Display system and modulation method thereof

Abstract

The invention provides a display system and a modulation method thereof, and relates to the technical field of display, the display system comprises an optical machine and a waveguide arranged at a light outlet of the optical machine, and further comprises an optical modulation lens assembly and / or a modulation grating, the optical modulation lens assembly is located between the optical machine and the waveguide, and the modulation grating is arranged on the waveguide. Wavefront from the ray machine is adjusted through the optical modulation lens assembly and / or the modulation grating, so that a far-focus or infinite-distance virtual image is formed at the exit pupil position of the waveguide. Divergent light generated by a near-focus output light machine can be converted into parallel light, so that the system can form far-focus or infinite-distance virtual image display. And the modulated light enters the waveguide in a plane wave or approximate plane wave form, is propagated in the waveguide at a fixed angle, and is finally coupled to human eyes through the exit pupil grating. And after receiving the parallel light, human eyes can sense a virtual image at a far-focus or infinite-distance position, so that natural and comfortable watching experience is realized. An existing near-focus optical machine can be adapted with the minimum change, and meanwhile the waveguide structure is kept compact.

Description

Technical Field

[0001] This application relates to the field of display technology, specifically to a display system and its modulation method. Background Technology

[0002] In existing technologies, a large number of optical engine systems on the market are designed as near-focus output projection optical engines. The imaging surface of this type of optical engine is located within a short distance (typically tens to hundreds of millimeters) of the output end. This design offers advantages such as short optical paths and high integration in short-focus projection and near-eye displays. However, when such near-focus optical engines are used in conjunction with waveguide systems, their output light is divergent. The image formed after propagation through the waveguide still retains the near-focus display characteristics, meaning the virtual image is positioned close to the eyes. This forces the human eye to continuously adjust the lens focal length to focus on the image, causing visual fatigue and discomfort, and failing to meet the needs of prolonged wear or immersive displays.

[0003] To address the aforementioned issues, the industry has undertaken several technological attempts. For example, some research has proposed adjusting the focal length by modifying the projection lens group within the optical engine; or introducing a variable-focus liquid crystal lens to switch between near and far focus. However, such solutions suffer from structural complexity, high cost, and difficulty in maintaining optical axis consistency. Furthermore, some solutions attempt to change the direction of the coupled light by adjusting the exit pupil grating structure of the waveguide, but these typically only allow for minor adjustments to the exit angle and cannot fundamentally achieve the conversion from near-focus imaging to infinity imaging.

[0004] The market demand for infinity imaging waveguide display systems is growing, especially in near-eye display devices such as AR smart glasses. Users desire virtual images located at infinity to match the viewing experience with real-world distant scenes, reducing visual convergence and focusing conflicts. However, existing combinations of near-focus optical engines and waveguide systems struggle to achieve this effect. Therefore, there is an urgent need for a solution that can modulate the output light into parallel light to achieve infinity display without altering the original optical engine structure. Summary of the Invention

[0005] The purpose of this application is to provide a display system and its modulation method, which can realize parallel light modulation of the near-focus output optical engine to obtain a display effect of far focus or infinity.

[0006] One aspect of this application provides a display system including an optical engine and a waveguide disposed at the light output port of the optical engine, and further including an optical modulation lens assembly and / or a modulation grating. The optical modulation lens assembly is located between the optical engine and the waveguide, and the modulation grating is disposed on the waveguide. The wavefront from the optical engine is adjusted by the optical modulation lens assembly and / or the modulation grating to form a far-focus or infinity virtual image at the exit pupil position of the waveguide.

[0007] Optionally, when an optical modulation lens assembly is disposed between the optomechanism and the waveguide, 1 / f = 1 / L is satisfied. 1 / S0; f is the focal length of the optical modulation lens assembly, L is the target design distance, and S0 is the geometric distance of the output virtual image of the optomechanical system.

[0008] Optionally, when the modulation grating is disposed on the waveguide, n satisfies in ·sinθ i +m·λ / Λ=n wg ·sinθ wg ;n in It is the refractive index of the incident medium, θ i Where is the incident angle of the waveguide, m is the diffraction order, λ is the operating wavelength, Λ is the grating period, and n wg It is the refractive index of the waveguide material, θ wg It is the angle at which light propagates within the waveguide.

[0009] Optionally, the modulation grating satisfies Λ(x) = Λ0 + kx; Λ0 is the period of the center position of the modulation grating, k is a coefficient, and x is the lateral coordinate along the surface of the modulation grating.

[0010] Optionally, when the optical modulation lens assembly and the modulation grating are included, the optical modulation lens assembly satisfies: 1 / Rres=1 / R+1 / f, where R is the original wavefront radius of curvature, Rres is the residual radius of curvature, and f is the focal length of the optical modulation lens assembly. Meanwhile, the modulation grating satisfies: Δn·h(x)≈ x² / (2Rres), where Δn is the refractive index difference between the grating material and the waveguide material, and h(x) is the local thickness of the grating at position x.

[0011] Optionally, the optical modulation lens assembly includes a single negative focal length lens, or a double or multiple composite lens, or a freeform surface lens, and the distance between it and the light outlet of the optical engine is 1mm to 10mm.

[0012] Optionally, the modulation grating includes an entrance pupil grating, a dilation pupil grating, or an exit pupil grating.

[0013] Another aspect of this application provides a modulation method for a display system, employing the above-described display system, including: Receive wavefront from the optical engine; The wavefront is modulated by an optical modulation lens assembly and / or a modulation grating to make it a plane wave or a spherical wave with reduced curvature for propagation within the waveguide.

[0014] Optionally, modulating the wavefront using an optical modulation lens assembly and / or a modulation grating to make it a plane wave or a spherical wave with reduced curvature for propagation within the waveguide includes: When the optical modulation lens assembly is used, 1 / f = 1 / L is satisfied. 1 / S0; f is the focal length of the optical modulation lens assembly, L is the target design distance, and S0 is the geometric distance of the output virtual image of the optomechanical system; When the modulation grating is used, n satisfies in ·sinθ i +m·λ / Λ=n wg ·sinθ wg ;n in It is the refractive index of the incident medium, θ i Where is the incident angle of the waveguide, m is the diffraction order, λ is the operating wavelength, Λ is the grating period, and n wg It is the refractive index of the waveguide material, θ wg It is the angle at which light propagates within the waveguide.

[0015] Optionally, modulating the wavefront using an optical modulation lens assembly and / or a modulation grating to make it a plane wave or a spherical wave with reduced curvature for propagation within the waveguide includes: When the optical modulation lens assembly and the modulation grating are used, the optical modulation lens assembly modulates the wavefront curvature 1 / R of the optomechanical output into a residual curvature 1 / Rres, satisfying 1 / Rres=1 / R0+1 / f, where R is the original wavefront curvature radius, Rres is the residual curvature radius, and f is the focal length of the optical modulation lens assembly. The modulation grating further compensates for the residual wavefront, satisfying Δn·h(x)≈ x² / (2Rres), where Δn is the refractive index difference between the grating material and the waveguide material, and h(x) is the local thickness of the grating at position x.

[0016] The display system and modulation method provided in this application, by setting an optical modulation lens assembly and / or modulation grating, can convert the divergent light generated by the near-focus output optical engine into parallel light, thereby enabling the system to form a virtual image display at a far-focus or infinity. The modulated light enters the waveguide in the form of a plane wave or near-plane wave, propagates at a fixed angle in the waveguide, and is finally coupled out to the human eye by the exit pupil grating. After receiving the parallel light, the human eye can perceive the virtual image at a far-focus or infinity position, achieving a natural and comfortable viewing experience. The system architecture of this application can be adapted to existing near-focus optical engines with minimal modifications while maintaining a compact waveguide structure. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments of this application will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is one of the schematic diagrams of the display system structure provided in this embodiment; Figure 2 This is a schematic diagram of the optical modulation lens assembly structure of the display system provided in this embodiment; Figure 3 This is a comparison diagram of the light before and after modulation of the optical modulation lens assembly of the display system provided in this embodiment; Figure 4 This is the second schematic diagram of the display system structure provided in this embodiment.

[0019] Icons: 10-Optical mechanism; 11-Optical modulation lens assembly; 12-Waveguide; 120-Modulation grating; 121-Entry pupil grating; 122-Exit pupil grating. Detailed Implementation

[0020] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings.

[0021] In the description of this application, it should be noted that the terms "inner" and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product is in use. They are used only for the convenience of describing this application and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application. Furthermore, the terms "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0022] Current optical waveguide display systems generally use near-focus output optical engines as the image light source. The output light from these engines has a certain divergence angle, and their imaging surface is located near the engine's exit. When these optical engines are used in conjunction with optical waveguides, the light propagates in a near-focus state after being coupled into the waveguide through the entrance pupil grating. The resulting virtual image, after being coupled out through the exit pupil grating, is still relatively close, requiring users to continuously refocus on this near-distance virtual image when viewing the displayed content. Prolonged viewing can easily cause eye fatigue, dizziness, and other discomfort, and also affects image clarity and visual stability.

[0023] In view of this, to solve the above technical problems, please refer to Figure 1As shown, this application embodiment provides a display system including an optical engine 10 and a waveguide 12 disposed at the light output port of the optical engine 10, and also includes an optical modulation lens assembly 11 and / or a modulation grating 120. The optical modulation lens assembly 11 is located between the optical engine 10 and the waveguide 12, and the modulation grating 120 is disposed on the waveguide 12. The wavefront from the optical engine 10 is adjusted by the optical modulation lens assembly 11 and / or the modulation grating 120 to form a far-focus or infinity virtual image at the exit pupil position of the waveguide 12.

[0024] For the optical modulation lens assembly 11, it is used to change the output wavefront form of the optomechanical system 10; for the modulation grating 120, taking the entrance pupil grating 121 as an example, the entrance pupil grating 121 is used to perform diffraction wavefront shaping on the incident light of the waveguide 12. The two can be used as independent solutions, or they can be combined and configured in the same system to meet different optomechanical system 10 parameters, volume constraints and waveguide 12 design requirements.

[0025] By setting an optical modulation lens assembly 11 between the optomechanical system 10 and the waveguide 12, or by designing specific parameters for the entrance pupil grating 121 of the waveguide 12, or by using a combination of both, the divergent light emitted by the optomechanical system 10 can be wavefront shaped and collimated before entering the waveguide 12 or during transmission inside the waveguide 12. This achieves the wavefront conversion of the near-focus divergent light output by the optomechanical system 10 into parallel light, so that the light entering the waveguide 12 propagates in the form of a plane wave, thereby forming a far-focus or infinity virtual image at the exit pupil position.

[0026] Specifically, in the scheme based on the optical modulation lens assembly 11, the distance between the optical modulation lens assembly 11 and the output port of the optomechanical system 10 is 1mm to 10mm. The near-focus divergent light output from the optomechanical system 10 first undergoes wavefront shaping through the optical modulation lens assembly 11. By selecting a negative focal length lens or a lens with a special curved surface profile that matches the position of the virtual image of the optomechanical system 10, the divergent light output from the optomechanical system 10 is converted into approximately parallel light after passing through the optical modulation lens assembly 11 and before entering the waveguide 12. The principle is based on the laws of optical imaging. By controlling the correspondence between the focal length of the optical modulation lens assembly 11 and the position of the output virtual image of the optomechanical system 10, the optical modulation lens assembly 11 is made equivalent to an independent collimating component. The light modulated by the optical modulation lens assembly 11 is incident on the waveguide 12 in an approximately plane wave form, which is beneficial for propagating at a fixed angle in the waveguide 12 and maintaining the parallel light characteristics required for telephoto or infinity imaging at the exit pupil.

[0027] In the scheme based on modulation grating 120, the divergent light is directly incident on entrance pupil grating 121. By designing the period of entrance pupil grating 121, the refractive index difference between the modulation grating 120 material and the waveguide 12 material, the etching depth, the duty cycle, and possible graded periodic structures, the divergent light, after being incident on modulation grating 120, undergoes diffraction to produce a specified phase distribution, ultimately forming a propagation mode with a plane wavefront. The design of modulation grating 120 is based on the diffraction equation and wavefront propagation principle. By controlling the spatial frequency of the modulation grating 120 structure, the diffracted light satisfies the parallel propagation condition of waveguide 12. For beams with a large incident angle range or different wavelengths, a graded periodic modulation grating 120 or a local phase modulation structure can be further used to ensure that different incident rays obtain a relatively flat wavefront distribution, thereby guaranteeing the consistency of telephoto or infinity imaging within the overall field of view.

[0028] In the hybrid approach, the optical modulation lens assembly 11 provides primary collimation, while the modulation grating 120 further performs local phase modulation to obtain higher wavefront quality.

[0029] Through the aforementioned optical modulation lens assembly 11 and / or modulation grating 120, the original near-focus imaging characteristics of the optomechanism 10 are converted into parallel light output without altering the main structure of the optomechanism 10. The placement of the modulation lens assembly and modulation grating 120, their optical path relationship with the optomechanism 10 / waveguide 12, and the correspondence between the parameters of the modulation grating 120 required for wavefront collimation and the focal length of the optical modulation lens assembly 11 are explained. Through the comprehensive application of this structure and principle, the existing near-focus optomechanism 10 can be adapted to a far-focus or infinity imaging waveguide 12 system, achieving a more natural visual display experience.

[0030] The display system provided in this application, by setting the optical modulation lens assembly 11 and / or modulation grating 120, can convert the divergent light generated by the near-focus output optical engine 10 into parallel light, thereby enabling the system to form a virtual image display at a far-focus or infinity. This application is applicable to near-eye display systems based on waveguide 12. The modulated light enters the waveguide 12 in the form of a plane wave or near-plane wave, propagates at a fixed angle in the waveguide 12, and is finally coupled out to the human eye by the exit pupil grating 122. After receiving the parallel light, the human eye can perceive the virtual image at a far-focus or infinity position, achieving a natural and comfortable viewing experience. The system architecture of this application can be adapted to the existing near-focus optical engine 10 with minimal modifications, while maintaining the compact structure of the waveguide 12, making it suitable for various application scenarios such as AR glasses, mixed reality displays, and head-mounted display devices.

[0031] Specifically, in the optical modulation lens assembly 11 scheme, the optical modulation lens assembly 11 is disposed between the light output port of the optomechanical system 10 and the entrance pupil of the waveguide 12. The optical modulation lens assembly 11 is composed of one or more lenses with negative focal lengths or specific freeform surface profiles. By controlling the correspondence between its focal length and the position of the virtual image of the optomechanical system 10, the diverging light output by the optomechanical system 10 is transformed into parallel light or approximately parallel light after passing through the lens.

[0032] For example, the optical modulation lens assembly 11 is a monolithic negative focal length lens structure: it uses a concave lens that matches the position of the virtual image of the optical engine 10, so that the light rays are collimated behind the lens. This structure is simple and suitable for scenarios with a small divergence angle and where the exit of the optical engine 10 is close to the position of the virtual image.

[0033] The optical modulation lens assembly 11 is a dual- or multi-layer composite lens structure: it is composed of a negative focal length lens and an aberration-compensating lens, which can perform higher-precision wavefront shaping on the optomechanical 10 beam with a large divergence angle or asymmetric beam, and reduce aberrations before entering the waveguide 12.

[0034] The optical modulation lens assembly 11 is a freeform lens structure: it adopts a lens with a non-rotationally symmetric curved surface, and realizes customized wavefront correction and collimation functions through curved surface design to adapt to the situation of optical path asymmetry or excessively large optical cone of the optomechanical 10.

[0035] Generally, the optical modulation lens assembly 11 is fixed in front of the output face of the optomechanical 10 by a mechanical bracket, aligned with the optical axis of the optomechanical 10 and kept at a fixed distance, and its output light enters the entrance pupil of the waveguide 12 in a form that is closer to a plane wave.

[0036] The modulation grating 120 scheme designs the structural parameters of the entrance pupil grating 121 region of the waveguide 12, causing the diverging light entering the waveguide 12 to be diffracted into a plane wave or near-plane wave at the entrance pupil, thereby directly obtaining the imaging conditions for telephoto or infinity. This scheme does not require adding an additional lens between the optomechanical system 10 and the waveguide 12, making it suitable for compact structures that are sensitive to size.

[0037] The structure and implementation of the entrance pupil grating 121 include: Uniform periodic modulation grating 120 structure: By selecting specific period Λ, depth h, duty cycle D, and refractive index difference Δn, the diffracted light rays satisfy the parallel propagation condition within waveguide 12. The selection of the period is based on the design of the combination of the output angle and wavelength of the optomechanical system 10.

[0038] Gradient periodic modulation grating 120 structure: When the output light cone of the optomechanical 10 is large or the wavefront is uneven, a periodic gradient is introduced inside the modulation grating 120 region to make the positions corresponding to different incident angles receive different phase compensation, so as to achieve overall wavefront smoothing.

[0039] Holographic modulation grating 120 or multilayer refractive modulation grating 120 structure: A specific phase distribution is obtained through multilayer photolithography or holographic recording, enabling the modulation grating 120 to perform more precise wavefront modulation on beams of different wavelengths and different field directions.

[0040] The modulation grating 120 is directly integrated into the coupling region of the waveguide 12 and is formed by photolithography, nanoimprinting, or holographic recording. Its thickness is typically less than that of the waveguide 12, thus not increasing the system volume. Besides designing the entrance pupil grating 121 to modulate the incident light into parallel light (plane wave), other grating regions of the waveguide 12, such as the pupil dilation grating and the exit pupil grating, can also be modulated; there are no limitations on this. However, in the modulation grating 120 scheme, the entrance pupil grating 121 is preferentially modulated because the modulation effect is generally better before the light is reflected and propagates in the waveguide 12.

[0041] In some applications, using only the optical modulation lens assembly 11 or only the modulation grating 120 may result in insufficient design tolerance. For example, using only the optical modulation lens assembly 11 may require a larger aperture or a longer focal length, thus increasing the size; if the modulation grating 120 is used alone to perform the full collimation function, the period or depth of the modulation grating 120 needs to be significantly adjusted, which may affect the coupling efficiency, bandwidth or field of view. Therefore, a combined structure using the optical modulation lens assembly 11 and the modulation grating 120 can also be adopted. The implementation of this combined structure includes: the optical modulation lens assembly 11 performing primary collimation, and the modulation grating 120 performing secondary wavefront correction. The optical modulation lens assembly 11 first adjusts the diverging light from the optomechanical 10 to a smaller divergence angle or near-parallel light; the entrance pupil grating 121 then finely modulates the residual wavefront error, ensuring the incident wave meets the parallel propagation condition of the waveguide 12. The optical modulation lens assembly 11 reduces the optical cone angle of the optomechanical 10, while the entrance pupil grating 121, maintaining normal design parameters, compresses the originally highly divergent beam to a range acceptable to the modulation grating 120, allowing the entrance pupil grating 121 to complete modulation without sacrificing efficiency or bandwidth. The entrance pupil grating 121 provides local compensation; the optical modulation lens assembly 11, with its small-size design, does not need to achieve complete collimation, only partial collimation. The entrance pupil grating 121 compensates for the remaining wavefront, optimizing the overall structural thickness and size.

[0042] The physical structure of the combined scheme is as follows: optomechanical system 10 → optical modulation lens assembly 11 → entrance pupil grating 121 → waveguide 12 → exit pupil grating 122. This structure can ensure the accuracy of wavefront modulation while achieving a reasonable balance between size, efficiency, and manufacturing process.

[0043] The modulation principle of the optical modulation lens assembly 11 and / or modulation grating 120 is explained below.

[0044] The modulation principle of the optical modulation lens assembly 11: The optical principles used in this application mainly include the collimation principle of divergent light, the diffraction wavefront control principle, and the parallel mode propagation mechanism inside waveguide 12. The overall optical path conversion process is as follows.

[0045] The image light output from the optomechanical system 10 typically forms a virtual image located near the exit of the optomechanical system 10, with its wavefront exhibiting a divergent state. Let the geometric distance of the virtual image output by the optomechanical system 10 be S0. To ensure that the obtained light becomes parallel after passing through the modulation lens, according to the principles of optical imaging, the focal length f of the modulation lens and the position of the virtual image of the optomechanical system 10 must satisfy the following relationship: 1 / f = 1 / S0 + 1 / S′; where S′ is the image distance, i.e., the target imaging distance behind the lens.

[0046] When the target is parallel light output, let S′→∞, then we have: f≈S0.

[0047] Simplified derivation process: The geometric distance of the virtual image output by the optical engine 10 is S0. For the lens, this virtual image belongs to the object-side virtual object, so the object distance is S = -S0.

[0048] The thin lens imaging formula is defined as follows: 1 / f = 1 / S + 1 / S′; When the target is displayed at infinity, an infinity virtual image can be achieved, S′→∞, at which point 1 / S′≈0, therefore: f≈-S0; If the target is designed at a distance L, a far-focus virtual image can be achieved, then S′=L. Substituting this, we get: 1 / f = 1 / L - 1 / S0.

[0049] Therefore, by designing a negative focal length lens that matches the position of the virtual image of the optical engine 10, the output wavefront of the optical engine 10 is collimated behind the lens. If the output beam of the optical engine 10 has off-axis, aberration, or wavefront differences in different field of view directions, phase compensation can be achieved by using a compound lens or a freeform surface lens, so that its wavefront when entering the waveguide 12 is closer to an ideal plane wave.

[0050] Modulation principle of grating 120: The principle of modulation phase by modulation grating 120 is that by setting microstructures with specific period, depth, duty cycle and refractive index difference in the entrance pupil region of waveguide 12, the incident light obtains position-related phase delay when passing through modulation grating 120, thereby reshaping the wavefront of diverging light so that it presents a wavefront form close to a plane wave after diffraction.

[0051] Specifically, the modulation grating 120 is composed of periodic or quasi-periodic microstructures. The height and refractive index of the microstructures at different locations cause different optical path lengths at those locations, resulting in different phase retardations of the light rays after passing through the modulation grating 120. The wavefront of the diverging light is spherical, and the phase distribution of the light rays at different locations is inconsistent. By designing the phase retardation of the modulation grating 120 at each spatial location to compensate for the original phase difference of the incident light, the overall smoothing of the wavefront is achieved.

[0052] The 120-period Λ of the modulation grating determines the diffraction angle, and its modulation effect follows the diffraction coupling equation: n in ·sinθ i +m·λ / Λ=n wg ·sinθ wg ; where n in It is the refractive index of the incident medium, θ i λ is the incident angle, m is the diffraction order, λ is the operating wavelength, Λ is the modulation grating period of 120°, and n is the wavelength of the diffraction grating. wg The refractive index of waveguide 12 material, θ wg It is the angle of light propagation within waveguide 12.

[0053] By adjusting Λ, different incident angles θ can be achieved. i The divergent light enters waveguide 12 at a more uniform angle after diffraction, forming a parallel propagation mode. If the incident angle range is large, a gradually changing periodic modulation grating 120 can be used to make the period of the modulation grating 120 change with the spatial coordinates, so that the light rays at different incident angles fall at different period positions and obtain appropriate phase compensation, thereby achieving overall wavefront smoothing under a large field of view.

[0054] The depth h, duty cycle D, and refractive index difference Δn of the modulation grating 120 determine the magnitude of the phase retardation. By designing these parameters, the phase distribution of the outgoing wave can be precisely controlled, so that the diffracted wavefront tends to be a plane wave shape when it propagates in space.

[0055] In summary, by controlling the diffraction direction through the structural period and controlling the phase retardation through the difference between the microstructure height and refractive index, the modulation grating 120 can diffract and modulate the incident spherical divergent wave into a plane wave, thereby realizing the conversion of the divergent light from the optomechanical 10 into parallel light.

[0056] Simplified derivation: The phase of a spherical wave with radius of curvature R in the plane of the modulation grating 120 can be written as: φ in (x) = π·x² / (λ·R); φ in (x) is the phase distribution of the incident spherical wave at position x; The phase delay provided by the modulation grating 120 is determined by the refractive index difference Δn and the local thickness h(x): Δφ(x)=(2π / λ)·Δn·h(x); Δn is the refractive index difference between the modulation grating 120 material and the waveguide 12 material, and h(x) is the local thickness of the modulation grating 120 at position x; To achieve compensation from spherical waves to plane waves, the following must be satisfied: φ grating (x)= π·x² / (λ·R); φ grating It is the phase compensation amount provided by the modulation grating 120 at position x; Let Δφ(x) = φ grating (x), we can obtain: Δn·h(x)≈ x² / (2R); To further satisfy the waveguide 12 coupling angle requirement, the modulation grating 120 period Λ(x) must satisfy the diffraction coupling equation: n in ·sinθ i (x)+m·λ / Λ(x)=n wg ·sinθ wg .

[0057] The combination principle of optical modulation lens assembly 11 and modulation grating 120: The combined scheme enables the optical modulation lens assembly 11 and the modulation grating 120 to undertake different wavefront shaping tasks, thereby giving the overall modulation process greater tolerance and controllability.

[0058] In this scheme, the diverging light output from the optomechanical system 10 is first collimated by the optical modulation lens assembly 11, which greatly reduces and unifies the divergence angle of the beam. The light after passing through the optical modulation lens assembly 11 enters the entrance pupil grating 121 with a small divergence angle or weak convergence. The entrance pupil grating 121 then performs local phase modulation on the remaining wavefront error, so that the diffracted wavefront becomes a plane wave.

[0059] The optical modulation lens assembly 11 is responsible for correcting the main convergence of the wavefront, while the entrance pupil grating 121 is responsible for fine phase compensation, thus avoiding the design limitations of a single solution. For example, the optical modulation lens assembly 11 does not need to be designed with an excessively large aperture or excessively short focal length, and the modulation grating 120 does not need to perform the entire collimation function through extreme periods or depths. The combination of the two allows the beam wavefront to achieve higher flatness when entering the waveguide 12, while keeping the device size and manufacturing complexity within a reasonable range.

[0060] Simplified derivation: The optical modulation lens assembly 11 first adjusts the original wavefront curvature 1 / R to the residual curvature 1 / Rres. The relationship between these two curvatures and the focal length f of the optical modulation lens assembly 11 is as follows: 1 / Rres = 1 / R + 1 / f; The modulation grating 120 is then used to compensate for the spherical wave with residual curvature 1 / Rres, and its phase delay satisfies: Δn·h(x)≈ x² / (2Rres); Under the combined scheme, modulation grating 120 still needs to satisfy the coupling equation: n in ·sinθ i (x)+m·λ / Λ(x)=n wg ·sinθ wg .

[0061] The optical modulation lens assembly 11 and / or modulation grating 120 described above will be explained through the following specific embodiments.

[0062] In Example 1, as Figure 2 , Figure 3 As shown, a near-focus collimation scheme based on the optical modulation lens assembly 11 is implemented. The optical modulation lens assembly 11 is used to convert the output of the near-focus optical engine 10 into parallel light. The optical engine 10 is designed to output an image with a virtual image position of approximately 6m, meaning that without the additional optical modulation lens assembly 11, the viewing distance corresponding to the outgoing light from the optical engine 10 is approximately 6m. To achieve telephoto or infinity display, this embodiment places a weak negative lens as the optical modulation lens assembly 11 between the optical engine 10 and the entrance pupil of the waveguide 12. This lens is used to collimate the divergent wavefront of the approximately 6m focused light, making the light entering the waveguide 12 nearly parallel.

[0063] (a) Output conditions of Opto-mechanical 10: In this embodiment, the optical engine 10 forms a virtual image after passing through the internal projection lens group, and the virtual image is located approximately in front of the exit of the optical engine 10: S0 = 6m = 6000mm; Observed from the exit of the optical engine 10, the virtual image is located in the space 6m in front. Therefore, the light emitted from the optical engine 10 is a divergent light from the "6m virtual image point", and its wavefront can be approximated as a spherical wave.

[0064] For the modulation lens placed in front of the exit of the optical engine 10, this "6m virtual image" can be regarded as the object-side virtual object of the lens, and the corresponding object distance is denoted in the imaging formula as: S≈-6000 mm; the negative sign indicates the object-side virtual image, which is the standard notation convention for the virtual image formed by the previous optical system—optical mechanism 10—to be transmitted to this optical modulation lens assembly 11.

[0065] (II) Design principle of optical modulation lens assembly 11: To convert the aforementioned diverging wavefront into parallel light, the optical modulation lens assembly 11 must satisfy the following condition: when the object side is the 6m virtual image, the image side is at the far focal point or infinity. According to the thin lens imaging formula: 1 / f = 1 / S + 1 / S'; Where f is the focal length of the optical modulation lens assembly 11, S is the object distance, and S' is the image distance (if the target is at infinity, S'→∞; or, if the target is the target design distance L, S'=L, for example, L is greater than 15m to achieve display at a longer distance).

[0066] Substitution conditions: 1 / f=1 / (-6000)+0→f≈-6000mm.

[0067] Therefore, theoretically, placing a weak negative lens with a focal length of approximately -6000mm near the exit of the optical engine 10 is sufficient to collimate the diverging light corresponding to the 6m virtual image into parallel light. The optical power of the lens at this time is approximately: Φ = 1 / f ≈ -0.167 D; It is a very weak negative lens and can be designed into a thin structure with extremely small curvature without increasing the system size.

[0068] (III) Actual arrangement of optical modulation lens assembly 11: In actual assembly, the optical modulation lens assembly 11 can be arranged close to the light outlet of the optomechanical system 10: The optical modulation lens assembly 11 is 2mm to 5mm from the main surface of the optical engine 10 at the light outlet. The aperture of the optical modulation lens assembly 11 is slightly larger than the effective aperture of the beam emitted from the optomechanical system 10.

[0069] Since 2mm to 5mm is negligible compared to 6000mm, the object distance for the optical modulation lens assembly 11 can still be considered as -6000mm. Therefore, the modulation conditions can be designed according to f≈-6000mm.

[0070] (iv) Wavefront collimation effect: After passing through the aforementioned optical modulation lens assembly 11, the wavefront of the 6m virtual image originally projected by the optomechanical system 10 is reshaped into a near-plane wave, as shown below. Figure 3 As shown. By optimizing the curvature of the optical modulation lens assembly 11 using optical software, the wavefront RMS can be controlled within 0.05λ, ensuring that the light entering the waveguide 12 meets the parallel propagation requirements.

[0071] After parallel light enters the entrance pupil grating 121 of the waveguide 12, it propagates within the waveguide 12 at a fixed propagation angle and is finally coupled out by the exit pupil grating 122 to the human eye, forming a virtual image at a far focal length or infinity.

[0072] In Example 2, as Figure 4 As shown, a technique for collimating divergent light is provided by using an entrance pupil grating 121 in waveguide 12. The entrance pupil grating 121 modulates the phase distribution of the incident divergent light, converting the wavefront corresponding to the 6m virtual image from the optomechanical system 10 into a near-plane wavefront, thereby enabling the light to propagate in a parallel mode after entering waveguide 12, achieving telephoto or infinity display.

[0073] The entrance pupil grating 121 experiences a position-dependent phase delay Δφ(x) formed by its spatial period Λ, etching depth h, refractive index difference Δn, and duty cycle D. The optical path difference of light rays at the entrance pupil grating 121 can be expressed as: ; The wavefront from the 6m virtual image can be approximated at the plane of the entrance pupil grating 121 as follows: ; To obtain a plane wave, the following conditions must be met: ; The output after compensation is: ; The thickness distribution of the corresponding entrance pupil grating 121 satisfies: ; This spatially correlated phase compensation can reshape the wavefront into a planar wavefront.

[0074] Based on the output wavelength range of the optomechanical system 10 (e.g., 460nm~630nm) and the geometric distance S0=6m from the virtual image, the parameters of the entrance pupil grating 121 can be selected within the following range: The relationship between the entrance pupil angle and the insertion angle satisfies the diffraction insertion equation: n in ·sinθ i +m·λ / Λ=n wg ·sinθ wg ; in: θ i The incident angle of the divergent light emitted by the optical engine 10; θ wg : Internal propagation angle of waveguide 12; m: Diffraction order, usually taken as m=+1; To achieve parallel propagation (θ) wg (Fixed), Λ needs to be matched according to different incident angles.

[0075] The typical range is: Λ = 420nm~520nm; The etching depth is used to control the phase delay Δφ, with a typical range of h = 150 nm. At 250nm, this depth provides a phase quantity suitable for compensating for the curvature of a 6m virtual image.

[0076] Typical refractive index difference: Δn = 0.05 0.15, Duty Cycle (Gateline Width / Period): D=0.4 0.6, Δn and h determine the phase compensation capability, while D affects the diffraction efficiency and wavefront shaping quality.

[0077] When the output angle range of the optical engine 10 is large (e.g., ±10°), the entrance pupil grating 121 can be designed with a gradual period: Λ(x) = Λ0 + kx; Λ0 is the period of the center position of the modulation grating 120, k is a coefficient, and x is the lateral coordinate along the surface of the modulation grating 120; when the modulation scheme of the modulation grating 120 is not used, i.e. k is 0, it is equivalent to the entire modulation grating 120 being Λ0.

[0078] This allows light rays with different incident angles to receive appropriate phase compensation at different positions, thus ensuring that the wavefront remains flat under a large field of view.

[0079] Verification using optical simulation tools such as RCWA or FDTD shows that, under the above parameter conditions, the following can be achieved: output wavefront RMS < 0.05λ, beam principal mode close to plane wave, and diffraction efficiency up to 60%. With 80% reduction, most residual aberrations are effectively suppressed, making it suitable for near-focus systems where the virtual image distance of the Optical Engine 10 is as far as several meters.

[0080] The modulated light enters the waveguide 12 as a plane wave, propagates at a stable angle inside, and is coupled out by the exit pupil grating 122 to present a virtual image at a far focal length or infinity in the human eye.

[0081] In Example 3, the design continues for the case where the focal length of the optical engine 10 is 6m. This example uses the combined action of the optical modulation lens assembly 11 and / or modulation grating 120 for illustration. The two are designed and modulated together, so that both have sufficient optimization margin. Taking the wavelength of the optical engine 10 as 460nm~630nm as an example, the center wavelength is 520nm. The specific design principle is as follows: Step 1: The optical modulation lens assembly 11 is aligned once until the residual curvature is 1 / Rres.

[0082] The goal is not to have the optical modulation lens assembly 11 directly output a plane wave, but to first convert the original curvature 1 / R into a more "gentle" residual curvature 1 / Rres, and then have the modulation grating 120 complete the final compensation.

[0083] Select the target residual radius of curvature, for example: Rres = 1000mm; Equivalent optical relationship of optical modulation lens assembly 11: The original wavefront curvature 1 / R and the lens power 1 / f1 are combined into the residual curvature 1 / Rres: 1 / Rres = 1 / R + 1 / f; Solve for the focal length f of the lens.

[0084] Substituting R=6000mm and Rres=1000mm: ; ; The equivalent focal length of the lens is designed as follows: f≈ 1200 mm (negative lens, optical power approximately) 0.83D) Structural implementation: A single concave lens or a slightly freeform concave lens is used; the distance between the lens and the exit of the optical engine 10 can be 2mm to 5mm, serving as a mechanical assembly clearance and considered a minor correction in the imaging relationship; the lens aperture covers the output aperture of the optical engine 10. In this case, after passing through the lens, the wavefront curvature changes from R = 6000 mm to Rres≈1000 mm.

[0085] Step 2: Design the phase distribution of the entrance pupil grating 121 for the residual curvature 1 / Rres.

[0086] Behind the lens, the entrance pupil grating 121 observes a spherical wave with a radius of curvature of Rres: ; To compensate for it to be a plane wave, the entrance pupil grating 121 needs to provide a reverse phase: ; The phase retardation of the entrance pupil grating 121 is determined by the refractive index difference Δn and the local thickness h(x): ; Make it equal to the phase that needs to be compensated: ; The thickness distribution design relationship is obtained: ; Substituting Rres = 1000 mm: ; In practical design: Given Δn (e.g., 0.08), the spatial distribution of h(x) can be obtained: ; h(x) can be discretized into multi-level steps or an approximately continuous contour, which can be achieved by photolithography or nanoimprinting.

[0087] Step 3: Design the period Λ(x) of the entrance pupil grating 121 to match the field of view.

[0088] The entrance pupil grating 121 not only performs phase compensation but also needs to control different incident angles θ. i The light rays at a predetermined angle θ wg Coupled waveguide 12.

[0089] Diffraction coupling equation: n in ·sinθ i (x)+m·λ / Λ(x)=n wg ·sinθ wg ; in: θ i (x): The geometric relationship between the field of view of the corresponding optomechanical 10 and the position x of the modulation grating 120; θ wg : The desired propagation angle in waveguide 12 (fixed); m: Diffraction order, usually taken as m = +1; n in : Refractive index of the incident medium, approximately 1.0 (air) or refractive index of the adhesive; The design process is as follows: Based on the field of view of the optical engine 10, the incident angle θ corresponding to different x values ​​is calculated. i (x); Given the waveguide 12 operating mode angle θ wg (e.g., 45°); For each x, use the above formula to solve for the local period Λ(x); By combining Λ(x) and h(x), a two-dimensional structure is formed that satisfies both the coupling angle and the phase compensation requirements.

[0090] In engineering, a compromise design can be made within a certain range, allowing Λ(x) to change gradually rather than be strictly point-to-point matched, in order to simplify the processing.

[0091] In Example 3, as Figure 1As shown, the optical modulation lens assembly 11 and the modulation grating 120 work together to significantly improve the design tolerance of both. The optical modulation lens assembly 11 only needs to perform weak collimation once, without needing to achieve extremely low optical power, thus allowing it to be designed to be thinner, easier to manufacture, and have a smaller aperture. The modulation grating 120 only needs to compensate for the residual wavefront behind the lens, significantly reducing the requirements for phase gradient and etching depth, and decreasing the range of period variation, thereby improving diffraction efficiency and reducing manufacturing difficulty. The combination of the two makes the system thinner and easier to manufacture, while also being more feasible in terms of field of view, efficiency, and consistency.

[0092] Based on this, embodiments of this application also disclose a modulation method for a display system, employing any of the above-mentioned display systems, the method comprising: Step 200: Receive the wavefront from the optomechanical unit 10.

[0093] The geometric distance of the virtual image corresponding to the wavefront is S0.

[0094] Step 201: Modulate the wavefront by means of the optical modulation lens assembly 11 and / or modulation grating 120 to make it a plane wave or a spherical wave with reduced curvature for propagation in the waveguide 12.

[0095] When the optical modulation lens assembly 11 is used alone, 1 / f = 1 / L is satisfied. 1 / S0; f is the focal length of the optical modulation lens assembly 11, L is the target design distance, and S0 is the geometric distance of the output virtual image of the optomechanical 10.

[0096] When modulation grating 120 is used alone, n is satisfied. in ·sinθ i +m·λ / Λ=n wg ·sinθ wg ;n in It is the refractive index of the incident medium, θ i Here, m is the incident angle of waveguide 12, λ is the diffraction order, λ is the operating wavelength, Λ is the period of modulation grating 120, and n is the wavelength of the waveguide. wg The refractive index of waveguide 12 material, θ wg It is the angle of light propagation within waveguide 12. When the optical modulation lens assembly 11 and the modulation grating 120 are used for modulation, the optical modulation lens assembly 11 modulates the wavefront curvature output by the optomechanical 10 into the residual curvature, which satisfies 1 / Rres=1 / R+1 / f; The modulation grating 120 further compensates for the residual wavefront, satisfying Δn·h(x)≈ x² / (2Rres), where Δn is the refractive index difference between the modulation grating 120 material and the waveguide 12 material, and h(x) is the local thickness of the modulation grating 120 at position x.

[0097] The modulation method of this display system includes the same structure and beneficial effects as the display system in the foregoing embodiments. The structure and beneficial effects of the display system have been described in detail in the foregoing embodiments and will not be repeated here.

[0098] The above description is merely an embodiment of this application and is not intended to limit the scope of protection of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A display system, characterized in that, include: The optical engine and the waveguide disposed at the output port of the optical engine also include an optical modulation lens assembly and / or a modulation grating. The optical modulation lens assembly is located between the optical engine and the waveguide, and the modulation grating is disposed on the waveguide. The wavefront from the optical engine is adjusted by the optical modulation lens assembly and / or the modulation grating to form a far-focus or infinity virtual image at the exit pupil position of the waveguide.

2. The display system according to claim 1, characterized in that, When an optical modulation lens assembly is provided between the optomechanism and the waveguide, 1 / f = 1 / L is satisfied. 1 / S0; f is the focal length of the optical modulation lens assembly, L is the target design distance, and S0 is the geometric distance of the output virtual image of the optomechanical system.

3. The display system according to claim 1, characterized in that, When the modulation grating is disposed on the waveguide, n satisfies in ·sinθ i +m·λ / Λ=n wg ·sinθ wg ;n in It is the refractive index of the incident medium, θ i Where is the incident angle of the waveguide, m is the diffraction order, λ is the operating wavelength, Λ is the grating period, and n wg It is the refractive index of the waveguide material, θ wg It is the angle at which light propagates within the waveguide.

4. The display system according to claim 3, characterized in that, The modulation grating satisfies Λ(x) = Λ0 + kx; Λ0 is the period of the center position of the modulation grating, k is a coefficient, and x is the lateral coordinate along the surface of the modulation grating.

5. The display system according to claim 1, characterized in that, When including an optical modulation lens assembly and a modulation grating, the optical modulation lens assembly satisfies: 1 / Rres=1 / R+1 / f, where R is the original wavefront radius of curvature, Rres is the residual radius of curvature, and f is the focal length of the optical modulation lens assembly. Meanwhile, the modulation grating satisfies: Δn·h(x)≈ x² / (2Rres), where Δn is the refractive index difference between the grating material and the waveguide material, and h(x) is the local thickness of the grating at position x.

6. The display system according to any one of claims 1 to 5, characterized in that, The optical modulation lens assembly includes a single negative focal length lens, or a double or multiple composite lens, or a freeform surface lens, and the distance between it and the light output port of the optical engine is 1mm to 10mm.

7. The display system according to any one of claims 1 to 5, characterized in that, The modulation grating includes an entrance pupil grating, a dilation pupil grating, or an exit pupil grating.

8. A modulation method for a display system, employing the display system according to any one of claims 1 to 7, characterized in that, The method includes: Receive wavefront from the optical engine; The wavefront is modulated by an optical modulation lens assembly and / or a modulation grating to make it a plane wave or a spherical wave with reduced curvature for propagation within the waveguide.

9. The modulation method for the display system according to claim 8, characterized in that, The modulation of the wavefront using an optical modulation lens assembly and / or a modulation grating to make it a plane wave or a spherical wave with reduced curvature for propagation within the waveguide includes: When the optical modulation lens assembly is used, 1 / f = 1 / L is satisfied. 1 / S0; f is the focal length of the optical modulation lens assembly, L is the target design distance, and S0 is the geometric distance of the output virtual image of the optomechanical system; When the modulation grating is used, n satisfies in ·sinθ i +m·λ / Λ=n wg ·sinθ wg ;n in It is the refractive index of the incident medium, θ i Where is the incident angle of the waveguide, m is the diffraction order, λ is the operating wavelength, Λ is the grating period, and n wg It is the refractive index of the waveguide material, θ wg It is the angle at which light propagates within the waveguide.

10. The modulation method of the display system according to claim 8, characterized in that, The modulation of the wavefront using an optical modulation lens assembly and / or a modulation grating to make it a plane wave or a spherical wave with reduced curvature for propagation within the waveguide includes: When the optical modulation lens assembly and the modulation grating are used, the optical modulation lens assembly modulates the wavefront curvature of the optomechanical output into a residual curvature, satisfying 1 / Rres=1 / R0+1 / f, where R is the original wavefront curvature radius, Rres is the residual curvature radius, and f is the focal length of the optical modulation lens assembly. The modulation grating further compensates for the residual wavefront, satisfying Δn·h(x)≈ x² / (2Rres), where Δn is the refractive index difference between the grating material and the waveguide material, and h(x) is the local thickness of the grating at position x.

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