gobo

A gobo (or GOBO) derived from "Go Between" or GOes Before Optics -originally used on film sets, is a physical template slotted inside, or placed in front of, a lighting source, used to control the shape of emitted light.

In the design of an artificial environment in which lighting instruments are used, it is sometimes desirable to manipulate the shape of the light which is cast over a space or object. To do so, a piece of material with patterned holes through which light passes is placed in the beam of light to allow only the desired "shape" or pattern through, while blocking the rest of the light, casting a specific shadow/light into the space.