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Патент USA US3078459

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Feb. 19, 1963
c. R. coRsoN ETAL
3,078,454
SYSTEM FOR AUTOMATIC CONTROL OF A PPI DISPLAY
FOR OPTIMUM PHOTOGRAPHY
Filed July 12, 1960
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3,6?8,454
Patented Feb. 19, 1953
2
embodiments illustrated from the accompanying drawings
3,078,454
SYSTEM FOR AUTOMATIC CONTRQL 01*‘ A PPH
DEPLAY FOR OPTHMUM PHGTQGRAPHY
Carl R. Cor-son, Canoga Park, Caliii, and Lawrence H.
Gilligan, Nashua, N.H., assignors to the United States
of America as represented by the Secretary of the Air
Force
Filed July 12, 1960, Ser. No. 42,451
10 Claims. (Cl. 343-5)
The invention relates to a system for determining an
indication of brightness to which a photographic ?lm
would be exposed and adjusting this brightness to a level
suitable for proper ?lm exposure.
When radar photographs are obtained for reconnais
sance or training purposes, it is important that the photo
graphs portray all picture details that were contained in
and hereinafter to be described.
In the drawings:
FIG. 1 is a block diagram of the system for detection
and storage of the control signal;
FIG. 2 is a block diagram for the automatic gain con
trol system for automatic control; and
FIG. 3 is a block diagram of the variable density ?lter
type of automatic control.
Referring now more particularly to FIG. 1, there is
illustrated the detection and storage portion of this in
vention. The incoming video of one PPI scan is operated
upon by the peak detector 10. The function of the peak
detector 10 is to feed the peak amplitude of the video
15 signal into the storage circuit 12 where the signal is re
the original radar display. Since the radar operator is usu
ally concerned with other objectives, such as navigation
and bombing, very little time and effort is spent in adjust
tained for the duration of the one PPI scan. The shutter
mechanism of the camera which is to take the picture of
the PPI display actuates a pulse that is fed to difierentiator
22. As the shutter of the camera is closed, the pulse ob
tained from the actuation of the shutter mechanism is
shaped by the differentiator 22 to provide a sharp leading
edge and used to trigger multivibrator 18. The output
pulse from the multivibrator 18 opens the readout gate
ing optimum recording of the radar display.
2!? to transfer the peak video from the storage circuit 12
In order to automatically control the display for
photographic purposes, the strongest signal of any given 25 to storage circuit 24. The peak signal is retained in
storage circuit 24 for the duration of the next PPI scan.
PPI scan must be placed at a predetermined position on
ing the camera or display for proper ?lm exposure. This
invention provides two methods for automatically obtain
the ?lm sensitivity curve. Therefore, some form of video
information, such as kinescope beam current or the video
driving voltage, must be peak detected, and the peak value
The output circuit 26 operates on the stored information
in storage circuit 24 to produce a D.C. analogue suitable
for the control system which is used.
The trailing edge of the output of multivibrator 18 also
for each PPI scanned must be stored until readout and
triggers multivibrator 16. The output of multivibrator 16
used to adjust the light level reaching the ?lm. This volt
clamps storage circuit 12 by means of a gated clamp 14
tage is then stored during the period that its controlling
to remove all stored information in preparation for the
in?uence is desired, and the control device is thereby
next PPI scan.
constantly presented with a D.C. analogue of the peak
The incoming video can be readily obtained from two
signal from the previous scan.
35
sources, directly from the cathode of the kinescope or the
The novel system is inherently advantageous over prior
video driving voltage to the kinescope. If the video in
art systems. The system requires no external sensing
formation to be detected is taken directly from the kine
device, such as a photo tube, and therefore is more com
scope, as a function of beam current, it will contain cer—
pact, less cumbersome, and more reliable than systems
40 tain arti?cally produced signals, such as range rings,
used in the prior art.
heading marker, and cross-hairs. In order that these wave
There are two automatic control devices speci?cally
forms are not detected as peak video, it will be necessary
contemplated and described. ()ne is an automatic gain
to cancel them with inverted arti?cial video before apply
control device which adjusts the amplitude of the video
ing the incoming video to the peak detector 10.
drive such that the largest signal input to the kinescope
The D.C. analogue in the automatic control system
causes a predetermined brightness to occur. This device
has the advantage of providing instantaneous adjustment. 45 illustrated in FIG. 2 is applied to an automatic gain type
circuit. This automatic gain circuit is in its simplest
The second control device contemplated is a variable
form composed of a main ampli?er 39 having a feedback
density ?lter device which adjusts the percentage of total
path and a variable-gain feedback ampli?er 34 in the
light output from the kinescope that is permitted to reach
the ?lm. This device has the advantage of compensating 50 feedback path. The radar video signal is applied to the
main ampli?er 3%}. The action of the feedback variable
for the aging of the system up to and including the elec
tron gun of the kinescope.
The invention can be used in any application where it
is desired to obtain optimum photography from an un—
attended indicator. Typical uses for the system are for 55
radarscope photography and reproduction of a single tele
vision frame for publicity purposes.
It is an object of this invention to provide a system for
gain ampli?er in this circuit is two-fold.
It acts as an
automatic gain control circuit wherein the output of the
main ampli?er 30 is maintained constant within narrow
limits regardless of variations in the video signal strength.
Further, through the action of the D.C. analogue output,
which acts to vary the total gain in the feedback path, B,
the variable gain ampli?er 34 adjusts the amplitude of
the video drive such that the largest signal input to the
kinescope causes a predetermined brightness to occur.
quiring an external sensing device.
60
Since the desired gain in ampli?er 30 is inversely propor
It is another object of this invention to provide a system
tional to the peak video signal, the 1/3 characteristic of
which determines an indication of the peak brightness to
the feedback ampli?er 34 is utilized to provide the ‘de
which the ?lm would be exposel and adjust this brightness
sired function.
automatic control of a PPI radar display without re
to a level suitable for the proper ?lm exposure.
A mixer circuit 40 is provided to combine the ‘ampli?ed
It is speci?cally an object of this invention to provide 65 radar video from the main ampli?er 3t} and ampli?ed
a system which samples either the video driving voltage
‘arti?cial video from ampli?er 38. The arti?cial video,
to the kinescope or the kinescope cathode current, de
such as range rings, heading marker, and cross-hairs must
termines the peak value during the PPI scan, and adjusts
be separately ampli?ed to a ?xed level by ampli?er 38.
the system for the correct ?lm exposure.
The intensity of the scanning ray of the kinescope or
The nature of the invention, further objects and advan 70 image reproducing device 44 is thus modulated or con
tages will appear more fully by consideration of the
trolled in accordance with the video-frequency voltages
3,078,454
3
4
derived from mixer 40 and impressed upon the control
grid 46 in the usual manner.
peak detecting, a ?rst means for storing said peak ampli
tude information detected by said means for peak detect
ing, a second means for storing said peak amplitude in
.
FIG. 3 shows a block diagram of the variable density
?lter type of automatic control which adjusts the per
centage of the total light output from the kinescope 44
formation for a predetermined time, means for trans
that is permit-ted to reach the ?lm 80.
?rst means for storing to said second means for storing,
ferring the said peak amplitude information from said
The camera’s
shutter mechanism is indicated schematically at 78. The
variable density ?lter 76 is mechanically linked through
linkage 72 to servo motor 64.
means for removing said peak amplitude information
from said ?rst storage means, an output circuit for oper
ating on said information in said second storage means to
The servo motor is ener~
gized by voltage from batteries 52 and 54, and the voltage 10 produce a D.C. analogue of'said peak amplitude infor
applied through the chopper 50 and the ampli?er 58 to
mation, means for Iadjusting light output from the said
the motor. The D.C. analogue voltage output of the
kinescope that is permitted to reach the photographic
detector and storage circuit is fed into chopper 50 and
?lm, and means for applying said D.C. analogue to said
compared with the D.C. voltage from the movable arm
means for adjusting for controlling same.
70 of the potentiometer 63. The movable arm 70 is 15
3. In an apparatus for automatic control of a PPI
mechanically connected to servo motor 64. Any differ
radar display on a kinescope for optimum photography
ence in amplitude between the two D.C. voltages appears
with a shutter operated camera, the. combination com
as a square wave at the output of chopper 50. This error
prising: a source of video information from a ?rst PPI
signal is ampli?ed in the servo ampli?er 62 and used
scan, means for peak detecting the peak amplitude of
to drive the motor 64. The motor drives the variable
said video coupled to said source, a ?rst means for stor
density ?lter 76 and the potentiometer arm 70 in the
ing said peak amplitude information detected by said
direction such as to reduce the error signal to the point
means for peak detecting, a second means for storing said
where no error exists.
,
peak amplitude information for the duration of the next
It is desirable to monitor the kinescope cathode current
PPI scan, a differentiator for shaping pulses to provide
for the variable density type of control and use this video 25 sharp leading edges thereon, means for applying a pulse
signal to feed the detector and storage circuit, since the
to the said di?ferentiator when the shutter mechanism of
light output from the face of the kinescope is directly
the said camera closes, a multivibrator coupled to said
proportional to the ultor current (until blooming of the
diiferentiator, a readout gate connectedbetween said ?rst
phosphorous occurs). In kinescopes that utilize a “zero
and second means for storage, said multivibrator apply
screen current” electron gun, the ultor current and the 30 ing a gating pulse to said readout gate when said multi~
cathode current are nearly identical. Monitoring the
vibrator is triggered by a sharp leading edged pulse from
kinescope cathode current, as indicated above in the dis
said di?erentiator, means for removing said peak ampli
cussion of the detector and storage circuit, requires can
tude information from said ?rst storage means in prepara
celling the ‘arti?cial video before the. peak detection proc
tion for the said next PPI scan, an output circuit for
ess occurs. In addition to this it is necessary to control 35 operating on said information in said second storage
the amplitude of the arti?cial video drive to- the kinescope
means to produce a D.C. analogue of said peak ampli~
as'the target video varies in amplitude. If this is not
tude information, means for adjusting light output from
done, the arti?cial video will be saturating ‘the ?lm when
the said kinescope that ispermitted to reach the pho
small amplitude target video is being compensated for
tographic ?lm, and means for applying said D.C. ana
by reducing the density of the ?lter between the kinescope 40 logue to said means for adjusting for controlling same.
and the camera.
While the invention has been described with reference
4. A system for automatic control of a radar display
for optimum photography with a shutter operated camera
in part: to a PPI type of image-reproducing device, the
invention ‘is not intended to be limited thereto.
comprising: a kinescope, means for’ peak amplitude de
The sys
tem is, not limitedto the examples of embodiments
45
shown and described, but may on the contrary, be ca
pable of many modi?cations, without departing ‘from the
spirit of the invention.
'
We claim: '
1. In an apparatus for automatic control of a PPI 50
radar display on a kinescope for optimum photography,
tecting, means for monitoring video information to said
kinescope and supplying the said video information to
said means for detecting, a ?rst means for storing said
peak amplitude information detected by said means for
peak detecting, a second means for storing said peak
amplitude information for a predetermined time, a differ
entiator for shaping pulses to provide sharp leading edges
thereon, means for applying a pulse to the said differ
entiator when the shutter mechanism of the said camera
closes, a multivibrator coupled to said differentiator, a
peak amplitude of said video coupled to said source, a
readout gate connected between said ?rst and second
first means for storing said peak amplitude information 55 means for storage, said multivibrator applying a gating
detected by said means for peak detecting, a second
pulse to said readout gate when said multivibrator is
the combination comprising: a source of video informa
tion from a ?rst PPI scan, means for peak detecting the
means for storing said peak amplitude information for
the duration of the next PPI scan, means for transferring
the said peak amplitude information from said ?rst means
triggered by a sharp leading edged pulse from said differ
entiator, means for removing said peak amplitude in
formation from said ?rst storage means, an output cir
for storing to said second means for storing, means for 60 cuit for operating on said information in said second
removing said peak amplitude information from said
?rst storagemeans in preparation for the said next PPI
scan, an output circuit :for operating on said information
in said second storage means to produce a D.C. analogue
of said peak amplitude information, means for adjusting
light output from the said kinescope that is permitted to
reach the photographic ?lm, and means for applying said
D.C. analogue to said means for adjusting for controlling
same.
2. A system for automatic control of .a radar display
for optimum photography comprising: a kinescope,
storage means'to produce a D.C. analogue of said peak
amplitude information, means for adjusting light output
from the said kinescope that is permitted to reach the
photographic ?lm, and means for applying said D.C. ana
logue to said means for adjusting for controlling same.
5. In an apparatus for automatic control of a PPI
radar display on a kinescope for optimum photography,
the combination‘comprising: a source of video informa
tion from a ?rst PPI scan, means for peak detecting the
peak amplitudeof said video coupled to said source, a
?rst means for storing said peak amplitude information
means for peak amplitude detecting, means .for moni
detected by said means for peak detecting, a second
toring video information to said kinescope and sup-.
meansfor storing said peak amplitude informationfor the
plying the said video information to said means for 75 duration of the next PPI scan, means for transferring the
3,078,454
6
5
pressing the output of said mixer circuit on the intensity
said peak amplitude information from said ?rst means
control grid of said kinescope.
for storing to said second means for storing, means for
8. A system for automatic control of a radar display
removing said peak amplitude information from said ?rst
storage means in preparation for the said next PPI scan,
an output circuit for operating on said information in
said second storage means to produce a D.C. analogue
of said peak amplitude information, a source of radar
video, a main ampli?er having a feedback path, a vari
for optimum photography comprising: a kinescope, means
for peak amplitude detecting, means for monitoring video
information to said kinescope and supplying the said
grid of said kinescope.
said peak amplitude information from said ?rst storage
video information to said means for detecting, a ?rst
means for storing said peak amplitude information de
tected by said means for peak detecting, a second means
able gain ampli?er in said feedback path, means for
applying said radar video to the input of said main am 10 for storing said peak amplitude information for a pre
determined time, means for transferring the said peak
pli?er, means for applying said D.C. analogue to said
amplitude information from said ?rst means for storing
variable gain ampli?er, and means for impressing the
to said second means for storing, means for removing
output of said main ampli?er on the intensity control
6. A system for automatic control of a radar display 15 means, an output circuit for operating on said informa
tion in said second storage means to produce a D.C.
for optimum photography with a shutter operated camera
analogue of said peak amplitude information, a source
comprising: a kinescope, means for peak amplitude de
of radar video, a main ampli?er having a feedback path,
tecting, means for monitoring video information to said
a variable gain ampli?er in said feedback path, means for
kinescope and supplying the said video information to
applying said radar video to the input of said main ampli~
said means for detecting, a ?rst means for storing said
?er, means for applying said D.C. analogue to said varia
peak amplitude information detected by said means for
ble gain ampli?er, a source of arti?cial video, an ampli?er
peak detecting, a second means for storing said peak am
coupled to the said source of arti?cial video for amplify
plitude information for a predetermined time, a differ
ing said arti?cial video to a ?xed level, a mixer circuit,
entiator for shaping pulses to provide sharp leading edges
thereon, means for applying a pulse to the said differ 25 means for applying the outputs of said main ampli?er and
said arti?cial video ampli?er to said mixer circuit, and
entiator when the shutter mechanism of the said camera
means for impressing the output of said mixer circuit on
closes, a multivibrator coupled to said ditferentiator,
the intensity control grid of said kinescope.
a readout gate connected between said ?rst and second
9. A system for automatic control of a radar display
means for storage, said multivibrator applying a gating
for optimum photography comprising: a kinescope, means
pulse to said readout gate when said multivibrator is
triggered by a sharp leading edged pulse from said dif
for peak amplitude detecting, means for monitoring video
ferentiator, means for removing said peak amplitude in
formation from said ?rst storage means, an output circuit
for operating on said information in said second storage
means to produce a D.C. analogue of said peak ampli 35
information to said kinescope and supplying the said
tude information, a source of radar video, a main ampli
?er having a feedback path, a variable gain ampli?er
in said feedback path, means for applying said radar
video to the input of said main ampli?er, means for
for storing said peak amplitude information for a pre
determined time, means for transferring the said peak
amplitude information from said ?rst means for storing
applying said D.C. analogue to said variable gain ampli
?er, and means for impressing the output of said ma-in
ampli?er on the intensity control grid of said kinescope.
video information to said means for detecting, a ?rst
means for storing said peak amplitude information de
tected by said means for peak detecting, a second means
to said second means for storing, means for removing
40
said peak amplitude information from said ?rst storage
means, an output circuit for operating on said informa
tion in said second storage means to produce a D.C. ana
7. in an apparatus for automatic control of a PPI
logue of said peak amplitude information, a chopper
radar display on a kinescope for optimum photography
means having ?rst and second terminals for comparing
with a shutter operated camera, the combination com 45 D.C. voltages and producing an error signal when said
voltages are unequal, a potentiometer, means for apply
prising: a source of video information from a ?rst PPI
scan, means for peak detecting the peak amplitude of
said video coupled to said source, a ?rst means for stor
ing the said D.C. analogue to said ?rst terminal of said
chopper means, means for applying the voltage at the
arm of said potentiometer to said second terminal of said
means for peak detecting, a second means for storing 50 chopper means, a variable density ?lter placed in front
of the screen of the said kinescope, means responsive to
said peak amplitude information for the duration of the
said error signal for driving said ?lter and said potenti
next PPI scan, a di?erentiator for shaping pulses to pro
ometer in the direction such as to reduce the said error
vide sharp leading edges thereon, means for applying
signal.
a pulse to the said differentiator when the shutter mecha
10. In an apparatus for automatic control of a PPI
nism of the said camera closes, a multivibrator coupled 55
radar display on a kinescope for optimum photography
to said diiferentiator, a readout gate connected between
with a shutter operated camera, the combination com
said ?rst and second means for storage, said multivibrator
prising: a source of video information from a ?rst PPI
applying a gating pulse to said readout gate when said
ing said peak amplitude information detected by said
scan, means for peak detecting the peak amplitude of
multivibrator is triggered by a sharp leading edged pulse
from said differentiator, means for removing said peak 60 said video coupled to said source, a ?rst means for stor
ing said peak amplitude information detected by said
amplitude information from said ?rst storage means in
means for peak detecting, a second means for storing said
preparation for the said next PPI scan, an output circuit
peak amplitude information for the duration of the next
for operating on said information in said second storage
PPI scan, a differentiator for shaping pulses [to provide
means to ‘produce a D.C. analogue of said peak amplitude
sharp leading edges thereon, means for applying a pulse
information, a source of radar video, a main ampli?er 65
to the said ditferentiator when the shutter mechanism of
having a feedback path, a variable gain ampli?er in said
the said camera closes, a multivibrator coupled to said
feedback path, means for applying said radar video to
ditferentiator, a readout gate connected between said
the input of said main ‘ampli?er, means for applying said
?rst and second means for storage, said multivibrator
D.C. analogue to said variable gain ampli?er, a source
70 applying a gating pulse to said readout gate When said
of arti?cial video, an ampli?er coupled to the said
multivibrator is triggered by a sharp leading edged pulse
source ‘of arti?cial video for amplifying said arti?cial
from said differentiator, means for removing said peak
video to a ?xed level, a mixer circuit, means for apply
amplitude information from said ?rst storage means in
ing the outputs of said main ampli?er and said arti?cial
preparation for the said next PPI scan, an output circuit
video ampli?er to said mixer circuit, and means for im 75 for operating on said information in said second storage
"397189154
7
means to produce a DC. analogue of said peak amplitude
information, a chopper means having ?rst and second
terminals for comparing D.C. voltages and producing an 7
error signal when said voltages ‘are unequal, a potenti
ometer, means for applying the said D.C. analogue to
said ?rst terminal of said chopper means, means for ap
plying the voltage at the arm of said potentiometer to said
second terminal of said chopper means, a variable density
?lter placed in front of the screen of the said kinescope,
means responsive to said error signal for driving said
?lter and said potentiometer in the direction such as to
reduce the said error signal.
No references cited.
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