What do you know about differential interference difference microscopy (DIC)?
The ability to see and measure small phase changes, similar to a phase microscope, gives colourless and transparent specimens variations in light, dark and colour, thus enhancing contrast. Polarising and interfering components are fitted to the basic structure of an ordinary optical microscope, as well as a 360° rotating stage. It in turn makes use of the principle of interference of polarised light. As shown in Fig. 7, a polarising lens and a beam-disintegrating prism are placed above the light source. The linearly polarised light from the polarising lens passes through the beam decomposition prism, and then splits into two linearly polarised light rays that vibrate perpendicular to each other. The two light rays are refracted by the concentrator and directed to the sample. Due to the different refractive indices of each point in the sample, the phase of some of the light waves changes and is shifted laterally due to interference. The two rays of light pass through the objective lens and are combined by a group of beam-disintegrating prisms and interfered with by a bias-detecting mirror. Each point of the final image is a hybrid image consisting of two overlapping images of the same point on the object, making it recognisable to the naked eye.
Differential Interference Difference Microscope can also observe colourless and transparent objects that cannot be seen in the ordinary bright field of view, and can observe cells, ** and other living organisms, and the image is three-dimensional, more detailed and more realistic than the image of the phase microscope. It can be used for more detailed study of various parts of living cells. If white light is used for illumination, different phases are shown in various colours, and the colours will change when the stage is rotated. Monochromatic illumination produces contrast between light and dark, and the various components show different contrasts. Differential Interference Difference (DID) microscopes can also be used as a highly precise ultra-micro-optical balance for estimating dry objects with a safe accuracy as small as 1 x -14 g. The microscope can also be used as an ultra-micro-optical balance with a high degree of precision. As the concentration of solids contained in a cell increases by one per cent, its refractive index increases by 0.0018. The refractive index of each phase of a cell can be estimated from the difference in the species between it and the region of interest (the suspension region), and thus the dry weight of certain components of a cell can be further calculated.
