Optical imaging system and endoscope

Abstract

The utility model discloses an optical imaging system and an endoscope. The optical imaging system comprises a first lens, a second lens, a third lens, a triple cemented lens group, a double cemented lens group and a steering prism which are sequentially arranged from an object side to an image side. Wherein the object side surface of the first lens is a convex surface at the optical axis, and the image side surface of the first lens is a concave surface at the optical axis; the second lens is a 30-degree steering prism; the object side surface of the third lens is a plane, and the image side surface of the third lens is a convex surface; the object side surface and the image side surface of the fourth lens in the triple cemented lens group are convex surfaces, the object side surface and the image side surface of the fifth lens are concave surfaces, and the object side surface and the image side surface of the sixth lens are convex surfaces; the object side surface of the seventh lens in the doublet lens group is a plane, the image side surface of the seventh lens is a convex surface, the object side surface of the eighth lens is a concave surface, and the image side surface of the eighth lens is a convex surface. According to the optical imaging system and the endoscope, at least the problems that an optical imaging system of the endoscope is large in aperture and large in imaging distortion can be solved.

Description

Technical Field

[0001] This application relates to the field of medical device technology, and more specifically, to an optical imaging system and an endoscope. Background Technology

[0002] Current endoscopes include optical endoscopes and electronic endoscopes. Optical endoscopes typically consist of an optical imaging system and an optical image transmission system, relying on high-quality optical components. Electronic endoscopes, on the other hand, image the observed object onto electronic imaging elements such as charge-coupled devices (CCDs) or complementary metal-oxide-semiconductor (CMOS) sensors. They employ high-resolution CCD or CMOS imaging elements, resulting in high-resolution and lifelike images. They generally image through a miniature optical system at the front end, including multiple lens groups responsible for focusing information about the observed object onto the imaging element.

[0003] Existing endoscopes typically employ a large-aperture design to capture more light and thus improve image brightness. However, the large-aperture design of endoscopic optical imaging systems suffers from problems such as significant image distortion, large system size, and high manufacturing costs. Utility Model Content

[0004] The main objective of this application is to provide an optical imaging system and an endoscope to solve the problems of large aperture and large imaging distortion in endoscope optical imaging systems.

[0005] According to one aspect of this application, an optical imaging system is provided, comprising a first lens, a second lens, a third lens, a cemented triplet lens group, a cemented doublet lens group, and a steering prism arranged sequentially from the object side to the image side, wherein...

[0006] Both the object-side surface and the image-side surface of the first lens are aspherical, and the object-side surface of the first lens is convex at the optical axis, while the image-side surface of the first lens is concave at the optical axis.

[0007] The second lens is a 30° swivel prism;

[0008] The object-side surface of the third lens is a plane, and the image-side surface of the third lens is a convex surface;

[0009] The three-colloidal lens group includes a fourth lens, a fifth lens, and a sixth lens, wherein the fourth lens, the fifth lens, and the sixth lens are all spherical mirrors, the object-side and image-side of the fourth lens are both convex, the object-side and image-side of the fifth lens are both concave, and the object-side and image-side of the sixth lens are both convex.

[0010] The cemented doublet lens assembly includes a seventh lens and an eighth lens, wherein both the seventh lens and the eighth lens are spherical mirrors, the object-side surface of the seventh lens is a plane, the image-side surface of the seventh lens is a convex surface, the object-side surface of the eighth lens is a concave surface, and the image-side surface of the eighth lens is a convex surface.

[0011] Furthermore, the optical imaging system satisfies the following relationship: 4≤TTL / ImgH≤4.5, where TTL is the optical path distance on the optical axis from the object side of the first lens in the optical imaging system to the imaging surface of the optical imaging system, and ImgH is the maximum image height of the imaging surface.

[0012] Furthermore, the optical imaging system satisfies the following relationship: 6.2≤f / EPD≤6.5, where f is the effective focal length of the optical imaging system and EPD is the entrance pupil diameter of the optical imaging system.

[0013] Furthermore, the optical imaging system satisfies the following relationship: D≤3.6mm, where D is the maximum diameter of the optical imaging system.

[0014] Furthermore, the optical imaging system satisfies the following relationship: 1.9mm≤f*tan(Semi-FOV)≤2.1mm, where f is the effective focal length of the optical imaging system and Semi-FOV is half of the maximum field of view of the optical imaging system.

[0015] Furthermore, the effective focal length f1 of the first lens satisfies the relationship: -1.95mm < f1 < -1.88mm.

[0016] Furthermore, the effective focal length f3 of the third lens satisfies the relationship: 3.45mm < f3 < 3.62mm.

[0017] Furthermore, the effective focal length f of the three-cemented lens group 456 The following relationship is satisfied: 11.8mm < f 456 <12.5mm; and / or,

[0018] The effective focal length f4 of the fourth lens satisfies the following relationship: 5mm < f4 < 6mm; and / or,

[0019] The effective focal length f5 of the fifth lens satisfies the following relationship: -3mm < f5 < -2mm; and / or,

[0020] The effective focal length f6 of the sixth lens satisfies the following relationship: 3mm < f6 < 4mm.

[0021] Furthermore, the effective focal length f7 of the seventh lens satisfies the relationship: 4mm < f7 < 4.5mm; and / or,

[0022] The effective focal length f8 of the eighth lens satisfies the following relationship: -5.8mm < f8 < -5.2mm; and / or,

[0023] The difference in effective focal length between the seventh lens and the eighth lens satisfies the relationship between the sum of the effective focal lengths of the seventh lens and the eighth lens: -7.8 < (f7 - f8) / (f7 + f8) < -7.2.

[0024] On the other hand, this application also provides an endoscope that includes the aforementioned optical imaging system.

[0025] In this application, by setting up a first lens, a second lens, a third lens, a cemented triplet lens group, a cemented doublet lens group, and a steering prism, only the object-side and image-side surfaces of the first lens are aspherical lenses, while the remaining lenses are spherical lenses. This allows light to be focused to the desired position within a shorter distance, further improving light utilization efficiency and enabling the optical imaging system to achieve good imaging results with a smaller aperture, thus reducing imaging distortion. Simultaneously, through the rational design and combination of the lenses, this application can effectively correct aberrations and chromatic aberrations, enabling the optical imaging system to provide high imaging quality across the entire field of view. Furthermore, this application facilitates the miniaturization of endoscopes and, to some extent, reduces the production cost of the optical imaging system and simplifies the manufacturing process. Attached Figure Description

[0026] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:

[0027] Figure 1 This is a schematic diagram of the structure of the optical imaging system disclosed in the embodiments of this application;

[0028] Figure 2 This is a diagram of the optical modulation transfer function of the optical imaging system disclosed in the embodiments of this application;

[0029] Figure 3 This is a distortion curve diagram of the optical imaging system disclosed in the embodiments of this application;

[0030] Figure 4 This is an astigmatism curve diagram of the optical imaging system disclosed in the embodiments of this application;

[0031] Figure 5 This is a chromatic aberration curve of the optical imaging system disclosed in the embodiments of this application.

[0032] The above figures include the following reference numerals:

[0033] 10. First lens; 20. Second lens; 30. Third lens; 40. Cemented triplet lens group; 41. Fourth lens; 42. Fifth lens; 43. Sixth lens; 50. Cemented doublet lens group; 51. Seventh lens; 52. Eighth lens; 60. Steering prism; 70. Protective glass. Detailed Implementation

[0034] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0035] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0036] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of this application. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following drawings denote similar items; therefore, once an item is defined in one drawing, it need not be further discussed in subsequent drawings.

[0037] As mentioned in the background section, existing endoscopes typically employ a large-aperture design to obtain a greater amount of light, thereby improving image brightness. However, the large-aperture design of endoscopic optical imaging systems suffers from problems such as significant image distortion, large system size, and high manufacturing costs. Therefore, this application provides an optical imaging system that solves the problems of large aperture and significant image distortion in endoscopic optical imaging systems. The optical imaging system of this application will be described in detail below with reference to the accompanying drawings.

[0038] See Figures 1 to 5As shown, this application provides an optical imaging system, which includes a first lens 10, a second lens 20, a third lens 30, a cemented triplet lens group 40, a cemented doublet lens group 50, and a steering prism 60 arranged sequentially from the object side to the image side.

[0039] Specifically, the object-side and image-side surfaces of the first lens 10 are both aspherical, and the object-side surface of the first lens 10 is convex at the optical axis, while the image-side surface of the first lens 10 is concave at the optical axis; the second lens 20 is a 30° turning prism; the object-side surface of the third lens 30 is planar, and the image-side surface of the third lens 30 is convex; the cemented lens group 40 includes a fourth lens 41, a fifth lens 42, and a sixth lens 43, and all of these are spherical mirrors. Specifically, the object-side and image-side surfaces of the fourth lens 41 are convex, the object-side and image-side surfaces of the fifth lens 42 are concave, and the object-side and image-side surfaces of the sixth lens 43 are convex; the cemented doublet lens group 50 includes a seventh lens 51 and an eighth lens 52, both of which are spherical mirrors. The object-side surface of the seventh lens 51 is planar, and the image-side surface of the seventh lens 51 is convex, while the object-side surface of the eighth lens 52 is concave, and the image-side surface of the eighth lens 52 is convex.

[0040] In this application, the object-side surface of the first lens 10 is convex at the optical axis, and the image-side surface is concave at the optical axis. The combination of convex and concave surfaces helps to initially converge and diverge light over short distances, shortening the propagation distance of light between lenses and facilitating the small-aperture design of the optical imaging system. Furthermore, both the object-side and image-side surfaces of the first lens 10 are aspherical. Aspherical design allows for flexible control of light refraction, effective aberration correction, significantly reduced edge field-of-view imaging variations, reduced imaging distortion, and improved image quality. Light passing through the first lens 10 is effectively converged and transmitted to the second lens 20, which is a 30° turning prism. After the 30° turning prism changes the direction of light transmission, the light is transmitted to the third lens 30. Specifically, the object-side surface of the third lens 30 is planar, and the image-side surface is convex. The convex surface further converges the light passing through the first lens 10 and the second lens 20, helping to reduce the overall aperture of the optical imaging system while ensuring image quality.

[0041] When light passes through the first lens 10 and the second lens 20 and enters the third lens 30, it is prone to producing a large field curvature on the imaging surface. This application corrects aberrations and improves image sharpness by setting up a cemented triplet lens group 40 and a cemented doublet lens group 50. Specifically, the cemented triplet lens group 40 includes a fourth lens 41, a fifth lens 42, and a sixth lens 43. The object-side and image-side surfaces of the fourth lens 41 are both convex, the object-side and image-side surfaces of the fifth lens 42 are both concave, and the object-side and image-side surfaces of the sixth lens 43 are both convex. The fourth lens 41, fifth lens 42, and sixth lens 43 in the cemented triplet lens group 40 each employ different convex and concave surface designs. By rationally selecting lens materials and radii of curvature, this application can further correct and compensate for various aberrations. For example, the double convex surfaces of the fourth lens 41 and the sixth lens 43 help converge light, while the double concave surface of the fifth lens 42 can be used to balance the optical power of the system, while simultaneously correcting aberrations such as astigmatism and coma. The cemented doublet group 50 includes a seventh lens 51 and an eighth lens 52. The object-side surface of the seventh lens 51 is flat, and its image-side surface is convex. The object-side surface of the eighth lens 52 is concave, and its image-side surface is convex. By placing the cemented doublet group 50 on the image side of the triplet group 40, aberrations are further corrected, improving the imaging sharpness of the optical imaging system. Finally, a steering prism 60 is provided. This steering prism 60 refracts light at a specific angle, thereby changing the direction of light propagation to meet the design requirements of the optical imaging system.

[0042] In other words, this application, by setting up a first lens 10, a second lens 20, a third lens 30, a cemented triplet lens group 40, a cemented doublet lens group 50, and a steering prism 60, wherein only the object-side and image-side surfaces of the first lens 10 are aspherical lenses, while the rest are spherical lenses, can converge light to the desired position within a shorter distance, further improving light utilization efficiency. This allows the optical imaging system to achieve better imaging results with a smaller aperture, reducing imaging distortion. Simultaneously, through the rational design and combination of the lenses, this application can effectively correct aberrations and chromatic aberrations, enabling the optical imaging system to provide high imaging quality across the entire field of view. Furthermore, this application facilitates the miniaturization of endoscopes and, to some extent, reduces the production cost of the optical imaging system and simplifies the manufacturing process.

[0043] Furthermore, in this application, the optical imaging system satisfies the relationship: 4 ≤ TTL / ImgH ≤ 4.5. For example, TTL / ImgH can be 4, 4.1, 4.2, 4.3, 4.4, or 4.5. Here, TTL is the optical path distance along the optical axis from the object side of the first lens 10 to the image plane, and ImgH is the maximum image height of the imaging plane. Satisfying the above relationship is beneficial for achieving a larger imaging surface in the optical imaging system, improving the shooting effect, and also enabling the optical imaging system to be thinner and lighter. When TTL / ImgH > 4.5, the total length of the optical imaging system is too large, which is not conducive to achieving the ultra-thin characteristics of the optical imaging system.

[0044] Furthermore, in this application, the optical imaging system satisfies the relationship: 6.2 ≤ f / EPD ≤ 6.5, for example, f / EPD can be 6.2, 6.3, 6.4, or 6.5, etc. Where f is the effective focal length of the optical imaging system, and EPD is the entrance pupil diameter of the optical imaging system. Satisfying the above relationship allows the optical imaging system to achieve a large aperture while maintaining telephoto characteristics, enabling more incident light to enter the optical imaging system, improving the relative brightness of the optical imaging system, and thus obtaining a clear, high-quality imaging effect.

[0045] Furthermore, in this application, the optical imaging system satisfies the relationship: D ≤ 3.6 mm, for example, 3.6 mm, 3.5 mm, 3.4 mm, etc. Where D is the maximum diameter of the optical imaging system. A smaller D value allows the endoscope's optical imaging system to better adapt to the body's natural cavities or small surgical incisions; a smaller beam diameter or lens size helps reduce optical errors such as aberrations and chromatic aberration; a smaller size facilitates better integration of the optical imaging system, allowing the endoscope to integrate more functional modules.

[0046] Furthermore, in this application, the optical imaging system satisfies the relationship: 1.9mm ≤ f*tan(Semi-FOV) ≤ 2.1mm. For example, the value of f*tan(Semi-FOV) can be 1.9mm, 2.0mm, or 2.1mm. Here, f is the effective focal length of the optical imaging system, and Semi-FOV is half of the maximum field of view of the optical imaging system. When the optical imaging system satisfies the above relationship, it achieves miniaturization while ensuring a large field of view, thus capturing a sufficiently large scene. This constraint on the focal length allows the system to achieve better imaging results at that focal length, avoiding image quality degradation due to an excessively large field of view or an unsuitable focal length. Additionally, this setting allows the optical imaging system to achieve a larger image height on the imaging plane, thereby improving image resolution and detail, which is beneficial for clear imaging of target objects.

[0047] Furthermore, in this application, the effective focal length f1 of the first lens 10 satisfies the relationship: -1.95mm < f1 < -1.88mm. For example, the effective focal length f1 of the first lens 10 can be -1.94mm, -1.93mm, -1.92mm, -1.90mm, and -1.89mm, etc. The first lens 10 has negative optical power, which can effectively increase the field of view of the optical imaging system and increase the light flux of the optical imaging system, playing an excellent auxiliary role in improving the relative illumination of the optical imaging system. When the effective focal length of the first lens 10 is within the above range, the first lens 10 can initially converge or diverge light to a suitable angle, allowing it to pass smoothly through subsequent lenses and optical elements, and under the constraint of a small aperture, it can still ensure the propagation accuracy of light and the imaging quality. Furthermore, within this focal length range, the first lens 10 can bend and refract light in a special way, thereby compensating for or reducing aberrations in the optical imaging system, such as spherical aberration and chromatic aberration. This helps to improve the clarity and accuracy of the image, making the images obtained by the electronic endoscope more realistic and clear, and facilitating doctors to accurately observe and diagnose lesions.

[0048] Furthermore, in this application, the second lens 20 is a 30° swivel prism, with its object-side surface forming a 30° angle with the optical axis, and its image-side surface being a plane forming a 90° angle with the optical axis. The 30° angle between the object-side surface of the second lens 20 and the optical axis allows light to enter the lens at a specific 30° angle, and after internal reflection, exit at a 90° angle perpendicular to the image-side surface of the second lens 20. This changes the direction of light propagation, allowing the light path to bend within a limited space, which helps achieve a small-aperture design for the optical imaging system. The 30° swivel prism minimizes light loss during refraction and reflection, ensuring sufficient light reaches the imaging element, thereby improving the brightness and contrast of the image. The specific 30° angle helps reduce optical distortion, ensuring image quality and accuracy, which is beneficial for doctors to accurately observe and judge lesions. The 30° swivel prism angle also facilitates integration and coordination with other optical components, enabling miniaturized and integrated designs.

[0049] Furthermore, in this application, the effective focal length f3 of the third lens 30 satisfies the relationship: 3.45mm < f3 < 3.62mm. For example, the effective focal length f3 of the third lens 30 can be 3.46mm, 3.48mm, 3.50mm, and 3.60mm, etc. When the effective focal length of the third lens 30 meets the above range, the third lens 30 can appropriately converge the light rays passing through the first lens 10 and the 30° turning prism. Under the premise of satisfying the small aperture design of the optical imaging system, this allows the optical imaging system to have a suitable image distance and object distance relationship, thereby forming a clear image on imaging elements such as image sensors. This helps to improve the resolution and contrast of the image, providing doctors with high-quality images for observation and diagnosis. In this application, the object-side surface of the third lens 30 is flat, the image-side surface of the third lens 30 is convex, and an aperture stop (not shown in the figure) is provided on its flat surface. This configuration, with the object-side surface of the third lens 30 being planar, facilitates precise control over the direction and convergence of light propagation, preventing inconsistent light scattering or refraction angles due to the irregularity of the object-side surface, which could affect imaging performance. Conversely, setting the image-side surface of the third lens 30 to be convex allows for better correction of optical defects such as aberrations and chromatic aberration, improving image quality and accuracy. Simultaneously, placing the system's aperture stop at the planar surface of the third lens 30 effectively compresses the exit angle of light passing through the second lens 20, thereby reducing the overall aperture of the optical imaging system and facilitating miniaturization. Of course, the aperture stop can also be placed in other locations; specific adjustments and designs are made according to actual conditions, and this application does not impose specific limitations.

[0050] Furthermore, in this application, the effective focal length f of the triplex lens group 40 is... 456 The following relationship is satisfied: 11.8mm < f 456 <12.5mm. For example, the effective focal length f of the cemented lens group 40 is... 456The values ​​can be 11.9mm, 12.0mm, 12.2mm, and 12.4mm, etc. When the effective focal length of the triplet lens group 40 meets the above range, the optical imaging system can obtain a suitable magnification and imaging range under small aperture conditions, ensuring that the formed image has high clarity, resolution, and contrast, thereby providing doctors with clear and accurate images of the human body, facilitating the observation and diagnosis of lesions. The effective focal length f4 of the fourth lens 41 satisfies the relationship: 5mm < f4 < 6mm. For example, the effective focal length of the fourth lens 41 can be 5.1mm, 5.5mm, or 5.9mm. The effective focal length f5 of the fifth lens 42 satisfies the relationship: -3mm < f5 < -2mm. For example, the effective focal length of the fifth lens 42 can be -2.9mm, -2.7mm, -2.5mm, or -2.1mm. The effective focal length f6 of the sixth lens 43 satisfies the relationship: 3mm < f6 < 4mm. For example, the effective focal length of the sixth lens 43 can be 3.1mm, 3.5mm, or 3.9mm. With this configuration, the fourth lens 41 can finely correct light, compensate for aberrations and chromatic aberration, and improve the quality and accuracy of the image. The fifth lens 42 performs special processing on the light in the optical imaging system, expanding the observation range while ensuring image quality, which helps to discover more potential lesions. The sixth lens 43 can further enhance the detail of the image. Furthermore, the fourth lens 41, the fifth lens 42, and the sixth lens 43 respectively satisfy the following conditions: the fourth lens 41 is a high-refractive-index lens with a positive effective focal length; the fifth lens 42 is a low-refractive-index lens with a negative effective focal length; and the sixth lens 43 is a high-refractive-index lens with a positive effective focal length. These three lenses are cemented together to form a symmetrical triplet structure, which effectively balances the chromatic aberration generated by the entire system. Simultaneously, to increase the image height, the angle of light rays passing through the lenses increases. The triplet lens assembly 40 can also balance the tolerance sensitivity caused by the increased light angle. The resulting higher-order aberrations can balance other aberrations in the system, achieving aberration balance while increasing the image height. This application, through the cooperation of various lenses and lens assemblies throughout the optical imaging system, can achieve high-quality imaging in a small-aperture design, meeting the practical needs of endoscopes in medical diagnosis.

[0051] Furthermore, in this application, the effective focal length f7 of the seventh lens 51 satisfies the relationship: 4mm < f7 < 4.5mm. For example, the effective focal length of the seventh lens 51 can be 4.1mm, 4.2mm, or 4.4mm, etc. The effective focal length f8 of the eighth lens 52 satisfies the relationship: -5.8mm < f8 < -5.2mm. For example, the effective focal length of the eighth lens 52 can be -5.7mm, -5.6mm, -5.5mm, or -5.3mm, etc. In this application, the eighth lens 52 is a meniscus lens with negative optical power, effectively increasing the divergence angle of light and increasing the image height. Furthermore, in this application, the difference in effective focal length between the seventh lens 51 and the eighth lens 52 and the sum of their effective focal lengths satisfy the relationship: -7.8 < (f7 - f8) / (f7 + f8) < -7.2. For example, the value of (f7 - f8) / (f7 + f8) can be -7.7, -7.6, -7.4, and -7.3, etc. In this application, the seventh lens 51 and the eighth lens 52 are combined into a cemented doublet group 50 with positive optical power. By controlling the difference in effective focal length between the seventh lens 51 and the eighth lens 52 and the sum of their effective focal lengths, the contribution of the two lenses to aberrations can be controlled, compensating for the residual aberrations generated by the preceding optical imaging system, and keeping the aberrations of the entire optical imaging system within a reasonable range.

[0052] As described above, the optical imaging system of this application has an overall optical aperture of less than or equal to 3.6 mm. This system comprises a first lens 10, a second lens 20, a third lens 30, a cemented triplet lens group 40 (including a fourth lens 41, a fifth lens 42, and a sixth lens 43), a cemented doublet lens group 50 (including a seventh lens 51 and an eighth lens 52), and a steering prism 60. The first lens 10 is an aspherical lens, while the others are spherical lenses. By combining and adjusting the focal lengths of each lens group, the field curvature and aberrations of the optical imaging system are effectively corrected. Experimental verification shows that the effective focal length of the optical imaging system of this application is 1.9 mm < f < 2.3 mm, and the field of view is greater than 86°. Under this field of view, the distortion across the entire field of view can be controlled within -7%, and the relative illumination across the entire field of view can reach over 85%.

[0053] In this design, both the object-side surface and the image-side surface of the first lens 10 are aspherical surfaces, and all of these aspherical surfaces are even-order aspherical surfaces. The surface shape formula equation for the even-order aspherical surface is as follows:

[0054]

[0055] Where z is the height along the optical axis; c is the curvature of the surface; k is the conic coefficient; r is the diameter along the radial direction; and A, B, C, and D are all aspherical coefficients.

[0056] The optical imaging system of this application will be described in detail below with specific examples.

[0057] Example 1

[0058] See Figures 1 to 5 As shown, according to Embodiment 1 of this application, an optical imaging system is provided, which includes a first lens 10, a second lens 20, a third lens 30, a cemented triplet lens group 40, a cemented doublet lens group 50, and a steering prism 60 arranged sequentially from the object side to the image side.

[0059] The first lens 10 has aspherical object-side and image-side surfaces, with the object-side surface of the first lens 10 being convex at the optical axis and the image-side surface of the first lens 10 being concave at the optical axis; the second lens 20 is a 30° turning prism; the third lens 30 has a planar object-side surface and a convex image-side surface; the cemented triplet lens group 40 includes a fourth lens 41, a fifth lens 42, and a sixth lens 43, all of which are spherical mirrors. Specifically, the object-side and image-side surfaces of the fourth lens 41 are convex, the object-side and image-side surfaces of the fifth lens 42 are concave, and the object-side and image-side surfaces of the sixth lens 43 are convex; the cemented doublet lens group 50 includes a seventh lens 51 and an eighth lens 52, both of which are spherical mirrors. The object-side surface of the seventh lens 51 is planar, and the image-side surface of the seventh lens 51 is convex, while the object-side and image-side surfaces of the eighth lens 52 are concave and convex.

[0060] During actual assembly, a protective glass 70 is provided on the object side of the first lens 10 to protect the optical imaging system.

[0061] Table 1 shows the characteristic parameters of the optical imaging system in this embodiment. The units for radius and thickness are mm, and the focal length of the imaging system is 2 mm < f < 2.1 mm.

[0062] Surface name radius r Thickness d Refractive index nd Abbe number Vd surface — — 51 — — The object side of the first protective lens spherical unlimited 0.28 1.76 72.2 The image side of the first protective lens spherical unlimited 0.11 — — The object side of the first lens aspherical 10.97 0.28 1.82 42.7 Image side of the first lens aspherical 1.55 0.7 — — The object side of the second lens spherical unlimited 3.92 2.1 25.4 Image side of the second lens spherical unlimited — — — aperture spherical unlimited — — — The object side of the third lens spherical unlimited 1.44 1.72 28.3 The image side of the third lens spherical -3.04 0.11 — — The object side of the fourth lens spherical 7.9 0.91 1.49 81.5 Image side of the fourth lens spherical -4.86 — — — The object side of the fifth lens spherical -4.86 0.28 1.85 36.6 Image side of the fifth lens spherical 3.67 — — — object side of the sixth lens spherical 3.67 1.02 1.49 81.5 Image side of the sixth lens spherical -3.31 0.11 — — object side of the seventh lens spherical unlimited 0.95 1.49 81.5 Image side of the seventh lens spherical -2.37 — — — The object side of the eighth lens spherical -2.37 0.28 1.83 37.2 Image side of the eighth lens spherical -4.51 0.45 — — Object-side surface of the directional prism spherical unlimited 3.5 1.51 64.2 Image side of the turning prism spherical unlimited 0.3 — — Image — unlimited — — —

[0063] Table 2 shows the relevant parameters for the conic coefficients and higher-order coefficients of even-order aspherical surface types.

[0064]

[0065]

[0066] Figure 2The optical modulation transfer function diagram of the optical imaging system in this embodiment is shown. Figure 3 The distortion curve of the optical imaging system disclosed in this embodiment is shown; Figure 4 An astigmatism curve of the optical imaging system disclosed in this embodiment is shown; Figure 5 A chromatic aberration curve of the optical imaging system disclosed in this embodiment is shown. Figure 3 The horizontal axis represents the distortion rate (%). Figure 4 The horizontal axis represents the focal length in mm, where T represents the meridional curvature and S represents the sagittal curvature. Figure 5 This represents the chromatic aberration curves of light with wavelengths of 656.3nm, 587.6nm, 546.1nm, 486.1nm, and 435.8nm after passing through each lens of an optical imaging system. The horizontal axis represents the focal length, in mm. According to... Figures 2 to 5 As can be seen, the optical imaging system given in Example 1 can achieve good imaging quality.

[0067] On the other hand, this application also provides an endoscope that includes the aforementioned optical imaging system, and therefore, the endoscope includes all the technical effects of the aforementioned optical imaging system. Since the technical effects of the optical imaging system have already been described in detail above, they will not be repeated here.

[0068] For ease of description, spatial relative terms such as "above," "on top of," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation beyond the orientation of the device as described in the figures. For example, if the device in the figures were inverted, a device described as "above" or "on top of" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0069] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore cannot be construed as limiting the scope of protection of this application.

[0070] The above are merely preferred embodiments of this application and are not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. An optical imaging system, characterized in that, It includes a first lens (10), a second lens (20), a third lens (30), a cemented triplet lens group (40), a cemented doublet lens group (50), and a steering prism (60) arranged sequentially from the object side to the image side. The object-side surface and the image-side surface of the first lens (10) are both aspherical, and the object-side surface of the first lens (10) is convex at the optical axis, while the image-side surface of the first lens (10) is concave at the optical axis. The second lens (20) is a 30° turning prism; The object side of the third lens (30) is a plane, and the image side of the third lens (30) is a convex surface; The triple-colloidal lens assembly (40) includes a fourth lens (41), a fifth lens (42), and a sixth lens (43), wherein the fourth lens (41), the fifth lens (42), and the sixth lens (43) are all spherical mirrors, the object-side surface and the image-side surface of the fourth lens (41) are both convex, the object-side surface and the image-side surface of the fifth lens (42) are both concave, and the object-side surface and the image-side surface of the sixth lens (43) are both convex. The doublet lens assembly (50) includes a seventh lens (51) and an eighth lens (52), wherein the seventh lens (51) and the eighth lens (52) are both spherical mirrors, the object side of the seventh lens (51) is a plane, the image side of the seventh lens (51) is a convex surface, the object side of the eighth lens (52) is a concave surface, and the image side of the eighth lens (52) is a convex surface.

2. The optical imaging system according to claim 1, characterized in that, The optical imaging system satisfies the following relationship: 4≤TTL / ImgH≤4.5, where TTL is the optical path distance on the optical axis from the object side of the first lens (10) in the optical imaging system to the imaging surface of the optical imaging system, and ImgH is the maximum image height of the imaging surface.

3. The optical imaging system according to claim 1, characterized in that, The optical imaging system satisfies the following relationship: 6.2≤f / EPD≤6.5, where f is the effective focal length of the optical imaging system and EPD is the entrance pupil diameter of the optical imaging system.

4. The optical imaging system according to claim 1, characterized in that, The optical imaging system satisfies the following relationship: D≤3.6mm, where D is the maximum diameter of the optical imaging system.

5. The optical imaging system according to claim 1, characterized in that, The optical imaging system satisfies the following relationship: 1.9mm≤f*tan(Semi-FOV)≤2.1mm, where f is the effective focal length of the optical imaging system and Semi-FOV is half of the maximum field of view of the optical imaging system.

6. The optical imaging system according to any one of claims 1 to 5, characterized in that, The effective focal length f1 of the first lens (10) satisfies the following relationship: -1.95mm < f1 < -1.88mm.

7. The optical imaging system according to any one of claims 1 to 5, characterized in that, The effective focal length f3 of the third lens (30) satisfies the following relationship: 3.45mm < f3 < 3.62mm.

8. The optical imaging system according to any one of claims 1 to 5, characterized in that, The effective focal length f of the triplex lens group (40) 456 The following relationship is satisfied: 11.8mm < f 456 <12.5mm; and / or, The effective focal length f4 of the fourth lens (41) satisfies the following relationship: 5mm < f4 < 6mm; and / or, The effective focal length f5 of the fifth lens (42) satisfies the following relationship: -3mm < f5 < -2mm; and / or, The effective focal length f6 of the sixth lens (43) satisfies the following relationship: 3mm < f6 < 4mm.

9. The optical imaging system according to any one of claims 1 to 5, characterized in that, The effective focal length f7 of the seventh lens (51) satisfies the following relationship: 4mm < f7 < 4.5mm; and / or, The effective focal length f8 of the eighth lens (52) satisfies the following relationship: -5.8mm < f8 < -5.2mm; and / or, The difference in effective focal length between the seventh lens (51) and the eighth lens (52) satisfies the relationship between the sum of the effective focal lengths of the seventh lens (51) and the eighth lens (52): -7.8 < (f7-f8) / (f7+f8) < -7.

2.

10. An endoscope, characterized in that, The endoscope includes the optical imaging system according to any one of claims 1 to 9.

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