Ultraviolet Multi-Channel Imaging of Sweat Latent Fingerprints and Analysis of Its Characteristics Over Time
YU Jin-tao1, 2, 3, LI Qing-ling1, 2, 3 , LI Lei1, 2, 3, YIN Da-yi1, 2, 3*
1. Key Laboratory of Infrared System Detection and Imaging Technology, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai 200083, China
2. Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai 200083, China
3. University of Chinese Academy of Sciences，Beijing 100049, China
Abstract：The uniqueness and lifetime invariance of fingerprints enable fingerprints to verify a person’s identity information, which has a wide range of applications in the field of biometrics. The sweat latent fingerprint has special reflection, scattering and fluorescence characteristics for ultraviolet light, so the sweat latent fingerprint can be extracted by the ultraviolet band, and the scene and target samples are not polluted. At present, there are extensive researches on fingerprint extraction in the ultraviolet band, but there are few studies on the change of fingerprint with time. Generally, the changes of the content of sweat latent fingerprint components are generally measured by chemical methods. The study found that the UV spectral characteristics of each component of the fingerprint are different, and the volatilization degree of these components is also inconsistent with time. The multi-channel UV imaging system is used to perform gaze imaging on the sweat latent fingerprint, and the DN value of each channel is found to change with time. The degree is not the same, and the fingerprint can be timely analyzed by studying the change of the DN value of each channel. First, the reflectance spectra of substances that are easily contacted by fingers such as sweat, alcohol, and edible oil were studied by ultraviolet spectrometer and xenon lamp, and the reflection spectrum characteristics of these materials were obtained. Then, for these types of fingerprints, a multi-channel UV imaging device was developed, which has three UV channel pairs at 240～280 nm (channel 1), 280～315 nm (channel 2) and 315～340 nm (channel 3). The gaze imaging was performed to obtain a clear fingerprint image, and the average values of the 10 points with the highest code value on the fingerprint image were compared, and the relationship between the DN value and the time change of different channels was obtained. The experimental results show that the sweat latent fingerprint has good imaging characteristics in the ultraviolet band, and its imaging DN value gradually decreases with time. The imaging DN values of the three fingerprints in channel 1 of 240～280 nm were reduced to the first day. The imaged DN values of the three fingerprints in channel 2 of 320～340 nm on day 7 decreased to 0.57, 0.61, and 0.60 on the first day, respectively; the three fingerprints in channel 3 of 340～420 nm were respectively reduced by 0.62, 0.60, and 0.59. The imaging DN values on the seventh day were reduced to 0.56, 0.63, and 0.58 on the first day, respectively. The experimental results show that the spectral characteristics of different types of fingerprints in the ultraviolet band are not consistent, the imaging DN is not the same, and the law of change with time is different, but the volatilization of fingerprint components has a certain law, imaging DN value from the first day By the seventh day, it will be reduced to about 60%, which can reflect the volatile nature of the fingerprint to some extent. Combined with the ultraviolet multi-channel imaging system, the variation law of fingerprints can be well studied, which provides an important means for fingerprint research in criminal investigation.
Key words：Fingerprint; Reflection spectrum; Material composition; Variation law
庾金涛，李清灵，李 磊，尹达一. 指纹紫外光谱特性研究及变化规律分析[J]. 光谱学与光谱分析, 2019, 39(12): 3705-3710.
YU Jin-tao, LI Qing-ling , LI Lei, YIN Da-yi. Ultraviolet Multi-Channel Imaging of Sweat Latent Fingerprints and Analysis of Its Characteristics Over Time. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2019, 39(12): 3705-3710.
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