Patent Publication Number: US-7896802-B2

Title: Endoscope insertion portion

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a continuation application of PCT/JP2006/300097 filed on Jan. 6, 2006 and claims benefit of Japanese Application No. 2005-003195 filed in Japan on Jan. 7, 2005, the entire contents of which are incorporated herein by this reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an endoscope insertion portion of an endoscope having a plurality of observation optical systems. 
     2. Description of the Related Art 
     Conventionally, endoscopes have been widely used in the medical field and the like. With an endoscope, for example, internal organs in a body cavity can be observed by inserting an elongated insertion portion into the body cavity, and various treatments can be performed using a treatment instrument inserted into a treatment instrument insertion channel as necessary. At a distal end of the insertion portion, a bending portion is provided. By operating an operation portion of the endoscope, observing direction of an observation window at a distal end portion can be changed. 
     In general, an endoscope is provided with an air/water feeding nozzle for cleaning for a case where body fluid or the like adheres on an outer surface of the objective optical system of the endoscope to disturb the observation when the endoscope is inserted into the body cavity. The outer surface of the objective optical system of the endoscope can be secured of a clean observation field of view with, for example, a cleaning liquid spouted out or air sprayed from the air/water feeding nozzle. 
     For example, an endoscope having a plurality of objective optical systems is proposed as described in Japanese unexamined patent publication No. 06-154155. This endoscope has a plurality of image pickup units, wherein the plurality of objective optical systems and an aperture of an air/water feeding nozzle are located at a distal end of an insertion portion to line up on a generally straight line. 
     Endoscopes used in recent years have a duct used for inserting various forceps and sucking body fluid, filth or the like in the body cavity (hereinafter referred to as treatment instrument channel), and a duct used for spraying a cleaning liquid in a direction of a diseased part to clean mucous membranes or the like adhering on a diseased part as a region to be inspected (hereinafter referred to as forward water-feeding channel). Respective aperture portions of the treatment instrument channel and the forward water-feeding channel are disposed on a distal end surface of a distal end portion. 
     Japanese unexamined patent publication No. 03-165731, for example, discloses an endoscope disposed with only one image pickup unit, in which a convex portion is provided between a lens and a nozzle. Further, Japanese Patent Laid-Open No. 2003-210388, for example, discloses an endoscope including a distal end cover having a distal end surface with a flat portion, an observation window protruding to a predetermined height from the flat portion, a gradient portion formed between a distal end surface periphery of the observation window and the flat portion, and illumination windows protruding from the flat portion to the same predetermined height as the observation window and provided to oppose to each other over the observation window. 
     SUMMARY OF THE INVENTION 
     To achieve the above-described objects, the present invention provides an endoscope insertion portion to be inserted into a body cavity and comprising a distal end portion at distal end part, the endoscope insertion portion comprising: a plurality of observation windows for leading incident light to each of a plurality of image pickup portions, the plurality of observation windows being disposed to the distal end portion; and an air/water feeding portion for spouting out a gas or liquid toward the plurality of observation windows, the air/water feeding portion being disposed to the distal end portion, wherein on the distal end portion, an outer surface is formed between the plurality of observation windows oriented in a spouting direction of the air/water feeding portion, the outer surface being in the same plane as surfaces of the plurality of observation windows. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an illustrative view schematically showing an endoscope system. 
         FIG. 2  is a perspective view showing a distal end cover of an endoscope. 
         FIG. 3  is a perspective view showing the distal end cover of the endoscope. 
         FIG. 4  is a plan view of the distal end cover as viewed from the front. 
         FIG. 5  is a section view of the distal end portion and a bending portion cut along V-V line of  FIG. 4 . 
         FIG. 6  is a section view of the distal end portion cut along VI-VI line of  FIG. 4 . 
         FIG. 7  is a section view showing a diverging part of an air/water feeding duct. 
         FIG. 8  is a section view of the distal end portion cut along VIII-VIII line of  FIG. 4 . 
         FIG. 9  is a section view of the distal end portion cut along IX-IX line of  FIG. 4 . 
         FIG. 10  is a section view of the distal end portion cut along X-X line of  FIG. 5 . 
         FIG. 11  is a section view of the bending portion cut along XI-XI line of  FIG. 5 . 
         FIG. 12  is a plan view of the distal end cover as viewed from the front. 
         FIG. 13  is a plan view of the distal end cover as viewed from the front. 
         FIG. 14  is a section view of a distal end part of the distal end portion provided with the distal end cover, cut along the XIV-XIV line of  FIG. 4 . 
         FIG. 15  is a section view of the distal end part of the distal end portion provided with the distal end cover, cut along the XV-XV line of  FIG. 4 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S) 
     First Embodiment 
     Referring to the drawings, an embodiment of the present invention is described below. 
     First, based on  FIG. 1 , configuration of an endoscope system according to the present embodiment is described.  FIG. 1  is an illustrative view schematically showing a configuration of the endoscope system according to the first embodiment of the present invention. 
     As shown in  FIG. 1 , an endoscope system  1  of the present embodiment includes: an endoscope  2  capable of performing normal light observation and fluorescent light observation; a light source device  3  for supplying illumination light to the endoscope  2 ; a processor  4  serving as a signal processing device for performing signal processing for the endoscope  2 ; a monitor  5  which is inputted with a video signal outputted from the processor  4  to display an endoscope image for normal observation or fluorescent light observation; an air/water feeding device  6  for feeding air and water; and a forward water-feeding device  6   a  for forwardly feeding water. 
     The endoscope  2  includes: an endoscope insertion portion (hereinafter simply referred to as insertion portion)  11  elongated to facilitate insertion into a body cavity; an operation portion  12  connected to a proximal end of the insertion portion  11 ; and a universal cable  13  extending from a side portion of the operation portion  12 . A connector  14  provided to an end portion of the universal cable  13  is detachably connected to the light source device  3 . 
     The insertion portion  11  of the endoscope  2  includes: a rigid distal end portion  15  formed at a distal end of the insertion portion  11 ; a bending portion  16  formed at a proximal end of the distal end portion  15 ; and a flexible tube portion  17  having flexibility formed from the proximal end of the bending portion  16  to the operation portion  12 . 
     In the insertion portion  11 , a light guide  21  for transmitting illumination light is inserted. The light guide  21  is inserted into the universal cable  13  via the operation portion  12 , and has a proximal end portion  22  connected to a light guide connector not shown protruding from the connector  14 . 
     A distal end part of the light guide  21  is fixed in the distal end portion  15 . Note that at the distal end part of the distal end portion  15  is disposed an illumination lens  25  of an illuminating unit described below which is an illumination optical system, and illumination light is radiated from the light guide  21  via the illumination lens  25 . On a distal end surface of the distal end portion  15 , a distal end cover  24  is provided. 
     Note that, in the present embodiment, the light guide  21  is inserted in the insertion portion  11 , being, for example, diverged in the operation portion  12  to be split twofold in the insertion portion  11 . Distal end surfaces of the respective light guides  21  split twofold are each located near rear surfaces of the two illumination lenses  25  provided on the distal end cover  24 . 
     Also, in the insertion portion  11  is provided a treatment instrument channel (also referred to as forceps channel) which is a first duct (omitted in  FIG. 1 ) for rendering a treatment instrument such as a forceps insertable into the insertion portion  11 . A distal end of the treatment instrument channel has an aperture at a distal end surface of the distal end cover  24 . 
     The treatment instrument channel diverges near the proximal end of the insertion portion  11 . One of the diverged treatment instrument channels is inserted up to a treatment instrument insertion port not shown disposed to the operation portion  12 . The other of the diverged treatment instrument channels communicates with a suction channel in through the insertion portion  11  and the universal cable  13 , with a proximal end being connected to an absorbing portion not shown serving as absorbing means via the connector  14 . 
     In the distal end portion  15 , two image pickup units are disposed. In the present embodiment, there are incorporated a normal-light-observing image pickup unit (hereinafter referred to as normal light image pickup unit)  31 A which is a first image pickup portion configuring first image pickup means for normal light observation, and a fluorescent-light-observing image pickup unit (hereinafter referred to as fluorescent light image pickup unit)  31 B which is a second image pickup portion configuring second image pickup means for special observation. 
     Note that the second image pickup portion configuring the second image pickup means, which in the present embodiment is a fluorescent-light-observing image pickup unit capable of performing fluorescent light observation which is a special observation, may be, for example, an image pickup unit for night vision observation, an image pickup unit for infrared observation, or the like, and is not limited to use for fluorescent light observation in particular. 
     To the normal light image pickup unit  31 A and the fluorescent light image pickup unit  31 B, respective one ends of a signal cables  38   a ,  38   b  are connected. Respective other ends of the signal cables  38   a ,  38   b  are inserted into the operation portion  12  and the universal cable  13 , and are switchably connected to a common signal cable  43  in a relay board  42  provided in the connector  14 . 
     The common signal cable  43  is connected to a processor  4  in through a scope cable  44  connected to the connector  14 . 
     In the processor  4 , there are provided driving circuits  45   a ,  45   b  for respectively driving image pickup devices of the normal light image pickup unit  31 A and the fluorescent light image pickup unit  31 B; a signal processing circuit  46  for performing signal processing to image pickup signals respectively outputted from the two image pickup devices via the relay board  42 ; and a control circuit  47  for controlling operation state of the signal processing circuit  46  or the like. 
     Also, the operation portion  12  of the endoscope  2  is provided with control switches  48   a ,  48   b ; an air/water feeding button  63 ; a bending operation knob not shown; a switch not shown (also referred to as tele-zoom button) for performing tele-zoom operation of the normal light image pickup unit  31 A; a forward water-feeding button not shown; and the above-described treatment instrument insertion port (not shown). 
     The control switches  48   a ,  48   b  are connected to the control circuit  47  of the processor  4  via signal lines  49   a ,  49   b , respectively. In the present embodiment, for example, the control switch  48   a  generates a signal for switching instruction, and the control switch  48   b  generates, for example, a signal for freezing instruction. 
     The relay board  42  performs, responsive, for example, to operation of the control switch  48   a , a switching operation such that, from a state where one of the signal cables  38   a ,  38   b  respectively connected to the image pickup devices is connected to the common signal cable  43 , the other signal cable is connected to the signal cable  43 . 
     Specifically, for example, by operating the control switch  48   a , a switching signal is outputted to the relay board  42  via a switching signal line  49   c  which is inserted in the scope cable  44  and electrically connected to the control circuit  47 . The relay board  42  connected with the switching signal line  49   c  is configured such that an input terminal for signals from the control circuit  47  is normally in L (LOW) level, with a switching control terminal pulled down, and in this state, the signal cable  38   a  of the normal light image pickup unit  31 A is connected to the common signal cable  43 . Also in an activation starting state, the switching control terminal is in the L level. That is, unless a switching instruction is performed, the relay board  42  is set to a normal light observation state. 
     When a user operates the control switch  48   a  in this state, a control signal is applied by which a signal from the control circuit  47  becomes H (HIGH) level at the input terminal of the relay board  42  via the switching signal line  49   c . Then, the relay board  42  pulls up the switching control terminal, and in this state, the signal cable  38   b  of the fluorescent light image pickup unit  31 B is connected to the common signal cable  43 . 
     When the control switch  48   a  is further operated, the switching control terminal is supplied with an L level signal, and the signal cable  38   a  of the normal light image pickup unit  31 A is connected to the common signal cable  43 . 
     With the operation of the control switch  48   a , the control circuit  47  sends a control signal also to the control circuit  58  in the light source device  3  via the control signal line  49   d  in the scope cable  44 . Then, in response to the control signal, the control circuit  58  controls to obtain a state of generating normal observation light or excitation light for fluorescent light observation. Further, the control circuit  47  controls operation state of the signal processing circuit  46  so that the same is operated corresponding to respective image pickup devices of the normal light image pickup unit  31 A and the fluorescent light image pickup unit  31 B. 
     The light source device  3  includes: a lamp  51  for generating white light including wavelength of the excitation light; a collimator lens  52  for bringing light of the lamps  51  into a parallel luminous flux; a rotary filter  53  disposed in an optical path of the collimator lens  52 , and provided in a circuit direction with an RGB filter that respectively pass lights of wavelength bands of R (RED), G (GREEN) and B (BLUE) in visible light wavelength band (380 to 780 nm), for example; and a condensing lens  54  for condensing transmission light of the rotary filter  53  and radiates the light to the proximal end portion  22  of the light guide  21 . 
     The rotary filter  53  provided with the RGB filter is also provided, on an outside of the circuit direction, with an excitation light filter for passing excitation light with a wavelength band shorter than that of visible light. The rotary filter  53  is rotatably driven by a motor  55 . Further, the motor  55  is mounted to a rack  56  and can be moved in a direction orthogonal to an illumination optical axis as shown in an arrow, by means of a gear-equipped motor  57  engaging with the rack  56 . 
     The gear-equipped motor  57  is controlled by a control circuit  58 . The control circuit  58  is connected to the control circuit  47  of the processor  4  via the control signal line  49   d , and is operated by the control switch  48   a  to perform a corresponding control operation. 
     On the distal end portion  15 , there is also located an air/water feeding nozzle  60  which is an air/water feeding portion configuring air/water feeding means such that a spouting port thereof faces outer surfaces of respective object lenses (hereinafter also referred to as observation lenses) of the normal light image pickup unit  31 A and the fluorescent light image pickup unit  31 B located on the distal end cover  24 . 
     The air/water feeding nozzle  60  is connected to an air/water feeding duct  61  whose distal end sides are joined to unite, as described below. A proximal end side of the air/water feeding duct  61  diverges into an air feeding duct  61   a  and a water feeding duct  61   b.    
     The air feeding duct  61   a  and the water feeding duct  61   b  communicating with the air/water feeding nozzle  60  are inserted up to the connector  14  of the universal cable  13 , and connected to the air/water feeding device  6  incorporating a pump not shown for feeding air and water. 
     The air feeding duct  61   a  and the water feeding duct  61   b  are interposed with the above-described air/water feeding button  63  in the operation portion  12  present at a halfway of the ducts. Air and water are fed by operating the air/water feeding button  63 . 
     This causes the air/water feeding nozzle  60  to blow a gas such as air or a liquid such as distilled water to outer surfaces of respective object lenses of the normal light image pickup unit  31 A and the fluorescent light image pickup unit  31 B located in a spouting direction, so as to remove and clean off body fluid, accretion or the like so that image pickup and observation field of view can be ensured in a clean state. 
     The insertion portion  11  is also provided inside with a forward water-feeding channel (omitted in  FIG. 1 ) which is a second duct for feeding a liquid such as distilled water to a region to be inspected in the body cavity. A distal end of the forward water-feeding channel has an aperture on a distal end surface of the distal end cover  24 . 
     The forward water-feeding channel is connected to the forward water-feeding device  6   a , and interposed with a forward water-feeding button not shown disposed to the operation portion  12 . When the forward water-feeding button is operated, a liquid such as distilled water is sprayed from the distal end surface of the insertion portion  11  toward an insertion direction into the body cavity. By this, body fluid or the like adhered to a region to be inspected in the body cavity can be cleaned. Note that, as shown in  FIG. 1 , a cable extending from the forward water-feeding device  6   a  is connected with a foot switch  6   b . Also by operating the foot switch  6   b , a user can spray a liquid such as distilled water toward the insertion direction into the body cavity from the distal end surface of the insertion portion  11 . 
     As shown in  FIGS. 2 to 4 , on the distal end cover  24  disposed to the distal end portion  15  of the insertion portion  11 , there are disposed: an observation lens  31   a  which is a first observation window of the normal light image pickup unit  31 A; an observation lens  31   b  which is a second observation window of the fluorescent light image pickup unit  31 B; two illumination lenses  25   a ,  25   b ; an aperture portion  26  of the treatment instrument channel; and an aperture portion  27  of the forward water-feeding channel. On the distal end cover  24 , the air/water feeding nozzle  60  is located such that a spouting port  60   a  faces the observation lenses  31   a ,  31   b , as described above. 
     Note that  FIGS. 2 and 3  are each a perspective view showing the distal end cover part of the endoscope, and  FIG. 4  is a plan view of the distal end cover as viewed from the front. The two observation lenses  31   a ,  31   b  are optical members. 
     Specifically, an observation lens  31   a  is disposed at the generally center of the distal end surface of the distal end cover  24  in a generally circle shape when the distal end portion  15  is viewed from the distal end. Further, on the distal end surface of the distal end cover  24 , the illumination lenses  25   a  and  25   b  are disposed in a manner sandwiching the observation lens  31   a , on right and left sides as viewed toward the surface of  FIG. 4 . Moreover, on the distal end surface of the distal end cover  24 , there are disposed the aperture portion  27  of the forward water-feeding channel at an upper right side of the observation lens  31   a ; the air/water feeding nozzle  60  on an upper left side; the observation lens  31   b  on a lower right side; and the aperture portion  26  of the treatment instrument channel on a lower left side, as viewed toward the surface of  FIG. 4 . 
     Note that locations of the observation lenses  31   a ,  31   b , the aperture portions  26 ,  27 , and the air/water feeding nozzle  60  disposed on the distal end cover  24  in the present embodiment will be described in detail later. 
     Next, referring to  FIGS. 5 to 11 , internal configuration of the distal end part of the insertion portion  11  of the endoscope  2  of the present embodiment is described. Note that  FIG. 5  is a section view of the distal end portion and the bending portion cut along V-V line of  FIG. 4 ;  FIG. 6  is a section view of the distal end portion cut along VI-VI line of  FIG. 4 ;  FIG. 7  is a section view showing a diverging part of the air/water feeding duct;  FIG. 8  is a partial section view of the distal end portion cut along VIII-VIII line of  FIG. 4 ;  FIG. 9  is a partial section view of the distal end portion cut along IX-IX line of  FIG. 4 ;  FIG. 10  is a section view of the distal end portion cut along X-X line of  FIG. 5 ; and  FIG. 11  is a section view of the bending portion cut along XI-XI line of  FIG. 5 . 
     As shown in  FIG. 5 , in the bending portion  16  of the endoscope  2 , a plurality of circular ring-shaped bending pieces  7  are rotatably provided in a linked manner. The bending pieces  7  each include on an inner circumferential surface four wire guards  7   a  fixedly provided thereon by means such as welding. The four wire guards  7   a  are fixed on an inner circumferential surface of one bending piece  7  at positions shifted by about 90 degrees from each other about the insertion axis (see  FIG. 10 ). 
     The plurality of bending pieces  7  are coated, in a manner covering outer circumferences thereof, with a bending braid  9  made of a thin wire knitted in a pipe shape. The bending braid  9  is watertightly covered by an outer covering  10 , thereby forming the bending portion  16 . 
     The outer covering  10  provides a covering such that the insertion portion  11  including the distal end portion  15 , the bending portion  16 , and the flexible tube portion  17  forms one body over the entire length. An outer peripheral distal end part of the outer covering  10  is fixedly adhered with a spool adhering portion  10   a  in the distal end portion  15 . 
     Also, in the insertion portion  11 , four bending operation wires  8  are inserted which are bending operation means extending from the bending portion  16  toward a proximal end thereof. Distal end parts of these four bending operation wires  8  are respectively held and fixed, shifted by about 90 degrees from each other about the insertion axis, by four fixing portions  18   a  (see  FIG. 11 , only one is shown in  FIG. 5 ) of a fixing ring  18  provided in the distal end portion  15 . Proximal end side parts of the bending operation wires  8  are insertingly provided in the respective wire guards  7   a  provided to the bending pieces  7 . 
     Note that the distal end portion  15  and each of the bending pieces  7  are connected in a linked manner such that the bending operation wires  8  held and fixed by the respective fixing portions  18   a  of the fixing ring  18  provided in the distal end portion  15  and inserted into the respective wire guards  7   a  of the bending pieces  7  are in a generally straight line, in a state where the insertion axis of the bending portion  16  is in a generally straight line. 
     Also, the proximal end portions of the bending operation wires  8  are connected to a bending operation mechanism not shown provided in the operation portion  12  (see  FIG. 1 ) and connected to the bending operation knob, so as to be alternately pulled or relaxed. 
     By the four bending operation wires  8  each being pulled or relaxed through a predetermined operation of the bending operation knob, the bending portion  16  is operated to be bent in four directions. These four directions are up/down and left/right four directions of an endoscope image photographed by each of the image pickup units  31 A,  31 B and displayed on the monitor  5  as discussed below. 
     Also, two of the bending operation wires  8  as a first bending operation member configuring a first bending operation means for operating the bending portion  16  in up/down direction, and the other two of the bending operation wires  8  as a second bending operation member configuring a second bending operation means for operating the bending portion  16  in the left/right direction, respectively make pairs. That is, the two bending operation wires  8  respectively inserted and held in the two wire guards  7   a  in a direction corresponding to the up/down direction of the bending pieces  7  in the bending portion  16  are the first bending operation member. The other two bending operation wires  8  respectively inserted and held in the two wire guards  7   a  in the directions corresponding to the left/right direction in the bending pieces  7  in the bending portion  16  are the second bending operation member. 
     In the distal end portion  15 , there are disposed a columnar member  15   a  made of a rigid metal and formed with a plurality of, seven in the present embodiment, hole portions; and a circular ring-shaped reinforcing ring  15   b  fitted onto a proximal end side outer circumference portion of the columnar member  15   a . The fixing ring  18  including the above-described four fixing portions  18   a  is inserted and fitted on an inner circumferential side of the reinforcing ring  15   b  of the distal end portion  15 . Further, a proximal end part of the reinforcing ring  15   b  is connected to a distal-most bending piece  7 . 
     Two of the seven hole portions formed on the columnar member  15   a  of the distal end portion  15  form distal end parts of the treatment instrument channel  19  and the forward water-feeding channel  20 . In the five remaining hole portions are respectively disposed the above-described normal light image pickup unit  31 A, the fluorescent light image pickup unit  31 B, the air/water feeding nozzle  60 , and two illumination lens units described below. 
     The treatment instrument channel  19  includes the aperture portion  26  having an aperture on the distal end cover  24  provided on the distal end surface of the distal end portion  15 ; a generally cylindrical tube member  19   a  inserted and fitted in the hole portion of the columnar member  15   a  of the distal end portion  15 ; and a treatment instrument duct  19   b  made of a flexible tube, whose distal end part covers a proximal end portion of the tube member  19   a  and is connected and fixed to the proximal end portion with a spool. 
     The treatment instrument duct  19   b  is inserted in through the insertion portion  11 , and has a proximal end with an aperture at the treatment instrument insertion port (not shown in  FIG. 1 ) in the operation portion  12 , as described above. 
     Also, the forward water-feeding channel  20  having the aperture portion  27  similarly on the distal end cover  24  includes a generally cylindrical tube member  20   a  inserted and fitted in the hole portion of the columnar member  15   a  of the distal end portion  15 ; and a forward water-feeding duct  20   b  covering the proximal end part of the tube member  20   a  and having a distal end part connected and fixed to the proximal end part with a spool. 
     The forward water-feeding duct  20   b  is inserted up to the connector  14  though the insertion portion  11 , the operation portion  12 , and the universal cable  13 , and is connected to the forward water-feeding device  6   a . Note that, as described above, the forward water-feeding duct  20   b  which is the forward water-feeding channel  20  is interposed with the forward water-feeding button (not shown) in operation portion  12 . 
     As shown in  FIG. 6 , the air/water feeding nozzle  60  is a tubular member bent in a generally L shape, and has a proximal end part inserted and fitted in the hole portion of the columnar member  15   a  of the distal end portion  15  such that the spouting port  60   a  on the distal end side is oriented toward outer surface sides of the respective observation lenses  31   a ,  31   b.    
     To a proximal end side of the hole portion of the columnar member  15   a  corresponding to the air/water feeding nozzle  60 , a distal end part of the tube member  62  is inserted. A proximal end part of the tube members  62  is connected with the air/water feeding duct  61 . Note that the tube member  62  and the air/water feeding duct  61  are connected and fixed by means of a spool. 
     As shown in  FIG. 7 , the air/water feeding duct  61  has a proximal end part connected to a diverging tube  50 . The diverging tube  50  has divergence ends respectively connected to distal end parts of the air feeding duct  61   a  and the water feeding duct  61   b . This brings the air/water feeding duct  61  into communication with the air feeding duct  61   a  and the water feeding duct  61   b . Note that each of the ducts  61 ,  61   a ,  61   b  and the diverging tube  50  are connected and fixed by means of a spool. Respective connecting portions and the entire periphery of the diverging tube  50  are applied, for example, with an adhesive or the like, so that the each connecting portion is airtightly (watertightly) held. 
     Two of the seven hole portions formed on the columnar member  15   a  of the distal end portion  15  are each inserted and fitted with an illumination lens unit  23  from the distal end side. Proximal end parts of these two hole portions are respectively inserted with distal end parts of the light guide  21 . 
     As shown in  FIGS. 8 and 9 , the illumination lens unit  23  includes a plurality of illumination lenses  25  and a holding barrel  23   a  for holding the illumination lenses  25 . Note that the two illumination lens units  23  in the present embodiment respectively include the illumination lenses  25   a ,  25   b  present at the distal-most ends of the illumination lenses  25 . 
     The light guide  21  has a distal end part covered with a cylindrical member  21   a , and is coated with an outer covering  29  made of a plurality of strings of fibers bundled together. The cylindrical member  21   a  has a proximal end part connected and fixed to a tube  28  whose distal end part is fixed with a spool. The light guide  21  coated by the outer covering  29  passes in through the tube  28 . 
     Note that one of the seven hole portions of the columnar member  15   a  is disposed with the normal light image pickup unit  31 A, including the observation lens  31   a , which is a first observation optical system fixed by a first observation optical system fixing member as first observation optical system fixing means such as a screw and adhesive, for example. This hole portion configures a first observation optical system disposition portion which is a first observation optical system disposition means. 
     Another one of the hole portions is disposed with the fluorescent light image pickup unit  31 B, including the observation lens  31   b , which is a second observation optical system fixed by a second observation optical system fixing member as second observation optical system fixing means, such as a screw and adhesive, for example. This hole portion configures a second observation optical system disposition portion which is a second observation optical system disposition means. 
     Further, in other two hole portions, the two illumination lens units, respectively including the illumination lenses  25 , which are first and second illumination optical systems are respectively fixed and located by first and second illumination optical system fixing means such as a screw and adhesive, for example. Of these two hole portions, one configures a first illumination optical disposition portion as a first illumination optical disposition means, and the other configures a second illumination optical disposition portion as a second illumination optical disposition means. 
     Also, of the seven hole portions, a hole portion in which the air/water feeding portion is located configures an air/water feeding portion disposition portion as air/water feeding portion disposition means in which is fixed and located the air/water feeding nozzle  60  by a first air/water feeding portion fixing portion such as a screw and adhesive, for example. 
     Further, of the seven hole portions, a hole portion in which the treatment instrument channel  19  which is a first endoscope duct is located configures a first endoscope duct disposition portion as first endoscope duct disposition means. 
     Also, a hole portion in which the forward water-feeding channel  20  as a second endoscope duct is located configures a second endoscope duct disposition portion as second endoscope duct disposition means. The treatment instrument channel  19  is fixed and located in one of the seven hole portions by a first endoscope duct fixing member as first endoscope duct fixing means such as a screw and an adhesive, for example. The forward water-feeding channel  20  is fixed and located in one another hole portion by a second endoscope duct fixing member as second endoscope duct fixing means such as a screw and adhesive, for example. 
     Returning to  FIG. 6 , the normal light image pickup unit  31 A includes a lens unit  32 , an image pickup device  33  such as CCD (Charge Coupled Device) and CMOS (Complementary Metal-Oxide Semiconductor), and a circuit board  34 . 
     The lens unit  32  includes first to fourth lens groups  32 A to  32 D, and first to fourth lens barrels  32   a  to  32   d . In the present embodiment, the first lens group  32 A formed by four object lenses containing the observation lens  31   a  is held by the first lens barrel  32   a . The second lens  32 B formed by one object lens is held by the second lens barrel  32   b . Further, the third lens group  32 C formed by two object lenses is held by the third lens barrel  32   c . Still further, the fourth lens group  32 D formed by three object lenses is held by the fourth lens barrel  32   d.    
     Incidentally, the second lens barrel  32   b  for holding the second lens  32 B is a moving barrel which can advance and retreat in a photographing optical axis direction for zooming. Note that the second lens barrel  32   b  is moved to advance and retreat in the photographing optical axis direction by a driving portion serving as driving means such as, for example, a motor and actuator not shown provided to the normal light image pickup unit  31 A when a zooming operation lever not shown provided to the operation portion  12  is operated by a user. 
     The driving portion for moving the second lens barrel  32   b  to advance and retreat in the photographing optical axis direction is supplied with a drive-stop signal through a signal line  38   c  shown in  FIG. 10 . The signal line  38   c  is inserted from the normal light image pickup unit  31 A up to the operation portion  12  in through the insertion portion  11 . 
     The image pickup device  33  is provided, on a light receiving surface side, with a cover lens  33   a  adjacently provided on a proximal end side of an object lens at the proximal-most end of the fourth lens barrel  32   d , and outputs an electrical signal corresponding to an optical image to the circuit board  34 . The circuit board  34  includes electrical parts and a wiring pattern, photoelectrically converts an optical image from the image pickup device  33  to an electric image signal, and then outputs the image signal to the signal cable  38   a . Note that the circuit board  34  is connected with a plurality of signal lines of the signal cable  38   a  by means of soldering or the like. 
     The cover lens  33   a , the image pickup device  33 , the circuit board  34 , and a distal end part of the signal cable  38   a  have respective outer circumference portions unitedly covered by an insulation sealing resin or the like, and are coated by a reinforcing circular ring portion  35   a  and an insulating tube  35   b.    
     The signal cable  38   a  transmits image signals acquired by the image pickup device  33  and the circuit board  34  of the normal light image pickup unit  31 A to the signal processing circuit  46  of the processor  4  via the relay board  42  and the signal cable  43  of the connector  14  shown in  FIG. 1 . 
     Meanwhile, like the normal light image pickup unit  31 A, the fluorescent light image pickup unit  31 B includes a lens unit  36 , an image pickup device  38  such as CCD and CMOS, and a circuit board  39 . 
     The lens unit  36  includes first and second lens groups  36 A,  36 B and first and second lens barrels  32   a ,  32   b . In the present embodiment, the first lens group  36 A formed by seven object lenses including the observation lens  31   b  is held by the first lens barrel  36   a , and the second optical lens  36 B is held by the second lens barrel  36   b.    
     The image pickup device  38  is provided, on a light receiving surface side, with a cover lens  40  adjacently provided on a proximal end side of an object lens at the proximal-most end of the second lens barrel  36   b . The image pickup device  38  outputs an electrical signal of an optical image to the circuit board  39 . 
     The circuit board  39  includes electrical parts and a wiring pattern, like the circuit board  34  of the normal light image pickup unit  31 A. The circuit board  39  is connected with a plurality of signal lines of the signal cable  38   a  by means of soldering or the like. The circuit board  39  photoelectrically converts an optical image from the image pickup device  38  to an electric image signal, and then outputs the image signal to the signal cable  38   b.    
     The cover lens  40 , the image pickup device  33 , the circuit board  34 , and a distal end part of the signal cable  38   a  have respective outer circumference portions unitedly covered by an insulation sealing resin or the like, and are coated by a reinforcing circular ring portion  35   a  and the insulating tube  35   b.    
     The signal cable  38   b  transmits image signals acquired by the image pickup device  38  and the circuit board  39  of the fluorescent light image pickup unit  31 B to the signal processing circuit  46  of the processor  4  via the relay board  42  and the signal cable  43  of the connector  14  shown in  FIG. 1 . 
     The above-described normal light image pickup unit  31 A and the fluorescent light image pickup unit  31 B are respectively inserted into predetermined hole portions provided to the columnar member  15   a  of the distal end portion  15 , and are firmly fixed thereto with a fixing member such as a screw along with an adhesive or the like. 
     In the present embodiment, the observation lens  31   a  provided at the distal end of the normal light image pickup unit  31 A has a lens diameter (caliber) that is larger than a lens diameter of the observation lens  31   b  located at the distal end of the fluorescent light image pickup unit  31 B. 
     Also, setting directions of the image pickup units  31 A,  31 B in the distal end portion  15  are determined such that respective light receiving surfaces of the two image pickup devices  33 ,  38  are orthogonal to the insertion axis of the insertion portion  11 , and horizontal transfer directions and vertical transfer directions of the two image pickup devices  33 ,  38  agree to each other, respectively. 
     Further, subject images photographed by the image pickup units  31 A,  31 B are displayed on the monitor  5  (see  FIG. 1 ). Note that up/down direction of the monitor  5  agrees with vertical transfer direction of the CCD or CMOS device of each of the image pickup devices  33 ,  38 , and left/right direction of the monitor  5  agrees with horizontal transfer direction of the CCD or CMOS device of each of the image pickup devices  33 ,  38 . In other words, up/down and left/right directions of an endoscope image photographed by each of the image pickup units  31 A,  31 B agree with up/down and left/right directions of the monitor  5 . 
     Up/down and left/right directions of the bending portion  16  of the insertion portion  11  are determined to correspond to the up/down and left/right directions of an endoscope image displayed on the monitor  5 . That is, the four bending operation wires  8  inserted in through the bending portion  16  are pulled and relaxed by a predetermined operation of the bending operation knob provided to the operation portion  12  as described above, so as to render the bending portion  16  bendable in up/down and left/right four directions corresponding to the up/down and left/right directions of an image displayed on the monitor  5 . 
     In other words, setting directions of the image pickup units  31 A,  31 B in the distal end portion  15  are determined such that horizontal transfer directions and vertical transfer directions of the image pickup devices  33 ,  38  respectively agree so that up/down and left/right directions of an endoscope image displayed on the monitor  5  always agree with those directions of the bending operation directions of the bending portion  16  even when normal light observation and fluorescent light observation are switched from one to the other. 
     Thus, the user can perform bending operation of the bending portion  16  in up/down and left/right directions without having a sense of incongruity about those directions of an endoscope image displayed on the monitor  5  when endoscope images with normal light and fluorescent light are switched from one to the other. 
     Note that, in the description below, up/down direction as a first direction will be described as up/down direction of an endoscope image displayed on the monitor  5  and up/down direction in which the bending portion  16  is operated to be bent. Normally, the monitor  5  is installed such that up/down direction thereof generally agrees with plumb up/down direction. Further, left/right direction as a second direction which is generally orthogonal to the up/down direction is identical to the left/right direction of an endoscope image displayed on the monitor  5  and the left/right direction in which the bending portion  16  is operated to be bent. 
     Here, actions of the above-described endoscope system  1  are described. 
     As shown in  FIG. 1 , a user connects the connector  14  of the endoscope  2  to the light source device  3 , and further connects one end of the scope cable  44  to the connector  14  and the other end of the scope cable  44  to the processor  4 . The user also connects the air feeding duct  61   a  and the water feeding duct  61   b  to the air/water feeding device  6 . 
     Then, the user turns on power switches of the light source device  3  and the like to bring these devices into operation state. At this time, the respective control circuits  47 ,  58  of the processor  4  and the light source device  3  are rendered capable of transmitting and receiving control signals. 
     The relay board  42  is set to select the normal light image pickup unit  31 A side in activation state. Also, the control circuit  47  performs a control operation so that a normal light observation state is set. That is, the control circuit  47  sends a control signal to the control circuit  58  of the light source device  3 , to make a setting to obtain a state of supplying illumination light for normal light observation. 
     Further, the control circuit  47  controls to drive the driving circuit  45   a  and sets operation state of the signal processing circuit  46  to normal light observation mode. 
     The user inserts the insertion portion  11  of the endoscope  2  in the body cavity, to make a setting so that a diseased part of the diagnosis object can be observed. 
     The light source device  3  is brought into a state of supplying illumination light for normal light observation as described above. In this state, the rotary filter  53  is rotationally driven by the motor  55 , with the RGB filter located in an illumination optical path. Then, RGB illumination lights are supplied to the light guide  21  in a surface sequential manner. Synchronously therewith, the driving circuit  45   a  outputs a driving signal to illuminate a diseased part or the like in the body cavity of the patient through the illumination lenses  25   a ,  25   b.    
     The illuminated subject such as a diseased part is focused on a light receiving surface of the image pickup device  33  through the lens unit  32  of the normal light image pickup unit  31 A, and is subject to photoelectric conversion. Then, the image pickup device  33 , when applied with a driving signal, outputs photoelectrically converted signals. The signals are inputted to the signal processing circuit  46  via the signal cable  38   a  and the common signal cable  43  selected by the relay board  42 . 
     The signals inputted to the signal processing circuit  46  are subject to A/D conversion therein, and thereafter temporarily stored in an RGB memory. 
     Subsequently, the signals stored in the RGB memory are simultaneously read out into synchronized R, G, B signals, which are further D/A converted into analog R, G, B signals to be color displayed on the monitor  5 . 
     If the user desires to inspect the diseased part in more detail by fluorescent light observation in addition to normal light observation, the user turns on the control switch  48   a . Then, on receiving the switching instruction signal, the control circuit  47  performs switching control of the relay board  42 , and sets the light source device  3  to a state of supplying excitation light for fluorescent light observation via the control circuit  58 . 
     The control circuit  47  also controls the driving circuit  45   b  into operation state, and sets the signal processing circuit  46  to a processing mode for fluorescent light observation. 
     In this case, the control circuit  58  in the light source device  3  causes the gear-equipped motor  57  to move the rotary filter  53  along with the motor  5  in a direction orthogonal to an illumination optical path, so that the excitation light filter is located in the illumination optical path. 
     In this state, light from the lamp  51  is transmitted by the excitation light filter in a wavelength band of about, for example, 400 to 450 nm, to be supplied to the light guide  21 . The excitation light is then irradiated to a diseased part or the like in the body cavity, through the illumination lenses  25   a ,  25   b.    
     When the diseased part or the like irradiated with the excitation light is an abnormal region such as of carcinoma tissues, the part absorbs the excitation light and emits fluorescent light stronger than in a case of a normal organization. The light of the region emitting the fluorescent light is focused on the light receiving surface of the image pickup device  38  through the lens unit  36  of the fluorescent light image pickup unit  31 B, and then is subject to photoelectric conversion. 
     The image pickup device  38 , when applied with a driving signal from the driving circuit  45   b , outputs photoelectrically converted signals. In this case, the signals are amplified in the image pickup device  38  and then outputted therefrom. The signals are inputted to the signal processing circuit  46  through the signal cable  38   b  and the common signal cable  43  selected by the relay board  42 . 
     The signals inputted into the signal processing circuit  46  are A/D converted therein, and then stored in the RGB memory, simultaneously, for example. 
     Thereafter, the signals stored in the RGB memory are simultaneously read out into synchronized R, G, B signals, which are further D/A converted into analog R, G, B signals to be displayed on the monitor  5  in a black and white manner. 
     Note that the signals inputted into the signal processing circuit  46  may be provided in pseudo colors and displayed by comparing the signals in level with a plurality of thresholds and changing colors to be assigned depending on the comparison result. 
     Thus, the present embodiment, which is capable of performing the normal light observation as well as the fluorescent light observation, can realize an endoscope facilitating diagnosis compared with an endoscope only for normal light observation. Moreover, the present embodiment, which is provided with the respective image pickup unit  31 A,  31 B, can obtain fine normal light observation images and special light observation images. 
     Specifically, when performing a fluorescent light image pickup in particular, it is necessary to capture light weaker than in normal observation: light preferably having a high signal to noise ratio. In this case, using a normal image pickup device for both observations easily results in an image having low signal to noise ratio. However, the present embodiment can obtain a fluorescent light image with a good signal to noise ratio by adopting the image pickup device  38  suitable for fluorescent light image pickup, which is more sensitive to light relative to the image pickup device  33  for normal observation. 
     Further, provided with the switching relay board  42  to connect only one of the two image pickup units  31 A,  31 B to the processor  4 , the endoscope system  1  can be formed to be more compact than when the two image pickup unit  31 A,  31 B each always has to be driven and signal processed. 
     Still further, the present embodiment can reduce diameter of the insertion portion  11 , relieve pain given to a patient in insertion, and expand the insertable application area, because the single air/water feeding nozzle  60  is used to spray gas or liquid onto the outer surfaces of the both observation lenses  31   a ,  31   b  to set the surfaces to a clean state to allow securing good observation field of view. 
     Yet still further, the endoscope  2  of the present embodiment, having an similar exterior structure to that of an existing endoscope only including an image pickup unit for normal light observation, can also be used as an endoscope for normal light observation in a similar manner with an existing endoscope by connecting the endoscope  2  via the scope cable  44  to a processor not shown for driving and signal processing an existing endoscope only including an image pickup unit for normal light observation. In other words, the endoscope  2  can also be used connected to an existing processor, while maintaining compatibility similar to that for the existing endoscope only including the image pickup unit for normal light observation. 
     Here, the endoscope  2  of the present embodiment has various characteristics (effects) owing to structures described below. 
     First, referring to  FIG. 12 , there are described in detail, dispositions of the air/water feeding nozzle  60  and each of the observation lenses  31   a ,  31   b  disposed on the distal end cover  24 . 
       FIG. 12  is a front view showing a distal end surface of the distal end cover. Note that, in the following description, center of the distal end cover  24  is denominated as O 0 , center of the observation lens  31   a  of the normal light image pickup unit  31 A as O 1 , and center of the observation lens  31   b  of the fluorescent light image pickup unit  31 B as O 2 . Also, centers of the two illumination lenses  25   a ,  25   b  described below are respectively denominated as O 3 , O 4 , center of the aperture portion  26  of the treatment instrument channel  19  as O 5 , and center of the aperture portion  27  of the forward water-feeding channel  20  as O 6 . Further, a line passing through the center O 0  of the distal end surface of the distal end cover  24  and oriented in a bending up/down direction of the bending portion  16  is denominated as a perpendicular line X, and a line in a bending left/right direction as a horizontal line Y. Note that, in the following description, the perpendicular line X in the present embodiment is regarded as a line equated with a plumb line. 
     As described above, the air/water feeding nozzle  60  is disposed on the upper left side on the distal end surface of the distal end cover  24  as viewed toward the surface of  FIG. 12 , such that the spouting port  60   a  of the air/water feeding nozzle  60  faces the observation lens  31   a . Note that, the air/water feeding nozzle  60  may also be disposed on the upper right side on the distal end surface of the distal end cover  24  as viewed toward the surface of  FIG. 12 , such that the spouting port  60   a  of the air/water feeding nozzle  60  faces the observation lens  31   a . At this time, the air/water feeding nozzle  60  and each of the observation lenses  31   a ,  31   b  are located on the distal end surface of the distal end cover  24  so as to line up on a generally straight line. 
     In the present embodiment, the air/water feeding nozzle  60  is disposed on the distal end surface of the distal end cover  24  such that gas or liquid such as distilled water or air is spouted out from the spouting port  60   a  of the air/water feeding nozzle  60  in the direction of an arrow line AR in the drawing. The air/water feeding nozzle  60  spouts out, in a spreading manner, the gas or liquid such as distilled water or air into a gas/liquid spouting area A from the spouting port  60   a . Note that the arrow line AR is a line in a direction generally orthogonal to the distal end surface of the air/water feeding nozzle  60  including the spouting port  60   a , and passing through the center of a hole surface of the spouting port  60   a.    
     Setting direction of the air/water feeding nozzle  60  about an axis thereof, that is, direction in which the spouting port  60   a  faces, is determined such that an observation optical axis passing through the center O 1  of the observation lens  31   a  intersects the above-described arrow line AR. In other words, the direction in which spouting port  60   a  of the air/water feeding nozzle  60  faces is determined such that the arrow line AR as the spouting direction of the gas or liquid such as distilled water or air is in a predetermined angle θ as a first angle with respect to the perpendicular line X. 
     On the other hand, the observation lens  31   b  of the fluorescent light image pickup unit  31 B is disposed on a lower right side on the distal end surface of the distal end cover  24  toward the surface of  FIG. 10 , such that an outer surface of the observation lens  31   b  has a part intersecting at least the arrow line AR when the distal end cover  24  is viewed from a distal end thereof. The observation lens  31   b  is also disposed on the distal end surface of the distal end cover  24  such that the center O 2  of the observation lens  31   b  is located on a side lower than the line segment of the arrow line AR. 
     As described above, the air/water feeding nozzle  60  and the two observation lenses  31   a ,  31   b  are adjacently provided on the generally straight line on the distal end surface of the distal end cover  24 . 
     In detail, a line a linking the center O 1  of the observation lens  31   a  of the normal light image pickup unit  31 A and the center O 2  of the observation lens  31   b  of the fluorescent light image pickup unit  31 B is slightly shifted toward a lower side when the distal end cover  24  is viewed from the distal end surface side thereof, with a predetermined angle θ 2  with respect to the arrow line AR. In other words, a line b linking the center of a hole surface of the spouting port  60   a  of the air/water feeding nozzle  60  and the center O 2  of the observation lens  31   b  is slightly shifted toward a lower side when the distal end cover  24  is viewed from the distal end surface side, with a predetermined angle θ 3  with respect to the arrow line AR. 
     This determines respective disposition positions of the observation lenses  31   a ,  31   b  on the distal end cover  24 . In line with these positions, direction of the spouting port  60   a  of the air/water feeding nozzle  60  (direction of the arrow line AR) is determined. Further, the angles θ 2 , θ 3  are set in ranges such that the gas/liquid spouting area A from the air/water feeding nozzle  60  includes the entire outer surface of the observation lens  31   b.    
     Note that the gas/liquid spouting area A of the air/water feeding nozzle  60  is set to entirely include an outer surface of the observation lens  31   a  of the normal light image pickup unit  31 A when viewed from the distal end side of the distal end cover  24 . 
     Also, the observation lens  31   a  having a lens diameter (caliber) larger than an outer diameter of the observation lens  31   b  is disposed on the distal end surface of the distal end cover  24 , close to the air/water feeding nozzle  60 . 
     That is, the distal end cover  24  has the air/water feeding nozzle  60  at a position on an upper side than the horizontal line Y generally bisecting the bending up/down direction of the bending portion  16  with respect to a direction viewed from the distal end surface side, that is, up/down direction of the vertical transfer direction in which the respective image pickup devices  33 ,  38  included in the image pickup units  31 A,  31 B perform processings. In other words, the air/water feeding nozzle  60  is disposed on the distal end cover  24 , apart from the horizontal line Y in an opposite direction from the spouting direction (arrow line AR direction). 
     Further, on the distal end cover  24 , the air/water feeding nozzle  60  is disposed such that a section surface in a direction orthogonal to a longitudinally directed axis of the air/water feeding nozzle  60  (axis parallel to the insertion direction) does not exist on the perpendicular line X which bisects a left/right direction (which is reverse to the bending left/right direction of the bending portion  16 ) relative to the direction as viewed from the distal end surface side of the distal end cover, that is, left/right direction of the vertical transfer direction in which the image pickup devices  33 ,  38  included in the respective image pickup units  31 A,  31 B perform processings. 
     Note that, in the present embodiment, the air/water feeding nozzle  60  is disposed on a position on the distal end surface of the distal end cover  24 , so as to be apart from the perpendicular line X in a left direction by a predetermined distance, when viewed from the distal end surface side of the distal end cover  24 . That is, the air/water feeding nozzle  60  is located such that a longitudinal axis thereof is present at a position which is on an upper side than the horizontal line Y bisecting the distal end cover  24  into upper and lower sides and is shifted toward left side from the perpendicular line X bisecting the distal end cover  24  into right and left sides, when viewed from the distal end surface side of the distal end cover  24 . 
     As a result of the foregoing, the endoscope  2  of the present embodiment can be secured of a good observation field of view by using the single air/water feeding nozzle  60  to spray gas or liquid onto the outer surfaces of the respective observation lenses  31   a ,  31   b  to set the surfaces in a clean state, when the air/water feeding nozzle  60 , the observation lens  31   a  of the normal light image pickup unit  31 A, and the observation lens  31   b  of the fluorescent light image pickup unit  31 B provided on the distal end surface of the distal end cover  24  are located on a generally straight line. 
     Also, the longitudinal axis of the air/water feeding nozzle  60  is shifted toward an upper side than the horizontal line Y bisecting the distal end cover  24  to upper and lower sides, and by a predetermined distance from the perpendicular line X bisecting the distal end cover  24  to right and left sides. Therefore, when the insertion portion  11  is in a generally straight line, the air/water feeding duct  61  communicating with the air/water feeding nozzle  60  is generally straightly inserted in through the distal end portion  15  and the bending portion  16 , without coming into contact with the four fixing portions  18   a  of the fixing ring  18  disposed in the distal end portion  15  and the four wire guards  7   a  respectively provided on the bending pieces  7  disposed in the bending portion  16 . 
     Further, because the above-described disposition of the air/water feeding nozzle  60  prevents the air/water feeding duct  61  from coming into contact in the bending portion  16  with the four bending operation wires  8  respectively inserted and held in the four wire guards  7   a  of each of the bending pieces  7 , movement of the bending operation wire  8  due to pulling and relaxing is not obstructed, and deterioration of the bending operation wire  8  due to scratch can be prevented. 
     As a result of the foregoing, the endoscope  2  of the present embodiment can reduce the diameter of the insertion portion  11 , particularly of the distal end portion  15  and the bending portion  16 , relieve pain given to a patient in insertion, and expand the insertable application area in the body cavity. 
     In addition, the endoscope  2  is generally used with the bending up/down direction of the bending portion  16  being adjusted to up/down direction of the plumb direction by the user. Therefore, liquid such as distilled water spouted out from the spouting port  60   a  of the air/water feeding nozzle  60  flows toward a lower side, on a side farther from the spouting port  60   a , due to the effect of gravity. 
     Further, in a case where gas or liquid such as distilled water or air is spouted out from the spouting port  60   a  of the air/water feeding nozzle  60 , and at the same time suction is performed through the treatment instrument channel  19 , the liquid or gas is applied with a drawing force toward the aperture portion  26  due to the suction force from the aperture portion  26  of the treatment instrument channel  19  provided on a lower side on distal end cover  24 , and is thereby changed in flow direction toward the bending lower side. 
     Under such circumstances, in the endoscope  2  of the present embodiment, the observation lens  31   b  of the fluorescent light image pickup unit  31 B is located on the distal end surface of the distal end cover  24  such that the line a linking the center O 2  thereof with the center O 1  of the observation lens  31   a  of the normal light image pickup unit  31 A is shifted by a predetermined angle θ 2  toward the bending lower side of the bending portion  16  with respect to the arrow line AR which is the spouting direction of a liquid such as distilled water spouted out from the spouting port  60   a  of the air/water feeding nozzle  60 . 
     Accordingly, on the distal end surface of the distal end cover  24 , the observation lens  31   b  positioned farther than the observation lens  31   a  from the air/water feeding nozzle  60  is efficiently sprayed with a liquid such as distilled water flowing down toward the bending lower side than the spouting direction due to the effect of gravity. The observation lens  31   b  is thus cleaned into a clean state and secured of a good observation field of view. Further, the observation lens  31   b  is likewise efficiently sprayed with gas or liquid such as distilled water or air whose flow is changed to the bending lower side by suction performed, to be cleaned into a clean state and secured of a good observation field of view. 
     Furthermore, the endoscope  2  inserted in the body cavity of the patient has the insertion portion  11  adhered with filth or the like. Incidentally, the distal end surface of the distal end cover  24  is generally perpendicular to the insertion direction and is therefore easily adhered with filth or the like. In particular, the observation lens  31   a  of the normal light image pickup unit  31 A and the observation lens  31   b  of the fluorescent light image pickup unit  31 B are required to be surely cleaned of adhering filth or the like in order to secure respective observation fields of view. 
     In particular, the endoscope  2  is required to secure better observation field of view for the normal light observation than for the fluorescent light observation in which tone of tissue pigments are observed, because normal light is more frequently used than the fluorescent light observation to observe a patient&#39;s body cavity. 
     Also, gas or liquid such as distilled water or air spouted out from the spouting port  60   a  of the air/water feeding nozzle  60  has larger spouting force on the side closer to the spouting port  60   a . On a farther side in the spouting direction, the spouting force decreases and density of the gas or liquid also decreases due to spreading thereof. 
     Under such circumstances, in the endoscope  2  of the present embodiment, the observation lens  31   a  of the normal light image pickup unit  31 A having a larger lens diameter (caliber) than that of the observation lens  31   b  of the fluorescent light image capturing unit  31 B is disposed at a position closer to the air/water feeding nozzle  60  on the distal end surface of the distal end cover  24 , as shown in  FIG. 11 . As described above, the entire outer surface of the observation lens  31   a  is included in the spouting area A of the gas or liquid such as distilled water or air spouted out from the spouting port  60   a  of the air/water feeding nozzle  60 . 
     Thus, in the endoscope  2 , the observation lens  31   a  having a larger lens diameter (caliber) easily adhered with body fluid, filth or the like is closer to the air/water feeding nozzle  60 , and accordingly, cleanability of the observation lens  31   a  can be improved without being affected by decrease of spouting force and density of gas or liquid such as distilled water or air spouted out from the spouting port  60   a.    
     Note that as described above, the air/water feeding nozzle  60 , the observation lens  31   a  of the normal light image pickup unit  31 A, and the observation lens  31   b  of the fluorescent light image pickup unit  31 B are adjacently provided on a generally straight line on the distal end surface of the distal end cover  24  shown in  FIG. 12 , in the endoscope  2  of the present embodiment. Further, on the arrow line AR which is the spouting direction of gas or liquid such as distilled water or air to be spouted out from the spouting port  60   a  of the air/water feeding nozzle  60 , other components are not disposed on the distal end surface of the distal end cover  24 . 
     That is, on the arrow line AR, other components are not disposed on an outer circumferential side on the distal end surface of the distal end cover  24  from the observation lens  31   b  of the fluorescent light image pickup unit  31 B. 
     With such a configuration, the gas or liquid that cleaned the filth adhering on each of the observation lenses  31   a ,  31   b  flows toward an outer edge portion of the distal end cover  24  in the arrow line AR direction which is the spouting direction, without flowing to the other components. As a result, when the gas or liquid such as distilled water or air is spouted out from the air/water feeding nozzle  60 , the distal end surface of the distal end cover  24  of the endoscope  2  is surely cleaned. 
     Next, referring to  FIGS. 12 and 13 , dispositions of the two illumination lenses  25   a ,  25   b , the aperture portion  26  of the treatment instrument channel  19 , and the aperture portion  27  of the forward water-feeding channel  20  disposed on the distal end cover  24  are described in detail. 
     As described above, on the distal end surface of the distal end cover  24 , the two illumination lenses  25   a ,  25   b  are disposed at positions in the bending left/right direction to sandwich the observation lens  31   a  of the normal light image pickup unit  31 A disposed at the generally center of the surface, the aperture portion  26  of the treatment instrument channel  19  is disposed at a position on a lower left side of the observation lens  31   a , and the aperture portion  27  of the forward water-feeding channel  20  is disposed at a position on an upper right side of the observation lens  31   a.    
     Also, as shown in  FIG. 12 , respective entire hole surfaces of the aperture portion  26  of the treatment instrument channel  19  and the aperture portion  27  of the forward water-feeding channel  20  are disposed on the distal end surface of the distal end cover  24  which is outside the gas/liquid spouting area A which is an area in which gas or liquid such as distilled water or air is spouted out in a spreading manner. 
     In detail, as shown in  FIG. 13 , the aperture portion  26  of the treatment instrument channel  19  is disposed in an area B in the distal end surface of distal end cover  24 , which is an area on a lower side of the distal end surface of the distal end cover  24  bisected along the arrow line AR indicating the spouting direction of gas or liquid such as distilled water or air from the spouting port  60   a  of the air/water feeding nozzle  60 , and not including the spouting area A of the gas or liquid. 
     The aperture portion  27  of the forward water-feeding channel  20  is disposed in an area C on the distal end surface of the distal end cover  24 , which is an area on an upper side of the distal end surface of the distal end cover  24  bisected along the arrow line AR, and not including the spouting area A of the gas or liquid. 
     In other words, on the distal end surface of the distal end cover  24 , the aperture portions  26 ,  27  are respectively disposed at positions generally symmetric about the arrow line AR indicating the spouting direction of the gas or liquid such as distilled water or air. That is, the aperture portion  26 ,  27  are disposed on the distal end surface of the distal end cover  24  such that the center O 5  of the aperture portion  26  and the center O 6  of the aperture portion  27  are positioned apart from each other by a predetermined distance. 
     As described above, the endoscope  2  of the present embodiment can prevent the gas or liquid such as distilled water or air spouted out from the air/water feeding nozzle  60  from flowing into the aperture portions  26 ,  27 , because the aperture portion  26  of the treatment instrument channel  19  and the aperture portion  27  of the forward water-feeding channel  20  are disposed in an area outside the gas/liquid spouting area A by the air/water feeding nozzle  60  on the distal end surface of the distal end cover  24 . 
     This allows the gas or liquid such as distilled water or air spouted out from the air/water feeding nozzle  60  to be surely sprayed onto the observation lens  31   b  of the fluorescent light image pickup unit  31 B on a farther side. As a result, the observation lens  31   b  of the fluorescent light image pickup unit  31 B is surely and efficiently sprayed with the gas or liquid to be cleaned into a clean state, thus securing a good observation field of view. 
     Also, the aperture portion  26 ,  27  are disposed on the distal end surface of the distal end cover  24  such that the respective centers O 5 , O 6  are apart from each other by a predetermined distance. This allows the endoscope  2  to spout out a liquid toward a diseased part in the body cavity, without being affected by the suction force to the aperture portion  26 , when spouting out a liquid such as distilled water from the aperture portion  27  of the forward water-feeding channel  20  while performing sucking action from the aperture portion  26  through the treatment instrument channel  19 . That is, the endoscope  2  of the present embodiment is configured to prevent the spouting direction of the liquid spouted out from the aperture portion  27  from being disturbed by the sucking from the aperture portion  26 . 
     Incidentally, in the endoscope  2  of the present embodiment, the distal end cover  24  is provided on the distal end portion  15 . Referring to  FIGS. 2 to 4  and  FIGS. 14 and 15 , characteristics of the distal end cover  24  are described in more detail below.  FIG. 14  is a section view of the distal end part of the distal end portion provided with the distal end cover, cut along the XIV-XIV line of  FIG. 4 .  FIG. 15  is a section view of the distal end part of the distal end portion provided with the distal end cover, cut along the XV-XV line of  FIG. 4 . 
     As shown in  FIGS. 2 to 4 , on the distal end surface of the distal end cover  24 , there are three stepped portion  24   a  to  24   c  formed by circumferences of the two observation lenses  31   a ,  31   b  and each of the illumination lenses  25   a ,  25   b  in a convex shape toward the distal end side of the distal end surface. 
     As shown in  FIG. 4 , an observation-lens-side stepped portion (hereinafter simply referred to as stepped portion)  24   a  formed around the two observation lenses  31   a ,  31   b  is formed from the circumference of the observation lens  31   a  up to an outer edge portion of the distal end cover  24  in the gas/liquid spouting direction of the air/water feeding nozzle  60  in a manner including the circumference of the observation lens  31   b . That is, on the distal end surface of the distal end portion  15 , the stepped portion  24   a  provides a flat surface between the outer surfaces of the observation lenses  31   a ,  31   b  in the gas/liquid spouting direction of the air/water feeding nozzle  60 . 
     Meanwhile, illumination-lens-side stepped portions (hereinafter simply referred to as stepped portions)  24   b ,  24   c  respective formed around the illumination lenses  25   a ,  25   b  are formed from circumferences of the illumination lenses  25   a ,  25   b  up to the outer edge portion of the distal end cover  24 . 
     That is, the stepped portion  24   a  to  24   c  formed on the distal end cover  24  have surfaces separate from one another on respective circumferences of the two observation lens  31   a ,  31   b  and each of the two illumination lenses  25   a ,  25   b.    
     As shown in  FIG. 14 , the observation lenses  31   a ,  31   b  have outer surfaces that are generally in the same surface, i.e. at the same height on the distal end surface of the distal end cover  24 , as the outer surface of the stepped portion  24   a  of the distal end cover  24 . In other words, the observation lenses  31   a ,  31   b  and the stepped portion  24   a  oriented in the gas/liquid spouting direction of the air/water feeding nozzle  60  have outer surfaces which are generally at the same height on the distal end surface of the distal end cover  24 . 
     This causes gas or liquid such as distilled water or the air from the spouting port  60   a  of the air/water feeding nozzle  60  to pass over the outer surface of the observation lens  31   a , and efficiently flows from the outer surface of the stepped portion  24   a  between the observation lenses  31   a ,  31   b  to the outer surface of the observation lens  31   b.    
     As a result, the endoscope  2  of the present embodiment is configured such that, because no steps exist between the observation lenses  31   a ,  31   b , gas or liquid spouted out from the air/water feeding nozzle  60  smoothly flows to efficiently and surely passing the outer surface of the observation lens  31   b , thus flowing onto the outer edge portion of the distal end cover  24 . 
     Accordingly, by spraying gas or liquid from the spouting port  60   a  of the air/water feeding nozzle  60 , the endoscope  2  can bring in a clean state the outer surface of the observation lens  31   b  located farther than the air/water feeding nozzle  60 . 
     Further, on the distal end surface of the distal end cover  24 , the endoscope  2  has a step such that the outer surface of the distal end cover  24  on which the air/water feeding nozzle  60  is provided is lower by a predetermined length (height) L 1  relative to the outer surface of the stepped portion  24   a  of the distal end cover  24  formed around the observation lenses  31   a ,  31   b , as shown in  FIG. 14 . 
     This provides an effect of making it difficult for liquid such as distilled water from the spouting port  60   a  of the air/water feeding nozzle  60  sprayed onto the observation lenses  31   a ,  31   b  to stay on the outer surfaces of the observation lenses  31   a ,  31   b , that is, liquid drainability is improved. 
     Furthermore, as shown in  FIG. 15 , on the distal end surface of the distal end cover  24 , respective hole surfaces (outer surfaces of the distal end cover  24  on which the aperture portion  26 ,  27  are provided) of the aperture portion  26  of the treatment instrument channel  19  as a component and the aperture portion  27  of the forward water-feeding channel  20  are provided on a surface that is lower by a predetermined length (height) L 2  relative to the respective outer surfaces of the observation lenses  31   a ,  31   b  (only the observation lens  31   a  is shown in  FIG. 15 ) and the stepped portion  24   a . In other words, the respective hole surfaces of the aperture portions  26  and  27  are disposed on the distal end surface of the distal end portion  15  that is shifted by the predetermined length L 2  toward a proximal end side from the respective outer surfaces of the observation lens  31   a ,  31   b  and the stepped portion  24   a . Note that the length L 2  may be the same as the length L 1 . 
     As described above, the distal end cover  24  has a convex shape protruding in the height direction of the outer surface, with the independent stepped portion  24   a  having an outer surface in the same height as the outer surfaces of the observation lens  31   a ,  31   b . Note that, in the present embodiment, respective outer surfaces of the stepped portion  24   a  formed around the observation lenses  31   a ,  31   b  and the stepped portions  24   b ,  24   c  respectively formed around the illumination lenses  25   a ,  25   b  are formed in a plane of the same height, independent from one another. 
     In the endoscope  2  configured as described above, gas or liquid that has cleaned filth or the like adhered on the observation lenses  31   a ,  31   b  is prevented from flowing into the aperture portion  26  of the treatment instrument channel  19  and the aperture portion  27  of the forward water-feeding channel  20 , but flows toward the outer edge portion of the distal end cover  24  in the arrow line AR direction as the spouting direction. As a result, the distal end surface of the distal end cover  24  of the endoscope  2  is surely cleaned when sprayed with gas or liquid such as air or distilled water is spouted out from the air/water feeding nozzle  60 . 
     In the endoscope  2  of the present embodiment having the above-mentioned various characteristics (effects), the air/water feeding nozzle  60  provided on the distal end surface of the distal end cover  24 , the observation lens  31   a  of the normal light image pickup unit  31 A, and the observation lens  31   b  of the fluorescent light image capturing unit  31 B are located on a generally straight line, and further the distal end cover  24  is provided with the stepped portion  24   a  having an outer surface in generally the same surface as the respective outer surfaces of the observation lenses  31   a ,  31   b . Thus, by means of the single air/water feeding nozzle  60 , the outer surfaces of the observation lenses  31   a ,  31   b  are sprayed with gas or liquid to be set in a clean state, thus secured of good observation field of view. 
     Note that the special light observation may be not only the fluorescent light observation but also that using a magnification optical system with a magnification of histological observation level (preferably not less than 100 times level) such as for cells and gland structure. 
     Furthermore, the present invention is not limited only to the above-described embodiment, but may be variously modified without departing from the spirit and scope of the invention.