Optical filters on linear halogen-lamps prepared by dip-coating

Spectral intensity distributions of linear incandescent lamps are tailored to special applications by means of reflecting as well as absorbing multilayer filters. A dip-coating technique is used for deposition of films on the outside of tubular lamp envelopes. Film thickness homogeneity is within < 3%. With this technique a variety of high refractory oxides can be used. Coatings on quartz-glass are investigated. SiO2 is used for layers of low refractive index, oxides of Ti, I-if, Zr, Nb, Ta and their mixtures are used for layers of high refractive index and Fe2O3 for absorbing layers. Infrared reflecting filters for use up to 1000 degrees C and of about 8 mu m total thickness are prepared by using TiO2 . Ta2O5 as high index material. Lamps with these coatings are produced for process heating, for lighting and for personal warming at reduced glare. (C) 1997 Elsevier Science B.V.