Method of phase contrast

Method of phase contrast - a method used for reception of images of the transparent and colorless objects invisible at supervision on a method of a light field. Alive unpainted animal tissues concern to such methods. Essence of a method what even at very small distinctions in parameters of refraction of different elements of a preparation the light wave which is passing through them, has different changes on a phase (gets a phase relief). Not perceived directly neither an eye, nor a photographic plate, these phase changes by means of the special optical device will be transformed to changes of amplitude of a light wave, in changes of brightness («a peak relief») which can be seen an eye or are fixed on a photosensitive layer. In the received visible image distribution of brightnesses (amplitudes) reproduces a phase relief. The image received thus is called phase-contrast. The phase-contrast device can be established on any light microscope and consists from: a set of objectives with special phase plates; condenser with a turning disk. In it the ring diaphragms corresponding phase plates in each objectives of auxiliary telescope for adjustment of phase contrast are established. The auxiliary telescope is inserted instead of an ocular. Adjust it so that were sharply visible a phase plate (in the form of a dark ring) and a ring diaphragm (in the form of a light ring of the same diameter). These rings are combined by means of adjusting s crews on condenser.

Owing to application of this method of microscopy contrast of alive unpainted microorganisms sharply increases also they look dark on a light background (positive phase contrast) or light on a dark background (negative phase contrast). The phase -contrast microscopy is applied also to studying cells of culture of a fabric, supervision of action of various viruses on cells. Biological microscopes with a return arrangement of optics are often applied in these cases. Such microscopes are called the inverted microscopes. Objectives are located from below, and condenser - from above at such microscopes.

Polarizing microscopy

The polarizing microscopy is a method of supervision in polarized light for microscopic research of the preparations including optically anisotropic elements (or entirely consisting of such elements). For e xample minerals, some animal and vegetative tissues Optical properties of anisotropic microobjects are various in various directions and are shown differently depending on orientation of these objects concerning a direction of supervision and a plane of polarization of light falling on them. Supervision can be spent both in passing, and in reflected light. Light radiated by the lighter, pass through a polarizer. The polarization received by this light varies at the subsequent passage of light through a preparation (or reflection from it). These changes are studied by means of the analyzer and various optical equalisers. The analysis of such changes gives the basic optical characteristics of anisotropic microobjects: force of double refraction, quantity of optical axes and their orientations, rotation of a plane of polarization, dichroism.