The shadow mask is one of the technologies used to manufacture cathode ray tube (CRT) televisions and computer displays that produce color images. Another approach is the aperture grille, better known by its trade name, Trinitron.

The shadow mask is the critical component of the colour picture tube and the important component for the choice of colour , its function concentrates on the limitation of electronics bound diameter and the screening direction , the electronics bound which is sent by the electronics gun goes scanning , during the scanning process , we should guarantee every bound gathering into the small holes situated on the screen , then these bounds will point to the regularized position through the small holes on the flat mask , and then three basic colours will be produced , at the same time , those useless electronics will be blocked by the mask board.