IMPROVED SCREEN FOR REAR PROJECTION VIEWERS

• Document Type: CREST
• Collection: NGA Records (Formerly NIMA)
• Document Number (FOIA) /ESDN (CREST): CIA-RDP79B00873A001900010090-5
• Release Decision: RIFPUB
• Original Classification: K
• Document Page Count: 3
• Document Creation Date: December 28, 2016
• Document Release Date: September 6, 2012
• Sequence Number: 90
• Publication Date: March 17, 1964
• Content Type: MISC

4
Declassified and Approved For Release 2012/09/06: CIA-RDP791500873A001900010090-5
Lo'*4=- 141\4:0Z-
17 March 1964
DEVELOPMENT OBJECTIVES
IMPROVED SCREEN FOR REAR PROJECTION VIEWERS
1. INTRODUCTION.
These development objectives describe the requirements for improvement in
the performance of rear-projection viewer screens.
Rear projection viewers are commonly used for assessing information content
of aerial photography. For this purpose, the photography is generally repro-
duced as positive transparencies on roll film. Depending on the quality and
scale of the original image, projection magnifications from 5X to 50X are used.
Most of the objectionable limitations in the character of the projected image
can be attributed to the screen. These are particularly unacceptable at the
higher magnifications.
2. CONCEPT.
2.1. Purpose. Rear-projection screens are typically some sort of dif-
fusing medium. In this application, the diffuser is necessarily mounted on
a rigid support such as glass -- generally on the back, away from the viewer
Such a system has several objectionable characteristics:
2.1.1. Causes dispersion and diffraction, thereby introducing color and
graininess.
2.1.2. Back-scatters as much as 50% of the incident illumination, thereby
reducing efficiency.
2.1.3. Reflects a high percentage of ambient light and internally reflects
a considerable portion of the dispersed projection light -- both effects signi-
ficantly diminish contrast.
A rear-projection screen should be developed which would significantly
minimize these degrading effects.
2.2. Scope. Developments which would alleviate all the limitations
described in 2.1.1., 2.1.2. and 2.1.3, are required; at the same time, atten-
tion must be given to the following:
2.2.1. Resolution must be comparable to that of existing screens.
2.2.2. Size as large as 30"x30" must be feasible.
2.2.3. Economy must be consistent with that of typical rear projection
viewers.
2.3. Philosophy. Numerous approaches to the solution of this problem
should be considered and evaluated by the contractor. Each approach should
be pursued until it is proven unfeasible, and the approach and its evaluation
should be completely documented to that point. If an approach proves feasible,
then its documentation should be augmented by an operational 12"x12" sample.
The deliverable items will consist of a report which chronicles all investi-
gation and evaluation, and 12"x12" breadboards of all developments believed
to be significant in light of the stated objectives.
Declassified and Approved For Release 2012/09/06: CIA-RDP79B00873A001900010090-5
4
"
Declassified and Approved For Release 2012/09/06: CIA-RDP79B00873A001900010090-5
3. REQUIREMENTS.
3.1. Appearance. The screen should reproduce or.transmit an image with
minimum color contribution and graininess. -Appearance approaching that of
the virtual image ina direct-viewing optical system is the goal.
3-.2. Efficiency. Conventional light-scattering screens exhibit mutually
exclusive properties of axial gainiand angular gain. To increase angular gain
(luminance) more scattering is.required, and this, in turn, decreases axial
gain. More important, this also increases back-scattering and reduces effi-
ciency. Consequently, it is required that the improved screen display rela-
tively uniform luminance (?15%) over a? solid angle of 900 centered on the
axial ray with less than 15% back-scattering.
3-.3. :Contrast. The primary property which degradets contrast in conven-
tional screens is internal and external reflectance. The improved screen
should minimize this property. A reflectance characteristic approaching that
of black velvet is ideal.
In an ambient light level of '5 foot-lamberts and an incident signal
intensity range of 2000 to 1, the improved screen should display a brightness
range of 1000 to 1.
34. Resolution. The improved screen should exhibit a resolution of
10 lines per.millimeter at 90% modulation transfer function: the desired goal
is 20 lines per millimeter at 90% MTF.
Declassified and Approved For Release 2012/09/06: CIA-RDP79B00873A001900010090-5
I
Declassified and Approved For Release 2012/09/06: CIA-RDP79B00873A001900010090-5
tfrei6#71,153-
i
Arze Z,0#6 919?
2,A1024/Ce
ZOS.4/7;e4J7 #1166.- 70 '014er.,
L/69/Y-7
3,
i/YeeeVin55*- gr---A7
I. oeseer",t7ce- - . g, eAr- -4,-S' c .441, 7 -76# ''''I''
e____biz__-,ove-.0,6 teerPeogffiziwilr
.1
.514-,J6 z,2s--e-,7z Ili "77,e241 I Ax, Ar011 A-2,, Arv ". ,,? ,.. A.?e-, A .-
11/401/21- a.?40Veihke 1/104?
teal YClAPIO 716, eg-a
Declassified and Approved For Release 2012/09/06: CIA-RDP79B00873A001900010090-5