A Fourier transform spectrometer with heterodyne modulation achieved by a moving diffraction grating has been developed for the near-infrared (NIR) region. The grating simultaneously acts as a beam splitter and a modulator, which realizes the optical frequency shift of incident light for increasing the sensitivity of measurements by the heterodyne detection technique. The differences in diffraction angle among broad spectra are compensated by a collimating mirror and plane mirrors. The proposed spectrometer is used for the measurements of spectra in the NIR region. The signal-to-noise ratio of measurements is improved sevenfold with a heterodyne modulation of 410 Hz. As examples, this spectrometer is applied for quantitative calibration and discrimination of organic solutions. The measurement of transmission spectra of a grape is also demonstrated.
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