Method of a dark field

Methods of microscopy are selected depending on character and properties of studied objects as they, influence picture contrast.

The method of a dark field in passing light (Dark-field microscopy) is used for receiving of images of transparent not absorbing objects, which cannot be visible, if to apply a method of a light field. Frequently it is biological objects. Light from the lighter and mirrors goes on a preparation with condenser a special design - condenser of a dark field. After an output from condenser the basic part of the light rays, which have not changed the direction at passage through a transparent preparation, forms a bunch in the form of a hollow cone and does not pass in an objective (which is inside of this cone). The image in a microscope is formed by means of only small part of the beams dispersed by microparticles of a preparation being on subject glass inside of a cone and the past through an objective. Dark-field microscopy is based on Tyndall effect, known example is detection of motes in air at illumination by their narrow beam of a s unlight.

On a dark background light images of elements of structure of the preparation, differing from an environment a parameter of refraction are visible. Using this method, it is impossible to define by the form images, particles are transparent or opaque, they have a greater or smaller parameter of refraction in comparison with an environment. At carrying out dark-field research subject glasses should be not thicker than 1,1-1,2 mm, cover glass- 0,17 mm, without scratchs and dirtying. At manufacturing of a preparation it is necessary to avoid presence bubbles and large particles (these defects will be visible brightly luminescent and will not allow to observe a preparation).

Поиск по сайту: