Uneven light from a window.
The same light, redistributed by prism tiles in the window.
Anidolic lighting systems use anidolic optical components to light rooms. Light redirected by these systems does not converge to a focal point or form an image,[1] hence the name (from an, without, and eidolon, image[2]).
Anidolic lighting uses non-imaging mirrors, lenses, and light guides to capture exterior sunlight and direct it deeply into rooms, while also scattering rays to avoid glare. The human eye's response to light is non-linear, so a more even distribution of the same amount of light makes a room appear brighter.
It is most challenging to effectively capture and redistribute light on cloudy, overcast days,[2] when the sunlight is diffuse.