Passive imaging
~ devices depend on light coming from the scene, using a video camera with a filter
~ sensitivity of system is subject to ambient conditions, such as temperature and amount of light
Active imaging
~ system uses fiber laser input for illumination, which enables it to function independently of ambient conditions
~ CO2 lasers cannot illuminate several of the primary gases of interest to industry, such as methane or other hydrocarbons
~ a hydrocarbon leak detector device has been developed for use in petroleum refineries and a natural gas (methane) imaging system
~ both systems use a technique called backscatter absorption gas imaging (BAGI) to illuminate a scene with infrared (IR) laser radiation
~ any target gases present in the scene absorb the laser light, creating dark clouds in the video image of an IR camera
~ portable imager makes a gas plume visible to an operator via a real time video picture
~ instrument rapidly scans a two-dimensional area, accelerating the gas survey procedure

Two methods of optical imaging by Sandia

Benefits
~ could reduce costs, minimize gas lost to leaks, and improve safety margins in the gas industry
~ imager device would be suitable for a variety of operational scenarios
~ a handheld device, rather than a vehicle mounted one, offers greater flexibility in detecting gas leaks in tight places,
~ including leak detection in production facilities (e.g. natural gas compressor stations)
~ and leak location assistance during excavation activities
~ it should be possible to extend this concept to detect other harmful or toxic gases and vapors in the environment
~ future areas of development include measuring gas concentrations to a high degree of specificity,
~ using alternative laser sources, and reduction of detection threshold
~ targeted customers are in the petroleum and petrochemical industries