CHARGING. Charge the IR indicator in daylight, UV or fluorescent light prior to use and recharge when sensitivity drops after IR radiation or self discharge. The duration of charging depends on the intensity of the exciting light. When charging with filtered sunlight it takes some seconds; with moderate twilight it might be several minutes. Especially when charging with incandescent bulbs, it should be regarded that a full charge can only be obtained with IR free excitation light, because the IR part leads to a simultaneous discharge during excitation. To separate the IR and the red part from the exciting light, the combination of the filters BG39 and BG3 from SCHOTT has been proven usefull. As optimal excitation source we recommand the fluorescent lamps DULUX S 9W/71 BLUE and 9W/78 UVA from OSRAM, which can be used without any filter.
INDICATOR OPERATION. The indicator operation corresponds to a discharge of the energy storing phosphor. The discharge is controlled by IR radiation and is shown as a bluish green emission, whose strength is proportional to the intensity of the IR light. The light yield during the discharge is not constant, but decreases continously at constant IR radiation. The discharge duration is inversely proportional the radiant intensity of the stimulated bluish green light. The rise and fall time of the bluish green emission lies in the nanosecond range. To separate unwanted visible parts of the radiation to be examined the filters RG780 to RG1000 from SCHOTT are recommanded. The IR indicator IR-A2 can be used transmissive as well as reflective. Shield surrounding light.
SELF DISCHARGE. As every energy store, the infrared indicator IR-A2 shows a selfdischarge, which can be observed as an extremely weak emission of green light. The intensity of this green emission or phosphorescence depends on the charging intensity and is highest directly after intensive UV excitation. It takes several weeks for a (nearly) complete self discharge; the saturation charge holds some minutes.
INVERSE OPERATION. Here the discharge of the indicator from IR radiation and the self discharge radiation (phosphorescence) are used. Submit the card immeadiately after charging for a well defined time to the IR source, then estimate in the dark. the higher the IR intensity and the duration of radiation, the lower will be the phosphorescence. You may support the phosphorescence by IR radiation of the whole area. Advantage of this operation: Use at visually unaccessible places.
UV DETECTION. The IR indicator IR-A2 transforms UV light directly in bluish grees light. Therfore it can be used as UV indicator for near ultraviolet light.
CAUTION. To avoid eye damage from laser beams, always use laser safety glasses!