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Applied Optics

Applied Optics


  • Vol. 35, Iss. 7 — Mar. 1, 1996
  • pp: 1088–1094

Fast, automatically darkening welding filter offering an improved level of safety

Stephen Palmer  »View Author Affiliations

Applied Optics, Vol. 35, Issue 7, pp. 1088-1094 (1996)

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A mode of operation is introduced for the standard 90° twisted nematic (TN) liquid-crystal cell when placed together with an interference filter and positioned between crossed polarizers such that a small stimulating voltage of between ±2.0 and ±3.0 V is required in order to attain the light state. Further incrementation of the driving electronics reverts the system back to a darker phase. Such cells offer advantages over those of the standard 90° TN device operating in the normally white mode, in that the unit maintains the fast response time from the light to the dark state associated with the employment of TN cells placed between crossed polarizers. In addition, a low transmittance state is achieved when the unit is in the inactivated phase; this is an effect usually correlated with the normally black mode of operation. These cells are therefore ideal candidates for incorporation into fast, automatically darkening, welding filters that are designed to change rapidly from the light to the dark protective state, while offering an improved level of safety by not holding in a potentially hazardous light state should the controlling electronics malfunction. The requirement for this phenomenon to be observed is that the cell displays a low optical transmittance over the green wavelengths of the visible spectrum when in the inactivated phase and placed between crossed polarizers. The presence of an interference filter that possesses a peak transmittance over the central part of the visible spectrum is also necessary. It is shown that there are only two possible cell types that satisfy this criteria, and the optical properties of such cells are analyzed in some detail.

© 1996 Optical Society of America

Original Manuscript: January 25, 1995
Revised Manuscript: May 30, 1995
Published: March 1, 1996

Stephen Palmer, "Fast, automatically darkening welding filter offering an improved level of safety," Appl. Opt. 35, 1088-1094 (1996)

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  1. Hörnell Innovation AB, Tunavägen 281, 781 73 Borlänge, Sweden.
  2. B. Bahadur, Liquid Crystals: Applications and Uses (World Scientific, Singapore, 1990), Vol. 1, Chap. 12.2.3.
  3. H. A. Macleod, Thin Film Optical Filters, 2nd ed. (Hilger, Bristol, 1986), Chap. 5.
  4. C. H. Gooch, H. A. Tarry, “The optical properties of twisted nematic liquid crystal structures with twist angles less than 90°,” J. Phys. D 8, 1575–1584 (1975).
  5. MathSoft, Inc., 201 Broadway, Cambridge, Mass. 02139.
  6. Colorimetry, The CIE 1931 Standard Colorimetric Observer for daytime viewing, Pub. 15 E-1.3.1 (Commission Internationale de L’Eclairage, Paris, 1971).
  7. Deutsches Institut für Normung Standards Taschenbuch, Optik: Augenoptik und Augenschutz (Oskar Zach GmbH, Berlin, 1991), Chap. 1, p. 107.
  8. Lichtmesstechnik, Helmholtzstraße 9, Berlin 10, Germany.
  9. Deutsches Institut für Normung, Westliche 56, 7530 Pforzheim, Germany.
  10. Merck Postfach 41 19, Frankfurterstrasse 250, 6100 Darmstadt 1, Germany.
  11. Dodwell Hi-Tech KK, Kowa No. 16 Annex, 9-20 Akasaka 1-Chome, Minato-ku, Tokyo 107, Japan.
  12. S. T. Wu, A. M. Lackner, “Mylar-film compensated π and parallel aligned liquid crystal cells for direct-view and projection displays,” Appl. Phys. Lett. 64, 2047 (1994).
  13. S. Gunz, L. Ghisleni, “Blendschutzvorrichtung,” European patentEP 0550384 A1 (7July1993).
  14. L. Pohl, G. Weber, R. Eidenschink, G. Baur, W. Fehrenbach, “Liquid crystal display element,” U.S. patent 4,398,803 (16August1983).
  15. L. Pohl, G. Weber, R. Eidenschink, G. Baur, W. Fehrenbach, “Low-Δn-twisted nematic cell with improved optical properties,” Appl. Phys. Lett. 38, 497–499 (1981).
  16. Nitto Denko Corporation, 1-1-2 Shimohozumi, Ibaraki, Osaka, Japan.

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