Types of Microscopes and All Their Uses
Microscopes come in wildly different shapes and form factors, all of them having unique capabilities that work in different mediums and produce unique results based on them. Electron microscopes and acoustic microscopes both work with invisible waves in our air but produce vastly different images from one another and at different magnification levels.
In this article, we’re going to explain the difference between the different types of microscopes and microscopy to hopefully give you a better idea of how these various elements work and which one might be best for your unique application.
The origins of the simple microscope date back to the end of the 16th century, when Dutch glassmakers Hans Janssen and son Zacharias Janssen produced two maneuvering lenses that could fluctuate between three and nine times magnification. While no early models exist, there is a Janssen microscope in a Middleburg museum that can magnify images up to ten times.
Robert Hooke, the author of Micrographia, improved this original design, who further developed them to include features seen in telescopes, like an eyecup and separate draw tubes. However, his microscopes struggled to produce clear images and instead suffered from spherical aberrations, making them unideal for research purposes.
However, an admirer of Hooke’s work went on to improve these attempts. Thus Antony van Leeuwenhoek would develop a microscope capable of magnifying over 200x, with the brightest and clearest images known at the time. While other microscope engineers were noted scientists and researchers, Antony did not possess a university degree and only spoke Dutch; nevertheless, he discovered bacteria, red blood cells, and more.
Antony is known to have made over 500 microscope-like devices, some of which don’t quite fit the bill of what we know to be microscopes. He had a great skill for grinding lenses together, naturally good eyesight and understanding how lighting could affect lens construction. With all of these talents, he wrote of his findings to the Royal Society of London, who would translate his letters from Dutch into English and published them.
In modern times, the compound microscope is known as a device containing two optical elements known as the objective lens and optical lens, the latter of which provides a majority of the magnification and the former making it more visible to the human eye.
It provides immense levels of magnification of 400x or even 1000x, with high resolution through immersion techniques. Of course, these techniques encounter limits, and other forms of microscopy were developed to compensate.
Electron microscopes are used to obtain high-resolution images, particularly in biomedical fields. As published by the state of Virginia, an electron microscope is capable of identifying features on a molecular level; however, this doesn’t actually produce a traditional image.
Electrons were discovered in 1897 by J.J. Thompson. With Louis de Broglie showcasing how these electrons behaved live radiation on a short wavelength, Ernst Ruska was then able to harness these wavelengths for imaging purposes and make the first electron microscope.
How Does An Electron Microscope Work?
An electron microscope utilizes a stream of high voltage electrons that are kept within a vacuum and funneled towards a specimen using a positive electrical charge. This stream is then focused on a single electron beam, which is focused on a magnetic lens. That beam is then affected by the sample, and these interactions are measured with a microscopy camera to construct an image.
There are primarily two types of electron microscopes: Transmission electron microscopes (TEM) and scanning electron microscopes (SEM).
A TEM produces images of specimens that appear to be flat at 50 to 50 million times magnification; an SEM does the same but from 5 to 500,000 times with a three-dimensional image of surface features.
Scanning Electron Microscopes
The SEM utilizes electrons focused down to a fine point, which is then scanned across the specimen. These electrons are controlled by scan coils affixed within the field lens to be properly tracked and measured as they move in three-dimensional space. Then, secondary low-voltage electrons are emitted from the specimen and back into the detector, which is how these electrons are ultimately measured. These measurements are traditionally calculated through a computer, which receives the electrons through an electronic console and then translates that data into an image on its screen.
Electron Microscopy Uses
As the University of Massachusetts Medical School explains, electron microscopes are nanotechnology used to produce high-resolution images of both biological and non-biological specimens.
These images provide valuable information on the structural basis of both cell function and cell disease by enabling research on the detailed structure of organic materials like tissues, cells, organelles, and macromolecular complexes.
The light microscope, or compound microscope, is the most traditional model of microscope that utilizes an objective and optical lens to magnify a specimen that is illuminated with traditional light. These light sources are placed directly beneath the sample and aimed upward into the lens, allowing the light to channel directly through the objective lens, into the optical lens, and out of the eyepiece on the other side.
While these may not offer the same magnification levels as other microscopes, they produce colored images in three dimensions for scanning larger specimens, like grows in a petri dish.
Scanning Light Microscopes
A scanning light microscope is a standard optical microscope that collects quality images by scanning them with a CMOS computer sensor to produce a two-dimensional image. These operate with most of the same properties as a standard compound microscope but utilize this chip to produce high-quality digital scans that can be distributed and recorded for further analysis.
Light Microscopy Uses
Light microscopes are used for a large variety of scientific activities, especially with objective lenses tailored for your needs. This includes medical research, technical engineering, and silicone quality assurance.
Another use is historical analysis to determine the age of an artifact or sample. Objective lenses are also designed for subjects like confocal microscopy, deep tissue imaging, and analysis of quantum structures.
The USB Computer Microscope
A USB 3.0 computer microscope is a self-contained device that offers quick, high-quality image acquisition leading directly into a computer. This electronic implement takes the place of the optical lens, capturing your image in a digital format for further analysis and study rather than viewing, describing, and documenting by the human eye.
These devices feature sensors ranging from 1.1” down to 1/2.3” and provide clarity of up to 15 megapixels, making them useful for other forms of research like histology, hematology, semiconductor inspection, archiving, metrology, and more.
The Pocket Microscope
A pocket microscope is a simple marvel of optical engineering, as it is a microscope that fits within a large pocket. These are perhaps the most similar to the original microscopes. However, these implements still feature varying levels of optical zoom, manual focus, and even LED lighting.
While these devices do not offer the same levels of magnification seen in other optical microscopes and cannot connect to a computer, they are flexible tools for classroom environments or living subjects.
The Acoustic Microscope
As detailed by Hawaii’s School of Ocean and Earth Science and Technology, the acoustic microscope samples an image with ultrasound waves, the reflection of which is used to map spatial distribution.
This technique was first used in the 1940s by Leningrad scientist Sokolov who observed an acoustical image that he converted onto a television display.
Two Stanford University students. Lemons and Quate created the first scanning acoustic microscope in 1973, which was mechanically driven and operated in a transmission mode. This technology was improved, and acoustic microscopes now operate in a reflection mode.
There are three distinguishing factors of an acoustic microscope: far-field wave imaging, the use of acoustic waves, and image generation via scanning. The latter differentiates acoustic from traditional optical microscopes, while the former two separate it from an electron microscope, as it utilizes specific frequencies between 100 megahertz and two gigahertz.
Here a grayscale image is created as an ultrasound beam is focused through water, to a sample, and then back again, with just one single voltage arriving back at the sensor.
These microscopes work differently, each offering a unique value, whether image magnification, resolution, color, or format. You know there are fine differences between acoustic and electron microscopes, and some optical microscopes come in form factors small enough to fit into a pocket.
While there are many to choose from, it is important to do your research and find the one that is specifically best for you, and hopefully, now you have an idea of where to begin looking.
For help finding the right microscope and lens, visit Navitar.
Antony van Leeuwenhoek | ucmp.berkeley.edu
What Is an Electron Microscope (EM) and How Does It Work? | VHA Diagnostic Electron Microscopy Program
What is Electron Microscopy? | UMASS Medical School
School of Ocean and Earth Science and Technology - Acoustic Microscopy | hawaii.edu
Custom Microscope Objectives - Microscope Objectives | Navitar