Rubberband方法中分段数量的选择对基线校正效果的影响分析

针对混合气体红外光谱在应用现场基线漂移和畸变、基线校正方法Rubberband方法中分段数量的选择不确定等问题进行探讨,通过遍历的形式筛选出针对烃类气体在中红外波段、波数分辨率为4 cm-1的情况下,优选出分段数量在50~120之间、基线点的曲线拟合方法选择分段三次Hermite插值方法时,其基线估计和校正的效果较为理想.同时针对Rubberband方法易将吸收点误判为基线点的问题,使用中位数和偏离度首先剔除分段内的明显吸收点,然后将剩余谱线点采用偏最小二乘方法设定一定的阈值范围进行基线点的筛选,筛选出的基线点在整个波段采用分段三次Hermite插值方法进行基线的估计.从实测的光谱基线校正效果来看,提出的算法使用简单,并适合于在线连续分析的应用场合.

Influence analysis of Rubberband's piecewise quantity on baseline correction effect

The problems of baseline drifting and distortion of mixed gases infrared spectra in the application field and the uncertain choice of the Rubberband's piecewise quantity were discussed. In the situation of the spectrometer resolution of 4 cm-1 and mid-infrared band for the hydrocarbon gases, the baseline estimation and correction would be more ideal in the case of the piecewise quantity was set in the 50-120 and piecewise cubic Hermite interpolation method was selected to fit the baseline points by the ergodic method. For the problem of absorption points,which was mistaked as the baseline points, first of all, the obvious absorption points within the segment were eliminated by the method of the median and deviation. And then, the baseline points were selected by the partial least square method and certain threshold was set in the residual baseline points. Lastly, the selected baseline points was used to estimate the baseline by piecewise cubic Hermite interpolation method in the whole band. From the baseline correction result of the measured spectra, the provided method was simple and fast, and also suitable for on-line continuous analysis applications.