36
9.2 Color Processing
Baumer color cameras are balanced to a color temperature of 5000 K.
Oversimplified, color processing is realized by 4 modules.
Camera
Module
Bayer
Processor
Color
Transfor
mation
RGB
r
g
b
r'
g'
b'
r''
b''
g''
Y
White balance
The sensor's r (red), g (green) and b (blue) color signals are amplified in total and digitized
within the camera module.
Within the
Bayer processor, the raw signals r', g' and b' are amplified using independent
factors for each color channel. Then, the missing color values are interpolated, which re-
sults in new color values (r'', g'', b''). The luminance signal Y is also generated.
The next step is color transformation. Here, the previously generated color signals r'', g''
and b'' are converted to the chroma signals U and V, which conform to the standard. Then,
these signals are transformed into the desired output format. The following steps are then
processed simultaneously:
Transformation to RGB
▪
or YUV color space
▪
External color adjustment
Color
▪
adjustment as a physical balance of the spectral sensitivities
A sub-sampling of the chroma signals can be carried out to reduce the data rate of YUV
signals. Here, the following items can be customized to the desired output format:
Order of data output
▪
Sub-sampling of the chroma components to
▪
YUV 4:2:
2 or
YUV 4:1:
1
Data rate is limited to 8 bits
▪
9.3 Color Adjustment – White Balance
The white balance is used to sensitize the camera to the color temperature of the light at
the pickup location.
This feature is available on all color cameras in the Baumer VLU series, and takes place
within the Bayer processor.
White balance means independent adjustment of the three color channels, red, green and
blue by using a correction factor for each channel.
User-specific
9.3.1
Color Adjustment
The user-specific color adjustment in Baumer color cameras means you can adjust the
correction factors for each color gain. This way, you can adjust the amplification of each
color channel exactly to suit your needs. The correction factors for the color gains range
from 1 to 4.
non-adjusted
histogramm
histogramm after
user-specific
color adjustment
Figure 25 ►
Color processing mod-
ules of Baumer color
cameras.
Figure 26 ►
Examples of histo-
grams for a non-ad-
justed image and for
an image after user-
specific white balance
adjustment.
Summary of Contents for USB3 Vision
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