B&K Precision 1253 - Manual - Manual (Page 29)

4. Convergence Calibration
Convergence calibration is the process of aligning the separate red, green and blue CRT beams in direct-view
monitors, or the projected red, green and blue images from separate CRTs in projection systems, so that they
precisely overlap everywhere in the picture. This is particularly crucial in HDTV displays in order to maximize
resolution and avoid color fringing on fine lines or edges in the picture. It is normally not necessary to adjust
convergence in fixed-pixel projection devices such as LCD and DLP projectors because their convergence is
mechanical in nature and should have been permanently adjusted at the factory.
BK-1253 Convergence Adjustment Patterns:
The 16:9 Crosshatch pattern is the ideal pattern for adjusting convergence. Each of the three primary colors should
overlap the others without color fringing. With all three colors turned on the grid pattern should be completely white
against the black background.
Convergence Adjustment Procedure:
Different displays provide a wide range of electronically adjustable convergence controls. In many projectors these
controls duplicate the function of the geometry adjustment controls, but are individually adjustable for each red,
green and blue primary color. It is good practice to only adjust green when doing the geometry adjustment. Then
turn off the blue CRT beam (this function is provided in most display calibration menus) and adjust the convergence
of the red CRT beam to match the green beam using the red convergence controls. It is then easiest to adjust the
blue CRT beam with only the red and blue beams turned on. Finally turn on all three beams to verify the
convergence adjustments.