Anti-Reflection CoatingsThin film anti-reflection coatings greatly reduce the light loss in multi-element lenses by making use of phase changes and the dependence of the reflectivity on index of refraction. A single quarter-wavelength coating of optimum index can eliminate reflection at one wavelength. Multi-layer coatings can reduce the loss over the visible spectrum. The idea behind anti-reflection coatings is that the creation of a double interface by means of a thin film gives you two reflected waves. If these waves are out of phase, they partially or totally cancel. If the coating is a quarter wavelength thickness and the coating has an index of refraction less that the glass it is coating then the two reflections are 180 degrees out of phase.
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Index Reflection concepts | ||
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Multi-Layer Anti-Reflection CoatingsA single layer anti-reflection coating can be made non-reflective only at one wavelength, usually at the middle of the visible. Multiple layers are more effective over the entire visible spectrum. |
Index Reflection concepts Reference Meyer-Arendt | ||
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Single Layer Antireflection CoatingA single layer anti-reflection coating can be made non-reflective only at one wavelength, usually at the middle of the visible. Multiple layers are more effective over the entire visible spectrum. Single layer antireflection coatings are generally calculated for a midrange wavelength like 550 nm (green). With the assumption of a coating thickness of a quarter wavelength in the medium, the reflection can be calculated by using the normal incidence reflection coefficients. |
Index Reflection concepts Reference Meyer-Arendt | ||
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