| 摘要 |
The invention relates to an optical device for concentrating light of selectable frequency or frequency band, consisting of a body (11) made from optical material, for example glass having an outer surface (13) through which the light to be concentrated enters the body, there being provided in the body a tubular cavity (12) into which the light is refracted and in which the light is directed in the longitudinal direction (10) of the tube, possibly with multiple total reflection on the cavity inner wall, to the light exit end (14) of the tube. <IMAGE>
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