Long working distance high-resolution side-viewing endoscopic oct probe

Abstract

This invention relates to the field of optical coherence tomography (OCT) and discloses a long-working-distance, high-resolution side-view endoscopic OCT probe, comprising a single-mode fiber. One end of the single-mode fiber is connected to a first gradient refractive index lens. A first glass capillary is fixedly connected to one side of the first gradient refractive index lens. A second gradient refractive index lens is fixedly connected to the middle of the end of the first gradient refractive index lens furthest from the single-mode fiber. Both the light incident surfaces of the first and second gradient refractive index lenses are coated with near-infrared transmission films. A second glass capillary is fixedly connected to the other side of the first gradient refractive index lens. By combining gradient refractive index lenses with low and high gradient constants, a beam shaper is constructed, reducing the beam emitted from the single-mode fiber to below the mode field diameter of the single-mode fiber, increasing its divergence angle, and significantly reducing manufacturing difficulty and sensitivity to errors.

Description

Technical Field

[0001] This invention relates to the field of optical coherence tomography (OCT) technology, specifically to a long-working-distance, high-resolution, side-viewing endoscopic OCT probe. Background Technology

[0002] Optical coherence tomography (OCT) is an emerging biomedical optical imaging technology that enables non-contact, non-invasive, high-resolution imaging of the structure and physiological function of biological tissues. It has broad application prospects in the early detection of diseases and in vivo biopsy.

[0003] Optical coherence tomography (OCT) technology has evolved into three types: time-domain OCT systems, spectral-domain OCT systems, and swept-frequency OCT systems. Early time-domain OCT systems achieved tomographic imaging of biological samples through axial mechanical scanning. Spectral-domain and swept-frequency OCT systems, on the other hand, can image without axial scanning, achieving high-speed and high-sensitivity OCT. However, all three types of OCT systems have limitations because the light wavelengths they use can only penetrate a few millimeters into tissues, making it impossible to directly penetrate the human body outside the body for tomographic imaging of internal organs. Only by developing endoscopic techniques based on OCT systems can high-resolution imaging of internal human organs be achieved. The core component of an endoscopic OCT system is the endoscopic OCT probe. Since many human organs are large luminal organs with radii exceeding 10 mm, while the working distance of an endoscopic OCT system is only about 2 mm, designing and manufacturing an endoscopic OCT probe with a long working distance is essential for convenient imaging and reducing patient discomfort.

[0004] Traditional probes, such as those with dual-gradient refractive index lenses, have extremely strict tolerance requirements for the lens and the optical spacing of the beam expander, resulting in high manufacturing costs. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a long working distance, high resolution, side-viewing endoscopic OCT probe, solving the problem of high manufacturing costs of traditional endoscopic OCT probes.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a long working distance, high-resolution side-viewing endoscopic OCT probe, comprising a single-mode optical fiber, one end of which is connected to a first gradient refractive index lens, one side of which is fixedly connected to a first glass capillary, and the middle of the end of the first gradient refractive index lens away from the single-mode optical fiber is fixedly connected to a second gradient refractive index lens, both the light incident end face of the first gradient refractive index lens and the light incident end face of the second gradient refractive index lens are coated with a near-infrared transmission film, the other side of which is fixedly connected to a second glass capillary, and the end of the second gradient refractive index lens away from the first gradient refractive index lens is fixedly connected to a spherical collimating lens.

[0007] Preferably, one end of the single-mode optical fiber passes through the middle of the first glass capillary and is connected to the middle of one end of the first gradient refractive index lens.

[0008] Preferably, one end of the second gradient refractive index lens passes through the middle of the second glass capillary and is fixedly connected to the middle of one end of the first gradient refractive index lens.

[0009] Preferably, the sample to be tested is disposed on one side of the spherical collimating lens.

[0010] Preferably, the first gradient refractive index lens and the second gradient refractive index lens include gradient refractive index lenses with low gradient constants and high gradient constants.

[0011] Preferably, the spherical collimating lens is used to focus a reduced beam of light with a large divergence angle onto the object being measured after it has been propagated through a uniform refractive index.

[0012] Preferably, the single-mode optical fiber is used to transmit optical signals to a first gradient refractive index lens.

[0013] Preferably, the transmittance of the near-infrared transmission film in the optical band is not less than the value required for endoscopic OCT imaging.

[0014] Working principle: During use, the light source emits a light signal, which is transmitted through a single-mode fiber to the incident end of the first gradient refractive index lens. The first gradient refractive index lens initially shapes the beam with a certain divergence angle emitted from the single-mode fiber, converting it into a parallel beam. After passing through the first gradient refractive index lens, the beam approaches a parallel beam and enters the second gradient refractive index lens. The second gradient refractive index lens provides stronger focusing, causing the light to converge rapidly within the lens. Ultimately, the spot size is reduced to below the mode field diameter of the single-mode fiber 1, increasing the divergence angle of the light. The light then enters the spherical collimating lens. Through the spherical shape and uniform refractive index propagation characteristics of the spherical collimating lens, the light is refracted and converged, focusing onto the object being measured, thereby achieving high-resolution imaging over long working distances.

[0015] This invention provides a long-working-distance, high-resolution, side-viewing endoscopic OCT probe. It offers the following advantages:

[0016] 1. This invention combines gradient refractive index lenses with low and high gradient constants to form a beam shaper, which reduces the beam emitted from a single-mode fiber to below the mode field diameter of the single-mode fiber, thereby increasing its divergence angle. Compared with the traditional method of using air gaps and gradient refractive index lenses to form a beam shaper, this invention significantly reduces the processing difficulty and sensitivity to errors, improves processing efficiency, and reduces the scrap rate, thus solving the problem of high manufacturing cost of traditional endoscopic OCT probes.

[0017] 2. The gradient refractive index lens, glass capillary, and spherical collimating lens used in this invention are selected based on common market specifications and mature manufacturing processes. This avoids reliance on specially customized components, rather than using specially customized lenses that require complex manufacturing processes and high-precision machining. This significantly reduces production costs. Furthermore, the precise fixing and positioning of the glass capillary simplifies the component assembly process, reduces the need for high-precision alignment and complex processing equipment, and makes the production process simpler and more efficient. This is conducive to the mass production and widespread application of the probe, and enhances the product's market competitiveness.

[0018] 3. The present invention performs preliminary processing on the beam emitted from the single-mode fiber using a first gradient refractive index lens, then reduces the beam spot to below the single-mode fiber mode field diameter using a second gradient refractive index lens to increase the beam divergence angle, and then performs precise focusing using a spherical collimating lens, ultimately achieving high-resolution imaging over long working distances.

[0019] 4. The endoscopic OCT probe of this invention has a compact structure and simple connection, making it easy to integrate with existing OCT systems. Its standard optical interface and clear signal transmission path allow it to be easily integrated as a module into existing OCT imaging systems without requiring large-scale modifications or redesigns to the existing system. This facilitates the upgrading and technological improvement of existing OCT equipment, and can rapidly improve the endoscopic imaging performance of the system without changing the overall system architecture, saving time and costs for system upgrades and accelerating the promotion and application of this technology in different application scenarios. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of the present invention;

[0021] Figure 2 This is a schematic diagram of the light path when the present invention is used;

[0022] Figure 3 This is a schematic diagram of the beam shaper design of the present invention, showing the beam spot effect.

[0023] Figure 4 This is a schematic diagram illustrating the effect of changing the length of the spherical lens on the probe performance parameters according to the present invention;

[0024] Figure 5 This is a schematic diagram of the sensitivity analysis of the present invention.

[0025] Among them, 1. Single-mode optical fiber; 2. First glass capillary; 3. First gradient refractive index lens; 4. Second glass capillary; 5. Second gradient refractive index lens; 6. Spherical collimating lens; 7. Sample under test; 8. Near-infrared transmission film. Detailed Implementation

[0026] The technical solution of the present invention will now be clearly and completely described 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.

[0027] Please see the appendix Figure 1This invention provides a long working distance, high resolution side-viewing endoscopic OCT probe, including a single-mode fiber 1. One end of the single-mode fiber 1 is connected to a first gradient refractive index lens 3. A first glass capillary 2 is fixedly connected to one side of the first gradient refractive index lens 3. A second gradient refractive index lens 5 is fixedly connected to the middle of the end of the first gradient refractive index lens 3 away from the single-mode fiber 1. Both the light incident end face of the first gradient refractive index lens 3 and the light incident end face of the second gradient refractive index lens 5 are coated with a near-infrared transmission film 8. A second glass capillary 4 is fixedly connected to the other side of the first gradient refractive index lens 3. A spherical collimating lens 6 is fixedly connected to the end of the second gradient refractive index lens 5 away from the first gradient refractive index lens 3.

[0028] One end of the single-mode fiber 1 passes through the middle of the first glass capillary tube 2 and is connected to the middle of one end of the first gradient refractive index lens 3.

[0029] One end of the second gradient refractive index lens 5 passes through the middle of the second glass capillary tube 4 and is fixedly connected to the middle of one end of the first gradient refractive index lens 3.

[0030] The sample to be tested 7 is placed on one side of the spherical collimating lens 6.

[0031] The first gradient refractive index lens 3 and the second gradient refractive index lens 5 include gradient refractive index lenses with low gradient constants and high gradient constants.

[0032] The spherical collimating lens 6 is used to focus a reduced beam of light with a large divergence angle onto the object being measured 7 after it has been propagated through a uniform refractive index.

[0033] The single-mode fiber 1 is used to transmit the optical signal to the first gradient refractive index lens 3.

[0034] The transmittance of the near-infrared transmission film layer 8 in the optical band is not less than the value required for endoscopic OCT imaging.

[0035] Specifically, the optical signal is transmitted to the incident end of the first gradient refractive index lens 3 through the single-mode fiber 1. Due to the small core diameter of the single-mode fiber 1, the optical signal propagates in a single mode within it, ensuring high coherence and low loss. When the optical signal enters the first gradient refractive index lens 3, the slow change in its refractive index from the center to the edge due to the low gradient constant of the first gradient refractive index lens 3 causes the optical signal to be refracted. According to the light propagation principle of the gradient refractive index lens, the propagation path of the light in the lens will gradually change, initially shaping the beam with a certain divergence angle emitted from the single-mode fiber 1, converting it towards the direction of a parallel beam. Thus, through the low gradient constant value and lens length of the first gradient refractive index lens 3, the beam approaches a parallel beam after passing through the first gradient refractive index lens 3, providing good initial conditions for subsequent processing.

[0036] The approximately parallel beam processed by the first gradient refractive index lens 3 enters the second gradient refractive index lens 5. The second gradient refractive index lens 5 has a high gradient constant, so its refractive index changes more drastically from the center to the edge, which can have a stronger converging effect on the light, so that the light converges rapidly inside the lens, and finally reduces the spot size to below the mode field diameter of the single-mode fiber 1. The purpose of this is to increase the divergence angle of the light, which provides favorable conditions for the converging effect of the subsequent spherical collimating lens 6, because a smaller spot size corresponds to a larger aperture angle, which can make full use of the converging capability of the spherical collimating lens 6.

[0037] The near-infrared transmission film layer 8 on the light incident end face of the first gradient refractive index lens 3 and the second gradient refractive index lens 5 ensures high transmittance of the light signal in the near-infrared band when passing through these two lenses. By reducing reflection loss, more light energy can be effectively passed through the lenses, thereby improving light utilization efficiency and imaging quality.

[0038] The first glass capillary tube 2 and the second glass capillary tube 4 are mainly used to fix and position the corresponding lenses to ensure the relative positional accuracy between them. The inner diameter of the glass capillary tube should be selected according to the outer diameter of the component it accommodates. Generally speaking, the inner diameter of the first glass capillary tube 2 should be slightly larger than the outer diameter of the single-mode fiber 1, and a certain gap (e.g., 0.1mm to 0.2mm) should be left to facilitate the insertion and fixation of the single-mode fiber 1, while ensuring the relative positional accuracy between the single-mode fiber 1 and the first gradient refractive index lens 3.

[0039] For the second glass capillary 4, its inner diameter should match the outer diameter of the second gradient refractive index lens 5 to ensure that the second gradient refractive index lens 5 can stably pass through and be fixed at one end of the first gradient refractive index lens 3. The material of the glass capillary can be quartz glass, which has good chemical stability and thermal stability and can ensure dimensional stability under different environments.

[0040] The light beam, reduced in size by the second-gradient refractive index lens 5 and having a large divergence angle, enters the spherical collimating lens 6. Due to the spherical shape and uniform refractive index propagation characteristics of the spherical collimating lens 6, the light will be refracted and converged according to the principles of geometric optics. Based on the focal length of the lens and the radius of curvature of the spherical surface, the light will be converged to a longer working distance after passing through the spherical collimating lens 6, thereby achieving imaging at a long working distance.

[0041] Please see the appendix Figure 2 -Appendix Figure 5The product parameters of this invention have been simulated on multiple platforms, including Matlab, Zemax, and Virtua llab, all of which show that it can achieve a working distance of more than 10mm while maintaining high lateral resolution (focal spot less than 20μm). The reason for this effect is that it uses a combination of gradient refractive index lenses with low gradient constant and high gradient constant to form a beam shaper, which reduces the beam emitted from single-mode fiber 1 to below the mode field diameter of the single-mode fiber, increases its divergence angle, and thus effectively controls the focal spot below the mode field diameter. This allows for better utilization of the focusing effect of the spherical lens, which focuses the beam at 10mm and reduces the beam waist radius to achieve high lateral resolution.

[0042] Furthermore, to verify the feasibility of actual processing, the components of the probe were disturbed within a certain length range during the experiment, and the changes in performance parameters were recorded to verify the probe sensitivity and manufacturing tolerance. The results showed that the probe designed in this way has better sensitivity and greater anti-interference ability compared with the current long working distance probes, which means that the manufacturing difficulty is lower.

[0043] In terms of product manufacturing, we use commonly available lens parameters for design. Compared with the specially customized lens parameters required for currently designed long-working-distance endoscope probes, our costs and procurement difficulties are lower, which facilitates mass production.

[0044] By combining gradient refractive index lenses with low and high gradient constants to form a beam shaper, the beam emitted from single-mode fiber 1 is reduced to below the mode field diameter of the single-mode fiber, increasing its divergence angle. Compared with the traditional method of using air gaps and gradient refractive index lenses to form a beam shaper, the processing difficulty and sensitivity to errors are reduced by tens of times, the processing efficiency is improved and the scrap rate is reduced, thus solving the problem of high manufacturing cost of traditional endoscopic OCT probes.

[0045] The focusing part uses a spherical collimating lens 6, which propagates the reduced beam with a large divergence angle through a uniform refractive index and then focuses it onto the object under test 7. Compared with the traditional use of optical interval beam expanders and gradient refractive index lenses as the focusing part, this reduces costs, while improving the working distance and lateral resolution and improving the processing tolerance.

[0046] In summary, this invention is based on gradient refractive index lenses and spherical lenses. It uses two gradient refractive index lenses to form a beam shaper. The diverging spot of the beam emitted from the single-mode fiber is first turned into a parallel beam after passing through the first gradient refractive index lens 3. Then, the beam is focused at the end by the second gradient refractive index lens 5, reducing it to below the mode field diameter of the single-mode fiber. The advantage of this is that the aperture angle of the beam and the mode field diameter of the spot are mutually constrained. A smaller mode field diameter can obtain a larger aperture angle to better utilize the focusing property of the spherical lens. Then, the reduced beam is expanded by the spherical lens with a constant refractive index and focused on the object to be measured by the focusing property of the spherical surface at the end, so as to achieve scanning imaging with a working distance of more than 10mm and maintain a high lateral resolution (20um).

[0047] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A long-working-distance, high-resolution side-viewing endoscopic OCT probe, comprising a single-mode optical fiber (1), characterized in that: One end of the single-mode fiber (1) is connected to a first gradient refractive index lens (3). A first glass capillary (2) is fixedly connected to one side of the first gradient refractive index lens (3). A second gradient refractive index lens (5) is fixedly connected to the middle of the end of the first gradient refractive index lens (3) away from the single-mode fiber (1). Both the light incident end face of the first gradient refractive index lens (3) and the light incident end face of the second gradient refractive index lens (5) are coated with a near-infrared transmission film (8). A second glass capillary (4) is fixedly connected to the other side of the first gradient refractive index lens (3). A spherical collimating lens (6) is fixedly connected to the end of the second gradient refractive index lens (5) away from the first gradient refractive index lens (3). The first gradient refractive index lens (3) and the second gradient refractive index lens (5) are gradient refractive index lenses with low gradient constant and high gradient constant, respectively. The outer diameter of the first gradient refractive index lens (3) is larger than the outer diameter of the second gradient refractive index lens (5).

2. The long working distance, high resolution side-viewing endoscopic OCT probe according to claim 1, characterized in that: One end of the single-mode optical fiber (1) passes through the middle of the first glass capillary (2) and is connected to the middle of one end of the first gradient refractive index lens (3).

3. The long working distance, high resolution side-viewing endoscopic OCT probe according to claim 1, characterized in that: One end of the second gradient refractive index lens (5) passes through the middle of the second glass capillary (4) and is fixedly connected to the middle of one end of the first gradient refractive index lens (3).

4. The long working distance, high resolution, side-viewing endoscopic OCT probe according to claim 1, characterized in that: The sample to be tested (7) is placed on one side of the spherical collimating lens (6).

5. The long working distance, high resolution, side-viewing endoscopic OCT probe according to claim 1, characterized in that: The spherical collimating lens (6) is used to focus the reduced beam of light with a large divergence angle onto the object under test (7) after it has been propagated through a uniform refractive index.

6. The long working distance, high resolution side-viewing endoscopic OCT probe according to claim 1, characterized in that: The single-mode fiber (1) is used to transmit optical signals to the first gradient refractive index lens (3).

7. The long working distance, high resolution side-viewing endoscopic OCT probe according to claim 1, characterized in that: The near-infrared transmission film (8) has a transmittance in the light band that is not less than the value required for endoscopic OCT imaging.

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