Thin-Film Optical Coating Calculator

Find the anti-reflection coating thickness for a wavelength.

Coating thickness (nm) 99.638

Formula: t = λ ÷ (4·n)

Step-by-step with your numbers:

1. Values used:

2. Wavelength = 550 nm

3. Coating refractive index = 1.38

5. Coating thickness = 99.638nm

Did we solve your problem today?

A quarter-wave coating cancels reflections at a chosen wavelength.

The math behind it

For an anti-reflection layer, thickness t = λ ÷ (4·n). Reflections from the two surfaces interfere destructively.

550 nm with n = 1.38 → about 99.6 nm.

Why do lenses look purple?

The coating cancels green best, so leftover red and blue give a purple tint.