Experience-independent fingerprint imaging using a dark-field ring light illumination system

Latent fingerprint is the most common biological evidence at crime scenes. Traditionally, police search and shoot the latent fingerprints through the illumination of alternative light source (ALS). However, it may cause incomplete or incorrect fingerprint image when the operator's experience is insufficient. This problem may reduce the credibility of criminal identification. In this study, an uniform light source with a dark field characteristics was developed to overcome this problem. Optical simulations and experiments were performed to verify its performance. The results show that the developed system can provide images with high contrast, high uniformity and high repeatability. The operator's experience difference does not have a significant impact on the measurement results. This system can replace the traditional ALS lighting system and construct a standard measurement. This study developed a novel solution for criminal identification, identity authentication and related applications.