Thin film optical coatings. 7: Two-layer coatings close to antireflection

This paper examines the residual reflection of two-layer coatings close to antireflection. Residual reflection can be induced either by fluctuations or errors in the thickness of the layers. Fluctuations in thickness, resulting from insufficiently accurate measuring equipment, lead to the notions of stability and tolerances. When reflection is substantial, a method of calculation is proposed for determining thicknesses effectively deposited.