Shading correction: compensation for illumination and sensor inhomogeneities.

The interaction between objects in real space, the illumination, and the camera frequently leads to a situation in which a microscope image exhibits significant shading across the field of view. In general this shading effect is undesirable and requires elimination, especially for quantitative microscopy. Starting with a simple mathematical model, this unit develops procedures to correct images for the shading thus introduced in the image-formation process. Two cases are distinguished: the a priori, which assumes the availability of calibration images in addition to the images of interest; and the a posteriori, which assumes that only the recorded images of interest are available.