Basic principles of image sensors

Defects

Large matrices sometimes present defects. They are categorized in the table 4. Matrices with few defects are more expensive than those with many defects. Some manufacturers classify their chips in grades: grade 1 being of better quality than grade 2, etc... These grades are given according to the nature, the number and the location of the defects for a standard lighting of the sensor.

According to the application, the location of the defects can be important.

The sweet spot has to be completely operational, whereas more substantial defects can be tolerated as we get closer to the periphery of the matrix.

Table 4: Definitions of the standard defects in CCD matrices
Table 4: Definitions of the standard defects in CCD matrices [zoom...]Info

Do not confuse the dead pixel with the dark pixel. The dark pixel is a reference shielded pixel that establishes a benchmark for the dark current.

Some manufacturers show their grade selection criteria. The figure 21 takes the example of the Kodak KAF0401E.

Figure 21: Grade criteria examples (source Kodak)
Figure 21: Grade criteria examples (source Kodak) [zoom...]Info
AccueilNouvelle pageInformations sur le cours (ouvrir dans une nouvelle fenêtre)CCD chip sizeSize and architecture