The method for eliminating bright spot in the field of view center in UV fingerprint identification camera system

UV fingerprint identification camera system is a very useful tool in the field of criminal investigation. But its image quality is often influenced by the bright spot in the FOV center of the system. In this paper, the operation principle of fingerprint identification and camera system is described. The generation of the bright spot is analyzed and some methods are given to eliminate it. It is pointed out that the phenomenon is mainly caused by off-axis stray light from the system. The methods to eliminate the bright spot include, adopting an object lens with higher extinction performance, using a view-field diaphragm with proper diameter and position, or evaporating a UV absorbing film on the input window surface outside the active area. The experimental result shows that the methods meet the fingerprint identification and storage requirements in criminal investigation.