Microscopes are high-tech equipment that enable us to see the world at an entirely different level. What most people don’t know is that the first compound microscope was created in 1590, by Dutch spectacle makers Hans and Zacharias Janssen.
There are many types of microscopes available on the market today, with two of the most common being light microscopes and electron microscopes. It’s crucial to understand what they are and how they are different, to ensure your lab has the right equipment for your needs.
A light microscope may also be referred to as an optical microscope. It uses light, at approximately the 400 to 700 nm wavelength to illuminate the objects under view. The lenses are made of glass, and the image is formed by the absorption of light. Light microscopes are lightweight and fairly small. They do not operate under a vacuum.
You can use a variety of specimen types, including fixed or unfixed, stained or unstained, living or dead. It doesn’t take a lot of work to prepare specimens for the microscope. Generally, it can be done within a few minutes to a few hours.
The specimen can be 5 micrometers or thicker, and does not have to be dehydrated before looking at it. The specimen is stained with colored dyes to make it properly visible. The specimen is then mounted on the glass slide, and can be magnified up to 1,500x. That may sound impressive, but it’s on the low-end of what microscopes can do. Focusing the image is done by mechanically adjusting the lens position.
Light microscopes tend to have low resolving power, with a poor surface view. They present flat images in color, but it is possible to see living processes like cell division and microscopic pond life. There are no special settings required for the room where the microscope is housed. Images are viewed directly with the human eye through the eyepiece.
Light microscopes are simple to use and do not require the use of high voltage power or filaments. There is no radiation risk. They are affordably priced and have low maintenance costs.
Types of light microscopes include:
Light microscopes are well suited to the majority of basic functions, and it is common to see them in schools. Uses include examining:
The electron microscope was invented in 1931 by the physicist Ernst Ruska and engineer Max Knoll. It has become an indispensable tool in microbiology and quality control and assurance. It uses a beam of electrons, rather than visible light, as the light source to make objects larger and present a more detailed picture. The images are formed by the transmission or scattering of electrons.
How an electron microscope works is different than a light microscope. For example, unlike a light microscope, electron microscopes operate under a high vacuum, and rely on electron optical lenses to help produce an image. A typical EM lens systems includes a condenser-objective lens, objective lens, and objective mini lens, which all operate together to magnify the electron beam and the information it carries from the specimen.
With an electron microscope, you cannot observe live specimens. The specimen must be fixed or stained. Preparing the specimen is more labor intensive, generally requires a high skill level, and can take a few days to complete. The process usually requires the use of corrosive chemicals and involves interpreting the images due to artifacts.
The specimen is ultra thin – usually 0.1 micrometers or below. This type of microscope only uses dehydrated or dead specimens. Specimens are coated with heavy metals to reflect electrons and are mounted on a metallic grid that is mostly copper. Focusing is done by adjusting the power of the electric current to the lenses.
Electron microscopes have high magnification ability, up to 1,000,000x. They also have high resolving power, about 250x that of a light microscope. The high resolution helps generate highly detailed image that provide excellent insight into the internal structure of cells, but forms in grayscale. Rather than being viewed directly by the eyes through an eyepiece, images are viewed on either a zinc sulfate fluorescent screen or a photographic plate.
Unlike with a light microscope, living processes cannot be viewed. In transmission electron microscopy (TEM), you can only view images in 2D. If you use scanning electron microscopy (SEM), depth is added to make it seem like a 3D image.
Electron microscopes have to be used in a highly controlled environment, where pressure, temperature, and humidity are regulated. They also require a high voltage current of at least 50,000 volts, and tungsten filaments. They include a cooling system to reduce the heat generated by the high voltage current. There is a risk of radiation leakage.
Because electron microscopes are highly complex, they are often limited to specialized functions, such as research. They are most often used in the study of external structures – the ultrastructure of cells and other very small organisms.
Furthermore, there are different types of electron microscopes. The two main types include scanning electron microscopes (SEM) and transmission electron microscopes (TEM). SEM relies on a beam of electrons moves back and forth across the surface of the specimen – whether it is tissue or a cell. This creates a detailed 3D image of the surface. Meanwhile, TEM cuts the sample into thin slices before it is imaged. In this technique, the electron beams pass through the slice instead of over the surface. This results in detailed images of the internal cell structures.
It’s all depends. Electron microscopes offer some key advantages compared to optical microscopes, such as higher range of magnification and higher resolution, both of which allow the end-user to generate more detailed images.
However, one limitation to electron microscopy is that samples must be placed under vacuum, meaning live cells cannot be imaged. In contrast, light microscopes can be used to observe both live and dead cells. As well, sample preparation takes less time—typically several minutes to a few hours. Meanwhile, electron microscopy sample prep can take several days.
Both light microscopes and electron microscopes have their place in science. The better choice depends on the task at hand and the nature of your research, and the costs you’re willing or able to incur for research and development.
Unlike most light microscopes, which aren’t always that expensive, electron microscopes are highly complex, expensive to purchase, and expensive to maintain. If you require one in your lab, opting to lease significantly reduces the upfront costs of procuring an electron microscope from the manufacturer of your choice. So leasing not only gets you the equipment you need, it also helps extend your budget. Furthermore, it's typically faster to lease equipment than raise additional capital for a major purchase.
Whatever microscope you're interested in, consider leasing with Excedr. Our goal is to make it easier for labs of all sizes and their teams to have an impact on peoples’ and patients’ lives by helping them access the equipment they need most.