What are Reflections?
When light travels and hits a medium with a different index of refraction than the one it is currently moving in, some of it is reflected. For example, about 4% of the light is reflected at the border, or interface, between air and acrylic sheets. Then, when light travels from acrylic to air, another 4% of the light is reflected at the interface for a total of 8% of the light reflecting towards the viewer.
Principles of Anti-Reflection
Anti-reflection technology takes advantage of light’s wave-like properties, manipulating how it reflects off a surface. The principle is to force the wave phase of the incident light and the interference light to be out of sync so as to cause the destructive interference of light.。
Increasing Reflections
When two waves have their peaks and troughs overlap, it is said to be in-phase. The peaks are added together to make bigger peaks and troughs, resulting in stronger reflections.
Reducing Reflections
When two waves reflect in a way that the peaks of one wave match the troughs of another, it is said to be out-of-phase. The peaks cancel each other out to make smaller peaks, resulting in weaker reflections.
Single-Layer vs Multi-Layer AR
Single-Layer AR
A single thin-film interference layer can reduce the strength of reflections.
Multi-Layer AR
By stacking more thin-film interference layers, we can increase the number of out-of-phase waves, and therefore reduce the amplitude even further.
What are some real world applications of anti-reflective coatings?
Anti-reflective coatings are often used to reduce the reflected light from natural and artificial lighting, diminish the effects of internal reflections in displays, and increase the amount of transmitted light of cover panels. Some familiar examples include televisions and monitors, automotive HUDs, camera lens and sensor covers, eyeglasses, and more.