An optical lens

Abstract

This specification provides an optical lens comprising, from the object side along the optical axis, a front lens group, an aperture stop, and a rear lens group. The front lens group includes a first lens and a prism arranged sequentially from the object side along the optical axis. The prism is used to change the direction of light propagation in the optical lens. The rear lens group includes a second lens, a third lens, and a cemented lens composed of a fourth lens and a fifth lens arranged sequentially from the object side along the optical axis. The optical lens satisfies the following conditions: , . Where is the effective focal length of the rear lens group, is the total effective focal length of the optical lens, is the center thickness of the second lens, is the aperture of the second lens, is the center thickness of the third lens, and is the aperture of the third lens.

Description

[0001] Cross-referencing This specification claims priority to Chinese application No. CN202411962964.4, filed on December 27, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This manual relates to the field of optical imaging in digestive endoscopy, and in particular to an optical lens. Background Technology

[0003] In the field of medical endoscopy, the duodenoscope, as an important diagnostic tool, is mainly used to observe and assist in the treatment of digestive system diseases, especially in the duodenum, liver, gallbladder, and pancreas. The design of a side-view duodenoscope allows the field of view of the camera device to form a certain angle with the scope body, thus enabling clear observation of the duodenal papilla structure and surface mucosa. However, existing duodenoscopes, in order to achieve miniaturization, typically have small image planes and cannot be equipped with high-resolution image sensors, resulting in low resolution; moreover, their aberration correction capabilities are limited.

[0004] Therefore, it is hoped that an optical lens can be proposed that can balance a large image size and miniaturization, and has strong aberration correction capabilities. Summary of the Invention

[0005] One embodiment of this specification provides an optical lens, comprising: a front lens group, which includes a first lens and a prism arranged sequentially along the optical axis from the object side, the prism being used to change the direction of light propagation in the optical lens; an aperture stop; and a rear lens group, which includes a second lens, a third lens, and a cemented lens composed of a fourth lens and a fifth lens arranged sequentially along the optical axis from the object side. The optical lens satisfies the following condition: , ;in, The effective focal length of the rear lens group. The total effective focal length of the optical lens. The center thickness of the second lens. The aperture of the second lens is [missing information]. The center thickness of the third lens. This is the aperture of the third lens.

[0006] In some embodiments, the second lens and the third lens satisfy at least one of the following conditions: , ,or ,in, Let be the radius of curvature of the third lens near the image-side surface. Let be the radius of curvature of the second lens near the object-side surface. Let be the radius of curvature of the third lens near the object-side surface. Let be the radius of curvature of the second lens near the image-side surface. The Abbe number of the second lens. Let be the Abbe number of the third lens.

[0007] In some embodiments, the second lens is a biconvex lens with positive optical power, and the third lens is a biconvex lens with positive optical power.

[0008] In some embodiments, the prism satisfies the following condition: the angle between the incident surface and the exit surface is in the range of 94.5°-115.5°.

[0009] In some embodiments, the prism satisfies the following condition: the angle of incidence of the reflecting surface of the prism... satisfy: .

[0010] In some embodiments, the distance from the incident light to the reflecting surface in the prism is equal to the distance from the reflected light to the exiting surface.

[0011] In some embodiments, the prism and aperture satisfy the following conditions: ,in, This is the distance between the aperture and the exit surface of the prism.

[0012] In some embodiments, the first lens and the prism satisfy at least one of the following conditions: ,or ,in, Let be the air equivalent length from the prism's incident surface to its exit surface. Let be the refractive index of the first lens. The distance between the first lens and the prism is denoted as .

[0013] In some embodiments, the cemented lens satisfies the following conditions: ,in, The effective focal length of the cemented lens. For image height.

[0014] In some embodiments, the first lens is a plano-concave lens with negative optical power, and satisfies the following condition: ,in, The effective focal length of the first lens is denoted as .

[0015] The embodiments in this specification can achieve miniaturization of the optical lens while maintaining a large image plane by designing the lens type, optical power, and optical parameters of each lens in the front and rear lens groups of the optical lens, and at the same time have strong aberration correction capabilities. Attached Figure Description

[0016] This specification will be further described by way of exemplary embodiments, which will be described in detail with reference to the accompanying drawings. These embodiments are not limiting; in these embodiments, the same reference numerals denote the same structures, wherein: Figure 1 These are schematic diagrams of the optical lens structure shown in some embodiments of this specification; Figure 2 This is a schematic diagram showing the radii of curvature of the second and third lenses according to some embodiments of this specification; Figure 3 This is a schematic diagram of a prism according to some embodiments of this specification; Figure 4 This is a schematic diagram of the MTF curve of an optical lens according to some embodiments of this specification; Figure 5 This is a schematic diagram of the distortion curve of an optical lens according to some embodiments of this specification; Figure 6 This is a schematic diagram of magnification chromatic aberration of an optical lens according to some embodiments of this specification. Detailed Implementation

[0017] To more clearly illustrate the technical solutions of the embodiments in this specification, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are merely some examples or embodiments of this specification. For those skilled in the art, these drawings can be applied to other similar scenarios without creative effort. Unless obvious from the context or otherwise specified, the same reference numerals in the drawings represent the same structures or operations.

[0018] It should be understood that the terms “system,” “device,” “unit,” and / or “module” used herein are one way to distinguish different components, elements, parts, sections, or assemblies at different levels. However, if other terms can achieve the same purpose, they may be replaced by other expressions.

[0019] As indicated in this specification and claims, unless the context clearly indicates otherwise, the words "a," "an," "an," and / or "the" do not specifically refer to the singular and may also include the plural. Generally speaking, the terms "comprising" and "including" only indicate the inclusion of expressly identified steps and elements, which do not constitute an exclusive list, and the method or apparatus may also include other steps or elements.

[0020] Flowcharts are used in this specification to illustrate the operations performed by the system according to embodiments of this specification. It should be understood that the preceding or following operations are not necessarily performed in exact order. Instead, the steps can be processed in reverse order or simultaneously. Furthermore, other operations can be added to these processes, or one or more steps can be removed from them.

[0021] The optical lenses described in this manual can be used in the field of medical endoscopes, such as duodenoscopes. It should be understood that, based on the design concepts described in this manual, they can also be applied to other optical systems that require miniaturization and a large image size.

[0022] Figure 1 This is a structural schematic diagram of an optical lens 100 according to some embodiments of this specification.

[0023] like Figure 1 As shown, the optical lens comprises, arranged sequentially along the optical axis from the object side: a front lens group G1, an aperture stop SI0, and a rear lens group G2. With the aperture stop SI0 as the boundary, the front lens group G1 is a combination of optical lenses closer to the object side, and the rear lens group G2 is a combination of optical lenses closer to the image side.

[0024] An object refers to an internal anatomical structure or pathological tissue that is observed, imaged, and analyzed through an optical lens during an endoscopic examination. For example, objects may include, but are not limited to, the duodenal papilla, bile duct, and duodenal wall.

[0025] In some embodiments, the front lens group G1 includes a first lens L1 and a prism P arranged sequentially from the object side along the optical axis.

[0026] In some embodiments, in order to allow a wide range of light to enter the optical lens 100 and ensure that the optical lens 100 can observe a sufficiently large range and achieve a large field of view, the first lens L1 near the object side can be designed to have a diverging effect on the light incident into it. Therefore, the first lens L1 can have a negative optical power.

[0027] In some embodiments, the first lens L1 can be a plano-concave lens. For example... Figure 1 As shown, the first side surface of the first lens L1 (i.e., the incident surface of light) is flat, which helps to constrain the focal length of the first lens L1 and reduce field curvature and distortion. The second side surface of the first lens L1 (i.e., the exit surface of light) is concave, which causes large-angle light rays entering from the first side surface to diverge, increasing the width of the light rays entering the receiving surface. The divergence of the incident light rays by the second side surface of the first lens L1 increases the focal length, which helps to reduce distortion.

[0028] A flat surface can characterize the surface of an optical element (e.g., the first side surface of the first lens L1) as having no curvature in any direction, i.e., the surface is completely flat. A concave surface can characterize the surface of an optical element (e.g., the second side surface of the first lens L1) as having an inwardly recessed shape. For example... Figure 1 As shown, the first lens L1 is a plano-concave lens, with its thickness in the middle being less than the thickness at the edges.

[0029] In some embodiments, in order to reasonably control the ratio of the effective focal length of the first lens L1 to the total effective focal length of the optical lens 100, if the effective focal length of the first lens L1 is too small, the diffusion capability of the first lens L1 is weak, the range of light received is smaller, and the field of view of the optical lens 100 is smaller; while if the effective focal length of the first lens L1 is too large, the refractive index of the first lens L1 is larger, which can achieve a large field of view, but the first lens L1 needs to be made of a material with a high refractive index or adopt a surface shape with a small radius of curvature, which will cause large chromatic aberration and increase the processing difficulty. As the field of view increases, the off-axis aberration will increase, and the light around the image plane will become darker. Therefore, taking into account the field of view, chromatic aberration, and ease of processing, the effective focal length of the first lens L1 and the total focal length of the optical lens 100 satisfy condition (1): (1), in, The effective focal length of the first lens. This represents the total effective focal length of the optical lens. Preferably, the first lens L1 further satisfies: .

[0030] Effective focal length refers to the focal length that an optical element (e.g., first lens L1, optical lens 100, etc.) can actually achieve.

[0031] In some embodiments of this specification, by relating to the optical power and type of the first lens L1, the ratio of the effective focal length of the first lens L1 to the total effective focal length of the optical lens 100 is reasonably controlled, which helps to balance the field of view, aberration control, light intensity distribution and chromatic aberration, and is also beneficial to processing, thereby optimizing the imaging performance and overall design efficiency of the optical lens 100.

[0032] In some embodiments, the prism P is used to change the direction of light propagation in the optical lens 100.

[0033] In some embodiments, prism P is a reflecting prism. In some embodiments, prism P can be a triangular prism (a prism with three planes). In some embodiments, to reduce the size of the optical lens 100, the triangular prism can be chamfered to become a pentaprism (a prism with five planes). An exemplary pentaprism is shown below. Figure 1 As shown.

[0034] In some embodiments, such as Figure 1As shown, the incident surface of prism P is perpendicular to the optical axis, and light rays emitted from the second side of the first lens L1 enter prism P. The reflecting surface of prism P is coated with an internal reflection film, causing the light rays to be reflected at the reflecting surface of prism P, thus achieving a reversal of the light path. The exit surface of prism P is perpendicular to the optical axis after the light path reversal; the light rays are reflected by the reflecting surface of prism P and exit from the exit surface. In some embodiments, prism P can be equivalent to a parallel plate, which will not cause aberrations in the optical system. The angle setting of the reflecting surface of prism P can control the reversal angle of the optical axis. For more description of prism P, please refer to [link to relevant documentation]. Figure 3 And its related descriptions.

[0035] In some embodiments, such as Figure 1 As shown, the front lens assembly G1 also includes a flat glass F1, wherein the first side (the incident surface of light) of the flat glass F1 is a plane, and the second side (the emitting surface of light) of the flat glass F1 is a plane.

[0036] The flat glass F1 is positioned in front of the first lens, close to the object side.

[0037] In some embodiments, the flat glass F1 may be made of sapphire.

[0038] In some embodiments of this specification, the flat glass F1 serves to protect the lens module within the optical lens 100. The flat glass, made of sapphire, offers high wear resistance and impact resistance, preventing scratches from affecting optical performance. Furthermore, the first side of the flat glass F1 is designed as a flat, groove-free structure, avoiding water accumulation and facilitating cleaning and disinfection. Simultaneously, the second side of the flat glass F1 also maintains a flat design, ensuring that light emanating from the second side introduces almost no aberrations, allowing it to smoothly enter subsequent optical components. Although cutting and grinding sapphire is challenging, the flat design of both sides of the flat glass reduces processing difficulty and saves costs.

[0039] In optical systems, an aperture (SIO) is a device or opening used to control the amount of light passing through.

[0040] In some embodiments, such as Figure 1 As shown, the aperture stop SIO can be positioned between the prism P and the second lens L2. By increasing the aperture stop SIO, the width of the off-axis beam entering the rear optical system can be limited, which helps to reduce the radius of the blur spot, correct field curvature distortion, and improve image quality.

[0041] In some embodiments, the size of the aperture SIO can be designed to be larger than a preset size threshold to prevent the image information entering the receiving surface from being too small, which would affect the value of the MTF curve. The preset size threshold can be set by a professional technician or by system default.

[0042] MTF is a function used to describe the transmission performance of an optical system. MTF describes the relative amplitudes of different spatial frequency components that an optical system can transmit, thus quantifying the optical system's response capability to different spatial frequencies.

[0043] The MTF curve measures the overall resolution and contrast of an optical lens and can be obtained by professional technicians through experiments.

[0044] For more information on MTF curves, please refer to [link / reference]. Figure 4 And its related descriptions.

[0045] The rear lens group G2 is located behind the aperture SIO and in front of the imaging sensor. The rear lens group G2 is able to receive light passing through the front lens group G1 and the aperture SIO and focus it on the imaging plane to form a clear image.

[0046] In some embodiments, the rear lens group G2 includes a second lens L2, a third lens L3, and a cemented lens composed of a fourth lens L4 and a fifth lens L5 arranged sequentially along the optical axis from the object side.

[0047] In some embodiments, in order to collect light emitted from the aperture SIO and reduce the height of the peripheral light, thereby miniaturizing the optical lens 100, the second lens L2 may be designed to have positive optical power.

[0048] In some embodiments, the second lens is a biconvex lens. For example, the first side surface (i.e., the incident surface) of the second lens L2 is convex, and the second side surface (i.e., the exit surface) is convex.

[0049] In some embodiments, the second lens L2 is a biconvex lens, which enables light to converge twice on the second lens L2, thereby reducing the beam aperture and helping to initially correct aberrations, especially astigmatism, thereby reducing the correction pressure on subsequent optical components.

[0050] In some embodiments, in order to converge the light emitted through the second lens L2, make the light entering the subsequent optical elements of the optical lens 100 smoother, reduce the aperture, and reduce the sensitivity of the optical lens 100, the third lens L3 can be designed to have positive optical power.

[0051] In some embodiments, the third lens L3 is a biconvex lens. For example, the first side surface (i.e., the incident surface) of the third lens L3 is convex, and the second side surface (i.e., the exit surface) is convex.

[0052] In some embodiments, the third lens L3 is a biconvex lens, which enables light to converge twice on the third lens L3, thereby reducing the beam aperture and helping to initially correct aberrations, especially astigmatism, thereby reducing the correction pressure on subsequent optical components.

[0053] In some embodiments, the structure of the third lens L3 is similar to that of the second lens L2, forming an approximately symmetrical structural design. This utilizes the symmetrical front and rear mirror surfaces to eliminate lens eccentricity distortion and chromatic aberration. Light passing through the symmetrical structure achieves more uniform color and clarity. It should be understood that "approximately symmetrical structure" refers to a structure where the two sides of the third lens L3 and the second lens L2 are axially symmetrical about the perpendicular bisector of the optical axis segment between the second lens L2 and the third lens L3. Figure 1 As shown, the second side surface (i.e., the exit surface) of the second lens L2 and the first side surface (i.e., the incident surface) of the third lens L3 are symmetrical with respect to the perpendicular bisector of the optical axis between the second lens L2 and the third lens L3. In other words, the convex structure of the second side surface of the second lens L2 is similar to that of the first side surface of the third lens L3. The first side surface (i.e., the incident surface) of the second lens L2 and the second side surface (i.e., the incident and exit surfaces) of the third lens L3 are symmetrical with respect to the perpendicular bisector of the optical axis between the second lens L2 and the third lens L3. In other words, the convex structure of the first side surface of the second lens L2 is similar to that of the second side surface of the third lens L3.

[0054] In some embodiments, the rear lens group G2 of the optical lens 100 satisfies the following conditions (2) and (3): (2), (3), in, The effective focal length of the rear lens group G2, The total effective focal length of the optical lens is 100. The center thickness of the second lens. The aperture of the second lens is [missing information]. The center thickness of the third lens. This is the aperture of the third lens.

[0055] The effective focal length of the rear lens group G2 refers to the equivalent focal length of the rear lens group G2 in the optical system. This focal length is determined by the interaction of all lenses in the rear lens group G2.

[0056] Center thickness refers to the thickness of a lens at its center (e.g., where the optical axis passes through the center).

[0057] The aperture refers to the maximum diameter through which light rays can pass through a lens.

[0058] In some embodiments, when the effective focal length of the rear lens group G2 is too small, the refractive power of the rear lens group G2 becomes stronger, causing light to converge prematurely, resulting in an insufficiently large image plane. Furthermore, the lenses in the rear lens group G2 need to be selected with high refractive index or designed with a small radius of curvature, which is not conducive to aberration correction and increases the manufacturing difficulty. When the effective focal length of the rear lens group G2 is too large, the refractive power of the rear lens group G2 becomes weaker, causing the image plane to be positioned too far back, increasing the length of the rear lens group G2, which is not conducive to the miniaturization of the optical system. Therefore, in order to achieve a large image plane and miniaturization, as well as to improve aberration correction capability and facilitate manufacturing, the ratio of the effective focal length of the rear lens group G2 to the total effective focal length of the optical lens 100 satisfies the above condition (2).

[0059] In some embodiments, when the ratio of the center thickness of the second lens L2 to the aperture of the second lens L2 is... The ratio of the center thickness of the third lens L3 to the aperture of the third lens L3 The ratio between When the ratio L2 approaches 1, the structural proportions of the second lens L2 and the third lens L3 become nearly identical, which is beneficial for correcting distortion problems in the system. However, the thickness of the third lens L3 is too small, which is not conducive to light divergence, resulting in a smaller imaging height. When the ratio L2 approaches the upper limit (i.e., 1.4), the relative thickness of the third lens L3 increases. Although the imaging height increases, which is beneficial for achieving a large image plane, the beam width is too large, which exacerbates off-axis aberration problems. Moreover, the structural proportions of the second lens L2 and the third lens L3 are not similar, which will affect the correction of aberrations such as distortion. Therefore, in order to balance a large image plane and aberration correction capability, the center thickness and aperture of the second lens L2 and the third lens L3 must meet the above conditions (3).

[0060] In some embodiments of this specification, the optical lens 100 includes a front lens group G1, an aperture stop S10, and a rear lens group G2. The front lens group G1 consists of a first lens L1 and a prism P, whereby the prism P is used to change the direction of light propagation and optimize the optical path. The aperture stop S10 limits the amount of light entering the optical lens, improving image contrast and sharpness. The rear lens group G2 consists of a second lens L2, a third lens L3, and a cemented lens (i.e., a cemented lens composed of a fourth lens L4 and a fifth lens L5) arranged sequentially. By precisely controlling the ratio between the effective focal length and the total effective focal length of the rear lens group G2, as well as the range of the ratio between the center thickness of the second lens L2 and the third lens L2 and the aperture, this optical lens 100 not only provides excellent image quality and reduces aberrations, but also maintains a balance in overall size and weight, making the lens more compact and facilitating the reduction of the diameter of the endoscope tip. In addition, the optical lens 100 uses a prism P to deflect the light path to achieve side-view observation. In order to reduce the diameter and miniaturize the endoscope lens, it is necessary to control the radial dimension and axial length of the optical lens 100. The optical design of the light-incident side of the prism P directly affects the radial dimension of the optical lens 100, and the optical design of the light-exit side of the prism P directly affects the axial length of the optical lens 100. In order to control the size of the optical lens 100 and balance the length of the light-incident side and the light-exit side of the prism P, the prism P is set after the first lens L1 and before the second lens L2 (along the optical axis from the object side).

[0061] Figure 2 This is a schematic diagram showing the radii of curvature of the second and third lenses according to some embodiments of this specification. For example... Figure 2 As shown, the radius of curvature of the second lens L2 near the object surface (i.e., the incident surface) is... The radius of curvature of the second lens L2 near the image-side surface (i.e., the exit surface) is... The radius of curvature of the third lens L3 near the object surface (i.e., the incident surface) is... The radius of curvature of the third lens L3 near the image-side surface (i.e., the exit surface) is... .

[0062] In some embodiments, the radius of curvature of the third lens L3 is close to that of the image-side surface. The radius of curvature of the second lens L2 near the object surface The ratio satisfies condition (4): (4).

[0063] The radius of curvature refers to the distance from the center of the lens to the outermost edge of the curved surface (i.e., the vertex of the curved surface).

[0064] In some embodiments, when the ratio of curvature radii is Approaching the upper limit of 1, the structures of the second lens L2 and the third lens L3 become similar, and aberrations such as distortion are well corrected; however, the refractive power of the third lens L3 is insufficient, which is not conducive to the correction of transverse aberrations in the back-end system, and the beam width transmitted to the back-end optical elements increases, which is not conducive to the miniaturization of the optical lens 100. When the ratio of curvature radii is... When the image quality is close to the lower limit of 0.8, the second lens L2 and the third lens L3 cannot form a symmetrical structure, resulting in insufficient ability to correct aberrations such as image distortion, which affects the final imaging effect. Therefore, in order to ensure better aberration correction capability and to consider the requirement of miniaturization, the second lens L2 and the third lens L3 must meet the above condition (4).

[0065] In some embodiments, the radius of curvature of the third lens L3 is close to that of the object surface. The radius of curvature of the second lens L2 near the image-side surface The ratio satisfies condition (5): (5).

[0066] In some embodiments, the radius of curvature of the third lens L3 is close to that of the object surface. The radius of curvature of the second lens L2 near the image-side surface This affects the focal length of the lens, and also influences whether the second lens L2 and the third lens L3 can form a symmetrical structure. When the third lens L3 is close to the radius of curvature of the object surface... The radius of curvature of the image-side surface of the second lens L2 ratio When the ratio approaches the lower limit of 1, although the ability to correct distortion is improved, the object surface of the third lens L3 has a weaker ability to refract light, resulting in a more divergent beam. This weakens the correction effect on astigmatism and field curvature, affecting the final image quality. Conversely, when the ratio of the two radii of curvature mentioned above approaches the upper limit of 1.04, although it can better correct off-axis aberrations, the reduction in the radius of curvature may lead to excessive beam concentration, thereby reducing the image size and affecting the overall performance of the image. Therefore, in order to better correct aberrations and take into account a large image plane, the second lens L2 and the third lens L3 satisfy the above condition (5).

[0067] In some embodiments, the ratio between the Abbe number of the second lens L2 and the Abbe number of the third lens L3 satisfies condition (6): (6), in, The Abbe number of the second lens. Let be the Abbe number of the third lens.

[0068] The Abbe number, also known as the "dispersion coefficient," is used to measure the degree of light dispersion in a transparent medium. The Abbe number represents an index of the dispersion ability of a transparent medium; the smaller the value, the more severe the dispersion.

[0069] In some embodiments, when the ratio between the Abbe number of the second lens L2 and the Abbe number of the third lens L3 is close to the lower limit of 1.1, the Abbe number of the third lens L3 is relatively large. Since the Abbe number is inversely proportional to the refractive index, a higher Abbe number means a lower refractive index, which weakens the refractive power of the third lens L3, increases the length of the rear optical system, and is not conducive to the miniaturization design of the optical lens 100. At the same time, transverse chromatic aberration and on-axis chromatic aberration may become more significant. Conversely, when the ratio between the Abbe number of the second lens L2 and the Abbe number of the third lens L3 is close to the upper limit of 1.35, the Abbe number of the third lens L3 is small, indicating that its dispersion correction capability is insufficient. Moreover, the refractive power of the third lens L3 is enhanced, which reduces the beam width entering the rear optical system, thereby reducing the image plane height and affecting the image quality. Therefore, to balance a large image plane and miniaturization, the Abbe number of the second lens L2 and the Abbe number of the third lens L3 satisfy condition (6).

[0070] In some embodiments, in order to achieve the corresponding technical effect, the second lens L2 and the third lens L3 may satisfy any one of the above conditions (4)-(6). For example, the second lens L2 and the third lens L3 may only satisfy the above condition (4). For example, the second lens L2 and the third lens L3 may only satisfy the above condition (5). For example, the second lens L2 and the third lens L3 may only satisfy the above condition (6).

[0071] In some embodiments, in order to simultaneously ensure aberration correction capability while considering miniaturization and the need for a large image plane, the second lens L2 and the third lens L3 can satisfy any two of the above conditions (4)-(6). For example, the second lens L2 and the third lens L3 can satisfy the above conditions (4) and (5). For example, the second lens L2 and the third lens L3 can satisfy the above conditions (4) and (6). For example, the second lens L2 and the third lens L3 can satisfy the above conditions (5) and (6).

[0072] In some embodiments, in order to better ensure aberration correction capability, while taking into account miniaturization and large image area requirements, the second lens L2 and the third lens L3 can simultaneously satisfy the above conditions (4), (5) and (6).

[0073] In some embodiments of this specification, by rationally designing the optical parameters (e.g., radius of curvature, Abbe number) of the second lens L2 and the third lens L3, it is possible to balance the large image plane with the miniaturization of the optical lens 100, while ensuring that the optical lens 100 has good aberration correction capabilities.

[0074] In some embodiments, the fourth lens L4 has positive optical power and the fifth lens L5 has negative optical power.

[0075] In some embodiments, the fourth lens L4 is a positive lens, which converges the light emitted from the third lens L3, and is used in conjunction with the fifth lens L5, which has negative optical power. In some embodiments, the fifth lens L5 is a negative lens, which can better receive and diverge the light emitted from the fourth lens L4. When used in conjunction with the fourth lens L4, it can reduce aberrations and improve the resolving power of the optical lens. In addition, the negative lens function of the fifth lens L5 acts as a divergent lens, which can increase the height and width of the light beam reaching the receiving surface, thereby increasing the image size.

[0076] In some embodiments, the fourth lens L4 is made of low-dispersion crown glass and the fifth lens L5 is made of high-dispersion flint glass. The chromatic aberrations of the two lenses are opposite to each other to optimize the chromatic aberration at the three wavelengths of blue (486.1 nm), green (546.1 nm) and red (656.3 nm) and achieve minimum chromatic aberration.

[0077] In some embodiments, the fourth lens L4 is a biconvex lens. For example, the first side surface (i.e., the incident surface) of the fourth lens L4 is convex, and the second side surface (i.e., the exit surface) is convex.

[0078] In some embodiments, the fifth lens L5 is a biconcave lens. For example, the first side surface (i.e., the incident surface) of the fifth lens L5 is concave, and the second side surface (i.e., the exit surface) is concave.

[0079] In some embodiments, the fourth lens L4 and the fifth lens L5 are cemented together to form a single cemented lens, achieving complementary dispersion values ​​and correcting chromatic aberration. Simultaneously, compared to a single lens, the spherical aberration of the cemented lens composed of the fourth lens L4 and the fifth lens L5 is significantly smaller. In some embodiments, when the cemented lens is in an infinite conjugate state, i.e., when the incident light source originates from an object at infinity, the spherical aberration of the cemented lens is minimized. In this state, because the incident light is parallel to the optical axis, the cemented lens can effectively reduce the focusing differences of light rays at different angles caused by the curvature of the lens surface, thereby optimizing image quality and achieving minimal spherical aberration.

[0080] Spherical aberration refers to the aberrations caused by the spherical surface of a lens when light passes through it.

[0081] In some embodiments, the cemented lens composed of the fourth lens L4 and the fifth lens L5 satisfies condition (7): (7), in, The effective focal length of the cemented lens. For image height.

[0082] Image height refers to the length of a line segment perpendicular to the optical axis on the image plane in an optical system.

[0083] In some embodiments, when the effective focal length of the cemented lens When the value approaches the upper limit of -4.7, the cemented lens exhibits negative optical power overall, causing the light rays reaching the image plane to diverge, resulting in a larger image height. Furthermore, the refractive power of the cemented lens is not excessive, making it less likely to introduce excessive off-axis aberrations. When the effective focal length of the cemented lens... When the value approaches the lower limit of -5.5, the refractive power of the cemented lens is too strong, which will introduce off-axis aberrations and affect the image quality. Therefore, in order to achieve a large image plane and low aberrations, the cemented lens composed of the fourth lens L4 and the fifth lens L5 satisfies condition (7).

[0084] In some embodiments of this specification, by reasonably controlling the ratio of the effective focal length to the image height of the cemented lens, an optical lens 100 with a large image plane and low aberration can be achieved.

[0085] In some embodiments, such as Figure 1 As shown, the optical lens 100 may further include an image sensor G disposed on the image side to obtain an image IMA of the object.

[0086] In some embodiments, the image sensor G may be a charge-coupled device (CCD) or a complementary metal oxide semiconductor element (CMOS).

[0087] Figure 3 This is a schematic diagram of a prism according to some embodiments of this specification.

[0088] In some embodiments, the duodenal papilla is slightly angled forward of the endoscope's forward direction. To facilitate observation of the duodenal papilla and medical procedures, the endoscope's observation direction needs to be slightly angled backward relative to the forward direction, so that the instrument is centered in the image after extension. Therefore, prism P needs to meet condition (8): such as Figure 3 As shown, the angle between the incident and exit surfaces of prism P Within the range of 94.5°-115.5°. Preferably, the angle between the incident and exit surfaces of prism P is... It is 105°.

[0089] In some embodiments, in order to achieve a viewing angle of the optical lens 100 within the range of 94.5°-115.5°, the incident angle of the reflecting surface of the prism P is designed. (like Figure 3 As shown) satisfies condition (9): (9).

[0090] In some embodiments, in order to achieve the corresponding technical effect, prism P can satisfy any one of the above conditions (8) and (9). In some embodiments, prism P can satisfy the above conditions (8) and (9) simultaneously.

[0091] The duodenal papilla is the common opening of the common bile duct and pancreatic duct. When an endoscope is inserted into the duodenum, it is necessary to observe the duodenal papilla. Instruments are inserted into the duodenal papilla to reach the common bile duct or pancreatic duct for medical procedures. The duodenal papilla is slightly angled forward of the endoscope's direction of travel. To facilitate observation of the duodenal papilla and the medical procedure, the endoscope's observation direction needs to be slightly angled backward relative to its forward direction. If the viewing angle of the optical lens is 90° (side view), the tip of the treatment instrument will not be centered in the image, affecting the operator's observation and operation. Therefore, this embodiment optimizes the observation angle by designing the angle between the incident and exit surfaces of prism P and / or the incident angle of the reflecting surface of prism P. This ensures that when the treatment instrument is extended, its tip is precisely centered in the image, thereby improving the operator's observation efficiency and operational accuracy.

[0092] In some embodiments, the prism P has a symmetrical structure, which simplifies its installation. For example, as... Figure 3 As shown, the distance h1 from the incident light to the reflecting surface in prism P is equal to the distance h2 from the reflected light to the exiting surface.

[0093] In some embodiments of this specification, by designing the structure of prism P as symmetrical, the assembly and adjustment steps can be simplified, and the assembly and adjustment accuracy and efficiency can be improved.

[0094] In some embodiments, the distance between the aperture SIO and the exit surface of the prism P satisfies condition (10): (10) in, The distance between the aperture and the exit surface of the prism, such as Figure 2 As shown.

[0095] The position of the aperture stop affects the optical performance of the off-axis field of view. Light rays exiting the exit surface of prism P pass through the aperture stop SIO. The distance between the aperture stop SIO and the exit surface of prism P... When the distance approaches the upper limit of 0.2, the off-axis beam width after passing through the aperture is too small, resulting in insufficient image signal reaching the receiving surface and deteriorating image quality. This is because the distance between the aperture SIO and the exit surface of the prism P is too small. When the beam width approaches the lower limit of 0.1, the off-axis beam width after the aperture stop becomes too large, resulting in increased off-axis aberrations. Furthermore, an excessively wide beam width increases the aperture of subsequent lenses, making it difficult to miniaturize the optical lens 100. Therefore, in some embodiments, the aperture stop SIO and the prism P satisfy condition (10).

[0096] By properly controlling the distance between the exit surface of the aperture SIO and the prism P, the beam width of the off-axis field of view can be optimized to ensure sufficient image signal, while controlling aberrations within an acceptable range, thereby achieving miniaturization of the optical system and improvement of imaging performance.

[0097] In some embodiments, the air equivalent length from the incident surface to the exit surface of prism P satisfies condition (11): (11), in, Let be the air equivalent length from the prism's incident surface to its exit surface.

[0098] Air equivalent length refers to the equivalent length of light when it travels through air, which is the conversion of the actual path length of light in a medium.

[0099] In some embodiments, when the ratio of the air equivalent length to the effective focal length of the optical lens 100 is close to the lower limit of 1, the size of the prism P is too small, which will limit the light-passing aperture, resulting in insufficient image information reaching the receiving surface and affecting the imaging quality. When the ratio of the air equivalent length to the effective focal length of the optical lens 100 is close to the upper limit of 1.5, it will cause the optical lens 100 to be too long, and the subsequent optical aperture will become larger, which is not conducive to the miniaturization of the optical lens 100. Therefore, the prism P satisfies the above condition (11).

[0100] In some embodiments, the incident surface of prism P receives the outgoing light from the first lens L1. The divergence effect of the first lens L1 ensures that the field of view can reach 100°. The size of the aperture of prism P affects the size of the field of view of optical lens 100. The aperture of the incident surface of prism P is determined by the refractive index of the first lens L1 and the distance between the first lens L1 and prism P. The ratio of the refractive index of the first lens L1 to the distance between the first lens L1 and prism P satisfies condition (12): (12) in, Let L1 be the refractive index of the first lens. Let L1 be the distance between the first lens L1 and the prism P.

[0101] The distance between the first lens L1 and the prism P refers to the distance between the exit surface of the first lens L1 and the incident surface of the prism P.

[0102] In some embodiments, when the ratio of the refractive index of the first lens L1 to the distance between the first lens L1 and the prism P is close to the lower limit of 1.45, the deflection force of the first lens L1 on the light decreases or the distance to the incident surface of the prism P increases. This results in a smaller beam width from the first lens L1 into the subsequent optical elements, leading to a smaller aperture required for the prism P, which in turn reduces the field of view of the lens and lowers the image plane height. When the ratio of the refractive index of the first lens L1 to the distance between the first lens L1 and the prism P is close to the upper limit of 1.85, the beam width entering the prism is larger, exacerbating the astigmatism problem and hindering the miniaturization of the optical lens 100. Therefore, the first lens L1 and the prism P must satisfy the above condition (12).

[0103] In some embodiments, in order to achieve the corresponding technical effect, the first lens L1 and the prism P can satisfy one of the above conditions (11) and (12). In some embodiments, in order to ensure sufficient light transmission aperture and image information while balancing the size and imaging performance of the optical system, so as to realize a small, efficient and high-quality optical system, the first lens L1 and the prism P can simultaneously satisfy the above conditions (11) and (12).

[0104] By rationally controlling the ratio of the air equivalent length inside prism P to the effective focal length of optical lens 100, it is possible to balance the size and imaging performance of the optical system while ensuring sufficient light transmission aperture and image information, thus achieving a small, efficient, and high-quality optical system. Rational control of the refractive index of the first lens and the ratio of the distance between the first lens and the prism helps to ensure both good imaging quality and miniaturization and high efficiency of the optical system.

[0105] In some embodiments, in order to achieve the corresponding technical effect, each optical element in the optical lens 100 (e.g., first lens L1, second lens L2, third lens L3, fourth lens L4, fifth lens L5, prism P, aperture SI0, etc.) can satisfy any one of the above conditions (1)-(12). In some embodiments, in order to achieve the combined technical effect, each optical element in the optical lens 100 can satisfy any two or more combinations of the above conditions (1)-(12). For example, each optical element in the optical lens 100 can simultaneously satisfy the above conditions (1)-(12). Combining the above conditions (1)-(12), Table 1 shows the basic parameter table of the exemplary optical lens 100, where the prism P is equivalently unfolded into a parallel plate. The units of radius of curvature and thickness / distance are millimeters (mm).

[0106] Table 1

[0107] In some embodiments, the optical lens 100 has a total system length of 10.4748 mm, an image height (IH) of 1.1124 mm, a field of view of 100°, and a system F-number of 6.0.

[0108] Figure 4 This is a schematic diagram of the MTF curve of an optical lens according to some embodiments of this specification, wherein the MTF of the optical system is better than 0.65@65lp / mm across the entire wavelength range. For example... Figure 4 As shown, the horizontal axis of the MTF curve represents spatial frequency, and the vertical axis represents the OTF magnitude.

[0109] The OTF magnitude refers to the magnitude of the Optical Transfer Function (OTF), that is, the amplitude part of the OTF. OTF is a complex function, and its magnitude (MTF) is a real number.

[0110] In some embodiments, such as Figure 4 As shown, across the entire spectral range, the optical system exhibits an OTF modulus (or equivalent, MTF) exceeding 0.65 in the spatial frequency range of 0 lp / mm to 65 lp / mm, indicating that the optical system possesses excellent imaging performance and can effectively transmit image contrast.

[0111] Figure 5 This is a schematic diagram of the distortion curve of an optical lens according to some embodiments of this specification.

[0112] The distortion curve of an optical lens refers to the variation of magnification within the field of view of an image at a fixed working distance. The magnitude of distortion changes with wavelength, and the distortion curves for different wavelengths do not coincide.

[0113] In some embodiments, the optical system requires optical distortion of -30%, meaning that the magnification of the central portion of the image is 30% smaller than that of the edge portion.

[0114] A negative distortion value usually indicates barrel distortion, meaning that the magnification ratio at the center of the image is smaller than that at the edges.

[0115] Figure 6 This is a schematic diagram illustrating the magnification chromatic aberration of an optical lens according to some embodiments of this specification. For example... Figure 6 As shown, the chromatic difference range for each band is less than 1 μm.

[0116] Therefore, in summary Figure 4 , Figure 5 , Figure 6 The results show that the optical lens provided in the embodiments of this specification can achieve good imaging quality.

[0117] The basic concepts have been described above. Obviously, for those skilled in the art, the detailed disclosure above is merely illustrative and does not constitute a limitation of this specification. Although not explicitly stated herein, those skilled in the art may make various modifications, improvements, and corrections to this specification. Such modifications, improvements, and corrections are suggested in this specification and therefore remain within the spirit and scope of the exemplary embodiments described herein.

[0118] Furthermore, this specification uses specific terms to describe embodiments thereof. For example, "an embodiment," "one embodiment," and / or "some embodiments" refer to a particular feature, structure, or characteristic associated with at least one embodiment of this specification. Therefore, it should be emphasized and noted that references to "an embodiment," "one embodiment," or "an alternative embodiment" in different locations throughout this specification do not necessarily refer to the same embodiment. Moreover, certain features, structures, or characteristics in one or more embodiments of this specification can be appropriately combined.

[0119] Furthermore, unless expressly stated in the claims, the order of processing elements and sequences, the use of numbers and letters, or other names described in this specification are not intended to limit the order of the processes and methods described herein. Although various examples have been discussed in the foregoing disclosure of some embodiments of the invention that are currently considered useful, it should be understood that such details are for illustrative purposes only, and the appended claims are not limited to the disclosed embodiments; rather, the claims are intended to cover all modifications and equivalent combinations that conform to the spirit and scope of the embodiments described herein. For example, while the system components described above can be implemented using hardware devices, they can also be implemented solely using software solutions, such as installing the described system on existing servers or mobile devices.

[0120] Similarly, it should be noted that, in order to simplify the description disclosed herein and thus aid in the understanding of one or more embodiments of the invention, the foregoing description of embodiments in this specification may sometimes combine multiple features into a single embodiment, drawing, or description thereof. However, this method of disclosure does not imply that the subject matter of this specification requires more features than those mentioned in the claims. In fact, the embodiments contain fewer features than all the features of a single embodiment disclosed above.

[0121] In some embodiments, numbers describing the quantity of components and attributes are used. It should be understood that such numbers used in the description of embodiments are modified in some examples with the terms "approximately," "approximately," or "generally." Unless otherwise stated, "approximately," "approximately," or "generally" indicates that the numbers are allowed to vary by ±20%. Accordingly, in some embodiments, the numerical parameters used in the specification and claims are approximate values, which may be changed depending on the characteristics required by individual embodiments. In some embodiments, numerical parameters should take into account specified significant digits and employ a general method of digit reservation. Although the numerical ranges and parameters used to confirm their breadth of range in some embodiments of this specification are approximate values, in specific embodiments, such values ​​are set as precisely as feasible.

[0122] For each patent, patent application, patent application publication, and other material such as articles, books, specifications, publications, and documents referenced in this specification, the entire contents of which are incorporated herein by reference. This excludes historical application documents that are inconsistent with or conflict with the content of this specification, as well as documents that limit the broadest scope of the claims in this specification (currently or subsequently appended to this specification). It should be noted that in the event of any inconsistency or conflict between the descriptions, definitions, and / or terminology used in the supplementary materials to this specification and the content of this specification, the descriptions, definitions, and / or terminology used in this specification shall prevail.

[0123] Finally, it should be understood that the embodiments described in this specification are merely illustrative of the principles of the embodiments described herein. Other variations may also fall within the scope of this specification. Therefore, alternative configurations of the embodiments described herein are intended to be illustrative rather than limiting, and should be considered consistent with the teachings of this specification. Accordingly, the embodiments described herein are not limited to those explicitly introduced and described herein.

Claims

1. An optical lens, characterized in that, Including those arranged sequentially along the optical axis from the object side: A front lens assembly, comprising a first lens and a prism arranged sequentially from the object side along the optical axis, wherein the prism is used to change the direction of light propagation in the optical lens; Aperture; and The rear lens assembly includes a second lens, a third lens, and a cemented lens composed of a fourth lens and a fifth lens arranged sequentially along the optical axis from the object side. The optical lenses satisfy the following conditions: ， ， in, The effective focal length of the rear lens group. The total effective focal length of the optical lens. The center thickness of the second lens. The aperture of the second lens is [missing information]. The center thickness of the third lens. This is the aperture of the third lens.

2. The optical lens according to claim 1, characterized in that, The second lens and the third lens satisfy at least one of the following conditions: ， ,or ， in, Let be the radius of curvature of the third lens near the image-side surface. Let be the radius of curvature of the second lens near the object-side surface. Let be the radius of curvature of the third lens near the object-side surface. Let be the radius of curvature of the second lens near the image-side surface. The Abbe number of the second lens. Let be the Abbe number of the third lens.

3. The optical lens according to claim 2, characterized in that, The second lens is a biconvex lens with positive optical power, and the third lens is a biconvex lens with positive optical power.

4. The optical lens according to any one of claims 1-3, characterized in that, The prism satisfies the following condition: The angle between the incident surface and the exit surface is in the range of 94.5°-115.5°.

5. The optical lens according to any one of claims 1-3, characterized in that, The prism satisfies the following condition: The angle of incidence of the reflecting surface of the prism satisfy: .

6. The optical lens according to any one of claims 1-3, characterized in that, The distance from the incident light to the reflecting surface in the prism is equal to the distance from the reflected light to the exiting surface.

7. The optical lens according to any one of claims 1-3, characterized in that, The prism and aperture satisfy the following conditions: ， in, This is the distance between the aperture and the exit surface of the prism.

8. The optical lens according to any one of claims 1-3, characterized in that, The first lens and prism satisfy at least one of the following conditions: ,or ， in, Let be the air equivalent length from the prism's incident surface to its exit surface. Let be the refractive index of the first lens. The distance between the first lens and the prism is denoted as .

9. The optical lens according to any one of claims 1-3, characterized in that, The cemented lens satisfies the following conditions: ， in, The effective focal length of the cemented lens. For image height.

10. The optical lens according to any one of claims 1-3, characterized in that, The first lens is a plano-concave lens with negative optical power, and satisfies the following conditions: ， in, The effective focal length of the first lens is denoted as .

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