Optical systems utilize waveplates to simultaneously
encode information for increasing image
depth of field and for providing a
depth map of the imaged object or sample. These waveplates are configured to result in a focus-invariant
point spread function in one focal region, and to result in
point spread functions that vary as a function of range within the imaged object in a different focal region. For example, a basic compound
microscope might have a specially shaped
waveplate inserted at the back
aperture plane of the
microscope objective to manipulate the phase of the
wavefront. An image formed on one side of the plane of best focus is focus invariant, and is brought into focus by a restoring
algorithm. An image formed on the other side of the plane of best focus captures
point spread functions comprising rings that vary with depth within the imaged object.