Design and performances of a mid-infrared CH4 detection device with novel three-channel-based LS-FTF self-adaptive denoising structure

A novel mid-infrared (MIR) CH4 concentration detection device using three-channel-based least-square fast transverse filtering (LS-FTF) self-adaptive denoising structure was proposed. By introducing an additional noise-channel besides the traditional detection-channel and reference-channel, the noises can be well removed using the LS-FTF denoising algorithm. The detection procedure was described, and the key modules including the optical part and electrical part were designed and fabricated. Thorough experiments performed for the fabricated device show that the absolute detection error is less than 5%, and by quantifying the detected voltage using software, the minimum detection level is 8 ppm and the detection sensitivity is 9 ppm within the detection range of 8–1000 ppm. The measured maximum response time is less than 10 s, and the absolute detection error with temperature-compensation is less than 5%. The proposed three-channel-based LS-FTF denoising structure can also be adapted to other similar detection systems for noise elimination.