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1. (WO2013115970) AUTOMATIC WELDING FILTER WITH TUNABLE SPECTRAL TRANSMISSION

Pub. No.:    WO/2013/115970    International Application No.:    PCT/US2013/021512
Publication Date: Fri Aug 09 01:59:59 CEST 2013 International Filing Date: Wed Jan 16 00:59:59 CET 2013
IPC: G02B 5/20
A61F 9/06
Applicants: 3M INNOVATIVE PROPERTIES COMPANY
Inventors: MAGNUSSON, Kristina, M.
JAREFORS, Kenneth
Title: AUTOMATIC WELDING FILTER WITH TUNABLE SPECTRAL TRANSMISSION
Abstract:
The present invention relates to an automatic welding filter that changes from a light transmission state to a dark transmission state in response to incident welding light and includes a colour-tunable filter whose spectral transmittance can be varied to optimise the visual appearance of a welding task. The colour-tunable filter comprises at least one low twist liquid crystal cell disposed between polarisation filters having substantially parallel polarisation directions. The user is able to adjust the colour of the automatic welding filter in the dark transmission state, independently of the shade, in response to a user selected colour signal which alters the birefringence properties of the low twist liquid crystal cell.