Color effects – Interference makes the difference

Interference coating systems consist of a number of thin layers with different optical properties and thicknesses. Light is reflected more weakly or strongly at each interface of successive adjoining layers. Reflection is stronger the greater the difference between the refractive index of each layer. In a system using multiple layers, the radiation is reflected at each interface. All these many, often endlessly, reflecting rays are subject to interference effects, depending on wavelength and the thickness of the layer.

Selecting the right combination of numbers, sequence, thickness and optical qualities for the layers ensures that certain wavelength fields are strongly reflected and other waves are allowed to pass through. Each of these thin layers can be transparent, partially absorbent or highly absorbent.

The effective thickness of the layers in this interference system varies with the angle at which the light is received. As the properties of the filter are dependent on the thickness of the layer, the effect of the system is also influenced.