Abstract:
An endoscope cable for use in an endoscope viewing apparatus for viewing an objective has an image viewing cable end portion for association with an image viewing device, a distal, image forming end portion including image forming means for forming an image of the objective, an image transmission means for transmitting the image from the image forming means to the image viewing cable end and a plurality of illumination light conducting fibers extending from an illumination light receiving end at the image viewing cable end to an illumination light emitting end at the image forming end of the cable. A first set of the illumination light conducting fibers has an illumination light emitting end portion axis parallel to the cable image forming end portion axis. A second set of the illumination light conducting fibers has an illumination light emitting end portion axis at a first acute angle to the cable image forming end portion axis. A third set of the illumination light conducting fibers has an illumination light emitting end portion axis at a second acute angle to the cable image forming end portion axis.

Description:
TECHNICAL FIELD 
     The present invention relates to endoscope apparatus and devices for illuminating viewing objectives which are being viewed through endoscope apparatus. More particularly, the present invention relates to endoscopic viewing objective illumination devices which conduct illumination light from a light source at the viewing end of an endoscope apparatus cable to the image forming end of the cable through illumination light conducting optical fibers. Most particularly, the present invention relates to the geometric configuration of such illumination light conducting fibers in proximity to the image forming end of the cable of an endoscope apparatus. 
     BACKGROUND OF THE INVENTION 
     Fiber-optic endoscopic viewing systems are now in common use in industrial and medical applications. The use of endoscopic equipment has become commonplace in locksmithing and other industrial applications to allow otherwise hidden mechanical components to be viewed and manipulated. Endoscopic surgical and exploratory procedures are steadily replacing more traditional invasive surgical procedures in contemporary medical practice. 
     Generally, objects and scenes which are the viewing objective of fiber-optic endoscopic viewing systems are typically in very poorly illuminated or totally dark environments and illumination of the viewing objective must be provided to allow it to be readily observed through the endoscope. Fiber-optic viewing systems of the prior art have utilized flexible, light conducting fiber elements within the endoscope cable to conduct illumination light from a high power light source, such as an incandescent or arc lamp, located at the viewing end of the cable to the distal imaging end of the cable. Typically, each of the illumination light conducting fibers lies adjacent to a central fiber-optic image bundle of the cable with its illumination light conducting fiber axis running generally in set apart parallel relation to the coinciding axes of the endoscope cable and image bundle over the entire length of the endoscope cable. The polished, light emitting end face of each of the illumination light conducting fibers is generally normal to all three axes. 
     This geometric arrangement of the prior art apparatus does not provide complete and uniform illumination of the viewing field of the image forming device of the fiber-optic image bundle at the image forming end of the endoscope cable. Such image forming devices generally have a conically shaped viewing field expanding with distance from the image forming end of the cable at about a 45 to 50 degree angle to the central cable end axis while light emitted from the face of each of the illumination light conducting fibers is concentrated in a conically shaped illumination field expanding with distance from the end of the fiber at about a 20 degree angle to the central illumination light conducting fiber end axis. Thus, the entire viewing field may not be utilized in viewing distant viewing objectives for lack of sufficient illumination of the viewing objective in the outer portion of the viewing field. Further, the overlapping illumination fields of the illumination light conducting fibers results in nonuniform illumination of the viewing objective within the area of sufficient illumination within the viewing field, most particularly varying with radial distance from the center of the viewing field. Typically, an annular shaped area of relatively intense light is created about the center of the view field. 
     Some endoscopic viewing systems of the prior art have attempted to mitigate these problems by twisting the distal, image forming end of the endoscope apparatus cable such that the center of the illumination field of each of the illumination light conducting fibers angels outwardly along a chord of the cable cross section at an angle to the cable centerline. While this creates some diffusion of the viewing field illumination, all of the conical illumination fields of the illumination light conducting fibers are displaced at equal angles and an annular area about the center of the view field will still be more intensely illuminated than the rest of the field. Further, constructing an endoscope cable of this configuration is a difficult process. 
     Other endoscopic viewing systems of the prior art have attempted to mitigate these problems by the placement of small, domed lenses on the light emitting ends of the illumination light conducting fibers. Such lenses may be formed in place by placement of drops of transparent epoxy on the light emitting end surfaces of the fibers. While some diffusion of the illumination light is achieved by these systems, a more intensely illuminated annular area will still exist about the center of the view field. 
     DISCLOSURE OF THE INVENTION 
     It is an object of the present invention to provide view objective illumination for an endoscope apparatus utilizing flexible, light conducting fiber elements within an endoscope cable to conduct illumination light from the image viewing end of the cable to the image forming end, which will provide illumination of the entire viewing field 
     It is an object of the present invention to provide view objective illumination for an endoscope apparatus utilizing flexible, light conducting fiber elements within an endoscope cable to conduct illumination light from the image viewing end of the cable to the image forming end, which will provide generally uniform illumination of the view objective along a radius of the viewing field. 
     It is a further object of the present invention to provide view objective illumination for an endoscope apparatus utilizing flexible, light conducting fiber elements within an endoscope cable to conduct illumination light from the image viewing end of the cable to the image forming end, which will provide uniform illumination of the view objective. 
     In keeping with the above objectives, an endoscope apparatus comprising a preferred embodiment of the present invention includes an endoscope cable with an image viewing end, and an image forming end with an image forming device. A fiber-optic image bundle extends from the image forming device to the image viewing end of the cable. Sixteen illumination light conducting fiber elements run generally adjacent to, and at equally spaced radial intervals about, the optical-fiber image bundle over the length of the endoscope cable. A light source at the image viewing end of the cable provides light which is conducted by the illumination light conducting fiber elements from the image viewing end of the endoscope cable to the image forming end of the cable where the light is emitted through end faces of the illumination light conducting fiber elements to radiate upon and illuminate the view objective. At the image forming end portion of the endoscope cable, the cable, image forming device and fiber optic image bundle have a common axis including a common image forming end portion axis. Each of the illumination light conducting fiber elements has a central axis including an image forming end portion axis. Four of the illumination light conducting fiber elements, located at equally spaced intervals about the image forming device, have image forming end portion axes which are parallel with the common image forming end portion axis. Four of the illumination light conducting fiber elements, located at equally spaced intervals about the image forming device, and at equally spaced intervals between the first four illumination light conducting elements, have image forming end portion axes which are at a 10 degree angle to the common image forming end portion axis. The remaining eight of the illumination light conducting fiber elements, located at equally spaced intervals about the image forming device, have image forming end portion axes which are at a 20 degree angle to the common image forming end portion axis. Each illumination light conducting fiber element has a polished end face generally normal to its image forming end portion axis. 
     Other objects, advantages and aspects of the invention will become apparent upon perusal of the following detailed description and claims and upon reference to the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an end view of the image forming end of an endoscope cable of an endoscope apparatus of the prior art. 
     FIG. 2 is a sectional view of an image forming end portion of an endoscope cable of an endoscope apparatus of the prior art. 
     FIG. 3 is an end view of an endoscope cable of an endoscope apparatus comprising a preferred embodiment of the present invention. 
     FIG. 4 is a sectional view of an endoscope cable of an endoscope apparatus comprising a preferred embodiment of the present invention taken at plane IV—IV of FIG.  3 . 
     FIG. 5 is a sectional view of an endoscope cable of an endoscope apparatus comprising a preferred embodiment of the present invention taken at plane V—V of FIG.  3 . 
     FIG. 6 is a sectional view of an endoscope cable of an endoscope apparatus comprising a preferred embodiment of the present invention taken at plane VI—VI of FIG.  3 . 
     FIG. 7 is an end view of an endoscope cable of an endoscope apparatus comprising an alternative embodiment of the present invention. 
     FIG. 8 is a sectional view of an endoscope cable of an endoscope apparatus comprising an alternative embodiment of the present invention taken at plane VIII—VIII of FIG.  7 . 
     FIG. 9 is a sectional view of an endoscope cable of an endoscope apparatus comprising an alternative embodiment of the present invention taken at plane IX—IX of FIG.  7 . 
     FIG. 10 is a sectional view of an endoscope cable of an endoscope apparatus comprising an alternative embodiment of the present invention taken at plane X—X of FIG.  7 . 
    
    
     DETAILED DESCRIPTION 
     An end view of a distal image forming end portion of an endoscope cable of an endoscope apparatus of the prior art is shown in FIG.  1 . FIG. 2 is a side view, in section, of the distal image forming end portion of endoscope cable  10  of the endoscope apparatus of the prior art shown in FIG.  1 . Body  12  of endoscope cable  10  is fabricated of a of a flexible material and encases central fiber-optic image bundle  14  and illumination light conducting fibers  16 . As shown in FIG. 1, illumination light conducting fibers  16  typically surround fiber-optic image bundle  14  and image window  20 , and lay adjacent to fiber-optic bundle  14  over the length of the cable from its image viewing end to its distal, image forming end. Thus, the central axis of each of illumination light conducting fibers  16  generally lies in set apart parallel relation to the central axis of cable  10  over its entire length. The central axis of the image forming end portion of each of illumination light conducting fibers  16 , proximate to end face  18 , is generally parallel to the image forming end portion of the common axis of cable  10 , fiber-optic image bundle  14  and the image forming device incorporating lenses  22  and  24 . When in use, the image viewing end of cable  10  is attached to an endoscope apparatus having a bright light source lamp which radiates light upon the viewing end faces of illumination light conducting fiber elements  16 . A portion of the light is conducted by illumination light conducting fibers  16  from the viewing end of the cable, along the length of cable  10  to the image forming end of the cable where the light is emitted from end faces  18  of illumination light conducting fibers  16  to illuminate the endoscopic viewing objective. When the objective is illuminated, light reflected by the objective passes through image window  20  and is focused by imaging lenses  22  and  24  to form an image on imaging end face  26  of image bundle  14 . The image is then conducted along fiber-optic image bundle  14  over the length of cable  10  to the viewing end of the cable where it is typically coupled to a television camera to allow display of the image for viewing on an electronic image viewing monitor. 
     Typically, image forming devices such as the lens assembly of the image forming end of prior art endoscope cable  10  of FIGS. 1 and 2, have a conically shaped viewing field expanding with distance from the end of the cable at an angle α to the central cable image forming end portion axis of about 45 to 50 degrees, while light emitted from the face of each of illumination light conducting fiber faces  18  is concentrated in a conically shaped illumination field expanding with distance from the end of the fiber at an angle β to the central fiber portion end axis of about 20 degrees. Thus, the entire viewing field may not be utilized in viewing distant viewing objectives for lack of sufficient illumination of the viewing objective in the outer portion of the viewing field. Further, overlapping of the illumination fields of illumination light conducting fibers  16  results in nonuniform illumination of the viewing objective within the area of sufficient illumination varying both with angular position about the viewing field and, most particularly, with radial distance from the center of the viewing field. 
     An end view of a distal image forming end portion of an endoscope cable of an exemplary endoscope apparatus comprising a preferred embodiment of the present invention is shown in FIG.  3 . FIGS. 4,  5  and  6  are sectional views of the distal image forming end portion of endoscope cable  110  of the exemplary endoscope apparatus comprising a preferred embodiment of the present invention shown in FIG. 3 taken at cutting planes IV—IV, V—V, and VI—VI, respectively, of FIG.  3 . Similar elements to the endoscope apparatus cable of FIGS. 1 and 2 are numbered similarly. Similar to the construction of endoscope cable  10 , body  112  of endoscope cable  110  is fabricated of a flexible material and encases central fiber-optic image bundle  114 . Body  112  of endoscope cable  110  of the preferred embodiment of the present invention also encases  16  illumination light conducting fibers  140 ,  160  and  180  which extend from the viewing end of endoscope cable  110  to the image forming end of cable  110 . Illumination light conducting fibers  140 ,  160  and  180  all have central axes which are generally parallel to the common axis of cable  110  and central fiber-optic image bundle  114  over the length of the cable. 
     The central axes of the four illumination light conducting fiber elements  140  of cable  110  of the exemplary endoscope apparatus comprising a preferred embodiment of the present invention are parallel to the central axis of cable  110  over the entire cable length, including the central axis of image forming end portion  144  of each of fibers  140  proximate each end face  142 , which are generally parallel to the common axis of fiber-optic image bundle  114  and cable  110 , including the image forming device incorporating lenses  122  and  124 . The central axes of the four illumination light conducting fiber elements  160  of cable  110  of the exemplary endoscope apparatus comprising a preferred embodiment of the present invention are parallel to the central axis of cable  110  over the cable length from the viewing end of the cable to the image forming end portion. However, the central axis of image forming end portion  164  of each of fibers  160  proximate each end face  162  forms an angle with the common axis of fiber-optic image bundle  114  and cable  110 , including the image forming device incorporating lenses  122  and  124 . In the preferred embodiment of FIGS. 3 through 6, the angle formed between the axis of each end portion  164  with the common axis is an acute angle, δ, of about 10 degrees. The central axes of the eight illumination light conducting fibers  180  of cable  110  of the exemplary endoscope apparatus comprising a preferred embodiment of the present invention are parallel to the central axis of cable  110  over the cable length from the viewing end of the cable to the image forming end portion. However, the central axis of image forming end portion  184  of each of fibers  180  proximate each end face  182  forms an angle with the common axis of fiber-optic image bundle  114  and cable  110 , including the image forming device incorporating lenses  122  and  124 . In the preferred embodiment of FIGS. 3 through 6, the angle formed between the axis of each end portion  184  with the common axis is an acute angle, θ, of about 20 degrees. 
     A viewing end portion of an endoscope cable of the preferred embodiment of the present invention shown in FIGS. 3 through 6 may be constructed by fabricating the main body of the cable in a conventional manner and allowing the illumination light conducting fibers to extend beyond the main body of the cable beyond the point at which it is desired that the completed cable terminate. The image forming end of the main cable body can then be fixed in a jig which is also adapted to engage the individual illumination light conducting fibers at a point beyond the point at which it is desired that the completed cable terminate to hold the fibers under tension at he desired angular position about the central cable axis and at the desired angular position relative to the cable axis. A plug may also be positioned on the end of the fiber-optic image bundle to assist in creating a cavity for an image forming device. The space between and about the drawn illumination light conducting fibers may then be filled sufficiently with a plastic material, such as an epoxy resin, which will harden into a suitably machineable state. Once hardened, the illumination light conducting fibers may be cut, the end surfaces of the cable machined to the desired shape, the plug removed, the image forming device installed, and the illumination light conducting fiber end faces polished to complete fabrication of the cable image forming end portion. 
     An end view of a distal image forming end portion of an endoscope cable of an exemplary endoscope apparatus comprising an alternative embodiment of the present invention is shown in FIG.  7 . FIGS. 8,  9  and  10  are sectional views of the distal image forming end portion of endoscope cable  210  of the exemplary endoscope apparatus comprising an alternative embodiment of the present invention shown in FIG. 7 taken at cutting planes VIII—VIII, IX—IX, and X—X, respectively, of FIG.  7 . Elements similar to those of the earlier disclosed embodiment of FIGS. 3 through 6 are numbered similarly. As in the previous embodiment of FIGS. 3 through 6, body  212  of endoscope cable  210  is fabricated of a flexible material and encases central fiber-optic image bundle  214 . Body  212  of endoscope cable  210  of the alternative embodiment of the present invention encases  16  illumination light conducting fibers  240 ,  260  and  280  which extend from the viewing end of endoscope cable  210  to the image forming end of cable  210 . Illumination light conducting fibers  240 ,  260  and  280  all have central axes which are generally parallel to the common axis of cable  210  and central fiber-optic image bundle  214  over the length of the cable. 
     As with the earlier, preferred embodiment of FIGS. 3 through 6, the central axes of the four illumination light conducting fiber elements  240  of cable  210  of the exemplary endoscope apparatus comprising an alternative embodiment of the present invention are parallel to the central axis of cable  210  over the entire cable length, including the central axis of image forming end portion  244  of each of fibers  240  proximate each end face  242 , which are generally parallel to the common axis of fiber-optic image bundle  214  and cable  210 , including the image forming device incorporating lenses  222  and  224 . The central axes of the four illumination light conducting fiber elements  260  of cable  210  of the exemplary endoscope apparatus comprising an alternative embodiment of the present invention are parallel to the central axis of cable  210  over the cable length from the viewing end of the cable to the image forming end portion. However, the central axis of image forming end portion  264  of each of fibers  260  proximate each end face  262  forms an angle with the common axis of fiber-optic image bundle  214  and cable  210 , including the image forming device incorporating lenses  222  and  224 . In the alternative embodiment of FIGS. 7 through 10, the angle formed between the axis of each end portion  264  with the common axis is an acute angle, δ, of about 10 degrees. The central axes of the eight illumination light conducting fibers  280  of cable  210  of the exemplary endoscope apparatus comprising an alternative embodiment of the present invention are parallel to the central axis of cable  210  over the cable length from the viewing end of the cable to the image forming end portion. However, the central axis of image forming end portion  284  of each of fibers  280  proximate each end face  282  forms an angle with the common axis of fiber-optic image bundle  214  and cable  210 , including the image forming device incorporating lenses  222  and  224 . In the alternative embodiment of FIGS. 7 through 10, the angle formed between the axis of each end portion  284  with the common axis is an acute angle, θ, of about 20 degrees. 
     End cap  250  of endoscope cable  210  comprising the alternative embodiment of the present invention is made of a rigid material, such as metal or plastic., and covers the image forming end portion of endoscope cable  210 . End surface  228  of end cap  250  lies in a plane normal to the axis of the image forming end portion of cable  210  and has an inner edge defining view port  270  to allow light reflected by the viewing objective to enter through image window  220 . End surface  228  has four illumination light conducting fiber ports  252  through which end portions  244  of fibers  240  pass such that end faces  242  of fibers  240  conform to surface  228  of end cap  250 . Conical surface  227  of end cap  250  is joined to end surface  228  at the outer edge of end surface  228  and is relieved from the plane of surface  228  at angle δ. Conical surface  227  is provided with four illumination light conducting fiber ports  254  through which end portions  264  of fibers  260  pass such that end faces  262  of fibers  260  conform to conical surface  227  of end cap  250 . Conical surface  229  of end cap  250  is joined to conical surface  227  at the outer edge of conical surface  227  and is relieved from the plane of surface  228  at angle θ. Conical surface  229  is provided with eight illumination light conducting fiber ports  256  through which end portions  284  of fibers  280  pass such that end faces  282  of fibers  280  conform to conical surface  229  of end cap  250 . Cylindrical wall  259  extends from the outer edge of conical surface  229  to an inner edge  272  of end cap  250 . Inner edge  272  may be a simple planar circle, as shown in FIGS. 8 through 10, or may be elliptical or even three dimensional, such as a scalloped or surreted edge to assist in maintaining the rotational stability of the cap about the axis of the image forming end portion of cable  210 . 
     A viewing end portion of an endoscope cable of the alternative embodiment of the present invention shown in FIGS. 7 through 10 may be constructed by fabricating the main body of the cable in a conventional manner and allowing the illumination light conducting fibers to extend beyond the main body of the cable beyond the point at which it is desired that the finally formed cable terminate. The image forming end of the main cable body can then be fixed in a jig and image forming device housing  270  fitted to the polished image bundle end face. Illumination light conducting fibers are then fed through illumination light conducting fiber ports  252 ,  254 , and  256  as appropriate as end cap  250  is positioned appropriately in the jig and the illumination light conducting fibers tensioned to correctly position them. A plastic material, such as an epoxy resin, which will harden suitably, is then injected into end cap  250 . The illumination light conducting fiber end faces and cap are then polished to complete fabrication of the cable image forming end portion. 
     While an exemplary endoscope cables comprising a preferred embodiment of the present invention has been shown, it will be understood, of course, that the invention is not limited to those embodiments. Modification may be made by those skilled in the art, particularly in light of the foregoing teachings. For example, rather than bending the distal image forming end portions of the illumination light conducting fibers outwardly from the endoscope cable centerline, prism lenses might be utilized to angle the illumination field centerline of desired fibers from the fiber end portion centerline at desired angles, for example, 10 degrees and 20 degrees. Those familiar with the art will realize that it is also possible to utilize a miniature video camera as the image forming device to transmit an electrical signal to the viewing end of the endoscope cable to be displayed on a video monitor. It is, therefore, contemplated by the appended claims to cover any such modification which incorporates the essential features of this invention or which encompasses the spirit and scope of the invention.