(Sanitized)SPLIT FORMAT LIGHT TABLE, PRELIMINARY TESTS

• Document Type: CREST
• Collection: NGA Records (Formerly NIMA)
• Document Number (FOIA) /ESDN (CREST): CIA-RDP78B04770A002000050009-7
• Release Decision: RIPPUB
• Original Classification: C
• Document Page Count: 5
• Document Creation Date: December 28, 2016
• Document Release Date: December 4, 2002
• Sequence Number: 9
• Publication Date: March 4, 1968
• Content Type: MFR

Approved For Releatffi1ft "AIr78B04770A002000050009-7
NPIC/TSSG/EP/820-68
4 March 1968
25X1
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25X1
Split Format Light Table, Preliminary Tests
1. The 0 Split Format Light Table is a prototype unit purchased
as an off-the-shelf item. The purpose of this unit was to incorporate two
new features into the standard light tables - a light source up to 3000
foot lamberts (Ft.L.) and a film loop takeup capability from zero to 72
inches. In the course of building this table, other changes were incorporated.
A new optics carriage was designed and installed and an electric clutch
mechanism was designed for the carriage. The masks for the light surfaces
.were placed under the glass and remotely operated.
2. The increased illumination is attained by using two grids, similar
to 0 918 light grids, and a redesigned power supply. The heat
generated by this is dissipated by a liquid cooling system. The two light
sources are controlled by a single on-off switch, and separate brightness
controls for each grid. The on-off switch actually controls the cooling
liquid pump. When the flow rate of the liquid reaches a certain value, a
flow switch closes a relay for the grid power. At initial turn on, it takes
up to 8 minutes for the grid relay to close. On occasion, an unstable
condition of the flow switch opening and closing at low frequency has been
noted.
3. The light source does not produce 3000 Ft.L. Although the
illumination is above 3000 Ft.L. when the machine is turned on, it drops
off rapidly. After 30 minutes, the values are 2455 Ft.L. for the left side
and 2835 Ft.L. for the right. The maximum values after 2 hours are 2220 Ft.L.
on the left side and 2565 on the right (see Attachment 1). At the minimum
setting of the brightness controls the maximum values on the surface are
115 Ft.L. on the left and 130 Ft.L. on the right. After 2 hours of
operation at maximum brightness with 2.0 density film on the lighted
surfaces, the temperature on the surfaces was measured at 135?F.
4. The takeup mechanism can handle a loop of film up to 79 inches long.
The levers which open and close the center of the table are hard to operate.
The rollers in the center of the table are too close together and cause
binding of the film when a loop is taken up and the table is fully closed.
These are minor problems. The takeup feature itself is well designed and
easily operated.
Declass Review by
NIMA/DOD
CONFIDENTIAL
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Approved For Release 2003/01/28 : CIA-RDP78BO477OA002000050009-7
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5. The optics carriage is designed to take all viewing devices currently
in use. It can be locked in the X and Y directions by the use of an
electric clutch. In these two directions, fine feed mechanisms are used'
when the locking mechanism is actuated. The carriage can be freed by a
push-button switch on the optics mount. The Z movement of the carriage is
done by a coarse or fine manual drive on the optics mount. There is no
locking feature in this direction.
6. In the X and Y directions, it takes a force of more than 10 pounds
to move the carriage with the clutch turned on. With the clutch off, the
break away force is 4 to 5 pounds in both directions. It takes a force of
2 to 5 pounds to sustain movement in the X direction,, and less than 2
pounds in the Y direction. The X motion is therefore very rough.
7. The masking devices are located below the glass. They are
manually operated by controls to the left and right of the table. The film
rollers at either end of the table interfere with easy, rapid operation of
the shade controls. These should be moved to a more accessible location.
8. An attempt was made to measure the parallelism of the carriage
travel and the lighted surface. It was found that the distance from the
carriage to the table varies up to .027 inches (see Attachment 2). This is
caused by a combination of uneven glass on the lighted surfaces and skew
tendencies of the carriage. As matters stand, the optics currently in use
will not stay in focus from one end of the table to the other.
9. This memorandum has listed items which should be corrected by the
manufacturer prior to final evaluation, and is not intended to be a final
report.
25X1
Equipment Performance Branch, DED
ATTACHMENT: 1 Grid for Illumination Measurements
2 Variations in Distance from Carriage
to Table
CONFIDENTIAL
Approved For Release 2003/01/28 : CIA-RDP78BO477OA002000050009-7
 Approved For Release 203/01/28 : CIA-RDP78B04770A002000050009-7
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 ATTACHMENT 1 SHEET 2
Approved For Release 2003/01/28 : CIA-RDP78BO477OA002000050009-7
GRID POSITION
1
2
MAXIMUM BRIGHTNESS
LEFT RIGHT
1500 1455
1625 1515
1280 1550
1956 2125
2170 2510
1870 2355
2080 2565
2265 2620
1990 2477
2125 2125
2170 2532
1917 2265
1550 1500
1650 1722
1455 1500
MINIMUM BRIGHTNESS
3 53
8 115
Approved For Release 2003/01/28 : CIA-RDP78BO477OA002900050009-7
 Approved For Release 2003/01/28 : CIA-RDP78B04770A002000050009-7
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Approved For Release 2003/01/28 : CIA-RDP78B04770A002000050009-7