If you are thinking of buying a microscope, it is good to learn a bit about the resolution before choosing a model.
Your microscope’s resolution will affect a few different things, such as how clear the image is and how many details you can see on your specimen.
Resolution is an important factor to consider when studying microorganisms and other things at cellular levels.
However, each microscope model is different, and you will get a different level of resolution depending on the kind of scope it is and its individual specifications.
If you want to learn more about this topic, you have come to the right place. This guide will explain what resolution is and how different types of microscopes impact resolution.
Furthermore, we will cover why the resolution is important and how to calculate microscope resolution.
Let’s dive into it.
What Is Resolution
When you hear the word “resolution,” you may think of PPI or pixels per inch.
When it comes to computers or television screens, resolution refers to how many pixels per inch the screen displays. The more pixels there are, the higher the quality the image is.
While the overall concept is a bit similar, microscope resolution works a bit differently.
A microscope’s resolution refers to the amount of detail that the microscope can pick up. The higher the resolution there is, the more clear the image will be.
Another way to explain microscope resolution is the shortest noticeable distance between two parts of a specimen that the camera or observer can differentiate.
A few factors determine the resolution of a microscope.
If all of the optical components are aligned correctly, are working together properly, and have a high numerical aperture, the machine will have a high resolution.
Furthermore, the wavelength of light that the instrument uses to illuminate the specimen also affects resolution.
In general, shorter wavelengths of light can produce higher resolution than long wavelengths in a microscope.
There are also two basic concepts that you must consider when calculating the resolution of a microscope, including Abbe’s diffraction limit and the Rayleigh Criterion.
We will go over these mathematical concepts further in a later section.
Does Type of Microscope Impact Resolution
There are a few different types of microscopes, and each will provide a different level of resolution, some better than others.
This section will review the five main kinds of microscopes and how they affect resolution. Let’s take a look.
- Compound microscope: Compound microscopes do not have high resolution. This is because the length of the light waves that illuminate the objects can only go up to 700 nanometers. What this means is that the microscope cannot distinguish parts of a specimen that are closer than 200 nanometers.
- Stereo microscope: Stereo microscopes are similar to compound microscopes because they both have low resolution. The length of the light waves on stereo microscopes also limits the resolution. Most stereo microscopes will have a resolution of about 120 nanometers.
- Confocal microscope: Confocal microscopes use laser beams instead of regular light to illuminate objects. Due to the way they are built, these machines have both high magnification levels and high resolution. Most confocal microscopes have a resolution of about 1.2 nanometers.
- Scanning electron microscope: Scanning electron microscopes have high resolution but are still slightly lower than confocal microscopes. Although the microscope’s resolution is limited by the electron beam and the interaction of electrons, it still has a resolution of around 10 nanometers.
- Transmission electron microscope: Transmission electron microscopes have high resolutions. These machines use similar technology as scanning electron microscopes, but they can distinguish differentiating parts of a specimen as close as 0.2 nanometers apart.
Why Is Resolution Important
You may be wondering why your microscope’s resolution is important. There are actually a few reasons why you should ensure you use a microscope with high resolution.
This section will review all of the different reasons why the resolution is important and how it can improve your experience while studying different specimens.
You Can See More Detail
The first and most noticeable reason why the resolution is important is that you can see more detail.
If you are studying specimens for scientific reasons or even as a hobby, you will want a high resolution to see all of the details of the object you are studying.
Even if you have a high magnification, microscopes with low resolution will not provide clear images.
You are bound to miss some vital details of the object you are looking at and won’t be able to study it as well on a molecular level.
The Image Will Be Less Blurry
Another beneficial side effect of high resolution is that your image will be less blurry.
Even if you are into microscopes as a hobby, the worst thing is looking through your microscope only to see blurred images.
However, a microscope with a high resolution will produce crystal clear images, helping you observe more accurate findings.
You Can Use a Higher Magnification Level
If you want to study specimens at a high magnification level, you will need an instrument with high resolution.
While some microscopes will work fine at 50x magnification power with low resolution, you will soon notice you will need better resolution for studying objects at higher magnification levels such as 2000x.
When you use an instrument with good resolution, you will have the freedom to zoom in and study your specimen much more closely than you could with a low-resolution machine.
You Can Study Things at a Molecular Level
One of the main reasons why the resolution is important is that you can study things at a molecular level with high resolution.
For instance, you won’t be able to study molecules with a compound microscope since they don’t have high resolution.
However, you can study molecules and atoms using an electron microscope since these machines offer resolutions of around 10 and 0.2 nanometers.
Calculating Microscope Resolution
Calculating a microscope’s resolution involves a few steps, including the Rayleigh Criterion and Abbe’s diffraction limit.
The Rayleigh Criterion refers to the point that two sources of light are distinguishable from one another. Abbe’s diffraction limit refers to the resolution limit of a microscope.
In this section, you will learn how to calculate your microscope’s resolution by using a few different equations.
Refer to the table below to learn the essential equations you will need to use for this process.
The first column will list the equation itself, the second column will explain what equation it is, and the third column will cover what each variable represents.
To calculate the resolution, make sure to start from the top of the table and work your way down. By the last equation, you should have your answer.
| NA = n x sin ɑ | Objective numerical aperture equation | n = refractive index of the imaging medium ɑ = half of the objective angular aperture |
| d = λ/2 NA | Abbe’s diffraction formula for the microscope’s lateral resolution | λ = wavelength of the light that the microscope uses to illuminate the object |
| d = 2 λ/NA2 | Abbe’s diffraction formula for the microscope’s axial resolution | λ = wavelength of the light that the microscope uses to illuminate the object |
| R = 1.22 λ/NAobj+NAcond | The Rayleigh Criterion | λ = wavelength of the light that the microscope uses to illuminate the object NAobj = the numerical aperture of the objective lens NAcond = the numerical aperture of the microscope’s condenser |
These are all of the equations you will need. It is important to calculate your microscope’s resolution since it will help you understand your machine better and its limitations.
After you know what the resolution is, you can know what kind of specimens you can study.
Furthermore, another piece of information you can gain from the resolution limit is at what level you can study specimens, such as cellular and molecular levels.
With these four equations, you will have all of the information you need. Just remember to take your time and double-check your answers.
Conclusion
Microscope resolution refers to how much detail the machine can pick up when illuminating or scanning a specimen. In other words, the higher the resolution, the more clear the image will be.
The resolution of a microscope also refers to the shortest noticeable distance that the instrument can pick up between two parts of a specimen.
Different kinds of microscopes will have different levels of resolution. Compound and stereo microscopes are on the lower end of the scale, only having a resolution of 120-200 nanometers.
On the other hand, confocal, scanning electron, and transmission electron microscopes have much higher resolutions of 0.2 to 10 nanometers.
There are a few reasons why microscope resolution matters. First of all, you will see things in more detail, and your image will not be blurry.
You will also be able to use a higher magnification level with a high-resolution microscope.
It is a good idea to calculate the resolution of your microscope. Doing so will help you understand the machine better and know its limitations.
You will need to complete four equations, including Abbe’s diffraction formula and the Rayleigh criterion.
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