Patent Publication Number: US-2021169312-A1

Title: Endoscope

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a Continuation of PCT International Application No. PCT/JP2019/033256 filed on Aug. 26, 2019 claiming priority under 35 U.S.C § 119(a) to Japanese Patent Application No. 2018-169148 filed on Sep. 10, 2018. Each of the above applications is hereby expressly incorporated by reference, in its entirety, into the present application. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an endoscope that includes a treatment tool lead-out port and an elevator on the distal end side of an insertion section. 
     2. Description of the Related Art 
     As an ultrasonic endoscope, an endoscope is known that includes an electron-scanning ultrasonic transducer in a distal end portion of an insertion section of the endoscope and in which a treatment tool lead-out port is disposed on the proximal end side of the ultrasonic transducer in the distal end portion. In an endoscopic inspection using the ultrasonic endoscope, for example, while acquiring an ultrasound image of a treatment target area (including an observation target area, an inspection area, and the like) by using the ultrasonic transducer, cells are sampled by inserting a puncture treatment tool, which has been led out to the inside of a body through a treatment tool insertion channel and a treatment tool lead-out port, into the treatment target area. In order to treat a desired position with such a treatment tool, it is necessary to change the lead-out direction in which the treatment tool is led out from the treatment tool lead-out port, which is formed in the distal end portion of the insertion section. Therefore, a treatment tool elevating mechanism is provided inside the treatment tool lead-out port of the distal end portion of the insertion section (see JP2014-132923A). 
     The treatment tool elevating mechanism includes an elevator housing chamber, an elevator, an elevator rotating mechanism, and the like. The elevator housing chamber is provided in the treatment tool lead-out port of the distal end portion of the insertion section. The elevator is supported so as to be rotatable around a rotational axis in the elevator housing chamber. The elevator rotating mechanism rotates the elevator in response to an elevator rotating operation performed on an operation section of the ultrasonic endoscope. 
     In an outer surface of the distal end portion of the insertion section, the treatment tool lead-out port, an observation window for observing a treatment target area, and, in addition, an illumination window that emits illumination light toward an treatment target area and the like are provided. Therefore, a light guide (optical fiber cable) that guides illumination light from a light source device to the illumination window is inserted through the inside of the insertion section. 
     A light guide distal end portion, which is a distal end portion of the light guide on a side facing the illumination window, generates heat by absorbing a part of illumination light. Therefore, the temperature of the distal end portion of the insertion section increases. JP2003-153852A discloses an endoscope apparatus in which, in a distal end portion of an insertion section, a region in which a light guide is fixed and the other region are separated and a heat insulator is provided at the boundary between these regions. Thus, increase in the temperature of the distal end portion of the insertion section due to generation of heat in the distal end portion is prevented. 
     SUMMARY OF THE INVENTION 
     JP2014-132923A does not describe suppression of increase in the temperature of the distal end portion of the insertion section due to generation of heat in the light guide distal end portion. When a heat insulator is provided in the distal end portion of the insertion section as in the endoscope apparatus described in JP2003-153852A, a problem arises in that the number of components of the distal end portion increases and the diameter of the distal end portion increases. 
     The present invention has been made against such a background, and an object thereof is to provide an endoscope that can suppress increase in the temperature of a distal end portion of an insertion section while preventing increase in the number of components and increase in the diameter of the distal end portion. 
     An endoscope for achieving the object of the present invention includes: a distal end portion body that is provided on a distal end side of an insertion section and that has a distal end, a proximal end, and a longitudinal axis; a treatment tool lead-out port that is formed in the distal end portion body and that leads out a treatment tool inserted through an inside of the insertion section; an elevator support member that is provided in the distal end portion body, that is made of a metal, and that rotatably supports an elevator that controls a lead-out direction in which the treatment tool is led out from the treatment tool lead-out port; a light guide that is inserted through the inside of the insertion section and that emits illumination light through an illumination window formed in the distal end portion body; and a light guide holding portion that is provided in the elevator support member and that holds a light guide distal end portion of the light guide on the illumination window side. 
     With the endoscope, it is possible to suppress increase in the temperature of the light guide distal end portion by transferring heat generated in the light guide distal end portion to the elevator support member made of a metal. 
     In an endoscope according to another aspect of the present invention, the light guide holding portion is a groove that is formed in an outer wall of the elevator support member and to which the light guide distal end portion is fitted. Thus, it is possible to transfer heat generated in the light guide distal end portion to the elevator support member. 
     In an endoscope according to another aspect of the present invention, the distal end portion body comprises an outer case including an outer case body and a cover, the outer case body has an opening portion and houses the elevator support member and the elevator in the opening portion, and the cover is removably attached to the opening portion and, when attached to the opening portion, presses the light guide distal end portion, which is fitted to the groove, against the groove and fixes the light guide distal end portion. Thus, the heat dissipation ability of the light guide distal end portion is improved, because the closeness of contact between the light guide distal end portion and the elevator support member is improved. 
     An endoscope according to another aspect of the present invention includes: an elevator housing chamber that is provided inside the treatment tool lead-out port of the distal end portion body and that houses the elevator; a treatment tool insertion channel that is provided in the insertion section and through which the treatment tool is inserted; a through hole that is formed in the elevator support member and that communicates with the elevator housing chamber; and a metal pipe that connects the treatment tool insertion channel and the through hole of the elevator support member. Thus, it is possible to further improve the heat dissipation ability of the light guide distal end portion, because it is possible to transfer heat generated in the light guide distal end portion further to the metal pipe via the elevator support member. 
     An endoscope according to another aspect of the present invention includes a bending portion that is connected to a proximal end side of the distal end portion body in the insertion section, the bending portion has a plurality of rings that are made of a metal and that are coupled along the longitudinal axis, and the elevator support member is connected directly or indirectly via another metal member to a distal end ring that is positioned on a most distal end side of the bending portion among the plurality of rings. Thus, it is possible to further improve the heat dissipation ability of the light guide distal end portion, because it is possible to transfer heat generated in the light guide distal end portion further to the ring made of a metal via the elevator support member. 
     An endoscope according to another aspect of the present invention includes an observation window that is provided in the distal end portion body and a nozzle that is provided in the distal end portion body and that ejects a fluid toward the observation window, and the illumination window is provided, in the distal end portion body, in an ejection range of the fluid ejected from the nozzle. Thus, it is possible to cool the light guide distal end portion via the illumination window by using a fluid ejected from the nozzle. 
     In an endoscope according to another aspect of the present invention, when a direction perpendicular to both of the longitudinal axis and a normal direction of an opening surface of the treatment tool lead-out port is defined as a width direction of the treatment tool lead-out port, the observation window is provided in the distal end portion body at a position on one side in the width direction relative to the treatment tool lead-out port, and the illumination window is provided in the distal end portion body at a position on the other side, which is opposite to the one side, relative to the treatment tool lead-out port. 
     In an endoscope according to another aspect of the present invention, the illumination window is a first illumination window that is provided in a proximal end side region that is positioned in the distal end portion body at a position shifted from the treatment tool lead-out port toward a proximal end side of the distal end portion body, and, when a direction perpendicular to both of the longitudinal axis and a normal direction of an opening surface of the treatment tool lead-out port is defined as a width direction of the treatment tool lead-out port, the observation window is provided in the distal end portion body at a position on one side in the width direction with respect to the proximal end side region. 
     In an endoscope according to another aspect of the present invention, the illumination window includes the first illumination window and a second illumination window that is disposed in the distal end portion body at a position on the other side, which is opposite to the one side, with respect to the proximal end side region. 
     An endoscope according to another aspect of the present invention includes an ultrasonic transducer that is provided in the distal end portion body and that is positioned on a distal end side of the distal end portion body relative to the treatment tool lead-out port. 
     The present invention can suppress increase in the temperature of the distal end portion of the insertion section while preventing increase in the number of components and increase in the diameter of the distal end portion. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view of an ultrasonic inspection system to which an endoscope according to the present invention is applied; 
         FIG. 2  is a schematic view illustrating the pipe line configuration of the ultrasonic endoscope; 
         FIG. 3  is an external perspective view of a distal end portion of an insertion section; 
         FIG. 4  is a right side view of the distal end portion of the insertion section; 
         FIG. 5  is an exploded perspective view of the distal end portion of the insertion section; 
         FIG. 6  is a perspective view of an elevating case; 
         FIG. 7  is a front view of the elevating case when the elevating case is seen from the outer case distal end side; 
         FIG. 8  is a schematic view of an example of an elevator operating mechanism; 
         FIG. 9  illustrates rotation of an elevator in response to an operation on an operating lever; 
         FIG. 10  is a top view of the outer case; 
         FIG. 11  illustrates an observation axis and an observation range of an observation window, a first illumination axis and a first illumination range of a first illumination window, and a second illumination axis and a second illumination range of a second illumination window; 
         FIG. 12  is a side view of the distal end portion of the insertion section that is inserted into a lumen; 
         FIG. 13  is a perspective view of the elevating case and light guides that are held by the elevating case; 
         FIG. 14  is a schematic view of a bending portion; 
         FIG. 15  is an external perspective view of a distal end portion of an ultrasonic endoscope according to another embodiment in which the disposition of the first illumination window is different; 
         FIG. 16  is a perspective view of an elevating case according to another embodiment and a second light guide held by the elevating case; and 
         FIG. 17  illustrates another example of a holding structure of an elevating case for holding light guide distal end portions. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     [Configuration of Ultrasonic Inspection System and Ultrasonic Endoscope] 
       FIG. 1  is a schematic view of an ultrasonic inspection system  2  to which an endoscope according to the present invention is applied. As illustrated in  FIG. 1 , the ultrasonic inspection system  2  includes an ultrasonic endoscope  10  that captures an image of the inside of a lumen  154  (also called a body cavity, see  FIG. 12 ) of a subject to be examined, an ultrasonic processor device  12  that generates an ultrasound image, an endoscopic processor device  14  that generates an endoscopic image, a light source device  16  that supplies to the ultrasonic endoscope  10  illumination light for illuminating the inside of the lumen  154 , and a monitor  18  that displays the ultrasound image and the endoscopic image. 
     The ultrasonic endoscope  10  corresponds to an endoscope according to the present invention and includes an insertion section  20 , an operation section  22 , and a universal cord  24 . 
     The insertion section  20  is inserted into the lumen  154  (see  FIG. 12 ) of various types. The operation section  22  is joined to the proximal end side of the insertion section  20  and receives an operation by an operator. 
     The operation section  22  is connected to one end side of the universal cord  24 . On the other end side of the universal cord  24 , an ultrasonic connector  27  connected to the ultrasonic processor device  12 , an endoscopic connector  28  connected to the endoscopic processor device  14 , and a light source connector  30  connected to the light source device  16  are provided. To the light source connector  30 , a water supply tank  118  is connected via an air/water supply tube  32 , and a suction pump  124  is connected via a suction tube  34 . 
     The ultrasonic processor device  12  generates an ultrasound image based on an ultrasonic detection signal output from the ultrasonic endoscope  10 . The endoscopic processor device  14  generates an endoscopic image based on an image pick-up signal output from the ultrasonic endoscope  10 . 
     To the light source device  16 , the insertion section  20 , the operation section  22 , the universal cord  24 , and the incident ends of light guides  128  (see  FIG. 2 ) inserted through the inside of the light source connector  30  are connected. The light source device  16  supplies illumination light to the incident ends of the light guides  128 . The illumination light is emitted to a treatment target area from the light guides  128  through illumination windows  90 A and  90 B (see  FIG. 3 ) described below. 
     The monitor  18  is connected to both of the ultrasonic processor device  12  and the endoscopic processor device  14 , and displays an ultrasound image generated by the ultrasonic processor device  12  and an endoscopic image generated by the endoscopic processor device  14 . It is possible to selectively display only one of the ultrasound image and the endoscopic image or to display both of these images. 
     In the operation section  22 , an air/water supply button  36  and a suction button  38  are arranged to be parallel, and a pair of angle knobs  42 , an operating lever  43 , a treatment tool insertion port  44 , and the like are provided. 
     The insertion section  20  has a distal end, a proximal end, and a longitudinal axis; and has a distal end portion  50 , a bending portion  52 , and a soft portion  54  that are arranged in order from the distal end side toward the proximal end side. The distal end portion  50  is made of a rigid material and also referred to as a “distal end rigid portion”. An ultrasonic transducer  62  is provided at the distal end portion  50 , and a balloon  64  that surrounds and covers the ultrasonic transducer  62  is removably attached to the distal end portion  50 . 
     One end of the bending portion  52  is joined to the proximal end side of the distal end portion  50 , and the other end thereof is joined to the distal end side of the soft portion  54 . The bending portion  52  is configured to be bendable, and is remotely operated to be bent by rotating the pair of angle knobs  42 . Thus, it is possible to direct the distal end portion  50  in a desired direction. 
     The soft portion  54  is small in diameter, large in length, and flexible; and couples the bending portion  52  and the operation section  22 . 
       FIG. 2  is a schematic view illustrating the pipe line configuration of the ultrasonic endoscope  10 . As illustrated in  FIG. 2 , inside the insertion section  20  and the operation section  22 , a treatment tool insertion channel  100 , an air/water supply pipe line  102 , and a balloon pipe line  104 , one end which communicates with an inner space of the balloon  64 , are provided. 
     One end side of the treatment tool insertion channel  100  is connected to an elevating case  200  (see  FIG. 3 ) described below, and the other end side of the treatment tool insertion channel  100  is connected to the treatment tool insertion port  44  in the operation section  22 . Thus, the treatment tool insertion port  44  and a treatment tool lead-out port  94  described below (see  FIG. 3 ) communicate with each other via the treatment tool insertion channel  100 . A suction pipe line  106  branches off from the treatment tool insertion channel  100 , and the suction pipe line  106  is connected to the suction button  38 . 
     One end side of the air/water supply pipe line  102  is connected to an air/water supply nozzle  92  described below (see  FIG. 3 ), and the other end side of the air/water supply pipe line  102  branches into an air supply pipe line  108  and a water supply pipe line  110 . The air supply pipe line  108  and the water supply pipe line  110  are each connected to the air/water supply button  36 . 
     One end side the balloon pipe line  104  is connected to a supply/discharge port  70  that opens in an outer peripheral surface of the distal end portion  50  at a position inside of the balloon  64 , and the other end side of the balloon pipe line  104  branches into a balloon water supply pipe line  112  and a balloon water discharge pipe line  114 . The balloon water supply pipe line  112  is connected to the air/water supply button  36 , and the balloon water discharge pipe line  114  is connected to the suction button  38 . 
     To the air/water supply button  36 , one end side of an air supply source pipe line  116 , which communicates with an air supply pump  129 , and one end side of a water supply source pipe line  120 , which communicates with the water supply tank  118 , are connected, in addition to the air supply pipe line  108 , the water supply pipe line  110 , and the balloon water supply pipe line  112 . The air supply pump  129  continuously operates during an ultrasonic observation. 
     A branch pipe line  122  branches off from the air supply source pipe line  116 , and the branch pipe line  122  is connected to an inlet of the water supply tank  118  (above the liquid level). The other end side of the water supply source pipe line  120  is inserted to the inside of the water supply tank  118  (below the liquid level). Water in the water supply tank  118  is supplied to the water supply source pipe line  120  when the internal pressure of the water supply tank  118  increases as the air supply pump  129  supplies air from via the branch pipe line  122 . 
     A known two-step switching button is used as the air/water supply button  36 . In response to an operation by an operator, the air/water supply button  36  switches among leakage of air supplied from the air supply source pipe line  116 , ejection of air from the air/water supply nozzle  92 , ejection of water from the air/water supply nozzle  92 , and supply of water into the balloon  64 . Description of a specific switching method, which is a known technology, will be omitted here. 
     To the suction button  38 , one end side of a suction source pipe line  126  is connected, in addition to the suction pipe line  106  and the balloon water discharge pipe line  114 . The suction pump  124  is connected to other end side of the suction source pipe line  126 . The suction pump  124  also continuously operates during an ultrasonic observation. The suction button  38  is a two-step switching button, as with the air/water supply button  36 . 
     In response to an operation by an operator, the suction button  38  switches among connection of the suction source pipe line  126  to the outside (atmosphere), suction of various aspirates from the treatment tool lead-out port  94  (see  FIG. 3 ), and discharge of water in the balloon  64 . Description of a specific switching method, which is a known technology, will be omitted here. 
     Referring back to  FIG. 1 , as described below in detail, the operating lever  43  of the operation section  22  is used to change the lead-out direction in which a treatment tool (not shown, the same applies hereafter) is led out from the treatment tool lead-out port  94  (see  FIG. 3 ). 
     [Configuration of Distal End Portion of Insertion Section] 
       FIG. 3  is an external perspective view of the distal end portion  50  of the insertion section  20 .  FIG. 4  is a right side view of the distal end portion  50  of the insertion section  20 .  FIG. 5  is an exploded perspective view of the distal end portion  50  of the insertion section  20 . In  FIGS. 3 and 5 , illustration of the balloon  64  is omitted. In  FIG. 5 , illustration of the light guides  128  is omitted. 
     As illustrated in  FIGS. 3 to 5 , the distal end portion  50  includes an outer case  72  (also referred to as a “housing”) corresponding to a distal end portion body in the present invention. The outer case  72  has a distal end that constitutes a distal end of the insertion section  20 , a proximal end that is connected to the bending portion  52 , and a longitudinal axis LA. Hereafter, the distal end side of the outer case  72  will be referred to as the “outer case distal end side”, and the proximal end side of the outer case  72  will be referred to as the “outer case proximal end side”. 
     In the outer case  72 , from the outer case distal end side toward the outer case proximal end side, an ultrasonic observation portion  60  that acquires an ultrasonic detection signal, the treatment tool lead-out port  94  for a treatment tool, a first inclined surface  86 A, a second inclined surface  86 B, and an endoscope observation portion  80  that acquires an image pick-up signal are provided. Inside the outer case  72 , an elevator housing chamber  94   a  and an elevator  96  that are positioned inside of the treatment tool lead-out port  94 , and the elevating case  200  (also referred to as an “elevator assembly”) that rotatably supports the elevator  96  and that is made of a metal are provided. Moreover, the outer case  72  includes a lever housing cover  76 . 
     The treatment tool lead-out port  94  opens in an outer surface of the outer case  72  at a position between the ultrasonic observation portion  60  and the endoscope observation portion  80  (the first inclined surface  86 A). From the treatment tool lead-out port  94 , a treatment tool, which is inserted through the inside of the treatment tool insertion channel  100  of the insertion section  20 , is led out. Hereafter, as illustrated in  FIG. 3 , a direction perpendicular to both of the longitudinal axis LA and the normal direction NV of the opening surface of the treatment tool lead-out port  94  will be referred to as the “width direction WD” of the treatment tool lead-out port  94 , one side in the width direction WD will be referred to as the “L side”, and the other side opposite to the one side in the width direction WD will be referred to as the “R side”. 
     The first inclined surface  86 A and the second inclined surface  86 B are inclined surfaces that are inclined toward the outer case proximal end side from an orientation parallel to the width direction WD and perpendicular to longitudinal axis LA. As described below in detail, the inclination angle of the first inclined surface  86 A and the inclination angle of the second inclined surface  86 B are different. 
     The first inclined surface  86 A is formed on the outer surface of the outer case  72  at a position that is on the outer case proximal end side relative to the treatment tool lead-out port  94  in the direction along the longitudinal axis LA, and is formed from a region in which the treatment tool lead-out port  94  is formed to a region on the L side thereof in the width direction WD. In the first inclined surface  86 A, an observation window  88  of the endoscope observation portion  80 , a first illumination window  90 A, and the air/water supply nozzle  92  are provided. The first inclined surface  86 A may be divided into a region in which the observation window  88  is provided, a region in which the first illumination window  90 A is provided, and a region in which the air/water supply nozzle  92  is provided. 
     The second inclined surface  86 B is formed on the outer surface of the outer case  72  at a position that is on the outer case distal end side relative to the first inclined surface  86 A in the direction along the longitudinal axis LA, and is formed on the R side relative to a region in which the treatment tool lead-out port  94  is formed in the width direction WD. A second illumination window  90 B is provided in the second inclined surface  86 B. The second inclined surface  86 B may be formed, in the direction along the longitudinal axis LA, at the same position as the first inclined surface  86 A or at a position on the outer case proximal end side of the first inclined surface  86 A. 
     The ultrasonic observation portion  60  is provided in the outer case  72  at a position on the outer case distal end side relative to the treatment tool lead-out port  94 . The ultrasonic observation portion  60  includes the ultrasonic transducer  62  constituted by a plurality of ultrasonic vibrators. The ultrasonic vibrators of the ultrasonic transducer  62  are successively driven based on drive signals input from the ultrasonic processor device  12 . Thus, the ultrasonic vibrators successively generate ultrasound toward a treatment target area, and receive ultrasonic echoes (echo signals) reflected by the treatment target area. The ultrasonic vibrators output ultrasonic detection signals (electric signals), which correspond to the received ultrasonic echoes, to the ultrasonic processor device  12  via a signal cable (not shown) inserted through the inside of the insertion section  20 , the universal cord  24 , and the like. As a result, an ultrasound image is generated by the ultrasonic processor device  12 . 
     The balloon  64  is attached to the outer case  72  at a position on the outer case distal end side relative to the treatment tool lead-out port  94 , has a bag-like shape that surrounds and covers the ultrasonic transducer  62 , and prevents attenuation of ultrasound and an ultrasonic echo. The balloon  64  is made of an elastic material such as latex rubber, and an elastic locking ring  66  is provided at an open end on the outer case proximal end side thereof. In a part of the outer case  72  between the ultrasonic observation portion  60  and the treatment tool lead-out port  94 , a locking groove  68  is provided around the entire circumference of the outer case  72  in circumferential direction. The balloon  64  is removably attached the outer case  72  by fitting the locking ring  66  to the locking groove  68 . 
     The endoscope observation portion  80  has the observation window  88  provided in the first inclined surface  86 A. Although illustrations are omitted, in a region in the outer case  72  and behind the observation window  88 , an observation optical system (an objective lens and the like) that constitutes the endoscope observation portion  80 , an imaging device such as a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor) device, and the like are disposed. The imaging device picks up an observation image captured through the observation window  88 . The imaging device outputs an image signal of the observation image to the endoscopic processor device  14  through a signal cable (not shown) inserted through the inside of the insertion section  20 , the universal cord  24 , and the like. As a result, an endoscopic image is generated by the endoscopic processor device  14 . 
     As described below in detail, the first illumination window  90 A and the second illumination window  90 B each emit illumination light in the forward direction thereof. In a region in the outer case  72  and behind the illumination windows  90 A and  90 B, the emission ends of the aforementioned light guides  128  are disposed. Accordingly, by coupling the light source connector  30  to the light source device  16  as illustrated in the aforementioned  FIG. 2 , illumination light emitted from the light source device  16  is guided to the illumination windows  90 A and  90 B via the light guides  128 , and the illumination light is emitted from the illumination windows  90 A and  90 B. 
     The air/water supply nozzle  92  is disposed on the first inclined surface  86 A at a position in the vicinity of the observation window  88 . The air/water supply nozzle  92  is connected to one end side of the air/water supply pipe line  102  illustrated in the aforementioned  FIG. 2 , and ejects a fluid such as water or air toward the observation window  88  in order to wash away foreign substances and the like that adhere to the surface of the observation window  88 . 
     The outer case  72  houses the ultrasonic observation portion  60  and the endoscope observation portion  80 , which are described above, and the elevator  96  and the elevating case  200 , which are described below. A part in the outer case  72  on the outer case proximal end side relative to the ultrasonic observation portion  60  is divided into two in the up-down direction in the figure along a plane parallel to both of the longitudinal axis LA and the width direction WD. Therefore, the outer case  72  is constituted by an outer case body  72   a , which is positioned on the lower side in the figure, and an outer case cover  72   b , which is positioned on the upper side in the figure. 
     The outer case body  72   a  houses the ultrasonic observation portion  60  and has the locking groove  68  in a distal end part on the outer case distal end side relative to the treatment tool lead-out port  94 . The outer case body  72   a  has an opening portion  71  that is provided in a part on the outer case proximal end side relative to the locking groove  68  and that is covered by the outer case cover  72   b  (see  FIG. 5 ). The outer case body  72   a  houses a part of each of the elevator  96  and the elevating case  200  in the opening portion  71 . 
     In a side surface of the distal end part of the outer case body  72   a  on the L side, a groove portion  74  (see  FIG. 4 ), which is formed along the longitudinal axis LA, and the supply/discharge port  70 , which opens at an end portion of the groove portion  74  on the outer case proximal end side, are formed. Thus, it is possible to supply water into the balloon  64  through the supply/discharge port  70  or to discharge water in the balloon  64  through the supply/discharge port  70 . 
     The outer case cover  72   b  is removably attached to the opening portion  71  of the outer case body  72   a . In the outer case cover  72   b , from the outer case distal end side toward the outer case proximal end side, the aforementioned treatment tool lead-out port  94 , the first inclined surface  86 A, and the second inclined surface  86 B are formed. The outer case cover  72   b  covers the endoscope observation portion  80  and two light guides  128  that guide illumination light to the illumination windows  90 A and  90 B. 
     When the outer case cover  72   b  is attached to the opening portion  71  of the outer case body  72   a , the elevator housing chamber  94   a , which is a space for housing the elevator  96 , is formed inside the treatment tool lead-out port  94 . A partition wall  73  (see  FIG. 5 ), which constitutes a side surface of the elevator housing chamber  94   a  on the L side, is formed astride both of the outer case body  72   a  and the outer case cover  72   b.    
     In side surfaces of the outer case body  72   a  and the outer case cover  72   b  on the R side at a position facing a lever housing chamber  212  (see  FIG. 5 ) of the elevating case  200  described below, a fitting hole  75  (see  FIG. 5 ), to which the lever housing cover  76  is fitted, is formed astride the outer case body  72   a  and the outer case cover  72   b.    
     The elevator housing chamber  94   a  communicates with the treatment tool insertion port  44  through the aforementioned treatment tool insertion channel  100  (see  FIG. 2 ) and the like. Therefore, a treatment tool inserted into the treatment tool insertion port  44  is led into the lumen  154  (see  FIG. 12 ) from the treatment tool lead-out port  94  via the treatment tool insertion channel  100 , the elevator housing chamber  94   a , and the like. 
     The elevator  96  is rotatably supported by the elevating case  200  in the elevator housing chamber  94   a  via a rotation shaft  216  (see  FIG. 6 ). The elevator  96  has an arc-shaped guide surface  96   a  that guides a treatment tool, which has been led into the elevator housing chamber  94   a , toward the treatment tool lead-out port  94 . Thus, the elevator  96  changes the direction of the treatment tool, which has been guided into the elevator housing chamber  94   a  from the treatment tool insertion channel  100 , and leads out the treatment tool from the treatment tool lead-out port  94 . As described below in detail, the elevator  96  rotates in the elevator housing chamber  94   a  around the rotation shaft  216  in response to an operation on the operating lever  43 , and thereby changes the lead-out direction in which the treatment tool is led out from the treatment tool lead-out port  94  into the lumen  154  (see  FIG. 12 ). Accordingly, the elevator  96  controls the lead-out direction in which the treatment tool is led out from the treatment tool lead-out port  94 . 
     The lever housing cover  76  is fitted to the fitting hole  75  in the outer surface of the outer case  72 . In a state of being fitted to the fitting hole  75 , the lever housing cover  76  is removably attached to the elevating case  200  by using bolts  77  that extend through the lever housing cover  76  (see  FIG. 5 ). 
     [Configuration of Elevating Case] 
       FIG. 6  is a perspective view of the elevating case  200 , and  FIG. 7  is a front view of the elevating case  200  when the elevating case  200  is seen from the outer case distal end side. As illustrated in  FIGS. 6 and 7  and the aforementioned  FIG. 5 , the elevating case  200  corresponds to an elevator support member in the present invention, and is made of, for example, a corrosion-resistant metal material. The elevating case  200  has a base  202  and a partition wall  204  extending from the base  202  toward the outer case distal end side. 
     A distal end surface on the outer case distal end side of the base  202  constitutes a side surface of the elevator housing chamber  94   a  on the outer case proximal end side. In the base  202 , a through hole  202   a  that is parallel to the longitudinal axis LA and that communicates with the elevator housing chamber  94   a  and the treatment tool insertion channel  100  is formed. Thus, the treatment tool insertion channel  100  and the elevator housing chamber  94   a  communicate with each other via the through hole  202   a.    
     Two light guide holding grooves  203 A and  203 B are formed in an upper surface (a surface on the treatment tool lead-out side) of the outer wall of the base  202 . Here, the two light guides  128 , respectively corresponding to the illumination windows  90 A and  90 B, are disposed along the upper surface of the base  202 , because the illumination windows  90 A and  90 B are disposed on the upper side of the elevating case  200  (on a side in a direction perpendicular to both of the longitudinal axis LA and the width direction WD). Thus, with each of the light guide holding grooves  203 A and  203 B, one of emission end of each of the light guides  128  is held at a position facing the first illumination window  90 A, and the other emission end of each of the light guides  128  is held at a position facing the second illumination window  90 B. 
     The partition wall  204  is provided between the elevator  96  (the elevator housing chamber  94   a ) and an elevator elevating lever  210  (the lever housing chamber  212 ) described below. The partition wall  204  has a side wall  206 , which is a side surface on the R side thereof, and a counter wall  208 , which is a side surface on the L side thereof and faces the elevator  96 . 
     In the side wall  206 , the lever housing chamber  212 , which houses the elevator elevating lever  210 , is formed. In a bottom surface of the lever housing chamber  212  on the elevator  96  side, a holding hole  214  (see  FIG. 6 ), which extends through the partition wall  204  in the width direction WD (the axial direction of the rotation shaft  216 ), is formed. The holding hole  214  connects the lever housing chamber  212  and the elevator housing chamber  94   a  to each other. The holding hole  214  rotatably supports the rotation shaft  216 . The lever housing chamber  212  has a fan-like shape around the rotation shaft  216 , because the elevator elevating lever  210  in the lever housing chamber  212  rotates (swings) around the rotation shaft  216 . 
     A wire insertion hole  224  (see  FIG. 6 ), through which an operating wire  222  is inserted, is formed in a side wall of the lever housing chamber  212  on the outer case proximal end side. 
     Bolt holes  220 , into which the aforementioned bolts  77  are screwed, are formed in a region of the side wall  206  that is a peripheral region of the lever housing chamber  212  and that is covered by the lever housing cover  76 . The number of the bolts  77  and the bolt holes  220  is not particularly limited. 
     The counter wall  208  constitutes a side surface of the elevator housing chamber  94   a  on the R side. The holding hole  214  opens in the counter wall  208 . A cutout portion  208   a  (see  FIG. 7 ), into which a part of the elevator  96  enters, is formed in the counter wall  208 . 
     The elevator elevating lever  210  rotates the elevator  96  around the rotation shaft  216  in response to an operation on the operating lever  43 . One part of the rotation shaft  216  having a two-part structure is provided at one end portion of the elevator elevating lever  210 , and the operating wire  222  is coupled to the other end portion of the elevator elevating lever  210 . 
     One part of the rotation shaft  216  having a two-part structure is provided at one end portion of the elevator elevating lever  210  as described above, and the other part of the rotation shaft  216  is provided at one end portion of the elevator  96 . The elevator elevating lever  210  and the elevator  96  are coupled to each other via the rotation shaft  216  having a two-part structure. For example, in the present embodiment, one part and the other part of the rotation shaft  216  having a two-part structure are coupled to each other by using a bolt  211  extending through one end side of the elevator elevating lever  210 , and thereby the elevator elevating lever  210  and the elevator  96  are coupled to each other via the rotation shaft  216  (see  FIG. 6 ). Thus, the elevator elevating lever  210  rotates (swings) around the rotation shaft  216  together with the elevator  96 . 
     The operating wire  222  has, on one end side thereof, a distal end side coupling portion  222   a  (see  FIG. 5 ) that is coupled to the elevator elevating lever  210  in the lever housing chamber  212 . The other end side of the operating wire  222  extends from the wire insertion hole  224  of the lever housing chamber  212  through the insertion section  20  and is coupled to an elevator operating mechanism  226  (see  FIG. 8 ) in the operation section  22 . 
       FIG. 8  is a schematic view of an example of the elevator operating mechanism  226 . As illustrated in  FIG. 8 , the operating wire  222  has, on the proximal end side thereof, a proximal end side coupling portion  222   b  that is coupled to the elevator operating mechanism  226 . The elevator operating mechanism  226  includes the operating lever  43 , a rotary drum  226 A to which the operating lever  43  is coupled and that is rotatable in a predetermined angular range, a crank member  226 B that is coupled to the rotary drum  226 A, and a slider  226 C that is coupled to the crank member  226 B. The proximal end side coupling portion  222   b  is coupled to the slider  226 C. 
     When the operating lever  43  is operated to rotate the rotary drum  226 A, the elevator elevating lever  210  swings as the operating wire  222  is pushed and pulled via the crank member  226 B and the slider  226 C, and the elevator  96  rotates (swings) around the rotation shaft  216  in response to the swing of the elevator elevating lever  210 . 
       FIG. 9  illustrates rotation of the elevator  96  in response to an operation on the operating lever  43 . As shown in a part IXA in  FIG. 9 , when the operating lever  43  is operated to rotate the rotary drum  226 A in one direction, the operating wire  222  is pushed, and thereby the elevator elevating lever  210  rotates around the rotation shaft  216  in a direction SW 1 . Thus, the elevator  96  rotates to a lowered position due to the rotation. 
     As shown in a part IXB in  FIG. 9 , when the operating lever  43  is operated to rotate the rotary drum  226 A in the opposite direction, the operating wire  222  is pulled, and thereby the elevator elevating lever  210  rotates around the rotation shaft  216  in a direction SW 2  opposite to the direction SW 1 . Thus, the elevator  96  rotates to an elevated position due to the rotation. Thus, it is possible to cause the elevator  96  to be displaced (elevated or lowered) by operating the operating lever  43  to rotate the rotation shaft  216  via the operating wire  222 , the elevator elevating lever  210 , and the like. 
     [First Illumination Window, Second Illumination Window, and Observation Window] 
       FIG. 10  is a top view of the outer case  72 . As illustrated in  FIG. 10 , the first illumination window  90 A is formed in a proximal end side region ER in the aforementioned first inclined surface  86 A. The proximal end side region ER is a region in the outer surface of the outer case  72  that is at a position shifted from the treatment tool lead-out port  94  toward the outer case proximal end side. 
     To be more specific, the proximal end side region ER is a region in the outer case  72  that is positioned on the outer case proximal end side relative to the treatment tool lead-out port  94  in the direction along the longitudinal axis LA and that is in an area where the treatment tool lead-out port  94  is formed in the width direction WD. Thus, it is possible to illuminate a treatment tool led out from the treatment tool lead-out port  94  and a treatment target area thereof with illumination light emitted from the first illumination window  90 A. 
     Moreover, when an end portion of the elevator  96  opposite to one end portion at which the rotation shaft  216  is provided is defined as the other end portion of the elevator  96 , the first illumination window  90 A is provided at a position in the outer case  72  (the proximal end side region ER) on the outer case proximal end side relative to the other end portion of the elevator  96 , at least when the elevator  96  is in the lowered position. In other words, the other end portion of the elevator  96  is positioned on the outer case distal end side relative to the first illumination window  90 A, at least when the elevator  96  is in the lowered position. Thus, it is possible to illuminate a treatment tool led out from the treatment tool lead-out port  94  and a treatment target area thereof with illumination light emitted from the first illumination window  90 A. 
     More preferably, the first illumination window  90 A is provided on the outer case proximal end side relative to the other end portion of the elevator  96  even when the elevator  96  is in the elevated position (that is, irrespective of the rotation position of the elevator  96 ). Thus, even when the elevator  96  is rotated (fully elevated) to the elevated position, it is possible to illuminate a treatment tool led out from the treatment tool lead-out port  94  and a treatment target area thereof with illumination light emitted from the first illumination window  90 A. 
     As described above, the observation window  88  is provided in the first inclined surface  86 A. The observation window  88  is provided in the outer case  72  at a position on the outer case proximal end side relative to the treatment tool lead-out port  94  in the direction along the longitudinal axis LA, as with the first illumination window  90 A. Thus, through the observation window  88 , it is possible to observe a treatment tool led out from the treatment tool lead-out port  94  and a treatment target area thereof. 
     The observation window  88  is provided in the first inclined surface  86 A at a position on the L side with respect to the proximal end side region ER. By thus disposing the observation window  88  and the first illumination window  90 A in the same first inclined surface  86 A, that is, at substantially the same position in the direction along the longitudinal axis LA, it is possible to illuminate an observation range  150 B (see  FIG. 11 ) of the observation window  88  with illumination light emitted from the first illumination window  90 A. 
     The second illumination window  90 B is provided in the second inclined surface  86 B of the aforementioned outer case  72 . As described below in detail, the second illumination window  90 B differs from the first illumination window  90 A in the emission direction of illumination light. 
     The air/water supply nozzle  92  is provided on the first inclined surface  86 A at a position on the L side relative to the observation window  88 . As described above, the air/water supply nozzle  92  cleans the observation window  88  by ejecting a fluid such as water or air to the observation window  88 . In order that both of the illumination windows  90 A and  90 B are included in the ejection range of a fluid ejected from the air/water supply nozzle  92  at this time, the position where the first illumination window  90 A is formed in the proximal end side region ER and the position where the second illumination window  90 B is formed in the second inclined surface  86 B are each adjusted. Thus, it is possible to cool the illumination windows  90 A and  90 B and the light guide distal end portions  141 A and  141 B (see  FIG. 13 ) of the light guides  128  by using a fluid ejected from the air/water supply nozzle  92 . 
       FIG. 11  illustrates an observation axis  150 A and the observation range  150 B of the observation window  88 , a first illumination axis  151 A and a first illumination range  151 B of the first illumination window  90 A, and a second illumination axis  152 A and a second illumination range  152 B of the second illumination window  90 B. In  FIG. 11  (also in  FIG. 12  described below), in order to prevent complexity of the figure, the axes and the areas are illustrated on the assumption that the observation window  88  and the illumination windows  90 A and  90 B are at the same position. 
     As illustrated in  FIG. 11 , the observation axis  150 A is an axis extending from the observation window  88  in the normal direction thereof, the first illumination axis  151 A is an axis extending from the first illumination window  90 A in the normal direction thereof, and the second illumination axis  152 A is an axis extending from the second illumination window  90 B in the normal direction thereof. The observation axis  150 A, the first illumination axis  151 A, and the second illumination axis  152 A are each an inclined axis that is inclined toward the outer case distal end side from an orientation perpendicular to both of the width direction WD and the longitudinal axis LA. The observation axis  150 A and the first illumination axis  151 A are parallel to a normal line of the first inclined surface  86 A, and the second illumination axis  152 A is parallel to a normal line of the second inclined surface  86 B. 
     An observation axis angle θ 0  is the inclination angle of the observation axis  150 A with respect to a reference axis LB parallel to the longitudinal axis LA as seen in the width direction WD (the side in the direction perpendicular to the plane of the figure). A first illumination axis angle θ 1  is the inclination angle of the first illumination axis  151 A with respect to the reference axis LB as seen in the width direction WD. A second illumination axis angle θ 2  is the inclination angle of the second illumination axis  152 A with respect to the reference axis LB as seen in the width direction WD. The reference axis LB is an axis that intersects the observation axis  150 A for the observation axis angle θ 0 , is an axis that intersects the first illumination axis  151 A for the first illumination axis angle θ 1 , and is an axis that intersects the second illumination axis  152 A for the second illumination axis angle θ 2 . 
     The observation axis angle θ 0  and the observation range  150 B are each set at a value such that, as seen in the width direction WD, it is possible to observe through the observation window  88  an angular range from one to the other of the outer case distal end side of the outer case  72  [the insertion direction side (forward-direction side) of the insertion section  20 ] and a treatment tool led out from the treatment tool lead-out port  94  and a treatment target area thereof. Preferably, the observation axis angle θ 0  and the observation range  150 B have values such that it is possible to observe a treatment tool led out from the treatment tool lead-out port  94  and a treatment target area thereof in a state in which the elevator  96  is rotated to the elevated position. 
     The first illumination axis  151 A and the observation axis  150 A are parallel (including “substantially parallel”), because the first illumination axis angle θ 1  and the observation axis angle θ 0  are equal (including “substantially equal”). The first illumination range  151 B includes the observation range  150 B at least as seen in the width direction WD. Thus, the first illumination window  90 A can illuminate the aforementioned angular range (the observation range  150 B) with illumination light. 
     The second illumination axis  152 A is inclined further toward the outer case distal end side than the first illumination axis  151 A, because the second illumination axis angle θ 2  is smaller than the first illumination axis angle θ 1 . In other words, the inclination angle of the second inclined surface  86 B is closer to the right angle with respect to the reference axis LB than the inclination angle of the first inclined surface  86 A. 
     When the difference between the first illumination axis angle θ 1  and the second illumination axis angle θ 2  is denoted by Δθ, the second illumination range  152 B is inclined toward the outer case distal end side by the difference Δθ with respect to the first illumination range  151 B. Accordingly, the second illumination range  152 B partially overlaps the first illumination range  151 B. 
     In this case, the second illumination axis angle θ 2  (the difference Δθ) is set at a value such that the observation range  150 B is included in the second illumination range  152 B at least as seen in the width direction WD. Therefore, the second illumination window  90 B can also illuminate the aforementioned angular range (the observation range  150 B) with illumination light. 
       FIG. 12  is a side view of the distal end portion  50  of the insertion section  20  that is inserted into the lumen  154 . As illustrated in  FIG. 12  and the aforementioned  FIG. 11 , the second illumination window  90 B (the second illumination axis  152 A and the second illumination range  152 B) is inclined toward the outer case distal end side by the difference Δθ relative to the first illumination window  90 A (the first illumination axis  151 A and the first illumination range  151 B), and thereby it is possible to increase the amount of illumination light with which the second illumination window  90 B illuminates the insertion direction side of the insertion section  20 . As a result, for example, when the insertion section  20  is inserted into a narrow lumen  154 , the visibility of an inner wall of the lumen  154  on the insertion direction side of the insertion section  20  (forward visibility) is improved. 
     Moreover, the second illumination window  90 B is inclined toward the outer case distal end side by the difference Δθ relative to the first illumination window  90 A, and thereby, when illuminating an inner wall of a narrow lumen  154  such as the duodenum, it is possible to reduce the amount of illumination light emitted from the second illumination window  90 B to the inner wall compared with the amount of illumination light emitted from the first illumination window  90 A to the inner wall. Thus, it is possible to reduce the amount of illumination light emitted to the inner wall of the lumen  154 , compared with a case where the second illumination axis angle θ 2  and the first illumination axis angle θ 1  are the same. As a result, occurrence of halation of an endoscopic image, which may occur if an excessive amount of illumination light is emitted to the inner wall of the lumen  154 , is prevented. As necessary, it may be configured that illumination through only the second illumination window  90 B can be selectively performed. 
     Because the first illumination window  90 A is disposed in the aforementioned proximal end side region ER, the first illumination window  90 A can illuminate a treatment tool led out from the treatment tool lead-out port  94  and a treatment target area thereof constantly from one side (the proximal end side region ER side). Thus, the treatment target area is prevented from being shadowed by the elevator  96 , the treatment tool, or the like as seen from the first illumination window  90 A. Moreover, because the way in which a treatment tool is illuminated with illumination light does not change depending on displacement of the treatment tool due to rotation of the elevator  96 , it is possible to prevent the visibility of an endoscopic image from decreasing and to prevent a treatment tool led out from the treatment tool lead-out port  94  and a treatment target area thereof from deviating from the first illumination range  151 B. As a result, it is possible to reliably illuminate a treatment tool led out from the treatment tool lead-out port  94  and a treatment target area thereof with illumination light emitted from the first illumination window  90 A, and thus it is possible to improve the visibility of the treatment tool and the treatment target area. 
     Moreover, the first illumination window  90 A (the first illumination axis  151 A and the first illumination range  151 B) is inclined toward the outer case proximal end side by the difference Δθ relative to the second illumination window  90 B (the second illumination axis  152 A and the second illumination range  152 B), and thereby it is possible to increase the amount of illumination light with which the first illumination window  90 A illuminates a treatment tool led out from the treatment tool lead-out port  94  and a treatment target area thereof. As a result, it is possible to improve the visibility of the treatment tool and the treatment target area, because it is possible to reliably illuminate the treatment tool and the treatment target area with illumination light. 
     Thus, by using such a combination of the first illumination window  90 A and the second illumination window  90 B, it is possible to improve the forward visibility of the insertion section  20  and the visibility of the treatment tool and the treatment target area. 
     [Modifications of First Illumination Window, Second Illumination Window, and Observation Window] 
     In the present embodiment, the entirety of the first illumination window  90 A is within the proximal end side region ER in the width direction WD. However, a part of the first illumination window  90 A may protrude from the proximal end side region ER toward the L side or the R side. However, preferably, the entirety of the first illumination window  90 A is within the proximal end side region ER in the width direction WD, in order that the first illumination window  90 A can illuminate a treatment tool and a treatment target area thereof with illumination light irrespective of the rotation position of the elevator  96 . 
     In the present embodiment, the first illumination axis angle θ 1  of the first illumination axis  151 A of the first illumination window  90 A is less than 90°. However, the first illumination axis angle θ 1  may be 90° (including “substantially 90°”), depending on the size of the first illumination range  151 B of the first illumination window  90 A. That is, the proximal end side region ER (the first inclined surface  86 A) may be a surface parallel to the longitudinal axis LA. 
     In the present embodiment, the observation window  88  is formed at a position in the first inclined surface  86 A and on the L side of the proximal end side region ER. However, the position where the observation window  88  is formed is not particularly limited. However, in order to constantly observe a treatment tool led out from the treatment tool lead-out port  94  and a treatment target area thereof, preferably, the observation window  88  is provided in the outer case  72  at a position on the outer case proximal end side relative to the treatment tool lead-out port  94 . 
     In the present embodiment, the second illumination window  90 B is formed in the second inclined surface  86 B. However, the position where the second illumination window  90 B is formed is not particularly limited. In the above embodiment, the second illumination axis angle θ 2  is smaller than the first illumination axis angle θ 1 . However, the second illumination axis angle θ 2  may be larger than the first illumination axis angle θ 1 , or these angles may be the same. Moreover, in the embodiment, the second illumination window  90 B is provided in the outer case  72  at a position on the outer case distal end side relative to the proximal end side region ER. However, the second illumination window  90 B may be provided at a position on the outer case proximal end side relative to the treatment tool lead-out port  94 . Furthermore, the second illumination window  90 B may be omitted, provided that the first illumination window  90 A alone can reliably provide the aforementioned forward visibility and the visibility of a treatment tool and a treatment target area. 
     In the present embodiment, the observation axis  150 A and the first illumination axis  151 A are parallel. However, these axes may not be parallel. For example, the observation axis angle θ 0  may be an angle between the first illumination axis angle θ 1  and the second illumination axis angle θ 2 . 
     [Heat Dissipation of Light Guide Distal End Portion] 
       FIG. 13  is a perspective view of the elevating case  200  and the light guides  128  (a first light guide  128 A and a second light guide  128 B) held by the elevating case  200 . 
     As illustrated in  FIG. 13 , the light guides  128  include the first light guide  128 A, which emits illumination light through the first illumination window  90 A, and the second light guide  128 B, which emits illumination light through the second illumination window  90 B. The first illumination window  90 A and the second illumination window  90 B constitute an illumination window in the present invention. 
     The first light guide  128 A has the light guide distal end portion  141 A that is a distal end part on a side facing the first illumination window  90 A. A distal end part of the light guide distal end portion  141 A on the emission end side is inclined by the aforementioned first illumination axis angle θ 1  with respect to a proximal end part of the light guide distal end portion  141 A, which is parallel to the longitudinal axis LA. 
     The second light guide  128 B has the light guide distal end portion  141 B that is a distal end part on a side facing the second illumination window  90 B. A distal end part of the light guide distal end portion  141 B is inclined by the aforementioned second illumination axis angle θ 2  with respect to a proximal end part of the light guide distal end portion  141 B, which is parallel to the longitudinal axis LA. 
     Here, a metal member such as a mouthpiece is attached to the distal end part of each of the light guide distal end portions  141 A and  141 B. A proximal end part of each of the light guide distal end portions  141 A and  141 B is covered by a tube of various types. 
     When emitting illumination light from the emission ends thereof, the light guide distal end portions  141 A and  141 B generate heat by absorbing a part of the illumination light. Therefore, in the present embodiment, heat dissipation of the light guide distal end portions  141 A and  141 B is performed by using the elevating case  200 . 
     As described above, in the upper surface of the outer wall of the base  202  of the elevating case  200 , the two light guide holding grooves  203 A and  203 B (see  FIGS. 5 and 6 ), each of which corresponds to a light guide holding portion and a groove according to the present invention, are formed. 
     The proximal end part of the light guide distal end portion  141 A is fitted to the light guide holding groove  203 A. Thus, the light guide holding groove  203 A holds the light guide distal end portion  141 A at a position such that the distal end part (emission end) thereof faces the first illumination window  90 A. The proximal end part of the light guide distal end portion  141 B is fitted to the light guide holding groove  203 B. Thus, the light guide holding groove  203 B holds the light guide distal end portion  141 B at a position such that the distal end part (emission end) thereof faces the second illumination window  90 B. 
     In order to further reduce the size of the distal end portion  50 , the light guide distal end portions  141 A and  141 B may be fixed to the light guide holding grooves  203 A and  203 B by using an adhesive, without providing mouthpieces, tubes, and the like on the light guide distal end portions  141 A and  141 B. 
     The elevating case  200 , which is made of a metal, has a higher thermal conductivity than the light guide distal end portions  141 A and  141 B. Heat is transferred from the light guide distal end portions  141 A and  141 B to the elevating case  200 , because the elevating case  200  and the light guide distal end portions  141 A and  141 B are directly in contact with each other or are indirectly in contact with each other via metal members such as mouthpieces. Thus, it is possible to perform heat dissipation of the light guide distal end portions  141 A and  141 B. 
     When the outer case cover  72   b  (corresponding to a cover in the present invention), which is illustrated in the aforementioned  FIGS. 3 to 5 , is attached to the opening portion  71  of the outer case body  72   a , the light guide distal end portions  141 A and  141 B are pressed by an inner surface of the outer case cover  72   b  toward an upper surface of the elevating case  200 . Thus, by the outer case cover  72   b , the light guide distal end portions  141 A and  141 B are pressed against the inside of the light guide holding grooves  203 A and  203 B and fixed. As a result, the heat dissipating ability of the light guide distal end portions  141 A and  141 B is improved, because the closeness of contact between the light guide distal end portions  141 A and  141 B and the elevating case  200  is improved. A pressing part, such as a projection, for pressing the light guide distal end portions  141 A and  141 B may be provided on the inner surface of the outer case cover  72   b.    
     A metal pipe  145  is connected to the outer case proximal end side of the elevating case  200 . The metal pipe  145  connects the treatment tool insertion channel  100  and the through hole  202   a  of the elevating case  200 . Thus, the treatment tool insertion channel  100  and the elevator housing chamber  94   a  communicate with each other via the metal pipe  145  and the through hole  202   a . Therefore, a treatment tool inserted through the inside of the treatment tool insertion channel  100  is guided to the elevator housing chamber  94   a  through the metal pipe  145  and the through hole  202   a.    
     The metal pipe  145 , which is made of a metal, has a higher thermal conductivity than the light guide distal end portions  141 A and  141 B. Therefore, it is possible to transfer heat generated in the light guide distal end portions  141 A and  141 B further to the metal pipe  145  via the elevating case  200 . Thus, it is possible to further improve the heat dissipating ability of the light guide distal end portions  141 A and  141 B. 
     In the present embodiment, heat of the light guide distal end portions  141 A and  141 B is transferred to the bending portion  52  via the elevating case  200 . 
       FIG. 14  is a schematic view of the bending portion  52 . As illustrated in  FIG. 14 , the bending portion  52  includes a plurality of rings  160  (also referred to as “nodal rings” or “bridges”) that are made of a metal and that are coupled along the longitudinal axis LA, and a tube  161  that covers the rings  160 . The rings  160  that are adjacent to each other are rotatably coupled via a crimp pin  162 . Because the coupling structure of the rings  160  is a known technology, description of the details thereof will be omitted here. 
     Each of the rings  160 , which is made of a metal, has a higher thermal conductivity than the light guide distal end portions  141 A and  141 B, as with the aforementioned elevating case  200  and the metal pipe  145 . 
     A plurality of angle wires (not shown) are inserted through the inside of the rings  160 . One end side of each of the angle wires is connected to the distal end portion  50 , and other end side of each of the angle wires is coupled to a pulley (not shown) that is rotated by using the pair of angle knobs  42 . Thus, the bending portion  52  is remotely operated to be bent (angle operation) by rotating the pair of angle knobs  42  of the operation section  22 . As a result, it is possible to direct the distal end portion  50  in a desired direction. 
     A ring  160  that is positioned on the most distal end side (the distal end portion  50  side) of the bending portion  52  among the rings  160  (hereafter referred to as a “distal end ring  160 A) is fixed to the outer case  72  in a state in which the distal end ring  160 A is connected (coupled) to the outer case proximal end side of the outer case  72  by using a bolt (not shown) or the like. 
     At this time, a proximal end part of the base  202  of the elevating case  200  on the outer case proximal end side is inserted into the distal end ring  160 A. The proximal end part of the base  202  is fixed to the inside of the distal end ring  160 A by using a metal bolt  165  (corresponding to another metal member in the present invention) that extends through the distal end ring  160 A from the outer peripheral side to the inner peripheral side thereof. Therefore, the elevating case  200  and the distal end ring  160 A are indirectly connected to each other via the bolt  165 . The elevating case  200  and the distal end ring  160 A may be directly connected to each other by providing a holding portion that holds the proximal end part of the base  202 , a contact portion that contacts the base  202 , or the like in the distal end ring  160 A. 
     Thus, by indirectly connecting the elevating case  200  and the distal end ring  160 A via a metal member such as the bolt  165 , by directly connecting these, or by using both of the indirect and direct connections, it is possible to transfer heat generated in the light guide distal end portions  141 A and  141 B to the distal end ring  160 A and the other rings  160  via the elevating case  200 . Thus, it is possible to further improve the heat dissipating ability of the light guide distal end portions  141 A and  141 B. 
     Advantageous Effects of Present Embodiment 
     As described above, with the present embodiment, the light guide distal end portions  141 A and  141 B are each held by the elevating case  200  made of a metal, and thereby it is possible to perform heat dissipation of the light guide distal end portions  141 A and  141 B by transferring heat generated in the light guide distal end portions  141 A and  141 B to the elevating case  200 . Thus, increase in the temperature of the light guide distal end portions  141 A and  141 B can be suppressed without providing a heat insulator in the distal end portion  50 . As a result, increase in the temperature of the distal end portion  50  can be suppressed while preventing increase in the number of components and increase in the diameter of the distal end portion  50 . 
     Moreover, in the present embodiment, the metal pipe  145 , the distal end ring  160 A (the rings  160 ), and the like are connected to the elevating case  200 , and thereby it is possible to transfer heat, which has been transferred from the light guide distal end portions  141 A and  141 B to the elevating case  200 , further from the elevating case  200  to the metal pipe  145 , the distal end ring  160 A, and the like. As a result, it is possible to further improve the heat dissipating ability of the light guide distal end portions  141 A and  141 B. 
     Furthermore, with the present embodiment, because both of the illumination windows  90 A and  90 B are disposed in the ejection range of a fluid ejected from the air/water supply nozzle  92  (corresponding to a nozzle in the present invention), it is possible to cool the light guide distal end portions  141 A and  141 B via the illumination windows  90 A and  90 B by using the fluid ejected from the air/water supply nozzle  92 . As a result, increase in the temperature of the light guide distal end portions  141 A and  141 B, that is, increase in the temperature of the distal end portion  50  can be suppressed. 
     [Ultrasonic Endoscopes According to Other Embodiments] 
     In the ultrasonic endoscope  10  according to the embodiment described above, the first illumination window  90 A is disposed in the proximal end side region ER of the outer case  72 . However, the first illumination window  90 A may be disposed outside of the proximal end side region ER of the outer case  72 . 
       FIG. 15  is an external perspective view of a distal end portion  50  of an ultrasonic endoscope  10  according to another embodiment in which the disposition of the first illumination window  90 A is different. As illustrated in  FIG. 15 , the ultrasonic endoscope  10  according to the other embodiment basically has the same configuration as the ultrasonic endoscope  10  according to the embodiment described above, except for the following differences: the first inclined surface  86 A of the outer case  72  has an observation window region  86 A 1 , a nozzle region  86 A 2 , and an illumination window region  86 A 3  that are parallel to each other; and the disposition of the first illumination window  90 A in the outer case  72 . Therefore, elements that are the same as those of the embodiment described above will be denoted by the same numerals and descriptions thereof will be omitted. Hereafter, a direction opposite to the normal direction of the first inclined surface  86 A will be referred to as an “anti-normal direction”. 
     The observation window region  86 A 1 , the nozzle region  86 A 2 , and the illumination window region  86 A 3  are each an inclined surface that constitutes a part of the first inclined surface  86 A and that has the aforementioned first illumination axis  151 A as a normal line. The observation window region  86 A 1  is formed in the first inclined surface  86 A at a position that is on the outer case proximal end side relative to the treatment tool lead-out port  94  in the direction along the longitudinal axis LA and that is on the L side relative to the treatment tool lead-out port  94  in the width direction WD. The aforementioned observation window  88  is provided in the observation window region  86 A 1 . 
     The nozzle region  86 A 2  is formed in the first inclined surface  86 A at a position that is on the anti-normal side relative to the observation window region  86 A 1  and that is on the L side relative to the observation window region  86 A 1  in the width direction WD. The nozzle region  86 A 2  is shifted furthest toward the anti-normal side in the first inclined surface  86 A. The aforementioned air/water supply nozzle  92  is provided in the nozzle region  86 A 2 . 
     The illumination window region  86 A 3  is formed in the first inclined surface  86 A at a position that is on the normal side of the first inclined surface  86 A relative to the tip of the air/water supply nozzle  92  and that is on the L side relative to the treatment tool lead-out port  94  in the width direction WD. The illumination window region  86 A 3  is shifted furthest toward the normal side of the first inclined surface  86 A in the first inclined surface  86 A. The first illumination window  90 A according to the other embodiment is formed in the illumination window region  86 A 3 . 
     As in the embodiment described above, according to the other embodiment, the first illumination window  90 A (the first illumination axis  151 A and the first illumination range  151 B) is inclined toward the outer case proximal end side by the difference Δθ relative to the second illumination window  90 B (the second illumination axis  152 A and the second illumination range  152 B). Thus, the first illumination window  90 A can illuminate a treatment tool and a treatment target area thereof with illumination light. 
     At this time, the first illumination window  90 A according to the other embodiment is provided in the aforementioned illumination window region  86 A 3 , that is, at a position on the L side relative to the elevating case  200  in the width direction WD. Therefore, in the other embodiment, the first light guide  128 A is disposed in the outer case  72  not on the upper surface of the base  202  but at a position separated from the base  202  toward the L side. Thus, in the other embodiment, only the light guide distal end portion  141 B of the second light guide  128 B is held by the elevating case  200 . Accordingly, in the other embodiment, the second light guide  128 B corresponds to a light guide in the present invention, and the second illumination window  90 B corresponds to an illumination window in the present invention. 
       FIG. 16  is a perspective view of an elevating case  200  according to another embodiment and the second light guide  128 B held by the elevating case  200 . As illustrated in  FIG. 16 , the elevating case  200  according to the other embodiment has basically the same structure as the elevating case  200  according to the embodiment described above, except that only the light guide holding groove  203 B is formed in the upper surface thereof and the light guide distal end portion  141 B is held by the light guide holding groove  203 B. Thus, with the other embodiment, it is possible to transfer heat generated in the light guide distal end portion  141 B to the elevating case  200  and to further transfer the heat via the elevating case  200  to the metal pipe  145 , the distal end ring  160 A (the rings  160 ), and the like. 
     In this way, with the other embodiment, it is possible to suppress increase in the temperature of the light guide distal end portion  141 B, because heat dissipation of the light guide distal end portion  141 B is performed by using the elevating case  200  made of a metal. As a result, with the other embodiment, increase in the temperature of the distal end portion  50  can be suppressed, compared with a case where the temperatures of both of the light guide distal end portions  141 A and  141 B increase as in existing endoscopes. Thus, because it is not necessary to provide a heat insulator and the like in the distal end portion  50 , increase in the number of components and increase in the diameter of the distal end portion  50  is prevented. 
     In the other embodiment described above, the observation window region  86 A 1 , the nozzle region  86 A 2 , and the illumination window region  86 A 3 , which differ from each other, are formed in the first inclined surface  86 A. However, the observation window region  86 A 1 , the nozzle region  86 A 2 , and the illumination window region  86 A 3  may be formed in the same plane that does not have a step. In the other embodiment described above, the observation window region  86 A 1  (the observation axis  150 A) and the illumination window region  86 A 3  (the first illumination axis  151 A) in the first inclined surface  86 A are formed to be parallel. However, these regions may be formed not to be parallel. Moreover, the first illumination window  90 A may be omitted, provided that, for example, the aforementioned forward visibility and the visibility of the treatment tool and the treatment target area can be reliably obtained by using only the second illumination window  90 B. 
     OTHERS 
     In the embodiment described above, the light guide holding grooves  203 A and  203 B are formed in the upper surface of the outer wall the elevating case  200  (the base  202 ). However, the light guide holding grooves  203 A and  203 B may be formed in a surface other than the upper surface of the outer wall. 
       FIG. 17  illustrates another example of a holding structure of an elevating case  200  for holding the light guide distal end portions  141 A and  141 B. In the embodiment described above, the light guide distal end portions  141 A and  141 B are held by the light guide holding grooves  203 A and  203 B formed in the upper surface of the elevating case  200 . However, the light guide distal end portions  141 A and  141 B may be held by using another means. 
     As illustrated in  FIG. 17 , as a light guide holding portion in the present invention, two through holes  230 A and  230 B (or tubes) may be provided in a base  202  of the elevating case  200  so as to extend from a distal end surface on the outer case distal end side thereof to a proximal end surface on the outer case proximal end side thereof. The light guide distal end portion  141 A is inserted through the inside of the through hole  230 A and fixed, and the light guide distal end portion  141 B is inserted through the inside of the through hole  230 B and fixed. Thus, heat generated in the light guide distal end portions  141 A and  141 B can be transferred to the elevating case  200 , and advantageous effects that are the same as those of the embodiment described above can be obtained. Also in the other embodiment illustrated in  FIG. 16 , the through hole  230 B may be formed in the base  202  of the elevating case  200 . 
     A light guide holding portion in the present invention is not particularly limited, provided that the light guide holding portion has a structure that holds the light guide distal end portions  141 A and  141 B and that can transfer heat of the light guide distal end portions  141 A and  141 B to the elevating case  200 . 
     In the embodiment described above, an example in which the elevator  96  is rotated via the operating wire  222  and the elevator elevating lever  210  is described. However, a method for rotating the elevator  96  is not particularly limited, and a known method can be used. 
     In the embodiment described above, the first inclined surface  86 A, the observation window  88 , and the first illumination window  90 A are parallel. However, the observation window  88  and the first illumination window  90 A may not be parallel to the first inclined surface  86 A. Likewise, the second illumination window  90 B may not be parallel to the second inclined surface  86 B. 
     In the embodiment described above, the ultrasonic endoscope  10  that includes the ultrasonic observation portion  60  (the ultrasonic transducer  62 ) has been described as an example. However, the present invention is applicable to any endoscope that includes the elevator  96  for guiding a treatment tool, for example, a side-viewing endoscope such as a duodenoscope. 
     REFERENCE SIGNS LIST 
     
         
         
           
               2  ultrasonic inspection system 
               10  ultrasonic endoscope 
               12  ultrasonic processor device 
               14  endoscopic processor device 
               16  light source device 
               18  monitor 
               20  insertion section 
               22  operating unit 
               24  universal cord 
               27  ultrasonic connector 
               28  endoscopic connector 
               30  light source connector 
               32  tube 
               34  tube 
               36  air/water supply button 
               38  suction button 
               42  angle knob 
               43  operating lever 
               44  treatment tool insertion port 
               50  distal end portion 
               52  bending portion 
               54  soft portion 
               60  ultrasonic observation portion 
               62  ultrasonic transducer 
               64  balloon 
               66  locking ring 
               68  locking groove 
               70  supply/discharge port 
               71  opening portion 
               72  outer case 
               72   a  outer case body 
               72   b  outer case cover 
               73  partition wall 
               74  groove portion 
               75  fitting hole 
               76  lever housing cover 
               77  bolt 
               80  endoscope observation portion 
               86 A first inclined surface 
               86 A 1  observation window region 
               86 A 2  nozzle region 
               86 A 3  illumination window region 
               86 B second inclined surface 
               88  observation window 
               90 A first illumination window 
               90 B second illumination window 
               92  air/water supply nozzle 
               94  treatment tool lead-out port 
               94   a  elevator housing chamber 
               96  elevator 
               96   a  guide surface 
               100  treatment tool insertion channel 
               102  air/water supply pipe line 
               104  balloon pipe line 
               106  suction pipe line 
               108  air supply pipe line 
               110  water supply pipe line 
               112  balloon water supply pipe line 
               114  balloon water discharge pipe line 
               116  air supply source pipe line 
               118  water supply tank 
               120  water supply source pipe line 
               122  branch pipe line 
               124  suction pump 
               126  suction source pipe line 
               128  light guide 
               128 A first light guide 
               128 B second light guide 
               129  air supply pump 
               141 A light guide distal end portion 
               141 B light guide distal end portion 
               145  metal pipe 
               150 A observation axis 
               150 B observation range 
               151 A first illumination axis 
               151 B first illumination range 
               152 A second illumination axis 
               152 B second illumination range 
               154  lumen 
               160  ring 
               160 A distal end ring 
               161  tube 
               162  crimp pin 
               165  bolt 
               200  elevating case 
               202  base 
               202   a  through-hole 
               203 A light guide holding groove 
               203 B light guide holding groove 
               204  partition wall 
               206  side wall 
               208  counter wall 
               208   a  cutout portion 
               210  elevator elevating lever 
               211  bolt 
               212  lever housing 
               214  holding hole 
               216  rotation shaft 
               220  bolt hole 
               222  operating wire 
               222   a  distal end side coupling portion 
               222   b  proximal end side coupling portion 
               224  wire insertion hole 
               226  elevator operating mechanism 
               226 A rotary drum 
               226 B crank member 
               226 C slider 
               230 A through-hole 
               230 B through-hole 
             ER proximal end side region 
             LA longitudinal axis 
             LB reference axis 
             NV normal direction 
             WD width direction 
             Δθ difference 
             θ 0  observation axis angle 
             θ 1  first illumination axis angle 
             θ 2  second illumination axis angle