What is Doming?
The shadow or slot mask inside the CRT is a thin sheet of steel or InVar positioned a half an inch or so behind the phosphor screen. The flatter the screen, the more susceptible it will be to thermal expansion effects: With individual phosphor dots spaced as as little as .13 mm apart (for a .22 mm dot pitch CRT), it doesn’t take much inaccuracy in their position to result in a noticeable effect. (See the section: How to Compute Effective Dot Pitch.) As a result, high resolution CRTs tend to be more susceptible to doming problems. (Portions from: Jac Jamar (jamar@comp.snads.philips.com).) • Doming is a deformation of the shadow mask or its support structure caused by heating and subsequent expansion in bright (high beam current) areas of the picture. This causes a shift in position of the finely spaced holes or slots in the mask. The result will be color purity problems – discoloration and brightness variations. For a .28 mm dot pitch CRT, a change of only .14 mm in the position of a ho
