U.S. Philips Corporation

Gunter Frank

Heiner Kostlin

Bruno Vitt

Ronald J Campbell

Hans Auding

Leo M Sprengers

Lieselotte Brock

The optical interference filter is assembled from alternating amorphous SiO.sub.2 layers and layers made of mixed oxides chosen from

Optical interference filter

A thin-film heating element is formed of a temperature-stable, electrically insulating substrate having a thin, electrically conductive metal oxide film which is doped with foreign atoms which compensate each other in pairs and which each consist of at least one acceptor-forming element and one donor-forming element the metal oxide film being provided with connecting electrodes; the metal oxide film being doped with maximally 10% of each of the foreign atoms compensating each other in pairs, the quantity of the atoms differing maximally 10%.

Thin-film heating element

A method of making a heat-reflecting filter consisting of a tin-doped indium oxide layer on a carrier. A tin-doped indium oxide layer is provided on a carrier by spraying a heated carrier with a solution of an indium salt and a tin salt. The layer is then reduced at 350.degree.-400.degree. C. by means of a gas flow of hydrogen, nitrogen together with oxygen or air.

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Aachen, Germany

Gunter Frank