Panoramic endoscopic imaging system

Abstract

The invention provides a panoramic endoscopic imaging system. The panoramic endoscopic imaging system comprises a panoramic annular lens module and a relay lens module which are sequentially arranged in the optical axis direction. The panoramic annular lens module comprises a panoramic annular lens, and the optical axis of the panoramic annular lens coincides with the optical axis of the relay lens module; the imaging light sequentially passes through the first refracting surface, the first reflecting surface, the second reflecting surface and the second refracting surface of the panoramic annular lens. The first refracting surface and the second refracting surface are plated with antireflection films, and the first reflecting surface and the second reflecting surface are plated with inner reflecting films. The system is composed of a panoramic annular lens module and a relay lens module, high-quality imaging of inner walls of cavities with different inner diameters is achieved by optimizing light path design and lens parameters, and the system has the advantages of being high in resolution, high in view utilization rate, low in distortion and even in illumination.

Description

Technical Field

[0001] This invention relates to the field of optical imaging technology, specifically a panoramic endoscopic imaging system. Background Technology

[0002] For the inspection of the inner wall of a cavity, the most common imaging system solutions on the market currently include two main types: one is an endoscope solution based on fiber optic image bundles, and the other is an endoscope imaging solution based on macro fisheye. The fiber optic image bundle-based endoscope solution has two main drawbacks: firstly, the imaging resolution is relatively low; secondly, the field of view is usually downwards along the cavity rather than perpendicular to the inner wall, resulting in low utilization of the imaging field and low inspection efficiency. If a reflector is used to adjust the endoscope's field of view to be perpendicular to the inner wall, only a portion of the inner wall can be observed in a single image. In this case, the endoscope must be rotated a full circle to complete the image of the entire inner wall, again resulting in low inspection efficiency. The disadvantages of the macro fisheye-based endoscope imaging solution include: poor image consistency between the center and edges of the field of view, significant overall distortion, and poor illumination uniformity at the edges.

[0003] Therefore, there is an urgent need to provide an endoscope system with high resolution, high field of view utilization, low edge distortion, and uniform illumination to meet the needs of internal cavity inspection. Summary of the Invention

[0004] Based on this, the present invention provides a panoramic endoscopic imaging system, which consists of a panoramic ring lens module and a relay lens module. By optimizing the optical path design and lens parameters, high-quality imaging of the inner wall of cavities with different inner diameters can be achieved. The system features high resolution, high field of view utilization, low distortion, and uniform illumination.

[0005] This invention provides a panoramic endoscopic imaging system, comprising a panoramic annular lens module and a relay lens module arranged sequentially along the optical axis;

[0006] The panoramic ring lens module includes a panoramic ring lens, the optical axis of which coincides with the optical axis of the relay lens module; wherein, the imaging light passes sequentially through the first refractive surface, the first reflective surface, the second reflective surface, and the second refractive surface of the panoramic ring lens; the first refractive surface and the second refractive surface are coated with anti-reflection films, and the first reflective surface and the second reflective surface are coated with internal reflection films.

[0007] Optionally, the second refracting surface and the first reflecting surface have the same radius of curvature.

[0008] Optionally, the substrate material of the panoramic annular lens may include glass or plastic.

[0009] Optionally, along the optical axis from the image side to the object side, the relay lens module includes:

[0010] A first spherical lens with positive optical power, an aperture stop, a second spherical lens with positive optical power, a third spherical lens with positive optical power, a fourth spherical lens with negative optical power, a fifth spherical lens with positive optical power, a sixth spherical lens with negative optical power, a seventh spherical lens with positive optical power, and an eighth spherical lens with positive optical power.

[0011] Optionally, the third spherical lens and the fourth spherical lens constitute a cemented doublet, and the sixth spherical lens and the seventh spherical lens constitute a cemented doublet.

[0012] Optionally, the focal length of each lens in the relay lens module satisfies the following relationship with the overall focal length of the relay lens module:

[0013] 5.510≤f1 / f≤9.183; 1.299≤f2 / f≤2.165; 0.334≤f3 / f≤0.557; -0.535≤f4 / f≤-0.321;

[0014] 1.862≤f5 / f≤3.103; -0.634≤f6 / f≤-0.380; 0.269≤f7 / f≤0.448; 0.450≤f8 / f≤0.750;

[0015] Wherein, f is the overall focal length of the relay lens module, f1 is the focal length of the first spherical lens, f2 is the focal length of the second spherical lens, f3 is the focal length of the third spherical lens, f4 is the focal length of the fourth spherical lens, f5 is the focal length of the fifth spherical lens, f6 is the focal length of the sixth spherical lens, f7 is the focal length of the seventh spherical lens, and f8 is the focal length of the eighth spherical lens.

[0016] Optionally, the refractive index and Abbe number of each lens material in the relay lens module satisfy the following ranges:

[0017] 1.578≤Nd1≤1.658, 60.223≤Vd1≤66.562; 1.567≤Nd2≤1.648, 53.822≤Vd2≤59.487;

[0018] 1.508≤Nd3≤1.585, 59.637≤Vd3≤65.915; 1.647≤Nd4≤1.731, 29.603≤Vd4≤32.719;

[0019] 1.691≤Nd5≤1.777, 48.912≤Vd5≤54.060; 1.623≤Nd6≤1.706, 33.710≤Vd6≤37.259;

[0020] 1.580≤Nd7≤1.661, 57.350≤Vd7≤63.387; 1.740≤Nd8≤1.829, 24.434≤Vd8≤27.006;

[0021] Wherein, Nd1 and Vd1 are the refractive index and Abbe number of the first spherical lens material, respectively; Nd2 and Vd2 are the refractive index and Abbe number of the second spherical lens material, respectively; Nd3 and Vd3 are the refractive index and Abbe number of the third spherical lens material, respectively; Nd4 and Vd4 are the refractive index and Abbe number of the fourth spherical lens material, respectively; Nd5 and Vd5 are the refractive index and Abbe number of the fifth spherical lens material, respectively; Nd6 and Vd6 are the refractive index and Abbe number of the sixth spherical lens material, respectively; Nd7 and Vd7 are the refractive index and Abbe number of the seventh spherical lens material, respectively; and Nd8 and Vd8 are the refractive index and Abbe number of the eighth spherical lens material, respectively.

[0022] Optionally, by adjusting the back cutoff of the relay lens module, focusing and imaging of the inner walls of cavities with different inner diameters can be achieved.

[0023] Optionally, the back cutoff value of the relay lens module is in the range of 2.47mm to 2.97mm.

[0024] Optionally, the panoramic endoscopic imaging system has a field curvature of less than 0.05 mm, an F-Theta distortion of less than 5%, and a relative illumination of greater than 88%.

[0025] In summary, a panoramic endoscopic imaging system includes a panoramic annular lens module and a relay lens module arranged sequentially along the optical axis. The panoramic annular lens module includes a panoramic annular lens, the optical axis of which coincides with the optical axis of the relay lens module. The imaging light rays sequentially pass through a first refractive surface, a first reflective surface, a second reflective surface, and a second refractive surface of the panoramic annular lens. The first and second refractive surfaces are coated with anti-reflection films, and the first and second reflective surfaces are coated with internal reflection films. The system, composed of the panoramic annular lens module and the relay lens module, achieves high-quality imaging of the inner walls of cavities with different inner diameters through optimized optical path design and lens parameters. The system features high resolution, high field-of-view utilization, low distortion, and uniform illumination. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the structure of a panoramic endoscopic imaging system provided in an embodiment of this application;

[0027] Figure 2 This is a schematic diagram of the structure of a panoramic ring lens provided in an embodiment of this application;

[0028] Figure 3 for Figure 1 A schematic diagram of the optical path for a panoramic endoscopic imaging system measuring a cavity with an inner diameter of 15 mm is provided.

[0029] Figure 4 for Figure 1 A panoramic endoscopic imaging system is provided to measure the MTF (Mean Transformation Factor) of a cavity with an inner diameter of 15 mm;

[0030] Figure 5 for Figure 1 A panoramic endoscopic imaging system is provided to measure the field curvature and distortion of a cavity with an inner diameter of 15 mm.

[0031] Figure 6 for Figure 1 A panoramic endoscopic imaging system is provided to measure the relative illumination map of a cavity with an inner diameter of 15 mm;

[0032] Figure 7 for Figure 1 A schematic diagram of the optical path for measuring a cavity with an inner diameter of 32.5 mm in a panoramic endoscopic imaging system is provided.

[0033] Figure 8 for Figure 1 A panoramic endoscopic imaging system is provided to measure the MTF (Mean Transformation Factor) of a cavity with an inner diameter of 32.5 mm;

[0034] Figure 9 for Figure 1 A panoramic endoscopic imaging system is provided to measure field curvature and distortion maps of a cavity with an internal diameter of 32.5 mm;

[0035] Figure 10 for Figure 1 A panoramic endoscopic imaging system is provided to measure the relative illumination map of a cavity with an inner diameter of 32.5 mm;

[0036] Figure 11 for Figure 1 A schematic diagram of the optical path for a panoramic endoscopic imaging system measuring a cavity with an inner diameter of 50 mm is provided.

[0037] Figure 12 for Figure 1 A panoramic endoscopic imaging system is provided to measure the MTF (Mean Transformation Factor) of a cavity with an inner diameter of 50 mm;

[0038] Figure 13 for Figure 1 A panoramic endoscopic imaging system is provided to measure field curvature and distortion maps of a cavity with an inner diameter of 50 mm;

[0039] Figure 14 for Figure 1 A panoramic endoscopic imaging system is provided to measure the relative illumination map of a cavity with an inner diameter of 50 mm.

[0040] Explanation of reference numerals in the attached figures:

[0041] Figure 1 In the diagram: OBJ is the object plane, M1 is the panoramic ring lens module, PAL is the panoramic ring lens, X is the optical axis of the panoramic ring lens, M2 is the relay lens module, RL1 is the first spherical lens, S is the aperture stop, RL2 is the second spherical lens, RL3 is the third spherical lens, RL4 is the fourth spherical lens, RL5 is the fifth spherical lens, RL6 is the sixth spherical lens, RL7 is the seventh spherical lens, RL8 is the eighth spherical lens, and IMA is the image plane.

[0042] Figure 2 In the diagram: 11 is the first refractive surface, 12 is the second refractive surface, 21 is the first reflecting surface, and 22 is the second reflecting surface.

[0043] Figure 3 In the diagram: H1 is the distance between the corresponding object plane OBJ of the measuring cavity and the optical axis X of the panoramic annular lens PAL; α1 is the corresponding maximum lower half field of view; and β1 is the corresponding maximum upper half field of view.

[0044] Figure 7 In the diagram: H2 is the distance between the corresponding object plane OBJ of the measuring cavity and the optical axis X of the panoramic annular lens PAL; α2 is the corresponding maximum lower half field of view; and β2 is the corresponding maximum upper half field of view.

[0045] Figure 11 In the diagram: H3 is the distance between the corresponding object plane OBJ of the measuring cavity and the optical axis X of the panoramic annular lens PAL; α3 is the corresponding maximum lower half field of view; and β3 is the corresponding maximum upper half field of view.

[0046] like Figure 3 , Figure 7 and Figure 11 As shown, in this embodiment, the distances between the corresponding object surface OBJ of the measuring cavity and the optical axis X of the panoramic annular lens PAL are H1=7.5mm, H2=16.25mm, and H3=25mm, respectively. That is, the measurable cavity inner diameter range corresponding to this embodiment is 15~50mm. The focusing imaging of the inner wall of the cavity with different inner diameters is achieved by adjusting the back cutoff of the relay lens module M2. Detailed Implementation

[0047] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. It is understood that the specific embodiments described herein are merely illustrative of the present application and not intended to limit it. Furthermore, it should be noted that, for ease of description, only the parts relevant to the present application are shown in the drawings, not the entire structure. Various modifications and variations can be made to the present application without departing from its spirit or scope, which will be apparent to those skilled in the art. Therefore, the present application is intended to cover modifications and variations of the present application that fall within the scope of the technical solutions claimed in the corresponding claims and their equivalents. It should be noted that the implementation methods provided in the embodiments of the present application can be combined with each other without contradiction.

[0048] Figure 1 This is a schematic diagram of the structure of a panoramic endoscopic imaging system provided in an embodiment of this application. Figure 2 This is a schematic diagram of a panoramic annular lens provided in an embodiment of this application. (Reference) Figure 1 and Figure 2 This application provides a panoramic endoscopic imaging system 100, which includes components along the optical axis direction (…). Figure 1 A panoramic annular lens module M1 and a relay lens module M2 are arranged sequentially in the X-direction. The panoramic annular lens module M1 includes a panoramic annular lens PAL, wherein the optical axis direction is the optical axis direction of the panoramic annular lens PAL. The optical axis of the panoramic annular lens PAL coincides with the optical axis of the relay lens module M2. By precisely aligning the optical axes of the two, this application can ensure the geometric consistency of imaging, which is beneficial to reducing edge distortion and ensuring the continuity of the optical path and the stability of imaging. The panoramic annular lens PAL includes a first refractive surface 11, a first reflective surface 21, a second reflective surface 22, and a second refractive surface 12. The imaging light passes through the first refractive surface 11, the first reflective surface 21, the second reflective surface 22, and the second refractive surface 12 of the panoramic annular lens PAL in sequence to complete the panoramic annular imaging and transmit it to the relay lens module M2 behind it. After being shaped by the relay lens module M2, it is efficiently projected onto the photosensitive surface (image plane IMA) of the imaging sensor. The first refractive surface 11 and the second refractive surface 12 are coated with antireflective films, which can minimize reflection loss, improve light transmission efficiency, and increase field of view utilization. The first reflective surface 21 and the second reflective surface 22 are coated with internal reflection films, which can ensure that light has extremely high energy utilization and signal-to-noise ratio when reflected inside the lens, improve imaging resolution, and thus improve the overall imaging quality and illumination uniformity of the system. For example, the antireflective film has an antireflection band of visible light and near-infrared light; the internal reflection film has a reflection band of visible light and near-infrared light. This application, by combining antireflective film and high-reflection film, greatly improves light energy utilization and can obtain bright and clear images under low illumination.

[0049] It should be noted that the embodiments of this application may reasonably add anti-reflection coatings and internal reflection coatings according to the cavity detection and imaging sensor imaging principles, and the embodiments of this application are not limited thereto.

[0050] In summary, the panoramic endoscopic imaging system provided in this application embodiment has a compact structure due to the folding of the optical path by a panoramic ring lens. The folded optical path can make the axial length of the panoramic endoscopic imaging system extremely short, which is especially suitable for endoscopic application scenarios with strict space constraints. It has high reliability and can acquire panoramic ring imaging of the surrounding environment without rotating or moving the lens. The image is then transmitted to the imaging sensor clearly and with low distortion through a relay lens module.

[0051] For example, the panoramic endoscopic imaging system provided in this application embodiment can be applied in medical endoscopy, such as laparoscopy, arthroscopy, hysteroscopy and other surgeries. Doctors can simultaneously observe the tissue environment in front of the instrument and the surrounding tissue environment, thereby improving the safety of the surgery.

[0052] For example, the panoramic endoscopic imaging system provided in this application embodiment can be applied to the endoscopic inspection of industrial pipelines, such as to quickly and comprehensively detect cracks and corrosion on the inner wall of the pipeline without rotating the probe.

[0053] For example, the panoramic endoscopic imaging system provided in this application embodiment can be applied to reconnaissance in narrow spaces, such as in security and rescue, to conduct panoramic observation in gaps and holes.

[0054] Based on the above embodiments, refer to Figure 2 The second refractive surface 12 and the first reflective surface 21 have the same radius of curvature.

[0055] In this embodiment, the second refractive surface 12 is a refractive surface responsible for refracting light from inside the panoramic annular lens (PAL); the first reflective surface 21 is a reflective surface responsible for reflecting light inside the panoramic annular lens (PAL). This application designs both surfaces to have the same radius of curvature. On one hand, this effectively utilizes the internal space of the lens, resulting in smoother light transitions and facilitating lens volume reduction. On the other hand, during lens manufacturing, both surfaces can utilize the same processing template, tool, or inspection template, such as an aspherical or spherical master mold, which significantly reduces manufacturing costs and cycle time. Simultaneously, it ensures a high degree of consistency between the two optical surfaces, reducing optical performance fluctuations caused by surface shape errors.

[0056] For example, the panoramic annular lens (PAL) is fabricated using a spherical lens, which has a simple overall structure, a wide range of processing and assembly tolerances, and does not require high-precision processing technology and platforms. It has advantages such as short processing cycle and low processing cost.

[0057] Based on the above embodiments, refer to Figure 1 and Figure 2 The substrate material of the panoramic annular lens (PAL) includes glass or plastic. In the embodiments of this application, the panoramic annular lens (PAL) can not only use traditional optical glass, but also polymer materials with superior optical properties. For example, the panoramic annular lens (PAL) uses high-refractive-index, low-dispersion optical glass, such as the H-ZF or H-LAK series. High refractive index helps to obtain stronger light refraction ability under the same curvature, thereby further compressing the physical thickness of the lens while maintaining a large viewing angle; low dispersion characteristics can effectively suppress chromatic aberration and ensure color fidelity and high clarity of imaging from visible light to near-infrared bands (such as 400-850nm). Polymer materials include, but are not limited to, polymethyl methacrylate (PMMA), polycarbonate (PC), cyclic olefin polymers (COP / COC), polystyrene (PS), etc.

[0058] It should be noted that glass or plastic are various types known to those skilled in the art, and this application embodiment will not elaborate on them or limit them.

[0059] Based on the above embodiments, continue to refer to Figure 1 Along the optical axis ( Figure 1 (In the X direction), the relay lens module M2 includes a first spherical lens RL1 with positive optical power, an aperture stop S, a second spherical lens RL2 with positive optical power, a third spherical lens RL3 with positive optical power, a fourth spherical lens RL4 with negative optical power, a fifth spherical lens RL5 with positive optical power, a sixth spherical lens RL6 with negative optical power, a seventh spherical lens RL7 with positive optical power, and an eighth spherical lens RL8 with positive optical power. The aperture stop S refers to the aperture that limits the amount of light passing through the lens.

[0060] Optical power is equal to the difference between the image-side convergence and the object-side convergence of the light beam, and its value is the reciprocal of the focal length. It characterizes the ability of a wide-angle lens to deflect light. The larger the absolute value of the optical power, the stronger the ability to bend light; the smaller the absolute value of the optical power, the weaker the ability to bend light. When the optical power is positive, the refraction of light is converging; when the optical power is negative, the refraction of light is diverging. Optical power can be used to characterize a single refractive surface of a lens (i.e., one surface of the lens), a single lens, or a lens group formed by multiple lenses.

[0061] In the embodiments of this application, combined with Figure 1As shown in the optical path, this application has deeply optimized and systematically expanded the optical structure of the relay lens module M2. This module is not a simple optical path transmission unit, but a precisely designed aberration correction and relay imaging optical module. It adopts a complex combination of eight spherical lenses, and through the combination and spatial arrangement of positive, positive, positive, negative, positive, negative, positive, positive, it realizes high-quality relay transmission and imaging of the special image plane generated by the panoramic ring module, and transmits the panoramic ring imaging clearly and with low distortion to the imaging sensor.

[0062] Specifically, a first spherical lens RL1 with positive optical power receives panoramic annular imaging from the panoramic annular lens PAL, converging light rays at large angles and correcting the field curvature of the panoramic annular lens PAL. An aperture stop S limits the aperture of the image light rays, reducing stray light. A second spherical lens RL2 and a third spherical lens RL32 with positive optical power continue to converge the image light rays and correct the field curvature. Optionally, a third spherical lens RL3 with positive optical power and a fourth spherical lens RL4 with negative optical power are combined to form a cemented doublet, creating an achromatic lens group, which helps reduce the optical path volume and eliminate chromatic aberration. The fourth spherical lens RL4 with negative optical power, in conjunction with the front and rear positive lenses, helps to efficiently correct axial chromatic aberration, ensuring that light rays of different wavelengths converge at the same point. Furthermore, a fifth spherical lens RL5 with positive optical power is provided to converge the image light rays. The sixth spherical lens RL6 with negative optical power and the seventh spherical lens RL7 with positive optical power form a cemented doublet, creating an achromatic lens group that further reduces the optical path volume and eliminates chromatic aberration. Finally, the eighth spherical lens RL8 with positive optical power efficiently projects the corrected light onto the imaging sensor.

[0063] Based on the above embodiments, refer to Figure 1 In this embodiment, the focal lengths of each lens in the relay lens module M2 and the overall focal length of the relay lens module M2 are further rationally designed. Specifically, the focal lengths of each lens in the relay lens module M2 and the overall focal length of the relay lens module M2 satisfy the following relationship:

[0064] 5.510≤f1 / f≤9.183; 1.299≤f2 / f≤2.165; 0.334≤f3 / f≤0.557; -0.535≤f4 / f≤-0.321.

[0065] 1.862≤f5 / f≤3.103; -0.634≤f6 / f≤-0.380; 0.269≤f7 / f≤0.448; 0.450≤f8 / f≤0.750.

[0066] Where f is the overall focal length of the relay lens module M2, f1 is the focal length of the first spherical lens RL1, f2 is the focal length of the second spherical lens RL2, f3 is the focal length of the third spherical lens RL3, f4 is the focal length of the fourth spherical lens RL4, f5 is the focal length of the fifth spherical lens RL5, f6 is the focal length of the sixth spherical lens RL6, f7 is the focal length of the seventh spherical lens RL7, and f8 is the focal length of the eighth spherical lens RL8. Since focal length is equal to the reciprocal of optical power, this application optimizes the optical power distribution of the eight spherical lenses through the above focal length range design, controls the curvature of the lens surface, balances various aberrations, etc., thereby ensuring that the panoramic endoscopic imaging system obtains a clear image with high resolution, low distortion, color fidelity, and uniform image plane.

[0067] Based on the above embodiments, refer to Figure 1 In this embodiment, the refractive index Nd and Abbe number Vd parameters of each lens material in the relay lens module M2 are further designed rationally.

[0068] Refractive index is the ratio of the speed of light in a vacuum to the speed of light in a medium. It is mainly used to describe a material's ability to refract light. Different materials have different refractive indices; the higher the refractive index, the slower the light travels in that material. The Abbe number is an index used to represent the dispersion ability of a transparent medium; it can also be called the dispersion coefficient. The more severe the dispersion of the medium, the smaller the Abbe number; conversely, the less severe the dispersion, the larger the Abbe number. Generally speaking, refractive index and Abbe number are inversely proportional. This means that materials with higher refractive indices tend to have lower Abbe numbers, and vice versa.

[0069] Specifically, the refractive index Nd and Abbe number Vd of each lens material in the relay lens module M2 satisfy the following ranges:

[0070] 1.578≤Nd1≤1.658, 60.223≤Vd1≤66.562; 1.567≤Nd2≤1.648, 53.822≤Vd2≤59.487.

[0071] 1.508≤Nd3≤1.585, 59.637≤Vd3≤65.915; 1.647≤Nd4≤1.731, 29.603≤Vd4≤32.719.

[0072] 1.691≤Nd5≤1.777, 48.912≤Vd5≤54.060; 1.623≤Nd6≤1.706, 33.710≤Vd6≤37.259.

[0073] 1.580≤Nd7≤1.661, 57.350≤Vd7≤63.387; 1.740≤Nd8≤1.829, 24.434≤Vd8≤27.006.

[0074] Wherein, Nd1 and Vd1 are the refractive index and Abbe number of the material of the first spherical lens RL1, respectively; Nd2 and Vd2 are the refractive index and Abbe number of the material of the second spherical lens RL2, respectively; Nd3 and Vd3 are the refractive index and Abbe number of the material of the third spherical lens RL3, respectively; Nd4 and Vd4 are the refractive index and Abbe number of the material of the fourth spherical lens RL4, respectively; Nd5 and Vd5 are the refractive index and Abbe number of the material of the fifth spherical lens RL5, respectively; Nd6 and Vd6 are the refractive index and Abbe number of the material of the sixth spherical lens RL6, respectively; Nd7 and Vd7 are the refractive index and Abbe number of the material of the seventh spherical lens RL7, respectively; and Nd8 and Vd8 are the refractive index and Abbe number of the material of the eighth spherical lens RL8, respectively. This application optimizes the refractive index Nd and Abbe number Vd distribution of the eight spherical lenses through the above-mentioned design, which can correct aberrations, make the light smoother, and ensure that the light is efficiently projected onto the imaging sensor, thereby ensuring that the panoramic endoscopic imaging system obtains a clear image with high resolution, low distortion, color fidelity and uniform image plane.

[0075] Based on the above embodiments, this application embodiment achieves focusing imaging of the inner walls of cavities with different inner diameters by adjusting the back intercept of the relay lens module M2 during cavity measurement. The back intercept of the relay lens module M2, also known as the back working distance, refers to the axial distance from the last surface (vertex) of the last lens element (eighth spherical lens RL8) in the relay lens module M2 to the final imaging surface IMA (i.e., the image sensor target surface) of the system. This application uses the optical axis direction of the panoramic annular lens PAL (… Figure 1 (In the X direction) Adjust the distance between the eighth spherical lens RL8 and the image plane IMA to achieve focusing and imaging of the inner wall of the cavity with different inner diameters.

[0076] Optionally, the back cutoff value of the relay lens module M2 is in the range of 2.47mm to 2.97mm.

[0077] Based on the above embodiments, the panoramic endoscopic imaging system 100 has a field curvature of less than 0.05 mm, an F-Theta distortion of less than 5%, and a relative illumination of greater than 88%.

[0078] In summary, the panoramic endoscopic imaging system provided in this application has the following advantages compared with existing endoscopic technologies:

[0079] 1) Compared with endoscope solutions based on fiber optic image bundles, the panoramic endoscopic imaging system provided in this application embodiment has high imaging resolution, high field of view utilization and high detection efficiency.

[0080] 2) Compared with the endoscopic imaging scheme based on macro fisheye, the panoramic endoscopic imaging system provided in this application embodiment has good consistency between the center and edge imaging of the field of view, low F-Theta distortion, and uniform overall illumination.

[0081] 3) The panoramic endoscopic imaging system provided in this application uses a global surface lens design, which has a simple overall structure, a large range of processing and assembly tolerances, and does not require high-precision processing technology and platform. It has advantages such as short processing cycle and low processing cost.

[0082] The following describes in further detail, with reference to the accompanying drawings, specific embodiments of the panoramic endoscopic imaging system applicable to the above-described embodiments.

[0083] Example

[0084] refer to Figure 1 and Figure 2 As shown, the panoramic endoscopic imaging system provided in this application embodiment includes a system along the optical axis ( Figure 1 A panoramic ring lens module M1 and a relay lens module M2 are arranged sequentially in the X-direction. The panoramic ring lens module M1 includes a panoramic ring lens PAL, the optical axis of which coincides with the optical axis of the relay lens module M2. The panoramic ring lens module M1 satisfies the following condition:

[0085] The first refractive surface 11 has a spherical shape with a radius of curvature of 10.250 mm; the second refractive surface 12 and the first reflective surface 21 have the same spherical shape with a radius of curvature of 5.995 mm; the second reflective surface 22 has a spherical shape with a radius of curvature of 6.516 mm; the center thickness of the panoramic annular lens PAL is 6.65 mm, and the glass material is H-K9L. The first and second refractive surfaces 11 and 12 are coated with antireflective coatings, and the first and second reflective surfaces 21 and 22 are coated with internal reflection coatings. The second refractive surface 12 and the first reflective surface 21 have the same radius of curvature. The antireflective coating has an antireflection band in the visible light and near-infrared bands; the internal reflection coating has a reflection band in the visible light and near-infrared bands.

[0086] The lens data for the first spherical lens RL1 to the eighth spherical lens RL8 in the relay lens module M2 are shown in Table 1 below:

[0087] Table 1 Lens data of each lens in the relay lens module

[0088]

[0089] In Table 1, the surface number M is assigned according to the surface sequence of each lens; "S" represents the aperture stop; the radius of curvature R represents the curvature of the lens surface, with a positive value indicating that the surface bends towards the image plane and a negative value indicating that the surface bends towards the object plane; the thickness represents the central axial distance between the current surface and the next surface; the refractive index Nd represents the ability of the material between the current surface and the next surface to deflect light, with "\" indicating that the current position is air and the refractive index is 1. The Abbe number Vd represents the dispersion characteristics of the material between the current surface and the next surface, with "\" indicating that the current position is air and the Abbe number is 1; the more severe the dispersion of the medium, the smaller the Abbe number; conversely, the less severe the dispersion of the medium, the larger the Abbe number.

[0090] Figure 3 for Figure 1 A schematic diagram of the optical path for measuring a 15mm inner diameter cavity in a panoramic endoscopic imaging system is provided. Figure 4 for Figure 1 A panoramic endoscopic imaging system is provided to measure the MTF (Mean Transformation Factor) of a cavity with an inner diameter of 15 mm. Figure 5 for Figure 1 A panoramic endoscopic imaging system is provided to measure the field curvature and distortion of a cavity with an inner diameter of 15 mm. Figure 6 for Figure 1 A panoramic endoscopic imaging system is provided to measure the relative illumination map of a cavity with an inner diameter of 15 mm. Figure 7 for Figure 1 A schematic diagram of the optical path for a panoramic endoscopic imaging system measuring a cavity with an inner diameter of 32.5 mm is provided. Figure 8 for Figure 1 A panoramic endoscopic imaging system is provided to measure the MTF (Mean Transformation Factor) of a cavity with an internal diameter of 32.5 mm. Figure 9 for Figure 1 A panoramic endoscopic imaging system is provided to measure field curvature and distortion maps of a cavity with an internal diameter of 32.5 mm. Figure 10 for Figure 1 A panoramic endoscopic imaging system is provided to measure the relative illumination map of a cavity with an internal diameter of 32.5 mm. Figure 11 for Figure 1 A schematic diagram of the optical path for a panoramic endoscopic imaging system measuring a cavity with an inner diameter of 50 mm is provided. Figure 12 for Figure 1 A panoramic endoscopic imaging system is provided to measure the MTF (Mean Transformation Factor) of a cavity with an inner diameter of 50 mm. Figure 13 for Figure 1 A panoramic endoscopic imaging system is provided to measure field curvature and distortion maps of a cavity with an inner diameter of 50 mm. Figure 14 for Figure 1 A panoramic endoscopic imaging system is provided to measure the relative illumination map of a cavity with an inner diameter of 50 mm.

[0091] like Figure 3 , Figure 7 and Figure 11 As shown, in this embodiment, the maximum lower half field of view α1=α2=α3=30° and the maximum upper half field of view β1=β2=β3=10° are corresponding to the panoramic endoscopic imaging system. This indicates that a single imaging can obtain a 40° side view, which has the advantage of large-angle imaging.

[0092] refer to Figure 4 , Figure 8 and Figure 12 MTF (Modulation Transfer Function), also known as spatial contrast transfer function or spatial frequency contrast sensitivity function, is a function of spatial frequency that reflects the ability of an optical system to transmit sinusoidal modulation schemes of various frequencies. MTF is an important indicator of lens performance, including a "wave optics MTF" that considers the wave nature of light (diffraction effect) and a "geometric optics MTF" that does not consider diffraction effects. Generally, in lens design, an MTF > 0.22 is sufficient for human visual perception. Figure 4 , Figure 8 and Figure 12 It can be seen that when the spatial frequency of the geometric MTF transfer function of the panoramic endoscopic imaging system in this embodiment is 160 lp / mm, the MTF is ≥0.3. This indicates that the panoramic endoscopic imaging system can perform panoramic annular imaging of cavity inner diameters of 15mm, 32.5mm, and 50mm in the entire field of view, and the high-resolution imaging requirements of the cavity inner wall are met after the imaging light beam is expanded.

[0093] refer to Figure 5 , Figure 9 and Figure 13 In the left coordinate system of the figure, the horizontal axis represents the field curvature of the panoramic endoscopic imaging system, in mm; the vertical axis represents the normalized image height, without units. In the right coordinate system of the figure, the horizontal axis represents the distortion (F-Theta) of the panoramic endoscopic imaging system, in %; the vertical axis represents the normalized image height, without units. Figure 5 , Figure 9 and Figure 13As can be seen, the panoramic endoscopic imaging system provided in this embodiment performs panoramic annular imaging of cavity inner diameters of 15mm, 32.5mm, and 50mm across the entire field of view, with an imaging field curvature of less than 0.05mm and F-Theta distortion of less than 5%. This indicates that the system can effectively control field curvature, meaning that the difference in image quality between the center and the periphery is small during imaging. Simultaneously, the system achieves good distortion correction, resulting in minimal imaging distortion.

[0094] refer to Figure 6 , Figure 10 and Figure 14 The relative illumination map reflects the uniformity of illumination across the entire image area of ​​a panoramic endoscopic imaging system, i.e., the brightness difference between the edges and the center. It is an important indicator for evaluating lens image quality, especially crucial for large-format and wide-angle lenses. Figure 6 , Figure 10 and Figure 14 As can be seen, the panoramic endoscopic imaging system provided in this application embodiment performs panoramic ring imaging of cavity inner diameters of 15mm, 32.5mm, and 50mm within the entire field of view, with an imaging relative illumination greater than 88%. This indicates that the panoramic endoscopic imaging system has strong uniformity of illumination across the entire image area, strong adaptability of the field of view, good consistency, and can effectively transmit even edge light.

[0095] Note that the above description is merely a preferred embodiment of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein. Features of various embodiments of the present invention can be partially or wholly coupled or combined with each other, and can cooperate and be technically driven in various ways. Various obvious changes, readjustments, combinations, and substitutions can be made by those skilled in the art without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments. Many other equivalent embodiments may be included without departing from the concept of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A panoramic endoscopic imaging system, characterized in that, It includes a panoramic ring lens module and a relay lens module arranged sequentially along the optical axis; The panoramic ring lens module includes a panoramic ring lens, the optical axis of which coincides with the optical axis of the relay lens module; wherein, the imaging light passes sequentially through the first refractive surface, the first reflective surface, the second reflective surface, and the second refractive surface of the panoramic ring lens; the first refractive surface and the second refractive surface are coated with anti-reflection films, and the first reflective surface and the second reflective surface are coated with internal reflection films.

2. The panoramic endoscopic imaging system according to claim 1, characterized in that, The second refractive surface and the first reflective surface have the same radius of curvature.

3. The panoramic endoscopic imaging system according to claim 1, characterized in that, The substrate material of the panoramic annular lens includes glass or plastic.

4. The panoramic endoscopic imaging system according to claim 1, characterized in that, Along the optical axis from the image side to the object side, the relay lens module includes: A first spherical lens with positive optical power, an aperture stop, a second spherical lens with positive optical power, a third spherical lens with positive optical power, a fourth spherical lens with negative optical power, a fifth spherical lens with positive optical power, a sixth spherical lens with negative optical power, a seventh spherical lens with positive optical power, and an eighth spherical lens with positive optical power.

5. The panoramic endoscopic imaging system according to claim 4, characterized in that, The third spherical lens and the fourth spherical lens constitute a cemented doublet lens, and the sixth spherical lens and the seventh spherical lens constitute a cemented doublet lens.

6. The panoramic endoscopic imaging system according to claim 4, characterized in that, The focal length of each lens in the relay lens module satisfies the following relationship with the overall focal length of the relay lens module: 5.510≤f1 / f≤9.183; 1.299≤f2 / f≤2.165; 0.334≤f3 / f≤0.557; -0.535≤f4 / f≤-0.321; 1.862≤f5 / f≤3.103; -0.634≤f6 / f≤-0.380; 0.269≤f7 / f≤0.448; 0.450≤f8 / f≤0.750; Wherein, f is the overall focal length of the relay lens module, f1 is the focal length of the first spherical lens, f2 is the focal length of the second spherical lens, f3 is the focal length of the third spherical lens, f4 is the focal length of the fourth spherical lens, f5 is the focal length of the fifth spherical lens, f6 is the focal length of the sixth spherical lens, f7 is the focal length of the seventh spherical lens, and f8 is the focal length of the eighth spherical lens.

7. The panoramic endoscopic imaging system according to claim 4, characterized in that, The refractive index and Abbe number of each lens material in the relay lens module satisfy the following ranges: 1.578≤Nd1≤1.658, 60.223≤Vd1≤66.562; 1.567≤Nd2≤1.648, 53.822≤Vd2≤59.487; 1.508≤Nd3≤1.585, 59.637≤Vd3≤65.915; 1.647≤Nd4≤1.731, 29.603≤Vd4≤32.719; 1.691≤Nd5≤1.777, 48.912≤Vd5≤54.060; 1.623≤Nd6≤1.706, 33.710≤Vd6≤37.259; 1.580≤Nd7≤1.661, 57.350≤Vd7≤63.387; 1.740≤Nd8≤1.829, 24.434≤Vd8≤27.006; Wherein, Nd1 and Vd1 are the refractive index and Abbe number of the first spherical lens material, respectively; Nd2 and Vd2 are the refractive index and Abbe number of the second spherical lens material, respectively; Nd3 and Vd3 are the refractive index and Abbe number of the third spherical lens material, respectively; Nd4 and Vd4 are the refractive index and Abbe number of the fourth spherical lens material, respectively; Nd5 and Vd5 are the refractive index and Abbe number of the fifth spherical lens material, respectively; Nd6 and Vd6 are the refractive index and Abbe number of the sixth spherical lens material, respectively; Nd7 and Vd7 are the refractive index and Abbe number of the seventh spherical lens material, respectively; and Nd8 and Vd8 are the refractive index and Abbe number of the eighth spherical lens material, respectively.

8. The panoramic endoscopic imaging system according to claim 1, characterized in that, By adjusting the back cutoff of the relay lens module, focusing and imaging of the inner walls of cavities with different inner diameters can be achieved.

9. The panoramic endoscopic imaging system according to claim 8, characterized in that, The back cutoff value of the relay lens module ranges from 2.47mm to 2.97mm.

10. The panoramic endoscopic imaging system according to claim 1, characterized in that, The panoramic endoscopic imaging system has a field curvature of less than 0.05 mm, an F-Theta distortion of less than 5%, and a relative illumination of greater than 88%.

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