指紋を非破壊に可視化するための光計測手法 —時間分解分光法とハイパースペクトルイメージング—

抄録

Optical methods for visualizing fingerprints non-destructively in criminal investigation using the time-resolved spectroscopy and hyperspectral imaging are reviewed. Fluorescence emitted by photoexcited latent fingerprints is utilized for non-destructive visualization of fingerprints. Fluorescence spectrum of fingerprints when excited by an ultraviolet laser has two peaks at 340 and 440 nm, and that the most effective excitation wavelength was 280 nm. Furthermore, the relative intensity of the two peaks at 340 and 440 nm was shown to change over time by ultraviolet irradiation. The time-resolved spectroscopy using a nanosecond pulsed tunable laser was utilized to visualize fingerprints. It was effective in visualizing fingerprints when the background fluorescence was strong. This method was also effective for visualization of other body fluids. Among the components of fingerprints, measurement of excitation-emission matrix revealed that some amino acids contribute to the fluorescence spectra of fingerprints. A portable hyperspectral imager was developed to visualize fingerprints at crime scenes. One of its successful applications is to separate overlapping fingerprints, which was not able to use as evidence before. Using differences in fluorescence spectra of overlapping fingerprints, overlapping fingerprints were successfully separated by statistical analyses. A light irradiation system for efficient hyperspectral imaging was fabricated using motorized stages.