1. A waveguide apparatus, comprising: a planar waveguide having an at least partially transparent optical element comprising a first end, a second end, a first face, and a second face, wherein the planar waveguide is configured to permit light beams emitted by or reflected from physical objects that are located on a far side of the planar waveguide relative to a viewer to reach at least one eye of the viewer; and a plurality of diffractive optical elements comprising two dynamic diffractive optical elements and operatively coupled to the planar waveguide, wherein the two dynamic diffractive optical elements have different diffractive lens aspects such that when each of the two dynamic diffractive elements is alternatively switched on, the each of the two dynamic diffractive elements focuses light to a different focus distance, the first and second ends of the planar waveguide are opposed to each other along a length of the planar waveguide, the first and the second faces of the planar waveguide form an at least partially internally reflective optical path along a portion of the length of the planar waveguide, and the plurality of diffractive optical elements are configured to interrupt the at least partially internally reflective optical path to provide a respective plurality of optical paths between an exterior and an interior of the planar waveguide via the first face thereof at respective positions along the portion of the length of the planar waveguide.