Development and characterization of an inexpensive LED-based light source for high-frame-rate schlieren imaging

This work presents characterization results of a 623 nm light emitting diode (LED) based light source developed for low-cost, high frame rate schlieren imaging. The LED was overdriven up to 20 times the rated current while generating 100 ns pulses at a 1 MHz repetition rate. Circuit response, pulse train characteristics, and temperature effects were observed over a large range of input voltages. Relative brightness data was measured with a photodiode and further examined within a schlieren system. Flow visualization of a decaying Mach 3 shock wave were obtained with the system. The wave was produced in a shock tube facility used for aerodynamic measurements. The effect of the light source on image quality, including motion blur are analyzed. Furthermore, shock velocity measurements obtained from the schlieren images are reported.