IMAGE ENHANCEMENT IN LINEAR, COHERENT OPTICAL SYSTEMS

• Document Type: CREST
• Collection: NGA Records (Formerly NIMA)
• Document Number (FOIA) /ESDN (CREST): CIA-RDP78B04747A003100010020-5
• Release Decision: RIPPUB
• Original Classification: K
• Document Page Count: 1
• Document Creation Date: December 28, 2016
• Document Release Date: February 9, 2000
• Sequence Number: 20
• Content Type: REPORT

Approved For ReleVe 2000/05/10: CIA-RDP78B04747-A00310001
(Abstract)
IMAGE ENCE E T IN LIB, COHBR .NT OPTICAL SYSTUM
ttek Corporation
STATOTHR
A linear, coherent optical system in. its most elementary form has
its basis in a point source located in the focal plane of a collimating
lens.. This collimator illuminates an object transparency with a plane
wave (coherently). A second tens collects this light and brings it to a
focus, farming a Praunhofeer diffraction pattern. The diffraction pattern
constitutes a spatial frequency analysis of the object. A subsequent out
of lenses transforms the diffraction pattern into an image. The system
is linear, from object to image, in light amplitude,
Such a system provides a unique means for image enhancement in that
these spatial frequencies are displayed, in amplitude and phase, in a
particular plans within the optical system. By inserting "filters" of
various configurations and transmissive properties into this plane, the
quality and makeup of the image may be controlled. Thus,. it is entirely
possible to attenuate those frequencies which contribute to the gross
characteristics of the object transparency while passing, untouched, those
which contribute to the high-frequency detail. This operation provides an
went in edge sharpness and image contrast, and is the basic principle
enhancement.
Since filtering is the basis of enhanceament, the filters are probably
the most important single item in the system. There are three basic filter
types; 1) sharp cutoff, occluding, 2) frequency attenuating, and 3)
frequency matching. The first is useful for men suration, as it destroys
image tone and improves contrast in the vicinity of an edge. By using a
two-step photographic process, such filters may be used for enhancement.
The second is especially suited for enhancement and performance of optimum
filtering, since the transmissive properties are continuous, can assume a
wide variety of cross sections, and do not sharply cut off. It is with
this type of filter that spatial filtering should achieve its greatest use-
fulnass. The third type is useful for obtaining relative improvement of
one subject within an object transparency over its general background.
These concepts have been embodied in a scientific instrument, the
:gee Enhancement Viewer. It is a linear, coherent optical system which
has been mechanised to perform spatial filtering operations in a rapid and
efficient manner and to facilitate the enhancement of optical images. That
instrument, at present, uses sharp cutoff, occluding filters exclusively.
These filters are positioned automatically in the optical path, at the
of .of the operator who can simultaneously observe the consequent effects
s. object transparencies are immersed in a fluid gate to minimize
to of emulsion scratches and other coherence-destroying irregularities*
is capable of wide adjustment (for additional or different optical
elements) and can mount many filter types.
Approved For Release 2000/05/10 : CIA-RDP78B04747A003100010020-5