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Патент USA US2114572

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April 19, 1938.
H. c. RESSLER
CATHODE RAY TUBE SYSTEM
Filed June 1, 1936
2,114,572
2,114,572
Patented Apr. 19,1938 .
,
, ‘UNITED. FSfl'ATES. {PATENT caries
.
,
w
__
anws
ca'rnona any man mm _.
I nun c. me, new York.‘ N. 1., assignor to
‘Radio Inventions, Ina, New York, N. Y.,' a cor-g
, poration of New York
' Application June 1, last, w No. 82,693
»
-11Claims.
(01.25040 ‘
This invention relates to cathode ray tubes. _ may be de?ected while of low velocity and may
_
More, particularly it relates to such tubes 01! the be accelerated after such de?ection, in order to
types commonly employed in the cathode ray secure a brilliant screen spot.
'
cscillograph.
1
‘
Yet another purpose of this invention is to
v
My invention deals particularly with means and
methods for focusing a stream of electrons upon
accelerate an electron stream whose direction of
motion is subject to de?ection, and yet have such acceleration act upon the electron stream so that
the screen of a cathode ray tube, and for de
?ecting the so-focused stream in order to trace .its initial direction of motion alter de?ection will
some particular pattern upon the screen such as not __be altered by the accelerating forces after
10
.
l0 the reproduction of an image transmitted by tele~ g‘ ward applied to the stream.
A still further object of my invention is to pro
vision,‘ or the reproduction of geometric ?gures
for purposes of electrical analysis.
vide electrostatic ?eld producing, or screening
means located between de?ecting systems, so that
the de?ecting action of the second system will be
‘
Cathode ray tubes, ‘as hitherto constructed;
have been unable to secure at the same time a
l5. high degree of sensitivity and a high velocity of
the electron stream impinging upon thescreen.
By the term “sensitivity”, I refer to the displace
ment or de?ection of the electron stream tov a
comparatively great extent, by the use of a rela
20 tively low de?ecting voltage applied to electro
static plates. The high velocityof the electron,
stream when it impinges upon the screen is de
sirable in order that a high degree of luminosity
' may be produced by such impingement.
‘Furthermore, cathode ray tubes have encoun
' tered great di?lculty because of certain irregular
_ de?ection effects-giving rise to an irregular or
distorted curve or other ?gure upon the screen.
, Such irregularities in reproduction have been
w especially harmful when it has been desired to
.
reproduce a television image.
.
_
In the type of cathode ray tube employed with
-' electrostatic“ de?ection to produce a two dimen
sional image upon the screen, ‘the distortion e1
,5 facts which have been found especially trouble
some have been the effects which gave rise to an
image of these-called keystone type. By this
substantially independent of the de?ecting action 15
of the preceding system.
-
Another purpose of this invention is to provid
means for securing in a cathode ray tube, elec
trostatic ?elds of radial nature, whereby electrons
having di?erent radial paths from a common
center will encounter an accelerating ?eld oi uni
form or ‘varying intensity but invariably directed
substantially along said radial paths, and thus
will be accelerated without change of direction.
Still another object of my invention is to‘pro
' vide a plurality of de?ecting systems acting upon
a single electron stream, where the second and
subsequent de?ecting systems are so constructed
that the electron‘ stream passing through the
complex de?ecting system will be subject to de
?ecting and/or accelerating fields of such char
acter that the angular de?ection caused by the
?rst elements of the de?ecting system will remain
unchanged despite the transverse or other de?ec
‘tion caused by later de?ecting elements.
Another object of this invention is to combine
‘ in a single cathode ray tube the qualities of high
type of distortion, is meant the lengthening of de?ectionsensitivity and high luminosity.
such an image either in its vertical or its hori
m zontal dimension, at one side only. That is to‘
A still further purpose of this invention is to
provide a cathode ray tube whose screen displays 40
a two-dimensional image, wherein the displayed
has one side lengthened with respect to the corre ~image'will be substantially free from distortion
. sponding opposite side, so that obtuse angles ap
due to the keystone e?fect.
pear on one side of the ?gure and acute angles
I have illustrated the principles involved in my
. i say, a ?gure‘ which should be truly rectangular,
‘5 on the corresponding opposite side of the ?gure.
The reasons iorthe distortion e?ects above
'
described have been obscure and not well-known 4
. in the ‘art, but I have discovered the underlying
- reasons for certain of these distortion e?ects and
go have devised an apparatus and a method oi’ oper
ating the same which will to a very great degree,
or even completely, overcome - these" distortion
eilects.
'
One purpose of my invention is to produce av
invention and certain embodiments thereof in the 45
accompanying drawing where
‘ Fig. 1 represents schematically a portion of the
interior of a cathode ray tube.
2 shows in detail a pair of accelerating
anodes as used in the system of Fig'. 1.
Fig. 3 illustrates a conventional tube system
shown in order to illustrate the keystone e?ect.
Fig.1 illustrates diagrammatically the appear
55. cathode ray tube in which the electron stream ance of images upon the screen of a cathode ray
can be subjected to the ‘action of a de?ecting ?eld tube, illustrating the production of the keystone
.
while the velocity of the stream is comparatively eii'ect.
Fig. 5 represents‘ schematically a simpli?ed
low, thus securing a high degree of sensitivity.
Another object 0! my invention is to construct form of my invention as applied to a cathode ray
I ‘
” a cathoderay tube whereby theelectron stream 7 oscillograph tube.
2 .
2,114,572
Fig. 6 illustrates diagrammatically the electro
other words, point 26 may be looked upon as the
virtual common center of origin of the variously
de?ected electron streams coming from de?ection
system I9, 20. Since plates 2| and 22 produ'ce
therebetwcen a radial ?eld centered at the point
static ?elds of the system of Fig. 5.
Fig. '7 illustrates yet another modi?cation,
wherein a special form of de?ecting plate is em
ployed.
_
e
Referring now to Fig. 1, the cathode III is
26, it will be seen that electrons entering slot 23,
' shown enclosed in a shielding element II, with
provided that they always come from a single
central source 26, will encounter between plates
2| and 22 a uniform radial ?eld of traverse, so
that the acceleration of these electrons will be 10
accomplished without any change in their direc
tion of motion due to the fact that such motion
which it cooperates to form the so—called electron
gun. Elements l2 and iii are metal plates pro—
vided with slots l4 and i5 respectively, through
which the electron stream passes in order to se
cure a proper de?nition thereof, and for other
purposes as set forth in copending application _ and such accelerating ?eld are both identical in
Serial Number 738,220 ?led August 3rd, 1934.
direction.
In this application the production of an elec
tron stream of a desired cross section, direction
of motion, and whose component electrons have
a substantially uniform velocity is disclosed, but
it is to be understood that this present invention
29 may be used in connection with any other method
of securing an electron stream having approxi
mately these characteristics. While it is desir
able that electron stream have the qualities just
described yet this present invention will func
tion, even if to a less perfect degree, upon elec
tron streams which do not possess precisely the y
qualities Just enumerated.
The electron stream emerging from the aper
30 tures ll and I5 is denoted by reference numeral
l6 and this stream then passes through an aper
ture il in an anode structure i8, which may be
iii the form of a metal plate, disc or other suit
able shape.
It can be seen that the particular system Just 16
illustrated and described is suited for acting upon
an electron stream which has motion in one di
mension ‘only.
However, unless the accelerating ?eld between
anodes 2| and 22 is made of too high a value, the 20
rays passing through slot 24 may then be further
de?ected in a dimension at right angles to the
dimension in which de?ecting system I8, 20 has
already caused them to be. de?ected. Thus. by
dividing‘ the accelerating action into two stages,
it ‘is possible to construct a cathode ray tube ac
cording to this invention, which shall be operative
to give two dimensional scanning.
It is to be understood that the principles of this,
invention are equally operative with de?ecting
elements which produce a substantially uniform
and concentrated magnetic ?eld and since the
equivalency of these two types of de?ecting struc
~At l9 and 20 I have shown two de?ecting plates ' tures is well known in the art, it is thought un
of the electrostatic type, producing a substan
necessary to explain the operation of my inven
40
tially uniform electrostatic ?eld therebetween.
Located beyond de?ecting plates l9 and 20, lies
tion in detail, when a magnetic de?ecting hold is
another anode 2| in the form of a cylindrical
My system provides a short path of traverse for
the electron stream, permitting the use of low
metal plate (see Fig. 2).
Beyond plate 2| lies still another anode 22. also
in the form of a cylindrical plate.
Plates 2|
'
velocity and yet a?ording a comparatively high 40
sensitivity of de?ection.
At the same time it
minimizes the shielding and shadowing dlf?c?ll.
slots 23 and 24 extending in a
?es which present themselves when a low velocity
electron stream has a long traverse path, or when
the path between the de?ecting system and the
screen is not free of obstructions.
Referring now to Fig. 3 I have here shown A
ection at right
‘tron stream can readily pass after being de?ected
substantially only in one direction. The electron
stream it, after passage through de?ection sys
tem I9, 20 has its direction of motion altered ac
cording to the relative electrostatic charges upon
the respective plates of this system, and I have
illustrated by means of a series of lines 25, 25 they
varied direction of motion which this stream may
de?ecting system of the conventional type em
ployed in two-dimensional cathode ray tubes. A
pair of de?ecting plates 29 and 30 de?ect the 50
stream in one dimension and as previously ex
plained this stream will seem to originate from a
assume. It is to be understood that at any one
virtual central point 3| located between these
instant, the electron stream can only occupy the
position shown by a single one of these lines.
While I have shown plates ‘19 and 20 as being
parallel it is to be understood that they may be
plates. After leaving these plates, the electron
stream then passes through another pair of plates 65
obliquely disposed, relatively to each other, as well
known in the art.
I
-
_
The anode_2l is electrically connected with the
anode I8, so'that the electron stream is not sub
I stontioily accelerated in its passage-through de
65
'
and 22 are provided respeqtivel with elongated
angle-s10 slots [4 and |5,'through which the elec
60
employed.
35
?ection system i9, 20. Anode 22 has applied to
it an accelerating potential, with respect to anode
2|, so that the electron stream which has passed
through slot 23 will be accelerated during its
passage between this slot and slot 24 in anode 22.
its well known in the art that by the proper
design of plates l9 and 20, the electron stream
which has been acted upon by these plates so as
sequentially to occupy the various lines of direc
tion, as indicated at 25, may be considered al
ways 10 emanate from _a ?xed point 25, located
in the space between these de?ecting plates. In
32 and 33 which are perpendicular to the ?rst set
and which de?ect the beam in the other dimen
sion'. If both these sets of plates are independ
ent from one another and if the relative poten
tial of each plate of a given set is simultaneously
equal in degree, but of opposite sign with'respect
to the anode of the electron system, then the two
sets of plates will theoretically function independ
ently of one another.
However, in actual practice, not only is it ex
tremely di?lcult to keep each set of plates sym
metrically charged with respect to the anode po
tential at a given instant, but also for reasons
of practical construction and for minimizing the
number of external connections necessary in a 70
tube employing'such a system, it is frequently de
sirable-to connect one de?ecting plate of each
pair directly to the anode. Under such condi
tions, I have discovered that the second de?ect
ing system not only will act to displace the elec 75
2,1357:
tron beam in the desired direction, but inaddi
tlon it will aifect the velocity of the electron
‘ stream, due to the fact that the mean instanta
neous potential or the de?ecting plates will be
?nite and either positive or negative with respect
to the potential of the anode proper, and not zero
as desired.
In Fig. 3 I have illustrated by the line 0Q the
path of a ray leaving de?ecting system 29, 30,
when the mean potential of the deflecting plates
32 and 33 is the potential of the anode proper,
i. e., when no electrical signals are being applied
to these last mentioned plates. If we now con
3
system 32, 33. This plate 50 is connected to the
anode of the system.
The shield 50 isa segment of a cylindrical sur—
face, whose center is the point 3| located in de
?ecting system 29, 30. Since the de?ected rays
leaving the plates 29, 30 are radial about point 3 i,
and since the ?eld shown by the dotted lines of
Fig. 6 is also radial, these rays will suffer no dis
placement of direction for the reasons previously
pointed out in connection with Figs. 1 and 2.
Referring now additionally to Fig. 6, I have
here illustrated by dotted lines the electrostatic
equipotential lines existing in the plane 01’ the
drawing and between the adjacent edges of the
plates of the respective de?ecting systems. It 15
will be noted that the interpositioning of plate 50
has caused the electrostatic ?eld between tne
sider that plate 33, the insulated oneo! the pair
15 of plates 32, 33, has applied to it a voltage posi
tive with respect to the anode voltage of the sys
tem, this positive voltage will cause the electron
stream to assume the position denoted by the line two sets of plates to assume a substantially radial
OR, since the ?eld thus establishedbetween plates form, thus allowing independent action or" the
29,_30, and 32, 33, gives the beam a net accelera
two sets of plates and eliminating the keystone
tion in the forward direction, whereas the beam - e?ect just described.
,
has a component of motion in two directions, due
While for purposes of clarity I have described
to its radial nature, as previously described. '
shield 50 as centered about point 3|, yet in prac~
It is' to be understood that the motion‘ of the . tice- I' have found that it often is desirable to give
stream within the rear plates is really a parabola, this element a greater degree of curvature. to ‘
although it appears a straight line, due to its
relatively slight curvature, and that the curva
ture between the rear and forward plates has been
exaggerated, in order to more clearly display the
3O principles of my invention.
This change of direction of the beam takes
place principally between the forward edges of
plates 29, 30 and the rear edges of plates 32, 33, so
that during this portion of its path of traverse,
35 the ray is curved concavely downward.
A similar analysis will show that a negative
potential applied to insulated plate of the pair
32, 33 will decelerate the electron stream with re
spect to its forward motion, so that the line OP
will represent the line of direction of the stream.
under such conditions.
-
Considering now additionally Fig. 4, the point
40 represents the center of the pattern which the
electron stream can place upon the screen. The
45 lines XX and YY represent the conventional axes
of a Cartesian system of coordinates. The lines
~4i, 42 and 43, 44 represent two lines parallel to
the X axis of this system, and manifestly in re
constructing a television image for example, it is
50 desirable that all the horizontal elements of the
picture take up positions which will correspond
to such lines, with respect to their being parallel
to the X axis. However, in the case of the sys
tem shown in Fig. 4, it will be evident that the
as line 43, 44 which should be parallel to the X axis,
compensate for any departure from the assiuned
radial path, such as may occur when the accele~
rat-ing ?eld is produced by a plane electrode.
The mode of construction shown in Fig. 5 thus
practically or completely eliminates the species
of distortion giving rise to the keystone e?ect,
since the direction of the ray is not altered when
it passes from one set of de?ecting plates to an
other.
,
I. While I have shown the pairs of de?ecting
plates of dissimilar sizes, it is to be understood
that they may be of the same size.
InFig. 7 I have shown an alternative method
of producing such a radial ?eld between de?ect
ing plates 23, 30 and a second set of de?ecting
plates 53, and 54. In this case each plate, 53
and 54. has both of its curved edges in the
shape of arcs approximately concentric with
point of ray origin 3|. Such a shape of plate
will establish a substantially radial electrostatic
?eld between the two sets of plates.
I have found, however, that a still better result
is had by making-the curved edge nearest the
point of ray origin at 3! a true circular arc cen
tering on 3 I, and by making the curved edge more 50
distant from the origin according to a curve hav
ing a smaller average curvature. The optimum
form for this more remote edge, when the plates
53 and 54 are used in conjunction with a sub
stantially planar accelerating electrode, is de
will actually take up a position corresponding to _. termined by the polar equation:
55
the line 45, 46. The reason for this displacement,
D
will be apparent when it is considered that the,
R=R°+ cos 0
electron stream at the instant it- is at the left
where R is the distance from the point 3| to the
hand end of line 45, 46, will be subjected to a de
50
celerating action of de?ecting plates 32, 33, as more remote edge of the plate. R0 is the uniform
distance
from
the
point
3|
to
the
nearer
edge
of
just described in the discussion of Fig. 3, causing
an increase in the vertical displacement of the the plate. D is the distance between the nearer
.10
-At the right hand end of line 45, 46, the elec
tron stream will be accelerated by the system 32,
33, thus causing a decrease in the net vertical
displacement of the spot. This species of dis
tortion just described is the so-calied keystone
eii'ect.
Referring now to Fig. 5 I have there shown a
radially shaped shield 50 provided with a longi:
tudinal slot 5| and located between the ?rst de
75 ?ecting system 29, 30 and the-second de?ecting
0
I and more remote edges 01' the plate in the direc
tion ‘of ‘the axis or the system, and 0 is the angle
measured from the axis of the system.
65
' This mode of constructing the de?ecting plates
is more expensive, and such plates more difficult
to correctly mount in a tube, than the simpler
form shown in Figs. 3 to 6 inclusive, but is ad
70
vantageous in certain cases.
The ?elds of force shown ‘in the various ?gures
ofrny drawing are to be understood as illustra
tive and not as mathematically exact.
While I have shown and described certain em
9,114,573‘
-
.
'irom said point of ray origin to the arc of the
segment nearer the centre, D is the minimum dis
»' bodiments of my invention, yet it is to be under
stood that this invention is not limited to the
speci?c forms herein shown, but merely to the
tance between the nearer and the more remote '
extent of the claims hereunto appended. Fur
thermore it is to be understood that many varia
tlons oi the forms here shown are possible with
arcs, and 0 is the angle measured from the ion
means for causing said cathode ray stream to
out departing from thespirit'oi this invention.
pass between said-plates, including connections
gitudinal axis of said de?ecting system, and
to sources oi’ electrical energy. .
,Iclaim:
1. In a cathode ray tube, the method of se
curing distortionless projection of an electron
7. A cathode ray de?ection and acceleration
system including means ior, generating cathode 10
stream which includes ‘generating said stream, ‘ rays, means for de?ecting said rays so that they
de?ecting said stream, and passing the-de?ected
will have substantially a unique virtual point of
origin, and means for accelerating the de?ected
stream through an electrical ?eid whose ac~
rays, said last accelerating means comprising
celerating action upon said de?ected stream is
always coincident in direction with the motion of
said stream after de?ection.
-
_
_
‘
7..
two spaced-apart cylindrical conducting sheets
having slits therein and being curved about a
-
2. A cathode ray de?ection. and acceleration
system including in the order- speci?ed, means‘
for producing an electron stream, means ior'deé
20 ?eeting said stream, and means for accelerating
the de?ected stream, said last means producing‘
a substantially radial electrostatic ?eld about the
virtual point of origin of said stream, located
within said de?ecting means.
-
3. A cathode ray tube system including a tube
25
' center substantially coincident with
unique
point oi ray origin.
8. A cathode ray tube system including cathode
ray accelerating apparatus for operation upon 20
cathode rays having a common point of virtual
origin, comprising two spaced-apart cylindrical
conducting .sheets curved about said common
point of origin of said rays and also including
means .i'or generating said cathode rays and 25
having an anode. two sets oi de?ecting plates at
bringing them to said common point 0! virtual
right angles to one another and a slitted electro-.
static shield located between said two sets of
origin..
plates and having a radius of curvature substan
means for producing an electron stream; means
for de?ecting said stream in one plane so that
said stream shall at all times have substantially
a single virtual point of origin, means for. de
.
9. 'A cathode ray de?ecting system including
30 tially about the virtual center oi ray origin lo
cated within said ?rst set of de?ecting plates,
said- shield being connected to said anode and
also including means for applying electrical
?eeting said stream in another plane and cor- ‘ ‘
rective means positioned between, said two de
4. In a cathode ray system, a tube having an ?ecting means and comprising a slitted cylin
anode and means for producing, an electron drically-shaped conducting sheet whose radius
energy to said de?ecting plates.
-
of curvature is ?nite and greater than the radius
direction about a virtual focal point or origin, ‘ oi curvature centered about said virtual point
stream, means for de?ecting said stream in one
slitted shielding means substantially concentric ' oi oncin.
.
10. A cathode ray system including means for
generating an electron stream, means receiving
said stream and de?ecting it substantially in one
direction only, and means for accelerating said
to said de?ecting means.
I
_
-'
'
stream alter it has been de?ected, said last
5. A cathode ray tube system including a tube ‘means comprising means ior producing about
having a conducting slitted shield. located be
the point of virtual origin of said stream, located
tween two mutually perpendicular de?ecting sys ‘within said de?ecting means, an electrostatic
tems, and curved about a central point substan ' ?eld substantially radial in character whose ac
tially coincident with the virtual point of cathode celerating action upon said‘ de?ected stream is
ray origin oi the ?rst de?ecting system, and substantially coincident in direction with the 60
connected to the anode of the tube-and including direction or motion. or said stream after de?ec
means for producing and'proiecting a cathode' tion, said accelerating means exerting substan
with said point or origin and connected to said
anode, means located beyond said shielding
means for de?ecting said stream in another di
rection and means for applying electrical energy
.tially no de?ecting. action upon said stream. '
11. A cathode ray system comprising means
system comprising two conducting plates closely for generating an electron stream, means for 55
adjacent to one another and-.between'which the de?ecting said stream, means for generating an
ray beam along said system of elements.
.
6. In a cathoderay tube system, a de?ecting
electrostatic ?eld exerting .a force upon the
cathode ray stream passes, said plates taking the
form substantially oi’ outer portions of segments
oi a circle whose vcenter is substantially at the
point oi virtual origin of said cathode ray. stream,
the arc oi said segment more remote from the
electron stream substantially along the direc
tion of its motion, said stream alter de?ection
passing through said ?eld, the accelerating action 60
upon the de?ected stream being such that the
direction oi’, linear motion 01 the stream upon
centre being deiined by the polar equation:
1 entering and passing through the ?eld remains
substantially the same and the projection of
H
65
r
,
I
,1 I; l, the stream-is substantially undistorted.
" "where, R is the distance from‘ the point, of ray origin to said arc,v_Ro is the unii’orm distance _
-
,l
I
.
noon 0. RESSLER.
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