Compact Infrared Bandpass Sampling Fourier Transform Spectrometer and Stepwise Continuous Spectrum Reconstruction Method

To overcome the limitations of complex dispersion structures, low diffraction efficiency at band edges, and continuous spectral aliasing in dispersion-interference coupled static Fourier transform spectrometers operating in the 3–5 μm mid-infrared band, a compact bandpass sampling Fourier transform spectrometer based on a horizontal roof mirror and a segmented blazed grating with differentiated blaze angles (HRMSG-FTS) and a stepwise continuous spectrum reconstruction method (SCSR) were proposed. The HRMSG-FTS integrates dispersion and compensation through dual-pass coupling of the segmented blazed grating and the horizontal roof mirror, thereby reducing system complexity and improving diffraction efficiency at the band edges. Simulation results show that the HRMSG-FTS achieves a spectral resolution of 0.625 cm−1 while significantly reducing the longitudinal system size, and improves diffraction efficiency at the band edges by more than 20% compared with a single-blaze-angle grating. To mitigate continuous spectral aliasing, the SCSR method progressively decouples and accurately reconstructs the aliased spectrum. Simulations show that the reconstruction error coefficient is reduced from 0.683 to 0.031, and the effectiveness of SCSR is verified experimentally. The proposed system and method combine compactness with high accuracy and are suitable for applications such as airborne atmospheric monitoring, industrial gas detection, and portable infrared spectral analysis.