Browsing by Author "Gibson, Graham"

Now showing 1 - 2 of 2
  • Thumbnail Image
    ItemOpen Access
    Imaging of methane gas using a scanning, open-path laser system
    (IOP Publishing Ltd, 2006-02) Gibson, Graham; van Well, Ben; Hodgkinson, Jane; Pride, Russ D.; Strzoda, Rainer; Murray, Stuart; Bishton, Steve; Padgett, Miles
    We have developed an imaging system for the detection and visualization of methane gas leaks. The system is based on a distributed feedback InGaAs laser diode emitting at 1.65μm, the beam from which is directed at neighbouring objects. The backscattered light is collected by a Fresnel lens and the gas concentration is deduced from the reduction in collected intensity as measured using a second derivative wavelength modulation technique. The incident laser and the collected beam are both scanned over an area to form an image of the gas emission. To ease the task of locating the source of the emission, we combine the resulting low-resolution image of the gas emission with a high-resolution colour image of the scene. Our results show that the system can image a gas cloud of 1mm effective thickness at a range of several metres, sufficient to detect a gas leak of 1 litre min−1 in light to moderate winds.
  • Thumbnail Image
    ItemOpen Access
    An open-path, hand-held laser system for the detection of methane gas
    (Institute of Physics, 2005-06) van Well, Ben; Murray, Stuart; Hodgkinson, Jane; Pride, Russ D.; Strzoda, Rainer; Gibson, Graham; Padgett, Miles
    We have developed an open-path hand-held gas detector incorporating a distributed feedback InGaAs laser diode at 1.65 µm. Incorporated into a hand-held transceiver unit, the emitted laser beam is backscattered from nearby surfaces, collected and focused onto an amplified InGaAs detector using a 150 mm diameter plastic Fresnel lens. At ranges of 4–5 m, a typical backscattered signal is tens of nanowatts of laser light. Applying second derivative wavelength modulation spectroscopy gives a sensitivity to methane of better than 10 parts per million over a one metre path length. A number of demonstration units have been fabricated and successfully evaluated by end users.