CHANGE DETECTOR OPERATION MANUAL

• Document Type: CREST
• Collection: NGA Records (Formerly NIMA)
• Document Number (FOIA) /ESDN (CREST): CIA-RDP78B04747A002500010001-3
• Release Decision: RIPPUB
• Original Classification: K
• Document Page Count: 20
• Document Creation Date: December 28, 2016
• Document Release Date: December 20, 2001
• Sequence Number: 1
• Publication Date: August 2, 1965
• Content Type: MISC

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STATINTL
STATINTL
Declass Review by NIMA/DOD
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CHANGE DETECTOR
OPERATION MANUAL
2 A.; u S t 1,965
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SECTION I - INTRODUCTION
This manual has been prepared to acquaint the Change Detector
operator with the operational features of the Change Detector Evalua-
tion Model. A brief description of the system operation is included
in order to give more meaning to the description of the operational
controls. All of the controls necessary for operation of the system
are described in detail. A list of pertinent operational specifica-
tions is presented in order to show the system capabilities and
limitations. Finally, a recommended set-up and operating procedure
is presented to enable the operator to proceed logically from the
point where the films are inserted, through the registration process
to the detection of changes. No attempt has been made to emphasize
the advantages of one method of change detection available in the
system over another since this is left to the operators discretion.
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SECTION II - SYSTEM! DESCRIPTION
STATINTL
A. GENERAL
The change detector is a device that will manually or auto-
matically register two photographic images and display any differ-
ences or changes between the two images. After insertion of the
two films, and an identification of the areas of comparative
coverage a manual alignment of the two film images must be
accomplished to obtain a coarse registration. Once this coarse
registration is obtained, the display system may be activated to
view gross changes requiring less registration accuracy, or the
automatic registration system may be activated to obtain the fine
degree of alignment required to detect changes of a higher order
of resolution. Upon completion of the registration process the
changes or difference between the two photographs are displayed
on two display monitors. Various techniques for change enhance-
ment and minimization of unwanted change are available when de-
sired. Position readouts of the observed changes can then be
accomplished.
B. MANUAL REGISTRATION
Registration of the two photographic images may require up to six
degrees of freedom. Translational displacement (X and Y) of one
image relative to the other is necessary since it is unlikely that
the center of the two photographs will have an identical geo-
graphic location. The rotation of one image relative to the other
is necessary to compensate for differences in azimuth. The
magnification of one image relative to the other must be adjustable
to compensate for differences in scale factor due to variations
in camera focal lengths and altitude. Unless highly stabilized
camera mounts were employed to obtain the imagery, tip and tilt
corrections are also necessary to complete the registration
process
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These six degrees of registration freedom are available in the
manual registration controls. With an image of each photograph
displayed on its respective monitor, a manual alignment of the
azimuth difference of the two photographs should be accomplished
first since this is the most easily recognized registration
error. The translational corrections and scale factor alignment
should then be performed. If the tip and tilt errors are known,
their corrections can also be inserted at this time. If only a
coarse registration is desired, the change detection function can
be activated and the changes observed on the monitor displays.
When a finer degree of registration is desired the automatic
registration system should be activated.
C. AUTOMATIC REGISTRATION
With the activation of the automatic registration system, the
scanning displays are made inoperable and an area correlation of
the two photographs is performed automatically. A backlight is
activated behind one of the films and the resultant scene is
imaged on the other film. The light transmitted through the second
film is a measure of the correlation of the two films and is
focused on a phototube which generates the electronic correlation
STATINTL signals. If both films are of the same polarity, i.e. both posi-
tives or both negatives, a maximum of transmitted light will
result when the two films are perfectly correlated. The sequence
of operations to obtain an automatic registration of the two films
is as follows: an X and Y search and lock-on is performed to get
within the dynamic lock-on range of the correlation function;
the dynamic lock-on or nutation system is activated and the X and
Y displacement errors are eliminated by a translation of .the X,Y
registration mechanism which moves the image of one film across
the other until the error signal Is at null. Similarly, azimuth
and scale factor errors are eliminated by sensing the errors
generated by the nutation process and driving the azimuth and
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scale factor correction mechanisms until the error signals are
nulled.
D. READOUT
Upon completion of the automatic registration function the system
is programmed to proceed automatically to the readout mode. The
following methods for change detection are available in the
system:
1. Side-by-side comparison - each film image displayed
on a monitor.
20 Flicker change detection - each film image alternately
displayed on a single monitor at a low frequency rate.
3. Video difference change detection - a subtraction of the
two film images, either right minus left or left minus
right o
4. Video difference cloud and shadow rejection - the video
difference technique with added circuitry to minimize
the effect of undesirable shadow and cloud changes on
the change display.
5. Video difference change enhance - a rapid method for
determining the existence of changes by displaying all
changes in one polarity (white) against a background which
may be completely blanked out when desired.
In addition, to fully utilize the resolution capability of the
system, an area of interest may be selected and a blow-up of
the area made for a detailed inspection. Cross-hairs located at
each film plane enable the operator to locate the areas of
interest. Readout indicators which correspond to the cross-hair
positions permit position recording of the areas of interest.
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With the exception of the film loading switches, all controls necessary
to operate the change detector are located on the control panel which
is shown in Figure 1. Controls associated with the right film and
right display monitor are generally located on the right side of the
control panel and those associated with the left film and monitor are
located on the left side of the panel o
The POWER-ON switch located in the upper right corner of the control
panel controls the complete system power. Approximately 1 minute and
30 seconds are required after this switch is activated before full
power is applied to the system.
The film polarity switches, LEFT FILM POS-NEG and RIGHT FILM POS-NEG
provide the proper display polarity on the respective display monitors.
To obtain the best grey scale reproduction of the input films these
switches should be set to the position corresponding to the polarity
of the input films, i.e. POS for film positives and NEG for film
negatives.
STATINTL Film motion is accomplished by activating the controls associated
with the RIGHT FILM ADVANCE controls and '-,EFT FILM ADVANCE controls
Both control groups contain a SLOW-FAST switch which enables two
basic film speeds to be employed, a slow speed for film positioning
and a fast speed for film stewing o A vernier control on each of the
speed ranges plus film direction control is provided by the REV - FWD
lever arm. Film speed is proportional to the displacement of the
REV - FWD lever arm which is spring loaded to return to the center
or stop position when pressure is released.
Manual registration of the two images can be accomplished by pushing
the MANUAL register switch. This activates the RIGHT FILM MANUAL
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ALIGNMENT and LEFT FILM MANUAL ALIGNMENT control groups. The RIGHT
FILM MANUAL ALIGNMENT control group contains a "Y" CONTROL which per-
mits vertical adjustment of the right film image, an "XB9 CONTROL
which permits lateral adjustment of the right film image; and a
ROTATION CONTROL which rotates the right film image for manual adjust-
ment of azimuth errors between the two film images. The LEFT FILM
MANUAL ALIGNMENT control group contains a B0Y00 CONTROL and ?BX" CONTROL
which permit vertical and horizontal adjustment of the left film image,
and the SCALE CONTROL which provides a scale factor correction capa-
bility between the two images. Additional manual registration capa-
bility is provided by the LEFT FILM - TIP and RIGHT FILM - TILT controls
located on the left side of the control panel. These controls provide
a limited degree of correction for film images containing tip and tilt
distortions. The LEFT FILM - TIP control provides correction about an
axis centered in the left film aperture which is parallel to the
vertical dimension of the left film. The RIGHT FILM - TILT control
provides a correction about an axis centered in the right film aperture
which is parallel to the horizontal dimension of the right film.
Automatic registration of the two images is achieved by activating
the AUTO registration switch located in the lower right center of the
control panel e Approximately 80 seconds is required for the auto-
matic registration sequence. Activation of the AUTO register switch
deactivates the manual registration controls except for the two tip
and tilt controls. Completion of the automatic registration sequence
is indicated when the AUTO register switch button disengages and the
indicator light goes out. The two SCALE CORRECTION lights CCW and CW
give an indication that the scale factor adjustment servos have been
moved from the position set manually by tle automatic registration
process, If further manual scale factor correction is determined to
be necessary after automatic registration has taken place, the
SCALE FACTOR control should be rotated in the direction indicated
until the light goes out. This must be done prior to reactivation
of the MANUAL registration switch to prevent the scale factor servos
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from returning to the position that was originally set in manually;
thus losing the benefit gained by the automatic registration, The
ROTATION CORRECTION lights, CCW and CW operate in the same manner..
as the SCALE CORRECTION lights,. Ifs, after automatic registration,
further manual adjustment of the rotational displacement between the
two images is desired, the ROTATION CONTROL should be moved in the
direction indicated by the light,
The displays available on the left monitor are controlled by the group
of five switches located on the left center of the panel, These in-
clude: LEFT FILM, RIGHT FILM, FLICKER (alternate display of left and
right film images), VIDEO DIFF9 L-R (left film minus right film), and
VIDEO DIFFF, R-L (right film minus left film), The FLICKER RATE control
located above the FLICKER switch allows adjustment of the rate at
which the two images are presented on the left monitor in the flicker
mode. The two CONTRAST controls for the LEFT FILM and RIGHT FILM are
located above the two video difference switches. The system normally
employs automatic contrast control circuitry to provide a constant
contrast display for both the left film image and the right film image
regardless of the film contrasts, The LEFT FILM and RIGHT FILM CONTRAST
STATINTL controls are normally used as vernier controls to adjust for slight
differences in contrast left by the automatic contrast control system.
For those cases where the range of the CONTRAST controls is not
sufficient, two toggle switches labeled AUTO-MANUAL have been provided
on the front of the control panel. When the switches are in the AUTO
position the automatic contrast circuitry is operative, The MANUAL
position permits full contrast variation on the CONTRAST controls.
The display presented on the right monitor is controlled by the follow-
ing switches.- LEFT FILM, RIGHT FILMS SWWDOW REJECT, CLOUD REJECT, and
CHANGE ENHANCE. The latter three switches may be operated individually
or in any combination to provide the m ximum capability for rejection
of undesired changes. Activation of either the LEFT FILM or RIGHT
FILM switch is required to disengage any of the other three switches
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The operation of the shadow and cloud rejection circuitry is based on
the criterion that shadows will be the darkest areas of an image-and
clouds the lightest (assuming positive films). Changes attributed to
shadows and clouds which appear on the video difference display can
be detected and returned to a neutral grey contrast level by the
shadow and cloud rejection circuitry. The level at which the shadow
and cloud changes are detected and rejected is determined by the
SHADOW REJECT LEVEL and CLOUD REJECT LEVEL controls. The CHANGE EN-
HANCE display presents all changes between the two sets of imagery as
light areas against a dark background. The CHANGE ENHANCE BACKGROUND
control allows the background level to be varied from a point where
all of the changes are presented to a point where only the highest
contrast changes are presented.
Any area of both of the film images within the film apertures may be
selected and magnified through the use of the AREA SELECTION joystick
and the MAGNIFICATION INCREASE-DECREASE switches. A movement of the
joystick toward the display monitors results in a display of the
upper portion of the film images. Similarly, a right hand movement
of the joystick results in a display of the right side of the film
STATINTL images. Simultaneous rotation of both film images to provide viewing
from any orientation is available by rotating the ORIENTATION OF BOTH
IMAGES control.
Cross hairs, located at each film plane are controlled by the RIGHT
FILM CROSS-HAIR joystick and. LEFT FILM CROSS-HAIR joystick. Cross-
hair position measurements may be obtained from X and Y CROSS-HAIR
POSITION meters adjacent to each joystick. The meters read directly
in centimeters. A zero reading on all the meters indicates that the
cross hairs are centered in the film apertures.
Three focus controls are available in the system. The LEFT LENS FOCUS
and RIGHT LENS FOCUS controls are used to adjust the optical focus of
the system. The FILM CRT FOCUS control is used to adjust the elec-
tronic focus of the scanning cathode ray tube light source. The focus
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controls should be set after the MAGNIFICATION INCREASE switch has
set the magnification to near maximum in order to obtain maximum focus
sensitivity. After the system has been allowed to warm-up to its
normal operating temperature, further adjustment of these controls is
not normally necessary.
Any of four preset frame lengths may be counted by utilizing the
FRAME LENGTH SELECTOR switch and FRAME COUNTER associated with each
film. In addition, any frame number series may be set into the FRAME
COUNTER by rotating the SET control. Films whose frame lengths are not
the same may be inserted in the respective film magazines with no
loss in counting accuracy. When films having frame lengths longer
than the 70 millimeter film aperture width are inserted the FRAME POSI-
TION INDICATOR may be used to measure the distance the film has
traveled from a reference point to the area of interest within the
viewing aperture. These indicators which read directly in milli-
meters, when used in conjunction with the cross hairs, allow an area
of interest to be measured directly with respect to a reference point.
Due to the counting rate limitation of the indicators they only
operate when the film advance speed switches are in the SLOW position.
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SECTION IV a OPERATIONAL SPECIFICATIONS
The following table lists the specifications which are pertinent to
the operation of the system:
Film Input Data
Film
Film Aperture Size
Film Speed
Slow Mode
Fast Mode
Frame Counter Accurac
Position No. 1 2.3) in
2 ( 10.4 5) in
3 30) in
4 (30.7) in
Image Registration
Manual X Registration
Manual Y Registration
Manual Rotation
Manual Scale Factor
Tip
Tilt
STATINTL Automatic Registration Time
Display Data
Film to Monitor Magnification
Magnification Control Range
Resolution
Minimum Magnification
Maximum Magnification
Flicker Rate
Cross-Hair Position Accuracy
70-mm roll, 250 ft max
70-mm x 70-mm
0 - .2 inches/sec
0 - 24 inches/sec
5 frames for 250 ft of film
1 to if ft It -f
C
- 1 if
C- 1 fr
ff it it 1f
n fr it II
50 percent of aperture for both
left and right controls
? 50 percent of aperture for both
left and right controls
? 180 degrees
2X
? 5 degrees
+ 5 -3 degrees
80 see
OX
Approx. 6 line pairs/mm
Approx. 30 line pairs/mm
1/2 to 6 cycles/see
? 5 percent of film aperture
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SECTION V - RECOMMENDED OPERATING PROCEDURE
The operating procedure outlined below is intended to provide a
logical sequence of operations starting with the initial equipment set-
up and proceeding through the manual and automatic registration
process for aligning the two sets of comparative imagery which results
in displays of the changes that are suitable for analysis. Initial
set-up of the system is accomplished as follows:
Activate POWER-ON switch. Allow approximately 1 minute for all
power supplies to come ono
Set LEFT FILM POS NEG and RIGHT FILM POS-NEG switches according
to film polarities to be used.
Set LOAD-OPERATE switches located on film magazines to LOAD
position.
Insert films as shown in diagram of Figure 2.
Return switches to OPERATE position and close doors on registra-
STATINTL tion compartment.
Select proper frame length position on each FRAME LENGTH SELECTOR.
Push RESET on FRAME COUNTERS.
Using SET control insert initial frame number into FRAME COUNTERS.
Center AREA SELECTION, LEFT and RIGHT CROSS-HAIR joysticks.
Activate LEFT FILM switch on left monitor and RIGHT FILM switch
on right monitor.
Set contrast control switches to AUTO and adjust LEFT FILM and
RIGHT FILM contrast controls to mid-range.
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Figure 2. Film Loading Diagram
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Move LEFT FILM ADVANCE FWD to obtain image display on left
monitor.
Adjust ORIENTATION OF BOTH IMAGES control for horizontal
display on left monitor.
Move RIGHT FILM ADVANCE FWD to obtain image display on right
monitor.
Activate MAGNIFICATION INCREASE switch-and hold until magnifica-
tion reaches near maximum.
Adjust FILM CRT FOCUS and observe best image focus on either
monitor.
Adjust LEFT LENS FOCUS, observe on left monitor.
Adjust RIGHT LENS FOCUS, observe on right monitor. Further
adjustment of these controls is not normally necessary
after the system has warmed up.
Return MAGNIFICATION DECREASE to minimum magnification.
With all controls set as previously stated the process of identifying
overlapping areas on the two sets of imagery and positioning the
respective areas within the film apertures may proceed.
Depress MANUAL REGISTRATION switch and observe cross-hair
position and rotation on right monitor.
Adjust ROTATION, X and Y controls of the RIGHT FILM MANUAL
ALIGNMENT.control group to center the cross hairs.
Observe and center the cross hairs on the left monitor using
only the X and Y controls of the LEFT FILM MANUAL ALIGNMENT
control. group.
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The centers of the film apertures should now be aligned in the center
of their respective display monitors.
Set FILM ADVANCE switches to FAST and activate the REV-FWD
FILM ADVANCE controls.
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Identification of the areas of interest on each film roll may be
accomplished by utilizing the frame counters if the frame number is
known, or by observation of the images appearing on two display
monitors. When the two overlapping areas of interest have been
identified the FILM ADVANCE switches should be set to the SLOW posi-
tion. If a frame length longer than the 70 millimeter aperture is
being used, the reference point on the frame should be set over the
cross hair and the RESET and SET buttons on the FRAME POSITION INDICA-
TOR depressed. The reading on the FRAME POSITION INDICATOR can then
be added to the reading of the X CROSS-HAIR POSITION meter when
measuring positions within the area of interest. By manipulating the
REV-FWD controls of the film advances, center the horizontal overlap
area of the two images in the center of the respective displays.
Manual registration of the two images proceeds as follows:
Set the left monitor display to either of the VIDEO DIFF modes
and the right monitor display to CHANGE ENHANCE.
Observe either or both monitors and adjust.ROTATION CONTROL
for minimum azimuth error,
Adjust RIGHT FILM MANUAL X and Y controls alternately with
LEFT FILM MANUAL X and Y controls to obtain minimum X and Y
errors between the images while keeping the center of the
overlap area centered within the displays.
Adjust SCALE CONTROL for minimum scale difference between the
two images.
If the tip and tilt errors are known for the film images they may be
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inserted into. the TIP and TILT controls at this time. If these
errors are not known the TIP and TILT controls should be set to zero
since the position of these controls may adversely affect the auto-
matic registration process.
Following the manual registration process the AUTO REGISTRATION
switch may be activated. Approximately 80 seconds is required to
perform automatic registration of the two images. The end of the
automatic registration cycle is indicated by a disengagement of the
AUTO switch and dimming of the switch lamp.
The registered images may be received at this time by activating either
the VIDEO DIFF switches or the FLICKER switch on the left monitor
control and the CHANGE ENHANCE switch on the right monitor control.
Adjust either CONTRAST control for best correlation in the video
difference mode or for identical contrast in the flicker mode. The
FLICKER RATE control may be adjusted for optimum flicker frequency.
If it is determined that further registration is necessary a manual
vernier adjustment may be performed as follows:
Adjust SCALE CONTROL and ROTATION CONTROL in the direction in-
dicated by their respective correction lights until the
lights are extinguished.
Activate the MANUAL REGISTRATION switch and proceed with manual
adjustment of registration controls.
Often when a large degree of misregistration has been left after the
initial manual registration has been performed.,a residual error
remains after the automatic..cycle. This error can be minimized by
depressing the AUTO register switch a second time and allowing the
system to complete another automatic cycle.
The methods of change detection available to each display monitor
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have been explained previously. The switches controlling these
methods are self-explanatory. The AREA SELECTION joystick together
with the MAGNIFICATION switches permit any area within the film
apertures to be analyzed in detail. Both images may be rotated
simultaneously by using the ORIENTATION OF BOTH IMAGES control. The
use of the cross hairs and cross-hair position meters for location
of position of changes is not dependent on the AREA SELECTION joystick
position or the amount of magnification since the cross hairs are
located at the film planes. The meters read directly in centimeters
with zero indicating the center of the film aperture,
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