基于空间外差的拉曼信号处理方法研究

空间外差拉曼光谱技术是近年兴起的一种超光谱探测技术，它既具有拉曼光谱测量的非接触、快速、简单、可重复、无需样品准备等特点，更具有空间外差的超光谱分辨率、高通量、无运动部件优点，能在被测物质特征波长中心范围探测，实现微弱拉曼光信号的直接测量。由于被测信号微弱、光学元件加工精度、器件封装及仪器安装误差等原因，会导致空间外差拉曼光谱仪(SHRS)接收到的干涉图存在光强分布不均匀、干涉条纹倾斜或扭曲等现象，从而使普通光谱恢复方法得到光谱信号准确度下降或无法识别。根据SHRS探测到的干涉图所存在的误差特点，将二维傅里叶变换应用于SHRS干涉图的光谱复原，提出基于二维频域谱重采样的最强直线方向光谱提取方法，以实现SHRS光谱的获取。提取过程为：将采集的目标干涉图进行二维傅里叶变换，获得二维频谱图，通过使用相同实验系统采集的单波长或多波长光源的二维频谱信号特征峰的位置信息，拟合获取光信息强度最大方向直线方程。然后根据该直线与目标二维频谱图各列交点坐标位置，确定重采样贡献像元及权重。对拟合直线方程经过的所有列像元进行重采样，得到最终的光谱信号。将该方法应用于自行搭建实验系统采集的三叶草干涉图数据，同时与其他方法光谱复原结果进行对比。结果表明：与一维行平均光谱法比较，该方法获取的光谱在探测波段中心区域信号强度更加明显，同时消除了探测器热噪声的影响；与二维频谱中心行直接提取法比较，该方法是该方法的改进版本，两者结果比较接近。但是由于考虑到干涉条纹y分量的影响，沿二维频谱信号最强方向重采样得到的最终光谱，其主峰半峰宽更窄、边频噪声强度更小，且随着y分量的增加，光谱复原效果及优势将越发明显。该方法是空间外差拉曼光谱技术数据处理的一种有益补充与尝试。

Research on Raman Signal Processing Method Based on Spatial Heterodyne

Spatial heterodyne Raman spectroscopy is a hyperspectral detection technology that has emerged in recent years.It has the characteristics of non-contact,fast,simple,repeatable and no sample preparation required for Raman spectroscopy,but also the advantages of high resolution,high throughput and no moving can detect signals in the characteristic wavelength center range of the measured realize the direct measurement of weak Raman optical signals.Due to the weak signal to be measured,the machining accuracy of optical components,and the errors caused by device packaging and instrument installation,the interferogram received by the spatial heterodyne Raman spectrometer(SHRS)will have uneven light intensity distribution,interference fringe tilt or distortion.Therefore,the accuracy of the spectrum signal obtained by the ordinary spectrum recovery method is reduced or even hard to be identified.According to the error characteristics of the interferogram detected by SHRS,the two-dimensional Fourier transform is applied to the spectral restoration of the SHRS interferogram and a method of extracting the strongest line direction spectrum based on two-dimensional frequency domain spectrum resampling is proposed.The extraction process is to perform a two-dimensional Fourier transform on the collected interferogram of the target to obtain a two-dimensional spectrogram.By using the position information of the characteristic peaks of the two-dimensional spectrum signal of the single-wavelength or multi-wavelength light source collected by the same experimental system,the linear equation of the maximum direction of the light information intensity is obtained by fitting.According to the coordinate position of the intersection point of the straight line and each column of the target two-dimensional spectrogram,the pixels and the weight contributed by the resampling are determined.All columns of pixels is resampled along the fitted linear equation to obtain the final spectral signal.The method is applied to the clover interferogram data,and the recovered spectrum is compared with those obtained by other methods.The results show:compared with the one-dimensional row average spectroscopy method,the spectrum obtained by this method has a more obvious signal intensity in the center area of the detection eliminates the influence of the noise at the same time;compared with the direct extraction method of the two-dimensional spectrum center row,it slightly improves the recovered spectrum.However,due to the influence of the y component of the interference fringe,the final spectrum obtained by resampling along the strongest direction has a narrower half-width of the main peak and a smaller side frequency noise intensity.If the influence of the y component increases,the spectrum restoration effect of this method will become more obvious.This method is a useful supplement and an attempt for data processing of spatial heterodyne Raman spectroscopy.