Long-working-distance high-resolution side-looking endoscopic OCT (optical coherence tomography) probe

Abstract

The invention relates to the field of optical coherence tomography, and discloses a long-working-distance high-resolution side-looking endoscopic OCT probe which comprises a single-mode optical fiber, one end of the single-mode optical fiber is connected with a first gradient refractive index lens, one side of the first gradient refractive index lens is fixedly connected with a first glass capillary, and the other side of the first gradient refractive index lens is fixedly connected with a second glass capillary. A second gradient refractive index lens is fixedly connected to the middle of the end, away from the single-mode fiber, of the first gradient refractive index lens, and the light incidence end face of the first gradient refractive index lens and the light incidence end face of the second gradient refractive index lens are both plated with near-infrared transmission film layers. And the other side of the first gradient refractive index lens is fixedly connected with a second glass capillary tube. The gradient refractive index lenses with low gradient constants and the gradient refractive index lenses with high gradient constants are combined to form the beam shaper, the beam emitted by the single-mode optical fiber is reduced to be smaller than the diameter of a mode field of the single-mode optical fiber, the divergence angle of the beam is increased, and the machining difficulty and the sensitivity to errors are remarkably reduced.

Description

Technical Field

[0001] The invention relates to the technical field of optical coherence tomography, in particular to a long-working-distance, high-resolution side-view endoscopic OCT probe. Background Art

[0002] Optical coherence tomography (OCT) is an emerging biomedical optical imaging technology that can achieve non-contact, non-destructive, 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] Since the development of optical coherence tomography technology, three types of systems have been formed: time-domain OCT system, spectral domain OCT system and swept frequency OCT system. The early time-domain OCT system realizes tomographic imaging of biological samples through axial mechanical scanning, while the spectral domain OCT system and swept frequency OCT system can image without axial scanning, realizing high-speed and high-sensitivity optical coherence tomography. However, for the above three types of OCT systems, since the light bands used can only penetrate a few millimeters in the tissue, they cannot directly penetrate the human body in vitro to perform tomographic imaging of internal tissues and organs. Only by developing endoscopic technology based on the OCT system can OCT technology be applied to high-resolution imaging of internal tissues and organs of the human body. The core component of the endoscopic OCT system is the endoscopic OCT probe. Since many organs of the human body are large lumen organs with a radius of more than 10 mm, and the working distance of the endoscopic OCT system is only about 2 mm, it is very necessary to design and manufacture an endoscopic OCT probe with a long working distance to facilitate imaging and reduce the pain of patients.

[0004] Traditional probes, such as probes with dual gradient refractive index lenses, have extremely strict tolerance requirements on the lens and the length of the beam expansion optical spacing, resulting in high manufacturing costs. Summary of the invention

[0005] In view of the shortcomings of the prior art, the present invention provides a long working distance and high resolution side-view endoscopic OCT probe to solve the problem of high manufacturing cost of traditional endoscopic OCT probes.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solutions: a long working distance high-resolution side-view endoscopic OCT probe, comprising a single-mode optical fiber, one end of the single-mode optical fiber is connected to a first gradient refractive index lens, one side of the first gradient refractive index lens is fixedly connected to a first glass capillary, 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, 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 both coated with a near-infrared transmission film layer, the other side of the first gradient refractive index lens 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, a sample to be measured is arranged 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 a low gradient constant and a high gradient constant.

[0011] Preferably, the spherical collimating lens is used to converge the reduced light beam with a large divergence angle onto the object to be measured through the spherical surface after propagation through a uniform refractive index.

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

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

[0014] Working principle: When in use, the light source emits a light signal, which is transmitted to the incident end of the first gradient refractive index lens through the single-mode optical fiber. The light beam with a certain divergence angle emitted by the single-mode optical fiber is preliminarily shaped by the first gradient refractive index lens to convert it into the direction of a parallel light beam, so that the light beam is close to a parallel light beam after passing through the first gradient refractive index lens, and the light beam enters the second gradient refractive index lens. The second gradient refractive index lens has a stronger convergence effect on the light, so that the light beam converges quickly in the lens, and finally the spot size is reduced to below the mode field diameter of the single-mode optical fiber 1, the divergence angle of the light beam is increased, and the light beam enters the spherical collimating lens. The spherical shape and uniform refractive index propagation characteristics of the spherical collimating lens refract and converge the light beam, so that it converges on the object to be measured, thereby achieving high-resolution imaging over a long working distance.

[0015] The present invention provides a long working distance high resolution side-view endoscopic OCT probe, which has the following beneficial effects:

[0016] 1. The present invention forms a beam shaper by combining a gradient refractive index lens with a low gradient constant and a gradient refractive index lens with a high gradient constant, thereby reducing the light beam emitted from the single-mode optical fiber to below the mode field diameter of the single-mode optical fiber and increasing its divergence angle. Compared with the conventional method of using an air spacer and a gradient refractive index lens to form a beam shaper, the present invention significantly reduces the processing difficulty and sensitivity to errors, improves the processing efficiency and reduces the scrap rate, thereby solving the problem of high production cost of conventional endoscopic OCT probes.

[0017] 2. The parameters of the gradient refractive index lens, glass capillary and spherical collimating lens used in the present invention are selected based on common specifications and mature manufacturing processes on the market, avoiding dependence on special customized parts, rather than special customized lenses that require complex manufacturing processes and high-precision processing, greatly reducing production costs. The precise fixation and positioning of the glass capillary simplifies the assembly process of the parts, reduces the demand for high-precision alignment and complex processing equipment, makes the production process simpler and more efficient, is conducive to the mass production and promotion and application of the probe, and improves the market competitiveness of the product.

[0018] 3. The present invention performs preliminary processing on the output light beam of the single-mode optical fiber through the first gradient refractive index lens, and then uses the second gradient refractive index lens to reduce the light spot to below the mode field diameter of the single-mode optical fiber, thereby increasing the beam divergence angle, and then uses the spherical collimating lens to accurately converge the light beam, thereby finally achieving high-resolution imaging over a long working distance.

[0019] 4. The endoscopic OCT probe of the present invention has a compact structure and simple connection, and is easy to integrate with the existing OCT system. Its standard optical interface and clear signal transmission path allow it to be easily integrated into the existing OCT imaging system as a module without the need for large-scale transformation or redesign of the existing system, which facilitates the upgrade and technical improvement of existing OCT equipment and can quickly improve the endoscopic imaging performance of the system without changing the overall system architecture, saving time and cost for system upgrades and accelerating the promotion and application of the technology in different application scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a structural schematic diagram of the present invention;

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

[0022] Figure 3 A schematic diagram of the light spot effect after the beam shaper of the present invention is designed;

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

[0024] Figure 5 It is a schematic diagram of 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. measured sample; 8. near-infrared transmission film layer. DETAILED DESCRIPTION

[0026] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] Please see attached Figure 1An embodiment of the present invention provides a long working distance high-resolution side-view endoscopic OCT probe, including a single-mode optical fiber 1, one end of the single-mode optical fiber 1 is connected to a first gradient refractive index lens 3, one side of the first gradient refractive index lens 3 is fixedly connected to a first glass capillary 2, the middle of the end of the first gradient refractive index lens 3 away from the single-mode optical fiber 1 is fixedly connected to a second gradient refractive index lens 5, 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 both coated with a near-infrared transmission film layer 8, the other side of the first gradient refractive index lens 3 is fixedly connected to a second glass capillary 4, and the end of the second gradient refractive index lens 5 away from the first gradient refractive index lens 3 is fixedly connected to a spherical collimating lens 6.

[0028] 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 .

[0029] 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 .

[0030] A sample 7 to be measured is arranged 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 a low gradient constant and a high gradient constant.

[0032] The spherical collimating lens 6 is used to converge the reduced light beam with a large divergence angle onto the object to be measured 7 through the spherical surface after propagation through a uniform refractive index.

[0033] The single-mode optical 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 optical fiber 1. Since the core diameter of the single-mode optical fiber 1 is small, the optical signal propagates therein in a single mode, thereby ensuring high coherence and low loss of the optical signal. When the optical signal enters the first gradient refractive index lens 3, since the first gradient refractive index lens 3 has a low gradient constant, the slow change of its refractive index from the center to the edge causes the optical signal to refract. According to the light propagation principle of the gradient refractive index lens, the propagation path of the light in the lens will gradually change, and the light beam with a certain divergence angle emitted by the single-mode optical fiber 1 is preliminarily shaped to be converted into the direction of a parallel light beam. Therefore, through the low gradient constant value and lens length of the first gradient refractive index lens 3, the light beam is close to a parallel light beam after passing through the first gradient refractive index lens 3, thereby providing good initial conditions for subsequent further processing.

[0036] The approximately parallel light 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. Therefore, its refractive index changes more dramatically from the center to the edge, which can have a stronger convergence effect on the light, so that the light converges quickly in the lens, and finally reduces the spot size to below the mode field diameter of the single-mode optical fiber 1. The purpose of this is to increase the divergence angle of the light and provide favorable conditions for the convergence 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 convergence ability of the spherical collimating lens 6.

[0037] The near-infrared transmission film layer 8 on the light incident end faces 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 the two lenses, and reduces reflection loss so that more light energy can effectively pass through the lens, thereby improving light utilization efficiency and imaging quality.

[0038] The first glass capillary 2 and the second glass capillary 4 are mainly used to fix and position the corresponding lenses to ensure the relative position accuracy between them. The inner diameter of the glass capillary should be selected according to the outer diameter of the component to be accommodated. Generally speaking, the inner diameter of the first glass capillary 2 should be slightly larger than the outer diameter of the single-mode optical fiber 1, and a certain gap (for example, 0.1mm to 0.2mm) should be left to facilitate the insertion and fixation of the single-mode optical fiber 1, while ensuring the relative position accuracy between the single-mode optical 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 penetrate and be fixed at one end of the first gradient refractive index lens 3. The material of the glass capillary can be selected from quartz glass, which has good chemical stability and thermal stability and can ensure dimensional stability under different environments.

[0040] The light beam that has been narrowed by the second gradient refractive index lens 5 and has 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, according to the principles of geometric optics, the light will be refracted and converged. According to the focal length of the lens and the spherical curvature radius, the light will be converged to a farther working distance after passing through the spherical collimating lens 6, thereby achieving imaging at a long working distance.

[0041] Please see attached Figure 2 -Attached Figure 5The parameters of the product of the present invention have been tested on multiple platforms, including Matlab, Zemax and Virtuallab, and all show that a working distance of more than 10 mm can be achieved while maintaining a high lateral resolution (focal spot is less than 20 μm). The reason for achieving this effect is that a gradient refractive index lens with a low gradient constant and a high gradient constant is combined to form a beam shaper, which reduces the light beam emitted from the single-mode optical fiber 1 to below the mode field diameter of the single-mode optical fiber and increases its divergence angle, thereby well controlling the focal spot to be below the mode field diameter to better utilize the convergence effect of the spherical lens, thereby converging the light beam at 10 mm and reducing the beam waist radius to achieve a high lateral resolution.

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

[0043] In terms of physical product processing, we use common lens parameters on the market for design. Compared with the currently designed long-working-distance endoscope probes that require specially customized lens parameters, our costs and procurement difficulty are lower, which facilitates batch processing and production.

[0044] A beam shaper is formed by combining a low gradient constant and a high gradient constant gradient index lens, which reduces the light beam emitted by the single-mode optical fiber 1 to below the mode field diameter of the single-mode optical fiber and increases its divergence angle. Compared with the traditional method of using an air spacer and a gradient refractive index lens to form a beam shaper, the processing difficulty and sensitivity to errors are reduced by dozens of times, the processing efficiency is improved and the scrap rate is reduced, thereby solving the problem of high production cost of traditional endoscopic OCT probes.

[0045] The focusing part adopts a spherical collimating lens 6, which converges the reduced light beam with a large divergence angle onto the object to be measured 7 through a spherical surface after propagation through a uniform refractive index; compared with the traditional use of optical interval beam expanders and gradient refractive index lenses as the converging part, it reduces costs, while increasing the working distance and lateral resolution and improving the processing tolerance.

[0046] In summary, the present invention is based on a gradient refractive index lens and a spherical lens, and utilizes two gradient refractive index lenses to form a beam shaper, and the divergent light spot of the light beam emitted from the single-mode optical fiber is first converted into a parallel light beam after passing through the first gradient refractive index lens 3, and then the light beam is converged at the end through the second gradient refractive index lens 5 to be reduced to less than the mode field diameter of the single-mode optical fiber. The advantage of this is that since the aperture angle of the light beam and the light spot mode field diameter are mutually restricted, a small mode field diameter can obtain a large aperture angle to better utilize the convergence of the spherical lens, and then a spherical lens with a constant refractive index is used to expand the reduced light beam and converge the light beam on the object to be measured through the convergence of the end sphere, so as to achieve a working distance of more than 10 mm and maintain scanning imaging with a high lateral resolution (20 um).

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

Claims

1. A long working distance high resolution side-view endoscopic OCT probe, comprising a single mode optical fiber (1), characterized in that: One end of the single-mode optical fiber (1) is connected to a first gradient refractive index lens (3), one side of the first gradient refractive index lens (3) is fixedly connected to a first glass capillary (2), a middle portion of an end of the first gradient refractive index lens (3) away from the single-mode optical fiber (1) is fixedly connected to a second gradient refractive index lens (5), a light incident end face of the first gradient refractive index lens (3) and a light incident end face of the second gradient refractive index lens (5) are both plated with a near-infrared transmission film layer (8), the other side of the first gradient refractive index lens (3) is fixedly connected to a second glass capillary (4), and an end of the second gradient refractive index lens (5) away from the first gradient refractive index lens (3) is fixedly connected to a spherical collimating lens (6).

2. The long working distance high resolution side-view 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-view 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-view endoscopic OCT probe according to claim 1, characterized in that: A sample to be measured (7) is arranged on one side of the spherical collimating lens (6).

5. The long working distance high resolution side-view endoscopic OCT probe according to claim 1, characterized in that: The first gradient refractive index lens (3) and the second gradient refractive index lens (5) include gradient refractive index lenses with a low gradient constant and a high gradient constant.

6. The long working distance high resolution side-view endoscopic OCT probe according to claim 1, characterized in that: The spherical collimating lens (6) is used to converge the shrunk light beam with a large divergence angle onto the object to be measured (7) through the spherical surface after propagation through a uniform refractive index.

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

8. The long working distance high resolution side-view endoscopic OCT probe according to claim 1, characterized in that: 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.

Images