MIL-C-675C

Abstract

This specification establishes the minimum optical and durability requirements for magnesium fluoride interference films used as anti-reflection coatings on optical materials. <b><u>Intended Use:</u></b> The magnesium fluoride coating covered by this specification is applied to the surface of optical elements to increase light transmission and reduce reflections. The requirements defined by Figures 1 and 2 for transmission difference and maxium reflectance respectively, apply to coatings employed in the visible spectrum. Optical requirements for magnesium fluoride coatings used in ultraviolet or infrared spectral applications must be independently determined and specified. The durability requirements established in this specification insure a level of quality consistent with military requirements. Additional durability requirements to confirm the suitability of a magnesium fluoride coating in a particular application should be considered when it is established that a coated optical element (coating and substrate) will exhibit the capability to satisfy the additional requirements. This specification permits certain cosmetic defects, such as stains, on coated optical elements. This requirement is established to permit the acceptance of coated elements where the defect is strictly aesthetic and the optical and durability properties of the coating are not impaired. The attention of optical designers is directed to this requirement for non-focal plane optical as it may be necessary to rescind this requirement on an individual basis when cosmetic defects cannot be tolerated on the optical elements. <br>