Automatic Tap Balancing - Smartek Vision Giganetix GC Series User Manual

4 Image Acquisition

4.3.3 Automatic Tap Balancing

Various models of the Giganetix series are equipped with dual tap CCD sensors. Like described in 4.1.2 -
Multi-Tap CCD Sensor Readout, it is necessary to match the signal levels of all taps to receive a uniform
overall image. Cameras of the Giganetix series (GC, GC-S90, GC-BL) therefore provide an Automatic Tap
Balancing mechanism, which by default continuously adjusts the gain and black level of each tap.
The Automatic Tap Balance algorithm calculates the mean value of every n-th pixel residing along both sides
of each tap border. Figure 94 shows this exemplarily on the basis of a 2-tap image, where relevant pixels at
a TbpVerticalStep of 5 are tagged in green.
Tap Border
Left Tap Right Tap
Adjacent Pixels
Figure 94: 2-Tap Sensor - Unbalanced Image (left) and Schematic of Adjacent Pixels
The algorithm takes into account only pixels where the difference between adjacent pixels on different
taps is less than TbpPixelDiffTreshold. The resulting values on both taps are averaged over a count
of frames defined in TbpFramesToAvg and compared; if the difference between the taps is larger than
TbpTapDiffTreshold or TbpTapDiffTresholdPercent, the gain will be adjusted based on the size of the difference.
In this process, also the difference in black level on both taps is calculated and corrected if bigger than
TbpTapDiffTresholdBL.
An overview of the parameters is shown in Table 49 and can be accessed via the camera properties by the
GigEVisionClient or directly via the API.
113
SMARTEK Vision Giganetix User Manual Version 2.1.4