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Патент USA US3048741

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Aug. 7, 1962
3,048,729
w. R. PERRY
CATHODE RAY SCREEN STRUCTURE
Fviled Jan. 19, 1961
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INVENTOR.
WILLIAM
R. PERRY
BYW/?
ATTORNEY
ICC
3,048,729
Patented Aug. 7, 1962
2
Another object of this invention is to provide a cathode
3,048,729
CATHODE RAY SCREEN STRUCTURE
William R. Perry, 325 Warminster St., Hatboro, Pa.
Filed Jan. 19, 1961, Ser. No. 83,851
6 Claims. (Cl. 313-92)
(Granted under Title 35, U8. Code (1952), sec. 266)
ray tube structure for use in a radar screen or in a tele
vision viewing screen in which the contrast is virtually
unaffected by the level of ambient illumination.
With these and other objects in view as will herein
after more fully appear and which will be more partic
ular-1y pointed out in the appended claims reference is now
made to the following description taken in connection
The invention herein described may be manufactured
with the accompanying drawings in which:
and used by or for the Government of the United States
FIG. 1 illustrates a cathode ray tube partially broken
of America for governmental purposes without the pay 10
away
to show the multi-layer screen structure.
ment of any royalties thereon or therefor.
FIG. 2 shows the screen structure of FIG. 1, magni?ed
This invention relates to cathode ray tube screens and
several times.
more particularly to a particular screen structure for im
proving image contrast.
In FIG. 1 there is shown the general con?guration of
The contrast on the surface of a cathode ray viewing 15 a cathode ray tube 10 in ‘which reference numeral 11
tube between that portion of the screen illuminated by am
bient light only and that portion of the screen illuminated
indicates the face portion of the glass envelope 12. A
transparent phosphor or ?uorescent material is deposited
on and forms a layer 13 on the internal portion of the
face 11. The phosphor is of such ‘a nature as to be trans
the cathode ray tube. This adverse effect on the con 20 parent to visible light while at the same ‘time to be ?uores
cent when bombarded With electrons from a conventional
trast is generally known to be caused by the re?ection
electron gun commonly used in cathode ray tubes. A thin
of the ambient light off of the ?uorescent material neces
metal coating 14 is deposited on the other side of the
sary in the construction of cathode ray screens. Various
phosphor layer to form therewith a specularly re?ecting
methods are employed to reduce this contrast destroying
re?ection of ambient light. Many of these methods em 25 surface 15. The coating of metal is thin enough to per
mit bombarding electrons to pass. through. On the other
ploy combinations of light ?lters to prevent the re?ected
side of the face 11 there is a quarter wavelength ?lter
light from passing back through the screen. Another
16 optically bonded to the face 11 in any convenient
method for reducing re?ection and thus increasing con
manner. A polarizing ?lter 17 is bonded to the quarter
trast uses a light absorbing material on the back of the
wavelength ?lter and may form the external surface of
“a ?uorescent material.
the tube face. The polarizing ?lter and the quarter wave
This invention contemplates ‘a particular screen struc
by ambient light plus electron bombardment is adversely
affected by strong ambient light originating external to
_
ture which virtually eliminates ambient light re?ection
and thus vastly‘ improves the contrast. This purpose is
accomplished by the unique combination of a transparent
length ?lter may be the combined plastic commercial
product of the Polaroid Corporation.
The manner by which the screen structure 19 functions
35 to reduce to a negligible amount the effect that external
ambient light, no matter how intense, has on image con
?ecting surface with a particular ?lter arrangement. The
trast will now be discussed. Polarizing ?lter 17 passes
transparent phosphor having a specular re?ecting surface
?uorescent material or phosphor having a specularly re
external ambient light of one speci?c polarity’. Quarter
wavelength ?lter 16 then translates the polarized light an
the surface. In a conventional screen structure, even in 40 angle of 45 degrees. The light then re?ects off specularly
is necessary to insure that light re?ecting from the surface
maintains unaffected the polarization of incident light on
re?ecting interface 15 and because it is a specularly re
one utilizing ?lters, where the ?uorescent material is not
?ecting interface, the re?ected light has the same polarity
transparent and is therefore light diffusing, it is not pos
as the incident light. The light then passes back through
sible to accurately control the polarization of re?ected
quarter wavelength ?lter 16 and is further translated an
light and thus some light due to re?ection will always be
45 other 45 degrees. The total change in polarity of the
visible.
re?ected light as it reaches polarizing ?lter 17 is at an
Speci?cally, this invention contemplates a cathode ray
angle of 90 degrees to the principal plane of the polarizer.
tube screen which utilizes a transparent phosphor adjacent
In other words, the re?ected light at interface 18 has been
the internal face of the tube having a thin coating of metal
rotated in polarity 90 degrees relative to the incident light
such as aluminum thereon forming a specularly re?ecting
surface with the phosphor. On the external side of the 50 arriving at interface 18. Therefore, the re?ected light is
blocked by polarizer 17.
tube face a polarizing ?lter and a quarter wavelength
The face 11 of the envelope 12. may be placed on the
?lter are arranged in \side-by-side relationship with the
external side of ?lter 17 instead of being interposed be
polarizing ?lter being closer to the eye of an observer.
tween the transparent phosphor and the ?lters. Also a
Thus, light coming from an external source is polarized
by the polarizer, translated forty-?ve degrees by the quar 55 nonre?ective coating, as used on lenses in cameras, etc.,
ter wavelength ?lter, and is re?ected from the specularly
re?ecting surface. Since it is specular re?ection the forty
?ve degree translation of the light is maintained until it
may be added to the ?rst surface of the polarizing ?lter to
decrease re?ections from the surface.
It should be clear from the above description that
passes back through the quarter wavelength ?lter again
image contrast is greatly improved by the unique combina
where it is given an additional translation of forty-?ve 60 tion of a transparent phosphor having a specularly re
?ecting ‘surface with a quarter wavelength ?lter and a
degrees in the same direction so that the total translation
polarizing ?lter. The transparent phosphor forming a
of the light becomes ninety degrees with respect to the
specularly re?ecting surface with a thin coating of op
polarizing plane of the polarizing ?lter. The result, of
course, is that the re?ected light is not visible to the eye 65 tically opaque material is an essential part of the com
bination of the invention. If the ?lter arrangement de
of an observer. Thus, it should be seen that the com
scribed above were used with a conventional phosphor
bination of the transparent phosphor having a specularly
layer, that is one which diffuses light, it should be obvious
re?ecting surface with the two ?lters is the basic idea
that much of the re?ected light would be changed in po
behind this invention.
Therefore, it is an object of this invention to provide 70 larity upon reflection and thus the polarity of much of the
light reaching the polarizer 17 would not be at a 90 de
a cathode ray tube screen which greatly improves contrast
gree angle to the plane of the polarizer and a substan~
by virtually eliminating re?ected ambient light.
Y-
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3,048,729
4
tial amount of the light would then be visible to an ob
server’s eye.
It should be understood, of course, that the foregoing
disclosure relates to only a preferred embodiment of the
invention and that other modi?cations may be made there
in Without departing from the spirit ‘and the scope of the
invention as set forth in the appended claims.
What is claimed is:
1. A screen for a cathode ray tube, comprising: a non
light dilfusing layer of ?uorescent material having a spec
ularly re?ecting surface on one side thereof, a polarizing
?lter, a quarter wavelength ?lter, said quarter wavelength
?lter being interposed between said polarizing ?lter and
the other side of said layer.
2. A screen for a cathode ray tube, comprising in com
bination: a layer of transparent phosphor having a spec
ularly re?ecting surface on one side thereof, a polarizing
ing of metal on the other side of said layer forming a spec
ularly re?ecting interface therewith, a quarter wavelength
?lter, a polarizing ?lter, said quarter wavelength ?lter
interposed between the external surface of the tube ‘face
and said polarizing ?lter.
5. In combination with a cathode ray tube having a
tube face, a polarizing ?lter, a quarter wavelength ?lter,
said quarter wavelength ?lter interposed between said po
larizing ?lter and the external surface of the tube face,
a layer of non-light diffusing ?uorescent material op
tically bonded on one side to the internal surface of the
tube face, a thin ?lm of metal on the other side of said
layer forming a specularly re?ecting surface therewith.
6. In combination with a cathode ray tube, a polariz
ing ?lter forming the external portion of the screen of said
tube, a quarter wavelength ?lter optically bonded on one
side to said polarizing ?lter and on the other side to the
?lter, a quarter wavelength ?lter, said quarter Wavelength
glass envelope of said tube, a transparent phosphor layer
?lter being interposed between said polarizing ?lter and
optically bonded on one side to the internal side of the
the other side of said layer.
20 glass envelope of said tube, a thin metal coating on the
3. In a cathode ray tube having a face, a transparent
other side of said phosphor layer forming a specularly
phosphor layer optically bonded on the inner ‘side of said
re?ecting surface with said phosphor layer whereby am
face, a thin coating of metal on the inner side of said
bient light passing through said ?lters is specularly re
phosphor layer forming a specular re?ecting interface
?ected and on reaching said polarizing ?lter is polarized
therewith, a quarter wavelength ?lter optically bonded 25 ninety degrees to the principal plane of said polarizing
to the outer side of said face, a polarizing ?lter optically
bonded to the outer side of said quarter wavelength
?lter.
?lter and is unable to pass therethrough.
References Cited in the ?le of this patent
. 4. A screen for a cathode ray tube, comprising in com
bination: a transparent phosphor layer having one side 30
adjacent the internal surface of the tube face, a thin coat
UNITED STATES PATENTS
2,958,801
Herriott ______________ __ Nov. 1, 1960
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