TEST AND EVALUATION REPORT (Sanitized) GLIDE STAGES AND PLATENS FOR THE HIGH POWER STEREOVIEWER

• Document Type: CREST
• Collection: NGA Records (Formerly NIMA)
• Document Number (FOIA) /ESDN (CREST): CIA-RDP78B04560A007200010037-9
• Release Decision: RIPPUB
• Original Classification: C
• Document Page Count: 19
• Document Creation Date: December 28, 2016
• Document Release Date: April 12, 2002
• Sequence Number: 37
• Publication Date: July 1, 1973
• Content Type: REPORT

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NATIONAL PHOTOGRAPHIC
INTERPRETATION CENTER
TECHNICAL
PUBLICATION
TEST AN?_EVALUATION REPORT
GLIDE STAGES AND PLATENS
FOR THE HIGH POWER STEREOVIEWER
CONFIDENTIAL
NPIC/R-15/73
JULY 1973
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WARNING
This document contains information affecting
the national defense of the United States.
within the meaning of Title 15, sections
793 and 794, of the U.S. Code, as amended.
Its transmission or revelation of its contents
to or receipt by an unauthorized person is
prohibited by law.
CLASSIFIED BY: 013170
Exempt from General Declassification Schedule
of E.O. 11652, Exemption Category: 5B(2)
AUTOMATICALLY DECLASSIFIED ON
DA & P60RNft1WW02/(
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 Approved For Release 20Q"?D .11-15/73
TECHNICAL PUBLICATION
TEST AND EVALUATION REPORT
25X1
GLIDE STAGES AND PLATENS
FOR THE HIGH POWER STEREOVIEWER
JULY 1973
Comments and queries regarding this report are welcomed.
25X1
NATIONAL PHOTOGRAPHIC INTERPRETATION CENTER
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 CONFIDENTIAL NPIC/R-1473
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The 120X Capability for the Zoom 240 System consists of
15X eyepieces and 2.65X mono and stereo obiecti es. These
prototype components were made by to NPIC 25X1
specifications. Two types of eyepieces are required by the
contract: the first is designed to fit Zoom 240's with small
image rotation prisms; the second (to be delivered in August
1973) is designed to fit all Zoom 240's.
Acceptance, engineering, and operational suitability
testing were performed from January to May 1973. Most of the
design goals were met by the prototype components. On-axis
resolution with the 2.65X stereo objectives is 456 line pairs/
mm, and with the mono objective the resolution is 512 line
pairs/mm. Visual transmission of the stereo optics at 120X
is 1.3 percent. Normal optics at 60X have a visual transmission
of 3.1 percent.
Most users found the 120X magnification to be sufficiently
high. However, vibration of the light tables is considered
to be a serious problem. The larger field of view of the l5X
eyepieces was well received.
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CONFIDENTIAL NPIC/R-1+/73
25X1
This report contains acceptance test results, certain
human-factor engineering evaluation results, and a summary of
operational evaluation reports from two operating components
in TEB plans similar testing when the second
set of 15X eyepieces arrive; these eyepieces are scheduled
to be delivered in August 1973.
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The 120X capability is provided by 15X (nominal) eye-
pieces and 2.65X (nominal) objectives on a Zoom 240 which itself
has a 3X magnification capability. Two sets of 15X eyepieces
are required by the contract: the first set will fit the newest
version of the Zoom 240, which has smaller image rotation
prisms and the second set will fit any Zoom 240 with large
or small image rotation prisms or even no prisms at all.
The first set of 15X eyepieces was received at NPIC on 14 Decem-
ber 1972. Preacceptance testing of these eyepieces was accom-
plished before delivery on 13 December 1972 and was reported
in memorandum TEB-083/72, dated 20 December 1972. The 2.65X
-stereo objectives were received at NPIC on 22 January 1973.
Acceptance testing of the 2.65X stereo objectives with 15X
eyepieces was completed. on 7 February 1973. Acceptance testing
of the 2.65X monoscopic objective was completed on 15 February
1973. The operational evaluation was completed on 14 May 1973,
and the engineering evaluation tests were conclud.ed on 30 May
1973.
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CONFIDENTIAL NPIC/R-1473
2. SUMMARY
2.1 Acceptance Tests
The requirement for high power system magnification of
120X was satisfied. The magnification of the eyepieces
measured an acceptable 15.8X.
Eye relief measured 20 mm exactly as required.
On-axis resolution with the stereo objectives was 456
1/mm or'75 percent of the design goal. With the mono objec-
tive the resolution at 120X was 512 1/mm or 84 percent of the
design goal.
Field of view at the eyepiece focal plane measured 19.6
mm as required.
Optical distortion of the 120X system was measured to
be within the 7 percent maximum over 77 to 80 percent of the
respective stereo and mono fields of view.
Working distance with the stereo objective is 5.9 mm.
This is much better than the 1.5 mm goal.
The requirement that the system be designed such that no
modules have to be removed when switching from mono to stereo
or vice versa was not met.
Image quality of the 120X stereo capability was comparable
to the standard Zoom 240 system as required. In the mono-
scopic mode, image quality was degraded in the sense that the
tipped field phenomenon is more severely manifested at higher
magnification with shallower depth of focus.
2.2 Engineering Evaluation
Visual transmission of the stereo system at 120X is 1.3
percent. The standard components have a transmission of 3.1
percent at 60X magnification.
The-5.9 mm working distance of the stereo objectives is
less than the thickness of the commonly used green plastic
holddown rings and prohibits their use.
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NPIC/R-1+/73
The theoretical depth of field of the 120X stereo system
is 28 micrometers. This value relates favorably with an
observed loss of two AF resolution target elements at the
extreme ends of a 42 micrometer focus range.
The focus mechanism originally provided on the AIL 1540
light table is a limiting factor in the use of 120X capability
due to the small depth of field. However, performance of the
focus mechanism is judged to be satisfactory on tables which
have been modified by changing the focus mechanism gear ratio.
2.3 Operational Suitability Evaluation
Most users considered image vibration to be a serious
problem when using the high magnification provided by these
optics.
Twenty-five PI's unanimously reported that the 120X mag-
nification was sufficient. With this increased magnification
of the 240 system, the need for chipping films should decrease.
Illumination through the optics seems adequate. How-
ever, not enough light passes through the viewing ports of
the stereo objectives. Several users believed that stereo
fusion could be achieved faster without using the viewing
ports.
One operating component commented that the large diameter
eyepieces were bothersome since they pressed against the user's
nose.
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NPIC/R-1+/73
3. CONCLUSIONS AND RECOMMENDATIONS
The 120X Capability for the Zoom 240 essentially met
contractual objectives and specifications.
In general, the 120X capability was accepted as being
useful. However, engineering and operational evaluation
uncovered several problems.
TEB concluded, in agreement with the operating components,
that the 120X capability will be severely limited by vibra-
tions. If the 120X capability is procured in quantity, TEB
recommends that the light table vibration problems be pursued
vigorously.
The low illumination and parallax problems associated
with the viewing ports make the value of this feature
questionable. A separate T?E report, NPIC/R-13/73, covers
the viewing port feature in detail.
Use of the mono objective is seriously hampered by the
need to remove the 2.65X stereo objectives. With this handi-
cap and from the comments received from the operating compo-
nents, the value of this feature is also questionable.
TEB also recommends that the focus mechanism of the AIL
light tables, as originally provided, be improved before
providing the PIs with the 120X capability.
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4. DESCRIPTION OF EQUIPMENT
NPIC/R-11+73
The 120X capability consists of a set of 15X prototype
eyepieces that will fit the newer Zoom 240 microstereoscopes
(image rotation version with 55 mm minimum IPD), a set of
2.65X prototype objectives for stereoscopic viewing on the
Zoom 240 stereoscope system, and a prototype 2.65X monoscopic
objective. The zoom system of the Zoom 240 goes up to 3X,
which together with the eyepieces and objectives provides the
120X (nominal) magnification.
The eyepieces are physically large (40.45 mm diameter)
as is evident in Figure 1. A closeup view of the objectives
is shown in Figure 2. Visible is the quarter-turn locking
flange that joins the stereo objective to the rhomboid arm.
The monoscopic objective has a large diameter thread for
mounting.
The stereo objectives have viewing ports for straight-
through viewing of the imagery under the objectives. Each
stereo objective has a white dot on the viewing port window
for alignment purposes. One of the two objectives has a
second white dot on the beam splitter to aid the PI in align-
ing the imagery with the field of the 120X system.
Figure 2. Monoscopic (Center) and Stereoscopic 2.65X (Nominal)
Objectives
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5. TEST DETAILS
5.1 Acceptance Tests
NPIC/R-1) /73
Optical Magnification
The design goal for the system magnification at high
power is 120X. The eyepieces shall have a minimum magnifica-
tion of 15X.
Test Method - The first test is to measure the maximum
total system magnification (linear). Mount a diopter tele-
scope on an angle measuring table so that their axes intersect
at 90 degrees. Place the axis of rotation of the table so
that it intersects the optical axis of the eyepiece and lies
in the plane of its exit pupil. Measure the angle subtended
by the diopter telescope'positions when viewing the ends of
a known or measurable distance in the object plane. Set the
eyepiece and rhomboid focal adjustments at their midpoints
(see Section 5.2) and record the IPD setting.
The second test is to determine the angular magnification
of the eyepieces. Use the TEB Centering Eyepiece with reticle
and a scale at the film plane to measure the linear magnifica-
tion of the objectives. Divide the previously determined total
system magnification by the linear magnification of the objec-
tive and zoom to obtain the angular magnification of the eye-
piece.*
Test Results - IPD setting minimum.
Side
Mono
Left
Right
Object
plane distance
1.00 mm
0.1 mm
0.1 mm
Angle
subtended
26.950
2.70
2.70
Linear
magnification
122X'
120X
120X
* Jenkins E White Fundamentals of Optics, 3rd. ed. (p. 177)
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NPIC/R-14/73
Objective*
1 Dot
2 Dot
Eyepiece scale
7.60
mm
7.55
mm
Film plane scale
1.00
mm
1.00
mm
Magnification (linear)
7.60X
7.55X
Total magnification
120X
120X
Eyepiece magnification (angular) 15.8X 15.9X
Conclusions - These requirements are satisfied.
Eye Relief..
The eyepieces shall have a minimum eye relief of 20 mm.
Test Method - Place a viewing screen above the eyepiece
such that the smallest, sharpest spot of light is visible.
Measure the screen's height above the highest part of the eye-
piece.
Conclusion - The eyepieces meet this requirement.
Field of View
The design goal for the eyepiece focal plane diameter is
19.6 mm.
Test Method - Focus the Zoom 240 microstereoscope system
with the X o jectives and 15X eyepieces on a grid. Remove
an eyepiece and position a viewing screen at the eyepiece focal
plane. Note how many grid squares lie within 19.6 mm on the
viewing screen. Replace the eyepiece and note whether or not
the same number of grid squares are visible.
Conclusion - This goal is satisfied.
* The stereo objectives have no serial numbers to identify
them, but one has a single alignment dot in its viewing port
and the other has two dots for alignment.
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Optical Resolution
The design goal is 609 line pairs/millimeter.
Test Method - Focus the system at 120X magnification on
a high-contrast USAF Tribar resolution target in the center of
the field of view. Record the smallest target element in each
case that meet the following criteria:
1) A space visible between and along the length of
each pair of adjacent bars.
2) The three bars can be counted.
Test Results - The smallest resolvable target (TEB #28)
element was 8,6 (456 line pairs/mm) with the stereo objectives.
The resolution was 9,1 (512 line pairs/mm) with the monoscopic
objective, however, refocusing was required for off-axis read-
ings.
Conclusion - The eyepieces and stereo objectives are
within 25 percent of this design goal. And with the monoscopic
objective, are within 16 percent of the goal.
Optical Distortion
The design goal is a maximum of 7 percent.
Test Method - Use the test method for measuring magnifica-
tion, both on axis and near the edge of the field of view.
Calculate the difference in percent.
Test Results - With stereo objectives the maximum distor-
tion is 7-1/2 percent plus or minus 4 percent, due to uncer-
tainty of measuring system. Measurements were made out to
77 percent of the field of view. The monoscopic objective
cannot be focused on both the left and right sides of the
field of view simultaneously at 120X. With refocusing, the
distortion is less than 7 percent out to 80 percent of the
field of view.
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Conclusion - This design goal is met over the central
77 percent o t e field-of-view (FOV) diameter with the stereo
objectives. The monoscopic objective meets this design goal
out to about 80 percent of the field of view.
Working Distance
The design goal is 1.5 mm.
Conclusion - The 5.9 mm working distance for the stereo
objectives an 3.4 mm for the mono greatly exceeds the design
goal (see the fifth paragraph in Section 5.2).
Parfocality
It is a design goal that the system be designed such that
the operator does not have to remove any modules when switch-
ing from mono to stereo or vice versa. Refocusing may be
necessary.
Test Method - Mount the 15X eyepieces and 2.65X objectives
on a Zoom 240 stereoscope system. Determine whether the Zoom
240 can be switched back and forth between the mono and stereo
viewing modes.
Test Result - There is up to 0.66 mm interference between
the stereo o ectives and the surface of the light table when
the mono objective is focused.
Conclusion - This design goal is not met.
Image Quality
It is a design goal that there be no noticeable degrada-
tion of image quality-when switching-from lOX WF eyepieces
and 2X objectives to the proposed 120X viewing system on a
Zoom 240 (53-70-25).
Test Method - Focus on a grid target that fills the
field of view. Use a slow scan motion and notice the develop-
ment of curvature in the grid lines as they traverse the field
of view.-Examine the image for other image degradation.
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Test Result - The only noticeable image degradation in the
stereo objectives was the barrel distortion near the edges of
the field of view. The standard lOX eyepiece and 2X stereo
objective system had a barely detectable amount of the opposite
kind of distortion (pincushion).
The standard lOX eyepieces with 2X monoscopic objective
can be focused on lines 3 mm apart on the light table. However,
with the 15X eyepieces and 2.65X monoscopic objective, lines
2 mm apart not only cannot be focused simultaneously for a
given eye, but when refocusing (with the scope carriage control)
from the center of the field of view to the left or right line,
the focus for one eye always gets worse as the other gets better.
Conclusion - The stereo objectives with the 15X eyepieces
meet the requirement; only one PI out of 25 in the operational
evaluation even commented on any distortion. That PI's com-
ponent reported that the distortion was no worse than the
standard Zoom 240 system.
In the monoscopic viewing mode, the image is. degraded,
therefore, the design goal is not met for the mono case.
Eyepiece Interchangeability
It is a design goal that the 15X eyepieces be interchange-
able with standard lOX eyepieces on the Zoom 240 pod (53-70-25).
Conclusion - This design goal is met.
5.2 Engineering Evaluation
System Magnification
The magnification can be changed up to 4 percent on the
left side by focusing the left eyepiece tube of the Zoom 240
all the way down. It can be changed up to 6 percent on either
side by changing the rhomboid arm focus from one extreme to the
other. Note that refocusing is accomplished with the micro
scope carriage control in each case.
Viewfinder Dots
The 2.65X stereo objective with two alignment dots in its
viewing port was found to point to a spot 0.3 mm outside the
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NPIC/R-1+/73
field of view at 120X. If properly aligned, the concept of
two alignment dots to eliminate parallax would probably be
satisfactory. The viewing port feature has. previously been
evaluated in detail in TF;E Report NPIC/R-13/73.
Light Transmission
The visual transmission in the stereo mode was measured
to be 1.2 percent and 1.3 percent at 120X. The standard lOX
eyepiece and 2X stereo objective yielded a visual transmission
of 3.1 percent at 60X. In the mono mode the transmission was
3.4 percent at 120X. And the standard lOX eyepieces with the
2X objective had a transmission of 6.9 percent at 60X.
Depth of Field
The theoretical depth of field at 120X was calculated to
be 28 micrometers, which supposedly is the threshhold (zero)
loss in resolution range (25 micrometers = 0.001 inch). This
value is not in conflict with the following measured results
which were obtained by using a very precise micrometer head
to position an Air Force resolution target in the object plane.
It was determined by averaging an appropriate number of read-
ings that a loss of two target elements occurs. at the extreme
ends of a 42 micrometer focus range and a loss of four elements
at the ends of a 78 micrometer focus range.
To lock a stereo objective to a rhomboid arm, it is
necessary to turn it about 30 degrees about an axis parallel
to the surface of the light table. It happens that if a 2X
objective has been in focus and the 2.65X objective is in-
stalled without raising the microscope carriage, part of the
lower surface of the latter will strike the table (or film).
This is because the 2.65X stereo objectives extend further
toward the light table surface than do the 2X stereo objectives.
It should be noted that the 2.65X stereo objectives have
a working distance of about 5.9 mm which will not clear the
green plastic holddown rings used by IEG. The 2.65X mono-
scopic-objective has an even smaller working distance of about
3.4 mm.
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NPIC/R-1)+73
Eyeguards adapted to fit the 40.45 mm outside diameter
of. the 15X eyepieces were provided. They effectively cut out
most of the extraneous light for four observers (T&E engineers).
They do, however, restrict the useable field of view of one of
the observers by about 32 percent (linear). The eyeguards
keep him from getting close enough to the exit pupils.
The eyeguards fit snugly on the eyepieces, and the 15X
eyepieces are 3.5 times heavier (158 grams) than the usual lOX
eyepieces. These two facts can cause the unwary, when intend-
ing to remove the eyoguard, to unexpectedly lift the eyepiece
out of the eyepiece tube and then lose their grip so that they
drop it.
The performance of the focusing mechanism originally
provided on the AIL 1540 light tables has been poor with the
60X Zoom 240 optics used in the past. The smaller depth of
field of these new 120X optics makes it prohibitively dif-
ficult to use them on light tables with the original focus
mechanism. However, performance is judged to be satisfactory
on tables which have been modified by changing the focus
mechanism gear ratio.
5.3 Operational Evaluations
The two operating components that evaluated the eyepieces,
stereo objectives, and monoscopic objective reported that most
PIs consider light table vibrations a more serious problem with
the increased magnification of 120X. One of the components
found that this serious problem can be reduced from harmful to
"slightly bothersome" at worst with the ESD plate and clamp
vibration attenuator.*
* Described in a limited distribution Memorandum for the
Record "Temporary Vibration Fix for the AIL 1540 Light
Table," NPIC/TSG/ESD/TEB-124/71, dated 31 August 1971.
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eliminateu. fins does not apply to PIs engaged in third-
phase, detailed photointerpretation.
Use of the mono objective is seriously hampered by the
need to remove the 2.65X stereo objectives before the mono
objective can be focused according to both operating components.
They conclude that the prototype monoscopic objective does not
add to the 120X capability.
One operating component stated that the closeness of the
stereo objectives to the imagery bars the use of all known
film holddowns.
NPIC/R-11/73
The twenty PIs from one operating component and five PIs
from the other component unanimously reported, that the 2.65X
stereo objectives with the 1SX eyepieces provide a magnifica-
tion capability.on their light tables that is sufficient. One
PI reported that one piece of ground order of battle equipment
was readily identified that was not identifiable on the old
Zoom 240 system. Many PIs felt that their need for the 25X1
High Power Stereoviewer and the l IM-5 would ho rarl?r 9c11
The increased field of view provided by the new eyepieces
was well received by all PIs. One PI stated that he would
search at 28X (minimum zoom setting) with the 120X capability
rather than at 28X with his current optics. One operating
component commented on the human engineering aspect of the
large diameter eyepieces being uncomfortable against the user's
nose. This component also reported that the PI's nose hit the
edges of the large diameter eyepieces.
More extensive comments made by one of the components
o The illumination from 0 1540 and
light tables is adequate for the 1 em except
for the viewing ports.
o The user must crane his neck to look through the view-
ing ports.
o While the two-dot version of the viewing port eased
the parallax problem, the majority of their PIs
believe that stereo fusion can be achieved faster
without using the viewing ports.
o Use of the viewing ports eliminates guesswork in find-
ing the same imagery area in both rhomboids.
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NPIC/R-1)+73
o Some of their PIs felt that more light was needed
through the viewing ports.
Distribution List
Activity No. of Copies
NPIC/TSG/TOS (through Ch/TSG)
1
NPIC/TSG/RED Ch
1
NPIC/TSG/RED Project Officer
1
NPIC/TSG/ESD
9
NPIC/PSG/RERD/PB
3
NPIC/PSG/R&RD Library
2
NPIC/PS/PAB
NPIC/IEG/TPS
DDI/IAS/Tech. Adv.
DIA/DIAAP-9/Tech. & Dev. Br.
Army/SPAD/PSO
EXRAND Rm 5S330)
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