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Патент USA US3052815

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Sept. 4, 1962
R. K. H. GEBEL
3,052,807
IMAGE ORTHICON WITH A NARROW RANGE OF ELECTRON
ENERGY IN THE SCANNING BEAM
Filed Jan. 29, 1960
2 Sheets-Sheet l
Ty;
Ty; a.
INVENTOR.
R. K. H. GEBE
BY
?Lab...
ATTORNEY
AGENT
Sept. 4, 1962
R. K. H. GEBEL
3,052,807
IMAGE ORTHICON WITH A NARROW RANGE OF ELECTRON
ENERGY IN THE SCANNING BEAM
2 Sheets-Sheet 2
Filed Jan. 29, 1960
1-4
27 q
ZOJ
26
24
I
23
INVENTOR.
R. K.H. G EL
BY Wm
ATTORNEY
AGENT
M
United grates Patent 0 " ice
3,�,8�Patented Sept. 4, 1962
2
1
provided by potentiometer 111, and serves as a means for
3,052,807
controlling the beam intensity. Plates 5 and 9 are at
the same positive potential relative to the cathode, which
Radames K. H. Gebel, Dayton, Ohio, assignor to the
potential is'supplied by potentiometer 12. The vector 13
represents the axial magnetic ?eld normally provided for
in image orthicons.
?IMAGE ORTI-HCON WITH A NARROW RANGE OF
ELECTRON ENERGY IN THE SCANNING BEAM
United States of America as represented by the Secre
tary of the Air Force
Filed Jan. 29, 1960, Ser. No. 5,570
3 Claims. (Cl. 313-82)
(Granted under Title 35, US. Code (1952), see. 266)
Electrons emitted from the emitter 3 of the cathode
pass through aperture 6 and are accelerated toward aper
ture 7 by the positive ?eld produced by positive plate 5.
10 The electrons pass through aperture 7 and into the space
The invention described herein may be manufactured
and used by or for the United States Government for
governmental purposes without payment to me offany
royalty thereon.
between plates 5 and 9 with a velocity determined by
the potential of plate 5 relative to the cathode. As a
result of the tilt of the cathode the velocity vector of
the electrons passing through aperture 7 makes an angle
,beam of a conventional tube is one of the reasons for
on with respect to the z axis. Consequently the velocity
vector of the electrons has a component parallel to the
tube axis 2, and magnetic ?eld vector B, and a compo
nent transverse to the tube axis and the magnetic ?eld
low beam modulation since, at low light levels, the in
vector B. These two components result in a helical move
cal paths having different diameters depending upon the
initial energies of the electrons. A barrier having a small
be intercepted by plate 9. Consequently, the stream of
electrons passing through aperture 10 and continuing in
aperture is then placed to intercept all electrons except
the axial direction have a very narrow range of kinetic
A low beam modulation factor impairs the perform
ance of image orthicon tubes at low light levels. The
wide energy distribution of the electrons in the scanning
formation on the target plate consists of such a small 20 ment of the electron through the space between plates 5
and 9 as represented by the path 13. The y?z, x-??z and
charge that only the very ?fastest electrons in the beam
y-x projections of path 13? are shown in FIGS. 2, 3, 2a
reach the target plate and are effective as charge neu
and 3a. The diameter d of the helix 13 for each elec
tralizers. Since these electrons produce the beam modu
tron, as will be seen later, is determined by the kinetic
lation, the percentage modulation is low.
' In accordance with the invention, the beam modulation 25 energy of the electron when it ?emerges from aperture 7,
and the angle a.
percentage is increased by limiting the energy of the
With proper selection of the distance 1/2 all electrons
,bearn?s electrons to a very narrow range. Brie?y, this is
within a very narrow predetermined range of kinetic en
accomplished by restricting the electrons emitted from the
ergies will have helical paths of substantially the same
cathode to a very narrow beam at an angle to the longi
diameter d and will pass through aperture 10. Elec
tudinal axis of the tube. . The transverse components of
trons having kinetic energies above or below this range
the electrons? velocities together with the axial magnetic
will have helical paths of greater or lesser diameter and
?eld of the tube cause the electrons to travel along heli
energies as desired for the scanning beam of an image
orthicon operating at low light levels.
The values of d, the diameter of helix 13, and l, the
those traveling ?along the helix having the diameter estab- ,
'l-ished by the position of the aperture, or helices having ?
?diameters very close to this value. The electrons passing
through the aperture will therefore have substantially the
lead of the helix are determined as follows:
'same energies.
A more detailed description of the invention will be
(0111.)
d=??????-=?????7???.??
_7_n<a_B Sin a 1.759Xl0 B sin a
(1)
given with reference to the accompanying drawings in
which
FIG. 1 is a fractional view showing the essential fea
.
where
45
tures of the invention,
V=magnitude of the velocity vector of the electrons
FIGS. 2, 2a, 3 and 3a are projections of the helical
emerging from aperture 7
electron path of FIG. 1,
?FIG. 4 is -a diagram illustrating certain geometric rela
tionships in FIG. 1, and
FIG. 5 is a partial view of an image orthicon incorpo
i=electron change to mass ra.tio=l.759><107 emu.
50 m
(approx.)
7
_
rating the invention.
Referring to FIG. 1, 1 is a cathode cylinder having a
heating element 2 and, on its end, a small pellet 3 of an
et?cient thermionic emitter such as barium oxide. Two
where
closely spaced metallic plates 4 and 5 are positioned nor 55 u=energy of electrons in electron-volts emerging from
vmal to the axis z, which may be the longitudinal axis of
aperture 7 (equals initial energy of electrons plus po
(2)
v=1/2%10m=59.36>< 106W cmJsec.
an image orthicon tube, with plate 4 adjacent to emitter
tential at aperture 7).
3. Plates 4 and 5 have small apertures 6 and '7 of, for
substituting Equation 2 in Equation 1
example, 0.1 mm. diameter in alignment with the axis 8
of the cathode. There is also provided a third metallic 60
plate 9 parallel to plate 5 and at a distance 1/2 therefrom.
cm.
(3)
Plate 9 has a small aperture 10, which may be of the
same size as apertures 6? and 7, having its center in the
x?z plane at a distance d from the z axis. Plate 4 has
The lead I of the helix may be determined as follows:
an adjustable negative potential relative to the cathode, 65
one turn of the helical curve is unrolled onto a plane
3,052,807
3
4
surface, ?as shown in FIG. 4, the helix becomes a straight
trons leaving aperture 10 has an absolute range of 5%,
line, forming the hypotenuse of ?a right triangle. The
or differs ill/2% from the average value.
angle a between B and the electron velocity vector in
FIG. 5 illustrates a possible arrangement of an image
FIG. 1 is identical to the angle a in FIG. 4; therefore,
orthicon tube incorporating the invention. The conven
the path length L traveled ?by the electrons in one turn
tional image ort-hicon is well known in the art and de
of the helix is given by
scribed in the literature; for example, in an article entitled
?The Image Orthicon? by Rose, Weimer and Law, ap
__ 1rd
(4)
_sin a
pearing in the July 1946 issue of the Proceedings of the
Institute of Radio Engineers. Only the cathode end of
From FIG. 4 it is also seen that
10 the tube is shown in FIG. 5. Elements are numbered to
(5)
l=L cos a
correspond to FIG. 1. The plate 9', which is the ?rst
dynode of the tube?s electron multiplier, may also serve
substituting the value of L from Equation 4 in Equation
the function of plate 9 in FIG. 1. The beam 13 is
5 gives
caused to scan the target electrode by sweep yoke 20 in
(6)
l=1rd cos a
conventional manner.
considering a speci?c example, assume
B=13.4 Gauss
w=3 volts
dicated at 22, 23, 24, 25 and ?26, respectively. Coil 27
20 provides the axial magnetic ?ux B.
a=60�
I claim:
1. Apparatus for use in a cathode ray tube for produc
then, from Equation 3,
d
The electrons in excess of those
required to neutralize the charge on the target return along
path 21 to ?rst dynode 9' of the electron multiplier, the
remaining dynodes and output electrode of which are in~
ing an electron beam having a very narrow range of elec
(am/s
=(13.4)(O.S66):1 cm?
25
and, substituting in Equation 6
tron energies, said apparatus comprising: a pair of paral
lel spaced metallic equipotential plates; means for pro
ducing a constant magnetic ?eld normal to said plates in
the space between said plates; means for injecting a nar
row beam of electrons into said space through a small
aperture in one of said plates, said beam making an acute
1_0.57741r =0.905
cm.
2_
2
If the diameter of aperture 10 is 0.1 mm. then, letting Ad
angle with said magnetic ?eld whereby each injected
equal this diameter,
electron travels through said space along a helical path
having a diameter and lead determined by the electron
velocity; and a small circular aperture in the other of said
dm,,=d+A2_d= 1.005 cm.
plates so positioned as to pass only those electrons whose
35
dmin=d?椋l=
.995 cm.
2
paths substantially coincide with a single helical path,
whereby the electrons passing through the aperture have
and
umag=71 �
?mitt: 69 6
Then, from the rearrangement of Equation 3
substantially the same velocities.
2. Apparatus for use in a cathode ray tube for produc
ing an electron beam having a very narrow range of elec
40 tron energies, said apparatus comprising: an electron gun
structure designed to produce a narrow beam of elec
trons at an acute angle to a predetermined reference axis,
said gun structure comprising an electron emitting cath
ode, a beam intensity control electrode in the form of a
45 metallic plate positioned close to said cathode and hav
ing a small aperture through which a portion of the elec
trons emitted by said cathode pass, means for maintain
ing said beam intensity control electrode at an adjustable
negative potential relative to the cathode, an accelerating
50 electrode in the form of a metallic plate parallel to and
close to said beam intensity control electrode and having
The energy module
umod :
an aperture of substantially the same size as the aperture
a max_ dim sin2 C(mnx
u min_ d121,?, sin2 01min
dmin
Sin-2 amin
where
dines: min + Ad
in the beam intensity control electrode, means for main
taining said accelerating electrode at a postiive potential
relative to said cathode, said plate being normal to said
reference axis, and said cathode and said apertures being
in alignment, with the axis of alignment intersecting said
reference axis at the center of the aperture in said accel
erating electrode and making an acute angle with said
60 reference axis; a third metallic plate normal to said refer
ence axis and spaced a predetermined distance from said
Sin2 (am,n+Aa):cOs2 Aa+ sin 2A0l
accelerating electrode; means for maintaining said third
plate at the same potential as said accelerating electrode;
sin2 Aa
sin 2A0? .
means for establishing a magnetic ?eld parallel to said ref
_~? 21
?_ f
? >>A
+tan2 Otmiu
+1781} cumin (1 am?
(2)
erence axis in the space between said accelerating elec
Hence
trode and said third plate, whereby each electron entering
?this space through the aperture in said accelerating elec
Ad 2
sin 2Aa
trode travels a helical path the diameter and lead of which
depends upon the electron velocity; and a small aperture
70
or, for the speci?c case,
in said third plate so positioned as to pass only those elec
trons Whose paths substantially coincide with a single
__
0.01
2
0.0698
sln2
04min
tan (1min
umod=(1+dmin) (1+ta4n amin)
?Md-(H0095) (1+ 2.605
= (1.021) (1.027) = 1.05
helical path whereby the electrons leaving said aperture
have substantially the same velocities.
Or, in other words, the energy distribution of the elec 75 3. Apparatus as claimed in claim 2 in which the center
3,052,807
6
of the aperture in said third plate lies at a distance d from
velocity vector of the electrons entering the space between
said reference axis in a plane containing said reference axis
and normal to the plane de?ned by said reference axis
said accelerating electrode and said third plate through the
aperture in said accelerating electrode.
and said axis vof alignment, and in which the spacing be-
tween ?said accelerating electrode and said third plate 5
equals
d
_
_
References Cited In the ?le of this Patent
UNITED STATES PATENTS
L553?-
2,429,55s
Marton ______________ __ Oct. 21, 1947
2
2,500,455
2,638,561
Fisher ______________ __ Mar. 14, 1950
Sziklai ______________ .._ May 12, 1953
2,310,091
Harsh _______________ __ Oct 15, 1957
where a is the angle between the magnetic ?eld and the 10
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