Barco Projector Toolset, Reference Manual

Page: 134 / 245

8. Configurator, Projector adjustment settings
One can conclude here that a good color tracking can only be met by using three previ-
ously (input) balanced color signals
Analog Digital Conversion
The analog color signals must pass through an Analog/Digital conversion circuit prior to any digital pro-
cessing in the PMP.
A typical ADC transforms the analog value into an 8 bit coded digital signal.
The graphic shows that when converting a signal containing a DC offset component the range of the
converter is not optimally used.
Black level
Δ
R
ADC
0
255
i1 : superfluous information
i2 : video information
Image 8-24
One can conclude here that a good data conversion can only be met by using three
previously (input) balanced color signals
The objective of input balancing
The objective in input balancing is to “set” the same black level and the same white level for the three
colors of a particular input source.
Black level setting : brightness
White level setting : contrast
The same absolute black and white level for the three colors allows the same reference for Brightness
and Contrast control of the picture !
These two references also set the range in which the ADC will work for that particular source (this explains
also why each input balance setting is linked to a particular source and thus saved in the image
fi le).
8.5.9.2 Adjusting the input balance
How can it be done ?
To balance the three color signals of a particular source there are conditions; in fact we must know the
black and the white level of the source i.e. :
1. The source in question must be able to generate a white signal, ideally a 100% white (background)
full screen pattern
2. The source in question must be able to generate a black signal, ideally a 100% black (background)
full screen pattern
130 R5976924 PROJECTOR TOOLSET 16/04/2009