10. Settings
Image10-19
WARNING:Lamp runtime reset as well as the lamp replacement can only be done by a Barco authorized
technician.
10.8 Input BalanceCAUTION:Theinp ut balance adjustmentis only for Barco authorized technicians !
Introduction: Unbalanced color signals
Whentransporting 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 isthe case of data color signals (R, G, B),image 10-20 ,we
arequite sure that the amplitude of these color signals is subject to alterations.
Anexample of alteration may be a DC component added tothe signal, in the form of a DC offset repositioning the black level, since
thisbla ck level (“brightness”) will become crucial later on ( clamping circuit) it will result in “black not being black”.
Anothervalue that is subject to alteration is the amplitude of the signal, resulting in an altered “Gain” of the signal (“white level” or
contrast ).
Thealterations 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
Image10-20
Black lev
e
∆
G
∆Β
∆
R
R
GB
Image10-21
Analog Digital Conversion
Theanalog color signals must pass through an Analog/Digital conversion circuit prior to any digital processing in the PMP.
Atypical ADC transforms the an alogvalue into an 8 bit co ded digitals ignal.
Thegraphic shows that when converting a signal containing a DC offset component the range of the converter is not optimally used.
76 R5976741 MGP 15 MEDICAL GRADE PROJECTOR 28/04/2004