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4.11 Pixel Correction
Generally speaking, image sensors (CCD, CMOS and so on) have fixed
pattern noise and photo response non-uniformity. Lens shadings and light
sources also can cause non-uniformity. The camera is set to the optimal
correction before shipping in order to provide images of high grade.
The camera also has the function of user white correction to cope with lens
shading and non-uniform illumination, or to lose the irregular sensitivity
generated by the thing changed into the lighting of a different spectrum
characteristic completely.
Cal_bl: Output data of each pixel at perfectly dark (digital) Cal_wh: Output
data of each pixel in uniform illumination (digital) Target_Val : Target value for
correction (10bit digital) Vin :Input data (digital) Vout :Output data (digital) The
corrected data is expressed in the following equation. Vout=(Vin-Cal_bl) x
Target_val / (Cal_wh-Cal_bl)
Waveform before bit correction
Output
Pixel Number
Waveform after bit correction
Output
Pixel Number
Figure 4-11-1 Waveform before and after bit correction
XCM4040SAT2
UME-0009-01