46
NED
XCM2080SAT4
/
XCM2040SAT4
UME-0006-04
4.12 Pixel Correction
Generally speaking, image sensors (CCD, CMOS and so on) have fixed pattern
noise and photo response non-uniformity. When you use the lens,
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.
Cal_bl : Output data of each pixel at perfectly dark (factory correction)
Cal_wh : Output data of each pixel in uniform illumination (factory correction)
or in taking a picture of subject for correction (user white correction)
Target_Val : Target value for user correction (10bit output conversion value)
Vin:Input data (Before correction) Vout :Output data (After correction)
The corrected data is expressed in the following equation.
Vout=(Vin-Cal_bl) x Target_val / (Cal_wh-Cal_bl)
Image“before”user arbitrary pixel Green line is Luminance Profile
is corrected.
Image“after”user arbitrary pixel Green line is Luminance Profile
is corrected.
Figure 4-12-1 Waveform and image before and after bit correction
Luminance Profile
