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Unstained transparent specimens (phase objects), e.g. native living cells, chromosomes and bacteria, are usually be examined in phase contrast, interference contrast or dark field illumination when a light microscope is used. These methods have several characteristic limitations. In dark field, some transparent objects, e.g. small bacteria, are barely visible; fine structures inside of them are oftenly not visible and the margins of such cells can show blooming effects. In phase contrast, the discernment of fine details can be reduced by halo artifacts; the intensity of contrast is constant and not variable. Interference contrast images are free from halo artifacts, but their contrast may be lower than in corresponding phase contrast or dark field images. In all illumination techniques, the resolving power is dependent on the wavelength of the visible light spectra and the numerical aperture of the lenses; the usual limit of light microscopic resolution is about 0,20 mikrometers. Luminance contrast is a new illumination technique characterized by several advantages in comparison with the usual examination methods, mentioned above. The light path is completely different from common dark field, phase and interference contrast. With the help of luminance contrast, phase objects can be examined in several variations of contrast effects, which are similar to dark field, phase and interference contrast. Therefore, these variants have been named luminance dark field, luminance phase contrast and luminance interference contrast. In difference to common dark field, the illumination of specimens is much more homogeneous; central structures inside of them are also visible in high contrast. In difference to common phase and interference contrast, the intensity of contrast is adjustable in tiny steps; halo artifacts are reduced or non-existent. In all variants of luminance contrast, the specimen occurs in a self-luminous, flourescent manner. Probably because of this reason, also very small structures can be visible in luminance contrast which are lower than the usual resolving power of the respective optical system. Fundamental improvements of the resolving power result from this. Because of their extraordinary contrast , excellent sharpnesss and supramicroscopic resolution, the quality of luminance contrast images is visibly improved when compared with conventional illuminating modes, also in thin-layer preparations. The contours of cell membranes and cell walls including their superficial structures are contrasted in an extraordinary clarity. Discontinuances of these structures, for example pores or perforations in nucleus membranes or cell walls can be detected accurately as well as various intracellular structures. Also fine nuances in the cytoplasm of bacteria and other cells are visible, especially in luminance dark field. Moreover, this method is suitable for examinations of fine structures in crystallizations and other particles in preparations without coverslips. Luminance contrast can be achieved by using a modified condenser and modified objectives with glass lenses or by using microscopic mirror objectives (Cassegrain-Schwarzschild type). Images taken with mirror objectives are characterized by a high planeness and a high saturation and clarity of colors; the faithfulness of color detection is higher than in apochromatic lenses. As specimens occur as self illuminating bodies, luminance contrast is also comparable to flourescence techniques aud suitable to be combined with them.Thus, luminance contrast might also be capable to give new improving impulses for flourescence microscopy. For luminance contrast, a patent has been applied. Further information about all relevant technical detail are given at the URL: www.luminance-contrast.com.
Native dental bacillus in Luminance contrast
Native epithelial cell in luminance interference contrast, white light,
Piper, J.: Copyright: Joerg Piper, Bad Bertrich, Germany, 2007
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