Microscopes have gained immense popularity since the first light or simple microscope was invented in the late 1670s. These tools are essential for scientists, biologists, teachers, or students, to see tiny objects that are otherwise invisible to the naked eye. Nowadays, microscopes have reached such an advanced stage that you can even see a particle as small as the size of an atom.
These tools are broadly utilized in different fields, including medicine, microbiology, biology, chemistry, and genetics. Various parameters are observed while buying a new type of microscope as it has several parts to play their specific functions and show results. One such is the working distance. This article will explain all about the working distance in a microscope, its importance, and its relationship with other microscope parts.
What is Working Distance?
It is an appropriate distance between the objective lens and the specimen being viewed by the observer. Working distance is always positioned to maintain a clear focus on the sample. There are typically two types of working distances, including the objective and stage. Despite being different, these parameters function together to let you examine a clear specimen image.
Objective Working Distance
The distance that goes vertically from the objective lens to the specimen and results in a sharp image is called the objective working distance. As the name indicates, this distance starts from the objective lens to provide the magnified image of the sample. However, some microscopes add the thickness of the slide to be included in the total distance.
Stage Working Distance
As the name suggests, the stage working distance refers to the vertical distance that focuses the specimen by moving the microscope stage. Together with the objective working distance, it works to provide a viewable image of the specimen. Both of these distances help an observer check the thickness or size of the sample.
Importance of Working Distance
Like other parts of a microscope, working distance also holds great significance, such as providing ease of use. The type of specimen, microscopic or large, decides the length of the working distance. There is always a sufficient space between the lens and the sample that quickly lets the light pass through it to create a good focus; thus, it is essential. Scientists or researchers planning to observe large specimens set their microscopes at longer distances that help them perform procedures such as dissection. It can be further explained by taking an example of a dissecting microscope. Here, a longer working distance is necessary to allow room for dissecting tools and prevent specimen damage during an examination.
Similarly, shorter working distances are positioned to view smaller specimens, such as germ cells. These short distances require higher magnification and resolution for better accuracy as the objective lens is closer to the specimen under observation. However, it can be challenging to maintain a good focus through shorter distances due to requiring more precision.
Relationship of Working Distance with Magnification
The increase or decrease in the working distance of a microscope has a direct effect on the magnification. A microscope with higher magnification, such as 2000x microscopes, has a shorter distance, usually seen to be 9mm. While on the other hand, a lower magnification objective lens has a longer working distance that is typically used to view large samples, e.g., for research.
Relationship of Working Distance with Resolution and Depth of Field
The field depth is the point where the observed specimen appears large. The working distance of a microscope directly affects the resolution and depth of field as it determines the accurate distance between the lens and sample. A longer working distance results in a greater depth of field, which means more specimen is easily focused. Just like that, a shorter working distance works best for a shallower depth of field, such as bees hovering over a flower.
The Bottom Line
A microscope’s working distance is crucial as it promotes ease of use and defines the magnification. Other than that, the intensity of magnification and resolution also depend on this distance. It is essential to consider the working distance when selecting a microscope for a specific application to ensure it is suitable for its intended use. A longer working distance benefits larger specimens, whereas a shorter one is useful for higher magnification and better resolution. It should be carefully considered when selecting a microscope for a particular function.
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