| ACTA | American Cardiology Technologists Association; automatic computerized transverse axial [scanning] |
|---|---|
| ADP | adenopathy; adenosine diphosphate; administrative psychiatry; approved drug product; area diastolic ... |
| AED | antiepileptic drug; antihidrotic ectodermal dysplasia; automatic external defibrillator |
| AGC | absolute granulocyte count; automatic gain control |
| AICD | automatic implantable cardioverter defibrillator |
| paraboloid dark field condenser | <microscopy> A lens of parabolic shape. The vertex end is ground back so that its focus can be brought into coincidence with the specimen on the slide. A central stop is provided to block the central rays. It is used chiefly for medium- power work. (05 Aug 1998) |
|---|---|
| Cassegrainian darkfield condenser | <microscopy> Named after Cassegrain, astronomer of the 17th century. A high-power, dark field con-denser to be used with objective apertures as high as 1.3. It is sometimes called the luminous spot ring condenser (Zeiss). (05 Aug 1998) |
| condenser | <microscopy> In microscopy, the lens mounted before the microscope stage, which transmits light to the object. There are two main categories of condensers: (1) bright field and (2) dark field. Bright field condensers are of four distinct types: (a) Abbe condenser,, an uncorrected condenser composed of two separable lenses, (b) aplanatic condenser, (c) achromatic condenser which has full corrections for colour and spherical aberrations, (d) aplanatic achromatic condenser. The dark field condenser for low powers may be nothing more than a low-power bright field condenser with a central stop. Medium- or high-powered dark field condensers are usually of the cardioid or paraboloid type. The lamp lens is loosely called a condenser lens, but light-collecting lens is a more definite term. All microscope condensers must be carefully focused and aligned for best results. (05 Aug 1998) |
| condenser, Abbe | <microscopy> Originally a two-lens substage condenser combination designed by Ernst Abbe. It lacks chromatic correction though designed for a minimum of spherical aberration and has only a very low-angle aplanatic cone. It may be rated with a numerical aperture as high as 1.3. (05 Aug 1998) |
| condenser circle | <microscopy> The image of the aperture iris diaphragm of the substage condenser as seen in the back focal plane of the objective. (05 Aug 1998) |
| condenser, dark field | <microscopy> A condenser forming a hollow cone of light with its apex (or focal point) in the plane of the specimen. When used with an objective having a numerical aperture lower than the minimum numerical aperture of the hollow cone, only light deviated by the specimen enters the objective. Objects are seen as bright images against a dark background. The ordinary bright field condenser of low power, used with a central stop, makes a good dark field condenser. They all form a dark field while illuminating the specimen with a hollow cone of light. The lower limiting aperture of the condenser must be greater than the numerical aperture of the objective with which it is to be used. Thus, no direct light enters the objective, the specimen is seen by reflected or scattered light on a dark background. See: condensers See: special dark field condensers: paraboloid, cardioid and Cassegrainian. (05 Aug 1998) |
| condenser, darkfield, bispheric | <microscopy> A dark field condenser consisting of a convex spherical reflector mounted concentric with a larger concave reflector. The rays are formed into a diverging cone by the convex reflector. The annular concave reflector then forms a hollow converging cone which is focused on the subject. See (05 Aug 1998) |
| condenser, darkfield, paraboloid | <microscopy> A dark field condenser consisting of a reflecting surface in the form of a segment of a paraboloid of revolution. Parallel rays entering the condenser around the periphery of the central stop are reflected from the curved surfaces and converge at the focus of the paraboloid. See (05 Aug 1998) |
| condenser, variable-focus | <microscopy> Essentially an Abbe condenser in which the upper lens element is fixed and the lower movable. The lower lens may be used to focus the illumination between the elements so that it emerges from the stationary lens as a large diameter parallel bundle. The field of low-power objectives may thus be filled without removing the top element. at the opposite extreme it can be adjusted to have a numerical aperture as high as 1.3. See: illumination, critical. (05 Aug 1998) |
| dark-field condenser | An apparatus for throwing reflected light through the microscope field, so that only the object to be examined is illuminated, the field itself being dark. (05 Mar 2000) |