CN116802531A

CN116802531A - Near-eye display device, optical structure and wafer level preparation method thereof

Info

Publication number: CN116802531A
Application number: CN202180060602.4A
Authority: CN
Inventors: 向恩来; 赵瑜
Original assignee: Ningbo Sunny Opotech Co Ltd
Current assignee: Ningbo Sunny Opotech Co Ltd
Priority date: 2020-07-14
Filing date: 2021-06-15
Publication date: 2023-09-22
Also published as: WO2022012245A1; CN113933992A

Abstract

A near-eye display device, an optical structure, and a method of manufacturing a wafer level are disclosed. The method comprises the following steps: providing a first waveguide substrate, wherein the first waveguide substrate is provided with a plurality of first diffraction grating structures and a plurality of first datum points for positioning, and the first diffraction grating structures are arranged according to a preset period; distributing adhesive on the surface of the first waveguide substrate based on the periodic distribution rule of the first datum point and the first diffraction grating structure; providing a second waveguide substrate, wherein the second waveguide substrate is provided with a plurality of second diffraction grating structures which are arranged in the same period as the first waveguide substrate and a plurality of second datum points for positioning; aligning and superposing the second waveguide substrate on the first waveguide substrate to form an optical structure imposition structure; and dividing the optical structure imposition structure to obtain a plurality of optical structures suitable for use in a near-eye display device. Thus, the optical structure is manufactured by adopting the wafer-level manufacturing method, and the manufacturing efficiency is high.

Description

Near-eye display device, optical structure and wafer level preparation method thereof

Technical Field

The present application relates to near-eye display devices, and more particularly, to near-eye display devices, optical structures suitable for use in near-eye display devices, and wafer level manufacturing methods thereof.

Background

In recent years, near-eye display devices (e.g., virtual reality devices, augmented reality devices) have received increased attention. Compared with virtual reality, the augmented reality device can construct a virtual scene based on a physical environment, and brings brand new experience to users. The augmented reality technology includes two technical directions: conventional Birdbath schemes, and projector plus waveguide chip schemes. The traditional Birdbath scheme is difficult to further promote due to the large size and the angle of view, relatively poor experience is difficult to be favored by consumers, and the scheme using the waveguide chip is relatively smaller and more attractive, so that the user experience is better.

The waveguide sheet may diffuse light along the waveguide sheet through a diffraction grating or transflective surface so that a viewer may view an image over the entire viewable area of the waveguide sheet. However, both the diffraction grating structure and the semi-transparent and semi-reflective surface have wavelength selectivity, the diffraction efficiency of the light rays with different wavelengths is different, and the transmittance of the light rays with different wavelengths on the semi-transparent and semi-reflective surface is also different, so that an image observed by a viewer at the exit pupil of the waveguide sheet has a certain degree of color cast. In addition, the diffraction angles of the light rays with different wavelengths are different, so that the view angle of the displayed image of the waveguide sheet is limited, and meanwhile, the image is easy to distort.

In order to solve the above technical problems, chinese patent (patent No. CN210243962U, whose reference is british patent No. GB 2573793) proposes to use a plurality of waveguide sheets to transmit light rays of different wavelengths, respectively. However, there are a number of technical problems associated with such optical structures constructed from multilayer waveguide sheets in particular implementations (e.g., during manufacturing processes).

First, if two waveguide sheets are attached directly together (i.e., there is no gap between them) or there is some contact, the total internal reflection transmission of light within the waveguide sheets will be destroyed. For a multilayer waveguide sheet to constitute an optical structure, if errors such as positioning errors and/or assembly errors occur during its installation, this will result in a mating error in the final optical structure, such that the output image is ghost. That is, the optical structure formed by the multi-layer waveguide sheet has high requirement on the matching precision, which presents a great difficulty for the manufacturing and assembling process.

Second, consistency between different waveguide plates is difficult to ensure, which undoubtedly increases the difficulty of fabrication.

Also, errors in the waveguide sheet itself occur in the grating fabrication, such as the fact that the nanoimprinted master is not fully parallel to the waveguide material, resulting in optical deviations in the multilayer waveguide sheet when mounted even with relatively high parallelism.

In addition, the existing preparation method has low passing efficiency, and is difficult to realize mass industrial production.

Accordingly, there is a need for an optimized process for preparing optical structures suitable for use in near-eye display devices to produce optical structures that meet the requirements.

Disclosure of Invention

An advantage of the present application is to provide a near-eye display device and an optical structure and a wafer-level manufacturing method thereof, in which the optical structure is manufactured by the wafer-level manufacturing method, and the manufacturing efficiency is high, and the method is suitable for mass production of optical structures composed of multiple optical waveguides.

Another advantage of the present application is to provide a near-eye display device and an optical structure and a wafer-level manufacturing method thereof, wherein the optical structure manufactured by the wafer-level manufacturing method has high fitting accuracy and reliability.

Another advantage of the present application is to provide a near-eye display device and an optical structure and a wafer level manufacturing method thereof, in which the consistency between the optical waveguides of each layer in the optical structure manufactured by the wafer level manufacturing method is high.

Other advantages and features of the application will become apparent from the following description, and may be realized by means of the instrumentalities and combinations particularly pointed out in the claims.

To achieve at least one of the above advantages, the present application provides a method for preparing a wafer level optical structure suitable for a near-eye display device, comprising:

providing a first waveguide substrate, wherein the first waveguide substrate is provided with a plurality of first diffraction grating structures and a plurality of first datum points for positioning, and the first diffraction grating structures are arranged according to a preset period;

distributing adhesive on the surface of the first waveguide substrate based on the periodic distribution rule of the first datum point and the first diffraction grating structure; and

providing a second waveguide substrate, wherein the second waveguide substrate is provided with a plurality of second diffraction grating structures which are arranged in the same period as the first waveguide substrate and a plurality of second datum points for positioning;

aligning and stacking the second waveguide substrate on the first waveguide substrate to form an optical structure imposition structure, wherein in the optical structure imposition structure, the first waveguide substrate and the second waveguide substrate have preset gaps, the gaps range from 40 μm to 60 μm, and a plurality of first diffraction grating structures of the first waveguide substrate respectively correspond to a plurality of second diffraction grating structures of the second waveguide substrate; and

Dividing the optical structure imposition structure to obtain a plurality of optical structures suitable for use in a near-eye display device.

In the wafer level manufacturing method according to the present application, the plurality of first fiducial points include a part of the first fiducial points for locating adhesive laying positions;

wherein, based on the periodic distribution rule of the first datum point and the first diffraction grating structure, an adhesive is arranged on the surface of the first waveguide substrate, and the method comprises the following steps: and distributing the adhesive on the surface of the first waveguide substrate based on the part of the first datum point for positioning the adhesive distribution position and the periodic distribution rule of the first diffraction grating structure.

In the wafer level manufacturing method according to the present application, the plurality of first fiducial points include another part of the first fiducial points for locating a stacking position of the second waveguide substrate;

wherein the second waveguide substrate is stacked in alignment with the first waveguide substrate to form an optical structure imposition structure, comprising: and superposing the second waveguide substrate on the first waveguide substrate based on the alignment between the other part of the first datum point and the second datum point to form an optical structure imposition structure.

In the method of manufacturing a wafer level according to the present application, the further portion of the first fiducial points are uniformly distributed along the perimeter of the first waveguide substrate.

In the wafer-level manufacturing method according to the present application, the second waveguide substrate is stacked in alignment with the first waveguide substrate to form an optical structure imposition structure, comprising:

projecting a projection image with a positioning pattern on at least three first diffraction grating structures which are not positioned on the same straight line through a projector respectively, wherein part of light of the projection image enters the first waveguide substrate from a coupling-in area of the first diffraction grating structure and is coupled out of a first projection image from a coupling-out area of the first diffraction grating structure to an imaging device after total internal reflection; the other part of light of the projection image is coupled out from the first waveguide substrate towards the direction of the corresponding second diffraction grating structure of the second waveguide substrate, enters the second waveguide substrate from the coupling-in area of the second diffraction grating structure, and is coupled out from the coupling-out area of the second diffraction grating structure to the imaging device after being totally internally reflected;

Adjusting a relative positional relationship between the first waveguide substrate and the second waveguide substrate based on an offset between the positioning pattern of the first projection image and the positioning pattern of the second projection image, respectively; and

and in response to the offset meeting a preset threshold range, stacking the second waveguide substrate on the first waveguide substrate.

In the method of manufacturing a wafer level according to the present application, at least three first diffraction grating structures not on the same line are uniformly distributed along the circumferential direction of the first waveguide substrate setting with respect to the center of the first waveguide substrate setting.

In the wafer level manufacturing method according to the present application, dividing the optical structure imposition structure to obtain a plurality of optical structures suitable for a near-eye display device includes: the optical structure imposition structure is divided along a reference line set by the part of the first reference point for positioning the adhesive laying position.

In the wafer level manufacturing method according to the present application, the reference line set by the partial first reference point for locating the adhesive laying position is located between the inner edge and the outer edge of the adhesive.

In the wafer level manufacturing method according to the present application, the reference line set by the partial first reference point for locating the adhesive laying position is located outside the outer edge of the adhesive.

In the wafer-level manufacturing method according to the present application, the adhesive has a thickness dimension in the range of 40 μm to 60 μm and a width dimension in the range of 1mm to 3mm.

In the wafer level manufacturing method according to the present application, the adhesive has a non-closed shape.

In the wafer level manufacturing method according to the present application, the adhesive has a shape of a ring having at least one notch.

In the wafer level manufacturing method according to the present application, the adhesive includes a plurality of particles embedded therein and uniformly distributed, and the diameter range of the particles is smaller than or equal to the size of the gap between the first waveguide substrate and the second waveguide substrate.

In the wafer-level manufacturing method according to the present application, the diameter of the particles ranges from 40 μm to 60 μm.

In the wafer level manufacturing method according to the present application, the first diffraction grating structure is a surface relief grating structure or a volume hologram grating structure.

According to another aspect of the present application, there is also provided an optical structure suitable for use in a near-eye display device, comprising:

A first optical waveguide having a first diffraction grating structure;

the first optical waveguide and the second optical waveguide are staggered with each other relative to the projection direction of the projector towards the first optical waveguide and have a preset gap between the first optical waveguide and the second optical waveguide; and

and an adhesive disposed between the first optical waveguide and the second optical waveguide, wherein a gap between the first optical waveguide and the second optical waveguide ranges from 40 μm to 60 μm.

In the optical structure according to the present application, the adhesive has a thickness dimension in the range of 40 μm to 60 μm and a width dimension in the range of 1mm to 3mm.

In the optical structure according to the present application, the adhesive includes a plurality of particles embedded therein and uniformly distributed, the particles having a diameter in a range of less than or equal to a gap between the first optical waveguide and the second optical waveguide.

In the optical structure according to the application, the particles have a diameter in the range of 40 μm to 60 μm.

In the optical structure according to the present application, the optical structure further includes a light shielding layer provided at a side portion of the first optical waveguide and/or a side portion of the second optical waveguide.

In the optical structure according to the present application, the parallelism between the first optical waveguide and the second optical waveguide is 4' or less.

According to still another aspect of the present application, there is also provided a near-eye display device including:

an optical structure as described above; and

a projector configured to project a projected image to the optical structure.

Further objects and advantages of the present application will become fully apparent from the following description and the accompanying drawings.

These and other objects, features and advantages of the present application will become more fully apparent from the following detailed description, the accompanying drawings and the appended claims.

Drawings

The above and other objects, features and advantages of the present application will become more apparent by describing embodiments of the present application in more detail with reference to the attached drawings. The accompanying drawings are included to provide a further understanding of embodiments of the application and are incorporated in and constitute a part of this specification, illustrate the application and together with the embodiments of the application, and not constitute a limitation to the application. In the drawings, like reference numerals generally refer to like parts or steps.

Fig. 1 illustrates a schematic diagram of an optical structure suitable for use in a near-eye display device according to an embodiment of the application.

Fig. 2 illustrates a flow chart of a method of wafer level fabrication of the optical structure according to an embodiment of the present application.

Fig. 3 illustrates a schematic diagram of a process for preparing the optical structure according to an embodiment of the present application.

FIG. 4A illustrates a schematic diagram of an adhesive placement during the fabrication of the optical structure according to an embodiment of the present application.

FIG. 4B illustrates a schematic view of an adhesive placement during the fabrication of the optical structure according to an embodiment of the present application

FIG. 4C illustrates a schematic diagram of another placement adhesive during the fabrication of the optical structure according to an embodiment of the present application.

FIG. 4D illustrates a schematic diagram of another placement adhesive during the fabrication of the optical structure according to an embodiment of the present application.

Fig. 5 illustrates a schematic view of the adhesive according to an embodiment of the present application.

Fig. 6 illustrates a schematic diagram of a split optical structure imposition structure in the manufacturing process of the optical structure according to an embodiment of the present application.

Fig. 7 illustrates a schematic diagram of another split optical structure imposition structure in the manufacturing process of the optical structure according to an embodiment of the present application.

Fig. 8 illustrates a schematic view of a positioning pattern for positioning during the preparation of the optical structure according to an embodiment of the present application.

Fig. 9 illustrates a schematic view of imaging effects of the positioning pattern during the preparation of the optical structure according to an embodiment of the present application.

Fig. 10 illustrates a schematic diagram of a near-eye display device according to an embodiment of the present application.

Detailed Description

Hereinafter, exemplary embodiments according to the present application will be described in detail with reference to the accompanying drawings. It should be apparent that the described embodiments are only some embodiments of the present application and not all embodiments of the present application, and it should be understood that the present application is not limited by the example embodiments described herein.

Exemplary optical Structure

As shown in fig. 1, an optical structure suitable for a near-eye display device according to an embodiment of the present application is illustrated, wherein the optical structure 10 is configured to expand a projected image projected by a projector 20 to an entire viewable area of the optical structure 10. In the embodiment of the present application, as shown in fig. 1, the optical structure 10 includes a first optical waveguide 11 and a second optical waveguide 12, the first optical waveguide 11 and the second optical waveguide 12 are laterally staggered with respect to each other with a predetermined gap therebetween with respect to a projection direction by a projector 20 toward the first optical waveguide 11, that is, as shown in fig. 1, in the embodiment of the present application, the first optical waveguide 11 and the second optical waveguide 12 are staggered with respect to each other with a predetermined gap therebetween along a thickness direction thereof, the first optical waveguide 11 is used for guiding out a portion of light of the projected image, and the second optical waveguide 12 is used for guiding out another portion of light of the projected image. In particular, in the embodiment of the present application, the gap between the first optical waveguide 11 and the second optical waveguide 12 is in the range of 40 μm to 60 μm, and the parallelism between the first optical waveguide 11 and the second optical waveguide 12 is 4 'or less, preferably 2' or less.

It should be noted that the first optical waveguide 11 and the second optical waveguide 12 may be used to transmit light with different wavelengths, or may be used to transmit light with different incident angles, respectively. For example, in a specific application scenario of the present application, the light of the projected image may be configured with light having a plurality of wavelengths, for example, having a first primary color, a second primary color, and a third primary color (more specifically, for example, the first primary color is red, the second primary color is green, and the third primary color is blue), wherein the first optical waveguide 11 is configured to derive light of the first primary color and a part of the second primary color, and the second optical waveguide 12 is configured to derive light of a part of the second primary color and the third primary color.

More specifically, as shown in fig. 1, the first optical waveguide 11 includes a first diffraction grating structure 111 having a coupling-in region and a coupling-out region, wherein a portion of the light of the projected image enters the first waveguide from the coupling-in region of the first diffraction grating 111 and is coupled out of the coupling-out region of the first diffraction grating structure 111 after total internal reflection. The second optical waveguide 12 includes a second diffraction grating structure 121 having a coupling-in region and a coupling-out region, wherein another portion of the projected image is coupled out from the first optical waveguide 11 in the direction of the second diffraction grating structure 121 of the second optical waveguide 12, enters the second optical waveguide 12 from the coupling-in region of the second diffraction grating structure 121, and is coupled out from the coupling-out region of the second diffraction grating structure 121 after total internal reflection. Accordingly, the projected image coupled out of the first optical waveguide 11 and the projected image coupled out of the second optical waveguide 12 are superimposed on each other and viewed by a viewer.

In the embodiment of the present application, the first diffraction grating structure 111 and the second diffraction grating structure 121 may be implemented as a surface relief grating structure or a holographic grating structure, which is not limited to the present application.

As shown in fig. 1, the optical structure 10 further includes an adhesive 13 disposed between the first optical waveguide 11 and the second optical waveguide 12. In particular, in the embodiment of the present application, the adhesive 13 has a relatively small thickness dimension (i.e., a height dimension) and a relatively wide width dimension. Specifically, in the embodiment of the present application, the thickness dimension of the adhesive 13 is in the range of 40 μm to 60 μm, and the width dimension thereof is in the range of 1mm to 3mm.

In a specific example of the present application, the adhesive 13 includes a plurality of particles 131 embedded therein to determine the positional relationship between the first optical waveguide 11 and the second optical waveguide 12 during the preparation of the optical structure 10 by the plurality of particles 131. In the embodiment of the present application, the diameter of the particle 131 ranges from 40 μm to 60 μm and is smaller than or equal to the size of the gap between the first optical waveguide 11 and the second optical waveguide 12. Preferably, the diameter of the particle 131 is approximately equal to the size of the gap between the first optical waveguide 11 and the second optical waveguide 12, so as to limit and position the particle 131. More preferably, in the embodiment of the present application, the particles 131 are uniformly distributed in the adhesive 13, and herein, the uniform distribution of the particles 131 means that the particles 131 have similar lateral gaps therebetween and the diameters of the particles 131 themselves are substantially the same.

In order to avoid that external stray light enters the optical structure 10 from the side to form stray light, in the embodiment of the present application, the optical structure 10 further includes a light shielding layer 14 disposed on the side of the first optical waveguide 11 and/or the side of the second optical waveguide 12, where the light shielding layer 14 may be generated by a black coating process, for example, an inkjet method or an inking method.

It should be understood that, in order to enable the projected image coupled out of the first optical waveguide 11 and the projected image coupled out of the second optical waveguide 12 to be perfectly fused, a better visual experience is obtained, and a preset installation positional relationship between the first optical waveguide 11 and the second optical waveguide 12 needs to be satisfied. That is, in the specific manufacturing process of the optical structure 10, a high installation and matching precision is required between the first optical waveguide 11 and the second optical waveguide 12 of the optical structure 10, and if the relative positional relationship or matching precision between the two cannot meet the preset requirements, undesirable visual phenomena such as color cast, uneven color, color cast display, rainbow effect and the like will occur.

In order to meet the above requirements, in the embodiment of the present application, the optical structure 10 is manufactured by using a wafer-level based manufacturing method, so as to meet the above requirements.

In summary, an optical structure 10 suitable for a near-eye display device according to an embodiment of the present application is illustrated, which has high matching accuracy and reliability, and the consistency between the optical waveguides of each layer in the optical structure 10 is high.

Although in the above example, the optical structure 10 includes two optical waveguides (i.e., the first optical waveguide 11 and the second optical waveguide 12) as an example, in other examples of the present application, the optical structure 10 may further include a greater number of optical waveguides, for example, include a third optical waveguide, which is not limited to the present application.

Schematic preparation procedure

As shown in fig. 2, the method for preparing a wafer level of an optical structure according to an embodiment of the present application includes the steps of: s110, providing a first waveguide substrate 101, wherein the first waveguide substrate 101 is provided with a plurality of first diffraction grating structures 111 arranged according to a preset period and a plurality of first datum points 112 used for positioning; s120, distributing adhesive on the surface of the first waveguide substrate 101 based on the periodic distribution rule of the first datum point 112 and the first diffraction grating structure 111; s130, providing a second waveguide substrate 102, wherein the second waveguide substrate 102 is provided with a plurality of second diffraction grating structures 121 and a plurality of second datum points 122 which are used for positioning, and the second diffraction grating structures 121 are arranged in the same period as the first waveguide substrate 101; s140, stacking the second waveguide substrate 102 on the first waveguide substrate 101 in alignment to form an optical structure imposition structure 110, wherein in the optical structure imposition structure 110, the first waveguide substrate 101 and the second waveguide substrate 102 have a preset gap, the gap ranges from 40 μm to 60 μm, and the plurality of first diffraction grating structures 111 of the first waveguide substrate 101 respectively correspond to the plurality of second diffraction grating structures 121 of the second waveguide substrate 102; and S150, dividing the optical structure imposition structure 110 to obtain a plurality of optical structures 10 suitable for the near-eye display device.

In step S110, a first waveguide substrate 101 is provided, the first waveguide substrate 101 having a plurality of first diffraction grating structures 111 arranged according to a predetermined period and a plurality of first reference points 112 for positioning. Here, the plurality of first reference points 112 includes a part of the first reference points 112 for locating the layout positions of the adhesive 13 and another part of the first reference points 112 for locating the stacking positions of the second waveguide substrates 102.

In particular, the first waveguide substrate 101 may be prepared based on the manner as illustrated in fig. 3. The process of preparing the first waveguide substrate 101 first involves producing an imprint template. In this example, a process of producing an imprint template includes: firstly, providing a silicon wafer and plating a mask layer on a silicon wafer substrate; then spin coating a resist layer thereon; patterning is then performed using an exposure technique such as interference exposure or electron beam exposure; then, the resist pattern is transferred to the mask layer by etching the same, and the remaining resist layer is stripped by an oxygen plasma method; then, using a reactive ion beam etching process to make an ion beam incident on the silicon wafer substrate; and removing the mask layer by using a standard wet etching process after etching is finished, so that the grating template with good uniformity can be obtained. To increase production efficiency, UV resin can be spin coated on larger silicon wafers and more imprint templates printed by nanoimprint techniques as described above; the UV resin is then cured by ultraviolet exposure, and the above steps are repeated to mass produce multi-pattern imprint templates.

The imprinting template is used for preparing a plurality of first diffraction grating structures 111 which are arranged in a preset period on the first waveguide substrate 101. Specifically, the process of preparing a plurality of first diffraction grating structures 111 arranged in a predetermined period on the first waveguide substrate 101 includes: mark points are marked on the first waveguide substrate 101 for machine vision positioning, wherein the Mark points can be the first datum points 112 or other positioning datum points; then, a plurality of first diffraction grating structures 111 arranged at a certain period are manufactured on the first waveguide substrate 101 using the above-described grating template; next, a functional layer is coated on the surface of the first waveguide substrate 101, so that the first waveguide substrate 101 with the plurality of first diffraction grating structures 111 is obtained.

It is worth mentioning that in the above example, the first diffraction grating structure 111 made by grating template is a surface relief grating. It should be understood that in other examples, the volume hologram grating (i.e., the first diffraction grating structure 111 is a volume hologram grating structure) may be manufactured by other processes, which is not limited by the present application.

In step S120, an adhesive 13 is disposed on the surface of the first waveguide substrate 101 based on the periodic distribution rule of the first reference point 112 and the first diffraction grating structure 111.

In the example illustrated in fig. 3, the process of disposing the adhesive 13 on the surface of the first waveguide substrate 101 includes: first, part of the first reference points 112 for locating the laying position of the adhesive 13 among the plurality of first reference points 112 is identified with machine vision; next, the adhesive 13 is uniformly coated on the surface of the first waveguide substrate 101 by an adhesive coating apparatus in a periodic arrangement of grating positions.

That is, in the embodiment of the present application, the adhesive 13 is disposed on the surface of the first waveguide substrate 101 based on the periodic distribution rule of the first reference point 112 and the first diffraction grating structure 111, including: the adhesive 13 is disposed on the surface of the first waveguide substrate 101 based on the periodic distribution rule of the part of the first reference point 112 for locating the placement position of the adhesive 13 and the first diffraction grating structure 111.

Preferably, in this example, the adhesive 13 has a layout shape similar to the contour of the first optical waveguide 11. The thickness dimension of the adhesive 13 is in the range of 40 μm to 60 μm, the width dimension thereof is in the range of 1mm to 3mm, preferably the thickness dimension (i.e., the height dimension) of the adhesive 13 is 50 μm, and the width dimension thereof is preferably 1mm, for both aesthetic appearance and bonding reliability.

It is worth mentioning that in practice, it is difficult to directly apply the adhesive 13 to achieve the aspect ratio of the adhesive 13 as described above (the aspect ratio that can be achieved by applying the adhesive 13 is generally about 1:2), and when the second waveguide substrate 102 is stacked on the first waveguide substrate 101, the height dimension of the adhesive 13 disposed therebetween is depressed, so that, in step S120, the disposition height of the adhesive 13 can be appropriately increased, for example, the disposition height is increased to 160 μm, whereby, when the second waveguide substrate 102 is stacked on the first waveguide substrate 101, the height dimension of the adhesive 13 can be depressed to approximately 50 μm while the width is maintained at 1mm to 2mm. That is, in this example, the adhesive 13 may be formed between the first waveguide substrate 101 and the second waveguide substrate 102 in a coating-before-pressing manner.

It is also noted that in an embodiment, the adhesive 13 may be applied in a single turn (as shown in fig. 4A) or multiple turns, and then the turns of the adhesive 13 may be crushed and fused by stacking the second waveguide substrate 102 (as shown in fig. 4B) to achieve the desired height and width.

Meanwhile, the adhesive 13 may have a closed shape (as shown in fig. 4C), or the adhesive 13 may have an unsealed profile, for example, with a segmented coating and a gap left (as shown in fig. 4D). Wherein when the adhesive 13 is provided to have a closed contour, it is preferable that the adhesive 13 is a glue that does not require heat curing, such as a UV glue that is cured by ultraviolet light, a UV glue that is cured by both ultraviolet light and natural light, a moisture-curing glue, a hot melt glue, or the like. When the adhesive 13 is configured without a closed contour, a thermosetting adhesive or a UV thermosetting adhesive having a relatively high viscosity may be preferably used, and the non-closed arrangement may also prevent the first waveguide substrate 101 and the second waveguide substrate 102 from being damaged (e.g., deformed or even cracked) due to thermal expansion of the gas in the closed space formed between the first waveguide substrate 101 and the second waveguide substrate 102 when the adhesive 13 is cured by heating. Of course, when the adhesive 13 is provided without a closed contour, non-heat curing glue may also be used to increase production efficiency. Furthermore, when the adhesive 13 is configured without a closed profile, after curing the adhesive 13, the notch should be sealed off to prevent contaminants such as dust, moisture, etc. from entering between the first waveguide substrate 101 and the second waveguide substrate 102, which affects the performance of the optical structure 10 that is ultimately worth.

Preferably, in the embodiment of the present application, as shown in fig. 5, the adhesive 13 is implemented as the adhesive 13 including the plurality of particles 131 embedded therein. Accordingly, the plurality of particles 131 can effectively limit the distance between the first waveguide substrate 101 and the second waveguide substrate 102 from being too small or too large. That is, the plurality of particles 131 disposed in the adhesive 13 can position the first waveguide substrate 101 and the second waveguide substrate 102 with a limit and provide a preliminary positioning. Preferably, a plurality of the particles 131 are uniformly disposed in the adhesive 13.

In step S130, a second waveguide substrate 102 is provided, where the second waveguide substrate 102 has a plurality of second diffraction grating structures 121 and a plurality of second reference points 122 for positioning, which are arranged in the same period as the first waveguide substrate 101. It should be appreciated that the second waveguide substrate 102 can be manufactured in a process similar to that described for the first waveguide substrate 101, so that there is a better consistency between the two.

In step S140, the second waveguide substrate 102 is stacked in alignment with the first waveguide substrate 101 to form an optical structure imposition structure 110, wherein in the optical structure imposition structure 110, the first waveguide substrate 101 and the second waveguide substrate 102 have a preset gap in a range of 40 μm to 60 μm, and the plurality of first diffraction grating structures 111 of the first waveguide substrate 101 correspond to the plurality of second diffraction grating structures 121 of the second waveguide substrate 102, respectively.

Specifically, in one embodiment of the present application, the process of stacking the second waveguide substrate 102 on the first waveguide substrate 101 in alignment to form the optical structure imposition structure 110 includes: first identifying another portion of the plurality of first fiducial points 112 and the second fiducial point 122 for locating a stacking position of the second waveguide substrate 102 with machine vision; then, based on the alignment between the other portion of the first fiducial 112 and the second fiducial 122, the second waveguide substrate 102 is stacked on the first waveguide substrate 101 to form an optical structure imposition structure 110.

That is, in this embodiment, the aligning stacking of the second waveguide substrate 102 to the first waveguide substrate 101 to form the optical structure imposition structure 110 includes: based on the alignment between the other portion of the first fiducial 112 and the second fiducial 122, the second waveguide substrate 102 is stacked on the first waveguide substrate 101 to form an optical structure imposition structure 110. Preferably, the further portion of the first reference points 112 is evenly distributed along the circumference of the first waveguide substrate 101.

It should be noted that the distance between the first waveguide substrate 101 and the second waveguide substrate 102 may be measured by laser ranging or other means during stacking to ensure that the distance between the first waveguide substrate 101 and the second waveguide substrate 102 is maintained between 40 μm and 60 μm, preferably 50 μm, to ensure that an air layer exists between the first waveguide substrate 101 and the second waveguide substrate 102 to ensure physical conditions for total reflection and diffraction of light. Of course, when the adhesive 13 embeds the plurality of particles 131, the distance between the first waveguide substrate 101 and the second waveguide substrate 102 may also be limited by the particles 131. It should be noted that the plurality of particles 131 embedded between the adhesives 13 can also effectively ensure parallelism between the first waveguide substrate 101 and the second waveguide substrate 102.

In another example of the present application, the process of aligning and stacking the second waveguide substrate 102 to the first waveguide substrate 101 to form the optical structure imposition structure 110 includes: firstly, projecting a projection image with a positioning pattern 103 on at least three first diffraction grating structures 111 which are not positioned on the same straight line on the first waveguide substrate 101 through a projector, wherein part of light of the projection image enters the first waveguide substrate 101 from a coupling-in area of the first diffraction grating structures 111 and is coupled out of a first projection image from a coupling-out area of the first diffraction grating structures 111 to an imaging device after total internal reflection; another part of the light of the projected image is coupled out from the first waveguide substrate 101 towards the corresponding second diffraction grating structure 121 of the second waveguide substrate 102, enters the second waveguide substrate 102 from the coupling-in region of the second diffraction grating structure 121, and couples out a second projected image from the coupling-out region of the second diffraction grating structure 121 to the imaging device after total internal reflection; then, based on the amounts of offset between the positioning patterns 103 of the first projection image and the positioning patterns 103 of the second projection image, respectively, the relative positional relationship between the first waveguide substrate 101 and the second waveguide substrate 102 is adjusted; then, in response to the offset amount satisfying a preset threshold range, the second waveguide substrate 102 is stacked on the first waveguide substrate 101. Preferably, at least three first diffraction grating structures 111, which are not located on the same straight line, are uniformly distributed along the circumferential direction set by the first waveguide substrate 101 with respect to the center set by the first waveguide substrate 101.

In this example, in a specific implementation, the projector, the first waveguide substrate 101, and the imaging device may be fixed at preset positions, and the second waveguide substrate 102 may be adjustably mounted to a side portion of the first waveguide substrate 101 to change a relative positional relationship with the first waveguide substrate 101 by adjusting a pose (including a position and a posture) of the second waveguide substrate 102. For example, the second waveguide substrate 102 may be fixed to an adjustment platform by clamping or sucking, where the adjustment platform is adapted to adjust the pose of the second waveguide substrate 102 in six degrees of freedom (X, Y, Z, rotation about X/Y/Z axes, respectively). Of course, the relative positional relationship between the first waveguide substrate 101 and the second waveguide substrate 102 may be adjusted in other manners, which is not a limitation of the present application. For example, the second waveguide substrate 102 may be fixed at a predetermined position to selectively adjust the pose of the first waveguide substrate 101; alternatively, the pose of the first waveguide substrate 101 and the second waveguide substrate 102 may be adjusted simultaneously, which is not limited by the present application.

Further, a projected image having a positioning pattern 103 is projected on the first waveguide substrate 101 by the projector. In this example, the projected image projected by the projector includes a positioning pattern 103, such as a cross pattern (as shown in fig. 8), a dot pattern, a checkerboard pattern, etc., that can be used to characterize the direction and position of the projected image.

It should be understood that when there is an angle difference between the first diffraction grating structure 111 of the first waveguide substrate 101 and the second diffraction grating structure 121 of the second waveguide substrate 102 corresponding to the first diffraction grating structure 111 (as shown in fig. 3), light coupled out of the first waveguide substrate 101 and light coupled out of the second waveguide substrate 102 exit at an angle, that is, there is an offset between the first projection image and the second projection image, the effect of which is shown in fig. 9. As shown in fig. 9, the image generated by the imaging device includes two cross patterns. Accordingly, by measuring the amount of offset between the two cross patterns, the amount of adjustment required between the second waveguide substrate 102 and the first waveguide substrate 101 can be obtained.

Specifically, in this example, the offset to be measured includes the distance of the offset between the two cross patterns and the direction of the offset to determine the amount and direction of angle adjustment required between the second waveguide substrate 102 and the first waveguide substrate 101. In this way, the relative positional relationship between the first waveguide substrate 101 and the second waveguide substrate 102 is continuously adjusted in real time by means of the cyclic measurement, calculation, adjustment, measurement until the offset calculated based on the image acquired by the imaging device satisfies a preset threshold range. That is, when the offset amount satisfies a preset threshold range, the superimposed positional relationship between the first waveguide substrate 101 and the second waveguide substrate 102 is determined.

In step S150, the optical structure imposition structure 110 is divided to obtain a plurality of optical structures 10 suitable for use in a near-eye display device. There are various ways to cut the optical structure imposition structure 110, and preferably, a laser cutting scheme is used.

It will be appreciated that different cutting paths are possible in different ways of laying the adhesive 13. For example, in the dicing method as illustrated in fig. 6, the outer edge of the adhesive 13 is adjacent to the edge of the first optical waveguide 11 or the second optical waveguide 12 after dicing. For another example, in the cutting mode shown in fig. 7, the adhesive 13 is cut through at the time of cutting so that the width of the adhesive 13 left in the optical structure 10 is 1mm to 2mm. It should be noted that, since the adhesive 13 is actually disposed, it is not possible to ensure that the edge of the adhesive 13 is absolutely smooth, the cutting scheme as illustrated in fig. 7 may enable the edges of the first optical waveguide 11 and the second optical waveguide 12 in the final optical structure 10 to be flush with the edge of the adhesive 13, which is also more advantageous for the subsequent blackening process.

The optical structure imposition structure 110 may be divided along a reference line set by the portion of the first reference point 112 for locating the adhesive 13 layout position when the dicing process is performed. That is, in an embodiment of the present application, dividing the optical structure imposition structure 110 to obtain a plurality of optical structures 10 suitable for use in a near-eye display device includes: the optical structure imposition structure 110 is divided along a reference line set by the part of the first reference point 112 for positioning the adhesive 13 layout position.

In particular, when the reference line set by the part of the first reference point 112 for locating the laying position of the adhesive 13 is located between the inner edge and the outer edge of the adhesive 13, a cutting scheme as illustrated in fig. 7 can be realized. When the reference line set by the part of the first reference point 112 for locating the laying position of the adhesive 13 is located outside the outer edge of the adhesive 13, a cutting scheme as illustrated in fig. 6 can be realized.

Further, after the plurality of optical structures 10 are obtained by dividing the optical structure imposition structure 110, a light shielding layer 14 (not shown) is further disposed on the side of the first optical waveguide 11 and/or the side of the second optical waveguide 12. In a specific example of the present application, a black coating process may be performed on the side portions of the first optical waveguide 11 and the second optical waveguide 12 to form the light shielding layer 14 to avoid that external light enters the first optical waveguide 11 and the second optical waveguide 12 from the side to form stray light, which affects the visual experience, where the black coating process may use an inkjet method or an inking method.

It should be noted that the wider the ink spray, the higher the thickness, and the higher the thickness tends to cause uneven ink surface of the spray, and the higher the ink layer thickness is, the less advantageous the assembly of the optical structure 10. Preferably, in the embodiment of the present application, the light shielding layer may be formed by spraying multiple times, so that the light shielding layer has a larger width and a smaller thickness.

Further, the preparation process of the optical structure 10 may further include providing a frame on a side portion of the optical structure 10 to protect the optical structure 10 from being bumped or scratched when the optical structure is mounted on a module or a wearable device.

In summary, the wafer-level manufacturing process of the optical structure 10 suitable for the near-eye display device according to the embodiment of the present application is illustrated, which can mass-produce the optical structure 10 with high manufacturing efficiency, and is suitable for mass production of the optical structure 10 composed of the multi-layer optical waveguide. And, the optical structure 10 manufactured by the wafer-level manufacturing method has high matching precision and reliability.

Schematic near-to-eye display device

According to yet another aspect of the present application, there is also provided a near-eye display device. Fig. 10 illustrates a schematic diagram of a near-eye display device according to an embodiment of the present application, as shown in fig. 10, the near-eye display device 100 includes a projector and an optical structure 10 as described above, wherein the projector projects a projection image onto the optical structure 10, and the optical structure 10 performs pupil expansion on the projection image for a viewer to view, so as to obtain an enhanced visual experience of display.

It will be appreciated by persons skilled in the art that the embodiments of the invention described above and shown in the drawings are by way of example only and are not limiting. The objects of the present invention have been fully and effectively achieved. The functional and structural principles of the present invention have been shown and described in the examples and embodiments of the invention may be modified or practiced without departing from the principles described.

Claims

A method of preparing a wafer level optical structure suitable for use in a near-eye display device, comprising:

providing a first waveguide substrate, wherein the first waveguide substrate is provided with a plurality of first diffraction grating structures and a plurality of first datum points for positioning, and the first diffraction grating structures are arranged according to a preset period;

distributing adhesive on the surface of the first waveguide substrate based on the periodic distribution rule of the first datum point and the first diffraction grating structure; and

providing a second waveguide substrate, wherein the second waveguide substrate is provided with a plurality of second diffraction grating structures which are arranged in the same period as the first waveguide substrate and a plurality of second datum points for positioning;

aligning and stacking the second waveguide substrate on the first waveguide substrate to form an optical structure imposition structure, wherein in the optical structure imposition structure, the first waveguide substrate and the second waveguide substrate have preset gaps, the gaps range from 40 μm to 60 μm, and a plurality of first diffraction grating structures of the first waveguide substrate respectively correspond to a plurality of second diffraction grating structures of the second waveguide substrate; and

Dividing the optical structure imposition structure to obtain a plurality of optical structures suitable for use in a near-eye display device.
The wafer level manufacturing method according to claim 1, wherein the plurality of first fiducial points includes a part of the first fiducial points for locating adhesive placement locations;

wherein, based on the periodic distribution rule of the first datum point and the first diffraction grating structure, an adhesive is arranged on the surface of the first waveguide substrate, and the method comprises the following steps: and distributing the adhesive on the surface of the first waveguide substrate based on the part of the first datum point for positioning the adhesive distribution position and the periodic distribution rule of the first diffraction grating structure.
The wafer level manufacturing method according to claim 2, wherein the plurality of first fiducial points includes another part of the first fiducial points for locating a stacking position of the second waveguide substrate;

wherein the second waveguide substrate is stacked in alignment with the first waveguide substrate to form an optical structure imposition structure, comprising: and superposing the second waveguide substrate on the first waveguide substrate based on the alignment between the other part of the first datum point and the second datum point to form an optical structure imposition structure.
A method of wafer level fabrication as recited in claim 3, wherein the further portion of the first fiducial is uniformly distributed along the perimeter of the first waveguide substrate.
The wafer level fabrication method of claim 2, wherein aligning the second waveguide substrate to the first waveguide substrate to form an optical structure imposition structure comprises:

projecting a projection image with a positioning pattern on at least three first diffraction grating structures which are not positioned on the same straight line through a projector respectively, wherein part of light of the projection image enters the first waveguide substrate from a coupling-in area of the first diffraction grating structure and is coupled out of a first projection image from a coupling-out area of the first diffraction grating structure to an imaging device after total internal reflection; the other part of light of the projection image is coupled out from the first waveguide substrate towards the direction of the corresponding second diffraction grating structure of the second waveguide substrate, enters the second waveguide substrate from the coupling-in area of the second diffraction grating structure, and is coupled out from the coupling-out area of the second diffraction grating structure to the imaging device after being totally internally reflected;

Adjusting a relative positional relationship between the first waveguide substrate and the second waveguide substrate based on an offset between the positioning pattern of the first projection image and the positioning pattern of the second projection image, respectively; and

and in response to the offset meeting a preset threshold range, stacking the second waveguide substrate on the first waveguide substrate.
The wafer level fabrication method of claim 5, wherein at least three non-collinear first diffraction grating structures are uniformly distributed along a circumference of the first waveguide substrate setting relative to a center of the first waveguide substrate setting.
The wafer level fabrication method of claim 2, wherein dividing the optical structure imposition structure to obtain a plurality of optical structures suitable for use in a near-eye display device comprises: the optical structure imposition structure is divided along a reference line set by the part of the first reference point for positioning the adhesive laying position.
The wafer level manufacturing method according to claim 7, wherein the reference line set by the part of the first reference point for locating the adhesive placement position is located between an inner edge and an outer edge of the adhesive.
The wafer level manufacturing method according to claim 7, wherein the reference line set by the part of the first reference point for locating the adhesive placement position is located outside the outer edge of the adhesive.
The wafer level manufacturing method according to claim 1, wherein the adhesive has a thickness dimension in the range of 40 μm to 60 μm and a width dimension in the range of 1mm to 3mm.
The wafer level manufacturing method of claim 10, wherein the adhesive has a non-closed shape.
The wafer level manufacturing method of claim 11, wherein the adhesive has a shape of a ring with at least one notch.
The wafer level fabrication method of claim 10, wherein the adhesive comprises a plurality of particles embedded therein and uniformly distributed, the particles having a diameter in a range less than or equal to a gap size between the first waveguide substrate and the second waveguide substrate.
The wafer level manufacturing method of claim 13, wherein the particles have a diameter ranging from 40 μιη to 60 μιη.
The wafer level fabrication method of claim 1, wherein the first diffraction grating structure is a surface relief grating structure or a volume holographic grating structure.
An optical structure suitable for use in a near-eye display device, comprising:

a first optical waveguide having a first diffraction grating structure;

the first optical waveguide and the second optical waveguide are staggered with each other relative to the projection direction of the projector towards the first optical waveguide and have a preset gap between the first optical waveguide and the second optical waveguide; and

and an adhesive disposed between the first optical waveguide and the second optical waveguide, wherein a gap between the first optical waveguide and the second optical waveguide ranges from 40 μm to 60 μm.
The optical structure of claim 16, wherein the adhesive has a thickness dimension in the range of 40-60 μm and a width dimension in the range of 1-3 mm.
The optical structure of claim 17, wherein the adhesive comprises a plurality of particles embedded therein and uniformly distributed, the particles having a diameter in a range less than or equal to a gap between the first optical waveguide and the second optical waveguide.
An optical structure as claimed in claim 18, wherein the particles have a diameter in the range 40-60 μm.
The optical structure of claim 16, further comprising a light shielding layer disposed on a side of the first optical waveguide and/or a side of the second optical waveguide.
The optical structure of claim 16, wherein a parallelism between the first optical waveguide and the second optical waveguide is 4' or less.
A near-eye display device, comprising:

the optical structure of any one of claims 16-21; and

a projector configured to project a projected image to the optical structure.