Tektronix WFM 601i, User Manual

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Measurement Theory
WFM 601i Serial Component Monitor
3–23
NOTE . Since the vertical dimension of the graticule target boxes indicate a 2%
luminance gain error and the horizontal dimension a 2% color difference gain
error, each color bar can be evaluated for encoding accuracy with these limits.
Peak-to-peak gain can be evaluated with the parade display mode, but only the
lightning display shows the relative level or coding accuracy of Y, P
B
, and P
R
for
each of the eight primary colors.
Diamond Display
The WFM 601i converts the Y, P
B,
and P
R
components recovered from the serial
signal to R, G, and B to form the Diamond display.
The diamond display is a simplified vector display for the GBR (RGB) format.
Like the lightning display, it is an alternating line display. The first half of the
display is made up of B+G on the vertical axis and B–G on the horizontal axis.
The second half of the display is made up of inverted R+G on the vertical axis
and R–G on the horizontal axis. The resulting display is the vertices of two
diamonds which form the RGB gamut limits. See Figure 3-13.
The graticule used with this display has no targets or specified tolerances. It
consists of dotted lines that scribe the two diamonds, which defines the color
gamut. Any signal outside the gamut limits, scribed by the graticule, may not be
reproducible by a color monitor, or is subject to clipping. This robust system of
gamut limits is an accurate method of determining whether the gamut limit
violation will cause a serious picture degradation.
Monochrome signals appear as a vertical line. Nonlinear component processing,
such as from a gamma corrector that destroys white balance, will cause the
vertical axis to deviate. B–G errors will affect the top diamond and R–G errors
will affect the lower diamond.
As with the lightning display, any bending of the transitions indicates timing
delays. When a color bar signal is applied, the vertical axis becomes an indicator
of delay errors. B to G timing errors affect only the upper diamond while R to G
timing errors affect only the lower diamond.