An eyepiece lens

Abstract

This invention discloses an eyepiece lens comprising an aperture stop, a first lens, a second lens, a third lens, a fourth lens, and a fifth lens arranged sequentially along the optical axis from the observation side to the display side. The first lens is a glass spherical lens with positive optical power, the second lens is a glass spherical lens with positive optical power, the third lens is a glass spherical lens with negative optical power, the fourth lens is a glass spherical lens with negative optical power, and the fifth lens is a glass spherical lens with positive optical power. This invention, through a design using an all-glass 5G structure and by combining lens materials and rationally allocating optical power, achieves an eyepiece lens with a long exit pupil distance, low distortion, low aberrations, and low cost, reaching an exit pupil distance of 48mm and distortion less than 1.5%.

Description

Technical Field

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

[0002] An eyepiece is a visual optical device used to observe the image formed by an optical system in front. It is a component of visual optical instruments such as telescopes and microscopes. Its main function is to magnify the real image obtained by the objective lens again, thereby forming a clear virtual image at the distance of clear vision. Therefore, its quality will ultimately affect the quality of the image. This requires the eyepiece to have high resolution, low distortion, and high magnification. Furthermore, if used in handheld observation devices, the eyepiece also needs to have a long exit pupil distance and a long back intercept.

[0003] Current eyepieces generally suffer from various problems, such as small exit pupil distance (typically less than 22mm), large distortion, and severe chromatic aberration. Therefore, the development of eyepieces with longer exit pupil distances, smaller distortion, and better image quality is particularly important. Furthermore, existing eyepieces with smaller aberrations often use aspherical lenses, which increases the difficulty of processing and manufacturing costs. Summary of the Invention

[0004] This invention provides an eyepiece lens to achieve an all-glass spherical eyepiece lens with a long interpupillary distance, low distortion, low aberration, and low cost.

[0005] This invention provides an eyepiece lens, comprising an aperture stop, a first lens, a second lens, a third lens, a fourth lens, and a fifth lens arranged sequentially along the optical axis from the observation side to the display side;

[0006] The first lens is a glass spherical lens with positive optical power, the second lens is a glass spherical lens with positive optical power, the third lens is a glass spherical lens with negative optical power, the fourth lens is a glass spherical lens with negative optical power, and the fifth lens is a glass spherical lens with positive optical power.

[0007] Optionally, the eyepiece lens satisfies the following condition: 1.47≤EX / f≤1.62;

[0008] Where EX is the axial distance from the aperture stop to the observation side surface of the first lens, and f is the effective focal length of the eyepiece lens.

[0009] Optionally, the eyepiece lens satisfies the following condition: 0.9 ≤ f5 / f ≤ 1.2;

[0010] Where f5 is the focal length of the fifth lens, and f is the effective focal length of the eyepiece lens.

[0011] Optionally, the eyepiece lens satisfies the following condition: 0.8 ≤ f2 / f5 ≤ 1.42;

[0012] Where f2 is the focal length of the second lens and f5 is the focal length of the fifth lens.

[0013] Optionally, the eyepiece lens satisfies the following condition: -2.41 ≤ f1 / f3 ≤ -1.81;

[0014] Where f1 is the focal length of the first lens and f3 is the focal length of the third lens.

[0015] Optionally, the eyepiece lens satisfies the following condition: -2.5≤R1 / R2≤-1.18;

[0016] Wherein, R1 is the radius of curvature of the observation side surface of the first lens, and R2 is the radius of curvature of the display side surface of the first lens.

[0017] Optionally, the eyepiece lens satisfies the following condition: 1.21≤R7 / R8≤1.38;

[0018] Wherein, R7 is the radius of curvature of the observation side surface of the fourth lens, and R8 is the radius of curvature of the display side surface of the fourth lens.

[0019] Optionally, the eyepiece lens satisfies the following condition: 0.36 ≤ BF / f ≤ 0.44;

[0020] Wherein, BF is the back focal distance of the eyepiece lens, and f is the effective focal length of the eyepiece lens.

[0021] Optionally, the eyepiece lens satisfies the following condition: 2.84 ≤ TTL / f ≤ 2.93;

[0022] Where TTL is the center distance from the observation side surface of the first lens to the image plane of the eyepiece lens, and f is the effective focal length of the eyepiece lens.

[0023] Optionally, the eyepiece lens satisfies the following condition: |vd4-vd5|≤23.55;

[0024] Wherein, vd4 is the Abbe number of the fourth lens, and vd5 is the Abbe number of the fifth lens.

[0025] In this embodiment of the invention, the first, second, and fifth lenses are configured to have positive optical power, while the third and fourth lenses are configured to have negative optical power. Essentially, this positive-positive-negative-negative-positive optical power distribution allows light to pass through the optical system more smoothly, balancing the distribution of aberrations and thus achieving better overall aberration correction, reducing distortion, and ensuring sufficiently clear image quality. Furthermore, using glass spherical lenses for all five lenses utilizes the properties of glass to reduce the sensitivity of the optical system's imaging process to temperature, minimizing lens deformation at different temperatures and ensuring clear imaging even in high and low temperature environments. Therefore, this embodiment of the invention ultimately achieves an eyepiece lens with a long exit pupil distance, low distortion, low aberrations, and low cost by designing an all-glass 5G structure and rationally allocating optical power through the combination of lens materials. The exit pupil distance reaches 48mm, and the distortion is less than 1.5%. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the structure of an eyepiece lens provided in Embodiment 1 of the present invention;

[0027] Figure 2 for Figure 1 The field curvature distortion curve of the eyepiece lens is shown.

[0028] Figure 3 for Figure 1 The image shows the ray fan diagram of the eyepiece lens;

[0029] Figure 4 for Figure 1 The defocus MTF diagram of the eyepiece lens is shown.

[0030] Figure 5 This is a schematic diagram of the structure of an eyepiece lens provided in Embodiment 2 of the present invention;

[0031] Figure 6 for Figure 5 The field curvature distortion curve of the eyepiece lens is shown.

[0032] Figure 7 for Figure 5 The image shows the ray fan diagram of the eyepiece lens;

[0033] Figure 8 for Figure 5 The defocus MTF diagram of the eyepiece lens is shown.

[0034] Figure 9 This is a schematic diagram of the structure of an eyepiece lens provided in Embodiment 3 of the present invention;

[0035] Figure 10 for Figure 9 The field curvature distortion curve of the eyepiece lens is shown.

[0036] Figure 11 for Figure 9 The image shows the ray fan diagram of the eyepiece lens;

[0037] Figure 12 for Figure 9 The MTF diagram of the defocused eyepiece lens is shown. Detailed Implementation

[0038] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.

[0039] The terminology used in the embodiments of this invention is for the purpose of describing specific embodiments only and is not intended to limit the invention. It should be noted that directional terms such as "upper," "lower," "left," and "right" described in the embodiments of this invention are used to describe the angles shown in the accompanying drawings and should not be construed as limiting the embodiments of this invention. Furthermore, in the context, it should be understood that when referring to an element being formed "on" or "below" another element, it can be formed not only directly on or below the other element, but also indirectly on or below it through intermediate elements. The terms "first," "second," etc., are used for descriptive purposes only and do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0040] The term "comprising" and its variations as used in this invention are open-ended, meaning "including but not limited to". The term "based on" means "at least partially based on". The term "one embodiment" means "at least one embodiment".

[0041] It should be noted that the concepts of "first" and "second" mentioned in this invention are only used to distinguish the corresponding contents and are not used to limit the order or interdependence.

[0042] It should be noted that the terms "a" and "a plurality of" used in this invention are illustrative rather than restrictive. Those skilled in the art should understand that, unless otherwise expressly indicated in the context, they should be understood as "one or more".

[0043] Figure 1 This is a schematic diagram of the structure of an eyepiece lens provided in Embodiment 1 of the present invention, for reference. Figure 1The eyepiece lens includes an aperture stop STO, a first lens 10, a second lens 20, a third lens 30, a fourth lens 40, and a fifth lens 50 arranged sequentially along the optical axis from the observation side to the display side; wherein, the observation side is the side on which the observer uses the eyepiece lens to observe, and the display side is the side on which the observed object is located.

[0044] The first lens 10 is a glass spherical lens with positive optical power, the second lens 20 is a glass spherical lens with positive optical power, the third lens 30 is a glass spherical lens with negative optical power, the fourth lens 40 is a glass spherical lens with negative optical power, and the fifth lens 50 is a glass spherical lens with positive optical power.

[0045] First, for optical lenses, optical power equals the difference between the image-side beam convergence and the object-side beam convergence; it characterizes the optical system's ability to deflect light. The larger the absolute value of optical power, the stronger the bending ability of light; the smaller the absolute value, the weaker the bending ability. 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., a lens group).

[0046] In the eyepiece lens provided in this embodiment, each lens can be fixed in a lens barrel. Figure 1 (not shown in the image) such as Figure 1 As shown, in this embodiment of the invention, the first lens 10, the second lens 20, and the fifth lens 50 are configured to have positive optical power, while the third lens 30 and the fourth lens 40 are configured to have negative optical power. Essentially, this positive-positive-negative-negative-positive optical power distribution allows light to pass through the optical system more smoothly, balancing the distribution of aberrations and thus achieving better overall aberration correction, reducing distortion, and ensuring sufficiently clear image quality. Furthermore, in this embodiment of the invention, all five lenses are made of glass spherical lenses. The properties of glass can be utilized to reduce the sensitivity of the optical system's imaging process to temperature, minimizing lens deformation at different temperatures and ensuring clear imaging even in high and low temperature environments. Therefore, this embodiment of the invention ultimately achieves an eyepiece lens with a long exit pupil distance, low distortion, low aberrations, and low cost by designing an all-glass 5G structure and rationally allocating optical power through the combination of lens materials. The exit pupil distance reaches 48mm, and the distortion is less than 1.5%.

[0047] In an optional embodiment, the eyepiece lens satisfies the following condition: 1.47≤EX / f≤1.62; where EX is the on-axis distance from the aperture stop STO to the observation side surface of the first lens 10, and f is the effective focal length of the eyepiece lens.

[0048] Specifically, since the magnification of an eyepiece is the ratio of the human eye's visual distance to its effective focal length, a smaller effective focal length results in a higher magnification. However, a smaller effective focal length leads to a larger field of view, which in turn increases the lens's off-axis aberration, negatively impacting image quality. Conversely, a larger effective focal length results in greater chromatic aberration, which also hinders image quality. Within these constraints, the requirements for a large exit pupil distance and high magnification can be satisfied relatively well.

[0049] In an optional embodiment, the eyepiece lens satisfies the following condition: 0.9 ≤ f5 / f ≤ 1.2; where f5 is the focal length of the fifth lens 50 and f is the effective focal length of the eyepiece lens.

[0050] In an optional embodiment, the eyepiece lens satisfies the following condition: 0.8 ≤ f2 / f5 ≤ 1.42; where f2 is the focal length of the second lens 20 and f5 is the focal length of the fifth lens 50.

[0051] In an optional embodiment, the eyepiece lens satisfies the following condition: -2.41≤f1 / f3≤-1.81; where f1 is the focal length of the first lens 10 and f3 is the focal length of the third lens 30.

[0052] Specifically, by constraining the focal length variation range of the lens, rationally allocating the relative relationship between the focal lengths of the lenses and the ratio of the focal length of a single lens to the focal length of the optical system, light can pass through the optical system more smoothly, maximizing the balance of aberration distribution, reducing the overall aberration of the optical system, and reducing the sensitivity of tolerances, thus giving the lens good manufacturability.

[0053] In an optional embodiment, the eyepiece lens satisfies the following condition: -2.5≤R1 / R2≤-1.18; where R1 is the radius of curvature of the observation side surface of the first lens 10, and R2 is the radius of curvature of the display side surface of the first lens 10.

[0054] In an optional embodiment, the eyepiece lens satisfies the following condition: 1.21≤R7 / R8≤1.38; where R7 is the radius of curvature of the observation side surface of the fourth lens 40, and R8 is the radius of curvature of the display side surface of the fourth lens 40.

[0055] Specifically, by controlling the surface curvature radius of the corresponding lens, the shape of the lens is essentially restricted. This can constrain the lens's ability to refract light, reduce the generation of large light refraction angles, and have a beneficial effect on the control of eyepiece lens aberrations, thus contributing to the improvement of the image quality of the optical system.

[0056] In an optional embodiment, the eyepiece lens satisfies the following condition: 0.36≤BF / f≤0.44; where BF is the back focal distance of the eyepiece lens and f is the effective focal length of the eyepiece lens.

[0057] Specifically, if the upper limit of this constraint is exceeded, the focal length of the eyepiece lens will become shorter, and the off-axis aberration of the system will increase, which is detrimental to image quality improvement. Conversely, if the lower limit of this constraint is exceeded, the back focal length of the optical system will become too short, which is not conducive to the installation and replacement of components. By constraining the above conditions, sufficient back focal length space can be reserved while ensuring image quality, thus avoiding mechanical interference.

[0058] In an optional embodiment, the eyepiece lens satisfies the following condition: 2.84≤TTL / f≤2.93; where TTL is the center distance from the observation side surface of the first lens 10 to the image plane of the eyepiece lens, and f is the effective focal length of the eyepiece lens.

[0059] Specifically, the above conditions are essentially restrictions on the total optical length of the eyepiece lens, which ensures that the eyepiece lens has a relatively small total optical length, making the lens more compact and helping to achieve miniaturization.

[0060] In an optional embodiment, the eyepiece lens satisfies the following condition: |vd4-vd5|≤23.55; where vd4 is the Abbe number of the fourth lens 40 and vd5 is the Abbe number of the fifth lens 50.

[0061] Specifically, the Abbe constant represents the dispersion capability of an optical medium. The above condition essentially restricts the Abbe constants of the last two lenses of the lens to be similar, thereby better controlling the chromatic aberration of the lens and ensuring higher image quality.

[0062] Continue to refer Figure 1 In this embodiment of the invention, the eyepiece lens may also be provided with a flat glass plate 60; the flat glass plate 60 is located on the side of the fifth lens 50 away from the fourth lens 40. The flat glass plate 60 can be protective glass or a filter with a filtering function.

[0063] Based on the same inventive concept, this invention provides three different specific embodiments, the optical power relationship and related physical and optical parameter design ranges of which are shown in Table 1:

[0064] Table 1 shows the relationship between the optical power of each lens and the design values ​​of related physical and optical parameters in the three embodiments.

[0065] Scope of protection Example 1 Example 2 Example 3 lower limit upper limit EX / f 1.5419 1.5389 1.5519 1.47 1.62 f5 / f 1.0925 0.9817 1.0824 0.9 1.2 f2 / f5 0.9456 1.3795 1.3336 0.8 1.42 f1 / f3 -2.2966 -2.0009 -1.888 -2.41 -1.81 R1 / R2 -1.2598 -1.7624 -2.4255 -2.5 -1.18 R7 / R8 1.2641 1.2826 1.3374 1.21 1.38 BF / f 0.4038 0.3892 0.4279 0.36 0.44 TTL / f 2.8946 2.8737 2.9059 2.84 2.93 |vd4-vd5| 12.8 14.3 15.1 23.55

[0066] like Figure 1 The parameter design values ​​of each lens in the eyepiece lens of Embodiment 1 are shown in Table 2:

[0067] Table 2 shows a design value for each lens in the eyepiece lens of Example 1.

[0068]

[0069] The surface numbers in Table 2 are assigned according to the surface sequence of each lens; “Object” represents the object plane of the eyepiece lens; “STO” represents the aperture stop of the eyepiece lens; “IMAGE” represents the image plane of the eyepiece lens; the radius of curvature represents the curvature of the lens surface, with a positive value indicating that the surface bends towards the image plane and a negative value indicating that the surface bends towards the object plane; the thickness represents the central axial distance between the current surface and the next surface; the refractive index represents the ability of the material between the current surface and the next surface to deflect light; a blank space indicates that the current position is air and the refractive index is 1; the Abbe number represents the dispersion characteristics of the material between the current surface and the next surface.

[0070] Figure 2 for Figure 1 The diagram shows the field curvature distortion curve of the eyepiece lens. In the coordinate system on the left side of the diagram, the horizontal axis represents the magnitude of the field curvature in mm; the vertical axis represents the normalized image height (unitless); where T represents the meridion and S represents the sagitta; from Figure 2 It can be seen that the eyepiece lens provided in this embodiment effectively controls the field curvature, that is, during imaging, the difference between the image quality at the center and the image quality at the periphery is small; in the coordinate system on the right, the horizontal axis represents the magnitude of distortion, in percentage; the vertical axis represents the normalized image height, which has no unit; from Figure 2 As can be seen, the distortion of the lens provided in this embodiment has been well corrected, and the imaging distortion is small.

[0071] Figure 3 for Figure 1 The image shows a ray fan diagram of the eyepiece lens, where the horizontal axis represents the beam aperture and the vertical axis represents the transverse aberration. Figure 2 It can be seen that the eyepiece lens closely matches the horizontal coordinate in each band under each field of view, indicating that the transverse aberration of each wavelength in the system is well corrected. At the same time, there is no obvious chromatic aberration in each band, indicating that the chromatic aberration of the system is also well corrected, thus ensuring that the eyepiece lens can achieve the high-resolution imaging requirements.

[0072] Figure 4 for Figure 1 The image shows the defocus MTF plot of the eyepiece lens, where the horizontal axis represents the amount of defocus before and after the image face, and the vertical axis represents the magnitude of the optical transfer function. Different curves represent the trend of optical transfer function changes with increasing defocus at different field-of-view positions (image heights of 0, 2 mm, 4 mm, 6 mm, and 8.64 mm). Figure 4 It can be seen that the optical transfer function of the system is relatively high at 50 lp / mm for each field of view, indicating that the optical system can achieve high-resolution imaging requirements.

[0073] Figure 5This is a schematic diagram of the structure of an eyepiece lens provided in Embodiment 2 of the present invention, for reference. Figure 5 The parameter design values ​​of each lens in the eyepiece lens of this embodiment are shown in Table 3:

[0074] Table 3 shows a design value for each lens in the eyepiece lens of Example 2.

[0075]

[0076] The surface numbers in Table 3 are assigned according to the surface sequence of each lens; “Object” represents the object plane of the eyepiece lens; “STO” represents the aperture stop of the eyepiece lens; “IMAGE” represents the image plane of the eyepiece lens; the radius of curvature represents the curvature of the lens surface, with a positive value indicating that the surface bends towards the image plane and a negative value indicating that the surface bends towards the object plane; the thickness represents the central axial distance between the current surface and the next surface; the refractive index represents the ability of the material between the current surface and the next surface to deflect light; a blank space indicates that the current position is air and the refractive index is 1; the Abbe number represents the dispersion characteristics of the material between the current surface and the next surface.

[0077] Figure 6 for Figure 5 The diagram shows the field curvature distortion curve of the eyepiece lens. In the coordinate system on the left side of the diagram, the horizontal axis represents the magnitude of the field curvature in mm; the vertical axis represents the normalized image height (unitless); where T represents the meridion and S represents the sagitta; from Figure 5 It can be seen that the eyepiece lens provided in this embodiment effectively controls the field curvature, that is, during imaging, the difference between the image quality at the center and the image quality at the periphery is small; in the coordinate system on the right, the horizontal axis represents the magnitude of distortion, in percentage; the vertical axis represents the normalized image height, which has no unit; from Figure 5 As can be seen, the distortion of the lens provided in this embodiment has been well corrected, and the imaging distortion is small.

[0078] Figure 7 for Figure 5 The image shows a ray fan diagram of the eyepiece lens, where the horizontal axis represents the beam aperture and the vertical axis represents the transverse aberration. Figure 7 It can be seen that the eyepiece lens closely matches the horizontal coordinate in each band under each field of view, indicating that the transverse aberration of each wavelength in the system is well corrected. At the same time, there is no obvious chromatic aberration in each band, indicating that the chromatic aberration of the system is also well corrected, thus ensuring that the eyepiece lens can achieve the high-resolution imaging requirements.

[0079] Figure 8 for Figure 5The image shows the defocus MTF plot of the eyepiece lens, where the horizontal axis represents the amount of defocus before and after the image face, and the vertical axis represents the magnitude of the optical transfer function. Different curves represent the trend of optical transfer function changes with increasing defocus at different field-of-view positions (image heights of 0, 2 mm, 4 mm, 6 mm, and 8.64 mm). Figure 8 It can be seen that the optical transfer function of the system is relatively high at 50 lp / mm for each field of view, indicating that the optical system can achieve high-resolution imaging requirements.

[0080] Figure 9 This is a schematic diagram of the structure of an eyepiece lens provided in Embodiment 3 of the present invention, for reference. Figure 9 The parameter design values ​​of each lens in the eyepiece lens of this embodiment three are shown in Table 4:

[0081] Table 4 shows a design value for each lens in the eyepiece lens of Example 3.

[0082]

[0083] The surface numbers in Table 4 are assigned according to the surface sequence of each lens; "Object" represents the object plane of the eyepiece lens; "STO" represents the aperture stop of the eyepiece lens; "IMAGE" represents the image plane of the eyepiece lens; the radius of curvature represents the curvature of the lens surface, with a positive value indicating that the surface bends towards the image plane and a negative value indicating that the surface bends towards the object plane; the thickness represents the central axial distance between the current surface and the next surface; the refractive index represents the ability of the material between the current surface and the next surface to deflect light; a blank space indicates that the current position is air and the refractive index is 1; the Abbe number represents the dispersion characteristics of the material between the current surface and the next surface.

[0084] Figure 10 for Figure 9 The diagram shows the field curvature distortion curve of the eyepiece lens. In the coordinate system on the left side of the diagram, the horizontal axis represents the magnitude of the field curvature in mm; the vertical axis represents the normalized image height (unitless); where T represents the meridion and S represents the sagitta; from Figure 10 It can be seen that the eyepiece lens provided in this embodiment effectively controls the field curvature, that is, during imaging, the difference between the image quality at the center and the image quality at the periphery is small; in the coordinate system on the right, the horizontal axis represents the magnitude of distortion, in percentage; the vertical axis represents the normalized image height, which has no unit; from Figure 10 As can be seen, the distortion of the lens provided in this embodiment has been well corrected, and the imaging distortion is small.

[0085] Figure 11 for Figure 9 The image shows a ray fan diagram of the eyepiece lens, where the horizontal axis represents the beam aperture and the vertical axis represents the transverse aberration. Figure 11It can be seen that the eyepiece lens closely matches the horizontal coordinate in each band under each field of view, indicating that the transverse aberration of each wavelength in the system is well corrected. At the same time, there is no obvious chromatic aberration in each band, indicating that the chromatic aberration of the system is also well corrected, thus ensuring that the eyepiece lens can achieve the high-resolution imaging requirements.

[0086] Figure 12 for Figure 9 The image shows the defocus MTF plot of the eyepiece lens, where the horizontal axis represents the amount of defocus before and after the image face, and the vertical axis represents the magnitude of the optical transfer function. Different curves represent the trend of optical transfer function changes with increasing defocus at different field-of-view positions (image heights of 0, 2 mm, 4 mm, 6 mm, and 8.64 mm). Figure 12 It can be seen that the optical transfer function of the system is relatively high at 50 lp / mm for each field of view, indicating that the optical system can achieve high-resolution imaging requirements.

[0087] Note that the above description is merely a preferred embodiment of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments, combinations, and substitutions can be made without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and may include many other equivalent embodiments without departing from the concept of the present invention, the scope of which is determined by the scope of the appended claims.

Claims

1. An eyepiece lens, characterized in that, It includes an aperture stop, a first lens, a second lens, a third lens, a fourth lens, and a fifth lens arranged sequentially along the optical axis from the observation side to the display side; the number of lenses with optical power in the eyepiece lens is 5; The first lens is a glass spherical lens with positive optical power, the second lens is a glass spherical lens with positive optical power, the third lens is a glass spherical lens with negative optical power, the fourth lens is a glass spherical lens with negative optical power, and the fifth lens is a glass spherical lens with positive optical power. The eyepiece lens satisfies the following condition: 1.47≤EX / f≤1.62; Where EX is the axial distance from the aperture stop to the observation side surface of the first lens, and f is the effective focal length of the eyepiece lens; The eyepiece lens satisfies the following condition: 2.84≤TTL / f≤2.93; Where TTL is the center distance from the observation side surface of the first lens to the image plane of the eyepiece lens, and f is the effective focal length of the eyepiece lens.

2. The eyepiece lens according to claim 1, characterized in that, The eyepiece lens satisfies the following condition: 0.9 ≤ f5 / f ≤ 1.2; Where f5 is the focal length of the fifth lens, and f is the effective focal length of the eyepiece lens.

3. The eyepiece lens according to claim 1, characterized in that, The eyepiece lens satisfies the following condition: 0.8 ≤ f2 / f5 ≤ 1.42; Where f2 is the focal length of the second lens and f5 is the focal length of the fifth lens.

4. The eyepiece lens according to claim 1, characterized in that, The eyepiece lens satisfies the following condition: -2.41≤f1 / f3≤-1.81; Where f1 is the focal length of the first lens and f3 is the focal length of the third lens.

5. The eyepiece lens according to claim 1, characterized in that, The eyepiece lens satisfies the following condition: -2.5≤R1 / R2≤-1.18; Wherein, R1 is the radius of curvature of the observation side surface of the first lens, and R2 is the radius of curvature of the display side surface of the first lens.

6. The eyepiece lens according to claim 1, characterized in that, The eyepiece lens satisfies the following condition: 1.21≤R7 / R8≤1.38; Wherein, R7 is the radius of curvature of the observation side surface of the fourth lens, and R8 is the radius of curvature of the display side surface of the fourth lens.

7. The eyepiece lens according to claim 1, characterized in that, The eyepiece lens satisfies the following condition: 0.36 ≤ BF / f ≤ 0.44; Wherein, BF is the back focal distance of the eyepiece lens, and f is the effective focal length of the eyepiece lens.

8. The eyepiece lens according to claim 1, characterized in that, The eyepiece lens satisfies the following condition: |vd4-vd5|≤23.55; Wherein, vd4 is the Abbe number of the fourth lens, and vd5 is the Abbe number of the fifth lens.

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