Patent Publication Number: US-2009240108-A1

Title: Capsule endoscopy system and method of controlling operation of capsule endoscope

Description:
FIELD OF THE INVENTION 
     The present invention relates to a capsule endoscopy system for making medical diagnoses by means of endoscopic images captured by a capsule endoscope. The present invention relates also to a method of controlling operation of the capsule endoscope. 
     BACKGROUND OF THE INVENTION 
     Endoscopy with a capsule endoscope has recently been put into practical use. The capsule endoscope has its components, including an imaging device and an illumination light source, integrated into a micro capsule. A patient first swallows the capsule endoscope so that the imaging device captures images from interior of the patient, i.e. internal surfaces of patient&#39;s tracts, while the light source is illuminating those surfaces. Image data captured by the imaging device is transmitted as a radio signal to a receiver that the patient carries about. The image data is sequentially recorded on a storage medium like a flash memory, which is provided in the receiver. During or after the endoscopy, the image data is transmitted to an information managing apparatus like a workstation, where endoscopic images are displayed on a monitor for the sake of image interpretation and diagnosis. 
     The capsule endoscope captures images a given number of times per unit time, e.g. at a frame rate of 2 fps (frame per second). Since the capsule endoscope takes more than eight hours or so to complete capturing the images from each patient, the volume of the image data that have been taken and stored in the receiver gets huge at the end of each session of the endoscopy. So it takes a very long time and consumes much labor for the doctor to interpret all of the captured endoscopic images for the sake of diagnosis. For this reason, there has been a demand for reducing such images that are unnecessary for the diagnosis to the minimum, while capturing as many images from an important site for the diagnosis as possible. To meet the demand, such a capsule endoscope has been suggested that captures images according to a predetermined time schedule, for example, in JPA 2005-193066. 
     The above-mentioned prior art discloses an example, wherein the capsule endoscope raises the frame rate as it goes through an area of concern, like where there is a lesion, and lowers the frame rate after it goes past the area of concern. However, this prior art does not specify any concrete device for determining the area of concern, so it is still difficult to interpret the captured images in detail with respect to the area of concern. 
     In order to determine the area of concern, it may for example be possible to compare present information that the capsule endoscope obtains at present from the patient with past information on the patient. The present information may include endoscopic images and positional information on the positions where these images were taken, whereas the past information may be information on a past diagnosis for the patient, including an image of an area of concern and information on the position of the area of concern. Instead of the past information on the patient, it is possible to compare the present information with general information on medical cases, such as an image exemplar representative of a case of disease, to determine an area of concern. This method is applicable to a patient who gets the endoscopy for the first time. 
     Because the above-described methods of determining the area of concern need the information on the past diagnoses or on general cases, it is impossible to determine the area of concern without such information. Even if there is the diagnostic information or the general case information, if the information was obtained by a different kind of endoscope from the presently used endoscope, the difference between the endoscopes can induce such a problem that images taken at the same portion by the present endoscope and the other kind of endoscope have different features from each other. In that case, it is hard to determine the area of concern exactly. 
     Moreover, since the general case information or images are representative data sorted out from an enormous database built up through many diagnoses done in the past, an individual endoscopic image taken from a lesion of a patient is not always similar to the case image representative of the corresponding case. If the endoscopic images taken from the lesion of the patient are not similar to the corresponding case image, it is impossible to identify the lesion as an area of concern. 
     SUMMARY OF THE INVENTION 
     In view of the foregoing, a primary object of the present invention is to provide a capsule endoscopy system using a capsule endoscope and a method of controlling operation of the capsule endoscope, whereby an area of concern that may contain a lesion or the like is determined exactly without the need for the diagnostic information or the general case information. 
     A capsule endoscopy system of the present invention comprises a judging device that analyzes each endoscopic image immediately after it is obtained by an imaging device of a capsule endoscope, to judge by the result of analysis whether the endoscopic image contains any area of concern that has different image characteristics from surrounding areas. The judging device is mounted at least in one of the capsule endoscope, a portable apparatus and an information managing apparatus, wherein the capsule endoscope is swallowed by a test body, captures endoscopic images of internal portions of the test body through the imaging device, and sends the endoscopic images wirelessly. The portable apparatus is carried about by the test body, and receives the endoscopic images from the capsule endoscope and stores the received endoscopic images. The information managing apparatus stores and manages the endoscopic images that are transferred from the portable apparatus. 
     Preferably, the capsule endoscopy system of the present invention further comprises a control command generator for generating control commands for controlling operations of respective members of the capsule endoscope on the basis of a result of the judgment by the judging device, and an operation controller mounted in the capsule endoscope, for controlling operations of the respective members of the capsule endoscope in accordance with the control commands. The control command generator is mounted at least in one of the capsule endoscope, the portable apparatus and the information managing apparatus. 
     According to a preferred embodiment, the judging device divides each endoscopic image into a plurality of segments, examines similarity among these segments, and judges that an area of concern exists in the endoscopic image when there are some segments that bear relatively low similarities to other segments of the endoscopic image. The judging device detects image characteristic values from the respective segments, calculates differences in the image characteristic values between the respective segments, and estimates the similarity between the segments by comparing the calculated differences with predetermined threshold values. 
     According to another preferred embodiment, the judging device examines similarity between the latest endoscopic image obtained from the capsule endoscope and the preceding image obtained immediately before from the capsule endoscope. The judging device judges that an area of concern exists in the latest endoscopic image if the latest endoscopic image is not similar to the preceding image and the judging device has judged that no area of concern exits in the preceding image, or if the latest endoscopic image is similar to the preceding image and the judging device has judged an area of concern exits in the preceding image. 
     To estimate similarity between the segments of the latest endoscopic image and corresponding segments of the preceding image Preferably, the judging device preferably divides each endoscopic image into a plurality of segments, and judges that the latest endoscopic image is not similar to the preceding image when there are some segments that bear relatively low similarities to the corresponding segments of the preceding image. More preferably, the judging device detects image characteristic values from the respective segments of the latest and preceding endoscopic images, calculates differences in the image characteristic values between each individual segment of the latest endoscopic image and the corresponding segment of the preceding image, and estimates the similarity between each couple of the corresponding segments of the latest and preceding images by comparing the calculated differences with predetermined threshold values. 
     According to another preferred embodiment, the capsule endoscope comprises a multi-point ranging device for measuring distances from the capsule endoscope to a plurality of points of a subject in a present imaging field of the imaging device, and the judging device executes a cropping process for cutting a zone of a limited subject distance range out of each endoscopic image on the basis of the distances measured by the multi-point ranging device, and analyzes image data of the zone of the endoscopic image to judge whether any area of concern exits in the zone. 
     According to a further preferred embodiment, the control command generating device generates a first control command for driving the capsule endoscope in a regular imaging mode when the judging device judges that no area of concern exits, whereas the control command generating device generates a second control command for driving the capsule endoscope in a special imaging mode when the judging device judges that an area of concern exits, so the capsule endoscope may capture detailed images of the area of concern in the special mode. 
     The capsule endoscope of the capsule endoscopy system of the present invention may comprise at least two imaging devices facing different directions from each other and a direction sensor for detecting attitude and traveling direction of the capsule endoscope. In this embodiment, the control command generator determines respective facing directions of the imaging devices on the basis of the detected attitude and traveling direction of the capsule endoscope, and generates a control command for driving a forward one of the imaging devices, which presently faces forward in the traveling direction, in a regular imaging mode. When the judging device judges that an area of concern exits in an endoscopic image as captured by the forward imaging device, the control command generator generates a second control command for driving at least one of other imaging devices than the forward imaging device in a special imaging mode for capturing detailed images of the area of concern. 
     A method of controlling operations of a capsule endoscope that is swallowed by a test body, to capture endoscopic images of internal portions of the test body and output the endoscopic images wirelessly, wherein the method comprising steps of: 
     analyzing each endoscopic image immediately after it is obtained by the capsule endoscope; 
     judging by a result obtained by the analyzing step whether the endoscopic image contains any area of concern that has different image characteristics from surrounding areas; 
     generating control commands for controlling operations of respective members of the capsule endoscope on the basis of a result of the judging step; and 
     controlling operations of the respective members of the capsule endoscope in accordance with the control commands. 
     According to the present invention, since an area of concern, such as a lesion, generally has different features from its surrounding area, the endoscopic image itself is analyzed each time it is captured by the capsule endoscope, and the judgment about the presence of any area of concern is made merely by the result of analysis of the endoscopic image itself, without the need for the past diagnostic information on the patient or the case information on the general cases. Since the area of concern is determined in a real time fashion during the capsule endoscopy, it is possible to capture detailed images of the area of concern by switching the capsule endoscope to the special imaging mode as soon as the area of concern is discovered. Moreover, it comes to be possible to identify such a lesion that is not similar to the case information. Because the present invention does not need the diagnostic information or the case information, it is also unnecessary to consider differences between the capsule endoscopes used for obtaining the diagnostic information or the case information, on one hand, and the capsule endoscope used for the present endoscopy. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other objects and advantages of the present invention will be more apparent from the following detailed description of the preferred embodiments when read in connection with the accompanied drawings, wherein like reference numerals designate like or corresponding parts throughout the several views, and wherein: 
         FIG. 1  is a schematic diagram illustrating a capsule endoscopy system according to an embodiment of the present invention; 
         FIG. 2  is a sectional view illustrating an interior of a capsule endoscope of the capsule endoscopy system; 
         FIG. 3  is an explanatory diagram illustrating a multi-point ranging process for ranging an imaging field; 
         FIG. 4  is a block diagram illustrating an electric structure of the capsule endoscope; 
         FIG. 5  is a block diagram illustrating an electric structure of a data transceiver; 
         FIG. 6  is an explanatory diagram illustrating a cropping process for cutting image data of a check zone out of an image frame; 
         FIGS. 7A and 7B  are explanatory diagrams illustrating a distance range of the check zone relative to the capsule endoscope; 
         FIG. 8  is an explanatory diagram illustrating a judging process for judging whether any area of concern exists in the check zone; 
         FIG. 9  is a flowchart illustrating a sequence of an imaging mode selection process; 
         FIG. 10  is an explanatory diagram illustrating an example of an imaging condition table; 
         FIG. 11  is a block diagram illustrating an electric structure of a workstation; 
         FIG. 12  is a flowchart illustrating an overall operation of the capsule endoscopy system; 
         FIG. 13  is a flowchart illustrating an imaging mode selection process according to a second embodiment of the present invention; 
         FIG. 14  is a sectional view illustrating an interior of a capsule endoscope according to a third embodiment; 
         FIG. 15  is an explanatory diagram illustrating the third embodiment, wherein an optical axis of an objective lens system is veered toward an area of concern in a special imaging mode; 
         FIG. 16  is a sectional view illustrating an interior of a capsule endoscope according to a fourth embodiment; 
         FIGS. 17A and 17B  are explanatory diagrams illustrating the fourth embodiment, wherein an imaging device that faces forward in the traveling capsule endoscope captures images in a regular imaging mode, whereas another imaging device that faces rearward is driven in a special imaging mode; 
         FIG. 18  is an explanatory diagram illustrating a fifth embodiment; 
         FIG. 19  is a block diagram illustrating an electric structure of a capsule endoscope that analyzes image data and generates control commands by itself; and 
         FIG. 20  is a block diagram illustrating an electric structure of an endoscopy system, wherein a workstation analyzes image data from a capsule endoscope and generates control commands for the capsule endoscope. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     As shown in  FIGS. 1 and 2 , an endoscopy system  2  consists of a capsule endoscope  11  that is swallowed by a patient or test body  10 , a portable data transceiver  12  carried about by the patient  10 , and a workstation  13  that takes up endoscopic images as captured by the capsule endoscope  11  and displays the endoscopic images for a doctor to interpret them. In the capsule endoscopy system  2 , image data of the latest endoscopic image as captured by the capsule endoscope  11  is wirelessly transmitted to the data transceiver  12 , so the data transceiver  12  analyzes the endoscopic image to check if any concerned part like a lesion exits in the image. If there is, more detailed endoscopic images of the concerned part is captured by the capsule endoscope  11  after setting it to a special imaging mode. 
     The capsule endoscope  11  captures images from internal walls of tracts, e.g. bowels, of the patient  10 , to send data of the captured images to the data transceiver  12  sequentially as a radio wave  14   a.  The capsule endoscope  11  also receives control command as a radio wave  14   b  from the data transceiver  12 , and operates according to the control command. 
     The data transceiver  12  is provided with a liquid crystal display (LCD)  15  for displaying various setup screens and an operating section  16  for setting up the data transceiver  12  on the setup screens. The data transceiver  12  receives and stores the image data as transmitted from the capsule endoscope  11  on the radio wave  14   a.  The data transceiver  12  also analyzes the latest image data as obtained from the capsule endoscope  11 , to decide the imaging conditions of the capsule endoscope  11  by the result of the analysis. That is, the data transceiver  12  decides which imaging mode the capsule endoscope  11  is to be set to, and produces a control command for setting the capsule endoscope  11  to the decided imaging mode. The control command is sent from the data transceiver  12  to the capsule endoscope  11  on the radio wave  14   b.    
     The transmission of the radio waves  14   a  and  14   b  between the capsule endoscope  11  and the data transceiver  12  is carried out by way of antennas  18  and  20 , wherein the antenna  18  is mounted in the capsule endoscope  11 , as shown in  FIGS. 2 and 4 , whereas the antennas  20  are mounted on a shield shirt  19  that the patient  10  wears. Each of the antennas  20  has an electric field strength sensor  21  built therein for measuring the field strength of the radio wave  14   a  from the capsule endoscope  11 . 
     The capsule endoscope  11  has a regular imaging mode for obtaining image data of ordinary endoscopic images, and the special imaging mode for obtaining image data of high-definition endoscopic images. The capsule endoscope  11  is set to different imaging conditions in the special imaging mode from the regular imaging mode. Concretely, in the special imaging mode, the frame rate is raised, and the zooming magnification (field of view) and the exposure value (the shutter speed and the illumination light volume) are changed step by step at each exposure. 
     The workstation  13  is provided with a processor  24 , operating members  25 , including a keyboard and a mouse, and an LCD monitor  26 . The first processor  24  is connected to the data transceiver  12 , for example, through a USB cable  27 , to exchange data. The first processor  24  may be connected to the data transceiver  12  through wireless communication like infrared communication. During or after the endoscopy with the capsule endoscope  11 , the processor  24  takes up the image data from the data transceiver  12 , accumulates and manages the image data for individual patients, and produces TV images from the image data to display the TV images on the LCD  26 . 
     As shown in  FIG. 2 , the capsule endoscope  11  has a transparent front casing  30  and a rear casing  31  that is mated to the front casing  30  to form a water-tight room inside these casings  30  and  31 . The casings  30  and  31  have a cylindrical shape with one end open and the other end closed. The closed ends of the casings  30  and  31  are substantially semispherical. In the room inside the casings  30  and  31 , an objective lens system  32  and an imaging device  33 , such as a CCD image sensor or a CMOS image sensor, are mounted. While the capsule endoscope  11  is inside the patient  10 , the objective lens system  32  forms an optical image of an internal body part or site of the patient  10  on an image pickup surface of the imaging device  33 , so the imaging device  33  outputs an analog images signal corresponding to the optical image. Designated by  35  is an optical axis of the objective lens system  32 . 
     The objective lens system  32  is composed of a transparent convex optical dome  32   a,  a first lens holder  32   b,  the first lens system  32   c,  guide rods  32   d,  a second lens holder  32   e,  and a second lens  32   f.  The optical dome  32   a  is placed in the semispherical end of the front casing  30 . The first lens holder  32   b  is mounted to a rear end of the optical dome  32   a,  and is tapered off rearwards. The first lens system  32   c  is secured to the first lens holder  32   b.    
     The guide rods  32   d  are screw rods, which are mounted to the rear end of the first lens holder  32   b  in parallel to the optical axis  35 . The second lens holder  32   e  has female screw holes, through which the guide rods  32   d  are threaded, so that the second lens  32   f  moves in parallel to the optical axis  35  as the guide rods  32   d  is turned by a lens driver  36  that is constituted of a stepping motor and other minor elements. With the parallel movement of the second lens  32   f  to the optical axis  35 , the zooming magnification (focal length) of the objective lens system  32  varies, and thus the field of view (imaging field) of the objective lens system  32  varies correspondingly. The lens driver  36  varies zooming magnification of the objective lens system  32  so that each image is captured at a given zooming magnification and in a given field of view, which are designated by the control command. 
     Inside the casings  30  and  31 , an antenna  18  for sending and receiving the radio waves  14   a  and  14   b,  an illumination light source  38  for illuminating the body parts, an electric circuit board  39  having various electronic circuits mounted thereon, a button cell  40  and a multi-point ranging sensor  41  are mounted. 
     The multi-point ranging sensor  41  is an active sensor that consists of a photo emitter unit  41   a  and a photo sensor unit  41   b.  Each time the capsule endoscope  11  captures an endoscopic image, the multi-point ranging sensor  41  measures respective distances from the capsule endoscope  11  to a plurality of points of a subject, i.e. an internal body portion, which corresponds to the captured endoscopic image. As shown in  FIG. 3 , the multi-point ranging sensor  41  divides the imaging field A of the capsule endoscope  11  into a plurality of ranging blocks B, which are arranged in a matrix, and measures a distance to a representative point P of every block B. For example, the representative points P are located at respective centers of the ranging blocks B, although the point P is shown only in one of the ranging blocks B in  FIG. 3 , in order to avoid complicating the drawing. 
     The photo emitter unit  41   a  projects a near infrared ray toward the representative point P of one ranging block B to another in a predetermined sequence. A conventional method is usable for projecting the near infrared ray toward the respective representative points P. For example, the photo emitter unit  41   a  is turned around at least in a direction: a yaw direction that is around a vertical axis of the capsule endoscope  11 , or a pitch direction that is around a horizontal axis of the capsule endoscope  11 , thereby to scan the near infrared ray two-dimensionally across the imaging field A. Note that the ray projected from the photo emitter unit  41   a  is not limited to the near infrared ray, but may be a ray of another wavelength range insofar as it does not affect the imaging. 
     The near infrared ray is projected from the photo emitter unit  41   a  toward the representative point P, and is reflected from the representative point P and is received on the photo sensor unit  41   b.  The photo sensor unit  41   b  is for example a position sensitive detector (PSD). As known in the art, see for example JPA 2007-264068, the PSD outputs an electric signal as it receives the ray reflected from the representative point P, and the magnitude of the electric signal corresponds to the distance from the capsule endoscope  11  to the representative point P. So the electric signal output from the photo sensor unit  41   b  will be referred to as a distance measuring signal. Based on the distance measuring signal, the distance from the capsule endoscope  11  to the representative point P is calculated. Note that a distance signal conversion circuit  49  (see  FIG. 4 ) converts the distance measuring signal to a distance signal that represents the distance from the capsule endoscope  11  to the representative point P. 
     The photo emitter unit  41   a  projects the near infrared ray sequentially toward the respective representative points P of the ranging blocks B, so the photo sensor unit  41   b  sequentially receives the ray reflected from each of the representative points P and outputs the distance measuring signals that represent respective distances from the capsule endoscope  11  to the representative points P. This way, the multi-point ranging is done to measure the distances to the representative points P of the respective ranging blocks B of the imaging field A. 
     In  FIG. 4 , a CPU (operation control device)  45  controls the overall operation of the capsule endoscope  11 . The CPU  45  is connected to the lens driver  36 , the multi-point ranging sensor  41 , a ROM  46 , a RAM  47 , an imaging driver  48 , the distance signal conversion circuit  49 , a modulator circuit  50 , a demodulator circuit  51 , a power supply circuit  52  and an illuminator driver  53 . 
     The ROM  46  stores various programs and data for controlling the operation of the capsule endoscope  11 . The CPU  45  reads out necessary programs and data from the ROM  46  and develops them on the RAM  47 , to work out the read program sequentially. The RAM  47  temporarily memorizes data on the imaging conditions, including a frame rate, a zooming magnification (view field) and an exposure value (a shutter speed and a light volume), as designated by the control command from the data transceiver  12 . 
     The imaging driver  48  is connected to the imaging device  33  and a signal processing circuit  54 . The imaging driver controls the operation of the imaging device  33  and the signal processing circuit  54  so as to make an exposure at the frame rate and the shutter speed, which are designed by the control command. The signal processing circuit  54  processes the analog image signal output from the imaging device  33 , to convert the image signal to digital image data by means of correlated double sampling, amplification and analog-to-digital conversion. The signal processing circuit  54  also subjects the image data to gamma correction and other image processing. 
     The distance signal conversion circuit  49  is connected to the photo sensor unit  41   b,  and is supplied with the distance measuring signals from the photo sensor unit  41   b.  Then the distance signal conversion circuit  49  converts the respective distance measuring signals to the distance signals. The distance signal conversion circuit  49  may converts the distance measuring signal to the distance signal by means of a predetermined calculation formula or a data table or any other conventional method, so the detail of the conversion method will be omitted. The distance signals are fed to the CPU  45 . When the CPU  45  receives a set of the distance signals that represent the distances to the respective representative points P in the imaging field A, the CPU  45  outputs each set of the distance signals as multi-point distance information on the imaging field A to the modulator circuit  50 . 
     The modulator circuit  50  and the demodulator circuit  51  are connected to a receiver-transmitter circuit  55 , which is connected to the antenna  18 . The modulator circuit  50  modulates the digital image data from the signal processing circuit  54  and the multi-point distance information output from the CPU  45  to the radio wave  14   a.  That is, the image data and the multi-point distance information of the imaging field A from which the image data was obtained are modulated together into the radio wave  14   a.  The radio wave  14   a  is sent from the modulator circuit  50  to the receiver-transmitter circuit  55 . The receiver-transmitter circuit  55  amplifies and band-pass filters the radio wave  14   a,  and then outputs the radio wave  14   a  to the antenna  18 . The receiver-transmitter circuit  55  also amplifies and band-pass filters the radio wave  14   b  that is received on the antenna  18  from the data transceiver  12 , and then outputs the radio wave  14   b  to the demodulator circuit  51 . The demodulator circuit  51  demodulates the radio wave  14   b  to the original control command, and outputs the control command to the CPU  45 . 
     The power supply circuit  52  supplies power of the cell  40  to respective components of the capsule endoscope  11 . The illuminator driver  53  drives the illuminator light source  38  under the control of the CPU  45 , so that each image is captured under the illumination light volume that is designated by the control command. 
     As shown in  FIG. 5 , a CPU  57  (control command production device) controls the overall operation of the data transceiver  12 . A data bus  58  connects the CPU  57  to a ROM  59 , a RAM  60 , a modulator circuit  61 , a demodulator circuit  62 , an image processor circuit  63 , a data storage  64 , an input interface (I/F)  65 , a position detector circuit  66 , an image analyzer circuit (judging device)  67  and a database  68 . 
     To the data bus  58  are also connected an LCD driver  70  for controlling the display on the LCD  15 , a communication interface (I/F)  72  for a USB connector  71  to intermediate data exchange between the processor  24  and the data transceiver  12 , and a power supply circuit  74  for supplying power of a battery  73  to respective components of the data transceiver  12 . 
     The ROM  59  stores various programs and data for controlling the operation of the data transceiver  12 . The CPU  57  reads out necessary programs and data from the ROM  59  and develops them on the RAM  60 , to work out the read program sequentially. The CPU  57  also controls the respective components of the data transceiver  12  to operate in accordance with operational signals input through the operating section  16 . 
     The modulator circuit  61  and the demodulator circuit  62  are connected to a receiver-transmitter circuit  75 , which is connected to the antennas  20 . The modulator circuit  61  modulates the control command to the radio wave  14   b,  and outputs the radio wave  14   b  to the receiver-transmitter circuit  75 . The receiver-transmitter circuit  75  amplifies and band-pass filters the radio wave  14   b  from the demodulator circuit  61 , and then outputs the radio wave  14   b  to the antennas  20 . The receiver-transmitter circuit  75  also amplifies and band-pass filters the radio wave  14   a  that is received on the antennas  20  from the capsule endoscope  11 , and then outputs the radio wave  14   a  to the demodulator circuit  62 . The demodulator circuit  62  demodulates the radio wave  14   a  to the original image data and the multi-point distance information, and outputs the image data to the image processor circuit  63 . The multi-point distance information is temporarily stored in the RAM  60  or the like. 
     The image processor circuit  63  processes the image data as demodulated by the demodulator circuit  62 , and outputs the processed image data to the data storage  64  and the image analyzer circuit  67 . 
     The data storage  64  is, for example, a flash memory having a memory capacity of 1 GB or so. The data storage  64  stores and accumulates the image data as being sequentially output from the image processor circuit  63 . The data storage  64  has an ordinary image data storage section  64   a  and a focused image data storage section  64   b.  The ordinary image data storage section  64   a  stores image data obtained by the capsule endoscope  11  in the regular imaging mode, whereas the focused image data storage section  64   b  stores image data obtained by the capsule endoscope  11  in the special imaging mode. 
     The input interface  65  gets results of measurement from the electric field strength sensors  21 , and outputs the results to the position detector circuit  66 . The position detector circuit  66  detects a present position of the capsule endoscope  11  inside the patient  10  on the basis of the results of measurement of the electric field strength sensors  21 , and outputs information on the detected position of the capsule endoscope  11 , hereinafter referred to as imaging position data, to the data storage  64 . The data storage  64  records the imaging position data in association with the image data from the image processor circuit  63 . Since the method of detecting the position of the capsule endoscope  11  inside the test body on the basis of the field strength of the radio wave  14  from the capsule endoscope  11  is well known in the art, details of this method are omitted from the present description. 
     The image analyzer circuit  67  analyzes the image data of the latest image frame obtained by the capsule endoscope  11  as the image data of the latest image frame is fed from the image processor circuit  63 , to judge whether the image frame contains any area of concern  80  (see  FIG. 8 ) that has a different feature from its periphery and thus can be regarded a lesion or the like. The image analyzer circuit  67  is provided with a cropping processor  81 , an image characteristic value extractor  82  and a judgment section  83 . 
     The cropping processor  81  reads out the multi-point distance information from the RAM  60  in correspondence to the image data from the image processor circuit  63 , to process the image data for the cropping on the basis of the read multi-point distance information. Concretely, as shown in  FIGS. 6 ,  7 A and  7 B, a zone of a limited distance range from the capsule endoscope  11 : D 1  to D 2  (D 1 &lt;D 2 ), is defined to be a check zone C, and pixels in the check zone C are gained from the image frame. In other words, the judgment as to whether there is any area of concern  80  in the imaging field A is made only in the check zone C. Note that other areas than the check zone C in the imaging field A are hatched in  FIGS. 6 and 7 . A reference numeral  10   a  designates the body tract, and R designates the view field of the capsule endoscope  11  in  FIG. 7 . 
     The distance range D 1  to D 2  of the check zone C is so defined that all area in the body tract  10   a  will be checked over. Concretely, as shown in  FIGS. 7A and 7B , the check zone C(N) in the imaging field A(N) of the N th  image frame adjoins or overlaps the next check zone C(N+1) in the imaging field A(N+1) of the (N+1) th  image frame, wherein N is a natural number. 
     The cropping processor  81  crops or cuts image data of the check zone C out of the image frame, and writes the cropped image data temporarily in the RAM  60  or the like. Limiting the zone of checking for an area of concern  80  allows checking the content in the limited image zone in detail, which helps finding an area of concern  80  like a lesion even if it is very small. Although it is possible to check the whole imaging field A in detail, it takes too much time. Besides, where the imaging field A(N) and the next imaging field A(N+1) overlap widely, wide area of the subject would be redundantly checked twice or more if the image analyzer circuit  67  checks the whole area of each image frame. 
     Moreover, limiting the zone of checking for an area of concern  80  to the predetermined distance range D 1  to D 2  of each imaging field A contributes to accurate judgment as to whether there is any lesion in the check zone. Because the surface condition and color of the internal surface of the test body, such as an inner wall of a tract, is normally similar or uniform in a limited area, it becomes easier to distinguish an abnormal portion like a lesion from the normal portion. In other words, the wider the target area of the subject, the wider variation appears even in its normal surface condition and color. So it becomes more difficult to distinguish the lesion from the normal portion. 
     The image characteristic value extractor  82  (see  FIG. 5 ) reads out the cropped image data from the RAM  60 , and extracts image characteristic values of the cropped image data. As shown in  FIG. 8 , the characteristic value extractor  82  divides the check zone C into a plurality of segments, hereinafter called as the small blocks Bs, and extracts respective image characteristic values of the small blocks Bs from the cropped image data. The image characteristic values are numerical data representative of characteristics of the image data, such as color tint, color distribution, contour distribution, shape, spectral frequency distribution or components. In the present embodiment, image characteristic values representative of a blood vessel pattern in each of the small blocks Bs are extracted. Note that the small blocks Bs may correspond in size to the ranging blocks B or may have a smaller size than the ranging blocks B. 
     As exemplars of the image characteristic values representative of the blood vessel patterns, “direction distribution of vascular edges” and “magnitude distribution” are referable. “Direction distribution of vascular edges” represents the distribution of the directions in which edges of the blood vessels extend. More specifically, all blood vessels in the check zone C are segmentalized at constant intervals, and the distribution of the directions (0 to 180 degrees) of the blood vessel segments is detected as the direction distribution of vascular edges, wherein an appropriate direction is predetermined to be a referential direction (0 degree). 
     To detect “magnitude distribution”, four directional derivative filters of 3×3-pixel size are applied to each target pixel, to get the largest absolute value among output values from each of the four directional derivative filters, like as disclosed for example in JPA 09-138471, especially in  FIG. 4  of this prior art. Then, distribution of the largest values is taken as the magnitude distribution. Moreover, it is possible to use magnitude distributions in the respective directions. It is also possible to use another known device, such as prewitt filters or Sobel filters, as the directional derivative filters. 
     Since the method of extracting image characteristic values of the blood vessel patterns is well known in the art, the description of this method will be omitted. After extracting the image characteristic values of the small blocks Bs from the cropped image data, the characteristic value extractor  82  writes these image characteristic values temporarily in the RAM  60 . 
     The judgment section  83  reads out the image characteristic values of the small blocks Bs of the check zone C from the RAM  60 , and compares these image characteristic values, to judge whether there is any area of concern  80  like a lesion in the check zone C. The image characteristic values of such small blocks Bs that correspond to the area of concern  80  differ greatly from the image characteristic values of other small blocks Bs that correspond to normal area  85 . Therefore, if there is an area of concern  80  in the check zone C, some small blocks Bs in the check zone C have different image characteristic values from other small blocks Bs have. Namely, the check zone C includes a cluster of small blocks Bs that are less similar to other small blocks Bs if the area of concern  80  exits in the check zone C. 
     So the judgment section  83  compares the image characteristic values of the small blocks BS with each other, and judges that there is an area of concern  80  in the check zone C when there are a cluster of small blocks BS whose image characteristic values differ from ones of other small blocks BS to such an extent that is beyond a predetermined threshold value. For example, when some small blocks Bs have remarkably different image characteristic values from those of their neighboring small blocks BS, the judgment section  83  judges that an area of concern  80  exits in the check zone C. In that case, the judgment section  83  calculates differences between the image characteristic values of every couple of adjoining small blocks BS, and compares the calculated differences with respective threshold values. If all of the differences are less than the threshold values, the judgment section  83  judges that no area of concern  80  exits in the check zone C. 
     The judgment section  83  would get the same result when a lesion extends over the whole check zone C. Whether the lesion extends over the whole check zone C or not may be determined by referring to the image characteristic values of a previous image frame that is judged to have no lesion or area of concern  80 . However, since the probability of occurrence of such a case is very low, the present embodiment is designed to judge that no area of concern  80  exists in the check zone C when none of the calculated differences reach or exceed the threshold values. 
     When some of the calculated differences reach or exceed the threshold values, the judgment section  83  judges that there is an area of concern  80  in the check zone C. In that case, a border between a couple of small blocks Bs, of which the differences between the image characteristic values reach or exceed the threshold value, is held as a border between the area of concern  80  and other normal area  85  that is not a lesion. That is, one small block BS of this couple belongs to the area of concern  80 , while the other small block Bs of this couple belongs to the normal area  85 . 
     When the differences in image characteristic values between a couple of adjacent small blocks Bs are less than the predetermined threshold values, the judgment section  83  regards that the two small blocks Bs belong to the same part or group. Accordingly, if any of the calculated differences between the adjacent small blocks Bs are not less than the threshold values, the check zone C is divided into at least two fractions: the area of concern  80  and the normal area  85 . Then, the judgment section  83  determines which fraction of the check zone C is the area of concern  80 . Namely, the judgment section  83  determines which one of the adjacent two small blocks Bs should belong to the area of concern  80  when the calculated difference between them reaches or exceeds the threshold value. 
     For example, since the area of concern  80  is rarely larger than the normal area  85 , it is possible to determine the largest fraction to be the normal area  85 , and other fractions to be the area of concern  80 . Alternatively, it is possible to utilize the result of judgment on the check zone C of the previous image frame. Concretely, each time the judgment section  83  judges that no area of concern  80  exits in the check zone C, the judgment section  83  overwrites the RAM  60  with the image characteristic values of an arbitrary small block Bs in this check zone C. Because the surface condition and color of the inner wall of the body tract  10   a  little change within a limited area, the image characteristic values of the normal area  85  of the latest image frame little differs from the image characteristic values of written in the RAM  60 . Therefore, among the two or more fractions, one having such image characteristic values that differ the least from the image characteristic values written in the RAM  60  is identified as the normal area  85 , and other fraction or factions are determined to be the area of concern  80 . This way, those small blocks Bs which constitute the area of concern  80  are discriminated from others. However, the method of discriminating the area of concern  80  is not limited to the present embodiment. 
     As described so far, the judgment section  83  judges whether there is any area of concern  80  in the check zone C of the latest or present image frame. If there is an area of concern  80  in the check zone C, the judgment section  83  distinguishes the small blocks Bs that constitute the area of concern  80  in the above-described manner. The result of judgment and discrimination by the judgment section  83  are fed to the CPU  57 . The CPU  57  chooses the special imaging mode for the capsule endoscope  11  when the area of concern  80  exists in the check zone C, or chooses the regular imaging mode for the capsule endoscope  11  when any area of concern  80  does not exist in the check zone C. Note that the discrimination of those small blocks Bs which constitute the area of concern  80  is utilized in a third embodiment in a manner as set forth later with reference to  FIG. 14 , and is also usable to display a marker or the like indicating the area of concern  80  on the monitor  26  of the workstation  13 . 
     Next, a procedure for selecting the imaging mode of the capsule endoscope  11 , which is executed in the data transceiver  12 , will be described with reference to  FIG. 9 . When an endoscopy starts, the imaging device  33  of the capsule endoscope  11  captures an image from the subject in the field of view, i.e. the imaging field A, and the multi-point ranging sensor  41  makes the multi-point ranging of the imaging field A simultaneously. Image data of the captured image and the multi-point distance information on the imaging field A, from which the image data has been obtained, are sent on the radio wave  14   a  from the capsule endoscope  11  to the data transceiver  12 . 
     The data transceiver  12  receives the radio wave  14   a  on the antennas  20 , and transmits it via the receiver-transmitter circuit  75  to the demodulator circuit  62 , to demodulate it into the original image data and the multi-point distance information. The image data is output to the image processing circuit  63 , while the multi-point distance information is stored in the RAM  60 . The image data is subjected to various image processing in the image processing circuit  63  and is, thereafter, output to the image analyzer circuit  67 . 
     The cropping processor  81  of the image analyzer circuit  67  reads out the multi-point distance information from the RAM  60 , corresponding to the image data as fed from the image processing circuit  63 . On the basis of the read multi-point distance information, the cropping processor  81  determines the check zone C, and crops the image data to cut the check zone C out. The cropped image data is temporarily written in the RAM  60 . The image characteristic value extractor  82  reads out the cropped image data from the RAM  60 . 
     The characteristic value extractor  82  divides the check zone C, which corresponds to the cropped fragment of the image data, into a plurality of small blocks Bs, and extracts respective image characteristic values of the small blocks Bs from the cropped image data. The extracted image characteristic values of the small blocks Bs are temporarily written in the RAM  60 . The judgment section  83  reads out the image characteristic values of the small blocks Bs from the RAM  60 . 
     The judgment section  83  calculates differences in image characteristic values between every couple of adjoining small blocks Bs, and judges whether there is any area of concern  80  in the check zone C of the present image frame, depending upon whether any of the calculated differences reach or go beyond their threshold values. In other words, the judgment section makes the judgment as to whether any area of concern  80  exists in the check zone C, on the basis of a result of judgment as to whether there is a relative change in the image characteristic values in the check zone C, that is, whether there is such small blocks Bs that are less similar to other small blocks. 
     When the judgment section  83  judges that the check zone C of the present image frame contains an area of concern  80 , the judgment section  83  distinguishes those small blocks Bs which constitute the area of concern  80  by means of the above-described method. The judgment section  83  outputs the result of judgment and data of the distinguished small blocks Bs to the CPU  57 . 
     The CPU  57  chooses the special imaging mode for the capsule endoscope  11  when the judgment section  83  judges that the area of concern  80  exits in the check zone C of the present image frame. When the judgment section  83  judges that the area of concern  80  does not exit in the check zone C of the present image frame, the CPU  57  chooses the regular imaging mode for the capsule endoscope  11 . In the same way as described above, the data transceiver  12  repeats the imaging mode selection processes each time it receives a new frame of image data from the capsule endoscope  11 . 
     Note that the above imaging mode selection processes are repeated even after the capsule endoscope  11  is switched to the special imaging mode. But if an imaging field A of an endoscopic image (image data) obtained in the special imaging mode is narrower than the check zone, i.e. the distance range from D 1  to D 2  (see  FIG. 7 ), the cropping process is skipped. 
     Referring back to  FIG. 5 , after selecting the imaging mode on the basis of the result of judgment by the judgment section, the CPU  57  decides the imaging conditions: the zooming magnification (field of view), the frame rate, the exposure value (the shutter speed and the illumination light volume), in accordance with the selected imaging mode, with reference to an imaging condition table  87  in the database  68 . 
     As shown in  FIG. 10 , the imaging condition table  87  defines the imaging conditions for the regular imaging mode and those for the special imaging mode, wherein plural sets of imaging conditions are prepared for the special imaging mode, because the capsule endoscope  11  captures images while varying the zooming magnification and the exposure value stepwise in the special imaging mode. 
     As the frame rate F (fps: frame per second), a higher value Fb is preset for the special imaging mode than a frame rate Fa preset for the regular imaging mode. So the capsule endoscope  11  will not fail to capture an image of the area of concern  80  even if the capsule endoscope  11  suddenly travels faster in the special imaging mode. The high frame rate Fb enables the capsule endoscope  11  to capture more endoscopic images of the area of concern  80  during a period from when the area of concern  80  enters the field of view of the objective lens system  32  till the area of concern  80  exits the field of view, so it is possible to capture the images of the area of concern  80  while varying the zooming magnification and the exposure value stepwise. The low frame rate Fa for the regular imaging mode reduces the power consumption by the capsule endoscope  11 , and also reduces the number of endoscopic images captured from outside the area of concern  80 , i.e. unnecessary images for diagnosis. 
     As the zooming magnification Z, a value Za for the regular imaging mode is preset on a wide-angle side, whereas values Zb 1 , Zb 2 , Zb 3  . . . for the special imaging mode are preset on a telephoto side, so as to obtain enlarged images of the area of concern  80  in the special imaging mode. Moreover, in the special imaging mode, the zooming magnification is changed stepwise from the telephoto side toward the wide-angle side, or vise versa. Thus, at least an image of the area of concern  80  is captured at an optimum zooming magnification, i.e. at a maximum image magnification, wherever the area of concern  80  exists in the check zone C. 
     Since the capsule endoscope  11  captures images while moving through the tract  10   a,  there is a possibility that the area of concern  80  gets out of the field of view of the objective lens system  32  before the capsule endoscope  11  starts imaging in the special imaging mode. Therefore, at least one of the zooming magnification values Zb 1 , Zb 3 , Zb 3  . . . for the special imaging mode may be set closer to a wide-angle terminal than the zooming magnification value Za for the regular imaging mode, so as to provide a wider field of view in the special imaging mode than in the regular imaging mode. 
     The exposure value is determined by the shutter speed S (1/sec.) and the illumination light volume I, which is controlled by a drive current (mA) supplied to the illuminator light source  38 . The shutter speed S and the illumination light volume I are fixed in the regular imaging mode: S=Sa and I=Ia. On the other hand, in the special imaging mode, the shutter speed S and the illumination light volume I are gradually raised: S=Sb 1 , Sb 2 , Sb 3  . . . , I=Ib 1 , Ib 2 , Ib 3  . . . . Since the capsule endoscope  11  captures images while moving through the tract  10   a,  the condition of the illumination light incident on the subject, including the area of concern  80 , varies with a change in attitude of the capsule endoscope  11 . Capturing images while varying the exposure value (the shutter speed S and the illumination light volume I) stepwise will make the exposure condition of at least one of the captured images proper. In the regular imaging mode, the shutter speed S and the illumination light volume I are preferably set at lower level Sa and Ia than in the special imaging mode, because it reduces the power consumption by the capsule endoscope  11 . 
     As shown in  FIG. 5 , the CPU  57  selects the imaging mode of the capsule endoscope  11  on the basis of the result of judgment by the judgment section and the imaging condition table  87 , and decides the imaging conditions according to the selected imaging mode. Then the CPU  57  outputs a control command corresponding to the decided imaging conditions to the modulator circuit  61 . The modulator circuit  61  modulates the control command into the radio wave  14   b  and outputs it via the receiver-transmitter circuit  75  to the antennas  20 . Thus, the control command is sent wirelessly from the data transceiver  12  to the capsule endoscope  11 . 
     As shown in  FIG. 4 , the radio wave  14   b  is received on the antenna  18  of the capsule endoscope  11 , and is demodulated through the receiver-transmitter circuit  55  and the demodulator circuit  51  into the original control command. The control command is output to the CPU  45 , so the zooming magnification (field of view), the frame rate, the exposure value (the shutter speed and the illumination light volume), which are designated by the control command, are temporarily written in the RAM  47 . 
     The imaging driver  48  reads out the frame rate and the shutter speed from the RAM  47 , and controls the imaging device  33  and the signal processing circuit  54  so that an endoscopic image is captured at the frame rate and the shutter speed as designated by the control command. 
     The lens driver  36  reads out the zooming magnification from the RAM  47 , and adjusts the length of the objective lens system  32  by moving the second lens  32   f  so that the endoscopic image is captured at the zooming magnification as designated by the control command. 
     The illuminator driver  53  reads out the illumination light volume from the RAM  47 , and controls the drive current applied to the illuminator light source  38  so that the endoscopic image is captured under the illumination light whose volume is designated by the control command. Thus, the capsule endoscope  11  captures the endoscopic image under the imaging conditions designated by the control command. 
     Moreover, in the special imaging mode, the imaging device  48 , the lens driver  36  and the illuminator driver  53  control the imaging device  33 , the signal processing circuit  54 , the second lens  32   f  and the illuminator light source  38  respectively, so as to change the shutter speed, the zooming magnification and the illumination light volume stepwise. 
     A series of operations as described above: (1) image-capturing by the capsule endoscope  11 , (2) sending of an endoscopic image to the data transceiver  12 , (3) selecting the imaging mode, (4) generating the control command, (5) sending the control command to the capsule endoscope  11 , and (6) controlling operation of the respective components of the capsule endoscope  11  on the basis of the control command, are cyclically repeated till an ending command is sent from the data transceiver  12  to the capsule endoscope  11  at the end of the endoscopy. These operations are performed speedy enough as compared to the speed of movement of the capsule endoscope  11 . So the capsule endoscope  11  is switched to the special imaging mode as soon as the area of concern  80  is found in the regular imaging mode, before the area of concern  80  gets out of the field of view of the capsule endoscope  11 . 
     As shown in  FIG. 11 , the overall operation of the workstation  13  is under the control of a CPU  90 . The CPU  90  is connected via a data bus  91  to an LCD driver  92  for controlling the LCD  26 , a communication interface (I/F)  94  for intermediating data-exchange through a USB connector  93  between the workstation  13  and the data transceiver  12 , a data storage  95  and a RAM  96 . 
     The data storage  95  stores image data that is taken out of the focused image data storage section  64   b  of the data transceiver  12 . The data storage  95  also stores various programs and data necessary for the operation of the workstation  13 , software programs for assisting doctors to make diagnoses, and diagnostic information sorted according the individual patients. The RAM  96  stores temporarily those data as read out from the data storage  95 , and intermediate data as produced during various computing processes. When the assisting software is activated, a work window of the assisting software is displayed, for example, on the LCD  26 . On this window, the doctor can display and edit some images or enter the diagnostic information by operating the operating section  25 . 
     Now the operation of the capsule endoscopy system  2  as configured above will be described with reference to  FIG. 12 . Preliminary to an endoscopy, the doctor makes the patient  10  put on the shield shirt  19 , the antennas  20  and the data transceiver  12 , and turns the capsule endoscope  11  on. 
     When the patient  10  has swallowed the capsule endoscope  11  and gets ready for the endoscopy, the capsule endoscope  11  starts capturing images of the subject, i.e. the interior of the patient&#39;s tract, in the regular imaging mode. The illuminator light source  38  illuminates the subject, and an optical image of the subject is formed by the objective lens system  32  on the imaging surface of the imaging device  33 , so the imaging device  33  outputs the analog image signal corresponding to the optical image. The image signal is fed to the signal processing circuit  54 , and is converted to the digital image data through correlated double sampling, amplification, and analog-to-digital conversion. The image data is subjected to various image processing as described above with reference to  FIG. 4 . 
     With the start of the endoscopy, the multi-point ranging sensor  41  starts the multi-point ranging, wherein the multi-point ranging sensor  41  divides the imaging field A into the ranging blocks B of M×N matrix, and measures distances from the capsule endoscope  11  to the respective representative points P of the ranging blocks B. The multi-point ranging sensor  41  outputs the distance measuring signals to the distance signal converter circuit  49 , which converts the distance measuring signals to the distance signals, and outputs them to the CPU  45 . The CPU  45  outputs the distance signals of all the representative points P of the imaging field A as the multi-point distance information to the modulator circuit  50 . 
     The digital image data output from the signal processing circuit  54  and the multi-point distance information from the CPU  45  are modulated into the radio wave  14   a  in the modulator circuit  50 . The modulated radio wave  14   a  is amplified and band-pass filtered in the receiver-transmitter circuit  55  and is, thereafter, sent out from the antenna  18 . Thus, the image data and the multi-point distance information on the imaging field A, from which the image data is obtained, are wirelessly sent from the capsule endoscope  11  to the data transceiver  12 . At the same time, the electric field strength sensors  21 , which are attached to the antennas  20 , measure the strength of the electric field of the radio wave  14   a  from the capsule endoscope  11 , and input the results of measurement to the position detector circuit  66  of the data transceiver  12 . 
     The radio wave  14   a  is received on the antennas  20  of the data transceiver  12 , and is fed through the receiver-transmitter circuit  75  to the demodulator circuit  62 , which demodulates the radio wave  14   a  into the original image data and the multi-point distance information. The demodulated image data is subjected to various image processing in the image processor circuit  63 , and is output to the image analyzer circuit  67  and the data storage  64 . The demodulated multi-point distance information is temporarily written in the RAM  60 . 
     The position detector circuit  66  detects the present position of the capsule endoscope  11  inside the patient  10  on the basis of the results of measurement of the electric field strength sensors  21 , and outputs the detected present position as the imaging position data to the data storage  64 . The data storage  64  records the imaging position data in association with the image data from the image processor circuit  63 . The image data obtained in the regular imaging mode is stored in the ordinary image data storage section  64   a.  Note that the image data stored in the ordinary image data storage section  64   a  may be subjected to an appropriate data volume reduction process like a data compression process. 
     Each time the image analyzer circuit  67  is supplied with the image data from the image processing circuit  63 , the image analyzer circuit  67  reads out the multi-point distance information corresponding to the image data from the RAM  60 . Then, the image analyzer circuit  67 , including the cropping processor  81 , the image characteristic value extractor  82  and the judgment section  83 , carry out the imaging mode selection processes as described above with reference to  FIG. 9 : (a) cropping image data of the check zone C, (b) extracting image characteristic values of the individual small blocks Bs, (c) judging whether there is any area of concern  80  in the check zone C, and, if there is one, (d) distinguishing those small blocks BS which constitute the area of concern  80 . 
     The image analyzer circuit  67  outputs the result of judgment as to whether there is any area of concern  80 , and if there is one, data of the distinguished small blocks Bs that constitute the area of concern  80 . On the basis of the result of judgment by the image analyzer circuit  67 , the CPU  57  selects the imaging mode of the capsule endoscope  11  and refers to the imaging condition table  87  of the database  68  to decide the imaging conditions according to the selected imaging mode, see  FIG. 10 . Then the CPU  57  generates a control command designating the decided imaging conditions and outputs the control command to the modulator circuit  61 . The modulator circuit  61  modulates the control command into the radio wave  14   b,  and outputs it through the receiver-transmitter circuit  75  to the antennas  20 . Thus the control command is wirelessly sent from the data transceiver  12  to the capsule endoscope  11 . 
     The radio wave  14   b  is received on the antenna  18  of the capsule endoscope  11 , and is demodulated into the original control command through the receiver-transmitter circuit  55  and the demodulator circuit  51 . Then the control command is output to the CPU  45 . As a result, the imaging conditions designated by the control command, i.e. a frame rate, a zooming magnification and an exposure value (a shutter speed and an illumination light volume), are temporarily written in the RAM  47 . 
     The imaging driver  48  controls the imaging device  33  and the image processing circuit  54  so that endoscopic images are captured at the frame rate and the shutter speed as designated by the control command. The lens driver  36  controls the objective lens system  32  so that the endoscopic images are captured at the zooming magnification as designated by the control command. The illuminator driver  53  controls the drive current to the illuminator light source  38  so that the endoscopic images are captured at the illumination light volume as designated by the control command. 
     Consequently, if there is an area of concern  80  in the check zone C of an endoscopic image (image data frame) that is newly obtained in the regular imaging mode, the capsule endoscope  11  starts capturing images of the area of concern  80  in the special imaging mode. Concretely, the capsule endoscope  11  captures the images of the area of concern  80  at a higher frame rate while varying the zooming magnification and the exposure value stepwise. Thereby, at least one of the captured images will finely reproduce the area of concern  80 . The image data obtained in the special imaging mode is stored in the focused image data storage section  64   b  of the data storage  64  of the data transceiver  12 . 
     If there is no area of concern  80  in the check zone C, the capsule endoscope  11  continues image-capturing in the regular imaging mode. Since the frame rate, shutter speed and the illumination light volume are maintained in lower levels in the regular imaging mode as compared to the special imaging mode, power consumption by the capsule endoscope  11  is reduced. 
     When the judgment section  83  judges that the area of concern  80  does not exist in the check zone C of the latest image frame obtained in the special imaging mode, it means that the area of concern  80  gets out of the field of view of the capsule endoscope  11 . Then, the data transceiver  12  generates a control command for resetting the capsule endoscope  11  to the regular imaging mode, and sends this control command wirelessly to the capsule endoscope  11 . Thus, the capsule endoscope  11  is switched from the special imaging mode to the regular imaging mode. 
     Thereafter, the same operations as described above: (1) image-capturing by the capsule endoscope  11 , (2) sending of an endoscopic image to the data transceiver  12 , (3) selecting the imaging mode, (4) generating the control command, (5) sending the control command to the capsule endoscope  11 , and (6) controlling operation of the respective components of the capsule endoscope  11  on the basis of the control command, are cyclically repeated till the ending command is sent from the data transceiver  12  to the capsule endoscope  11  at an end of the endoscopy. 
     To conclude the endoscopy, the data transceiver  12  is connected to the processor  24  through the USB cable  27 , to transfer the image data from the focused image data storage section  64   b  of the data storage  64  of the data transceiver  12  to the processor  24 . Then the doctor operates the operating section  25  to display the fine endoscopic images of the area of concern  80 , which have been obtained in the special imaging mode, successively on the LCD  26 , to interpret them. 
     As described so far, in the capsule endoscopy system  2  of the present embodiment, the check zone C of each endoscopic image frame obtained at present by the capsule endoscope  11  is divided into the small blocks Bs, and the image characteristic values extracted from one small block Bs are compared with those extracted from another small block BS, to check relative variations in the image characteristic values. Based on the relative variations, the capsule endoscopy system  2  makes the judgment as to whether there is any area of concern  80  in the check zone C. Therefore, the capsule endoscopy system  2  can determine the area of concern  80  exactly without any diagnostic information on past diagnoses of the patient or case information on general cases. Moreover, the capsule endoscopy system  2  can identify such a lesion that is not similar to a general image of the lesion shown in the case information. Because the capsule endoscopy system  2  does not need the diagnostic information or the case information, there is no need for considering the difference between the endoscope used for the present endoscopy and ones used for obtaining the diagnostic information or the case information. 
     Now a second embodiment of the present invention will be described, which differs from the above-described first embodiment in the way of making the judgment as to whether any area of concern exits in the check zone C or not. 
     Like the first embodiment, the second embodiment divides the check zone C of the present image frame into the small blocks Bs and extracts image characteristic values of the small blocks Bs from the cropped image data of the check zone C. However, in the second embodiment, the judgment as to whether any area of concern  80  exits in the check zone C or not is made based on the degree of similarity between the image characteristic values of the small blocks Bs of the latest or present image frame and ones of the small blocks Bs of the preceding image frame that has been obtained immediately before the present image frame. Because the second embodiment may have the same structure as the first embodiment and merely differs from the first embodiment in the way of analyzing the image data, the second embodiment will be described with reference to the same drawings as used for the first embodiment. 
     In a data transceiver  12  of the second embodiment, a RAM  60  or another memory device stores image characteristic values of the small blocks Bs of the present image frame as well as image characteristic values of the small blocks Bs of the preceding image frame, which are extracted by an image characteristic value extractor  82  of an image analyzer circuit  67 . Each time the data transceiver  12  receives the image data newly from the capsule endoscope  11 , the image characteristic values of the preceding image frame are replaced with those image characteristic values which are extracted from the new image data. Thus, the RAM  60  always stores two sets of image characteristic values of the respective check zones C of the latest and preceding image frames. 
     The image analyzer circuit  67  reads out the image characteristic values from the RAM  60 , to calculate differences in the image characteristic values between each individual small block Bs of the present image frame and a corresponding small block Bs of the preceding image frame. For example, the corresponding small block Bs is one located in the same position (coordinative position) in the check zone C of the preceding image frame as the one small block Bs of the present image frame. The judgment section checks if any of the calculated differences reach or exceed the predetermined threshold values. Namely, the judgment section checks whether there are such small blocks Bs in the check zone C of the present image frame that have different image characteristic values from those the corresponding small blocks Bs of the preceding image frame have. 
     When none of the calculated differences reach or exceed the threshold values, the judgment section judges that an image fragment contained in the check zone C of the present image frame is similar to an image fragment contained in the check zone of the preceding image frame. Then, if the judgment section has judged that there is no area of concern  80  in the check zone C of the preceding image frame, the judgment section judges that no area of concern  80  exists in the check zone C of the present image frame. On the contrary, if the judgment section has judged that there is an area of concern  80  in the check zone C of the preceding image frame, the judgment section judges that the area of concern  80  exists in the check zone C of the present image frame too. This means that the area of concern  80  exists at the same position (small blocks Bs) in the check zone C of the present image frame as the position (small blocks Bs) in the check zone C of the preceding image frame. Such a result can be obtained for example while the capsule endoscope  11  stagnates in the tract  10   a,  or when a lesion (the area of concern  80 ) extends over a wide area of the tract  10   a.    
     On the other hand, when some of the calculated differences reach or exceed the threshold values, the judgment section judges that the present image frame has some small blocks Bs whose image characteristic values change from those of the same small blocks Bs of the preceding image frame, and that an image fragment contained in the check zone C of the present image frame is not similar to an image fragment contained in the check zone of the preceding image frame. Then, if the judgment section has judged that there is no area of concern  80  in the check zone C of the preceding image frame, the judgment section judges that an area of concern  80  exists in the check zone C of the present image frame. In that case, those small blocks Bs having the changed image characteristic values are considered to constitute the area of concern  80 . On the contrary, if the judgment section has judged that there is an area of concern  80  in the check zone C of the preceding image frame, it may probably be considered that the area of concern  80  does not exist in the present image frame, or there is a lesion or an area of concern  80  in the present image frame but it exists in a different position or has a different contour from the area of concern  80  of the preceding frame. Therefore, in that case, it is preferable to check whether any area of concern exists in the check zone C of the present frame on the basis of similarity in the image characteristic values between the small blocks Bs of the present frame, in the same way as described with respect to the first embodiment. 
     It is to be noted that the method of judgment according to the second embodiment is usable only when the present image frame is obtained in the same imaging mode as the preceding image frame. If the present image frame is obtained in the regular imaging mode while the preceding image frame was obtained in the special imaging mode, or in the opposite case, the quality of the present image frame differs from that of the preceding image frame due to the differences in zooming magnification and exposure value. Therefore, it is hard to distinguish the area of concern  80  by comparing the present and preceding image frames, which are obtained in the different imaging modes from each other. In that case, the judgment as to whether any area of concern  80  exists should be made according the method of the first embodiment. 
     The result of judgment by the judgment section is fed to the CPU  57 . The CPU  57  selects the imaging mode of the capsule endoscope  11  depending upon whether any area of concern  80  exits in the check zone C of the present image frame or not, in the manner as described above. 
     Next, the imaging mode selection processes of the second embodiment will be described with reference to  FIG. 13 . When an endoscopy starts, the capsule endoscope  11  stars capturing images of the object in the regular imaging mode and also starts the multi-point ranging. Thus, the capsule endoscope  11  wirelessly sends out image data of the captured images and the multi-point distance information sequentially to the data transceiver  12 . When the data transceiver  12  receives the image data of a first image frame, a cropping processor  81  crops image data pieces out of the check zone C, and the image characteristic extractor  82  extracts respective image characteristic values of the small blocks Bs, in the manner as described in the first embodiment. The extracted image characteristic values of the small blocks Bs of the first image frame are written in the RAM  60 . 
     As for the first or initial image frame, the judgment as to whether there is any area of concern  80  in the check zone C is preferably made according to the method of the first embodiment. Note that the following description is based on the assumption that no area of concern  80  exits in the check zone C of the first image frame. 
     After the image characteristic values of all small blocks Bs of the check zone C of a second or next image frame are written in the RAM  60 , the judgment section reads out the image characteristic values of the second and first image frames from the RAM  60 , to calculate differences in the image characteristic values between each individual small block Bs of the second or present image frame and the corresponding small block Bs of the first or preceding image frame. 
     When none of the calculated differences reach or exceed the threshold values, the judgment section judges that an image fragment contained in the check zone C of the present or second image frame is similar to an image fragment contained in the check zone of the preceding or first image frame. Since there is no area of concern  80  in the check zone C of the first image frame, the judgment section judges that no area of concern  80  exists in the check zone C of the second image frame. 
     On the other hand, when some of the calculated differences reach or exceed the threshold values, the judgment section judges that the second image frame has some small blocks Bs whose image characteristic values change from those of the same small blocks Bs of the first image frame. Then, since there is no area of concern  80  in the check zone C of the first image frame, the judgment section judges that an area of concern  80  exists in the check zone C of the second image frame, and distinguishes those small blocks Bs which have the changed image characteristic values and thus constitute the area of concern  80 . 
     The judgment section outputs the result of judgment and the data of the distinguished small blocks Bs to the CPU  57 . The CPU  57  selects the imaging mode of the capsule endoscope  11  depending upon whether any area of concern  80  exits in the check zone C of the second image frame. 
     As for the following image frames, each time the data transceiver  12  receives the image data of a new image frame from the capsule endoscope  11 , the judgment section calculates differences in image characteristic values between each individual small block Bs of the N th  or present image frame and the corresponding small block Bs of the (N−1) th  or preceding image frame, and judges the presence or absence of an area of concern  80  in the check zone C on the basis of the calculated differences in the same way as described above. 
     As described above, if some of the calculated differences reach or exceed the threshold values after it is judged that an area of concern  80  exists in the check zone C of the preceding or (N−1) th  image frame, the judgment section  83  makes the judgment as to whether any area of concern  80  exits in the check zone C of the present or N th  image frame according to the method of the first embodiment. Also when the N th  image frame and the (N−1) th  image frame have been obtained in the different imaging modes from each other, the judgment as to whether any area of concern  80  exits in the check zone C of the N th  image frame is made according to the method of the first embodiment. 
     As described so far, according to the second embodiment, the judgment as to whether any area of concern  80  exits in the check zone C of the present image frame is made by comparing the present image frame with the preceding image about whether there are any small blocks Bs in the present image frame, whose image characteristic values change from ones the corresponding small blocks Bs have in the preceding image frame. Therefore, the second embodiment achieves the same effect as described with respect to the first embodiment. 
     Next, a third embodiment of the present invention will be described. Although the first and second embodiments have been described on the presumption that the optical axis  35  of the objective lens system  32  of the capsule endoscope  11  is fixed in a direction parallel to a lengthwise direction of the capsule endoscope  11 , the present invention is not limited to this configuration. According to the third embodiment, the optical axis  35  of the objective lens system  32  is directed toward an area of concern  80  when the area of concern  80  is detected and the capsule endoscope  11  is switched to the special imaging mode. 
     In order to change the direction of the optical axis  35 , as shown for example in  FIG. 14 , the capsule endoscope  11  is provided with a container  98  containing the objective lens system  32 , the imaging device  33 , the illuminator light source  38 , the multi-point ranging sensor  41  and other necessary components for imaging, and a swaying mechanism  99  for the container  98 . The swaying mechanism  99  sways the container  98  so as to incline the optical axis  35  of the objective lens system  32  in an appropriate direction. As well known in the art, the description of the swaying mechanism  99  will be omitted. 
     As described with reference to  FIG. 8 , when it is judged that an area of concern  80  exists in the check zone C, the small blocks Bs constituting the area of concern  80  are distinguished. Then, it is determined how much and in what direction the area of concern  80  deviates from the center of the check zone C, i.e. the center of the imaging field A, which is on the optical axis  35  of the objective lens system  32  in the regular imaging mode. 
     The direction and amount of the deviation of the area of concern  80  from the center of the check zone C are determined, for example, by the image analyzer circuit  67 . As the deviation amount, the number of small blocks Bs or blocks B from the center to the area of concern  80  may be detected. Based on the deviation amount, the image analyzer circuit  67  determines an inclination angle of the optical axis  35  from the position in the regular imaging mode toward the area of concern  80 . The inclination angle of the optical axis  35  according to the deviation amount of the area of concern  80  may be predetermined by measurement. 
     When the direction and angle of inclination of the optical axis  35  are determined, the CPU  57  of the data transceiver  12  generates a control command on the basis of the direction and angle of inclination of the optical axis  35 , hereinafter referred to as optical axis adjustment information, and the imaging conditions as determined in the manner as described with respect to the first embodiment. The control command is sent wirelessly to the capsule endoscope  11 , so the CPU  45  of the capsule endoscope  11  controls the swaying mechanism  99  to sway the container  98  to incline the optical axis  35  of the objective lens system  32  according to the optical axis adjustment information received as the control command. Thereby, the objective lens system  32  is directed toward the area of concern  80 . 
     As shown in  FIG. 15 , the objective lens system  32  gets a pretty narrow field of view R 2 , as shown by solid line, by directing the optical axis  35  of the objective lens system  32  toward the area of concern  80  in the special imaging mode, in comparison with a field of view R 1  in the regular imaging mode, as shown by dashed line. Therefore, in the special imaging mode, the capsule endoscope  11  will capture images while focusing on the area of concern  80 . As a result, it becomes possible to obtain more enlarged and thus detailed endoscopic images of the area of concern  80  than those obtainable in the first embodiment. 
     Next a fourth embodiment of the present invention will be described. Although the capsule endoscope  11  used in the first and second embodiments has the objective lens system  32 , the imaging device  33 , the illuminator light source  38  and the multi-point ranging sensor  41  only on the side of the front casing  30 , the present invention is not limited to these embodiments. For example, as shown in  FIG. 16 , a capsule endoscope  100  may have an objective lens system  102 , an imaging device  103 , an illuminator light source  104  and a multi-point ranging sensor  105  consisting of a photo emitter unit  105   a  and a photo sensor unit  105   b  on the side of its rear casing  101 , beside an objective lens system  32 , an imaging device  33 , an illuminator light source  38  and a multi-point ranging sensor  41  on the side of its front casing  30 . Needless to say, both the front and rear casings  30  and  101  are transparent. The objective lens systems  32  and  102 , the imaging devices  33  and  103 , the illuminator light sources  38  and  104  and the multi-point ranging sensors  41  and  105  respectively have the same structures as described in the first embodiment. Therefore, the description of these elements will be omitted. Designated by  106  is an optical axis of the objective lens system  102 . 
     With the imaging devices  33  and  103  on the opposite sides, the capsule endoscope  100  captures images through one of these imaging devices  33  and  103 : one facing forward in the traveling direction of the capsule endoscope  100  is used in the regular imaging mode, whereas the other facing backward in the traveling direction of the capsule endoscope  100  is used in the special imaging mode. 
     The following description is based on the assumption that the capsule endoscope  100  travels through a tract  10   a  in a direction substantially parallel to the optical axes  35  and  106 , and that the capsule endoscope  100  can move with its front casing  30  forward or with its rear casing  101  forward. Whether the capsule endoscope  100  is moving with it front casing  30  forward or with its rear casing  101  forward is detected by a traveling direction detector or attitude sensor  107  that is built in the capsule endoscope  100 . The traveling direction detector  107  is for example a uniaxial accelerometer. The detection result by the traveling direction detector  107 , hereinafter referred to as traveling direction data, is seriatim sent together with the image data and the multi-point distance information to a data transceiver  12 . Hereinafter, we will explain that the capsule endoscope  100  travels in a first direction S 1  as it heads its front casing  30  forward, and that the capsule endoscope  100  travels in a second direction S 2  as it heads its rear casing  101  forward, as implied by arrows in  FIG. 16 . 
     Instead of the traveling direction detector  107 , it is possible to detecting the traveling direction of the capsule endoscope  100  on the basis of a variation in endoscopic images with time, which are successively obtained by the imaging device  33  or  103 . As well known in the art, the process of detecting the traveling direction of the capsule endoscope will be omitted. 
     On the basis of the traveling direction data from the traveling direction detector  107 , a CPU  57  of the data transceiver  12  (see  FIG. 5 ) generates a control command for driving the imaging device  33  to capture images of the subject in the regular imaging mode, while the capsule endoscope  100  is traveling in the first direction S 1 . On the other hand, while the capsule endoscope  100  is traveling in the second direction S 2 , the CPU  57  of the data transceiver  12  (see  FIG. 5 ) generates a control command for driving the imaging device  103  to capture images of the subject in the regular imaging mode. Simultaneously, the CPU  57  generates another control command for interrupting imaging of the imaging device that is located rearward in the traveling direction of the capsule endoscope  100 . The control commands generated by the CPU  57  are sent wirelessly to the capsule endoscope  100 . So the forward imaging device in the traveling direction captures images of the subject in the regular imaging mode, while the rearward imaging device stops imaging. 
     Accordingly, as shown in  FIG. 17A , while the capsule endoscope  100  is traveling in the first direction S 1 , the imaging device  33  captures images of the subject in the regular imaging mode, and the image data, the multi-point distance information and the traveling direction data are sent wirelessly from the capsule endoscope  100  to the data transceiver  12 . In the same way as described with respect to the above embodiments, the image analyzer circuit  67  of the data transceiver  12  judges whether any area of concern  80  exists in the check zone C of the imaging field A of the present image frame. Note that Rf and Rb represent respective fields of view of the objective lens system  32  and the objective lens system  102 . 
     After the image analyzer circuit  67  judges that the area of concern  80  exists in the check zone C, the CPU  57  of the data transceiver  12  judges whether the area of concern  80  enters the field of view Rb of the objective lens system  102 , as shown in  FIG. 17B . The judgment as to whether the area of concern  80  enters the field of view Rb of the objective lens system  102  may be made by means of any appropriate method. 
     For example, on the basis of the multi-point distance information as obtained by the multi-point ranging, which has been sent to the data transceiver  12  together with the image data, the CPU  57  measures a distance “d” between the capsule endoscope  100  and the area of concern  80  at the moment when the present image frame was obtained. Thereafter when the capsule endoscope  100  travels the distance “d” in the direction S 1 , the capsule endoscope  100  comes into a range around the area of concern  80 . Thereafter, when the capsule endoscope  100  travels farther a given distance “Δd” in the direction S 1 , the area of concern  80  enters the field of view Rb of the objective lens system  102 , wherein “Δd” is longer than a whole length of the capsule endoscope  100  and varies depending upon the individual capsule endoscopes, so the distance “Δd” may be predetermined by measurement. In conclusion, the area of concern  80  will enter the field of view Rb of the objective lens system  102  when the capsule endoscope  100  travels a distance “d+Δd” in the direction S 1  since the judgment that the area of concern  80  exits in the image frame obtained by the imaging device  33 . 
     In a case where the capsule endoscope  100  uses an accelerometer as the traveling direction detector  107 , information on the acceleration of the capsule endoscope  100  is wirelessly sent to the data transceiver  12 . The CPU  57  of the data transceiver  12  calculates a travel distance of the capsule endoscope  100  on the basis of the acceleration information obtained by the accelerometer of the capsule endoscope  100 , to judge that the area of concern  80  comes in the field of view Rb of the objective lens system  102  when the capsule endoscope  100  has moved by the distance “d+Δd” from the time when the area of concern  80  was found in the field of view of the imaging device  33 . 
     Alternatively, it is possible to start driving the imaging device  103  in the regular imaging mode when it is judged that the area of concern  80  exists in the check zone C of the present imaging field A of the imaging device  33 , and analyze each image frame obtained by the imaging device  103  in the image analyzer circuit  67  so as to detect whether the area of concern  80  exists in the check zone C of the image frame in the same manner as described above. When the area of concern  80  is found in the check zone C, the CPU  57  judges that the area of concern  80  enters the field of view Rb of the objective lens system  102 . 
     When it is judged that the area of concern  80  enters the field of view Rb of the objective lens system  102 , the CPU  57  of the data transceiver  12  generates a control command for driving the imaging device  103  to capture images of the area of concern  80  in the special imaging mode. The imaging conditions in the special imaging mode are decided in the same way as in the first embodiment. The control command is wirelessly sent from the data transceiver  12  to the capsule endoscope  100 . Thus, the imaging device  103  captures images of the area of concern  80  in the special imaging mode. 
     While the capsule endoscope  100  is traveling in the second direction S 2 , the same operations as described above are carried out in the fourth embodiment, except but the imaging device  33  (the objective lens system  32 ) and the imaging device  103  (the objective lens system  102 ) exchange the roles with each other, so the description of this case will be omitted. 
     Although the fourth embodiment has been described in connection with the capsule endoscope  100  that has the imaging devices  33  and  103  on the front and rear sides in the casings  30  and  101 , the present invention is also applicable to such a capsule endoscope  109  that can capture an optical image of the subject in a lateral direction of the capsule endoscope  109 , as shown in  FIG. 18 . The capsule endoscope  109  has an imaging unit  113  mounted in its middle position, which is constituted of an objective lens system  111  whose optical axis  110  is perpendicular to a lengthwise direction of the endoscope  109 , and an imaging device  112  placed behind the objective lens system  111 . Like the above embodiments, the capsule endoscope  109  also has an objective lens system  32  and an imaging device  33  on its front side, though they are not shown in  FIG. 18 . The objective lens system  32  has an optical axis  35  that coincides with the lengthwise axis of the capsule endoscope  109 . 
     Although it is not shown in the drawings, the capsule endoscope  109  is provided with a turning mechanism for turning the imaging unit  113  about the lengthwise axis of the capsule endoscope  109 . Thereby, the optical axis  110  of the objective lens system  111  can rotate through 360 degrees around the optical axis  35 . The objective lens system  111  and the imaging device  112  have the same structure as the objective lens system  32  and the imaging device  33 . 
     The capsule endoscope  109  is controlled to capture images of the subject through the imaging device  33  in the regular imaging mode, and the judgment as to whether any area of concern  80  exits in a check zone C of the present image frame is carried out in a data transceiver  12 . When it is judged that an area of concern  80  exits in the check zone C, a CPU  57  of the data transceiver  12  starts checking if the area of concern  80  comes in a field of view Rs of the objective lens system  111 , in the same manner as described with respect to the fourth embodiment. 
     When the CPU  57  judges that the area of concern  80  comes in the field of view Rs of the objective lens system  111 , the CPU  57  generates a control command for causing the optical axis  110  of the objective lens system  111  to turn in a direction toward the area of concern  80 , and a control command for driving the imaging device  112  to capture images in a special imaging mode. These control commands are sent wirelessly from the data transceiver  12  to the capsule endoscope  109 , so the imaging unit  113  is turned about the lengthwise axis of the capsule endoscope  109  to direct the optical axis  110  toward the area of concern  80  and thereafter the data transceiver  12  captures images of the area of concern  80  in the special imaging mode. Instead of turning the imaging unit  113  (the optical axis  110 ) about the lengthwise axis of the capsule endoscope  109  (the optical axis  35 ), it is possible to use a panorama lens for the objective lens system  111 , which has an angle of view of 360 degrees. 
     It is also possible to use a capsule endoscope that is provided with an objective lens system  111  and an imaging device  112  like the capsule endoscope  109  of  FIG. 18 , as well as objective lens systems  32  and  102  and imaging devices  33  and  103  like the capsule endoscope  100  of  FIG. 16 . Namely, the capsule endoscope having three imaging devices respectively viewing front, side and rear of the traveling direction of the capsule endoscope is usable in such a manner that the front-viewing imaging device is driven in the regular imaging mode, while the other imaging devices are driven in the special imaging mode to capture images of an area of concern. 
     In the above described embodiment, the data transceiver  12  carries out the image analysis or the judgment as to whether there is any area of concern in the check zone of the endoscopic image and generates the control commands. However, the present invention is not limited to these embodiments, but the image analysis and the generation of the control commands may be carried out within a capsule endoscope.  FIG. 19  shows an example of such capsule endoscope  116  that makes the image analysis and generates the control commands. 
     The  116  fundamentally has the same structure as the capsule endoscope  11  of the first embodiment, but the  116  is provided with an image analyzer circuit  117  and a memory  118 . The  117  and the memory  118  take the same functions as the image analyzer circuit  67  and the database  68  of the data transceiver  12  of the first embodiment, respectively. The  117  has the same imaging condition table  87  as the database  68  has. Note that the  116  is provided with the same members as the  11  has, although some of them such as a ROM  46 , a RAM  47  and a power supply circuit  52  are omitted from  FIG. 19 . 
     The  117  is fed with image data from a signal processing circuit  54 , and multi-point distance data from a CPU  45 . The  117  executes the imaging mode selection processes as described above with respect to the first and second embodiments: (a) cropping image data of the check zone C, (b) extracting respective image characteristic values of the small blocks Bs, (c) judging whether there is any area of concern  80  in the check zone C, and, if there is one, (d) distinguishing those small blocks Bs which constitute the area of concern  80 . 
     The  117  outputs the result of judgment to a CPU  45 . On the basis of the result of judgment by the image analyzer circuit  117 , the CPU  45  selects the imaging mode of the capsule endoscope  116  and refers to the imaging condition table  87  of the memory  118  to decide the imaging conditions according to the selected imaging mode. Then the CPU  45  generates a control command designating the decided imaging conditions and controls the respective components of the  116  according to the control command. In this embodiment, the  116  sends out a radio wave  14   a  to an external apparatus, like a data transceiver, but does not receive a radio wave  14   b  from the external apparatus. 
     It is also possible to configure a workstation  13  such that a processor  120  of the workstation  13  makes the image analysis and generates the control commands in place of the data transceiver  12  of the first embodiment or the  116 . In this embodiment, as shown in  FIG. 20 , a data transceiver  121  is wirelessly connected to the processor  120  of the workstation  13 . Then, (1) a capsule endoscope  11  sends the image data and the multi-point distance information to the  121  on a radio wave  14   a,  and (2) the image data and the multi-point distance information are sent from the  121  to the  120  on a radio wave  14   c.  So the  120  analyzes the image data and generates the control commands, and (3) the control commands are sent from the workstation  13  to the  121  on a radio wave  14   d,  and then (4) the control commands are sent from the  121  to the  11  on a radio wave  14   b.    
     Namely, the  121  relays or translates the image data and the multi-point distance information from the  11  to the  13 , and also relays the control commands from the  13  to the  11 . For this purpose, the  121  is provided with an antenna  122  and a receiver-transmitter circuit  123 , which are capable of multi-data-communication. The radio wave  14   a  from the  11  is received on the  122  and is fed through the  123  to a demodulator circuit  62 , to be demodulated into the original image data and the multi-point distance information. After the image data is processed in an image processing circuit  63 , the processed image data and the multi-point distance information are modulated into the radio wave  14   c  in a modulator circuit  61 . Note that the unprocessed image data may be modulated into the radio wave  14   c.  The radio wave  14   c  is fed through the  123  to the  122 , so the image data and the multi-point distance information are wirelessly sent from the  121  to the  120 . 
     The radio wave  14   d  as received on the  122  from the  120  is fed through the  123  to the demodulator circuit  62 . Directly after the demodulator circuit  62  demodulates the radio wave  14   d  into the original control command, the modulator circuit  61  modulates the control command into the radio wave  14   b.  The radio wave  14   b  is output through the  123  to the  122 , so the control command is wirelessly sent from the  121  to the  11 . 
     The  120  exchanges data, including the image data, the multi-point distance information and the control commands, with the  121  by way of an antenna  125 . The  120  is provided with a receiver-transmitter circuit  126 , a demodulator circuit  127 , an image analyzer circuit  129 , a database  130  and a modulator circuit  131 , beside those components which are described above with reference to  FIG. 11 , including a CPU  90 , an LCD driver  92 , and a data storage  95 . 
     The  129  has the same function as the image analyzer circuit  67  of the first embodiment. The database  130  corresponds to the database  68  of the  12  of the first embodiment, and stores an imaging condition table  87 . When the image data and the multi-point distance information is fed from the demodulator circuit  127 , the  129  executes the imaging mode selection processes as described above with respect to the image analyzer circuit  67 . 
     The result of judgment and other data obtained by the  129  are output to the CPU  90 . On the basis of the result of judgment, the CPU  90  generates a control command with reference to the imaging condition table  87  of the database  130 , and outputs the control command to the modulator circuit  131 . 
     The modulator circuit  131  modulates the control command into the radio wave  14   d  and outputs the radio wave  14   d  through the  126  to the antenna  125 , so the radio wave  14   d  representative of the control command is sent from the  120  to the  121 . 
     The control command is wirelessly sent via the  121  to the  11  in the manner as described above. Then the  11  captures images in the imaging mode designated by the control command. Providing the  13  with the function to execute the image analysis and the control command generation contributes to making the data transceiver  121  compact and minimizing the capsule endoscope. 
     Although the above described embodiments execute the image analysis and the control command generation in one of the data transceiver, the capsule endoscope and the processor, these embodiments are not limiting the present invention. It may be possible to provide all of the data transceiver, the capsule endoscope and the processor with the function for executing the image analysis and the control command generation, so that one of them is selected to execute this function. 
     In the first embodiment, the judgment as to whether any area of concern  80  exits in the check zone C of the present image frame is made on the basis of similarity between the individual small blocks Bs of the check zone C, which is detected by comparing image characteristic values of the adjoining small blocks Bs. On the other hand, in the second embodiment, the judgment as to whether any area of concern  80  exits in the check zone C of the present image frame is made on the basis of similarity between the check zone C of the present image frame and the check zone C of the preceding image frame, which is detected by comparing image characteristic values of each individual small block Bs of the present image frame with those of the corresponding small blocks Bs of the preceding image frame. It is possible to execute the judgment process of the first embodiment and the judgment process of the second embodiment continually and simultaneously. Thereby the judgment about the presence of the area of concern  80  would be more precise. 
     Although the above described embodiments vary the zooming magnification and the exposure value stepwise in the special imaging mode for capturing successive images of the area of concern  80 , the present invention is not limited to these embodiments, but it is possible to vary other factors of the imaging conditions stepwise. For example, it is possible to vary the focusing position or the kind or the number of the illuminator light sources. Then, the imaging device may capture images of the area of concern  80  at least once under proper focusing condition or proper lighting condition. Thus, high quality endoscopic images of the area of concern  80  would be obtained. 
     In the first embodiment makes the judgment about the presence of those small blocks Bs whose image characteristic values vary relatively largely from ones of other small blocks Bs by comparing differences in the image characteristic values between every couple of adjoining small blocks Bs with the threshold values. However, the present invention is not limited to this method, but any other similarity judging methods are usable to judge the presence of the small blocks Bs having different image characteristic values from others. For example, it is possible to calculate a degree of similarity in the image characteristic values between adjoining small blocks Bs by calculating a square sum of the differences, and compare the similarity degree with a predetermined threshold value. The same applies to the second embodiment. 
     Although the second embodiment makes the judgment as to whether there is any area of concern  80  in the check zone C of the present image frame on the basis of the similarity in the image characteristic values between the corresponding small blocks Bs of the respective check zones C of the present and preceding image frames, the present invention is not limited to this method. It is alternatively possible to calculate a degree of similarity between the respective check zones of the present and preceding image frames based on image characteristic values extracted from the cropped image data of the present image frame and ones of the preceding image frame. It is also possible to calculate a degree of similarity between the present and preceding image frames based on image characteristic values extracted respectively from the image data of the present and preceding image frames. 
     Although the judgment as to whether any area of concern  80  exits or not is made concerning the check zone C of the present image frame in the first and second embodiments, it is possible to check the presence of area of concern  80  across the whole imaging field A of the present image frame. 
     Although the illustrated capsule endoscopes change the zooming magnification by varying the focal length of the optical lens system, it is possible to vary the zooming magnification electronically. Where the zooming magnification is electronically varied, it is possible to make the field of view of the capsule endoscope variable by varying the magnification of the endoscopic image electronically through processing an image signal obtained by the imaging device  33 . 
     In the above described embodiments, the capsule endoscope is switched to the special imaging mode only when it is judged that an area of concern  80  exits in the check zone C of the present image frame. However, it is possible to switch the capsule endoscope to the special imaging mode at predetermined intervals, i.e. periodically or at every traveling distance. 
     Although the multi-point ranging of the imaging field A, see  FIG. 3 , is carried out by the active multi-point ranging sensor  41  in the above embodiments, the present invention is not limited to this method. For example, such a multi-focus multi-point ranging method as known from JPA 2003-037767 is applicable, wherein an optimum focus position to each individual ranging block B of the imaging field A is detected while changing the position of a focus lens from far to near, and estimate distances to the respective ranging blocks B by the detected focus positions. It is also possible to apply such a stereo-type multi-point ranging method as known from JPA 2007-151826 or JPA 2006-093860 to a capsule endoscope, wherein the capsule endoscope is provided with at least two sets of objective lens systems having parallel optical axes and imaging devices disposed behind the respective lens systems, so that distances to the respective ranging blocks B are detected based on parallaxes between images captured simultaneously by these imaging devices. 
     Thus, the present invention is not to be limited to the above embodiments but, on the contrary, various modifications will be possible without departing from the scope of claims appended hereto.