The oil immersion procedure is one of the many advancements of compound light microscopy. Understand how they work and how they can enhance the viewing of specimens.

The oil immersion procedure is mostly used on binocular compound and trinocular compound microscopes. But then again, there is a number of monocular compound microscope that is capable of them as well. These oil immersion lenses are part of the microscope’s package and usually, they have a magnification power of 100x. To identify if a lens is an oil immersion lens, manufacturers put a certain identifying mark on it like a red band around the housing of the lens.

If a microscope is subjected to magnifications that are greater than 500x, what happens is that the light becomes too much refracted that it merely passes through the air. And so to prevent that from happening, a mineral oil of high quality is used to serve as a medium to transmit the light. The high quality mineral oil that is normally used for this particular application is called the immersion oil. It is imperative that only the type of oil provided by microscope manufacturers and its parts suppliers are used at all times. Using any other type of oil may just damage the lens. Plus, it is important that the lens is cleaned with the prescribed lens paper right after using it with the oil immersion technique.

The principle of light microscopy is this: for objects to be seen clearly through the microscope, adequate light should enter through the objective lenses. In most modern microscopes this doesn’t pose to be a problem. But for the rather old oil immersion lenses, it certainly is. Oil immersion lenses are very narrow and that’s primarily the reason why light tends to miss them entirely. As a result, the image seen through the microscope has low resolutions and is a little blurred. And so to increase the resolution created with oil immersion lenses, a very small drop of oil is placed between the lens and the glass slide to be viewed.

The oil immersion compound light microscopy technique relies entirely on the refraction of light. And quite conveniently, the immersion oil that is used in the setup bends the light in the same way that the glass slide bends it as well. The result then is a better image with higher resolution. It then becomes possible to observe very small objects such as bacteria and other single celled organisms. In oil immersion compound light microscopy, or any type of microscopy for that matter, magnification at a fair resolution is very essential.

But there are certain points to remember before oil immersion compound light microscopy is to be applied. For one thing, users should use oil immersion lenses only when they have a fixed, not moving, or dead specimen to be viewed. And the samples should only be few micrometers thick also. In all reality, it is very impossible to view living things like protists at a magnification level of 1000x. Except of course, the one you are observing are very slow moving creatures.

But even if the oil immersion process is beneficial, there are some disadvantages associated to using them. The first of which is the fact that it can only be used with inert samples just like what was stated above. Oil is glutinous. And a moving sample would only distort the angle of refraction that the oil provides. Therefore, the oil must stay in contact and in only one position all the time. If you want to use oil immersion compound light microscopy with a wet mounted specimen, the specimen has to be very secure so that it will not move.

Oil immersion lenses can only be used with the right type of oils only. Therefore, dry lenses like the 400x lenses can’t be used. Oil has the ability to distort the images to be viewed under dry lenses. Therefore it needs through cleaning if it is going to be used right before dry lenses. Focusing can also be difficult with oil immersion lenses. For starters, using it with a high magnification lens requires that it is brought very closely to the sample being observed so that focusing it becomes possible. Doing this is a bit hard because most microscopes’ focal plane can be very shallow.

These are the principles behind the oil immersion compound light microscopy technique. Using them provide users of an added advantage in viewing very small specimens with a good resolution.