Endoscope adaptive lens

Abstract

The invention discloses an endoscope adaptive lens, which sequentially comprises front protective glass, rear protective glass, rear protective glass and rear protective glass from an object side to an image side along an optical axis, the first lens group has positive focal power, and the first lens group only comprises three lenses; the second lens group has negative focal power, and the second lens group only comprises three lenses; the third lens group has positive focal power, and the third lens group only comprises seven or eight lenses; a rear protective glass; wherein in the zooming process, the first lens group is fixedly arranged, the second lens group moves between the object side and the image side along the optical axis so as to realize continuous zooming between the wide-angle end and the telephoto end, and the third lens group moves between the object side and the image side along the optical axis so as to realize compensation of image surface position change in the zooming process; in the object distance changing process, the first lens group moves between the object side and the image side along the optical axis so as to achieve compensation of image surface position change in the object distance changing process.

Description

Technical Field

[0001] The present application relates to the field of optical devices, and in particular to an endoscope adapter lens. Background Art

[0002] In recent years, as the penetration rate of minimally invasive surgery has gradually increased, the use of endoscopes has continued to expand, requiring endoscope technology to continue to develop and innovate to obtain more information about the lesion area. As an optical component that connects the endoscope and the camera device, the imaging quality and imaging function requirements of the endoscope adapter lens are becoming increasingly important. The endoscope adapter lenses currently in use still have the following problems:

[0003] 1. The lens imaging quality is poor, and the captured image resolution is low, which cannot meet the 4K resolution requirements;

[0004] 2. The lens is too large to be miniaturized, and the doctor has poor hand-holding comfort during surgery.

[0005] 3. The entrance pupil position changes during lens zooming, the endoscope has poor adaptability, and the imaging is unstable;

[0006] 4. The lens imaging target surface is small, and it is impossible to realize the design of a large target surface;

[0007] 5. The lens back focus is not long enough and cannot adapt to the complex structure of the beam splitting switching system.

[0008] Therefore, in view of the current development status of endoscope adapter lenses, endoscope adapter lenses with high resolution, miniaturization, fixed entrance pupil position, large target area and long back focus are one of the current market demands. Summary of the invention

[0009] The present application provides an endoscope adapter lens, which sequentially includes, from the object side to the image side along the optical axis: a front protective glass; a first lens group with a positive optical power, the first lens group only includes three lenses, and sequentially includes a first lens, a second lens, and a third lens from the object side to the image side along the optical axis; a second lens group with a negative optical power, the second lens group only includes three lenses, and sequentially includes a fourth lens, a fifth lens, and a sixth lens from the object side to the image side along the optical axis; a third lens group with a positive optical power, the third lens group only includes seven lenses, and sequentially includes a seventh lens, 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; or, the third lens group only includes eight lenses, and sequentially includes a seventh lens, an eighth lens, a ninth lens, a tenth lens, an eleventh lens, a twelfth lens, a thirteenth lens, and a fourteenth lens from the object side to the image side along the optical axis; a rear protective glass; wherein, during the zooming process, the first lens group is fixedly arranged, the second lens group moves along the optical axis between the object side and the image side to achieve continuous zooming 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 the change in the image plane position during the zooming process; during the change in the object distance, the first lens group moves along the optical axis between the object side and the image side to compensate for the change in the image plane position during the change in the object distance.

[0010] According to an exemplary embodiment of the present application, the first lens has a negative optical power, its object side is convex, and its image side is concave; the second lens has a positive optical power, its object side is concave, and its image side is convex, or, its object side is convex, and its image side is concave; and the third lens has a positive optical power, its object side is convex, and its image side is convex or concave.

[0011] According to an exemplary embodiment of the present application, the fourth lens has a negative optical power, its object side is concave, and its image side is concave; the fifth lens has a positive optical power, its object side is concave, and its image side is convex; and the sixth lens has a negative optical power, its object side is concave, and its image side is convex or concave or flat.

[0012] According to an exemplary embodiment of the present application, the third lens group only includes seven lenses, and sequentially includes, from the object side to the image side along the optical axis: the seventh lens has a positive optical power, its object side is convex, and its image side is convex; the eighth lens has a positive optical power, its object side is convex, and its image side is convex; the ninth lens has a negative optical power, its object side is concave, and its image side is concave; the tenth lens has a positive optical power, its object side is convex, and its image side is convex; the eleventh lens has a negative optical power, its object side is concave, and its image side is concave; the twelfth lens has a positive optical power, its object side is convex, and its image side is convex; and the thirteenth lens has a negative optical power, its object side is concave, and its image side is convex.

[0013] According to an exemplary embodiment of the present application, the third lens group includes only eight lenses, which, in order from the object side to the image side along the optical axis, include: the seventh lens has a positive optical power, its object side is convex, and its image side is convex; the eighth lens has a positive optical power, its object side is convex or concave, and its image side is convex; the ninth lens has a negative optical power, its object side is concave, and its image side is concave; the tenth lens has a positive optical power, its object side is convex, and its image side is concave; the eleventh lens has a positive optical power, its object side is convex, and its image side is convex; the twelfth lens has a negative optical power, its object side is convex or concave, and its image side is concave; the thirteenth lens has a positive optical power, its object side is convex, and its image side is convex; and the fourteenth lens has a negative optical power, its object side is concave, and its image side is convex or concave or flat.

[0014] According to an exemplary embodiment of the present application, the fifth lens and the sixth lens form a first cemented lens, the eighth lens, the ninth lens, and the tenth lens form a second cemented lens, and the eleventh lens, the twelfth lens, and the thirteenth lens form a third cemented lens.

[0015] According to an exemplary embodiment of the present application, the fifth lens and the sixth lens form a first cemented lens, the eighth lens and the ninth lens form a second cemented lens, the tenth lens and the eleventh lens form a third cemented lens, and the twelfth lens, the thirteenth lens, and the fourteenth lens form a fourth cemented lens, where the Abbe number VdB11 of the eighth lens or the tenth lens, the Abbe number VdB12 of the ninth lens or the eleventh lens, the Abbe number VdB21 of the twelfth lens, the Abbe number VdB22 of the thirteenth lens, and the Abbe number VdB23 of the fourteenth lens satisfy the conditional expressions: 1.19 ≤ VdB11 / VdB12 ≤ 2.24, 8.89 ≤ VdB21*VdB23 / VdB22 ≤ 13.67.

[0016] According to an exemplary embodiment of the present application, the endoscopic adapter lens satisfies at least one of the following conditional expressions: 1.55 ≤ FG1 / Fw ≤ 2.14, -0.91 ≤ FG2 / Fw ≤ -0.63, 0.81 ≤ FG3 / Fw ≤ 1.08, 0.95 ≤ F7 / Fw ≤ 2.94, where FG1 is the effective focal length of the first lens group, FG2 is the effective focal length of the second lens group, FG3 is the effective focal length of the third lens group, F7 is the effective focal length of the seventh lens, and Fw is the effective focal length of the endoscopic adapter lens at the wide-angle end.

[0017] According to an exemplary embodiment of the present application, the endoscopic adapter lens satisfies at least one of the following conditional expressions: 0.10 ≤ d1 / FG1 ≤ 0.15, 0.07 ≤ d2 / TTL ≤ 0.11, 0.07 ≤ d3 / TTL ≤ 0.10, -14.63 mm ≤ FG2*FG3 / Fw ≤ -9.57 mm, -6.71 mm ≤ FG2*FG3 / Ft ≤ -4.38 mm, where d1 is the maximum stroke of the first lens group when the object distance moves from -2000 mm to infinity, d2 is the maximum stroke of the second lens group when moving from the wide-angle end to the telephoto end, d3 is the maximum stroke of the third lens group when moving from the wide-angle end to the telephoto end, FG1 is the effective focal length of the first lens group, FG2 is the effective focal length of the second lens group, FG3 is the effective focal length of the third lens group, Fw is the effective focal length of the endoscopic adapter lens at the wide-angle end, Ft is the effective focal length of the endoscopic adapter lens at the telephoto end, and TTL is the distance from the object side surface of the first lens to the image surface at infinity object distance.

[0018] According to an exemplary embodiment of the present application, the endoscopic adapter lens satisfies at least one of the following conditional expressions: 0.22 ≤ Fw / TTL ≤ 0.29, 0.48 ≤ Ft / TTL ≤ 0.63, 0.34 ≤ BFL / TTL ≤ 0.45, 0.14 ≤ Dmax / TTL ≤ 0.19, 0.09 ≤ H / TTL ≤ 0.14, 0.38 ≤ S / FG1 ≤ 0.54, where Fw is the effective focal length of the endoscopic adapter lens at the wide-angle end, Ft is the effective focal length of the endoscopic adapter lens at the telephoto end, TTL is the distance from the object side surface of the first lens to the image surface at infinity object distance, BFL is the distance from the image side surface of the rear protective glass to the image surface, Dmax is the maximum optical aperture of the seventh lens, H is the total image height of the endoscopic adapter lens, S is the entrance pupil distance of the endoscopic adapter lens at infinity object distance, and FG1 is the effective focal length of the first lens group.

[0019] According to an exemplary embodiment of the present application, the endoscopic adapter lens satisfies at least one of the following conditional expressions: 1.72 ≤ FG1 / Fw ≤ 1.95, -0.83 ≤ FG2 / Fw ≤ -0.70, 0.91 ≤ FG3 / Fw ≤ 0.98, 1.05 ≤ F7 / Fw ≤ 2.68, 0.11 ≤ d1 / FG1 ≤ 0.13, 0.08 ≤ d2 / TTL ≤ 0.10, 0.08 ≤ d3 / TTL ≤ 0.09, -13.30 mm ≤ FG2*FG3 / Fw ≤ -10.63 mm, -6.10 mm ≤ FG2*FG3 / Ft ≤ -4.87 mm, 0.24 ≤ Fw / TTL ≤ 0.27, 0.53 ≤ Ft / TTL ≤ 0.58, 0.38 ≤ BFL / TTL ≤ 0.41, 0.16 ≤ Dmax / TTL ≤ 0.17, 0.11 ≤ H / TTL ≤ 0.13, 0.42 ≤ S / FG1 ≤ 0.49, where FG1 is the effective focal length of the first lens group, FG2 is the effective focal length of the second lens group, FG3 is the effective focal length of the third lens group, F7 is the effective focal length of the seventh lens, Fw is the effective focal length of the endoscopic adapter lens at the wide-angle end, Ft is the effective focal length of the endoscopic adapter lens at the telephoto end, d1 is the maximum stroke of the first lens group when the object distance moves from -2000 mm to infinity, d2 is the maximum stroke of the second lens group when moving from the wide-angle end to the telephoto end, d3 is the maximum stroke of the third lens group when moving from the wide-angle end to the telephoto end, TTL is the distance from the object side surface of the first lens to the image surface at infinity object distance, BFL is the distance from the image side surface of the rear protective glass to the image surface, Dmax is the maximum optical aperture of the seventh lens, H is the full image height of the endoscopic adapter lens, and S is the entrance pupil distance of the endoscopic adapter lens when the object distance is infinity. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Other features, objects, and advantages of the present application will become more apparent by reading the detailed description of the non-limiting embodiments with reference to the following drawings. In the drawings:

[0021] Figure 1 FIG. 9 shows a schematic structural diagram of the endoscopic adapter lens according to Embodiment 1 of the present application at the wide-angle end;

[0022] Figure 2 FIG. 13 shows a schematic structural diagram of the endoscopic adapter lens according to Embodiment 1 of the present application at the telephoto end;

[0023] Figure 3 FIG. 17 shows a schematic structural diagram of the endoscopic adapter lens according to Embodiment 2 of the present application at the wide-angle end;

[0024] Figure 4 FIG. 21 shows a schematic structural diagram of the endoscopic adapter lens according to Embodiment 2 of the present application at the telephoto end;

[0025] Figure 5 Shows a schematic structural diagram of the endoscopic adapter lens according to Embodiment 3 of the present application when it is at the wide-angle end;

[0026] Figure 6 Shows a schematic structural diagram of the endoscopic adapter lens according to Embodiment 3 of the present application when it is at the telephoto end;

[0027] Figure 7 Shows a schematic structural diagram of the endoscopic adapter lens according to Embodiment 4 of the present application when it is at the wide-angle end;

[0028] Figure 8 Shows a schematic structural diagram of the endoscopic adapter lens according to Embodiment 4 of the present application when it is at the telephoto end;

[0029] Figure 9 Shows a schematic structural diagram of the endoscopic adapter lens according to Embodiment 5 of the present application when it is at the wide-angle end; and

[0030] Figure 10 Shows a schematic structural diagram of the endoscopic adapter lens according to Embodiment 5 of the present application when it is at the telephoto end. Detailed implementation manners

[0031] For a better understanding of the present application, various aspects of the present application are described in detail with reference to the accompanying 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.

[0032] In the accompanying drawings, for the sake of convenience of illustration, the thickness, size, and shape of the lens have been slightly exaggerated. Specifically, the spherical or aspherical shapes shown in the accompanying 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 accompanying drawings. The accompanying drawings are only for illustration and are not drawn strictly to scale.

[0033] In this document, 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 to be 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.

[0034] It should also be understood that the terms "comprising", "including", "having", "containing" and / or "including", when used in this specification, indicate the presence of the stated features, elements and / or components, but do not exclude the presence or addition of one or more other features, elements, components and / or combinations thereof. It should be noted that in this specification, the expressions of first, second, third, etc. are only used to distinguish one feature from another feature, and do not represent any limitation on the features. It should be noted that the longitudinal direction described herein is the direction perpendicular to the optical axis.

[0035] Unless otherwise defined, all terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which this application belongs. The terms should be interpreted to have 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.

[0036] It should be noted that, without conflict, the embodiments in this application and the features in the embodiments can be combined with each other. The following will describe this application in detail with reference to the drawings and in combination with the embodiments.

[0037] According to an exemplary embodiment of the present application, the endoscopic adapter lens sequentially includes a front protective glass, a first lens group, a second lens group, a third lens group, and a rear protective glass along the optical axis from the object side to the image side.

[0038] In an exemplary embodiment, the first lens group of the endoscopic adapter lens has a positive optical power. During the zooming process, the first lens group is fixedly arranged; during the change of the object distance (-2000 mm to infinity), the first lens group moves along the optical axis between the object side and the image side to compensate for the change of the image plane position during the change of the object distance, so that the endoscopic adapter lens has a better imaging position during the change of the object distance, the imaging quality is stable, and it can be adapted to various types of endoscopes with different requirements for the object distance; at the same time, the first lens group has a positive optical power, which is beneficial to correcting the field curvature of the lens at different object distances, and at the same time reducing the tolerance sensitivity of the first lens group to ensure the uniformity of the picture.

[0039] In an exemplary embodiment, the first lens group only includes three lenses, and sequentially includes a first lens, a second lens, and a third lens along the optical axis from the object side to the image side.

[0040] In an exemplary embodiment, the first lens may have a negative optical power, its object side surface may be convex, and its image side surface may be concave. The first lens has a negative optical power, and the object side surface is convex and the image side surface is concave, which can effectively control the astigmatism generated when the light enters the field of view, is beneficial to improving the imaging quality of the lens, and meets the 4K resolution requirement.

[0041] In an exemplary embodiment, the second lens may have a positive optical power. Its object side may be concave and its image side may be convex, or its object side may be convex and its image side may be concave. The second lens has a positive optical power, with a concave object side and a convex image side, or a convex object side and a concave image side, which can effectively balance various aberrations generated by the lens itself when transitioning field-of-view light rays, facilitating the improvement of the imaging quality of the lens, meeting the 4K resolution requirements, and at the same time facilitating the achievement of the beneficial effect of low distortion of the lens.

[0042] In an exemplary embodiment, the third lens may have a positive optical power, and its object side may be convex. The third lens has a positive optical power and a convex object side, which can effectively compensate for the distortion generated by the first lens, facilitating the achievement of the beneficial effect of low distortion of the lens. In an exemplary embodiment, the image side of the third lens may be convex or concave.

[0043] In an exemplary embodiment, the second lens group of the endoscopic adapter lens has a negative optical power, and its position along the optical axis is adjustable to achieve continuous zooming between the wide-angle end and the telephoto end of the endoscopic adapter lens.

[0044] In an exemplary embodiment, the second lens group includes only three lenses, which sequentially include a fourth lens, a fifth lens, and a sixth lens along the optical axis from the object side to the image side.

[0045] In an exemplary embodiment, the fourth lens may have a negative optical power, its object side may be concave, and its image side may be concave. The fourth lens has a negative optical power, a concave object side, and a concave image side, generating less astigmatism when transitioning field-of-view light rays, facilitating the improvement of the imaging quality of the lens and meeting the 4K resolution requirements.

[0046] In an exemplary embodiment, the fifth lens may have a positive optical power, its object side may be concave, and its image side may be convex. The fifth lens has a positive optical power, a concave object side, and a convex image side, which can effectively balance various aberrations generated by the lens itself when transitioning field-of-view light rays, facilitating the improvement of the imaging quality of the lens, meeting the 4K resolution requirements, and at the same time facilitating the achievement of the beneficial effect of low distortion of the lens.

[0047] In an exemplary embodiment, the sixth lens may have a negative optical power, and its object side may be concave. The sixth lens has a negative optical power and a concave object side, generating less spherical aberration or coma when transitioning field-of-view light rays, facilitating the improvement of the imaging quality of the lens and meeting the 4K resolution requirements. In an exemplary embodiment, the image side of the sixth lens may be convex or concave or flat.

[0048] In an exemplary embodiment, the fifth lens and the sixth lens can form a doublet lens to balance the system chromatic aberration when transitioning the off-axis field light, and at the same time make the light enter the third lens group smoothly, which is beneficial to improving the imaging quality of the lens and meeting the 4K resolution requirement.

[0049] In an exemplary embodiment, the third lens group of the endoscopic adapter lens has a positive focal power, and its position along the optical axis is adjustable to compensate for the shift of the image plane position during the zooming process of the endoscopic adapter lens, playing a role in focusing the image plane.

[0050] In an exemplary embodiment, the third lens group includes only seven lenses, which sequentially include a seventh lens, an eighth lens, a ninth lens, a tenth lens, an eleventh lens, a twelfth lens, and a thirteenth lens along the optical axis from the object side to the image side.

[0051] In an exemplary embodiment, the seventh lens can have a positive focal power, its object side can be a convex surface, and its image side can be a convex surface. The seventh lens has a positive focal power, with a convex object side and a convex image side, which can effectively balance various aberrations generated by the lens itself when transitioning the off-axis field light, is beneficial to improving the imaging quality of the lens and meeting the 4K resolution requirement, and at the same time is beneficial to achieving the beneficial effect of low distortion of the lens.

[0052] In an exemplary embodiment, the eighth lens can have a positive focal power, its object side can be a convex surface, and its image side can be a convex surface. The eighth lens has a positive focal power, with a convex object side and a convex image side, which generates small spherical aberration and astigmatism when transitioning the off-axis field light, is beneficial to improving the imaging quality of the lens and meeting the 4K resolution requirement.

[0053] In an exemplary embodiment, the ninth lens can have a negative focal power, its object side can be a concave surface, and its image side can be a concave surface. The ninth lens has a negative focal power, with a concave object side and a concave image side, which generates small chromatic aberration when transitioning the off-axis field light, is beneficial to improving the imaging quality of the lens and meeting the 4K resolution requirement.

[0054] In an exemplary embodiment, the tenth lens can have a positive focal power, its object side can be a convex surface, and its image side can be a convex surface. The tenth lens has a positive focal power, with a convex object side and a convex image side, which effectively corrects the system spherical aberration and coma when transitioning the off-axis field light, is beneficial to improving the imaging quality of the lens and meeting the 4K resolution requirement.

[0055] In an exemplary embodiment, the eighth lens, the ninth lens, and the tenth lens can form a triplet lens, which can effectively correct the system spherical aberration and chromatic aberration when transitioning the off-axis field light, and at the same time is beneficial to correcting the system secondary spectrum, and is beneficial to achieving the beneficial effect of infrared confocal of the lens.

[0056] In an exemplary embodiment, the eleventh lens may have a negative optical power, its object side may be concave, and its image side may be concave. The eleventh lens having a negative optical power, with a concave object side and a concave image side, produces less field curvature when transitioning field-of-view light rays, which is beneficial for improving the imaging quality of the lens and meeting the 4K resolution requirement.

[0057] In an exemplary embodiment, the twelfth lens may have a positive optical power, its object side may be convex, and its image side may be convex. The twelfth lens having a positive optical power, with a convex object side and a convex image side, produces less field curvature when transitioning field-of-view light rays, which is beneficial for improving the imaging quality of the lens and meeting the 4K resolution requirement.

[0058] In an exemplary embodiment, the thirteenth lens may have a negative optical power, its object side may be concave, and its image side may be convex. The thirteenth lens having a negative optical power, with a concave object side and a convex image side, can effectively balance various aberrations (except chromatic aberration) generated by the lens itself when transitioning field-of-view light rays, which is beneficial for improving the imaging quality of the lens, meeting the 4K resolution requirement, and at the same time is beneficial for achieving the beneficial effect of low distortion of the lens.

[0059] In an exemplary embodiment, the eleventh lens, the twelfth lens, and the thirteenth lens may form a cemented triplet lens, which can effectively correct various aberrations of the system when transitioning field-of-view light rays, making the light rays have a gentle trend, which is beneficial for improving the imaging quality of the lens, meeting the 4K resolution requirement, and at the same time is beneficial for achieving the beneficial effect of a long back focal length of the lens.

[0060] In an exemplary embodiment, the third lens group includes only eight lenses, which sequentially include a seventh lens, an eighth lens, a ninth lens, a tenth lens, an eleventh lens, a twelfth lens, a thirteenth lens, and a fourteenth lens along the optical axis from the object side to the image side.

[0061] In an exemplary embodiment, the seventh lens may have a positive optical power, its object side may be convex, and its image side may be convex. The seventh lens having a positive optical power, with a convex object side and a convex image side, produces less astigmatism and distortion when transitioning field-of-view light rays, which is beneficial for improving the imaging quality of the lens, meeting the 4K resolution requirement, and at the same time is beneficial for achieving the beneficial effect of low distortion of the lens.

[0062] In an exemplary embodiment, the eighth lens may have a positive optical power, and its image side may be convex. The eighth lens having a positive optical power, with a convex image side, produces less spherical aberration and field curvature when transitioning field-of-view light rays, which is beneficial for improving the imaging quality of the lens and meeting the 4K resolution requirement. In an exemplary embodiment, the object side of the eighth lens may be convex or concave.

[0063] In an exemplary embodiment, the ninth lens may have a negative optical power. Its object side may be concave, and its image side may be concave. The ninth lens having a negative optical power, with a concave object side and a concave image side, generates less field curvature and distortion when transitioning field-of-view light rays, which is beneficial to improving the imaging quality of the lens, meeting the 4K resolution requirement, and at the same time is beneficial to achieving the beneficial effect of low distortion of the lens.

[0064] In an exemplary embodiment, the eighth lens and the ninth lens may form a doublet lens, which can effectively correct the spherical aberration and chromatic aberration of the system when transitioning field-of-view light rays. At the same time, it is beneficial to correct the secondary spectrum of the system, which is beneficial to achieving the beneficial effect of infrared confocal of the lens.

[0065] In an exemplary embodiment, the tenth lens may have a positive optical power. Its object side may be convex, and its image side may be concave. The tenth lens having a positive optical power, with a convex object side and a concave image side, generates less spherical aberration and field curvature when transitioning field-of-view light rays, which is beneficial to improving the imaging quality of the lens and meeting the 4K resolution requirement.

[0066] In an exemplary embodiment, the eleventh lens may have a positive optical power. Its object side may be convex, and its image side may be convex. The eleventh lens having a positive optical power, with a convex object side and a convex image side, can effectively correct the spherical aberration and coma of the system when transitioning field-of-view light rays, which is beneficial to improving the imaging quality of the lens and meeting the 4K resolution requirement.

[0067] In an exemplary embodiment, the tenth lens and the eleventh lens may form a doublet lens, which can effectively correct various aberrations of the system when transitioning field-of-view light rays, make the light ray trend smooth, reduce the tolerance sensitivity, and is beneficial to improving the imaging quality of the lens and meeting the 4K resolution requirement.

[0068] In an exemplary embodiment, the endoscope adapter lens may satisfy: 1.19 ≤ VdB11 / VdB12 ≤ 2.24, where VdB11 is the Abbe number of the eighth lens or the tenth lens, and VdB12 is the Abbe number of the ninth lens or the eleventh lens. By making the endoscope adapter lens satisfy the above conditional formula and reasonably setting the Abbe numbers of the eighth lens, the ninth lens, the tenth lens, and the eleventh lens, the chromatic aberration can be effectively corrected, the defocus amount of the infrared spectrum relative to the visible spectrum can be reduced, which is beneficial to achieving the beneficial effect of infrared confocal of the lens; at the same time, it makes the light ray transition smooth, reduces the system tolerance sensitivity, and thus improves the lens assembly yield.

[0069] In an exemplary embodiment, the twelfth lens may have a negative optical power, and the image side may be concave. The twelfth lens having a negative optical power and a concave image side generates less field curvature when transitioning field-of-view light rays, which is beneficial for improving the imaging quality of the lens and meeting the 4K resolution requirement. In an exemplary embodiment, the object side of the twelfth lens may be convex or concave.

[0070] In an exemplary embodiment, the thirteenth lens may have a positive optical power, its object side may be convex, and its image side may be convex. The thirteenth lens having a positive optical power, a convex object side, and a convex image side generates less field curvature when transitioning field-of-view light rays, which is beneficial for improving the imaging quality of the lens and meeting the 4K resolution requirement.

[0071] In an exemplary embodiment, the fourteenth lens may have a negative optical power, and the object side may be concave. The fourteenth lens having a negative optical power and a concave object side generates less spherical aberration and field curvature when transitioning field-of-view light rays, which is beneficial for improving the imaging quality of the lens and meeting the 4K resolution requirement. In an exemplary embodiment, the image side of the fourteenth lens may be convex or concave or planar.

[0072] In an exemplary embodiment, the twelfth lens, the thirteenth lens, and the fourteenth lens may form a triple cemented lens, which can effectively correct various aberrations of the system when transitioning field-of-view light rays, making the light rays trend smoothly, beneficial for improving the imaging quality of the lens, meeting the 4K resolution requirement, and at the same time beneficial for achieving the beneficial effect of a long back focal length of the lens.

[0073] In an exemplary embodiment, the endoscopic adapter lens may satisfy: 8.89 ≤ VdB21 * VdB23 / VdB22 ≤ 13.67, where VdB21 is the Abbe number of the twelfth lens, VdB22 is the Abbe number of the thirteenth lens, and VdB23 is the Abbe number of the fourteenth lens. By making the endoscopic adapter lens satisfy the above conditional formula and reasonably setting the Abbe numbers of the twelfth lens, the thirteenth lens, and the fourteenth lens, chromatic aberration can be effectively corrected, and the defocus amount of the infrared spectrum relative to the visible spectrum can be reduced, which is beneficial for achieving the beneficial effect of infrared confocal of the lens; at the same time, the light rays transition smoothly, improving the imaging quality of the lens and meeting the 4K resolution requirement.

[0074] In an exemplary embodiment, the endoscopic adapter lens may further include a diaphragm. The diaphragm may be located between the third lens and the fourth lens, which can effectively limit the light passing amount entering the optical system, shorten the optical total length of the endoscopic adapter lens, and reduce the maximum optical aperture of the endoscopic adapter lens, which is beneficial for realizing the miniaturization feature of the endoscopic adapter lens.

[0075] In an exemplary embodiment, the distance TTL from the object side surface of the first lens to the image plane when the endoscopic adapter lens has an infinite object distance can satisfy: TTL ≤ 68 mm. Further, TTL can satisfy: 62.81 mm ≤ TTL ≤ 67.09 mm, achieving the requirement for a small volume of the endoscopic adapter lens.

[0076] In an exemplary embodiment, the present application sets the materials of all lenses to glass, which is beneficial to reducing the processing difficulty of the lenses. The glass lens can effectively suppress the shift of the back focal length of the endoscopic adapter lens caused by temperature changes, improving the stability of the endoscopic adapter lens. At the same time, the glass lens can effectively avoid the problem of blurred imaging caused by high-temperature or low-temperature environments, ensuring the normal use of the endoscopic adapter lens, facilitating the athermalization of the endoscopic adapter lens, and better correcting the system chromatic aberration, improving the resolution ability of the endoscopic adapter lens.

[0077] In an exemplary embodiment, the present application adopts a combination of spherical lenses and aspherical lenses, which is beneficial to reducing the processing difficulty of the lenses. The present application does not specifically limit the specific number of spherical lenses and aspherical lenses. When focusing on reflecting the imaging quality, the number of aspherical lenses can be increased, or 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.

[0078] In an exemplary embodiment, the endoscopic adapter lens can satisfy: 1.55 ≤ FG1 / Fw ≤ 2.14, where FG1 is the effective focal length of the first lens group and Fw is the effective focal length of the endoscopic adapter lens at the wide-angle end. By making the endoscopic adapter lens satisfy the above conditional formula and controlling the ratio range of the effective focal length of the first lens group and the effective focal length of the endoscopic adapter lens at the wide-angle end, the light converges gently into the optical system, which is beneficial to reducing the distortion of the optical system. Preferably, the endoscopic adapter lens can further satisfy: 1.72 ≤ FG1 / Fw ≤ 1.95, which is more beneficial to reducing the distortion of the optical system.

[0079] In an exemplary embodiment, the endoscopic adapter lens may satisfy: -0.91 ≤ FG2 / Fw ≤ -0.63, where FG2 is the effective focal length of the second lens group and Fw is the effective focal length of the endoscopic adapter lens at the wide-angle end. By making the endoscopic adapter lens satisfy the above conditional expression and controlling the ratio range of the effective focal length of the second lens group to the effective focal length of the endoscopic adapter lens at the wide-angle end, it is beneficial to achieve imaging performance while ensuring the zoom ratio required during the zoom process. Preferably, the endoscopic adapter lens may further satisfy: -0.83 ≤ FG2 / Fw ≤ -0.70, which is more beneficial to ensuring the zoom ratio required during the zoom process.

[0080] In an exemplary embodiment, the endoscopic adapter lens may satisfy: 0.81 ≤ FG3 / Fw ≤ 1.08, where FG3 is the effective focal length of the third lens group and Fw is the effective focal length of the endoscopic adapter lens at the wide-angle end. By making the endoscopic adapter lens satisfy the above conditional expression and controlling the ratio range of the effective focal length of the third lens group to the effective focal length of the endoscopic adapter lens at the wide-angle end, it is beneficial for the third lens group to collect the outgoing light of the second lens group, enabling the light to transition smoothly, effectively reducing the generation of aberration, and improving the imaging quality of the lens; at the same time, it is beneficial to compensate for the shift of the image plane position during the zoom process of the lens, playing a role in focusing the image plane. Preferably, the endoscopic adapter lens may further satisfy: 0.91 ≤ FG3 / Fw ≤ 0.98, which is more beneficial to improving the imaging quality and focusing the image plane.

[0081] In an exemplary embodiment, the endoscopic adapter lens may satisfy: 0.95 ≤ F7 / Fw ≤ 2.94, where F7 is the effective focal length of the seventh lens and Fw is the effective focal length of the endoscopic adapter lens at the wide-angle end. By making the endoscopic adapter lens satisfy the above conditional expression and controlling the ratio range of the effective focal length of the seventh lens to the effective focal length of the endoscopic adapter lens at the wide-angle end, it plays a role in light collection, which is beneficial to ensuring the light transmission amount of the lens; at the same time, it is beneficial to collect the outgoing light of the second lens group, enabling the light to transition smoothly, effectively reducing the generation of aberration, and improving the optical imaging quality. Preferably, the endoscopic adapter lens may further satisfy: 1.05 ≤ F7 / Fw ≤ 2.68, which is more beneficial to ensuring the light transmission amount of the lens and improving the imaging quality.

[0082] In an exemplary embodiment, the endoscopic adapter lens can satisfy: 0.10 ≤ d1 / FG1 ≤ 0.15, where d1 is the maximum travel of the first lens group when moving from an object distance of -2000 mm to an infinite object distance, and FG1 is the effective focal length of the first lens group. By making the endoscopic adapter lens satisfy the above conditional formula, controlling the ratio range of the maximum travel of the first lens group when moving from an object distance of -2000 mm to an infinite object distance and the effective focal length of the first lens group, it is possible to achieve clear focusing when the object distance changes from -2000 mm to infinity, and various types of endoscopes with different requirements for the object distance can be adapted. Preferably, the endoscopic adapter lens can further satisfy: 0.11 ≤ d1 / FG1 ≤ 0.13, which is more conducive to adapting various types of endoscopes with different requirements for the object distance.

[0083] In an exemplary embodiment, the endoscopic adapter lens can satisfy: 0.07 ≤ d2 / TTL ≤ 0.11, where d2 is the maximum travel of the second lens group when moving from the wide-angle end to the telephoto end, and TTL is the distance from the object side surface of the first lens to the image plane at an infinite object distance. By making the endoscopic adapter lens satisfy the above conditional formula, controlling the ratio range of the maximum travel of the second lens group when moving from the wide-angle end to the telephoto end and the distance from the object side surface of the first lens to the image plane at an infinite object distance is beneficial to ensuring that the second lens group has a faster zoom speed. Preferably, the endoscopic adapter lens can further satisfy: 0.08 ≤ d2 / TTL ≤ 0.10, which is more conducive to ensuring that the second lens group has a faster zoom speed.

[0084] In an exemplary embodiment, the endoscopic adapter lens can satisfy: 0.07 ≤ d3 / TTL ≤ 0.10, where d3 is the maximum travel of the third lens group when moving from the wide-angle end to the telephoto end, and TTL is the distance from the object side surface of the first lens to the image plane at an infinite object distance. By making the endoscopic adapter lens satisfy the above conditional formula, controlling the ratio range of the maximum travel of the third lens group when moving from the wide-angle end to the telephoto end and the distance from the object side surface of the first lens to the image plane at an infinite object distance is beneficial to ensuring that the third lens group has a faster focusing speed. Preferably, the endoscopic adapter lens can further satisfy: 0.08 ≤ d3 / TTL ≤ 0.09, which is more conducive to ensuring that the third lens group has a faster focusing speed.

[0085] In an exemplary embodiment, the endoscopic adapter lens can satisfy: -14.63 mm ≤ FG2 * FG3 / Fw ≤ -9.57 mm, where FG2 is the effective focal length of the second lens group, FG3 is the effective focal length of the third lens group, and Fw is the effective focal length of the endoscopic adapter lens at the wide-angle end. By making the endoscopic adapter lens satisfy the above conditional expression and controlling the ratio range of the product of the effective focal lengths of the second lens group and the third lens group to the effective focal length of the endoscopic adapter lens at the wide-angle end, it is beneficial for the second lens group and the third lens group to achieve a minimum lens focal length of 16.5 mm during linkage, while ensuring the linear correlation between zoom and compensation, and is beneficial for maintaining real-time clarity of the entire process imaging. Preferably, the endoscopic adapter lens can further satisfy: -13.30 mm ≤ FG2 * FG3 / Fw ≤ -10.63 mm, which is more beneficial for maintaining real-time clarity of the entire process imaging.

[0086] In an exemplary embodiment, the endoscopic adapter lens can satisfy: -6.71 mm ≤ FG2 * FG3 / Ft ≤ -4.38 mm, where FG2 is the effective focal length of the second lens group, FG3 is the effective focal length of the third lens group, and Ft is the effective focal length of the endoscopic adapter lens at the telephoto end. By making the endoscopic adapter lens satisfy the above conditional expression and controlling the ratio range of the product of the effective focal lengths of the second lens group and the third lens group to the effective focal length of the endoscopic adapter lens at the telephoto end, it is beneficial for the second lens group and the third lens group to achieve a maximum lens focal length of 36 mm during linkage, while ensuring the linear correlation between zoom and compensation, and is beneficial for maintaining real-time clarity of the entire process imaging. Preferably, the endoscopic adapter lens can further satisfy: -6.10 mm ≤ FG2 * FG3 / Ft ≤ -4.87 mm, which is more beneficial for maintaining real-time clarity of the entire process imaging.

[0087] In an exemplary embodiment, the endoscopic adapter lens can satisfy: 0.22 ≤ Fw / TTL ≤ 0.29, where Fw is the effective focal length of the endoscopic adapter lens at the wide-angle end, and TTL is the distance from the object side surface of the first lens to the image surface at an infinite object distance. By making the endoscopic adapter lens satisfy the above conditional expression and controlling the ratio range of the effective focal length of the endoscopic adapter lens at the wide-angle end to the distance from the object side surface of the first lens to the image surface at an infinite object distance, the length of the lens can be effectively limited, which is beneficial for realizing the miniaturization of the lens. Preferably, the endoscopic adapter lens can further satisfy: 0.24 ≤ Fw / TTL ≤ 0.27, which is more beneficial for realizing the miniaturization of the lens.

[0088] In an exemplary embodiment, the endoscopic adapter lens can satisfy: 0.48 ≤ Ft / TTL ≤ 0.63, where Ft is the effective focal length of the endoscopic adapter lens at the telephoto end, and TTL is the distance from the object side surface of the first lens to the image plane at an infinite object distance. By making the endoscopic adapter lens satisfy the above conditional formula, controlling the ratio range of the effective focal length of the endoscopic adapter lens at the telephoto end and the distance from the object side surface of the first lens to the image plane at an infinite object distance can effectively limit the length of the lens, which is beneficial to realizing the miniaturization of the lens. Preferably, the endoscopic adapter lens can further satisfy: 0.53 ≤ Ft / TTL ≤ 0.58, which is more beneficial to realizing the miniaturization of the lens.

[0089] In an exemplary embodiment, the endoscopic adapter lens can satisfy: 0.34 ≤ BFL / TTL ≤ 0.45, where BFL is the distance from the image side surface of the rear protective glass to the image plane, and TTL is the distance from the object side surface of the first lens to the image plane at an infinite object distance. By making the endoscopic adapter lens satisfy the above conditional formula, controlling the ratio range of the distance from the image side surface of the rear protective glass to the image plane and the distance from the object side surface of the first lens to the image plane at an infinite object distance enables the back focal space to meet the requirements of the C interface or a customized interface, and can be adapted to a variety of spectroscopic adapter systems, which is beneficial to adapting endoscopes with functions such as multispectral imaging at the front end; at the same time, it is beneficial to shortening the total length of the lens, making the overall lens compact and light, and convenient for hand-held use. Preferably, the endoscopic adapter lens can further satisfy: 0.38 ≤ BFL / TTL ≤ 0.41, which is more beneficial to adapting endoscopes with functions such as multispectral imaging at the front end and shortening the total length of the lens.

[0090] In an exemplary embodiment, the endoscopic adapter lens can satisfy: 0.14 ≤ Dmax / TTL ≤ 0.19, where Dmax is the maximum optical aperture of the seventh lens, and TTL is the distance from the object side surface of the first lens to the image plane at an infinite object distance. By making the endoscopic adapter lens satisfy the above conditional formula, controlling the ratio range of the maximum optical aperture of the seventh lens and the distance from the object side surface of the first lens to the image plane at an infinite object distance reduces the volume of the third lens group, which is beneficial to realizing the miniaturization of the lens. Preferably, the endoscopic adapter lens can further satisfy: 0.16 ≤ Dmax / TTL ≤ 0.17, which is more beneficial to realizing the miniaturization of the lens.

[0091] In an exemplary embodiment, the endoscopic adapter lens may satisfy: 0.09 ≤ H / TTL ≤ 0.14, where H is the full holographic height of the endoscopic adapter lens, and TTL is the distance from the object side surface of the first lens to the image plane at infinite object distance. By making the endoscopic adapter lens satisfy the above conditional expression and controlling the ratio range of the full holographic height of the endoscopic adapter lens and the distance from the object side surface of the first lens to the image plane at infinite object distance, it is beneficial to achieve the large target surface effect of the lens. Preferably, the endoscopic adapter lens may further satisfy: 0.11 ≤ H / TTL ≤ 0.13, which is more beneficial to achieve the large target surface effect of the lens.

[0092] In an exemplary embodiment, the endoscopic adapter lens may satisfy: 0.38 ≤ S / FG1 ≤ 0.54, where S is the entrance pupil distance of the endoscopic adapter lens at infinite object distance, and FG1 is the effective focal length of the first lens group. By making the endoscopic adapter lens satisfy the above conditional expression and controlling the ratio range of the entrance pupil distance of the endoscopic adapter lens at infinite object distance and the effective focal length of the first lens group, it is beneficial to increase the entrance pupil size of the lens, reduce the change amount of the entrance pupil position caused by the focusing of the first lens group, so as to stably receive the light from the front-end endoscope and adapt to more types of endoscopes. Preferably, the endoscopic adapter lens may further satisfy: 0.42 ≤ S / FG1 ≤ 0.49, which is more beneficial to increase the entrance pupil size of the lens.

[0093] The endoscopic adapter lens according to the above embodiment of the present application sequentially includes a front protective glass, a first lens group with positive optical power, a second lens group with negative optical power, a third lens group with positive optical power, and a rear protective glass along the optical axis from the object side to the image side. During the zooming process, the first lens group is fixedly arranged, the second lens group moves along the optical axis between the object side and the image side to achieve continuous zooming 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 the change in the image plane position during the zooming process; during the change of the object distance, the first lens group moves along the optical axis between the object side and the image side to compensate for the change in the image plane position during the change of the object distance. At the same time, by reasonably distributing the optical parameters such as the number of lenses, the optical power of the lenses, and the surface type included in each lens group, at least one beneficial effect such as high resolution (4K), miniaturization (the distance TTL from the object side surface of the first lens to the image plane of the endoscopic adapter lens at infinite object distance ≤ 68 mm), fixed entrance pupil position, large target surface (full holographic height ≥ 7.4 mm), long back focal length (the distance BFL from the image side surface of the rear protective glass to the image plane ≤ 25.7 mm), infrared confocal, and athermalization can be achieved.

[0094] However, those skilled in the art should understand that without departing from the technical solution claimed in the present application, the number of lenses constituting the endoscopic adapter lens can be changed to obtain the various results and advantages described in this specification.

[0095] The specific embodiments of the endoscope adapter lens applicable to the above embodiments will be further described with reference to the accompanying drawings.

[0096] Example 1

[0097] The following will refer to Figures 1 to 2 Describe the endoscope adapter lens according to Embodiment 1 of the present application. Figure 1 The structural schematic diagram of the endoscope adapter lens according to Embodiment 1 of the present application when it is at the wide-angle end is shown. Figure 2 The structural schematic diagram of the endoscope adapter lens according to Embodiment 1 of the present application when it is at the telephoto end is shown.

[0098] As Figure 1 and Figure 2 shown, the endoscope adapter lens sequentially includes, along the optical axis from the object side to the image side: a first lens group G1 with a positive optical power, a second lens group G2 with a negative optical power, and a third lens group G3 with a positive optical power.

[0099] During the zooming process, the first lens group G1 is fixedly arranged, the second lens group G2 moves along the optical axis between the object side and the image side to achieve continuous zooming between the wide-angle end and the telephoto end, and the third lens group G3 moves along the optical axis between the object side and the image side to compensate for the change in the image plane position during the zooming process; during the change in the object distance, the first lens group G1 moves along the optical axis between the object side and the image side to compensate for the change in the image plane position during the change in the object distance.

[0100] The first lens group G1 sequentially includes a first lens L1, a second lens L2, and a third lens L3 along the optical axis from the object side to the image side.

[0101] The first lens L1 has a negative optical power, its object side surface S4 is convex, and its image side surface S5 is concave.

[0102] The second lens L2 has a positive optical power, its object side surface S6 is concave, and its image side surface S7 is convex.

[0103] The third lens L3 has a positive optical power, its object side surface S8 is convex, and its image side surface S9 is convex.

[0104] The second lens group G2 sequentially includes a fourth lens L4, a fifth lens L5, and a sixth lens L6 along the optical axis from the object side to the image side.

[0105] The fourth lens L4 has a negative optical power, its object side surface S11 is concave, and its image side surface S12 is concave.

[0106] The fifth lens L5 has a positive optical power, its object side surface S13 is concave, and its image side surface S14 is convex.

[0107] The sixth lens L6 has a negative focal power, its object side S14 is concave, and its image side S15 is flat.

[0108] Among them, the fifth lens L5 and the sixth lens L6 form a doublet lens.

[0109] The third lens group G3 sequentially includes a seventh lens L7, an eighth lens L8, a ninth lens L9, a tenth lens L10, an eleventh lens L11, a twelfth lens L12, a thirteenth lens L13, and a fourteenth lens L14 along the optical axis from the object side to the image side.

[0110] The seventh lens L7 has a positive focal power, its object side S16 is convex, and its image side S17 is convex.

[0111] The eighth lens L8 has a positive focal power, its object side S18 is concave, and its image side S19 is convex.

[0112] The ninth lens L9 has a negative focal power, its object side S19 is concave, and its image side S20 is concave.

[0113] The tenth lens L10 has a positive focal power, its object side S21 is convex, and its image side S22 is concave.

[0114] The eleventh lens L11 has a positive focal power, its object side S22 is convex, and its image side S23 is convex.

[0115] The twelfth lens L12 has a negative focal power, its object side S24 is convex, and its image side S25 is concave.

[0116] The thirteenth lens L13 has a positive focal power, its object side S25 is convex, and its image side S26 is convex.

[0117] The fourteenth lens L14 has a negative focal power, its object side S26 is concave, and its image side S27 is flat.

[0118] Among them, the eighth lens L8 and the ninth lens L9 form a doublet lens, the tenth lens L10 and the eleventh lens L11 form a doublet lens, and the twelfth lens L12, the thirteenth lens L13, and the fourteenth lens L14 form a triplet lens.

[0119] The stop STO is disposed between the third lens L3 and the fourth lens L4.

[0120] The endoscopic adapter lens further includes a front protecting glass front CG disposed on the object side of the first lens L1, which has an object side S2 and an image side S3.

[0121] The endoscopic adapter lens further includes a bayonet positioning surface disposed on the object side of the front protecting glass front CG, which has a surface S1.

[0122] The endoscopic adapter lens further includes a rear protection glass CG disposed on the image side of the fourteenth lens L14, which has an object side surface S28 and an image side surface S29.

[0123] The endoscopic adapter lens further includes a beam splitter SG disposed on the image side of the rear protection glass CG, which has an object side surface S30 and an image side surface S31.

[0124] The endoscopic adapter lens further includes a chip protection glass CG disposed on the image side of the beam splitter SG, which has an object side surface S32 and an image side surface S33.

[0125] The light from the object surface OBJ sequentially passes through the surfaces S1 - S33 and finally forms an image on the imaging surface IMA. It should be noted that the object surface OBJ and the surfaces S1 to S33 are not shown in Figure 1 and Figure 2 are not shown.

[0126] Table 1 shows the basic parameter table of the endoscopic adapter lens of Embodiment 1, where the units of the radius of curvature and the thickness / distance are both millimeters (mm).

[0127] Table 1

[0128]

[0129]

[0130] In Embodiment 1, both the object side surface and the image side surface of the seventh lens are aspherical surfaces. The surface shape of the aspherical lens can be defined by, but not limited to, the following aspherical formula:

[0131]

[0132] where x is the sagitta, the distance from the vertex of the aspherical surface along the optical axis at a position with a height of h; c is the paraxial curvature of the aspherical surface, c = 1 / R (that is, the paraxial curvature c is the reciprocal of the radius of curvature R in Table 1 above); k is the conic coefficient; Ai is the correction coefficient of the i-th order of the aspherical surface. Table 2 below gives the conic coefficient k and the higher-order term coefficients A4, A6, A8, A10, A12, and A14 that can be used for the aspherical surfaces S16 to S17 in Embodiment 1.

[0133] Table 2

[0134] Surface number k A4 A6 A8 A10 A12 A14 S16 -1.636 -7.44E-07 -1.07E-06 -9.25E-09 -1.05E-09 2.69E-11 -9.59E-13 S17 -9.837 5.62E-05 -9.48E-07 -1.03E-08 -5.68E-10 1.36E-12 -4.91E-13

[0135] In Embodiment 1, the distance T1 corresponding to the OBJ row in Table 1 represents the object distance of the endoscopic adapter lens; the distance T2 corresponding to the S3 row in Table 1 represents the air gap on the optical axis between the front CG of the front protective glass of the lens and the first lens group G1 when the endoscopic adapter lens is at different object distances; the distance T3 corresponding to the S9 row in Table 1 represents the air gap on the optical axis between the first lens group G1 and the aperture STO when the endoscopic adapter lens is at different object distances; the distance T4 corresponding to the S10(STO) row in Table 1 represents the air gap on the optical axis between the aperture STO and the second lens group G2 when the endoscopic adapter lens is at the wide-angle end and the telephoto end; the distance T5 corresponding to the S15 row in Table 1 represents the air gap on the optical axis between the second lens group G2 and the third lens group G3 when the endoscopic adapter lens is at the wide-angle end and the telephoto end; the distance T6 corresponding to the S27 row in Table 1 represents the air gap on the optical axis between the third lens group G3 and the rear CG of the rear protective glass of the lens when the endoscopic adapter lens is at the wide-angle end and the telephoto end. When the lens is at the wide-angle end, the telephoto end, the object distance of -2000 mm, the object distance of 300 mm, and the object distance of infinity, the values (unit: mm) of the above variables T1, T2, T3, T4, T5, and T6 are shown in Table 3 below.

[0136] Table 3

[0137]

[0138] In this embodiment, the full holographic height of the endoscopic adapter lens is 7.4 mm; the effective focal length at the wide-angle end is 16.5 mm, and the effective focal length at the telephoto end is 36 mm; the maximum absolute distortion at the wide-angle end is 2.63%, and the maximum absolute distortion at the telephoto end is 0.35%; at the wide-angle end at a spatial frequency of 250 lp / mm, the MTF value of the central field of view is 0.43, and the MTF value of the maximum field of view is 0.41; at the telephoto end at a spatial frequency of 180 lp / mm, the MTF value of the central field of view is 0.18, and the MTF value of the maximum field of view is 0.17.

[0139] Example 2

[0140] The following refers to Figures 3 to 4 Describe the endoscopic adapter lens according to Embodiment 2 of the present application. Figure 3 FIG. shows a schematic structural diagram of the endoscopic adapter lens according to Embodiment 2 of the present application when it is at the wide-angle end, Figure 4 FIG. shows a schematic structural diagram of the endoscopic adapter lens according to Embodiment 2 of the present application when it is at the telephoto end.

[0141] As Figure 3 and Figure 4As shown, compared with Embodiment 1, the main differences in Embodiment 2 of the present application are as follows: the image side surface S9 of the third lens L3 is concave; the object side surface S18 of the eighth lens L8 is convex; the object side surface S24 of the twelfth lens L12 is concave; the image side surface S27 of the fourteenth lens L14 is convex; and the optical parameters such as the radius of curvature of each lens surface, the lens thickness, and the distance between lenses are different.

[0142] Table 4 shows the basic parameter table of the endoscope adapter lens in Embodiment 2, where the units of the radius of curvature and the thickness / distance are both millimeters (mm).

[0143] Table 4

[0144]

[0145]

[0146] In Embodiment 2, both the object side surface and the image side surface of the seventh lens are aspherical surfaces, and the surface shape of the aspherical lens can be defined by, but not limited to, the formula (1) given in Embodiment 1 above.

[0147] The following Table 5 gives the conic coefficients k and the higher-order term coefficients A4, A6, A8, A10, A12, and A14 that can be used for each of the aspherical surfaces S16 to S17 in Embodiment 2.

[0148] Table 5

[0149]

[0150]

[0151] In Embodiment 2, the distance T1 corresponding to the OBJ row in Table 4 represents the object distance of the endoscopic adapter lens; the distance T2 corresponding to the S3 row in Table 4 represents the air gap on the optical axis between the front CG of the protective glass in front of the lens and the first lens group G1 when the endoscopic adapter lens is at different object distances; the distance T3 corresponding to the S9 row in Table 4 represents the air gap on the optical axis between the first lens group G1 and the aperture STO when the endoscopic adapter lens is at different object distances; the distance T4 corresponding to the S10(STO) row in Table 4 represents the air gap on the optical axis between the aperture STO and the second lens group G2 when the endoscopic adapter lens is at the wide-angle end and the telephoto end; the distance T5 corresponding to the S15 row in Table 4 represents the air gap on the optical axis between the second lens group G2 and the third lens group G3 when the endoscopic adapter lens is at the wide-angle end and the telephoto end; the distance T6 corresponding to the S27 row in Table 4 represents the air gap on the optical axis between the third lens group G3 and the rear CG of the protective glass behind the lens when the endoscopic adapter lens is at the wide-angle end and the telephoto end. When the lens is at the wide-angle end, the telephoto end, the object distance of -2000 mm, the object distance of 300 mm, and the object distance of infinity, the values (unit: mm) of the above variables T1, T2, T3, T4, T5, and T6 are shown in Table 6 below.

[0152] Table 6

[0153]

[0154] In this embodiment, the full holographic height of the endoscopic adapter lens is 7.8 mm; the effective focal length at the wide-angle end is 16.5 mm, and the effective focal length at the telephoto end is 36 mm; the maximum absolute distortion at the wide-angle end is 2.96%, and the maximum absolute distortion at the telephoto end is 0.28%; at the wide-angle end at a spatial frequency of 250 lp / mm, the MTF value of the central field of view is 0.44, and the MTF value of the maximum field of view is 0.41; at the telephoto end at a spatial frequency of 180 lp / mm, the MTF value of the central field of view is 0.19, and the MTF value of the maximum field of view is 0.18.

[0155] Embodiment 3

[0156] The following refers to Figures 5 to 6 Describe the endoscopic adapter lens according to Embodiment 3 of the present application. Figure 5 FIG. shows a schematic structural diagram of the endoscopic adapter lens according to Embodiment 3 of the present application when it is at the wide-angle end, Figure 6 FIG. shows a schematic structural diagram of the endoscopic adapter lens according to Embodiment 3 of the present application when it is at the telephoto end.

[0157] As Figure 5 and Figure 6As shown in the figure, compared with Embodiment 1, the main differences in Embodiment 3 of the present application are as follows: the image side S9 of the third lens L3 is concave; the image side S15 of the sixth lens L6 is concave; the object side S24 of the twelfth lens L12 is concave; the image side S27 of the fourteenth lens L14 is convex; and the optical parameters such as the radius of curvature of each lens surface, the lens thickness, and the distance between lenses are different.

[0158] Table 7 shows the basic parameter table of the endoscope adapter lens in Embodiment 3, where the units of the radius of curvature and the thickness / distance are both millimeters (mm).

[0159] Table 7

[0160]

[0161]

[0162] In Embodiment 3, both the object side and the image side of the seventh lens are aspherical surfaces, and the surface profile of the aspherical lens can be defined by, but not limited to, the formula (1) given in Embodiment 1 above.

[0163] The following Table 8 gives the conic coefficients k and the higher-order term coefficients A4, A6, A8, A10, A12, and A14 that can be used for each of the aspherical surfaces S16 to S17 in Embodiment 3.

[0164] Table 8

[0165] Surface number k A4 A6 A8 A10 A12 A14 S16 4.417 -1.28E-04 -2.17E-06 1.21E-08 -1.20E-09 1.12E-11 -4.73E-13 S17 -4.939 5.03E-05 -1.30E-06 3.22E-08 -1.47E-09 1.69E-11 -4.13E-13

[0166] In Embodiment 3, the distance T1 corresponding to the OBJ row in Table 7 represents the object distance of the endoscope adapter lens; the distance T2 corresponding to the S3 row in Table 7 represents the air gap on the optical axis between the front CG of the front protective glass of the lens and the first lens group G1 when the endoscope adapter lens is at different object distances; the distance T3 corresponding to the S9 row in Table 7 represents the air gap on the optical axis between the first lens group G1 and the diaphragm STO when the endoscope adapter lens is at different object distances; the distance T4 corresponding to the S10(STO) row in Table 7 represents the air gap on the optical axis between the diaphragm STO and the second lens group G2 when the endoscope adapter lens is at the wide-angle end and the telephoto end; the distance T5 corresponding to the S15 row in Table 7 represents the air gap on the optical axis between the second lens group G2 and the third lens group G3 when the endoscope adapter lens is at the wide-angle end and the telephoto end; the distance T6 corresponding to the S27 row in Table 7 represents the air gap on the optical axis between the third lens group G3 and the rear CG of the rear protective glass of the lens when the endoscope adapter lens is at the wide-angle end and the telephoto end. When the lens is at the wide-angle end, the telephoto end, the object distance of -2000 mm, the object distance of 300 mm, and the object distance of infinity, the numerical values (unit: mm) of the above variables T1, T2, T3, T4, T5, and T6 are shown in the following Table 9.

[0167] Table 9

[0168]

[0169] In this embodiment, the full holographic height of the endoscope adapter lens is 7.8 mm; the effective focal length at the wide-angle end is 16.5 mm, and the effective focal length at the telephoto end is 36 mm; the maximum absolute value of distortion at the wide-angle end is 3.00%, and the maximum absolute value of distortion at the telephoto end is 0.32%; at the wide-angle end and at a spatial frequency of 250 lp / mm, the MTF value of the central field of view is 0.43, and the MTF value of the maximum field of view is 0.38; at the telephoto end and at a spatial frequency of 180 lp / mm, the MTF value of the central field of view is 0.18, and the MTF value of the maximum field of view is 0.17.

[0170] Embodiment 4

[0171] The following refers to Figures 7 to 8 Describe the endoscope adapter lens according to Embodiment 4 of the present application. Figure 7 FIG. shows a schematic structural diagram of the endoscope adapter lens according to Embodiment 4 of the present application when it is at the wide-angle end, Figure 8 FIG. shows a schematic structural diagram of the endoscope adapter lens according to Embodiment 4 of the present application when it is at the telephoto end.

[0172] As Figure 7 and Figure 8 shown, compared with Embodiment 1, the main difference in Embodiment 4 of the present application is that: the optical parameters such as the curvature radius of each lens surface, the lens thickness, and the distance between lenses are different.

[0173] Table 10 shows the basic parameter table of the endoscope adapter lens of Embodiment 4, where the units of the curvature radius and the thickness / distance are both millimeters (mm).

[0174] Table 10

[0175]

[0176]

[0177] In Embodiment 4, both the object side and the image side of the seventh lens are aspherical surfaces, and the surface profile of the aspherical lens can be defined by, but not limited to, the formula (1) given in Embodiment 1 above.

[0178] The following Table 11 gives the conic coefficients k and the higher-order term coefficients A4, A6, A8, A10, A12, and A14 for each of the aspherical surfaces S16 to S17 that can be used in Embodiment 4.

[0179] Table 11

[0180] Surface number k A4 A6 A8 A10 A12 A14 S16 -1.840 -1.42E-06 -1.20E-06 -5.72E-09 -1.14E-09 3.09E-11 -1.10E-12 S17 -6.077 5.67E-05 -9.76E-07 -1.26E-08 -3.66E-10 -4.51E-12 -4.82E-13

[0181] In Embodiment 4, the distance T1 corresponding to the OBJ row in Table 10 represents the object distance of the endoscopic adapter lens; the distance T2 corresponding to the S3 row in Table 10 represents the air gap on the optical axis between the front CG of the front protective glass of the lens and the first lens group G1 when the endoscopic adapter lens is at different object distances; the distance T3 corresponding to the S9 row in Table 10 represents the air gap on the optical axis between the first lens group G1 and the aperture STO when the endoscopic adapter lens is at different object distances; the distance T4 corresponding to the S10(STO) row in Table 10 represents the air gap on the optical axis between the aperture STO and the second lens group G2 when the endoscopic adapter lens is at the wide-angle end and the telephoto end; the distance T5 corresponding to the S15 row in Table 10 represents the air gap on the optical axis between the second lens group G2 and the third lens group G3 when the endoscopic adapter lens is at the wide-angle end and the telephoto end; the distance T6 corresponding to the S27 row in Table 10 represents the air gap on the optical axis between the third lens group G3 and the rear CG of the rear protective glass of the lens when the endoscopic adapter lens is at the wide-angle end and the telephoto end. When the lens is at the wide-angle end, the telephoto end, the object distance of -2000 mm, the object distance of 300 mm, and the object distance of infinity, the values (in mm) of the above variables T1, T2, T3, T4, T5, and T6 are shown in Table 12 below.

[0182] Table 12

[0183]

[0184] In this embodiment, the full holographic height of the endoscopic adapter lens is 7.4 mm; the effective focal length at the wide-angle end is 16.5 mm, and the effective focal length at the telephoto end is 36 mm; the maximum absolute distortion at the wide-angle end is 2.72%, and the maximum absolute distortion at the telephoto end is 0.37%; at the wide-angle end at a spatial frequency of 250 lp / mm, the MTF value of the central field of view is 0.44, and the MTF value of the maximum field of view is 0.40; at the telephoto end at a spatial frequency of 180 lp / mm, the MTF value of the central field of view is 0.18, and the MTF value of the maximum field of view is 0.17.

[0185] Embodiment 5

[0186] The following refers to Figures 9 to 10 Describe the endoscopic adapter lens according to Embodiment 5 of the present application. Figure 9 FIG. shows a schematic structural diagram of the endoscopic adapter lens according to Embodiment 5 of the present application when it is at the wide-angle end, Figure 10 FIG. shows a schematic structural diagram of the endoscopic adapter lens according to Embodiment 5 of the present application when it is at the telephoto end.

[0187] As Figure 9 and Figure 10As shown, compared with Embodiment 1, the main difference in Embodiment 5 of the present application is that: the object side surface S6 of the second lens L2 is a convex surface, and the image side surface S7 is a concave surface; the image side surface S15 of the sixth lens L6 is a concave surface;

[0188] The third lens group G3 sequentially includes a seventh lens L7, 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 along the optical axis from the object side to the image side;

[0189] The seventh lens L7 has a positive focal power, its object side surface S16 is a convex surface, and its image side surface S17 is a convex surface;

[0190] The eighth lens L8 has a positive focal power, its object side surface S18 is a convex surface, and its image side surface S19 is a convex surface;

[0191] The ninth lens L9 has a negative focal power, its object side surface S19 is a concave surface, and its image side surface S20 is a concave surface;

[0192] The tenth lens L10 has a positive focal power, its object side surface S20 is a convex surface, and its image side surface S21 is a convex surface;

[0193] The eleventh lens L11 has a negative focal power, its object side surface S22 is a concave surface, and its image side surface S23 is a concave surface;

[0194] The twelfth lens L12 has a positive focal power, its object side surface S23 is a convex surface, and its image side surface S24 is a convex surface;

[0195] The thirteenth lens L13 has a negative focal power, its object side surface S24 is a concave surface, and its image side surface S25 is a convex surface;

[0196] Among them, the eighth lens L8, the ninth lens L9, and the tenth lens L10 form a triple cemented lens, and the eleventh lens L11, the twelfth lens L12, and the thirteenth lens L13 form a triple cemented lens;

[0197] The endoscopic adapter lens further includes a rear CG of the lens rear protective glass disposed on the image side of the fourteenth lens L14, which has an object side surface S26 and an image side surface S27;

[0198] The endoscopic adapter lens further includes a beam splitter SG disposed on the image side of the rear protective glass rear CG, which has an object side surface S28 and an image side surface S29;

[0199] The endoscopic adapter lens further includes a chip protective glass CG disposed on the image side of the beam splitter SG, which has an object side surface S30 and an image side surface S31;

[0200] The optical parameters such as the curvature radius of each lens surface, the lens thickness, and the distance between the lenses are different.

[0201] Light from the object surface OBJ sequentially passes through each of the surfaces S1 - S31 and finally forms an image on the imaging surface IMA. It should be noted that the object surface OBJ and the surfaces S1 to S31 are not shown in Figure 9 and Figure 10 ;

[0202] Table 13 shows the basic parameter table of the endoscope adapter lens of Example 5, where the unit of the radius of curvature and the thickness / distance is millimeter (mm).

[0203] Table 13

[0204]

[0205]

[0206] In Example 5, both the object side and the image side of the seventh lens are aspherical surfaces. The surface profile of the aspherical lens can be defined by, but is not limited to, the formula (1) given in the above Example 1.

[0207] The following Table 14 gives the conic coefficients k and the higher - order term coefficients A4, A6, A8, A10, A12, and A14 that can be used for the aspherical surfaces S16 to S17 in Example 5.

[0208] Table 14

[0209] Surface number k A4 A6 A8 A10 A12 A14 S16 84.324 2.10E-05 -4.21E-07 1.81E-08 1.33E-09 -6.04E-11 8.42E-13 S17 -23.466 4.46E-05 -1.71E-07 3.39E-08 -1.21E-11 -1.74E-11 2.48E-13

[0210] In Example 5, the distance T1 corresponding to the OBJ row in Table 13 represents the object distance of the endoscope adapter lens; the distance T2 corresponding to the S3 row in Table 13 represents the air gap on the optical axis between the front CG of the lens front protection glass and the first lens group G1 when the endoscope adapter lens is at different object distances; the distance T3 corresponding to the S9 row in Table 13 represents the air gap on the optical axis between the first lens group G1 and the diaphragm STO when the endoscope adapter lens is at different object distances; the distance T4 corresponding to the S10(STO) row in Table 13 represents the air gap on the optical axis between the diaphragm STO and the second lens group G2 when the endoscope adapter lens is at the wide - angle end and the telephoto end; the distance T5 corresponding to the S15 row in Table 13 represents the air gap on the optical axis between the second lens group G2 and the third lens group G3 when the endoscope adapter lens is at the wide - angle end and the telephoto end; the distance T6 corresponding to the S25 row in Table 13 represents the air gap on the optical axis between the third lens group G3 and the rear CG of the lens rear protection glass when the endoscope adapter lens is at the wide - angle end and the telephoto end. When the lens is at the wide - angle end, the telephoto end, the object distance of - 2000 mm, the object distance of 300 mm, and the object distance of infinity, the numerical values (unit: mm) of the above variables T1, T2, T3, T4, T5, and T6 are shown in the following Table 15 respectively.

[0211] Table 15

[0212]

[0213]

[0214] In this embodiment, the full holographic height of the endoscope adapter lens is 7.8 mm; the effective focal length at the wide-angle end is 16.5 mm, and the effective focal length at the telephoto end is 36 mm; the maximum absolute distortion at the wide-angle end is 3.40%, and the maximum absolute distortion at the telephoto end is 0.31%; at the wide-angle end at a spatial frequency of 250 lp / mm, the MTF value of the central field of view is 0.44, and the MTF value of the maximum field of view is 0.37; at the telephoto end at a spatial frequency of 180 lp / mm, the MTF value of the central field of view is 0.19, and the MTF value of the maximum field of view is 0.18.

[0215] In summary, the conditions in Embodiments 1 to 5 satisfy the relationships shown in Table 16. In Table 16, the unit of the parameter is millimeter (mm).

[0216] Table 16

[0217] Conditional formula / Example 1 2 3 4 5 1.55 ≤ FG1 / Fw ≤ 2.14 1.943 1.726 1.768 1.918 1.772 -0.91 ≤ FG2 / Fw ≤ -0.63 -0.824 -0.716 -0.726 -0.801 -0.708 0.81 ≤ FG3 / Fw ≤ 1.08 0.978 0.934 0.924 0.967 0.910 0.95 ≤ F7 / Fw ≤ 2.94 1.071 1.146 1.073 1.056 2.673 0.10 ≤ d1 / FG1 ≤ 0.15 0.129 0.114 0.117 0.127 0.117 0.07 ≤ d2 / TTL ≤ 0.11 0.094 0.081 0.084 0.093 0.084 0.07 ≤ d3 / TTL ≤ 0.10 0.081 0.083 0.083 0.081 0.083 -14.63 ≤ FG2*FG3 / Fw ≤ -9.57 -13.295 -11.035 -11.075 -12.781 -10.634 -6.71 ≤ FG2*FG3 / Ft ≤ -4.38 -6.094 -5.058 -5.076 -5.858 -4.874 0.22 ≤ Fw / TTL ≤ 0.29 0.246 0.254 0.257 0.248 0.263 0.48 ≤ Ft / TTL ≤ 0.63 0.537 0.553 0.561 0.541 0.573 0.34 ≤ BFL / TTL ≤ 0.45 0.383 0.395 0.400 0.386 0.409 0.14 ≤ Dmax / TTL ≤ 0.19 0.161 0.163 0.166 0.163 0.169 0.09 ≤ H / TTL ≤ 0.14 0.110 0.120 0.122 0.111 0.124 0.38 ≤ S / FG1 ≤ 0.54 0.427 0.490 0.473 0.436 0.472

[0218] The present application also provides an imaging device, the electronic photosensitive element of which can be a charge-coupled device (CCD) or a complementary metal-oxide-semiconductor device (CMOS), and the imaging device is equipped with the endoscope adapter lens described above.

[0219] 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 technical features (but not limited to) having similar functions disclosed in the present application.

Claims

1. An endoscopic adapter lens, characterized in that, In order from the object side to the image side along the optical axis, it includes: A front protective glass; A first lens group with a positive optical power, the first lens group only includes three lenses, and in order from the object side to the image side along the optical axis, it includes a first lens, a second lens, and a third lens; A second lens group with a negative optical power, the second lens group only includes three lenses, and in order from the object side to the image side along the optical axis, it includes a fourth lens, a fifth lens, and a sixth lens; A third lens group with a positive optical power, the third lens group only includes seven lenses, and in order from the object side to the image side along the optical axis, it includes a seventh lens, an eighth lens, a ninth lens, a tenth lens, an eleventh lens, a twelfth lens, and a thirteenth lens; or, the third lens group only includes eight lenses, and in order from the object side to the image side along the optical axis, it includes a seventh lens, an eighth lens, a ninth lens, a tenth lens, an eleventh lens, a twelfth lens, a thirteenth lens, and a fourteenth lens; and A rear protective glass; Wherein, during the zooming process, the first lens group is fixedly arranged, the second lens group moves along the optical axis between the object side and the image side to achieve continuous zooming 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 the change in the image plane position during the zooming process; during the change in the object distance, the first lens group moves along the optical axis between the object side and the image side to compensate for the change in the image plane position during the change in the object distance.

2. The endoscope adapter lens according to claim 1, wherein The first lens has a negative optical power, its object side is convex, and its image side is concave; The second lens has a positive optical power, its object side is concave, and its image side is convex, or its object side is convex, and its image side is concave; and The third lens has a positive optical power, its object side is convex, and its image side is convex or concave.

3. The endoscope adapter lens according to claim 1, wherein The fourth lens has a negative optical power, its object side is concave, and its image side is concave; The fifth lens has a positive optical power, its object side is concave, and its image side is convex; and The sixth lens has a negative optical power, its object side is concave, and its image side is convex or concave or flat.

4. The endoscopic adapter lens according to claim 1, wherein The third lens group only includes seven lenses: The seventh lens has a positive optical power, its object side is convex, and its image side is convex; The eighth lens has a positive optical power, its object side is convex, and its image side is convex; The ninth lens has a negative optical power, its object side is concave, and its image side is concave; The tenth lens has a positive optical power, its object side is convex, and its image side is convex; The eleventh lens has a negative optical power, its object side is concave, and its image side is concave; The twelfth lens has a positive optical power, its object side is convex, and its image side is convex; and The thirteenth lens has a negative optical power, its object side is concave, and its image side is convex.

5. The endoscopic adapter lens according to claim 1, characterized in that, The third lens group only includes eight lenses: The seventh lens has a positive optical power, with its object side being convex and its image side being convex; The eighth lens has a positive optical power, with its object side being convex or concave and its image side being convex; The ninth lens has a negative optical power, with its object side being concave and its image side being concave; The tenth lens has a positive optical power, with its object side being convex and its image side being concave; The eleventh lens has a positive optical power, with its object side being convex and its image side being convex; The twelfth lens has a negative optical power, with its object side being convex or concave and its image side being concave; The thirteenth lens has a positive optical power, with its object side being convex and its image side being convex; and The fourteenth lens has a negative optical power, with its object side being concave and its image side being convex or concave or flat.

6. The endoscopic adapter lens according to claim 4, wherein The fifth lens and the sixth lens form a first cemented lens, the eighth lens, the ninth lens and the tenth lens form a second cemented lens, and the eleventh lens, the twelfth lens and the thirteenth lens form a third cemented lens.

7. The endoscopic adapter lens according to claim 5, wherein The fifth lens and the sixth lens form a first cemented lens, the eighth lens and the ninth lens form a second cemented lens, the tenth lens and the eleventh lens form a third cemented lens, and the twelfth lens, the thirteenth lens and the fourteenth lens form a fourth cemented lens. Among them, the Abbe number VdB11 of the eighth lens or the tenth lens, the Abbe number VdB12 of the ninth lens or the eleventh lens, the Abbe number VdB21 of the twelfth lens, the Abbe number VdB22 of the thirteenth lens and the Abbe number VdB23 of the fourteenth lens satisfy the conditional formula: 1.19 ≤ VdB11 / VdB12 ≤ 2.24, 8.89 ≤ VdB21*VdB23 / VdB22 ≤ 13.

67.

8. The endoscopic adapter lens according to any one of claims 1 to 7, characterized in that The endoscopic adapter lens satisfies at least one of the following conditional formulas: 1.55 ≤ FG1 / Fw ≤ 2.14, -0.91 ≤ FG2 / Fw ≤ -0.63, 0.81 ≤ FG3 / Fw ≤ 1.08, 0.95 ≤ F7 / Fw ≤ 2.94, where FG1 is the effective focal length of the first lens group, FG2 is the effective focal length of the second lens group, FG3 is the effective focal length of the third lens group, F7 is the effective focal length of the seventh lens, and Fw is the effective focal length of the endoscopic adapter lens at the wide-angle end.

9. The endoscopic adapter lens according to any one of claims 1 to 7, characterized in that, The endoscopic adapter lens satisfies at least one of the following conditional formulas: 0.10 ≤ d1 / FG1 ≤ 0.15, 0.07 ≤ d2 / TTL ≤ 0.11, 0.07 ≤ d3 / TTL ≤ 0.10, -14.63 mm ≤ FG2*FG3 / Fw ≤ -9.57 mm, -6.71 mm ≤ FG2*FG3 / Ft ≤ -4.38 mm, Wherein, d1 is the maximum travel of the first lens group when moving from an object distance of -2000 mm to an infinite object distance, d2 is the maximum travel of the second lens group when moving from the wide-angle end to the telephoto end, d3 is the maximum travel of the third lens group when moving from the wide-angle end to the telephoto end, FG1 is the effective focal length of the first lens group, FG2 is the effective focal length of the second lens group, FG3 is the effective focal length of the third lens group, Fw is the effective focal length of the endoscope adapter lens at the wide-angle end, Ft is the effective focal length of the endoscope adapter lens at the telephoto end, and TTL is the distance from the object side surface of the first lens to the image surface at an infinite object distance.

10. The endoscopic adapter lens according to any one of claims 1 to 7, characterized in that, The endoscope adapter lens satisfies at least one of the following conditional expressions: 0.22 ≤ Fw / TTL ≤ 0.29, 0.48 ≤ Ft / TTL ≤ 0.63, 0.34 ≤ BFL / TTL ≤ 0.45, 0.14 ≤ Dmax / TTL ≤ 0.19, 0.09 ≤ H / TTL ≤ 0.14, 0.38 ≤ S / FG1 ≤ 0.54, Wherein, Fw is the effective focal length of the endoscope adapter lens at the wide-angle end, Ft is the effective focal length of the endoscope adapter lens at the telephoto end, TTL is the distance from the object side surface of the first lens to the image surface at an infinite object distance, BFL is the distance from the image side surface of the rear protective glass to the image surface, Dmax is the maximum optical aperture of the seventh lens, H is the total image height of the endoscope adapter lens, S is the entrance pupil distance of the endoscope adapter lens at an infinite object distance, and FG1 is the effective focal length of the first lens group.

11. The endoscopic adapter lens according to any one of claims 1 to 7, characterized in that, The endoscope adapter lens satisfies at least one of the following conditional expressions: 1.72 ≤ FG1 / Fw ≤ 1.95, -0.83 ≤ FG2 / Fw ≤ -0.70, 0.91 ≤ FG3 / Fw ≤ 0.98, 1.05 ≤ F7 / Fw ≤ 2.68, 0.11 ≤ d1 / FG1 ≤ 0.13, 0.08 ≤ d2 / TTL ≤ 0.10, 0.08 ≤ d3 / TTL ≤ 0.09, -13.30 mm ≤ FG2*FG3 / Fw ≤ -10.63 mm, -6.10 mm ≤ FG2*FG3 / Ft ≤ -4.87 mm, 0.24 ≤ Fw / TTL ≤ 0.27, 0.53 ≤ Ft / TTL ≤ 0.58, 0.38 ≤ BFL / TTL ≤ 0.41, 0.16 ≤ Dmax / TTL ≤ 0.17, 0.11 ≤ H / TTL ≤ 0.13, 0.42 ≤ S / FG1 ≤ 0.49, Among them, FG1 is the effective focal length of the first lens group, FG2 is the effective focal length of the second lens group, FG3 is the effective focal length of the third lens group, F7 is the effective focal length of the seventh lens, Fw is the effective focal length of the endoscope adapter lens at the wide-angle end, Ft is the effective focal length of the endoscope adapter lens at the telephoto end, d1 is the maximum travel of the first lens group when moving from a object distance of -2000mm to an infinite object distance, d2 is the maximum travel of the second lens group when moving from the wide-angle end to the telephoto end, d3 is the maximum travel of the third lens group when moving from the wide-angle end to the telephoto end, TTL is the distance from the object side surface of the first lens to the image surface at an infinite object distance, BFL is the distance from the image side surface of the rear protective glass to the image surface, Dmax is the maximum optical aperture of the seventh lens, H is the total image height of the endoscope adapter lens, and S is the entrance pupil distance of the endoscope adapter lens at an infinite object distance.

Images