Editorial Feature

Phase-Contrast Microscope - Definition and Applications

A phase-contrast microscope is a type of light microscopy that intensifies contrasts of transparent and colorless objects by influencing the optical path of light.

Phase-contrast microscopy is an optical microscopy method that is vital in biological and medical research.

The phase-contrast microscope has the ability to show components in a cell or bacteria, which would otherwise be very difficult to see in a basic light microscope.

The idea of phase-contrast microscopy was first described in 1934 by Dutch physicist Frits Zernike. Upon realization of the importance of the phase-contrast microscope, Zernike was awarded the Nobel Prize in Physics in 1953.

The phase-contrast microscope operates on the basis of the fact that when light passes via a transparent part of a specimen, it travels slower and tends to be shifted compared to the uninfluenced light.

However, this difference in phase is not visible to the human eye. A transparent phase-plate in the phase-contrast microscope assists in increasing the change in phase to half a wavelength, thus causing a difference in brightness, and leading to the transparent object shining out in contrast to its surroundings.

In biological and medical research, transparent and colorless components in a cell can be clearly studied by using the phase-contrast microscope. Cell division is no longer a mystery, as the phase-contrast microscope can be used to examine the whole process in detail.

Applications

In cases where high magnifications are needed, and the specimen is colorless or the color of the fine details of the specimen does not show up well, the phase-contrast microscope is the ideal choice compared to bright field microscopy.

For instance, cilia and flagella can be viewed with bright field microscopy, but the sharp contrast can only be seen via a phase-contrast microscope. Likewise, clear details of the amoebae can be seen via a phase-contrast microscope.

High-contrast images of transparent specimens, such as micro-organisms, thin tissue slices, living cells in culture, latex dispersions, lithographic patterns, glass fragments, and sub-cellular particles, like nuclei and organelles, can be viewed in detail.

Sources and Further Reading

 

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