Outcoupling grating for augmented reality system

An eyepiece for projecting an image to an eye of a viewer, the eyepiece comprising:

• a waveguide having a first surface;
• an incoupling grating optically coupled to a first region of the waveguide, the incoupling grating configured to diffract image light incident on the waveguide in a direction substantially perpendicular to the first surface into the waveguide to be propagated therein in a first direction;
• a first diffractive optical element (DOE) optically coupled to a second region of the waveguide, the first DOE configured to diffract the image light propagating in the waveguide toward a second direction different from the first direction;
• and
• a second DOE optically coupled to the second region of the waveguide, the second DOE including:
• a plurality of first ridges protruding from the first surface of the waveguide and arranged as a periodic array having a period, each respective first ridge having a respective first width in a direction of the period that varies as a function of a position of the respective first ridge in the direction of the period;
• and
• a plurality of second ridges, each respective second ridge protruding from a corresponding first ridge and having a respective second width that is less than a corresponding first width of the corresponding first ridge, each respective second width varying as a function of the position of the corresponding first ridge in the direction of the period;
• wherein the second DOE is configured to diffract a first portion of the image light diffracted by the first DOE toward the eye as a first order reflection, and to diffract a second portion of the image light diffracted by the first DOE away from the eye as a first order transmission.

An eyepiece for projecting an image to an eye of a viewer, the eyepiece comprising:

• a waveguide having a first surface;
• an incoupling grating optically coupled to a first region of the waveguide, the incoupling grating configured to diffract image light incident on the waveguide in a direction substantially perpendicular to the first surface into the waveguide to be propagated therein in a first direction;
• a first diffractive optical element (DOE) optically coupled to a second region of the waveguide, the first DOE configured to diffract the image light propagating in the waveguide toward a second direction different from the first direction;
• and
• a second DOE optically coupled to the second region of the waveguide, the second DOE including:
• a plurality of first ridges protruding from the first surface of the waveguide and arranged as a periodic array having a period, each respective first ridge having a respective first width in a direction of the period;
• and
• a plurality of second ridges, each respective second ridge protruding from a corresponding first ridge and having a respective second width that is less than a corresponding first width of the corresponding first ridge;
• wherein a ratio of the respective second width of the respective second ridge to the corresponding first width of the corresponding first ridge varies as a function of a position of the corresponding first ridge in the direction of the period, and wherein the second DOE is configured to diffract a first portion of the image light diffracted by the first DOE toward the eye as a first order reflection, and to diffract a second portion of the image light diffracted by the first DOE away from the eye as a first order transmission.