DIRECT IMAGE VIEWER, SPECIFICATION FOR

• Document Type: CREST
• Collection: NGA Records (Formerly NIMA)
• Document Number (FOIA) /ESDN (CREST): CIA-RDP78B04747A001500020042-8
• Release Decision: RIPPUB
• Original Classification: K
• Document Page Count: 16
• Document Creation Date: December 28, 2016
• Document Release Date: February 13, 2002
• Sequence Number: 42
• Publication Date: July 10, 1964
• Content Type: OUTLINE

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8-7506 STATINTL
10 July 1964
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DECLASS REVIEW by NIMA/DOD
STATINTL
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10 July 1964
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1.1 This specification describes the performance and
technical characteristics of an Experimental Direct Ii,.age
(High Resolution) Viewer. The Direct Image Viewer employs
a unique optical approach, involving diffraction gratings,
to provide an observer with an enlarged aerial image which
can be viewed simultaneously with both eyes.
1.2 Major features of this viewer include the elircmina-
tion of performance limitations imposed by the use of rear
projection diffusion screens, and the achievement of high
magnification viewing qualities comparable to advanced micro-
scope viewing objectives.
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STATINTL
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STATINTL
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2.1 The following drawings form a part of this speci-
fication:
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Dwg. 11o. 7506L1 Layout Dual Magnification,
Direct Image Viewer
Dwg. No. 7506L2 Assembly, YY Translator,
Direct Image Viewer
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3.1 Design - The overall configuration of the Experi-
mental Direct Image Viewer specified herein shall be in
general conlorr;lance with Drawing No. 7506L1.
The viewer si-all employ materials of highest commercial
quality consistent with its intended performance and speci-
fied operating environments.
STATINTL
3.2 Performance Characteristics - The performance charac-
teristics of the Experimental Direct Image Viewer shall consist
of tYe following general values:
3.2.1 Magnification - Dual individual magnifications
of 5X and 50X.
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3.2.2 Observable Film Area - The observable film
area shall consist of a nominal two (2) inch
by two (2) inch square area in the film
plane at 5X magnification, and two-tenths
inch by two-tenths inch square area in the
film plane at 50X magnification.
3.2.3 Film Size - The viewer shall possess a capa-
bility f r viewing single frames of either
73 r.jn or ' nch film chips. 4.4 5
3.2.4 Exit Pupil Size - The nominal size of the
composite exit pupil shall be 3.5 inches square.
3.2.5 System Resolution - At 5X magnification, the
Experimental Direct Image Viewer shall be
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capable of providing a system AWAR resolution
of 60 lines per millimeter over the used field
when referred to a high contrast target in the
object plane. At 50X magnification, the viewer
shall be capable of providing aurr of 200
OA bi$/ s -
lines per millimeterpat the film plane with a
high contrast target while employing commer-
cially available lens. The resolution goal of
the system when operating at 50X shall be 200
lines per millimeter as viewed in the object
plane for a low contrast (1.6:1) target.
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3.2.6 Light Intensity - The lamp intensity shall be
variable and of sufficient brightness to allow
the measurement of a 0.05 density difference
over a required density range of 0 to 1.8. As
a design goal, the viewer will provide a capa-
bility of measuring a desirable density differ-
ence of 0.02 over a density range of 0 to 2.5.
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3.2.8 Film Positioning - The viewer shall incorporate
a provision for remote film positioning through
X and Y translations to permit full coverage view-
ing areas for either 70mm and 5-inch film chips.
3.2.7 Illumination Spectrum - The illumination of the
viewer system shall be contained *o a narrow
band within the 450-550 millimicron portion of
the spectrum. . . 5 O ,,, G~ ~I r 1 _ C e d
3.2.9 Focusing - A manual fine focus controll shall be
provided for each viewer lens magnification.
3.2.10 Film Temperature - The temperature of the film
when mounted in the film plane of the viewer dur-
ing operation shall not exceed ambient (75?F.) by
more than 20?F. /I
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3.2.11 Viewer Controls - The Experimental Direct Image
Viewer shall contain a set of viewer controls,
front panel mounted, consisting of the following:
3.2.11.1 Power - ON/OFF
aflumewb&r
3.2.11.2 hfttti Intensity
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3.2.11.3 Magnification Selector, 5X and 50X
.3.2.11.4 Lens Focus, 5X and 50X
3.2.11.5 Film Translation
+ one inch 7
+ one inch Y
3.2 12 Power Consumption - The power consumption of
the viewer shall be approximately 800 watts of
110 volts, 60 cycle, electrical power.
3.2.13 Physical Size - (Reference
STATINTL
Dwg. No. 7506Ll).
The viewer shall consist of the following gen-
eral dimensions: Length - 66 inches, height -
26 inches, width - 29 inches.
;14 Weight - The weight of the viewer shall be
approximately 150 pounds.
3.3 Theory of Operation - In direct viewing optical instru-
ments, such as a microscope, the exit pupil is small, requiring
that the operator place his eye close to the eye piece for satis-
factory viewing. The present Experimental Direct Image Viewer,
with its larger optical elements and diffraction grating, enlarges
the exit pupil in a manner that the operator may view with both
eyes the image and still have adequate head movement. In the
absence of employing diffraction gratings in the present viewer,
a single small exit pupil would exist, which would restrict the
operator to the use of a single eye and no head movement when
viewing at high magnifications. Through the insertion of the
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gratings in the optical path, and the use of a narrow portion
of the spectrum, many exit pupils are created, which when arranged
side by side and placed both above and below one another, form a
matrix of exit pupils in space providing an effective viewing area
of 3.5 inches square, where the operator may place his eyes for
viewing. This unique approach results from the use of a special
field lens, and specially designed and built set of diffraction
gratings. Dear monochromatic light must be used in the viewer, or
the diffraction characteristics of the gratings will produce a
rainbow of images between matrix units (exit pupil images).
3.4 Technical Details
3.4.1 Viewer body, optical supports, and controls -
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3.4.1.1 Chassis - The viewer frame will be con-
structed from aluminum jig plate, and
rigid mounts will be supplied for all
optical elements. The large field lens
will be of a split design, and flange
mounted to one-inch thick plates. The
diffraction gratings will be mounted
between the field lens elements and
their one-inch separated flanges.
3.4.1.2 Film support and X-Y translation -
The film support system, as shown in
STATINTL Dwg. No. 7506L2, accomo-
dates both 70mm and 5-inch film chips.
The film will be held by a vacuum to a
flat glass plate free of striations.
The glass platen will be mounted on a
mechanical mechanism which will provide
controlled X and Y movement of 2 inches
and translate the film 9 inches in X to
change magnification.
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3.4.1.3 Objective lens mounting - The two
lenses will be flange mounted with the
position of the flange being manually
adjustable for fine focus.
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3.4.1.4 Auxiliary equipment - Two pieces of
equipment will be placed within the
viewer:
(1) The light source power supply will
be repackaged and mounted along one
side of the viewer enclosure;
(2) A small vacuum pump will be mounted
so as not to induce any vibration to the
optical path.
3.4.1.5 Viewer Housing - The viewer housing and
enclosure will have a hinged section at
the rear for access to the mechanism
and for inserting film and lamp replace-
ment. The front panel will contain the
controls and provide the proper mask
around the field lens and gratings.
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3.4.2 Viewer Optics
3.4.2.1 Field Lens - A symmetrical design multi-
element, 15-inch diameter, field lens
will be used. The lens will image the
exit pupil of the objective lens 20 inches
from its rear nodal point. The lens shall
be of a sufficiently high quality as not
to degrade the high resolution image
requirements of the viewer.
3.4.2.2 50X Magnification Components - A large
aperture photographic lens will be used
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with a modified exit pupil producing a
square opening. The resolution of the
viewer is dependent upon this lens, and
the best commercially available lens
with an f number approaching unity will
be used.
A multi-element condensed system will be
used to concentrate the light to the
small 0.2 x 0.2 inch square film area
while filling the objective lens.
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Field flatteners shall be employed to pro-
vide field curvature for optimum field
lens operation.
3.4.2.3 5X Magnification Components - A commer-
cially available 8.5 inch focal length
lens will be modified to contain a square
exit pupil equal in size to the 50X lens
case.
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The condenser system to be employed with
this lens will concentrate and illuminate
a 2 x 2 inch square area evenly.
Separate field flatteners will be used
for the same purpose employed with the
50X system.
Two additonal small mirrors will be
inserted in the path, one before and
one after the lens to provide the dual
5X magnification. The mirror in front
of the lens is movable to permit insert-
ing it or removing it from the optical
path. With film translation, the two
magnifications are obtained.
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3.4.2.4 Light Source - Two lamps and reflectors
shall be employed, one for each lens.
In addition, special interference filters
will be employed to provide the narrow
spectrum required.
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3.4.3 Diffraction Grating - In order to obtain the unique
optical multiplication of exit pupils required,
special diffraction gratings are required. Two
gratings are employed to diffract the light into
a multiplicity of exit pupils dispersed in two
directions 900 apart, thus providing a matrix of
exit pupil images.
3.4.3.1 For the prescribed magnification levels
and the size of the multiple exit pupil
required, a minimum of nine (9) orders
of diffraction are required, a central
order and four (4) on each side. The
difficulty of the grating design is that
all orders should receive the same amount
of energy so that each exit pupil appears
of the same brightness to the observer.
3.4.3.2 The gratings shall be of a 10 x 10 inch
ruled surface, which influences the field
of view of the system and the observable
film size. Special ruling techniques are
required and will be used to produce these
gratings.
3.4.3.3 The light is diffracted by one grating in
one direction, and then each diffracted
exit pupil is spread out in the other
direction by a second grating. The
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cascaded diffraction gratings produce
a decrease in light intensity, which is
then enhanced by the use of a narrow
band light source. Compensation is pro-
vided in the condensers, high intensity
lamps and the small f/number projection
lens at the high magnification.
3.4.3.4 The nominal angular deviation of the
various orders shall be:
First order 1 0 94
Second order 2 0 18'
Third order 3? 27'
Fourth order 4? 35'
The tolerance for each of the above devi-
ations shall be + 10% of the above angles.
3.4.3.5 Intensity variations throughout the nine
orders shall be no greater than 40% be-
tween adjacent orders and no greater than
a 2:1 ratio between the lowest and highest
order in the nine central orders.
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3.4.3.6 The transmission of the order which trans-
mits the minimum amount of light shall be
at least ?/Tof the light intensity falling
on an individual grating.
3.4.3.7 The glass quality to be used in the manu-
facture of the diffraction gratings shall
be greater than striae free through the
faces.
3.4.3.8 A maximum of 10 arc minutes of slope error
shall be a permissible planeness (figure)
of the glass.
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4.0 QUALITY ASSURANCE PROVISIONS
4.1 The optical components will be inspected and tested
to demonstrate compliance to the performance requirements stated
in Section 3.2.
4.2 The diffraction gratings will be inspected and tested
to show compliance to the performance requirements stated in
Section 3.2
4.3 A set of complete viewer acceptance tests will be con-
ducted to demonstrate satisfactory operation of all the functions
and specifications stated in Section 3.0.
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This viewer will be packaged and prepared for shipment and
delivered in accordance with accepted commercial practices.
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