Endoscope optical system, endoscope, and endoscope system

Abstract

The present application provides an endoscopic optical system, an endoscope, and an endoscopic system, wherein the endoscopic optical system includes an aperture and a lens assembly; the lens assembly includes a target lens, and the target surface of the target lens is coated with a filter film layer; wherein the difference between the curvature of the target surface and the incident wavefront curvature of each field of view principal ray on the target surface is within a set curvature range, so that the incident angle of each field of view principal ray on the target surface of the target lens is less than or equal to the set angle. The present application effectively eliminates or reduces the adverse effects of wavelength drift while reducing the use of filters. Therefore, while reducing wavelength drift, the present application also has a simple structure and low cost for the endoscopic optical system.

Description

Technical Field

[0001] The present application relates to the technical field of endoscopes, and in particular to an endoscope optical system, an endoscope, and an endoscope system. Background Art

[0002] In some special applications, endoscope optical systems require the use of filters coated with filter films to filter out unwanted wavelengths. However, endoscopes generally have a large field of view. Given a certain thickness of the filter film, the larger the incident angle of the light, the longer the optical path of the light within the filter film, making it more likely that the filtered wavelength will drift toward longer wavelengths and the transmitted wavelength will drift toward shorter wavelengths, causing the endoscope image to appear blue at a larger field of view.

[0003] In order to solve the above problems, the related art reduces the impact of wavelength drift by improving the coating process of the filter film layer of the filter. However, the filter film layer is often obtained by superimposing multiple film layers. The coating process is complicated, and the filter film layer needs to be plated on a substrate to form a filter film, which increases the manufacturing cost. Summary of the Invention

[0004] The purpose of this application is to provide an endoscopic optical system, an endoscope, and an endoscopic system, which can reduce wavelength drift while having a simple structure and low cost. The specific scheme is as follows:

[0005] The present application provides an endoscope optical system, comprising an aperture and a lens assembly;

[0006] There is a target lens in the lens group, and the target surface of the target lens is coated with a filter film layer;

[0007] The difference between the curvature of the target surface and the incident wavefront curvature of each field chief ray of the target surface is within a set curvature range, so that the incident angle of each field chief ray on the target surface of the target lens is less than or equal to the set angle.

[0008] Optionally, the set angle is determined according to a maximum wavelength deviation allowed by the endoscope optical system.

[0009] Optionally, the set angle is less than or equal to 10.9°.

[0010] Optionally, the set angle is 0°.

[0011] Optionally, the lens group includes a first lens, a second lens, a third lens and a fourth lens arranged in sequence along the incident direction of light, and the aperture is arranged between the second lens and the third lens;

[0012] The first lens has negative refractive power and its image surface is concave; the second lens and the third lens both have positive refractive power and their object surfaces and image surfaces are convex; the fourth lens has negative refractive power and its object surface is concave;

[0013] The target lens is the second lens and / or the third lens;

[0014] When the target lens is the second lens, the target surface is the object surface of the second lens;

[0015] When the target lens is the third lens, the target surface is the image surface of the third lens.

[0016] Optionally, the endoscope optical system satisfies any one of the following relationships:

[0017] (1)3.4<|fa / f|<3.8, and 2.8<|fb / f|<3.2;

[0018] (2)0.5 <R1 / R2<0.8;

[0019] (3)5.0 <TTL / ImgH<6.5;

[0020] Wherein, f is the total focal length of the endoscope optical system; fa is the focal length of the optical front group consisting of the first lens and the second lens; fb is the focal length of the optical rear group consisting of the third lens and the fourth lens;

[0021] R1 is the curvature radius of the image surface of the first lens; R2 is the curvature radius of the object surface of the second lens;

[0022] TTL is the on-axis distance from the object plane to the image plane of the first lens; the ImgH is the maximum image height of the endoscope optical system.

[0023] Optionally, the lens group includes a fifth lens, a sixth lens, a seventh lens, and an eighth lens arranged in sequence along the light incident direction, and the aperture is arranged between the fifth lens and the sixth lens;

[0024] The fifth lens has negative refractive power and its image surface is concave; the sixth lens and the seventh lens both have positive refractive power and their image surfaces are convex; the eighth lens has negative refractive power and its object surface is concave;

[0025] The target lens is the sixth lens and / or the seventh lens;

[0026] When the target lens is the sixth lens, the target surface is the image surface of the sixth lens;

[0027] When the target lens is the seventh lens, the target surface is the image surface of the seventh lens.

[0028] Optionally, the filter film layer is an infrared filter film layer or an ultraviolet filter film layer.

[0029] The present application provides an endoscope, comprising: the endoscope optical system as described above.

[0030] The present application provides an endoscope system, comprising: the endoscope as described above.

[0031] The present application provides an endoscope optical system, comprising an aperture and a lens group; a target lens is present in the lens group, and a target surface of the target lens is coated with a filter film layer; wherein the difference between the curvature of the target surface and the curvature of the incident wavefront of each field of view main ray of the target surface is within a set curvature range, so that the incident angle of each field of view main ray on the target surface of the target lens is less than or equal to the set angle.

[0032] It can be seen that the lens group in the endoscope optical system of the present application includes a target lens, and the difference between the curvature of the target surface of the target lens and the curvature of the incident wavefront of each field of view chief ray on the target surface is within the set curvature range, so that the incident angle of each field of view chief ray on the target surface of the target lens is less than or equal to the set angle. Among them, the smaller the difference between the curvature of the target surface of the target lens and the curvature of the incident wavefront of each field of view chief ray on the surface, the smaller the incident angle of each field of view chief ray on the target surface, and the closer it is to vertical incidence. Therefore, when the filter film layer is coated on the target surface, the optical path of each field of view chief ray in the filter film layer can be close to the optical path of the vertically incident ray in the filter film layer, thereby reducing wavelength drift. Therefore, the present application does not need to adopt a complex coating process, can effectively eliminate or reduce the adverse effects of wavelength drift, and reduces production costs; at the same time, the present application also reduces the use of filters, making the structure of the endoscope optical system simpler; therefore, while reducing wavelength drift, the present application has a simple structure and low cost for the endoscope optical system.

[0033] The present application also provides an endoscope and an endoscope system, which have the above-mentioned beneficial effects and will not be described in detail here. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without any creative work.

[0035] Figure 1A schematic structural diagram of an endoscope optical system provided in an embodiment of the present application;

[0036] Figure 2 A schematic diagram of light incident on a lens in an endoscope optical system according to an embodiment of the present application;

[0037] Figure 3 A schematic structural diagram of another endoscope optical system provided in an embodiment of the present application;

[0038] Figure 4 A schematic structural diagram of another endoscope optical system provided in an embodiment of the present application;

[0039] Figure 5 A schematic structural diagram of another endoscope optical system provided in an embodiment of the present application. DETAILED DESCRIPTION

[0040] To make the purpose, technical solutions, and advantages of the embodiments of this application more clear, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0041] Currently, endoscope optical systems require the use of filters coated with filter films to filter out unwanted wavelengths in some special environments. However, endoscopes generally have a large field of view. Given a certain thickness of the filter film, the larger the incident angle of light, the longer the optical path in the filter film, and the more likely wavelength drift will occur, causing the endoscope image to appear blue, affecting endoscope performance and observation effects. Related technologies reduce wavelength shift when light is incident at a larger angle by changing the structure of the filter film. However, the filter film is often obtained by stacking multiple film layers, resulting in a complex coating process and high manufacturing costs. Furthermore, the filter film needs to be plated on a substrate to form a filter film, making the structure of the endoscope optical system even more complex.

[0042] In view of this, embodiments of the present application provide an endoscopic optical system, an endoscope including the endoscopic optical system, and an endoscopic system including the endoscope.

[0043] In which, there is a target lens in the lens group of the endoscope optical system, and the target surface of the target lens is coated with a filter film layer; wherein, the difference between the curvature of the target surface and the incident wavefront curvature of each field of view main light of the target surface is within a set curvature range, so that the incident angle of each field of view main light on the target surface is less than or equal to the set angle.

[0044] Based on this, after reaching the target surface of the target lens, the principal rays of each field of view of the endoscope optical system can all enter the target surface at an angle of incidence less than or equal to a set angle. Furthermore, because the filter film layer of approximately uniform thickness is coated on the target surface, the angle of incidence of each principal ray of view entering the filter film layer is substantially the same as the angle of incidence of each principal ray of view entering the target surface. Consequently, the optical path of each principal ray of view passing through the filter film layer coated on the target surface deviates slightly from the optical path of a perpendicularly incident ray (i.e., a ray with an incident angle of 0) passing through the filter film layer. This ensures that the optical path of each principal ray of view within the filter film layer is substantially consistent (or, the optical path difference is within an acceptable range). This reduces wavelength drift and improves endoscopic image quality. Furthermore, the endoscope optical system directly coats the filter film on the target lens, reducing the need for filters and simplifying the structure.

[0045] The endoscope optical system provided in the embodiments of the present application is described in detail below with reference to the accompanying drawings.

[0046] Please refer to Figure 1 , Figure 1 The schematic diagram of the structure of an endoscope optical system provided in an embodiment of the present application specifically includes: an aperture 100 and a lens group 300. Furthermore, a chip protection glass 200 may also be included.

[0047] The aperture 100 is a fixed aperture 100, used to limit the central width of the principal light rays entering each field of view of the endoscope optical system. Specifically, the aperture 100 can be a thin metal sheet with a hole, typically circular in shape, with its center coinciding with the optical axis and its plane perpendicular to the optical axis. Its location can be set according to the specific application of the endoscope optical system.

[0048] In some feasible implementations, the endoscope optical system further includes: chip protection glass 200. The chip protection glass 200 is mainly for the front protection of the chip. This embodiment does not make any specific limitations on this. The user can set it according to actual needs as long as it can achieve the purpose of this embodiment.

[0049] The lens group 300 is composed of a plurality of lenses, including a target lens (e.g., Figure 1 The second lens 320a shown in FIG. Figure 3 The third lens 330a shown in FIG. Figure 4 The sixth lens 320b shown in FIG. Figure 5Specifically, the target lens refers to a lens having a target surface, wherein the difference between the curvature of the target surface and the incident wavefront curvature of each field of view chief ray on the target surface (i.e., the incident wavefront curvature of each field of view chief ray of the endoscope optical system on the target surface) is within a set curvature range, so that the incident angle of each field of view chief ray on the target surface is less than or equal to the set angle. In other words, the difference between the curvature of a surface of at least one target lens in the endoscope optical system and the incident wavefront curvature of each field of view chief ray on the surface is minimized, and the incident angles of all field of view chief rays on the surface are less than or equal to the set angle.

[0050] The target surface of the target lens is coated with a filter layer 400. This filter layer 400 can be customized based on actual needs and includes, but is not limited to, an infrared filter layer, a UV filter layer, or a low-angle shift filter layer. It is understood that since the incident angle of all field-of-view chief rays on the target surface is less than or equal to the set angle, even with a uniform thickness of the filter layer 400, significant wavelength shift will not occur. Therefore, in this embodiment, the filter layer 400 can be coated on the target surface using a conventional coating process, which reduces process requirements and complexity, thereby saving costs.

[0051] Specifically, in this embodiment, in order to balance the requirements for the curvature of the target surface, the "set angle" can be determined based on the maximum wavelength offset allowed by the endoscopic optical system. Among them, it has been found through research that in the endoscopic optical system, the color cast of the endoscopic image caused by the wavelength drift within the range of 30nm is not perceptible to the human eye. According to the wavelength drift theory, it can be calculated that when a wavelength drift of 30nm occurs, the incident angle of the light on the target surface is 10.9°. Therefore, in a feasible implementation, the "set angle" can be made less than or equal to 10.9°. In this case, medical staff cannot observe the color cast problem in the endoscopic image obtained. Specifically, the incident angle of the main light of each field of view on the target surface of the target lens can be less than or equal to any one of 5°, 6.5°, 8°, 9.5°, 10.5°, and 10.9°, and can be customized according to actual needs. Of course, it is understood that the smaller the "set angle," the closer the angle of incidence of each field of view chief ray on the target surface approaches normal incidence, and the less wavelength shift will be produced. Therefore, in another achievable embodiment, the angle of incidence of each field of view chief ray on the target surface of the target lens can be set to 0°. In this case, the curvature of the target surface of the target lens 310 is equal to the incident wavefront curvature of each field of view chief ray incident on the target surface. Accordingly, the angle of incidence of all field of view chief rays on the target surface is 0° (i.e., normal incidence). In this case, the optical path length of each field of view chief ray passing through the filter layer 400 is equal, and wavelength shift will not occur.

[0052] It is understood that during the optical design process, optical requirements (e.g., imaging requirements and other limiting conditions) can usually be input into the optical design software, which will then output a lens assembly that meets the optical requirements, as well as the parameters of each lens in the lens assembly (including but not limited to: curvature, focal length, thickness, refractive index, etc.). It can be seen that in practical applications, as long as the incident angle of each field of view principal ray of the target surface given by the optical design software is less than or equal to the set angle, the curvature of the target surface given by the optical design software can meet the requirement that "the difference from the incident wavefront curvature of each field of view principal ray of the target surface is within the set curvature range"; further, the curvature of the target surface can be determined based on this.

[0053] Therefore, in a specific embodiment, the lens group can be designed first according to the imaging requirements of the endoscope, and then the incident angle of the main light of each field of view on each surface in the lens group is calculated. If the incident angle of the main light of each field of view on one of the surfaces is less than or equal to the set angle, then this surface can be determined as the target surface, and the lens containing the target surface can be determined as the target lens.

[0054] For example, Figure 2 The figure shows the incident light on a lens in an endoscope optical system. The solid lines represent the principal rays for each field of view, and the dashed lines represent the normal at the intersection of the principal rays and surface 1. α is the angle between the principal ray and the normal. If the angles between the principal rays for all fields of view and the surface normal on surface 1 are less than or equal to a set angle, then surface 1 is selected as the target surface. The curvature of this target surface can be determined based on the lens parameters provided by the optical design software.

[0055] If all surfaces of a lens assembly designed according to the imaging requirements of an endoscope do not meet the requirement that the incident angle of the principal ray in each field of view is less than or equal to the set angle, then a surface closest to the requirement can be found. In the optical design software, the incident angle of the principal ray in each field of view on this surface can be controlled so that it is less than or equal to the set angle. At the same time, the curvature, spacing, material and other parameters of other surfaces can be reasonably changed through methods such as aberration optimization and tolerance allocation to meet the imaging requirements. In this way, an endoscope optical system that meets both the imaging requirements and the coating requirements of this embodiment can be obtained.

[0056] Based on the above technical solution, the lens group 300 in the endoscope optical system in this embodiment has a target lens, and the difference between the curvature of the target surface of the target lens and the curvature of the incident wavefront of each field of view main ray on the target surface is within the set curvature range, so that the incident angle of each field of view main ray on the target surface of the target lens is less than or equal to the set angle, wherein, the smaller the difference between the curvature of the target surface of the target lens and the curvature of the incident wavefront of each field of view main ray on the surface, the smaller the incident angle of each field of view main ray on the target surface, and the closer it is to vertical incidence, thereby, the filter film When layer 400 is set on the target surface, the optical path of the main light of each field of view in the filter film layer 400 can be close to the optical path of the vertically incident light in the filter film layer 400, thereby reducing wavelength drift. Therefore, this embodiment does not need to adopt a complex coating process, and can effectively eliminate or reduce the adverse effects of wavelength drift, thereby reducing production costs; at the same time, this embodiment also reduces the use of filters, making the structure of the endoscope optical system simpler; therefore, while reducing wavelength drift, this embodiment has a simple structure and low cost for the endoscope optical system.

[0057] Specifically, in one achievable implementation, as Figure 1 or Figure 3 As shown, the lens group 300 of an endoscopic optical system provided in this embodiment includes: a first lens 310a, a second lens 320a, a third lens 330a and a fourth lens 340a arranged in sequence along the light incident direction (i.e., from the object plane to the image plane), and the aperture 100 is arranged between the second lens 320a and the third lens 330a.

[0058] The first lens 310a has negative optical power and its image surface is concave; the second lens 320a and the third lens 330a both have positive optical power and their object surfaces and image surfaces are convex; the fourth lens 340a has negative optical power and its object surface is concave.

[0059] In the endoscope optical system, the target lens may be the second lens 320a and / or the third lens 330a. When the target lens is the second lens 320a, the target surface is the object surface of the second lens 320a; when the target lens is the third lens 330a, the target surface is the image surface of the third lens 330a.

[0060] Specifically, when the object plane of the second lens 320a is used as the target plane, please refer to Figure 1The filter layer 400 is disposed on the object surface of the second lens 320a. After passing through the first lens 310a, the chief rays of each field of view pass through the second lens 320a. The angle of incidence of each chief ray of view incident on the object surface (target surface) of the second lens 320a is less than or equal to a set angle (e.g., 10.9°). Therefore, the optical path difference of each chief ray of view passing through the filter layer 400 is small, reducing wavelength drift. After filtering, each chief ray of view converges at the aperture 100, which limits the central width of each chief ray of view. After passing through the aperture 100, each chief ray of view passes through the third lens 330a and the fourth lens 340a in sequence before reaching the chip surface to form an image.

[0061] For example, when the image plane of the third lens 330a is used as the target plane, please refer to Figure 3 The filter layer 400 is disposed on the image plane of the third lens 330a. After passing through the first lens 310a and the second lens 320a, the chief rays of each field of view converge at the aperture 100. The aperture 100 limits the central width of each chief ray of view. The rays then pass through the third lens 330a. The angle of incidence of each chief ray of view entering the image plane (target plane) of the third lens 330a is less than or equal to a set angle (e.g., 10.9°). Therefore, the optical path length difference of each chief ray of view passing through the filter layer 400 is small, reducing wavelength drift. After filtering, each chief ray of view further passes through the fourth lens 340a before reaching the chip surface to form an image.

[0062] In addition, in order to facilitate design and processing, the endoscope optical system can also satisfy any of the following relationships:

[0063] (1)3.4<|fa / f|<3.8, and 2.8<|fb / f|<3.2;

[0064] (2)0.5 <R1 / R2<0.8;

[0065] (3)5.0 <TTL / ImgH<6.5;

[0066] Wherein, f is the total focal length of the endoscope optical system; fa is the focal length of the optical front group G1 composed of the first lens 310a and the second lens 320a; fb is the focal length of the optical rear group G2 composed of the third lens 330a and the fourth lens 340a;

[0067] R1 is the curvature radius of the image surface of the first lens 310a; R2 is the curvature radius of the object surface of the second lens 320a;

[0068] TTL is the on-axis distance from the object plane to the image plane of the first lens 310a; ImgH is the maximum image height of the endoscope optical system.

[0069] In another possible implementation, Figure 4 or Figure 5 As shown, the embodiment of the present application provides another lens group 300 of an endoscope optical system, including: a fifth lens 310b, a sixth lens 320b, a seventh lens 330b and an eighth lens 340b arranged in sequence along the light incident direction; and an aperture 100 is arranged between the fifth lens 310b and the sixth lens 320b.

[0070] The fifth lens 310b has negative refractive power and its image surface is concave; the sixth lens 320b and the seventh lens 330b both have positive refractive power and their image surfaces are convex; the eighth lens 340b has negative refractive power and its object surface is concave.

[0071] In the endoscope optical system, the target lens can be the sixth lens 320b and / or the seventh lens 330b; when the target lens is the sixth lens 320b, the target surface is the image surface of the sixth lens 320b; when the target lens is the seventh lens 330b, the target surface is the image surface of the seventh lens 330b.

[0072] When the image plane of the sixth lens 320b is used as the target plane, please refer to Figure 4 The filter layer 400 is disposed on the image plane of the sixth lens 320b. After passing through the fifth lens 310b, the chief rays of each field of view converge at the aperture 100, which limits the central width of each chief ray. The rays then pass through the sixth lens 320b. The angle of incidence of each chief ray entering the image plane of the sixth lens 320b is less than or equal to the set angle. Therefore, the optical path length difference of each chief ray passing through the filter layer 400 is small, reducing wavelength drift. After filtering, each chief ray further passes through the seventh lens 330b and the eighth lens 340b before reaching the chip surface to form an image.

[0073] When the image plane of the seventh lens 330b is used as the target plane, please refer to Figure 5 The filter layer 400 is disposed on the image plane of the seventh lens 330b. Each field of view chief ray passes through the fifth lens 310b and converges at the aperture 100. The aperture 100 limits the central width of each field of view chief ray. The chief ray then passes through the sixth lens 320b and is incident on the seventh lens 330b. The incident angle of each field of view chief ray entering the image plane (target plane) of the seventh lens 330b is less than or equal to the set angle. Therefore, the optical path length difference of each field of view chief ray passing through the filter layer 400 is relatively small. After being filtered, each field of view chief ray further passes through the eighth lens 340b before reaching the chip surface to form an image.

[0074] An endoscope provided in an embodiment of the present application is introduced below. The endoscope described below and the endoscope optical system described above can be referenced to each other.

[0075] An embodiment of the present application provides an endoscope, comprising: the endoscope optical system as described above.

[0076] It is understood that the endoscope may further include: an operating portion for the user to hold and control, an insertion portion connected to the operating portion and capable of being inserted into the body cavity, a connector for connecting to other devices in the endoscope system, and a cable for connecting the operating portion and the connector. The endoscope optical system is provided at the head end of the insertion portion to image tissues in the body cavity. The specific implementation of such components can be referred to the prior art, and therefore, this embodiment will not be described in detail.

[0077] Since the embodiments of the endoscope part correspond to the embodiments of the endoscope optical system part, the embodiments of the endoscope part refer to the description of the embodiments of the endoscope optical system part, which will not be repeated here.

[0078] An endoscope system provided in an embodiment of the present application is introduced below. The endoscope system described below and the endoscope described above can be referenced to each other.

[0079] An embodiment of the present application provides an endoscope system, including: the endoscope as described above.

[0080] It is understood that the endoscope system may further include an image processing device, an endoscope light source, a monitor, etc. The specific implementation of such devices may also refer to the prior art, and therefore, this embodiment will not elaborate on this.

[0081] Since the embodiments of the endoscope system part correspond to the embodiments of the endoscope part, the embodiments of the endoscope system part refer to the description of the embodiments of the endoscope part, which will not be repeated here.

[0082] The various embodiments in the specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to in detail.

[0083] The above is a detailed introduction to an endoscopic optical system, an endoscope, and an endoscopic system provided by the present application. Specific examples are used herein to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only intended to help understand the method and core ideas of the present application. It should be pointed out that, for those skilled in the art, without departing from the principles of the present application, several improvements and modifications can be made to the present application, and these improvements and modifications also fall within the scope of protection of the claims of the present application.

Claims

1. An endoscope optical system, comprising an aperture and a lens group, characterized in that: There is a target lens in the lens group, and the target surface of the target lens is coated with a filter film layer; wherein the difference between the curvature of the target surface and the incident wavefront curvature of each field chief ray of the target surface is within a set curvature range, so that the incident angle of each field chief ray on the target surface of the target lens is less than or equal to the set angle; The set angle is less than or equal to 10.9°.

2. The endoscope optical system according to claim 1, wherein: The set angle is determined according to a maximum wavelength shift allowed by the endoscope optical system.

3. The endoscope optical system according to claim 1, wherein: The setting angle is 0°.

4. The endoscope optical system according to claim 1, wherein: The lens group includes a first lens, a second lens, a third lens and a fourth lens arranged in sequence along the incident direction of light, and the aperture is arranged between the second lens and the third lens; The first lens has negative refractive power and its image surface is concave; the second lens and the third lens both have positive refractive power and their object surfaces and image surfaces are convex; the fourth lens has negative refractive power and its object surface is concave; The target lens is the second lens and / or the third lens; When the target lens is the second lens, the target surface is the object surface of the second lens; When the target lens is the third lens, the target surface is the image surface of the third lens.

5. The endoscope optical system according to claim 4, wherein: The endoscope optical system satisfies any one of the following relationships: (1)3.4<|fa / f|<3.8, and 2.8<|fb / f|<3.2; (2)0.5 <R1 / R2<0.8; (3)5.0 <TTL / ImgH<6.5; Wherein, f is the total focal length of the endoscope optical system; fa is the focal length of the optical front group consisting of the first lens and the second lens; fb is the focal length of the optical rear group consisting of the third lens and the fourth lens; R1 is the curvature radius of the image surface of the first lens; R2 is the curvature radius of the object surface of the second lens; TTL is the on-axis distance from the object plane to the image plane of the first lens; the ImgH is the maximum image height of the endoscope optical system.

6. The endoscope optical system according to claim 1, wherein: The lens group includes a fifth lens, a sixth lens, a seventh lens, and an eighth lens arranged in sequence along the incident direction of light, and the aperture is arranged between the fifth lens and the sixth lens; The fifth lens has negative refractive power and its image surface is concave; the sixth lens and the seventh lens both have positive refractive power and their image surfaces are convex; the eighth lens has negative refractive power and its object surface is concave; The target lens is the sixth lens and / or the seventh lens; When the target lens is the sixth lens, the target surface is the image surface of the sixth lens; When the target lens is the seventh lens, the target surface is the image surface of the seventh lens.

7. The endoscopic optical system according to any one of claims 1 to 6, wherein: The filter film layer is an infrared filter film layer or an ultraviolet filter film layer.

8. An endoscope, characterized in that: include: An endoscopic optical system according to any one of claims 1 to 7.

9. An endoscope system, characterized in that: include: The endoscope according to claim 8.

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