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Figure 27 ►

Distinction of "hot" and

"cold" pixels within the

recorded image.

Figure 88 ►

Charge quantity of "hot"

and "cold" pixels com-

pared with "normal"

pixels.

Figure 29 ►

Schematic diagram of

the Baumer pixel

correction.

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