A thin sheet of metal with small holes poked through it used to focus the light from the electron beam on most CRT monitors. See also Slot Mask.
Central component in all color television screens and computer monitors. The shadow mask is a thin metal plate covered with very small holes that define the pixels in a CRT. It is mounted inside the screen close to the front glass. Without the shadow mask it is not possible to project a color image on the screen.
Inside the color monitor just behind the screen, it is drilled with small holes, each of which corresponds to a triad. The shadow mask helps guide the electron beams so that each beam hits only one phosphor dot in the triad.