Abstract: Objective In view of the limitations of optical coherence tomography (OCT) technology in the process of document inspection, a new numerical algorithm is developed from a deeper level, so as to realize the quantitative processing of OCT data set, and to provide supplementary evidence for document identification. Methods In this study, a frequency-domain OCT system with a central wavelength of 905 nm was used for in situ nondestructive testing of different printing ink and handwriting samples. Matlab programming software was also used to develop a set of numerical algorithms to perform a series of numerical analyses on OCT data set. In addition to applying the calculated results to the basic tomography visualization, the ink-paper interfaces were also identified accurately. Moreover, based on the established three-dimensional coordinate system, the surface average intensity (SAI) in different depth directions were calculated. Results By comparing SAI profiles of 14 handwriting samples, the different printing ink and handwritten handwriting were successfully distinguished. The SAI profiles of laser printing ink and pigment ink handwriting have an extreme value, while the SAI profiles of inkjet printing ink and dye ink handwriting were smoother. Conclusion Based on the quantitative analysis of OCT technology, it can provide an effective method for document identification. The OCT characterization results have a certain guiding role, and can lay a foundation for enriching the existing ecosystem of measurement techniques.

Key words: document identification, optical coherence tomography（OCT）, handwriting test, tampered （contaminated）documents identification

摘要： 目的 针对光学相干断层成像（optical coherence tomography，OCT）技术在文件鉴定过程中存在的局限性，从更深层面上开发新的数值算法，实现对OCT数据集进行量化处理，为文书鉴定提供补充证据。方法 采用一套中心波长为    905 nm的频域OCT系统对不同的打印墨迹以及手写字迹样本进行原位无损检验，并应用Matlab编程软件开发一套数值算法，对OCT数据集进行一系列的数值分析，除了将计算结果应用于基本的层析成像可视化外，还实现对墨迹-纸张界面的精确识别。此外，基于所建立的三维坐标系计算不同深度方向上的面平均光学强度（surface average intensity，SAI）。结果 通过对比14种字迹样本的SAI剖面曲线，成功区分了不同的打印墨迹以及手写字迹，激光打印墨迹的SAI曲线与颜料墨水笔迹的SAI类似，均存在一个极值，而喷墨打印墨迹和染料墨水笔迹的SAI曲线均较为平滑。结论 基于OCT技术的定量分析，可为文书鉴定提供一种有效的分析手段，且表征结果具有一定的指导作用，为丰富现有的方法体系奠定基础。

关键词: 文书鉴定, 光学相干断层成像技术, 笔迹检验, 篡改（污损）文件检验