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Патент USA US3031606

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April 24, 1962
D. W. DAVIS
INFORMATION sT ORAGE DISPLAY TUBE AND
STORAGE SCREEN ASSEMBLY THEREF'OR
Filed Dec. 18, 1957
/9
3,031,597
Unite States
3,@3L597
° ate .t
Patented Apr. 24, i962
1
2
3,031,597
' I have found that by controlling the relative voltages
¿applied to the front and back metal screens, each opening
INFORMATION ASTORAGE DISPLAY TUBE AND
STORAGE SCREEN ASSEMBLY THEREFOR
Dean W. Davis, Fort Wayne, Ind., assigner to Interna
tional Telephone and Telegraph Corporation
Filed Dec. 18, 1957, Ser. No. '703,659
5 Claims.
(Cl. 315-12)
vcan be made lto function as an electron optical lens with
.an adjustable focal length so that the flood electrons pass
ing through the storage screen openings can be focused
With their point of convergence `at or near the display
screen thereby still further improving the resolution of
5
'
the resulting display image. Furthermore, with my im
This invention relates to charge storage tubes, such as
proved storage 'screen assembly, I4 have found that the
signal-to-image and image-to-image display tubes, and
10 provision of the additional front metal screen permits the
more particularly to a storageV screen Iassembly for such
application of a negative potential to the back screen and
tubes.
pulsing the front screen positive during the erasing opera
tion thereby obtaining a faster erasing action. In addi
tion, by the provision of the additional front screen, it is
possible to eliminate the separate collector screen with
Charge storage tubes of the signal-to-image display
variety conventionally include an evacuated envelope with
an electron gun assembly for> providing a high -velocity
“pencil” writing electronbeam and’another electron gun
assembly for providing a' low velocity “flood” electron
beam disposed at one end of the envelope, anda lumines
' the front screen assuming its Vfunction thereby preventing
re-distribution of secondary electrons, eliminating writing
beam dispersion between the collector and insulator, per
mitting optimum utilization of current, and providing bet
screen assembly is ‘conventionally positioned within the 20 ter uniformity of the field at the dielectric surface. The
provision of my improved storage screen assembly there
envelope intermediate the electron guns and lthe viewing
‘ Vcent viewing screen disposed at the other end.
A storage
`screen and‘has conventionally been formed of a sheet ofV
fore results in a greatly improved storage tube having a
dielectric material having a plurality of openings formed
brighter display image With higher resolution, faster writ
ing and erasing speed, and better uniformity.
therethrough with a line screen in contact with or coated
on the side of the dielectric sheet, the dielectric material 25
of the storage screen assembly being positioned toward the
electron guns.
A tine-mesh metal collector screen is
also conventionally positioned within the envelope in
front of the storage screen, ,i.e., on the side thereof toward
thejelectron guns. During f‘writing,” the pencilj beam
is caused to scan the storage screen, the beam commonly
being modulated- by applying an input signal to a control
grid of the high velocity electron gun. Impingement of
It is accordingly the object of my invention to provide
t an improved storage screen assembly for charge storage
tubes.
Another object of my invention is to provide an im
proved storage screen assembly for information storage
tubes of the display type.
A further object of my invention is the provision of an
improved storage screen‘assembly for charge storage tubes
which incorporates a metal screen on the front surface of
Vthe high velocity electron beam upon the dielectric'sur
the dielectric layer.
face of the storage screen assembly causes the emission
-of secondary electrons which are collected by the collec
tor screen and thus elemental charges areformed on the
.`d ie let
cric sur f ace o f th e s t orage screen ro or t iona lt o
Yet another object of my invention is the provision of
an improved storage screen assembly for charge storage
the modulation of the pencil beam. In the Í‘reading”
operation, low‘ velocity floodwelectrons from the flood
electron gun are directed toward the storage screen assem
bly and pass through the openings therein onto the display
screen, being modulated by the elemental charges on the
V‘dielectric surface thereby causing an image to `appear on
'
‘ `
tubes of the display type which provides improved resolu
»Y tion of the displayed image'.
A still further object of my invention is the provision
so of an improved >charge storage tube of the display type
incorporating anV improvedv storage screen assembly with
cooperating means for improving the resolution of the
displayed image.
Yet another object of this invention is the provision of
»the display screen in accordance with the charge pattern 45 <a charge storage tube incorporating my improved storage
’screen assembly with cooperating means for increasing
on the storage screen.
t
. .
In prior storage screen assemblies known to the appli
the erasing speed.
cant, with a metal screen in contact with the back surface
’ A A further object of my invention is the provision of a
of the dielectric sheet only, i.e. the surface toward the
»charge storage tube incorporating an improved storage
display screen, an elemental charge on the dielectric sheet 50 screen assembly which permits elimination of the sep
>in the region of one opening therein could controlV` the
flood electrons in adjacent openings, thus tending to re
`duce the resolution of the resulting display image. Fur
thermore, with priorfstorage screen assemblies, the poten
arate collector screen provided in prior charge storage
tubes.
’
' The above-mentioned and other features and objects
V`of this invention and the manner of attaining them will
`tial gradients within each opening tended to focus the 55 become more iapparent Vand the invention itself will be
best understood'by reference to the following descrip
flood electrons in front of the display screen again reduc
tion Vof an embodiment of the invention taken in conjunc
ing the resolution of the display image.
I have found that-by providing a second metal screen
in contactl With or coated on the front surface of the di
tion with the accompanying drawings, wherein:
"
~ '~ FIG. l is a cross-sectional view of a signal-to-image
electric sheet, i.e. the side towad the electron gun, with 60 >charge storage tube incorporating my improved storage
the openings in the second metal screen being respectively
s_creen assembly.
l
’in registry with and slightly larger than the openings in
the dielectric sheet thereby exposing a portion of the front
surface of the dielectric sheet around each opening there
FlG. 2 is a. fragmentary»cross-sectional view illustrating
my improved storage screen assembly and its ñoodrbeam
’ focusing action; and
in, the web portions of the second metal screen effectively 65
FIG. 3 is a fragmentary front view of my improved
isolate each opening in the dielectric sheet and its sur
‘storage screen assembly taken along the line 3_3 of
rounding marginal peripheral dielectric surface from
FIG. 2.
every other opening so that the elemental charge sur
Referring now to the drawing, there is shown a signal-l
rounding each opening cannot control the ñow of flood
70. to-_image display tube,> generally identified asl, which
Y electrons through adjacent screen openings, thereby im
y proving the resolution of the display image. Furthermore,
comprises an enclosing envelope 2, conventionally formed
of glass. An electron gun assembly 3, of any conven
3,031,597
3
4
tional design, is positioned on the axial center line of the
envelope 2 and provides a low velocity ñood electron
beam for reading-out the stored signal. Another elec
tron gun assembly d, also of conventional design, is pro
vided offset from the low velocity gun 3 for providing a
In accordance with my invention, I provide a second
relatively thin metal screen 19 contacting the web por
tions 20 surrounding the front openings 15 in the front
side 16 of the dielectric sheet 10, the screen 19 having its
high velocity pencil beam for writing the information
openings 21 respectively in registry with but substantially
larger than the openings 15 thereby exposing a portion
upon storage screen assembly 5. The pencil beam pro
vided by high velocity electron gun 4 is caused to scan
the front surface of storage screen assembly 5 by con
rounding each of the front openings 15. This metal
front screen 19 may be evaporated onto the front side
22 of the front surface 16 of the dielectric sheet 10 sur
ventional focusing and deflecting elements (not shown). 10 or surface 16 of the dielectric sheet 10 in the same man
A luminescent viewing screen 6 is formed at the end 7
of envelope 2 remote from the electron guns 3 and 4.
ner as the metal back screen 18 and etched with acid to
The inner surface of the envelope 2 intermediate the
Referring now again particularly to FIG. 2, in prior
charge storage tubes having only the back metal screen
guns 3 and 4 and the storage screen assembly 5 is conven
tionally coated with a conductive coating 8 as is common
in the art. A tine-mesh metal collector screen 9 is posi
tioned within the envelope 2 closely spaced from the stor
age screen assembly S on the side thereof toward the
electron guns 3 and 4.
v
ReferringV now more particularly to FIG. 2, my im
proved storage screen assembly 5 includes a relatively
thin sheet 10 of dielectric material, such as glass, having
a plurality of geometrically arranged, Iclosely spaced, rel
atively small openings 11 formed therethrough. The
openings 11 are tapered, as at 12, so that the openings
13 on the back side 14 of the dielectric sheet 10 are larger
than the openings 15 on the front side 16 of the dielec
tric sheet 10.
The dielectric sheet 10 is preferably, but not neces
expose the dielectric front surface 16.
18, without the additional front metal screen 19, the back
metal screen 18 was conventionally connected to a slightly
positive source of potential 33, such as plus 20 volts, by
lead 23. The whole frontsurface 16 of the dielectric
sheet 10 during the reading operationis at a potential of
zero volts or even slightly minus; it cannot have a poten
tial higher than zero because it is being struck by the flood
ing electrons as shown by the dashed lines 23. Thus,
with the back screen 13 at a slightly positive potential and
the front surface 16 of the dielectric sheet 10 either Zero
or slightly minus, equipotential lines having a configura
tion shown by the dashed lines 24 were formed which
tended to cause the flood electron streams 23 to bend and
cross over, as at ‘25, the ñood electron streams diverging
after the point 25, as at 26, thus adversely affecting the
sarily, formed of fotoceram with the openings 11 suitably 30 resolution of the resulting display image on the display
etched therethrough. lFotoform glass is a recently de
screen 6.
With my improved storage screen assembly 5 having
veloped glass product which has a photo-sensitive mate
rial therein and which may be etched in a ratio of 5 to 1.
Thus, a fine-mesh screen mask may be laid on a fotoform
the metal front screen 19, the frontscreen 19 may be
connected to a suitable source of potental 34, by lead 27
glass plate approximately tive mils thick and exposed to 35 so that the equipotential lines in the front openings 15
form a divergent electron lens which may be adjusted in
ultraviolet light; the portions of the plate which have
essence to cause the low velocity flood electrons entering
been exposed to the ultraviolet light may then be etched
openings I15 to diverge. The net focusing action of the
with suitable acid, the exposed areas etching five times
divergent electron lens in the openings 15 and the con
faster than the unexposed areas. In this manner, the
openings or holes 11 may be etched entirely through the 40 vergent electron lens in the openings 11 therefore can
be made dependent upon the relative potential gradient
sheet or plate 10, and the front and back surfaces or sides
14 and 16 then ground smooth to obtain a plate on the
of the back screen 18 and the front screen 19 with respect
to the exposed portion 22 of the front surface 16 so
order of three mils thick. The plate is then baked, which
results in a further change in the properties thereof to
that the point of convergence of the ñood electron streams
provide greatly increased resistivity, the resulting disc or 45 can be moved outwardly to the display screen 6, as at 29
so that the resolution of the resulting display image is
wafer which may, for example, be two inches in diameter,
improved. It is thus seen that byfapplying appropriate
three mils thick with the openings 11 defining as high as
a 500 mesh screen being referred to as fotoceram.
It is
potentials on the front and back screens 18 and 19 re
spectively by means of leads 23 and 27, each opening 11
etching a fine-mesh screen in a thin glass plate is not the 50 in the dielectric sheet 10 with its corresponding openings
subject of this invention and it is possible that other
in the front and back metal screens in essence forms an
electron lens which permits focusing of the image on the
means may be found for providing a plurality of geo
metrically arranged, closely spaced small openings in a
display screen 6 during the reading operation to obtain
optimum resolution. In a typical signal-to-image stor
dielectric sheet. The etching of the fotoform glass sheet
is performed on the back surface or side 14, thus pro
age tube, both the front and back metal screens 18 and
viding the taper 12 in the openings 11, it having been
19 may, for example, have 20 volts positive applied there
on with a potential of plus 150 volts being applied to the
found that a taper of approximately 10 degrees is satis
to be understood> that the above described method of
factory. It is desirable to provide this taper, so that the
collector screen 9 from source 35 by a lead 29, a poten
tial of plus 7,000 yvolts applied on the display screen 6
4, and the larger openings 13 face toward the display 60 from source 36 by lead 30, and a potential of 25 Volts
smaller openings 15 face toward the electron guns 3 and
screen 6, in lorder to prevent the low velocity flood beam
from the electron gun 3 from striking the walls of the
openings 111 and thus providing an unwanted charge pat
tern on the storage screen assembly.
Storage screens incorporating a fotoceram dielectric
layer with etched openings formed therein have been
provided in prior charge storage tubes. In such tubes
it has been common practice to evaporate a thin layer
of metal, such as aluminum onto the web portions 17 sur
being applied on the accelerating anode 8 from source
37 by lead 31. It is thus seen that by raising the average
potential just in front of the front openings 15 on the
front side 16 of the dielectric sheet 10, the flood beam
can be properly focused to improve the resolution of the
resulting display image.
It will further be seen that in prior charge storage
tubes which did not incorporate the front metal screen
19, the incremental charges on the front surface 16 of the
rounding the openings 13 in the back side of surface 14 70 dielectric sheet 10 produced by the modulated writing
' of the dielectric sheet 10 thereby to provide a relatively
thin metal screen 18 on the back side 14 of dielectric
sheet 10 with its openings in registry with the openings
11 in the dielectric sheet 10 and substantially coextensive
therewith.
beam will control or at least effect flood electrons during
the flooding operation, not only in the immediate open
ing 1v1, but also in adjacent openings. =In my improved
storage screen assembly, the front screen 19 acts as a
75 separator between the «front charge storage elements of
Vspense?
5
6
the dielectric sheet 10; the writing beam electrons which
strike the metal web portions 32 of the front screen 19
' It Will now be seenv that my improved storage screen
withthe front metal screen 19 makes possible the pro
vision of an improved display type storage tube since it
permits focusing of the image section of the tube, >thus
improving resolution. It additionally improves resolu
tion by reducing overlap of incremental charge areas'on
the :front surface of the storage insulator. My improved
do not charge any portion of the dielectric sheet and only
the areas Z2 surrounding each >front opening I15 are
charged. ' Thus, during the reading operation, the incre
mental charges on each >area 22 surrounding a particular '
front opening 1‘5 will affect or modulate the flood elec
trons passing through that opening only and will not affect
storage screen assembly further reduces the size of the
the ñood electrons passing through adjacent openings.
incremental storage elements, makes possible faster
erasing by permitting positive pulsing of the front surface
-It will be seen that the additional front screen 19> has
little effect on the primary writing beam during the writ
ing operation since the writing beam provided by the
writing electron gun 4 has high velocity. However, with
of the dielectric sheet, and also prevents redistribution
of secondary electrons. My improved storage screen
out the front screen 19, some of the secondary electrons
tion of the collector screen with the front metal screen
emitted from the front surface 16 of the dielectric sheet
10 due to impingement of the writing beam thereon tend
to migrate to an adjacent front surface rather than to the
taking over the collector screen functions, thus eliminat
ing flood beam dispersion between the collector screen
collector screen, such action being referred to as redistri
bution of secondary electnons. This redistribution of sec
tion of the flood beam electrons.
assembly further may make possible the complete elimina
and the dielectric sheet, and permitting maximum utiliza
ondary electrons tends to erase incremental charge ele
ments which have just been written on adjacent dielectric
arcas, thus lowering the contrast of the ultimate display
image. The additional front screen 19 of my invention
collects these random secondary electnons or directs them
away from the front surface -16 so that they do not charge
adjacent dielectric areas.
While, my improved storage screen assembly has been
.illustrated and described in connection with a signal~to-
image display tube, it will be readily apparent that <it is
equally applicable to an image-to-irnage display tube.
g
While I have described above the principles of my in- ,
vention in connection with specific apparatus, it is to be `
It will now be seen that my improved storage screen
assembly with the provision of the additional front
screen 19 may permit the complete elimination of the
collector screen 9 with the front screen `19 having a suit
«It is thus seen that
charge storage tubes incorporating my improved storage
screen assembly will provide a brighter display image
having higher'resolution, and such tubes will have faster
Writing and erasing speed and better uniformity..
clearly understood that this description is made only by
30 way of example and not as a limitation to' the scope of
able positive potential, applied thereon by leadI 27 at the
proper level to secure the above-mentioned focusing
my invention.
What is claimed is:
~
'
,
the flooding beam.
In prior display type signal-to-image tubes known to
'1. A storage display screen assembly for charge stof-_.
age tubes comprising: a relatively thin self~suppcrtingñat
sheet of dielectric'material having a plurality of relatively
small uniformly tapered openings formed therethrough so
the applicant, in order to erase the stored image from the
storage screen, a positive pulse was applied to the back
screen which raised the potential of the front surface so
that the openings on one side of said sheet are larger than
the openings on the other side of said sheet; a relatively
thin flat metal screen in contact with and supported by
action during the reading operation, and with appropriate
voltages applied to the gun 3 and electrode 8 to collimate
Y that the ñood electrons in striking the front surface would
charge the front surface negative. Thus in such prior
devices, the ñood electrons passing through the openings
said one side of said sheet and having its openings respec
tively in registry and substantially coextensive with said
larger sheet openings; and another relatively thin flat
metal screen in contact with and supported by the other
in the storage screen during erasing served no useful pur
side of said sheet andrhaving its openings respectively in
pose but undesirably reduced the contrast of the display.
With my improved storage screen assembly, the back 45 registry with and larger than said smalier sheet openings
thereby exposing a portion of said other side of said sheet
screen 18 can be made negative, such as at -10 volts by
connection to source 38 by a switch 39 so that the flood
around each of said smaller sheet openings.
‘
2. In a display-type charge storage tube, flood electron
electrons will not pass through the openings 111 and the
beam source means disposed at one end of said tube and a
front screen 19 can be pulsed, with, for example, plus 40
volts lby connection to source 40 by a switch 41, thus 50 viewing screen disposed at the other end thereof, and a
storage screen assembly comprising: a relatively thin sheet
raising the potential of the front surface 15 of the dielec
of dielectric material having a plurality of relatively
tric sheet 10 so that a larger amount of flood electrons
small openings formed therethrough; a first relatively thin
strike the front insulator surface 22 surrounding the front
metal screen in contact with one side of said sheet and
openings 15 of the dielectric sheet `10, thus providing
faster erasing action.
55 having its openings respectively in registry with said
sheet openings; and a second relatively thin metal screen
When the collector screen 9 only is provided in front
in contact with the other side ofsaid sheet and having its
of the storage screen assembly, the potential of the front
openings respectively in registry with and larger than said
surface 16 of the dielectric sheet 16 is substantially lower
sheet openings thereby exposing a portion of said other
than that of the collector 9, and there is a decelerating
elfect as the flood electrons approach the dielectric sheet 60 side of said sheet around each ofisaid sheet openings; said
storage screen assembly being disposed with said second
10, and some of the flood electrons will be deñected and
repelled at a distance substantially before the plane of the
metal screen facing said electron beam source means; and
front surface 16 and will return to the collector screen 9.
means for impressing approximately equal positive poten
By eliminating the collector screen 9 and utilizing the
tials on both of said screens to form electron lenses for
front screen 19 as the collector screen, the collector screen 65 focusing said flood electron beam onto said display screen.V
has in essence been moved directly up to the front sur
3. In a display-type charge storage tube, flood electron
beam source means disposed at one Vend of said tube and
face ‘16 of the dielectric sheet 10 and thus the velocity
of the flood` electrons is maintained relatively high up to
the very sur-face of the dielectric sheet 10 so that they
are not so easily deflected. Thus with my. improved
storage screen assembly which permits complete elimina
tion of a separate collector screen, turning back of ñood
electrons is eñectively prevented, thus more ñood elec
trons pass through the openings in the screen and produce
a brighter display image on the screen 6.
75
a viewing screen disposed at the other end thereof, and a
storage screen .assembly comprising: a relatively thin
sheet of dielectric material having a plurality of relatively
small openings formed therethrough; a first relatively
thin metal screen in contact with one side of said sheet
and having its openings respectively in registry with said
sheet openings; and a second relatively thin metal screen
in contact with the other side of said sheet and having its
3,031,597
Si
openings respectively in registry with and larger than said
sheet openings thereby exposing a portion of said other
side of said sheet around each of said sheet openings; said
storage screen assembly being disposed with said second
a plurality of geometrically arranged closely spaced uni
tormly tapered openings formed therethrough so that the
means for impressing a negative potential on said tirst
openings on one side of said sheet are larger than the>
openings on the other side of said sheet; a relatively thin
layer of metal deposited on the web portions of said one
side of said sheet to form a first metal screen having its.
screen and a positive potential on said second screen for
erasing the information stored on said storage screen as
openings respectively in registry and substantially coexten
sive with said larger sheet openings; a relatively thin layer
metal screen facing said electron beam source means; and
of metal deposited on the web portions of said other side
4. In a display-type charge storage tube, flood electron 10 of said sheet to form a second metal screen having its
sembly.
beam source means disposed at one end of said tube and
a viewing screen disposed at the other end thereof, and a
openings respectively in registry with and larger than said
storage screen assembly comprising: a relatively thin
sheet of dielectric material having a plurality of relatively
small openings formed therethrough; a ñrst relatively
smaller sheet openings; said storage screen assembly be
ing disposed between said electron beam source and said
viewing screen with said second metal screen facing to
ward said electron beam source; and means for impressing
thin metal screen in contact with one side of said sheet
approximately equal positive potentials on said metal
screens during operation of said ñood electron beam
source so that each of said sheet openings and its respec
sheet openings; and a second relatively thin metal screen
tive screen openings form a compound electron lens for
in contact with the other side of said sheet and having its
openings respectively in registry with and larger than said 20 focusing said flood electron beam onto said viewing screen.
sheet openings thereby exposing a portion lof said other
side of said sheet around each of said sheet openings; said
References Cited in the tile of this patent
storage screen assembly being disposed with said second
UNITED STATES PATENTS
metal screen facing said electron beam source means;
2,118,186
Farnsworth ___________ __ May 24, 1938
means for at times impressing approximately equal posi
and having its openings respectively in registry with said
tive potentials on both of said screens to form electron
lenses for focusing said ñood electrons onto said display
screen during reading of the information stored on said
storage screen assembly; and means for at other times
2,240,186
2,259,506
2,507,958
2,790,929
Iams ________________ __ Apr.
Young et al. __________ __ Oct.
Cassman _____________ __ May
Herman et al __________ __ Apr.
29,
21,
1.1,
30,
1941
1941
1950
1957
impressing a negative potential on said first screen and a ‘
2,824,249
Hansen ______________ __ Feb. 18, 1958
-positive potential pulse on said second screen for erasing
2,843,799
Hook et al. __________ __ July l5, 1958
the information stored in said storage screen assembly.
5. ln a displayetype charge storage tube, a high velocity
2,857,551
2,873,398
2,887,597
Hansen ______________ __ Oct. 21, 1958
Crost ________________ __ Feb. 10, 1959
Smith et al ____________ __ May 19, 1959
634,318
886,457
Great Britain _________ __ Mar. 15, 1950
France ________________ __ July 5, 1943
writing electron beam source and a low velocity flood
electron beam source disposed at one end of said tube 35
and a viewing screen disposed at the other end thereof,
and a storage screen assembly comprising: a relatively
thin self-supporting flat sheet of dielectric material having
FOREIGN PATENTS
UNITED STATES PATENT OFFICE
CERTIFICATE OF CORRECTION
Patent No. 3.031„597
April 24„ 1962
Dean W. Davis
It is hereby certified that error appears in the above numbered pat
ent requiring correction and that the said Letters Patent should read as
corrected below.
Column 6, line 33, strike out "display" and insert the
Same before "tubes" in line 34, same column 6.
Signed and sealed this 4th day of September- 1962.
SEAL)
kttest:
ERNEST w. swlDER
‘fleeting Uffícer
DAVID L. LADD
Commissioner of Patents
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