Waveguide with coherent interference mitigation

A wearable display comprising:

• a light source for providing a beam of image light carrying a plurality of image frames at a frame rate;
• a pupil-replicating waveguide comprising:
• a waveguide body having opposed surfaces for guiding the beam of image light therebetween;
• an out-coupling element in an optical path of the beam for out-coupling a plurality of portions of the beam at a plurality of spaced apart locations along the optical path;
• and
• electrodes coupled to at least a portion of the waveguide body for modulating an optical path length of the optical path of the beam to create time-varying phase delays between different portions of the plurality of portions of the beam out-coupled by the out-coupling element;
• and
• a controller operably coupled to the electrodes of the pupil-replicating waveguide and configured to apply an electrical signal to the electrodes to modulate the optical path length.

A method for expanding a beam of image light, the method comprising:

• propagating the beam along an optical path in a pupil-replicating waveguide;
• out-coupling, using an out-coupling element in an optical path of the beam, a plurality of portions of the beam at a plurality of spaced apart locations along the optical path;
• and
• modulating, by applying an electrical signal to electrodes coupled to at least a portion of the pupil-replicating waveguide, an optical path length of the optical path of the beam to create time-varying phase delays between different portions of the plurality of portions of the beam out-coupled by the out-coupling element.