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Different types of microscopes and how they’re used

Microscopes are used to magnify objects (or areas of an object) that are too small to inspect with the naked eye. What kind of microscope you’ll need for your specific sample, however, will depend on many things, including the size and type of your sample, as each microscope is based on different technologies and have different advantages.

In this article, we’ll go through 5 different types of microscope and their varieties to showcase their differences.

Different types of microscopes:

We will also provide examples of how the different types of microscopes are typically used.

Compound microscopes with Transmitted or Reflected light

Although compound microscopes are available in two different versions, both are characterized by their eyepiece and their primary magnification being via objectives and secondary magnification via an eyepiece, usually 10x.

Where the compound microscopes varieties differ however is in terms of light source. With Transmitted light compound microscopes, the sub-stage illumination lights the samples from below, allowing light to transmit through the sample to the lens. Transmitted light compound microscopes can also structure or adapt the illumination system through their sub-stage condenser to provide greater contrast to samples that have none themselves. These microscopes are typically used in biological applications to inspect blood cells, parasites, bacteria, and various kinds of tissue.

If the sample itself is not transparent and requires light illumination from the top to reflect from the sample, a Reflected light compound microscope is used. Examples of applications for the Reflected light compound microscope include metal failure analysis, wafer inspection and anything where light can’t pass through.

When choosing a microscope, it’s important to know that compound microscopes use two lenses to create a two-dimensional image and can typically provide higher magnification levels than stereo or other low power microscopes.

A magnified printed circuit board

Stereo microscopes

Despite its lower working magnification capabilities, stereo microscope are defined by their ability to recreate three-dimensional images of objects via the eyepieces. This is most identical to how the human eye works and is thus a much more natural way to inspect samples where depth perception is important.

Stereo microscopes, in general, also have a longer working distance than compound microscopes, making them ideal for larger samples, and are based around reflected light microscopy.

Stereo microscopes can therefore be used to inspect many types of samples that do not require light to pass through them or are too large to be viewed with a compound microscope. Stereo microscopes are thus used across industries to inspect, assemble, and work on objects as they fit a magnification role and working distance needed for these types of tasks.

Inverted microscope with Transmitted or Reflected light

As opposed to the types of microscopes explained so far, the inverted microscope is special in that it allows the user to place a sample on a flat stage, with the objective placed underneath the stage. The Inverted microscope, however, is similar to the two compound microscopes variants in that it also has both a transmitted and reflected light variety depending on the application needs.

The inverted reflected light microscope allows the smooth side of a non-transparent object, e.g. a piece of metal, to be placed on the stage to prevent the sample from rolling over or rocking back and forth as it’s inspected for fractures and faults.

Although the technology behind the two types of inverted microscopes is practically the same, samples for the inverted transmitted light microscope are placed in a petri dish rather than directly on the stage. This is to allow the microscope to be used in areas such as in-vitro fertilization, live cell imaging and neuroscience.

Two operators inspecting seed using a digital microscope

Digital microscopes

A digital microscope is characterized by not having an ocular or eyepiece. Instead of using a eyepiece, a small sensor is used in the camera to create an optically simpler solution with dramatically broader magnification capabilities.

Instead of viewing the sample trough an ocular, the digital microscope is connected to a computer or monitor with a USB or HDMI cable. This makes image capturing very easy and allows the microscope to utilize software and specialized apps to measure sample sizes directly on-screen and use heads-up displays as part of the sample analysis.

Using a monitor also makes the digital microscope a more comfortable solution as operators can look straight ahead rather than downwards through an ocular. Creating a more comfortable setup can relieve operators of neck and back pain, reduce sick leave days, improve efficiency and overall job satisfaction.

Due to its high image quality and documentation capabilities, the digital microscope can be used for quality control in a variety of industries, including electronic manufacturing, seed analysis, forensics, plastic molding and medical device manufacturing.

 

Field pocket microscopes

Like digital microscopes, Field pocket microscopes (also sometimes referred to as USB microscopes) don’t have an ocular – but they are significantly smaller, more compact and made to be portable.

While being more affordable than other microscope options, the field pocket microscope is compromised in terms of optical quality, lighting and working distance – and quality wise, it’s often subpar to the laboratory based microscopes.

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