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The quality of the images produced by conventional phase contrast microscopy can be significantly improved when the usual annular masks in the phase-contrast condenser are excentrically aligned with the phase rings in the objectives or replaced by other elements with a small aperture for the transmitted light.. By this, the specimen is only illuminated from one defined direction by oblique light beams. Compared with conventional phase contrast, the following parameters are improved when relief phase contrast is used: - three-dimensionality / relief effects of 3D imaging - contrast - depth of focus - planarity of the images - contour sharpness (sometimes) - colour resolution and colour purity (sometimes) - lower halo artifacts (sometimes) Several ways for the technical implementation of relief phase contrast exist; these are dependent or independent of the position of the condenser aperture diaphragm. Thus, the various parameters which are influenced
by the illuminating aperture can be adapted to the individual features of the specimen. In contrast to conventional phase contrast, objectives from different manufacturers can be used simultaneously, so that
their compatibility is improved. Copyright: Joerg Piper, Bad Bertrich, Germany, 2007 |
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[Introduction] |