Diffractive waveguide and device

Abstract

The application provides a diffraction waveguide, comprising: a waveguide substrate; the waveguide substrate has a first surface and a second surface which are parallel to each other; a coupling-out structure and a coupling-in structure arranged on the first surface and / or the second surface; the coupling-in structure is used for coupling an image beam into the waveguide substrate; the coupling-out structure is used for diffraction coupling out the image beam transmitted in the waveguide substrate from the waveguide substrate; a resonant grating structure is connected to the second surface of the waveguide substrate through a connecting piece and corresponds to the coupling-out structure; the resonant grating structure is used for at least partially reflecting the image beam leaked from the second surface of the waveguide substrate back into the waveguide substrate for transmission and then diffraction coupling out from the first surface of the waveguide substrate through the coupling-out structure. The technical scheme alleviates the light leakage problem of the waveguide.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of AR, and in particular to a diffractive waveguide and a device. BACKGROUND

[0002] Augmented Reality (AR) is a technology that fuses the real world and virtual information, and an AR display system usually includes a micro projector and an optical display screen. The AR display system projects the image light beams emitted by the micro projector into the human eye through the optical display screen, and meanwhile, the user can see the real world through the optical display screen. The micro projector provides virtual content for the AR display system, and the optical display screen is usually a transparent optical component to pass through the real content. A waveguide is a path for implementing the optical display screen. When the refractive index of a transmission medium is greater than that of the surrounding medium and the incidence angle in the waveguide is greater than the critical angle of total reflection, the light can be totally reflected without leakage in the waveguide. After the light from the micro projector is coupled into the waveguide, it continues to propagate losslessly in the waveguide until it is coupled out by a subsequent structure. Currently, the waveguides on the market are usually divided into geometric array waveguides and diffractive waveguides, and the diffractive waveguides are further divided into volume holographic waveguides and surface relief grating waveguides. The essence of the diffractive waveguide is to couple the incident light into the waveguide through grating diffraction. The surface relief grating waveguide has obvious advantages in many schemes due to its high design freedom and mass production by nanoimprinting.

[0003] The image light beams emitted by the micro projector enter the optical waveguide through the grating effect of the coupling-in area. The image light beams continue to be totally reflected between the two planes of the waveguide and propagate forward. When the image light beams reach the coupling-out area, they are diffracted again under the grating effect of the coupling-out area and are coupled out while propagating. Since the grating has two orders of transmission and reflection, there will be image light beams emitted not only on the side of the human eye but also on the outside opposite to the human eye, which is called light leakage. Light leakage affects the appearance experience and may leak the viewing information of the user, which is a problem that needs to be solved in the industry. SUMMARY

[0004] The present application provides a diffractive waveguide and a device to alleviate the problem of light leakage.

[0005] According to a first aspect of the present application, a diffractive waveguide is provided, comprising:

[0006] a waveguide substrate; the waveguide substrate has a first surface and a second surface which are parallel to each other; the first surface is the surface of the waveguide substrate close to the side of the human eye; and the second surface is the surface of the waveguide substrate away from the side of the human eye;

[0007] out-coupling structures disposed on the first surface and / or the second surface; the in-coupling structures are configured to in-couple image beams into the waveguide substrate and propagate within the waveguide substrate, and the out-coupling structures are configured to out-couple the image beams propagating within the waveguide substrate from the waveguide substrate;

[0008] a resonant grating structure connected to the second surface of the waveguide substrate via a connecting member and corresponding to the out-coupling structures; the resonant grating structure is configured to at least partially reflect the image beams leaked from the second surface of the waveguide substrate back into the waveguide substrate and out-couple the image beams from the first surface of the waveguide substrate via the out-coupling structures.

[0009] Optionally, the resonant grating structure comprises:

[0010] a resonant grating substrate; and

[0011] a grating stack formed on the resonant grating substrate; wherein the grating stack comprises N grating layers, and the refractive indices of the N grating layers are different; wherein N is an integer greater than or equal to 2.

[0012] Optionally, the connecting member is implemented as a dielectric layer, which is configured to connect the resonant grating structure and the waveguide substrate and fill the gaps between the grating units in the grating stack, and the refractive index of the dielectric layer is lower than the refractive index of the waveguide substrate.

[0013] Optionally, the refractive indices of the grating layers increase successively in a direction away from the resonant grating substrate.

[0014] Optionally, the grating stack is a multilayer stack structure or a multilayer conformal structure.

[0015] Optionally, the out-coupling structures are divided into a plurality of out-coupling sub-regions, and the out-coupling sub-regions are obtained according to the effective out-coupling positions corresponding to the image beams of each field of view, each out-coupling sub-region corresponds to a field of view range; different resonant grating structures are configured for different out-coupling sub-regions; the angle response range of the resonant grating structure configured for each out-coupling sub-region is adapted to the field of view range corresponding to the out-coupling sub-region.

[0016] Optionally, the working wavelength range of the resonant grating structure corresponds to the wavelength range of the image beams.

[0017] The angle response range of the resonant grating structure is a set of angles between two angles at which the zero-order reflection efficiency of the image beams in the working wavelength range of the resonant grating structure reaches a threshold when the image beams are incident on the resonant grating structure.

[0018] Optionally, the angle response range of the resonant grating structure is related to a resonant grating parameter; wherein the resonant grating parameter at least includes any one or a combination of a resonant grating inclination angle, a resonant grating period, a resonant grating depth, a resonant grating duty cycle, a resonant grating refractive index, a resonant grating substrate thickness, and a resonant grating substrate refractive index.

[0019] Optionally, the out-coupling structure is divided into a plurality of out-coupling sub-regions according to a one-dimensional direction; wherein the plurality of out-coupling sub-regions are distributed in a strip shape along the one-dimensional direction; the one-dimensional direction represents a propagation direction of the image light beam in the waveguide substrate.

[0020] Optionally, the out-coupling structure is divided into a plurality of out-coupling sub-regions according to a one-dimensional direction; wherein the plurality of out-coupling sub-regions are distributed in a strip shape along the one-dimensional direction; the one-dimensional direction represents a propagation direction of the image light beam in the waveguide substrate.

[0021] Optionally, the out-coupling structure is divided into a plurality of out-coupling sub-regions according to a two-dimensional direction; wherein the plurality of out-coupling sub-regions are distributed in a grid shape.

[0022] Optionally, the out-coupling structure is divided into a plurality of out-coupling sub-regions according to a two-dimensional direction; wherein the plurality of out-coupling sub-regions are distributed in a grid shape.

[0023] Optionally, the out-coupling structure is divided into a plurality of out-coupling sub-regions, the out-coupling sub-regions are divided according to the out-coupling positions corresponding to the image light beams of different wavelengths, each out-coupling sub-region corresponds to a wavelength range, different out-coupling sub-regions are configured with different resonant grating structures; the wavelength response range of the resonant grating structure configured in each out-coupling sub-region is adapted to the wavelength range corresponding to the out-coupling sub-region.

[0024] Optionally, the out-coupling structure is divided into a plurality of out-coupling sub-regions according to a one-dimensional direction; wherein the plurality of out-coupling sub-regions are distributed in a strip shape along the one-dimensional direction; the one-dimensional direction represents a propagation direction of the image light beam in the waveguide substrate.

[0025] Optionally, the out-coupling structure is divided into a plurality of out-coupling sub-regions according to a one-dimensional direction; wherein the plurality of out-coupling sub-regions are distributed in a strip shape along the one-dimensional direction; the one-dimensional direction represents a propagation direction of the image light beam in the waveguide substrate.

[0026] Optionally, the working wavelength range of the resonant grating structure corresponds to the field of view angle range of the image light beam.

[0027] The wavelength response range of the resonant grating structure is a wavelength set in which the zero-order reflection efficiency of the image light beam of the working angle range of the resonant grating structure reaches a threshold value after the image light beam is incident on the resonant grating structure.

[0028] Optionally, the wavelength response range of the resonant grating structure is related to a resonant grating parameter; wherein the resonant grating parameter at least includes any one or a combination of a resonant grating inclination angle, a resonant grating period, a resonant grating depth, a resonant grating duty cycle, a resonant grating refractive index, a resonant grating substrate thickness, and a resonant grating substrate refractive index.

[0029] According to the second aspect of the present application, there is also provided a device comprising the diffraction waveguide of any one of the first aspect of the present application.

[0030] The diffraction waveguide provided by the present application eliminates part of the light leakage by arranging the resonant grating structure on the second surface of the waveguide substrate opposite to the coupling-out structure, so that the image beams leaked from the second surface of the waveguide substrate are reflected back into the waveguide substrate by the resonant grating structure for continuous propagation, thereby alleviating the problem of light leakage and protecting the user to a certain extent when viewing information. Moreover, the image beams reflected back into the waveguide substrate by the resonant grating structure can also be diffracted and coupled out from the first surface of the waveguide substrate through the coupling-out structure, thereby improving the light energy utilization rate.

[0031] Further, different resonant grating structures with different angle response ranges and working wavelengths are arranged corresponding to different regions of the coupling-out structure, which can also adjust the field of view uniformity and color uniformity, and achieve the technical effect of more uniform image information brightness entering the user. BRIEF DESCRIPTION OF DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without any creative labor.

[0033] Figure 1 is a schematic diagram of the principle of light leakage of a traditional diffraction optical waveguide;

[0034] Figure 2 is a schematic diagram of the structure of a diffraction waveguide provided by an embodiment of the present application;

[0035] Figure 3 is a schematic diagram of a resonant grating structure provided by a specific embodiment of the present application Figure 1 ;

[0036] Figure 4 is a schematic diagram of a resonant grating structure provided by a specific embodiment of the present application Figure 2 ;

[0037] Figure 5 is a schematic diagram of a resonant grating structure provided by a specific embodiment of the present applicationFigure 3 ;

[0038] Figure 6 is a schematic diagram of zero-order reflection efficiency of an image beam incident to a resonant grating structure as shown in Figure 4 ;

[0039] Fig. 7(a) is a schematic diagram of an α field of view according to an embodiment of the present application;

[0040] Fig. 7(b) is a schematic diagram of a β field of view according to an embodiment of the present application;

[0041] Fig. 7(c) is a schematic diagram of a relationship between a beam field of view and a total reflection angle according to an embodiment of the present application;

[0042] Figure 8 is a schematic diagram of a coupling-out sub-region according to one-dimensional direction division according to an embodiment of the present application;

[0043] Figure 9 is a schematic diagram of a coupling-out sub-region according to two-dimensional direction division according to an embodiment of the present application;

[0044] Figure 10 is a schematic diagram of a coupling-out sub-region according to one-dimensional direction division according to another embodiment of the present application.

[0045] Legend of reference signs:

[0046] 101 - waveguide substrate;

[0047] 102 - coupling-in structure;

[0048] 103 - coupling-out structure;

[0049] 104 - resonant grating structure;

[0050] 1041 - resonant grating substrate;

[0051] 1042 - grating stack;

[0052] 10421, 10422 and 10423 - grating layer;

[0053] 105 - connecting member. DETAILED DESCRIPTION

[0054] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0055] The terms "first", "second", "third", "fourth" and the like in the description and in the claims of the present application, and above-mentioned drawings, if any, are used to distinguish between similar objects and not necessarily for describing a particular sequential or chronological order. It is to be understood that the use of the terms so-termed "first", "second", "third", "fourth" and the like, if any, in the description and in the claims of the present application is not used to designate a certain order or sequence, except when expressly stated otherwise. It is to be understood that the data thus designated can be interchanged, where appropriate, so that the embodiments of the present application described herein can be carried out in orders other than those illustrated or described herein. Moreover, the terms "comprising", "having", "including" and any variations thereof, are intended to cover a non-exclusive inclusion, for example, a process, method, system, product or apparatus that comprises a list of steps or units not necessarily comprising only those listed or inherent to such process, method, product or apparatus.

[0056] Reference Figure 1 The image light beam emitted by the optical engine (i.e. the micro projector) passes through the coupling-in region grating to enter the optical waveguide, and the image light beam continuously totally reflects between the two planes of the waveguide to propagate forward, and when the image light beam reaches the coupling-out region, it is diffracted again under the action of the coupling-out region grating to propagate and couple out. Since the grating has two orders of transmission and reflection, not only will there be image light beam emission on the side of the human eye (part of the transmission diffraction order satisfies the coupling-out condition and couples out of the waveguide), but also there will be image light beam emission on the side of the waveguide opposite to the human eye (part of the reflection diffraction order no longer satisfies the total reflection condition and transmits out of the waveguide), which is referred to as light leakage. Light leakage will affect the appearance experience, and there is a risk of leaking the user's viewing information.

[0057] Thus, the problem in the prior art is that the image light beam no longer satisfies the total reflection condition during propagation in the waveguide, and is emitted from the side of the waveguide opposite to the human eye.

[0058] In view of this, the present application provides a resonant grating structure at a position corresponding to the coupling-out region on the side of the waveguide, and since the resonant grating structure has a very high reflection 0th order efficiency for image light beams in the visible light range, it can at least partially reflect the leaked diffraction orders back into the waveguide substrate for transmission, and then diffract and couple out from the first surface of the waveguide substrate through the coupling-out structure, so that the light leakage is recovered, which not only alleviates the problem of light leakage, but also improves the energy utilization rate.

[0059] As can be seen, the technical solution provided by the present application not only alleviates the problem of light leakage, protects the viewing information and optimizes the user experience, but also improves the energy utilization rate.

[0060] In addition, the resonant grating structure can achieve high 0th order reflection efficiency for light beams in a specific angular response range and a specific working bandwidth by optimization, and thus the resonant grating structures with different working bandwidths and angular response ranges are arranged at positions corresponding to the coupling-out area on the outer side of the waveguide to reflect and recycle the light leakage of different image beams, and the image uniformity can be adjusted.

[0061] The technical solutions of the present application are described in detail below with specific examples. The following specific examples can be combined with each other, and the same or similar concepts or processes can not be described in some examples.

[0062] Reference Figure 2 According to an embodiment of the present application, a diffractive waveguide is provided, which includes a waveguide substrate 101, a coupling-out structure 103, a coupling-in structure 102, and a resonant grating structure 104. Wherein:

[0063] The waveguide substrate 101 is used to propagate image beams; the waveguide substrate 101 has a first surface and a second surface which are parallel to each other; the first surface is the surface of the waveguide substrate 101 close to the human eye; the second surface is the surface of the waveguide substrate 101 away from the human eye;

[0064] The coupling-out structure 103 and the coupling-in structure 102 are arranged on the first surface of the waveguide substrate 101; the coupling-in structure 102 is used to couple the image beams into the waveguide substrate 101 and transmit them in the waveguide substrate 101, and the coupling-out structure 103 is used to diffract and couple out the image beams transmitted in the waveguide substrate 101 from the waveguide substrate 101;

[0065] After the image beams are incident on the coupling-out structure 103 arranged on the first surface, a plurality of diffraction orders (including transmission orders and reflection orders) are generated by the diffraction effect of the coupling-out structure 103, the transmission orders satisfying the coupling-out condition are emitted from the first surface of the waveguide substrate 101, that is, part of the image beams are diffracted and coupled out from the first surface of the waveguide substrate 101, the reflection orders satisfying the total reflection condition continue to be totally reflected in the waveguide substrate 101, and the reflection orders not satisfying the total reflection condition are emitted from the second surface of the waveguide substrate 101, that is, part of the image beams are diffracted and coupled out from the second surface of the waveguide substrate 101, resulting in light leakage; since the light leakage from the second surface of the waveguide substrate 101 will affect the appearance experience and may also leak the user's viewing information, the resonant grating structure 104 is arranged on the second surface;

[0066] The resonant grating structure 104 is connected to the second surface of the waveguide substrate 101 through a connecting member 105 and corresponds to the coupling-out structure 103; the resonant grating structure 104 is used to reflect the image light beams leaked from the second surface of the waveguide substrate 101 back into the waveguide substrate 101 at least partially, and then diffract and couple out from the first surface of the waveguide substrate 101 through the coupling-out structure 103.

[0067] In the above embodiment, the coupling-in structure 102 and the coupling-out structure 103 are both arranged on the side surface of the waveguide substrate 101 close to the human eye, and the diffraction order of the leaked light is the reflection order generated by the diffraction of the coupling-out structure 103. In another embodiment, the coupling-in structure 102 can also be arranged on the side surface of the waveguide substrate 101 away from the human eye, and can also be arranged on both the side surface of the waveguide substrate 101 close to the human eye and the side surface of the waveguide substrate 101 away from the human eye to improve the light coupling-in efficiency. The coupling-out structure 103 can also be arranged on the side surface of the waveguide substrate 101 away from the human eye, and the diffraction order of the leaked light is the transmission order generated by the diffraction of the coupling-out structure 103, and the normal coupling-out diffraction order is the reflection order generated by the diffraction of the coupling-out structure 103. Of course, the coupling-out structure 103 can also be arranged on both the side surface of the waveguide substrate 101 close to the human eye and the side surface of the waveguide substrate 101 away from the human eye, and the coupling-out structures 103 on the two surfaces have alignment requirements.

[0068] In practice, only one resonant grating structure 104 can be arranged on the second surface of the waveguide substrate 101, and multiple different resonant grating structures 104 can also be arranged on the second surface of the waveguide substrate 101. The resonant grating structure 104 has a very high reflection 0th order efficiency for image light beams of a specific angle range and / or a specific wavelength range; different resonant grating structures 104 have a very high reflection 0th order efficiency for image light beams of different angle ranges and / or different wavelength ranges.

[0069] The present application provides a diffraction waveguide, by arranging a resonant grating structure 104 on the second surface of the waveguide substrate 101 corresponding to the coupling-out structure 103, so that the image light beams leaked from the second surface of the waveguide substrate 101 are at least partially reflected back into the waveguide substrate 101 by the resonant grating structure 104, and continue to propagate in the waveguide substrate 101 and then couple out from the first surface of the waveguide substrate 101 through the diffraction of the coupling-out structure 103, which not only alleviates the problem of light leakage, protects the user to a certain extent when watching information, improves the user experience, but also improves the light energy utilization rate of the diffraction waveguide by recycling the leaked light.

[0070] In one embodiment, the resonant grating structure comprises: a resonant grating substrate; and a grating stack formed on the resonant grating substrate; wherein the grating stack comprises N grating layers, the refractive indices of adjacent grating layers in the N grating layers are different; and N is an integer greater than or equal to 2.

[0071] In an implementation, the grating stack is a multi-layered structure or a multi-layer conformal structure.

[0072] For example, referring to Figures 3-5 As shown in FIG. 1, the resonant grating structure 104 includes a resonant grating substrate 1041 and a grating stack 1042 formed on the resonant grating substrate 1041. In this embodiment, the grating stack 1042 is a multi-layered structure, and the grating stack 1042 includes three grating layers 10421, 10422 and 10423. Figure 3 In this embodiment, the grating stack 1042 is a multi-layer conformal structure, and the grating stack 1042 includes two grating layers 10421 and 10422. Figure 4 In this embodiment, the grating stack 1042 is a multi-layer conformal structure, and the grating stack 1042 includes two grating layers 10421 and 10422. Figure 5 In an implementation, the grating units of each grating layer form a certain angle with the surface of the resonant grating substrate, and the angles formed by the grating units of different grating layers with the surface of the resonant grating substrate can be the same or different.

[0073] For example, referring to

[0074] In this embodiment, the grating units of each grating layer form a right angle with the surface of the resonant grating substrate, and referring to Figure 3 In this embodiment, the grating units of each grating layer form an acute angle with the surface of the resonant grating substrate. Referring to Figure 4 In this embodiment, the grating units of each grating layer form an acute angle with the surface of the resonant grating substrate. Referring to Figure 3 In this embodiment, the grating units of each grating layer form an acute angle with the surface of the resonant grating substrate. Referring to Figure 4 In this embodiment, the grating units of each grating layer form an acute angle with the surface of the resonant grating substrate. Referring to

[0075] In a specific embodiment, the resonant grating substrate 1041 has a thickness of 200 nm-1000 nm, a refractive index of 1.4-1.5, and a height of 1 um-500 um.

[0076] In this application, the resonant grating structure is connected to the second surface of the waveguide substrate through a connecting member. In an embodiment, the connecting member 105 is implemented as a dielectric layer, which is used to connect the resonant grating structure 104 and the waveguide substrate 101, and fill the gaps between the grating units in the grating stack 1042. In this embodiment, since when the refractive index of the waveguide substrate 101 is greater than that of the surrounding medium, and the incident angle in the waveguide substrate 101 is greater than the critical angle of total reflection, the light can be totally reflected without leakage in the waveguide substrate 101, in order to ensure that the total reflection of the light beam in the waveguide substrate 101 is not destroyed, preferably, the refractive index of the dielectric layer is configured to be lower than the refractive index of the waveguide substrate 101. Considering the refractive index range of existing materials, the refractive index of the specific dielectric layer can be between 1.3-1.4, but is not limited thereto.

[0077] In one embodiment, the connector 105 is implemented as an adhesive, and the adhesive is provided on the edge of the resonant grating structure 104. The resonant grating structure 104 is connected to the waveguide substrate 101 with the aid of the adhesive, so that a gap exists between the resonant grating substrate 1041 and the waveguide substrate 101, and the gap is filled with air.

[0078] It should be noted that when the resonant grating structure is connected to the second surface of the waveguide substrate via a connector, it should have no effect or minimal effect on the transmission of the ambient light beam.

[0079] It is understood that in order to recycle the leaked image light beam, the resonant grating structure must have a high reflectivity for the incident light beam. In this application, by arranging the refractive index of each grating layer to increase in a direction away from the resonant grating base, the resonant grating structure can achieve extremely high zero-order reflectivity for image light beams within a specific angle range and / or a specific wavelength range.

[0080] refer to Figure 6 , which shows the image beam incident on Figure 4 The diagram below shows how the zero-order reflection efficiency of the resonant grating structure changes with the image beam field angle. The horizontal axis is the field angle, and the vertical axis is the zero-order reflection efficiency. Figure 6 As can be seen, the image beam has a reflectivity greater than 50% within a field of view between -11° and 11°, and the zero-order reflectivity reaches 90% at ±11°. Therefore, when this resonant grating structure is used to eliminate light leakage, 50% of the image beam energy can be recycled within a field of view between -11° and 11°, and 90% of the energy can be recycled within a field of view of ±11°.

[0081] In one embodiment, the refractive index of the N grating layers can be configured such that adjacent grating layers have different refractive indices, which can also enable the resonant grating structure to have a higher zero-order reflectivity for image light beams within a specific angle range and / or a specific wavelength range.

[0082] It should be noted that the working wavelength range of the resonant grating structure corresponds to the wavelength range of the image beam, so that the resonant grating structure has little or no influence on the transmission of ambient light beams when working. The angular response range of the resonant grating structure is the set of angles between the two angles at which the zero-order reflection efficiency of the image beam in the working wavelength range of the resonant grating structure reaches a threshold after the image beam is incident on the resonant grating structure. The working angular range of the resonant grating structure corresponds to the field of view angle range of the image beam, so that the resonant grating structure has little or no influence on the transmission of ambient light beams when working. The wavelength response range of the resonant grating structure is the set of wavelengths at which the zero-order reflection efficiency of the image beam in the working angular range of the resonant grating structure reaches a threshold after the image beam is incident on the resonant grating structure. The threshold can be 50% or a higher percentage. As shown in the angular response curve of FIG. 8, the angular response range is -11°—11°. Figure 6

[0083] In this application, the angular response range of the resonant grating structure is related to the resonant grating parameters; the wavelength response range of the resonant grating structure is also related to the resonant grating parameters; the resonant grating parameters at least include any one or a combination of the resonant grating inclination, the resonant grating period, the resonant grating depth, the resonant grating duty cycle, the resonant grating refractive index, the resonant grating substrate thickness, and the resonant grating substrate refractive index.

[0084] That is, by adjusting the resonant grating parameters of the resonant grating structure, the angular response range and the wavelength response range of the resonant grating structure and the response value in the response range can be controlled.

[0085] Since different structural parameters can obtain different working bandwidths, this application partitions and sets the resonant grating structure according to the field of view angle distribution and / or wavelength distribution of the out-coupled light beams of the first surface of the waveguide substrate, and sets the corresponding structural parameters, so that the resonant grating structures in different regions are used for specific reflection of light beams with different field of view angles and / or different wavelengths, which can improve the field of view uniformity and color uniformity.

[0086] In one embodiment, the out-coupling structure is divided into a plurality of out-coupling sub-regions, and the out-coupling sub-regions are divided according to the effective out-coupling positions corresponding to the image beams of each field of view angle, so that: each out-coupling sub-region corresponds to a field of view angle range; different resonant grating structures are configured for different out-coupling sub-regions; and the angular response range of the resonant grating structure corresponding to each out-coupling sub-region is adapted to the field of view angle range corresponding to the out-coupling sub-region.

[0087] ​It can be understood that the effective coupling-out position corresponding to the image beam of a field of view is a position from which the image beam of the field of view can be coupled out and received by the human eye within the eye movement range, so as to be effectively utilized. Since the angle response range of the resonant grating structure corresponding to each coupling-out sub-region is adapted to the field of view range corresponding to the coupling-out sub-region, the resonant grating structure corresponding to each coupling-out sub-region has a very high 0th-order reflection efficiency for the image beam in the field of view range corresponding to the coupling-out sub-region, so that the image beam reflected back by the resonant grating structure can be effectively utilized, and the field of view uniformity can be improved.

[0088] The resonant grating structures with different resonant grating parameters have different angle response ranges; the resonant grating structures with different angle response ranges are arranged on the second surface of the waveguide substrate and correspond to the coupling-out sub-regions.

[0089] In the parameter modulation, the 0th-order reflection efficiency of the resonant grating structure for the leaked diffraction orders reflected by the resonant grating structure for the light beams in the working wavelength and the angle response range can reach 99%.

[0090] In an embodiment, the resonant grating structure is a slanted grating; the parameters of the resonant grating structure are set as follows: the inclination angle range is -45°-45°; the grating period range is 200 nm-500 nm; the grating duty cycle range is 20%-80%; the grating layer depth range is 50 nm-300 nm, and the resonant grating substrate thickness range is 1 um-500 um. Specifically, in an example, the parameters of the resonant grating structure are configured as follows: the period is between 200 nm and 400 nm; the duty cycle is between 20% and 80%; the inclination angle is between 0° and 45°; and the working wavelength of the resonant grating structure is 465 nm-625 nm.

[0091] In an example, the resonant grating structure includes a resonant grating substrate and two grating layers; the upper grating layer is made of a high-refractive-index material such as titanium oxide, niobium oxide, etc., has a refractive index of about 2.3-2.6, and has a grating height of about 50-300 nm, preferably 200-300 nm; the lower grating layer is made of a low-refractive-index material such as magnesium fluoride, silicon oxide, etc., has a refractive index of about 1.4-1.7, and has a grating height of about 50-300 nm, preferably 100-200 nm; and the resonant grating substrate is made of a low-refractive-index material, has a refractive index of about 1.4-1.6, and has a height of about 1 um-500 um, preferably 300-400 um. Of course, in another embodiment, the grating layers can further include more layers of different materials, and the refractive index gradually decreases from top to bottom.

[0092] In one embodiment, the partitioning of the out-coupling region can be into a plurality of out-coupling sub-regions in one dimension. In another embodiment, the partitioning of the out-coupling region can be into a plurality of out-coupling sub-regions in two dimensions in a grid pattern. The following two embodiments are used to illustrate the partitioning of the out-coupling region:

[0093] In one embodiment, when only considering the field of view in one dimension, the out-coupling structure is partitioned into a plurality of out-coupling sub-regions, which includes: the out-coupling structure is partitioned into a plurality of out-coupling sub-regions in one dimension; the plurality of out-coupling sub-regions are distributed in a strip pattern in the one dimension; each out-coupling sub-region corresponds to a field of view range in the one dimension, and each resonant grating structure also corresponds to an out-coupling sub-region arranged in the one dimension, which represents the propagation direction of the image beam in the waveguide substrate. The angle response range corresponding to each different resonant grating structure decreases in size in turn from the center of the out-coupling structure in the one dimension to the center of the out-coupling structure in the opposite direction of the one dimension.

[0094] Generally, the image beam emitted by the optical machine includes a field of view in two directions. The partitioning of the out-coupling region can be into a plurality of out-coupling sub-regions in one of the two directions. As shown in FIG. 7(a), the field of view in the direction of the arrangement of the in-coupling structure and the out-coupling structure is defined as the a-direction field of view, and the other direction is the b-direction field of view as shown in FIG. 7(b). As shown in FIG. 7(c), for the a-direction field of view, the field of view range is assumed to be [F1, F2], where F1 = -φ and F2 = φ, and the angle value of the total reflection angle of the beam after being incident on the waveguide is θ, then the angle value of the total reflection angle corresponding to F1 to F2 gradually decreases.

[0095] As shown in FIG. 8(a), the out-coupling structure is partitioned into a plurality of out-coupling sub-regions in the a-direction. In addition, the out-coupling region can also be partitioned in the b-direction, and the partitioning method is similar to that in the a-direction, which will not be described herein. Figure 8

[0096] In one embodiment, the out-coupling structure is partitioned into a plurality of out-coupling sub-regions corresponding to the field of view range in the one dimension, and each resonant grating structure also corresponds to an out-coupling sub-region arranged in the one dimension, which enhances the beam in the corresponding field of view of each out-coupling sub-region and improves the uniformity of the field of view in the one dimension.

[0097] Continuing to refer to FIG. 8(a), Figure 8 ​, assuming that the field of view angle in the α direction is [-30°, 30°, in the coupling-out sub-region Out3 area (the boundary field of view angle effective coupling-out area) of the coupling-out structure, the corresponding area S3 is provided with a resonant grating structure (the boundary field of view angle reflection high-efficiency resonant grating structure), which can be designed by structure parameters to make the light leakage mainly used for reflecting the boundary field of view angle (the boundary field of view angle effective coupling-out area corresponds to a field of view angle range in one-dimensional direction, for example, 20°-30°) image beam; the resonant grating structure (the direction larger field of view angle reflection high-efficiency resonant grating structure) of the coupling-out sub-region Out4 area (the direction larger field of view angle effective coupling-out area) corresponding to the area S4 can be designed by structure parameters to make the light leakage mainly used for reflecting the larger field of view angle (the direction larger field of view angle effective coupling-out area corresponds to a field of view angle range in one-dimensional direction, for example, 10°-20°) beam; the light leakage used for reflecting the gradually decreasing field of view angle beam is provided in the gradually approaching coupling-out center sub-area. Assuming that the field of view angle in the α direction is [F1, F2], F1=-φ, F2=φ, the field of view angle of the light ray tilted to the coupling-out structure in the α direction is defined as positive, that is, when the field of view angle is positive, the total reflection angle is small when the light ray propagates in the waveguide substrate, and when the field of view angle is negative, the total reflection angle is large when the light ray propagates in the waveguide substrate, that is, when the beam field of view angle changes from -φ to φ, the reflection angle of the beam coupled into the waveguide substrate gradually decreases, that is, the resonant grating structure far from the coupling-in structure reflects the light beam with a small total reflection angle, and the resonant grating structure close to the coupling-in structure reflects the light beam with a large total reflection angle.

[0098] In another specific embodiment, when considering the field of view angle in the two-dimensional direction, the coupling-out structure is divided into a plurality of coupling-out sub-areas according to the two-dimensional direction; the plurality of coupling-out sub-areas are distributed in a grid shape. The two-dimensional direction includes a one-dimensional direction and a first direction, and the first direction is perpendicular to the one-dimensional direction; specifically, after the coupling-out structure is divided into a plurality of coupling-out sub-areas according to the one-dimensional direction, the plurality of coupling-out sub-areas are divided again according to the first direction to form a plurality of grid-shaped coupling-out sub-areas, as shown in FIG. 6. Figure 9 As shown in FIG. 6, along the first direction to the center position of the coupling-out structure and along the opposite direction of the first direction to the center position of the coupling-out structure, the angle size of the angle response range corresponding to each different resonant grating structure decreases in turn; thereby forming a distribution in which the angle response range gradually expands outward from the center of the coupling-out structure as a starting point.

[0099] In the coupling-out structure, each coupling-out sub-area corresponds to a field of view angle range in the two-dimensional direction, and each resonant grating structure also corresponds to the arrangement of the coupling-out sub-area in the two-dimensional direction, thereby enhancing the light beam of the corresponding field of view angle of each coupling-out sub-area and improving the field of view uniformity in the one-dimensional direction and the first direction.

[0100] In one embodiment, the width of the plurality of coupling-out units distributed in a grid shape is between 1-3 mm.

[0101] In a specific example, as shown in FIG. 1, Out1 and Out2 are taken as examples to make a detailed description of the coupling-out structure according to two-dimensional directions as follows: Figure 9

[0102] The light beam corresponding to the effective coupling-out area of the field of view angle range FOV1 is Out1, Out1 can be taken as a coupling-out sub-area, the area corresponding to the second surface of Out1 is S1, and the resonant grating structure in S1 can be designed by structure parameters to make the light beam of FOV1 have a higher reflectivity, i.e., the high-efficiency resonant grating structure is configured in FOV1; the light beam corresponding to the effective coupling-out area of the field of view angle range FOV2 is Out2, Out2 can be taken as a coupling-out sub-area, the area corresponding to the second surface of Out2 is S2, and the resonant grating structure in S2 can be designed by structure parameters to make the light beam of FOV2 have a higher reflectivity, i.e., the high-efficiency resonant grating structure is configured in FOV2.

[0103] In an embodiment, the light beam in the angle response range corresponding to each different resonant grating structure is reflected back to the waveguide substrate, and then enters the eye movement range after being coupled out from the corresponding coupling-out unit.

[0104] In an embodiment, the coupling-out structure is divided into a plurality of coupling-out sub-areas, the coupling-out sub-areas are divided according to the coupling-out positions corresponding to the image light beams of various wavelengths, each coupling-out sub-area corresponds to a wavelength range, different resonant grating structures are configured in different coupling-out sub-areas, and the wavelength response range of the resonant grating structure configured in each coupling-out sub-area is adapted to the wavelength range corresponding to the coupling-out sub-area.

[0105] In an embodiment, the coupling-out structure is divided into a plurality of coupling-out sub-areas according to a one-dimensional direction; the plurality of coupling-out sub-areas are distributed in a strip shape along the one-dimensional direction; the one-dimensional direction represents the propagation direction of the image light beam in the waveguide substrate; and along the one-dimensional direction, the wavelength size of the wavelength response range corresponding to each different resonant grating structure decreases in turn.

[0106] As can be known from the diffraction formula, the angles of total reflection transmission of light rays of different wavelengths at the same incident angle in the waveguide are different, for example, the angle of red light is much larger than that of blue light, therefore, the blue light acts more times in the front half of the coupling-out area, and the energy is seriously consumed, resulting in that the blue light energy in the rear half is less. In this case, the image will present a phenomenon of half blue and half red. At this time, the red light needs to be compensated in the front half of the coupling-out area, and the blue light needs to be compensated in the rear half, for reference to Figure 10 ​In the region S5 corresponding to the out-coupling sub-region Out5 (the front half of the out-coupling region) of the out-coupling structure, a resonant grating structure is arranged, which is designed to mainly reflect red light beams by means of structural parameters; in the region S6 corresponding to the out-coupling sub-region Out6 (the rear half of the out-coupling region) of the out-coupling structure, a resonant grating structure is arranged, which is designed to mainly reflect blue light beams by means of structural parameters.

[0107] In an embodiment, the resonant grating structure is arranged to take into account both the wavelength response and the angle response, the out-coupling structure is divided into a plurality of out-coupling sub-regions, each out-coupling sub-region is obtained according to an effective out-coupling position corresponding to an image light beam of a wavelength, each out-coupling sub-region corresponds to a wavelength range and an angle range, different resonant grating structures are configured for different out-coupling sub-regions; the wavelength response range of the resonant grating structure configured for each out-coupling sub-region is adapted to the wavelength range corresponding to the out-coupling sub-region, and the angle response range of the resonant grating structure configured for each out-coupling sub-region is adapted to the angle range corresponding to the out-coupling sub-region.

[0108] In practice, each out-coupling sub-region corresponds to a different angle range, and a plurality of out-coupling sub-regions correspond to the same wavelength range. For example, as shown in FIG. 6, a plurality of out-coupling sub-regions are divided along a one-dimensional direction, and the resonant grating structure arranged in the region corresponding to each out-coupling sub-region is mainly used to reflect image light beams of different angle ranges. Figure 8 For example, as shown in FIG. 6, a plurality of out-coupling sub-regions are divided along a one-dimensional direction, and the resonant grating structure arranged in the region corresponding to each out-coupling sub-region is mainly used to reflect image light beams of different angle ranges.

[0109] According to an embodiment of the present application, there is also provided a device comprising the diffractive waveguide according to any one of the preceding embodiments. The device is an augmented reality device, and can be implemented as an augmented reality glasses.

[0110] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit the same; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that the technical solutions recorded in the foregoing embodiments can still be modified, or some or all of the technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A diffractive waveguide, characterized by, The application relates to a waveguide substrate, a resonant grating structure and a coupling-out structure. The waveguide substrate has a first surface and a second surface which are parallel to each other; the first surface is the surface of the waveguide substrate close to a human eye; the second surface is the surface of the waveguide substrate away from the human eye. The coupling-out structure and the coupling-in structure are arranged on the first surface and / or the second surface; the coupling-in structure is used for coupling image beams into the waveguide substrate and transmitting the image beams in the waveguide substrate; the coupling-out structure is used for diffractively coupling out the image beams transmitted in the waveguide substrate from the waveguide substrate. The resonant grating structure is connected to the second surface of the waveguide substrate through a connecting member and corresponds to the coupling-out structure; the resonant grating structure is used for at least partially reflecting the image beams leaked from the second surface of the waveguide substrate back into the waveguide substrate and then diffractively coupling out the image beams from the first surface of the waveguide substrate through the coupling-out structure. The resonant grating structure comprises a resonant grating substrate and a grating stack formed on the resonant grating substrate; the grating stack comprises N grating layers, and the refractive indexes of the N grating layers are different; N is an integer greater than or equal to 2; the refractive indexes of the grating layers are sequentially increased in a direction away from the resonant grating substrate. The connecting member is implemented as a dielectric layer which is used for connecting the resonant grating structure and the waveguide substrate and filling the gaps between the grating units in the grating stack; the refractive index of the dielectric layer is lower than that of the waveguide substrate. The grating stack is a multilayer laminated structure or a multilayer conformal structure. The coupling-out structure is divided into a plurality of coupling-out sub-regions; the coupling-out sub-regions are obtained according to the effective coupling-out positions of the image beams corresponding to different field angles; each coupling-out sub-region corresponds to a field angle range; different resonant grating structures are configured for different coupling-out sub-regions; the angle response range of the resonant grating structure corresponding to each coupling-out sub-region is adapted to the field angle range corresponding to the coupling-out sub-region. The working wavelength range of the resonant grating structure corresponds to the wavelength range of the image beams; the angle response range of the resonant grating structure is a set of angles between two angles at which the zero-order reflection efficiency of the image beams in the working wavelength range of the resonant grating structure reaches a threshold value after the image beams are incident on the resonant grating structure. The angle response range of the resonant grating structure is related to resonant grating parameters; the resonant grating parameters at least include any one or a combination of the following: a resonant grating inclination, a resonant grating period, a resonant grating depth, a resonant grating duty cycle, a resonant grating refractive index, a resonant grating substrate thickness and a resonant grating substrate refractive index. The coupling-out structure is divided into a plurality of coupling-out sub-regions according to a one-dimensional direction; the coupling-out sub-regions are distributed in a strip shape along the one-dimensional direction; the one-dimensional direction represents the propagation direction of the image beams in the waveguide substrate.

2. The diffractive waveguide of claim 1, wherein, ​ 3. The diffractive waveguide of claim 1, wherein, ​ 4. The diffractive waveguide of claim 1, wherein, ​ 5. The diffractive waveguide of claim 4, wherein, ​ 6. The diffractive waveguide of claim 4, wherein, ​ 7. The diffractive waveguide of claim 4, wherein, ​ The angle size of the angle response range corresponding to each different resonant grating structure decreases in turn along the one-dimensional direction to the center position of the out-coupling structure and in the opposite direction of the one-dimensional direction to the center position of the out-coupling structure.

8. The diffractive waveguide of claim 4, wherein, The out-coupling structure is divided into a plurality of out-coupling sub-regions according to a two-dimensional direction; wherein the plurality of out-coupling sub-regions are distributed in a grid shape. The light beam in the angle response range corresponding to each different resonant grating structure enters the eye movement range after being coupled out from the corresponding out-coupling sub-region.

9. The diffractive waveguide of claim 1, wherein, The out-coupling structure is divided into a plurality of out-coupling sub-regions, which are divided according to the coupling-out positions corresponding to image beams of different wavelengths, each out-coupling sub-region corresponding to a wavelength range, and different resonant grating structures are configured for different out-coupling sub-regions; the wavelength response range of the resonant grating structure configured for each out-coupling sub-region is adapted to the wavelength range corresponding to the out-coupling sub-region.

10. The diffractive waveguide of claim 9, wherein, The out-coupling structure is divided into a plurality of out-coupling sub-regions according to a one-dimensional direction; wherein the plurality of out-coupling sub-regions are distributed in a strip shape along the one-dimensional direction; the one-dimensional direction represents the propagation direction of the image beam in the waveguide substrate. And along the one-dimensional direction, the wavelength size of the wavelength response range corresponding to each different resonant grating structure decreases in turn.

11. The diffractive waveguide of claim 9, wherein, The working angle range of the resonant grating structure corresponds to the field of view angle range of the image beam. The wavelength response range of the resonant grating structure is a set of wavelengths for which the zero-order reflection efficiency of the image beam in the working angle range of the resonant grating structure reaches a threshold after the image beam is incident on the resonant grating structure.

12. The diffractive waveguide of claim 9, wherein, The wavelength response range of the resonant grating structure is related to resonant grating parameters; wherein the resonant grating parameters at least include any one or a combination of resonant grating inclination, resonant grating period, resonant grating depth, resonant grating duty cycle, resonant grating refractive index, resonant grating substrate thickness, and resonant grating substrate refractive index.

13. An augmented reality device, characterized by The diffractive waveguide includes the diffractive waveguide of any one of claims 1-12.

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