The Quantification of the Contrast for Latent Fingerprint Development Based on Fluorescent Spectrometry
SHEN Dun-pu1, LI Ming1, 2, YUAN Chuan-jun1, 2, YU Hai-feng1, WANG Meng1, 2*
1. Department of Trace Examination, National Police University of China, Shenyang 110035, China
2. Key Laboratory of Impression Evidence Examination and Identification Technology, Ministry of Public Security, Shenyang 110035, China
Abstract：Latent fingerprint development is considered as one of the most important technologies in forensic sciences. After fingerprint development, researchers usually evaluate the effect of fingerprint development according to whether the outline is complete, whether the ridges are clear and coherent, whether the detail features are obvious, and whether the background interference is serious, etc. . However, all above descriptions for evaluation are subjective, which are lack of objectivity, accuracy and scientificity. In order to quantitatively evaluate the effect of fingerprint development objectively, comprehensively and accurately, the contrast of fingerprint development was systematically studied by spectral analysis, and then the accurate quantitative evaluation was achieved. Firstly, we proposed the concept of contrast as the contrast between the fingerprint (signal) and the background (noise), for fingerprint development based on fluorescent methods. The contrast were depended on differences of fluorescent intensity (Intensity Index, I) and fluorescent color (Chroma Index, C) between the friction ridges and the background. Secondly, the substrates, fingerprint developing powders as well as fingerprints developed after fluorescent powder were characterized by spectral instrument and chromaticity software. The calculation method of the fingerprint development contrast, which was defined as the common logarithmic value of I and multiply by C, was finally established. Then, combined with the vision effects and the spectral analysis results, the accuracy of calculated fingerprint development contrast was verified. The results showed that our method had been successfully used in evaluating the contrast of fingerprint development based on fluorescent spectral analysis methods. Finally, combined with spectral analysis technology, the influence factors of the fingerprint development contrast, including the differences of fluorescent intensity, fluorescent color and luminescent mechanisms between the fingerprint development powders, were analyzed in detail. The experimental results showed that the quantitative method of fingerprint development contrast based on spectral analysis could quantitatively evaluate the effect of fingerprint development objectively, scientifically and comprehensively. Moreover, according to Intensity Index and Chroma Index, we summarized the approaches to promote the contrast of fingerprint development, providing beneficial references for the selection of fingerprint development methods in practice applications.
沈敦璞，李 明，袁传军，于海峰，王 猛. 基于荧光光谱方法计算手印显现对比度的研究[J]. 光谱学与光谱分析, 2020, 40(01): 91-97.
SHEN Dun-pu, LI Ming, YUAN Chuan-jun, YU Hai-feng, WANG Meng. The Quantification of the Contrast for Latent Fingerprint Development Based on Fluorescent Spectrometry. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2020, 40(01): 91-97.
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