ABSTRACT
Optical diffusers are often used to condition raw illumination and make it useful in a variety of applications. Some examples of conditioning include homogenization, controlled spread and distribution, and intensity shaping. Diffusers also help reduce sensitivity to variations in source properties, amplitude or phase, and provide a stable output beam. Common diffusers include ground glass,1 holographic diffusers,2 opal glass,3 and volume diffusers.4 With the exception of opal glass, a very inefficient Lambertian diffuser, other diffusers are notorious for spreading light with a Gaussian intensity profile in the far field. Therefore, unless one is specifically looking for a Gaussian profile, common diffusers find most applicability in homogenization and spreading, not beam shaping. (Here we will be concerned with surface diffusers so we will not have much to say about volume diffusers, of which opal glass is an example. Narrow-angle volume diffusers also tend to produce Gaussian scatter.) For general beam shaping, until recently diffractive optical elements (DOEs) were the only viable approach,5 even though these are limited to monochromatic illumination and small divergence angles, unless a strong zero diffraction order can be tolerated.
