Projector compensation with in-coupler grating line offset

Abstract

Certain aspects of the present disclosure include an optical device. The optical device generally includes an in-coupler (IC) configured to receive light from the projector, where the IC includes at least one grating line offset (GLO) associated with one or more phase deviations of the light from the projector. The apparatus also includes a waveguide and an out-coupler (OC), wherein the IC is configured to redirect light from the projector through the waveguide to the OC.

Description

TECHNICAL FIELD

[0001] Certain aspects of the present disclosure generally relate to waveguide displays. More particularly, the present disclosure provides a waveguide with an in-coupler implemented with projector compensation. BACKGROUND

[0002] Augmented reality (AR) is a technology that merges virtual and real worlds to provide an immersive experience for a user. Creating virtual images that blend with a real environment is important for AR displays. AR can be implemented with a waveguide that includes an in-coupler (IC) and an out-coupler (OC), where the IC redirects light from a projector toward the OC, and the OC redirects the light toward the user's eye. SUMMARY

[0003] Certain aspects of the present disclosure include an optical device. The optical device generally includes an in-coupler (IC) configured to receive light from a projector, where the IC includes at least one grating line offset (GLO) associated with one or more phase deviations of the light from the projector. The device also includes a waveguide and an out-coupler (OC), where the IC is configured to redirect the light from the projector through the waveguide to the OC.

[0004] Certain aspects of the present disclosure include a method for optical signal processing. The method generally includes receiving light from a projector via an IC. The method also includes imposing at least one phase shift on the light via the IC, where, to impose the at least one phase shift, the IC includes at least one GLO associated with one or more phase deviations of the light from the projector. The method can also include redirecting the light from the projector through a waveguide to an OC via the IC. BRIEF DESCRIPTION OF DRAWINGS

[0005] So that the manner in which the above recited features of the present disclosure can be understood in detail, a more particular description can be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this disclosure and are therefore not to be considered limiting of its scope, for the description can admit to other equally effective embodiments.

[0006] Figure 1 An optical device with a waveguide and an in-coupler (IC) is illustrated in accordance with certain aspects of the present disclosure.

[0007] Figure 2A Phase deviations of light from a projector are illustrated.

[0008] Figure 2BAn example of a GLO implemented for an IC according to certain aspects of this disclosure to reduce the effects of phase deviation of light from a projector is illustrated.

[0009] Figure 3 A flowchart illustrating an example operation for optical signal processing according to certain aspects of this disclosure is provided.

[0010] For ease of understanding, the same element symbols have been used to denote common elements in all figures where possible. It is contemplated that elements and features of one embodiment may be beneficially incorporated into other aspects without further description. Detailed Implementation

[0011] The inlet coupler (IC) of the waveguide combiner diffracts light from the projector into total internal reflection (TIR) ​​(e.g., total internal reflection within a medium, such as a waveguide). Some aspect guides shift the grating lines across the IC, resulting in a spatially varying phase on the diffracted light from the projector. This phase shift can be used to compensate for defect effects in the projector output. As used herein, compensation refers to any reduction in defect effects, and not necessarily complete compensation for such effects.

[0012] Augmented reality (AR) waveguide combiners can be designed to assume that the projector output is a plane wave with a flat wavefront. Real-world projectors are typically not like this, and any deviation from a flat wavefront can degrade the system's modulation transfer function (MTF) or sharpness. MTF refers to the ability of an optics device to transfer the contrast of an object from its input to its output. From the user's perspective, deviations can manifest as blurry virtual images and suppress the readability of small text or lines. Some approaches mitigate these effects of flat wavefront deviations by implementing grating line offset (GLO) for the waveguide's integrated circuitry (IC).

[0013] Figure 1 According to certain aspects of this disclosure, an optical device 100 having a waveguide 110 and an IC 106 is shown. As shown, light 104 can be received from a projector 102. Light 104 can be guided to the IC 106. The IC 106 redirects the light to a TIR within the waveguide 110 until the light 104 reaches an OC 108. As shown, the OC 108 can redirect the light to a user 112.

[0014] Figure 2A The diagram illustrates the phase deviation of light 104 from projector 102. In other words, as shown, projector aberrations can cause phase deviations. These phase deviations are directed from projector 102 to IC 106 and ultimately to user 112, where the user perceives these phase deviations as image blurring, as illustrated.

[0015] Figure 2BAccording to certain aspects of this disclosure, a GLO implemented for IC 106 is shown for reducing the effects of these phase deviations in the light from projector 102. As shown, the light received from the projector via IC 106 has a phase deviation. These phase deviations can be reduced by the GLO implemented for IC 106. As shown, due to the GLO of IC 106, the light redirected from IC may have a flat wavefront.

[0016] The GLO used to compensate for phase aberration depends on the projector output. The phase aberration between the pupil and the flat wavefront can be measured at multiple wavelengths and field of view (FOV) points. Measurements can be used to identify the GLO for each grating line. In some aspects, a compensation map can be identified, including the average wavefront aberration at the wavelength and FOV. In some aspects, the correction map can be identified based on different weights associated with different wavelengths and FOV points (based on their contribution to the MTF). For example, if the first wavelength contributes more to the MTF than the second wavelength, the first wavelength can be assigned a higher weight than the second wavelength. Once the compensation map is identified, the phase shift can be calculated for one or more grating lines of the IC 106. For example, the phase shift of a grating line across an IC can be identified using a given expression:

[0017]

[0018] Where Δr is GLO, and is the phase shift of the light associated with GLO, where m is a non-zero integer corresponding to the diffraction order associated with the diffraction event of IC. The figure shows grating lines 204, 206, 212, 214, 220, and 222 with equal periods (Λ), and grating lines 202, 208, 210, 216, 218, and 224 with GLO. GLO refers to any offset of a grating line relative to the position of grating lines if the grating lines are periodic (having equal periods). For example, GLO can refer to the distance between grating lines 212 and 210. As shown, GLO can be positive, such as grating line 202 shifted to the right relative to grating line 204, or negative, such as grating line 210 shifted to the left relative to grating line 212.

[0019] Other techniques for applying phase shift to the projector output may include using external optics or varying the depth and / or duty cycle of the IC grating. Compared to any form of external optics, grating line offset can be designed into the IC grating with minimal additional cost (e.g., product cost or area). The phase applied by grating line offset may not affect the light that is diffracted to the TIR and then re-illuminates the grating, compared to spatially varying depths or duty cycles within the IC grating. These secondary phase shifts (e.g., spatially varying depths or duty cycles) can introduce further aberrations to the wavefront. Furthermore, variable geometry can introduce spatially varying diffraction efficiencies. Therefore, using GLO to apply phase shift to the IC provides a more efficient technique for reducing the effects of projector aberrations compared to other described techniques.

[0020] Figure 3 According to certain aspects of this disclosure, a flowchart of an example operation 300 for optical signal processing is provided. Operation 300 may be performed by an optical device (e.g., optical device 100).

[0021] At block 302, the optical device can receive light from a projector (e.g., projector 102) via an IC (e.g., IC 106). At block 304, the optical device can shift at least one phase (e.g., ...) via an IC. The light is applied. To apply at least one phase shift, the IC may include at least one GLO (e.g., Δr) associated with one or more phase deviations of the light from the projector. In some aspects, at least one GLO may include different GLOs applied to at least two grating lines of the IC. At least one GLO may be determined based on the average value of the phase deviations of the light. In some aspects, different weights may be applied to different wavelengths or FOVs of the light associated with the optical device. At least one GLO of the IC may be determined based on different weights. Different weights may be determined based on the contribution of different wavelengths or FOVs to the modulation transfer function of the optical device.

[0022] In some aspects, at least one GLO may include an offset between a grating line of the IC (e.g., grating line 202) and a grating line of the IC having periodic grating lines (e.g., grating line 204). At least one GLO may be associated with a phase shift determined by the light to reduce the effect of one or more phase deviations in one or more image metrics. At block 306, the optical device may redirect light from the projector through a waveguide (e.g., waveguide 110) to an OC (e.g., OC 108) via the IC.

[0023] While the foregoing addresses various aspects of this disclosure, other and further aspects of this disclosure may be designed without departing from its essential scope, and the scope of this disclosure is defined by the appended claims.

Claims

1. An optical device, comprising: An input coupler (IC) is configured to receive light from a projector, wherein the IC includes at least one grating line offset (GLO) associated with one or more phase deviations of the light from the projector. waveguide; as well as An output coupler (OC) is provided, wherein the IC is configured to redirect the light from the projector to the OC via the waveguide.

2. The optical device of claim 1, wherein the at least one GLO comprises different GLOs applied to at least two grating lines of the IC.

3. The optical device of claim 1, wherein the at least one GLO is determined based on the average value of the phase deviation of the light.

4. The optical device of claim 1, wherein different weights are applied to different wavelengths or fields of view (FOV) of the light associated with the optical device, and wherein the at least one GLO of the IC is determined based on the different weights.

5. The optical device of claim 4, wherein the different weights are determined based on the contribution of the different wavelengths or FOVs to the modulation transfer function of the optical device.

6. The optical device of claim 1, wherein the at least one GLO is an offset of the grating line of the IC from the grating line of the IC having periodic grating lines.

7. The optical device of claim 1, wherein the at least one GLO is associated with a determined phase shift to be applied to the light to reduce the effect of the one or more phase deviations in one or more image metrics.

8. A method for optical signal processing, comprising: Light from the projector is received via an input coupler (IC); The light is applied to at least one phase shift via the IC, wherein, in order to apply the at least one phase shift, the IC includes at least one grating line offset (GLO) associated with one or more phase offsets of the light from the projector. as well as The light from the projector is redirected to the outgoing coupler (OC) via the IC through a waveguide.

9. The method of claim 8, wherein the at least one GLO comprises different GLOs applied to at least two grating lines of the IC.

10. The method of claim 8, wherein the at least one GLO is determined based on the average value of the phase deviation of the light.

11. The method of claim 8, wherein different weights are applied to different wavelengths or fields of view (FOV) of the light associated with the optical device, and wherein the at least one GLO of the IC is determined based on the different weights.

12. The method of claim 11, wherein the different weights are determined based on the contribution of the different wavelengths or FOVs to the modulation transfer function of the optical device.

13. The method of claim 8, wherein the at least one GLO includes offset of the grating lines of the IC from the grating lines of the IC having periodic grating lines.

14. The method of claim 8, wherein the at least one GLO is associated with a determined phase shift to be applied to the light to reduce the effect of the one or more phase deviations in one or more image metrics.

15. A virtual reality (AR) device, comprising: Projector; An input coupler (IC) is configured to receive light from the projector, wherein the IC includes at least one grating line offset (GLO) associated with one or more phase deviations of the light from the projector. waveguide; as well as An output coupler (OC) is provided, wherein the IC is configured to redirect the light from the projector to the OC via the waveguide.

16. The AR device of claim 15, wherein the at least one GLO comprises different GLOs applied to at least two grating lines of the IC.

17. The AR device of claim 15, wherein the at least one GLO is determined based on the average value of the phase deviation of the light.

18. The AR device of claim 15, wherein different weights are applied to different wavelengths or fields of view (FOV) of the light associated with the AR device, and wherein the at least one GLO of the IC is determined based on the different weights.

19. The AR device of claim 18, wherein the different weights are determined based on the contribution of the different wavelengths or FOVs to the modulation transfer function of the AR device.

20. The AR device of claim 15, wherein the at least one GLO is an offset of the grating line of the IC from the grating line of the IC having periodic grating lines.

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