SOME COMMENTS ON COHERENT IMAGERY

• Document Type: CREST
• Collection: NGA Records (Formerly NIMA)
• Document Number (FOIA) /ESDN (CREST): CIA-RDP78B04747A002700020030-8
• Release Decision: RIPPUB
• Original Classification: K
• Document Page Count: 6
• Document Creation Date: December 28, 2016
• Document Release Date: June 26, 2002
• Sequence Number: 30
• Publication Date: April 13, 1964
• Content Type: MEMO

Approved For Release 2002/07/12 : CIA-RDP78604747A002700020030-8
This memo will atteupt t clarify
ee eneeoheeen
Declass Review by NIIVIA / DoD
STAT
Figure la shows a cohexant imaeing yi with prov
We optical configura4on i ly ae ae illus
performs only one task, for ttns Le to fel reepectively?
the transform and image formation from the transforee A e
is shown in Figure lh. en thee system,. Le ceebinee the
need be corrected only on axia to few* an imege of the go
while Le, in conjunction with Lel at be corrected to ima
while both Le and liworm at the sewe F number, df wed by he frequency content of
the negative, the diameter of Le is larger than L5 by the diaMeter of the negative. In
addition, es well be explaireld late e, the aystem in Pegure la le more sensitive to duet,
scratches And other localiced lens defectn.
ering0
ice each lens
formation of
oufiguration
end ID Le
raneform plane
field, In addition,
In chant immgery there is rder to tha light
This order is lacking in the case cf in' car illemeeateone
determines the degree of coherence. The eegree of r
light can he aeparated into two cozpovents, oedoe devil
coherence, and osier along the optical axie eallee Leeper
eemPonamta are elmesk independent. Spatial]. 'erence is m
collimation or sulvefrontllatnaaa. Teeecee',
wavelengths present in the light.
eating rtivm.
The dig this or
n t3?i lIt.;irng
ti d spatial
. two
degree of
LV --
Let na consider the effect of the degree of spatial and
imagery. First we nmet distinvieh between distance reeolutio
and frequency resolution in the traesfoze piaam. The reeoletie
in the image intensity is of the order of the reciprical
frequency of the transform plane, and ia endependeut of the ,de
It is the retolution element of the neeativee visible in the
upon the degree of spatial coherence. On the other hand,
frequency in the transfemm plane for perfect spatial end
order of the reciprecalof the negative diseetar. If the ee
im such that the image of the nource in the transform plane S equal
renolution element, then the system in spatially coherent0, If the de
coherence is such that when the source image is diffr cted by theh
of a negative to the c4 toff frequency of the transform elave,_the d
ranee upon
ge plane
n distance
utoff
spatial cohetence0
is dependent
=element in
ee is of the
al coherence
frequency
of temporal STAT
quency eonteut
tar of the mource
Approved For Release 2002/07/12 : CIA-RDP78604747A002700020030-8
Approved For Release 2002/
;u L(esearcfl
7/12_: CIA-RDP78130474Z,P002700020030-8_
STAT Page 2 01; 6
image increases less than one frequency resolution element then the system is temporally
coherent. Resolution in the frequency plane is controlled by the source image size at -
low spatial frequencies and by the spread in wavelength at high spatial frequenciee. In
the systems shown in Figure 1, resolution in the frequency plane depend* upon the quality
of eel or 1.1 and Lz while recolution in the image plane depends only upon the quality of
or L2 and L3. The question thus becomes what is the effect of resolution in the
frequency plane on?resolution in the image plane?
First we consider the effect of temporal coherence on the image. :The image intensity
is the mum Of the image intoneitiem formed at each of the wavelengthe present in the
illeminating light. The most ieportant effeet of a spread in wavelength is on L5. By
tectricting the range of wavelengths to a small fraction the design of L5 is simplified,
beeeese chromaticaberrations are elieinated.
a=t ee consider spatial coherceee. Lens design does not depend upon the degree of
spatial coherence. The degree of spatial coherence is easily varied by varing the size
of an iris diaphragm at the source for a thermal source. Temporal coherence cannot be ?
varied nearly as easily. If the object electric field transmission of the negative
conteins no frequenciea greater than Kee the cutoff frequency of the transform plane is
Kt and the image of the source in the transform plane extends to Ks then for an unapodized ?
transform plane, when Ko