All-optical extended depth of field imaging system

We describe a novel approach whereby a phase mask consisting of several spatially multiplexed Fresnel lenses (FL) positioned in the pupil of an imaging system increases the depth of field (DOF) significantly. Each FL acts essentially as a corrective lens with a slightly different focal length. Keeping the detector plane in a fixed location, each individual FL provides perfect imaging for different object planes, with a certain DOF tolerance around it. Allowing the individual DOFs to overlap slightly, the resulting composite DOF of the imaging system is highly extended. Nevertheless, the increased DOF is coupled with a reduction in image contrast and resolution. System analysis and simulation results are presented.