Abstract:
An embodiment of the present invention relates to a radiation emitting device comprising:
       a radiation emitter for generating radiation;   a waveguide;   a lens placed between the radiation emitter and the waveguide and directing a first portion of the radiation towards the waveguide;   a sleeve that comprises a reflective inner surface and is placed between the radiation emitter and the waveguide, said inner reflective surface coupling a second portion of the radiation into the waveguide;   wherein the lens and the sleeve are separate components that can be positioned relative to each other during fabrication of the radiation emitting device.

Description:
[0001]    The invention relates to a radiation emitting device and to methods for fabricating radiation emitting devices. In particular, the invention relates to radiation emitting devices that can be used in endoscopy applications. 
       BACKGROUND OF THE INVENTION 
       [0002]    European Patent EP 1 348 143 describes a radiation emitting device that comprises a radiation emitter, a waveguide, and a parabolic mirror placed between the radiation emitter and the waveguide. 
         [0003]    Further radiation emitting devices with parabolic mirrors are disclosed in Japanese Patent Applications JP05113526A and JP 2003262763A. 
         [0004]    U.S. Patent Application US 2010/0243870 describes a radiation emitting device that comprises a radiation emitter, a waveguide, and a lens placed between the radiation emitter and the waveguide. 
       OBJECTIVE OF THE PRESENT INVENTION 
       [0005]    An objective of the present invention is to provide a radiation emitting device that can be fabricated in a reliable fashion. 
         [0006]    A further objective of the present invention is to provide a method for reliably fabricating radiation emitting devices. 
       BRIEF SUMMARY OF THE INVENTION 
       [0007]    An embodiment of the present invention relates to a radiation emitting device comprising:
       a radiation emitter for generating radiation;   a waveguide;   a lens placed between the radiation emitter and the waveguide and directing a first portion of the radiation towards the waveguide;   a sleeve that comprises a reflective inner surface and is placed between the radiation emitter and the waveguide, said inner reflective surface coupling a second portion of the radiation into the waveguide;   wherein the lens and the sleeve are separate components that can be positioned relative to each other during fabrication of the radiation emitting device.       
 
         [0013]    An advantage of this embodiment of the invention is that the divergence and/or intensity of the emitted radiation at the distal end of the waveguide may be adjusted and optimized during fabrication. This is possible because the lens and the sleeve are separate components and can be positioned relative to each other during the fabrication. 
         [0014]    The inner reflective surface of the sleeve preferably forms a truncated cone. 
         [0015]    The diameter of the truncated cone preferably narrows in a linear fashion. In other words, with respect to the cross section, the sidewall of the truncated cone preferably forms a straight line or has a linear slope. This allows achieving a predefined divergence of the emitted radiation at the distal end of the waveguide. A predefined divergence is advantageous to adapt to different endoscopy applications. 
         [0016]    The lens is preferably positioned inside the truncated cone of the sleeve. 
         [0017]    The radiation emitter may be carried by a carrier. The carrier and the sleeve are preferably separate components that can be positioned relative to each other during fabrication of the radiation emitting device. 
         [0018]    The waveguide preferably comprises a core and a cladding. The diameter of the lens is preferably smaller than the diameter of the waveguide&#39;s core. 
         [0019]    The waveguide is preferably connected to the sleeve. 
         [0020]    According to a preferred embodiment, the sleeve has a first opening facing the waveguide, and a second opening facing the radiation emitter. The first opening is preferably larger than the second opening. The diameter of the waveguide&#39;s core preferably corresponds to the diameter of the sleeve&#39;s first (wider) opening. 
         [0021]    The emitting surface of the radiation emitter may be positioned in the same plane as the carrier&#39;s surface that faces the waveguide. 
         [0022]    The lens may have a hemispherical or any other shape. 
         [0023]    In case of a hemispherical lens the bottom surface of the hemispherical lens is preferably positioned in the same plane as the carrier&#39;s surface and the emitting surface of the radiation emitter. 
         [0024]    The waveguide may be a multimode optical fiber or rod. Alternatively, the waveguide may consist of a bundle of optical fibers or rods. 
         [0025]    The radiation emitter may be a light emitting semiconductor diode. 
         [0026]    A further embodiment of the present invention relates to a method of fabricating a radiation emitting device, comprising the steps of:
       placing a lens between a radiation emitter that is capable of generating radiation, and a waveguide, said lens being capable of directing a first portion of the radiation towards the waveguide;   placing a sleeve between the radiation emitter and the waveguide, said sleeve comprising a reflective inner surface that is capable of coupling a second portion of the radiation into the waveguide;   activating the radiation emitter and inputting light in a proximal end of the waveguide; and   adjusting the distance between the lens and the sleeve or the penetration depth of the lens inside the sleeve in order to achieve a predefined divergence of the light beams that exit the waveguide at a distal end of the waveguide.       
 
         [0031]    Preferably, a lens-emitter-carrier unit is pre-fabricated. Then, the step of adjusting the distance between the lens and the sleeve may be carried out by adjusting the distance between the pre-fabricated lens-emitter-carrier unit and the sleeve. 
         [0032]    Further, the waveguide may be connected to the sleeve to form a pre-fabricated waveguide-sleeve unit. Then, the step of adjusting the distance between the lens and the sleeve may carried out by adjusting the distance between the pre-fabricated waveguide-sleeve unit and the lens. 
         [0033]    Further, a lens-emitter-carrier unit may be pre-fabricated, and a waveguide may be connected to the sleeve to form a pre-fabricated waveguide-sleeve unit. Then, the step of adjusting the distance between the lens and the sleeve may be carried out by adjusting the distance between the pre-fabricated waveguide-sleeve unit and the prefabricated lens-emitter-carrier unit. 
         [0034]    A further embodiment of the present invention relates to a method of fabricating a radiation emitting device, comprising
       placing a lens between a radiation emitter that is capable of generating radiation, and a waveguide, said lens being capable of directing a first portion of the radiation towards the waveguide;   placing a sleeve between the radiation emitter and the waveguide, said sleeve comprising a reflective inner surface that is capable of coupling a second portion of the radiation into the waveguide;   activating the radiation emitter and inputting light in a proximal end of the waveguide; and   adjusting the distance between the lens and the sleeve in order to achieve a predefined maximum coupling ratio between the radiation emitter and the waveguide and/or to achieve a maximum radiation at the distal end of the waveguide.       
 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0039]    In order that the manner in which the above-recited and other advantages of the invention are obtained will be readily understood, a more particular description of the invention briefly described above will be rendered by reference to specific embodiments thereof which are illustrated in the appended figures. Understanding that these figures depict only typical embodiments of the invention and are therefore not to be considered to be limiting of its scope, the invention will be described and explained with additional specificity and detail by the use of the accompanying drawings in which 
           [0040]      FIG. 1  shows the adjustment of a pre-fabricated emitter-carrier unit with respect to a pre-fabricated waveguide-sleeve unit, 
           [0041]      FIG. 2  shows the intensity of radiation as a function of the radiation angle of two distances D 1  and D 2  between the pre-fabricated emitter-carrier unit and the pre-fabricated waveguide-sleeve unit of  FIG. 1 , 
           [0042]      FIG. 3  shows an exemplary embodiment of a radiation emitting device that comprises the emitter-carrier unit and the waveguide-sleeve unit of  FIG. 1 , 
           [0043]      FIG. 4  visualizes the radiation angle versus location in the plane of the emitting surface of a radiation emitter of the radiation emitting device of  FIG. 3 , 
           [0044]      FIG. 5  visualizes the radiation angle versus location in the plane of a proximal end of a waveguide of the radiation emitting device of  FIG. 3 , as well as the acceptance angle and acceptance location of a waveguide, 
           [0045]      FIG. 6  visualizes the influence of a sleeve of the waveguide-sleeve unit of the radiation emitting device of  FIG. 3 , and 
           [0046]      FIG. 7  shows a further exemplary embodiment of a radiation emitting device. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0047]    The preferred embodiments of the present invention will be best understood by reference to the drawings, wherein identical or comparable parts are designated by the same reference signs throughout. It will be readily understood that the present invention, as generally described herein, could vary in a wide range. Thus, the following more detailed description of the exemplary embodiments of the present invention, is not intended to limit the scope of the invention, as claimed, but is merely representative of presently preferred embodiments of the invention. 
         [0048]    An exemplary embodiment of a method for fabricating a radiation emitting device  10  will be explained hereinafter referring to  FIGS. 1-6 . 
         [0049]    An emitter-carrier unit  20  is pre-fabricated by positioning a radiation emitter  30  on top of a carrier  40 . The radiation emitter  30  may be a semiconductor diode such as a luminescence diode (LED) or laser diode. 
         [0050]    The radiation emitter  30  may be monolithically integrated into the carrier  40  or fabricated separately. In the latter case, the pre-fabricated radiation emitter  30  may be simply placed on the surface  50  of the carrier  40  or in a recess  55  provided in the surface  50 . As can be seen in  FIG. 1 , the emitting surface  60  of the radiation emitter  30  is preferably positioned in the same plane as the surface  50  of the carrier  40 . The pre-fabricated radiation emitter  30  may comprise a plurality of layers that may differ in their function, for instance layers that generate radiation and other layers which do not. As such, the term “emitting surface  60 ” refers to the surface where the generated radiation leaves the pre-fabricated radiation emitter  30 , and not necessarily to the layer where the radiation is generated. Furthermore, additional layers may be arranged on top of the pre-fabricated radiation emitter  30  at a later stage. Those additional layers may then be considered to be a part of the pre-fabricated radiation emitter  30 , and the term “emitting surface  60 ” then refers to the uppermost layer. 
         [0051]    In order to create a pre-fabricated lens-emitter-carrier unit  70 , a lens  80  is placed and fixed on top of the emitter-carrier unit  20  and in particular on top of the emitting surface  60  of the radiation emitter  30 . 
         [0052]    The lens  80  may have a hemispherical shape as shown or any other shape. In case of a hemispherical shape, the circular bottom  90  of the lens  80  may be positioned in the same plane as the carrier&#39;s surface  50  and the emitting surface  60  of the radiation emitter  30 . 
         [0053]    Additionally, a waveguide-sleeve unit  100  is pre-fabricated by connecting a waveguide  110  with a sleeve  120 . The waveguide  110  of  FIG. 1  is a multimode fiber or rod, and consists of an inner core  111  and an outer cladding  112 . Alternatively, the waveguide  110  may be comprised of a bundle of singlemode or multimode fibers, or singlemode or multimode rods. 
         [0054]    The sleeve  120  has a first opening that faces the waveguide  110 , and a second opening that faces the radiation emitter  30 . It can be seen that the first opening is larger or wider than the second opening. The inner surface  125  is reflective and forms a reflective truncated cone. 
         [0055]    In  FIG. 1 , which shows the cross section of the truncated cone, it can be seen that the diameter of the truncated cone preferably narrows in a linear fashion. In other words, with respect to the cross section, the sidewall of the truncated cone preferably forms a straight line or has a linear slope. The angle γ (see  FIG. 3 ) of the linear slope is preferably between 10° and 20° (e.g. 15°). 
         [0056]    The sleeve  120  may consist of metal (e.g. aluminium). 
         [0057]    Furthermore,  FIG. 1  shows that the diameter of the inner core  111  of the waveguide  110  preferably corresponds to the diameter of the sleeve&#39;s first (wider) opening. The diameter of the lens  80  is preferably smaller than the diameter of the inner core  111 . 
         [0058]    Then, the distance D between the pre-fabricated waveguide-sleeve unit  100  and the pre-fabricated lens-emitter-carrier unit  70  is adjusted relative to each other. Thereby, the lens  80  is positioned inside the sleeve  120  and placed between the radiation emitter  30  and the waveguide  110 . As such, the lens  80  can direct a first portion P 1  of radiation that is generated by the radiation emitter  30 , towards the waveguide  110 . 
         [0059]    A second portion of the radiation P 2  that is generated by the radiation emitter  30 , is coupled into the waveguide  110  by the reflective inner surface  125  of the sleeve  120 . 
         [0060]    In a further step, the radiation emitter  30  is activated and light is inputted in the proximal end  130  of the waveguide  110 . Then, the distance D between the pre-fabricated waveguide-sleeve unit  100  and the pre-fabricated lens-emitter-carrier unit  70 , and the penetration depth of the lens  80  inside the sleeve  120  is adjusted to generate either a maximum radiation or a predefined divergence at the distal end  140  of the waveguide  110 . For instance, the predefined divergence may be the maximum divergence that can be obtained by adjusting the distance D between the pre-fabricated waveguide-sleeve unit  100  and the pre-fabricated lens-emitter-carrier unit  70 . 
         [0061]    If the radiation device  10  is meant to be used as an endoscope or as a part of an endoscope apparatus, the distance D is preferably chosen such that the divergence at the distal end  140  of the waveguide  110  reaches its predefined value (e.g. the maximum value that is obtainable). 
         [0062]      FIG. 2  shows the radiation intensity I(φ) at the distal end  140  of the waveguide  110  over the radiation angle φ for two different distances D=D 1  and D=D 2 . It can be seen that the divergence and the overall radiation power varies if the distance D between the pre-fabricated waveguide-sleeve unit  100  and the pre-fabricated lens-emitter-carrier unit  70  is changed. The overall radiation power Ptotal may be calculated as follows: 
         [0000]    
       
         
           
             
               P 
               total 
             
             = 
             
               
                 ∫ 
                 
                   
                     - 
                     90 
                   
                    
                   ° 
                 
                 
                   
                     + 
                     90 
                   
                    
                   ° 
                 
               
                
               
                 
                   I 
                    
                   
                     ( 
                     ϕ 
                     ) 
                   
                 
                  
                 
                     
                 
                  
                 
                    
                   ϕ 
                 
               
             
           
         
       
     
         [0063]    When the optimum distance between the pre-fabricated waveguide-sleeve unit  100  and the pre-fabricated lens-emitter-carrier unit  70  is found, the relative position between both units may be fixed, for instance with an adhesive  150  as shown in an exemplary fashion in  FIG. 3 . 
         [0064]    As discussed above with respect to  FIG. 1 , the diameter of the truncated cone preferably narrows in a linear fashion. A linear slope yields the advantage that a collimation of radiation that is reflected by the inner surface  125  is achieved. As a result, a predefined divergence of radiation at the distal end  140  of the waveguide  110  may be achieved. This is advantageous if the radiation emitting device  10  is used as an endoscope or as a part of an endoscope apparatus. 
         [0065]      FIG. 3  further illustrates the influence of the sleeve  120  in further detail. It is assumed that the radiation angle α of radiation P 2  is larger than the acceptance angle of the waveguide  110 . As such, the radiation P 2  would not be coupled into the waveguide  110  and would not reach the distal end  140  of the waveguide  110 . 
         [0066]    However, the inner surface  125  of the sleeve  120  reduces the radiation angle α of the emitted radiation P 2  with respect to the waveguide  110 . This effect depends on the slope or angle γ of the truncated cone. The angle reduction may be calculated as follows: 
         [0000]      β=α−2γ
 
         [0000]    wherein α describes the emission angle before reflexion at the inner surface  125  and β describes the emission angle after reflexion at the inner surface  125 . 
         [0067]    The reduction of the radiation angle with respect to the proximal end  130  of the waveguide  110  provides that the radiation P 2  can be coupled into the waveguide  110 . 
         [0068]    The influence of the sleeve  120  on the coupling efficiency will be explained below in further detail with reference to  FIGS. 4-6 . 
         [0069]      FIG. 4  shows a curve RA that visualizes the angle φ of the emitted radiation versus location with respect to the plane of the emitting surface  60  in an exemplary fashion. It is assumed that the diameter of the emitting surface  60  is 2 mm and that the maximum radiation angle is 65° (1.1 rad).  FIG. 4  shows that the radiation angle φ varies over the location. The radiation angle φ reaches its maximum in the center area (location 0 mm) of the emitting surface  60 , and approaches zero at both edges of the emitting surface  60  (location±1 mm). 
         [0070]    In  FIG. 5 , the curve RA visualizes the radiation angle φ of the radiation versus the location in the plane of the proximal end  130  of the waveguide  110  (see  FIG. 1 ). It can be seen that the curve RA has changed its shape (compared with  FIG. 4 ) and that the radiation angle φ is larger than in  FIG. 4 . In  FIG. 5 , it is assumed in an exemplary fashion that the distance between the proximal end  130  of the waveguide  110  and the emitting surface  60  is 2 mm. 
         [0071]    Furthermore,  FIG. 5  shows a curve AA that visualizes the acceptance angle range of the waveguide  110 . It is assumed in an exemplary fashion that the acceptance angle is 80° (±40°) and that the diameter of the waveguide core is 3 mm. 
         [0072]    The area F 1 , where the section surrounded by curve RA and the section surrounded by curve AA overlap, determines the first portion P 1  of the radiation that is directly coupled by the lens  80  into the waveguide  110  (see  FIG. 1 ). 
         [0073]    The remaining two sections F 2  and F 3  that are surrounded by curve RA but lie outside the section surrounded by curve AA, determine the radiation that would not be coupled into the waveguide  110  without the sleeve  120 . 
         [0074]      FIG. 6  shows the influence of the sleeve  120  on the coupling efficiency. It can be seen that sections F 2  and F 3  of  FIG. 5  are folded into the acceptance range of the waveguide  110 . The folded sections F 2 ′ and F 3 ′ describe the second portion P 2  (see  FIG. 1 ) of radiation that is coupled via the sleeve  120  into the waveguide  110 . 
         [0075]      FIG. 7  shows a second exemplary embodiment of a radiation emitting device  10 . Here, the distance between the waveguide  110  and the pre-fabricated emitter-carrier unit  20  is determined by the length L of the sleeve  120 , only, since the pre-fabricated emitter-carrier unit  20  is directly mounted on the sleeve  120 . An adjustment between the fabricated emitter-carrier unit  20  and the waveguide-sleeve unit  100  is therefore not mandatory. For the rest, the radiation emitting device  10  of  FIG. 7  corresponds to embodiment of  FIG. 3 . 
       REFERENCE SIGNS 
       [0000]    
       
           10  radiation emitting device 
           20  emitter-carrier unit 
           30  radiation emitter 
           40  carrier 
           50  surface of carrier 
           55  recess 
           60  emitting surface of radiation emitter 
           70  lens-emitter-carrier unit 
           80  lens 
           90  bottom 
           100  waveguide-sleeve unit 
           110  waveguide 
           111  inner core 
           112  outer cladding 
           120  sleeve 
           125  reflective inner surface 
           130  proximal end 
           140  distal end 
           150  adhesive 
         RA curve 
         AA curve 
         D distance 
         D 1  distance 
         D 2  distance 
         F 1  area 
         F 2  section 
         F 3  section 
         F 2 ′ section 
         F 3 ′ section 
         L length of the sleeve 
         P 1  first portion of radiation 
         P 2  second portion of radiation 
         φ, γ angle 
         α, γ radiation angle