Microscope

An optical instrument that augments the power of the eye to see small objects. The name microscope was coined by Johannes Faber (1574-1629) who in 1628 borrowed from the Greek to combined micro-, small with skopein, to view. Although the first microscopes were simple microscopes, most (if not all) optical microscopes today are compound microscopes.

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An instrument that gives an enlarged image of an object or substance that is minute or not visible with the naked eye; usually the term denotes a compound m.; for low magnifications, the term simple m., or magnifying glass, is used. [micro- + G. skopeo, to view]

- binocular m. a m. having two eyepieces; it may be a compound m. or a stereoscopic m..

- color-contrast m. a type of m. in which the condenser stop is of one color and the annulus is a complement of it so that unstained objects are observed in one color on a field of the other.

- comparator m. a device constructed with one or more microscopes having micrometer eyepieces used to measure dimensional changes during setting or temperature changes.

- compound m. a m. having two or more magnifying lenses.

- confocal m. a m. that allows the observer to visualize objects in a single plane of focus, thereby creating a sharper image (usually the objects are fluorescent molecules); a refinement of this m. uses optical sectioning and a computer to record serial sections. This permits three-dimensional reconstruction.

- dark-field m. a m. that has a special condenser and objective with a diaphragm or stop that scatters light from the object observed, with the result that the object appears bright on a dark background.

- electron m. a visual and photographic m. in which electron beams with wavelengths thousands of times shorter than visible light are utilized in place of light, thereby allowing much greater resolution and magnification; in this technique, the electrons are transmitted through a very thin section of an embedded and dehydrated specimen maintained in a vacuum.

- fluorescence m. fluorescence microscopy.

- flying spot m. a m. in which a moving spot of light is imaged in the object plane, the energy transmitted by the specimen being detected with a photoelectric cell; the light source may be a cathode ray tube, a scanning disk or drum, or an oscillating mirror.

- infrared m. a m. that is equipped with infrared transmitting optics and that measures the infrared absorption of minute samples with the aid of photoelectric cells; images may be observed with image converters or television.

- interference m. a specially constructed m. in which the entering light is split into two beams which pass through the specimen and are recombined in the image plane where the interference effects make the transparent (invisible) refractile object details become visible as intensity differences; permits measurements of light retardation, index of refraction, and thickness and mass of specimen; it is useful in the examination of living or unstained cells.

- laser m. a m. in which a laser beam is focused on a microscopic field, causing it to vaporize; the emitted radiation is analyzed by means of a microspectrophotometer; at a low intensity the laser is employed as the light source in an interference m..

- light m. a class of m. that forms a magnified image using visible light.

- opaque m. SYN: epimicroscope.

- operating m. SYN: surgical m..

- phase m., phase-contrast m. a specially constructed m. that has a special condenser and objective containing a phase-shifting ring whereby small differences in index of refraction are made visible as intensity or contrast differences in the image; particularly useful for examining structural details in transparent specimens such as living or unstained cells and tissues.

- polarizing m. a m. equipped with a polarizing filter below and above the specimen which 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 biological or chemical specimens.

- Rheinberg m. a modified form of dark-field m. in which the central opaque stop in the condenser is replaced by a colored filter, producing a background of contrasting color against which the specimen is illuminated.

- scanning electron m. a m. in which the object in a vacuum is scanned in a raster pattern by a slender electron beam, generating reflected and secondary electrons from the specimen surface that are used to modulate the image on a synchronously scanned cathode ray tube; with this method a three-dimensional image is obtained, with both high resolution and great depth of focus.

- simple m., single m. a m. that has a single magnifying lens.

- stereoscopic m. a m. having double eyepieces and objectives and thus independent light paths, giving a three-dimensional image.

- stroboscopic m. a m. that has a light source that flashes at a constant rate so that an analysis of the motility of an object may be made; it may be used for high speed or low speed (time-lapse) cinephotomicrography.

- surgical m. a binocular m. used to obtain good visualization of fine structures in the operating field; in the standing type of m., a motorized zoom lens system operated by hand or foot controls provides an adjustable working distance; in headborne models, interchangeable oculars provide the magnification needed. SYN: operating m..

- television m. a m. in which the image is observed by a television camera that produces a television display; it is used for quantitative studies, display to a large audience, or examinations in ultraviolet and infrared regions of the spectrum.

- ultra-m. ultramicroscope.

- ultrasonic m. a m. that has lenses designed to use acoustic energy so that the ultrasonic wavelengths may be utilized; by means of transducers, the information is translated to a form that may be visualized or recorded.

- ultraviolet m. a m. having optics of quartz and fluorite that allow transmission of light waves shorter than those of the visible spectrum, i.e., below 400 nm; the image is made visible by photography, fluorescence of special glasses, or television; in a scanning instrument the receptor is a multiplier phototube.

- x-ray m. a m. in which images are obtained by using x-rays as an energy source that are recorded on a very fine-grained film, or the image is enlarged by projection; if film is used, it may be examined with the light m. at fairly high magnifications.

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mi·cro·scope 'mī-krə-.skōp n

1) an optical instrument consisting of a lens or combination of lenses for making enlarged images of minute objects esp COMPOUND MICROSCOPE see LIGHT MICROSCOPE, PHASE-CONTRAST MICROSCOPE, POLARIZING MICROSCOPE, REFLECTING MICROSCOPE, ULTRAVIOLET MICROSCOPE

2) an instrument using radiations other than light or using vibrations for making enlarged images of minute objects <an acoustic \microscope> see ELECTRON MICROSCOPE, SCANNING ELECTRON MICROSCOPE, X-RAY MICROSCOPE

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n.

an instrument for producing a greatly magnified image of an object, which may be so small as to be invisible to the naked eye. Light or optical microscopes use light as a radiation source for viewing the specimen and combinations of lenses to magnify the image; these are usually an objective and an eyepiece. See also electron microscope, operating microscope, ultramicroscope.

• microscopical adj.

• microscopy n.

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mi·cro·scope (miґkro-skōp″) [micro- + -scope] an instrument used to obtain an enlarged image of small objects and reveal details of structure not otherwise distinguishable.