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Патент USA US3087098

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April 23, 1963
R. W. HUNTER ETAL
3,087,088
ELECTRON DISCHARGE DEVICE
Filed May 17, 1960
9
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April 23, 1963
R. W. HUNTER ETAL
3,087,088
ELECTRON DISCHARGE DEVICE
Filed May 17, 1960
2 Sheets-Sheet 2
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Patented Apr. 23, 1963
2
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Papp, both assigned to the assignee of the present ap
338M988
ELECTRQN DESCHARGE DEVIQE
Roger ‘W. Hunter and Irene K. Haak, Fort Wayne, Ind,
assignors to international Teiephone and Telegraph
Corporation
plication.
While the construction of the aforesaid Farnsworth,
Rudnick et al. and Papp patents have eliminated many
of the disadvantages of direct viewing storage tubes
incorporating an oil-axis writing gun, the flood beam
provided by such constructions does not have the desired
it) Ciairns. (Ci. 3:15-12)
uniformity of current density and velocity, nor the desired
This invention relates generally to electron discharge
normal incidence, particularly in the case of a tube
devices of the cathode ray tube type, and more particu 10 having a spherically curved storage screen and phosphor
larly to charge storage tubes such as direct viewing
viewing screen; a spherically curved storage screen is
signal-to-image storage tubes.
desirable for optimum writing resolution and a spherically
Direct viewing storage tubes are conventionally pro
curved display screen is necessary in instances when the
vided with a storage screen assembly including a ?ne
tube is incorporated in a re?ective optical projection
Filied May 17, 196i}, der. 'N . 29,665
mesh metal backing screen coated on one side with a 15
dielectric material having ‘secondary emission properties,
and a ?ne mesh metal collector screen closely spaced
from the dielectric side of the storage screen. The stor
age screen assembly is disposed between a phosphor dis
play or viewing screen and an electron gun assembly which 20
system.
.
It is therefore a general object of our invention to
provide an improved electron discharge device having
an annular electron gun and a cooperating electron op
tical system wherein the electron beam impinges upon
a target electrode with normal incidence and 'with uni-v
provides a high velocity “writing” electron beam which is
form current density and velocity distribution over the
caused to scan the storage screen assembly by means of
entire electrode.
conventional de?ection and focusing means. The high
Our invention, in its broader aspects, provides an
velocity electron beam impinging upon the dielectric
electron discharge device having an envelope with a large
material screen displaces secondary electrons which are 25 area target electrode disposed therein. An annular elec
collected by the collector screen, thus leaving a positive
tron gun is provided in the envelope spaced axially from
charge on the dielectric material screen caused by a
the target electrode and including an annular cathode.
de?ciency in electrons thereon. The high velocity elec
First electron optical means are provided adjacent the
tron beam may be modulated in accordance with an
gun ‘for converging the electron emission ‘from each
incoming signal with the result that discrete areas of the
elemental segment of the cathode to a waist forwardly
storage screen de?ned by the openings therein will have
of the gun, and second electron optical means are pro
different charges thereon, thereby ‘forming a pattern or
vided ‘for diverging the emission from the Waist into direc
charge image on the storage screen corresponding to the
tions generally along radii from a point on the axis of
input signal; this charge image will be retained on the
the gun and forwardly thereof, thereby forming a virtual
storage screen for a substantial period of time, and may
cathode adjacent the said point and distributing the emis—
be “read-out” at any time during its existence. The
sion ‘from each elemental segment of the cathode over
charge image is “read-out” by providing a second elec
the entire area of the target electrode.
tron gun assembly which directs a ?ood beam of low
The above-mentioned and other features and objects
velocity electrons onto the storage screen. These low
of this invention and the manner of attaining them will
velocity electrons pass through the openings in the storage 4.0 become more apparent and the invention itself will be
screen, being modulated in accordance with the elemental
best understood by reference to the following descrip
charges thereon, and impinge upon the phosphor display
tion of an embodiment of the invention taken in conjunc
screen to provide a visible display of the charge image
tion with the accompanying drawings, wherein:
stored on the storage screen.
In one common form of direct viewing storage tube,
the ?ood gun and the writing gun are mounted side-by
side facing the storage screen which necessitates that one
or both of the guns be displaced from the axial center line
of the tube. In order to eliminate undesirable shading
in the displayed image, it is necessary that the ?ood
beam be of uniform current density and velocity distribu
tion over the entire area of the storage screen, and it is
FIG. 1 is. a cross-sectional view of a direct viewing
storage tube incorporating our invention and having
spherically curved storage and display screens;
FIG. 2 is a fragmentary cross-sectional view of the
tube of FIG. 1 diagrammatically illustrating the path
followed by the electron emission from each elemental
segment of the annular ?ood gun and typical equipoten
tial lines provided by ‘the electron optical system which
provide such paths; and
also necessary that the low velocity electrons of the flood
1FIG. 3 is a cross-sectional view of an electron dis~
beam impinge upon the storage screen with normal
charge device incorporating our invention and having
incidence. Since it is easier to collimate the ?ood beam 55 flat storage and display screens.
when the ?ood gun is located on the axis of the tube,
Referring now to FIGS. 1 and 2, there is shown a
-it has been common practice to locate the writing gun
direct viewing storage tube, generally identi?ed as 10,
inclined to and offset from the axis of the tube, which,
having an evacuated envelope 12 with an elongated
however, produces keystoning and other distorting effects.
cylindrical portion 14 closed by a spherically curved
In order to eliminate the aforementioned dif?culties 60 faceplate 16. The inner surface of faceplate 16 is coated
inherent in a direct viewing storage tube having an offset
with a suitable phosphor layer 18 to form a display
writing gun, it has been proposed to provide an on-axis
screen, as is well known in the art. An end-wall portion
writing gun with an annular or ring ?ood gun coaxial
‘20 joins the end of cylindrical portion 14 of envelope 12
therewith and such a construction is shown in Patent
remote from faceplate 16 and terminates in an enlarged
Number 2,754,449 to Philo T. Farnsworth, and assigned 65 neck portion 22 which in turn is joined to a smaller elon
to the assignee of the present application. It has further
been proposed to provide a ring ?ood gun and cooperating
electron optical system in which the electron emission
from each elemental segment of the ring gun is distributed
over the entire area of the storage screen and such con
gated neck portion 24, as shown. A conventional writing
gun 26 is provided in neck portion 24 of envelope 12
concentric with axis 28 of tube '10 for directing the high
velocity “writing” electron beam toward storage screen
assembly St}. The writing beam is focused and de?ected
structions are shown in Patents 2,864,020 to Paul Rud
by conventional elements which do not form a part of this
nick and Michael F. Toohig, and 2,927,235 to George
invention and which are not shown.
3,087,088
3
:2.
Storage screen assembly 30 comprises a spherically
Distance between display screen 18 and
curved collector screen 32 and a spherically curved stor
age screen 34; storage screen 34 is formed of an insulating
Distance between storage screen 34 and
storage screen 34 _______________ _. .3 inch.
layer 36 facing writing gun 26 and a conductive ?ne mesh
screen 38 facing phosphor screen 18. In the illustrated
collector screen 32 ______________ _. .1 inch.
Axial length of conductive coating 66 __. 2.7 inches.
Axial length of conductive coating 64 __. 2.75 inches.
Inner and outer diameters of anode shell
embodiment, faceplate 16 and thus phosphor display
screen 18, storage screen 34 and collector screen 32 all
have a common center of curvature on tube axis 28, as
at 40.
Flood electron gun assembly 42 is positioned in the en
larged neck portion 22 of envelope 12 and is of the general
type shown in the aforesaid patents of Rudnick et al. and
Papp. Flood gun 42 comprises an annular cathode 44
which is ‘heated by any suitable means (not shown) and
which is surrounded by an annular hollow anode shell 46.
Anode shell 46 is provided with an annular aperture 48 in
vits front edge. An inner ring or sleeve electrode 50* is
positioned within anode shell 46 with its forward edge
lying in a plane generally coextensive with the forward
edge of anode shell 46, as shown, and an annular electrode
52 surrounds anode shell 46 and is disposed in generally
the same plane with the forward edge of the anode shell 46.
In accordance with our invention, annular aperture 48
in the forward edge of anode shell 46 is arranged to
inject the electron emission from each elemental segment
of the annular cathode 44 forwardly and radially inwardly
toward the axis 28 at an acute angle with respect thereto.
This injection of the electron emission from each ele
mental segment of the annular cathode 44 at an angle
with respect to the axis 28 is accomplished in the illus
trated embodiment by disposing the upper edge 54 of
aperture 48 on a line 56 generally parallel with axis 28
and disposing the bottom edge 58 of aperture 48 on a
line 60 from cathode 44 which de?nes an acute angle “a”
with line 56; in a speci?c embodiment of a tube incorporat
46 ____________________________ _. 1.255 inches and
1.795 inches,
respectively.
10
Diameter of annular cathode 44 _____ _. 1/16 inch.
Angle “a” _______________________ _. 41°.
The above tube was operated with the following potentials
15
applied:
Cathode 44 _______________________ __ Ground.
Anode shell 46 ____________________ __ +16 volts.
Sleeve electrode 50 _________________ __ +100 volts.
Annular electrode 52, conductive layer 62,
20
conductive belt 66, and collector screen
32 _____________________________ __ +250 volts.
Conductive belt 64 _________________ -_ ‘+30 volts.
Conductive backing layer 38 of storage
screen 34 _______________________ __ ,+ 100 volts.
25 Phosphor display screen 18 __________ __ +15,000‘ volts;
The above described direct viewing storage tube pro
vided a visual display image without shading and was ob
served to have uniform current distributions by visual ob
servation of the erasure of the charge on storage screen
34 down to zero brightness level.
' Referring now to FIG. 2, in which representative plots
of equipotential lines are shown, it will be seen that con
ductive coating 62 and annular electrode 52 will provide
equipotential lines as shown by the dashed lines 72 and
that rearward conductive belt 64 will provide equipoten~
ing our invention, to be hereinafter more fully described,
tial lines as shown by dashed lines 74 and 76. As indi
the optimum angle "a” was found to be 41°.
cated, the electron emission from each elemental segment
A coating 62 of suitable conductive material, such as
of the annular cathode 44 is injected through the annular
aquadag, is formed on the inner surface of end wall 20
aperture 48 in the anode shell 46' at an angle initially in
40
and spaced belts 64 and 66 of suitable conductive ma
clined toward axis 28. It will further be seen that the
terial, such as aquadag, are formed on the inner surface
electron emission vfrom each elemental segment of annular
of cylindrical portion 14 of envelope 12. In the speci?c
cathode 44 is initially diverging directly forward of annu
embodiment shown in FIGS. 1 and 2, coating 62 on rear
lar aperture 48, as at 78. It is well known that a beam of
wall 20 is electrically connected to annular electrode 52
electrons tends to pass through an electrostatic ?eld in a
and also to the forward belt 66. When connected to suit 45 direction normal thereto. Thus, it will be seen from. the
able sources of potential, the rear wall coating 62 and rear
general con?guration of equipotential lines 72, 74 and 76
conductive belt 64 cooperate to converge the electron emis
provided by conductive layer 62 and conductive belt 64,
sion injected through‘ annular aperture 48 from each
that the electron emission from each elemental segment of
elemental segment of annular cathode 44 to form a waist
annular cathode ‘44 tends to be converged to form waist 68
forwardly of gun 42 in the general region of the center of 50 in the region of the conductive belt 64. The electrostatic
curvature '40, as at 68. ‘In the illustrated embodiment,
?eld provided by the forward conductive belt 66 is repre
collector screen 32 is electrically connected to the for
sented by the equipotential lines 78 which thus tend to
ward belt 66 and with a suitable potential applied thereto,
diverge the electron emission from each elemental segment
conductive belt 66 cooperates to diverge the electron emis
of the annular cathode 44 from the Waist 68 outwardly
sion from each elemental segment of cathode 44 along 55 until the emission generally follows radii 80‘ from center of
radii from point 40 as at’70, the effect of such divergence
curvature 40. It is desirable that the potentials applied
being to provide in essence a virtual cathode adjacent
to rearward coating 62, forward conductive belt 66 and
center of curvature point .40. It is thus seen that the elec
collector screen 32 be relatively close and with a substan
tron emission from each elemental segment of annular
tially lower potential being applied to belt ‘64; in the em
cathode 44 will impinge upon the spherically curved stor 60 bodiment shown in FIG. 1, coating 62, belt 66 and col
age screen assembly 30 and the spherically curved display
lector screen 32 are all operated at the same potential.
screen 18 with essentially normal incidence, thereby pro
It will now be seen that by virtue of the initial inwardly
viding uniform current density and velocity distribution
inclined diverging injection of the electron emission from.
over the entire area of the storage screen assembly 30 and
each elemental segment of the annular cathode 44, as at
65
display screen v18.
78, ‘followed by the convergence of the emission to waist
In a speci?c direct viewing storage tube constructed in
68 and then divergence of the emission as at 70‘ into a di
accordance with FIG. 1, the following physical dimensions
rection along radii 80 from center of curvature 40, a
were provided:
virtual cathode is formed approximately at the center
Outside diameter of cylindrical portion
70 of curvature 40 so that the electron emission from eachv
elemental segment of annular cathode 44 is distributed
14' ___________________________ __ 5% inches.
over the entire area of storage screen assembly 30 and
Distance from center of faceplate 16 to
phosphor display screen 18, impinging upon storage screen
?ood gun 42 ___________________ _. 8 inches.
assembly 30 with normal incidence and with the ?ood
Distance from inner surface'of faceplate
.
16 to center of curvature 40 ______ ... 7.1 inches.
75 beam therefore having uniform current density and veloc
3,087,088
6
Ivan
ity distribution over the entire area of the storage screen
What is claimed is:
_ V
assembly 30 and phosphor display screen 18.
1. An electron discharge device comprising: an enve
It will be seen that the cooperative relationship of the
lope; a large area target electrode in said envelope; means
annular ?ood gun 42 and the electron optical system has
for directing an annular cross-sectional electron beam of
the effect of providing a ?ood beam emanating from a
primary electrons forwardly toward said target electrode
virtual cathode or point source along the axis of the tube
including an annular electron gun in said envelope spaced
forwardly of the annular ?ood gun, which point can be
axially from and emitting primary electrons toward said
located approximately at the center ‘of the curvature of
target electrode said gun including an annular cathode;
storage screen assembly ‘30 and faceplate 16 by suitable
?rst electron optical means adjacent said gun for converg
proportioning ‘of conductive belts 64 and 66 and the 10 ing the electron emission from each elemental segment
choice of potentials applied to the several tube elements.
of said cathode to a waist forwardly of said gun; and
While it will be readily apparent that our improved annu
second electron optical means for diverging said emission
lar ?ood gun con?guration and cooperating electron opti
from said waist into directions generally along radii from
cal system is particularly advantageous for use in a tube
a point on the axis of said gun and forwardly thereof,
having a spherically curved storage screen assembly and 15 thereby forming a virtual cathode adjacent said point and
faceplate, it also can be employed to provide uniform cur
distributing said emission from each elemental segment
rent density and velocity distribution over a ?at storage
of said cathode over the entire area of said target elec
screen assembly and phosphor display screen by suitable
trode.
2. An electron discharge device comprising: an enve
collimation of the beam following its divergence, as de
scribed below.
20 lope; a large area target electrode in said envelope; an
annular electron gun in said envelope spaced axially from
Refer-ring now to FIG. 3, in which like elements are
said target electrode for directing an electron beam for
indicated by like reference numerals, there is shown a
direct viewing storage tube 82 in which the cylindrical
wardly toward said target electrode, said gun including
portion 84 of envelope 86 is elongated and provided with
an annular cathode and means for initially injecting the
a flat faceplate 88 with phosphor display screen 90 being 25 electron emission from each element segment of said
cathode forwardly and radially inwardly at an angle to
deposited on the inner surface thereof. It will be seen
that the storage screen assembly 92 formed of collector
ward the axis of said gun; ?rst electron optical means
adjacent said gun for converging said emission to a waist
screen ‘94 and storage screen 96 is likewise ?at or planar.
forwardly of said gun; and second electron optical mean-s
In this embodiment, the forward conductive belt 98 is
elongated in order to provide the necessary collimation 30 between said ?rst electron optical means and said target
of the ?ood beam following its divergence, and in con
electrode for diverging said emission from said waist into
directions generally along radii from a point on said axis
trast with the embodiment of FIG. 1, the forward con
forwardly of said gun thereby forming a virtual cathode
ductive belt 98 is not operated at the same potential as
adjacent said point and distributing said emission from
the collector screen 94 and rear wall coating 62, but on
the contrary at a somewhat lower potential, such as +200 35 each elemental segment of said cathode over the entire
area of said target electrode.
volts, as shown.
3. An electron discharge device comprising: an enve
Operation of the tube 82 during ?ooding of the storage
lope; a large area target electrode in said envelope; an
screen assembly 92 and phosphor display screen 90 is
annular electron gun in said envelope spaced axially from
similar to the operation of the tube of FIG. 1. Here,
the emission from each elemental segment of annular 40 said target elect-rode for directing an electron beam for
cathode 44 is injected forwardly and radially inwardly at
wardly toward said target electrode, said gun including
an angle with respect to axis 28, as at 78, and then con
an annular cathode surrounded by an annular anode shell,
said anode shell having an annular aperture formed
verged to form waist 68 by virtue of the cooperation of
rear conductive belt 64, rear wall coating 62, and annular
electrode 52. The emission from each element-a1 segment
of annular cathode 44 is then diverged as at 70‘ in the
direction along radii extending forwardly from point 100
under the in?uence of the rearward section of conductive
belt 98. Following divergence '70, emission from each
elemental segment of annular cathode 44 is converged
and collimated, as at 102, under the cooperative in?uence
of the forward section of conductive belt 98 and collector
therein which faces forwardly and radially inwardly at
an angle toward the axis of said gun ‘for initially inject
ing said electron beam from said cathode forwardly at an
acute angle toward said axis; a sleeve electrode concentric
within said anode shell; an annular electrode concentric
outside of said shell; and ?rst and second axially spaced
electrode sleeves arranged end-to-end between said annu
lar electrode and said target electrode, said sleeve and
annular electrodes and said ?rst electrode sleeve cooper
ating with said gun to converge said emission to at waist
forwardly of said gun, said second electrode sleeve co
shown in FIG. 3, the electron emission from each elemen
tal segment of annular cathode 44 again is distributed over 55 operating with said gun to diverge said emission from
said waist along radii from a point on said axis forwardly
the entire area of storage screen assembly 92, and phos
of said gun thereby forming a virtual cathode adjacent
phor display screen 90, the further that the ?ood beam has
said point and distributing said emission from each ele
uniform current density and velocity distribution over
mental segment of said cathode over the entire area of said
the storage screen assembly and phosphor display screen,
impinging upon the same with normal incidence.
60 target electrode.
4. The combination of claim 3 further comprising
It will now be readily comprehended that by virtue of
power supply means providing a plurality of different
the provision of a ?ood electron beam of uniform current
direct current voltages, wherein said cathode is connected
density, velocity and distribution over the entire area of
to a reference voltage of said power supply, wherein said
the storage screen assembly and the phosphor display
screen with the electron emission ‘from each elemental 65 anode shell, ?rst electrode sleeve and sleeve electrode are
respectively connected to progressively higher voltages of
segment of the annular cathode being distributed over
said power supply, and wherein said annular electrode and
the entire area of the target, and with the electrons im
second electrode sleeve are respectively connected to still
pinging thereupon with normal incidence, higher beam
higher voltages of said power supply, said last-named
current may be employed than has heretofore been the
case with prior storage tubes utilizing annular ?ood guns. 70 voltages being relatively close.
5. The combination of claim 3 wherein said envelope
While we have described above the principles of our
has a cylindrical portion and a rear wall portion ter
invention in connection with speci?c apparatus, it is to be
clearly understood that this description is made only by
minating in a neck portion with said gun arranged
way of example and not as a limitation to the scope of our
therein, wherein the forward edge of said sleeve electrode
invention.
75 and said annular electrode are in generally the same
screen 94. It will now be seen that with the arrangement
3,087,088
electrode sleeves respectively comprise bands of conduc
edge of said‘aperture lying on a second line extending
from said cathode and de?ning an acute angle with said.
?rst line.
9. The combination of claim 1 wherein said- target‘
electrode is flat and further comprising other electron
tive material coated on the inside surface of said cylin
lens means for collimating- said emission following said
drical portion of said envelope.
diverging thereof.
6. The combination of claim 4 wherein said target
electrode comprises a collector screen, a storage electrode
10. The combination of claim 3 wherein said target
electrode is ?at and comprisesa collector screen, a stor
plane with the forward edge of said anode shell, wherein
a'band of conductive material is coated on the inside
surface-of said rear wall and is electrically connected to
said annular electrode, and wherein said ?rst and second
on the side of said collector screen remote from said 10 age screen on the side of said collector screen remote
from said gun, said storage screen comprising an in—
gun, said storage screen comprising an insulating layer
sulating layer facing said collector screen and a con
facing said collector screen and a conductive fine mesh
screen‘ remote therefrom, and a phosphor display screen
on the side of said storage screen remote from said gun,
ductive layer remote therefrom, and a phosphor display
screen on the side of said storage screen remote from
wherein said collector screen is connected to a voltage 15 said gun, and further comprising. power supply means
of said‘ power supply relatively close to the voltage of
said; second electrode sleeve, wherein said conductive
layer is connected to a voltage of said power supply
lower than said second electrode sleeve and higher than
said- ?rst electrode sleeve, and- wherein said phosphor
screen is connected to the highest voltage of said power
providing a plurality of different direct current voltages
with said cathode connected to a-reference voltage of said
power supply, and with said anode shell, ?rst electrode
sleeve, sleeveelectrode, second electrode sleeve and an
nular electrode being respectively connected. to progres
sively higher voltages of said power supply, wherein said
supply.
collector screen is connected to said annular electrode,
wherein said conductive layer is connected to a voltage
7. The combination of claim 1 wherein said target
of said power supply lower than said second electrode
electrode is spherically curved and wherein said point
is adjacent the center of curvature of said target elec 25 sleeve, and wherein said display screen is connected to
the highest voltage of said power supply.
trode.
8. The combination of claim 2 wherein said means
for injecting'electron emission comprises an annular
anode shell surrounding said cathode with an annular
aperture formed in its forward edge, the upper edge of 30
said aperture lying on a ?rst line extending from said
cathode and generally parallel with said axis, the lower
References Cited in the ?le of this patent
UNITED STATES PATENTS
2,452,044
72,962,623
2,967,971
FOX _________________ _._ Oct. 26, 1948’
Beintema ____________ __ Nov. 29, 1960'
Beintema _____________ __ Jan.‘ 10, 1961
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