Abstract:
An image observation apparatus comprising an image display unit for displaying an observation image and a supporting mechanism for supporting the image display unit movably and adjustably in the directions of three, substantially perpendicular axes. Since the supporting mechanism of this image observation apparatus can move and adjust the image display unit in three orthogonal axial directions, an operator need not select a plurality of articulates for operating them when he/she wants to move the image display unit to a desired axial direction. Further, one of the three axes can be a rotational axis for turnably supporting the image display unit around the operator. According to this configuration, the image display unit can be independently moved and adjusted in three axial directions, while the observation angle of the observer with respect to the display face of the image display unit is kept constant.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2004-224665, filed Jul. 30, 2004, the entire contents of which are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to an image observation apparatus used for observing an operative site in an enlarged scale during a surgical operation. The fields of surgical operations include neurosurgery, ophthalmology and orthopedic surgery and the like. 
     2. Description of the Related Art 
     In recent years, surgical operations are often performed in a style in which an image of an operative site is displayed on an image display unit such as an LCD monitor of a display apparatus. The surgeon observes the displayed image on the display unit to carry out a desired treatment. In practice, however, many treating devices or other observation devices are concentrated near the operative site. Therefore, it is desirable that the image observation apparatus be easily installed at a position that does not interfere with those many other devices. Specifically, if the image observation apparatus is located such that the surgeon has to look up, the surgeon becomes fatigued over time. Therefore, as a first requirement, when the image observation apparatus needs to be moved, it is desirable that the image display unit of the image observation apparatus be kept at a sufficient distance from the surgeon within the same horizontal plane, i.e., at the height of the surgeon&#39;s eyes. 
     On the other hand, the surgeon may often need to observe the operative site directly, without using the image observation apparatus. In the course of an operation, the surgeon may need to alternate between using the monitor observation and direct-viewing of the operative site. Therefore, as a second requirement, it is desirable that the image observation apparatus be easily movable away from the operative site when the apparatus is not in use. 
     In a lengthy operation, moreover, many surgeons often attend the operation alternately. Therefore, as a third requirement, it is desirable that the position of the image observation apparatus be easily adjustable during the operation to accommodate the height of the current surgeon. 
     In addition to the first to third requirements described above, the image observation apparatus should be sized to save space in the crowded operating room where many devices are arranged around the patient. Therefore, if a supporting device of the image observation apparatus is large-sized or if an additional space is required for the position change of an image display unit, it difficult to arrange necessary devices in the operating room. This difficulty may leads to a problem of lowering efficiency of the operation. 
     In view of such a problem, JP-A-7-16238 and JP-A-11-318936 have proposed an image observation apparatus, in which a display device such as a monitor is movably provided in three dimensional space with a multi-articulated arm-structure having a plurality of articulations for supporting the image display device. An operator must select a plurality of appropriate arms and actuate the selected arms to locate the display device at a disable position. 
     JP-A-2003-233031 has proposed an image observation apparatus wherein a display device, as an image display unit, comprises an image projecting unit and a light reflecting member instead of the monitor. The image projecting unit and light reflecting member are arranged to face each other while keeping their relative positions constant through a support member having a similar multi-articulated arm structure. In this display device of JP-A-2003-233031, moreover, there is also disclosed a technique, in which the second requirement can be met by making the light reflecting unit detachable from the support member. 
     BRIEF SUMMARY OF THE INVENTION 
     This invention seeks to provide an image observation apparatus comprising: an image display unit for displaying an observation image; and a supporting mechanism that movably and adjustably supports the image display unit along and about three substantially perpendicular axes. 
     Thus, the observer can move the image display unit in a desirable axial direction without having to select and control a plurality of articulations. 
     One of the three axial movements can be realized with a rotational axis for rotationally supporting the image display unit around the observer. 
     According to this configuration, the image display unit can be independently moved and adjusted in three axial directions, one of which includes movement around a rotational axis that traces a locus around the observer, while the observation angle of the observer with respect to the display face of the image display unit is kept constant. As a result, movement of the image display unit can be controlled conveniently and easily without any complicated control being required as in the prior art for adjusting the position of the image display unit finely. Therefore, observer fatigue is reduced, which improves the operation efficiency. 
     The three axes of the supporting mechanism may include a rotational axis positioned substantially over the cervical vertebrae of the observer. 
     According to the configuration described above, the image display unit can be independently moved and adjusted around the axis passing through the cervical vertebrae of the observer through the supporting mechanism, while keeping the observation angle of the observer constant. Thus, unlike the prior art, the moving operation is convenient and easy without the need for complicated control to adjust the position of the image display unit finely. 
     Moreover, the supporting mechanism can include a first rotational axis, which is not a member of the three axes, for turnably supporting the image display unit. In this case, a second rotational axis, which is a member of the three axes, and a linking mechanism for linking the turning angle of the first rotational axis with the turning angle of the second rotational axis is provided. 
     According to the above configuration, when the position of the image display unit is independently moved and adjusted in the three axes including the second rotational axis through the supporting mechanism, the first rotational axis is rotated through the linking mechanism between the second and first rotational axes according to the rotation of the second rotational axis, and the observation angle is kept constant with respect to the display face of the image display unit. As a result, the moving operation can be likewise made convenient and easy, reducing surgeon fatigue. Moreover, the image display unit can be moved around the first axis so that a simple structure for removing the image display unit is realized. This configuration improves efficiency. 
     As described above, this invention provides an image observation apparatus with a simple configuration that improves the efficiency of movements and adjustments thereof, and thus, the overall efficiency of the operations. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other features, aspects and advantages of the apparatus and methods of the present invention will become better understood with regard to the following description, appended claims, and accompanying drawings, where: 
         FIG. 1  is a perspective view showing a construction of an image observation apparatus according to a first embodiment of the invention; 
         FIG. 2  is a sectional view showing a support structure of  FIG. 1 ; 
         FIG. 3  is a perspective view showing an imaging system of  FIG. 1 ; 
         FIG. 4  is a perspective view showing a construction of an image observation apparatus according to a second embodiment of the invention; 
         FIG. 5  is a sectional view showing a support structure of  FIG. 4 ; 
         FIG. 6  is a sectional view indicated in  FIG. 5 ; 
         FIG. 7  is a perspective view showing a construction of an image observation apparatus according to a third embodiment of the invention; 
         FIG. 8  is a partially sectional view showing a portion of a support structure of  FIG. 7 ; 
         FIG. 9  is a perspective view showing a construction of a modification example of the image observation apparatus according to the third embodiment of the invention; 
         FIG. 10  is a sectional view showing a main part of support structure of  FIG. 9 ; 
         FIG. 11  is a sectional view showing a stowage or protected state of  FIG. 10 ; 
         FIG. 12  is a sectional view indicated in  FIG. 10 ; 
         FIG. 13  is a sectional view indicated in  FIG. 10 ; 
         FIG. 14  is a perspective view showing a construction of an image observation apparatus according to a fourth embodiment of the invention; 
         FIG. 15  is a top plan view showing an arrangement and construction of a major portion of  FIG. 14 ; 
         FIG. 16  is a top plan view shown for explaining an adjusting action of  FIG. 14 ; 
         FIG. 17  is a perspective view showing a construction of an image observation apparatus according to a fifth embodiment of the invention; and 
         FIG. 18  is a perspective view showing a configuration of a control system of  FIG. 17 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Embodiments of the invention will be described below with reference to the accompanying drawings. 
       FIG. 1  shows an image observation apparatus according to a first embodiment of the invention. A base  1  is placed on the floor behind a surgeon  2  or an observer, and a housing  3  of a hollow structure is erected thereon from the base  1 . In this housing  3 , as shown in  FIG. 2 , one end of a vertical mover  4  is fitted to move freely in the vertical direction through a cross roller bearing  5 . The housing  3 , vertical mover  4  and cross roller bearing  5  are contained in a vertical slide mechanism forming part of a supporting mechanism. 
     Between the lower end of the vertical mover  4  and the housing  3 , moreover, there is arranged a balance spring  27 , operating under compression. The upper end of the vertical mover  4  is bent toward the surgeon  2  and extends to the vicinity of the head of the surgeon  2 . This extension has a through hole  6  formed in its distal end. This through hole  6  has its center axis  7  arranged substantially in alignment with the direction of vertical axis of the cervical vertebrae of the surgeon  2 . In this through hole  6 , there is inserted turnably and snugly a pivot (rotational axis)  9 , which is formed at the proximal end of a turning member  8 . 
     This pivot  9  is equipped at its distal end with a threaded portion  11 , which protrudes from the through hole  6  and is fastened by a nut  10 . As a result, the turning member  8  is turnably assembled with the through hole  6  of the vertical mover  4 . In short, the through hole  6  and pivot  9  are contained in a vertical turning mechanism or journal. 
     The turning member  8  is formed substantially in an L-shape and has its distal end  12  extended horizontally and toward the surgeon  2  so that the end  12  is inserted slidably and snugly in a longitudinal mover  13  having a substantially hollow structure. In the inner wall near the proximal end of the longitudinal mover  13 , a pin  14  protrudes, which snugly fits in a groove  16  formed in the distal end  12  of the turning member  8 , in the direction of an extension axis  15  of the distal end  12 . The longitudinal mover  13  and the turning member  8  form a longitudinal slide mechanism of the aforementioned supporting mechanism. 
     To the distal end of the longitudinal mover  13 , moreover, is attached an image display unit such as an LCD (Liquid Crystal Display)  17  ( FIG. 1 ). This LCD  17  is equipped at its two sides with operating knobs  18 . 
     In  FIG. 1 , numeral  19  designates an endoscope, which is gripped by the surgeon  2  and arranged at a desired position of an operative site  21  of a patient  20 . This endoscope  19  is optically connected at its proximal end not only to a CCD  22  or the like as an image pickup member but also to a light source device  24  through a light guide cable  25  ( FIG. 3 ). Of these, the CCD  22  is electrically connected through a connection cable  251  with a camera controller  23 , which is electrically connected with the LCD  17  through a video signal cable  26 . 
     During surgery with the configuration thus far described, the surgeon  2  inserts at first the endoscope  19  into the operative site  21  of the patient  20  and manipulates the endoscope  19  to take an image of the operative site. The optical image is converted into electric signals by the CCD  22  so that the electric signals are input to the camera controller  23  through the connection cable  251 . Then, the camera controller  23  processes the electric signals to create image signals, and outputs the image signals to the LCD  17  through the video signal cable  26  so that the image of the operative site  21  or the observation image picked up by the endoscope  19  is displayed on the LCD  17 . Here, the surgeon  2  performs a desired treatment at the operative site  21  while observing the image information displayed on the LCD  17 . 
     Next will be described the works for the surgeon  2  to move the LCD  17  in case the treating device or another observing device interferes with the LCD  17  during the operation. At first, in case the surgeon  2  intends moving the LCD  17  back and forth in the direction of his or her view, the surgeon  2  grips and moves the knobs  18  back and forth in the direction of the arrow X, as shown in  FIG. 1 . This X-direction control force applied to the knobs  18  is transmitted to the longitudinal mover  13  through the LCD  17 . This control force direction is aligned with the direction of the axis  15  of the extension of the distal end  12  of the turning member  8  so that the longitudinal mover  13  slides with respect to the turning member  8 . The pin  14  allows sliding movements of the longitudinal mover  13  and the turning member  8  but prevents turning movement therebetween around the extension axis  15 . As a result, the LCD  17  slides only in the direction of the extension axis  15  without any turning motion, and its longitudinal position is adjusted. 
     When the surgeon  2  applies control force to the knobs  18  in the direction of arrow Y, as shown in  FIG. 1 , the control force is transmitted to the turning member  8  through the LCD  17  and the longitudinal mover  13  so that the pivot  9  is turned relative to the through hole  6 . As a result, the LCD  17  is turned around the center axis  7 . This center axis  7  is substantially aligned with the cervical vertebrae of the surgeon  2 . Without changing the body position with respect to the operative site, therefore, the surgeon  2  is enabled to face the LCD  17  at all times by turning his or her head toward the LCD  17 . This control force in the direction Y is perpendicular to the axial direction of the extension axis  15  so that the aforementioned longitudinal mover  13  does not move relative to the turning member  8 . 
     Next will be described the case, in which the LCD  17  is removed so that the surgeon may observe the operative site in a direct view during a series of operations. At first, the surgeon  2  grips the knobs  18  of the LCD  17  and applies the control force in the direction of Z, as shown in  FIG. 1 . This control force, as applied to the knobs  18 , is transmitted through the longitudinal mover  13  and the turning member  8  to the vertical mover  4 . The cross roller bearing  5  arranged between the housing  3  and the vertical mover  4  is permitted to move only in the direction Z so that the LCD  17  is moved in the direction Z. 
     At this time, the weight of the structure from the LCD  17  to the vertical mover  4  is supported by the action of the balance spring  27 . Even if, therefore, the surgeon  2  releases the knobs  18 , the LCD  17  does not naturally move in the vertical direction but is held at the moved position. Thus, the surgeon  2  can move, if necessary, the LCD  17  upward away from the operative site  21 . 
     Even if another surgeon  2  having a different body size takes over during the operation, the LCD  17  can be set in the desired state by the same controls. Specifically, the position adjustment of the LCD  17  in the height direction due to the difference in the heights of the surgeons can be easily made by the moving adjustment in the direction Z. 
     Thus, by the image observation apparatus, the LCD  17  displaying the observing image is made adjustable independently of the three substantially perpendicular axis directions X, Y and Z including the turning axis positioned substantially on the cervical vertebrae of the surgeon  2 . The axial direction is the direction to which each axis allows the LCD  17  (display unit) to move. 
     In the image display device of the first embodiment, a simple configuration is realized without using the arm structure of a complicated link mechanism, such as an electromagnetic brake or the like. Moreover, highly precise movement adjustment of the LCD  17  can be realized to greatly contribute to improvements in the operation efficiency. 
     The first embodiment has been described for the case in which an observation image such as the image of the operative site is captured by using the endoscope  9 . However, the invention is not be limited thereto but can be used to display image information acquired by other well-known devices such as stereoscopic endoscopes, surgical microscopes, ultrasonic diagnostic apparatus, MRIs, CTs and the like. In case image information having a parallax is guided to the eyes of the surgeon  2  as in the stereoscopic endoscope apparatus or the surgical microscope, a display part such as the aforementioned LCD  17  can be replaced by the so-called “parallax barrier” type three-dimensional image display apparatus or the like, as disclosed in JP-A-5-107663. This replacement is likewise applicable to all the other embodiments. 
     Moreover, the first embodiment has been described for the case where the vertical balance utilizes the balance spring  27 . But, this balance spring may also be replaced by a coil spring or a counter weight. 
     Moreover, the first embodiment has been described for the case in which the cross roller bearing  5  is used in the vertical slide mechanism and in which the slip bearing structure is used in the longitudinal slide mechanism. However, the invention is not be limited thereto, but those mechanisms can be additionally configured by using various regulating members such as spline bearings for moving the two members in only one moving direction relative to each other. 
       FIG. 4  to  FIG. 6  show an image observation apparatus according to a second embodiment of the invention. In  FIG. 4  to  FIG. 6 , portions identical to those of the first embodiment have the same common reference numerals and perform the same functions. 
     This embodiment provides a chair  28  for the surgeon  2  to sit on during the operation, which chair is equipped on its bottom with casters  29  at predetermined positions, to enable the surgeon  2  to move on the floor selectively. This chair  28  has a seat  30  ( FIG. 5 ) and a vertical pivot  31  below the seat  30 . This vertical pivot  31  has a center axis  32  substantially aligned with the cervical vertebrae of the surgeon  2  when the surgeon  2  is seated. The vertical pivot  31  is inserted in a through hole  34  formed in a support member  33  thereby to support the support member  33  snugly and turnably. 
     The vertical pivot  31  is provided at its proximal end with a flanged portion  36  corresponding to the through hole  34  and at its distal end with a threaded portion  37 . As a result, the vertical pivot  31  is turnably assembled with the support member  33  by inserting its threaded portion  37  from one side into the through hole  34  of the support member  33  and by fastening a nut  35  on its threaded portion  37  while its flanged portion  36  abuts the circumference of one side of the through hole  34 . The vertical pivot  31 , the support member  33  and the nut  35  are contained in a vertical turning mechanism. 
     The sectional shape of the support member  33  is substantially a C-shape, preferably having its upper side opened ( FIG. 6 ). The support member  33  is horizontally extended to the back of the surgeon  2 , i.e., the seat  30 . In the recess of that support member  33 , moreover, there is housed one such horizontal portion  39  of a substantially L-shaped vertically moving housing  38  snugly movable in the extending direction through a cross roller bearing  41  composing the longitudinal slide mechanism. 
     This vertical moving housing  38  has its other vertical portion  40  formed into a hollow structure to receive a vertical mover  42  through the cross roller bearing  5  and the balance spring  27  substantially as in the first embodiment. Moreover, the vertical mover  42  is bent at its upper end toward the surgeon  2  into an L-shape having an upper end, to which the aforementioned LCD  17  is attached through an arm member  43 . In the described embodiment, the LCD  17 , the surgeon  2  and the extending direction of the support member  33  are arranged to lie substantially on one line. 
     For the described configuration, the manner of moving the LCD  17  is now described for the case where an operating device or another observing apparatus interferes with the LCD  17  during the operation. In case the LCD  17  is moved back and forth in the viewing direction of the surgeon  2 , the surgeon  2  grips the knobs  18  to bring the LCD  17  back and forth in the arrow direction X, as shown in  FIG. 4 . Then, the control force in the direction X, as applied to the knobs  18 , is transmitted to the vertical moving housing  38  through the LCD  17 , the arm member  43  and the vertical mover  42 . Here, the vertical moving housing  38  is arranged movably in the direction X with respect to the support member  33  through the cross roller bearing  41  so that it is horizontally moved in the direction X with respect to the support member  33  thereby to bring the LCD  17  in the horizontal direction. 
     When the surgeon  2  applies the control force to the knobs  18  in the direction of arrow Y, as shown in  FIG. 4 , the control force is sequentially transmitted as in the aforementioned case of the movement in the direction X and finally to the support member  33 . Then, the vertical pivot  31  engaging with the through hole  34  of the support member  33  is so turnably arranged as to have its turning direction aligned to the direction Y so that the LCD  17  is turned around the center axis  32  and positionally adjusted in the direction Y. 
     In this second embodiment, too, as in the first embodiment, the vertical pivot  31  of the chair  28  is aligned substantially with the position of the cervical vertebrae of the surgeon  2 . As a result, the surgeon  2  always remains facing the LCD  17  merely by turning his or her neck without changing his or her body position with respect to the operative site. 
     Now will be described the case in which the LCD  17  is removed for the surgeon  2  to observe the operative site directly, for example during a series of operations. In this case, the surgeon  2  grips at first the knobs  18  of the LCD  17  and applies the control force in the direction of arrow Z, as shown in  FIG. 4 . Then, the control force applied to the knobs  18  is transmitted to the vertical mover  42  through the LCD  17  and the arm member  43 . As a result, the LCD  17  is moved in the direction Z as in the first embodiment, so that it assumes a non-interfering position. 
     For surgeons of different body sizes who alternate during the operation, the movements and adjustments are made in the directions X, Y and Z in the control procedure as described above. For example, the position adjustment of the LCD  17  in the height direction due to the height difference of a particular surgeon  2  is made by adjusting the movements in the direction Z. 
     According to the second embodiment, no mechanical portion is provided in the vicinity of the operative site, owing to the arranging of the longitudinal slide mechanism and the vertical turning mechanism below the seat  30  of the surgeon  2 . As a result, it is possible to utilize space more effectively. 
     Moreover, the configuration is made as such those mechanisms are arranged in the assembly of the seat  28  for the surgeon  2 . As a result, when the surgeon  2  is seated on the chair  28 , the turning center necessarily aligns substantially with the cervical vertebrae of the surgeon  2 . Therefore, the surgeon  2  can concentrate on the operating procedures without paying attention to the position of the turning center or his or her position. This contributes to improving the operation efficiency. 
       FIG. 7  and  FIG. 8  show an image observation apparatus according to a third embodiment of the invention. In FIG.  7  and  FIG. 8 , the portions that correspond to those of the first and second embodiments are not described, but bear the same reference numerals. 
     In the third embodiment, the configuration from the seat  28  to the vertical moving housing  38  is substantially similar to that of the second embodiment. The lower end of a vertical mover  45  is movably inserted (as in the second embodiment) into the vertical portion  40  of the vertical moving housing  38 . 
     To the upper end of the vertical mover  45  are attached a pair of image projecting units  46  or the image projecting mechanism disclosed in JP-A-2003-233031, for example. At an intermediate portion of the vertical mover  45  there is arranged a horizontal arm unit  44  through a later-described transverse switching mechanism  47  and a later-described horizontal arm unit housing mechanism  48 . At the distal end of the horizontal arm unit  44  is arranged an image projection panel  49  or the well-known beam reflecting member disclosed in JP-A-2003-233031. Moreover, the horizontal arm unit  44  is equipped at its intermediate portion with a grasping grip  56 . 
     Now there will be described in detail the transverse switching mechanism  47 , which is arranged at the vertical mover  45  ( FIG. 8 ). Specifically, the vertical mover  45  is equipped with a through hole  57  around the center axis  58  of the image projection panel  49 . A transverse switching stem  59  is engaged snugly and turnably by that through hole  57 . This transverse switching stem  59  is fixed at one end in a housing  64  and is fastened and fixed at its other end by a nut  65 . 
     In the outer circumference of the transverse switching stem  59 , are formed a pair of fixing holes  63   a  and  63   b,  symmetrically with respect to the center axis  58 . These fixing holes  64   a  and  63   b  are selectively engaged by the externally threaded distal end  62  of a transverse fixing knob  61 . This transverse fixing knob  61  is adjustably fastened in a threaded hole  60  formed in the vertical mover  45 . 
     The details of the horizontal arm unit housing mechanism  48  are as follows. In the housing  64 , a hole  67  is formed on a center axis  66  perpendicularly to the center axis  58 . In this hole  67  is snugly and turnably inserted a housing stem  68 , which is formed at the proximal end of the horizontal arm unit  44 . The housing stem  68  of the horizontal arm unit  44  is equipped at its two ends with flanges  69   a  and  69   b , which are formed to correspond to the two ends of the hole  67  of the housing  64 . These flanges  69   a  and  69   b  clamp the two ends of the hole  67  of the housing  64 . The flange  69   b  on the distal end side is serrated at its end face to engage with a serrated or coarse portion  72  formed on a push member  71 . 
     In the outer circumference of the push member  71  are formed a plurality of grooves  73  at a predetermined interval substantially in parallel with the center axis  66 . Pins  74  disposed in the housing  64  are so engaged by those grooves  73  as to slide only in the direction of the center axis  66  thereby to make the so-called “spline structure”. 
     Moreover, a housing knob  76  abuts at its distal end against the end face of the push member  71 . Specifically, the housing knob  76  is equipped at its distal end with a threaded portion  761 , which is adjustably fastened at the end of the housing  64  in a threaded hole  75  formed around the center axis  66 . 
     The details of a joint structure of the horizontal arm unit  44  and the image projection panel  49  are now described. Specifically, the horizontal arm unit  44  is equipped at its distal end with a cylindrical receiving joint member  51 . This receiving joint member  51  is equipped in its side face with a threaded hole  52 , which is directed toward the cylindrical center direction of the receiving joint member  51 . At a position symmetric to that threaded hole  52  with respect to the cylinder center is disposed a positioning pin  53 . This positioning pin  53  protrudes in the cylindrical center direction from the wall face of the inner cylinder of the receiving joint member  51 . Moreover, a threaded portion  541  of a fixing knob  54  is adjustably fastened into the threaded hole  52  of the receiving joint member  51 . 
     On the other hand, the image projection panel  49  is equipped on the two upper ends with substantially similar joint members  50   a  and  50   b . One of these joint members  50   a  and  50   b  is selectively engaged snugly by the receiving joint member  51 . These joint members  50   a  and  50   b  are equipped in their longitudinal direction with grooved portions  55   a  and  55   b , one of which is selectively engaged snugly by the positioning pin  53 . 
     Next is described the procedure for moving the image projection panel  49  when the treating device or another observing device interferes with the image projection panel  49  during an operation. 
     When the surgeon  2  intends moving back and forth the image projection panel  49  in the direction of his or her view, the surgeon  2  grasps the grip  56  to apply the control force back and forth in the direction of arrow X, as shown in  FIG. 7 . The control force in the direction X, as applied to the grip  56 , is transmitted sequentially through the horizontal arm unit  44 , the horizontal arm unit housing mechanism  48  and the transverse switch mechanism  47  and further to the vertical mover  45 . Then, the X-direction force applied to the vertical mover  45  is transmitted, as in the second embodiment, to the vertical moving housing  38 . 
     Because the cross roller bearing  41  moves only in the direction X between the vertical moving housing  38  and the support member  33 , the vertical moving housing  38  is horizontally moved in the direction X with respect to the support member  33  so that the image projection panel  49  and the image projecting units  46  are horizontally moved and adjusted together in the direction X. 
     When the surgeon  2  applies the control force in the direction of arrow Y, as shown in  FIG. 4 , to the grip  56 , the control force is transmitted in the same order as that for the case of moving in the direction X so that it is finally transmitted to the support member  33 . Here, the vertical pivot  31  engaged by the through hole  34  of the support member  33  is turnably disposed in the direction Y so that the image projection panel  49  and the image projecting units  46  are turned on the center axis  32  and adjusted in the direction Y. 
     As with the first and second embodiments, the vertical pivot  31  is substantially aligned with the cervical vertebrae of the surgeon  2  so that the relation between the relative positions of the image projecting units  46 , the image projection panel  49  and the eyes of the surgeon  2  is always fixed. As a result, the surgeon  2  is enabled to continue the observation merely by turning his or her head toward the image projection panel  49  without changing his or her body position with respect to the operation site. 
     The case where use of the image projection panel  49  is dispensed with so that the surgeon  2  may observe the operation site directly in a series of operations is described as follows. First, the surgeon  2  grasps the grip  56  of the horizontal arm unit  44  and applies a control force in direction of arrow Z, as shown in  FIG. 6 . This control force applied to the grip  56  is transmitted, in an order substantially similar to that of the aforementioned case of the direction X, to the vertical mover  45 . Then, the vertical mover  45  is moved in the direction Z, as in the first and second embodiments, so that the image projection panel  49  and the image projecting units  46  are vertically moved together in the direction Z. 
     Moreover, when surgeons  2  having different body sizes alternate during an operation, adjusting the height difference in the position of the image projection panel  49  due to the height differences between the surgeons  2  is easily accomplished. 
     In  FIG. 7 , moreover, the horizontal arm unit  44  is arranged for lefthand operation. However, this configuration can also be modified such that the horizontal arm unit  44  is arranged on the righthand side according to particular needs. In such modification, the surgeon  2  turns at first the transverse fixing knob  61  to loosen its engagement with the threaded hole  60 . Then, the transverse fixing knob  61  releases its externally threaded distal end  62  from the fixing hole  63   a  of the transverse switching stem  59  thereby to release their mutual engagement. In this state, the transverse switching stem  59  is freely turnable with respect to the through hole  57  of the vertical mover  45 . Therefore, the surgeon  2  turns the horizontal arm unit  44  by 180 degrees around the center axis  58 . Then, the fixing hole  63   b  of the transverse switching stem  59  is arranged at a position to confront the transverse fixing knob  61 . Thus, the surgeon can alone fasten the transverse fixing knob  61  into the threaded hole  60  and insert the same into the fixing hole  63   b  of the transverse switching stem  59  so that it is fixed with respect to the vertical mover  45 . 
     Next, the surgeon  2  turns back the fixing knob  54  to loosen it. Then, the joint member  50   a  and the receiving joint member  51  are released from their fixed states. Then, the surgeon  2  pulls out the image projection panel  49  in the groove direction of the grooved portion  55   a  of the joint member  50   a  to relieve the image projection panel  49  from the receiving joint member  51 . Subsequently, the joint member  50   b  is inserted into the receiving joint member  51  by engaging the positioning pin  53  with the grooved portion  55   b . Here, the positioning pin  53  and the grooved portion  55   b  engage so that the image projection panel  49  is arranged at the same position as that when the horizontal arm unit  44  is arranged on the lefthand side of the surgeon  2 . Then, the fixing knob  54  is fastened again to fix the joint member  50   b  and the receiving joint member  51 . 
     To store the apparatus, the surgeon  2  first loosens the housing knob  76  to open the push member  71  slidably in the direction of the center axis  66 . Then, the push member  71  is released from the abutting force between the serrated portion  72  and the end face of the flange  69   b  of the housing stem  68  so that the housing stem  68  can turn on the center axis  66 . Here, the surgeon  2  turns the horizontal arm unit  44  downward. When the housing knob  76  is fastened again in this state, the fastening force by the threaded portion  75  urges axially the push member  71  in the direction of the center axis  66  so that the serrated portion  72  of the push member  71  and the end face of the flange  69   b  come into abutting engagement. Thus, the housing stem  68  is positioned and fixed in the turned position. Here, the push member  71  retains a desired fixing force because its serrated portion  72  abuts against and engages with the serrated end face of the flange  69   b.    
     In addition to effects substantially similar to those of the second embodiment, the third embodiment requires less storage by providing the horizontal arm unit housing mechanism  48 . Moreover, the horizontal arm unit  44  is arranged on the side of the surgeon  2  so that the position of the grip  56  is closer to the hand of the surgeon  2 . Therefore, the movement of the hand can be reduced for the moving control thereby to lighten surgeon fatigue. This also contributes to improving the operation efficiency. 
     According to the third embodiment, moreover, the provision of the transverse switching mechanism  47  permits the arrangement of the horizontal arm unit  44  on either side of the surgeon  2  in accordance with need. As a result, it is possible to adjust modes according to the operation&#39;s needs, to improve the overall operation efficiency. 
     The third embodiment should not be limited to the mode described above but can also be configured by adding a retracting mechanism  77  such as one shown in  FIG. 9  to  FIG. 13 . In  FIG. 9  to  FIG. 13 , parts used in third embodiment bear the same designations and will not be described again. 
     Specifically, one horizontal portion  79  of a substantially L-shaped vertical moving housing  78  is movably assembled, like the horizontal portion  39  of the vertical moving housing  38 , with the chair  28  ( FIG. 9 ). The other vertical portion  80  of the vertical moving housing  78  is formed as a hollow structure, and a vertical mover  81  is jointed to the vertical portion  80  through a vertical slide mechanism  82 . The aforementioned image projecting unit  46  or the image projecting mechanism is attached to the upper end of the vertical mover  81 . 
     At the intermediate portion of the vertical mover  81 , there are sequentially arranged the retracting mechanism  77  ( FIG. 10 ), a transverse switching mechanism  102  ( FIG. 12 ) and the transverse switching stem  59  which has the same configuration as that of the foregoing third embodiment. This series configuration from the transverse switching stem  59  through the horizontal arm unit  44  to the image projection panel  49  is similar to that of the third embodiment. 
     The details of the vertical slide mechanism  82  are as follows. The vertical mover  81  is inserted movably and snugly only in the direction of arrow Z in  FIG. 9  into the inner wall of the vertical portion  80  of the vertical moving housing  78  through a cross roller bearing  83  ( FIG. 13 ). A spring member  84  ( FIG. 10 ) is compressed and arranged between that vertical mover  81  and the vertical moving housing  78 . 
     The spring member  84  is preferably a gas spring for establishing a constant spring force over the entire range in which the vertical mover  81  can move with respect to the vertical moving housing  78 . The spring force is substantially equalized to the falling weight, which is exerted from the vertical mover  81  on the spring member  84 . 
     The retracting mechanism  77  includes a retracting piece  85  constituting the retracting mechanism  77  which comprises on its two side faces two stems of a retracting stem  86  and a hollow retracting stem  87 , which are conjugated with respect to the center axis  58  ( FIG. 12 ). On the other hand, the vertical mover  81  is provided with a hollow portion  88  having two side walls, in which through holes  90  and  91  are formed around a retracting stem center  89  perpendicular to the center axis  58 . These retracting stem  86  and hollow retracting stem  87  rotatably engage with the through holes  90  and  91 , respectively. 
     From the side of the retracting piece  85 , protrudes a pivot pin  92 , which turnably supports one end of a link rod  93  ( FIG. 11 ). This link rod  93  is equipped in its other end with a hole  100  ( FIG. 13 ), in which there is turnably inserted a pivot pin  99  of a protrusion  98  embedded in a semicircular plate  94 . This semicircular plate  94  is formed substantially into a D-shape by forming a flat portion  111  at a distance L from the center of a disc having a diameter R ( FIG. 10  to  FIG. 13 ). From the semicircular plate  94 , protrudes a pin  96 , which is conjugate with the disc center and which is turnably engaged by a pivot hole  97  formed in the vertical mover  81  ( FIG. 13 ). Moreover, the flat portion  111  of the semicircular plate  94  abuts a flat portion  110  formed on the inner wall of the vertical portion  80  of the vertical moving housing  78  ( FIG. 10 ). 
     The vertical portion  80  of the vertical moving housing  78  is equipped at its upper end with an R-shaped recess  101 , which corresponds to such an R-shape as is conjugate with respect to the center portion of the disc center of the semicircular plate  94 . The peripheral wall of the semicircular plate  94  is in sliding contact with that recess  101  ( FIG. 11 ). 
     Moreover, the retracting piece  85  is equipped at its upper portion with a protrusion  109 , which retains one end of a spring  107 . The other end of this spring  107  is retained by a protrusion  108 , which is formed in the hollow portion  88  of the vertical mover  81 . 
     Next, the transverse switching mechanism  102  will be described in detail. Specifically, the transverse switching stem  59  is engaged snugly and turnably by a through hole  103  formed in the retracting piece  85  ( FIG. 12 ). A threaded portion of a transverse switching knob  104  is adjustably screwed into an internally threaded portion  105  of the hollow retracting stem  87  arranged in the retracting piece  85 . The threaded portion of the transverse switching knob  104  is equipped at its distal end with an engagement portion  106 , which is snugly retained by the fixing hole  63   a  of the transverse switching stem  59 . 
     The procedure for moving the image projection panel  49  when the treating device or another observing device interferes with the image projection panel  49  during the operation is as follows. 
     In case the surgeon  2  intends moving the image projection panel  49  back and forth in the direction of his or her view, the surgeon  2  grasps the grip  56  of the horizontal arm unit  44  to apply the control force back and forth in the direction of arrow X, as shown in  FIG. 9 . The control force in the direction X, as applied to the grip  56 , is transmitted through the horizontal arm unit  44 , the horizontal arm unit housing mechanism  48 , the transverse switch mechanism  47  and the retracting mechanism  77  and further to the vertical mover  81 . Then, the control force transmitted to the vertical mover  81  is transmitted as in the third embodiment to the vertical moving housing  78 . Then, the vertical moving housing  78  is horizontally moved in the direction X with respect to the support member  33 , because it is arranged to move only in the direction X through the cross roller bearing  41  with respect to the support member  33 . In accordance with this movement, the image projection panel  49  and the image projecting units  46  are horizontally moved together in the direction X and adjusted. 
     When the control force is applied by the surgeon  2  in the direction of arrow Y, as shown in  FIG. 9 , to the grip  56  of the horizontal arm unit  44 , the control force is transmitted as in the movement in the direction X to the support member  33 . Since the support member  33  is disposed turnably around the vertical pivot  31  engaged by the through hole  34 , it has a turning direction aligned to the direction Y. By the turning motions, the image projection panel  49  and the image projecting units  46  are turned together on the center axis  32  and adjusted in the direction Y. 
     Here, the vertical pivot  31  is substantially aligned with the cervical vertebrae of the surgeon  2  so that the relation between the relative positions of the image projecting units  46 , the image projection panel  49  and the eyes of the surgeon  2  is also always maintained. As a result, the surgeon  2  is enabled to continue the observation merely by turning his or her head toward the image projection panel  49  without changing his or her body position with respect to the operative site. 
     In case the image projection panel  49  is retracted so that the surgeon  2  may observe the operative site in direct view during a series of procedures, the surgeon  2  grasps the grip  56  of the horizontal arm unit  44  and applies a control force in direction of arrow Z (i.e., upward), as shown in  FIG. 9 . Then, the vertical mover  81  is moved to the uppermost end of the moving range in the direction Z for the vertical moving housing  78 , and the retracting piece  85  is turned around the retracting stem center  89  when the control force in the direction Z is further applied. As a result, the image projection panel  49  is turned together with the horizontal arm unit  44  around the retracting stem center  89 , as indicated by broken lines in  FIG. 9 . In these series of controls, during moving in the Z direction, the flat portion  111  arranged in the semicircular plate  94  and the flat portion  110  arranged in the vertical moving housing  78  abut each other so that the semicircular plate  94  does not turn around the disc center  95 . As a result, the retracting piece  85  made together with the semicircular plate  94  into a parallel link mechanism does not turn around the retracting stem center  89 . 
     On the other hand, when the vertical mover  81  is positioned at the uppermost end of the moving range in the direction Z, as shown in  FIG. 11 , the abutment between the flat portion  110  and the flat portion  111  for regulating the turning motions of the semicircular plate  94  around the disc center  95  vanishes so that the retracting piece  85  can turn around the retracting stem center  89 . When the surgeon  2  turns the retracting piece  85  around the retracting stem center  89 , the semicircular plate  94  forming the parallel link mechanism together with the retracting piece  85  turns around the disc center  95 . Then, the R-portion of the semicircular plate  94  comes into abutment against the R-shaped recess  101  arranged in the vertical moving housing  78 . In this state, the movement in the direction Z is regulated. By the action of the spring  107 , moreover, the balance around the retracting stem center  89  is maintained no matter what the position of the turning state around the retracting stem center  89  of the retracting piece  85 . Even if, therefore, the surgeon  2  releases the grip  56 , the image projection panel  49  and the horizontal arm unit  44  do not fall, but keep the moving positions. 
     In case the surgeon  2  changes places during the operation with another surgeon having a different body size, the newly assigned surgeon  2  grasps the grip  56  of the horizontal arm  44  to apply the control force in the direction of arrow Z, as shown in  FIG. 9 . Then, the control force thus applied to the grip  56  is transmitted as in the case of the direction X to the vertical mover  81  so that the vertical mover  81  is moved in the direction Z by the action of the cross roller bearing  83 . In response to the movement of the vertical mover  81  in the direction Z, the image projection panel  49  and the image projecting unit  46  are vertically moved together in the direction Z. Thus, the position adjustment of the image projection panel  49  in the height direction due to the height difference between the surgeons  2  is realized by the movement adjustment in the direction Z. 
     In addition to the effects of the third embodiment, in the present embodiment, the image projection panel  49  can be brought to and arranged at a higher position than the operative site by the retracting mechanism  77 . The image projection panel  49  thus does not interfere with other devices concentrated near the operative site, thereby improving the operation efficiency. 
       FIG. 14  shows an image observation apparatus according to a fourth embodiment of the invention. In  FIG. 14 , portions corresponding to the first to third embodiments are not described, but marked with common reference numerals. 
     Specifically, a base  112  constituting the supporting mechanism is equipped at its bottom with a plurality of casters  113 , which are arranged at a predetermined interval and can move as the longitudinal slide mechanism, for example, only in the direction of arrow X. The image observation apparatus can move on the floor in the direction X with the plural casters  113 . From the base  112 , there is vertically arranged (in the direction Z) a column  114  having a distal end, onto which a vertical mover  115  acting as the vertical slide mechanism and having a hollow structure is mounted to slide in the vertical direction (the direction Z). 
     From the upper end of the vertical mover  115 , there is arranged a vertical pivot (a rotational axis)  116 . This vertical pivot  116  is inserted into a through hole  118 , which is formed in one end of a chassis member  117  having a general bow shape so that it is assembled snugly and turnably in the through hole  118 . The aforementioned image projecting unit  46  is attached to the chassis member  117  through a column member  119 . 
     On the distal end of the vertical pivot  116 , on the other hand, there is turnably fitted a first pulley  120 , which constitutes a turn transmission mechanism. On the chassis member  117 , moreover, there are individually pivotally mounted a second pulley  123 , a third pulley  124  and a fourth pulley  125 , which are arranged sequentially at the plurality of curbed portions from the proximal end to distal end of the chassis member  117 . These first to fourth pulleys  120 ,  123 ,  124  and  125  are preferably set to have equal diameters. 
     On the upper end of the fourth pulley  125 , there is coaxially stacked a drive gear  126  having a pitch circle diameter P. In the distal end of the chassis member  117 , moreover, there is formed a through hole  129 , in which a stem member  128  is turnably inserted (another rotational axis). On one end of the stem member  128  is fitted a driven gear  127 , which meshes with the drive gear  126 . To the other end of the stem member  129  is attached the substantially central portion of the upper side of the image projection panel  49 . Here, the driven gear  127  has a pitch circle diameter Q and has a module set identical to that of the drive gear  126 . 
     On the other hand, a timing belt  130  runs between the first pulley  120  and the second pulley  123 , and a timing belt  131  runs between the second pulley  123  and the third pulley  124 . Moreover, a further timing belt  132  extends between the third pulley  124  and the fourth pulley  125 . The chassis member  117  is so covered with a cover  121  as to shield the first to fourth pulleys  120 ,  123 ,  124  and  125 , the drive gear  126  and the driven gear  127 . Here, these first to fourth pulleys  120 ,  123 ,  124  and  125  are associated through the timing belts  130 ,  131  and  132  to configure a mechanism for facing an image. 
     The image projection panel  49  supported by the stem member  128  of the chassis member  117  is arranged in such relation to the surgeon  2  that the surgeon  2  and the turning center of the vertical pivot  116  are aligned on an axis  133  extending in the normal direction from the center of the image projection panel  49 , as shown in  FIG. 15 . Moreover, the image projected from the image projecting unit  46  in the direction of an axis  134  is so reflected by the image projection panel  49  that it may be focused on the position of a distance d on the axis  133 . Here, the surgeon  2 , the vertical pivot  116  and the image projection panel  49  are arranged in such a manner that the distance from the image projection panel  49  to the observing position of the surgeon  2  is set to d and the distance from the image projection panel  49  to the center of the vertical pivot  116  is set to D ( FIG. 15 ). 
     In case, therefore, the chassis member  117  is turned by θ degrees on the vertical pivot from the position of  FIG. 15 , an angle of α degrees is made, as shown in  FIG. 16 , between the axis  134  joining the center of the vertical pivot  116  and the center of the image projection panel  49  and an axis  135  joining the surgeon  2  and the center of the image projection panel  49 . 
     The relation between the reduction ratio ε of the drive gear  126  and the driven gear  127  and the θ is desired to satisfy the following relation, but this relation cannot be realized by the ratio of P/Q of the pitch circle diameters:
 
ε={sin −1 ( D/d ·sin θ)}/2θ−½.
 
     For θ=30 degrees, the reduction ration ε1 is expressed by:
 
ε1=sin −1 ( D/ 2 d )/60−½= P/Q.  
 
Here, a series of components from the vertical pivot  116  through the chassis member  117  to the stem member  128  configure a vertical turning mechanism (a linking mechanism).
 
     In the configuration thus far described, the surgeon  2  moves the image projection panel  49  selectively, in case the treating device or another observing device interferes with the image projection panel  49  during the operation. In the first case, in which the surgeon  2  intends moving the image projection panel  49  back and forth in the direction of his or her view, the surgeon  2  grasps the chassis member  117  to apply the control force in the longitudinal direction or the directions of arrow X, as shown in  FIG. 14 . Then, the control force in the direction X is transmitted through the chassis member  117  and the vertical mover  115  to the column  114 . As a result, the casters  113  are forced to move in the direction X so that the apparatus is moved and adjusted in its entirety in the direction X. 
     When the surgeon  2  applies the control force in the direction Y, on the other hand, the chassis member  117  is turned around the vertical pivot  116 . In case the chassis member  117  is turned by θ degrees, as shown in  FIG. 16 , the first pulley  120  and the chassis member  117  turn relative to each other. Then, the second pulley  123 , the third pulley  124  and the fourth pulley  125  are sequentially turned by the timing belts  130 ,  131  and  132 , so that the drive gear  126  is turned by θ degrees. At this time, the drive gear  126  turns the driven gear  127  to turn the image projection panel  49  through the stem member  128 . Here, the turning angle of the image projection panel  49 , i.e., the turning angle of the driven gear  127 , is α/2 degrees according to the relation of the gear ratio of P/Q, as shown in  FIG. 16 . 
     Specifically, the driven gear  127  has the following relation to the turning angle α/2, in case the drive gear  126  turns by the angle θ with the drive gear  126  of the pitch circle diameter P and the driven gear  127  of the pitch circle diameter Q meshing with each other:
 
α/2= P·θ/Q   (1).
 
     Next, the following relation holds for the case where the angle between the axis  133  and the axis  135  shown in  FIG. 16  is designated by θ′:
 
α=θ′−θ  (2).
 
The following formula is deduced from equations (1) and (2):
 
 P/Q =(θ′−θ)/(2·θ)  (3).
 
In the configuration shown in  FIG. 16 , the following relation holds:
 
 d ·sin θ′= D ·sin θ  (4).
 
The relation of the aforementioned reduction ratio ε can be deduced on the basis of equations (3) and (4).
 
     Now will be described the case in which retraction is taken of the image projection panel  49  so that the surgeon  2  may observe the operative site in direct view during a series of operations, for example. This control is also likewise adjusted in case the surgeons  2  having different body sizes alternate during the operation. 
     Specifically, the surgeon  2  grasps the chassis member  117  and applies the control force in the direction of arrow Z, as shown in  FIG. 14 . This control force applied to the chassis member  117  is transmitted, as in the case of the aforementioned control of the direction X, to the vertical mover  115  so that this vertical mover  115  is moved in the direction Z relative to the column  114 . As a result, the image projection panel  49  and the image projecting unit  46  are moved together vertically in the direction Z. In other words, the position adjustment of the image projection panel  49  in the height direction due to the height difference between the surgeons  2  is made by the movement in the direction Z. 
     According to the fourth embodiment, the vertical pivot  116  can be arranged on the axis of the vertical mover  115  having no relation to the position of the cervical vertebrae of the surgeon  2 , so that the appearance and shape can be simplified. As a result, it is possible to realize a configuration that is not likely to obstruct the operation, thereby to improve the operation efficiency as much as possible. 
     The fourth embodiment has been described for the case where the turning angle of α/2 of the image projection panel  49  is determined by the ratio of the pitch circle diameters of the drive gear  126  and the driven gear  127 . However, the invention is not limited thereto but can also be configured such that the decision is made by altering the external diameters of the first to fourth pulleys  120 ,  123 ,  124  and  125 . 
     Moreover, the fourth embodiment is exemplified by the example using the image projection panel  49  and the image projecting unit  46  disclosed in JP-A-2003-233031, as the image display member. However, the invention is not so limited, but can also be configured by using LCD or other displays. In this modification, however, the turning angle of α/2 should be doubled to α. 
       FIG. 17  shows an image observation apparatus according to a fifth embodiment of the invention. In  FIG. 17 , portions corresponding to the third embodiment are not described, but merely marked with the same reference numerals. 
     In this fifth embodiment, the substantially L-shaped vertical moving housing  38  of the third embodiment is replaced by a vertical moving housing  136  having a substantially straight hollow structure. This vertical moving housing  136  is turnably erected at its proximal end from the aforementioned base  112  through a vertical pivot  137 . This base  112  is provided with plural casters  113  at a predetermined interval. The image observation apparatus can move on the floor through those casters  113 . 
     Into the distal end of the vertical moving housing  136  is also movably inserted one end of the vertical mover  45 , with which the aforementioned horizontal arm unit  44  through the transverse switching mechanism  47  and the horizontal arm unit housing mechanism  48  are associated. To the distal end of the horizontal arm unit  44  is attached an extension arm  138 , which extends to the center of the image projection panel  49 . 
     At the distal end of the extension arm  138  is provided a panel pivot  139  that can turn in the vertical direction, as shown in  FIG. 18 . A motor  140  is also arranged at the distal end of the extension arm  138 . This motor  140  has its turning output spindle connected to the panel pivot  139 . Moreover, the motor  140  is electrically connected through a connection cable  144  with a control circuit  143  contained in the display image confronting mechanism. 
     At the vertical mover  45 , moreover, there is arranged an ultrasonic length measuring device  141 , which is positioned on the back of the head of the surgeon  2 . At the aforementioned base  112 , moreover, there is arranged a rotary encoder  142 , which has a turning input shaft connected to the vertical pivot  137 . These ultrasonic length measuring device  141  and rotary encoder  142  are electrically connected with the aforementioned control circuit  143  through the connection cable  144 . 
     The control circuit  143  controls the turning angle β of the motor  140  according to the following relation, where the distance from the center of the vertical pivot  137  to the image projection panel  49  is designated by D, the distance from the image projection panel  49  to the observing position of the surgeon  2  is designated by d, and the turning angle of the vertical pivot  137  is designated by θ:
 
β=½·{sin −1 ( D/d ·sin θ)−θ}.
 
     In the configuration thus made, the surgeon  2  grasps the grip  56  and applies the control force in the direction of arrow X, as shown in  FIG. 17 , in the case where the treating device or another observing device interferes with the image projection panel  49  during the operation. Then, the control force is transmitted to the vertical moving housing  136  through the arm unit  44  and the vertical mover  45  so that the casters  113  of the base  112  raising the vertical moving housing  136  are moved in the direction X to adjust the longitudinal direction. 
     Where, on the other hand, the surgeon  2  applies the control force in the direction Y to the grip  56 , the control force is transmitted to the vertical moving housing  136  through the arm unit  44  and the vertical mover  45  so that the vertical pivot  137  is turned relative to the base  112 . This turning angle θ is detected by the rotary encoder  142 , which outputs its detection signal to the control circuit  143 . Simultaneously with this, the distance from the ultrasonic length measuring device  141  to the surgeon  2  is detected by the ultrasonic length measuring device  141 , and the detection signal is input to the control circuit  143 . In response, the control circuit  143  calculates the distance d from the image projection panel  49  to the observing position of the surgeon  2 , which distance is obtained from the initially given distance D by the ultrasonic distance measuring device  141 , and creates a motor drive signal so that the motor  140  is turned by the angle β on the basis of that motor drive signal. 
     As a result, even where the surgeon  2  moves the image projection panel  49  by turning it by the angle θ around the center of the vertical pivot  137 , the surgeon  2  is able to look at the observation image from the image projection panel  49  at all times merely turning only his or her face toward the image projection panel  49 , without moving the body. 
     According to the fifth embodiment, the image projection panel  49  can be reliably directed toward the surgeon  2  by the control of the control circuit  143 . Moreover, the controllability can be improved to improve the operation efficiency. 
     While there has been shown and described what is considered to be preferred embodiments of the invention, it will, of course, be understood that various modifications and changes in form or detail could readily be made without departing from the spirit of the invention. It is, therefore, intended that the invention be not limited to the exact forms described and illustrated, but should be constructed to cover all modifications that may fall within the scope of the appended claims.