Patent Publication Number: US-2017367569-A1

Title: Illumination apparatus, endoscope and endoscope system

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a Continuation Application of PCT Application No. PCT/JP2015/062425, filed Apr. 23, 2015, the entire contents of all of which are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an illumination apparatus, an endoscope and an endoscope system. 
     2. Description of the Related Art 
     For example, Jpn. Pat. Appin. KOKAI Publication No. 2011-248022 discloses an illumination apparatus which includes a single optical fiber. The illumination apparatus includes an ellipsoidal diffusion body which serves as a light converter disposed on a distal end surface of the optical fiber, in order to convert a laser beam, which is primary light guided by the optical fiber, to illumination light which is irradiated in a wide range. 
     BRIEF SUMMARY OF THE INVENTION 
     According to one embodiment of the invention, an illumination apparatus includes a light source module configured to emit primary light; a light guide configured to guide the primary light emitted from the light source module; 
     a light converter disposed on a distal end surface of the light guide, the light converter being configured to emit illumination light, which is generated by converting optical characteristics of the primary light that is guided by the light guide, in a forward direction which is on the light converter side of the distal end surface, and in a backward direction which is on the light guide side of the distal end surface; a light collector configured to collect backward illumination light, which is the illumination light emitted backward from the light converter, into the light guide, such that the backward illumination light is guided backward by the light guide; and a heat exhauster configured to convert the backward illumination light, which is guided by the light guide, to heat, and to exhaust the heat. 
     Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter. 
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention, and together with the general description given above and the detailed description of the embodiments given below, serve to explain the principles of the invention. 
       FIG. 1A  is a schematic view of an illumination apparatus according to a first embodiment of the present invention. 
       FIG. 1B  is a view illustrating the configuration of a distal end portion of a light guide and a light converter. 
       FIG. 1C  is a view illustrating the configuration of a light source portion and a heat exhauster. 
       FIG. 2A  is a view for explaining Mie scattering. 
       FIG. 2B  is a view for explaining Rayleigh scattering. 
       FIG. 3A  is a view illustrating the configuration of a distal end surface of a light guide according to Modification 1 of the first embodiment. 
       FIG. 3B  is a view illustrating the configuration of a distal end surface of a light guide according to Modification 2 of the first embodiment. 
       FIG. 4A  is a view illustrating the configuration of a distal end portion of a light guide and a light converter according to a second embodiment of the present invention. 
       FIG. 4B  is a view illustrating the configuration of a light source portion and a heat exhauster according to the second embodiment. 
       FIG. 5A  is a view illustrating the configuration of a distal end portion of a light guide and a light converter according to a third embodiment of the present invention. 
       FIG. 5B  is a view illustrating a modification of the configuration of the distal end portion of the light guide and the light converter. 
       FIG. 5C  is a side view of the configuration illustrated in  FIG. 5B . 
       FIG. 5D  is a view illustrating the configuration of a light source portion and a heat exhauster according to the third embodiment. 
       FIG. 6A  is a view illustrating a fourth embodiment of the present invention,  FIG. 6A  being a schematic perspective view of an endoscope system including the illumination apparatus according to the first embodiment. 
       FIG. 6B  is a view illustrating the configuration of the endoscope system illustrated in  FIG. 6A . 
       FIG. 7A  is a view illustrating Modification 1 of the fourth embodiment of the invention,  FIG. 7A  being a schematic perspective view of an endoscope system including an endoscope in which the illumination apparatus according to the first embodiment is mounted. 
       FIG. 7B  is a view illustrating the configuration of the endoscope system illustrated in  FIG. 7A . 
       FIG. 8A  is a view illustrating Modification 2 of the fourth embodiment of the invention,  FIG. 8A  being a schematic perspective view of an endoscope system including an endoscope in which the illumination apparatus according to the first embodiment is mounted. 
       FIG. 8B  is a view illustrating the configuration of the endoscope system illustrated in  FIG. 8A . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Incidentally, in some of the drawings, depiction of some members is omitted for the purpose of clearer illustration, such as omission of depiction of diffusion particles  41  in  FIG. 1A . 
     First Embodiment 
     [Configuration] 
     A first embodiment will be described with reference to  FIG. 1A ,  FIG. 1B ,  FIG. 1C ,  FIG. 2A , and  FIG. 2B . 
     [Configuration 1 of Illumination Apparatus  10 ] 
     As illustrated in  FIG. 1A ,  FIG. 1B  and  FIG. 1C , an illumination apparatus  10  includes a light source module  20  which emits primary light PL such as a laser beam; a light guide (light guide member)  30  which guides the primary light PL which is emitted from the light source module  20 ; and a light converter (light conversion portion)  40  which is disposed on a distal end surface  31   a  of the light guide  30 . 
     [Light Source Module  20 ] 
     As illustrated in  FIG. 1C , the light source module  20  includes a light source  21  which emits the primary light PL; and a light focusing portion  23  which focuses the primary light PL, which is emitted from the light source  21 , onto the light guide  30 . 
     As illustrated in  FIG. 1C , the light focusing portion  23  includes a light focusing lens which focuses the primary light PL onto a proximal end surface  31   b  of the light guide  30 . The proximal end surface  31   b  is a surface on a side opposite to the distal end surface  31   a.    
     [Light Guide  30 ] 
     The light guide  30  as illustrated in  FIG. 1A ,  FIG. 1B  and  FIG. 1C  includes an optical fiber. The light guide  30  is preferable that the light guide  30  is, for example, a multi-mode optical fiber which guides a plurality of modes of the primary light PL and backward illumination light BL (to be described later). The optical fiber may be a single-mode optical fiber. The material of the light guide  30  is, for instance, silica glass, plastic, or resin. The light guide  30  is a bendable rod-like member. The distal end surface  31   a  is perpendicular to a center axis of the light guide  30 , and a side surface of the light guide  30  is parallel to the center axis of the light guide  30 . The distal end surface  31   a  may be formed by cutting the light guide  30  by a general cleaver, or may be formed by polishing the light guide  30  after cleaving. The distal end surface  31   a  is smooth. It is preferable that the NA of the light guide  30  is high. Specifically, the NA is 0.22 or more. 
     As illustrated in  FIG. 1B  and  FIG. 1C , the light guide  30  includes a core  33  which guides the primary light PL and the backward illumination light BL, and a cladding  35  which is provided on an outer periphery of the core  33  and has a refractive index that is lower than the refractive index of the core  33 . The cladding  35  has a function of confining the primary light PL in the core  33 . A distal end surface of the core  33 , which is included in the distal end surface  31   a,  is a planar surface. The refractive index of the core  33  is substantially equal to or higher than the refractive index of a contact part of the light converter  40 , the contact part being in contact with the distal end surface of the core  33 . 
     The distal end surface  31   a  includes the distal end surface of the core  33 , and a distal end surface of the cladding  35 , which is flush with the distal end surface of the core  33 . The distal end surface  31   a,  the distal end surface of the core  33 , and the distal end surface of the cladding  35  are planar. 
     [Light Converter  40 ] 
     The light converter  40  of the present embodiment, as illustrated in  FIG. 1A ,  FIG. 1B  and  FIG. 1C , emits illumination light L, which is generated by converting optical characteristics of the primary light PL that is guided by the light guide  30 , in a forward direction which is on the light converter  40  side of the distal end surface  31   a,  and in a backward direction which is on the light guide  30  side of the distal end surface  31   a.  The light converter  40  functions, for example, as a light distribution converter (light distribution conversion portion) which converts a light distribution of the primary light PL which is emitted from the light guide  30 . Thus, the light converter  40  includes one or more diffusion particles  41  which diffuse the primary light PL that is emitted from the core  33 , and an enclosing member  43  which encloses the diffusion particles  41  together in the state in which the diffusion particles  41  are dispersed. The diffusion particles  41  are dispersed in the inside of the enclosing member  43 , and are sealed by the enclosing member  43 . The light converter  40 , which includes the distal end surface  31   a,  functions as a diffusion member. 
     The diffusion particles  41  are fine particles formed of a metal or a metal compound. Such diffusion particles  41  are, for instance, alumina or titanium oxide. The grain size of the diffusion particles  41  is several μm. Incidentally, fluorescent particles may be used in place of the diffusion particles  41 . The fluorescent particles absorb the primary light PL, and generate fluorescence of a wavelength which is different from the wavelength of the primary light PL. However, since the generated fluorescence travels also in directions other than the forward direction, it can be said that the fluorescent particles are diffusion particles in a broad sense. 
     The absorptance of the diffusion particles  41  with respect to the primary light PL is preferably, for example, 20% or less, and is more preferably 10% or less. Thereby, for example, when the light converter  40  functions as the light distribution converter, the diffusion particles  41  can absorb a small light amount, and can efficiently convert the primary light PL to illumination light L. Since the amount of absorbed primary light PL decreases, heat generation can be reduced. The distal end portion of the light guide  30  and the light converter  40 , which are a distal end portion of the illumination apparatus  10 , are built in the distal end portion of an insertion module  121  which is provided in an endoscope  120  (see  FIG. 6A  and  FIG. 6B ). If the temperature of the light converter  40  rises, the temperature of the distal end portion of the insertion module  121  rises due to heat. In some cases, the heat of the distal end portion affects a conduit (conduit portion) through which the insertion module  121  is inserted. However, in the present embodiment, since the rise in temperature of the light converter  40  is suppressed, such concern can be reduced. For example, the conduit is a lumen of a patient. 
     The refractive index of the diffusion particles  41  is different from the refractive index of the enclosing member  43 . For example, it is preferable that the refractive index of the diffusion particles  41  is higher than the refractive index of the enclosing member  43 , and is 1.5 or more. Thereby, the diffusion particles  41  can enhance the diffusivity of the primary light PL. 
     The light distribution angle of the light converter  40  is controlled by, for example, the density of diffusion particles  41  relative to the enclosing member  43 , the thickness of the light converter  40 , etc. 
     The enclosing member  43  is formed of a member which transmits the primary light PL. Such enclosing member  43  is, for example, a transparent silicone resin or a transparent epoxy resin. The enclosing member  43  has a high transmittance with respect to the primary light PL. The enclosing member  43  seals the diffusion particles  41 . 
     As illustrated in  FIG. 1B , the light converter  40  is formed, for example, in a dome shape. In a concrete formation method, the enclosing member  43  prior to curing, which encloses the diffusion particles  41 , is coated on the distal end surface  31   a.  The enclosing member  43  is formed in a dome shape due to a surface tension of the enclosing member  43 . By the amount of coating being controlled, the curvature of the dome is controlled. By the enclosing member  43  being cured, the light converter  40  is formed. It is preferable that, in the cross section in the optical axis direction of the light guide  30 , the central angle of the outer arc of the light converter  40  having the dome shape is 180 degrees or less. Thereby, the light converter  40  is prevented from flowing out to the side surface of the light guide  30  from the distal end surface  31   a.  The optical axis means the center axis of the illumination light L which is emitted in the forward direction from the distal end surface  31   a.    
     [Diffusion Phenomenon] 
     Here, referring to  FIG. 2A  and  FIG. 2B , a diffusion phenomenon will be described. In order to make the description simpler, the behavior of the primary light PL at a time when the primary light PL is incident on one diffusion particle  41  will be illustrated. 
     Diffusion phenomena are generally classified into Mie scattering illustrated in  FIG. 2A , and Rayleigh scattering illustrated in  FIG. 2B . 
     The Mie scattering illustrated in  FIG. 2A  occurs when the diameter of the diffusion particle  41  is substantially equal to the wavelength of the primary light PL. In the Mie scattering, a forward scattering component FS, which is indicative of a component of forward scattering of the primary light PL, is large, and a backward scattering component BS, which is indicative of a component of backward scattering of the primary light PL, is small. 
     The Rayleigh scattering illustrated in  FIG. 2B  occurs when the diameter of the diffusion particle  41  is about 1/10 of the wavelength of the primary light PL. In the Rayleigh scattering, the forward scattering component FS is substantially equal to the backward scattering component BS. 
     If consideration is given to the luminance of the forward illumination light FL which is emitted in the forward direction from the distal end surface  31   a,  it is preferable to utilize the Mie scattering in which the forward scattering component FS is greater than the backward scattering component BS. On the other hand, when primary light PL of multiple colors is scattered, the wavelength dependency of scattering needs to be considered. It is generally thought that the wavelength dependency of Mie scattering is greater than the wavelength dependency of Rayleigh scattering. In order to eliminate non-uniformity in color of the forward illumination light FL, the Rayleigh scattering is preferable. 
     In this manner, the setting of the diameter of the diffusion particle  41  is selected in accordance with the purpose of use. In the present embodiment, it is assumed that the illumination apparatus  10  uses Mie scattering. Thus, the diameter of the diffusion particle  41  is, for example, about 1/10 or more of the wavelength of the primary light PL. Specifically, when the wavelength of the primary light PL, which is used as the illumination light L, is, for example, about 400 nm to about 800 nm, the diameter of the diffusion particle  41  is 40 nm or more. 
     In the description thus far, the diffusion phenomenon of one diffusion particle  41  has been described. In the light converter  40  of the present embodiment, many diffusion particles  41  are enclosed in the enclosing member  43 . The diffusion phenomenon of such light converter  40  is substantially the same as the diffusion phenomenon of one diffusion particle  41 . 
     [Configuration 2 of Illumination Apparatus  10 ] 
     As illustrated in  FIG. 1B , the illumination apparatus  10  further includes a light collector (light collect portion)  50  which collects backward illumination light BL into the light guide  30 , such that the illumination light emitted backward (hereinafter referred to as backward illumination light BL) from the light converter  40  is guided backward by the light guide  30 . The light collector  50  collects the backward illumination light BL into the light guide  30  which is provided behind the light collection portion  50 . The light collector  50  includes the distal end surface of the core  33  in the distal end surface  31   a  and the light converter  40 . 
     The light guide  30  has a reception angle which is defined by the NA. The backward illumination light BL, which is made incident on the core  33  by the light collector  50  at an angle of not greater than the reception angle, is guided by the light guide  30  toward the light source  21  while being repeatedly reflected in the inside of the light guide  30 . Specifically, the backward illumination light BL is guided in a direction reverse to the direction of travel of the primary light PL, and reversely travels in the light guide  30  in the direction reverse to the direction of the travel of the primary light PL. 
     In the meantime, the backward illumination light BL, which is made incident on the core  33  at an angle of greater than the reception angle, is unable to reflect at the interface between the core  33  and cladding  35 , and leaks out from the light guide  30  to the outside. Thus, in order to guide the backward illumination light BL up to the light source  21 , it is preferable that the NA of the light guide  30  is as large as possible. Specifically, if the NA of the light guide  30  is greater than the incidence angle of the backward illumination light EL on the core  33 , the entire backward illumination light BL can be received in the light guide  30 . 
     In order to make a greater amount of backward illumination light EL incident on the core  33 , it is preferable that the cross-sectional area of the core  33  is large and the cross-sectional area of the cladding  35  is small. For example, the diameter of the cladding  35  is not greater than 1.1 times the diameter of the core  33 . 
     It is preferable that the refractive index of the core  33  is equal to or greater than the refractive index of the enclosing member  43 . The material of the core  33  is, for example, silica glass, and the refractive index of the core  33  is, for example, 1.46. The material of the enclosing member  43  is, for example, silicone resin, and the refractive index of the enclosing member  43  is, for example, 1.5. 
     For example, the diameter of the core  33  is 100 μm, the diameter of the cladding  35  is 110 μm, and the NA is 0.22 or more. The optical fiber is a multi-mode optical fiber which guides a plurality of modes of the primary light PL and backward illumination light BL. The optical fiber has such an NA that the optical fiber receives 20% or more of the backward illumination light BL which is emitted backward by the light converter  40 . 
     [Configuration 3 of Illumination Apparatus  10 ] 
     As illustrated in  FIG. 1C , the illumination apparatus  10  further includes a heat exhauster (heat exhaust portion)  60 . which converts the backward illumination light BL, that is guided by the light guide  30 , to heat H, and which exhausts the heat H. For example, when the light converter  40  is built in the distal end portion (see  FIG. 6A  and  FIG. 6B ) of the insertion module  121 , as described above, the heat exhauster  60  is provided in the light source  21  of the light source module  20  to which a universal cord  125  of the endoscope  120  is connected. In this manner, the heat exhauster  60  is provided apart from the light converter  40  and the position of diffusion. The heat exhauster  60  is provided on a side opposite to the light converter  40  via the light guide  30 . 
     As illustrated in  FIG. 1C , the heat exhauster  60  includes a heat converter (heat conversion portion)  61  which absorbs the backward illumination light BL and converts the absorbed backward illumination light BL to heat H; and a heat radiator (heat radiation portion)  63  which radiates the heat H. 
     As illustrated in  FIG. 1C , in the light source  21  on which the backward illumination light BL, after guided by the light guide  30 , is irradiated by the light focusing portion  23 , the heat converter  61  is a light emission element of the light source  21 , which is included in the light source module  20  and emits the primary light PL. The heat converter  61  is thermally connected to the heat radiator  63  via a base plate  71  and a Peltier element  73 . The heat H, which is generated from the light source  21  in accordance with the emission of the primary light PL, and the heat H, which is generated from the light source  21  by the irradiation of the backward illumination light BL, are transferred to the heat radiator  63  via the base plate  71  and Peltier element  73 . 
     The heat radiator  63  radiates heat to the outside. Incidentally, as illustrated in  FIG. 7B , when light sources  21 V and  21 B (to be described later) are provided in the inside of the endoscope  120 , the heat exhauster  60 , the depiction of which is omitted in  FIG. 7B , is also provided in the inside of the endoscope  120 . In this case, the “outside” means an atmosphere within the endoscope  120 . 
     The temperature of the heat conversion member  61  is measured by a temperature measuring sensor (temperature measuring portion)  75  which is mounted on the base plate  71 . The temperature measuring sensor  75  includes, for example, a thermistor. If the heat conversion member  61  is irradiated with the backward illumination light BL, there is concern that the operation of the heat converter  61  becomes unstable. As a result, there is concern that the emission of the primary light PL becomes unstable. By the temperature measuring sensor  75  measuring the temperature of the heat converter  61 , heat transfer to the Peltier element  73  is properly performed for the heat converter  61 , and the operation of the heat converter  61  is stabilized. 
     [Function] 
     As illustrated in  FIG. 1C , the primary light PL is emitted from the light source  21  and is focused on the light guide  30  by the light focusing portion  23 . The primary light PL is guided by the light guide  30 , and travels to the light converter  40 . As illustrated in  FIG. 1B , the light converter  40  diffuses the primary light PL, and the forward illumination light FL and backward illumination light BL are generated. The forward illumination light FL irradiates a to-be-illuminated portion. 
     As illustrated in  FIG. 1B , the backward illumination light BL is collected into the core  33  by the light collector  50 . Thus, when the primary light PL is guided by the light guide  30  and is then diffused, the backward illumination light BL is exactly made incident on the light guide  30 . Since the backward illumination light BL is neither irradiated on, nor absorbed by, other members near the light converter  40 , a temperature rise of the distal end portion of the insertion module  121 , which includes these other members, can be suppressed. Accordingly, when the insertion module  121  is inserted in, for example, a conduit, even if the distal end portion comes indirect contact with the conduit, there is no concern that the conduit is damaged by heat. In this manner, in the present embodiment, since the temperature rise of other members near the light converter  40  is suppressed, the influence on the conduit by the heat can be reduced. 
     As illustrated in  FIG. 1C , the backward illumination light BL is guided by the light guide  30 , and irradiates the light source  21  via the light focusing portion  23 . At this time, the backward illumination light BL is guided in the direction reverse to the direction of the travel of the primary light PL, reversely travels in the light guide  30  in the direction reverse to the direction of the travel of the primary light PL, and returns to the light source  21 . The light emission element of the light source  21 , which is the heat converter  61 , absorbs the backward illumination light BL and converts the absorbed backward illumination light BL to heat H. This heat H is radiated to the outside by the heat radiator  63  via the base plate  71  and Peltier element  73 . This “outside” means, for example, an outside environment of the endoscope  120 , or an atmosphere within the endoscope  120 . 
     The heat converter  61  and heat radiator  63  convert light to heat H at a location apart from the light converter  40 , and radiates the heat H at a location apart from the light converter  40 . Thus, in the present embodiment, the heat generation of the distal end portion of the insertion module  121  at a time of illumination, in which the light converter  40  is provided, can be suppressed to a minimum. 
     [Advantageous Effects] 
     As described above, in the present embodiment, when the light is guided by the light guide  30  and is then diffused, the backward illumination light BL is exactly made incident on the light guide  30 , without the backward illumination light BL being absorbed by other members near the light converter  40 . In addition, the light can be converted to the heat H at a location apart from the light converter  40 , by the light guide  30  and heat exhauster  60 . Thereby, the heat generation of the distal end portion of the insertion module  121  at a time of illumination, in which the light converter  40  is provided, can be suppressed to a minimum. 
     The light guide  30  guides the primary light PL and backward illumination light BL. Thus, compared to a case in which a light guide  30  for primary light PL and a light guide  30  for backward illumination light BL are provided separately from each other, the number of structural parts can be reduced and the configuration can be simplified. When the illumination apparatus  10  is mounted in the endoscope  120 , a contribution can be made to the reduction in diameter of the insertion module  121 . 
     The heat exhauster  60  converts the backward illumination light BL, which is guided by the light guide  30 , to heat H, and exhausts the heat H. This heat exhauster  60  is provided on the side opposite to the light converter  40  via the light guide  30 . Hence, the light can be converted to the heat H at a location apart from the light converter  40 , and the heat H can be radiated at a location apart from the light converter  40 . 
     The heat converter  61  is a light emission element of the light source  21 . Thus, compared to a case in which a heat conversion member  61 , which is different from the light emission element, is provided as one member, the number of structural parts can be reduced and the configuration can be simplified. 
     In the meantime, when the light guide  30  is provided in the inside of the insertion module  121  which has a diameter of, for example, ten-odd mm, the light guide  30  guides 5% or more of the backward illumination light BL which is emitted backward by the light converter  40 . In addition, the heat exhauster  60  converts 5% or more of the backward illumination light BL, which is emitted backward by the light converter  40 , to the heat H. Thereby, the temperature of the distal end portion of the insertion module  121  can be prevented from rising up to a dangerous range. 
     When the light guide  30  is provided in the inside of the insertion module  121  which has a diameter of, for example, 5 mm to 10 mm, the light guide  30  guides 10% or more of the backward illumination light BL which is emitted backward by the light converter  40 . In addition, the heat exhauster  60  converts 10% or more of the backward illumination light BL, which is emitted backward by the light converter  40 , to the heat H. Thereby, the temperature of the distal end portion of the insertion module  121  can be prevented from rising up to a dangerous range. 
     When the light guide  30  is provided in the inside of the insertion module  121  which has a diameter of, for example, 5 mm or less, the light guide  30  guides 20% or more of the backward illumination light BL which is emitted backward by the light converter  40 . In addition, the heat exhauster  60  converts 20% or more of the backward illumination light BL, which is emitted backward by the light converter  40 , to the heat H. Thereby, the temperature of the distal end portion of the insertion module  121  can be prevented from rising up to a dangerous range. 
     Incidentally, the distal end surface  31   a  of the light guide  30  does not need to be limited to a planar surface. Hereinafter, configurations of the distal end surface  31   a  will be described as Modifications 1 and 2. 
     [Modification 1] 
     As illustrated in  FIG. 3A , the light guide  30  includes a core  33  which guides the primary light PL and backward illumination light BL, and a cladding  35  which is provided on an outer periphery of the core  33  and has a refractive index that is lower than the refractive index of the core  33 . In the light collection portion  50 , the distal end surface of the core  33 , which is included in the distal end surface  31   a,  is a concave surface. The refractive index of the core  33  is substantially equal to or lower than the refractive index of a contact part of the light converter  40 , the contact part being in contact with the distal end surface of the core  33 . The distal end surface of the cladding  35  may include a concave surface which is, for example, continuous with the core  33 , or may be a planar surface. 
     Thereby, a lens effect occurs at the interface between the core  33  and the light converter  40 , and the light distribution of the backward illumination light BL, which is incident on the core  33 , can be narrowed. As a result, compared to the first embodiment, a greater amount of light can be made fall within the NA of the light guide  30 , and the backward illumination light BL can efficiently be collected. 
     [Modification 2] 
     As illustrated in  FIG. 3B , the light guide  30  includes a core  33  which guides the primary light PL and backward illumination light BL, and a cladding  35  which is provided on an outer periphery of the core  33  and has a refractive index that is lower than the refractive index of the core  33 . In the light collection portion  50 , the distal end surface of the core  33 , which is included in the distal end surface  31   a,  is a convex surface. The refractive index of the core  33  is substantially equal to or higher than the refractive index of a contact part of the light converter  40 , the contact part being in contact with the distal end surface of the core  33 . The distal end surface of the cladding  35  may include a convex surface which is, for example, continuous with the core  33 , or may be a planar surface. 
     Thereby, Modification 2 can obtain the same advantageous effects as Modification 1. 
     Second Embodiment 
     Hereinafter, referring to  FIG. 4A  and  FIG. 4B , only the points different from the first embodiment will be described. 
     As illustrated in  FIG. 4A , in the light guide  30 , the optical fiber is a double-cladding fiber including a core  33 , a first cladding  35   a  which is provided on an outer periphery of the core  33  and has a refractive index that is lower than the refractive index of the core  33 , and a second cladding  35   b  which is provided on an outer periphery of the first cladding  35   a  and has a refractive index that is lower than the refractive index of the first cladding  35   a.  The light collector  50  includes a distal end surface of the core  33  and a distal end surface of the first cladding  35   a  in the distal end surface  31   a,  and includes the light converter  40 . 
     As illustrated in  FIG. 4A , when the light guide  30  guides primary light PL which is emitted from the light source  21 , the core  33  guides the primary light PL. When the light guide  30  guides backward illumination light BL, the core  33  and first cladding  35   a  guide the backward illumination light BL. 
     When the optical fiber is the double-cladding fiber, backward illumination light BL with a high NA, which failed to be reflected at the interface between the core  33  and first cladding  35   a,  is exactly reflected at the interface between the first cladding  35   a  and second cladding  35   b,  and is exactly confined in the optical fiber. In addition, the backward illumination light BL is exactly guided to the heat exhauster  60 . Thus, the heat generation of the distal end portion of the insertion module  121 , in which the light converter  40  is provided, can be suppressed. 
     As illustrated in  FIG. 4B , the heat exhauster  60  further includes an additional heat converter (additional heat conversion portion)  65  which is disposed on the outside of the optical path of the primary light PL. The additional heat converter  65  includes a hole (hole portion)  65   a,  through which the primary light PL can pass, and has a cylindrical shape. A part of the additional heat converter  65  is directly attached to the heat radiator  63 , such that the hole  65   a  is disposed between the light focusing portion  23  and the proximal end surface  31   b  of the light guide  30  in the direction of travel of the primary light PL, and that the primary light PL passes through the hole  65   a.  The additional heat converter  65  is irradiated with the backward illumination light BL which is emitted from the core  33  and first cladding  35   a.  The additional heat converter  65  is formed of a member which has a high heat conductivity, and has a surface coated with a light absorbing film. The additional heat converter  65  is formed of, for example, aluminum or brass. 
     In the present embodiment, the light emission element, which is the heat converter  61 , and the additional heat converter  65  are provided, and these components convert the backward illumination light BL to the heat H in a sharing manner. Thus, the heat generation of the distal end portion of the insertion module  121 , in which the light converter  40  is provided, can be suppressed, the temperature rise of the light source  21  can be suppressed, and the light source  21  can stably be driven. 
     The large/small relationship of the NA will be described. As regards the NA of the primary light PL, the NA of the backward illumination light BL which is emitted from the core  33 , and the NA of the backward illumination light BL which is emitted from the first cladding  35   a,  it is assumed that the NA of the primary light PL is lowest, the NA of the backward illumination light BL, which is emitted from the core  33 , is second highest, and the NA of the backward illumination light BL, which is emitted from the first cladding  35   a,  is highest. In accordance with this, the size of the hole  65   a  is adjusted. Specifically, if the hole  65  has such a size as to pass most of the primary light PL, the backward illumination light BL, which is emitted from the core  33  and first cladding  35   a,  can irradiate the additional heat converter  65 , and the backward illumination light BL can be converted to the heat H by the additional heat converter  65 . Thereby, the heat generation of the distal end portion of the insertion module  121 , in which the light converter  40  is provided, can be suppressed, the temperature rise of the light source  21  can be suppressed, and the light source  21  can stably be driven since the light source  21  is not irradiated with the backward illumination light BL. 
     In the meantime, as illustrated in  FIG. 4A , a surface  40   a  of the light converter  40  may be formed to have asperities. In order to form asperities, the diffusion particles  41  may be exposed to the surface  40   a  of the light converter  40  by adjusting the density of the diffusion particles  41 , or the surface of the enclosing member  43  may be formed to have asperities. Thereby, the reflection at an interface between the surface of the light converter  40  and external air can be reduced. 
     Third Embodiment 
     Hereinafter, referring to  FIG. 5A ,  FIG. 5B ,  FIG. 5C  and  FIG. 5D , only the points different from the first and second embodiments will be described. 
     As illustrated in  FIG. 5A , the optical fiber includes a core  33 , a cladding  35  which is provided on an outer periphery of the core  33  and has a refractive index that is lower than the refractive index of the core  33 , and a reflection film  37  which is provided on an outer periphery of the cladding  35  and is configured to reflect the backward illumination light BL, which is emitted from the cladding  35 , toward the cladding  35 . The light collector  50  includes a distal end surface of the core  33  and a distal end surface of the cladding  35  in the distal end surface  31   a,  and includes the light converter  40 . 
     The reflection film  37  is formed of a member which has a high reflectance with respect to the wavelength of the backward illumination light BL. Such reflection film  37  is formed of, for example, gold, silver, aluminum, or nickel. The reflection film  37  is provided, for example, over the entire circumference of the cladding  35 , and is continuous over the entire peripheral edge of the distal end surface  31   a  which is a part where the optical fiber is connected to the light converter  40 . For example, in the axial direction of the optical fiber, the reflection film  37  is provided from the distal end surface  31   a,  which is the part where the optical fiber is connected to the light converter  40 , to the proximal end surface  31   b.  In this manner, the reflection film  37  is provided on the entirety of the optical fiber. When this reflection film  37  is provided, backward illumination light BL with a high NA, which failed to be reflected at the interface between the core  33  and cladding  35 , is exactly reflected by the reflection film  37 , and is exactly confined in the optical fiber. In addition, the backward illumination light BL is exactly guided to the heat exhauster  60 . Thus, the heat generation of the distal end portion of the insertion module  121 , in which the light converter  40  is provided, can be suppressed. 
     In the meantime, as illustrated in  FIG. 5B  and  FIG. 5C , the reflection film  37  may be provided on only a part of the optical fiber. 
     The reflection film  37  is provided, for example, over the entire circumference of the cladding  35 , and is continuous over the entire peripheral edge of the distal end surface  31   a  which is a part where the optical fiber is connected to the light converter  40 . In the axial direction of the optical fiber, the reflection film  37  is provided over only a predetermined length from the distal end surface  31   a  toward the proximal end surface  31   b.  In the vicinity of the light converter  40 , the backward illumination light BL is confined in the optical fiber by the reflection film  37 , and leaks out from the optical fiber at a location apart from the light converter  40 . Thus, the backward illumination light BL can be converted to heat at a location apart from the light converter  40 . In addition, the heat generation of the distal end portion of the insertion module  121 , in which the light converter  40  is provided, can be suppressed. 
     As illustrated in  FIG. 5C , the reflection film  37  is further provided only partly in the circumferential direction of the optical fiber, between the location apart by the above-described predetermined length and the proximal end surface  31   b.  The reflection film  37  does not reach the proximal end surface  31   b,  and is further provided over a predetermined length from the location apart by the above-described predetermined length. In this case, locations where the backward illumination light BL leaks from the optical fiber can be distributed, and local heat generation can be avoided. In this case, the reflection film  37  may be provided linearly along the axial direction of the optical fiber, or may be provided in a curved shape. This reflection film  37  may be provided up to the proximal end surface  31   b.    
     As illustrated in  FIG. 5D , a heat converter (heat conversion portion)  61   a  is disposed on an extension line of the optical axis of the light guide  30 . The optical axis means, for example, the center axis of the backward illumination light BL which is emitted from the proximal end surface  31   b.  This heat converter  61   a  is additionally provided, separately from the light emission element of the light source  21 , which is the heat converter  61 . The heat converter  61   a  is thermally connected to a heat radiator (heat radiation portion)  63   a.  The heat radiator  63   a  radiates heat to the outside. This “outside” means, for example, an outside environment of the endoscope  120 , or an atmosphere within the endoscope  120 . 
     The light emission element of the light source  21 , which is disposed in the light source module  20  and emits the primary light PL, is disposed in a position different from a position on the extension line of the optical axis. The light emission element is inclined to the optical axis, such that the primary light PL is incident on the light guide  30  within the NA of the optical fiber, with an inclination to the light guide  30 . 
     Thus, the heat generation of the distal end portion of the insertion module  121 , in which the light converter  40  is provided, can be suppressed, the temperature rise of the light source  21  can be suppressed, and the light source  21  can stably be driven. 
     [Others] 
     The double-cladding fiber of the second embodiment can be combined with the configurations of the first and third embodiments and the configurations of Modifications 1 and 2 of the first embodiment. 
     The additional heat converter  65  of the second embodiment can be combined with the configurations of the first and third embodiments and the configurations of Modifications 1 and 2 of the first embodiment. 
     The reflection film  37  of the third embodiment can be combined with the configurations of the first and second embodiments and the configurations of Modifications 1 and 2 of the first embodiment. 
     The configuration of the third embodiment, in which the light emission element of the light source  21  is disposed in a position different from a position on the extension line of the optical axis, can be combined with the configurations of the first and second embodiments and the configurations of Modifications 1 and 2 of the first embodiment. 
     Fourth Embodiment 
     Referring to  FIG. 6A  and  FIG. 6B , a description is given of an endoscope system  110  including the illumination apparatus  10  of the first embodiment. Incidentally, in the present embodiment, although the illumination apparatus  10  of the first embodiment is, by way of example, mounted in the endoscope system  110 , the restriction to this is unnecessary. The illumination apparatus  10  of the other embodiments may be mounted. In the present embodiment, for the purpose of clearer illustration, the depiction of the heat exhauster  60 , base plate  71 , Peltier element  73  and temperature measuring sensor  75  is omitted. 
     [Endoscope System  110 ] 
     An endoscope system  110  as illustrated in  FIG. 6A  is installed, for example, in an examination room or an operating room. The endoscope system  110  includes an endoscope  120  which captures an image of, for example, an inside of a conduit (conduit portion) such as a lumen of a patient or the like, and an image processor (image processing apparatus)  130  which processes the image of the inside of the conduit, the image being captured by an imager (imaging unit (for example, CCD, CMOS), not shown) of the endoscope  120 . The endoscope system  110  further includes a display (display portion)  140  which is connected to the image processor  130  and displays the image which was processed by the image processor  130 , and a light source module  20  which emits primary light PL for illumination light L that is emitted from the endoscope  120 . The display  140  has a monitor, for example. 
     The endoscope  120  as illustrated in  FIG. 6A  functions, for example, as an insertion apparatus which is inserted into the conduit. The endoscope  120  may be a forward-viewing endoscope  120  or a side-viewing endoscope  120 . 
     The endoscope  120  of the present embodiment is described as being, for example, an endoscope  120  for medical use, but the restriction to this is unnecessary. The endoscope  120  may also be an endoscope  120  for industrial use, which is inserted in a conduit of an industrial product, such as a pipe, or an insertion instrument, such as a catheter, which includes only an illumination optical system. 
     As illustrated in  FIG. 6A , the endoscope  120  includes an insertion module  121  which is hollow and elongated and is inserted into, for example, the conduit such as the lumen; and an operation portion  123  which is coupled to a proximal end portion of the insertion module  121  and operates the endoscope  120 . The endoscope  120  includes a universal cord  125  which is connected to the operation portion  123  and is made to extend from a side surface of the operation portion  123 . 
     As illustrated in  FIG. 6A , the insertion module  121  includes a housing (housing portion)  121   a  which is provided on at least a part of the insertion module  121  and has flexibility. This housing  121   a  includes, for example, a flexible tube (flexible tube portion). 
     As illustrated in  FIG. 6A , the operation portion  123  includes a housing (housing portion)  123   a  having desired rigidity. 
     As illustrated in  FIG. 6A , the universal cord  125  includes a housing (housing portion)  125   a  which has flexibility and has desired rigidity. The universal cord  125  includes a connector (connection portion)  125   b  which is attachable/detachable to/from the image processor  130  and light source module  20 . The connector  125   b  detachably connects the light source module  20  and endoscope  120  to each other, and detachably connects the endoscope  120  and image processor  130  to each other. The connector  125   b  is provided in order to enable data transmission/reception between the endoscope  120  and image processor  130 . 
     The image processor  130  includes a housing (housing portion)  130   a  having desired rigidity. 
     Although not illustrated, the image processor  130  and light source module  20  are electrically connected to each other. 
     As illustrated in  FIG. 6A , the light source module  20  includes a housing (housing portion)  20   a  having desired rigidity. The light source module  20  is a separate body from the endoscope  120 , and is provided on an outside of the endoscope  120 . 
     [Illumination Apparatus  10 ] 
     As illustrated in  FIG. 6B , the endoscope system  110  further includes an illumination apparatus  10  which emits illumination light L toward the outside from the distal end portion of the insertion module  121 . 
     As illustrated in  FIG. 6A , the illumination apparatus  10  includes the above-described light source module  20 ; a light guide path  171  that is the above-described light guide  30 , which is provided in the light source module  20  and in the endoscope  120  including the insertion module  121 , is optically connected to the light source  21  of the light source module  20 , and guides the primary light PL which is emitted from the light source  21 ; and the above-described light converter  40 . 
     [Light Source  21 V,  21 B,  21 G,  21 R] 
     As illustrated in  FIG. 6B , in the light source module  20 , a plurality of light sources  21  can be provided. In the description below, the respective light sources  21  are referred to as light sources  21 V,  21 B,  21 G and  21 R. The light sources  21 V,  21 B,  21 G and  21 R are mounted on a control board (not shown) which forms a controller (control portion)  153  that controls the light sources  21 V,  21 B,  21 G and  21 R individually, and the controller  153  is electrically connected to a controller (control portion)  155 . The controller  155  controls the entirety of the endoscope system  110  including the endoscope  120 , display  140  and light source module  20 . The controller  155  may be arranged in the image processor  130 . The controller  153  and the controller  155  have, for example, a hardware circuitry including ASIC. 
     The light sources  21 V,  21 B,  21 G and  21 R emit primary lights PL having mutually optically different wavelengths. The light sources  21 V,  21 B,  21 G and  21 R emit, for example, the primary lights PL having high coherence, such as laser beams. 
     The light source  21 V includes, for example, a laser diode which is a light emission element (heat converter  61 ) that emits a violet laser beam. A central wavelength of the laser beam is, for example, 405 nm. 
     The light source  21 B includes, for example, a laser diode which is a light emission element (heat converter  61 ) that emits a blue laser beam. A central wavelength of the laser beam is, for example, 445 nm. 
     The light source  21 G includes, for example, a laser diode which is a light emission element (heat converter  61 ) that emits a green laser beam. A central wavelength of the laser beam is, for example, 510 nm. 
     The light source  21 R includes, for example, a laser diode which is a light emission element (heat converter  61 ) that emits a red laser beam. A central wavelength of the laser beam is, for example, 630 nm. 
     The light emission elements (heat converters  61 ) of the light sources  21 V,  21 B,  21 G and  21 R are disposed in the insides of housings (housing portions)  25 V,  25 B,  25 G and  25 R of the respective light sources  21 V,  21 B,  21 G and  21 R. In addition, light focusing portions  23  are disposed in the housings  25 V,  25 B,  25 G and  25 R. 
     Each of the light sources  21 V,  21 B,  21 G and  21 R is optically connected to a light coupler (light coupling portion)  157  (to be described later) via a single light guide (light guide member)  171   a.  The light guide  171   a  includes, for example, an optical fiber. Primary lights PL, which are emitted from the light emission elements of the light sources  21 V,  21 B,  21 G and  21 R, are focused on the single light guides  171   a  by the light focusing portions  23 . Then, the primary lights PL are guided to the light coupler  157  by the light guides  171   a.  The light sources  21 V,  21 B,  21 G and  21 R, the controllers  153  and  155 , and single light guides  171   a  are provided in the inside of the housing  20   a.    
     For example, when white illumination is performed, the light source  21 B, light source  21 G and light source  21 R are used. If four or more light sources  21  are provided, white-light observation using white light with high color rendering properties can be performed. When the light source  21 V and light source  21 G are used, special-light observation utilizing light absorption properties of hemoglobin can be performed. In the special-light observation, a blood vessel is displayed with emphasis. When a light source  21  which emits near-infrared light is used, observation utilizing near-infrared light can be performed. The light source  21  can be selected in accordance with the observation. In the present embodiment, visible light is used, but the restriction to this is unnecessary. 
     [Light Coupler  157 ] 
     As illustrated in  FIG. 6B , the illumination apparatus  10  further includes the light coupler  157  which is provided in the inside of the housing  20   a  of the light source module  20 , and couples the plurality of primary lights PL, which are emitted from the light sources  21 V,  21 B,  21 G and  21 R, into single light. 
     The light coupler  157  makes the primary lights PL, which are guided by the four light guides  171   a,  incident on a single light guide (light guide member)  171   b.  In this manner, in the present embodiment, the light coupler  157  includes four input ports and one output port. The number of input ports is equal to the number of light sources  21 . The number of output ports is not particularly limited. At the input ports, the light guides  171   a  include fine optical fibers, and the light guides  171   a  are bundled. At the output port, the light guide  171   b  includes a thick optical fiber. The thick light guide  171   b  has a greater thickness than the bundled light guides  171   a.  The thick light guide  171   b  is fused on the bundled light guides  171   a  such that the thick light guide  171   b  is optically connected to the bundled light guides  171   a.  The light coupler  157  functions as a light combiner. 
     [Light Separator  159 ] 
     As illustrated in  FIG. 6B , the illumination apparatus  10  further includes a light separator (light separating portion)  159  which is provided in the inside of the housing  20   a  of the light source module  20 , and separates the primary light PL, which was coupled by the light coupler  157 , into a plurality of primary lights PL. 
     The light separator  159  makes the primary light PL, which was guided by the single light guide  171   b,  incident on, for example, two light guides (light guide members)  171   c.  In this manner, in the present embodiment, the light separator  159  includes one input port and two output ports. The number of input ports of the light separator  159  is equal to the number of output ports of the light coupler  157 . The number of output ports is not limited, if this number is plural. In other words, it should suffice if the number of light guides  171   c  is plural. The light separator  159  separates the primary light PL, for example, at a desired ratio. In this embodiment, the ratio is, for example, 50:50. It is not necessary that the ratio be equal between the respective output ports. The light separator  159  functions as a coupler. 
     In the structure of the light separator  159 , the light guide  171   b  and one of the light guides  171   c  are one piece. In other words, the light guide  171   b  and one of the light guides  171   c  function as a member in common, for example, as an optical fiber in common. Another light guide  171   c  is fused to this one light guide, and the fused portion is further melted and drawn. Thereby, the primary light PL is transferred between the light guide  171   b  and the other light guide  171   c.    
     In the present embodiment, the input port of the light separator  159  is optically connected to the output port of the light coupler  157 . Thereby, the primary light PL, which is input to the light separator  159 , is separated into the two light guides  171   c  at a ratio of, for example, 50:50. 
     Incidentally, although not illustrated, the light separator  159  may be provided in an inside of the housing  123   a  of the operation portion  123  of the endoscope  120 . In this manner, it should suffice if the light separator  159  is provided in either the light source module  20  or the endoscope  120 . 
     As illustrated in  FIG. 6B , when the light separator  159  is provided in the light source module  20 , the light guide  171   b  is provided in the inside of the housing  20   a  of the light source module  20 , and the light guides  171   c  are provided in the inside of the housing  20   a  of the light source module  20  and in an inside of the endoscope  120 . Although not illustrated, when the light separator  159  is provided in the endoscope  120 , the light guide  171   b  is provided in the inside of the housing  20   a  of the light source module  20  and in the inside of the endoscope  120 , and the light guides  171   c  are provided in the inside of the endoscope  120 . 
     [Light Guide Path  171 ] 
     As illustrated in  FIG. 6B , the light guide path  171  includes the above-described light guides  171   a  which are provided in the light source module  20 . The light guides  171   a  are optically connected to the light sources  21  and the light coupler  157 . The light guides  171   a  guide the primary lights PL from the light sources  21 V,  21 B,  21 G and  21 R to the light coupler  157 . 
     The light guide path  171  further includes the light guide  171   b  which is provided in the light source module  20  when the light separator  159  is provided in the light source module  20  as illustrated in  FIG. 6B , and which is provided in the light source module  20 , connector  125   b,  universal cord  125  and operation portion  123  when the light separator  159  is provided, although not illustrated, in the operation portion  123 . The light guide  171   b  guides the primary light PL from the light coupler  157  to the light separator  159 . 
     The light guide path  171  further includes the light guides  171   c  which are provided in the light source module  20 , connector  125   b,  universal cord  125 , operation portion  123  and insertion module  121  when the light separator  159  is provided in the light source module  20  as illustrated in  FIG. 6B , and which is provided in the operation module  123  and insertion module  121  when the light separator  159  is provided, although not illustrated, in the operation portion  123 . The light guides  171   c  are optically connected to light converters  40 . The light guides  171   c  guide the primary lights PL, which are emitted from the light source module  20 , from the light separator  159  to the light converters  40 . The light guides  171   c  may be directly connected to the light converters  40 , or may be indirectly connected to the light converters  40  via a member (not shown, for example, lens). 
     As illustrated in  FIG. 6B , the light guides  171   c,  which are provided in the insertion module  121 , are provided in the inside of the housing  121   a  of the insertion module  121 . 
     The light guides  171   a,    171   b  and  171   c  include single optical fibers. In this embodiment, these single optical fibers are provided over the entirety of the light guide path  171 , but the restriction to this is unnecessary. It should suffice if single optical fibers are provided on at least a part of the light guide path  171 . If single optical fibers are provided on a part of the light guide path  171 , a bundle fiber may be provided on the other part of the light guide path  171 . 
     The single optical fibers functioning as the light guides  171   a  guide the primary lights PL which were emitted from the light sources  21 . 
     In the light guides  171   c,  a plurality of single optical fibers are provided, and the optical fibers are single fibers of mutually different systems. In other words, these optical fibers are different members although these optical fibers have the same optical function of light guiding. Moreover, in other words, the light guides  171   c  include a plurality of single optical fibers of one kind, respectively. In this case, the light guides  171   c  function not as a bundle fiber, but as single optical fibers. The respective single optical fibers of the light guides  171   a,    171   b  and  171   c  are single fibers of mutually different systems, and, in other words, these optical fibers are mutually different members although having the same optical function of light guiding. 
     As illustrated in  FIG. 6B , when the light separator  159  is provided in the light source module  20 , the light guides  171   c,  which are provided in the light source module  20 , are different members from the light guides  171   c  which are provided on the connector  125   b  side. 
     Although not illustrated, when the light separator  159  is provided in the operation portion  123 , the light guide  171   b,  which is provided in the light source module  20 , is a different member from the light guide  171   b  which is provided on the connector  125   b  side. 
     The light guide  30  of the first embodiment functions as the light guides  171   a,    171   b  and  171   c.    
     Here, a brief description is given of a method in which the light guides  171   c  provided on the light source module  20  side, as illustrated in  FIG. 6B , are optically connected to the light guides  171   c  provided on the connector  125   b  side. 
     As regards the light guides  171   c  provided in the light source module  20 , the light guides  171   c  are inserted in a plug (plug unit)  191  which is provided in the light source module  20  and holds the light guides  171   c.    
     The above-described content also applies to the light guides  171   c  provided on the connector  125   b  side. The plug unit  191  on the connector  125   b  side is provided in the connector  125   b.    
     As illustrated in  FIG. 6B , the housing  20   a  of the light source module  20  includes a light adapter  193  which is fixed to the housing  20   a.  The plug unit  191  on the light source module  20  side is attached in advance to the light adapter  193 . 
     If the connector  125   b  is connected to the light source module  20 , the plug unit  191  on the connector  125   b  side is inserted in the light adapter  193 . Thereby, the light guides  171   c  on the light module side  20  side are optically connected to the light guides  171   c  on the connector  125   b  side. The plug unit  191  on the connector  125   b  side is attachable/detachable to/from the light adapter  193  of the light source module  20 . 
     [Light Converter  40 ] 
     As illustrated in  FIG. 6B , the light converters  40  are provided in the inside of the distal end portion of the insertion module  121 . The light converters  40  are optically connected to the light guides  171   c,  and convert the primary lights PL, which are guided by the light guides  171   c,  to illumination light L. The light converters  40  emit the illumination light L to the outside of the endoscope  120 , and irradiate the to-be-illuminated part with the illumination light L. 
     [Heat Exhauster  60 ] 
     Although illustration is omitted, in the present embodiment, the heat exhauster  60 , base plate  71 , Peltier element  73  and temperature measuring sensor  75  are provided in the inside of the housing  20   a.    
     [Function] 
     Primary lights PL are emitted from the light emission elements of the light sources  21 V,  21 B,  21 G and  21 R, and are focused on the light guides  171   a  by the light focusing portions  23 . The primary lights PL are guided to the light coupler  157  by the light guides  171   a,  and are coupled by the light coupler  157 . The coupled primary light PL is guided to the light separator  159  by the light guide  171   b,  and is separated by the light separator  159 . The separated primary lights PL are guided to the light converters  40  by the light guides  171   c.    
     The light guide portion  40  diffuses the primary light PL, and the forward illumination light FL and backward illumination light BL are generated. The forward illumination light FL irradiates the to-be-illuminated part. 
     Like the first embodiment, the backward illumination lights BL are collected into the cores  33  of the light guides  171   c  by the light collectors  50  which are not shown in  FIG. 6A  and  FIG. 6B . The backward illumination lights BL are guided to the light separator  159  by the light guides  171   c,  and are coupled by the light separator  159  which has also the function of the light coupler  157 . The coupled backward illumination light BL is guided to the light coupler  157  by the light guide  171   b.  The backward illumination light BL is separated by the light coupler  157  which has also the function of the light separator  159 , and the separated backward illumination lights BL are returned to the light sources  21 V,  21 B,  21 G and  21 R by the light guides  171   a.  In this manner, the backward illumination light BL is guided in the direction reverse to the direction of the travel of the primary light PL, reversely travels in the light guide path  171  in the direction reverse to the direction of the travel of the primary light PL, and returns to the light source  21 V,  21 B,  21 G,  21 R. 
     In the light sources  21 V,  21 B,  21 G and  21 R, the backward illumination lights BL are focused by the light focusing portions  23  on the respective light emission elements of the light sources  21 V,  21 B,  21 G and  21 R, which are the heat converters  61 . Each light emission element, which is the heat converter  61 , absorbs the backward illumination light BL, and converts the absorbed backward illumination light BL to heat H. The heat H is radiated to the outside by the heat radiator  63  via the base plate  71  and Peltier element  73 , the depiction of which is omitted in  FIG. 6A  and  FIG. 6B . This “outside” means, for example, an outside environment of the endoscope  120 , or an atmosphere within the endoscope  120 . 
     The heat converter  61  and heat radiator  63  convert the light to the heat H at a location apart from the light converter  40 . Thus, in the present embodiment, the heat generation of the distal end portion of the insertion module  121  at a time of illumination, in which the light converter  40  is provided, can be suppressed to a minimum. 
     [Advantageous Effects] 
     In the present invention, even when the endoscope system  110  includes the illumination apparatus  10 , the same advantageous effects as in the first embodiment can be obtained. 
     [Modification 1] 
     Referring to  FIG. 7A  and  FIG. 7B , Modification 1 of the fourth embodiment will be described. Incidentally, in the present modification, for the purpose of clearer illustration, the depiction of the heat exhauster  60 , base plate  71 , Peltier element  73  and temperature measuring sensor  75  is omitted. 
     In the endoscope system  110  illustrated in  FIG. 6A  and  FIG. 6B , the endoscope  120  is directly connected to various apparatuses via the universal cord  125  including the connector  125   b.    
     However, in the present modification, as illustrated in  FIG. 7A  and  FIG. 7B , the universal cord  125  is omitted, and the endoscope  120  is configured as a wireless type. In this case, the endoscope  120  is of such a wireless type that radio signals are transmitted/received between the operation portion  123  and image processor  130 . 
     In addition, the endoscope  120  incorporates the illumination apparatus  10 . 
     The illumination apparatus  10  of the present modification uses illumination light L of a narrow band. Thus, as illustrated in  FIG. 7B , for example, light sources  21 V and  21 B are provided. 
     [Radio Unit in Illumination Apparatus  10 ] 
     As illustrated in  FIG. 7B , the illumination apparatus  10  includes a radio (radio portion)  201  which is provided in the image processor  130  and outputs radio signals for controlling, for example, the light sources  21 V and  21 B and an imager (imaging unit (for example, CCD, CMOS)); and a controller (control portion)  203  which is electrically connected to the radio  201  and controls the endoscope system  110 . The radio  201  and controller  203  are provided in the inside of the housing  130   a  having desired rigidity. 
     As illustrated in  FIG. 7B , in the present modification, the light sources  21 V and  21 B are provided in the inside of the housing  123   a  of the operation portion  123 . 
     As illustrated in  FIG. 7B , the illumination apparatus  10  further includes a radio (radio portion)  211  which receives a radio signal that was output from the radio  201 ; and a controller (control portion)  213  which controls the light sources  21 V and  21 B, based on the radio signal received by the radio  211 . The radio  211  and controller  213  are provided in the inside of the housing  123   a  of the operation portion  123 . The light sources  21 V and  21 B are mounted on a control board (not shown) on which the controller  213  is formed. 
     As illustrated in  FIG. 7B , the illumination apparatus  10  further includes a supplier (supply portion)  215  which supplies energy to the radio  211 , controller  213  and light sources  21 V and  21 B. The supplier  215  is provided in the inside of the housing  123   a  of the operation portion  123 . The supplier  215  includes, for example, a battery which supplies energy that is electric power. The supplier  215  also supplies energy to the respective members of the endoscope  120 . 
     The above-described radio  201 , controller  203 , radio  211  and controller  213  function as a radio unit of the illumination apparatus  10  which is mounted in the wireless-type endoscope system  110 . The controller  203  and the controller  213  have, for example, a hardware circuitry including ASIC. 
     The radio  201  may transmit a signal, which includes a driving condition of the light sources  21 V and  21 B, to the radio  211 . Based on this driving condition, the controller  213  controls the light sources  21 V and  21 B. 
     The radio  211  may generate a video signal, based on an imaging signal of a to-be-illuminated part which was imaged by the imager (not shown), may convert the video signal to a radio signal, and may transmit the radio signal to the radio  201 . The controller  203  converts the radio signal to a video signal, and executes image processing on the video signal. The display  140  displays the video signal as a video image. 
     The radio  211  may transmit residual amount information, which indicates a residual amount of energy in the supplier  215 , to the radio  201 . In addition, the display  140  may display this residual amount information. 
     In this manner, various pieces of information are transmitted/received between the radios  201  and  211 . 
     [Light Coupler/Separator  217 ] 
     As illustrated in  FIG. 7B , the light sources  21 V and  21 B are provided in the inside of the housing  123   a  of the operation portion  123 . Thus, in consideration of the space in the housing  123   a,  the illumination apparatus  10  includes a light coupler/separator (light coupling/separating portion)  217  which is provided in the inside of the housing  123   a  of the operation portion  123  and has the function of the light coupler  157  and the function of the light separator  159  in the first embodiment. The light coupler/separator  217  functions as a light combiner and a coupler. 
     As illustrated in  FIG. 7B , the light coupler/separator  217  is optically connected to a light guide (light guide member)  171   a  which is optically connected to the light source  21 V, and also optically connected to a light guide (light guide member)  171   a  which is optically connected to the light source  21 B. The light coupler/separator  217  is further optically connected to light guides (light guide members)  171   c  which are optically connected to the light converters  40 . In this manner, the light coupler/separator  217  includes two input ports and two output ports. The number of input ports of the light coupler/separator  217  is equal to the number of light sources  21 . The number of output ports is not particularly limited, if the number is plural. In other words, it should suffice if the number of light guides  171   c  is plural. 
     The light coupler/separator  217  couples the primary light PL which was emitted from the light source  21 V and guided by the light guide  171   a,  and the primary light PL which was emitted from the light source  21 B and guided by the light guide  171   a.    
     The light coupler/separator  217  separates the coupled primary light PL into a plurality of primary lights PL. The light coupler/separator  217  separates the primary light PL, for example, at a desired ratio. In this modification, the ratio is, for example, 50:50. It is not necessary that the ratio be equal between the respective output ports. 
     [Heat Exhauster  60 ] 
     Although illustration is omitted, in the present modification, the heat exhauster  60 , base plate  71 , Peltier element  73  and temperature measuring sensor  75  are provided in the inside of the housing  123   a.    
     In the present modification, the illumination apparatus  10  is included in the wireless-type endoscope  120 , but the restriction to this is unnecessary. The illumination apparatus  10  may be included in the endoscope  120  illustrated in the fourth embodiment. 
     [Advantageous Effects] 
     In the present modification, even when the endoscope  120  incorporates the illumination apparatus  10 , the same advantageous effects as in the first and second embodiments can be obtained. 
     [Modification 2] 
     Referring to  FIG. 8A  and  FIG. 8B , Modification 2 of the fourth embodiment will be described. Incidentally, in the present modification, for the purpose of clearer illustration, the depiction of the heat exhauster  60 , base plate  71 , Peltier element  73  and temperature measuring sensor  75  is omitted. A light source  21  includes a housing (housing portion)  25  in which a light emission element (heat converter  61 ) and a light focusing portion  23  are included. 
     As illustrated in  FIG. 8A  and  FIG. 8B , the illumination apparatus  10  may be inserted into a treatment instrument insertion channel  121   b  from a treatment instrument insertion port (treatment instrument insertion portion)  123   b.  In this case, the endoscope  120  is a separate body from the illumination apparatus  10 . The illumination apparatus  10  is insertable/removable into/from the endoscope  120 . 
     A light guide  30  is inserted through a housing (housing portion)  127   a  of an auxiliary universal cord  127 . The housing  127   a  has flexibility and has desired rigidity. The light guide  30  is inserted through the treatment instrument insertion channel  121   b  via the housing  127   a,  such that the light converter  40  is disposed in the distal end portion of the insertion module  121 . 
     The auxiliary universal cord  127  is fixed to the housing  20   a.  The light converter  40  is fixed to the distal end portion of the housing  127   a.    
     [Advantageous Effects] 
     In the present modification, even when the illumination apparatus  10  is inserted through the treatment instrument insertion channel  121   b,  the same advantageous effects as in the first embodiment can be obtained. 
     In the state in which the endoscope system  110  and endoscope  120  include the illumination apparatus  10  in advance, an illumination apparatus  10  is additionally provided. Thereby, a greater amount of illumination light L can be irradiated on a to-be-observed object. In short, in the present modification, the illumination apparatus  10  can also function as an auxiliary illumination apparatus  10 . 
     Incidentally, in the present modification, it is not necessary that the endoscope system  110  and endoscope  120  include the illumination apparatus  10  in advance, as illustrated in  FIG. 7A  and  FIG. 7B  and in  FIG. 8A  and  FIG. 8B . In this case, the configuration of the endoscope system  110  and endoscope  120  can be simplified. 
     Although illustration is omitted, in the present modification, the heat exhauster  60 , base plate  71 , Peltier element  73  and temperature measuring sensor  75  are provided in the inside of the housing  20   a.    
     The endoscope  120  of the present modification may be of a wireless type as illustrated in Modification 1. 
     The present invention is not limited directly to the above-described embodiments. At the stage of practicing the invention, the structural elements may be modified and embodied without departing from the spirit of the invention. Various inventions may be made by suitably combining a plurality of structural elements disclosed in the embodiments.