INSTRUCTIONS FOR USING THE(Sanitized) EYEPIECE WITH THE (Sanitized) HIGH POWER STEREOVIEWER (TWIN DYNAZOOM MICROSTEREOSCOPE)

• Document Type: CREST
• Collection: NGA Records (Formerly NIMA)
• Document Number (FOIA) /ESDN (CREST): CIA-RDP78B04747A001500030044-5
• Release Decision: RIPPUB
• Original Classification: C
• Document Page Count: 7
• Document Creation Date: December 28, 2016
• Document Release Date: January 30, 2002
• Sequence Number: 44
• Publication Date: April 6, 1966
• Content Type: REGULATION

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INSTRUCTIONS FOR USING THE II FILAR
EYEPIECE WITH THE IIHIGH POWER STEREOVIEWER
(TWIN DYNAZOOM MICROSTEREOSCOPE)
I
filar eyepieces for linear measurement and gonipeter
eyepieces for angular measurement are now available for use on the
High Power Stereoviewer. A minor modification to the
Dynazoom barrels permits attachment of the eyepieces to either barrel.
The goniometer eyepiece is operated by rotating a reticle in relation to
a 360? scale which is clamped to the microscope tube.
Extreme caution must be exercised when making distance measurement:
with the filar eyepiece. The operator should be certain that only one
zoom and objective setting is used for each set of calculations, since
the slightest alteration of the variable magnification is enough to
invalidate the results. Consequently, a preliminary examination of the
area in which measurements are required is recommended to select the
proper magnification for optimum resolution of the imagery. If stereo
mensuration is desired, the special compensating eyepiece mated for
each measuring eyepiece must be employed. This procedure provides for
both optical path and color correction and eye relief equalization.
All settings and accessories should be rechecked if the operator leaves
his equipment during a measurement series.
B. DESCRIPTION.
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Filar (or screw micrometer) eyepiece provides higher accuracy
than simple, fixed scale micrometer eyepieces by means of a 15X
compensating eyepiece matched with
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scale and a movable crosshair are visible in the view field. The
crosshair consists of a "vertic
line completely bisecting the field
and a short "horizontal" line defining the mid-point of the vertical
one. One full turn of the micrometer causes the crosshair to move
across one interval on the fixed scale. On its circumference this drum
carries a scale of 100 intervals. To make use of the eyepiece, several
calibrations and several measurements should be averaged.
C. CALIBRATING THE FILAR EYEPIECE.
Before making any measurements, it is necessary to know what actual
ground distance on the image corresponds to one interval of the eyepiece
scale. In order to determine this value, the following steps are taken.
(I) Select the desired magnification and remove the film from the stages.
(2) Replace the standard eyepiece with the filar eyepiece and focus
with one eye on the filar scale by rotating the black knurled cap
of the eyelens to the point of sharpest definition of the scale.
(3) Place a stage micrometer or precision scale on the Dynazoom stage
Is beneath the filar eyepiece. Focus on the scale with the Stereoviewer coarse
focus adjustment and align the stage micrometer with the filar micro-
meter scale. This may be done by rotating the filar eyepiece in the
microscope tube. Subsequent stereoscopic image measurements will
undoubtedly require filar eyepiece rotation, in any case.
(4) The eyepiece micrometer and the image of the object micrometer must
be in the same plane, free from parallax. Check this by moving the head
slightly. The two scales must not appear to move with respect to one
another. The microscope fine focus adjustment must be used to eliminate
all parallax.
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(5) Adjust the X,Y traverse controls of the Stereoviewer stage until
the zero line of the stage micrometer scale coincides with the
zero line of the fixed filar micrometer scale. If the lines on
the filar scale are much finer than those of the image of the
stage micrometer, align the filar zero line with the center of the
zero vertical line on the stage micrometer. From these coincident
lines, scan across the superimposed scales to the number "10" line
on the filar scale and read the corresponding scale indication on
? the stage micrometer. One interval of the eyepiece micrometer *hen
corresponds to the ratio, R. where:
0
Stage Micrometer Distance
For example, if 10 intervals in the eyepiece coincided with 18 intervals
in the stage micrometer, one eyepiece interval (R) would equal
18/10 stage micrometer interval, or 1.8.
During this process, it is best to ignore any dimensional
indications on the stage micrometer, such as mm, inches, or
decimal points. Merely count the discrete intervals subtended.
(6) To obtain an actual ground dimension, the stage/filar ratio (R)
must be defined in terms of the specific photography used. This
is done in two steps:
a. Multiply the absolute value of one stage micrometer interval (ST)
by the scale factor (SF=reciprocal of the scale) of the photography
to obtain the ground distance represented by one stage micrometer
interval on the film imagery (STg).
STg = Si x S.F.
CONFIDENTIAL
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For example, if one stage micrometer interval equals 0.1
millimeter and the photo scale factor is 30,000, one stage micro-
meter interval equals 3,000 millimeters, or 3.0 meters.
multiply the ground stage micrometer interval (SIg) by
the stage/filar ratio (R) to obtain the ground distance represented
by one interval on the fixed filar scale (FIg).
F,Ig=SIgxR
For example, using the values obtained above, one interval
in the fixed filar scale equals 3.0 times 1.8 or 5.4 meters.
NOTE: These two steps, of course, can be combined into one
formula, as:
FTg = SI x S.F. x R
D. MEASURING WITH THE FILAR EYEPIECE.
The value of FIg is then noted for all subsequednt measurements
Is
performed in the area of the film in which the scale remains the same.
Actual measurements on the photography are obtained by marking off the
desired distance in the image with the movable hairline in the filar
eyepiece. The following steps are necessary to perform each measurement:
(I) Start by placing the target image to be measured in the center
of the field of view (defined by the movable filar crosshair when
set to correspond with the "6" line of the fixed filar scale).
(2) Rotate the linear dimension of the image to be measured until it
coincides with thy,"horizontal" (short) filar crosshair line. This
may be accomplished with the optical image rotation control ring of
the High Power Stereoviewer when measuring a monoscopic image; however,
it is strongly recommended that the filar eyepiece be rotated to
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accomplish this alignment when viewing a stereo pair (see E.2. below).
(3) Align the movable crosshair on the~!'right"edge of the image to be
measured. Record the scale indication and the drum reading (FRI).
(4) Move crosshair until it has aligned with the "left" end of the image.
Care must be taken that the two "settings" are on a common subject
in the stereo image. For example, measure the top or eaves of a
building The base of the building may only be used if there is no
appreciable slope to the ground surface. Record the scale indication
and drum reading. (FR2)
(5) Subtract the second reading from the first.
For example if FRI = 7.79 and
FR2 = 3.50, then
FR = 7.79 - 3.50 = 4.29 units.
(6) This total filar reading is then multiplied by the ground value
obtained for one interval on the fixed filar scale (Fig) to obtain
true ground distance (GD):
GD = FR x FIg
For example, the values obtained above (Fig = 5.4 meters and
FR = 4.29), give a ground distance of approximately 23.17 meters.
E. DISCUSSION OF PROBLEMS IN USING THE FILAR EYEPIECE WITH STEREOSCOPIC
IMAGES.
(I) Since there are no common X, Y motions available on the High Power
Stereoviewer, stereo fusion can be maintained only by concurrent
movement of the corresponding X, Y controls on each stage. If the
stereo -image is misaligned, it can be corrected by a final adjustment
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of one stage relative to the other. These concurrent motions
must be accompanied frequently by the P.I. to place the individual
target images at the center of the view field for optimum viewing
and measurement.
(2) To get the full advantage of measuring in stereo (i.e., retaining
the three-dimensional effect), the stereo base line of the two
conjugate images must be rotated to correspond with the operator's
eye base while using the Stereoviewer. On the other hand, in order
? to make a series of rapid, linear measurements, the image must be
successfully rotated to correspond with the scale in the filar eyepiece.
However, excessive rotation of the image will destroy the stereo
effect or introduce pseudo-stereo. Consequently, the operator
should align the filar scale on successive target images by rotating
the filar eyepiece in the microscope barrel in concert with
concurrent X, Y motions of the film stages.
F. SUMMARY.
0 (I) To Calibrate Filar Eyepiece
a. Select magnification for measuring imagery and do not change
during calibration and measurement.
b. Remove film from Stereoviewer stage.
c. Focus filar scale with black, knurled eyelens cap.
d. Place stage micrometer on microscope stage and focus image with
Stereoviewer controls.
e. Align stage micrometer image with fixed filar scale.
f. Check parallax.
g. Align the scales so that the zero lines coincide.
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h. Determine stage/filar ratio which equals the subtended stage
micrometer distance divided by 10 units on the fixed filar scale.
R = Sd Example: R = 18 1.8
10 10 _
i. Determine ground distance of filar interval on specific photo
image, which equals the stage micrometer interval times the
scale factor times the stage/filar ratio.
Frg = Sr x S.F. x R
Example: Fig = O.Imm X 30,000 X 1.8 = 5.4 meters.
(2) To Measure Image With Filar Eyepiece
a. Position target image in center of view field.
b. Rotate filar eyepiece until the short crosshair coincides
with the dimension to be measured.
c. Obtain initial filar seeting by positioning crosshair at "right"
edge of image and noting scale and drum reading (FRI).
d. Align crosshair with "left" end of image and note scale and
drum readings (FR2).
? e. Obtain total filar reading (FR) by subtracting the second
reading from the first.
FR = FR I - FR2
Example: FR = 7.79 - 3.50 = 4.29
f. Determine true ground distance of image which equals the filar
reading times the filar interval ground distance.
GD = FR x Fl g
Example: GD = 4.29 x 5.4 = 23.17 meters.
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