Decollimation is the process or result of parallel light rays spreading apart or converging as they travel. It occurs when a highly directional beam, such as a laser or a tightly focused spotlight, passes through an imperfect optic or a diffusing medium. Engineers measure decollimation to determine how quickly a beam loses intensity over long throws.
Heard on the job
The heat warped the reflector, causing severe decollimation and turning our tight spot into a messy flood.
Related terms
Beam angle
The angle across a light's beam at which intensity has fallen to 50 percent of its center value.
Throw
The distance from a lighting fixture to the surface or subject it lights, which sets beam size and intensity.
Lens
A shaped piece of transparent material designed to bend and focus light rays.