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00ct' 3, 1946.
v. H. FRAENCKEL Erm.
LIGHT IMPULSE SYSTEM
Filed Deo. 22, 1941
2,409,030 I
Patented Óct. É, 1946
. 2,459,
s'rsi‘ss PATLNTA orrice
2,409,030
LIGHTfllVIPULSE SYSTEM
Victor H. Fraenckel and Siegfried Hansen, Sehe
nectady, N. Y., vassignors to General Electric
Com-pany,- a corporation of New York
Application December 22, 1941, Serial No.423,984
'10 lClaims. (Cl. 315-59)
2
1
The present invention relates primarily to iin
provements in apparatus Afor locating objects and
elements alight-impulse projecting device, a de-'
vice for receiving Vand detecting the projected
measuring distances by the transmission and re
flection of light-impulses, that is to say, by im»
pulses of electromagnetic waves within the visible
light-impulses as Ythey are reflected from a dis
or near-visible range.
It is a primary object of the invention to ‘pro- `
tant object, and ¿means for visibly indicating the
' time required for the reflection of the light-im
pulses so as to proyide Aa measure of the distance
to the reflecting object.
The light-projecting device comprises in its
vide in such apparatus an improved light-im
general aspects a, light-impulse generator i0 and
pulse generator which is capable of meeting the
requirement that the duration of the generated 10 a reflector H for focusing ,in a narrow beam the
light radiations developed by the gener-ator. The
impulses shall be a small fraction of the time
light-receiving _means consists of a focusing mir
required for the reflection of the impulses from
ror I3; preferably of parabolic form, and a light
an object positioned at any material distance
sensitive agency I4, typically a photocell, ar
from the impulse source.
It is a further object to provide a generator 15 ranged at `the focal point of the mirror. The
transmitting vand Vreceiving means are preferably
adapted to produce light-impulses of extremely
oriented 'm `the same direction and are arranged
high instantaneous intensity.
to have their orientation varied simultaneously
In the attainment of the foregoing objects an
both in elevation and yin azimuth in order that
important feature of the invention consists in
the surrounding >space may be scanned for re.
the use of electrodes adapted to sustain an in
ñecting objects such, for example, as distant
tense spark-discharge in combination with a
aircraft.
charge-storing agency which is of such charac
`The distance-indicating means comprises a
ter and which is so connected to the electrodes
that the resultant circuit represents a discharge
cathode .-ray tube I8, `of which only the screen
system oi extremely small inductance. By al 2.5 portion is illustrated in Fig. 1. This tube is of
conventional `character and includes means'for
ternately charging an appropriately constructed
>generating an electron Abeam and .additional
charge-storing agency and thereafter discharg
means for Ade_iiecting the beam in mutually per
ing it through the connected electrodes, it proves
pendicular _directions to `cause Aa 4confipiexftrace to
possible to produce light-impulses which have'an
eiiective duration of less than one-tenth micro-_ 30
_ be developed on the screen of the tube. {I‘he
operation of the tube is «controlled by Vmea-ns re
second but which are nevertheless of suiiicient '
sponsive both to the »transmission and reception
intensity to be >reflected »in Ydetectable amounts
of light-impulses developed-by the generator l0,
from objects at a distance of many miles. Be
the nature of the means used in this connection
cause of the extreme brevity of the impulses in
volved, the location of such objects can, with” 2.35 being _explained lmore 'fully hereinafter. y
In the use of >the apparatus as s_o far described
the assistance of a detecting system responsive
the generator lo is actuated in such ¿fashion as
to such impulses, be determined with'an error of
to cause it to produce a series of regularly spaced
only a few feet, and even higher accuracies are
light-,impulses of short duration. AS each im
possible under favorable conditions.
The features of the invention which we desire 40 pulse is generated it is caused-through the agency
of a photosensitive element 2,53 .(e.V g. a photoìcell)
to protect herein are pointed out with particu
to initiate a deflection of the electron beam of
larity in the appended claims. The invention it
the cathode ray tube I8 in such a `manner as to
self, together with its further objects and rad
produce a horizontal trace A on the screen of
vantages, thereof may best be understood byref
erence to the following description Ytaken in con 45 the tube. This is accomplished through a saw
tooth .wave generator 2i w-hichis under the con
nection with the drawing in which Fig. 1 repre
trol of the photocell _20, and an amplifier 22 >for
sents schematically a distance-measuring«system
applying vthe .saw-tooth potential in amplified
suitably embodying the invention; Figf2 is a sec
form to the lhorizontal _deñeeting electrodes (not
tional view oi a light-impulse generator of Y»the
type which characterizes the invention; Fig. 3
is a sectional view taken on line 3_3 of Fig. 2;
and Fig. ¿l is a cross-section of one ofthe con
denser units of Fig. 2.
_
50
shown) ofthe cathode ray tube.
In order to
protect vthe screen of the >tube and for other rea
sons `an auxiliary apparatus represented bythe
rectangle 23 Vis provided for blanki'ng out the
electron beam at intervals when `the vbeam-_de
Referring to Fig. l there is shown a distance
measuring system which includes as its maior 55 iiecting means is not active and also during „peri- '
2,409,030
3
ods when, after an initial deflection, the beam is
being returned to its original starting point. The
blanking means employed in this connection are
4l.
4
One terminal of the condenser assembly is
indicated as a bridging conductor 45 and the
other terminal comprises the wall structure of
a conductive container 41 which closely sur
rounds the condenser assembly. Electrode 4G is
larly described herein. The nature and function
directly connected to the terminal 4G and the
of devices serving this purpose are fully ex- V
electrode 4l is supported from one end of the
plained, for example, in “Cathode Ray »Tubesf’ by
cylinder 'i1 as indicated.
M. Von Ardenne (Pitman and Sons', Ltd. London,
For the purpose of charging the condenser as
1939) pages 278 to 288.
The light-impulse receiver I4 is connected 10 sembly there is provided a high voltage trans
conventional and do not require to be particu
prised Within the rectangle 39) to the vertical
deilecting plates of the cathode ray tube i8.
Consequently, upon receipt of reflected waves by
former 59 which is connected through a regu
lating inductance 5l to an alternating current
supply source 52. The secondary of the trans
former 5G is connected to the terminals of the
pulse from'the object under surveillance. If this
and 3 of the drawing.
through suitable amplifying apparatus (com
the receiver, a secondary -deflection'of the beam 15 condenser assembly through conductors 5e and
55, the conductor 55 being insulatingly sealed
is produced at an instant dependent upon the
through the wall of the container All' and being
time required for the reflection of the transmit-.l
in series with an interference suppressing resistor
ted light-impulse from the distant object tc
51 which connects to the condenser terminal 4S.
'ward which the transmitting and receiving means
In the operati-on of the system thus provided
are directed. This deflection produces on the
the
condenser assembly is charged at each cycle
screen of the cathode ray tube a trace B which
of the alternating potential supplied from the
is transverse to the trace A and the relative lo
transformer EG. The electrodes dû and il! are
cation of which provides an indication of the dis- _
so adjusted that the gap between them can break
tance of the reflecting object.
down just before the condensers attain maximum
A light-impulse system of the type so far de
charge, whereby one discharge is produced dur
scribed po-ssesses an advantage over detecting
ing each full cycle of potential reversal. Be
systems which employ other types of electro
cause of the extremely low inductance of the
magnetic waves in that it may be made very
circuit in which the condensers and the elec
highly directional in character because of the
possibility of optically focusing the propagated 30 trodes are included, the resultant spark between
the electrodes is of extremely short duration.
light rays in a narrowly confined beam. How
Moreover, since all the energy of the condensers
ever, considerable difiiculty exists in providing a
is discharged within this very brief interval of
light-impulse generator capable of developing
time, the intensity of the resultant light-impulse
impulses which are of sufñciently short duration
to permit the system to function in its intended 35 is extremely high, reaching in some cases 50,000
Watts of peak output or even higher. These ad
manner and which at the same time have a suf~
vantageous results are a function of the nature
iicient intensity to permit the detection of im
of the light-generating apparatus employed, and
pulses reflected from objects at a distance of
»for this reason it is desirable to consider in some
several miles. In this connection it is partic
ularly important that the duration o-f the gen 40 what greater detail the construction of a partic
-ular light generator which we have successfully
erated light-impulse shall be a small fraction of
vused. Such a generator is represented in Figs. 2
the time required for the reflection of the im
Y
The construction shown in Fig. 2 comprises an
condition is not fulfilled, a clearly defined indi
cation cannot be obtained on the screen of the 45 elongated container of which the principal part
.is in the form of a metal cylinder Gil. This cyl
cathode ray tube because of ,swamping of the
`inder is closed at one end by means of a semi~
trace produced by the reflected signal through
Vspherical glass window E! which is secured to
the effects of radiations proceeding directly from
-the extremity of the cylinder by means of a
the transmitting apparatus.
Another factor which is important to the suc 50 clamping ring S2. Suitable gasket material 63
is provided in connection with the edge of the
cessful operation of a system of the type under
window part 6I to assure that the resultant joint
consideration consists in the possibility of ob
>shall be of gas-tight character. The end of the
taining light-impulses having a very steep wave
`cylinder t8 remote from the windo-w 6l is closed
front, that is to say, a very abrupt rise from Zero
light intensity to maximum light intensity. For 55 by the combination of a heavy annular ring S5,
which is Welded to the cylinder, and a tapered
insulator 61 held in vacuum-tight relation with
respect to the ring GS by means of a clamping
pulse generating system must be of such char
ring 69 and a gasket joint lo. The resultant
acter as to produce an impulse which attains
its maximum value in a time less than that re 60 gas-tight enclosure is iilled with a gas under
As will appear more clearly at a later
-v pressure.
-quired for light waves to travel about 25 feet.
point, it is the main function of the gaseous ñlling
In view of the tremendous velocity of light, this
Y to provide a suitable atmosphere for a light-pro
obviously signifies a very steep wave front in
»ducing discharge to be produced within the en
deed.
The requirements stated in the foregoing are 65 closure. For the purposes of the present inven
_ tion it is preferred to use in this connection ni
Very satisfactorily fulñlled by the use of a light
- trogen- or one of the rare gases such as argon or
generator of the character illustrated in Fig. l.
neon, pressures of from one atmosphere up to
This comprises a pair of mutually spaced elec
100 pounds per square inch being suitable.
trodes fic, fil-l adapted to be intermittently sup
Within the metal cylinder E9 and extending lon
plied with discharge current from a high capac 70
.,gitudinally with respect to it there is provided
ity charge-storage agency. In the arrangement
a charge storage system in the form of an vas
shown in Fig. 1 theV charge-storage agency is il
example, if distance measurements are to be made
with an error of less than 5G feet, the light-im
Vlustrated as comprising two banks of series-con
. sembly of condensers '13. These condensers are
- arranged in four rows or charge-storing units
-nected condensers 43 and 44, which banks are
connected in parallel across the electrodes 4S and 75 which are positioned symmetrically with respect
'2,409,636
5
to the axis of the cylinder 60 (see Figjîßi and .the
individual condensers of which »areconne'cted ln
when employed in a gaseous discharge medium,
such as irîiitrogen, argon or neon, breakdown be
>tween’them may be causedfto‘occur automatically
whenever 'the impressed voltage exceeds a value
readily attainable vwith aA condenser assembly of
series by »means of bridging 'strapsv'lâ extending
between adjacent terminals of theconde'n'sers.
The screws or bolts 'il which are employed to 'se
cure the bridging straps 15 to the condenser ter
the type illustrated. ln a particular case, it vhas
minals may advantageously extend through the
condenser structure so 'as to facilitate mounting
the various condensers on insulating mounting
rings ‘i9 positioned within the condenser .ass‘em-f
bly.
~
'
6
aluminum. When they are so constituted sand
been vfound 'possible to produce vsuccessive dis
>charges-'by repetitively charging the parallel con
nected condense-r banks to 'a voltagenn >the iorder
of v10,000 to 20,000 volts. -The impulse 'discharges
thus resulting prove to be of highly luminous
.
One terminal of each 'of the ycondenser 'rows
is connected to a centrally positioned conductive
quality, yielding >in `'some cases `a peak intensity
of »50,000 watts or more.
In Vorder to permitcharging `of the lcondenser
assembly from an external Voltage source, a lead
-in vconductor 95 is 'sealed through the Yextremity
body Si! which thus provides a 'common `clmnec
tion point for the condenser 'assemblyas va whole.
This connection may be made, ffor example, by
means of bolts '82 which 'are respectively Ain con
lof the insulator 81, being connected to the .tere
tact with the terminals of the v-e'nd 'condensers of
ininal 80 within the sealed enclosure through the
each row and which extend into 'screw-threaded
engagement with the Ymetal body 80. The cylin 20 intermediation of a series of current-limiting v.ref
sistors 91. A connection to the other terminal
drical casing 60 is made to vvserve as a common
of the condenser assembly may obviously befm'ade
connection point for the other end of the -con’
by anixing a conductor (not shown) to Athe sur»
den'ser assembly by connecting‘it tothe terminals
face of the metal cylinder t0 or .any associated
of the'condens'ers at the extremities of the vari
'
25 metal part.
ous condenser rows as indicated at 84.
In order insulatingly to separate the resistors
Each of the condensers 13 is preferably made
Q1 from the condensers 13 and thus to .minimize
of a flat electrode construction (as distinguished
the likelihood of undesired breakdown, an axially
from a spirally wound construction) iso that the
extending insulating cylinder JHM] is interposed
internal inductance of each condenser is in»
herently small. The preferred 'construction is 30 between them. -A larger insulating cylinder, in
illustrated in Fig. 4 which shows on Aan enlarged
scale a longitudinal section of one of the con»
'densers i3, the thickness of the internal elements
being greatly exaggerated for purposes of clarity. _
The condenser includes a large number `of inter
leaved metal electrodes 85 which are suitably
formed of aluminum foil and which vare sepa
rated by mica sheets 8e. Every other ’electrode
is in contact with a metal bushing >`«81 while the
alternate electrodes connect with -a bushing te,
of the condenser are encased in an insulating
substance such as a synthetic resin.
The arrangement of the condensers withinvthe "î
cylinder Se is »such that the various condenser
rows are relatively close to theinternal lsurface
of the cylinder. Since the cylinder provides the
return path for current flowing from the ‘ter-l
minal 8B through the condenser assembly, the '
loop inductance of the -completeßcircuit measured
between the terminal l86 and »a "closely adiacent
point on the cylinder 66 is very low. rlîhis cir
cumstance is made use oi in connection with the
present invention by mounting -discharge elec-‘`
trodes 9E! and Si in direct electrical ‘connection
with the condenser terminal ASù 'and-with the
metal cylinder 653, the ñrst such connection being
through a short, conductive rod 9.2 which extends
outwardly 'from the terminal r’lll and the second
connection being through an -apertured metal
wall part 93' which is in direct contact with the
end of the cylinder 6U. By virtue of this disposi'
tion of the parts the entire condenser discharge
circuit, including the electrodes 90 vand 3|, is of
extremely small inductance (in aparticular case
about .05 microhenry as compared with a ca
pacity of .01 microfarad for the condenser bank).
Accordingly., once the condensers are charged,
-they may be abruptly discharged through the
electrodes to produce an intense spark of remark
ably short duration (i. e. less than one micro
`
'
metal cylinder Si) fora similar purpose.
-
The mode of use of a »light-impulse generator
of the character shown in Fig. 2 hasalreadybeen
explained in connection with lthe »description .of
Fig. -1. In applying the `generator of Fig. >2 'to
the system of Fig. 1 it will be understood that the
electrodes 9e and 9| correspond to the :electrodes
'-40 |38 and -lll, the condensers T3 to the condensers
the two bushings providing externally 4accessible
terminals for ythe condenser. The active ypar-ts
second).
dicated at lill, is interposed -between the Vcon
denser assembly -and the .inner wall surface of v.the
'
"The electrodes 90 'and '9|"lnay suitably be fc'on- K _
'stituted o'f a low work function metal, such asv
d3 and "44, etc.
-
A system of the character ldescribed is applica
ble to the detection and location of aircraft,i to
cloud height measurement, and to distance meas
urement generally. Under certain circum
stances, it also has utility rfor marine -purposes
in making ‘sub-'surface observations, for example,
in the detection ‘and location of 'submerged sub
marines.
y
While the invention has been described by ref
erence to 'a particular :embodiment thereof, it will
be understood that ‘numerous 'changes may be
made bythose'skilled in the art without‘departn
ing from the invention. We, therefore, desire in
the appended claims to cover all such variations
as come within the true spirit and scope of the
foregoing disclosure.
What we claim as new and desire to -seoure by
Letters Patent of the United States is:
1. In a system in which light l.impulses >are
`transmitted to a distant object :and thereafter
corresponding reflected impulses are received
from said *object in a time dependent upon ~the
distance to the object, the combination which
comprises a charge-storing agency, »mea-ns for
periodically charging the said agency, a~~s-parkdischarge type of light source, and v`circuit 'con
neetions between the charge-storing -agency and
the light source for allowing the intermittent dis-'
charge of the former through the latter, said
charge-storing agency and said circuit-connec
tions being of such small inductance that the
duration Aof each of the resultant light impulses
is Ja fraction of -the time required Lf‘or -reflection
aeoacso
of such impulses from the aforesaid distantob
ject.V
t,
c
v'
,_
8
1y connecting the terminals of the charge-storing
agency to the` respective electrodes, whereby the
said agency is enabled, upon charging, to create
between the electrodes a light-producing spark of
2. In a> system in which light impulses are
transmitted to a distant object and correspond
ing reflected impulses are thereafter received in 5 extremely short duration.
a time dependent upon the >distance vto the ob
V6. A light-impulse generator comprising a con
ject, the combination which comprises a charge
denser assembly of hollow elongated configura
storing agency ' of small internal inductance,
tion, terminal means for the assembly at its re
means for periodically charging the said agency,
spective extremities for permitting charging and
a pair of gas-immersed electrodes positioned in 10 discharging of the assembly, a conductive struc
close „physical ‘proximity to the Acharge-storing
agency, `and direct conductive connections be
tween the terminals of said agency and said elec
trodes for allowing the intermittent discharge of
the former through the latter, the resultant dis
charge circuit being of such small inductance
that the duration of each light impulse generated
between the electrodes, upon the occurrence of a
discharge is a fraction of the time required for re
ture closely surrounding and extending from end
to end of the said assembly, a first sparking elec
trode havinga direct conductive connection to the
said structure near one end thereof, a second
sparking electrode cooperatively spaced with re
spect to the ñrst electrode `and directly connected'
to the assembly terminal means which is near said
one end- of the conductive structure,'and a con
nection between the remaining assembly terminal
flection of said impulses from the aforesaid dis
meansand the other end of the conductive struc
tant
ture, whereby the loop circuit through the con
object.
.
l
Y
3. In a system in which light impulses Aare
denser assembly Y and the conductive structure
transmitted to a distant object and correspond
provides a low inductance discharge path from
ing reflected impulses are thereafter received in
the assembly to the said sparking electrode.
a time dependent upon 'the distance to the object, 25
'7. A light-impulse generator comprising a con
.the combinationv which includes an enclosing cas
denser assembly of elongated hollow configura
ing having .a light-transmitting wall part, a
tion, said assembly including a plurality of capac
charge-storing agency within the casing, means
itive units arranged so that current flow is length
for periodically charging the said agency, a pair
wise through the assembly, terminal `means for
of mutually spaced electrodes within the casing 30 the assembly at its respective extremities, a con
adjacent to the said light-transmitting wall part
and inV close proximity to the charge-storing
agency, and direct conductive connections be
ductive casing closely surrounding and extending
from end-to-end of the assembly, a first sparking
electrode having a direct conductive connection to
tween the charge-storing agency and the said
the said casing near one end thereof, a second
electrodes for allowing the intermittent discharge 35 sparking electrode cooperatively spaced with re
of the former through the latter, the resultant
spect to the first electrode and directly connected
discharge circuit being of such small inductance
to the assembly terminal means which is near
that the duration of each of thelight impulses
said one end of the casing, and a connection be
generated upon the occurrence of a discharge is
tween the remaining assembly terminal means
a fraction of the time required for reflection of
and the other end of the said casing, Vwhereby the
said impulses from the aforesaid distant object.
loop circuit through the condenser assembly and
4. In a system in which light impulses are
the casing provides’a low inductance discharge
transmitted to a distant object and correspond
path from the assembly through the said sparking
ing reflected impulses are thereafter received
electrodes.
_
from said object in a time dependent upon the 45
8. A light impulse generator comprising an as
distance to the object, the combination which in
sembly of charge-storing units extending parallel
cludes a condenser assembly aranged so thatY cur
to a common axis, said assembly having at one
rent flow is from end to end through the assem
end thereof a common connection point to which
bly, terminal means for the assembly at its re
the adjacent extremities of the various charge
spective extremities, a circuit including said tel" 50 storing units are connected, a conductive struc
minal means for periodically charging the assem
ture closely surrounding the assembly and extend
bly, a conductive structure closely surrounding
ing from end-to-end thereof, said structure pro
the assembly and extending lengthwise of it, a
viding a common connection point for the Various
ñrst sparking electrode having a direct conduc
charge-storing units at the end of the assembly
tive connection to the said structure near one end 55 remote _from the first-named connection point,
thereof, a second sparking electrode directly con
cooperatively spaced electrodes located adjacent
nected to the vassembly terminal means which is
to said first-named connection point, a direct con
near said one end of the conductive structure,
ductive connection between one of said electrodes
and a connection between the remaining assem
and said first-named connection point, and a di
bly terminal means and the other end of the con 60 rect- conductive connection ybetween the other
ductive structure, the resultant loop circuit from
electrode and an adjacent point’of said conductive
the condenser assembly through the sparking
structure, the resultant discharge path from the
electrodes being of such small» inductance that
said assembly through the electrodes being of
the duration of each of the light-pulses generated
such small inductance that the assembly is en
by discharge of the' assembly through the elec 65 abled, upon charging,>to‘create between the elec
trodes- is a fraction of the time required for re
.trodesa light-producing spark of extremely short
flection of such impulses from the aforesaid dis
duration.
tant object. Y '
`
v9. Alight impulse generator comprising a gas
5. A light impulse generator comprising an en
closing casing, a charge-storing agency within 70 ' ñlled metal casing having a light-transmitting
window at one end thereof, an assembly of charge
the casing, a pair of mutually spaced electrodes
within the casing in proximity to the charge-stor
¿storing unitswíthin said metal casing and ex
ing agency, a light-transmitting wall part in
tending longitudinally thereof so that current flow
corporated in said casing adjacent to the said
through the assembly. is lengthwise of the casing,
electrodes, and low inductance conductors-direct 75 said units -havingîa common connection-point at
2,409,030
the end of the casing adjacent the said window
and a complementary common connection point
for the other end of the assembly being provided
by the casing itself, a pair of mutually spaced
electrodes within the casing and in proximity to
the said window, a first conductive means con
necting one ci :aid electrodes directhT to said iirst
10
and a complementary common connection point
for the other end of the assembly being provided
by the casing itself, conductive means sealed
through said casing at the end thereonF remote
from said window and. extending longitudinally
of the casing within said charge-storing assem
bly, said conductive means connecting with the
assembly at said first-named common connec
tion
point and serving as an element of a supply
conductive means connecting the other electrode
directly to the wall of the casing, whereby a low 10 circuit for charging the assembly, a pair of mu
named common connection point, and a second
inductance current path is provided between the
charge-storing assembly and the electrodes.
10. A light impulse generator comprising a gas
ñlled metal casing having a light-transmitting
tually spaced electrodes within the casing and in
proximity to the said window, a iirst conductive
member connecting one of said electrodes to said
first-named common connection point, and a sec
window at one end thereof, an assembly of 15 ond conductive member connecting the other elec
charge-storing units arranged in hollow config
uration within the casing and extending longi
trode directly to the wal1 of the casing, whereby
a low indue-tance discharge circuit is provided be
tween th-e charge-storing assembly and the elec
trodes.
VICTOR H. FRAENCKEL.
units having a common connection point at the 20
SIEGFRIED HANSEN.
end of the casing adjacent to the said window
tudinally thereof so that current flow through
the assembly is lengthwise of the casing, said
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