Endoscope optical system, endoscope objective lens, and endoscope

Abstract

The present application relates to a kind of endoscope optical system, endoscope objective and endoscope.Endoscope optical system includes sequentially by object side to image side along optical axis first lens group with negative focal power, diaphragm and second lens group with positive focal power, the first lens group sequentially by object side to image side along optical axis first lens and second lens with positive focal power with negative focal power of first lens, the second lens group sequentially by object side to image side along optical axis third lens with positive focal power, fourth lens with positive focal power and fifth lens with negative focal power with positive focal power;Endoscope optical system satisfies:0.9≤IH / f≤1.1.The above-mentioned endoscope optical system, can give consideration to wide-angle characteristic and the realization of high imaging quality.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of endoscopes, in particular to an endoscope optical system, an endoscope objective lens and an endoscope. BACKGROUND

[0002] With the rapid development of medical equipment, endoscopes are increasingly widely used in the medical field, and thus the industry has increasingly high requirements for the performance of endoscopes. In order to maximize the acquisition of images of lesion areas and avoid the risk of missing, the industry usually requires endoscopes to have wide-angle characteristics to meet the demand of large-range image acquisition, thereby facilitating comprehensive examination of lesion areas. However, the current endoscopes, while achieving wide-angle characteristics, are prone to cause a decline in imaging quality, and the current endoscopes are difficult to achieve both wide-angle characteristics and high imaging quality. SUMMARY

[0003] Therefore, it is necessary to provide an endoscope optical system, an endoscope objective lens and an endoscope to solve the problem that the current endoscopes are difficult to achieve both wide-angle characteristics and high imaging quality.

[0004] An endoscope optical system, characterized in that,

[0005] includes, in order from the object side to the image side along the optical axis, a first lens group having negative refractive power, a diaphragm and a second lens group having positive refractive power, the first lens group includes, in order from the object side to the image side along the optical axis, a first lens having negative refractive power and a second lens having positive refractive power, and the second lens group includes, in order from the object side to the image side along the optical axis, a third lens having positive refractive power, a fourth lens having positive refractive power and a fifth lens having negative refractive power;

[0006] and the endoscope optical system satisfies the following conditional expression:

[0007] 0.9≤IH / f≤1.1;

[0008] wherein IH is half of the image height corresponding to the maximum field angle of the endoscope optical system, and f is the effective focal length of the endoscope optical system.

[0009] In one of the embodiments, the object side surface and the image side surface of the third lens and the object side surface and the image side surface of the fourth lens are all convex, and the curvatures of the object side surface and the image side surface of the third lens and the object side surface and the image side surface of the fourth lens are the same.

[0010] In one of the embodiments, the endoscope optical system satisfies the following conditional expression:

[0011] 0.16≤IH / TTL≤0.19;

[0012] Wherein, TTL is the distance on the optical axis from the object side of the first lens to the imaging surface of the endoscope optical system, that is, the total optical length of the endoscope optical system.

[0013] In one embodiment, the endoscopic optical system satisfies the following condition:

[0014] 0.6≤LG1 / LG2≤1.0;

[0015] Wherein, LG1 is the distance from the object side of the first lens to the aperture on the optical axis, and LG2 is the distance from the aperture to the image side of the fifth lens on the optical axis.

[0016] In one embodiment, the endoscopic optical system satisfies the following condition:

[0017] 0.3≤d1 / f≤0.5;

[0018] Wherein, d1 is the thickness of the first lens on the optical axis, that is, the center thickness of the first lens.

[0019] In one embodiment, the endoscopic optical system satisfies the following condition:

[0020] 0.9≤Bf / f≤1.5;

[0021] Wherein, Bf is the distance on the optical axis from the image side of the fifth lens to the imaging surface of the endoscope optical system.

[0022] In one embodiment, the endoscopic optical system satisfies the following condition:

[0023] 0.6 ≤ R² / SD12 ≤ 0.78;

[0024] Wherein, R2 is the radius of curvature of the image-side surface of the first lens at the optical axis, and SD12 is the maximum effective aperture of the image-side surface of the first lens.

[0025] In one embodiment, the endoscopic optical system satisfies the following condition:

[0026] 1.2≤|fG1 / f|≤2.5;

[0027] Where fG1 is the effective focal length of the first lens group.

[0028] In one embodiment, the endoscopic optical system satisfies the following condition:

[0029] 1.1≤fG2 / f≤1.6;

[0030] Where fG2 is the effective focal length of the second lens group.

[0031] In one embodiment, the endoscopic optical system satisfies the following condition:

[0032] 0.8 ≤ f34 / f ≤ 1.0;

[0033] Where f34 is the combined focal length of the third lens and the fourth lens.

[0034] In one embodiment, the endoscopic optical system satisfies the following condition:

[0035] 30≤Vd4-Vd5≤40;

[0036] Wherein, Vd4 is the Abbe number of the fourth lens at 587.56 nm (d line), and Vd5 is the Abbe number of the fifth lens at 587.56 nm (d line).

[0037] In one embodiment, the endoscopic optical system satisfies the following condition:

[0038] Nd5≥1.85;

[0039] Wherein, Nd5 is the refractive index of the fifth lens at 587.6 nm (d line).

[0040] An endoscope objective includes a photosensitive element and an endoscope optical system as described in any of the above embodiments, wherein the photosensitive element is disposed on the image side of the endoscope optical system.

[0041] An endoscope comprising the aforementioned endoscope objective.

[0042] The aforementioned endoscopic optical system, with its first lens group having negative optical power and second lens group having positive optical power forming a reverse telephoto structure, contributes to the maximum field of view of the endoscopic optical system and shortens its overall length. The first lens, with its negative optical power, helps to expand the field of view. The second lens, with its positive optical power, helps to correct aberrations generated by the first lens. The third and fourth lenses, with their positive optical power, help to shorten the overall length of the endoscopic optical system and effectively share the positive optical power required by the system, thus reducing its sensitivity. The fifth lens, with its negative optical power, helps to correct aberrations generated by the fourth lens and also helps to correct chromatic aberration. By satisfying 0.9 ≤ IH / f ≤ 1.1, the system expands the field of view to achieve wide-angle characteristics while also improving image quality, thus achieving a balance between wide-angle performance and high image quality. Below the lower limit of 0.9 ≤ IH / f ≤ 1.1, the field of view of the endoscopic optical system is too small, resulting in a smaller observation range of the lesion area during use, thus increasing the risk of missed diagnoses. Above the upper limit of 0.9 ≤ IH / f ≤ 1.1, the field of view of the endoscopic optical system is too large, resulting in severe deterioration of image quality at the edges of the field of view, which is not conducive to obtaining clear images of the lesion area and affects the accuracy of diagnosis.

[0043] The aforementioned endoscopic optical system achieves a balance between miniaturization, wide-angle capabilities, and high imaging quality. Attached Figure Description

[0044] Figure 1 This is a schematic diagram of the endoscope optical system in the first embodiment;

[0045] Figure 2A This is a field curvature astigmatism curve of the endoscope optical system in the first embodiment;

[0046] Figure 2B This is a distortion curve diagram of the endoscope optical system in the first embodiment;

[0047] Figure 2C This is a magnification chromatic aberration curve of the endoscope optical system in the first embodiment;

[0048] Figure 3 This is a schematic diagram of the endoscope optical system in the second embodiment;

[0049] Figure 4A This is a field curvature astigmatism curve of the endoscope optical system in the second embodiment;

[0050] Figure 4B This is a distortion curve of the endoscope optical system in the second embodiment;

[0051] Figure 4CThis is a magnification chromatic aberration curve of the endoscope optical system in the second embodiment;

[0052] Figure 5 This is a schematic diagram of the endoscope optical system in the third embodiment;

[0053] Figure 6A This is a field curvature astigmatism curve of the endoscope optical system in the third embodiment;

[0054] Figure 6B This is a distortion curve diagram of the endoscope optical system in the third embodiment;

[0055] Figure 6C This is a magnification chromatic aberration curve of the endoscope optical system in the third embodiment;

[0056] Figure 7 This is a schematic diagram of the endoscope optical system in the fourth embodiment;

[0057] Figure 8A This is a field curvature astigmatism curve of the endoscope optical system in the fourth embodiment;

[0058] Figure 8B This is a distortion curve diagram of the endoscope optical system in the fourth embodiment;

[0059] Figure 8C This is a magnification chromatic aberration curve of the endoscope optical system in the fourth embodiment;

[0060] Figure 9 This is a schematic diagram of the endoscope optical system in the fifth embodiment;

[0061] Figure 10A This is a field curvature astigmatism curve of the endoscopic optical system in the fifth embodiment;

[0062] Figure 10B This is a distortion curve diagram of the endoscope optical system in the fifth embodiment;

[0063] Figure 10C This is a magnification chromatic aberration curve of the endoscope optical system in the fifth embodiment. Detailed Implementation

[0064] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0065] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0066] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0067] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0068] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0069] It should be noted that when an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or there may be an intervening element. When an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation.

[0070] Please see Figure 1 In some embodiments of this application, the endoscopic optical system 100 includes, along the optical axis from the object side to the image side, a first lens group G1 with negative optical power and a second lens group G2 with positive optical power. The first lens group G1 with negative optical power and the second lens group G2 with positive optical power constitute a reverse telephoto structure, which helps to maximize the field of view of the endoscopic optical system 100 and shortens the overall length of the endoscopic optical system 100.

[0071] Specifically, the first lens group G1, along the optical axis from the object side to the image side, includes a first lens L1 with negative optical power and a second lens L2 with positive optical power. The second lens group G2, along the optical axis from the object side to the image side, includes a third lens L3 with positive optical power, a fourth lens L4 with positive optical power, and a fifth lens L5 with negative optical power. The first lens L1, with its negative optical power, helps to expand the field of view of the endoscope optical system 100. The second lens L2, with its positive optical power, helps to correct the aberrations generated by the first lens L1. The third lens, L3, and the fourth lens L4, with their positive optical power, help to shorten the overall length of the endoscope optical system 100 and effectively share the positive optical power required by the endoscope optical system 100, thus reducing the sensitivity of the endoscope optical system 100. The fifth lens L5, with its negative optical power, helps to correct the aberrations generated by the fourth lens L4 and also helps to correct the chromatic aberration of the endoscope optical system 100.

[0072] In some embodiments, the object-side and image-side surfaces of the third lens L3 and the fourth lens L4 are both convex surfaces, and their curvatures are the same. In other words, the third lens L3 and the fourth lens L4 have identical structures, and the object-side and image-side surfaces of both lenses are mirror-symmetrical. Setting the third lens L3 and the fourth lens L4 as identical biconvex lenses allows them to share a single tooling and mold during injection molding, thus reducing system processing costs. Furthermore, since the object-side and image-side surfaces of both the third lens L3 and the fourth lens L4 are mirror-symmetrical, there is no need to distinguish between them during system assembly, nor between their object-side and image-side surfaces. This improves system assembly efficiency and yield while maintaining miniaturization.

[0073] It is understood that the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, and the fifth lens L5 are coaxially arranged, and the common axis of all lenses in the endoscope optical system 100 is the optical axis of the endoscope optical system 100. The endoscope optical system 100 also includes an image plane IMA located on the image side of the fifth lens L5. The image plane IMA is the imaging surface of the endoscope optical system 100. After the incident light is adjusted by the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, and the fifth lens L5, it can be imaged onto the image plane IMA.

[0074] In some embodiments, the endoscope optical system 100 is provided with an aperture stop S, which can be positioned between the first lens group G1 and the second lens group G2, that is, between the second lens L2 and the third lens L3. The centrally positioned aperture stop S, combined with the anti-measuring structure formed by the first lens group G1 with negative optical power and the second lens group G2 with positive optical power, is beneficial for achieving a wide-angle and miniaturized endoscope optical system 100.

[0075] In some embodiments, the endoscope optical system 100 further includes a protective glass CG disposed between the fifth lens L5 and the image plane IMA, the protective glass CG being used to protect the photosensitive element disposed at the image plane IMA. In some embodiments, the endoscope optical system 100 further includes a filter F, the filter F being disposed between the second lens L2 and the third lens L3. The filter F is used to filter out interfering light, preventing interfering light from reaching the image plane IMA and affecting normal imaging. For example, the filter F can be an infrared cut-off filter, used to block light in the near-infrared region that may be sensed by the photosensitive element.

[0076] In some embodiments, the object-side and image-side surfaces of each lens in the endoscope optical system 100 are aspherical, meaning the surface shapes of the object-side and image-side surfaces of each lens may differ near the optical axis and around the circumference. The use of aspherical structures improves the flexibility of lens design and effectively corrects spherical aberration, thus improving image quality. In other embodiments, the object-side and image-side surfaces of each lens in the endoscope optical system 100 may also be spherical, meaning the surface shapes of the object-side and image-side surfaces of each lens are the same near the optical axis and around the circumference. It should be noted that the above embodiments are merely examples of some embodiments of this application; in some embodiments, the surface of each lens in the endoscope optical system 100 can be any combination of aspherical or spherical surfaces.

[0077] In some embodiments, the lenses in the endoscope optical system 100 can be made of either glass or plastic. Using plastic lenses reduces the weight of the endoscope optical system 100 and lowers production costs, while also allowing for a slimmer design due to the smaller size of the endoscope optical system 100. Using glass lenses provides the endoscope optical system 100 with excellent optical performance and high temperature resistance. It should be noted that the lenses in the endoscope optical system 100 can also be made of any combination of glass and plastic, and do not necessarily have to be made entirely of glass or entirely of plastic.

[0078] Furthermore, in some embodiments, the endoscopic optical system 100 satisfies the condition: 0.9 ≤ IH / f ≤ 1.1; where IH is half the image height corresponding to the maximum field of view of the endoscopic optical system 100, and f is the effective focal length of the endoscopic optical system 100. Specifically, IH / f can be: 0.985, 0.988, 0.992, 0.994, 0.995, 0.998, 1.002, 1.004, 1.006, or 1.008. When the above condition is satisfied, while expanding the field of view of the endoscopic optical system 100 to achieve wide-angle characteristics, it is also beneficial to improve the imaging quality of the endoscopic optical system 100, thereby achieving both wide-angle characteristics and high imaging quality. Below the lower limit of the above condition, the field of view of the endoscopic optical system 100 is too small, resulting in a smaller observation range of the lesion area during use, thereby increasing the risk of missed detection. If the upper limit of the above condition is exceeded, the field of view of the endoscope optical system 100 becomes too large, resulting in a severe deterioration of the image quality of the edge field of view, which is not conducive to obtaining clear images of the lesion area and affects the accuracy of diagnosis.

[0079] With the aforementioned optical power characteristics and satisfying the aforementioned conditions, the endoscope optical system 100 can achieve both miniaturization, wide-angle characteristics, and high imaging quality.

[0080] It should be noted that, in some embodiments, the endoscope optical system 100 can be matched with a photosensitive element having a rectangular photosensitive surface, and the image plane IMA of the endoscope optical system 100 coincides with the photosensitive surface of the photosensitive element. In this case, the effective pixel area on the image plane IMA has both a horizontal direction and a diagonal direction, so the maximum field of view can be understood as the maximum field of view of the endoscope optical system 100 in the diagonal direction, and IH can be understood as half the length of the effective pixel area in the diagonal direction on the image plane IMA of the endoscope optical system 100.

[0081] In addition, in this application, the image plane IMA can be understood as a virtual plane formed by the convergence point of system light rays on the image side of the fifth lens L5. When the endoscope optical system 100 is matched with the photosensitive element, the image plane IMA coincides with the photosensitive surface of the photosensitive element, so that the light rays adjusted by the system can form a clear image on the photosensitive surface.

[0082] In some embodiments, the endoscope optical system 100 satisfies the condition: 0.16 ≤ IH / TTL ≤ 0.19; where TTL is the distance on the optical axis from the object surface of the first lens L1 to the image plane IMA of the endoscope optical system 100, i.e., the total optical length of the endoscope optical system 100. Specifically, IH / TTL can be: 0.175, 0.176, 0.177, 0.178, 0.179, 0.180, or 0.183. Satisfying the above condition is beneficial for shortening the total length of the endoscope optical system 100, achieving miniaturization, and also beneficial for expanding the image plane IMA of the endoscope optical system 100, giving the endoscope optical system 100 a large image plane characteristic, thereby facilitating the matching of higher pixel photosensitive elements and obtaining good image quality. Below the lower limit of the above condition, the total length of the endoscope optical system 100 is too large, which is not conducive to meeting the requirements of miniaturization design. If the total length of the endoscope optical system 100 exceeds the upper limit of the above condition, it will be too small, which will increase the sensitivity of processing and manufacturing, thereby reducing the production yield of the endoscope optical system 100; at the same time, it will also result in insufficient space for the endoscope optical system 100 to deflect light, which is not conducive to improving the imaging quality.

[0083] In some embodiments, the endoscopic optical system 100 satisfies the condition: 0.6 ≤ LG1 / LG2 ≤ 1.0; where LG1 is the distance on the optical axis from the object side of the first lens L1 to the aperture S, and LG2 is the distance on the optical axis from the aperture S to the image side of the fifth lens L5. Specifically, LG1 / LG2 can be: 0.696, 0.705, 0.733, 0.769, 0.811, 0.833, 0.854, 0.893, 0.901, or 0.924. Satisfying the above condition is beneficial for reducing the maximum effective aperture of the first lens L1 and the fifth lens L5, thereby facilitating the miniaturization design of the endoscopic imaging system 100. Exceeding the upper limit of the above condition increases the maximum effective aperture on the object side of the first lens L1, which is detrimental to the realization of miniaturization design. Below the lower limit of the above condition, the maximum effective aperture on the image side of the fifth lens L5 increases, which is also detrimental to the realization of miniaturization design.

[0084] In some embodiments, the endoscope optical system 100 satisfies the condition: 0.3 ≤ d1 / f ≤ 0.5; where d1 is the thickness of the first lens L1 along the optical axis, i.e., the center thickness of the first lens L1. Specifically, d1 / f can be: 0.365, 0.368, 0.370, 0.373, 0.382, 0.388, 0.395, 0.402, 0.411, or 0.419. Satisfying the above condition is beneficial for the processing and assembly of the first lens L1, and also for the miniaturization design of the endoscope optical system 100. Below the lower limit of the above condition, the center thickness of the first lens L1 is too small, making the first lens L1 prone to breakage during processing and assembly. Above the upper limit of the above condition, the center thickness of the first lens L1 is too large, resulting in an increased incident height of light on the first lens L1, which is detrimental to improving image quality and also hinders the miniaturization design of the endoscope optical system 100.

[0085] In some embodiments, the endoscope optical system 100 satisfies the condition: 0.9 ≤ Bf / f ≤ 1.5; where Bf is the distance on the optical axis from the image-side surface of the fifth lens L5 to the image plane IMA of the endoscope optical system 100, i.e., the back focal length of the endoscope optical system 100. Specifically, Bf / f can be: 0.921, 0.935, 0.955, 0.974, 1.011, 1.098, 1.114, 1.222, 1.255, or 1.284. Satisfying the above condition is beneficial to improving the assembly yield of the endoscope optical system 100, and also beneficial to the miniaturization design of the endoscope optical system 100. Below the lower limit of the above condition, the back focal length of the endoscope optical system 100 is too short, resulting in insufficient focusing space during assembly, thereby leading to a decrease in assembly yield. Above the upper limit of the above condition, the back focal length of the endoscope optical system 100 is too long, which is not conducive to achieving miniaturization design.

[0086] In some embodiments, the endoscope optical system 100 satisfies the condition: 0.6 ≤ R2 / SD12 ≤ 0.78; where R2 is the radius of curvature of the image-side surface of the first lens L1 at the optical axis, and SD12 is the maximum effective aperture of the image-side surface of the first lens L1. Specifically, R2 / SD12 can be: 0.678, 0.680, 0.683, 0.684, 0.685, 0.687, 0.689, 0.690, 0.692, or 0.693. Satisfying the above condition helps to reduce the radial dimension of the first lens L1, thereby facilitating the miniaturization design of the endoscope optical system 100. Exceeding the upper limit of the above condition results in an overly flat image-side surface of the first lens L1, reducing the optical power of the first lens L1, which leads to an increase in the incident height of light on the first lens L1, and consequently, an increase in the radial dimension of the first lens L1, which is detrimental to the miniaturization design of the endoscope optical system 100.

[0087] In some embodiments, the endoscope optical system 100 satisfies the condition: 1.2 ≤ |fG1 / f| ≤ 2.5; where fG1 is the effective focal length of the first lens group G1. Specifically, |fG1 / f| can be: 1.390, 1.425, 1.551, 1.638, 1.748, 1.892, 1.902, 2.133, 2.203, or 2.237. Satisfying the above condition expands the field of view while also shortening the overall length of the endoscope optical system 100, thus achieving both wide-angle characteristics and miniaturization. Exceeding the upper limit of the above condition results in a small optical focal length for the first lens group G1, which is detrimental to achieving wide-angle characteristics. Simultaneously, the distance from the first lens L1 to the aperture stop S on the optical axis increases, leading to an increased incident height of light on the first lens L1, which is detrimental to miniaturization. If the optical focal length of the first lens is too large, it will increase the incident height of light on the first lens L1 while achieving wide-angle characteristics, which is not conducive to the miniaturization design of the endoscope optical system 100.

[0088] In some embodiments, the endoscope optical system 100 satisfies the condition: 1.1 ≤ fG2 / f ≤ 1.6; where fG2 is the effective focal length of the second lens group G2. Specifically, fG2 / f can be: 1.114, 1.134, 1.158, 1.225, 1.287, 1.304, 1.369, 1.393, 1.402, or 1.425. Satisfying the above condition is beneficial for the assembly and focusing of the endoscope optical system 100, and also for the realization of miniaturization design. Below the lower limit of the above condition, the optical focal length of the second lens group G2 is too large, resulting in an excessively short back focal length, which is detrimental to the assembly and focusing of the endoscope optical system 100. Above the upper limit of the above condition, the optical focal length of the second lens G2 is too small, resulting in an excessively long back focal length, which is detrimental to the realization of miniaturization design.

[0089] In some embodiments, the endoscope optical system 100 satisfies the condition: 0.8 ≤ f34 / f ≤ 1.0; where f34 is the combined focal length of the third lens L3 and the fourth lens L4. Specifically, f34 / f can be: 0.891, 0.902, 0.914, 0.925, 0.937, 0.944, 0.958, 0.967, 0.972, or 0.983. Satisfying the above condition is beneficial for the processing and assembly of the third lens L3 and the fourth lens L4, and also for the miniaturization design of the endoscope optical system 100. Below the lower limit of the above condition, the combined focal length of the third lens L3 and the fourth lens L4 is too large, resulting in excessive curvature of the surface of the third lens L3 and the fourth lens L4, which is detrimental to the processing and assembly of the third lens L3 and the fourth lens L4. If the upper limit of the above conditional expression is exceeded, the combined optical focal length of the third lens L3 and the fourth lens L4 is too small, resulting in a larger overall length of the endoscope optical system 100, which is not conducive to the realization of miniaturization design.

[0090] In some embodiments, the endoscopic optical system 100 satisfies the condition: 30 ≤ Vd4 - Vd5 ≤ 40; where Vd4 is the Abbe number of the fourth lens L4 at 587.56 nm (d line), and Vd5 is the Abbe number of the fifth lens L5 at 587.56 nm (d line). Specifically, Vd4-Vd5 can be: 32.1, 32.3, 32.5, 32.7, 32.8, 33.0, 33.1, 33.2, 33.5, or 33.8. Satisfying the above condition allows for a reasonable configuration of the difference in Abbe numbers between the fourth lens L4 and the fifth lens L5, which is beneficial for effectively correcting aberrations such as chromatic aberration, coma, and astigmatism, thereby improving image quality. Below the lower limit of the above condition, the difference in Abbe numbers between the fourth lens L4 and the fifth lens L5 is too small, which is not conducive to the correction of chromatic aberration. If the Abbe number of the fourth lens L4 exceeds the upper limit of the above conditional expression, the refractive index of the fourth lens L4 will be too small, which is not conducive to correcting aberrations such as coma and astigmatism.

[0091] In some embodiments, the endoscopic optical system 100 satisfies the condition: Nd5 ≥ 1.85; where Nd5 is the refractive index of the fifth lens L5 at 587.6 nm (d-line). Satisfying this condition means the fifth lens L5 is a high-refractive-index negative-power lens, which helps reduce the absolute value of the Petzval sum of the endoscopic optical system 100, corrects the field curvature of the endoscopic optical system 100, and thus improves image quality. Below the lower limit of the condition, the absolute value of the Petzval sum of the endoscopic optical system 100 is too large, making it difficult to effectively correct the field curvature, which is detrimental to improving image quality.

[0092] The reference wavelength for the above effective focal length and combined focal length values ​​is 587.6 nm (d line).

[0093] Based on the descriptions of the above embodiments, more specific embodiments and accompanying drawings are provided below for detailed explanation.

[0094] First Embodiment

[0095] Please see again. Figure 1 , Figure 1 This is a schematic diagram of the endoscope optical system 100 in the first embodiment. The endoscope optical system 100 includes, from the object side to the image side, a first lens L1 with negative optical power, a second lens L2 with positive optical power, an aperture S, a filter F, a third lens L3 with positive optical power, a fourth lens L4 with positive optical power, a fifth lens L5 with negative optical power, and a protective glass CG.

[0096] The object-side surface and image-side surface of the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, and the fifth lens L5 are all spherical.

[0097] The object-side surface of the first lens L1 is flat, and the image-side surface is concave.

[0098] The object-side surface of the second lens L2 is convex, while the image-side surface is planar.

[0099] The object-side surface of the third lens L3 is convex, and the image-side surface is also convex.

[0100] The object-side surface of the fourth lens L4 is convex, and the image-side surface is also convex.

[0101] The object-side surface of the fifth lens L5 is concave, while the image-side surface is flat.

[0102] Table 1 below shows detailed parameters of each lens in the endoscope optical system 100 in the first embodiment, including radius of curvature, thickness, refractive index, Abbe number, effective focal length f, maximum field of view 2ω, and effective aperture value FNO. The reference wavelength for the refractive index and Abbe number of each lens is 587.6 nm, and this is also true in other embodiments. The image plane IMA in Table 1 can be understood as the imaging plane of the endoscope optical system 100. The elements from the object plane (not shown) to the image plane IMA are arranged sequentially from top to bottom according to the elements in Table 1. The first row of the first lens L1 represents the object-side surface of the first lens L1, the second row represents the image-side surface of the first lens L1, and so on. The first value in the "thickness" parameter column of the first lens L1 is the thickness of the first lens L1 on the optical axis 110, and the second value is the distance from the image-side surface of the first lens L1 to the rear surface in the image-side direction (the object-side surface of the second lens L2) on the optical axis 110. The meanings of the other values ​​in the thickness parameter column can be deduced from this.

[0103] It should be noted that in this embodiment and the following embodiments, the endoscope optical system 100 may also omit the filter F and the protective glass CG, but in this case, the distance from the image side of the second lens L2 to the object side of the third lens L3 and the distance from the image side of the fifth lens L5 to the image plane IMA remains unchanged.

[0104] Table 1

[0105]

[0106] In addition, the values ​​of each conditional expression of the endoscope optical system 100 in the first embodiment are detailed in Table 6. The effects of each conditional expression can be referred to the above description. The values ​​of each conditional expression in the second, third, fourth and fifth embodiments can also be obtained from Table 6, and will not be repeated hereafter.

[0107] Please see Figure 2A , Figure 2B and Figure 2C . Figure 2A This is a field curvature astigmatism curve of the endoscope optical system 100 in the first embodiment, generated by... Figure 2A It can be seen that the sagittal field curvature and meridional field curvature of the endoscope optical system 100 are both small, and the field curvature and astigmatism of each field of view are well corrected. The center and edge of the field of view have clear imaging, which is conducive to the endoscope optical system 100 obtaining a large depth of field effect.

[0108] Figure 2B This is a distortion curve diagram of the endoscope optical system 100 in the first embodiment, from... Figure 2B It can be seen that the distortion of the maximum field of view of the endoscope optical system 100 is less than 60%, the distortion within the effective observation field of view is less than 50%, the image distortion caused by the main beam is small, and the imaging quality of the system is excellent. Among them, the reference wavelength for the field curvature astigmatism curve and the distortion curve is 587.6nm, and the same applies to other embodiments.

[0109] Figure 2C This is a magnification chromatic aberration curve of the endoscope optical system 100 in the first embodiment, derived from... Figure 2C It can be seen that the maximum difference between the wavelengths of 656.3nm and 486.1nm is less than 2µm, indicating that the magnification chromatic aberration of the 100-magnification endoscope optical system is well corrected and has good imaging quality.

[0110] Second Embodiment

[0111] Please see Figure 3 , Figure 3This is a schematic diagram of the endoscope optical system 100 in the second embodiment. The endoscope optical system 100 includes, from the object side to the image side, a first lens L1 with negative optical power, a second lens L2 with positive optical power, an aperture S, a filter F, a third lens L3 with positive optical power, a fourth lens L4 with positive optical power, a fifth lens L5 with negative optical power, and a protective glass CG.

[0112] The object-side surface and image-side surface of the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, and the fifth lens L5 are all spherical.

[0113] The object-side surface of the first lens L1 is flat, and the image-side surface is concave.

[0114] The object-side surface of the second lens L2 is convex, and the image-side surface is also convex.

[0115] The object-side surface of the third lens L3 is convex, and the image-side surface is also convex.

[0116] The object-side surface of the fourth lens L4 is convex, and the image-side surface is also convex.

[0117] The object side of the fifth lens L5 is concave, and the image side is convex.

[0118] In addition, the parameters of the endoscope optical system 100 are given in Table 2, and the definitions of each parameter can be derived from the first embodiment, and will not be repeated here.

[0119] Table 2

[0120]

[0121] Please see Figure 4A , Figure 4B and Figure 4C . Figure 4A This is a field curvature astigmatism curve of the endoscope optical system 100 in the second embodiment, generated by... Figure 4A It can be seen that the sagittal field curvature and meridional field curvature of the endoscope optical system 100 are both small, and the field curvature and astigmatism of each field of view are well corrected. The center and edge of the field of view have clear imaging, which is conducive to the endoscope optical system 100 obtaining a large depth of field effect.

[0122] Figure 4B This is a distortion curve diagram of the endoscope optical system 100 in the second embodiment, from... Figure 4B It can be seen that the endoscope optical system 100 has small distortion, the image distortion caused by the main beam is small, and the imaging quality of the system is excellent.

[0123] Figure 4C This is a magnification chromatic aberration curve of the endoscope optical system 100 in the second embodiment, derived from... Figure 4CIt can be seen that the magnification chromatic aberration of the endoscopic optical system 100 has been well corrected, resulting in good imaging quality.

[0124] Third Embodiment

[0125] Please see Figure 5 , Figure 5 This is a schematic diagram of the endoscope optical system 100 in the third embodiment. The endoscope optical system 100 includes, from the object side to the image side, a first lens L1 with negative optical power, a second lens L2 with positive optical power, an aperture S, a filter F, a third lens L3 with positive optical power, a fourth lens L4 with positive optical power, a fifth lens L5 with negative optical power, and a protective glass CG.

[0126] The object-side surface and image-side surface of the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, and the fifth lens L5 are all spherical.

[0127] The object-side surface of the first lens L1 is flat, and the image-side surface is concave.

[0128] The object-side surface of the second lens L2 is convex, while the image-side surface is planar.

[0129] The object-side surface of the third lens L3 is convex, and the image-side surface is also convex.

[0130] The object-side surface of the fourth lens L4 is convex, and the image-side surface is also convex.

[0131] The object side of the fifth lens L5 is concave, and the image side is convex.

[0132] In addition, the parameters of the endoscope optical system 100 are given in Table 3, and the definitions of each parameter can be derived from the first embodiment, and will not be repeated here.

[0133] Table 3

[0134]

[0135] Please see Figure 6A , Figure 6B and Figure 6C . Figure 6A This is a field curvature astigmatism curve of the endoscope optical system 100 in the third embodiment, generated by... Figure 6A It can be seen that the sagittal field curvature and meridional field curvature of the endoscope optical system 100 are both small, and the field curvature and astigmatism of each field of view are well corrected. The center and edge of the field of view have clear imaging, which is conducive to the endoscope optical system 100 obtaining a large depth of field effect.

[0136] Figure 6B This is a distortion curve diagram of the endoscope optical system 100 in the third embodiment, from... Figure 6BIt can be seen that the endoscope optical system 100 has small distortion, the image distortion caused by the main beam is small, and the imaging quality of the system is excellent.

[0137] Figure 6C This is a magnification chromatic aberration curve of the endoscope optical system 100 in the third embodiment, derived from... Figure 6C It can be seen that the magnification chromatic aberration of the endoscopic optical system 100 has been well corrected, resulting in good imaging quality.

[0138] Fourth embodiment

[0139] Please see Figure 7 , Figure 7 This is a schematic diagram of the endoscope optical system 100 in the fourth embodiment. The endoscope optical system 100 includes, from the object side to the image side, a first lens L1 with negative optical power, a second lens L2 with positive optical power, an aperture S, a filter F, a third lens L3 with positive optical power, a fourth lens L4 with positive optical power, a fifth lens L5 with negative optical power, and a protective glass CG.

[0140] The object-side surface and image-side surface of the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, and the fifth lens L5 are all spherical.

[0141] The object-side surface of the first lens L1 is flat, and the image-side surface is concave.

[0142] The object-side surface of the second lens L2 is convex, and the image-side surface is also convex.

[0143] The object-side surface of the third lens L3 is convex, and the image-side surface is also convex.

[0144] The object-side surface of the fourth lens L4 is convex, and the image-side surface is also convex.

[0145] The object side of the fifth lens L5 is concave, and the image side is convex.

[0146] In addition, the parameters of the endoscope optical system 100 are given in Table 4, and the definitions of each parameter can be derived from the first embodiment, and will not be repeated here.

[0147] Table 4

[0148]

[0149] Please see Figure 8A , Figure 8B and Figure 8C . Figure 8A This is a field curvature astigmatism curve of the endoscope optical system 100 in the fourth embodiment, generated by... Figure 8AIt can be seen that the sagittal field curvature and meridional field curvature of the endoscope optical system 100 are both small, and the field curvature and astigmatism of each field of view are well corrected. The center and edge of the field of view have clear imaging, which is conducive to the endoscope optical system 100 obtaining a large depth of field effect.

[0150] Figure 8B This is a distortion curve diagram of the endoscope optical system 100 in the fourth embodiment, from... Figure 8B It can be seen that the endoscope optical system 100 has small distortion, the image distortion caused by the main beam is small, and the imaging quality of the system is excellent.

[0151] Figure 8C This is a magnification chromatic aberration curve of the endoscope optical system 100 in the fourth embodiment, derived from... Figure 8C It can be seen that the magnification chromatic aberration of the endoscopic optical system 100 has been well corrected, resulting in good imaging quality.

[0152] Fifth embodiment

[0153] Please see Figure 9 , Figure 9 This is a schematic diagram of the endoscope optical system 100 in the fifth embodiment. The endoscope optical system 100 includes, from the object side to the image side, a first lens L1 with negative optical power, a second lens L2 with positive optical power, an aperture S, a filter F, a third lens L3 with positive optical power, a fourth lens L4 with positive optical power, a fifth lens L5 with negative optical power, and a protective glass CG.

[0154] The object-side surface and image-side surface of the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, and the fifth lens L5 are all spherical.

[0155] The object-side surface of the first lens L1 is flat, and the image-side surface is concave.

[0156] The object side of the second lens L2 is convex, and the image side is concave.

[0157] The object-side surface of the third lens L3 is convex, and the image-side surface is also convex.

[0158] The object-side surface of the fourth lens L4 is convex, and the image-side surface is also convex.

[0159] The object side of the fifth lens L5 is concave, and the image side is convex.

[0160] In addition, the parameters of the endoscope optical system 100 are given in Table 5, and the definitions of each parameter can be derived from the first embodiment, and will not be repeated here.

[0161] Table 5

[0162]

[0163] Please see Figure 10A , Figure 10B and Figure 10C . Figure 10A This is a field curvature astigmatism curve of the endoscope optical system 100 in the fifth embodiment, derived from... Figure 10A It can be seen that the sagittal field curvature and meridional field curvature of the endoscope optical system 100 are both small, and the field curvature and astigmatism of each field of view are well corrected. The center and edge of the field of view have clear imaging, which is conducive to the endoscope optical system 100 obtaining a large depth of field effect.

[0164] Figure 10B This is a distortion curve diagram of the endoscope optical system 100 in the fifth embodiment, from... Figure 10B It can be seen that the endoscope optical system 100 has small distortion, the image distortion caused by the main beam is small, and the imaging quality of the system is excellent.

[0165] Figure 10C This is a magnification chromatic aberration curve of the endoscope optical system 100 in the fifth embodiment, derived from... Figure 10C It can be seen that the magnification chromatic aberration of the endoscopic optical system 100 has been well corrected, resulting in good imaging quality.

[0166] Table 6

[0167]

[0168]

[0169] This application also provides an endoscope objective (not shown), including a photosensitive element and the endoscope optical system 100 described in any of the above embodiments. The photosensitive surface of the photosensitive element coincides with the image plane IMA of the endoscope optical system 100. Specifically, the photosensitive element can be a charge-coupled device (CCD) or a complementary metal-oxide-semiconductor sensor (CMOS sensor). Using the above-described endoscope optical system 100 in the endoscope objective achieves a balance between miniaturization, wide-angle characteristics, and high image quality, thereby facilitating the application of the endoscope objective in endoscopes.

[0170] This application also provides an endoscope (not shown), including a housing and an endoscope objective as described in any of the above embodiments. The endoscope objective is disposed within the housing, which can be the tube of the endoscope objective. Endoscopes can be applied in the medical field, such as for medical diagnosis of patients. Specifically, endoscopes include, but are not limited to, endoscopes used to observe digestive organs, bronchi, nasal cavity, pharynx, urinary organs, and uterus. By using the aforementioned endoscope objective in an endoscope, the endoscope objective can achieve a combination of miniaturization, wide-angle characteristics, and high imaging quality. This allows the endoscope to be used in the medical field to minimize damage to patients, acquire images of lesion areas over a wide area to avoid missed diagnoses, and form high-resolution images of lesions, improving diagnostic accuracy.

[0171] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0172] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. An endoscope optical system, characterized in that, Along the optical axis from the object side to the image side, it sequentially includes a first lens group with negative optical power, an aperture stop, and a second lens group with positive optical power. The first lens group, along the optical axis from the object side to the image side, sequentially includes a first lens with negative optical power and a second lens with positive optical power. The second lens group, along the optical axis from the object side to the image side, sequentially includes a third lens with positive optical power, a fourth lens with positive optical power, and a fifth lens with negative optical power. The image side of the first lens is concave. Furthermore, the endoscopic optical system satisfies the following condition: 0.9≤IH / f≤1.1; Wherein, IH is half the image height corresponding to the maximum field of view of the endoscope optical system, and f is the effective focal length of the endoscope optical system.

2. The endoscopic optical system according to claim 1, characterized in that, The object-side and image-side surfaces of the third lens and the fourth lens are both convex surfaces, and the curvatures of the object-side and image-side surfaces of the third lens and the fourth lens are the same.

3. The endoscopic optical system according to claim 1, characterized in that, The following conditions must be met: 0.16≤IH / TTL≤0.19; Wherein, TTL is the distance on the optical axis from the object side of the first lens to the imaging surface of the endoscope optical system.

4. The endoscopic optical system according to claim 1, characterized in that, The following conditions must be met: 0.6≤LG1 / LG2≤1.0; Wherein, LG1 is the distance from the object side of the first lens to the aperture on the optical axis, and LG2 is the distance from the aperture to the image side of the fifth lens on the optical axis.

5. The endoscopic optical system according to claim 1, characterized in that, The following conditions must be met: 0.3≤d1 / f≤0.5; Where d1 is the thickness of the first lens on the optical axis.

6. The endoscopic optical system according to claim 1, characterized in that, The following conditions must be met: 0.9≤Bf / f≤1.5; Wherein, Bf is the distance on the optical axis from the image side of the fifth lens to the imaging surface of the endoscope optical system.

7. The endoscopic optical system according to claim 1, characterized in that, The following conditions must be met: 0.6 ≤ R² / SD12 ≤ 0.78; Wherein, R2 is the radius of curvature of the image-side surface of the first lens at the optical axis, and SD12 is the maximum effective aperture of the image-side surface of the first lens.

8. The endoscopic optical system according to claim 1, characterized in that, The following conditions must be met: 1.2≤|fG1 / f|≤2.5; Where fG1 is the effective focal length of the first lens group.

9. The endoscopic optical system according to claim 1, characterized in that, The following conditions must be met: 1.1≤fG2 / f≤1.6; Where fG2 is the effective focal length of the second lens group.

10. The endoscopic optical system according to claim 1, characterized in that, The following conditions must be met: 0.8 ≤ f34 / f ≤ 1.0; Wherein, f34 is the combined focal length of the third lens and the fourth lens.

11. An endoscope objective, characterized in that, Includes a photosensitive element and an endoscope optical system according to any one of claims 1-10, wherein the photosensitive element is disposed on the image side of the endoscope optical system.

12. An endoscope, characterized in that, Includes the endoscope objective as described in claim 11.

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