Testing lens and near-to-eye display testing device

Abstract

The embodiment of the invention provides a test lens and a near-to-eye display test device. The test lens comprises a diaphragm, a front group lens, a middle group lens, a rear group lens and a photosensitive device. The diaphragm is used for limiting the aperture of incident light; from the object side to the image side, the front group lens comprises a first doublet lens having positive focal power; the second doublet lens has negative focal power; the diaphragm forms an intermediate image between the front-group lens and the middle-group lens through the front-group lens; the middle-group lens comprises at least three sub-lens groups from the object side to the image side, and the focal powers of the at least three sub-lens groups are arranged in a positive and negative alternating manner; the diaphragm passes through the front group lens and the middle group lens, and forms at least partial overlapping areas of the light of each view field between the middle group lens and the rear group lens; from the object side to the image side, the rear group lens comprises: a third doublet lens having positive focal power; the fourth doublet lens has negative focal power; and the photosensitive device is used for receiving light rays passing through the front group lens, the middle group lens and the rear group lens in sequence.

Description

Technical Field

[0001] This application relates to the field of optical testing technology, and more specifically, to a test lens and a near-eye display testing device. Background Technology

[0002] In recent years, near-eye display technologies (such as virtual reality headsets and augmented reality glasses) have seen rapid development in consumer electronics, medical, educational, and industrial fields, with their display effects relying on the imaging performance of optical lenses. However, with the continuous improvement of resolution, field of view (FOV), and refresh rate of near-eye display devices, the need for evaluating their optical image quality has become increasingly urgent.

[0003] To overcome the limitations of subjective evaluation, the industry has proposed objective testing schemes based on optical testing equipment. However, existing test lenses generally suffer from the following problems: traditional test lenses are not designed to fully consider the large field of view and high resolution requirements of near-eye displays, resulting in a sharp decline in image quality at the edges of the field of view; and near-eye display systems are extremely sensitive to geometric distortion, while existing test lenses struggle to achieve low-distortion imaging across the entire field of view. Therefore, when testing near-eye display devices, it is impossible to accurately measure and evaluate their geometric distortion, leading to biases in the evaluation of the optical image quality of near-eye display devices.

[0004] In view of the problems existing in the prior art, it is necessary to provide a new technical solution to solve the technical defects of poor testing effect of existing test lenses. Summary of the Invention

[0005] The purpose of this application is to provide a testing lens and a near-eye display testing device to solve the technical defects of the existing testing lens in terms of poor testing effect.

[0006] According to a first aspect of this application, a test lens is provided. The test lens includes, arranged coaxially from the object side to the image side: an aperture stop, a front lens group, a middle lens group, a rear lens group, and a photosensitive device; wherein, The aperture is used to define the diameter of the incident light rays; The front lens group, from the object side to the image side, includes: a first cemented doublet lens with positive optical power; and a second cemented doublet lens with negative optical power; the light rays pass through the front lens group to form an intermediate image between the front lens group and the middle lens group. The middle lens group includes at least three sub-lens groups from the object side to the image side, and the optical power of the at least three sub-lens groups is arranged in an alternating positive and negative manner; the light rays pass through the front lens group and the middle lens group, forming at least a partial overlap area between the middle lens group and the rear lens group; The rear lens group, from the object side to the image side, includes, in sequence: a third cemented doublet with positive optical power; and a fourth cemented doublet with negative optical power. The photosensitive device is used to receive the light rays that pass through the front lens, the middle lens and the rear lens in sequence.

[0007] Optionally, the first cemented doublet lens includes a third lens and a fourth lens, both with positive optical power, arranged sequentially from the object side to the image side.

[0008] Optionally, the third lens is a biconvex lens, and the fourth lens is a concave-convex lens, with its concave surface facing the object side and its convex surface facing the image side.

[0009] Optionally, the second cemented doublet lens includes a fifth lens and a sixth lens, both with negative optical power, arranged sequentially from the object side to the image side.

[0010] Optionally, the fifth lens is a biconvex lens; the sixth lens is a biconcave lens.

[0011] Optionally, the front lens group further includes: a first lens and a second lens, both disposed on the object side of the first cemented doublet lens and arranged sequentially from the object side to the image side; the first lens and the second lens are both meniscus lenses with positive optical power.

[0012] Optionally, the middle lens group, from the object side to the image side, sequentially includes: a first sub-lens group with positive optical power; a second sub-lens group with negative optical power; and a third sub-lens group with positive optical power; wherein, The first sub-lens group includes, from the object side to the image side, a seventh lens having positive optical power and an eighth lens having positive optical power. The second sub-lens group, from the object side to the image side, includes, in sequence: a ninth lens with negative optical power; a tenth lens with negative optical power; and an eleventh lens with positive optical power. The third sub-lens group includes: a twelfth lens with positive optical power.

[0013] Optionally, the beam aperture between the ninth lens and the tenth lens is minimized.

[0014] Optionally, let the sag at the maximum aperture on the object side of the ninth lens be S1, and the sag at the maximum aperture on the image side be S2, then the following condition is satisfied: 1.6 < S2 / S1 < 2; let the sag at the maximum aperture on the object side of the tenth lens be S3, and the sag at the maximum aperture on the image side be S4, then the following condition is satisfied: 1.1 < S4 / S3 < 1.5.

[0015] Optionally, along the optical axis, the air gap between the eleventh lens and the twelfth lens is greater than the air gap between the eleventh lens and the tenth lens.

[0016] Optionally, if the air gap between the eleventh lens and the twelfth lens is M3, then M3 accounts for 4% to 7% of the TTL of the test lens.

[0017] Optionally, the third cemented doublet lens includes, from the object side to the image side, a thirteenth lens with negative optical power and a fourteenth lens with positive optical power. The thirteenth lens is a convex-concave lens, with the convex surface of the lens closer to the object side and the concave surface closer to the image side; The fourteenth lens is a biconvex lens.

[0018] Optionally, the fourth cemented doublet lens includes, from the object side to the image side, a fifteenth lens with negative optical power and a sixteenth lens with negative optical power. The fifteenth lens is a biconvex lens, and the sixteenth lens is a biconcave lens.

[0019] Optionally, the rear lens group further includes a seventeenth lens located on the image side of the fourth cemented doublet lens, the seventeenth lens having positive optical power.

[0020] Optionally, if the air gap between the front lens group and the middle lens group is M1, then M1 accounts for 5% to 9% of the test lens TTL; if the air gap between the middle lens group and the rear lens group is M2, then M2 accounts for 11% to 15% of the test lens TTL.

[0021] According to a second aspect of this application, a near-eye display testing apparatus is provided. The near-eye display testing apparatus includes a testing lens as described in the first aspect, and further includes a near-eye display device and an image processor, wherein light emitted from the near-eye display device is captured by the testing lens to form image information, and then sent to the image processor.

[0022] One technical advantage of this application is: In the technical solution provided in this application embodiment, the distortion introduced by the front lens in the "positive-negative" double bonding form and the distortion generated by the middle lens in the "positive-negative-positive" alternating optical power form compensate each other. Then, the rear lens is corrected again by "positive-negative" double bonding. Through the step-by-step compensation mechanism, the TV distortion of the entire field of view is suppressed to ≤1%, and MTF>0.45 is achieved in the entire field of view spatial frequency. This meets the objective evaluation requirements of near-eye display systems that are extremely sensitive to geometric distortion, and improves the accuracy of the test results.

[0023] 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

[0024] 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.

[0025] Figure 1 The diagram shown is an optical architecture diagram of a test lens provided in an embodiment of this application.

[0026] Figure 2 The image shown is the optical path of the test lens provided in an embodiment of this application. Figure 1 .

[0027] Figure 3 As shown Figure 2 The distortion diagram of the test lens.

[0028] Figure 4 As shown Figure 2 MTF curve of the test lens.

[0029] Figure 5 The image shown is the optical path of the test lens provided in an embodiment of this application. Figure 2 .

[0030] Figure 6 As shown Figure 5 MTF chart of the test lens.

[0031] Figure 7 The image shown is the optical path of the test lens provided in an embodiment of this application. Figure 3 .

[0032] Figure 8 As shown Figure 7 MTF chart of the test lens.

[0033] Figure 9 The image shown is the optical path of the test lens provided in an embodiment of this application. Figure 4 .

[0034] Figure 10 As shown Figure 9 MTF chart of the test lens.

[0035] Explanation of reference numerals in the attached figures: 100. Front lens group; 101. Middle lens group; 102. Rear lens group; 200. First cemented doublet lens; 201. Second cemented doublet lens; 202. Third cemented doublet lens; 203. Fourth cemented doublet lens; 1011, First sub-lens group; 1012, Second sub-lens group; 1013, Third sub-lens group; 1. First lens; 2. Second lens; 3. Third lens; 4. Fourth lens; 5. Fifth lens; 6. Sixth lens; 7. Seventh lens; 8. Eighth lens; 9. Ninth lens; 10. Tenth lens; 11. Eleventh lens; 12. Twelfth lens; 13. Thirteenth lens; 14. Fourteenth lens; 15. Fifteenth lens; 16. Sixteenth lens; 17. Seventeenth lens; 18. Aperture; 19. Photosensitive device. 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] The test lens provided in this application embodiment can be applied to optical display devices that require evaluation of image quality, such as near-eye display devices and micro-projection devices.

[0043] In applications, near-eye display devices and micro-projection devices can be configured as wearable or portable devices according to actual needs. For example, near-eye display devices can be configured as head-mounted near-eye display devices such as AR or VR glasses or AR or VR helmets, while micro-projection devices can be configured as portable micro-projection devices such as handheld projectors.

[0044] This application provides a test lens. (Refer to...) Figure 1 , reference Figure 2 , Figure 5 , Figure 7 and Figure 9 The test lens includes, from the object side to the image side, a series of elements arranged coaxially: an aperture stop 18, a front lens group 100, a middle lens group 101, a rear lens group 102, and a photosensitive element 19. The aperture stop 18 is used to define the diameter of the incident light rays. The front lens group 100 includes, from the object side to the image side, a first cemented doublet 200 having positive optical power and a second cemented doublet 201 having negative optical power; the light rays pass through the front lens group 100 to form an intermediate image between the front lens group 100 and the middle lens group 101. The middle lens group 101 includes at least three sub-lens groups from the object side to the image side, and the optical power of the at least three sub-lens groups is arranged in an alternating positive and negative manner; the light rays pass through the front lens group 100 and the middle lens group 101, forming at least a partial overlap area between the middle lens group 101 and the rear lens group 102 for each field of view. The rear lens group 102 includes, from the object side to the image side, a third cemented doublet 202 with positive optical power and a fourth cemented doublet 203 with negative optical power.

[0045] The photosensitive device 19 is used to receive the light rays that pass sequentially through the front lens 100, the middle lens 101 and the rear lens 102.

[0046] As is understandable, optical power characterizes the ability of an optical system to deflect light. The larger the absolute value of optical power, the stronger the ability to bend light; the smaller the absolute value of optical power, the weaker the ability to bend light. When optical power is positive, the refraction of light is converging; when optical power is negative, the refraction of light is diverging. Optical power can be used to characterize a single refractive surface of a lens (i.e., one surface of the lens), a single lens, or a system formed by multiple lenses (i.e., the cemented lens provided in the embodiments of this application).

[0047] In the embodiments of this application, the aberration contribution of the cemented lenses shown by the first cemented doublet lens 200 to the fourth cemented doublet lens 203 is composed of two parts: a) the "intrinsic" spherical aberration, coma, and distortion of the single lens - which are directly related to the sign of its own optical power; b) the "bending" contribution of the cemented surface (i.e., the internal interface) - which is related to the radius of curvature of the cemented surface and the difference in refractive index on both sides, and can produce aberrations with the opposite sign to the overall optical power.

[0048] In this embodiment, the test lens is configured with an aperture stop 18, a front lens group 100, a middle lens group 101, a rear lens group 102, and a photosensitive element 19, arranged sequentially along the optical axis from the object side to the image side. That is, this application, through a five-segment optical architecture of "aperture stop 18 - front lens group - middle lens group - rear lens group - photosensitive element 19", can still control the principal ray incident angle (CRA) within a small angle range under conditions of a large field of view on the object side. The test lens achieves an MTF (Mean Transmission Factor) > 0.55 across the entire field of view under large field of view conditions, meeting the requirements of VR / AR test lenses, solving the problem of sudden image quality degradation at the edges of traditional test lenses, and realizing complete acquisition of high-resolution images across the entire field of view for near-eye display devices.

[0049] In this embodiment of the application, the aperture 18 is located at the foremost end of the test lens and is used to simulate the pupil of the human eye, which can limit the light transmission aperture of the test lens.

[0050] Optionally, to better utilize the test lens to simulate the human eye, aperture 18 is used as the system aperture stop 18, and its light-passing aperture is optically conjugated to form the entrance pupil, with an entrance pupil diameter D. ep Limited to 3.8 mm ≤ D ep Within a range of ≤4.5mm, the beam cross-section entering the system is limited to achieve control over the object-side beam energy and the image-side NA.

[0051] Aperture 18 further matches the object-side focal plane position of the front lens 100, thus increasing the entrance pupil distance L. ep (The distance between the entrance pupil and the vertex of the first optical surface along the optical axis) should be maintained at 9mm ≤ L. ep With a focal length of ≤12mm, an approximate telecentric incidence condition is formed, which not only suppresses object-side stray light but also provides a stable principal ray distribution for subsequent lens groups, ensuring uniform illumination across the entire field of view.

[0052] The front lens group 100, from the object side to the image side, is composed of a first cemented doublet 200 with positive optical power and a second cemented doublet 201 with negative optical power, forming a "positive-negative" optical power distribution. Light rays passing through the front lens group 100 are conjugately imaged between the front lens group 100 and the middle lens group 101, forming an intermediate image plane. (Refer to...) Figure 2 Position A indicates the location where the intermediate image plane is formed. That is, in the test lens of this application, the aperture stop 18 is located at the foremost point. The incident light passes through the front lens 100 and forms an intermediate image at the optical conjugate surface between the front lens 100 and the middle lens 101. This intermediate image is the first real image plane of the system.

[0053] By placing the aperture stop 18 in front and completing a real image imaging in the front optical path, the first convergence of the beam aperture and aberration pre-allocation are achieved, which significantly reduces the beam height and deflection angle of the subsequent lens groups, thereby reducing the effective aperture and tolerance sensitivity of the middle and rear lens groups 102. At the same time, the intermediate image plane is a "segmented correction node" built into the system, which allows the distortion, field curvature and chromatic aberration introduced by the large field of view to be optimized independently in the front and rear sections, improving the uniformity of the full field of view imaging and enhancing the adaptability of the test lens to different near-eye display pupil structures.

[0054] Meanwhile, this "positive-negative" double-cemented structure, while providing pre-convergence of the principal ray in the large field of view of the object side, introduces spherical and chromatic aberrations of opposite signs. This allows for early compensation of the optical path difference between edge rays and paraxial rays, thereby controlling primary spherical aberration and axial chromatic aberration within a small range. This provides the optical foundation for subsequent lens groups to achieve higher-order aberration decomposition and high-resolution imaging across the entire field of view. In short, the front lens 100 can initially converge and correct light rays, and the combination of positive and negative optical powers can effectively balance aberrations, laying the foundation for subsequent improvements in image quality.

[0055] The middle lens group 101 consists of at least three sub-lens groups arranged sequentially along the optical axis from the object side to the image side, with the optical power of each sub-lens group configured in an alternating positive and negative manner, forming a "positive-negative-positive" optical power sequence. After the light rays pass sequentially through the front lens group 100 and the middle lens group 101, at least a partial overlap area of ​​the principal rays of each field of view is formed in the common optical path interval between the middle lens group 101 and the rear lens group 102, constituting an equivalent "field stitching node," as shown in the reference. Figure 2 Position B is the location of at least a partial overlap of the principal rays of each field of view.

[0056] The alternating positive and negative optical power arrangement structure compensates for the aberration components introduced by each field of view step by step, reducing spherical aberration, coma, and field curvature in the edge and center fields of view, thereby controlling the MTF difference across the entire field of view within a small range and improving imaging uniformity and consistency. At the same time, the overlapping area reduces the effective aperture of the rear lens 102 and the incident angle of the principal ray, and suppresses the brightness attenuation caused by the difference in the field of view, ensuring the uniformity of relative illumination.

[0057] The rear lens group 102 is composed of a third cemented doublet 202 with positive optical power and a fourth cemented doublet 203 with negative optical power, forming a "positive-negative" reverse optical power combination from the object side to the image side. This "positive-negative" cemented doublet structure produces residual spherical aberration, chromatic aberration, and distortion components with opposite signs in front of the final image, achieving simultaneous cancellation of higher-order aberrations left over from the front and middle groups, thereby suppressing the full field-of-view (TV) distortion to ≤1% and improving the edge field-of-view MTF, thus completing beam convergence and high-fidelity imaging.

[0058] The photosensitive device 19 is used to receive light rays that pass sequentially through the front lens 100, the middle lens 101, and the rear lens 102, and convert the optical signals into electrical signals, thereby realizing the recording and detection of images. For example, the photosensitive device 19 can be a photosensitive chip.

[0059] In summary, in this embodiment, the distortion introduced by the front lens 100 through a "positive-negative" cemented doublet is mutually compensated with the distortion generated by the alternating "positive-negative-positive" optical power of the middle lens 101. Then, the distortion is corrected again by the rear lens 102 through a "positive-negative" cemented doublet. Through a step-by-step compensation mechanism, the TV distortion in the entire field of view is suppressed to ≤1%, and MTF > 0.45 is achieved at the spatial frequency of the entire field of view. This meets the objective evaluation requirements of near-eye display systems that are extremely sensitive to geometric distortion, and improves the accuracy of the test results.

[0060] The front lens 100 employs a combination of positive and negative optical power cemented doublets, while the middle lens 101 features an alternating arrangement of positive and negative optical power. This design effectively corrects aberrations in the lens system, particularly controlling aberrations at the edges of the field of view. Specifically, when the front lens 100 and the middle lens 101 are used together, the test lens of this application can significantly reduce aberrations at the edges of the field of view, such as spherical aberration and coma, resulting in clearer and sharper images at the edges. This solves the problem of a sharp decline in image quality at the edges of traditional lenses and improves the imaging quality across the entire field of view.

[0061] The middle lens 101, through a specific optical power arrangement and structural design, ensures that light rays from different fields of view form at least a partial overlap area between the middle lens 101 and the rear lens 102. This design enables comprehensive correction of light rays from different fields of view, effectively controlling geometric distortion. Given the extreme sensitivity of near-eye display systems to geometric distortion, the test lens of this application achieves low-distortion imaging across the entire field of view, accurately measuring and evaluating the geometric distortion of near-eye display devices. This provides more precise data for evaluating the optical image quality of near-eye display devices, meeting the optical testing requirements of near-eye display technology.

[0062] Furthermore, the middle lens 101 forms at least a partial overlap area for the light rays from each field of view within itself, which is equivalent to having a "field-of-view stitching node" built into the optical system. This ensures that the principal rays from different fields of view are pre-coaxial before reaching the rear lens group, reducing the aperture and tolerance sensitivity of the rear lens group 102 and shortening the overall length of the lens. For example, in the case of a test lens containing 17 lenses, the total optical length of the test lens is 320mm, the maximum effective aperture is 40mm, and the focal length is 27.1mm, balancing the requirements of a large field of view, low distortion, and miniaturization.

[0063] In summary, the test lens of this application, through the coordinated design of the front, middle, and rear lens groups 102, ensures uniform processing and control of light throughout the entire lens system. The overlap of light rays from different fields of view in specific areas, along with comprehensive aberration correction, guarantees good uniformity and consistency in imaging across different fields of view. Whether in the central or peripheral fields of view, similar imaging effects are achieved, improving the accuracy and reliability of the test lens in evaluating the optical performance of near-eye display devices.

[0064] According to the embodiments of this application, the optical architecture of the front lens 100 is defined.

[0065] In one specific embodiment, the front lens group 100, from the object side to the image side, includes: a first lens 1, a second lens 2, a first cemented doublet lens 200, and a second cemented doublet lens 201. Wherein, The first lens 1 and the second lens 2 are both disposed on the object side of the first cemented doublet lens 200 and arranged sequentially from the object side to the image side; the first lens 1 and the second lens 2 are both meniscus lenses with positive optical power.

[0066] The first cemented doublet 200 includes a third lens 3 and a fourth lens 4, both with positive optical power, arranged sequentially from the object side to the image side. The third lens 3 is a biconvex lens, and the fourth lens 4 is a concave-convex lens, with its concave surface facing the object side and its convex surface facing the image side. The second cemented doublet 201 includes a fifth lens 5 and a sixth lens 6, both with negative optical power, arranged sequentially from the object side to the image side. The fifth lens 5 is a biconvex lens; the sixth lens 6 is a biconcave lens.

[0067] In this embodiment, the front lens group 100 is composed of a first lens 1, a second lens 2, a first cemented doublet lens 200, and a second cemented doublet lens 201 sequentially from the object side to the image side; wherein, the first lens 1 and the second lens 2 are both meniscus lenses with positive optical power, and the meniscus faces the object side; the first cemented doublet lens 200 is formed by cementing a third lens 3 (biconvex) with positive optical power and a fourth lens 4 (concave-convex, with the concave surface facing the object side); the second cemented doublet lens 201 is formed by cementing a fifth lens 5 (biconvex) with negative optical power and a sixth lens 6 (biconcave).

[0068] In the front lens group 100, two positive meniscus lenses form a "positive-positive" pre-convergence unit at the front end. While keeping the height of the principal ray in the large field of view constant, it is used to compress the incident angle of the object-side principal ray, which significantly reduces the deflection load that the subsequent cemented surface needs to bear.

[0069] It should be noted that the first lens 1 and the second lens 2 can be omitted in the front lens group 100, and only the first cemented doublet 200 and the second cemented doublet 201 are retained. In this case, by increasing the positive optical power of the first cemented doublet 200 by 8%-15% and simultaneously increasing the difference in the curvature radius of its cementing surface, the object-side principal ray convergence function originally undertaken by the two positive meniscus lenses is integrated into the incident surface of the first cemented doublet 200. Thus, while keeping the principal ray height of the large field of view unchanged, the incident angle of the object-side principal ray can be compressed.

[0070] In the front lens group 100, the positive spherical aberration introduced by the two meniscus lenses at the front end can cause problems such as blurring and reduced contrast in the image. The spherical aberration and coma generated at the cemented interface by the "biconvex + concave-convex" positive optical power combination of the first cemented doublet 200 (the spherical aberration and coma are generated by the optical power of each lens included in the first cemented doublet 200 and the curvature of the cemented surface) cancel out the spherical aberration introduced by the front meniscus lens. This cancellation effect can effectively reduce the influence of spherical aberration and coma on imaging, allowing light to be focused more accurately on the image plane, improving the sharpness and contrast of the image, especially in the middle field of view, where the image quality is significantly improved.

[0071] After correction by the first cemented doublet lens 200, the front lens group 100 system may still have some cumulative spherical aberration and distortion. The second cemented doublet lens 201 introduces spherical aberration and distortion in the opposite direction with a "biconvex + biconcave" negative optical power combination (spherical aberration and distortion are generated by the optical power of each lens included in the second cemented doublet lens 201 and the curvature of the cemented surface), forming a secondary compensation with the cumulative spherical aberration and distortion of the front group. This secondary compensation can further optimize the aberration distribution, especially in the edge field of view. The MTF of the edge field of view is an important indicator of the sharpness of the image at the edge. Through the secondary compensation of the second cemented doublet lens 201, the MTF of the edge field of view can be effectively improved, so that the image at the edge field of view can maintain a high level of sharpness and resolution, reduce the image quality degradation problem at the edge field of view, and achieve a uniform improvement in image quality across the entire field of view.

[0072] TV distortion is a crucial indicator of the degree of image distortion in a lens. Lower TV distortion results in images that more closely resemble real-world scenes, enhancing the visual experience. This technical solution utilizes the synergistic effect of the front-end meniscus lens, the first cemented doublet 200, and the second cemented doublet 201 to progressively correct and optimize spherical aberration, coma, and distortion, laying a preliminary foundation for achieving ≤1% TV distortion across the entire system. This means that through the combined design of these lenses throughout the lens system, the degree of image distortion can be effectively controlled, resulting in more realistic and accurate images that meet the demands of high-precision imaging.

[0073] According to an embodiment of this application, the optical architecture of the middle lens 101 is defined. In this embodiment, the middle lens 101 includes three sub-lens groups. The optical power distribution of the three sub-lens groups is positive-negative-positive.

[0074] Specifically, the middle lens group 101, from the object side to the image side, includes: a first sub-lens group 1011 with positive optical power; a second sub-lens group 1012 with negative optical power; and a third sub-lens group 1013 with positive optical power; wherein... The first sub-lens group 1011 includes, from the object side to the image side, a seventh lens 7 having positive optical power and an eighth lens 8 having positive optical power. The second sub-lens group 1012 includes, from the object side to the image side, the following elements in sequence: a ninth lens 9 with negative optical power; a tenth lens 10 with negative optical power; and an eleventh lens 11 with positive optical power. The third sub-lens group 1013 includes: a twelfth lens 12, having positive optical power.

[0075] In this embodiment, the first sub-lens group 1011 includes a seventh lens 7 and an eighth lens 8, both with positive optical power. The seventh lens 7 is a biconvex lens, and the curvature of the convex surface facing the object side of the seventh lens 7 is less than the curvature of the surface facing the image side. The eighth lens 8 is a convex-concave meniscus lens, which includes a convex surface facing the object side and a concave surface facing the image side.

[0076] The second sub-lens group 1012 includes a ninth lens 9, a tenth lens 10, and an eleventh lens 11, wherein the optical power of the ninth lens 9 is negative, the optical power of the tenth lens 10 is negative, and the optical power of the eleventh lens 11 is positive. The ninth lens 9 is a biconcave lens, the tenth lens 10 is a meniscus lens, and the tenth lens 10 includes a concave surface facing the object side and a convex surface facing the image side; and the eleventh lens 11 is a meniscus lens, and the eleventh lens 11 includes a concave surface facing the object side and a convex surface facing the image side.

[0077] The third sub-lens group 1013 includes a twelfth lens 12 with positive optical power. The twelfth lens 12 is a meniscus lens and includes a convex surface facing the object side and a concave surface facing the image side.

[0078] Specifically, the first sub-lens group 1011 consists of a seventh lens 7 (a biconvex lens with a lesser curvature towards the object side than towards the image side) and an eighth lens 8 (a meniscus lens) with positive optical power. The seventh lens 7 allows light rays at different incident angles to converge appropriately, and its more curved surface towards the image side better guides the light rays towards the image plane, reducing spherical aberration. The meniscus shape of the eighth lens 8 further fine-tunes the light rays, working in conjunction with the seventh lens 7 to effectively correct the residual positive spherical aberration transmitted from the front lens group 100, enabling the light to be focused more accurately on the photosensitive device 19 and improving image sharpness.

[0079] In the second sub-lens group 1012, the ninth lens 9 (biconcave lens) and the tenth lens 10 (meniscus lens, concave surface facing the object side, convex surface facing the image side) have negative optical power, enabling them to produce negative spherical aberration. These negative power cancels out the positive spherical aberration produced by the first sub-lens group 1011, further optimizing the spherical aberration correction effect. The positive optical power of the eleventh lens 11 (meniscus lens, concave surface facing the object side, convex surface facing the image side) allows for appropriate convergence adjustment of the previously corrected light rays, ensuring that spherical aberration is comprehensively and effectively corrected throughout the entire middle lens group 101, providing a high-quality light convergence foundation for the final image. The positive optical power of the twelfth lens 12 (meniscus lens, convex surface facing the object side, concave surface facing the image side) in the third sub-lens group 1013 performs final convergence and astigmatism correction, enabling the light rays to form a sharp image point on the image plane, thus improving image quality.

[0080] In the middle lens group 101, the beam aperture between the ninth lens 9 and the tenth lens 10 is the smallest. Let the elevation of the ninth lens 9 at its maximum aperture on the object side be S1, and the elevation of the ninth lens 9 at its maximum aperture on the image side be S2, then the following condition is satisfied: 1.6 < S2 / S1 < 2. Let the elevation of the tenth lens 10 at its maximum aperture on the object side be S3, and the elevation of the tenth lens 10 at its maximum aperture on the image side be S4, then the following condition is satisfied: 1.1 < S4 / S3 < 1.5.

[0081] In this embodiment, in the test lens, the ninth lens 9 and the tenth lens 10 are located approximately in the middle of the test lens along the optical axis, and the minimum beam aperture is formed between the two; after the light is initially diverged by the ninth lens 9, it enters the tenth lens 10 in a contracted state, realizing a secondary shaping path of "first diverging and then converging".

[0082] In this embodiment, the minimum aperture position is placed at the center of the system, ensuring the lowest beam height in the mid-axis section. This effectively reduces the radial dimensions of the tenth lens 10 and subsequent lenses, lowering the weight of the test lens. The ninth lens 9 uses negative optical power to compensate for residual spherical aberration in the front section, while the tenth lens 10 introduces refraction again in the beam concentration area using a meniscus. This two-stage relay significantly reduces the optical path difference between the edge rays and the principal rays, suppressing the generation of higher-order spherical aberrations and coma, and improving overall field-of-view sharpness. Furthermore, the minimum aperture position at the center of the system and the central "waist" structure distribute aberration correction tasks evenly across the front and rear sections, reducing the sensitivity of individual lenses to curvature and center offset, ensuring high imaging repeatability and consistency of the test lens during mass production.

[0083] In this embodiment, the sagittal ratio of the ninth lens 9 and the tenth lens 10 is specifically defined. A sagittal ratio greater than 1 means that the lens has a concave shape, and this concave shape can produce strong negative optical power at the waist position (i.e., the position where the beam aperture is the smallest) in the beam propagation path.

[0084] From an optical principle perspective, when light propagates to the beam waist, a concave lens with strong negative optical power exerts an additional reverse deflection effect on the peripheral rays. In an optical system, the front lens group often produces residual positive spherical aberration during the light-converging process. This reverse deflection of the peripheral rays effectively cancels out the residual positive spherical aberration. The cancellation of positive spherical aberration allows light to converge more accurately onto the image plane during imaging, thus significantly improving image quality.

[0085] Furthermore, this method of correcting aberrations by utilizing the specific sagittal ratio of the ninth lens 9 and the tenth lens 10 reduces the need for additional lenses to correct aberrations. In conventional optical system designs, multiple different types of lenses are typically required to correct various aberrations, increasing the axial dimension of the entire optical system. However, in this embodiment, by rationally designing the sagittal ratio of the ninth lens 9 and the tenth lens 10, and utilizing their resulting strong negative optical power to correct aberrations, the number of required lenses can be reduced, thereby effectively shortening the axial dimension of the middle lens group 101.

[0086] For example, in the actual structure of the middle lens group 101, the ninth lens 9, the tenth lens 10, and the eleventh lens 11 are arranged compactly within the middle lens group 101. This compact layout is due to the special design of the ninth lens 9 and the tenth lens 10, which, while fulfilling their own optical functions, also undertake part of the aberration correction task, achieving miniaturization and compact design of the middle lens group 101 while ensuring overall optical performance. This design is beneficial for the miniaturization and weight reduction of optical equipment.

[0087] In the middle lens group 101, the lens in the second sub-lens group 1012 closest to the third sub-lens group 1013 is the eleventh lens 11, and the third sub-lens group 1013 contains only the twelfth lens 12. Along the optical axis, the air gap between the eleventh lens 11 and the twelfth lens 12 is greater than the air gap between the eleventh lens 11 and the tenth lens 10.

[0088] In one specific embodiment, the air gap between the eleventh lens 11 and the twelfth lens 12 is M3, and M3 accounts for 4% to 7% of the test lens TTL.

[0089] In this embodiment, by increasing the air gap between the eleventh lens 11 and the twelfth lens 12, that is, increasing the proportion of M3 in the TTL, the beam obtains sufficient aperture expansion space at the junction of the negative and positive sub-lens groups, reducing the required edge thickness of the twelfth lens 12 and avoiding the risk of grinding and breakage caused by excessively thin lenses.

[0090] Furthermore, widening the air gap between the eleventh lens 11 and the twelfth lens 12 is equivalent to inserting a "focal gap" between negative and positive optical powers, which can independently optimize the incident height and exit angle of the twelfth lens 12 and reduce the advanced spherical aberration and coma caused by optical power jumps.

[0091] In this embodiment, by limiting M3 to the range of 4%–7% TTL, it is possible to prevent the loss of aberration correction freedom due to excessively small gaps, while also avoiding the waste of axial dimensions due to excessively large gaps. This achieves a balance between image quality improvement and miniaturization, ensuring that the test lens maintains low distortion and high resolution across the entire field of view while maintaining a compact structure.

[0092] According to the embodiments of this application, the optical architecture of the rear lens 102 is defined.

[0093] In one specific embodiment, the rear lens group 102 includes the third cemented doublet 202, the fourth cemented doublet 203, and the seventeenth lens 17 from the object side to the image side.

[0094] The third cemented doublet lens 202 includes, from the object side to the image side, a thirteenth lens 13 with negative optical power and a fourteenth lens 14 with positive optical power; the thirteenth lens 13 is a convex-concave lens, with the convex surface of the convex-concave lens close to the object side and the concave surface close to the image side; the fourteenth lens 14 is a biconvex lens.

[0095] The fourth cemented doublet lens 203 includes, from the object side to the image side, a fifteenth lens 15 with negative optical power and a sixteenth lens 16 with negative optical power; the fifteenth lens 15 is a biconvex lens and the sixteenth lens 16 is a biconcave lens.

[0096] The optical power of the seventeenth lens 17 is positive.

[0097] In this embodiment, the third cemented doublet 202 is paired with "negative-positive" optical power, generating spherical aberration and chromatic aberration at the cemented interface. This cancels out the spherical aberration left by the middle group and reduces the exit angle of the principal ray, leaving a light deflection margin for subsequent lenses. In the third cemented doublet 202, the refractive index of the convex lens is 80% to 90% of that of the concave lens, ensuring that the cemented surface has sufficient curvature compensation capability while avoiding excessive refractive index difference on both sides of the cemented surface from introducing coma and dispersion.

[0098] The fourth cemented doublet 203 adopts a "double convex-double concave" double negative structure, introducing spherical aberration and distortion (which are caused by the overall negative optical power and the curvature of the cemented surface) near the image side. These aberrations have opposite signs to those of the third cemented doublet 202, achieving secondary compensation and minimizing both spherical and chromatic aberration across the entire field of view. Furthermore, it suppresses TV distortion to a low level without requiring additional aspherical surfaces. In the fourth cemented doublet 203, the refractive index of the convex lens accounts for 80% to 90% of that of the concave lens, ensuring sufficient curvature compensation capability of the cemented surface while avoiding excessive refractive index difference on both sides of the cemented surface that could introduce coma and dispersion.

[0099] The seventeenth lens 17 at the very end of the optical power performs the final convergence of the beam after two cementing corrections, and at the same time controls the angle of the emitted principal ray so that the incident angle of the principal ray matches the photosensitive device 19, improving the consistency of edge pixel response and achieving a unity of low distortion, high resolution and high relative illumination.

[0100] According to an embodiment of this application, in the test lens, the air gap between the front lens group 100 and the middle lens group 101 is M1, then M1 accounts for 5% to 9% of the test lens TTL, and the air gap between the middle lens group 101 and the rear lens group 102 is M2, then M2 accounts for 11% to 15% of the test lens TTL.

[0101] In this embodiment, the air gap between the front lens 100 and the middle lens 101 is M1, which is set to 5%–9% of the TTL. This allows the front lens exit beam to achieve a moderate aperture expansion at the intermediate image plane, avoiding an excessively large gap that would cause a sudden increase in the height of the off-axis principal ray and thus increase the aperture of the middle lens 101.

[0102] The air gap between the middle lens 101 and the rear lens 102 is M2, which is set to 11%–15% of the TTL. This allows the emitted beam from the middle lens to diverge sufficiently, reducing the incident angle of the light from the first surface of the rear lens (the surface of the seventeenth lens 17 facing the object side) and decreasing spherical aberration and coma. At the same time, it leaves an axial margin for matching the main ray with the image plane, ensuring that the receiving angle of the photosensitive device 19 is within the optimal range and improving the consistency of edge pixel response.

[0103] In this embodiment, the sixth lens 6 is a negative power spherical lens, and its thickness accounts for 3% to 5% of the test lens TTL. The seventh lens 7 is a positive power spherical lens, and its thickness accounts for 3.1% to 5.1% of the test lens TTL. The sixteenth lens 16 is a negative power spherical lens, and its thickness accounts for 3.2% to 5.2% of the test lens TTL.

[0104] In this embodiment of the application, the thicknesses of the seventh lens 7, the eighth lens 8, the ninth lens 9 and the twelfth lens 12 are set to T1, T2, T3 and T4 respectively, which satisfies: 4<(T1+T2) / (T3+T4)<5.2.

[0105] In this embodiment, the thickness of the negative and positive key lenses is limited to 3%-5.2% of the TTL to ensure sufficient mechanical strength at the lens edges, avoid the risk of breakage during deep concave grinding, and suppress axial dimensional expansion caused by excessive thickness. Furthermore, (T1+T2) / (T3+T4) is maintained within the range of 4-5.2% to provide sufficient axial space for the positive power lens relative to the negative power lens, balancing the overcorrected aberrations generated by the front lens group and achieving full-field image plane flattening and low distortion.

[0106] The imaging effect of the test lens will be explained below through examples.

[0107] Example 1 Reference Figure 1 and Figure 2 The test lens, from the object side to the image side, includes, in sequence: aperture 18, first lens 1, second lens 2, first cemented doublet 200 (third lens 3 and fourth lens 4 cemented together), second cemented doublet 201 (fifth lens 5 and sixth lens 6 cemented together); seventh lens 7, eighth lens 8, ninth lens 9, tenth lens 10, eleventh lens 11 and twelfth lens 12; third cemented doublet 202 (thirteenth lens 13 and fourteenth lens 14), fourth cemented doublet 203 (fifteenth lens 15 and sixteenth lens 16), seventeenth lens 17 and photosensitive device 19.

[0108] In this embodiment of the application, the overall focal length range of the test lens is -28mm to -26mm; the focal length range of the front lens 100 is 32mm to 37mm; the focal length range of the middle lens is 130mm to 160mm; and the focal length range of the rear lens is 60mm to 75mm.

[0109] In the embodiments of this application, the FOV of the test lens is 60°; the entrance pupil diameter is 3.8mm~4.5mm; the entrance pupil distance is 9mm~12mm; the pixel size is 6μm~9μm; the distortion is <1%; the operating wavelength is 460~650nm; and the image plane size is 29mm~34mm.

[0110] Table 1 shows the effective focal length range of each lens in the test lens.

[0111] Table 1:

[0112] Table 2 shows some detailed parameters of each lens in the test lens.

[0113] Table 2:

[0114] Reference Figure 3 and Figure 4 As shown, the maximum relative distortion across the entire field of view is less than 1%, the curve is flat, and there are no visible "waves," indicating that TV distortion has been adequately corrected. Figure 4 Within the spatial frequency range of 0-65 cycles / mm, the MTF of the entire field of view is higher than 0.5, with good consistency between the edge and the center, and excellent lens resolution.

[0115] Example 2 Reference Figure 5 The test lens, from the object side to the image side, includes, in sequence: aperture 18, first lens 1, second lens 2, first cemented doublet 200 (third lens 3 and fourth lens 4 cemented together), second cemented doublet 201 (fifth lens 5 and sixth lens 6 cemented together); seventh lens 7, eighth lens 8, ninth lens 9, tenth lens 10, eleventh lens 11 and twelfth lens 12; third cemented doublet 202 (thirteenth lens 13 and fourteenth lens 14), fourth cemented doublet 203 (fifteenth lens 15 and sixteenth lens 16), seventeenth lens 17 and photosensitive device 19.

[0116] In this embodiment, the effective focal length of each lens is the same as that provided in Embodiment 1.

[0117] Table 3 shows some detailed parameters of each lens in this embodiment.

[0118] Table 3:

[0119] Reference Figure 6 Within the spatial frequency range of 0-65 cycles / mm, the MTF of the entire field of view is higher than 0.5, with good consistency between the edge and the center, and excellent lens resolution.

[0120] Example 3 Reference Figure 7The test lens, from the object side to the image side, includes, in sequence: aperture 18, first lens 1, second lens 2, first cemented doublet 200 (third lens 3 and fourth lens 4 cemented together), second cemented doublet 201 (fifth lens 5 and sixth lens 6 cemented together); seventh lens 7, eighth lens 8, ninth lens 9, tenth lens 10, eleventh lens 11 and twelfth lens 12; third cemented doublet 202 (thirteenth lens 13 and fourteenth lens 14), fourth cemented doublet 203 (fifteenth lens 15 and sixteenth lens 16), seventeenth lens 17 and photosensitive device 19.

[0121] In this embodiment, the effective focal length of each lens is the same as that provided in Embodiment 1.

[0122] Table 4 shows some detailed parameters of each lens in this embodiment.

[0123] Table 4:

[0124] Reference Figure 8 Within the spatial frequency range of 0-65 cycles / mm, the MTF of the entire field of view is higher than 0.49, with good consistency between the edge and the center, indicating excellent resolution of the tested lens.

[0125] Example 4 Reference Figure 9 The test lens, from the object side to the image side, includes, in sequence: aperture 18, first lens 1, second lens 2, first cemented doublet 200 (third lens 3 and fourth lens 4 cemented together), second cemented doublet 201 (fifth lens 5 and sixth lens 6 cemented together); seventh lens 7, eighth lens 8, ninth lens 9, tenth lens 10, eleventh lens 11 and twelfth lens 12; third cemented doublet 202 (thirteenth lens 13 and fourteenth lens 14), fourth cemented doublet 203 (fifteenth lens 15 and sixteenth lens 16), seventeenth lens 17 and photosensitive device 19.

[0126] In this embodiment, the effective focal length of each lens is the same as that provided in Embodiment 1.

[0127] Table 5 shows some detailed parameters of each lens in this embodiment.

[0128] Table 5:

[0129] Reference Figure 10Within the spatial frequency range of 0-65 cycles / mm, the MTF of the entire field of view is higher than 0.45, with good consistency between the edge and the center, indicating excellent resolution of the test lens.

[0130] This application also provides a near-eye display testing device. The near-eye display testing device includes the aforementioned testing lens, a near-eye display device, and an image processor. Light emitted from the near-eye display device is captured by the testing lens to form image information, which is then sent to the image processor. The near-eye display device is an augmented reality imaging device or a virtual reality imaging device. The image processor can be a computer or other device capable of image processing.

[0131] 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.

[0132] 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. A test lens, characterized in that, The system comprises, arranged coaxially from the object side to the image side, an aperture stop (18), a front lens group (100), a middle lens group (101), a rear lens group (102), and a photosensitive element (19); wherein, The aperture (18) is used to define the diameter of the incident light; The front lens group (100) comprises, from the object side to the image side, a first cemented doublet (200) having positive optical power and a second cemented doublet (201) having negative optical power; the light rays pass through the front lens group (100) to form an intermediate image between the front lens group (100) and the middle lens group (101); The middle lens group (101) includes at least three sub-lens groups from the object side to the image side, and the optical power of the at least three sub-lens groups is arranged in an alternating positive and negative manner; the light rays pass through the front lens group (100) and the middle lens group (101) to form at least a partial overlap area of ​​each field of view light rays between the middle lens group (101) and the rear lens group (102); The rear lens group (102) includes, from the object side to the image side, a third cemented doublet (202) having positive optical power and a fourth cemented doublet (203) having negative optical power. The photosensitive device (19) is used to receive the light rays that pass sequentially through the front lens (100), the middle lens (101) and the rear lens (102).

2. The test lens according to claim 1, characterized in that, The first doublet lens (200) includes a third lens (3) and a fourth lens (4) with positive optical power arranged sequentially from the object side to the image side.

3. The test lens according to claim 2, characterized in that, The third lens (3) is a biconvex lens, and the fourth lens (4) is a concave-convex lens with its concave surface facing the object side and its convex surface facing the image side.

4. The test lens according to claim 1, characterized in that, The second doublet lens (201) includes a fifth lens (5) and a sixth lens (6) arranged sequentially from the object side to the image side, both with negative optical power.

5. The test lens according to claim 4, characterized in that, The fifth lens (5) is a biconvex lens; the sixth lens (6) is a biconcave lens.

6. The test lens according to any one of claims 1 to 5, characterized in that, The front lens group (100) further includes: a first lens (1) and a second lens (2), both of which are disposed on the object side of the first cemented doublet lens (200) and arranged sequentially from the object side to the image side; the first lens (1) and the second lens (2) are both meniscus lenses with positive optical power.

7. The test lens according to claim 1, characterized in that, The middle lens group (101) comprises, from the object side to the image side, the following sub-lens group (1011) having positive optical power; a second sub-lens group (1012) having negative optical power; and a third sub-lens group (1013) having positive optical power; wherein... The first sub-lens group (1011) includes, from the object side to the image side, a seventh lens (7) having positive optical power and an eighth lens (8) having positive optical power. The second sub-lens group (1012) includes, from the object side to the image side, the following elements in sequence: a ninth lens (9) having negative optical power; a tenth lens (10) having negative optical power; and an eleventh lens (11) having positive optical power; The third sub-lens group (1013) includes: a twelfth lens (12) having positive optical power.

8. The test lens according to claim 7, characterized in that, The beam aperture is smallest between the ninth lens (9) and the tenth lens (10).

9. The test lens according to claim 8, characterized in that, Let the sag at the maximum aperture on the object side of the ninth lens (9) be S1, and the sag at the maximum aperture on the image side be S2, then the following condition is met: 1.6 < S2 / S1 < 2; Let the sag at the maximum aperture on the object side of the tenth lens (10) be S3, and the sag at the maximum aperture on the image side be S4, then the following condition is met: 1.1 < S4 / S3 < 1.

5.

10. The test lens according to claim 7, characterized in that, Along the optical axis, the air gap between the eleventh lens (11) and the twelfth lens (12) is greater than the air gap between the eleventh lens (11) and the tenth lens (10).

11. The test lens according to claim 10, characterized in that, The air gap between the eleventh lens (11) and the twelfth lens (12) is M3, and M3 accounts for 4% to 7% of the TTL of the test lens.

12. The test lens according to claim 1, characterized in that, The third cemented doublet lens (202) includes, from the object side to the image side, a thirteenth lens (13) with negative optical power and a fourteenth lens (14) with positive optical power. The thirteenth lens (13) is a convex-concave lens, with the convex surface of the convex-concave lens close to the object side and the concave surface of the convex-concave lens close to the image side; The fourteenth lens (14) is a biconvex lens.

13. The test lens according to claim 1, characterized in that, The fourth cemented doublet lens (203) includes, from the object side to the image side, a fifteenth lens (15) with negative optical power and a sixteenth lens (16) with negative optical power. The fifteenth lens (15) is a biconvex lens, and the sixteenth lens (16) is a biconcave lens.

14. The test lens according to any one of claims 12-13, characterized in that, The rear lens group (102) also includes a seventeenth lens (17) located on the image side of the fourth cemented doublet lens (203), and the optical power of the seventeenth lens (17) is positive.

15. The test lens according to claim 1, characterized in that, The air gap between the front lens (100) and the middle lens (101) is M1, then M1 accounts for 5% to 9% of the test lens TTL. The air gap between the middle lens (101) and the rear lens (102) is M2, then M2 accounts for 11% to 15% of the test lens TTL.

16. A near-eye display testing device, characterized in that, The device includes the test lens as described in any one of claims 1 to 15, and further includes a near-eye display device and an image processor, wherein light emitted from the near-eye display device is captured by the test lens to form image information and is sent to the image processor.

Images