Eyepiece optical system, eyepiece system, and observation apparatus

Abstract

The utility model discloses an eyepiece optical system, an eyepiece system and observation equipment, and belongs to the technical field of optics. The eyepiece optical system comprises a first lens, a glued lens group and a fourth lens which are sequentially arranged from an object plane to an image plane along the optical axis direction; the first lens is a positive meniscus lens, the surface, facing the object plane, of the first lens is a convex surface, and the surface, facing the image plane, of the first lens is a concave surface; the glued lens group has negative focal power, the surface, facing the object surface, of the glued lens group is a convex surface, and the surface, facing the image surface, of the glued lens group is a concave surface; the fourth lens is a biconvex lens; the concave surface of the first lens and the convex surface, facing the object surface, of the fourth lens are aspheric surfaces. The first lens, the cemented lens group and the fourth lens cooperate with each other, the convex surface of the first lens is designed to be an aspheric surface, the initial aberration of incident light can be better controlled, and the convex surface, facing the object surface, of the fourth lens is also an aspheric surface, so that the aberration can be further corrected, the distribution of the light at the exit pupil position is optimized, the exit pupil diameter is enlarged, and the imaging quality is improved.

Description

Technical Field

[0001] This application belongs to the field of optical technology, and particularly relates to an eyepiece optical system, an eyepiece system, and an observation device. Background Art

[0002] An eyepiece optical system is usually used together with a front objective lens to magnify the image formed by the objective lens, and can be used in various devices such as telescopes / microscopes, and is widely used in industries such as military, industrial instruments, security, and medical.

[0003] In low-light night vision scenarios, which are usually carried out under extremely low light (low light) conditions, the eyepiece optical system is usually used in combination with an image intensifier to amplify weak light signals, making night observation possible and clear. Since the above eyepiece optical system is designed for a single use and scenario, in other scenarios, such as on a sight, the imaging effect and user experience of this eyepiece optical system are poor.

[0004] That is, there is an urgent need for an eyepiece optical system with multiple uses to solve the problems of poor imaging effect and user experience. Utility Model Content

[0005] This application aims to at least solve the problems of poor imaging effect and user experience existing in the eyepiece optical system in the prior art.

[0006] In a first aspect, this application provides an eyepiece optical system, including: a first lens, a cemented lens group, and a fourth lens arranged in sequence from the object plane to the image plane along the optical axis direction;

[0007] The first lens is a positive meniscus lens, the surface of the first lens facing the object plane is convex, and the surface of the first lens facing the image plane is concave;

[0008] The cemented lens group has a negative focal power, the surface of the cemented lens group facing the object plane is convex, and the surface of the cemented lens group facing the image plane is concave;

[0009] The fourth lens is a biconvex lens;

[0010] Wherein, the concave surface of the first lens and the convex surface of the fourth lens facing the object plane are aspherical surfaces;

[0011] The air gap t34 between the cemented lens group and the fourth lens is adjustable.

[0012] According to an embodiment of this application, the distance between the convex surface of the first lens and the convex surface of the fourth lens facing the image plane is less than 24 mm; or, the air gap t34 between the cemented lens group and the fourth lens satisfies: 3.3 mm < t34 < 28.5 mm.

[0013] According to an embodiment of the present application, the focal length f1 of the first lens and the length TTL from the convex surface of the first lens to the image plane satisfy the following conditions:

[0014] 1.23 < |f1 / TTL| < 1.66.

[0015] According to an embodiment of the present application, the focal length f23 of the cemented lens group and the length TTL from the convex surface of the first lens to the image plane satisfy the following conditions:

[0016] 2.8 < |f23 / TTL| < 4.2.

[0017] According to an embodiment of the present application, the cemented lens group includes: a second lens and a third lens arranged in sequence from the object plane to the image plane along the optical axis, and the second lens and the third lens are cemented together; the second lens is a positive meniscus lens, and the third lens is a negative meniscus lens.

[0018] According to an embodiment of the present application, the first lens, the second lens, and the fourth lens are crown glass lenses, and the third lens is a flint glass lens; the total weight of the first lens, the second lens, the third lens, and the fourth lens is less than 26 g.

[0019] According to an embodiment of the present application, the total optical focal length f of the eyepiece optical system is between 27 mm and 40 mm.

[0020] In a second aspect, the present application provides an eyepiece system, which includes: the eyepiece optical system according to any one of the above embodiments;

[0021] And,

[0022] An image intensifier or a display screen disposed along the optical axis on the image plane side of the fourth lens.

[0023] According to an embodiment of the present application, when the eyepiece system includes the image intensifier, the distance between the convex surface of the fourth lens facing the image plane and the anode surface of the image intensifier is greater than 14 mm; the distance between the convex surface of the first lens and the convex surface of the fourth lens facing the image plane is less than 24 mm; so that the total optical focal length f of the eyepiece optical system is equal to 27 mm;

[0024] When the eyepiece system includes the display screen, the air gap t34 between the cemented lens group and the fourth lens is adjustable and satisfies 3.3 mm < t34 < 28.5 mm, so that the total optical focal length f of the eyepiece optical system continuously varies between 33 mm and 40 mm.

[0025] In a third aspect, the present application provides an observation device, which includes: the eyepiece system described in any of the above embodiments.

[0026] One or more of the above technical solutions in the embodiments of the present application have at least one of the following technical effects:

[0027] The first lens, the cemented lens group, and the fourth lens cooperate with each other. The convex surface of the first lens is designed as an aspherical surface, which can better control the initial aberration of the incident light and guide the light into the cemented lens group. The cemented lens group can further regulate the path of the incident light to ensure that the light is corrected before entering the fourth lens, providing a basis for the final imaging. The fourth lens is a biconvex lens, and the convex surface of the fourth lens facing the object surface is also an aspherical surface. This can further correct the aberration, optimize the distribution of light at the exit pupil position, expand the exit pupil diameter, improve the imaging quality, reduce or avoid losing the observed target, and improve the user experience;

[0028] At the same time, the distance between the fourth lens and the cemented lens group is adjustable, enabling the eyepiece optical system to serve multiple purposes. In low-light night vision scenarios, it can be used in conjunction with an image intensifier to obtain clear images; in the sighting device usage scenario, adjusting the air gap realizes continuous variation of the focal length of the eyepiece optical system to meet the requirements of different eyepiece magnifications and improve the user experience.

[0029] Additional aspects and advantages of the present application will be given in part in the following description, become apparent in part from the following description, or be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The above and / or additional aspects and advantages of the present application will become apparent and be readily understood from the description of the embodiments in conjunction with the following drawings, where:

[0031] Figure 1 is a schematic structural diagram of the eyepiece optical system provided by an embodiment of the present application;

[0032] Figure 2 is a schematic structural diagram of the eyepiece optical system after the air gap t34 is changed in the embodiment of the present application;

[0033] Figure 3 is an MTF curve graph of the eyepiece optical system in the first embodiment when the exit pupil diameter is 10 mm;

[0034] Figure 4 is an MTF curve graph of the eyepiece optical system in the first embodiment when the exit pupil diameter is 18 mm;

[0035] Figure 5 is a chromatic aberration curve graph of the eyepiece optical system in the first embodiment;

[0036] Figure 6 is the aberration curve graph of the eyepiece optical system in the first embodiment;

[0037] Figure 7 is the structural schematic diagram of the eyepiece optical system in the second embodiment;

[0038] Figure 8 is the schematic diagram of the zooming method of the eyepiece optical system in the second embodiment;

[0039] Figure 9 is the MTF curve graph when the focal length of the eyepiece optical system in the second embodiment is 27 mm;

[0040] Figure 10 is the MTF curve graph when the focal length of the eyepiece optical system in the second embodiment is 33 mm;

[0041] Figure 11 is the MTF curve graph when the focal length of the eyepiece optical system in the second embodiment is 40 mm.

[0042] Reference signs:

[0043] 101, the first lens; S1, the convex surface of the first lens; S2, the concave surface of the first lens;

[0044] 102, the second lens; S3, the convex surface of the second lens; S4, the concave surface of the second lens;

[0045] 103, the third lens; S5, the convex surface of the third lens; S6, the concave surface of the third lens;

[0046] 104, the fourth lens; S7, the first convex surface of the fourth lens; S8, the second convex surface of the fourth lens;

[0047] Air gap t34. Detailed implementation manners

[0048] The embodiments of the present application will be described in detail below. Examples of the embodiments are shown in the accompanying drawings, where the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the accompanying drawings are exemplary and are only used to explain the present application and should not be construed as a limitation to the present application.

[0049] Reference will be made below to Figures 1 - 11 describe an eyepiece optical system, an eyepiece system, and an observation device according to an embodiment of the present application.

[0050] The eyepiece optical system includes: a first lens 101, a cemented lens group, and a fourth lens 104 arranged in sequence along the optical axis direction from the object surface to the image surface (Ima).

[0051] The object surface is the plane where the object is located in the eyepiece optical system, and the image surface (Ima) is the plane where the image is formed in the eyepiece optical system.

[0052] Among them, the first lens 101 is a positive meniscus lens. The surface of the first lens 101 facing the object surface is convex, and the surface of the first lens 101 facing the image surface is concave.

[0053] The convex surface of the first lens 101 is an aspherical surface, which can better control the initial aberration of the incident light and guide the light into the cemented lens group. The first lens 101 can reduce the imaging burden of the subsequent lenses.

[0054] The cemented lens group has a negative focal power. The surface of the cemented lens group facing the object surface is convex, and the surface of the cemented lens group facing the image surface is concave.

[0055] The cemented lens group can be formed by cementing two lenses, such as being formed by cementing the second lens 102 and the third lens 103 which will be described below. In this way, the reflection loss at the interface between the two lenses can be effectively reduced, and the overall light transmittance can be improved.

[0056] The fourth lens 104 is a biconvex lens. The convex surface of the fourth lens 104 facing the object surface is also an aspherical surface, which can further correct the aberration, effectively guide the light to the exit pupil position, optimize the distribution of the light at the exit pupil position, expand the exit pupil diameter, and improve the imaging quality.

[0057] Among them, the distance between the fourth lens 104 and the cemented lens group is adjustable, which can realize the continuous change of the focal length of the eyepiece optical system, so as to meet the requirements of using different eyepiece magnifications.

[0058] That is to say, for the eyepiece optical system provided in this application, the first lens 101, the cemented lens group and the fourth lens 104 cooperate with each other. The convex surface of the first lens 101 is designed as an aspherical surface, which can better control the initial aberration of the incident light and guide the light into the cemented lens group. The cemented lens group can further regulate the path of the incident light, ensure that the light is corrected before entering the fourth lens 104, and provide a basis for the final imaging. The fourth lens 104 is a biconvex lens, and the convex surface of the fourth lens 104 facing the object surface is also an aspherical surface. In this way, the aberration can be further corrected, the distribution of the light at the exit pupil position can be optimized, the exit pupil diameter can be expanded, the imaging quality can be improved, the imaging quality can be improved, the loss of the observed target can be reduced or avoided, and the user experience can be improved.

[0059] Meanwhile, the distance between the fourth lens 104 and the cemented lens group is adjustable, enabling the eyepiece optical system to serve multiple purposes. In low-light night vision scenarios, it can be used in conjunction with an image intensifier to obtain clear images. In sighting device usage scenarios, by adjusting the air gap t34, continuous variation of the focal length of the eyepiece optical system can be achieved, meeting the requirements for different eyepiece magnifications and enhancing the user experience.

[0060] Specifically, the distance between the convex surface of the first lens 101 and the convex surface of the fourth lens 104 facing the image plane is less than 24 mm; alternatively, the air gap t34 between the cemented lens group and the fourth lens 104 is adjustable and satisfies 3.3 mm < t34 < 28.5 mm.

[0061] In specific applications, the eyepiece optical system can have at least the following two different usage scenarios:

[0062] I. In low-light night vision scenarios: The exit pupil diameter of traditional low-light night vision systems is between 8 and 12 mm. Although it can meet the requirement of clear imaging within a certain eye movement range, alignment operations are still required during large jolts or when using binoculars handheld.

[0063] For the eyepiece optical system of this application, the concave surface of the first lens 101 and the convex surface of the fourth lens 104 facing the object plane are aspherical surfaces, capable of achieving an exit pupil diameter index of 18 mm, greatly improving the eye observation speed, enabling the user to obtain good observation effects, and thus, in cooperation with a night vision image intensifier, amplifying weak light signals to obtain clear images.

[0064] In actual implementation, the distance between the convex surface of the first lens 101 and the convex surface of the fourth lens 104 facing the image plane is less than 24 mm, so that the total optical focal length f of the eyepiece optical system is equal to 27 mm.

[0065] II. In sighting device usage scenarios, there is an air gap t34 between the cemented lens group and the fourth lens 104.

[0066] By adjusting the air gap t34, a high magnification is used when the user needs to observe nearby objects, and a low magnification is used when the user needs to observe distant objects to improve the imaging effect, meet the user's needs, and enhance the user experience.

[0067] In actual implementation, the air gap t34 between the cemented lens group and the fourth lens 104 is adjustable and satisfies 3.3 mm < t34 < 28.5 mm, so that the total optical focal length f of the eyepiece optical system varies continuously between 33 mm and 40 mm.

[0068] Such as Figure 1As shown, in actual implementation, the cemented lens group includes: a second lens 102 and a third lens 103 arranged in sequence along the optical axis from the object plane to the image plane. The second lens 102 and the third lens 103 are cemented together. The second lens 102 is a positive meniscus lens, and the third lens 103 is a negative meniscus lens.

[0069] Furthermore, the first lens 101, the second lens 102, and the fourth lens 104 are crown glass lenses, and the third lens 103 is a flint glass lens; the total weight of the first lens 101, the second lens 102, the third lens 103, and the fourth lens 104 is less than 26 g.

[0070] In some embodiments, the eyepiece optical system satisfies the following conditions:

[0071] 1.23 < |f1 / TTL| < 1.66;

[0072] Wherein, f1 represents the focal length of the first lens 101; TTL is the overall optical length of the eyepiece optical system, representing the length from the convex surface of the first lens 101 to the image plane.

[0073] Under this condition, an appropriate ratio of focal length to overall length can ensure good imaging while achieving a larger exit pupil diameter.

[0074] In some embodiments, the eyepiece optical system satisfies the following conditions:

[0075] 2.8 < |f23 / TTL| < 4.2;

[0076] Wherein, f23 represents the focal length of the cemented lens group, and TTL is the overall optical length of the eyepiece optical system, representing the length from the convex surface of the first lens 101 to the image plane.

[0077] Under this condition, spherical aberration and astigmatism can be reduced, enabling light to be evenly distributed at the exit pupil and achieving a larger exit pupil diameter.

[0078] In actual implementation, the weights of the first lens 101, the cemented lens group, and the fourth lens 104 are less than 26 g.

[0079] This application also provides an eyepiece system, including the eyepiece optical system of any one of the above; and an image intensifier or a display screen arranged along the optical axis on the image plane side of the fourth lens 104.

[0080] The eyepiece system may have two different structural forms:

[0081] One: The eyepiece system includes: an eyepiece optical system and an intensifier.

[0082] The distance between the convex surface of the fourth lens 104 facing the image plane and the anode surface of the image intensifier is greater than 14 mm; the distance between the convex surface of the first lens 101 and the convex surface of the fourth lens 104 facing the image plane is less than 24 mm; so that the total optical focal length f of the eyepiece optical system is equal to 27 mm;

[0083] In this embodiment, the eyepiece system can be used in a low-light night vision scenario. The image intensifier is arranged along the optical axis and is located on the side of the fourth lens 104 facing the image plane.

[0084] By limiting the distance between the first lens 101 and the fourth lens 104, the total length of the eyepiece system can be reduced, making it more compact; the distance between the convex surface of the fourth lens 104 facing the image plane and the anode surface of the image intensifier is greater than 14 mm, which can help optimize the light path, minimize the loss and distortion of light before entering the image intensifier, and ensure that the image intensifier can receive high-quality images.

[0085] Second: The eyepiece system includes: an eyepiece optical system and a display screen.

[0086] The air gap t34 between the cemented lens group and the fourth lens 104 is adjustable and satisfies 3.3 mm < t34 < 28.5 mm, so that the total optical focal length f of the eyepiece optical system varies continuously between 33 mm and 40 mm.

[0087] In this embodiment, the eyepiece system can be used in the scenario of a sight. The display screen is arranged along the optical axis and is located on the image plane. By adjusting the air gap t34, the continuous variation of the total optical focal length f of the eyepiece optical system is achieved, and clear image display can be provided at different magnifications while maintaining a large field of view.

[0088] The display screen includes but is not limited to an OLED display screen.

[0089] On the premise of the above embodiments, the present application will be further described in two specific embodiments below. In each of the following specific embodiments, the center thickness / spacing, curvature radius, and material selection of each lens in the eyepiece optical system are somewhat different. For specific differences, refer to the parameter tables of each embodiment.

[0090] First Embodiment

[0091] As Figure 1 shown, it is a schematic structural diagram of an eyepiece optical system provided by an embodiment of the present application.

[0092] The eyepiece optical system includes: a first lens 101, a second lens 102, a third lens 103, and a fourth lens 104 arranged in sequence along the optical axis from the object plane to the image plane.

[0093] Among them, the material of the first lens 101 is crown glass, the material of the second lens 102 is crown glass, the material of the third lens 103 is flint glass, and the material of the fourth lens 104 is crown glass.

[0094] The surface of the first lens 101 facing the object surface is a convex surface S1, and the surface of the first lens 101 facing the image surface is a concave surface S2.

[0095] The surface of the second lens 102 facing the object surface is a convex surface S3.

[0096] The surface of the second lens 102 facing the image surface is a concave surface S4, the surface of the third lens 103 facing the object surface is a convex surface S4, and the second lens 102 and the third lens 103 are mutually cemented to form a cemented lens group.

[0097] The surface of the third lens 103 facing the image surface is a concave surface S5.

[0098] The surface of the fourth lens 104 facing the object surface is a first convex surface S6, and the surface of the fourth lens 104 facing the image surface is a second convex surface S7.

[0099] Table 1 shows the specific parameters of the eyepiece optical system described in this embodiment.

[0100] Table 1

[0101] Surface number Radius of curvature Central thickness / Spacing Refractive index S1 21.5 5 1.52 S2 52.2 0.1 S3 14.9 5.5 1.49 S4 55.1 1 1.76 S5 17.2 1.2 S6 35.2 7 1.52 S7 -22.2 -

[0102] Among them, the S2 surface and the S6 surface are aspherical surfaces.

[0103] Table 2 shows the aspherical coefficients of the eyepiece optical system described in this embodiment.

[0104] Table 2

[0105]

[0106] In this embodiment, a specific implementation can obtain an eyepiece optical system with a total optical focal length of 27 mm, a maximum exit pupil diameter of 18 mm, and a full field of view of 40°. This eyepiece optical system can be used in low-light night vision scenarios.

[0107] Among them, the length from the convex surface S1 of the first lens 101 to the second convex surface S7 of the fourth lens 104 is 23.5 mm, the weight of the eyepiece optical system is 25.6 g, the maximum effective aperture of the eyepiece optical system is 28 mm, and the exit pupil distance is 25 mm.

[0108] Next, the imaging quality of the eyepiece optical system in this embodiment is introduced.

[0109] Figure 3 It is the MTF curve graph when the exit pupil diameter of the eyepiece optical system in this embodiment is 10 mm.

[0110] The MTF (Modulation Transfer Function) can comprehensively reflect the imaging quality of an optical system. The smoother the shape of the MTF curve and the higher its height relative to the X-axis, the better the imaging quality of the system.

[0111] In the figure: F1:T Diff.Limit and F1:R Diff.Limit represent the diffraction limit curves of the eyepiece optical system in the tangential (T) and radial (R) directions.

[0112] F1:T(ANG)0.000deg and F1:R(ANG)0.000deg represent the MTF curves of the field center (half field angle is 0 degrees) in the tangential and radial directions.

[0113] F2:T(ANG)5.000deg and F2:R(ANG)5.000deg represent the MTF curves of the eyepiece optical system in the tangential and radial directions at a half field angle of 5 degrees.

[0114] F3:T(ANG)10.000deg and F3:R(ANG)10.000deg represent the MTF curves of the eyepiece optical system in the tangential and radial directions at a half field angle of 10 degrees.

[0115] F4:T(ANG)15.000deg and F4:R(ANG)15.000deg represent the MTF curves of the eyepiece optical system in the tangential and radial directions at a half field angle of 15 degrees.

[0116] F5:T(ANG)20.000deg and F5:R(ANG)20.000deg represent the MTF curves of the eyepiece optical system in the tangential and radial directions at a half field angle of 20 degrees.

[0117] From Figure 3 it can be seen that even at relatively high spatial frequencies (such as 20 - 30 lp / mm), the MTF values of most curves are greater than or close to 0.4, indicating excellent imaging quality.

[0118] Figure 4 This is the MTF curve graph when the exit pupil diameter of the eyepiece optical system in this embodiment is 18 mm.

[0119] From Figure 4 it can be seen that even at relatively high spatial frequencies (such as 20 - 30 lp / mm), the MTF values of most curves are greater than or close to 0.4, indicating excellent imaging quality.

[0120] Figure 5 This is the longitudinal chromatic aberration curve graph of the eyepiece optical system in this embodiment.

[0121] FromFigure 5 It can be seen that within a relatively large half field of view angle (15° to 20°), the longitudinal chromatic aberration is small, the color distortion of the optical system is low, and the imaging is relatively accurate.

[0122] Figure 6 It is the aberration curve diagram of the eyepiece optical system in this embodiment.

[0123] From Figure 6 It can be seen that for most curves, the aberration values at the center of the field of view (0 field of view) and the intermediate field of view (0.7 field of view) are less than ±0.01 mm, with good aberration control and excellent imaging quality. At the edge of the field of view (1 field of view), the normalized clear aperture value is 0.5, and for most curves, the aberration values are close to ±0.02 mm, indicating that the aberration control is also good and the imaging quality is relatively excellent.

[0124] Second Embodiment

[0125] Based on the first embodiment, without changing the curvature radii, central thicknesses, aspheric parameters, materials, and front - rear position sequences of the first lens 101, the second lens 102, the third lens 103, and the fourth lens 104, only by changing the air gap t34 between the third lens 103 and the fourth lens 104 and the back focal length BFL, a continuous change in the focal length from 27 mm to 40 mm can be achieved.

[0126] In this embodiment, a specific implementation can obtain an eyepiece optical system with an exit pupil distance of 55 mm and an exit pupil diameter of 10 mm. At the same time, this eyepiece optical system can be assembled with an OLED display screen and used in the sighting device scenario.

[0127] The OLED display screen can be selected with a theoretical specification of 0.39 inches or a maximum size of 0.61 inches, and this embodiment does not make any restrictions.

[0128] Figure 7 It is the structural schematic diagram of the eyepiece optical system in this embodiment; Figure 8 It is the schematic diagram of the zooming method of the eyepiece optical system in this embodiment.

[0129] As Figure 7 and Figure 8 shown, the fourth lens 104 moves to the right along the optical axis, and the back focal length of this eyepiece optical system is changed in real - time, and the focal length of this eyepiece optical system continuously changes from 27 mm to 33 mm.

[0130] The fourth lens 104 continues to move to the right along the optical axis, and clear imaging can be achieved at any position during the change from 33 mm to 40 mm to meet the user's requirements for different focal lengths. At the same time, the focal length of this eyepiece optical system determines its magnification, and thus the magnification of this eyepiece optical system can be continuously changed according to the above - mentioned moving method.

[0131] Figure 9 It is the MTF curve graph when the focal length of the eyepiece optical system in this embodiment is 27 mm.

[0132] From Figure 9 it can be seen that even at relatively high spatial frequencies (such as 20 - 30 lp / mm), the MTF values of most curves are greater than or close to 0.4, and the imaging quality is excellent.

[0133] Figure 10 It is the MTF curve graph when the focal length of the eyepiece optical system in this embodiment is 33 mm.

[0134] From Figure 10 it can be seen that even at relatively high spatial frequencies (such as 20 - 30 lp / mm), the MTF values of most curves are greater than or close to 0.3, and the imaging quality is relatively excellent.

[0135] Figure 11 It is the MTF curve graph when the focal length of the eyepiece optical system in this embodiment is 40 mm.

[0136] From Figure 11 it can be seen that at medium - low spatial frequencies (5 - 15 lp / mm), the MTF values of most curves are greater than or close to 0.4. Even though the performance is slightly weaker at high spatial frequencies, in most practical applications, it can still provide good imaging quality.

[0137] In summary, one or more of the above - mentioned technical solutions in the embodiments of the present application have at least one of the following technical effects:

[0138] First, the eyepiece optical system has the characteristics of small volume and light weight. For example, the weights of the first lens, the cemented lens group, and the fourth lens are less than 26 g. Through reasonable layout and design, a volume smaller than that of a traditional eyepiece optical system is achieved. At the same time, by using lightweight optical materials, the system weight is further reduced.

[0139] Second, the eyepiece optical system has an ultra - large exit pupil diameter. For example, in the first embodiment, the maximum exit pupil diameter of the eyepiece optical system is 18 mm. The larger the exit pupil diameter, the more comfortable it feels when the human eye observes. Even if there is a small amount of non - coincidence between the human eye visual axis and the optical system optical axis, the observed target will not be lost, which can greatly improve the eye - on observation speed and enable the user to obtain good observation effects.

[0140] Third, the eyepiece optical system can serve multiple purposes. In addition to being used in low - light night vision scenarios, this eyepiece optical system can also be used in scenarios of sights with OLED displays, and can achieve clear imaging in both cases, obtaining a good user experience.

[0141] Meanwhile, the focal length of the eyepiece optical system can be continuously changed by adjusting the air gap t34, meeting the requirements of different eyepiece magnifications and improving the user experience.

[0142] In addition, the present application also provides an observation device, which includes but is not limited to low-light night vision devices or optoelectronic products such as sights, such as telescopes.

[0143] The observation device includes the eyepiece optical system described in any of the above embodiments. Since the eyepiece optical system of the observation device can adopt all the technical solutions of all the above embodiments, it at least has all the beneficial effects brought by the technical solutions of the above embodiments, which will not be elaborated here one by one.

[0144] In this specification, the various embodiments are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0145] Finally, it should be noted that unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field of the present application; the terms used in the description of the present application in the specification are only for the purpose of describing specific embodiments and are not intended to limit the present application; the terms "include", "comprise" and "have" and any other variants thereof in the present application are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements but also includes other elements not expressly listed, or also includes elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "including one..." does not exclude the existence of additional identical elements in the process, method, article or device including the said element. In the present application, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations.

[0146] In the description of this specification, the descriptions referring to terms "some embodiments", "the first embodiment", "the second embodiment", etc. mean that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0147] Although embodiments of the present application have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present application. The scope of the present application is defined by the claims and their equivalents.

Claims

1. An eyepiece optical system, characterized in that, Comprising: A first lens, a cemented lens group, and a fourth lens arranged in sequence along the optical axis from the object surface to the image surface; The first lens is a positive meniscus lens, the surface of the first lens facing the object surface is convex, and the surface of the first lens facing the image surface is concave; The cemented lens group has a negative optical power, the surface of the cemented lens group facing the object surface is convex, and the surface of the cemented lens group facing the image surface is concave; The fourth lens is specifically a biconvex lens; Wherein, the concave surface of the first lens and the convex surface of the fourth lens facing the object surface are aspherical surfaces; the air gap t34 between the cemented lens group and the fourth lens is adjustable.

2. The eyepiece optical system according to claim 1, characterized in that, The distance between the convex surface of the first lens and the convex surface of the fourth lens facing the image surface is less than 24 mm; or, the air gap t34 between the cemented lens group and the fourth lens satisfies: 3.3 mm < t34 < 28.5 mm.

3. The eyepiece optical system according to claim 1, characterized in that The focal length f1 of the first lens and the length TTL from the convex surface of the first lens to the image surface satisfy the following conditions: 1.23 < |f1 / TTL| < 1.

66.

4. The eyepiece optical system according to claim 1, characterized in that, The focal length f23 of the cemented lens group and the length TTL from the convex surface of the first lens to the image surface satisfy the following conditions: 2.8 < |f23 / TTL| < 4.

2.

5. The eyepiece optical system according to claim 1, wherein The cemented lens group includes: a second lens and a third lens arranged in sequence along the optical axis from the object surface to the image surface, and the second lens and the third lens are cemented together; the second lens is a positive meniscus lens, and the third lens is a negative meniscus lens.

6. The eyepiece optical system according to claim 5, characterized in that, The first lens, the second lens, and the fourth lens are crown glass lenses, and the third lens is a flint glass lens; the total weight of the first lens, the second lens, the third lens, and the fourth lens is less than 26 g.

7. The eyepiece optical system according to claim 1, characterized in that, The total optical focal length f of the eyepiece optical system is between 27 mm and 40 mm.

8. An eyepiece system, characterized in that, Comprising: The eyepiece optical system according to any one of claims 1 to 7; And An image intensifier or a display screen arranged along the optical axis on the image surface side of the fourth lens.

9. The eyepiece system according to claim 8, wherein When the eyepiece system includes the image intensifier, the distance between the convex surface of the fourth lens facing the image surface and the anode surface of the image intensifier is greater than 14 mm; the distance between the convex surface of the first lens and the convex surface of the fourth lens facing the image surface is less than 24 mm; so that the total optical focal length f of the eyepiece optical system is equal to 27 mm; When the eyepiece system includes the display screen, the air gap t34 between the cemented lens group and the fourth lens is adjustable and satisfies 3.3 mm < t34 < 28.5 mm, so that the total optical focal length f of the eyepiece optical system continuously varies between 33 mm and 40 mm.

10. An observation device, characterized in that, Comprising the eyepiece system according to any one of claims 8 - 9.

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