The three electron beams for each pixel are guided through a single hole in the shadow mask, each striking a different-color dot on the display face. Aperture grilles consist of a phosphor pattern of stripes rather than dots on the display face. Like the holes in the shadow mask, the slots both restrict and position the electron beams as they make their way to the display face. Instead of dot pitch, aperture grille monitors refer to screen pitch , the distance between successive stripes of the same color, and slot pitch , the distance between the slots. The only real display issue with the aperture grille is that it is held in place by thin wires running horizontally behind the display, which are often visible to the user.
Aperture grilles can also loosen over time, causing some distortion.
The newer NEC and Panasonic displays offer neither a shadow mask nor an aperture grille, but a kind of hybrid called a slot mask . The slot mask consists of oval-shaped holes that allow more of the electron beams to reach the phosphors, thereby resulting in a brighter display. The only real distortion potential stems from the oval shapes, but since electron beams grow increasingly oval as they near the sides and corners of the display, the shapes don't produce new forms of fuzziness but only exacerbate existing distortion possibilities. Trapezoid distortion alters the rectangularity of the display. The electronic controls that are part of the monitor determine how the beams from the electron guns move through the deflection system and strike the phosphors, adjusting for the constantly differing angles and paths taken by the beams on their way to the display face.