Patent Publication Number: US-8985771-B2

Title: Image capturing apparatus and capturing method

Description:
BACKGROUND 
     1. Technical Field 
     The invention relates to an image capturing apparatus and a capturing method. Particularly, the invention relates to an image capturing apparatus and a capturing method for capturing an eye image. 
     2. Related Art 
     The eye is a window to a soul, and through the eyes, people can feel light and color of the world. Cone cells and rod cells in the eye used for perceiving lights and color are all located on retina of a fundus, which are unique tissues capable of converting light into physiological electric signals. Blood vessels used for supplying blood and nutrients to the eye are also located on the fundus. When the fundus has a problem of vessel proliferation or rupture, for example, has symptoms of macular degeneration and haemorrhage, etc., it is likely to cause death of the cone cells and rod cells on the retina, which may result in loss of vision of a patient. Therefore, in eye disease diagnosis and preventive health care, observation and tracking of images of the fundus are very important. 
     Generally, limited by a pupil size, in a single one-angle shooting of a conventional fundus image shooting method, even if pupil dilation drug such as a mydriatic agent is used, a fundus image range that can be captured is only a viewing angle of about 30 to 40 degrees. Therefore, if an image of an edge of the fundus is to be captured, the patient is asked to stare a reference point, and then the point where the eye stares is continually moved around in a slow and stable speed, so as to continually obtain a plurality of images of the fundus. Then, a data processing device such as a computer, etc. is used to synthesize the images of the fundus through specific image synthesis software. However, an illumination light used for repeatedly capturing the images of the fundus may also cause discomfort and fatigue of the eye of the patient, which may cause unconscious blink of the eye or nystagmus to influence an image capturing quality. Moreover, since the images of the fundus are obtained through multiple shoots, an exposure value and a white balance for each shooting are different, and the obtained images need to be corrected before being synthesized by a large-scale calculator such as a computer, etc., such that difficulty in correction is increased to influence the quality of the synthesized image. If the quality of the synthesized image is influenced, a medical staff is not easy to identify a microvascular image of the fundus, which may cause judgement difficulty and even delay a timing of treatment of the patient. Therefore, it is important to quickly obtain a complete and clear image of the fundus. 
     SUMMARY 
     The invention is directed to an image capturing apparatus, which is capable of capturing images of a plurality of different zones of an eye. 
     The invention is directed to a capturing method, by which a plurality of images of an eye are simultaneously captured from different directions for synthesis. 
     An embodiment of the invention provides an image capturing apparatus, which is configured to capture an image of an eye, and the image capturing apparatus includes a plurality of image sensing modules and at least one light source. Each of the image sensing modules includes an image sensor and a lens. The light source emits an illumination light, and the illumination light irradiates the eye. The eye reflects the illumination light into an image light. The image light includes a plurality of sub-image beams, and the sub-image beams are transmitted to the image sensors of the image sensing modules through the lenses of the image sensing modules, respectively. 
     In an embodiment of the invention, the illumination light irradiates a fundus of the eye through a pupil of the eye, the fundus reflects the illumination light into the image light, and the sub-image beams of the image light are respectively transmitted to the image sensing modules through the pupil. 
     In an embodiment of the invention, image capturing ranges of two adjacent image sensing modules on the fundus are partially overlapped. 
     In an embodiment of the invention, optical axes of the lenses of the image sensing modules are not parallel to each other, and the optical axes of the lenses pass through the pupil of the eye. 
     In an embodiment of the invention, each of the image sensing modules further includes an actuator, which is connected to at least one of the image sensor and the lens to focus the image sensing module. 
     In an embodiment of the invention, each of the image sensing modules further includes a micro processing unit, which is electrically connected to the corresponding image sensor to obtain data of an image produced by the sub-image beam detected by the image sensor. 
     In an embodiment of the invention, the image capturing apparatus further includes a processing unit, which is electrically connected to the image sensing modules to synthesize a plurality of images of the eye that are respectively produced by the sub-image beams detected by the image sensors. 
     In an embodiment of the invention, the images of the eye detected by two of the adjacent image sensors are partially overlapped. 
     In an embodiment of the invention, the processing unit compares the coinciding portions of the images to serve as a correction reference used when the images are synthesized. 
     In an embodiment of the invention, the processing unit includes a first comparison module, a second comparison module, a third comparison module, a fourth comparison module and a determination module. The first comparison module compares coinciding portions of a first peripheral image in the peripheral images and the central image. The second comparison module compares coinciding portions of a second peripheral image in the peripheral images and the central image. The third comparison module calculates an average image of coinciding portions of the first peripheral image and the second peripheral image, and compares coinciding portions of the average image and the central image. The fourth comparison module calculates a gradient image of the coinciding portions of the first peripheral image and the second peripheral image, and compares coinciding portions of the gradient image and the central image. The determination module determines a minimum comparison difference of comparison results of the first to the fourth comparison modules, where when a comparison difference of the first comparison module is the minimum, the determination module uses data of the first peripheral image for the coinciding portions of the first peripheral image and the second peripheral image; when a comparison difference of the second comparison module is the minimum, the determination module uses data of the second peripheral image for the coinciding portions of the first peripheral image and the second peripheral image; when a comparison difference of the third comparison module is the minimum, the determination module uses data of the average image for the coinciding portions of the first peripheral image and the second peripheral image; and when a comparison difference of the fourth comparison module is the minimum, the determination module uses data of the gradient image for the coinciding portions of the first peripheral image and the second peripheral image. 
     In an embodiment of the invention, the processing unit first performs a correction of reducing pincushion distortion on the images of the eye, and then synthesizes the images performed with the correction of reducing pincushion distortion. 
     An embodiment of the invention provides a capturing method for capturing an image of an eye. The capturing method includes simultaneously capturing a plurality of images of the eye from different directions, and synthesizing the images. 
     In an embodiment of the invention, the images of the eye are a plurality of images of a fundus of the eye, and the step of simultaneously capturing the images of the eye from different directions includes capturing the images of the fundus of the eye through a pupil of the eye. 
     In an embodiment of the invention, two adjacent images of the fundus of the eye are partially overlapped. 
     In an embodiment of the invention, the step of synthesizing the images includes comparing the coinciding portions of the images to serve as a correction reference used when the images are synthesized. 
     In an embodiment of the invention, the correction reference includes at least one of a color correction reference, a coordinate conversion correction reference and a noise reduction correction reference. 
     In an embodiment of the invention, the images of the eye include a central image and a plurality of peripheral images adjacent to the central image. 
     In an embodiment of the invention, the step of synthesizing the images includes: (a) comparing coinciding portions of a first peripheral image in the peripheral images and the central image; (b) comparing coinciding portions of a second peripheral image in the peripheral images and the central image; (c) calculating an average image of coinciding portions of the first peripheral image and the second peripheral image, and comparing coinciding portions of the average image and the central image; (d) calculating a gradient image of the coinciding portions of the first peripheral image and the second peripheral image, and comparing coinciding portions of the gradient image and the central image; and (e) determining a minimum comparison difference in comparison results of the step (a) to the step (d), where when a comparison difference of the step (a) is the minimum, data of the first peripheral image is used for the coinciding portions of the first peripheral image and the second peripheral image; when a comparison difference of the step (b) is the minimum, data of the second peripheral image is used for the coinciding portions of the first peripheral image and the second peripheral image; when a comparison difference of the step (c) is the minimum, data of the average image is used for the coinciding portions of the first peripheral image and the second peripheral image; and when a comparison difference of the step (d) is the minimum, data of the gradient image is used for the coinciding portions of the first peripheral image and the second peripheral image. 
     In an embodiment of the invention, data of the central image is used for a central zone of the central image, and data of the peripheral images is used for portions of a surrounding zone of the central image that coincide with the central zones of the adjacent peripheral images. 
     In an embodiment of the invention, the capturing method further includes performing a correction of reducing pincushion distortion on the images before the images are synthesized, where the step of synthesizing the images is synthesizing the images performed with the correction of reducing pincushion distortion. 
     According to the above descriptions, the image capturing apparatus according to the embodiments of the invention uses a plurality of image sensing modules to respectively capture a plurality of images of the eye. In this way, time required for shooting eye images for multiple times is decreased, and the eye images of a wide viewing angle are obtained. In the capturing method according to the embodiments of the invention, a plurality of images of the eye can be simultaneously captured from different directions, and the images can be synthesized. By synthesizing the simultaneously captured images, a phenomenon of uneven brightness and contrast between the images obtained by shooting the eye for multiple times is avoided, so as to improve efficiency and accuracy for synthesizing the images. 
     In order to make the aforementioned and other features and advantages of the invention comprehensible, several exemplary embodiments accompanied with figures are described in detail below. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. 
         FIG. 1A  is a cross-sectional view of an image capturing apparatus according to an embodiment of the invention. 
         FIG. 1B  is a front view of the image capturing apparatus in the embodiment of  FIG. 1A . 
         FIG. 1C  is a schematic diagram of the image capturing apparatus in the embodiment of  FIG. 1A . 
         FIG. 2  is a block diagram of the image capturing apparatus in the embodiment of  FIG. 1A . 
         FIG. 3  is a schematic diagram of a plurality of overlapped fundus images according to the embodiment of  FIG. 1A . 
         FIG. 4  is a flowchart illustrating a capturing method according to the embodiment of  FIG. 1A . 
         FIG. 5  is a flowchart illustrating detailed steps of a step S 20  of  FIG. 4 . 
         FIG. 6  is a flowchart illustrating a process of capturing a fundus image according to the embodiment of  FIG. 4 . 
     
    
    
     DETAILED DESCRIPTION OF DISCLOSED EMBODIMENTS 
       FIG. 1A  is a cross-sectional view of an image capturing apparatus according to an embodiment of the invention.  FIG. 1B  is a front view of the image capturing apparatus in the embodiment of  FIG. 1A . Referring to  FIG. 1A  and  FIG. 1B , in the present embodiment, the image capturing apparatus  10  is used to capture images of an eye  20 . The image capturing apparatus  10  includes a plurality of image sensing modules  100  and at least one light source  200 . Each of the image sensing modules  100  includes an image sensor  110  and a lens  120 . The image sensor  110  can be a complementary metal-oxide-semiconductor (CMOS) sensor, a charge coupled device (CCD) or any other optical sensor adapted to receive images. Moreover, in the present embodiment, the lens  120  can be driven by a voice coil motor. In the present embodiment, the image capturing apparatus  10  includes 5 image sensing modules  101 ,  102 ,  103 ,  104  and  105 , and in other embodiments, the image capturing apparatus  10  may include more or less image sensing modules  100  according to an actual requirement, which is not limited by the invention. Meanwhile, in the present embodiment, the image capturing apparatus  10  includes four light sources  200 , and in other embodiments, the number and distribution of the light sources  200  can be designed according to an actual requirement to achieve a purpose of illumination, which is not limited by the invention. The light source  200  can be a light-emitting diode (LED) or any other suitable light-emitting device, and a light emitted therefrom is a visible light or an invisible light such as infrared, etc., which is not limited by the invention. The light source  200  emits an illumination light L, and the illumination light L irradiates the eye  20 . The eye  20  reflects the illumination light L into an image light B, and the image light B includes a plurality of sub-image beams BS, and the sub-image beams BS are respectively transmitted to the image sensors  110  through the lenses  120  of the image sensing modules  100 . 
     In detail, in the present embodiment, the illumination light L can irradiate a fundus F of the eye  20  through a pupil P of the eye  20 . The fundus F reflects the illumination light L into the image light B, and the sub-image beams BS of the image light B are respectively transmitted to the image sensing modules  100  through the pupil P. Image capturing ranges of two adjacent image sensing modules  100  on the fundus F are partially overlapped. Moreover, optical axes X of the lenses  120  of the image sensing modules  100  can be unparallel to each other, and the optical axes X of the lenses  120  pass through the pupil P of the eye  20 . For example, the image sensing module  101  in  FIG. 1A  has an optical axis X1, the image sensing module  102  has an optical axis X2, and the image sensing module  103  has an optical axis X3, where the optical axis X1, the optical axis X2 and the optical axis X3 that are not parallel to each other passes through the pupil P, such that the image sensing module  101 , the image sensing module  102  and the image sensing module  103  can respectively capture images of different zones on the fundus F from different directions. Namely, the image sensing module  101  can capture an image of a fundus zone F1, the image sensing module  102  can capture an image of a fundus zone F2, and the image sensing module  103  can capture an image of a fundus zone F3. The fundus zone F1 and the fundus zone F2 are partially overlapped, and the fundus zone F2 and the fundus zone F3 are partially overlapped. In this way, the image capturing apparatus  10  can simultaneously capture images of different zones on the fundus F to aid a medical staff to study more comprehensive eye image information of a patient, so as to improve accuracy and efficiency of clinical diagnosis of the medical staff. 
     In detail, referring to  FIG. 1A , in the present embodiment, the image sensing module  100  further includes an actuator  130 , which is connected to at least one of the image sensor  110  and the lens  120  to focus the image sensing module  100 . The actuator  130  can be a voice coil motor (VCM) or other types of motor. For example, in the present embodiment, the actuator  130  can drive the image sensing modules  101 ,  102  and  103  to respectively focus on the fundus F of the eye  20 . As an eye diopter varies along with people, and even if in a same eye, the diopters of seeing the fundus from different angles through the pupil are also different, the actuator  130  is used to respectively control focusing of each of the image sensing modules  100 , which is adapted to local diopter difference of the eye and is also adapted to different eyes, so as to shorten a fundus shooting time and improves the image quality. 
     Moreover, the image sensing module  100  further includes a micro processing unit  140 , which is electrically connected to the corresponding image sensor  100  to obtain data of an image produced by the sub-image beam BS detected by the image sensor  100 . The micro processing unit  140  is a microprocessor such as an image signal processor (ISP), etc. For example, in the present embodiment, the image sensing module  101  includes a micro processing unit  141 , the image sensing module  102  includes a micro processing unit  142 , and the image sensing module  103  includes a micro processing unit  143 . Namely, each of the image sensing modules  100  may have the respective micro processing unit  140  to serve as a fundus image processing sub-system. Moreover, the image capturing apparatus  100  may further include a processing unit  150 , which is electrically connected to the image sensing modules  100  to synthesize a plurality of images of the eye  20  that are respectively produced by the sub-image beams BS detected by the image sensors  110 . The processing unit  150  can be a digital signal processor (DSP). For example, referring to  FIG. 2 , in the present embodiment, the image sensing modules  101 ,  102 ,  103 ,  104  and  105  respectively have the corresponding micro processing units  141 ,  142 ,  143 ,  144  and  145 , and the image sensing modules  101 ,  102 ,  103 ,  104  and  105  also have corresponding random access memories (RAMs) RAM1, RAM2, RAM3, RAM4 and RAM5 to store image information processed by the micro processing units  141 ,  142 ,  143 ,  144  and  145 . Moreover, the processing unit  150  may synthesize image information coming from the image sensing modules  101 ,  102 ,  103 ,  104  and  105  and processed by the micro processing unit  140 , and may store a synthesized result or computed data in a memory unit SR, where the memory unit SR is, for example, a synchronous dynamic random access memory (SDRAM). Therefore, image synthesis efficiency is effectively increased and a high cost caused by using a fast processor is saved. Meanwhile, in the present embodiment, since the micro processing unit  140  used in collaboration with the processing unit  150  can reduce the fundus shooting time, fundus images of different zone captured from different angles can be continuously processed, and the synthesized fundus image can be displayed on a display unit DU, such that the image capturing apparatus  10  may have a live view function to assist focusing the fundus image, so as to improve efficiency and accuracy for synthesizing the images. 
     In detail, referring to  FIG. 1A ,  FIG. 1B  and  FIG. 3 , in the present embodiment, the images of the eye  20  detected by two adjacent image sensors  110  are partially overlapped, and the images of the eye  20  may include a central image P0 and a plurality of peripheral images P adjacent to the central image P0. The processing unit  150  may compare the coinciding portions of the images to serve as a correction reference used when the images are synthesized. The correction reference includes at least one of a color correction reference, a coordinate conversion correction reference and a noise reduction correction reference. In detail, referring to  FIG. 1A ,  FIG. 1C  and  FIG. 3 , the processing unit  150  may include a first comparison module M1, a second comparison module M2, a third comparison module M3, a fourth comparison module M4 and a determination module MJ. The first comparison module M1 compares coinciding portions of a first peripheral image P1 in the peripheral images P and the central image P0, i.e. compares data of the first peripheral image P1 in a coinciding zone P01 (i.e. a zone drawn with oblique lines) with data of the central image P0 in the coinciding zone P01. The second comparison module M2 compares coinciding portions of a second peripheral image P2 in the peripheral images P and the central image P1, i.e. compares data of the second peripheral image P2 in a coinciding zone P02 (i.e. a zone drawn with cross lines) with data of the central image P0 in the coinciding zone P02. The third comparison module M3 calculates an average image of coinciding portions of the first peripheral image P1 and the second peripheral image P2, and compares coinciding portions of the average image and the central image P0, i.e. after averaging data of the first peripheral image P1 in a coinciding zone P12 (a zone simultaneously drawn with oblique lines and cross lines) and data of the second peripheral image P2 in the coinciding zone P12, the third comparison module M3 compares the averaged data with data of the central image P0 in the coinciding zone P12. The fourth comparison module M4 calculates a gradient image of the coinciding portions of the first peripheral image P1 and the second peripheral image P2, and compares coinciding portions of the gradient image and the central image P0, i.e. after performing gradient image computation on data of the first peripheral image P1 in the coinciding zone P12 and data of the second peripheral image P2 in the coinciding zone P12, the fourth comparison module M4 compares data of a computation result thereof with data of the central image P0 in the coinciding zone P12. The determination module MJ determines a minimum comparison difference of comparison results of the first to the fourth comparison modules M1, M2, M3 and M4, where when a comparison difference of the first comparison module M1 is the minimum, the determination module MJ uses data of the first peripheral image P1 for the coinciding portions of the first peripheral image P1 and the second peripheral image P2. When a comparison difference of the second comparison module M2 is the minimum, the determination module MJ uses data of the second peripheral image P2 for the coinciding portions of the first peripheral image P1 and the second peripheral image P2. When a comparison difference of the third comparison module M3 is the minimum, the determination module MJ uses data of the average image for the coinciding portions of the first peripheral image P1 and the second peripheral image P2. When a comparison difference of the fourth comparison module M4 is the minimum, the determination module MJ uses data of the gradient image for the coinciding portions of the first peripheral image P1 and the second peripheral image P2. In this way, the images received by the image sensing module  100  can be synthesized in a manner of the minimum difference and the most correct content. Generally the central image P0 is an image close to a central zone of the fundus F, which has a distortion such as a pincushion distortion smaller than that of the image at a zone away from the central zone of the fundus F, which is easy to be corrected. As the central image P0 is taken as a reference image, and errors of the central image P0 and the other peripheral images P are referred to synthesize the images of the fundus F, accuracy of image synthesis is further enhanced. The number of the peripheral images P illustrated in  FIG. 3  is only used as an example; the actually computed images can be different according to the number of the actually captured images, which is not limited by the invention. 
     Moreover, in the present embodiment, the central image P0 is partially overlapped with the peripheral images P (which are, for example, the first peripheral image P1, the second peripheral image P2, the third peripheral image P3 and the fourth peripheral image P4, and in other embodiments, the number of the peripheral images can be increased or decreased according to an actual requirement, which is not limited by the invention). Since the human eye has diopter, in the image of the fundus F, an image distortion at an outer edge of the image is obvious compared to that at a central portion. In the present embodiment, the processing unit  150  may use data of the central image P0 for a central zone CZ of the central image P0, and the processing unit  150  may use data of the peripheral images P for coinciding portions of the surrounding zone SZ of the central image P0 and the central zones CZ of the peripheral images P. Namely, when the images of the fundus F are synthesized, it is better to use the central portion of a single fundus image as far as possible, and avoid using the zone at the outer edge of the image that has an obvious image distortion. In the present embodiment, since the processing unit  150  can first perform a correction of reducing pincushion distortion on the images of the eye  20  for subsequent synthesis, particularly on an outer edge portion of the image that has a severe image distortion, the manner of correcting the pincushion distortion can generally add extra image points to compensate resolution decrease caused by the correction. Therefore, the method of avoiding using the image edge to synthesize the images of the fundus F can mitigate decrease of image quality caused by the additionally added image points. 
     The first comparison module M1, the second comparison module M2, the third comparison module M3, the fourth comparison module M4 and the determination module MJ can be programs stored in a storage medium of the image capturing apparatus  10 , which can be located into the processing unit  150  to execute the aforementioned functions. Alternatively, in other embodiments, the first comparison module M1, the second comparison module M2, the third comparison module M3, the fourth comparison module M4 and the determination module MJ can also be hardware devices composed of logic circuit components, which can be used to execute the aforementioned functions. 
       FIG. 4  is a flowchart illustrating a capturing method according to an embodiment of the invention. Referring to  FIG. 1A ,  FIG. 3  and  FIG. 4 , in the present embodiment, the capturing method is used to capture an image of the eye  20 . The capturing method includes simultaneously capturing a plurality of images P of the eye  20  from different directions (step S 10 ). The capturing method further includes synthesizing the images P (step S 20 ). The images P of the eye  20  are a plurality of images P of the fundus F of the eye  20 , and the step S 10  of simultaneously capturing the images P of the eye  20  from different directions includes capturing the images P of the fundus F of the eye  20  through a pupil P of the eye  20 . In this way, the simultaneously captured images of the fundus F have similar brightness and contrasts, which avails the subsequent image synthesis, and saves a computation time of the image synthesis and improves the quality of the synthesized image, and avails the clinical diagnosis of eye diseases. 
     The images of the fundus F of the eye  20  include the central image P0 and a plurality of peripheral images P adjacent to the central image P0. Moreover, the step S 20  of synthesizing the images may include comparing the coinciding portions of the images to serve as a correction reference used when the images are synthesized. Moreover, in the present embodiment, before synthesizing the images, the capturing method further includes performing a correction of reducing pincushion distortion on the images (step S 10   a ), where the step S 20  of synthesizing the images is to synthesize the images performed with the correction of reducing pincushion distortion, and the effect of synthesizing the images is as that described in the embodiment of  FIG. 1A , which is not repeated. 
     In detail, referring to  FIG. 5 , the step S 20  of synthesizing the images includes: (a) comparing coinciding portions of a first peripheral image P1 in the peripheral images P and the central image P0 (step S 20   a ); (b) comparing coinciding portions of a second peripheral image P2 in the peripheral images P and the central image P0 (step S 20   b ); (c) calculating an average image of coinciding portions of the first peripheral image P1 and the second peripheral image P2, and comparing coinciding portions of the average image and the central image P0 (step S 20   c ); (d) calculating a gradient image of the coinciding portions of the first peripheral image P1 and the second peripheral image P2, and comparing coinciding portions of the gradient image and the central image P0 (step S 20   d ); and (e) determining a minimum comparison difference in comparison results of the step (a) to the step (d) (step S 20   e ). In detail, when a comparison difference of the step (a) is the minimum, data of the first peripheral image P1 is used for the coinciding portions of the first peripheral image P1 and the second peripheral image P2; when a comparison difference of the step (b) is the minimum, data of the second peripheral image P2 is used for the coinciding portions of the first peripheral image P1 and the second peripheral image P2; when a comparison difference of the step (c) is the minimum, data of the average image is used for the coinciding portions of the first peripheral image P1 and the second peripheral image P2; when a comparison difference of the step (d) is the minimum, data of the gradient image is used for the coinciding portions of the first peripheral image P1 and the second peripheral image P2. Data of the central image P0 is used for the central zone CZ of the central image P0, and data of the peripheral images P is used for coinciding portions of the surrounding zone SZ of the central image P0 and the central zones CZ of the peripheral images P. Detailed process and effect of synthesizing the images are as that described in the embodiment of  FIG. 1A . The step (a) to the step (e) can be executed by the first comparison module M1, the second comparison module M2, the third comparison module M3, the fourth comparison module M4 and the determination module MJ, and details thereof can refer to descriptions of the functions executed by these modules, which are not repeated. Moreover, the sequence of the aforementioned steps is only used as an example, which is not limited by the invention. 
     For example, referring to  FIG. 6 , in the present embodiment, the flow of shooting the fundus images may includes following steps. The pupil P is automatically detected (step S 5 ), and it is determined whether the pupil P is detected (step S 6 ), and if an image of the pupil P is not detected, the step S 5  of detecting the pupil P is repeated. If the image of the pupil P is detected, a plurality of images of the eye  20  are simultaneously captured from different directions (step S 10 ), and the lenses  120  are driven to focus (step S 11 ). Then, the lenses  120  (for example, N lenses  120  of a lens 1, a lens 2, . . . , and a lens N, where N is a positive integer greater than 1) on the image sensing module  100  can respectively focus (step S 12 ), and it is determined whether the focus is successful (step S 13 ). If the focus is not successful, the step S 12  is returned to again focus. After all of the lenses  120  (including the lenses  120  located at the central portion and peripheral portion of the image sensing apparatus  10 ) complete focusing (step S 14 ), the image sensing module  100  is driven to capture images (step S 15 ). The image sensing module  100  and the lens  120  can be used to capture images of the fundus F (step S 16 ). Then, the processing unit  150  is used to synthesize the images (step S 20 ) to output the fundus images (step S 30 ). In this way, the image sensing apparatus  10  can automatically detect physiological information of human eye, and output a large-range and clear fundus image to facilitate medical staff to diagnose. 
     In summary, the image capturing apparatus according to the embodiments of the invention can be used to simultaneously capture a plurality of fundus images of different portions of the eye, and since the fundus images can be nearly simultaneously captured, the brightness and the contrasts thereof are similar. Then, the processing unit is used to compare differences of the coinciding portions of the fundus images, and the fundus images are synthesized in a manner of the minimum difference between the images, which may effectively save a time required for synthesizing the images, and quickly obtain the fundus images with a large range and good image quality. Moreover, each of the image sensing modules may include an actuator, by which the image sensing modules can simultaneously focus on different zones of the fundus from different angles, which may save a time required for capturing the eye images, decrease an eye burden of a patient and increase a success rate of capturing the large-range and clear fundus image, so as to improve medical quality and diagnosis accuracy of the medical staff. 
     It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the invention cover modifications and variations of this invention provided they fall within the scope of the following claims and their equivalents.