phase-contrast microscope

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July 2, 2026

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urinalysis A urine sample prepared for examination under a phase-contrast microscope.

A phase-contrast microscope is a specialized optical microscope that makes transparent specimens visible by converting differences in phase into differences in light intensity. Many biological objects, like cell structures, are nearly transparent and do not show contrast with conventional microscopes.12

This type of microscope exploits slight variations in the refractive index (R.I.) between the specimen and its surrounding medium. Light passing through these variations experiences a change in its optical path, causing a shift in the light's phase. The phase-contrast microscope converts these phase shifts into detectable variations in brightness, allowing the structures to be seen. This invention was developed by Frits Zernike in 1934.2

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microscope
Phase-contrast microscopes
Many biological objects of interest consist of cell structures such as nuclei that are almost transparent; they transmit as much light as the mounting medium that surrounds them does. Because there is no colour or transmission contrast in such an object, it is…
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Many biological objects of interest consist of cell structures such as nuclei that are almost transparent; they transmit as much light as the mounting medium that surrounds them does. Because there is no colour or transmission contrast in such an object, it is…
Read More

Frits Zernike
…for his invention of the phase-contrast microscope, an instrument that permits the study of internal cell structure without the need to stain and thus kill the cells.
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…for his invention of the phase-contrast microscope, an instrument that permits the study of internal cell structure without the need to stain and thus kill the cells.
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optics
Filtering
The phase-contrast microscope can be considered to be an example of an optical processing system, and the concepts understood by reference to Figure 9. Only the simplest form will be considered here. The spatial frequency spectrum of the phase object is formed and the phase of…
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The phase-contrast microscope can be considered to be an example of an optical processing system, and the concepts understood by reference to Figure 9. Only the simplest form will be considered here. The spatial frequency spectrum of the phase object is formed and the phase of…
Read More