Baumer EXG50 Benutzerhandbuch - Seite 20
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Figure 23 ►
Aggregation of charge
carriers from four pixels
in bidirectional binning.
Figure 24 ►
Color processing mod-
ules of Baumer color
cameras.
20
4.1.9. Brightness Correction (Binning Correction)
The aggregation of charge carriers may cause an overload. To prevent this, binning cor-
rection was introduced. Here, three binning modes need to be considered separately:
Binninig
Realization
1x2
1x2 binning is performed within the sensor, binning correction also takes
place here. A possible overload is prevented by halving the exposure time.
2x1
2x1 binning takes place within the FPGA of the camera. The binning cor-
rection is realized by aggregating the charge quantities, and then halving
this sum.
2x2
2x2 binning is a combination of the above versions.
Binning 2x2
Charge quantity
4.2. Color Processing
Baumer color cameras are balanced to a color temperature of 5000 K.
Oversimplified, color processing is realized by 4 modules.
r
g
Camera
Module
b
The color signals r (red), g (green) and b (blue) of the sensor are amplified in total and
digitized within the camera module.
Within the Bayer processor, the raw signals r', g' and b' are amplified by using of indepen-
dent factors for each color channel. Then the missing color values are interpolated, which
results in new color values (r'', g'', b''). The luminance signal Y is also generated.
The next step is the 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.
Afterwards theses signals are transformed into the desired output format. Thereby the
following steps are processed simultaneously:
▪
Transformation to color space RGB
▪ External color adjustment
▪
Color
adjustment as physical balance of the spectral sensitivities
In order to reduce the data rate of YUV signals, a subsampling of the chroma signals can
be carried out. Here the following items can be customized to the desired output format:
▪
Order of data output
▪
Subsampling of the chroma components to
▪
Limitation of the data rate to 8 bits
4.3. Color Adjustment – White Balance
This feature is available on all color cameras of the Baumer EXG series and takes
place within the Bayer processor.
White balance means independent adjustment of the three color channels, red,
green and blue by employing of a correction factor for each channel.
Y
r'
r''
Color-
g'
Bayer
Transfor-
g''
Processor
b'
mation
b''
White balance
or YUV
YUV 4:2:2 or YUV 4:1:1
Total charge
quantity of the
4 aggregated
pixels
Super pixel
RGB