A-15VTG 400/400D • Appendix
19. Checkerboard
The checkerboard consists of sixteen rectangles with half being
black (0%) and half being white (100%). This pattern is commonly
used to measure contrast ratio of the display system and is the
prescribed pattern for performing contrast ratio measurement
within the ANSI procedure.
Fundamentally, contrast ratio is the ratio of the peak white luminance value
divided by the minimum luminance value near black. By mathematical
definition, as the black level approaches true zero light output, contrast ratio
approaches infinity. This pattern may be used to perform the ANSI contrast ratio
measurement regimen or other methods as well. The user may “invert” the
pattern which will change the luminance of the starting rectangle and
subsequent rectangles from the original luminance level to the opposite level.
Distortion of the 100% white rectangles on a CRT-based or plasma type display
indicate a condition of overdrive.
20. Bounce (automatic)
Some operating conditions of displays may only be evaluated or
perceived with moving images or images that change in average
duty cycle (picture content) over time. The APL (Average Picture
Level) bounce pattern provides just such a test. The central area is
comprised of a large white rectangle with a black crosshair pattern. The pattern
automatically changes between full white and full black continuously at one-
second intervals.
This duty cycle shift assists evaluation of black level shift. For CRT-based
displays, high voltage regulation performance may be evaluated. High voltage
variations with image duty cycle changes cause one or more combinations of
distortion among the components of the pattern such as the white rectangle, the
lines within the white rectangle, or the lines surrounding the pattern.
21. Bounce (manual toggle)
This version of the APL (Average Picture Level) bounce is static and
may be exercised by the user at will. Use the Invert function on the
VTG’s soft keys to cause the pattern to invert, or shift, at any
moment desired. This capability is used when evaluation under
conditions of random performance is desired. See the automatic version of the
APL bounce pattern for more information.
1 sec.
1 sec.
Bounce Pattern
The white box in the center of the pattern toggles between black and white once every
second. The border on the outside of the pattern does not change .
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