FREE ESSAY ON FIBER-OPTICS ENDOSCOPY

FIBER-OPTICS ENDOSCOPY

FIBER -OPTICS
"ENDOSCOPIC PHOTOGRAPHY"
SUBMITTED TO : Sabri ALTINTA?
SUBMITTED BY : Burak AKAY
9703163
BO?AZ?C? UNIVERSITY
MECHANICAL ENGINEERING DEPARTMENT
MATERIAL SCIENCE TERM PROJECT
SUMMER 2000
ABSTRACT
Fiber optics produced by special methods from silica glass and quartz which replaced
copper wire is very useful in telecommunications, long distance telephone lines and in
examining internal parts of the body (endoscopy). Equipment for photography is available
with all current fiber-optic endoscopes. Through a process known as total internal
reflection, light rays beamed into the fiber can propagate within the core for great
distances with remarkably little attenuation or reduction in intensity.
In general, the methods of fiber production fall into three categories; (a) the extrusion
method for synthetic fibers; (b) hot drawing of fibers from molten bulk material through
an orifice; and (c) drawing of uncoated, coated and multiple fibers from assemblies of
rods and tubes fed through a hollow cylindrical furnace.
Three forms of fiber optics components have been proposed for the improvement of the
image quality, field angle and photographic speed of various types of optical systems.
These fiber optics elements, in the form of a field flattener, a conical condenser and
distortion corrector, can be used separately or combined into a single unit called a
"Focon". 
BO?AZ?C? UN?VERS?TES?
MAK?NA MUHEND?SL??? DEPARTMANI
MALZEME DERS? DONEM PROJES?
YAZ OKULU 2000
OZET
Gunumuzde bak?r tellerin yerini alan silikon cam?ndan ve kristalinden uretilen fiber
optikler, telekomunikasyonda, uzun mesafeli telefon hatlar?nda ve insan vucudunun i?
k?s?mlar?n? inceleyen endoskopilerde kullan?lmaktad?r. Foto?raf ekipmanlar?nda da butun
fiber-optik endoskoplara kullan?lmaktad?r. Tam i? yans?ma olarak bilinen i?lem yoluyla,
fiberin i?inde toplanan ???k ???nlar?, uzun mesafeler boyunca ?iddetinde ku?uk bir azalma
ve bozulmayla yol alabilmektedir.
Genellikle, fiber uretimleri u? kategoridedir; Sentetik fiber uretiminde d???na ??karma
methodu; Erimi? dokme maddelerden a??zlar?na do?ru olu?an fiberlerin s?cak ?izimleriyle,
kaplanm??,kaplanmam?? veya kar???k fiberlerin ?izimleriyle. 
U? ?e?it olan fiber optik par?alar?; goruntu kalitesini, ?e?itli optik sistemlerdeki alan
a??s? ve fotografik h?zlar? geli?tirmek i?in du?unulmu?tur. Bu fiber optik elemanlar?;
alan duzle?tirici, konik yo?unla?t?r?c? ve sapma duzenleyici ?ekillerindedir ve ayr? veya
"Focon" ad? verilen unite i?in birle?mi? olarak kullan?labilirler. 
LIST OF FIGURES
Figure 2.1 Photograph of the earliest bundle of uncoated aligned fibers Page 7
Figure 3.1 Core of a step index fiber Page 8
Figure 3.2 Schematic diagram of a typical fiber drawing Page 9
Figure 3.3 Preform manufacturing apparatus used in Silica-Quartz Page 11
Figure 3.4 Comparison of static,dynamic and spitial filtering imagery Page 12
Figure 4.1 Field flattener system of photography Page 13
Figure 4.2 Showing the image transmission through a conical fiber bundle Page 14
Figure 4.3 Fiber optics distortion correctors Page 14
Figure 4.4 Limiting resolution of Focon system Page 15
Figure 5.1 Single lens reflex camera Page 16
TABLE OF CONTENTS
1. INTRODUCTION
2. HISTORY OF FIBER OPTICS
3. WHAT IS FIBER OPTICS?
3.1 WHAT IS SILICA?
3.2 WHAT IS QUARTZ?
3.3 WHAT IS ENDOSCOPIC PHOTOGRAPHY?
4. ENDOSCOPIC PHOTOGRAPHY ELEMENTS
4.1 FIELD FLATTENER
4.2 CONICAL CONDENSER
4.3 DISTORTION CORRECTOR
4.4 FOCON RESOLUTION
5. ENDOSCOPIC PHOTOGRAPHY TECHNIQUES
5.1 COLOUR PHOTOGRAPHY WITH FIBRE-OPTIC ENDOSCOPES
5.2 CINE- ENDOSCOPY
5.3 CLOSED CIRCUIT COLOUR TELEVISION ENDOSCOPY
5.4 GASTRO-CAMERA EXAMINATION
6. CONCLUSION
7. REFERENCES
8. APPENDIX
1. INTRODUCTION
The technology of fiber drawing for nonoptical applications is old and fairly standard.
Very-small-diameter glass and quartz fibers were made as early as by Faraday. In the
early stages of the production of glass fibers on an industrial scale, the main
application of the fibers was envisaged in the textile industry. More recently, they have
been used for insulation against sound, heat and electricity. Presently, very fine fibers
are being made of materials such as glass, quartz, nylon, polystyrene, polymethylcrylate.
Of these, glasses, quartz and plastics are preferred for optical use because of their
higher visible light transmission, longer thermal working range, better surface
characteristics and mechanical strength. Furthermore, it has been shown that glass fibers
can have greater tensile strength than can be expected from the bulk material. 
2. HISTORY OF FIBER OPTICS
The conduction of light along transparent cylinders by multiple total internal
reflections is a fairly old and well known phenomenon. It is entirely possible that
grecian and other ancient glassblowers observed and used this phenomenon in fabricating
their decorative glassware. In fact, the basic techniques used by the old Venetian
glassblowers for making 'millifiore' form an important aspect of present-day fiber optics
technology. However, the earliest recorded scientific demonstration of this phenomenon
was given by John Tyndall in 1870. In demostration Thyndall used an illuminated vessel of
water and showed that, when a stream of water was allowed to flow through a hole in the
side of the vessel, light was conducted along the curved path of the stream.
In 1951 when A.C.S. van Heel in Holland and H.H. Hopkins and N.S. Kapany studied on the
transmission of images along an aligned bundle of flexible glass fibers. But it was the
year 1956 that Kapany first applied the term 'fiber optics' to this field and described
its principle and various of possible applications. Kapany defines fiber optics as the
art of the guidance of light, in the ultraviolet, visible and infrared regions of the
spectrum, along transparent fibers through predetermined paths.
Between 1957 and 1960 Potter, Reynolds, Reiffel and Kapany investigated the use of
scintillating fibers for tracking high energy particles. Potter also investigated the
theory of skew ray propagation along fibers in some detail.
One of the biggest application area of fiber optics is in medicine. Hirschowitz have been
working on the developement of fiber optics gastroduodenal endoscopes and Kapany have
been researching fiber optics in gastrocopy, bronchoscopy, retroscopy and cyctoscopy. 
Kapany, Drougard and Ohzu have made basic studies on image transfer characteristics of
fiber assemblies.
3. WHAT IS OPTICAL FIBRES?
Optical fibres are glass or plastic waveguides for transmitting visible or infrared
signals. Since plastic fibres have high attenuation and are used only in limited
applications, they will not be considered here. Glass fibres are frequently thinner than
human hair and are generally used with LEDs or semiconductor lasers that emit in the
infrared region. For wavelengths near 0.8 to 0.9 m, gallium arsenide-aluminum gallium
arsenide (GaAs-AlxGa1 - xAs) sources are used, and, for those of 1.3 and 1.55 m, indium
phosphide-gallium indium arsenide phosphide (InP-GaxIn1 - xAsyP1 - y) sources are
employed. As noted earlier, optical fibres consist of a glass core region that is
surrounded by glass cladding. The core region has a larger refractive index than the
cladding, so that the light is confined to that region as it propagates along the fibre.
Fibre core diameters ranges between 1 and 100 m, while cladding diameters are between 100
and 300 m.
Fibres with a larger core diameter are called multimode fibres, because more than one
electromagnetic-field configuration can propagate through such a fibre. A single-mode
fibre has a small core diameter, and the difference in refractive index between the core
and cladding is smaller than for the multimode fibre. Only one electromagnetic-field
configuration propagates through a single-mode fibre. Such fibres have the lowest losses
and are the most widely used, because they permit longer transmission distances. They
have a constant refractive index in the core with a diameter between 1 and 10 m. The
index in the cladding layer decreases by roughly 0.1 to 0.3 percent. This type of fibre
is called a step-index fibre.
The multimode fibres may be step-index fibres with diameters between 40 and 100 m. The
refractive index step between the core and cladding is approximately 0.8 to 3 percent. In
a graded-index fibre, the core refractive index varies as a function of radial distance.
In such a fibre, a ray in the centre of the core travels more slowly than one near the
edge, because the speed of propagation v is related to refractive index n as v = c/n,
where c is the speed of light. The ray near the edge has a longer zigzag path than the
ray in the centre. The transit times of the rays are thus equalized.
Both single-mode and multimode fibres are made of silica glass. The refractive indexes of
the silica are varied with dopants such as germanium dioxide (GeO2), phosphoric oxide
(P2O5), and boric oxide (B2O3). Vapour-phase growth reactions are used to obtain the
preform rod, which is then drawn into optical fibres. For example, a GeO2-SiO2 film may
be deposited inside a silica tube. In this case, the GeO2 increases the core refractive
index. In another method, preforms for low-loss, single-mode fibres are made by first
depositing a low-index borosilicate layer on the inner surface of the silica tube and
then depositing a silica layer or inserting a pure fused silica rod before collapsing the
preform. The preform is then drawn into the optical fibre and covered with a polymer
coating.
There are a number of factors that contribute to attenuation in an optical fibre.
Rayleigh scattering is caused by microscopic variations in the refractive index of a
fibre and is proportional to 4. Absorption by hydroxyl (OH) ions increases the absorption
and gives the minim in loss at 1.3 and 1.55 m. At longer wavelengths; absorption by the
atomic vibrations in the silicon-oxygen atoms rapidly increases the loss. Single-mode
fibres commercially available for communications systems have losses as low as 0.2
decibel per kilometre. The low fibre loss permits increased repeater spacing and lower
system cost. High-bit-rate digital systems without repeaters have been demonstrated for
fibre lengths of more than 100 kilometres.
Fibre splicing techniques have been developed so that repairs can be made in the field
with losses of only 0.1 to 0.3 decibel. A variety of optical connectors are used,
providing both ease of use and low loss of only a few tenths of a decibel. Fibres are
combined into many different kinds of cables, which can be laid both in the ground and
under the sea.
3.1 WHAT IS SILICA?
Of the various glass families of commercial interest, most are based on silica, or
silicon dioxide (SiO2), a mineral that is found in great abundance in
nature--particularly in quartz and beach sands. Glass made exclusively of silica is known
as silica glass, or vitreous silica. (It is also called fused quartz if derived from the
melting of quartz crystals.) 
Silica glass is used where high service temperature, very high thermal shock resistance,
high chemical durability, very low electrical conductivity, and good ultraviolet
transparency are desired. However, for most glass products, such as containers, windows,
and lightbulbs, the primary criteria are low cost and good durability, and the glasses
that best meet these criteria are based on the soda-lime-silica system. After silica, the
many soda-lime glasses have as their primary constituents soda, or sodium oxide (Na2O;
usually derived from sodium carbonate, or soda ash), and lime, or calcium oxide (CaO;
commonly derived from roasted limestone). To this basic formula other ingredients may be
added in order to obtain varying properties. For instance, by adding sodium fluoride or
calcium fluoride, a translucent but not transparent product known as opal glass can be
obtained. Another silica-based variation is borosilicate glass, which is used where high
thermal shock resistance and high chemical durability are desired--as in chemical
glassware and automobile headlamps. Crystal tableware was made of glass containing high
amounts of lead oxide (PbO), which imparted to the product a high refractive index (hence
the brilliance), a high elastic modulus (hence the sonority, or ring), and a long working
range of temperatures. Lead oxide is also a major component in glass solders or in
sealing glasses with low firing temperatures.
3.2 WHAT IS QUARTZ?
Quartz has attracted attention from the earliest times; water - clear crystals were known
to the ancient Greeks as krystallos - hence the name crystal, or more commonly rock
crystal, applied to this variety. The name quartz is an old German word of uncertain
origin first used by Georgius Agricola in 1530.
Quartz has great economic importance. Many varieties are gemstones, including amethyst,
citrine, smoky quartz, and rose quartz. Sandstone, composed mainly of quartz, is an
important building stone. Large amounts of quartz sand (also known as silica sand) are
used in the manufacture of glass and ceramics and for foundry molds in metal casting.
Crushed quartz is used as an abrasive in sandpaper, silica sand is employed in
sandblasting, and sandstone is still used whole to make whetstones, millstones, and
grindstones. Silica glass (also called fused quartz) is used in optics to transmit
ultraviolet light. Tubing and various vessels of fused quartz have important laboratory
applications, and quartz fibres are employed in extremely sensitive weighing devices.
Quartz is the second most abundant mineral in the Earth's crust after feldspar. It occurs
in nearly all-acid igneous, metamorphic, and sedimentary rocks. It is an essential
mineral in such silica-rich felsic rocks as granites, granodiorites, and rhyolites. It is
highly resistant to weathering and tends to concentrate in sandstones and other detrital
rocks. Secondary quartz serves as a cement in sedimentary rocks of this kind, forming
overgrowths on detrital grains. Microcrystalline varieties of silica known as chert,
flint, agate, and jasper consist of a fine network of quartz. Metamorphism of
quartz-bearing igneous and sedimentary rocks typically increases the amount of quartz and
its grain size.
Quartz exists in two forms: (1) alpha-, or low, quartz, which is stable up to 573? C
(1,063? F), and (2) beta-, or high, quartz, stable above 573? C. The two are closely
related, with only small movements of their constituent atoms during the alpha-beta
transition. The structure of beta-quartz is hexagonal, with either a left- or
right-handed symmetry group equally populated in crystals. The structure of alpha-quartz
is trigonal, again with either a right- or left-handed symmetry group. At the transition
temperature the tetrahedral framework of beta-quartz twists, resulting in the symmetry of
alpha-quartz; atoms move from special space group positions to more general positions. At
temperatures above 867? C (1,593? F), beta-quartz changes into tridymite, but the
transformation is very slow because bond breaking takes place to form a more open
structure. At very high pressures alpha-quartz transforms into coesite and at still
higher pressures, stishovite. Such phases have been observed in impact craters.
Quartz is piezoelectric: a crystal develops positive and negative charges on alternate
prism edges when it is subjected to pressure or tension. The charges are proportional to
the change in pressure. Because of its piezoelectric property, a quartz plate can be used
as a pressure gauge, as in depth-sounding apparatus.
Just as compression and tension produce opposite charges, the converse effect is that
alternating opposite charges will cause alternating expansion and contraction. A section
cut from a quartz crystal with definite orientation and dimensions have a natural
frequency of this expansion and contraction (ie. vibration) that is very high measured in
millions of vibrations per second. Properly cut plates of quartz are used for frequency
control in radios, televisions, and other electronic communications equipment and for
crystal-controlled clocks and watches.
3.3 WHAT IS ENDOSCOPIC PHOTOGRAPHY?
With the use of modern light -weight single lens reflex cameras employing either
automatic exposure control or through-the-lens metering, good half or whole frame 35mm
colour photographs can be taken. Distal cameras (intragastric cameras), producing 5mm or
6mm colour pictures and electronic distal flash, are also available in some
fibre-endoscopes. Endoscopic photography is the available equipment and the best method
of obtaining the best possible colour photographs.
It is possible to obtain high-quality colour transparencies of bowel lesions. These are
generally employed for patient records, teaching and research. They are not usually
employed for diagnosis since visual inspection and biopsy will already have been
performed. An exception is in so called gastro-camera diagnosis where miniature
photographs are taken from within the stomach as an aid to the detection of early gastric
cancer. 
Endoscopic cine-photography is useful for recording motility, endoscopic techniques, and
unusual lesions. It can be also be used to make teaching films. Close circuit colour
television endoscopy is already in routine use in some centres of Japan, the United
States and Europe and will undoubtedly find a wider use, especially for teaching and
training. This equipment is naturally very costly but cheaper equipment can be
anticipated. 
4. ENDOSCOPIC PHOTOGRAPHY ELEMENTS
4.1 FIELD FLATTENER
In lens design, it is desirable that the image coincide with the Gaussian image plane so
that the whole field may be in focus simultaneously. In this case, the Petzval sum of the
optical system must be zero or, at most, be a small residual to compensate for the
secondary effects of higher-order astigmatism and oblique spherical aberration. When the
third-order astigmatism coefficient is zero, it is well-known that the sagittal and
tangential image surfaces coincide with the Petzval surface. The curved fields of such an
astigmatic lens system can be flattened by using a bundle of fibers. The shape and
curvature of the entrance end of the bundle is determined by the image surface of the
lens system that precedes it. The other end of the fiber bundle may be flat if the system
is to be used for direct observation or photography, as shown in Fig. 4.1.However, when
an image is field flattened in this manner, there is an interaction between the lens
distortion coefficient and a distortion term introduced on field flattening. Distortion
term shows the exit pupil of a lens system through which a principal ray passes at an
inclination U' and intersects the Petzval surface at the point P and the Gaussian image
plane at the point Q. Since the principal ray does not intersect the Gaussian plane when
a field flattener is used but is intercepted by a fiber at the Petzval surface, the
effective image size is changed by an amount OQ' = δh. And δh = hG - h where hG
is the Gausiian image height and h is the intersection height of the principal ray at the
Gaussian image plane.
There are several methods available for the production of a field flattener. In one of
these methods, the fibers are ground and polished along the curve desired according to
the Fresnel element, and then the entrance ends of the fibers are displaced to lie on the
curved image surface. Obviously, this method suffers from technological limitations and
is acceptable only when low-resoluti?on field flatteners are required. A second method
consisting of lapping the field flattener in against a metallic master. In the third,
most promising method, a Fresnel surface is produced at the curved surface of the fiber
assembly with a master, employing an epoxy of the type used for making diffraction
grating replicas. 
4.2 CONICAL CONDENSER
A conical fiber bundle is placed at the focal end of a lens system to increase the
photographic speed of the system by utilizing the flux-condensing property of a cone.
However, the condensing ratio of a glass-coated glass cone is determined by the ratio f-
ratio and the field angle of the preceding image forming system, as well as the
refractive indices of the fiber core and coating materials. If we make some simplifying
assumptions of a meridional ray propagation in a cone with axial length many times
greater than its diameter. 
For cones located off-axis at the image plane and with bend sides, there are obvious
deviations. Figure 4.2 shows an image transmitted by a conical fiber bundle having a 2,5
: 1 ratio.
4.3 DISTORTION CORRECTOR
It is possible to fabricate fiber bundles with the capability of correcting for
pin-cushion and barrel distortion. It is also possible to evolve techniques for
fabricating fiber bundles to compensate for the distortion term introduced in large-angle
line scan systems and S-shaped distortion of the type introduced in electron-optical
systems. Figure 4.3 shows images transmitted through two fiber plates, demonstrating the
correction capability for pin-cushion and barrel distortion. Such fused fiber assemblies
are fabricated by subjecting to well defined thermal and pressure gradients.
As another intersting example of the application of a combination of field flattener and
distortion corrector, we shall cite the problem of a wide-angle spot scan systems in
which a severe distortion term proportional to the field angle is introduced because of a
change in spot size. In such a system, it is also desirable to use a curved image fieldto
facilitate the mechanical synchronization of the two scanning functions of the
data-acqusition and print-out systems.
4.4 FOCON RESOLUTION
Of importance in the determination of the overall performance of a lens-fiber optics
combination is the angular resolution (Rang) of an image-forming system of a aperture
diameter, D, which, according to classical theory, is given by the formula:
Rang = D/1.22λ
By inserting the value of the focal ratio (F), it is possible to determine the linear
resolution (Rang), which is given by the following expression;
Rlin = 1/1.22Fλ
On the other hand, the linear displacement between two points which can be resolved by
static fiber optics is between 2d + 3t and d + 2t, where d is the fiber diameter and t
(≈ 0.5 μ) is the spacing between them. The resolution is then given by the
reciprocal of this quantity. Waveguide effects and evanescent wave coupling between the
fibers can be avoided if the fiber diameter is greater than or equal to πλ when
the fiber numerical aperture is close to unity. Such a fiber will propagate approximately
20 modes of wavelength, λ. Thus the optimum static resolution that can be obtained
with fibers is approximately 1/ πλ + 2t. Consequently, for λ = 0.5 μ,
a maximum static resolution of 220 to 350 lines / mm can be expected with high resolution
fiber optics. Of course, dynamic scanning can be used to improve the resolution. Thus the
highest linear resolution obtainable with a fiber bundle is considered to be equivalent
to that of a diffraction-limited f/4 lens.
Figure 4.4 shows a curve of the resolution of fiber conical condenser used in conjunction
with diffraction-limited lenses of a given f-number. Each curve corresponds to a conical
condenser of φ = a2/a1 (no2 - n'2)1/2, where a1/a2 is the cone ratio, and no and n'
are the refractive indices of the fiber core and coating, respectively.
5. ENDOSCOPIC PHOTOGRAPHY TECHNIQUES
5.1 COLOUR PHOTOGRAPHY WITH FIBRE-OPTIC ENDOSCOPES
This technique is the one of employed in great majority of endoscopic examinations.
Photographs are taken through the endoscope by a camera placed on the eyepiece. This
means that whatever the operator sees will be recorded photographically. The
disadvantages of this method are that the fibre-matrix is also photographed. In addition,
any imperfections in the operator's view, such as poor focus or bad picture composition,
will be reflected in the photograph. To this extent the problems are similar to those of
conventional photography, but otherwise there are few similarities.
When employing a proximal camera for endoscopic photography the following points should
be remembered.
1. A single lens reflex (SLR) camera must be employed.
2. Through the lens exposure metering (TTL metering) must be employed, unless there is
automatic exposure control of the light source output.
3. A medium focal length lens, eg 70-105 mm or 'telephoto' lens, may be required with
some endoscopes and must be focussed at infinity.
4. The camera lens must be focussed at infinity.
5. Photography must be carried out at aperture if a camera lens is employed.
6. It may not with some endoscopes be necessary to use a camera lens.
7. It is not usually possible to vary the ligthing.
8. High speed film is usually necessary and must be of the correct type.
5.2 CINE ENDOSCOPY
Although cine endoscopy is employed routinely by some authorities to record lesions,
motility , etc, it is usually reserved for occasional use in teaching because of the cost
equipping with suitable cameras and films.
Suitable cine cameras include: Super-8 Kodak M-30 with power-operated zoom lens (from
f/1.9) and Beaulieu R-16 B medical camera (16 mm). The Beaulieu R-16 B Euratom camera is
undergoing evaluation at present. It houses an automatic light control system in place of
the lens turret consisting of a graded neutral density filter wheel coupled to the
exposure meter. This wheel is adjusted by a small servo motor so that the light reaching
the film remains constant. This novel form of light control provides and alternative to
the iris diaphragm which, as we have already seen, is not possible with endoscopy
photography. At the present, however, this camera is nut fully tested. Probably the best
currently available system is the standard 16 mm Beaulieu R-16 B medical camera,
employing a suitable adaptor supplied by the manufacturer for their endoscopes.
5.3 CLOSED CIRCUIT COLOUR TELEVISION ENDOSCOPY
In a number of Japanese centers and in some centers in the USA and Europe, closed circuit
colour television endoscopy is employed for demonstration and teaching. The results, as
might be expected, are variable, but it is possible, by employing the best available
equipment to produce excellent television images with good colour reproduction.
Television technology is highly developed, nevertheless it will be useful to discuss the
items that make up an effective system for endoscopy and to point out the weak links.
A succesful system for use in gastro-intestinal endoscopy would consist of: a colour
television camera; a flexible optical coupling between the television camera and the
endoscope; a light control system; colour television monitor(s); a fibre-optic endoscope,
and a suitable light source.
5.4 GASTRO-CAMERA EXAMINATION
Gastro-camera examination of the stomach is an investigation in which a flexible tube is
passed into the stomach and multiple colour photographs taken employing a miniature
camera and flash lamp mounted distally on the tube. This method was developed by the
Japanese in 1950 in an attempt to diagnose gastric cancer, a disease that accounts for
more deaths in Japan than any other form of cancer. Diagnosis is based on a complete
photographic survey of the stomach, followed by careful inspection of the transparencies.
Suspicious areas are noted and the patient called back for full fibre-endoscopy and
biopsy, or alternatively surgical biopsy.
The term gastro-camera is understood to include 'blind' gastro -cameras which do not have
visual control and 'visually controlled' instruments with image blundles. With the
'blind' gastro-cameras the tip of the instrument is positioned by observing the light
from it through the abdominal wall. Clearly this must take place in darkened room.
6. CONCLUSION
Fibre-optic endoscopy has established itself as an important diagnostic tool in the
investigation and management of disease of the gastric-intestinal tract. Considerable
advances have been made in the design and construction of fibre-optic endoscopes and
their support systems, over the past ten years. It is unlikely that development will take
place at the same pace over the next decade. We are now entering a phase of consolidation
during which objective evaluation of each area of endoscopy will take place as the
techniques become more widely used. Advances will be made in producing serviceable
instruments and local servicing facilities are likely to be increased and streamlinid.
Fibre bundle technology will probably not strive to produce smaller fibres since the
limit has already been nearly reached. Design will probably concentrate on reliability,
and cheaper meth-pds of production. Endoscope support systems, such as light sources,
will probably improve with the development of more powerful, cooler and reliable lamps.
The great advantage of flexibility provides the key to the use of optical communication
within as well as outside medicine. As a result of this technology medical fibre-optics
are likely to receive the benefit of cheaper more dispensible fibre-bundles. These are,
at present, the most expensive items in a Fibre endoscope.
7. REFERENCES
1) Kapany, N.S., Fiber Optics, Academic Press, New York, 1967
2) Buck, J.A., Fundamentals of Optical Fibers, Wiley-Interscience Publication, New York,
1995
3) Salmon, P.R., Fibre Optic Endoscopy, Pitman Medical Publishing, New York, 1974
4) http://www.britanicca.com
5) http://www.ibmpatent.com