Patent Publication Number: US-2023135724-A1

Title: Endoscope system

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a Continuation of PCT International Application No. PCT/JP2021/011184 filed on 18 Mar. 2021, which claims priority under 35 U.S.C § 119(a) to Japanese Patent Application No. 2020-117762 filed on 8 Jul. 2020. The above application 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 system. 
     2. Description of the Related Art 
     Endoscopes are widely used in the medical field and the industrial field. An endoscope includes an insertion part to be inserted into an object to be examined, and irradiates an object to be observed with illumination light from a distal end portion of the insertion part. A light guide unit for guiding illumination light, which is supplied from a light source device, to the distal end portion of the insertion part is provided in the endoscope. The light guide unit guides illumination light, and the object to be observed is illuminated with the illumination light, so that the inside of the object to be examined can be observed. 
     In an endoscope disclosed in JP1994-296584A (JP-H06-296584A), a light guide unit comprises a plurality of light guides. The light guide is formed of, for example, a fiber bundle in which quartz fibers or multi-component fibers are bundled. Among these fiber bundles, a fiber bundle formed of quartz fibers is excellent in flexibility but has a high attenuation rate of light. Accordingly, in the endoscope disclosed in JP1994-296584A (JP-H06-296584A), a lens is disposed between the plurality of light guides. Since this lens is used, a reduction in the amount of light and deterioration in the distribution of light are prevented, and light emitted from an end portion of a light source-side light guide is transmitted to an end portion of a distal end portion-side light guide. 
     However, there is an endoscope in which a bendable part is provided at a distal end of an insertion part to allow a user to observe a portion to be observed at various angles or to easily insert the insertion part. In the endoscope disclosed in JP1994-296584A (JP-H06-296584A), the end portions of the light guides and the lens are disposed in a bendable part. 
     SUMMARY OF THE INVENTION 
     However, since the end portions of the light guides and the lens are disposed in the bendable part in the endoscope disclosed in JP1994-296584A (JP-H06-296584A), there is a possibility that an optical axis is shifted. That is, in a case where the bendable part is bent, central axes of the end portions of the light source-side light guide and the distal end portion-side light guide facing the lens do not coincide with the central axis of the lens for preventing a reduction in the amount of light and deterioration in the distribution of light. For this reason, there is a high probability that deterioration in performance, such as a reduction in the amount of light and deterioration in the distribution of light, will occur. 
     An object of the present invention is to provide an endoscope system that can prevent a reduction in the amount of illumination light and deterioration in the distribution of the illumination light regardless of an operation state of an endoscope. 
     An endoscope system according to an aspect of the present invention comprises: an endoscope that includes an insertion part, an illumination light-emission end, and a light guide unit; and a light source device. The light guide unit includes a light guide and an optical member, and the optical member is provided in the endoscope at a portion that is closer to a proximal end side than to the illumination light-emission end and that has stiffness. The insertion part is to be inserted into an object to be examined. The illumination light-emission end is provided at a distal end portion of the insertion part. The light guide unit guides illumination light. The light source device is connected to the endoscope, includes a plurality of light sources emitting color lights different from each other, and emits illumination light in which a plurality of color lights are mixed by the light sources. The light guide includes a light guide that guides the illumination light emitted from the light sources to the illumination light-emission end in a case where the endoscope is connected to the light source device. The optical member suppresses a variation in a relative intensity of each color light of the illumination light, which is guided by the light guide and is emitted from the illumination light-emission end, with respect to a light distribution angle. 
     It is preferable that the light guide unit includes a plurality of the light guides and the optical member is a lens member disposed between the plurality of light guides. 
     It is preferable that the light guide and the lens member are disposed at a position where an emission point of the illumination light guided by the light guide is closer to the lens member than to a focal point of the lens member on an incident side. 
     It is preferable that lens surfaces of the lens member are disposed to have intervals from an emission end and an incident end of the light guides. 
     It is preferable that the endoscope includes a connector to be connected to the light source device, and the optical member is disposed in the connector. It is preferable that the connector includes a light guide rod that is to be inserted into the light source device in a case where the connector is connected to the light source device, and the optical member is disposed in the light guide rod. 
     It is preferable that the insertion part includes a bendable part that changes an orientation of the distal end portion, and the optical member is provided in the endoscope at a portion other than the bendable part. 
     It is preferable that the endoscope includes an operation part connected to the insertion part, and the optical member is provided in the operation part. 
     It is preferable that a dimension from an incident end to an emission end of a light guide, which is positioned on an incident side of the optical member, among the plurality of light guides in a direction of an optical axis is 5 mm or more. It is preferable that an antireflection film is formed on a lens surface of the lens member. 
     It is preferable that, in a case where a relative intensity of one color light among the plurality of color lights emitted from the light sources is used as a reference, the lens member makes a relative intensity of the other color light have a difference of ±5% or less from the relative intensity of the color light used as the reference. 
     According to the endoscope system of the aspect of the present invention, it is possible to prevent a reduction in the amount of illumination light and deterioration in the distribution of the illumination light regardless of an operation state of an endoscope. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is an external view of an endoscope system. 
         FIG.  2    is a block diagram showing a schematic configuration of the endoscope system. 
         FIG.  3    is an external perspective view of a light source device. 
         FIG.  4    is an external perspective view of a connector. 
         FIG.  5    is a front view of the connector. 
         FIG.  6    is an exploded perspective view of the connector. 
         FIG.  7    is a cross-sectional view of a main portion of the connector. 
         FIG.  8    is a cross-sectional view of a main portion enlarging a part of  FIG.  7    and showing a configuration around a lens member. 
         FIG.  9    is a perspective view of a spacer member, a lens member, and an O-ring. 
         FIG.  10    is a diagram illustrating a positional relationship between a first light guide, a second light guide, and a lens member. 
         FIG.  11    is an end view showing the shape of an end surface of an incident end of the first light guide. 
         FIG.  12    is an end view showing the shape of an end surface of an emission end of the second light guide. 
         FIG.  13    shows illumination characteristics showing the relative intensity of each color light of illumination light with respect to a light distribution angle at a position in a light guide unit where the illumination light has not yet passed through the lens member. 
         FIG.  14    shows illumination characteristics showing the relative intensity of each color light of illumination light with respect to a light distribution angle at a position in the light guide unit where the illumination light has passed through the lens member. 
         FIG.  15    is a cross-sectional view of a main portion showing a configuration of a connector of a second embodiment. 
         FIG.  16    is an external view showing a configuration of an endoscope of a third embodiment. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     First Embodiment 
     [Schematic Configuration of Endoscope System] 
     As shown in  FIG.  1   , an endoscope system  10  includes an endoscope  12 , a light source device  14 , a processor device  16 , a monitor  18 , and a console  20 . The endoscope  12  is, for example, a rigid endoscope, such as a laparoscope, and comprises an elongated rigid insertion part  21  that is to be inserted into an object to be examined, an L-shaped grip part  22  that is connected to a proximal end portion of the insertion part  21 , a soft universal cable  23  of which a distal end portion is connected to the insertion part  21  via the grip part  22 , and a switch-disposition member  24  that is provided in a middle portion of the universal cable  23 . 
     A connector  25  is provided at a proximal end portion of the universal cable  23 , and the endoscope  12  is attachably and detachably connected to a light source device-side connector  41  of the light source device  14  via the connector  25 . The universal cable  23  is a cable in which a light guide unit  26  (see  FIG.  2   ) for guiding illumination light emitted from the light source device  14 , a control line for controlling an image pickup sensor  33  provided in a distal end portion  21 A of the insertion part  21 , a signal line for transmitting image signals output from the image pickup sensor  33  in a case where an image of an object to be observed irradiated with illumination light is picked up, a power line for supplying power to each part, such as the image pickup sensor, and the like are integrated. The control line, the signal line, and the power line are not shown in FIG.  2  to reduce the complexity of  FIG.  2   . 
     The endoscope system  10  according to this embodiment has a configuration in which power, optical signals, and the like are transmitted between the endoscope  12  and the light source device  14  via the connector  25  and the light source device-side connector  41  in a contactless manner. Further, for example, an image selector switch, which is used to switch an image displayed on the monitor  18  to a normal picked-up image and a special light image (for example, a white light (WL) image, a blue laser imaging (BLI) image, a linked color imaging (LCI) image, or a low-oxygen imaging image), can be applied as an operation switch  24 A disposed on the above-mentioned switch-disposition member  24 . Furthermore, the operation switch is not limited thereto, and an image stop switch, an image pickup switch, a zoom switch comprising a telephoto button and a wide button, a washing switch for the distal end portion of the insertion part, a light amount-adjustment switch, a sensitivity-adjustment switch, or the like can also be applied. 
     [Schematic Configuration of Endoscope] 
     As shown in  FIG.  2   , the distal end portion  21 A of the insertion part  21  is provided with an observation unit  27  and an illumination light-emission end (hereinafter, simply referred to as an emission end)  28 . The observation unit  27  comprises an observation window  29 , an image pickup lens group  31  and a prism  32  that are disposed behind the observation window  29 , and the image pickup sensor  33 . 
     The image pickup sensor  33  is, for example, a color sensor including primary color filters, and comprises three types of pixels, that is, B pixels (blue pixels) including blue color filters, G pixels (green pixels) including green color filters, and R pixels (red pixels) including red color filters. The blue color filter mainly transmits violet to blue light. The green color filter mainly transmits green light. The red color filter mainly transmits red light. In a case where the image of the object to be observed is picked up using the primary color image pickup sensor  33  as described above, a maximum of three types of images, that is, a B image (blue image) obtained from B pixels, a G image (green image) obtained from G pixels, and an R image (red image) obtained from R pixels, can be simultaneously obtained. 
     A charge coupled device (CCD) image sensor or a complementary metal oxide semiconductor (CMOS) image sensor can be applied as the image pickup sensor  33 . Further, the image pickup sensor  33  of this embodiment is a primary color sensor, but a complementary color sensor can also be used. A complementary color sensor includes, for example, cyan pixels provided with cyan color filters, magenta pixels provided with magenta color filters, yellow pixels provided with yellow color filters, and green pixels provided with green color filters. In a case where a complementary color sensor is used, images obtained from the respective color pixels described above can be converted into B images, G images, and R images by complementary color-primary color conversion. Further, a monochrome sensor not provided with color filters may be used as the image pickup sensor  33  instead of the color sensor. In this case, the images having the respective colors can be obtained from the sequential image pickup of the object to be observed using illumination light having the respective colors, such as B, G, and R. 
     [Schematic Configuration of Processor Device] 
     The processor device  16  controls the amount and emission time of illumination light that is emitted from the light source device  14 , the operation of the image pickup sensor  33 , and the like, and generates an endoscopic image using image signals that are obtained from the image pickup of the object to be observed irradiated with illumination light. The processor device  16  is electrically connected to the monitor  18  and to the console  20 . The monitor  18  displays the endoscopic image generated by the processor device  16 , information about the endoscopic image, and the like. The console  20  is a user interface that receives an input operation, such as function settings. 
     [Schematic Configuration of Light Source Device] 
     As shown in  FIG.  2   , the light source device  14  comprises a light source unit  42 , a light source controller  43 , a wireless communication unit  44 , and a wireless power supply unit  45 . The light source unit  42  emits illumination light that is used to illuminate the object to be observed. The light source controller  43  controls the light source unit  42 . Although not shown, the light source device  14  comprises the processor device  16  and a signal transmission unit that transmits control signals, image signals, and the like. 
     The light source unit  42  includes semiconductor light sources, such as a plurality of color light emitting diodes (LEDs). The light source controller  43  adjusts the turning on or off of the LEDs or the drive currents or drive voltages of the LEDs to control the amount of illumination light to be emitted. The semiconductor light sources of the light source unit  42  are not limited to LEDs and may be laser diodes (LDs) or the like. 
     The light source unit  42  includes four color LEDs, that is, a violet light emitting diode (V-LED)  42   a , a blue light emitting diode (B-LED)  42   b , a green light emitting diode (G-LED)  42   c , and a red light emitting diode (R-LED)  42   d.    
     The LEDs  42   a  to  42   d  emit color lights different from each other. For example, the V-LED  42   a  emits a violet light V having a wavelength range of 380 nm to 420 nm. The B-LED  42   b  emits a blue light B having a wavelength range of 420 nm to 500 nm. The G-LED  42   c  emits a green light G having a wavelength range of 480 nm to 600 nm. The R-LED  42   d  emits a red light R having a wavelength range of 600 nm to 650 nm. Lights emitted from the LEDs  42   a  to  42   d  may have the same central wavelength and the same peak wavelength, and may have different central wavelengths and different peak wavelengths. 
     The light source controller  43  independently controls the turning on or off of the respective LEDs  42   a  to  42   d , the amounts of lights emitted at the times of turning on thereof, and the like to adjust the emission time, emission period, amount, and spectrum of illumination light. The control of the turning on or off of each of the LEDs, which is performed by the light source controller  43 , varies depending on each observation mode. Reference brightness can be set by the console  20  or the like. 
     In the case of a normal mode, the light source controller  43  turns on all the V-LED  42   a , the B-LED  42   b , the G-LED  42   c , and the R-LED  42   d . Accordingly, in the normal mode, polychromatic light for a normal mode, which includes a violet light, a blue light, a green light, and a red light, is emitted from the light source device  14  as normal light. Since a violet light, a blue light, a green light, and a red light are mixed in the normal light and the normal light has an intensity equal to or higher than a certain intensity from a blue light wavelength range to a red light wavelength range, the normal light is a substantially white light. A white light includes not only broadband light that includes all the wavelength ranges of a blue light component, a green light component, and a red light component like a white light emitted from a xenon lamp, but also illumination light in which lights having wavelength ranges of at least three color light components, such as a blue light component, a green light component, and a red light component, are mixed. 
     In the case of a special mode, the light source controller  43  turns on all the V-LED  42   a , the B-LED  42   b , the G-LED  42   c , and the R-LED  42   d  but sets a light amount ratio between a violet light, a blue light, a green light, and a red light in this case such that a ratio of a violet light is increased. Accordingly, a special light is a bluish light. The case of the normal mode in which a white light is emitted as illumination light will be mainly described below. 
     Further, the light source device  14  is electrically connected to the processor device  16 , and the connector  25  of the endoscope  12  is connected to the processor device  16  via the light source device  14 . The transmission and reception of image signals and the like between the light source device  14  and the connector  25  are via wireless communication. For this reason, the light source device  14  transmits image signals and the like, which are transmitted to and received from the connector  25  wirelessly, to the processor device  16 . Furthermore, the light source device  14  supplies power, which is used to drive the image pickup sensor  33  and the like, to the connector  25  but also supplies this power wirelessly. 
     As shown in  FIG.  3   , the light source device-side connector  41  is provided with locking portions  41 A and  41 B, a contact surface  41 C, a fitting recess  41 D, and a connection hole  41 E. The contact surface  41 C is a flat surface that is in contact with a front surface  61 A of the connector  25  to be described later. The locking portions  41 A and  41 B are provided at positions protruding from the contact surface  41 C. In a case where the connector  25  is connected, the locking portions  41 A and  41 B are locked to the connector  25  and maintain connection. The fitting recess  41 D is a recess that is recessed from the contact surface  41 C by one step, and a fitting projection  61 B of the connector  25  to be described later is fitted to the fitting recess  41 D. The connection hole  41 E is a through-hole provided in the fitting recess  41 D, and a light guide rod  65  of the connector  25  is inserted into the connection hole  41 E. 
     In a case where the connector  25  is connected to the light source device-side connector  41 , the light guide rod  65  is inserted into the connection hole  41 E of the light source device-side connector  41 , so that an incident end  51 A of a first light guide  51  faces the light source unit  42  of the light source device  14 . Accordingly, illumination light emitted from the light source unit  42  is transmitted via the first light guide  51  and a lens member  53 , and is emitted to a front side of the insertion part  21  from an emission end  28  of a second light guide  52 . 
     Further, the wireless communication unit  44  that wirelessly communicates with a wireless communication unit  63  of the connector  25  and the wireless power supply unit  45  that supplies power to a wireless power receiving unit  64  of the connector  25  are provided behind a lower portion of the contact surface  41 C. The wireless communication unit  44  includes an image signal receiving unit  46  (see  FIG.  2   ). The image signal receiving unit  46  receives image signals from an image signal transmission unit  66  of the connector  25 . A connection hole  44 A of the wireless communication unit  44  is formed of a hole portion having a shape that allows a connection pin  63 A of the connector  25  to be inserted. The wireless power supply unit  45  is, for example, a coil (so-called primary coil), and supplies power to the wireless power receiving unit  64  with a contactless power transmission method, such as an electromagnetic induction method or a magnetic resonance method. 
     In a case where the connector  25  of the endoscope  12  is connected to the light source device-side connector  41  of the light source device  14 , illumination light emitted from the light source unit  42  is incident on the light guide unit  26  of the endoscope  12  via, for example, light guide members (not shown), such as a prism and a light guide rod. 
     The light guide unit  26  is built in the endoscope  12  including the universal cable  23  and the connector  25 , and guides illumination light up to the distal end portion  21 A of the endoscope  12 . The distal end portion  21 A is provided with the emission end  28 . The emission end  28  is disposed around the observation window  29 , and is a distal end of the second light guide  52  to be described later. In this embodiment, the observation window  29  and the emission end  28  are exposed from a distal end surface of the distal end portion  21 A. Illumination light emitted from the light source unit  42  is guided from the light source unit  42  by the light guide unit  26  and is applied to the object to be observed from the emission end  28 . 
     The light guide unit  26  includes the first light guide  51 , the second light guide  52 , and the lens member  53 . Each of the light guides  51  and  52  is a fiber bundle in which optical fibers are bundled. The lens member  53  corresponds to an optical member of the claims. The optical fibers forming the light guides  51  and  52  are, for example, quartz fibers or multi-component fibers. In this embodiment, the first light guide  51 , a part of the second light guide  52 , and the lens member  53  are provided in the connector  25  and are more specifically provided in the light guide rod  65  (see  FIG.  7   ). The structure of the light guide rod  65  will be described later. 
     [Schematic Configuration of Connector] 
     As shown in  FIG.  4   , the connector  25  includes an outer case  61 , a shield case  62  (see  FIG.  6   ), the wireless communication unit  63 , the wireless power receiving unit  64 , and the light guide rod  65 . Hereinafter, a posture in which the connector  25  is correctly connected to the light source device  14  is defined as “connection posture”, a connection direction in which the connector  25  is connected to the light source device  14  in the connection posture is defined as a Z direction, a vertical direction of the connector  25  in the connection posture is defined as a Y direction, and a direction in a horizontal plane perpendicular to the Z direction and to the Y direction is defined as an X direction. A positive side in the Z direction is defined as a side on which the light source device  14  is positioned as viewed from the connector  25 , a positive side in the Y direction is defined as a vertical upper side, and a positive side in the X direction is defined as a left side as viewed from a negative side in the Z direction. Hereinafter, the positive side in the Z direction, which is the connection direction of the connector  25 , may be referred to as a proximal end side or a proximal end portion, and a negative side in the Z direction may be referred to as a distal end side or a distal end portion. 
     The outer case  61  houses the wireless communication unit  63  and the wireless power receiving unit  64 , and the light guide rod  65  protrudes from the front surface  61 A that is positioned on a side facing the light source device  14  in the connection posture. The wireless communication unit  63  wirelessly communicates with the light source device  14 . The wireless power receiving unit  64  receives power that is wirelessly supplied from the light source device  14 . Since a position where the light guide rod  65  protrudes is present on a vertical upper side in the connection posture, the outer case  61  houses the wireless communication unit  63  and the wireless power receiving unit  64  on a vertical lower side in the connection posture. 
     The fitting projection  61 B, which is to be fitted to the fitting recess  41 D of the light source device-side connector  41 , is provided at a proximal end portion of the light guide rod  65 , and the fitting projection  61 B protrudes from the front surface  61 A. A central axis L LG  of the light guide rod  65  is parallel to the Z direction. 
     As shown in  FIG.  5   , the light guide rod  65  is disposed in the middle of the front surface  61 A in the X direction. Further, an upper surface  61 C of the outer case  61 , which is positioned on the vertical upper side in the connection posture, is a curved surface, and a lower surface  61 D thereof, which is positioned on a vertical lower side in the connection posture, is a flat surface. The light guide rod  65  is provided on a side of the front surface  61 A close to the upper surface  61 C. In contrast, the wireless communication unit  63  and the wireless power receiving unit  64  are housed to be arranged on the right and left on a side of the front surface  61 A close to the lower surface  61 D. 
     The wireless communication unit  63  includes the image signal transmission unit  66  (see  FIG.  2   ). Electronic components, such as a substrate, of the image signal transmission unit  66  are housed in the shield case  62  made of metal. The image signal transmission unit  66  wirelessly transmits image signals, which are obtained from the image pickup of the object to be observed irradiated with illumination light, to the image signal receiving unit  46  of the light source device  14 . Wireless communication performed by the wireless communication unit  63  is optical communication, and it is preferable that this wireless communication is, for example, near-infrared communication using near-infrared light (light having a wavelength of about 0.7 μm to 2.5 μm). 
     The wireless communication unit  63  includes the connection pin  63 A. The connection pin  63 A includes an emission end for optical signals at a distal end portion thereof, and can transmit and receive optical signals to and from the wireless communication unit  44  of the light source device  14  in a case where the connection pin  63 A is connected to the connection hole  44 A of the light source device-side connector  41 . Accordingly, image signals of the image signal transmission unit  66  are optically transmitted to the image signal receiving unit  46  of the light source device  14  in a contactless manner. The image signals optically transmitted to the image signal receiving unit  46  are transmitted to the processor device  16 . The image signals, which are transmitted to the processor device  16  from the endoscope  12  via the light source device  14 , are subjected to image processing and are displayed on the monitor  18  as an endoscopic image. The functions of the wireless communication unit  44  of the light source device  14  and the wireless communication unit  63  of the connector  25  are not limited to the above-mentioned functions, and may be to transmit and receive control signals that are used to control, for example, the image pickup sensor  33  and the like of the endoscope  12 . 
     The wireless power receiving unit  64  is, for example, a coil (so-called secondary coil), and receives power that is supplied from the wireless power supply unit  45  provided in the light source device  14  with a contactless power transmission method. 
     The wireless power receiving unit  64  is fixed to the shield case  62 . Since an endoscope which supplies power using a primary coil and a secondary coil is publicly known in JP2016-67534A, the detailed description thereof will be omitted here. Since the wireless power receiving unit  64  is provided behind the front surface  61 A as shown in  FIG.  5   , the wireless power receiving unit  64  receives power supplied from the light source device  14  through the front surface  61 A. The wireless power receiving unit  64  supplies power to each part of the endoscope  12 , such as the image pickup sensor  33 . 
     In a case where the connector  25  is connected to the light source device-side connector  41 , the connector  25  is locked at the upper surface  61 C and at the lower surface  61 D of the outer case  61 , and connection is maintained. As described above, the light source device-side connector  41  is provided with the locking portions  41 A and  41 B. Correspondingly, a groove  61 E to which the locking portion  41 A of the light source device  14  is to be fitted is provided on the upper surface  61 C of the connector  25 , and a groove  61 F to which the locking portion  41 B of the light source device  14  is to be fitted is provided on the lower surface  61 D of the connector  25 . 
     As shown in  FIG.  6   , the outer case  61  includes a case body  68 , and a case lid  69  and the case lid  69  is combined with a proximal end portion of the case body  68 , so that the outer case  61  is formed in a hollow shape. The case body  68  and the case lid  69  of the outer case  61  are made of a resin having high heat resistance and high chemical resistance. 
     The case lid  69  is provided with the front surface  61 A and the fitting projection  61 B described above, and includes a part of the upper surface  61 C and the lower surface  61 D. An O-ring  71 , which is a sealing member, is fitted to an outer peripheral surface of a rear end portion of the case lid  69 . The O-ring  71  is one of a plurality of sealing members that seal the inside of the outer case  61 . 
     A lead-out hole  61 G, through which the light guide rod  65  is led to the outside, is formed at a central portion of the fitting projection  61 B. The proximal end portion of the light guide rod  65  is fixed to a bracket  72  that is disposed in the outer case  61 . The bracket  72  is formed in an L shape, and is fixed to the inside of the case body  68 . The bracket  72  is fixed to an inner peripheral surface  69 A (see  FIG.  7   ) of the case lid  69 , so that the light guide rod  65  is supported by the case body  68  and the case lid  69 . 
     An elastic O-ring  73  is fitted to an outer peripheral surface of the light guide rod  65 , and the light guide rod  65  is fitted to the lead-out hole  61 G via the O-ring  73 . As with the O-ring  71 , the O-ring  73  is also one of a plurality of sealing members that seal the inside of the outer case  61 . 
     [Schematic Configuration of Light Guide Rod] 
     As shown in  FIG.  7   , the light guide rod  65  comprises a first light guide rod  74  and a second light guide rod  75 . The first light guide rod  74  and the second light guide rod  75  are made of metal or the like having high stiffness and have a cylindrical shape. The first light guide rod  74  houses an incident window  76 , the first light guide  51 , the second light guide  52 , and the lens member  53  therein. The incident window  76  is a transparent cover glass and is fixed to a proximal end portion of the first light guide rod  74 . Illumination light emitted from the light source unit  42  passes through the incident window  76 , and is incident on the first light guide  51 . An elastic O-ring  81  is fitted to an inner peripheral surface of the proximal end portion of the first light guide rod  74 . The O-ring  81  is deformed between the incident window  76  and the first light guide rod  74  and is in close contact with both the incident window  76  and the first light guide rod  74 , so that airtightness at the proximal end portion of the first light guide rod  74  is ensured. 
     The first light guide  51 , the second light guide  52 , and the lens member  53  are fixed in the first light guide rod  74  in a state where the first light guide  51  is held by a first ferrule  77 , the second light guide  52  is held by a second ferrule  78 , and the lens member  53  is held by a spacer  79 . 
     As shown in  FIG.  8   , the first ferrule  77  is formed in the shape of a cylinder in which a light guide-insertion hole  77 A penetrating in an axial direction is provided at the center thereof. The first light guide  51  is inserted into the light guide-insertion hole  77 A. The first light guide  51  is fixed to the light guide-insertion hole  77 A by being adhered with, for example, an adhesive or the like. An elastic O-ring  82  is fitted to an outer peripheral surface of the first ferrule  77 . 
     The first ferrule  77  is inserted up to a position close to the incident window  76  from the distal end side of the first light guide rod  74  together with the first light guide  51  and the O-ring  82 , and is fitted to the inner peripheral surface of the first light guide rod  74 . Accordingly, the first light guide  51  is fixed to the first light guide rod  74  together with the first ferrule  77 . Further, the O-ring  82  is deformed between the first ferrule  77  and the first light guide rod  74  and is in close contact with both the first ferrule  77  and the first light guide rod  74 , so that airtightness between the first ferrule  77  and the first light guide rod  74  is ensured. 
     The second ferrule  78  is formed in the shape of a cylinder in which a light guide-insertion hole  78 A penetrating in an axial direction is provided at the center thereof. A proximal end portion of the second light guide  52  is inserted into the light guide-insertion hole  78 A. The second light guide  52  protrudes from the distal end side of the light guide-insertion hole  78 A, and is fixed to the distal end portion  21 A of the endoscope  12  through the second light guide rod  75 , the connector  25 , the universal cable  23 , the grip part  22 , and the insertion part  21 . 
     The proximal end portion of the second light guide  52  is fixed to the light guide-insertion hole  78 A by being adhered with, for example, an adhesive or the like. An opening portion  78 B is provided on a proximal end surface of the second ferrule  78  facing the first ferrule  77 . The opening portion  78 B is a circular opening portion that is formed to have an inner diameter larger than the inner diameter of the light guide-insertion hole  78 A. The spacer  79  is fitted to the opening portion  78 B. Further, a locking groove  78 C is formed in the opening portion  78 B. 
     A large-diameter portion  78 D that has a large outer diameter and a small-diameter portion  78 E that has an outer diameter smaller than the outer diameter of the large-diameter portion  78 D are formed on an outer peripheral surface of the second ferrule  78 . The large-diameter portion  78 D is fitted to the inner peripheral surface of the first light guide rod  74 . Accordingly, the proximal end portion of the second light guide  52  is fixed to the first light guide rod  74  together with the second ferrule  78 . A proximal end of the second light guide  52  protrudes into the opening portion  78 B from the proximal end side of the light guide-insertion hole  78 A. Further, the small-diameter portion  78 E has a gap between the small diameter portion  78 E and the inner peripheral surface of the first light guide rod  74 . 
     As shown in  FIG.  9   , the spacer  79  is formed in the shape of a disc in which a through-hole  79 A penetrating in an axial direction is provided at the center thereof. The spacer  79  includes a lens member holding portion  79 B and an O-ring housing portion  79 C on the distal end side of the through-hole  79 A. The lens member holding portion  79 B is an opening portion that is slightly larger than the through-hole  79 A, and is formed to have an inner diameter corresponding to the outer diameter of the lens member  53 . An outer peripheral surface of the lens member  53  is fitted to the lens member holding portion  79 B, so that the lens member holding portion  79 B holds the lens member  53 . 
     The O-ring housing portion  79 C is an opening portion that is formed to have an inner diameter slightly larger than the inner diameter of the lens member holding portion  79 B. The O-ring housing portion  79 C houses an elastic O-ring  83  therein. The inner diameter of the O-ring  83  is smaller than the outer diameter of the lens member  53  and the outer diameter of the proximal end portion of the second light guide  52 . 
     A locked portion  79 E is formed on an outer peripheral surface  79 D of the spacer  79 . The locked portion  79 E may be an annular protrusion along the outer peripheral surface  79 D, or may be a plurality of protrusions protruding from the outer peripheral surface  79 D. The locked portion  79 E is locked to the locking groove  78 C of the opening portion  78 B. The outer peripheral surface  79 D of the spacer  79  is formed to correspond to an inner peripheral surface of the opening portion  78 B. 
     The spacer  79  is fixed to the opening portion  78 B of the second ferrule  78  in a state where the lens member  53  is held in the lens member holding portion  79 B and the O-ring  83  is housed in the O-ring housing portion  79 C. The outer peripheral surface  79 D is fitted to the inner peripheral surface of the opening portion  78 B, and the locked portion  79 E is locked to the locking groove  78 C. Accordingly, since the position of the spacer  79  relative to the opening portion  78 B is restricted, the spacer  79  is not separated from the opening portion  78 B. 
     As described above, the proximal end of the second light guide  52  protrudes into the opening portion  78 B. For this reason, in a case where the spacer  79  is fixed to the opening portion  78 B of the second ferrule  78 , the proximal end of the second light guide  52  protrudes into the spacer  79  and presses the O-ring  83  to the proximal end side. Since the lens member  53  is pressed by the second light guide  52  via the O-ring  83 , the lens member  53  is pushed to the proximal end side of the spacer  79 . 
     The lens member  53  is fixed to the second ferrule  78  via the spacer  79 , and the second ferrule  78  is fitted to the first light guide rod  74 , so that the lens member  53  is fixed to the first light guide rod  74 . The lens member  53  is pressed toward the proximal end side by the O-ring  83  and is in contact with the edge of the through-hole  79 A. Accordingly, the position of the lens member  53  relative to the spacer  79  in the axial direction is restricted. 
     As shown in  FIG.  8   , the second light guide rod  75  is combined with the distal end side of the first light guide rod  74 . The second light guide rod  75  includes a fitting portion  75 A at a proximal end portion thereof. The fitting portion  75 A is formed to have an outer diameter smaller than the outer diameter of an outer peripheral surface of a portion of the second light guide rod  75  having the largest outer diameter, and is fitted to the inner peripheral surface of the first light guide rod  74 . Further, an end portion  75 B of the fitting portion  75 A closest to the proximal end side is formed to have a small thickness, and is inserted into the gap between the small-diameter portion  78 E of the second ferrule  78  and the inner peripheral surface of the first light guide rod  74 . 
     The fitting portion  75 A and the inner peripheral surface of the first light guide rod  74  are fitted to each other, so that the first light guide rod  74  and the second light guide rod  75  are combined with each other and the position of the second ferrule  78  is restricted. Accordingly, the second ferrule  78  is not separated to the distal end side. Combining the first light guide rod  74  with the second light guide rod  75  is not limited thereto, and an adhesive, a connection member, or the like may be used to connect both the first light guide rod  74  and the second light guide rod  75 . 
     Further, an elastic O-ring  84  is fitted to the fitting portion  75 A. The O-ring  84  is deformed between the inner peripheral surface of the first light guide rod  74  and the fitting portion  75 A and is in close contact with both the inner peripheral surface of the first light guide rod  74  and the fitting portion  75 A, so that airtightness between the first light guide rod  74  and the second light guide rod  75  is ensured. Since the O-rings  81 ,  82 , and  84 , and the like are mounted on the first light guide rod  74  and on the second light guide rod  75  as described above, saturated water vapor having high pressure and high temperature is prevented from entering the first light guide rod  74  and the second light guide rod  75  in a case where the endoscope  12  is subjected to sterilization treatment using an autoclave. 
     As described above, the first light guide  51 , the second light guide  52 , and the lens member  53  are fixed in the first light guide rod  74  via the first ferrule  77 , the second ferrule  78 , and the spacer  79 . Accordingly, the lens member  53  is disposed between the first and second light guides  51  and  52 . Further, since the first light guide  51 , the second light guide  52 , and the lens member  53  are held at the centers of the first ferrule  77 , the second ferrule  78 , and the spacer  79 , respectively, the central axis L LG  of the light guide rod  65  coincides with the central axes of the first light guide  51 , the second light guide  52 , and the lens member  53 . 
     As shown in  FIG.  10   , the lens member  53  is a plano-convex lens of which an incident side-lens surface  53 A is planar and an emission side-lens surface  53 B is convex. The lens member  53  may be a biconvex lens, a meniscus lens, or the like without being limited thereto. It is preferable that an antireflection film called an anti-reflective (AR) coating is formed on each of the lens surfaces  53 A and  53 B of the lens member  53 . Accordingly, a reduction in the amount of illumination light in the light guide unit  26  can be further prevented.  FIG.  10    is a diagram illustrating a positional relationship between the first light guide  51 , the second light guide  52 , and the lens member  53  of the light guide unit  26 , and the coatings and the like of the first light guide  51  and the second light guide  52  are not shown in  FIG.  10    in order to reduce the complexity of the drawing. 
     Since the lens surface  53 A of the lens member  53  is in contact with the edge of the through-hole  79 A and the lens surface  53 B of the lens member  53  is pressed from the O-ring  83 , the position of the lens member  53  in the axial direction is restricted. Accordingly, the lens surfaces  53 A and  53 B of the lens member  53  are disposed to have intervals from an emission end  51 B of the first light guide  51  and an incident end  52 A of the second light guide  52 . Specifically, the lens surface  53 A has a gap D 1  from the emission end  51 B of the first light guide  51 . It is preferable that the gap D 1  is larger than 0 mm and 0.5 mm or less. 
     Meanwhile, since at least a part of the O-ring  83  is interposed between the lens member  53  and the second light guide  52 , the lens surface  53 B has a gap D 2  from the incident end  52 A of the second light guide  52 . It is preferable that the gap D 2  is larger than 0 mm and 0.5 mm or less. 
     In the light guide unit  26  of this embodiment, the incident end  51 A of the first light guide  51  facing the light source unit  42  is a circular end surface as shown in  FIG.  11   , but the emission end  28  of the second light guide  52  at the distal end portion  21 A is formed in an arc shape positioned around the observation unit  27  as shown in  FIG.  12    for the convenience of the disposition of components at the distal end portion  21 A. Accordingly, it is difficult to dispose the lens member  53  at the distal end portion  21 A. On the other hand, since there is no component that hinders the disposition of the lens member  53  in the light guide rod  65 , it is easy to dispose the lens member  53  in the light guide rod  65 . 
     The first light guide  51  and the lens member  53  are disposed at a position where an emission point of the first light guide  51  is closer to the lens surface  53 A than to a focal point P of the lens member  53  on an incident side. Accordingly, after illumination light emitted from the emission point of the first light guide  51  passes through the lens member  53 , the illumination light travels in a direction where the illumination light is diffused. Accordingly, the light guide unit  26  using the lens member  53  can obtain effects of preventing a reduction in the amount of light and preventing deterioration in the distribution of light. The first light guide  51  forms an emission point at the emission end  51 B. For this reason, it is preferable that a dimension L1 from the incident end  51 A to the emission end  51 B of the first light guide  51  in the axial direction is 5 mm or more. 
     The first and second light guides  51  and  52  guide illumination light emitted from the light source unit  42  to the emission end  28  in a case where the connector  25  is connected to the light source device-side connector  41  of the light source device  14  as described above. As described above, the lens member  53  is a lens for preventing a reduction in the amount of illumination light, which is guided by the first and second light guides  51  and  52  and is emitted from the emission end  28 , and deterioration in the distribution of the illumination light. Specifically, the lens member  53  is a lens for suppressing a variation in the relative intensity of each color light of the illumination light, which is guided by the first and second light guides  51  and  52  and is emitted from the emission end  28 , with respect to a light distribution angle. 
     Graphs shown in  FIGS.  13  and  14    are measurement results of illumination characteristics showing the relative intensity of each color light (LED light) of the illumination light with respect to a light distribution angle at a position ( FIG.  13   ) in the light guide unit  26  where the illumination light has not yet passed through the lens member  53  and at a position ( FIG.  14   ) in the light guide unit  26  where the illumination light has passed through the lens member  53 . The relative intensity mentioned here is a ratio of the intensity of each color LED light at a light distribution angle other than 0° to the intensity of each color LED light at a light distribution angle of 0° in a case where the intensity of each color LED light at a light distribution angle of 0° is set as 1. The intensity of light is the density of the luminous flux of light within a unit solid angle. 
     As shown in  FIG.  13   , a violet light V, a blue light B, a green light G, and a red light R, which are LED lights emitted from the light source unit  42  and guided by the light guide unit  26 , have variations in relative intensity with respect to a light distribution angle at a position where the illumination light has not yet passed through the lens member  53 , specifically, at the emission end  51 B of the first light guide  51 . Particularly, a variation in relative intensity at a light distribution angle of about ±25° is large. 
     On the other hand, as shown in  FIG.  14   , a violet light V, a blue light B, a green light G, and a red light R, which are LED lights emitted from the light source unit  42  and guided by the light guide unit  26 , have the same relative intensity with respect to a light distribution angle at a position where the illumination light has passed through the lens member  53 , specifically, at the emission end  28  of the second light guide  52 . That is, a variation in relative intensity can be suppressed. The same relative intensity mentioned here means that a difference in the relative intensities of the respective color lights of the illumination light with respect to a light distribution angle is very small, and it is preferable that all the relative intensities of a violet light V, a blue light B, and a red light R have a difference of ±5% or less from the relative intensity of a green light G in a case where the relative intensity of a green light G is used as a reference. 
     As described above, in this embodiment, the light guide unit  26  includes the first light guide  51 , the second light guide  52 , and the lens member  53 , and the first light guide  51 , the second light guide  52 , and the lens member  53  are fixed in the first light guide rod  74  having stiffness. Accordingly, the positions of optical axes of the first light guide  51 , the second light guide  52 , and the lens member  53  are not shifted from each other. For this reason, the light guide unit  26  can prevent a reduction in the amount of illumination light and deterioration in the distribution of the illumination light via the lens member  53  regardless of the operation state of the endoscope  12 . 
     Further, the endoscope  12  needs to be subjected to sterilization treatment whenever being used. In this case, it is common to perform sterilization treatment using an autoclave. During this sterilization treatment, the connector  25  including the light guide rod  65  is exposed to saturated water vapor having high temperature and high pressure (for example, 135° C. and 5 atmospheres) for about 20 minutes. 
     In a case where the lens member  53 , the first light guide  51 , and the second light guide  52  are in contact with each other and sterilization treatment using an autoclave is repeatedly performed, there is a possibility that the lens member  53  may be damaged by being pressed from the first and second light guides  51  and  52  due to a difference between the thermal expansion coefficient of the lens member  53  and the thermal expansion coefficients of the first and second light guides  51  and  52 . However, since the lens member  53  has the gaps D 1  and D 2  from end surfaces of the first and second light guides  51  and  52  in the present invention, the lens member  53  and the first and second light guides  51  and  52  are not in contact with each other even though the endoscope  12  is subjected to sterilization treatment. For this reason, the lens member  53  is not damaged. That is, even though sterilization treatment is repeatedly performed, a reduction in the amount of illumination light and deterioration in the distribution of the illumination light caused by the light guide unit  26  can be prevented. Further, since the lens member  53  has the gaps D 1  and D 2 , an adhesive used to fix the first and second light guides  51  and  52  does not adhere to the lens member  53 . 
     Second Embodiment 
     An example in which the lens member  53  for preventing a reduction in the amount of light and deterioration in the distribution of light is disposed in the light guide rod  65  has been described in the first embodiment. However, the present invention is not limited thereto, and the lens member  53  may be disposed in a portion of the connector  25  other than the light guide rod  65 . In an example shown in  FIG.  15   , the lens member  53  is disposed in an outer case  91  of a connector  90 . A configuration except for the connector  90  is the same as the configuration of the endoscope system  10  according to the first embodiment, and the same components and the like as in the first embodiment will be denoted by the same reference numerals as those in the first embodiment, and the detailed description thereof will be omitted. 
     As with the connector  25  of the first embodiment, the connector  90  is provided at a proximal end portion of the universal cable  23  and is attachably and detachably connected to the light source device-side connector  41  of the light source device  14 . The connector  90  comprises the outer case  91 , a light guide rod  92 , and a lens member holding portion  93 . As with the outer case  61  of the connector  25  of the first embodiment, the outer case  91  houses the wireless communication unit  63 , the wireless power receiving unit  64 , and the like, and a light guide rod  92  protrudes from a front surface  61 A that is positioned on a side facing the light source device  14 . Unlike the light guide rod  65  of the connector  25  of the first embodiment, the light guide rod  92  holds only the first light guide  51  and does not hold the second light guide  52  and the lens member  53 . 
     As in the first light guide rod  74  of the first embodiment, the first light guide  51 , the second light guide  52 , and the lens member  53  are fixed in the lens member holding portion  93  via the first ferrule  77 , the second ferrule  78 , and the spacer  79 . Accordingly, the lens member  53  is disposed between the first and second light guides  51  and  52 . Further, as in the first embodiment, the incident end  51 A of the first light guide  51  faces the light source unit  42 , and the emission end  28  of the second light guide  52  is disposed at the distal end portion  21 A. Accordingly, the light guide unit  26  guides illumination light, which is generated from the light source unit  42 , up to the distal end portion  21 A of the endoscope  12 . Furthermore, the O-ring  83  is housed in the spacer  79 , and the O-ring  83  is interposed between the lens member  53  and the second light guide  52  as in the first embodiment. For this reason, the lens member  53  and the second light guide  52  are disposed to have an interval therebetween. 
     The lens member holding portion  93  is fixed in the outer case  91 . The outer case  91  and the lens member holding portion  93  are formed of, for example, resin components and have high stiffness. Further, an O-ring or the like (not shown) is provided in a gap between the components of the outer case  91 , so that airtightness is ensured. Accordingly, the lens member holding portion  93  does not require a configuration in which airtightness is ensured. That is, since the O-rings  81 ,  82 , and  84  and the like used to ensure airtightness do not need to be provided unlike in the first light guide rod  74  of the first embodiment, the number of components can be reduced. 
     Since the outer case  91  and the lens member holding portion  93  have stiffness, the positions of the optical axes of the first light guide  51 , the second light guide  52 , and the lens member  53  are not shifted from each other. For this reason, as in the first embodiment, the light guide unit  26  can prevent a reduction in the amount of illumination light and deterioration in the distribution of the illumination light via the lens member  53  regardless of the operation state of the endoscope. 
     Third Embodiment 
     Examples in which the lens member  53  for preventing a reduction in the amount of light and deterioration in the distribution of light is disposed in the connectors  25  and  90  have been described in the first and second embodiments. However, the present invention is not limited thereto, and the lens member  53  may be disposed in other components of the endoscope having stiffness. In an example of an endoscope  100  shown in  FIG.  16   , an operation part  102  connected to an insertion part  101  is provided, and the lens member  53  is disposed in the operation part  102 . A configuration except for the endoscope  100  is the same as the configuration of the endoscope system  10  according to the first embodiment, and the same components and the like as in the first embodiment will be denoted by the same reference numerals as those in the first embodiment, and the detailed description thereof will be omitted. 
     As with the endoscope  12  of the first embodiment, the endoscope  100  is, for example, a rigid endoscope, such as a laparoscope, and comprises an elongated rigid insertion part  101  that is to be inserted into an object to be examined, an operation part  102  that is connected to a proximal end portion of the insertion part  101 , and a soft universal cable  23  that is connected to the operation part  102 . A connector  103  is provided at a proximal end portion of the universal cable  23 , and the endoscope  100  is attachably and detachably connected to the light source device-side connector  41  of the light source device  14  via the connector  103 . Unlike the connectors  25  and  90  of the first and second embodiments, the connector  103  holds only the first light guide  51  and does not hold the second light guide  52  and the lens member  53 . 
     The insertion part  101  includes a distal end part  101 A and a bendable part  101 B. As with the distal end portion  21 A of the endoscope  12  of the first embodiment, the distal end part  101 A is provided with the observation unit  27  and the emission end  28 . The bendable part  101 B is connected to the distal end part  101 A and is provided to be bendable. The operation part  102  is provided with a bending operation lever  102 A, operation buttons (not shown), and the like. The bending operation lever  102 A is an operation member that is used to bend the bendable part  101 B. Since the bendable part  101 B is bent, the orientation of the distal end part  101 A can be changed. 
     The operation part  102  is formed of, for example, a resin component and has high stiffness. It is preferable that the lens member  53  is provided in the endoscope  100  at a portion other than the bendable part  101 B. More specifically, the lens member  53  is provided in the operation part  102 . As with the lens member holding portion  93  of the second embodiment, a holding portion (not shown) in which the first light guide  51 , the second light guide  52 , and the lens member  53  are fixed is integrally provided in the operation part  102 . 
     In a case where the lens member  53  is provided in the bendable part  101 B and the bendable part  101 B is bent, the positions of the optical axes of the first light guide  51 , the second light guide  52 , and the lens member  53  are shifted from each other. On the other hand, the lens member  53  is provided in the operation part  102  in this embodiment. Since the operation part  102  has stiffness, the positions of the optical axes of the first light guide  51 , the second light guide  52 , and the lens member  53  are not shifted from each other. For this reason, as in the first embodiment, the light guide unit  26  can prevent a reduction in the amount of illumination light and deterioration in the distribution of the illumination light via the lens member  53  regardless of the operation state of the endoscope. 
     An endoscope to be used as a laparoscope has been described in the above-mentioned embodiments by way of example, but the present invention can also be applied to, for example, endoscopes used for other uses, such as an industrial use, and the like. 
     EXPLANATION OF REFERENCES 
     
         
         
           
               10 : endoscope system 
               12 : endoscope 
               14 : light source device 
               16 : processor device 
               18 : monitor 
               20 : console 
               21 : insertion part 
               21 A: distal end portion 
               22 : grip part 
               23 : universal cable 
               24 : switch-disposition member 
               24 A: operation switch 
               25 : connector 
               26 : light guide unit 
               27 : observation unit 
               28 : illumination light-emission end 
               29 : observation window 
               31 : image pickup lens group 
               32 : prism 
               33 : image pickup sensor 
               41 : light source device-side connector 
               41 A: locking portion 
               41 B: locking portion 
               41 C: contact surface 
               41 D: fitting recess 
               41 E: connection hole 
               42 : light source unit 
               42   a : V-LED 
               42   b : B-LED 
               42   c : G-LED 
               42   d : R-LED 
               43 : light source controller 
               44 : wireless communication unit 
               44 A: connection hole 
               45 : wireless power supply unit 
               46 : image signal receiving unit 
               51 : first light guide 
               51 A: incident end 
               51 B: emission end 
               52 : second light guide 
               52 A: incident end 
               53 : lens member 
               53 A,  53 B: lens surface 
               61 : outer case 
               61 A: front surface 
               61 B: fitting projection 
               61 C: upper surface 
               61 D: lower surface 
               61 E,  61 F: groove 
               61 G: lead-out hole 
               62 : shield case 
               63 : wireless communication unit 
               63 A: connection pin 
               64 : wireless power receiving unit 
               65 : light guide rod 
               66 : image signal transmission unit 
               68 : case body 
               69 : case lid 
               71 : O-ring 
               72 : bracket 
               73 : O-ring 
               74 : first light guide rod 
               75 : second light guide rod 
               75 A: fitting portion 
               75 B: end portion 
               76 : incident window 
               77 : first ferrule 
               77 A: light guide-insertion hole 
               78 : second ferrule 
               78 A: light guide-insertion hole 
               78 B: opening portion 
               78 C: locking groove 
               78 D: large-diameter portion 
               78 E: small-diameter portion 
               79 : spacer 
               79 A: through-hole 
               79 B: lens member holding portion 
               79 C: O-ring housing portion 
               79 D: outer peripheral surface 
               79 E: locked portion 
               81 ,  82 ,  83 ,  84 : O-ring 
               90 : connector 
               91 : outer case 
               92 : light guide rod 
               93 : lens member holding portion 
               100 : endoscope 
               101 : insertion part 
               101 A: distal end part 
               101 B: bendable part 
               102 : operation part 
               102 A: bending operation lever 
               103 : connector 
             D 1 , D 2 : gap 
             L LG : central axis 
             P: focal point