Optical displays

A method of propagating light, the method comprising:

• exposing an apparatus to a light source, whereby the light propagates within a portion of the apparatus,
• wherein the apparatus comprises:
• an optical substrate for propagating light received from a light source;
• a first set of one or more switchable diffractive elements in the substrate;
• and
• a second set of one or more switchable diffractive elements in the substrate, each diffractive element in the second set corresponding to a diffractive element in the first set, each of the diffractive elements in the first and second sets configured to switch between on and off states, one of the states for diffracting light and the other state for allowing light to pass through, each of the first set of diffractive elements configured to diffract the light at an angle for propagation in the substrate, and each of the second set of diffractive elements configured to diffract the light for display.

A method of propagating light, the method comprising:

• exposing an apparatus to a light source, whereby the light propagates within a portion of the apparatus,
• wherein the apparatus comprises:
• a substrate for propagating light received from a light source;
• a first set of one or more switchable Bragg gratings or holographic polymer dispersed liquid crystal devices in the substrate;
• and
• a second set of one or more switchable Bragg gratings or holographic polymer dispersed liquid crystal devices in the substrate, each Bragg grating or liquid crystal device in the second set corresponding to a Bragg grating or liquid crystal device in the first set, each of the Bragg gratings or liquid crystal devices in the first and second sets configured to switch between on and off states, one of the states for diffracting light and the other state for allowing light to pass through, each of the first set of Bragg gratings or liquid crystal devices configured to diffract the light at an angle for propagation in the substrate, and each of the second set of Bragg gratings or liquid crystal devices configured to diffract the light for display.