bm2cal : flatfield auto calibration

When some images of the same object are recorded moving only the detector, the data contain not only information on the object but also on the recording instrument. Then this program was intended in order to try flatfield auto calibration from such data.

But up to now it seems more used to reconstruct image obtained moving the detector. This allow to obtain not too noisy detector flatfield by using fluorescence of solutions in which zones associated with direct beam are removed.

• Short example.
• Input file.
• Inline help.

Procedure

Input file

The program bm2cal is not intended to use console input. It use a small file which name is given as argument and which contains all internal commands.

Simple reconstruction

In the following example, we wish to build an image called img obtained using the shifted image : img_raw1.edf, img_raw2.edf, img_raw3.edf. For each input file, we specify its position the @SHIFT x y command, x and y and specified in pixel units. Then the resulting image is writen in file img.edf using the @PRINT img.edf command.

In the source image, the invalid pixel have been set to 0 (or 1), to excluded this pixels from the calculation we specify a low limit for valid pixels LOW_LIMIT=2. Pixels lower will be excluded. Is some pixels can not be calculated, they will be set to LOW_LIMIT-1 in the output file.

# img.dat (bm2cal.dat)
# simple reconstruction
LOW_LIMIT=2
@NEW  img
@RAW  img_raw1.edf
@SHIFT  0.0 0.0
@RAW  img_raw2.edf
@SHIFT  0.0 -1.0
@RAW  img_raw3.edf
@SHIFT  1.0 1.0
@PRINT img.edf

The inline help

The command bm2cal -h will display its principal key words.

d2pluo2 BM2IMG/calib> bm2cal -h
## bm2cal : detector flatfield autocalibration
## berar@esrf.fr (d2am),  Jan 31 2002
usage : bm2cal data_file
   the data file has the following structure
   img_files contain only one frame (dark and cosmic corrected)
   see bm2cal.html for parameters
   Inside the program the image are kept as integers with 32 bits
   see also parameters in bm2cal.ini file