Create a flat-field image for line-scan instruments
Overview
Parameters
Example 1
Description
This program creates flat-field images for line scan, push frame, and framing instruments.
All input cubes should have the same number of samples; any images in the list that do not
have the same number of samples as the first image will not be used. The names of the cube
files used to create the flat-field image must be entered using an ASCII file (FROMLIST) with
one filename per line (any line beginning with a '#' or '//' is treated as a comment). The
specific equation for each camera type is below.
Line Scan
A frame is a NUMLINES line section of data. The equation for the final single line, single
band, flat field file is:
Sum( Sum(FrameColumn) / Average(Frame) * ValidPixels(FrameColumn) ) /
TotalColumnValidPixels
Push Frame
The equation for the final single framelet, single band flat field file is: Average(
PixelInFramelet1, PixelInFramelet2, PixelInFramelet3, ... )
Framing
The equation for the final single framelet, single band flat field file is: Average(
PixelInCube1, PixelInCube2, PixelInCube3, ... )
Warning: This program creates potentially large temporary files
For a framing camera, this is the maximum standard deviation of each image. For a push
frame camera, this is the maximum standard deviation of each framelet. For a line scan
camera, this is the maximum standard deviation of NUMLINES lines. Data that exceeds
this standard deviation will be ignored.
Line scan cameras collect a cube a single line of data at a time. Push frame cameras collect
multiple lines of cube data at once. Framing cameras collect an entire cube of data at
once.
Type
string
Default
LINESCAN
Option List:
Option
Brief
Description
LINESCAN
Line scan camera
Line scan cameras collect a cube a single line of data at a time. This option makes
the flat field a single line of data.
Exclusions
FRAMELETHEIGHT
Inclusions
NUMLINES
PUSHFRAME
Push frame camera
Push frame cameras take multiple lines of cube data at once. This option makes the
flat field a single framelet of data.
Exclusions
NUMLINES
Inclusions
FRAMELETHEIGHT
FRAMING
Framing camera
Framing cameras collect an entire cube of data at once. This option makes the
flat field the size of one of the input images.
A single line often does not have enough data in it to perform good tolerance
calculations. The tolerance calculations will be performed on this many lines as
a time, and if found to be invalid, this many lines will be excluded from the output
flat file calculations at a time.
This is a typical run for makeflat. files.lis is a list file generated by a "ls *.cub >
files.lis" command. The files inside of files.lis are between 20,000 lines and 200,000
lines of data (variable length). The file flat.linescan.cub is the flat-field output given
these cubes and the file exclude.txt is a detailed output of what was excluded.
GUI Screenshot
Line-Scan Run
This is a typical run for the linescan mode
Parameter Name:
IMAGETYPE
This is a typical run for makeflat. files.lis is a list file generated by a "ls *.cub >
files.lis" command. The files inside of files.lis are between 20,000 lines and 200,000
lines of data (variable length). The file flat.linescan.cub is the flat-field output given
these cubes and the file exclude.txt is a detailed output of what was excluded.
Line-Scan Input Image
This is a section of one of the inputs listed in files.lis
Parameter Name:
FROMLIST
This is the input to makeflat. Notice the vertical lines persistent throughout the
image and the dark area on the right-hand side.
Line-Scan Calibrated Image
This is input that has been calibrated
This is the same section of image data as before, except calibrated with the
flat-field file that was generated by dividing by the flat field file. The vertical
lines and darkness have completely gone away.
