CN115373062A - Diffractive optical waveguide device and method therefor - Google Patents

Diffractive optical waveguide device and method therefor Download PDF

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Publication number
CN115373062A
CN115373062A CN202110534774.2A CN202110534774A CN115373062A CN 115373062 A CN115373062 A CN 115373062A CN 202110534774 A CN202110534774 A CN 202110534774A CN 115373062 A CN115373062 A CN 115373062A
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light
waveguide layer
waveguide
layer
grating structure
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黄鹏
黄河
张雅琴
楼歆晔
林涛
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Shanghai Kunyou Technology Co ltd
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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/0001—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems
    • G02B6/0011—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems the light guides being planar or of plate-like form
    • G02B6/0033—Means for improving the coupling-out of light from the light guide
    • G02B6/005—Means for improving the coupling-out of light from the light guide provided by one optical element, or plurality thereof, placed on the light output side of the light guide
    • G02B6/0055—Reflecting element, sheet or layer
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/0001—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems
    • G02B6/0011—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems the light guides being planar or of plate-like form
    • G02B6/0013—Means for improving the coupling-in of light from the light source into the light guide
    • G02B6/0023—Means for improving the coupling-in of light from the light source into the light guide provided by one optical element, or plurality thereof, placed between the light guide and the light source, or around the light source
    • G02B6/0026—Wavelength selective element, sheet or layer, e.g. filter or grating
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/0001—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems
    • G02B6/0011—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems the light guides being planar or of plate-like form
    • G02B6/0033—Means for improving the coupling-out of light from the light guide
    • G02B6/005—Means for improving the coupling-out of light from the light guide provided by one optical element, or plurality thereof, placed on the light output side of the light guide
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/0001—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems
    • G02B6/0011—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems the light guides being planar or of plate-like form
    • G02B6/0065—Manufacturing aspects; Material aspects
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/0001—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems
    • G02B6/0011—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems the light guides being planar or of plate-like form
    • G02B6/0075—Arrangements of multiple light guides
    • G02B6/0076—Stacked arrangements of multiple light guides of the same or different cross-sectional area

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  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Optical Couplings Of Light Guides (AREA)

Abstract

A diffractive optical waveguide apparatus and method. The diffraction light waveguide device comprises an optical waveguide component, a grating structure component and a selective reflection component. The optical waveguide assembly includes a first waveguide layer and a second waveguide layer stacked on each other. The grating structure assembly includes an incoupling grating structure and an outcoupling grating structure disposed on the first waveguide layer, wherein the incoupling grating structure is used for diffracting a light beam to couple into the first waveguide layer, and the outcoupling grating structure is used for diffracting the light beam to couple out the first waveguide layer. The selective reflection assembly includes a first selective reflection layer stacked between the first waveguide layer and the second waveguide layer, and the first selective reflection layer is used for selectively reflecting light rays with a first diffraction angle in the light beam and selectively transmitting light rays with a second diffraction angle in the light beam, wherein the first diffraction angle is larger than the second diffraction angle so as to effectively improve the color uniformity of the light guide.

Description

Diffractive optical waveguide device and method therefor
Technical Field
The present invention relates to the field of augmented reality technology, and more particularly to a diffractive light waveguide apparatus and method.
Background
Augmented reality is a technology for seamlessly integrating virtual world information and real world information, and the pixels on a micro projector are projected to human eyes through an optical display screen and see the real world through the optical display screen at the same time, namely, virtual content provided by the micro projector and a real environment are overlaid to the same picture or space in real time to exist at the same time, so that a user obtains the experience of fusion of virtual and reality.
In order to realize an augmented reality display scheme, an optical waveguide technology is currently generally used, that is, when the refractive index of a transmission medium is greater than that of a surrounding medium and the incident angle in the waveguide is greater than a total reflection critical angle, light can be totally reflected within the waveguide to be transmitted without leakage. Thus, after image light from the projector is coupled into the waveguide, the image light continues to propagate within the waveguide without loss until it is coupled out by a subsequent structure. Currently, waveguides on the market are generally classified into geometric array waveguides and diffractive optical waveguides, wherein the diffractive optical waveguides are further classified into volume holographic waveguides and surface relief grating waveguides. While the nature of diffractive optical waveguides is to couple incident light into or out of the waveguide through the grating, surface relief grating waveguides offer significant advantages in many scenarios due to the extremely high degree of design freedom and the mass producibility afforded by nanoimprint processing.
Specifically, technical parameters of a diffraction light waveguide (hereinafter, referred to as an AR waveguide) in augmented reality mainly include a field angle FOV, a viewing distance eye relief, an eye box size eye box, and the like. The field angle is typically expressed in terms of a diagonal angle, e.g., 40 °, corresponding to a field angle of about 35 ° (H) 20 ° (V) for a scale of 16; the visual range is usually about 20-25mm, and the wearing requirements of most users can be basically met, including the users wearing myopia or hyperopia glasses; the orbit size determines the range of free movement of the user's eyes, and larger sizes are less likely to lose images, and are therefore more adaptable. The horizontal size of the orbit needs to be capable of adapting to the range of the exit pupil distance of human eyes and leave enough margin for different horizontal wearing references of users, the vertical size of the orbit needs to be adapted to the vertical wearing reference of the users, and the orbit size of 15mm (H) × 10mm (V) is generally considered to meet the basic requirements of user experience. The AR waveguide takes high efficiency and good uniformity as optimization targets, and the purpose of high efficiency is to achieve higher luminance output under the same input of the micro projector, so that the picture seen by human eyes is sufficiently bright; the uniformity includes FOV uniformity, i.e., the full-field picture viewed by human eyes has better brightness and color uniformity, and eyebox uniformity, i.e., the brightness difference received by human eyes at different positions of the eyebox (or when worn by users with different interpupillary distances and different heights of the nose bridge) is as small as possible, and it is expected that the different positions have better FOV uniformity.
However, since the grating is a diffractive optical device operating for a certain wavelength, the incoupling gratings in the existing AR waveguides necessarily have different diffractive properties for light of different wavelengths, e.g. different diffraction angles for light of different wavelengths are generated, i.e. the larger the wavelength, the larger the diffraction angle. As shown in fig. 1, when the coupling-in grating 12P of the conventional AR waveguide 1P diffracts the same image light 100P to generate a first coupling-in light 101P with a larger wavelength and a second coupling-in light 102P with a smaller wavelength, such that the diffraction angle of the first coupling-in light 101P is larger than that of the second coupling-in light 102P, during the total reflection transmission in the waveguide substrate 11P, the total reflection period length P corresponding to the first coupling-in light 101P is equal to the total reflection period length P 1 A total reflection period length P greater than that of the second coupled light 102P 2 . When the first incoupling light 101P and the second incoupling light 102P reach the outcoupling grating 13P, respectively, each time the first incoupling light 101P and the second incoupling light 102P encounter the outcoupling grating 13P, a first outcoupling light 103P and a second outcoupling light 104P are generated, respectively, so that the distance between two adjacent first outcoupling lights 103P is equal to the total reflection period length P corresponding to the first incoupling light 101P 1 And the distance between two adjacent second coupled-out lights 104P is equal to the total reflection period length P corresponding to the second coupled-in light 102P 2 。
In other words, the pitch of the first outcoupled light 103P is greater than the pitch of the second outcoupled light 104P, i.e. the second outcoupled light 104P is distributed more densely, and the first outcoupled light 103P is distributed more sparsely, so that the conventional AR waveguide 1P has less first outcoupled light 103P due to the large pitch of the first outcoupled light 103P, even no first outcoupled light 103P enters the human eye, while the conventional AR waveguide 1P has more second outcoupled light 104P enters the human eye due to the small light pitch of the second outcoupled light 104P. In this way, different diffraction angles may result in different total reflection period lengths, and as a result of the different total reflection period lengths, there is a difference in density of coupled-out light rays with different wavelengths (colors), that is, the smaller the wavelength is, the denser the wavelength is, the larger the wavelength is, the more sparse the wavelength is, which is reflected as color non-uniformity on a color image synthesized by light of various colors displayed by the existing AR waveguide 1P, resulting in poor color uniformity of an augmented reality device configured with the existing AR waveguide 1P, and failing to provide a high-quality visual experience for a user.
Disclosure of Invention
An advantage of the present invention is to provide a diffractive optical waveguide device and a method thereof, which can effectively improve color uniformity of an optical waveguide.
Another advantage of the present invention is to provide a diffractive optical waveguide device and a method thereof, wherein in an embodiment of the present invention, the diffractive optical waveguide device can equalize the densities of the coupled-out light beams with different wavelengths (colors) to improve the color uniformity of the displayed color image.
Another advantage of the present invention is to provide a diffractive optical waveguide device and a method thereof, wherein in an embodiment of the present invention, the diffractive optical waveguide device can increase the total reflection period length of the short-wavelength light by increasing the number of waveguide layers, so that the total reflection period lengths of the light with different wavelengths are substantially consistent, which is helpful for optimizing the color uniformity of the optical waveguide.
Another advantage of the present invention is to provide a diffractive optical waveguide device and a method thereof, wherein in an embodiment of the present invention, the diffractive optical waveguide device can increase the coupling-out density of long-wavelength light by decreasing the effective thickness of the waveguide layer, and can decrease the coupling-out density of short-wavelength light by increasing the effective thickness of the waveguide layer, so that the coupling-out densities of the long-wavelength light and the short-wavelength light are consistent, and a user can conveniently view a color image with high color uniformity.
Another advantage of the present invention is to provide a diffractive optical waveguide device and a method thereof, wherein in an embodiment of the present invention, the diffractive optical waveguide device can adjust effective thicknesses of waveguide layers corresponding to light with different wavelengths through a selective reflection layer, so that coupling-out densities of the light with different wavelengths are substantially the same, thereby optimizing color uniformity of a color image and improving image quality.
Another advantage of the present invention is to provide a diffractive optical waveguide device and a method thereof, wherein in an embodiment of the present invention, the diffractive optical waveguide device can modulate the equivalent total reflection period lengths of the light beams with different wavelengths in the optical waveguide, so that the coupled-out light beams with different wavelengths have approximately equal light coupling-out intervals, thereby improving color uniformity and improving the visual experience of users.
Another advantage of the present invention is to provide a diffractive optical waveguide device and a method thereof, wherein in an embodiment of the present invention, the diffractive optical waveguide device can modulate the coupling-out densities of different colors of light by adding a waveguide layer and a selective reflection layer to obtain mutually close coupling-out ray densities, thereby improving the color uniformity of the optical waveguide.
Another advantage of the present invention is to provide a diffractive optical waveguide device and a method thereof, wherein in an embodiment of the present invention, the diffractive optical waveguide device can achieve good energy distribution uniformity at the entrance pupil of the human eye, which helps to reduce the image dark angle problem caused by the non-uniform field angle.
It is another advantage of the present invention to provide a diffractive optical waveguide apparatus and method thereof wherein expensive materials or complex structures are not required in the present invention in order to achieve the above objects. The present invention, therefore, successfully and effectively provides a solution that not only provides a diffractive optical waveguide apparatus and method therefor, but also increases the practicality and reliability of the diffractive optical waveguide apparatus and method therefor.
To achieve at least one of the above advantages or other advantages and objects, the present invention provides a diffractive light waveguide apparatus, including:
an optical waveguide assembly, wherein the optical waveguide assembly includes a first waveguide layer and a second waveguide layer stacked on each other;
a grating structure assembly, wherein the grating structure assembly comprises an incoupling grating structure and an outcoupling grating structure disposed on the first waveguide layer, wherein the incoupling grating structure is configured to diffract a light beam to couple into the first waveguide layer, and the outcoupling grating structure is configured to diffract the light beam to couple out the first waveguide layer; and
a selective reflection assembly, wherein the selective reflection assembly comprises a first selective reflection layer stacked between the first waveguide layer and the second waveguide layer, and the first selective reflection layer is configured to selectively reflect light of the light beam having a first diffraction angle and selectively transmit light of the light beam having a second diffraction angle, wherein the first diffraction angle is greater than the second diffraction angle.
According to an embodiment of the present application, the incoupling grating structure is configured to diffract the image light into a first incoupling light with a larger diffraction angle and a second incoupling light with a smaller diffraction angle, and the first selective reflection layer is configured to reflect the first incoupling light and transmit the second incoupling light, so that the first incoupling light propagates in the first waveguide layer by equivalent total reflection, and the second incoupling light propagates in the first waveguide layer and the second waveguide layer by total reflection.
According to an embodiment of the application, the refractive index of the first waveguide layer is equal to the refractive index of the second waveguide layer.
According to an embodiment of the application, the thickness d of the first waveguide layer 1 And a thickness d of said second waveguide layer 2 The ratio between is implemented as:
Figure BDA0003069376300000041
whereinT is the period of the incoupling grating structure; n is the refractive index of the optical waveguide assembly; lambda [ alpha ] 1 Is the wavelength of the first coupled-in light; lambda [ alpha ] 2 Is the wavelength of the second coupled-in light.
According to an embodiment of the present application, the first selective reflection layer is for reflecting red and green light and transmitting blue light.
According to an embodiment of the present application, the optical waveguide assembly further includes a third waveguide layer stacked on the second waveguide layer, and the second waveguide layer is located between the first waveguide layer and the third waveguide layer, wherein the selective reflection assembly further includes a second selective reflection layer stacked between the second waveguide layer and the third waveguide layer, and the second selective reflection layer is used for selectively reflecting the light with the second diffraction angle in the light beam and selectively transmitting the light with the third diffraction angle in the light beam, wherein the second diffraction angle is larger than the third diffraction angle.
According to an embodiment of the present application, the incoupling grating structure is configured to diffract image light into first band light, second band light, and third band light with sequentially decreasing diffraction angles, wherein the first selective reflection layer is configured to reflect the first band light and transmit the second band light and the third band light, so that the first band light propagates within the first waveguide layer by equivalent total reflection, the second selective reflection layer is configured to reflect the second band light and transmit the third band light, so that the second band light propagates within the first waveguide layer and the second waveguide layer by equivalent total reflection, and the third band light propagates within the first waveguide layer, the second waveguide layer, and the third waveguide layer by total reflection.
According to an embodiment of the application, the thickness d of the first waveguide layer 1 And a thickness d of the third waveguide layer 3 The ratio between is implemented as:
Figure BDA0003069376300000051
wherein t is the period of the incoupling grating structure; n is the refractive index of the optical waveguide assembly; lambda [ alpha ] 1 Is the wavelength of the first band of wavelengths of light; lambda 2 Is the wavelength of the light in the second wavelength band; lambda 3 Is the wavelength of the third band of light.
According to an embodiment of the present application, the first selective reflection layer is configured to reflect red light and transmit green light and blue light, and the second selective reflection layer is configured to reflect green light and transmit blue light.
According to an embodiment of the application, the incoupling grating structure and the outcoupling grating structure are implemented as one-dimensional gratings or two-dimensional gratings formed on the surface of the first waveguide layer, respectively.
According to an embodiment of the application, the grating structure assembly further comprises a pupil-expanding grating structure arranged in the first waveguide layer, and the pupil-expanding grating structure is located in the coupling grating structure and the optical path between the coupling grating structures, for splitting the light coupled in by the coupling grating structure into different orders of diffracted light, so as to be transmitted to different positions of the coupling grating structure along different propagation directions.
According to an embodiment of the application, the incoupling grating structures and the outcoupling grating structures are formed side by side on the upper surface of the first waveguide layer, and the first selective reflection layer is glued between the lower surface of the first waveguide layer and the second waveguide layer.
According to an embodiment of the present application, the first selective reflection layer has wavelength selectivity for reflection of light.
According to an embodiment of the present application, the first selective reflection layer has a direction selectivity for the reflection of light.
According to another aspect of the present application, an embodiment of the present application further provides a method for optimizing color uniformity, comprising the steps of:
diffracting the image light to form first and second coupled-in lights coupled into the first waveguide layer, wherein a diffraction angle of the first coupled-in light is larger than that of the second coupled-in light;
reflecting the first coupled light from the first waveguide layer to enter the first waveguide layer for total reflection, so that the first coupled light is equivalently transmitted in the first waveguide layer in a total reflection manner back and forth;
transmitting the second coupling light from the first waveguide layer, so that the second coupling light enters the first waveguide layer for total reflection after entering the second waveguide layer superposed on the first waveguide layer, and then enters the first waveguide layer for total reflection, so that the second coupling light is transmitted in the first waveguide layer and the second waveguide layer in a back-and-forth total reflection manner; and
diffracting the transmitted first and second coupled-in lights to form a first coupled-out light and a second coupled-out light coupled out of the first waveguide layer.
According to an embodiment of the present application, the first coupled-in light is reflected and the second coupled-in light is transmitted by a first selective reflection layer stacked between the first waveguide layer and the second waveguide layer.
According to an embodiment of the present application, the thickness of the first waveguide layer and the thickness of the second waveguide layer are reasonably selected such that the equivalent total reflection period length corresponding to the first incoupling light is equal to the equivalent total reflection period length corresponding to the second incoupling light.
According to another aspect of the present application, an embodiment of the present application further provides a method for optimizing color uniformity, comprising the steps of:
diffracting the image light to form first, second, and third wavelength bands of light coupled into the first waveguide layer, wherein diffraction angles of the first, second, and third wavelength bands of light become smaller in order;
reflecting the first waveband light from the first waveguide layer to enter the first waveguide layer for total reflection, so that the first waveband light is transmitted back and forth in the first waveguide layer in an equivalent total reflection manner;
transmitting the second band of wavelengths and the third band of wavelengths from the first waveguide layer to enter a second waveguide layer stacked on the first waveguide layer;
reflecting the second band light from the second waveguide layer to enter the first waveguide layer for total reflection, so that the second band light is transmitted back and forth in the first waveguide layer and the second waveguide layer with equivalent total reflection;
transmitting the third band of light from the second waveguide layer to enter the first waveguide layer for total reflection after entering the third waveguide layer stacked on the second waveguide layer, so that the third band of light is transmitted back and forth in the first waveguide layer and the third waveguide layer in a total reflection manner; and
diffracting the transmitted first, second, and third bands of light to couple out of the first waveguide layer.
According to an embodiment of the present application, the first wavelength band light is reflected and the second wavelength band light and the third wavelength band light are transmitted through a first selective reflection layer laminated between the first waveguide layer and the second waveguide layer; and reflecting the second wavelength band light and transmitting the third wavelength band light through a second selective reflection layer stacked between the second waveguide layer and the third waveguide layer.
According to another aspect of the present application, an embodiment of the present application further provides a method of manufacturing a diffractive optical waveguide device, including the steps of:
arranging a grating structure assembly in the first waveguide layer, wherein an in-coupling grating structure in the grating structure assembly is used for diffracting the image light into light rays with a first diffraction angle and light rays with a second diffraction angle; and
and superposing a first selective reflection layer between the first waveguide layer and the second waveguide layer, wherein the first selective reflection layer is used for reflecting the light rays with the first diffraction angle and transmitting the light rays with the second diffraction angle, and the first diffraction angle is larger than the second diffraction angle.
According to an embodiment of the present application, the method for manufacturing a diffractive optical waveguide device further includes:
and superposing a second selective reflection layer between the second waveguide layer and the third waveguide layer, wherein the in-coupling grating structure is further configured to diffract the image light into light rays having a third diffraction angle, and the second selective reflection layer is configured to reflect the light rays having the second diffraction angle and transmit the light rays having the third diffraction angle, wherein the second diffraction angle is greater than the third diffraction angle.
According to an embodiment of the present application, the step of disposing the grating structure assembly in the first waveguide layer, wherein the in-coupling grating structure in the grating structure assembly is configured to diffract the image light into the light with the first diffraction angle and the light with the second diffraction angle, includes the steps of:
manufacturing a mother board, wherein the mother board is provided with a grating structure to be transferred corresponding to the grating structure assembly; and
and processing the surface of the first waveguide layer by using the master plate through a nano-imprinting method to form the grating structure assembly.
Further objects and advantages of the invention will be fully apparent from the ensuing description and drawings.
These and other objects, features and advantages of the present invention will become more fully apparent from the following detailed description, the accompanying drawings and the claims.
Drawings
Fig. 1 shows a schematic optical path diagram of a conventional optical waveguide device.
Fig. 2 is a perspective view of a diffractive optical waveguide device according to an embodiment of the present invention.
Fig. 3 shows a schematic optical path diagram of the diffractive optical waveguide device according to the above embodiment of the present invention.
Fig. 4 shows a schematic diagram of the principle that the diffractive optical waveguide device modulates the period length of total reflection according to the above embodiment of the present invention.
Fig. 5 is a schematic diagram showing a reflection spectrum of a selective reflection component in the diffractive light waveguide apparatus according to the above-described embodiment of the present application.
Fig. 6 and 7 show a first modified embodiment of the diffractive optical waveguide device according to the above-described embodiment of the present invention.
Fig. 8 is a schematic diagram showing a reflection spectrum of a selective reflection component in the diffractive light waveguide apparatus according to the above-described first modified embodiment of the present invention.
Fig. 9 shows a second variant implementation of the diffractive optical waveguide device according to the above-described embodiment of the present invention.
Fig. 10 shows a schematic structural diagram of a near-eye display device according to an embodiment of the present application, which is configured with the diffractive optical waveguide apparatus according to the above-described modified embodiment of the present application.
FIG. 11 is a flow chart illustrating a method of optimizing color uniformity according to an embodiment of the present application.
Fig. 12 shows a variant implementation of the method of optimizing color uniformity according to the above-described embodiment of the present application.
Fig. 13 and 14 are schematic flow charts of a method of manufacturing a diffractive optical waveguide device according to an embodiment of the present application.
Detailed Description
The following description is presented to disclose the invention so as to enable any person skilled in the art to practice the invention. The preferred embodiments in the following description are given by way of example only, and other obvious variations will occur to those skilled in the art. The underlying principles of the invention, as defined in the following description, may be applied to other embodiments, variations, modifications, equivalents, and other technical solutions without departing from the spirit and scope of the invention.
It will be understood by those skilled in the art that in the present disclosure, the terms "longitudinal", "lateral", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate orientations or positional relationships that are based on those shown in the drawings, which are merely for convenience in describing the present disclosure and to simplify the description, and do not indicate or imply that the device or element so referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus the terms above should not be construed as limiting the present disclosure.
In the present invention, the terms "a" and "an" are to be understood as meaning "one or more" in the claims and the description, that is, one element may be present in one embodiment, and another element may be present in plural in number. The terms "a" and "an" should not be construed as limiting the number unless the number of such elements is explicitly recited as one in the present disclosure, but rather the terms "a" and "an" should not be construed as being limited to only one of the number.
In the description of the present invention, it is to be understood that the terms "first," "second," and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance. In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "connected" and "connected" should be interpreted broadly, and may be, for example, a fixed connection, a detachable connection, or an integral connection; can be mechanically or electrically connected; they may be directly connected or indirectly connected through an intermediate. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.
In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.
In recent years, with the rapid development of augmented reality technology, devices or apparatuses capable of realizing augmented reality are becoming more popular and used. However, as shown in fig. 1, different diffraction angles result in different total reflection period lengths, and as a result of the different total reflection period lengths, there is a difference in density of coupled-out light beams with different wavelengths (colors), that is, the smaller the wavelength is, the denser the wavelength is, the larger the wavelength is, the more sparse the wavelength is, which is reflected as color unevenness on a color image synthesized by light of each color displayed by the existing AR waveguide 1P, resulting in poor color uniformity of an augmented reality device equipped with the existing AR waveguide 1P, and failing to provide a high-quality visual experience for a user.
In order to solve the above problems, the present application provides a diffractive optical waveguide device and method and an apparatus thereof, which can increase the total reflection period length of short wavelength light by increasing the number of waveguide layers, so that the coupling-out density of light with different wavelengths is balanced, thereby effectively improving the color uniformity of the optical waveguide. Specifically, as shown in fig. 2 to 5, a diffractive optical waveguide device 1 according to an embodiment of the present application is illustrated, wherein the diffractive optical waveguide device 1 may include an optical waveguide assembly 10, a grating structure assembly 20, and a selective reflection assembly 30, wherein the optical waveguide assembly 10 includes a first waveguide layer 11 and a second waveguide layer 12 stacked on each other; wherein the grating structure assembly 20 comprises an incoupling grating structure 21 and an outcoupling grating structure 22 arranged in the first waveguide layer 11, wherein the incoupling grating structure 21 is configured to diffract light beams for incoupling into the first waveguide layer 11, and the outcoupling grating structure 22 is configured to diffract the light beams for outcoupling out of the first waveguide layer 11; wherein the selective reflection component 30 includes a first selective reflection layer 31 stacked between the first waveguide layer 11 and the second waveguide layer 12, and the first selective reflection layer 31 is used for selectively reflecting light rays having a first diffraction angle in the light beam and selectively transmitting light rays having a second diffraction angle in the light beam, wherein the first diffraction angle is larger than the second diffraction angle.
Thus, as shown in fig. 3, when an image light beam 100 is projected to the incoupling grating structure 21 of the grating structure assembly 20, the incoupling grating structure 21 diffracts the image light 100 into a first incoupling light beam 101 with a larger wavelength and a second incoupling light beam 102 with a smaller wavelength, so as to incouple into the first waveguide layer 11,such that the diffraction angle θ of the first coupled-in light 101 1 Greater than the diffraction angle θ of the second coupled-in light 102 2 (ii) a Then, the first incoupling light 101 is reflected by the first selective reflection layer 31 to be transmitted back and forth within the first waveguide layer 11 to the outcoupling grating structure 22, and the second incoupling light 102 is transmitted through the first selective reflection layer 31 to be transmitted back and forth within the optical waveguide component 10 to the outcoupling grating structure 22 by total reflection; finally, the first incoupling light 101 is diffracted by the outcoupling grating structure 22 into first outcoupled light 103 for outcoupling the first waveguide layer 11, and the second outcoupled light 102 is diffracted by the outcoupling grating structure 22 into second outcoupled light 104 for outcoupling the first waveguide layer 11.
It is noted that, since the wavelength of the first coupled-in light 101 is greater than that of the second coupled-in light 102, the diffraction angle θ of the first coupled-in light 101 is larger than that of the second coupled-in light 102 1 Larger than the diffraction angle theta of the second coupled-in light 102 2 Therefore, if the first incoupled light 101 and the second incoupled light 102 propagate in the first waveguide layer 11 in a total reflection manner, the total reflection period length corresponding to the first incoupled light 101 is greater than the total reflection period length corresponding to the second incoupled light 102, resulting in that the outcoupled light with larger wavelength is more sparse, and the outcoupled light with smaller wavelength is more dense.
However, as shown in fig. 3 and fig. 4, the diffractive optical waveguide device 1 of the present application selectively reflects the first coupled-in light 101 and selectively transmits the second coupled-in light 102 by adding the second waveguide layer 12 and utilizing the first selective reflection layer 31, so that the first coupled-in light 101 still propagates in the first waveguide layer 11 in a back-and-forth reflective manner, and the equivalent total reflection period length p corresponding to the first coupled-in light 101 is made to be equal to the equivalent total reflection period length p 1 ' is equal to the total reflection period length corresponding to the first coupled-in light 101; the second incoupling light 102 propagates in the first waveguide layer 11 and the second waveguide layer 12 by total reflection, so that the equivalent total reflection period length p corresponding to the second incoupling light 102 2 ' is increased to be larger than the total reflection period corresponding to the second incoupling light 102Length of the period p 2 So that the equivalent total reflection period length p corresponding to the second coupled light 102 2 ' can approach, or even equal to, the equivalent total reflection period length p corresponding to the first coupled-in light 101 1 ', so as to achieve a balance between the coupling-out densities of the first coupled-out light 103 and the second coupled-out light 104, thereby obtaining the diffractive optical waveguide device 1 with better color uniformity.
In addition, the equivalent total reflection period length refers to a distance between two adjacent total reflection positions of the coupled light on the first waveguide layer 11, and then the equivalent total reflection period length corresponding to the coupled light with the same wavelength (diffraction angle) is in positive correlation with the effective thickness of the waveguide layer, that is, the equivalent total reflection period length p =2h × tan θ, where h is the effective thickness of the waveguide layer and θ is the diffraction angle. That is to say, the equivalent total reflection period length p corresponding to the first coupled-in light 101 in the present application 1 ' is in positive correlation with the thickness of the first waveguide layer 11, and the equivalent total reflection period length p corresponding to the second incoupling light 102 2 ' is positively correlated to the sum of the thicknesses of the first waveguide layer 11 and the second waveguide layer 12.
Preferably, the refractive index of the first waveguide layer 11 is equal to the refractive index of the second waveguide layer 12, e.g. the refractive index n of the optical waveguide assembly 10 is between 1.4 and 2.3. It is understood that the optical waveguide assembly 10 can be, but is not limited to being, implemented by a glass material, so as to allow ambient light to be seen by human eyes through the optical waveguide assembly 10 while coupling-in light is reflectively transmitted back and forth within the optical waveguide assembly 10 to be coupled out, thereby facilitating the user to obtain an augmented reality experience. Of course, in other examples of the present application, the optical waveguide assembly 10 may also be, but is not limited to be, implemented to be made of a light-transmitting resin material, a light-transmitting polymer material, or the like. In addition, the refractive index of first waveguide layer 11 may also be different from the refractive index of second waveguide layer 12.
In an example of the present application, as shown in fig. 3, light of two wavelengths (for example, the wavelength of the first incoupling light 101 is 625nm, and the wavelength of the second incoupling light 102 is 465 nm) is transmittedFor example, the following steps are carried out: first, a waveguide substrate with a suitable thickness is selected as the first waveguide layer 11, so that the equivalent total reflection period length p corresponding to the first incoupling light 101 1 ' sufficiently small to ensure that a sufficient amount of said first outcoupled light 103 is coupled out of said first waveguide layer 11 into the human eye; next, a waveguide substrate having a suitable thickness is selected as the second waveguide layer 12 to be stacked below the first waveguide layer 11, and a reflective film capable of reflecting the first incoupling light 101 and transmitting the second incoupling light 102 is selected as the first selective reflection layer 31 to be stacked between the first waveguide layer 11 and the second waveguide layer 12, so that the first incoupling light 101 is transmitted by equivalent total reflection only within the first waveguide layer 11, and the second incoupling light 102 is transmitted by total reflection within the first waveguide layer 11 and the second waveguide layer 12. Thus, it can be seen that: an equivalent total reflection period length p corresponding to the first coupled light 101 1 ' is implemented as:
Figure BDA0003069376300000121
the equivalent total reflection period length p corresponding to the second coupled light 102 2 ' is implemented as:
Figure BDA0003069376300000122
wherein: h is the effective thickness of the optical waveguide assembly 10; d 2 The thickness of the second waveguide layer 12; t is the period of the incoupling grating structure 21; n is the refractive index of the optical waveguide assembly 10; lambda [ alpha ] 1 And λ 2 Respectively the wavelength of the first incoupling light 101 and the wavelength of the second incoupling light 102.
More preferably, the equivalent total reflection period length p corresponding to the first coupled-in light 101 1 ' equal to the equivalent total reflection period length p corresponding to the second incoupling light 102 2 ’。
At this time, due to the first selective reflectionThe thickness of layer 31 is typically much smaller than the thickness d of said first waveguide layer 11 1 As said thickness d of the first waveguide layer 11 1 Between 0.4mm and 0.15mm, whereas the thickness of the first selective reflection layer 31 is typically between 50nm and 400nm, the thickness of the first selective reflection layer 31 is negligible, i.e. d 1 ＝h-d 2 (ii) a The ratio between the thickness of said first waveguide layer 11 and the thickness of said second waveguide layer 12 is preferably implemented as:
Figure BDA0003069376300000123
wherein: d 1 The thickness of said first waveguide layer 11; d is a radical of 2 The thickness of the second waveguide layer 12; t is the period of the incoupling grating structure 21; n is the refractive index of the optical waveguide assembly 10; lambda [ alpha ] 1 Is the wavelength of the first incoupled light 101; lambda [ alpha ] 2 Is the wavelength of the second incoupled light 102.
According to the above-mentioned embodiment of the present application, the types of the incoupling grating structure 21 and the outcoupling grating structure 22 in the grating structure assembly 20 can be adjusted according to specific requirements, for example, the incoupling grating structure 21 and the outcoupling grating structure 22 can be, but are not limited to, implemented as surface relief gratings, so as to be processed and formed on the surface of the first waveguide layer 11 by a nano-imprint technique or the like. Of course, in other examples of the present application, the incoupling grating structure 21 and the outcoupling grating structure 22 may also be implemented as holographic gratings, so as to form periodic light and dark alternate stripes or the like in the first waveguide layer 11 by holographic exposure.
Preferably, as shown in fig. 3, the first waveguide layer 11 is implemented as a parallel waveguide having a certain thickness and having an upper surface 111 and a lower surface 112 parallel to each other, wherein the incoupling grating structure 21 and the outcoupling grating structure 22 are formed side by side on the upper surface 111 of the first waveguide layer 11, and the first selective reflection layer 31 is attached to the lower surface 112 of the first waveguide layer 11.
Thus, the image light 100 is diffracted by the incoupling grating structure 21 into the first incoupling light 101 and the second incoupling light 102 to be incoupled into the first waveguide layer 11 from the upper surface 111 of the first waveguide layer 11 and to exit from the lower surface 112 of the first waveguide layer 11 to the first selective reflection layer 31; then, the first incoupling light 101 is reflected back to the first waveguide layer 11 by the first selective reflection layer 31, and then is reflected back to the first waveguide layer 11 by the first selective reflection layer 31 after being totally reflected by the upper surface 111 of the first waveguide layer 11, and such repetition is performed, so that the first incoupling light 101 is equivalently totally reflected and transmitted to the outcoupling grating structure 22 in the first waveguide layer 11, so as to be diffracted into the first outcoupling light 103 to be outcoupled from the first waveguide layer 11; meanwhile, the second coupled light 102 firstly passes through the first selective reflection layer 31 to enter the second waveguide layer 12, and then after being totally reflected by the lower surface of the second waveguide layer 12, passes through the first selective reflection layer 31 again to enter the first waveguide layer 11 and totally reflected by the upper surface 111 of the first waveguide layer 11, and repeating this, so that the second coupled light 102 is totally reflected and transmitted to the coupling-out grating structure 22 in the first waveguide layer 11 and the second waveguide layer 12, so as to be diffracted into the second coupled light 104 to be coupled out of the first waveguide layer 11.
It is understood that, in other examples of the present application, the incoupling grating structure 21 and the outcoupling grating structure 22 may also be formed side by side on the lower surface 112 of the first waveguide layer 11, or the incoupling grating structure 21 and the outcoupling grating structure 22 are formed on the upper surface 11 and the lower surface 112 of the first waveguide layer 11 in a staggered manner, respectively, as long as the first waveguide layer 11 can be correspondingly incoupled into light and outcoupled from the first waveguide layer 11, which is not described in detail herein.
More preferably, the first selective reflection layer 31 is implemented as a layer of reflection film glued to the lower surface 112 of the first waveguide layer 11, and the second waveguide layer 12 is glued below the first selective reflection layer 31Side surfaces so as to closely overlap the first selective reflection layer 31 between the first waveguide layer 11 and the second waveguide layer 12, prevent an air gap from being formed between the first waveguide layer 11 and the second waveguide layer 12, and avoid the second incoupling light 102 from being totally reflected on the lower surface 112 of the first waveguide layer 11 and the upper surface of the second waveguide layer 12 to affect the equivalent total reflection period length p corresponding to the second incoupling light 102 2 ’。
According to the above embodiments of the present application, the first selective reflection layer 31 can reflect light of a selected wavelength band and transmit light of a non-selected wavelength band. In particular, the first selectively reflective layer 31 is capable of reflecting and transmitting a proportion of light in a selected wavelength band. For example, the first selective reflection layer 31 may have a reflectance of light of a selected wavelength band of 70% or more, and the first selective reflection layer 31 may have a transmittance of light of a non-selected wavelength band of 80% or more.
Preferably, although the first selective reflection layer 31 has wavelength selectivity for the reflection of light in the above examples, the first selective reflection layer 31 may also have direction selectivity for the reflection of light. For example, the first selective reflection layer 31 can efficiently reflect light from a specific wavelength in the first waveguide layer 11, but cannot efficiently reflect light from the second waveguide layer 12, so as to improve the overall optical energy utilization efficiency of the device.
It should be noted that although the above embodiment only exemplifies the propagation of light rays of two wavelengths in the diffractive optical waveguide device 1, the first selective reflection layer 31 is used for selectively reflecting light rays of a single wavelength; in practice, the diffractive optical waveguide device 1 can be used for transmitting RGB three-color light, that is, the first selective reflection layer 31 is used for selectively reflecting light of multiple wavelengths or a specific wavelength range.
In another example of the present application, the image light 100 may be implemented as RGB three-color light, wherein the first incoupling light 101 may include red light and green light, and the second incoupling light 102 may include blue light, that is, the first selective reflection layer 31 may be capable of reflecting red light and green light and transmitting blue light. In this way, red and green light coupled in via the incoupling grating structures 21 will be reflected by the first selective reflection layer 31 to propagate with equivalent total reflection back and forth within the first waveguide layer 11 to the outcoupling grating structures 22, being coupled out of the first waveguide layer 11; the blue light coupled in through the incoupling grating structure 21 is transmitted to the outcoupling grating structure 22 through the first selective reflection layer 31 by total reflection back and forth within the first waveguide layer 11 and the second waveguide layer 12, and is coupled out of the first waveguide layer 11.
Preferably, the first selective reflection layer 31 may be implemented by stacking a plurality of wavelength selective reflection films. For example, in an example of the present application, the first selective reflection layer 31 has a reflection spectrum distribution as shown in fig. 5, and is used for reflecting light having a wavelength of more than 520nm and transmitting light having a wavelength of less than 500 nm.
It will be appreciated that red light typically has a wavelength between 610nm and 680nm, green light typically has a wavelength between 520nm and 570nm, and blue light typically has a wavelength between 440nm and 465 nm. Although the diffraction angle of red light is large and the diffraction angle of blue light is small, the diffraction angle of green light is slightly smaller than that of red light, so that, because the diffraction angle of green light is not much different from that of red light, the first selective reflection layer 31 in the diffractive optical waveguide device 1 of the present application can simultaneously reflect red light and green light, so that the first waveguide layer 11 can simultaneously support the transmission of red light and green light, and the second waveguide layer 12 cooperates with the first waveguide layer 11 to support the transmission of only blue light. In other words, although the diffractive optical waveguide device 1 of the present application only modulates the coupling-out density of blue light, the coupling-out densities of red light and green light are not greatly different due to the fact that the diffraction angles corresponding to red light and green light are not greatly different, and therefore the diffractive optical waveguide device 1 of the present application can still achieve optimization of color uniformity to a certain extent.
To further optimize the color uniformity, fig. 6 to 8 show a first variant of the diffractive optical waveguide device 1 according to the above-mentioned embodiment of the present application, wherein the optical waveguide assembly 10 of the diffractive optical waveguide device 1 may further include a third waveguide layer 13, and the selective reflection assembly 30 may further include a second selective reflection layer 32, wherein the third waveguide layer 13 is stacked on the second waveguide layer 12 on a side away from the first waveguide layer 11, and the second selective reflection layer 32 is stacked between the second waveguide layer 12 and the third waveguide layer 13 for selectively reflecting light having the second diffraction angle in the light beam and selectively transmitting light having a third diffraction angle, wherein the second diffraction angle is larger than the third diffraction angle. In other words, the second waveguide layer 12 is stacked between the first waveguide layer 11 and the third waveguide layer 13, wherein the first selective reflection layer 31 is stacked between the first waveguide layer 11 and the second waveguide layer 12, and the second selective reflection layer 32 is stacked between the second waveguide layer 12 and the third waveguide layer 13.
Illustratively, as shown in fig. 7, the first selective reflection layer 31 is used to selectively reflect a first wavelength band of light 101' in a light beam and selectively transmit other wavelength bands of light in the light beam; the second selective reflection layer 32 is used for selectively reflecting the second wavelength band light 102 'in the light beam and selectively transmitting the third wavelength band light 103' in the light beam, wherein the wavelength of the first wavelength band light 101 'is greater than that of the second wavelength band light 102', and the wavelength of the second wavelength band light 102 'is greater than that of the third wavelength band light 103'. For example, the first band of light 101', the second band of light 102', and the third band of light 103' may be implemented as red light, green light, and blue light in sequence.
Preferably, the first selective reflection layer 31 is used to reflect red light and transmit green and blue light; the second selective reflection layer 32 is for reflecting green light and transmitting blue light. For example, in an example of the present application, the reflection spectrum distribution of the first selective reflection layer 31 and the second selective reflection layer 32 is as shown in fig. 8, wherein the first selective reflection layer 31 is used for reflecting light with a wavelength greater than 610nm and transmitting light with a wavelength less than 570 nm; and the second selective reflection layer 32 is used for reflecting light with a wavelength between 520nm and 570nm and transmitting light with a wavelength less than 460nm or a wavelength more than 620 nm.
Thus, when a beam of RGB three-color image light is projected to the incoupling grating structure 21 of the grating structure assembly 20, the incoupling grating structure 21 diffracts the RGB three-color image light into red light R, green light G, and blue light B whose diffraction angles become smaller in order to be incoupled into the first waveguide layer 11; then, the red light R is reflected by the first selective reflection layer 31 to be transmitted to the outcoupling grating structure 22 with equivalent total reflection in the first waveguide layer 11, the green light G is transmitted through the first selective reflection layer 31 to enter the second waveguide layer 12, and then is reflected by the second selective reflection layer 32 to be transmitted to the outcoupling grating structure 22 with equivalent total reflection in the first waveguide layer 11 and the second waveguide layer 12, and the blue light B is transmitted through the first selective reflection layer 31, the second waveguide layer 12, and the second selective reflection layer 32 to be transmitted to the outcoupling grating structure 22 with total reflection back and forth in the optical waveguide assembly 10; finally, the red light R, the green light G and the blue light B are all coupled out of the first waveguide layer 11 by the coupling-out grating structure 22.
It should be noted that, as shown in fig. 7, the diffractive optical waveguide device 1 of the present application is formed by adding the second waveguide layer 12 and the third waveguide layer 13, and using the first selective reflection layer 31 to reflect red light and transmit green light and blue light, and using the second selective reflection layer 32 to reflect green light and transmit blue light, so that the red light propagates in the first waveguide layer 11 with equivalent total reflection, and the equivalent total reflection period length T corresponding to the red light is obtained 1 Keeping the original shape; and the green light propagates in the first waveguide layer 11, the first selective reflection layer 31 and the second waveguide layer 12 with equivalent total reflection, so that the equivalent total reflection period length T corresponding to the green light 2 Is increased to be close to or even equal to the equivalent total reflection period corresponding to the red lightDegree T 1 (ii) a The blue light propagates through the first waveguide layer 11, the first selective reflection layer 31, the second waveguide layer 12, the second selective reflection layer 32, and the third waveguide layer 13 by total reflection, so that an equivalent total reflection period length T corresponding to the blue light is obtained 3 Is further increased to approach, or even equal to, the equivalent total reflection period length T corresponding to the red light 1 Thereby, the coupling-out density corresponding to the red light, the green light and the blue light is balanced, and the diffraction optical waveguide device 1 with better color uniformity is obtained.
Preferably, the refractive index of third waveguide layer 13 is equal to the refractive index of second waveguide layer 12, e.g. the refractive index n of optical waveguide assembly 10 is between 1.4 and 2.3. It is understood that in other examples of the present application, the refractive index of third waveguide layer 13 may also be different from the refractive index of second waveguide layer 12.
In addition, since the thickness of the first waveguide layer 11 is typically between 0.4mm and 1.5mm, and the thickness of the first selective reflection layer 31 and the second selective reflection layer 32 are both between 50nm and 400nm, which is much smaller than the thickness of the first waveguide layer 11, the thickness of the first selective reflection layer 31 and the second selective reflection layer 32 can be ignored when calculating the equivalent total reflection period length.
Thus, in analogy to the above-described embodiment according to the present application, in said first variant embodiment according to the present application: the equivalent total reflection period length T corresponding to the first waveband light 101 1 Is implemented as:
Figure BDA0003069376300000171
the equivalent total reflection period length T corresponding to the second waveband light 102 2 Is implemented as:
Figure BDA0003069376300000172
the equivalent total reflection period length T corresponding to the third band light 103 3 Is implemented as:
Figure BDA0003069376300000173
wherein: d 1 、d 2 And d 3 The thicknesses of the first waveguide layer 11, the second waveguide layer 12, and the third waveguide layer 13, respectively; t is the period of the incoupling grating structure 21; n is the refractive index of the optical waveguide assembly 10; lambda [ alpha ] 1 、λ 2 And λ 3 The wavelengths of the first band of light 101', the second band of light 102', and the third band of light 103', respectively.
Preferably, the equivalent total reflection period length T corresponding to the first band of wavelengths 101' is 1 Equal to the equivalent total reflection period length T corresponding to the second waveband light 102 2 Is equal to the equivalent total reflection period length T corresponding to the third wavelength band light 103 3 。
In other words, the ratio between the thickness of the first waveguide layer 11 and the thickness of the second waveguide layer 12 is preferably implemented as:
Figure BDA0003069376300000174
wherein: d 1 The thickness of said first waveguide layer 11; d is a radical of 2 The thickness of the second waveguide layer 12; t is the period of the incoupling grating structure 21; n is the refractive index of the optical waveguide assembly 10; lambda [ alpha ] 1 Is the wavelength of the first band of wavelengths of light 101'; lambda 2 Is the wavelength of the second band of wavelengths of light 102'.
The ratio between the thickness of the first waveguide layer 11 and the thickness of the third waveguide layer 13 is preferably implemented as:
Figure BDA0003069376300000181
wherein d is 1 The thickness of said first waveguide layer 11; d 3 Is the thickness of the third waveguide layer 13; t is the period of the incoupling grating structure 21; n is the refractive index of the optical waveguide assembly 10; lambda [ alpha ] 1 Is the wavelength of the first band of wavelengths of light 101'; lambda [ alpha ] 2 Is the wavelength of the second band of wavelengths light 102'; lambda 3 Is the wavelength of the third band of light 103'.
It is to be noted that, according to the above-described embodiments of the present application, the incoupling grating structure 21 may be, but is not limited to be, implemented as a one-dimensional grating or a two-dimensional grating. For example, when the incoupling grating structure 21 is implemented as a one-dimensional grating, the incoupling grating structure 21 may be implemented as, but not limited to, a rectangular grating, a skewed tooth grating, a sawtooth grating, or the like; when the incoupling grating structure 21 is implemented as a two-dimensional grating, the incoupling grating structure 21 may also be replaced by a plurality of one-dimensional gratings stacked together.
Likewise, the outcoupling grating structure 22 may also be implemented, but not limited to, as a one-dimensional grating or a two-dimensional grating. In particular, when the outcoupling grating structure 22 is implemented as the two-dimensional grating, the outcoupling grating structure 22 has both an outcoupling function and a pupil-expanding function.
It should be noted that, when the incoupling grating structure 21 adopts a one-dimensional grating and the outcoupling grating structure 22 adopts a two-dimensional grating, light rays incoupled through the incoupling grating structure 21 are diffracted by the outcoupling grating structure 22 into 0-order diffracted light propagating along the original direction and ± 1-order diffracted light propagating to two sides in a beam-expanding manner, which results in no light rays being outcoupled at the vertex angle position of a part of the area where the outcoupling grating structure 22 is located, i.e., a so-called field-of-view dark angle is formed, which seriously affects the uniformity and integrity of the optical waveguide display image.
Therefore, in order to solve the above problem, fig. 9 shows a second variant implementation of the diffractive optical waveguide device 1 according to the above embodiment of the present application, wherein the grating structure assembly 20 of the diffractive optical waveguide device 1 may further include a pupil-expanding grating structure 23, wherein the pupil-expanding grating structure 23 is disposed on the first waveguide layer 11, and the pupil-expanding grating structure 23 is located in the optical path between the incoupling grating structure 21 and the outcoupling grating structure 22, so that the light incoupled via the outcoupling grating structure 21 is first split into different orders of diffracted light by the pupil-expanding grating structure 23 to be transmitted to different positions of the outcoupling grating structure 22 along different propagation directions, and then coupled out of the first waveguide layer 11 by the outcoupling grating structure 22, so as to couple out the light in the whole area of the outcoupling grating structure 22, which helps to improve the field dark angle.
The pupil grating structure 23 may be implemented, for example, as one or more relief gratings for diffracting the coupled-in light to function as a beam splitter. It is noted that the pupil grating structure 23 may be implemented as one or more two-dimensional relief gratings, or as one or more one-dimensional relief gratings superimposed together; may also be implemented as one or more one-dimensional relief gratings; it can also be implemented as a combination of one-dimensional relief gratings and two-dimensional relief gratings.
It should be noted that, as shown in fig. 9, the diffracted lights split by the pupil grating structure 23 may include, but are not limited to, 0 th order diffracted light and at least one ± 1 st order diffracted light, wherein the at least one ± 1 st order diffracted light may be one of +1 st order diffracted light and-1 st order diffracted light, or two of +1 st order diffracted light and-1 st order diffracted light. Because this application diffraction optical waveguide device 1 first via the image light beam splitting that pupil expanding grating structure 23 will be coupled in becomes the direction of propagation different 0 order diffraction light with at least a 1 st order diffraction light makes the not equidirectional diffraction light homoenergetic transmit extremely coupling grating structure 22, so that cover whole coupling grating structure 22, and then by coupling grating structure 22 couples out first waveguide layer 11 is watched by the user, consequently this application diffraction optical waveguide device 1 not only can improve the light energy utilization ratio of image light, but also can solve the field of view vignetting problem that causes because of the light disappearance. Meanwhile, the coupling grating structure 22 of the diffractive optical waveguide device 1 of the present application can further split light in the waveguide while coupling out the diffracted light, so that different coupling light energies compensate each other, and uniformity of the coupling light is improved, that is, uniformity of energy distribution of the coupling light at the entrance pupil of the human eye is increased, and the problem of image dark angle caused by non-uniform energy of the field angle is improved.
According to another aspect of the present application, as shown in fig. 10, the present application further provides a near-eye display device 7, wherein the near-eye display device 7 may include an optical machine 71 for projecting a light beam, a device body 70, and the above diffractive optical waveguide apparatus 1, wherein the optical machine 71 and the diffractive optical waveguide apparatus 1 are correspondingly disposed in the device body 70, such that the light beam provided by the optical machine 71 is diffracted by the incoupling grating structures 21 into incoupling light with different wavelengths to couple into the optical waveguide assembly 10, and then the incoupling light with different wavelengths propagates to the incoupling grating structures 22 along different propagation light paths in the optical waveguide assembly 10 to be uniformly coupled out by the incoupling grating structures 22 to be received by the eyes of a user to see corresponding images.
More specifically, as shown in fig. 10, the equipment main body 70 of the near-eye display equipment 7 may include a beam portion 72 and a pair of temple portions 73, wherein the temple portions 73 extend rearward from the left and right sides of the beam portion 72, respectively, to form the equipment main body 70 having an eyeglass frame structure. The diffractive optical waveguide device 1 is provided below the beam portion 72 as a spectacle lens for near-eye display.
It is to be noted that, in an example of the present application, as shown in fig. 10, the incoupling grating structure 21 in the diffractive optical waveguide device 1 is located at the middle upper portion of the first waveguide layer 11 to correspond to the beam portion 72 of the device body 70; at this time, the optical engine 71 is adapted to be mounted to the beam portion 72 of the device main body 70, so that when the near-eye display device 7 is worn by a user, the optical engine 71 is correspondingly located near the forehead of the user, which helps to reserve a larger mounting space for the optical engine 71.
According to another aspect of the present application, as shown in fig. 11, an embodiment of the present application further provides a method for optimizing color uniformity, which may include the steps of:
s110: diffracting the image light 100 to form first incoupled light 101 and second incoupled light 102 coupled into the first waveguide layer 11, wherein the diffraction angle of the first incoupled light 101 is larger than the diffraction angle of the second incoupled light 102;
s120: reflecting the first incoupling light 101 from the first waveguide layer 11 to enter the first waveguide layer 11 for total reflection, so that the first incoupling light 101 propagates equivalently totally reflected back and forth in the first waveguide layer 11;
s130: transmitting the second incoupling light 102 from the first waveguide layer 11 to enter the first waveguide layer 11 for total reflection after entering the second waveguide layer 12 stacked on the first waveguide layer 11 for total reflection, so that the second incoupling light 102 is transmitted in the first waveguide layer 11 and the second waveguide layer 12 by total reflection back and forth; and
s140: the transmitted first incoupled light 101 and the second incoupled light 102 are diffracted to form first outcoupled light 103 and second outcoupled light 104 coupled out of the first waveguide layer 11.
It should be noted that, in the method for optimizing color uniformity of the present application, the step S120 and the step S130 are not in sequence, and may be performed simultaneously or sequentially.
Preferably, the outcoupling density of the second outcoupled light 104 is close to the outcoupling density of the first outcoupled light 103, i.e. the first outcoupled light 103 and the second outcoupled light 104 have the same or similar outcoupling density. In other words, the distance between two adjacent first outcoupled light 103 is equal or approximately equal to the distance between two adjacent second outcoupled light 104. For example, the term "close" may refer to a difference between a distance between two adjacent first outcoupled lights 103 and a distance between two adjacent second outcoupled lights 104 within a certain threshold range, such as ± 50nm or the like.
More preferably, in the method of optimizing color uniformity of the present application: the first incoupled light 101 is reflected and the second incoupled light 102 is transmitted by the first selective reflection layer 31 laminated between the first waveguide layer 11 and the second waveguide layer 12.
Most preferably, the thickness of the first waveguide layer 11 and the thickness of the second waveguide layer 12 are chosen such that the equivalent total reflection period length corresponding to the first incoupling light 101 is equal to the equivalent total reflection period length corresponding to the second incoupling light 102.
It should be noted that fig. 12 shows a variant implementation of the method for optimizing color uniformity according to the above-mentioned embodiment of the present application, wherein the method for optimizing color uniformity may include the steps of:
s210: diffracting the image light 100 to form a first band of light 101', a second band of light 102', and a third band of light 103 'coupled into the first waveguide layer 11, wherein diffraction angles of the first band of light 101', the second band of light 102', and the third band of light 103' become smaller in order;
s220: reflecting the first band of wavelengths 101 'from the first waveguide layer 11 to enter the first waveguide layer 11 for total reflection, so that the first band of wavelengths 101' propagates equivalently totally reflectively back and forth in the first waveguide layer 11;
s230: transmitting the second wavelength band light 102 'and the third wavelength band light 103' from the first waveguide layer 11 to enter a second waveguide layer 12 stacked on the first waveguide layer 11;
s240: reflecting the second band of wavelengths of light 102 'from the second waveguide layer 12 into the first waveguide layer 11 for total reflection, such that the second band of wavelengths of light 102' propagates equivalently totally reflectively back and forth in the first waveguide layer 11 and the second waveguide layer 12;
s250: transmitting the third band light 103 'from the second waveguide layer 12 to enter a third waveguide layer 13 stacked on the second waveguide layer 12 to be totally reflected back to the first waveguide layer 11 to be totally reflected again, so that the third band light 103' is transmitted totally reflected back and forth in the first waveguide layer 11 and the third waveguide layer 13; and
s260: diffracting the transmitted first 101', second 102' and third 103' wavelength bands of light to couple out the first waveguide layer 11.
It is noted that, in the method for optimizing the vignetting of the field of view according to the above-described variant of the present application: reflecting the first band of wavelengths light 101' and transmitting the second band of wavelengths light 102' and the third band of wavelengths light 103' through a first selective reflection layer 31 laminated between the first waveguide layer 11 and the second waveguide layer 12; and reflects the second band of wavelengths light 102 'and transmits the third band of wavelengths light 103' through a second selective reflection layer 32 that is laminated between the second waveguide layer 12 and the third waveguide layer 13.
According to another aspect of the present application, as shown in fig. 13, an embodiment of the present application further provides a method for manufacturing a diffractive optical waveguide device, which may include the steps of:
s310: arranging a grating structure assembly 20 in the first waveguide layer 11, wherein the in-coupling grating structure 21 in the grating structure assembly 20 is configured to diffract the image light 100 into light rays having a first diffraction angle and light rays having a second diffraction angle; and
s320: a first selective reflection layer 31 is stacked between the first waveguide layer 11 and the second waveguide layer 12, wherein the first selective reflection layer 31 is used for reflecting the light rays with the first diffraction angle and transmitting the light rays with the second diffraction angle, and the first diffraction angle is larger than the second diffraction angle.
It should be noted that the sequence of step S310 and step S320 in the method for manufacturing a diffractive optical waveguide device of the present application may be interchanged, that is, step S320 may be performed before step S310.
Illustratively, in an example of the present application, as shown in fig. 14, the step S310 of the method for manufacturing a diffractive optical waveguide device may include the steps of:
s311: manufacturing a mother board, wherein the mother board is provided with a grating structure to be transferred corresponding to the grating structure assembly 20; and
s312: the grating structure assembly 20 is formed on the surface of the first waveguide layer 11 by a nano-imprint method using the master.
It is to be noted that, according to the above-mentioned embodiment of the present application, in the step S311 of the method for manufacturing a diffractive optical waveguide device, the motherboard may be manufactured by using an etching process. For example, the etching process may include, but is not limited to, laser direct writing, electron beam direct writing, mask lithography, and two-beam interference exposure, among others.
It is to be noted that, as shown in fig. 13, the method for manufacturing a diffractive optical waveguide device according to the above-described embodiment of the present application may further include the steps of:
s330: a second selective reflecting layer 32 is stacked between the second waveguide layer 12 and the third waveguide layer 13, wherein the in-coupling grating structure 21 is further configured to diffract the image light into light having a third diffraction angle, and the second selective reflecting layer 32 is configured to reflect the light having the second diffraction angle and transmit the light having the third diffraction angle, wherein the second diffraction angle is larger than the third diffraction angle.
It will be appreciated that in this example of the present application, the incoupling grating structure 21 is used to diffract the image light 100 into three beams of light with successively smaller diffraction angles, such as red, green and blue light. In addition, the sequence of the step S310, the step S320, and the step S330 in the method for manufacturing a diffractive optical waveguide device of the present application may also be interchanged, and details thereof are not repeated herein.
It will be appreciated by persons skilled in the art that the embodiments of the invention described above and shown in the drawings are given by way of example only and are not limiting of the invention. The objects of the invention have been fully and effectively accomplished. The functional and structural principles of the present invention have been shown and described in the examples, and any variations or modifications of the embodiments of the present invention may be made without departing from the principles.

Claims (22)

1. A diffractive light waveguide apparatus, comprising:
an optical waveguide assembly, wherein the optical waveguide assembly includes a first waveguide layer and a second waveguide layer stacked on each other;
a grating structure assembly, wherein the grating structure assembly comprises an incoupling grating structure and an outcoupling grating structure disposed on the first waveguide layer, wherein the incoupling grating structure is configured to diffract a light beam to couple into the first waveguide layer, and the outcoupling grating structure is configured to diffract the light beam to couple out the first waveguide layer; and
a selective reflection assembly, wherein the selective reflection assembly comprises a first selective reflection layer stacked between the first waveguide layer and the second waveguide layer, and the first selective reflection layer is used for selectively reflecting light rays with a first diffraction angle in the light beam and selectively transmitting light rays with a second diffraction angle in the light beam, wherein the first diffraction angle is larger than the second diffraction angle.
2. The diffractive light waveguide apparatus according to claim 1, wherein said incoupling grating structure is configured to diffract image light into first incoupling light having a larger diffraction angle and second incoupling light having a smaller diffraction angle, and said first selectively reflective layer is configured to reflect the first incoupling light and transmit the second incoupling light such that the first incoupling light propagates with equivalent total reflection within said first waveguide layer and the second incoupling light propagates with total reflection within said first waveguide layer and said second waveguide layer.
3. The diffractive optical waveguide apparatus of claim 2 wherein the index of refraction of the first waveguide layer is equal to the index of refraction of the second waveguide layer.
4. The diffractive light waveguide device of claim 3 wherein the thickness d of the first waveguide layer 1 And a thickness d of said second waveguide layer 2 The ratio between is implemented as:
Figure FDA0003069376290000011
wherein t is a period of the incoupling grating structure; n is the refractive index of the optical waveguide assembly; lambda [ alpha ] 1 Is the wavelength of the first coupled-in light; lambda [ alpha ] 2 Is the wavelength of the second coupled-in light.
5. The diffractive light waveguide apparatus according to claim 2, wherein said first selectively reflective layer is operative to reflect red and green light and transmit blue light.
6. The diffractive optical waveguide device of claim 1, wherein the optical waveguide assembly further comprises a third waveguide layer stacked on the second waveguide layer and the second waveguide layer is positioned between the first waveguide layer and the third waveguide layer, wherein the selective reflection assembly further comprises a second selective reflection layer stacked between the second waveguide layer and the third waveguide layer and configured to selectively reflect light of the optical beam having the second diffraction angle and to selectively transmit light of the optical beam having a third diffraction angle, wherein the second diffraction angle is greater than the third diffraction angle.
7. The diffractive optical waveguide apparatus according to claim 6, wherein said incoupling grating structure is configured to diffract image light into a first band of light, a second band of light, and a third band of light with successively smaller diffraction angles, wherein said first selective reflection layer is configured to reflect the first band of light and transmit the second band of light and the third band of light so that the first band of light propagates with equivalent total reflection within said first waveguide layer, wherein said second selective reflection layer is configured to reflect the second band of light and transmit the third band of light so that the second band of light propagates with equivalent total reflection within said first waveguide layer and said second waveguide layer, and the third band of light propagates with total reflection within said first waveguide layer, said second waveguide layer, and said third waveguide layer.
8. The diffractive light waveguide device of claim 7 wherein the thickness d of the first waveguide layer 1 And a thickness d of the third waveguide layer 3 The ratio between is implemented as:
Figure FDA0003069376290000021
wherein t is the period of the incoupling grating structure; n is the refractive index of the optical waveguide assembly; lambda [ alpha ] 1 Is the wavelength of the first band of wavelengths of light; lambda 2 Is the wavelength of the light in the second wavelength band; lambda [ alpha ] 3 Is the wavelength of the light of the third wavelength band.
9. The diffractive light waveguide apparatus of claim 6 wherein said first selectively reflective layer is operative to reflect red light and transmit green and blue light and wherein said second selectively reflective layer is operative to reflect the green light and transmit the blue light.
10. The diffractive optical waveguide apparatus according to any one of claims 1 to 9, wherein said incoupling grating structure and said outcoupling grating structure are respectively implemented as one-dimensional gratings or two-dimensional gratings formed at the surface of said first waveguide layer.
11. The diffractive optical waveguide device according to claim 10, wherein the grating structure assembly further comprises a pupil grating structure disposed in the first waveguide layer, and the pupil grating structure is located in the optical path between the incoupling grating structure and the outcoupling grating structure for splitting light incoupled via the incoupling grating structure into different orders of diffracted light to be transmitted to different positions of the outcoupling grating structure along different propagation directions.
12. The diffractive optical waveguide apparatus according to any one of claims 1 to 9, wherein said incoupling grating structures and said outcoupling grating structures are formed side-by-side on an upper surface of said first waveguide layer, and said first selectively reflective layer is glued between a lower surface of said first waveguide layer and said second waveguide layer.
13. The diffractive light waveguide apparatus according to any one of claims 1 to 9, wherein said first selectively reflective layer is wavelength selective for light reflection.
14. The diffractive light waveguide apparatus according to one of claims 1 to 9, wherein the first selectively reflective layer has a directional selectivity for the reflection of light rays.
15. A method for optimizing color uniformity, comprising the steps of:
diffracting the image light to form first and second coupled-in lights coupled into the first waveguide layer, wherein a diffraction angle of the first coupled-in light is larger than that of the second coupled-in light;
reflecting the first coupled light from the first waveguide layer to enter the first waveguide layer for total reflection, so that the first coupled light is transmitted back and forth in the first waveguide layer in an equivalent total reflection manner;
transmitting the second coupling light from the first waveguide layer, so that the second coupling light enters the first waveguide layer for total reflection after entering the second waveguide layer superposed on the first waveguide layer, and then enters the first waveguide layer for total reflection, so that the second coupling light is transmitted in the first waveguide layer and the second waveguide layer in a back-and-forth total reflection manner; and
diffracting the transmitted first and second coupled-in lights to form a first coupled-out light and a second coupled-out light coupled out of the first waveguide layer.
16. The method of claim 15 wherein the first coupled-in light is reflected and the second coupled-in light is transmitted by a first selectively reflective layer laminated between the first waveguide layer and the second waveguide layer.
17. The method according to claim 15 or 16, wherein the thickness of the first waveguide layer and the thickness of the second waveguide layer are chosen appropriately such that the period length of the equivalent total reflection corresponding to the first coupled-in light is equal to the period length of the equivalent total reflection corresponding to the second coupled-in light.
18. A method for optimizing color uniformity, comprising the steps of:
diffracting the image light to form first, second, and third wavelength bands of light coupled into the first waveguide layer, wherein diffraction angles of the first, second, and third wavelength bands of light become smaller in order;
reflecting the first waveband light from the first waveguide layer to enter the first waveguide layer for total reflection, so that the first waveband light is transmitted back and forth in the first waveguide layer in an equivalent total reflection manner;
transmitting the second and third wavelength bands of light from the first waveguide layer to enter a second waveguide layer stacked on the first waveguide layer;
reflecting the second band light from the second waveguide layer to enter the first waveguide layer for total reflection, so that the second band light is transmitted back and forth in the first waveguide layer and the second waveguide layer with equivalent total reflection;
transmitting the third band of light from the second waveguide layer to enter the first waveguide layer for total reflection after entering the third waveguide layer superposed on the second waveguide layer for total reflection, so that the third band of light is transmitted in the first waveguide layer and the third waveguide layer in a back-and-forth total reflection manner; and
the transmitted light of the first, second and third wavelength bands is diffracted to couple out the first waveguide layer.
19. The method for optimizing color uniformity of claim 18, wherein the first wavelength band of light is reflected and the second wavelength band of light is transmitted by a first selectively reflective layer laminated between the first waveguide layer and the second waveguide layer; and reflecting the second wavelength band light and transmitting the third wavelength band light through a second selective reflection layer stacked between the second waveguide layer and the third waveguide layer.
20. A method of manufacturing a diffractive optical waveguide device, comprising the steps of:
arranging a grating structure component on the first waveguide layer, wherein an in-coupling grating structure in the grating structure component is used for diffracting the image light into light rays with a first diffraction angle and light rays with a second diffraction angle; and
and superposing a first selective reflection layer between the first waveguide layer and the second waveguide layer, wherein the first selective reflection layer is used for reflecting the light with the first diffraction angle and transmitting the light with the second diffraction angle, and the first diffraction angle is larger than the second diffraction angle.
21. The method of manufacturing a diffractive light waveguide apparatus as claimed in claim 20, further comprising the steps of:
and superposing a second selective reflection layer between the second waveguide layer and the third waveguide layer, wherein the in-coupling grating structure is further configured to diffract the image light into light rays having a third diffraction angle, and the second selective reflection layer is configured to reflect the light rays having the second diffraction angle and transmit the light rays having the third diffraction angle, wherein the second diffraction angle is greater than the third diffraction angle.
22. The method of manufacturing a diffractive optical waveguide device according to claim 20 or 21, wherein said step of disposing a grating structure element in the first waveguide layer, wherein the incoupling grating structure in the grating structure element is for diffracting image light into light having a first diffraction angle and light having a second diffraction angle, comprises the steps of:
manufacturing a mother board, wherein the mother board is provided with a grating structure to be transferred corresponding to the grating structure component; and
and processing the surface of the first waveguide layer by using the master plate through a nano-imprinting method to form the grating structure assembly.
CN202110534774.2A 2021-05-17 2021-05-17 Diffractive optical waveguide device and method therefor Pending CN115373062A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2024077907A1 (en) * 2022-10-12 2024-04-18 深圳市光途显示科技有限公司 Display device, virtual image display method, and manufacturing method for display device

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2024077907A1 (en) * 2022-10-12 2024-04-18 深圳市光途显示科技有限公司 Display device, virtual image display method, and manufacturing method for display device

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