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Köhler illumination is a method of specimen illumination used for transmitted and reflected light (trans- and epi-illuminated) optical microscopy.Köhler illumination acts to generate an even illumination of the sample and ensures that an image of the illumination source (for example a halogen lamp filament) is not visible in the resulting image.
Critical illumination acts to form an image of the light source on the specimen to illuminate it. [2] This image is formed by the condenser or collector lens. This illumination is bright but not always even, as any structure in the light source (for example the filament of a light bulb) will be visible in the
August Karl Johann Valentin Köhler (4 March 1866 – 12 March 1948) was a German professor and early staff member of Carl Zeiss AG in Jena, Germany.He is best known for his development of the microscopy technique of Köhler illumination, an important principle in optimizing microscopic resolution power by evenly illuminating the field of view.
Diagram illustrating the light path through a dark-field microscope. The steps are illustrated in the figure where an inverted microscope is used. Light enters the microscope for illumination of the sample. A specially sized disc, the patch stop (see figure), blocks some light from the light source, leaving an outer ring of illumination. A wide ...
Polarizing microscope operating principle Depiction of internal organs of a midge larva via birefringence and polarized light microscopy. Polarized light microscopy can mean any of a number of optical microscopy techniques involving polarized light. Simple techniques include illumination of the sample with polarized light.
Tilting the illumination has the effect of shifting the diffraction pattern across the objective aperture (which also lies in the back focal plane). Now the standard ptychographical shift invariance principle applies, except that the diffraction pattern is acting as the object and the back focal plane stop is acting like the illumination ...
Sample illumination is transmitted (i.e., illuminated from below and observed from above) white light, and contrast in the sample is caused by attenuation of the transmitted light in dense areas of the sample. Bright-field microscopy is the simplest of a range of techniques used for illumination of samples in light microscopes, and its ...
The success of the phase-contrast microscope has led to a number of subsequent phase-imaging methods. In 1952, Georges Nomarski patented what is today known as differential interference contrast (DIC) microscopy. [8] It enhances contrast by creating artificial shadows, as if the object is illuminated from the side.