U.S. patent number 3,676,671 [Application Number 04/764,175] was granted by the patent office on 1972-07-11 for devices of fiberoptic and vacuum tube construction.
Invention is credited to Edward Emanuel Sheldon.
United States Patent |
3,676,671 |
Sheldon |
* July 11, 1972 |
DEVICES OF FIBEROPTIC AND VACUUM TUBE CONSTRUCTION
Abstract
This invention relates to novel fluorescent and photoelectric
screens which comprise supporting means constructed by a plurality
of light conducting novel guides operating by internal reflection
of light and mounted in a two-dimensional array. The invention is
also directed to the use of such means in photoelectric inspection
devices.
Inventors: |
Sheldon; Edward Emanuel (New
York City, NY) |
[*] Notice: |
The portion of the term of this patent
subsequent to October 3, 1984 has been disclaimed. |
Family
ID: |
25069891 |
Appl.
No.: |
04/764,175 |
Filed: |
October 1, 1968 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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498959 |
Oct 20, 1965 |
3423620 |
|
|
|
158638 |
Dec 4, 1961 |
3279460 |
|
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624829 |
Nov 28, 1956 |
3021834 |
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Current U.S.
Class: |
250/368;
250/227.2 |
Current CPC
Class: |
H01J
31/50 (20130101); H01J 31/28 (20130101); H01J
2231/50015 (20130101); H01J 2231/50068 (20130101) |
Current International
Class: |
H01J
31/08 (20060101); H01J 31/28 (20060101); H01J
31/50 (20060101); H01j 001/54 () |
Field of
Search: |
;250/71,71.5,227
;313/65S ;350/96B |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Lawrence; James W.
Assistant Examiner: Willis; Davis L.
Parent Case Text
This invention relates to novel photoelectric instruments for the
transfer of images and represents a division of my co-pending Ser.
No. 498,959 filed Oct. 20, 1965 and now U.S. Pat. No. 3,423,620,
which was a division of Ser. No. 158,638 filed Dec. 4, 1961 and now
U.S. Pat. No. 3,279,460. The aforesaid 3,279,460 was a
continuation-in-part of Ser. No. 624,829 filed Nov. 28, 1956 and
now U.S. Pat. No. 3,021,834 and has a common subject matter with
Ser. No. 415,669 filed Mar. 11, 1954 and now U.S. Pat. No.
2,877,368.
Claims
What I claim is:
1. A device comprising in combination fluorescent means emitting
fluorescent light, said fluorescent means mounted in a first vacuum
tube, a plurality of light conducting guides, said guides
conducting said light by internal reflection, said light guides
having a construction in which said light guides comprise an inner
core of material transparent to a visible light and of a high index
of refraction and are precoated with a material of a lower index of
refraction than said core, said lower index material forming a
peripheral part of said guides, said peripheral part preventing
escape of said light at least partially from one of said light
guides to adjacent guides, said peripheral part having the
thickness not exceeding a few microns, in said guides furthermore
the external surface of said core being polished exactly preventing
thereby further the escape of said conducted light from one of said
light guides to adjacent guides, said precoated guides united
together into a two-dimensional array for conducting said light and
forming at least a part of the endwall of said vacuum tube, said
fluorescent means mounted on the ends of said light guides, said
guides having an input area for said light and an exit area for
said light, and photoelectric means for receiving said light from
said exit area and utilizing said light, said photoelectric means
mounted in a second vacuum tube, said second vacuum tube having its
own endwall comprising at least a part thereof constructed of a
plurality of light conducting members, said members conducting said
light by internal reflection, said members comprising an inner core
of material transparent to visible light and of a high index of
refraction and precoated with a material of a lower index of
refraction than said core, said lower index of refraction material
forming a peripheral part of said members, said peripheral part
preventing at least partially escape of said light from one of said
members to adjacent members and having the thickness not exceeding
a few microns, in said light conducting members furthermore the
external surface of said core being polished exactly preventing
thereby further the escape of said conducted light from one of said
members to adjacent members, said photoelectric means mounted on
the ends of said light conducting members.
2. A device as defined in claim 1 in which said light conducting
guides are parallel to each other at least in a part of their
length and in which said input area and said exit area are on the
opposite ends of said light conducting members.
3. A device as defined in claim 1 in which said photoelectric means
are mounted on the ends of substantially all said light conducting
members.
4. A device as defined in claim 1 in which said inner core of said
members is of inorganic material.
5. A device as defined in claim 1 in which said light conducting
members define a cross-sectional area in said endwall, and which
comprises light opaque means between said cores of said light
conducting members.
6. A device as defined in claim 4 in which said light conducting
members define a cross-sectional area in said endwall, and which
comprises light opaque means between said cores of said light
conducting members.
7. A device as defined in claim 4 in which said photoelectric means
are in contact with said ends of said light conducting members.
8. A device as defined in claim 7 in which said light conducting
members define a cross-sectional area in said endwall, in which
said photoelectric means are mounted on said ends of substantially
all said members, and which device comprises light opaque means
between said cores of said light conducting members.
9. A device as defined in claim 8 in which said photoelectric means
produce a beam of free electrons, in which said second vacuum tube
comprises electrostatic means for focusing said beam, and in which
the outside surface of said endwall of said second vacuum tube has
a planar configuration.
10. A device as defined in claim 8 in which the outside surface of
said endwall of said second vacuum tube has a planar
configuration.
11. A device as defined in claim 4 in which said second vacuum tube
comprises means for producing electrical signals corresponding to
said conducted light.
12. A device as defined in claim 7 in which said input area and
said exit area are on the opposite ends of said light conducting
members, in which said light conducting members define a
cross-sectional area in said endwall, in which the outside surface
of said endwall of said second vacuum tube has a planar
configuration, and in which device said second vacuum tube
comprises means for producing electrical signals corresponding to
said conducted light.
13. A composite device comprising in combination fluorescent means
emitting fluorescent light and supporting means, said fluorescent
means mounted on said supporting means, said supporting means
comprising a plurality of solid light conducting guides and having
a construction in which said light guides comprise an inner core of
inorganic material transparent to a visible light and of a high
index of refraction and are precoated with a material of a lower
index of refraction than said core, said lower index of refraction
material forming a peripheral part of said guides, said peripheral
part preventing at least partially escape of said light from said
light guides to adjacent guides, said peripheral part having the
thickness not exceeding a few microns, in said guides furthermore
the external surface of said core being polished exactly preventing
thereby further the escape of said conducted light from one of said
light guides to adjacent guides, said guides having an input area
for said light and an exit area for said light, said fluorescent
means mounted on the ends of said light conducting guides, said
guides conducting said fluorescent light by internal reflection
from said input area to said exit area, said precoated guides
united together into a two-dimensional array, said supporting means
forming at least a part of the endwall of a vacuum tube.
14. A device as defined in claim 13 in which said light conducting
guides define a cross-sectional area in said endwall and in which
said fluorescent means are mounted on the ends of substantially all
said light conducting guides.
15. A device as defined in claim 14 in which said fluorescent means
are mounted in contact with said ends of said light conducting
guides.
16. A device as defined in claim 14 in which cores of said light
conducting guides are transparent to ultraviolet light.
17. A device as defined in claim 13 which comprises light opaque
means between said cores of said light conducting guides.
18. A device as defined in claim 13 which comprises in addition
means for receiving said conducted light.
19. A device as defined in claim 17 in which said light conducting
guides define a cross-sectional area in said endwall, and in which
said vacuum tube comprises means for producing a beam of electrons
to irradiate said fluorescent means.
Description
The purpose of my invention is to intensify the image of the
examined internal parts or passages so that the final image will be
presented to the observer with the luminosity facilitating
inspection of said image.
Another objective of this invention is to change, decrease or
amplify the contrast of the image of the examined part.
Another purpose of my invention is to enable simultaneous
observation by many examiners of close or remote locations, which
was not possible until now.
Another purpose of my invention is to provide means for
simultaneous visual inspection, and photographic recording of the
examined area which also has never been possible before.
Another purpose of this invention is to provide means for
inspection of inaccessible channels, such as hollow parta of
machinery or of other inaccessible tortuous passages. My device may
be introduced inside of a part which cannot be inspected visually
without dismantling or destroying the whole machine and will
transmit the image of said part to the observer outside of said
part. My invention will be especially useful for the examination of
coils and pipes or other curved structures. My device can be also
used as a probe to be inserted into a solid object and to transmit
information about its internal structure.
The objectives of my inventions were realized by a novel device
which is flexible to allow its introduction into the examined part
regardless of its curvature or angulations and which after its
introduction into the examined part will produce a light image of
said part. Video signals are reconverted in receivers outside of
the examined part into visible images for inspection or recording.
My intrascopic device can produce black and white images, as well
as multicolor images, showing faithfully or arbitrarily the colors
of the examined part.
In particular this novel device besides other inventive features
makes the use of a television pick-up tube consisting of two
separate independent elements which can be introduced separately
into the examined part and which after introduction work in
cooperation as a television camera. As each of these two separate
elements is smaller in size than any conventional television camera
can be made, this novel television camera can be introduced into
locations which, because of small size or tortuous shape of
passages leading to them, were inaccessible to the most
miniaturized television cameras known in the art.
Another marked improvement in my novel television camera is
elimination of magnetic deflecting and focusing coils which are
bulky and occupy so much space that even a small television tube
using them cannot be introduced into narrow passages. The use of
conventional electrostatic deflecting system results in a marked
distortion of images especially in pick-up tubes using the slow
scanning electron beam. These drawbacks are eliminated in my
intrascope and therefore in spite of its very small size it is
capable of producing images of a good definition and contrast.
In the drawings:
FIG. 1 represents a partially sectioned view of the novel
instrument for inspection of inaccessible parts;
FIG. 1a shows a modification of the intrascope;
FIGS. 1A, 1B, 1C and 1D show modifications of the image sensitive
member;
FIG. 1b shows the intrascope in combination with the pushing guide
for introduction of component parts of the television camera into
the intrascope;
FIG. 2 shows the intrascope provided with a modification of the
television camera;
FIGS. 2a, 2b, and 2c represent modifications of the television
camera;
FIGS. 2d and 2e represent a cross-sectional perspective view of
supporting element for the composite target in the television
camera;
FIG. 3 shows a modification of the intrascope having an optical
system;
FIGS. 4, 4a and 4b show simplified cameras for the intrascope;
FIG. 5 shows an intrascope without illuminating source;
FIG. 5a is a simplified form of intrascope shown in FIG. 5;
FIG. 6 represents an intrascope for producing color images;
FIG. 6a represents color disc;
FIG. 7 represents a modification of the intrascope for color
images;
FIG. 7a represents a simplified form of an intrascope for color
images;
FIGS. 8a and 8b represent a modification of pick-up tube;
FIG. 9 shows a novel flexible flying spot tube;
FIGS. 9a, 9b and 9c show modifications of the flexible flying spot
tube;
FIG. 10 shows a modification of the endoscope having flexible
vacuum tube;
FIGS. 11 and 12 show a novel flexible television pick-up tube;
FIGS. 13, 14, 15 show a novel endoscope having image conductor;
FIGS. 15a, 15b, 15c and 15d show modifications of the novel
endoscope with image conductor;
FIG. 16 shows a novel flexible light source;
FIG. 17 shows a novel vacuum tube having a telescopic electron
gun.
This new device which may be called the intrascope or endoscope 1
is shown in FIG. 1. The handle 2 is a hollow tube of diameter
corresponding to the examined part. The handle may be rigid or
semi-flexible or completely flexible according to the part to be
examined. At the end of the handle begins the flexible part 2a of
the intrascope which also has width and length suitable for the
size of the examined part. In case the intrascope is used for
examination of fragile parts, the part 2a must be very flexible and
pliable in order to avoid damage to the wall of the examined part.
This basic feature of the material for the flexible part of the
intrascope is therefore that it must be easily bent and molded by
the walls of the passages in which it is being introduced. Such
material may be rubber 26 or a suitable plastic, of the type used
by Davol Rubber Company of Providence, Rhode Island. In case the
intrascope is used for investigation of sturdy parts or of
machinery, the part 2a may be more rigid. The flexible part 2a of
the intrascope may be in such a case made of the stainless steel
spiral sheet designed not only for durability but also to maintain
the proper degree of flexibility and elasticity. The metal spiral
is tapered to insure its uniform bending. The intrascope may be
covered with an outer tubing 26a such as of neoprene. This prevents
dust particles and moisture from affecting the optical and pick-up
system located inside of the intrascope. At the end of the flexible
part there is a semi-flexible tip 3 which may be screwed on the
flexible part and can be easily removed giving thereby access to
the inner structures of the intrascope. The tip consists of a
rubber conical finger and serves to facilitate the gliding of the
intrascope within the examined part. In order to facilitate the
introduction of the intrascope into parts which have no curves, my
device can be made semi-rigid by inserting into it a semi-rigid
stilet. In case the intrascope is used as a probe for insertion
into a solid object, the tip 3 should preferably be rigid and
sharply pointed to be able to pierce the examined object. In some
cases the tip is provided with one or more windows at its end to
transmit the light to the examined part and to receive the image of
said part. The tip may also have a semi-spherical or other
shape.
In some cases the examined part has to be distended by air or fluid
insufflation prior to the examination. A special air pump
attachment 44 and a channel 44a in the intrascope is provided for
this purpose. The channel 44a may also serve to evacuate contents
of the examined part before examination to improve visibility. The
knob 45 on the proximal end of the intrascope serves to indicate to
the examiner the position of windows 12 and 18 of the intrascope.
In examination of living bodies, the layer 26 or 26a should be of a
highly dielectric material to prevent any short circuits.
In the distal end of the flexible part of the intrascope there is a
housing box 5 containing the illumination system 7. The box 5 may
also be attached to the inner walls of the intrascope by means of
the brackets or may be held by springs. It is obvious that there
are many means for attachment of the box 5 which are well known in
the art. All walls of the housing box 5 except the one facing the
television pick-up tube 16 are provided with windows 10 for
transmission of the light from the illuminating system 7. These
windows are correlated with the windows 12 in the flexible part of
the intrascope which transmit the light from the illuminating
system to the examined part. In some cases the windows 12 may be
made to extend over the circumference of the intrascope. In some
cases the window to transmit illumination from the light source to
the examined part may also be provided in the distal end of the
intrascope instead of being in its side walls, and in such case the
tip may be made of transparent material or may be omitted. Windows
12 may be provided with shutters which can be controlled from the
proximal end of the intrascope which is outside of the examined
part.
The illuminating system may consist of the electrical bulb 7. The
electrical bulb may be mounted in the housing box 5 by means of a
socket 7a. In some cases it is advantageous to use the objective
lens 11 between the light bulb and window 12 in order to
concentrate the light on one field. The lens may be held in
position by brackets 11a. The light bulb is activated by the source
of electrical power 9 situated outside of the examined part. Such a
source may be the commercial electrical current or battery of dry
cells. The flexible electrical cable 8 leads from the socket 7a to
said outside source of electrical current 9. The cable is a
lacquered, double insulated electric wire, is covered in addition
with liquid rubber and is vulcanized in order to prevent a short
circuit. The housing unit 5 may be in some cases omitted and the
light source may be attached to the socket 7a which is held by
brackets. In some cases electrical power of very high frequency is
preferable.
In the flexible part 2a proximally to the housing box 5, there is a
rigid non-transparent housing compartment 14 containing the optical
system 15 and the novel television pick-up tubes 16a and 16b. The
housing 14 has an opening 17 in which the optical system 15 is
lodged and which serves to admit the image of the examined part.
This opening is correlated with windows 18 in the flexible part of
the intrascope which transmit the image of the examined part. In
some cases the windows 18 may be made to extend over all the
circumference of the intrascope. The windows 18 may be provided
with shutters operated from the proximal end of the intrascope
which is externally to the examined part. The housing 14 containing
the television pick-up tubes 16a and 16b and the optical system may
be attached to the inner wall of the flexible part 2a of the
intrascope by means of brackets or may be held by springs 27a. As
the housing box fits into the encasing holding member 26 and is
held by it tightly, in some cases no additional supporting means
such as springs are necessary.
The optical system 15 may consist of 90.degree. gable prism 20 and
of lens 21. The optical system may have its own housing unit
instead of being lodged in the compartment 14 and may then be
introduced into the intrascope separately.
In some cases it is desirable to have a large field of vision and
at the same time to preserve the necessary demagnification of the
examined part. In such case, instead of the prism 20, a rotating
mirror should be used. The mirror has first surface coating which
eliminates the reflections and is activated by the magnetic
solenoid placed beneath the mirror. The solenoid is connected by
the elasticcable with the controls outside of the examined part and
can tip the mirror from the retrograde position to the forward
position, giving thereby an additional field of vision without the
necessity of moving the intrascope. The image of the examined part
is reflected by the mirror on the objective lens which focuses said
image on the photocathode of the novel television pick-up tube 16b
described below. In case the demagnification of the examined part
is not necessary a large field of viSion can be obtained by using
the lens providing 80.degree. field of vision instead of the usual
45.degree.-50.degree. . The image produced by the optical system is
inverted but it can be reverted to the original position either by
an additional lens or electronoptically in the viewing tube. The
rotating mirror may also serve to admit image either through window
18 or 18a without rotating the whole camera 16.
The housing box 14 contains the novel miniature television camera
16 which was designed to reduce to the minimum the size of the
television camera. The television pick-up tubes known previously in
the art could be miniaturized only to a certain degree, which was
not sufficient in certain applications as some of the examined
parts are two small to allow the introduction even of the smallest
conventional pick-up tube. This is true especially for the type of
tubes having external deflecting coils such as of magnetic or
electro-magnetic type, and in such situations, my novel camera 16
will be very suitable as it does not require any external
deflecting or focusing coils at all. The camera 16 consists of two
vacuum tubes 16a and 16b. The tube 16a has an electron gun 28 which
produces an electron beam 29. The electron beam 29 is focused by
electrostatic field 30. The electron-optical system for focusing
the electron beam 29 may be simplified and markedly reduced in
length by using the unipotential electrostatic lens instead of the
usual two-lens system. The electron beam 29 is deflected by
electrostatic plates 30a and 30b in two perpendicular to each other
planes. The electrostatic plates are energized by signals from
saw-tooth generators 32 which are situated outside of the examined
part. The generators 32 are connected with electrostatic plates 30a
and 30b by means of flexible wires. One deflecting field is
produced by the horizontal deflection plates 30a and may have line
frequency such as 5- 15,000 cycles per second. Another deflecting
field is provided by the vertical deflection plates 30b and may
have field frequency such as 15- 60 cycles per second. In this way
the electron beam 29 is made to scan the fluorescent screen 31 in a
regular television raster. The fluorescent screen 31 may be in some
cases provided with electron-transparent metallic conducting
backing layer 31a such as of aluminum. The fluorescent screen 31
must be of a phospher of a very short persistence in order to
obtain a good resolution of the image. ZnO has decay time of 1
micro-second and is suitable for this purpose. Still better results
may be obtained by means of ZnS phospher and using only
ultra-violet component of its fluorescent emission which has decay
time of one-tenth micro-second. In some cases, it is preferable to
make the fluorescent screen 31 of semi-spherical curved shape as it
will improve definition of the flying light spot. The fluorescent
layer 31 may also be deposited on a supporting mesh screen instead
of being deposited on the wall of the vacuum tube. This will
improve definition of the flying light spot.
The vacuum tube 16a operates in combination with the vacuum tube
16b forming together the novel television camera 16. The vacuum
tube 16b has a photoemissive electrode 33 which may be deposited or
attached to one of the walls of said vacuum tube. In some cases it
is preferable to provide a light transparent conducting layer 33,
such as of material known in the trade as "Nesa", or of compounds
of tin or of cadmium, on the side of said photoemissive electrode
33 facing the fluorescent screen 31. Such a layer must be very
thin, e.g., of the order of microns in order not to impair the
definition of images produced by the novel pick-up tube. The
photoemissive electrode 33 may be of CsOAg or of caesium, sodium,
lithium or rubidium on antimony, arsenic or bismuth, or of a
mixture oF aforesaid elements. At the opposite end of the vacuum
tube 16b there is provided a photocathode 34 which consists of a
light transparent signal plate 34a, a light transparent insulating
layer 34b and a photoemissive mosaic 34c. The signal plate 34a may
be a thin transparent layer of metal or other conducting material.
The insulating layer 34b may be of mica, silica, or other
transparent dielectric material and photoemissive mosaic 34c may be
of CsOAg or of caesium, rubidium, potassium or lithium on antimony,
arsenic or bismuth, or of a mixture of aforesaid elements. In some
cases the photoemissive layer 34c may be, instead of a mosaic, also
of continuous type. In cases in which electrostatic focusing field
23 is used to focus the scanning electron beam 33a on the mosaic
34c, much better resolution will be obtained by making such mosaic
of a curved semispherical shape. In addition, the use of such
spherically shaped photocathode will eliminate instability of the
image which is very marked when using electrostatic fields for
focusing a slow electron beam.
It should be understood that the photocathode or screen 34a may be
of photoconductive or photovoltaic type. FIGS. 1A illustrates the
photoconductive type of the photocathode 34A which comprises a
light-transparent conducting layer 34a and a photoconductive layer
34C. The photoconductive layer 34C may be of various sulphides,
selenides, especially those containing zinc, cadmium or lead, of
oxides such as PbO, CaO or ZnO, of tellurides, antimonides,
especially containing indium or of compounds of titanium, such as
barium or lead titanates. In some cases a mixture of two or more of
aforesaid elements will produce better results. In some cases
various activators like Cu or S are added to the layer 34C to
modify its characteristics. It should be understood that the
photoconductive layer 34C may be an evaporated layer, sintered
layer, a layer embedded in a plastic, a crystalline layer, a mosaic
of crystals or a single crystal. In some cases a light-transparent
dielectric layer may be provided between the layer 34a and 34C. The
photocathode 34A may be of convex shape or of a planar shape.
Furthermore, the layer 34a may be mounted on the side of the
photoconductive layer 34C which faces the electron beam. In
addition the conducting layer 34a should be in some cases connected
to a source of an electrical potential to provide a biasing
electrical field across the layer 34C. The remaining parts of the
tube 16B are the same as of the tube 16b.
The light image of the examined part is projected by the optical
system on the photocathode 34 of the vacuum tube 16b. The light
image produces emission of photoelectrons frOm the layer 34c. As a
result, a positive charge image having the pattern of said light
image is left on the photoemissive mosaic 34c. Both vacuum tubes
16a and 16b are held in opposition to each other and in such a
manner that the fluorescent screen 31 of the vacuum tube 16a is
adjacent to the photoemissive electrode 33 of the tube 16b. The
scanning electron beam 29 impinging on the fluorescent screen 31
produces a light spot at each point of its impingement. The
scanning illumination excites the photoemissive electrode 33 and
produces thereby a fine scanning beam of photoelectrons 33a. The
photoelectron beam 33a is of the scanning type because it is
produced by the scanning electron beam 29. The photoelectron beam
33a may be further focused by electrostatic fields 23. In this
construction is is preferable to use focusing fields because the
separation of the fluorescent screen 31 from the photoemissive
electrode 33 by the thickness of the wall of the vacuum tubes 16
and 16b causes certain unsharpness of the photoelectron beam 33.
The electron beam 33a may be of high velocity such as used in the
iconoscope type of television pick-up tubes or may be of a slow
velocity. In this embodiment of my invention, I use the slow
scanning electron beam. It is to be understood, however, that the
fast scanning electron beam may be used in my invention as well.
The electron beam 33a scanning across the charge image stored in
the mosaic 34c converts said image into electrical signals which
appear at the signal plate 34a. These electrical signals can be
converted into video signals over the resistance in the manner well
known in the art. The video signals are transmitted by the flexible
coaxial cable 43 from the intrascope within the examined part to
the video amplifiers 43a outside of said part. The amplified
signals are transmitted from the amplifiers to the viewing tube of
kinescope type 37 and are reconstructed therein into the visible
image representing the image of the examined part. The viewing tube
may be of kinescope type and does not have to be described in
detail as it is well known in the art. The examined part will
appear on the fluorescent screen 37a of the viewing tube where it
can be inspected by many examiners. Transmission of the image from
the amplifier 43a to the viewing tube can be done by coaxial cable
43 or by high frequency waves. The image can be sent, therefore,
not only to the immediate but also to the remote receivers or may
be transmitted to multiple independent viewing tubes for the
benefit of many examiners, which was one of the objectives of this
invention. The image on the viewing tube 37 may also be
photographed simultaneously with the intrascopic examination in
order to make a permanent record, which was another purpose of this
invention. It should be understood that the electrical signals from
the pick-up tube may be fed into various utilization circuits
instead of into image reproducing receivers
The contrast of the reproduced image may be changed, diminished or
increased according to the needs of particular examination by using
amplifiers provided with variable mu tubes, or by the use of
kinescope in which gamma can be controlled. The signal to noise
ratio of this system and therefore the definition of the reproduced
image may be improved by using in amplifiers discrimination
circuits which reject signals below the predetermined amplitude and
eliminate therefore most of the noise signals. The coaxial cable 43
within the examined part may be encased in the above-described
means 26 or 26a for inserting intrascope or may be attached to
them.
The voltages for the operation of the tubes 16a and 16b are
supplied through the flexible electrical wires 8a from the source
of the electrical power 9 outside of the examination. In this same
way the horizontal and vertical synchronizing circuits, focusing
fields and deflecting circuits are supplied with electrical energy
from the outside source of power 9. The synchronizing circuits are
not described in detail as they are well known in the art and it is
believed they would only complicate the drawings. In some cases the
coaxial cable maybe outside of said inserting means 26 or 26a.
Another modification of the tube 16b is shown in FIG. 1B. The tube
16B' has a composite photocathode 34B. FIG. 1B shows a vacuum tube
provided with one composite image-sensitive screen. The
photocathode or screen 34B has a photoemissive layer 123, a
dielectric layer 124, a photoconductive layer 125 and a transparent
conducting layer 126. The image of the examined part is formed in
the mosaic layer 123. The image sensitive screen 122 is illuminated
by the fluing spot from the tube 16a through the light transparent
layer 126. The scanning illumination changes the conductivity of
the layer 125 and converts thereby the electrical pattern stored in
layer 123 into successive electrical signals corresponding to the
image of the examined part. The electrical signals are conducted to
the receivers outside of the examined part where they are
reconverted into visible images in the manner well known in the
television art. It should be understood that electrical signals may
also be fed into different utilization circuits, such as using an
"absorption negative," which are well known in non-destructive
testing in industry.
Another modification of the tube 16b in which a photoconductive
photocathode is used instead of a photoemissive photocathode 34, is
shown in FIG. 1C. The tube 16C comprises only photocathode 34A
which may be of convex or planar shape. The materials for the
photocathode 34A were described above. In some cases the
photocathode 34A may have two different photoconductive layers,
such as layer 125 and 125a adjacent to each other. The layers 125
and 125a are preferably separated by a light impervious layer.
In some cases the composite photocathode or screen described in
FIG. 1C may have a construction in which both photoemissive and
photoconductive layers are used. Such a photocathode will have a
mosaic photoemissive layer on the side exposed to the image forming
radiation, a photoconductive layer, and a light transparent
conducting layer on the side facing the source of scanning
illumination. The image of the examined part is received by the
mosaic layer and is converted into a charge image. The scanning
illumination converts said stored charge image into successive
electrical signals which are taken off the conducting layer.
Another embodiment of the image sensitive pick-up element is shown
in FIG. 1D. In this embodiment the image sensitive element is not a
vacuum tube but a solid screen 127 which comprises two
photoconductive layers 125 and 125a and light transparent
conducting layers 128 and 129, such as of cadmium, oxide, tin
oxide, tin chloride or of noble metals, adjacent to the
photoconductive layers on either side of the screen. The image of
the examined part is projected on one side of said screen 127 and
is converted into an electrical pattern of electrical conductivity
changes in the layer 125. The flying light spot conducted by the
light image conductor 114 is projected on the opposite side of
screen 127, produces an increase of electrical conductivity of the
layer 125a, and converts thereby the electrical pattern in layer
125 into successive electrical signals. The electrical signals are
conducted to the receivers outside of the examined part and may be
reproduced as visible images in the manner well known in the
television art. In addition, the electrical signals may be fed into
various utilization circuits and may actuate various devices as it
is known in the industrial sorting or testing of materials. In some
cases it is preferable to place a light opaque layer 125b between
the photoconductive layers 125 and 125a. Furthermore it is
advisable to connect the layers 125 and 125a to the terminals of a
source of an electrical potential to provide a biasing field across
said layers. Suitable photoconductive materials for layer 125 or
125a are selanides or sulphides of lead, cadmium or tellurium;
oxides such as lead oxide or zinc oxide, antimonides, especially
indium antimonide, and titanium compounds such as barium or lead
titanates. It should be understood that all these materials may be
used as evaporated layers, sintered layers, mosaic layers, layers
embedded in plastic, single crystals or a mosaic of crystals. The
layers 128 and 125 may be continuous or in the form of a mesh
screen or a grid.
It should be understood that the relative position of the flying
spot kinescope such as 16a and of the image sensitive member, such
as 16b, 16b', or 127 or any modifications thereof, may be reversed.
This means that in some cases the flying spot kinescope instead of
being situated proximally in relation to the image sensitive member
is now situated distally in relation to the image sensitive
member.
The housing 14 containing the television camera can be rotated in
its position in the intrascope so that the optical system 15 can be
made to face the window 18 or 18a and to "see" thereby various
areas of the circumference of the examined part. The rotation of
the camera can be accomplished by means of a pusher 15a which fits
into extensions 10b of the box 14. The rotation of the camera may
be preferable in some cases to the rotation of the whole intrascope
which allows the accomplishment of the same purpose.
The main rigid portion of the flexible intrascope is the television
camera 16. Therefore the shorter the television camera is, the
easier it will be for the intrascope to pass through sharply
angulated or curved passages. One of the advantages of the novel
pick-up tube 16 is that it makes it possible to break up the
smallest pick-up tube into two component parts such as tubes 16a
and 16b and introduce each of said tubes into the examined part
separately, reducing thereby considerably the rigid portion of the
intrascope which is due to the television camera, as shown in FIG.
1a.
To accomplish these objectives, the flexible intrascope 1a is
introduced first into the examined part while containing only the
box 5 housing the light source 7. Inside of the intrascope 1a,
proximally to the box 5, there is a ring-like partition which
serves as a stop 27 for the pick-up tube 16b which is to be
introduced later. It is obvious that the shape of this stop may
vary. The rest of the intrascope 1a is empty. The intrascope 1a is
introduced first into the examined part. As the only rigid part in
the intrascope is now the box 5, which is very small, this
intrascope can easily pass even through very narrow and curved
passages. After the intrascope 1a has been introduced into the
examined part for a desired distance, which can be read easily on
the markings provided on the outside wall of the intrascope, the
next step begins. Now the housing box 14b, in which the vacuum
pick-up tube 16b is mounted, is introduced into the intrascope. The
housing box 14b is pushed into the intrascope until it reaches the
stop 27, which can be also ascertained by the X-ray control. The
box 14b may be held against the stop 27 by spring extensions 27a on
said stop 27. The housing box 14b may be pushed into its position
by a flexible elastic guide 15a, which is fitted into the proximal
end of the housing box 14a. For this purpose the housing box 14b is
provided with a ring like extension 10a at its base as shown in
FIG. 1a, which has spring-like properties. The head of the flexible
pusher 15a fits into this extension and is kept in position by it.
The flexible pusher 15a may also be provided with electrical coils
6a at its distal end, which is adjacent to the element to be
introduced into the intrascope. The coils 6a are connected to the
source of electrical power situated outside of the examined part.
In this way the head of the pusher may be given electromagnetic
properties by closing the circuit, energizing the said coils 6a.
The pusher 15a will be held, therefore, in the elements to be
introduced into the intrascope, such as boxes 14a, 14b or the
optical system 15, not only by the mechanical pressure of the
extensions 10a or 10b but by magnetic attraction as well. When the
pusher 15a is to be withdrawn, the current supplying the coils 6a
is shut off. To facilitate the guiding of the box 14b into the
intrascope, a set of threads 86 may be used, which are at the end
attached to the stop 27 and which are threaded through the
perforations in the extensions 87 of the house box 14b. After the
box 14b has been introduced into its proper position, the
intrascope, the pusher 15a, is removed. Another set of threads 89
is attached to the extensions 88 in the housing unit 14b and serves
to pull out said box 14b to the exterior of the examined part when
the examination is finished. This arrangement is shown in FIG.
1b.
The housing box may be omitted in some cases and the tube 16b may
be introduced into the intrascope without any housing and will be
held in position by the same means as described above for holding
the box 14b.
After the box 14b with the tube 16b has been introduced, the box
14a housing the tube 16a is introduced now into the intrascope in a
similar manner as was described above. Both boxes 14b and 14a have
openings at their proximal and distal ends respectively, which
makes it possible to bring the fluorescent screen 31 of the tube
16a in close apposition to the photoemissive electrode 33 in the
tube 16b. The boxes 14a and 14b are provided with mechanical means
for securing a good contact of the proximal end of the tube 16b
with the distal end of the tube 16a. One way of providing such a
contact is to make the compartment 14a fit inside of the
spring-like flange 27a at the proximal end of the compartment 14b.
The housing box 14a contains vacuum tube 16a which has been
described above. The housing box 14a is provided with springlike
extensions 10b which serve to accommodate the head of the pushing
guide 15a.
The housing box 14a is pushed into the intrascope until it reaches
the position of the stop 27b. This can also be checked by the X-ray
control. The stop 27b is so situated that when the housing box 14a
reaches it, the tubes 16a and 16b will be in apposition to each
other. In some cases flexible coils, which can be converted into
magnets by passing through them an alternating current from an
outside source of electrical power, may be provided on the stops 27
and 27b or at extensions 10a or 10b of the intrascope to help the
positioning of boxes 14a and 14b. In this way the rigid portion of
the intrascope, which has to pass through a narrow passage or acute
curvature, is now only a fraction of the rigid part of intrascopes,
which use even the smallest pick-up tube of conventional type. This
represents an important improvement as it makes it possible to
introduce the intrascope into parts which were not accessible
previously to examination. In case the size of the pick-up tube is
not of critical importance, one of standard television tubes, after
being miniaturized, may be used as well.
The size of the kinescope tube 16a may be reduced considerably if
it can be operated at a low voltage and produce at said low voltage
sufficient illumination of the electrode 33. One way of
accomplishing this purpose is disclosed in my U.S. Pat. No.
2,586,391 which discloses amplifying screen consisting of a light
reflecting layer, a fluorescent layer, a light transparent
separating layer and a photoemissive layer. Said screen is disposed
in the kinescope between the electron gun and the fluorescent image
reproducing screen. The same objective may also be obtained by
using between the electron gun and the image reproducing screen a
secondary electron emissive electrode, which may be of a solid type
or preferably of mesh screen, is of material having a high
secondary electron emission ratio, such as Ag:Mg or it may have
deposited on a mesh screen a layer of a highly electron emissive
material, such as of CsO or of CaSb. As six to 10 electrons may be
emitted by said screen for each incident electron, the voltage of
the kinescope may be considerably reduced. The electron-optical
field between said secondary electron-emissive electrode and the
fluorescent screen 31 will focus the divergent secondary electrons
into fine beams so that the definition of the image will not be
markedly impaired.
There are certain drawbacks in the intrascope 1 or 1a described
above. The separation of the fluorescent screen 31 from the
photoemissive electrode 33 by the thickness of the wall of the
vacuum tube 16a and of the tube 16b causes some unsharpness of the
photoelectron beam 33a. This unsharpness is due to diffusion of
light spot from fluorescent screen 31 as it travels through
distance equal to the thickness of the walls of the tubes 16a and
16b. By the time the light spot reaches the photoemissive electrode
33, it has spread so that it cannot produce any more a fine
photoelectron beam. Besides the fluorescent light spot suffers in
the glass walls of the tubes 16a and 16b multiple internal
reflections so that part of the fluorescent light will be scattered
and will strike different separated areas of the electrode 33
reducing thereby further definition and contrast. Furthermore, it
is not always possible to introduce component parts of intrascope
separately as was described before. In some examinations, the time
available is very limited so that intrascope must be ready for the
use as soon as possible. In such cases, another modification of my
invention is more suitable. This embodiment 1b of the intrascope is
shown in FIG. 2. In this embodiment of invention, the tubes 16a and
16b are replaced by one vacuum tube 16c having a composite target
19 described below. The fluorescent layer 31b of phosphors
described above is deposited on one side of a very thin light
transparent separating partition 19a, whereas the photoemissive
layer 33b of one of the materials described above is deposited on
the opposite side of said partition. The partition 19a may be of
mica, glass, or of a suitable plastic and should preferably be very
thin, such as of the order of a fraction of millimeter in order not
to impair definition of images produced by the said television
pick-up tube. Better results may be obtained if the partition 19a
is conductive. This may be accomplished by using for the partition
a conductive material or by coating the partition on the side,
which supports the photoemissive layer, with a light transparent
conducting layer, such as is known in the trade under the name of
"Nesa", indium compounds or of cadmium compounds. In some cases the
composite target 19 may be deposited on the photocathode 34 instead
of being supported by the side walls of said pick-up tube. In this
event the separating layer 19a may preferably be reduced to the
thickness of a fraction of one micron.
The partition 19a may be placed in its position within the tube 16c
by means of a metallic ring 98 having a flange 99 which supports
the partition, whereas the ring itself is attached to the walls of
the tube. The cross-sectional perspective view of the ring 98 and
partition 19a is shown in FIGS. 2d and 2e. Instead of a metallic
ring 98, the transparent separating layer 19a, the fluorescent
layer 31 and photoemissive layer 33b may also be supported by the
mesh screen of conducting or insulating material 82 as shown in the
pick-up tube 16d and 16e and 16e' illustrated in FIGS. 2a, 2b and
2c. Instead of a mesh screen a supporting layer of continuous type
may be used and may be made of one of the materials used for the
separating layer 19a which are either light transparent or electron
transparent. In some cases it is preferable to make the fluorescent
layer 31b and the photoemissive layer 33b of semi-spherical curved
shape. In some cases the separating partition 19a may be omitted
and the fluorescent layer 31b and photoemissive electrode 33b are
both supported by the mesh screen 82 or by supporting element of
continuous type 19a without any separating layer. This arrangement
is possible only in cases in which the photoemissive layer 33b and
fluorescent layer 31b do not inactivate each other and the
photoemissive layer 33b is conductive. The other elements of the
novel pick-up tubes 16c, 16d and 16e are the same as described
above. At one end of the tube 16c there is disposed an electron gun
28 which produces an electron beam 29. The electron beam 29 is
focused by electrostatic field 30 and is deflected by electrostatic
plates 30a and 30b in two perpendicular to each other planes. The
electrostatic plates are energized by signals from saw-tooth
generators 32 which are situated outside of the examined part. The
generators 32 are connected with electrostatic plates 30a and 30b
by means of flexible wires. In this way the electron beam 29 is
made to scan the fluorescent layer 31a of the composite target 19
in a regular television raster. The fluorescent layer 31b may also
be provided with an electron transparent metallic conducting
backing layer 31a such as of aluminum. The fluorescent scanning
light spot produces a scanning photoelectron beam from the
photoemissive electrode 33b which may be of CsOAg or of caesium,
lithium or rubidium on antimony, arsenic or bismuth. At the
opposite end of the vacuum tube 16c there is provided photocathode
34 which consists of a light transparent signal plate 34a, a light
transparent insulating layer 34b and of a photoemissive mosaic 34c.
The signal plate 34a may be a thin transparent layer of metal or
other conducting material. The insulating layer 34b may be of mica
or other transparent dielectric material and photoemissive mosaic
34c may be of CsOAg or of caesium, rubidium or lithium on antimony,
arsenic or bismuth, as was described above.
In some cases it is preferable to focus the scanning electron beam
33a on the photocathode 34. The focusing has to be done by means of
electrostatic field 30a. In such event the photocathode 34 or its
photoemissive mosaic 34c should be preferably of curved
semi-spherical shape. The rest of the operation of the intrascope
1b using the television camera 16c is the same as was described
above. A considerable improvement in definition of reproduced
images may be achieved by making the fluorescent screen 31 of
grainless phosphors.
The housing box may be omitted in some cases and the television
tube may be introduced into the intrascope without any housing and
will be held then in position by the same means as were described
above for holding the housing box.
In some cases the part to be examined is too small or too curved to
accommodate even the television camera 16. For example the
introduction of the intrascope 1a through narrow passages may be in
some cases accomplished because of separate two-step insertion of
the tubes 16a and 16b, but their subsequent assembling together in
side of the intrascope proves to be impossible because of the lack
of sufficient space. In such cases, it may be necessary to keep the
tubes 16a and 16b apart from each other and to use an optical
system 15c to focus the scanning illumination produced by the tube
16a on the photoemissive electrode 33 in the tube 16b, as shown in
intrascope 1c, illustrated in FIG. 3.
In some cases the optical system 15c may be housed in the
compartment 14b. In other cases it may be placed preferably in
compartment 14a. It must be added that the use of the optical
system 15c makes it necessary to increase the output of light from
the fluorescent screen 31, as only 2 percent of the light will now
reach the photoemissive electrode 33. The rest of the operation of
the intrascope 1c is the same as was described above for the
intrascope 1 or 1a.
This arrangement will be useful in locations which are known in
advance as not to cause any bending of the intrascope in the area
between said tubes 16a and 16b. It may be also of value in the
examination of parts where the degree of such angulation between
the tubes 16a and 16b is known in advance so that it may be
overcome by the choice of a suitable optical system.
In order to reduce pin-cushion distortion inherent in electrostatic
deflection system used in cameras described above and illustrated
in FIGS. 1 to 3, I make the fluorescent screen of a semi-spherical
shape. Furthermore, the photoemissive electrode 33 may be
preferably also shaped semi-spherically to reduce further
pincushion effects. In addition the photocathode 34 of the pick-up
tube may also preferably have a curved semi-spherical shape which
will help overcome further distortion due to electrostatic focusing
field 30a. The use in combination of a curved fluorescent screen 31
and of a curved photocathode 34 represents an important improvement
of my camera over devices of the prior art. The definition of the
flying light spot may be considerably improved by depositing screen
31 on a supporting mesh screen 83 which was described above,
instead of on the wall of the tube 16.
In case extremely bright images have to be investigated the
photocathode 34 of the pick-up tubes described above may be
provided with a layer of phosphor on the side facing said image,
which converts the radiation of strong intensity into a
fluorescence or phosphorescence of weak intensity, so that the
pick-up tube will not be damaged by excessive illumination. Such
phosphors are well known in the art. Therefore it is believed that
their description is not necessary.
In some cases it is preferable to reduce further the rigid part of
the intrascope by providing the source of image forming radiation
outside of the intrascope. This embodiment of my invention is shown
in FIG. 5.
The photocathode of the pick-up tube 16b.sub.2 may also be made to
provide a panoramic view of the examined part. The photocathode
34e' in this modification extends in a curved semi-spherical manner
to the side was of the pick-up tube, as shown in FIG. 5. One window
12a in this modification is preferably situated at the end of the
intrascope.
The novel intrascope 1 or 1a may be further simplified as shown in
FIG. 4. In this embodiment of my invention only one novel pick-up
tube 16f is used. The pick-up tube 16f has a photoemissive
photocathode 34g which consists of a layer 34a transparent to image
forming radiation, a dielectric layer 34b, also transparent to the
image forming radiation, and photoemissive mosaic 34c. In a close
spacing from the photocathode 34g, such as not exceeding 0.25
millimeter but preferably much smaller, there is disposed a
fluorescent screen 34e. The screen 34e may be supported by a light
transparent supporting layer such as of mica or may be supported by
a mesh screen 82 as was described above. The fluorescent screen 34e
may be in some cases provided with an electron transparent light
reflecting conducting layer 34f on the side facing the electron gun
28. In some cases, said fluorescent layer 34e and backing layer 34f
may be deposited on the photoemissive mosaic 34c, as shown in FIG.
4. In such event a light transparent separating layer 34d may be
preferably interposed between said photoemissive and fluorescent
layers. At the other end of the tube there is disposed an electron
gun 28 which produces an electron beam 29 for scanning said
fluorescent layer 34g in television raster. The image of the
examined part is projected on said composite photocathode 34g and
produces a charge image in the photoemissive mosaic 34c, which has
the pattern of said projected image. The scanning electron beam
produces scanning light spot in the fluorescent layer 34e. The
light spot scans the adjacent photoemissive layer 34c. The
impingement of the light spot causes photoemission of electrons
which is modulated by the charge image established in the mosaic
34c by the projected previously image of the examined part. The
signals produced by the scanning light spot appear at the signal
plate 34a and can be converted over suitable resistor into video
signals in the manner well known in the television art. The light
transparent separating layer 34d is necessary to prevent
detrimental chemical interaction between the photoemissive layer
34c and fluorescent layer 34e. In order to preserve sharpness of
the scanning light spot, said separating layer must not exceed 0.15
millimeter in thickness. The layer 34d may be dielectric, such as
of mica, non-conductive glass or plastics. In some cases it is
preferable to use a conductive layer and in such event the
separating layer may be of glass, mica, plastics coated with the
material known as "Nesa" manufactured by Pittsburgh Plate Glass
Company. It may also be made of tin salts, such as halides or
oxides, cadmium salts or metal powders, such as of silver. In some
cases it is preferable to make the separating layer of the two
layers adjacent to each other, one of them being an insulating or
semi-conducting layer, another one being a conducting layer. It is
obvious that the composite photocathode 34g may be deposited on the
wall of the vacuum tube or may be held by supporting means within
the vacuum tube independently of the end walls of said tube. Such
supporting means may be either in the form of mesh screen or of a
continuous element which were both described above. The fluorescent
layer 34e must be of phosphors having a very short persistence,
such as of the order of 1 micro-second, which were described above.
The electron transparent layer 34f serves to improve efficiency of
the light output from the fluorescent layer 34e and may be of
aluminum. In some cases it may be omitted.
This system may also be used in the way shown in the intrascope 1a
which has optical system between pick-up tube 16a and tube 16b and
it is shown in FIG. 4a. In such case the novel pick-up tube 16b'
has the mosaic photocathode 34 described above but the electrode 33
is eliminated; see FIG. 4a. The scanning of charge image produced
on the photoemissive mosaic 34c is accomplished by the fluorescent
light spot from the tube 16a' which is projected on the mosaic 34c
by lens 15c. The impingement of the flying light spot which skans
the photocathode 34 in television raster produces photoemission
from the layer 34c, which is modulated by charge image present
thereon. As a result successive electrical signals are formed which
can be taken off the signal plate 34a and can be converted into
video signals in the manner well known in the art.
This novel television camera can also be used by placing the novel
tube 16b' in close apposition to the tube 16a'; see FIG. 4b.
The fluorescent screen 34e if made of a curved semi-spherical shape
will help to reduce pin-cushion distortion inherent in
electrostatic deflection system. In addition the photocathode of
the pick-up tube 16b' may also preferably have a curved
semi-spherical shape which will help overcome further distortion
due to electrostatic scannong. The use in combination of a curved
fluorescent screen and of a curved photocathode represents an
important improvement of my camera.
The intrascope illustrated in FIGS. 4, 4a and 4b may also be
simplified by providing the source of image forming radiation
outside of the intrascope as was explained above.
In case a true color image of the examined part is wanted, a
rotating color wheel 50, drum, or truncated cone, composed of
plural, e.g., three primary chromatic filters 51, 52 and 53, is
placed before the television pick-up tube 16b; see FIG. 6. A
similar wheel 50a rotating synchronously with the first color wheel
50 is placed in front of the picture tube 37 in the receiver. Each
examined field is scanned and reproduced in succession through a
different primary color in the filter wheel. Therefore, three
colored images, red, yellow and blue are projected on the final
viewing screen 56 in one-fortieth second. The persistance of vision
lasts longer than one-fortieth of a second. Therefore, these three
color images fuse in the mind of the observer and a multi-colored
reproduction 57 corresponding to the true colors of the examined
part results. The color wheels 50 and 50a are driven by induction
motor located outside of the examined part, synchronized by
synchronization stage which compares the incoming pulses with
locally generated ones and thereby controls the speed and the phase
of the disc. Since the color wheels synchronization is obtained
from the video wave form, the phasing of the color filters is
automatically selected, that is, a given color automatically
appears before the receiver tube when that color is present before
the pick-up tube, as it is well known in television art. The motor
may also be located in the examined part.
The illuminating system 5 in this modification of the intrascope is
the same as described above and shown in FIG. 1. The mounting of
the illuminating system also may be the same as shown in FIG. 1.
The optical system 15 is essentially the same as described above
and shown in FIG. 1. In some cases additional lenses may be used
between the rotating wheel 50 and the television pick-tube 16b, 16f
or any other pick-up tube described above for a better focusing of
the image of the examined part on the photocathode of the pick-up
tube. The mounting of the optical system may be the same as shown
in FIG. 1. The rotating color wheel 50 in front of the television
pick-up tube has three sections of colored glass corresponding to
three basic chromatic values such as red 51, blue 52 and yellow 53,
and may be mounted on the bracket 59. The rotating wheel is
activated by the synchronous motor situated outside of the examined
part and connected to the wheel by means of the flexible insulated
cable.
The image of the examined part is projected by the optical system
onto the photocathode of the television pick-up tube through the
rotating multicolor wheel 50 and is converted by said television
pick-up tube into video signals having the pattern of the examined
part in the same way as was explained above. The video signals are
transmitted by the flexible co-axial cable to the amplifier outside
of the examined part. The amplified video signals are conducted by
the coaxial cable to the viewing tube 37 of the kinescope type. The
video signals modulate the scanning beam 60 of the kinescope 37.
The modulated scanning beam in the kinescope striking the
fluorescent screen 61 of the kinescope is reproducing the images of
the examined part. These images are projected through the color
wheel 50a rotating synchronously with the similar color wheel 50 in
front of the pick-up tube. In this way three colored images of the
examined part are projected on the final screen 56 in one-fortieth
of a second, blending thereby into one multicolored image due to
persistence of the vision of the observer. The resulting
multicolored images 57 can be visually examined on the screen 56 or
may be recorded. It is obvious that with all intrascopes described
above this color system may be used.
Instead of a rotating color disc or drum the color images may be
produced by using sequentially three sources of illumination, such
as a source of red light, a source of yellow light and a source of
blue light. First the red light, for example, is flashed on the
examined object and the "red image " is produced thereby and is
transmitted to receivers. Next the yellow light is flashed on and
the "yellow image" is produced and transmitted to receivers. Next
the blue light is flashed on the examined object and the "blue
image" is produced and transmitted to receivers. If the red, yellow
and blue images are all produced in one-fortieth of a second, they
will blend in examiner's eye into a multicolor image without the
use of any rotating color filters.
In some cases the use of the rotating color disc, drum or truncated
cone may not be convenient and a system using a stationary color
filter may be preferable. It is obvious that the rotating color
disc may be replaced by stationary color filters such as dichroic
mirrors, but in such case two or three pick-up tubes must be
provided in the intrascope. It is to be understood that all such
color television systems come also within the scope of my
invention. In order to use a stationary color filter with one
pick-up tube only it is necessary to split the image by suitable
optical means into plural, e.g., two or three images and to project
said split images through the stationary color filter on separate
areas of the photocathode. This embodiment of my invention is shown
in FIG. 7. The image 64 of the examined part is projected by lens
65 between two mirrors 66 and 67. The mirrors are parallel to each
other and equidistant from the optical axis. The mirrors produce
from the original image 64 multiple secondary images such as 64a,
64b, 64c, etc. The lens 65a projects the image 64 and the secondary
image 64a and 64b on the different areas A, B and C of the
photocathode 68 of the pick-up tube, which may be of any type
described above. There are many optical systems for splitting the
image of the examined part into plural symmetrical images, which
are well known in the art; see U. S. Pats. Nos. 2,389,646 and
2,465,652, and it is to be understood that the description of such
an optical system used in my intrascope should be considered only
in an illustrative and not in a limiting way.
Each photocathode 68 has signal plate 69, dielectric layer 70 and
photoemissive mosaic layer 71, as was described above. Three
symmetrical images are projected on different areas, A, B and C of
the photocathode without overlapping each other. The stationary
color filter having plural elements, such as the red one 67, the
yellow one 67a, and the blue one 67b, are provided outside of the
pick-up tube in cooperative relation with said three different
areas A,B and C of the photocathode for receiving the original
image 64 and symmetrical images 64a and 64b. The filters may also
be positioned inside of the pick-up tube in front of the
photocathode. Therefore the image 64a' which passes through the red
filter 67 will produce in the area A image 64a' having "red"
information. The image 64 which passes through the yellow filter
67a will produce in the area B image 64' providing "yellow "
information, and the image 64b produced by the filter 67b will form
in area C image 61b' , which provides "blue" information. The
scanning electron beam 33a produced by the flying spot light, as
explained above, scans these images on the photocathode and
produces video signals having the pattern of said "red", "yellow"
and "blue" images. When the area A of the photocathode is scanned
video signals are produced which after amplification and
improvement of their contrast are fed into "red" kinescope. Next
the electron beam 33a scans the area B and image 64' and converts
said image into video signals. These video signals correspond to
the "yellow" image 64' and are fed into "yellow" kindescope. In the
same way the video signals corresponding to the "blue" image 64b'
are fed into the "blue" kinescope. It is obvious that instead of
multiple kinescopes a single tricolor kinescope may be used as
well. It is also evident that the scanning of the charge images on
the photocathode does not have to proceed systematically from the
area A to area B but also may be completely interlaced. The basic
feature of all these arrangements is that video signals derived
from the scanning of the area A of the photocathode have to be fed
into "red" channel, the signals produced by scanning area B of the
photocathode have to be fed into "yellow" channel and signals from
area C should be fed into "blue" channel.
It is obvious that there are many systems which can produce plural
non-overlapping images and it is to be understood that all such
systems come within the scope of this invention. It is also obvious
that optical means or filters may be used to split not the whole
image simultaneously into plural symmetrical images but to split
each line of the image into three non-overlapping line images.
These line images may be projected through multicolor filter to
produce non-overlapping color line images. Each of said lines will
then be scanned and converted into "red", "yellow" and "blue" video
signals, as was explained above.
The television camera of the type shown in FIGS. 4, 4a and 4b can
also be used in this novel color television intrascope. FIG. 7a
shows the use of the pick-up tube 16g for producing color images.
It is obvious that the same system may be used with pick-up tubes
16b' or 16b.sub.2 . The novel pick-up tube 16g has a mosaic
photocathode 76 which consists of a light transparent conducting
layer 76a, light transparent dielectric layer 76b and of
photoemissive mosaic layer 76c. The above mentioned layers may be
of the materials described above. The photocathode 76 may be
divided into plural areas such as three independent from each other
photocathodes, as was shown in FIG. 7. This may be accomplished
also by the insulating means which extend from the conducting layer
76a into photoemissive layer 76c. In another modification instead
of this plural photocathode, three independent photocathodes may be
deposited on the walls of the pick-up tube or may be mounted in the
inside of said pick-up tube in such a manner that the edges of said
photocathodes do not come in contact with each other. In the
preferred form of this system, the optical projection of split
images is of such a manner that said images do not overlap each
other on the photocathode but fall in three separate areas A, B and
C. In such case, only the signal plate 76a has to be divided into
three different areas such as 76A, 76B and 76C which are insulated
from each other or are non-contiguous to each other. In order to be
able to transmit "red" video signals only to the "red" channel,
"yellow" video signals only to the "yellow" channel and "blue"
video signals only to the "blue" channel in this modification, the
photoemissive mosaic 76c and its dielectric layer 76b do not have
to be split any more into independent non-contiguous units. By the
use of one of the optical systems described above, the image of the
examined part is split into three separate images which are
projected on three separate areas 76A, 76B and 76C. Each of the
conducting signal plates of said photocathodes is connected to its
own color channel only. In this way the signals from the signal
plate 76A will be, for example, directed to the "red" kinescope,
the signals from the signal plate 76B to the "yellow" kinescope and
signals from the signal plate 76C will be fed into the "blue"
kinescope.
Another way to produce color images is to subject various areas A,
B and C of the photocathode or the scanning beam to modulation by
signals of different frequencies from an outside generator and by
making each primary color channel responsive only to one frequency
which is made arbitrarily representative of said primary color. In
this way the "red" , "yellow" and "blue" images will be fed into
"red" "yellow" and "blue" channels respectively by means of
appropriate filters or decoders. This arrangement allows the use of
one signal plate instead of three signal plates in the systems
described above.
My invention is not limited to visible light images. It should be
understood that my intrascope may be made responsive to invisible
images on either side of visible spectrum by using appropriate
photosensitive layer in the photocathode of the television camera.
It is to be understood also that my intrascope may serve for
receiving images formed not only by various electromagnetic
radiations, such as ultra-violet, infra-red, etc. but also by
particles radiation such as neutrons, alpha particles, protons,
electrons or by ions. In such case, the photocathode of the pick-up
tube described above may be provided with an atomic particle
sensitive phosphor on the side facing said image or may have a
special electron or other atomic particles emissive
photocathode.
FIG. 8 shows a pick-up tube 16h having atomic particles sensitive
photocathode which is responsive to an atomic particles image and
emits secondary atomic particles having the pattern of said image.
It is to be understood that the photocathode 77 is shown only for
illustration as there are many types of photocathodes sensitive to
atomic particles, as evidenced by my above mentioned patents. The
target 78 is scanned by a slow electron beam 33a from the electrode
33 in the manner described above. The electrons of the scanning
beam 33a are deposited on the dielectric layer 79 of the target and
are stored there. At the time of impingement of the beam of gamma
rays or of atomic particles from the photocathode 77, the
dielectric layer 79 becomes conductive. The electrons of the
scanning beam 33a can now pass through the dielectric layer 79 to
the signal plate 80 and produce video signals. In some cases the
photocathode 77 may be in apposition with the target 78.
The above described type of pick-up tube may also operate using a
fast scanning electron beam instead of a slow beam. This
modification is preferable in cases in which the particles emitted
by the photocathode 77 have small velocity, for example, in case of
a photoemissive cathode. In such case the signal plate 80 should be
on the side of the target 79 which faces the scanning electrode 33.
The rest of the operation of this intrascope may be the same as
described above.
The storage target may also be of the composite type and may
consist of a fluorescent light reflecting layer 81, a fluorescent
layer 81a, a light transparent dielectric layer 81b, such as of
mica, glass or silica, and a photoemissive mosaic layer 81a, as
shown in FIG. 8a. In some cases the photocathode 77 and the
composite storage target 83 may be in apposition to each other,
which means contiguous to each other. In some applications the
storage target 83 may also be used instead of the photocathode 77
and will serve to receive an image of invisible radiation and to
convert said image into a charge image. Also the target 78 may
serve as a photocathode; see FIG. 8b.
Furthermore, my intrascope may serve for investigating images
produced by supersonic radiation. In such case, the photocathode of
the pick-up tubes described above is replaced by the supersonic
sensitive photocathode, for example, of quartz, compounds of
titanium, such as barium titanate or lead titanate, or Rochelle
Salt or ADP. The intrascope must have at its distal end a membrane
and must also have a medium to transmit supersonic vibrations to
pick-up tube. Instead of amembrane, the end-wall of pick-up tube
may form the end of intrascope and will then receive supersonic
image directly.
When using an invisible radiation for producing an image of the
examined part, the color reproduction of said image may also be
obtained, as it is explained in my U.S. Pat. No. 2,593,925. Another
system for color reproduction of invisible radiation images is to
make separate sub-photocathodes A, B and C, as described above,
selectively sensitive to different groups of frequencies present in
said invisible radiation image. For example, sub-photocathode A may
be made to receive radiation only of wavelength 3-4,000 A. Either
by means of a special selective filter in front of said
sub-photocathode or by making the photosensitive surface
selectively responsive only to said wavelength. In the same manner
the sub-photocathode B will receive only radiation of 1,000-2,000
A. It is obvious that the wavelengths quoted above should be
considered only in an illustrative and not in a limiting sense. In
the same manner radiation on the far end of the spectrum may be
arbitrarily divided in various groups of frequencies. By assigning
arbitrarily three color channels, such as "red", "yellow" and
"blue" to said three sub-photocathodes, a multicolor reproduction
of an invisible image may be obtained. Also, the rotating color
disc or drum which is provided instead of visible color filters
with filters selective for various frequencies present in the
invisible image may be used for the same purpose. This modification
will then allow the use of only one photocathode instead of three
sub-photocathodes.
In many cases it is preferable to have the source of invisible
light or of other image forming radiation used for examination
independent of my intrascope and outside of the intrascope. In such
arrangement the source of image forming radiation may be introduced
prior to or subsequent to introduction of the intrascope into the
examined part. This embodiment of my invention will facilitate the
insertion of the intrascope as it will reduce the size of its rigid
parts.
The novel television cameras described above both for invisible and
visible image forming radiation operate by means of the
photoemissive effect or by means of bombardment induced
conductivity effect. It should be understood, however, that similar
television cameras which may use a photoconductive or photovoltaic
effect instead of a photoemissive effect, described above, come
also within the scope of my invention.
It is evident that all intrascope used for receiving images or
signals of ionizing radiations, such as gamma rays, electrons,
neutrons, protons, etc. may serve to reproduce images without
having any optical system. In such case the window of the
intrascope is preferably situated at the distal end of the
intrascope, as shown in FIGS. 5 and 6.
All the intrascopes described above may be further reduced in size
by omitting the encasing and holding member 26, as shown in FIG.
5a. In this modification of my invention, the television pick-up
tube may be of any of the types described above. The television
pick-up tube may be inserted into the examined part by means of a
flexible or semi-flexible pushing guide 15a, according to the type
of the examined object. The television camera, e.g., 16e, is placed
in a housing compartment 92 which is provided at its proximal end
with extensions 94 for receiving the head of the guide 15a. At the
other end of the housing compartment an extension is provided for
the optical system 93. In some cases a semi-flexible transparent
tip or a tip 90 having window 91 therein may be provided at the end
of the housing 92. In some cases additional windows with lenses may
preferably be added in the side walls of the housing box 92. In
such event the photocathode of the pick-up tube 16e should
preferable be of a panoramic type, as was shown in FIG. 5.
The intrascopes of the type described above may be further
simplified by omitting the housing box 92 and introducing
television pick-up tube into the examined part without any
protective compartment. In such case an extension or a socket are
provided at the proximal end of the television camera to
accommodate the head of the guide 15a. Another extension is
provided at the distal end of the television pick-up tube to
support the optical system 93.
In this modification of my intrascope the head of the pushing guide
15a may be fitted into extension at the proximal end of the camera
tube in he same manner as was described above for fitting the guide
15a into extensions in the housing compartment. The pushing guide
may also be screwed onto the socket mounted at the proximal end of
the pick-up tube. Also, electromagnetic coils described above may
preferably be used in this modification of my invention to secure a
good contact.
In some applications is may be desirable to remove the guide 15a
from the camera tube after its insertion. In such case the camera
is provided with the threads 89 described above to pull out said
tube after examination is concluded. In some applications the
pick-up tube may be encased in an inflatable transparent sheath
which is inflated after the insertion of intrascope.
It is obvious that all those simplified intrascopes described above
may also be used for producing color images of the examined part in
the manner described above. It is also to be understood that these
simplified intrascopes may be used in combination with a source of
an invisible radiation either of corpuscular or of undulant type.
Furthermore, it is to be understood that the simplified intrascope
may use pick-up devices based on the photoconductive or
photovoltaic effect instead of the photoemissive effect described
above.
For producing color images in come cases instead of separate signal
plates, a circuit having keying amplifiers may be used as well.
This circuit activates amplifiers for video signals in a
predetermined time sequence so that the signals coming from the
area A and representing "red" signals are amplified by amplifiers,
whereas signals from the "yellow" area B and "blue" area C are not
amplified and therefore are not reproduced. Next when the "yellow"
area B is scanned, the amplifiers receiving "yellow" signals are
activated by said keying circuits, whereas amplifiers for "red" and
"blue" signals are kept inactive. The keying amplifiers are well
known in the art. It is believed, therefore, that their detailed
description would only serve to complicate the drawings. In some
cases, equalizing circuits should be provided in addition, in order
to equalize differences in signals caused by different exposure
time of the area A, B and C to the image forming radiation.
It should be understood that the relative position of the flying
spot kinescope, such as 16a, 112 or 109, and of the image sensitive
member, such as shown in FIG. 1 or in 4a, or in FIG. 8, or in any
modifications of the invention described in specification may be
reversed. This means that in some cases the flying spot kinescope,
instead of being situated proximally in relation to the image
sensitive member is now situated distally in relation to the image
sensitive member. It should be understood that such modification of
the position of the elements of the endoscope comes within the
scope of my invention.
In some examinations the television endoscope or intrascopes
described above are still too bulky to be introduced into narrow
passages or cavities. For such cases I devised a novel intrascope
in which one or all of the vacuum tubes used in the intrascopes,
such as television pick-up tube or image-sensitive tube or flying
spot tube, also known as a kinescope tube, are constructed in such
a manner that all of their sidewalls or a part of their sidewalls
or their endwalls are flexible to conform to the tortuous
configuration of the passages.
Reference is now made to FIG. 9, which illustrates one of the
embodiments of this invention. In this embodiment the novel flying
spot kinescope 85 has flexible portions 86 and 87 in the sidewalls
88. The tube 85 has section A which houses the electron gun 90 and
which is of a rigid material, such as glass, metal or a ceramic.
Also the section B which houses two pairs of deflection plates 30a
and 30b is of rigid material, such as glass, metal or ceramic. The
endwalls 93 and 93a may also be of rigid material, such as glass,
metal or ceramic. The fluorescent screen 94 with a metallic
electron pervious backing layer 95 and deposited on the endwall
93.
In some cases the backing layer 95, preferably may be omitted.
Between the section A and the section B, the sidewall 88 has the
flexible section 87. Between the section B and the endwall 93 is
mounted another flexible section 86. The sections 86 and 87 are
made of a flexible material which has malleability to conform to
configuration of examined part. I found that the flexible sections
86 and 87 may be made of a a plastic material, such as of one of
fluorocarbons. In particular, I found that tetra-fluoroethylene or
its derivatives, such as Teflon made by DuPont Company of
Wilmington, Delaware, are suitable for this purpose. I also found
that polyesters, such as Mylar or Cronar manufactured by DuPont
Company of Wilmington, Delaware, may be used for this purpose. In
addition, silicone plastics, such as Silastic, made by Dow-Corning
and isocyanate plastics, such as Eccosorb AN made by Emerson and
Cumming, may be useful. If discovered that these plastic materials
with the exception of tetra-fluoroethylene, are slightly pervious
to the air and as a result they do not maintain well vacuum in the
tubes. I found, however, that this difficulty could be overcome by
metallizing, such plastic materials, with a thin layer of aluminum
or other metals. This metallization will not impair the flexible
nature of the above described materials. It should be added that
ordinary rubbers proved to be unsatisfactory for this purpose.
THe flexible sections 86 and 87 are fused to the adjacent rigid
parts by means of Korvar seals or by bending them with heat
resistant glues, such as "Ardalit", manufactured by Ciba Company,
or preferably with DuPont fabrics and finishes Department's
adhesives 4684 and 4695. When using 4695 to adhere a polyester,
such as "Mylar" to the glass, the adhesive should be coated on
polyester, solvents evaporated, then combined with glass at
350.degree. F. followed sometimes by an additional 10 minutes
curing at 350.degree. F. When adhering polyesters to a metal, such
as aluminum, copper, brass or steel, the above described procedure
may be followed as well. The resulting bond was found to withstand
flexion well. The presence of flexible sections 86 and 87 will
allow the vacuum tube to conform to configuration of the passages
through which the endoscope has to pass to enter the examined part.
In many examinations, especially in the human body, the main
difficulty resides in constricted passages which lead to the
examined organ. For example, the stomach has ample room to
accommodate the endoscope, but the esophagus at the junction with
the stomach forms a sharp anterior angulation which has a small
diameter and which can accommodate only a small rigid object. The
rigid part of tube 85 is now only the electron gun which can be
made small enough for the passage through the esophagus or other
narrow passages. The only other rigid parts of the tube 85 are the
deflecting plates 30a and 30b, which are small per se and which,
furthermore, being separated from the electron gun by the flexible
part 87 of the tube do not contribute any more to the length of the
rigid portion of the tube.
THe novel endoscope 84, shown in FIG. 10 is provided with a vacuum
tube having flexible walls 86 and 87 will now be able to pass in
all patients through the esophagus into the stomach, as such a
vacuum tube used in my device will be able to conform to the shape
of the esophagus.
The tube 85, after the passage through the esophagus or any other
similar narrow passages, will be distorted in shape and will,
therefore, not be able to function. For example, the electron beam
from the electron gun 90 may now be directed to the sidewall 88 of
the tub instead of to the fluorescent screen 94, as shown in FIG.
9a. In order to reestablish the original shape of the vacuum tube,
which is essential for its operation, I use two flexible conduits
96 and 97, which are attached to the sidewalls of the vacuum tube
and to the distal endwalls 93 of said vacuum tube. In some cases
they should be attached also to rigid section B. The conduits 96
and 97 may be of flexible materials, such as were described above.
The conduits 96 and 97 extend beyond the vacuum tube to the outside
of the examined part and are connected to a source 98 of compressed
air, oxygen or liquid. This source 98 is disposed outside of the
examined part. When the endoscope is in the location in which there
is enough space for vacuum tube to reestablish its normal
configuration, the valve 99 which controls the passage of the air
is opened and the pressure of the compressed air will cause
straightening of the bent tube 85. Instead of the air or oxygen
also a fluid under pressure may be used as well. The use of
pneumatic or hydraulic means to reestablish the proper
configuration of the vacuum tube represents an important feature of
my invention as otherwise the whole endoscope would fail to
operate. The conduits 96 and 97 are in addition provided with a
valve 100 controlled openings at the distal and to provide
insufflation of air or liquid into examined cavity as it may be
necessary in some examinations. The valve 100 serves also as a
safety outlet in case the return of fluid or air from the conduits
96 or 97 should fail. In such an accident the endoscope could not
be withdrawn from the pateint's body as the vacuum tube 88 would
not be able to fold and to conform to the configuration of
passages. By opening the valve 100, the escape of fluid or air is
provided which will reestablish flexibility and malleability of the
vacuum tube 85.
In some cases in which the geometric configuration of the tube is
not very critical, instead of flexible conduits 96 and 97, used to
reestablish the original shape of the tube, we may use flexible
sections 86 and 87 made of a resilient material, which will by
itself revert to the original form after the pressure by the walls
of the passage is removed. I found that materials, such as silicone
rubbers, manufactured by Dow-Corning Co. are suitable for this
purpose.
I found that when using fluorocarbons as a plastic material for
flexible sections 86 and 87, a complication arises due to escape of
negative fluorine ions during the baking of the tube. These
negative ions cause a fast deterioration of the fluorescent screen
or of the photocathode. I found that this difficulty could be
solved by providing a flexible conducting grid opposite the
flexible sections 86 and 87 and which is connected to the source of
a positive electrical potential during the baking of the tube and
which intercepts the negative ions, or by metallizing the inner
surface of plastic material by deposition of a layer of
aluminum.
It should be added that the baking of the vacuum tubes having
flexible sections should be preferably done at temperatures below
150.degree. C.
The flexible conduits in some cases may be preferably attached to
light transparent extensions 100a mounted on the sides of the
endwall of the vacuum tube instead of being attached directly to
the endwall of the vacuum tube, as shown in FIG. 9b.
In some cases it is preferable to make the whole sidewall 88a of
the vacuum tube 85 flexible instead of having a combination of
rigid and flexible sections as was described above. In such case
the electron gun is mounted on the endwall 93a of the tube which is
of rigid material. This construction is shown in FIG. 9c. In other
cases it is necessary to make the endwall of the tube of a flexible
material or to insert a flexible section into said endwall. The
flexible endwall may be used in combination with a flexible
sidewall or with a rigid sidewall.
It should be furthermore understood that the flexible construction
of the electron tubes applies also to non-vacuum tubes, such as gas
tubes, like Geiger-Muller tubes, proportional counters, ionization
chambers, etc.
In some cases the pressure source 98 should be preferably located
within the examined body or examined part. The pressure source 98
may be located within the endoscope or outside of endoscope. In
some cases, instead of pneumatic or hydraulic means, mechanical
means, such as springs or telescoping rods may be used to
reestablish the shape of vacuum tube 85.
It should be furthermore understood that the novel construction of
the vacuum tube described above applies not only to the kinescope
type of tubes but also to all types of television pick-up tubes,
one of which is illustrated in FIG. 11, or to all image sensitive
vacuum tubes described in this specification, some of which are
illustrated in FIGS. 1, 1A, 1B, 1C, 2a, 8b, etc.
The novel pick-up tube 110 may be of photoemissive type,
photoconductive type or photovoltaic type. Suitable materials for
photoemissive photocathodes are CsOAg or CsSb or other metal
alkali, such as K, Na or Rb with Sb, As, or Bi.
Suitable photoconductive materials are selenium, or its compounds,
sulphides of lead, cadmium or tellurium, oxides such as lead oxide
or zinc oxide, antimonides, especially indium antimonide. It should
be understood that all these materials may be used as evaporated
layers, sintered layers, mosaic layers, layers embedded in plastic,
single crystals or a mosaic of crystals.
In addition, the television pick-up tube 110 may have an image
sensitive screen which combines both photoemissive and
photoconductive layers. The photocathodes or screens 111 may be of
continuous type or of mosaic type. The photocathodes or screens 111
may have a planar shape or may be preferably of convex shape. The
scanning electron beam may be of high velocity type of of a low
velocity type. In conclusion, it should be understood that all
types of television pick-up tubes or of image sensitive tubes come
within the scope of this invention.
The novel endoscope 84 having flexible vacuum tube 85 is shown in
FIG. 10. It should be understood that the image sensitive element
16b or any of its modifications described in this specification
could be constructed with partially or totally flexible sidwalls,
as was described above. The remaining parts of the endoscope 84 may
have construction illustrated in FIGS. 1 to 8. The image sensitive
member and tube 85 may be in contact with each other.
The novel pick-up tube 110 has the photocathode 111, the deflecting
plates 112 and 113 and the electron gun 117 for producing the
scanning electron beam and electrostatic focusing means 23, as is
well known in the television art. In addition to novel pick-up tube
110 has flexible sections 86 and 87 in the sidewalls which were
described in detail above. Besides the novel pick-up tube 110 has
flexible conduits 96 and 97 connected to an extraneous source of
compressed gas or liquid, as was described above.
It should be understood that the novel pick-up tube 110 may have
the whole sidewall 88b made of a flexible material, as was
described above, and as it is shown in FIG. 12. The use of a
flexible television pick-up tube 110 in the endoscope may be in
some cases preferable to the use of a television system composed of
two separate elements, as described above.
In another embodiment of invention, illustrated in FIG. 13, the
kinescope 109 which produces the flying spot illumination of the
image sensitive member 120, which may have construction of tube 16b
or 16B' or 16C, or of screen 127, or of any modifications thereof,
is disposed outside of the examined part and has, therefore, no
limitations any longer as to its size or flexiblity. The kinescope
109 has a similar construction as the flying spot kinescope 16a
described above. It should be understood, however, that it can be
now of magnetic or electrostatic type as it is not limited any more
as to size. The flying spot light produced by the electron beam 112
is projected by a suitable optical system 113 on a flexible novel
light conductor 114.
The image conductor 114 consists of multiple fibers of material
having a high refractive index such as quartz, rutile or special
plastics. In many applications the image conductor must be flexible
and easily malleable. In such cases, acrylic plastics, such as
Lucite or polysterenes may be used. Especially Lucite is suitable
for this purpose because it causes smaller losses of conducted
light then other materials. Lucite and other above-mentioned
materials characterized by a high refractive index have the
property of internal reflection of the light conducted by them.
Such materials cannot conduct a whole image as such but they can
conduct well a light signal, which means an image point. The size
of the image point I found is determined by the diameter of a
single conducting fiber 114A. In my image conductor I assembled a
bundle of such fibers which form a mosaic-like end-faces and which,
therefore, can conduct plurality of image points. All these image
points will reproduce at the other end-face of the image conductor
the original image, provided that the ends of image conducting
fibers remain in their original spatial relationship. Each fiber
114A should have, as was explained above, a diameter corresponding
to the size of one image point. The diameter of 0.1 millimeter is
well suitable for the purposes of my invention. In order to conduct
an image of an area, e.g., of one square centimeter, we must have
many fibers, the number of fibers being dependent on the resolution
of reproduced image that we desire. If the resolution of the
conducted image should be four lines per millimeter, and if the
image is of one square centimeter in size, we will need 40 fibers
of 0.25 millimeter in diameter. The light conducting fibers should
be polished on their external surface very exactly Each of them
must also be coated with a very thin light opaque layer 114B to
prevent spreading of light from one fiber to another. I found that
without said light-impervious coating, the image will be destroyed
by leakage of light from one tube to another. The light opaqued
layer should have a lower index of refraction than the light
conducting fiber itself. Such a coating may have a thickness of
only a few microns. I found a great improvement of flexibility of
the light conductor 114 can be obtained by having the light
conducting fibers 114A glued together only at their end-faces 114a
and 114b. This is a very important feature of my device because the
main requirement from the light conductor 114 is its flexibility
and malleability. If the fibers 114A are flued together along their
entire length, the flexibility and malleability is so much reduced
that it may not be possible to use it in many examinations in which
the walls or passages are fragile and may be damaged by a rigid
instrument. I found unexpectedly that having the conducting fibers
114A free along their path between the end-faces will not cause any
deterioration of the conducted image. I found that in spite of the
fact that fibers between their end-surfaces were freely movable,
there was no blurring of the conducted image. It must be
understood, however, that the fibers 114A at both end-faces of the
conductor 114 must rigidly maintain their spatial relationship.
Another important feature of this construction is that the diameter
of the light conductor 114 can be now increased because no space
consuming binder or flue is present between the fibers 114A except
at their end-faces. Instead of using the binder at the end-faces of
fibers 114A, they may also be held together at their end-faces by
fine mesh screen. Each fiber is threaded through one opening of
said mesh screen and is being held by said screen in constant
position. It may be added that smaller loss of light may be
obtained if the fibers 114A are hollow inside instead of being
solid.
The number of fibers that can be used in many examinations will be
limited by the diameter of the passages through which may
intrascope has to pass. As in many situations, the channel may be
only 1-2 cm wide, it will be impossible to use a great number of
fibers or a singlerod of a large diameter. I succeeded in
overcoming this limitation by using in combination the light
conductor 114 with a demagnifying optical system 140. By the use of
the demagnifying optical system I can reduce the examined field to
the diameter of the image conductor 114. If the optical system will
demagnify the image five times, I can examine the field having 25
cm.sup.2 with the image conductor having the diameter of only 1
cm.sup.2. This combination of a light conductor with an optical
system represents a very important feature of my invention, as it
is not always practical or feasible to limit the examined field
only to the diameter of the image conductor.
The light image conductor 114 may be introduced into examined part
simultaneously with the intrascope. In some cases it is preferable
to introduce my intrascope first and then insert the image
conductor into intrascope. In some cases the optical system 113 or
140 may be attached to the end-face 114b of the image conductor to
make one unit.
In some cases it is possible to use a light conductor 114 (which
consists of a single large rod instead of plural fibers 114) as was
described above. The material for the "single rod conductor" may be
flexible acrylic plastics, polysterenes or Lucite. The light
conducting rod must be coated with a light-impervious layer 114B of
material having a lower index of refraction than the rod itself,
such as carbon, graphite or Aluminum, except on the surfaces which
serve to admit the light or to let the light escape from the
conductor. The single rod conductor cannot conduct an image but
only successive light signals.
The proximal end 114a of the light conductor 114 must be maintained
in a fixed spatial relationship with the flying spot kinescope 109
by mechanical means which may be constructed in the form of a
perforated rigid member 117. The light conductor 114 passes through
the aperture of said member and is attached thereto. The member 117
is rigidly attached to the kinescope 109 and establishes thereby
fixed relationship between the proximal end 114 of conductor and
the kinescope 109. The light conductor 114 directs the successive
light spots produced by the flying spot kinescope into the
endoscope 115. The scanning light spots emerging from the distal
end 114b of the conductor 114 are focused by a suitable optical
system 113a on the image sensitive member 120. The impingement of
scanning illumination converts the electrical pattern which
represents the image of the examined part and which is stored in
said member 120 into successive electrical signals. The electrical
signals are conducted to the outside of the examined part by wires
43 or by printed circuits and are fed into receivers to reproduce
the image. In addition, electrical signals may be used to activate
various circuits or devices used for industrial sorting and
testing. The distal end 114b of the light conductor 114 must also
be maintained in a fixed position in relation to the image
sensitive member 120, which may be of any type described above,
such as tube 16b or 16B' or 16c or screen 127, when the image of
the examined part is transmitted. The rigid plates or rods 116 and
117 with rigid extensions 116a and 117a, to which the distal end
114b of the light conductor is attached, serve to maintain the
distal end of the light conductor in a fixed position. I found
furthermore that the endoscope 102 will not operate properly if the
distal end 114 of the light conductor 114 and the image sensitive
element 120 are not maintained in a fixed position. The rigid rods
118 and 119 connected to the image pick-up element 120 serve for
this purpose. It should be understood that instead of rods, a rigid
box, which incloses both the element 120 and the end 114b of the
conductor, will provide their immobilization as well. The remaining
parts of the endoscope 102 may be the same as described above.
It should be understood that the image sensitive element 120 may
have many embodiments, all of which come within the scope of this
invention. The pick-up element 120 may have flexible sidewalls, as
was described above, in some sections or throughout the whole
length of sidewalls. Furthermore, element 120 may have completely
rigid sidewalls when used in combination with a light conductor
114. The image pick-up element 120 may be of photoemissive type or
may be of photoconductive type or of photovoltaic type and may
comprise any material described above.
Another improvement of the endoscope is shown in FIG. 14. I found
that the loss of light conducted by the conductor 114 becomes very
high if the conductor extends over the length of a few feet. It is
necessary, therefore, to utilize all the light available from the
flying spot kinescope 109. The optical system 113 or 113a in the
fastest form still causes a loss of at least 90 percent of useful
light. I found, therefore, that in examinations of remote parts, it
was necessary to eliminate the optical system 113 or 113a or both.
FIG. 14 shows flying spot kinescope 122, in which all of the
endwall 111a or a part of said endwall is replaced by the light
conductor 114, which may be of materials described above, but
preferably should be of quartz. The proximal end-face 114a of the
conductor 114 may be flush with the rest of the endwall of the
kinescope 122 or may extend inside of the kinescope 122. The
fluorescent screen 94 is deposited on said end-face 114a. This
construction eliminates the optical system and in spite of it,
there is no loss of sharpness of the scanning light spot, because
of a close apposition of the fluorescent screen 94 and of the light
conductor 114.
A similar construction is used in the distal end 114b of the
conductor whereby the distal end 114b enters into image sensitive
member 120 to establish an optical contact with the image sensitive
screen, such as 34, 34A, 34B or 111 disposed in said image
sensitive member.
The same construction may be applied advantageously to the
embodiment of invention shown in FIG. 1D whereby the distal end 114
of the light conductor 114 will be in contact with the screen
127.
A rotating mirror 21a may be used in addition to lens 21 to receive
the image through various windows. The remaining parts of the
endoscope 103 may be the same as described above.
It should be understood that in examinations in which the
definition of the image is not important, the image conductor 114
may be placed in contact with the endwall of the flying spot
kinescope or with the endwall of the image sensitive member either
of television type or of image reproducing type, without
penetrating into such a vacuum tube or photocell.
In another embodiment of invention the flying light spot tube is
used to produce a scanning illumination of the examined body
instead of the scanning illumination of the image sensitive
element, as was described above, and is disposed outside of the
examined body. This endoscope 104 is shown in FIG. 15. The
kinescope 109a may be of any of constructions described above, such
as the tube 16a, 109 or 122. The light conductor 114 may be the
same as was described above. The flying spot is projected by the
optical system 150 onto the examined part.
The optical system 150 is an important feature of this invention.
As the diameter of the image conductor 114 is limited by the narrow
passages, the field of the examined body, which may be scanned
through the image conductor, is necessarily limited. By using,
however, an optical system 150, which produces five-fold
enlargement, it is possible now to cover the field of the examined
part, which is five times larger. This feature proved to be very
important in some examinations.
The reflected light spot is admitted through the window 18 to the
image sensitive element 131, which in this construction may be in
the form of a multiplier phototube. In some cases the solid state
photoconductive devices, such as photodiodes or phototransistors,
may be used as an image sensitive element instead of a vacuum tube
131. It should be understood that the multiplier phototubes, such
as 131, photodiodes or photocells, such as 127, cannot produce an
image without the use of a scanning illumination for forming
plurality of successive image points. The use of an ordinary field
illumination in combination with phototubes or photocells will
produce only signals but not images.
The reflected successive light spots are converted by the element
131 into successive electrical signals. Electrical signals are
conducted outside of the examined part and may be reconverted into
visible images, as is well known in television art. It should be
understood that the electrical signals may be also fed into various
utilization circuits provided with "absorption negatives" or other
mechanism used for sorting and testinG materials. I found that an
essential feature of this embodiment of endoscope is the
maintenance of a fixed spatial relationship between the flying spot
kinescope 109a and the proximal end 114a of the light conductor
114. The distal end 114b of the light conductor 114 also must be
immobilized. The immobilization of the kinescope 109 and of the
proximal end 114a of the light conductor was described above. The
fixed spatial relationship between the distal end 114b of the light
conductor and window 12 may be provided by rigid rods 116a and
117a, or by enclosing the distal end of the light conductor in a
rigid light-impervious box 147.
Furthermore, if no such box is used, there must be provided
light-impervious partitions 142 which prevent the light from the
light image conductor 114 to reach the image sensitive element 131
before being modulated and reflected by the examined part.
In some cases the flying spot kinescope 109 may be mounted inside
of the endoscope or may be introduced inside of the examined body
or object but will remain outside of the endoscope.
In some cases the scanning illumination of the examined part is
directed through the distal end of the endoscope 105 as it is shown
in FIG. 15a. the light from the light conductor 114, which may
extend beyond the endoscope through the opening 151, is focused on
the examined part by the optical system 150. The reflected light is
admitted into endoscope through windows 152 or 153 and is focused
by lenses 152a or 153a on the image sensitive member 131 or 132a or
both.
Another important improvement of all the endoscopes described above
is the use of a flexible source of illumination instead of
conventional, rigid bulbs or lamps. The flexible light source 135
is illustrated in FIG. 16. the light source 135 comprises
fluorescent layer 138, a light transparent conducting layer 137,
another light transparent layer conducting layer 139. One of
conducting layers 137 and 139 may be light opaque instead of being
light transparent The layers 137 or 139 may be continuous or
preferably in the form of a fine mesh or grid. The layers 137 and
139 are connected to an extraneous source of A-C or D-C electrical
potential, preferably, however, of A-C type. The electrical
potential of 100 - 1,000 volts and frequency of 50 cycles per
second up to 1,000 cycles per second for A-C type are sufficient to
provide 10 ft. candles of illumination without producing any heat.
This feature is of great importance in examination of the living
bodies where the heat generated by conventional filament type of
bulbs may be injurious to the adjacent tissues. The fluorescent
material is embedded in a a dielectric medium 138c. This dielectric
medium just be of a flexible and light transparent material. Some
of materials described above were found very suitable for this
purpose. In particular, polyesters, such as Mylar or Cronar,
silicones or terphalates, proved to be suitable for the purposes of
this invention.
The illuminescent materials used for the layer 138 are sulphides or
selenides activated with copper or any other phosphors which have
electroluminescent properties. The flexible light source 135 may be
made as a thin panel and may be disposed on the sidewalls or on the
endwall of the endoscope.
The length of the flying spot kinescope 16a, 85 or 109 or any of
its modifications is an important factor in the construction of
endoscopes. The rigid part of the flying spot tube is due to the
electron gun 28 or 90. Shortening of the electron gun would help
therefore to reduce the rigid part of the flying spot tube. In some
cases it is possible to image the source 163 of the electron beam
on the fluorescent screen instead of imaging the cross-over of the
electron beam on the fluorescent screen 31 or 94. This will allow
shortening of the electron gun and thereby shortening of the tube
16a or 85 or 109. Also construction of the electron gun known as
Wehnelt cylinder will permit reducing of the length of the electron
gun. The electrostatic focusing field is provided in Wehnelt
cylinder by the electrode adjacent to the filament of the electron
gun.
In cases in which a small electron beam is necessary for a good
definition of images, it is necessary to use a two-lens electron
gun 164, which is shown in FIG. 17. Such a gun comprises filament
163 for emission of electrons, the first focusing electrode A, the
first anode B, the second focusing electrode C and the second anode
D, which may have the form of a conducting coating on the wall of
the tube. This construction results in a longer electron gun than
the one described above. In order to shorten this electron gun 164
without sacrificing sharpness of the electron beam, the members C
and B are made movable on tracks or slide channels 162 and 165, so
that they may be telescoped into each other before the insertion of
the endoscope into the examined part. The knobs 154 and 155 serve
to move the electrodes B and C. Racks 158 and 159 are secured on
the outside wall of electrodes B and C respectively. Pinions 157
and 157a are mounted on shafts 156 and 156a respectively. The
shafts 156 and 156 a extend beyond the sidewall of the tube and are
rotatable by knobs 154 and 155. The telescoping of the electrodes B
and C will cause a considerable reduction of the length of the
electron gun which was the purpose of this invention.
Another improvement of the endoscope is the use of the flying spot
tube, which has instead of the electron gun only an electron
emitter. The electron beam produced by the electron emitting source
is injected along the edge of the tube and travels to the opposite
endwall of said tube which houses the fluorescent screen 94. A
plurality of transparent deflecting plates is mounted in front of
fluorescent screen 94 and serves to direct the electron beam to
successive points on the fluorescent screen to produce thereby
aluminescent raster for scanning illumination. This embodiment of
invention allows shortening of flyingspot tube, which is of great
importance to the endoscope.
In some examinations it may be possible to use a conventional
source of light in combination with an oscillating mirror, instead
of using a flying spot kinescope. the oscillating mirror may be
made to vibrate in both horizontal and vertical planes. The
oscillating mirror may be mounted on a pivot and may be energized
by solenoids through which the current of high frequency is
flowing. One set of coils serve to move the mirror in horizontal
axis. Another set of coils is vibrating the mirror on vertical
axis. The action of both coils makes the mirror oscillate in such a
manner that the light reflected by said mirror will scan the area
on which it is projected in the same manner as the flying spot
which is produced by a cathode-ray tube. The construction of an
oscillating mirror is well known in the art and it is believed
therefore that its further detailed description will only serve to
complicate the drawings. It may be preferable, however, if the
oscillating mirror is mounted outside of the examined body to
vibrate the mirror only in one plane, such as horizontal plane, and
to use an optical drum to produce the vertical scanning
displacement of the light spot from the mirror.
It was explained above that the light conductor of a single rod
type cannot be used for conducting or transmitting images. I found,
however, thatit is possible to use a single rod light conductor for
transmission of images by a device illustrated in FIG. 15d. In this
embodiment of invention the source of scanning illumination, such
as e.g., the flying spot kinescope 16a or 109 illuminates in a
scanning manner the examined part and produced a successive
imagepoints of the examined part. Each of said image points is
projected successively on the single rod light conductor 114C
which, as explained above, can conduct only a single light signal,
which means a single image point. The successive light signals are
fed into phototube 131, which may be disposed inside the examined
or outside of the examined part. The phototube is preferably a
vacuum tube of multiplier type. In some examinations, a
photoconductive photocell or a junction type of a photocell may be
used for this purpose. The phototube 131 converts successive light
signals into successive electrical signals. The electrical signals
are fed into an image reproducing device, such as e.g., kinescope
16A. The kinescopes 16a and 16A are connected by synchronizing
circuits which are well known in the television art. Therefore,
each image point produced by kinescope 16a will appear on the
fluorescent screen of the kinescope 16A in a proper spatial
relationship. If all image points will arrive in a rapid succession
and in a proper spatial distribution, I found that a complete image
of the examined part will be reproduced in kinescope 16A in spite
of using a single rod conductor. The remaining parts of this
endoscope may be the same as was described above.
Another advantage of this embodiment resides in discovery that if a
single rod conductor has one of its side surfaces exposed, which
means abraded and uncoated, it will be able to pick up light
signals produced by kinescope 16a along its entire exposed surface.
This will solve the problem of examination of large fields, as we
will not be limited any more tothe field which has the size of the
end-face of the light conductor.
In some cases it is preferable to have the image sensitive member
outside of the examined body. The endoscope 106 which represents
this embodiment of invention is illustrated in FIG. 15b. The
endoscope 106 has light source, which may be of conventional type,
or in the form of a flexible electro-luminescent lamp shown in FIG.
16. The light source illuminates the examined part through window
12. It should be understood that the light source may also be
disposed outside the endoscope and this applies to all embodiments
of invention. The image of the examined part is admitted to the
endoscope through window 18 and is focused on the image conductor
114 which comprises plurality of light conducting fibers. The
conducted image emerges from the conductor 114 outside of the
examined part or outside of the examined body and may be viewed by
the Examiner. In some examinations the emerging image has a very
low brightness. It is advisable in such cases to direct the image
to the image amplifying tube 120A or to a television camera The
image reproducing tube120A has a photoelectric photocathode 145
which receives the conducted image and converts into an electron
beam 143 and an image reproducing fluorescent screen 44 which to be
reconverts the electron beam into an intensified visible image.
In some cases the end-face of the image conductor should be
preferably disposed within the image amplifying tube 120A, or
within the television pick-up tube in a similar manner as was
described in FIG. 14. This endoscope may be used for producing
color images of the examined part, as was described above. The use
of rotating color filters 50 and 50a is one way of producing color
images.
In some examinations it is preferable to have the image sensitive
member and the source of scanning illumination both to be within
the examined part. The endoscope 107, which represents this
embodiment of invention, is shown in FIG. 15c. The scanning
illumination may sometimes be delivered to the image sensitive
member by an optical system, but I found that it is preferable to
use the image conductor 114 for this purpose as relative positions
of aforesaid members cannot be predicted and optical systems
fail.
FIG. 15c shows a modification of the endoscope in which the
illumination is provided by a conventional source of light, such as
electrical bulb 7, or by electro-luminescent source of light 135.
This illumination is piped into the examined part through a
flexible conductor 114c. The light conductor is in the form of a
single rod as it does not serve to conduct an image but only
illumination. The flexible light conductor 114c may be situated
inside of the endoscope or outside of the endoscope. If it is
outside of the endoscope it may be moved towards the wall of the
examined part by shortening the thread or wire attached to its
distal end. In this way the light may be brought closer to the
examined part or may be even inserted into a narrow channel
adjacent to the examined part which is not accessible to the
endoscope itself.
It should be understood that the endoscope shown in FIG. 15b may
have the image tube 120A or the image sensitive member, such as 16b
and its modifications, 120 or 127, or a television pick-up tube
disposed inside of the examined body. In such a case the end-face
114a of the image conductor is also within the examined body and
may be inside of the endoscope or may be outside of the endoscope.
The operation of such device as follows: the end-face 114b receives
the image of the examined part through window 18. The image
projected on the end-face 114b may be demagnified by the optical
system 140 to reduce the size of the image to the size of
cross-section of the image conductor 114. The image emerging at the
proximal end-face 114a may be projected in the image sensitive
member, such as 16b or its modifications described above, 120 or
127, or on a television pick-up tube, and will be thereby converted
into electrical signals, as was described above. The electrical
signals may be led to the outside of the examined body by a coaxial
cable, as was explained above. The television pick-up tube may be
of photoemissive type, photoconductive type, or photovoltaic type,
and may use fast or slow scanning electron beam. The novelty of the
combination of the image conductor with a television system resides
in the ability of the intrascope provided with this combination to
penetrate into locations which are inaccessible to television
pick-up systems. The television pick-up system can then transmit
the image to the outside of the examined body and it can do it
regardless of the distance between the television tube and the
outside. The image conductor on the other hand is limited in its
ability to conduct an image for longer distance because of
prohibitive loss of light.
I found that in some cases the combination of two different colors
of illumination of the examined part allows the production of the
image of pathological lesions in a color which was characteristic
of a disease, facilitating thereby diagnosis. For this purpose an
additional light source may be placed either outside of the
endoscope or inside of the endoscope. If it is placed inside of the
endoscope it may be piped to the examined part by a flexible light
conductor in the form of a single rod 114C, as shown in FIG. 15c.
The additional light may be a visible color, or it may be an
invisible light, such as ultra-violet or infra-red light. It should
be understood that all types of endoscopes may serve to produce
true or arbitrary color images of the examined part in the manner
described above.
Another important discovery was that supersonic waves can also be
conducted by the image conductor 114 or 114C. By using as a source
of image forming radiation piezoelectric or magnetostrictive
generators of supersonic waves and conducting said waves to the
examined part, we may produce supersonic images. Piezoelectric
generators may be in the form of oscillating crystals of quartz,
titanium compounds, such as titanates, Rochelle salts and other
similar materials. The piezoelectric or magnetostrictive generators
can be disposed within the examined body or may be disposed outside
of the examined body. The supersonic waves may be directed to the
examined part by supersonic lenses or preferably by means of the
image conductor 114. The supersonic waves reflected or transmitted
by the examined part may be directed to the supersonic image
sensitive member by the same image conductor 114 or preferably by
an additional image conductor. The supersonic sensitive member may
have the form of piezoelectric elements, such as were described
above for the supersonic generator, but smaller in size. In another
embodiment of invention, the supersonic image sensitive member is a
vacuum tube provided with a piezoelectric continuous or mosaic
electrode mounted on the inside of the endwall of said tube. Said
piezoelectric screen or electrode receives the supersonic image of
the examined part through the endwall of said tube and converts
said image into an electrical pattern of potentials or charges
which correspond to said supersonic image. Such a vacuum tube is
provided with a source of electron beam, such as electron gun for
irradiation of said piezoelectric screen or electrode. The electron
beam scans said piezoelectric screen or target and converts thereby
the electrical pattern present on said screen or electrode into
electrical signals in the manner well known in the television
art.
It was also found that the light should be in some cases a
polarized light. I found that in many examinations, especially in
examination of the human body, the light scattered by the fluids
contained in the examined part produces deterioration of contrast
and detail of the image. In order to overcome this difficulty, a
sheet 160 or a prism of material, such as calcite or tourmaline,
which polarizes the light, is placed in front of the light source
7, 109 or 135. Another filter 161, which transmits only the
polarized light and reflects the scattered light, is placed in
front of the image pick-up member 16a, 16B, 16C, 16D, 120,131 or
127. The scattered light is not polarized and will be therefore
reflected by the filter 161. As a result, it will, therefore, be
prevented from reaching the image pick-up element and will not fog
the image any more. This improvement applies to all embodiments of
invention.
Another complication encountered in operation of this device was
fogging of the windows 12 or 18, 152, 153 or any other windows, due
to condensation of vapor when entering the parts having a higher
temperature, such as recesses of the living body. I found that the
use of electrically conducting glass for windows, which is
connected to an extraneous source of the electrical potential,
prevents the condensation of vapor. Another solution of this
problem is to provide a double-walled window containing a
transparent silica gell. This improvement applies to all
embodiments of my device.
It should be understood that in all embodiments of invention the
source of illumination may be disposed in such a manner that its
long axis is in the long axis of the endoscope or that its long
axis is perpendicular to the long axis of the endoscope.
It should be understood that in all embodiments of my invention,
the light source of source of an invisible image forming radiation
may be disposed inside of the endoscope or may be disposed outside
of the endoscope. Furthermore said source of image forming
radiation may be supported by the endoscope or may be completely
independent of the endoscope. This applies to sources of field
illumination and of scanning illumination.
It should be also understood that the term "light" used in
specification and in appended claims comprises both visible and
invisible radiations and also represents both electro-magnetic,
acoustic and corpuscular radiations.
It should be further understood that in all embodiments of
invention the source of image forming radiation may be disposed
outside of the examined body and projected into the examined body
by a suitable optical system or by a light conductor.
As various possible embodiments might be made of the above
invention, and as various changes might be made in the embodiment
above set forth, it is to be understood that all matter herein set
forth or shown in the accompany drawings is to be interpreted as
illustrative and not in a limiting sense.
* * * * *