Experimental Study Of Fingerprint Extraction From Sign Pen Writing Background Based On Visible Spectral Imaging Technology

In general,the fingerprint in sign pen writing background refers to the ink or inkpad fingerprint pressed on various types of paper with the background of sign pen writing.Meanwhile,to completely extract such fingerprint is of great significance to solve criminal cases,because it is the common physical evidence.Considering that high time consumption,complex operation and small application of traditional extraction methods,such as physical evidence photography and image processing,it is especially important to find a convenient,efficient,and non-destructive fingerprint extraction method.By means of selecting 32 different brands and colors of inks or inkpads(3 inks and 29inkpads),different brands and colors of 20 sign pens,and 8 different types of writing paper in the market,a total of 32 ink or inkpad fingerprint samples and 5120 fingerprints pressed on sign pen background were made in this paper.Based on visible spectral imaging technology and photoluminescence principle,the spectral data of experimental samples were acquired and processed through visible multispectral imager.With the help of direct image observation and extensive experimental data statistics,the reliable data and feasible technical methods for extracting fingerprints from sign pen writing background were scientifically and quantitatively summarized.Besides,an experimental study was conducted on extracting fingerprints from sign pen writing background on different paper types,fingerprint extraction affecting factors,and the optimal conditions for fingerprint extraction,so as to provide data information and technical support for extracting fingerprint from sign pen writing background in the actual public security work as well as scientific research.Experiments completed in this study: 1.Photoluminescence characteristics test of 32 different brands and colors of inks or inkpads;2.Experiment of extracting 3200 ink or inkpad pressed fingerprints from sign pen writing background on five kinds of blank writing paper,including copy paper,white paper,kraft paper,leather paper,and newsprint;3.Experiment of extracting 1920 ink or inkpad pressed fingerprints from sign pen writing background on three kinds of writing paper with different complicated backgrounds,including draft paper produced by People's Public Security University of China,Deli checkered letter writing paper,and Jinmeilai two-page bill;4.Experiment of influencing factors of exposure amount on fingerprint extraction;5.experiment of influencing factors of wavelength step on fingerprint extraction.Findings in this study: 1.Visible spectral imaging technology can effectively check the photoluminescence characteristics of ink or inkpad.2.Visible spectral imaging technology can effectively eliminate the sign pen background written on 5 different blank writing papers ofcopy paper,white paper,kraft paper,leather paper and newsprint,so as to help extract ink or inkpad pressed fingerprints;under the same photoluminescence condition,the fingerprint extraction effect from high to low respectively is white paper,copy paper,newsprint,kraft paper,and leather paper;the fingerprint extraction effect varies in different photoluminescence conditions,and 510 nm green light is the best optimal photoluminescence band for fingerprint extraction as shown in this study.3.Visible spectral imaging technology can effectively eliminate the sign pen writing background written on the draft paper produced by People's Public Security University of China,Deli checkered letter writing paper,and Jinmeilai two-page bill,so as to help extract ink or inkpad pressed fingerprints.4.On the premise of keeping other experimental conditions unchanged,the exposure amount affects the fingerprint extraction effect,which means that the increased the exposure amount,the better the fingerprint extraction effect.So a large exposure amount shall be guaranteed in order to improve the accuracy of fingerprint extraction.5.Under the same experimental conditions,the smaller the wavelength step value,the better the fingerprint extraction effect.In consideration of achieving a better extraction effect and higher work efficiency,the smaller wavelength step is more recommended.