CN116299834A

CN116299834A - Diffractive optical waveguide and AR device

Info

Publication number: CN116299834A
Application number: CN202310170091.2A
Authority: CN
Inventors: 邵陈荻; 游旭; 兰富洋; 周兴; 关健
Original assignee: Meta Bounds Inc
Current assignee: Meta Bounds Inc
Priority date: 2023-02-27
Filing date: 2023-02-27
Publication date: 2023-06-23

Abstract

The invention discloses a diffraction optical waveguide and an AR device. The diffractive optical waveguide includes: the optical waveguide substrate is provided with a coupling-in region and a coupling-out region, and the coupling-out region comprises a first region and a second region; the coupling-out grating is arranged in the coupling-out region, the part of the coupling-out grating, which is positioned in the first region, is provided with at least a first grating vector, the part of the coupling-out grating, which is positioned in the second region, is provided with at least a second grating vector, and the directions of the first grating vector and the second grating vector are different; the coupling-in grating is arranged in the coupling-in area, wherein the coupling-in grating is provided with a third grating vector, an included angle between the direction of the vector sum of the first grating vector and the second grating vector and the third grating vector is smaller than a preset angle, and the difference between the length of the vector sum and the length of the third grating vector is smaller than a preset value. By arranging two coupling-out areas with different grating vectors, the total area of the waveguide grating is reduced and the energy utilization rate is improved.

Description

Diffractive optical waveguide and AR device

Technical Field

The invention belongs to the technical field of enhanced display, and particularly relates to a diffraction optical waveguide and AR equipment.

Background

In the field of augmented reality (Augmented reality, AR) and Mixed Reality (MR), compared with Bird path (BB), wormhole (off-axis reflection), free-form surface prism and other display schemes, the optical waveguide scheme is lighter and thinner and the eye box is larger, so that the optical waveguide has wider application prospect. An eye box refers to a two-dimensional area where the human eye can see the light of a given field of view completely at a given viewing distance (the light of each angle of view can be observed). In the optical waveguide scheme, compared with an array optical waveguide using a partial transflective film, the manufacturing process of the diffraction optical waveguide is lower in difficulty, and grid-shaped dark stripes are not generated when two-dimensional pupil expansion (two-dimensional exit pupil expansion) is realized, so that the diffraction optical waveguide is more focused.

The difficulty in the study of diffractive optical waveguides is how to reduce the waveguide area and how to further increase the eyebox. Compared with the optical waveguide design of an all-one-dimensional grating, the optical waveguide design with a two-dimensional grating proposed by US10359635B2 (Wave Optics) can achieve two-dimensional pupil expansion without turning areas, so that a larger eye box can be provided.

The gratings of the light guide coupling-out region in the prior art are typically one-dimensional gratings or two-dimensional gratings. The coupled gratings are all one-dimensional gratings, the grating vectors are identical, and the total area of the waveguide grating is larger; when the coupling-out grating is a two-dimensional grating, energy waste exists although the total area is small. Therefore, the total grating area of the waveguide and the energy utilization are difficult to be compatible.

Disclosure of Invention

The invention solves the technical problems that: how to solve the problem that the reduction of the total grating area of the waveguide and the improvement of the energy utilization rate are difficult to be compatible.

A diffractive optical waveguide, the diffractive optical waveguide comprising:

the optical waveguide substrate is provided with a coupling-in region and a coupling-out region, and the coupling-out region comprises a first region and a second region;

the coupling-out grating is arranged in the coupling-out region, the part of the coupling-out grating, which is positioned in the first region, is provided with at least a first grating vector, the part of the coupling-out grating, which is positioned in the second region, is provided with at least a second grating vector, and the directions of the first grating vector and the second grating vector are different;

the coupling-in grating is arranged in the coupling-in area and is used for coupling light into the optical waveguide substrate for total reflection conduction and coupling out through the coupling-out grating, the coupling-in grating is provided with a third grating vector, an included angle between the vector sum direction of the first grating vector and the second grating vector and the third grating vector is smaller than a preset angle, and the difference between the length of the vector sum and the length of the third grating vector is smaller than a preset value.

Preferably, the reciprocal size of the first grating vector, the second grating vector and the third grating vector ranges from 200nm to 2um.

Preferably, the portion of the outcoupling grating located in said first region also has a second grating vector.

Preferably, the coupling-out grating comprises two one-dimensional gratings or equivalent one-dimensional gratings located in the first area, one of the two one-dimensional gratings or equivalent one-dimensional gratings has a first grating vector and the other one has a second grating vector, and the two one-dimensional gratings or equivalent one-dimensional gratings are sequentially arranged in the thickness direction of the optical waveguide substrate and at least partially overlap.

Preferably, the out-coupling grating comprises a two-dimensional grating in the first region, the two-dimensional grating having the first grating vector and the second grating vector.

Preferably, the out-coupling grating further comprises a one-dimensional grating or equivalent one-dimensional grating located within the second region and having the second grating vector.

Preferably, the out-coupling region further comprises a third region, the first region being located between the second region and the third region, the portion of the out-coupling grating located in the third region having a second grating vector.

Preferably, the coupling-out grating is located in a portion of the first region having a groove depth, and/or a duty cycle, and/or refractive index characteristics, and/or absorption characteristics that taper from the center of the first region in a direction towards the second region and/or towards the third region.

Alternatively, the depth of the portion of the outcoupling grating located in the first region, and/or the duty cycle, and/or the refractive index characteristic, and/or the absorption characteristic, is graded from the center of the first region in the direction of the incoupling center line.

Preferably, the material of the optical waveguide substrate comprises at least one of glass, resin, optical plastic and transparent ceramic, and the coupling-out grating is located on the grating of the first region and the grating of the second region on the side of the optical waveguide substrate close to the human eye and/or far from the human eye.

Preferably, the coupling-in grating and the coupling-out grating can be realized by a surface relief grating or a volume holographic grating, and the grating thickness of the surface relief grating or the volume holographic grating is between 10nm and 2 um; when the coupling-in grating and the coupling-out grating comprise surface relief gratings, the cross-section of the surface relief grating comprises a straight groove envelope, and/or a helical tooth envelope, and/or a blaze envelope, and/or a step envelope, and/or a curved envelope.

Preferably, the high refractive index portion of the surface relief grating or the volume holographic grating has a refractive index between 1.5 and 3.0 and the low refractive index portion has a refractive index between 1.0 and 1.5.

Preferably, the included angles between the central connecting lines of the coupling-in region and the coupling-out region and the horizontal line are respectively 0-90 degrees corresponding to the left eye and 90-180 degrees corresponding to the right eye.

Preferably, the coupling-in grating and/or the coupling-out grating has at least one coating on the side far from human eyes or the side close to human eyes, and the non-grating area of the optical waveguide substrate has at least one coating, and the material of the coating comprises a dielectric material and/or a metal material.

The invention also discloses an AR device comprising any one of the above diffractive optical waveguides.

The invention discloses a diffraction optical waveguide and AR equipment, which have the following technical effects:

by providing two out-coupling regions with different grating vectors, the total area of the waveguide grating can be reduced and the energy utilization can be improved.

Drawings

FIG. 1 is a top view of a diffractive optical waveguide according to a first embodiment of the present invention;

FIG. 2 is a schematic diagram of grating vectors of the coupling-in region and the coupling-out region according to a first embodiment of the present invention;

FIG. 3 is a schematic view showing the distribution of gratings along the thickness direction of a waveguide in a first area according to a first embodiment of the present invention;

FIG. 4 is a schematic view showing another distribution of gratings along the thickness direction of a waveguide in a first area according to a first embodiment of the present invention;

FIG. 5 is a schematic diagram of an equivalent one-dimensional grating according to a first embodiment of the present invention;

FIG. 6 is a schematic diagram showing a distribution of a two-dimensional grating along a thickness direction of a waveguide in a first region according to a first embodiment of the present invention;

FIG. 7 is a top view of another grating geometry diffractive optical waveguide according to a first embodiment of the present invention;

FIG. 8 is a top view of a diffractive optical waveguide with a plurality of zones disposed in a coupling-out region according to a first embodiment of the present invention;

FIG. 9 is a schematic diagram showing the center-to-center relationship between the coupling-in area and the coupling-out area according to the first embodiment of the present invention;

fig. 10 is a schematic cross-sectional view of a different type of grating according to a first embodiment of the present invention.

Detailed Description

The present invention will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

It will be understood that when an element is referred to as being "disposed on" another element, it can be directly on the other element or be indirectly on the other element.

It should also be noted that in the drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components; in the description of the present invention, it should be understood that, if there is an azimuth or positional relationship indicated by terms such as "upper", "lower", "left", "right", etc., based on the azimuth or positional relationship shown in the drawings, it is only for convenience of describing the present invention and simplifying the description, but it is not indicated or implied that the apparatus or element referred to must have a specific azimuth, be constructed and operated in a specific azimuth, and thus, terms describing the positional relationship in the drawings are merely for exemplary illustration and are not to be construed as limitations of the present patent, and specific meanings of the terms described above may be understood by those skilled in the art according to specific circumstances.

Before describing various embodiments of the present invention in detail, the technical idea of the present invention will be briefly described first: in the scheme in the prior art, only one grating vector is arranged in the whole coupling-out region, and the pupil expansion direction is single, so that gratings in other regions are required to be matched, and the total area of the optical waveguide is large; in the second scheme, two grating vectors in different directions are arranged in the whole coupling-out area, the pupil expansion direction is various, the coupling-out can be directly performed without other grating matching, so that the area is small, but the coupling-out area is larger than the actually required area because the coupling-out can be performed at all positions, and the energy waste is serious. If gratings with different grating vectors are arranged at different positions of the coupling-out region, and the direction and the size of the grating vectors are specially arranged, the high energy of the first scheme and the small area of the second scheme can be considered. Therefore, the invention provides a diffraction optical waveguide, which divides a coupling-out area into a first area and a second area, gratings with different grating vectors are respectively arranged in the two areas, and light rays coupled into the optical waveguide substrate by the coupling-in grating for total reflection conduction can be coupled out by the coupling-out grating. Therefore, by providing the out-coupling regions with different grating vectors, the total area of the waveguide grating can be reduced and the energy utilization can be improved.

It should be noted that the grating having one grating vector is not limited to a one-dimensional grating, but may also include the equivalent one-dimensional grating described in the present invention, i.e., a two-dimensional grating having one dominant grating vector; the grating having two grating vectors is not limited to a two-dimensional grating, but may be a one-dimensional grating having different grating vectors overlapped one above the other.

As shown in fig. 1, the diffractive optical waveguide of the first embodiment includes an optical waveguide substrate 10, an out-coupling grating, and an in-coupling grating. The optical waveguide substrate 10 has a coupling-in region 11 and a coupling-out region 12 thereon, the coupling-out region 12 including a first region 121 and a second region 122. The light spots of different fields of view of the optical waveguide substrate 10 are coupled in via the coupling-in region 11, the partial total reflection path being located in the first region 121 and the partial total reflection path being located in the second region 122, the arrow in the figure indicating the direction of the total reflection path. The coupling-out grating is disposed in the coupling-out region 12, the portion of the coupling-out grating located in the first region 121 has at least a first grating vector, and the portion of the coupling-out grating located in the second region 122 has at least a second grating vector, and the directions of the first grating vector and the second grating vector are different. The coupling-in grating is disposed in the coupling-in region 11, and is used for coupling light into the optical waveguide substrate 10 for total reflection conduction and coupling out through the coupling-out grating, wherein the coupling-in grating has a third grating vector, an included angle between a vector sum direction of the first grating vector and the second grating vector and the third grating vector is smaller than a preset angle, and a difference between a length of the vector sum and a length of the third grating vector is smaller than a preset value. Illustratively, as shown in fig. 2, the direction of the vector sum of the first grating vector and the second grating vector is the same as the direction of the third grating vector, i.e., the included angle is equal to 0, and the length of the vector sum is equal to the length of the third grating vector, i.e., the difference between the lengths is 0. The preset angle is illustratively selected to be 5 deg., and the period deviation corresponding to the preset value is 10 nanometers.

Wherein the direction of the grating vector corresponds to the direction of the grating period, and the length of the grating vector is proportional to the reciprocal of the grating period. The direction of the grating vector can be positive and negative. As shown in fig. 2, for the left-eye waveguide, k is taken _x The direction (projection of the grating vector in the x-direction) is positive. The vector sum of the first grating vector and the second grating vector is equal to the third grating vector, and the first grating vector, the second grating vector and the opposite vector of the third grating vector can be connected end to form a closed triangle. The lengths of the first grating vector and the second grating vector can be the same or different, and when the lengths of the first grating vector and the second grating vector are the same, the first grating vector, the second grating vector and the third grating vector are ideally connected to form a closed triangle which is an isosceles triangle.

Further, the portion of the outcoupling grating located in the first region 121 also has a second grating vector. When the first region 121 has only one grating vector, the coupling-out energy is high, but the coupling-out energy of different fields of view is not uniform, so that the second grating vector is added to slightly reduce the cost of the coupling-out energy to improve the field of view uniformity. As one of the implementation manners, the coupling-out grating includes two one-dimensional gratings or equivalent one-dimensional gratings located in the first area 121, one of the two one-dimensional gratings or equivalent one-dimensional gratings has a first grating vector and the other one of the two one-dimensional gratings or equivalent one-dimensional gratings has a second grating vector, and the two one-dimensional gratings or equivalent one-dimensional gratings are sequentially disposed in the thickness direction of the optical waveguide substrate 10 and at least partially overlap. As shown in fig. 3, in the thickness direction of the optical waveguide substrate 10, one-dimensional grating or equivalent one-dimensional grating is located on the outer surface (the far-human-eye side of the optical waveguide substrate 10) or the inner surface (the near-human-eye side of the optical waveguide substrate 10) of the optical waveguide substrate 10, and the other one-dimensional grating or equivalent one-dimensional grating is located inside the optical waveguide substrate 10. In another embodiment, as shown in fig. 4, one of the one-dimensional gratings or equivalent one-dimensional gratings is located on the outer surface of the optical waveguide substrate 10 (the side of the optical waveguide substrate 10 away from the human eye) and the other one-dimensional grating or equivalent one-dimensional grating is located on the inner surface of the optical waveguide substrate 10 (the side of the optical waveguide substrate 10 close to the human eye) in the thickness direction of the optical waveguide substrate 10. In another embodiment, two grating portions are superimposed overlapping in the waveguide thickness direction, both on the outer surface (the eye-far side of the optical waveguide substrate 10) or the inner surface (the eye-near side of the optical waveguide substrate 10) of the optical waveguide substrate 10. In another embodiment, three gratings are stacked in the thickness direction of the waveguide, two gratings being located on the outer and inner surfaces of the optical waveguide substrate 10, respectively, and the other being located inside the optical waveguide substrate 10. In the thickness direction, the two gratings are partially or completely overlapped, so that a two-dimensional pupil expansion effect is obtained, and the required area of the optical waveguide substrate 10 is reduced. When two gratings are used to generate two different grating vectors (a first grating vector and a second grating vector) for the first region 121, a one-dimensional grating and an equivalent one-dimensional grating may also be used in combination. Fig. 5 shows a schematic structure of an equivalent one-dimensional grating.

As another embodiment, one grating may be used to create two different grating vectors for the first region 121, the coupled-out grating comprising a two-dimensional grating at the first region 121, the two-dimensional grating having a first grating vector and a second grating vector, as shown in fig. 6, when the two-dimensional grating at the first region 121 is located on the outer surface (the side of the optical waveguide substrate 10 facing away from the human eye) or the inner surface (the side of the optical waveguide substrate 10 facing away from the human eye) of the optical waveguide substrate 10.

The first region and the second region may have polygonal geometries. Illustratively, as shown in fig. 1, the first region 121 is rectangular in shape and the second region 122 is also rectangular in shape. In another embodiment, the coupling-out region 12 may be provided with chamfers or rounded corners, for example, as shown in fig. 7, the shape of the first region 121 is rectangular and the shape of the second region 122 is irregular after one corner of the rectangle is removed. Further, the area of the second region 122 is not more than half the area of the coupling-out region, and uniformity is ensured.

Further, the out-coupling grating also includes a one-dimensional grating or equivalent one-dimensional grating having a second grating vector located within the second region 122.

Further, as shown in fig. 8, the coupling-out region 12 further includes a third region 123, the first region 121 is located between the second region 122 and the third region 123, and a portion of the coupling-out grating located in the third region 123 has a first grating vector. Illustratively, the out-coupling grating further comprises a one-dimensional grating or equivalent one-dimensional grating located in the third region 123. The three regions in this embodiment are all rectangular in shape, and in other embodiments, the three regions may have other shapes.

Wherein at least one of the groove depth, the duty cycle, the refractive index, the absorption characteristics of the portion of the outcoupling grating located in the first region 121 is graded from the center of the first region 121 in a direction towards the second region 122 and/or towards the third region 123. When the grating in the first area 121 is a one-dimensional grating, the duty ratio counts only one period direction, and when the grating in the first area 121 includes a two-dimensional grating or an equivalent one-dimensional grating, the duty ratio comprehensively considers two period directions. The duty cycle may be counted in a profile range equal to or greater than the average refractive index at half the thickness of the microstructure.

In another embodiment, at least one of the groove depth, the duty cycle, the refractive index, and the absorption characteristics of the portion of the coupling-out grating located in the first region 121 is graded from the center of the first region 121 along the coupling-in and coupling-out center line direction.

When the outcoupling region 12 comprises three regions, a first region 121, a second region 122 and a third region 123, the gratings of the three regions may be in the same plane or in different planes. Further, the geometry of the individual regions may be symmetrical or asymmetrical. The area of the first region 121 does not exceed half the area of the coupling-out region 12, and high energy utilization is ensured.

Further, in other embodiments, as shown in fig. 9, the line direction of the center of the coupling-in region 11 and the center of the coupling-out region 12 has a θ orientation. For the left eye light waveguide, the value of theta is 0-90 degrees, and the right eye light waveguide is symmetrically arranged, wherein the value is 90-180 degrees.

Further, the coupling-in grating and the coupling-out grating of the first embodiment may be implemented using a diffraction relief grating (embossing or etching), or using a holographic exposure method. The surface relief may have the cross-sectional envelopes of a to e in fig. 10, i.e., straight groove envelope, helical tooth envelope, blaze envelope, step envelope, and curved envelope, and the cross-section of the volume hologram grating is shown as f in fig. 10. The thickness/groove depth (or similar definition) of the grating single-layer structure is between 10nm and 2um.

Further, the high refractive index portion of the surface relief grating or the volume hologram grating has a refractive index of between 1.5 and 3.0 and the low refractive index portion has a refractive index of between 1.0 and 1.5.

Specifically, the first area and/or the second area of the coupling-out grating are provided with a plurality of sub-subareas, different sub-subareas are provided with the same grating vector, and the microstructure morphology, and/or the groove depth, and/or the refractive index and/or the absorption of different sub-subareas in the same area are different; the boundaries of each sub-partition are defined by straight line segments and/or curved line segments.

The optical waveguide substrate of the diffraction optical waveguide can be one or more layers of substrate structures, and the substrate can be glass, resin, plastic, transparent ceramic or the like or a combination of several of the substrates. Further, the coupling-in grating and the coupling-out grating may have one or more coating layers on the side far from the human eye or the side near the human eye, and the optical waveguide substrate may have a coating layer at the position without the grating. The coating area may be regular or irregular in shape. The plating film may include a dielectric material or a metal material.

The second embodiment also discloses an AR device, which includes the diffractive optical waveguide in the first embodiment. Further, the AR device further comprises a projection means for projecting light towards the coupling-in grating. AR devices include, but are not limited to, AR glasses, AR head-display devices. It will be appreciated that the complete AR device should also have other necessary basic components, but other components are not important to the present embodiment and are therefore not shown in the figures and not described in detail in the specification, and are well known to those skilled in the art.

While certain embodiments have been shown and described, it would be appreciated by those skilled in the art that changes and modifications may be made without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.

Claims

1. A diffractive optical waveguide, the diffractive optical waveguide comprising:

2. The diffractive optical waveguide according to claim 1, characterized in that the reciprocal of the first, second and third grating vectors corresponds to a grating period, and the grating period size ranges from 200nm to 2um.

3. The diffractive optical waveguide according to claim 1, characterized in that the portion of the outcoupling grating located in the first region also has a second grating vector.

4. A diffractive optical waveguide according to claim 3, characterized in that the outcoupling grating comprises two one-dimensional or equivalent one-dimensional gratings in the first region, one of the two one-dimensional or equivalent one-dimensional gratings having a first grating vector and the other having a second grating vector, and the two one-dimensional or equivalent one-dimensional gratings being arranged in sequence and at least partially overlapping in the thickness direction of the optical waveguide substrate.

5. A diffractive optical waveguide according to claim 3, characterized in that the out-coupling grating comprises a two-dimensional grating in the first region, the two-dimensional grating having the first grating vector and the second grating vector.

6. The diffractive optical waveguide according to claim 1, characterized in that the out-coupling grating further comprises a one-dimensional grating or equivalent one-dimensional grating located within the second region and having the second grating vector.

7. The diffractive optical waveguide according to claim 1, characterized in that the outcoupling region further comprises a third region, the first region being located between the second region and the third region, the portion of the outcoupling grating located in the third region having a first grating vector.

8. The diffractive optical waveguide according to claim 1, characterized in that the area of the second region does not exceed half the area of the coupling-out region.

9. The diffractive optical waveguide according to claim 7, characterized in that the area of the first region does not exceed half the area of the coupling-out region.

10. A diffractive optical waveguide according to claim 7, characterized in that the coupling-out grating is located in the portion of the first region having a groove depth, and/or a duty cycle, and/or refractive index characteristics, and/or absorption characteristics that taper from the centre of the first region in a direction towards the second region and/or towards the third region.

11. A diffractive optical waveguide according to claim 1, characterized in that the depth of the grooves of the portion of the coupling-out grating located in the first region, and/or the duty cycle, and/or the refractive index characteristics, and/or the absorption characteristics, are graded in the direction of the coupling-in coupling-out center line.

12. The diffractive optical waveguide according to claim 1, characterized in that the material of the optical waveguide substrate comprises at least one of glass, resin, optical plastic, transparent ceramic, the out-coupling grating being located in the first region and the grating being located in the second region being located on the side of the optical waveguide substrate close to the human eye and/or remote from the human eye.

13. The diffractive optical waveguide according to claim 1, characterized in that the coupling-in grating and the coupling-out grating can be realized by a surface relief grating or a volume holographic grating, the grating thickness of which is between 10nm and 2 um; when the coupling-in grating and the coupling-out grating comprise surface relief gratings, the cross-section of the surface relief grating comprises a straight groove envelope, and/or a helical tooth envelope, and/or a blaze envelope, and/or a step envelope, and/or a curved envelope.

14. The diffractive optical waveguide according to claim 13, characterized in that the high refractive index part of the surface relief grating or the volume hologram grating has a refractive index between 1.5-3.0 and the low refractive index part has a refractive index between 1.0-1.5.

15. The diffractive optical waveguide according to claim 1, characterized in that the angle between the central line of the coupling-in region and the coupling-out region and the horizontal line corresponds to a value range of 0 ° to 90 ° for the left eye and a value range of 90 ° to 180 ° for the right eye.

16. The diffractive optical waveguide according to claim 1, characterized in that the first region and/or the second region has a plurality of sub-regions, different sub-regions within the same region having the same grating vector, the microstructure morphology, and/or groove depth, and/or refractive index, and/or absorption of different sub-regions being different; the boundaries of each sub-partition are defined by straight line segments and/or curved line segments.

17. A diffractive optical waveguide according to claim 1, characterized in that the coupling-in grating and/or the coupling-out grating has at least one coating on the side facing away from the human eye or on the side facing towards the human eye and/or the grating-free region of the optical waveguide substrate has at least one coating, the material of the coating comprising a dielectric material and/or a metallic material.

18. An AR device comprising the diffractive optical waveguide of any one of claims 1 to 17.