Accurate measurement method for for optical parameter of edible oil by terahertz time-domain spectrum

Abstract

The invention discloses a method for accurately determining optical parameters of edible oil by utilizing a terahertz time-domain spectroscopy. By utilizing a transmission terahertz time-domain spectroscopy (THz-TDS) device, a THz time-domain spectroscopy of a sample cell without a sample is measured as a reference signal, and then a THz time-domain spectroscopy of the sample cell with the sample is measured as a sample signal; and a measurement value of a transmission coefficient of the sample in a terahertz waveband can be obtained by evaluating the ratio of Fourier transforms of the sample signal to the reference signal, then a three-layer transmission function model containing a container is utilized, and a Nelder-Mead search method and a trust region smoothing method are used to fit the measurement value of the transmission coefficient of the sample in the terahertz waveband, thereby accurately determining the refractive index and the absorption coefficient of the edible oil in a corresponding terahertz waveband. The method fully considers multiple reflection effect during the propagation of THz wave in a plurality of layers of media, considers the influence of noise and measurement error, effectively improves the measurement accuracy of the optical parameters of the edible oil, and helps to apply a THz-TDS technology to quantitative detection occasions such as component analysis of the edible oil and so on.

Description

technical field [0001] The invention belongs to the technical field of terahertz waves, and relates to a method for accurately measuring optical parameters of edible oil by using terahertz time domain spectrum. Background technique [0002] Terahertz (Terahertz or THz) waves usually refer to electromagnetic waves with a frequency in the range of 0.1 to 10 THz. The energy of the photons is about 1 to 10 meV, which is roughly equivalent to the energy of the transition between molecular vibration and rotational energy levels. Most polar molecules such as water molecules and ammonia molecules have a strong absorption of THz radiation, and the transition between the vibrational energy level and rotational energy level of many organic macromolecules (DNA, protein, etc.) is also just in the THz range. Therefore, the THz spectrum (including emission, reflection and transmission spectra) of substances contains rich physical and chemical information, and its absorption and dispersion ...

AI Technical Summary

Problems solved by technology

The existing terahertz spectrum calculation model is a simplified calculation model, which does not consider the effect of multiple reflections, nor the influence of measurement errors, which is not conducive to quantitative detection occasions such as component analysis

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