Exploration And Experimental Research On New Techniques Of Discrimination Of Added Printing Documents

The identification of added printed documents has always been one of the major problems in questioned document examination.Its identification not only involves the distinguish of species and individuals of the printed documents,but also refers to the printing regularities.In recent years,with the continuous innovation of office equipment,the difficulty of added printing documents has also increased,especially the identification of added printing documents by the same machine.Based on this,this article study on new technology for identification of printed documents through experimental research for related identification.The introductory part of the article introduces the research background of the mechanism documents.And discuss the domestic and foreign research of identification of added printing documents and its necessity and complexity.Based on this,some experimental plan and program were developed.The research direction of added printing document identification technology for the same machine or different machine,laser or inkjet printers had been determined,which lays the foundation for the following related technical introduction and experimental analysis.The first two chapters of this article mainly analyze the theoretical basis and practical requirements of added printing documents from the perspectives of the concept,definition,classification,characteristics,identification objectives,and technical methods.It provides a basis for the following experimental design and sample making.In this context,Chapter 3 specifically introduces the design ideas of all experiments in this article,and lists the market usage of experimental equipment and the preparation of printed samples.Starting from the fourth chapter of the article,the author emphatically introduced the research situation and experimental conclusions of the new technology of identification om added printing documents.First of all,the fourth chapter is based on laser printing with different grayscale dots or lines as the starting point to study the new identification technology of laser-based printing documents with different machines.This experiment has studied 95 laser printers of different brands and models.A total of 331 documents within different gray-scale images edited by PDF or Execl are printed in color or black and white printing modes.Through observation,it is found that although the gray-scale dots or lines of some brands and models of laser printers are similar,the gray-scale dots or lines on the document have regularity.Accordingly,by comparing the patterns of the suspicious and the undisputed content on the printed documents,it can be distinguished whether the two are produced by the same laser printer,so as to further determine whether the questioned document has been altered.Secondly,Chapter 5 takes the effect of the secondary fusion on the microscopic morphology of toner to study the new technology of the identification on added printing documents by the same machine.This experiment has studied 17 different brands and models of laser printers and produced 170 documents.Through a stereo microscope,as the number of fusing times increased,some areas in the toner micrograph will become brighter or darker.After calculating the average gray scale of the toner microscopic morphology,it is found that the secondary fusion of some laser printers become more flat on the surface area of the thermoplastic resin,and the average gray scale increases accordingly;while the secondary fusion of some laser printers makes the toner particle dispersion area more uneven,and the average gray value decreases.Based on this,by comparing the microscopic morphology of the toner on the printed documents with suspicious additions and undisputed content,as well as measuring and analyzing the gray average of each area on the microscopic morphology,so as to further determine whether the questioned documents has been altered.Finally,the sixth chapter studies the new technology of inkjet printing documents based on the operating regularity of the stepper motor.The experiment studied 22 different brands and models of thermal inkjet printers,and a total of 154 documents were printed.Through observation,it is found that the maximum length of the print heads of the 22 inkjet printers is not the same;the difference in the distribution of splashed ink dots of inkjet printings is mainly affected by the running direction and speed of the stepper motor(nozzle);the track of the stepper motor was able to be determined by the periodic morphological characteristics of the ink marks combined with the maximum gauges,and could be used to judge how many times a document was printed.According to this,the trajectory of the stepper motor can be used to identify and judge the number of times of operating on the inkjet printed documents.To sum up,To study the techniques for identification of laser or inkjet printed documents by the same machine or different machine,this article uses experiments to study the gray-scale dot morphology of laser printed documents,the influence of secondary fusion on the microscopic morphology of toner and the operating regularity of stepper motor of inkjet printer.The process and results of these experimental studies may not only be applied to the identification of altered printed documents,but also help us analyze the regularities of laser or inkjet printers and the formation process of printed documents.