Anti-Reflective Glass Coatings

Specification 1079, Coating No. 525

Specification 1081, Coating No. 527

Our standard magnesium fluoride, low reflective coatings are used on binoculars, telescopes. These coatings eliminate approximately half of the reflection per glass surface. Special coatings of single or multiple layers can be used to reduce reflection per glass surface to 1% or less, depending on the index of glass. Used in many instrument covers and other applications where glare can be hazardous, these coatings are highly efficient and meet military specifications.

Regular Low Reflection Coating No. 525
Magnesium fluoride applied to reduce reflectance to less than 2% per surface in the range of greatest sensitivity as seen by the human eye fulfills the spectral and environmental requirements of MIL-C-675A. See specification 1079, Coating No. 525.

SLR - Special Low Reflection Coating No. 526
is a multi-layer coating to reduce reflectance to less than .5% average from 450 to 625 millimicrons per surface.

Adherence
No visible part of the mirror 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.

Durability
No evidence of film removal of film abrasion shall result from one or both of the following tests:

1. 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.
2. 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.

HELR - Hi-Efficiency Low Reflection Coating No. 527
is a multi-layer coating to reduce reflectance to less than .5% average from 425 to 700 millimicrons per surface. This coating fulfills the spectral and environmental requirements of MIL-C-14806A. See Specification 1081, Coating No. 527.

Infrared Region
Low reflection coatings can be applied to IR transmitting materials tailored to minimize reflectivity up to 15 microns. Coating materials are selected to give optimum results for varying indices.

Angle of Incidence
Low reflection coatings are tailored for highest efficiency at normal incidence and will maintain satisfactory reducing reflections at angles of incidence up to 30°. Low reflection coatings can be tailored to optimum efficiency at other specified angles of incidence.

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:

1. 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.
2. 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.
3. 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.