Making the invisible visible

October 8 is World Sight Day. On this occasion, we want to explore inventions that make the otherwise invisible visible.

October 8 is World Sight Day. On this occasion, we want to explore inventions that make the otherwise invisible visible.

We live in a world in which seeing is the most important sense. From screens to road signs, many objects that surround us every day would lose their purpose if we could not see them. Yet, there are even more things we cannot see than things we can see. Be they very small like viruses, bacteria or even atoms, or very distant like the stars of other galaxies.

It can be especially challenging to see in harsh environments with high temperatures, dangerous or chemically volatile substances, or areas not accessible to humans. However, various branches of industry need to be able to see in these particular places.

Tokamak fusion reactors, for example, use a powerful magnetic field in a ring shape to confine hot plasma. This presents a very challenging environment for imaging, as the strong magnetic field of the reactors will erase images acquired with a traditional digital camera. Another example is steel mills, where temperatures are hot enough to melt plastic and prevent digital cameras from operating properly. Nevertheless, it is necessary to check for spills when cranes are transporting hot fluid iron in large buckets.

For these tricky environments, image bundles can offer a flexible, but robust solution. They can be used in tight spaces and also withstand high temperatures and hazardous chemicals. At the same time, they do not interfere with electricity or react to magnetic fields. Because they use light and no electricity, optical fibers can reach distant positions and close gaps between a camera and an area that needs to be imaged.

These image bundles consist of thousands and thousands of wafer-thin glass fibers, with each individual fiber guiding exactly one pixel. To transport an entire image, the fibers at the beginning and end of the cable must be arranged in exactly the same configuration.

Glass fibers arranged in the same way at both ends of a cable can transport images.
Tokamak reactors present a very challenging environment for imaging.

Fiber bundles are used in many areas. For example, endoscopes are equipped with fiber optic bundles that transport images from the inside of the body and make them visible to doctors. The glass fibers offer the advantage that they can withstand the high temperatures involved in sterilization and can be disinfected easily. Furthermore, they do not emit any substances and are biocompatible.

Another area of application is police operations. Glass fibers are used in night vision goggles that help police officers see in the dark. Night vision uses a process called residual light amplification in which the residual light in a dark room or outdoor environment is converted into electrons. However, the process produces an upside-down image — not exactly practical when hunting down criminals. This is where image bundles that invert pictures can help. Again, the arrangement of the glass fibers is decisive: instead of running parallel to each other, the bundle of fibers is twisted to turn the image around.

From glasses to light bulbs to microscopes, many objects help us see in everyday life. The somewhat trickier applications, however, are handled by glass fibers.

08. Oktober 2020

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Dr. Haike Frank
Lighting & Imaging
SCHOTT AG

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