A multi-element focusing based photoacoustic-oct dual modality endoscopic imaging system

Abstract

The application relates to a photoacoustic-OCT dual-mode endoscopic imaging system based on multi-element focusing, which 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 rotating retracting 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 signal receiver are arranged in the endoscope probe, the optical assembly focuses combined laser beams of the OCT and the photoacoustic and irradiates the target tissue; ultrasonic signals generated after the target tissue is irradiated by pulsed laser are received by the photoacoustic signal receiver and converted into ultrasonic electric signals, which are sent to the data acquisition module; the rotating retracting module controls the endoscope probe to perform three-dimensional body data scanning, and the data acquisition module receives an OCT interference signal and ultrasonic electric signals of the photoacoustic signal receiver. Compared with the prior art, the application has a large working distance, high resolution and is less affected by water.

Description

Technical Field

[0001] This invention relates to the field of biomedical device technology, and in particular to a photoacoustic-OCT dual-modal endoscopic imaging system based on multi-element focusing. Background Technology

[0002] As a product 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 optical or ultrasonic single-modal endoscopes often have limitations, failing to provide sufficient information for comprehensive diagnosis and analysis when dealing with complex biological tissues. Photoacoustic imaging and optical coherence tomography (OCT), as two advanced imaging technologies, are highly complementary. Photoacoustic imaging is effective in imaging substances with high absorption coefficients, while OCT excels in imaging tissues with low scattering and low absorption. Combining these two technologies in a single system allows for the simultaneous acquisition of both imaging information, providing more comprehensive and accurate diagnostic results. In practical applications, photoacoustic imaging typically requires water as a conductive medium; however, OCT imaging is significantly affected by water absorption at wavelengths of 1310 nm and above, limiting imaging depth and quality. Furthermore, traditional endoscopic catheter designs often employ GRIN lenses or single spherical lenses for focusing. Using GRIN lenses requires a refractive prism to transform the optical path, increasing the rigidity of the probe's front section and complicating integrated probe assembly. Another approach is to fabricate a spherical shape at the fiber optic end to achieve fiber convergence, and then grind a total reflection surface or apply a metal coating to the end to achieve lateral focusing of the light. However, this method is typically applicable to air, while photoacoustic endoscopic imaging catheters usually require water as a medium. Due to the insufficient refractive index difference between fiber optics and water, the radius of curvature of the fiber optic spherical lens needs to be drastically reduced, leading to increased aberrations in the imaging system and difficulty in achieving a large working distance. Furthermore, in photoacoustic imaging, there is a minimum distance limitation between the ultrasonic transducer and the focusing spherical lens; therefore, a larger working distance is usually required to ensure better reception of ultrasonic signals by the ultrasonic transducer. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the existing technology, such as incomplete imaging information from single-modal endoscopes, significant influence of the conduction medium on the design of multimodal endoscope imaging catheters, and insufficient working distance, and to provide a photoacoustic-OCT dual-modal endoscope imaging system based on multi-element focusing, which has a large working distance, high resolution, and is less affected by water.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] This invention provides a photoacoustic-OCT dual-modal 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 endoscope 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 endoscope probe is equipped with an optical component and a photoacoustic signal receiver. The optical component focuses the combined laser beam of OCT and photoacoustic signals onto 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. Then, it is amplified by a signal amplifier and sent to the data acquisition card. The rotation and retraction module controls the endoscope probe to perform three-dimensional volume data scanning. The data acquisition module receives the OCT interference signal and the ultrasonic electrical signal from the photoacoustic signal receiver, and reconstructs the required endoscopic image through analysis, displaying a photoacoustic-OCT dual-modal image of the target tissue.

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

[0010] The signal control module sends a specified trigger signal to the SLD light source, which emits a broadband laser with a center wavelength of 850nm and a -3dB bandwidth of 100nm. After being split 50:50 by the fiber coupler, one laser beam exits from the first fiber collimator, passes through the first focusing lens, is converged to the reflector, and then returns to the fiber coupler along the same path. 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 (OCT) module. The other laser beam exiting from the fiber coupler reaches the endoscope probe and irradiates the target tissue. The scattered light then returns to the fiber coupler along the same path. The two returning beams interfere at the fiber coupler. The interference light is transmitted through the fiber to the second fiber collimator and exits. After being split by the grating, the emitted light is converged by the second focusing lens to the linear scanning camera. The scattered light from the OCT returns to the fiber along the same 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 pulsed light source, a first lens, and a second lens arranged sequentially. The pulsed light source is controlled by a trigger signal synchronized with the optical coherence tomography module, provided by a signal control module. The emitted laser is a high-frequency pulsed light with a wavelength of 532 nm.

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

[0013] Furthermore, the rotation and retraction module controls the endoscope probe to perform axial movement and multi-angle circular scanning, thereby performing multi-region laser scanning of the target tissue and obtaining three-dimensional image information of the imaging area. Specifically, a rotary motor drives the photoelectric slip ring to rotate via a belt, and then drives the entire endoscope probe to rotate via a torque spring, while another retraction motor drives the rotary platform to move axially.

[0014] Furthermore, the endoscope probe consists of optical components and a photoacoustic signal receiver. The outer diameter of the endoscope probe is controlled within 1 mm, meeting the current clinical needs for diseases involving small-diameter lumens.

[0015] Furthermore, the optical components and photoacoustic signal receiver are arranged side by side in a custom-made metal capillary. The optical components include: single-mode fiber, coreless fiber, graded-index fiber, and spherical lens; the front end of the metal capillary has a light-transmitting window, 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. The ultrasonic transducers use interconnected coaxial cables for ultrasonic electrical signal transmission. The ultrasonic transducers are placed at one end of the light-transmitting window. The core wire of the coaxial cable is bonded to the backing layer of the ultrasonic transducer with silver paste, and the shielding wire is bonded to the inside of the metal capillary with silver paste. The ultrasonic transducer receives the ultrasonic signal generated by the target tissue being excited by laser, converts the ultrasonic signal into an ultrasonic electrical signal, and transmits it to the data acquisition module through the coaxial cable 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 cable used to transmit photoacoustic electrical signals pass together through the torque spring. A thinner stepped end of the torque spring is inserted into the metal capillary tube, and the outer wall of the torque spring and the inner side of the metal capillary tube are bonded together with AB glue.

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

[0019] Furthermore, one end of the torque spring is connected to the rotation retraction module, which includes a photoelectric slip ring. The photoelectric slip ring comprises a central optical signal transmission section and an outer peripheral electrical signal transmission section. Laser light from the optical fiber is transmitted to the endoscope probe via the optical signal transmission section, and the ultrasonic electrical signal converted by the ultrasonic transducer is transmitted to the data acquisition module via the electrical signal transmission section. The photoelectric slip ring is driven by a rotary motor, causing the endoscope probe to rotate and perform a 360° scan. The rotor end of the photoelectric slip ring rotates, causing the torque spring to transmit torque to the front end of the endoscope probe. Axial movement is driven by a corresponding retraction motor, which can move the endoscope probe axially along the optical fiber direction. This enables three-dimensional scanning of the target tissue.

[0020] Furthermore, the optical component employs an integrated lens with multiple focusing elements, comprising, in sequence: a single-mode fiber, a coreless fiber, a graded-index fiber, and a spherical lens; the combination of the graded-index fiber and the spherical lens achieves light focusing, the spherical lens being located at the end of the fiber optic probe, and the spherical lens including a reflecting surface located outside the spherical lens; the single-mode fiber is connected to the coreless fiber, allowing the laser beam to first diverge before entering the graded-index fiber, utilizing the graded-index fiber to pre-shape the beam before it reaches the spherical lens, thereby controlling the divergence of the beam when it enters the spherical lens;

[0021] The light beam is transmitted through a single-mode fiber to a coreless fiber for initial divergence. Then, the divergence of the beam is controlled by a graded-index fiber when it enters the spherical lens. The beam spot becomes larger while the divergence angle of the beam decreases or converges. The light with a smaller divergence angle is reflected by the reflective surface of the spherical lens. The reflected light passes through the exit surface of the spherical lens and converges at the side of the integrated lens, thereby achieving focused light in a liquid environment with a high refractive index, and simultaneously achieving 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] It features a long working distance, high resolution, and less susceptibility to water. This invention integrates photoacoustic and OCT imaging methods through an integrated endoscopic probe, simplifying the detection process. Furthermore, it employs a multi-focusing element probe design to achieve better resolution with a minimal probe diameter and allows for a longer working distance without sacrificing resolution. The added graded-index fiber segment reduces focusing power loss when the spherical lens is immersed in a high-refractive-index medium, making it more advantageous for imaging in aquatic environments. Attached Figure Description

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

[0026] Figure 2 This is a schematic diagram of the overall optical path implementation;

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

[0028] Figure 4 This is a schematic diagram of a multi-element focusing integrated lens.

[0029] Figure reference numerals: 110-Signal control module; 120-Optical coherence tomography module; 130-Photoacoustic signal excitation module; 140-Beam common path module; 150-Endoscope probe; 160-Rotation and retraction module; 170-Data acquisition module; 121-SLD light source; 122-Fiber optic coupler; 123-First fiber optic collimator; 124-First focusing lens; 125-Reflecting mirror; 126-Second fiber optic collimator; 127-Graded grating; 128-Second focusing lens; 129-Linear scanning camera; 131-Pulse light source; 132-First lens; 133-Second lens; 151-Single-mode fiber; 152-Coreless fiber; 153-Graded refractive index fiber; 154-Spherical lens; 155-Ultrasonic transducer; 156-Coaxial cable; 157-Metal capillary; 158-Torque spring; 171-Signal amplifier; 172-Data acquisition card. Detailed Implementation

[0030] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. Component models, material names, connection structures, control methods, algorithms, and other features not explicitly described in this technical solution are considered 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 the other component or connected to the other component through an intermediary component. In the following embodiments, "connection" should be understood as "electrical connection," "communication connection," etc., if the connected components, circuits, modules, units, etc., have electrical signal or data transmission with each other.

[0032] Example 1

[0033] This embodiment provides a photoacoustic-OCT dual-modal 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 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 to perform corresponding functions; the signal control module 110 is provided with a frequency-adjustable trigger signal by a signal control card to synchronously 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.

[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 endoscope probe 150 is equipped with an optical component and a photoacoustic signal receiver. The optical component focuses the combined laser beam of OCT and photoacoustic signals onto 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 endoscope probe 150 to perform three-dimensional volume data scanning. The data acquisition module 170 receives the OCT interference signal and the ultrasonic electrical signal from the photoacoustic signal receiver, and reconstructs the desired endoscopic image through analysis, displaying a photoacoustic-OCT dual-modal image of the target tissue.

[0036] In specific implementation methods, such as Figure 2 As shown, the optical coherence tomography module 120 includes an SLD light source 121, an optical fiber coupler 122, a first optical fiber collimator 123, a first focusing lens 124, a mirror 125, a second optical fiber collimator 126, a grating 127, a second focusing lens 128, and a linear scanning camera 129 arranged sequentially.

[0037] The signal control module 110 sends a specified trigger signal to the SLD light source 121. The SLD light source 121 emits a broadband laser with a center wavelength of 850nm and a -3dB bandwidth of 100nm. After being split 50:50 by the fiber coupler 122, one laser beam exits from the first fiber collimator 123, passes through the first focusing lens 124, converges to the reflector 125, and then returns to the fiber coupler 122 along the same 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. The reference arm optical path of 0; another laser emitted from the fiber coupler 122 reaches the endoscope probe 150 and irradiates the target tissue, and the scattered light returns to the fiber coupler 122 through the original path; the two return lights 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 then converged by the second focusing lens 128 into the linear scanning camera 129; the scattered light of OCT returns to the optical fiber through the original path, and the interference information is received by the linear scanning camera 129 and transmitted to the data acquisition card 172.

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

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

[0040] In a specific implementation, the rotation and retraction module 160 controls the endoscope probe 150 to perform axial movement and multi-angle circular scanning, thereby performing multi-region laser scanning of the target tissue and obtaining three-dimensional image information of the imaging area. Specifically, a rotary motor drives the photoelectric slip ring to rotate via a belt, and then drives the entire endoscope probe 150 to rotate via a torque spring 158, while another retraction motor drives the rotating platform to move axially.

[0041] In a specific embodiment, the endoscope probe 150 consists of optical components and a photoacoustic signal receiver. The outer diameter of the endoscope probe 150 is controlled within 1 mm, meeting the current clinical needs for diseases involving small-diameter lumens.

[0042] In specific implementation methods, such as Figure 3As shown, the optical components and photoacoustic signal receiver are arranged side by side in a custom-made metal capillary 157. The optical components include: a single-mode fiber 151, a coreless fiber 152, a graded refractive index fiber 153, and a spherical lens 154. A light-transmitting window is opened 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. The ultrasonic transducer 155 uses interconnected coaxial cables 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 cable 156 is bonded to the backing layer of the ultrasonic transducer 155 with silver paste, and the shielding wire is bonded to the inside of the metal capillary tube 157 with silver paste. The ultrasonic transducer 155 receives the ultrasonic signal generated by the target tissue being excited by the laser, converts the ultrasonic signal into an ultrasonic electrical signal, and transmits it to the signal amplifier 171 through the coaxial cable 156. After amplification, the signal is transmitted to the data acquisition card 172 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 cable 156 used to transmit photoacoustic electrical signals pass together through the torque spring 158. A thinner stepped end of the torque spring 158 is inserted into the metal capillary tube 157. The outer wall of the torque spring 158 and the inner side of the metal capillary tube 157 are bonded together with AB glue.

[0045] To ensure that the ultrasonic transducer 155 can receive the ultrasonic signal of the target tissue perpendicularly 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 as possible to the ultrasonic transducer 155, while ensuring that the two are parallel and coaxial.

[0046] In a specific embodiment, one end of the torque spring 158 is connected to the rotation retraction module 160. The rotation retraction module 160 is equipped with a photoelectric slip ring, which includes a central optical signal transmission part and an outer peripheral electrical signal transmission part. 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 rotary motor, which drives the endoscope probe 150 to rotate and perform a 360° scan. 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 a corresponding retraction motor, which can drive the endoscope probe 150 to move axially along the optical fiber direction. This enables three-dimensional scanning of the target tissue.

[0047] Example 2

[0048] This embodiment provides a photoacoustic-OCT dual-modal endoscopic imaging system based on multi-element focusing, such as... Figure 1 As shown, the system 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 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 to perform corresponding functions. Preferably, the signal control module 110 is provided with a frequency-adjustable trigger signal by a signal control card to synchronously 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.

[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 endoscope probe 150 is equipped with an optical component and a photoacoustic signal receiver. The optical component focuses the combined laser beam of OCT and photoacoustic signals onto 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 endoscope probe 150 to perform three-dimensional volume data scanning. The data acquisition module 170 receives the OCT interference signal and the ultrasonic electrical signal from the photoacoustic signal receiver, and reconstructs the desired endoscopic image through analysis, displaying a photoacoustic-OCT dual-modal image of the target tissue.

[0051] In specific implementation methods, such as Figure 2 As shown, the optical coherence tomography module 120 includes an SLD light source 121, an optical fiber coupler 122, a first optical fiber collimator 123, a first focusing lens 124, a mirror 125, a second optical fiber collimator 126, a grating 127, a second focusing lens 128, and a linear scanning camera 129 arranged sequentially.

[0052] The signal control module 110 sends a specified trigger signal to the SLD light source 121. The SLD light source 121 emits a broadband laser with a center wavelength of 850nm and a -3dB bandwidth of 100nm. After being split 50:50 by the fiber coupler 122, one laser beam exits from the first fiber collimator 123, passes through the first focusing lens 124, converges to the reflector 125, and then returns to the fiber coupler 122 along the same 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. The reference arm optical path of 0; another laser emitted from the fiber coupler 122 reaches the endoscope probe 150 and irradiates the target tissue, and the scattered light returns to the fiber coupler 122 through the original path; the two return lights 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 then converged by the second focusing lens 128 into the linear scanning camera 129; the scattered light of OCT returns to the optical fiber through the original path, and the interference information is received by the linear scanning camera 129 and transmitted to the data acquisition card 172.

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

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

[0055] In a specific implementation, the rotation and retraction module 160 controls the endoscope probe 150 to perform axial movement and multi-angle circular scanning, thereby performing multi-region laser scanning of the target tissue and obtaining three-dimensional image information of the imaging area. Specifically, a rotary motor drives the photoelectric slip ring to rotate via a belt, and then drives the entire endoscope probe 150 to rotate via a torque spring 158, while another retraction motor drives the rotating platform to move axially.

[0056] In a specific embodiment, the endoscope probe 150 consists of optical components and a photoacoustic signal receiver. The outer diameter of the endoscope probe 150 is controlled within 1 mm, meeting the current clinical needs for diseases involving small-diameter lumens.

[0057] like Figure 4As shown, the optical component employs an integrated lens with multiple focusing elements, comprising, in sequence: a single-mode fiber 151, a coreless fiber 152, a graded-index fiber 153, and a spherical lens 154; the combination of the graded-index fiber 153 and the spherical lens 154 achieves light focusing. The spherical lens 154 is located at the end of the fiber optic probe and includes a reflecting surface located outside the spherical lens 154; the single-mode fiber 151 is connected to the coreless fiber 152, allowing the laser beam to diverge before entering the graded-index fiber 153. The graded-index fiber 153 pre-shapes the beam before it reaches the spherical lens 154, thereby controlling the divergence of the beam when it enters the spherical lens 154.

[0058] The light beam is transmitted through a single-mode fiber 151 to a coreless fiber 152 for initial divergence. Then, the divergence of the beam is controlled by a graded-index fiber 153 when it enters the spherical lens. The beam spot becomes larger while the divergence angle of the beam becomes smaller or converges. The light with a smaller divergence angle is reflected by the reflective surface of the spherical lens 154. The reflected light passes through the exit surface of the spherical lens 154 and converges at the side of the integrated lens, thereby achieving focused light in a liquid environment with a high refractive index, and simultaneously achieving a large working distance and high resolution.

[0059] In a specific embodiment, the reflective surface of the spherical lens 154 is obtained by grinding the spherical 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 provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any 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 invention should be within the protection scope of the present invention.

Claims

1. A multi-element focusing based photoacoustic-OCT dual modality endoscopic imaging system, characterized in that, The application relates to an optical coherence tomography and photoacoustic endoscope system. The signal control module (110) is used for controlling the optical coherence tomography module (120), the photoacoustic signal excitation module (130), the rotating retracting 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 endoscope probe (150) is provided with an optical assembly and a photoacoustic signal receiver, the optical assembly focuses combined laser beams of OCT and photoacoustic and irradiates the target tissue; the ultrasonic wave signal generated after the target tissue is irradiated by the pulsed laser is received by the photoacoustic signal receiver and is converted into an ultrasonic electric signal, and then the ultrasonic electric signal is sent to the data acquisition module (170); the rotating retracting module (160) controls the endoscope probe (150) to perform three-dimensional body data scanning, the data acquisition module (170) receives the OCT interference signal and the ultrasonic electric signal of the photoacoustic signal receiver, and analyzes and reconstructs into required endoscopic images, and displays the photoacoustic-OCT bimodal image of the target tissue; The optical assembly adopts an integrated lens of a plurality of focusing elements, and comprises, in sequence, a single-mode optical fiber (151), a coreless optical fiber (152), a graded-index optical fiber (153) and a ball lens (154); the combination of the graded-index optical fiber (153) and the ball lens (154) realizes light focusing, the ball lens (154) is located at the tail end of the optical fiber probe, the ball lens (154) comprises a reflecting surface, and the reflecting surface is located outside the ball lens (154); the single-mode optical fiber (151) is connected with the coreless optical fiber (152), so that laser is first diverged and then enters the graded-index optical fiber (153), the graded-index optical fiber (153) is used for pre-shaping before the light beam reaches the ball lens (154), so that the divergence of the light beam entering the ball lens (154) is controlled; Light is transmitted to the coreless optical fiber (152) through the single-mode optical fiber (151) to be initially diverged, and then the divergence of the light beam entering the ball lens is controlled through the graded-index optical fiber (153), the light spot is enlarged, the divergence angle of the light beam is reduced or converges, the light rays with a smaller divergence angle are reflected by the reflecting surface of the ball lens (154), the reflected light rays are converged at the side end of the integrated lens through the exit surface of the ball lens (154), so that the optical fiber is focused in a liquid environment with a large refractive index, and a large working distance and high resolution can be realized.

2. The multi-element focusing based photoacoustic-OCT dual modality endoscopic imaging system of claim 1, wherein, 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 mirror (125), a second fiber collimator (126), a grating (127), a second focusing lens (128), and a linear scanning camera (129) arranged in sequence. The signal control module (110) gives a specified trigger signal to the SLD light source (121), and the SLD light source (121) emits broadband laser. After the light is split by the fiber coupler (122), one way of the laser is emitted from the first fiber collimator (123) and then converges to the mirror (125) through the first focusing lens (124), and returns to the fiber coupler (122) via the original path, wherein the first fiber collimator (123), the first focusing lens (124), and the mirror (125) are coaxially arranged as the reference arm optical path of the optical coherence tomography module (120). Another way of the laser emitted from the fiber coupler (122) reaches the endoscope probe (150) and is irradiated on the target tissue, and the scattered light returns to the fiber coupler (122) via the original path. The two returned lights interfere at the fiber coupler (122), and the interference light is transmitted to the second fiber collimator (126) through the fiber, and then the emitted light converges to the linear scanning camera (129) through the grating (127) and the second focusing lens (128). The scattered light of the OCT returns to the fiber via the original path, 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 multi-element focusing based photoacoustic-OCT dual modality endoscopic imaging system of claim 1, wherein, The photoacoustic signal excitation module (130) comprises a pulsed light source (131), a first lens (132), and a second lens (133) arranged in sequence, and the pulsed light source (131) is controlled to emit light by the signal control module (110) according to the trigger signal synchronized with the optical coherence tomography module (120).

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

5. The multi-element focusing based photoacoustic-OCT dual modality endoscopic imaging system of claim 1, wherein, The rotary retracting module (160) controls the endoscope probe (150) to move axially and to perform multi-angle ring scanning, so as to perform laser scanning on the target tissue in multiple regions and to obtain three-dimensional image information of the imaging region.

6. The multi-element focusing based photoacoustic-OCT dual modality endoscopic imaging system of claim 1, wherein, The optical assembly and the photoacoustic signal receiver are placed side by side in the metal capillary (157), and the optical assembly comprises a single-mode optical fiber (151), a coreless optical fiber (152), a graded-index optical fiber (153), and a ball lens (154). A light transmission window is formed at the front end of the metal capillary (157), and the rear end of the metal capillary (157) is connected with a torque spring (158). The photoacoustic signal receiver is a block-shaped ultrasonic transducer (155) which uses coaxial wires (156) connected to each other to transmit ultrasonic electrical signals; the ultrasonic transducer (155) is placed at one end of the light transmission window, the core wire of the coaxial wire (156) is adhered to the backing layer of the ultrasonic transducer (155) by silver glue, and the shielding wire is adhered to the inside of the metal capillary (157) by silver glue; the ultrasonic transducer (155) receives the ultrasonic signals generated by the target tissue after being excited by laser, and converts the ultrasonic signals into ultrasonic electrical signals, which are transmitted to the data acquisition module (170) through the coaxial wire (156) for corresponding data processing, analysis and display; The single-mode optical fiber (151) for transmitting OCT sample light and photoacoustic excitation light and the coaxial wire (156) for transmitting photoacoustic electrical signals pass through the torque spring (158) together, the stepped end of the torque spring (158) is inserted into the metal capillary (157), and the outer wall of the torque spring (158) and the inside of the metal capillary (157) are adhered by AB glue.

7. The multi-element focusing based photoacoustic-OCT dual modality endoscopic imaging system of claim 6, wherein, One end of the torque spring (158) is connected to the rotary retraction module (160), and the rotary retraction module (160) is provided with an optical and electrical slip ring, which includes a central optical signal transmission part and a peripheral electrical signal transmission part; the laser in the optical fiber is transmitted to the endoscope probe (150) through the optical signal transmission part, the converted ultrasonic electrical signals in the ultrasonic transducer (155) are transmitted to the signal amplifier (171) through the electrical signal transmission part, and the photoacoustic signals are transmitted to the data acquisition card (172) after amplification; the optical and electrical slip ring is driven by a rotary motor to rotate the endoscope probe (150) for 360° scanning; the rotor end of the optical and electrical slip ring rotates to drive the torque spring (158) to transmit torque to the front end of the endoscope probe (150).

8. The multi-element focusing based photoacoustic-OCT dual modality endoscopic imaging system of claim 1, wherein, The reflecting surface of the ball lens (154) is obtained by grinding the ball lens, and the reflecting surface can be coated with a reflective film. The reflecting surface of the ball lens (154) is obtained by grinding the ball lens, and the reflecting surface can be coated with a reflective film.

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