Super-sensitive explosives detector uses light, sound

摘要

Using a laser and a device that converts reflected light into sound, researchers at the Department of Energy's Oak Ridge National Laboratory (Oak Ridge, TN; www.ornl.gov) can detect explosives at distances exceeding 20 m. The method is a variation of photoacoustic spectroscopy and involves illuminating the sample with an eye-safe pulsed light source and allowing the scattered light to be detected by a quartz crystal tuning fork. "We match the pulse frequency of the illuminating light with the mechanical resonant frequency of the quartz crystal tuning fork, generating acoustic waves at the tuning fork's air-surface interface," said Charles Van Neste of ONRL's Biosciences Division. "This produces pressures that drive the tuning fork into resonance."