Driven by applications from the automobile industry, the prices for thermal imaging cameras have fallen dramatically in recent years. The technology has now reached the mass market, for example as a thermal imaging add-on for smartphones. The industry also benefits from this development in the monitoring of welding processes with CO2 lasers. The advantage is obvious: errors such as welding spatter or hairline cracks are detected more quickly.
Today's thermal imaging cameras are based on bolometer arrays that detect radiation in the range of 8-12 µm. CO2 lasers emit at 10.6 µm. Their wavelength is therefore perfectly seen by these cameras, and the intense laser light overshadows the processes actually observed. The infrared eye is blinded.
A so-called notch filter that “hides” specific wavelengths, provides a remedy. To date, such filters have been widespread in the Vis and NIR range and are mainly used in Raman laser spectroscopy or confocal microscopy. For wavelengths in the medium and long infrared range only a very small product range has been available thus far. However, a notch filter is currently being developed that is precisely tailored to the radiation of CO2 lasers. At 10.6 µm, the design provides for selective attenuation by a factor of 1000, while the entire thermal image is only approx. 20% darker. Approximately one-third of this darkening is due to the fact that the 250-nm-wide band elimination filter also almost completely suppresses a very small part of the useful signal around the notch.
The filter is designed as an accessory for professional thermal imaging cameras. If you are interested in this new product, please contact us in advance.
