阅读说明：本技术 成像系统中的动态入耦合光栅 (Dynamic incoupling grating in imaging system ) 是由 J·I·特里斯纳迪 P·圣西莱尔 C·卡尔里斯勒 于 2019-08-28 设计创作，主要内容包括：一种用于将图像光场投射到观看者的眼睛以形成虚拟内容的图像的目镜包括：波导；光源,其被配置为传递要入射在波导上的光束；控制器,其耦合到光源并被配置为在多个时隙中调制光束的强度；动态输入耦合光栅(ICG),其被配置为对于每个时隙以与相应的场角对应的相应的全内反射(TIR)角将光束的相应的部分衍射到波导中；以及出耦合衍射光学元件(DOE),其被配置为以相应的场角将光束的每个相应的部分朝向眼睛衍射出波导,从而将光场投射到观看者的眼睛。(An eyepiece for projecting an image light field to an eye of a viewer to form an image of virtual content comprising: a waveguide; a light source configured to deliver a light beam to be incident on the waveguide; a controller coupled to the light source and configured to modulate an intensity of the light beam in a plurality of time slots; a dynamic in-coupling grating (ICG) configured to diffract, for each time slot, a respective portion of the optical beam into the waveguide at a respective Total Internal Reflection (TIR) angle corresponding to a respective field angle; and an out-coupling Diffractive Optical Element (DOE) configured to diffract each respective portion of the light beam out of the waveguide toward the eye at a respective field angle, thereby projecting a light field to the eye of a viewer.)

1. An eyepiece for projecting an image light field to an eye of a viewer, the eyepiece comprising:

a waveguide configured to propagate light via internal reflection;

a dynamic in-coupling grating (ICG) formed on a first lateral region of the waveguide;

a light source configured to generate a light beam transmitted to the dynamic ICG;

a controller coupled to the light source and the dynamic ICG, the controller configured to:

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

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

an exit pupil expander coupled to a second lateral region of the waveguide and configured to direct each respective portion of the light beam out of the waveguide at the respective field angle toward the eye of the viewer, thereby projecting the image light field to the eye of the viewer.

2. The eyepiece of claim 1, wherein the dynamic ICG comprises a Surface Acoustic Wave (SAW) modulator coupled to an oscillating electrical signal source that provides an oscillating electrical signal to the SAW modulator under control of the controller to generate respective acoustic waves that propagate on a surface of the SAW modulator such that the SAW modulator diffracts the respective portion of the optical beam into the waveguide at the respective angle in each respective time slot.

3. The eyepiece of claim 2, wherein:

the SAW modulator includes a substrate and a transducer attached to the substrate; and

the transducer is coupled to the oscillating electrical signal source to drive the transducer to generate the respective acoustic waves.

4. The eyepiece of claim 3, wherein the transducer comprises a piezoelectric transducer.

5. The eyepiece 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 first transducer is configured to vibrate on a first axis;

the second transducer is configured to vibrate on a second axis orthogonal to the first axis; and

the first transducer and the second transducer are coupled to the oscillating electrical signal source to drive the first transducer and the second transducer to generate the respective acoustic waves.

6. The eyepiece of claim 2, wherein:

the SAW modulator includes a substrate; and

the substrate includes a material exhibiting a piezoelectric effect that generates the corresponding acoustic wave.

7. The eyepiece of claim 6, wherein the material exhibiting the piezoelectric effect comprises one of: fused silica, lithium niobate, arsenic trisulfide, tellurium dioxide, tellurate glass, or lead silicate.

8. The eyepiece of claim 6, wherein the SAW modulator is an integral part of the waveguide.

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

10. The eyepiece of claim 1, wherein the light beam is incident on a surface of the dynamic ICG at a non-zero offset angle relative to a direction normal to the surface of the dynamic ICG.

11. The eyepiece of claim 1, wherein the dynamic ICG operates in a transmissive mode.

12. The eyepiece of claim 1, wherein the dynamic ICG operates in a reflective mode.

13. The eyepiece of claim 12, further comprising a static grating coupled to the waveguide, the static grating configured to diffract a portion of the light beam toward the dynamic ICG at a non-zero offset angle relative to a direction normal to a surface of the dynamic ICG.

14. The eyepiece of claim 1, wherein:

the beam is incident on a surface of the dynamic ICG via propagation of the beam in a first direction;

the intensity of the light beam in the time slot sequence corresponds to the intensity of the image light field in a first angular field of view, FOV, range;

the light source is further configured to generate a second light beam transmitted to the dynamic ICG;

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

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

15. The eyepiece of claim 1, wherein the waveguide is transparent such that the image light field is superimposed on an external image transmitted through the waveguide to the eye of the viewer.

16. The eyepiece of claim 1, wherein the exit pupil expander comprises a Diffractive Optical Element (DOE) configured to diffract each respective portion of the light beam out of the waveguide toward the eye of the viewer at the respective field angle.

17. The eyepiece 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.

18. 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 in 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 in 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 in-coupling grating ICG;

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

19. The method of claim 18, wherein:

the dynamic ICG includes a surface acoustic wave, SAW, modulator coupled to an oscillating electrical signal source; and

the method comprises the following steps: controlling, by the controller, operation of the oscillating electrical signal source to provide an oscillating electrical signal to the SAW modulator to generate respective acoustic waves propagating on a surface of the SAW modulator such that the SAW modulator diffracts the respective portion of the optical beam into the waveguide at the respective angle in each respective time slot.

20. The method of claim 19, wherein:

the SAW modulator includes a substrate and a piezoelectric transducer attached to the substrate;

the oscillating electrical signal is provided to the piezoelectric transducer to generate the corresponding acoustic wave; and

the corresponding acoustic wave propagates on the surface of the substrate.

21. The method of claim 19, wherein:

the SAW modulator includes a substrate, a first transducer attached to the substrate, and a second transducer attached to the substrate;

the first transducer is configured to vibrate on a first axis;

the second transducer is configured to vibrate on a second axis orthogonal to the first axis; and

the first transducer and the second transducer are coupled to the oscillating electrical signal source to drive the first transducer and the second transducer to generate the respective acoustic waves.

22. The method of claim 19, wherein:

the SAW modulator includes a substrate; and

the substrate includes a material exhibiting a piezoelectric effect that generates the corresponding acoustic wave.

23. The method of claim 22, wherein the material exhibiting the piezoelectric effect comprises one of: fused silica, lithium niobate, arsenic trisulfide, tellurium dioxide, tellurate glass, or lead silicate.

24. The method of claim 22 wherein the SAW modulator is an integral part of the waveguide.

25. The method of claim 18, wherein said light beam is incident on a surface of said dynamic ICG in a direction perpendicular to said surface of said dynamic ICG.

26. The method of claim 18, wherein said light beam is incident on a surface of said dynamic ICG at a non-zero offset angle relative to a direction normal to said surface of said dynamic ICG.

27. The method of claim 18, wherein the dynamic ICG operates in a transmissive mode.

28. The method of claim 18, wherein the dynamic ICG operates in a reflective mode.

29. The method of claim 28, comprising: redirecting the light beam via a static grating coupled to the waveguide, the static grating configured to diffract a portion of the light beam toward the dynamic ICG at a non-zero offset angle relative to a direction normal to a surface of the dynamic ICG.

30. The method of claim 18, comprising:

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

propagating the second beam onto the dynamic ICG;

controlling, by the controller, the dynamic ICG to diffract respective portions of the second optical beam into the waveguide at respective angles; and

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

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 intensity of the light beam in the sequence of time slots corresponds to the intensity of the image light field in a first angular field of view, FOV, range,

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, an

Wherein the intensity of the second light beam in the sequence of time slots corresponds to the intensity of the image light field in a second angular FOV range different from the first angular FOV range.

31. The method of claim 18, wherein the waveguide is transparent such that the image light field is superimposed on an external image transmitted through the waveguide to the eye of the viewer.

32. The method according to claim 18, wherein each respective portion of the light beam is directed out of the waveguide towards the eye at the respective field angle via a diffractive optical element, DOE, configured to diffract each respective portion of the light beam out of the waveguide towards the eye at the respective field angle.

33. The method of claim 18, wherein said light beam propagates to said dynamic ICG on an optical axis having a fixed position and orientation relative to said dynamic ICG.

34. An eyepiece for projecting an image light field to an eye of a viewer to form 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 in-coupling grating (ICG) formed on a first lateral region of the waveguide corresponding to the input pupil, the dynamic ICG configured to:

for each time slot, diffracting 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

scanning the TIR angle from one time slot to the next according to the modulation of the optical beam; and

an out-coupling 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 at the respective field angle towards the eye, thereby projecting the image light field to the eye of the viewer.

35. The eyepiece of claim 34, wherein the dynamic ICG comprises a Surface Acoustic Wave (SAW) modulator comprising:

a layer of piezoelectric material; and

a transducer coupled to a source of oscillating electrical signals;

wherein the oscillating electrical signal source is configured to drive the transducer at a plurality of frequencies, each respective frequency corresponding to a respective time slot, to generate a respective acoustic wave in the layer of piezoelectric material with a respective spatial periodicity, such that the dynamic ICG diffracts the respective portion of the optical beam into the waveguide at the respective TIR angle in the respective time slot.

36. The eyepiece of claim 35, wherein the transducer comprises a piezoelectric transducer.

37. The eyepiece of claim 35, wherein the transducer comprises:

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

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

38. The eyepiece of claim 35, wherein the piezoelectric material comprises one of: fused silica, lithium niobate, arsenic trisulfide, tellurium dioxide, tellurate glass, or lead silicate.

39. The eyepiece of claim 38, wherein the waveguide comprises one of: fused silica, lithium niobate, arsenic trisulfide, tellurium dioxide, tellurium glass, or lead silicate, and the piezoelectric material layer is an integral part of the waveguide.

40. The eyepiece of claim 34, wherein the light beam is incident on the waveguide at substantially normal incidence.

41. The eyepiece of claim 34, wherein the light beam is incident on the waveguide at a non-zero oblique angle.

42. The eyepiece of claim 34, wherein the dynamic ICG operates in a transmissive mode.

43. The eyepiece of claim 34, wherein the dynamic ICG operates in a reflective mode.

44. The eyepiece of claim 34, 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.

45. The eyepiece of claim 34, wherein:

the light beams are incident on the waveguide at a first angle of incidence, and the intensities of the light beams in the plurality of time slots correspond to intensities of the image in a first angular field of view, FOV, range; and

the light source is further configured to deliver a second light beam incident on the waveguide at the input pupil at a second angle of incidence different from the first angle of incidence, and the light source is further configured to modulate an intensity of the second light beam in the plurality of time slots, each time slot corresponding to a respective field angle, and the intensity of the second light beam in the plurality of time slots corresponding to an intensity of the image in a second angular FOV range different from the first angular FOV.

Background

Various imaging systems, such as Spatial Light Modulator (SLM) -based projectors, micro-electro-mechanical systems (MEMS) scanners, and fiber optic scanners, have been considered to provide image-wise modulated light in augmented reality glasses including eyepieces. Despite significant advances, it is becoming increasingly difficult to reduce the size of illumination systems. Therefore, there is a need for new scalable imaging architectures that allow further miniaturization.

Disclosure of Invention

An eyepiece and related method are disclosed that employ a dynamic Input Coupling Grating (ICG) to couple an input light beam into a waveguide and controllably scan the input light beam to form an image light field that is output from the waveguide to an eye of a viewer. In many embodiments, the intensity of the input light beam is modulated in conjunction with the scanning of the input light beam via dynamic ICG to generate an image light field as a combination of time periods of the input light beam scanned to corresponding X and Y coordinate locations in the image light field. By using both modulation of the input light beam and corresponding scanning of the modulated input light beam, a simplified light source may be used that propagates the input light beam along a fixed one-dimensional propagation path, allowing the light source to have a reduced size relative to devices and methods in which a two-dimensional light field is transmitted onto a non-dynamic in-coupling grating.

According to some embodiments, an eyepiece for projecting an image light field to an eye of a viewer includes a waveguide, a dynamic Input Coupling Grating (ICG), a light source, a controller, and an exit pupil expander. The waveguide is configured to propagate light via internal reflection. The dynamic ICG is formed on a first lateral region of the waveguide. The light source is configured to generate a light beam that is transmitted to the dynamic ICG. A controller is coupled to the light source and the dynamic ICG. The controller is configured to modulate the intensity of the light beam in a sequence of time slots. Each time slot in the sequence of time slots corresponds 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 corresponds to the intensity of the image light field at the respective field angle. The controller is configured to control the dynamic ICG to diffract, for each time slot of the sequence of time slots, a respective portion of the optical beam into the waveguide at a respective angle corresponding to a respective field angle. An exit pupil expander is coupled to the second lateral region of the waveguide and configured to direct each respective portion of the light beam out of the waveguide at a respective field angle toward the eye of the viewer, thereby projecting the image light field to the eye of the viewer.

According to some embodiments, a method of projecting an image light field to an eye of a viewer is provided. The method includes modulating, by a controller, an intensity of a light beam in a sequence of time slots. Each time slot in the sequence of time slots corresponds 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 corresponds to the intensity of the image light field at the respective field angle. The beam propagates onto a dynamic in-coupling grating (ICG). The dynamic ICG is controlled by the controller to diffract, for each time slot of the sequence of time slots, a respective portion of the optical beam into the waveguide at a respective angle corresponding to a respective field angle. Each respective portion of the light beam is directed out of the waveguide toward the eye at a respective field angle, thereby projecting the image light field to the eye of the viewer.

According to some embodiments, an eyepiece for projecting an image light field to an eye of a viewer to form an image of virtual content includes a waveguide configured to propagate light therein. The waveguide may include an input pupil. The eyepiece may further include: a light source configured to deliver a light beam to be incident on the waveguide at an input pupil; and a controller coupled to the light source and configured to modulate the intensity of the light beam in a plurality of time slots. Each time slot may correspond to a respective field angle of the image. The intensity of the light beam in each time slot may correspond to the intensity of the image at the respective field angle. The eyepiece may further include a dynamic in-coupling grating (ICG) formed on a first lateral region of the waveguide corresponding to the input pupil. The dynamic ICG may be configured to diffract, for each time slot, a respective portion of the optical beam into the waveguide at a respective Total Internal Reflection (TIR) angle corresponding to a respective field angle, and to scan the TIR angle from one time slot to the next according to the modulation of the optical beam. The eyepiece may further include an out-coupling Diffractive Optical Element (DOE) coupled to the 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 a respective field angle to project a light field to the eye of the viewer.

According to some embodiments, a method of projecting a light field to an eye of a viewer to view an image of virtual content includes providing a light beam incident on a dynamic Input Coupling Grating (ICG). The dynamic ICG may include a Surface Acoustic Wave (SAW) modulator. The SAW modulator may include a layer of piezoelectric material and a transducer. The SAW modulator may be coupled to a first lateral region of the waveguide. The method may further include modulating the intensity of the light beam in a plurality of time slots corresponding to a plurality of field angles. The intensity of the light beam in each time slot may correspond to the intensity of the image at the respective field angle. The method may further include applying an oscillating electrical signal to the transducer at a plurality of frequencies over a plurality of time slots to generate respective acoustic waves in the layer of piezoelectric material at respective spatial periods in the respective time slots, such that the dynamic ICG diffracts respective portions of the optical beam into the waveguide at respective Total Internal Reflection (TIR) angles in the respective time slots. Each respective frequency may correspond to a respective time slot. A corresponding portion of the light beam may propagate in the waveguide. The method may further comprise: using a Diffractive Optical Element (DOE) coupled to a second lateral region of the waveguide, each respective portion of the light beam propagating in the waveguide is outcoupled toward the eye at a respective field angle, thereby projecting a light field at a plurality of field angles to the eye for viewing an image of the virtual content.

Drawings

Fig. 1A is a schematic perspective view of a pair of augmented reality glasses according to some embodiments.

Fig. 1B illustrates an example augmented reality system, according to some embodiments.

Fig. 2 is a schematic side view of a portion of an eyepiece of the augmented reality glasses shown in fig. 1 according to some embodiments.

FIG. 3 illustrates an imaging system that may be used to project an image light field through an eyepiece to an observer's eye, according to some embodiments.

Fig. 4 schematically illustrates an eyepiece including a dynamic incoupling grating (ICG) in accordance with some embodiments.

FIG. 5 schematically illustrates the functionality of the dynamic ICG shown in FIG. 4, in accordance with some embodiments.

Fig. 6A schematically illustrates compact eyewear according to some embodiments.

Fig. 6B schematically illustrates compact eyewear according to some embodiments.

Fig. 7A schematically illustrates a one-dimensional (1D) dynamic ICG based on a Surface Acoustic Wave (SAW) modulator, in accordance with some embodiments.

Fig. 7B schematically illustrates a SAW modulator-based two-dimensional (2D) dynamic ICG, in accordance with some embodiments.

Fig. 8A schematically illustrates a 2D kinematic ICG in a transmission geometry eyepiece according to some embodiments.

Fig. 8B schematically illustrates a 2D kinematic ICG in a reflective geometry eyepiece according to some embodiments.

Fig. 9 schematically illustrates an eyepiece including two 1D kinematic ICGs cascaded with respect to one another, in accordance with some embodiments.

FIG. 10A schematically illustrates an eyepiece where an input beam is at an offset angle θ from normal incidence, according to some embodiments_biasIncident on the dynamic ICG.

FIG. 10B schematically illustrates an eyepiece including a static diffraction grating to produce a skew angle θ 'for an input beam incident on a dynamic ICG, in accordance with some embodiments'_bias。

Fig. 11 schematically illustrates a configuration in which two input beams are used to increase the total field of view (FOV), according to some embodiments.

Fig. 12 schematically illustrates an eyepiece with a 1D dynamic ICG in a transmission geometry according to some embodiments.

Fig. 13 illustrates a k-vector diagram of the first order diffraction of the 1D dynamic ICG shown in fig. 12, in accordance with some embodiments.

Fig. 14 illustrates a k-vector diagram for a 2D dynamic ICG for a normal incidence input beam, in accordance with some embodiments.

Fig. 15 illustrates a k-vector diagram for a 2D dynamic ICG for a normal incidence input beam superimposed on a waveguide Total Internal Reflection (TIR) diagram, in accordance with some embodiments.

Fig. 16 illustrates a k-vector diagram for a 2D dynamic ICG with an angularly deflected input beam superimposed on a waveguide Total Internal Reflection (TIR) diagram in accordance with some embodiments.

Fig. 17 illustrates a k-vector diagram for a 2D dynamic ICG with an input beam angularly deflected to shift the dynamic grating region to a TIR region superimposed on a waveguide Total Internal Reflection (TIR) diagram, in accordance with some embodiments.

Fig. 18 is a simplified flow diagram illustrating a method of projecting a light field to an eye of a viewer to view an image of virtual content, in accordance with some embodiments.

FIG. 19 is a flow diagram illustrating a method of projecting an image light field to an eye of a viewer, in accordance with some embodiments.

Detailed Description

According to some embodiments of the present disclosure, an eyepiece includes a waveguide and a dynamic input-coupled grating (ICG) coupled to the waveguide. The dynamic ICG is configured to scan a fixed input laser beam into the waveguide within a two-dimensional TIR angular range. By modulating the intensity of the laser beam in a sequence of time slots according to the position of an image point in the field of view synchronized with the scanning of the dynamic ICG, the viewer can see a complete image field display. This imaging paradigm may eliminate the need for an external projector, and thus may provide compact, lightweight eyewear. Such eyewear may be used, for example, in augmented reality systems or other wearable displays and computing products.

A diffraction grating is an optical component that deflects light through an angle that depends on the wavelength of the light and the angle of incidence on the grating. The diffraction grating may have a periodic structure with a period on the order of the wavelength of light used with the diffraction grating. The periodic structure may be a surface relief of the transparent material or a volume modulation of the refractive index of the transparent material. The operation of a diffraction grating may be controlled by the grating equation:

wherein, theta_mIs the angle (diffraction angle) of the beam emerging from the diffraction grating with respect to a vector perpendicular to the grating surface; λ is the wavelength; m is an integer-valued parameter called the diffraction "order"; d is the period of the grating; and theta_iIs the angle of incidence of the input beam with respect to a vector normal to the grating surface.

The gratings may also be blazed, i.e. given a specific periodic profile, so as to concentrate the light they diffract into a specific "order" specified by a specific value of the order parameter m. The grating may be reflective, in which case light exits the grating on the same side as the light is incident on the grating, or transmissive, in which case light exits primarily on the opposite side of the grating from the incident light.

Fig. 1A is a perspective view of a pair of augmented reality glasses 100 according to some embodiments. The eyeglass 100 comprises a frame 102, the frame 102 comprising a left arm 104 and a right arm 106 connected by a front piece 108. The front piece 108 supports a left eyepiece 110 and a right eyepiece 112. For purposes of discussion, and with particular reference to right eyepiece 112, right eyepiece 112 includes a right stacked plurality of waveguides 114. The right stacked waveguide 114 is transparent so that the person wearing the glasses 100 can see the real world when wearing the augmented reality glasses 100 and the virtual content can be superimposed and displayed in the real world environment. As shown in fig. 1, a right front waveguide 116 included in right stacked waveguide 114 includes a right front selectively actuatable (activatable) incoupling grating 118, a right front orthogonal pupil expander 120, and a right front exit pupil expander 122. As described in U.S. patent 9,612,403 entitled "Planar Waveguide Apparatus with Diffraction elements(s) and System Employing Same" to above et al, exit pupil expander 122 may be designed to impart different field curvatures to the exiting light corresponding to different virtual source lights. Similarly, left eyepiece 110 includes a left stacked waveguide 124, which left stacked waveguide 124 includes a left front waveguide 126. As shown in fig. 1, the left front waveguide includes a left front selectively actuatable in-coupling grating 128, a left orthogonal pupil expander 130, and a left exit pupil expander 132. The left eyepiece 110 is also transparent. A left image-wise modulated light source 134 and a right image-wise modulated light source 136 are supported inside the left arm 104 and the right arm 106, respectively, of the frame 102 and are selectively optically coupled to the left stacked waveguide 124 and the right stacked waveguide 114, respectively.

Fig. 1B illustrates an example augmented reality system 150, the example augmented reality system 150 operable to render virtual content (e.g., virtual objects, virtual tools, and other virtual constructs, such as applications, features, characters, text, numbers, and other symbols) in a field of view of a user 152, and may include a head-mounted wearable display device 154 and a computing device 156. The head-mounted wearable display device 154 may include a pair of augmented reality glasses 100 similar to the glasses shown in fig. 1A. The computing device 156 may include components (e.g., processing components, power components, memory, etc.) that perform a number of processing tasks to present relevant virtual content to the user 152.

Computing device 156 may be operably and/or communicatively coupled to head-mounted wearable display device 154 by a connection 158 (e.g., a wired lead connection, a wireless connection, etc.). The computing device 156 may be removably attached to the hip 203 of the user 152 in a belt-coupled style configuration. In other examples, the computing device 156 may be removably attached to another part of the body of the user 152, attached to or located within clothing or other accessories (e.g., a frame, hat, or helmet, etc.) worn by the user 152, or located in another location within the environment of the user 152.

Fig. 2 is a schematic side view of right eyepiece 112 shown in fig. 1A. Note that for illustration purposes, the placement of in-coupling grating 118, orthogonal pupil expander 120, and exit pupil expander 122 has been changed in fig. 2 relative to the placement shown in fig. 1. Although not shown, the structure of the left eyepiece 110 is a mirror image of the structure of the right eyepiece 112. As shown in fig. 2, the right stacked plurality of waveguides 114 of the right eyepiece 112 includes, in addition to the right front waveguide 116, a right second waveguide 202 disposed behind the right front waveguide 116, a right third waveguide 204 disposed behind the right second waveguide 202, a right fourth waveguide 206 disposed behind the right third waveguide 204, a right fifth waveguide 208 disposed behind the right fourth waveguide 206, and a right rear waveguide 210 disposed behind the right fifth waveguide 208. Each of the second to fifth waveguides 202, 204, 206, 208 and the back waveguide 210 has a second to sixth in-coupling grating 118b, 118c, 118d, 118e, 118f, respectively. The in-coupling gratings 118a, 118b, 118c, 118d, 118e, 118f may be designed, for example, with a grating pitch and profile (e.g., blazed profile) to deflect image-wise modulated light at angles above the critical angle of normal incidence to the waveguides 116, 202, 204, 206, 208. The second to fifth waveguides 202, 204, 206, 208 and the rear waveguide 210 each further comprise one of another set of orthogonal pupil expanders 214 and one of another set of exit pupil expanders 216.

During a separate time sub-frame period, the right image-wise modulated light source 136 suitably outputs image-wise modulated light for different color channels and for different virtual object depths. The particular sequence of color channels and depth planes may be repeated periodically at the video frame rate. The stacked six waveguides 114 may include two sets of three waveguides, where each of the two sets includes red, green, and blue (RGB color) channel waveguides, and each of the two sets emits light having one of two virtual object distances (object distances) determined by a field curvature of the emitted light. Light emitted from the front of right eyepiece 110 is directed back to eye position 220.

Fig. 3 shows an imaging system 310 that can be used to project an image light field through an eyepiece 320 to an eye 330 of a viewer. Imaging system 310 may include a Spatial Light Modulator (SLM) 312. SLM312 can comprise, for example, a Liquid Crystal On Silicon (LCOS) display, a Digital Light Processing (DLP) chip, or the like. An illumination source (not shown), such as a Light Emitting Diode (LED), laser, etc., may provide (quasi) collimated light illumination 314 for incidence on SLM 312. SLM312 may spatially modulate illumination 314 to form a two-dimensional (2D) image of virtual content by controlling the amount of transmission (or reflection) of light incident on each pixel. The imaging system 310 may further include a projection lens 316. SLM312 can be positioned at the back focal plane of projection lens 316. By the corresponding pixel P in position (x)_P，y_P) Where the transmitted light may be transformed by eyepiece 320.

The beam is incident on an in-coupling grating (ICG)322 of an eyepiece 320, which couples a portion of the incident light into a waveguide 326 as a beam in the respective propagation directionThe Total Internal Refraction (TIR) beam. Each TIR beam is replicated in waveguide 326 as multiple TIR beams, all with the same propagation direction. An Exit Pupil Expander (EPE)324 couples the TIR beam out of eyepiece 320 as multiple output beams, all in the same propagation direction toward the eye 330 of the observerReplication of the bundle to the viewerThe image can be viewed from an effectively larger exit pupil and is therefore referred to as an exit pupil expander. The pupil of the observer's eye 330 collects many of these beams, which will then be focused by the eye's lens to a specific location (x) on the retina_P’，y_P’) In (1). Thus, the corresponding pixel P is at position (x)_P，y_P) The transmitted light can be converted into corresponding directions by the eyepiece 320To a propagating parallel bundle of rays. For clarity, the second coordinate yP and the second angle are suppressed in fig. 3 and subsequent figures

Various imaging systems, such as Spatial Light Modulator (SLM) -based projectors, micro-electro-mechanical systems (MEMS) scanners, and fiber optic scanners, have been considered to provide image-wise modulated light in augmented reality glasses that include an eyepiece, such as eyepiece 320 shown in fig. 3. Despite significant advances, it is becoming increasingly difficult to reduce the size of projectors. For example, a typical size of an SLM-based projector may be about 15mm (excluding the illumination module); a typical size for a fiber optic scanner is about 10mm (excluding the illumination module); and a typical size of a MEMS scanner is about 10mm (excluding the illumination module).

As described above, each pixel location (x) on SLM312 (or other type of 2D scanner, such as a fiber optic scanner)_P，y_P) Respective propagation directions in free spaceRespective TIR propagation directions inside the waveguide 326And the corresponding image position (x) at the retina of the observer's eye 330_P′，y_P′) There may be a one-to-one correspondence between them. In accordance with the present disclosureSome embodiments of (1), TIR propagation directionCan be generated directly in the eyepiece and can scan all points in the image field. This new imaging paradigm may eliminate the need for an external imaging system 310 and thus may enable a very compact configuration of eyewear.

Fig. 4 schematically illustrates eyepiece 400 according to some embodiments. Eyepiece 400 includes a waveguide 410, a two-dimensional (2D) dynamic ICG420 coupled to a first lateral region of waveguide 410, and a Diffractive Optical Element (DOE)412 (such as an orthogonal pupil expander OPE and/or an exit pupil expander EPE) coupled to a second lateral region of waveguide 410. Having a fixed propagation direction (e.g., perpendicular to the waveguide 410,) Is incident on the dynamic ICG 420. The input beam 402 may be intensity modulated in one or more time slots such that, for each time slot, the intensity of the input beam 402 corresponds to the relative brightness of a corresponding image point P in the image field (the image point P may be similar to a pixel (x) on the SLM312 shown in FIG. 3_P，y_P))。

FIG. 5 schematically illustrates actions of dynamic ICG420, in accordance with some embodiments. Dynamic ICG420 is configured to diffractively couple input optical beam 402 into waveguide 410 as a TIR beam. As shown in FIG. 5, the TIR angle of diffracted beam 510 may be dynamically changed from time slot to time slot in synchronization with the modulation of input beam 402, such that the TIR angle for each time slotCorresponding to the respective image field P. Thus, by scanning the TIR angle over a range of TIR angles in one or more time slotsThe entire image field may be scanned.

Referring again to FIG. 4, for the data inRespective TIR angles in respective time slotsEPE 412 has a corresponding propagation direction towards observer's eye 430The TIR beam is coupled out of eyepiece 400. The pupil of the observer's eye 430 collects the output beam, which is then focused by the eye's lens to a specific location (x) on the retina_P'，y_P'). Scanning for TIR angles over a range of TIR angles while dynamic ICG420 is in one or more time slotsWhile correspondingly scanning the propagation direction of the output beamCovering the entire image field (note that for clarity only one direction of propagation is shown in figure 4)。

Thus, as described above, the dynamic ICG420 integrates the ICG functionality and the scanner functionality in a single device, thereby eliminating the need for a separate imaging system 310 as shown in fig. 3. Accordingly, the eyeglasses can be manufactured with significantly reduced size and weight compared to conventional eyeglasses. In some embodiments, for example, dynamic ICG420 may have no moving parts, unlike a fiber optic scanner or a MEMS scanner. An eyepiece incorporating dynamic ICG420 may provide other advantages. For example, higher brightness and lower power consumption may be achieved because there are fewer optical components that cause additional losses.

In some embodiments, synchronized colors may be used. In these embodiments, red (R), green (G), and blue (B) information may exist simultaneously as collinear R, G, B beams from R, G, B lasers, respectively. When scanning three collinear R, G, B beams across the image field, the amount of each color at any point (pixel) can be controlled by modulating the three lasers independently but simultaneously. Conversely, sequential colors may be used if a single LCOS is shared to generate R, G, B images of one color at a time.

Fig. 6A schematically illustrates compact eyewear according to some embodiments. The compact eyewear may include an eyepiece (e.g., similar to eyepiece 400) that includes a dynamic ICG (e.g., similar to dynamic ICG 420). A compact light source module mounted on the glasses can provide an input light beam incident on the dynamic ICG at a fixed propagation direction. In some embodiments, the compact light source module may emit collimated light. In some embodiments, the compact light source module may emit light with a narrow spectrum/beam spread. In some embodiments, the compact light source module may include one or more lasers. For example, a compact light source module may include a red laser, a blue laser, and a green laser. In some embodiments, the compact light source module may be in a head-mounted wearable display device (e.g., similar to head-mounted wearable display device 154 shown in fig. 1B). In some embodiments, the compact light source module may include one or more LEDs. For example, the one or more LEDs may be one or more superluminescent LEDs (sleds). In some embodiments, the controller may be used to operate a compact light source module, such as a mobile compact light source module and/or a modulated compact light source module. The controller may be used to load an image into one or more of the beams.

Fig. 6B schematically illustrates compact eyewear according to some embodiments. Here, a separate light source package may provide the input light beam via an optical fiber. In some embodiments, the compact light source module may be in a belt pack (e.g., in the computing device 156 shown in fig. 1B) and may be delivered to the head-mounted wearable display device via optical fibers. Since the operation of a dynamic ICG may be polarization independent, the input beam may be unpolarized. Thus, efficient fiber transmission can be achieved by using fibers that remain unpolarized.

Fig. 7A schematically illustrates a one-dimensional dynamic ICG based on a Surface Acoustic Wave (SAW) modulator, in accordance with some embodiments. SAW modulators use acoustic waves (e.g., at radio frequencies) to diffract light using the acousto-optic effect. A transducer (e.g., a piezoelectric transducer) is attached to the substrate of the SAW modulator. The oscillating electrical signal may drive the transducer to vibrate, which may generate acoustic waves that propagate on the substrate surface. This acoustic wave (which may be referred to as a surface acoustic wave or SAW) may cause the surface to deform and form a diffraction grating. The substrate may include a material exhibiting a piezoelectric effect, such as fused silica, lithium niobate, lithium tantalate, langasite, arsenic trisulfide, tellurium dioxide, tellurate glass, lead silicate, and the like. The substrate may comprise a material that exhibits piezoelectric effect when initially manufactured, or a material that exhibits piezoelectric effect may be deposited onto the substrate. For each pixel, a 2D specific diffraction grating is created with a specific grating pitch that will diffract light in a specific direction. Changing the diffraction grating by changing the grating pitch will result in a change in direction.

An optical beam ("In") incident on a diffraction grating formed by SAW may be diffracted In either a transmissive geometry or a reflective geometry (e.g., on a metalized surface). Fig. 7A shows a SAW modulator in a transmission geometry. As shown, various diffraction orders (e.g., -1, 0, +1 order) may be obtained. The period of the diffraction grating may depend on the frequency of the driving electrical signal. The diffraction angle (e.g., in the first order diffraction) depends on the period of the diffraction grating. Thus, by modulating the frequency of the driving electrical signal, the diffracted light can scan a range of angles.

The SAW modulator described above can be extended to the two-dimensional (2D) case. Fig. 7B schematically illustrates a 2D SAW modulator in a transmission geometry, in accordance with some embodiments. A first transducer for X-axis motion and a second transducer for Y-axis motion are attached to the substrate. A first oscillating electrical signal RF (RF)_xThe first transducer may be driven to vibrate along the X-axis and the second oscillating electrical signal RF (RF)_yThe second transducer can be driven to vibrate along the Y-axis, which together can create a 2D SAW propagating on the substrate surface. The 2D SAW may cause the substrate surface to deform and form a 2D diffraction grating. The incident beam may be diffracted by a diffraction grating (only shown in FIG. 7B for clarity)The primary diffraction order, e.g., the first order). By scanning drive electrical signals (RF) along X and Y axes, respectively_xAnd (RF)_yFor example, the diffracted light may scan a 2D angle, e.g., in an x-y pattern (raster scan) or a spiral patternAnd (3) a range.

In some embodiments, multiple drive frequencies may be superimposed on each other. For example, one or more electrical signals may be combined along the X-axis into a composite drive signal, where each respective electrical signal corresponds to a respective frequency. In this manner, a group of pixels (or an entire line of pixels) along the X-axis can be addressed simultaneously. In some embodiments, the acoustic wave may be modulated by superposition of RF signals. In some embodiments, two gratings may be superimposed and light may be diffracted according to the diffraction characteristics (e.g., pitch and/or amplitude) of each of the two gratings. For example, if there is a first grating and a second grating and the first grating and the second grating are superimposed, light incident thereon will be diffracted and separated in a direction determined by both a first pitch of the first grating and a second pitch of the second grating and have an amplitude related to a first amplitude of the first grating and a second amplitude of the second grating. The frequency of the first RF signal may determine a first pitch of the first grating and the amplitude of the first RF signal may determine an amplitude of the first grating. Similarly, the frequency of the second RF signal may determine a second pitch of the second grating, and the amplitude of the second RF signal may determine an amplitude of the second grating. In some embodiments, multiple gratings may be superimposed and light diffracted from the multiple gratings may follow all of the multiple gratings.

It may be noted that the grating amplitude may depend on the electrical power delivered to the one or more transducers. Thus, in some embodiments, in addition to modulating the frequency of the drive electrical signal, image intensity modulation may be performed by the SAW modulator by modulating the electrical power of the drive electrical signal.

It should also be noted that a diffraction grating that is constantly changing due to frequency/amplitude modulation can help reduce coherence artifacts that may be produced by a static grating. For example, coherence artifacts produced by a static grating can manifest as shading across the image field. The constantly changing diffraction grating may produce a "sliding" shading that may be less noticeable when the eye integrates light in the response time window.

In some embodiments, as shown in FIG. 5, a SAW modulator can be formed on the surface of a waveguide. For example, a layer of piezoelectric material (such as lithium niobate) and one or more transducers may be attached to the surface of the waveguide. In some embodiments, the SAW modulator may be formed below the surface of the waveguide. For example, a layer of piezoelectric material may be embedded in the waveguide, and one or more transducers may be coupled to the layer of piezoelectric material. In some embodiments, the SAW modulator may be an integral part of the waveguide. For example, the waveguide may comprise a piezoelectric material, such as lithium niobate. One or more transducers may be formed on a first lateral region of a surface of the waveguide to generate a SAW in the first lateral region of the surface.

It should be understood that although a SAW modulator is discussed above as an example of a dynamic ICG, other types of analog scanning techniques may be used for a dynamic ICG.

Fig. 8A schematically illustrates a 2D kinematic ICG in a transmission geometry eyepiece according to some embodiments. The eyepiece includes a waveguide having a first surface and a second surface opposite the first surface. The 2D dynamic ICG is coupled to a first surface of the waveguide. Note that this configuration is similar to the configuration shown in fig. 4 and 5. The intensity modulated input beam is typically incident on a 2D dynamic ICG. As described above with reference to FIG. 5, the 2D dynamic ICG is modulated in synchronization with the intensity modulation of the input beam so that it has a propagation angle in the transmission geometryOne or more corresponding diffracted beams of the range propagate in the waveguide. Each propagation angleCorrespond to the respectiveOf the image field P. It should be understood that while the 2D dynamic ICG is shown as being positioned over the first surface of the waveguide, this is not required. In some embodiments, the 2D dynamic ICG may be embedded in the waveguide or may be an integral part of the waveguide.

Fig. 8B schematically illustrates a 2D kinematic ICG in a reflective geometry eyepiece according to some embodiments. The eyepiece includes a waveguide having a first surface and a second surface opposite the first surface. The 2D dynamic ICG is coupled to a second surface of the waveguide. The intensity modulated input beam passes through the waveguide and is normally incident on the 2D dynamic ICG. The 2D dynamic ICG is modulated in synchronism with the intensity modulation of the input beam so as to have a propagation angle in the reflection geometryOne or more corresponding diffracted beams of the range propagate in the waveguide. Each propagation angleCorresponding to the respective image field P. It should be understood that although the 2D dynamic ICG is shown as being positioned below the second surface of the waveguide, this is not required. In some embodiments, the 2D dynamic ICG may be embedded in the waveguide or may be an integral part of the waveguide.

Fig. 9 schematically illustrates an eyepiece including two one-dimensional (1D) dynamic ICGs cascaded with respect to one another, in accordance with some embodiments. The eyepiece includes a waveguide having a first surface and a second surface opposite the first surface. The first 1D dynamic ICG is coupled to a second surface of the waveguide. A second 1D dynamic ICG is coupled to the first surface of the waveguide. An intensity modulated input beam passes through the waveguide and is normally incident on the first 1D dynamic ICG.

The first 1D dynamic ICG is modulated in synchronization with the intensity modulation of the input beam such that one or more corresponding diffracted beams having a range of propagation angles θ in the reflection geometry propagate in the waveguide. The left and right arrows below the first 1D dynamic ICG shown in fig. 9 indicate that the input light beam is dispersed into one or more propagation angles θ in the plane of the paper.

The light beam diffracted by the first 1D dynamic ICG in the range of the propagation angle θ is incident on the second 1D dynamic ICG. The second 1D dynamic ICG is modulated in synchronism with the intensity modulation of the input beam so as to have a propagation angle in the reflection geometryOne or more corresponding diffracted beams of the range propagate in the waveguide. The dots and crosses over the second 1D dynamic ICG shown in fig. 9 indicate that the light beams are dispersed into one or more propagation angles in a plane perpendicular to the paperIn some embodiments, because the input beam is diffracted twice (through the first 1D dynamic ICG, then the second 1D dynamic ICG), the coupling efficiency may not be as high as in the case with a single 2D dynamic ICG shown in fig. 8A and 8B (the effective diffraction efficiency may be on the order of η |)²Where η is the diffraction efficiency of a single ICG).

In some cases, it may be desirable to have the input beam at a skew angle θ_biasIncident on the dynamic ICG. FIG. 10A schematically illustrates an eyepiece where an input beam is at an offset angle θ from normal to the surface of a dynamic ICG, according to some embodiments_biasIncident on the dynamic ICG. In the transmissive mode, at a dynamic modulation angleA diffracted beam in the range propagates in the waveguide. May be oriented in any direction at θ orOr a combination thereof (although shown only for theta in fig. 10A for clarity).

In some cases, it may be desirable to have a bias angle θ_biasTo facilitate propagation in the waveguide via Total Internal Reflection (TIR). For example, depending on the possible raster vectors that can be generated by the dynamic ICG,propagation angle of diffracted beam generated from normally incident input beamThe range may not satisfy the TIR condition of the waveguide. In such cases, the skew angle θ of the input beam_biasAn additional "kick (kick)" may be provided to make the propagation angleThe range satisfies the TIR condition of the waveguide (as discussed in further detail below with reference to fig. 17).

Figure 10B schematically illustrates an eyepiece including a static diffraction grating coupled to a first surface of a waveguide. The input beam is normally incident on the static diffraction grating and is deflected by the static diffraction grating at a deflection angle θ'_biasAnd (4) diffraction. Then, the diffracted beam is at a bias angle θ'_biasIncident on the dynamic ICG and diffracted by the dynamic ICG to a dynamic modulation angle in a reflection modeWithin the range. In this embodiment, because the input beam is diffracted twice (by the static diffraction grating followed by the dynamic ICG), the coupling efficiency may not be as high as in the case shown in fig. 10A.

In some cases, the modulation range of the dynamic ICG may not be sufficient to cover the entire field of view (FOV). In some embodiments, multiple input beams may be used to increase the image field of view. FIG. 11 schematically shows a configuration using two input beams ("IN 1" and "IN 2"). The eyepiece may include a static ICG coupled to the first surface of the waveguide and a dynamic ICG coupled to the second surface of the waveguide. First input light beam "IN 1" is at a first offset angle θ_1,biasIs incident on the static ICG and is diffracted by the static ICG at a first diffraction angle. A first input light beam "IN 1" diffracted by the static ICG is then diffracted by the dynamic ICG to a dynamically modulated first Total Internal Reflection (TIR) angle Δ θ_1,TIRWithin the range. Second input light beam "IN 2" at a second skew angle θ_2,biasIncident on and from the static ICGDiffraction at two diffraction angles. A second input beam "IN 2" diffracted by the static ICG is then diffracted by the dynamic ICG to a dynamically modulated second TIR angle Δ θ_2,TIRWithin the range. TIR Angle Δ θ_TIRMay be the first TIR angle of the dynamic modulation Δ θ_1,TIRSecond TIR Angle Δ θ for Range and dynamic modulation_2,TIRSum of the ranges. Thus, a larger field of view can be achieved than in the case of a single input beam. For example, the first TIR angle θ_1,TIRMay be in the range of 40 ° to 55 ° (i.e., Δ θ)_1,TIR15 °), and a second TIR angle θ_2,TIRMay be in the range of 55 to 70 (i.e., Δ θ)_2,TIR15 °). Therefore, the TIR angle Δ θ_TIRMay be 30.

It should be understood that two or more of the configurations shown in fig. 8A-8B, 9, 10A-10B, and 11 may be combined, according to some embodiments.

In some embodiments, full RGB colors may be achieved using a stack of three waveguides (e.g., as shown in fig. 2), each configured as one of the RGB colors. The colors may be separated using a split pupil configuration or a columnar configuration, as described in U.S. patent 10,371,896, the contents of which are incorporated herein by reference.

Let the SAW velocity be v_sAnd the RF drive frequency is f, the SAW grating period Λ is_sCan be expressed as:

Λ_s＝v_s/f. (1)

as shown in FIG. 12, consider having an input angle of incidence θ_inTransmission dynamic ICG. Suppose the RF frequency range supported by the modulator is f_minTo f_max. Further assume that the first order diffraction is via TIR (with refractive index n) inside the waveguide over the operating RF frequency range_g) Propagation (otherwise an angular skew may be used, as discussed below with reference to fig. 17). Fig. 13 shows a k-vector diagram of first order diffraction based on conservation of lateral momentum. The k vector diagram can be represented by the following equation:

nk_T，TIR＝k_T，in+K， (2)

wherein K is an amplitude of 2 pi/lambda_sThe dynamic raster vector of (1).From equation (2), the Bragg-Snell equation is as follows:

as a numerical example, assume θ_in0 ° (normal incidence), λ 530nm, n 1.8, v_s＝600m/s，f_min1.2GHz, and f_max2.0 GHz. Using equation (3), one may find θ_TIR(f_min) 36.1 ° (above the critical angle of 34.4 °) and θ_TIR(f_max) 79.0 °. Using a 0.375 μm pitch EPE, the TIR beam can be coupled out to span an angular field of view (FOV) of 41.4 ° (i.e., ± 20.7 °).

Assuming that the length of the dynamic grating is set to D using a fourier transform lens with a focal length F, the spot size on the transform plane can be expressed as D ═ 2F λ/D. By usingWill be 2F, image sizeThus, the number of resolution points across the scanned image can be expressed as:

assuming that the length D of the dynamic grating is 2mm, the one in example 1 is usedAnd the number of resolution points may be 1426 (corresponding to a 1.74arcmin angular resolution).

The minimum pixel time may be the time that the SAW has traversed the grating length D. Transient considered pixel time T_pixelCan be assumed to be around three times this ratio,

according to equation (5), for v_s600m/s and D2 mm, pixel time T_pixel＝10μs。

Fig. 14 shows a k-vector diagram of a 2D dynamic ICG for a normal incidence input beam. For purposes of illustration, consider a 2D dynamic ICG with two orthogonal eigenmodes propagating in the + and-directions. The shaded region 1420 in K-space represents all the grating vectors K of magnitude 2 π/Λ s that can be generated by the 2D dynamic ICG. The shaded region 1420 may be referred to herein as a dynamic raster region. The subscripts "min" and "max" correspond to the minimum and maximum RF frequencies, respectively. In some embodiments, a broadband transducer may be used to achieve a larger dynamic grating area 1420, thereby achieving a wider FOV.

To illustrate the propagation inside the eyepiece waveguide, it may be useful to overlap the upper graph with the waveguide TIR graph, as shown in fig. 15. The annular region 1510 bounded by the two circles 1512 and 1514 represents k-space where TIR may occur in the waveguide. The overlap of the dynamic grating region 1520 (i.e., the shaded region) and the TIR annular region 1510 represents k-space in which diffracted beams generated by the 2D dynamic ICG may propagate in the waveguide via TIR.

As shown in fig. 16, an angular bias may be applied to improve TIR zone utilization. For example, note the larger shaded region 1620 in FIG. 16 as compared to shaded region 1520 shown in FIG. 15.

For relatively small dynamic grating vectors, the dynamic grating region may be located outside of TIR region 1510. In such cases, as shown in fig. 17, an angular skew may be used to shift the dynamic grating region 1720 into the TIR region 1510. As described above, skew may be introduced by using a particular external angle of incidence (as shown in fig. 10A) or by using a static grating (as shown in fig. 10B).

In summary, the concept of very compact glasses using dynamic ICG is proposed. The dynamic ICG may be configured to scan a fixed input laser beam into a two-dimensional TIR angular range in the eyepiece. By modulating the laser beam intensity according to the image point position, the entire image field can be seen by the observer. This new imaging paradigm may eliminate the need for an external projector and thus may enable a very compact configuration of glasses.

Fig. 18 is a flow diagram illustrating a method 1800 of projecting a light field to an eye of a viewer to view an image of virtual content, in accordance with some embodiments. Method 1800 may be accomplished using any suitable components, assemblies, and methods, including but not limited to any suitable components, assemblies, and methods described herein.

The method 1800 may include, at 1802, providing a beam incident on a dynamic in-coupling grating (ICG). The dynamic ICG may include a Surface Acoustic Wave (SAW) modulator. The SAW modulator may include a layer of piezoelectric material and a transducer. The SAW modulator may be coupled to a first lateral region of the waveguide.

Method 1800 may further include, at 1804, modulating an intensity of the optical beam in one or more time slots corresponding to the one or more field angles. The intensity of the light beam in each time slot corresponds to the intensity of the image at the respective field angle. The method 1800 may further include, at 1806, applying an oscillating electrical signal to the transducer at one or more frequencies in a plurality of time slots. Each respective frequency corresponds to a respective time slot. Accordingly, respective acoustic waves are generated in the layer of piezoelectric material at respective spatial periods in the respective time slots, such that the dynamic ICG diffracts respective portions of the optical beam into the waveguide at respective Total Internal Reflection (TIR) angles in the respective time slots. A corresponding portion of the light beam propagates in the waveguide.

The method 1800 may further include, at 1808, using a Diffractive Optical Element (DOE) coupled to the second lateral region of the waveguide, out-coupling each respective portion of the light beam propagating in the waveguide toward the eye at a respective field angle. Thus, the light field is projected at one or more field angles to the eye to view an image of the virtual content.

It should be appreciated that the particular actions shown in fig. 18 provide particular ways of projecting a light field to a viewer's eye to view an image of virtual content, according to some embodiments. Other sequences of actions may also be performed according to some embodiments. For example, some embodiments may perform the actions outlined above in a different order. Further, various acts illustrated in FIG. 18 may include multiple sub-acts that may be performed in various orders as appropriate to the single act. Further, additional actions may be added or deleted depending on the particular application. One of ordinary skill in the art would recognize many variations, modifications, and alternatives.

Fig. 19 is a flow diagram illustrating a method 1900 of projecting an image light field to an eye of a viewer, in accordance with some embodiments. Any suitable components, assemblies, and methods (including but not limited to any suitable components, assemblies, and methods described herein) may be used to perform method 1900.

The method 1900 includes, at 1902, modulating, by a controller, an intensity of a light beam in a sequence of time slots. Each time slot in the sequence of time slots corresponds 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 corresponds to the intensity of the image light field at the respective field angle.

The method 1900 includes, at 1904, propagating the beam onto a dynamic in-coupling grating (ICG). In many embodiments, the beam propagates to the dynamic ICG on a fixed optical path without any lateral scanning of the beam or beam variation transverse to the fixed optical path. In many embodiments, the light beam is propagated to a fixed point on the ICG. Accordingly, the light source for generating and transmitting the light beam onto the dynamic ICG may have a reduced size relative to a light source configured for two-dimensional scanning of the light beam or two-dimensional variation in the light beam transverse to the propagation direction of the light beam.

The method 1900 includes, at 1906, controlling, by the controller, the dynamic ICG to diffract, for each time slot in the sequence of time slots, a respective portion of the optical beam into the waveguide at a respective angle corresponding to a respective field angle. In many embodiments, the controller controls the modulation of the intensity of the light beam in conjunction with the control of the dynamic ICG so as to effect a two-dimensional scan of the light beam to form an image light field that is projected onto the eye of the viewer.

Method 1900 includes, at 1908, projecting the image light field to the eye of the viewer by directing each respective portion of the light beam out of the waveguide toward the eye at a respective field angle. Thus, the image light field is projected at one or more field angles to the eye of the viewer. Method 1900 may be used to project an image light field to a viewer's eye in any suitable application, including but not limited to superimposing the image light field on an external image viewed by the viewer's eye.

It should be appreciated that the particular actions shown in fig. 19 provide particular ways of projecting the image light field to the eyes of the viewer, according to some embodiments. Other sequences of actions may also be performed according to some embodiments. For example, some embodiments may perform the actions outlined above in a different order. Further, various acts illustrated in FIG. 19 may include multiple sub-acts that may be performed in various orders as appropriate to the single act. In addition, other actions may be added or deleted depending on the particular application. One of ordinary skill in the art would recognize many variations, modifications, and alternatives.

It is also understood that the examples and embodiments described herein are for illustrative purposes only and that various modifications or changes in light thereof will be suggested to persons skilled in the art and are to be included within the spirit and purview of this application and scope of the appended claims.