| focusing device | <microscopy> A device which effectively increases the angular aperture of the electron beam illuminating the object, rendering the focus more critical. (05 Aug 1998) |
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| focusing glass | <microscopy> A hand magnifier, used at the focal plane of a camera, usually with the ground glass removed. Its purpose is to examine the image for critical focus. It is, as a rule, a low-power magnifier so mounted that it is in focus when supported on a piece of clear glass at the focal plane of the cam- era, for studying the image. It operates equally well on the aerial image. (05 Aug 1998) |
| focusing magnifier | <microscopy> A low-power light microscope, telescope, or simple lens used to observe the electron image formed on a fluorescent screen. (05 Aug 1998) |
| dynamic focusing | <microscopy> An automatic focusing adjustment of the electron beam in high-quality cathode-ray or video image pickup tubes. The beam is made to land with the properly shaped minimum-sized spot regardless of its position in the raster scan (05 Aug 1998) |
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| isoelectric focusing | <technique> Electrophoresis in a stabilised pH gradient. High resolution method for separating molecules, especially proteins, that carry both positive and negative charges. Molecules migrate to the pH corresponding to their isoelectric point. The gradient is produced by electrophoresis of amphiphiles, heterogenous molecules giving a continuum of isoelectric points. Resolution is determined by the number of amphiphile species and the evenness of distribution of their isoelectric points. (18 Nov 1997) |