Panoramic endoscopic optical system

Abstract

The application provides a panoramic endoscopic optical system, which comprises a front objective lens group, a relay rod lens group and a rear adapter lens group arranged in sequence along an optical axis; the front objective lens group comprises a panoramic annular lens and an objective lens group arranged in sequence along the optical axis, the optical axis of the panoramic annular lens coincides with the optical axis of the objective lens group, the objective lens group comprises eight spherical lenses and an aperture stop, the optical power combination of the first to eighth spherical lenses is positive, positive, positive, negative, positive, negative, positive and positive; the system is designed by the relay lens group and the adapter lens group, and light captured by the front panoramic annular objective lens is efficiently conducted to the rear end of the system, so that a large target surface and a high-pixel imaging chip can be arranged at a position far from the probe, the imaging resolution, the detection efficiency and the system versatility are significantly improved while the panoramic imaging advantage is ensured.

Description

Technical Field

[0001] The present invention relates to the field of optical imaging technology, and in particular to a panoramic endoscopic optical system. Background Technology

[0002] In the fields of industrial inspection and medical diagnostics, high-precision imaging of the morphology and defects of the inner walls of narrow cavities (such as pipes, engine cylinders, and natural human cavities) is of great significance. Currently, common cavity inner wall imaging solutions on the market mainly include endoscope solutions based on fiber optic image bundles and endoscope imaging solutions based on macro fisheye lenses.

[0003] However, all of the above solutions have significant shortcomings. For example, the fiber optic image bundle-based solution is limited by the discrete sampling characteristics of the fiber bundle, resulting in generally low imaging resolution. Furthermore, its field of view is usually parallel to the cavity axis, making it difficult to directly acquire a frontal image perpendicular to the inner wall. Even with the aid of a mirror to change the optical path, a full rotation is required to complete the full wall scan, leading to low detection efficiency. While the macro fisheye lens-based solution can achieve large field of view imaging, it suffers from poor image consistency between the center and edges of the field of view, severe barrel distortion, significant edge illumination attenuation, and poor illumination uniformity.

[0004] In recent years, endoscopic solutions based on panoramic annular imaging (PAL) technology have been proposed, which can acquire a 360° circumferential lateral field of view using a single panoramic annular lens. However, in this type of solution, the imaging chip must usually be placed inside the front probe. Due to the limited cavity space, only small-surface chips can be used, which not only limits the imaging accuracy and pixel count, but also makes it difficult to adapt to common industrial camera interfaces. Furthermore, the heat dissipation problem of the front chip is also extremely prominent. Summary of the Invention

[0005] Based on this, the present invention provides a panoramic endoscopic optical system. Through a sophisticated design of relay and adapter lenses, this system efficiently transmits the light captured by the front-end panoramic ring objective lens to the rear end of the system. This allows for the placement of a large-area, high-pixel imaging chip at a location far from the probe, significantly improving imaging resolution, detection efficiency, and system versatility while maintaining the advantages of panoramic imaging.

[0006] In a first aspect, embodiments of this application also provide a panoramic endoscopic optical system, comprising:

[0007] The front objective lens group, the relay rod lens group, and the rear adapter lens group are arranged sequentially along the optical axis.

[0008] The front objective lens group includes a panoramic annular lens and an objective lens group arranged sequentially along the optical axis; wherein, the optical axis of the panoramic annular lens coincides with the optical axis of the objective lens group; 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 annular lens, enters the objective lens group, and then passes through the relay rod lens group and the rear adapter lens group to form an image on the image plane.

[0009] The objective lens group, from the object side to the image side, includes the following:

[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] The third spherical lens and the fourth spherical lens form a cemented doublet lens group, and the sixth spherical lens and the seventh spherical lens form a cemented doublet lens group.

[0012] Optionally, in the panoramic annular lens, the first refractive surface and the second refractive surface are coated with antireflective films, the first reflective surface and the second reflective surface are coated with internal reflection films, and the second refractive surface and the first reflective surface have the same radius of curvature.

[0013] Optionally, the ratio of the focal length of each spherical lens in the objective lens group to the overall focal length of the objective lens group satisfies the following relationship:

[0014] ; ; ; ;

[0015] ; ; ; ;

[0016] in, The overall focal length of the objective lens group is [missing information]. , , , , , , , These are the focal lengths of the first spherical lens to the eighth spherical lens, respectively.

[0017] Optionally, the refractive index and Abbe number of each spherical lens in the objective lens group satisfy the following relationship:

[0018] , ; , ;

[0019] , ; , ;

[0020] , ; , ;

[0021] , ; , ;

[0022] in, , , , , , , , These are the refractive indices of the first spherical lens to the eighth spherical lens, respectively. , , , , , , , These are the Abbe numbers of the first spherical lens to the eighth spherical lens, respectively.

[0023] Optionally, the relay rod lens group includes at least one sub-rod lens group, and the sub-rod lens group adopts a symmetrical structural design;

[0024] The sub-rod mirror group, from the object side to the image side, includes the following:

[0025] A first lens with positive optical power, a second lens with negative optical power, a third lens with positive optical power, a fourth lens with positive optical power, a fifth lens with negative optical power, and a sixth lens with positive optical power.

[0026] The second lens and the third lens form a cemented doublet lens group, the fourth lens and the fifth lens form a cemented doublet lens group, and all the lenses in the sub-rod lens group are spherical lenses.

[0027] Optionally, the ratio of the focal length of each spherical lens in the sub-bar lens group to the overall focal length of the sub-bar lens group satisfies the following relationship:

[0028] ; ; ; ;

[0029] ; ;

[0030] in, The overall focal length of the sub-rod lens group is [missing information]. , , , , , These are the focal lengths of the first lens to the sixth lens, respectively.

[0031] Optionally, the refractive index and Abbe number of each spherical lens in the sub-bar lens group satisfy the following relationship:

[0032] , ; , ;

[0033] , ; , ;

[0034] , ; , ;

[0035] in, , , , , , These are the refractive indices of the first lens to the sixth lens, respectively. , , , , , These are the Abbe numbers of the first lens to the sixth lens, respectively.

[0036] Optionally, the rear adapter lens assembly includes, from the object side to the image side, the following components in sequence:

[0037] A first rear lens with positive optical power, a second rear lens with positive optical power, a third rear lens with negative optical power, a fourth rear lens with negative optical power, a fifth rear lens with positive optical power, a sixth rear lens with negative optical power, a seventh rear lens with positive optical power, an eighth rear lens with negative optical power, and a ninth rear lens with positive optical power.

[0038] Wherein, the second rear lens and the third rear lens constitute a cemented doublet lens group, the fourth rear lens and the fifth rear lens constitute a cemented doublet lens group, the sixth rear lens and the seventh rear lens constitute a cemented doublet lens group, and the eighth rear lens and the ninth rear lens constitute a cemented doublet lens group.

[0039] The doublet lens group, consisting of the sixth and seventh rear lenses, can move back and forth along the optical axis to achieve focusing and imaging of the inner walls of cavities with different inner diameters.

[0040] Optionally, the ratio of the focal length of each spherical lens in the rear adapter lens group to the overall focal length of the rear adapter lens group satisfies the following relationship:

[0041] ; ; ;

[0042] ; ; ;

[0043] ; ; ;

[0044] in, This refers to the overall focal length of the rear adapter lens group. , , , , , , , , These are the focal lengths of the first rear lens to the ninth rear lens, respectively.

[0045] Optionally, the refractive index and Abbe number of each rear lens in the rear adapter lens group satisfy the following relationship:

[0046] , ; , ;

[0047] , ; , ;

[0048] , ; , ;

[0049] , ; , ;

[0050] , ;

[0051] in, , , , , , , , , The refractive indices of the first rear lens to the ninth rear lens are respectively. , , , , , , , , These are the Abbe numbers of the first rear lens to the ninth rear lens, respectively.

[0052] In summary, the panoramic endoscopic optical system provided by this invention, consisting of a three-section panoramic endoscopic optical architecture comprising a front objective lens group, a relay rod lens group, and a rear adapter lens group, achieves stable imaging with high resolution, low distortion, and high uniformity illumination over a wide working distance range by systematically optimizing the number of lenses, optical power, cementation state, material parameters, and focal length ratio within each group. Attached Figure Description

[0053] Figure 1 A schematic diagram of the structure of a panoramic endoscopic optical system provided in an embodiment of this application;

[0054] Figure 2 This is a schematic diagram of the structure of the front objective lens assembly provided in an embodiment of this application;

[0055] Figure 3 This is a schematic diagram of the structure of the panoramic ring lens provided in an embodiment of this application;

[0056] Figure 4 A schematic diagram of the panoramic annular lens field of view provided in an embodiment of this application;

[0057] Figure 5 This is a schematic diagram of the relay rod lens assembly provided in an embodiment of this application;

[0058] Figure 6 This is a schematic diagram of the sub-rod mirror assembly provided in an embodiment of this application;

[0059] Figure 7 This is a schematic diagram of the structure of the rear adapter lens assembly provided in the embodiments of this application;

[0060] Figure 8 This is a schematic diagram of the focusing of the rear adapter lens group provided in an embodiment of this application;

[0061] Figure 9 A schematic diagram of the optical path of a panoramic endoscopic optical system provided in this application, measuring a cavity with an inner wall diameter of 15 mm.

[0062] Figure 10 for Figure 9 The embodiment provides an MTF chart with a measurement chamber inner wall diameter of 15 mm;

[0063] Figure 11 for Figure 9 The embodiment provides a field curvature and distortion map of a measuring cavity with an inner wall diameter of 15 mm;

[0064] Figure 12 for Figure 9 The embodiment provides a relative illumination diagram for a measuring cavity with an inner wall diameter of 15 mm;

[0065] Figure 13 A schematic diagram of the optical path of a panoramic endoscopic optical system provided in this application, measuring a cavity with a diameter of 32.5 mm.

[0066] Figure 14 for Figure 13 The embodiment provides an MTF chart for a measurement chamber with an inner wall diameter of 32.5 mm;

[0067] Figure 15 for Figure 13 The embodiment provides field curvature and distortion diagrams for a measuring cavity with an inner wall diameter of 32.5 mm;

[0068] Figure 16 for Figure 13 The embodiment provides a relative illumination map of the inner wall diameter of the measuring cavity, which is 32.5 mm.

[0069] Figure 17 A schematic diagram of the optical path of a panoramic endoscopic optical system provided in this application, measuring a cavity with a diameter of 50 mm.

[0070] Figure 18 for Figure 17 The embodiment provides an MTF chart with a measurement chamber inner wall diameter of 50 mm;

[0071] Figure 19 for Figure 17 The embodiment provides a field curvature and distortion map of a measuring cavity with an inner wall diameter of 50 mm;

[0072] Figure 20 for Figure 17 The embodiment provides a relative illumination map of the inner wall diameter of the measuring cavity, which is 50 mm. Detailed Implementation

[0073] 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.

[0074] Figure 1 This is a schematic diagram of the structure of a panoramic endoscopic optical system provided in an embodiment of this application. Figure 2 This is a schematic diagram of the front objective lens assembly provided in an embodiment of this application, with reference to... Figure 1 and Figure 2 This invention provides a panoramic endoscopic optical system, comprising a front objective lens group M1, a relay rod lens group M2, and a rear adapter lens group M3 arranged sequentially along the optical axis. Imaging rays emitted from the object plane OBJ pass through these three lens groups sequentially and are finally imaged at the image plane IMA. The front objective lens group M1, located at the very front of the system, is used to capture a 360° panoramic annular field of view and form a preliminary image-side beam. It includes a panoramic annular lens PAL and objective lens groups (O1~O8) arranged sequentially along the optical axis. The optical axis of the panoramic annular lens PAL and the optical axis of the objective lens groups (e.g., ...) are aligned. Figure 2(As shown in the X direction) coincides. The imaging light rays sequentially pass 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, and then enter the objective lens group (O1~O8), and then pass through the relay rod lens group M2 and the rear adapter lens group M3 to form an image on the image plane. The objective lens group (O1~O8) from the object side to the image side includes, in sequence, a first spherical lens O1 with positive optical power, an aperture stop S, a second spherical lens O2 with positive optical power, a third spherical lens O3 with positive optical power, a fourth spherical lens O4 with negative optical power, a fifth spherical lens O5 with positive optical power, a sixth spherical lens O6 with negative optical power, a seventh spherical lens O7 with positive optical power, and an eighth spherical lens O8 with positive optical power. Among them, the third spherical lens O3 and the fourth spherical lens O4 form a cemented doublet lens group, and the sixth spherical lens O6 and the seventh spherical lens O7 form a cemented doublet lens group.

[0075] It's important to explain that optical power equals the difference between the convergence of the beam at the image plane and the convergence of the beam at the object plane; it characterizes the ability of an optical system to deflect light. The larger the absolute value of the optical power, the stronger its ability to bend light; the smaller the absolute value, the weaker its 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 system of multiple lenses (i.e., a lens group).

[0076] In the objective lens group, the optical power and material selection of each lens are rigorously matched. The first spherical lens O1, as the first lens in the front group, uses positive optical power to converge the outgoing beam from the panoramic annular lens PAL. It also controls the incident angle of peripheral rays and reduces off-axis aberrations through a larger radius of curvature. The aperture stop S is positioned after the first spherical lens O1 to limit the aperture of the imaging beam, balancing resolution and depth of field. The second spherical lens O2, also with positive optical power, compensates for spherical aberration caused by the first spherical lens O1 and further compresses the beam aperture. The third spherical lens O3, with positive optical power, and the fourth spherical lens O4, with negative optical power, are cemented together. This cemented assembly handles chromatic aberration correction and field curvature compensation for large-aperture rays. The fifth spherical lens O5, with positive optical power, relays the beam transmission and corrects residual coma. The sixth spherical lens O6, with negative optical power, and the seventh spherical lens O7, with positive optical power, are cemented together again. This cemented assembly can be used to correct advanced astigmatism and distortion. Simultaneously, the arrangement of the negative optical power lens in front and the positive optical power lens behind ensures a smooth transition in the principal ray angle, matching the requirement for positive incidence at the rear. The eighth spherical lens O8, using positive optical power as the final lens, is responsible for converging the beam at a suitable aperture angle and exit height to the entrance port of the relay rod lens group M2, ensuring pupil alignment. This double-cemented structure not only effectively corrects positional chromatic aberration and magnification chromatic aberration of the system, but also helps reduce the curvature of each lens and lower advanced spherical aberration through the distribution of refraction angles on the cemented surfaces.

[0077] It should be emphasized that all eight lenses in the objective lens group in this embodiment are spherical lenses. Compared with aspherical lenses, spherical lenses are easier to grind and polish, have a higher yield, and are more affordable, making them suitable for mass production. By combining multiple spherical lenses into a lens group, the aberrations produced by different lenses can be designed to cancel or balance each other, thereby achieving an overall imaging effect that eliminates spherical aberrations.

[0078] Based on the above embodiments, Figure 3 This is a schematic diagram of the structure of the panoramic ring lens provided in an embodiment of this application. Figure 4 This is a schematic diagram of the panoramic annular lens field of view provided in an embodiment of this application, with reference to... Figure 3In the panoramic annular lens (PAL), the first refractive surface 11 and the second refractive surface 12 are coated with anti-reflection films, and the first reflecting surface 21 and the second reflecting surface 22 are coated with internal reflection films. The second refractive surface 12 and the first reflecting surface 21 have the same radius of curvature. In this embodiment, the panoramic annular lens (PAL) has a unique refracting optical path design. After the imaging light is emitted from the inner wall of the cavity under test, it passes sequentially through the first refractive surface 11, the first reflecting surface 21, the second reflecting surface 22, and the second refractive surface 12 of the panoramic annular lens (PAL), and then exits into the subsequent objective lens group (O1~O8). Both the first refractive surface 11 and the second refractive surface 12 are coated with anti-reflection films to improve light transmittance and reduce stray light; both the first reflecting surface 21 and the second reflecting surface 22 are coated with internal reflection films to ensure reflection efficiency and reduce light energy loss. Specifically, the second refractive surface 12 and the first reflecting surface 21 are configured to have the same radius of curvature. This structural feature ensures that the two sides have the same surface shape, which not only simplifies the processing and inspection, but more importantly, it can effectively compensate for off-axis aberrations (especially astigmatism and coma) introduced by the reflecting surface. This ensures that the annular beam after reflection can still exit in a nearly parallel or concentric state, providing good wavefront quality for aberration correction of the subsequent objective lens group.

[0079] Based on the above embodiments, to ensure the achievement of the aforementioned aberration correction effect, this invention explicitly constrains the focal length allocation of each spherical lens in the objective lens group. Specifically, the ratio of the focal length of each spherical lens in the objective lens group to the overall focal length of the objective lens group satisfies the following relationship:

[0080] ; ; ; .

[0081] ; ; ; .

[0082] in, The overall focal length of the objective lens group. Let O1 be the focal length of the first spherical lens. The focal length of the second spherical lens O2 is... Let O3 be the focal length of the third spherical lens. Let O4 be the focal length of the fourth spherical lens. Let O5 be the focal length of the fifth spherical lens. Let O6 be the focal length of the sixth spherical lens. Let O7 be the focal length of the seventh spherical lens. This refers to the focal length of the eighth spherical lens O8. The above ratio range ensures that each lens can achieve a reasonable optical power without producing excessive higher-order aberrations, thus enabling the entire objective lens group to maintain a large relative aperture while possessing excellent aberration balance capabilities.

[0083] Furthermore, embodiments of this application optimize the refractive index and Abbe number of each spherical lens in the objective lens group, combined with... Figure 2 The refractive indices of the first spherical lens O1 to the eighth spherical lens O8 are set as follows: , , , , , , , The Abbe numbers of the first spherical lens O1 to the eighth spherical lens O8 are respectively , , , , , , , The refractive index and Abbe number of each spherical lens in the objective lens group satisfy the following relationship:

[0084] , ; , .

[0085] , ; , .

[0086] , ; , .

[0087] , ; , .

[0088] in, and These are the refractive index and Abbe number of the first spherical lens O1, respectively. and These are the refractive index and Abbe number of the second spherical lens O2, respectively. and These are the refractive index and Abbe number of the third spherical lens O3, respectively. and These are the refractive index and Abbe number of the fourth spherical lens O4, respectively. and These are the refractive index and Abbe number of the fifth spherical lens O5, respectively. and These are the refractive index and Abbe number of the sixth spherical lens O6, respectively. and These are the refractive index and Abbe number of the seventh spherical lens O7, respectively. and These are the refractive index and Abbe number of the eighth spherical lens O8, respectively.

[0089] It needs to be explained that 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, also known as 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. This application uses the aforementioned material combination for the refractive indices and Abbe numbers of the first spherical lens O1 to the eighth spherical lens O8. Through a reasonable combination of high refractive index and low (or high) dispersion, sufficient dispersion difference is provided for the cemented doublet, allowing axial and transverse chromatic aberrations to be fully corrected, while also considering processing costs and thermal stability.

[0090] Based on the above embodiments, Figure 5 This is a schematic diagram of the relay rod lens assembly provided in an embodiment of this application. Figure 6 This is a schematic diagram of the sub-rod lens assembly provided in an embodiment of this application, with reference to... Figure 1 The relay rod lens group M2 is positioned between the front objective lens group M1 and the rear adapter lens group M3, and is used to transmit the intermediate image formed by the front objective lens group M1 over a long distance with near 1:1 magnification and without aberrations to the back end of the system. In the embodiments of this application, reference is made to... Figure 5 The relay rod lens group M2 can be composed of three identical sub-rod lens groups M2-1, M2-2, and M2-3 arranged sequentially along the optical axis. In other embodiments of this application, the number of sub-rod lens groups in the relay rod lens group M2 is at least one, and the specific number is not limited and can be reasonably adjusted according to the transmission distance requirements.

[0091] Specifically, refer to Figure 6Each sub-rod lens group adopts a symmetrical structural design. From the object side to the image side, the sub-rod lens group includes a first lens RL1 with positive optical power, a second lens RL2 with negative optical power, a third lens RL3 with positive optical power, a fourth lens RL4 with positive optical power, a fifth lens RL5 with negative optical power, and a sixth lens RL6 with positive optical power. The second lens RL2 and the third lens RL3 form a cemented doublet, and the fourth lens RL4 and the fifth lens RL5 form a cemented doublet. All lenses in the sub-rod lens group are spherical lenses. The advantages of spherical lenses are described above and will not be repeated here.

[0092] This application employs a symmetrical structure design for the sub-rod lens group. For example, the first lens RL1 and the sixth lens RL6 are symmetrical and both have positive optical power; the second lens RL2 and the fifth lens RL5 are symmetrical and both have negative optical power; the third lens RL3 and the fourth lens RL4 are symmetrical and both have positive optical power; and the cemented assembly is also symmetrically distributed. This symmetrical structure is beneficial for compensating for off-axis aberrations such as coma, distortion, and transverse chromatic aberration, ensuring that the wavefront shape of light remains unchanged during long-distance transmission.

[0093] Specifically, the first lens RL1 (positive optical power) and the sixth lens RL6 (positive optical power) together perform the main axial converging function and control the beam aperture; the second lens RL2 (negative optical power) is cemented with the third lens RL3 (positive optical power), and the fourth lens RL4 (positive optical power) is cemented with the fifth lens RL5 (negative optical power). These two sets of symmetrical cemented doublet lens groups are located at the conjugate position of the pupil. Through the alternation of symmetrical optical powers of negative-positive-positive-negative, field curvature and spherical aberration can be effectively corrected, while the principal rays are made to propagate approximately parallel between the groups, thereby reducing the sensitivity to assembly errors.

[0094] Similarly, embodiments of the present invention further define the focal length ratio of the sub-bar lens group. Combined with Figure 6 Set the overall focal length of the sub-bar lens group. The focal lengths of the first lens RL1 to the sixth lens RL6 are respectively , , , , , The ratio of the focal length of each spherical lens in the sub-bar lens group to the overall focal length of the sub-bar lens group satisfies the following relationship:

[0095] ; ; ; ;

[0096] ; This proportional limitation ensures that each lens in the sub-bar lens group bears an appropriate optical power, achieving mutual cancellation of aberrations in a symmetrical structure, and simultaneously guaranteeing pupil matching between each sub-bar lens group when multiple sub-bar lens groups are used.

[0097] Meanwhile, embodiments of the present invention further define the refractive index and Abbe number of each spherical lens in the sub-bar lens group, referring to... Figure 6 The refractive indices of the first lens RL1 to the sixth lens RL6 are set as follows: , , , , , The Abbe numbers of the first lens RL1 to the sixth lens RL6 are respectively , , , , , The refractive index and Abbe number of each spherical lens in the sub-bar lens group satisfy the following relationship:

[0098] , ; , .

[0099] , ; , .

[0100] , ; , .

[0101] The sub-rod lens group provided in this application uses this material combination and is paired with a symmetrical bonding design, so that each sub-rod lens group can achieve good self-correction of chromatic aberration. When multiple sub-rod lens groups are connected in series, the cumulative chromatic aberration is almost zero, thereby ensuring that the light still has high-fidelity image color during long optical path transmission in the relay rod lens group M2.

[0102] Based on the above embodiments, Figure 7 This is a schematic diagram of the structure of the rear adapter lens assembly provided in an embodiment of this application. Figure 8 This is a schematic diagram of the focusing of the rear adapter lens group provided in the embodiments of this application, combined with... Figure 1 , Figure 7 and Figure 8The rear adapter lens group M3 is located between the relay rod lens group M2 and the image plane IMA. It is used to transfer and focus the parallel or near-parallel beam transmitted via relay onto the back-end imaging chip, and at the same time provide focusing function to adapt to the inner wall of the cavity with different radial distances (i.e. different inner diameters). Specifically, the rear adapter lens group M3 includes, from the object side to the image side, a first rear lens A1 with positive optical power, a second rear lens A2 with positive optical power, a third rear lens A3 with negative optical power, a fourth rear lens A4 with negative optical power, a fifth rear lens A5 with positive optical power, a sixth rear lens A6 with negative optical power, a seventh rear lens A7 with positive optical power, an eighth rear lens A8 with negative optical power, and a ninth rear lens A9 with positive optical power.

[0103] In this system, all lenses in the rear adapter lens group M3 are spherical lenses. The second and third rear lenses A2 and A3 form a cemented doublet lens group; the fourth and fifth rear lenses A4 and A5 form a cemented doublet lens group; the sixth and seventh rear lenses A6 and A7 form a cemented doublet lens group; and the eighth and ninth rear lenses A8 and A9 form a cemented doublet lens group. The cemented doublet lens group consisting of the sixth and seventh rear lenses A6 and A7 can move back and forth along the optical axis to achieve focusing and imaging of the inner walls of cavities with different inner diameters.

[0104] Specifically, the first rear lens A1, with positive optical power, is used to smooth and converge edge rays from the relay rod lens group M2, reducing their angle of incidence. The second rear lens A2 (positive optical power) is cemented with the third rear lens A3 (negative optical power) to correct the secondary spectrum over a wide spectral range. The fourth rear lens A4 (negative optical power) is cemented with the fifth rear lens A5 (positive optical power), and this group, through a negative-positive combination, is used to compensate for the positive field curvature accumulated at the front end.

[0105] Furthermore, the sixth rear lens A6 (negative power) and the seventh rear lens A7 (positive power) are cemented together. This cemented lens assembly can move back and forth as a whole along the optical axis (e.g., Figure 8 As shown), this constitutes a doublet lens group, i.e., a floating focusing group. When this floating focusing group moves towards the object, it is... Figure 8 Moving from position (a) to position (b) and then to position (c) is suitable for focusing on the inner wall (large inner diameter) of the cavity, which is farther away; when the floating focusing group moves towards the image side, that is, from... Figure 8 Moving from position (c) to position (b) to position (a) is suitable for focusing on the inner wall (small inner diameter) of the cavity that is closer to the center.

[0106] Among them, combined Figure 4 , Figure 8Figure (a) shows the focusing state of the rear adapter lens group when the radius H1 of the inner wall of the cavity under test is 7.5 mm and the image is clear; Figure 8 Figure (b) shows the focusing state of the rear adapter lens group when the radius H2 of the inner wall of the cavity under test is 16.25 mm and the image is clear; Figure 8 Figure (c) shows the focusing state of the rear adapter lens group when the radius H3 of the inner wall of the cavity under test is 25mm and the image is clear. The focusing group is cemented to ensure that it does not change chromatic aberration during movement and the movement is small (4.25mm in this embodiment), but it can enable the system to focus on an inner wall diameter range of 15mm to 50mm, thus achieving a wide range of object distance adjustment.

[0107] Furthermore, the eighth rear lens A8 (negative optical power) and the ninth rear lens A9 (positive optical power) are cemented together as the final cemented lens of the rear adapter lens group M3. This is used to correct advanced spherical aberration and astigmatism, and to adjust the principal ray angle to a near-perpendicular incidence state that matches the chip's microlens array, thereby improving the chip's response efficiency. The combination of various lenses with different object distances (inner diameters) provides clear focusing capabilities.

[0108] Based on the above embodiments, this embodiment of the invention further limits the ratio of the focal length of each spherical lens in the rear adapter lens group M3 to its overall focal length, setting the overall focal length of the rear adapter lens group M3 to be... The focal lengths of the first rear lens A1 to the ninth rear lens A9 are respectively , , , , , , , , The ratio of the focal length of each spherical lens in the rear adapter group M3 to the overall focal length of the rear adapter group M3 satisfies the following relationship:

[0109] ; ; .

[0110] ; ; .

[0111] ; ; .

[0112] This application adopts this proportional range limitation to ensure that the aberration drift of the system is minimized when the focusing group moves, and the optical power distribution of each lens group is conducive to achieving a larger working distance and matching a large target surface.

[0113] Based on the above embodiments, this embodiment of the invention further optimizes the refractive index and Abbe number of each rear lens in the rear adapter lens group M3, setting the refractive indices of the first rear lens A1 to the ninth rear lens A9 as follows: , , , , , , , , The Abbe numbers of the first rear lens A1 to the ninth rear lens A9 are respectively , , , , , , , , The refractive index and Abbe number of each rear lens in the M3 rear adapter group satisfy the following relationship:

[0114] , ; , .

[0115] , ; , .

[0116] , ; , .

[0117] , ; , .

[0118] , .

[0119] The rear adapter lens assembly M3 provided in this application uses the above-mentioned material combination to ensure that the multiple cemented assemblies have sufficient dispersion difference to eliminate residual chromatic aberration, while each lens has excellent light transmittance, so that the entire system has good transmittance in the visible to near-infrared bands.

[0120] In summary, the panoramic endoscopic optical system provided by this invention, through the cooperation of the relay rod lens group and the rear adapter lens group, efficiently guides the light collected by the front-end panoramic ring lens to the rear end. This not only allows for the adaptation to imaging chips with larger target surfaces and higher pixel counts, significantly improving the resolution and accuracy of endoscopic imaging, but also ensures compatibility with industrial cameras using universal interfaces, resulting in superior system adaptability and versatility. Furthermore, the rear-mounted imaging chip layout helps improve the overall heat dissipation performance, enhancing the system's operational stability and reliability.

[0121] The present invention will be further illustrated below by a set of specific embodiments, but these examples do not constitute any limitation on the present invention.

[0122] like Figure 3 As shown, the panoramic annular lens PAL satisfies:

[0123] The first refractive surface 11 has a spherical shape and a radius of curvature of 10.000 mm; the second refractive surface 12 and the first reflective surface 21 have the same spherical shape and a radius of curvature of 5.850 mm; the second reflective surface 22 has a spherical shape and a radius of curvature of 6.357 mm; the center thickness of the panoramic annular lens PAL is 6.70 mm, and the glass material is H-K9L.

[0124] Combination Figure 2 As shown in Table 1, the lens data of each lens in the objective lens group M1, from the first spherical lens O1 to the eighth spherical lens O8, are as follows.

[0125] Table 1

[0126]

[0127] In Table 1, the surface numbers are assigned according to the order of the lens surfaces from the object side to the image side; "STO" represents the aperture stop; the radius of curvature represents the curvature of the lens surface, with a positive value indicating that the surface bends towards the object plane and a negative value indicating that the surface bends towards the image plane; "Infinity" indicates that the surface is flat and the radius of curvature is infinite; the thickness represents the central axial distance between the current surface and the next surface, with both the radius of curvature and thickness in millimeters / mm; the refractive index Nd represents the ability of the material between the current surface and the next surface to deflect light, with a blank space indicating that the current location 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; 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.

[0128] Combination Figure 5 and 6As shown, the relay rod lens group M2 consists of three identical sub-rod lens groups M2-1, M2-2, and M2-3, each employing a symmetrical structural design. The lens data for each lens in the sub-rod lens group, from the first lens RL1 to the sixth lens RL6, are shown in Table 2 below.

[0129] Table 2

[0130]

[0131] In Table 2, the surface numbers are assigned according to the order of the lens surfaces from the object side to the image side; the radius of curvature represents the degree of curvature of the lens surface, with a positive value indicating that the surface bends towards the object plane and a negative value indicating that the surface bends towards the image plane; the thickness represents the central axial distance between the current surface and the next surface, with both the radius of curvature and thickness in millimeters per millimeter (mm); the refractive index Nd represents the ability of the material between the current surface and the next surface to deflect light, with a blank space indicating that the current location 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; 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.

[0132] like Figure 7 As shown in Table 3, the lens data of the first rear lens A1 to the ninth rear lens A9 of the rear adapter lens group M3 are shown below.

[0133] Table 3

[0134]

[0135] In Table 3, the surface numbers are assigned according to the order of the lens surfaces from the object side to the image side; the curvature diameter represents the degree of curvature of the lens surface, with positive values ​​indicating that the surface bends towards the object plane and negative values ​​indicating that the surface bends towards the image plane; the thickness represents the central axial distance between the current surface and the next surface, with both curvature diameter and thickness in millimeters per millimeter (mm); the refractive index Nd represents the ability of the material between the current surface and the next surface to deflect light, with a blank space indicating that the current location 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; 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.

[0136] in, Figure 4In the diagram: H1 is the distance between the object plane OBJ and the optical axis X of the panoramic annular lens PAL when the inner wall diameter of the cavity is 15mm; H2 is the distance between the object plane OBJ and the optical axis X of the panoramic annular lens PAL when the inner wall diameter of the cavity is 32.5mm; and H3 is the distance between the object plane OBJ and the optical axis X of the panoramic annular lens PAL when the inner wall diameter of the cavity is 50mm. Therefore, the measurable inner wall diameter range of the cavity provided in this embodiment is 15~50mm. For the maximum lower half field of view, This represents the maximum upper half field of view.

[0137] like Figure 4 As shown, in this embodiment, the distances H1=7.5mm, H2=16.25mm, and H3=25mm between the object plane OBJ and the optical axis X of the panoramic annular lens PAL, respectively. This means the measurable cavity inner wall diameter range for this embodiment is 15~50mm. Adjusting the forward and backward movement of the cemented doublet formed by the sixth rear lens A6 and the seventh rear lens A7 in the rear adapter lens group M3 allows for focusing and imaging of the cavity inner wall with different inner diameters. The forward and backward adjustment amount of the cemented doublet formed by the sixth rear lens A6 and the seventh rear lens A7 is 4.25mm. In this embodiment, the corresponding maximum lower half-field of view... The corresponding maximum upper half field of view A single image can obtain a 40° side view.

[0138] Furthermore, combined with Figure 10 , Figure 14 and Figure 18 The modulation transfer function (MTF) shown in the figure is represented by the following axes: the horizontal axis represents spatial frequency, indicating the number of black and white line pairs per millimeter; the vertical axis represents the modulation modulus (MTF), where 0 ≤ MTF ≤ 1. The MTF curve represents the resolving power of the panoramic endoscopic optical system at different frequencies in different fields of view, meridional, and sagittal directions. It reflects the image quality of the object after passing through the panoramic endoscopic optical system; the higher the MTF value, the higher the imaging quality of the panoramic endoscopic optical system. Figure 10 , Figure 14 and Figure 18 It is known that the panoramic endoscopic optical system provided in this application embodiment has an MTF value of ≥0.3 at a spatial frequency of 120lp / mm throughout the entire field of view, which meets the high-resolution imaging requirements of the cavity inner wall.

[0139] Furthermore, combined with Figure 11 , Figure 15 and Figure 19The field curvature and distortion diagrams shown are as follows: In the left coordinate system, the horizontal axis represents the magnitude of the field curvature of the panoramic endoscopic optical system, in mm; the vertical axis represents the normalized image height, without units. In the right coordinate system, the horizontal axis represents the magnitude of distortion (F-Tan (Theta)), in %; the vertical axis represents the normalized image height, without units. Figure 11 , Figure 15 and Figure 19 As can be seen, the field curvature of the panoramic endoscopic optical system provided in this embodiment is less than 0.13 mm across the entire field of view, indicating that the field curvature of the system is effectively controlled, meaning that the difference in image quality between the center and the periphery is small during imaging. The F-Theta distortion is less than 6%, indicating that the system distortion is well corrected and the imaging distortion is small.

[0140] Furthermore, combined with Figure 12 , Figure 16 and Figure 20 The relative illuminance diagram shown has the following dimensions: the vertical direction represents the illuminance value, normalized to the central field of view; the horizontal direction represents the field of view, with units and size consistent with the set field of view units and size. The curves in the diagram represent the illuminance values ​​under each field of view. The panoramic endoscopic optical system provided in this embodiment has a total field of view relative illuminance greater than 94%, with uniform and consistent illumination, indicating that the system meets the illuminance requirements in each field of view.

[0141] In this embodiment, the light from the front panoramic ring lens PAL is guided to the rear end through the relay rod lens group M2 and the rear adapter lens group M3, eliminating the space limitation of the chip being placed at the front of the probe, and can be matched with industrial cameras with a target surface of up to 1 inch and C interface.

[0142] In summary, the panoramic endoscopic optical system provided in this application has at least the following advantages compared with existing endoscopic technologies:

[0143] 1) Compared with endoscopic imaging schemes based on fiber optic transmission image bundles, this optical system effectively avoids the resolution loss caused by fiber discrete sampling, and has higher imaging resolution, more efficient field of view utilization and more efficient detection.

[0144] 2) Compared with endoscopic imaging schemes based on macro fisheye, this optical system significantly improves the imaging consistency between the center and edge of the field of view while maintaining a large field of view. It has lower F-Theta distortion and more uniform overall illumination, which is beneficial for subsequent image processing and quantitative analysis.

[0145] 3) Compared to the chip-front solution with only a panoramic ring imaging objective, this optical system introduces a relay rod lens group and a rear adapter lens group to guide the imaging light to the rear end, which can match imaging chips with larger target surfaces and higher pixel counts, thereby further improving the accuracy of endoscopic imaging; at the same time, it supports industrial cameras with universal interfaces and has better equipment compatibility; in addition, placing the chip at the rear end is more conducive to heat dissipation, which helps to improve the stability and reliability of the system during long-term operation.

[0146] 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 optical system, characterized in that, include: The front objective lens group (M1), the relay rod lens group (M2), and the rear adapter lens group (M3) are arranged sequentially along the optical axis. The front objective lens group (M1) includes a panoramic annular lens (PAL) and an objective lens group arranged sequentially along the optical axis; wherein, the optical axis of the panoramic annular lens (PAL) coincides with the optical axis of the objective lens group; the imaging light passes sequentially 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, enters the objective lens group, and then is imaged onto the image plane by the relay rod lens group (M2) and the rear adapter lens group (M3); The objective lens group, from the object side to the image side, includes the following: A first spherical lens (O1) with positive optical power, an aperture stop, a second spherical lens (O2) with positive optical power, a third spherical lens (O3) with positive optical power, a fourth spherical lens (O4) with negative optical power, a fifth spherical lens (O5) with positive optical power, a sixth spherical lens (O6) with negative optical power, a seventh spherical lens (O7) with positive optical power, and an eighth spherical lens (O8) with positive optical power. The third spherical lens (O3) and the fourth spherical lens (O4) form a cemented doublet lens group, and the sixth spherical lens (O6) and the seventh spherical lens (O7) form a cemented doublet lens group.

2. The panoramic endoscopic optical system according to claim 1, characterized in that, In the panoramic annular lens (PAL), the first refractive surface (11) and the second refractive surface (12) are coated with antireflective coatings, the first reflective surface (21) and the second reflective surface (22) are coated with internal reflective coatings, and the second refractive surface (12) and the first reflective surface (21) have the same radius of curvature.

3. The panoramic endoscopic optical system according to claim 2, characterized in that, The ratio of the focal length of each spherical lens in the objective lens group to the overall focal length of the objective lens group satisfies the following relationship: ； ； ； ； ； ； ； ； in, The overall focal length of the objective lens group is [missing information]. , , , , , , , These are the focal lengths of the first spherical lens (O1) to the eighth spherical lens (O8), respectively.

4. The panoramic endoscopic optical system according to claim 2, characterized in that, The refractive index and Abbe number of each spherical lens in the objective lens group satisfy the following relationship: ， ； ， ； ， ； ， ； ， ； ， ； ， ； ， ； in, , , , , , , , These are the refractive indices of the first spherical lens (O1) to the eighth spherical lens (O8), respectively. , , , , , , , These are the Abbe numbers of the first spherical lens (O1) to the eighth spherical lens (O8), respectively.

5. The panoramic endoscopic optical system according to claim 1, characterized in that, The relay rod lens group (M2) includes at least one sub-rod lens group, which adopts a symmetrical structure design and consists entirely of spherical lenses; The sub-rod mirror group, from the object side to the image side, includes the following: A first lens (RL1) with positive optical power, a second lens (RL2) with negative optical power, a third lens (RL3) with positive optical power, a fourth lens (RL4) with positive optical power, a fifth lens (RL5) with negative optical power, and a sixth lens (RL6) with positive optical power. The second lens (RL2) and the third lens (RL3) together form a cemented doublet lens group, and the fourth lens (RL4) and the fifth lens (RL5) together form a cemented doublet lens group.

6. The panoramic endoscopic optical system according to claim 5, characterized in that, The ratio of the focal length of each spherical lens in the sub-bar lens group to the overall focal length of the sub-bar lens group satisfies the following relationship: ； ； ； ； ； ； in, The overall focal length of the sub-rod lens group is [missing information]. , , , , , These are the focal lengths of the first lens (RL1) to the sixth lens (RL6), respectively.

7. The panoramic endoscopic optical system according to claim 5, characterized in that, The refractive index and Abbe number of each spherical lens in the sub-rod lens group satisfy the following relationship: ， ； ， ； ， ； ， ； ， ； ， ； in, , , , , , These are the refractive indices of the first lens (RL1) to the sixth lens (RL6), respectively. , , , , , These are the Abbe numbers of the first lens (RL1) to the sixth lens (RL6), respectively.

8. The panoramic endoscopic optical system according to claim 1, characterized in that, The rear adapter lens group (M3) includes, from the object side to the image side, the following: The rear lens assembly comprises a first rear lens (A1) with positive optical power, a second rear lens (A2) with positive optical power, a third rear lens (A3) with negative optical power, a fourth rear lens (A4) with negative optical power, a fifth rear lens (A5) with positive optical power, a sixth rear lens (A6) with negative optical power, a seventh rear lens (A7) with positive optical power, an eighth rear lens (A8) with negative optical power, and a ninth rear lens (A9) with positive optical power. The cemented doublet lens assembly formed by the sixth rear lens (A6) and the seventh rear lens (A7) can move back and forth along the optical axis to achieve focusing and imaging of the inner walls of cavities with different inner diameters. The lenses in the rear adapter lens group (M3) are all spherical lenses; the second rear lens (A2), the third rear lens (A3), the fourth rear lens (A4), the fifth rear lens (A5), the sixth rear lens (A6), the seventh rear lens (A7), the eighth rear lens (A8), and the ninth rear lens (A9) respectively constitute cemented doublet lens groups.

9. The panoramic endoscopic optical system according to claim 8, characterized in that, The ratio of the focal length of each spherical lens in the rear adapter lens group (M3) to the overall focal length of the rear adapter lens group (M3) satisfies the following relationship: ； ； ； ； ； ； ； ； ； in, This refers to the overall focal length of the rear adapter lens group (M3). , , , , , , , , These are the focal lengths of the first rear lens (A1) to the ninth rear lens (A9), respectively.

10. The panoramic endoscopic optical system according to claim 9, characterized in that, The refractive index and Abbe number of each rear lens in the rear adapter lens group (M3) satisfy the following relationship: ， ； ， ； ， ； ， ； ， ； ， ； ， ； ， ； ， ； in, , , , , , , , , These are the refractive indices of the first rear lens (A1) to the ninth rear lens (A9), respectively. , , , , , , , , These are the Abbe numbers of the first rear lens (A1) to the ninth rear lens (A9), respectively.

Images