透射光谱成像技术检验黑色签字笔涂抹掩盖字迹研究

目的 对透射光谱成像技术和反射光谱成像技术检验黑色签字笔间涂抹掩盖字迹进行比较研究,探寻一种无损、高效、直观的黑色签字笔涂抹掩盖字迹的显现方法,提高黑色签字笔间涂抹掩盖字迹显现效率。方法根据不同黑色签字笔油墨物质成分不同,不同物质对光的透射率各异的特征,在相同条件下使用反射光谱成像技术与透射光谱成像技术分别对多个黑色签字笔间涂抹掩盖字迹实验样本进行检验。本文将显现效果分为可显现和不可显现两类。分类标准为从未看过原字迹的非文检人员是否可以辨认出被涂抹掩盖字迹。结果 利用透射光谱成像检验系统检验黑色签字笔涂抹掩盖字迹样本,306个样本中,可显现的有231个,不可显现的75个,显效率为75.49%;反射光谱成像技术检验306个样本,其中可显现的有159个,不可显现的有147个,显现效率为51.96%。实验结果表明透射光谱成像检验黑色签字笔涂抹掩盖字迹的显现率高于反射光谱成像检验的检验。结论 除了无法显现原字迹与涂抹掩盖笔迹的油墨物质成分、浓度以及组成配比相同或相近的样本之外,透射光谱成像技术能检验常规的光谱成像技术无法显现的黑色签字笔间涂抹掩盖字迹,其显现效果和效率都优于反射光谱成像技术,是一种高效的显现方法 ,可以应用于刑事物证检验领域。     

SEM检验漆膜厚度鉴别同种颜色的汽车油漆

目的研究扫描电子显微镜测量漆膜厚度的方法对颜色相近的汽车油漆的区分能力。方法应用扫描电子显微镜对不同汽车厂家生产的12块蓝色油漆进行总厚度及分层厚度测量,并对所得数据进行t检验分析。结果在所有两两比对的66组样品对中,在置信度为95％时,用总厚度及分层厚度进行区分,区分率达到100％。结论用扫描电子显微镜微观测量油漆样品总厚度及分层厚度的方法,可对颜色相近的汽车油漆进行有效区分。     

光谱成像中光谱基准点选取的研究

目的研究物证检验应用光谱成像标准化规范化的操作技术方法。方法比较相同数据采集条件下选择不同光谱基准点区分物质的效果。结果选择不同基准点对光谱成像检验效果影响很大。结论应用光谱成像方法检验物证时针对不同检验目的选择不同基准点具有很强的规律性。     

光谱成像在物证检验中的初步实验研究

目的研究运用光谱成像技术进行物证形态检验的可能性和方法。方法比较相同条件下使用普通照相方法与光谱成像方法拍摄多种痕迹物证的效果。结果光谱成像检验的能力和效果都具有明显优势。结论光谱成像检验技术的出现使物证形态检验学的发展进入了一个崭新的阶段。     

发光光谱成像检验人民币真伪研究

目的建立鉴别人民币真伪和假币来源同一的检验方法。方法运用发光光谱成像技术对1999版和2005版真币人民币各50张、1999版和2005版假币各12张进行检验。结果真假人民币之间和不同来源的假币之间均能较好的区分开,区分效果明显。结论发光光谱成像技术可以有效鉴别真假人民币和假币来源是否同一。     

光谱成像检验技术

光谱成像组合了光谱技术和成像技术。通过运用成像光谱仪 ,光谱成像方法可以记录被检验物体在一个较宽光谱范围内均匀密集分布的窄波段反射光或荧光亮度分布影像 ,形成含有物体亮度信息和光谱信息的光谱影像集。这种技术方法可以用于物证的形态特征检验和物质成分检验。相对传统光谱检验或成像检验技术 ,光谱成像检验的能力和效果都具有明显优势。     

运用光谱成像技术区分同色棉纤维

目的研究同色棉纤维的检验方法。方法运用成像光谱法对红、蓝、黑3个颜色组的棉纤维进行区分。结果红色棉纤维的鉴别率为62．2％，蓝色棉纤维的鉴别率为77．8％，黑色棉纤维的鉴别率为69．6％。结论实验结果表明，光谱成像技术可以区分大部分同色棉纤维。拓宽了纤维检验的方法，解决了同色棉纤维的区分问题，该方法能够用于对微量同色棉纤维的快速鉴别。     

基于光谱成像的人血和两种动物血痕迹的函数型数据分析

目的研究现场勘查和实验室检验鉴定中光谱成像技术显现和区分人体血液痕迹与动物血液痕迹的能力。方法使用光谱成像技术分别采集人血、鸡血、蛇血在不同介质表面的光谱影像数据,利用函数型数据分析方法依次分析了四种介质上的血迹数据,主要的分析方法包括:1)基于函数型数据主成分分析定量确定三种血迹光谱主成分贡献率及差异主要集中的波段;2)利用三种血迹的主成分进行聚类分析;3)基于函数型数据Fisher判别分析对样本进行判别。结果利用函数型数据进行血迹种类判别,对四种介质上三种血迹的识别准确率分别达到了96.6%、98.8%、99.0%和94.6%。结论研究表明,利用光谱成像技术和函数型分析方法来区分现场人血与动物血痕迹物证是行之有效的。     

油漆物证检验中血液干扰的去除

对一起交通肇事逃逸案件中死者衣服上油漆碎片与嫌疑车漆片的成分进行比对检验。红外光谱检验结果显示,死者衣服上沾有血迹区域提取的油漆碎片与其他部位提取的油漆碎片谱图有差异。对凝固的血迹进行检验,发现差异可能来自于血液污染。通过红外光谱差谱技术将血迹区域提取的油漆碎片的红外谱图进行处理,所得谱图与衣服上其他区域提取油漆的红外谱图无明显差异,证实死者衣服上只有一种油漆,且与嫌疑车漆片成分相同,这为证实嫌疑车的肇事事实提供了科学依据。     

光谱成像检验同种同色涂抹掩盖字迹研究

目的建立一种无损、灵敏、直观的同种同色涂抹掩盖字迹的显现方法。方法依据涂抹掩盖字迹油墨物质的同色异谱特征,利用可见光滤波型多光谱成像检验系统进行检验。结果黑色圆珠笔、蓝色圆珠笔、黑色签字笔和蓝色签字笔相互涂抹掩盖形成的同种同色涂抹掩盖样本,利用可见光滤波型多光谱成像检验系统进行检验,显效率分别为90.5%、69.1%、49.5%、78.6%,显现效果良好。结论多光谱成像技术可以显现同种同色涂抹掩盖字迹,且具有良好的显现效果。     

Color analysis of apparently achromatic automotive paints by visible microspectrophotometry

Chromatic secondary pigments are utilized in achromatic automotive paints to create unique paint systems. These pigments may not be observable in reflected light; however, utilizing visible microspectrophotometry (MSP) discriminating data may be gathered. This study analyzed 160 apparently achromatic automotive paints via this technique for spectral evidence of secondary pigmentation. These results were compared with visual observations made via polarizing light microscopy. Positive spectral results were attained in approximately 25% of the black and gray/silver topcoat sample sets, whereas the white topcoat and gray undercoat set yielded no probative spectral data. The black sample set did yield several samples that produced spectral evidence of pigmentation when no visual chromatic data was observed. The results of this study suggest that paint analysis schemes should incorporate visible MSP for apparently achromatic black and gray/silver paint samples.     

Forensic applications of infrared chemical imaging: multi-layered paint chips

This paper examines the potential of infrared chemical (hyperspectral) imaging as a technique for the forensic analysis of automotive paint chips in particular, and multicomponent (e.g., layered) samples in general. Improved sample preparation procedures for the infrared analysis of paint chips are detailed, with the recommendation that where mounting resins are chemically incompatible with the sample, it is better to mount and section the sample in a soft wax from which the sections can be removed and pressed into a KBr disk for transmission analysis. Infrared chemical images of multilayered paint chips have been successfully obtained, with the chief advantage over conventional infrared analysis being that thousands of infrared spectra are collected in a few minutes across the whole sample, at a spatial resolution of around 5 microm. As with conventional infrared spectroscopy, chemical species can be identified from their spectra, but the wealth of information available can be also extracted in a number of different ways that make multicomponent spectral (and hence chemical) comparisons between two samples easy to visualize and understand. In one approach, the infrared chemical images of two paint chips being compared side-by-side can be viewed as a "movie," in which each frame is an intensity map of the two samples at a given wavenumber (frequency) value. In another approach, the spectra (pixels) in the image files are classified into chemically similar groups, resulting in a "cluster" image that makes it possible to simultaneously compare all of the layers in two paint chips. These methods are applicable to other multicomponent samples, and also to other chemical imaging techniques.     

Analysis and discrimination of architectural paint samples via a population study

This study involved the comparative analysis and discrimination of 964 architectural paint samples collected in the United States and Canada. The samples were evaluated to determine the extent to which randomly collected architectural finishes can be discriminated following standard operating protocols for paint analysis. The study also provides a basis for assessing the significance of a result in which a pair or group are undifferentiated. The techniques utilized were stereomicroscopy, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) with both backscatter electron imaging (BSI) and energy dispersive spectroscopy (EDS), and pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). To assess the layer characteristics (e.g., number, color, sequence, thickness), stereomicroscopy was used with FTIR and/or SEM as needed. The use of visual and microscopic evaluations in concert with FTIR resulted in 42 undifferentiated pairs, a discrimination of 99.99%. Adding SEM and Py-GC/MS analysis resulted in further discrimination of 31 pairs, resulting in eleven undiscriminated pairs of samples. At the conclusion of the study, samples that remained undifferentiated proved to originate from the same source. Therefore, no random pairs were indistinguishable at the conclusion of all examinations.     

Characterization of Blue Pigments Used in Automotive Paints by Raman Spectroscopy

Micro‐Raman spectroscopy was applied to forensic identification of pigments in paint chips and provided differentiation between paint samples. Sixty‐six blue automotive paint samples, 26 solid and 40 metallic were examined. It was found that the majority of the collected Raman spectra provided information about the pigments present. However, in some cases, fluorescence precluded pigment identification. Using laser excitation at longer wavelengths or pretreatment to effect photobleaching often resulted in reduced fluorescence, particularly for solid color samples, and allowed pigment identification. The examined samples were compared pairwise taking into account number, location, and intensity of absorption bands in their infrared spectra. The estimated discrimination power ranged from 97% for solid paint samples to 99% for metallic paint samples.     

汽车罩光漆的ATR-FTIR法检验

目的通过对油漆样品罩光漆成膜物质的检验以区分不同汽车厂家的油漆样品。方法采用衰减全反射红外光谱法（Fourier Transform Infrared Spectroscopy Attenuated Total Reflection Spectroscopy,ATR-FTIR）研究15个汽车厂家提供的356份油漆样品的罩光漆成膜物质。结果在所有油漆样品中,丙烯酸漆出现的频率最高,氨基漆出现的频率最低;在所有厂家中,使用丙烯酸漆的厂家最多,使用氨基氨酯混合漆的厂家最少;在使用相同罩光漆的不同厂家的油漆样品中,通过比较红外谱图可以对样品进一步区分。结论 ATR-FTIR法能够在一定程度上区分不同汽车厂家的油漆样品,从而大大缩小侦查范围,对于涉车案件的快速侦破具有非常重要的作用。     

常见油漆稀料的GC／MS的检验及分类研究

目的对常用油漆稀料的检验分析方法及分类进行研究,并建立SPME-GC／MS对纵火案件中油漆稀料快速、灵敏、准确的分析方法。方法采用SPME-GC／MS法对5种不同型号品牌的常见油漆稀料进行分析。结果确定了样品处理方法和仪器分析最佳条件。实验的5种油漆稀料样本根据组分特征和结构特征的不同可归纳为4类。结论该研究结果可为纵火案件中油漆稀料残留物提供一种新的检验方法和检验依据。     

Using Paint to Investigate Fires: An ATR‐IR Study of the Degradation of Paint Samples Upon Heating

Fire investigation is a challenging area for the forensic investigator. The aim of this work was to use spectral changes to paint samples to estimate the temperatures to which a paint has been heated. Five paint samples (one clay paint, two car paints, one metallic paint, and one matt emulsion) have been fully characterized by a combination of attenuated total reflectance Fourier transform infrared (ATR‐IR), Raman, X‐ray fluorescence spectroscopy and powder X‐ray diffraction. The thermal decomposition of these paints has been investigated by means of ATR‐IR and thermal gravimetric analysis. Clear temperature markers are observed in the ATR‐IR spectra namely: loss of ν(C = O) band, >300°C; appearance of water bands on cooling, >500°C; alterations to ν(Si–O) bands due to dehydration of silicate clays, >700°C; diminution of ν(CO₃) and δ(CO₃) modes of CaCO₃, >950°C. We suggest the possible use of portable ATR‐IR for nondestructive, in situ analysis of paints.     

Identification of tiny and thin smears of automotive paint following a traffic accident

Three complementary methods in the order of stereomicroscopy, micro-FT-IR spectroscopy and solubility tests were used for the purpose of matching known and questioned paint samples in an auto accident case. Grayish green paint smears scattered on a silvery gray coated plastic bar were taken from a blue car and referred to as questioned samples. Green paint chips were collected as known samples from a green car. These were analyzed to determine whether the paint smears found in the blue car could have been the transfers from the green car. Although each of the three methods, when used alone, suffered from unequal bases for making comparison (i.e., layering whole paint vs. smeared paint), insufficient specificity of methodology and the interfering background coating beneath the smeared paint, the limitations were significantly relieved when three methods were used in combination. Based on the results presented in this report, the questioned grayish green paint smears collected from the blue car and the known green paint chips from the green car are of the same class of paint; that is, the possibility of the above stated paint transfers cannot be eliminated.     

Detection of latent bloodstains beneath painted surfaces using reflected infrared photography

Bloodstain evidence is a highly valued form of physical evidence commonly found at scenes involving violent crimes. However, painting over bloodstains will often conceal this type of evidence. There is limited research in the scientific literature that describes methods of detecting painted-over bloodstains. This project employed a modified digital single-lens reflex camera to investigate the effectiveness of infrared (IR) photography in detecting latent bloodstain evidence beneath a layer or multiple layers of paint. A qualitative evaluation was completed by comparing images taken of a series of samples using both IR and standard (visible light) photography. Further quantitative image analysis was used to verify the findings. Results from this project indicate that bloodstain evidence can be detected beneath up to six layers of paint using reflected IR; however, the results vary depending on the characteristics of the paint. This technique provides crime scene specialists with a new field method to assist in locating, visualizing, and documenting painted-over bloodstain evidence.     

Discriminating red spray paints by optical microscopy, Fourier transform infrared spectroscopy and X-ray fluorescence

Red spray paints from different European suppliers were characterised to determine the discriminating power of a sequence of analysing techniques. A total of 51 red spray paints were analysed with the help of three techniques: (1) optical microscopy, (2) Fourier transform infrared spectrometry and (3) X-ray fluorescence. Infrared spectra were classified according to binder type, filler and pigment composition and a searchable spectral library was created. Due to the difference in the elemental composition of spray paints, a further discrimination was possible. The microscopic analysis was not taken into consideration for classification purposes. The structure of the substrate under a paint coating strongly affects the surface characteristics of this spray paint. Together with the spectral library, a database of information of spray paints was build.