How Auto Darkening Welding Helmet Filters / Lens Work


Auto-Darkening Filters (ADF) turn dark the moment an arc is struck and transparent again when welding stops – all the time with full UV/IR protection. Auto Darkening Welding Filter / Lens was invented by Dr Ake Hornell, Sweden in 1974. Each filter is a laminate of different layers: a UV/IR filter (A), three polarizers (B) and three liquid crystal elements (C). The UV/IR filter continually blocks harmful radiation, regardless of whether the filter is in the light or dark state or whether the auto-darkening function is operational. Aided by surface-mounted electronics, the liquid crystal elements act as shutters that detect and react to the welding arc by instantly becoming either dark, or light, as needed. Liquid Crystal Elements ( C ) twist the light on getting signal from Arc Sensors as per need through Electronics. The level of protection from the UV/IR filter is constant; equivalent a shade 13 passive welding filter.
Before Welding:
With the auto-darkening welding helmet in the safe down position, you can clearly see through the welding filter. Both of your hands are free and the electrode can be precisely positioned.
During Welding:
Within 0.0001 Second ( at room temperature) of the arc strike, the filter is switched to the dark state.
After Welding: 
The filter automatically returns to the light state after welding is complete, allowing your immediate and safe inspection of the weld pool, as well as preparation for the next weld.
Good Quality Welding Helmets incorporating auto-darkening filters confirms to the European Standards EN 175, EN 166 and EN 379 as well as many National Standards.
For More Details:

R B Khatri, Director India
Aketek Industries AB Sweden

Polariser Films ( B ) Helps in Auto Darkening