拉曼光谱3D成像技术确定黑色交叉笔画顺序的研究

在文书鉴定中,经常涉及对交叉笔画的检验,进而判断文件是否存在篡改、变造,此外,交叉笔画的检验也有助于判断笔迹个性特征、笔顺特征。本文采用拉曼光谱3D成像技术对多品牌不同型号的黑色圆珠笔和国产签字笔进行实验筛选,结合现有交叉笔画检验方法中如笔画连续性、收敛现象等特征,分析该方法判断交叉笔画书写顺序适用的各种情形:经赋色的笔画3D模型大量出现明显的“峰谷”异色现象,且表现一致,则能够得出准确结论;当现象明显存在但表现不一致或现象不明显时,需结合笔画连续性在3D模型中的特征分析判断,亦能得出正确结论,但准确率受数据处理的优劣及成像效果的影响较大;无法检测的情形,即无法获得有效拉曼光谱信息或无法区分两种油墨光谱信息时,该方法失效。笔者认为采用拉曼光谱3D成像技术在一定条件下能够对交叉笔画书写顺序进行相对客观、准确的判断,受鉴定人员主观影响较小,值得更加深入全面的研究,以便推广应用。

Study of Raman Spectroscopy 3D Profilometry to Determine the Sequence of Black Pen Ink Crossings

In handwriting identification,when a case involves forged or altered strokes and figures problems the appraiser usually needs to examine the crossing section of the suspected material to confirm whether there is a forgery in the document.In addition,the study on the sequence determination of the crossing line can help appraiser to estimate the thumbprint of the handwriting and the character of the writing sequence.And also,those identification methods have reference value for the sequential identification of crossed writing and seal stamps documents.This paper draws experience from the existing methods with the common features,such as continuity of strokes and convergence phenomenon,and tests several types of black pens by Raman spectroscopy.Through the design of experiment to compare and choose the best parameters of the instrument and software settings,including microscope lens,laser wavelength,laser output power,spectral range,single acquisition time,cumulative acquisition times,scanning step,get the best experimental parameters and acquisition method and comparison principle.The experimental results of Raman spectrum 3D imaging are discussed in classification,analysis whether the application of this method to determine the writing order of cross strokes is useful.When preponderance and unanimous heterochromia phenomenon can be observed between the“hills and valleys”,an accurate conclusion can be drawn.When the heterochromia phenomenon is obvious but not incongruent or the phenomenon is not obvious,it need to combine the characteristics of stroke continuity in the 3D model to get the correct conclusion,but the accuracy is greatly influenced by the data processing and the 3D model imaging effect.At the same time,the undetectable situation is summarized,that is,when the Raman spectrum information is unable to be obtained effectively or the spectral information those are homology cannot be distinguished,the method is invalid.Based on the analysis and summarize of the experimental result,it can be sure that the Raman spectroscopy 3D profilometry techniques can get relatively objective and accurate judgment on the determination of sequence of black pen ink crossings under certain conditions,and the conclusion is affected little by the appraiser’s subjective judgment.It is worth a more thorough and comprehensive study in order to promote the application.