Opt. Express 25, 2998–3005 (2017)

The ability to image the presence of invisible gases has applications in industrial and environmental monitoring settings. Now, Graham Gibson and co-workers from the University of Glasgow and M Squared Lasers Ltd, UK have developed a real-time imaging system for gas leak detection based on a single-pixel detector and structured illumination. Light from an InGaAs laser diode was sent to a scene containing a methane gas cell with two tubes to collect any gas leaks. A set of orthogonal mask patterns and their corresponding inverse patterns were generated by a high-speed digital micromirror device (DMD). The total intensity of the backscattered laser light from the scene was detected by an InGaAs photodiode that was synchronized with the the DMD. For every alternative reconstruction frame, the wavelength of the laser diode was electrically tuned away from the methane absorption transition at 1.651 μm. By taking the difference of the single-pixel intensity measurement between alternate frames, images were obtained of the gas only. The gas image information was aligned and overlaid on images from a high-resolution, colour CMOS camera. Images with an effective 16 × 16 pixel resolution could be reconstructed at a frame rate of 25 Hz, allowing the source of the leak to be easily identified.