In 1981, a Swedish manufacturer named Hornell introduced the Speedglas Auto-Darkening Filter, an LCD electronic shutter that darkens automatically when sensors detect the bright welding arc.
With such electronic auto-darkening helmets, the welder no longer has to get ready to weld and then nod their head to lower the helmet over their face. The advantage of an Auto-Darkening Filter (ADF) versus a traditional passive filter is that the welder does not need to adjust the position of welding helmet manually which not only saves time but also reduces the risk of exposure to the extremely bright and harmful light generated by the welding process.
In January 2004, 3M acquired all assets of Hornell, including the Speedglas auto darkening helmets brand name and patents. Speedglas helmets are now sold by 3M.