Eyepiece collimation system of AR glasses

Abstract

The invention relates to the technical field of optical design, in particular to an eyepiece collimation system of AR glasses, which comprises a lens group and a light combination prism, the light combination prism is preposed and arranged between a micro display and the lens group, and the light combination prism combines RGB information light provided by the micro display in different directions to form a light beam; and the lens group comprises a first lens, a third lens, a second lens and a fourth lens, the front and rear surfaces of the first lens and the third lens are free-form surfaces, and the rear surfaces of the second lens and the fourth lens are spherical surfaces. According to the invention, the light combination prism is arranged in front, so that the overall size of an eyepiece collimation system of the diffraction optical waveguide near-to-eye display system is obviously simplified, and AR equipment tends to be miniaturized and light; and by adjusting and optimizing the lens group structure, the design number of free-form surfaces is reduced, and the optical design structure is simplified and the optical detection difficulty is reduced on the premise of ensuring that each optical performance meets the index requirements.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical design, and in particular relates to an eyepiece collimation system of AR glasses. Background Art

[0002] In recent years, near-eye display systems have gradually penetrated into our lives. People's pursuit of displayed images is not limited to its size, but also its clarity and detail performance. At the same time, more emphasis is placed on the design concept of lightness and miniaturization, so that near-eye display systems, especially those used in AR glasses, can maintain miniaturization while steadily improving image quality. Various optical components are used in near-eye display systems, from traditional lens groups to free-form surfaces, holographic optical components, and optical waveguides, and each step is towards a clearer development.

[0003] The augmented reality near-eye display system is mainly used in AR devices to superimpose virtual information on real scenes. At present, optical waveguide technology is its important direction. The waveguide structure is equivalent to a total reflection system. The light propagates horizontally in the waveguide. Its special structure simplifies the optical layout of the near-eye display system, folds the optical path, reduces the complexity of the optical system, and has little effect on the aberration of the system. Its use can reduce the size and weight of the device to meet the needs of lightness and is easy to wear. The near-eye display system has developed from monochrome and single angle to multi-color and large field of view. The layout array optical waveguide and surface relief optical waveguide are mainly used on the market, especially the surface relief optical waveguide, which can allow the image of the micro display to pass through the eyepiece collimation system, and the light is emitted in parallel and enters the input coupling grating. Diffraction occurs, and its angle is greater than the critical angle of total reflection in the waveguide. The light propagates to the output coupling grating, and the light is coupled out of the waveguide to reach the human eye, so that the virtual image is superimposed on the real scene.

[0004] The eyepiece collimation system has a great influence on the imaging effect. During the design process, factors such as the matching with the micro display size, field of view, and exit pupil distance need to be considered. The eyepiece collimation system design currently on the market usually places the light-combining prism between the lens group and the waveguide. This design requires three sets of lens groups, which greatly increases the overall size of the system.

[0005] Therefore, there is an urgent need to optimize the existing eyepiece collimation system to achieve a smaller system size and a simpler optical path structure while maintaining imaging quality. Summary of the invention

[0006] In view of this, the present invention aims to provide an eyepiece collimation system for AR glasses, simplifies the structure of the existing eyepiece, and significantly simplifies the overall size of the eyepiece collimation system of the diffraction light waveguide near-eye display system by placing a light-combining prism in front, making the AR device more miniaturized and lightweight.

[0007] To achieve the above object, the technical solution created by the present invention is implemented as follows: The invention provides an eyepiece collimation system for AR glasses, which is arranged between a micro display and a waveguide, and includes: a mirror group, and a light combining prism arranged between the micro display and the mirror group; The light combining prism is used to combine the information lights from different directions provided by the micro display; The mirror group is used to collimate the combined light beam passing through the light combining prism and control the distortion. The mirror group at least includes: A first lens, wherein both front and rear surfaces thereof are free-form surfaces; A second lens, whose front and rear surfaces are both spherical; A third lens, both front and rear surfaces of which are free-form surfaces; The fourth lens has front and rear surfaces that are both spherical.

[0008] Preferably, the light combining prism is used to combine information lights of different colors in three directions provided by the micro display.

[0009] Preferably, the first lens and the third lens are made of a first material, the second lens and the fourth lens are made of a second material, the light-combining prism is made of a third material, and the first material, the second material and the third material are different from each other.

[0010] Preferably, the front and rear surfaces of the first lens and the third lens are both free-form surfaces represented by a sixth-order XY polynomial.

[0011] Preferably, the normalized radius of the front and rear free-form surfaces of the first lens and the third lens is 1, the conic surface constant is -1, and the even-order coefficients of X are all variables.

[0012] Preferably, the first lens is a convex-concave free-form surface lens, the second lens is a biconvex spherical lens, the third lens is a concave free-form surface lens, and the fourth lens is a biconvex spherical lens.

[0013] Compared with the prior art, the invention can achieve the following beneficial effects: The present invention places a light-combining prism in front to combine the red, green and blue spectral information lights emitted by the micro-display, and then uses a lens group to collimate and correct the light. The collimated light is then transmitted to the exit pupil position through a waveguide for observation by the user. This design solves the problem that the traditional eyepiece collimation system must use three lens groups by placing the light-combining prism in front, reduces the number of lens groups required, simplifies the optical path, and thus reduces the overall size and weight of the system, reduces the manufacturing cost and maintenance cost, and has positive significance for the miniaturization and lightweight of AR glasses. Simulation verification shows that various performance indicators of the system of the present invention meet or exceed industry standards.

[0014] The present invention has made an innovative design to the lens group, combining a spherical surface with a free-form surface. According to the transfer function evaluation and the point diagram, the combined design of the present invention improves the optical imaging quality. The present invention can effectively control distortion and correct aberration through the free-form surface, so that the distortion is less than 1.5%, which is within the acceptable range of the human eye, and the relative illumination is high, so that AR glasses can be used in scenes with strong lighting. In addition, compared with the traditional design that uses all free-form surface lenses, the present invention reduces the number of free-form surface designs as much as possible, reducing the difficulty of CGH detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The drawings constituting part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments and descriptions of the present invention are used to explain the present invention and do not constitute an improper limitation on the present invention. In the drawings: Figure 1 is a schematic diagram of reverse propagation of unidirectional information light in an eyepiece collimation system provided in an embodiment of the present invention; Figure 2 is a schematic diagram of forward propagation of unidirectional information light in an eyepiece collimation system provided in an embodiment of the present invention; Figure 3 is a schematic diagram of reverse propagation of information light in the upper and lower and left directions in the eyepiece collimation system provided in an embodiment of the present invention; Figure 4 is a schematic diagram of reverse propagation of information light in the upper and left directions in the eyepiece collimation system provided by an embodiment of the present invention; Figure 5 It is a flow chart of mirror optimization design in an eyepiece collimation system provided according to an embodiment of the present invention.

[0016] Reference numerals include: First lens 1, second lens 2, third lens 3, fourth lens 4, and light-combining prism 5. DETAILED DESCRIPTION

[0017] In order to make the purpose, technical scheme and advantages of the invention clearer, the invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the invention and do not constitute a limitation to the invention. Similar components in different embodiments use associated similar component numbers. In the following embodiments, many detailed descriptions are to enable the invention to be better understood. However, those skilled in the art can easily recognize that some of the features can be omitted in different situations, or can be replaced by other components, materials, and methods. In some cases, some operations related to the invention are not shown or described in the specification, in order to avoid the core part of the invention being overwhelmed by too much description, and for those skilled in the art, it is not necessary to describe these related operations in detail, and they can fully understand the related operations according to the description in the specification and the general technical knowledge in the art.

[0018] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other to form various implementation methods. At the same time, the steps or actions in the method description can also be interchanged or adjusted in a manner that is obvious to those skilled in the art. Therefore, the various sequences in the specification and the drawings are only for the purpose of clearly describing a certain embodiment and are not meant to be a necessary sequence, unless otherwise specified that a certain sequence must be followed.

[0019] In the description of the invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the invention, unless otherwise specified, the meaning of "multiple" is two or more.

[0020] In the description of the invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the invention can be understood according to specific circumstances.

[0021] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments.

[0022] In one embodiment of the present invention, see Figure 1 and Figure 2 , provides an eyepiece collimation system for AR glasses, Figure 1 The left side is a diffractive optical waveguide, and the right side is a microdisplay, which is a schematic diagram of a reverse propagation structure; Figure 2 The left side is a microdisplay, and the right side is a diffractive optical waveguide, which is a schematic diagram of a forward propagation structure. Figure 1 and Figure 2 Only one direction of information light is shown. The eyepiece collimation system includes a lens group and a light-combining prism 5, which are arranged between the microdisplay and the diffraction light waveguide of the AR glasses to combine and collimate the three-directional information light emitted by the microdisplay and project it onto the waveguide, and transmit the collimated combined light to the exit pupil position through the waveguide for the wearer to observe. It can be understood that the three-directional information light here refers to the red, green, and blue (RGB) three-color light of the microdisplay showing the picture. Figure 3 and Figure 4 As shown, Figure 3 The information light in two directions is shown in Figure 4 The two directions of information light are also shown.

[0023] In the traditional design, the three RGB lights are collimated separately through three mirror groups, and then injected into the light-combining prism, and the RGB lights are combined by the light-combining prism and projected onto the waveguide. In order to achieve the miniaturization and lightweight of AR glasses and reduce the number of optical components, the light-combining prism 5 in the embodiment of the present invention innovatively adopts a front design, and the light-combining prism 5 is arranged between the micro-display and the mirror group. The RGB lights are combined by the light-combining prism 5, and then the combined light is collimated and the distortion is corrected by the mirror group, and the collimated combined light is projected onto the waveguide for the wearer to observe the AR image shown on the micro-display. This design only requires one set of mirror groups, which effectively simplifies the optical structure. The material of the light-combining prism 5 is HK9L_CDGM.

[0024] The lens group is used to collimate the combined light after the light combining prism 5 combines the light, and control the field of view distortion to reduce it to less than 1.5%, so as to ensure that the field of view distortion can be within the acceptable range of the human eye. The lens group includes: a first lens 1, a second lens 2, a third lens 3 and a fourth lens 4 arranged in sequence on the optical path from the waveguide to the micro display, wherein the first lens 1 and the third lens 3 are both designed as free-form surface lenses, and the front surface of the first lens 1 is convex, and the rear surface is concave, where the front surface refers to the mirror surface on the side close to the waveguide, and the rear surface refers to the mirror surface on the side away from the waveguide. The front surface of the third lens 1 is convex, and the rear surface is concave. The free-form surfaces of the first lens 1 and the third lens 3 can both be expressed by XY polynomials, and the normalized radius of the free-form surface is set to 1, and the conic surface constant is set to -1, which can effectively control distortion and correct aberrations. In the XY polynomial, the even-order coefficients of X are all variables, and these variables can be freely adjusted in the specific parameter design process to optimize the optical performance. The second lens 2 and the fourth lens 4 are both designed as spherical lenses to avoid using a large number or all of free-form surface lenses, which increases the difficulty of CGH detection of the optical system. The present invention not only reduces the number of free-form surfaces and simplifies the detection process through the combined application of free-form surfaces and spherical surfaces, but also effectively reduces the complexity of the optical path and the difficulty of mirror preparation, thereby improving the reliability and stability of the system. The second lens 2 and the fourth lens 4 are both biconvex spherical lenses, which are used to cooperate with the first lens 1 and the third lens 3 to collimate the light.

[0025] In the embodiment of the present invention, the traditional double-gluing design is abandoned to improve the structural stability.

[0026] Regarding the material selection of the light-combining prism 5 and the different lenses in the lens group, in order to correct the secondary spectrum, in the embodiment of the present invention, the dispersion characteristics and Abbe number differences of different materials are comprehensively considered, and the final matching scheme is determined by comparing different material combinations, that is, the first lens 1 and the third lens 3 are made of the same preparation material, both EP9000 (first material); the second lens 2 and the fourth lens 4 are made of the same preparation material, both PMMAO (second material); the preparation material of the light-combining prism 5 is HK9L_CDGM (third material). Finally, EP9000 with an applicable band of 404.656nm-1013.98nm and PMMAO with an applicable band of 365nm-1014nm are selected. The refractive index of EP9000 is 1.671 and the Abbe number is 19.2, and the refractive index of PMMAO is 1.492 and the Abbe number is 57.2. Both have high light transmittance and heat resistance, which meet the requirements of thin and lightweight lenses.

[0027] Through the combination design of different materials, the secondary spectrum is corrected, the imaging quality is significantly improved, and the imaging chromatic aberration is reduced.

[0028] In addition, the materials of the above-mentioned light-combining prism 5 and different lenses in the lens group can be adjusted according to the dispersion characteristics and Abbe number differences. Changing the materials of part or all of the mirror bodies, materials with different refractive indices or optical properties, will directly affect the imaging effect of the system.

[0029] See also Figure 5 , the specific process of mirror parameter design in the above structure is as follows: Based on the reverse design of the eyepiece collimation system mentioned above, according to the specific parameters of the diffraction optical waveguide and microdisplay and the basic performance index requirements, the double Gaussian lens is selected as the starting point of the design. According to the design indicators, the double Gaussian lens is optimized as the initial structure. Starting from the imaging target, the design scheme of the optical system is reversely derived to ensure that the projection effect meets the requirements. The image telecentric effect can be achieved through reverse design. Within a reasonable distance range, the magnification of the object is independent of the object distance, that is, the image height will not change when the object distance changes, thereby ensuring the consistency of the measured object size. The designed structure is flipped to the actual application situation. The information is sent by the microdisplay, and the parallel light is output to the waveguide through the light-combining prism and lens group after collimation, and continues to propagate.

[0030] In the embodiment of the present invention, the specific parameters of the micro display and the diffractive light waveguide used with the eyepiece collimation system are as follows: The microdisplay uses Chip_A chip, which has a resolution of 640×480, effective pixels of 640×480, and pixel size of , the display area size is .

[0031] The diffraction optical waveguide used is the SIDW30B monochrome side-projection product of Zhige Technology, with a field of view (FOV) of 30°, a maximum entrance pupil diameter of 5mm, an exit pupil distance of 20mm, a waveguide grating area transmittance greater than 85%, and an energy utilization rate of 650nit / lm.

[0032] S110: First, limit the overall length (OAL) of the eyepiece collimation system to less than 15 mm and minimize the overall length of the structure. By optimizing the layout and design of optical components, reduce unnecessary space waste and ensure the compactness of the system.

[0033] S120: Limit the effective focal length (EFL) to an appropriate value. The specific value of the effective focal length (EFL) affects the F-number. It is necessary to ensure that the lens has good light transmission capability. The F-number is an indicator of the lens' light transmission capability. The smaller the F-number, the better the light transmission capability. By adjusting the parameters of the optical components, ensure that the F-number meets the design requirements.

[0034] S130: According to the size of the waveguide and the microdisplay, the imaging range of the object plane and the image plane is limited. Through calculation and simulation, the imaging range of the object plane and the image plane is determined to ensure that the size of the optical system matches that of the waveguide and the chip. The size of the light-combining prism 5 is designed to be 4×4×5mm 3 .

[0035] S140: constrain the local angle of incidence (AOI) of the image plane, modify the constraint range, optimize the optical design, and adjust the parameters of the lens group to make the local angle of incidence (AOI) of the image plane close to 0°, thereby achieving image telecentricity and ensuring the consistency of imaging quality.

[0036] S150: Add free-form surfaces to the lens assembly and add constraints to further optimize the lens surfaces in the lens assembly. Through simulation and optimization, adjust the parameters of the free-form surfaces to reduce distortion and add additional constraints when necessary.

[0037] S160: Make minor adjustments to the optimized lens assembly to ensure that parameters such as the center thickness, edge thickness, and distance between two lenses of each lens meet the design requirements.

[0038] Through the above design optimization, the working band of the eyepiece collimation system of the embodiment of the present invention is 450nm, 550nm, and 630nm, the bandwidth is 30nm, the effective total length is 12.89nm, and the field of view angle is 24°. The entrance pupil diameter of the eyepiece collimation system is 3.4mm, and the effective focal length (EFL) is 5.88 , the F number is only 1.73, which ensures the light transmission ability of the system.

[0039] In addition, an aperture is set in the eyepiece collimation system to constrain the optical path. By changing the position of the aperture, the optical structure in different situations is obtained and compared with the design indicators. Adjusting the aperture forward will result in a more suitable and easier-to-adjust solution.

[0040] The optimized eyepiece collimation system is simulated by CodeV software. After simulation verification, it is found that when the maximum spatial frequency of the optimized eyepiece collimation system is 133.33lp / mm, the transfer function of each field of view is greater than 0.69, and when the spatial frequency is 40lp / mm, the transfer function of each field of view is greater than 0.9, which has good imaging quality. By observing the point array diagram, it can be seen that the RMS value of each field of view is less than the pixel unit, which proves that the imaging performance of the eyepiece collimation system of the present invention is good. The eyepiece collimation system of the present invention has pincushion distortion, and the maximum distortion value of the whole field of view is -1.40%, and the distortion values ​​are less than 1.5%, which meets the distortion value requirements in the industry and is within the distortion range that the human eye can accept. And the relative illumination value is high, and the relative illumination value of each field of view reaches more than 94%. It can meet the use in daily lighting environment.

[0041] In short, the above description is only a preferred embodiment of this specification and is not intended to limit the protection scope of this specification. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of this specification shall be included in the protection scope of this specification.

[0042] The systems, devices, modules or units described in one or more of the above embodiments may be implemented by a computer chip or entity, or by a product having a certain function. A typical implementation device is a computer. Specifically, the computer may be, for example, a personal computer, a laptop computer, a cellular phone, a camera phone, a smart phone, a personal digital assistant, a media player, a navigation device, an email device, a game console, a tablet computer, a wearable device, or a combination of any of these devices.

[0043] It should also be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, commodity or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, commodity or device. In the absence of more restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the process, method, commodity or device including the elements.

[0044] Each embodiment in this specification is described in a progressive manner, and the same or similar parts between the embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the system embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiment.

[0045] The above is a description of a specific embodiment of the specification. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps recorded in the claims can be performed in an order different from that in the embodiments and still achieve the desired results. In addition, the processes depicted in the drawings do not necessarily require the specific order or continuous order shown to achieve the desired results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

Claims

1. An eyepiece alignment system for AR glasses, which is arranged between a microdisplay and a waveguide, characterized in that: include: A mirror assembly, and a light combining prism disposed between the micro display and the mirror assembly; The light combining prism is used to combine information lights from different directions provided by the micro display; The mirror group is used to collimate the combined light beam passing through the light combining prism and control distortion. The mirror group at least includes: A first lens, wherein both front and rear surfaces thereof are free-form surfaces; A second lens, whose front and rear surfaces are both spherical; A third lens, both front and rear surfaces of which are free-form surfaces; The fourth lens has front and rear surfaces that are both spherical.

2. The eyepiece alignment system of AR glasses as claimed in claim 1, characterized in that: The light combining prism is used to combine information lights of different colors in three directions provided by the micro display.

3. The eyepiece alignment system of AR glasses as claimed in claim 1, characterized in that: The first lens and the third lens are made of a first material, the second lens and the fourth lens are made of a second material, the light-combining prism is made of a third material, and the first material, the second material and the third material are different from each other.

4. The eyepiece alignment system of AR glasses as claimed in claim 1, characterized in that: The front and rear surfaces of the first lens and the third lens are both free-form surfaces represented by a 6th-order XY polynomial.

5. The eyepiece alignment system of AR glasses as claimed in claim 4, characterized in that: The normalized radius of the front and rear free-form surfaces of the first lens and the third lens is 1, the conic surface constant is -1, and the even-order coefficients of X are all variables.

6. The eyepiece alignment system of AR glasses as claimed in claim 1, characterized in that: The first lens is a convex-concave free-form surface lens, the second lens is a biconvex spherical lens, the third lens is a concave free-form surface lens, and the fourth lens is a biconvex spherical lens.

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