Patent Publication Number: US-9846027-B2

Title: Measuring apparatus, method, and program

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the benefit under 35 U.S.C. Section 111, of International Application Number PCT/JP2009/050168, filed Jan. 9, 2009, which claimed priority to Japanese application Number 2008-002130, filed Jan. 9, 2008, the contents of which are incorporated herein by reference. 
     TECHNICAL FIELD 
     The present invention relates to a measuring apparatus, method and program, and more particularly to a measuring apparatus, method and program with which a distance between two points that are not within one photographing range can be measured. 
     BACKGROUND ART 
     There have been an imaging device, such as a digital camera, which can be connected to a microscope so as to measure a distance between two points on the photographed digital image. In the case of such a conventional imaging device, however, only a distance between two points existing in a same photographic field of view (hereafter also called “photographing range”) can be measured, therefore a dedicated apparatus, such as a measuring microscope and a range finder, is used for measuring a distance between two points that are not within one photographing range (e.g. see Patent Document 1).
     [Patent Document 1] Patent No. 3652014   

     Such a dedicated apparatus, however, is expensive, and a simple means for measuring a distance between two points that are not within one photographing range is demanded for a microscope other than a measuring microscope. 
     DISCLOSURE OF THE INVENTION 
     With the foregoing in view, it is an object of the present invention to provide means for measuring a distance between two points that are not within one photographing range. 
     A measuring apparatus according to a first aspect of the present invention is a measuring apparatus for measuring a distance between two points of a start point and an end point, using a plurality of images photographed while shifting a photographing range of a measurement target, comprising: coordinate calculation means for calculating coordinates of the start point in an image in which the start point is set, and coordinates of the end point in an image in which the end point is set, and storing the calculated coordinates in a storage unit; representative point setting means for setting a representative point in the image in which the start point is set, at the position of coordinates that are different from those of the start point, storing the coordinates of the representative point and characteristic quantity of a neighborhood image, searching the representative point that is set most recently in each image after the image in which the start point is set to the image in which the end point is set, setting a new representative point at the position of coordinates that are different from the coordinates of the detected representative point, and storing the coordinates of the new representative point and characteristic quantity of the neighborhood image in the storage unit; representative point searching means for searching the representative point in each image from the image in which the start point is set to the image in which the end point is set, based on the characteristic quantity of the neighborhood image of the representative point that is set most recently, and storing the coordinates of the detected representative point in the storage unit; vector calculation means for calculating a vector between two points in a same image respectively, for the start point and the representative point in the image in which the start point is set, for the representative points which are set at different positions in a same image, and for the representative point and the end point in the image in which the end point is set, using the stored coordinates of the start point, the representative points and the end point; and distance calculation means for calculating a distance between the start point and the end point based on the vector from the start point to the end point, that is determined by adding all the calculated vectors. 
     A measuring method according to the first aspect of the present invention is a measuring method for measuring a distance between two points of a start point and an end point, using a plurality of images photographed while shifting a photographing range of a measurement target, comprising: a start point coordinate obtaining step of obtaining coordinates of the start point in an image in which the start point is set; a first representative point setting step of setting, in the image in which the start point is set, a representative point which is different from the start point, and obtaining the coordinates of the representative point which is set and characteristic quantity of a neighborhood image; a representative point searching step of searching the representative point in each image from the image in which the start point is set to the image in which the end point is set, based on the characteristic quantity of the neighborhood image of the representative point that is set most recently, and obtaining the coordinates of the representative point that is set most recently; a second representative point setting step of setting a new representative point at the position of coordinates that are different from the coordinates of the representative point detected in the representative point searching step, and obtaining the coordinates of the new representative point and the characteristic quantity of the neighborhood image; an end point coordinate obtaining step of obtaining coordinates of the end point in the image in which the end point is set; a vector calculation step of calculating a vector between two points in a same image respectively, for the start point and the representative point in the image in which the start point is set, for the representative points which are set at different positions in the same image, and for the representative point and the end point in the image in which the end point is set, using the obtained coordinates of the start point, the representative points and the end point; and a distance calculation step of calculating a distance between the start point and the end point based on the vector from the start point to the end point that is determined by adding all the calculated vectors. 
     A program according to the first aspect of the present invention is a program for causing a computer to execute a processing for measuring a distance between two points of a start point and an end point, using a plurality of images photographed while shifting a photographing range of a measurement target, the program causing the computer to execute the processing comprising: a start point coordinate obtaining step of obtaining coordinates of the start point in an image in which the start point is set; a first representative point setting step of setting, in the image in which the start point is set, a representative point which is different from the start point, and obtaining the coordinates of the representative point which is set and characteristic quantity of a neighborhood image; a representative point searching step of searching the representative point in each image from the image in which the start point is set to the image in which the end point is set, based on the characteristic quantity of the neighborhood image of the representative point that is set most recently, and obtaining the coordinates of the representative point that is set most recently; a second representative point setting step of setting a new representative point at the position of coordinates that are different from the coordinates of the representative point detected in the representative point searching step, and obtaining the coordinates of the new representative point and the characteristic quantity of the neighborhood image; an end point coordinate obtaining step of obtaining coordinates of the end point in the image in which the end point is set; a vector calculation step of calculating a vector between two points in a same image respectively, for the start point and the representative point in the image in which the start point is set, for the representative points which are set at different positions in the same image, and for the representative point and the end point in the image in which the end point is set, using the obtained coordinates of the start point, the representative points and the end point; and a distance calculation step of calculating a distance between the start point and the end point based on the vector from the start point to the end point that is determined by adding all the calculated vectors. 
     A measuring apparatus according to a second aspect of the present invention is a measuring apparatus for measuring a distance between two different points on a subject surface, comprising: an image forming optical system for forming an image of the subject surface; imaging means for picking up an image formed by the image forming optical system; control means for obtaining at least a photographed image including one of the two different points and a photographed image including the other of the points while relatively shifting the imaging means with respect to the subject surface from the one to the other of the two points, and controlling the imaging means so that a part of areas of the photographed images picked up by the imaging means overlap; setting means for setting a representative point for measuring a distance in the overlapped area, out of the respective photographed images; and calculation means for determining, from each of the photographed images, the difference of coordinates between two points out of the one point, the other point and the representative point existing in each of the photographed images, and calculating a distance between the two points using the difference of the coordinates determined for each of the photographed images. 
     According to the first aspect of the present invention, coordinates of a start point in an image in which the start point is set are stored, a representative point which is different from the start point is set in the image in which the start point is set, coordinates of the representative point which is set and characteristic quantity of the neighborhood image are stored, the representative point is searched using the characteristic quantity of the neighborhood image of the representative point that is set most recently in the respective images from the image in which the start point is set to the image in which the end point is set, coordinates of the dedicated representative point are stored and a new representative point is set, the coordinates of the new representative point and characteristic quantity of the neighborhood image are stored, coordinates of the end point in the image in which the end point is set are stored, a vector between the respective two points connecting two points out of the start point, the representative points and the end point is calculated for each image using the stored coordinates of the start point, the representative points and the end point, and the distance between the start point and the end point is calculated based on the vector from the start point to the end point, which is determined by adding all the calculated vectors. 
     According to the second aspect of the present invention, an image formed by the image forming optical system is picked up, at least a photographed image including one of the two different points on the subject surface and a photographed image including the other of the points are obtained while relatively shifting the imaging means with respect to the subject surface from the one point to the other point, the imaging means is controlled so that a part of areas of the photographed images picked up by the imaging means overlap, a representative point for measuring a distance is set in the overlapped area, out of the respective photographed images, the difference of coordinates between two points out of the one point, the other point and the representative point existing in each of the photographed images is determined from each of the photographed images, and a distance between the two points is calculated using the difference of the coordinates determined for each of the photographed images. 
     According to the first aspect or second aspect of the present invention, a distance between two points that are not within one photographing range can be measured. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram depicting an embodiment of a measuring system to which the present invention is applied; 
         FIG. 2  is a flow chart depicting a measuring processing executed by the measuring system; 
         FIG. 3  is a flow chart depicting a measuring processing executed by the measuring system; 
         FIG. 4  is a diagram depicting an example of the measuring processing; 
         FIG. 5  is a diagram depicting an example of the measuring processing; 
         FIG. 6  is a diagram depicting an example of the measuring processing; 
         FIG. 7  is a diagram depicting an example of the measuring processing; and 
         FIG. 8  is a diagram depicting a method for calculating a distance between two points. 
     
    
    
     EXPLANATION OF REFERENCE NUMERALS 
     
         
           1  measuring system 
           11  microscope 
           12  camera head 
           13  camera control unit 
           42  image processing circuit 
           43  specified position address calculation circuit 
           44  representative point setting circuit 
           45  representative point searching circuit 
           47  CPU 
           48  storage circuit 
           49  measurement result notification circuit 
           50  display element 
           61  vector calculation unit 
           62  distance calculation unit 
           63  control unit 
       
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     Embodiments of the present invention will now be described with reference to the drawings. 
       FIG. 1  is a diagram depicting an embodiment of a measuring system to which the present invention is applied. A measuring system  1  in  FIG. 1  is a system that can measure a distance between two points in a measurement target which is set on a stage  33  of a microscope  11  constituted by a standard observation microscope which is different from a measuring microscope. In the measuring system  1 , a camera head  12  is installed on the microscope  11  so that the imaging surface of a picture element  21  becomes approximately parallel with the image formation surface in the optical system of the microscope  11 , and an interface circuit  23  of the camera head  12  is connected to an interface circuit  41  of a camera control unit  13  via a camera interface cable  14 . A revolver  35  of the microscope  11 , an interface (not illustrated) for providing the formation of the entire microscope  11 , and a CPU (Central Processing Unit)  47  of the camera control unit  13  are inter-connected via a cable  15 . 
     The camera head  12  is comprised of the picture element  21  constituted by a CCD (Charge Coupled Device) or CMOS (Complementary Metal Oxide Semiconductor), an A/D (Analog/Digital) conversion element  22 , and an interface circuit  23 . The camera control unit  13  is comprised of the interface circuit  41 , an image processing circuit  42 , a specified position address calculation circuit  43 , a representative point setting circuit  44 , a representative point searching circuit  45 , a user interface unit  46  constituted by a mouse, touch panel or key switch, the CPU  47 , a storage circuit  48 , a measurement result notification circuit  49 , and a display element  50  constituted by an LCD (Liquid Crystal Display), for example. The CPU  47  implements the functions of a vector calculation unit  61 , distance calculation unit  62  and control unit  63  by executing a predetermined control program. 
     Now the processing when the measurement target being set on the stage  33  of the microscope  11  is photographed and the photographed image is displayed in the measuring system  1  will be described. 
     The light emitted from an illumination apparatus  31  of the microscope  11  is irradiated onto the measured target on the stage  33  via a condenser lens  32 . An image of the illuminated measurement target is formed on the imaging plane of the picture element  21  of the camera head  12  by an objective lens  34  and an image forming optical system, which is not illustrated, in a lens barrel unit  36 . The image of the measurement target is converted into an electric photographing signal by the picture element  21 , and is converted into a digital photographing signal by the A/D conversion element  22 , and is then transferred to the camera control unit  13  via the interface circuit  23  and the camera interface cable  14 . 
     The digital photographing signal which is transferred to the camera control unit  13  is received by the interface circuit  41 , and is supplied to the image processing circuit  42 . The image processing circuit  42  executes a predetermined image processing on the digital photographing signal based on the control by the control unit  63 , and generates a digital image signal. The image processing circuit  42  performs, for example, pixel interpolation processing so that an individual pixel has three data of red, green and blue if the camera head  12  supports colors, or a color balance processing among the red, green and blue data. The image processing circuit  42  also performs pixel defect correction processing, filter processing and contour enhancement processing, for example, when necessary. 
     The image processing circuit  42  supplies the generated digital image signal to the specified position address calculation circuit  43 , representative point setting circuit  44 , representative point searching circuit  45  and display element  50 . The display element  50  displays an image based on the digital image signal that is supplied from the image processing circuit  42 . Hereafter an image based on the digital image signal is also simply called an “image”. 
     In the measuring system  1 , the above photographing processing and display processing are repeatedly executed at a predetermined frame rate, and a plurality of images photographed by the camera head  12  are displayed on the display element  50  of the camera control unit  13 . 
     The stage  33  of the microscope  11  can be moved in the lateral direction (x direction, direction perpendicular to the page face in  FIG. 1  (direction penetrating the page face from top to bottom)), longitudinal direction (y direction, lateral direction on the page face in  FIG. 1 ), and vertical direction (z direction, longitudinal direction on the page face in  FIG. 1 ) of the microscope  11 . By moving the stage  33  in the lateral direction, the photographing range of the measurement target on the stage  33  by the camera head  12  moves in the lateral direction (x direction), and by moving the stage  33  in the longitudinal direction, the photographing range of the measurement target on the stage  33  by the camera head  12  moves in the longitudinal direction (y direction). 
     Now the measuring processing executed by the measuring system  1  will be described according to the flow charts in  FIG. 2  and  FIG. 3  with reference to  FIG. 4  to  FIG. 8 . 
     To measure a distance between two points of the measurement object on the stage  33  of the microscope  11  using the measuring system  1 , the user moves the stage  33  of the microscope  11  while viewing the image displayed on the display element  50 , and sets the start point of the distance to be measured, via the user interface unit  46 . And when the information to indicate the position of the start point, which is set by the user, is supplied from the user interface unit  46  to the control unit  63 , this measuring processing is started. 
     For example, this measuring processing is started when the start point Ps is set while the image G 1  in  FIG. 4  is displayed on the display element  50 , and the information to indicate the position of the start point Ps is supplied from the user interface unit  46  to the control unit  63 . In  FIG. 4  and the later mentioned  FIG. 5  to  FIG. 7 , only a range of the image that is photographed by the camera head  12  and displayed on the display element  50  is shown, where the dots and shaded portion are merely for assisting explanation, and are not in the actual photographed and displayed image. 
     In step S 1 , the specified position address calculation circuit  43  calculates the coordinates of the start point in the coordinate system in the image currently obtained, and stores the result. In concrete terms, the control unit  63  of the CPU  47  supplies the information to indicate the position of the start point set by the user to the specified position address calculation circuit  43 . The specified position address calculation circuit  43  calculates the coordinates of the start position in the image in which the start position is set, and has the storage circuit  48  store the result. 
     In step S 2 , the representative point setting circuit  44  sets a representative point in the image in which the start point is set, based on the control of the control unit  63 . For example, in the image in which the start point is set, a pixel which is in a different position from the start point, where predetermined characteristic quantity is maximum, and is easy to distinguish from other pixels, is set to the representative point. Examples of the characteristic quantity used for setting the representative point are contrast or edge intensity and color information, which are obtained from each pixel and adjacent pixels thereof. 
     Further, before the representative point extends out of the image in the next frame by movement of the stage  33  of the microscope  11 , a representative point is set out of the pixels in the center portion Rc which is a range which is away from the four sides of the image G 1  by the distance d (unit is a pixel) as shown in  FIG. 4 . Here the distance d is calculated by the following Expression (1).
 
[Expression 1]
 
 d =(maximum moving speed (mm/sec.) of stage×magnification of objective lens/(frame rate (fps)×pixel pitch (mm))×α  (1)
 
     In Expression (1), the maximum moving speed of the stage indicates a maximum value of a moving distance of the stage  33  in one second, that can be assumed to be the standard method of use. α denotes a margin ratio and is set to 1.1. In other words, the distance d is a maximum value (assumed value) of the distance that a pixel moves in one frame by moving the stage  33  multiplied by the margin ratio. Therefore as  FIG. 4  shows, it becomes less likely for the representative point Pr 1  to extend out of the image in the next frame by setting the representative point Pr 1  in the center portion Rc of the image G 1 . 
     The pixel pitch of the picture element  21  used for Expression (1) is a value uniquely determined by the camera to be used. The frame rate of the camera head  12  is set in the communication control unit  13  by communication with the camera head  12  or the setting by the user. 
     In step S 3 , the coordinates of the representative point and characteristic quantity of the neighborhood image are obtained by the representative point setting circuit  44 . In the case of the example in  FIG. 4 , for example, the representative point setting circuit  44  has the storage circuit  48  store the coordinates of the representative point Pr 1 , and also obtains the pixel value in a predetermined range (e.g. 5×5 pixels) in a predetermined range centering around the representative point Pr 1  as the characteristic quantity of the neighborhood image of the representative point Pr 1 , and has the storage circuit  48  store it. The characteristic quantity of the neighborhood pixels of the representative point is not limited to the pixel values, but a value obtained by performing various filter processings and image transformation processings on the neighborhood pixels of the representative point may be used. 
     In step S 4 , the control unit  63  determines whether the end point is set. If it is determined that the end point is not set, the processing advances to step S 5 . 
     In step S 5 , the control unit  63  determines whether a new image in a different photographing range is obtained. If it is determined that a new image is not obtained, the processing returns to step S 4 , and the processings in step S 4  and step S 5  are repeatedly executed until it is determined that the end point is set in step S 4 , or until it is determined that a new image is obtained in step S 5 . 
     If it is determined that a new image in a different photographing range is obtained in step S 5 , on the other hand, the processing advances to step S 6 . 
     In step S 6 , the representative point searching circuit  45  searches a representative point that is most recently set in a new image based on control by the control unit  63 . In concrete terms, the representative point searching circuit  45  reads the characteristic quantity of the neighborhood image of the representative point that is set most recently that is stored in the storage circuit  48 . The representative point searching circuit  45  searches an area where similarity with the read characteristic quantity is maximum and is more than a predetermined threshold, in the new image using such a method as pattern matching. In other words, in the new image, the representative point searching circuit  45  searches an area, which is similar to the neighborhood image of the representative point in the image in which the representative point is set. 
     In step S 7 , the representative point searching circuit  45  determines whether a representative point is found. The representative point searching circuit  45  detects an area, where similarity with the characteristic quantity of the neighborhood image of the representative point is maximum and is more than a predetermined threshold, in a new image, and determines that a representative point is found and processing advances to step S 8  if the position of the representative point that is set most recently is specified. 
     In step S 8 , the control unit  63  determines whether setting a new representative point is necessary. For example, if the representative point Pr 1  is detected in the edge Re, which is in a range outside the center portion Rc of the image G 2 , as shown in  FIG. 5 , the representative point searching circuit  45  determines that setting a new representative point is necessary, and the processing advances to step S 9 . 
     In step S 9 , the camera control unit  13  stores the coordinates of the representative point in the new image. For example, the representative point searching circuit  45  has the storage circuit  48  store the coordinates of the representative point Pr 1  in the image G 2 . 
     In step S 10 , the representative point setting circuit  44  sets a new representative point based on control by the control unit  63 . For example, the representative point setting circuit  44  sets a new representative point Pr 2  in the center portion Rc in the image G 2  by a similar processing as step S 2 . 
     Then the processing returns to step S 3 , and in step S 3 , the coordinates of the newly set representative point and the characteristic quantity of the neighborhood image are stored in the storage circuit  48 . In this way, the representative point that is set most recently is searched in the new image, and the coordinates of the detected representative point are stored, then the new representative point is set, and the coordinates of the newly set representative point and the characteristic quantity of the neighborhood image are stored, whereby the new representative point is set for the new image. 
     Then the processings in step S 3  to step S 10  are repeated until it is determined that the end point is set in step S 4  or until it is determined that a representative point cannot be found out in step S 7 . 
     On the other hand, in step S 8 , if the representative point searching circuit  45  detects the representative point Pr 1  in the center portion Rc of the newly obtained image G 2 , for example, the control unit  63  determines that setting a new representative point is not necessary, and processing returns to step S 4  without performing the processings in step S 9  and step S 10 , and step S 4  and subsequent processings are executed. In other words, if the representative point exists in the center portion Rc, a new representative point is not set, but the representative point detected by the representative point searching circuit  45  is continuously used. Thereby the processing time can be decreased and the storage capacity required for storing the coordinates of representative points can be decreased. In the present invention, the processing in step S 8  is not always necessary, and this processing in step S 8  may be omitted if an increase in the processing times causes any problems. 
     If it is determined that a representative point is not detected in the newly obtained image in step S 7 , that is, for example, if a representative point extends out from the image, or if an area, where similarity with the characteristic quantity of a neighborhood image of the representative point is maximum and is more than the predetermined threshold, could not be detected in the new image in step S 6  due to the influence of noise or other factors, processing advances to step S 11 . 
     In step S 11 , the measurement result notification circuit  49  notifies the failure of measurement based on control by the control unit  63 . For example, the measurement result notification circuit  49  notifies the failure of measuring the distance by displaying a predetermined message or image on the display element  50 , or lighting or flashing a lamp, which is not illustrated. Then the measurement process ends. 
     After setting the start point of a distance to be measured, the user moves the stage  33  of the microscope  11  while viewing the image displayed on the display element  50 , and sets the coordinates of the end point of the distance to be measured via the user interface unit  46 . When the information to indicate the position of the end point set by the user is supplied from the user interface unit  46  to the control unit  63 , it is determined that the end point is set in step S 4 , and processing advances to step S 12 . 
     Here, the explanation will be made using, as an example, a case in which the representative point Pr 2  is detected in the edge portion Re in the image G 3  in  FIG. 6  after the representative point PR 2  is set in the image G 2  in  FIG. 5  as mentioned above, the representative point Pr 3  is newly set, the Pr 3  is detected in the edge portion Re in the image G 4  in  FIG. 7 , and the end point Pe is set after the representative point Pr 4  is newly detected. 
     In step S 12 , the representative point searching circuit  45  detects the representative point that is set most recently in the image in which the end point is set, and stores the coordinates of the representative point. 
     Also in step S 12 , the coordinates of the end point are calculated in similar processing as step S 1  and stored in the storage circuit  48 . 
     In step S 13 , the vector calculation unit  61  calculates the vectors between the respective two points using the coordinates of the start point and the representative point which was set when the start point was set, coordinates of the representative point searched and detected in a same image and the newly set representative point in this image, and the coordinates of the representative point which was searched and detected when the end point was set, which are stored in the storage circuit  48 . Needless to say, if there are a plurality of images in which searching of the representative point that is set most recently and setting a new representative point were preformed in a same image respectively from the setting of the start point to the end point, the vectors between the representative points searched and detected for a same number of times as the number of images and newly set representative points, are calculated. 
     To calculate the vectors, the vector v 1  (X 1 , Y 1 ) from the start point Ps to the representative point Pr 1  is determined by subtracting the coordinates of the start point Ps from the coordinates of the representative point Pr 1  in the image G 1  in  FIG. 4 , for example. In the same way, the vector v 2  (X 2 , Y 2 ) from the representative point Pr 1  to the representative point Pr 2  is determined by subtracting the coordinates of the representative point Pr 1  from the coordinates of the representative point Pr 2  in the image G 2  in  FIG. 5 , the vector v 3  (X 3 , Y 3 ) from the representative point Pr 2  to the representative point Pr 3  is determined by subtracting the coordinates of the representative point Pr 2  from the coordinates of the representative point Pr 3  in the image G 3  in  FIG. 6 , the vector v 4  (X 4 , Y 4 ) from the representative point Pr 3  to the representative point Pr 4  is determined by subtracting the coordinates of the representative paint Pr 3  from the coordinates of the representative point Pr 4  in the image G 4  in  FIG. 7 , and the vector v 5  (X 5 , Y 5 ) from the representative point Pr 4  to the end point Pe is determined by subtracting the coordinates of the representative point Pr 4  from the coordinates of the end point Pe in the image G 4 . 
     In step S 14 , the distance calculation unit  62  determines the distance between the start point and the end point. The distance between the start point and the end point can be calculated by calculating the total of each vector from the start point to the end point, and the vector from the start point to the end point can be determined by adding all the vectors calculated in step S 13 . 
     For example, as  FIG. 8  shows, the vector V se  from the start point Ps to the end point Pe can be determined by adding the vectors v 1  to v 5 . Therefore the distance Di (unit: pixel) on the image from the start point Ps to the end point Pe is determined by the following Expression (2).
 
[Expression 2]
 
 Di=| {right arrow over (V se )}|=√{square root over (( X 1+ X 2+ X 3+ X 4+ X 5) 2 +( Y 1+ Y 2+ Y 3+ Y 4+ Y 5) 2 )}  (2)
 
     The distance Da (unit: mm) between the start point Ps and the end point Pe on the actual measurement target is determined by the following Expression (3).
 
 Da=Di x  pixel patch÷magnification of objective lens   (3)
 
     The distance calculation unit  62  obtains the magnification of the objective lens  34  being used for photographing the measurement target by obtaining the setting position of the revolver  35  via the cable  15 , for example. The user may set the magnification of the objective lens  34  being used for photographing the measurement target in the distance calculation unit  62 . 
     It is also acceptable to specify, to the camera control unit  13 , a range corresponding to 1 mm in the image photographed by the camera head  12 , cause the camera control unit  13  to learn how many pixels correspond to 1 mm, and calculate the actual distance Da by the following Expression (4) using this value (unit: pixels/mm) (hereafter called “calibration value”).
 
 Da=Di ÷calibration value   (4)
 
     In step S 15 , the measurement result notification circuit  49  notifies the measurement result based on the control by the control unit  63 . For example, the measurement result notification circuit  49  displays the measured distance between the start point and the end point on the display element  50 . Then measurement processing ends. 
     In this way, the distance between two points that are not within one photographing range can be easily measured merely by connecting the camera head  12  and the camera control unit  13  to the microscope  11 . 
     In the above description, an example of setting a new representative point when a representative point is detected in the edge portion Re of each image was shown, but a new representative point may be set for each frame in images after the image in which the start point is set to the image in which the end point is set, omitting the processing in step S 8 . In this case, the processing time and the capacity required for storing the coordinates of the representative points increase, but the probability of a representative point extending out of the image and causing a failure of measurement can be decreased. 
     The CPU  47  can obtain the operation sate of the microscope  11 , such as the moving information of the stage  33 , via the cable  15 , in addition to the magnification information of the objective lens  34 . Therefore in step S 8 , for example, the control unit  63  may obtain the moving information of the stage  33  from the microscope  11 , and determine whether setting a new representative point is required or not based on the quantity of change of the imaging range caused by movement of the stage  33 . 
     The position to set a representative point may be fixed, such as a pixel at the center of each image. Thereby the time required for processing to set a representative point can be decreased. In this case, however, a representative point may be set in a pixel of which contrast or edge intensity is weak, which increases the probability of error in detecting a representative point during search processing. 
     Further, in the above description, an example of moving the photographing range of the measurement target by moving the stage  33  of the microscope  11  was shown, but the photographing range may be moved by moving the camera head  12  in a direction parallel to the top face of the stage  33 . 
     Also in the above description, an example of measuring the distance between two points was shown, but in the measuring system  1 , a vector of two points which are not within one photographing range can be calculated. Hence a positional relationship of three or more points, which are not within one photographing range, can be determined, and for example, the shape of a graphic (e.g. circle) determined by a plurality of points, and the angle between two sides, can be measured. 
     Further, in the above description, an example of applying the present invention to a system for measuring a distance between two points using a microscope was described, but the present invention can be applied to a device and system measuring the distance between two points which are set on a moving image of a photographed measurement target, regardless whether the measurement target is optically enlarged or reduced. 
     The above mentioned series of processings may be executed by hardware or software. To execute the series of processings by software, programs constituting the software are installed from a program recording media onto a computer built into dedicated hardware or a general purpose personal computer that can execute various functions by installing various programs. 
     The programs executed by the computer may be programs in which the processings are performed in a time series according to the sequence explained in the present description, or may be programs in which the processings are performed in parallel, or at a required timing, such as when called up. 
     In the present description, the term “system” refers to a complete device that is constituted by a plurality of apparatuses and means. 
     Embodiments of the present invention are not limited to the above mentioned embodiments, but numerous modifications can be made without departing from the spirit and scope of the invention.