White balance – ALLIED Vision Technologies Marlin F-201 User Manual
Page 70
Description of the data path
MARLIN Technical Manual V2.4.0
70
White balance
Marlin color cameras have both manual and automatic white balance. White
balance is applied so that non-colored image parts are displayed non-col-
ored.
White balance does not use the so called PxGA® (Pixel Gain Amplifier) of the
analog front end (AFE) but a digital representation in the FPGA in order to
modify the gain of the two channels with lower output by +9.5 dB (in 106
steps) relative to the channel with highest output.
The following screenshot is taken from the data sheet of the AFE and illus-
trates the details:
The analog color signal, coming in pulse amplitude modulation from the sen-
sor is in the form of the BAYER™ color pattern sequence. It is initially pro-
cessed in the CDS (correlated double sampler) then bypasses the PxGA before
further amplification and digitization.
From the user's point, the white balance settings are made in register 80Ch
of IIDC V1.3. This register is described in more detail below.
Figure 36: Block diagram of AFE (Source: Analog Devices)