  Imaging volume of an iris recognition system has been restricting the
throughput and cooperation convenience in biometric applications. Numerous
improvement trials are still impractical to supersede the dominant fixed-focus
lens in stand-off iris recognition due to incremental performance increase and
complicated optical design. In this study, we develop a novel all-in-focus iris
imaging system using a focus-tunable lens and a 2D steering mirror to greatly
extend capture volume by spatiotemporal multiplexing method. Our iris imaging
depth of field extension system requires no mechanical motion and is capable to
adjust the focal plane at extremely high speed. In addition, the motorized
reflection mirror adaptively steers the light beam to extend the horizontal and
vertical field of views in an active manner. The proposed all-in-focus iris
camera increases the depth of field up to 3.9 m which is a factor of 37.5
compared with conventional long focal lens. We also experimentally demonstrate
the capability of this 3D light beam steering imaging system in real-time
multi-person iris refocusing using dynamic focal stacks and the potential of
continuous iris recognition for moving participants.
