CN217821054U - Fixed focus optical adapter and 4K endoscope - Google Patents

Abstract

The utility model relates to a tight optics adapter and 4K endoscope. The fixed focus optical adapter includes: the lens comprises a first lens with positive focal power, wherein the object side surface of the first lens is a convex surface; a second lens having a negative optical power, the second lens having concave object and image side surfaces; the first cemented lens group with positive focal power comprises a third lens and a fourth lens which are cemented with each other, and the image side surface of the fourth lens is a convex surface; the second cemented lens group with negative focal power comprises a fifth lens and a sixth lens which are cemented with each other, and the image side surface of the sixth lens is a convex surface; and the object side surface of the seventh lens is a convex surface. The fixed-focus optical adapter can realize good imaging quality and can also shorten the size of a 4K endoscope.

Description

Fixed focus optical adapter and 4K endoscope

Technical Field

The utility model relates to a 4K endoscope imaging technology field especially relates to a tight optical adapter and 4K endoscope.

Background

A medical endoscope is a medical device that can enter a human body for observation, diagnosis or treatment, and generally includes a camera main unit, a camera head, and an endoscope mirror, wherein the camera head is communicated with the endoscope mirror through an optical adapter to realize an optical path, and the optical adapter is divided into a fixed focal length adapter (i.e., a fixed focus optical adapter) and a variable focal length adapter (i.e., a variable focus optical adapter) according to functions.

With the rapid development of endoscopes, the performance requirements of endoscopes are also increasing. Among them, in order to obtain a clear image of a lesion region to the maximum extent and to improve the accuracy of diagnosis, a 4K (ultra high definition) endoscope having a good imaging quality has been proposed in the industry. However, the current 4K endoscope is easy to increase in size while achieving good imaging quality, and is not favorable for assembly and use of the 4K endoscope.

SUMMERY OF THE UTILITY MODEL

Accordingly, it is desirable to provide a fixed focus optical adapter and a 4K endoscope, which can achieve a good imaging quality and can also shorten the size of the 4K endoscope, and which is advantageous for assembly and use of the 4K endoscope.

A fixed-focus optical adapter, wherein the number of lenses with optical power in the fixed-focus optical adapter is seven, and the fixed-focus optical adapter sequentially comprises the following components from an object side to an image side along an optical axis:

a first lens having a positive optical power, an object side surface of the first lens being convex;

a second lens having a negative optical power, the second lens having concave object and image side surfaces;

the first cemented lens group with positive focal power comprises a third lens and a fourth lens which are cemented with each other, and the image side surface of the fourth lens is a convex surface;

the second cemented lens group with negative focal power comprises a fifth lens and a sixth lens which are cemented with each other, and the image side surface of the sixth lens is a convex surface;

and the object side surface of the seventh lens is a convex surface.

In some embodiments, the fixed focus optical adapter satisfies the following conditional expression:

0.4≤f2/(f2-f3)≤0.75；

wherein f2 is an effective focal length of the first lens, and f3 is an effective focal length of the second lens.

In some embodiments, the fixed focus optical adapter satisfies the following conditional expression:

0.32≤CT4/f4≤0.52；

wherein, CT4 is a distance on an optical axis from an object-side surface of the third lens element to an image-side surface of the fourth lens element, and f4 is a combined focal length of the third lens element and the fourth lens element.

In some embodiments, the fixed focus optical adapter satisfies the following conditional expression:

0.11≤|CT5/f5|≤1.31；

wherein CT5 is an axial distance between an object-side surface of the fifth lens element and an image-side surface of the sixth lens element, and f5 is a combined focal length of the fifth lens element and the sixth lens element.

In some embodiments, the fixed-focus optical adapter further includes a first protection element disposed on an object side of the first lens, and the fixed-focus optical adapter satisfies the following conditional expression:

0.51≤CT2/(T12+T23)≤1.1；

wherein, CT2 is the thickness of the first lens element on the optical axis, T12 is the distance from the image-side surface of the first protection element to the object-side surface of the first lens element on the optical axis, and T23 is the distance from the image-side surface of the first lens element to the object-side surface of the second lens element on the optical axis.

In some embodiments, the fixed-focus optical adapter further includes a second protection element, the second protection element is disposed between the seventh lens and the imaging surface of the fixed-focus optical adapter, and the fixed-focus optical adapter satisfies the following conditional expression:

2.15≤CT6/T67≤4.36；

wherein CT6 is the thickness of the seventh lens element on the optical axis, and T67 is the distance from the image-side surface of the seventh lens element to the object-side surface of the second protection element on the optical axis.

In some embodiments, the fixed focus optical adapter satisfies the following conditional expression:

10deg≤Semi-FOV≤15deg；

20mm≤f≤25mm；

wherein the Semi-FOV is half of the maximum field angle of the fixed-focus optical adapter, and f is the effective focal length of the fixed-focus optical adapter.

In some embodiments, the third lens has a negative optical power, the fourth lens has a positive optical power, the fifth lens has a negative optical power, and the sixth lens has a positive optical power; and/or the presence of a gas in the gas,

the image side surface of the first lens is a convex surface, the object side surface of the third lens is a concave surface, the image side surface of the third lens is a concave surface, the object side surface of the fourth lens is a convex surface, the object side surface of the second lens is a concave surface, the image side surface of the fifth lens is a concave surface, the object side surface of the sixth lens is a convex surface, and the image side surface of the seventh lens is a concave surface.

In some embodiments, the fixed focus optical adapter further comprises a stop disposed on an object side of the first lens.

A 4K endoscope comprising a fixed focus optical adapter as described in any of the embodiments above.

In the fixed-focus optical adapter, the first lens has positive focal power, and the object side surface of the first lens is a convex surface, so that incident light can be effectively converged, and the on-axis size of a system can be compressed; meanwhile, the angle of the light entering the first lens is favorably and reasonably configured, so that the size of the system is reduced, the light can be effectively captured, and the field angle of the system cannot be too small. The second lens has negative focal power and a concave surface type, can effectively diverge the light converged by the first lens, and simultaneously enables the structure of the system to be more compact. The first cemented lens group has positive focal power, the image side surface of the fourth lens is a convex surface, and the fourth lens is matched with the first lens and the second lens on the object side, so that the focal power distribution of the system can be effectively balanced, the aberration such as distortion of the system can be effectively corrected, the light imaging of a large-angle incidence system is clearer, the aberration sensitivity of the system can be reduced, and the imaging quality of the system can be improved. The second cemented lens group has negative focal power, and the image side surface of the sixth lens is a convex surface, so that light rays can smoothly transit in the second cemented lens group, and the light ray tendency of the system can be reasonably controlled, thereby being beneficial to inhibiting ghost images and aberration; meanwhile, the optical power of the system can be reasonably distributed, so that the tolerance sensitivity of the system is effectively reduced, and the manufacturing and assembly of the system are facilitated. The introduction of the first and second cemented lens groups can also effectively correct chromatic aberration of the system, thereby further improving the imaging quality of the system. The seventh lens has positive focal power, the object side surface of the seventh lens is a convex surface, and the seventh lens can be effectively matched with the second cemented lens group, so that light can be effectively transmitted to an imaging surface, the size of the imaging surface of the system is enlarged, the system can be easily matched with a large-size photosensitive element to obtain high resolution, the angle of the light incident on the imaging surface can be effectively reduced, the incident angle of the light on the imaging surface can be easily matched with the photosensitive element, the relative illumination of imaging can be improved, and the resolution of the system can be improved; in addition, the back focal length of the system is increased, so that the focusing space of the system is increased, the depth of field of the system is improved, and the system can adapt to more different shooting scenes. The reasonable distribution of the focal power of the second cemented lens group and the seventh lens is beneficial to reducing the tolerance sensitivity of the second cemented lens group and the seventh lens, and further reducing the design and processing difficulty of the second cemented lens group and the seventh lens. The optical adapter with the fixed focus has the advantages that the refractive power and the surface configuration are achieved, the depth of field of the system can be effectively improved, meanwhile, aberrations such as distortion and chromatic aberration of the system can be effectively corrected, the fixed focus optical adapter can have a small size while achieving good imaging quality, assembly and use of the system in a 4K endoscope are facilitated, meanwhile, the field angle of the system cannot be too small, and image taking requirements of 4K endoscope diagnosis can be met.

Drawings

FIG. 1 is a schematic diagram of a fixed focus optical adapter in some embodiments;

FIG. 2 is a graph of a transfer function of a fixed focus optical adapter in some embodiments;

FIG. 3 is an out-of-focus plot of a fixed focus optical adapter in some embodiments;

FIG. 4 is a dot diagram of a fixed focus optical adapter in some embodiments;

FIG. 5 is a graph of field curvature and distortion for a fixed focus optical adapter in some embodiments.

Detailed Description

In order to make the above objects, features and advantages of the present invention more comprehensible, embodiments of the present invention are described in detail below with reference to the accompanying drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. The invention may be embodied in many other forms different from those described herein and similar modifications may be made by those skilled in the art without departing from the spirit and scope of the invention and, therefore, the invention is not to be limited to the specific embodiments disclosed below.

In the description of the present invention, it is to 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", and the like, indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for convenience of description and simplicity of description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore, should not be construed as limiting the present invention.

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

In the present invention, unless otherwise expressly stated or limited, the terms "mounted," "connected," and "fixed" are to be construed broadly and may, for example, be fixedly connected, detachably connected, or integrally formed; can be mechanically or electrically connected; they may be directly connected or indirectly connected through intervening media, or they may be connected internally or in any other suitable relationship, unless expressly stated otherwise. The specific meaning of the above terms in the present invention can be understood according to specific situations by those skilled in the art.

In the present application, unless expressly stated or limited otherwise, the first feature may be directly on or directly under the second feature or indirectly via intermediate members. Also, a first feature "on," "over," and "above" a second feature may be directly or diagonally above the second feature, or may simply indicate that the first feature is at a higher level than the second feature. A first feature "under," "beneath," and "under" a second feature may be directly under or obliquely under the second feature, or may simply mean that the first feature is at a lesser elevation than the second feature.

It will be understood that when an element is referred to as being "secured to" 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 as used herein are for illustrative purposes only and do not denote a unique embodiment.

Referring to fig. 1, the present application provides a fixed focus optical adapter 10 that may be used in a medical device, such as a hard or soft tube endoscope. In some embodiments, the fixed-focus optical adapter 10 includes, in order from an object side to an image side along an optical axis 110, a first lens element E2, a second lens element E2, a first cemented lens group E4 including a third lens element and a fourth lens element, a second cemented lens group E5 including a fifth lens element and a sixth lens element, and a seventh lens element E6, wherein the third lens element and the fourth lens element are arranged in order from the object side to the image side along the optical axis 110, and the fifth lens element and the sixth lens element are arranged in order from the object side to the image side along the optical axis 110. In some embodiments, the system can further include a first protection element E1 disposed on the object side of the first lens element E2 and a second protection element E7 disposed on the image side of the seventh lens element E6.

The first protective element E1 has an object-side surface S1 and an image-side surface S2, the first lens E2 has an object-side surface S4 and an image-side surface S5, the second lens E3 has an object-side surface S6 and an image-side surface S7, the third lens has an object-side surface S8 and an image-side surface S9, the fourth lens has an image-side surface S10, the fifth lens has an object-side surface S11 and an image-side surface S12, the sixth lens has an image-side surface S13, the seventh lens E6 has an object-side surface S14 and an image-side surface S15, and the second protective element E7 has an object-side surface S16 and an image-side surface S17. The system also comprises an imaging surface S18 positioned on the image side of the second protective element E7, and the light can enter the imaging surface S18 for imaging after being adjusted by each lens of the system. The first protective element E1 and the second protective element E7 can protect each lens of the system and the photosensitive element provided at the image forming surface S18.

Specifically, in some embodiments, the first lens E2 has positive optical power, and the object-side surface S4 of the first lens E2 is a convex surface, which can effectively converge incident light rays, and is beneficial to compressing the on-axis size of the system; meanwhile, the angle of light rays entering the first lens E2 can be reasonably configured, so that the system size can be reduced, the light rays can be effectively captured, and the field angle of the system cannot be too small. The second lens E3 has negative focal power and a concave surface type, and can effectively diverge the light rays converged by the first lens E2, and meanwhile, the structure of the system is more compact. The third lens and the fourth lens are glued to form a first glued lens group E4, the first glued lens group E4 has positive focal power, the image side surface S10 of the fourth lens is a convex surface and is matched with the first lens E2 and the second lens E3 on the object side, the focal power distribution of the system can be effectively balanced, and therefore aberrations such as distortion of the system can be effectively corrected, light imaging of a large-angle incidence system is clearer, meanwhile, the aberration sensitivity of the system is favorably reduced, and the imaging quality of the system is improved. The fifth lens and the sixth lens are glued to form a second cemented lens group E5, the second cemented lens group E5 has negative focal power, the image side surface S13 of the sixth lens is a convex surface, light can smoothly transit in the second cemented lens group E5, and the light trend of the system can be reasonably controlled, so that ghost images and aberration can be inhibited; meanwhile, the optical power of the system can be reasonably distributed, so that the tolerance sensitivity of the system is effectively reduced, and the manufacturing and assembly of the system are facilitated. The introduction of the first cemented lens group E4 and the second cemented lens group E5 can also effectively correct chromatic aberration of the system, thereby further improving the imaging quality of the system. The seventh lens element E6 has positive focal power, the object-side surface S14 of the seventh lens element E6 is a convex surface, and can effectively cooperate with the second cemented lens group E5, which is beneficial to effectively transmitting light to the imaging surface S18, thereby enlarging the size of the imaging surface of the system, making the system more easily match with a large-sized photosensitive element to obtain high resolution, and simultaneously effectively reducing the angle of light incident on the imaging surface, making the incident angle of light on the imaging surface S18 more easily match with the photosensitive element, thereby facilitating the improvement of the relative illumination of imaging, and improving the resolution of the system; in addition, the back focal length of the system is increased, so that the focusing space of the system is increased, the depth of field of the system is improved, and the system can adapt to more different shooting scenes. The reasonable distribution of the focal powers of the second cemented lens group E5 and the seventh lens group E6 is beneficial to reducing the tolerance sensitivities of the second cemented lens group E5 and the seventh lens group E6, thereby reducing the design and processing difficulties of the second cemented lens group E5 and the seventh lens group E6.

The depth of field of the system can be effectively improved by the aid of the refractive power and the surface configuration, and meanwhile aberrations such as distortion and chromatic aberration of the system can be effectively corrected, so that the fixed-focus optical adapter 10 can have a small size while achieving good imaging quality, assembly and use of the system in a 4K endoscope are facilitated, the field angle of the system cannot be too small, and image taking requirements of 4K endoscope diagnosis can be met.

In some embodiments, the maximum effective aperture of the first lens E2 is smaller than the maximum effective aperture of the second lens group E5, and the maximum effective aperture of the second lens E3 is smaller than the maximum effective aperture of the first lens E2. Therefore, the light trend of the system is restrained, and the size of the system is shortened.

Further, in some embodiments, fixed focus optical adapter 10 satisfies the conditional expression: f 2/(f 2-f 3) is more than or equal to 0.4 and less than or equal to 0.75; wherein f2 is the effective focal length of the first lens E2, and f3 is the effective focal length of the second lens E3. When the conditional expressions are met, the relation between the effective focal lengths of the first lens E2 and the second lens E3 can be reasonably configured, the first lens E2 and the second lens E3 are favorable for forming good matching and effectively balancing the aberration, so that the front end of the system can not generate serious aberration when introducing and compressing light, and the imaging quality of the system is favorable for being improved.

In some embodiments, fixed focus optical adapter 10 satisfies the conditional expression: CT4/f4 is more than or equal to 0.32 and less than or equal to 0.52; wherein, CT4 is a distance on the optical axis 110 from the object-side surface S8 of the third lens element to the image-side surface S10 of the fourth lens element, i.e., a center thickness of the first cemented lens group E4, and f4 is a combined focal length of the third lens element and the fourth lens element, i.e., a combined focal length of the first cemented lens group E4. When the condition formula is met, the ratio of the central thickness to the effective focal length of the first cemented lens group E4 can be reasonably configured, light can smoothly transit in the first cemented lens group E4, aberration of a system can be corrected, positive focal power of the first lens E1 can be shared, focal power configuration of the system can be reasonably balanced, tolerance sensitivity of the system can be reduced while the on-axis size of the system is shortened, and design and manufacturing difficulty of each lens of the system can be reduced.

In some embodiments, fixed focus optical adapter 10 satisfies the conditional expression: the absolute value CT5/f5 is more than or equal to 0.11 and less than or equal to 1.31; wherein, CT5 is a distance on the optical axis 110 from the object-side surface S11 of the fifth lens element to the image-side surface S13 of the sixth lens element, i.e. a center thickness of the second cemented lens group E5, and f5 is a combined focal length of the fifth lens element and the sixth lens element, i.e. an effective focal length of the second cemented lens group E5. When the condition formula is met, the ratio of the central thickness to the effective focal length of the second cemented lens group E5 can be reasonably configured, so that the second cemented lens group E5 is favorable for smoothly transferring light to the imaging surface S18, the size of the imaging surface S18 of the system is favorably enlarged, the incident angle of the light on the imaging surface S18 is more easily matched with the photosensitive element, and the imaging quality of the system is improved; meanwhile, the on-axis size of the system can be shortened, and the effect of small size is achieved.

In some embodiments, the first protective element E1 and the second protective element E7 may both be flat glass plates. Of course, the first protective element E1 and the second protective element E7 may be made of any other suitable material having high light transmittance and capable of protecting the respective lenses of the system and the photosensitive elements disposed on the image forming surface S18.

In some embodiments, the fixed focus optical adapter satisfies the conditional expression: CT 2/(T12 + T23) is more than or equal to 0.51 and less than or equal to 1.1; wherein, CT2 is a thickness of the first lens element E2 on the optical axis 110, i.e. a center thickness of the first lens element E2, T12 is a distance between the image-side surface S2 of the first protection element E1 and the object-side surface S4 of the first lens element E2 on the optical axis 110, i.e. an air gap between the first protection element E1 and the first lens element E2 on the optical axis 110, and T23 is a distance between the image-side surface S5 of the first lens element E2 and the object-side surface S6 of the second lens element E3 on the optical axis 110, i.e. an air gap between the first lens element E2 and the second lens element E3 on the optical axis. When the above conditional expressions are satisfied, the relationship between the center thickness of the first lens E2 and the air space between the first protective element E1, the first lens E2, and the second lens E3 can be configured reasonably, which is beneficial to compressing the on-axis size of the system, so that the system can realize the effect of small size; meanwhile, the structure of the system is not too compact, and the assembly of the system is facilitated; in addition, the space between the first protection element E1 and the first lens E2 is favorably enlarged, and the design of the long back focal length of the system is matched, so that the focusing moving space of the system is favorably further enlarged, the depth of field of the system is improved, and the system can adapt to more different use scenes.

In some embodiments, fixed focus optical adapter 10 satisfies the conditional expression: CT6/T67 is more than or equal to 2.15 and less than or equal to 4.36; wherein, CT6 is a thickness of the seventh lens element E6 on the optical axis 110, and T67 is a distance from the image-side surface S15 of the seventh lens element E6 to the object-side surface S16 of the second protective element E7 on the optical axis 110. When the condition is met, the on-axis size of the system is shortened, the structure of the system is not compact, and the assembly yield of the system is improved; in addition, the seventh lens E6 and the second protection element E7 are provided with a sufficient space therebetween, and the design of the long back focal length of the system is matched, so that the focusing moving space of the system is further improved, the depth of field of the system is improved, and the system can adapt to more different use scenes.

It should be noted that in some embodiments, the lenses of the system move synchronously between the first protective element E1 and the imaging surface S18 to achieve focusing of the system, and in other embodiments, the lenses of the system also move synchronously between the first protective element E1 and the second protective element E2 to achieve focusing of the system.

In some embodiments, the third lens has negative focal power, the fourth lens has positive focal power, and the first cemented lens group E4 is composed of two lenses with positive and negative focal powers, so that aberrations such as chromatic aberration of the system can be effectively balanced, and the imaging quality of the system is further improved. In some embodiments, the fifth lens has a negative optical power and the sixth lens has a positive optical power. The second cemented lens group E5 consists of two lenses with positive and negative focal powers, so that aberration such as chromatic aberration of the system can be effectively balanced, and the imaging quality of the system is further improved.

In some embodiments, the image-side surface S5 of the first lens element E2 is convex, the object-side surface S8 of the third lens element is concave, the image-side surface S9 of the third lens element is concave, the object-side surface S9 of the fourth lens element is convex, the object-side surface S11 of the fifth lens element is concave, the image-side surface S12 of the fifth lens element is concave, the object-side surface S12 of the sixth lens element is convex, and the image-side surface S15 of the seventh lens element E6 is concave. The surface type characteristics are met, the light path of the system can be further optimized, the on-axis size of the system can be further shortened, and the imaging quality of the system is improved.

In some embodiments, the fixed-focus optical adapter 10 further includes a stop S3, and the stop S3 may be disposed on the object side of the first lens E2 or between any two lenses in the system. Specifically, in some embodiments, the stop S3 is disposed between the first protective element E1 and the first lens E2. The arrangement of the diaphragm S3 at the front end is matched with the refractive power and the surface type configuration of each lens in the system, so that the trend of light rays in the system is favorably limited, the on-axis size of the system is favorably further compressed, and the structure of the system is more compact.

In some embodiments, fixed focus optical adapter 10 satisfies the conditional expression: semi-FOV is less than or equal to 15deg when deg is less than or equal to 10 deg; f is more than or equal to 20mm and less than or equal to 25mm; where Semi-FOV is half of the maximum field angle of the fixed focus optical adapter 10, and f is the effective focal length of the fixed focus optical adapter 10. The field angle and the effective focal length range of the system are reasonably configured, the total length of the system is favorably compressed by matching with the refractive power and the surface type design of each lens of the system, meanwhile, the aberration sensitivity of the system can be reduced, the imaging quality of the system is improved, in addition, the field angle of the system is not too small, and the image taking requirement of 4K endoscope diagnosis can be met.

In some embodiments, the object-side surface and the image-side surface of each lens of the system are spherical, and the arrangement of the spherical surfaces is also favorable for reducing the design and manufacturing difficulty of the system and also favorable for reducing the size of the system while achieving the above effects, thereby being favorable for the application of the system in a 4K endoscope. In some embodiments, the lens of the system may be made of glass or plastic, or may be made of any combination of glass and plastic, and the manufacturing difficulty and the manufacturing cost of the system are reduced by using commonly available materials.

In some embodiments, the system satisfies the following data: f 2/(f 2-f 3) =0.41; CT4/f4=0.4; CT5/f5=0.15; CT 2/(T12 + T23) =0.73; CT6/T67=3.7; f =22.1mm; TTL =27.7mm; wherein, TTL is a distance from the object-side surface S4 of the first lens element E2 to the image plane S18 on the optical axis 110, i.e. the total optical length of the fixed-focus optical adapter 10. The results obtained by satisfying the above data can be derived from the above description, and it can be seen from the above data that the system has the advantage of small size, facilitating the assembly and application of the system in 4K endoscopes.

Referring to fig. 2, 3, 4 and 5, fig. 2 is a graph of a transfer function (MTF) of the system in some embodiments, fig. 3 is a graph of a defocus of the system in some embodiments, fig. 4 is a plot of a point of the system in some embodiments, and fig. 5 is a graph of curvature of field and a graph of distortion of the system in some embodiments, in order from left to right. As can be seen from fig. 2 to 5, when the resolution of the system satisfies 250lp/mm, the MTF value of the full field is greater than 0.2 and is close to the diffraction limit, the scattered spots in the system dot-column diagram are all smaller than airy spots, the diameters of the light spots are all contained in the airy spots and are at the diffraction limit, and the distortion of the system is controlled within 2%. Therefore, the system has the effects of low distortion and high imaging quality.

It should be noted that, in the present application, the description of the gluing of two lenses is understood to describe the definition of the relative position of the two lenses, for example, the image side surface of one lens matches and offsets with the object side surface of the other lens, and the two lenses are relatively fixed, but cannot be understood as the definition of the gluing process of the two lenses. The two lenses are cemented together by optical cement, or are abutted and fixed relatively by other means such as structural members, and the like, all within the scope of the cementing of the two lenses described in the present application. In the present application, the object side surface of a certain element is described, which means the surface of the element facing the object side, and the image side surface of the certain element is described, which means the surface of the element facing the image side. In some embodiments, the lenses in the system are coaxial, and the common axis of the lenses is the optical axis 110 of the system.

The application still provides a get for instance module, including light sensing element and above-mentioned arbitrary embodiment fixed focus optical adapter 10, light sensing element locates the image side of fixed focus optical adapter 10, and light can incide to light sensing element and form images after the regulation of fixed focus optical adapter 10. Specifically, the photosensitive element 210 may be a Charge Coupled Device (CCD) or a Complementary Metal-Oxide Semiconductor (CMOS) Device.

In some embodiments, the present application further provides a 4K endoscope, which includes a fixing member and the image capturing module according to any of the above embodiments, wherein the image capturing module is disposed on the fixing member. Specifically, the image capturing module can be applied to a fixed focus optical adapter of a 4K endoscope, and the fixing member can be a mechanical structure for supporting the image capturing module. The 4K endoscope may be any suitable hard or flexible tube endoscope. Adopt foretell fixed focus optical adapter 10 in the fixed focus optical adapter of 4K endoscope, fixed focus optical adapter 10 has effects such as small, low distortion, big depth of field, big back focus and high imaging quality for the system rear end has sufficient space and the butt joint of photosensitive element, is favorable to the equipment of system in the 4K endoscope simultaneously and is favorable to reducing the volume of 4K endoscope, thereby is favorable to promoting the application scope and the imaging quality of 4K endoscope.

The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.

The above-mentioned embodiments only represent some embodiments of the present invention, and the description thereof is specific and detailed, but not to be construed as limiting the scope of the present invention. It should be noted that, for those skilled in the art, without departing from the spirit of the present invention, several variations and modifications can be made, which are within the scope of the present invention. Therefore, the protection scope of the present invention should be subject to the appended claims.

Claims (10)

1. A fixed focus optical adapter, wherein the number of lenses having optical power in the fixed focus optical adapter is seven, and the fixed focus optical adapter comprises, in order from an object side to an image side along an optical axis:

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

a second lens having a negative optical power, the second lens having concave object and image side surfaces;

the first cemented lens group with positive focal power comprises a third lens and a fourth lens which are cemented with each other, and the image side surface of the fourth lens is a convex surface;

the second cemented lens group with negative focal power comprises a fifth lens and a sixth lens which are cemented with each other, and the image side surface of the sixth lens is a convex surface;

and the object side surface of the seventh lens is a convex surface.

2. The fixed-focus optical adapter according to claim 1, wherein the following conditional expression is satisfied:

0.4≤f2/(f2-f3)≤0.75；

wherein f2 is an effective focal length of the first lens, and f3 is an effective focal length of the second lens.

3. The fixed-focus optical adapter according to claim 1, wherein the following conditional expression is satisfied:

0.32≤CT4/f4≤0.52；

wherein CT4 is a distance on an optical axis from an object-side surface of the third lens element to an image-side surface of the fourth lens element, and f4 is a combined focal length of the third lens element and the fourth lens element.

4. The fixed-focus optical adapter according to claim 1, wherein the following conditional expression is satisfied:

0.11≤|CT5/f5|≤1.31；

wherein CT5 is a distance on an optical axis from an object-side surface of the fifth lens element to an image-side surface of the sixth lens element, and f5 is a combined focal length of the fifth lens element and the sixth lens element.

5. A fixed focus optical adapter according to claim 1, further comprising a first protective element provided on an object side of the first lens, and the fixed focus optical adapter satisfies the following conditional expression:

0.51≤CT2/(T12+T23)≤1.1；

wherein, CT2 is the thickness of the first lens element on the optical axis, T12 is the distance from the image-side surface of the first protection element to the object-side surface of the first lens element on the optical axis, and T23 is the distance from the image-side surface of the first lens element to the object-side surface of the second lens element on the optical axis.

6. The fixed-focus optical adapter according to claim 1, further comprising a second protection element provided between the seventh lens and an imaging surface of the fixed-focus optical adapter, and the fixed-focus optical adapter satisfies the following conditional expression:

2.15≤CT6/T67≤4.36；

wherein CT6 is the thickness of the seventh lens element on the optical axis, and T67 is the distance from the image-side surface of the seventh lens element to the object-side surface of the second protection element on the optical axis.

7. The fixed-focus optical adapter according to claim 1, wherein the following conditional expression is satisfied:

10deg≤Semi-FOV≤15deg；

20mm≤f≤25mm；

wherein the Semi-FOV is half of the maximum field angle of the fixed-focus optical adapter, and f is the effective focal length of the fixed-focus optical adapter.

8. The fixed focus optical adapter of claim 1, wherein the third lens has a negative optical power, the fourth lens has a positive optical power, the fifth lens has a negative optical power, and the sixth lens has a positive optical power; and/or the presence of a gas in the gas,

the image side surface of the first lens is a convex surface, the object side surface of the third lens is a concave surface, the image side surface of the third lens is a concave surface, the object side surface of the fourth lens is a convex surface, the object side surface of the fifth lens is a concave surface, the image side surface of the fifth lens is a concave surface, the object side surface of the sixth lens is a convex surface, and the image side surface of the seventh lens is a concave surface.

9. The fixed-focus optical adapter according to claim 1, further comprising a diaphragm provided on an object side of the first lens.

10. A 4K endoscope, comprising a fixed focus optical adapter according to any of claims 1-9.

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