CN115327762B - 4K zoom optical adapter and endoscope - Google Patents

Abstract

The application relates to a 4K zoom optical adapter and an endoscope. The 4K zoom optical adapter includes: the first lens with positive focal power is convex in object side surface; the first zoom group comprises a second lens with negative focal power and a third lens with negative focal power, the second lens is biconcave, and the object side surface of the third lens is concave; a second variable power group having positive optical power, the second variable power group including a fourth lens having positive optical power and a fifth lens having positive optical power, the fourth lens and the fifth lens being biconvex; the sixth lens with negative focal power is biconcave; the seventh lens with positive focal power is biconvex; the first variable power group, the second variable power group, and the sixth lens are movable between the first lens and the seventh lens. The 4K zoom optical adapter has good imaging quality.

Description

4K zoom optical adapter and endoscope

Technical Field

The application relates to the technical field of endoscope imaging, in particular to a 4K zoom optical adapter and an endoscope.

Background

A medical endoscope is a medical device which can enter a human body to observe, diagnose or treat, and generally comprises a camera host, a camera head and an endoscope mirror, wherein the camera head is in optical path communication with the endoscope mirror through an optical adapter, and the optical adapter is functionally divided into a fixed focal length adapter (i.e. a zoom optical adapter) and a variable focal length adapter (i.e. a zoom optical adapter).

With the rapid development of endoscopes, the performance requirements of the endoscopes are also increasing in industry. In order to obtain clear images of a focus area to the greatest extent and improve the accuracy of diagnosis, 4K (ultra high definition) endoscopes with good imaging quality are proposed in the industry. However, the current 4K zoom optical adapter has poor imaging quality, and is difficult to meet the requirement of high imaging quality of a 4K endoscope.

Disclosure of Invention

Based on this, it is necessary to provide a 4K zoom optical adapter and an endoscope aiming at the problem that the imaging quality of the current 4K zoom optical adapter is poor.

A 4K-zoom optical adapter, the number of lenses having optical power in the 4K-zoom optical adapter being seven, the 4K-zoom optical adapter comprising, in order from an object side to an image side along an optical axis:

a first lens with positive focal power, wherein the object side surface of the first lens is a convex surface at a paraxial region;

the first zoom group comprises a second lens with negative focal power and a third lens with negative focal power, wherein the second lens is biconcave at a paraxial region, and the object side surface of the third lens is concave at the paraxial region;

the second variable power group comprises a fourth lens with positive focal power and a fifth lens with positive focal power, and the fourth lens and the fifth lens are biconvex at a paraxial region;

a sixth lens with negative focal power, wherein the sixth lens is biconcave at a paraxial region; the method comprises the steps of,

a seventh lens having positive optical power, the seventh lens being biconvex at a paraxial region;

wherein at least one of the first variable magnification group, the second variable magnification group, and the sixth lens is movable along an optical axis between the first lens and the seventh lens to realize an optical zoom function.

In one embodiment, the 4K zoom optical adapter satisfies the following conditional expression:

0.5≤100*(D1/TTL)≤1.0；

1.5≤10*(D2/TTL)≤2.5；

1.2≤10*(D3/TTL)≤2.2；

wherein D1 is the maximum moving distance of the first variable-magnification group, D2 is the maximum moving distance of the second variable-magnification group, and D3 is the maximum moving distance of the compensation group.

In one embodiment, the 4K zoom optical adapter satisfies the following conditional expression:

6≤f2/CT2≤6.8；

9≤f8/CT8≤11；

wherein f2 is an effective focal length of the first lens, CT2 is a thickness of the first lens on the optical axis, f8 is an effective focal length of the seventh lens, and CT8 is a thickness of the seventh lens on the optical axis.

In one embodiment, the 4K zoom optical adapter satisfies the following conditional expression:

2.0≤|f2/f34|≤2.8；

1.6≤f3/f34≤2.2；

2.1≤f4/f34≤2.7；

wherein f2 is an effective focal length of the first lens, f3 is an effective focal length of the second lens, f4 is an effective focal length of the third lens, and f34 is an effective focal length of the first zoom group.

In one embodiment, the 4K zoom optical adapter satisfies the following conditional expression:

1.8≤f5/f56≤2.6；

1.4≤f6/f56≤2.4；

wherein f5 is an effective focal length of the fourth lens, f6 is an effective focal length of the fifth lens, and f56 is an effective focal length of the second zoom group.

In one embodiment, the 4K zoom optical adapter satisfies the following conditional expression:

1.2≤(f6-f7)/f56≤2.0；

wherein f6 is an effective focal length of the fifth lens, f7 is an effective focal length of the sixth lens, and f56 is an effective focal length of the second zoom group.

In one embodiment, the 4K zoom optical adapter satisfies the following conditional expression:

CT5/T95 is less than or equal to 1.5 and less than or equal to 2.2; and/or the number of the groups of groups,

8.5≤R16/CT8≤10；

wherein, CT5 is the thickness of the fourth lens element on the optical axis, T95 is the distance between the stop and the object-side surface of the fourth lens element on the optical axis, R16 is the radius of curvature of the object-side surface of the seventh lens element on the optical axis, and CT8 is the thickness of the seventh lens element on the optical axis.

In one embodiment, the 4K zoom optical adapter satisfies the following conditional expression:

13≤f8/Nd8≤15；

wherein f8 is the effective focal length of the seventh lens, and Nd8 is the refractive index of the seventh lens.

In one embodiment, the 4K zoom optical adapter satisfies the following conditional expression:

15mm≤f≤32mm；

4≤FNO≤4.2；

15°≤FOV≤30°；

wherein f is the effective focal length of the 4K zoom optical adapter, FNO is the f-number of the 4K zoom optical adapter, and FOV is the maximum field angle of the 4K zoom optical adapter.

In one embodiment, an object side surface of the fourth lens is an aspheric surface; and/or the number of the groups of groups,

and the object side surface of the seventh lens is an aspheric surface.

An endoscope comprising a 4K zoom optical adapter as described in any of the embodiments above.

According to the 4K zoom optical adapter, the first zoom group, the second zoom group and the sixth lens capable of moving along the optical axis are configured to achieve the optical zoom function, the application range of the 4K zoom optical adapter is improved, meanwhile, the seventh lens is configured to effectively correct the aberration of the 4K zoom optical adapter at the image side of the sixth lens, and the focal power and the surface type configuration of each lens of the 4K zoom optical adapter are matched, so that the effects of large aperture, miniaturization, good imaging quality and the like are achieved, and the application of the 4K zoom optical adapter in a 4K endoscope is facilitated.

Drawings

FIG. 1 is a schematic diagram of a 4K zoom optical adapter in some embodiments;

FIG. 2 is a schematic diagram of a 4K zoom optical adapter in a wide-angle state according to some embodiments;

FIG. 3 is a schematic diagram of a 4K zoom optical adapter in a tele state according to some embodiments;

FIG. 4 is a graph of the transfer function of the 4K zoom optical adapter in the wide-angle state of the first embodiment;

FIG. 5 is a defocus graph of the 4K zoom optical adapter of the first embodiment in the wide-angle state;

FIG. 6 is a point diagram of the 4K zoom optical adapter in the wide-angle state of the first embodiment;

FIG. 7 is a graph of field curvature and distortion in the wide-angle state of the 4K zoom optical adapter of the first embodiment;

FIG. 8 is a graph of the transfer function of the 4K zoom optical adapter in the wide-angle state of the second embodiment;

FIG. 9 is a defocus graph of the 4K zoom optical adapter in the wide-angle state of the second embodiment;

FIG. 10 is a point-to-point diagram of the 4K zoom optical adapter in the wide-angle state of the second embodiment;

FIG. 11 is a graph of field curvature and distortion in the wide-angle state for a 4K zoom optical adapter according to the second embodiment;

FIG. 12 is a graph of a transfer function of the 4K zoom optical adapter in a wide-angle state according to the third embodiment;

FIG. 13 is a defocus graph of the 4K zoom optical adapter in the wide-angle state of the third embodiment;

fig. 14 is a point diagram of the 4K zoom optical adapter in the wide-angle state in the third embodiment;

fig. 15 is a graph of curvature of field and distortion of the 4K zoom optical adapter in the wide-angle state in the third embodiment.

Detailed Description

In order that the above objects, features and advantages of the application will be readily understood, a more particular description of the application will be rendered by reference to the appended drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application. The present application may be embodied in many other forms than described herein and similarly modified by those skilled in the art without departing from the spirit of the application, whereby the application is not limited to the specific embodiments disclosed below.

In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings are merely for convenience in describing the present application and simplifying the description, and do not indicate or imply that the device or element being referred to must have a specific orientation, be configured and operated in a specific orientation, and therefore should not be construed as limiting the present application.

Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include at least one such feature. In the description of the present application, the meaning of "plurality" means at least two, for example, two, three, etc., unless specifically defined otherwise.

In the present application, unless explicitly specified and limited otherwise, the terms "mounted," "connected," "secured," and the like are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally formed; can be mechanically or electrically connected; either directly or indirectly, through intermediaries, or both, may be in communication with each other or in interaction with each other, unless expressly defined otherwise. The specific meaning of the above terms in the present application can be understood by those of ordinary skill in the art according to the specific circumstances.

In the present application, unless expressly stated or limited otherwise, a first feature "up" or "down" a second feature may be the first and second features in direct contact, or the first and second features in indirect contact via an intervening medium. Moreover, a first feature being "above," "over" and "on" a second feature may be a first feature being directly above or obliquely above the second feature, or simply indicating that the first feature is level higher than the second feature. The first feature being "under", "below" and "beneath" the second feature may be the first feature being directly under or obliquely below the second feature, or simply indicating that the first feature is less level than the second feature.

It will be understood that when an element is referred to as being "fixed" or "disposed" on another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and the like are used herein for illustrative purposes only and are not meant to be the only embodiment.

Referring to fig. 1, the present application provides a 4K zoom optical adapter 10 that can be used in medical devices, such as hard tube endoscopes or flexible tube endoscopes. In some embodiments, the 4K zoom optical adapter 10 includes, in order from an object side to an image side along the optical axis 110, a first lens E2, a first variable magnification group G1, a second variable magnification group G2, a compensation group G3, and a rear fixed group. The first variable magnification group G1 includes a second lens E3 and a third lens E4 arranged in order from the object side to the image side along the optical axis 110. The second variable magnification group G2 includes a fourth lens E5 and a fifth lens E6 arranged in order from the object side to the image side along the optical axis 110. The compensation group G3 includes a sixth lens E7. The rear fixed group includes a seventh lens E8. Wherein, in some embodiments, one, two or three of the first variable magnification group G1, the second variable magnification group G2 and the compensation group G2 can move along the optical axis 110 between the first lens E2 and the rear fixed group to realize the optical zoom function of the 4K zoom optical adapter 10. In some embodiments, the 4K zoom optical adapter 10 further includes an imaging surface S20 disposed on the image side of the seventh lens E8, and the incident light can be incident on the imaging surface S20 for imaging after being adjusted by each lens in the 4K zoom optical adapter 10.

In some embodiments, the 4K zoom optical adapter 10 may further include a first protection element E1 disposed on the object side of the first lens E2 and a second protection element E9 disposed on the image side of the seventh lens E8. The first protection element E1 and the second protection element E9 may each be a protection glass for protecting a lens in the 4K zoom optical adapter 10 and a photosensitive element provided at the imaging surface S20.

The first protection element E1 has an object side surface S1 and an image side surface S2, the first lens element E2 has an object side surface S3 and an image side surface S4, the second lens element E3 has an object side surface S5 and an image side surface S6, the third lens element E4 has an object side surface S7 and an image side surface S8, the fourth lens element E5 has an object side surface S10 and an image side surface S11, the fifth lens element E6 has an object side surface S12 and an image side surface S13, the sixth lens element E7 has an object side surface S14 and an image side surface S15, the seventh lens element E8 has an object side surface S16 and an image side surface S17, and the second protection element E10 has an object side surface S18 and an image side surface S19.

Specifically, in some embodiments, the first lens element E2 has positive optical power, the object-side surface S3 of the first lens element E2 is convex at the paraxial region 110, and the image-side surface S4 is planar. The first variable magnification group G1 has negative focal power, the second lens element E3 has negative focal power, the third lens element E4 has negative focal power, the paraxial region 110 of the second lens element E3 is biconcave, the object-side surface S7 of the third lens element E3 is concave at the paraxial region 110, and the image-side surface S8 is planar. The second variable power group G2 has positive power, the fourth lens element E5 has positive power, the fifth lens element E6 has positive power, and both the fourth lens element E5 and the fifth lens element E6 are biconvex at the paraxial region 110. The sixth lens E7 has negative power, and the sixth lens E7 is biconcave at the paraxial region 110. The seventh lens E8 has positive power, and the seventh lens E8 is biconvex at the paraxial region 110.

In the 4K zoom optical adapter 10, the first zoom group G1, the second zoom group G2, and the compensation group G3, which are movable along the optical axis 110, are configured to implement an optical zoom function, so that the application range of the 4K zoom optical adapter 10 is increased, and meanwhile, the seventh lens E8 is configured as a rear fixed group to effectively correct the aberration of the 4K zoom optical adapter 10 on the image side of the compensation group G3, so that the 4K zoom optical adapter 10 is beneficial to implementing the effects of large aperture, miniaturization, good imaging quality, and the like, and is beneficial to the application of the 4K zoom optical adapter 10 in a 4K endoscope.

The first lens E2 has positive focal power, and is beneficial to converging incident light rays in cooperation with the convex surface type of the object side surface S3 of the first lens E2 at the paraxial region 110, thereby being beneficial to shortening the total length of the 4K zoom optical adapter 10 and realizing miniaturization design. The first zoom group G1 has negative focal power, the second lens element E3 and the third lens element E4 have negative focal power, and the concave surface shapes of the object-side surface S5, the image-side surface S6 and the object-side surface S7 of the third lens element E4 at the paraxial region 110 are matched with each other, so that light rays converged by the first lens element E1 are reasonably transited in the first zoom group G1, aberration of the first lens element E1 is effectively corrected, aberration sensitivity of the 4K zoom optical adapter 10 is reduced, and imaging quality of the 4K zoom optical adapter 10 is improved. The second zoom group G2 has positive focal power, the fourth lens element E5 and the fifth lens element E6 both have positive refractive power, and the combination of the biconvex shape of the fourth lens element E5 and the fifth lens element E6 at the paraxial region 110 is beneficial to smooth transition of light in the second zoom group G2, thereby being beneficial to reducing aberration sensitivity of the 4K zoom optical adapter 10, improving imaging quality of the 4K zoom optical adapter 10, and simultaneously being beneficial to further shortening total length of the 4K zoom optical adapter 10 by combining positive focal power of the first lens element E2, and realizing miniaturization design. The sixth lens element E7 has negative focal power, and is beneficial to diverging light to the imaging surface S20 in cooperation with the biconcave surface of the sixth lens element E7 at the paraxial region 110, so that the incident angle of light on the imaging surface S20 can be better matched with the photosensitive element, and the relative illuminance and the imaging quality of the 4K zoom optical adapter 10 are improved. The seventh lens E8 has positive focal power, and is beneficial to enlarging the back focal space of the 4K zoom optical adapter 10 by matching with the biconvex shape of the seventh lens E8 at the paraxial region 110, so that the 4K zoom optical adapter 10 can be matched with an image pickup module of an image space in a 4K endoscope better, and the requirement of the 4K endoscope on high imaging quality is met.

In some embodiments, the image side S4 of the first lens E2 and the image side S8 of the third lens E4 are planar, facilitating the manufacture and assembly of the 4K zoom optical adapter 10. Of course, the image side surface S4 of the first lens E2 and the image side surface S8 of the third lens E4 may be any of convex and concave surfaces as long as the 4K zoom optical adapter 10 can achieve the above large aperture, miniaturization, and good imaging quality.

In some embodiments, the object side and/or image side of at least one lens in the 4K zoom optical adapter 10 is spherical and the object side and/or image side of at least one lens is aspherical. For example, in some embodiments, the object-side surfaces and the image-side surfaces of the first to sixth lenses E2 to E7 and the image-side surface S17 of the seventh lens element E8 are spherical, and the object-side surface S16 of the seventh lens element E8 is aspheric. In other embodiments, the object-side surfaces and the image-side surfaces of the first lens element E2-third lens element E4, the image-side surface S11 of the fourth lens element E5, the object-side surfaces and the image-side surfaces of the fifth lens element E6-sixth lens element E7, and the image-side surface S17 of the seventh lens element E8 are spherical surfaces, and the object-side surface S10 of the fourth lens element E5 and the object-side surface S16 of the seventh lens element E8 are aspheric surfaces. The matching arrangement of the spherical surface and the aspherical surface, in combination with the refractive power and the surface configuration of each lens, can effectively correct the aberration of the 4K zoom optical adapter 10 and improve the imaging quality of the 4K zoom optical adapter 10 while reducing the size of the 4K zoom optical adapter 10 to realize miniaturized design.

In some embodiments, the lenses in the 4K zoom optical adapter 10 are made of glass, and the use of glass lenses enables the 4K zoom optical adapter 10 to have excellent optical performance and high temperature resistance.

Referring to fig. 1, fig. 2, and fig. 3, fig. 2 is a schematic structural diagram of the 4K zoom optical adapter 10 in a wide-angle state in some embodiments, and fig. 3 is a schematic structural diagram of the 4K zoom optical adapter 10 in a tele state in some embodiments. It can be seen that the 4K zoom optical adapter 10 changes the effective focal length of the 4K zoom optical adapter 10 by movement of the first variable magnification group G1, the second variable magnification group G2, and the compensation group G3 along the optical axis 110 between the first lens E2 and the seventh lens E8, thereby realizing an optical zoom function.

Further, in some embodiments, the effective focal length of the 4K zoom optical adapter 10 gradually increases as the second variable magnification group G2 and the compensation group G3 move along the optical axis 110 in a direction toward the first lens E2 and away from the seventh lens E8. Of course, the effective focal length of the 4K zoom optical adapter 10 may have a different relationship with the movement rules of the first zoom group G1, the second zoom group G2, and the compensation group G3 along the optical axis 110 according to the different lens designs or the difference before and after the focal length state change, for example, when the focal length state of the lens is changed, only one or three of the first zoom group G1, the second zoom group G2, and the compensation group G3 may move along the optical axis 110.

In some embodiments, the effective focal length of the 4K zoom optical adapter 10 is 16mm when the 4K zoom optical adapter 10 is in the wide-angle state, and the effective focal length of the 4K zoom optical adapter 10 is 32mm when the 4K zoom optical adapter 10 is in the tele state. The 4K zoom optical adapter 10 may further include a mid state between the wide-angle state and the tele state, and the effective focal length of the 4K zoom optical adapter 10 may be 23 or 24mm when the 4K zoom optical adapter 10 is in the mid state. Of course, the wide-angle state, the mid-focal state, and the telephoto state are only examples of three focal length states of the 4K zoom optical adapter 10, and the effective focal length of the 4K zoom optical adapter 10 may be any value between the wide-angle state and the telephoto state, for example, the effective focal length of the 4K zoom optical adapter 10 may be any value between 16mm and 32mm, depending on the difference in positions of the first zoom group G1, the second zoom group G2, and the compensation group G3 on the optical axis 110.

In some embodiments, the 4K zoom optical adapter 10 further includes a stop S9, where the stop S9 may be disposed on the object side of the first lens E2, or between any two lenses. Specifically, in some embodiments, the diaphragm S9 is disposed between the third lens E4 and the fourth lens E5, and is beneficial to the 4K zoom optical adapter 10 to achieve a large aperture characteristic and good imaging quality in cooperation with the focal power and the surface design of each lens. In some embodiments, the stop S9 is disposed on the object side of the fourth lens element E5, and when the second zoom group G2 moves along the optical axis 110 between the first zoom group G1 and the compensation group G3, the stop S9 can move synchronously with the fourth lens element E5, so as to facilitate the 4K zoom optical adapter 10 to have a large aperture characteristic and good imaging quality in different focal length states.

In some embodiments, the 4K zoom optical adapter 10 satisfies the conditional expression: less than or equal to 0.5 and less than or equal to 100 (D1/TTL) and less than or equal to 1.0; 1.5.ltoreq.10 (D2/TTL). Ltoreq.2.5; 1.2.ltoreq.10 (D3/TTL). Ltoreq.2.2; wherein D1 is the maximum moving distance of the first variable-magnification group G1, D2 is the maximum moving distance of the second variable-magnification group G2, and D3 is the maximum moving distance of the compensation group G3. In some embodiments, D1 may be a distance between the object-side surface S5 of the second lens element E3 in the telephoto state and the object-side surface S5 of the second lens element E3 in the wide-angle state on the optical axis 110, D2 may be a distance between the object-side surface S10 of the fourth lens element E5 in the telephoto state and the object-side surface S10 of the fourth lens element E5 in the wide-angle state on the optical axis 110, and D3 may be a distance between the object-side surface S14 of the sixth lens element E7 in the telephoto state and the object-side surface S14 of the sixth lens element E7 in the wide-angle state on the optical axis 110. When the above conditional expression is satisfied, the moving strokes of the first zoom group G1, the second zoom group G2 and the compensation group G3 on the optical axis 110 can be reasonably configured, so that the first zoom group G1, the second zoom group G2 and the compensation group G3 can be well matched, the optical zoom function of the 4K zoom optical adapter 10 is effectively realized, and the focal power and the surface configuration of each lens are matched, so that the 4K zoom optical adapter 10 can have good imaging quality.

In some embodiments, the 4K zoom optical adapter 10 satisfies the conditional expression: f2/CT2 is more than or equal to 6 and less than or equal to 6.8; wherein f2 is the effective focal length of the first lens element E2, and CT2 is the thickness of the first lens element E2 on the optical axis 110, i.e. the center thickness of the first lens element E2. When the above conditional expression is satisfied, the ratio of the effective focal length and the center thickness of the first lens E2 can be reasonably configured, so that the first lens E2 has enough positive focal power to converge incident light, and meanwhile, the center thickness of the first lens E2 is not excessively large, thereby being beneficial to shortening the total length of the 4K zoom optical adapter 10, and in addition, the surface type of the first lens E2 is not excessively curved, thereby being beneficial to manufacturing and forming of the first lens E2.

In some embodiments, the 4K zoom optical adapter 10 satisfies the conditional expression: f8/CT8 is more than or equal to 9 and less than or equal to 11; wherein f8 is the effective focal length of the seventh lens element E8, and CT8 is the thickness of the seventh lens element E8 on the optical axis 110. When the above conditional expression is satisfied, the ratio of the effective focal length to the center thickness of the seventh lens E8 can be reasonably configured, which is favorable for reasonably configuring the back focal space of the 4K zoom optical adapter 10, so that the 4K zoom optical adapter 10 is easier to match with other image pickup modules of the 4K endoscope, and meanwhile, the surface shape of the seventh lens E8 is also favorable to avoid excessive bending, thereby being favorable for manufacturing and forming the seventh lens E8.

In some embodiments, the 4K zoom optical adapter 10 satisfies the conditional expression: 2.0-2/34-2.8; f3/f34 is less than or equal to 1.6 and less than or equal to 2.2; f4/f34 is more than or equal to 2.1 and less than or equal to 2.7; wherein f2 is the effective focal length of the first lens element E2, f3 is the effective focal length of the second lens element E3, f4 is the effective focal length of the third lens element E4, and f34 is the effective focal length of the first zoom lens group G1, i.e., the combined focal length of the second lens element E3 and the fourth lens element E4. When the above conditional expression is satisfied, the relationship among the effective focal lengths of the first lens E2, the second lens E3, the third lens E4 and the first zoom group G1 can be reasonably configured, which is favorable for reasonably distributing the focal power of the 4K zoom optical adapter 10, thereby being favorable for reducing the height of the light rays exiting the first lens E2 and further favorable for realizing the large aperture characteristic; in addition, the surface shapes of the first lens E2, the second lens E3 and the third lens E4 are optimized, and the manufacturing and molding of the lenses are facilitated.

In some embodiments, the 4K zoom optical adapter 10 satisfies the conditional expression: f5/f56 is more than or equal to 1.8 and less than or equal to 2.6; f6/f56 is more than or equal to 1.4 and less than or equal to 2.4; wherein f5 is an effective focal length of the fourth lens element E5, f6 is an effective focal length of the fifth lens element E6, and f56 is an effective focal length of the second variable magnification group G2. When the above conditional expressions are satisfied, the relationship among the effective focal lengths of the fourth lens E5, the fifth lens E6 and the second zoom group G2 can be reasonably configured, which is favorable for reasonably distributing the focal power of the 4K zoom optical adapter 10, thereby being favorable for effectively converging light rays of the second zoom group G2, further shortening the total length of the 4K zoom optical adapter 10, and realizing miniaturization design; meanwhile, the surface shapes of the fourth lens E5 and the fifth lens E6 are also beneficial to optimization, and the manufacturing and molding of the lenses are also beneficial.

In some embodiments, the 4K zoom optical adapter 10 satisfies the conditional expression: (f 6-f 7)/f56 is more than or equal to 1.2 and less than or equal to 2.0; wherein f6 is an effective focal length of the fifth lens element E6, f7 is an effective focal length of the sixth lens element E7, i.e., an effective focal length of the compensation group G3, and f56 is an effective focal length of the second zoom group G2, i.e., a combined focal length of the fifth lens element E6 and the sixth lens element E7. When the above conditional expressions are satisfied, the ratio of the effective focal lengths of the fifth lens E5, the sixth lens E7 and the second zoom group G2 can be reasonably configured, so that light can reasonably transit between the second zoom group G2 and the compensation group G3, thereby being beneficial to reducing the aberration sensitivity of the 4K zoom optical adapter 10, reducing the risk of ghost images, further improving the imaging quality of the 4K zoom optical adapter 10, and simultaneously being beneficial to optimizing the surface shapes of the fifth lens E6 and the sixth lens E7, and being beneficial to manufacturing and forming of the lenses.

In some embodiments, the 4K zoom optical adapter 10 satisfies the conditional expression: CT5/T95 is less than or equal to 1.5 and less than or equal to 2.2; wherein, CT5 is the thickness of the fourth lens element E5 on the optical axis 110, i.e. the center thickness of the fourth lens element E5, and T95 is the distance between the stop S9 and the object-side surface S10 of the fourth lens element E5 on the optical axis 110. When the above conditional expression is satisfied, the ratio of the center thickness of the fourth lens E5 to the air space between the stop S9 and the fourth lens E5 on the optical axis 110 can be reasonably configured, which is favorable for shortening the total length of the 4K zoom optical adapter 10, realizing a miniaturized design, and also favorable for light to effectively reach the fourth lens E5 through the stop S9 and be effectively deflected to the image side by the fourth lens E5, thereby being favorable for realizing a large aperture characteristic.

In some embodiments, the 4K zoom optical adapter 10 satisfies the conditional expression: R16/CT8 is more than or equal to 8.5 and less than or equal to 10; wherein R16 is a radius of curvature of the object side surface S16 of the seventh lens element E8 at the optical axis 110, and CT8 is a thickness of the seventh lens element E8 on the optical axis 110, i.e. a center thickness of the seventh lens element E8. When the above conditional expression is satisfied, the ratio of the radius of curvature of the object side surface S16 of the seventh lens element E8 at the optical axis 110 to the center thickness of the seventh lens element E8 can be reasonably configured, which is favorable for reasonably configuring the shape of the seventh lens element E8, so that the surface shape of the seventh lens element E8 is not excessively curved, which is favorable for manufacturing and shaping the seventh lens element E8, and meanwhile, the seventh lens element E8 is favorable for effectively balancing the aberration of the 4K zoom optical adapter 10, reducing the risk of ghost images, and further improving the imaging quality of the 4K zoom optical adapter 10.

In some embodiments, the 4K zoom optical adapter 10 satisfies the conditional expression: f8/Nd8 is more than or equal to 13 and less than or equal to 15; where f8 is the effective focal length of the seventh lens E8, nd8 is the refractive index of the seventh lens E8. When the above conditional expression is satisfied, the ratio of the effective focal length of the seventh lens E8 to the refractive index of the seventh lens E8 can be reasonably configured, which is favorable for the seventh lens E8 to effectively deflect the light to the imaging surface S20, thereby being favorable for improving the imaging quality and the imaging relative illuminance of the 4K zoom optical adapter 10.

In some embodiments, the 4K zoom optical adapter 10 satisfies the conditional expression: f is more than or equal to 15mm and less than or equal to 32mm; FNO is more than or equal to 4 and less than or equal to 4.2; FOV is more than or equal to 15 degrees and less than or equal to 30 degrees; where f is the effective focal length of the 4K zoom optical adapter 10, FNO is the f-number of the 4K zoom optical adapter 10, and FOV is the maximum field angle of the 4K zoom optical adapter 10. When the above condition is satisfied, the optical power and the surface configuration of each lens of the 4K zoom optical adapter 10 are matched, which is favorable for realizing the effects of large aperture, miniaturization, good imaging quality and the like, and meanwhile, the 4K zoom optical adapter 10 has a sufficient zoom range, so that the application range of the 4K zoom optical adapter 10 can be improved.

In some embodiments, the first lens E2 is movable along the optical axis 110 between the first protection element E1 and the first magnification-varying group G1 to achieve an optical focusing function of the 4K zoom optical adapter 10.

Based on the above description, three embodiments are given below by way of example, and of course, the specific arrangement of the 4K zoom optical adapter 10 is not limited to the following three embodiments as long as the above-described optical power and surface type characteristics can be satisfied to obtain the corresponding effects.

Among these, three examples satisfy the data of table 1 below, and the effects that can be obtained by satisfying the following data can be deduced from the above description.

TABLE 1

Further, in the first embodiment, the f-number FNO, the effective focal length f, the total optical length TTL, the maximum field angle FOV, the half image height IMH, the distance T23 between the image side S4 of the first lens element E2 and the object side S5 of the second lens element E3 (i.e. the air gap between the first lens element E2 and the first zoom group G1 on the optical axis 110), the distance T49 between the image side S8 of the third lens element E4 and the aperture S9 on the optical axis 110 of the 4K zoom optical adapter 10 in the wide-angle state, the mid-focal state and the telephoto state, the distance T67 between the image side surface S13 of the fifth lens element E6 and the object side surface S14 of the sixth lens element E7 (i.e., the air spacing between the second variable magnification group G2 and the compensation group G3) on the optical axis 110, and the distance T78 between the image side surface S15 of the sixth lens element E7 and the object side surface S16 of the seventh lens element E8 on the optical axis 110 are given in table 2 below. The 4K zoom optical adapter 10 can realize a large aperture characteristic, a compact design, and a good imaging quality in cooperation with the power and the surface configuration of each lens, satisfying the following data.

TABLE 2

Parameters (parameters)	Wide angle state	Middle energizer state	Long focal length
				FNO	4	4.1	4.2
f(mm)	16	24	32
				TTL(mm)	43	43	43
FOV(°)	28.7	19.7	15.1
				IMH(mm)	4.075	4.075	4.075
T23(mm)	3.04	3.31	2.95
				T49(mm)	10.71	5.35	0.8
T67(mm)	0.86	1.65	3.22
				T78(mm)	4.19	8.49	11.83

In the first embodiment, the object-side surfaces and the image-side surfaces of the first to sixth lenses E2 to E7 and the image-side surface S17 of the seventh lens element E8 are spherical, and the object-side surface S16 of the seventh lens element E8 is aspheric. The aspherical coefficients of the object side surface S16 of the seventh lens E8 in the first embodiment are given in table 3. Wherein, from top to bottom, YRadius represents a radius of curvature of the object side surface S16 of the seventh lens element E8 at the optical axis 110, K-a12 represents types of aspheric coefficients, respectively, wherein K represents a conic coefficient, A4 represents four-time aspheric coefficients, A6 represents six-time aspheric coefficients, A8 represents eight-time aspheric coefficients, and so on. In addition, the aspherical coefficient formula is as follows:

where Z is the distance from the corresponding point on the aspheric surface to the plane tangential to the surface vertex, r is the distance from the corresponding point on the aspheric surface to the optical axis 110, c is the curvature of the aspheric vertex, K is the conic coefficient, ai is the coefficient corresponding to the i-th higher term in the aspheric surface formula.

TABLE 3 Table 3

Y Radius	21.815
		Conic Constant(K)	-3.904
A4	8.904e-006
		A6	1.836e-006
A8	-2.585e-007
		A10	1.966e-008
A12	-8.471e-010

Referring to fig. 1, 4, 5, 6 and 7, fig. 4 is a transfer function (MTF) graph of the 4K-zoom optical adapter 10 in the wide-angle state in the first embodiment, fig. 5 is a defocus graph of the 4K-zoom optical adapter 10 in the wide-angle state in the first embodiment, fig. 6 is a point-column diagram of the 4K-zoom optical adapter 10 in the wide-angle state in the first embodiment, and fig. 7 is a field curve graph and a distortion graph of the 4K-zoom optical adapter 10 in the wide-angle state in the first embodiment, respectively, from left to right. As can be seen from fig. 4 to fig. 7, when the resolution of the 4K zoom optical adapter 10 in the first embodiment satisfies 250lp/mm, the full field of view MTF is greater than 0.2, and is close to the diffraction limit, the diffuse spots in the central field of view point chart are all small Yu Aili spots, and are basically at the diffraction limit, and the 4K zoom optical adapter 10 has good imaging quality. Of course, only the imaging quality of the 4K-zoom optical adapter 10 in the wide-angle state is taken as an example in the drawing, and the 4K-zoom optical adapter 10 also has good imaging quality in the mid-focal state and in the telephoto state.

The parameters of the 4K zoom optical adapter 10 in the second embodiment are given in table 4 below, and the meaning of the parameters can be obtained from the first embodiment.

TABLE 4 Table 4

Parameters (parameters)	Wide angle state	Middle energizer state	Long focal length
				FNO	4	4.1	4.2
f(mm)	16	24	32
				TTL(mm)	43	43	43
FOV(°)	28.7	19.84	15.18
				IMH(mm)	4.075	4.075	4.075
T23(mm)	3.07	3.24	2.62
				T49(mm)	10.26	5.05	0.6
T67(mm)	0.7	1.58	3.56
				T78(mm)	3.21	7.36	10.46

In the second embodiment, the object-side surfaces and the image-side surfaces of the first lens element E2-third lens element E4, the image-side surface S11 of the fourth lens element E5, the object-side surfaces and the image-side surfaces of the fifth lens element E6-sixth lens element E7, and the image-side surface S17 of the seventh lens element E8 are spherical surfaces, and the object-side surface S10 of the fourth lens element E5 and the object-side surface S16 of the seventh lens element E8 are aspheric surfaces. The aspherical coefficients of the object-side surface S110 of the fourth lens element E5 are given in table 5 below, the aspherical coefficients of the object-side surface S16 of the seventh lens element E8 are given in table 6 below, and the meanings of the parameters in tables 5 and 6 can be obtained from the first embodiment.

TABLE 5

Y Radius	151.961
		Conic Constant(K)	-56.953
A4	-3.841e-006
		A6	-2.657e-006
A8	5.393e-007
		A10	-3.907e-008
A12	-1.711e-009

TABLE 6

Y Radius	17.632
		Conic Constant(K)	-3.580
A4	5.249e-005
		A6	9.017e-007
A8	-1.382e-007
		A10	9.512e-009
A12	-3.806e-010

Referring to fig. 8, 9, 10 and 11, fig. 8 is a transfer function (MTF) graph of the 4K-zoom optical adapter 10 in the wide-angle state in the second embodiment, fig. 9 is a defocus graph of the 4K-zoom optical adapter 10 in the wide-angle state in the second embodiment, fig. 10 is a point diagram of the 4K-zoom optical adapter 10 in the wide-angle state in the second embodiment, and fig. 11 is a field curve graph and a distortion graph of the 4K-zoom optical adapter 10 in the wide-angle state in the second embodiment, respectively, from left to right. As can be seen from fig. 8 to 11, the 4K zoom optical adapter 10 in the second embodiment also has good imaging quality.

The parameters of the 4K zoom optical adapter 10 in the third embodiment are given in table 7 below, and the meaning of the parameters can be obtained from the first embodiment.

TABLE 7

Parameters (parameters)	Wide angle state	Middle energizer state	Long focal length
				FNO	4	4.1	4.2
f(mm)	16	23	32
				TTL(mm)	43	43	43
FOV(°)	28.7	20.78	15.22
				IMH(mm)	4.075	4.075	4.075
T23(mm)	2.73	2.92	2.53
				T49(mm)	10.78	6.07	0.6
T67(mm)	0.83	1.43	3.06
				T78(mm)	3.72	7.64	11.86

In the third embodiment, the object-side surfaces and the image-side surfaces of the first lens element E2-third lens element E4, the image-side surface S11 of the fourth lens element E5, the object-side surfaces and the image-side surfaces of the fifth lens element E6-sixth lens element E7, and the image-side surface S17 of the seventh lens element E8 are spherical surfaces, and the object-side surface S10 of the fourth lens element E5 and the object-side surface S16 of the seventh lens element E8 are aspheric surfaces. The aspherical coefficients of the object-side surface S10 of the fourth lens element E5 are given in table 8 below, the aspherical coefficients of the object-side surface S16 of the seventh lens element E8 are given in table 9 below, and the meanings of the parameters in tables 8 and 9 can be obtained from the first embodiment.

TABLE 8

Y Radius	70.392
		Conic Constant(K)	1.561
A4	6.969e-007
		A6	-1.102e-007
A8	2.022e-008
		A10	-1.065e-009
A12	-7.597e-011

TABLE 9

Y Radius	16.098
		Conic Constant(K)	-3.627
A4	7.949e-005
		A6	2.0862e-007
A8	-7.560e-008
		A10	5.754e-009
A12	-2.467e-010

Referring to fig. 12, 13, 14 and 15, fig. 12 is a transfer function (MTF) graph of the 4K-zoom optical adapter 10 in the wide-angle state in the third embodiment, fig. 13 is a defocus graph of the 4K-zoom optical adapter 10 in the wide-angle state in the third embodiment, fig. 14 is a point diagram of the 4K-zoom optical adapter 10 in the wide-angle state in the third embodiment, and fig. 15 is a field curve graph and a distortion graph of the 4K-zoom optical adapter 10 in the wide-angle state in the third embodiment, respectively, from left to right. As can be seen from fig. 12 to 15, the 4K zoom optical adapter 10 in the third embodiment also has good imaging quality.

The application also provides an image capturing module, which comprises a photosensitive element and the 4K zoom optical adapter 10 in any embodiment, wherein the photosensitive element is arranged on the image side of the 4K zoom optical adapter 10, and light can be incident on the photosensitive element for imaging after being regulated by the 4K zoom optical adapter 10. Specifically, the photosensitive element 210 may be a charge coupled element (Charge Coupled Device, CCD) or a complementary metal oxide semiconductor device (Complementary Metal-Oxide Semiconductor Sensor, CMOS Sensor).

In some embodiments, the present application also provides an endoscope comprising a fixture and a 4K zoom optical adapter 10,4K zoom optical adapter 10 as described in any of the above embodiments provided on the fixture. Specifically, the 4K-zoom optical adapter 10 may be an optical adapter for an endoscope, and the fixing member may be a mechanical structure that supports the 4K-zoom optical adapter 10. The endoscope may be any suitable hard tube endoscope or flexible tube endoscope. The 4K zoom optical adapter 10,4K zoom optical adapter 10 adopted in the endoscope has the effects of large aperture, miniaturization, good imaging quality and the like, is beneficial to the assembly of the 4K zoom optical adapter 10 in the endoscope, is beneficial to the reduction of the volume of the endoscope, and improves the imaging quality of the endoscope, thereby being beneficial to the improvement of the application range and the optical performance of the endoscope.

The technical features of the above-described embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above-described embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.

The above examples illustrate only a few embodiments of the application, which are described in detail and are not to be construed as limiting the scope of the application. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the application, which are all within the scope of the application. Accordingly, the scope of protection of the present application is to be determined by the appended claims.

Claims (11)

1. A 4K zoom optical adapter, wherein the number of lenses that have optical power in the 4K zoom optical adapter is seven, the 4K zoom optical adapter includes in order from the object side to the image side along the optical axis:

a first lens with positive focal power, wherein the object side surface of the first lens is a convex surface at a paraxial region;

the first zoom group comprises a second lens with negative focal power and a third lens with negative focal power, wherein the second lens is biconcave at a paraxial region, and the object side surface of the third lens is concave at the paraxial region;

the second variable power group comprises a fourth lens with positive focal power and a fifth lens with positive focal power, and the fourth lens and the fifth lens are biconvex at a paraxial region;

the compensation group comprises a sixth lens with negative focal power, and the sixth lens is biconcave at a paraxial region; the method comprises the steps of,

the rear fixed group comprises a seventh lens with positive focal power, and the seventh lens is biconvex at a paraxial region;

wherein at least one of the first variable magnification group, the second variable magnification group, and the compensation group is movable along an optical axis between the first lens and the rear fixed group to realize an optical zoom function;

the 4K zoom optical adapter further comprises a diaphragm, wherein the diaphragm is arranged between the third lens and the fourth lens, and the 4K zoom optical adapter meets the following conditional expression:

1.5≤CT5/T95≤2.2；

8.5≤R16/CT8≤10；

wherein, CT5 is the thickness of the fourth lens element on the optical axis, T95 is the distance between the stop and the object-side surface of the fourth lens element on the optical axis, R16 is the radius of curvature of the object-side surface of the seventh lens element on the optical axis, and CT8 is the thickness of the seventh lens element on the optical axis.

2. The 4K zoom optical adapter of claim 1, wherein the 4K zoom optical adapter satisfies the following conditional expression:

0.5≤100*(D1/TTL)≤1.0；

1.5≤10*(D2/TTL)≤2.5；

1.2≤10*(D3/TTL)≤2.2；

wherein D1 is the maximum movement distance of the first variable magnification group, D2 is the maximum movement distance of the second variable magnification group, and D3 is the maximum movement distance of the sixth lens.

3. The 4K zoom optical adapter of claim 1, wherein the 4K zoom optical adapter satisfies the following conditional expression:

6≤f2/CT2≤6.8；

9≤f8/CT8≤11；

wherein f2 is an effective focal length of the first lens, CT2 is a thickness of the first lens on the optical axis, and f8 is an effective focal length of the seventh lens.

4. The 4K zoom optical adapter of claim 1, wherein the 4K zoom optical adapter satisfies the following conditional expression:

2.0≤|f2/f34|≤2.8；

1.6≤f3/f34≤2.2；

2.1≤f4/f34≤2.7；

wherein f2 is an effective focal length of the first lens, f3 is an effective focal length of the second lens, f4 is an effective focal length of the third lens, and f34 is an effective focal length of the first zoom group.

5. The 4K zoom optical adapter of claim 1, wherein the 4K zoom optical adapter satisfies the following conditional expression:

1.8≤f5/f56≤2.6；

1.4≤f6/f56≤2.4；

wherein f5 is an effective focal length of the fourth lens, f6 is an effective focal length of the fifth lens, and f56 is an effective focal length of the second zoom group.

6. The 4K zoom optical adapter of claim 1, wherein the 4K zoom optical adapter satisfies the following conditional expression:

1.2≤(f6-f7)/f56≤2.0；

wherein f6 is an effective focal length of the fifth lens, f7 is an effective focal length of the sixth lens, and f56 is an effective focal length of the second zoom group.

7. The 4K zoom optical adapter of claim 1, wherein the 4K zoom optical adapter satisfies the following conditional expression:

13≤f8/Nd8≤15；

wherein f8 is the effective focal length of the seventh lens, and Nd8 is the refractive index of the seventh lens.

8. The 4K zoom optical adapter of claim 1, wherein the 4K zoom optical adapter satisfies the following conditional expression:

15mm≤f≤32mm；

4≤FNO≤4.2；

15°≤FOV≤30°；

wherein f is the effective focal length of the 4K zoom optical adapter, FNO is the f-number of the 4K zoom optical adapter, and FOV is the maximum field angle of the 4K zoom optical adapter.

9. The 4K zoom optical adapter of claim 1, wherein the fourth lens has an aspheric object-side surface.

10. The 4K zoom optical adapter of claim 1, wherein the object side of the seventh lens is aspheric.

11. An endoscope comprising the 4K zoom optical adapter of any one of claims 1-10.