阅读说明：本技术 一种具有高效率高均匀性的波导装置 (Waveguide device with high efficiency and high uniformity ) 是由 饶鹏辉 王一 于 2021-09-01 设计创作，主要内容包括：本发明公开了一种具有高效率高均匀性的波导装置,包括：波导；耦入元件,贴合波导设置,用于将光耦入波导；耦出元件,贴合波导设置,用于将经波导全反射传导的光耦出至人眼,耦入元件和耦出元件为衍射光栅或全息光栅,且至少其一远离波导的一侧设有多个周期性分布的多边形凸脊；膜层,为折射率为2.0～2.5的透光材质,并覆盖凸脊上贴合波导以外的面、以及覆盖介于相邻凸脊之间的波导上,膜厚为1nm～100nm且相对面膜厚不同。通过光栅上覆盖膜层,并将不同侧面膜层镀制不同厚度,并选用高折射率透光材料,使得在不同入射角度下兼顾高平均效率以及低一致性误差,从而获得高亮度、高成像质量的耦出图像。(The invention discloses a waveguide device with high efficiency and high uniformity, comprising: a waveguide; a coupling-in element arranged in abutment with the waveguide for coupling light into the waveguide; the coupling-out element is attached to the waveguide and used for coupling out light which is totally reflected and conducted by the waveguide to human eyes, the coupling-in element and the coupling-out element are diffraction gratings or holographic gratings, and one side of at least one side of the coupling-out element, which is far away from the waveguide, is provided with a plurality of periodically distributed polygonal convex ridges; the film layer is made of a light-transmitting material with the refractive index of 2.0-2.5, covers the surfaces of the ridges except the waveguide and covers the waveguide between the adjacent ridges, the film thickness is 1-100 nm, and the film thickness of the opposite surfaces is different. The film layers are covered on the grating, the film layers on different side surfaces are coated with different thicknesses, and the high-refractive-index light-transmitting material is selected, so that high average efficiency and low consistency error are considered under different incidence angles, and coupled-out images with high brightness and high imaging quality are obtained.)

1. A waveguide device having high efficiency and high uniformity, comprising: the waveguide device with high efficiency and high uniformity comprises:

a waveguide (3);

a coupling-in element (2) arranged in abutment with the waveguide (3) for coupling light into the waveguide (3);

the coupling-out element (4) is arranged to be attached to the waveguide (3) and used for coupling out light which is totally reflected and conducted through the waveguide (3) to human eyes (5), the coupling-in element (2) and the coupling-out element (4) are diffraction gratings or holographic gratings, and one side of at least one side of the coupling-out element, which is far away from the waveguide (3), is provided with a plurality of periodically distributed polygonal convex ridges;

and the film layer (6) has a refractive index of 2.0-2.5, covers the surfaces of the ridges, which are attached to the outside of the waveguide (3), and covers the waveguide (3) between the adjacent ridges, and has a film thickness of 1-100 nm and different opposite surface film thicknesses.

2. The waveguide apparatus of claim 1 having high efficiency and high uniformity, wherein: the period of the diffraction grating or the holographic grating is 250 nm-500 nm, the modulation depth is 50 nm-350 nm, and the duty ratio is 20% -80%.

3. The waveguide apparatus of claim 1 having high efficiency and high uniformity, wherein: the material of the film layer (6) is one of TiO2, Ta2O5 and ZrO 2.

4. The waveguide apparatus of claim 1 having high efficiency and high uniformity, wherein: the diffraction grating and the holographic grating are rectangular gratings or inclined gratings.

5. The waveguide apparatus of claim 4 having high efficiency and high uniformity, wherein: the inclination angle alpha of the inclined grating satisfies the following conditions: alpha is more than 0 degree and less than or equal to 70 degrees.

6. The waveguide apparatus of claim 4 having high efficiency and high uniformity, wherein: the film thickness of the film layer (6) is 10nm-90 nm.

7. The waveguide apparatus of claim 1 having high efficiency and high uniformity, wherein: the waveguide (3) is coated with an antireflection film.

Technical Field

The invention belongs to the technical field of optical devices, and particularly relates to a waveguide device with high efficiency and high uniformity.

Background

Augmented Reality (AR), Mixed Reality (MR), and HUD (heads up display) systems primarily include a computational control unit, an optical micro-projection engine, and an optical coupler. The computing control unit is used for controlling the optical micro-projection engine to provide a collimated image, and the optical coupler is used for expanding the collimated image provided by the micro-projection engine, projecting the collimated image into a real world scene and fusing the collimated image with the real world scene, so that a user can obtain the image.

In AR, MR and HUD systems, an optical coupler is a key part of the system, in order to ensure that the whole system is small, light and thin in size and convenient to wear, a Diffractive Optical Element (DOE) or a Holographic Optical Element (HOE) is generally used as a coupling-in element and a coupling-out element of the optical coupler, and a collimated image provided by an optical micro-projection engine is coupled into a high refractive index optical waveguide through the coupling-in element, is transmitted in the optical waveguide based on the principle of total reflection, is copied through the coupling-out element and is coupled out of the optical waveguide, and is fused with a real world scene. For the incoupling element, patent publication US09513480B2 "Waveguide" shows a straight binary surface relief grating, i.e. a rectangular grating, by applying which collimated light of different angles of incidence provided by an optical micro-projection engine is coupled into a high refractive index optical Waveguide to obtain a corresponding first diffraction order: t +1, T0 and T-1 diffraction orders, wherein the T +1 diffraction orders are subjected to total reflection transmission in the optical waveguide; also shown is a tilted binary surface relief grating, i.e., a tilted grating, to achieve the same effect.

Wherein, the average efficiency ME of the incident light with different incidence angles after being coupled into the device is as follows:

E_ndiffraction efficiency of the first diffraction order for the nth angle of incidence;

wherein, the consistency error UE of the incident light with different incident angles after being coupled into the element is as follows:

E_maxfor maximum diffraction efficiency over the entire range of incident angles, E_minThe minimum diffraction efficiency over the entire range of incident angles.

The rectangular grating coupling-in element is widely applied to the scheme of diffraction light waveguide due to simple structure and easy processing, but due to the structural characteristics of the rectangular grating coupling-in element, namely, grooves among ridges of the rectangular grating coupling-in element are straight binary structures, diffraction orders have symmetry, and diffraction efficiency is equal, most incident energy cannot be diffracted to the required first diffraction order. The first diffraction order can not guarantee higher average efficiency when having lower consistency error under different incident angles, and the imaging quality is low. For the tilted grating coupling-in element, a tilt angle α is additionally introduced relative to the rectangular grating, so that for different incident angles, the first diffraction order has higher average efficiency, but cannot simultaneously ensure lower consistency error, and the imaging quality is low.

Disclosure of Invention

The present invention is directed to solve the above problems, and an object of the present invention is to provide a waveguide device with high efficiency and high uniformity, in which a film layer is covered on an incoupling element or an outcoupling element, and the film layers on different sides are coated with different thicknesses, and the film layer is made of a transparent material with a high refractive index, so that the average efficiency and uniformity can be further improved, and the coupled-out image with high brightness and high imaging quality can be obtained by considering both high average efficiency and low uniformity error at different incident angles.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

the invention provides a waveguide device with high efficiency and high uniformity, which comprises:

a waveguide;

a coupling-in element arranged in abutment with the waveguide for coupling light into the waveguide;

the coupling-out element is attached to the waveguide and used for coupling out light which is totally reflected and conducted by the waveguide to human eyes, the coupling-in element and the coupling-out element are diffraction gratings or holographic gratings, and one side of at least one side of the coupling-out element, which is far away from the waveguide, is provided with a plurality of periodically distributed polygonal convex ridges;

and the film layer has a refractive index of 2.0-2.5, covers the surfaces of the ridges except the waveguide and covers the waveguide between the adjacent ridges, and has a film thickness of 1-100 nm and different opposite surface film thicknesses.

Preferably, the period of the diffraction grating or the holographic grating is 250nm to 500nm, the modulation depth is 50nm to 350nm, and the duty ratio is 20% to 80%.

Preferably, the material of the film layer is one of TiO2, Ta2O5 and ZrO 2.

Preferably, the diffraction grating and the holographic grating are rectangular gratings or slanted gratings.

Preferably, the tilt angle α of the tilted grating satisfies: alpha is more than 0 degree and less than or equal to 70 degrees.

Preferably, the film thickness of the film layer is 10nm to 90 nm.

Preferably, the waveguides are coated with an anti-reflective film.

Compared with the prior art, the invention has the beneficial effects that: the film layer is covered on the coupling-in element or the coupling-out element, the film layers on different side surfaces are coated with different thicknesses, and the film layers are made of high-refractive-index light-transmitting materials, so that the average efficiency and uniformity can be further improved, the high average efficiency and low consistency error are considered under different incidence angles, and the coupling-out image with high brightness and high imaging quality is obtained.

Drawings

FIG. 1 is a schematic diagram of a waveguide device according to the present invention;

FIG. 2 is a schematic diagram of a film structure of a rectangular grating according to the present invention;

FIG. 3 is a schematic diagram of a structure of a tilted grating according to the present invention;

FIG. 4 is a graph showing the relationship between the incident angle and the diffraction efficiency before and after the addition of the film layer of the rectangular grating according to the present invention;

FIG. 5 is a graph showing the relationship between the incident angle and the diffraction efficiency before and after the addition of the film layer of the tilted grating according to the present invention;

FIG. 6 is a graph showing the relationship between the incident angle and the diffraction efficiency of the rectangular grating according to the present invention at different film thicknesses;

FIG. 7 is a graph showing the relationship between the incident angle and the diffraction efficiency of the tilted grating of the present invention at different film thicknesses.

Description of reference numerals: 1. an optical micro-projection engine; 2. a coupling-in element; 3. a waveguide; 4. a coupling-out element; 5. the human eye; 6. and (5) film layer.

Detailed Description

The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

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

As shown in fig. 1 to 5, a waveguide device having high efficiency and high uniformity, comprises:

a waveguide 3;

a coupling-in element 2 arranged in abutment with the waveguide 3 for coupling light into the waveguide 3;

the coupling-out element 4 is arranged by being attached to the waveguide 3 and used for coupling out the light which is totally reflected and conducted by the waveguide 3 to human eyes 5, the coupling-in element 2 and the coupling-out element 4 are diffraction gratings or holographic gratings, and one side of at least one side of the coupling-out element, which is far away from the waveguide 3, is provided with a plurality of periodically distributed polygonal convex ridges;

and a film layer 6 having a refractive index of 2.0 to 2.5, covering the surface of the ridge except the waveguide 3 and covering the waveguide 3 between adjacent ridges, the film thickness being 1nm to 100nm and the opposite surfaces having different film thicknesses.

The light emitted by the optical micro-projection engine 1 enters the incoupling element 2, and the incoupling element 2 couples the light into the waveguide 3 for total reflection and conduction, and then the light is coupled out to the human eye 5 through the outcoupling element 4, so that the wearer can obtain the required image. The film layer 6 is made of a high-refractive-index material, the refractive index is 2.0-2.5, the film layer is transparent in a visible light range, the film layer with the nanometer thickness can be prepared by an Atomic Layer Deposition (ALD) method, and the preparation of the grating can be realized by photoetching, etching and nanoimprint methods. The film layers with high refractive indexes and different thicknesses are added on the side surfaces, so that the effective refractive index distribution of different field angles incident to the grating area can be changed, the effect of respectively modulating different field angles is realized, high average efficiency and low consistency error are considered under different incident angles, high efficiency and high uniformity are achieved, and coupled-out images with high brightness and high imaging quality are obtained.

In one embodiment, the period of the diffraction grating or the holographic grating is 250nm to 500nm, the modulation depth is 50nm to 350nm, and the duty ratio is 20% to 80%. Is convenient for processing, and helps to ensure the required diffraction order and obtain high-quality imaging.

In one embodiment, the material of the film 6 is one of TiO2, Ta2O5, and ZrO 2. The grating is made of a film material with high reflectivity, and the overall diffraction efficiency and uniformity of the grating can be improved.

In one embodiment, the diffraction grating and the holographic grating are rectangular gratings or slanted gratings.

In one embodiment, the tilt angle α of the tilted grating satisfies: alpha is more than 0 degree and less than or equal to 70 degrees.

In one embodiment, the film thickness of the film 6 is 10nm to 90 nm.

In one embodiment, the waveguides 3 are coated with an anti-reflective film. If the upper and lower surfaces of the waveguide 3 are both coated with AR films, the reflectivity can be reduced to achieve the anti-reflection purpose.

Specifically, the coupling-in element 2 and the coupling-out element 4 are both rectangular gratings (as shown in fig. 2) or tilted gratings (as shown in fig. 3), the coverage of the film layer in the figure may be the outermost edge side surface of the rectangular gratings or the tilted gratings along the array direction or further extend and cover to a part of the waveguide 3 on the basis of the outermost edge side surface, the bottom surface of the grating is attached to the waveguide 3, and the film layer 6 satisfies: tt ≠ Tb, Tl ≠ Tr, where Tt is the top surface film thickness of the grating, Tb is the surface film thickness of the waveguide 3, Tl is the left surface film thickness of the grating, Tr is the right surface film thickness of the grating, Tl and Tr are opposite surfaces, and Tb and Tt are opposite surfaces.

As shown in fig. 4 and 6, in the case of using a rectangular grating, the grating period of the rectangular grating of fig. 4 is 390nm, the modulation depth is 350nm, and the duty ratio is 58%; the rectangular grating of fig. 6 has a grating period of 369.7nm, a modulation depth of 191.8nm and a duty cycle of 36.8%. Fig. 4 shows a gray curve (E) indicating diffraction efficiencies at different incident angles when the film layer 6 is not added in the prior art, where the average efficiency is only 17.86% and the uniformity error is 2.82% when the incident angle is in the range of-10 ° to 10 °; in fig. 4, the black curve (E') shows diffraction efficiencies at different incident angles when Tl is 56nm, Tb is 80nm, Tt is 60nm, and Tr is 60nm, the average efficiency is 44.7%, the overall average efficiency is increased from 17.86% to 44.7%, and the uniformity error is substantially maintained. In fig. 6, the gray curve (efficiency 1) is the diffraction efficiency at different incident angles when Tl is 79nm, Tb is 36nm, Tt is 10nm, and Tr is 10nm, and when the incident angle is in the range of-10 ° to 10 °, the average efficiency is 41.3%, and the uniformity error remains substantially constant; the black curve (efficiency 2) in fig. 6 shows diffraction efficiencies at different incident angles when Tl is 74nm, Tb is 42nm, Tt is 15nm, and Tr is 15nm, and the average efficiency is 46%, and the uniformity error remains substantially unchanged. Therefore, after the film layer is added, the average efficiency of the rectangular grating can be improved, meanwhile, the consistency error is basically unchanged, and the method has high efficiency and high uniformity.

As shown in fig. 5 and 7, in the case of using the tilted grating, the tilt angle of the tilted grating in fig. 5 is 33 °, the grating period is 390nm, the modulation depth is 350nm, and the duty ratio is 58%; the tilt angle of the tilted grating of fig. 7 was 34.5 °, the grating period was 372nm, the modulation depth was 314nm, and the duty cycle was 44.65%. Fig. 5 shows a gray curve (E) indicating diffraction efficiencies at different incident angles when the film layer 6 is not added in the prior art, and when the incident angle is in the range of-10 ° to 10 °, the average efficiency can reach 72.3%, but the uniformity error is 14.9%; the black curve (E') in fig. 5 shows the diffraction efficiency at different incident angles when the film layer 6 is added, the average efficiency is 80.75%, the uniformity error is 6.28%, the average efficiency is increased from 72.3% to 80.75%, and the uniformity error is decreased from 14.5% to 6.28%. The gray curve (efficiency 1) in fig. 7 is the diffraction efficiency at different incident angles when Tl is 23nm, Tb is 10nm, Tt is 88nm, and Tr is 45.6nm, and when the incident angle is in the range of-10 ° to 10 °, the average efficiency is 82.5% and the uniformity error is 7.2%; in fig. 7, the black curve (efficiency 2) is diffraction efficiency at different incident angles when Tl is 10nm, Tb is 25nm, Tt is 83nm, and Tr is 90nm, and the average efficiency is 85% and the uniformity error is 8.9%. For tilted gratings, the average efficiency can be improved and the consistency error can be reduced.

In summary, by covering the coupling-in element or the coupling-out element with the film layers, and plating the film layers on different side surfaces with different thicknesses, and selecting the film layers from the high-refractive-index light-transmitting material, the average efficiency and uniformity can be further improved, so that the high average efficiency and low uniformity error can be considered under different incident angles, and the coupling-out image with high brightness and high imaging quality can be obtained. It should be noted that the coupling-in element 2 and the coupling-out element 4 may also be triangular gratings or blazed gratings, or different types of gratings, or the gratings may be designed according to actual requirements.

The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.

The above-mentioned embodiments only express the more specific and detailed embodiments described in the present application, but not be construed as limiting the claims. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the concept of the present application, which falls within the scope of protection of the present application. Therefore, the protection scope of the present patent shall be subject to the appended claims.