Symmetrical endoscope relay objective lens with long conjugate distance

Abstract

The invention discloses a long conjugate distance symmetric endoscope relay objective lens, which relates to the technical field of endoscope optics and comprises a first lens group, an aperture diaphragm and a second lens group. The first lens group comprises a first lens, a second lens, a third lens and a fourth lens which are sequentially arranged from the object side to the image side along the optical axis; the aperture diaphragm is arranged on the image side of the first lens group; the second lens group is arranged on the image side of the aperture diaphragm and is arranged in mirror symmetry with the first lens group relative to the aperture diaphragm; wherein the first lens is a negative-focal-length meniscus lens, the second lens is a positive-focal-length approximate plano-convex lens, the third lens is a negative-focal-length meniscus lens, the fourth lens is a positive-focal-length meniscus lens, and the second lens, the third lens and the fourth lens form a triplet lens group by adopting a gluing process. According to the invention, a symmetric optical architecture is adopted, aberration can be effectively corrected, the conjugate distance is increased, the splicing number of relay objective lenses is reduced, the assembly difficulty is reduced, and the system is suitable for visible light and near-infrared light imaging scenes.

Description

Technical Field

[0001] This invention relates to the field of endoscopy technology, and in particular to an endoscopy relay objective with a long conjugate distance symmetry. Background Technology

[0002] Minimally invasive surgery now relies heavily on endoscopic imaging systems, and the rigid endoscope at the front end of these systems is an optical device that penetrates deep into the human body to directly observe human tissues; it is one of the core components of any endoscopic imaging system. The current optical design of rigid endoscopes on the market consists of: an objective lens, a relay objective lens, and an eyepiece. The relay objective lens plays a crucial role in rigid endoscope imaging, including long-distance image stitching, maintaining resolution and brightness, correcting optical aberrations, and adapting to the constraints of rigid structures. There are two existing relay objective design schemes. One is to directly customize the relay objective based on the total length of the required relay imaging optical path without using symmetrical group splicing. The advantage is that it can better correct optical aberrations and obtain better image quality. The disadvantage is that customization leads to higher costs, and there is no assembly compensation for secondary or tertiary imaging between the lens groups, which places high demands on the precision of the rigid lens assembly. The second is to use a symmetrical splicing optical design. The advantage is that the symmetrical lens groups facilitate the assembly of rigid lenses, and the number of splicing lenses required can be calculated based on the total length of the actual relay imaging optical path and the imaging requirements of the front-end objective. The disadvantage is that as the number of spliced ​​relay objectives increases, the residual aberrations in the imaging will have a cumulative effect. This requires that the design aberration margin of each individual relay objective be small enough, otherwise the relay imaging effect will be compromised, thus increasing the difficulty of optical design.

[0003] To address the aforementioned problems, this invention proposes a long conjugate distance symmetrical endoscope relay objective to solve the technical problems of existing relay objectives, such as large cumulative aberration effects, poor versatility, difficult assembly, and high cost. Summary of the Invention

[0004] The purpose of this section is to outline some aspects of the embodiments of the present invention and to briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section, as well as in the abstract and title of the invention, to avoid obscuring the purpose of this section, the abstract and title of the invention, and such simplifications or omissions shall not be used to limit the scope of the invention.

[0005] In view of the problems of large cumulative aberration effects, poor versatility, high assembly precision requirements and high cost of existing endoscope relay objectives, this invention is proposed.

[0006] Therefore, the problem to be solved by this invention is how to increase the conjugate distance of the relay objective while ensuring imaging quality, so as to reduce the number of stitches, reduce the cumulative aberration effect, improve the versatility of the relay objective, and reduce the assembly difficulty.

[0007] To solve the above-mentioned technical problems, the present invention provides the following technical solution: In a first aspect, embodiments of the present invention provide a long conjugate distance symmetrical endoscope relay objective, comprising a first lens group, an aperture stop, and a second lens group, wherein... The first lens group includes a first lens 101, a second lens 102, a third lens 103 and a fourth lens 104 arranged sequentially from the object side to the image side along the optical axis; The aperture stop is disposed on the image side of the first lens group; The second lens group is disposed on the image side of the aperture stop, and the second lens group is arranged in a mirror symmetrical manner with respect to the aperture stop and the first lens group; The first lens 101 is a meniscus lens with a negative focal length; the second lens 102 is an approximately plano-convex lens with a positive focal length; the third lens 103 is a meniscus lens with a negative focal length; and the fourth lens 104 is a meniscus lens with a positive focal length. The second lens 102, the third lens 103, and the fourth lens 104 are assembled into a three-cemented lens group using a cementing process.

[0008] As a preferred embodiment of the symmetrical endoscope relay objective with long conjugate distance described in this invention, the total conjugate length of the endoscope relay objective is 140mm to 150mm, and the magnification is -1.

[0009] As a preferred embodiment of the long conjugate distance symmetrical endoscope relay objective of the present invention, the diameter of the endoscope relay objective is 3mm to 6mm.

[0010] As a preferred embodiment of the long conjugate distance symmetrical endoscope relay objective of the present invention, wherein the F-number of the endoscope relay objective is less than or equal to 5.

[0011] As a preferred embodiment of the long conjugate distance symmetrical endoscope relay objective of the present invention, the first lens 101 has a focal length range of -115mm to -125mm, a refractive index range of 1.90 to 2.0, and an Abbe number range of 25 to 35.

[0012] As a preferred embodiment of the long conjugate distance symmetrical endoscope relay objective of the present invention, wherein: the focal length of the triple cemented lens group is in the range of 28mm to 37mm, the refractive index is in the range of 1.7 to 2.0, and the Abbe number is in the range of 25 to 65.

[0013] As a preferred embodiment of the long conjugate distance symmetrical endoscope relay objective of the present invention, wherein the modulation transfer function (MTF) value of the endoscope relay objective is greater than 0.2 at a spatial frequency of 250 lp / mm.

[0014] As a preferred embodiment of the long conjugate distance symmetrical endoscope relay objective of the present invention, the endoscope relay objective is suitable for imaging scenarios of visible light and near-infrared light.

[0015] Secondly, embodiments of the present invention provide an endoscope, which includes: a relay lens disposed between the objective lens and the eyepiece.

[0016] Compared with existing technologies, the advantages of this invention are as follows: The endoscope relay objective adopts a symmetrical optical design architecture, including a first lens group and a second lens group arranged in a mirror-symmetric manner with respect to the aperture stop. This allows for the mutual cancellation of on-axis and off-axis aberrations with fewer lens surfaces and materials, achieving superior imaging quality for the relay objective. Simultaneously, by increasing the object-image conjugate distance, the number of relay objectives used in the relay imaging optical path is reduced, thereby reducing the cumulative aberration effect. The special optical surface design and optimized combination of optical materials enable excellent imaging quality in both white light and fluorescence scenarios. The fewer individual lenses greatly facilitate assembly and debugging in actual optical production, reducing the loss of optical imaging resolution caused by assembly and meeting the needs of low-cost mass production. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein: Figure 1 This is a schematic diagram of the structure of the symmetrical endoscope relay objective lens with long conjugate distance in an embodiment of the present invention; Figure 2 This is a schematic diagram of the structure for increasing the relay imaging optical path length of the long conjugate distance symmetrical endoscope relay objective in an embodiment of the present invention; Figure 3 This is a relative illumination curve of the relay objective lens in a symmetrical endoscope with a long conjugate distance in an embodiment of the present invention. Figure 4 This is a dot diagram of the symmetrical endoscope relay objective lens with long conjugate distance in an embodiment of the present invention; Figure 5 This is a modulation transfer function (MTF) curve of the long conjugate distance symmetrical endoscope relay objective in an embodiment of the present invention; Explanation of reference numerals in the attached drawings: First lens 101, second lens 102, third lens 103, fourth lens 104, relay objective 201, and relay objective 202. Detailed Implementation

[0018] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0019] Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without inventive effort should fall within the scope of protection of this invention.

[0020] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0021] As mentioned in the background section, existing endoscopic relay objectives suffer from problems such as large cumulative aberration effects, poor versatility, high assembly precision requirements, and high cost. To address these issues, this invention provides a long conjugate distance symmetrical endoscopic relay objective. By setting the structure and parameters of each optical element in the endoscopic relay objective, it achieves an optical structure with symmetrical arrangement about the aperture stop. This satisfies the requirement of a long conjugate distance while the approximate symmetry of the optical surfaces of each optical element mutually cancels out some aberrations, resulting in smaller aberrations in endoscopic imaging. Furthermore, the endoscopic relay objective has lower tolerance sensitivity, meeting the needs of low-cost mass production.

[0022] Please refer to the long conjugate distance symmetrical endoscope relay objective disclosed in the embodiments of this invention. Figures 1-5 The endoscope relay objective adopts a symmetrical optical design architecture, including: a first lens group, an aperture stop, and a second lens group. The first lens group includes a first lens 101, a second lens 102, a third lens 103, and a fourth lens 104 arranged sequentially from the object side to the image side along the optical axis. The aperture stop is located on the image side of the first lens group and is used to limit the beam imaging aperture. The second lens group is located on the image side of the aperture stop and is arranged in a mirror-symmetric manner with respect to the aperture stop. The second lens group includes a fifth lens, a sixth lens, a seventh lens, and an eighth lens arranged sequentially from the object side to the image side along the optical axis.

[0023] Specifically, the first lens 101 is a meniscus lens with a negative focal length; the second lens 102 is an approximately plano-convex lens with a positive focal length; the third lens 103 is a meniscus lens with a negative focal length; and the fourth lens 104 is a meniscus lens with a positive focal length. The second lens 102, the third lens 103, and the fourth lens 104 are bonded together using a cementing process to form a three-layer cemented lens group. They are bonded together with UV-cured resin glue, and the centering deviation is controlled to form a relatively long lens group with a positive focal length.

[0024] Furthermore, the relay objective employs a symmetrical optical design architecture, which can cancel out on-axis and off-axis aberrations with fewer lens surfaces and materials, resulting in superior imaging quality. The relay objective of this invention has a diameter controlled between 3mm and 6mm and is symmetrically arranged about the central aperture, effectively correcting optical aberrations and facilitating the assembly of the entire rigid lens.

[0025] In an optional embodiment, the first lens 101 has a focal length ranging from -115mm to -125mm, a refractive index ranging from 1.90 to 2.0, and an Abbe number ranging from 25 to 35.

[0026] In an optional embodiment, the focal length of the triplex lens group ranges from 28 mm to 37 mm, the refractive index ranges from 1.7 to 2.0, and the Abbe number ranges from 25 to 65.

[0027] In an optional embodiment, the total conjugate length of the object-image relay objective is 140mm to 150mm, with a magnification of -1 and an F-number of 5 or less. By increasing the object-image conjugate distance, the number of relay objectives can be increased according to the distance between the rigid endoscope and the relay imaging optical path. Only a small number of relay objectives are needed to complete the standard relay imaging optical path distance, so the accumulated optical aberrations are very small and can be basically ignored.

[0028] In optional embodiments, the special optical lens surface shape and optical material combination design enable the relay objective to have high imaging quality not only in visible light scenarios but also in near-infrared light scenarios, thus increasing the application scenarios of the relay objective in fluorescence surgery.

[0029] Furthermore, such as Figure 2 As shown, if it is necessary to increase the length of the relay imaging optical path, it is done by splicing. The image plane of the relay objective 201 coincides with the object plane of the relay objective 202. After the relay objective 201 is placed in the mirror cavity, the relay objective 202 is placed in a mirror-symmetrical manner with respect to the image plane of the relay objective 201. Because the conjugate distance of the relay objective increases, only two sets of relay objectives are needed to meet the relay imaging optical path requirements of most rigid mirrors.

[0030] Specifically, the relay objectives can be compatible with any objective and eyepiece in terms of object height and image height, increasing their versatility and serving as a platform-based common accessory for the same product category. Furthermore, because fewer relay objectives are stacked, the requirements for assembly precision are reduced. Each symmetrical relay objective can have its gap and center deviation adjusted outside the rigid lens cavity to within the optical imaging tolerance range, and can then be reinserted as a separate component into the lens cavity, improving assembly efficiency without affecting the final product's imaging capability.

[0031] The above technical solution will be described in more detail below with reference to specific embodiments.

[0032] Example, reference Figures 1-5 ,like Figure 1 As shown, Figure 1 The left side is the object side, and the right side is the image side. From the object side to the image side, the lenses are, in order, the first lens 101, the second lens 102, the third lens 103, the fourth lens 104, the aperture stop, and the image plane.

[0033] Specifically, the first lens 101 is a meniscus lens with a negative focal length, the second lens 102 is an approximately plano-convex lens with a positive focal length, the third lens 103 is a meniscus lens with a negative focal length, and the fourth lens 104 is a meniscus lens with a positive focal length. The second lens 102, the third lens 103, and the fourth lens 104 are assembled into a cemented three-layer lens group using a cemented three-layer bonding process. The fifth, sixth, seventh, and eighth lenses are arranged in a mirror-symmetric manner with respect to the aperture stop, relative to the first lens 101, the second lens 102, the third lens 103, and the fourth lens 104.

[0034] Furthermore, as shown in Table 1, the data such as the radius of curvature, spacing, refractive index, and Abbe number of each optical element in this embodiment are listed.

[0035] Table 1 shows the structural data of the endoscope relay objective in this embodiment. surface radius of curvature spacing Refractive index Abbe number 1 unlimited 2.404 - - 2 -5.013 3.527 1.850 28.300 3 -7.078 0.200 - - 4 28.689 50.975 1.900 25.400 5 -101.066 2.000 1.580 63.400 6 -9.629 12.536 1.600 34.800 7 -25.664 0.859 - - Aperture stop unlimited 0.859 - - 7 25.664 12.536 1.600 25.400 8 9.629 2.000 1.580 63.400 9 101.066 50.975 1.900 34.800 10 -28.689 0.200 - - 11 7.078 3.527 1.850 28.300 12 5.013 2.404 - - Image - - - - The imaging quality of the endoscope relay objective in this embodiment is relatively good. For its relative illumination curve, dot plot, and MTF curve, please refer to [link to relevant documentation]. Figures 3-5 Combining the data from the table Figures 3 to 5 As can be seen from the curve, the endoscope relay objective in this embodiment can achieve the following optical performance.

[0036] Specifically, such as Figure 3 As shown, in terms of relative illumination, the difference between the illumination at the center and edge of the field of view is less than 3%, and the overall uniformity of the image plane exceeds 95%, so there will be no problems with image shadows or overexposure.

[0037] Furthermore, such as Figure 4As shown in the dot plot, the blur spots depicting different fields of view are all within the Airy disk range of the lens imaging, indicating that the optical architecture design has reached the limits of physical optics, representing excellent optical imaging performance.

[0038] Preferably, the Airy disk is the smallest spot shape formed by a point source on the image plane under the diffraction limit of an optical system. Due to the wave nature of light, even if an ideal aberration-free lens images a mathematical point, it will still form a diffraction pattern with a central bright spot and concentric dark / bright rings on the image plane. The diffraction limit refers to the smallest imaging spot and the corresponding imaging performance limit determined by aperture diffraction under the condition of no aberration. Any actual aberration will cause the performance to be lower than this limit.

[0039] Furthermore, such as Figure 5 As shown, in terms of modulation transfer function (MTF), the MTF of the relay objective can exceed 0.2 at a frequency of 250 lp / mm, which perfectly matches the imaging diffraction limit of the relay objective and reaches the maximum value of the theoretical design.

[0040] The present invention also provides an endoscope, which includes an objective lens, an eyepiece, and an endoscope relay objective lens as described in any of the above embodiments, wherein the endoscope relay objective lens is disposed between the objective lens and the eyepiece.

[0041] In summary, the endoscopic relay objective of this invention adopts a symmetrical optical design architecture, including a first lens group and a second lens group arranged in a mirror-symmetric manner with respect to the aperture stop. This allows for the mutual cancellation of on-axis and off-axis aberrations with fewer lens surfaces and materials, achieving superior imaging quality for the relay objective. Simultaneously, by increasing the object-image conjugate distance, the number of relay objectives used in the relay imaging optical path is reduced, thereby mitigating the cumulative aberration effect. The special optical surface design and optimized combination of optical materials ensure excellent imaging quality in both white light and fluorescence environments. The reduced number of individual lenses greatly facilitates assembly and debugging in actual optical production, minimizing the loss of optical imaging resolution caused by assembly and meeting the demands of low-cost mass production.

[0042] The above examples illustrate the present invention only to aid in understanding it and are not intended to limit the scope of the invention. Those skilled in the art can make various simple deductions, modifications, or substitutions based on the principles of this invention.

Claims

1. A long conjugate distance symmetrical endoscope relay objective, characterized in that: It includes a first lens group, an aperture stop, and a second lens group, wherein, The first lens group includes a first lens (101), a second lens (102), a third lens (103) and a fourth lens (104) arranged sequentially from the object side to the image side along the optical axis. The aperture stop is disposed on the image side of the first lens group; The second lens group is disposed on the image side of the aperture stop, and the second lens group is arranged in a mirror symmetrical manner with respect to the aperture stop and the first lens group; The first lens (101) is a meniscus lens with a negative focal length; the second lens (102) is an approximately plano-convex lens with a positive focal length; the third lens (103) is a meniscus lens with a negative focal length; and the fourth lens (104) is a meniscus lens with a positive focal length. The second lens (102), the third lens (103), and the fourth lens (104) are assembled into a three-cemented lens group using a cementing process.

2. The endoscopic relay objective lens with long conjugate distance symmetry as described in claim 1, characterized in that: The total conjugate length of the image in the endoscope relay objective is 140mm to 150mm, and the magnification is -1.

3. The symmetrical endoscope relay objective with long conjugate distance as described in claim 1 or 2, characterized in that: The diameter of the endoscope relay objective is 3mm to 6mm.

4. The symmetrical endoscope relay objective with long conjugate distance as described in claim 1 or 2, characterized in that: The F-number of the objective lens in the endoscope is less than or equal to 5.

5. The symmetrical endoscope relay objective with long conjugate distance as described in claim 1, characterized in that: The first lens (101) has a focal length range of -115mm to -125mm, a refractive index range of 1.90 to 2.0, and an Abbe number range of 25 to 35.

6. The symmetrical endoscope relay objective with long conjugate distance as described in claim 1, characterized in that: The focal length of the triplex lens group ranges from 28mm to 37mm, the refractive index ranges from 1.7 to 2.0, and the Abbe number ranges from 25 to 65.

7. The symmetrical endoscope relay objective with long conjugate distance as described in claim 1 or 2, characterized in that: The modulation transfer function (MTF) of the endoscope relay objective lens is greater than 0.2 at a spatial frequency of 250 lp / mm.

8. The symmetrical endoscope relay objective with long conjugate distance as described in claim 1 or 2, characterized in that: The endoscope relay objective is suitable for imaging scenarios involving visible and near-infrared light.

9. An endoscope, characterized in that, It includes an objective lens, an eyepiece, and an endoscope relay objective lens of the long conjugate distance symmetry type as described in any one of claims 1 to 8, wherein the endoscope relay objective lens is disposed between the objective lens and the eyepiece.

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