PHASE CONTRAST MICROSCOPE

 PHASE CONTRAST MICROSCOPE

·       Phase Contrast Microscope is a Light microscopy technique used to enhance the Contrast of Images of Transparent and Colourless specimens.

·       Phase Contrast Microscope was first described in 1934 by Dutch Physicist Frits Zernike for which later in 1953 he was awarded the Nobel Prize in Physics.

·       Phase Contrast Microscope enables visualization of cells and cell components that would be difficult to see using an ordinary Light microscope.

·       Phase Contrast Microscopy is especially useful for the examination of internal structures in living microorganisms. In addition, it is not necessary to fix (attach the microbes to the microscope slide) or stain the specimen that could distort or kill the microorganisms.

·       In Phase Contrast Microscope, Specimen is contrasted against a Gray background.

·       Fluorescence staining can be used in combination with Phase contrast to further improve the visualization of samples.

Working Principle of Phase Contrast Microscope

 

 

·       Illumination produced by the Light source (Tungsten Halogen Lamp) is directed through a specialized Annular Diaphragm (also called as Condenser Annulus or Annular ring) which is positioned below the Condenser lens.

·       Light passing through the Annular Diaphragm illuminates the Specimen.

·       In a Phase Contrast Microscope, two sets of Light rays are formed.

ü  One set of Light rays comes directly from the Light source.

ü  The other set comes from light that is Diffracted (also called as Reflected or Scattered) from a particular structure in the Specimen.

·       When the two sets of Light rays (Direct rays and Scattered or Diffracted rays) are brought together in the Diffraction plate (also called as Phase plate), they form an image of the Specimen on the Ocular lens, containing areas that are relatively light (in phase), through shades of Gray, to Black.

 Uses

·       Phase contrast microscope is especially useful for studying

ü  Unstained cells.

ü  Microbial motility

ü  Determining the shape of living cells

ü  Internal structures and Cell organelles in Living organisms

ü  Detecting bacterial components such as Endospores and Inclusion bodies.

ü  Fibers

ü  Glass fragments

ü  Thin tissue slices  

·       Phase contrast microscopes also are widely used in studying Eukaryotic cells.