polarizing microscope(redirected from Petrographic microscope)
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a microscope equipped with a polarizing filter below and above the specimen that forms an image by the influence of specimen birefringence on polarized light; the polarizing direction of the two filters is typically adjustable, which, together with a graduated rotating stage, permits measurement of the angular value of different refractive indices in either biologic or chemical specimens.
an instrument used to obtain an enlarged image of small objects and reveal details of structure not otherwise distinguishable.
one using very high frequency ultrasound waves, which are focused on the object; the reflected beam is converted to an image by electronic processing.
one with two eyepieces, permitting use of both eyes simultaneously.
the standard bench microscope used in histology and requiring stained tissue sections.
the standard laboratory microscope used in veterinary science; consists of a two lens system whereby the image formed by the system near the object (objective) is magnified by the one nearer the eye (eyepiece).
used for examining unstained, often living cells, in which light is only directed into the objective lens if it is deflected by an object in its path. The object is thus viewed as a white structure in an otherwise black (darkfield) background.
one using an electron beam of very short wavelength as the source of illumination. It has a resolving power of 2 nm (which is 100 times greater than with the light microscope). Includes the transmission electron microscope and the scanning electron microscope (below). See also immunoelectron microscopy.
one used for the examination of specimens stained with fluorochromes or fluorochrome complexes, e.g. a fluorescein-labeled antibody, which fluoresces in ultraviolet light. See also fluorescence microscopy.
a microscope similar to the phase contrast microscope but delivers a three-dimensional image. Called also Nomarski interference phase microscope.
used for examining unstained or stained particles or the cellular structure of tissues that have been cut into sections and stained. It has a resolving power of 0.2 μm. Modern light microscopes have an eyepiece and objective lenses which provide magnification, and a condenser beneath the stage which gathers and focuses light on the object being examined.
one designed for use in performance of delicate surgical procedures, e.g. on the middle ear, eye or small vessels of the heart.
phase microscope, phase-contrast microscope
a form of light microscope useful for examining living, unstained structures, including animal cells and bacteria, e.g. leptospira. The phase of the light wave passing through different structures in the cell, e.g. nucleus vs. thin part of the cytoplasm, is changed by different amounts and thereby provides contrast.
based on the phenomenon of birefringence; useful in the study of bone and muscle.
scanning electron microscope (SEM)
an electron microscope that produces a high-magnification image of the surface of a metal-coated specimen (shadow casting) by scanning an electron beam and building up an image from the electrons reflected at each point. Particularly useful for determining the three-dimensional structure of objects.
one that consists of a single lens.
one used in the examination of the corneal endothelium.
a binocular microscope modified to give a three-dimensional view of the specimen.
see operating microscope (above).
transmission electron microscope, TEM
one that resembles an inverted light microscope in that the beam of electrons generated from a heated filament at the top of the instrument passes down through a column where it is focused by magnetic coils (lenses) and is differentially scattered when it passes through the specimen. The image is recorded either on a photographic plate or on a phosphorescent screen.
uses an ultraviolet light source; useful in histochemical studies; only photographic images are available.