Description of the data path
GUPPY Technical Manual
V4.0.1
71
White balance
The color cameras have both manual and automatic white balance. White bal-
ance is applied so that non-colored image parts are displayed non-colored.
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 512
steps) relative to the channel with highest output.
The following screenshot is taken from the datasheet 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.
Figure 32: Block diagram of AFE (Source: Analog Devices)