DYNAMIC INCOUPLING GRATINGS IN IMAGING SYSTEMS

1 . A method of projecting an image light field to an eye of a viewer, the method comprising:

modulating, by a controller, an intensity of a light beam in a sequence of time slots, each time slot of the sequence of time slots corresponding to a respective field angle of the image light field, the intensity of the light beam in each time slot of the sequence of time slots corresponding to an intensity of the image light field at the respective field angle;

propagating the light beam onto a dynamic input coupling grating (ICG);

controlling the dynamic ICG, by the controller, to diffract a respective portion of the light beam into a waveguide at a respective angle corresponding to the respective field angle for each time slot of the sequence of time slots; and

directing each respective portion of the light beam out of the waveguide toward the eye at the respective field angle, thereby projecting the image light field to the eye of the viewer.

2 . The method of claim 1 , wherein the dynamic ICG comprises a surface acoustic wave (SAW) modulator coupled to an oscillating electric signal source, the method further comprising:

controlling, by the controller, operation of the oscillating electric signal source to supply an oscillating electric signal to the SAW modulator to generate respective acoustic waves that propagate on a surface of the SAW modulator.

3 . The method of claim 2 , wherein the SAW modulator comprises a substrate and a piezoelectric transducer attached to the substrate, the method further comprising:

supplying the oscillating electric signal to the piezoelectric transducer to generate the respective acoustic waves; and

propagating the respective acoustic waves on a surface of the substrate.

4 . The method of claim 2 , wherein the SAW modulator includes a substrate, a first transducer attached to the substrate, and a second transducer attached to the substrate, the method further comprising:

configuring the first transducer to vibrate in a first axis;

configuring the second transducer to vibrate in a second axis orthogonal to the first axis; and

coupling the first transducer and the second transducer to the oscillating electric signal source to drive the first transducer and the second transducer to generate the respective acoustic waves.

5 . The method of claim 2 , wherein the SAW modulator includes a substrate including a material that exhibits a piezoelectric effect that generates the respective acoustic waves.

6 . The method of claim 5 , wherein the material that exhibits the piezoelectric effect comprises one of fused silica, lithium niobate, arsenic trisulfide, tellurium dioxide, tellurite glass, or lead silicate.

7 . The method of claim 2 , wherein the SAW modulator is an integral part of the waveguide.

8 . The method of claim 1 , wherein the light beam is incident on a surface of the dynamic ICG in a direction perpendicular to the surface of the dynamic ICG.

9 . The method of claim 1 , wherein the light beam is at a non-zero bias angle relative to a direction perpendicular to a surface of the dynamic ICG.

10 . The method of claim 1 , further comprising:

modulating, by the controller, an intensity of a second light beam in the sequence of time slots;

propagating the second light beam onto the dynamic ICG;

controlling the dynamic ICG, by the controller, to diffract a respective portion of the second light beam into the waveguide at a respective angle; and

directing each respective portion of the second light beam out of the waveguide toward the eye at the respective field angle,

wherein the light beam is incident on a surface of the dynamic ICG via propagation of the light beam in a first direction,

wherein the intensities of the light beam in the sequence of time slots correspond to intensities of the image light field in a first range of angular field of view (FOV),

wherein the second light beam is incident on the surface of the dynamic ICG via propagation of the second light beam in a second direction different from the first direction, and

wherein the intensities of the second light beam in the sequence of time slots correspond to intensities of the image light field in a second range of angular FOV different from the first range of angular FOV.

11 . The method of claim 1 , wherein the waveguide is transparent, the method further comprising superimposing the image light field on an external image transmitted through the waveguide to the eye of the viewer.

12 . The method of claim 1 , wherein each respective portion of the light beam is directed out of the waveguide toward the eye at the respective field angle via a diffractive optical element (DOE), the method further comprising configuring the DOE to diffract each respective portion of the light beam out of the waveguide toward the eye at the respective field angle.

13 . The method of claim 1 , wherein the light beam propagates to the dynamic ICG on an optical axis having a fixed position and orientation relative to the dynamic ICG.

14 . An eyepiece for projecting an image light field to an eye of a viewer for forming an image of virtual content, the eyepiece comprising:

a waveguide configured to propagate light therein, the waveguide including an input pupil;

a light source configured to deliver a light beam to be incident on the waveguide at the input pupil;

a controller coupled to the light source and configured to modulate an intensity of the light beam in a plurality of time slots, each time slot corresponding to a respective field angle of the image, and the intensity of the light beam in each time slot corresponding to an intensity of the image at the respective field angle;

a dynamic input coupling grating (ICG) formed on a first lateral region of the waveguide corresponding to the input pupil, wherein the dynamic ICG is configured to:

for each time slot, diffract a respective portion of the light beam into the waveguide at a respective total internal reflection (TIR) angle corresponding to a respective field angle; and

scan the TIR angle from one time slot to a next time slot in accordance with modulation of the light beam; and

an outcoupling diffractive optical element (DOE) coupled to a second lateral region of the waveguide and configured to:

diffract each respective portion of the light beam out of the waveguide toward the eye at the respective field angle; and

project the image light field to the eye of the viewer.

15 . The eyepiece of claim 14 , wherein the dynamic ICG comprises a surface acoustic wave (SAW) modulator including:

a layer of a piezoelectric material; and

a transducer coupled to an oscillating electric signal source configured to:

drive the transducer at a plurality of frequencies, each respective frequency corresponding to a respective time slot; and

create a respective sound wave in the layer of the piezoelectric material with a respective spatial period;

wherein the dynamic ICG is further configured to diffract the respective portion of the light beam into the waveguide at the respective TIR angle in the respective time slot.

16 . The eyepiece of claim 15 , wherein the transducer comprises:

a piezoelectric transducer; or

a first transducer configured to vibrate in a first axis; and

a second transducer configured to vibrate in a second axis orthogonal to the first axis.

17 . The eyepiece of claim 15 , wherein the piezoelectric material comprises one of fused silica, lithium niobate, arsenic trisulfide, tellurium dioxide, tellurite glass, or lead silicate.

18 . The eyepiece of claim 15 , wherein:

the waveguide comprises one of fused silica, lithium niobate, arsenic trisulfide, tellurium dioxide, tellurite glass, or lead silicate; and

the layer of the piezoelectric material is an integral part of the waveguide.

19 . The eyepiece of claim 14 , wherein the light beam is incident on the waveguide substantially at a non-zero bias angle.

20 . The eyepiece of claim 14 , further comprising a static grating coupled to the waveguide at the input pupil and configured to receive the light beam and diffract a portion of the light beam at a bias angle toward the dynamic ICG.