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Патент USA US2404173

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July 16, 1946.
J. A. HANSEN
2,404,173
,
TELEVISION SIGNAL GENERATOR
Filed July‘ 5, 1941
VIDEO
FREQUENCY
AMPLIFIER
TELEVISION
TRANSMITTING
APPARATUS
0..
VIVS\NA L
v
I?
<5
523
FIELD
SCANNING
GENERATOR
TIMING
GENERATOR
GENERATOR
'
INVENTOR
JOHN A. HANSEN
BY
ATTORNEY
I;
of
Patented July 16, 1946’
2,404,173 ;
UNITED‘ STATES PATEN '1" OFFICE
.
2,404,173
, TELEVISION SIGNAL GENERATOR
John A. Hansen, Bayside, N. Y., 'assignor, by'mesn'e
assignments, to Hazeltine Research, Inc., Chi
cago, 111., a corporation of Illinois
Application July 5, 1941, Serial No.‘401,'080
8 Claims.
1
(C1. 178-172)
This invention relates to television signal gen
erators and, particularly, to television signal gen
craters of the type including a cathode-ray tele
vision signal-generating'tube.
-
The operating characteristics of television
signal generators of the type which includes
a cathode-ray signal-generating tube vary
rather critically with the value
of the tube
2
pl’itude of. these spurious pulses varies with the
magnitude of the beam current of the tube and
that a suitable control effect can be derived
therefrom to control the beam current in the de
' sired manner mentioned above.
It is an object of the present invention, there
fore, to provide an improved television signal gen
erator vof the type including a cathode-ray sig
beam current. Speci?cally, the shading e?ect
nal-generating tube which is not subject to one
characteristic of tubes of ‘this type and the 10 or more of the above-mentioned disadvantages
sensitivity of such a, signal-generating tube
of television signal generators of the prior art.
vary with variations of the beam current of
It is another object of the invention to provide
the tube. Many factors, such as a variation
an improved television signal generator includ
of the unidirectionalv supply potential, changes
ing acathode-raysi‘gnal-generating tube in which
in temperature, etc., may cause. the beam ‘cur-' 15 the beam current of th'etube-is maintained sub
rent of the‘ tube to vary. In‘. a conventional
television transmitter which includes a tube of
stantially constant'during trace scanning periods
the type under consideration; it ‘is customary to
In ‘accordance with the invention, a television‘
signal generator comprises a cathode-ray tele
provide a manual control for the beam current ’
of the signal generator.
'
of the signal-generating tube and it. is necessary 20 visiorr signal-generating tube including a source
for the operator to vary the adjustment from
of beam current and a beam-control electrode
time-to-time to maintain a value of beam current
and means for‘ deriving. a signal output from the
which provides most satisfactory operation.
tube which includes video-frequency television
Since the value of beam current for optimum
signal components and spurious periodic pulses
sensitivity does not usually correspond to that
of larger amplitudethan the television signal
giving minimum shading effect-sin practice, it is
components, which pulses vary in amplitude with
customary to adjust the beam. current to that
variations. of. the beam current. The signal gen~
value which provides a reasonable compromise
erator of the invention also comprises means re‘
between the shading e?ectfln the signaioutput
sponsivev primarily to the periodic pulsesfor de
and maximum sensitivity. However; in some 30' riving a unidirectional control effect and means
television signal transmitter installations it is
for utilizing .the control effect to maintain the‘
necessary to leave the transmitters unattended.
beam. current of the signal-generating tubesub
It is particularly desirable, therefore, to provide
stantiallyv constant during trace periods of the
an arrangement for automatically maintaining
signal generator.‘
I
a predetermined optimum'value of beam current
For a better. understanding of the invention,
in a cathode -ray television ‘signal-generating tube
together with otherwand further objects thereof,
independent of variations in operating conditions.
reference is had- to the following description.
It is well known that the output signal of a
taken ‘in connection with the accompanying draw~>
television signal-generating tube vof the type un—
ing and. its scope will be pointed out in the ap
der consideration includes spurious pulses which 40 pended claims.
are generated due to any sudden changes in the
' The single ‘?gure of‘ the drawing is a schematic
beam current, which changes may be caused, for
diagram. of a complete television transmitting
example, by spot-translation velocity changes or
by the fact that the beamtravels from the pho'-“
tosensitive target to the nonphotosensitive mar
gin or backing plate‘ of the target‘, as weilas the
desired video-frequency television signal. com
ponents developed by light from the object't'o be,
televised and incident on the photosensitive ele
ments of the mosaic. The spurious pulses in't'hev
output signal of the tube have an amplitude which
is many times that of the desired video-frequency‘
television signal components and frequencies cor~
responding to the line-scanning and ?eld-scam
ning frequencies. It has been found-that. the am 55 >
. system including a television signal generator in
accordance with the invention.
.
Referring now more particularly to the draw
ing, the television transmitting system repre
sented. includes a‘ conventional camera or pro
jector 1'0" and a cathode-ray tube II. This tube
comprises ‘an elongated envelope l2 including a
cylindrical end portion or neck and an enlarged
end portion. ’ In the neck of the tube l I there are
disposed a source of beam current such as a cath
ode IS,‘ a beam-control electrode I 6, a ?rst anode
H, a second anode“! and a collector electrode
“3a. in‘ the order named, these electrodes c0n~
2,404,173
3
,
.
l,
: '
.
‘1
‘J- \
Ti
4
I ~
. antenna system 32, 33 in a conventional manner.
; stituting what is conventionally referred to in l
Line-synchronizing pulses and ?eld-synchroniz
I‘ the art as an electron gun. The collector anode
18a preferably comprises a metallic ?lm or coat
ing pulses developed in timinggenerator 23 and
applied to transmitting apparatus 3|’ are also
modulated upon the. carrier signal for transla
tion with the video-frequency signal generated
‘ ing on the inner ‘surface of the envelope l2; as
5 shown. A photosensitive target I9 is disposed in
i the enlarged end portion of, the tube. The target
in tube ||.
'
»
may be constructed in a conventional manner and
' i ,Co'ming now'tq-the portion of the system con
_ ‘ include athin sheet .of dielectricirnaterial‘, such‘. i
stitutin'g the- present invention-‘,iin order to derive
as mica, having atransparent metallic coatin'g'ror'i '
signal :plate facing the camera Ill, and a photo
. ~
10 a normal operating bias 'for signal-generating
sensitive mosaic front surface of suitable ma-fi ' tube H, there is provided a duplex recti?er 39
including cathode 40 and anode 4| for rectifying
a'signal ‘output ‘from line-scanning ‘generator 2|.
l-terial, such as a silver-caesium-oxygen mixture ‘
Q‘ or compound, thereby providing, in effect, a mull"
The signal input for diode 4|], 4| derived from
titude. of minute“"éondensers,having the signal _. _
plate as a common electrode. Suitable operating ‘1.5". line-scanning generator 2| is' applied thereto
throughrcondenserllt and load resistors 43 and
potentials are supplied to the several electrodes ‘
of tube H from a source of-unidirectional oper
--44 connected in. series. Resistor 44 is by-passed
" by a condenser 45 while resistors 43 and 44 in.
series are by-passed by a condenser 38. The di
the drawing a line-scanning generator 2| and 20 rect current path for diode 4|), 4| is completed
by means of a resistor 46 connected between cath
a ?eld-scanning generator 22 which are timed by
ating potential, such' as a battery '20; '
‘ "
" ‘
There are also provided'i'n the transmitter‘. of ‘
ode 40 and ground. The voltage developed across
resistor 44 is applied as an operating bias to the
control electrode I6 of tube I! through a resistor
l a timing generator 23 and whichhave their out
put circuits connected to de?ecting plates 25 and
25hr tube II, respectively. "The output circuit
'
of tube || include'sa load resistor28 connected 25 Hand .a resistor 48 in series.
In order to, derive a control e?ect which varies
to. the signal plate of target .|9 through'a cou
primarily with the spurious periodic pulses gen
pling condenser j29 and to a conventional video-n
erated inv tube ||,Itube 39 includes a diode 50, 5|
frequency ampli?er 3B’ of one or, more stages,‘
coupledrto the output circuit of video-frequency
which, in turn, is coupled to a conventional tele
ampli?er 3|! through‘ av coupling condenser 52, a
' vision ‘transmitting apparatus, indicated gen
erally at 3|, andterminated in an antenna sys
condenser 53 coupled in‘ parallel with resistor 41,.
chronizingr signals‘ are also applied from timing
vided for diode 50, 5| which includes resistor 41
and a resistor 55; the. inclusion of resistor 41. in
and a condenser 54., A direct current path is pro
tern33, 33. Line-synchronizing and'?eld-syn
generator 237 to the television transmitting ,appag
ratus 3| for transmission with,_the video-free
, the. load circuit of diode 50, 5|.provides a means
for utilizing the control effect derived from diode
so, 5| to maintainithe beam currentof'tube ||
substantially constant during .Ytrace periods of
quency :signalgenerated intube |,|._. Y ‘
The apparatus just describedjn general, rep
resents _a conventional television transmitting
systemrand, the'construction and operation of
such apparatus, being well known in the .art, _a
detailed description thereof is unnecessary here:
the signal-generating tube ll.
40,
in., In brief,’ however,’ inrthe operation, of. the
‘
apparatus described,.imagesjof ,theisceneto'be;
transmittedare projected by the camera It on.
.
,
In ordertocutoff the beam current of tube
H, during ?eld-retrace scanning periods, periodic, .‘
pulses are derived/from ?eld-scanning generator
2.2 and. applied through a condenser 51 to beam-V,
control-electrode
|6.‘_
.
.
.
,
I‘
the mosaic surface of target T|9 effectingphotoj-z 4.5.; .In consideringthe operation of the circuit just
emission by ‘the various mosaic elements in 3.01‘,
cordanoe. withthe light intensity at. theVcorre
spending elements of the, image'being transmit-:
ted; __Electrons are generated, vaccelerated/and
developed into abeam bythe electron gun come‘;
prising elements |5-+-| 8, inclusive, the beam being‘,
focused on the target l9 and causingsecondarye.
electron emission byv the elementary mosaic ele-.
described, it wilLbeseen. that an output from
lineescanning.generatorll’ is recti?ed by diode >
4.8, 4| to provide across the load circuit thereof ‘
includingresistors 43, '44, a sourceof unidirec
tional voltage which is negative. with respect to
ground. The :portion of this voltage across resis
tor.44.is applied through resistor 41 and isolating
resistor48, tothe- beam-control electrode l6 of
tube. »| Lto provide a. suitable normal negative op
ments of a value varying in accordance .withits.
potential as determined byits photoemission dur 55: erating bias for the. beam-control electrode l6 of
the tube. However, this bias voltage is substan
ing the preceding scanning. cycle. Potentials of
tially, constant and, unless other precautions were
saw-tooth wave form, generated by the.genera-.
taken, thebeam current of tube || would. vary
tors 2| and 22, are applied to the scanning plates
with variations. in operating conditions, as. de
25 and 26, respectively, thereby producing electro-.
static ?elds which de?ect the beam in two direc-j 60 scribed above, thereby necessitating a manual
adjustment ..of1the beamcurrent to an optimum
tions'normal to each other, causing it to ,scan‘
valuesuch that satisfactory sensitivity and min
‘?elds or series of parallel lines on'the targetQin
imum. shading characteristics areimparted to
the usual manner. , The secondary. electrons
which are emitted from the mosaic elements are
the
tube,.||.
..
‘
_.
I.
.
'
L
;
collected by the collector electrode |Ba.v Voltages 65 ~ Inasmuch as .the signal output from tube | I
which is. amplified by ‘video-frequency ampli?er‘
are thereby developed at the backing plate ‘of
3|!- includes, .in addition to, the‘. desired video-fre
quency television components, spurious periodic
signals. of. larger amplitude than the television
resistor 28, a video-frequency voltage which varies.
with variations in light and shade in the succes-g -7-0 signal.;components, as mentioned abovewhich
spurious signals vary in amplitudeywith variations
sive incremental areas of the scene to be trans:
of the beam current of the tube, these spurious
mitted. This video-frequency voltage is ampliy.
?edin the video-frequencyvampli?er 3iirand is. pulses can beutilized to control the beam current
utilized in the transmitting apparatus 3| tomod-H of tube |l_ to; maintain it at‘ any preselectedop
target 19 which,’ in turn, cause to be developed
in'the output circuit of tube H, which includes
ulate, a carrierwave. fvhieh is broadcast iron; the‘ 75
tirnum operating value. __ The. circuit 4]., 5.3. of .
2,404,173"
5
>
,6
recti?er 50, 5| is given such a time constant that
and modi?cations as fall within-the true spirit
it operates as a peak recti?er for developing in
the load circuit 41, 55 a voltage or control effect
and scope of the invention.
What is claimed is:
1. A‘television signalgenerator comprising, a
which varies with the peak value of these spurious
pulses and, inasmuch as'the resistor 41' is in
cathode-ray television signal-generating tube in‘ >
cluding a source of beam current and arbeam- v
eluded in series in the'grid-cathode path of tube ~
II, the portion of this voltage developed across
control electrode, means for deriving a’ signal
resistor 4'! serves to control the beam‘ current
output from saidv tube including video-frequency‘
of tube H. By proper selection of circuit con-v
television signal components and. spurious peri
stants, this control voltage may be made effective 10 odic pulses of larger amplitude than said televi
to maintain the beam current substantially con
sion signal components which pulses vary in am
stant during trace periods of tube lil. rlJhe time
plitude with variations of said beam current,
constant of the circuit is preferably not apprea
means responsive primarily to said periodic pulses
ciably shorter than the ?eld-scanning period of
for deriving a unidirectional control effect, and
the systemand may be, for example, only slightly 15 means for utilizing said control effect to main
greater than the ?eld period;
tainr'sa'id beam current substantially constant dur
ing' trace periods of said signal generator.
' The pulses derived from ?eld-scanning genera
tor-2,2 and applied through condenser 5'! to the
2. A television signal generator comprising, a
cathode-ray television signal-generating tube in
beam-control electrode l6 serve to cut off the
beam current during the ?eld-retrace periods, in 20 cluding a source of beam current and a beam
a manner which is well understood by those
skilled in the, art, to avoid the appearance of
control electrode, means for deriving a signal
output from said tube including video-frequency
spurious lines in they reproduced image. If the
television signal components and spurious peri
tube beam current is not cut oil during ?eld~
odic pulses of larger amplitude than said televi
retrace periods the charge pat-tern on the mosaic 25 sion signal components which pulses vary in am
is ‘disturbed in such fashion that a record of the
plitude with variations of said beam current, a
spot path during retrace remains on the mosaic
recti?er responsive primarily to said periodic
for some portion of the ensuing traceperiod.
pulses for deriving a control potential, and means
During the ensuing trace period this disturbed
for utilizing said control potential to maintain
said beam current substantially constant. during
condition of the mosaic is translated into a nor
mal television signal which is then reproduced
by the picture of the system. It will be under
' trace periods of said signal generator.
3. A television signal generator comprising, a
stood that this feature of the circuit can be
omitted, if desired.
While applicant doesnot intend to be limited
to any particular circuit design, there follows a
tabulation of design information which has been
cathode-ray television signal-generating tube in- ‘
cluding a source of beam current and a beam
35
television signal components and spurious peri
odic pulses of larger amplitude than said televi
sion signal components which pulses vary in am
plitude with variations of said beam current, a
peak recti?er responsive primarily to said peri
odic pulses for deriving a control potential, and
found to be particularly useful in practicing the
invention:
Tube ll __________________________ __ Type 1847
Tube 39 __________________________ __ Type 6H6
Resistor l3 _________________ __megohms__
Resistor 28 _____________________ __do_____
Resistor 43 ___________________ __kilohms__
Resistor 44 _________________ __megohms__
10
2.2
100
means for utilizing said control potential to main
tain said beam current substantially constant dur
ing trace periods of said signal generator.
1.5 45
4. A television signal generator comprising, a
Resistor 46 ___________________ __kilohms__
Resistor 41 __________________ __megohm__
Resistor 48 _____________________ __do____
250
1
1
Resistor 55 ___________________ _gkilohms"
220
Condenser
Condenser
Condenser
Condenser
Condenser
Condenser
250 50
29
38
42
45
52
53
control electrode, means for deriving a signal
output from said tube including video-frequency
cathode-ray television signal-generating tube in
cluding a source of beam current and a beam
control electrode, means for deriving a signal
output from said tube including video-frequency
television signal components and blacker-than
black spurious periodic pulses of larger amplitude
than said television signal components which
pulses vary in amplitude with variations of said
beam current, a peak recti?er responsive
primarily to said periodic pulses for deriving a
unidirectional control potential, and means for
"utilizing said control potential to maintain said
beam current substantially constant during trace
______ __micro-microfarads__
_____________ __microfarad__ 0.01
______ __micro-microfarads__
500
_____________ __microfarad__
0.1
_________________ __do__‘____ 0.002
_________________ __do______
0.1 55
Condenser 54 _________________ __do ____ __
0.25
Condenser 51 ______ __micro-microfarads__
500
Line-scanning frequency _______________ __
Field-scanning frequency ______________ __
2000
10
It will be understood that an average recti?er
can be used in place of the peak recti?er 50, 5|
and that, if a peak recti?er is used, it can be
60 periods of said signal generator.
4
5. A television signal generator comprising, a
cathode-ray television signal-generating tube in
cluding a source of beam current and a beam
caused to be responsive to the peaks of the signal
control electrode, a ?eld-scanning means for said
of either polarity although the recti?er is pref 65 signal-generating tube, means for deriving a sig
erably made to be responsive to peaks of the sig
nal output from said tube including video
nals which correspond to light values which are
frequency television signal components and
blacker than black.
spurious periodic pulses of larger amplitude than
While there has been described what is at
said television signal components which pulses
present considered to be the preferred embodi 70 vary in amplitude’ with variations of said beam
ment of this invention, it will be obvious to those
current, means responsive primarily to said
skilled in the art that various changes and modi
periodic pulses for deriving a unidirectional con
?cations may be made therein without departing
trol effect and including means for eliminating
from the invention, and it is, therefore, aimed
variations in said control effect at the frequency
in the appended claims to cover all such changes 75 of said ?eld-scanning means, and means for
2,404,173
7
‘ utilizing said control e?ect to maintain said beam
current substantially constant during trace
1 periods of said signal generator.
6. A television signal generator comprising, a
cathode-ray television signal-generating tube in
cluding a source of beam current and a beam
control electrode, a ?eld-scanning means for said
3 signal-generating tube; means for deriving a sig
nal output , from
said
tube
including video
'frequency television signal ''components- and
spurious periodic pulses of larger amplitude than
3 said television signal components which pulses
vary in amplitude with variations of said beam
current, means responsive primarily to said
periodic pulses for deriving a unidirectional con
trol e?ect and including a recti?er and a load
circuit having a time constant not appreciably 1
shorter than the period ‘of said ?eld-scanning‘
means for eliminating variations in said control
e?ect, and means for utilizing said'control effect
to maintain said beam current substantially con
8
spurious periodic pulses of larger amplitudethan
saidrtelevision signal components which pulses
‘vary in amplitude with variations of said beam
current; means responsive primarily to said
periodic pulses for deriving a unidirectional con
trol potentiaLand means for applying said con
trol potential to said electrode in series with said
bias potential to maintain said beam current sub
stantially constant during trace periods of said
signal generator.
"
8. A television signal generator comprising, a
cathode-ray television signal-generating tube in
cluding a source of beam current and a beam-,
control electrode, a ?eld-scanning generator for
said tube, means for deriving a signal output from
said tube including video-frequency television sig
nal components and spurious periodic pulsesof
larger amplitude than said television signal com
ponents which pulses vary in amplitude jwith
variations of said beam current, means responsive
primarily to said periodic pulses for deriving a
unidirectional control e?ect, means for utilizing
stant during trace periods of said signal genera
said control effect to maintain said beam current
tor.
‘
substantially constant during trace periods of said
,7. A television signal generator comprising, a
cathode-ray signal-generating tube including a 25 signal generator, and means for deriving blocking
pulses from said ?eld-scanning generator and
source of beam currentand a beam-control elec
applying them to said beam-control electrode to
' trode, means for applying a unidirectional op
cut off the beam current of said tube during ?eld;
erating bias potential to said electrode, means for
retrace periods of said scanning generator.
deriving a signal output from said tube including
' video-frequency television signal components and 30
JOHN A. HANSEN.
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