Design of a Wide Working Range Lens for Iris Recognition

Abstract

This paper presents a methodology to solve the problem of narrow working range of lens for iris recognition. For iris recognition, working range of the lens is limited by the depth of field of the imaging lens. This paper proposes a design of a lens with liquid lens as a key component. The designed lens has a wide working range and can acquire high resolution images. The designed parameters include 19.2–20.3 mm focal lens, work distance from 250 mm to 450 mm, less than 0.5 % distortion, 2.8 working F number, 4 mm image diameter, 840 nm–870 nm wavelength of operating spectrum. At 166 lp/mm, the lens can acquire iris image over all field of view with MTF > 0.3. The lens is composed of fours spherical lenses and one liquid lens. Without moving parts inside, the structure of designed lens is simple and convenient to control.