利用暗记特征鉴别彩色激光打印、复印文件

目的探讨激光打印机的暗记特征,为鉴别彩色激光打印、复印文件找到一种有效的方法。方法根据不同物质对光的反射特性及蓝色与黄色互补特性的原理,采用420nm左右蓝光照射方法,对部分品牌彩色激光打印、复印文件进行了初步分析研究,总结了暗记点阵形态特征、小点形态特征、出现位置特征和排列含义等特征。结果此方法对彩色激光打印、复印机具的种类鉴别和个体鉴别简便、有效。     

扫描电镜/能谱法检验激光打印文件

目的 应用扫描电镜/能谱法检验不同品牌和型号激光打印机的打印文件,实现对不同机型打印文件的区分。方法 收集不同品牌和型号激光打印机10台,利用扫描电镜/能谱仪对相同的打印字符进行无机元素分析,获得样品的能谱图和mapping分析图,对样品进行定量和半定性分析;同时收集10个不同品牌的A4静电复印纸,分析纸张对实验结果的影响。结果 依据所含元素的种类可以将10台激光打印机分为四类;依据主要元素相对百分含量的比值,对不同品牌和型号激光打印文件进行区分;研究结果表明纸张因素对定性结果影响较小,对定量结果影响较大。结论 扫描电镜/能谱法可以简单、快速、无损的区分和识别激光打印文件,可以应用于二次打印文件的检验,为侦查破案提供线索。     

激光打印机打印文件形成时间的研究

运用激光打印机打印文件的原理 ,分析了打印文件上的痕迹及其形成原因。并对八百余份自1998年8月1日至1999年7月31日同机打印的连续样本上所留痕迹进行研究 ,发现 :激光打印文件的痕迹随时间呈一定的变化规律和特点。因此 ,鉴定中通过检材上打印机的打印痕迹 ,结合充分的打印样本 ,可以认定或排除打印文件的形成时间     

栅格特征在打印文件检验中的应用研究

目的通过对打印文字栅格特征进行实验研究,总结其稳定性和易引起特征变化的因素,为二次添加打印和换页变造文件检验探索新的思路。方法以500个常用汉字为主要研究对象,选用不同品牌、不同型号激光打印机,设置不同分辨率或质量模式,用同一台电脑或不同台电脑安装不同驱动程序,打印中易宋体常用字不同字号的样本。通过对打印文字笔画细节特征进行比对分析,总结打印文字栅格特征的规律特点。结果打印文字存在三类栅格特征,一是横笔段厚度特征,二是竖笔段宽度特征,三是斜笔画阶梯特征。同一台打印机一次打印的文件,相同字体字号文字的栅格特征反映相同;不同打印机或同一台打印机连接不同版本操作系统的电脑,或安装不同驱动程序,或选择不同的打印分辨率,栅格特征可能发生变化。结论栅格特征在同一次打印的文件中具有稳定性,在不同硬件和软件环境下可能发生改变,可以为换页文件和二次添加打印文件检验提供新的思路。     

基于过程解析法的同机添加打印文件鉴别方法

利用喷墨打印机二次添加打印,特别是同机添加打印变造文件,是文件检验工作中的难题。喷墨打印机采用串行接字方式,内部结构复杂,喷嘴数目多,同一型号打印机又有多种质量模式。因此,在打印图文上往往留有较多的打印特征,如对接重叠线、对接错位线、横向白线、卫星墨点、墨点错位等。分析爱普生、惠普、佳能三个品牌的20台喷墨打印机不同质量模式的打印文件,发现这些特征重复再现频率较高,不同台打印机打印文件特征差异较大,同一台打印机在不同质量模式下特征出现的位置也不尽相同。通过提取打印文件上的打印特征,分析字车运行方向和打印图文pass数值,分解打印过程并制作检验图谱,判断打印文件的可疑区域是否符合打印规律,为确定二次添加打印提供帮助,提升检验过程的规范性、检验意见的准确性和结果依据的可读性。     

微束X射线荧光分析法鉴别激光打印机墨粉的研究

目的利用微束X射线荧光分析法（μ-XRF）研究激光打印机用墨粉的鉴别。方法利用μ-XRF对9台不同型号激光打印机用墨粉、对应的打印字迹、提取的字迹墨粉所含元素进行定性、半定量的分析。结果根据检出元素种类的不同,可将9台不同型号激光打印机用墨粉、对应的打印字迹、提取的字迹墨粉分成7类、4类、4类,区分率分别为94.4%、75%、69.4%。结论本研究所建立的μ-XRF鉴别激光打印机墨粉方法具有微区、原位无损检验等优点,对提高激光打印文件检验水平具有现实意义。     

荧光法判断激光打印文件朱墨时序的研究

目的 建立荧光法判断激光打印文件朱墨时序的检验方法,并分析不同型号的激光打印机制成的文件与不同材质的印章印文的采墨时序的特征.方法 利用VSCS000文检仪和Photoshop软件,采用荧光法对激光打印文件与印章印文交叉部位的特征进行检验,并对不同型号的打印机制成文字与不同材质的印章印文交叉部位的荧光特征进行分析比对.结果 发现常出现的共性特征为:制成文字先墨后朱,交叉部位的黑色墨迹颜色变淡并可见紫色荧光;先末后墨,交叉部位常常出现黑色墨迹缺损的现象,在缺损处可见紫色荧光点.但也表现出其特有的特征.结论 不同型号的打印机制成的文件与不同材质的印章朱墨时序所表现出来的特征不尽相同,在具体案件鉴定中应进行综合判断.     

无交叉笔画状态下激光打印文字与中性笔书写文字形成时序的实验研究

目的探索无交叉笔画状态下激光打印文字与中性笔书写文字的时序特征及变化规律,以求运用于案件检验。方法以两种不同时序,请5名志愿者分别执不同中性笔在120张A4纸张上书写文字,并使用4台不同型号激光打印机打印文字,再运用奥博视频层晰显微镜对实验样本进行放大观察。结果证实在两种时序条件下制作的实验样本之间存在诸多差异性特征。结论这些差异性特征为准确判定无交叉笔画状态下激光打印文字与中性笔书写文字的时序提供了基础实验依据。     

显微共焦激光拉曼光谱仪分析激光打印黑色墨粉字迹

激光打印机是常用办公设备,案件中经常会涉及到激光打印文件的检验,运用显微共焦激光拉曼光谱仪检验激光打印黑色墨粉字迹是一种快速、无损、灵敏度高的检验方法,可以对墨粉成分进行定性分析,在司法实践中,此种方法对激光打印黑色墨粉具有较好的检验效果,应用前景广阔。     

针式打印文件检验的探讨

针式打印机是一种常用的办公机具,从针式打印机的结构和打印原理出发,阐述了针式打印文件种类鉴别和个体识别所依据的打印特征,为针式打印文件的检验鉴定进行操作层面的探讨。     

利用彩色文件上的图文特征鉴别喷墨打印机品牌

目的通过彩色文件上的图文特征鉴别喷墨打印机的品牌。方法在体视显微镜下观察采用不同喷墨机理的惠普、佳能和爱普生三大品牌喷墨打印机打印的彩色图文。结果通过对彩色图文上六种墨迹形态特征的比较,发现三大品牌喷墨打印机打印的彩色图文存在明显差异。结论依据这六种特征对三大品牌的喷墨打印机进行鉴别。     

线聚焦显微激光拉曼光谱技术区分激光打印墨粉

目的利用Renishaw InVia激光显微拉曼光谱仪对打印墨粉进行区分。方法用785nm激发波长,采取线聚焦模式,50倍物镜条件下,测定了惠普等8个品牌25种硒鼓型号的30份激光打印机打印墨迹样品的拉曼光谱。结果 30种样品墨迹的谱图进行了分析,根据拉曼的异同,可将30种样品分为5大类。结论线聚焦显微激光拉曼光谱可用于区分不同种类激光打印墨粉。     

Technical Note: Analyzing the effect of repeated fusing on toner to examine printing alterations made by the same laser printer

With continuous innovations in laser printing technology, the number of cases of falsification using laser printers is increasing annually. Difficulties in identifying printing alternations, especially laser-printed alternations by the same printer are increasing. Effectively, repeated printing on the same page by the same printer means the original toner on the document was fused repeatedly. Thus, this study mainly investigates the effects of second fusing on the microscopic morphology of toner to examine whether documents have been tampered with. To detect the influence of fusing on the microscopic morphology of toner, 170 documents printed by 17 different models of laser printers from 5 brands were studied. It was found that, according to microscopic observations, the micrographs of toner may become brighter, darker or both with repetition of the fusing process. By calculating the average gray value of the micrographs of toner, it was found that, in some laser printers, the gray value of the thermoplastic accumulation area will increase after a second fusing, and the gray value of the toner particle dispersion area will decrease. In conclusion, by comparing the micrographs of toner from suspicious and reliable contents on the same page or in the same document, together with the measurement and analysis of average gray values, it is possible to examine the once- and twice-fused document contents, and further determine whether the document has been altered.     

A Preliminary Study on Sources of Banding Artifacts for the Identification of Monochromatic Laser Printers,

The analysis of questioned documents printed with monochromatic toner has been a great challenge to document examiners. Banding artifacts, which are often perceived in the outputs of laser printers, could be a solution to the identification of printers. In this study, sources other than the gear transmission errors were discovered for some primary banding frequency components. By detecting the angular velocity variation of photosensitive drums and other rotating parts of the tested printers and comparing them with the banding signals extracted from the printouts, the authors located the sources of banding frequency components. It was shown that the sources of some primary and persistent banding signals, which were previously unknown, were traced to the periodic velocity variations of the motors or the timing belts. As inherent signatures, banding artifacts could be promising features for discriminating documents printed by individual laser printers.     

多光谱成像技术检验富士施乐C4300彩色激光打印复印一体机形成文件

目的研究富士施乐C4300彩色激光打印复印一体机形成文件的跟踪暗码,对富士施乐C4300彩色激光打印复印一体机形成文件进行识别。方法使用多光谱成像仪对6台富士施乐C4300彩色激光打印复印一体机形成的文件进行观察。结果该6台机器形成文件的跟踪暗码存在特征差异。结论通过跟踪暗码的差异,能够对富士施乐C4300彩色激光打印复印一体机形成文件进行识别。     

The use of an electrostatic detection device to identify individual and class characteristics on documents produced by printers and copiers--a preliminary study

The market is inundated with inkjet printers, laser printers, and photocopiers, which are often used in criminal activities. Many of these office machines are built by various manufacturers, hence they are constructed with different hardware designs (e.g. "rolling" and "grabbing" mechanisms) that have changed over the years due to technological advances. Examinations of printed documents that involve the chemical analysis of ink colorants and the identification of physical machine defects such as trash marks are essential for the forensic examiner, but new techniques are needed to more closely identify a machine model or group of models. An electrostatic detection device (EDD) provide forensic examiners with a nondestructive method to examine indentations on a document. In this work, an EDD is used to detect latent physical markings left on documents by printers and photocopiers. Seventeen inkjet printers, 12 laser printers, and 3 photocopy machines were used to produce test documents. Physical markings were detectable in the large majority of the documents and were reproducible 100% of the time.     

Classification algorithm using halftone features of counterfeit bills and CNN

With recent advancements in image processing and printing technology, home printers have improved in performance and grown more widespread. As such, they have been increasingly used in counterfeiting and forgery. Most counterfeit bills in Korea have been created using home scanners and printers. The identification of printer model is thus necessary to rapidly track down criminals and solve crimes. Household printers can be largely divided into inkjet and laser printers. These two types of printers print halftone textures instead of continuous images. This study proposed a technique of printer classification based on halftone textures that can be observed in printed documents. Since halftone textures are expressed as periodic lattices, the images were transformed via FFT, which is highly effective at expressing periodicity. ResNet, known for its superior gradient flow, was used for training. The experiment was conducted on 12 color laser jets and 2 inkjets. Scans of bills printed by each printer were used, and halftone texture analysis was performed on these images for printer model classification. Each image was cropped into several parts; one of the cropped parts was analyzed. The analysis showed that laser printers could be 100% distinguished from inkjet printers. An accuracy of 98.44% was achieved in make classification. When 50 cropped images were used instead of a single image, the technique achieved 100% accuracy in model classification. The proposed technique is non-destructive; it offers high accessibility and efficiency as it can be performed using a scanner alone, without requiring additional optical equipment.     

Examination of spur marks found on inkjet-printed documents

In this paper, we propose the examination of spur mark evidence on inkjet-printed documents. Spur marks are tool marks created by the spur gears in the paper conveyance system of many inkjet printers. The relationship between printouts and printers were investigated by comparing the spur marks found on printed documents with reference spur marks sampled from known printers. The comparison was based on two characteristics of spur marks: pitch and mutual distance. These characteristics extracted the geometric features of spur marks and provided information on the type of spur gears and their location in the paper conveyance system. The spur marks on a printout matched the reference spur marks within three percent of the measured values. Spur marks were considered to be effective class characteristics to identify certain brands of inkjet printers since spur gears are used in many types of these machines.     

Visualizing latent fingerprints on color-printed papers using ultraviolet fluorescence

Laser detection of latent fingerprints on a white paper has been performed, previously. Ultraviolet fluorescence from various kinds of printer toner and ink used for home printers were measured to study fluorescence imaging of fingerprints on a color-printed white paper. The experimental system consisted of a nanosecond pulsed tunable laser and a cooled CCD camera. Excitation wavelengths are 230 and 280 nm. Fourteen printers consisting of three color laser printers, three color inkjet printers, five monochrome laser printers, two monochrome copy machines, and a color copy machine were tested. Toner and ink of most printers exhibited fluorescence in the region from 360 to 550 nm. In most cases, clear fluorescence images were obtained by time-resolved imaging with a band-pass filter and 280-nm excitation. However for toners from laser color printers that showed strong fluorescence, better results were obtained with 230-nm excitation. Latent fingerprints on a photograph page and a black-character page of a newspaper were also imaged.     

Raman spectroscopy and laser desorption mass spectrometry for minimal destructive forensic analysis of black and color inkjet printed documents

Inkjet ink analysis is the best way to discriminate between printed documents, or even though more difficult, to connect an inkjet printed document with a brand or model of printers. Raman spectroscopy and laser desorption mass spectrometry (LDMS) have been demonstrated as powerful tools for dyes and pigments analysis, which are ink components. The aim of this work is to evaluate the aforementioned techniques for inkjet inks analysis in terms of discriminating power, information quality, and nondestructive capability. So, we investigated 10 different inkjet ink cartridges (primary colors and black), 7 from the HP manufacturer and one each from Epson, Canon and Lexmark. This paper demonstrates the capabilities of three methods: Raman spectroscopy, LDMS and MALDI-MS. Raman spectroscopy, as it is preferable to try the nondestructive approach first, is successfully adapted to the analysis of color printed documents in most cases. For analysis of color inkjet inks by LDMS, we show that a MALDI matrix (9-aminoacridine, 9AA) is needed to desorb and to ionize dyes from most inkjet inks (except Epson inks). Therefore, a method was developed to apply the 9AA MALDI matrix directly onto the piece of paper while avoiding analyte spreading. The obtained mass spectra are very discriminating and lead to information about ink additives and paper compositions. Discrimination of black inkjet printed documents is more difficult because of the common use of carbon black as the principal pigment. We show for the first time the possibility to discriminate between two black-printed documents coming from different, as well as from the same, manufacturers. Mass spectra recorded from black inks in positive ion mode LDMS detect polyethylene glycol polymers which have characteristic mass distributions and end groups. Moreover, software has been developed for rapid and objective comparison of the low mass range of these positive mode LDMS spectra which have characteristic unknown peaks.