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HELR - Hi-Efficiency Low Reflection
Coating No. 527
Specification No. 1081
| Spectrophotometric curve shown in the visible region
is measured at 15° from the normal incidence. |
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| *When the coated element is used at angles other
than 15° incidence, curve peaks will shift . For angles greater
than 15°, the curve peaks will shift down scale. |
Reflection
The following table indicates the reflectance from
a single surface of a substrate having indices of refraction within the
range of 1.47 - 1.55, coated with our HELR coating:
Wavelength Range Nanometers |
0° to 15° incl. |
Reflectance Percentage for Angle of Incidence
Shown
|
30° |
450 to 675 incl. |
0.6 |
Absolute |
1.0 |
500 to 620 incl. |
0.35 |
Average |
0.5 |
425 to 700 incl. |
0.5 |
Average |
0.6 |
Light Absorption
Within the wavelength range of 425 - 700 millimicrons,
light loss in the coating shall not exceed the following limits per surface.
| Maximum average absorption |
0.5% |
| Maximum absolute absorption |
2.0% |
| Maximum diffuse reflectance |
0.1% |
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.
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.
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