FOURTH LETTER REPORT ON EVALUATION (U) (14 FEBRUARY 1966 TO 14 MARCH 1966)

• Document Type: CREST
• Collection: NGA Records (Formerly NIMA)
• Document Number (FOIA) /ESDN (CREST): CIA-RDP78B04747A002900030014-3
• Release Decision: RIPPUB
• Original Classification: K
• Document Page Count: 3
• Document Creation Date: December 28, 2016
• Document Release Date: June 19, 2002
• Sequence Number: 14
• Publication Date: March 14, 1966
• Content Type: REPORT

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Approved Fof elease 2002/07/10 :CIA-RDP78B047002900030014-3
FOURTH LETTER REPORT ON EVALUATION (U)
(14 February 1966 to 14 March 1966)
DECLASS REVIEW by NIMA/DOD
Approved For Release 2002/07/10 : CIA-RDP78BO4747AO02900030014-3
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Letter Report on Evaluation (U)
I. Work for Reporting Period
During the past month the two pinhole interferometer was completed, some
experiments performed, and the results evaluated. The arrangement was a pair
of 50 micron diameter pinholes separated about 500 microns apart in the object
plane. The laser was in all cases operated in single mode. The first experiment
was to remove the ground glass completely and examine the contrast of the fringes
produced. As expected the fringes were very high contrast indicating a high degree
of spatial coherence for this pinhole separation. The next case consisted of
replacing the ground glass in its regular position in front of the laser but not per-
mitting it to rotate. An auxiliary lens was used to focus the laser beam into a
small spot on the ground glass surface. The fringes were again found to be high
contrast indicating that the unevenness of the stationary ground glass surface did not
appreciably reduce the spatial coherence for this pinhole separation. As the spot
size on the ground glass was increased by slightly defocussing the lens the fringe
contrast remained high.
However, in the next part of the experiment the ground glass was rotated as
it would be operationally. We found that in this case the contrast of the fringes was
reduced considerably for both the focussed and defocussed spot illumination indicating
that the rotating ground glass in effect reduces the spatial coherence of the laser
illumination.
Therefore, in the situation in which the enlarger was intended to be used, the
rotating ground glass is acting to reduce the spatial coherence of the object illumi-
nation. .
Approved For Release 2002/07/10 : CIA-RDP78BO4747AO02900030014-3
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To parallel this work images of L" targets were made 25X1
for each of the above cases. The effects which one would expect on the basis of
the interferometer measurements were observed. In the extremely coherent (high
fringe contrast) cases a phase reversal was observed in the images. The less
coherent cases produced fewer artifacts such as edge ringing and dust particle
effects but also reduced the contrast of the object at the same time.
II. Work for Next Period
During the coming month we will experimentally and analytically examine
the images of edges of various contrasts. Very high acuity - edges have been
obtained for this work. They were made with an electron beam apparatus and are
much sharper than an edge produced photographically. Further direct measurements
of the spatial coherence in the object plane will be made.
III. Visits to Contractor
No visits were made to the contractor during the reporting period.
IV. Changes in Personnel
None
V. Progress of Work
As of this reporting data approximately 25% of the work program has been
completed and 25% of the contract funds have been expended. Now that the enlarger
checkout, camera back modifications , and computer programming are essentially
completed we expect that the completion rate will be substantially increased. No
delays in completing the contracted program within funds or within specified
completion dates are anticipated.
Approved For Release 2002/07/10 : CIA-RDP78BO4747AO02900030014-3