The 18 types of microscopes (and their characteristics)

There are such small things that the human eye simply cannot see them. That is why something is needed that can increase them, and that is why there are instruments as linked to the scientific world as microscopes.

The first was invented by Anton van Leeuwenhoek and since then not only has his invention been sophisticated but also other types have been created that work to observe things that this Dutch merchant would never have believed exist.

Today we will find out the different types of microscope, as well as to see what they are used for, what they are made of and how they work. Do not miss them.

    The 18 types of microscope (explained)

    The microscope is an instrument which, if it had never been invented, of course science would not be as advanced as it is today. Science and technology have been greatly improved since a Dutch merchant named Anton van Leeuwenhoek, a little bored the guy, decided to experiment with several magnifying glasses in the middle of the 17th century and invented, like someone who does not want the thing, an instrument through which to observe things as small as red blood cells or sperm .

    It has been four centuries since this gentleman invented the prototype of the microscope and scientists, in their desire to know what this little world looks like that the human eye cannot see with the naked eye, have designed new types of microscopes. , some of which are sophisticated and powerful that they allow us to see even viruses and atoms. The technical improvements of the many microscopes that were invented they have led to improvements in both medicine and industrial technology and biology.

    Throughout this article we will learn about the 18 types of microscopes that exist, how they work and for which areas of knowledge they are basically used.

    1. Optical microscope

    The optical microscope was the first microscope in history. This instrument marked a before and after in biology and medicine since this invention, despite its relative technological simplicity, made it possible to see cells for the first time.

    The main feature of this instrument is that visible light is the element that allows the sample to be seen. A light beam illuminates the object to be observed, passes through it and is led to the eye of the observer who receives an enlarged image thanks to a system of lenses. The light microscope is useful for most microscopy tasks because it allows you to see cells and tissue details that we couldn’t see with the naked eye.

    However, this microscope is the simplest of all. Its resolution limit is marked by light diffraction, a phenomenon by which light rays are inevitably deflected by space. As a result, the maximum that can be obtained with an optical microscope is 1500 magnifications.

      2. Transmission electron microscope

      The transmission electron microscope was invented in the 1930s and was a real revolution in the first half of the last century. This microscope allows a higher number of magnifications to be achieved than optics, since it does not use visible light as a visualization element but uses electrons.

      Transmission electron microscopes are much more complex than optical microscopes and it shows in the way samples are viewed.

      The mechanism of this microscope is based on focusing electrons on an ultrathin sample, much thinner than those normally prepared for observation under a light microscope. The image is obtained from the electrons which pass through the sample and then impact on a photographic plate. To get the right flow of electrons inside these microscopes, they must be empty.

      The electrons are accelerated towards the sample using a magnetic field. Once they hit it, some electrons will pass through it while others will bounce back and scatter. This is explained by images with dark areas, where electrons have bounced back, and bright areas, which are where electrons have passed through, forming a black and white image of the sample.

      Transmission electron microscopes are not limited by the wavelength of visible light, making them capable of magnifying an object up to 1,000,000 times. Thanks to this, we can not only see bacteria with these instruments, but also much smaller bodies such as viruses.

        3. Scanning electron microscope

        The scanning electron microscope is based on the influence of electrons on the sample to obtain visualization, but differs from transmission in that in this case particles do not impact the whole sample at once, but do so by passing through different points. You could say he is scanning the sample.

        With this microscope, the image is not obtained from the electrons impacting on a photographic plate after passing through the sample. Here, the operation is based on the properties of the electrons which, after impact on the sample, undergo changes. Part of its initial energy is transformed into X-rays or heat emission. By measuring these changes, all the information needed to make an enlarged reconstruction of the sample can be obtained, as if it were a map.

        4. Fluorescence microscope

        Fluorescence microscopes they form an image thanks to the fluorescent properties of the sample which is observed through them. This sample is illuminated by a xenon or mercury vapor lamp. A traditional light beam is not used but it is worked with gases.

        These substances illuminate the preparation with a specific wavelength, which allows the elements that make up the sample to begin to emit their own light. In other words, here the sample itself is the one that emits light instead of illuminating it so that it can be observed. This instrument is widely used in biological and analytical microscopy, being a technique that gives a lot of sensitivity and specificity.

        5. Confocal microscope

        Confocal microscope can be considered as a type of fluorescence microscope in which the sample is not fully illuminated, but a scan is performed as in the case of the scanning electron microscope. Its main advantage over traditional fluorescence is that the confocal allows reconstruction of the sample by obtaining three-dimensional images.

          6. Tunneling microscope

          The scanning tunneling microscope allows us to see the atomic structure of particles. This instrument uses the principles of quantum mechanics, capturing electrons and making a high-resolution image in which each atom can be distinguished from the others. It is a fundamental tool in the field of nanotechnology, it is used to produce changes in the molecular composition of substances and to obtain three-dimensional images.

          7. X-ray microscope

          The X-ray microscope, as the name suggests, does not use traditional light or electrons, but uses X-rays to view the sample. This radiation of very short wavelength is absorbed by the electrons of the sample, which makes it possible to know the electronic structure of the preparation..

            8. Atomic force microscope

            The atomic force microscope does not detect light or electrons. Its operation is based on scanning the surface of the preparation to detect the forces that occur between the atoms of the microscope probe and the atoms on the surface.
            This instrument detects the forces of attraction and repulsion of atoms, very light energies, which allows a mapping of the surface of the sample thus obtaining three-dimensional images as if a topographic map were being carried out.

            9. Stereoscopic microscope

            Stereoscopic microscopes are a variation of traditional optics, although these have the particularity of allowing a three-dimensional visualization of the preparation. They are equipped with two eyepieces, unlike traditional eyepieces which only have one, and the image that reaches each is slightly different. By combining what both eyepieces capture, the desired three-dimensional effect is formed.

            Although it does not reach as many magnifications as traditional optics, the stereoscopic microscope is often widely used in areas where simultaneous handling of samples is required.

              10. Petrographic microscopes

              The petrographic microscope, also called a polarized light microscope, is based on the principles of optics but with the particularity that it has two polarizers, one in the condenser and the other in the eyepiece. These parts of the microscope reduce the refraction of light and the amount of brightness.

              This instrument is used to observe minerals and crystalline objects, as if they were traditionally illuminated, the resulting image would be blurry and difficult to appreciate. It is also a type of microscope that is very useful when analyzing tissue that can cause light refraction, such as muscle tissue.

              11. Field ion microscope

              The field ion microscope is used in materials science because allows to see the arrangement of the atoms of the preparation. Its function is similar to the atomic force microscope, allowing the gas atoms absorbed by a metal tip to be measured to construct a reconstruction of the sample surface at the atomic level.

                12. Digital microscopes

                The digital microscope is a tool capable of capturing an image of the sample and projecting it. Its main feature is that, instead of having an eyepiece, he has a cameraa. Although their resolution limit is lower than that of the traditional optical microscope, digital can be very useful for observing everyday objects and, thanks to the fact that they are able to keep images of preparations, this device is very interesting in terms of business.

                13. Reflected light microscope

                In the case of reflected light microscopes, light does not pass through the sample but is reflected when it affects the preparation and is directed towards the goal. These microscopes are used to work with opaque materials which, although cut very finely, do not allow light to pass through.

                14. Ultraviolet light microscope

                Ultraviolet light microscopes do not illuminate the preparation with visible light, but use ultraviolet light as the name suggests. This type of light has a shorter wavelength, which results in higher resolution.

                In addition, they are able to detect a greater number of contrasts, which makes them especially useful when the samples are too transparent and could not be seen with the traditional light microscope.

                15. Compost microscopes

                The composite microscope includes any optical instrument equipped with at least two lenses. Normally the original optical microscopes used to be simple, whereas most modern ones are compound, having several lenses as much in the objective as in the eyepiece.

                16. Dark field microscopes

                Darkfield microscopes illuminate the sample obliquely. The light rays that hit the target do not come directly from the light source, but are scattered throughout the sample. In this case, it is not necessary to dye the sample in order to be able to visualize it, and these microscopes make it possible to work with cells and tissues that are too transparent to be observed with conventional illumination techniques.

                17. Transmitted light microscope

                Under a transmitted light microscope a beam of light passes through the preparation and is the most widely used illumination system in optical microscopes. Due to this method, the sample must be cut very thinly to make it semi-transparent and so that light can pass through it.

                18. Phase contrast microscope

                The phase contrast microscope works with the physical principle that makes light travel at different speeds depending on the medium through which it travels. Using this property, this instrument it collects the speeds at which light has circulated while passing through the sample, makes a reconstruction, and thus obtains an image. This type of microscope makes it possible to work with living cells because it is not necessary to stain the sample.

                Bibliographical references

                • Bhagat, N. (2016) “5 important types of microscopes used in biology (with diagram)”. Debate on biology.
                • Gajghate, S. (2016) “Introduction to microscopy”. India: Agartala National Institute of Technology.
                • Harr, M. (2018) “Different Types of Microscopes and Their Uses”. science.com.
                • Osier, Kai and Heintzmann, Rainer. (2007). Improvement of the interferometric resolution of confocal microscopes. Express optics. 15. 12206-16. 10.1364 / OE.15.012206.

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