What is Ultraviolet Microscopy?

By Yolanda Smith, B.Pharm.Reviewed by Afsaneh Khetrapal, BSc

Ultraviolet (UV) microscopy is a type of light microscopy that utilizes UV light to generate a magnified image of the sample being analyzed. As a result of the shorter wavelength of UV light than visible light, it is possible to view samples with greater magnification and resolution.

Light source

There are six main sub-categories of light microscopy, which include:

• Bright field microscopy
• Dark field microscopy
• Ultraviolet microscopy
• Fluorescence microscopy
• Phase contrast microscopy
• Differential interference contrast (DIC)

UV microscopy is a type of light microscopy that uses UV light to view samples at a greater resolution than is possible with visible light. The light source typically ranges from deep blue to UV light wavelengths (180-400 nm) to give a magnification approximately double that which can be achieved with white light.

Purpose of ultraviolet microscope

There are two primary advantages which the use of UV microscopy can offer; improved image resolution and increased contrast enhancement.

The resolution of an optical microscope depends on the wavelength of the light source. The short wavelength of UV light helps to improve the image resolution beyond the diffraction limit of optical microscopes using normal white light.

The response of the sample to UV light is greater than that achieved by use of white light, in respect to the surroundings. As a result, there is an increased contrast in the image created by the microscope so that it is easier to view the samples.

Microscope resolution with ultraviolet light

UV microscopy uses UV light as the source for the microscope, rather than visible light. UV light has a wavelength between 180 and 400 nm, which is less than the wavelength of visible light (400-700 nm).

The resolution power of a microscope is directly proportional to the wavelength of the light. This means that it is possible to observe smaller objects with a light source that has a smaller wavelength. In fact, UV microscopy is able to produce magnification of images to a high resolution, approximately double that of visible light.

History

Early in the twentieth century, two scientists from Germany named August Köhler and Moritz von Rohr, were the first to develop UV microscopy. They used the concept of the shorter wavelength of UV light to extend the possibility of creating a microscope with a higher resolution than traditional optical microscopy.

The glass lenses usually used in optical microscopes created a cloudy or unclear image when used at the shorter wavelength of UV light. As a result, it was necessary to make some changes to accommodate the type of light being utilized. In particular, a reflecting microscope with quartz lenses was a solution to this problem.

This interest in UV light in microscopy techniques may have helped to bring about the introduction of electron beam microscopy. It was recognized that an electron beam could be used as a source of very short wavelength and the possibility to create images of a sample with even higher resolution, beyond the diffraction limit of visible and UV light.

Fluorescence microscopy

UV microscopes have commonly been used in fluorescent microscopy. In this case, the UV light that reflects the image of the sample stains to the fluorescence to create an image that can be viewed.

References

1. https://www.britannica.com/technology/microscope/The-theory-of-image-formation#ref986433
2. http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2672.1958.tb00127.x/epdf
3. https://link.springer.com/chapter/10.1007%2F978-3-642-74065-7_8#page-1

Further Reading

• All Microscopy Content
• Advances in Fluorescence Microscopy
• Applications in Light Microscopy
• Electron Microscopy: An Overview
• Brief History of Microscopy