An all-fiber ultrasonic endoscope, imaging system

Abstract

This invention discloses an all-fiber ultrasonic endoscope and imaging system, belonging to the field of ultrasonic endoscopic imaging. It includes a guide fiber, a dielectric mirror, a sensing film, a heat-insulating film, an excitation film, a focusing acoustic reflector, and a lateral guide tube. Excitation laser light passes through the dielectric mirror, sensing film, and heat-insulating film, is absorbed by the excitation film, and generates ultrasonic waves, which are then transmitted laterally out of the endoscope through the lateral opening of the lateral guide tube. The Fabre-Perot cavity formed by the dielectric mirror causes multi-beam interference of the signal light, modulating the ultrasonic wave signal laterally transmitted into the endoscope onto the intensity of the interference light. This invention forms an integral structure by sequentially covering the end face of the guide fiber with the dielectric mirror, sensing film, heat-insulating film, and excitation film, and then fixing the guide fiber, focusing acoustic reflector, and lateral guide tube together. This reflects the ultrasonic waves propagating along the guide fiber to the side, allowing the fiber optic ultrasonic endoscope to simultaneously achieve lateral excitation and lateral detection of ultrasonic waves using a single optical fiber.

Description

Technical Field

[0001] This invention belongs to the field of ultrasound endoscopic imaging, and more specifically, relates to an all-fiber ultrasound endoscope and imaging system. Background Technology

[0002] Ultrasonic imaging technology utilizes the advantages of short wavelength and strong penetrating power of ultrasound waves, and has wide applications in medical imaging, especially in endoscopic imaging. Ultrasonic imaging technology generates ultrasonic pulses through an ultrasonic transducer with ultrasonic excitation function. These pulses reach the surface of the object under test and are reflected by the object. Ultrasonic sensors with ultrasonic detection function detect the ultrasonic signals, achieving imaging of the surface or interior of the object under test, and further enabling analysis of the surface and internal structure of the object.

[0003] Fiber optic ultrasound endoscopes, using optical fibers as a carrier, have attracted widespread attention in recent years due to their advantages of small size, high flexibility, and resistance to electromagnetic interference. A typical fiber optic ultrasound endoscope consists of an ultrasound excitation section and an ultrasound sensing section. The ultrasound excitation section is mainly based on the photoacoustic effect, where photoacoustic materials convert the energy of an excitation laser into emitted ultrasonic waves. Commonly used photoacoustic materials are a mixture of a high optical absorption material, such as carbon black, graphene, or carbon nanotubes, and a high thermal expansion coefficient elastic material, such as polydimethylsiloxane (PDMS). The ultrasound sensing section detects ultrasonic signals by measuring changes in the physical parameters of the sensor caused by the ultrasound. Currently, ultrasound sensing sections mainly include fiber optic grating type and microring resonator type. The ultrasound excitation and sensing sections of this type of fiber optic ultrasound endoscope are difficult to integrate, thus limiting the system size and restricting its application in specific scenarios, such as endoscopic imaging of blood vessels. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the purpose of this invention is to provide an all-fiber ultrasound endoscope and imaging system, which aims to solve the technical problem that existing fiber ultrasound endoscopes cannot simultaneously realize lateral ultrasound excitation and ultrasound sensing on a single fiber.

[0005] To achieve the above objectives, according to one aspect of the present invention, an all-fiber ultrasound endoscope is provided, comprising: a guide fiber, a dielectric mirror, a sensing film, a heat-insulating film, an excitation film, a focusing acoustic reflector, and a lateral guide tube; the output end face of the guide fiber is a flat end face, and the sensing film is wrapped by the dielectric mirror and covered on the flat end face; the guide fiber and the focusing acoustic reflector are fixed inside the lateral guide tube having a lateral opening;

[0006] The guiding optical fiber is used to guide the transmission of the excitation laser incident from its input end. The excitation laser passes through the dielectric mirror, the sensing film, and the heat insulation film in sequence and irradiates the excitation film. The excitation film absorbs the light energy of the excitation laser and converts it into heat energy. The heat energy causes the temperature of the excitation film to rise and undergo thermoelastic expansion, thereby generating an ultrasonic signal. The ultrasonic signal is reflected by the focusing acoustic reflector and transmitted out of the endoscope through the lateral opening of the lateral guiding tube. The heat insulation film blocks the heat energy from being conducted from the excitation film to the sensing film.

[0007] The guiding fiber is also used to guide the transmission of signal light incident from its input end. The signal light is reflected between the dielectric mirrors that encapsulate the sensing film and undergoes multi-beam interference, and then propagates in the reverse direction in the guiding fiber.

[0008] When the all-fiber ultrasound endoscope detects the ultrasound to be tested, the signal light is transmitted along the guide fiber and reflected by the medium mirror. The ultrasound is transmitted into the endoscope through the lateral opening of the lateral guide tube and reflected by the focusing acoustic reflector. The medium mirror is excited by the ultrasound to be tested, which compresses the sensing film and changes its thickness. The change frequency is equal to the frequency of the incident ultrasound, thereby changing the cavity length of the Fabry-Perot resonator formed by the medium mirror. This, in turn, changes the optical power of the reflected light that is transmitted in the reverse direction in the guide fiber and causes multi-beam interference. By detecting the optical power of the reflected light, the ultrasound signal can be detected.

[0009] Preferably, the dielectric mirror is a dielectric thin film formed by alternating deposition of two different inorganic materials with a refractive index of 1.5-2.9, which has a reflectivity of more than 95% for signal light wavelengths and a transmittance of more than 80% for excitation laser wavelengths, and the film thickness is 1μm-100μm.

[0010] Preferably, the sensing film is a polymer material with a Young's modulus of 100 MPa to 100 GPa, has a transmittance of over 90% for both the signal light wavelength and the excitation laser wavelength, and has a coefficient of thermal expansion of less than 10. -4 / °C, film thickness is 1μm-1mm;

[0011] Preferably, the heat insulation film is a heat insulation material with a thermal conductivity of less than 0.1 W / (m·K), has a transmittance of more than 95% for the excitation laser wavelength, and has a film thickness of 1μm-10μm;

[0012] Preferably, the excitation film is a light-absorbing material with high optical absorption in the excitation laser band, a particle size of 10 nm-1 μm, and a thermal expansion coefficient greater than 10. -4 The polymer mixture is composed of 1μm-500μm at a temperature of ℃.

[0013] Preferably, the guiding optical fiber is a double-clad optical fiber, comprising a core, an inner cladding, and an outer cladding arranged from the inside out;

[0014] The fiber core uses single-mode transmission at the signal light wavelength for transmitting the signal light.

[0015] The inner cladding layer uses multimode transmission at the excitation laser wavelength for the transmission of the excitation laser.

[0016] The outer cladding layer is used to confine the excitation laser and the signal light;

[0017] Preferably, the signal light is a narrow-linewidth laser, and the excitation laser is a pulsed light or a modulated continuous light;

[0018] Preferably, the dielectric mirror has good adsorption properties with the guiding optical fiber, the sensing film, the heat insulation film, and the excitation film;

[0019] Preferably, the focusing acoustic reflector is a cylindrical concave spherical reflector with a diameter of 0.2mm-3mm and a focal length of 2-10mm, and the material is an acoustic reflective material with an acoustic impedance of 18 MPa·s / m or higher.

[0020] Preferably, the lateral guide tube is a cylindrical metal tube with a diameter of 0.3mm-5mm, and the metal tube has a lateral opening with a length of 2mm-10mm and a width of 1mm-5mm. The focusing acoustic reflector is fixed inside the lateral guide tube opposite to the guiding optical fiber, with a distance of 2mm-10mm between them, and the focal length is consistent with that of the focusing acoustic reflector.

[0021] According to another aspect of the present invention, a fiber optic ultrasound endoscope imaging system is provided, comprising an all-fiber ultrasound endoscope as described above, and further comprising: an excitation laser, a narrow linewidth laser, an optical circulator, a feedback control device, a photodetector, a data acquisition device, a double-clad coupler, and an electric displacement stage controller.

[0022] The output of the excitation laser is connected to the multimode input of the double-clad coupler;

[0023] The first port of the optical circulator is connected to the output of the narrow linewidth laser, the second port is connected to the single-mode input of the double-clad coupler, and the third port is connected to the input of the photodetector.

[0024] The DC output terminal of the photodetector is connected to the input terminal of the feedback control device, and the AC output terminal is connected to the input terminal of the data acquisition device.

[0025] The output of the feedback control device is connected to the control terminal of the narrow linewidth laser.

[0026] The output end of the double-clad coupler is connected to the all-fiber ultrasound endoscope, which is fixed on the electric displacement stage and the electric displacement stage is moved by the electric displacement stage controller.

[0027] The excitation laser is used to generate an excitation laser, which is input to the multimode input of the optical circulator; the narrow-linewidth laser is used to generate a narrow-linewidth laser as a signal light; the optical circulator is used to input the signal light to the single-mode input of the double-clad coupler; the double-clad coupler is used to couple the excitation laser input from the multimode input with the signal light input from the single-mode input and input it to the all-fiber ultrasound endoscope, and also to reverse the reflected light transmitted from the all-fiber ultrasound endoscope and input it back to the single-mode input; the optical circulator is also used to reverse the transmission of the single-mode input from the double-clad coupler. The reflected light is input to the photodetector; the photodetector converts the intensity of the reflected light into a voltage signal, and inputs the DC component of the voltage signal to the feedback control device and the AC component to the data acquisition system; the feedback control device is used to measure the reflection spectrum of the all-fiber ultrasonic endoscope and control the output wavelength of the narrow-linewidth laser to be located at the point of maximum reflection spectrum slope; the data acquisition system is used to acquire, quantize, and store the voltage signal as the imaging data for that scanning point; the motorized stage controller is used to control the motorized stage to move to the next scanning point after the imaging data is stored.

[0028] Before the imaging system begins imaging scanning, the operating point of the all-fiber ultrasonic endoscope needs to be determined. The feedback control device controls the narrow-linewidth laser to output a narrow-linewidth laser wavelength for scanning, and plots the reflection spectrum of the all-fiber ultrasonic endoscope using the DC component of the voltage signal output from the DC output terminal of the photodetector. The feedback control device controls the output wavelength of the narrow-linewidth laser to the point of maximum reflection spectrum slope, and monitors the changes in the reflection spectrum of the all-fiber ultrasonic endoscope in real time through the DC component of the voltage signal output from the DC output terminal of the photodetector during imaging scanning, and provides real-time feedback control to stabilize the output wavelength of the narrow-linewidth laser 2 at the point of maximum reflection spectrum slope.

[0029] Preferably, the multimode input end of the double-clad coupler is a multimode fiber, the single-mode input end is a single-mode fiber, and the output end is a double-clad fiber; the double-clad fiber at the output end of the double-clad coupler has the same parameters as the double-clad fiber of the all-fiber ultrasonic endoscope guiding fiber.

[0030] Preferably, the sampling rate of the photodetector is greater than 100MHz;

[0031] Preferably, the step size accuracy of the electric displacement stage controller is less than 10 μm;

[0032] Preferably, the feedback control device includes a data acquisition card and a narrow linewidth laser controller; the data acquisition card is used to acquire, quantize, and store the DC voltage signal output by the photodetector; the narrow linewidth laser controller is used to control the wavelength of the signal light output by the narrow linewidth laser.

[0033] In summary, compared with the prior art, the above-described technical solutions conceived by this invention can achieve the following beneficial effects:

[0034] 1. This invention forms an integral structure by sequentially covering the end face of the guiding optical fiber with a dielectric mirror, a sensing film, a heat insulation film, and an excitation film, and then fixing the guiding optical fiber with a focusing acoustic reflector and a lateral guiding tube to reflect the ultrasonic waves propagating along the direction of the guiding optical fiber to the side, so that the all-fiber ultrasonic endoscope can simultaneously realize the lateral excitation and lateral detection of ultrasonic waves with a single optical fiber.

[0035] 2. This invention introduces a wavelength-selective transmissive medium mirror into an all-fiber ultrasonic endoscope, allowing the excitation laser to be transmitted through the medium mirror to the excitation film and absorbed by it to generate ultrasonic waves. The signal light is reflected between the two medium mirrors and undergoes multi-beam interference, modulating the detected ultrasonic signal onto the intensity of the reflected light. Ultrasonic excitation and ultrasonic detection are achieved simultaneously using a single optical fiber in the all-fiber ultrasonic endoscope.

[0036] 3. This invention introduces a heat-insulating film into the all-fiber ultrasonic endoscope, so that the heat generated by the excitation film during ultrasonic excitation cannot be conducted to the sensing film and cause thermal expansion of the sensing film, thus preventing crosstalk between the ultrasonic excitation process and the ultrasonic detection process.

[0037] 4. This invention uses double-clad fiber as the guiding fiber. The signal light is transmitted in single mode within the fiber core, avoiding intermodal interference of the signal light and reducing noise in ultrasonic detection. The excitation light is transmitted in the inner cladding. Taking advantage of the large effective area of ​​the inner cladding, high-energy excitation laser transmission is achieved below the fiber damage threshold, which improves the ultrasonic intensity generated by the all-fiber ultrasonic endoscope.

[0038] 5. This invention constructs a Fabry-Perot resonant cavity by wrapping a sensing film with two dielectric mirrors, modulating the ultrasonic signal detected by the endoscope onto the intensity signal of the reflected light, significantly improving the system's sensitivity and enabling low-noise equivalent pressure ultrasonic endoscopic detection. Simultaneously, the use of a Fabry-Perot interferometric sensor makes the imaging system insensitive to interference such as vibrations in the external environment, further improving the system's stability.

[0039] 6. This invention introduces a feedback control system for narrow-linewidth lasers. By real-time monitoring of the DC component of the reflected light intensity and real-time feedback control of the output wavelength of the narrow-linewidth laser, the problem of decreased sensing sensitivity caused by spectral drift due to temperature changes in the external environment is avoided in all-fiber ultrasonic endoscope sensing films, thus effectively improving the sensitivity and stability of the system. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of the structure of the all-fiber ultrasonic endoscope in this invention;

[0041] Figure 2 This is a schematic diagram of the all-fiber ultrasound endoscopic imaging system of the present invention;

[0042] In all the accompanying drawings, the same reference numerals are used to denote the same elements or structures, including: 1, excitation laser; 2, narrow linewidth laser; 3, optical circulator; 4, feedback control device; 5, photodetector; 6, data acquisition device; 7, double-clad coupler; 8, motorized stage controller; 9, all-fiber ultrasonic endoscope; 91, guide fiber; 92, excitation laser; 93, signal light; 94, dielectric mirror; 95, sensing film; 96, thermal insulation film; 97, excitation film; 98, focusing acoustic reflector; 99, lateral guide tube. Detailed Implementation

[0043] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0044] Figure 1 This is a schematic diagram of the all-fiber ultrasound endoscope in this invention. Figure 1As shown, this invention proposes an all-fiber ultrasonic endoscope, comprising a guide fiber 91, a dielectric mirror 94, a sensing film 95, a heat-insulating film 96, an excitation film 97, a focusing acoustic reflector 98, and a lateral guide tube 99. The guide fiber 91 is a double-clad fiber, with its inner cladding used to transmit excitation laser 92 and its core used to transmit signal light 93. The proximal end face of the guide fiber 91 is polished or cut flat, and a layer of cured ultraviolet adhesive wrapped in a wavelength-selective dielectric film is deposited on the proximal end face of the guide fiber 91, serving as the dielectric mirror 94 and the sensing film 95. When excited by the ultrasonic wave to be measured, the dielectric mirror 94 presses the sensing film 95, causing a change in its thickness. The frequency of this change is equal to the frequency of the incident ultrasonic wave, thereby altering the cavity length of the Fabry-Perot resonator formed by the dielectric mirror 94. This changes the optical path of the signal light 93, modulating the detected ultrasonic signal onto the phase of the signal light 93, and subsequently altering the optical power of the reflected light that undergoes multi-beam interference and propagates backward in the guiding fiber 91. A layer of Parylene C film is deposited on the outer surface of the dielectric mirror 94 as the heat insulation film 96. This prevents the heat from the excitation film 97 during ultrasonic excitation from being conducted to the sensing film 95, thus preventing thermal expansion of the sensing film and preventing crosstalk between the ultrasonic excitation process and the ultrasonic detection process. A layer of cured carbon black and polydimethylsiloxane (PDMS) mixture is deposited on the surface of the heat insulation film 96 as the excitation film 97. This layer absorbs the excitation laser and generates an ultrasonic signal through a photoacoustic effect. A 45° cylindrical concave reflector is fixed at the front end of the guiding optical fiber 91, serving as the focusing acoustic reflector 98. This reflector reflects the ultrasonic signal generated by the excitation film 97 to the lateral propagation direction of the guiding optical fiber 91, and reflects the laterally propagating ultrasonic signal to be measured to the direction directly opposite the guiding optical fiber 91. An aluminum tube with a lateral opening serves as the lateral guide tube 99, used to fix the guiding optical fiber 91 and the focusing acoustic reflector 98, ensuring a 1 mm gap between the excitation film 97 deposited on the proximal end face of the guiding optical fiber 91 and the focusing acoustic reflector 98. The lateral opening direction of the lateral guide tube 99 is aligned with the reflection direction of the focusing acoustic reflector 98, allowing the ultrasonic signal to be input and output to the all-fiber ultrasonic endoscope 9 in a fixed direction.

[0045] Specifically, the core diameter of the guiding fiber 91 is less than 10 micrometers, and the transmission mode is single-mode transmission, with the signal light 93 propagating within the core. The inner cladding diameter of the guiding fiber 91 is greater than 10 micrometers, and the transmission mode is multimode transmission, with the excitation laser 92 propagating within the inner cladding. Further explanation is provided: the outer cladding of the guiding fiber 91 is used to confine the excitation laser 92 and the signal light 93.

[0046] Specifically, the core diameter of the guiding fiber 91 is 9 micrometers, the inner cladding diameter is 105 micrometers, and the outer cladding diameter is 125 micrometers. The input excitation laser 92 is pulsed light or modulated continuous light, and the signal light 93 is a narrow linewidth laser.

[0047] Specifically, the dielectric mirror 94 is a dielectric thin film formed by alternating deposition of two different inorganic materials with refractive indices of 1.5-2.9. It has a transmittance of more than 80% for the wavelength of the excitation laser 92 and a reflectance of more than 95% for the wavelength of the signal light 93. The film thickness is 1μm-100μm, and it has good adsorption properties with the guiding optical fiber 91 and the sensing thin film 95.

[0048] Specifically, the sensing film 95 is made of a polymer material with a Young's modulus of 100 MPa-100 GPa, has a transmittance of over 90% for the wavelengths of the excitation laser 92 and the signal light 93, and has a coefficient of thermal expansion of less than 10. -4 The film has a temperature of 0°C, a thickness of 1 μm-1 mm, and good adsorption properties with the medium mirror 94.

[0049] Specifically, the heat insulation film 96 is a heat insulation material with a thermal conductivity of less than 0.1 W / (m·K), has a transmittance of more than 95% for the excitation laser wavelength, a film thickness of 1μm-10μm, and good adsorption with the dielectric mirror 94.

[0050] Specifically, the excitation film 97 is a light-absorbing material with an optical absorption rate of over 80% at the wavelength of the excitation laser 92, a particle size of 10nm-1μm, and a thermal expansion coefficient greater than 10. -4 The polymer mixture is composed of a temperature range of ℃, the film thickness is 1μm-500μm, and it has good adsorption properties with the heat insulation film 96.

[0051] Specifically, the focusing acoustic reflector 98 is a cylindrical concave spherical reflector with a diameter of 0.2mm-3mm and a focal length of 2-10mm, and the material is an acoustic reflective material with an acoustic impedance of 18 MPa·s / m or higher.

[0052] Specifically, the lateral guide tube 99 is a cylindrical metal tube with a diameter of 0.3mm-5mm. The metal tube has a lateral opening with a length of 2mm-10mm and a width of 1mm-5mm. The focusing acoustic reflector 98 is fixed inside the lateral guide tube 99, directly opposite the guiding optical fiber 91. The two are 2mm-10mm apart and have the same focal length as the focusing acoustic reflector 98.

[0053] Furthermore, this invention also proposes a method for fabricating the above-mentioned all-fiber ultrasonic endoscope, the specific steps of which include:

[0054] S1, cut or grind one end of the guide fiber 91 flat, and use a vacuum evaporation coating method to alternately deposit multiple layers of silicon dioxide and titanium dioxide onto the flat end face of the guide fiber 91 as the inner surface of the dielectric mirror 94.

[0055] S2, immerse one end of the guide fiber 91 with the inner surface of the dielectric mirror 94 into the liquid UV adhesive, let it stand for 1 minute, and slowly pull out the guide fiber 91 at a speed of 10μm / s. Use a UV curing lamp to irradiate the end face of the fiber until the UV adhesive adsorbed on the end face of the fiber is completely cured to form a sensing film 95.

[0056] It should be noted that the end face of the optical fiber is irradiated with a UV curing lamp for two hours. After the coating is completed, the optical fiber is suspended vertically for one week to allow the UV adhesive to achieve maximum heat resistance.

[0057] S3, a dielectric film identical to the inner surface of the dielectric mirror 94 is deposited onto the surface of the sensing film 95 using a vacuum evaporation deposition method, serving as the outer surface of the dielectric mirror 94.

[0058] S4, a layer of Pyrelin C is deposited on the outer surface of the dielectric mirror 94 using a vapor deposition method as a heat insulation film 96.

[0059] S5. Mix carbon black and PDMS at a mass ratio of 1:5, stir evenly, and place in a vacuum drying oven for two hours to remove air bubbles from the mixture.

[0060] S6, immerse one end of the guide fiber 91 with the heat insulation film 96 into a mixture of carbon black and PDMS, let it stand for 1 minute, and slowly pull out the guide fiber 91 at a speed of 10 μm / s. Use a heating lamp to irradiate the end face of the fiber until the mixture adsorbed on the end face of the fiber is completely cured to form an excitation film 97.

[0061] It should be noted that the fiber end face is irradiated with a heating lamp for two hours. After the dip-coating is completed, the fiber is suspended vertically for one week to allow the mixture of carbon black and PDMS to fully cure.

[0062] S7, the guiding fiber 91 and the cylindrical concave spherical reflector 98, which serves as the focusing acoustic reflector, are fixed inside the lateral opening aluminum tube 99, which serves as the lateral guiding tube. The excitation film 97 deposited on the guiding fiber 91 is 2 mm away from the 45° reflecting surface of the focusing acoustic reflector 98. The lateral opening of the lateral guiding tube 99 is consistent with the reflection direction of the focusing acoustic reflector 98.

[0063] To further explain, the dielectric mirror 94 is a dielectric film formed by alternating deposition of multiple layers of silicon dioxide and titanium dioxide. It is a periodically refractive index modulated structure, capable of producing high reflectivity for light of a specific wavelength and high transmittance for light of another specific wavelength. By designing the parameters of the dielectric film, it is made to have high transmittance for the excitation laser wavelength 92 and high reflectivity for the signal light wavelength 93.

[0064] When the excitation laser 92 is injected into the all-fiber ultrasonic endoscope 9, it will pass through the medium mirror 94, the sensing film 95 and the heat insulation film 96 in sequence along the guide fiber 91, and finally irradiate the excitation film 97, causing the excitation film 97 to generate a temperature rise and undergo thermoelastic expansion, compressing the surrounding medium and generating outward propagating ultrasonic waves.

[0065] The ultrasonic waves generated by the all-fiber ultrasonic endoscope 9 are reflected by the focusing acoustic reflector 98 and propagate out of the all-fiber ultrasonic endoscope 9 from the lateral opening of the lateral guide tube 99. The ultrasonic waves, after being reflected by the object under test and carrying the imaging information of the object under test, enter the all-fiber ultrasonic endoscope 9 from the lateral opening of the lateral guide tube 99. After being reflected by the focusing acoustic reflector 98, they are focused on the medium mirror 94 and press against the sensing film 95, modulating the imaging information of the object under test carried by the ultrasonic waves onto the intensity of the interference light.

[0066] When the signal light 93 is injected into the all-fiber ultrasound endoscope 9, multi-beam interference occurs due to the Fabre-Perot cavity formed by the dielectric mirror 94, forming interference light that propagates in the opposite direction along the guide fiber 91. The intensity of the interference light is:

[0067]

[0068] in It is the intensity of the incident signal light 93. It is the reflectivity of one side surface of the dielectric mirror 94 at the wavelength of the signal light 93. The optical path length of the signal light 93 after one reflection from the surfaces on both sides of the dielectric mirror 94 is [missing information]. The refractive index of the sensing film 95 material is... It is the physical length between the two surfaces of the dielectric mirror 94.

[0069] The ultrasonic wave to be tested acts on the dielectric mirror 94, causing it to press the sensing film 95, thereby changing the optical path of the signal light 93. The intensity of the interference light is modulated through multi-beam interference.

[0070] Figure 2 This is a schematic diagram of the fiber optic ultrasound endoscopic imaging system of this invention. Figure 2As shown, the present invention also proposes an imaging system for an all-fiber ultrasonic endoscope prepared by the above preparation method, including an excitation laser 1, a narrow linewidth laser 2, an optical circulator 3, a feedback control device 4, a photodetector 5, a data acquisition device 6, a double-clad coupler 7, an electric displacement stage controller 8, and an all-fiber ultrasonic endoscope 9.

[0071] To further explain, the output of the excitation laser 1 is connected to the multimode input of the double-clad coupler 7, the output of the narrow-linewidth laser 2 is connected to the first port of the optical circulator 3, the second port of the optical circulator 3 is connected to the single-mode input of the double-clad coupler 7, the third port of the optical circulator 3 is connected to the input of the photodetector 5, the AC output of the photodetector 5 is connected to the input of the data acquisition device 6, the DC output of the photodetector 5 is connected to the input of the feedback control device 4, the output of the feedback control device 4 is connected to the control terminal of the narrow-linewidth laser 2, and the output of the double-clad coupler 7 is connected to the all-fiber ultrasonic endoscope 9, which is fixed on an electric displacement stage controlled by the electric displacement stage controller 8.

[0072] Specifically, the excitation laser 1 generates a high-energy pulsed laser, which serves as the excitation laser 92 and is coupled into the multimode input of the double-clad coupler. The narrow-linewidth laser 2 generates a continuous narrow-linewidth laser, which serves as the signal light 93. This signal light is input through the first port of the optical circulator 3 and output from the second port to the single-mode input of the double-clad coupler. The excitation laser 92 and the signal light 93 are coupled through the double-clad coupler 7 and then input into the all-fiber ultrasonic endoscope 9. The signal light 93 undergoes multi-beam interference in the all-fiber ultrasonic endoscope 9, forming a reverse-propagating interference beam. This beam is input into the output of the double-clad coupler 7 and output from the single-mode input to the second port of the optical circulator 3, and then output from the third port to the input of the photodetector 5. The photodetector 5 converts the light intensity signal received at its input into an electrical signal, and outputs two separate signals: a DC component and an AC component. The AC component is output from the AC output to the input of the data acquisition device 6, and the DC component is output from the DC output to the feedback control device 4. The data acquisition device 6 acquires, quantifies, and stores the voltage signal input from the input terminal as the scanning data for that imaging scanning point. The output terminal of the feedback control device 4 is connected to the control terminal of the narrow linewidth laser 2 to control the output narrow linewidth laser wavelength. The electric displacement stage controller 8 is used to control the scanning movement of the all-fiber ultrasonic endoscope 9 fixed on the electric displacement stage.

[0073] To further clarify, the operating point of the all-fiber ultrasonic endoscope 9 needs to be determined before the imaging system begins imaging scanning. The feedback control device 4 controls the wavelength of the narrow-linewidth laser output by the narrow-linewidth laser 2 for scanning, and plots the reflection spectrum of the all-fiber ultrasonic endoscope 9 using the DC component of the voltage signal output from the DC output terminal of the photodetector 5. The feedback control device 4 controls the output wavelength of the narrow-linewidth laser 2 to the point of maximum reflection spectrum slope, and monitors the changes in the reflection spectrum of the all-fiber ultrasonic endoscope 9 in real time through the DC component of the voltage signal output from the DC output terminal of the photodetector 5 during imaging scanning, and provides real-time feedback control to stabilize the output wavelength of the narrow-linewidth laser 2 at the point of maximum reflection spectrum slope.

[0074] Specifically, the wavelength of the excitation laser 92 output by the excitation laser 1 is 1064nm, and the wavelength of the signal light 93 output by the narrow linewidth laser 2 is 1550nm.

[0075] Specifically, the multimode input end of the double-clad coupler 7 is a multimode fiber, the single-mode input end is a single-mode fiber, and the output end is a double-clad fiber with the same parameters as the double-clad fiber of the guide fiber 1 in the all-fiber ultrasound endoscope 9.

[0076] Specifically, the sampling rate of the photodetector 5 is greater than 100MHz.

[0077] Specifically, the step size accuracy of the electric displacement stage controller 8 is less than 10 μm.

[0078] The all-fiber ultrasonic endoscope proposed in this invention can be used for ultrasonic excitation and detection in different media environments, such as water, air and other liquid environments.

[0079] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A full-fiber ultrasonic endoscope, characterized in that, include: The components include a guiding fiber (91), a dielectric mirror (94), a sensing film (95), a heat-insulating film (96), an excitation film (97), a focusing acoustic reflector (98), and a lateral guiding tube (99). The output end of the guiding optical fiber (91) is a flat end face. The dielectric mirror (94), the sensing film (95), the heat insulation film (96) and the excitation film (97) are sequentially covered on the flat end face. The guiding optical fiber (91) and the focusing acoustic reflector (98) are fixed inside the lateral guiding tube (99). The lateral opening direction of the lateral guiding tube (99) is consistent with the reflection direction of the focusing acoustic reflector (98). The guiding fiber (91) is a double-clad fiber, comprising a core, an inner cladding, and an outer cladding arranged from the inside out. The core transmits the signal light (93) in single-mode at the wavelength of the signal light (93) and is used to transmit the signal light (93). The inner cladding transmits the excitation laser (92) in multi-mode at the wavelength of the excitation laser (92) and is used to transmit the excitation laser (92). The outer cladding is used to confine the excitation laser (92) and the signal light (93). The dielectric mirror (94) is a dielectric thin film formed by alternating deposition of two different inorganic materials with refractive indices of 1.5-2.

9. The two surfaces constitute the two cavity surfaces of the Fabre-Paro cavity, so that the signal light (93) is repeatedly reflected on the two cavity surfaces and undergoes multi-beam interference in the guiding optical fiber (91). When the all-fiber ultrasonic endoscope is used for lateral ultrasonic excitation, the excitation laser (92) is transmitted along the guide fiber (91), passes through the medium mirror (94), the sensing film (95) and the heat insulation film (96), is absorbed by the excitation film (97) and excites an ultrasonic signal. The ultrasonic signal is reflected by the focusing acoustic reflector (98) and transmitted laterally out of the all-fiber ultrasonic endoscope along the lateral opening of the lateral guide tube (99), thereby realizing the lateral excitation of ultrasonic waves. When the all-fiber ultrasonic endoscope is used for lateral ultrasonic detection, the signal light (93) is transmitted along the guide fiber (91) and reflected by the medium mirror (94). The ultrasonic wave to be tested is transmitted from the lateral opening of the lateral guide tube (99) into the all-fiber ultrasonic endoscope and reflected by the focusing acoustic reflector (98). It is focused on the medium mirror (94) and presses the sensing film (95) to change its thickness, thereby changing the optical path of the signal light (93). The medium mirror (94) forms a Fabre-Perot cavity, which causes the signal light (93) to undergo multi-beam interference in the guide fiber (91), modulating the ultrasonic information onto the intensity of the interference light. Lateral ultrasonic detection is achieved by detecting the intensity of the interference light.

2. The all-fiber ultrasonic endoscope according to claim 1, characterized in that, The medium mirror (94) has a transmittance of more than 80% for the wavelength of the excitation laser (92) and a reflectance of more than 95% for the wavelength of the signal light (93).

3. The all-fiber ultrasonic endoscope according to claim 1, characterized in that, The heat insulation film (96) is a heat insulation material with a thermal conductivity of less than 0.1 W / (m·K), has a transmittance of more than 95% for the wavelength of the excitation laser (92), and has a film thickness of 1μm-10μm.

4. The all-fiber ultrasonic endoscope according to claim 1, characterized in that, The excitation film (97) is a light-absorbing material with a particle size of 10 nm-1 μm and a thermal expansion coefficient greater than 10. -4 The polymer mixture at / ℃, wherein the excitation film (97) has an absorption rate of more than 80% for the wavelength of the excitation laser (92), and a coefficient of thermal expansion greater than 10. -4 / ℃, thickness ranges from 1μm to 500μm.

5. The all-fiber ultrasonic endoscope according to claim 1, characterized in that, The focusing acoustic reflector (98) is a cylindrical concave spherical reflector with a diameter of 0.2mm-3mm and a focal length of 2-10mm, and the material is an acoustic reflective material with an acoustic impedance of 18MPa·s / m or higher.

6. The all-fiber ultrasonic endoscope according to claim 1, characterized in that, The lateral guide tube (99) is a cylindrical metal tube with a diameter of 0.3mm-5mm. The metal tube has a lateral opening with a length of 2mm-10mm and a width of 1mm-5mm. The focusing acoustic reflector (98) is fixed inside the lateral guide tube (99) opposite to the guiding optical fiber (91). The two are 2mm-10mm apart and have the same focal length as the focusing acoustic reflector (98).

7. The all-fiber ultrasonic endoscope according to claim 1, characterized in that, The ultrasonic wave to be tested acts on the dielectric mirror (94), causing it to press against the sensing film (95), thereby changing the optical path of the signal light (93). The intensity of the interference light is modulated through multi-beam interference, and the intensity of the interference light is... ,in It is the intensity of the incident signal light (93). It is the reflectivity of one side surface of the dielectric mirror (94) at the wavelength of the signal light (93). The optical path length of the signal light (93) after one reflection from both sides of the dielectric mirror (94) is [missing information]. It is the refractive index of the sensing film (95) material. It is the physical length between the two surfaces of the dielectric mirror (94). It is the wavelength of the signal light (93).

8. A fiber optic ultrasound endoscopic imaging system, characterized in that, The all-fiber ultrasonic endoscope as described in any one of claims 1-7 further includes: an excitation laser (1), a narrow linewidth laser (2), an optical circulator (3), a feedback control device (4), a photodetector (5), a data acquisition device (6), a double-clad coupler (7), and an electric displacement stage controller (8). The single-mode input of the double-clad coupler (7) is a single-mode fiber, the multimode input is a multimode fiber, and the output is a double-clad fiber with the same parameters as the guiding fiber (91). The double-clad coupler includes a core, an inner cladding, and an outer cladding arranged from the inside out. The core transmits the signal light (93) in single-mode mode and is used to transmit the signal light (93). The inner cladding transmits the excitation laser (92) in multimode mode and is used to transmit the excitation laser (92). The outer cladding is used to confine the excitation laser (92) and the signal light (93). The output of the excitation laser (1) is connected to the multimode input of the double-clad coupler (7), the output of the narrow-linewidth laser (2) is connected to the first port of the optical circulator (3), the second port of the optical circulator (3) is connected to the single-mode input of the double-clad coupler (7), the third port of the optical circulator (3) is connected to the input of the photodetector (5), the AC output of the photodetector (5) is connected to the input of the data acquisition device (6), the DC output of the photodetector (5) is connected to the input of the feedback control device (4), the output of the feedback control device (4) is connected to the control of the narrow-linewidth laser (2), the output of the double-clad coupler (7) is connected to the all-fiber ultrasonic endoscope (9), and the all-fiber ultrasonic endoscope is fixed on an electric displacement stage controlled by the electric displacement stage controller (8). The excitation laser (1) is used to generate pulsed laser light as excitation laser (92), which is coupled into the multimode input of the double-clad coupler. The narrow-linewidth laser (2) generates continuous narrow-linewidth laser light as signal light (93), which is input through the first port of the optical circulator (3) and output from the second port to the single-mode input of the double-clad coupler. The excitation laser (92) and the signal light (93) are coupled through the double-clad coupler (7) and input into the all-fiber ultrasound endoscope. The signal light (93) undergoes multi-beam interference in the all-fiber ultrasound endoscope to form a reverse-propagating interference light, which is input into the output of the double-clad coupler (7) and output from the single-mode input to the second port of the optical circulator (3), and output from the first port of the optical circulator (3). The three-port output is connected to the input of the photodetector (5). The photodetector (5) converts the light intensity signal received at its input into an electrical signal and outputs it as a DC component and an AC component. The AC component is output from the AC output to the input of the data acquisition device (6), and the DC component is output from the DC output to the feedback control device (4). The data acquisition device (6) is used to acquire, quantize, and store the voltage signal input at the input as scanning data for the imaging scanning point. The output of the feedback control device (4) is connected to the control of the narrow linewidth laser (2) to control the output narrow linewidth laser wavelength. The electric displacement stage controller (8) is used to control the scanning movement of the all-fiber ultrasonic endoscope fixed on the electric displacement stage.

9. A fiber optic ultrasound endoscopic imaging system according to claim 8, characterized in that, The core diameter is 8μm~12μm, and the inner cladding diameter is 10μm~200μm.

10. A fiber optic ultrasound endoscopic imaging system according to claim 8, characterized in that, The feedback control device (4) is used to measure the reflection spectrum of the all-fiber ultrasonic endoscope. When the imaging system performs scanning imaging, it monitors the drift of the reflection spectrum by the DC component of the voltage signal output by the photodetector (5) and controls the output wavelength of the narrow linewidth laser (2) to be located at the position of maximum reflection spectrum slope.

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