Remote sensing of vehicle emitted carbon oxides employing wavelength modulation spectroscopy and a segment modulation method

Vehicle exhaust emission is one of the major atmospheric pollution sources. Excessive emitters, which make up 10 percent of all vehicles, contribute more than half of the total pollution emission. To identify these excessive emitters, a remote-sensing device (RSD) with a laser wavelength around 1580 nm is built. To increase the system sensitivity, a segment modulation method is proposed so that the 2f signals of CO2 and CO can be optimized, respectively. In vitro tests show that the linearity reached .999 and .998 for CO2 and CO, respectively. A field test is also conducted to monitor the dilution process of exhaust emission after the vehicle passes the RSD.