Remote sensor detects alcohol-impaired drivers

Dec. 1, 1995

2 min read

A sensing device capable of remotely monitoring the atmospheric alcohol content within moving cars has been developed by engineers at Science Applications International (Torrance, CA) working with researchers from the University of California (Los Angeles, CA) and AT&T Bell Laboratories (Murray Hill, NJ). Described in paper MS2.4 at the Lasers and Electro-Optics Society (LEOS) 1995 Annual Meeting (San Francisco, CA) in November, the laser alcohol analyzer is based on wavelength modulation spectroscopy and uses a III-V distributed-feedback tunable single-mode diode laser to monitor alcohol absorption in the 1.392-µm wavelength range. In operation, the injection current of the diode laser is sinusoidally modulated causing the laser output to scan over the absorption line of alcohol. The laser output passes through the passenger compartment of the moving vehicle and is detected at the other side. When the detector output signal is mixed with the laser modulation signal, all the harmonics of the modulation frequency are recovered and allow measurement of the absorptivity, which is related to alcohol concentration.

According to the system`s developers, a breadboard laboratory set up can detect 5 µl of alcohol in a 1-m3 air sample and demonstrates the feasibility of law-enforcement authorities using the analyzer for sobriety check-point applications. The ability to screen vehicles without stopping them would eliminate many of the disadvantages of currently used random check points where all vehicles must stop for a driver sobriety check.