Endoscope attachment for changing angle of view

The present invention provides an endoscopic sheath for protecting and/or changing an angle of view of an endoscope. The sheath has a distal portion configured to engage a distalmost portion of an endoscope imaging optics. The distal portion houses structure for changing the angle of view of an endoscope. In a preferred embodiment, this structure includes a prism. The distal portion may additionally house structure for changing the angle of illumination of an illumination portion of an endoscope. This structure may be a prism or a curved light guide or at least one angled optical fiber. Both the structure for changing the angle of view of an endoscope and the optical member for changing the angle of illumination of an endoscope may be positioned within the distal portion to align with the respective imaging or illumination elements of the endoscope.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The invention relates to accessories for endoscopes and, more particularly, 
to endoscope sheaths which change an angle of view of an endoscope. 
2. Description of the Related Art 
Endoscopes have long been used in surgery to view internal portions of a 
patient's body from a narrow incision in the body exterior or through a 
naturally occurring hollow viscus. Endoscopes used for this purpose are 
long, slender instruments having a shaft which is either rigid or 
flexible, depending upon the procedure being performed. In general, 
endoscopes include an objective lens positioned adjacent a distal end, and 
an image transmission system which may include a fiber optic bundle, relay 
rods or lenses, or a solid state sensor to transmit the image to the 
viewer. Endoscopes also are usually equipped with an illumination system, 
such as a fiber optic bundle, which illuminates the area being imaged. 
Generally, a camera adapter is provided at the proximal end of the 
endoscope to permit the image to be displayed on a monitor for viewing by 
the entire surgical team. It is also known to provide a fluid and/or gas 
conduit which permits the surgeon to clean the distal-most imaging lens 
and/or clear the region in front of the distal-most lens for optical 
viewing. See, for example, U.S. Pat. Nos. 4,667,656; 4,770,163; and 
4,838,246. 
Most endoscopes used for medical procedures have a fixed forward viewing 
angle. Different areas of the body can be imaged by changing the position 
of the endoscope or, in the case of flexible endoscopes, by bending the 
distal tip. In these endoscopes, the objective lens is disposed 
perpendicular to the longitudinal axis of the instrument such that the 
area directly in front of the instrument is viewed by the user. Other 
configurations for endoscopes include side-viewing, and oblique angle of 
view endoscopes. 
In certain procedures, in addition to forward viewing endoscopes, it is 
desirable to have the capability for changing the angle of view during 
different stages of the procedure. For example, when examining the lining 
of a body cavity, e.g., esophagus, intestinal walls, it is advantageous to 
employ a side-viewing or oblique angle of view endoscope. Presently, the 
ability to view at different angles can only be accomplished by 
maintaining a variety of expensive high quality reusable side-viewing 
endoscopes. 
It is known in the art to provide attachments which change the angle of 
view of conventional reusable endoscopes. Typical devices of this type are 
disclosed in U.S. Pat. Nos. 4,747,661 and 4,787,370. In general, such 
attachments fit adjacent only the distal end of the endoscope and include 
complex optical elements which increase the cost of the endoscopes and 
reduce their efficacy for single-use applications. Additionally, many of 
the known attachments require special adaptive elements on the distal end 
of the endoscope in order to properly secure the attachment. The 
attachments do not cover substantially the elongated endoscopic portion of 
the endoscope. As a result, it is difficult to clean and re-sterilize the 
expensive and delicate optics of the endoscope prior to reuse. 
Accordingly, it would be advantageous to provide a device which may be 
readily inserted over or connected to an endoscope and which functions in 
changing the angle of view of the scope without the need for complex 
attachments. It would also be advantageous if such device extends 
substantially the length of the elongated endoscopic portion of the 
endoscope to protect the endoscope from contamination. It would be a 
further benefit if the device incorporated an integral illumination and/or 
irrigation system which provides properly aimed illumination of the area 
to be viewed and irrigation of the viewing lens surface of the endoscopic 
sheath and/or the surgical field. It would also be desirable to provide a 
coupler between a light source and the illumination system which improves 
the accumulated light by increasing the packing fraction of the fibers at 
the coupler interface. It would be further desirous if the device could be 
employed for single use applications. 
SUMMARY OF THE INVENTION 
Generally stated, the present invention is directed to an endoscopic sheath 
for protecting and/or changing an angle of view of an endoscope. A distal 
portion of the sheath houses structure for changing the angle of view of 
an endoscope. In a preferred embodiment, this structure includes a prism. 
The distal portion of the sheath may additionally house structure for 
changing the angle of illumination of the illumination optics portion of 
an endoscope. This may be a prism, a mirror, a curved light guide, or 
structure for angling at least one optical fiber. Both the structure for 
changing the angle of view of an endoscope and the optical member for 
changing the angle of illumination of an endoscope are positioned within 
the sheath distal portion to align with the respective imaging or 
illumination elements of the endoscope.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring now to the drawings, in which like reference numerals identify 
similar or identical elements throughout the several views, FIG. 1 
illustrates an endoscope sheath in accordance with the principles of the 
present invention. Endoscope sheath 10 is configured and dimensioned to be 
positioned over a conventional forward-viewing endoscope 1000 to change 
the angle of view of the endoscope. 
Referring now to FIG. 1, in conjunction with FIG. 3, endoscope 1000 may be 
any known conventional endoscope and may be either rigid or flexible. The 
preferred endoscope to be used with endoscope sheath 10 of the present 
invention includes endoscope housing 1002 and an elongated endoscopic 
portion 1004 extending distally of the housing 1002. Examples of 
endoscopes which can readily be utilized with elongated sheath 10 of the 
present invention are disclosed in U.S. Pat. Nos. 3,089,484; 3,257,902; 
4,784,118; 4,964,710 and 5,188,092, the contents of each being 
incorporated herein by reference. As used herein, "distal" refers to the 
portion of the endoscope or endoscope sheath furthest from the operator, 
i.e., in the direction of the endoscopic portion from housing 1002, while 
"proximal" refers to the portion closest to the operator. 
A function of endoscopic portion 1004 is to transfer illuminating light 
from endoscope housing 1002 to the distal end of the endoscopic portion 
1004 to provide illuminating light to the operative site. In an exemplary 
configuration, endoscopic portion 1004 includes an outer covering 1006 and 
an annular array of fiber optic elements 1008 extending between proximal 
illuminating coupling port 1010 of endoscope housing 1002 and the distal 
end of endoscopic portion 1004 to convey light to the distal end of the 
endoscope. Preferably, the fiber optic elements 1008 are positioned 
adjacent the inner wall of the outer covering in an annular configuration 
as shown in FIG. 3. Any known illumination source may be connected via a 
light guide 200 (FIG. 2) to coupling port 1010 to provide the illuminating 
light for the fiber optics 1008. Such illumination sources include, for 
example, the Lumatec model Superlite light source, halogen lamps, Argon or 
He-Ne-lasers, tungsten filament incandescent lamps, etc. 
Endoscopic portion 1004 incorporates an image transferring system which may 
include a plurality of fiber optic elements 1012 (FIG. 4) to transfer an 
image formed at an image plane to eyepiece 1014 of the endoscope (FIG. 1) 
for viewing. Alternatively, a series of optical lens components may be 
used instead of fiber optics 1012 to transfer the image to the viewer. 
Known relay optical systems include those shown and described in U.S. Pat. 
Nos. 3,089,484; 3,257,902 and the aforementioned 4,964,710. It is also 
envisioned that a video system including a monitor may be operatively 
connected to housing 1002, such as by coupling to eyepiece 1014, to 
provide a video image of the body tissue being viewed. While the preferred 
embodiments of the present invention will be described in conjunction with 
an endoscope having a central image transferring system and an annular 
array of illumination fibers, it will be understood by those skilled in 
the art that the endoscope sheath could be readily adapted for use with 
other endoscope configurations such as non-concentric imaging and 
illumination optics. 
Referring now to FIGS. 1 and 2, in conjunction with FIGS. 3 and 4, the 
novel endoscope sheath 10 of the present invention will be described in 
detail. Endoscope sheath 10 includes a housing portion 12 and an elongated 
sheath portion 14 extending distally from the housing portion 12. Housing 
portion 12 includes a proximal illuminating inlet connector 16 for 
reception of a light guide or tube 200 (FIG. 2) which is connected to a 
light source such as those described above with respect to the endoscope. 
Endoscope sheath 10 is preferably of sufficient length to extend over 
substantially the entire endoscopic portion 1004 of endoscope 1000 to 
protect and isolate of the endoscope during surgical procedures and 
prevent direct contact of endoscopic portion 1004 with the body and body 
fluids. Thus, the user may conveniently switch to and from different 
angles of view without needing to keep multiple clean endoscopes on hand. 
Elongated sheath 14 is preferably formed of a sufficiently rigid material 
such as a biocompatible plastic, stainless steel or the like to be placed 
over a rigid endoscope. Where the sheath is used with a rigid endoscope 
the sheath itself need not have considerable rigidity in and to itself 
since support is provided by the rigid endoscope. The inner diameter of 
elongated sheath 14 preferably approximates the outer diameter of 
endoscopic portion 1004 to form a friction fit between the sheath and the 
endoscope to maintain endoscope sheath 10 on endoscope 1000 during the 
surgical procedure. In the alternative, the inner portion of elongated 
sheath 14 of endoscope sheath 10 may be provided with a compressible 
material having a first non-compressed internal diameter slightly smaller 
than the outer diameter of the endoscopic portion 1004. Insertion of the 
endoscopic portion 1004 initially expands the compressible material of 
elongated sheath 14, which then returns to its original diameter to 
frictionally engage endoscopic portion 1004. Other means to maintain 
endoscope 1000 within endoscope sheath 10 can be utilized such as clamps, 
screws, a bayonet fastener, collets, etc. See, for example, U.S. Pat. No. 
5,217,441. 
Referring now to FIGS. 2-4, endoscope sheath 10 may also be provided with 
an illumination system which preferably includes a fiber optic bundle 18 
which extends from the inlet connector 16 of housing 12 through a channel 
20 (FIG. 4) formed in the wall of elongated sheath 14 to the distal end 
portion 22 of the elongated sheath 14. Optical fiber bundle 18 may be 
fabricated from any suitable optical material including glass and optical 
plastics. A preferred material for optical fiber 18 is polymethyl 
methacrylate (PMMA) having a relatively large numerical aperture to 
provide a field of illumination equal to or greater than the angled field 
of view. The integral illumination system of endoscope sheath 10 enables 
the surgeon to alter the illumination angle to illuminate the new, angled 
area to be viewed independent of the illumination system of the endoscope. 
Further details of the illumination system are discussed below. As will be 
appreciated, where the sheath contains a separate illumination system, the 
endoscope used therewith need not contain a second illumination system. 
Thus, it is contemplated that the sheath could be used with an endoscope 
having only an imaging optical system without an illumination optical 
system. 
Referring to FIG. 4, the distal end portion 22 of elongated sheath portion 
14 houses the optical elements used to change the angle of view of the 
endoscope. In general, these optical elements include an optical member 24 
which cooperates with imaging portion 1012 of the endoscope 1000 to change 
the angle of view of the imaging portion. In this embodiment, optical 
member 24 comprises a 30.degree. deflection prism used to change the 
direction of view of endoscope 1000 from forward-viewing to viewing at an 
oblique angle, i.e., at a 30.degree. angle relative to the longitudinal 
axis of endoscope 1000. In a preferred embodiment, prism 24 is a hybrid 
prism, i.e., one which principally reflects light, but, also refracts the 
light so as to change the angle of view. In the alternative and depending 
on the particular application, prism 24 may be a full reflection prism or 
a full refraction prism. A full refraction prism is preferably used when 
it is desirable to change the angle of view less than about 30.degree. 
relative to the endoscopic axis since such refraction prisms may introduce 
undesirable aberrations, e.g., chromatic aberration, when used as the sole 
means for changing the angle of view. Reflecting surface 25 of prism 24 
may be a metalized mirror having an aluminum base which is coated with at 
least one layer of silicon dioxide and possibly one or more coats of black 
paint to protect the metalized layer. 
The optical components of distal end portion 22 of endoscope sheath 10 also 
includes a concave lens 26 which is positioned between prism 24 and the 
area to be viewed. Lens 26 assists in directing the incident rays through 
optical member 24 and acts as a window, sealing the prism from the 
external environment. A convex lens 28 is positioned between optical prism 
member 24 and objective lens 1016 disposed at the distal end of the 
endoscope image transferring system 1012. Concave lens 26, prism 24 and 
convex lens 28 couple the image into the endoscope which maintaining the 
field of view, albeit at an altered angle. Preferably, the optical 
components are arranged in an afocal system thus avoiding the need for 
refocusing of the instrument. Although depicted in FIG. 4 as two separate 
elements, optical member 24 and convex lens 28 may alternatively be formed 
as a single element, e.g., as a prism having a proximal surface portion 
configured as a convex lens. The optical components of endoscope sheath 10 
may be fabricated from suitable optical materials such as glass or optical 
plastics. 
Fiber bundle 18 of the illumination system of endoscope sheath 10 is curved 
downwardly at its distal end towards the center axis of elongated sheath 
12 to orient the tips of the illumination fibers to provide uniform 
illumination to the angled field of view. Such orientation of fiber bundle 
18 alters the angle of illumination from a position at substantially 
0.degree. relative to the longitudinal axis of the endoscope 1000 to an 
angle of about 30.degree. relative to the axis to correspond to the angle 
of view provided by prism 24. Accordingly, the area to be viewed will be 
directly illuminated by the illumination system. Further, it is preferable 
to provide for an opaque barrier, such as barrier sheath portion 30 to 
separate the curved distal end of fiber bundle from the optical components 
24, 26. Barrier portion 30 reduces veiling glare by disposing the 
illumination outlet distal to and offset from the imaging optics. 
Referring now to FIGS. 5-8, there is illustrated an alternative embodiment 
of the endoscope sheath of the present invention. Endoscope sheath 31 
includes housing portion 33 and an elongated sheath portion 35 extending 
distally from the housing portion 33. Elongated sheath 35 is dimensioned 
to extend over substantially the entire endoscopic portion of an endoscope 
of the type described in connection with the embodiment of FIG. 1. 
A light guide 37 is integrally formed with endoscope sheath 31 through 
housing portion 33 and includes a fiber optic light guide tube 39 and 
light source coupler 41 attached to one end portion of the guide tube 39. 
Light guide tube 39 includes an optical fiber bundle 43 (FIGS. 6 and 8) 
having a plurality of individual optical fibers 43a which extend through 
the length of the tube and into proximal housing portion 33 of endoscope 
sheath 31 where the fibers extend to the distal end portion 45 of 
elongated sheath 35. 
The optical fibers 43a of fiber bundle 43 are arranged in a clover leaf 
configuration as shown in FIG. 8 within light tube 39. The optical fibers 
43a are arranged in a side by side configuration (similar to the 
configuration of optical fibers 18 in FIG. 3) and through a channel formed 
in the wall of elongated sheath 35 to the distal end portion 45 of 
endoscope sheath 31. Preferably, optical bundle 43 includes 5 optical 
fibers however any number of fibers may be used depending on the 
application and design specifications. The fibers preferably are 
fabricated from polymethylmethacrylate (PMMA) and have a fluorinated 
polymer cladding. The diameter of each fiber is about 1.5 mm. 
Referring particularly to FIGS. 6 and 7, in conjunction with FIG. 5, light 
guide coupler 41 includes coupler housing 47 which is fabricated from a 
metallic material such as aluminum. Coupler housing 47 includes a 
plurality of longitudinal bores 49 extending completely therethrough which 
are formed by a drilling or boring operation. Alternatively, the coupler 
with a bore, could be extruded from any suitable heat resistant material, 
such as, metal, ceramic or heat resistant plastic. Longitudinal bores 49 
house a plurality of cylindrically shaped glass rods 51 which extend from 
light source inlet end portion 41a of coupler 41 to a position identified 
by reference numeral 53 intermediate the inlet end 41a and light tube 
coupler end 41b of the coupler. The remaining portion of coupler housing 
47 defined between position 53 (FIG. 6) and light tube coupler end 41b 
accommodates the ends of optical fibers which extend beyond light tube 39. 
In particular, the size and number of glass rods preferably correspond 
identically with the size and number of fibers in the fiber optic bundle. 
A single optical fiber 43a is positioned within each longitudinal bore 49 
of coupler housing 47 such that each single fiber 43a is in face to face 
contacting relation with a single glass rod 51 at position 53. Optical 
bundle 43 may be secured within coupler 41 by conventional means. 
Specifically a heat resistant adhesive or friction fit is preferred. 
FIG. 6A shows an alternative preferred coupling 47a configured 
substantially similar to coupling 47 of FIG. 6 with the exception of inner 
bore 119. In this embodiment, inner bore 119 is substantially circular in 
cross-section and dimensioned to receive a pair of glass rod mounting 
sleeves 111 and a fiber optic mounting sleeve 113 therein. Preferably, 
both the glass rod mounting sleeve 111 and fiber optic mounting sleeve 113 
are fabricated from an engineering metal or plastic and are spaced apart 
so as to inhibit the conduction of heat longitudinally through coupling 
47a. The fibers 43a of the fiber optic bundle 43 extend proximally of 
fiber optic mounting sleeve 113 and are positioned in abutment with glass 
rods 49. This configuration establishes air gaps 117 between sleeves 111 
and 113 which inhibit heat conduction to fibers 43a. 
The face to face arrangement of glass rods 51 and optical fibers 43a within 
the longitudinal bores of coupler housing 47 increases the coupling 
efficiency of the fibers 43a and glass rods 51, which thereby results in a 
high transmittance of light from the glass rods to the optical fibers with 
minimal light loss. For example, in a seven-fiber fiber optic bundle 
system the relative output of a system with this arrangement of fibers and 
glass rods was at least double that of conventional fiber optic systems 
having a high number of fibers and better than conventional liquid 
systems. 
Glass rods 51 are preferably fabricated from a heat resistant material such 
as clad glass rods, i.e., glass rods having a (glass) cladding with a 
lower index of refraction than that of the core glass material. Such clad 
glass rods are available from Electro Fiber Optics. Preferably, the 
diameter of each glass rod 51 is identical to the diameter of each 
individual optical fiber 43a, i.e., about 1.5 mm. Also, in the preferred 
embodiment, 5 glass rods 51 are provided to supply light to the five 
individual optical fibers 432 of optical bundle 43. 
Referring now to FIG. 9, there is illustrated an alternative embodiment of 
the endoscope sheath of the present invention. Endoscope sheath 40 is 
similar in most respects to endoscope sheath 10 of FIGS. 1-4 and includes 
an elongated sheath portion 42 extending from a housing portion (not 
shown) and having incorporated therein an integral illumination system in 
the form of a fiber optic bundle 44 which extends through a channel 46 
formed in sheath portion 42. In this embodiment, the distal end portion 48 
of endoscope sheath 40 employs a 60.degree. deflection prism element 50 to 
alter the angle of view 60.degree. relative to the axis of the endoscope. 
In addition, at the extreme distal end portion 48 of the elongated sheath 
40 at a position adjacent the distal end of fiber optic bundle 44 is a 
prism element 52. Prism element 52 changes the angle of illumination from 
substantially 0.degree. relative to the endoscope axis to 60.degree. 
relative to the endoscope axis to correspond to the 60.degree. angle of 
view. Thus, the oblique area to be viewed is directly illuminated by the 
illumination system. A concave lens 53 may be disposed adjacent prism 52 
and functions in diverging the light rays passing through prism 52 to 
increase the area of the body cavity illuminated by fiber optic bundle 44. 
An opaque barrier portion 54 is present between the distal light emitting 
end of fiber bundle 44 and prism 50 to reduce veiling glare. Distal end 
portion 48 also includes a concave lens 56 and convex lens 58 which 
function in a similar manner to their corresponding components described 
in connection with the embodiments of FIGS. 1-4. 
FIG. 10 illustrates an alternate embodiment of the endoscope sheath of the 
present invention. Endoscope sheath 60 includes an elongated sheath 
portion 62 which is positioned over endoscope 1100 having illumination 
system 1102 in the form of fiber optic bundles. Endoscope sheath 60 does 
not have an independent illumination system as the prior two embodiments. 
Endoscope sheath 60 includes an elongated sheath portion 62 and a distal 
end portion 64 connected to the sheath portion 62. Distal end portion 64 
includes an optical element 66 which changes both the angle of view of the 
imaging system 1104 of the endoscope 1100 and for changing the angle of 
illumination of the illumination portion 1102 of the endoscope. Element 66 
is a prism which aligns with both the imaging system 1104 and the 
illumination portion 1102 of endoscope 1100 and can direct/reflect light 
for illumination and imaging at substantially the same angle to the 
longitudinal axis. 
Referring now to FIGS. 11, 12, 13A, 13B and 14-17, there is illustrated 
another alternative embodiment of the present invention. Endoscope sheath 
70 includes an elongated sheath member 72 and a prism mount 74 which is 
adapted to be mounted to the distal end portion of elongated sheath member 
72. Elongated sheath 72 is to be positioned over the endoscopic portion 
1004 of the endoscope 1000 and includes an illumination system in the form 
of fiber optic bundle 76 and a fluid and/or gas conduit 78 which extends 
along the length of the sheath member 72. As illustrated in FIG. 17, fiber 
optic bundle 76 and conduit 78 extend through channels 80, 82 respectively 
formed in a wall of sheath member 72. An illumination inlet connector 84 
at the proximal end of sheath member 72 receives an illumination guide 
tube 500 extending from a light source to supply the fiber optic bundle 76 
with light. An inlet port 86 is also formed on the proximal end portion of 
the elongated sheath 72 and receives a fluid supply tube 600. The fluid 
mechanism includes an outlet port or nozzle 88 which directs over and/or 
is in front of the distalmost lens surface 102 of prism mount 74 to clean 
the lens surface so as to remove body fluids which may accumulate thereon 
during the surgical procedure and/or to clear the region in front of the 
lens to enhance viewing. 
The novel prism mount 74 is adapted to be positioned within and attached to 
the distal end portion of the sheath member 72. Prism mount 74 preferably 
defines an outer diameter which is substantially equal to or slightly less 
than the inner diameter of the distal end of sheath member 72 to form a 
frictional fit between the two components to thereby mount the prism mount 
74 to the sheath member. Adhesives and/or sealing compounds may be used to 
secure the prism mount to the sheath member and to seal the distal end of 
the sheath. Prism mount 74 includes a 30.degree. hybrid prism 90 for 
changing the angle of view approximately 30.degree. relative to the axis 
of the endoscope. FIG. 12 illustrates the ray path and orientation through 
the optical elements of prism mount 74. The geometrical characteristics of 
the optical components of prism mount 74 are defined by lens surfaces A-F 
as shown in FIG. 12. The on-axis geometrical and optical parameters of the 
optical components of optical sheath 70 are recorded in Table 1 below. 
Table 1 is a follows: 
TABLE 1 
______________________________________ 
Surface Radius Thickness Medium Index 
______________________________________ 
A 0.488 0.035 Bk7 1.52 
B Plano N/A F2 1.62 
C Plano N/A F2 1.62 
D Plano N/A F2 1.62 
E Plano .081 AIR 1.00 
F 0.371 .087 .sup.1 Epoxy 
1.56 
G Plano 
______________________________________ 
*dimensions are in inches 
.sup.1 Emerson & Cuming Stycast 1267 Epoxy 
FIGS. 13A and 13B illustrate the specific dimensions and angles of a 
preferred 30.degree. hybrid prism in accordance with the invention. Table 
2 below outlines these dimensions in detail. Table 2 is as follows: 
TABLE 2 
______________________________________ 
Surface or Angle 
Dimension Angle (degrees) 
______________________________________ 
i 0.117 N/A 
ii 0.304 N/A 
iii 0.253 N/A 
iv 0.240 N/A 
v 0.011 N/A 
vi 0.387 N/A 
.alpha. N/A 108.degree.46' 
.beta. N/A 19.degree.12' 
______________________________________ 
* dimensions are in inches 
Prism 90 is preferably inserted within a correspondingly dimensioned 
opening 92 (FIGS. 14-16) formed in the wall of prism mount 74 and secured 
within the prism mount by snap fit or other friction fit, adhesives or the 
like. The upper portion of prism mount 74 defines a recessed region 94 
which is dimensioned to accommodate the optical fibers 76 extending from 
elongated sheath member 72. Prism mount 74 also includes angled channel 96 
adjacent recessed region 94 which accommodates the extreme distal end of 
the optical fibers 76. Channel 96 bends the fibers towards the 
longitudinal axis of endoscopic portion 1004 to alter the illumination 
angle in a manner similar to that described in connection with the 
embodiments of FIGS. 1-4, i.e., channel 96 redirects optical fibers 76 
such that the light rays are directed from prism mount 74 at a 30.degree. 
angle relative to the axis of the endoscope. The barrier portion 98 (FIG. 
17) defined between channel 96 and the optical components of prism mount 
74 minimizes veiling glare in a manner similar to that described above. 
Prism mount 74 may also contain a channel 100 which receives the distal 
end of fluid conduit 78. Channel 100 terminates in nozzle 88 which directs 
fluid over and/or in front of lens surface 102 to clean the lens surface 
and/or clear the region in front of the lens for optimal viewing. The 
remaining optical components of prism mount 74 include concave lens 104 
positioned at the distal end of prism mount 74 and having lens surface 
102, and convex lens 106 disposed at the proximal end surface of prism 88. 
Lens 102 and lens 106 function in a similar manner to their corresponding 
lenses of the embodiment of FIGS. 1-4. Sealants may be used to seal the 
distal end of the sheath, such as at fibers 76 and conduit 78. 
Referring now to FIGS. 18-21, there is illustrated another alternative 
embodiment of the present invention. Endoscope sheath 110 is similar to 
the endoscope sheath described in connection with the embodiment of FIGS. 
13-17 and includes an elongated sheath 112 having an fiber-optic bundle 
illumination system 114. Elongated sheath 112 includes aligning insert 
members 116 (FIG. 19) disposed within the interior of sheath 112. Insert 
members 116 may extend along the length of elongated sheath 112 and are 
dimensioned to reduce the effective inner diameter of elongated sheath 112 
to approximate the outer diameter of endoscopic portion 1004. Insert 
members 116 may also serve to form a friction fit between the sheath 110 
and the endoscope portion 1004. Aligning inserts 116 also define a channel 
118 to accommodate the fiber optic bundle 114. See FIG. 19. Similar 
inserts are shown in FIG. 11. It is contemplated that the elongated sheath 
and alignment inserts could be integrally molded together as one piece to 
reduce cost and facilitate assembly. It is also contemplated that the 
plurality of illumination fibers in the sheath may be replaced by a light 
transmissive solid molded plastic light guide conforming to the shape of 
the illumination channel in the sheath, or a liquid-containing light guide 
similarly conforming to the light channel. 
Prism mount 120 includes a 60.degree. prism 122 which is mounted within the 
prism mount 120 for changing the angle of view 60.degree. relative to the 
longitudinal axis of the endoscope. Prism 122 includes wing portions 123 
(FIG. 21) disposed on opposing side walls thereof which engage flanges 125 
of prism mount 120. Because the distal tip of the prism is captured in 
notch-forming tabs on the mount the notch-forming tabs, wing portions and 
flanges securely hold prism 122 to the mount. Prism mount 120 also 
includes a light guide 124 which may be integrally formed with prism mount 
120 and disposed adjacent the distal end of fiber optic bundle 114. Light 
guide 124 alters the angle of illumination 60.degree. relative to the axis 
of the endoscope without requiring bending of the fiber optic bundle 114. 
Light guide 124 preferably has a total internal reflection surface Y for 
directing illumination from the fibers toward the angled field of view. 
Prism mount 120 also includes an opaque barrier 126 (FIG. 20A) positioned 
between light guide 124 and prism 122. The barrier 126 comprises a 
reflective or opaque layer such as foil which fits into channel 127 
between prism 122 and light guide 124 and extends proximally to the 
overlap mirrored surface of prism 122. Barrier 126 minimizes veiling glare 
and leakage of light between prism 122 and light guide 124. 
As best shown in FIG. 20B, the remaining optical components of prism mount 
120 include convex lens surface 128 which is formed on the proximal 
surface of prism 122 and lens 130 molded into the mount. Lenses 128, 130 
function in a similar manner to their corresponding lens components of the 
embodiment of FIGS. 1-4. Advantageously, prism mount 120 may be integrally 
molded of plastic or glass to include lens 130 and light guide 124 
obviating the need for separate formation and mounting of these 
components. Further, as previously mentioned, the prism mount system 
advantageously includes wing portions 123 on the prism and flanges 125 on 
the mount for engaging and retaining prism 122, thereby facilitating 
assembly of prism to the mount in snap-fit relation. Thus, where prism 
mount 120 has integrally formed therein the concave lens 130, the device 
may be assembled by simple snap-fitting prism 122 onto mount 120, fitting 
mount 120 to sheath 112 with fibers 114 abutting total integral reflection 
light guide 124, and mounting the tip to the sheath. Prism mount 120 can 
engage sheath 112 by friction or other fit with or without adhesives or 
sealants, as required. 
Referring to FIG. 20B, the geometrical characteristics of the optical 
components mounted in prism mount 120 are defined by lens surfaces H-N. 
The on-axis geometrical and optical parameters of the optical components 
are recorded in Table 3 below. Table 3 is as follows: 
TABLE 3 
______________________________________ 
Surface Radius Thickness Medium Index 
______________________________________ 
H 0.4671 N/A Polystyrene 
1.59 
I Plano N/A Polystyrene 
1.59 
J Plano N/A Polystyrene 
1.59 
K Plano 0.0793 Air 1.00 
L 0.4904 0.0440 Polystyrene 
1.59 
M Plano N/A 
______________________________________ 
FIG. 20B also illustrates the specific dimensions and angles of the optical 
components of prism mount 120. Table 4 outlines these dimensions in 
detail. Table 4 is as follows: 
TABLE 4 
______________________________________ 
Surface or Angle Dimension Angle 
______________________________________ 
x 0.2145 N/A 
xi 0.3516 N/A 
.theta. N/A 99.5.degree. 
.alpha. N/A 28.5.sup. 
______________________________________ 
Referring now to FIG. 22, there is illustrated a kit 201 incorporating the 
previously described endoscope sheaths of the present invention. The kit 
201 may include an endoscope 1000 and one or more of the endoscopic 
sheaths S each having a different angle of view. For example, sheaths with 
a 30.degree. prism and/or a 60.degree. prism can be packaged with an 
endoscope in a single kit so the user can select (and interchange) the 
sheath and place it over the endoscope prior to insertion into the body to 
achieve the desired angle of view in the surgical procedure. It is also 
envisioned that a 0.degree. sheath could be included to protect the 
endoscope and maintain the cleanliness of the scope during non-oblique 
imaging. Thereafter, when a change of the angle of view is required to 
perform the surgery, a sheath incorporating a 30.degree. or a 60.degree. 
prism may be interchanged with the 0.degree. sheath. A further advantage 
of a 0.degree. sheath is that an improved illumination system having a 
higher transmission efficiency may be used in place of or to supplement 
the illumination system of the endoscope. Yet a further advantage is that 
an endoscope not having a fluid and/or gas conduit for cleaning the 
distal-most imaging lens and/or clearing the region in front of the 
distal-most lens can be provided with such a conduit by using a sheath 
having such a conduit. The package used may include a molded plastic cover 
or lid 202 and a base 204 which is secured to the lid along respective 
peripheral portions thereof. Alternatively, it is contemplated that a kit 
may be provided containing a plurality of endoscope sheaths without an 
endoscope. Such a kit may be useful, for example, with reusable 
endoscopes. 
Referring now to FIG. 23, there is illustrated another alternative 
embodiment of the endoscope sheath of the present invention. Endoscope 
sheath 150 includes elastic sheath member 152 which is fabricated from a 
flexible material such as latex rubber and is attached to prism mount 154 
in any known manner such as by welding, adhesives or the like. The elastic 
sheath 152 may be pulled onto endoscopic portion 1004 and extend 
proximally to enclose substantially all of the elongated endoscopic 
portion of the endoscope. Elastic sheath 152 is preferably dimensioned to 
form a snug fit about the endoscopic portion 1002. Prism mount 154 
includes a prism to change the angle of view as previously described. This 
embodiment of endoscopic sheath may have particular application with 
flexible endoscopes. FIG. 24 illustrates the endoscope sheath 150 of FIG. 
23 packaged along with a conventional endoscope 1000 as part of a kit 
having a 30.degree. endoscope sheath and 60.degree. endoscope sheath. 
While the invention has been particularly shown and described with 
reference to the preferred embodiments, it will be understood by those 
skilled in the art that various modifications and changes in form and 
detail may be made without departing from the scope and spirit of the 
invention. For example, it is conceivable that other prisms such as 
45.degree. prism or right angle prism may be readily employed. 
Additionally, plural prism systems, and rotatable prisms which change the 
angle of view from forward to side viewing, e.g., roof prisms can also be 
utilized. Such rotatable prisms may be controlled proximally by the user. 
Accordingly, modifications such as those suggested above, but not limited 
thereto, are to be considered within the scope of the invention.