MONTHLY LETTER PROGRESS REPORT,(Sanitized)

• Document Type: CREST
• Collection: NGA Records (Formerly NIMA)
• Document Number (FOIA) /ESDN (CREST): CIA-RDP78B04770A001200040001-5
• Release Decision: RIPPUB
• Original Classification: S
• Document Page Count: 18
• Document Creation Date: December 28, 2016
• Document Release Date: April 27, 2005
• Sequence Number: 1
• Publication Date: November 30, 1965
• Content Type: LETTER

Approved F Release 2005/06/06: CIA-RDP78Bb41A'001200040001 t
Mailing Address
Monthly letter progress report,
Comments on Status
November 30. 1965
Task I - Item 1 "Special Investigations"
Two visitations were made this month at the request
of the Technical Representative of the Contracting Officer
to
Task II - Item 1 "Submicron Measurement Error Analysis"
In reviewing the test data on floor vibration measure-
ments conducted by Bureau of Standards in 1960, it became
evident that a better presentation of the data would be
desirable. In the October progress report it was s3ggested
that a vibration power spectrum presentation of Gar / cps
vs cps would be more useful. A brief literature review
of the fundamental concept has reinforced our opinion that
the vibration data should be presented as a power spectrum
rather than isolated amplitude and frequency numbers.
Further work on this item was deferred in favor of more
urgent work on items 6 and -8.
Task II - Item 5 "Lamps for Rear Projection Viewers"
The technical data received on the new high pressure
are lamps under development show considerable promise for
these lamps. If they prove to be truly applicable to rear
projection viewers, it appears that a 400 watt lamp will do
the same or better job than a 1000 watt tungsten lamp.
Although analysis of the lamps was begun, completion was
deferred in favor of more urgent work on items 6 and 8.
Task II - Item-6 "Evaluation Criteria"
A technical report on Item 6 was completed and final
draft is being prepared for submission.
NGA Review Complete
.Approved For Release 2005/06/06 : CIA-RDP78BO477OA001200040001-5
25X1
25X1
 Approved FRelease 2005/06/06: CIA-RDP78B049JOA001200040001-5
25X1 November 30, 1965
Comments on Status on inue
Task II - Item 8 "Laser Metrology"
Fundamental work on item 8 was initiated and the data
will be reviewed with the Technical Representative of the
Contracting Officer. The technical report was blocked out
but additional analytical work will be required before it
can,be completed.
25X1
Approved For Release 2005/06/06 : CIA-RDP78BO477OA001200040001-5
 Approved For ease 2005/06/06: CIA-RDP78B047701200040001-5
25X1
Vlsi to NPIC on 14 January 19640
1. enclosed a e Dr. comments concerning
the performance, of the Microscope and viewing
Conditions which he observed during his trip to
25X1
{
'z submi ;,,red this memorandum during
h.. sa to adquarters on {:.5 February 1964.
ientific Advisory Board
2 ! proved For Release 2005/06/06: CIA-RDP78BO47 flA001i0O0'0400
25X1
25X1
25X1
 Approved For Remorse 2005/06/06 : CIA-RDP78B04770AQ,Q1200040001-5
MEMORANDUM FOR THE RECORD
SUBJECT: Comments on Trip to NPIC, 14 January 1964.
1. These are a part of my observations made at NPIC
during my visit of 14 January 1964. I asked to see materials
of the best quality. I was shown KH 4 and KH 7 samples,
including the resolution targets near Washington, D. C., and
other samples from the flights that occurred over Washington
on 26 December 1963, and a number of the other best photoraphs
thus far achieved. My interest in the inspection of these'-'
materials was not so much in the materials themselves as it
was in the performance of the microscope and the viewing condi-
tions. It seems to me that the end product of the whole recon-
naissance system is the light that enters the eye of the inter-
preter. It is his interpretation of what he is able to see
that prpduces the final intelligence of value to our country,and
I am not-convinced that everything has been done to maximize
his ability to extract the best possible retinal image from the
pictures.
2. This is a natural interest of mine partly because I
have, since World War Ii days, been a member of the Armed Forces-
National Research Council Committee on Vision, and partly
because all of my activities have been devoted exclusively to
visibility matters for many years. I was interested, therefore,
in looking at the microscope from the standpoint of the visual
performance achieved with it and the viewing conditions under
which the photo-interpreters presumably operate.
Approved For Release 2005/06/06 : CIA-RDPhB04770AOAi2Q0040001-5
 Approved For Re&se 2005/06/06 : CIA-RDP78BO477OAQ A200040001-5
3. 1 endeavored to ask questions concerning the way in
which the actual interpreters use the microscopes. I did not
meet any of the interpreters or see them in the performance
of their work. So f, as 1 am aware, the interpreters use
the same type of microsco;)e :.:,.d presumably work under the same
sorts of conditions that I cxperienced during my visit on
14 January. From many things that have been said both in the
various presentations I have heard and in the responses to the
questions I have asked, I realize that the Agency is well aware
of some of the shortcomings of the microscope and the viewing
conditions under which it is used. For,example: I recall from
the briefings that studies have been made of means for increas-
ing the apparent luminance of the diffusing surface against
which transparencies are viewed. This is an important matter
because, at high power, the exit pupil of the microscope is
quite small and produces retinal illumination lower than is
desirable in the darker portions of the scenes. I am convinced
that any observer can obtain more information from the film at
high power if more light could be made available. I am prepared
to believe that the optical design of these constructions has
been carefully considered and that a larger exit pupil is not
practicable. If this is true, there seems to be little recourse
except to'increase the light available below the transparencies.
4. The performance of the observer can also be increased
by improving the contrast rendition of the microscope. No
one to whom I talked had any information concerning the contrast
.rendition of the system as now exists. My impression is that
the system is far from being poor in this respect, but on the -
other hand, I would be surprised if worthwhile improvement could
not be achieved rather easily. Quantitative measurements of
co -cast rendition which I have seen on other high quality micro-
scopes indicates that improvement is almost always possible if
a small opaque stop can be introduced at the transparency. In
one installation with which I am familiar, a thin piece of metal
containing a hole only large enough to allow the microscope to
inspect the portion of the transparency corresponding to the
field of view of the scope was provided in order to prevent light
from other portions of the picture from reaching the microscopic
Approved For Release 2005/Q6/06 CIA-RDP78B04770A001200040001-5
 Approved For Rel a 2005/06/06: CIA-RDP78B04770A0Q200040001-5
objective lens. It produced a very noticeable improvement
in the apparent contrast of the photographs, particularly at
high power. Such a result could be achieved automatically
if illuminated diffusing glass beneath the transparency is
replaced by a lamp housing from which light is emitted only
by a small area directly beneath the microscopic objective.
5. In the present instrument the large illuminated
diffusing glass produces a very distracting glare field into
which the observer is forced to look. I understand that some
operators make a practice of covering this illuminated area
with opaque material, such as cardboard, in order to diminish
this glare. I heartily endorse this practice and strongly urge
its adoption and extension. I understand also that the inter-
preters tend to turn off the lights in the room while looking
into the, microscope. This also is a desirable practice. Unless
both ofthese precautions are taken, the observer will be
surrounded by enough room light to impair his visual performance
unless well fitted eye cups are provided.
6. The small plastic shields with which the present
instrument is provided are virtually. useless and doubtless are
seldom used. A dramatic improvement in visual performance
can be effected simply by using ones hands to form eye cups
before the microscope. The full improvement is not experienced
until all of the stray light is excluded. I strongly recommend
that thd'existing microscope be fitted with very good soft
rubber eye cups. It would be desirable to have these specially
made for each photo-interpreter so that he can achieve a com-
fortable, tight fit. If such cups are provided, the glare
produced by the large illuminated diffusing glass will be negated,
except for the deleterious effect arrising from abrupt changes
in his adaptation which will occur when he lifts his eyes from
the eye cups and looks at the brightly lightly lighted field
beneath the microscope. Presumably it is necessary for him to
do this at frequent intervals. Despite the fact that adaptation
is a comparatively rapid process at high light levels, visual
performance will be degraded for periods of several seconds after
the eyes are returned to the eye, cups if there is any form of
glare source?in the working enviornmerit. Glare-free viewing
conditions in the work space outside the microscope eye-piece
is highly desirable.
Approved For Release 2005/06/06 : CIA-RDP78BO477OA001200040001-5
 Approved For Rase 2005/06/06: CIA=RDP?78b04770AW1200040001-5
7. My visual inspection of the microscope made me
believe that achromatigation conditions could be improved,
particularly at high power. It is possible that some of the
chromatic effects which I soc;ied to observe stem from the
spectral distribution of the light from the illuminating system.
It is possible that the spectral distribution of the light
from the diffusing glass has a very different composition than
that which was assu;1ied by the lens designer who achromatized
the microscope. This might be wort'a reviewing. In any event,
reduction of chromatic effects in these microscopes could improve
visual performance on the part of the photo-interpreters.
8. The microscopes eye pieces have focussing adjustments
but these are not provided with diopter markings. The adjust-
ments for:.interpupillary distance, moreover, do noL appear to
.have a calibration scale. The photo-interpreter should not be
expected to operate eye piece adjustments and make settings of
interpupillary distance by trial and error. Just as in the
case of military looko ;-:,s, his refractive correction and inter-
pupillary distance should be determined carefully by clinical
procedures, and he should set the diopter rings and the inter-
papillary adjustment in accordance with clinical findings before
he attempts to look through the microscope. If the clinical
work is done properly and if the microscope is properly adjusted
and calibrated, the observer will have his eyes properly aligned
with the optic axis of the instrument and provided with the
optimum (spherical) correction. In no other way will he obtain
the best visual performance of which the microscope is capable.
9. The photo-interpreters should not wear spectacles
while looking through the microscope. These will not be necessary
unless he is inflicted by astigmatism or some other visual
defect for which ordinary eye piece focussing adjustments do
not provide a correction. Each photo-interpreter should be given
a very careful periodic opthaimic examination. Provisions should
be made in the microscope for introducing cylinders (and prisms
and if needed), tailored to the prescription of each man. Spec-
tacles will then not be necessary.
Approved For Release 2005/06/06 :'CI - P78B04770A001200040001-5
 Approved For Remise 2005/06/06: CIA-RDP78B04770A0iL1,100040001-5
10. I wish particularly to emphasize the loss in
visual accuity in the use of microscopes such as those now
employed by the Agendy if the observer has uncorrected
astigmatism, even astigmatic defects so slight as ordinarily
to be considered as sub-clinical. These can quite demon-
stratively impair his visual performance.
11. The effect of small amounts of the astigmatism
can be quite insidious, because the interpreter is ordinarily
looking ai: non-sharp images and must endeavor to discriminate
fine details buried in soft or grainy photographic images.
He has no way to know whether the unresolved image he sees
is truly representative of the film or whether part of the
apparent loss of resolution is created by astigmatic or other
defects in his own eyes. He should not be asked to make this
judgement; rather, he should be subjected to frequent, care-
ful othal:,.ic examinations and he should be provided wiLh full
corrections on each eye piece. In f act,,,.I would strongly urge
, '.:that the ,oto-interpreter on ,t,hose visual performance: s'o._.much
depends.1ould have very careful
-special eye examinations not
,less fro aeiitly than -,nce a month, primarily in order to detect
small chL.nges in astigmatism which may develop. Experience
may indicate whether such tests should be done less frequently
or morerequently than :ontilly, but clearly a testing program
.should be instituted by the A ency and should be mandatory and
not left to the discretion of lie individual photo-interpreter
or his private nnthal mnl nrri st or optometri st Nn detectab e
sub-clinical astigmatism shou--d go uncorrected.
12. It would be desirable to give careful consideration to
imn-oving the comfort of the p oto-interpreter while working
th -cgh the microscope. Professional attention to such items
as seats, arm rests, head rests, etc. should be given and these
should be tailored to the stature and requirements of each
photo-interpreter. The accoustical enviornment should also be
considered and everything done to eliminate distraction, dis-
comfort, and fatigue for these men.
Approved For Release 2005/06/06 CIA-RDP78B04770A001200040001-5
 Approved For ReIe 2005/06/06 : CIA-FbPP8BQj4770AQQJ200040001-5
13. Visual performance varies with age. I understand
that the group of photo-i~.: erpreters used by the Agency
contains a wide spectrum of age. he visual capabilities of
the men should be considered and possibly measured. Critical
materials might profitably be looked at by more than one,
individual, inasmuch as there maybe a trade-off between the
effects of age on visual performance and interpretation
capabilities.
14. Finally, a review might profitably be made of design
compromises of the microscope, primarily if.it affects their
performance at high power. A different instrument with higher
power capability might reveal more information in some instances
than can.be obtained with the present microscope. It was my
impression that more power would have been helpful in a few
instances.
15..' A study might also be made of the color and the
spectral distribution of the lighting. Small second order
improvements might result from a change of lighting.
25X1
p Cics Pane
Scientific Advisory Board
Approved For Release 2005/06/06 : CIAzRl P78B04770A001200040001-5
 Approved FovmWlease 2005/06/06 : CIA-RDP78BO47 1001200040001-5
preprint no. 11
LIGHT SOURCES
High-Pressure Sodium Discharge Arc Lamps
By W. C. Louden and K. Schmidt
T HE potential of sodium and other metallic atoms
for use in light production was examined by
Dushman' and others.2 These results stimulated work
by Fonda and Young-' and in 1932 they demonstrated
low-pressure sodium lamps in several installations.
The lamps were characterized by their monochro-
matic yellow color and had an efficacy of 30 to 70
lumens per watt. Highway lighting installations were
the principal use for these early lamps as application
to other use was limited for esthetic considerations.
Commercial history of high-pressure discharge are
lamps began in the early 1920's with the development
of mercury lamps. Developments in the mercury
lamp since Elenbaas,+, by Noel' and others," have
resulted in a generally accepted light source that has
replaced the low-pressure sodium lamp in almost all
the old installations. However, the low-pressure so-
dium lamp still finds wide application in European
countries where development work has continued.
Efficacies of over 120 lumens per watt are now com-
mon through improvements in techniques and inno-
vations in arc tube designs. The lamps are popular
in those countries that pay a premium for electrical
power.
The low-pressure lamp operates with a sodium
pressure of several microns. Special arc-tube glasses
and glazes have been developed to resist the corrosive
chemical characteristics of the sodium. Higher so-
dium pressures achieved by increasing arc-tube tem-
peratures cannot be attained in conventional glass or
quartz arc tubes as rapid chemical action darkens the
arc tube. This reduces the efficacy and eventually
causes failure of the lamp. Therefore, all commer-
cially available sodium lamps, even with recent inno-
vations and increased efficacy,, have a characteristic
yellow color with the associated poor color rendition.
Schmidt7, " has studied high-pressure discharges
through the vapors of alkali metals, sodium, potas-
A paper presented at the National Technical Conference of the
illuminating Engineering Society, August 29 to September 2,
1965, New York, N. Y. Au'rnoas: General Electric Co.; Large
Lamp Dept,, Nela Park, Cleveland, Ohio.
sium, rubidium and cesium, and discovered that
sodium provides the highest efficacy in a light source
with a good color rendition. The high-pressure so-
dium discharge is enclosed in an arc-tube envelope
of high-temperature, alkali-vapor-resisting, high-
density, polycrystalline aluminia. Nelson" and Rig-
den10 have since made similar studies and have sub-
stantiated these findings. Operation of the high-
pressure sodium discharge differs from that of the
high-pressure mercury-metallic-iodide discharge" in
that the discharge is wall stabilized with high-volume
loading, the sodium pressure is higher by a factor of
several hundred, and it is primarily the sodium atoms
that are excited. The iodide lamp operates constricted
and convection determined, the sodium pressure is
ordinarily a few torr; it uses mercury as well as
metal iodides, and atoms of all the metals and mer-
cury are excited. The high-pressure sodium lamp dif-
fers from the former low-pressure sodium lamp in
that the discharge is wall stabilized with high-volume
loading and the sodium pressure in the arc is 200
torr compared to several microns, about 100,000
times higher than in the older light source.
Physical Construction
A 400-watt high-pressure sodium discharge arc
tube is shown in Fig. 1. The arc tube (B) is sintered,
high-density polycrystalline alumina manufactured by
a process12 that promotes controlled grain growth.
The alumina tubes produced by this process are
translucent and have a total transmission of light in
the visible region greater than 90 per cent. The trans.
lucent alumina is highly resistant to alkali vapor at
high temperatures. As a comparison, a high-pressure
sodium arc operating in a conventional quartz are
tube would cause chemical darkening of the quartz
by forming sodium silicate in less than an hour of
operation. The translucent alumina shows no attack
even after 10,000 hours of operation. Subassemblies
A and C, consisting of metal end-caps and standard
Approved For Release 2005/06/06 : CIA-RDP78BO477OA001200040001-5
 Approved For nee ease 2005/06/06 : CIA-RDP78B04770A001200040001-5
Figure 1. The 400-watt
high-pressure sodium
discharge arc tube and
operating outside-wall
and seal temperatures.
11---Translucent, alumina
arc tube; .4 and C-
metal end cap subassem-
blies; D-closed exhaust
tube.
electrode structures, are sealed to the alumina tube.
A metal tube. D, on one end of the structure serves
as a means for exhausting and for dosing the are tube
with an amalgam of sodium and mercury. This tube
is sealed off after processing is completed. The final
lamp structure, similar in outward appearance to
other high-pressure discharge lamps, is shown in
g. 2. The translucent alumina are tube is supported
by a metal framework in an evacuated outer glass
jacket. As in the mercury-metallic-iodide lamp, evac-
uation of the outer jacket serves to increase lamp
ellicacy by reducing conduction heat losses from the
are tube.
Discharge Mechanism
I n the low-pressure sodium lamp almost all the en-
ergy is radiated in the sodium D-lines. Since they are
located in the yellow portion of the eye-sensitivity
curve, very high efficacies can be obtained but the
color rendition of the source is poor. As the sodium
vapor pressure is increased, a great percentage of the
total radiation is emitted on either side of the D-lines
and the line radiation becomes imprisoned or self-
reversed. As a result, the source loses its characteris-
tic monochromatic yellow color to become golden
white with a significant amount of energy in the red.
Mercury is added to the sodium in the discharge tube
and acts only as a buffer gas. Little radiation of mer-
cury lines is apparent in the visible region. Mer-
cury raises the voltage gradient of the arc, permitting
higher efficacies in the current range of 2.5 to 5.0
amperes.
Stable operation of the discharge is maintained
with a reservoir of liquid sodium amalgam located
in the exhaust appendage. By a careful balance of
heat flow the appendage temperature is held constant;
thus the sodium and mercury pressure in the dis-
charge is constant.
The discharge is operated wall stabilized with an
arc length of 70 min between electrode tips. The tube
diameter, 7 mm, is small enough for the positive
column to be stabilized only by heat conduction to
the wall. Convection disturbances in the arc chamber
are negligible.
Design Characteristics
The scope of this paper has been limited to a dis-
cussion of the measurements made on a representa-
tive sample of the high-pressure sodium discharge
lamp. The reader is referred to Reference 8 for fur-
ther details concerning the discharge and its charac-
teristic The variation of design parameters has not
been included as investigation of all variables has not
been completed.
The spectral-energy distribution'; of a 400-watt
lamp operated at three different wattage inputs is
shown in Figs. 3a, b and c. Since the discharge char-
acteristics depend on the temperature of the liquid
Figure 2. Complete 400-watt high-pressure sodium dis-
charge lamp assembly.
Approved For Release 2005/06/06 : CIA-RDP78BO477OA001200040001-5
 Approved Foi elease 2005/06/06 CIA-RDP78BO47 001200040001-5
tal The operating temperatures of the 400-watt are
tube are indicated in Fig. 1. High-pressure mercury
are tubes generally operate with a center bulb-wall
temperature of 700 to 800 C and a seal temperature
of 400 to 500 C. By virtue of the high-density trans-
lucent alumina the center arc tube wall can be oper-
ated at 1280 C, and proprietary seal design allows
operation of the seals at 720 to 725 C.
,10 o
11 The electrical-characteristic curves for the 400-watt
700 sodium. lamp are illustrated in Figs. 4 and 5. The
operating points for the three energy distribtuions in
(b) Fig. 3 are indicated by the circles on the volt-ampere
characteristics. These curves represent the measur-
able characteristics of a typical lamp operated on an
adjustable choke ballast. As mentioned under "Dis-
charge Mechanism," the reservoir of liquid sodium
amalgam in the appendage is maintained at a con-
stant temperature. However, in making characteristic
Figure 3. High-pressure sodium discharge lamp spec-
tral distribution: (a) 3.0 amps, 68.5 volts and 185 watts;
(b) 4.4 amps, 105 volts and 400 watts; (c) 5.0 amps,
Figure 4. Lamp volts and lamp watts as a function of
arc current for a 400-watt high-pressure sodium lamp.
143 volts and 620 watts.
a
amalgam, a change in energy input results in it change of the amalgam temperature. The effect of
temperature and vapor pressure can be seen on the
energy distribution. As the wattage increases (pres-
sure increases) the line win
broadenin
be
g
g
comes
more apparent. The lamp color changes from a light
yellow at 185 watts to a golden white at 400 to 620
watts. The golden-white color may be obtained in
any wattage, however, by varying the length and Figure 5. Lamp efficacy and red factor as a function of
arc current for a, 400-watt high-pressure sodium lamp.
Approved For Release 2005/06/06 : CIA-RDP78BO477OA001200040001-5
 Approved For Release 2005/06/06 : CIA-RDP78BO477OA001200040001-5
rneasurernrnts Un it liriished lamp the app,-nda'gc tern
perature r.xifl virrv and adjust itself to a diii rent
i.ilur- dependent upon the ballast conditins. I here-
h-I.4, it wound a;ipear that the volt-arnpeI eltar.Ji ti-r-
3ic has pusiiivt dupe when actuallt thJe charac_
r~ riA i' i; u(-uat Iv'e at any sinsie IIvnaou upcr