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Патент USA US2114610

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April 19, 1938.
‘
'
K. SCHLESINGE'R
2,114,610
TELEVISION TUBE
Filed July 21, 1933
7/7Ver7 for:
2,114,610
Patented Apr. 19, 1938
UNITED STA ES PATENT OFFICE
2,114,610
TELEVISION TUBE
Kurt Schlesinger, Berlin, Germany
Application July 21, 1933, Serial No. 681,466
In Germany July 25, 1932
5 Claims.
(Cl. 250—27.5)
The object of the invention is a method of pro
ducing television images of large size with cath
ode ray tubes.
It has been found that in the attempt to in
5 crease the size of a television image there is very
quickly reached with a given number of lines
per image a de?ned limit, above which the image
impression, with a given distance of the eye of
the observer, noticeably deteriorates. This mo
ment occurs when due to enlargement of the
current. The size of the image point produced
by means of a given electron-optical system is in
proportion to the surface of the cathode.
Large points with high density of ray current _
may be produced in particularly simple fashion
by the use of indirectly heated large-surface cath
odes.
According to the invention there are em
ployed for this purpose more particularly indi
rectly heated cathodes, the emissive surface of
which possesses the form of a cup, preferably
spacing between the lines this spacing between
the lines, with a given width of the recording
point, is equal to or greater than the lines them
selves.
On the other hand it is undoubtedly known that
open towards the tube space, of a suitable and
preferably not excessive diameter. The cup, for
example, may have a diameter of 1-5 millimetres,
an increase of size with a given intensity of
vision tubes having good developed electron-opti
light and size of image point always encounters
the difficulty that the surface brightness of the
image decreases. With a given size of image
20 point it is only possible to proceed beyond this
stage by increasing the intensity of the image
point, which from a technical point of view is a
dif?cult matter.
According to the invention two requirements
25 for large total intensity and good psychological
effect with a given number of lines are connected
up by means of an adapted dimensioning in such
a manner that an optimal total effect is obtained.
Brie?y the dimensioning consists in that the size
30 of the image point, with constant density of light,
i. e., with cathode ray tubes having a constant
ray current density per square millimetre, is so
selected that the lines are disposed closely to
gether. If 2 lines are present and h. is the height
35 of the usual size, the point accordingly requires
to be brought to the size
h
2
40 This value may naturally be increased to a slight
extent; an over-dimensioning of this kind, how
ever, is not essentially favourable, because assum
ing the image point is substantially square or cir
cular the maximum sharpness of the contour
45 capable of being obtained is determined by ex
actly the same size, viz., the spacing of the lines.
The measure according to the invention of em
ploying large points represents for the construc
tion of cathode ray tubes a very pleasant simpli?
cation.
It has been found that a reduction of
the image point with a pre-determined size of
the source of emission, for example the cathode
(or the intermediate diaphragm), is much more
difficult than a simultaneous increase in the size
of image point and the total strength of the ray
55
10
and be connected with a, say, loop-like heating
element, possibly by welding. When using tele- ‘
cal systems (for example, according to the United
States Patent No. 2,049,781), which enable the
emissive surface to be reproduced on the screen, it
is possible in simple fashion to provide the point
with a suitable form. ' Thus, for example, it is
o
possible in accordance with the invention to fur
nish the cup cathode with a rectangular emissive
surface (the greatest expanse of which may con~
veniently be disposed vertically to the direction
of the line), and in this manner to obtain image
points of rectangular form, which have been found
to be particularly favourable for the method ac
cording to the invention.
The invention will be more fully understood
from the appended drawing, whereof
Fig. 1 shows a Braun tube furnished with a
cathode according to the invention, while in
Fig. 2 an embodiment of the cathode is shown H
on a larger scale, and
Fig. 3 shows a line-screen according to the in
vention.
In the drawing
l is the bulb of the cathode ray tube, 2 a Weh
nelt-cylinder, 3 the cathode, 4, 5 and 6 elements
of the electron-optical system, ‘I and 8 de?ecting
means and 9 the ?uorescent screen.
In Fig. 2, 3 is the cathode body, [0 the heating
?lament, l I the preferably rectangular emis
sive body, arranged in a recess of the cathode 45
body; I2 is the preferably earthed heating line.
As is shown in Fig. 3, the width of each of the
lines I4 is equal to
11
Z
2 being the number of the lines. It is self under
stood, that practically no separating lines are to
be seen in the image.
It is particularly convenient to determine once
2
2,114,610
and for all for a, particular tube the form and size
of the image by corresponding selection of the
cathode (or an intermediate diaphragm to be
reproduced on the screen in place of the cathode)
and to dimension accordingly the means deter
mining the dimensions of the optical screen, so
that the total arrangement is adjusted to a size
of image, which may be varied only within very ,
narrow limits.
10
15
20
39
4.0'
45
50
Naturally, however, it is also possible to vary
the size of the image point in other fashion, and
trol the intensity of the electron emission from
said area, a picture receiving screen, de?ecting
means ior producing on said picture receiving
screen a line screen having the height of h units
and comprising z lines, said de?ecting means
comprising means to de?ect the cathode ray
in regular periods in the direction in which the
height of the line screen is taken, said de?ecting
means further ‘comprising means to de?ect the
cathode ray in periods of 2/2 the length of the 10
first mentioned periods in a direction perpendic
to alter the strength of the ray current accord- _ ular to the ?rst mentioned direction, and an
ingly, so that the tube supplies image points of electron optical system acting on the lines of an
different size but constant or practically con
optical lens for reproducing said area on said
stant surface intensity. Tubes of this nature fluorescent screen for producing a light spot hav
may readily be employed for the production of ing a heightrof h/z units taken in the same direc
images of desired size. The adjustment of the tion in which the height of the line screen is
size of the image point may be performed--par
taken.
ticularly in the case of high-vacuum tubes-by
3. A high vacuum electron discharge tube com
suitable adjustment of the electron-optical sys
prising an indirectly heated cathode furnished 20
tem (displacement of the focal point in such with an emissive area having the shape of the
fashion that the same falls in front of or be
light spot to be reproduced, means to control
hind the image screen). The adjustment of the the intensity of the electron emission from said
strength of the ray current may be e?ected, for
area, a picture receiving screen, de?ecting means
example, by the application of a suitable con
for producing on said picture receiving screen
stant grid bias to the intensity control grid of a line screen having the height of h units and‘
the tube.
comprising 2 lines, said de?ecting means com.
The formation and dimensioning of the image prising means to de?ect the cathode ray in reg
point in accordance with the invention is of par
ular periods in the direction in which the height
ticular importance in connection with a size of
of the line screen is taken, said de?ecting means 3 O
image of more than approximately 3 x 4 cm. By further comprising means to de?ect the cathode
using the method according to the invention it ray in periods of 1/2 the length of the ?rst men
is possible, even when employing relatively small tioned periods in a direction perpendicular to the
numbers of image points, to produce images of ?rst mentioned direction, and an electron optical
large size, which have a considerable strength of system acting on the. lines of an optical lens
light and are well recognizable even at a con
for reproducing said area on said ?uorescent
siderable distance without auxiliary measures of screen sfor producing a light spot having a height
any kind, such as projection or the like, and of 11/2 units taken in the same direction ‘in which
reveal the maximum sharpness of image which the height of the line screen is taken.
is capable of being obtained with the particular
4. In a cathode ray tube more particularly for .40
number of image points concerned.
television purposes comprising a picture receiv
. I claim:
ing screen: the combination comprising an in
1. A high vacuum electron discharge tube com
directly heated cathode having in its surface fac
prising a thermionic cathode, a control electrode ing said picture receiving surface a recess and
surrounding said cathode for controlling the in
an emissive substance in said recess, and means .7.
tensity of the electron emission from said cath
for electron-optically reproducing the area of said
ode, an image receiving screen, an electrostatical electron emissive substance on said picture re
electron-optical system acting on the lines of an
ceiving surface.
7
optical lens, said electron-optical system being
5. In a cathode ray tube more particularly for
arranged between said cathode and said screen, television purposes comprising a picture receiv
an electrode having an opening of non-circular ing screen: the combination comprising an in
shape interposed between said cathode and said
electron-optical system, said electron-optical sys
directly heated cathode having in its surface at
the side thereof facing said picture receivingsur—
tem reproducing on said screen said non-circular
55 opening for producing an image point, and means
face a recess and anelectron-emissive substance
in said recess, the area of said emissive sub
for de?ecting said image point in two directions
perpendicular to each other for scanning said
stance being of non-circular shape, and means
electron-optically reproducing the area of said
screen.
electron emissive substance on said picture re
2. A high vacuum electron discharge tube com
rising an electron emissive area having the shape
of the light spot to be reproduced, means to con
ceiving surface to produce a non-circular image,
spot on said picture receiving surface.
60
KURT SCHLESINGER.
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