Patent Publication Number: US-2007118020-A1

Title: Endoscope and methods of producing and repairing thereof

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
      This application is a continuation of PCT international application Ser. No. PCT/JP2005/013601 filed Jul. 25, 2005 which designates the United States, incorporated herein by reference, and which claims the benefit of priority from Japanese Patent Application No. 2004-217880, filed Jul. 26, 2004, incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to an endoscope having an illumination lens which is located at a distal end of an insertion portion and used in illuminating a test region, and methods of producing and repairing thereof.  
      2. Description of the Related Art  
      Conventionally, as is well known, the endoscope is widely used in the medical field and the like. In the endoscope, a long and thin insertion portion can be inserted into a body cavity to observe an organ in the body cavity and, if needed, various treatments can be performed using a treatment instrument inserted into an insertion channel of the treatment instrument.  
      A bendable portion and a distal end portion are provided at the distal end of the insertion portion, and an observation direction of an objective lens of an observation optical system arranged in the distal end portion can be changed by operating an operation unit of the endoscope to bend a bendable portion.  
      In the distal end portion, an illumination lens is also arranged to illuminate the test region (for example, an observation region in the body cavity). Particularly, the illumination lens is fixed to a distal end portion main body and a cover member for covering the distal end portion, and a distal end face of the illumination lens is exposed in an opening formed in the cover member. The illumination lens may be fitted in and fixed to a frame which is fixed to the distal end portion main body and cover member. A rear end face of the illumination lens abuts on or comes close to the distal end face of a long and thin light guide arranged in an endoscope insertion portion.  
      The rear end face of the light guide is configured such that the illumination light is supplied from a light source device. Therefore, the illumination light is supplied from the light source device to the light guide and output from the light guide, and the illumination lens outputs the illumination light toward the inside of the body cavity.  
      A bonding agent is usually used to fix the illumination lens to the cover member and distal end portion main body because of easy fixing. In addition to the bonding agent, there is also proposed a configuration in which shapes of the illumination lens and cover member are devised to fix the illumination lens more strongly.  
      For example, Japanese Patent Application Laid-Open No. 2002-85326 proposes a configuration, wherein the illumination lens is formed in a tapered shape by forming a diameter of the distal end portion smaller than a diameter of the rear end portion, the illumination lens is fitted in the cover-member opening whose diameter is formed smaller than the diameter of the rear end portion of the illumination lens, an outer periphery of the rear end portion of the illumination lens is fixed to a distal end portion main body with the bonding agent, and thereby the illumination lens is fixed to the cover member and distal end portion main body.  
      According to the above configuration, movement of illumination lens is regulated in an insertion axis direction by causing the tapered peripheral surface of the illumination lens on the inner periphery of the opening. Therefore, in the configuration proposed in Japanese Patent Application Laid-Open No. 2002-85326, the illumination lens can be fixed more strongly to the distal end portion main body and opening provided in the cover member, compared to the case where the illumination lens is fixed only with the bonding agent.  
      In the case where a lens defect such as chipping or flaws is generated in the illumination lens, it is necessary to replace the illumination lenses. In this case, it is difficult to replace the illumination lens with new one while the lens shape is maintained, because the illumination lens is fixed to the opening and the distal end portion main body with the bonding agent as described above. Therefore, in replacing the illumination lens fixed with the bonding agent, there is known a technique, wherein a bonded portion of the illumination lens is removed by cutting the illumination lens using a cutting tool such as a drill and the illumination lens is taken out from the distal end portion.  
      However, as described above, the distal end face of the light guide abuts on or comes close to the rear end face of the illumination lens. Furthermore, in Japanese Patent Application Laid-Open No. 2002-85326, the outer periphery of the rear end portion of the illumination lens is bonded and fixed to the distal end portion main body.  
      Therefore, in removing the bonded portion with the drill, sometimes there is generated a problem that the distal end face of the light guide is damaged from the drill, when the drill proceeds to the rear end portion of the illumination lens to take out the illumination lens from the distal end portion.  
     SUMMARY OF THE INVENTION  
      An endoscope according to one aspect of the present invention includes an illumination lens which is fitted in a frame while a distal end face of the illumination lens is exposed, the frame being arranged in an insertion portion distal end, a bonded portion in an outer periphery of the illumination lens being fixed to an inner periphery of the frame with a bonding agent; and a light guide which is arranged in the frame while a distal end face of the light guide is orientated toward a rear end face of the illumination lens. A non-bonding portion which prevents adhesion of the bonding agent is formed between the bonded portion of the illumination lens and the distal end face of the light guide in the frame.  
      An endoscope according to another aspect of the present invention includes an illumination lens which is fitted in a frame while a distal end face of the illumination lens is exposed, the frame being arranged in an insertion portion distal end, an outer periphery of the illumination lens being fixed to an inner periphery of the frame with a bonding agent; and a light guide which is arranged in the frame while a distal end face of the light guide is orientated toward a rear end face of the illumination lens. A bonded portion is formed on the distal end face side in the outer periphery of the illumination lens, the bonded portion being fixed to an inside of the frame by the bonding agent, and a non-bonding portion is formed on the rear end face side in the outer periphery of the illumination lens, the non-bonding portion not being fixed to the frame by the bonding agent.  
      An endoscope producing method according to still another aspect of the present invention forming a lens fitting circumferential surface in an inner periphery of a frame arranged in an insertion portion distal end; continuously forming a circumferential groove having a diameter larger than that of the lens fitting circumferential surface at the back of the lens fitting circumferential surface, the circumferential groove being located in the inner periphery of the frame; applying a tentative fixing bonding agent onto the lens fitting circumferential surface; fitting an illumination lens in the lens fitting circumferential surface of the frame such that a rear end portion is latched in the circumferential groove while a rear end face is orientated toward a distal end face of a light guide arranged in the circumferential groove in order to output illumination light; and fixing the illumination lens to the inner periphery of the frame by causing a real fixing bonding agent to penetrate between an outer periphery of the illumination lens tentatively fixed with the tentative fixing bonding agent and the lens fitting circumferential surface of the frame.  
      A method according to still another aspect of the present invention is of repairing an endoscope having a frame in which a lens fitting circumferential surface and a circumferential groove are formed in an inner periphery, the circumferential groove being continuously formed at the back of the lens fitting circumferential surface while having a diameter larger than that of the lens fitting circumferential surface, an illumination lens being fixed to the lens fitting circumferential surface in the frame by a bonding agent in the endoscope. The method includes cutting the illumination lens in a range of the lens fitting circumferential surface to removed the bonding agent located between the lens fitting circumferential surface and the illumination lens.  
      The above and other objects, features, advantages and technical and industrial significance of this invention will be better understood by reading the following detailed description of presently preferred embodiments of the invention, when considered in connection with the accompanying drawings.  
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a front view showing a schematic configuration of an endoscope according to a first embodiment of the invention;  
       FIG. 2  is a front view showing a distal end face of an insertion portion in the endoscope of  FIG. 1 ;  
       FIG. 3  is a sectional view showing a schematic configuration of a distal end portion taken along line III-III of  FIG. 2 ;  
       FIG. 4  is an enlarged sectional view showing a distal end side of a light guide unit of  FIG. 3 ;  
       FIG. 5  is an enlarged sectional view showing fixing between an illumination lens and a frame in the light guide unit of  FIG. 4 ;  
       FIG. 6  is an enlarged sectional view showing the fixing between the illumination lens and the frame when the illumination lens whose outer periphery abuts on an output end face of a light guide is used as the illumination lens of  FIG. 5 ;  
       FIG. 7  is an enlarged sectional view showing a modification in the configuration of the light guide unit of  FIG. 4 ;  
       FIG. 8  is an enlarged sectional view showing a distal end side of the light guide unit of an endoscope according to a second embodiment of the invention;  
       FIG. 9  is an enlarged sectional view showing the fixing between the illumination lens and the frame in the light guide unit of  FIG. 8 ;  
       FIG. 10  is an enlarged sectional view showing the distal end side of the light guide unit of an endoscope according to a third embodiment of the invention;  
       FIG. 11  is an enlarged sectional view showing the fixing between the illumination lens and the frame in the light guide unit of  FIG. 10 ;  
       FIG. 12  is an enlarged exploded sectional view showing the distal end side of the light guide unit of the endoscope according to the third embodiment of the invention; and  
       FIG. 13  is an enlarged sectional view showing the distal end side of the light guide unit of an endoscope according to a fourth embodiment of the invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      Exemplary embodiments of the invention will be described below with reference to the drawings. In the following embodiments, the endoscope in which a wide angle lens having a viewing angle of 140° or larger is arranged in an observation optical system is described by way of example.  
     First Embodiment  
       FIG. 1  is a front view showing a schematic configuration of an endoscope according to a first embodiment of the invention.  
      As shown in  FIG. 1 , an endoscope  1  includes an operation unit  2 , an insertion portion  3 , and a universal cord  3   a . The operation unit  2  controls the bending operation and a channel system. The insertion portion  3  is inserted into the body cavity while the rear end side of the insertion portion  3  is connected to the operation unit  2 . The universal cord  3   a  is extended from the operation unit  2 , and the universal cord  3   a  has a connector unit  41  at the distal end thereof. The connector unit  41  is connected to a light source device (not shown) through a predetermined connector.  
      A tube  8 , a bendable portion  9 , and a distal end portion  10  are provided in the insertion portion  3 . The tube  8  has flexibility, the bendable portion  9  is provided on the distal end side of the tube  8 , and the distal end portion  10  is provided on the distal end side of the bendable portion  9 . An imaging device (not shown) is incorporated in the distal end portion  10 , and the imaging device takes an image of a test region, e.g., a region in the body cavity.  
      A bending operation knob (not shown) is arranged in the operation unit  2 , and the bending operation knob remotely curves the bendable portion  9 . The bending operation knob is operated to generate tensile action and releasing action in an operation wire (not shown) inserted through the insertion portion  3 , which allows the bendable portion  9  to be bent in four directions.  
       FIG. 2  is a front view showing a distal end face of the insertion portion in the endoscope of  FIG. 1 .  
      As shown in  FIG. 2 , an objective lens  32   a , three illumination lenses  33   a  which are of the illumination optical system, an opening  24  for the treatment instrument or the like, an air supply and water supply nozzle  25 , and a forward water-supply port  26  are arranged in a distal end face  10   m  of the distal end portion  10  of the endoscope insertion portion  3 . The air supply and water supply nozzle  25  supplies air and water to clean dirt of the objective lens  32   a  or the three 3 illumination lenses  33   a  when the distal end portion  10  is inserted into the body cavity. The forward water-supply port  26  cleans blood, mucus, and the like of a diseased part in the body cavity. Accordingly, plural openings are made in the distal end face  10   m  of the distal end portion  10  to arrange the objective lens  32   a , the three illumination lenses  33   a , the opening  24  for the treatment instrument or the like, the air supply and water supply nozzle  25 , and the forward water-supply port  26 .  
      The three illumination lenses  33   a  are arranged near a circumferential periphery portion of the objective lens  32   a  at predetermined angular intervals. The opening  24  for the treatment instrument or the like, the air supply and water supply nozzle  25 , and the forward water-supply port  26  are arranged between the illumination lenses  33   a  and near the circumferential periphery portion of the objective lens  32   a.    
       FIG. 3  is a sectional view showing a schematic configuration of the distal end portion taken along line III-III of  FIG. 2 ,  FIG. 4  is an enlarged sectional view showing the distal end side of the light guide unit of  FIG. 3 ,  FIG. 5  is an enlarged sectional view showing the fixing between the illumination lens and the frame in the light guide unit of  FIG. 4 , and  FIG. 6  is an enlarged sectional view showing the fixing between the illumination lens and the frame when the illumination lens whose outer periphery abuts on the output end face of the light guide is used as the illumination lens of  FIG. 5 .  
      As shown in  FIG. 3 , a distal end rigid portion  31  is arranged in the distal end portion  10  of the endoscope  1 . Long holes  31   a ,  31   b , and  31   c  are made in the distal end rigid portion  31 . An imaging unit  32 , a light guide unit  33 , and an air supply and water supply nozzle  25  are arranged in the long holes  31   a ,  31   b , and  31   c  respectively.  
      The long holes  31   a  and  31   c  in which the imaging unit  32  and the air supply and water supply nozzle  25  are arranged are made in parallel with an insertion axis direction Z of the endoscope insertion portion  3 . The long hole  31   b  in which the light guide unit  33  is arranged is made in the direction of an axis  33 LA oblique to the direction of an axis  32 LA in which an later-mentioned observation optical system  32   b  of the distal end rigid portion  31  is arranged. Actually three long holes  31   b  are made although not shown.  
      On the distal end side in the insertion axis direction Z of the distal end rigid portion  31 , a cap  40  is topped to cover a front face and an outer periphery surface of the distal end rigid portion  31 . Openings  40   a ,  40   b , and  40   c  are formed in the cap  40 . The imaging unit  32 , the light guide unit  33 , the air supply and water supply nozzle  25  and the like are arranged in the openings  40   a ,  40   b , and  40   c . The openings  40   a ,  40   b , and  40   c  formed in the cap  40  correspond to the openings formed in the distal end face  10   m  of the distal end portion  10 .  
      The openings  40   a  and  40   c  in which the imaging unit  32  and the air supply and water supply nozzle  25  are arranged are formed in parallel with the insertion axis direction Z. The opening  40   b  in which the light guide unit  33  is arranged is formed in the direction of the axis  33 LA oblique to the direction of the axis  32 LA of the cap  40 . Although not shown, actually three openings  40   b  are formed so as to become equal to the number of long holes  31   b.    
      The imaging unit  32  is inserted into the long hole  31   a  and the opening  40   a  in parallel to the insertion axis direction, and the imaging unit  32  is fixed to the long hole  31   a  and the opening  40   a  using a filler. In  FIG. 3 , the long hole  31   a  is made in the substantial center of the distal end rigid portion  31 , and the opening  40   a  is formed in the substantial center of the cap  40 .  
      The imaging unit  32  includes an observation optical system  32   b  and an imaging device (not shown). The observation optical system  32   b  is formed by the plural wide angle lenses, and the wide angle lens has an objective lens  32   a  having the wide viewing angle of 140° or larger. The imaging device such as CCD is provided on the rear end side of the observation optical system  32   b.    
      The light guide unit  33  mainly includes a single illumination lens  33   a  and a light guide  33   b . In the illumination lens  33   a , the rear end face is formed in a plane of curvature  33   ak  projected toward the direction of the light guide  33   b . The light guide  33   b  includes plural optical fibers provided on the rear end side of the illumination lens  33   a . The three light guide units  33  are arranged so as to surround the imaging unit  32 .  
      A metal pipe  33   c  which is of a hard pipe-shape member is coated on the outer periphery of the light guide  33   b , and the outer periphery of the light guide  33   b  is fixed to the inside of the metal pipe  33   c  with the bonding agent or the like. As described above, the light guide  33   b  includes the plural optical fibers, and an output end face  33   bs  orientated toward the rear end face of the illumination lens  33   a  is polished. Although the light guide  33   b  includes the plural optical fibers in the first embodiment, sometimes a glass rod (not shown) or a lens (not shown) is arranged between the output end face  33   bs  and the rear end face of the illumination lens  33   a . In this case, the light guide  33  including the glass rod or lens is referred to as light guide  33   b , and the output end face of the glass rod or lens is referred to as output end face  33   bs  of light guide  33   b.    
      The distal end side of the light guide  33   b  and the illumination lens  33   a  are fitted in and fixed to a frame  33   d  which is arranged in the long hole  31   b  of the distal end rigid portion  31  and in the opening  40   b  of the cap  40 . Specifically, the frame  33   d  is formed in a substantially cylindrical shape in which the outer periphery of the distal end is tapered such that the opening of the distal end is decreased in diameter. As shown in  FIGS. 4 and 5 , the inner periphery of the frame  33   d  is formed by a lens fitting circumferential surface  33   dn  and a circumferential groove  33   dm . The lens fitting circumferential surface  33   dn  has the diameter substantially equal to the diameter of the illumination lens  33   a . The circumferential groove  33   dm  is formed at the back of the peripheral surface  33   dn  while continued in the insertion axis direction Z, and the circumferential groove  33   dm  has the diameter larger than the diameter of the lens fitting circumferential surface  33   dn.    
      The distal end side of the light guide  33   b  coated with the metal pipe  33   c  is fitted in the circumferential groove  33   dm , and the outer periphery on the distal end side is fixed to the circumferential groove  33   dm  with the bonding agent or the like.  
      As shown in  FIG. 5 , the illumination lens  33   a  is fitted in and fixed to the frame  33   d . Specifically, a bonded portion  33   ac  of the outer periphery of the illumination lens  33   a  is bonded to the lens fitting circumferential surface  33   dn  with a bonding agent  100 , and thereby the illumination lens  33   a  is fixed to the inside of the frame  33   d.    
      A distal end face  33  as of the illumination lens  33   a  is exposed outward from the distal end portion  10  of the insertion portion  3  through the opening  40   b  of the cap  40 . The distal end face  33  as is flush with the distal end face of the cap  40 .  
      The plane of curvature  33   ak  of the illumination lens  33   a  abuts on the output end face  33   bs  of the light guide  33   b . The plane of curvature  33   ak  of the illumination lens  33   a  may not abut on but come close to the output end face  33   bs  of the light guide  33   b  unless optical properties such as color shading are degraded.  
      A non-bonding portion  70  is formed between the bonded portion  33   ac  of the outer periphery of the illumination lens  33   a  and the output end face  33   bs  of the light guide  33   b . The non-bonding portion  70  is a space provided between the outer periphery of the rear end portion of the illumination lens  33   a  and the inner periphery of the frame  33   d , and the non-bonding portion  70  is formed by the circumferential groove  33   dm  provided in the inner periphery of the frame  33   d  in a mode in which the non-bonding portion  70  is separated from at least the outer periphery of the rear end portion of the illumination lens  33   a . In the insertion axis direction Z of the non-bonding portion  70 , there is a distance of 0.5 mm or larger between the bonded portion  33   ac  and the output end face  33   bs  of the light guide  33   b.    
      A method of fitting and fixing the illumination lens  33   a  in and to the frame  33   d  will be described below. A tentative fixing bonding agent is applied to several points of the lens fitting circumferential surface  33   dn  of the frame  33   d . Then, the illumination lens  33   a  is fitted in the lens fitting circumferential surface  33   dn  in the frame  33   d  such that the plane of curvature  33   ak  of the illumination lens  33   a  abuts on the output end face  33   bs  of the light guide  33   b.    
      In the case where the light guide  33   b  is not previously fitted in the frame  33   d , the illumination lens  33   a  is fitted in the lens fitting circumferential surface  33   dn  in the frame  33   d  to an assumed position where the plane of curvature  33   ak  abuts on the output end face  33   bs  of the light guide  33   b.    
      Then, the real fixing bonding agent  100  having a regulated amount is applied to a gap  33   p  (see  FIG. 5 ) between the outer periphery of the distal end of the illumination lens  33   a  and the inner periphery of the distal end of the frame  33   d . Then, as shown in  FIG. 5 , the applied bonding agent  100  permeates and penetrates between the outer periphery of the illumination lens  33   a  and the lens fitting circumferential surface  33   dn  of the frame  33   d.    
      A part of the bonding agent  100  penetrates to the circumferential groove  33   dm  of the frame  33   d . At this point, because the non-bonding portion  70  has the relatively wide space, the bonding agent  100  penetrating to the circumferential groove  33   dm  does not adhere to the outer periphery of the illumination lens  33   a  in the non-bonding portion  70 .  
      Finally, the bonding agent  100  is dried to fix the illumination lens  33   a  to the inside of the frame  33   d  by the bonding agent  100 .  
      Returning to  FIG. 3 , the frame  33   d  is fixed to the distal end rigid portion  31  using a fixing screw or the like. The light guide  33   b  is extended rearward from the distal end rigid portion  31  and connected to an illumination device (not shown).  
      A part of the metal pipe  33   c  and the light guide  33   b  are covered with an outer covering tube  33   e . The outer covering tube  33   e  is fixed to the outer periphery of the metal pipe  33   c  by a tied string  33   g.    
      The metal pipe  33   c  is bent at a predetermined point P along the direction of the axis  32 LA of the observation optical system  32   b  from the axis oblique to the direction of the axis  32 LA as the optical axis in which the observation optical system  32   b  is arranged, i.e., the axis  33 LA of the illumination lens  33   a . As a result the light guide  33   b  is also bent at the predetermined point P along the bent shape of the metal pipe  33   c.    
      Accordingly, the light guide unit  33  is arranged in the axis  33 LA oblique to the direction of the axis  32 LA in which the observation optical system  32   b  is arranged. Because the observation optical system  32   b  is formed by the lens having the wide viewing angle, it is necessary that the light guide unit  33  illuminating the body cavity evenly illuminate the body cavity over the wide range.  
      The air supply and water supply nozzle  25  is fitted in and fixed to the long hole  31   c  of the distal end rigid portion  31  and the opening  40   c  of the cap  40 . For example, the air supply and water supply nozzle  25  is made of metal. An opening  25   a  is provided on the distal end side of the air supply and water supply nozzle  25 .  
      The opening  25   a  is provided such that the water or air discharged from the air supply and water supply nozzle  25  is ejected through the opening  25   a  toward the direction which is parallel to a plane orthogonal to the optical axis  32 LA of the imaging unit  32  and passes through both the surface of the objective lens  32   a  and the surface of the illumination lens  33   a . The air supply and water supply nozzle  25  is formed at the position, where the air supply and water supply nozzle  25  is not included in the viewing angle range of the objective lens  32   a , while projected from the distal end face  10   m  of the distal end portion  10  of the insertion portion  3 .  
      The rear end side of the air supply and water supply nozzle  25  is formed in a pipe shape, and an air supply and water supply tube  25   c  is connected to the rear end side through a connecting pipe  25   b . Therefore, a water supply channel is formed by the connecting pipe  25   b  and the air supply and water supply tube  25   c . The air supply and water supply tube  25   c  is fixed to the connecting pipe  25   b  by a tied string  25   d.    
      A part of the distal end rigid portion  31  is fixed to a part of a bending piece  35 . The rear end side of the distal end rigid portion  31  and the bending piece  35  are covered with an outer covering tube  36 . The outer covering tube  36  is fixed to the distal end rigid portion  31  by a tied string  37 .  
      Then, an endoscope repairing method which is the action of the endoscope  1  of the first embodiment having the above-described configuration will be described. Specifically, the illumination lens  33   a  replacement method will be described below.  
      A drill which is of the cutting tool is brought close to the distal end face  33  as of the illumination lens  33   a  fixed to the inside of the frame  33   d  along the optical axis from the outside, and the drill is caused to proceed to the distal end of the circumferential groove  33   dm , i.e., to the rear end of the bonded portion  33   ac  to cut the illumination lens. As a result, the bonding agent  100  of the bonded portion  33   ac  is removed in the illumination lens  33   a  by the cutting. This enables the fixing to be released between the illumination lens  33   a  and the frame  33   d.    
      Finally, the distal end portion  10  of the insertion portion  3  of the endoscope  1  is inclined downward to take out the illumination lens, in which the fixing is released and a part is cut, from the frame  33   d . Therefore, the illumination lenses  33   a  can be replaced. The method of fitting and fixing the new illumination lens  33   a  in and to the frame  33   d  is as described above.  
      Thus, in the endoscope  1  of the first embodiment, the circumferential groove  33   dm  having the diameter larger than that of the lens fitting circumferential surface  33   dn  is formed in the inner periphery of the frame  33   d  which the illumination lens  33   a  is fitted in and fixed to.  
      Conventionally, in replacing the illumination lenses  33   a , when the drill as the cutting tool is brought close to the distal end face  33  as along the optical axis from the outside to cut the illumination lens  33   a , sometimes the output end face  33   bs  is damaged by the distal end of the drill, because the bonded portion  33   ac  of the illumination lens  33   a  and the output end face  33   bs  of the light guide  33   b  are close to each other while the circumferential groove  33   dm  does not exist between the bonded portion  33   ac  and the output end face  33   bs.    
      On the contrary, in the first embodiment, because the circumferential groove  33   dm  having the diameter larger than that of the lens fitting circumferential surface  33   dn  is formed in the inner periphery of the frame  33   d , the non-bonding portion  70  is formed between the bonded portion  33   ac  of the illumination lens  33   a  and the output end face  33   bs  of the light guide  33   b . The non-bonding portion  70  has the distance of 0.5 mm or larger in the insertion axis direction Z, and the non-bonding portion  70  is formed by at least the circumferential groove  33   dm . Therefore, the bonding agent  100  penetrating to the circumferential groove  33   dm  does not adhere to the outer periphery of the illumination lens  33   a  in the non-bonding portion  70 , because the non-bonding portion  70  has the relatively wide space.  
      Accordingly, when the distal end of the drill is caused to proceed to the rear end of the bonded portion  33   ac , the distal end of the drill does not come into contact with the output end face  33   bs  of the light guide  33   b , so that the output end face  33   bs  is never damaged. This enables the illumination lenses  33   a  to be replaced without damaging the output end face  33   bs  of the light guide  33   b.    
      The first embodiment is not limited to the case where the rear end face of the illumination lens  33   a  is formed as the plane of curvature  33   ak  projected toward the direction of the light guide  33   b . For example, as shown in  FIG. 6 , the first embodiment can also be applied in the case where a part of a flat portion is formed in a concave shape with no plane of curvature  33   ak  in the rear end face of the illumination lens  33   a  while the flat portion abuts on the output end face  33   bs  of the light guide  33   b.    
      Specifically, as shown in  FIG. 6 , because the circumferential groove  33   dm  having the diameter larger than that of the lens fitting circumferential surface  33   dn  is formed in the inner periphery of the frame  33   d , even if a part of the flat portion is formed in the concave shape in the rear end face of the illumination lens  33   a  while the flat portion abuts on the output end face  33   bs  of the light guide  33   b , the non-bonding portion  70  is formed between the bonded portion  33   ac  of the illumination lens  33   a  and the output end face  33   bs  of the light guide  33   b . The non-bonding portion  70  has the distance of 0.5 mm or larger in the insertion axis direction Z and the non-bonding portion  70  is formed by at least the groove  33   dm.    
      Because the non-bonding portion  70  has the relatively wide space, the bonding agent  100  penetrating into the circumferential groove  33   dm  does not adhere to the outer periphery of the illumination lens  33   a  in the non-bonding portion  70 . Therefore, when the distal end of the drill is caused to proceed to the rear end of the bonded portion  33   ac , the distal end of the drill does not come into contact with the output end face  33   bs  of the light guide  33   b , so that the output end face  33   bs  is not damaged. Accordingly, the illumination lens  33   a  whose rear end of the outer periphery abuts on the output end face  33   bs  of the light guide  33   b  can be replaced with new one without damaging the output end face  33   bs  of the light guide  33   b.    
      A modification will be described below. In the first embodiment, the endoscope in which the wide angle lens having the viewing angle of 140° or larger is arranged in the observation optical system  32   b  is described as an example of the endoscope  1 . The invention is not limited to the first embodiment. Obviously the same effect can be obtained even if the invention is applied to an endoscope in which the lens having the usual viewing angle (140° or smaller) is used as the objective lens  32   a  and the observation optical system  32   b.    
      Accordingly, the light guide unit  33  may not be arranged in the axis  33 LA oblique to the direction of the axis  32 LA in which the observation optical system  32   b  is arranged, but arranged in the direction of the axis parallel to the axis  32 LA in which the observation optical system  32   b  is arranged.  
      In the first embodiment, the three illumination lenses  33   a  are arranged in the distal end portion. Alternatively, one illumination lens  33   a  or plural illumination lenses  33   a  may be arranged in the distal end portion. In this case, obviously the same number of light guide units  33  as the number of illumination lenses is provided.  
      In the first embodiment, the drill is cited as an example of the cutting tool used in cutting the illumination lens  33   a . The invention is not limited to the drill, but a reamer may be used and obviously any cutting tool may be used as long as the cutting tool can cut the illumination lens  33   a.    
      In the first embodiment, the plane of curvature  33   ak  of the illumination lens  33   a  abuts on the output end face  33   bs  which is of the distal end face of the light guide  33   b . However, because a force F (see  FIG. 7 ) for always pushing out the illumination lens  33   a  toward the distal end in the insertion direction is always applied to the illumination lens  33   a  from the light guide  33   b , there is a possibility that the fixing between the illumination lens  33   a  and the frame  33   d  with bonding agent  100  is released by the force F.  
      As shown in  FIG. 7 , a thin ring-shape plate member  90  may fixedly be arranged at a position where the plane of curvature  33   ak  of the circumferential groove  33   dm  of the frame  33   d  and the output end face  33   bs  abut on each other. Therefore, the distal end face of the metal pipe  33   c  coating the light guide  33   b  abuts on the plate member  90 .  
      Accordingly, although the plane of curvature  33   ak  of the illumination lens  33   a  and the output end face  33   bs  which is of the distal end face of the light guide  33   b  abuts on each other in the first embodiment, the plane of curvature  33   ak  and the output end face  33   bs  are arranged while separated from each other by the distance of 0.5 mm as shown in  FIG. 7 . The distance can be changed within the range with which the optical properties such as the color shading are not degraded.  
      Because the plate member  90  is fixed to the circumferential groove  33   dm , even if the force F for always pushing out the plate member  90  toward the distal end of the insertion direction is applied to the plate member  90  from the light guide  33   b , only the output end face  33   bs  or the distal end face of the metal pipe  33   c  covering the light guide  33   b  abuts on the plate member  90 , and the output end face  33   bs  does not abut on the plane of curvature  33   ak.    
      Therefore, the force F for always pushing out the illumination lens  33   a  toward the distal end of the insertion direction is not applied to the illumination lens  33   a  from the light guide  33   b , which prevents the possibility that the fixing between the illumination lens  33   a  and the frame  33   d  with the bonding agent  100  is released by the force F.  
      Furthermore, the plane of curvature  33   ak  and the output end face  33   bs  can easily be separated from each other by the use of the plate member  90 , compared with the case where the circumferential groove having the diameter larger than that of the circumferential groove  33   dm  is formed in the circumferential groove  33   dm  to separate the plane of curvature  33   ak  and the output end face  33   bs  from each other, and the use of the plate member  90  can secure the larger abutting area which the distal end face of the metal pipe  33   c  abuts on.  
     Second Embodiment  
       FIG. 8  is an enlarged sectional view showing the distal end side of the light guide unit of an endoscope according to a second embodiment of the invention, and  FIG. 9  is an enlarged sectional view showing the fixing between the illumination lens and the frame in the light guide unit of  FIG. 8 .  
      The configuration of an endoscope  201  of the second embodiment differs from that of the endoscope  1  shown in FIGS.  1  to  6  in that the circumferential groove is not formed in the inner periphery of the frame. Therefore, only the different points will be described, the same configuration as the first embodiment is designated by the same numeral, and the description will not be repeated.  
      As shown in  FIG. 8 , the distal end side of the light guide  33   b  and the illumination lens  33   a  are fitted in and fixed to a frame  133   d  which is arranged in the long hole  31   b  of the distal end rigid portion  31  and in the opening  40   b  of the cap  40 .  
      Specifically, the frame  133   d  is formed in a substantially cylindrical shape in which the outer periphery of the distal end is tapered such that the opening of the distal end is decreased in diameter. As shown in  FIGS. 8 and 9 , the inner periphery of the frame  133   d  is formed by a lens fitting circumferential surface  133   dn  having the diameter substantially similar to the diameter of the illumination lens  33   a.    
      The distal end side of the light guide  33   b  coated with the metal pipe  33   c  is fitted in the lens fitting circumferential surface  133   dn , and the outer periphery on the distal end side is fixed to the lens fitting circumferential surface  133   dn  with the bonding agent or the like.  
      As shown in  FIG. 8 , the illumination lens  33   a  whose rear end face is formed in the plane of curvature  33   ak  projected toward the direction of the light guide  33   b  is fitted in and fixed to the frame  133   d . Specifically, the bonded portion  33   ac  formed in a part of the outer periphery of the illumination lens  33   a  is bonded to the lens fitting circumferential surface  133   dn  with the bonding agent  100 , and thereby the illumination lens  33   a  is fixed to the inside of the frame  133   d.    
      The plane of curvature  33   ak  of the illumination lens  33   a  abuts on the output end face  33   bs  of the light guide  33   b . The plane of curvature  33   ak  of the illumination lens  33   a  may not abut on but come close to the output end face  33   bs  of the light guide  33   b  unless the optical properties such as the color shading are degraded.  
      A non-bonding portion  170  is formed between the bonded portion  33   ac  of the outer periphery of the illumination lens  33   a  and the output end face  33   bs  of the light guide  33   b . The non-bonding portion  170  is formed by a space between the plane of curvature  33   ak  and the inner periphery (lens fitting circumferential surface  133   dn ) of the frame  133   d , and the plane of curvature  33   ak  is formed by projecting the rear end face of the illumination lens  33   a  toward the direction of the light guide  33   b . In the insertion axis direction Z of the non-bonding portion  170 , there is the distance of 0.5 mm or larger between the bonded portion  33   ac  and the output end face  33   bs  of the light guide  33   b . Thus, the non-bonding portion  170  has the distance of 0.5 mm or larger between the bonded portion  33   ac  and the output end face  33   bs  of the light guide  33   b  by a curvature of the plane of curvature  33   ak  provided in the rear end face of the illumination lens  33   a.    
      Then, an endoscope repairing method which is the action of the endoscope  201  of the second embodiment having the above-described configuration will be described. Specifically, the illumination lens  33   a  replacement method will be described below.  
      The drill which is of the cutting tool is brought close to the distal end face  33  as of the illumination lens  33   a  fixed to the inside of the frame  133   d  along the optical axis from the outside, and the drill is caused to proceed to the rear end of the illumination lens  33   a , i.e., to the rear end of the bonded portion  33   ac  to cut the illumination lens. As a result, the bonding agent  100  of the bonded portion  33   ac  is removed in the illumination lens  33   a  by the cutting. This enables the fixing to be released between the illumination lens  33   a  and the frame  133   d.    
      Finally, the distal end portion  10  of the insertion portion  3  of the endoscope  201  is inclined downward to take out the illumination lens, in which the fixing is released and a part is cut, from the frame  33   d . Therefore, the illumination lenses  33   a  can be replaced.  
      Thus, in the endoscope  201  of the second embodiment, the rear end face of the illumination lens  33   a  is formed as the plane of curvature  33   ak  projected toward the direction of the light guide  33   b , so that the non-bonding portion  170  having the distance of 0.5 mm or larger in the insertion axis direction Z is formed between the bonded portion  33   ac  of the illumination lens  33   a  and the output end face  33   bs  of the light guide  33   b  by the curvature of the plane of curvature  33   ak . As a result, when the distal end of the drill is caused to proceed to the rear end of the bonded portion  33   ac  in the replacement, the distal end of the drill does not come into contact with the output end face  33   bs  of the light guide  33   b.    
      Accordingly, the output end face  33   bs  is not damaged, so that the illumination lenses  33   a  can be replaced without damaging the output end face  33   bs  of the light guide  33   b.    
      A modification will be described below. In the second embodiment, the same effect can also be obtained even if the second embodiment is applied to an endoscope in which the lens having the usual viewing angle (140° or smaller) is used as the observation optical system  32   b.    
      In the second embodiment, the three illumination lenses  33   a  are arranged in the distal end portion. Alternatively, one illumination lens  33   a  or plural illumination lenses  33   a  may be arranged in the distal end portion. In this case, obviously the same number of light guide units  33  as the number of illumination lenses is provided.  
      The thin ring-shape plate member  90  shown in  FIG. 7  may fixedly be arranged at the position where the plane of curvature  33   ak  of the lens fitting circumferential surface  133   dn  of the frame  133   d  and the output end face  33   bs  abut on each other.  
      In the second embodiment, the drill is cited as an example of the cutting tool used in cutting the illumination lens  33   a . The invention is not limited to the drill, but the reamer may be used and obviously any cutting tool may be used as long as the cutting tool can cut the illumination lens  33   a.    
     Third Embodiment  
       FIG. 10  is an enlarged sectional view showing the distal end side of the light guide unit of an endoscope according to a third embodiment of the invention, and  FIG. 11  is an enlarged sectional view showing the fixing between the illumination lens and the frame in the light guide unit of  FIG. 10 .  
      The configuration of an endoscope  301  of the third embodiment differs from that of the endoscope  201  shown in  FIGS. 8 and 9  in that an amount of bonding agent  100  penetrating between the outer periphery of the illumination lens  33   a  and the lens fitting circumferential surface  133   dn  of the frame  133   d  is adjusted. Therefore, only the different points will be described, the same configuration as the second embodiment is designated by the same numeral, and the description will not be repeated.  
      As shown in  FIG. 10 , the illumination lens  33   a  whose rear end of the outer periphery abuts on the output end face  33   bs  of the light guide  33   b  is fitted in and fixed to the inside of the frame  133   d . Specifically, as shown in  FIG. 11 , the bonded portion  33   ac  in the outer periphery of the illumination lens  33   a  is bonded to the lens fitting circumferential surface  133   dn  with the amount of bonding agent  100  (hereinafter referred to as non-abutting amount) having an extent in which the bonding agent  100  does not penetrate to the rear end of the outer periphery of the illumination lens  33   a , and thereby the illumination lens  33   a  is fixed to the inside of the frame  133   d.    
      A non-bonding portion  270  is formed between the bonded portion  33   ac  of the illumination lens  33   a  and the output end face  33   bs  of the light guide  33   b . The non-bonding portion  270  is provided between the outer periphery of the rear end portion of the illumination lens  33   a  and the inner periphery of the frame  133   d  which faces the outer periphery, and the non-bonding portion  270  is formed in a non-bonded area which suppresses the penetration of the bonding agent  100 . Specifically, the non-bonding portion  270  which is of the non-bonded area is formed by the penetration of the bonding agent  100  having the non-abutting amount from the gap  33   p  (see  FIG. 5 ) between the outer periphery of the distal end of the illumination lens  33   a  and the inner periphery of the distal end of the frame  33   d  to the gap between the outer periphery of the illumination lens  33   a  and the lens fitting circumferential surface  33   dn  of the frame  33   d . That is, the space is formed between the lens fitting circumferential surface  133   dn  and the outer periphery of the illumination lens  33   a . In the insertion axis direction Z of the non-bonding portion  270 , there is the distance of 0.5 mm or larger between the bonded portion  33   ac  and the output end face  33   bs  of the light guide  33   b . Thus, both the bonded portion  33   ac  fixed to the inside of the frame  33   d  with the bonding agent  100  and the non-bonding portion  270  not fixed to the frame  33   d  with the bonding agent  100  are formed respectively on the distal end face side and the read end face side in the outer periphery of the illumination lens  33   a.    
      In forming the non-bonding portion  270  as the non-bonded area, as shown in  FIG. 12 , the bonding agent  100  is applied to the region of the bonded portion  33   ac  of the illumination lens  33   a  except for the region of the non-bonding portion  270  before the illumination lens  33   a  is fitted in the frame  133   d , and the illumination lens  33   a  may be fitted in the frame  133   d.    
      When the non-bonding portion  270  is formed as the non-bonded area, in order to suppress the penetration of the bonding agent  100 , a coating (not shown) containing a stripping agent for stripping the bonding agent  100  may be performed to the outer periphery of the rear end portion of the illumination lens  33   a  and/or the inner periphery of the frame  133   d  which faces the outer periphery of the rear end portion of the illumination lens  33   a.    
      Then, an endoscope repairing method which is the action of the endoscope  301  of the third embodiment having the above-described configuration will be described. Specifically, the illumination lens  33   a  replacement method will be described below.  
      The drill which is of the cutting tool is brought close to the distal end face  33  as of the illumination lens  33   a  fixed to the inside of the frame  133   d  along the optical axis from the outside, and the drill is caused to proceed to the rear end of the bonded portion  33   ac  in the outer periphery of the illumination lens  33   a  to cut the illumination lens. As a result, the bonding agent  100  having the non-abutting amount is removed by the cutting. This enables the fixing to be released between the illumination lens  33   a  and the frame  133   d.    
      Finally, the distal end portion  10  of the insertion portion  3  of the endoscope  1  is inclined downward to take out the illumination lens  33   a , in which the fixing is released and a part is cut, from the frame  133   d . Therefore, the illumination lenses  33   a  can be replaced.  
      Thus, in the endoscope  301  of the third embodiment, the bonded portion  33   ac  in the outer periphery of the illumination lens  33   a  is fixed to the lens fitting circumferential surface  133   dn  with the bonding agent  100  having the non-abutting amount.  
      The non-bonding portion  270  having the distance of 0.5 mm or larger in the insertion axis direction Z is formed between the bonded portion  33   ac  of the illumination lens  33   a  and the output end face  33   bs  of the light guide  33   b . When the distal end of the drill is caused to proceed to the rear end of the bonded portion  33   ac  in the replacement, the distal end of the drill does not come into contact with the output end face  33   bs  of the light guide  33   b.    
      Accordingly, the output end face  33   bs  is not damaged, so that the illumination lenses  33   a  can be replaced without damaging the output end face  33   bs  of the light guide  33   b.    
      A modification will be described below. In the third embodiment, the illumination lens  33   a  in which the rear end of the outer periphery abuts on the output end face  33   bs  of the light guide  33   b  is illustrated by way of example. The invention is not limited to the illumination lens  33   a  of the third embodiment, but obviously the same effect as the third embodiment can be also obtained even if the illumination lens  33   a  in which the rear end face is formed in the plane of curvature  33   ak  projected toward the direction of the light guide  33   b  is used.  
      In the third embodiment, obviously the same effect can also be obtained even if the second embodiment is applied to an endoscope in which the lens having the usual viewing angle (140° or smaller) is used as the observation optical system  32   b.    
      In the third embodiment, the three illumination lenses  33   a  are arranged in the distal end portion. Alternatively, one illumination lens  33   a  or plural illumination lenses  33   a  may be arranged in the distal end portion. In this case, obviously the same number of light guide units  33  as the number of illumination lenses is provided.  
      The thin ring-shape plate member  90  shown in  FIG. 7  may fixedly be arranged at the position where the rear end face of the lens fitting circumferential surface  133   dn  of the frame  133   d  and the output end face  33   bs  abut on each other.  
      In the third embodiment, the drill is cited as an example of the cutting tool used in cutting the illumination lens  33   a . The invention is not limited to the drill, but the reamer may be used and obviously any cutting tool may be used as long as the cutting tool can cut the illumination lens  33   a.    
     Fourth Embodiment  
       FIG. 13  is an enlarged sectional view showing the distal end side of the light guide unit of an endoscope according to a fourth embodiment of the invention.  
      The configuration of an endoscope  301  of the fourth embodiment differs from that of the endoscope  201  shown in  FIGS. 8 and 9  in that groove portion is provided. Therefore, only the different points will be described, the same configuration as the second embodiment is designated by the same numeral, and the description will not be repeated.  
      As shown in  FIG. 13 , the illumination lens  33   a  whose rear end of the outer periphery abuts on the output end face  33   bs  of the light guide  33   b  is fitted in and fixed to the inside of the frame  133   d . Specifically, the bonded portion  33   ac  in the outer periphery of the illumination lens  33   a  is bonded to the lens fitting circumferential surface  133   dn  with the bonding agent  100 , and thereby the illumination lens  33   a  is fixed to the inside of the frame  133   d.    
      The non-bonding portion  270  is formed between the bonded portion  33   ac  of the illumination lens  33   a  and the output end face  33   bs  of the light guide  33   b . The non-bonding portion  270  is a space provided between the outer periphery of the rear end of the illumination lens  33   a  and the inner periphery of the frame  133   d . The non-bonding portion  270  is formed by a groove portion  133   dp  in the inner periphery of the frame  133   d  in the mode in which the groove portion  133   dp  is separated from the outer periphery of the rear end portion of the illumination lens  33   a , and the groove portion  133   dp  has the diameter larger than that of the lens fitting circumferential surface  33   dn . That is, the groove portion  133   dp  reserves the bonding agent  100  which penetrates from the gap  33   p  (see  FIG. 5 ) between the outer periphery of the distal end of the illumination lens  33   a  and the inner periphery of the distal end of the frame  33   d  to the gap between the outer periphery of the illumination lens  33   a  and the lens fitting circumferential surface  33   dn  of the frame  33   d , and the groove portion  133   dp  suppresses the penetration of the bonding agent  100  onto the rear side of the groove portion  133   dp . As a result, the non-bonding portion  270  is formed between the bonded portion  33   ac  of the illumination lens  33   a  and the output end face  33   bs  of the light guide  33   b . In the insertion axis direction Z of the non-bonding portion  270 , there is the distance of 0.5 mm or larger between the bonded portion  33   ac  (groove portion  133   dp ) and the output end face  33   bs  of the light guide  33   b.    
      Then, an endoscope repairing method which is the action of the endoscope  301  of the fourth embodiment having the above-described configuration will be described. Specifically, the illumination lens  33   a  replacement method will be described below.  
      The drill which is of the cutting tool is brought close to the distal end face  33  as of the illumination lens  33   a  fixed to the inside of the frame  133   d  along the optical axis from the outside, and the drill is caused to proceed to the rear end of the bonded portion  33   ac  in the outer periphery of the illumination lens  33   a  to cut the illumination lens. As a result, the bonding agent  100  having the non-abutting amount is removed by the cutting. This enables the fixing to be released between the illumination lens  33   a  and the frame  133   d.    
      Finally, the distal end portion  10  of the insertion portion  3  of the endoscope  301  is inclined downward to take out the illumination lens  33   a , in which the fixing is released and a part is cut, from the frame  133   d . Therefore, the illumination lenses  33   a  can be replaced. Thus, in the endoscope  301  of the fourth embodiment, the groove portion  133   dp  having the diameter larger than that of the lens fitting circumferential surface  133   dn  is formed in the inner periphery of the frame  133   d  which the illumination lens  33   a  is fitted in and fixed to. The non-bonding portion  270  having the distance of 0.5 mm or larger in the insertion axis direction Z is formed by the groove portion  133   dp  between the bonded portion  33   ac  of the illumination lens  33   a  and the output end face  33   bs  of the light guide  33   b . When the distal end of the drill is caused to proceed to the rear end of the bonded portion  33   ac  in the replacement, the distal end of the drill does not come into contact with the output end face  33   bs  of the light guide  33   b.    
      Accordingly, the output end face  33   bs  is not damaged, so that the illumination lenses  33   a  can be replaced without damaging the output end face  33   bs  of the light guide  33   b.    
      A modification will be described below. In the fourth embodiment, the illumination lens  33   a  in which the rear end of the outer periphery abuts on the output end face  33   bs  of the light guide  33   b  is illustrated by way of example. The invention is not limited to the illumination lens  33   a  of the fourth embodiment, but obviously the same effect as the fourth embodiment can be also obtained even if the illumination lens  33   a  in which the rear end face is formed in the plane of curvature  33   ak  projected toward the direction of the light guide  33   b  is used.  
      In the fourth embodiment, obviously the same effect can also be obtained even if the second embodiment is applied to an endoscope in which the lens having the usual viewing angle (140° or smaller) is used as the observation optical system  32   b.    
      In the fourth embodiment, the three illumination lenses  33   a  are arranged in the distal end portion. Alternatively, one illumination lens  33   a  or plural illumination lenses  33   a  may be arranged in the distal end portion. In this case, obviously the same number of light guide units  133  as the number of illumination lenses is provided.  
      The thin ring-shape plate member  90  shown in  FIG. 7  may fixedly be arranged at the position where the rear end face of the lens fitting circumferential surface  133   dn  of the frame  133   d  and the output end face  33   bs  abut on each other.  
      In the fourth embodiment, the drill is cited as an example of the cutting tool used in cutting the illumination lens  33   a . The invention is not limited to the drill, but the reamer may be used and obviously any cutting tool may be used as long as the cutting tool can cut the illumination lens  33   a.    
      Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.