Microscope-Differential Interference Contrast DIC
Differential interference microscopy appeared in the 60's, it can not only observe the colourless and transparent objects, and the image shows a relief magnificent three-dimensional sense, and has the phase contrast microscopy can not achieve some of the advantages, the observation effect is more realistic.
Principle.
Differential interference mirror inspection is the use of special Wollaston prisms to break down the light beam. Split out of the vibration direction of the beam perpendicular to each other and equal intensity, the beam were in close proximity to the two points through the object to be examined, in the phase of a slight difference. Due to the split distance of the two beams is very small, and no ghosting phenomenon, so that the image presents a three-dimensional three-dimensional feeling.
Differential Interference Picture
The physical principle of the DIC microscope is completely different from that of the phase contrast microscope, and the technical design is much more complex.DIC uses polarised light and has four special optical components: the polarizer, the DIC prism, the DIC slider and the analyser. The polariser is mounted directly in front of the concentrator system and polarises the light linearly. In the concentrator, a Roymers prism, the DIC prism, is installed, which breaks a beam of light into two beams of light (x and y) with different polarisation directions, both at a small angle. A condenser aligns the two beams of light in a direction parallel to the optical axis of the microscope. * Initially, the two beams of light are in phase, after passing through the adjacent area of the specimen, due to the thickness of the specimen and the refractive index of the different, caused the two beams of light occurred optical range difference. At the back focal plane of the objective lens is mounted the first Royals prism, the DIC glider, which combines the two beams of light into a single beam.
At this point the polarisation planes (x and y) of the two beams remain. Finally the beam passes through the first polarising device, the deflector. Before the beams form the DIC image of the eyepiece, the detector is at right angles to the direction of the polariser. The detector interferes with two perpendicular light waves by combining them into two beams of light with the same polarisation plane.The optical range difference between the x and y waves determines how much light is transmitted. When the optical range difference is 0, no light passes through the detector; when the optical range difference is equal to half of the wavelength, the light passing through reaches the maximum value. Thus, on a grey background, the specimen structure appears as a light-dark difference. In order to optimise the contrast of the image, the optical range difference can be changed by adjusting the longitudinal trim of the DIC slider, which changes the brightness of the image. Adjusting the DIC slider can make the fine structure of the specimen show a positive or negative projection image, usually one side of the light, and the other side of the dark, which creates an artificial three-dimensional sense of the specimen, similar to the relief on the marble.
