Frits ZernikeProfessor

When light passes through a transparent object, there is a change in the phase of the light waves, the position of the wave crests' in relation to one another. Our eye does not perceive this, but in the beginning of the 1930s, Frits Zernike developed a way to make it visible. A light beam is passed through an object while a reference beam goes by it. When the beams are brought together, they are strengthened or canceled out because of phase displacement, and the object is outlined more clearly in contrast to its surroundings. The phase contrast microscope became particularly important in the study of living cells.