Light Microscopy


The light microscope has the function of revealing fine detail in transparent (usually) or opaque specimens. Although much depends on the preparation of the specimen, an understanding of the operation of the microscope itself is a requirement to help distinguish a good image from an inferior one.

Keywords: light; magnification; microscope; optical; resolution

Figure 1.

A modern classroom microscope with mechanical stage and binocular head.

Figure 2.

Defining numerical aperture (NA).

Figure 3.

Images of the diatom Pleurosigma angulatum, to illustrate the function of the condenser aperture iris diaphragm. The objective used was a ×40, 0.65 NA achromat. The field size is 60 μm × 80 μm. In (b) aperture iris set to 7/8 of the objective NA as seen in the objective back focal plane. The image has optimal compromise between MRD (the ability to resolve the line pattern) and contrast. In (a) aperture iris opened too far. Flare has resulted in loss of image contrast, although the pattern can still be resolved. In (c) the aperture iris closed too far. Contrast and depth of field have been increased, but the effective objective NA has been reduced, the MRD adversely affected and the pattern is no longer resolved.


Further Reading

Bradbury S and Bracegirdle B (1998) Introduction to Light Microscopy. Oxford: Bios Scientific Publishers.

Kapitza HG (1994) Microscopy from the Very Beginning. Oberkochen, Germany: Carl Zeiss.

Oldfield R (1994) Light Microscopy; an Illustrated Guide. London: Wolfe Publications.

Schade K‐H (1995) Light Microscopy, Technology and Application, 2nd edn. Landsberg, Germany: Verlag Moderne Industrie.

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How to Cite close
Oldfield, Ronald J(Apr 2001) Light Microscopy. In: eLS. John Wiley & Sons Ltd, Chichester. [doi: 10.1038/npg.els.0002634]