eyepiece lens

Abstract

The application relates to an eyepiece lens, which comprises a first lens (L1) with positive refractive power, a second lens (L2) with positive refractive power, a third lens (L3) with negative refractive power and a fourth lens (L4) with positive refractive power arranged in sequence along an optical axis from an object side to an image side; the first lens (L1) is a convex-convex lens or a convex-concave lens; the second lens (L2) is a convex-concave lens; the third lens (L3) is a concave-concave lens; and the fourth lens (L4) is a convex-convex lens. The eyepiece lens has a feature that an exit pupil distance reaches 45 mm and a back focal length BFL is greater than or equal to 6.5 mm, which leaves sufficient working distance for eye safety under the premise of meeting diversified use scenarios, reserves space for assembly and focusing of optical elements, and avoids mechanism interference to affect the performance of the eyepiece lens.

Description

Technical Field

[0001] This invention relates to the field of optical imaging system technology, and more particularly to an eyepiece lens. Background Technology

[0002] As a typical optical system with large aberrations, the eyepiece is usually used in conjunction with the objective lens and is mainly used in products such as microscopes and telescopes. It features an external aperture and low distortion, and its image quality has been significantly improved with the development of technology.

[0003] However, most eyepieces on the market currently have a relatively small exit pupil distance, making it difficult to provide sufficient safety distance to protect the human eye in increasingly diverse usage scenarios. Furthermore, the short back focal length of most eyepieces often leads to interference and other issues when there are specific assembly or replacement requirements for internal lens components. Using only standard spherical lenses in the eyepiece design process makes aberration correction difficult, and the high glass density results in a bulky lens. Chinese patent CN217932272U discloses an eyepiece optical system with a long exit pupil and 1x inverted image, but its exit pupil distance is between 20mm and 35mm, which still cannot meet the higher requirements of various application scenarios. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the purpose of this invention is to provide an eyepiece lens with features such as long exit pupil distance and long back focal length, while having advantages such as low cost, lightweight, high yield and easy mass production.

[0005] To achieve the above-mentioned objective, the present invention provides an eyepiece lens, comprising: 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 positive optical power, arranged sequentially along the optical axis from the object side to the image side.

[0006] The first lens is a convex-convex lens or a convex-concave lens;

[0007] The second lens is a convex-concave lens;

[0008] The third lens is a concave-concave lens;

[0009] The fourth lens is a convex-convex lens.

[0010] According to one aspect of the present invention, the first lens is a glass spherical lens, and the second lens, the third lens and the fourth lens are plastic aspherical lenses.

[0011] According to one aspect of the invention, the eyepiece lens further includes an aperture stop located on the object side of the first lens.

[0012] According to one aspect of the invention, the focal length F1 of the first lens and the total focal length F of the eyepiece lens satisfy the condition: 1.48≤F1 / F≤1.75.

[0013] According to one aspect of the invention, the focal length F2 of the second lens and the total focal length F of the eyepiece lens satisfy the condition: 1.25≤F2 / F≤2.35.

[0014] According to one aspect of the invention, the focal length F3 of the third lens and the total focal length F of the eyepiece lens satisfy the condition: -0.72≤F3 / F≤-0.48.

[0015] According to one aspect of the invention, the focal length F4 of the fourth lens and the total focal length F of the eyepiece lens satisfy the condition: 0.56≤F4 / F≤0.74.

[0016] According to one aspect of the invention, the focal length F1 of the first lens and the focal length F2 of the second lens satisfy the condition: 0.64≤F1 / F2≤1.35.

[0017] According to one aspect of the invention, the focal length F3 of the third lens and the focal length F4 of the fourth lens satisfy the condition: -1.12≤F3 / F4≤-0.67.

[0018] According to one aspect of the invention, the sagitta SAG31 of the object side of the third lens at the maximum effective radius, the sagitta SAG32 of the image side of the third lens at the maximum effective radius, and the center thickness D3 of the third lens satisfy the condition: 0.78≤(SAG31+SAG32) / D3≤4.50.

[0019] According to one aspect of the invention, the radius of curvature R3 of the object side of the second lens and the radius of curvature R4 of the image side of the second lens satisfy the condition: 0.26≤R3 / R4≤0.65.

[0020] According to one aspect of the invention, the radius of curvature R5 of the object side of the third lens and the radius of curvature R6 of the image side of the third lens satisfy the condition: -2.10≤R5 / R6≤-0.50.

[0021] According to one aspect of the invention, the radius of curvature R7 of the object side of the fourth lens and the radius of curvature R8 of the image side of the fourth lens satisfy the condition: -0.52≤R7 / R8≤-0.05.

[0022] According to one aspect of the invention, the center distance C12 from the image side of the first lens to the object side of the second lens, the center distance C23 from the image side of the second lens to the object side of the third lens, the center distance C34 from the image side of the third lens to the object side of the fourth lens, and the center distance TL from the object side of the first lens to the image plane of the eyepiece lens satisfy the condition: 0.05≤(C12+C23+C34) / TL≤0.25.

[0023] According to one aspect of the invention, the center thickness D1 of the first lens, the center thickness D2 of the second lens, the center thickness D3 of the third lens, the center thickness D4 of the fourth lens, and the center distance TL from the object side of the first lens to the image plane of the eyepiece lens satisfy the condition: 0.54≤(D1+D2+D3+D4) / TL≤0.74.

[0024] According to one aspect of the invention, the back focal distance BFL of the eyepiece lens and the total focal length F of the eyepiece lens satisfy the condition: 0.23≤BFL / F≤0.46.

[0025] According to one aspect of the invention, the center distance TL from the object side of the first lens to the image plane of the eyepiece lens and the total focal length F of the eyepiece lens satisfy the condition: 1.28≤TL / F≤1.68.

[0026] According to the present invention, the eyepiece lens has the characteristics of an exit pupil distance of 45mm and a back focal distance BFL ≥ 6.5mm. While meeting diverse usage scenarios, it provides sufficient working distance for human eye safety, and at the same time reserves space for the assembly and focusing of optical components, avoiding mechanical interference that could affect the performance of the eyepiece lens.

[0027] According to the present invention, a hybrid glass-plastic lens, combining spherical and aspherical surface types, is employed. The plastic lens reduces the cost of the optical system, while the aspherical lens facilitates the correction of various aberrations, particularly off-axis aberrations, thus improving image quality. The eyepiece lens, combining plastic aspherical lenses and glass spherical lenses, meets the design requirements of lightweight, low cost, and high yield, and offers advantages such as ease of mass production. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly described below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0029] Figure 1 This diagram schematically illustrates the optical structure of the eyepiece lens according to Embodiment 1 of the present invention.

[0030] Figure 2 A schematic diagram illustrating the optical structure of the eyepiece lens in Embodiment 2 of the present invention;

[0031] Figure 3 A schematic diagram illustrating the optical structure of the eyepiece lens in Embodiment 3 of the present invention;

[0032] Figure 4 A schematic diagram illustrating the optical structure of the eyepiece lens in Embodiment 4 of the present invention;

[0033] Figure 5 This diagram illustrates the optical structure of the eyepiece lens in Embodiment 5 of the present invention. Specific Implementation

[0034] The description of the embodiments in this specification should be taken in conjunction with the accompanying drawings, which should form part of the complete specification. In the drawings, the shape or thickness of the embodiments may be exaggerated and may be indicated in a simplified or convenient manner. Furthermore, parts of the various structures in the drawings will be described separately; it is worth noting that elements not shown in the figures or not described in words are in a form known to those skilled in the art.

[0035] The description of the embodiments herein, including any references to directions and orientations, is for ease of description only and should not be construed as limiting the scope of the invention. The following description of preferred embodiments involves combinations of features, which may exist independently or in combination; the invention is not particularly limited to the preferred embodiments. The scope of the invention is defined by the claims.

[0036] like Figure 1 As shown in the figure, an eyepiece lens disclosed in this embodiment of the invention includes: an aperture stop STO arranged sequentially along the optical axis from the object side to the image side; a first lens L1 with positive optical power; a second lens L2 with positive optical power; a third lens L3 with negative optical power; and a fourth lens L4 with positive optical power. The object side of the first lens L1 is convex, and the image side is either convex or concave; the second lens L2 is meniscus-shaped, with a convex object side and a concave image side; both the object side and image side of the third lens L3 are concave; and both the object side and image side of the fourth lens L4 are convex. The first lens L1 is a glass spherical lens, and the second lens L2, third lens L3, and fourth lens L4 are all plastic aspherical lenses.

[0037] In the above scheme, the object-side surface of the first lens L1 is set as a convex surface, which can effectively collect the light from the front, avoid excessive divergence of the light entering the optical system, and facilitate a smoother path of the light from the rear, while balancing chromatic aberration and coma. Simultaneously, the first lens L1 is a glass lens, which can enhance the stability of the lens, reduce the impact of the environment on the overall system, and balance chromatic aberration correction and lens refractive power, thus improving the overall performance of the optical lens. The meniscus-shaped second lens L2 is beneficial for correcting astigmatism and field curvature, and its aspherical surface design is beneficial for correcting spherical aberration and distortion. The negative optical power third lens L3 is beneficial for canceling field curvature, chromatic aberration, and other aberrations in the optical path, and its aspherical surface design also benefits the correction of spherical aberration and distortion. The biconvex, positive optical power fourth lens L4 not only allows light rays from different fields of view to be spatially staggered to correct edge field aberrations, but also facilitates light convergence, ensures light transmission, improves relative illumination, and thus improves the imaging quality of the eyepiece lens.

[0038] The aforementioned optical architecture of the eyepiece lens employs a hybrid glass-plastic design, combining spherical and aspherical surface types. The plastic lens reduces the cost of the optical system, while the aspherical lens helps correct various aberrations, especially off-axis aberrations, thus improving image quality. The eyepiece lens, combining plastic aspherical lenses and glass spherical lenses, meets the requirements of lightweight and low-cost design, while also facilitating mass production.

[0039] According to one embodiment of the present invention, the focal length F1 of the first lens L1 and the total focal length F of the eyepiece lens satisfy the condition: 1.48 ≤ F1 / F ≤ 1.75. The focal length F2 of the second lens L2 and the total focal length F of the eyepiece lens satisfy the condition: 1.25 ≤ F2 / F ≤ 2.35. The focal length F3 of the third lens L3 and the total focal length F of the eyepiece lens satisfy the condition: -0.72 ≤ F3 / F ≤ -0.48. The focal length F4 of the fourth lens L4 and the total focal length F of the eyepiece lens satisfy the condition: 0.56 ≤ F4 / F ≤ 0.74. By rationally allocating the ratio of the focal length of a single lens to the focal length of the optical system, the light passing through the single lens transitions smoothly, resulting in better tolerances for individual components and assembly, good manufacturability, and improved resolving power of the optical system while reducing manufacturing costs. The third lens L3 has a reasonable negative power, which also helps in the correction of chromatic aberration, field curvature, and distortion.

[0040] According to one embodiment of the present invention, the focal length F1 of the first lens L1 and the focal length F2 of the second lens L2 satisfy the condition: 0.64 ≤ F1 / F2 ≤ 1.35. The focal length F3 of the third lens L3 and the focal length F4 of the fourth lens L4 satisfy the condition: -1.12 ≤ F3 / F4 ≤ -0.67. By setting the absolute value range of the focal lengths of the first lens L1, the second lens L2, the third lens L3, and the fourth lens L4 to be close, it is beneficial to ensure a smooth transition of light throughout the optical system, reduce the generation of higher-order aberrations in the system, and lower tolerance sensitivity.

[0041] According to an embodiment of the present invention, the sagitta SAG31 of the object-side surface of the third lens L3 at the maximum effective radius, the sagitta SAG32 of the image-side surface of the third lens L3 at the maximum effective radius, and the center thickness D3 of the third lens L3 satisfy the condition: 0.78≤(SAG31+SAG32) / D3≤4.50. It should be noted that the sagitta of the object-side surface (image-side surface) of the third lens L3 at the maximum effective radius refers to the distance along the optical axis from the point of maximum effective aperture of the object-side surface (image-side surface) of the third lens L3 to the intersection of the object-side surface (image-side surface) of the third lens L3 and the optical axis. The center thickness D3 of the third lens L3 can also be understood as the thickness of the third lens L3 along the optical axis. This allows for reasonable control of the sagitta and thickness of the third lens L3, preventing it from being too thin or too thick, thereby improving the imaging quality of the optical lens and also facilitating lens fabrication and molding, thus increasing manufacturing yield.

[0042] According to one embodiment of the present invention, the radius of curvature R3 of the object side of the second lens L2 and the radius of curvature R4 of the image side of the second lens L2 satisfy the condition: 0.26 ≤ R3 / R4 ≤ 0.65. The radius of curvature R5 of the object side of the third lens L3 and the radius of curvature R6 of the image side of the third lens L3 satisfy the condition: -2.10 ≤ R5 / R6 ≤ -0.50. The radius of curvature R7 of the object side of the fourth lens L4 and the radius of curvature R8 of the image side of the fourth lens L4 satisfy the condition: -0.52 ≤ R7 / R8 ≤ -0.05. By reasonably controlling the shapes of the second lens L2, the third lens L3, and the fourth lens L4, the refractive power (optical power) of the lens can be effectively controlled, the trend of light refraction can be slowed down, the difficulty of aberration correction can be reduced, and thus the relative illumination and resolving power of the optical lens can be improved.

[0043] According to one embodiment of the present invention, the center distances C12 from the image-side surface of the first lens L1 to the object-side surface of the second lens L2, C23 from the image-side surface of the second lens L2 to the object-side surface of the third lens L3, C34 from the image-side surface of the third lens L3 to the object-side surface of the fourth lens L4, and TL from the object-side surface of the first lens L1 to the center of the image plane IMA of the eyepiece lens satisfy the condition: 0.05 ≤ (C12 + C23 + C34) / TL ≤ 0.25. In a specific embodiment, C12, C23, and C34 can also be understood as the distances on the optical axis from the image-side surface of the first lens L1 to the object-side surface of the second lens L2, from the image-side surface of the second lens L2 to the object-side surface of the third lens L3, and from the image-side surface of the third lens L3 to the object-side surface of the fourth lens L4, respectively.

[0044] According to one embodiment of the present invention, the center thickness D1 of the first lens L1, the center thickness D2 of the second lens L2, the center thickness D3 of the third lens L3, the center thickness D4 of the fourth lens L4, and the center distance TL from the object side surface of the first lens L1 to the center of the image plane IMA of the eyepiece lens satisfy the condition: 0.54 ≤ (D1 + D2 + D3 + D4) / TL ≤ 0.74. In a specific embodiment, D1, D2, D3, and D4 can also be understood as the thicknesses of the first lens L1, the second lens L2, the third lens L3, and the fourth lens L4 along the optical axis, respectively.

[0045] By appropriately constraining the spacing between lenses and the center thickness of each lens, the difficulty of aberration correction can be reduced, making each lens more manufacturable and helping to reduce the sensitivity of the optical lens.

[0046] According to one embodiment of the present invention, the back focal length BFL of the eyepiece lens and the total focal length F of the eyepiece lens satisfy the condition: 0.23 ≤ BFL / F ≤ 0.46. Here, the back focal length BFL refers to the distance from the center of the image-side surface of the fourth lens L4 to the center of the image plane IMA. This satisfies the special requirements of the back focal length of the eyepiece optical lens, while reserving space for the installation, replacement, and focusing of optical components, and avoiding the impact of a shorter back focal length on the performance of the components within the eyepiece lens during assembly, replacement, or focusing.

[0047] According to one embodiment of the present invention, the center distance TL from the object side of the first lens L1 to the image plane IMA of the eyepiece lens and the total focal length F of the eyepiece lens satisfy the condition: 1.28 ≤ TL / F ≤ 1.68. This design can shorten the total length of the eyepiece optical lens.

[0048] According to the above design scheme, the eyepiece lens of the present invention has the characteristics of an exit pupil distance of 45mm and a back focal distance BFL ≥ 6.5mm. While meeting diverse usage scenarios, it leaves sufficient working distance for human eye safety, and at the same time reserves space for the assembly and focusing of optical components, avoiding mechanical interference that would affect the performance of the eyepiece lens.

[0049] The eyepiece lens of the present invention will be specifically described below with reference to five embodiments, accompanying drawings, and tables. In the following embodiments, the aperture stop STO is referred to as one side, the parallel plate CG as two sides, and the image plane IMA as one side.

[0050] The parameters for each embodiment that meets the above conditions are shown in Table 1 below:

[0051]

[0052]

[0053] Table 1

[0054] In an embodiment of the present invention, the aspherical lens of the eyepiece satisfies the following formula:

[0055]

[0056] In the above formula, z is the axial distance from the vertex to the surface at a position perpendicular to the optical axis at a height h; c represents the curvature at the vertex of the aspherical surface; k is the conic coefficient; A4, A6, A8, A 10 A 12 A 14 A 16 ...represent aspheric coefficients of the fourth, sixth, eighth, tenth, twelfth, fourteenth, and sixteenth orders, respectively.

[0057] Example 1

[0058] See Figure 1 In this embodiment, along the optical axis from the object side to the image side, the first lens L1 is a convex-convex lens, the second lens L2 is a convex-concave lens, the third lens L3 is a concave-concave lens, and the fourth lens L4 is a convex-convex lens. The first lens L1 is a glass lens, while the second lens L2, the third lens L3, and the fourth lens L4 are all plastic lenses.

[0059] The relevant parameters of each lens in the eyepiece lens of this embodiment include: surface number (Surf), surface type (Type), radius of curvature (Radius), thickness (Thickness), refractive index of the material (Nd), and Abbe number (Vd), as shown in Table 2 below.

[0060]

[0061]

[0062] Table 2

[0063] The aspherical coefficients of each aspherical lens in the eyepiece lens of this embodiment include: the quadratic surface constant K, the fourth-order aspherical coefficient A4, the sixth-order aspherical coefficient A6, the eighth-order aspherical coefficient A8, and the tenth-order aspherical coefficient A1. 10 12th order aspherical coefficient A 12 Fourteenth-order aspherical coefficient A 14 Sixteenth-order aspherical coefficient A 16 18th order aspherical coefficient A 18 and the 20th order aspherical coefficient A 20 As shown in Table 3 below.

[0064]

[0065]

[0066] Table 3

[0067] Combination Figure 1 As shown in Tables 1 to 3 above, the eyepiece lens of this embodiment has the characteristics of an exit pupil distance of 45mm and a back focal distance BFL ≥ 6.5mm. While meeting diverse usage scenarios, it leaves sufficient working distance for human eye safety, and at the same time, it reserves space for the assembly and focusing of optical components to avoid mechanical interference that would affect the performance of the eyepiece lens.

[0068] Example 2

[0069] See Figure 2 In this embodiment, along the optical axis from the object side to the image side, the first lens L1 is a convex-concave lens, the second lens L2 is a convex-concave lens, the third lens L3 is a concave-concave lens, and the fourth lens L4 is a convex-convex lens. The first lens L1 is a glass lens, while the second lens L2, the third lens L3, and the fourth lens L4 are all plastic lenses.

[0070] The relevant parameters of each lens in the eyepiece lens of this embodiment include: surface number (Surf), surface type (Type), radius of curvature (Radius), thickness (Thickness), refractive index of the material (Nd), and Abbe number (Vd), as shown in Table 4 below.

[0071]

[0072]

[0073] Table 4

[0074] The aspherical coefficients of each aspherical lens in the eyepiece lens of this embodiment include: the quadratic surface constant K, the fourth-order aspherical coefficient A4, the sixth-order aspherical coefficient A6, the eighth-order aspherical coefficient A8, and the tenth-order aspherical coefficient A1. 10 12th order aspherical coefficient A 12 Fourteenth-order aspherical coefficient A 14 Sixteenth-order aspherical coefficient A 16 18th order aspherical coefficient A 18 and the 20th order aspherical coefficient A 20 As shown in Table 5 below.

[0075] Surf 4 5 6 7 8 9 K -0.054 -1.994 0.423 -8.753 0.106 -0.086 <![CDATA[A4]]> 6.69E-09 -2.64E-05 7.67E-04 1.10E-03 -7.31E-04 9.94E-09 <![CDATA[A6]]> -2.92E-07 -1.48E-06 1.63E-05 7.71E-06 6.59E-06 -1.44E-10 <![CDATA[A8]]> -7.28E-08 -1.24E-08 -1.14E-06 -1.11E-07 -5.38E-07 -4.16E-12 <![CDATA[A 10 ]]> 1.57E-09 4.57E-10 2.90E-08 -6.38E-09 3.29E-08 -4.14E-14 <![CDATA[A 12 ]]> -1.75E-11 -1.30E-12 -4.59E-10 2.57E-12 -1.27E-09 2.52E-16 <![CDATA[A 14 ]]> 1.07E-13 -9.89E-15 4.66E-12 3.06E-12 2.93E-11 2.56E-17 <![CDATA[A 16 ]]> -2.66E-16 -6.41E-17 -2.86E-14 -4.06E-14 -4.01E-13 9.74E-19 <![CDATA[A 18 ]]> 1.10E-19 -1.41E-19 9.64E-17 1.78E-16 2.97E-15 2.89E-20 <![CDATA[A 20 ]]> -3.21E-21 5.56E-21 -1.44E-19 1.72E-19 -1.00E-17 6.47E-22

[0076] Table 5

[0077] Combination Figure 2 As shown in Tables 1, 4 and 5 above, the eyepiece lens of this embodiment has the characteristics of an exit pupil distance of 45mm and a back focal distance BFL ≥ 6.5mm. While meeting diverse usage scenarios, it leaves sufficient working distance for human eye safety, and at the same time reserves space for the assembly and focusing of optical components, avoiding mechanical interference that could affect the performance of the eyepiece lens.

[0078] Example 3

[0079] See Figure 3 In this embodiment, along the optical axis from the object side to the image side, the first lens L1 is a convex-convex lens, the second lens L2 is a convex-concave lens, the third lens L3 is a concave-concave lens, and the fourth lens L4 is a convex-convex lens. The first lens L1 is a glass lens, while the second lens L2, the third lens L3, and the fourth lens L4 are all plastic lenses.

[0080] The relevant parameters of each lens in the eyepiece lens of this embodiment include: surface number (Surf), surface type (Type), radius of curvature (Radius), thickness (Thickness), refractive index of the material (Nd), and Abbe number (Vd), as shown in Table 6 below.

[0081]

[0082] Table 6

[0083] The aspherical coefficients of each aspherical lens in the eyepiece lens of this embodiment include: the quadratic surface constant K, the fourth-order aspherical coefficient A4, the sixth-order aspherical coefficient A6, the eighth-order aspherical coefficient A8, and the tenth-order aspherical coefficient A1. 10 12th order aspherical coefficient A 12 Fourteenth-order aspherical coefficient A 14 Sixteenth-order aspherical coefficient A 16 18th order aspherical coefficient A18 and the 20th order aspherical coefficient A 20 As shown in Table 7 below.

[0084] Surf 4 5 6 7 8 9 K 0.022 0.217 -0.556 -3.100 0.087 6.003 4 4.07E-05 6.33E-05 7.97E-04 8.46E-04 -1.66E-04 5.44E-04 6 -3.14E-07 -2.18E-06 1.68E-05 7.51E-06 -5.23E-06 -2.50E-05 8 -8.09E-08 -2.56E-08 -1.14E-06 -1.24E-07 -4.69E-07 5.73E-07 10 1.61E-09 4.05E-10 2.89E-08 -7.16E-09 3.31E-08 -1.06E-08 12 -1.74E-11 -1.06E-12 -4.59E-10 9.45E-12 -1.31E-09 1.70E-10 14 1.07E-13 -2.49E-15 4.65E-12 3.10E-12 3.01E-11 -1.06E-12 16 -2.83E-16 1.14E-17 -2.86E-14 -3.95E-14 -4.02E-13 2.79E-15 18 -4.32E-20 1.70E-20 9.66E-17 1.93E-16 3.01E-15 -8.03E-17 20 0.00E+00 0.00E+00 -1.37E-19 -5.75E-19 -1.02E-17 5.46E-19

[0085] Table 7

[0086] Combination Figure 3 As shown in Tables 1, 6 and 7 above, the eyepiece lens of this embodiment has the characteristics of an exit pupil distance of 45mm and a back focal distance BFL ≥ 6.5mm. While meeting diverse usage scenarios, it leaves sufficient working distance for human eye safety, and at the same time, it reserves space for the assembly and focusing of optical components to avoid mechanical interference that would affect the performance of the eyepiece lens.

[0087] Example 4

[0088] See Figure 4 In this embodiment, along the optical axis from the object side to the image side, the first lens L1 is a convex-convex lens, the second lens L2 is a convex-concave lens, the third lens L3 is a concave-concave lens, and the fourth lens L4 is a convex-convex lens. The first lens L1 is a glass lens, while the second lens L2, the third lens L3, and the fourth lens L4 are all plastic lenses.

[0089] The relevant parameters of each lens in the eyepiece lens of this embodiment include: surface number (Surf), surface type (Type), radius of curvature (Radius), thickness (Thickness), refractive index of the material (Nd), and Abbe number (Vd), as shown in Table 8 below.

[0090]

[0091] Table 8

[0092] The aspherical coefficients of each aspherical lens in the eyepiece lens of this embodiment include: the quadratic surface constant K, the fourth-order aspherical coefficient A4, the sixth-order aspherical coefficient A6, the eighth-order aspherical coefficient A8, and the tenth-order aspherical coefficient A1. 10 12th order aspherical coefficient A 12 Fourteenth-order aspherical coefficient A 14 Sixteenth-order aspherical coefficient A 16 18th order aspherical coefficient A 18 and the 20th order aspherical coefficient A 20 As shown in Table 9 below.

[0093]

[0094]

[0095] Table 9

[0096] Combination Figure 4 As shown in Tables 1, 8 and 9 above, the eyepiece lens of this embodiment has the characteristics of an exit pupil distance of 45mm and a back focal distance BFL ≥ 6.5mm. While meeting diverse usage scenarios, it leaves sufficient working distance for human eye safety, and at the same time, it reserves space for the assembly and focusing of optical components to avoid mechanical interference that would affect the performance of the eyepiece lens.

[0097] Example 5

[0098] See Figure 5 In this embodiment, along the optical axis from the object side to the image side, the first lens L1 is a convex-convex lens, the second lens L2 is a convex-concave lens, the third lens L3 is a concave-concave lens, and the fourth lens L4 is a convex-convex lens. The first lens L1 is a glass lens, while the second lens L2, the third lens L3, and the fourth lens L4 are all plastic lenses.

[0099] The relevant parameters of each lens in the eyepiece lens of this embodiment include: surface number (Surf), surface type (Type), radius of curvature (Radius), thickness (Thickness), refractive index of the material (Nd), and Abbe number (Vd), as shown in Table 10 below.

[0100]

[0101]

[0102] Table 10

[0103] The aspherical coefficients of each aspherical lens in the eyepiece lens of this embodiment include: the quadratic surface constant K, the fourth-order aspherical coefficient A4, the sixth-order aspherical coefficient A6, the eighth-order aspherical coefficient A8, and the tenth-order aspherical coefficient A1. 10 12th order aspherical coefficient A 12 Fourteenth-order aspherical coefficient A 14 Sixteenth-order aspherical coefficient A 16 18th order aspherical coefficient A 18 and the 20th order aspherical coefficient A 20 As shown in Table 11 below.

[0104] Surf 4 5 6 7 8 9 K -0.052 0.07807 -0.517 0.208 -0.197 5.400 <![CDATA[A4]]> 6.23E-05 9.34E-05 7.27E-04 9.37E-04 1.27E-06 2.60E-04 <![CDATA[A6]]> -1.38E-06 -2.72E-06 1.75E-05 4.08E-06 -1.10E-05 -1.80E-05 <![CDATA[A8]]> -7.25E-08 -2.46E-08 -1.13E-06 -1.42E-07 -2.86E-07 4.66E-07 <![CDATA[A 10 ]]> 1.62E-09 4.14E-10 2.89E-08 -4.99E-09 3.01E-08 -9.46E-09 <![CDATA[A 12 ]]> -1.72E-11 -7.75E-13 -4.61E-10 -4.92E-12 -1.25E-09 1.63E-10 <![CDATA[A 14 ]]> 1.03E-13 -3.25E-15 4.65E-12 2.87E-12 2.92E-11 -9.79E-13 <![CDATA[A 16 ]]> -2.84E-16 -6.41E-18 -2.86E-14 -3.80E-14 -3.94E-13 3.84E-16 <![CDATA[A 18 ]]> 7.51E-20 2.92E-20 9.72E-17 1.89E-16 2.98E-15 -7.88E-17 <![CDATA[A 20 ]]> 0.00E+00 0.00E+00 -1.41E-19 -4.45E-19 -9.98E-18 6.43E-19

[0105] Table 11

[0106] Combination Figure 5As shown in Tables 1, 10 and 11 above, the eyepiece lens of this embodiment has the characteristics of an exit pupil distance of 45mm and a back focal distance BFL ≥ 6.5mm. While meeting diverse usage scenarios, it leaves sufficient working distance for human eye safety, and at the same time, it reserves space for the assembly and focusing of optical components to avoid mechanical interference that would affect the performance of the eyepiece lens.

[0107] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An eyepiece lens, comprising: The system comprises four lenses of positive optical power arranged sequentially along the optical axis from the object side to the image side: a first lens (L1), a second lens (L2), a third lens (L3), and a fourth lens (L4). The total number of lenses with optical power is four. The system is characterized by the following features: The first lens (L1) is a convex-convex lens or a convex-concave lens; The second lens (L2) is a convex-concave lens; The third lens (L3) is a concave-concave lens; The fourth lens (L4) is a convex-convex lens; The back focal distance BFL of the eyepiece lens and the total focal length F of the eyepiece lens satisfy the condition: 0.23≤BFL / F≤0.

46.

2. The eyepiece lens according to claim 1, characterized in that, The focal length F1 of the first lens (L1) and the total focal length F of the eyepiece lens satisfy the condition: 1.48≤F1 / F≤1.

75.

3. The eyepiece lens according to claim 1, characterized in that, The focal length F2 of the second lens (L2) and the total focal length F of the eyepiece lens satisfy the condition: 1.25≤F2 / F≤2.

35.

4. The eyepiece lens according to claim 1, characterized in that, The focal length F3 of the third lens (L3) and the total focal length F of the eyepiece lens satisfy the condition: -0.72≤F3 / F≤-0.

48.

5. The eyepiece lens according to claim 1, characterized in that, The focal length F4 of the fourth lens (L4) and the total focal length F of the eyepiece lens satisfy the condition: 0.56≤F4 / F≤0.

74.

6. The eyepiece lens according to claim 1, characterized in that, The focal length F1 of the first lens (L1) and the focal length F2 of the second lens (L2) satisfy the condition: 0.64≤F1 / F2≤1.

35.

7. The eyepiece lens according to claim 1, characterized in that, The sag of the object side of the third lens (L3) at the maximum effective radius, the sag of the image side of the third lens (L3) at the maximum effective radius, and the center thickness D3 of the third lens (L3) satisfy the condition: 0.78≤(SAG31+SAG32) / D3≤4.

50.

8. The eyepiece lens according to claim 1, characterized in that, The radius of curvature R3 of the object side of the second lens (L2) and the radius of curvature R4 of the image side of the second lens (L2) satisfy the condition: 0.26≤R3 / R4≤0.

65.

9. The eyepiece lens according to claim 1, characterized in that, The radius of curvature R5 of the object side of the third lens (L3) and the radius of curvature R6 of the image side of the third lens (L3) satisfy the condition: -2.10≤R5 / R6≤-0.

50.

10. The eyepiece lens according to claim 1, characterized in that, The radius of curvature R7 of the object side of the fourth lens (L4) and the radius of curvature R8 of the image side of the fourth lens (L4) satisfy the condition: -0.52≤R7 / R8≤-0.

05.

11. The eyepiece lens according to claim 1, characterized in that, The center distance C12 from the image side of the first lens (L1) to the object side of the second lens (L2), the center distance C23 from the image side of the second lens (L2) to the object side of the third lens (L3), the center distance C34 from the image side of the third lens (L3) to the object side of the fourth lens (L4), and the center distance TL from the object side of the first lens (L1) to the image plane (IMA) of the eyepiece lens satisfy the condition: 0.05≤(C12+C23+C34) / TL≤0.

25.

12. The eyepiece lens according to claim 1, characterized in that, The center thickness D1 of the first lens (L1), the center thickness D2 of the second lens (L2), the center thickness D3 of the third lens (L3), the center thickness D4 of the fourth lens (L4), and the center distance TL from the object side of the first lens (L1) to the image plane (IMA) of the eyepiece lens satisfy the condition: 0.54≤(D1+D2+D3+D4) / TL≤0.

74.

13. The eyepiece lens according to claim 1, characterized in that, The distance TL from the object side of the first lens (L1) to the center of the image plane (IMA) of the eyepiece lens and the total focal length F of the eyepiece lens satisfy the condition: 1.28≤TL / F≤1.68.

Images