fázalkontrasztos

Fáziskontraszt, also known as phase contrast, is a microscopy technique that allows unstained, transparent specimens to be visualized. It works by converting differences in the refractive index of a specimen into differences in amplitude or intensity, which are then visible as contrast. This is achieved by introducing a phase shift to the light rays that pass through the specimen compared to the light rays that pass through the surrounding medium. Specialized optical components within the microscope, namely a phase plate and an annular diaphragm, are crucial for this process. The phase plate alters the phase of the light, while the annular diaphragm in the condenser limits the illumination to a ring. When the light passes through the specimen, variations in its optical path length cause phase shifts. These phase-shifted rays are then recombined with the unshifted background light, resulting in interference patterns that create contrast. This method is particularly valuable in biology for observing living cells and their internal structures without the need for staining, which can often kill or alter the cells. It provides a way to study dynamic processes in unstained live samples.