Trinitron The Trinitron tube is a type of CRT (cathode ray tube) developed by Sony Corporation. It differs from the standard tube types because it employs an aperture grille (wires stretched vertically down the screen) instead of the usual shadow mask (a metal plate with holes in it). Many observers believe that Trinitron tubes generate brighter, clearer images than those using shadow-mask technology. You can tell if you are looking at a Trinitron tube by the presence of one or two very thin black horizontal lines that cross the screen; these lines are the supports for the aperture grille. See also: aperture grille, CRT, shadow mask