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Патент USA US2404046

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July 16, 1946.
Filed June 21, 1941
2 Sheets-Sheet 1
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July 16, 1946.
2 Sheets-Sheet‘ 2
Filed June 21, 1941
Patented July 16, 1946
Leslie E. Flory, Oaklyn, N. .J., Ernest A. 'Massa,
Osborn, Ohio, and George A. Morton, Haddon
Heights, N. J ., assignors _to Radio Corporation
of America, a corporation of Delaware
Application June 21, 1941, \SerialiNo..399’,110
8 Claims. (01. 178-123
Our invention relates to television apparatus,
tubes and systems and is concerned primarily
with apparatus incorporating a tube in which
an electron beam having substantially zero veloc
ity is scanned over a target to generate signals
representative of an optical image for television
It has been customary to provide electronic
image transmitting tubes of either the storage or
non-storage type and to use either the resultant
electrostatic charges produced from storage or to
use the current image signals from the non
storage type to develop signalling impulses for
transmission of an optical image replica.
storage type of tube offers considerable increase 15
in the magnitude of the output signal energy ob
tained when a mosaic of photoemissive elements
Tubes which we :have designed .for'usev ‘without ’
a longitudinal magnetic ?eld and wherein the
electron; beam ' approaches the target ¢orl mosaic
electrode with substantially"zero'velocity have’ -
exhibited considerable distortional elTects which
we have termed “crawling” or f‘cree'ping” inas
much as the recreated image replica continuously
shifts or moves especially over vareas remote from
the center of the image; A fullycomprehensive
theory of why this crawling or creeping occurs
has not ‘been formulatedrbut. whenever, tubes
utilizing low velocity beam scanning have been
operated without a longitudinal magnetic-?eld
these crawling effects have been most objectione
.It. is an object of our’ invention to" provide
highly sensitive television apparatus and syse
tems capable of developing picture replicas with
is scanned with a high velocity electron beam,
out "distortion wherein a (low velocity electron
however, the non-uniformity of secondary elec
tron collection and emission saturation results 20 bea'mri’s ‘directed upon a target by purely ~elec'
in a signal-to-noise ratio which is not as high as
might be desired.
trostati-c *means. It is :another object to provide
a lighttranslating and scanning system which
Local variations in the potential distribution
will simplify the translation of optical effects into_
on the mosaic generate spurious signals which
are usually referred to as dark spot signals in
that they produce a non-uniform gradation of
shading corresponding, not to the desired dis
tribution of light and shade of the optical image
television‘signalling impulses with a; minimum of
dlstortionale?'ects. It is a further object vto pro
vide a television transmitting tube wherein .elec
formed on the mosaic, but to random areas of
light and shade which do not correspond to those
of the desired image. Since the ?eld utilized for
collecting secondary electrons emitted by a mo- ‘
saic electrode under scansion is modi?ed by the
electron scanning beam and consequently is of
unequal intensity or e?ect over the scanned area
of the electrode, it has been found di?icult to
.trostatic charges ‘representative of the light and
shade areas of an'optical image may be neutral
ized over a relatively'large extended _area,‘and
it is ‘a still ‘further object to minimize orjsube
stantially ‘eliminate distortional effects occa
sioned by grazing incidence of an ‘electron beam
In accordance with our invention we provide
television apparatus incorporating a tube wherein
the electron beam is directed along paths oblique
collect uniformly the secondary electron emis
with respect‘ to the surface of a target and then
sion from the surface of the mosaic electrode
directthe electrons of the beam along paths sub-y
whereby it might be ampli?ed such as by second
stantially normal to the elemental surface areas
ary emission ampli?cation.
4.0 of the target‘by correlating theobliquity of the
original paths, the position and contour of the
The above di?iculties may be obviated by pro
viding a tube and system wherein the tube gen
target, and the effects of an electrostatic ?eld
immediately adjacent the target. These and ”
erates an electron beam which is directed’ upon
the target or mosaic electrode with a velocity ap
other objects, features and advantages of our in
vention will become apparent upon consideration
proaching zero so that no secondary electrons
of the following description and the accompany:
are liberated which would inherently be distrib
uted non-uniformly over the surface of the mo
ing drawings vin which’:
‘ ‘
Figure 1 is a longitudinal view of television
saic electrode and cause what has been referred
transmitting apparatus incorporating our inven
to above as dark spot signals. A low velocity
beam scanning tube and system is described by 50 tion;
Figure 2 is a graph showing electron beam
Albert Rose in his U. S. Patent 2,213,174 which
utilizes a magnetic ?eld to direct the beam along
trajectories in a conventional’ television trans
paths normal to the target. The use of magnetic
mitting tube; and
. ,
q ‘
?eld generating means is often disadvantageous
Figure 3 is a graph similar to that; of Figure}
for use in compact television camera units and 55 showing trajectories of- the electron beam‘ in a
especially in application where it is desired to
In of
the type of Figure
of our invention
.' .
combine the Rose tube with reflection type opti
cal systems, inasmuch as the magnetic means
as shown in ‘Figure 1, the apparatus includes a
discharge device or tube comprising ‘a highly
which surrounds the Rose tube occupies consid
60 evacuated glass envelope or bulb l with a tubular
erable space and intercepts considerable light.
arm or neck section enclosing _a conventional
type electron‘ gun to form and direct’ an electron
beam upon a target or mosaic electrode 2 which,
in accordance with our invention, is of a prede: ‘
termined contour. The target is symmetrically
positioned in the enlarged portion of the en
velope so that its projected surface is substan- _
tially perpendicular to the longitudinal axis of
the drawings ‘of Figure 1, this meansmay com
prise one or more conductors (t'wo'being shown)
adjacent the target, such as the electrodes l5
and I5 maintained at the desired positive poten
tials with respect to the cathode by the battery 9.
These electrodes may comprise electrically con
ductive coatings on the inner wall of the bulb l
adjacent the mosaic electrode, although it is
within the spirit of our invention to provide these
the bulb I and so that it may be scanned by a
beam of electrons from the electron gun and may 10 electrodes in the form of wire mesh screens lon
gitudinally displaced along and transverse to the
also have projected thereon an optical image of
longitudinal axis of the tube. The function of
which a signal replica is to be transmitted. As
the electrodes !5 and I6 will be considered in
shown, the mosaic electrode 2 is preferably de
considerable detail in connection with Figures 2
posited or formed on the inner surface of the
and 3.
end ‘wall of the envelope'which may in this case
Referring more particularly to the con?gura
determine the predetermined contour of the mo
saic electrode.
tion and construction‘ of the mosaic electrode 2.
this electrode is preferably of spherical form with
The electron gun is of a conventional type and
its center of curvature intermediate the center
comprises a cathode 5 from which an electron
stream may be drawn,‘ a control electrode 6 con 20 of deflection and the‘ target surface, and while
this electrode may be‘ supported within the bulb
nected to the usual biasing battery, and a ?rst
l, we have shown the structure as being formed
anode 1 maintained positive with respect to the
directly on the inner wall of the bulb I which in
cathode 5. The electron stream leaving the ?rst
this case has a curvature corresponding to the
anode ‘I is accelerated and concentrated into an
electron scanning beam and directed toward the 25 desired curvature of the ‘electrode. While any
form of light responsive electrode capable of re
surface of_ the target or mosaic electrode 2 facing
solving individual elemental'areas of light and
the electron gun by a second anode 8 which is
shade into elemental 'chargeareas may be used,
preferably a conductive coating on‘ a portion of
we prefer to pro'vide‘an electrode of the semi
the inner surface of the envelope I. The ?rst
anode ‘I and the second anode 8 are maintained 30 transparent type including alight permeable elec
at the desired positive potentials‘by a potential
source represented as the battery 9. Although
we have shown one form of a suitable electron
gun other forms may serve to equal advantage.
Intermediate the ?rst anode ‘I and ‘mosaic elec
trode ‘2 and at a predetermined distance from
thermosaic electrode as measured along the'elec
‘tron gun axis We provide conventional electron
beam de?ection means such as the coils l0 and
trically conducting} ?lm, such as the metal ?lm
20 deposited directly on the inner end wall of the
bulb l. The electrically conducting ?lm 20 serves
as a signal plate in capacitive relation with the
photosensitized particles of the mosaic 22 and is
connected to a translating device such as the am
pli?er 25 and to a potential at or near that of
the cathode l5 through an output impedance 26.
This connection, as indicated above, causes the
II to de?ect the beam from its axial path and 40 mosaic 22 to assume an average potential which
is equal to or near the cathode potential, thereby
sweep the beam in horizontal and vertical planes
decelerating the electron ‘beam adjacent the tar
from a center point of de?ection such as the point
get. The metal'?lm 20 may be provided with a
l2.v It will ‘be noted that as the electron beam
non-‘conducting coating 2|, such as of aluminum
leaves the electron gun 2, its path is coaxial with
oxide, china‘ clay, glass or'othe'r dielectric ma
the ‘?rst anode, but upon reaching the center of
terial. The ‘coating 2| ‘is likewise substantially
de?ection I2 the beam is deviated or de?ected
transparent and bears on its exposed surface a
from this path and approaches the target from
mosaic 22 of phot'osensitized metallic particles so
this point as a de?ection center. It will likewise
that an optical image such as represented by the
be appreciated that in the absence of further
de?ection means or electrostatic lenses between 50 arrow 23 may be focused thereon through a lens
system 24. Inasmuch ‘as the‘ mosaic electrode is
the center of de?ection l2 and the mosaic elec
of spherical con?guration, the lens system may
trode, the electron beam trajectories would be
be designed to provide a spherical image ?eld, or
straight lines. As the electrons comprising the
re?ection optical systems inherently producing
electron beam leave the junction of the ?rst and
second anodes they are directed along converg 55 a spherical image fleld‘may be substituted for
the particular lens system 24, as shown in the
'ing paths, only the central or average path of
which is shown in Figure 1. Furthermore, the
For a better understanding of the principles
average potential of the mosaic electrode is main
underlying our invention, reference may be had
tained substantially equal to the potential of the
to Figure 2 which shows a graph of electron beam
cathode 5, as explained in greater detail here
trajectories in a tube incorporating a, plane tar
after, so that the electrons are decelerated in the
get and an electron lens immediately adjacent
vicinity of the mosaic electrode to a velocity of
the target. As shown in Figure 2, the target rep
substantially zero.
resented at 30 is of planar form, only a portion
In accordance with our invention we so modify
the electron beam trajectories intermediate the 65 of the target being shown to‘ one side of the axis
31 on which the center of deflection I2 is located
center of ‘de?ection and the target and likewise
at a predetermined distance from the target. The
provide the target of predetermined con?gura
positions of the ‘second anode 8 and the electron
tion preferably of spherical form with its center
lens forming electrodes ‘l5 and I6 are shown, it
of curvature located on‘the electron gun axis and
preferably between the center of de?ection and 70 being assumed that potentials of 1000, 600 and
450 volts with respect to cathode are applied to
these electrodes respectively} Assuming a, unit
charge on the surface of the target 30 such as
comprise one or more electrodes surrounding the
might be occasioned by light representative of a
electron beam between the second anode 8 and
the target or mosaic electrode 2. Referring to 75 uniform illumination over the surface of the tar
the target surface. More particularly, the means
to modify the electron beam trajectories may
get, an electron beam approaching the target
along the axis 3| of unit intensity is collectedl'by
the target to neutralize the unit charge. If, how
ever, the beam is de?ected at the center of de
?ection l2 through an angle of approximately 3°
with the axis, the electron beam trajectory will
be as shown at 32. The electrostatic ?eld devel
oped by the electrodes l5 and I6 for the poten
face area :along paths substantially normal there
to. Figure'3 is .a'graph similar to thatshown in
Figure 2 wherein the radius of curvature of the
target has been correlated with and chosen with
respect to the voltages applied to the electrodes
l5 and I6 and with respect to the initial center
of de?ection. In accordance with our invention
and as shown by Figure 3 the electron beam ap
proaches the mosaic along paths which are sub-'
stantially normal to elemental surface areas. It
tials referred to above is a ?eld of such intensity
as to form equi-potential ?eld gradients sub
stantially corresponding to the normal decelera
tion ?eld gradients through which the electron
beam approaches the target. Thus the potentials
will be noted that the trajectories 32’, 34’, 36’
and 38' have points of nearest approach 33’, 35’,
31' and 39' which are substantially coincident
of the electrodes I5 and is are here chosen such
with thesurface of the target. It is likewise noted
that they have little if any effect on the electron 15 that the radius of curvature of the equi-potential
beam trajectories.
The axial velocity of the
line marked 25 along the axis of the tube is sub
stantially equal to the radius of curvature of the
proach the target, but the radial velocity, that is,
target over the principal portion of its length.
a velocity transverse to the axis, remains sub
Thus, while the graph of Figure 3 applies to' a
stantially constant so that the electron beam, in 20 tube having a potential of 200 volts applied to the
stead of approaching at the original 3° angle of
electrode It, a slight increase in this‘ potential
will produce an even closer symmetry between
de?ection, increases its effective de?ection adja
cent the target so that the beam is shifted from
the'target curvature and that of the adjacent
equi-potential ?eld.
the intended point of contact with the target and
As a particular example of a tube made in ac
fails to reach the target because when the elec
trons reach their nearest point 33 of approach to
cordance with our invention and of which the
the target, the electrons are re?ected and return
graph of Figure 3 is representative, the axial dis
in the general direction of the electron gun.
tance between the center of de?ection and the
This effect is even more pronounced with larger
target was made equal to 9. inches with aradius
angles of de?ection. For a de?ection of approx- '
of curvature of the target of '7 inches, the po
imately 5%“ the trajectory as shown at 34 ap
tential of the electrodes 8, l5 and I6 beingequal,
proaches the target at its nearest point 35 which
to approximately 1000, 500 and 200 volts respec
tively, the target being rectangular and measur
is even farther removed from the target than
point 33. Similarly, for larger angles of de?ec
ing 11/2 x 2 inches. This tube, made in accord
tion, such as approximately 7° and 8°, the elec
ance with our invention, exhibited a ‘minimum of
distortion due to non-normal approach of the
tron beam follows the trajectories 3t and 38, the
nearest points of approach to the target being
electron beam and resultant crawling effects, as
well as a minimum of spherical aberration ef
the points 31 and 39. It will be noted that as
the angle of de?ection increases, the distance be
fects occasioned by the electron lens between the
tween the target and the nearest point of ap 40 second anode and target.
While we have described our invention with re- ‘
proach for the various trajectories increases cor
spect to the provision of a tube and system where
respondingly, and it will be evident that while a
unit picture charge may be neutralized by the
in more uniform approach of the electron beam
to the target is obtained, it should be understood
beam having an axial trajectory, the beam will
have progressively less effect upon a unit charge
that the principal criterion for satisfactory oper
ation is the path along which the electron beam
as the angle of de?ection is increased. Actual
approaches the target surface, this path being
measurements have shown that a unit charge ca
pable of being neutralized by an axial trajectory
normal to the elemental surface areas of the
target. We have observed that the rate of the.
beam must be increased to 12, 20, 46 and 70 units
for the four trajectories respectively, as shown 50 crawling or creeping effect in both horizontal and
in Figure 2.
vertical directions is the same which seems to in
While it is possible to partially compensate the
dicate that this effect is associated with the in
stability of accumulations of charges over the
effects produced by non-uniform distances of
mosaic‘surfacepthis instability resulting in the
approach of the beam to the target by increas
ing the strength of the electron lens formed be 55 moving charge excesses and de?ciencies causing
the effect. Therefore, while we have not sought
tween the electrodes 8, l5 and I6, we have found
to set forth a positive explanation of the e?'ect
that lens strengths sufficient to overcome even a
it will be appreciated that we have overcome the
major portion of the difficulties introduce severe
spherical aberration elfects so that the resulting
di?iculty by so correlating the target contour and '
picture replica, while of more uniform response, 60 the desired beam trajectories that‘ the beam ap
becomes distorted with respect to the original
proaches along a path normal to the elemental
target surface and thereby eliminating the crawl
picture content. However, in accordance with
ing or creeping distortion. Furthermore while we
our invention, these di?iculties may be overcome
have indicated the preferred embodiments of our
by providing only a small lens action immedi
electron beam decreases as the electrons ap
ately adjacent the target by forming the target 65
in such a manner that its surface is substantial
ly coincident with the electrostatic ?eld gradient
_ adjacent the surface.
In this manner the radius
of curvature of the target is made substantially
equivalent to the radius of curvature of adjacent
equi-potential ?eld gradients and preferably less
than the radius of de?ection which may be de
?ned as the axial distance between the center of
de?ection and the target. This results in the
electron beam approaching the elemental sur
invention of which we are now aware, and have '
provided ‘a tube and system for avoiding the for
mation of certain distortional effects it will be
apparent that many variations maybe made
therein without departing from the scope of our
70 invention as set forth in the appended claims,
We claim:
1. Apparatus for television transmission com
prising an evacuated envelope having an ‘end
portion which is spherically concave to the in
75 terior thereof, a. substantially transparent "elec
trically conducting electrode on one surface of
said end portion, a mosaic of light sensitive photo
trajectories substantially radially incident on said
emissive particles adjacent said electrode and in
capacitive relation therewith the exposed surface
5. Apparatus for television transmission com
prising a tube having an electron gun to develop
an electron beam, an oppositely disposed light
of said mosaic conforming to the spherical con
cavity of said end portion, an electron gun op
sensitive target positioned transversely to the
axial path of said beam to receive electrons of
positely disposed from said mosaic to develop an
electron beam, scanning means to direct said
said beam, said target being spherically concave
with respect to said gun and having its center
beam along paths oblique with respect to the
radii of said curved end portion and centered at 10 of curvature lying on said axial path, means more
remote from said target than said center of curva
a point more remote from said mosaic than the
ture to deflect said beam over said spherically
center of spherical concavity thereof, and means
concave target whereby said beam follows trajec
to divert said beam from the oblique paths imme
tories oblique to the radii of said target, and
diately adjacent said mosaic to paths radially in
means adjacent said target to de?ect said beam
cident thereon to develop signals in response to 15 to follow trajectories substantially radially inci
light projected upon said mosaic.
dent on said target said last-mentioned means
2. Television signal generating apparatus com
including said target and a plurality of electrodes
prising an evacuated envelope, an electron gun
adjacent said target.
within said envelope to develop a high velocity
6. Apparatus for developing signals for tele
electron beam, a target having a great multiplic 20 vision transmission comprising a tube having an
ity of electrostatic charge retaining mosaic ele
electron source, an anode to accelerate electrons
ments arranged on a spherical surface which is
concave with respect to said electron gun, the said
from said source, a target having a ?nite radius
of curvature, the ,center of curvature lying on the
target being symmetrically disposed and trans
axis between said source, anode and target, means
verse to the axis of said beam, means to de?ect
surrounding the said axis at a region more re
said beam at a predetermined rate through a
mote from said target than the center of con
vertical angle and means to de?ect said beam
cavity thereof to scan said electrons over paths
at a predetermined higher rate through a hori
obliquely incident on said target, means includ
zontal angle said last two mentioned means be
ing said target to decelerate said electrons to a
ing positioned about the beam axis at a region 30 substantially zero velocity in the vicinity of said
more remote from said target than the center
target, said means including an electrode adja
of concavity thereof, means to develop an electro
cent said target to direct electrons from said
static image of varying electrostatic charge in
tensity over the surface of said target, a plurality
of electrodes between said de?ection means and
target, and means to decelerate and direct said
beam following said de?ection along paths radial
to the surface of said target to develop signals
substantially proportional to said charges and
in a time sequence determined by the uniform
paths to paths radially incident on said target.
7. Apparatus for developing signals for tele
vision transmission comprising a tube having an
electron source, an anode to accelerate electrons
from said source, a target having a ?nite radius
of spherical curvature, the center of curvature
40 lying on the axis between said source, anode and
rates of de?ection.
3. Apparatus for television transmission com
prising a tube having an electron gun to develop
an electron beam, an oppositely disposed light
sensitive target positioned transversely to the
target, means surrounding the said axis at‘ a re
gion more remote from said target than the cen
ter of concavity thereof to scan said electrons
over paths normally oblique to the surface of said
target, means including said target to develop an
electrostatic equipotential ?eld directly adjacent
said target which is of spherical curvature con
forming substantially to the curvature of said
target to direct electrons from said paths to paths
axial path of said beam to receive electrons of
said beam, said target being concave with re
spect to said gun, means to de?ect said beam
from a center of de?ection further removed from
50 radially incident on said target.
the said concave target than the center of curva
8. Apparatus for developing signals for televi
ture thereof whereby said beam follows trajec
sion transmission comprising a tube having an
tories oblique to said target, and a plurality of
evacuated envelope a portion of which‘ is adapted
electrodes adjacent said concave target to de?ect
to bear a light sensitive target, an electron source,
said beam to follow trajectories substantially
55 an anode to accelerate electrons from said source,
radially incident on said concave target.
a target having a ?nite radius of spherical curva
4. Apparatus for television transmission com
ture between said envelope portion and said elec
prising a tube having an evacuated envelope one
tron source, the center of curvature of said target
portion of which is spherically concave with re
lying on the axis between said source, anode and
spect to its interior, an electron gun oppositely 60 target, means surrounding a portion of said axis
disposed from said concave portion to develop an
and between said source and said center of curva
electron beam, a light sensitive target adapted
ture to scan said electrons over portionsof paths
to develop elemental charges representative of the
light and shade areas of an optical image deposit
normally oblique with respect to said target,
means including said target to decelerate said
ed on and conforming to the concavity of said 65 electrons to a substantially zero velocityin the
portion to receive electrons ?owing along a path
vicinity of said target, said means including an
from said electron gun, beam de?ection means
electrode adjacent said target to develop a spher
surrounding a portion of said beam path at a
ical equipotential ?eld which substantially congreater distance from said target than the center
forms ‘to the curvature of said target immediately
of curvature of said concave portion to de?ect said 70 adjacent the surface thereof whereby electrons
beam from a center of de?ection removed from
are de?ected from said paths to paths radially
the center of curvature of said concave portion
incident on said target.
whereby said beam follows non-.radial trajectories
toward said target, and means adjacent said
target to modify the trajectories of said beam to 75
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