Objective, relay and miniaturized confocal scanning probe with same

Abstract

The application discloses a miniaturized confocal scanning probe, which comprises a relay lens and an objective lens arranged in sequence along an optical axis. The relay lens is composed of at least one group of serially connected structural groups, has a magnification of 1x, adopts a structure combined by a single lens and a double cemented lens group, and the absolute value of the focal length of each lens is not more than 1.5 times of the focal length of the single group of structural groups. The objective lens comprises a plurality of positive focal length lenses arranged along the optical axis, and the focal length distribution has the characteristics of short at both ends and long in the middle. An image point displacement group and a compensation group are arranged in the objective lens, and the two groups can relatively axially displace along the optical axis to realize tomographic imaging at different depths without changing the relative position of the objective lens and a sample. The overall aperture of the probe can reach 7mm, the imaging depth is more than 300mu m, and the length of the probe can be flexibly adjusted by increasing or decreasing the number of relay lens groups to adapt to different application scenarios such as gynecology and oral cavity, thereby filling the technical blank in the field of high-resolution confocal imaging in hard scenes.

Description

Technical Field

[0001] This invention relates to the field of optical imaging technology, and more particularly to objective lenses, image-rotating lenses, and miniaturized confocal scanning probes having the same. Background Technology

[0002] Confocal endoscopes have broad application prospects in the medical field. Their core functionality relies on miniaturized probes containing image-rotating lenses and objectives to achieve precise imaging, and they are widely used in the diagnosis and surgical assistance of various diseases. Currently, flexible endoscopic confocal systems, traditional image-rotating lenses, and traditional objectives all have significant shortcomings that limit the imaging quality, scenario adaptability, and application accuracy of confocal endoscopes, as detailed below: 1. Flexible endoscopic confocal systems, based on fiber optic transmission and lacking traditional image-rotating and objective lens structures, while offering advantages in miniaturization and low cost, suffer from multiple performance limitations due to structural design constraints, making them unsuitable for rigid environments such as gynecology and dentistry: a. Poor operational stability: In rigid environments without flexible channel support (such as oral mucosa and cervical surface), the lack of rigid support makes it difficult to accurately locate the observation area, and probe movement can easily lead to blurred images or field of view shifts; b. Limited detection depth: Laser transmission and focusing rely on fiber optics, lacking precise objective lens focusing capabilities. Due to scattering loss, the imaging depth is generally below 100μm, failing to cover the 100-200μm lesion areas commonly found in gynecological cervical lesions and oral submucosal lesions; c. Insufficient durability. Flexible optical fibers and microlens modules are prone to bending and damage during repeated insertion operations in rigid environments, failing to meet the high-frequency usage requirements of routine clinical examinations; d. Insufficient imaging quality and resolution, lacking coordinated correction from professional objectives and image-rotating mirrors, relying solely on fiber optic coupling systems for light transmission, with numerical aperture (NA) generally below 0.5 (below the ≥0.65 standard required for accurate diagnosis), and lateral resolution only reaching the micrometer level upper limit, unable to clearly present subcellular structural details; simultaneously, the limitation of the spacing between individual fiber cores in the fiber bundle easily produces honeycomb artifacts, reducing the number of fibers and leading to image pixelation, and fiber optic transmission easily introduces noise, reducing the image signal-to-noise ratio, resulting in grid-like noise and signal attenuation, which algorithmic denoising cannot completely eliminate, further blurring the boundaries of lesion details.

[0003] 2. Traditional image-rotating mirrors are one of the core components of rigid endoscope probes. The mainstream approach uses a Hopkins rod lens structure (such as a dual Hopkins rod lens group or a simple cemented lens group). Its performance directly affects the imaging resolution and image quality stability, and it has two major shortcomings: a. Weak aberration correction capability: It can only preliminarily correct primary aberrations and cannot effectively compensate for higher aberrations such as field curvature and spherical aberration. Especially when the probe diameter is compressed to within 10mm in miniaturized scenarios, the superposition of aberrations between the image-rotating mirror and the objective lens will lead to blurred images and severe edge distortion, with relative distortion values ​​generally around 10%; b. Insufficient structural stability: Traditional image-rotating systems mostly use a dual rod lens group tandem structure. The length of a single rod lens is relatively long, and during the insertion and operation of a rigid probe, it is prone to image shift due to slight deformation. When working in conjunction with the objective lens, it further aggravates the image quality instability problem.

[0004] 3. The objective lens is the core imaging component of a confocal endoscope probe. Traditional objective lens designs are limited by structure, manufacturing process, and application scenarios, resulting in multiple shortcomings, especially when miniaturization and high-precision imaging requirements are required: a. There is a significant contradiction between aperture and diameter. High-NA (≥0.65) commercial objectives typically have a diameter ≥15mm, while endoscope probes need to meet the miniaturization requirements of small diameter (≤10mm). Existing designs cannot achieve high NA with small diameters, easily leading to excessive spherical aberration, chromatic aberration, and field curvature. Small-diameter designs directly limit the effective light-transmitting area and curvature adjustment space of the objective lens. To meet the high NA aperture angle requirements, high-curvature surfaces, short focal lengths, and strictly compressed lens group spacing are required, resulting in a significant reduction in the optical freedom of aberration correction. The correction space is compressed by more than 60% compared to conventional large-diameter objectives, making it impossible to offset the inherent aberrations caused by high NA through traditional multi-lens combinations. Miniaturization solutions often require sacrificing NA (reducing it to 0.3-0.5) or using non-infinite conjugate designs, making it difficult to balance high NA and aperture. a. The need for modular integration and image-switching mirror coordination; b. Lack of refractive index adaptation capability. Existing high-NA objectives are mostly designed for ideal scenarios with uniform refractive index media such as air and pure water. In deep imaging of samples with non-uniform refractive index such as biological tissues, they cannot dynamically adapt to changes in refractive index; c. Poor tomographic imaging coordination. Existing confocal scanning tomography mostly adopts the overall moving objective or sample z-axis scanning method. This method changes the conjugate position of the object and image, causing the preset aberration correction parameters of the objective to fail. At the same time, it disrupts the pupil connection with other lens groups such as image-switching mirrors, and the edge field of view light is not effectively received, which aggravates aberration superposition and causes problems such as distortion of the 3D reconstruction model, missed defect detection, and blurred details of biological tissues; d. The spherical lens design has great limitations. When using traditional spherical lens combinations to correct aberrations in small-aperture scenarios, multiple lenses are required to balance various aberrations, resulting in an increase in the size and weight of the objective group. It also requires extremely high coaxiality accuracy with the image-switching mirror, making assembly complex, debugging difficult, and maintenance costly. Summary of the Invention

[0005] The purpose of this invention is to achieve the above objectives. To this end, the invention provides the following technical solutions: On one hand, the present invention provides an objective lens for a confocal endoscope, comprising multiple lenses arranged along the optical axis, wherein the multiple lenses are provided with an image point displacement group and a compensation group; The image point displacement group and the compensation group are configured to make relative axial displacements under the action of external forces; and the image point displacement group and the compensation group are configured to compensate for aberrations caused by changes in the refractive index of the sample medium and / or changes in imaging depth while the focal plane changes, so as to maintain confocal imaging quality.

[0006] Preferably, the image point displacement group is a meniscus lens assembly with its concave surface facing the sample side to ensure the flatness of the image surface during the chromatography process.

[0007] Preferably, the compensation group includes at least a biconcave lens and a negative meniscus lens to compensate for spherical aberration contributions.

[0008] Preferably, it also includes a double-sided aspherical mirror positioned near the image plane to eliminate on-axis and off-axis aberrations during the chromatography process.

[0009] Preferably, the objective lens comprises 13 lenses arranged sequentially along the optical axis from the object side to the image side. During use, the end of the objective lens closest to the sample is defined as the image end, and the portion connecting to the image-rotating mirror is defined as the object end. The object and image are conjugate, and the image-rotating mirror, connected to the object end of the objective lens, ultimately forms an image at the sample. The second, third, and fourth lenses are combinations of biconcave lenses, negative meniscus lenses, and biconcave lenses, forming a compensation group; the tenth and eleventh lenses are combinations of meniscus lenses, forming an image point displacement group. The twelfth lens is an aspherical lens to eliminate on-axis and off-axis aberrations during tomography, and the thirteenth lens is a flat plate.

[0010] Preferably, during the tomography process, the displacement of the image point displacement group and the compensation group is determined according to the imaging depth, wherein the biological tissue imaging depth d≤300μm and the biological tissue refractive index n satisfies 1.3≤n≤1.51.

[0011] The displacement Δ1 of the image point displacement group and the displacement Δ2 of the compensation group satisfy the following rules: First, the direction of the optical axis from away from the object to near the object is defined as forward (this concept continues in the subsequent specification). When the distance between the image point displacement group and the adjacent lens in front is shortened by Δ1, the distance between the image point displacement group and the adjacent lens group behind is increased by Δ1 accordingly. When the distance between the compensation group and the adjacent lens group in front is increased by Δ2, the distance between the compensation group and the adjacent lens group behind is shortened by Δ2 accordingly.

[0012] Where, Δ1>d±30μm, Δ2 <d±20μm。

[0013] Preferably, the shapes of each lens are selected as shown in the table below:

[0014] Where f1 is the effective focal length of the first lens, f2 is the effective focal length of the second lens, f3 is the effective focal length of the first cemented doublet (the third and fourth lenses), f4 is the effective focal length of the fifth lens, f5 is the effective focal length of the sixth lens, f6 is the effective focal length of the seventh lens, f7 is the effective focal length of the second cemented doublet (the eighth and ninth lenses), f8 is the effective focal length of the tenth lens, f9 is the effective focal length of the eleventh lens, f10 is the effective focal length of the twelfth lens, and f is the effective focal length of the objective lens. T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, and T12 are the center thicknesses along the optical axis of the first, second, third, fourth, fifth, sixth, seventh, eighth, ninth, tenth, eleventh, and twelfth lenses, respectively, and ∑T is the sum of the center thicknesses along the optical axis from the first lens to the twelfth lens. D1 is the distance between the rear surface of the first lens and the front surface of the second lens; D2 is the distance from the rear surface of the second lens to the front surface of the first cemented doublet; D3 is the distance from the rear surface of the first cemented doublet to the front surface of the fifth lens; D4 is the distance from the rear surface of the fifth lens to the front surface of the sixth lens; D5 is the distance from the rear surface of the sixth lens to the front surface of the seventh lens; D6 is the distance from the rear surface of the seventh lens to the front surface of the second cemented doublet; D7 is the distance from the rear surface of the second lens to the front surface of the tenth cemented doublet; D8 is the distance from the rear surface of the tenth lens to the front surface of the eleventh lens; D9 is the distance from the rear surface of the eleventh lens to the front surface of the twelfth lens; and D10 is the distance from the rear surface of the twelfth lens to the front surface of the thirteenth lens. n represents the refractive index, and vd represents the Abbe number.

[0015] On the other hand, the present invention provides an image-rotating mirror for a confocal endoscope, comprising at least one tandemly connected structural group, each of the structural groups having a magnification of 1x, so as to maintain imaging quality while extending the optical path length, and by tandemly connecting different numbers of structural groups, it can be adapted to probes with different length requirements.

[0016] Preferably, each of the structural groups comprises two completely symmetrical sub-structural groups, wherein the sub-structural groups are a first lens, a second lens, a third lens, a fourth lens, and a fifth lens arranged sequentially along the optical axis from the far end of the center of symmetry to the center of symmetry, and the optical power of the five lenses is positive, negative, positive, negative, and positive, respectively.

[0017] Preferably, the first and second lenses are spherical lenses, and the third, fourth, and fifth lenses are aspherical lenses.

[0018] Preferably, the shapes of each lens are selected as shown in the table below:

[0019] Where f1 is the effective focal length of the first lens, f2 is the effective focal length of the second lens, f3 is the effective focal length of the third lens, f4 is the effective focal length of the fourth lens, and f5 is the effective focal length of the fifth lens. T1, T2, T3, T4, and T5 are the center thicknesses along the optical axis of the first, second, third, fourth, and fifth lenses, respectively, and ∑T is the sum of the center thicknesses along the optical axis of the first, second, third, fourth, and fifth lenses, i.e. D1 is the distance from the rear surface of the first lens to the front surface of the second lens, D2 is the distance from the rear surface of the third lens to the front surface of the fourth lens, and D3 is the distance from the rear surface of the fifth lens to the image plane. n represents the refractive index, and vd represents the Abbe number.

[0020] Finally, the present invention also provides a miniaturized confocal scanning probe, including a rotating mirror and an objective lens arranged sequentially along the optical axis; the probe has the characteristics of small aperture and high resolution, can realize deep tissue imaging, and the overall length of the probe can be flexibly adjusted by increasing or decreasing the number of rotating mirror groups to adapt to different application scenarios.

[0021] Preferably, it further includes a drive mechanism, which controls the axial displacement of the image point displacement group and the compensation group through a cam curve; the cam curve describes the correspondence between the lens group displacement and the tomography depth, exhibits a linear characteristic and has no inflection point; the drive mechanism controls the lens group displacement with an accuracy of less than 2μm and a repeatability accuracy in the range of ±0.3μm to ±1μm.

[0022] Preferably, the overall diameter of the probe is 7mm, and the imaging depth reaches more than 300μm.

[0023] Compared with the prior art, the technical solution provided by this invention has the following advantages: 1. Small diameter and high resolution, flexible and portable operation: The probe has the characteristics of small diameter and high resolution. The overall diameter can be reduced to about 7mm, which makes it extremely portable and flexible, and can be easily inserted into the body cavity. The probe itself is lightweight, and doctors can operate it freely like an ultrasound probe or endoscope, which is suitable for the needs of narrow cavity examination.

[0024] 2. Adaptable to multiple scenarios, filling technological gaps: It can be flexibly adapted to diverse scenarios such as operating rooms (real-time intraoperative assessment of surgical margins), emergency rooms, gynecology / dental clinics, etc., breaking through the limitations of traditional technologies; the overall length of the probe can be flexibly adjusted by increasing or decreasing the number of image-shifting mirror groups, adapting to rigid scenarios such as gynecology and dentistry, balancing operational rigidity and durability; it can achieve deep tissue imaging above 300μm, covering typical areas of early lesion occurrence, filling the gap in the field of high-resolution confocal imaging in rigid scenarios.

[0025] 3. Simplified operation and real-time optical biopsy: It is easy to integrate into a confocal system and can acquire cell-level resolution images on-site in clinics and other settings. It can distinguish normal tissue, inflammation, dysplasia and cancer cells in real time; it significantly reduces blind biopsies, shortens the diagnosis cycle, reduces medical costs, improves the efficiency of diagnosis and treatment, and at the same time ensures image quality and improves diagnostic accuracy.

[0026] 4. No dynamic aberrations introduced: The relative displacement of the two sets of mirrors only adjusts the position of the focal plane, without changing the relative posture of the objective lens and the sample, the conjugate relationship between the object and the image, or the alignment of the optical axis. This avoids tilting, eccentricity aberrations, and disruption of the conjugate relationship caused by mechanical movement. The relative displacement positioning accuracy of the mirror groups is higher, which can make the deep focal spot stably fall within the depth of focus range, avoid 'dynamic defocus aberration', and ensure the consistency of imaging resolution between deep and shallow layers.

[0027] 5. Aberration synergistic compensation for excellent correction effect: Combining the thickness of biological tissue with the range of refractive index variation, the curvature, spacing and dispersion parameters of the two sets of mirrors are pre-calibrated and synergistically optimized. During relative displacement, the accumulated aberrations in the deep region can be dynamically offset to ensure that the aberration control accuracy meets the high NA requirements within the entire tomographic depth range.

[0028] The technical solution of the present invention will be further described in detail below through embodiments. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the structure of the first structural group in the image-rotating mirror provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the objective lens provided in an embodiment of the present invention; Figure 3 The optical path diagram of the confocal scanning probe provided in the embodiment of the present invention; Figure 4 The relative position change curves of the image point displacement group and the compensation group are provided in the embodiments of the present invention; Figure 5 This is a dot diagram showing the result of splicing together three sets of image-rotating mirrors and objective lenses. Detailed Implementation

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0032] As described in the background section, there is an urgent need to design a miniaturized, high-resolution confocal scanning probe that can be adapted to multiple scenarios, which has become a research focus for those skilled in the art.

[0033] Based on the above research, this invention provides a miniaturized confocal scanning probe, which has an image rotating mirror and an objective lens arranged sequentially along the optical axis.

[0034] The first priority is the design of the image-rotating mirror.

[0035] Common confocal scanning systems typically consist of a galvanometer (scanning device), followed by a scanning mirror and a tube mirror, and finally an objective lens. However, due to the scanning angle of the galvanometer (which is usually quite large) and the pupil connection between the mirror groups, this structure limits the probe's length and size, making it unsuitable for medical applications. Therefore, a 1x magnification rotating mirror is specifically added between the tube mirror and the objective lens to form a confocal endoscopic probe. Otherwise, if other magnifications are used, the magnification will constantly change with the number of rotating mirror groups, leading to inaccurate matching of objective lens specifications, resulting in decreased overall system performance. Furthermore, the number of rotating mirror groups cannot be arbitrarily adjusted according to the application scenario. Therefore, a 1x magnification is essential to allow for different probe length requirements when using rotating mirrors with varying numbers of groups.

[0036] like Figure 1 As shown, the image-rotating mirror provided by this invention is composed of at least one structural group connected in series. This structural group consists of two completely symmetrical sub-structural groups. The mirror aberration of a single image-rotating mirror is extremely small, which can maximize the imaging performance of the probe.

[0037] like Figure 2As shown, each substructure group includes 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 negative optical power, and a fifth lens with positive optical power, arranged sequentially along the optical axis from the far end of the axis of symmetry to the axis of symmetry. The first and second lenses are spherical lenses, while the third, fourth, and fifth lenses are aspherical lenses. Specifically, the front surfaces of the third and fifth lenses are aspherical, and the rear surface of the fourth lens is aspherical.

[0038] The above-described structural group configuration allows for a probe length of at least 70mm with a single group, at least 120mm with two groups, and at least 170mm with three groups. The technical standard for determining the number of lenses is the probe length required for the actual application. In each structural group, the first lens primarily focuses the light; the second and third lenses, forming a cemented doublet, primarily mitigate chromatic aberration and distortion; and the fourth and fifth lenses, also forming a cemented doublet, further focus the light, limiting the aperture of the structure and further eliminating chromatic aberration and distortion, thus improving image quality. Furthermore, the fourth and fifth lenses are meniscus lenses close to the image plane, mitigating field curvature. The length of a single group can be further increased or decreased by adding or removing the number of lenses. The placement of cemented lenses and single lenses also affects the accuracy of the image. There are no specific requirements. Cementing the mirrors helps to eliminate chromatic aberration and reduce aberrations introduced by light refraction. The symmetrical structure helps to eliminate various aberrations. There are two cemented lenses in the lens group, and the rest are single lenses. Since the magnification of the image-switching mirror group is 1x, the number of splices in the image-switching mirror group will not change the relevant parameters of the objective lens. In order to meet the requirements of light path refraction under small aperture, high curvature lenses are used in the optical path, and they are paired with cemented doublet lenses to eliminate spherical aberration, field curvature, chromatic aberration and other aberrations caused by light during long-distance transmission. The aspherical processing technology is applied to the image-switching mirror and the objective lens, and the combination of high refractive mirrors makes the overall optical path smoother.

[0039] Based on the previous example, the shapes of each lens are selected as shown in the table below:

[0040] Where f1 is the effective focal length of the first lens, f2 is the effective focal length of the second lens, f3 is the effective focal length of the third lens, f4 is the effective focal length of the fourth lens, and f5 is the effective focal length of the fifth lens. T1, T2, T3, T4, and T5 are the center thicknesses along the optical axis of the first, second, third, fourth, and fifth lenses, respectively, and ∑T is the sum of the center thicknesses along the optical axis of the first, second, third, fourth, and fifth lenses, i.e. D1 is the distance from the rear surface of the first lens to the front surface of the second lens, D2 is the distance from the rear surface of the third lens to the front surface of the fourth lens, and D3 is the distance from the rear surface of the fifth lens to the image plane. n represents the refractive index, and vd represents the Abbe number.

[0041] Secondly, there's the design of the objective lens.

[0042] like Figure 3 As shown, the objective lens includes lenses numbered one through thirteen arranged sequentially along the optical axis from the object side to the image side. It includes an image point displacement group and a compensation group, which can be relatively axially displaced along the optical axis to achieve tomographic imaging at different depths. Specifically, the end of the objective lens closest to the sample during use is defined as the image end, and the portion connected to the image-rotating mirror is defined as the object end. That is, according to... Figure 3 The diagram shows the leftmost end of the image-rotating mirror, where the object and image are conjugate. The image-rotating mirror end connects to the object end of the objective lens, ultimately forming an image on the sample. The left-to-right imaging sequence also conforms to the general optical axis imaging order.

[0043] Confocal scanning optical systems often require auxiliary imaging elements such as prisms, filters, and polarizers. Finite conjugate objectives, lacking parallel light paths, introduce aberrations when auxiliary imaging optical elements are introduced. In such cases, infinite conjugate objectives have a clear advantage. The refractive index of biological tissue samples is generally between 1.3 and 1.5. If tomographic effects are achieved by directly moving the objective axis, uncontrollable aberrations will be introduced in high numerical aperture objectives. Therefore, we define the compensation group and image point displacement group within the lens group based on the light path and the proportion of aberrations it bears. This objective consists of thirteen lenses in total. The third and fourth lenses are combined into a cemented doublet, the eighth and ninth lenses are combined into a cemented doublet, and the rest are single-element lenses. The refractive index of the thirteen lenses varies between 1.5 and 1.95, and all are environmentally friendly glass. The twelfth lens is a double-sided aspherical mirror, requiring the setting of a conic coefficient and higher-order terms. The thirteenth lens is a plastic protective window made of medical-grade polycarbonate, which has high hardness and good light transmission. Meanwhile, the second, third, and fourth lenses form a compensation group, and the tenth and eleventh lenses form an image point displacement group. The core principle is to use the relative position changes of the compensation group and the image point displacement group within the objective lens during the confocal process to achieve changes in the working distance without changing the resolution, which is especially beneficial for biological tissue imaging.

[0044] More specifically, the first lens is a negative power meniscus lens to receive light from a large field of view. It slightly diverges the light rays from each field of view while gradually converging the light rays at the edges of each field, effectively controlling the aperture. The second, third, and fourth lenses are biconcave lenses, negative meniscus lenses, and combinations of biconcave lenses, which contribute significantly to spherical aberration and can flexibly cancel out positive and negative aberrations. The fifth lens is a biconvex lens that causes the light rays at the edges of each field of view to intersect at the aperture stop, maximizing the light diameter at the aperture stop, with the overall light path resembling a ribbon. The sixth, seventh, tenth, and eleventh lenses are four positive meniscus lenses, helping the system increase the numerical aperture and achieve high resolution. The eighth and ninth lenses, forming a cemented doublet, primarily eliminate chromatic aberration, ensuring that all wavelengths are imaged at the same position. The tenth and eleventh lenses are positioned close to the image plane, with their curvature pointing towards the sample, further eliminating field curvature and ensuring a flat image plane. The twelfth lens is an aspherical lens; by controlling the higher-order coefficients, the center and edge regions have different curvatures. During light propagation, the aberrations accumulated in the central field of view differ from those at the edges. Aspherical surfaces effectively address this issue, ultimately ensuring consistent imaging performance. The thirteenth lens is a flat plate, which is inexpensive as a consumable in the medical field and maintains the stability of biological tissue during imaging. This is achieved by ensuring close contact with the biological sample during use, mitigating air gaps caused by surface irregularities and preventing slight vibrations from affecting imaging. The confocal probe, as a crucial component of medical devices, requires contact testing with the human body during use. This process avoids imaging errors caused by minor vibrations of the operator or test subject, maximizing the accuracy of the test area. Considering this usage method, the thirteenth lens in this patent is made of medical-grade polycarbonate (PC). As a medical consumable, it is exempt from biocompatibility testing, and the breakage of glass materials during use avoids potential injury. The spherical aberration of the thirteenth lens's front surface contributes significantly (negative spherical aberration), while the eleventh lens has positive spherical aberration. The two not only partially cancel each other out but also balance the excess spherical aberration of the second, third, and fourth lenses.

[0045] The shapes of each lens are selected as shown in the table below:

[0046] Where f1 is the effective focal length of the first lens, f2 is the effective focal length of the second lens, f3 is the effective focal length of the first cemented doublet (the third and fourth lenses), f4 is the effective focal length of the fifth lens, f5 is the effective focal length of the sixth lens, f6 is the effective focal length of the seventh lens, f7 is the effective focal length of the second cemented doublet (the eighth and ninth lenses), f8 is the effective focal length of the tenth lens, f9 is the effective focal length of the eleventh lens, f10 is the effective focal length of the twelfth lens, and f is the effective focal length of the objective lens. T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, and T12 are the center thicknesses along the optical axis of the first, second, third, fourth, fifth, sixth, seventh, eighth, ninth, tenth, eleventh, and twelfth lenses, respectively, and ∑T is the sum of the center thicknesses along the optical axis from the first lens to the twelfth lens. D1 is the distance between the rear surface of the first lens and the front surface of the second lens; D2 is the distance from the rear surface of the second lens to the front surface of the first cemented doublet; D3 is the distance from the rear surface of the first cemented doublet to the front surface of the fifth lens; D4 is the distance from the rear surface of the fifth lens to the front surface of the sixth lens; D5 is the distance from the rear surface of the sixth lens to the front surface of the seventh lens; D6 is the distance from the rear surface of the seventh lens to the front surface of the second cemented doublet; D7 is the distance from the rear surface of the second cemented doublet to the front surface of the tenth lens; D8 is the distance from the rear surface of the tenth lens to the front surface of the eleventh lens; D9 is the distance from the rear surface of the eleventh lens to the front surface of the twelfth lens; and D10 is the distance from the rear surface of the twelfth lens to the front surface of the thirteenth lens. n represents the refractive index, and vd represents the Abbe number.

[0047] The selection principles for the image point displacement group and compensation group follow the principle of larger incident angles. Generally, the larger the incident angle, the greater the aberrations produced by the light on the lens. Spherical aberration is the fundamental aberration; coma and astigmatism are also affected by spherical aberration. Spherical aberration is generally balanced by mutual compensation between positive and negative spherical aberrations. The compensation group itself has a relatively large spherical aberration; by changing the axial displacement, it can more flexibly compensate for excess spherical aberration within a certain range. The image point displacement group mainly changes the working distance. A longer working distance results in a deeper imaging depth, but due to refractive index mismatch, the resolution is affected. At this time, the objective lens performance decreases to a certain extent, and the system produces excess spherical aberration. This part needs to be compensated by the compensation group. This ensures excellent image quality throughout the depth imaging process.

[0048] During the chromatography process, while the distance between lens 1 and lens 2 decreases by Δ2, the distance between the cemented doublet composed of lenses 3 and 4 and lens 5 increases by Δ2; the distance between the cemented doublet composed of lenses 8 and 9 and lens 10 increases by Δ1, and the distance between lenses 11 and 12 decreases by Δ1. Where Δ1 > d ± 30 μm, Δ2 <d±20μm。

[0049] In practical applications, the entire probe is designed as a single mechanical unit. Only the motor drives the image point displacement group and the compensation group to make corresponding axial displacements, while the other lenses simply rotate without any displacement. The motor has a corresponding axial displacement accuracy at the micrometer level.

[0050] like Figure 4 As shown, Figure 4 This is a cam curve diagram, where the horizontal axis represents the tomography depth, and the vertical axis represents the air gap between the image point displacement group and the compensation group relative to their respective preceding lens. This cam curve is relatively linear, with no inflection points (the curve's increasing and decreasing trends are consistent, and there is no particularly prominent point where the trend differs from other data points), ensuring the feasibility of relative movement of the lens groups and providing valuable reference for subsequent mechanical design.

[0051] A motion groove can be set at the outer diameter of the lens barrel according to the cam curve. When the motor drives the lens barrel to rotate, the image point displacement group and the compensation group will move axially according to the trajectory of the cam curve, thereby imaging biological tissue to a certain depth. The cam curve accurately describes the motion trajectory of the compensation group and the image point displacement group. The linearity of the cam curve directly affects the actual machining process, and is essentially a linear correspondence between the lens group displacement and the cam rotation angle. If the cam curve has inflection points or nonlinear characteristics, it will have a significant impact on multiple dimensions such as machining, motion performance, and imaging stability.

[0052] The movement of the axially displaced lenses is achieved through a mechanical coupling mechanism of "cam groove - transmission pin - linear guide," which converts the rotational motion of the lens barrel into the axial linear motion of the lens assembly. During operation, the motor drives the lens barrel to rotate, and the outer diameter of the lens barrel replicates the cam curve. Lenses other than the displacement lens assembly rotate without displacement, while the compensation group and the axial displacement group move axially. Generally, the cam curve controls the displacement of the lens assembly with an accuracy of less than 2μm and a repeatability of ±0.3~±1μm.

[0053] Based on the probe structure described in the above specific embodiments, the overall probe diameter can be approximately 7mm, resulting in a very small overall size that allows for convenient operation and deep insertion into internal human cavities. Simultaneously, the internal optical path utilizes some aspherical lenses, which serve to redirect the optical path and correct aberrations. Furthermore, the number of image-rotating mirror groups can be increased or decreased depending on the application, making it more versatile.

[0054] In summary, this invention provides a miniaturized confocal scanning probe that, while maintaining image quality, also extends the overall structural length to a certain extent, enabling observation of specific parts of the human body. Compared to traditional moving objective lens solutions, this invention employs a 'relative axial displacement of the two sets of mirrors within the objective lens' approach, fundamentally solving the aberration control challenge in high-NA deep imaging and demonstrating broad application prospects.

[0055] The various parts of this manual are described in a combination of parallel and progressive methods. Each part focuses on the differences between the other parts, and the same or similar parts can be referred to each other.

[0056] Example 1 Note: (Lens 1-10 constitute a structural group. In actual use, three structural groups are spliced ​​together to obtain the image-rotating mirror to meet the length requirement of ≥170mm for the probe).

[0057] Table 1: Lens parameter table of a miniaturized confocal probe provided in this embodiment.

[0058] Table 2: Design parameters of each parameter of the miniaturized confocal probe.

[0059] To ensure proper pupil matching between the image inverter and the objective lens, and to guarantee normal lens assembly, the exit pupil position of the image inverter must be greater than or equal to the entrance pupil position. Otherwise, lens overlap may occur when the two parts are joined together. Evaluation of the imaging quality of this imaging example structure: like Figure 5 As shown, this is a dot plot after stitching together three sets of rotating mirrors and objectives. The light spots of each visible structure are almost entirely distributed within the Airy disk, and the imaging quality is close to the diffraction limit. Structures 1, 2, 3, 4, 5, and 6 correspond to tomography depths of 0, 10, 100, 110, 200, and 300 µm, respectively.

[0060] Table 3: Imaging quality of optical structures at different tomographic depths for inverting / reducing image groups and single objectives.

[0061] Finally, it should be noted that the described embodiments are merely some, not all, of the embodiments of the present invention. Those skilled in the art will understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the claims and their equivalents; that is, all other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. An objective lens for a confocal endoscope, characterized by, It consists of 13 lenses sequentially arranged along the optical axis from the object side to the image side, and an image point shifting group and a compensation group are arranged among the 13 lenses; The image point shifting group and the compensation group are configured to perform relative axial displacement under external force; Moreover, the image point shifting group and the compensation group are configured to compensate for aberrations caused by changes in the refractive index of a sample medium and / or changes in imaging depth while the focal plane is changed, so as to maintain confocal imaging quality; Wherein: The ratio of the effective focal length of each lens to the effective focal length of the objective lens, and the ratio of the center thickness along the optical axis to the sum of the center thicknesses of the twelve lenses satisfy the following relationship: The object side surface of the first lens is a convex surface, and the image side surface thereof is a concave surface. The ratio of the effective focal length f1 of the first lens to the effective focal length f of the objective lens satisfies -6.47<f1 / f<-5.47, and the ratio of the center thickness T1 of the first lens to the total thickness ∑T satisfies 0.07<T1 / ∑T<0.15; The second lens is a biconcave lens. The ratio of the effective focal length f2 of the second lens to f satisfies -2.63<f2 / f<-1.63, and the ratio of the center thickness T2 of the second lens to the total thickness ∑T satisfies 0.01<T2 / ∑T<0.09; The third lens and the fourth lens form a doublet cemented lens. The object side surface of the third lens is a convex surface, and the image side surface thereof is a concave surface. The fourth lens is a biconvex lens. The ratio of the effective focal length f3 thereof to f satisfies 3.59<f3 / f<4.

59. Wherein the ratio of the center thickness T3 of the third lens to the total thickness ∑T satisfies 0.01<T3 / ∑T<0.09, and the ratio of the center thickness T4 of the fourth lens to the total thickness ∑T satisfies 0.07<T4 / ∑T<0.15; The fifth lens is a biconvex lens. The ratio of the effective focal length f4 of the fifth lens to f satisfies 17.4<f4 / f<18.4, and the ratio of the center thickness T5 of the fifth lens to the total thickness ∑T satisfies 0.02<T5 / ∑T<0.10; The object side surface of the sixth lens is a convex surface, and the image side surface thereof is a concave surface. The ratio of the effective focal length f5 of the sixth lens to f satisfies 22.27<f5 / f<23.27, and the ratio of the center thickness T6 of the sixth lens to the total thickness ∑T satisfies 0.01<T6 / ∑T<0.09; The object side surface of the seventh lens is a convex surface, and the image side surface thereof is a concave surface. The ratio of the effective focal length f6 of the seventh lens to f satisfies 20.79<f6 / f<21.79, and the ratio of the center thickness T7 of the seventh lens to the total thickness ∑T satisfies 0.01<T7 / ∑T<0.09; The eighth lens and the ninth lens form a doublet cemented lens. The eighth lens is a biconcave lens, and the ninth lens is a biconvex lens. The ratio of the effective focal length f7 thereof to f satisfies 22.1<f7 / f<23.

1. Wherein the ratio of the center thickness T8 of the eighth lens to the total thickness ∑T satisfies 0.01<T8 / ∑T<0.09, and the ratio of the center thickness T9 of the ninth lens to the total thickness ∑T satisfies 0.08<T9 / ∑T<0.16; The object side surface of the tenth lens is a convex surface, and the image side surface thereof is a concave surface. The ratio of the effective focal length f8 of the tenth lens to f satisfies 16.92<f8 / f<17.92, and the ratio of the center thickness T10 of the tenth lens to the total thickness ∑T satisfies 0.01<T10 / ∑T<0.09; The object side of the eleventh lens is a convex surface and the image side is a concave surface, the effective focal length f9 thereof and f satisfy 3.09<f9 / f<4.09, the central thickness T11 thereof and the total thickness ∑T satisfy 0.04<T11 / ∑T<0.12; The object side of the twelfth lens is a convex surface and the image side is a concave surface, the effective focal length f10 thereof and f satisfy 13.14<f10 / f<14.14, the central thickness T12 thereof and the total thickness ∑T satisfy 0.01<T12 / ∑T<0.09; The thirteenth lens is a flat plate; During tomography, the displacement amounts of the image point displacement group and the compensation group are determined according to the imaging depth, and the displacement amount Δ1 of the image point displacement group and the displacement amount Δ2 of the compensation group satisfy: Δ1>d±30μm, Δ2<d±20μm, wherein d is the imaging depth of biological tissue.

2. A miniaturized confocal scanning probe, characterized in that, Comprises the objective lens and the image rotating lens according to claim 1, which are sequentially arranged along the optical axis; The image rotating lens is arranged between the tube lens and the objective lens, and is used for prolonging the length of the probe to go deep into the human body cavity while maintaining the pupil connection of the system; The objective lens realizes tomographic imaging of deep tissues through the relative axial displacement of the image point displacement group and the compensation group; It further comprises a driving mechanism, which controls the axial displacement of the image point displacement group and the compensation group.

3. The miniaturized confocal scanning probe according to claim 2, characterized in that, The image rotating lens comprises at least one connectable structural group in series, each said structural group has a magnification of 1×, so as to prolong the optical path length while maintaining imaging quality, and can adapt to probes with different length requirements by connecting different numbers of structural groups in series.

4. The miniaturized confocal scanning probe according to claim 3, characterized in that, Each said structural group consists of two completely symmetric sub-structural groups, said sub-structural groups are a first lens, a second lens, a third lens, a fourth lens and a fifth lens sequentially arranged along the optical axis from the distal end of the symmetry center to the symmetry center, and the optical power of the five lenses is positive, negative, positive, negative, negative in sequence.

5. The miniaturized confocal scanning probe according to claim 4, characterized in that, Said first lens and second lens are spherical lenses, and said third lens, fourth lens and fifth lens are aspherical lenses.

Images