An optical module and a near-eye display device

Abstract

This application provides an optical module and a near-eye display device. The optical module, from the aperture stop to the single-chip full-color image source, sequentially includes: a first lens with positive optical power, a second lens with positive optical power, a third lens with negative optical power, and a fourth lens with negative optical power; wherein, the surface of the fourth lens facing the image source has the maximum aperture D1 in the optical module, and the total optical length TTL of the optical module satisfies 1.6 < TTL / D1 < 1.9; furthermore, the center thicknesses of the first lens, second lens, third lens, and fourth lens on the optical axis are T1, T2, T3, and T4 respectively, satisfying 1.4 < (T3 + T4) / (T1 + T2) < 1.7.

Description

Technical Field

[0001] This application relates to the field of optical imaging technology, and more specifically, to an optical module and a near-eye display device. Background Technology In recent years, augmented reality (AR) near-eye display systems have shown rapid development. In the practical application of AR glasses, breakthroughs must be achieved in several key indicators to bring users a better wearing experience, specifically covering aspects such as lightweight and miniaturized design, low power consumption, large field of view (FOV) presentation, and high brightness display.

[0002] The optical engine (image generation unit), as a core component in AR glasses that determines image quality and overall device size, is undergoing rapid technological iteration. Early development solutions often employed Digital Light Processing (DLP) optical engines; however, these engines have significant drawbacks, namely their large size and high power consumption. In recent years, single-green Micro-LED (μLED) optical engines have achieved mass production applications due to their self-emissive characteristics, high brightness display, and low power consumption. However, this solution also has limitations, supporting only monochrome displays and failing to meet diverse display requirements.

[0003] Regardless of the technical solution employed, the beam output by the optical engine must be coupled to a waveguide or other near-eye imaging element via an optical engine lens or imaging lens assembly to achieve the final image display. With the continuous shrinking of panel sizes and the gradual reduction in pixel pitch, traditional lens assemblies face severe challenges, specifically the need to simultaneously cope with the dual pressures of shortening total optical length (TTL) and expanding field of view (FOV). In this context, traditional lens assemblies must strike a balance between multiple performance indicators such as large aperture, short back focal length, low distortion, and temperature drift suppression to ensure image quality and system stability; however, existing technologies struggle to effectively meet these requirements.

[0004] Therefore, in order to solve the problems existing in the prior art, it is necessary to provide a new type of optical module. Summary of the Invention

[0005] The purpose of this application is to provide an optical module and a near-eye display device to address at least one technical defect in the prior art.

[0006] According to a first aspect of this application, an optical module is provided. The optical module, from the aperture stop to the monolithic full-color image source, includes, in sequence: A first lens with positive optical power, a second lens with positive optical power, a third lens with negative optical power, and a fourth lens with negative optical power; Among them, the surface of the fourth lens facing the image source has the largest light passing aperture D1 in the optical module, and the total optical length TTL of the optical module and D1 satisfy: 1.6 < TTL / D1 < 1.9; Moreover, the central thicknesses of the first lens, the second lens, the third lens, and the fourth lens on the optical axis are T1, T2, T3, and T4 respectively, satisfying: 1.4 < (T3 + T4) / (T1 + T2) < 1.7.

[0007] Optionally, the air gap on the optical axis between the second lens and the third lens is M1, and the air gap on the optical axis between the third lens and the fourth lens is M2; Among them, M1 and TTL satisfy: 0.03·TTL ≤ M1 ≤ 0.07·TTL; and M2 and TTL satisfy: 0.08·TTL ≤ M2 ≤ 0.12·TTL.

[0008] Optionally, T3 and TTL satisfy: 0.15·TTL ≤ T3 ≤ 0.19·TTL; and T4 and TTL satisfy: 0.25·TTL ≤ T4 ≤ 0.29·TTL.

[0009] Optionally, the first lens has a first surface facing the diaphragm and a second surface facing the second lens; the sagittal height of the first surface at the maximum light passing aperture is denoted as S1, and the sagittal height of the second surface at the maximum light passing aperture is denoted as S2, satisfying: 9 < S1 / S2 < 14.

[0010] Optionally, the fourth lens has a seventh surface facing the third lens and an eighth surface facing the image source; the sagittal height of the seventh surface at the maximum light passing aperture is denoted as S3, and the sagittal height of the eighth surface at the maximum light passing aperture is denoted as S4, satisfying: 2.3 < S4 / S3 < 2.9.

[0011] Optionally, the third lens has a fifth surface facing the second lens and a sixth surface facing the fourth lens, and the light passing aperture of the fifth surface is larger than that of the sixth surface.

[0012] Optionally, the included angle between the lens tangent line at the maximum light passing aperture of the fifth surface of the third lens facing the second lens and the optical axis is A1, and the included angle between the lens tangent line at the maximum light passing aperture of the sixth surface of the third lens facing the fourth lens and the optical axis is A2, satisfying: 35° < A2 - A1 < 65° and 0.45 < A1 / A2 < 0.75.

[0013] Optionally, the included angle between the lens tangent at the maximum clear aperture of the seventh surface of the fourth lens facing the third lens and the optical axis is A3, and the included angle between the lens tangent at the maximum clear aperture of the eighth surface of the fourth lens facing the image source and the optical axis is A4, satisfying: -5° < A3 - A4 < 15° and 0.95 < A3 / A4 < 1.25.

[0014] Optionally, the effective focal length range of the first lens is 3 mm to 4 mm, the effective focal length range of the second lens is 9 mm to 12 mm, the effective focal length range of the third lens is -3.5 mm to -2.5 mm, and the effective focal length range of the fourth lens is -40 mm to -30 mm.

[0015] Optionally, the first lens to the fourth lens are all aspherical lenses.

[0016] Optionally, the refractive index range of the first lens and the second lens is: 1.53 to 1.62, and the refractive index range of the third lens and the fourth lens is: 1.63 to 1.68.

[0017] According to the second aspect of the present application, a near-eye display device is provided. The near-eye display device includes the optical module as described in the first aspect.

[0018] One technical effect of the present application is that: In the technical solution provided by the embodiments of the present application, the optical module is sequentially provided with a first lens with a positive optical power, a second lens with a positive optical power, a third lens with a negative optical power, and a fourth lens with a negative optical power from the aperture stop to the single-chip full-color image source direction. This specific combination of lenses, combined with the limitation of the optical total length TTL and the maximum clear aperture D1 of the fourth lens facing the image source surface (1.6 < TTL / D1 < 1.9), effectively shortens the optical total length while ensuring the imaging quality, and reasonably controls the size of the clear aperture.

[0019] The positive and negative optical powers of this optical module are alternately configured, and with the thickness ratio of (T3 + T4) / (T1 + T2) = 1.4 to 1.7, the thicknesses of each lens are reasonably distributed. This thickness distribution method helps to optimize the propagation path of light in the lens group, reduce the refraction and reflection losses of light inside the lens, reduce aberration, thereby improving the clarity and contrast of imaging, and ensuring high-quality imaging effects.

[0020] Through the following detailed description of the exemplary embodiments of this specification with reference to the drawings, other features and advantages of this specification will become clear. Description of the Drawings

[0021] 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.

[0022] Figure 1 The diagram shows the optical architecture of the optical module provided in this application embodiment. Figure 1 .

[0023] Figure 2 The diagram shows the angle between the lens tangent and the optical axis of the third lens provided in this embodiment.

[0024] Figure 3 The diagram shows the angle between the lens tangent and the optical axis of the fourth lens provided in this embodiment.

[0025] Figure 4 As shown Figure 1 Optical distortion diagram of optical architecture.

[0026] Figure 5 As shown Figure 1 MTF curve of the optical architecture.

[0027] Figure 6 The diagram shows the optical architecture of the optical module provided in this application embodiment. Figure 2 .

[0028] Figure 7 As shown Figure 6 MTF curve of the optical architecture.

[0029] Figure 8 The diagram shows the optical architecture of the optical module provided in this application embodiment. Figure 3 .

[0030] Figure 9 As shown Figure 8 MTF curve of the optical architecture.

[0031] Figure 10 The diagram shows the optical architecture of the optical module provided in this application embodiment. Figure 4 .

[0032] Figure 11 As shown Figure 10 MTF curve of the optical architecture.

[0033] Figure 12 The diagram shows the optical architecture of the optical module provided in this application embodiment. Figure 5 .

[0034] Figure 13 As shown Figure 12 MTF curve of the optical architecture.

[0035] Explanation of reference numerals in the attached figures: 1. First lens; 2. Second lens; 3. Third lens; 4. Fourth lens; 5. Aperture stop; 6. Full-color image source; 11. First surface; 12. Second surface; 21. Third surface; 22. Fourth surface; 31. Fifth surface; 32. Sixth surface; 41. Seventh surface; 42. Eighth surface. Detailed Implementation

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] The technical solution of this application will be further described below with reference to the embodiments and accompanying drawings.

[0042] This application provides an optical module. (Refer to...) Figure 1 , Figure 6 , Figure 8 , Figure 10 , Figure 12 The optical module, from aperture 5 to the single-chip full-color image source 6, includes the following in sequence: The first lens 1 has positive optical power, the second lens 2 has positive optical power, the third lens 3 has negative optical power, and the fourth lens 4 has negative optical power. The fourth lens 4 has a surface facing the image source with the largest light-transmitting aperture D1 in the optical module, and the total optical length TTL of the optical module satisfies D1: 1.6 < TTL / D1 < 1.9. Furthermore, the center thicknesses of the first lens 1, the second lens 2, the third lens 3, and the fourth lens 4 on the optical axis are T1, T2, T3, and T4 respectively, satisfying: 1.4 < (T3 + T4) / (T1 + T2) < 1.7.

[0043] In this embodiment, the optical module has four lenses arranged sequentially from the aperture stop 5 to the single full-color image source 6, namely a first lens 1 with positive optical power, a second lens 2 with positive optical power, a third lens 3 with negative optical power, and a fourth lens 4 with negative optical power.

[0044] For example, refer to Figure 1 , Figure 6 , Figure 8 , Figure 10 , Figure 12 The first lens 1 is a meniscus lens, with its first surface 11 facing the aperture 5 being convex and its second surface 12 facing the second lens 2 being concave. The second lens 2 is a meniscus lens, with its third surface 21 facing the first lens 1 being convex and its fourth surface 22 facing the third lens 3 being concave. The third lens 3 is a biconcave lens, with its fifth surface 31 facing the second lens 2 being concave and its sixth surface 32 facing the fourth lens 4 being concave. The fourth lens 4 is a meniscus lens, with its seventh surface 41 facing the third lens 3 being concave and its eighth surface 42 facing the image source being convex.

[0045] Specifically, based on the optical power limitations of the first lens 1 to the fourth lens 4 in this application, the effective focal length range of the first lens 1 is 3mm to 4mm, the effective focal length range of the second lens 2 is 9mm to 12mm, the effective focal length range of the third lens 3 is -3.5mm to -2.5mm, and the effective focal length range of the fourth lens 4 is -40mm to -30mm.

[0046] By setting the effective focal length of the first lens 1 to 3mm to 4mm, it undertakes the main converging function and forms a sufficiently large positive optical power within a short optical length to compress the beam aperture and establish the exit pupil position in advance, leaving aberration correction space for subsequent lenses and meeting the compact requirements of the AR module for an ultra-thin structure.

[0047] The effective focal length of the second lens 2 is set to 9mm to 12mm, providing a moderate positive optical power. Together with the first lens 1, it forms a positive-positive optical power combination, sharing the tasks of field curvature and chromatic aberration correction. At the same time, it avoids the sensitive tolerance caused by excessive optical power of a single lens, improving assembly yield and thermal stability.

[0048] The effective focal length of the third lens 3 is set to -3.5 mm to -2.5 mm, giving the negative lens group the main negative optical power, forming a strong contrast with the positive lens group, effectively canceling the field curvature and astigmatism caused by the positive optical power, ensuring that the imaging surface is flat under a large field of view, and meeting the visual requirements of AR display for low field curvature and low distortion.

[0049] The fourth lens 4 has an effective focal length of -40 mm to -40 mm, providing weak negative light power for fine-tuning the beam emission angle and aberration balance. At the same time, it expands the light collection capability at the maximum aperture D1, so that the emitted beam of the single full-color image source 6 is completely captured, improving light energy utilization and display brightness, and realizing a lightweight optical module with high brightness, low power consumption and a large field of view.

[0050] In this embodiment, light is emitted from the surface of the monolithic full-color image source 6. The image source of this optical module is the monolithic full-color image source 6. The monolithic integrated design eliminates the complex color combining prisms found in multi-chip display schemes, resulting in a compact and lightweight optical module. Furthermore, the monolithic full-color image source 6, through the direct mixing of the three primary color pixels, can cover most of the color range that the human eye can distinguish, significantly reducing image color deviation and improving light efficiency and brightness optimization.

[0051] For example, the monolithic full-color image source 6 can be a Micro LED monolithic full-color image source 6.

[0052] Light rays emitted from the surface of the single-chip full-color image source 6 first enter the fourth lens 4. The surface of the fourth lens 4 facing the image source has the largest aperture D1 in this optical module. This large aperture design allows the fourth lens 4 to fully collect various types of light rays emitted from the image source, especially those rays that deviate from the optical axis at large angles, reducing light loss and ensuring efficient light transmission. The fourth lens 4 has negative optical power, and when light enters it, it diverges. For light rays that are originally close to the optical axis, they will diverge slightly after passing through the fourth lens 4; for light rays that deviate from the optical axis at large angles, the fourth lens 4 will further increase their divergence angle. This divergence is an initial adjustment of the light propagation direction, preparing for further processing by subsequent lenses. At the same time, the total optical length TTL of the optical module and the maximum aperture D1 satisfy the condition 1.6 < TTL / D1 < 1.9, ensuring sufficient light collection while reasonably controlling the propagation space of light behind the fourth lens 4, allowing the light to proceed in an orderly manner during subsequent transmission. That is, the fourth lens 4 is used to collect a wide-angle beam with a large geometric coupling efficiency (e.g., greater than 85%) and to reduce the initial divergence of the beam, while introducing negative chromatic aberration pre-compensation.

[0053] The light beam exiting through the fourth lens 4 then enters the third lens 3. The third lens 3 also has negative optical power. When the light beam diverged by the fourth lens 4 enters the third lens 3, it continues to diverge. However, unlike the diverging effect of the fourth lens 4, the third lens 3 performs more precise control over the degree of divergence based on the initial propagation state of the light and the overall design requirements of the optical module. It further optimizes the angular distribution of the light, ensuring that the light is more evenly distributed in the subsequent optical space after passing through the third lens 3. Simultaneously, it further corrects aberrations that may occur during propagation, improving the transmission quality of the light. Furthermore, based on the fact that the center thicknesses of the first lens 1, the second lens 2, the third lens 3, and the fourth lens 4 on the optical axis are T1, T2, T3, and T4 respectively, and satisfy the condition 1.4 < (T3 + T4) / (T1 + T2) < 1.7, the combination of the center thicknesses of the third lens 3 and the fourth lens 4 works in conjunction with the combination of the center thicknesses of the first lens 1 and the second lens 2 to jointly influence the propagation characteristics of light at the third lens 3, ensuring that the light can be transmitted along a predetermined path and angle. Simply put, the third lens 3 also has negative optical power, and together with the fourth lens 4, it satisfies a thickness ratio of (T3 + T4) / (T1 + T2) = 1.4 to 1.7, further balancing the positive field curvature and chromatic aberration generated by the subsequent positive lens group, and reducing the astigmatism of the principal rays in the peripheral field of view within the meridional and sagittal sections.

[0054] After pre-correction by the negative lens group, the light beam passes sequentially through the second lens 2 and the first lens 1. Upon entering the second lens 2, the light's propagation direction changes, and it begins to converge towards the optical axis. The second lens 2 then reverses the divergence of the light, gradually converging it. Based on the angle and position information of the light, it precisely adjusts the propagation path, ensuring the light moves more orderly towards the optical axis during subsequent transmission. Simultaneously, it further corrects aberrations generated during divergence, improving image sharpness. The positive optical power of the second lens 2, combined with the negative optical power of the third lens 3 and the fourth lens 4, forms a complex control process of first diverging and then converging the light. This control method effectively optimizes the propagation state of the light, laying the foundation for high-quality final imaging.

[0055] In other words, in the optical module of this application, the cooperation of the second lens 2 and the first lens 1 performs main convergence of the transmitted light, so that the transmitted light enters the pupil forming stage. Both the second lens 2 and the first lens 1 have positive optical power, which is used to converge the beam and form a virtual exit pupil of appropriate size at the aperture stop 5. The virtual exit pupil is conjugate with the entrance pupil of the subsequent waveguide input grating or holographic coupling surface, ensuring that the paraxial height difference of the main light in the field of view range of 0° to 35° is small on the side of the aperture stop 5, so as to achieve low distortion and large field of view compatibility.

[0056] Finally, the light propagates to the first lens 1, which also has positive optical power. The first lens 1 further converges the light after it has passed through the second lens 2, making the light propagate more concentrated along the optical axis. It adjusts the light to the appropriate position and angle, ensuring that the light accurately reaches the aperture 5 and enters the subsequent optical system or is received by a receiving device such as the human eye in optimal condition. The first lens 1 plays a final, precise adjustment role in the entire light transmission process, ensuring that the light emitted from the image source ultimately presents a clear, accurate, and distortion-free image through convergence and aberration correction.

[0057] Throughout the transmission process, TTL and D1 are kept at 1.6 < TTL / D1 < 1.9, which allows the optical module to retain sufficient edge light transmission height while shortening the total length to ≤6mm. The alternation of positive and negative optical power and the thickness ratio constraint further complement the temperature coefficient of refractive index and the coefficient of thermal expansion, which can maintain high-resolution imaging.

[0058] In this embodiment, the optical module is arranged sequentially from the aperture stop 5 to the single full-color image source 6, consisting of a first lens 1 with positive optical power, a second lens 2 with positive optical power, a third lens 3 with negative optical power, and a fourth lens 4 with negative optical power. This specific lens combination, combined with the limitation on the total optical length TTL and the maximum aperture D1 of the fourth lens 4 facing the image source surface (1.6 < TTL / D1 < 1.9), effectively shortens the total optical length of the optical module while ensuring image quality, and reasonably controls the aperture size. Compared with traditional optical modules, it can achieve effective light convergence and transmission within a limited space, reducing the overall size and weight of the optical module. This facilitates the miniaturization and lightweight design of the device, meeting the needs of near-eye display devices with extremely high portability requirements, such as AR glasses, and improving user comfort and experience.

[0059] This optical module features an alternating configuration of positive and negative optical powers, coupled with a thickness ratio of (T3+T4) / (T1+T2) = 1.4–1.7, to rationally distribute the thickness of each lens. This thickness distribution helps optimize the propagation path of light within the lens group, reducing refraction and reflection losses within the lenses, lowering aberrations, and thus improving image clarity and contrast, ensuring high-quality imaging. Simultaneously, the rational thickness distribution enhances the structural stability of the optical module, reducing deformation caused by uneven or unreasonable lens thickness, ensuring the stability and reliability of the optical module's performance during long-term use. Furthermore, by limiting the materials of the negative lens group (third and fourth lenses 4) and the positive lens group (first and second lenses 2), combined with a thickness ratio distribution of 1.4–1.7, the refractive index temperature coefficient and thermal expansion coefficient compensate for each other, ensuring that the AR device maintains focus stability even when the ambient temperature changes, improving mass production yield and reducing assembly costs.

[0060] The design of this optical module comprehensively considers multiple key parameters such as total optical length, aperture, and lens thickness, achieving a balance between a large aperture and a short back focal length while maintaining a compact design. The large aperture ensures sufficient light enters the optical module, improving the system's light utilization efficiency and enhancing display brightness; the short back focal length helps to further shorten the overall length of the optical module, enabling a more compact structural design. Furthermore, this design achieves a good balance between multiple performance indicators such as large field of view (FOV), low distortion, and temperature drift suppression, meeting the diverse performance requirements of optical modules in different application scenarios and providing a superior optical solution for devices in fields such as AR near-eye displays.

[0061] According to an embodiment of this application, the air gap between the second lens 2 and the third lens 3 on the optical axis is M1, and the air gap between the third lens 3 and the fourth lens 4 on the optical axis is M2. Among them, M1 and TTL satisfy: 0.03·TTL≤M1≤0.07·TTL; and M2 and TTL satisfy: 0.08·TTL≤M2≤0.12·TTL.

[0062] In the embodiments of this application, the quantization of air gaps M1 and M2 and total optical length TTL ensures that the distance between the second lens 2 and the third lens 3 is 0.03·TTL ≤ M1 ≤ 0.07·TTL, and the distance between the third lens 3 and the fourth lens 4 is 0.08·TTL ≤ M2 ≤ 0.12·TTL. This ensures that even with the TTL compressed to 6mm, sufficient edge ray height margin is still provided for the negative lens group, avoiding edge attenuation that is usually caused by short TTL.

[0063] In this embodiment, the smaller M1 between the second lens 2 and the third lens 3 can shorten the on-axis beam aperture of the positive-negative power transition zone and reduce the outer diameter of the second lens 2.

[0064] The larger M2 between the third lens 3 and the fourth lens 4 makes the negative light power plane of the fourth lens 4 closer to the image source, expands the usable diameter-to-height ratio of the maximum light-passing aperture D1, achieves an ultra-thin specification of TTL / D1<1.9, and ensures that the wide-angle beam of a single full-color Micro-LED is completely captured.

[0065] The aforementioned air gap ratio, in conjunction with the (T3+T4) / (T1+T2) thickness ratio, enables the second lens 2 and the third lens 3 to collaboratively correct spherical aberration and coma generated during light propagation. The collaboration between the third lens 3 and the fourth lens 4 further facilitates the correction of aberrations such as astigmatism, field curvature, and distortion. Through the synergistic effect of the air gap and thickness ratio, a lightweight, compact, large field-of-view, low-distortion, and high-resolution integrated imaging performance is achieved.

[0066] According to the embodiments of this application, T3 and TTL satisfy: 0.15·TTL≤T3≤0.19·TTL; and T4 and TTL satisfy: 0.25·TTL≤T4≤0.29·TTL.

[0067] In this embodiment, by limiting the center thickness T3 of the third lens 3 to 0.15·TTL≤T3≤0.19·TTL and the center thickness T4 of the fourth lens 4 to 0.25·TTL≤T4≤0.29·TTL, the negative lens group still has sufficient physical thickness within the ultra-thin TTL (≤6mm) to introduce the required negative optical power and bear the main field curvature and chromatic aberration correction.

[0068] In this embodiment, the quantization ratio of T3, T4 and TTL limits the total thickness of the negative lens group (T3+T4) to the range of 0.40·TTL to 0.48·TTL, maintaining a thickness balance with the positive lens group (T1+T2) of 1.4 < (T3+T4) / (T1+T2) < 1.7, thus avoiding the problem of excessive module size and weight due to excessive lens thickness.

[0069] According to the embodiments of this application, refer to Figure 1 , Figure 6 , Figure 8 , Figure 10 , Figure 12 The first lens 1 has a first surface 11 facing the aperture stop 5 and a second surface 12 facing the second lens 2; the sag of the first surface 11 at the maximum light-transmitting aperture is denoted as S1, and the sag of the second surface 12 at the maximum light-transmitting aperture is denoted as S2, satisfying: 9 < S1 / S2 < 14.

[0070] In this embodiment, by limiting the ratio of the height S1 of the first surface 11 of the first lens 1 facing the aperture stop 5 to the height S2 of the second surface 12 of the second lens 2 (9 < S1 / S2 < 14), the first lens 1 forms a large crescent shape while maintaining positive optical power. Its first surface 11 has a sufficiently strong converging ability, which can highly compress the principal rays of the edge field of view at the virtual exit pupil, thereby achieving a large diagonal field of view within a compact space of TTL / D1 < 1.9 while ensuring relative illumination. The quantization range of S1 / S2 increases the difference between the curvature of the incident surface and the curvature of the exit surface of the first lens 1, reduces the incident angle of the edge rays of the large field of view inside the lens, significantly reduces advanced spherical aberration and off-axis coma, and improves image quality.

[0071] In addition, the strong meniscus design with S1 / S2>9 pushes the virtual exit pupil position toward the stop 5 side, shortening the conjugate distance between the exit pupil and the subsequent waveguide input grating, and reducing the alignment tolerance sensitivity of the waveguide coupling prism.

[0072] According to the embodiments of this application, refer to Figure 1 , Figure 6 , Figure 8 , Figure 10 , Figure 12 The fourth lens 4 has a seventh surface 41 facing the third lens 3 and an eighth surface 42 facing the image source; the sag of the seventh surface 41 at the maximum aperture is denoted as S3, and the sag of the eighth surface 42 at the maximum aperture is denoted as S4, satisfying: 2.3 < S4 / S3 < 2.9.

[0073] In this embodiment, by limiting the ratio of the height S3 of the seventh surface 41 of the fourth lens 4 facing the third lens 3 to the height S4 of the eighth surface 42 facing the image source to 2.3 < S4 / S3 < 2.9, the fourth lens 4 forms an asymmetrical shape of "shallow crescent-deep crescent". Its eighth surface 42 has a larger height at the maximum light-passing aperture D1, thereby expanding the effective collection solid angle without increasing the TTL, improving the light energy utilization rate, and meeting the requirements of high-brightness near-eye display.

[0074] The aforementioned sag-to-height ratio ensures that the negative optical power of the fourth lens 4 is mainly concentrated on the eighth surface 42, while the seventh surface 41 remains relatively flat. This effectively distributes the aberration correction load of the negative lens group, reduces astigmatism and distortion in the off-axis field of view, ensures imaging consistency under a large field of view, and meets the optical requirements of AR glasses for low distortion and a large FOV.

[0075] In addition, the asymmetric sagittal height structure S4 / S3 > 2.3 enables the fourth lens 4 to maintain the edge thickness within the machinable range while keeping the central thickness satisfying 0.25·TTL ≤ T4 ≤ 0.29·TTL, avoiding the problem of excessive thinning at the edge caused by the deep meniscus structure, and improving the lens forming stability and structural strength. And by controlling S4 / S3 < 2.9, the high incident angle reflection caused by the excessive curvature of the eighth surface 42 is avoided, effectively suppressing the generation of reflection ghosts and stray light, improving the imaging contrast of the system, enhancing the clarity and visual comfort of the AR display screen, and ensuring the high imaging quality of the optical module under a compact structure.

[0076] According to an embodiment of the present application, the third lens 3 has a fifth surface 31 facing the second lens 2 and a sixth surface 32 facing the fourth lens 4, and the clear aperture of the fifth surface 31 is larger than the clear aperture of the sixth surface 32.

[0077] In this embodiment, by setting the clear aperture of the fifth surface 31 of the third lens 3 facing the second lens 2 to be larger than the clear aperture of the sixth surface 32 facing the fourth lens 4, an asymmetric clear aperture structure with a larger front and a smaller rear is formed, which can improve the uniformity of the peripheral field illumination without increasing the outer diameter of the lens.

[0078] The larger clear aperture of the fifth surface 31 helps to share the aberration correction function of the negative lens group and improve the astigmatism and distortion correction capabilities of the off-axis field; at the same time, the smaller clear aperture of the sixth surface 32 is beneficial to controlling the lens spacing and air gap accuracy and enhancing the coaxial stability during lens assembly.

[0079] On the premise of keeping the optical power distribution unchanged, the asymmetric clear aperture structure optimizes the lens profile, forms a transitional convergence of the third lens 3 in the lens group, reduces the use of materials in the ineffective area, reduces the overall weight, and meets the design requirements of AR glasses for light weight and structural compactness.

[0080] According to an embodiment of the present application, referring to Figure 2 , the included angle between the lens tangent at the maximum clear aperture of the fifth surface 31 of the third lens 3 facing the second lens 2 and the optical axis is A1, and the included angle between the lens tangent at the maximum clear aperture of the sixth surface 32 of the third lens 3 facing the fourth lens 4 and the optical axis is A2, satisfying: 35° < A2 - A1 < 65° and 0.45 < A1 / A2 < 0.75.

[0081] In this embodiment, it is defined that the included angle A1 between the tangent line of the maximum clear aperture of the fifth surface 31 of the third lens 3 and the optical axis and the included angle A2 between the tangent line of the sixth surface 32 and the optical axis satisfy 35° < A2 - A1 < 65° and 0.45 < A1 / A2 < 0.75, so that the third lens 3 forms an asymmetric wedge structure with a gentle front and a steep rear. Without increasing the center thickness of the lens, it can effectively increase the deflection ability of the negative optical power to the chief ray of the marginal field of view, improve the freedom degree of off-axis aberration correction, and ensure imaging consistency under a large field angle.

[0082] The included angle difference A2 - A1 > 35° enables the sixth surface 32 to have a stronger negative optical power contribution, jointly承担 the functions of field curvature and astigmatism correction with the fourth lens 4, and reduces the aberration burden of the subsequent positive lens group; at the same time, A2 - A1 < 65° avoids the high-order coma and scattering introduced by excessive deflection, maintains the low-distortion imaging characteristics of the system, and meets the optical requirements of AR display for low distortion and large FOV.

[0083] By controlling A1 / A2 > 0.45, it is ensured that the fifth surface 31 has a sufficient incident light receiving angle, so that the light beam from the second lens 2 can fully enter the third lens 3, avoiding vignetting of marginal rays; A1 / A2 < 0.75 restricts the ineffective clear aperture area caused by the overly gentle fifth surface 31, optimizes the lens aperture utilization rate, and improves the compactness and lightweight level of the module.

[0084] In this embodiment, the asymmetric included angle configuration enables the third lens 3 to form a controllable light beam convergence and deflection transition in the optical path, enhances the adjustability of the negative lens group to the light beam shape, is beneficial to achieving short back focal length and low field curvature imaging in cooperation with the fourth lens 4, and ensures imaging quality.

[0085] According to the embodiment of the present application, referring to Figure 3 , the included angle between the lens tangent line at the maximum clear aperture of the seventh surface 41 of the fourth lens 4 facing the third lens 3 and the optical axis is A3, and the included angle between the lens tangent line at the maximum clear aperture of the eighth surface 42 of the fourth lens 4 facing the image source and the optical axis is A4, satisfying: - The included angle difference A2 - A1 > 35° enables the sixth surface

[0086] In this embodiment, it is defined that the included angle A3 between the tangent line of the maximum clear aperture of the seventh surface 41 of the fourth lens 4 and the optical axis and the included angle A4 between the tangent line of the eighth surface 42 and the optical axis satisfy -5° < A3 - A4 < 15° and 0.95 < A3 / A4 < 1.25. While ensuring the negative optical power, it suppresses the sudden deflection of the chief ray of the marginal field of view, reduces the risk of high-order coma and scattering, and achieves low-distortion imaging under a large field angle.

[0087] The aforementioned angle difference A3-A4>-5° ensures that the seventh surface 41 is slightly gentler than the eighth surface 42, reducing interface reflection energy and suppressing ghosting; A3-A4<15° avoids the expansion of the ineffective light-transmitting area caused by the seventh surface 41 being too gentle, maintaining the compact shape of the lens and meeting the space constraints of AR glasses for ultra-thin modules.

[0088] By controlling A3 / A4 > 0.95, the slopes of the front and rear surfaces tend to be consistent, forming an approximately equal meniscus structure. This is beneficial for symmetrical material flow during injection molding or compression molding, reducing internal stress and birefringence, and improving the optical stability of the lens. Limiting A3 / A4 < 1.25 retains a moderate degree of asymmetry, providing the necessary degrees of freedom for negative power distribution and aberration correction, and enhancing the system's tolerance to temperature changes.

[0089] In this embodiment, the micro-meniscus slope configuration enables the fourth lens 4 to form a continuous and smooth light transition surface at the maximum light transmission aperture D1, effectively collecting large-angle beams from the image source and improving light energy utilization; at the same time, it reduces the sensitivity to subsequent air gaps, enhances the coaxiality of lens assembly, improves the consistency and yield of mass production, and ensures high imaging reliability of the optical module under the conditions of miniaturization.

[0090] According to the embodiments of this application, the first lens 1 to the fourth lens 4 are all aspherical lenses.

[0091] In this embodiment, the first lens 1 to the fourth lens 4 are all aspherical, which can flexibly introduce higher-order surface shape degrees of freedom without increasing the number of lenses, effectively correct spherical aberration, coma, astigmatism and distortion, realize high-resolution imaging under a large field of view, and meet the stringent requirements of AR near-eye display for image clarity.

[0092] In addition, the aspherical structure allows each lens to maintain the required optical power while reducing the thickness difference between the center and the edge, thus reducing the size and weight of the lens and contributing to the overall miniaturization of the module, making it suitable for the compact assembly space of AR glasses.

[0093] According to an embodiment of this application, the refractive index range of the first lens 1 and the second lens 2 is 1.53~1.62, and the refractive index range of the third lens 3 and the fourth lens 4 is 1.63~1.68.

[0094] In this embodiment, the refractive indices of the first lens 1 and the second lens 2 are set in the range of 1.53 to 1.62, enabling the positive lens group to provide converging optical power while maintaining low dispersion, reducing the amount of axial chromatic aberration, leaving chromatic aberration correction margin for the subsequent negative lens group, and improving the color reproduction accuracy of the single full-color image source 6. The refractive indices of the third lens 3 and the fourth lens 4 are set in the range of 1.63 to 1.68, giving the negative lens group higher refractive power, achieving the required negative optical power with a shorter radius of curvature, reducing the difference between the center thickness and edge height of the lens, which is beneficial for module thinning and enhances the correction efficiency for field curvature and astigmatism.

[0095] In this embodiment, the positive and negative lens groups adopt a differentiated refractive index configuration, which can utilize the dispersion difference between the high refractive index negative lens and the low refractive index positive lens to achieve synchronous compensation of axial and magnification chromatic aberration, reduce the number of lenses, simplify the structure, and reduce assembly sensitivity.

[0096] The optical module provided in this application is described in detail below with reference to specific embodiments.

[0097] Example 1 Reference Figure 1 The optical module, along the direction from the aperture stop 5 to the image source, includes: a first lens 1 with positive optical power, a second lens 2 with positive optical power, a third lens 3 with negative optical power, and a fourth lens 4 with negative optical power. The maximum effective aperture D1 in the optical module is 2.8 mm.

[0098] The optical module has the following characteristics: total optical length 4.53 mm (including the total length from the image source to the aperture 5); FOV: 34°; entrance pupil diameter: 2.1~2.5 mm; entrance pupil distance: 0.1 mm; image source size: 2.3 μm~2.7 μm; distortion: <10%; operating wavelength: 505 nm~550 nm; image plane size: 2.8 mm~3.2 mm. Table 1 shows some optical parameters of the first lens 1 to the fourth lens 4, and Table 2 shows the aspherical parameters of the first lens 1 to the fourth lens 4.

[0099] Table 1:

[0100] Table 2:

[0101] Combination Figure 4 and Figure 5 At a spatial frequency of 200 cycles / mm, the MTF values ​​in both the meridional and sagittal directions are higher than 0.5 across the entire field of view, meeting the requirements for high-resolution imaging. Furthermore, the module distortion is less than 10%, ensuring that the geometric distortion of the image is within the acceptable range for the human eye, thus achieving near-eye display performance with a large field of view, low distortion, and high definition.

[0102] Example 2 Reference Figure 6 The optical module, along the direction from the aperture stop 5 to the image source, includes: a first lens 1 with positive optical power, a second lens 2 with positive optical power, a third lens 3 with negative optical power, and a fourth lens 4 with negative optical power. The maximum effective aperture D1 in the optical module is 2.8 mm.

[0103] The optical module has the following characteristics: total optical length: 4.53 mm (including the total length from the image source to the aperture 5); FOV: 34°; entrance pupil diameter: 2.1~2.5 mm; entrance pupil distance: 0.1 mm; image source size: 2.3 μm~2.7 μm; distortion: <10%; operating wavelength: 505 nm~550 nm; image plane size: 2.8 mm~3.2 mm. Table 3 shows some optical parameters of the first lens 1 to the fourth lens 4, and Table 4 shows the aspherical parameters of the first lens 1 to the fourth lens 4.

[0104] Table 3:

[0105] Table 4:

[0106] Combination Figure 7 At a spatial frequency of 200 cycles / mm, the MTF values ​​in both the meridional and sagittal directions are higher than 0.5 across the entire field of view, meeting the requirements for high-resolution imaging.

[0107] Example 3 Reference Figure 8 The optical module, along the direction from the aperture stop 5 to the image source, includes: a first lens 1 with positive optical power, a second lens 2 with positive optical power, a third lens 3 with negative optical power, and a fourth lens 4 with negative optical power. The maximum effective aperture D1 in the optical module is 2.8 mm.

[0108] The optical module has the following characteristics: total optical length 4.53 mm (including the total length from the image source to the aperture 5); FOV: 34°; entrance pupil diameter: 2.1~2.5 mm; entrance pupil distance: 0.1 mm; image source size: 2.3~2.7 μm; distortion: <10%; operating wavelength: 505~550 nm; image plane size: 2.8 mm~3.2 mm. Table 5 shows some optical parameters of the first lens 1 to the fourth lens 4, and Table 6 shows the aspherical parameters of the first lens 1 to the fourth lens 4.

[0109] Table 5:

[0110] Table 6:

[0111] Combination Figure 9 At a spatial frequency of 200 cycles / mm, the MTF values ​​in both the meridional and sagittal directions are higher than 0.5 across the entire field of view, meeting the requirements for high-resolution imaging.

[0112] Example 4 Reference Figure 10 The optical module, along the direction from the aperture stop 5 to the image source, includes: a first lens 1 with positive optical power, a second lens 2 with positive optical power, a third lens 3 with negative optical power, and a fourth lens 4 with negative optical power. The maximum effective aperture D1 in the optical module is 2.8 mm.

[0113] The optical module has the following characteristics: total optical length 4.53 mm (including the total length from the image source to the aperture 5); FOV: 34°; entrance pupil diameter: 2.1~2.5 mm; entrance pupil distance: 0.1 mm; image source size: 2.3~2.7 μm; distortion: <10%; operating wavelength: 505~550 nm; image plane size: 2.8 mm~3.2 mm. Table 7 shows some optical parameters of the first lens 1 to the fourth lens 4, and Table 8 shows the aspherical parameters of the first lens 1 to the fourth lens 4.

[0114] Table 7:

[0115] Table 8:

[0116] Combination Figure 11 At a spatial frequency of 200 cycles / mm, the MTF values ​​in both the meridional and sagittal directions are higher than 0.5 across the entire field of view, meeting the requirements for high-resolution imaging.

[0117] Example 5 Reference Figure 12 The optical module, along the direction from the aperture stop 5 to the image source, includes: a first lens 1 with positive optical power, a second lens 2 with positive optical power, a third lens 3 with negative optical power, and a fourth lens 4 with negative optical power. The maximum effective aperture D1 in the optical module is 2.8 mm.

[0118] The optical module has the following characteristics: total optical length 4.53 mm (including the total length from the image source to the aperture 5); FOV: 34°; entrance pupil diameter: 2.1~2.5 mm; entrance pupil distance: 0.1 mm; image source size: 2.3~2.7 μm; distortion: <10%; operating wavelength: 505~550 nm; image plane size: 2.8 mm~3.2 mm. Table 9 shows some optical parameters of the first lens 1 to the fourth lens 4, and Table 10 shows the aspherical parameters of the first lens 1 to the fourth lens 4.

[0119] Table 9:

[0120] Table 10:

[0121] Combination Figure 13 At a spatial frequency of 200 cycles / mm, the MTF values ​​in both the meridional and sagittal directions are higher than 0.5 across the entire field of view, meeting the requirements for high-resolution imaging.

[0122] This application also provides a near-eye display device. The near-eye display device includes the optical module described above. Exemplarily, the near-eye display device can be AR glasses or an AR head-mounted device, etc.

[0123] 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.

[0124] 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 module, characterized in that, The optical module consists of four lenses. In the direction from the aperture (5) to the single-chip full-color image source (6), the four lenses are, in sequence: a first lens (1) with a positive optical power, a second lens (2) with a positive optical power, a third lens (3) with a negative optical power, and a fourth lens (4) with a negative optical power; wherein, the surface of the fourth lens (4) facing the image source has the largest light transmission aperture D1 in the optical module, and the total optical length TTL of the optical module and D1 satisfy: 1.6 < TTL / D1 < 1.9; and, the central thicknesses of the first lens (1), the second lens (2), the third lens (3), and the fourth lens (4) on the optical axis are T1, T2, T3, and T4, respectively, satisfying: 1.4 < (T3 + T4) / (T1 + T2) < 1.

7.

2. The optical module according to claim 1, characterized in that, The air gap on the optical axis between the second lens (2) and the third lens (3) is M1, and the air gap on the optical axis between the third lens (3) and the fourth lens (4) is M2; wherein, M1 and TTL satisfy: 0.03·TTL ≤ M1 ≤ 0.07·TTL; and M2 and TTL satisfy: 0.08·TTL ≤ M2 ≤ 0.12·TTL.

3. The optical module according to claim 1, characterized in that, T3 and TTL satisfy: 0.15·TTL ≤ T3 ≤ 0.19·TTL; and T4 and TTL satisfy: 0.25·TTL ≤ T4 ≤ 0.29·TTL.

4. The optical module according to claim 1, characterized in that, The first lens (1) has a first surface (11) facing the aperture (5) and a second surface (12) facing the second lens (2); the sagittal height of the first surface (11) at the maximum light transmission aperture is denoted as S1, and the sagittal height of the second surface (12) at the maximum light transmission aperture is denoted as S2, satisfying: 9 < S1 / S2 < 14.

5. The optical module according to claim 1, characterized in that, The fourth lens (4) has a seventh surface facing the third lens (3) and an eighth surface facing the image source; the sagittal height of the seventh surface at the maximum light transmission aperture is denoted as S3, and the sagittal height of the eighth surface at the maximum light transmission aperture is denoted as S4, satisfying: 2.3 < S4 / S3 < 2.

9.

6. The optical module according to claim 5, characterized in that, ​ 7. The optical module according to claim 1 or 6, characterized in that, ​ 8. The optical module according to claim 1 or 5, characterized in that, The included angle between the lens tangent line at the maximum clear aperture of the seventh surface of the fourth lens (4) facing the third lens (3) and the optical axis is A3, and the included angle between the lens tangent line at the maximum clear aperture of the eighth surface of the fourth lens (4) facing the image source and the optical axis is A4, satisfying: -5° < A3 - A4 < 15° and 0.95 < A3 / A4 < 1.

25.

9. The optical module according to claim 1, characterized in that, The effective focal length range of the first lens (1) is from 3 mm to 4 mm, the effective focal length range of the second lens (2) is from 9 mm to 12 mm, the effective focal length range of the third lens (3) is from -3.5 mm to -2.5 mm, and the effective focal length range of the fourth lens (4) is from -40 mm to -30 mm.

10. The optical module according to claim 1, characterized in that, The first lens (1) to the fourth lens (4) are all aspherical lenses.

11. The optical module according to claim 1, characterized in that, The refractive index range of the first lens (1) and the second lens (2) is: 1.53 to 1.62, and the refractive index range of the third lens (3) and the fourth lens (4) is: 1.63 to 1.

68.

12. A near-eye display device, characterized in that, The near-eye display device includes the optical module according to any one of claims 1 - 11.

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