Waveguide and diffraction grating for augmented reality or virtual reality display for reducing the visible appearance of grating structures

A waveguide for use in a virtual reality or augmented reality device, the waveguide comprising:

• an input region comprising optical structures configured to couple image bearing light into the waveguide so that it propagates under total internal reflection (TIR) within the waveguide;
• and
• an output region comprising optical structures configured to receive image bearing light from the input region in a direction along a first axis and outcouple the light towards a viewer,
• wherein the output region comprises a plurality of zones, the plurality of zones comprising:
• a first zone, the first zone comprising:
• a first rectangular periodic array of optical structures arranged on a plane, the first rectangular periodic array forming a first 2D lattice with rectangular symmetry;
• and a second rectangular periodic array of optical structures arranged on the plane, the second rectangular periodic array forming a second 2D lattice with rectangular symmetry;
• wherein the first rectangular array of optical structures is overlaid on the second rectangular array of optical structures in the plane such that the arrays are spatially offset from one another on the plane in both orthogonal directions of the lattice by a factor of between 40% and 60% of the period of the first rectangular array;
• and
• a second zone, the second zone comprising a 1D linear grating or the second zone comprising a plurality of optical structures defining first and second diffractive optical elements, wherein each of the plurality of optical structures has a shape, when viewed in the plane of the waveguide, having respective sides that are parallel to the first and second diffractive optical elements and wherein the side or sides that are parallel to the first diffractive optical element have a different length to the side or sides that are parallel to the second diffractive optical element in order to provide a difference in diffraction efficiency between the first and second diffractive optical elements.

A waveguide for use in a virtual reality or augmented reality device, the waveguide comprising:

• an input region comprising optical structures configured to couple image bearing light into the waveguide so that it propagates under total internal reflection (TIR) within the waveguide;
• and
• an output region comprising optical structures configured to receive image bearing light from the input region in a direction along a first axis and outcouple the light towards a viewer,
• wherein an output region of the waveguide comprises a plurality of zones, the plurality of zones comprising:
• a first zone, comprising optical structures having a first set of characteristics, wherein the optical structures in the first zone are arranged in the plane of the waveguide such that they have a first periodicity;
• a second zone, comprising optical structures having a second set of characteristics;
• and
• a transition zone, located between the first zone and the second zone, the transition zone comprising optical structures having a periodicity equal to the first periodicity along at least a transition direction, the transition zone having a first side located adjacent to the first zone, and a second side located adjacent to the second zone, wherein the optical structures in the transition zone gradually change in their characteristics across the transition zone between the first side and the second side such that there is a gradual change from the optical structures in the first zone to the optical structures in the second zone whilst maintaining the periodicity of the optical structures along the transition direction throughout the transition zone;
• and
• a non-diffractive zone, wherein the non-diffractive zone comprises optical structures having at least one of a shape, size or periodicity such that the image bearing light undergoing TIR in the waveguide is substantially not diffracted by the optical structures in the non-diffractive zone.