GB494128A - Improvements in lamps adapted to emit ultra-violet radiation accompanied by substantially no visible light - Google Patents

Abstract

494,128. Colour filters. GENERAL ELECTRIC CO., Ltd. (Patent-Treuhand-Ges. fur Elektrische Gl³hlampen) July 16, 1937, No. 19769. [Class 97 (i)] [Also in Group XI] A lamp, adapted to emit U.V. radiation accompanied. by substantially no visible light comprises a source such as a high pressure mercury vapour discharge lamp, which in operation emits visible light and both long U.V. (of wave-length 3300 to 4000 A.U and short U.V (of wave-length less than 3300 A.U), and at least two different filters chosen from the following kinds, viz : those transmitting (a) both long and short U.V, (b) long U.V only, (c) short U.V only, (d) both visible light and long U.V but no short U.V, (e) both visible light and short U.V but no long U.V, means being provided for introducing alternatively into the beam two filters of the above kinds or two combinations of such filters of which one filter or combination (A) transmits long U.V but no visible light or short U.V and the other (B) transmits short U.V but no visible light or long U.V. In the example shown in Fig. 1, the opening of a parabolic reflector 1 surrounding a high pressure mercury vapour lamp 3 is closed by two filters of which the inner one 6 is of pure " black " glass and the outer one 7, which is removable, of glass transmitting long U.V but not short U.V. Another filter (not shown) which transmits short but not long U.V is provided and can be substituted for the filter 7. Fig. 2a shows a modification in which two filters 8, 9 of the same characteristics as the two outer filters 7 and having a foundation of pure " black " glass, are constituted by the two halves of a rotatable cylinder disposed between the lamp 3 and the reflector 4.