LED ILLUMINATION LAMPS
Light emitting diode (LED) arrays are the most convenient and cost effective means to excite the pressure and temperature sensitive paints to fluorescence. Using the correct light source is critical to the accuracy of the measurement. PSP and TSP require a sufficiently energetic, low noise, stable illumination source if quality pressure data is to be acquired. Any variation in output illumination from the excitation source will look like a pressure change to the camera. ISSI LED arrays contain proprietary optical and electrical filtering to achieve very stable illumination for excitation of our paints.
Molecules within the paint layer are excited by a narrow band LED light source of a specific peak wavelength. Once excited, these molecules will either fluoresce, emitting a photon of a longer wavelength, are quenched by local oxygen molecules (pressure sensitive paint) or are thermally quenched (temperature sensitive paint). This quenching rate determines the fluorescent intensity of the paint layer. The fluorescent levels can be used to estimate pressure or temperature using a previously determined calibration of the paint.
LEDs are available in 2-, 3- and 4-inch sizes and with air-, vortex- or water-cooling. Each model is also available with one of two drivers. The DM driver is used to operate the LED in long-pulse or continuous mode and the DMHP driver is used for short-pulse, high power mode. Each LED head can be driven with either of the available drivers. All models of LEDs are available in 400- and 460-nm wavelengths.
ISSI LEDs Mounted on Wind Tunnel PSP Test (Left), ISSI LEDs Mounted in Fast PSP Flight Test with Calspan Corporation (Right)