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April 8, 1947.
H. w. LEvERENz
2,4l 8,780
ALKALI HALIDE TARGET WIT’H CONTRASTING COLORS
._ _ _
49005
> Pica/Vie
ß
Iäâ'oan 6500F? 7200”
.5250
67509
INVENTOR
#Waar @Zwam/z
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,Y'
"
AoRNEY
2,418,780
Fatented Apr. 8, 1947
UNITED STATES PATENT OFFICE
2,418,780
ALKALI HALIDE TARGET WITH CON
TRASTING COLORS
Humboldt W. Leverenz, Princeton, N. J ., assignor
to Radio Corporation of America, a corporation
of Delaware
Application November 28, 1942, Serial No. 467,173
17 Claims. (Cl. 250-164)
1
My invention relates to methods and means
for portraying intelligence and particularly to
‘targets comprising materials which change color
under electron bombardment, such as targets in
corporating alkali halide crystals and their meth
od of operation.
It is known that alkali halides, notably potas
slum chloride, have the property of developing
color centers under electron bombardment. For
example, when such an alkali halide target is
scanned by an electron beam, electrons are in~
jected into the crystal or crystals in the scanned
area thereby developing a group of color centers
of a density depending upon the instantaneous
intensity of the electron beam. This colora
tion has been used to produce images for tele
vision and oscillograph purposes. The recent
development of aircraft position and distance in
dicating equipment utilizing cathode ray tubes
2
will become apparent when considered in view of
the following description and the accompanying
drawing, wherein:
Figure 1 shows a cathode ray tube made in
accordance with my invention;
Figure 2 shows the characteristics of a target
as shown in Figure 1; and
Figure 3 shows an enlarged fragmentary por
tion of a target made and operated in accord
ance with my invention.
,
I have shown in Figure 1 one type of cathode
ray tube utilizing a target made and operated in _
accordance with my invention wherein the eñect
of the electron beam trace on the target may be
viewed either by transmitted light and it should
be understood that this showing of a ,tube is
merely exemplary and various other modiñca
tions and arrangements may be utilized to an
equal advantage as hereinafter explained. Re
wherein the electron beam of the cathode ray 20 ferring to Figure 1, the tube comprises a khighly
tube is sequentially pulsed to form on the target
evacuated envelope or bulb l of cylindrical shape
a trace portraying intelligence, such as the
with a neck or arm section enclosing a conven
tional electron gun. I The cylindrical portion of
trajectory of the aircraft, necessitates the de
the .bulb I is provided at one end with a window 2
velopment of high contrast between the areas
of a target indicating aircraft position and dis 25 so that ultra-violet light from a substantially
constant light source 3 may be projected through
tance with respect to the surrounding areas of
the window and upon a target 5 which may be
the target. In addition, it is required to observe
supported independently of the envelope wall
the trajectory as a visible trace during a rela
as shown or deposited directly upon the inner
tively long period of time. Luminescent mate
rials have been used for this application although 30 surface of the window'Z. The eiîects of the
trace on the target may be viewed through a
the majority of such materials have a flash char
second window 6, preferably from a position as
acteristic which tends to reduce the dark-adapat 1.
tation of the eye. While a target of alkali halide
The electron gun assembly 8 may be of any
material is ideally suited for this application,
greater contrast between old or “remembered” » one of the conventional types either of the mag
netic focus or of the electrostatic focus type as
information and newly received information is
desired.
One method of distinguishing newly
shown.
The electron beam developed by the
electron gun 8 is modulated in intensity, such as
by grid control from a receiver 9 and scanned
tion is described in my copending application,
40 over the target 5 by horizontal and vertical de
¿Serial No. 466,272 ñled November 20, 1942.
iiection coils H and V supplied with operating
It is an object of my invention to provide
currents of the desired wave form depending
methods .and means for increasing the visible
upon the type of trace whether of circular, radial
contrast from an alkali halide target scanned
or rectangular form.
by a cathode ray beam. It is another object to
intensify the light output in pre-determined 45 In accordance with my invention I utilize a
light source capable of exciting to luminescence
spectral regions from an alkali halide target and
'one of two portions of a luminescent screen com
to provide an improved method of portraying in
prising two diiierent luminescent materials, or
telligence and rendering such intelligence semi
phosphors, to luminescence and I so choose the
permanent. It is a further object of my inven
phosphor material of one of the screen portions
tion to increase the contrast between excited
to have a spectral emission characteristic falling
and nonexcited areas of such a target and to
within, corresponding to or substantially over
differentiate newly received information from in
received information from remembered informa
formation previously portrayed utilizing targets
lapping the spectral absorption characteristics
of an associated alkali halide target. An alkali
of the alkali halide type. These and other ob
jects, features, and advantages of my invention 55 halide .target of the potassium chloride type has
2,418,780
4
a peak spectral absorption at approximately
may then be deposited by vaporization from a
5500 A. and in accordance with my invention I
halide source allowing the vapor to condense on
the exposed surface of the phosphor screen por
provide a phosphor exposed to the halide target.
the said phosphor having an emission character
istic which Peaks preferably at a correspond
lng frequency. such as at 5500 A. Further in ac
tion I2.
The advantages of my invention accrue from
the fact that the halide i0 is sumciently translu
cent to the electron beam from the electron gun
8 to allow penetration thereof by the beam into
cordance with my invention I provide a second
luminescent screen portion of a phosphor having
a differently colored luminescence than that of
the phosphor portion I2 exciting this portion to
the first mentioned portion and having an emis 10 luminescence under the beam. Simultaneously I
sion band which is different than the absorption
excite the screen portion II such as by exposure
band ofthe alkali halide and preferably falls
to ultra-violet light from the source 3 to provide
without the alkali halide absorption band.
uniform illumination visible to the observer at
Referring to Figure 2 the fullline curve repre-the position 1. However. the alkali halide under
serits the absorption characteristic of an alkali 15 the action of the electron beam produces color
halide. such as potassium chloride, the absorp
centers I3 which, since the emission band of the
tion extending over the range from 4900 A. to
screen portion Il overlaps the absorption band
7000 A. with its peak at 5500 A. Ichave shown
‘ of the halide when excited to form color centers,
also in Figure 2 in dashed outline a curve de
absorbs the ‘light from the screen portion Il
noted as Emission No._1. representative of the 20 thereby developing a dark trace. This dark trace
emission characteristic of a luminescent material
ispersistent for a period of from a number of
forming one portion of my screen such as a
seconds to several minutes depending upon the
manganese-activated alpha willemite. havinar an
time required for the dissipation of the color
emission spectrum extervdinar from approximately
centers. However. in accordance with my in
4900 A. to 6500 A. and peaked at about 5230 A. 25 vention, the beam not only develops the color
The third curve in dash-dot outline denoted
centers in the halide I0, but likewise develops
Emission No. 2 is representative of the second
portion of rnv screen structure and is chosen to
luminescence at the point of penetration and
incidence upon the screen portion I2. The ma
have an emission under corpuscular or cathode
terial of the screen portion I2 however is chosen
ray bombardment materiallv outside the absorp 30 to have an emission band such as shown by the
tion hand of the alkali halide. As shown. the
dot-dash curve of Figure 2 lying without the ab
emission band of this portion extends from ap
sorption band of the halide. Consequently. the
proximately 5500 Ã. to above ’i000 A.. peaking at
luminescence developed by the phosphor portion
approximatelv 6750 A. A suitable material is a
I2 is not absorbed by the color centers I3 but is
copper or silver-activated zinc cadmium sulphide
transmitted to the Aobserver through the color
having a luminescence in the red portion of the
centers. Consequently, the presence of the elec
spectrum. It will be noted from an examination
tron beam is denoted by the _iiash of luminescence
of the curves shown in Figure 2 that the spectral
from the screen portion I2 followed by the dark
emission curve of the phosphor. such as alpha
trace produced by the color centers I3.
willemite. is substantially coincident and sub 40 Preferably the material of the phosphor por
stantially overlaps the spectral absorption curve
tion I2 is chosen to have low phosphorescent per
of the halide. whereas that oi' the zinc cadmium
sistence following excitation by the beam to pre
sulphide screen portion does not materially over
vent reduction in contrast betwen the areas of
lap the halide absorption curve.
the halide having color centers and the surround
45
’I‘he light source 3 has a predominate emission
ing illumination provided by the screen portion
inthe absorption band of the first phosphor. A
II. Furthermore, a selective barrier layer i4,
low-pressure mercury lamp. emitting predomi
pervious to the luminescence from l2, may be
nantly at 2537 A., may be used to excite the man
provided between these two portions to prevent
ganese-activated alpha willemite. A medium
penetration of electrons through the phosphor
pressure mercury lamp, such as the commercial 50 portion I2 and upon the portion Il. Depending
H-4 type, having substantial emission at 3650 A.,
upon the initial beam velocity, the penetration
5461 A., and 5790 A. is particularly suitable as an
effect may be minimized by providing a relatively
ultra-violet source to excite sulphide phosphors
thick phosphor layer adjacent the halide. Siml
although other light sources such as a fluorescent
larly, the barrier layer I4 maybe of material
lamp or screen having the required frequency
absorbent
to the ultra-violet light from the source
band may be used.
'
3 to prevent incidence on and consequent exci
Referring again to Figure 1, the target 5 may
tation of the phosphor portion I2. Such a selec
be deposited in one of several manners, either
tive barrier layer may comprise a silicate such
on the window 2 of the envelope i, or upon a.
as potassium or sodium silicate deposited upon
carrier such as a sheet of glass, not shown, to
the screen portion II prior to the deposition of
support the target 5 clear of the window. More
the portion I2 and the halide target I 0. How
particularly, as indicated above, the target 5 com
ever, the barrier layer I4 may comprise a thin
prises in addition to the support, not shown. a
sheet of mica or glass which is impervious to the
crystal or layer of crystals of an alkali halide
I0 and a dual phosphor screen comprising the 65 electron beam as Well as to the ultra-violet light
from the source 3. Alternatively, the phosphor
iirst phosphor portion Il, and a second phosphor
portion may be relatively thick so that substan
portion l2 between the portion Il and the halide
I0. For example, the first phosphor portion II
tially all of the ultra-violet light from the source
may be deposited preferably by a settling opera
3 is absorbed. It will be appreciated that the
tion followed by the deposition of the phosphor 70 choice of phosphor material for the portion Il
portion I2. This settling may comprise one oper
may be made so that its emission spectrum lies
ation wherein the materials are successively set
without the luminescent absorption spectrum of
tled through a liquid suspension as disclosed by
the phosphor portion I2 to prevent excitation
W. H. Painter in his application Serial No. 423,643,
thereof and consequent reduction in contrast in
ñled December 19, 1941. The alkali halide I0 75 asmuch as the color centers are substantially
2,418,780
-6
transparent to light from the phosphor por
prevent incidence of said beam on said second
tion l2.
screen.
.
4. Cathode ray apparatus as claimed in claim 3
I have referred above to two particular phos
phor materials suitable for forming the phosphor
wherein said screens are rendered luminescent
under ultra-violet light and said last mentioned
means is highly absorbent to ultra-violet light.
5. The combination with a target having the
activated zinc cadmium sulphide respectively.
property of absorbing light in accordance with
Assuming a potassium chloride target I0 further
the intensity of incident energy of a luminescent
specific examples of suitable phosphor material
10 screen having an emission band in the absorp
combinations are:
tion band of said target, and a second luminescent
screen adapted to be excited by a portion of said
Phosphor layer ll
Phosphor layer l2
incident energy having an emission band sub
screen portions Il and l2 as comprising man
ganese-activated alpha zinc silicate? and silver
stantially without the absorption band of said
zns (9o-80%) cds (io-20%)':cu
ZnS (55~45%) CdS (45-55%):Ag
a-ZmGcOuMn
ZnS (550%) ZnSe (2140%):Ag
'
znsnig
MgWQi
ZnBeS1O4zMn
CdBzOlzMn
15 target whereby the light developed-by said second
The above phosphor materials may be used inter
changeably although oxygen-containing phos
screen is substantially unabsorbed by said target.
6. The combination with a target having the
property of developing color centers when-sub
jected to electron bombardment of a luminescent
20 screen adjacent said target having an emission
band substantially without the absorption band
phors are best excited by 2537 A. ultra-violet,
while the sulphides are best excited by 3650 A.
ultra-violet.
of said color centers and a second luminescent
1. Cathode ray apparatus comprising an evacu
ated envelope, means to develop an electron beam,
a target capable of developing color centers when
fluorescence between said screen and said target
whereby simultaneous cathode ray excitation of
screen exposed to said target having an emission
band extending within the absorption band of
While I have described my invention with par» 25 said color centers.
ticular reference to a. halide comprising potas
7. The combination with an alkali halide target
sium chloride, it will be appreciated that other
adapted to develop color centers when bombarded
halides or other reversibly colorable materials
by an electron beam of a luminescent screen
may be used to substantially equal advantage and
adjacent said target having a luminescence wave
the prinf‘iples above set forth as to the choice 30 length overlapping the light absorption wave
of the phosphor emission band with respect to the
length of said alkali halide target and a lumi
halide absorption band is equally valid for other
nescent screen having a luminescence wavelength
halides in addition to potassium chloride and
substantially without the absorption wavelength
of said target positioned between said ñrst men
for other substances, such as magnesium oxide,
which may be similarly reversibly colored by 35 tioned screen and said target.
corpuscular or undulatory energy. Consequently,
8. The combination with a potassium chloride
I do not wish to be limited to the specific struc
target adapted to be bombarded with cathode
rays to develop light-absorbing color centers
tures and constituents or to the inode of opera
tion except as specifically set forth and limited
therein of a luminescent screen having a yellow
in the appended claims.
40 blue fluorescence to illuminate said target and
a second luminescent screen having a red-yellow
I claim:
impinged by said electron beam, a luminescent
screen of material having a luminescence emis
sion band substantially without the light absorp
tion of said halide target when impinged by said
said target and said second screen by >cathode
rays produces substantial emission of yellow-red
fluorescence visible through said target and si
multaneous substantial absorption of yellow-blue
fluorescence.
beam in a position to be excited by a portion
9. The combination comprising a substantially
of said beam following impingement on said tar
translucent
film of an alkali halide, a pair of
get, and a second luminescent screen of material 50 luminescent screens optically exposed to said
having a luminescence emission band overlapping
film, said screens lying to one side of said film,
the light absorption band of said target positioned
the screen nearest adjacent the said film having
to develop light incident on said target.
a spectral emission characteristic substantially
2. Cathode ray apparatus comprising an evacu
without the spectral absorption characteristic of
55
ated envelope, means to develop an electron
said ñlm, the other of said screens having a spec
beam, a pair of coextensive luminescent screens
tral emission characteristic substantially within
having different luminescence emission wave
the spectral absorption characteristic of said
length bands, and an alkali halide target havingr
iilm.
a light absorption band overlapping the emission
10. The method of portraying intelligence
band of one of said screens positioned between 60 comprising producing color centers having a pre
the said means and the other of said screens.
3. Cathode ray apparatus comprising an evacu
determined spectral opacity wavelength band
over an area, illuminating said area with lumi
ated envelope, means within said envelope to de
nescent light having a spectral band at least in
velop an electron beam, an alkali halide target of
cluding the spectral opacity wavelength of said
insuiñcient thickness to absorb said beam exposed 65 produced color centers, and developing lumines
to said means, a luminescent screen positioned to
be impinged by said beam following penetration
cence over the area of saidY color centers of a
wavelength substantially without said opacity
wavelength band whereby _intelligence is por
trayed
by the selective absorption and transmis
70
absorption band of said target when impinged by
sion of light by said color centers.
said beam, a second luminescent screen adjoined
of said target, said screen havingl a luminescence
emission band of longer wavelength than the
the side of said first mentioned screen opposite
said target, said second screen having an emis
1l. The method of portraying intelligence
comprising producing a succession of displaced
spectrally opaque color centers representative of
sion band overlapping the absorption band of
said target, and means between said screens to 75 the intelligence to be portrayed, projecting lumi
9,418,780
nescent light having a frequency band including ‘
the opaque spectral band of said color centers
signals. a translucent target adapted to develop
momentary opacity for a predetermined wave
upon said developed color centers, intercepting
band of light upon bombardment by the electrons
said light over the area of said color centers, de
of said beam, means for scanning said beam over
veloping luminescence without the absorption
said target, a phosphor screen, means whereby
band of said color centers, and projecting said
said screen is scanned by a part oi' the electrons
light through said color centers whereby intelli
of said beam, said screen developing under action
gence is portrayed both by the transmission and
of said part of the electrons a wave band of light
absorption of said developed color centers.
mainly outside the wave band to which said tar
12. The method of developing an instantaneous 10 get is momentarily opaque, a second phosphor
and semi-permanent record of intelligence com
screen, and means for developing light in said
prising developing a succession of displaced color
second screen having a wave band mainly with
centers having a predetermined spectral opacity,
in that to which said target is momentarily
in a time and spatial sequence representative of
the intelligence to be recorded, projecting lumi 15
I6. In a cathode ray device for portraying sig
nescent light having a spectral band width in
nals, means for producing a cathode beam, means
cluding a portion of the spectral opacity band
for varying the intensity of said beam by said
width of said color centers upon said developed
signals, a translucent target adapted to develop
color centers, intercepting said light with said
momentary opacity for a predetermined wave
color centers, and transmitting light of a diñer 20 band of light upon bombardment by the electrons
ent color than said luminescent light through
of said beam, means for scanning said beam over
said color centers whereby the transmission
said target, a phosphor screen, means whereby
through said color centers represents an instan
said screen is scanned by a part of the electrons
taneous record and the light intercepted by said
of said beam, said screen developing in the area
color centers represents a semi-permanent rec
25 under action of said part of the electrons a wave
ord of said intelligence.
band of light mainly outside the wave band to
13. In a cathode ray device for portraying sig
which said target is momentarily opaque, and
nals, means for producing a cathode beam, means
a second phosphor screen projecting its light
for varying the intensity of said beam by said
onto said target having a wave band mainly
signals, a translucent target adapted to develop 30 within that to which said target is momentarily
momentary opacity for a predetermined wave
opaque.
_
band of light upon bombardment by the electrons
17. In a cathode ray device for portraying
of said beam, means for scanning said beam over
signals, means for producing a cathode beam,
said target, a phosphor screen, means whereby
means for varying the intensity o! said beam by
said screen is scanned by an electron stream
said signals, a translucent target adapted to de
of intensity proportional to the intensity of said 35 velop momentary opacity for a predetermined
beam, said screen developing under action of
wave band of light upon bombardment by the
said electron stream a wave band of light mainly
electrons of said beam, means for scanning elec
outside the wave band to which said target is
trons of said beam over and through said target.
momentarily opaque and means for projecting
a phosphor screen adjacent said target adapted
onto said target light having a wave band mainly
to receive the electrons passing therethrough
within that to which said target ls momentarily
and developing under action thereof light mainly
opaque.
,
outside the wave band to which said target is
14. In a cathode ray device for portraying sig
momentarily opaque, a second phosphor screen.
nals, means for producing a cathode beam, means 45 means for developing light in said second screen
for varying the intensity of said beam by said
having a wave band mainly within that to which
signals, a translucent target adapted to develop
said target is momentarily opaque, and means
momentary opacity for a predetermined Wave
for vie'wing the light passing from said screens
band of light upon bombardment by the elec
through said target.
trons of said beam, means for scanning said
50
HUMBOLDT W. LEVERENZ.
beam over said target, a phosphor screen, means
whereby said screen is scanned by an electron
REFERENCES CITED
opaque.
‘
Y
stream of intensity proportional to the intensity
The following references are of record in the
of said beam. said screen developing under action
file of thispatent:
of said electron stream, light mainly outside the
wave band to which said target is momentarily 55
UNITED STATES PATENTS
opaque, means for projecting onto said target
Number
Name
Datelight having a wave band mainly within that
2,096,986 « Ardenne _________ __ Oct. 26, 1937
to which said target is momentarily opaque and
2,163,918
‘fSchwartz ________ _.. June 2'7, 1939
means for viewing through said target said de
veloped and projected light.
15. In a cathode ray device for portraying sig
nals, means for producing a cathode beam, means
for varying the intensity of said beam by said
60
2,239,769
Number
>514,776
Batchelor _________ _.. Apr. 29, 1941
FOREIGN PATENTS
Country
Date
British .......... ..»_ Nov. >17,- 1939
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