Welcome to Microscope Basics! So, what is microscopy?
Microscopy is the study and use of a microscope to enable enlarged and magnified viewing of a subject, quite simply. Generally, it’s using a series of curved lenses to take what something looks like, and make it bigger as well as more detailed. It’s like using a magnifying glass, except this time you’re taking another magnifying glass to make it even bigger.
This allows for objects smaller than the naked eye can see become visible, and essentially is what allowed our world to evolve medically into what it is today. Without a microscope, it would be impossible to see cells and understand how even much of our own bodies work!
What can I do with a microscope?
If you can think of it, you can probably view it with a microscope. There are so many brilliant minds that are constantly working with microscopes, and using that same brilliance to modify microscopes for specific applications. What started as just two convex lenses in a tube has evolved into a mass industry, where even one company can make thousands of different configurations, for an even greater number of applications needed.
Besides the usual viewing of bacteria and cells that microscopes, they are often used for coin inspection for coin collectors, cleaning for gun enthusiasts, reworking circuit boards for those in the electronics industry, core samples for oil drillers, and even tissue cultures for lab technicians or researchers. Some even get fancy enough to take images of individual atoms using a series of lenses, lasers, and other bombardment of electrons against their samples (the very advanced scanning electron microscope is one of such devices)!
What kind of microscope is right for me?
This is probably the most common question asked by microscope newbies. What do I need to look at what I want to look at? It’s a great question, with many different answers–and that’s why it can be overwhelming at first. But, once you take a little time to learn about how microscopes work, it all makes sense on exactly what you need to purchase to view your desired samples. I will go in more depth about each kind of microscope below, with links to detailed information on each common type of microscope available to you as an average user, but here’s a brief bit of general information to help you get started.
There are two main branches of microscopy–low power microscopy, and high power microscopy.
Low power microscopes are used for viewing opaque objects that you want to see additional details of. Usually they are top lit, as they’re meant for opaque samples (ones you can’t pass light through). These are common for coins, rocks, stamps, circuit boards, and entire bugs. They are called “stereo” microscopes not because they are binocular (which they almost all are), but because the path of light is split into two entirely separate paths from the dual lenses all the way to each eyepiece. Offsetting the two lenses slightly is what creates a 3D view, giving you depth of field in the sample.
High power microscopes are single path of light microscopes, and are meant to view translucent samples (ones that light can pass through), usually items on slides. These are the kinds you see in labs most often, used to view bacteria cells, blood cells, etc. They can have a single eyepiece (monocular), two eyepieces (binocular), or even three eyepieces (trinocular, with one being intended for a camera to be installed). These have a set of objectives on them that are cycled between for various magnification powers, and are a single lens that is split into the number of eyepieces that the unit has. So the image is exactly the same in each eyepiece, and you have a flat plane of viewing, instead of the depth of a stereo microscope. These are often called compound microscopes, as they are made (basically) with two convex lenses that collect light and magnify/focus it to a point–the two lenses compound their power to create magnification.
How does a microscope work?
A microscope uses a series of curved lenses placed at specific distances away from each other to take an image and magnify it, while adding resolution to the image. What that means in plain English is best explained with an analogy.
Imagine a magnifying glass. When you look through it, the curved lens makes the image look bigger. This is great, but what if we need even more magnification? You can make the lens more curved, but that only works so far–you’ll hit a limiting point where the lens can’t be any more curved and still give an image out. That, and the more you curve the lens, the smaller the image will be in the middle that’s in focus.
So to solve this, you can take a second magnifying glass, and place it at the point where the image from the first is focused. It’s a curved lens, so that means the image is focused onto a single point beyond the lens–this is where you put your eye to see the image in the first magnifying glass. If you put a second glass there and hold it still, you’ll see an even more enlarged image–without sacrificing the size in the middle of the glass that you can see. It looks big, bright, and detailed!
With this concept in mind, imagine those magnifying glasses are built inside of the microscope. The first lens is called an “objective” and the second is called an “eyepiece.” The objective is close to a sample, and is what initially picks up the image, where the second one is what focuses it and magnifies it further so your eye can see it. This is true for any microscope, and even telescopes (which use concave lenses instead of convex lenses, allowing you to see far off stars and planets as if they were very close).
Now, since the samples are very small, and light takes space, you need a light source of some kind to emit light into the objective in order for it to do its job. Without any light, it has nothing to magnify or focus. So that’s why you need a light source that’s appropriate for your sample–from the top if you have an opaque object (called reflected light), or from the bottom if you have a translucent object (called transmitted light). Shining light through an opaque sample won’t work since it will just bounce off, so you won’t get any light in the objective–and that’s no good. Having reflected light on a translucent sample will just pass through it, so you might not be able to see anything, or if the base reflects light back, it might not give you a detailed enough image to see your cells–also not good.
Detail in a microscope is what everyone is concerned with, and that’s determined by the resolution of a microscope. This is measured by a specification called a numerical aperture, or NA rating for short. This is a bit more complicated as it involves trigonometry, but we will get into defining that below. Just know that the higher the NA rating, the more resolution a microscope has, which means you can see (or resolve) much smaller details of your sample than a lower NA rating microscope can.
Also, a microscope is more than just two lenses. Generally, there is a prism in the microscope head that functions simply to redirect the light from the objective up to the eyepieces. This allows the microscope’s ocular tube to be angled comfortably for viewing seated or standing (30 degree angled tubes are more comfortable for sitting generally, while 45 degree tubes are better for standing).
I’m still not sure what microscope I need. What do I need to get to view _______?
While you can feel free to send me an email or leave me a comment below, and I’ll be happy to help offer all the assistance I can, here are a number of the more specialized kinds of microscope and a brief description on each. If you click the link there, it will take you to an information page with more specific information on that unit.
Note that this section is still under construction as I have time, so if you don’t see an answer that you need, send me a message and I’ll be happy to help you one on one!
1. Compound Microscopes – Like what you see in a lab, a microscope that views slides with a bright background. There are many types of compound microscopes, for more specific applications.
1a. Darkfield Microscopes – These are compound microscopes with a special condenser (what focuses the light onto the slide underneath the stage) that lights the samples from an angle around a surface that blocks direct light, giving you a dark background. Used commonly for live blood analysis.
1b. Phase Contrast Microscopes – These are compound microscopes with a set of special condensers and objectives that allow you to shift what wavelength the beam of light hits your eye or camera, which makes mostly translucent samples now visible. Commonly used to inspect urine crystals, saliva samples, and water for contaminants (such as sewage treatment plants).
1c. Metallurgical Microscopes – Compound microscopes with a twist–these have special lighting systems that sends the light down through the objective and reflects back up through the objective, letting you see high magnification values on opaque objects. Commonly used for fault inspection, coating thickness inspection, silicon wafer inspection, and other “metalline” sample viewing.
1d. Inverted Microscopes – Inverted microscopes are flipped around, with the objectives on the bottom and the light on the top. This lets you see samples inside beakers, flasks, and petri dishes that would not normally fit on a compound microscope stage.
1e. Polarized Light Microscopes – When one uses cross polarized light to shine onto a sample with minerals in it, the different elements in the mineral shine different colors, which allows a skilled user to differentiate what kinds of minerals are inside the sample material being viewed.
2. Stereo Microscopes – These are low power microscopes that offer a 3D, “stereoscopic” image, allowing one to inspect opaque objects (they have top lights at minimum) that have depth to them with accuracy. They can be used for a large variety, and are common for hobbyists–things like coins, rocks, stamps, bugs, circuit boards, stone setting, engraving, gun cleaning, and watch repair are all common uses for a stereo microscope.
2a. Inspection Microscopes – These kinds of stereo microscopes are the most versatile ones, as there is a huge variety of items that can be inspected. They are usually simpler than most, and can even have only a single ocular tube and path of light since they are meant to quickly and easily check a sample.
2b. Dissecting Microscopes – These microscopes typically have top lights, but can from time to time have bottom lights also. They’re characterized by their large, flat stages meant to hold the sample that is being dissected, and generally have little else below.
2c. Gemology Microscopes – Gemological stereo microscopes are meant to help with stone inspection and stone setting. These are more advanced in that they have an iris and darkfield condenser on the bottom light source, and usually a set of on stage tweezers to hold the stone in place.
2d. Industrial Microscopes – These microscopes are heavy duty in nature, and typically have long reaching boom arms or articulating arms. They’re meant to be used for working on circuit boards, welding, or inspection of industrially machined parts for quality assurance. They can be used by hobbyists as well, however, as they are not more complicated than inspection microscopes.
2e. Common Main Objective Microscopes (CMO) – Common main objective stereo microscopes use a different type of light path. They use one single objective, much like a compound microscope does, in order to provide the exact same image to the various eyepieces. This is done to provide a clearer image to the user of a flat plane, and is generally not intended to be used for items where depth needs to be measured.
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