WO2023134671A1

WO2023134671A1 - Display device, diffractive optical waveguide for display, and design method therefor

Info

Publication number: WO2023134671A1
Application number: PCT/CN2023/071571
Authority: WO
Inventors: 赵兴明; 范真涛; 田克汉
Original assignee: 北京驭光科技发展有限公司
Priority date: 2022-01-13
Filing date: 2023-01-10
Publication date: 2023-07-20
Also published as: CN115166895B; CN115166895A

Abstract

A diffractive optical waveguide (1) for display, comprising a waveguide substrate (1a), and a coupling-in area (10) and a coupling-out area (20) which are disposed on the waveguide substrate (1a). A hybrid grating is formed in the coupling-out area (20) and the coupling-out area (20) comprises a plurality of subareas. The hybrid grating comprises a plurality of coupling-out gratings (21) and at least one light return grating (22) which are respectively formed in different subareas. The at least one light return grating (22) is located between the coupling-out gratings (21). The light return grating (22) in the hybrid grating can prevent light energy from leaving the coupling-out area (20), so that the light energy can be fully coupled out of the coupling-out gratings (21). Moreover, the light propagating in the coupling-out area (20) is allowed to be redirected/allocated more flexibly, so that the uniformity of an emergent light field is further improved.

Description

Display device, diffractive optical waveguide for display and design method thereof

This application claims the priority of the Chinese patent application with the application number 202210038388.9 and the title of the invention "display device, diffractive optical waveguide for display and its design method" submitted to the China Patent Office on January 13, 2022, the entire contents of which are passed References are incorporated in this application.

technical field

The invention relates to a display technology based on diffraction, in particular to a diffractive optical waveguide for display, a display device and a design method of a diffractive optical waveguide.

Background technique

With the high development of semiconductor technology, the way of interaction between human and computer is developing rapidly. Among them, augmented reality (Augmented Reality, AR) display can provide human beings with more dimensional information, and has attracted widespread attention. AR glasses are one of the important mediums in the field of augmented reality display. Diffractive optical waveguide has the advantages of strong mass production, thinness, etc. It is gradually recognized in the field of AR display and is expected to become the mainstream technology development direction in the field of AR in the future.

Current diffractive optical waveguides for AR displays have deficiencies. The overall optical coupling efficiency of the diffractive optical waveguide is not high enough, resulting in insufficient bright field of view for AR display. In addition, the outcoupling efficiency of the outcoupling grating of the existing diffractive optical waveguide is basically the same in the entire range of the outcoupling grating, which causes the outcoupling light flux to gradually decrease with the continuous outcoupling during the light propagation process, resulting in artificial When the eye moves in the window of the diffractive light waveguide, the image observed changes in brightness and darkness. In order to improve the coupling efficiency of the diffractive optical waveguide and improve the uniformity of the energy distribution of the outgoing light, a diffractive optical waveguide as shown in Figure 16 is proposed, in which an in-coupling grating a, an out-coupling grating b and a return grating are arranged on the waveguide substrate. light grating c. The coupling-in grating a couples incident light carrying image information into the waveguide substrate. The outcoupling grating b expands the light carrying image information in the plane where the waveguide substrate is located, and at the same time couples the light out of the waveguide substrate. The light return grating c is arranged around the end of the outcoupling grating b away from the incoupling grating a, and is used to return the light that leaves the outcoupling grating b and continues to propagate in the waveguide substrate to the outcoupling grating b. However, the improvement of the overall optical coupling efficiency of the diffractive optical waveguide by the design shown in Fig. 16 is still very limited. In addition, the outgoing light field out of the grating b tends to be in a non-uniform state where the central area (as shown by the dashed box in FIG. 15 ) is dark and the surrounding area is bright, resulting in poor display effect.

Contents of the invention

The object of the present invention is to provide a diffractive optical waveguide for display, a display device including the diffractive optical waveguide, and a design method of the diffractive optical waveguide, so as to at least partly overcome the deficiencies in the prior art.

According to one aspect of the present invention, a diffractive optical waveguide for display is provided, which includes a waveguide substrate and an in-coupling area and an out-coupling area arranged on the waveguide substrate, and an external light beam is coupled to the optical waveguide through the in-coupling area. in the waveguide substrate and propagates by total reflection, wherein the incoupling region is formed with an incoupling grating configured to couple an external light beam into the waveguide substrate so that it passes through total reflection in the propagation in the waveguide substrate; the outcoupling region is formed with a hybrid grating and includes a plurality of partitions, and the hybrid grating includes a plurality of outcoupling gratings and at least one light return grating respectively formed in different partitions; the outcoupling grating configured to diffract at least a portion of the light propagating therein out of the waveguide substrate; Returning in a direction opposite to the direction of propagation; wherein the at least one light return grating is located between the outcoupling gratings.

Advantageously, the number of the plurality of partitions is greater than or equal to 20.

Advantageously, the plurality of partitions are regular partitions.

Advantageously, said plurality of partitions comprises irregular partitions.

Advantageously, each of the divisions formed with the light-reflecting grating has an area smaller than the average pupil area of a human eye.

Advantageously, the grating period of the light return grating is half of the grating period of the outcoupling grating in the same direction.

Advantageously, the at least one light-retrospective grating includes a plurality of two-dimensional light-retrospective gratings respectively formed in different partitions.

Advantageously, at least one two-dimensional retro-reflective grating has a different optical structure than the other two-dimensional retro-reflective grating.

Advantageously, said at least one retro-retro grating comprises a plurality of one-dimensional retro-retro gratings formed in different partitions.

Advantageously, at least one one-dimensional retro-reflective grating has a different grating vector from another one-dimensional retro-reflective grating; or at least one one-dimensional retro-reflective grating has the same grating vector and a different optical structure from another one-dimensional retro-reflective grating .

Advantageously, the plurality of outcoupling gratings includes a plurality of two-dimensional outcoupling gratings respectively formed in different partitions, and at least one two-dimensional outcoupling grating has a different optical structure from another two-dimensional outcoupling grating.

Advantageously, the plurality of outcoupling gratings further includes a plurality of one-dimensional outcoupling gratings formed in different partitions, and the grating period of the one-dimensional outcoupling grating is in the same direction as that of the two-dimensional outcoupling grating The cycle is the same.

Advantageously, the plurality of two-dimensional outcoupling gratings have the same first, second and third grating vectors, and the plurality of one-dimensional outcoupling gratings include a first grating vector having the first grating vector At least two of a one-dimensional grating, a second one-dimensional grating having said second grating vectors, and a third one-dimensional grating having said third grating vectors.

Advantageously, at least one one-dimensional outcoupling grating has the same grating vector and a different optical structure than another one-dimensional outcoupling grating.

Advantageously, at least one subregion of the outcoupling region is formed as a non-diffractive subregion without a diffractive structure, and the area of each non-diffractive subregion is smaller than the average pupil area of a human eye.

Advantageously, the coupling-in grating causes the external light beam to propagate in the waveguide substrate and form a first path of light propagating toward the hybrid grating and a second path of light not propagating toward the hybrid grating; and the The diffractive optical waveguide further includes an in-coupling end-return light grating disposed on the waveguide substrate, and the in-coupling end-return light grating is configured to diffract the second light so that it propagates toward the hybrid grating.

According to another aspect of the present invention, a display device is provided, which includes the above-mentioned diffractive optical waveguide.

Advantageously, said display device is a near-eye display device and comprises a lens comprising said diffractive optical waveguide and a frame for holding the lens close to the eye.

Advantageously, the display device is an augmented reality display device or a virtual reality display device.

According to another aspect of the present invention, a design method for the above-mentioned diffractive optical waveguide for display is provided, the design method includes the following processing:

Processing (1): Divide the target area to form multiple partitions;

Processing (2): Allocating the plurality of partitions, selecting a plurality of partitions as outcoupling partitions, selecting at least one partition as a light return partition, at least one of the light return partitions is located between the plurality of outcoupling partitions ;as well as

Processing (3): configuring an outcoupling grating in the outcoupling section, and configuring a light return grating in the light return section.

Advantageously, the processing (1) includes regular partitioning of the target area.

Advantageously, said processing (1) comprises random partitioning of at least a part of said target area.

Advantageously, the processing (2) further includes: selecting at least one partition from the plurality of partitions as a non-diffraction partition, and the area of each non-diffraction partition is smaller than the average pupil area of a human eye.

Advantageously, in the processing (3), the arranging the outcoupling grating in the outcoupling section includes: arranging a two-dimensional outcoupling grating in a part of the outcoupling section, and arranging a one-dimensional outcoupling grating in another part of the outcoupling section. out raster.

Advantageously, in the processing (2), selecting a plurality of partitions as the light return partitions; and in the processing (3), configuring the light return grating in the light return partitions includes: in a part of the light return partitions A two-dimensional light-reflective grating is configured, and a one-dimensional light-reflective grating is configured in another part of the light-reflective partition.

Advantageously, the processing (3) further includes: taking at least one parameter of the optical structure of the outcoupling grating and at least one parameter of the optical structure of the light-reflecting grating as optimization variables, and optimizing the outcoupling grating performing an optimization process with the light return grating to obtain an optimization result of the target area, wherein the optimization target of the optimization process includes the light energy distribution uniformity of the outgoing light field of the diffractive optical waveguide and/or the diffracted light Optical energy coupling efficiency of the waveguide.

Advantageously, the design method also includes:

Processing (4): changing the division of the target area to form multiple new partitions, and repeatedly performing processing (2) and processing (3) based on the new multiple partitions to obtain multiple optimization results; and

Processing (5): According to an optimization result that best meets the optimization objective, determine the divisions of the diffractive optical waveguide and the corresponding optical structures of the gratings.

Advantageously, the diffractive optical waveguide further includes an in-coupling end return light grating arranged on the waveguide substrate, and the in-coupling grating allows the external light beam to propagate in the waveguide substrate and form a light beam propagating toward the hybrid grating The first path of light and the second path of light not propagating toward the hybrid grating; the coupling-in end return light grating is configured to diffract the second path of light so that it propagates toward the hybrid grating, And the design method further includes: configuring the coupling-in grating and the coupling-in end return light grating.

Advantageously, the diffractive optical waveguide further includes an in-coupling end return light grating arranged on the waveguide substrate, and the in-coupling grating allows the external light beam to propagate in the waveguide substrate and form a light beam propagating toward the hybrid grating The first path of light and the second path of light not propagating toward the hybrid grating; the coupling-in end return light grating is configured to diffract the second path of light so that it propagates toward the hybrid grating; The design method further includes: configuring the coupling-in grating and the coupling-in end-return grating; and in the processing (3), based on the configured coupling-in grating and the coupling-in end-return grating, The outcoupling grating and the light return grating are optimized.

According to the embodiment of the present invention, the outcoupling grating and the light return grating are mixed in the outcoupling region. On the one hand, the light return grating can prevent the light energy from leaving the outcoupling region, which is conducive to fully coupling out the light energy through the outcoupling grating. ; On the other hand, it allows more flexible redirection/distribution of the light propagating in the outcoupling region, which is beneficial to further improving the uniformity of the outgoing light field of the diffractive optical waveguide.

Description of drawings

Other characteristics, objects and advantages of the present invention will become more apparent by reading the detailed description of non-limiting embodiments made with reference to the following drawings:

FIG. 1 is a schematic diagram of an example of a diffractive optical waveguide according to an embodiment of the present invention;

Figure 2 schematically shows an example of a two-dimensional outcoupling grating vector;

Figure 3 schematically shows an example of a grating vector outcoupling a grating in one dimension;

Fig. 4 schematically shows an example of a grating vector of a two-dimensional retro-reflective grating;

Fig. 5 schematically shows the relationship between the optical structure arrangement period of the two-dimensional outcoupling grating and the two-dimensional light return grating;

Fig. 6 schematically shows an example of a grating vector of a one-dimensional retro-reflective grating;

Fig. 7 is a grating vector analysis diagram in the optical path of the outcoupled light without passing through the light return grating in the outcoupling region;

Fig. 8 is a grating vector analysis diagram in the optical path of the outcoupled light through the action of the backlight grating in the outcoupling region;

Fig. 9 schematically shows the grating vector coupled into the grating and coupled into the end-return light grating;

10 is a schematic diagram of another example of a diffractive optical waveguide according to an embodiment of the present invention;

11 is a flow chart of a method for designing a diffractive optical waveguide according to Embodiment 1 of the present invention;

12 is a flow chart of a method for designing a diffractive optical waveguide according to Embodiment 2 of the present invention;

Fig. 13 schematically shows an example of the optical structure of the initialized grating and the optical structure of the optimized grating;

Figure 14 shows a flowchart of an exemplary method of optimizing an optical structure;

15 is a flow chart of a method for designing a diffractive optical waveguide according to Embodiment 3 of the present invention;

Fig. 16 is a schematic diagram of a diffractive optical waveguide for display in the prior art.

Detailed ways

The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain related inventions, rather than to limit the invention. For ease of description, only parts related to the invention are shown in the drawings. It should be noted that, in the case of no conflict, the embodiments in the present application and the features in the embodiments can be combined with each other.

FIG. 1 schematically shows an example of a diffractive optical waveguide for display according to an embodiment of the present invention, that is, a diffractive optical waveguide 1 . As shown in FIG. 1 , the diffractive optical waveguide 1 includes a waveguide substrate 1 a and an in-coupling region 10 and an out-coupling region 20 disposed on the waveguide substrate 1 a. The light beam outside the waveguide substrate 1a is coupled into the waveguide substrate 1a through the in-coupling grating 10a formed in the in-coupling region 10 and propagates in the waveguide substrate 1a by total reflection, and then is transmitted from the waveguide substrate 1a by diffraction in the outcoupling region 20 coupled out.

As shown in FIG. 1 , the outcoupling region 20 is formed with a hybrid grating and includes a plurality of partitions. According to an embodiment of the present invention, the hybrid grating of the outcoupling region 20 includes a plurality of outcoupling gratings 21 and at least one return grating 22 respectively formed in different partitions, and at least one return grating 22 is located between the outcoupling gratings 21 . The outcoupling grating 21 is configured to outcouple at least a part of the light propagating therein from the waveguide substrate 1a by diffraction. The light return grating 22 is configured to diffract the light entering it from the outcoupling grating 21 in a direction of propagation, so that it mainly returns in a direction opposite to the direction of propagation.

According to the embodiment of the present invention, the outcoupling grating and the light return grating are mixed in the outcoupling region, so that the light return grating can be placed between the outcoupling gratings (the light return grating and the outcoupling grating can be formed on different parts of the waveguide substrate). on the surface). In this way, on the one hand, the light return grating can prevent the light energy from leaving the outcoupling area, so that it is beneficial to fully couple the light energy through the outcoupling grating to provide, for example, a brighter display; The light return grating in also allows more flexible redirection/distribution of the light propagating in the outcoupling region, which is beneficial to further improve the uniformity of the outgoing light field of the diffractive optical waveguide.

Advantageously, a large number of partitions are formed in the outcoupling region 20 of the diffractive optical waveguide 1, so that the above-mentioned "mixing" effect is better. For example, the number of divisions of the outcoupling region 20 is preferably greater than or equal to 20, more preferably greater than or equal to 50.

In the example shown in FIG. 1 , the outcoupling region 20 comprises a plurality of irregular divisions. These irregular partitions can be generated in a random manner using a computer program and screened through optimized processing. Compared with the case of using regular partitions, irregular partitions are not constrained by the rules for partitioning partitions, so they can have a higher degree of design freedom, making it easier to approach the optimal solution for the design of diffractive optical waveguides based on the irregular partitions . Of course, it should be understood that the outcoupling region of the diffractive optical waveguide according to the embodiment of the present invention may also include regular partitions or a combination of regular partitions and irregular partitions.

In the diffractive waveguide 1 , the area of each subregion formed with the retro-reflective grating 22 is preferably smaller than the average pupil area of a human eye, more preferably less than half of the average pupil area of a human eye. This is especially advantageous for the case where the light return grating and the outcoupling grating are formed on the same surface of the waveguide substrate.

The outcoupling grating and light return grating that can be used in the diffractive optical waveguide according to the embodiment of the present invention will be described in more detail below with reference to FIG. 1 and FIG. 2 to FIG. 9 .

Continuing to refer to FIG. 1, the plurality of outcoupling gratings 21 in the outcoupling region 20 of the diffractive optical waveguide 1 may include a plurality of two-dimensional outcoupling gratings (corresponding to unfilled regions in FIG. 1) 21a respectively formed in different partitions. .

In this application, "grating vector" is used to describe the periodic characteristics of the grating structure, wherein the direction of the "grating vector" is parallel to the direction along which the structure of the grating is periodically changed/arranged (for example, perpendicular to the grating lines/grooves direction) and is consistent with the propagation direction of the positive first-order diffracted light of the grating; the size of the "grating vector" is 2π/d, where d is the period of the grating structure in the direction of the "grating vector", also known as "grating period" .

Fig. 2 schematically shows an example of grating vectors that can be used for the two-dimensional outcoupling grating 21a of the diffractive optical waveguide 1 according to an embodiment of the present invention. Two-dimensional gratings consist of optical structures arranged periodically in two dimensions in a plane. In the example shown in FIG. 2, the two-dimensional outcoupling grating 21a is a grating whose optical structure is arranged in a hexagonal shape, which has a first grating vector G1, a second grating vector G2 and a third grating vector G3 (see FIG. 2 Arrows shown), can be equivalent to the superposition of three one-dimensional gratings as shown in the figure. In the illustration of FIG. 2 , for the sake of clarity, the grating vectors G1 , G2 , and G3 are drawn separately, but it should be understood that the above three grating vectors exist/form at any place of the two-dimensional outcoupling grating 21 a. It should be understood that the two-dimensional outcoupling grating that can be used in the outcoupling region of the diffractive optical waveguide according to the embodiment of the present invention is not limited to a grating with an optical structure arranged in a hexagon, and is not limited to a grating with three grating vectors .

In order to improve the optical coupling efficiency of the diffractive optical waveguide 1, preferably, the plurality of two-dimensional outcoupling gratings 21a have the same grating vectors as each other.

Preferably, at least one two-dimensional outcoupling grating 21a has a different optical structure than the other two-dimensional outcoupling grating 21a. Here, the different optical structures of the two-dimensional grating may comprise optical structures with different cross-sectional shapes, cross-sectional dimensions and/or different heights or depths (height of convex optical structures or depth of concave optical structures). By changing the optical structure of different two-dimensional outcoupling gratings 21a, the diffraction efficiency of the grating can be changed, thereby adjusting the light outcoupling efficiency of the corresponding partition, and helping to improve the uniformity of the output light field of the diffractive optical waveguide.

Optionally, according to a preferred embodiment of the present invention, the outcoupling grating 21 may also include a plurality of one-dimensional outcoupling gratings 21b formed in different partitions. Various one-dimensional outcoupling gratings 21b-1, 21b-2, and 21b-3 are shown in FIG. 1 with different grating vectors. FIG. 3 schematically shows an example of the grating vectors of the one-dimensional outcoupling gratings 21b-1, 21b-2, and 21b-3. In the example shown in FIG. 3, the one-dimensional outcoupling grating 21b-1 has a first grating vector G1, the one-dimensional outcoupling grating 21b-2 has a second grating vector G2, and the one-dimensional outcoupling grating 21b-3 has a third grating Vector G3. Here, the first grating vector G1 , the second grating vector G2 and the third grating vector G3 are the above-mentioned three grating vectors of the two-dimensional outcoupling grating 21 a in the same outcoupling region 20 . Correspondingly, the grating periods of these one-dimensional outcoupling gratings 21b are the same as those of the two-dimensional outcoupling gratings 21a in the same direction.

It should be understood that although the outcoupling grating 21 of the diffractive optical waveguide 1 is shown in FIG. or more kinds of one-dimensional outcoupling gratings, for example, may include a first one-dimensional grating having the first grating vector, a second one-dimensional grating having the second grating vector, and a second one-dimensional grating having the third grating vector At least two of the third one-dimensional gratings.

From the perspective of processing and manufacturing, one-dimensional gratings are easier to process than two-dimensional gratings, and the reduction degree of grating design is higher. Therefore, according to the embodiments of the present invention, the diffractive optical waveguide using a combination of one-dimensional and two-dimensional outcoupling gratings in the outcoupling region is easier to manufacture, which is beneficial to reduce costs and improve yield.

Furthermore, advantageously, at least one one-dimensional outcoupling grating 21b may have the same grating vector and a different optical structure than the other one-dimensional outcoupling grating 21b. Here, different optical structures of a one-dimensional grating may include optical structures with different groove inclination angles, groove duty cycles, and/or different heights or depths (height of convex-shaped optical structures or depth of concave-shaped optical structures) . By changing the optical structure of different one-dimensional outcoupling gratings 21b, the diffraction efficiency of the grating can be changed, thereby adjusting the light outcoupling efficiency of the corresponding partition, and helping to improve the uniformity of the output light field of the diffractive optical waveguide.

In the diffractive optical waveguide 1 according to the embodiment of the present invention, the grating period of the light return grating 22 in the outcoupling region 20 is half of the grating period of the outcoupling grating 21 in the same direction. As shown in FIG. 1 , the light retro grating 22 may include a plurality of two-dimensional light retro gratings 22 a formed in different partitions. Alternatively or in addition, the light retro grating 22 may include a plurality of one-dimensional light retro gratings 22b formed in different divisions. Various one-dimensional retro-reflective gratings 22b-1, 22b-2 and 22b-3 are shown in FIG. 1 with different grating vectors.

Figure 4 schematically shows an example of the grating vectors of the two-dimensional light return grating 22a that can be used in the diffractive optical waveguide 1 according to an embodiment of the present invention; The relationship between the arrangement period of the optical structure of the grating 22a. Referring to Fig. 4 and Fig. 5, the arrangement periods Tx', Ty' of the two-dimensional light-returning grating 22a are respectively half of the arrangement periods Tx, Ty' of the two-dimensional outcoupling grating 21a in the same direction; correspondingly, the two-dimensional The grating period of the light return grating 22a is half of the grating period of the two-dimensional outcoupling grating 21a in the same direction. From the grating vector shown in Figure 4, the two-dimensional retro-retro grating 22a has a first retro-retro grating vector G1 ', a second retro-retro grating vector G2' and a third retro-retro grating vector G3' (see Fig. arrows), and the directions of the grating vectors G1', G2', G3' are the same as the grating vectors G1, G2, G3 of the two-dimensional outcoupling grating 21a, and their magnitude is twice that of the latter.

Preferably, at least one two-dimensional light-retrofitting grating 22a has a different optical structure from another two-dimensional light-retrofitting grating 22a, such as optical structures having different cross-sectional shapes, cross-sectional dimensions and/or different heights or depths. In this way, the efficiency of returning light in different partitions can be adjusted, which is beneficial to realize finer light redirection and distribution, and helps to improve the uniformity of the outgoing light field of the diffractive optical waveguide.

Various one-dimensional retro-reflective gratings 22b-1, 22b-2 and 22b-3 are shown in FIG. 1 with different grating vectors. FIG. 6 schematically shows an example of grating vectors of the one-dimensional retro-reflective gratings 22b-1, 22b-2, and 22b-3. In the example shown in FIG. 6, the one-dimensional retro-retro grating 22b-1 has the first retro-retro grating vector G1', the one-dimensional retro-retro grating 22b-2 has the second retro-retro grating vector G2', and the one-dimensional retro-retro grating 22b -3 has a third light-back grating vector G3'. Here, the first light retro grating vector G1', the second light retro grating vector G2' and the third light retro grating vector G3' are the three grating vectors described above of the two-dimensional light retro grating 22a.

Although three kinds of one-dimensional light-retrospective gratings respectively having grating vectors G1', G2', and G3' are shown in FIG. Fewer or more types of 1D retro-reflective gratings.

Preferably, at least one one-dimensional retro-retro grating 22b has a different grating vector than the other one-dimensional retro-retro grating 22b.

Preferably, at least one one-dimensional retro-reflective grating 22b has the same grating vector and a different optical structure as another one-dimensional retro-reflective grating 22b, for example, has a different groove inclination angle, a groove duty ratio and/or a different height or Deep optical structure. In this way, the efficiency of returning light in different partitions can be adjusted, which is beneficial to realize finer light redirection and distribution, and helps to improve the uniformity of the outgoing light field of the diffractive optical waveguide. Moreover, since the one-dimensional grating is easier to process than the two-dimensional grating, and the reduction degree of the grating design is higher, it is beneficial to reduce the cost and improve the yield.

Fig. 7 shows the grating vector analysis diagrams of three kinds of optical paths of the light coupled out when not passing through the light return grating in the outcoupling region in the diffractive optical waveguide 1 (respectively see figure (a) and figure (b) in Fig. 7 ) and figure (c)); Fig. 8 shows the grating vector analysis diagrams of three kinds of optical paths of the light coupled out when passing through the light-retrospective grating in the outcoupling region in the diffractive optical waveguide 1 (respectively see the figure in Fig. 8 (a), graph (b) and graph (c)). The grating vector G10 shown in FIGS. 7 and 8 is the grating vector coupled into the grating 10a. It should be understood that the grating vectors G1, G2, G3 and their opposite vectors -G1, -G2, -G3 shown in Fig. 7 and Fig. 8 may be due to the effect of the two-dimensional outcoupling grating 21a, or may be due to the one-dimensional coupling The function of the exit grating 21b; the grating vectors -G1', -G2', -G3' shown in Figure 8 can be due to the effect of the two-dimensional light return grating 22a, or the one-dimensional light return grating 22b.

As shown in Fig. 7 and Fig. 8, in the diffractive optical waveguide 1, through the incoupling grating 10a and through the action of the outcoupling grating 21 in the outcoupling region 20 or the joint action of the outcoupling grating 21 and the return light grating 22, from The grating vector sum of the diffracted gratings in the optical path of the light coupled out by the waveguide substrate 1a is zero. In this way, the light coupled out from the waveguide substrate 1a maintains the same angle as the light incident on the coupling grating 10a, so that the display information carried by the incident light can be restored.

Referring back to FIG. 1 , in addition to the outcoupling grating 21 and the light return grating 22 , the outcoupling region 20 can also form a non-diffractive section 23 without a diffractive structure in at least one section. The area of each non-diffraction zone 23 is preferably smaller than the average pupil area of a human eye, more preferably less than half of the average pupil area of a human eye.

In addition, referring to FIG. 1 , the diffractive optical waveguide 1 according to the embodiment of the present invention may further include an in-coupling end return optical grating 30 disposed on the waveguide substrate 1 a. The incoupling grating 10a of the diffractive optical waveguide 1 is configured to diffract the external light beam incident on it, and form the first path of light propagating towards the hybrid grating in the outcoupling region 20 by, for example, positive first-order diffraction, while it is not fully The suppressed negative first order diffraction also forms a second path of light that does not propagate towards the hybrid grating. The in-coupling end return light grating 30 is configured to diffract the second light that does not propagate towards the hybrid grating so that it propagates toward the hybrid grating.

FIG. 9 schematically shows a grating vector G10 coupled into the grating 10 a and a grating vector G30 coupled into the end-return light grating 30 . In the example shown in FIG. 9, both the coupling-in grating 10a and the coupling-in end return grating 30 are one-dimensional gratings, the direction of the grating vector G30 is the same as that of the grating vector G10, and its magnitude is twice that of the grating vector G10. As shown in FIG. 9 , the light sequentially passes through the in-coupling grating 10 a and the in-coupling end return light grating 30 , and the sum of the grating vectors in the optical path is equal to the grating vector G10 of the in-coupling grating 10 a. Coupling into the end-return optical grating 30 is beneficial to improve the optical coupling efficiency of the entire diffractive optical waveguide 1 .

For illustrative purposes only, Fig. 10 shows another example of a diffractive optical waveguide according to an embodiment of the present invention, namely a diffractive optical waveguide 1'. As shown in Fig. 10, a diffractive optical waveguide 1' includes a waveguide substrate 1a' and an in-coupling region 10' and an out-coupling region 20' disposed on the waveguide substrate 1a'. The diffractive optical waveguide 1' may have substantially the same structure as the diffractive optical waveguide 1 introduced with reference to FIG.

In addition, as shown in Fig. 10, the in-coupling region 10' of the diffractive optical waveguide 1' according to the embodiment of the present invention may be non-centered with respect to the out-coupling region 20'.

The diffractive optical waveguide according to the embodiment of the present invention can be applied in a display device. Such a display device is, for example, a near-eye display device, which includes a lens and a frame for holding the lens close to the eye, wherein the lens may include a diffractive optical waveguide according to an embodiment of the present invention as described above. Preferably, the display device may be an augmented reality display device or a virtual reality display device.

Next, the design method of the diffractive optical waveguide for display according to the embodiment of the present invention will be introduced with reference to FIG. 11 to FIG. 15 .

FIG. 11 is a flow chart of a diffractive optical waveguide design method M100 according to Embodiment 1 of the present invention. The design method M100 can be used for the design of the diffractive optical waveguide according to the embodiment of the present invention. As shown in Figure 11, the design method M100 includes the following processes:

S110: Divide the target area to form multiple partitions;

S120: Allocate a plurality of partitions, select a plurality of partitions as outcoupling partitions, select at least one partition as a light return partition, so that at least one of the light return partitions is located among the plurality of outcoupling partitions; and

S130: Configure an outcoupling grating in the outcoupling partition, and configure a light return grating in the light return partition.

Here, the "target area" corresponds to the outcoupling area of the diffractive optical waveguide according to the embodiment of the present invention. According to the embodiment of the present invention, the division of the target area may be regular division/partitioning or random division/partitioning. Correspondingly, the processing S110 may include regular partitioning of the target area, or random partitioning of the target area; or, processing S110 may include random partitioning of a part of the target area and regular partitioning of another part. As an example only, when dividing, the outcoupling area may be divided according to a predetermined partition rule to form partitions, or a computer program may be used to generate partitions according to certain preset conditions. For example, based on the predetermined number of partitions, the partition seeds are formed by randomly sprinkling points in the target region (the outcoupling region), and then based on these partition seeds, for example, a Voronoi partition map is generated, and a multiple of the outcoupling regions is formed corresponding to the Voronoi partition map. partitions. It should be understood that the design method according to the present invention is not limited to specific division rules or methods.

Preferably, through processing S110, a large number of partitions are formed on the target area, for example, the number is greater than or equal to 20, more preferably the number is greater than or equal to 50.

In processing S120, multiple partitions may be selected as the light return partitions. Preferably, among the multiple partitions, a partition with an area smaller than the average pupil area of the human eye is selected as the light return partition; more preferably, a partition with an area smaller than half the average pupil area of the human eye is selected as the light return partition.

According to other embodiments of the present invention, processing S120 may also include: selecting at least one partition whose area is smaller than the average pupil area of the human eye from the plurality of partitions as a non-diffractive partition; preferably, selecting a partition whose area is smaller than half the average pupil area of the human eye partitions as non-diffractive partitions. No diffractive structures are formed in the non-diffractive zones.

After the outcoupling zone and the light return zone are determined, enter into processing S130.

In processing S130, a two-dimensional outcoupling grating may be arranged in a part of the outcoupling partitions, and a one-dimensional outcoupling grating may be arranged in another part of the outcoupling partitions. Preferably, a plurality of two-dimensional outcoupling gratings are configured such that they have the same grating vectors as each other.

Furthermore, preferably, the one-dimensional outcoupling gratings are configured such that their grating periods are the same as those of the two-dimensional outcoupling gratings in the same direction. For example, it is possible to configure a two-dimensional outcoupling grating with a first grating vector, a second grating vector, and a third grating vector, and configure a first one-dimensional grating with the first grating vector, a second one-dimensional At least two of a grating and a third one-dimensional grating having a third grating vector.

In processing S130, a two-dimensional light retro grating may be arranged in the light retrospective partition, or a one-dimensional light retro grating may be arranged. Preferably, a two-dimensional light-retrospective grating may be configured in a part of the light-retrospective divisions, and a one-dimensional light-retrospective grating may be configured in another part of the light-retrospective divisions.

According to an embodiment of the present invention, the light-returning gratings are configured such that their period is half of the grating period of the outcoupling grating in the same direction, which means that the light-returning grating has the same direction as the outcoupling grating and twice the size of the latter. Raster vector. Preferably, a plurality of two-dimensional retro-reflective gratings are configured such that they have the same grating vectors as each other.

In addition, as described above, the diffractive optical waveguide according to the embodiment of the present invention may include an in-coupling end-return light grating configured to diffract the second light from the in-coupling grating so that it goes toward Hybrid grating propagation; correspondingly, the design method M100 according to the embodiment of the present invention may further include configuring the coupling-in grating and the coupling-in end-return grating. It should be understood that the configuration of the coupling-in grating and the coupling-in end-return light grating in the design method M100 may be performed before or after the processes S110, S120 and/or S130 described above, or may be performed in parallel with these processes.

FIG. 12 is a flowchart of a diffractive optical waveguide design method M200 according to Embodiment 2 of the present invention. As shown in Figure 12, the design method M200 includes the following processes:

S210: Divide the target area to form multiple partitions;

S220: Allocate multiple partitions, select a plurality of partitions as outcoupling partitions, and select at least one partition as a light return partition, so that at least one of the light return partitions is located between the multiple outcoupling partitions;

S231: Initialize the outcoupling grating in the outcoupling section, and initialize the light return grating in the light return section; and

S232: Using at least one parameter of the optical structure of the outcoupling grating and at least one parameter of the optical structure of the light return grating as optimization variables, optimize the outcoupling grating and the light return grating to obtain an optimization result of the target area .

The processes S210 and S220 may be the same as or similar to the processes S110 and S120 in the design method M100 shown in FIG. 11 , and will not be repeated here.

The difference between the design method M200 and the design method M100 is that in the design method M200, after the initial configuration of the grating is performed through the process S231, the optical structure of the grating is further optimized through the process S232, so as to realize the optimized configuration of the grating.

Relevant content and implementation of the process S231 may be the same as those described above for the process S130 of the design method M100, and will not be repeated here.

In the process S232, the optimization target of the optimization process may include uniformity of light energy distribution in the outgoing light field of the diffractive optical waveguide. In some implementation manners, the non-uniformity of light energy distribution within the range of the human eye window (the range of human eye activity that can see images) can be used to characterize the light energy distribution uniformity of the exit light field of the diffractive optical waveguide. In other implementation manners, the uniformity of light energy within the viewing angle range that can be received/viewed by human eyes at any position can be used to characterize the uniformity of light energy distribution of the outgoing light field of the diffractive optical waveguide. In other implementation manners, the above two methods for characterizing the uniformity of light energy distribution may also be used in combination, for example, through weighted calculation.

Alternatively or additionally, the optimization objective of the optimization process may include light energy coupling efficiency. If the incident light energy of the in-coupling grating entering the diffractive optical waveguide is I _in , and the total optical energy exiting the out-coupling grating is I _E , then the optical energy coupling efficiency of the diffractive optical waveguide is r=I _E /I _in . As an example, the method 1 for designing a diffractive optical waveguide according to an embodiment of the present invention may set the optical energy coupling efficiency r greater than or equal to a predetermined value as one of the optimization objectives.

The optimization variables may include parameters such as cross-sectional shape and/or cross-sectional size of the optical structure of the outcoupling grating and light-reflecting grating, groove inclination angle and/or duty cycle, and/or height or depth of the optical structure.

"Optimization processing" here refers to such a processing process: by changing the assignment of optimization variables (such as at least one parameter of the grating optical structure) to obtain a plurality of evaluation results corresponding to the optimization target (such as representing the uniformity of light energy distribution and/or or the value of light energy coupling efficiency), and based on whether it meets the optimization goal, select one of the evaluation results and assign the corresponding optimization variable and other parameters (such as partition conditions) as the optimization result.

For illustrative purposes only, the optical structure of the outcoupling grating/light-return grating initialized in the design method M200 is schematically shown in FIG. 13 (see the cross-section of the hexagonal arrangement shown in the left figure in FIG. The square optical structure A) and the optimized optical structure B of the outcoupling grating/return grating (see the figure on the right side of Fig. The cross-sectional dimensions of the optical structure B). In the example shown in FIG. 13 , optimization is performed with parameters including at least the cross-sectional shape and size of the optical structure as optimization variables. For example, in the optimization process, starting from the initialized optical structure A, genetic algorithm (GA), particle swarm algorithm (PSO), simulated annealing algorithm (SA), etc. can be used to change the cross-sectional shape and size of the optical structure, etc. Parameters, based on the changed parameters, the simulation settlement is carried out, such as the light energy distribution uniformity index and/or the light energy coupling efficiency index, and the optimized optical structure is determined according to the degree of conformity between the index and the optimization purpose, for example, in Figure 13 Structure B shown in the figure on the right.

For ease of understanding, FIG. 14 shows a flowchart of an exemplary method M10 for optimizing an optical structure. For example, after the outcoupling grating and the return light grating are initialized through processing S231 in the design method M200, the method M10 may be executed to optimize the optical structure. As shown in Fig. 14, according to the method M10, firstly execute the processing S11, wherein based on the initialized grating, calculate and record the light energy distribution uniformity index γ ₀ and/or the light energy coupling efficiency index r ₀ calculated by the simulation, and record as the most Excellent result. Then, in processing S12, change the grating (such as the outcoupling grating and the light return grating) optimization variables (the cross-section/morphology, depth/height, etc. of the optical structure of the two-dimensional grating; the duty ratio of the optical structure of the one-dimensional grating, Depth/height, etc.), and calculate the current simulation result after changing the optimization variable in processing S13, that is, the light energy distribution uniformity index γ _i and/or the light energy coupling efficiency index r _i . Next, in processing S14, it is judged whether the current simulation result is better than the recorded optimal result, and the judgment result is that the current simulation result is better than the optimal result, then processing S15 is performed, that is, the current simulation result is recorded as the optimal result, and at the same time Reset the count to 0; if the current simulation result is not better than the optimal result, enter processing S16, wherein the count is +1. After processing S15 and processing S16 are completed, both enter processing S17, wherein it is judged whether the count is greater than a predetermined value n. If the count is greater than the predetermined value n, enter processing S18 and output the assignment of the optimization variable corresponding to the last recorded optimal result and other parameters as the optimization result of the optimization processing method M10.

It should be understood that the above-mentioned method M10 introduced with reference to FIG. 14 is only exemplary and not restrictive;

In addition, as described above, the diffractive optical waveguide according to the embodiment of the present invention may include an in-coupling end-return light grating configured to diffract the second light from the in-coupling grating so that it goes toward Hybrid grating propagation; correspondingly, the design method M200 according to the embodiment of the present invention may also include configuring the coupling-in grating and the coupling-in end return light grating; and processing 232 based on the configured coupling-in grating and coupling-in end return light Grating, to optimize the outcoupling grating and return light grating. In some embodiments, the configuration of the coupling-in grating and the coupling-in end return light grating in the design method M200 is performed before processing S232; The optical structure of the output grating and the return grating, as well as the optical structure of the coupling-in grating and the coupling-in end return grating, so as to realize the optimized processing of these gratings.

The method for designing a diffractive optical waveguide according to an embodiment of the present invention may further combine, for example, optimization of partitions of target regions while optimizing the grating structure. For the purpose of illustration only, FIG. 15 shows a flowchart of a diffractive optical waveguide design method M300 according to Embodiment 3 of the present invention.

The processes S310, S320, S331, and S332 of the design method M300 are the same as the processes S210, S220, S231, and S232 of the design method M200 introduced with reference to FIG. 12 , and will not be repeated here.

Compared with the design method M200, the design method M300 further includes processing S340, wherein the division of the target area is changed to form multiple new partitions. As shown in FIG. 15 , the method M300 is designed to return to processing S320 after processing S340 to repeatedly execute processing S320 to processing S332 based on the new multiple partitions to obtain multiple optimization results.

The design method M300 also includes processing S350, wherein according to an optimization result that best meets the optimization objective, the divisions of the diffractive optical waveguide and the corresponding optical structure of the grating are determined.

Design method M300 may execute a judging process S335 after processing S332, and decide whether to execute processing S340 or enter processing S350 according to the judgment result. In the example shown in FIG. 15 , the judgment S335 is "whether to traverse the preset partitioning method", if the judgment result is "No", then enter the processing S340, if the judgment result is "Yes", then enter the processing S350. However, it should be understood that the determination conditions in the above determination S335 are only exemplary and not restrictive. For example, the above judgment may also be whether the number of partitions traverses a predetermined range or not.

The above description is only a preferred embodiment of the present application and an illustration of the applied technical principle. Those skilled in the art should understand that the scope of the invention involved in this application is not limited to the technical solution formed by the specific combination of the above-mentioned technical features, but should also cover the technical solution formed by the above-mentioned technical features without departing from the inventive concept. Other technical solutions formed by any combination of or equivalent features thereof. For example, a technical solution formed by replacing the above-mentioned features with technical features with similar functions disclosed in (but not limited to) this application.

Claims

A diffractive optical waveguide for display, comprising a waveguide substrate and an in-coupling area and an out-coupling area arranged on the waveguide substrate, an external light beam is coupled into the waveguide substrate through the in-coupling area and propagated through total reflection ,in,

The incoupling region is formed with an incoupling grating configured to couple an external light beam into the waveguide substrate so as to propagate within the waveguide substrate by total reflection;

The outcoupling region is formed with a hybrid grating and includes a plurality of partitions, the hybrid grating includes a plurality of outcoupling gratings and at least one light return grating respectively formed in different partitions;

The outcoupling grating is configured to outcouple at least a portion of the light propagating therein from the waveguide substrate by diffraction;

The light return grating is configured to diffract light entering it from the outcoupling grating in a direction of propagation so that it returns predominantly in a direction opposite to the direction of propagation;

Wherein the at least one light return grating is located between the outcoupling gratings.
The diffractive optical waveguide according to claim 1, wherein the number of the plurality of divisions is greater than or equal to 20.
The diffractive optical waveguide according to claim 1, wherein the plurality of divisions are regular divisions.
The diffractive optical waveguide of claim 1, wherein said plurality of divisions comprises irregular divisions.
The diffractive optical waveguide according to claim 1, wherein the divisions where the light-retrofit grating is formed each have an area smaller than an average pupil area of a human eye.
The diffractive optical waveguide according to claim 1, wherein the grating period of the light return grating is half of the grating period of the outcoupling grating in the same direction.
The diffractive optical waveguide according to claim 1 or 6, wherein said at least one retro-retro grating comprises a plurality of two-dimensional retro-retro gratings respectively formed in different sections.
The diffractive optical waveguide of claim 7, wherein at least one two-dimensional retro-retro grating has a different optical structure than another two-dimensional retro-retro grating.
7. The diffractive optical waveguide of claim 7, wherein said at least one retro-retro grating comprises a plurality of one-dimensional retro-retro gratings formed in different divisions.
The diffractive optical waveguide of claim 9, wherein at least one one-dimensional retro-retro grating has a different grating vector from another one-dimensional retro-retro grating; Grating Same grating vector and different optical structure.
The diffractive optical waveguide according to claim 1, wherein said plurality of outcoupling gratings comprises a plurality of two-dimensional outcoupling gratings respectively formed in different partitions, and at least one two-dimensional outcoupling grating has an Different optical structures of outcoupling gratings.
The diffractive optical waveguide according to claim 11, wherein the plurality of outcoupling gratings further comprises a plurality of one-dimensional outcoupling gratings formed in different subsections, and the grating period of the one-dimensional outcoupling gratings is the same as that of the two-dimensional outcoupling gratings. The grating periods of the two-dimensional outcoupling gratings in the same direction are the same.
The diffractive optical waveguide according to claim 12, wherein the plurality of two-dimensional outcoupling gratings have the same first grating vector, second grating vector and third grating vector, and the plurality of one-dimensional outcoupling gratings At least two of a first one-dimensional grating having the first grating vectors, a second one-dimensional grating having the second grating vectors, and a third one-dimensional grating having the third grating vectors are included.
A diffractive optical waveguide according to claim 12 or 13, wherein at least one one-dimensional outcoupling grating has the same grating vector and a different optical structure than another one-dimensional outcoupling grating.
The diffractive optical waveguide according to claim 1, wherein at least one subregion of the outcoupling region is formed as a non-diffractive subregion without a diffractive structure, and the area of each non-diffractive subregion is smaller than the average pupil area of a human eye.
The diffractive optical waveguide according to claim 1, wherein said in-coupling grating causes said external beam to propagate in said waveguide substrate and forms a first path of light propagating toward said hybrid grating and a first path of light not directed toward said hybrid grating The second path of light propagating; and the diffractive optical waveguide further includes an in-coupling end return light grating disposed on the waveguide substrate, and the in-coupling end return light grating is configured to diffract the second light, to propagate towards the hybrid grating.
A display device, comprising the diffractive optical waveguide according to any one of claims 1-16.
The display device of claim 17, wherein the display device is a near-eye display device and includes a lens and a frame for holding the lens close to the eye, the lens including the diffractive optical waveguide.
The display device according to claim 17 or 18, wherein the display device is an augmented reality display device or a virtual reality display device.
A method for designing a diffractive optical waveguide for display, the diffractive optical waveguide includes a waveguide substrate and an in-coupling grating, an out-coupling grating and a light-return grating formed on the waveguide substrate, the in-coupling grating is configured to couple an external light beam to in the waveguide substrate so that it propagates within the waveguide substrate by total reflection;

The outcoupling grating is configured to outcouple at least a portion of the light propagating therein from the waveguide substrate by diffraction;

The light return grating is configured to diffract light entering it from the outcoupling grating in a direction of propagation so that it returns predominantly in a direction opposite to the direction of propagation;

Wherein, the design method includes the following processing:

Processing (1): Divide the target area to form multiple partitions;

Processing (2): Allocating the plurality of partitions, selecting a plurality of partitions as outcoupling partitions, selecting at least one partition as a light return partition, at least one of the light return partitions is located between the plurality of outcoupling partitions ;as well as

Processing (3): configuring an outcoupling grating in the outcoupling section, and configuring a light return grating in the light return section.
The design method according to claim 20, wherein the number of the plurality of partitions is greater than or equal to 20.
The design method according to claim 20, wherein said processing (1) includes regular partitioning of said target area.
The design method according to claim 20, wherein said processing (1) includes irregularly partitioning at least a part of said target area.
The design method according to claim 20, wherein, the processing (2) further comprises: selecting at least one partition from the plurality of partitions as a non-diffraction partition, and the area of each of the non-diffraction partitions is smaller than the human eye mean pupil area.
The design method according to claim 20, wherein, in the processing (3), configuring the outcoupling grating in the outcoupling partition comprises: configuring a two-dimensional outcoupling grating in a part of the outcoupling partition, and configuring a two-dimensional outcoupling grating in another A one-dimensional outcoupling grating is arranged in a part of the outcoupling partitions.
The design method according to claim 20, wherein, in the processing (2), a plurality of partitions are selected as light return partitions; and

In the process (3), the arranging the light-retrospective grating in the light-retrospective section includes: configuring a two-dimensional light-retrospective grating in a part of the light-retrospective section, and arranging a one-dimensional light-retrospective grating in another part of the light-retrospective section.
The design method according to any one of claims 20-26, wherein the processing (3) further comprises: at least one parameter of the optical structure of the outcoupling grating and the optical structure of the return light grating At least one parameter is an optimization variable, and the optimization process is performed on the outcoupling grating and the light return grating to obtain the optimization result of the target area, wherein the optimization target of the optimization process includes the output of the diffractive optical waveguide The light energy distribution uniformity of the incident light field and/or the light energy coupling efficiency of the diffraction light waveguide.
The design method as claimed in claim 27, further comprising:

Processing (4): changing the division of the target area to form multiple new partitions, and repeatedly performing processing (2) and processing (3) based on the new multiple partitions to obtain multiple optimization results; and

Processing (5): According to an optimization result that best meets the optimization objective, determine the divisions of the diffractive optical waveguide and the corresponding optical structures of the gratings.
The design method according to claim 20, wherein the diffractive optical waveguide further comprises an in-coupling end optical grating arranged on the waveguide substrate, and the in-coupling grating makes the external light beam inside the waveguide substrate propagating and forming a first path of light propagating toward the hybrid grating and a second path of light not propagating toward the hybrid grating; the coupling-in terminal return light grating is configured to diffract the second path of light, so that which propagates towards the hybrid grating; and

The design method further includes: configuring the coupling-in grating and the coupling-in end return optical grating.
The design method according to claim 27, wherein the diffractive optical waveguide further comprises an in-coupling end optical grating disposed on the waveguide substrate, and the in-coupling grating makes the external light beam inside the waveguide substrate propagating and forming a first path of light propagating toward the hybrid grating and a second path of light not propagating toward the hybrid grating; the coupling-in end return light grating is configured to diffract the second path of light to cause it to propagate towards said hybrid grating;

The design method further includes: configuring the coupling-in grating and the coupling-in end return optical grating; and

In the processing (3), optimization processing is performed on the outcoupling grating and the light return grating based on the configured incoupling grating and incoupling end light return grating.