27
Gamma Correction
8.1.5
With this feature, Baumer SXG cameras offer the possibility of compensating nonlinearity
in the perception of light by the human eye.
For this correction, the corrected pixel intensity (Y') is calculated from the original intensity
of the sensor's pixel (Y
original
) and correction factor
γ
using the following formula (in over-
simplified version):
Y' = Y
original
γ
8.1.6 Region of Interest (ROI)
With this function it is possible to predefine a so-called Region of Interest (ROI) or Partial
Scan. This ROI is an region of pixels of the sensor. On image acquisition, only the infor
-
mation of these pixels is sent to the PC. Therefore all the lines of the sensor need not be
read out, which decreases the readout time (t
readout
). This increases the frame rate.
This function is employed, when only a region of the field of view is of interest. It is coupled
to a reduction in resolution.
The ROI is specified by four values:
▪ Offset X - x-coordinate of the first relevant pixel
▪ Offset Y - y-coordinate of the first relevant pixel
▪ Size X - horizontal size of the ROI
▪ Size Y - vertical size of the ROI
Start ROI
End ROI
8.1.7 ROI Readout
For the readout of the ROI, the vertical subdivision of the sensor (see 6.1.3.
Readout
Modes) is unimportant – only the horizontal subdivision is of note.
Both sensor halves are read out simultaneously as displayed in the subsequent figure.
The readout is line based, which means always a complete line of pixels needs to be read
out and afterwards the irrelevant information is discarded.
Due to the fact, that the sensor halves are always read out symmetrically, the readout time
t
readout
is significantly affected both by the size of the ROI and also by its position.
▲ Figure 20
Non-linear perception of
the human eye.
H - Perception of bright-
ness
E - Energy of light
H
E
0
◄ Figure 21
Parameters of the ROI.
◄ Figure 22
ROI:
Readout.
