Monitoring single parameter evolution over the course of interferogram acquisition in FTIR systems: Application to gas leak measurement

This study presents a novel methodology for retrieving the temporal evolution of a single physical parameter throughout the course of measurements conducted with imaging-FTIR systems. Rather than operating in the spectral domain, the proposed approach performs parameter fitting directly in the interferogram (i.e., the time or Optical Path Difference (OPD) domain). The method is based on a linearization of the incoming radiance, formulated as a function of a single parameter. This enables the decomposition of the interferogram into an average component and a fluctuating component. The calculation of the derivative of this component with respect to the parameter of interest makes it possible to retrieve the instantaneous value of the parameter. Validation is conducted via numerical simulations and subsequently applied to a real-world scenario involving a gas leak, where the fluctuating parameter is the column density of the gas. By achieving temporal resolution within a single measurement, this methodology addresses the inherent temporal resolution limitations of imaging FTIR systems. These advancements significantly enhance the applicability of FTIR systems for studying the temporal dynamics of scenarios requiring high temporal resolution. • This work introduces a method to retrieve a parameter’s temporal evolution (e.g., gas column density) during an FTIR measurement. By achieving temporal resolution within a single measurement, the proposed approach addresses a weakness of imaging FTIR systems: their low temporal resolution. • Instead of operating in the spectral domain, this methodology is based on fitting the interferogram directly in the time or Optical Path Difference domain. • The method is applied to a real gas leak scenario, successfully retrieving the gas column density over time.