® 16k/8k CXP Color
32
e2v semiconductors SAS 2014
6.2.7
Flat Field Correction
How is performed the Flat Field Correction ?
What is the Flat Field correction (FFC) ?
The Flat Field Correction is a digital correction on each pixel which allows :
To correct the Pixel PRNU (Pixel Response Non Uniformity) and DSNU (Dark Signal Non Uniformity)
To Correct the shading due to the lens
To correct the Light source non uniformity
Before
After
How is calculated / Applied the FFC ?
The FFC is a digital correction on the pixel level for both Gain and Offset.
Each Pixel is corrected with :
o
An Offset on 8 bits (Signed Int 5.3). They cover a dynamic of
16LSB in 12bits with a resolution of 1/8 LSB
12bits.
o
A Gain on 12 bits (Unsigned Int 14) with a max gain value of x5. Gain : U12 (1+Gain/1024) => x1 to x3.999 by
step of 1/1024
o
The calculation of the new pixel value is : P’ = ( P + Off).(1 + Gain/1024)
The FFC is always processed separately on each color and with the max pixel value of each color as reference. Then the
white balance has to be performed after the FFC.
How to perform the Flat Field Correction ?
FPN/DSNU Calibration
Cover the lens
Launch the FPN Calibration : Grab and calculation is performed in few seconds
