Determination of the Sequence of Intersecting Lines Between Toners and Seals by Laser Fluorescence Microscope

Abstract

Fluorescence microscope is considered to be one of the most effective ways to examine the sequence of intersecting seal and toner lines of questioned documents. In reality, however, the toner (mainly divided into compact and noncompact toners) and seal of a questioned document have such a complex morphology and sequence of crossing lines that current methods cannot meet the requirement of practical document identification. In view of the challenges of document examination, a laser fluorescence microscope and method are developed in this study. The developed microscope provides additional functionality to traditional fluorescence microscopes of transmitted light modality, laser excitation, selectable excitation wavelength, and selectable fluorescence filters. The results obtained from the method of comparisons between transmitted light and fluorescence modalities were positive under most conditions, particularly for noncompact toner examination for which a 100% accuracy rate and 90% detection rate were achieved in blind testing.

Interpol questioned documents review 2019–2022

“…including any other technology used to prepare the document. The following 64 articles [ [548] , [549] , [550] , [551] , [552] , [553] , [554] , [555] , [556] , [557] , [558] , [559] , [560] , [561] , [562] , [563] , [564] , [565] , [566] , [567] , [568] , [569] , [570] , [571] , [572] , [573] , [574] , [575] , [576] , [577] , [578] , [579] , [580] ] [ [581] , [582] , [583] , [584] , [585] , [586] , [587] , [588] , [589] , [590] , [591] , [592] , [593] , [594] , [595] , [596] , [597] , [598] , [599] , [600] , [601] , [602] , [603] , [604] , [605] , [606] , [607] , [608] , [609] , [610] , [611] ], combined with 17 presentations [...…”

Determination of crossing sequences between seal impression and laser‐printed lines based on characteristics of the toner molten state

“…In addition to the above operating conditions, the light source was switched to a 470 nm CL6000 LED excitation light source and was equipped with a 590 nm LED Epodye Fluor filter. The sequence of intersecting lines determined by the fluorescence method mainly depends on the existence of seal fluorescence on the surface of the toner; the details of this method are presented in a previous report [10,11].…”

“…Scraping to strip off the toner line to observe what was underneath seems to be a suitable technique to determine the sequence of intersecting lines between toners and seals, but the drawback of this method lies in the destruction of the sample [4]. Recently, a laser fluorescence technique was reported and shown by Chinese document examiners to be most effective in the examination of seal and toner line sequences [10]; however, some stamp-pad inks sold in the market still display no fluorescence. Therefore, as each method has its own limitations and scope of application, the combination of a variety of methods ensures the results of the scientific analyses are more meaningful.…”

The factors influencing the identification of the chronological intersecting sequence between ink and toner

“…Optical microscopes are now generally used to observe the apparent morphology of intersections because of their rapidity, nondestructive nature, and low cost [3][4][5]. In addition to optical microscopes, other nondestructive equipment has been employed, such as 3-D Laser Profilometry [6], laser fluorescence microscopes [7], and attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectral imaging techniques [8]. However, with the methods mentioned above, the judgments are mainly based on the operator's subjective experience and perception.…”