Beam multiplier that can be used as an exit-pupil expander and related system and method

A beam multiplier, comprising:

• a beam-multiplying layer having first and second opposite sides, the second side operable to generate output beamlets of light from an input beam of light;
• an electro-optic layer having first and second opposite sides adjacent to the beam-multiplying layer and having an adjustable index of refraction, the first side of the electro-optic layer adjacent to the second side of the beam-multiplying layer;
• a first electrode adjacent to the first side of the beam-multiplying layer;
• a second electrode adjacent to the second side of the electro-optic;
• and
• a mirror aligned to receive light through the beam-multiplying layer and the electro-optic layer and reflect the light back through the beam-multiplying layer and the electro-optic layer to generate the fixed pattern of output beamlets.

An optical device, comprising:

• a transmissive diffraction grating having a diffraction characteristic and a fixed diffraction pattern;
• a mirror aligned to receive light through the transmissive diffraction grating and reflect the received light through the transmissive diffraction grating;
• and
• a structure operable to alter the diffraction characteristic of the diffraction grating.

An optical device, comprising:

• an optical diffractive element having a bumpy transmissive surface with an optical characteristic;
• a reflector operable to reflect through the bumpy transmissive surface of the optical element light received from the optical element;
• and
• a structure operable to alter the optical characteristic of the bumpy transmissive surface of the optical element.