ELECTRONIC RESOLUTION METER.

• Document Type: CREST
• Collection: NGA Records (Formerly NIMA)
• Document Number (FOIA) /ESDN (CREST): CIA-RDP78B04747A001800100037-2
• Release Decision: RIPPUB
• Original Classification: K
• Document Page Count: 2
• Document Creation Date: December 28, 2016
• Document Release Date: April 17, 2001
• Sequence Number: 37
• Content Type: REQ

STATINTL
Approved For Release 2001/07/16 : CIA-RDP78BO4747AO01800100037-2
ELECTRONIC RESOLU3'ZON METER.
A device is required which will ascertain the resolution of a
photographic image, so that the quality of photographs may be measured,
and the capabilities of the system which produced the photograph
ascertained immediately. It is required that the device function
from operational photographs, rather than standard test patterns.
Thus, the basic problem is to automatically measure resolution in a
manner that is relatively independent of the size and contra3t of the
objects photographed.
If the photograph is scanned with a flying spot scanner1 the
signal obtained from a photoelectric cell viewing the spot can provide
a means for measuring resolution. This is so because the frequency
content of the signal bears a direct relationship to the resolution.
The presence of high frequencies in the signal indicates high resol-
ution.
A device may be constructed which consists of a simple flying
spot scanner which produces a small spot of light which is focused on
the plane of the image and moved rapidly across a portion of the
photograph. It will be possible to accomodate either positives,
negatives, opaque prints, or transparancies, all with the same
machine. -A fixed scanning pattern may be employed and the p'~otograph
may be positioned so, that the resolution of selected portions may
be ascertained. A direct reading meter output, calibrated in lines
per millimeter, may be provided.
In the electronic circuits connected to the photocell output,
the frequency analysis must be made in a manner which will give a
measurement that is independent of the objects in the photograph.
DECLASS REVIEW by NIMA/DOD
Approved For Release 2001/07/16 : CIA-RDP78BO4747AO01800100037-2
 Approved For Release 2001/07/16 : CIA-RDP78BO4747AO01800100037-2
(2)
This may be accomplished first, by adjusting the vido signal to a
fixed peak-to-peak value by means of an automatic gain control. The
entire signal is applied to a differentiating circuit which provides
an output proportional to the time rate of change of picture intensity.
A peak reading voltmeter applied to the -ifferentiating circuit
output then provides a measure of resolution. By confining the scan to
a small area of the photograph, resolution readings may be obtained
both in the regions of low and high contrast.
A more elaborate, and perhaps more accurate measurement,
particularly whigi-the area scanned contains both very light and
very,dark objects, may be obtained as follows. The output of the
differentiating circuit, together with o running average of the video
signal amplitude X, are applied to a quotient circuit which computes
A dx
The output of this circuit is a measure of the percentage rate
of change of picture gray level per unit distance along the photograph,
and is therefore independent of the particular value of A. A peak
reading voltmeter again is
than the average value, of
The value of A is obtained
instantaneous value of the
Thus A is a measure of the
variation level.
used, so that the highest value, rather
this quantity is recorded on the meter,
by integrating (with an RC filter) the
peak to peak excursion of the video signal.
short time average of the picture intensity
Approved For Release 2001/07/16 : CIA-RDP78BO4747AO01800100037-2