scan·ning electron microscope (sk n  ng)n. Abbr. SEM An electron microscope that forms a three-dimensional image on a cathode-ray tube by moving a beam of focused electrons across an object and reading both the electrons scattered by the object and the secondary electrons produced by it. |
scanning electron microscope (SEM),
an instrument similar to an electron microscope in that a beam of electrons is used to scan the surface of a specimen. The beam is moved in a point-to-point manner over the surface of the specimen. These electrons are deflected, collected, accelerated, and directed against a scintillator. The large number of photons thus created are converted into an electric signal that, in turn, modulates the beam scanning the surface of the specimen. The image produced appears to be three-dimensional and lifelike. Compare electron microscope, transmission scanning electron microscope.
microscope [mi´kro-skōp]
an instrument used to obtain an enlarged image of small objects and reveal details of structure not otherwise distinguishable.
The light path of a darkfield microscope. From Hart and Shears, 1997.
acoustic microscope one using very high frequency ultrasound waves, which are focused on the object; the reflected beam is converted to an image by electronic processing.
binocular microscope one with two eyepieces, permitting use of both eyes simultaneously.
compound microscope one consisting of two lens systems whereby the image formed by the system near the object is magnified by the one nearer the eye.
darkfield microscope one so constructed that illumination is from the side of the field so that details appear light against a dark background.
electron microscope one in which an electron beam, instead of light, forms an image for viewing, allowing much greater magnification and resolution. The image may be viewed on a fluorescent screen or may be photographed. Types include scanning and transmission electron microscopes.
fluorescence microscope one used for the examination of specimens stained with fluorochromes or fluorochrome complexes, e.g., a fluorescein-labeled antibody, which fluoresces in ultraviolet light.
light microscope one in which the specimen is viewed under ordinary illumination.
operating microscope one designed for use in performance of delicate surgical procedures, e.g., on the middle ear or small vessels of the heart.
phase microscope (phase-contrast microscope) a microscope that alters the phase relationships of the light passing through and that passing around the object, the contrast permitting visualization of the object without the necessity for staining or other special preparation.
scanning electron microscope (SEM) an electron microscope that produces a high magnification image of the surface of a metal-coated specimen by scanning an electron beam and building an image from the electrons reflected at each point.
simple microscope one that consists of a single lens.
slit lamp microscope a corneal microscope with a special attachment that permits examination of the endothelium on the posterior surface of the cornea.
stereoscopic microscope a binocular microscope modified to give a three-dimensional view of the specimen.
transmission electron microscope (TEM) an electron microscope that produces highly magnified images of ultrathin tissue sections or other specimens. An electron beam passes through the metal-impregnated specimen and is focused by magnetic lenses into an image.
x-ray microscope one in which x-rays are used instead of light, the image usually being reproduced on film.
scanning electron microscope (SEM),
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