Endoscope adaptive lens

Abstract

The utility model discloses an endoscope adaptive lens. The endoscope adaptive lens sequentially comprises a first lens group with positive focal power, a second lens group with negative focal power and a third lens group with positive focal power from an object side to an image side along an optical axis, wherein the first lens group sequentially comprises a first lens, a second lens and a third lens from the object side to the image side along the optical axis; the second lens group sequentially comprises a fourth lens, a fifth lens, a sixth lens and a seventh lens from the object side to the image side along the optical axis; the third lens group sequentially comprises an eighth lens, a ninth lens, a tenth lens, an eleventh lens, a twelfth lens and a thirteenth lens from the object side to the image side along the optical axis.

Description

Technical Field

[0001] This application relates to the field of optical elements, and more particularly, to an endoscope adapter lens. Background Art

[0002] With the rapid development of endoscopes, the industry has increasingly higher requirements for the performance of endoscopes. Among them, in order to obtain clear images of the lesion area to the greatest extent and improve the accuracy of diagnosis, the industry has put forward 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 lens: 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 requirements; 2) The size of the zoom endoscope adapter lens is large, making it impossible to miniaturize the entire camera; 3) The entrance pupil position changes during the zooming process of the zoom endoscope adapter lens, resulting in unstable imaging. Summary of the Utility Model

[0004] This application provides an endoscope adapter lens, which sequentially includes, from the object side to the image side along the optical axis: 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; wherein, the first lens group sequentially includes, from the object side to the image side along the optical axis: a first lens, a second lens, and a third lens; the second lens group sequentially includes, from the object side to the image side along the optical axis: a fourth lens, a fifth lens, a sixth lens, and a seventh lens; the third lens group sequentially includes, from the object side to the image side along the optical axis: an eighth lens, a ninth lens, a tenth lens, an eleventh lens, a twelfth lens, and a thirteenth lens.

[0005] In one embodiment, the first lens group is a fixed group, and its distance relative to the imaging surface is fixed; the second lens group is a zoom group, which moves between the object side and the image side along the optical axis to achieve continuous zooming between the wide-angle end and the telephoto end; the second lens group is a compensation group, which moves between the object side and the image side along the optical axis to compensate for the change in the image plane position during the zooming process.

[0006] In one embodiment, the first lens has positive optical power; the second lens has negative optical power; and the third lens has positive optical power.

[0007] 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.

[0008] In one embodiment, the fourth lens has negative optical power; the fifth lens has positive optical power; the sixth lens has positive optical power; and the seventh lens has negative optical power.

[0009] In one 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.

[0010] In one embodiment, the eighth lens has a positive focal power; the ninth lens has a positive focal power; the tenth lens has a negative focal power; the eleventh lens has a positive focal power; the twelfth lens has a negative focal power; and the thirteenth lens has a positive focal power.

[0011] In one embodiment, 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; and the object side surface and the image side surface of the thirteenth lens are both convex.

[0012] In one embodiment, the endoscopic 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 endoscopic adapter lens at the wide-angle end.

[0013] In one embodiment, the endoscopic 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 endoscopic adapter lens at the wide-angle end.

[0014] In one embodiment, the endoscopic 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 endoscopic adapter lens at the wide-angle end.

[0015] In one embodiment, the endoscopic adapter lens satisfies: 0.6 < ENP / Fw < 1.0, where ENP is the distance from the entrance pupil position of the endoscopic adapter lens to the position 3 mm 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.

[0016] In one embodiment, the endoscopic adapter lens satisfies: 0.2 < ENP / Ft < 0.5, where ENP is the distance from the entrance pupil position of the endoscopic adapter lens to the position 3 mm on the object side of the front protective glass of the endoscopic adapter lens, and Ft is the total effective focal length of the endoscopic adapter lens at the telephoto end.

[0017] In one embodiment, the endoscopic adapter lens satisfies: 0.2 < d2 / d3 < 0.5, where d2 is the axial distance between the positions of the second lens group on the optical axis when the endoscopic adapter lens is at the wide-angle end and when the endoscopic adapter lens is at the telephoto end, and d3 is the axial distance between the positions of the third lens group on the optical axis when the endoscopic adapter lens is at the wide-angle end and when the endoscopic adapter lens is at the telephoto end.

[0018] In one embodiment, the endoscopic adapter lens satisfies: 0 < d2 / Ft < 0.2, where d2 is the axial distance between the positions of the second lens group on the optical axis when the endoscopic adapter lens is at the wide-angle end and when the endoscopic adapter lens is at the telephoto end, and Ft is the total effective focal length when the endoscopic adapter lens is at the telephoto end.

[0019] In one embodiment, the Abbe number Vd of at least one lens in the second lens group G2 satisfies: 18 ≤ Vd G2 ≤ 30.

[0020] In one embodiment, the refractive index Nd of at least one lens in the second lens group G2 satisfies: 1.8 ≤ Nd G2 ≤ 2.1.

[0021] In one embodiment, the endoscopic adapter lens satisfies: 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.

[0022] In one embodiment, the endoscopic 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.

[0023] In one embodiment, the endoscopic adapter lens satisfies: 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 surface of the first lens to the imaging surface of the endoscopic adapter lens.

[0024] In one embodiment, the endoscopic adapter lens satisfies: 1.2 < D8w / D8t < 1.9, where D8w is the effective clear aperture of the image side surface of the eighth lens when the endoscopic adapter lens is at the wide-angle end and D8t is the effective clear aperture of the image side surface of the eighth lens when the endoscopic adapter lens is at the telephoto end.

[0025] In one embodiment, the endoscopic adapter lens satisfies: 0.2 < D9w / f910 < 0.5, where D9w is the effective full aperture of the object side of the ninth lens at the wide-angle end of the endoscopic adapter lens, and f910 is the combined focal length of the ninth lens and the tenth lens.

[0026] The endoscopic adapter lens provided by the embodiment of the present application includes three lens groups. By reasonably setting the optical power of the first lens group to the third lens group and the number of lenses, system aberrations can be corrected, the tolerance sensitivity can be reduced, and the resolution can be improved, which is beneficial to achieving at least one of the beneficial effects such as high resolution, small volume, infrared confocal, wide object distance range, and unchanged entrance pupil position during zooming of the endoscopic adapter lens provided by the present application. Description of the Drawings

[0027] By reading the detailed description of the non-limiting embodiments with reference to the following drawings, other features, objects, and advantages of the present application will become more apparent:

[0028] Figure 1A and Figure 1B are respectively schematic structural diagrams of the endoscopic adapter lens according to Embodiment 1 of the present application at the wide-angle end and the telephoto end;

[0029] Figure 2A and Figure 2B are respectively schematic structural diagrams of the endoscopic adapter lens according to Embodiment 2 of the present application at the wide-angle end and the telephoto end;

[0030] Figure 3A and Figure 3B are respectively schematic structural diagrams of the endoscopic adapter lens according to Embodiment 3 of the present application at the wide-angle end and the telephoto end; and

[0031] Figure 4A and Figure 4B are respectively schematic structural diagrams of the endoscopic adapter lens according to Embodiment 4 of the present application at the wide-angle end and the telephoto end. Detailed Embodiments

[0032] To better understand the present application, more detailed descriptions of various aspects of the present application will be made with reference to the drawings. It should be understood that these detailed descriptions are only descriptions of the exemplary embodiments of the present application and do not limit the scope of the present application in any way. Throughout the specification, the same reference numerals refer to the same elements. The expression "and / or" includes any and all combinations of one or more of the associated listed items.

[0033] It should be noted that in this specification, the expressions such as first, second, third, etc. are only used to distinguish one feature from another, and do not represent any limitation on the features. Therefore, without departing from the teachings of the present application, the first lens discussed below may also be referred to as the second lens or the third lens.

[0034] In the drawings, for the sake of clarity, the thickness, dimensions and shape of the lenses have been slightly exaggerated. Specifically, the spherical or aspherical shapes shown in the drawings are shown by way of example. That is, the spherical or aspherical shapes are not limited to the spherical or aspherical shapes shown in the drawings. The drawings are for illustrative purposes only and are not drawn to an exact scale.

[0035] In this context, the paraxial region refers to the region near the optical axis. If the lens surface is convex and the position of the convex surface is not defined, it means that the lens surface is convex at least in the paraxial region; if the lens surface is concave and the position of the concave surface is not defined, it means that the lens surface is concave at least in the paraxial region. The surface of each lens closest to the object being photographed is called the object side surface of the lens, and the surface of each lens closest to the imaging surface is called the image side surface of the lens.

[0036] It should also be understood that the terms "comprises", "comprising", "has", "including" and / or "including having", when used in this specification, denote the presence of the stated features, elements and / or components, but do not preclude the presence or addition of one or more other features, elements, components and / or combinations thereof. Further, when an expression such as "at least one of..." appears after a list of listed features, it modifies the entire list of listed features rather than an individual element in the list. Further, when describing embodiments of the present application, the use of "may" means "one or more embodiments of the present application". And the term "exemplary" is intended to refer to an example or illustration.

[0037] 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 terms (such as those defined in a common dictionary) should be interpreted as having a meaning 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.

[0038] It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments may be combined with each other. The present application will be described in detail below with reference to the drawings and in combination with the embodiments.

[0039] The features, principles and other aspects of the present application are described in detail below.

[0040] The endoscope adapter lens according to an exemplary embodiment of the present application may include three lens groups with optical powers, namely, a first lens group with a positive optical power, a second lens group with a negative optical power, and a third lens group with a positive optical power. These three lens groups are arranged in sequence along the optical axis from the object side to the image side. Among them, the first lens group includes, in sequence along the optical axis from the object side to the image side: a first lens, a second lens, and a third lens; the second lens group includes, in sequence along the optical axis from the object side to the image side: a fourth lens, a fifth lens, a sixth lens, and a seventh lens; the third lens group includes, in sequence along the optical axis from the object side to the image side: an eighth lens, a ninth lens, a tenth lens, an eleventh lens, a twelfth lens, and a thirteenth lens.

[0041] In an exemplary embodiment of the present application, when the object distance changes, the first lens group is a fixed group, and its distance relative to the imaging plane is fixed. The second lens group and the third lens group move along the optical axis. Among them, 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 zoom 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 the zooming process to ensure real-time clarity of imaging; that is, the third lens group moves along the optical axis in correspondence with the movement of the second lens group to achieve the compensation effect of the change in the image plane position during the zooming process, so that the endoscope adapter lens has a better imaging position during continuous zooming and the imaging quality is stable.

[0042] In an exemplary embodiment, the number of lenses with optical powers in the first lens group is three. The first lens group includes, in sequence along the optical axis from the object side to the image side: a first lens with a positive optical power, a second lens with a negative optical power, and a third lens with a positive optical power.

[0043] In an exemplary 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.

[0044] In an exemplary embodiment, the first lens group includes two lenses with positive optical powers and one lens with a negative optical power. More specifically, the first lens is a convex-convex lens with a positive optical power, the second lens is a lens with a negative optical power and a concave object side surface, and the third lens is a convex-convex lens with a positive optical power. The two double-convex lenses with positive optical powers are beneficial to the correction of field curvature at different object distances; setting the object side surface of the first lens to be convex and the image side surface to be convex is beneficial to reducing distortion.

[0045] In an exemplary embodiment, the first lens and the second lens can form a doublet lens, and by reasonably matching the materials of the first lens and the second lens, the purpose of correcting axial chromatic aberration can be achieved.

[0046] In an exemplary embodiment, the number of lenses with optical power in the second lens group is four. The second lens group sequentially includes, from the object side to the image side along the optical axis: 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.

[0047] In an exemplary 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.

[0048] In an exemplary embodiment, the sixth lens and the seventh lens can form a doublet lens, which is beneficial to both the correction of field curvature and the reduction of the defocus amount of the infrared spectrum relative to the visible spectrum, realizing the infrared confocal function of the lens.

[0049] In an exemplary embodiment, the number of lenses with optical power in the third lens group is six. The third lens group sequentially includes, 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; a thirteenth lens with positive optical power.

[0050] In an exemplary embodiment, the image side surface of the eighth lens is convex, which is beneficial to correcting field curvature; the object side surface of the ninth lens is convex and the image side surface is convex, which is beneficial to reducing the light height and reducing 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; the object side surface and the image side surface of the thirteenth lens are both convex.

[0051] In an exemplary embodiment, the third lens group may include a positive optical power lens with a convex image side surface and at least one positive optical power lens with two convex surfaces.

[0052] In an exemplary embodiment, the third lens group may include two cemented lenses.

[0053] In an exemplary embodiment, the ninth lens and the tenth lens can form a doublet lens. More specifically, a doublet lens is formed by the ninth lens with positive optical power and the tenth lens with negative optical power, which is beneficial to the mutual compensation of positive spherical aberration and negative spherical aberration and is beneficial to improving the resolution of the system.

[0054] In an exemplary embodiment, the eleventh lens, the twelfth lens and the thirteenth lens can form a triplet lens. By reasonably matching the optical powers of each lens, it is beneficial to correct chromatic aberration and reduce the sensitivity of the system to tolerances.

[0055] In an exemplary embodiment, the endoscopic adapter lens according to the present application further includes a diaphragm disposed between the first lens group and the second lens group. The diaphragm is beneficial to converging the light entering the lens, reducing the incident angle of the light to 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 diaphragm can be disposed between the third lens and the fourth lens. However, it should be noted that the position of the diaphragm disclosed herein is only an example and not a limitation; in an alternative embodiment, the diaphragm can also be disposed at other positions according to actual needs.

[0056] 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 of waterproofing, dustproofing, and scratch resistance.

[0057] In an exemplary embodiment, the endoscopic adapter lens according to the present application can 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. Reasonably controlling the effective focal length of the first lens group and the total effective focal length of the endoscopic adapter lens at the wide-angle end is beneficial to the light converging gently into the optical system and effectively reducing the distortion of the optical system.

[0058] In an exemplary embodiment, the endoscopic adapter lens according to the present application can 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. By reasonably controlling the focal length value of the second lens group, the imaging performance is achieved while ensuring the required zoom ratio during the zoom process.

[0059] In an exemplary embodiment, the endoscopic adapter lens according to the present application can 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. Reasonably distributing the focal length value of the third lens group is beneficial to the third lens group collecting the outgoing light of the second lens group, making the optical transition gentle, and being beneficial to the correction of the field curvature at different object distances.

[0060] In an exemplary embodiment, the endoscopic adapter lens according to the present application can satisfy: 0.6 < ENP / Fw < 1.0, where ENP is the distance from the entrance pupil position of the endoscopic adapter lens to 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. By reasonably controlling the position of the entrance pupil, the endoscopic adapter lens can stably receive the light of the endoscopic objective lens, and can also reduce the change of spherical aberration and distortion during the entire zoom process to obtain high imaging performance.

[0061] In an exemplary embodiment, the endoscopic 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 endoscopic adapter lens to the object side 3 mm position of the front protective glass of the endoscopic adapter lens, and Ft is the total effective focal length of the endoscopic adapter lens at the telephoto end. By reasonably controlling the position of the entrance pupil, the endoscopic adapter lens can stably receive the light from the endoscopic objective lens, and can also reduce the changes in spherical aberration and distortion during the entire zooming process to obtain high imaging performance.

[0062] In an exemplary embodiment, the endoscopic 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 endoscopic adapter lens at the wide-angle end and the positions of the second lens group on the optical axis of the endoscopic 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 endoscopic adapter lens at the wide-angle end and the positions of the third lens group on the optical axis of the endoscopic adapter lens at the telephoto end. By controlling the ratio of the moving distance of the zoom group to the moving distance of the compensation group, the focusing reaction is fast during the zooming process, which is beneficial to improving the focusing sensitivity.

[0063] In an exemplary embodiment, the endoscopic 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 endoscopic adapter lens at the wide-angle end and the positions of the second lens group on the optical axis of the endoscopic adapter lens at the telephoto end, and Ft is the total effective focal length of the endoscopic 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 can also control the volume of the lens and reduce the design cost.

[0064] In an exemplary embodiment, the Abbe number VdG2 of at least one lens in the second lens group of the endoscopic adapter lens according to the present application can satisfy: 18 ≤ Vd G2 ≤ 30. By reasonably setting the Abbe number of the lens in the second lens group, the chromatic aberration of the second lens group can be effectively corrected, thereby improving the imaging quality of the optical system.

[0065] In an exemplary embodiment, the refractive index Nd of at least one lens in the second lens group of the endoscopic adapter lens according to the present application G2 can satisfy: 1.8 ≤ Nd G2 ≤ 2.1. By reasonably setting the refractive index of the lens in the second lens group, the distortion of the second lens group can be effectively corrected, thereby improving the imaging quality of the optical system.

[0066] In an exemplary embodiment, the endoscope adapter lens according to the present application can 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. By reasonably setting the ratio of the thickness of the second lens group on the optical axis to the thickness of the third lens group on the optical axis, the volume of the third lens group is relatively small, which is beneficial to realizing the miniaturization of the lens.

[0067] In an exemplary embodiment, the endoscope adapter lens according to the present application can 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 passing amount.

[0068] In an exemplary embodiment, the endoscope adapter lens according to the present application can satisfy: 0.1 ≤ Dmax / TTL ≤ 0.3, where Dmax is the maximum clear aperture of the endoscope adapter lens, and TTL is the axial distance from the object side surface of the first lens to the imaging surface of the endoscope adapter lens. Satisfying 0.1 ≤ Dmax / TTL ≤ 0.3 is beneficial to, under the condition of a certain total system optical length, by controlling the maximum clear aperture of the endoscope adapter lens during the zooming process of the endoscope adapter lens, making the maximum clear aperture of the endoscope adapter lens relatively small, which is beneficial to realizing a small volume (or miniaturization).

[0069] In an exemplary embodiment, the endoscope adapter lens according to the present application can satisfy: 1.2 < D8w / D8t < 1.9, where D8w is the effective clear aperture of the image side surface of the eighth lens of the endoscope adapter lens at the wide-angle end, and D8t is the effective clear aperture of the image side surface of the eighth lens of the endoscope 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 is beneficial to the illuminance uniformity between the wide-angle end and the telephoto end.

[0070] In an exemplary embodiment, the endoscope adapter lens according to the present application can satisfy: 0.2 < D9w / f910 < 0.5, where D9w is the effective clear aperture of the object side surface of the ninth lens of the endoscope 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, beneficial to the correction of aberration, and improving the lens resolution.

[0071] In an exemplary embodiment, the first lens to the thirteenth lens may be spherical lenses or aspherical lenses. The present application does not specifically limit the specific number of spherical lenses and aspherical lenses. When focusing on imaging quality, the number of aspherical lenses can be increased, and even all lenses can be aspherical lenses. The characteristic of an aspherical lens is that the curvature continuously changes from the center to the periphery of the lens. Different from a spherical lens with a constant curvature from the center to the periphery, an aspherical lens has better curvature radius characteristics and has the advantages of improving distortion aberration and astigmatism aberration. After using an aspherical lens, it is possible to eliminate the aberration that appears during imaging as much as possible, thereby improving the imaging quality of the lens. Optionally, the first lens to the thirteenth lens are all spherical lenses, which have low cost and good tolerances.

[0072] The endoscopic adapter lens of the present application has excellent resolution, with a resolution of over 4K.

[0073] During the zooming process of the endoscopic adapter lens of the present application, the position of the entrance pupil remains unchanged, which is beneficial to maintaining the stability of the image plane.

[0074] The endoscopic adapter lens of the present application can be used in a wide range of object distances. Throughout the zooming process, it can ensure clear focusing for object distances from 0.5m to infinity, and the imaging effect is good.

[0075] The endoscopic adapter lens of the present application can achieve infrared confocal, ensuring the imaging performance in the infrared band in the design, and combined with the use of an infrared fill light, enabling the lens to be applicable to night scenes and the endoscopic field.

[0076] By reasonably setting the optical power of each lens group and the optical power, surface shape of each lens, the present application is beneficial for the endoscopic adapter lens to have good capabilities of correcting optical aberration and chromatic aberration when switching between the wide-angle end and the telephoto end, and at the same time is beneficial for reducing the tolerance sensitivity of the system and improving the uniformity of the image, etc.

[0077] Optionally, in other alternative exemplary embodiments, the above endoscopic adapter lens may further include a filter for correcting color deviation and / or a protective glass for protecting the photosensitive element located on the imaging surface.

[0078] The endoscopic adapter lens according to the above embodiment of the present application can adopt multiple lenses, such as the thirteen lenses mentioned above. By reasonably distributing optical parameters such as the optical power, surface shape, central thickness of each lens, and the on-axis distance between each lens, the endoscopic adapter lens provided by the present application has at least one beneficial effect such as high resolution (4K), small volume, infrared confocal, wide range of object distances used (object distance from 0.5m to infinity), and the position of the entrance pupil remaining unchanged during the zooming process, and can be adapted to the endoscopic adapter lens.

[0079] However, those skilled in the art should understand that, without departing from the technical solution claimed in this application, the number of lenses constituting the endoscopic adapter lens can be changed to obtain the various results and advantages described in this specification. For example, although thirteen lenses are described as an example in the embodiment, the endoscopic adapter lens is not limited to including thirteen lenses. If necessary, the endoscopic adapter lens may also include other numbers of lenses.

[0080] Specific embodiments of the endoscopic adapter lens applicable to the above embodiments will be further described below with reference to the accompanying drawings.

[0081] Example 1

[0082] The following refers to Figure 1A and Figure 1B to describe the endoscopic adapter lens 100 according to Embodiment 1 of this application. Figure 1A FIG. is a schematic structural diagram of the endoscopic adapter lens 100 according to Embodiment 1 of this application at the wide-angle end, Figure 1B and FIG. is a schematic structural diagram of the endoscopic adapter lens 100 according to Embodiment 1 of this application at the telephoto end.

[0083] As Figure 1A and Figure 1B shown, the endoscopic adapter lens 100 sequentially includes, from the object side to the image side: a positioning surface D, a front protective glass CG1, a first lens group G1 with positive optical power, a diaphragm STO (not shown), a second lens group G2 with negative optical power, a third lens group G3 with positive optical power, a rear protective glass CG2, and an imaging surface IMA.

[0084] In this embodiment and the following embodiments, the positioning surface D is located at a position 3 mm on the object side of the front protective glass CG1 of the endoscopic adapter lens.

[0085] In Embodiment 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.

[0086] The first lens group G1 includes a first lens L1, a second lens L2, and a third lens L3. The first lens L1 may have positive optical power, its object side surface S4 is convex, and its image side surface S5 is convex. The second lens L2 may have negative optical power, its object side surface S5 is concave, and its image side surface S6 is concave. The third lens L3 may have positive optical power, its object side surface S7 is convex, and its image side surface S8 is convex. The first lens L1 and the second lens L2 are cemented together to form a doublet lens.

[0087] 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 may have a negative optical power, its object side S9 is convex, and its image side S10 is concave. The fifth lens L5 may have a positive optical power, its object side S11 is convex, and its image side S12 is concave. The sixth lens L6 may have a positive optical power, its object side S13 is concave, and its image side S14 is convex. The seventh lens L7 may have a negative optical power, its object side S14 is concave, and its image side S15 is convex. The sixth lens L6 and the seventh lens L7 are cemented together to form a doublet lens.

[0088] The third lens group G3 includes an eighth lens L8, a ninth lens L9, a tenth lens L10, an eleventh lens L11, a twelfth lens L12, and a thirteenth lens L13. The eighth lens L8 may have a positive optical power, its object side S16 is convex, and its image side S17 is convex. The ninth lens L9 may have a positive optical power, its object side S18 is convex, and its image side S19 is convex. The tenth lens L10 may have a negative optical power, its object side S19 is concave, and its image side S20 is convex. The eleventh lens L11 may have a positive optical power, its object side S21 is convex, and its image side S22 is convex. The twelfth lens L12 may have a negative optical power, its object side S22 is concave, and its image side S23 is concave. The thirteenth lens L13 may have a positive optical power, its object side S23 is convex, and its image side S24 is convex. The ninth lens L9 and the tenth lens L10 are cemented together to form a doublet lens. The eleventh lens L11, the twelfth lens L12, and the thirteenth lens L13 are cemented together to form a triplet lens.

[0089] The stop STO is disposed between the first lens group G1 and the second lens group G2. More specifically, the stop STO is disposed between the third lens L3 and the fourth lens L4.

[0090] Light from the object sequentially passes through each surface (i.e., sequentially passes through the front protective glass CG1, the first lens L1 to the thirteenth lens L13, and the rear protective glass CG2) and finally forms an image on the imaging surface IMA, where an image sensing chip may be disposed at the imaging surface.

[0091] Table 1 shows the basic parameter table of the endoscope adapter lens 100 of Embodiment 1, where the units of the radius of curvature and the thickness / distance are both millimeters (mm).

[0092]

[0093]

[0094] Table 1

[0095] In Embodiment 1 and the following embodiments, when the object distance changes, the first lens group G1 remains stationary, and 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 endoscopic adapter lens can be switched from the wide-angle end to the telephoto end or from the telephoto end to the wide-angle end, so that the total effective focal length of the endoscopic adapter lens is continuously variable. At the same time, by adjusting the position of the third lens group G3 on the optical axis, the image plane can be clearly focused during the zooming process of the endoscopic adapter lens.

[0096] Table 2 shows the values of T1, T2, and T3 in Table 1 when the endoscopic adapter lens 100 is at the wide-angle end and the telephoto end, respectively. Table 2 also shows the total effective focal length F and the aperture value Fno of the endoscopic adapter lens 100 of Embodiment 1, where F and Fno change as the endoscopic adapter lens 100 is switched from the wide-angle end to the telephoto end or from the telephoto end to the wide-angle end.

[0097] Wide-angle end Telephoto end F (mm) 14 (Fw) 31.9 (Ft) Fno 2.72 6.20 T1 (mm) 0.50 2.94 T2 (mm) 10.19 0.96 T3 (mm) 8.46 15.24

[0098] Table 2

[0099] Example 2

[0100] The following refers to Figure 2A and Figure 2B describe the endoscopic adapter lens 200 according to Embodiment 2 of the present application. Figure 2A is a schematic structural diagram of the endoscopic adapter lens 200 according to Embodiment 2 of the present application when it is at the wide-angle end, Figure 2B is a schematic structural diagram of the endoscopic adapter lens 200 according to Embodiment 2 of the present application when it is at the telephoto end.

[0101] In this embodiment and the following embodiments, for the sake of simplicity, some descriptions similar to those in Embodiment 1 will be omitted.

[0102] As Figure 2A and Figure 2B shown, the endoscopic adapter lens 200 sequentially includes, from the object side to the image side: a positioning surface D, a front protective glass CG1, a first lens group G1 with a positive optical power, a diaphragm STO (not shown), a second lens group G2 with a negative optical power, a third lens group G3 with a positive optical power, a rear protective glass CG2, and an imaging surface IMA.

[0103] In Embodiment 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.

[0104] The first lens group G1 includes a first lens L1, a second lens L2, and a third lens L3. The first lens L1 may have a positive optical power, with its object side S4 being convex and its image side S5 being convex. The second lens L2 may have a negative optical power, with its object side S5 being concave and its image side S6 being convex. The third lens L3 may have a positive optical power, with its object side S7 being convex and its image side S8 being convex. The first lens L1 and the second lens L2 are cemented together to form a doublet lens.

[0105] 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 may have a negative optical power, with its object side S9 being convex and its image side S10 being concave. The fifth lens L5 may have a positive optical power, with its object side S11 being convex and its image side S12 being concave. The sixth lens L6 may have a positive optical power, with its object side S13 being concave and its image side S14 being convex. The seventh lens L7 may have a negative optical power, with its object side S15 being concave and its image side S16 being convex.

[0106] The third lens group G3 includes an eighth lens L8, a ninth lens L9, a tenth lens L10, an eleventh lens L11, a twelfth lens L12, and a thirteenth lens L13. The eighth lens L8 may have a positive optical power, with its object side S17 being concave and its image side S18 being convex. The ninth lens L9 may have a positive optical power, with its object side S19 being convex and its image side S20 being convex. The tenth lens L10 may have a negative optical power, with its object side S20 being concave and its image side S21 being convex. The eleventh lens L11 may have a positive optical power, with its object side S22 being convex and its image side S23 being convex. The twelfth lens L12 may have a negative optical power, with its object side S23 being concave and its image side S24 being concave. The thirteenth lens L13 may have a positive optical power, with its object side S24 being convex and its image side S25 being convex. The ninth lens L9 and the tenth lens L10 are cemented together to form a doublet lens. The eleventh lens L11, the twelfth lens L12, and the thirteenth lens L13 are cemented together to form a triplet lens.

[0107] The stop STO is disposed between the first lens group G1 and the second lens group G2. More specifically, the stop STO is disposed between the third lens L3 and the fourth lens L4.

[0108] Light from the object sequentially passes through each surface (i.e., sequentially passes through the front protective glass CG1, the first lens L1 to the thirteenth lens L13, and the rear protective glass CG2) and finally forms an image on the imaging surface IMA, where an image sensing chip may be disposed at the imaging surface.

[0109] Table 3 shows the basic parameter table of the endoscope adapter lens 200 of Embodiment 2, where the units of the radius of curvature and the thickness / distance are both millimeters (mm).

[0110]

[0111]

[0112] Table 3

[0113] Table 4 shows the values of T1, T2, and T3 in Table 3 when the endoscopic adapter lens 200 is at the wide-angle end and the telephoto end, respectively. Table 4 also shows the total effective focal length F and the aperture value Fno of the endoscopic adapter lens 200 of Example 2, where F and Fno change as the endoscopic adapter lens 200 switches from the wide-angle end to the telephoto end or from the telephoto end to the wide-angle end.

[0114] 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

[0115] Table 4

[0116] Example 3

[0117] The following refers to Figure 3A and Figure 3B describe the endoscopic adapter lens 300 according to Embodiment 3 of the present application. Figure 3A is a schematic structural diagram of the endoscopic adapter lens 300 according to Embodiment 3 of the present application when it is at the wide-angle end, Figure 3B is a schematic structural diagram of the endoscopic adapter lens 300 according to Embodiment 3 of the present application when it is at the telephoto end.

[0118] As Figure 3A and Figure 3B shown, the endoscopic adapter lens 300 sequentially includes, from the object side to the image side: a positioning surface D, a front protective glass CG1, a first lens group G1 with a positive optical power, a diaphragm STO (not shown), a second lens group G2 with a negative optical power, a third lens group G3 with a positive optical power, a rear protective glass CG2, and an imaging surface IMA.

[0119] In Embodiment 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.

[0120] The first lens group G1 includes a first lens L1, a second lens L2, and a third lens L3. The first lens L1 may have a positive optical power, its object side surface S4 is a convex surface, and its image side surface S5 is a convex surface. The second lens L2 may have a negative optical power, its object side surface S5 is a concave surface, and its image side surface S6 is a convex surface. The third lens L3 may have a positive optical power, its object side surface S7 is a convex surface, and its image side surface S8 is a convex surface. The first lens L1 and the second lens L2 are cemented together to form a doublet lens.

[0121] 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 may have a negative optical power, with its object side S9 being convex and its image side S10 being concave. The fifth lens L5 may have a positive optical power, with its object side S11 being convex and its image side S12 being concave. The sixth lens L6 may have a positive optical power, with its object side S13 being concave and its image side S14 being convex. The seventh lens L7 may have a negative optical power, with its object side S14 being concave and its image side S15 being convex. The sixth lens L6 and the seventh lens L7 are cemented together to form a doublet lens.

[0122] The third lens group G3 includes an eighth lens L8, a ninth lens L9, a tenth lens L10, an eleventh lens L11, a twelfth lens L12, and a thirteenth lens L13. The eighth lens L8 may have a positive optical power, with its object side S16 being concave and its image side S17 being convex. The ninth lens L9 may have a positive optical power, with its object side S18 being convex and its image side S19 being convex. The tenth lens L10 may have a negative optical power, with its object side S19 being concave and its image side S20 being convex. The eleventh lens L11 may have a positive optical power, with its object side S21 being convex and its image side S22 being convex. The twelfth lens L12 may have a negative optical power, with its object side S22 being concave and its image side S23 being concave. The thirteenth lens L13 may have a positive optical power, with its object side S23 being convex and its image side S24 being convex. The ninth lens L9 and the tenth lens L10 are cemented together to form a doublet lens. The eleventh lens L11, the twelfth lens L12, and the thirteenth lens L13 are cemented together to form a triplet lens.

[0123] The aperture stop STO is disposed between the first lens group G1 and the second lens group G2. More specifically, the aperture stop STO is disposed between the third lens L3 and the fourth lens L4.

[0124] Light from the object sequentially passes through each surface (i.e., sequentially passes through the front protective glass CG1, the first lens L1 to the thirteenth lens L13, and the rear protective glass CG2) and finally forms an image on the imaging surface IMA, where an image sensing chip may be disposed at the imaging surface.

[0125] Table 5 shows the basic parameter table of the endoscope adapter lens 300 of Embodiment 3, where the units of the radius of curvature and the thickness / distance are both millimeters (mm).

[0126]

[0127]

[0128] Table 5

[0129] Table 6 shows the values of T1, T2, and T3 in Table 5 when the endoscopic adapter lens 300 is at the wide-angle end and the telephoto end, respectively. Table 6 also shows the total effective focal length F and the aperture value Fno of the endoscopic adapter lens 300 of Example 2, where F and Fno change as the endoscopic adapter lens 300 switches from the wide-angle end to the telephoto end or from the telephoto end to the wide-angle end.

[0130] 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

[0131] Table 6

[0132] Example 4

[0133] Refer to the following Figure 4A and Figure 4B to describe the endoscopic adapter lens 400 according to Embodiment 4 of the present application. Figure 4A is a schematic structural diagram of the endoscopic adapter lens 400 according to Embodiment 4 of the present application when it is at the wide-angle end, Figure 4B is a schematic structural diagram of the endoscopic adapter lens 400 according to Embodiment 4 of the present application when it is at the telephoto end.

[0134] As Figure 4A and Figure 4B shown, the endoscopic adapter lens 400 sequentially includes, from the object side to the image side: a positioning surface D, a front protective glass CG1, a first lens group G1 with a positive optical power, a diaphragm STO (not shown), a second lens group G2 with a negative optical power, a third lens group G3 with a positive optical power, a rear protective glass CG2, and an imaging surface IMA.

[0135] In Embodiment 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.

[0136] The first lens group G1 includes a first lens L1, a second lens L2, and a third lens L3. The first lens L1 may have a positive optical power, its object side surface S4 is a convex surface, and its image side surface S5 is a convex surface. The second lens L2 may have a negative optical power, its object side surface S5 is a concave surface, and its image side surface S6 is a convex surface. The third lens L3 may have a positive optical power, its object side surface S7 is a convex surface, and its image side surface S8 is a convex surface. The first lens L1 and the second lens L2 are cemented together to form a doublet lens.

[0137] 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 may have a negative optical power, with its object side S9 being convex and its image side S10 being concave. The fifth lens L5 may have a positive optical power, with its object side S11 being convex and its image side S12 being concave. The sixth lens L6 may have a positive optical power, with its object side S13 being concave and its image side S14 being convex. The seventh lens L7 may have a negative optical power, with its object side S14 being concave and its image side S15 being concave. The sixth lens L6 and the seventh lens L7 are cemented together to form a doublet lens.

[0138] The third lens group G3 includes an eighth lens L8, a ninth lens L9, a tenth lens L10, an eleventh lens L11, a twelfth lens L12, and a thirteenth lens L13. The eighth lens L8 may have a positive optical power, with its object side S16 being concave and its image side S17 being convex. The ninth lens L9 may have a positive optical power, with its object side S18 being convex and its image side S19 being convex. The tenth lens L10 may have a negative optical power, with its object side S19 being concave and its image side S20 being convex. The eleventh lens L11 may have a positive optical power, with its object side S21 being convex and its image side S22 being convex. The twelfth lens L12 may have a negative optical power, with its object side S22 being concave and its image side S23 being concave. The thirteenth lens L13 may have a positive optical power, with its object side S23 being convex and its image side S24 being convex. The ninth lens L9 and the tenth lens L10 are cemented together to form a doublet lens. The eleventh lens L11, the twelfth lens L12, and the thirteenth lens L13 are cemented together to form a triplet lens.

[0139] The stop STO is disposed between the first lens group G1 and the second lens group G2. More specifically, the stop STO is disposed between the third lens L3 and the fourth lens L4.

[0140] Light from the object sequentially passes through each surface (i.e., sequentially passes through the front protective glass CG1, the first lens L1 to the thirteenth lens L13, and the rear protective glass CG2) and finally forms an image on the imaging surface IMA, where an image sensing chip may be disposed at the imaging surface.

[0141] Table 7 shows the basic parameter table of the endoscope adapter lens 400 of Embodiment 4, where the units of the radius of curvature and the thickness / distance are both millimeters (mm).

[0142]

[0143]

[0144] Table 7

[0145] Table 8 shows the values of T1, T2, and T3 in Table 7 when the endoscopic adapter lens 400 is at the wide-angle end and the telephoto end, respectively. Table 8 also shows the total effective focal length F and the aperture value Fno of the endoscopic adapter lens 400 of Example 4, where F and Fno change as the endoscopic adapter lens 400 switches from the wide-angle end to the telephoto end or from the telephoto end to the wide-angle end.

[0146] 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

[0147] Table 8

[0148] In summary, Examples 1 to 4 respectively satisfy the relationships shown in Table 9.

[0149]

[0150]

[0151] Table 9

[0152] The above description is only the preferred embodiments of the present application and the description of the applied technical principles. Those skilled in the art should understand that the scope of the invention involved in the present application is not limited to the technical solutions formed by the specific combination of the above technical features, but also covers other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the inventive concept. For example, the technical solutions formed by mutually replacing the above features with the (but not limited to) technical features having similar functions disclosed in the present application.

Claims

1. An endoscope adapter lens, characterized in that: The lens system includes, in order from the object side to the image side along the optical axis: 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; wherein, The first lens group includes, in order from the object side to the image side along the optical axis: a first lens, a second lens and a third lens; The second lens group includes, in order from the object side to the image side along the optical axis: a fourth lens, a fifth lens, a sixth lens and a seventh lens; The third lens group includes, in order from the object side to the image side along the optical axis, an eighth lens, a ninth lens, a tenth lens, an eleventh lens, a twelfth lens and a thirteenth lens.

2. The endoscope adapter lens according to claim 1, characterized in that: The first lens group is a fixed lens group, and its distance relative to the imaging plane is fixed; The second lens group is a zoom group, which 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 second lens group is a compensation group, which moves between the object side and the image side along the optical axis to compensate for changes in the image plane position during zooming.

3. The endoscope adapter lens according to claim 1, characterized in that: The first lens has positive refractive power, and both the object side surface and the image side surface thereof are convex; The second lens has negative optical power, and its object side surface is concave; and The third lens has positive refractive power, and both the object-side surface and the image-side surface are convex.

4. The endoscope adapter lens according to claim 1, characterized in that: The fourth lens has negative optical power, and its image side surface is concave; The fifth lens has positive refractive power, its object side surface is convex, and its image side surface is concave; The sixth lens has positive refractive power, its object side surface is concave, and its image side surface is convex; and The seventh lens element has negative optical power, and its object side surface is concave.

5. The endoscope adapter lens according to claim 1, characterized in that: The eighth lens has positive refractive power, and its image side surface is convex; The ninth lens has positive refractive power, and its object side surface is convex, and its image side surface is convex; The tenth lens has negative optical power, its object side surface is concave, and its image side surface is convex; The eleventh lens has positive refractive power, and both the object side surface and the image side surface are convex; The twelfth lens has negative optical power, and both the object side surface and the image side surface thereof are concave surfaces; and The thirteenth lens has positive refractive power, and both the object-side surface and the image-side surface are convex.

6. The endoscope adapter lens according to claim 2, characterized in that: The endoscope adapter lens satisfies any one of the following conditional expressions: 1.2 <FG1 / Fw<1.5,-0.8<FG2 / Fw<-0.5,0.9<FG3 / Fw<1.2,0.6<ENP / Fw<1.0,0.2<ENP / Ft<0.5,0.2<d2 / d3<0.5,0<d2 / Ft<0.2,1.2<D8w / D8t<1.9, Wherein, FG1 is the effective focal length of the first lens group, Fw is the total effective focal length of the endoscopic adapter lens at the wide-angle end, FG2 is the effective focal length of the second lens group, FG3 is the effective focal length of the third lens group, ENP is the distance from the entrance pupil position of the endoscopic adapter lens to the object side 3 mm position of the front protective glass of the endoscopic adapter lens, Ft is the total effective focal length of the endoscopic adapter lens at the telephoto end, d2 is the axial distance between the position of the second lens group on the optical axis of the endoscopic adapter lens at the wide-angle end and the position of the second lens group on the optical axis of the endoscopic adapter lens at the telephoto end, d3 is the axial distance between the position of the third lens group on the optical axis of the endoscopic adapter lens at the wide-angle end and the position of the third lens group on the optical axis of the endoscopic adapter lens at the telephoto end, D8w is the effective full aperture of the image side of the eighth lens of the endoscopic adapter lens at the wide-angle end, and D8t is the effective full aperture of the image side of the eighth lens of the endoscopic adapter lens at the telephoto end.

7. The endoscopic adapter lens according to any one of claims 1 to 6, characterized in that The Abbe number Vd of at least one lens in the second lens group G2 Satisfy: 18 ≤ Vd G2 ≤30.

8. The endoscopic adapter lens according to any one of claims 1 to 6, characterized in that The refractive index Nd of at least one lens in the second lens group G2 Satisfy: 1.8≤Nd G2 ≤2.

1.

9. The endoscopic adapter lens according to any one of claims 1 to 6, characterized in that The endoscopic adapter lens satisfies any one of the following conditional expressions: 0.2 < TG2 / TG3 < 0.5, 1.5 < f8 / FG3 < 2.5, 0.1 ≤ Dmax / TTL ≤ 0.3, wherein, TG2 is the thickness of the second lens group on the optical axis, TG3 is the thickness of the third lens group on the optical axis, f8 is the effective focal length of the eighth lens, FG3 is the effective focal length of the third lens group, Dmax is the maximum full 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.

10. The endoscopic adapter lens according to any one of claims 1 to 6, characterized in that The endoscopic adapter lens satisfies: 0.2 < D9w / f910 < 0.5, wherein, D9w is the effective full 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.

Images