculating an AF evaluation value will be described later, and calculated AF evaluation values are stored in the AF evaluation value memory unit  21   c.    
       FIG. 6  is a diagram illustrating a principle of focus detection by contrast detection. This focus detection system utilizes a fact that particular high frequency components of brightness signal becomes maximum when an image is in focus, and the focus state detecting unit detects and uses high frequency components of an input luminance signal as an AF evaluation value. A horizontal axis indicates the position of the focusing lens  9 , and a vertical axis indicates the level of AF evaluation value. At in-focus position M 2 , the AF evaluation value is at a maximum, and at position M 1  where the image is widely out of focus, the AF evaluation value is small. In this exemplary embodiment, by utilizing this principle of contrast detection, focus correction suitable for the aberration of a human eye optical system is performed. 
     In step S 7 , by using the above-described principle of contrast detection, it is detected whether a maximum point at position M 2  illustrated in  FIG. 6  is included in AF evaluation values stored in step S 6 . If a decision at step S 7  is made for the first time, a maximum point cannot be determined, accordingly the processing proceeds to step S 3 , where the focusing lens  9  is driven. 
     In step S 7 , if a maximum point is detected among the AF evaluation values, in step S 8 , the focus state detecting unit  21  calculates an amount of movement of the focusing lens  9 . The amount of movement of the focusing lens  9  in step S 8  denotes a drive amount of the focusing lens  9  up to a detection position of a maximum point M 2  of the AF evaluation value. On the basis of the drive amount of the focusing lens  9  calculated in step S 8 , the lens drive control unit  22  in step S 9  sends a signal to the focus lens drive unit  23  to drive the focusing lens  9 , with which automatic focusing is finished. 
     As described above, automatic focusing is completed by driving the focusing lens  9  in step S 9  based on the driven amount of the focusing lens  9  calculated in step  8 . However, after step S 9 , steps S 2  to S 5  may be performed to obtain an AF evaluation value. When this AF evaluation value is compared with the AF evaluation value in which a maximum point has been determined for the first time, if a difference between the two AF values is lower than a threshold value, automatic focusing may be completed. 
     On the other hand, if a maximum point is not detected in the AF evaluation value in step S 7 , the processing proceeds to step S 3  and the focusing lens drive unit  23  drives the focusing lens for a predetermined distance. Then, again in step S 2 , pattern recognition is performed, and in step S 4 , a focus detection range is determined. As described above, even if the examined eye E is displaced during automatic focusing, the focus detection range can follow the movement of the examined eye E. If pattern recognition or maximum point detection in the AF evaluation value is unsuccessful after a predetermined number of trials, the processing may be stopped considering that an error has occurred. 
       FIG. 7  is a diagram illustrating a fundus image displayed on the display monitor  25 , in which a positional relation does not widely change among a papilla portion N, a medium and large blood vessel portion V, and a yellow spot portion Y inherent in the fundus region, though there are personal differences. Generally, the above-mentioned positional relation of the left eye and the right eye is mirror-reversed. 
       FIG. 8  is a diagram illustrating an AF evaluation value when the focus detection range is a regional pattern of the medium and large blood vessel portion V. As a method for easily detecting high frequency components from an image, an AF evaluation value is calculated, in which when luminance signals are compared between a target pixel and 8 adjacent pixels on left and right, up and down, and on diagonal sides of the target pixel, a largest difference value is taken as an AF evaluation value of the target pixel. An image G 1  is an example of a clipped piece of an image when the medium and large blood vessel portion V extends in a vertical direction, in which the pixels have luminance signals “0” or “1”. 
     When this focus detection method is applied to the image, AF evaluation values are given with respect to the pixels as illustrated in an image G 2 . A total of AF evaluation values of the pixels can be taken as an AF evaluation value of an entire image. 
     To calculate easily and at a high speed an AF evaluation value, it is possible to adopt a method in which by comparing luminance signals between a target pixel and two adjacent pixels, if there is no difference, an AF evaluation value is “0” or if there is a difference, an AF evaluation value is “1”. According to this method, since the number of pixels to be compared is smaller than in the preceding method, load on calculation can be reduced. However, if the luminance signals between a target pixel and two vertically adjacent pixels are compared, an image G 3  is output, in which edges of the medium and large blood vessel portion V as a target cannot be detected. 
     On the other hand, if this method is applied to an image G 4  in which the medium and large blood vessel portion V extends in the horizontal direction, an image is output as illustrated in an image G 5 , and results can be obtained similar to the image G 2  which includes AF evaluation values calculated by the preceding method. In other words, while if a detection method utilizing directional dependence described above is selected, arithmetic operation time can be reduced, images to be used need to be appropriately selected. 
     As described above, in the images G 1  and G 4 , differences in luminance are compared between each pixel and adjacent pixels, and expressed in bit maps as illustrated in the images G 2  and G 5  respectively. A larger difference between adjacent pixel values means a larger difference in luminance between the adjacent pixels. 
     The medium and large blood vessel portion V discussed in an example of the present exemplary embodiment runs in an arc form roughly around the yellow spot Y on the fundus Er. A blood vessel portion, which forms a thick blood trunk, is located near the papilla portion N. Therefore, since the edges of the medium and large blood vessel portion V are located in a direction of ±45°, if a detection method is adopted which enables selection of that direction, low-load high-speed automatic focusing can be achieved without sacrificing the sensitivity of AF evaluation value. 
     While the medium and large blood vessel portion V on the fundus Er was used for pattern recognition of a fundus image according to the present embodiment, other portions, such as regional patterns of the papilla portion N and the yellow spot portion may be stored in the fundus image pattern memory  21   d  and automatic focusing can also be performed on those regions. 
     As described above, by automatically determining a focus detection range by pattern recognition, the operability of automatic focusing can be improved. Since the focus detection position can follow the movement of the examined eye E, focusing accuracy can be improved. 
     Since the focus state detecting unit  21  refers to a luminance value of each pixel when calculating an AF evaluation value, it may be detected whether the luminance value of the determined focus detection range has saturated. If saturation has occurred, the focus state detection unit  21  sends a signal to the illumination light quantity control unit  24  to control a light quantity of the observation light source  1 , which enables automatic focusing with high accuracy. When contrast detection is to be performed on the papilla portion N where “whitening” is likely to occur, for example, by adjusting the light quantity of the illumination optical system, a fundus image with high accuracy and diagnostic value can be obtained. 
     In the first exemplary embodiment, pattern recognition is performed on a specific region on the fundus Er. In the second exemplary embodiment, before automatic focusing is started, the examiner selects a region of the fundus Er where a focus detection range is to be set and a focus detection range is determined based on this selection to perform automatic focusing. 
     In the second exemplary embodiment, the fundus pattern memory  21   d  contains a plurality of fundus image patterns, including regional patterns, such as the papilla portion N, the yellow portion Y, and the medium and large blood vessel portion V. The examiner preliminarily selects a region to be focused on based on a subject&#39;s case by using a region selecting device, such as a cursor on the display monitor  25 . This operation corresponds to selecting one of a plurality of fundus image patterns in the fundus position detecting unit  21   a . The examiner  1  detects a position of a selected fundus image pattern based on output of the fundus image sensing unit  11 , and notifies a selected position to the focus detection range determining unit  21   b . This operation and a subsequent operation are similar to those in the first exemplary embodiment. 
     The examiner  1  is here supposed to select one fundus region, but may select a plurality of regions. In this case, AF evaluation values are calculated for the plurality of regions, and only a total of those values may be used as an overall evaluation value. By detecting a maximum value of an overall evaluation value, an evenly focused image can be obtained, which covers a plurality of regions selected by the examiner. By this method, a focused fundus image can be captured in a region of interest for the examiner, so that a fundus image with high diagnostic value can be provided. 
     As described above, by recognizing a pattern of a region which the examiner wants to look at in diagnosis, and determining a focus detection range, a fundus image high in diagnostic value can be obtained. In the papilla portion N, the medium and large blood vessel portion V, an yellow spot portion Y, where a relatively large number of high frequency components are included in an image, a proper focus detection range can be determined, and contrast detection can be performed with high accuracy. 
     Contrast detection can be performed with high accuracy by chiefly detecting the medium and large blood vessel portion V where there are little personal differences, but not the papilla portion N where personal differences tend to be highly irregular. In addition, because the running direction of the medium and large blood vessels V can be identified easily, by detecting the contrast in a direction orthogonal to the medium and large blood vessel portion V, high-speed low-cost contrast detection can be performed with high accuracy and less calculation load. 
     The examiner selects a focus detection range from among a plurality of fundus regions so that images having high diagnostic value and representing pathological changes which the examiner wants to investigate can be obtained. 
     In a second exemplary embodiment, the examiner selects a focus detection range before automatic focusing is started. In a third exemplary embodiment, the examiner selects a focus detection range from among specific regions obtained by pattern recognition processing, and performs automatic focusing. 
     Like the second exemplary embodiment, in the third exemplary embodiment, the fundus image pattern memory contains a plurality of fundus image patterns, including regional patterns of the papilla portion N, the yellow spot portion Y, and the medium and large blood vessel portion V. In a third exemplary embodiment, differences from the first and second embodiments are that positions of plural fundus image patterns are detected based on output of the fundus image sensing unit  11 , and that information about those positions is delivered to the focus detection range determining unit  21   b.    
     In the third exemplary embodiment, the focus detection range determining unit  21   b  includes a focus detection range correcting unit  21   e  and a focus detection range selecting unit  21   f  as illustrated in  FIG. 9 . The focus detection range display unit  25   a  on the display monitor  25  supplies the examiner with a plurality of specific regions of a fundus image extracted by the fundus position detecting unit  21   a . Using a cursor as the focus detection range selecting unit  21   f , the examiner selects one region, for which a focus detection range is to be set, from among the supplied specific regions. The specific region of a fundus image may be supplied to the examiner when a predetermined number of pattern recognition have been detected or when the focusing lens  9  has moved an entire movable range. 
     The examiner corrects a size of the focus detection range with the focus detection range correcting unit  21   e . Thus, the examiner can manually correct the position and the size of the focus detection range, and can capture a fundus image focusing correctly on a region the examiner wants to observe. 
     While the examiner selects one fundus region in the third embodiment, like in the second embodiment, it is possible for the examiner to select a plurality of regions. Supply of information about the specific regions of the selected fundus image and subsequent operations are similar to the first embodiment. 
     In the second and third embodiments, AF evaluation values are calculated for one or more focus detection ranges selected by the examiner from among a plurality of fundus image regions obtained by pattern recognition processing. In a fourth embodiment, however, AF evaluation values are calculated for all regions of a plurality of fundus images obtained by pattern recognition, and an evaluation about the maximum values and then, automatic focusing are performed. 
     In the fourth embodiment, the focus state detecting unit  21  calculates AF evaluation values for a plurality of fundus image specific regions of a fundus image extracted by the fundus position detecting unit  21   a . The focus state detecting unit  21  can obtain images focused evenly at a plurality of regions extracted by pattern recognition by using a total value of the AF evaluation values as an overall evaluation value, and by detecting a maximum value of the overall evaluation value. 
     In the fourth embodiment, as illustrated in  FIG. 10 , the focus detection range determining unit  21   b  includes a focus detection range limiting unit  21   g . The focus detection range limiting unit  21   g  automatically determines, as a focus detection range, one region with a highest AF evaluation value from among the specific regions of the fundus image extracted by the fundus position detecting unit  21   a , and sends the focus detection range to the focus state detecting unit  21 . The selected specific region of the fundus image is sent to the focus detection range determining unit  21   b , and subsequent operations are performed similar to the preceding embodiments. Thus, a fundus image in sharp focus can be captured automatically, and a fundus camera with excellent AF operability can be provided. 
     Because a focus detection range can be determined automatically, the AF performance can be improved. 
     In the first to fourth embodiments, positions of specific regions of the fundus image are detected only by pattern recognition by the fundus position detecting unit  21   a . In a fifth embodiment, by combining pattern recognition of the papilla portion N and left-eye/right-eye detection, the medium and large blood vessel portion V including specific high frequency components is detected and automatic focusing is performed. 
       FIG. 11  is an external view of a fundus camera according to a fifth embodiment, in which a table  32 , movable in the back-forth and left-right directions as indicated by arrows, is mounted on a pedestal  31 . A housing  33  containing an optical system of a fundus camera illustrated in  FIG. 1 , a display monitor  25 , and an operation bar  35  fitted with a shooting button  34  are mounted on the table  25 . 
     The examiner operates the operation bar  35 , and adjusts the table  32  in the left/right direction on a horizontal plane to match the left and right eyes of a subject. Since a left/right eye detecting unit  36  is disposed between the pedestal  31  and the table  32 , the left-right position of the housing  33  can be detected, so that it is known which of the subject&#39;s examined eyes E is being observed and photographed. 
       FIG. 12  is a diagram illustrating a detection method by the left/right eye detecting unit  36 . A low portion  31   a  and a high portion  31   b , showing a height difference, are formed on the upper surface of the pedestal  31 . The left/right eye detecting unit  36  is made of a micro switch and provided on a bottom surface of the table  32 . The left/right eye detecting unit  36  turns on, for example, when it comes above the low portion  31   a  of the pedestal  31 , and turns off, when it comes on the high portion  31   b  of the pedestal  31 . In other words, by positioning the low portion  31   a  on the left side and the high portion  31   b  on the right side, the on/off state of the left/right eye detecting unit  36  can be detected, and the tested eye, left or right, facing the housing  33  can be detected. 
     A method will be described by which to detect a focus detection range, above all, the medium and large blood vessel portion V illustrated in  FIG. 7  the left eye or right eye is detected by the left/right eye detecting unit  36  and pattern recognition of the papilla portion N is performed by the fundus position detecting unit  21   a.    
     When a specific region is detected on a fundus Er and it can be determined which of a subject&#39;s eyes is being observed, it is possible to predict a structure of the fundus Er. Therefore, the medium and large blood vessel portion V can be detected by detecting the left eye or right eye with the L-R eye detecting unit  36  and by pattern recognition of the papilla portion N. A detected medium and large blood vessel portion V is sent to the focus detection range determining unit  21   b  and a subsequent operation are performed similar to the preceding embodiments. 
     In the fifth embodiment, only the papilla portion N that allows easy pattern recognition is detected, and based on this detection, other regions on the fundus Er are determined as a focus detection range. Accordingly, there is a possibility that a specific region on the fundus Er deviates from the focus detection range due to personal differences. Therefore, a focus detection range correcting unit  21   e  is provided to enable the examiner to manually correct the position and the size of the focus detection range, so that a sharply focused fundus image can be obtained of a region the examiner wants to investigate. 
     By identifying the medium and large blood vessel portion V or the yellow spot portion Y using efficient pattern recognition of the papilla region N and adopting the left/right eye detecting unit, a focus detection range can be determined more accurately. Therefore, calculation load is reduced, calculation time is shortened, and high-speed automatic focusing can be realized. 
     While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all modifications, equivalent structures, and functions. 
     This application claims priority from Japanese Patent Application No. 2009-201291 filed Sep. 1, 2009, which is hereby incorporated by reference herein in its entirety.