Phase Contrast Microscope

Phase Contrast Microscopes: The Invention of the Century
A now world-renowned physicist Frits Zernike develops phase contrast microscopes early in the 20th century. Phase contrast microscopes are considered the next-generation microscopes used inside laboratories found inside hospitals, classrooms, and research centers. A phase contrast microscope adapts a certain type of technology that allows users to see a more detailed version of the specimen they are observing.

As the name suggests, phase contrast microscopes is a product of a new discovery in microscopy and light. In one of his experiments, Frits Zernike found out that speeding the direct path of light into the microscope’s lens might actually produce some sort of a pattern into specimen under observation. These patterns, in turn, make the specimen’s images look a little dark against a lighter background.

Using this principle, Zernike proceeded to develop symmetry of rings to be placed inside the condenser as well and the objective lens. His further studies show that this concept is most applicable on specimens colorless or transparent in nature. With that being said, phase contrast microscope is most useful when the subjects used are protozoa, sperm tails, bacteria’s, and other unstained cells.

Since then, phase contrast microscopes became widely used to examine biological tissues. It is quite hard to distinguish biological tissues from their environment, as these organisms tend to blend well with their surroundings. Under ordinary microscopes, the image of cheek cells produced was mere lines and they appear very far apart. However, if observed using a phase contrast microscope, the same image produced was more detailed - the cell’s nuclei are even seen with each of them appearing as dots under the microscope.

Unlike ordinary light microscopes, phase contrast microscopes do not require staining just to view the specimens on the slide. Additionally, it is also quite possible to observe cell division cycles using these devices. Because of this, phase contrast microscopes have garnered momentous recognition all over the world, which eventually brought over a prestigious Nobel Prize to its inventor in 1953.

A regular Phase Contrast Microscope package consists of four objective lenses, one telescope used for centering, and of course, the Zernike condenser lens. This phase condenser lens also contains two long adjustment screws so that it can be aligned properly to the phase ring.

Here’s the proper way of using a phase contrast microscope:
1. First, set the microscope on bright field mode of BF mode. The bright field setting can be found on the thumb wheel. Basically, the BF setting allows you to use the different phase objectives as merely standard BF lenses. But aside from this, the microscope also has a 10, 20, 40, and 100x setting respectively.
2. Focus on your specimen. To do this, try to adjust the condenser’s height for best image quality. Keep on adjusting until optimum setting is achieved.
3. Set the turret to phase setting. Check your condenser turret and ensure that it is placed on the right phase setting. The moment that is done, gently take the specimen out. It would be placed back after alignment.
4. Center the condenser. After removing the specimen, use the special controls that are sticking out from the two sides of the condenser’s back. The purpose of these controls is use to center the condenser. Use it as designed.
5. Remove the eyepiece lens. Take one lens of the telescope and put the centering eyepiece instead. The tube also has a setscrew that you can adjust in order to focus the eyepiece well. To know if you have done it correctly, look into the telescope. You are supposed to find two rings. Align these rings until they become concentric. Once they are, then the microscope is all optimized and set for phase contrast mode.
6. Remove the centering eyepiece. The centering telescopic eyepiece is only used for aligning the microscope. So when it is aligned, you can then take it out and put back the original eyepiece lens. At this point, you are also put the specimen back there again so you can start observing it.

These are the six basic steps that you need to do every time you are to use a phase contrast microscope. You also are to redo these steps if and when you need to change the objectives. Doing this is more of a precaution though, for it ensures that you are observing the specimens quite accurately. Even if you change objectives, you will find that the device is still well aligned just like before.

Phase contrast microscopes can also double as dark field microscopes. This is also one of the reasons why this device has become very popular. True enough, phase contrast microscopes give you more than you ever bargained for.