Objective optical system, objective system, and observation apparatus

Abstract

The utility model discloses an objective optical system, an objective system and observation equipment, and belongs to the technical field of optical systems. The objective optical system comprises a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens and a seventh lens, the object side surface of the first lens is a convex surface, the image side surface of the first lens is a convex surface, and light rays entering the first lens can be converged. The object side surface of the second lens is a convex surface, and the image side surface of the second lens is a concave surface; the object side surface of the third lens is a concave surface, and the image side surface of the third lens is a concave surface; the object side surface of the fourth lens is a convex surface, and the image side surface of the fourth lens is a convex surface; the object side surface of the fifth lens is a convex surface, and the image side surface of the fifth lens is a concave surface; the object side surface of the sixth lens is a convex surface, and the image side surface of the sixth lens is a convex surface; the object side surface of the seventh lens is a concave surface, and the image side surface of the seventh lens is a plane; the objective optical system provided by the utility model can meet the comprehensiveness of actual application requirements.

Description

Technical Field

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

[0002] The objective optical system can be an important component of a head-mounted low-light night vision device equipped with an image intensifier. The traditional objective optical system is generally composed of eight or more spherical lenses, which makes the length of the objective optical system longer, and in practical applications, makes the low-light night vision device bulky and not suitable for long-term wearing on the head, especially in situations where rapid movement or long-term use is required.

[0003] In addition, in the related art, when the effective cathode of the image intensifier is certain, a focal length of 25 mm or less is used to ensure that the field of view meets the requirements. However, too small a focal length will also reduce the action distance and viewing distance, limit the effectiveness of the low-light night vision device in long-distance observation, and at the same time, too small a focal length may also cause problems such as optical distortion, affecting the imaging quality. To make up for the decline in imaging quality caused by reducing the focal length, a correction lens needs to be introduced, which further makes the low-light night vision device bulky.

[0004] It can be seen that the traditional objective optical system is difficult to find a balance among lightweight, imaging quality, and viewing distance. Even if it performs well in one aspect, there are still deficiencies in meeting the comprehensiveness of actual application requirements. Utility Model Content

[0005] This application aims to at least solve the deficiencies in the traditional objective optical system in meeting the comprehensiveness of actual application requirements and being difficult to find a balance among lightweight, imaging quality, and viewing distance.

[0006] In a first aspect, this application provides an objective optical system, which sequentially includes, from the object side to the image side along the optical axis:

[0007] A first lens with positive optical power, the object side surface of the first lens is convex near the optical axis, and the image side surface of the first lens is convex near the optical axis;

[0008] A second lens with positive optical power, the object side surface of the second lens is convex near the optical axis, and the image side surface of the second lens is concave near the optical axis;

[0009] A third lens with negative optical power, the object side surface of the third lens is concave near the optical axis, and the image side surface of the third lens is concave near the optical axis;

[0010] A fourth lens with positive optical power, the object side surface of the fourth lens is convex near the optical axis, and the image side surface of the fourth lens is convex near the optical axis;

[0011] The fifth lens with a negative optical power, the object side of the fifth lens is convex near the optical axis, and the image side of the fifth lens is concave near the optical axis;

[0012] The sixth lens with a positive optical power, the object side of the sixth lens is convex near the optical axis, the image side of the sixth lens is convex near the optical axis, and the object side of the sixth lens is cemented to the image side of the fifth lens;

[0013] The seventh lens with a negative optical power, the object side of the seventh lens is concave near the optical axis, and the image side of the seventh lens is flat;

[0014] According to the objective optical system of the present application, the objective optical system provided by the present application has a lighter weight and a smaller length. The first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens and the seventh lens cooperate with each other, and can also achieve a larger field of view and a larger viewing distance, and the overall imaging effect is excellent, which can meet the comprehensiveness of actual application requirements.

[0015] According to an embodiment of the present application, the objective optical system satisfies the following conditions:

[0016] 0.79 < f1 / TTL < 1.12;

[0017] 1.82 < f2 / TTL < 2.17;

[0018] 5.9 < |r31 / r32| < 6.3;

[0019] 4.2 < |r41 / t4| < 4.7;

[0020] 0.22 < |r52 / TTL| < 0.31;

[0021] 1.32 < |f7 / r71| < 1.67;

[0022] Wherein, f1 represents the focal length of the first lens; TTL represents the distance from the object side of the first lens to the image plane of the objective optical system on the optical axis; f2 represents the focal length of the second lens; r31 represents the curvature radius of the object side of the third lens; r32 represents the curvature radius of the image side of the third lens; r41 represents the curvature radius of the object side of the fourth lens; t4 represents the central thickness of the fourth lens; r52 represents the curvature radius of the image side of the fifth lens; f7 represents the focal length of the seventh lens; r71 represents the curvature radius of the object side of the seventh lens.

[0023] According to an embodiment of the present application, the distance from the object side of the first lens to the image side of the seventh lens is less than 35 mm, so that the total optical focal length of the objective optical system is 27 mm.

[0024] According to an embodiment of the present application, the object side and the image side of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, and the seventh lens are both spherical surfaces.

[0025] According to an embodiment of the present application, the material of the first lens is crown glass, the material of the second lens is flint glass, the material of the third lens is flint glass, the material of the fourth lens is crown glass, the material of the fifth lens is flint glass, the material of the sixth lens is flint glass, and the material of the seventh lens is flint glass.

[0026] According to an embodiment of the present application, the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, and the seventh lens can move synchronously, and the distance between the object side of the first lens and the object surface of the objective optical system is greater than 250 mm.

[0027] According to an embodiment of the present application, the weights of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, and the seventh lens are less than 19.9 g.

[0028] In a second aspect, the present application provides an objective lens system, including the objective optical system described in any one of the above and an image intensifier;

[0029] The image intensifier is arranged along the optical axis direction and is disposed on one side of the image side of the seventh lens, and the distance between the AVG window of the image intensifier and the image side of the seventh lens is greater than 1.9 mm.

[0030] In a third aspect, the present application provides an observation device, including an objective lens system.

[0031] According to an embodiment of the present application, the observation device includes: a low-light night vision device.

[0032] One or more of the above technical solutions in the embodiments of the present application have at least one of the following technical effects:

[0033] The objective optical system provided by the present application has a lighter weight and a smaller length. The first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, and the seventh lens cooperate with each other, and can also achieve a larger field of view and viewing distance, and the overall imaging effect is excellent, which can meet the comprehensiveness of actual application requirements.

[0034] The additional aspects and advantages of the present application will be partially given in the following description, partially become obvious from the following description, or be understood through the practice of the present application. Description of the Drawings

[0035] 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:

[0036] Figure 1 is the lens serial number diagram of the objective optical system provided by the embodiment of the present application;

[0037] Figure 2 is the surface serial number diagram of the lenses of the objective optical system provided by the embodiment of the present application;

[0038] Figure 3 is the MTF curve diagram of the objective optical system embodiment of the present application;

[0039] Figure 4 is the relative illumination curve diagram of the objective optical system embodiment of the present application;

[0040] Figure 5 is the ray aberration diagram of the objective optical system embodiment of the present application.

[0041] Reference numerals:

[0042] 101, the first lens; 102, the second lens; 103, the third lens; 104, the fourth lens; 105, the fifth lens; 106, the sixth lens; 107, the seventh lens; 901, the AVG window of the image intensifier;

[0043] S1, the object side surface of the first lens; S2, the image side surface of the first lens; S3, the object side surface of the second lens; S4, the image side surface of the second lens; S5, the object side surface of the third lens; S6, the image side surface of the third lens; S7, the object side surface of the fourth lens; S8, the image side surface of the fourth lens; S9, the object side surface of the fifth lens; S10, the image side surface of the fifth lens; S11, the object side surface of the sixth lens; S12, the image side surface of the sixth lens; S13, the object side surface of the seventh lens; S14, the image side surface of the seventh lens. Detailed implementation manners

[0044] The embodiments of the present application will be described in detail below. Examples of the embodiments are shown in the 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 with reference to the drawings are exemplary only for explaining the present application and should not be construed as limiting the present application.

[0045] Reference is made below to Figures 1-5 to describe the objective optical system according to the embodiments of the present application.

[0046] The objective lens optical system sequentially includes, from the object side to the image side along the optical axis: a first lens 101 with positive optical power, a second lens 102 with positive optical power, a third lens 103 with negative optical power, a fourth lens 104 with positive optical power, a fifth lens 105 with negative optical power, a sixth lens 106 with positive optical power, and a seventh lens 107 with negative optical power.

[0047] The above lenses in the objective lens optical system should be coaxially arranged, and the common axis of the lenses is the optical axis of the objective lens optical system, and each lens can be installed in the lens barrel to form the lens of the observation device.

[0048] Each of the above lenses has an object side surface and an image side surface, where the object side surface is the surface of the lens facing the object side, and the image side surface is the surface of the lens facing the image side. At the same time, there is also an object plane and an image plane in the objective lens optical system. The object plane is the plane where the object is located, and the image plane is the plane where the image is formed in the objective lens optical system.

[0049] It should be understood that when it is described that a lens surface has a certain surface shape near the optical axis, that is, the lens surface has that surface shape near the optical axis.

[0050] The object side surface of the first lens 101 is convex near the optical axis, and the image side surface of the first lens 101 is convex near the optical axis, which is beneficial to converging the light rays incident on the first lens 101.

[0051] The object side surface of the second lens 102 is convex near the optical axis, and the image side surface of the second lens 102 is concave near the optical axis. The second lens 102 further converges the light rays, making the light rays smoothly enter at a reasonable angle, and at the same time can reduce aberration.

[0052] The object side surface of the third lens 103 is concave near the optical axis, and the image side surface of the third lens 103 is concave near the optical axis; the third lens 103 is used to diverge the light rays to offset the excessive converging effect of the first lens 101 and the second lens 102 before.

[0053] The object side surface of the fourth lens 104 is convex near the optical axis, and the image side surface of the fourth lens 104 is convex near the optical axis; the fourth lens 104 converges the light rays again, further correcting the light path, and helps to ensure the imaging quality of the objective lens optical system.

[0054] The object side surface of the fifth lens 105 is convex near the optical axis, and the image side surface of the fifth lens 105 is concave near the optical axis.

[0055] The object side surface of the sixth lens 106 is convex near the optical axis, the image side surface of the sixth lens 106 is convex near the optical axis, and the object side surface of the sixth lens 106 is glued to the image side surface of the fifth lens 105.

[0056] The fifth lens 105 and the sixth lens 106 are cemented to form a cemented lens group. On the one hand, this cemented lens group can effectively correct aberrations; on the other hand, it also eliminates the air gap between the fifth lens 105 and the sixth lens 106, avoiding the need for additional support structures that may be required between individual lenses, making the objective optical system more compact.

[0057] The object side of the seventh lens 107 is concave near the optical axis, and the image side of the seventh lens 107 is flat; the concave surface of the seventh lens 107 helps to control the remaining aberrations, and the flat surface of the seventh lens 107 reduces optical distortion and allows light to be transmitted to the image plane, ensuring clear imaging on the image plane.

[0058] The first lens 101, the second lens 102, the third lens 103, the fourth lens 104, the fifth lens 105, the sixth lens 106, and the seventh lens 107 cooperate with each other to achieve a larger field of view and viewing distance, and the overall imaging effect is excellent.

[0059] At the same time, the number of lenses is less than that of traditional objective optical systems, enabling the lightweight of the objective optical system.

[0060] It can be seen that the objective optical system provided by this application has a lighter weight and a smaller length. The first lens 101, the second lens 102, the third lens 103, the fourth lens 104, the fifth lens 105, the sixth lens 106, and the seventh lens 107 cooperate with each other, can also achieve a larger field of view and viewing distance, and the overall imaging effect is excellent, meeting the comprehensiveness of actual application requirements.

[0061] In some embodiments, the objective optical system satisfies the following conditions:

[0062] 0.79 < f1 / TTL < 1.12;

[0063] Among them, f1 represents the focal length of the first lens 101; TTL represents the distance from the object side of the first lens 101 to the image plane of the objective optical system on the optical axis. It can ensure that the light converges moderately after entering the first lens 101, making it easier for the subsequent lenses to correct aberrations and improving the imaging quality.

[0064] 1.82 < f2 / TTL < 2.17;

[0065] Among them, f2 represents the focal length of the second lens 102; TTL represents the distance from the object side of the first lens 101 to the image plane of the objective optical system on the optical axis. It can ensure that the light converges moderately when passing through the second lens 102, thereby correcting aberrations.

[0066] 5.9 < |r31 / r32| < 6.3;

[0067] Among them, r31 represents the radius of curvature of the object side surface of the third lens 103; r32 represents the radius of curvature of the image side surface of the third lens 103. By controlling the ratio of r31 and r32, the system can optimize the imaging effect of the off-axis field of view while maintaining the imaging quality at the center.

[0068] 4.2 < |r41 / t4| < 4.7;

[0069] Among them, r41 represents the radius of curvature of the object side surface of the fourth lens 104; t4 represents the central thickness of the fourth lens 104. An appropriate ratio of r41 / t4 can help optimize the imaging quality.

[0070] 0.22 < |r52 / TTL| < 0.31;

[0071] Among them, r52 represents the radius of curvature of the image side surface of the fifth lens 105; TTL represents the distance from the object side surface of the first lens 101 to the image plane of the objective optical system on the optical axis. By controlling the ratio of r52 / TTL, the converging or diverging effect of light when passing through the fifth lens 105 can be finely adjusted, which can help correct the aberration in the system and ensure the image quality during final imaging.

[0072] 1.32 < |f7 / r71| < 1.67;

[0073] Among them, f7 represents the focal length of the seventh lens 107; r71 represents the radius of curvature of the object side surface of the seventh lens 107. By controlling the ratio of the focal length of the seventh lens 107 to the radius of curvature of the object side surface of the seventh lens 107, it can ensure that before the light reaches the image plane, it is corrected by the seventh lens 107 to improve the image quality during final imaging.

[0074] In actual implementation, the distance from the object side surface of the first lens to the image side surface of the seventh lens is less than 35 mm, so that the total optical focal length of the objective optical system is 27 mm.

[0075] In actual implementation, the total weight of the first lens 101, the second lens 102, the third lens 103, the fourth lens 104, the fifth lens 105, the sixth lens 106, and the seventh lens 107 is less than 19.9 g.

[0076] As Figure 1 shown, in some embodiments, the object side surfaces and the image side surfaces of the first lens 101, the second lens 102, the third lens 103, the fourth lens 104, the fifth lens 105, the sixth lens 106, and the seventh lens 107 are all spherical surfaces.

[0077] In the related art, in order to obtain better imaging quality, one or two aspherical lenses are used to correct the off-axis field aberration, which leads to an increase in the cost of the objective optical system and also greatly increases the difficulty of assembly and alignment.

[0078] All the lenses in this embodiment are spherical, which saves the cost of the objective optical system, greatly reduces the difficulty of optical processing and manufacturing, and has more engineering practice value.

[0079] In actual implementation, the first lens 101 can be a positive meniscus lens, and the material is crown glass. The second lens 102 can be a positive meniscus lens, and the material is flint glass. The third lens 103 can be a biconcave lens, and the material is flint glass. The fourth lens 104 can be a biconvex lens, and the material is crown glass. The fifth lens 105 can be a negative meniscus lens, and the material is flint glass. The sixth lens 106 can be a biconvex lens, and the material is flint glass. The seventh lens 107 can be a plano-concave lens, and the material is flint glass.

[0080] All the lenses in this embodiment are designed with spherical surfaces and are all conventional optical glasses without special and expensive rare glass materials, and the optical length of the system also has certain advantages compared with similar products.

[0081] On the premise of the above embodiments, the present application will be further described with a specific embodiment. In 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 table of this embodiment.

[0082] Figure 2 It is a surface serial number diagram of the lenses of the objective optical system provided by the embodiment of the present application.

[0083] The objective optical system sequentially includes, along the optical axis from the object side to the image side: a first lens 101, a second lens 102, a third lens 103, a fourth lens 104, a fifth lens 105, a sixth lens 106, and a seventh lens 107.

[0084] The object side surface S1 of the first lens 101 is convex near the optical axis, and the image side surface S2 of the first lens 101 is convex near the optical axis;

[0085] The object side surface S3 of the second lens 102 is convex near the optical axis, and the image side surface S4 of the second lens 102 is concave near the optical axis;

[0086] The object side surface S5 of the third lens 103 is concave near the optical axis, and the image side surface S6 of the third lens 103 is concave near the optical axis;

[0087] The object side surface S7 of the fourth lens 104 is convex near the optical axis, and the image side surface S8 of the fourth lens 104 is convex near the optical axis;

[0088] The object side surface S9 of the fifth lens 105 is convex near the optical axis, and the image side surface S10 of the fifth lens 105 is concave near the optical axis; the object side surface S10 of the sixth lens 106 is convex near the optical axis, and the image side surface S10 of the fifth lens 105 is cemented to the object side surface S10 of the sixth lens 106.

[0089] The image side surface S11 of the sixth lens 106 is convex near the optical axis.

[0090] The object side surface S12 of the seventh lens 107 is concave near the optical axis, and the image side surface S13 of the seventh lens 107 is flat.

[0091] Table 1 shows the parameters of each lens of the objective optical system.

[0092] Table 1

[0093]

[0094]

[0095] Among them, Table 1 shows the specific parameters of the objective optical system described in this embodiment.

[0096] In this embodiment, an objective optical system with a short focal length of 27 mm, an F number of 1.2, and a full field of view of 40° can be obtained. The length from the object side surface S1 of the first lens 101 to the image side surface S13 of the seventh lens 107 of the objective optical system is 34.4 mm, the weight is 19.8 g, and the maximum aperture is 23.4 mm.

[0097] Next, the imaging quality of the objective optical system in this embodiment will be introduced.

[0098] Figure 3 It is the MTF curve graph of the objective optical system embodiment of this embodiment. MTF (Modulation Transfer Function) can comprehensively reflect the imaging quality of the optical system. The smoother the MTF curve shape and the higher the relative height to the X-axis, the better the imaging quality of the system.

[0099] In the figure: F1:Diff.Limit represents the diffraction limit curve of the objective optical system.

[0100] F1(ANG)0.000deg represents the MTF curve at the center of the field of view (half field angle is 0 degrees).

[0101] F2:T(ANG)5.000deg and F2:R(ANG)5.000deg respectively represent the MTF curves of the objective optical system in the radial and tangential directions under the condition that the semi-field angle is 5 degrees. T represents the tangential direction, and R represents the radial direction.

[0102] F3:T(ANG)10.000deg and F3:R(ANG)10.000deg represent the MTF curves of the objective optical system in the radial and tangential directions under the condition that the semi-field angle is 10 degrees. T represents the tangential direction, and R represents the radial direction.

[0103] F4:T(ANG)15.000deg and F4:R(ANG)15.000deg represent the MTF curves of the objective optical system in the radial and tangential directions under the condition that the semi-field angle is 15 degrees. T represents the tangential direction, and R represents the radial direction.

[0104] F5:T(ANG)20.000deg and F5:R(ANG)20.000deg represent the MTF curves of the objective optical system in the radial and tangential directions under the condition that the semi-field angle is 20 degrees. T represents the tangential direction, and R represents the radial direction.

[0105] 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.

[0106] Figure 4 It is the relative illumination curve graph of the objective optical system embodiment of this embodiment.

[0107] From Figure 4 it can be seen that the decline trend of the relative illumination of the objective optical system is relatively gentle, indicating that the system maintains a relatively uniform illumination distribution within most of the field angle range. Even at the field edge (semi-field angle of 20°), users can obtain relatively clear and uniformly bright images.

[0108] Figure 5 It is the ray aberration graph of the objective optical system embodiment of this embodiment.

[0109] From Figure 5 it can be seen that for most curves at the center of the field of view (0 field of view), the aberration values are less than ±0.01 mm, with good aberration control and excellent imaging quality; at the middle field of view (0.7 field of view), the aberration begins to increase, but generally still remains within a small range, indicating that the imaging quality of the system is still good when approaching the middle position of the field of view; at the field edge (1 field of view), the increase in aberration is relatively obvious, indicating that the imaging quality is relatively poor in the field edge region.

[0110] In the above embodiments of the present application, by reasonably selecting the first lens 101, the second lens 102, the third lens 103, the fourth lens 104, the fifth lens 105, the sixth lens 106 and the seventh lens 107, while ensuring excellent imaging quality in the central field of view, slightly sacrificing the imaging quality in the off-axis field of view, an optical structure of 6 groups and 7 lenses is obtained. On the premise of using a focal length of 27 mm, a standard 40-degree field of view of the system is achieved. When observed with the eyepiece adapted to the present application, there is no noticeable distortion, and the overall imaging effect is excellent.

[0111] In summary, one or more of the above technical solutions in the embodiments of the present application have at least one of the following technical effects:

[0112] First, compared with the traditional structure of 8 lenses or more, the optical structure of 6 groups and 7 lenses saves one lens, has the same image quality as the traditional one, can obtain good visual senses, and can reduce the volume and weight of the system, realizing miniaturization and light weight.

[0113] Second, the optical structure of 6 groups and 7 lenses uses pure spherical optical glass, and the optical materials are all common optical grade materials, with no more than 4 types, and the system tolerance is relatively loose. Compared with the traditional use of 1-2 aspherical lenses, the cost is lower, the assembly process is simple, the engineering implementation value is high, and it is suitable for mass production.

[0114] Third, the optical structure of 6 groups and 7 lenses achieves the same imaging effect with fewer lenses. At the same time, using fewer lenses can reduce light energy loss, thereby improving the contrast and transmittance of the system, making the imaging clearer and more transparent. In addition, on the premise of ensuring excellent imaging quality in the central field of view, slightly sacrificing the imaging quality in the off-axis field of view, on the premise of using a focal length of 27 mm, a standard 40° field of view of the system is achieved, and there is no somatic visual distortion during actual observation, greatly improving the visual imaging sense.

[0115] Fourth, the traditional objective optical system mostly uses a 25-mm focal length design. The longer the focal length, the farther the viewing distance and the working distance. And the present application uses a 27-mm focal length to achieve a longer viewing distance and working distance.

[0116] The present application also provides an objective lens system, including: an image intensifier and the objective lens optical system according to any one of the above embodiments. The image intensifier is arranged along the optical axis direction and is disposed on one side of the image side of the seventh lens 107. The distance between the AVG window 901 of the image intensifier and the image side of the seventh lens 107 is greater than 1.9 mm.

[0117] In this embodiment, the distance between the AVG window 901 of the image intensifier and the image side of the seventh lens 107 is greater than 1.9 mm. Such a design can ensure that after the light passes through the seventh lens 107, it can better align with the AVG window 901 of the image intensifier, ensuring the imaging effect.

[0118] In actual implementation, the first lens 101, the second lens 102, the third lens 103, the fourth lens 104, the fifth lens 105, the sixth lens 106, and the seventh lens 107 can move synchronously, and the object distance of the objective optical system is greater than or equal to 250 mm. This can achieve a large range of focusing ability while maintaining high-quality imaging effects and the consistency of the field of view.

[0119] This application also provides an observation device, which includes but is not limited to a low-light night vision device, such as a head-mounted low-light night vision device with an image intensifier, or various head-mounted low-light night vision products such as single-tube, binocular, and low-light thermal fusion.

[0120] The observation device includes the objective lens system described in any of the above embodiments. Since the objective lens system of the observation device can adopt all the technical solutions of the above embodiments, it has at least all the beneficial effects brought by the technical solutions of the above embodiments, which will not be elaborated one by one here.

[0121] 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.

[0122] Finally, it should also 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 to which this application belongs; the terms used in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including", "comprising" and "having" in this application and any other variants thereof 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 explicitly listed, or also includes elements inherent to such a process, method, article or device. Without further limitation, the element defined by the statement "including one..." does not exclude the existence of another identical element in the process, method, article or device including the said element. In this 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.

[0123] In the description of this specification, the descriptions referring to the 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 may be combined in any one or more embodiments or examples in a suitable manner.

[0124] Although the 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, and the scope of the present application is defined by the claims and their equivalents.

Claims

1. An objective optical system, characterized in that, It includes, in order from the object side to the image side along the optical axis: A first lens with positive optical power, the object side surface of the first lens is convex near the optical axis, and the image side surface of the first lens is convex near the optical axis; A second lens with positive optical power, the object side surface of the second lens is convex near the optical axis, and the image side surface of the second lens is concave near the optical axis; A third lens with negative optical power, the object side surface of the third lens is concave near the optical axis, and the image side surface of the third lens is concave near the optical axis; A fourth lens with positive optical power, the object side surface of the fourth lens is convex near the optical axis, and the image side surface of the fourth lens is convex near the optical axis; A fifth lens with negative optical power, the object side surface of the fifth lens is convex near the optical axis, and the image side surface of the fifth lens is concave near the optical axis; A sixth lens with positive optical power, the object side surface of the sixth lens is convex near the optical axis, the image side surface of the sixth lens is convex near the optical axis, and the object side surface of the sixth lens is cemented to the image side surface of the fifth lens; A seventh lens with negative optical power, the object side surface of the seventh lens is concave near the optical axis, and the image side surface of the seventh lens is flat.

2. The objective optical system according to claim 1, wherein The objective optical system satisfies the following conditions: 0.79 < f1 / TTL < 1.12; 1.82 < f2 / TTL < 2.17; 5.9＜|r31 / r32|＜6.3； 4.2＜|r41 / t4|＜4.7； 0.22 < |r52 / TTL| < 0.31; 1.32＜|f7 / r71|＜1.67； Wherein, f1 represents the focal length of the first lens; TTL represents the distance on the optical axis from the object side surface of the first lens to the image plane of the objective optical system; f2 represents the focal length of the second lens; r31 represents the curvature radius of the object side surface of the third lens; r32 represents the curvature radius of the image side surface of the third lens; r41 represents the curvature radius of the object side surface of the fourth lens; t4 represents the central thickness of the fourth lens; r52 represents the curvature radius of the image side surface of the fifth lens; f7 represents the focal length of the seventh lens; r71 represents the curvature radius of the object side surface of the seventh lens.

3. The objective optical system according to claim 1, characterized in that, The distance from the object side surface of the first lens to the image side surface of the seventh lens is less than 35 mm, so that the total optical focal length of the objective optical system is 27 mm.

4. The objective optical system according to claim 1, wherein The object side surfaces and image side surfaces of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens and the seventh lens are all spherical surfaces.

5. The objective optical system according to claim 4, characterized in that, The materials of the first lens and the fourth lens are crown glass; the materials of the second lens, the third lens, the fifth lens, the sixth lens and the seventh lens are flint glass.

6. The objective optical system according to claim 1, wherein The weights of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens and the seventh lens are less than 19.9 g.

7. An objective lens system, characterized in that, It includes the objective optical system according to any one of claims 1-6 and an image intensifier; The image intensifier is arranged along the optical axis direction and is disposed on one side of the image side of the seventh lens.

8. The objective lens system according to claim 7, characterized in that, The distance between the AVG window of the image intensifier and the image side of the seventh lens is greater than 1.9 mm.

9. The objective lens system according to claim 7, characterized in that, The first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens and the seventh lens can move synchronously, and the object distance of the objective optical system is greater than or equal to 250 mm.

10. An observation device, characterized in that, It includes the objective optical system according to any one of claims 7-9.

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