Augmented reality head-mounted display device and method

Abstract

This invention discloses an augmented reality head-mounted display device and method. The device includes a housing and an optical system disposed therein. The optical system includes a microdisplay and an off-axis reflective optical combiner composed of first to fourth freeform mirrors. Light emitted from the microdisplay is reflected four times sequentially by the four freeform mirrors before finally entering the human eye. The surface shape of each freeform mirror is designed to fit the contours of different areas of the face, with the concave reflective surfaces of the second and fourth freeform mirrors facing the human eye. The optomechanical module formed by the microdisplay and the first freeform mirror can be disposed on the side, forehead, or cheek area of ​​the wearer's face, and the third freeform mirror can fit the bridge of the nose or forehead. This invention significantly reduces the system size and weight through off-axis four-reflective light path folding, achieving a compact structure. The fitted mirror design reduces facial pressure, improves wearing comfort, and facilitates a large field of view and high-quality image display.

Description

Technical Field

[0001] This invention relates to the field of optical display technology, and more particularly to an augmented reality head-mounted display device and method. Background Technology

[0002] Augmented reality head-mounted display technology, as an important branch of near-eye display technology, aims to seamlessly overlay virtual information onto the user's real-world field of vision through an optical system integrated into the head-mounted device, thereby achieving immersive interactive experiences in various fields such as industry, medicine, and education. The core optical system of this technology typically consists of two parts: a microdisplay and an optical combiner.

[0003] Currently, devices for augmented reality displays mainly follow two technical routes: video transmissive and optical transmissive. Video transmissive helmets capture images of the real-world environment through built-in cameras, process them, and synthesize them with virtual images before displaying them on a miniature screen in front of the user. This process involves multiple stages of image acquisition, processing, and display, which can easily introduce unavoidable information delays. Therefore, current research and development focus on optical transmissive solutions. This approach allows users to directly observe the real environment through lenses or prisms with specific optical structures, while simultaneously projecting virtual images into the user's eyes through reflection, diffraction, or projection.

[0004] In optical transmissive helmets, the design of the optical combiner directly determines the device's size, image quality, and wearing experience. Existing technologies can be broadly categorized into two types: one is optical waveguide technology based on diffraction principles, and the other is traditional combiner structures based on the principles of geometric optics refraction and reflection. Optical waveguide technology mainly includes arrayed waveguides and surface-embossed grating structures. Arrayed waveguides utilize total internal reflection within the waveguide for transmission, but are prone to producing "Venetian blind" visual artifacts, and their field of view is limited by the total internal reflection angle. Surface-embossed gratings couple light into and out of the waveguide through a fine diffraction grating structure, achieving a thinner and lighter form factor and a larger field of view, but generally suffer from color inhomogeneity, rainbow effects, and insufficient overall display brightness due to the correlation between diffraction efficiency and wavelength. On the other hand, traditional geometric optics combiner solutions also have their limitations. The Birdbath structure uses a combination of beam splitters and concave mirrors to reflect virtual light and transmit real light, but its field of view is limited, and the multiple reflections by the beam splitter cause significant light energy loss. Freeform prism structures increase design freedom and field of view by integrating internal total reflection and partial reflection surfaces. However, their optical elements are relatively thick and require additional design to correct refractive aberrations caused by ambient light passing through the prism. Freeform mirror structures optimize the optical path using aspherical lenses, offering lower light energy loss and a larger potential field of view. However, how to compress these structures into truly compact, lightweight structures that conform to the contours of the human face while maintaining excellent optical performance, thus addressing the issue of user comfort during extended wear, remains a key design challenge for this technology.

[0005] In summary, all existing technical solutions have shortcomings to varying degrees in terms of size, image quality, optical efficiency, or wearing comfort. Summary of the Invention

[0006] Therefore, the technical problem to be solved by the present invention is to overcome the problems of large size and insufficient compactness of optical systems in existing augmented reality head-mounted display devices, as well as poor wearing comfort due to structural design.

[0007] To address the aforementioned technical problems, the present invention provides an augmented reality head-mounted display device, comprising: The housing has an internal space for accommodating optical components and a fixing structure for wearing; An optical system, disposed within the housing, includes: Microdisplays are used to generate images; An optical combiner, which is an off-axis reflective structure, includes a first freeform mirror, a second freeform mirror, a third freeform mirror, and a fourth freeform mirror; The first freeform mirror is disposed on the light-emitting side of the microdisplay and is used to receive and reflect light from the microdisplay. The second and fourth freeform mirrors are disposed inside the housing on the side away from the human eye, and are located in front of the wearer's eyes when worn. The concave surfaces of the second and fourth freeform mirrors both face the image plane area where the human eye is located. The third freeform surface mirror is disposed inside the outer shell close to the wearer's eye and is located at the bridge of the wearer's nose when worn. The non-optical surface of the third freeform surface mirror conforms to the contour of the wearer's nose. The second freeform mirror is disposed in the reflected light path of the first freeform mirror, and receives and reflects light from the first freeform mirror; The third freeform mirror is disposed in the reflected light path of the second freeform mirror and is used to receive and reflect light from the second freeform mirror; The fourth freeform mirror is disposed in the reflected light path of the third freeform mirror, receives and reflects light from the third freeform mirror, and guides the light to the image plane area where the human eye is located.

[0008] In one embodiment of the present invention, the microdisplay and the first freeform mirror together constitute an optical engine module, which is disposed on the housing and located in the side area of ​​the wearer's face when worn.

[0009] In one embodiment of the present invention, the first freeform mirror conforms to the side profile of the wearer's face when worn.

[0010] In one embodiment of the present invention, the microdisplay and the first freeform mirror together constitute an optical engine module, which is located in the forehead area of ​​the wearer when worn.

[0011] In one embodiment of the present invention, the first freeform mirror conforms to the contour of the wearer's forehead when worn.

[0012] In one embodiment of the present invention, the distance between the reflective concave edge of the second and fourth freeform mirrors and the skin around the eyes is less than or equal to 50 mm.

[0013] The present invention also provides an augmented reality head-mounted display device, comprising: The housing has an internal space for accommodating optical components and a fixing structure for wearing; An optical system, disposed within the housing, includes: Microdisplays are used to generate images; An optical combiner, which is an off-axis reflective structure, includes a first freeform mirror, a second freeform mirror, a third freeform mirror, and a fourth freeform mirror; The first freeform mirror is disposed on the light-emitting side of the microdisplay to receive and reflect light from the microdisplay; and the first freeform mirror is disposed on the cheek area on the side of the wearer's nose. The second and fourth freeform mirrors are disposed inside the housing on the side away from the human eye, and are located in front of the wearer's eyes when worn. The concave surfaces of the second and fourth freeform mirrors both face the image plane area where the human eye is located. The third freeform surface mirror is disposed inside the housing close to the wearer's forehead, and the non-optical surface of the third freeform surface mirror conforms to the contour of the wearer's forehead; The second freeform mirror is disposed in the reflected light path of the first freeform mirror, and receives and reflects light from the first freeform mirror; The third freeform mirror is disposed in the reflected light path of the second freeform mirror and is used to receive and reflect light from the second freeform mirror; The fourth freeform mirror is disposed on the reflected light path of the third freeform mirror, receiving and reflecting light from the third freeform mirror, while simultaneously receiving and transmitting light from the real scene, guiding the light to the image plane area where the human eye is located.

[0014] In one embodiment of the present invention, the second freeform mirror and the fourth freeform mirror are two physically separate independent optical elements.

[0015] In one embodiment of the present invention, the second freeform mirror and the fourth freeform mirror are integrated on the same optical substrate to form an integrated optical component with a continuous reflective surface.

[0016] The present invention also provides an augmented reality head-mounted method, implemented using the augmented reality head-mounted display device.

[0017] The technical solution of the present invention has the following advantages compared with the prior art: The augmented reality head-mounted display device of this invention employs an off-axis four-reflector optical path structure, achieving multiple optical path folding within the optical system. This enables image relay and transmission within a limited space, significantly reducing the size of the optical system and the overall weight of the device, making the structure more compact, lightweight, and easy to wear and carry. The surface shape of each freeform mirror is specifically designed according to the contours of the human face, with the concave reflective surface facing the face. This allows the device to fit the user's face more closely, reducing the concentrated pressure on the forehead, bridge of the nose, and temples felt by traditional head-mounted devices, effectively improving comfort during extended use. Simultaneously, this design considers optical performance. The off-axis reflection structure avoids chromatic aberration and image distortion problems caused by transmission elements. The optical path arrangement facilitates a large field of view and high image quality. Furthermore, the detachable or integrated design of the second and fourth freeform mirrors provides flexibility for aesthetic integration and optical adjustments. Attached Figure Description

[0018] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0019] Figure 1 This is a schematic diagram of the augmented reality head-mounted display device when the second and fourth freeform surface mirrors are designed separately and independently in Embodiment 1 of the present invention; Figure 2 This is a schematic diagram of the augmented reality head-mounted display device when the second and fourth freeform mirrors are integrated into the same freeform mirror in Embodiment 1 of the present invention; Figure 3 This is a schematic diagram of the single-line optical path structure of the augmented reality head-mounted display device in Embodiment 1 of the present invention; Figure 4 This is a schematic diagram of the dual-eye path structure of the augmented reality head-mounted display device in Embodiment 1 of the present invention; Figure 5 This is a schematic diagram of the augmented reality head-mounted display device when the second and fourth freeform surface mirrors are designed separately and independently in Embodiment 2 of the present invention; Figure 6 This is a schematic diagram of the augmented reality head-mounted display device when the second and fourth freeform mirrors are integrated into the same freeform mirror in Embodiment 2 of the present invention; Figure 7 This is a schematic diagram of the optical path structure of the augmented reality head-mounted display device in Embodiment 2 of the present invention; Figure 8 This is a schematic diagram of the augmented reality head-mounted display device when the second and fourth freeform surface mirrors are designed separately and independently in Embodiment 3 of the present invention; Figure 9 This is a schematic diagram of the augmented reality head-mounted display device when the second and fourth freeform mirrors are integrated into the same freeform mirror in Embodiment 3 of the present invention.

[0020] Explanation of reference numerals in the accompanying drawings: 1. Microdisplay; 2. First freeform mirror; 3. Second freeform mirror; 4. Third freeform mirror; 5. Fourth freeform mirror; 6. Human eye; 7. Human face. Detailed Implementation

[0021] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0022] Example 1: like Figure 1 As shown, the augmented reality head-mounted display device of the present invention includes: The housing has an internal space for accommodating optical components and a fixing structure for wearing; An optical system, disposed within the housing, includes: Microdisplay 1, used to generate images; An optical combiner, which is an off-axis reflective structure, includes a first freeform mirror 2, a second freeform mirror 3, a third freeform mirror 4, and a fourth freeform mirror 5; The first freeform mirror 2 is disposed on the light-emitting side of the microdisplay 1 and is used to receive and reflect light from the microdisplay 1. The second freeform mirror 3 and the fourth freeform mirror 5 are disposed inside the housing on the side away from the human eye. When worn, they are located in front of the wearer's eyes 6. The concave surfaces of the second freeform mirror 3 and the fourth freeform mirror 5 both face the image plane area where the human eye is located. The third freeform surface mirror 4 is disposed inside the outer shell close to the wearer's eye and is located at the bridge of the wearer's nose when worn. The non-optical surface of the third freeform surface mirror conforms to the contour of the wearer's nose. The second freeform mirror 3 is disposed in the reflected light path of the first freeform mirror 2, and receives and reflects light from the first freeform mirror 2; The third freeform mirror 4 is disposed in the reflected light path of the second freeform mirror 3, and is used to receive and reflect light from the second freeform mirror 3; The fourth freeform mirror 5 is disposed on the reflected light path of the third freeform mirror 4, receives and reflects light from the third freeform mirror 4, and guides the light to the image plane area where the human eye 6 is located.

[0023] The augmented reality head-mounted display device provided by this invention achieves compact transmission and imaging of virtual images through an off-axis reflective optical combiner structure and a four-stage reflection optical path design. The device comprises a microdisplay 1 and sequentially arranged first freeform surface mirrors 2, 3, 4, and 5, forming a highly efficient optical path emitted from the microdisplay 1, reflected four times, and finally guided to the human eye 6. This structure not only significantly reduces the internal layout space of the optical system and lightens the overall weight, but also achieves a natural fit to the contours of the human head through the spatial arrangement and surface design of the mirrors. While ensuring a large field of view and good image quality, it significantly improves wearing stability and comfort, making it particularly suitable for augmented reality applications requiring extended use.

[0024] In this embodiment, the inner side of the outer shell refers to the inner surface of the structure facing and close to the wearer's face when the device is worn; correspondingly, the outer side of the outer shell refers to the side facing away from the face and towards the external environment.

[0025] In this embodiment, the device's optical system is based on an off-axis four-reflector optical path structure design. From the microdisplay 1 to the image plane of the human eye 6, it sequentially includes: microdisplay 1 (as the system object plane), first freeform surface mirror 2, second freeform surface mirror 3, third freeform surface mirror 4, and fourth freeform surface mirror 5, ultimately forming an image on the human eye 6. This optical system achieves optical path folding through four reflections, completing image transmission within a compact space. Simultaneously, by utilizing the surface shape freedom of each freeform surface mirror, it significantly improves the device's wearing comfort and structural integration while achieving a large field of view and high imaging quality.

[0026] In each freeform mirror, the first freeform mirror 2 and the third freeform mirror 4 are installed inside the housing close to the wearer's eyes, so that their optical reflection faces away from the wearer's face; the second freeform mirror 3 and the fourth freeform mirror 5 are installed inside the housing away from the wearer's eyes, so that their optical reflection faces the wearer's face. This structure is conducive to building and completing a compact optical path transmission within the limited gap between the device and the face 7.

[0027] In this embodiment, the microdisplay 1 and the first freeform mirror 2 constitute an optomechanical module and are arranged on the side of the device housing. This layout naturally conforms to the side contour of the face 7, avoiding pressure on the user's forehead or temples when wearing the device. The surface shape of the first freeform mirror 2 is specially designed so that its reflective surface conforms to the side curve of the wearer's face. On the one hand, it realizes the first reversal and folding of light, compressing the space occupied by the optomechanical module in the device. On the other hand, it also makes the overall structure more in line with the head contour, reducing the foreign body sensation and local load when wearing it.

[0028] The second freeform mirror 3 and the fourth freeform mirror 5 are positioned in front of the wearer's field of vision. They work together optically to correct aberrations and guide the optical path.

[0029] like Figure 1 As shown, this embodiment can adopt a separate and independent design, that is, the second freeform surface mirror 3 and the fourth freeform surface mirror 5 are arranged as two independent lenses. This arrangement is beneficial for independent adjustment and optimization during the optical debugging stage.

[0030] like Figure 2 As shown, in this embodiment, the second freeform mirror 3 and the fourth freeform mirror 5 can also be integrated on the same optical substrate to form a continuous reflective surface. This integrated structure not only reduces the number of assembly steps and components, lowers system complexity and assembly tolerances, but also improves the consistency and stability of the optical interface. The reflective concave surfaces of both lenses face the human eye 6, causing the reflected light to converge toward the human eye 6, avoiding stray light interference, and helping to expand the effective field of view.

[0031] The third freeform surface lens 4 is located in the middle of the optical path, corresponding to the wearer's nose bridge. Its surface shape is optimized based on the curvature characteristics of the human nose bridge, allowing it to not only serve as a key node in the optical path transition but also to structurally conform naturally to the nose bridge. This avoids the rigid pressure exerted on the nose bridge by the lens frame in traditional designs, significantly improving comfort during extended wear. Furthermore, the surface design of the third freeform surface lens 4 also addresses astigmatism and field curvature correction, enhancing the image sharpness at the edges of the field of view.

[0032] The fourth freeform mirror 5 is disposed in the reflected light path of the third freeform mirror 4. The optical surface of the fourth freeform mirror 5 is coated with a semi-transparent and semi-reflective film, which receives and reflects light from the third freeform mirror 4, and at the same time receives and transmits light from the real scene, guiding the light to the image plane area where the human eye is located.

[0033] In terms of specific optical design, each freeform mirror in this embodiment is characterized by an extended polynomial surface shape, which has a high degree of freedom and can be used to finely correct the aberration characteristics of off-axis multi-reflection systems.

[0034] Among them, the maximum number of terms of the surface shape of the fourth freeform mirror 5 is set to 44, and its reflective concave surface is precisely facing the human eye 6 side to ensure that the final imaging light can be precisely focused on the retina, thereby improving image sharpness and visual realism. The third freeform mirror 4 also adopts an extended polynomial surface with a maximum term of 44. Its surface shape fits the contour of the bridge of the nose and effectively corrects the image plane curvature and distortion caused by multiple folds in the optical path. The surface parameters of the second freeform mirror 3 are designed in coordination with those of the fourth freeform mirror 5, with a maximum number of terms of 44. It mainly plays the role of beam shaping and aberration balancing in the system. It avoids the central occlusion problem common in coaxial systems through off-axis reflection, thereby improving the system transmittance and imaging brightness. The first freeform mirror 2 is also optimized based on a 44-term extended polynomial surface shape, which enables it to effectively control the astigmatism and coma of the incident beam while realizing the folding of the side optical path, providing a good initial wavefront for the subsequent optical path.

[0035] In addition, to further achieve a compact structure and a close fit to the face, the spatial pose of each freeform mirror in the device coordinate system has been specially optimized.

[0036] To clearly describe the spatial position and orientation of each optical element within the device, a right-handed Cartesian coordinate system is used. The coordinate system has its origin at the center of the human pupil: the Z-axis follows the line of sight when the eye is looking straight ahead, pointing outwards from the device; the Y-axis is horizontal, perpendicular to the Z-axis, pointing positively to the wearer's left; the X-axis is vertical, perpendicular to the YZ plane, pointing downwards. The positional offset and tilt angle of each freeform mirror are described based on this coordinate system.

[0037] Preferably, the first freeform mirror 2 is offset from the optical axis by 10-20mm in the y direction. This offset is determined according to the relative position of the human eye pupil and the side area of ​​the human face in the system, and is used to balance the fit between the optical path fold and the side contour.

[0038] The second freeform mirror 3 is offset from the optical axis by 30-40mm in the y-direction and tilted counterclockwise by 30-40° around the x-axis. This distance and angle setting ensures that the mirror angle of the second freeform mirror 3 conforms to the external contour of the front of the face and forms a good connection with the optical path of the fourth freeform mirror 5. Furthermore, this offset ensures that the distance between the concave edge of the second freeform mirror 3 and the wearer's skin around the eyes is controlled to be less than or equal to 50mm. This safe distance design effectively prevents the lens from accidentally contacting the skin during wear or head movement, thus preventing discomfort or damage, while also preserving necessary space for movement and heat dissipation around the eyes. This is a key ergonomic consideration for improving wearing safety and long-term comfort.

[0039] The third freeform mirror 4 is offset from the optical axis by -20 to -10 mm in the y direction (i.e., biased towards the inside of the bridge of the nose). This design is based on the relative position of the human pupil and the bridge of the nose to ensure that the non-optical surface of the third freeform mirror 4 can fit closely with the contour of the bridge of the nose. The third freeform mirror 4 is tilted counterclockwise by 40-50° around the x-axis to further optimize the matching degree with the curve of the bridge of the nose.

[0040] The fourth freeform lens 5 is offset from the human pupil by 40-50mm in the z-direction. It is also tilted counterclockwise by 10-30° around the x-axis, an angle smaller than that of the second freeform lens 3. This tilt allows the reflective surface of the fourth freeform lens 5 to better conform to the outer contour of the forehead and periorbital area of ​​the face, forming a smooth optical path transition together with the second freeform lens 3. This distance not only considers the optical path connection with the second freeform lens 3 and the fit to the forehead contour, but also adheres to the design that the safe distance between the edge of the concave reflective surface of the second freeform lens 3 and the periorbital skin is no more than 50mm. This safe distance avoids direct pressure from the lens on sensitive areas such as the brow bone and upper orbital margin, significantly reducing the foreign body sensation and local pressure during wear. It also provides reliable spatial tolerance for optical adjustment and structural fixation of the lens.

[0041] like Figure 3 As shown, the optical path structure of the single-eye optical system in this embodiment is illustrated. The optical path is emitted from the microdisplay 1, and is reflected sequentially by the first freeform mirror 2, the second freeform mirror 3, the third freeform mirror 4 and the fourth freeform mirror 5, and finally imaged onto the human eye 6.

[0042] The aforementioned optical system exhibits stable imaging quality across the entire field of view, with no significant chromatic aberration or distortion.

[0043] like Figure 4 As shown, the optical system layout structure of the binocular optical system is further demonstrated. The left and right optical systems are symmetrically arranged, and the optomechanical modules are located on both sides of the head. They are naturally connected in the middle through optical components in the bridge of the nose area, realizing binocular vision fusion and stereo imaging. The overall structure is compact, the contour fits well, and there are no obvious external protrusions.

[0044] In this embodiment of the invention, through the synergistic design of off-axis four-reflection path and fitted freeform surface mirror, the device size and weight are significantly reduced while achieving superior imaging performance and wearing comfort, making it particularly suitable for augmented reality application scenarios that require long-term use.

[0045] Example 2: like Figure 5 and Figure 6 As shown, the present invention provides an augmented reality head-mounted display device. Based on the same inventive concept as Embodiment 1, the device also includes a housing and an optical system disposed within the housing. The optical system consists of a microdisplay 1 and an optical combiner including four freeform mirrors.

[0046] In this embodiment, the basic optical path structure of the optical system is the same as that in Embodiment 1. That is, after the light is emitted from the microdisplay 1, it is reflected four times in sequence by the first freeform mirror 2, the second freeform mirror 3, the third freeform mirror 4 and the fourth freeform mirror 5, and finally imaged on the image plane area where the human eye 6 is located, forming an off-axis four-reflection optical path, realizing the effective folding and compact layout of the optical path.

[0047] Unlike Embodiment 1, in this embodiment, the optomechanical module, jointly formed by the microdisplay 1 and the first freeform mirror 2, is installed in the forehead region of the device housing. Specifically, in the wearing state, the optomechanical module is located in front of or slightly above the wearer's forehead. The surface shape of the first freeform mirror 2 has been specially optimized to conform to the contour curve of the wearer's forehead. This layout allows the optomechanical module to integrate more naturally into the forehead structure of the head-mounted device, avoiding additional burden on the temporal or ear areas, and is particularly suitable for head-mounted designs with constraints on lateral space or a preference for frontal support.

[0048] like Figure 5 As shown, in one specific implementation of this embodiment, the second freeform mirror 3 and the fourth freeform mirror 5 are designed separately and independently, that is, they are two physically separate independent optical elements, respectively fixed in corresponding positions inside the housing. This split design facilitates independent tilting, translation, and other degrees of freedom adjustment of the two lenses during the optical assembly and adjustment stage, so as to accurately correct aberrations and optimize image quality.

[0049] like Figure 6 As shown, in another implementation of this embodiment, the second freeform mirror 3 and the fourth freeform mirror 5 can also be integrated onto the same optical substrate to form an integrated component with a continuous optical reflective surface. This integrated design helps improve system stability, reduce assembly tolerance sensitivity, and makes the front of the device look simpler and smoother.

[0050] like Figure 7 The optical path structure of this embodiment is shown in the figure. Light is emitted from the microdisplay 1 and is reflected sequentially by the first freeform mirror 2, the second freeform mirror 3, the third freeform mirror 4, and the fourth freeform mirror 5, and finally imaged onto the image plane area where the human eye 6 is located.

[0051] In the specific optical design of this embodiment, the fourth freeform mirror 5 is characterized by an extended polynomial surface shape, with a maximum number of terms set to 44. The reflective concave surface of this mirror is precisely oriented towards the image plane area where the human eye 6 is located, ensuring that the light from the third freeform mirror 4 is accurately reflected and guided to the pupil of the human eye 6, which is the key to achieving the final imaging positioning accuracy; The third freeform surface lens 4 also adopts an extended polynomial surface shape with a maximum term of 44. Its surface design, while meeting the requirements for optical path reversal, is specifically optimized for fit to the wearer's nose bridge contour. When worn, the lens sits above the nose bridge, and its back surface (non-optical surface) is shaped to match the nose bridge curve, thereby dispersing contact pressure and significantly improving the comfort of the nose pad area. The second freeform mirror 3 also has an extended polynomial surface shape with a maximum of 44 terms. Its concave reflective surface faces the human eye 6 and its main function is to shape the light beam and correct some of the aberrations introduced by the front mirror. Its optical parameters are designed in coordination with those of the fourth freeform mirror 5 to ensure that the system has a sufficient field of view and good image sharpness. The first freeform mirror 2 is optimized using an extended polynomial surface shape (maximum number of terms 44). Its reflective surface is convex and faces the second freeform mirror 3. This mirror not only achieves the first folding of the light path from the forehead region to the eye region, but its surface shape also closely matches the contour of the wearer's forehead, allowing the optical engine module to be integrated into the forehead frame in a thin and contoured manner, further reducing the overall size of the device and the pressure on the forehead when wearing it.

[0052] To optimize the wearing experience and optical path efficiency under the forehead layout, the spatial pose of each freeform mirror in this embodiment has also been refined.

[0053] Preferably, the first freeform mirror 2 is offset from the optical axis by 10-20mm in the negative x direction and tilted counterclockwise by 60-65° around the x-axis, so that the curvature of the forehead of the face is coordinated with the requirement of the first fold of the optical path.

[0054] The second freeform mirror 3 is offset from the optical axis by 30-40mm in the negative x-direction and tilted counterclockwise by 30-40° around the x-axis. This ensures a safe distance from the eye area and allows the mirror angle of the second freeform mirror 3 to naturally conform to the contours of the forehead and temples. The edge of the concave surface of the second freeform mirror 3 maintains a safe distance of less than or equal to 50mm from the skin around the eyes to achieve a safe and comfortable wearing experience.

[0055] The third freeform mirror 4 is offset from the optical axis by 10-20mm in the positive x-direction and tilted counterclockwise by 40-50° around the x-axis to ensure that the shape of the back of the third freeform mirror 4 is highly consistent with the nose bridge curve and to distribute contact pressure. The fourth freeform mirror 5 is offset from the human pupil by 40-50mm in the z-direction and tilted counterclockwise by 10-30° around the x-axis. This allows the fourth freeform mirror 5 to receive light from the third freeform mirror while its outer surface smoothly blends into the contours of the forehead and brow bone. The distance parameter also takes into account the constraint of a safe distance (≤50mm) between the edge of the reflective concave surface and the skin around the eyes, effectively preventing the lens from pressing on the area around the eyes and improving the wearability of the device.

[0056] The augmented reality head-mounted display device provided in this embodiment offers users another efficient, compact, and ergonomic structural option by arranging the optical engine module in the forehead area and combining it with a first freeform mirror 2 that conforms to the forehead contour. The first freeform mirror 2 has a convex design with the reflective surface facing the second freeform mirror, and the optical path folding angle ranges from 35 to 70°.

[0057] This scheme complements the side layout scheme of Embodiment 1, together demonstrating the flexibility of the off-axis four-reflector optical path structure of the present invention in adapting to different wearing habits and appearance design requirements. Meanwhile, the two design variations of the second freeform surface mirror 3 and the fourth freeform surface mirror 5—both detachable and integrated—provide multiple feasible engineering paths for optical performance optimization and appearance integration.

[0058] Example 3: This embodiment provides an augmented reality head-mounted display device. Based on the same inventive concept as Embodiments 1 and 2, the device also includes a housing and an optical system disposed within the housing. The optical system consists of a microdisplay 1 and an off-axis reflective optical combiner containing four freeform mirrors. The core off-axis four-reflector optical path principle is consistent with the aforementioned embodiments. The difference lies in that this embodiment features a downward-facing structural center of gravity design, which solves the problems of poor image-to-real-scene integration, insufficient field-of-view matching, and increased pressure when wearing traditional devices.

[0059] In this embodiment of the invention, the augmented reality head-mounted display device includes: The outer shell has an internal space for accommodating optical components and a fixing structure for wearing; in this embodiment, the inner side of the outer shell refers to the inner surface of the side facing and close to the wearer's face 7 when worn, and the outer side of the outer shell refers to the side away from the face and facing the external environment.

[0060] The housing has an internal space for accommodating optical components and a fixing structure for wearing; An optical system, disposed within the housing, includes: Microdisplay 1, used to generate images; An optical combiner, which is an off-axis reflective structure, includes a first freeform mirror 2, a second freeform mirror 3, a third freeform mirror 4, and a fourth freeform mirror 5; The first freeform mirror 2 is disposed on the light-emitting side of the microdisplay 1 to receive and reflect light from the microdisplay 1; and the first freeform mirror 2 is disposed on the cheek area on the side of the wearer's nose. The second freeform mirror 3 and the fourth freeform mirror 5 are disposed inside the housing on the side away from the human eye. When worn, they are located in front of the wearer's eyes. The concave surfaces of the second freeform mirror 3 and the fourth freeform mirror 5 both face the image plane area where the human eye is located. The third freeform mirror 4 is disposed inside the housing and close to the wearer's forehead, and the non-optical surface of the third freeform mirror 4 conforms to the contour of the wearer's forehead; The second freeform mirror 3 is disposed in the reflected light path of the first freeform mirror 2, and receives and reflects light from the first freeform mirror 2; The third freeform mirror 4 is disposed in the reflected light path of the second freeform mirror 3, and is used to receive and reflect light from the second freeform mirror 3; The fourth freeform mirror 5 is disposed on the reflected light path of the third freeform mirror 4, receiving and reflecting light from the third freeform mirror 4, while receiving and transmitting light from the real scene, guiding the light to the image plane area where the human eye is located.

[0061] Specifically, the microdisplay 1 and the first freeform mirror 2 together constitute an optomechanical module, which is mounted on the outer shell and positioned on the cheek area next to the wearer's nose when worn. This arrangement shifts the main weight-bearing area of ​​the device from the traditional forehead or temple to the cheek area, effectively distributing the overall weight of the device by utilizing the natural weight-bearing capacity of the cheekbone, and significantly reducing the local pressure on the forehead and bridge of the nose. The first freeform mirror 2 is located on the light-emitting side of the microdisplay 1, and its non-optical surface conforms to the contour of the wearer's cheek, ensuring the stability of the fit between the device and the cheek area while achieving the initial folding of the optical path.

[0062] The second freeform mirror 3 and the fourth freeform mirror 5 are located inside the housing on the side away from the human eye 6. When worn, they are located in front of the wearer's human eye 6. The reflective concave surfaces of both are precisely oriented towards the visual axis of the human eye 6, working together to complete beam shaping and aberration correction to ensure image quality.

[0063] The third freeform surface mirror 4 is located inside the outer shell on the side close to the wearer's eye 6. When worn, it is positioned on the wearer's forehead, and its non-optical surface conforms to the contour of the wearer's forehead. While the third freeform surface mirror 4 undertakes the functions of optical path deflection and aberration correction in the optical system, its forehead-fitting design provides auxiliary support and stability, forming multi-point support with the main weight-bearing area of ​​the cheek, further enhancing the stability and comfort of wearing it.

[0064] The optical path connection relationship in this embodiment is as follows: The second freeform mirror 3 is disposed on the reflected light path of the first freeform mirror 2, receiving and reflecting light from the first freeform mirror 2. Its reflection angle has been specially optimized so that the light beam is transmitted along the path adapted to the lower viewing axis. The third freeform mirror 4 is disposed on the reflected light path of the second freeform mirror 3, receiving and reflecting light from the second freeform mirror 3, and completing the folding and lower field-of-view aberration correction in the middle section of the light path. The fourth freeform mirror 5 is disposed in the reflected light path of the third freeform mirror 4. Its optical surface is coated with a semi-transparent and semi-reflective film, which can receive and reflect virtual image light from the third freeform mirror 4, so that the light beam enters the pupil of the human eye 6 precisely along the wearer's visual axis; at the same time, it receives and transmits real scene light without distortion.

[0065] like Figure 8 As shown, in one specific implementation of this embodiment, the second freeform mirror 3 and the fourth freeform mirror 5 are two physically separate independent optical elements, which are respectively fixed to corresponding positions inside the housing.

[0066] like Figure 9 As shown, in another specific implementation of this embodiment, the second freeform mirror 3 and the fourth freeform mirror 5 are integrated on the same optical substrate to form an integrated optical component with a continuous reflective surface.

[0067] In this embodiment, each freeform mirror is characterized by an extended polynomial surface shape, with the maximum number of terms set to 44. Specifically, the first freeform mirror 2 effectively controls astigmatism and coma of the incident beam while achieving optical path folding in the cheek area; the second freeform mirror 3 undertakes beam shaping and aberration balancing; the third freeform mirror 4, while conforming to the forehead contour, effectively corrects image plane curvature and distortion caused by multiple optical path folds; and the fourth freeform mirror 5 has its reflective concave surface precisely aligned with the visual axis of the human eye 6, ensuring that the imaging light rays converge precisely on the retina.

[0068] To further adapt to usage scenarios where the line of sight is downward, this embodiment uses the same right-handed Cartesian coordinate system as the previous embodiment to define the spatial pose of each optical element: with the center of the human eye's pupil as the origin, the Z-axis points outward along the line of sight of the human eye looking straight ahead, the Y-axis is horizontal and points to the wearer's left side as positive, and the X-axis is vertical and points downward as positive. The position offset and tilt angle of each freeform mirror are based on this coordinate system.

[0069] Preferably, the first freeform mirror 2 is offset from the optical axis by 10-20mm in the positive X direction and tilted around the corresponding axis at an appropriate angle so that its reflective surface fits precisely with the cheek contour, while ensuring that the optical path refraction angle matches the forward-looking optical path.

[0070] The second freeform mirror 3 is offset from the pupil of the human eye 6 by 40-50mm in the Z direction and tilted counterclockwise by 30-40° around the X axis. This parameter design ensures that the mirror angle naturally fits the facial contour and forms a smooth optical path connection with the fourth freeform mirror 5. At the same time, it ensures that the distance between the edge of the reflective concave surface of the second freeform mirror 3 and the wearer's skin around the eyes is ≤50mm, ensuring wearing safety.

[0071] The third freeform mirror 4 is offset from the optical axis by 20-30mm in the negative X direction and tilted counterclockwise by 40-50° around the X axis, so that its non-optical surface is highly consistent with the forehead curve, dispersing the contact pressure, while the optical path reversal angle is precisely matched with the frontal optical path.

[0072] The fourth freeform mirror 5 is offset from the pupil 6 of the human eye 40-50mm in the Z direction and tilted counterclockwise 10-30° around the X axis, so that the mirror does not obstruct the wearer's field of vision while receiving the light path. The distance between the edge of its reflective concave surface and the skin around the eyes is also controlled to ≤50mm to avoid pressure on the sensitive area around the eyes.

[0073] The core optical path of this embodiment is as follows: After the light is emitted from the microdisplay 1, it undergoes four consecutive reflections through the first freeform mirror 2, the second freeform mirror 3, the third freeform mirror 4, and the fourth freeform mirror 5. The virtual image is compactly transmitted through multiple optical path folding, and finally imaged along the wearer's visual axis onto the image plane area where the human eye 6 is located. It is seamlessly integrated with the real ambient light in the downward field of view through the fourth freeform mirror 5 to form an augmented reality visual image.

[0074] This embodiment distributes the weight of the device downwards by positioning the center of gravity of the optical engine module in the cheek area, effectively avoiding the concentrated pressure on the forehead and bridge of the nose caused by traditional head-mounted devices, thus improving wearing comfort. This embodiment, along with the side layout of Embodiment 1 and the forehead layout of Embodiment 2, combines the flexibility of the off-axis four-reflector structure of this invention in adapting to different ergonomic needs and wearing habits. Furthermore, the separate and integrated design variations of the second freeform surface mirror 3 and the fourth freeform surface mirror 5 provide multiple feasible implementation paths for the engineering application of the device.

[0075] Example 4: This embodiment provides an augmented reality head-mounted display method, which is implemented by using an augmented reality head-mounted display device as described in any of Embodiments 1 to 3.

[0076] The augmented reality head-mounted display method includes the following steps: The device is worn on the head so that each freeform mirror in the optical combiner is positioned in the corresponding facial contour area. The microdisplay is activated to generate and emit a beam of light carrying image information; The light beam undergoes four consecutive reflections through the first, second, third, and fourth freeform mirrors to form a folded and corrected optical path. The light beam, after being reflected by the fourth freeform mirror, eventually enters the human eye and merges with the light of the real scene observed through the device to form an augmented reality visual image.

[0077] The augmented reality head-mounted display method, based on the device's off-axis four-reflector path and fitted mirror design, achieves efficient transmission and display of virtual images while maintaining a compact structure and comfortable wear.

[0078] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. An augmented reality head-mounted display device, characterized in that, include: The housing has an internal space for accommodating optical components and a fixing structure for wearing; An optical system, disposed within the housing, includes: Microdisplays are used to generate images; An optical combiner, which is an off-axis reflective structure, includes a first freeform mirror, a second freeform mirror, a third freeform mirror, and a fourth freeform mirror; The first freeform mirror is disposed on the light-emitting side of the microdisplay and is used to receive and reflect light from the microdisplay. The second and fourth freeform mirrors are disposed inside the housing on the side away from the human eye, and are located in front of the wearer's eyes when worn. The concave surfaces of the second and fourth freeform mirrors both face the image plane area where the human eye is located. The third freeform surface mirror is disposed inside the outer shell close to the wearer's eye and is located at the bridge of the wearer's nose when worn. The non-optical surface of the third freeform surface mirror conforms to the contour of the wearer's nose. The second freeform mirror is disposed in the reflected light path of the first freeform mirror, and receives and reflects light from the first freeform mirror; The third freeform mirror is disposed in the reflected light path of the second freeform mirror and is used to receive and reflect light from the second freeform mirror; The fourth freeform mirror is disposed on the reflected light path of the third freeform mirror, receiving and reflecting light from the third freeform mirror, while simultaneously receiving and transmitting light from the real scene, guiding the light to the image plane area where the human eye is located.

2. The augmented reality head-mounted display device according to claim 1, characterized in that: The microdisplay and the first freeform mirror together constitute an optical engine module, which is disposed on the outer shell and located in the side area of ​​the wearer's face when worn.

3. The augmented reality head-mounted display device according to claim 2, characterized in that: The first freeform mirror conforms to the side profile of the wearer's face when worn.

4. The augmented reality head-mounted display device according to claim 1, characterized in that: The microdisplay and the first freeform mirror together constitute an optical engine module, which is located in the forehead area of ​​the wearer when worn.

5. The augmented reality head-mounted display device according to claim 4, characterized in that: The first freeform mirror conforms to the contour of the wearer's forehead when worn.

6. The augmented reality head-mounted display device according to claim 1, characterized in that: The distance between the edge of the concave surface of the second and fourth freeform mirrors and the skin around the eye is less than or equal to 50 mm.

7. An augmented reality head-mounted display device, characterized in that, include: The housing has an internal space for accommodating optical components and a fixing structure for wearing; An optical system, disposed within the housing, includes: Microdisplays are used to generate images; An optical combiner, which is an off-axis reflective structure, includes a first freeform mirror, a second freeform mirror, a third freeform mirror, and a fourth freeform mirror; The first freeform mirror is disposed on the light-emitting side of the microdisplay to receive and reflect light from the microdisplay; and the first freeform mirror is disposed on the cheek area on the side of the wearer's nose. The second and fourth freeform mirrors are disposed inside the housing on the side away from the human eye, and are located in front of the wearer's eyes when worn. The concave surfaces of the second and fourth freeform mirrors both face the image plane area where the human eye is located. The third freeform surface mirror is disposed inside the housing close to the wearer's forehead, and the non-optical surface of the third freeform surface mirror conforms to the contour of the wearer's forehead; The second freeform mirror is disposed in the reflected light path of the first freeform mirror, and receives and reflects light from the first freeform mirror; The third freeform mirror is disposed in the reflected light path of the second freeform mirror and is used to receive and reflect light from the second freeform mirror; The fourth freeform mirror is disposed on the reflected light path of the third freeform mirror, receiving and reflecting light from the third freeform mirror, while simultaneously receiving and transmitting light from the real scene, guiding the light to the image plane area where the human eye is located.

8. The augmented reality head-mounted display device according to claim 1 or 7, characterized in that: The second freeform mirror and the fourth freeform mirror are two physically separate independent optical elements.

9. The augmented reality head-mounted display device according to claim 1 or 7, characterized in that: The second freeform mirror and the fourth freeform mirror are integrated on the same optical substrate to form an integrated optical component with a continuous reflective surface.

10. An augmented reality head-mounted method, characterized in that: It is implemented using an augmented reality head-mounted display device as described in any one of claims 1 to 9.

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