Optical system and smart head-mounted device

Abstract

The embodiment of the application provides an optical system and an intelligent head-mounted device; the optical system comprises, in sequence along the same optical axis, an imaging assembly, a diffractive optical element and a display screen; the imaging assembly comprises, in sequence, a first lens, a reflective polarization element, a phase retardation plate, a second lens and a light splitting element; the first lens and the second lens are both aspherical lenses; the diffractive optical element is glued with the display screen; the diffractive optical element mainly comprises a substrate and a microstructure arranged on the substrate, and the microstructure is used for phase modulation of light from the display screen, so that the light is bent and dispersed in propagation; through the phase modulation of the light by the microstructure, a chromatic aberration effect opposite to the chromatic aberration generated by the imaging assembly can be generated; when the light modulated by the microstructure enters the imaging assembly, the chromatic aberration generated by the microstructure and the chromatic aberration generated by the imaging assembly are offset to each other, so that the compensation of the chromatic aberration of the imaging assembly is realized.

Description

Technical Field

[0001] This application relates to the field of optical display technology, and more specifically, to an optical system and a smart head-mounted device. Background Technology

[0002] With the development of virtual reality (VR) technology, VR optical display devices have been widely used in various fields. VR optical display devices provide an immersive experience, allowing users to isolate themselves from external interference and obtain a more realistic visual experience. However, traditional VR optical systems mostly use multiple aspherical lenses or Fresnel lenses, resulting in poor edge imaging quality and severe transverse chromatic aberration, affecting the user experience. To improve this problem, common methods include increasing the number of aspherical lenses or using freeform off-axis systems, but these methods often increase the complexity and weight of the optical system. Summary of the Invention

[0003] The purpose of this application is to provide a new technical solution for an optical system and a smart head-mounted device.

[0004] In a first aspect, this application provides an optical system, which includes an imaging component, a diffractive optical element, and a display screen arranged sequentially along the same optical axis;

[0005] The imaging assembly includes a first lens, a reflective polarizing element, a phase retardation plate, a second lens, and a beam splitter arranged sequentially.

[0006] Both the first lens and the second lens are aspherical lenses;

[0007] The diffractive optical element is bonded to the display screen;

[0008] The diffractive optical element mainly consists of a substrate and microstructures disposed on the substrate. The microstructures are used to phase modulate the light from the display screen, causing the light to bend and disperse during propagation. The phase modulation of the light by the microstructures can produce a chromatic aberration effect that is opposite to the transverse chromatic aberration produced by the imaging component.

[0009] When the light modulated by the microstructure enters the imaging component, the transverse chromatic aberration generated by the microstructure cancels out the transverse chromatic aberration generated by the imaging component, thereby compensating for the transverse chromatic aberration of the imaging component and correcting the transverse chromatic aberration of the optical system.

[0010] Optionally, the surface of the microstructure is a binary surface, and the expression of the binary surface is: M = (A1ρ) / (A1ρ) 2 +A2ρ 4 +A3ρ 6 +A4ρ8 ); where M is the diffraction order, A1 is the second phase coefficient used to correct chromatic aberration, A2, A3, and A4 are aspherical phase coefficients, and ρ is the normalized polar radius.

[0011] Optionally, the diffraction order is 1, -1.07E+06≤ρ 2 ≤-1.04E+06, 2.39E+07≤ρ 4 ≤2.41E+07, -3.16E+08≤ρ 6 ≤-3.09E+08, 1.04E+09≤ρ 8 ≤1.09E+09.

[0012] Optionally, the maximum thickness of the first lens is T. 1Max The minimum thickness of the first lens is T. 1Mix The first lens satisfies: 0.14 < (T) 1Max -T 1Mix ) / T 1Max <1;

[0013] The center thickness T2 of the second lens is: T2 > 8mm.

[0014] Optionally, the center thickness T1 of the first lens and the center thickness T2 of the second lens are respectively: 2mm≤T1≤10mm and 2mm≤T2≤10mm.

[0015] Optionally, the radius of curvature of the surface of the first lens away from the display screen is R1, and the radius of curvature of the surface of the first lens close to the display screen is R2, wherein R1 and R2 satisfy: 55mm < |R1| + |R2| < 80mm.

[0016] Optionally, the radius of curvature R1 of the surface of the first lens away from the display screen is -35mm < R1 < -20mm, and the radius of curvature R2 of the surface of the first lens close to the display screen is -45mm < R2 < -35mm.

[0017] Optionally, the radius of curvature R3 of the surface of the second lens near the display screen is -40mm < R3 < -30mm.

[0018] Optionally, the optical system satisfies: in, The optical power of the first lens is... The optical power of the second lens is [value]. The total optical power of the optical system is given.

[0019] Optionally, the straight-line distance between the first lens and the exit pupil position of the optical system is d, where 0 < d < 15 mm;

[0020] The exit pupil diameter of the optical system is D, where 4mm < D < 6mm.

[0021] Optionally, the total length of the optical system is L, where 30mm < L < 40mm, and the field of view (FOV) of the optical system is 140° < FOV < 160°.

[0022] Optionally, the size of the display screen is 60mm to 75mm.

[0023] Optionally, the first lens and the second lens are cemented together;

[0024] The beam splitter is disposed on the side surface of the second lens near the display screen; the phase delay film and the reflective polarizing element form a composite film and are disposed on the bonding surface of the first lens and the second lens.

[0025] Optionally, the first lens and the second lens are made of resin material;

[0026] The first lens and the second lens are even-order aspherical lenses.

[0027] Secondly, this application provides a smart head-mounted device, the smart head-mounted device comprising:

[0028] The outer casing; and

[0029] The optical system as described in the first aspect.

[0030] The beneficial effects of this application are as follows:

[0031] This application provides an optical system as a large field-of-view, achromatic refraction-diffraction hybrid VR optical system. By employing aspherical lenses and various optical films to construct the imaging components, it effectively corrects various aberrations in the optical system, especially aberrations at the edge of the field of view, significantly improving image quality and ensuring that the image seen by the user is both clear and distortion-free. The entire optical system arranges a first lens, a reflective polarizing element, a phase retardation plate, a second lens, a beam splitter, and diffractive optical elements along the same optical axis, achieving a folded and compact layout of the optical path. This design not only reduces the size and weight of the system but also improves light utilization, making it particularly suitable for VR devices with strict space requirements, providing users with a lighter and more comfortable wearing experience.

[0032] Most importantly, the introduction of diffractive optical elements, whose microstructures can modulate incident light, compensates for transverse chromatic aberration generated by the imaging components themselves. This design effectively reduces or even eliminates transverse chromatic aberration in the optical system, significantly improving color reproduction and image sharpness.

[0033] The bonding design between diffractive optical elements and the display screen not only simplifies the system structure but also enhances the mechanical stability and durability of the optical system. This design allows the optical system to better withstand external shocks and vibrations, maintaining stable performance over the long term.

[0034] Other features and advantages of this specification will become clear from the following detailed description of exemplary embodiments with reference to the accompanying drawings. Attached Figure Description

[0035] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments of this specification and, together with their description, serve to explain the principles of this specification.

[0036] Figure 1 This is one of the schematic diagrams of the structure and optical path of the optical system provided in the embodiments of this application;

[0037] Figure 2 A graph showing the transverse aberration of an optical system without diffractive optical elements.

[0038] Figure 3 for Figure 1 The diagram shows the transverse aberration curves of the optical system (with diffractive optical elements added);

[0039] Figure 4 for Figure 1 The modulation transfer function diagram of the optical system (with diffractive optical elements added) is shown;

[0040] Figure 5 This is the second schematic diagram of the structure and optical path of the optical system provided in the embodiments of this application;

[0041] Figure 6 for Figure 5 The diagram shows the transverse aberration curves of the optical system (with diffractive optical elements added);

[0042] Figure 7 for Figure 5 The modulation transfer function diagram of the optical system (with diffractive optical elements added) is shown;

[0043] Figure 8 This is the third schematic diagram of the structure and optical path of the optical system provided in the embodiments of this application;

[0044] Figure 9 for Figure 8The diagram shows the transverse aberration curves of the optical system (with diffractive optical elements added);

[0045] Figure 10 for Figure 8 The modulation transfer function diagram of the optical system (with diffractive optical elements added) is shown;

[0046] Explanation of reference numerals in the attached figures:

[0047] 1. First lens; 2. Second lens; 3. Diffractive optical element; 4. Display screen; 5. Reflective polarization element; 6. Phase retardation plate; 7. Beam splitter; 01. Human eye. Detailed Implementation

[0048] Various exemplary embodiments of the present application will now be described in detail with reference to the accompanying drawings. It should be noted that, unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the present application.

[0049] The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the scope of this application and its application or use.

[0050] Technologies and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, such technologies and equipment should be considered part of the specification.

[0051] In all the examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.

[0052] It should be noted that similar labels and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be discussed further in subsequent figures.

[0053] The optical system and smart head-mounted device provided in the embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0054] According to one embodiment of this application, an optical system is provided, see [link to relevant documentation]. Figure 1 , Figure 5 and Figure 8The optical system includes an imaging component, a diffractive optical element 3, and a display screen 4 arranged sequentially along the same optical axis. The imaging component includes a first lens 1, a reflective polarizing element 5, a phase retardation plate 6, a second lens 2, and a beam splitter 7 arranged sequentially. Both the first lens 1 and the second lens 2 are aspherical lenses. The diffractive optical element 3 is cemented to the display screen 4. The diffractive optical element 3 mainly consists of a substrate and microstructures disposed on the substrate. The microstructures are used to phase modulate the light from the display screen 4, causing the light to bend and disperse during propagation. Through the phase modulation of the light by the microstructures, a chromatic aberration effect opposite to that produced by the imaging component can be generated. When the light modulated by the microstructures enters the imaging component, the chromatic aberration generated by the microstructures cancels out the chromatic aberration generated by the imaging component, thereby compensating for the chromatic aberration of the imaging component and correcting the chromatic aberration of the optical system.

[0055] The optical system provided in this application embodiment is described in [reference]. Figure 1 , Figure 5 and Figure 8 The optical system comprises three main optical components arranged sequentially along the same optical axis from the human eye side (human eye 01) to the image source side (display screen 4): an imaging component, a diffractive optical element, and the display screen 4. The following provides a detailed description of each optical component.

[0056] The imaging component is designed as a folded optical path structure containing two lenses.

[0057] The imaging component includes a first lens 1 located near the human eye 01. The first lens 1 adopts an aspherical design, which can control the refraction path of light. Compared with traditional spherical lenses, it can more effectively reduce aberrations, especially aberrations in the edge field of view, laying the foundation for high-quality imaging.

[0058] The imaging component includes a second lens 2, which also adopts an aspherical design. When paired with the first lens 1, the two aspherical lenses work together to further correct aberrations and improve imaging quality.

[0059] It should be noted that the imaging component of this application includes, but is not limited to, two lenses, and the number of lenses can be increased depending on the specific circumstances.

[0060] Optionally, the first lens 1 and the second lens 2 adopt an even-order aspherical design.

[0061] The imaging component in this application adopts a folded optical path design, which includes not only optical lenses, but also multiple optical elements, such as a reflective polarization element 5, a phase retardation plate 6, and a beam splitter 7.

[0062] A reflective polarizing element (also known as a polarizing reflector) is a polarizing reflector that reflects horizontally linearly polarized light and transmits vertically linearly polarized light, or reflects linearly polarized light at any other specific angle and transmits linearly polarized light perpendicular to that angle. In other words, a reflective polarizing element can reflect or transmit light according to its polarization state.

[0063] In the imaging assembly provided in this application embodiment, the reflective polarization element 5 interacts with a specific state of polarized light (such as S-light or P-light) to achieve specific path control of the light.

[0064] The phase delay plate 6 can be used to change the polarization state of light, such as converting linearly polarized light into circularly polarized light, or converting circularly polarized light into linearly polarized light.

[0065] The phase delay plate 6 in this application is, for example, a quarter-wave plate, which is located between the beam splitter 7 and the reflective polarizing element 5. It ensures that the light can be reflected or transmitted in subsequent paths by adjusting the phase of the light.

[0066] The beam splitting element 7 is, for example, a thin film or coating with specific beam splitting characteristics, which can be used to reflect and transmit incident light in a certain proportion.

[0067] The beam-splitting element 7 in this application is, for example, a semi-transparent and semi-reflective film, which allows a portion of light to pass through while reflecting the other portion.

[0068] It should be noted that the reflectivity and transmittance of the beam splitter 7 can be flexibly adjusted according to specific needs, and this embodiment does not impose any restrictions on this.

[0069] In the optical system provided in this application embodiment, the phase retardation plate 6 is located between the beam splitter 7 and the reflective polarization element 5. These three optical elements, together with the first lens 1 and the second lens 2, can form a folded optical path.

[0070] The introduction of the diffractive optical element 3 is an innovation in the optical system of this application. The diffractive optical element 3 mainly consists of a substrate and microstructures disposed on the substrate. These microstructures have specific shapes and arrangements that enable phase modulation of incident light. Specifically, when light passes through these microstructures, it bends and disperses. This phase modulation of light is crucial for correcting the transverse aberrations (including vertical chromatic aberration) of the entire optical system.

[0071] The phenomenon of light diffraction involves the bending and dispersion of light when it encounters an obstacle or passes through a small aperture. The diffractive optical element 3 introduced in this application utilizes this principle, modulating the phase of incident light through microstructures on its surface. The microstructure design of the surface of the diffractive optical element 3 can introduce specific phase changes, causing light of different wavelengths to bend and disperse to varying degrees during propagation. This phase modulation can precisely adjust the propagation path of light, thereby correcting transverse aberrations, especially transverse chromatic aberration.

[0072] Transverse aberrations, such as transverse chromatic aberration, are focal point shifts caused by the difference in refractive index when light of different wavelengths passes through the imaging component. In this application, the microstructure of the diffractive optical element 3 can perform phase modulation on light of different wavelengths before incidence, causing them to bend and disperse to varying degrees during propagation, thereby ensuring that all wavelengths of light can be accurately focused onto the same plane. This characteristic greatly improves color reproduction and image sharpness, allowing users to enjoy a more realistic and natural visual experience.

[0073] See also in this application. Figure 1 The diffractive optical element 3 mainly consists of a substrate and microstructures disposed on the substrate. The microstructures are used to phase modulate the light from the display screen 4, causing the light to bend and disperse during propagation. The phase modulation of the light by the microstructures can generate a chromatic aberration effect opposite to that generated by the imaging component. When the light modulated by the microstructures enters the imaging component, the chromatic aberration generated by the microstructures cancels out the chromatic aberration generated by the imaging component, thereby compensating for the chromatic aberration of the imaging component and correcting the chromatic aberration of the optical system.

[0074] Therefore, the diffractive optical element 3 can correct the transverse aberrations (including transverse chromatic aberration) of the imaging component, improving the color accuracy and clarity of the image. This is particularly important for VR optical display systems, as they require high color fidelity and high resolution to provide an immersive user experience.

[0075] The optical system provided in this application has the following significant advantages:

[0076] (1) Large field of view, anti-hysteresis chromatic aberration design:

[0077] The optical system described in this application is a large-field-of-view, achromatic refraction-diffraction hybrid VR optical system design, with particular emphasis on correcting transverse aberrations. Specifically, by employing a combination of aspherical lenses to construct the imaging components, various aberrations in the optical system are effectively corrected, including but not limited to chromatic aberration (especially transverse chromatic aberration) and aberrations at the edge of the field of view such as spherical aberration, coma, and astigmatism. These correction measures significantly improve image quality, ensuring that the image seen by the user is both clear and distortion-free, with accurate color reproduction.

[0078] (2) High-efficiency optical path folding and compact layout:

[0079] The entire optical system is meticulously arranged along the same optical axis, comprising a first lens 1, a reflective polarizing element 5, a phase retarder 6, a second lens 2, a beam splitter 7, and a diffractive optical element 3, achieving efficient folding and a compact layout of the optical path. This design not only significantly reduces the size and weight of the optical system but also improves light utilization, making it particularly suitable for VR devices with strict space requirements, providing users with a lighter and more comfortable wearing experience.

[0080] (3) Correction of vertical color difference:

[0081] The introduction of the diffractive optical element 3 is a major highlight of the optical system provided in this application. The microstructure on the diffractive optical element 3 can modulate the incident light, thereby compensating for the transverse chromatic aberration generated by the imaging component itself. This design effectively reduces or even eliminates the transverse chromatic aberration of the optical system, further improving color reproduction and image clarity, and bringing users a more realistic and delicate visual experience.

[0082] (4) Enhance the mechanical stability and durability of the optical system:

[0083] The bonding design between the diffractive optical element 3 and the display screen 4 not only simplifies the structure of the optical system but also enhances its mechanical stability and durability. This is because the diffractive optical element 3 is relatively thin and requires additional support elements to ensure its strength. This bonding design between the diffractive optical element 3 and the display screen 4 in this application allows the optical system to better resist external impacts and vibrations, maintain long-term stable performance, reduce user maintenance costs, and protect the display screen.

[0084] In summary, the optical system provided in this application embodiment achieves multiple beneficial effects such as a large field of view, complete elimination of chromatic aberration, optical path folding, compact layout, and enhanced mechanical stability, effectively improving the overall performance of VR devices.

[0085] In some examples of this application, the surface of the microstructure is a binary surface, and the expression for the binary surface is: M = (A1ρ) / (A1ρ) 2 +A2ρ4 +A3ρ 6 +A4ρ 8 ); where M is the diffraction order, A1 is the second phase coefficient used to correct chromatic aberration, A2, A3, and A4 are aspherical phase coefficients, and ρ is the normalized polar radius.

[0086] According to this example of the application, by introducing a secondary phase coefficient A1, this binary surface design can effectively correct the transverse chromatic aberration (a type of transverse aberration) of the optical system. This has a significant effect on improving image quality, especially in multi-wavelength color imaging scenarios.

[0087] The introduction of aspherical phase coefficients A2, A3, and A4 enables the diffractive optical element 3 to compensate for aspherical aberrations of the optical system while correcting transverse chromatic aberration, i.e., to perform aspherical aberration correction. This helps improve the imaging performance of the optical system, especially in the peripheral field of view.

[0088] Furthermore, the binary surface design allows for flexible control of the phase and intensity distribution of light rays by adjusting various coefficients, thereby meeting different optical design requirements. This provides more possibilities for the optimized design of optical systems.

[0089] In some examples of this application, the diffraction order is 1, -1.07E+06≤ρ 2 ≤-1.04E+06, 2.39E+07≤ρ 4 ≤2.41E+07, -3.16E+08≤ρ 6 ≤-3.09E+08, 1.04E+09≤ρ 8 ≤1.09E+09.

[0090] By strictly limiting the range of values ​​for the normalized polar radius ρ, the microstructure size and shape of the diffractive optical element 3 can be controlled. This helps ensure that the optical performance of the diffractive optical element 3 meets design requirements and improves the overall imaging quality of the optical system.

[0091] At a specific diffraction order, such as the first order in this example, the diffraction efficiency of the diffraction optical element 3 can be maximized by optimizing the range of the normalized polar radius ρ. This means that more light rays will be guided to the predetermined direction, thereby improving the light energy utilization and imaging brightness of the optical system.

[0092] Precise control of the microstructure parameters of the diffractive optical element 3 helps to enhance the stability of the optical system. This can reduce the sensitivity of the optical system to changes in the external environment and improve the reliability and durability of the optical system.

[0093] In summary, the two examples described above in this application significantly improve the performance of the diffractive optical element 3 in correcting transverse chromatic aberration, aspherical aberration, and increasing light energy utilization by introducing a binary surface design and controlling the range of diffraction order and normalized polar radius. These technical effects work together to achieve better imaging quality and user experience throughout the entire optical system.

[0094] The surface structure of the diffractive optical element 3 is designed based on a comprehensive formula that combines Snell's law with the light deflection effect caused by the additional phase of diffraction.

[0095] Specifically, the formula is: n2sinθ2 - n1sinθ1 = MλT; where n1 represents the refractive index of the incident medium, n2 is the refractive index of the exiting medium, θ1 is the incident angle of the light, θ2 is the exit angle of the light, M represents the diffraction order, λ is the wavelength of the incident light, and T represents the grating period of the diffraction optical element 3. This formula quantifies the deflection of light as it passes through the microstructure of the diffraction optical element, ensuring the accuracy of the optical path design.

[0096] In the technical solution provided in this application embodiment, the microstructure surface of the diffractive optical element 3 adopts a Binary 2 surface design, which is a surface type in which the grating shape is precisely defined by a polynomial in polar coordinates. This design can introduce continuous phase changes on the cross-section of the microstructure surface, thereby achieving fine control of the diffraction power. The Binary 2 surface type not only provides high design flexibility but also ensures the optimization of diffraction efficiency, further enhancing the performance of the entire optical system.

[0097] Through the above design, the diffractive optical element 3 of this application can effectively correct transverse aberration and significantly improve the imaging quality of the optical system. At the same time, this surface design also provides a new technical path for the development of large field-of-view VR optical systems, which helps to achieve a more compact, lightweight and high-performance optical system design.

[0098] In some examples of this application, the maximum thickness of the first lens 1 is T. 1Max The minimum thickness of the first lens 1 is T. 1Mix The first lens 1 satisfies: 0.14 < (T) 1Max -T 1Mix ) / T 1Max <1; The center thickness T2 of the second lens 2 is: T2>8mm.

[0099] In this example of the application, the maximum thickness T on the first lens 1 1Max It is the dimension of the thickest part of its physical structure, while the minimum thickness T 1MixThis is the dimension of its thinnest part. Based on this, the thickness variation of the first lens 1 must satisfy: 0.14 < (T) 1Max -T 1Mix ) / T 1Max <1. This means that there is a certain proportional relationship between the thickness variation of the first lens 1 and its maximum thickness. Thus, the first lens 1, in terms of shape, is neither too flat (to avoid limited optimization of optical performance) nor too steep (to avoid excessive manufacturing difficulty).

[0100] Meanwhile, the center thickness T2 of the second lens 2 is designed to be greater than 8 mm. This requirement aims to ensure that the second lens 2 has sufficient thickness to support its optical design, especially for surfaces that make significant contributions to optical path folding and aberration correction, while maintaining structural stability and superior optical performance.

[0101] In other words, the thickness design of the first lens 1 takes into account the thickness variation at different positions, while the second lens 2 emphasizes sufficient thickness in its central part. Both are designed to meet specific optical performance requirements while taking into account manufacturing feasibility and overall system performance.

[0102] The design of the first lens 1 and the second lens 2 in this example can reduce the field curvature and distortion of the entire optical system to a certain extent.

[0103] In some examples of this application, the center thickness T1 of the first lens 1 and the center thickness T2 of the second lens 2 are: 2mm≤T1≤10mm, 2mm≤T2≤10mm.

[0104] The minimum thickness of the lens at its center is set at 2mm, primarily for structural strength and manufacturing considerations. Lenses need a certain thickness to ensure their physical stability and durability; however, lenses that are too thin may be difficult to manufacture while maintaining the precision and flatness of their optical surfaces.

[0105] Setting the upper limit of 10mm for the center thickness of the lens is based on considerations of the overall size and weight of the optical system. In VR optical systems, the thickness of the lens directly affects the overall size and weight of the system. An excessively thick lens increases the system's volume and weight, reducing wearing comfort and portability.

[0106] The center thickness of a lens affects its optical properties, including optical power, aberration characteristics, and transmittance. While maintaining a constant refractive index, increasing the lens thickness typically enhances optical power, but may also introduce more aberrations. By designing the center thickness of two lenses within the range of 2mm to 10mm, sufficient optical power can be ensured while aberrations can be controlled by optimizing the surface shape and material selection of each lens, thus guaranteeing that the optical system's optical performance meets design requirements.

[0107] In this example, the thickness range design of the two lenses helps reduce the overall weight and size of the optical system, thereby improving user comfort. The lighter weight and smaller size reduce pressure on the head and face, improving comfort during extended wear.

[0108] Sufficient lens thickness ensures structural stability and prevents deformation or damage due to external forces during use. This is crucial for ensuring the long-term stable operation of the optical system.

[0109] Furthermore, setting a reasonable center thickness range can reduce the manufacturing difficulty and cost of lenses. Lenses that are too thin or too thick can increase the technical difficulty and cost of the manufacturing process. Selecting a lens center thickness within the range of 2mm to 10mm can improve manufacturing efficiency and yield while ensuring performance.

[0110] Therefore, the decision to select 2mm to 10mm as the center thickness range for the first lens 1 and the second lens 2 was made after comprehensively considering factors such as structural strength, manufacturing process, optical performance, and wearing comfort. This design choice helps to achieve high performance, lightweight design, and good manufacturing feasibility for the optical system.

[0111] See some examples in this application. Figure 1 The radius of curvature of the surface of the first lens 1 away from the display screen 4 is R1, and the radius of curvature of the surface of the first lens 1 close to the display screen 4 is R2. R1 and R2 satisfy: 55mm < |R1| + |R2| < 80mm.

[0112] According to this example of the application, this condition is intended to optimize the imaging quality of the optical system and reduce the tolerance sensitivity of the optical system, thereby reducing the manufacturing difficulty.

[0113] See Figure 1R1 and R2 refer to the radii of curvature of the two surfaces of the first lens 1, respectively. Specifically, R1 refers to the radius of curvature of the surface of the first lens 1 closest to the human eye (near eye 01), and R2 refers to the radius of curvature of the surface of the first lens 1 closest to the image source (near display screen 4). Both radii of curvature of the first lens 1 are negative. |R1|+|R2| represents the sum of the absolute values ​​of R1 and R2, that is, the sum of the absolute values ​​of the radii of curvature of the two surfaces.

[0114] Furthermore, the condition 55mm < |R1| + |R2| < 80mm restricts the range of the sum of the absolute values ​​of R1 and R2, which cannot be too small or too large.

[0115] An excessively small value of |R1|+|R2| may cause the surface of the first lens 1 to be too steep, increasing the manufacturing difficulty and potentially introducing large aberrations, thus affecting the image quality.

[0116] An excessively large |R1|+|R2| value may make the surface of the first lens 1 too flat, which will not be able to effectively converge or diverge light, thus affecting the image quality and potentially increasing the overall size and weight of the optical system.

[0117] By setting an appropriate radius of curvature, the first lens 1 can effectively converge or diverge light rays, thereby improving the imaging quality of the entire optical system. A suitable radius of curvature helps correct various aberrations, such as chromatic aberration and spherical aberration, resulting in a clearer and sharper final image.

[0118] It should be noted that the tolerance sensitivity of an optical system refers to the degree to which the optical system is sensitive to errors during the manufacturing and assembly process.

[0119] By optimizing the radius of curvature of the lenses within an optical system, the system's sensitivity to errors can be reduced, allowing it to maintain good imaging performance even with manufacturing and assembly errors. This helps reduce processing difficulty and costs, and improves product yield and consistency.

[0120] The condition 55mm < |R1| + |R2| < 80mm proposed in this example optimizes the curvature radius range of the first lens 1, thereby improving optical imaging quality while reducing the tolerance sensitivity and manufacturing difficulty of the optical system. This is of great significance for developing high-performance, low-cost, large-field-of-view VR optical systems.

[0121] See some examples in this application. Figure 1The radius of curvature R1 of the surface of the first lens 1 away from the display screen 4 is -35mm < R1 < -20mm, and the radius of curvature R2 of the surface of the first lens 1 close to the display screen 4 is -45mm < R2 < -35mm.

[0122] According to this example of the present application, the radii of curvature of the two surfaces of the first lens 1 are R1 and R2, respectively, with R1 ranging from -35mm to -20mm and R2 ranging from -45mm to -35mm. By setting R1 and R2 within the above ranges, it can be ensured that the first lens 1 has a moderate converging and diverging effect on light, neither too strong nor too weak, thereby optimizing image quality. A suitable radius of curvature helps to reduce aberrations such as chromatic aberration and spherical aberration, improving image sharpness and contrast.

[0123] While ensuring image quality, the size of the first lens 1 can be controlled by setting a reasonable radius of curvature, thereby controlling the size of the entire optical system. This helps to achieve a compact and lightweight design of the optical system, improving the user experience.

[0124] Furthermore, setting a reasonable range for the radius of curvature helps improve the manufacturing feasibility of the lens. An excessively large radius of curvature may result in a lens surface that is too flat, increasing manufacturing difficulty; while an excessively small radius of curvature may result in a lens surface that is too steep, also increasing manufacturing difficulty.

[0125] See some examples in this application. Figure 1 The radius of curvature R3 of the surface of the second lens 2 near the display screen 4 is -40mm < R3 < -30mm.

[0126] As an important component of the optical system, the setting of the radius of curvature R3 of the second lens 2 has a significant impact on the imaging quality. By setting R3 within the range of this example, it can be ensured that the second lens 2 works in conjunction with the first lens 1, further reducing aberrations and improving imaging quality.

[0127] The range of curvature radius R3 provided in this example helps to enhance the stability of the optical system. When the curvature radius R3 of the second lens 2 is within a reasonable range, the sensitivity of the optical system to the external environment is reduced, and the impact of changes in temperature and humidity on image quality is decreased.

[0128] Regarding the design of the radii of curvature of the first lens 1 and the second lens 2, especially the design that the radii of curvature of both surfaces of the first lens 1 are negative, and the design that the radii of curvature of the surface of the second lens 2 near the image source side are negative, there are several advantages:

[0129] (1) Can optimize image quality

[0130] The first lens 1 has negative radii of curvature on both surfaces, meaning it is a biconcave lens. This design helps to converge light emitted from the display screen 4 on the image source side, allowing the light to be properly focused before entering the human eye 01, thereby reducing aberrations and improving image quality. Especially for large field-of-view optical systems, the biconcave lens design can better correct aberrations at the edges of the field of view, enhancing the overall visual experience.

[0131] The second lens 2 has a negative radius of curvature on the surface near the image source, indicating that the surface is concave. This helps to further converge or adjust the light emitted from the display screen 4, working in conjunction with the first lens 1 to optimize image quality.

[0132] (2) Achieve a compact system design

[0133] A negative radius of curvature design typically means that the lens surface tends to be more concave, which helps reduce the lens thickness, thus making the entire optical system more compact while achieving the same optical performance. For VR optical display devices, compact design not only helps improve wearing comfort but also reduces the size and weight of the device, making it easier to use and carry.

[0134] It is evident that the design of negative radii of curvature on both surfaces of the first lens 1 and negative radii of curvature on the surface of the second lens 2 near the image source has significant advantages in optimizing imaging quality, compact design, and enhancing visual experience.

[0135] In some examples of this application, the optical system satisfies: in, The optical power of the first lens 1 is [value missing]. The optical power of the second lens 2, The total optical power of the optical system is given.

[0136] When the optical system satisfies This condition ensures that the sum of the optical powers of the first lens 1 and the second lens 2 remains within a reasonable ratio to the total optical power of the optical system. This optimized allocation of optical power helps balance the imaging contribution of each lens, preventing any single lens from bearing too much imaging burden, thereby reducing aberrations.

[0137] Under wide field-of-view conditions, light rays are incident on the surfaces of the optical system at relatively large angles. By appropriately allocating the optical power of the first lens 1 and the second lens 2, the light rays can undergo smoother refraction and focusing as they pass through these two lenses, thereby reducing the angle of incidence of the light rays on the surfaces of the optical system. A lower angle of incidence helps to reduce reflection and scattering, further improving the transmittance of light.

[0138] A lower angle of incidence is beneficial for correcting various aberrations, especially off-axis aberrations. Off-axis aberration is a common problem in large field-of-view optical systems, causing blurring and distortion at image edges. By optimizing the optical power distribution and reducing the angle of incidence, the optical system in this application can better correct off-axis aberrations and improve the imaging quality of the entire field of view.

[0139] Spot size is one of the important indicators for measuring the imaging quality of an optical system. A smaller spot size means that the image points are more concentrated and the image is sharper. By optimizing the optical power distribution and improving aberration correction, the optical system in this application can effectively reduce the spot size and improve the resolution and contrast of the image.

[0140] when A value less than 0.15 means that the sum of the optical powers of the first lens 1 and the second lens 2 is relatively small. This may lead to insufficient aberration correction and decreased image quality, especially under large field-of-view conditions. A smaller optical power allocation may also increase the sensitivity of the optical system to manufacturing tolerances and assembly errors. Even small manufacturing deviations or improper assembly can have a significant impact on image quality, increasing production difficulty and cost.

[0141] when When the value is greater than 0.2, the sum of the optical power of the first lens 1 and the second lens is relatively large, which may mean that more lenses or optical elements are needed to balance the optical power of the optical system. This will increase the complexity and size of the optical system, which is not conducive to achieving a compact design.

[0142] More lenses or optical components mean higher material and manufacturing costs. Furthermore, complex optical systems may require more precise assembly and adjustment processes, further increasing costs.

[0143] A larger optical power distribution can lead to a larger angle of incidence of light at each lens surface, thus increasing the difficulty of aberration correction. Especially under large field-of-view conditions, aberrations at the edges of the field of view may be more severe, affecting image quality. A larger angle of incidence can also cause more light to be reflected and scattered at the lens surfaces, resulting in light loss. This not only reduces light transmittance but may also introduce additional stray light, affecting image quality.

[0144] Therefore, the example proposed in this application This range is based on a comprehensive consideration of the performance of the optical system.

[0145] In some examples of this application, the straight-line distance between the first lens 1 and the exit pupil position of the optical system is d, 0 < d < 15 mm; the exit pupil diameter of the optical system is D, 4 mm < D < 6 mm.

[0146] Setting the straight-line distance d between the first lens 1 and the exit pupil position of the optical system to be within the range of 0 < d < 15 mm helps to achieve a compact design of the optical system. A smaller d value means that the optical path can be folded more compactly, reducing the overall length and volume of the optical system, making it more suitable for space-constrained applications such as VR optical display devices.

[0147] For VR optical display devices, a smaller optical system size and weight can significantly improve user comfort. A compact optical design reduces pressure and discomfort on the face, allowing users to wear VR optical display devices for longer periods of time and with greater comfort.

[0148] In this example of the application, the exit pupil diameter D is set within the range of 4mm < D < 6mm, ensuring that the optical system can provide a larger exit pupil diameter. A larger exit pupil diameter can accommodate changes in interpupillary distance for different users, reduce the black border phenomenon during viewing, and improve the continuity and immersion of the visual experience.

[0149] In some examples of this application, the total length of the optical system is L, 30mm < L < 40mm, and the field of view (FOV) of the optical system is 140° < FOV < 160°.

[0150] The optical system provided in this application embodiment has a total system length L between 30mm and 40mm, ensuring the overall compactness of the optical system. In VR optical display devices, a compact optical system means a smaller device size and weight, which is crucial for improving user wearing comfort.

[0151] The optical system provided in this application embodiment has a field of view (FOV) set between 140° and 160°, achieving the design goal of a large field of view. A larger field of view can provide users with a wider range of vision and enhance the immersive experience of virtual reality.

[0152] Compared to traditional optical systems based on folded optical paths, the field of view (FOV) of the optical system in this application can be increased to 1.5 times or more than that of traditional optical systems. A large field of view is particularly important in VR applications because it can reduce distortion and blurring at the edges of the viewer's field of view, thus improving the overall visual experience.

[0153] In the optical system provided in the embodiments of this application, see Figure 1 The display screen 4 is located on the image source side, and the display screen 4 is used to emit light for imaging display.

[0154] Optionally, a screen protective glass can be provided on the light-emitting surface of the display screen 4.

[0155] The screen protector effectively isolates external dust, fingerprints, and other contaminants, thus keeping the surface of the display screen 4 clean. This is crucial for the optical system, as any dirt on the screen surface can affect light transmission and image quality. The screen protector not only isolates dirt but also effectively prevents the display screen 4 from physical damage such as scratches and impacts. This is significant for extending the lifespan of the display screen 4 and improving the overall durability of the device.

[0156] In some examples of this application, the size of the display screen 4 is 60mm to 75mm.

[0157] The size of the display screen 4 is designed primarily to complement the wide field of view. This size not only provides a wider field of view, allowing users to immerse themselves in a more realistic and immersive visual experience, but also ensures that image details are fully displayed, making every minute detail clearly visible. At the same time, the large display screen can better coordinate with the overall design of the optical system, optimizing the light propagation path, reducing aberrations, and further improving image quality.

[0158] See some examples in this application. Figure 1 The first lens 1 and the second lens 2 are bonded together; the beam splitter 7 is disposed on the surface of the second lens 2 near the display screen 4; the phase delay film 6 and the reflective polarizing element 5 form a composite film and are disposed on the bonding surface of the first lens 1 and the second lens 2.

[0159] In the imaging components provided in this application, see Figure 1 The beam splitting element 7 can be disposed on the surface of the second lens 2 near the display screen 4 by plating or bonding; the phase delay film 6 and the reflective polarizing element 5 form a composite film and are disposed on the adhesive surface of the first lens 1 and the second lens 2 by bonding.

[0160] The beam splitter 7 is, for example, a semi-transparent and semi-reflective film (BS), the phase delay plate 6 is, for example, a quarter-wave plate (QWP), and the reflective polarization element 5 is a polarizing reflective film (RP).

[0161] In this example of the application, the imaging assembly is a cemented assembly, in which all optical elements are cemented together, simplifying the assembly process. Simultaneously, the cementation of the first lens 1 and the second lens 2, i.e., the cementation of two aspherical lenses, also helps to reduce chromatic aberration and improve image quality.

[0162] In some examples of this application, the first lens 1 and the second lens 2 are made of resin material; the first lens 1 and the second lens 2 are even-order aspherical lenses.

[0163] Optionally, both the first lens 1 and the second lens 2 are made of optical resin material, with a refractive index n of 1.5 < n < 1.6 and an Abbe number v of 55 < v < 57.

[0164] The first lens 1 and the second lens 2 are made of optical resin material. Compared with traditional glass material, resin material has a lower density, thus significantly reducing the overall weight of the entire optical system. In VR optical display devices, weight reduction is crucial for improving user comfort and reducing strain on the neck and head.

[0165] Resin materials have excellent processability, making them easy to mass-produce through processes such as injection molding. This not only reduces the difficulty of lens processing but also improves production efficiency and helps reduce production costs. Furthermore, the ease of processing resin materials allows for more flexible and diverse lens surface shapes, facilitating aspherical designs.

[0166] In this example of the application, both the first lens 1 and the second lens 2 are even-order aspherical lenses. The even-order aspherical design provides a more flexible optical surface shape, thereby better correcting aberrations and improving image quality. Compared with spherical lenses, aspherical lenses have significant advantages in aberration correction, especially at large field angles. Aspherical lenses can significantly reduce aberrations such as field curvature and distortion, providing a clearer and more realistic visual experience.

[0167] In this application, the combination of the low dispersion properties of resin materials and even-order aspherical design further enhances the imaging quality of the optical system. The low dispersion of the resin material helps reduce chromatic aberration, while the even-order aspherical design corrects other types of aberrations. This design enables the optical system to maintain good imaging performance over a wider wavelength range, providing more realistic color reproduction and detail.

[0168] VR optical display devices require support for a large field of view to provide an immersive visual experience. Even-order aspherical lenses are better suited to accommodate large field of view requirements, reducing aberrations and distortions at the edges of the field of view and providing uniform image quality. Simultaneously, the lightweight and easily processable nature of resin materials facilitates the creation of more complex optical system structures, meeting the dual demands of VR devices for high image quality and portability.

[0169] See Figure 1 , Figure 5 and Figure 8 The optical transmission path of the optical system provided in this application embodiment is as follows:

[0170] Left-handed circularly polarized light from the display screen 4 is first modulated by the diffractive optical element 3 and then incident on the right surface of the second lens 2 (the surface near the display screen 4). After half of the light is transmitted by the beam splitter 7, it is incident on the left surface of the second lens 2 (the surface near the human eye O1). The phase retardation plate 6 and the reflective polarization element 5 are attached to the left surface of the second lens 2. The left-handed circularly polarized light first becomes vertically polarized light after passing through the phase retardation plate 6. When it is incident on the reflective polarization element 5, because the reflective polarization element 5 has a reflective vertical polarization... Due to the characteristics of polarization, the light is reflected and passes through the phase retardation plate 6 again to become left-handed circularly polarized light. After being transmitted through the second lens 2, it is reflected at the beam splitter 7 to become right-handed polarized light. The right-handed polarized light passes through the second lens 2 again and is converted into horizontally polarized light by the phase retardation plate. At this time, the reflecting polarization element 5 no longer reflects it, so it can continue to be transmitted to the first lens 1. After being refracted by the right surface (the surface near the display screen 4) and the left surface (the surface near the human eye 01) of the first lens 1, it finally enters the human eye 01 to form an image.

[0171] In this application, the diffractive optical element 3 is designed with a first-order diffraction order and its coefficient structure is specifically optimized, with the maximum term coefficient reaching as high as 4. Before the introduction of the diffractive optical element 3, the transverse aberration of the optical system was quite significant. Specifically, see [link to relevant documentation]. Figure 2 , Figure 2 An optical module without the diffractive optical element 3 is shown; it can be clearly seen that the transverse aberration of this optical system exceeds 160 μm. However, by introducing the diffractive optical element 3 into the optical system, see [link to relevant documentation]. Figure 3 This significantly reduces the vertical aberration of the optical system to below 30μm, achieving a remarkable aberration correction effect.

[0172] The optical system provided in this application exhibits superior performance in color control, with its maximum chromatic aberration controlled within 25 μm. Compared to traditional VR optical systems, this application represents a significant advancement in improving the quality of multi-wavelength color imaging. Furthermore, the modulation transfer function (MTF) of the optical system maintains an excellent level above 0.3 at a spatial frequency of 30 line pairs / mm, further demonstrating its outstanding capabilities in high-resolution imaging.

[0173] From the perspective of optimizing the imaging components and combining them with the diffractive optical element 3, the optical system of this application has the following beneficial effects:

[0174] From the perspective of the benefits brought by the optimization of imaging components:

[0175] The imaging component employs a design where aspherical lenses are cemented together. This design effectively corrects various aberrations in the optical system, such as spherical aberration, coma, and astigmatism, especially aberrations at the edge of the field of view. Compared to traditional spherical lenses, aspherical lenses offer greater design freedom and can more precisely control the propagation path of light, thereby significantly improving image quality and ensuring clear, distortion-free images.

[0176] The tight bonding of the internal components of the imaging assembly not only simplifies the system structure but also enables efficient folding and compact layout of the optical path, reducing the system's size and weight. This compact layout makes the entire optical system more suitable for space-constrained applications, such as VR devices.

[0177] From the perspective of the benefits brought about by the introduction of diffractive optical element 3:

[0178] The microstructures on diffractive optical elements can modulate incident light, producing a chromatic aberration effect opposite to that produced by the imaging components, thereby compensating for the transverse chromatic aberration. This compensation mechanism effectively reduces or even eliminates the transverse chromatic aberration of the optical system, significantly improving color reproduction and image sharpness, resulting in more realistic and detailed images for the user.

[0179] The bonding design between the diffractive optical elements and the display screen enhances the system's mechanical stability and durability, enabling the optical system to better withstand external shocks and vibrations. This improved stability ensures that the optical system maintains stable performance output during long-term use.

[0180] The optimization of the imaging components and their integration with the diffractive optical element 3 achieves comprehensive correction of various aberrations (including chromatic aberration, spherical aberration, coma, astigmatism, etc.), significantly improving the imaging quality of the optical system. Users can enjoy clearer, distortion-free images with accurate color reproduction. The compact layout of the imaging components and the introduction of the diffractive optical element make the entire optical system more efficient and stable. The optical system of this application can better adapt to various usage environments and conditions, maintaining long-term stable performance output.

[0181] In summary, the optical system of this application achieves a comprehensive improvement in imaging quality and enhanced system performance and stability through the optimization of imaging components and the combination of diffractive optical elements, providing a superior optical solution for applications such as VR devices.

[0182] The optical system provided in this application will be further described below through Examples 1 to 3.

[0183] Example 1

[0184] See Figure 1 The optical system provided in this embodiment 1 includes a first lens 1, a reflective polarizing element 5, a phase retarder 6, a second lens 2, a beam splitter 7, a diffractive optical element 3, and a display screen 4 arranged sequentially along the same optical axis from the human eye side to the image source side.

[0185] The first lens 1 and the second lens 2 are even-order aspherical lenses, and the first lens 1 and the second lens 2 are bonded together and both are made of resin material;

[0186] The beam splitting element 7 is disposed on the surface of the second lens 2 near the image source surface;

[0187] The phase delay film 6 and the reflective polarizing element 5 form a composite film and are disposed on the bonding surface of the first lens 1 and the second lens 2;

[0188] The diffractive optical element 3 mainly consists of a substrate and a microstructure disposed on the substrate. The microstructure can modulate the incident light, causing the light to bend and disperse during propagation, thereby correcting the transverse chromatic aberration.

[0189] The display screen 4 emits light for imaging, and the diffractive optical element 3 is bonded to the light-emitting surface of the display screen 4.

[0190] Table 1 shows the surface parameters of each component of the optical system in this embodiment 1.

[0191] Table 1

[0192]

[0193]

[0194] For Table 1: S1 is the surface of the first lens 1 near the human eye 01 (left surface), and S2 is the surface of the first lens 1 near the display screen 4 (right surface);

[0195] S3 is the reflective polarization element 5, and S4 is the phase delay plate 6;

[0196] S5 is the surface of the second lens 2 near the human eye 01 (left surface), and S6 is the surface of the second lens 2 near the display screen 4 (right surface);

[0197] S7 is the surface of the diffractive optical element 7 near the human eye 01 (left surface), and S8 is the surface of the diffractive optical element 3 near the display screen 4 (right surface).

[0198] Table 2 shows the coefficients of higher-order terms for aspherical surfaces.

[0199] Table 2

[0200] Serial Number 4th 6th 8th 10th 12th 14th 16th S1 -3.41E-05 -2.32E-06 1.62E-08 -1.15E-11 -7.83E-14 -1.10E-15 4.18E-18 S2 -9.59E-05 1.00E-07 8.97E-11 -1.77E-12 -1.05E-14 7.80E-17 -1.14E-19 S5 -1.68E-05 -6.00E-09 -3.09E-11 1.08E-13 -5.86E-16 1.48E-18 -1.57E-21

[0201] Table 3 shows the coefficients of the microstructure surface of the diffractive optical element.

[0202] Table 3

[0203] Diffraction order Maximum number of terms <![CDATA[ρ 2 Item <![CDATA[ρ 4 Item <![CDATA[Ρ 6 Item <![CDATA[Ρ 8 Item 1 4 -1.05E+06 2.41E+07 -3.16E+08 1.08E+09

[0204] Figure 2 The diagram shows the transverse aberration of the optical system before the addition of diffractive optical elements. It can be clearly seen that the transverse aberration of the optical system exceeds 160 μm.

[0205] See Figure 1 In this embodiment 1, a diffractive optical element 3 is introduced into the optical system. See [link / reference]. Figure 3 The transverse aberration curve of the optical system provided in this embodiment 1 shows that the transverse aberration of the optical system is 26.7μm, which means that the transverse aberration of the optical system is greatly reduced to below 30μm, achieving a significant aberration correction effect.

[0206] Figure 4 for Figure 1 The modulation transfer function diagram of the optical system shown in this embodiment 1 shows that the average MTF value of the optical system at 60 lp / mm is greater than 0.3.

[0207] Example 2

[0208] See Figure 5The optical system shown in this embodiment 2 includes a first lens 1, a reflective polarizing element 5, a phase retardation plate 6, a second lens 2, a beam splitter 7, a diffractive optical element 3, and a display screen 4 arranged sequentially along the same optical axis from the human eye side to the image source side.

[0209] The first lens 1 and the second lens 2 are even-order aspherical lenses, and the first lens 1 and the second lens 2 are bonded together and both are made of resin material;

[0210] The beam splitting element 7 is disposed on the surface of the second lens 2 near the image source surface;

[0211] The phase delay film 6 and the reflective polarizing element 5 form a composite film and are disposed on the bonding surface of the first lens 1 and the second lens 2;

[0212] The diffractive optical element 3 mainly consists of a substrate and a microstructure disposed on the substrate. The microstructure can modulate the incident light, causing the light to bend and disperse during propagation, thereby correcting the transverse chromatic aberration.

[0213] The display screen 4 emits light for imaging, and the diffractive optical element 3 is bonded to the light-emitting surface of the display screen 4.

[0214] The optical architecture of the optical system shown in this embodiment 2 is basically the same as that of the optical system shown in embodiment 1 above. For the differences, please refer to Tables 4 to 6.

[0215] Table 4 shows the surface parameters of each component of the optical system in this embodiment 2.

[0216] Table 4

[0217] Serial Number Surface type Radius of curvature (mm) Thickness (mm) Refractive index Abbe number S1 even aspherical surface -31 2.6 1.5447 56.251 S2 even aspherical surface -40 0.1 / / S3 even aspherical surface -40 0.1 1.4918 57.441 S4 even aspherical surface -40 / 1.4918 57.441 S5 even aspherical surface -40 9.1 1.5447 56.251 S6 even aspherical surface -32.1 3.759 / / S7 Binary2 Inf 2 1.5168 64.167 S8 flat Inf / / /

[0218] Regarding Table 4: S1 is the surface of the first lens 1 near the human eye 01 (left surface), and S2 is the surface of the first lens 1 near the display screen 4 (right surface);

[0219] S3 is the reflective polarization element 5, and S4 is the phase delay plate 6;

[0220] S5 is the surface of the second lens 2 near the human eye 01 (left surface), and S6 is the surface of the second lens 2 near the display screen 4 (right surface);

[0221] S7 is the surface of the diffractive optical element 7 near the human eye 01 (left surface), and S8 is the surface of the diffractive optical element 3 near the display screen 4 (right surface).

[0222] Table 5 shows the coefficients of higher-order terms for aspherical surfaces.

[0223] Table 5

[0224] Serial Number 4th 6th 8th 10th 12th 14th 16th S1 -4.35E-05 -2.31E-06 1.63E-08 -1.12E-11 -7.76E-14 -1.10E-15 4.15E-18 S2 -9.43E-05 1.00E-07 6.66E-11 -1.75E-12 -1.04E-14 7.81E-17 -1.14E-19 S5 -1.72E-05 -5.90E-09 -2.95E-11 1.09E-13 -5.91E-16 1.48E-18 -1.56E-21

[0225] Table 6 shows the coefficients of the microstructure surface of the diffractive optical element.

[0226] Table 6

[0227] Diffraction order Maximum number of terms <![CDATA[ρ 2 Item <![CDATA[ρ 4 Item <![CDATA[Ρ 6 Item <![CDATA[Ρ 8 Item 1 4 -1.07E+06 2.40E+07 -3.09E+08 1.04E+09

[0228] See Figure 6 The transverse aberration curve of the optical system provided in this embodiment 2 shows that the transverse aberration of the optical system is 23.9 μm, achieving a significant aberration correction effect.

[0229] Figure 7 for Figure 5 The modulation transfer function diagram of the optical system shown in this embodiment 5 shows that the average MTF value of the optical system at 57 lp / mm is greater than 0.3.

[0230] Example 3

[0231] See Figure 8 The optical system shown in this embodiment 3 includes a first lens 1, a reflective polarizing element 5, a phase retarder 6, a second lens 2, a beam splitter 7, a diffractive optical element 3, and a display screen 4 arranged sequentially along the same optical axis from the human eye side to the image source side.

[0232] The first lens 1 and the second lens 2 are even-order aspherical lenses, and the first lens 1 and the second lens 2 are bonded together and both are made of resin material;

[0233] The beam splitting element 7 is disposed on the surface of the second lens 2 near the image source surface;

[0234] The phase delay film 6 and the reflective polarizing element 5 form a composite film and are disposed on the bonding surface of the first lens 1 and the second lens 2;

[0235] The diffractive optical element 3 mainly consists of a substrate and a microstructure disposed on the substrate. The microstructure can modulate the incident light, causing the light to bend and disperse during propagation, thereby correcting the transverse chromatic aberration.

[0236] The display screen 4 emits light for imaging, and the diffractive optical element 3 is bonded to the light-emitting surface of the display screen 4.

[0237] The optical architecture of the optical system shown in this embodiment 3 is basically the same as that of the optical system shown in embodiment 1 above. For the differences, please refer to Tables 7 to 9.

[0238] Table 7 shows the surface parameters of each component of the optical system in this embodiment 3.

[0239] Table 7

[0240] Serial Number Surface type Radius of curvature (mm) Thickness (mm) Refractive index Abbe number S1 even aspherical surface -25.3 2.6 1.5447 56.251 S2 even aspherical surface -40.5 0.1 / / S3 even aspherical surface -40 0.1 1.4918 57.441 S4 even aspherical surface -40 / 1.4918 57.441 S5 even aspherical surface -40 9.1 1.5447 56.251 S6 even aspherical surface -31.4 3.949 / / S7 Binary2 Inf 2 1.5168 64.167 S8 flat Inf / / /

[0241] Regarding Table 7: S1 is the surface of the first lens 1 near the human eye 01 (left surface), and S2 is the surface of the first lens 1 near the display screen 4 (right surface);

[0242] S3 is the reflective polarization element 5, and S4 is the phase delay plate 6;

[0243] S5 is the surface of the second lens 2 near the human eye 01 (left surface), and S6 is the surface of the second lens 2 near the display screen 4 (right surface);

[0244] S7 is the surface of the diffractive optical element 7 near the human eye 01 (left surface), and S8 is the surface of the diffractive optical element 3 near the display screen 4 (right surface).

[0245] Table 8 shows the coefficients of higher-order terms for aspherical surfaces.

[0246] Table 8

[0247] Serial Number 4th 6th 8th 10th 12th 14th 16th S1 -2.51E-05 -2.31E-06 1.62E-08 -1.15E-11 -7.83E-14 -1.10E-15 4.18E-18 S2 -9.43E-05 1.00E-07 8.97E-11 -1.77E-12 -1.05E-14 7.81E-17 -1.14E-19 S5 -1.72E-05 -6.77E-09 -3.29E-11 1.08E-13 -5.83E-16 1.48E-18 -1.57E-21

[0248] Table 9 shows the coefficients of the microstructure surface of the diffractive optical element.

[0249] Table 9

[0250] Diffraction order Maximum number of terms <![CDATA[ρ 2 Item <![CDATA[ρ 4 Item <![CDATA[Ρ 6 Item <![CDATA[Ρ 8 Item 1 4 -1.04E+06 2.39E+07 -3.16E+08 1.09E+09

[0251] See Figure 9 The transverse aberration curve of the optical system provided in this embodiment 3 shows that the transverse aberration of the optical system is 29.3 μm, achieving a significant aberration correction effect.

[0252] Figure 10 for Figure 8 The modulation transfer function diagram of the optical system shown in this embodiment 5 shows that the average MTF value of the optical system at 57 lp / mm is greater than 0.3.

[0253] According to another embodiment of this application, a smart head-mounted device is provided, the smart head-mounted device including a housing and an optical system as described above.

[0254] The smart head-mounted device provided in this application embodiment is, for example, a VR optical display device.

[0255] VR optical display devices can take the form of VR smart glasses or VR smart helmets, for example.

[0256] In the smart head-mounted device provided in the embodiments of this application, two optical systems can be set, one of which corresponds to the user's left eye and the other corresponds to the user's right eye.

[0257] The specific implementation of the smart head-mounted device in this application can refer to the various embodiments of the optical system described above. Therefore, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, and will not be described in detail here.

[0258] The above embodiments mainly describe the differences between the various embodiments. As long as the different optimization features between the various embodiments are not contradictory, they can be combined to form a better embodiment. For the sake of brevity, they will not be elaborated here.

[0259] While specific embodiments of this application have been described in detail by way of examples, those skilled in the art should understand that the above examples are for illustrative purposes only and are not intended to limit the scope of this application. Those skilled in the art should understand that modifications can be made to the above embodiments without departing from the scope and spirit of this application. The scope of this application is defined by the appended claims.

Claims

1. An optical system, characterized in that, It includes an imaging component, a diffractive optical element (3), and a display screen (4) arranged sequentially along the same optical axis; The imaging assembly includes a first lens (1), a reflective polarizing element (5), a phase retardation plate (6), a second lens (2), and a beam splitter (7) arranged sequentially. Both the first lens (1) and the second lens (2) are aspherical lenses; The diffractive optical element (3) is glued to the display screen (4); The diffractive optical element (3) is mainly composed of a substrate and a microstructure disposed on the substrate. The microstructure is used to perform phase modulation on the light from the display screen (4), so that the light bends and disperses during propagation. The phase modulation effect of the microstructure on the light can produce a chromatic aberration effect opposite to the transverse chromatic aberration produced by the imaging component. When the light modulated by the microstructure enters the imaging component, the transverse chromatic aberration generated by the microstructure cancels out the transverse chromatic aberration generated by the imaging component, thereby compensating for the transverse chromatic aberration of the imaging component and correcting the transverse chromatic aberration of the optical system. Wherein, the optical power φ1 of the first lens (1) is negative, the optical power φ2 of the second lens (2) is negative, and the surface shape of the first lens (1) and the second lens (2) is that the image side is concave near the axis and the object side is convex near the axis; The optical system satisfies: 0.15 < (|φ1| + |φ2|) / φ < 0.2; where φ1 is the optical power of the first lens (1), φ2 is the optical power of the second lens (2), and φ is the total optical power of the optical system.

2. The optical system according to claim 1, characterized in that, The surface of the microstructure is a binary surface, and the expression of the binary surface is: M = (A1) / (A1) ρ 2 +A2 ρ 4 +A3 ρ 6 +A4 ρ 8 Where M is the diffraction order, A1 is the second-order phase coefficient used to correct chromatic aberration, and A2, A3, and A4 are aspherical phase coefficients. ρ The radius is the normalized polar coordinate radius.

3. The optical system according to claim 2, characterized in that, The diffraction order is 1, -1.07E+06≤ ρ 2 ≤-1.04E+06, 2.39E+07≤ ρ 4 ≤2.41E+07, -3.16E+08≤ ρ 6 ≤-3.09E+08, 1.04E+09≤ ρ 8 ≤1.09E+09.

4. The optical system according to claim 1, characterized in that, The maximum thickness of the first lens (1) is T 1Max The minimum thickness of the first lens (1) is T 1Mix The first lens (1) satisfies: 0.14 < ( T 1Max - T 1Mix ) / T 1Max <1; The center thickness of the second lens (2) T 2 is: T 2 > 8 mm.

5. The optical system according to claim 4, characterized in that, The center thickness of the first lens (1) T 1 and the center thickness of the second lens (2) T 2 are respectively: 2mm≤ T 1≤10mm, 2mm≤ T 2≤10mm.

6. The optical system according to claim 1, characterized in that, The radius of curvature of the surface of the first lens (1) away from the display screen (4) is R1, and the radius of curvature of the surface of the first lens (1) close to the display screen (4) is R2. R1 and R2 satisfy: 55mm < |R1| + |R2| < 80mm.

7. The optical system according to claim 6, characterized in that, The radius of curvature R1 of the surface of the first lens (1) away from the display screen (4) is -35mm < R1 < -20mm, and the radius of curvature R2 of the surface of the first lens (1) close to the display screen (4) is -45mm < R2 < -35mm.

8. The optical system according to claim 6 or 7, characterized in that, The radius of curvature R3 of the surface of the second lens (2) near the display screen (4) is -40mm < R3 < -30mm.

9. The optical system according to claim 1, characterized in that, The straight-line distance between the first lens (1) and the exit pupil position of the optical system is d, 0 < d < 15 mm; The exit pupil diameter of the optical system is D, where 4mm < D < 6mm.

10. The optical system according to claim 1, characterized in that, The total length of the optical system is L, where 30mm < L < 40mm, and the field of view (FOV) of the optical system is 140° < FOV < 160°.

11. The optical system according to claim 10, characterized in that, The size of the display screen (4) is 60mm~75mm.

12. The optical system according to claim 1, characterized in that, The first lens (1) and the second lens (2) are glued together; The beam splitter (7) is disposed on the side surface of the second lens (2) near the display screen (4); the phase delay film (6) and the reflective polarizing element (5) form a composite film and are disposed on the bonding surface of the first lens (1) and the second lens (2).

13. The optical system according to claim 1, characterized in that, The first lens (1) and the second lens (2) are made of resin material; The first lens (1) and the second lens (2) are even-order aspherical lenses.

14. A smart head-mounted device, characterized in that, include: shell; and The optical system as described in any one of claims 1-13.

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