An FPGA-based lock-in detection system to enable chemical species tomography using TDLAS

Andrea Chighine , Edward Fisher , David Wilson, Michael Lengden, Walter Johnstone, Hugh McCann

Research output: Chapter in Book/Report/Conference proceedingConference contribution book

16 Citations (Scopus)
792 Downloads (Pure)


This paper presents the design, implementation and test of a compact, low-cost and fully digital signal recovery system for tunable diode laser absorption spectroscopy (TDLAS) in narrow line-width gas sensing applications. An FPGA-based digital lock-in amplifier (DLIA), in conjunction with TDLAS using the wavelength modulation spectroscopy (WMS) technique, is utilized to demodulate and extract first (1f) and second (2f) harmonic signals for a narrow CO2 feature in the spectrum region of 1997.2nm. The spectrum in this wavelength region shows suitably weak water absorption, enabling CO2 detection with high resolution. Gas-cell experiments were carried out using the DLIA and a conventional rack-mounted commercial lock-in amplifier. The comparison between the two systems shows good agreement, validating the feasibility of this approach and demonstrating the prospect for extension to a massively multichannel system to implement Chemical Species Tomography.
Original languageEnglish
Title of host publication2015 IEEE International Conference on Imaging Systems and Techniques (IST)
Place of PublicationPiscataway, NJ
Number of pages5
ISBN (Print)9781479986330
Publication statusPublished - Sept 2015


  • amplifiers
  • chemical variables measurment
  • measurement by laser beam
  • absorption
  • spectrochemical analysis
  • chemical species tomography


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