Optical diffusers alter the angular divergence of incident light, thereby reducing the sensitivity of a detection system to slight positional or angular changes in an incoming beam. This allows for directed intensity light patterns with high efficiency. Optical diffusers are generally plano windows with a polished front face and precision ground rear face. They are usually specified in heat resistant glass, but can be made in optical glass or fused silica. Square or rectangular windows and diffusers are also possible.
Optical diffusers use a number of different methods to diffuse light. They include holographic diffusers, opal diffusers, and greyed glass diffusers. All of these diffusers are manufactured to different specifications determined by the applications in which they are to be used.
Holographic optical diffusers provide a high level of diffusion transmission efficiency. They can be used to control the diffuse area of illumination and increase transmission efficiency to greater than 90% from filament lamps, LEDs, arc lamps, and other sources. New styles of holographic diffusers, that function in the UV range, are also available.
Opal glass diffuses light thoroughly and produces a near Lambertian source, however, it has a high scatter loss. They are similar to greyed glass diffusers, except that one surface is flashed with a milky white “opal” coating to diffuse light evenly.
Greyed glass optical diffusers are also known as ground glass diffusers. Although they diffuse light less thoroughly than opal glass diffusers, they do not lose as much light due to scattering. The scattering is a compromise of low scatter loss and medium diffusion. Typical applications for greyed glass optical diffusers include use in screens, illuminator diffusion, and targets.
In general, optical diffusers are found in a wide array of technical applications including aerospace and military, bar code scanning, computer screens and other monitors, imaging systems, inspection and monitoring, medical fields, materials processing, and optical sensing.