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10. Settings
Image 10-19
WARNING: Lamp runtime reset as well as the lamp replacement can only be done by a Barco authorized
technician.
10.8 Input Balance
CAUTION: The input balance adjustmentis only for Barco authorized technicians !
Introduction: Unbalanc
ed color signals
When transporting signals, there is always a risk of deterioration of the information contained in the signals.
In case of information contained in the amplitude of the signals which is the case of data color signals (R, G, B),image 10-20 ,we
are quite sure that the amplitude of these color signals is subject to alterations.
An example of alteration may be a DC component added to the signal, in the form of a DC offset repositioning the black level, since
this black level (“brightness”) will become crucial later on ( clamping circuit) it will result in “black not being black”.
Another value that is subject to alteration is the amplitude of the signal, resulting in an altered “Gain” of the signal (“white level” or
contrast ).
The alterations of the three color signals will happen independently i.e. the colors will end to be unbalanced, image 10-21
B
Black leve
0.7V
Image 10-20
Black lev
e
∆
G
∆Β
∆
R
R
G
B
Image 10-21
Analog Digital Conversion
The analog color signals must pass through an Analog/Digital conversion circuit prior to any digital processing 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.
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R5976741 MGP 15 MEDICAL GRADE PROJECTOR 28/04/2004