Phase contrast microscopy can be seen as one of the best methods for viewing translucent and transparent specimens or biological samples without the use of staining techniques and without resolution loss. For biological and medical researchers in the study of cultures, living cells and diverse applications outlined below, this technique has proved to be an invaluable and veritable tool.
Before the introduction and invention of phase contrast microscope, semi-transparent specimens and living cells were previously viewed in a bright-field microscope by different techniques of staining.

 

Superimposing a circular phase annulus found in the sub stage condenser accompanied with a circular phase ring found in the rear focal plane of the objective lens and samples or specimens being subjected to phase contrast illumination often come into sight surrounded by halos. This is simply referred to as the phase contrast effect. If used with plane light, they come into sight against a grayish background, and when used with a green filter, they come into sight against a green background in light path.
There are various types of phase contrast available as simple ones and they include 10x and 40x phase objectives with accompanying pre-centered slider or as a completely equipped phase contrast microscope with a Zernike condenser and a complete or full complement of phase objectives; centering phase telescope and 10x, 20x, 40x and 100x immersion objectives.
They are a type of microscopes called compound light microscope put into use for a wide variety of microscopic applications such as cellular biology and molecular research; medical and health diagnosis of health conditions; breeding of dogs; control of dust mite; waste water management; microbiological research such as parasitology, virology, bacteriology; paleontology; marine and water biology for animal and plant cells; the list is endless as it is not limited only to these applications only.
There are two different ways in which phase contrast can be performed, on inverted microscopes and upright microscopes. The most common type of both microscopes is the upright microscope, designed in a way that the objective lenses are placed or positioned above the sample or specimen, facing downward and usually having smaller working distances. The most durable and easy to use microscope for cell microscopy are the inverted microscope, they can be used for tissue culture work including diagnosis of tumor cells. There is the development of specialized long working distance phase contrast optical systems which is employed for tissue culture investigation and motility of sperm cells for in-vitro fertilization.
Chemical and industrial applications for the phase contrast include but not limited to: crystallography, polymer morphology investigations and mineralogy and also the study of fragments of glass.it can also find use in the scrutinization of commercial products which includes clays, oils, soaps, fats, pigments, drugs, foods, textiles, and paints. It is also commonly used in the analysis of fibers, mineral fibers, monitoring of environmental air pollution such as asbestos and identification of mold spore.
The most common technique used in viewing and studying live blood cells in the field of live blood cell analysis is the phase contrast technique.

It is worthy to note that the phase contrast technique has proved to be an important advancement in the field of microscopy that it fetched its inventor, Fritze Zernike a Nobel Prize in physics in the year 1953

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