太赫兹时域光谱无损检测核桃品质的研究

Evaluation of Walnut by Terahertz Nondestructive Technology

以核桃为研究对象,探讨太赫兹时域光谱技术对其变质情况、壳厚测量的研究。首先对虫蛀、霉变、正常核桃壳、仁标样采集太赫兹时域光谱,比较分析变质与正常核桃谱图及吸收谱差异,为剔除变质核桃打下基础。其次联用透射和反射式太赫兹时域光谱系统,创建核桃壳计算公式,在获取核桃壳理论折射率基础上,换算得到未知核桃壳厚,相对误差为3.7%。分别从物理、化学指标光谱响应特征差异入手,实现太赫兹无损检测核桃品质。

The deterioration and shell thickness of walnut were studied using the terahertz time domain spectroscopy. Firstly, the THz spectra of moth-eaten, moldy and normal walnuts were compared, and the bad walnuts were properly rejected due to the differences of absorption peaks. Secondly, the transmission-type and reflection-type terahertz time domain spectroscopy sys- tem was used simultaneously, and a new formula to calculate shell thickness of walnut was built in the THz system. Then the authors measured the shell thickness based on the detectable refractive index of walnut, and the relative error was 3. 7 %. Conse- quently, the quality of walnut was evaluated nondestructively according to physical and chemical indicators from walnut THz spectra respectively.