Adjustable-resolution static Fourier transform spectrometer based on coherent real light sources

In this paper, a new static Fourier transform spectrometer based on coherent real light sources is proposed. The system controls the shearing distance of the output beams by symmetrically translating two hollow retroreflectors, after which the beams pass through a rear lens to form interferograms on the detector. Unlike conventional designs that use a slit in front of a beam splitter cube, this configuration employs two real-image light sources formed by lenses to replace virtual sources. This approach realizes beam folding, increases optical throughput, and reduces overall system size, enabling high-resolution spectral measurements. Moreover, the system offers tunable spectral resolution, providing flexibility to accommodate different application scenarios. The theoretical spectral resolution of the system is 19.3 cm-1, while the measured resolution using a He-Ne laser (632.8 nm) is 22.6 cm-1. Furthermore, characteristic spectral lines at 545.494, 577.367, 580.272, 768.539, and 821.477 nm were obtained using a mercury-argon lamp as the test source, with wavelength errors within 0.011% compared to standard reference data. In the broadband spectroscopy test, a continuous spectrum ranging from 385 to 1250 nm was successfully reconstructed. In the signal-to-noise ratio (SNR) evaluation, the system maintained SNR levels of 25.5, 28.7, and 31.4 dB under varying shearing distances, indicating robust performance under weak-light and high-resolution conditions.