Endoscope adapter lens

Abstract

This application discloses an endoscope adapter lens, which includes, in sequence along the optical axis from the object side to the image side: a first lens group with positive optical power, which is a fixed group; a second lens group with negative optical power, which is a zoom group; and a third lens group with positive optical power, which is a compensation group; the second lens group moves along the optical axis between the object side and the image side to achieve continuous zoom between the wide-angle end and the telephoto end; and the third lens group moves along the optical axis between the object side and the image side to compensate for changes in the image plane position during zooming.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optical elements, in particular, to an endoscope adapter lens. BACKGROUND

[0002] With the rapid development of endoscopes, the industry has increasingly high requirements for the performance of endoscopes. In order to maximize the acquisition of clear images of lesion areas and improve the accuracy of diagnosis, the industry has proposed the demand for 4K (ultra-high definition) zoom endoscopes with good imaging quality.

[0003] However, there are still the following problems in the current zoom endoscope adapter lenses: 1) the imaging quality of the zoom endoscope adapter lens is poor, the resolution of the collected images is low, and it cannot meet the 4K requirement; 2) the size of the zoom endoscope adapter lens is large, so that the entire camera cannot be designed to be miniaturized; 3) the entrance pupil position changes in the zoom process of the zoom endoscope adapter lens, and the imaging is unstable. SUMMARY

[0004] The present application provides an endoscope adapter lens, which comprises, in order from the object side to the image side along the optical axis: a first lens group with positive refractive power, the first lens group being a fixed group; a second lens group with negative refractive power, the second lens group being a zoom group; a third lens group with positive refractive power, the third lens group being a compensation group; wherein the second lens group moves between the object side and the image side along the optical axis to realize continuous zooming between the wide-angle end and the long-focus end; and the third lens group moves between the object side and the image side along the optical axis to realize compensation of the change in the image plane position during zooming.

[0005] In one embodiment, the first lens group comprises, in order from the object side to the image side along the optical axis: a first lens with positive refractive power, a second lens with negative refractive power, and a third lens with positive refractive power.

[0006] In one embodiment, the object side surface and the image side surface of the first lens are both convex surfaces; the object side surface of the second lens is a concave surface; and the object side surface and the image side surface of the third lens are both convex surfaces.

[0007] In one embodiment, the second lens group comprises, in order from the object side to the image side along the optical axis: a fourth lens with negative refractive power, a fifth lens with positive refractive power, a sixth lens with positive refractive power, and a seventh lens with negative refractive power.

[0008] In one embodiment, the image side surface of the fourth lens is a concave surface; the object side surface of the fifth lens is a convex surface, and the image side surface is a concave surface; the object side surface of the sixth lens is a concave surface, and the image side surface is a convex surface; and the object side surface of the seventh lens is a concave surface.

[0009] In one embodiment, the third lens group comprises, in order from the object side to the image side along the optical axis, an eighth lens having positive refractive power, a ninth lens having positive refractive power, a tenth lens having negative refractive power, an eleventh lens having positive refractive power, a twelfth lens having negative refractive power, and a thirteenth lens having positive refractive power.

[0010] In one embodiment, the image side surface of the eighth lens is convex; the object side surface and the image side surface of the ninth lens are both convex; the object side surface of the tenth lens is concave, and the image side surface is convex; the object side surface and the image side surface of the eleventh lens are both convex; the object side surface and the image side surface of the twelfth lens are both concave; and the object side surface and the image side surface of the thirteenth lens are both convex.

[0011] In one embodiment, the endoscope adapter lens satisfies: 1.2 < FG1 / Fw < 1.5, where FG1 is the effective focal length of the first lens group, and Fw is the total effective focal length of the endoscope adapter lens at the wide-angle end.

[0012] In one embodiment, the endoscope adapter lens satisfies: -0.8 < FG2 / Fw < -0.5, where FG2 is the effective focal length of the second lens group, and Fw is the total effective focal length of the endoscope adapter lens at the wide-angle end.

[0013] In one embodiment, the endoscope adapter lens satisfies: 0.9 < FG3 / Fw < 1.2, where FG3 is the effective focal length of the third lens group, and Fw is the total effective focal length of the endoscope adapter lens at the wide-angle end.

[0014] In one embodiment, the endoscope adapter lens satisfies: 0.6 < ENP / Fw < 1.0, where ENP is the distance from the object side 3mm position of the front protective glass of the endoscope adapter lens to the entrance pupil position of the endoscope adapter lens, and Fw is the total effective focal length of the endoscope adapter lens at the wide-angle end.

[0015] In one embodiment, the endoscope adapter lens satisfies: 0.2 < ENP / Ft < 0.5, where ENP is the distance from the object side 3mm position of the front protective glass of the endoscope adapter lens to the entrance pupil position of the endoscope adapter lens, and Ft is the total effective focal length of the endoscope adapter lens at the telephoto end.

[0016] In one embodiment, the endoscope adapter lens satisfies: 0.2 < d2 / d3 < 0.5, where d2 is the axial distance between the position of the second lens group on the optical axis of the endoscope adapter lens at the wide-angle end and the position of the second lens group on the optical axis of the endoscope adapter lens at the telephoto end, and d3 is the axial distance between the position of the third lens group on the optical axis of the endoscope adapter lens at the wide-angle end and the position of the third lens group on the optical axis of the endoscope adapter lens at the telephoto end.

[0017] In one embodiment, the endoscope adapter lens satisfies: 0 < d2 / Ft < 0.2, where d2 is an on-axis distance between a position of the second lens group on the optical axis when the endoscope adapter lens is at the wide angle end and a position of the second lens group on the optical axis when the endoscope adapter lens is at the telephoto end, and Ft is a total effective focal length of the endoscope adapter lens when at the telephoto end.

[0018] In one embodiment, the Abbe number Vd of at least one lens in the second lens group satisfies: 18 < Vd < 30. G2 G2

[0019] In one embodiment, the refractive index Nd of at least one lens in the second lens group satisfies: 1.8 < Nd < 2.1. G2 G2

[0020] In one embodiment, the endoscope adapter lens satisfies: 0.2 < TG2 / TG3 < 0.5, where TG2 is a thickness of the second lens group on the optical axis, and TG3 is a thickness of the third lens group on the optical axis.

[0021] In one embodiment, the endoscope adapter lens satisfies: 1.5 < f8 / FG3 < 2.5, where f8 is an effective focal length of the eighth lens, and FG3 is an effective focal length of the third lens group.

[0022] In one embodiment, the endoscope adapter lens satisfies: 0.1 < Dmax / TTL < 0.3, where Dmax is a maximum clear aperture of the endoscope adapter lens, and TTL is an on-axis distance from a subject side surface of the first lens to an image plane of the endoscope adapter lens.

[0023] In one embodiment, the endoscope adapter lens satisfies: 1.2 < D8w / D8t < 1.9, where D8w is an effective clear aperture of an image side surface of the eighth lens when the endoscope adapter lens is at the wide angle end, and D8t is an effective clear aperture of the image side surface of the eighth lens when the endoscope adapter lens is at the telephoto end.

[0024] In one embodiment, the endoscope adapter lens satisfies: 0.2 < D9w / f910 < 0.5, where D9w is an effective clear aperture of a subject side surface of the ninth lens when the endoscope adapter lens is at the wide angle end, and f910 is a combined focal length of the ninth lens and the tenth lens.

[0025] ​​​​The endoscope adapter lens provided by the embodiment of the present application comprises three lens groups, i.e., a first lens group with positive refractive power, a second lens group with negative refractive power and a third lens group with positive refractive power. The first lens group is a fixed group, the second lens group is a zoom group, and the third lens group is a compensation group. By reasonably setting the refractive power and action mode of the first lens group to the third lens group, the endoscope adapter lens provided by the present application has at least one of the beneficial effects of high resolution, small size, infrared confocal, wide working distance range, and constant entrance pupil position during zooming. BRIEF DESCRIPTION OF DRAWINGS

[0026] Other features, objects, and advantages of the present application will become more apparent from the following detailed description of non-limiting embodiments made with reference to the accompanying drawings:

[0027] Figure 1A and Figure 1B are respectively structural schematic diagrams of an endoscope adapter lens according to an embodiment 1 of the present application at wide-angle end and long-focus end;

[0028] Figure 2A and Figure 2B are respectively structural schematic diagrams of an endoscope adapter lens according to an embodiment 2 of the present application at wide-angle end and long-focus end;

[0029] Figure 3A and Figure 3B are respectively structural schematic diagrams of an endoscope adapter lens according to an embodiment 3 of the present application at wide-angle end and long-focus end; and

[0030] Figure 4A and Figure 4B are respectively structural schematic diagrams of an endoscope adapter lens according to an embodiment 4 of the present application at wide-angle end and long-focus end. DETAILED DESCRIPTION

[0031] For a better understanding of the present application, various aspects of the present application will be described in more detail with reference to the accompanying drawings. It is to be understood that the detailed description is merely descriptive of exemplary embodiments of the present application and is not intended to limit the scope of the present application in any way. Throughout the specification, like reference numerals refer to like elements. The expression "and / or" includes any and all combinations of one or more of the associated listed items.

[0032] It should be noted that in the present specification, the expressions first, second, third, etc. are merely used to distinguish one feature from another feature, and do not represent any limitation on the features. Therefore, the first lens discussed below can also be referred to as the second lens or the third lens without departing from the teachings of the present application.

[0033] In the drawings, the thickness, size, and shape of the lenses have been exaggerated slightly for ease of explanation. Specifically, the shape of the spherical or aspherical surface shown in the drawings is shown by way of example. That is, the shape of the spherical or aspherical surface is not limited to the shape of the spherical or aspherical surface shown in the drawings. The drawings are merely examples and are not drawn to scale.

[0034] In this document, the paraxial region refers to a region near the optical axis. If a lens surface is convex and the position of the convex surface is not specified, it means that the lens surface is convex at least in the paraxial region. If a lens surface is concave and the position of the concave surface is not specified, it means that the lens surface is concave at least in the paraxial region. The surface of each lens closest to the object is referred to as the object side surface of the lens, and the surface of each lens closest to the image plane is referred to as the image side surface of the lens.

[0035] It should also be understood that the words "comprise", "comprising", "include", "including", and / or "contain", when used in this specification, mean the presence of stated features, elements, and / or components but do not preclude the presence or addition of one or more other features, elements, components, and / or groups thereof. In addition, when describing the embodiments of the present application, the use of "may" means that one or more embodiments of the present application. Also, the word "exemplary" is intended to mean an example or an illustration.

[0036] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. It should also be understood that the terms should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

[0037] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The present application will be described in detail below with reference to the accompanying drawings and in conjunction with the embodiments.

[0038] The features, principles, and other aspects of the present application are described in detail below.

[0039] The endoscope adapter lens according to the exemplary embodiments of the present application can include three lens groups with optical power, i.e., a first lens group with positive optical power, a second lens group with negative optical power, and a third lens group with positive optical power. The three lens groups are arranged in order along the optical axis from the object side to the image side, the first lens group is a fixed group, and the distance relative to the imaging surface is fixed. When the object distance changes, the second lens group and the third lens group move along the optical axis. The second lens group is a zoom group, and the second lens group can move along the optical axis between the object side and the image side to enable the endoscope adapter lens to achieve continuous zooming between the wide-angle end and the telephoto end. The third lens group is a compensation group, and the compensation group compensates for the defocus caused by the movement of the zoom group during zooming to ensure real-time clarity of imaging. That is, the third lens group moves along the optical axis in response to the movement of the second lens group to achieve compensation of the change in the image surface position during zooming, so that the endoscope adapter lens has a better imaging position and stable imaging quality during continuous zooming.

[0040] In the exemplary embodiments, the number of lenses with optical power in the first lens group is three, and the first lens group includes, in order along the optical axis from the object side to the image side, a first lens with positive optical power, a second lens with negative optical power, and a third lens with positive optical power.

[0041] In the exemplary embodiments, the object side surface and the image side surface of the first lens are both convex surfaces; the object side surface of the second lens is a concave surface; and the object side surface and the image side surface of the third lens are both convex surfaces.

[0042] In the exemplary embodiments, the first lens group includes two lenses with positive optical power and one lens with negative optical power. More specifically, the first lens is a convex-convex lens with positive optical power, the second lens is a lens with negative optical power and a concave object side surface, and the third lens is a convex-convex lens with positive optical power. The two convex-convex lenses with positive optical power are beneficial to the correction of field curvature at different object distances. The object side surface of the first lens is set to be convex, and the image side surface is set to be convex, which is beneficial to reducing distortion.

[0043] In the exemplary embodiments, the first lens and the second lens can form a doublet. By reasonably matching the materials of the first lens and the second lens, the purpose of correcting axial chromatic aberration can be achieved.

[0044] In the exemplary embodiments, the number of lenses with optical power in the second lens group is four, and the second lens group includes, in order along the optical axis from the object side to the image side, a fourth lens with negative optical power, a fifth lens with positive optical power, a sixth lens with positive optical power, and a seventh lens with negative optical power. At least two lenses with negative optical power in the second lens group are beneficial to increasing the light divergence speed and improving the zoom efficiency.

[0045] In the example embodiment, the image side surface of the fourth lens is concave; the object side surface of the fifth lens is convex, and the image side surface is concave; the object side surface of the sixth lens is concave, and the image side surface is convex; and the object side surface of the seventh lens is concave.

[0046] In the example embodiment, the sixth lens and the seventh lens can constitute a double cemented lens, which is beneficial to the correction of field curvature and the reduction of the defocus amount of the infrared spectrum relative to the visible spectrum, and realizes the infrared confocal function of the lens.

[0047] In the example embodiment, the number of lenses with optical power in the third lens group is six, and the third lens group comprises, in order from the object side to the image side along the optical axis: an eighth lens with positive optical power; a ninth lens with positive optical power; a tenth lens with negative optical power; an eleventh lens with positive optical power; a twelfth lens with negative optical power; and a thirteenth lens with positive optical power.

[0048] In the example embodiment, the image side surface of the eighth lens is convex, which is beneficial to the correction of field curvature; the object side surface of the ninth lens is convex, and the image side surface is convex, which is beneficial to the reduction of the height of light rays and the reduction of the generation of aberrations; the object side surface of the tenth lens is concave, and the image side surface is convex; the object side surface and the image side surface of the eleventh lens are both convex; the object side surface and the image side surface of the twelfth lens are both concave; and the object side surface and the image side surface of the thirteenth lens are both convex.

[0049] In the example embodiment, the third lens group can comprise at least one convex-convex positive power lens.

[0050] In the example embodiment, the third lens group can comprise two cemented lenses.

[0051] In the example embodiment, the ninth lens and the tenth lens can constitute a double cemented lens, and more specifically, the ninth lens with positive optical power and the tenth lens with negative optical power constitute a double cemented lens, which is beneficial to the mutual compensation of positive spherical aberration and negative spherical aberration, and is beneficial to the improvement of the resolution of the system.

[0052] In the example embodiment, the eleventh lens, the twelfth lens and the thirteenth lens can constitute a triple cemented lens, and through the reasonable matching of the optical power of each lens, it is beneficial to the correction of chromatic aberration and the reduction of the sensitivity of the system to tolerance.

[0053] In an exemplary embodiment, the endoscopic adapter lens according to the present application further includes an aperture disposed between the first lens group and the second lens group. The aperture is beneficial for converging the light entering the lens, reducing the incident angle of the light onto the image plane and the rear aperture diameter of the lens, and reducing the assembly sensitivity of the system. In the embodiment of the present application, the aperture may be disposed between the third lens and the fourth lens. However, it should be noted that the position of the aperture disclosed herein is only an example and not a limitation; in an alternative embodiment, the aperture may also be disposed at other positions according to actual needs.

[0054] In an exemplary embodiment, the endoscopic adapter lens according to the present application further includes a front protective glass disposed on the object side of the first lens and a rear protective glass disposed on the image side of the thirteenth lens. The protective glass plays a protective role in waterproofing, dustproofing, and scratch resistance.

[0055] In an exemplary embodiment, the endoscopic adapter lens according to the present application may satisfy: 1.2 < FG1 / Fw < 1.5, where FG1 is the effective focal length of the first lens group and Fw is the total effective focal length of the endoscopic adapter lens at the wide-angle end. Satisfying 1.2 < FG1 / Fw < 1.5 is beneficial for the light to converge gently into the optical system and effectively reduce the distortion of the optical system.

[0056] In an exemplary embodiment, the endoscopic adapter lens according to the present application may satisfy: -0.8 < FG2 / Fw < -0.5, where FG2 is the effective focal length of the second lens group and Fw is the total effective focal length of the endoscopic adapter lens at the wide-angle end. Satisfying -0.8 < FG2 / Fw < -0.5 is beneficial for achieving the imaging performance while ensuring the required zoom ratio during the zoom process.

[0057] In an exemplary embodiment, the endoscopic adapter lens according to the present application may satisfy: 0.9 < FG3 / Fw < 1.2, where FG3 is the effective focal length of the third lens group and Fw is the total effective focal length of the endoscopic adapter lens at the wide-angle end. Satisfying 0.9 < FG3 / Fw < 1.2 is beneficial for the third lens group to collect the outgoing light of the second lens group, enabling a smooth transition of the optics and facilitating the correction of field curvature at different object distances.

[0058] In an exemplary embodiment, the endoscopic adapter lens according to the present application may satisfy: 0.6 < ENP / Fw < 1.0, where ENP is the distance between the entrance pupil position of the endoscopic adapter lens and the 3 mm position on the object side of the front protective glass of the endoscopic adapter lens, and Fw is the total effective focal length of the endoscopic adapter lens at the wide-angle end. Satisfying 0.6 < ENP / Fw < 1.0 is beneficial for reasonably controlling the position of the entrance pupil, enabling the endoscopic adapter lens to stably receive the light from the endoscopic objective lens, and also reducing the changes in spherical aberration and distortion during the entire zoom process to obtain high imaging performance.

[0059] In an exemplary embodiment, the endoscope adapter lens according to the present application can satisfy: 0.2 < ENP / Ft < 0.5, where ENP is the distance from the entrance pupil position of the endoscope adapter lens to the 3 mm position on the object side of the front protective glass of the endoscope adapter lens, and Ft is the total effective focal length of the endoscope adapter lens at the telephoto end. Satisfying 0.2 < ENP / Ft < 0.5 is beneficial to reasonably control the position of the entrance pupil, enabling the endoscope adapter lens to stably receive the light from the endoscope objective lens, and also reducing the changes in spherical aberration and distortion during the entire zoom process to obtain high imaging performance.

[0060] In an exemplary embodiment, the endoscope adapter lens according to the present application can satisfy: 0.2 < d2 / d3 < 0.5, where d2 is the axial distance between the positions of the second lens group on the optical axis of the endoscope adapter lens at the wide-angle end and the positions of the second lens group on the optical axis of the endoscope adapter lens at the telephoto end, and d3 is the axial distance between the positions of the third lens group on the optical axis of the endoscope adapter lens at the wide-angle end and the positions of the third lens group on the optical axis of the endoscope adapter lens at the telephoto end. Satisfying 0.2 < d2 / d3 < 0.5 is beneficial to controlling the ratio of the moving distance of the zoom group to the moving distance of the compensation group, enabling a fast focus response during the zoom process and being beneficial to improving the focus sensitivity.

[0061] In an exemplary embodiment, the endoscope adapter lens according to the present application can satisfy: 0 < d2 / Ft < 0.2, where d2 is the axial distance between the positions of the second lens group on the optical axis of the endoscope adapter lens at the wide-angle end and the positions of the second lens group on the optical axis of the endoscope adapter lens at the telephoto end, and Ft is the total effective focal length of the endoscope adapter lens at the telephoto end. Satisfying 0 < d2 / Ft < 0.2 is beneficial to reducing the aberration generated between the first lens group and the second lens group, and at the same time can also control the volume of the lens and reduce the design cost.

[0062] In an exemplary embodiment, the Abbe number VdG2 of at least one lens in the second lens group of the endoscope adapter lens according to the present application can satisfy: 18 ≤ Vd G2 ≤ 30. Reasonably setting the Abbe number of the lenses in the second lens group can effectively correct the chromatic aberration of the second lens group, thereby improving the imaging quality of the optical system.

[0063] In an exemplary embodiment, the refractive index Nd of at least one lens in the second lens group of the endoscope adapter lens according to the present application G2 can satisfy: 1.8 ≤ Nd G2 ≤ 2.1. Reasonably setting the refractive index of the lenses in the second lens group can effectively correct the distortion of the second lens group, thereby improving the imaging quality of the optical system.

[0064] In an exemplary embodiment, the endoscopic adapter lens according to the present application may satisfy: 0.2 < TG2 / TG3 < 0.5, where TG2 is the thickness of the second lens group on the optical axis, and TG3 is the thickness of the third lens group on the optical axis. Satisfying 0.2 < TG2 / TG3 < 0.5 is beneficial to making the volume of the third lens group smaller and conducive to achieving lens miniaturization.

[0065] In an exemplary embodiment, the endoscopic adapter lens according to the present application may satisfy: 1.5 < f8 / FG3 < 2.5, where f8 is the effective focal length of the eighth lens, and FG3 is the effective focal length of the third lens group. Satisfying 1.5 < f8 / FG3 < 2.5 enables the eighth lens to have a short focal length for light collection, thereby ensuring the light transmission amount.

[0066] In an exemplary embodiment, the endoscopic adapter lens according to the present application may satisfy: 0.1 ≤ Dmax / TTL ≤ 0.3, where Dmax is the maximum clear aperture of the endoscopic adapter lens, and TTL is the axial distance from the object side of the first lens to the imaging surface of the endoscopic adapter lens. Satisfying 0.1 ≤ Dmax / TTL ≤ 0.3 is beneficial to making the maximum clear aperture of the endoscopic adapter lens smaller by controlling the maximum clear aperture during the zooming process of the endoscopic adapter lens under a certain total optical length of the system, which is conducive to achieving a small volume (or miniaturization).

[0067] In an exemplary embodiment, the endoscopic adapter lens according to the present application may satisfy: 1.2 < D8w / D8t < 1.9, where D8w is the effective clear aperture of the image side of the eighth lens of the endoscopic adapter lens at the wide-angle end, and D8t is the effective clear aperture of the image side of the eighth lens of the endoscopic adapter lens at the telephoto end. Satisfying 1.2 < D8w / D8t < 1.9 is beneficial to effectively converging the light entering the optical system and conducive to the uniform illuminance at the wide-angle end and the telephoto end.

[0068] In an exemplary embodiment, the endoscopic adapter lens according to the present application may satisfy: 0.2 < D9w / f910 < 0.5, where D9w is the effective clear aperture of the object side of the ninth lens of the endoscopic adapter lens at the wide-angle end, and f910 is the combined focal length of the ninth lens and the tenth lens. Satisfying 0.2 < D9w / f910 < 0.5 is beneficial to controlling the smooth transition of light, conducive to the correction of aberrations, and improving the lens resolution.

[0069] In an exemplary embodiment, the first to thirteenth lenses can be spherical lenses or aspherical lenses. This application does not specifically limit the number of spherical and aspherical lenses; when image quality is paramount, the number of aspherical lenses can be increased, and even all lenses can be aspherical. Aspherical lenses are characterized by a continuously changing curvature from the lens center to the periphery. Unlike spherical lenses, which have a constant curvature from the lens center to the periphery, aspherical lenses have better radius of curvature characteristics, offering advantages in improving distortion and astigmatism. Using aspherical lenses can minimize aberrations that occur during imaging, thereby improving the lens's image quality. Optionally, the object-side and image-side surfaces of the first to thirteenth lenses are both spherical mirror surfaces; spherical lenses are low-cost and have good tolerances.

[0070] The endoscope adapter lens of this application has excellent resolution, with a resolution of 4K or higher.

[0071] The endoscope adapter lens of this application maintains a constant entrance pupil position during zooming, which helps to maintain image plane stability.

[0072] The endoscope lens of this application has a wide range of object distances, and can ensure clear focus from 0.5m to infinity throughout the zoom range, resulting in good imaging effect.

[0073] The endoscope adapter lens of this application can achieve infrared confocal focusing, and its design ensures imaging performance in the infrared band. Combined with the use of infrared supplementary lighting, the lens can be used in nighttime scenes and the field of endoscopy.

[0074] This application, by reasonably setting the optical power of each lens group and the optical power and surface shape of each lens, is beneficial to the endoscope adapter lens to have a better ability to correct optical aberrations and chromatic aberrations when switching between wide-angle and telephoto ends. At the same time, it helps to reduce the tolerance sensitivity of the system and improve the uniformity of the image.

[0075] Alternatively, in other alternative exemplary embodiments, the endoscope adapter lens described above may also include a filter for correcting color deviation and / or a protective glass for protecting the photosensitive element located on the imaging surface.

[0076] The endoscope adapter lens according to the above embodiments of this application can use multiple lenses, such as the thirteen lenses mentioned above. By reasonably allocating the optical parameters such as the optical power, surface shape, center thickness of each lens, and on-axis spacing between each lens, the endoscope adapter lens provided by this application has at least one of the following beneficial effects: high resolution (4K), small size, infrared confocal, wide range of object distances (from 0.5m to infinity), and unchanged entrance pupil position during zooming. It can be adapted to endoscope adapter lenses.

[0077] However, those skilled in the art will understand that the number of lenses constituting the endoscope adapter lens can be varied to obtain the various results and advantages described herein without departing from the technical solutions claimed in this application. For example, although thirteen lenses have been described as an example in the embodiments, the endoscope adapter lens is not limited to including thirteen lenses. If desired, the endoscope adapter lens may also include other numbers of lenses.

[0078] The following describes in further detail, with reference to the accompanying drawings, specific embodiments of the endoscope adapter lens applicable to the above-described embodiments.

[0079] Example 1

[0080] The following is for reference Figure 1A and Figure 1B The endoscope adapter lens 100 according to Embodiment 1 of this application is described. Figure 1A This is a schematic diagram of the endoscope adapter lens 100 in the wide-angle end according to Embodiment 1 of this application. Figure 1B This is a schematic diagram of the endoscope adapter lens 100 in embodiment 1 of this application when it is at the telephoto end.

[0081] like Figure 1A and Figure 1B As shown, the endoscope adapter lens 100 includes, from the object side to the image side, the following components in sequence: positioning surface D, front protective glass CG1, first lens group G1 with positive optical power, aperture stop STO (not shown), second lens group G2 with negative optical power, third lens group G3 with positive optical power, rear protective glass CG2, and imaging surface IMA.

[0082] In this embodiment and the following embodiments, the positioning surface D is located 3mm from the object side of the front protective glass CG1 of the endoscope adapter lens.

[0083] In Example 1, the front protective glass CG1 has an object side surface S2 and an image side surface S3, and the rear protective glass CG2 has an object side surface S25 and an image side surface S26.

[0084] The first lens group G1 includes a first lens L1, a second lens L2, and a third lens L3. The first lens L1 has positive optical power, with its object-side surface S4 being convex and its image-side surface S5 being convex. The second lens L2 has negative optical power, with its object-side surface S5 being concave and its image-side surface S6 being convex. The third lens L3 has positive optical power, with its object-side surface S7 being convex and its image-side surface S8 being convex. The first lens L1 and the second lens L2 are cemented together to form a cemented doublet lens.

[0085] The second lens group G2 includes a fourth lens L4, a fifth lens L5, a sixth lens L6, and a seventh lens L7. The fourth lens L4 can have negative optical power, with its object-side surface S9 being concave and its image-side surface S10 being concave. The fifth lens L5 can have positive optical power, with its object-side surface S11 being convex and its image-side surface S12 being concave. The sixth lens L6 can have positive optical power, with its object-side surface S13 being concave and its image-side surface S14 being convex. The seventh lens L7 can have negative optical power, with its object-side surface S14 being concave and its image-side surface S15 being convex. The sixth lens L6 and the seventh lens L7 are cemented together to form a cemented doublet lens.

[0086] The third lens group G3 includes the eighth lens L8, the ninth lens L9, the tenth lens L10, the eleventh lens L11, the twelfth lens L12, and the thirteenth lens L13. The eighth lens L8 has positive optical power, with its object-side surface S16 being convex and its image-side surface S17 being convex. The ninth lens L9 has positive optical power, with its object-side surface S18 being convex and its image-side surface S19 being convex. The tenth lens L10 has negative optical power, with its object-side surface S19 being concave and its image-side surface S20 being convex. The eleventh lens L11 has positive optical power, with its object-side surface S21 being convex and its image-side surface S22 being convex. The twelfth lens L12 has negative optical power, with its object-side surface S22 being concave and its image-side surface S23 being concave. The thirteenth lens L13 has positive optical power, with its object-side surface S23 being convex and its image-side surface S24 being convex. Lens L9 (ninth lens) and lens L10 (tenth lens) are cemented together to form a cemented doublet lens. Lens L11 (eleventh lens), lens L12 (twelfth lens), and lens L13 (thirteenth lens) are cemented together to form a cemented triplicate lens.

[0087] The aperture stop STO is positioned between the first lens group G1 and the second lens group G2, and more specifically, the aperture stop STO is positioned between the third lens L3 and the fourth lens L4.

[0088] Light from the object passes through each surface in sequence (i.e., through the front protective glass CG1, the first lens L1 to the thirteenth lens L13, and the rear protective glass CG2 in sequence) and is finally imaged on the imaging surface IMA, where an image sensing chip may be provided.

[0089] Table 1 shows the basic parameters of the endoscope adapter lens 100 of Embodiment 1, where the units for radius of curvature and thickness / distance are millimeters (mm).

[0090]

[0091]

[0092] Table 1

[0093] In Embodiment 1 and the following embodiments, when the object distance changes, the first lens group G1 remains fixed, while the second lens group G2 and the third lens group G3 move along the optical axis. By changing the position of the second lens group G2 on the optical axis, the endoscope adapter lens can be switched from the wide-angle end to the telephoto end or from the telephoto end to the wide-angle end, making the total effective focal length of the endoscope adapter lens continuously variable. At the same time, by adjusting the position of the third lens group G3 on the optical axis, the image plane of the endoscope adapter lens can be clearly focused during zooming.

[0094] Table 2 shows the values ​​of T1, T2, and T3 in Table 1 when the endoscope adapter lens 100 is at the wide-angle and telephoto ends, respectively. Table 2 also shows the total effective focal length F and aperture value Fno of the endoscope adapter lens 100 in Embodiment 1, wherein F and Fno change as the endoscope adapter lens 100 switches from the wide-angle end to the telephoto end or vice versa.

[0095] Wide angle end Telephoto end F (mm) 14 (Fw) 31.9 (Ft) Fno 2.75 6.13 T1 (mm) 0.57 3.09 T2 (mm) 10.39 0.95 T3 (mm) 10.34 17.25

[0096] Table 2

[0097] Example 2

[0098] The following is for reference Figure 2A and Figure 2B Description of an endoscope adapter lens 200 according to Embodiment 2 of this application. Figure 2A This is a schematic diagram of the endoscope adapter lens 200 in the wide-angle end according to Embodiment 2 of this application. Figure 2B This is a schematic diagram of the endoscope adapter lens 200 in the telephoto end according to Embodiment 2 of this application.

[0099] In this embodiment and the following embodiments, for the sake of brevity, the omitted parts are similar to the description in Embodiment 1.

[0100] like Figure 2A and Figure 2B As shown, the endoscope adapter lens 200 includes, from the object side to the image side, the following components in sequence: positioning surface D, front protective glass CG1, first lens group G1 with positive optical power, aperture stop STO (not shown), second lens group G2 with negative optical power, third lens group G3 with positive optical power, rear protective glass CG2, and imaging surface IMA.

[0101] In Example 2, the front protective glass CG1 has an object side surface S2 and an image side surface S3, and the rear protective glass CG2 has an object side surface S26 and an image side surface S27.

[0102] The first lens group G1 includes a first lens L1, a second lens L2, and a third lens L3. The first lens L1 has positive optical power, with its object-side surface S4 being convex and its image-side surface S5 being convex. The second lens L2 has negative optical power, with its object-side surface S5 being concave and its image-side surface S6 being convex. The third lens L3 has positive optical power, with its object-side surface S7 being convex and its image-side surface S8 being convex. The first lens L1 and the second lens L2 are cemented together to form a cemented doublet lens.

[0103] The second lens group G2 includes a fourth lens L4, a fifth lens L5, a sixth lens L6, and a seventh lens L7. The fourth lens L4 can have negative optical power, with its object-side surface S9 being convex and its image-side surface S10 being concave. The fifth lens L5 can have positive optical power, with its object-side surface S11 being convex and its image-side surface S12 being concave. The sixth lens L6 can have positive optical power, with its object-side surface S13 being concave and its image-side surface S14 being convex. The seventh lens L7 can have negative optical power, with its object-side surface S15 being concave and its image-side surface S16 being convex.

[0104] The third lens group G3 includes the eighth lens L8, the ninth lens L9, the tenth lens L10, the eleventh lens L11, the twelfth lens L12, and the thirteenth lens L13. The eighth lens L8 has positive optical power, with its object-side surface S17 being concave and its image-side surface S18 being convex. The ninth lens L9 has positive optical power, with its object-side surface S19 being convex and its image-side surface S20 being convex. The tenth lens L10 has negative optical power, with its object-side surface S20 being concave and its image-side surface S21 being convex. The eleventh lens L11 has positive optical power, with its object-side surface S22 being convex and its image-side surface S23 being convex. The twelfth lens L12 has negative optical power, with its object-side surface S23 being concave and its image-side surface S24 being concave. The thirteenth lens L13 has positive optical power, with its object-side surface S24 being convex and its image-side surface S25 being convex. Lens L9 (ninth lens) and lens L10 (tenth lens) are cemented together to form a cemented doublet lens. Lens L11 (eleventh lens), lens L12 (twelfth lens), and lens L13 (thirteenth lens) are cemented together to form a cemented triplicate lens.

[0105] The aperture stop STO is positioned between the first lens group G1 and the second lens group G2, and more specifically, the aperture stop STO is positioned between the third lens L3 and the fourth lens L4.

[0106] Light from the object passes through each surface in sequence (i.e., through the front protective glass CG1, the first lens L1 to the thirteenth lens L13, and the rear protective glass CG2 in sequence) and is finally imaged on the imaging surface IMA, where an image sensing chip may be provided.

[0107] Table 3 shows the basic parameters of the endoscope adapter lens 200 of Example 2, where the units for radius of curvature and thickness / distance are millimeters (mm).

[0108]

[0109]

[0110] Table 3

[0111] Table 4 shows the values ​​of T1, T2, and T3 in Table 3 when the endoscope adapter lens 200 is at the wide-angle and telephoto ends, respectively. Table 4 also shows the total effective focal length F and aperture value Fno of the endoscope adapter lens 200 in Embodiment 2, wherein F and Fno change as the endoscope adapter lens 200 switches from the wide-angle end to the telephoto end or vice versa.

[0112] Wide angle end Telephoto end F (mm) 14 (Fw) 31.9 (Ft) Fno 2.69 6.13 T1 (mm) 0.49 2.88 T2 (mm) 10.22 1.00 T3 (mm) 8.44 15.27

[0113] Table 4

[0114] Example 3

[0115] The following is for reference Figure 3A and Figure 3B The endoscope adapter lens 300 according to Embodiment 3 of this application is described. Figure 3A This is a schematic diagram of the endoscope adapter lens 300 in the wide-angle end according to Embodiment 3 of this application. Figure 3B This is a schematic diagram of the endoscope adapter lens 300 in embodiment 3 of this application when it is at the telephoto end.

[0116] like Figure 3A and Figure 3B As shown, the endoscope adapter lens 300 includes, from the object side to the image side, the following components in sequence: positioning surface D, front protective glass CG1, first lens group G1 with positive optical power, aperture stop STO (not shown), second lens group G2 with negative optical power, third lens group G3 with positive optical power, rear protective glass CG2, and imaging surface IMA.

[0117] In Example 3, the front protective glass CG1 has an object side surface S2 and an image side surface S3, and the rear protective glass CG2 has an object side surface S25 and an image side surface S26.

[0118] The first lens group G1 includes a first lens L1, a second lens L2, and a third lens L3. The first lens L1 has positive optical power, with its object-side surface S4 being convex and its image-side surface S5 being convex. The second lens L2 has negative optical power, with its object-side surface S5 being concave and its image-side surface S6 being convex. The third lens L3 has positive optical power, with its object-side surface S7 being convex and its image-side surface S8 being convex. The first lens L1 and the second lens L2 are cemented together to form a cemented doublet lens.

[0119] The second lens group G2 includes a fourth lens L4, a fifth lens L5, a sixth lens L6, and a seventh lens L7. The fourth lens L4 can have negative optical power, with its object-side surface S9 being convex and its image-side surface S10 being concave. The fifth lens L5 can have positive optical power, with its object-side surface S11 being convex and its image-side surface S12 being concave. The sixth lens L6 can have positive optical power, with its object-side surface S13 being concave and its image-side surface S14 being convex. The seventh lens L7 can have negative optical power, with its object-side surface S14 being concave and its image-side surface S15 being convex. The sixth lens L6 and the seventh lens L7 are cemented together to form a cemented doublet lens.

[0120] The third lens group G3 includes the eighth lens L8, the ninth lens L9, the tenth lens L10, the eleventh lens L11, the twelfth lens L12, and the thirteenth lens L13. The eighth lens L8 has positive optical power, with its object-side surface S16 being concave and its image-side surface S17 being convex. The ninth lens L9 has positive optical power, with its object-side surface S18 being convex and its image-side surface S19 being convex. The tenth lens L10 has negative optical power, with its object-side surface S19 being concave and its image-side surface S20 being convex. The eleventh lens L11 has positive optical power, with its object-side surface S21 being convex and its image-side surface S22 being convex. The twelfth lens L12 has negative optical power, with its object-side surface S22 being concave and its image-side surface S23 being concave. The thirteenth lens L13 has positive optical power, with its object-side surface S23 being convex and its image-side surface S24 being convex. Lens L9 (ninth lens) and lens L10 (tenth lens) are cemented together to form a cemented doublet lens. Lens L11 (eleventh lens), lens L12 (twelfth lens), and lens L13 (thirteenth lens) are cemented together to form a cemented triplicate lens.

[0121] The aperture stop STO is positioned between the first lens group G1 and the second lens group G2, and more specifically, the aperture stop STO is positioned between the third lens L3 and the fourth lens L4.

[0122] Light from the object passes through each surface in sequence (i.e., through the front protective glass CG1, the first lens L1 to the thirteenth lens L13, and the rear protective glass CG2 in sequence) and is finally imaged on the imaging surface IMA, where an image sensing chip may be provided.

[0123] Table 5 shows the basic parameters of the endoscope adapter lens 300 of Embodiment 3, where the units for radius of curvature and thickness / distance are millimeters (mm).

[0124]

[0125]

[0126] Table 5

[0127] Table 6 shows the values ​​of T1, T2, and T3 in Table 5 when the endoscope adapter lens 300 is at the wide-angle and telephoto ends, respectively. Table 6 also shows the total effective focal length F and aperture value Fno of the endoscope adapter lens 300 in Embodiment 2, wherein F and Fno change as the endoscope adapter lens 300 switches from the wide-angle end to the telephoto end or vice versa.

[0128] Wide angle end Telephoto end F (mm) 14 (Fw) 31.9 (Ft) Fno 2.70 6.13 T1 (mm) 0.50 2.90 T2 (mm) 10.42 1.00 T3 (mm) 8.37 15.38

[0129] Table 6

[0130] Example 4

[0131] The following is for reference Figure 4A and Figure 4B The endoscope adapter lens 400 according to Embodiment 4 of this application is described. Figure 4A This is a schematic diagram of the endoscope adapter lens 400 in the wide-angle end according to Embodiment 4 of this application. Figure 4B This is a schematic diagram of the endoscope adapter lens 400 in the telephoto end according to Embodiment 4 of this application.

[0132] like Figure 4A and Figure 4B As shown, the endoscope adapter lens 400 includes, from the object side to the image side, the following components in sequence: positioning surface D, front protective glass CG1, first lens group G1 with positive optical power, aperture stop STO (not shown), second lens group G2 with negative optical power, third lens group G3 with positive optical power, rear protective glass CG2, and imaging surface IMA.

[0133] In Example 4, the front protective glass CG1 has an object side surface S2 and an image side surface S3, and the rear protective glass CG2 has an object side surface S25 and an image side surface S26.

[0134] The first lens group G1 includes a first lens L1, a second lens L2, and a third lens L3. The first lens L1 has positive optical power, with its object-side surface S4 being convex and its image-side surface S5 being convex. The second lens L2 has negative optical power, with its object-side surface S5 being concave and its image-side surface S6 being convex. The third lens L3 has positive optical power, with its object-side surface S7 being convex and its image-side surface S8 being convex. The first lens L1 and the second lens L2 are cemented together to form a cemented doublet lens.

[0135] The second lens group G2 includes a fourth lens L4, a fifth lens L5, a sixth lens L6, and a seventh lens L7. The fourth lens L4 can have negative optical power, with its object-side surface S9 being convex and its image-side surface S10 being concave. The fifth lens L5 can have positive optical power, with its object-side surface S11 being convex and its image-side surface S12 being concave. The sixth lens L6 can have positive optical power, with its object-side surface S13 being concave and its image-side surface S14 being convex. The seventh lens L7 can have negative optical power, with its object-side surface S14 being concave and its image-side surface S15 being concave. The sixth lens L6 and the seventh lens L7 are cemented together to form a cemented doublet lens.

[0136] The third lens group G3 includes the eighth lens L8, the ninth lens L9, the tenth lens L10, the eleventh lens L11, the twelfth lens L12, and the thirteenth lens L13. The eighth lens L8 has positive optical power, with its object-side surface S16 being concave and its image-side surface S17 being convex. The ninth lens L9 has positive optical power, with its object-side surface S18 being convex and its image-side surface S19 being convex. The tenth lens L10 has negative optical power, with its object-side surface S19 being concave and its image-side surface S20 being convex. The eleventh lens L11 has positive optical power, with its object-side surface S21 being convex and its image-side surface S22 being convex. The twelfth lens L12 has negative optical power, with its object-side surface S22 being concave and its image-side surface S23 being concave. The thirteenth lens L13 has positive optical power, with its object-side surface S23 being convex and its image-side surface S24 being convex. Lens L9 (ninth lens) and lens L10 (tenth lens) are cemented together to form a cemented doublet lens. Lens L11 (eleventh lens), lens L12 (twelfth lens), and lens L13 (thirteenth lens) are cemented together to form a cemented triplicate lens.

[0137] The aperture stop STO is positioned between the first lens group G1 and the second lens group G2, and more specifically, the aperture stop STO is positioned between the third lens L3 and the fourth lens L4.

[0138] Light from the object passes through each surface in sequence (i.e., through the front protective glass CG1, the first lens L1 to the thirteenth lens L13, and the rear protective glass CG2 in sequence) and is finally imaged on the imaging surface IMA, where an image sensing chip may be provided.

[0139] Table 7 shows the basic parameters of the endoscope adapter lens 400 of Example 4, where the units for radius of curvature and thickness / distance are millimeters (mm).

[0140]

[0141]

[0142] Table 7

[0143] Table 8 shows the values ​​of T1, T2, and T3 in Table 7 when the endoscope adapter lens 400 is at the wide-angle and telephoto ends, respectively. Table 8 also shows the total effective focal length F and aperture value Fno of the endoscope adapter lens 400 in Embodiment 4, wherein F and Fno change as the endoscope adapter lens 400 switches from the wide-angle end to the telephoto end or vice versa.

[0144] Wide angle end Telephoto end F (mm) 14 (Fw) 31.9 (Ft) Fno 2.72 6.13 T1 (mm) 0.36 2.77 T2 (mm) 10.33 1.03 T3 (mm) 8.45 15.34

[0145] Table 8

[0146] In summary, Examples 1 to 4 satisfy the relationships shown in Table 9.

[0147] Conditional / Example 1 2 3 4 1.2 < FG1 / Fw < 1.5 1.348 1.341 1.356 1.361 -0.8 < FG2 / Fw < -0.5 -0.591 -0.574 -0.582 -0.584 0.9 < FG3 / Fw < 1.2 0.954 0.929 0.950 0.931 0.6 < ENP / Fw < 1.0 0.786 0.786 0.700 0.786 0.2 < ENP / Ft < 0.5 0.345 0.345 0.307 0.345 0.2 < d2 / d3 < 0.5 0.364 0.350 0.343 0.351 0 < d2 / Ft < 0.2 0.079 0.075 0.075 0.076 18≤Vd G2 ≤30]]> 25.458 29.134 25.458 29.134 1.8≤Nd G2 ≤2.1]]> 2.000 1.835 2.000 2.000 0.2 < TG2 / TG3 < 0.5 0.323 0.285 0.295 0.299 1.5 < f8 / fG3 < 2.5 2.039 2.360 2.273 2.310 0.1 ≤ Dmax / TTL ≤ 0.3 0.216 0.223 0.217 0.223 1.2 < D8w / D8t < 1.9 1.712 1.600 1.720 1.723 0.2 < D9w / f910 < 0.5 0.255 0.341 0.318 0.337

[0148] Table 9

[0149] The above description is merely a preferred embodiment of this application and an explanation of the technical principles employed. Those skilled in the art should understand that the scope of the invention involved in this application is not limited to technical solutions formed by specific combinations of the above-described technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the inventive concept. For example, technical solutions formed by substituting the above features with (but not limited to) technical features with similar functions disclosed in this application.

Claims

1. An endoscope adapter lens, characterized by, in order from the object side to the image side along the optical axis, and a first lens group having positive refractive power, the first lens group being a fixed group; a second lens group having negative refractive power, the second lens group being a variable group; a third lens group having positive refractive power, the third lens group being a compensation group; wherein the second lens group moves along the optical axis between the object side and the image side to achieve continuous zooming between a wide angle end and a telephoto end; the third lens group moves along the optical axis between the object side and the image side to achieve compensation of image surface position variation during zooming; the number of lens groups having refractive power in the endoscope adapter lens is three; the number of lenses having refractive power in the endoscope adapter lens is thirteen; the first lens group includes, in order from the object side to the image side along the optical axis, a first lens having positive refractive power, a second lens having negative refractive power, and a third lens having positive refractive power; the second lens group includes, in order from the object side to the image side along the optical axis, a fourth lens having negative refractive power, a fifth lens having positive refractive power, a sixth lens having positive refractive power, and a seventh lens having negative refractive power; the third lens group includes, in order from the object side to the image side along the optical axis, an eighth lens having positive refractive power, a ninth lens having positive refractive power, a tenth lens having negative refractive power, an eleventh lens having positive refractive power, a twelfth lens having negative refractive power, and a thirteenth lens having positive refractive power; the endoscope adapter lens satisfies: 1.5 < f8 / FG3 < 2.5, where f8 is the effective focal length of the eighth lens and FG3 is the effective focal length of the third lens group.

2. The endoscope adapter lens according to claim 1, wherein the object side surface and the image side surface of the first lens are both convex; the object side surface of the second lens is concave; and the object side surface and the image side surface of the third lens are both convex.

3. The endoscope adapter lens according to claim 1, wherein the image side surface of the fourth lens is concave; the object side surface of the fifth lens is convex and the image side surface is concave; the object side surface of the sixth lens is concave and the image side surface is convex; and the object side surface of the seventh lens is concave.

4. The endoscope adapter lens according to claim 1, wherein the image side surface of the eighth lens is convex; the object side surface of the ninth lens is convex and the image side surface is convex; the object side surface of the tenth lens is concave and the image side surface is convex; the object side surface and the image side surface of the eleventh lens are both convex; the object side surface and the image side surface of the twelfth lens are both concave; the object side surface and the image side surface of the thirteenth lens are both convex.

5. The endoscope adapter lens according to any one of claims 1 to 4, wherein the endoscope adapter lens satisfies: 1.2 < FG1 / Fw < 1.5, where FG1 is the effective focal length of the first lens group and Fw is the total effective focal length of the endoscope adapter lens at the wide angle end.

6. The endoscope adapter lens according to any one of claims 1 to 4, wherein The endoscope adapter lens satisfies -0.8 < FG2 / Fw < -0.5, where FG2 is an effective focal length of the second lens group, and Fw is a total effective focal length of the endoscope adapter lens at a wide angle end.

7. The endoscope adapter lens according to any one of claims 1 to 4, wherein The endoscope adapter lens satisfies 0.9 < FG3 / Fw < 1.2, where FG3 is an effective focal length of the third lens group, and Fw is a total effective focal length of the endoscope adapter lens at a wide angle end.

8. The endoscope adapter lens according to any one of claims 1 to 4, wherein The endoscope adapter lens satisfies 0.6 < ENP / Fw < 1.0, where ENP is a distance from a position of an entrance pupil of the endoscope adapter lens to a position of 3 mm on an object side of a front protective glass of the endoscope adapter lens, and Fw is a total effective focal length of the endoscope adapter lens at a wide angle end.

9. The endoscope adapter lens according to any one of claims 1 to 4, wherein The endoscope adapter lens satisfies 0.2 < ENP / Ft < 0.5, where ENP is a distance from a position of an entrance pupil of the endoscope adapter lens to a position of 3 mm on an object side of a front protective glass of the endoscope adapter lens, and Ft is a total effective focal length of the endoscope adapter lens at a telephoto end.

10. The endoscope adapter lens according to any one of claims 1 to 4, wherein The endoscope adapter lens satisfies 0.2 < d2 / d3 < 0.5, where d2 is an on-axis distance between a position of the second lens group on the optical axis of the endoscope adapter lens at a wide angle end and a position of the second lens group on the optical axis of the endoscope adapter lens at a telephoto end, and d3 is an on-axis distance between a position of the third lens group on the optical axis of the endoscope adapter lens at a wide angle end and a position of the third lens group on the optical axis of the endoscope adapter lens at a telephoto end.

11. The endoscope adapter lens according to any one of claims 1 to 4, wherein The endoscope adapter lens satisfies 0 < d2 / Ft < 0.2, where d2 is an on-axis distance between a position of the second lens group on the optical axis of the endoscope adapter lens at a wide angle end and a position of the second lens group on the optical axis of the endoscope adapter lens at a telephoto end, and Ft is a total effective focal length of the endoscope adapter lens at a telephoto end.

12. The endoscope adapter lens according to any one of claims 1 to 4, wherein Abbe number Vd of at least one lens in the second lens group G2 satisfies: 18 ≤ Vd G2 ≤ 30.

13. The endoscope adapter lens according to any one of claims 1 to 4, wherein a refractive index Nd of at least one lens in the second lens group G2 satisfies: 1.8 ≤ Nd G2 ≤ 2.

1.

14. The endoscope adapter lens according to any one of claims 1 to 4, wherein The endoscope adapter lens satisfies 0.2 < TG2 / TG3 < 0.5, where TG2 is a thickness of the second lens group on the optical axis, and TG3 is a thickness of the third lens group on the optical axis.

15. The endoscope adapter lens according to any one of claims 1 to 4, characterized in that, the endoscope adapter lens satisfies 0.1 ≤ Dmax / TTL ≤ 0.3, where Dmax is a maximum effective light-passing full aperture of the endoscope adapter lens, and TTL is an on-axis distance from an object side surface of the first lens to an image plane of the endoscope adapter lens.

16. The endoscope adapter lens according to claim 1 or 4, characterized in that, the endoscope adapter lens satisfies 1.2 < D8w / D8t < 1.9, where D8w is an effective light-passing full aperture of an image side surface of the eighth lens when the endoscope adapter lens is at a wide-angle end, and D8t is an effective light-passing full aperture of the image side surface of the eighth lens when the endoscope adapter lens is at a telephoto end.

17. The endoscope adapter lens according to claim 1 or 4, characterized in that, the endoscope adapter lens satisfies 0.2 < D9w / f910 < 0.5, where D9w is an effective light-passing full aperture of an object side surface of the ninth lens when the endoscope adapter lens is at the wide-angle end, and f910 is a combined focal length of the ninth lens and the tenth lens.

18. The endoscope adapter lens of any one of claims 1 to 4, wherein, the endoscope adapter lens satisfies at least one of: 1.341 ≤ FG1 / Fw ≤ 1.361, -0.591 ≤ FG2 / Fw ≤ -0.574, 0.929 ≤ FG3 / Fw ≤ 0.954, 0.700 ≤ ENP / Fw ≤ 0.786, 0.307 ≤ ENP / Ft ≤ 0.345, 0.343 ≤ d2 / d3 ≤ 0.364, 0.075 ≤ d2 / Ft ≤ 0.079, 25. 458 < Vd G2 ≤ 29.134, 1.8 < Nd G2 ≤ 2.000, 0.285 ≤ TG2 / TG3 ≤ 0.323, 0.216 ≤ Dmax / TTL ≤ 0.223, wherein FG1 is an effective focal length of the first lens group, FG2 is an effective focal length of the second lens group, FG3 is an effective focal length of the third lens group, ENP is a distance from a position 3mm on the object side of a front protective glass of the endoscope adapter lens to an entrance pupil position of the endoscope adapter lens, Fw is a total effective focal length of the endoscope adapter lens at a wide angle end, Ft is a total effective focal length of the endoscope adapter lens at a telephoto end, d2 is an on-axis distance between a position of the second lens group on the optical axis at the wide angle end of the endoscope adapter lens and a position of the second lens group on the optical axis at the telephoto end of the endoscope adapter lens, d3 is an on-axis distance between a position of the third lens group on the optical axis at the wide angle end of the endoscope adapter lens and a position of the third lens group on the optical axis at the telephoto end of the endoscope adapter lens, Vd G2 is an Abbe number of at least one lens in the second lens group, Nd G2 is a refractive index of at least one lens in the second lens group, TG2 is a thickness of the second lens group on the optical axis, TG3 is a thickness of the third lens group on the optical axis, Dmax is a maximum clear aperture of the endoscope adapter lens, and TTL is an on-axis distance from a position on the object side of the first lens to an image plane of the endoscope adapter lens.

19. The endoscope adapter lens of claim 1 or 4, wherein, the endoscope adapter lens satisfies at least one of: 2.039 ≤ f8 / FG3 ≤ 2.360, 1.600 ≤ D8w / D8t ≤ 1.723, 0.255 ≤ D9w / f910 ≤ 0.341, where f8 is an effective focal length of the eighth lens, FG3 is an effective focal length of the third lens group, D8w is the effective light-passing full aperture of the image side surface of the eighth lens when the endoscope adapter lens is at the wide-angle end, D8t is the effective light-passing full aperture of the image side surface of the eighth lens when the endoscope adapter lens is at the telephoto end, D9w is the effective light-passing full aperture of the object side surface of the ninth lens when the endoscope adapter lens is at the wide-angle end, and f910 is the combined focal length of the ninth lens and the tenth lens.

Images