Apparatus for Providing Waveguide Displays with Two-Dimensional Pupil Expansion

An optical display, comprising:

• a first waveguide having a first surface and a second surface;
• an input coupler;
• a fold grating;
• an output grating;
• and
• an input image node (IIN),
• wherein said input coupler is configured to receive collimated first wavelength image modulated light from said IIN and to cause said first wavelength image modulated light to travel within the first waveguide via total internal reflection between said first surface and said second surface to the fold grating;
• wherein said fold grating is configured to provide pupil expansion in a first direction and to direct said first wavelength image modulated light to the output grating via total internal reflection between the first surface and the second surface;
• wherein said output grating is configured to provide pupil expansion in a second direction different than said first direction and to cause said first wavelength image modulated light to exit said first waveguide from said first surface or said second surface;
• wherein said first wavelength image modulated light undergoes a dual interaction with said fold grating;
• and
• wherein at least one selected from the group of said input coupler, said fold grating, and said output grating is a grating switchable between a diffracting and a non-diffracting state.