A contrast microscope, more properly a phase contrast microscope, is a microscope with components which greatly increase the contrast of objects on the stage, making them highly visible. Using a contrast microscope allows someone to see clearly, visualizing the structures involved in the object on the stage, and this type of microscope also allows observers to see cells and organisms while they are still alive and going through their life cycles, a distinct advantage.
Many living cells have components which are transparent or very close to it. When viewed on a regular microscope, these components basically wash out, making it impossible to see them. One way to address this problem is to dye the organism, with the dye providing contrast which causes these structures to pop out. However, it can be difficult to dye specimens, and the dying process can change the cell structures in addition to killing the organism, which makes it unsuitable for people who want to see things alive under the microscope to better understand them.
The phase contrast microscope relies on the fact that light changes as it passes through an object. Depending on the refractive index of various parts of a cell, the light will slow down as it passes through, moving “out of phase,” as it is known. With a special filter known as a phase plate between the specimen and the eyepiece to amplify this change, the researcher will be able to clearly see the transparent structures without needing to dye the specimen.
Differences between a phase contrast microscope and a regular microscope can seem like night and day. A relatively boring slide will suddenly teem with life when viewed under a contrast microscope, and the detailed, delicate structures of organisms and cells will suddenly become visible when they were not before. Using contrast microscopy, scientists can watch microorganisms go through their life cycles, and they can also study the detailed anatomy of such organisms.
The inventor of the phase contrast technique, Frederik Zernike, was recognized with a Nobel Prize in 1953 for his efforts. Contrast microscopy can be significantly more expensive than other types of light microscopy, because it requires special equipment. As a result, phase contrast microscopes are usually only seen in specialized environments like research laboratories. Students in high level science classes at colleges and universities may be given an opportunity to work with such microscopes for their research and to learn more about the field.