Design and characteristics of laser camera system with diffusion filter of small particles with average diameter larger than wavelength of laser ligh

Olsasky, M. J.

English

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NATIONAL AERONAUTiCS AND SPACE ADMINISTRATION 
WASHINGTON, D.C. 20546 
u ~ f / ~ c i e n t i f i c  & Technical Xnformation Divioion 
Attention8 Miaa Winnie M, Morgan 
FROM t ~ ~ / 0 f f i c e  of Assiqtaqt General Counsel fo r  
Patent Matters 
SUBJECT: Announcement of NASA-Owned U. S, Patents i n  STAR 
In accordance with the procedures agreed upon by Code GP 
and Code USI, t h e  attached NASA-owned U. 8. Patent is being 
fowarded f o r  abstracting and announcement i n  NASA STAR. 
The following information is provided: 
U, S. Patent No. 
Government o r  
Corporate Employee 
.. : 3;587,424 
Rocketdyne, Division of 
North American Aviation, Inc. 
Canoga Park, California 
Supplementary Corporate 
Source ( i f  applicable) : .
NASA Patent Case No, 
NOTE - I f  t h i s  patent  covers an invention made by . -w,,,, 
;A Contractor. the follawina i a annl4-=hl 
a rhmn-at- 
employee of a NAS - ---------a -- -rr*rr-reg 
yes NO Q 
Pursuant t o  Section 305(a) of the National Aeronautic= and 
- -  - --------- ---- 
Space Act, the  name of the  Administrator of NASA appears o 
the first  page of the patent; however, the name of the act--- 
inventor (author) appears a t  the  heading of Column No. 1 
the Specification,  following the  w o r e  . . with ren-p+ 
~ l i z a b e t h  A. ~agter I 
Enclosure 
Copy of Patent aited above/ 5 
0 
- .  
,* u2"' I 
(CODE) 
I =! - 8 
" (NASA CR OR TMX OR AD NUMBER) 
I 5  (CATEGORY) 
https://ntrs.nasa.gov/search.jsp?R=19710023934 2020-03-17T03:17:45+00:00Z
PATENTED JUN28 1971 
United States Patent 
(72) linventors T. 0. Pahe 
&pa~ty A d m h b t o r  of the K~e~onol 
A e e o w ~ W  md Spa= AdnrK-llea in 
rasm to ao h v e n h n  of; 
Mar& J. OEwky, 22721 Cdli~ns St., 
W d a d  Hi&, caw. 
I2 1 1 Appl. No. 753,974 
[ZZ] Filed Aug. 2@, 19613 
6451 Patented Jam 28,197l 
~54 1  atmEn CnaWsnA AND DHIFFWSEOW ~ T E R  
THEREFOR ' 
9 CJBks, 2 Daawlllg Figs. 
[Sf] U.S. Cl ........................................................ 95/11, 
33 1/94.5,352/84 
[51] In(. Ci ......................................................... E03b41/14. 
HO l s 3/00 
150) FkBrdid&msB ............................................ 95/11,11.5; 
352184; 33 1194.5 (Inquired) 
I561 References C M  
UMRED STATES PATENTS 
3,154,311 10iH964 Johnson ....................... 331/94.5(U)o 
3,294,002 1211966, Vitkine ......................... 342/84(X) 
3,366.439 It1968 Bucket al ..................... 9511 1.5(X) 
3,438,050 411969 Aschenbmnneret a!.. .. 13 1,"94.S(X j 
OTHER REFERENCES 
" A True Kerr-Cell Framing Camera" by Ma,lser et ai  
SMPTE, June 1962 
" Cit Develops Stroboscopic Laser Light" , P S & E %'ol 
7 ,  May- June 1963 
" From Flash Guns to Lasers", by Hood, EEECTRONBCS, 
Aug. 1963 
'"Kaigh Speed Framing Camera for Laser Roc! S tudy"  by 
Bickart, ELECTRONIC COMMUNICATBR, t oE 1, No. 1, 
Jan. 1966 
" Laser Applications" by Maiman, PHYSICS TODa4Y, iu iy  
1967 
Primary Examiner-Samoel S. Matthews 
Assistant Examiner-Robert P. Greiner 
Arrorneys-Monte F. Mott, 9. H. Warden and G. F. Ms$:oy 
ABSTRACT: A laser camera system incit~ding a dafrusaosr 
filter is disclosed. The diffusion filter as a Baser Esgho trans- 
parent receptacle containing a suspension of small pafllcles! 
having an average diameter laager than the wavsiergrh or aha 
laser light. The suspension is preferably a colioad~l SL ~ D C - P  ri J 
of milk or metal particles in water. 
3,587,424 
1 2 
LASER CAMERA AND DIFFUSION FILTER TEIEREFOR The anventron wall now become bencr ~rlder.;tond by 
reference to the following detaeled deserrgtson wileha coo 
CPRlGtN OF THE INVENTIBN sldered ~n conjunction with the accomparajarrg drawrgs 
The lnvewtmn descrabed hercnr was made in pehrrnance of 5 BRIEF DESCRIPTION OF THE DR.\WlNGS 
work under a NASA Contract and IS subject to the provyslons 
of Sect~on 305 of the NatlonaE Aeronautrcs and Space Ace of FIG 1 n a scbrmahc and block dtagram v!:w ?i a nhoto- 
1958, PubElc Law 85-548 (72 State 435 42 USC 2457) graphsc system according to the ~n-dention 
FIG 2 as a schernatsc vaew of a high-specd fieber camera 
BACKGROUND OF THE INVENTION system accordzng no the Inventnon. 
1 Field of the Invention 
The present nnventlon relates to an opk~cal filter and more DESCRIPTION OF THE PREFERRED TMFlfiDBF"EYTS 
particulariy to a dnlgusron filter for a pulsed laser Etghr source Referring now to FBG I ,  the laser carnerd ol sbe snvenltea 
of use In photography compmses generally a pulsed laser laghe source 10 lncluiiiag a 
2 Descriprnon of the Prloa Art I5 totally reflectn*ve end face 12 and a partrally reflect ve c7d faca 
The Ilght that ns emltted from a laser 1s monochromarnc, cob 14 A flat slded cell 16, trwsDarent to t"l Rliiser Pagh\ cdntann- 
h a t e d ,  coherent, lllnearly polarized and as highly intense The nng a collofidal suspensson 18 of powdered r~rafft rs place? ,n the 
R~gh lntensnty of the laser Izght pePmltS exposure of a large drea lrght path of the laser I@ a camera 20 1s situate$ EL. col'gci the 
of film The colhmated nature of the Lght makes the laser Lass- Pnght output from the cell 16 on a ]en$ 22 T\e 1 ~ .  3 1 2  2 a faxes 
ly adaptable to a varlet) of opPlcs1 systems and the extremely Z0 focus lens adapted to form a planar Image o f ~ l a e  rghi. ecerved 
short dueatlor\ of the light pulse permnrs hagR Image speeds from the cell 14 on a film plane 24 Film plane 24 .s eel-xrted :o 
over the film plane These properties make the Baser a very recelre a of photograyhrc filpn 25 
useful tool fin areas snvolv~ng photographic technlqrres When an object 26 1s placed warhnn the .,gE?' prelr of the 
Furthermore, a laser, when operated an the pulsed mode, acts laser 10 and a pulse of laser lrght 1s projected throra;js the cell 
both as a light source and a shutter Therefore, a hrgh-speed $6,  a ~lnglc exposure ofthc object 28 is *r~de-e  7 0 t-, . ;P-~er- 
iaser camera only requlres an acceptable optical System and a of film 25 Jt has been found accordnng go the itroc, rs+ 
means of obta~nnng a physical separatnon of each Bame of the srgnlficant amprovement over standard p h ~ j r ) g r ~ ,  "&h m * + ~ i ;  
film SeveraE such cameras hate been bulIt and operated, such ,s achieved When the cell B Q  1s PemoveA and  ti.^ c v k ~ ? s j  -
as the work reported by Eills, A $ and Fourney, M E 1963, 30 repeated, the developed film d~splays worrn$eecc *.reas ip.dhcai 
" ~ ~ ~ l r c a r r o n s  f 3 Ruby Laser to Mlgh Speed Photography," ~ n g  the presence of interference patterns 
Proc Bqst Elect. and Electronic Engnneers, 51, 5 pp 941- When the laser 1s operated ~n the free reannirg mode, IF: 
-942 output 1n thas mode rs irregular and the am9 iude varaac lii: a 
Though use of lasers high-speed photography ilghe random manner However, i h  1s still qunte useful for tak~rtg  sla- 
sources m the mode of operation as reported b~ Ellas ea 
. has 35 gie plctures However, for h~gh-speed photonsaphy t?e rin 
made it porszbie to photograph phenomena chat hereto- dom output of the laser must be controlled so that the  lasel 
fore not Ihe of the Easer E1ghr source del~vers a controlled ampiitude pulse of constant d ~ ~ d t i c ? ~  ori 
cause? anterference patterns xahach obscure important details command ~ ~ ~ ~ h ~ ~ ~ ~ ~ ~ ,  there a characrerlPrlc delgy 
of the event being photographed order to reach yopulatlon lnverslon after the 'aser *s  pbnped 
AND OFTHE INVENTION 40 with an external flash of light. This must be considere~l sn the 
successful operation of a high-speed framsng camera The 
Bt is therefore an obiect of the nnventron :o provide nm- neneral method utzlized in the art for conlrollaa~ the Paser out- 
- 
prove"Ie6nition in laser exposed photographs. put is by Q-spoiling. A typical Q-spoiling technique 3s to insert 
Another object ef the invention is to provide means for a Kerr cell in the cavity. The Kerr cell caw be pulsed ta key the 
eliminating interference patterns in laser light photography 45 laser to generate a series of spaced time pulses reqoired for 
with minimunr degradation of the frequency spectrum and in- high-speed photography. 
tensity of the laser light. Referring now to FIG. 2, a high-speed framing cameos 
Yet anather objeca of the invention is to provide means for system includes a pulsed laser 40 having a Kerr cell 42 in- 
variably controlling the degree of diffusion and attenuation of serted within the laser cavity, a diffusion filter-cell 44, a high- 
a laser light source for static and high-speed photography. '' speed framing camera 46 and the associated means to 
These and other objects and many attendant advantages of synchronize these elements. 
the invention will become apparent as the description The active material for the laser is a ruby rod SQ hatiing one 
proceeds. end cut in a wedge 58 so that the light propagating aio:ng the 
In accordance with the invention, a diffusing medium com- 55 rod 56 is reflected in a direction parallel to the incomirig ray. 
prising a stable suspension of small particles having an average The ruby rod 56 is positioned at one focus of a highly poElshec4 
diameter larger than the wave length of the laser light source is cavity 60 of elliptical cross section. A xenon light pump 62 i s  
interposed between the laser Eight source and a camera to positioned at the other focus of the cavity. A Fabrjr-Peroi in- 
remove the coherence of the laser beam without substantially terfeerornetric cavity is formed between the wedge erd  58 of 
affecting its other characteristics. If the particles are con- 60 the ruby rod 56 and a movable external dielectric partially 
siderably smaller than the wave length ofthe laser light, the in- transparent mirror 64. 
cident beam will be scattered rather than reflected by the par- The Kerr cell comprises a container filled with a liquid 65 
ticles. However, when the size of the particles is no longer that becomes doubly refracting when subjected tc an eiectri- 
small compared to the wave lengths of the laser light, ordinary cal field. A typical liquid is nitrobenzene. The container has 
diffuse reflection from the surface of the particles will occur 65 radiation transparent end walls 66 and 68 and a set ohieec- 
without degradation of the Frequency ofthe laser beam. trodes 70 and 72 are oppositely disposed along two other walls 
It is preferred, according to the invention, Po utilize a ofthe container. 
disperse phase of solid particles in a state of subdivision A filter cell 48 Raving fiat radiation transparerrt end walls 80 
adapted to form a colloidal suspension in a liquid disperse and 88 is positioned across the light path of ths Baser. The cell 
medium. In a solid-liquid colloidal suspension, the fine parti- 70 contains a translucent colioidal suspension 87 of powdered 
cles remain suspended and will not readily settle out, There- milk particles in water. 
fore, homogeneity without external. mixing of the suspension is The high-speed framing camera 46 comprises a Eight opaque 
inherently achieved. Suitable colloidal suspensoids according enclosure 92 containing a lens system 94 which co2ieces the in- 
to the invention are prepared by suspending colloidal size par- corning rays and focuses them on a fixed mirror 96. 'The rays 
ticles, such as milk solids or gold particles, in water. 75 are reflected from the mirror 96 onto a rotating reflector 98. 
3,587,424 
3 4 
On each r-~o~utao-~ f  the reflector 98, image-fortnmg rays are achieved under these conditions. From the pulse train 
'satrj~~o a tiEm plane 1069. High-speed framing cameras are enerated 6- the Rerr celt Q-spoiling.technique, it has been 
-crdi;y .I, 114ahla and the minor may be mator or ivr- found that t i e  pulse amplrtude repetltlon rate IS a function o f  
ban- i-iven a$ an tine Beckman and Whrtley Model No. 200 cavity length. The amplitude o f  the pulse has been found to 
V ,fir S seed Frasmsng Camera. 5 decrease with mcreasang cavity length. The duratnon o f  the 
Wni'a he Kerr ctll ~nser~ed in the laser cavlty, the direction pulse appears to be only dependent on the active material util- 
if .i c ; ~11r tded  k~ghl which ES propagating in the cavity is ized, the PumPlng Power developed In the flash lamp and the 
-, 7abes' dniv t h ~ b  etfectively increases the cavity loss coeffi- efficiency o f  Q-spoiling. 
-iea W p i ~ n  t ~ e  clectrncal field o f  the Kerr cell is turned on to Since the sensntrvity o f  ordinary photographic film is quite 
i t \  cua :er-save value by energizrng the electrodes the 10 poo"n the region o f  7000 A., special types of film must be 
:uias zatssar: csf @he laser light which passes twzce through the utilized. It has been found that Kodak 103-F Spectographic 
c 11 rna,dted 30' from the favored plane o f  polartzation. In film ~ h l c h  as a long density o f  0.8 at 7000 A. is quite ac- 
(111s \:ruan?on, rekeneration IS insufficient for osciEkatlans untrl ceptable for producing photographs according t~ the h e n -  
= m u c r  hfgher level o f  excitation is reached than I S  requlred 
'or os~aiX3t~ors *ith the Kerr cell absent. T o  produce a single 
.>uise, *4:: ken cell !s acilvated. The exciting flash lamp is then 
f ~ e d  *,r d atter a ~ h o r t  mterval, the Kerr celi is suddenly turned 
J:T l a  a time jess than about 0 02 microseconds The resulting 
pulse rn~rke s repawducib8e 
A pesxodis pulse Peaan IS  obtained by sw~tching the Kerr cell 
st sulraba~ chosen intervals The Kerr cell is operated by im- 
p-essing a bamng voltage from DC power supply PO2 across 
the eiectrodes 78 and 72,  and it I S  pulsed by rapidly seducing 
the btasis, voltage lo 0 on command from a pulse forming unrt 
436 wBdct generates pulses varylng from about 350 k~locycles 
2 1 66 iaegacycles These pulses modulate the DC power 
,uppi& 1102 &G the plates nn the Kerr cell. A timlng unit 104 IS  
tarnlseed to genent? a gatezl output to trigger the Eases power 
se twcrk  LO ar,d the Kerr cell pulse forming unit 906. The 
rtrnins itnit is tra~iered bv the swnchronlzation electronics as- 
rion. 
With the Kerr cell operating in the disclosed mode to pulse 
a ruby laser as described, controlled pulses at repetition rates 
o f  over 1.6 Misec. have been achieved. The pulse duration o f  
approximately 30 seconds can be utilized to expose photo- 
graphic film at rates o f  over 1.2 million frames per second. 
A Beckman and Whitely Model 200 camera was operated 
with its turbine drivers mirror rotating at about 1600 r.p.s. The 
camera was synchronized with a ruby laser which was pulsed 
at a rate o f  2'4%05 pulses per second for 150 microseconds. 
The definition achieved exceeds that possible in previous tests 
without a diffusion filter according to the invention. 
1r is to be understood that the foregoing relates ors?y to 
preferred embodiments o f  the invention and that numerous 
substitutions, modifications, and alterations are giernnisahlr 
without the departing from the scope o f  the invention a; 
defined in the following claims. 
. - 
iocrllci-cl ~ 8 t h  the rotattnni mirroi 98. The rotatton o f  the mir- 
at a lime, I,, sz; sensed by a magnetic pickup 120. The signal A photographic 'ys tem in 
rum qjgretn: plcic~lp 1Z@ 8s converted into a pulse by counter means for forming a pulse of   monochromatic^ col'i- 
t22 ;a?? : r i l l  pulse amplified in pulse amplifier 124. The am- mated, coherent and highly intense light along an optical 
p~ni1.x~ p dw ees applied to an oscilloscope 126 operating In a 35 path; 
,i?g's sheep generate reliable timing signals. These means d l s ~ o s e d  the O ~ P 1 c a l  path o f  said light 
mnng sigqahs ard  pulses form a pulse generator 128 are util- pulse; and 
*eil 4r nouir to tPae runtrag unit 184. The timing unit 104 in- filter means interposed between said source means and said 
IfadYtL: the ceqmnce o f  energizing the laser power network 110 camera means for diffusing said pulse o f  light comprising 
a-c p~I117g '89.6 Kerr cell to key the laser to deliver pulses 40 a container transparent to said light having flat end walls 
s acFso ??zed to the posrtlon o f  the rotating mirror normal to said light path, said container enclosing a 
Th: laser power network energizes the flash lamp by suspension o f  solid, colloidal particles in a liquid, said 
2 ~ve,r-g at Beast 160 joules o f  energy to the flash lamp 62. particles having an average diameter greater than the 
rhe Ca:b lamp durataon is about 1 millisecond. Durlng the wavelength o f  the light. 
flask l ~ n i p  duration, the voltage across the Kerr cell electrodes 45 2. The 'ystem ' I a i r n  in which mid 
;.i cdt  er 0 voirrnge by each pulse from the K~~~ cell pulse is a translucent, colloidal suspension o f  milk particles in water. 
'ormarig unit Due to the delay In reaching threshold for the 3. The system according to claim 1 in which said source 
* %a te*v -. , the flash lamp I S  first energized whlle the Kerr cell blas- means is a pulsed laser. 
I-g voltage %s ampressed on the Kerr cell electrodes. ~ f t ~ ~  4. The system according to claim 3 in which laser is a pulsed 
p< puintson rnvcrsaon has been reached, the Kerr cell is pu~\ed 50 "by laser and said system includes a pulsed Q-spoiling means 
., x sir be laser to dehver a controlled amplitude and pulsed for pulsing said laser. 
83%~ 5. A system according to claim 4 in which said pulsed Q- 
A r~ A i a ~ i e  actwe material for the laser is a 3-inch long, %- means a Kerr 
1'1183 Jizmeter total rnternal reflection ruby rod dope$ with 6. A system according to claim 1 in which said camera in- 
O 05 -,eFcenr: Cs"3 I O ~ S .  An EGG FX-42 xenon flash tube can 55 cludes a rotating mirror and a film plane; 
be ut3lr4"d as the pumping source for the laser. A total reflec- said mirror projecting multiple exposuws o f  an event to be 
t o r  6 "rmed at one end o f  the ruby rod and an external dlelec- photographed on said film plane. 
iric nair$ea havsng 90 percent reflection at 6934 A. forms the 7. A System according to claim 1 in which said colloidal 
orher sade of the Fabry-Perot ~nterferometric avaty. The cavi- suspension is a suspension of metal particles in liquid. 
t v  lengxh can be v,aaied by adjusting the position o f  the &Iec- 60 8. A method of recording an object comprising steps of :  
I-,c 1 ~ 1 1 ~ 5 ~  SC* that the space in between the mirrors 1s var~ed forming a pulse light; 
ocrwpcn 24 to 54 centimeters. The pumping circuit for the passing said pulse through a diffusing medium consisting es- 
FX-42 flash lamp del~vers more than the minimum threshold sentially o f  a colloidal suspension o f  metal particles in 
energy o f  160goules and usually less than about 1300 joules liquid, the particles having an average diameter greater 
The K, rr ce:; ns typncally fifled with nitrobenzene and is 65 than the wavelength of the light to diffuse said light, 
upe,atea at n vortage o f  about I0 kv. The duration of the Kerr illuminating said object with said diffused laser light; and 
celi guise -hen varred between 0.1 m~crosecond to 0.4 formlng a record o f  said illuminated object on a light sen- 
ir7ac~,>stbcond had a rise time o f  approximately 20 nsec. The sitized recording element. 
me time of rhas Paser IS approximately 10 nsec and has a dura- 9. A method according to claim 8 In which said metal 1s gold 
rrar-i of a.zot'2. er 20 nses for a total pulse duration o f  about 30 70 and said ]!quid Is water. 
~ S E C  71'1 rmtrp~"~ed ampl~tude pulses o f  l~ght at 1.5 mc. can be 


Laser camera and diffusion filter therefore Patent

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