Baumer EXG50c Manuale d'uso - Pagina 22

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Baumer EXG50c Manuale d'uso
Figure 27 ►
Distinction  of  "hot"  and 
"cold"  pixels  within  the 
recorded image.
Figure 28 ►
Charge quantity of "hot" 
and  "cold"  pixels  com-
pared  with  "normal" 
pixels.
Figure 29 ►
Schematic  diagram  of 
the Baumer pixel 
correction.
22
4.5 Pixel Correction
4.5.1 General information
A certain probability for abnormal pixels - the so-called defect pixels -  applies to the sen-
sors of all manufacturers. The charge quantity on these pixels is not linear-dependent on 
the exposure time.
The occurrence of these defect pixels is unavoidable and intrinsic to the manufacturing 
and aging process of the sensors.
The operation of the camera is not affected by these pixels. They only appear as brighter 
(warm pixel) or darker (cold pixel) spot in the recorded image.
Charge quantity
„Warm Pixel"
Charge quantity
„Cold Pixel"
4.5.2 Correction Algorithm
On  monochrome  cameras  of  the  Baumer  EXG  series,  the  problem  of  defect  pixels  is 
solved as follows:
▪ Possible defect pixels are identified during the production process of the camera. 
▪ The coordinates of these pixels are stored in the factory settings of the camera (see 
4�5�3� Defectpixellist).
▪ Once the sensor readout is completed, correction takes place:
▪ Before any other processing, the values of the two neighboring pixels on the left and 
the right side of the defect pixel, will be read out
▪ Then the average value of these 4 pixels is determined
▪ Finally, the value of the defect pixel is substituted by the previously determined 
average value
Defect Pixel
Warm Pixel
Cold Pixel
Charge quantity
„Normal Pixel"
Average Value
Corrected Pixel