Patent Publication Number: US-8531479-B2

Title: Endoscope apparatus and program

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an endoscope apparatus, which performs measurement on the basis of image data obtained by imaging a subject, and a program. 
     2. Description of Related Art 
     Industrial endoscope apparatuses are used to observe or check inside damage, corrosion, and the like of a boiler, a turbine, an engine, a pipe, and the like. Moreover, among the endoscope apparatuses, there is an endoscope apparatus having a function of measuring the lengths area and the like using the principle of triangulation on the basis of a measurement point designated on an image imaged by the endoscope. This endoscope apparatus has a plurality of kinds of optical adapters prepared to observe and check various objects, and a tip portion of the endoscope apparatus can be replaced. 
     An example of such an optical adapter includes a stereo optical adapter capable of imaging two subject images of the same subject. Using the stereo optical adapters the length, area and the like of the subject can be measured by calculating the three-dimensional spatial coordinates of the subject using the principle of triangulation on the basis of the coordinates of left and right optical system distance calculating points when the subject image is captured by the left and right optical systems. 
       FIG. 24  shows a display screen of an endoscope apparatus. A left image  901 L and a right image  901 R corresponding to left and right subject images captured by a stereo optical adapter are displayed on a display screen  900  shown in  FIG. 24 . In addition, cursors  902   a  and  902   b  for designating measurement points indicating measurement positions are displayed on the display screen  900 . The user can move the cursors  902   a  and  902   b  within the display screen  900  by inputting the movement instruction of the cursor  902   a  to the endoscope apparatus. 
     The display position of the cursor  902   a  is set on the basis of the instruction that the user inputs to the endoscope apparatus. When the cursor  902   a  is set in the left image  901 L, the matching process of calculating the position of a corresponding point on the right image  901 R corresponding to the display position of the cursor  902   a  is executed. The position of the corresponding point becomes the display position of the cursor  902   b . In addition, an image in which a surrounding region of the cursor  902   a  is enlarged is displayed in a zoom window  903   a , and an image in which a surrounding region of the cursor  902   b  is enlarged is displayed in a zoom window  903   b . Japanese Unexamined Patent Publication First Publication No. 2009-86553 discloses an endoscope apparatus which displays the same zoom windows as described above. 
     SUMMARY OF THE INVENTION 
     An endoscope apparatus according to an aspect of the invention includes: an imaging portion that images a subject to generate image data; a designation portion that designates a position in an image based on the image data; an image processing portion that processes the image data such that an enlarged image obtained by enlarging an image in a second region including the designated position overlaps a first region including the designated position designated by the designation portion; a display portion that displays the enlarged image and the image of the subject based on the image data processed by the image processing portion and displays a cursor at the designated position on the enlarged image; and a measurement processing portion that performs measurement on the basis of a measurement position indicated by the cursor by using the image data generated by the imaging portion. 
     The enlarged image displayed on the display portion moves according to the movement of the cursor. A program that controls an operation of an endoscope apparatus according to an aspect of the invention causes the endoscope apparatus to execute: a step of imaging a subject to generate image data; a step of designating a position in an image based on the image data; a step of processing the image data such that an enlarged image obtained by enlarging an image in a second region including the designated position overlaps a first region including the designated position that has been designated; a step of displaying the enlarged image and the image of the subject based on the image data processed by the image processing portion and displaying a cursor at the designated position on the enlarged image; and performing measurement on the basis of a measurement position indicated by the cursor by using the image data generated by the imaging portion. The enlarged image displayed on the display portion moves according to movement of the cursor. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view illustrating the entire configuration of an endoscope apparatus according to an embodiment of the invention. 
         FIG. 2  is a block diagram illustrating the internal configuration of the endoscope apparatus according to the embodiment of the invention. 
         FIG. 3  is a block diagram illustrating the functional configuration of a CPU provided in the endoscope apparatus according to the embodiment of the invention. 
         FIG. 4  is a flow chart illustrating the procedure of an operation of the endoscope apparatus according to the embodiment of the invention. 
         FIG. 5  is a flow chart illustrating the procedure of an operation of the endoscope apparatus according to the embodiment of the invention. 
         FIG. 6  is a flow chart illustrating the procedure of an operation of the endoscope apparatus according to the embodiment of the invention. 
         FIG. 7  is a flow chart illustrating the procedure of an operation of the endoscope apparatus according to the embodiment of the invention. 
         FIG. 8  is a flow chart illustrating the procedure of an operation of the endoscope apparatus according to the embodiment of the invention. 
         FIG. 9  is a view illustrating a display screen of the endoscope apparatus according to the embodiment of the invention. 
         FIG. 10  is a view illustrating a display screen of the endoscope apparatus according to the embodiment of the invention. 
         FIG. 11  is a view illustrating a display screen of the endoscope apparatus according to the embodiment of the invention. 
         FIG. 12  is a view illustrating a display screen of the endoscope apparatus according to the embodiment of the invention. 
         FIG. 13  is a view illustrating a display screen of the endoscope apparatus according to the embodiment of the invention. 
         FIG. 14  is a view illustrating a display screen of the endoscope apparatus according to the embodiment of the invention. 
         FIG. 15  is a view illustrating a display screen of the endoscope apparatus according to the embodiment of the invention. 
         FIG. 16  is a view illustrating a display screen of the endoscope apparatus according to the embodiment of the invention. 
         FIG. 17  is a view illustrating a display screen of the endoscope apparatus according to the embodiment of the invention. 
         FIG. 18  is a view illustrating a display screen of the endoscope apparatus according to the embodiment of the invention. 
         FIG. 19  is a view illustrating a display screen of the endoscope apparatus according to the embodiment of the invention. 
         FIG. 20  is a view illustrating a display screen of the endoscope apparatus according to the embodiment of the invention. 
         FIG. 21  is a view illustrating a display screen of the endoscope apparatus according to the embodiment of the invention. 
         FIG. 22  is a view illustrating a display screen of the endoscope apparatus according to the embodiment of the invention. 
         FIG. 23  is a reference view for explaining the method of calculating the three-dimensional coordinates of a measurement point using stereo measurement. 
         FIG. 24  is a view illustrating a display screen of a known endoscope apparatus. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Hereinafter, embodiments of the invention will be described with reference to the drawings.  FIG. 1  shows the configuration of an endoscope apparatus according to an embodiment of the invention. As shown in  FIG. 1 , an endoscope apparatus  1  includes an endoscope  2  and an apparatus body  3  connected to the endoscope  2 . The endoscope  2  includes a long and thin inserted portion  20  and an operating portion  6  for performing an operation required in executing various kinds of operation controls of the entire apparatus. The apparatus body  3  includes a monitor  4  (liquid crystal display), which is a display device that displays an image of a subject imaged by the endoscope  2 , contents of an operation control (for example, a processing menu), and the like, and a housing  5  having a control unit  10  (refer to  FIG. 2 ). 
     The inserted portion  20  is formed by connecting a hard tip portion  21 , a bent portion  22  which can be bent, for example, in the upper, lower, left, and right directions, and a flexible tube portion  23  with the flexibility sequentially from the tip side. Various kinds of optic adapters, such as a stereo optical adapter having two observation fields of view or a normal observation optical adapter having one observation field of view, are freely attached to the tip portion  21  or detached from the tip portion  21 . In the present embodiment, when performing measurement, left and right images which are a pair of subject images on the left and right sides are imaged by the stereo optical adapter capable of imaging two subject images of the same subject. 
     As shown in  FIG. 2 , an endoscope unit  8 , a CCU  9  (camera control unit), and a control unit  10  are provided in the housing  5 . A proximal end of the inserted portion  20  is connected to the endoscope unit  8 . The endoscope unit  8  is configured to include a light source driving device, which drives a light source (LED  29 ) built in the tip portion  21 , and a bending device for bending the bent portion  22  provided in the inserted portion  20 . 
     A imaging device  28  and the LED  29  are built in the tip portion  21 . The imaging device  28  generates an image signal by performing photoelectric conversion of a subject image formed through the optical adapter. The image signal output from the imaging device  28  is input to the CCU  9 . The image signal is converted into a video signal (image data), such as an NTSC signal, in the CCU  9  and is then supplied to the control unit  10 . The LED  29  generates illumination light irradiated to the subject. In the present embodiment, the LED  29  is provided in the tip portion  21 . However, the LED  29  may be disposed in the housing  5  so that the illumination light generated by the LED  29  is guided to the tip portion  21  through the optical fiber. In addition, other illumination excluding the LED may be used. 
     A video signal processing circuit  12  to which a video signal is input, a ROM  13 , a RAM  14 , a card I/F  15  (card interface), a USB I/F  16  (USB interface), an RS-232C I/F  17  (RS-232C interface), and a CPU  18  that executes these various functions on the basis of a main program and performs various controls are provided in the control unit  10 . 
     The CCU  9  and the endoscope unit  8  are connected to the RS-232C I/F  17 . In addition, the operating portion  6  which performs control and operation instructions of the CCU  9 , endoscope unit  8 , and the like is connected to the RS-232C I/F  17 . When a user operates the operating portion  6 , a communication required in controlling the CCU  9  and the endoscope unit  8  is performed on the basis of the operation. 
     The USB I/F  16  is an interface for electrically connecting the control unit  10  and a personal computer  31  with each other. By connecting the control unit  10  with the personal computer  31  trough the USB I/F  16 , various kinds of instruction controls, such as an instruction to display an endoscope image at the side of the personal computer  31  or image processing at the time of measurement can be performed. In addition, input and output of various kinds of control information or data, which is required for processing, between the control unit  10  and the personal computer  31  can be performed. 
     In addition, a memory card  32  can be freely attached to the card I/F  15  or detached from the card I/F  15 . By mounting the memory card  32  in the card I/F  15 , capturing of data such as control processing information or image information stored in the memory card  32  into the control unit  10  or recording of data such as control processing information or image information into the memory card  32  can be performed according to the control of the CPU  18 . 
     In order to display a mixed image obtained by mixing an endoscope image based on the video signal supplied from the CCU  9  with an operation menu using a graphic, the video signal processing circuit  12  performs processing for mixing a graphic image signal based on the operation menu, which is generated by the control of the CPU  18 , with the video signal from the CCU  9 , processing required for display the mixed image on the screen of the monitor  4 , and the like and supplies the display signal to the monitor  4 . In addition, the video signal processing circuit  12  may also perform processing for simply displaying an endoscope image or an image of an operation menu, independently. Accordingly, the endoscope image, the operation menu image, or the mixed image obtained by mixing the endoscope image with the operation menu image is displayed on the screen of the monitor  4 . 
     The CPU  18  controls an operation of the entire endoscope apparatus  1  by executing a program stored in the ROM  13  in order to control various circuit portions to perform desired processings. The CPU  18  uses the RAM  14  as a working area for temporarily storing data. 
       FIG. 3  shows the functional configuration of the CPU  18 . A cursor position designating portion  41  (designating portion) designates a position (cursor position) at which a cursor is displayed in the image displayed on the monitor  4 , on the basis of the result when the user has operated a cursor moving switch of the operating portion  6 . An enlarged image generating portion  42  (image processing portion) generates data of an enlarged image obtained by enlarging an image in a predetermined region including the cursor position designated by the cursor position designating portion  41 . A graphic processing portion  43  generates a graphic image signal for displaying on the display screen various kinds of information displayed by characters, numeric values, etc., the icon of a cursor, and the like. 
     A matching processing portion  44  performs matching processing for calculating a position of a corresponding point on a right image corresponding to the cursor position on a left age designated by the cursor position designating portion  41 . A measurement processing portion  45  executes processing for calculating the three-dimensional coordinates on the basis of the principle of triangulation or measurement processing for calculating the length, area, and the like of the subject. A main control portion  46  controls assignment of processing to each of the cursor position designating portion  41 , the enlarged image generating portion  42 , the graphic processing portion  43 , the matching processing portion  44 , and the measurement processing portion  45 , and controls the overall operation of the endoscope apparatus  1 . 
     Next, the basic principle of the measurement in the present embodiment will be described.  FIG. 23  shows the positional relationship between two left and right images on the three-dimensional spatial coordinate system with x, y, and z axes.  FIG. 23  shows a state where a point P, which is an object for measuring a distance (object distance) to the subject, is imaged on a right imaging surface  28 R and a left imaging surface  28 L of the imaging device  28 . In  FIG. 23 , it is assumed that points OR and OL are main points of the optical system, a distance f is a focal length, points QR and QL are image locations of the point P, and a distance L is the distance between the point OR and the point OL. In  FIG. 23 , expression (1) is obtained from the straight line QR-OR.
 
 x/xR={y −( L /2)}/{ yR −( L /2)}= z /(− f )   (1)
 
     In addition, expression (2) is obtained from the straight line QL-OL.
 
 x/xL={y +( L /2)}/{ yL +( L /2)}= z /(− f )   (2)
 
     The three-dimensional coordinates of the point P are obtained by solving the expression for x, y and z. As a result, the distance (object distance) from the point OR or the point OL to the subject is calculated. In addition, the three-dimensional length or the three-dimensional area can be calculated by calculating the three-dimensional coordinates of the point P for a plurality of measurement points and performing various operations using the three-dimensional coordinates. 
     Next, the display screen (display portion) of the present embodiment will be described.  FIG. 9  shows a display screen  100  at the start of a measurement mode. A pair of left and right images  101 L and  101 R with parallax, date and time information  103 , measurement operation information  104 , message information  105 , magnifying power information  106 , cursors  108   a  and  108   b , and the like are displayed on the display screen  100 . 
     The display screen  100  is configured to include a display region, which is provided in an I-shape in upper, lower, and middle parts of the screen of the display portion  4 , and two approximately rectangular display regions excluding the I-shaped display region. A left image  101 L is displayed in the left display region shown in the drawing, and a right image  101 R is similarly displayed in the right display region. The date and time information  103  is displayed in the lower part of the I-shaped display region. The measurement operation information  104 , the message information  105 , the magnifying power information  106 , object distance information  107  ( FIG. 12 ), and the like are displayed in the middle part of the I-shaped display region. The cursor  108   a  is displayed on the left image  101 L so as to overlap the left image  101 L, and the cursor  108   b  is displayed on the right image  101 R so as to overlap the right image  101 R. 
     The measurement operation information  104  displays the type of measurement operation, such as the distance between two points, the depth, the area, or the angle. The present embodiment describes the measurement operation of the distance between two points being performed. 
     The message information  105  displays information on the operation or measurement as various kinds of text information or numerical information. For example, in  FIG. 9 , operation guidance (example: “PUT M1” means input of a measurement point of a first point) is displayed. 
     The magnifying power information  106  displays the magnifying power of image displayed in a zoom window which will be described later. 
     The cursors  108   a  and  108   b  are used to input a measurement point on the display screen  100  The position of the cursor  108   a  is calculated by the cursor position designating portion  41  according to the operation input from the cursor moving switch of the operating portion  6 . The position of the cursor  108   b  is calculated by the matching processing portion  44  on the basis of the position of the cursor  108   a.    
     When the zoom switch of the operating portion  6  is operated and display of the zoom window is instructed, zoom windows  109   a  and  109   b  are displayed as shown in  FIG. 10  The zoom window  109   a  is displayed in the left image  101 L, and the zoom window  109   b  is displayed in the right image  101 R. 
     The cursor  108   a  and an enlarged image, which is obtained by enlarging an image within a predetermined range around the cursor  108   a  in the left image  101 L, are displayed in the zoom window  109   a . The cursor  108   b  and an enlarged image, which is obtained by enlarging an image within a predetermined range around the cursor  108   b  in the right image  101 R, are displayed in the zoom window  109   b.  The size of each of the zoom windows  109   a  and  109   b  is 60×60 pixels, for example. When the magnifying power is 2×, enlarged images obtained by enlarging, for example, images within the range of 30×30 pixels on the left and right images  101 L and  101 R are displayed in the zoom windows  109   a  and  109   b , respectively. The shapes of the cursors  108   a  and  108   b  displayed together with the zoom windows  109   a  and  109   b  may be different from those of the cursors  108   a  and  108   b  when the zoom windows  109   a  and  109   b  are not displayed. 
     The user can change the magnifying power of the enlarged image displayed in each of the zoom windows  109   a  and  109   b  by operating the zoom switch of the operating portion  6 . The zoom switch is configured to include a teleswitch for enlargement and a wide switch for reduction. The magnifying power is increased when the teleswitch is operated in a state where the zoom windows  109   a  and  109   b  are displayed. In addition the magnifying power is decreased when the wide switch is operated in a state where the zoom windows  109   a  and  109   b  are displayed. When the magnifying power is 1×, the zoom windows  109   a  and  109   b  are not displayed. 
     In addition, the user can move the zoom windows  109   a  and  109   b  together with the cursors  108   a  and  108   b  by operating the cursor moving switch of the operating portion  6 . For example, when an instruction to move the cursor  108   a  downward is input from the state of  FIG. 10  the zoom windows  109   a  and  109   b  move downward together with the cursors  108   a  and  108   b , as show in  FIG. 11 . In order to reduce the processing load of the endoscope apparatus  1 , the zoom windows  109   a  and  109   b  are not displayed during the movement of the cursor  108   a . The zoom windows  109   a  and  109   b  are displayed when the cursor  108   a  stops. 
     Hereinafter, the transition of the display screen will be described using the point-to-point measurement as an example. In the point-to-point measurement, a first measurement point and a second measurement point are set and the distance between the two points is calculated on the basis of the two measurement points. 
     When the user performs an operation of deciding a measurement point with the cursor moving switch of the operating portion  6  in a state where the cursor  108   a  is displayed at the desired position at which the user wants to set a first measurement point, the first measurement point is set at a position within a region of the zoom window  109   a , for example, at the position where the cursor  108   a  is displayed. Second overlay information, such as the first measurement point, is set on the basis of first overlay information, such as the zoom window  109   a  or the cursor  108   a . Moreover, on the display screen, the first overlay information may move with respect to the second overlay information.  FIG. 12  shows a state where the cursor  108   a  and the zoom window  109   a  have moved with respect to the first measurement point after the first measurement point was set on the basis of the zoom window  109   a . A first measurement point  110   a  is displayed on the left image  101 L, and a corresponding point  110   b  corresponding to the measurement point  110   a  is displayed on the right image  101 R. When the measurement point  110   a  is set, the zoom windows  109   a  and  109   b  become not to be displayed. If necessary, the user may display the zoom windows  109   a  and  109   b  again as shown in  FIG. 12  by operating the zoom switch of the operating portion  6 . 
     In addition, when the measurement point  110   a  is set, the object distance is calculated and the object distance information  107  is displayed. The object distance information  107  indicates the degree of the distance between the tip portion  21  of the inserted portion  20  and the subject. This object distance is calculated by the measurement processing portion  45 . The object distance is expressed by nine square indicators, and a smaller number of square indicators are displayed as the object distance becomes smaller. 
     Image matching information may be displayed instead of the object distance information. The image matching information indicates the matching degree between a designated position of one image (in this example, the left image  101 L) input by the examiner and the corresponding position of the other image (in this example, the right image  101 R). This matching degree is calculated by the matching processing portion  44 . The matching degree is expressed by nine square indicators, and a smaller number of square indicators are displayed as the matching degree becomes stronger (as images at the designated position further match each other). 
     In addition, although object distance information  107  is expressed by the square indicators in this example, it may be expressed by numeric values or in other forms. 
     Then, when the user performs an operation of deciding a measurement point with the cursor moving switch of the operating portion  6  in a state where the cursor  108   a  is displayed at the desired position at which the user wants to set a second measurement point, the second measurement point is set at the position where the cursor  108   a  is displayed. When the second measurement point is set, the distance between the two points is calculated and displayed on the display screen  100  as a measurement result. 
       FIG. 13  shows a state where the second measurement point is set. A second measurement point  111   a is displayed on the left image  101 L, and a corresponding point  111   b  corresponding to the measurement point  111   a  is displayed on the right image  101 R. In addition, measurement result informational  112  indicating the result of the point-to-point measurement is displayed in the middle part of the I-shaped display region. In addition, a measurement line  113  which connects the measurement point  110   a  and the measurement point  111   a  is displayed on the left image  101 L. 
     When the measurement point  111   a  is set, the zoom windows  109   a  and  109   b  become not to be displayed. If necessary, the user may display the zoom windows  109   a  and  109   b  again as shown in  FIG. 13  by operating the zoom switch of the operating portion  6 . Moreover, in the point-to-point measurement of the present embodiment, the point-to-point measurement may be performed again by setting the first and second measurement points again in a state where the measurement points  110   a  and  111   a  and the corresponding points  110   b  and  111   b  are displayed after the distance between two points is calculated and the measurement result information  112  is displayed. Accordingly, the cursors  108   a  and  108   b  and the zoom windows  109   a  and  109   b  can move with respect to the measurement points  110   a  and  111   a,  the corresponding points  110   b  and  111   b , and the measurement result information  112 . 
     Next, an operation of the endoscope apparatus  1  will be described with reference to the flow chart.  FIG. 4  shows the overall operation of the endoscope apparatus  1 . When the endoscope apparatus  1  is started, the main control portion  46  executes initialization (step SA). Then, the main control portion  46  monitors a signal input from the operating portion  6  through the RS-232C I/F  17  and determines whether or not the zoom switch for image magnification change is ON (step SB). When the zoom switch is ON, the main control portion  46  instructs the magnification change in electronic zoom processing for enlarging the image to the video signal processing circuit  12  (step SC). Then, the process proceeds to step SD. In addition, when the zoom switch is OFF in step SB, the process proceeds to step SD. 
     Then, the main control portion  46  monitors a signal input from the operating portion  6  through the RS-232C I/F  17  and determines whether or not a brightness switch for image brightness change is ON (step SD). When the brightness switch is ON, the main control portion  46  instructs the brightness change of the whole image to the video signal processing circuit  12  (step SE). Then, the process proceeds to step SF. In addition, when the brightness switch is OFF in step SD, the process proceeds to step SF. 
     Then, the main control portion  46  monitors a signal input from the operating portion  6  through the RS-232C I/F  17  and determines whether or not a live switch for changing the measurement mode to the live mode is ON (step SF). The endoscope apparatus  1  can operate in a plurality of operation modes (a live mode, a recording mode, a measurement mode, and a play mode). The live mode is a mode in which a moving image imaged by the endoscope  2  is displayed in real time. The recording mode is a mode in which image data imaged by the endoscope  2  is recorded in the memory card  32 . The measurement mode is a mode in which point-to-point measurement or the like is executed on the basis of the image data imaged by the endoscope  2 . The play mode is a mode in which image data recorded in the memory card  32  is read and an image of the image data is displayed. When the live switch is ON in a state where one of the recording mode, the measurement mode, and the play mode is operating, the main control portion  46  changes the operation mode to the live mode and instructs an operation in the live mode to each portion of the endoscope apparatus  1 . Then, the imaging device  28  images a subject and generates an image signal. The CCU  9  converts the image signal into a video signal. The video signal processing circuit  12  generates a display signal by mixing the video signal with the graphic image signal from the graphic processing portion  43  and outputs it to the monitor  4 . The monitor  4  displays the image on the basis of the display signal (step SG). Then, the process proceeds to step SH. In addition, when the live switch is OFF in step SF, the process proceeds to step SH. 
     Then, the main control portion  46  monitors a signal input from the operating portion  6  through the RS-232C I/F  17  and determines whether or not a menu switch is ON (step SH). When the menu switch is ON, the graphic processing portion  43  generates a graphic image signal for operation menu display and outputs it to the video signal processing circuit  12  (step SI). Then, the process proceeds to step SJ. In addition, when the menu switch is OFF in step SH, the process proceeds to step SJ. 
     Then, the main control portion  46  monitors a signal input from the operating portion  6  through the RS-232C I/F  17  and determines whether or not an LED switch for turning on the LED in the optical adapter is ON (step SJ). When the LED switch is ON, the main control portion  46  instructs starting of a lighting device to the endoscope unit  8  (step SK). Then, the process proceeds to step SL. In addition, when the LED switch is OFF in step SJ, the process proceeds to step SL. 
     Then, the main control portion  46  monitors a signal input from the operating portion  6  through the RS-232C I/F  17  and determines whether or not a recording switch for image recording is ON (step SL). When the recording switch is ON, the main control portion  46  changes the operation mode to the recording mode and records image data acquired from the video signal processing circuit  12  in the memory card  32  trough the card I/F  15  (step SM). Details of step SM will be described later. Then, the process proceeds to step SN. In addition, when the recording switch is OFF in step SL, the process proceeds to step SN. 
     Then, the main control portion  46  monitors a signal input from the operating portion  6  through the RS-232C I/F  17  and determines whether or not a play switch for image play is ON (step SN). When the play switch is ON, the main control portion  46  changes the operation mode to the play mode, reads image data from the memory card  32  through card I/F  15 , and outputs it to the video signal processing circuit  12  (step SO). Details of step SO will be described later. Then, the process proceeds to step SP. In addition, when the play switch is OFF in step SN, the process proceeds to step SP. 
     Then, the ma n control portion  46  monitors a signal input through a signal line (not shown) connected to the tip portion  21  of the inserted portion  20  and determines whether or not an optical adapter is attached (step SP). When the optical adapter is attached, the main control portion  46  checks the type of the optical adapter, reads environmental data corresponding to the type from the memory card  32  through the card I/F  15 , and stores it in the RAM  14  (step SQ). Checking the type of the optical adapter is performed by detecting the resistance value, which changes according to the type of the optical adapter, provided in the optical adapter, for example. Then, the process proceeds to step SR. In addition, when the optical adapter is not provided in step SP, the process proceeds to step SR. 
     Then, the main control portion  46  monitors a signal input from the operating portion  6  through the RS-232C I/F  17  and determines whether or not a measurement switch for stereo measurement is ON (step SR). When the measurement switch is ON, the main control portion  46  changes the operation mode to the measurement mode and makes each functional portion of the CPU  18  execute stereo measurement (step SS). Details of step SS will be described later. Then, the process proceeds to step ST. In addition, when the measurement switch is OFF in step SR, the process proceeds to step ST. 
     Then, the main control portion  46  monitors a signal input from the operating portion  6  through the RS-232C I/F  17  and determines whether or not a power switch for a power source is ON (step ST). When the power switch is OFF, the endoscope apparatus  1  ends the operation. In addition, when the power switch is ON in step ST, the process returns to step SB. 
     Next, the details of the above-described step SS (stereo measurement) will be described. The point-to-point measurement is exemplified below.  FIGS. 5 to 7  show the procedure of stereo measurement. First, initialization processing is executed (step SS 1 ). In the initialization processing, various variables stored in the RAM  14  are initialized. The various variables stored in the RAM  14  include a variable indicating a display/non-display state of a zoom window, a variable indicating the current cursor position, a variable indicating a state of decision/non-decision of a measurement point, a variable indicating the position of the decided measurement point, and the like. Moreover, the initialization processing is performed such that the display screen for measurement is displayed on the monitor  4  but the zoom window is not displayed (for example,  FIG. 9 ). 
     Then, the main control portion  46  determines whether or not the zoom window is displayed referring to the zoom window state variable stored in the RAM  14 . Then, the main control portion  46  monitors a signal input from the operating portion  6  through the RS-232C I/F  17  and determines whether or not the zoom switch is ON (step SS 2 ). 
     When the zoom window is not displayed and the zoom switch is ON, processing for displaying the zoom window is executed (step SS 3 ). Details of step SS 3  will be described later. By execution of the processing of step SS 3 , the zoom window is displayed on the display screen (for example,  FIG. 10 ). By the processing of step SS 3 , the zoom window state variable in the RAM  14  is updated to the value indicating ‘display’. The process proceeds to step SS 4  after step SS 3 . In addition, when the zoom switch is displayed in step SS 2  or when the zoom switch is OFF in step SS 2 , the process proceeds to step SS 4 . 
     In step SS 4 , the main control portion  46  determines whether or not the zoom window is displayed and whether or not the zoom switch is ON similar to step SS 2  (step SS 4 ). When the zoom window is displayed and the zoom switch is OFF, processing for making the zoom window not displayed is executed (step SS 5 ). By the processing of step SS 5 , the zoom window state variable in the RAM  14  is updated to the value indicating ‘non-display’. The process proceeds to step SS 6  after step SS 5 . In addition, when the zoom switch is not displayed in step SS 4  or when the zoom switch is ON in step SS 4 , the process proceeds to step SS 6 . 
       FIG. 5  shows that the processing of steps SS 2  to SS 5  is executed between steps SS 1  and SS 6 . However, when interruption occurs by the operation of the zoom switch of the operating portion  6 , the processing of steps SS 2  to SS 5  is executed at any processing timing of  FIGS. 5 to 7 . After the processing of steps SS 2  to SS 5  ends, processing is resumed from the state immediately before the processing of steps SS 2  to SS 5  is executed. 
     In step SS 6 , the main control portion  46  monitors a signal input from the operating portion  6  through the RS-232C I/F  17  and determines whether or not the cursor moving switch is ON (step SS 6 ). When the cursor moving switch is OFF, the process proceeds to step SS 12 . In addition, when the cursor moving switch is ON, the main control portion  46  determines whether or not the zoom window is displayed referring to the zoom window state variable stored in the RAM  14  (step SS 7 ). 
     When the zoom window is not displayed, processing for moving the cursor on the display screen is executed (stop SS 8 ). Details of the processing of step SS 8  will be described below. The cursor position designating portion  41  calculates the next cursor position by adding the movement amount, which is designated by the operation of the cursor moving switch, to the current cursor position referring to the current cursor position stored in the RAM  14 . The calculated next cursor position is stored in the RAM  14  as the current cursor position. 
     The matching processing portion  44  calculates the position of a corresponding point on the right image corresponding to the ‘next cursor position’ on the left image by matching processing using image pattern matching. The graphic processing portion  43  generates a graphic image signal for displaying the icon of a cursor and the like. The video signal processing circuit  12  generates a display signal by mixing the graphic image signal with the video signal from the CCU  9  such that the cursors are displayed at the position on the left image designated by the cursor position designating portion  41  and the position on the right image calculated by the matching processing portion  44 , and outputs it to the monitor  4 . The monitor  4  displays an image on the basis of the display signal. 
     As a result the cursor is displayed together with the image of the subject imaged by the endoscope  2 . While movement of the cursor is being instructed by the cursor moving switch, the above processing is repeatedly executed and the cursor moves on the display screen. When the input of the instruction to move the cursor is stopped, the process proceeds to step SS 12 . 
     When the zoom window is displayed in step SS 7 , processing for making the zoom window not displayed is executed (step SS 9 ). Then, similar to step SS 8 , processing for moving the cursor on the display screen is executed (step SS 10 ). While movement of the cursor is being instructed by the cursor moving switch, the processing described in step SS 10  is repeatedly executed and the cursor moves on the display screen. When the input of the instruction to move the cursor is stopped, the process proceeds to step SS 11 . 
     In step SS 11 , processing for displaying the zoom window is executed similar to step SS 3  (step SS 11 ). Details of step SS 11  will be described later. By execution of the processing of step SS 11 , the zoom window is displayed on the display screen. The process proceeds to step SS 12  after step SS 11 . 
     In step SS 12  shown in  FIG. 6 , the main control portion  46  monitors a signal input from the operating portion  6  through the RS-232C I/F  17  and determines whether or not there has been the input of a decision switch for deciding a first measurement point (step SS 12 ). When the first measurement point is not decided (decision switch is not input), the process proceeds to step SS 16 . In addition, when the first measurement point has been decided (decision switch has been input), the main control portion  46  determines whether or not the zoom window is displayed referring to the zoom window state variable stored in the RAM  14  (step SS 13 ). 
     When the zoom window is not displayed, the process proceeds to step SS 15 . In addition, when the zoom window is displayed, processing for making the zoom window not displayed is executed (step SS 14 ). Then, object distance calculating processing for calculating the object distance is executed (step SS 15 ). 
     Details of the processing of step SS 15  will be described below. The matching processing portion  44  calculates the position of a corresponding point on the right image, which corresponds to the position of the measurement point on the left image stored in the RAM  14 , by matching processing using image pattern matching. The measurement processing portion  45  calculates the three-dimensional coordinates (coordinates of the point P of  FIG. 23 ) on the basis of the positions of the measurement point and corresponding point. The measurement processing portion  45  calculates the object distance on the basis of the calculated three-dimensional coordinates. The object distance is a distance from the tip of the endoscope to the subject to be observed (object to be observed). For example, the object distance is calculated as a distance from the imaging device or the objective optical system to the subject to be observed. The calculated object distance is displayed on the display screen (for example,  FIG. 12 ). The process proceeds to step SS 16  after step SS 15 . 
     In step SS 16 , the main control portion  46  monitors a signal input from the operating portion  6  through the RS-232C I/F  17  and determines whether or not there has been the input of a decision switch for deciding a second measurement point (step SS 16 ). When the second measurement point is not decided (decision switch is not input), the process proceeds to step SS 21 . In addition, when the second measurement point has been decided (decision switch has been input), the main control portion  46  determines whether or not the zoom window is displayed referring to the zoom window state variable stored in the RAM  14  (step SS 17 ). 
     When the zoom window is not displayed, the process proceeds to step SS 19 . In addition, when the zoom window is displayed, processing for making the zoom window not displayed is executed (step SS 18 ). Then, similar to step SS 15 , object distance calculating processing for calculating the object distance is executed (step SS 19 ). 
     Then, measurement processing is executed (step SS 20 ). Details of the processing of step SS 20  will be described below. The measurement processing portion  45  calculates the distance between two points on the basis of the three-dimensional coordinates of the first measurement point calculated in step SS 15  and the three-dimensional coordinates of the second measurement point calculated in step SS 19 . The calculated distance between two points is displayed on the display screen (for example,  FIG. 13 ). The process proceeds to step SS 21  after step SS 20 . 
     In step SS 21 , the main control portion  46  determines whether or not to end the stereo measurement (step SS 21 ). For example when the instruction to end the stereo measurement has been input, the stereo measurement ends. In addition, when the stereo measurement is not ended, the process returns to step SS 2 . 
     Details of the processing of step SS 3  and SS 11  will be described below ( FIG. 7 ). The enlarged image generating portion  42  extracts data, which corresponds to an image in a predetermined region (for example, a region of 30×30 pixels) on the left image around the cursor position designated by the cursor position designating portion  41 , from the image data acquired from the video signal processing circuit  12 . In addition, the enlarged image generating portion  42  extracts data, which corresponds to an image in a predetermined region (for example, a region of 30×30 pixels) on the right image around the corresponding point on the right image corresponding to the cursor position on the left image, from the image data acquired from the video signal processing circuit  12 . In addition, the enlarged image generating portion  42  executes image enlarging processing on the basis of the extracted data to generate data of the left and right enlarged images (step SS 31 ). 
     The video signal processing circuit  12  processes the image data so that the left enlarged image generated by the enlarged image generating portion  42  overlaps the predetermined region (for example, a region of 60×60 pixels) on the left image around the cursor position designated by the cursor position designating portion  41 . Specifically, the video signal processing circuit  12  executes processing for rewriting data of the image data, which corresponds to the image in the predetermined region (for example a region of 60×60 pixels) on the left image, to the data of the left enlarged image. In addition, the video signal processing circuit  12  processes the image data so that the right enlarged image generated by the enlarged image generating portion  42  overlaps the predetermined region (for example, a region of 60×60 pixels) on the right image around the position of the corresponding point on the right image corresponding to the cursor position designated by the cursor position designating portion  41 . Specifically, the video signal processing circuit  12  executes processing for rewriting data of the image data, which corresponds to the image in the predetermined region (for example, a region of 60×60 pixels) on the right image around the corresponding point on the right image, to the data of the right enlarged image (step SS 32 ). As a result, the left and right enlarged images overlap the images of the subject imaged by the endoscope. 
     Then, the video signal processing circuit  12  generates a display signal by mixing the graphic image signal from the graphic processing portion  43  with the image data processed in step SS 32 . The graphic image signal includes the icon of a cursor, the frame of a zoom window, and the like. When the measurement point has been decided, the graphic image signal also includes the icon of the decided measurement point and the icon of the corresponding point. In addition, the main control portion  46  controls the video signal processing circuit  12  on the basis of the cursor position designated by the cursor position designating portion  41  and the corresponding point of the cursor position calculated by the matching processing portion  44 , such that the video signal processing circuit  12  mixes the image data and the graphic image signal so that the cursors are displayed at the cursor position designated by the cursor position designating portion  41  and the corresponding point. The monitor  4  displays an image on the basis of the display signal generated by the video signal processing circuit  12  (step SS 33 ). As a result, the zoom window and the like are displayed on the display screen. 
     In the processing shown in  FIGS. 5 to 7 , when the movement of a cursor is instructed while the zoom window is displayed, the zoom window is not displayed. However, it may be performed as follows. For example, the zoom window may not be displayed when the duration of a state where the cursor moving switch of the operating portion  6  is ON is 0.1 second or more, and the zoom window may move with the cursor while displayed when the duration of the state where the cursor moving switch is ON is less than 0.1 second. 
     In addition, in the processing shown in  FIGS. 5 to 7 , the measurement processing is executed after the second measurement point is decided. However, after the first measurement point is decided, the measurement processing may also be executed before the second measurement point is decided. In addition, in the processing shown in  FIGS. 5 to 7 , the object distance calculating processing is executed after the measurement point is decided. However, the distance measurement processing may be always executed irrespective of whether or not the measurement point has been decided. 
     In addition, when it is determined that the matching degree between the measurement point on the left image and the corresponding point on the right image is low in steps SS 3  and SS 11 , the zoom window on the right image may not be displayed. Moreover, also when the corresponding point on the right image is located outside the right measurement region as a result of matching using the matching processing portion  44 , the zoom window on the right image may not be displayed. 
     Next, a control when the zoom window overlaps other parts in the display screen will be described. Within the left measurement region where the left image is displayed and the right measurement region where the right image is displayed, first overlay information, such as the zoom window  109   a  or  109   b  which can move on the left image or right image, is preferentially displayed over second overlay information, such as the measurement points  110   a  or  11   a,  the corresponding points  110   b  and  111   b , and the measurement line  113 , when the first overlay information overlaps the second overlay information. Here, when the zoom window and the measurement point overlap each other, the zoom window is preferentially displayed over the measurement point. For example, when the zoom windows  109   a  and  109   b  have moved near the measurement point  110   a  and the corresponding point  110   b  from the state of  FIG. 13 , the zoom windows  109   a  and  109   b  are displayed and the measurement point  110   a  and the corresponding point  110   b  are not displayed as shown in  FIG. 14 . In this case, the graphic processing portion  43  does not generate a graphic image signal of the measurement points and the measurement line within the region where the zoom window is displayed. 
     The viewability of the zoom window is maintained by displaying the window preferentially over the measurement point as described above. 
     In the outside of the left measurement region where the left image is displayed and the right measurement region where the right image is displayed, third overlay information, such as the date and time information  103 , the measurement operation information  104 , the message information  105 , the magnifying power information  106 , the object distance information  107 , and the measurement result information  112 , is displayed preferentially over the first overlay information. Here, the other information is displayed preferentially over the zoom window. For example, when the zoom window  109   a  has moved to the right end of the left measurement region and the zoom window  109   b  has moved to the right end of the right measurement region from the state of  FIG. 12 , the shapes of the zoom windows  109   a  and  109   b  change as shown in  FIG. 15 . For this reason, the zoom windows  109   a  and  109   b  do not overlap information, such as the object distance information  107 . The first overlay information is displayed preferentially over the second overlay information, and the third overlay information is displayed preferentially over the first overlay information. 
     In the above case, if a predetermined region on the left image around the cursor position designated by the cursor position designating portion  41  protrudes from the left measurement region, the enlarged image generating portion  42  changes the shape of the predetermined region such that the predetermined region does not protrude from the left measurement region. In addition, if a predetermined region on the right image around the corresponding point of the cursor position calculated by the matching processing portion  44  protrudes from the right measurement region, the enlarged image generating portion  42  changes the shape of the predetermined region such that the predetermined region does not protrude from the right measurement region. The predetermined region is a region which is set as a region where the zoom window is displayed. The enlarged image generating portion  42  generates data of the enlarged image corresponding to the predetermined region the shape of which has been changed. In addition, the graphic processing portion  43  generates the graphic image signal obtained by changing the shape of the frame of the zoom window according to the change of the shape of the predetermined region. At this time, the frame of the zoom window shows a region where a measurement point can be input on the original image. 
     The visibility of information, such as the measurement result, is maintained by displaying the information displayed outside the measurement region preferentially over the zoom window as described above. However, the shape of the zoom window may not be changed except for the case where the zoom window protrudes from the right end of the left measurement region or the case where the zoom window protrudes from the left end of the right measurement region. For example, it may be like  FIG. 16 . At this time, the zoom windows  109   a  and  109   b  may not be displayed when the cursors  108   a  and  108   b  are located outside the measurement region. 
     Next, another example of the display screen of the present embodiment will be described.  FIG. 17  shows a display screen  120  at the start of measurement. A pair of left and right images  121 L and  121 R with parallax, measurement operation information  122 , an enlargement icon  123 , a reduction icon  124 , magnifying power information  125 , measurement result information  126 , object distance information  127 , cursors  128   a  and  128   b , and the like are displayed on the display screen  120 . 
     The display screen  120  is configured to include a display region, which is provided in the I-shape in upper, lower, and middle parts of the screen of the monitor  4 , and two rectangular display regions excluding the display region. The left image  121 L is displayed in the left display region shown in the drawing, and the right image  121 R is similarly displayed in the right display region. The measurement operation information  122 , the enlargement icon  123 , the reduction icon  124 , the magnifying power information  125 , the measurement result information  126 , and the object distance information  127  are displayed in the upper part of the I-shaped display region. The cursor  128   a  is displayed so as to overlap the left image  121 L, and the cursor  128   b  is displayed so as to overlap the right image  121 R. 
     The measurement operation information  122  displays the kind of measurement operation, such as the distance between two points, the depth, the area, and the angle. In the present embodiment, it is shown that the measurement operation of the distance between two points is performed. 
     The enlargement icon  123  is for raising the magnification of an image displayed in the zoom window to be described later. The reduction icon  124  is for lowering the magnification of the image displayed in the zoom window. The magnifying power information  125  shows the magnifying power of the image displayed in the zoom window. 
     The measurement result information  126  displays the measurement result, such as point-to-point measurement. Before measurement processing is executed, the measurement result is not displayed on the measurement result information  126 . The object distance information  127  shows the degree of the object distance. Before object distance calculating processing is executed, the object distance is not displayed on the object distance information  127 . 
     The cursors  128   a  and  128   b  are used to input a measurement point on the display screen  120 . The position of the cursor  128   a  is calculated according to the operation input from the cursor moving switch of the operating portion  6  by the cursor position designating portion  41 . The position of the cursor  128   b  is calculated on the basis of the position of the cursor  128   a  by the matching processing portion  44 . The cursor  128   a  changes to the arrow in the outside of the left measurement region where the left image  121 L is displayed. The magnifying power of the image displayed in the zoom window can be changed by operating the enlargement icon  123  and the reduction icon  124  with this arrow. 
     When the zoom switch of the operating portion  6  is operated and display of the zoom window is instructed, zoom windows  129   a  and  129   b  are displayed as shown in  FIG. 18 . The zoom window  129   a  is displayed in the left image  121 L, and the zoom window  129   b  is displayed in the right image  121 R. 
     The cursor  128   a  and an enlarged image, which is obtained by enlarging an image within a predetermined range around the cursor  128   a  in the left image  121 L, are displayed in the zoom window  129   a . The cursor  128   b  and an enlarged image, which is obtained by enlarging an image within a predetermined range around the cursor  128   b  in the right image  121 R, are displayed in the zoom window  129   b . The size of each of the zoom windows  129   a  and  129   b  is 60×60 pixels, for example. When the magnifying power is 2×, the enlarged images obtained by enlarging, for example, images within the range of 30×30 pixels on the left and right images  121 L and  121 R are displayed in the zoom windows  129   a  and  129   b , respectively. 
     The user can change the magnifying power of the enlarged image displayed in each of the zoom windows  129   a  and  129   b  by operating the enlargement icon  123  and the reduction icon  124 . The magnifying power is increased when the enlargement icon  123  is operated in a state where the zoom windows  129   a  and  129   b  are displayed. In addition, the magnifying power is decreased when the reduction icon  124  is operated in a state where the zoom windows  129   a  and  129   b  are displayed. When the magnifying power is 1×, the zoom windows  129   a  and  129   b  are not displayed. In addition, the user can move the zoom windows  129   a  and  129   b  together with the cursors  128   a  and  128   b  by operating the cursor moving switch of the operating portion  6 . 
     Hereinafter, the transition of the display screen will be described using the point-to-point measurement as an example. When the user performs an operation of deciding a measurement point with the cursor moving switch of the operating portion  6  in a state where the cursor  128   a  is displayed at the desired position at which the user wants to set a first measurement point, the first measurement point is set at the position where the cursor  128   a  is displayed.  FIG. 19  shows a state where the first measurement point is set. A first measurement point  130   a  is displayed on the left image  121 L, and a corresponding point  130   b  corresponding to the measurement point  130   a  is displayed on the right image  121 R. When the measurement point  130   a  is set the object distance is calculated and the object distance information  127  is displayed. 
     Then, when the user performs an operation of deciding a measurement point with the cursor moving switch of the operating portion  6  in a state where the cursor  128   a  is displayed at the desired position at which the user wants to set a second measurement point, the second measurement point is set at the position where the cursor  128   a  is displayed. When the second measurement point is set, the distance between the two points is calculated and displayed on the display screen  120  as a measurement result. 
       FIG. 20  shows a state where the second measurement point is set. A second measurement point  131   a  is displayed on the left image  121 L, and a corresponding point  131   b  corresponding to the measurement point  131   a  is displayed on the right image  121 R. In addition, the measurement result information  126  indicating the result of the point-to-point measurement is displayed. In addition, a measurement line  133  which connects the measurement points  130   a  and  131   a  to each other is displayed. Moreover, in the point-to-point measurement of the present embodiment, even after the distance between two points has been calculated and the measurement result information  126  is displayed, the point-to-point measurement may be performed again by setting new first and second measurement points in a state where the measurement points  130   a  and  131   a  and the corresponding points  130   b  and  131   b  are displayed. 
     In the transition of the display screen shown in  FIGS. 17 to 20 , it is assumed that reducing the processing load of the endoscope apparatus  1  is not essential. Accordingly, the zoom windows  129   a  and  129   b  are displayed even during the movement of the cursors  128   a  and  128   b . Moreover, even after the operation of deciding the measurement points  130   a  and  131   a  is performed, the zoom windows  129   a  and  129   b  are displayed. 
     Next, details of step SS (stereo measurement) when displaying the display screen shown in  FIGS. 17 to 20  will be described. The point-to-point measurement is exemplified below.  FIG. 8  shows the procedure of stereo measurement. In  FIG. 8 , the same processing as the processing shown in  FIGS. 5 and 6  is denoted by the same step number. The following explanation will be focused on a different part from the processing shown in  FIGS. 5 and 6 . 
     Processing of steps SS 1  to SS 5  is the same as the processing of steps SS 1  to SS 5  of  FIG. 5 . When the cursor moving switch is ON in step SS 6 , processing for moving the cursor is executed in step SS 8  while the display/non-display state of the zoom window is not changed. 
     When the first measurement point is decided in step SS 12 , object distance calculating processing is executed in step SS 15  to calculate the object distance while the display/non-display state of the zoom window is not changed. In addition, when the second measurement point is decided in step SS 16 , object distance calculating processing is executed in step SS 19  to calculate the object distance while the display/non-display state of the zoom window is not changed. Then, measurement processing is executed in step SS 20  to calculate the distance between the two points. 
     In the processing shown in  FIG. 8 , the measurement processing is executed after the second measurement point is decided. However, after the first measurement point is decided, the measurement processing may be executed before the second measurement point is decided. In addition, in the processing shown in  FIG. 8 , the object distance calculating processing is executed after the measurement point is decided. However, the object distance calculating processing may be always executed irrespective of whether or not the measurement point has been decided. 
     In addition, when it is determined that the matching degree between the measurement point on the left image and the corresponding point on the right image is low in step SS 3 , the zoom window on the right image may not be displayed. 
     Next, a control when the zoom window overlaps other parts in the display screen in transition of the display screen shown in  FIGS. 17 to 20  will be described. Within the left measurement region where the left image is displayed and the right measurement region where the right image is displayed, the second overlay information is displayed so as to be included in the first overlay information when the first overlay information which is movable on the left image or the right image overlaps the second overlay information. Here, when the zoom window and the measurement point overlap each other, the measurement point is displayed in the zoom window. For example, when the zoom windows  129   a  and  129   b  have moved near the measurement point  130   a  and the corresponding point  130   b  from the state of  FIG. 20 , the measurement point  130   a  is displayed together with the cursor  128   a  in the zoom window  129   a  and the corresponding point  130   b  is displayed together with the cursor  128   b  in the zoom window  129   b  as shown in  FIG. 21 . In addition, the measurement line  133  is also displayed in the zoom window  129   a . In addition, when the second overlay information, such as the measurement point  130   a  and the measurement line  133 , is thus displayed in the zoom window which is the first overlay information, both the original image and the second overlay information may be enlarged and displayed in the zoom window, or only the original image may be enlarged and the second overlay information may be displayed in the zoom window with the original size. 
     By displaying the measurement point and the corresponding point in the zoom window together with the enlarged image as described above, the positions of the measurement point and corresponding point can be checked in the zoom window. 
     In the outside of the left measurement region where the left image is displayed and the right measurement region where the right image is displayed, it is as follows. For example, when the zoom window  129   a  has moved to the lower end of the left measurement region and the zoom window  129   b  has moved to the lower end of the right measurement region from the state of  FIG. 20 , the zoom windows  129   a  and  129   b  are displayed outside the frame of the measurement region as shown in  FIG. 22  if the position of the cursor  128   a  is within the left measurement region. In addition, if the position of the cursor  128   a  is outside the left measurement region, the zoom windows  129   a  and  129   b  are not displayed and the cursor  128   a  changes to the arrow. If this arrow moves to the inside of the left measurement region, the cursors  128   a  and  129   b  and the zoom windows  129   a  and  129   b  are displayed again. 
     In the above case, when the cursor position designated by the cursor position designating portion  41  is within the left measurement region, the enlarged image generating portion  42  generates data of left and right enlarged images obtained by enlarging images in predetermined regions on the left and right images as described above. The graphic processing portion  43  generates a graphic image signal such that the frame of the zoom window, the enlarged image, the measurement point, and the like are displayed so as to overlap on the frame of the measurement region. 
     In addition, the enlarged image generating portion  42  does not generate data of the enlarged image if the cursor position designated by the cursor position designating portion  41  is outside the left measurement region. The graphic processing portion  43  generates a graphic image signal including an arrow instead of the zoom window and the cursor. 
     On the display screen  120 , information, such as a measurement result which is the third overlay information, is not displayed near the measurement regions where the left and right images are displayed. Accordingly, even if the zoom window is displayed across the measurement region, the visibility of the information, such as the measurement result, is not damaged. On the other hand, the visibility of the zoom window is maintained. The third overlay information is displayed such that the visibility is not damaged by the first overlay information. 
     As described above, in the present invention, the zoom window including the enlarged image around the cursor position is displayed together with the cursor at the cursor position designated by the cursor position designating portion  41 , and the zoom window moves corresponding to the movement of the cursor. For this reason, problems in checking the enlarged image are reduced. 
     Moreover, as shown in  FIG. 15 , when the zoom window attempts to protrude from the measurement region, the visibility of information such as the measurement result displayed outside the measurement region can be maintained by changing the shape of the zoom window such that the zoom window is not displayed outside the measurement region. 
     In addition, as shown in  FIG. 21 , when the zoom window overlaps the measurement point and the corresponding point, the positions of the measurement point and corresponding point can be checked in the zoom window by displaying the measurement point and the corresponding point in the zoom window together with the enlarged images. 
     While preferred embodiments of the invention have been described and illustrated above, it should be understood that these are exemplary of the invention and are not to be considered as listing. Additions, omissions, substitutions, and other modifications can be made without departing from the spirit or scope of the present invention. Accordingly, the invention is not to be considered as being limited by the foregoing description and is only limited by the scope of the appended claims. For example, although the point-to-point measurement was described in the stereo measurement, the control regarding the display of the zoom window may also be applied for other measurements. Moreover in the above-described embodiments, the zoom window or the cursor was exemplified as the first overlay information, the measurement point, the corresponding point, or the measurement line was exemplified as the second overlay information, and the date and time information, the measurement operation information, the message information) the magnifying power information, the object distance information, or the measurement result information was exemplified as the third overlay information. However, examples of the overlay information are not limited to those described above and may be suitably changed according to the usage of the endoscope apparatus, the purpose of use of the endoscope apparatus, and the like. For example, when the measurement result information is displayed on the left image, the measurement result information may be considered as the second overlay information instead of the third overlay information. 
     According to the invention, since the enlarged image is displayed at the designated position together with the cursor and the displayed enlarged image moves corresponding to the movement of the cursor, problems in checking the enlarged image are reduced.