Active remote sensing of atmospheric gases or smoke using a time-of-flight sensor

Abstract

An active remote sensing system comprises near-infrared laser diodes including one or more Bragg reflectors and having a pulsed output with duration between 0.5 to 2 nanoseconds. A first lens receives and directs the laser diode light to an object or an atmosphere. A detection system receives light reflected from the object or atmosphere, which comprises a second lens and spectral filters in front of a photodiode array. The detection system is synchronized to the laser diodes and performs a time-of-flight measurement. The time-of-flight measurement is performed at least in part by measuring a temporal distribution of photons in the light reflected from the object or the atmosphere. The signal-to-noise ratio of the measurement or reflected signal may be improved using change detection or increasing light intensity or optical power density. In another embodiment, an object may be identified based on water absorption measured at two wavelengths.