NED
UME-0001-04 XCM6040SAT4
43
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 be able to completely clear the
uneven brightness generated by changing spectral response level of the light
source. 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
