Detection of fingerprints on porous papers and performance evaluation

Abstract

At crime scenes, fingerprints are often found on paper. The visualization of invisible fingerprints, so-called latent fingerprints (LFPs), is critical in forensic investigation. Laser-induced fluorescence technology for fingerprint detection has the advantages of sensibility, high-resolution, non-destructiveness and non-contact. In this paper, the characteristics of commonly used paper and the interaction between ultraviolet light and porous paper are briefly analyzed firstly. Next the fingerprint detection device is introduced. Then the output energy of the laser is optimized and a series of experiments are carried out. Local gray value stretching and power enhancement algorithms are used to process the fingerprint fluorescence data, and the high contrast fingerprint images are obtained. The experimental results show that the fingerprint substance and paper are degraded in different degrees under the excitation of ultraviolet light, and the second or third detection can improve the signal-to-noise ratio of detection. By the method of this paper, clear fingerprint images can be obtained quickly, and more than 10 secondary fingerprint structures can be extracted from these fingerprint images, which provides quantitative evidences for criminal investigation.