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Beamsplitter Glass Coatings
Many systems utilize a sophisticated beamsplitter to
allow the pilot clear observation of the image on the mirror. FLABEG has
worked with the leading manufacturers of simulators for many years to
perfect large beamsplitters with neutral density design.
Most simulators today are used for commercial
and military flight training. There are many other applications in which
real image visual display systems are employed where cost, safely and
security are prime considerations.
Scope
This specification applies to the above coating
when it is applied to glass with an index of refraction of 1.523.
Materials and Workmanship
The coating process shall cause no injury to the
glass surface which would cause rejection of the optical element under
other applicable specification. Any optical element which has met the
requirements of other applicable specifications prior to coating shall
not be rejected after coating because of fine hair lines or other defects
in such optical element which are made more visible by the coating.
Adherence
No visible part of the coating shall be removed
by the cellulose tape test described here:
Test: The tacky surface of cellulose
tape shall be carefully placed in contact with a portion of the coated
surface and firmly rubber against that surface. It shall then be quickly
removed with a snap action that exerts the greatest possible stripping
action on the mirror surface.
Hardness
No evidence of film removal or film abrasion shall
be visible to the eye when any one or all of the following test are applied:
- The coated optical element shall be carefully washed
first in a solution consisting of one (1) ounce of sulphated alcohol,
one (1) ounce 15 Baume normal amomonium hydroxide, and one (1) gallon
water; then cleaned in acetone or grain alcohol and dried with lens
tissue or soft cloth.
- A thick past of U.S.P. precipitated chalk and water
shall be applied to the coating and allowed to dry, and then wiped off
with a soft cloth.
- A pad of clean dry cheese cloth (previously laundered)
3/8 inch in diameter, 1/2 inch thick, bearing with a force of one pound
on the coating shall be rubbed across the coated element in any direction
150 times.
Note: During the above tests, care
should be exercised to prevent contaminating abrasives contacting the
coated surface causing slight sleeks.
Durability
No evidence of film removal of film abrasion shall
result from one or both of the following tests:
- The coated element shall be placed in a thermostatically
controlled cabinet with a salt atmosphere at a temperature of 95°
F. plus or minus 4° F for 48 hours. The salt atmosphere shall be
obtained by allowing a stream of air bubble through a salt solution
containing about 1 1/2 pounds of sodium chloride per cubic foot of water.
- The coated element shall be placed in a thermostatically
controlled humidity cabinet with an atmosphere of at least 95% relative
humidity and at a temperature of 120° F. plus or minus 4° F.
for a continuous period of 24 hours.
Water Resistance
No evidence of film deterioration visible to the
eye shall result from the following test:
A drop (0.05 milliliter) of distilled water shall
be permitted to dry at room temperature on the coated surface and the
coated surface shall then be cleaned with acetone or grain alcohol.
Effect of Temperature
The coating shall function satisfactorily and shall
not be damaged by exposure to an ambient temperature of minus 60°
F. and plus 500° F.
* This production tolerance can be reduced for special
applications where closer tolerances are required.
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