Bright field microscopy
As bright field microscopy microscopy method refer to operations where that is object to be observed against a bright background, and this bright field illuminating the microscopic image. Colored and dark structures in the specimen absorb the light so that a corresponding image of the specimen is created in transmitted light. In addition to the simple lateral incident light illumination, brightfield microscopy is the oldest microscopic method. The term was coined to distinguish it from the dark field microscopy that emerged in the 19th century . Coming from light microscopy , the term is also used in transmission electron microscopy .
In light microscopy, the bright field is generated by the illuminating light, usually bundled by a condenser , falling from the back through the specimen into the objective . This transmitted light bright field microscopy is used, among other things, for thin, colored biological-medical preparations. It is by far the most widely used microscopy method. Less complex microscopes such as student microscopes generally work according to this principle, but so do many research microscopes.
Alternatively, the illumination can fall onto the specimen from the direction of the objective, usually with special incident light optics through the objective. This reflected light bright field microscopy is widespread in materials science , where opaque specimens are examined. in this case, the object is largely brightened due to the high proportion of the illuminating light reflected directly from the object surface back into the lens. In comparison to reflected light dark field microscopy, the object is illuminated with little shadow. For more information, see dark field microscopy .
Brightfield microscopy can be operated with so-called “simple microscopes”, which only have a single lens, or with “compound microscopes”, the typical design today, which is composed of an objective and an eyepiece. With these, the specimen can be illuminated with simply structured, so-called critical lighting, or with the optimized Koehler lighting that is more common today.
Simple and compound microscopes, incident and transmitted light, critical and Koehler lighting are described in more detail in the article light microscope .
literature
- Dieter Gerlach: The light microscope. An introduction to function, handling and special procedures for physicians and biologists . 2nd Edition. Georg Thieme Verlag, Stuttgart 1985, ISBN 3-13-530302-0 .
- Michael Volger (Ed .: Irene K. Lichtscheidl): Light microscopy online. Retrieved on July 22, 2013 (Theoretical introduction and instructions for practical application at the University of Vienna. Also available as a PDF file .).