Abstract:
An endoscope system including a solid-state image pickup device having a photosensitive area and configured to produce an electronic image; an optical system having a focal length and configured to transmit an optical image of an object incident onto the photosensitive area; a superimposing device configured to superimpose on the electronic image produced by the solid-state image pickup device scale information according to the focal length of the optical system; and a display configured to display the electronic image and the superimposed scale information. The focal length of the optical system is variable by means of a lever operated wire connected to a lens of the optical system and disposed in an endoscope inserter. Thus, an operator can easily measure the length of the object based on the scale information superimposed on the displayed electronic image.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention generally relates to an electronic endoscope system, and more specifically, to an electronic endoscope system capable of measuring a size of an object. This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2000-251852, filed on Aug. 23, 2000, the entire contents of which are incorporated herein by reference.  
           [0003]    2. Discussion of Background  
           [0004]    An endoscope system has been widely utilized for medical diagnosis or treatment. In diagnosis or treatment, an operator sometimes measures a size of an object inside a body with the endoscope.  
           [0005]    With a conventional endoscope, the operator has to use forceps for inserting a graduated band into a body cavity, put it near the object and compare a graduation on the band with the object. Both the graduation on the band and the object are displayed on the same monitor so that the operator can measure the size of the object.  
           [0006]    Such a graduated band is described in Japanese KOKAI (Disclosure) patent application No. 63-277028. However, it is often difficult to put the graduated band near the object due to the movement of the body cavity, which may cause a long measurement time. Additionally, the graduated band may be an obstacle to observe the object.  
           [0007]    Moreover, there is an endoscope system for magnifying the object by changing a focal length of an optical system disposed in an endoscope unit. The optical system like this is designed such that a depth of field is small when the object is magnified.  
           [0008]    The operator has to move the endoscope unit such that the object is located at the position within the depth of field. In such a case, it is difficult to put the graduated band near the object because a field of view is small. Further the size of the object cannot be measured correctly depending upon the experience of the operator.  
           [0009]    A technique that solves the above-described problems is disclosed in Japanese KOKAI (Disclosure) patent application No. 59-69721, which discloses an endoscope having a laser system for measuring a distance between an end of the endoscope unit and the object and superimposing a scale on an image of the object according to the distance. However this endoscope system is complicated and expensive due to the laser system. Further, it cannot measure the desired distance if the object to be observed is not actually irradiated by a laser beam.  
         SUMMARY OF THE INVENTION  
         [0010]    To solve these problems, an object of the present invention is to provide an endoscope system with which the operator can measure a size of an object easily.  
           [0011]    In order to accomplish this object, the present invention provides an endoscope system including a solid-state image pickup device having a photosensitive area and configured to produce an electronic image; an optical system having a focal length and configured to transmit an optical image of an object incident onto the photosensitive area; a superimposing device configured to superimpose on the electronic image produced by the solid-state image pickup device scale information according to the focal length of the optical system; and a display configured to display the electronic image and the superimposed scale information. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    A more complete appreciation of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:  
         [0013]    [0013]FIG. 1 is a general diagram showing an embodiment of the endoscope system according to the present invention;  
         [0014]    [0014]FIG. 2 is a longitudinal cross-sectional view showing an end of the endoscope unit of the embodiment shown in FIG. 1;  
         [0015]    [0015]FIG. 3 is a block diagram showing a system configuration of the embodiment of FIG. 1;  
         [0016]    [0016]FIG. 4 is a flowchart of the procedure of operating the endoscope system of FIG. 1;  
         [0017]    [0017]FIG. 5 is an illustration of an image of an object displayed on a monitor in a normal mode as a normal picture;  
         [0018]    [0018]FIG. 6 is an illustration of an image of an object displayed on a monitor in an enlargement mode to provide a zoom-in picture;  
         [0019]    [0019]FIG. 7 is an illustration of an image of the object displayed with a superimposed scale;  
         [0020]    [0020]FIG. 8 is an illustration of a second example of displayed scale information;  
         [0021]    [0021]FIG. 9 is an illustration of a third example of displayed scale information;  
         [0022]    [0022]FIG. 10 is a graph showing a relation between a distance from the center on a monitor and an actual length of the object;  
         [0023]    [0023]FIG. 11 is an illustration of another example of displayed scale information;  
         [0024]    [0024]FIG. 12 is an illustration of another example of displayed scale information;  
         [0025]    [0025]FIG. 13 is an illustration of an object image on which scale information is superimposed;  
         [0026]    [0026]FIG. 14 is an illustration of an object image and superimposed scale information resulting upon moving of the scale information relative to the object image.  
         [0027]    [0027]FIG. 15 is an illustration showing a menu for setting up of the system regarding storing the scale information; and  
         [0028]    [0028]FIG. 16 is a longitudinal cross-sectional view showing an operating handle of an endoscope unit. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0029]    Referring now to the drawings, wherein like reference numerals designate identical or corresponding parts through the several views, an embodiment according to the present invention will now be described.  
         [0030]    [0030]FIG. 1 is a general view showing an embodiment of the endoscope system according to the present invention, including an endoscope unit  100  to be inserted into a body cavity being examined to pick up an image for medical diagnosis, a main unit  140  connected to the endoscope unit  100  through a universal cord  130 , and a monitor  150  connected to the main unit  140  to display an electronic image of the body cavity. The universal cord  130  transmits image signals obtained by the endoscope part  100  to the main unit  140  and light from a light source unit to the endoscope unit  100 . The endoscope unit has an operating handle  120  and an inserter  110 . The operating handle  120  includes a first knob  121  to bend an end of the inserter  110  up or down, and a second knob  122  for curving the end to the right or the left, respectively. An operator rotates both knobs  121 ,  122  to search an object or region of interest. In the operating handle a lock lever is provided to lock movement of the both knobs.  
         [0031]    The main unit  140  may also be connected to a variety of recording devices, such as a camera unit  160 , a disk unit  170  and a printer unit  180  each for recording the electronic image. The camera unit  160  records the image onto a film, the disk unit  170  stores the image into a disk such as hard disk, a CD-R, a DVD or a magneto-optical disk. Moreover the printer unit  180  records the image by printing the image onto a paper receptor.  
         [0032]    The operating handle  120  has switches  123 ,  124  and  125 . The switch  123  is used when a moving image is changed to a still image (freezing), the switch  124  is used when the still image is stored into at least one of the camera unit  160  and the disk unit  170 . The switch  125  is used when the still image is printed by the printer unit  180 .  
         [0033]    With a switch (not shown) disposed at the main unit  140  the operator can select whether the still image is stored into the camera unit  160  or the disk unit  170  when the switch  124  is operated.  
         [0034]    During operation, the operator freezes the image using the switch  123  and then pushes the switch  124  or  125  to record the still image in by means of the camera unit  160 , the disk unit  170  or the printer unit  180 . Alternatively, the switch  124 / 125  can be set to initiate freezing and recording images without pressing the switch  123 . Furthermore the operator can select whether the still image is changed to the moving image automatically or not after storing. Such selections are made with switches (not shown) disposed on the main unit  140 .  
         [0035]    The main unit  140  further includes a switch  141  for triggering the timing when scale information indicating a graduation is displayed with the image on the monitor  150 , and a directional switch  142  for moving the position of the scale information on the monitor  150 . The scale information is described below. The operating part  120  further includes a lever  126  for changing the optical magnification of the image. The operator rotates the lever  126  to select for image display a zoom-in or a regular normal picture. In this embodiment the magnification is selectable from two levels.  
         [0036]    The magnification of the image is described herein below with reference to FIG. 2. FIG. 2 is a longitudinal cross-sectional view showing an end of the inserter  110  of the endoscope unit  100 . A light guide  210  is optically connected to the light source unit and transmits a light to the end of the inserter  110 . The light is emitted through the lens  220  disposed at the end of the inserter  110 .  
         [0037]    An optical image of the body cavity illuminated by the light goes through an optical system  230  and a prism  240  and arrives at a photosensitive area disposed on a CCD (Charge Coupled Device)  250 . The optical image is transformed to an electronic image signal by the CCD  250 , and fed to the main unit  140  through an electric cable  260  electrically connected to the CCD  250 . The inserter  110  has a channel  270  through which a surgical instrument, such as forceps, is disposed.  
         [0038]    The optical system  230  includes a first lens  231 , a second lens  232  and a third lens  233 . The first lens  230  is fixed at an end of the inserter  110  and the third lens  233  is located between the first lens  231  and the prism  240 . The second lens  233  is disposed between the first lens  231  and the third lens  233  and is mechanically connected to an end of a wire  234 . The other end of the wire  234  is connected to the lever  126 . The lens  232  is movable along the longitudinal direction according to the rotation of the lever  126 , which changes a focal length of the optical system  230 .  
         [0039]    In this embodiment, the optical system is varifocal and designed such that a depth of field becomes smaller to the optical system and the focal length becomes larger when the second lens  232  moves to the first lens  231 . In this case, the image is displayed as a zoom-in picture.  
         [0040]    On the other hand, the depth of field becomes far from the optical system and the focal length becomes smaller when the second lens  232  moves to the third lens  233 . In this case, the image is displayed as a normal picture.  
         [0041]    A sensor for detecting a position of the lever  126  that is used to change the focal length of the optical system is described with reference to FIG. 16, which is a longitudinal cross-sectional view showing an operating handle of an endoscope unit. A disk  300  is disposed in the operating handle  120  and fixed to the lever  126 . The disk  300  has a projection  310  projecting vertically on a surface of the disk  300 . The projection  310  is wound with the wire  234  connected to the second lens  232 . Moreover the disk  300  has a projection  320  that protrudes horizontally on a surface of the disk  300 . Switches  330  and  340  are located on opposite sides of the projection  320  in a movable direction of the disk  300 , respectively. When the projection  320  touches the switch  330 , the image is displayed as a normal picture on the monitor and when the projection  320  touches the switch  340  a zoom-in picture is displayed. The signal from each switch  330 ,  340  is fed to the main unit  140 , respectively.  
         [0042]    Next, the operation of this embodiment will be described with reference to FIG. 3, which is a block diagram showing an embodiment of the system configuration. The optical image of the body cavity illuminated by the light passes through the optical system  230  and the prism  240  and arrives at the photosensitive area disposed on the CCD  250 . The electronic image signal converted from the optical image by the CCD  250  is fed to a CCU  410  (camera control unit) that is disposed in the main unit  140 . The CCU  410  controls the CCD  250 , for example a read-out timing of the CCD  250 , and feeds the electronic image to a frame memory  420  that is also disposed in the main unit  140 . The electronic image signals read out from the frame memory  420  pass through a superimposing circuit  430  that superimposes scale information on the electronic image which is then displayed as a moving image on the monitor  150 .  
         [0043]    A scale information display processing unit  440 , disposed in the main unit  140 , includes a memory in which various types of scale information is stored corresponding to each focal length of the optical system  110 , and is used for determining the timing when the scale information is displayed according to some operations of the operator. The scale information stored in the main unit  140  is fed to the superimposing circuit  430  according to operations described below and then displayed on the monitor  150 . The scale information is determined according to the focal length of the optical system  110 .  
         [0044]    During operation, the operator rotates the lever  126  in order to change the focal length such that the image is displayed as zoom-in picture and moves the endoscope unit  100  back and forth to position an observation area of interest within the depth of field. If necessary, the operator may push one of the switches  123 ,  124  and  125  in order to freeze the image, store the image, or print the image, respectively.  
         [0045]    In this embodiment, there are four types of operations that generate the timing when the scale information is displayed. These operations are described below.  
         [0046]    (1) When the image is displayed as a zoom-in picture:  
         [0047]    The operator rotates the lever  126  then the disk  300  shown in FIG. 16 is rotated to the same direction as the lever  126 . The projection  310  is also rotated with the disk  300  and pulls or pushes the second lens  232  by means of the wire  234  to change the focal length. Additionally, the projection  320  is also rotated and touches the switch  330  or the switch  340 . One of the switches is turned ON when touched by the projection  320  and an output of the switch is fed to the scale information display processing unit  440 .  
         [0048]    For example, if the operator rotates the lever  126  clockwise, the second lens  232  is pushed toward the first lens  231  and the focal length is increased, which means the image is displayed as large picture. The projection  320  is also rotated and turns the switch  340  ON whose output is fed to the scale information display processing unit  440 . The scale information display processing unit  440  outputs the scale information to the superimposing circuit  430 . Then, the superimposing circuit  430  superimposes the scale information on the image read-out from the frame memory  420  and the superimposed image is displayed on the monitor  150 . The mechanism and manner to change and detect the focal length of the optical system are not limited to this embodiment, for example, the switch  330  may be omitted.  
         [0049]    (2) When the switch only for triggering the timing is turned ON:  
         [0050]    When the operator turns the switch  141  ON, the scale information display processing unit  440  receives a signal from the switch  141  and the output of the scale information display processing unit  440  is fed to the superimposing circuit  430 . Then, the superimposing circuit  430  superimposes the scale information on the image read-out from the frame memory  420  and the superimposed image is displayed on the monitor  150 .  
         [0051]    (3) In the case the timing is made when the switch for freezing the image turned ON:  
         [0052]    When the operator turns the switch  123  ON, the frame memory  420  receives an image freeze signal and the moving image is changed to a still image. The scale information display processing unit  440  also receives the freeze signal and the output of the scale information display processing unit  440  is fed to the superimposing circuit  430  so that the superimposing circuit  430  then superimposes the scale information and the still image. In addition, a delay time may be set in the scale information display processing unit  440  such that the scale information is displayed, for example, a second after the switch  123  is turned ON. In this case the operator can confirm the still image displayed on the monitor is adequate before the scale is displayed on the monitor.  
         [0053]    (4) When the switch for storing the image is turned ON:  
         [0054]    When the operator turns the switch  124  or  125  ON, the scale information display processing unit  440  receives the storing signal. The output of the scale information display processing unit  440  is fed to the superimposing circuit  430  and the superimposing circuit  430  then superimposes the scale information on the still image. The frame memory  420  also receives a storing signal and the moving image is changed to the still image. The camera unit  160 , a disk unit  170  or a printer unit  180  also receives the storing signal and the image with the scale information is recorded.  
         [0055]    In addition, a delay time may be set in the scale information display processing unit  440  such that the scale information is displayed, for example, a second after the switch  123  is turned ON. In this case the operator can confirm the still image displayed on the monitor is adequate before the scale is displayed on the monitor. If it is not adequate, the operator can cancel storing by pushing the switch  124  or  125  before the scale information appears on the display.  
         [0056]    Hereinafter what is displayed in the monitor is described with reference to FIGS.  4  to FIG. 7, especially in case (4) in regard to the timing of display of scale information when the switch for storing the image is turned ON. FIG. 4 is a flowchart explaining the procedure of using the endoscope system. FIG. 5 is an illustration showing an image of an object  510  displayed as a normal picture.  
         [0057]    Next, the operator changes the focal length of the optical system with the lever and moves the endoscope unit  100  such that the object  510  is located within the depth of field and the image of the object  510  is displayed as a zoom-in picture, as shown in FIG. 6. Then, the operator pushes the switch  124  or  125  then the image is changed from a moving image to a still image and the still image is recorded in the camera unit  160  or disk unit  170  or printed by the printer unit  180 . With a predetermined delay time after the switch  124  or  125  is turned ON, the scale information is superimposed on the image and the two are displayed together. FIG. 7 is an illustration showing the image and the scale information superimposed thereon. The scale information shown in FIG. 7 includes a number of vertically and horizontally extending lines on the monitor.  
         [0058]    If the center of the depth of field is located at a distance from the principal points of the optical system by about 2.3 mm and the image is magnified 60 times, the preferred distance between the lines may be 30 mm on the monitor (0.5 mm for actual scale). In this case the object located at the distance of 2-2.5 mm from the principal points of the optical system can be distinguished with an error of 0.1 mm-0.2 mm.  
         [0059]    Other types of scale information may be provided as shown in FIG. 8 and FIG. 9. The scale information shown in FIG. 8 comprises two lines which are crossed orthogonally with each other and each line is graduated with a predetermined distance. The scale information shown in FIG. 9 includes coaxial circular lines, which are separated by a predetermined distance. Other types of scale information may be used too, as long as it enables measurement of the length of the object.  
         [0060]    [0060]FIG. 10 is a graph showing a relation between a distance from the center of a monitor and actual length of the object on the condition that the object is located within the depth of field. In FIG. 10, a solid line indicates the average distortion characteristic of the optical system and dotted lines indicate the average distortion characteristic including the dispersion characteristic of the optical system. In order that the endoscope system has a wide field of view, the distortion characteristic of the optical system is designed such that the length of the object on the monitor is smaller than the actual length of the object.  
         [0061]    [0061]FIG. 11 is another example showing scale information according to the distortion characteristic. The lines of this scale information are arranged such that a distance between the lines located at the center of the monitor is larger than the distance between the lines located at the edge of the monitor. The distance between the lines are determined according to the distortion characteristic as shown in FIG. 10. The operator can avoid misunderstanding the length of the object using this scale information.  
         [0062]    [0062]FIG. 12 is another example showing scale information according to the distortion characteristic. The width of the lines located at the center of the monitor is smaller than the width between the lines located at the edge of the monitor in this scale information. The operator would less likely to misunderstand the length of the object using this scale information.  
         [0063]    The scale may be movable on the monitor in order that a line of the scale is located on the edge of the object.  
         [0064]    [0064]FIG. 13 is an illustration showing an image and the scale information in the case that a line of the scale information is not located on an edge of the object. In this situation it is difficult for the operator to measure the size of the object. According to the present invention, the operator can move the scale information using the directional switch  142  shown in FIG. 1 such that the line of the scale information is located on an edge of the object.  
         [0065]    The scale information display processing unit  440  receives the signal from the directional switch  142  and the output of the scale information display processing unit  440  is fed to the superimposing circuit  430 . The superimposing circuit  430  adjusts the position of the scale information according to the signal from the scale information display processing unit  440  and superimposes the scale information and the image. FIG. 14 is an illustration showing an image and the scale information that are superimposed when the scale information is moved. The superimposed image, which is the same as displayed on the monitor, is stored in the recording devices after the movement of the scale. The operator moves the scale information on the monitor, after displaying the scale information with the image. The operator then records the image with the image in the recording devices by pressing a button.  
         [0066]    The directional switch  142  may be disposed on the operating handle. In addition, the scale information may move automatically. In this case, first the scale information moves up and down repeatedly by a distance between the adjacent lines then the operator can stop it anytime with a stop switch disposed on the operating handle (not shown). After that, the scale information moves to the right or the left automatically by a distance between the lines and then the operator stops it again. Thus, the operator can move the scale information to a desired position merely by pushing the stop switch without the use of a directional switch.  
         [0067]    Additionally a numeric display of the distance between the adjacent lines may be provided with the scale information. In FIG. 7 and FIG. 8 the number 0.5 mm is displayed on the monitor. The operator can select whether the scale information is used or not when the image is frozen, copied and printed, respectively. If the operator prior to an examination sets that the scale information is used only when the image is frozen, the scale information is not stored when the image is copied and printed. In this case, the operator can measure the length of the object when the image is frozen.  
         [0068]    Moreover if the operator prior to an examination sets that the scale information is used only when the image is copied or printed, the operator can observe the still image without the scale information and the scale information is copied or printed with the image. FIG. 15 is an illustration showing a menu for setting whether the scale information is used or not. In FIG. 15, C indicates copying, P is printing and F is freezing. FIG. 15 shows that the scale information is not used when the image is copied and it is used when the image is printed or frozen.  
         [0069]    Hereinbefore the case that each switch for magnifying, freezing, coping and printing works independently is described. However the scale information may be used only when the magnifying switch and at least one of the freezing, coping or printing switches are turned ON together.  
         [0070]    A further image processing operation indicated by the operator may trigger use of the scale information, such as enhancement processing, contrast processing or color control processing, for example.  
         [0071]    This endoscope system can be applied to a surgical endoscope operated by an operator far from a patient. The present invention is not limited to this embodiment and can be modified if necessary.  
         [0072]    As above described, the focal length is selectable from two levels, but the number of the levels is not limited, and more than two levels can be implemented. In this case, the scale information display processing unit  440  stores a plurality of the types of scale information, and the adequate scale information according to each focal length is used.  
         [0073]    In the above described embodiment, each focal length has a corresponding single scale information, but a plurality of the types of scale information, for example, a distance between the lines is different such as 0.5 mm, 0.75 mm or 1 mm, can be selectively used for each focal length. The operator can select one of the scale types appropriate to the situation. Moreover the operator may select one of the scale information shown in FIG. 7 through FIG. 9.  
         [0074]    In the above described embodiment, the varifocal lens is used in the optical system, but a zoom lens may also be used. In this case, when the operator changes magnification, the object can be observed appropriately without the moving of the endoscope unit because both the focal length and the depth of field can be adjusted independently.  
         [0075]    According to this invention, the operator can measure the size of the object easily without detecting a distance between an endoscope part and the object.  
         [0076]    Numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein.