Confocal scanning microscopy is an imaging modality for "optical sectioning" of a sample, that is, the imaging of thin sections at high resolution and contrast without physically dissecting the sample. Confocal microscopy offers several advantages over conventional optical microscopy, including controllable depth of field, the elimination of image degrading out-of-focus information, and the ability to collect serial optical sections from thick specimens. The key to the confocal approach is the use of spatial filtering to eliminate out-of-focus light or flare in specimens that are thicker than the plane of focus.

It is a promising technique to characterize fluid flow in porous layers, as for example in paper. Confocal microscopy can provide information about the pore structure in 3D and imbibition phenomena of a liquid into the pores.