Research On Synchronous Oversampling Method Of Rotary Near Infrared Fourier Transform Spectrometer

Near infrared spectrometer is an important analytical instrument to study the infrared absorption characteristics of substances.According to the characteristics of infrared absorption,we can carry out qualitative detection of the substances quickly and non-destructively.Therefore,it is widely used in many industries.Near-infrared Fourier transform spectroscopy has many advantages,such as multichannel transmission,high luminous flux,high spectral resolution and so on.The traditional near-infrared Fourier transform spectrometer usually uses laser triggered sampling to realize uniform sampling with equal optical path difference interval.In recent years,synchronous oversampling method is gradually applied to Fourier transform spectrometer.In this paper,the application of synchronous oversampling in rotating mirror near infrared Fourier transform spectrometer is discussed.The main work of this paper includes:1)Fourier transform spectral restoration based on synchronous oversampling: a set of rotating mirror Fourier transform infrared spectral instrument based on synchronous oversampling is built.The instrument uses a high-speed synchronous sampling card(art-PCI8504)to oversample the laser and near-infrared interference signals at a sampling frequency of 4 MHz.Using software trigger,the near-infrared interference sampling signal is reconstructed with different sampling interval wavelength,and then the restored spectrum is obtained.Compared with laser triggered sampling,synchronous oversampling can improve the signal-to-noise ratio of restored spectrogram.With the shortening of the sampling interval wavelength,the signal-tonoise ratio increased.2)Research on the nonuniform change of optical path difference: compared with the traditional commercial Fourier transform infrared spectrometer,the optical path difference of the rotating mirror Fourier transform infrared spectrometer is nonuniform,which often leads to large sampling error.In the synchronous oversampling mode,the influence of nonuniform optical path difference on the signal-to-noise ratio and peak frequency shift of restored spectral image is small.In this paper,the synchronous oversampling of the rotating mirror type nearinfrared Fourier transform spectrometer is realized,which reduces the dependence of hardware.By simplifying the sampling process,the SNR of the restored spectrum is improved.However,because of the large amount of synchronous oversampling data,the recovery spectrum processing time is long.Therefore,its application still needs to be improved.