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Chapter 7 MicroMAX DIF Camera 101
Background subtraction allows you to automatically subtract any constant background in
your signal. This includes both constant offsets caused by the amplifier system in the
controller as well as time-dependent (but constant for a fixed integration time) buildup of
dark charge. The background subtract equation is:
(Raw image data – Background) = Corrected image data.
When background and flatfield operations are both perform
ed, background subtraction is
always performed first.
Flatfield Correction
Flatfield correction allows the user to divide out small nonuniformities in gain from pixel
to pixel. Flatfield correction is done before the images are saved to RAM or disk.
Directions for doing Flatfield correction are provided in the WinView/32 software
manual.
Mask Bleed-Through Correction
As described previously, the first image is stored under the mask while the second image
is being acquired. Although the mask is basically opaque (light attenuation is on the order
of 4000:1), a small amount of illumination does get through and could influence some
measurements. One solution would be to establish a correction file by taking the first
image with the light source dark, and the second image with the light source on. Any
bleed through the mask during the second image will appear in the first image. This data
could then be stored and used later to correct “real” first images in a post-processing math
operation.