Page 99 - PowerPoint 演示文稿

Anti-reflection Coated Lens 89

coating may be two layers or more. The basic problem of a single layer
antireflection coating is that the refractive index of the coating material is
too high, resulting in too strong reflection from the first surface which cannot
be cancelled completely by the comparatively weaker reflection from the
substrate surface. In a two layer coating, the first surface reflection is
cancelled by interference with two weaker reflections.

Fig. 8.6: Two layer coating
In a two layer coating, the outer layer is made of a low refractive index
and the inner layer is made of a high refractive index material compared to
the substrate.

Fig. 8.7: Interference in two layer coating