Extending the depth of field with chromatic aberration for dual-wavelength iris imaging

We propose a method of extending the depth of field to twice that achievable by conventional lenses for the purpose of a low cost iris recognition front-facing camera in mobile phones. By introducing intrinsic primary chromatic aberration in the lens, the depth of field is doubled by means of dual wavelength illumination. The lens parameters (radius of curvature, optical power) can be found analytically by using paraxial raytracing. The e ective range of distances covered increases with dispersion of the glass chosen and with larger distance for the near object point.