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Патент USA US2407907

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sept. ,'17, 1946.
2,407,906
A. ROSE
l LOW VELOCITY TELEVISION TRANSMITTING APFARATUS
FiledAug. 27, 1942
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2,407,906
Patented Sept. 17, 1946
UNITED STATES iPATENT VDFFICE
2,407,906
LOW VELOCITY TELEVISION TRANSMIT
TING APPARATUS
Albert Rose, East Orange, N. J., assignorto Ra
dio Corporation of America, a corporation of
Delaware
Application August 27, 1942, `Serial No. 456,344
10 Claims. (o1. 25o-_150)`
l
My invention relates to television transmitting
tubes and particularly to tubes utilizing low veloc
ity electron scanning beams.`
j
In the operation `of a> television `transmitting
tube of the low velocity electron beam scanning
type including a target 'or mosaic electrode with
an oppositely disposed electron gun and a com
bination -of magnetic-electrostatic deflection
means, the electrons of the scanning beam which
do not- reach the target because of their low
velocity return to a'collecting electrode at the
surface of which they ymay produce secondary
2
electrons of the beam being incident upon the
target in accordance with the electrostatic
charges thereon so that electrons not reaching
the target are returned along substantially the
same paths as the scanning `beam to an elec
tron `multiplier made in accordance with my in
vention. The said electron 'multiplier preferably
comprises an» electrode or electrodes symmetrically
surrounding the initial beam' path immediately
following its formation as a `beam and prior to
It has been customary to utilize a
its deflection by wholly magnetic means. More
particularly in accordance with my invention I
provide a structure comprising a cylinder, trun
usual electron multiplier in that in such a tele
vision tuJbe the virtual point `of origin varies in
Figure 1 is a longitudinal cross-sectional View
of television transmitting apparatus made in ac
electrons.
cated cone, annular `electrode or a plurality of
signal plate comprising a portion of the target
electrode from which the signal may be taken 15 such electrodes directly adjacent the point ‘of
the `ñnal beam formation and between said point
althoughthe signal may be» derived from the co1«
and the deñection means. Such points of beam
lecting electrode. With this latter arrangement,
formation may be'deñned as the -point where the
it is advantageous to provide means for develop“
cross-sectional areas of the beam is limited and
ing secondary electrons, such as shown by Iams
20 at which the beam has its »minimum diameter.
in his U. S. Patent 2,288,402.
The objects mentionedtabove as well as other
The requirements to be met in the design oi
objects, features, and advantages of my invention
a television transmitting tube incorporating an
will ‘be apparent when considered in view of the
electron multiplier for amplifying the return
following description taken in connecticn with
portion of the scanning beam 'diiîer in one-im
portant respect from the `requirements for the 25 the accompanying drawing in which:
cordance with my invention; and 1
accordance with the scanning òf the target and
Figures 2 and 3 show modilied forms of cer
consequently in conventional structures, such as
shown by Iams, the returning beam strikes at 30 tain of the electrodes shown iniFigure l.
In general, the apparatus of my invention com
various points on the ñrst electrode of the mul
prises an ‘evacuated envelope having a target
tiplier. If exceptional care is not taken in pre
`preferably ‘of the photo-sensitive mosaic type
paring the multiplier electrodes, some distortion
at one end thereof ` and an ‘electron source and
may be introduced in this type of structure.
an anode oppositely disposed therefrom to develop
Accordingly it is an object of my invention to
and project upon the target ‘an electron beam
provide a structure of the television transmitting
constrained along its path by a longitudinal mag
llow velocity multiplier type wherein more uni
netic ñeld and deiiected over the target by mag
form secondary amplifica-tion may be obtained.
netic means, such a plurality of magnetic coils
It is another object to provide such a structure
wherein the multiplier electrodes may be more 40 developing fields normally intersecting one an
easily processed. It is another object to provide
a structure wherein distortion produced `by non
uniformity of secondary electron emitting :sur
faces is minimized. It is still another object of
my invention to provide a tube wherein the‘elec
trodes may be made of such form and shape as to
minimize introduction of distortion and a struc
ture wherein the overall length of the tube may
` other so that the mosaic electrode may be. scanned
in mutually perpendicular directions. 'll‘he elec
tron source may be of the conventional type com
prising a small area cathode surrounded by a
_ conventional apertured grid -for purposes of elec
tron beam intensity'control being followed inthe
direction toward the target by an anode having
a beam limiting aperture. This aperture defines
the minimum electron cross-section and diameter
be decreased.
_
.
In accordance with my invention an electro 50 and is necessarily small to prevent returning
electrons ‘from approaching the cathode, which
static image corresponding in electrostatic energy
electrons might be redirected to the target. Im
distribution to an optical image is formed on a
target preferably of the photo-sensitive mosaic
mediately adjacent this defining apertured anode
and between this anode and the deflection means
type which is scanned in two mutually perpendicular directions Iby wholly magneticmeans, the 55 I provide sym‘metrical Vmeans surrounding the
3
2,407,906
electron beam path to collect secondary eleo
trons which may be developed by returning elec
trons impinging the anode or a series of such
electrodes for developing additional secondary
4
90° from their actual operating position for the _
sake of clarity in the drawing. However, the
coils I‘I and I8 may be superposed, in which case
the tube may -be made somewhat shorter.
electrons and collecting these electrons for the
In operation of the structure so far described
development of the television signals.
the electron beam follows an initial path 4 paral
Referring particularly to my tube structure and
lel with the longitudinal magnetic field developed
its associated apparatus as shown in Figure 1,
by the coil I6 until under the influence of the de
the tube comprises an elongated evacuated en
iiection coils I'I and I8 the beam is deflected and
velope I enclosing at one end thereof a target or 10 scanned over the target 2. Electrons of the beam
mosaic electrode 2 and at the opposite end an
are collectedV in accordance with the electro
electrode assembly 3 adapted to develop, limit,
define and project an electrode beam toward the
kmosaic electrode such as along the path 4 shown
by the dashed line. This path will be referred to
as the “initial electron path.” The mosaic elec
trode is preferably of the type described'in my
U. S. Patent No. 2,213,176 and includes a sheet
of insulation, s-uch as mica sheet 5, having on its
rear surface a semi-transparent electrically con 20
ducting condenser plate 6, usually referred to but
not used as a signal plate, and on the front sur
static charges developed by the optical image
light and electrons not being collected by the
mosaic then return in the direction of the elec
trode structure 3 over a return path 4a. Neglect
ing the transit time of the electrons, inasmuch
as their relative velocity is high in comparison
with the rate of change of‘deflection, the elec
trons follow substantially the same path while
returning as while approaching the target. I
have found that the return path deviates vfrom
the initial path and follows paths surrounding
the initial path depending on the deflection at
any instant of time. Consequently, the great ma
face a mosaic of mutually insulated and separated
photo-sensitive particles 1. Various methods of
manufacturing such electrodes are well known in 25 jority of the returning electrons become incident
the art and obviously photo-conductive or'photo
upon the anode I2, very few passing through the
. voltaic targets may -be utilized if desired. The
beam limiting aperture I3 because of its small
electrode structure 3 at the opposite end of the
envelope I comprises a cathode I0 from which
diameter and .because of therdivergen’ce between
the initial and return paths.
electrons may be drawn, a control electrode II 30 In accordance with my invention, I provide the
connected to the usual biasing .battery and an
beam limiting apertured anode I2 of secondary
anode I2 having a beam deiining aperture I3, this
electron
emitting material sovthat as the return
anode being maintained positive with respect to
ing electrons are reaccelerated by the anode I2,
the cathode I0 by a potential source I4 to ac
they impinge thereon and develop secondaryV
celerate the electron beam along the initial elec 35 electrons, and I provide means symmetrically
tron path 4. The beam defining aperture deter
surrounding the electron beam path to collect
mines the minimum cross-section of the beam
these secondary electrons or produce further sec
and substantially prevents electrons not reaching
ondaries which are then collected. Referring~
the target from entering the space between the
again to Figure 1, I have shown a cylindrical
cathode and anode as appears more particularly 40 electrode 20 immediately between the beam lim
hereinafter. Preferably the cathode III is con
iting apertured anode I2 and the first s_et of de
nected directly to the condenser plate 6 of the .
ñection coils I'I. The electrode 20 is preferably
mosaic electrode so that electrons approaching
maintained slightly positive with respect to the
the mosaic are decelerated to substantially zero
anode I2 to provide a iield capable of collecting
velocity, these electrons being collected or rejected
secondary electrons from the anode I2. , Any
by the mosaic in accordance with theintensity
secondary electrons which may be emitted on the
charges thereon developed by light representative
surface of the electrode 20 are likewise collected.
of an optical image.
'
Thus, the electrode 20 may be supplied from the
To direct the electron beam in a focused con
potential source I4 through an output impedance
dition between the beam defining apertured anode
2l so that the signal developed across this im
I2 and target, I provide a focusing coil I6 wholly
pedance by electrons being collected may be ap-V
enclosing Yand preferably extending beyond the
plied to a translating device such las the amplifier
space between the anode I2 >and the target 2.
22. From this showing of Figure 1, it will be
This focusing coil is so designed as to develop
a longitudinal magnetic field strength ’of ap 55 seen that the cylindrical electrode 20 is positioned
symmetrically with respect to the going electron
proximately 50-75 gausses which I have found
beam and likewise with respect to the returning
sufficient to maintain the electron beam in a
electrons so that electrons returning'from any
focused condition. Due to the presence of this
portion of the target are amplified in accordance
iield the electrons of the beam passingthrough
with the secondary emitting properties of the
the beam defining apertured anode with initial 60 anode I2 and uniformly collected by the elec
transverse velocity follow helical paths having a ' trode 20. The material of the anode, at least over
number of focal points along lthe beam path so
the surface exposed to the target 2, preferably has
that while I have referred to focusing of the
high secondary electron emitting properties.
beam, it will be appreciated that'the beam has a
Thus, the anode I2, as well as other electrodes
number of focal points along the beam path, the 65 provided for-‘secondary electron multiplication
potential between the anode' and cathode in
may be such as described by LeverenZ et al., U. S.
_combination -with the strength of the magnetic
Patent 2,233,276.
‘
.
'
’
field being so proportioned as to develop -a beam
A further advantage results from the use of my
focal point preferably in the plane of or on the
improved construction in that further secondary
surface of the target 2. In addition I provide, 70 electron emission may be obtained by interposing
preferably spaced .between the beam limiting
an electron permeable perforated electrode be
apertured anode and the target, magnetic means
tween the secondary electron paths and the elec
to deñect the beam in two mutually perpendicular
trode 20. Thus, I have shown a cylindrical Wire
directions such as two sets of magnetic deflection
mesh electrode 23 which may be operated at a
coils I'I and I8. The coils I1 are shown displaced 75 higher potential than the electrode 20 if a- second
adomos
stage -of `electron multiplication >is desired, .in
which "event, vthe youtput Vimpedance is connected
in 'the AAmesh `electrode circuit to the potential
source I4. ïHowever, improved operation is ob
tained even for single electron multiplicationfuti
lizingl-the mesh-electrode `23 connected to the elec
bytheianode ’|Í2, showever, have relatively `ilovv 1in
ìtiali'velocity andere more read-ily affected 'by Ethe
electrostatic fìelddeveloped between thelanode I2
andishield ‘125 bythe collecting electrode.. In ad
dition, `returning electrons follow non-symmetri
cal-paths surrounding the initial path and are
more subject to small potential gradients devel
trode 20 as shownat24.
'I have Afound in operating apparatus of the type
oped ‘by .the collecting electrode. Consequently,
described that secondary »electrons liberated ‘by
these secondary electrons may be collected read
the anode -'|‘2 orother electrodes adjacent thereto 10 ily‘wiïthout ‘introducing high potential gradients
may 'flow :in the direction ofthe mosaic `electrode
in `theelectron beam path.
and escape the ñeld developed by the electrodes
From the foregoing description relating to each
-20 -or'23, and`I therefore providea trap for 4these
of Figures-1,‘2,and i3, it will he noted lthat the
electrons comprising'an-electrode *25 preferably of
collecti-ng electrode or the second'secondary Velec
annular-form having a relatively large aperture 15 tron emitter symmetrically surrounds the initial
aligned‘with the 'axis of the .tube so that theelec
electron beam path. In effect -the conical struc
trons over the initial and returning »paths may
ture ‘shown `>-in Figure‘2 is a modification inter
be unimpeded. ‘The electrode 25 is operated at
mediate of those of Figures l and 3, the ‘cylindri
açpotential slightly negative with respect to the
cal structure 2|) being expanded at the end nearer
electrode -I 2 -so‘that electrons in 'the space between 20 the target to obtain theconical structure ^3|J, .this
the anode I2 and the «electrode "'25 are driven to
in Lturn being lfurther -expanded to form the an
the collector 20.
nular structure 35. Consequentlmeach of these
‘Referring to Figure `2 which shows a modifica
'electrodes whether in the form `of a cylinder,
tion of ‘my invention, the cylindrical electrode -20
frustum of `a cone or annular zhasïfa surface Jwhich
is replaced #by a truste-conical electrode 30 >which
-is _formed las Aa surfacenf revolution `about the in
is `likewise operated at a positive potential with
itial` electron beam path. The imaging aperture
respect to the anode I2 to collect electrons :there
‘I3 must be of exceedingly small diameter suchas
on. Immediately adjacent the conical collecting
itw'o-to-three thousandths of an inch to prevent
electrode, I'prefer ’to-‘provide a frusto-conical‘elec
`returning electrons from penetrating this aper
tron permeable yapertured electrode, such as a
ture. Furthermore, the minimum diameter of
Vformed `Wire mesh screen '3| , which may be oper
the electrode formed as a surface of revolution
ated 'at a positive -potential with respect to the
'electrode'SIL While I have shown in Figure 1 the
must ‘be «suflicient ‘in accordance with my inven
tion to >allow the returning electrons to reach'the
output impedance vbeing located in the circuit of
anode I2. I have found thata `minimum diameter
the electrode 20, additional -advantages may be 35 of one-quarter of an inch will 'allow substantially
yobtained either in the structure of Figure ‘l `or
all of `‘theïre’turning electrons to reach the anode. `
Figure 2 by connecting the output impedance ‘21|
Furthermore this limitingfdimension is controlled
"in part by the diameteriof the imaging aperture
|13. »Consequently the minimum diameter of .the
`directly to the cylindrical lscreen 23 or conical
'screen 3| whereupon the -screen maybe operated
at a slightly higher potential 'than the adjacent
surface of revolution maybe specified as a func
tion of the limiting `aperture diameter. ‘For ex
ample, I have -found this minimum diameter t0
~lbe preferably at least '75 to 100 times the beam
electrode and as the conical electrode 30 which in
turn is at `a slightly higher potential than the
Yanode 4`I 2. In the structure of Figure ‘2, secondary
electrons emitted ‘by the anode -I2 flow through
»the l»apertures of the screen 3| and impinge the ‘ «
Velectrode »3U liberating further secondary elec
trons which are then collected by the screen elec
-trodeSI and utilized in developing theoutput sig
nal across the impedance 2fI. The yconical form
of this electrode is found lto be conducive to more
“enicient emission of secondary electrons and lmore
uniform collection of these electrons. 'The inner
surface of the cylindrical or conical electrodes
may be roughened such as by “sand blasting Vor
»limiting aperture diameter.
Consequently, the
’effective ‘diameter yof the .anode I2 utilized "for
secondary “electron emission is likewise of similar
-value and lconsequently with the surface of revo
1-lution'electrode surrounding the `anode as shown
-in Figure 3, the anode -`I2 must be at least '75 `to
‘100 times the diameter of the limiting aperture
therein.
I claim:
-1. Television transmitting apparatus compris
>ing :an evacuated envelope, an electron Vsource
etching to increase the uniformity of secondary 55 within said envelope, a target oppositely disposed
’
-from said source adapted to receive electrons
I-have shown in FigurelS a‘further‘modiíication
l»from
said source, magnetic means to develop a
wherein the electrode I2 is of smaller diameter
magnetic ñel‘d extending from said >cathode to
`electron‘emission.
:but vperforms the same function as described, eX
said target, an anode having an electron beam
cept I provide an initial electron `collecting or‘sece 60 limiting aperture ‘between said source and said
fond multiplying electrode of annular form sur
rounding the anode |2-as` shown at 35. Secondary
electrons emitted from the anode I2 are made in
cident thereon for collection or for further .sec
»ondary Yelectron multiplication.
target, magnetic means between said anode and
-said target to deñect electrons Vpassing through
`said limiting aperture over the surface of said
target wherebyelectrons'not reaching said target
Obviously, `in 65 are returned to said anode along paths substan
view .of .the structures of Figures l and 2, a Wire
tially coincident with but surrounding the initial
mesh electrode 36 may be .provided immediately
path of electrons `iiowing toward said target, and
infront of the electrode 35 for final electron collection when the annular electrode 3‘5 is operated
‘as a .second secondary electron emitter.
In each „of the modifications of my invention
`described above, the electrons returning from the
target are accelerated to a velocity determined by
the potential of the anode I2 and incident there
on Yat that velocity. Secondary electrons emitted i
'means including `an electrode positioned about
-said 'initial path and between 'said anode fand said
70 `magnetic` means to intercept secondary electrons
developed <by electrons returning from said target
'incident on said anode.
Y
2. Television transmitting -apparatus including
an evacuated renvelope,> a cathode ,for liberating
»electrons within .saidaenvelope .a Á“target oppo
2,407,906
7
8
posedv cathode and target electrode within said
sitelydispo'sed fromV said cathode,= `a, .magnetic
coil surrounding the space between said cathode
and said target, an Aanode having an electron
beam forming and limiting aperture in the path
envelope, , a magnetic coilv surrounding4 said renve
lope to develop a magnetic field having longitudi
nal lines of force extending substantially, from
said cathode to said target to direct an electron
beam along an initial path toward said target, an
anode having an aperture in alignment between
said cathode and target'to formand direct an
electron beam toward said target, wholly mag
tions over the surface of said target and cause
the electrons not reaching said target to return 10 netic 'means `between said anode and target to
scan said beam over the surface of saidtarget
to said anode along paths substantially parallel
and to direct electrons not reaching said target
and surrounding the initial electron `bearn path,
along returning _paths surrounding said initial
and electrode means wholly removed fromV the
of electrons issuing from said cathode to direct
electrons along an initial path toward-said tar
get, wholly magnetic means to deflect the elec
tron beam in two mutually perpendicular direc
paths of returning electrons and surrounding
path to said anode, a cylindrical electrode wholly
said magnetic means to intercept secondary elec
trons developed by said returning electrons with
paths between said anode and said magnetic
means to receive secondary electronsA developed
said paths and lying between said anode .and 15 removed from said paths and surrounding .said
by said returning electrons on vthe surface of said
anode and means comprising an aperturedelec
out impingement of said returning electrons on
’said electrode means.
~
3. Television transmitting apparatus compris
20 trode between said cylindrical electrodeand said Y `
magnetic means to prevent said developed elec
t ing an evacuated envelope enclosing an electron
trons from reaching said target; '
- » f
. .
emitting cathode, an oppositely disposed target
7. Television transmitting apparatus'compris
to intercept a portion of the electrons emitted byv
ing an evacuated envelope yenclosing a >cathode
said cathode, a beam limiting'apertured anode
and target electrode, an apertured anode of sec
v25
of secondary electron emitting material inter
ondary electron emitting material adjacent said
posed between said cathode and target to limit
cathode to develop-_and direct an electron beam
the quantity of electrons flowing toward said
toward said target, a secondary electron emitting
target and to` intercept electrons not reaching
`cylindrical electrode immediately adjacent vsaid
said target, means to develop a longitudinal mag
netic field wholly Aenveloping-the space >between 30 vanode and exposed to the surface thereof nearer
said target, an electron collecting electrode sub
said anode and said target, magnetic means to
stantially coextensive with and within said cylin
deflect electrons approaching said target over
drical electrode, magnetic meansv to scan elec
the extended surface thereof, an electrode hav
trons passing through said apertured anode lover
ing a surface of revolution surrounding said beam
the surface of said target in the presenceof a
positionedbetween said anode and said magnetic
longitudinal magnetic ñeld whereby electrons not
deflection means to intercept secondary electrons
reaching -said target are.returned along paths
deflected on said anode, said 'electrode being
substantially parallel with and surrounding said
`wholly removed from the path of electrons flow
electron beam without impinging upon said cylin
ing between said anode and said target and be
40
tween said target and said anode. `
drical and coextensive electrodes.>
~ >
Y
‘
‘ 8. vTelevision transmitting apparatus compris
4, Television transmitting apparatus compris
ing an elongated envelope having a cathode and
ing a tube having an electron emitting cathode
target adjacent opposite ends thereof, an inter
todevelop a stream of electrons, an oppositely
mediate electrode structure comprising an aper
disposed target electrode, a secondary »electron
emitting anode having a beam limiting aperture 45 tured anode and an apertured secondary electron
shielding electrode in- the order named between
to form said electrons into a beam having a min
said cathode and target, a frusto-conical elec
imum diameter at said aperture, magnetic means
trode between said electrodes with its apex ad
to develop a longitudinal magnetic field with
-jacent said anode to receive electrons from said
lines of force extending from said cathode Yto
said target, whollymagnetic means to. deflect 50 cathode passing through said apertured elec
trodes but not reaching said target and a perfo
said beam over the surface of said target for
vrated electron collecting electrode substantially
collection in accordance with electrostatic image
coextensive with and lying within said‘frusto
developed thereon and to direct electronsV not
conical electrode to collect electrons for develop
reaching said target to said anode along paths
'
surrounding’the initial path of said beam to de 55 ment of television signals.
9. Television transmitting apparatus compris
velop secondary electrons thereon, an electrode
ing an elongated evacuated envelope,'a cathode,
having a surface of revolution about said initial
oppositely disposed target within said envelope,
beam path wholly removed from said surround
ing paths and between said anode and said mag
netic deflection means to intercept said second
magnetic means extending substantially over the
60
ary electrons andvdevelop additional secondary
electrons, and perforated electrode means sub
stantially coextensive with said electrode having
space between- said cathode and- said target to
constrain electrons as a beam ñowing between
a surface of revolution and between said elec
said cathode and target, an apertured anode' of
predetermined area aligned with its apertureV
in the path of said beam, an annular electrode
tween said electrode having a surface of revolu
tion and said magnetic deflection means, said in
a perforated electron collecting electrode in a»
trode and said surrounding paths to collect said 65 surrounding said anode having a minimum di
ameterat least 75 times the diameter of said
additional secondary electrons.
anode aperture to collect secondary electrons de
5. Apparatus for television transmission as de
veloped by the portion of said beam not reaching `
fined in claim 4 including an apertured secondary
said target and impinging on said anode. .
electron intercepting electrode positioned ’be
10. Apparatus as claimed in claim 9 including ,
tercepting electrode extending transversely to
plane substantially parallel with anddirectly ad
said initial beam path. ‘
jacent said annular electrode.
Y
6. Apparatus for television transmission com
prising an- evacuated envelope, an oppositely dis -751
'
ALBERT ROSE.v
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