WO2020177224A1

WO2020177224A1 - Diffraction gratings having multi-rectangular structure period and ar imaging device

Info

Publication number: WO2020177224A1
Application number: PCT/CN2019/088998
Authority: WO
Inventors: 宋强; 王景; 苏鹏华; 马国斌; 汪涛
Original assignee: 深圳珑璟光电技术有限公司
Priority date: 2019-03-07
Filing date: 2019-05-29
Publication date: 2020-09-10
Also published as: CN109696717A

Abstract

Diffraction gratings that have a multi-rectangular structure period and an AR imaging device, which relate to the technical field of diffraction gratings, and mainly solve the technical problems in which existing diffraction gratings are difficult to process, and have weak uniformity, low diffraction efficiency, and low degrees of freedom. The diffraction gratings that have the multi-rectangular structure period are comprised in each grating period (T). A plurality of rectangles (Z1, Z3, Z5) are etched on a substrate of each of the diffraction gratings, and the line width of each rectangle and pitches (Z2, Z4) of adjacent rectangles are different. The present diffraction gratings have the advantages of a relatively high diffraction efficiency, relatively high uniformity, easy processing, etc. The AR imaging device successively comprises an image generation part (1), a collimation part (2), a coupling-in grating (32), a waveguide plate (31), a coupling-out grating (33) and an image imaging part (4) according to a light transmission direction, and the coupling-in grating (32) and the coupling-out grating (33) are diffraction gratings that have the multi-rectangular structure period. The diffraction gratings that have the multi-rectangular structure period are applied into the AR imaging device, which meets the demand for the high-definition and high-efficient display effects of AR.

Description

Diffraction grating with multiple rectangular structure periods and AR imaging device

Technical field

The invention relates to the technical field of diffraction gratings, in particular to a diffraction grating with multiple rectangular structural periods and an AR imaging device.

Background technique

With the development of science and technology, AR (Augmented Reality), as a very smart and portable display technology, is slowly reaching the public. Its main feature is to superimpose virtual images on real scenes, which can make people You can also watch the real scene while watching the virtual screen. It is precisely because of the above characteristics of AR display that this technology is now more and more widely used in the security, education, medical, military, industrial, entertainment and other industries.

The grating waveguide solution is currently a mainstream solution for AR display, but the existing diffraction grating design solutions have many shortcomings, such as low degree of freedom, low diffraction efficiency, difficult to control diffraction uniformity, and difficulty in designing products and processing.

technical problem

The purpose of the present invention is to provide a diffraction grating and AR imaging device with multiple rectangular structure periods, which can solve many of the above shortcomings and has the advantages of higher diffraction efficiency, higher uniformity, and easy processing.

Technical solutions

A diffraction grating with multiple rectangular structure periods. In each grating period, a plurality of rectangles are etched on the substrate of the diffraction grating, and the line width of each rectangle and the distance between adjacent rectangles are equal different.

Optionally, in each grating period, the number of the rectangles is greater than or equal to 2.

Optionally, within different grating periods, the structures etched on the substrate of the diffraction grating are all the same.

Optionally, the angle of incidence of the diffraction grating is 25°-55°.

Optionally, TiO2 is plated on the diffraction grating.

Optionally, in each grating period, the number of rectangles, the line width of the rectangles, and the distance between adjacent rectangles are all determined according to actual product requirements.

An AR imaging device includes an image generation part, a collimation part, a grating waveguide part, and an image imaging part; the grating waveguide part includes a waveguide sheet, a coupling-in grating, and a coupling-out grating; the coupling-in grating and the coupling-out grating Gratings are respectively distributed at both ends of the waveguide sheet; the coupling-in grating and the coupling-out grating are both diffraction gratings with multiple rectangular structure periods;

The light emitted by the image generating part passes through the collimating part, exits as parallel light, and enters the coupling grating at a set angle; after being diffracted by the coupling grating, it enters the waveguide sheet, and Forward transmission in the form of total reflection, and then output through the coupling-out grating, and finally form an image in the image imaging section.

Optionally, the grating waveguide portion includes a total of three layers of waveguide plates for transmitting R, G, and B three-color light, and the coupling grating and the coupling grating and the two ends of each layer of the waveguide plate are respectively distributed Coupling the grating.

Optionally, the grating waveguide portion further includes an extended grating; the extended grating and the coupling-out grating are located at the same end of the waveguide sheet, and in the vertical direction, the extended grating is located between the coupling-out grating On; wherein, the extended grating is a diffraction grating with multiple rectangular structure periods.

Optionally, the image generating part is a display screen that generates a display screen; the collimating part is an optical system composed of multiple optical lenses.

Beneficial effect

The invention provides a diffraction grating with multiple rectangular structure periods and an AR imaging device. In the present invention, multiple rectangles are etched on the substrate of the diffraction grating in each grating period, and the line width of each rectangle and the distance between adjacent rectangles are different, so that the diffraction grating provided by the present invention has a higher Diffraction efficiency, high uniformity, easy processing, etc.; the present invention applies a diffraction grating with multiple rectangular structure periods to an AR imaging device to meet the requirements for AR high-definition and high-efficiency display effects.

Description of the drawings

In order to explain the embodiments of the present invention or the technical solutions in the prior art more clearly, the following will briefly introduce the drawings needed in the embodiments. Obviously, the drawings in the following description are only some of the present invention. Embodiments, for those of ordinary skill in the art, without creative labor, other drawings can be obtained from these drawings.

Fig. 1 is a topography diagram of a common rectangular grating in the prior art;

Figure 2 is a profile diagram of a common tilted grating in the prior art; Figure 2(a) is a profile view of a common tilted grating in the prior art; Figure 2(b) is another common tilted grating profile in the prior art Appearance map

3 is a topography diagram of a diffraction grating with multiple rectangular structure periods according to an embodiment of the present invention;

4 is a graph showing the relationship between the incident angle of light and the diffraction efficiency of a diffraction grating according to an embodiment of the present invention;

5 is a schematic structural diagram of an AR imaging device according to an embodiment of the present invention;

6 is an actual simulation diagram of an AR imaging device according to an embodiment of the present invention;

Figure 7 is an actual illuminance diagram of an embodiment of the present invention;

Fig. 8 is a top view of an expanded grating on a waveguide sheet according to an embodiment of the present invention.

The best mode of the invention

The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work shall fall within the protection scope of the present invention.

In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

The existing diffraction grating design scheme is mainly to design the appearance of the diffraction grating into a rectangular or inclined pattern.

For traditional rectangular gratings, although the processing difficulty is relatively low, the diffraction efficiency is also low, and it is difficult to achieve the requirements for high-definition and high-efficiency AR display effects. For tilted gratings, although the diffraction efficiency is higher than that of traditional rectangular gratings, its processing is quite difficult. At present, only a very small number of processors at home and abroad can manufacture them, and the cost is relatively high.

As shown in Figure 1-2, T is a period of a common grating. Since the diffraction efficiency of grating is related to wavelength and incident angle, it is obvious that the incident angle of rectangular grating has been fixed, so there is a big limitation in improving the diffraction efficiency; and although the inclined grating can change the inclination angle to make the grating diffraction efficiency reach the design However, the processing of gratings with oblique topography is more difficult and costly.

Based on this, the present invention proposes a diffraction grating with multiple rectangular structure periods, which aims to solve the difficulty in processing and improve the diffraction efficiency of the grating.

Embodiments of the invention

Example 1

In the diffraction grating with multiple rectangular structure periods provided by this embodiment, in each grating period, a plurality of rectangles are etched on the substrate of the diffraction grating, and the line width of each rectangle and the distance between adjacent rectangles are different. However, in different grating periods, the structure etched on the substrate of the diffraction grating is the same. Among them, in each grating period, the number of rectangles, the line width of rectangles, and the distance between adjacent rectangles are all determined according to actual product requirements.

Preferably, in each grating period, the number of rectangles is greater than or equal to 2.

Preferably, the angle of incidence of the diffraction grating is 25°-55°.

Preferably, TiO2 is plated on the diffraction grating.

Example 2

As shown in FIG. 3, T is one period of the diffraction grating with multiple rectangular structure periods provided in this embodiment. The main feature of the diffraction grating provided by this embodiment is that in a grating period T, N small rectangles (N is greater than or equal to 2) are etched on the substrate, and the line width and spacing of the N small rectangles are different, such as Z1, Z3 The width of Z5 is different, and the width of Z2 and Z4 are different, which makes it easy to process and also has higher diffraction efficiency.

The design concept of this embodiment is mainly to use the vector electromagnetic diffraction theory to optimize the break points of each small rectangle with diffraction efficiency and angular uniformity as the evaluation objective, so as to meet the design requirements. Therefore, the line width and spacing of N small rectangles are determined according to actual product requirements.

FIG. 4 shows the relationship between the light incident angle and the diffraction efficiency of a diffraction grating designed based on the multi-rectangular structure period provided by this embodiment. The diffraction grating is actually a specific form of a one-dimensional Daman grating. Due to the different incident angles of light, the diffraction efficiency of the grating will also be different. When the angle of incidence is 25°-55°, the diffraction efficiency of the diffraction grating can reach more than 77%, and the highest diffraction efficiency can reach more than 81.5%.

Compared with the existing diffraction gratings, the rectangular gratings in the traditional diffraction gratings have a simple rectangular shape, which is less difficult to process. However, because the shape is perpendicular to the substrate and the angle is fixed, the design variables are only within one period. Duty cycle, too few variables, the design space that can improve diffraction efficiency and uniformity is too small; for tilted gratings, the shape is not fixed and can be determined by the designer, and the variable that can be designed removes the space in a space In addition, there is the angle between the oblique side and the substrate. Compared with the rectangular grating, the design space for improving the diffraction efficiency and uniformity is larger. However, it is also because the oblique side has a certain angle with the substrate, so it is inclined. The processing of the grating will be more difficult; while the diffraction grating with multiple rectangular structure periods described in this embodiment has a microscopic appearance perpendicular to the substrate, and the processing difficulty is relatively low. At the same time, the designable variables (Z1, Z2, Z3, Z4, Z5). Therefore, the diffraction grating provided by this embodiment reduces the processing difficulty while improving the diffraction efficiency and uniformity.

Example 3

As shown in Figures 5 and 6, the AR imaging device provided by this embodiment includes an image generation unit 1, a collimation unit 2, a grating waveguide unit 3, and an image imaging unit 4; the grating waveguide unit 3 includes a waveguide sheet 31, a coupling Incoming grating 32 and outgoing grating 33; Incoming grating 32 and outgoing grating 33 are respectively distributed on both ends of the waveguide plate 31, that is, the incoming grating 32 is distributed on one end of the waveguide plate 31, and the outgoing grating 33 is distributed on the waveguide plate 31 The other end; the coupling-in grating 32 and the coupling-out grating 33 are diffraction gratings with multiple rectangular structural periods.

The light emitted by the image generating unit 1 passes through the collimating unit 2 and exits as parallel light and enters the coupling grating 32 at a set angle; after being diffracted by the coupling grating 32, it enters the waveguide sheet 31 and is in the form of total reflection It is transmitted forward, and then output through the coupling-out grating 33, and finally forms an image in the image imaging section 4.

For the wavelengths of different colored lights, the diffraction grating has different diffraction efficiencies. In this embodiment, preferably, the grating waveguide portion 3 includes a total of three layers of waveguide plates 31 for transmitting R, G, and B three-color light, and each A coupling-in grating 32 and a coupling-out grating 33 are respectively distributed at both ends of the layered waveguide sheet 31. When the grating waveguide section 3 includes three layers of waveguide plates 31, the parallel light enters the coupling grating 32 at a certain angle and then enters the three waveguide plates 31 of R, G, and B in three colors, and transmits forward in the form of total reflection. , And then output through the coupling out grating 33.

The image generating part is a display screen that generates a display image, such as Lcos, OLED, MicroOLED, etc.; the collimating part is an optical system composed of multiple optical lenses. Among them, the lens can be made of glass material or resin material or a combination of the two; the image imaging unit 4 is Lcos.

FIG. 7 is a graph of the actual illuminance uniformity of the display area in this embodiment.

Example 4

This embodiment is further defined on the basis of embodiment 3. In addition to all the components of embodiment 3, the grating waveguide section 3 also includes an expanded grating 34; as shown in FIG. 8, the expanded grating 34 and the coupling-out grating 33 are located At the same end of the same waveguide sheet 31, and in the vertical direction, the extended grating 34 is located above the outcoupling grating 33; among them, the extended grating 34 is also a diffraction grating with multiple rectangular structure periods.

In this embodiment, the coupling grating 32 is an integral grating for coupling the light emitted by the image generating unit 1 into the waveguide sheet 31. The light coupled into the waveguide sheet 31 follows the law of refraction and reflection on the waveguide sheet 31. Inwardly, it propagates to the extended grating 34, and the extended grating 34 performs exit pupil expansion processing on the light, which increases the field angle of the light passing through the grating, and finally the light enters the coupling-out grating 33 and is coupled out of the grating waveguide 3.

Both the expanded grating 34 and the out-coupling grating 33 include five regions with gradually increasing diffraction efficiency, which are used to make the brightness uniformity of the final image after the expanded output consistent.

In order to further improve the diffraction efficiency of the grating, the multi-rectangular structure period diffraction grating in Embodiment 2-4 is coated with a film with higher reflectivity such as TiO2 to improve the overall diffraction efficiency and uniformity of the grating.

The various embodiments in this specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments, and the same or similar parts between the various embodiments can be referred to each other.

In this article, specific examples are used to illustrate the principles and implementation of the present invention. The description of the above examples is only used to help understand the method and core idea of the present invention; at the same time, for those of ordinary skill in the art, according to the present invention There will be changes in the specific implementation and scope of application. In summary, the content of this specification should not be construed as limiting the present invention.

Claims

A diffraction grating with multiple rectangular structure periods, characterized in that, in each grating period, a plurality of rectangles are etched on the substrate of the diffraction grating, and the line width of each rectangle is equal to that of adjacent ones. The pitches of the rectangles are all different.
The diffraction grating according to claim 1, wherein in each grating period, the number of the rectangles is greater than or equal to 2.
3. The diffraction grating according to claim 1, wherein the structure etched on the substrate of the diffraction grating is the same in different grating periods.
The diffraction grating of claim 1, wherein the angle of incidence of the diffraction grating is 25°-55°.
The diffraction grating of claim 1, wherein the diffraction grating is plated with TiO2.
The diffraction grating according to claim 1, wherein in each grating period, the number of rectangles, the line width of the rectangles, and the distance between adjacent rectangles are all determined according to actual product requirements .
An AR imaging device, characterized in that the AR imaging device includes an image generation part, a collimation part, a grating waveguide part and an image imaging part; the grating waveguide part includes a waveguide sheet, a coupling-in grating and a coupling-out grating; The coupling-in grating and the coupling-out grating are respectively distributed on both ends of the waveguide sheet; the coupling-in grating and the coupling-out grating are both diffraction gratings with multiple rectangular structure periods;

The light emitted by the image generating part passes through the collimating part, exits as parallel light, and enters the coupling grating at a set angle; after being diffracted by the coupling grating, it enters the waveguide sheet, and Forward transmission in the form of total reflection, and then output through the coupling-out grating, and finally form an image in the image imaging section.
8. The AR imaging device according to claim 7, wherein the grating waveguide portion includes a total of three layers of waveguide plates for transmitting R, G, and B light, and both ends of each layer of the waveguide plate The coupling-in grating and the coupling-out grating are respectively distributed.
8. The AR imaging device according to claim 7, wherein the grating waveguide section further comprises an extended grating; the extended grating and the out-coupling grating are located at the same end of the waveguide sheet and are in a vertical direction, The extended grating is located on the out-coupling grating; wherein, the extended grating is a diffraction grating with multiple rectangular structure periods.
8. The AR imaging device according to claim 7, wherein the image generating part is a display screen that generates a display screen; and the collimating part is an optical system composed of a plurality of optical lenses.