PHOTOCHROMIC IMAGE PROCESSING

• Document Type: CREST
• Collection: NGA Records (Formerly NIMA)
• Document Number (FOIA) /ESDN (CREST): CIA-RDP78B04747A000100070008-6
• Release Decision: RIPPUB
• Original Classification: K
• Document Page Count: 5
• Document Creation Date: December 28, 2016
• Document Release Date: July 20, 2000
• Sequence Number: 8
• Content Type: OUTLINE

0 0 IC IMAGE.PROCF'zSING
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Prepared by
Declass Review, NIMA/DoD
1. PHOTOCHROMIC COATINGS
A. Immediate visibility (no development).
B. Reversible (prints a transparency either as a positive
or a negative).
C. High resolution and grain.free.
D. Ease of handling (no special precautions required).
E. Colored state optimum for humans.
V. Writing produced by exposure.to near UV.
G. Erasing achieved with green light after pre-coloring with
near UV.
H. Filter (colored) control by con-
filters ( (e.g. . green -
trast, red - no contrast).
1. Low sensitivity, thus must be used with light sources and
optical systems compatible with sensitivity. They cannot
be put in cameras for taking pictures (productsti Kn alvar
J. Useful life of approximately.1,000 UV exposures.
II. APPLICATION TO THE PHOTOGRAPHIC DARKROOM USING STANDARD EQUIPMENT
A. Photochromic masking - provides a means for making either a
positive or negative mask of the original transparency: can
.be contact or projection printed to a green sensitive emulsion,
1. Contrast suppression- a positive is made of the negative
(in register with it) by passing UV light through the
negative prior to printing. The sandwich is then used .as
the printing transparency.
2. Contrast enhancement
to - here forming the is
colored by UV prior g the
photographic negative and .the image isformed as a nega-
tiveby erasing illumination. The combination is then
printed.
3. Edge enhancement - this can be accomplished by placing
different spacers in ;the sandwich and/or controlling the
specula.rity of the illumination.
B. PhotQchromic Reversible Print Paper
l.. Sensitize by.heat (2 hour).
2. Color by UV and'erase with green.
3. Fix by heat.
4. Sensitive for ' hour.
5. Uncolored regions can be resensitized and colored by
a repetition of the process.
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III. IMAGE PROCE>SING BY PHOTO-INTERPRETERS
A. Present operational equipment - today this is primarily electronic
image processing through television. techniques. This provides:
1. Brightness control
.2. Contrast control
a.. Enhancement
b. Compression
C. Slicing and expansion
3. Signal. processing through filtering, delay and shaping to
optimize the system transfer function for particular
operations.
4. Operations can be controlled by the operator (dynamic
control).
5. By application of computers complex analysis can be
performed rapidly.
6. Costly equipment.
7. Reduced lines per field as compared to optical resolution.
8. Scanning problems exist for optimum results.
B. Desireable Objective - Optical Analog of the TV Image Processor
1. Optical communication theory leads to same transfer function
approach to optical systems as is used for electronic systems
and analogous image processing (for linear systems).
2. Some effects are very simple to obtain by spatial operations
within optical systems.
3. In,past, effects were principally used in phase contrast
.microscopy and Schleirin optical systems, but analytical
techniques have been much more cumbersome than those used
in electronics.
4. Fairly simple-to apply results of research in electrical
filter theory. to predict resultant imagery by. analogous
techniques in the optical case.
5., System is amenable to mathematical analysis and includes
present capabilities in general. Can determine what.user
does to get best image for a given situation.
6. User can develop a feel.for.spatial filtering.
7. Compatible for both manual. and automatic image evaluation
and manipulation.
C. Processing with Non - Coherent Optical Viewers
1. Low pass filtering by. aperture control possible.
a. Grain and fine detail can be minimized by stopping
down.
1. Projection lens - brightness loss occurs by
reducing aperture.
2. Eyeball `pinhole),- internal. feedback. tends to
overcome brightness loss.
b. One dimensional filtering can-give some very interest-
ing effects. A slit near the eyeball is quite effect-
ive.
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C. Slits in colored transparency,also of interest,
but attention must be paid to intensity level.
2, Unsharp_positi.ve W negative masking (dodging)
a Use of a dodging mask in the viewer allows variable
masking effects
1. Variable :distance between mask.and original
(defocus of mask)
2. Relief by misregistration.
b. Use of flicker effects to emphasize detail by
rapidly varying defocus and misregistra.tionin.2a.
C. Can relay image of mask into object-transparency
and smear this image to give controlled edge en-
hancement.
3. Multiple image production
a. An optical viewer can be considered an. infinite
number of projectors in parallel all focusing
simultaneously on the screen (with the identical
transparency as an input).
b. Analysis of-what can be done then is simple as it
amounts to considering,what can be done with a
number of projectors working together.to add in-
tensities at the screen (with no registration
problem).
C. A practical means of achieving the multiple
channels is to place an opaque ,mask with ,a number
of holes in it over the projection lens
1. Each can have its direction, color, optical
path., intensity and aperture varied inde-
pendently.
2. Can allow user to "tune up" system by ad-
justing each bundle for best results at a
given object.
d. Some interesting effects are possible, ultimate
value to the PI is unknowfn. Flicker, can be used
here ,as well.
4. Photochromic applications in non-coherent optical
systems
a.. Primarily useful to realize masks, sharp or un-
sharp, positive or negative, from the input-
trans-parency.
b. These masks can be viewed . as a single transparency
as well (with contrast manipulation,.. if desired).
C. Optimum brightness efficiency calls for eyepiece
viewing (deliver all photos to the user's eye).
5. Non-coherent systems are linear for intensity only, i.e.
I aF 'e 0 where I is intensity at image place and
is the transfer function. This is a, severe limitation
and leads one to coherent systems. where both phase and
amplitude can be controlled to provide great flexibility
in.image processing.
D. Image Processing with Coherent optical Viewers
1. The Fraunhofer diffraction plane provides means for
insertion of spatial filters
r
3
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III. D. 1 (coated)
a. Essentially the optics of single . slit. diffraction
experiment taught in,freshman..physics.
b. By moving object back from lens we~obtain.a real
image at the image plane beyond the diffraction
plane.
c. With this basic setup,.we:.can engage in some fairly
sophisticated spatial filtering operations.
2. The 'Fourier relationship between the object?plane,dif-
fract.ion..plane and image plane
.a.. Image can be represented mathematically,asthe
product of the .object and various transfer functions
in the system.
the two dimensional
b. The variables are~{ and
Fourier spatial.transformsof the various compo-
nents-within the system.
c. Since the optical analog of the time-frequency
relationship in electronics exists,.this system
allows-similar-linear operations,.but .in,space
rather than in time.
3. Operations on the object transparency diffraction
pattern are angularly related (quadrature),to the
original detail.
a. one dimensional operations can allow use of a
slit source
b. Two dimensional operations require a point source
A. operations possible with fixed density?masks.
a. Low pass filtering.
b. High pass filtering.
C. Band pass filtering.
d. Comb filters.
.e. Sine -wave filters.
f. Shifting functions.
5. Operations with photochromic.masks for density control
give dynamic capabilities to the-user.
.a.. Can rival TV in.ease of control.
b. Can provide-some functions not .realizable electri.
cally.
c. Phase control is more difficult.
6. Photochromic applications to coherent systems
a. Photochromic operations . at the object-plane,.;such
as dodging. and unsharp.masking.,:.are,still feasible.
b. The operator larneecontrol
a dynamicbfashion at the
diffraction p
c. Brightness feedback allows adaptation level to
remain .constant.
IV. GOALS OF IMAGE PROCESSING SYSTEMS
A. To provide interpreter with numerous enhancement capabilities
for finding signal (pattern)'in noise (background).
1. In a non-dynamic situation,. the interpreter should at
least be able to call out the change (in terms of how
processed in the lab) to get a required result.
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IV. A. 1 (contw.rd)
a. He should be able to call out a specific density
range to be compressed or expanded.
b. Photochromic image processing allows this without
much trial and error.
2. The more ideal case will allow the P1 to interest with
the image in terms of dynamic image operation. Flicker
could be of special use here.
B. To allow interpreter to completely eliminate enhancement
1. Enhancement means distortion in most respects and
after the initial contact and evaluation a more de-
tailed study might well call for the non-enhanced
image, except possibly for contrast correction. With
an available means for contrast amplification at fine
detail (no distortion), this would probably receive
great use.
2. Negative enhancement, or overeliminating enhancement
(image inversion) in a sense, should also be useful in
certain situations.
C. The over-all goal, to optimize the system for visual in-
spection, means we must make use of every technique avail-
able, i.e., flicker, color, enhancement, suppression,
pattern filters, etc. We feel photochromic coatings pro-
vide a means for achieving the desired effects.
Background References
Carlson, C. 0., Grafton, D. A., Tauber, A. S., "The Photochromic Micro-
Image Memory," presented at the Symposium on Large Capacity Memory Tech-
niques for Computing Systems, May 1961. Sponsored by Information Systems
Branch of Office of Naval Research.
t3of optical processes."
Elias, P. and Grey, D. S., "Fourier Treatment
JOSA, Vol. 42, No. 2 (Feb. 1952), pP
O'Neill, E. L., "Spatial Filtering in Optics." IRE Transactions on
information Theory, Vol. IT-2, No. 2 (June 1956), pp. 56 - 65.
porter, A. B., "On the Diffraction Theory of Microscopic Vision."
philosophical Magazine, Vol. II (1906), p. 154.
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