Living cells in culture can be examined by a variety of optical techniques, but reflected light microscopy can reveal details not afforded by other methods. The image presented in this section reveals differences in a fibroblast cell that are observed with two different reflected light modes.

Fibroblasts in Reflected Light Specimen: Fibroblasts in Culture Technique: Reflected Light (Fluorescence)

Reflected light microscopy is often referred to as incident light, epi-illumination, or metallurgical microscopy, and is the method of choice for fluorescence and for imaging specimens that remain opaque even when ground to a thickness of 30 micrometers. The range of specimens falling into this category is enormous and includes most metals, ores, ceramics, many polymers, semiconductor wafers, integrated circuits, slag, coal, plastics, paint, paper, wood, leather, glass inclusions, and a wide variety of specialized materials. Because light is unable to pass through these specimens, it must be directed onto the surface and eventually returned to the microscope objective by either specular or diffused reflection. As mentioned above, such illumination is most often referred to as episcopic illumination, epi-illumination, or vertical illumination (essentially originating from above), in contrast to diascopic (transmitted) illumination that passes through a specimen.