A critical step in Raman spectroscopy is baseline correction. This procedure eliminates the background signals generated by residual Rayleigh scattering or fluorescence. Baseline correction procedures relying on asymmetric loss functions have been employed recently. They operate with a reduced penalty on positive spectral deviations that essentially push down the baseline estimates from invading Raman peak areas. However, their coupling with polynomial fitting may not be suitable over the whole spectral domain and can yield inconsistent baselines. Their requirement of the specification of a threshold and the non-convexity of the corresponding objective function further complicates the computation. Learning from their pros and cons, we have developed a novel baseline correction procedure called the iterative smoothing-splines with root error adjustment (ISREA) that has three distinct advantages. First, ISREA uses smoothing splines to estimate the baseline that are more flexible than polynomials and capable of capturing complicated trends over the whole spectral domain. Second, ISREA mimics the asymmetric square root loss and removes the need of a threshold. Finally, ISREA avoids the direct optimization of a non-convex loss function by iteratively updating prediction errors and refitting baselines. Through our extensive numerical experiments on a wide variety of spectra including simulated spectra, mineral spectra, and dialysate spectra, we show that ISREA is simple, fast, and can yield consistent and accurate baselines that preserve all the meaningful Raman peaks.

中文翻译：

---

ISREA：用于拉曼光谱的高效保峰基线校正算法

拉曼光谱的一个关键步骤是基线校正。此过程消除了残余瑞利散射或荧光产生的背景信号。最近采用了依赖于非对称损失函数的基线校正程序。它们以减少对正光谱偏差的惩罚来运行，这基本上会降低侵入拉曼峰面积的基线估计。然而，它们与多项式拟合的耦合可能不适用于整个谱域，并且会产生不一致的基线。他们对阈值规范的要求和相应目标函数的非凸性进一步使计算复杂化。学习他们的优缺点，我们开发了一种新的基线校正程序，称为带根误差调整的迭代平滑样条 (ISREA)，它具有三个明显的优点。首先，ISREA 使用平滑样条来估计比多项式更灵活的基线，并且能够捕捉整个谱域的复杂趋势。其次，ISREA 模仿非对称平方根损失并消除了对阈值的需要。最后，ISREA 通过迭代更新预测误差和重新拟合基线避免了对非凸损失函数的直接优化。通过对各种光谱（包括模拟光谱、矿物光谱和透析液光谱）进行广泛的数值实验，我们表明 ISREA 简单、快速，并且可以产生一致且准确的基线，保留所有有意义的拉曼峰。