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Don’t just see red

SCHOTT’s new filter glass VG20 ensures a clear view while protecting against laser beams

Infrared lasers are playing an increasingly more critical and common role in medical and industrial applications, so much so that desired attributes of modern protective eyewear have expanded. In addition to being comfortable, lightweight and, of course, providing safety, it’s important that the eyewear conveys true color to the human eye. As a result, SCHOTT has developed the 1 mm thin, band-pass filter VG20 – an exceptionally lightweight, special filter glass that displays strong absorption in the near infrared (NIR) range.

VG20’s outstanding transmittance in the visible spectrum ensures the colorfast eyesight that today’s industrial and medical applications call for. At the same time the solid-colored glass safely provides the important protection from laser beams our delicate eyes require, comfortably and regardless of the angle of incidence. "By bringing more color into the glass, we have been able to produce a very thin optical filter that keeps radiation in the wavelength range of 600 – 1100 nm away from the eye," explained Dr.-Ing. Ralf Biertümpfel, Application Manager Filter Glass at SCHOTT Advanced Optics. "For laser safety eyewear, VG20 offers improved wearing comfort – it’s roughly one third lighter than conventional filter glass."

VG20 is extremely transparent in the visible range of the electromagnetic spectrum, conveying true colors with very little darkening. The cut-off wavelength λ05, at which the glass has a transmittance of 50 percent, is at 565 nm and then drops steeply. The green glass is suitable as protection from red and NIR lasers in a wavelength range above 650 nm, such as those lasers used in metrology and medical technologies. In wavelengths of 750 – 1100 nm, it is nearly impenetrable. In addition, the filter glass is highly climate-resistant: it stays moisture- and heat-proof, permanently transparent, and corrosion-free for hundreds of hours. The filter properties can also be optimized with additional coatings to address customer-specific applications.