A color separation one-tow-two optical waveguide display device based on a cascade waveguide

Abstract

The application discloses a color separation one-to-two light waveguide display device based on a cascade waveguide, which comprises a light engine, a color separation optical assembly, a cascade waveguide assembly and a dispersion compensation structure. The light engine generates input image light containing at least two color channels, and the color separation optical assembly separates the input image light into a first color channel light beam and a second color channel light beam. The cascade waveguide assembly comprises a first waveguide plate and a second waveguide plate stacked together, and each waveguide plate is provided with an entrance pupil grating, an expansion pupil grating and an exit pupil grating which are symmetrically arranged on the left and right sides of the entrance pupil grating, each color channel light beam is diffracted by the entrance pupil grating to form a transmission light propagating to the left and right, and the transmission light is diffracted by the expansion pupil grating and the exit pupil grating to form left and right output lights. The dispersion compensation structure is arranged between adjacent waveguide plates to compensate for the position and angle deviation of different color channel light beams. The application realizes one-to-two binocular full-color display through a single light engine, reduces the cost and power consumption, and reduces the influence of dispersion on display quality.

Description

Technical Field

[0001] This application relates to the field of near-eye display technology, specifically to a color-separated one-to-two optical waveguide display device based on cascaded waveguides. Background Technology

[0002] Augmented reality (AR) glasses are a significant development direction in the current consumer electronics field. Near-eye display systems generally consist of an image source and an optical transmission system. The image emitted by the image source is transmitted to the wearer's eye through the optical transmission system. The optical transmission system needs to have a certain transmittance so that the wearer can see the real environment while viewing the virtual image. Among various optical transmission schemes, diffractive waveguide technology has become the mainstream technology for AR glasses due to its large eye movement range and thinness. With continuous technological advancements, higher demands are being placed on the performance and cost of AR glasses, with the expectation of improving the image quality of full-color displays while reducing costs and power consumption.

[0003] In traditional diffractive waveguide schemes, two optical engines are typically used to drive the left and right eyes respectively to achieve binocular display. Furthermore, Chinese patent CN113219671A proposes a single-optical-engine binocular display scheme that uses the positive and negative diffraction orders of a single entrance pupil grating to split the input light into left and right paths, achieving a one-to-two binocular display. Chinese patent CN117492127A proposes a dual-coupled-input scheme, using a cubic prism and a deflection prism to split the light into two beams, which are then coupled into two independent entrance pupil gratings. Moreover, all of the above existing schemes use a single-layer waveguide plate to carry the full-band (red, green, and blue) image light.

[0004] However, the traditional scheme of using two separate optical engines to drive the left and right eye displays suffers from high hardware costs and high power consumption. The single-optical-engine binocular display scheme disclosed in CN113219671A requires the entrance pupil grating to use a binary grating with a symmetrical structure to ensure consistent positive and negative order efficiencies, resulting in low entrance pupil diffraction efficiency and limiting the brightness of the final displayed image. Dual-coupled entry schemes further increase the complexity of the optical system. Furthermore, when achieving full-color display, the above schemes suffer from image quality issues such as rainbow effects and color shifts due to the differences in diffraction characteristics of different wavelengths of light during waveguide propagation. Specifically, according to the grating diffraction equation, different wavelengths of light have different diffraction angles on the same grating, leading to differences in the total internal reflection step distance of different colors of light within the waveguide plate. This prevents different colors of light from overlapping spatially when exiting the exit pupil grating, resulting in rainbow effects and color shifts, thus affecting the user's visual experience. Summary of the Invention

[0005] In order to solve the technical problems in the prior art, this application provides a color-separated one-to-two optical waveguide display device based on cascaded waveguides.

[0006] The color-separated one-to-two optical waveguide display device based on cascaded waveguides provided in this application adopts the following technical solution:

[0007] A color-separated one-to-two optical waveguide display device based on cascaded waveguides, comprising:

[0008] A light engine for generating light from an input image that contains at least two color channels;

[0009] A color separation optical component is disposed on the light output path of the light engine to separate the input image light into at least a first color channel beam and a second color channel beam, wherein the first color channel beam and the second color channel beam have different and separate wavelength ranges.

[0010] A cascaded waveguide assembly includes a first waveguide plate and a second waveguide plate stacked together, wherein the first waveguide plate corresponds to the first color channel and the second waveguide plate corresponds to the second color channel.

[0011] The first waveguide plate has a first entrance pupil grating, a first left diffracting pupil grating, a first right diffracting pupil grating, a first left exit pupil grating, and a first right exit pupil grating. The first entrance pupil grating is configured to receive the first color channel beam and couple the first color channel beam into the first waveguide plate, causing total internal reflection in the direction of propagation to the first left diffracting pupil grating and the first right diffracting pupil grating. The first left diffracting pupil grating and the first right diffracting pupil grating are used to diffract the beam in the direction of the first left exit pupil grating and the first right exit pupil grating. The first left exit pupil grating and the first right exit pupil grating are used to couple out the first color channel beam.

[0012] A second entrance pupil grating, a second left diffracting pupil grating, a second right diffracting pupil grating, a second left exit pupil grating, and a second right exit pupil grating are formed on the second waveguide plate. The second entrance pupil grating is configured to receive the second color channel beam and couple the second color channel beam into the second waveguide plate, causing total internal reflection in the direction of propagation to the second left diffracting pupil grating and the second right diffracting pupil grating. The second left diffracting pupil grating and the second right diffracting pupil grating are used to diffract the beam in the direction of the second left exit pupil grating and the second right exit pupil grating. The second left exit pupil grating and the second right exit pupil grating are used to couple the second color channel beam out.

[0013] A dispersion compensation structure is disposed between the first waveguide plate and the second waveguide plate, and is configured to compensate for the positional and / or angular deviations of the first color channel beam and the second color channel beam caused by transmission through different waveguide plates.

[0014] In some embodiments, the cascaded waveguide assembly further includes a third waveguide plate, and the color separation optical assembly further separates the input image light into a third color channel beam; a third entrance pupil grating, a third left diffusing pupil grating, a third right diffusing pupil grating, a third left exit pupil grating, and a third right exit pupil grating are formed on the third waveguide plate; the first color channel beam is red light, the second color channel beam is green light, and the third color channel beam is blue light; the first waveguide plate, the second waveguide plate, and the third waveguide plate are stacked sequentially from the human eye side to the external side, and the dispersion compensation structure is provided between adjacent waveguide plates.

[0015] In some embodiments, the grating period of the first entrance pupil grating is set according to the center wavelength of the first color channel beam, and the grating period of the second entrance pupil grating is set according to the center wavelength of the second color channel beam; both the first entrance pupil grating and the second entrance pupil grating are multiple exposure volume holographic gratings, and the multiple exposure volume holographic grating records at least two sets of interference fringes in different directions to simultaneously generate diffraction in the left and right directions of the incident light; and the total diffraction efficiency of the first entrance pupil grating in the left and right directions of the first color channel beam is greater than 70%, and the total diffraction efficiency of the second entrance pupil grating in the left and right directions of the second color channel beam is greater than 70%.

[0016] In some embodiments, the first left and right expanding pupil gratings on the first waveguide plate are arranged in a mirror-symmetrical manner with the first entrance pupil grating as the center, and the first left and right exit pupil gratings are arranged in a mirror-symmetrical manner with the first entrance pupil grating as the center; the grating vectors of the first left expanding pupil grating and the first left exit pupil grating are designed such that the light emitted from the first left exit pupil grating is consistent with the incident direction of the first color channel beam; and the grating vectors of the first right expanding pupil grating and the first right exit pupil grating are designed such that the light emitted from the first right exit pupil grating is consistent with the incident direction of the first color channel beam;

[0017] The second left and second right expanding pupil gratings on the second waveguide plate are arranged in a mirror-symmetrical configuration with the second entrance pupil grating as the center, and the second left and second right exit pupil gratings are also arranged in a mirror-symmetrical configuration with the second entrance pupil grating as the center. The grating vectors of the second left expanding pupil grating and the second left exit pupil grating are designed such that the light emitted from the second left exit pupil grating is consistent with the incident direction of the second color channel beam. Furthermore, the grating vectors of the second right expanding pupil grating and the second right exit pupil grating are designed such that the light emitted from the second right exit pupil grating is consistent with the incident direction of the second color channel beam.

[0018] In some embodiments, the first left exit pupil grating, the first right exit pupil grating, the second left exit pupil grating, and the second right exit pupil grating have the same exit angle; the ratio of the grating period of the first left exit pupil grating to the center wavelength of the first color channel beam is equal to the ratio of the grating period of the second left exit pupil grating to the center wavelength of the second color channel beam; the ratio of the grating period of the first right exit pupil grating to the center wavelength of the first color channel beam is equal to the ratio of the grating period of the second right exit pupil grating to the center wavelength of the second color channel beam.

[0019] In some embodiments, the dispersion compensation structure includes at least one of a refractive index gradient layer, a dispersion compensation grating, and a multilayer dielectric film;

[0020] When the dispersion compensation structure includes a refractive index gradient layer, the refractive index of the refractive index gradient layer continuously transitions from a first refractive index near the first waveguide plate to a second refractive index near the second waveguide plate, wherein the range of the first refractive index is 1.5 to 1.7 and the range of the second refractive index is 1.7 to 2.0.

[0021] When the dispersion compensation structure includes a dispersion compensation grating, the grating period of the dispersion compensation grating is 500nm~2000nm, the diffraction efficiency is 1%~5%, and it is formed on the surface of the dispersion compensation structure.

[0022] When the dispersion compensation structure includes a multilayer dielectric film, the multilayer dielectric film includes 4 to 20 alternating high-refractive-index dielectric layers and low-refractive-index dielectric layers, each layer having a thickness of 50 nm to 200 nm, and producing different phase delays for light of different wavelengths.

[0023] In some embodiments, the color separation optical component is an X-cube color separation prism or a cascaded dichroic filter group; after the color separation optical component separates the input image light into at least a first color channel beam and a second color channel beam according to wavelength, the first color channel beam and the second color channel beam are guided to the positions of the first entrance pupil grating of the first waveguide plate and the second entrance pupil grating of the second waveguide plate respectively through a mirror group or a folding prism.

[0024] In some embodiments, both the first left pupil grating and the first right pupil grating are divided into 5 to 15 sub-pupil regions, and the diffraction efficiency of each sub-pupil region gradually increases in the direction away from the first entrance pupil grating; both the second left pupil grating and the second right pupil grating are divided into 5 to 15 sub-pupil regions, and the diffraction efficiency of each sub-pupil region gradually increases in the direction away from the second entrance pupil grating; the diffraction efficiency of the sub-pupil regions ranges from 5% to 95%;

[0025] Both the first left exit pupil grating and the first right exit pupil grating are divided into 5 to 15 sub-exit pupil regions. The diffraction efficiency of each sub-exit pupil region gradually increases in the direction away from the corresponding first left or right diffraction pupil grating. Both the second left and second right exit pupil gratings are divided into 5 to 15 sub-exit pupil regions. The diffraction efficiency of each sub-exit pupil region gradually increases in the direction away from the corresponding second left or right diffraction pupil grating. The diffraction efficiency of each sub-exit pupil region ranges from 5% to 95% to ensure the brightness uniformity of the displayed image within the eye movement frame.

[0026] In some embodiments, the thickness of the first waveguide plate and the second waveguide plate are both 0.3 mm to 0.8 mm, and the refractive index is both 1.7 to 2.1; the thickness of the dispersion compensation structure is 0.01 mm to 0.1 mm; the horizontal distance from the center of the first left exit pupil grating to the center of the first right exit pupil grating, and the horizontal distance from the center of the second left exit pupil grating to the center of the second right exit pupil grating are both 60 mm to 70 mm; the longitudinal distance from the center of the first entrance pupil grating to the center of the first left exit pupil grating along the plane of the first waveguide plate perpendicular to the left and right directions, and the longitudinal distance from the center of the second entrance pupil grating to the center of the second left exit pupil grating along the plane of the second waveguide plate perpendicular to the left and right directions are both 8 mm to 25 mm.

[0027] In some embodiments, the optical engine includes a microdisplay and a collimating optical component. The microdisplay is an LCOS microdisplay, a MicroLED microdisplay, a DLP microdisplay, or an LBS microdisplay. Both the first and second entrance pupil gratings are circular with diameters ranging from 2.5 mm to 7 mm. The projection positions of the first and second entrance pupil gratings on mutually parallel waveguide planes are horizontally offset, with the offset distance being less than the smaller of the radii of the first and second entrance pupil gratings.

[0028] In summary, this application includes at least one of the following beneficial technical effects:

[0029] 1. By using a single light engine in conjunction with a color separation optical component to separate the input image light into beams of different color channels, and by utilizing the pupil expansion grating and exit pupil grating that are mirror-symmetrically arranged on each waveguide plate in the cascaded waveguide component with the entrance pupil grating as the center, the beams of each color channel are diffracted to form guided light that propagates to the left and right respectively, and finally output from the left and right sides respectively, a one-to-two binocular display driven by a single light engine is realized. Compared with the traditional dual light engine solution, it is beneficial to reduce hardware costs, system power consumption and the overall weight of the head-mounted display device.

[0030] 2. By propagating different color channel beams in their respective independent waveguides, the rainbow effect and color shift caused by the difference in diffraction angles of different wavelengths of light in the same waveguide are reduced. At the same time, the multi-exposure volume holographic gratings on each waveguide have high diffraction efficiency only for specific wavelengths. Mismatched wavelengths are directly transmitted without diffraction, reducing optical crosstalk between different color levels.

[0031] 3. By setting a dispersion compensation structure between adjacent waveguide plates, the positional and angular deviations of the light beams from different color channels after propagating through different waveguide plates are compensated, so that the imaging positions of the left and right output lights of each color channel tend to coincide at the human eye, which is beneficial to improving the color saturation of the full-color binocular AR display.

[0032] 4. By designing the sum of the grating vectors of the entrance pupil grating, the expansion pupil grating, and the exit pupil grating on each waveguide plate to be zero, the output light direction is made consistent with the input light direction after the beam undergoes three consecutive diffractions through the entrance pupil, expansion pupil, and exit pupil, thus reducing image distortion and improving the angular fidelity of the final image.

[0033] 5. By designing the grating period of each exit pupil grating to be proportional to the center wavelength of the corresponding color channel beam, the output light of different color channels has a consistent exit direction at the human eye, and the color images are superimposed to form a full-color image without the need for additional angle calibration.

[0034] 6. By dividing the pupil expansion grating and the exit pupil grating into multiple sub-regions and gradually increasing the diffraction efficiency of each sub-region in the direction away from the entrance pupil grating or the pupil expansion grating, the energy attenuation caused by multiple diffraction coupling during the propagation of the beam in the waveguide plate is compensated, thereby improving the uniformity of the light intensity distribution of the final output light throughout the entire eye-tracking box and enhancing the brightness uniformity of the displayed image within the eye-tracking box. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the overall structure of a color-separated one-to-two optical waveguide display device based on a cascaded waveguide according to an embodiment of this application;

[0036] Figure 2 yes Figure 1 Schematic diagram of the exploded structure of the cascaded waveguide assembly 3;

[0037] Figure 3 yes Figure 1 A schematic diagram of the optical path between the optical engine 1 and the dichroic optical component 2;

[0038] Figure 4 yes Figure 1 Schematic diagram of beam propagation path on a single-layer waveguide plate;

[0039] Figure 5 This is a schematic diagram of the partitioning and diffraction efficiency gradient design of a grating on a single-layer waveguide plate according to an embodiment of this application.

[0040] Figure reference numerals: 1. Optical engine; 11. Microdisplay; 12. Collimating optical assembly; 2. Dichroic optical assembly; 21. Mirror group; 3. Cascaded waveguide assembly; WG1. First waveguide plate; IG1. First entrance pupil grating; EG1_L. First left diffraction pupil grating; EG1_R. First right diffraction pupil grating; OE1_L. First left exit pupil grating; OE1_R. First right exit pupil grating; WG2. Second waveguide plate; IG2. Second entrance pupil grating; EG2_L. Second left diffraction pupil grating; EG2_R. Second right diffraction pupil grating; OE2_L. Second left exit pupil grating; Pupil grating; OE2_R, second right exit pupil grating; WG3, third waveguide plate; IG3, third entrance pupil grating; EG3_L, third left dilator pupil grating; EG3_R, third right dilator pupil grating; OE3_L, third left exit pupil grating; OE3_R, third right exit pupil grating; DCS, dispersion compensation structure; L11~L16, sub-dilator pupil regions of the first left dilator pupil grating; R11~R16, sub-dilator pupil regions of the first right dilator pupil grating; L21~L27, sub-exit pupil regions of the first left exit pupil grating; R21~R27, sub-exit pupil regions of the first right exit pupil grating. Detailed Implementation

[0041] The technical solutions in the embodiments of this application will be further described in detail below with reference to the accompanying drawings. The following embodiments are only possible technical implementations of this application, but are not limited thereto. Those skilled in the art can combine the embodiments of this application to obtain other embodiments without creative effort, which are also within the protection scope of this application.

[0042] This application mainly uses a single-light engine color separation cascaded waveguide to achieve binocular display and dispersion compensation, which achieves the effect of reducing cost and power consumption and improving the image quality of full-color display. The following is a further detailed description of this application.

[0043] In the following description of this application, a coordinate system is established with reference to the wearer's facial orientation: the horizontal direction is defined as the left-right direction (the wearer's left hand is the left and the right hand is the right), the direction perpendicular to the left-right direction in the waveguide plate plane is defined as the longitudinal direction (the upper part is the side closer to the forehead and the lower part is the side closer to the chin), and the direction perpendicular to the waveguide plate plane is defined as the thickness direction (the side closer to the eyes is the inner side and the side farther from the eyes is the outer side).

[0044] Example 1

[0045] Please refer to Figures 1 to 4 The color-separated one-to-two optical waveguide display device based on cascaded waveguides provided in this application includes an optical engine 1, a color-separating optical component 2, a cascaded waveguide component 3, and a dispersion compensation structure DCS. The optical engine 1 generates input image light containing at least two color channels. The color-separating optical component 2 separates the input image light into a first color channel beam and a second color channel beam with different and separate wavelength ranges. The first waveguide plate WG1 of the cascaded waveguide component 3 corresponds to the first color channel, and the second waveguide plate WG2 corresponds to the second color channel. The dispersion compensation structure DCS is disposed between the first waveguide plate WG1 and the second waveguide plate WG2, and is configured to compensate for the positional and / or angular deviations of the first and second color channel beams caused by transmission through different waveguide plates, so as to achieve the overlap of the imaging positions of the left and right output lights at the human eye. This realizes binocular display of a single optical engine 1, while reducing the dispersion problem of full-color display and improving image quality. This is because the single-light engine 1 reduces the number of hardware components, lowers costs and power consumption, multi-layer waveguide color separation transmission reduces mutual interference between different wavelengths of light in a single waveguide, and the dispersion compensation structure DCS reduces imaging deviations caused by propagation in different waveguides.

[0046] Please refer to Figure 1 and Figure 3Specifically, the light engine 1 includes a microdisplay 11 and a collimating optical assembly 12. The microdisplay 11 can be an LCOS microdisplay, which features high resolution and high contrast, providing clear image display; it can also be a MicroLED microdisplay, which has advantages such as self-emission and fast response speed; or it can be a DLP microdisplay or an LBS microdisplay. The collimating optical assembly 12 includes at least one collimating lens, such as a convex lens. The microdisplay 11 is located on the focal plane of the collimating lens. The diverging light emitted by each pixel of the microdisplay 11 is converted into collimated parallel beams corresponding to different field-of-view angles after passing through the collimating lens, ensuring that the light can accurately enter the subsequent optical system. Physically, the light-emitting surface of the collimating optical assembly 12 is fixedly aligned with the light-incident surface of the dichroic optical assembly 2 through a precision mechanical structure or optical bonding process. In this embodiment, the microdisplay 11 in the light engine 1 generates an initial image beam through emission or reflection modulation, and the collimating optical assembly 12 shapes it into a collimated parallel beam with a small divergence angle. This mechanism enables the beam to meet the critical angle condition for total internal reflection (TIR) ​​after entering the waveguide system, which is beneficial to the transmission of the beam in the waveguide plate and the clarity of the final image at the human eye.

[0047] Please refer to Figure 3 The dichroic optical component 2 is an X-cube dichroic prism or a cascaded dichroic filter group. The X-cube dichroic prism is composed of four right-angled prisms cemented together, forming two intersecting dichroic film surfaces inside. Light of different wavelengths is reflected or transmitted on the dichroic film surfaces, thereby separating beams of different color channels from different exit surfaces. The cascaded dichroic filter group filters and separates light of specific wavelengths through different filters. After the dichroic optical component 2 separates the input image light into the first color channel beam and the second color channel beam, it guides them to the positions of the first entrance pupil grating IG1 of the first waveguide plate WG1 and the second entrance pupil grating IG2 of the second waveguide plate WG2 through the reflector group 21 or the folding prism. In this embodiment, the first color channel beam separated by the dichroic optical component 2 propagates along the first optical path, is reflected by the first reflecting surface in the mirror group 21, and then enters the first entrance pupil grating IG1 on the first waveguide plate WG1 at a preset incident angle; the second color channel beam separated by the dichroic optical component 2 propagates along the second optical path, is reflected by the second reflecting surface in the mirror group 21, and then enters the second entrance pupil grating IG2 on the second waveguide plate WG2 at a preset incident angle. The angle of each reflecting surface is determined according to the light output direction of the dichroic optical component 2 and the position of each entrance pupil grating to ensure that each color channel beam is accurately incident on the corresponding entrance pupil grating.

[0048] Please refer to Figure 2 and Figure 4Within the plane of each waveguide plate, the entrance pupil grating is positioned at the upper center of the waveguide plate, the dilating pupil gratings are positioned on the left and right sides of the entrance pupil grating and are approximately at the same horizontal height, and the exit pupil grating is positioned below the dilating pupil gratings. The beam diffracts from the entrance pupil grating and propagates horizontally to the left and right to the corresponding dilating pupil gratings, respectively. After diffracting by the dilating pupil gratings, it propagates vertically downwards to the exit pupil grating, and after diffracting by the exit pupil gratings, it exits the waveguide plate along the thickness direction.

[0049] Specifically, a first entrance pupil grating IG1, a first left diffusing pupil grating EG1_L, a first right diffusing pupil grating EG1_R, a first left exit pupil grating OE1_L, and a first right exit pupil grating OE1_R are formed on the first waveguide plate WG1. The first entrance pupil grating IG1 is circular with a diameter between 2.5mm and 7mm. Its grating period is set according to the center wavelength of the first color channel beam, and it is a multi-exposure volumetric holographic grating. In terms of specific setting and forming process, the first waveguide plate WG1 is a parallel flat plate glass with high flatness. The first entrance pupil grating IG1 is specifically set on the outer surface (away from the human eye side) or the inner surface (closer to the human eye side) of the first waveguide plate WG1. In this embodiment, the first entrance pupil grating IG1 is specifically set on the inner surface of the first waveguide plate WG1. To form this multi-exposure holographic grating, the process includes: firstly, spin-coating a photopolymer film with specific refractive index modulation capability onto the surface of the first waveguide plate WG1; then, using a laser matching the center wavelength of the first color channel beam, performing at least two holographic interference exposures: during the first exposure, the incident angles of the two interference beams are set so that the direction of the formed interference fringes corresponds to diffraction in the left direction; after the first exposure, the photopolymer film is partially pre-cured to fix the refractive index modulation distribution of the first set of interference fringes; during the second exposure, the incident angles of the two interference beams are adjusted so that the direction of the formed interference fringes corresponds to diffraction in the right direction. The exposure doses for the two exposures are controlled separately so that the refractive index modulation depths of the two sets of interference fringes are distributed according to a preset ratio, achieving a diffraction efficiency ratio of 0.8:1 to 1:0.8 in the left and right directions. Through the two exposures, two sets of periodic refractive index bright and dark fringe distributions with different directions are formed inside the photopolymer, and finally, the grating is cured and set by ultraviolet light. Two sets of interference fringes coexist and intersect within the photopolymer. Due to the angular selectivity of the volume holographic grating, each set of fringes only produces efficient diffraction in the incident direction that satisfies its own Bragg condition. The cross-coupling effect between the two sets of fringes on the diffraction efficiency can be controlled within an acceptable range by optimizing the exposure dose and the difference in fringe tilt angle. The multi-exposure volume holographic grating has the characteristic of high diffraction efficiency, with a total diffraction efficiency greater than 70% in the left and right directions of the first color channel beam, where the ratio of the diffraction efficiency in the left direction to the diffraction efficiency in the right direction is 0.8:1 to 1:0.8. The first entrance pupil grating IG1 is configured to receive the first color channel beam and couple the first color channel beam into the first waveguide plate WG1, while simultaneously diffracting to form a first left-propagating light and a first right-propagating light propagating to the left and right within the first waveguide plate WG1, respectively, and undergoing total internal reflection in the direction of propagation to the first left-expanding pupil grating and the first right-expanding pupil grating.Because the volumetric holographic grating contains two sets of interference fringes in different directions, the incident first color channel beam simultaneously satisfies the Bragg diffraction conditions of both sets of interference fringes, thus generating diffracted light in both left and right directions. Furthermore, due to the wavelength selectivity of the volumetric holographic grating, it efficiently diffracts only at specific wavelengths that satisfy the Bragg condition, while other wavelengths are directly transmitted without diffraction. Therefore, in the cascaded waveguide structure, the entrance pupil gratings on each waveguide plate do not diffract beams from non-corresponding color channels, achieving interlayer optical isolation. There is a synergistic effect between the volumetric holographic grating and the dichroic cascaded waveguide structure: the dichroic cascaded waveguide structure distributes beams from different color channels to different waveguide plates, while the wavelength selectivity of the volumetric holographic grating further ensures that each waveguide plate diffracts only the beam from its corresponding color channel; both together reduce interlayer optical crosstalk.

[0050] Please refer to Figure 4 and Figure 5The first left expanding pupil grating EG1_L and the first right expanding pupil grating EG1_R are arranged symmetrically in a mirror image with the first entrance pupil grating IG1 as the center. Specifically, they are disposed on the surface of the first waveguide plate WG1 and extend horizontally to both sides. Their formation process can be the same as that of the entrance pupil grating, using holographic exposure, or using nanoimprint lithography (NIL) combined with reactive ion etching (RIE) to form a surface relief structure on the waveguide plate surface. They are both divided into 5-15 sub-expanding pupil regions. Specifically, taking the division into 6 sub-expanding pupil regions as an example, the first left expanding pupil grating EG1_L is divided into 6 sub-regions L11 to L16 along the horizontal leftward direction, and the first right expanding pupil grating EG1_R is divided into 6 sub-regions R11 to R16 along the horizontal rightward direction. The diffraction efficiency of each sub-expanding pupil region gradually increases in the direction away from the first entrance pupil grating IG1, exhibiting a stepwise gradual increase from 5% to 90%. Taking the first left pupil grating EG1_L as an example, the diffraction efficiencies from region L11 (closest to IG1) to region L16 (farthest) are set as follows: 5% (L11), 15% (L12), 30% (L13), 50% (L14), 70% (L15), and 90% (L16). The diffraction efficiency distribution of regions R11 to R16 of the first right pupil grating EG1_R is mirror-symmetrical. The principle behind this gradual efficiency design is that as the light beam propagates from the entrance pupil grating to the left or right, a portion of the light energy is diffracted and coupled out each time it passes through a sub-pupil region, causing the energy of the beam to gradually weaken as it continues to propagate. By making the diffraction efficiency of the far-end region higher than that of the near-end region, the energy attenuation during beam propagation can be compensated, making the light energy diffracted and coupled out of each sub-region tend to be uniform. The intensity of the first left-guided light is uniformly expanded after diffraction by the first left-expanding pupil grating EG1_L; similarly, the intensity of the first right-guided light is also uniformly expanded after diffraction by the first right-expanding pupil grating EG1_R. The synergistic effect of this gradient efficiency design and the one-to-two symmetrical structure lies in the fact that the one-to-two structure requires the brightness and uniformity of the left and right beams to remain symmetrical. The gradient efficiency design, through a mirror-symmetrical efficiency distribution, ensures that the energy compensation degree of the left and right beams is consistent along their respective propagation paths, thereby guaranteeing the brightness symmetry of the binocular display and, consequently, the brightness uniformity of the displayed image within the final eye-tracking frame.

[0051] Please continue to refer to Figure 5The first left exit pupil grating OE1_L and the first right exit pupil grating OE1_R are also mirror-symmetrically arranged with the first entrance pupil grating IG1 as the center, specifically positioned at the location corresponding to the human eye's field of view on the first waveguide plate WG1. Their forming process is the same as that of the pupil dilator grating. They are also divided into 5-15 sub-exit pupil regions. Specifically, taking the division into 7 horizontal strip-shaped sub-exit pupil regions as an example, the first left exit pupil grating OE1_L is divided into 7 sub-regions from L21 to L27 from top to bottom, and the first right exit pupil grating OE1_R is divided into 7 sub-regions from R21 to R27 from top to bottom. In the direction away from the corresponding first left pupil dilator grating EG1_L or first right pupil dilator grating EG1_R, the diffraction efficiency of each sub-exit pupil region shows a stepwise gradual increase from 5% to 95%. Taking OE1_L as an example, the diffraction efficiencies from the top L21 region to the bottom L27 region are set as follows: 5% (L21), 15% (L22), 30% (L23), 45% (L24), 60% (L25), 78% (L26), and 95% (L27). The R21 to R27 regions of the first right exit pupil grating OE1_R also follow this pattern. Furthermore, the angle between the physical boundary line between adjacent sub-regions (including the sub-regions of the pupil grating and the exit pupil grating) and the horizontal direction is limited to between 20° and 160°. This angle limitation helps reduce diffraction stray light or spatial ghosting generated when the beam crosses the partition boundaries. The first left-guided light is diffracted by the first left-expanding pupil grating EG1_L and the first left-exiting pupil grating OE1_L to form the first left-output light; simultaneously, the first right-guided light is diffracted by the first right-expanding pupil grating EG1_R and the first right-exiting pupil grating OE1_R to form the first right-output light. The working process and technical effect of this structure are as follows: the left and right exiting pupil gratings further expand the beams after one-dimensional pupil expansion in a two-dimensional direction and couple them out of the waveguide plate, ultimately forming two large-area parallel beams directed towards the left and right eyes respectively. This "centrally coupled, bidirectional pupil expansion, and two-end exiting pupil" symmetrical diffraction mechanism, compared to the traditional single-eye single-waveguide scheme, allows for binocular display within the eye-tracking box range using only a single optical engine 1, reducing hardware costs and the overall weight of the head-mounted display device.

[0052] Please refer to Figure 4To ensure that the light emitted from the first left exit pupil grating is aligned with the incident direction of the first color channel beam, the grating vectors of the first left expansion pupil grating EG1_L and the first left exit pupil grating OE1_L are specifically designed. Similarly, the grating vectors of the first right expansion pupil grating EG1_R and the first right exit pupil grating OE1_R are also designed accordingly to ensure that the light emitted from the first right exit pupil grating is aligned with the incident direction of the first color channel beam. From a fundamental physical and mathematical perspective, this is achieved by ensuring that the sum of the grating vectors of the first entrance pupil grating IG1, the first left expansion pupil grating EG1_L, and the first left exit pupil grating OE1_L is zero, and also that the sum of the grating vectors of the first entrance pupil grating IG1, the first right expansion pupil grating EG1_R, and the first right exit pupil grating OE1_R is zero. Specifically, taking the left optical path on the first waveguide plate WG1 as an example, let the grating vector of the first entrance pupil grating IG1 be K_IG1, with its direction pointing to the left horizontally; the grating vector of the first left expanding pupil grating EG1_L be K_EG1_L, with its direction forming a certain angle with the horizontal direction, causing the beam to deflect from the horizontal propagation direction to the vertical downward propagation direction; the grating vector of the first left exit pupil grating OE1_L be K_OE1_L, with its direction causing the beam to deflect from the vertical propagation direction to a direction perpendicular to the waveguide plate plane. The three grating vectors satisfy the vector relationship K_IG1+K_EG1_L+K_OE1_L=0. The grating vector relationship of the right optical path is mirror-symmetrical to that of the left. This design ensures that the output light direction of each color channel is consistent with the input light direction. The working process and technical effect of this structure are as follows: during the process of the beam undergoing three consecutive diffractions—entrance pupil, expanding pupil, and exit pupil—the condition that the sum of the grating vectors (k-vectors) is zero can cancel out the dispersion angle deviation generated in each diffraction stage. This ensures that the angle of the image beam coupled out of the waveguide plate is consistent with the angle of the input beam initially emitted by the optical engine 1, thereby reducing image distortion and improving the angular fidelity of the final image.

[0053] Please refer to Figure 2 and Figure 4The second waveguide plate WG2 has a second entrance pupil grating IG2, a second left expanding pupil grating EG2_L, a second right expanding pupil grating EG2_R, a second left exit pupil grating OE2_L, and a second right exit pupil grating OE2_R. The second entrance pupil grating IG2 is also circular, with a diameter between 2.5mm and 7mm. Its grating period is set according to the center wavelength of the second color channel beam, and it is also a multi-exposure volume holographic grating, with a total diffraction efficiency of more than 70% for the second color channel beam in both left and right directions. The second entrance pupil grating IG2 is also configured to couple the second color channel beam into it and cause total internal reflection within it, diffracting to form a second left-propagating light beam propagating to the left and a second right-propagating light beam propagating to the right within the second waveguide plate WG2. The placement and forming process of each grating on the second waveguide plate WG2 are similar to those on the first waveguide plate WG1, and are processed separately through independent photolithography or exposure processes.

[0054] The second left pupil diffracting grating EG2_L and the second right pupil diffracting grating EG2_R are arranged symmetrically in mirror image to the second entrance pupil grating IG2, dividing the area into 5-15 sub-pupil regions. The diffraction efficiency of each sub-pupil region gradually increases in the direction away from the second entrance pupil grating IG2, ranging from 5% to 95%. The intensity of the second left-guided light is uniformly expanded after diffraction by the second left pupil diffracting grating EG2_L; similarly, the intensity of the second right-guided light is also uniformly expanded after diffraction by the second right pupil diffracting grating EG2_R.

[0055] The second left exit pupil grating OE2_L and the second right exit pupil grating OE2_R are arranged symmetrically in mirror image to the left and right of the second entrance pupil grating IG2, dividing the area into 5-15 sub-exit pupil regions. The diffraction efficiency of each sub-exit pupil region gradually increases in the direction away from the corresponding second left diffraction pupil grating EG2_L or second right diffraction pupil grating EG2_R, ranging from 5% to 95%. The second left guided light, after diffraction by the second left diffraction pupil grating EG2_L and the second left exit pupil grating OE2_L, forms the second left output light; simultaneously, the second right guided light, after diffraction by the second right diffraction pupil grating EG2_R and the second right exit pupil grating OE2_R, forms the second right output light.

[0056] Similar to the first waveguide plate, the grating vectors on the second waveguide plate are also specifically designed to ensure that the direction of the outgoing light rays is consistent. That is, physically, the sum of the grating vectors of the second entrance pupil grating IG2, the second left diffusing pupil grating EG2_L, and the second left exit pupil grating OE2_L is zero, and the sum of the grating vectors of the second entrance pupil grating IG2, the second right diffusing pupil grating EG2_R, and the second right exit pupil grating OE2_R is zero.

[0057] The first left exit pupil grating OE1_L, the first right exit pupil grating OE1_R, the second left exit pupil grating OE2_L, and the second right exit pupil grating OE2_R all have the same exit angle, ensuring that the output light directions of each color channel are consistent. The ratio of the grating period of the first left exit pupil grating OE1_L to the center wavelength of the first color channel beam is equal to the ratio of the grating period of the second left exit pupil grating OE2_L to the center wavelength of the second color channel beam; similarly, the ratio of the grating period of the first right exit pupil grating OE1_R to the center wavelength of the first color channel beam is equal to the ratio of the grating period of the second right exit pupil grating OE2_R to the center wavelength of the second color channel beam. This proportional relationship ensures that the output light from different color channels is directed in the same direction at the human eye, allowing different color images to be superimposed to form a full-color image without the need for additional angle calibration.

[0058] According to the grating diffraction equation (sinθ_m=sinθ_i+mλ / d, where θ_m is the diffraction angle, θ_i is the incident angle, m is the diffraction order, λ is the wavelength, and d is the grating period), the diffraction angle directly depends on the ratio of wavelength (λ) to grating period (d). If a broadband mixed light containing red, green, and blue wavelengths is all directed into a single grating within the same single-layer waveguide, the diffraction angle of the red light will be much larger than that of the blue light due to the longer wavelength. This difference in diffraction angles leads to a significant difference in the "step distance" between the red and blue light when they undergo total internal reflection (TIR) ​​inside the waveguide. Consequently, the red and blue light cannot overlap spatially when exiting the exit pupil grating, resulting in a rainbow effect and color shift.

[0059] This solution mitigates this problem through a cascaded waveguide design: since the first waveguide plate WG1 is dedicated to the first color (e.g., red light) and the second waveguide plate WG2 is dedicated to the second color (e.g., green light), a larger period d1 can be designed for the first exit pupil grating (e.g., OE1_L), and a smaller period d2 can be designed for the second exit pupil grating (e.g., OE2_L). This makes the ratio of the first color wavelength λ1 to d1 close to the ratio of the second color wavelength λ2 to d2 (i.e., a proportional relationship). This physically ensures that red and green light have nearly identical diffraction angles and total internal reflection step distances within their respective waveguides, allowing them to spatially overlap upon exiting, thus reducing color difference. Simultaneously, because green light enters the second waveguide plate WG2, which is specifically designed for its wavelength, even if red light penetrates the second waveguide plate WG2, it will only pass through directly without diffraction because red light does not satisfy the "Bragg diffraction matching condition" of the holographic grating on the second waveguide, thereby reducing crosstalk between different color levels.

[0060] Please refer to Figure 1 and Figure 2The dispersion compensation structure DCS is disposed in the physical gap between the first waveguide plate WG1 and the second waveguide plate WG2. This structure is fixed by optical bonding or vacuum coating. The compensation mechanism of the dispersion compensation structure DCS is as follows: In the cascaded waveguide structure, the first waveguide plate WG1 is located closer to the human eye, and the second waveguide plate WG2 is located farther from the human eye. The first color channel beam exits the exit pupil grating of the first waveguide plate WG1 and reaches the human eye directly, while the second color channel beam exits the exit pupil grating of the second waveguide plate WG2 and must pass through the dispersion compensation structure DCS and the first waveguide plate WG1 sequentially before reaching the human eye. During the passage through the dispersion compensation structure DCS and the first waveguide plate WG1, the second color channel beam will experience lateral displacement and angular deviation due to refraction, causing the imaging positions of the second color channel beam and the first color channel beam at the human eye to not coincide. The dispersion compensation structure DCS compensates for the deviations generated during the penetration process by applying a preset reverse displacement and / or reverse angular deflection to the second color channel beam.

[0061] Dispersion compensation DCS structures include at least one of the following forms:

[0062] A refractive index gradient layer is formed, with its refractive index continuously varying along the thickness direction (from a first refractive index near the first waveguide plate WG1 to a second refractive index near the second waveguide plate WG2, the first refractive index ranging from 1.5 to 1.7, and the second refractive index ranging from 1.7 to 2.0). The refractive index gradient layer can be prepared using a sol-gel method, where the concentration gradient of the sol components is controlled during spin coating, and a thin film with a continuously varying refractive index along the thickness direction is formed after heat treatment. When light beams emitted from different waveguide plates pass obliquely through the gap between the plates, lateral displacement occurs. The gradient refractive index layer can compensate for the lateral optical path displacement caused by the difference in physical thickness by guiding the bending trajectory of the light beam.

[0063] A dispersion compensation grating is formed on the surface of the dispersion compensation structure DCS. This is a micro / nano grooved structure with low diffraction efficiency, with a grating period of 500nm~2000nm and a diffraction efficiency of 1%~5%. It can be formed by electron beam lithography or nanoimprint lithography, and the diffraction efficiency can be precisely controlled within the range of 1%~5% by controlling the grating groove depth. The dispersion compensation grating applies a small reverse deflection angle (Δθ) to the specific wavelength beam passing through it, compensating for the slight angular deviation caused by the difference in dispersive refractive index of different wavelengths in the glass medium.

[0064] Multilayer dielectric thin films produce different phase delays for light of different wavelengths. By alternating vacuum sputtering deposition of high and low refractive index materials (including 4 to 20 alternating layers of high and low refractive index dielectrics, such as TiO2 / SiO2 alternating layers, with each layer having a thickness of 50nm to 200nm), the thin film interference effect is utilized to produce different phase delays for transmitted light of different wavelengths. This corrects the wavefront phase difference caused by the stacking of waveguide plate thicknesses for different color channel beams, making the wavefronts of the beams in each color channel tend to be consistent at the human eye.

[0065] Specifically, the positional and / or angular deviations are mainly caused by refraction of the color channel beam emitted from the waveguide plate furthest from the eye as it passes through the dispersion compensation structure and the waveguide plate closest to the eye before reaching the eye. A specific compensation calculation example illustrates the operation of the dispersion compensation structure DCS: Assume the first waveguide plate WG1 has a thickness of 0.5 mm and a refractive index of 1.9. The second color channel beam (green light, center wavelength 532 nm) exits from the exit pupil grating of the second waveguide plate WG2 at a 30° angle. When this green light passes through the dispersion compensation structure DCS and the first waveguide plate WG1, refraction will cause a lateral displacement of approximately 0.15 mm and an angular deviation of approximately 0.1°. The multilayer dielectric film corrects the wavefront phase difference by generating a specific phase delay for the green light. In the dispersion compensation structure DCS, the refractive index gradient layer guides light bending through continuous changes in its refractive index, compensating for a lateral displacement of approximately 0.10 mm. The dispersion compensation grating compensates for angular deviation by applying a reverse deflection angle of approximately 0.1°. The remaining lateral displacement of approximately 0.05 mm is compensated through phase modulation of the multilayer dielectric film. After comprehensive compensation by the dispersion compensation structure DCS, the image position deviation between the second color channel beam and the first color channel beam at the human eye can be reduced to within 0.02 mm, and the angular deviation can be reduced to within 0.05°.

[0066] The combined effect of these structures can compensate for the positional and / or angular deviations of the first and second color channel beams after propagation through different waveguides, so that the imaging positions of the first left output light and the second left output light at the human eye coincide, and the imaging positions of the first right output light and the second right output light at the human eye coincide.

[0067] The thickness of both the first waveguide plate WG1 and the second waveguide plate WG2 is 0.3mm-0.8mm, and their refractive index is 1.7-2.1. They are made of high-refractive-index optical glass. The thickness of the dispersion compensation structure DCS is 0.01mm-0.1mm. The horizontal distance from the center of the first left exit pupil grating OE1_L to the center of the first right exit pupil grating OE1_R, and the horizontal distance from the center of the second left exit pupil grating OE2_L to the center of the second right exit pupil grating OE2_R, are both set to the interpupillary distance of the human eye, at 60mm-70mm. The longitudinal distance along the plane of the first waveguide plate WG1 from the center of the first left exit pupil grating OE1_L, perpendicular to the left and right directions, and the longitudinal distance along the plane of the second waveguide plate WG2 from the center of the second entrance pupil grating IG2 to the center of the second left exit pupil grating OE2_L, perpendicular to the left and right directions, are both 8mm-25mm.

[0068] The projection positions of the first entrance pupil grating IG1 and the second entrance pupil grating IG2 on the mutually parallel waveguide plate plane can be aligned with each other; or they can be staggered in the horizontal direction, with the staggered distance being less than the smaller of the radius of the first entrance pupil grating IG1 and the radius of the second entrance pupil grating IG2, in order to reduce interlayer optical crosstalk.

[0069] The complete working process of this embodiment is as follows:

[0070] Step 1: The microdisplay 11 in the light engine 1 generates full-color image light containing at least two color channels, and the collimating optics 12 shapes the image light into a collimated parallel beam.

[0071] Step 2: The collimated input image light enters the color separation optical component 2, which separates the input image light into the first color channel beam and the second color channel beam according to wavelength.

[0072] Step 3: The separated first color channel beam is guided by the mirror group 21 or the folding prism to the first entrance pupil grating IG1 on the first waveguide plate WG1, and the second color channel beam is guided by the mirror group 21 or the folding prism to the second entrance pupil grating IG2 on the second waveguide plate WG2. The second color channel beam passes through the first waveguide plate WG1 before reaching the second entrance pupil grating IG2. Due to the wavelength selectivity of the first entrance pupil grating IG1, the second color channel beam is directly transmitted through the first waveguide plate WG1 without diffraction.

[0073] Step 4: After the first color channel beam is incident on the first entrance pupil grating IG1, due to the two sets of interference fringes recorded in the multiple exposure holographic grating, a first left-propagating light and a first right-propagating light are simultaneously generated. The first left-propagating light and the first right-propagating light propagate to the left and right horizontally in the first waveguide plate WG1 respectively through total internal reflection.

[0074] Step 5: After the first left-guided light reaches the first left-expanding pupil grating EG1_L, it is gradually diffracted and deflected to the vertically downward propagation direction, while simultaneously achieving one-dimensional expansion of the pupil in the horizontal direction. Since the diffraction efficiency of each sub-pupil region gradually increases in the direction away from the first entrance pupil grating IG1, the diffracted light energy tends to be uniformly distributed in the horizontal direction. The first right-guided light undergoes the same process in the first right-expanding pupil grating EG1_R.

[0075] Step Six: After the expanded pupil beam reaches the first left exit pupil grating OE1_L, it is gradually diffracted and coupled out of the first waveguide plate WG1, forming the first left output beam. Since the diffraction efficiency of each sub-exit pupil region gradually increases in the direction away from the first left expanded pupil grating EG1_L, the coupled light energy tends to be uniformly distributed in the longitudinal direction. The first right exit pupil grating OE1_R similarly couples the beam out to form the first right output beam.

[0076] Step 7: The second color channel beam undergoes the same process as steps 4 to 6 in the second waveguide plate WG2 to form the second left output beam and the second right output beam.

[0077] Step 8: After the second left and second right output beams exit from the second waveguide plate WG2, they first pass through the dispersion compensation structure DCS. The dispersion compensation structure DCS applies a preset reverse displacement and / or reverse angle deflection to the second color channel beam to pre-compensate for the positional and angular deviations that will occur when the beam subsequently passes through the first waveguide plate WG1 due to refraction. The second color channel beam, after being compensated by the dispersion compensation structure DCS, continues to pass through the first waveguide plate WG1 and reaches the human eye.

[0078] Step Nine: The first left output light and the dispersion-compensated second left output light are projected onto the left eye, forming a full-color image for the left eye; the first right output light and the dispersion-compensated second right output light are projected onto the right eye, forming a full-color image for the right eye. The wearer's left and right eyes each see the corresponding full-color image, achieving binocular display.

[0079] The implementation principle of this embodiment is as follows: This embodiment achieves binocular display using a single-optical engine 1 in conjunction with dichroic optical components 2 and cascaded waveguide components 3, reducing the number of optical engines used and thus lowering hardware costs and power consumption. Multiple waveguides correspond to beams of different color channels, reducing the dispersion problem of different wavelengths of light in traditional single-layer waveguides. The dispersion compensation structure DCS further reduces the deviation of beams of different color channels after propagation on different waveguides, ensuring that the different color images seen by the left and right eyes can be accurately superimposed, improving the image quality of the full-color AR display.

[0080] Example 2

[0081] Please refer to Figure 1 and Figure 2 The difference between this embodiment and the previous embodiment is that the cascaded waveguide assembly 3 further includes a third waveguide plate WG3, and the color separation optical assembly 2 further separates the input image light into a third color channel beam. The third waveguide plate WG3 has a third entrance pupil grating IG3, a third left diopter pupil grating EG3_L, a third right diopter pupil grating EG3_R, a third left exit pupil grating OE3_L, and a third right exit pupil grating OE3_R formed on it. The first color channel beam is red light, the second color channel beam is green light, and the third color channel beam is blue light. The first waveguide plate WG1, the second waveguide plate WG2, and the third waveguide plate WG3 are stacked sequentially from the human eye side to the external side, and a dispersion compensation structure DCS is provided between adjacent waveguide plates. The design parameters of the dispersion compensation structure DCS between the first waveguide plate WG1 and the second waveguide plate WG2 are optimized for the optical path of the second color channel beam (green light) passing through the first waveguide plate WG1 to reach the human eye. The design parameters of the dispersion compensation structure DCS between the second waveguide plate WG2 and the third waveguide plate WG3 are independently optimized for the optical path of the third color channel beam (blue light) passing through the second waveguide plate WG2, the dispersion compensation structure DCS between the first waveguide plate WG1 and the second waveguide plate WG2, and the first waveguide plate WG1 to reach the human eye. The refractive index gradient, grating period, and thin film parameters of the two dispersion compensation structures DCS are different. The working process and technical effects of this stacked structure are as follows: the three primary colors of red, green and blue are coupled into three independent and parallel waveguide plates for independent transmission, reducing the color shift problem caused by the difference in diffraction angle in a single waveguide layer due to broadband mixed light; since the grating of each waveguide layer (especially the multi-exposure volume holographic grating) has high angle and wavelength selectivity only for specific wavelengths (i.e., satisfying specific Bragg conditions), mismatched wavelengths will be directly transmitted, thus reducing signal crosstalk between layers; combined with the customized dispersion compensation structure DCS between adjacent waveguide layers, the positional and angular deviations caused by the physical stacking of the three layers are corrected, which ultimately helps to improve the color saturation of the full-color binocular AR display.

[0082] The structure, efficiency gradient characteristics, thickness parameters, and grating vector relationships of the third entrance pupil grating IG3, the third left expansion pupil grating EG3_L, the third right expansion pupil grating EG3_R, the third left exit pupil grating OE3_L, and the third right exit pupil grating OE3_R on the third waveguide plate WG3 are all matched with the grating parameters corresponding to the first waveguide plate WG1 or the second waveguide plate WG2 and independently optimized according to the center wavelength of the third color channel beam. Adding the third waveguide plate WG3 allows blue light to propagate in a dedicated waveguide plate. The grating parameters for blue light (including grating period, diffraction efficiency, etc.) are independently designed for the center wavelength of blue light (460nm), avoiding mutual interference caused by differences in diffraction angles when blue light propagates with red and green light in the same waveguide plate.

[0083] The implementation principle of this embodiment is as follows: by adding a third waveguide plate WG3 and a corresponding grating structure, independently optimized grating parameters can be provided for the beams of the red, green, and blue color channels, achieving more refined color separation transmission. By setting a dispersion compensation structure DCS between adjacent waveguide plates, the deviation between beams of different color channels is further compensated, so that the images of the three colors can be accurately superimposed at the human eye. Compared with the scheme using only two waveguide plates, the three-layer waveguide plate scheme allows each color channel beam to propagate in a waveguide plate independently optimized for its wavelength, reducing the reduction in diffraction efficiency and residual dispersion caused by grating parameter compromise when two different wavelengths of light share the same waveguide plate, thereby further improving color reproduction.

[0084] The above are specific embodiments of this application and do not constitute a limitation on the scope of protection of this application. Any other corresponding changes and modifications made based on the technical concept of this application should be included within the scope of protection of this application.

Claims

1. A color-separated one-to-two optical waveguide display device based on cascaded waveguides, characterized in that, include: A light engine (1) is used to generate light from an input image containing at least two color channels; A color separation optical component (2) is disposed on the light output path of the light engine (1) for separating the input image light into at least a first color channel beam and a second color channel beam, wherein the first color channel beam and the second color channel beam have different and separate wavelength ranges. The cascaded waveguide assembly (3) includes a first waveguide plate (WG1) and a second waveguide plate (WG2) stacked together, wherein the first waveguide plate (WG1) corresponds to the first color channel and the second waveguide plate (WG2) corresponds to the second color channel; The first waveguide plate (WG1) has a first entrance pupil grating (IG1), a first left diffracting pupil grating (EG1_L), a first right diffracting pupil grating (EG1_R), a first left exit pupil grating (OE1_L), and a first right exit pupil grating (OE1_R). The first entrance pupil grating (IG1) is configured to receive the first color channel beam and couple the first color channel beam into the first waveguide plate (WG1), causing total internal reflection in the direction of propagation to the first left diffracting pupil grating and the first right diffracting pupil grating. The first left diffracting pupil grating (EG1_L) and the first right diffracting pupil grating (EG1_R) are used to diffract the beam in the direction of the first left exit pupil grating (OE1_L) and the first right exit pupil grating (OE1_R). The first left exit pupil grating (OE1_L) and the first right exit pupil grating (OE1_R) are used to couple the first color channel beam out. The second waveguide plate (WG2) has a second entrance pupil grating (IG2), a second left diffracting pupil grating (EG2_L), a second right diffracting pupil grating (EG2_R), a second left exit pupil grating (OE2_L), and a second right exit pupil grating (OE2_R). The second entrance pupil grating (IG2) is configured to receive the second color channel beam and couple the second color channel beam into the second waveguide plate (WG2), causing total internal reflection in the direction of propagation to the second left diffracting pupil grating and the second right diffracting pupil grating. The second left diffracting pupil grating (EG2_L) and the second right diffracting pupil grating (EG2_R) are used to diffract the beam in the direction of the second left exit pupil grating (OE2_L) and the second right exit pupil grating (OE2_R). The second left exit pupil grating (OE2_L) and the second right exit pupil grating (OE2_R) are used to couple the second color channel beam out. as well as A dispersion compensation structure (DCS) is disposed between the first waveguide plate (WG1) and the second waveguide plate (WG2) and is configured to compensate for positional and / or angular deviations of the first color channel beam and the second color channel beam caused by transmission through different waveguide plates.

2. The color-separated one-to-two optical waveguide display device based on cascaded waveguides according to claim 1, characterized in that, The cascaded waveguide assembly (3) also includes a third waveguide plate (WG3), and the color separation optical assembly (2) further separates the input image light into a third color channel beam; the third waveguide plate (WG3) is formed with a third entrance pupil grating (IG3), a third left pupil grating (EG3_L), a third right pupil grating (EG3_R), a third left exit pupil grating (OE3_L), and a third right exit pupil grating (OE3_R); the first color channel beam is red light, the second color channel beam is green light, and the third color channel beam is blue light; the first waveguide plate (WG1), the second waveguide plate (WG2), and the third waveguide plate (WG3) are stacked sequentially from the human eye side to the outside side, and the dispersion compensation structure (DCS) is provided between adjacent waveguide plates.

3. The color-separated one-to-two optical waveguide display device based on cascaded waveguides according to claim 1, characterized in that, The grating period of the first entrance pupil grating (IG1) is set according to the center wavelength of the first color channel beam, and the grating period of the second entrance pupil grating (IG2) is set according to the center wavelength of the second color channel beam. Both the first entrance pupil grating (IG1) and the second entrance pupil grating (IG2) are multiple exposure volume holographic gratings. The multiple exposure volume holographic grating records at least two sets of interference fringes in different directions to simultaneously diffract the incident light to the left and to the right. Furthermore, the total diffraction efficiency of the first entrance pupil grating (IG1) for the first color channel beam in the left and to the right directions is greater than 70%, and the total diffraction efficiency of the second entrance pupil grating (IG2) for the second color channel beam in the left and to the right directions is greater than 70%.

4. The color-separated one-to-two optical waveguide display device based on cascaded waveguides according to claim 1, characterized in that, The first left pupil grating (EG1_L) and the first right pupil grating (EG1_R) on the first waveguide plate (WG1) are arranged in a mirror-symmetrical configuration with the first entrance pupil grating (IG1) as the center. The first left exit pupil grating (OE1_L) and the first right exit pupil grating (OE1_R) are also arranged in a mirror-symmetrical configuration with the first entrance pupil grating (IG1) as the center. The grating vectors of the first left pupil grating (EG1_L) and the first left exit pupil grating (OE1_L) are designed such that the light emitted from the first left exit pupil grating is consistent with the incident direction of the first color channel beam. Furthermore, the grating vectors of the first right pupil grating (EG1_R) and the first right exit pupil grating (OE1_R) are designed such that the light emitted from the first right exit pupil grating is consistent with the incident direction of the first color channel beam. The second left pupil grating (EG2_L) and the second right pupil grating (EG2_R) on the second waveguide plate (WG2) are arranged in a mirror-symmetrical configuration with the second entrance pupil grating (IG2) as the center. The second left exit pupil grating (OE2_L) and the second right exit pupil grating (OE2_R) are also arranged in a mirror-symmetrical configuration with the second entrance pupil grating (IG2) as the center. The grating vectors of the second left pupil grating (EG2_L) and the second left exit pupil grating (OE2_L) are designed such that the light emitted from the second left exit pupil grating is consistent with the incident direction of the second color channel beam. Furthermore, the grating vectors of the second right pupil grating (EG2_R) and the second right exit pupil grating (OE2_R) are designed such that the light emitted from the second right exit pupil grating is consistent with the incident direction of the second color channel beam.

5. The color-separated one-to-two optical waveguide display device based on cascaded waveguides according to claim 1, characterized in that, The first left exit pupil grating (OE1_L), the first right exit pupil grating (OE1_R), the second left exit pupil grating (OE2_L), and the second right exit pupil grating (OE2_R) have the same exit angle; the ratio of the grating period of the first left exit pupil grating (OE1_L) to the center wavelength of the first color channel beam is equal to the ratio of the grating period of the second left exit pupil grating (OE2_L) to the center wavelength of the second color channel beam; the ratio of the grating period of the first right exit pupil grating (OE1_R) to the center wavelength of the first color channel beam is equal to the ratio of the grating period of the second right exit pupil grating (OE2_R) to the center wavelength of the second color channel beam.

6. The color-separated one-to-two optical waveguide display device based on cascaded waveguides according to claim 1, characterized in that, The dispersion compensation structure (DCS) includes at least one of a refractive index gradient layer, a dispersion compensation grating, and a multilayer dielectric thin film; When the dispersion compensation structure (DCS) includes a refractive index gradient layer, the refractive index of the refractive index gradient layer continuously transitions from a first refractive index near the first waveguide plate (WG1) to a second refractive index near the second waveguide plate (WG2), wherein the range of the first refractive index is 1.5 to 1.7 and the range of the second refractive index is 1.7 to 2.

0. When the dispersion compensation structure (DCS) includes a dispersion compensation grating, the grating period of the dispersion compensation grating is 500nm~2000nm, the diffraction efficiency is 1%~5%, and it is formed on the surface of the dispersion compensation structure (DCS). When the dispersion compensation structure (DCS) includes a multilayer dielectric film, the multilayer dielectric film includes 4 to 20 alternating high-refractive-index dielectric layers and low-refractive-index dielectric layers, each layer having a thickness of 50 nm to 200 nm, and producing different phase delays for light of different wavelengths.

7. The color-separated one-to-two optical waveguide display device based on cascaded waveguides according to claim 1, characterized in that, The color separation optical component (2) is an X-cube color separation prism or a cascaded dichroic filter group; after the color separation optical component (2) separates the input image light into at least the first color channel beam and the second color channel beam according to the wavelength, the first color channel beam and the second color channel beam are guided to the positions of the first entrance pupil grating (IG1) of the first waveguide plate (WG1) and the second entrance pupil grating (IG2) of the second waveguide plate (WG2) respectively through the mirror group or the folding prism.

8. The color-separated one-to-two optical waveguide display device based on cascaded waveguides according to claim 1, characterized in that, The first left pupil grating (EG1_L) and the first right pupil grating (EG1_R) are each divided into 5 to 15 sub-pupil regions, and the diffraction efficiency of each sub-pupil region gradually increases in the direction away from the first entrance pupil grating (IG1); the second left pupil grating (EG2_L) and the second right pupil grating (EG2_R) are each divided into 5 to 15 sub-pupil regions, and the diffraction efficiency of each sub-pupil region gradually increases in the direction away from the second entrance pupil grating (IG2); the diffraction efficiency of the sub-pupil regions ranges from 5% to 95%; The first left exit pupil grating (OE1_L) and the first right exit pupil grating (OE1_R) are each divided into 5 to 15 sub-exit pupil regions. The diffraction efficiency of each sub-exit pupil region gradually increases in the direction away from the corresponding first left diffraction pupil grating (EG1_L) or the first right diffraction pupil grating (EG1_R). The second left exit pupil grating (OE2_L) and the second right exit pupil grating (OE2_R) are each divided into 5 to 15 sub-exit pupil regions. The diffraction efficiency of each sub-exit pupil region gradually increases in the direction away from the corresponding second left diffraction pupil grating (EG2_L) or the second right diffraction pupil grating (EG2_R). The diffraction efficiency of the sub-exit pupil regions ranges from 5% to 95% to ensure the brightness uniformity of the displayed image within the eye movement frame.

9. The color-separated one-to-two optical waveguide display device based on cascaded waveguides according to claim 1, characterized in that, The thickness of the first waveguide plate (WG1) and the second waveguide plate (WG2) are both 0.3mm~0.8mm, and the refractive index is both 1.7~2.1; the thickness of the dispersion compensation structure (DCS) is 0.01mm~0.1mm; the horizontal distance from the center of the first left exit pupil grating (OE1_L) to the center of the first right exit pupil grating (OE1_R), and the horizontal distance from the center of the second left exit pupil grating (OE2_L) to the center of the second right exit pupil grating (OE2_R) are both 60mm~70mm; the longitudinal distance from the center of the first entrance pupil grating (IG1) to the center of the first left exit pupil grating (OE1_L) along the plane of the first waveguide plate (WG1) perpendicular to the left and right directions, and the longitudinal distance from the center of the second entrance pupil grating (IG2) to the center of the second left exit pupil grating (OE2_L) along the plane of the second waveguide plate (WG2) perpendicular to the left and right directions are both 8mm~25mm.

10. The color-separated one-to-two optical waveguide display device based on cascaded waveguides according to claim 1, characterized in that, The light engine (1) includes a microdisplay (11) and a collimating optical component (12). The microdisplay (11) is an LCOS microdisplay, a MicroLED microdisplay, a DLP microdisplay, or an LBS microdisplay. The first entrance pupil grating (IG1) and the second entrance pupil grating (IG2) are both circular with a diameter of 2.5 mm to 7 mm. The projection positions of the first entrance pupil grating (IG1) and the second entrance pupil grating (IG2) on the mutually parallel waveguide plate plane are staggered in the horizontal direction. The staggered distance is less than the smaller value between the radius of the first entrance pupil grating (IG1) and the radius of the second entrance pupil grating (IG2).

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