The history of phase contrast microscopy was first realized in 1934 by Dutch physicist Frits Zernike. At some stage in his study of diffraction gratings, he valued both that it is necessary to interfere with a reference beam, and that to maximize the contrast achieved with the technique, it is necessary to introduce a phase shift to this reference so that the no-phase-change condition gives rise to completely destructive interference. The phase contrast system utilizes an optical mechanism to translate minute variations in phase into corresponding changes in amplitude, which can be visualized as differences in image contrast. The phase contrast microscope was awarded with the Nobel Prize in Physics, 1953.
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In the mid-1950s, a French optics theoretician named Georges Nomarski modified the Wollaston prism used for detecting optical gradients in specimens and converting them into intensity differences. Several implementations of this design, which is called differential interference contrast.

Differential interference contrast microscopy, also known as Nomarski Interference Contrast (NIC) or Nomarski microscopy, is an optical microscopy illumination technique used to enhance the contrast in unstained samples. It works on the principle of interferometry to gain information about the optical density of the sample, and to see invisible characteristics. It uses a complex lighting system that produces an image with the object appearing black to white on a grey background, similar to phase contrast microscopy, but without the bright diffraction halo. It is a method of deriving contrast in an unstained specimen from differences in index of refraction of specimen components. (more…)