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Патент USA US2109198

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Feb. 22, 1938.
Filed March 23, 1935
BY 7%. gm»
Patented Feb. 22, 1938
August Karolus, Leipzig, Germany, assignor to
Radio Corporation of America, a corporation of
Application March 23, 1935, Serial No. 12,536
In Germany March 26, 1934
5 Claims.
This invention relates to television apparatus
and to the method of transmission and recep
tion of television signaling impulses. The trans
mission apparatus herein disclosed is of a type
5 which is particularly adapted for use in conjunc
tion with the receiving apparatus shown and de
scribed in my copending application Serial No.
15,156, ?led April 8, 1935 (?led in Germany as
Serial No. K.l33,879 on April 19, 1934) although
10 it is to be understood that the disclosure is in
no way limited as to the particular form of the
cooperating receiver device.
The invention is predicated upon the suppo
sition and fact that for satisfactory television
work, the ?neness of scanning or resolution of
the picture must correspond to a ruled plate or
screen of 100 picture lines or better.
In addi
tion to developments in this direction designed
so as to ful?ll these requirements so far as the
20 equipment and the transmission methods are
concerned, i. e., of adapting ever increasing line
numbers, a, marked expansion in the transmission
range of electric telegraph channels has of late
become noticeable. It is a fact that both on ultra
25 short waves as well as on special cable lines fre
quency bands of 106 cycles may be transmitted
over satisfactory ranges of distance without the
requirements respecting the provision of ampli
(Cl. 178-71)
This invention is based upon the last mentioned
fact, and it is concerned with a television system
in which, in accordance with what precedes, the
picture modulation is conveyed from the sending
to the receiving apparatus over a single modu
lated carrier wave or over a single conductor,
Whereas at the sending or at the receiving points,
or at both places, if necessary, simultaneous
scanning and re-creation, as the case may be,
of a multiplicity or plurality of picture elements
takes place. What is thus secured, on the one
hand, is such a great Working safety and re
liability in transmission that it would be inob
tainable in paralleling several telegraphic chan
nels because of the dif?culties associated with 15
the balancing of the same.
On the other hand, because of the multiple
scanning, it will be possible to transmit scenes
and pictures of lower luminosity or with a greater
line division than has heretofore been the case,
while so far as reception is concerned, there are
available the advantages residing in greater lu
minosity of the televised picture and in ?ner
screening of the same. In fact, it is only in this
manner that in the scanning, for instance, of 25
living or moving persons the ?neness of scan
ning which is nowadays demanded becomes feas
ible at all.
It is, fundamentally speaking, known in the
art of television to subdivide the entire picture 30
?er means being unduly severe. This fact places
30 a different aspect upon the future and devel
opment of the television problem.
In the past, limitations were ‘imposed upon
every television development by the restricted
frequency transmission range of telegraphic
35 channels, and the ?neness of scanning, or in
other words, the number of picture lines, had to
be adapted to these resistance conditions. Hence,
it was not usually feasible to go beyond com
voltages generated in them is accomplished in
time sequence. However, in the arrangements
previously suggested for this purpose serious dif
?culties arise inasmuch as, without exception,
paratively coarse screens. With these coarse
40 screens it was not any too difficult to transmit
into an uninterrupted series or sequence of cur- 40
area or a single picture line so that each area is
associated with a separate photocell and then
to illuminate these cells simultaneously, while
the evaluation of the photoelectric currents or
they cause the conversion of luminous values
objects of moderate luminosity and to insure ad
rent impulses directly from the photo-elements.
equately bright received television
Inasmuch as the voltages thus becoming active
and operative, especially where the luminosity or
brightness of the picture is poor, turn out to be
extremely low, it follows that the stray or in- 45
terference level is comparatively high. On the
other hand, in case of a so-called picture mosaic,
the high frequency of line change-over presup
When the demand for substantially ?ner screens
became acute and inescapeable, it proved nec
essary in view of the unaltered or unimproved
transmission ranges of telegraphic channels to
connect a plurality of these in parallel so that a
portion or component of the picture could be
transmitted over each of these separate ~chan~
50 nels. Today, however, there are means and
ways known in the art making it possible to
transmit on a single modulated carrier wave or
poses a low coupling resistance in the input of
the modulation ampli?er and thus, so far as the 50
transmission process is concerned, an unfavorable
relationship between the useful or working am
over a single cable conductor the frequency band
of a picture divided almost into any desired ?neq
55 ness or any desired high number of lines,
plitude and the stray or interference level, not
to mention this circumstance that for arrange
ments of this sort it is, for the time being, still 55
impossible to insure adequate uniformity of pho
toelectric responsiveness throughout the whole
line sequence by simple ways and means.
The present invention has therefore as one of
its primary objects that of obviating these di?i
culties and defects by reason of the fact that the
scanning of luminous values occurring in time
sequence along a picture line composed of indi
vidual photocells is not brought about with the
may by means of subsequent ampli?cation be
raised to such amplitudes that, even in the pres
ence of lower brightness of the original picture
and or" marked irregularity of sensitiveness in
the p many scanning or pick-up photocells, very
powerful and balanced picture impulses lying
away above the stray level are obtained.
Because of the time-paralleled operation of the
29 many photelectric cells the maximum frequency
vanishingly low individual potentials of these cells
of brightness change amounts then to only 1/t, 10
themselves as is usually the custom, but rather
are brought about by an ampli?er associated with
each separate photocell so as to secure sufficient
whereas in the mode of scanning heretofore cus
tomary in the art it was p/t. As a result, it is
feasible to raise the grid resistances on which
preliminary or input ampli?cation of the signal
amplitude. In this connection, far more favor
able conditions respecting the stray or interfer
the various cells operate, seeing that because of
the reduced frequency of the photoelectric cur
rent harmful circuit capacitances no longer play
ence level as well as utilization of light are ob
the same harmful part as shunt resistances.
tainable, not to speak of the chance of equalizing
Hence, the control voltage of the photocells is
already multiplied at the input grid of the 10
many ampli?ers, though it will be raised to useful
values faithfully reproducing the brightness val
sensitivity disparities of the photoelectric cells
20 simply by adjusting the sensitiveness or response
of the various ampli?ers.
The invention has been illustrated according to
two preferred forms thereof by the accompanying
drawing wherein Fig. 1 shows one suitable ar
rangement for accomplishing the aims and ob
jects above set forth, and Fig. 2 shows a modi?ed
According to the invention, the optical trans
mitter causes the picture to be moved line by line
over a linear row of photoelectric cells extending
in the direction of the lines scanned and com
prising a plurality of constituent photocells, the
number of the latter being equal to the number
of picture elements or elementary areas contained
35 in a full line. For the purpose of considering the
method of television in this case the number of
separate points to be scanned may be denoted by
the letter in.
In order that the original picture
may be scanned or resolved in the said manner,
there is used, for instance, a projection device in
conjunction with a mirror wheel which directs
the light from each elemental strip of the sub
ject to be scanned so that all of the p many points
or “picture points” of a line are simultaneously
scanned photoelectrically with the result that 29
many current and voltage values are produced.
These current and voltage values must be evaluated and utilized for the control of the trans
mitter during the length of time t available for
scanning each picture line. For this purpose, a
high speed inertialess switch means, Within time
interval t, picks up p many different voltages (in
su?iciently ampli?ed form) and thus converts the
transmission values available in time sequence
into a series of corresponding telegraphic im
Between each photoelectric cell and the corre
sponding scanning device which may be a switch
photocell or contact of a cathode ray change-over
60 switch means or distributor, to be discussed later,
there is interposed a single-stage or multi-stage
variable tube type ampli?er having such a high
grid resistance that the time constant of the
input circuit is of the same order of magnitude
as the line duration 15. By suitable adjustment of
the gain of each ampli?er a compensation of the
sensitiveness disparities of each or" the p many
photoelectric cells is insured. This arrangement
makes it feasible to cause the photoelectric e?ect
produced from the picture point brightness, that
is the luminosity of each elementary area of the
subject, to be effective upon the various cells
throughout the duration of a line t, with the con
sequence that the picture signals or impulses,
which in themselves are several times stronger,
ues only by the variable or gain-controlled indi
vidual ampli?ers provided at points further along
in the system.
The high speed switch free from inertia which
is required both at the sending as well as at the
receiving end according to this invention, which
switch during the length of a line t picks up the
transmission values of all elementary areas con
secutively, may be of varied and different forms
of construction. At the transmitter end of the
system it is possible to cause an intense pencil
of light of constant value to pass at a suitable
rate of speed over a series of p many photoelectric
switch cells which are conjugated to the p many
scanning cells of the picture line or strip, i. e.,
the switches are suitably united with the output
ends of the ampli?ers controlled thereby so that
by becoming transmissive or conductive for cur
rent as the pencil of light impinges thereon, vol 40
ume regulated or “dosed” voltage impulses which
are proportional to the different brightness values
of the p many picture elements along the line or
strip of the picture result. These sequential con
trol impulses act through a series resistance com
mon to all of the 10 many discharge paths upon 45
the control grid of an electron tube which con—
stitutes the input of the transmitter ampli?er.
The releasing or scanning light ray pencil could
be shifted over the lines by the agency of a
mirror wheel arrangement of a kind known in the 50
earlier art.
Other ways and means of operating a system
of this type include substituting in the transmit
ter apparatus a cathode ray pencil for the light
ray pencil. This cathode ray pencil or beam, by 55
the aid of ways and means known in the prior
art, is rotationally swept over a circular sequence
or bank of circuit-making or closing contacts,
the number of these latter equally the number
p of elementary areas of the picture line. In a
fundamentally similar manner the switching ar
rangement, as hereinbefore described, causes the
conversion of the subsequently ampli?ed poten
tials simultaneously created by the luminous ac
tions in the 10 many scanning cells into a time 65
sequence of impulses to control the television
The switch action of the cathode ray pencil
and photoelectric release action could also be
combined in such a manner that the luminescence 70
produced by the influence of the impinging elec—
trons in a phosphorescent surface is caused to
act upon a bank or row of photocells disposed
opposite the said screen.
The preferable plan
is to guide the cathode ray pencil which is pref-.
erably of constant and stable intensity along a
circular path, it, of course, being the plan also
that the photoelectric cells are to be disposed
along the ensuing luminous track.
However, only a few of the conceivable and
possible ways and means adapted to insure high
speed scanning or pick-up of line values have
been mentioned in what precedes. In other
10 schemes for instance, the p many switch photo
electric cells, or the p many switch contacts of
the cathode ray tube could be replaced by p many
blocked electron tubes operated from the anode
end by the ampli?ed photocell potentials.
such a case the control grids of the electron tubes
Upon the switch photocells, in the direction of
the arrows a, b, c", d . . . r is caused to impinge
the constant light ?ux of the optical change~
over switch in such a way that the excita
tion propagating in the sense of the horizontal C1
arrow A returns cyclically at a periodicity t, that
is the length of a line of scanning. The photo
electrical discharge current impulses consecu
tively recurring at like time intervals t/p and
being of variable amplitude flow through the joint 10
resistance l5 and the return lead it, and the
drop of potential caused across the resistance 15
controls the input tube It of the ampli?er in the
transmitter (not shown).
In a modi?ed form of the arrangement shown 15
would have impressed thereon in time sequence
by Fig. 2, the switch photocells l’, 2', 3’, etc.,
brief unlocking positive voltage impulses. This
might be accomplished, for instance, by the aid
have been replaced. by the closing paths of a ro
of a surge or traveling wave whose transit time
20 along the p many control grids is equal to t,
and whose periodic production is synchronized
with the picture resolution or scanning. If the
electron tubes are equipped with two multiplica
tively acting control grids, as would be the case
with the usual form of hexode tube, then the p
many second control grids, in the presence of
constant plate potential, may be fed directly or
through ampli?ers, with the “brightness poten
tials” created by the 11: many scanning cells.
150 These will then govern the intensity prevailing at
any given instant of the plate current impulse
being ampli?ed at the same time in accordance
with the ampli?er function of the tube incidental
to the switch process, whereas the p many ?rst
tating cathode ray pencil 25, while the arrange
ment of the input of the transmitter ampli?er,
that is, the part comprising the conductor l3, 20
the resistor l5 and the tube It, has remained
unaltered. In this ?gure the numerals 9, H), ll,
52 . . . again denote the output resistances of
the amplifiers 5, 6, ‘l, 8 . . . (not again shown by
Fig. 2) across which the photoelectrically con 25
trolled brightness voltages of a line of elementary
areas or picture points result. The free ends of
the resistances are united with the 10 many elec
trodes ll, l6, l9, 29 . . . of the cathode ray tube‘
to which are coordinated p many grid-like coop
site the former. These systems act like p many
Faraday cages, the interior spaces of which are
rendered conductive sequentially by the cathode
ray pencil 25 penetrating therein. Each of these 35
grids merely ful?ll the function of opening and
closing or blocking the discharge path. All of
individual cells incidentally sets up a surge or
the discharge current surges exercise a control
ling action through a joint series resistance upon
impulse of current, the intensity of which is a
function of the fall of potential prevailing at a
the input tube of the transmitter ampli?er. The
given instant across the resistance (9, I0, ll,
40 tube arrangement as here described, however, is
erating electrodes 2!, 22, 23, 24 . . . placed oppo
52 . . .) coordinated thereto.
Having thus described the invention, what is
capable of a great many modi?cations in accord
ance with rules and laws known in the art.
The re-conversion at the receiving end of the
is the following:
sequence of impulses sent from the transmitter
end into a time parallel control of 110 many chan
translating elements positioned in line formation, 45
nels, fundamentally speaking, is accomplishable
an ampli?er system connected with each. of said
in accordance with the same scheme as at the
elements, said ampli?ers each having a time con
stant circuit associated therewith in the order
of the time duration of each scanning line, a load
circuit, and an inertialess high speed switching 50
sending end. In the receiver system a switch
pencil which is modulated in its intensity by the
electrical signals corresponds to the switch pencil
of constant intensity at the transmitter end.
Reference may now be had more speci?cally
to the forms of the invention exempli?ed and
schematically illustrated by Figs. 1 and 2 of the
drawing. Considering ?rst Fig. 1, the pick-up
photoelectric cells are indicated at l, 2, 3,
4 . . . p.
The varying light intensities of the
projected picture line or strip are caused to im
pinge on these cells in the direction of the ar
iii) rows.
The numerals 5, 6, ‘l, 8, etc., indicate the
p many separately‘ regulable ampli?ers, while
numerals 9, 10, ll, l2, etc., represent resistances
whose voltage fall is governed by the excitation
of the cells l, 2, 3, ll . . . , while additional ca
pacities, shown in dotted outline, if desired, may
be shunted in relation to these resistances 9, Hi,
. . .
In the case of Fig. 1, the assumption is made
that the high speed scanning of line values is
eiTected by the aid of light. For this purpose,
claimed and desired to secure by Letters Patent
1. In a television system, a plurality of light
device for sequentially connecting each ampli?er
with the load circuit.
2. In a television system, a plurality of light
translating elements positioned in line formation,
an ampli?er system connected with each of said 55
elements, each of said ampli?er systems having
a time constant circuit associated therewith in
the order of the time duration of each scanning
line of the subject of which an electro-optical
representation is to be produced, a load circuit, a 60
second light translating element serially con
nected with each of said ?rst-named light trans
lating elements, and an inertialess high speed
switching device for sequentially connecting each
ampli?er with the load circuit.
3. The television system claimed in claim 2
wherein said inertialess high speed switching de
the free ends of the resistances 9, 16, ll, l2 . . .
vice consists of a light ray pencil caused to sweep
across said second-named light translating ele
4. The television system claimed in claim 1,
with single-pole through-connection are united
with the p many switch photocells L8, 2’, 3',
vice consists of a cathode ray tube.
4' . . . 10' whose active cathodes are placed op
posite the anodes connected together by lead l3.
wherein said inertialess high speed switching de—
5. A television transmission system comprising
a plurality of light translating elements positioned 75
in line formation, an ampli?er system connected
with each of said elements, a time constant circuit
associated with each of said ampli?er systems
having a time constant in the order of the time
duration of each scanning line, a load circuit,
a second light translating element connected in
series with each of said amplifying devices and
the load circuit, said second-named light trans
lating elements being arranged in a closed cir
cular path, and an electronic‘ tube for sequen~
tially illuminating each of said second-named
light translating elements for connecting the
?rst-named light translating elements and the
shielded ampli?ers in sequence With the load
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