Photoacoustic-OCT (Optical Coherence Tomography) bimodal endoscopic imaging system based on multi-element focusing

Abstract

The invention relates to a photoacoustic-OCT (optical coherence tomography) bimodal endoscopic imaging system based on multi-element focusing. The photoacoustic-OCT bimodal endoscopic imaging system comprises a signal control module, an optical coherence tomography module, a photoacoustic signal excitation module, a light beam common-path module, an endoscope probe, a rotary withdrawing module and a data acquisition module, a sample arm of the optical coherence tomography module and the photoacoustic signal excitation module enter the endoscope probe through the light beam common-path module; an optical assembly and a photoacoustic receiver are arranged in the endoscope probe, and the optical assembly focuses OCT and photoacoustic combined laser and then irradiates target tissue with the focused OCT and photoacoustic combined laser; an ultrasonic signal generated after the target tissue is irradiated by the pulse laser is received by the photoacoustic signal receiver and converted into an ultrasonic electric signal, and the ultrasonic electric signal is sent to the data acquisition module; the rotation withdrawing module controls the endoscope probe to conduct three-dimensional body data scanning, and the data collecting module receives OCT interference signals and ultrasonic electric signals of the opto-acoustic receiver. Compared with the prior art, the device has the advantages of large working distance, high resolution and less influence by water.

Description

Technical Field

[0001] The present invention relates to the technical field of biomedical equipment, and in particular to a photoacoustic-OCT dual-modality endoscopic imaging system based on multi-element focusing. Background Art

[0002] As one of the products of the rapid development of modern medical science and technology, endoscopic imaging technology plays an irreplaceable role in the diagnosis of intraluminal diseases such as cardiovascular and cerebrovascular diseases and gastrointestinal tumors.

[0003] Traditional commonly used optical or ultrasonic single-modality endoscopes often have certain limitations. When facing complex biological tissues, they often cannot provide enough information for comprehensive diagnosis and analysis. As two advanced imaging technologies, photoacoustic imaging and optical coherence tomography have significant complementarity. Photoacoustic imaging is effective in imaging high-absorption coefficient materials, while OCT technology performs well in imaging low-scattering and low-absorption tissues. Combining these two technologies in one system can simultaneously obtain two types of imaging information, thereby providing more comprehensive and accurate diagnostic results. In practical applications, photoacoustic imaging usually requires water as a conductive medium. However, OCT imaging is greatly affected by water absorption at 1310nm and above, resulting in limited imaging depth and quality. In addition, the design of traditional endoscopic catheters usually uses GRIN lens focusing or single spherical lens focusing. When using GRIN lens focusing, a refractive prism is required to transform the light path, which increases the rigid length of the front section of the probe and makes the integrated assembly of the probe difficult. Another method is to process the end of the optical fiber into a spherical shape to achieve optical fiber convergence, and then grind a total reflection surface or metal coating at the end to achieve lateral focusing of the light. However, this method is usually applicable in air, while photoacoustic endoscopic imaging catheters usually require water as a medium. Due to the insufficient refractive index difference between optical fiber and water, the radius of curvature of the optical fiber ball lens needs to be greatly reduced, which will lead to increased aberrations in the imaging system and make it difficult to obtain a larger working distance. At the same time, in photoacoustic imaging, there is a minimum distance limit between the ultrasonic transducer and the focusing ball lens, so in order to ensure that the ultrasonic transducer can better receive ultrasonic signals, a larger working distance is usually required. Summary of the invention

[0004] The purpose of the present invention is to overcome the defects of the above-mentioned prior art, such as incomplete single-modality endoscopic imaging information, the multi-modality endoscopic imaging catheter design being greatly affected by the conductive medium, and insufficient working distance, and to provide a photoacoustic-OCT dual-modality endoscopic imaging system based on multi-element focusing, which has a large working distance, high resolution and is less affected by water.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] The present invention provides a photoacoustic-OCT dual-modality endoscopic imaging system based on multi-element focusing, comprising: a signal control module, an optical coherence tomography module, a photoacoustic signal excitation module, a beam common path module, an endoscopic probe, a rotation and retraction module and a data acquisition module; the signal control module is used to control the optical coherence tomography module, the photoacoustic signal excitation module, the rotation and retraction module and the data acquisition module to perform corresponding functions; the signal control module is provided with a frequency-adjustable Trigger signal by a signal control card for synchronously controlling the optical coherence tomography module, the photoacoustic signal excitation module, the rotation and retraction module and the data acquisition module.

[0007] The sample arm of the optical coherence tomography module and the photoacoustic signal excitation module enter the endoscope probe through the beam common path module;

[0008] The endoscopic probe is provided with an optical component and a photoacoustic receiver, and the optical component focuses the combined laser beam of OCT and photoacoustic and irradiates it to the target tissue; the ultrasonic signal generated by the target tissue after being irradiated with the pulsed laser is received by the photoacoustic signal receiver and converted into an ultrasonic electrical signal, which is then amplified by the signal amplifier and sent to the data acquisition card; the rotation and retraction module controls the endoscopic probe to perform three-dimensional volume data scanning, and the data acquisition module receives the OCT interference signal and the ultrasonic electrical signal of the photoacoustic receiver, and reconstructs it into the required endoscopic image through analysis, and displays the photoacoustic-OCT dual-modality image of the target tissue.

[0009] Further, the optical coherence tomography module includes an SLD light source, a fiber coupler, a first fiber collimator, a first focusing lens, a reflector, a second fiber collimator, a grating, a second focusing lens, and a linear scanning camera arranged in sequence;

[0010] The signal control module gives a designated trigger signal to the SLD light source, and the SLD light source emits a broadband laser with a central wavelength of 850nm and a -3dB bandwidth of 100nm. After being split 50:50 by the fiber coupler, one path of laser light is emitted from the first fiber collimator, converged to the reflector through the first focusing lens, and then returned to the fiber coupler by the original path, wherein the first fiber collimator, the first focusing lens, and the reflector are coaxially arranged as the reference arm optical path of the optical coherence tomography module; another path of laser light emitted from the fiber coupler reaches the endoscope probe and irradiates the target tissue, and the scattered light returns to the fiber coupler through the original path; the two return lights interfere at the fiber coupler, and the interference light is transmitted through the optical fiber to the second fiber collimator for emission, and the emitted light is converged to the linear scanning camera by the second focusing lens after being split by the grating; the scattered light of OCT returns to the optical fiber by the original path, and the interference information is received by the linear scanning camera and transmitted to the data acquisition card.

[0011] Furthermore, the photoacoustic signal excitation module includes a pulse light source, a first lens and a second lens arranged in sequence, and the pulse laser is controlled by a trigger signal given by the signal control module and synchronized with the optical coherence tomography module to emit light. The emitted laser is a high-frequency pulse light with a wavelength of 532nm.

[0012] Furthermore, the beam sharing module uses a wavelength division multiplexer to complete the combined transmission of the OCT beam and the photoacoustic excitation light.

[0013] Furthermore, the rotating retraction module controls the endoscope probe to perform axial movement and multi-angle annular scanning, thereby performing laser scanning of multiple regions of the target tissue and obtaining three-dimensional image information of the imaging region. Specifically, a rotating motor rotates through a belt-driven photoelectric slip ring, and then drives the entire endoscope probe to rotate through a torque spring, while another retraction motor drives the rotating platform to perform axial movement.

[0014] Furthermore, the endoscope probe is composed of an optical component and a photoacoustic signal receiver. The outer diameter of the endoscope probe is controlled within 1 mm, meeting the actual clinical needs for small inner diameter lumen diseases.

[0015] Furthermore, the optical component and the photoacoustic signal receiver are placed side by side in a customized metal capillary, and the optical component includes: a single-mode optical fiber, a coreless optical fiber, a gradient refractive index optical fiber and a ball lens; a light-transmitting window is provided at the front end of the metal capillary, and the rear end of the metal capillary is connected to a torque spring;

[0016] The photoacoustic signal receiver is a block-shaped ultrasonic transducer, which uses interconnected coaxial lines to transmit ultrasonic electrical signals; the ultrasonic transducer is placed at one end of the light-transmitting window, the core wire of the coaxial line is bonded to the backing layer of the ultrasonic transducer by silver glue, and the shielding wire is bonded to the inner side of the metal capillary by silver glue; the ultrasonic transducer receives the ultrasonic signal generated by the target tissue being excited by the laser, and converts the ultrasonic signal into an ultrasonic electrical signal, which is transmitted to the data acquisition module through the coaxial line for corresponding data processing, analysis and display;

[0017] The single-mode optical fiber used to transmit OCT sample light and photoacoustic excitation light and the coaxial line used to transmit photoacoustic electrical signals pass through the torque spring together, and a thinner stepped end of the torque spring is inserted into the metal capillary. The outer wall of the torque spring and the inner side of the metal capillary are bonded by AB glue.

[0018] To ensure that the ultrasonic transducer can vertically receive the ultrasonic signal of the target tissue under limited working distance conditions and maximize the receiving efficiency, the top of the spherical lens at the front end of the optical component is placed as close to the ultrasonic transducer as possible, while ensuring that the two are placed parallel and coaxially.

[0019] Furthermore, one end of the torque spring is connected to the rotation and withdrawal module, and a photoelectric slip ring is provided in the rotation and withdrawal module. The photoelectric slip ring includes an optical signal transmission part located in the center and an electrical signal transmission part located in the periphery. The laser in the optical fiber is transmitted to the endoscope probe through the optical signal transmission part, and the ultrasonic electrical signal converted in the ultrasonic transducer is transmitted to the data acquisition module through the electrical signal transmission part. The photoelectric slip ring is driven by a rotating motor to drive the endoscope probe to rotate for 360° scanning. The rotor end of the photoelectric slip ring rotates, driving the torque spring to transmit the torque to the front end of the endoscope probe. The axial movement transposition is driven by the corresponding withdrawal motor to drive the endoscope probe to move axially along the direction of the optical fiber. Three-dimensional scanning of the target tissue can be achieved.

[0020] Furthermore, the optical component adopts an integrated lens with multiple focusing elements, including: a single-mode optical fiber, a coreless optical fiber, a gradient refractive index optical fiber and a spherical lens arranged in sequence; the combination of the gradient refractive index optical fiber and the spherical lens realizes light focusing, the spherical lens is located at the end of the optical fiber probe, and the spherical lens includes a reflection surface, and the reflection surface is located outside the spherical lens; the single-mode optical fiber is connected to the coreless optical fiber, so that the laser enters the gradient refractive index optical fiber after being diverged, and the gradient refractive index optical fiber is used to pre-shape the light beam before it reaches the spherical lens, thereby controlling the divergence of the light beam when it enters the spherical lens;

[0021] Light is transmitted through a single-mode optical fiber to a coreless optical fiber for initial divergence, and then the divergence of the light beam when entering the spherical lens is controlled by a gradient refractive index optical fiber. The light spot becomes larger and the divergence angle of the light beam becomes smaller or converges. Light with a smaller divergence angle is reflected by the reflective surface of the spherical lens, and the reflected light passes through the exit surface of the spherical lens and converges at the side end of the integrated lens, thereby focusing light in a liquid environment with a large refractive index, and can simultaneously achieve a large working distance and high resolution.

[0022] Furthermore, the reflective surface of the spherical lens is obtained by grinding the spherical lens, and the reflective surface can be coated with a reflective film.

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] The invention has a large working distance, high resolution and is less affected by water. The present invention realizes the two methods of photoacoustic and OCT imaging through an integrated endoscope probe, which simplifies the detection procedure. In addition, it adopts a multi-focusing element probe design to obtain better resolution with the smallest probe diameter, and can achieve a longer working distance without sacrificing resolution. At the same time, the added gradient refractive index fiber segment reduces the loss of focusing power when the ball lens is immersed in a high refractive index medium, making it more advantageous in imaging in a water environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the structure of the photoacoustic-OCT dual-modality endoscopic imaging system;

[0026] Figure 2 It is a schematic diagram of the structure of the overall optical path;

[0027] Figure 3 is a cross-sectional view of an endoscope probe;

[0028] Figure 4 Schematic diagram of the structure of a multi-element focusing integrated lens.

[0029] Figure numerals: 110-signal control module; 120-optical coherence tomography module; 130-photoacoustic signal excitation module; 140-beam common path module; 150-endoscopic probe; 160-rotation and retraction module; 170-data acquisition module; 121-SLD light source; 122-fiber coupler; 123-first fiber collimator; 124-first focusing lens; 125-reflector; 126-second fiber collimator; 127-grating; 128-second focusing lens; 129-linear scanning camera; 131-pulse light source; 132-first lens; 133-second lens; 151-single-mode optical fiber; 152-coreless optical fiber; 153-gradient refractive index optical fiber; 154-spherical lens; 155-ultrasonic transducer; 156-coaxial line; 157-metal capillary; 158-torque spring; 171-signal amplifier; 172-data acquisition card. DETAILED DESCRIPTION

[0030] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. Component models, material names, connection structures, control methods, algorithms and other features not clearly described in this technical solution are all considered to be common technical features disclosed in the prior art.

[0031] It should be noted that when a component is considered to be "connected" to another component, it can be directly connected to another component, or connected to another component through an intermediate component. The "connection" in the following embodiments should be understood as "electrical connection", "communication connection", etc. if the connected components, circuits, modules, units, etc. have electrical signals or data transmission between each other.

[0032] Example 1

[0033] This embodiment provides a photoacoustic-OCT dual-modality endoscopic imaging system based on multi-element focusing, such as Figure 1As shown, it includes: a signal control module 110, an optical coherence tomography module 120, a photoacoustic signal excitation module 130, a beam common path module 140, an endoscopic probe 150, a rotation and retraction module 160 and a data acquisition module 170; the signal control module 110 is used to control the optical coherence tomography module 120, the photoacoustic signal excitation module 130, the rotation and retraction module 160 and the data acquisition module 170 to perform corresponding functions; the signal control module 110 provides a frequency-adjustable Trigger signal from a signal control card for synchronously controlling the optical coherence tomography module 120, the photoacoustic signal excitation module 130, the rotation and retraction module 160 and the data acquisition module 170.

[0034] The sample arm of the optical coherence tomography module 120 and the photoacoustic signal excitation module 130 enter the endoscope probe 150 through the beam common path module 140;

[0035] The endoscopic probe 150 is provided with an optical component and a photoacoustic receiver, and the optical component focuses the combined laser beam of OCT and photoacoustic and irradiates it to the target tissue; the ultrasonic signal generated by the target tissue after being irradiated with the pulsed laser is received by the photoacoustic signal receiver and converted into an ultrasonic electrical signal, and then sent to the data acquisition module 170; the rotation and retraction module 160 controls the endoscopic probe 150 to perform three-dimensional volume data scanning, and the data acquisition module 170 receives the OCT interference signal and the ultrasonic electrical signal of the photoacoustic receiver, and reconstructs it into the required endoscopic image through analysis, and displays the photoacoustic-OCT dual-modality image of the target tissue.

[0036] In a specific embodiment, Figure 2 As shown, the optical coherence tomography module 120 includes an SLD light source 121, a fiber coupler 122, a first fiber collimator 123, a first focusing lens 124, a reflector 125, a second fiber collimator 126, a grating 127, a second focusing lens 128, and a linear scan camera 129, which are arranged in sequence;

[0037] The signal control module 110 sends a designated trigger signal to the SLD light source 121, and the SLD light source 121 emits a broadband laser with a central wavelength of 850nm and a -3dB bandwidth of 100nm. After being split 50:50 by the fiber coupler 122, one path of laser light is emitted from the first fiber collimator 123, converged to the reflector 125 through the first focusing lens 124, and then returned to the fiber coupler 122 along the original path. The first fiber collimator 123, the first focusing lens 124, and the reflector 125 are coaxially arranged as the optical coherence tomography module 12 0; another path of laser light emitted by the fiber coupler 122 reaches the endoscopic probe 150 and irradiates the target tissue, and the scattered light returns to the fiber coupler 122 via the original path; the two paths of returned light interfere at the fiber coupler 122, and the interference light is transmitted through the optical fiber to the second fiber collimator 126 for emission, and the emitted light is split by the grating 127 and converged by the second focusing lens 128 to the linear scan camera 129; the original path of the scattered light of OCT returns to the optical fiber, and the interference information is received by the linear scan camera 129 and transmitted to the data acquisition card 172.

[0038] In a specific embodiment, the photoacoustic signal excitation module 130 includes a pulse light source 131, a first lens 132, and a second lens 133 arranged in sequence, and the pulse laser 131 is controlled by a trigger signal given by the signal control module 110 and synchronized with the optical coherence tomography module 120 to emit light. The emitted laser is a high-frequency pulse light with a wavelength of 532nm.

[0039] In a specific implementation, the beam sharing module 140 uses a wavelength division multiplexer to complete the combined transmission of the OCT beam and the photoacoustic excitation light.

[0040] In a specific embodiment, the rotating retraction module 160 controls the endoscopic probe 150 to perform axial movement and multi-angle annular scanning, thereby performing laser scanning of multiple regions of the target tissue to obtain three-dimensional image information of the imaging region. Specifically, a rotating motor rotates through a belt-driven photoelectric slip ring, and then drives the entire endoscopic probe 150 to rotate through a torque spring 158, while another retraction motor drives the rotating platform to perform axial movement.

[0041] In a specific embodiment, the endoscopic probe 150 is composed of an optical component and a photoacoustic signal receiver. The outer diameter of the endoscopic probe 150 is controlled within 1 mm, meeting the actual clinical needs for small inner diameter lumen diseases.

[0042] In a specific embodiment, Figure 3As shown, the optical component and the photoacoustic signal receiver are placed side by side in a customized metal capillary 157, and the optical component includes: a single-mode optical fiber 151, a coreless optical fiber 152, a gradient refractive index optical fiber 153 and a ball lens 154; a light-transmitting window is provided at the front end of the metal capillary 157, and the rear end of the metal capillary 157 is connected to a torque spring 158;

[0043] The photoacoustic signal receiver is a block-shaped ultrasonic transducer 155, and the ultrasonic transducer 155 uses mutually connected coaxial lines 156 to transmit ultrasonic electrical signals; the ultrasonic transducer 155 is placed at one end of the light-transmitting window, the core wire of the coaxial line 156 is adhered to the backing layer of the ultrasonic transducer 155 by silver glue, and the shielding wire is adhered to the inner side of the metal capillary 157 by silver glue; the ultrasonic transducer 155 receives the ultrasonic signal generated by the target tissue being excited by the laser, and converts the ultrasonic signal into an ultrasonic electrical signal, which is transmitted to the signal amplifier 171 through the coaxial line 156, and the signal is transmitted to the data acquisition card 172 after amplification for corresponding data processing, analysis and display;

[0044] The single-mode optical fiber 151 used to transmit OCT sample light and photoacoustic excitation light and the coaxial line 156 used to transmit photoacoustic electrical signals pass through the torque spring 158 together, and a thinner stepped end of the torque spring 158 is inserted into the metal capillary 157. The outer wall of the torque spring 158 and the inner side of the metal capillary 157 are bonded by AB glue.

[0045] To ensure that the ultrasonic transducer 155 can vertically receive the ultrasonic signal of the target tissue under limited working distance conditions and maximize the receiving efficiency, the top of the ball lens 154 at the front end of the optical component is placed as close to the ultrasonic transducer 155 as possible, while ensuring that the two are placed parallel and coaxially.

[0046] In a specific embodiment, one end of the torque spring 158 is connected to the rotation and withdrawal module 160, and a photoelectric slip ring is provided in the rotation and withdrawal module 160. The photoelectric slip ring includes an optical signal transmission part located in the center and an electrical signal transmission part located in the periphery. The laser in the optical fiber is transmitted to the endoscope probe 150 through the optical signal transmission part, and the ultrasonic electrical signal converted in the ultrasonic transducer 150 is transmitted to the data acquisition module 170 through the electrical signal transmission part; the photoelectric slip ring is driven by a rotating motor to drive the endoscope probe 150 to rotate for 360° scanning. The rotor end of the photoelectric slip ring rotates, driving the torque spring 158 to transmit torque to the front end of the endoscope probe 150. The axial movement transposition is driven by the corresponding withdrawal motor to drive the endoscope probe 150 to move axially along the optical fiber direction. Three-dimensional scanning of the target tissue can be achieved.

[0047] Example 2

[0048] This embodiment provides a photoacoustic-OCT dual-modality endoscopic imaging system based on multi-element focusing, such as Figure 1 As shown, it includes: a signal control module 110, an optical coherence tomography module 120, a photoacoustic signal excitation module 130, a beam common path module 140, an endoscopic probe 150, a rotation and retraction module 160 and a data acquisition module 170; the signal control module 110 is used to control the optical coherence tomography module 120, the photoacoustic signal excitation module 130, the rotation and retraction module 160 and the data acquisition module 170 to perform corresponding functions; preferably, the signal control module 110 provides a frequency-adjustable Trigger signal by a signal control card for synchronously controlling the optical coherence tomography module 120, the photoacoustic signal excitation module 130, the rotation and retraction module 160 and the data acquisition module 170.

[0049] The sample arm of the optical coherence tomography module 120 and the photoacoustic signal excitation module 130 enter the endoscope probe 150 through the beam common path module 140;

[0050] The endoscopic probe 150 is provided with an optical component and a photoacoustic receiver, and the optical component focuses the combined laser beam of OCT and photoacoustic and irradiates it to the target tissue; the ultrasonic signal generated by the target tissue after being irradiated with the pulsed laser is received by the photoacoustic signal receiver and converted into an ultrasonic electrical signal, and then sent to the data acquisition module 170; the rotation and retraction module 160 controls the endoscopic probe 150 to perform three-dimensional volume data scanning, and the data acquisition module 170 receives the OCT interference signal and the ultrasonic electrical signal of the photoacoustic receiver, and reconstructs it into the required endoscopic image through analysis, and displays the photoacoustic-OCT dual-modality image of the target tissue.

[0051] In a specific embodiment, Figure 2 As shown, the optical coherence tomography module 120 includes an SLD light source 121, a fiber coupler 122, a first fiber collimator 123, a first focusing lens 124, a reflector 125, a second fiber collimator 126, a grating 127, a second focusing lens 128, and a linear scan camera 129, which are arranged in sequence;

[0052] The signal control module 110 sends a designated trigger signal to the SLD light source 121, and the SLD light source 121 emits a broadband laser with a central wavelength of 850nm and a -3dB bandwidth of 100nm. After being split 50:50 by the fiber coupler 122, one path of laser light is emitted from the first fiber collimator 123, converged to the reflector 125 through the first focusing lens 124, and then returned to the fiber coupler 122 along the original path. The first fiber collimator 123, the first focusing lens 124, and the reflector 125 are coaxially arranged as the optical coherence tomography module 12 0; another path of laser light emitted by the fiber coupler 122 reaches the endoscopic probe 150 and irradiates the target tissue, and the scattered light returns to the fiber coupler 122 via the original path; the two paths of returned light interfere at the fiber coupler 122, and the interference light is transmitted through the optical fiber to the second fiber collimator 126 for emission, and the emitted light is split by the grating 127 and converged by the second focusing lens 128 to the linear scan camera 129; the original path of the scattered light of OCT returns to the optical fiber, and the interference information is received by the linear scan camera 129 and transmitted to the data acquisition card 172.

[0053] In a specific embodiment, the photoacoustic signal excitation module 130 includes a pulse light source 131, a first lens 132, and a second lens 133 arranged in sequence, and the pulse laser 131 is controlled by a trigger signal given by the signal control module 110 and synchronized with the optical coherence tomography module 120 to emit light. The emitted laser is a high-frequency pulse light with a wavelength of 532nm.

[0054] In a specific implementation, the beam sharing module 140 uses a wavelength division multiplexer to complete the combined transmission of the OCT beam and the photoacoustic excitation light.

[0055] In a specific embodiment, the rotating retraction module 160 controls the endoscopic probe 150 to perform axial movement and multi-angle annular scanning, thereby performing laser scanning of multiple regions of the target tissue to obtain three-dimensional image information of the imaging region. Specifically, a rotating motor rotates through a belt-driven photoelectric slip ring, and then drives the entire endoscopic probe 150 to rotate through a torque spring 158, while another retraction motor drives the rotating platform to perform axial movement.

[0056] In a specific embodiment, the endoscopic probe 150 is composed of an optical component and a photoacoustic signal receiver. The outer diameter of the endoscopic probe 150 is controlled within 1 mm, meeting the actual clinical needs for small inner diameter lumen diseases.

[0057] like Figure 4As shown, the optical component adopts an integrated lens with multiple focusing elements, including: a single-mode optical fiber 151, a coreless optical fiber 152, a gradient refractive index optical fiber 153 and a spherical lens 154 arranged in sequence; the combination of the gradient refractive index optical fiber 153 and the spherical lens 154 realizes light focusing, the spherical lens 154 is located at the end of the optical fiber probe, and the spherical lens 154 includes a reflecting surface, and the reflecting surface is located outside the spherical lens 154; the single-mode optical fiber 151 is connected to the coreless optical fiber 142, so that the laser enters the gradient refractive index optical fiber 153 after being diverged, and the gradient refractive index optical fiber 153 is used to pre-shape the light beam before it reaches the spherical lens 154, thereby controlling the divergence of the light beam when it enters the spherical lens 154;

[0058] The light is transmitted through the single-mode optical fiber 151 to the coreless optical fiber 152 for initial divergence, and then the divergence of the light beam when entering the spherical lens is controlled by the gradient refractive index optical fiber 153. The light spot becomes larger and the divergence angle of the light beam becomes smaller or converges. The light with a smaller divergence angle is reflected by the reflecting surface of the spherical lens 154, and the reflected light passes through the exit surface of the spherical lens 154 and converges at the side end of the integrated lens, thereby focusing the light in a liquid environment with a large refractive index, and can simultaneously achieve a large working distance and a high resolution.

[0059] In a specific implementation, the reflective surface of the ball lens 154 is obtained by grinding the ball lens, and the reflective surface can be coated with a reflective film.

[0060] Components not described in detail in this embodiment are all existing components that can be purchased through public channels.

[0061] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A photoacoustic-OCT dual-modality endoscopic imaging system based on multi-element focusing, characterized in that: include: A signal control module (110), an optical coherence tomography module (120), a photoacoustic signal excitation module (130), a beam common path module (140), an endoscope probe (150), a rotation and retraction module (160), and a data acquisition module (170); the signal control module (110) is used to control the optical coherence tomography module (120), the photoacoustic signal excitation module (130), the rotation and retraction module (160), and the data acquisition module (170); The sample arm of the optical coherence tomography module (120) and the photoacoustic signal excitation module (130) enter the endoscope probe (150) through the light beam common path module (140); The endoscopic probe (150) is provided with an optical component and a photoacoustic receiver, and the optical component focuses the combined laser beam of OCT and photoacoustic and irradiates the combined laser beam to the target tissue; the ultrasonic signal generated by the target tissue after being irradiated by the pulsed laser is received by the photoacoustic signal receiver and converted into an ultrasonic electrical signal, which is then sent to the data acquisition module (170); the rotation and retraction module (160) controls the endoscopic probe (150) to perform three-dimensional volume data scanning, and the data acquisition module (170) receives the OCT interference signal and the ultrasonic electrical signal of the photoacoustic receiver, and reconstructs them into the required endoscopic image through analysis, thereby displaying the photoacoustic-OCT dual-modality image of the target tissue.

2. The photoacoustic-OCT dual-modality endoscopic imaging system based on multi-element focusing according to claim 1, characterized in that: The optical coherence tomography module (120) comprises an SLD light source (121), a fiber coupler (122), a first fiber collimator (123), a first focusing lens (124), a reflector (125), a second fiber collimator (126), a grating (127), a second focusing lens (128), and a linear scanning camera (129) which are arranged in sequence; The signal control module (110) sends a designated trigger signal to the SLD light source (121), and the SLD light source (121) emits broadband laser light. After being split by the optical fiber coupler (122), one path of laser light is emitted from the first optical fiber collimator (123), converged by the first focusing lens (124) to the reflector (125), and then returns to the optical fiber coupler (122) along the original path. The first optical fiber collimator (123), the first focusing lens (124), and the reflector (125) are coaxially arranged as a reference arm optical path of the optical coherence tomography module (120); the optical fiber coupler (122) The other emitted laser beam reaches the endoscope probe (150) and irradiates the target tissue, and the scattered light returns to the optical fiber coupler (122) via the original path; the two returning lights interfere at the optical fiber coupler (122), and the interference light is transmitted to the second optical fiber collimator (126) via the optical fiber for emission, and the emitted light is split by the grating (127) and then converged by the second focusing lens (128) to the linear scanning camera (129); the original path of the scattered light of the OCT returns to the optical fiber, and the interference information is received by the linear scanning camera (129) and then transmitted to the data acquisition card (172) of the data acquisition module (170).

3. The photoacoustic-OCT dual-modality endoscopic imaging system based on multi-element focusing according to claim 1, characterized in that: The photoacoustic signal excitation module (130) comprises a pulse light source (131), a first lens (132) and a second lens (133) which are arranged in sequence, and the pulse laser (131) is controlled to emit light by a trigger signal given by the signal control module (110) and synchronized with the optical coherence tomography module (120).

4. The photoacoustic-OCT dual-modality endoscopic imaging system based on multi-element focusing according to claim 1, characterized in that: The beam common path module (140) uses a wavelength division multiplexer to complete the combined transmission of the OCT beam and the photoacoustic excitation light.

5. The photoacoustic-OCT dual-modality endoscopic imaging system based on multi-element focusing according to claim 1, characterized in that: The rotation and retraction module (160) controls the endoscopic probe (150) to perform axial movement and multi-angle annular scanning, thereby performing multi-region laser scanning on the target tissue and obtaining three-dimensional image information of the imaging area.

6. The photoacoustic-OCT dual-modality endoscopic imaging system based on multi-element focusing according to claim 1, characterized in that: The endoscope probe (150) is composed of an optical component and a photoacoustic signal receiver.

7. The photoacoustic-OCT dual-modality endoscopic imaging system based on multi-element focusing according to claim 6, characterized in that: The optical component and the photoacoustic signal receiver are placed side by side in a metal capillary (157), the optical component comprising: a single-mode optical fiber (151), a coreless optical fiber (152), a gradient refractive index optical fiber (153) and a ball lens (154); a light-transmitting window is provided at the front end of the metal capillary (157), and the rear end of the metal capillary (157) is connected to a torque spring (158); The photoacoustic signal receiver is a block-shaped ultrasonic transducer (155), and the ultrasonic transducer (155) uses interconnected coaxial lines (156) to transmit ultrasonic electrical signals; the ultrasonic transducer (155) is placed at one end of the light-transmitting window, the core wire of the coaxial line (156) is bonded to the backing layer of the ultrasonic transducer (155) by silver glue, and the shielding wire is bonded to the inner side of the metal capillary (157) by silver glue; the ultrasonic transducer (155) receives the ultrasonic signal generated by the target tissue when it is excited by the laser, and converts the ultrasonic signal into an ultrasonic electrical signal, which is transmitted to the data acquisition module (170) through the coaxial line (156) for corresponding data processing, analysis and display; A single-mode optical fiber (151) for transmitting OCT sample light and photoacoustic excitation light and a coaxial line (156) for transmitting photoacoustic electrical signals pass through a torque spring (158) together, and the stepped end of the torque spring (158) is inserted into a metal capillary (157). The outer wall of the torque spring (158) and the inner side of the metal capillary (157) are bonded together by AB glue.

8. The photoacoustic-OCT dual-modality endoscopic imaging system based on multi-element focusing according to claim 7, characterized in that: One end of the torque spring (158) is connected to the rotation and retraction module (160). The rotation and retraction module (160) is provided with a photoelectric slip ring, which includes a light signal transmission part located at the center and an electric signal transmission part located at the periphery. The laser in the optical fiber is transmitted to the endoscope probe (150) through the light signal transmission part, the ultrasonic electric signal converted in the ultrasonic transducer (155) is transmitted to the signal amplifier (171) through the electric signal transmission part, and the photoacoustic signal is transmitted to the data acquisition card (172) after amplification. The photoelectric slip ring is driven by a rotating motor to drive the endoscope probe (150) to rotate and scan 360 degrees. The rotor end of the photoelectric slip ring rotates to drive the torque spring (158) to transmit torque to the front end of the endoscope probe (150).

9. The photoacoustic-OCT dual-modality endoscopic imaging system based on multi-element focusing according to claim 6, characterized in that: The optical component adopts an integrated lens with multiple focusing elements, including: a single-mode optical fiber (151), a coreless optical fiber (152), a gradient refractive index optical fiber (153) and a spherical lens (154) arranged in sequence; the combination of the gradient refractive index optical fiber (153) and the spherical lens (154) realizes light focusing, the spherical lens (154) is located at the end of the optical fiber probe, and the spherical lens (154) includes a reflection surface, and the reflection surface is located outside the spherical lens (154); the single-mode optical fiber (151) is connected to the coreless optical fiber (142), so that the laser first diverges and then enters the gradient refractive index optical fiber (153), and the gradient refractive index optical fiber (153) is used to pre-shape the light beam before it reaches the spherical lens (154), thereby controlling the divergence of the light beam when it enters the spherical lens (154); Light is transmitted through a single-mode optical fiber (151) to a coreless optical fiber (152) for initial divergence, and then the divergence of the light beam when entering the spherical lens is controlled by a gradient refractive index optical fiber (153). The light spot becomes larger and the divergence angle of the light beam becomes smaller or converges. Light with a smaller divergence angle is reflected by the reflection surface of the spherical lens (154). The reflected light passes through the exit surface of the spherical lens (154) and converges at the side end of the integrated lens, thereby achieving focusing of the optical fiber in a liquid environment with a large refractive index, and simultaneously achieving a large working distance and a high resolution.

10. The photoacoustic-OCT dual-modality endoscopic imaging system based on multi-element focusing according to claim 9, characterized in that: The reflective surface of the ball lens (154) is obtained by grinding the ball lens, and the reflective surface can be coated with a reflective film.

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