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Патент USA US2133422

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0a. 18, 1938.
‘c, o. BROWNE
' '
2,133,422
TELEVISION AND THE LIKE SYSTEM
Filed Feb. 14, 1934
.?'y.1
114g. 5
W
z
INVENTOR
CECIL o. B
WNE
BYI7KZML
ATTODNITV
2,133,422
Patented Oct. 18, 1938 '
UNITED STATES PATENT OFFICE
2,133,422
TELEVISION AND THE LIKE SYSTEM
Cecil Oswald Browne, West Acton, London, Eng
land, assignor to Electric and Musical Indus
tries Limited, Hayes, England, a company of
Great Britain
Application February 14, 1934, Serial No. 711,083
'
In Great Britain February 15, 1933
(Cl. 178--69.5)
The scanning of the motion picture ?lm (which
The present invention relates to television and
12 Claims.
is not illustrated) may be carried out in any of
the like systems.
It is well known in television, picture transmis
i)
sion and the like, to scan the object to be trans
mitted in a series of parallel lines and to arrange
that there occurs, between the scanning of suc
cessive lines, a short interval during which syn
chronizing signals are transmitted. Thus the
transmitted signals comprise trains of picture
'10
signals separated by synchronizing signals.
The synchronizing signals are utilized at the
receiver to maintain a scanning device in syn
chronism with that at the trasmitter.
It has been found that a difficulty arises in
15 certain systems of this kind, in that the syn
chronizing signals tend to be delayed in relation
to the picture signals and the synchronizing sig
nals may therefore arrive at the receiver scan
ning device during the reproduction of the pic
.20 ture signals instead of in intervals between the
picture signals. To avoid this it has been nec
essary either to increase the interval between
the scanning of successive lines or else to mask
o? a part of the reproduced picture.
It is an object of the present invention to re
25
move or reduce this difficulty.
It is a further object of the present invention
to provide a method of transmitting and receiv
ing images of objects wherein there are gener
30 ated at a transmitter synchronizing signals and
trains of picture signals having intervals between
successive trains, each synchronizing signal be
ing transmitted simultaneously with a train of
picture signals and means being provided in the
35 transmission channel for delaying or advancing
the synchronizing signals relative to the picture
signals.
'
-
The invention will now be described,‘ by way of
example, as applied to a ?lm television system,
40 reference being made to the accompanying draw
ing in which
Fig. 1 shows .the wave form of signals trans-1
mitted in a known form of television system,
Fig. 2 shows the wave form. of signals trans
mitted in accordance with one form of the pres
ent invention,
Fig. 3 illustrates, in greater detail, a portion of
the curve shown in Fig. 2,
’
‘Fig. 4 is a circuit diagram of television trans
50
mitting apparatus arranged and adapted to op
erate in accordance with the present invention,
and
Fig. 5 is a circuit diagramof television receiv
ing apparatus adapted to receive the signals
55 transmitted by means of the apparatus of Fig. 4,
.the known ways, but preferably the ?lm is moved
vertically downward at a uniform speed past a
horizontal illuminated slit. An image of the
'strip of the ?lm at any instant illuminated is
swept, by one of a number of mirrors carried
on a rotating mirror drum, over an apertured
photo-electric cell, thereby scanning this strip
or line and generating in the cell picture signals 10
corresponding to the light and shade of the line
scanned. The drum is rotated about a vertical
axis and all the mirrors lie in planes parallel to
this axis. The arrangement is such that, after
one mirror has swept its image over the cell ap 15
erture, a short interval occurs before the next
mirror commences to sweep an image over the
cell.
In this manner there are generated in the
photo-cell a series of trains of picture signals of 20
the kind illustrated in Fig. 1.
During the scanning of each strip of the ?lm,
the mirror which is performing the scanning
function also sweeps an image of a second il
luminated slit over a second apertured photo 25
electric cell thereby generating in this cell an
electrical pulse known as a line pulse. The dura
tion of this line pulse is made approximately
equal to or less than the interval between suc
cessive trains of picture signals, that is to say, 30
less than the interval l shown in Fig. 1.
In a manner which will be described later
each line synchronizing pulse is converted into
a symmetrical train of pulses and superimposed
upon the picture signals as shown in Figs. 2 35
and 3.
‘
When one complete frame of the ?lm has been
scanned in this way, a rotating shutter becomes
operative to intercept thev light from the two
slits above referred to for a time about equal to 40
that required for the scanning. of ?ve lines.
Slightly before this time, during the scanning of
the ?lm image, a member rotating with the shut
ter uncovers a third illuminated aperture 01‘ slit
and allows light therefrom to fall upon a third 45
photo-electric cell generating in this cell what
is called a frame synchronizing pulse. The du
ration of the frame pulse is made approximately
‘equal toy or less than the time during which the
shutter is operative.
~
50
Both the line and frame pulses are converted
in any convenient way, one of which will be de
scribed later, into trains of oscillations at a sub
carrier frequency, ‘that is to say at a frequency
lower than that of the carrier on which the trans 55
2
2,133,422 I
mission is to be effected and‘ higher than the
highest frequency of importance in the picture
signals.
The duration of these trains are equal
to the durations of the line and frame pulses
respectively from which they are derived.
Referring now to Fig. 4, the trains of picture
26 from valve I2 consist of symmetrical trains of
sub-carrier frequency.
' In a similar manner the frame pulses applied
to the transformer 6 operate to raise the poten
tial of the grid of valve 2| above its normal neg
ative value so that current ?ows in the anode
signals, of the wave form illustrated in Fig. 1, circuit, whilst the sub-carrier oscillations ap
are ampli?ed in the thermionic valve 2, the pulses plied to transformer 8 have the effectof chop
generated at the line frequency are applied, as ping this current at sub-carrier frequency. The
10 indicated by the arrow 3, across the primary
frame pulse components are not removed, how
winding of the transformer 4 and the longer ' ever, since they serve a useful purpose at the
pulses generated at the frame frequency are ap
receiver which will be described later.
plied, as indicated by the arrow 5, to the pri
The parallel tuned circuit I4 is tuned to th
mary winding of the transformer 6. An oscillator sub-carrier frequency and is designed to have a
15 of any known or suitable hind, adapted to oscil
high impedance at this frequency relative to 15
late at the sub-carrier frequency is connected, that of the circuit 21 and resistance I5 so that
as indicated by the arrow ‘I, across the primary all components of sub-carrier frequency are re
winding of the transformer 8.
moved from the picture signals. The output of
The secondary winding of the transformer 4 is valve 26 for about three lines of the picture
connec‘ ed across a potentiometer resistance 3, a
scanned is thus somewhat as shown in Figs. 2 20
suitable portion of this resistance, that between
and 3.
‘
the sliding contact I0 and the point I I, being con
The arrangement may also be considered in
the following light.
nected in the grid-?lament circuit of a ther
mionic valve I2. The anode of valve I2 is com I
The valve 2 operates as a generator connected
25
nec‘ed, through resistance I3, the parallel tuned
circuit I4 and resistance I5, to the positive ter
minal of a source of current (not shown) the
negative terminal of this source being earthed.
Grid bias for the valve I2 is supplied by the
30
across a ?rst impedance I5 and either of valves 25
I2 or 2| operates as a generator connected across
impedances I4 and I5 in series, whilst an imped
ance 21 is connected in shunt with impedances
I4 and I5. Because at the sub-carrier frequency,
the impedance I4 is high compared to that of 30
shunt with the anode-?lament path of the valve ' either of impedances I5 and 21, the trains of sub
carrier frequency supplied to the grid of valve
I2 is a condenser I8 in series with an induct
battery I6 shunted by the condenser II.
In
ance I9.
The (secondary winding of the transformer 6
26 by valve I2 or 2I are ampli?ed and the com
ponents of sub-carrier frequency in the picture
35 is connected across a potentiometer resistance 2|]
a suitable portion of which is connected in the
signal are removed.
Referring now to Fig. 5, which illustrates ap
grid-?lament circuit of a thermionic valve 2|.
The anode of valve 2| is connected through cir
cuit I4 and resistance I5 to the positive side of a
40 source of current and grid bias for valve 2| is
supplied by battery 22 in shunt with which is a
condenser 23.
The filaments of the valves I2 and 2| are
paratus adapted to receive the signals trans
earthed as also is one end of the secondary wind
45 ing of transformer 3, the other end of this wind
ing being connected to points II and 24, so that
the secondary winding of transformer 8 is con
nected in the grid-?lament circuits of both of
valves I2 and 2|.
The anode of valve 2| is connected through
50
35
mitted with the aid of the apparatus of Fig. 3
and to reconstitute images of the transmitted
pictures upon a cathode ray tube, the composite 40
signal is applied, after detection and, if neces
sary, ampli?cation, to the grid-?lament circuit
of a thermionic valve 30. The anode of the
valve 30 is connected, through a resistance 3| to
the positive terminal of a source of current (not 45
shown) and the ?lament is earthed. In par
allel with the anode-?lament path of the valve
are connected in series, a condenser 32, a par
allel tuned circuit 33 tuned to the sub-carrier
frequency and circuit 34 consisting of a con 50
condenser 25 to the grid of a third thermionic denser and resistance in parallel.
The cathode of the cathode ray tube (not
valve 26, the output of which forms the com
shown) is earthed and the grid or modulator
mencement of the transmission channel. Cir
cuit 21 comprises a grid leak 28 for valve 26, and ’ electrode of the tube is connected to a point 35
between .the circuits 33 and 34. The circuits 33 55
a condenser 29 shown in dotted lines which rep
and 34 form two arms of a bridge, the other two
resents the'stray capacity of valve 26.
The operation of the arrangement is as fol— arms of which are constituted by a resistance 36
and a parallel tuned circuit 31 tuned to the sub
lows:
The valves I2 and 2| are biased negatively to carrier frequency.
The impedances of circuits 33 and 31, at the
60 such an extent that in the absence of line and
sub-carrier frequency, are high compared to
frame synchronizing pulses respectively, no cur
those of the resistance 36 and circuit 31 so that
rents flow in these valves. When a line synchro
nizing pulse is applied to the "primary winding
of transformer 4 the potential of the grid of valve
65 I2 is raised ‘positively with respect to the ?la
ment until current ?ows in the anode circuit;
on account of the oscillations of sub-carrier fre
quency applied to transformer 8, however, a
train of signals of sub-carrier frequency ?ows
70 in the anode circuit of valveuI2, the duration of
this train being equal to the duration of a line‘
synchronizing pulse. The shunt circuit I8, I3 is
designed to by-pass the line pulse frequency with
about vits ?rst ten harmonics so that the line
75 synchronizing signals supplied to the grid of valve
the component of sub-carrier frequency is sub
stantially eliminated from the signals developed
across the circuit 34 which are applied to the cath 65
ode ray tube. These signals thus consist of trains
of picture signals together with pulses at the
frame frequency.
The delay of the sub-carrier signals relative to
the picture signals (produced by the circuits tuned
to the sub-carrier frequency) is of the order. of
a few micro seconds and whilst this is suf?cient
to bring the line synchronizing signals into the
intervals between trains of picture signals, has
relatively little effect upon the position of the
3
2,183,422
frame signals relative to the trains of picture‘
signals.
successive trains comprising transmitting simul
taneously the synchronizing signals witha train
The pulses of frame frequency which were re
tained in the transmitted signals may therefore
be used to “black out” the picture in between
of video signals, forming each synchronizing sig- .
nal from a train of signals of a sub-carrier fre
frames.
quency, and delaying or advancing the synchro
nizing signals in time relationship relative to the
,
video signals in the transmission channel. -
Alternatively the pulses of frame frequency may
be removed from transmitted signals and the
2. The method claimed in the preceding claim
comprising in addition the step of removing from
timing of the generation of frame pulses at the
10 transmitter be so chosen that thegframe syn
the video signals that component thereof which is 10
chronizing signals of sub-carrier frequency occur,
at the receiver, in the intervals between pictures.
Since the impedance of resistance 36, at the
sub-carrier frequency is low compared to that of
15 the circuit 31, the trains of synchronizing signals
of sub-carrier frequency are selected from the
composite signal and passed on to the grid of
valve 38 where they are ampli?ed before being
detected, separated and applied to their appro
of the sub-carrier frequency.
3. The method of transmitting and receiving
images of objects wherein there are generated at
a transmitting station both synchronizing sig
nals and trains of video signals having time 15
intervals between successive trains which in
cludes the steps of producing synchronizing sig
nals in the form of a train of signals of a sub
carrier frequency, producing video signals, lim
iting the time durationof the synchronizing sig
20 priate synchronizing units (not shown).
nals to a period at least no greater than the dur
ation of the intervals of time between successive
trains of the video signals, removing from the
video signals that component thereof which cor
responds to the sub-carrier frequency, and con» 25
It is in the synchronizing units that the major
portion of the delay of the frame and line syn
chronizing signals relative to the picture signals
occurs.
25
Each set of synchronizing signals is used in
trolling in the receiver the delay or advance in
any known or suitable manner to control the gen
eration of a saw tooth wave, one of these waves
time of occurrence of the synchronizing signals
relative to the video signals in order to place the
serving to control the de?ection of the cathode
ray in one co-ordinate and the other to control
synchronizing signals in the time intervals be
30
tween successive trains of video signals.
4. In television apparatus wherein video and
synchronizing signals are transmitted upon a
30 the de?ection in the other co-ordinate. ’
If the moment at which the line signals are gen
erated at the transmitter in relation to the pic
ture signals has beenv correctly chosen, the return
strokes of the line scanning movements will occur
35 in the intervals between the reproduction of suc
cessive lines.
In Fig. 6 there is shown a receiver circuit ar
rangement somewhat similar to that shown in
Fig. 5, like parts in the two ?gures being given
like reference numbers. In the case of Fig. 6 how
single carrier frequency, means for producing
the synchronizing signals in the form of a wave
train of energy
of a sub-carrier frequency, 35
means for removing from the video signals that
component thereof which is of the sub-carrier
frequency, means for superimposing the syn
chronizing signals upon the video signals during
a scanning of an elemental strip of the object 40
‘ ever, the parallel tuned circuit 33, which serves to . of which the electro-optical representation is to
eliminate the component of sub-carrier frequency be produced, and means for controlling the time
from the picture signals also serves to select the period at which the produced synchronizing sig
nals are effective in the receiver to cause the
sub-carrier signals and pass them on to the am
45
plifying valve Bil.
_
synchronizing signals to appear in the time in 45
tervals between successive trains of video signal
'
The present invention is also applicable where
the picture signals are delayed more than the
energy.
synchronizing signals, the synchronizing signals in _ -
this case being generated and transmitted later
50 than if the delay did not take place.
The invention as set forth above will be seen
to provide means for in effect, advancing or re
5. The system claimed in the preceding claim
wherein the time control system for controlling
the synchronizing signals in time of occurrence 50
comprises a first and. second impedance connect
I, ed in series, a thermionic valve, and a third im
tarding the synchronizing signals in relation to pedance in parallel with said ?rst and second
the picture signals to compensate for delay oc ' impedances and connected across the output of
said thermionic valve, means for applying the 55
55 curring at another part of the system.
‘ In some forms of television and the like systems,
synchronizing signals are generated at the trans
mitter and are used to control the scanning both
at the transmitter and at the receiver. An exam
60 ple of such a system is one using a cathode ray
video signals across the first named impedance
and means for applying the synchronizing sig
nals across the ?rst and second impedance, the
said second impedance being of high value com
pared to that of the ?rst impedance measured 60
at radio frequency and said-second impedance
tube for generating the picture signals at the
transmitter. In applying the present invention ' being in the form of a tuned circuit tuned to the
to such a system, where the synchronizing sig
sub-carrier frequency.
nals are delayed in transmission more than the
6. Means for receiving television signals in the
65 picture signals or vice versa, means are provided
either at the transmitter or at the receiver for
suitably advancing or retarding the synchronizing
signals relatively to the picture signals so that
the delay introduced in transmission is com
70 pensated.
I claim:
form of a wave train of energy representing video 65
signals having intervals between successive
trains and synchronizing signals in the form of
trains of oscillations of a radio frequency super
imposed upon the video signals and wherein each
interval between successive trains of the video
1. A method of transmitting and receiving im
signals is at least equal to the duration of one
ages of objects wherein there are generated at
of the trains of radio frequency oscillations com
prising means for receiving the modulated car
rier, means for separating from the received car
the transmitter station synchronizing signals and
75 trains of video signals having intervals between
75
4
2,133,422
rier modulation oscillations of a sub-carrier fre
nizing signals superimposed upon said picture
quency, a pair of series connected circuits where
signals.
' in one of said circuits is of high impedance rela
‘
tive to the second at the sub-carrier frequency,
10. Apparatus according to claim 9 wherein
means are provided for generating said radio
whereby synchronizing signals are controlled as
frequency signals during the scanning of a strip
to time in order to delay or advance the effective
ness thereof to time periods separating successive
of said object.
11. Apparatus for transmitting images of
objects in the form of trains of picture signals
having intervals between successive trains and
synchronizing signals in the form or trains of 10
trains of the video signals.
,
7. A method of transmitting and receiving
10 images of objects wherein there are generated at
a transmitter synchronizing signals and trains
of picture signals having intervals between the
successive trains comprising the steps of gener
ating synchronizing signals and picture signals
15 simultaneously, and delaying or advancing the
synchronizing signals relative to the picture sig
nals prior to the transmission of said signals.
8. A method in accordance with claim '7 where
in there are generated synchronizing signals oi
20 duration substantially equal to the duration of
one of the intervals between successive trains of
picture signals.
9. Apparatus for transmitting images of objects
in the form of trains of picture signals having
oscillation of a radio frequency comprising means
for generating picture signals, means for gen
erating synchronizing signals of a radio fre
quency simultaneously with the generation of
said picture signals, means for compensating for 15
advancing or delaying of said synchronizing sig
nals relative to the picture signals at a receiver
comprising ?rst and second impedances con
nected in series, a third impedance connected in
parallel therewith, a thermionic valve having 20
anode, cathode, and control electrodes, said con
trol electrodes being connected to said third
impedance, means for applying picture signals
of a radio frequency comprising means for gen
across the ?rst impedance, means for applying
synchronizing signals across the ?rst and second
impedances, and means for transmitting said ad
vanced or delayed synchronizing signals super
erating picture signals, means for generating
imposed upon said picture signals.
intervals between successive trains and synchro
nizing signals in the form of trains of oscillation
synchronizing signals of a radio frequency simul
30 taneously with the generation of said picture sig
nals, means for compensating for advancing or
delaying of. said synchronizing signals relative to
the picture signals at a receiver, and means for
transmitting said advanced or delayed synchro
12. A method in accordance with claim 7
wherein there are generated synchronizing sig 30
nals of a radio frequency of_ a duration less than
the duration of one of the intervals between suc
cessive trains of picture signals.
CECIL OSWALD BROWNE.
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