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Regarding flat fielding of an image

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jyotirmoy kalita
jyotirmoy kalita on 28 Jun 2021
Answered: Bjorn Gustavsson on 28 Jun 2021
Sir,
I have a decomanded image of 11 bit. Now i want to apply flat field correction on my image. For the same i have 5 flat filed files for 5 visible band with dimension 1024x16. My image is 80 X 1024 with 16 pixel framelet height with 5 visible band. Please suggest me how may i apply these flat filed files to correct the images in MATLAB.

Answers (1)

Bjorn Gustavsson
Bjorn Gustavsson on 28 Jun 2021
By flat-field you mean correct the image intensities for vignetting (optical and mechanical), right?
If so provided that you're data is properly background-reduced and that your flat-field-data is the similarly back-ground reduced response to a flat illumination then it should in principle just be to divide the data with the flat-field data to correct for the variation over the image. However the sizes you give doesn't match up, which makes things confusing. I will assume that what you call data is the image in the 5 bands in sequence such that rows 1-16 corresponds to "band a", rows 17-32 to "band b" etc. Then something like this should work:
flatfield_stacked = [ff_data_bandA';ff_data_bandB';ff_data_bandC';ff_data_bandD';ff_data_bandE'];
ffc_data = data./flatfield_stacked;
You'll have to keep track of normalization and how the intensity-calibration is affected.
HTH

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