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Don't be blinded

The new VG20 filter glass from SCHOTT effectively protects people, as well as devices, against harmful infrared radiation

The human eye, as well as electronic components, must be protected from extremely intense infrared radiation during a variety of technical processes. No other filter glass can do this as effectively as the new VG20 from SCHOTT. VG20 begins absorbing 50 percent of the radiation at 565 nm, a yellowish green color, and blocks a thousand times better than conventional glass at an infrared wavelength of 850 nm.

“Following further, sophisticated development of our production technology, we managed to completely rid this glass of bubbles and striae (or streaks) so that it meets even the highest optical requirements,” explains Dr. Ralf Biertümpfel, Application Manager for Filter Glass at SCHOTT Advanced Optics. This also makes VG20 extremely climate resistant, remaining transparent and free from corrosion even after hundreds of hours in an 85 °C environment with 85 percent humidity.

For this reason, VG20 can be utilized in difficult environmental conditions. For instance, it can be paired together with residual light amplifiers in devices used by hunters, police officers, rescue workers and helicopter pilots. Residual light amplifiers are particularly sensitive within the infrared range, helping the user find his way in the dark, or search for either a person or wild game. But the illuminated displays of these devices — even light from a watch, smartphone or flashlight — can become a problem, as their intensive infrared radiation increases just as proportionally as that of a distant person. The residual light amplifier turns this into a bright, blinding spot on the screen. If a hunter’s watch or the displays inside a helicopter are covered with the VG20 filter glass, however, they can still be read without difficulty.

CCD sensors that record images in digital cameras and smartphones also require an effective infrared filter like VG20 because they react more sensitively to red and infrared radiation than the human eye, causing hot objects to be displayed much too brightly. Because VG20 blocks out red radiation to some degree and infrared radiation completely, the spectral sensitivity of the sensor adjusts to match that of the eye. A positive side effect here is that, due to the strong filter effect of VG20, the protective glass layers can be thinner, allowing the optical systems to be built more compactly. This suits the needs of an electronics industry that is interested in pursuing even greater miniaturization.