Dalsa Falcon2 4M, Руководство пользователя

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64 Falcon2 4M, 8M, and 12M Camera User's Manual
03-032-20107-03 Teledyne DALSA
Flat Field Correction and Defective Pixel Detection Overview
The Flat Field correction fu nction consists of u sing tw o coefficients p er p ixel w hich correct the gain and
offset of the corresp ond ing p ixel. These corrections com p ensate for the Photo-resp onse N on-u niform ity
(PRN U) and Fixed Pattern noise (FPN ) attribu tes u niqu e to each cam era sensor. In ad d ition, the cam era
su p p orts rep lacem ent of d efective p ixels (hot, d ead , blinking) w ith a valu e based on neighbou rhood
p ixels.
Correction Function Block Diagram
The follow ing sim p lified block d iagram show s the p rocessing ch ain that is ap p lied to the im age d ata (the
flat field and d efective p ixel blocks are highlighted ). N ote that each p rocessing block can be activated and
d eactivated ind ep end ently. For exam p le, the FPN and PRN U coefficients can be ap p lied ind ep end ently
or together u sing the
flatfieldCorrectionM ode.
Figure 22 Flat field and defective pixel processing
Flat Field Correction Algorithm Description
Flat Field Correction Algorithm –Method 1 (featu re: flatfieldCorrectionA lgorithm ) ap p lies the follow ing FFC
form u la for correcting p ixel valu es:
new PixelValue
x ,y
= ( sensorPixelValue
x ,y
–
FFCOffset
x ,y
) * FFCGain
x ,y
w here:

x & y are the Flat Field Correction Pixel coor d inates.
See the flatfieldCorrectionPixelX Coordinate and flatfieldCorrectionPixelY Coordinate featu res.

new PixelValue is the p ixel valu e after Flat Field Correction is ap p lied .

sensorPixelValue is the p ixel valu e before Flat Field correction is ap p lied .

FFCOffset is the offset coefficient valu e to su btract from the sensorPixelValu e.

FFCGain is the gain coefficient valu e that is m u ltip lied w ith the sensorPixelValu e.
The im p lem entation of this form u la requ ires that both the FPN and PRN U coefficient are stored in 16 bits.
For the Falcon2 w e reserve 7 bits for the FFCOffset (FPN ) coefficient and 9 bits for the FFCGain (PRN U)
coefficient. The FFCGain can be calcu lated as follow s:
FFCGain
x,y
= (FFCGainRaw
x,y
/ GainDivisor) + 1.0
w here:

x & y are the Flat Field Correction Pixel coord inates.

FFCGain is the floating p oint m u ltip lier of the sensorPixelValu e.

FFCGainRaw is the stored 9 bit valu e rep resenting the FFC gain valu e .

GainD ivisor is either 512 or 1024 d ep end ing on w hether the cam era w as calibrated in H ig h
resolu tion or high gain m od e. See flatfieldCalibrationGainM ode and flatfieldCorrectionGainM ode.