Cromaclear

A slit mask is a variant of the shadow mask color picture tubes.

In contrast to the shadow mask holes are elliptical or slit-shaped slit in the mask. As with the striped mask are here the phosphor layers adjacent to one another and are taken from different directions through the mask of electrons. Thereby it can be achieved that only the light-emitting layer of one color is always excited by the respective electron beam.

Objective of developing the slit mask was to combine the advantages of the shadow mask and aperture grille. The left figure below shows a macro shot of a white image area of ​​a so-called black matrix picture tube. In the diagram below right, the fluorescence color stripes for better illustration are shown in color, but they exist regardless of their color from an almost white powder.

Inferior aperture grille CRTs tend as well as shadow masks to the so-called doming - a bulge caused by thermal expansion of the mask, which leads to color errors.

The picture on the left matching schematic representation of the color formation (not mask angle and distance to scale)