CN116831629A - All-fiber ultrasonic endoscope and imaging system - Google Patents

Abstract

The invention discloses an all-fiber ultrasonic endoscope and an imaging system, and belongs to the field of ultrasonic endoscopic imaging. Including guiding optical fiber, dielectric mirror, sensing film, heat insulating film, excitation film, focusing acoustic reflector and lateral guiding tube. The exciting laser is absorbed by the exciting film and generates ultrasonic waves through the dielectric mirror, the sensing film and the heat insulation film, and the ultrasonic waves are transmitted out of the endoscope along the lateral opening of the lateral guide tube. The Fabry-Perot cavity formed by the dielectric mirror makes the signal light generate multi-beam interference, and modulates the ultrasonic signal laterally transmitted into the endoscope to the light intensity of the interference light. According to the invention, the dielectric mirror, the sensing film, the heat insulation film and the excitation film are sequentially covered on the end face of the guide optical fiber to form an integral structure, and the guide optical fiber, the focusing sound reflector and the lateral guide tube are fixedly combined, so that ultrasonic waves propagating along the direction of the guide optical fiber are reflected to the lateral direction, and the optical fiber ultrasonic endoscope can simultaneously realize lateral excitation and lateral detection of the ultrasonic waves by using a single optical fiber.

Description

An all-fiber ultrasonic endoscope and imaging system

Technical field

The invention belongs to the field of ultrasonic endoscopic imaging, and more specifically, relates to an all-fiber ultrasonic endoscope and imaging system.

Background technique

Ultrasound imaging technology takes advantage of the short wavelength and strong penetrability of ultrasound and has wide applications in medical imaging, especially endoscopic imaging and other fields. Ultrasonic imaging technology generates ultrasonic pulses through an ultrasonic transducer with ultrasonic excitation function. The pulses are reflected by the object to be measured after reaching the surface of the object to be measured. Ultrasonic signals are detected by ultrasonic sensors with ultrasonic detection functions to achieve imaging of the surface or interior of the object to be measured, and to further complete the analysis of the surface and internal structure of the object to be measured.

Fiber optic ultrasound endoscopes use optical fibers as carriers and have the advantages of small size, high flexibility, and resistance to electromagnetic interference. They have received widespread attention in recent years. Fiber optic ultrasound endoscopes usually consist of an ultrasound excitation part and an ultrasound sensing part. The ultrasonic excitation part is mainly based on the photoacoustic effect. The photoacoustic material converts the energy of the excitation laser into ultrasonic waves and emits them. Commonly used photoacoustic materials are mixed with a high optical absorption material, such as carbon black, graphene, carbon nanotubes, etc., and a high thermal expansion coefficient elastic material, such as polydimethylsiloxane (PDMS). The ultrasonic sensing part mainly realizes the detection of ultrasonic signals by measuring the changes in physical parameters of the sensor caused by ultrasonic waves. At present, the ultrasonic sensing parts mainly include fiber grating type, micro-ring resonant cavity type, etc. The ultrasonic excitation part and ultrasonic sensing part of this type of fiber optic ultrasonic endoscope are difficult to integrate, so the system size is difficult to further reduce, limiting its application in specific scenarios, such as endovascular imaging.

Contents of the invention

In view of the shortcomings of the existing technology, the purpose of the present invention is to provide an all-fiber ultrasonic endoscope and imaging system, aiming to solve the problem that the existing fiber optic ultrasonic endoscope cannot simultaneously achieve lateral ultrasonic excitation and ultrasonic transmission on one optical fiber. Feeling technical issues.

In order to achieve the above object, according to one aspect of the present invention, an all-fiber ultrasonic endoscope is provided, including: a guide fiber, a dielectric mirror, a sensing film, a heat insulation film, an excitation film, a focusing acoustic mirror, and a lateral guide. tube; the output end face of the guide optical 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 optical fiber and the focusing acoustic reflector are fixed on a device with a lateral opening in the lateral guide tube;

The guide 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-insulating film and irradiates onto the excitation film. The excitation film absorbs the excitation laser. Light energy is converted into thermal energy. The thermal energy causes the temperature of the excitation film to increase, causing thermoelastic expansion, and excites ultrasonic signals. The ultrasonic signals are reflected by the focused acoustic mirror and passed through the lateral opening of the lateral guide tube. The endoscope is transmitted out, and the heat-insulating film blocks the conduction of thermal energy from the excitation film to the sensing film;

The guide 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 wrapping the sensing film and undergoes multi-beam interference, and is then reversed in the guide fiber. transmission;

When the all-fiber ultrasonic endoscope detects the ultrasonic wave to be measured, the signal light is transmitted along the guide fiber and is reflected by the dielectric mirror. The ultrasonic wave is transmitted into the endoscope through the lateral opening of the lateral guide tube and is reflected by the Reflected by the focused sound mirror, the dielectric mirror is excited by the ultrasonic wave to be measured, pressing the sensing film and changing its thickness. The changing frequency is equal to the frequency of the incident ultrasonic wave, thereby changing the method composed of the dielectric mirror. The cavity length of the Bry-Perot resonator changes the optical power of the reflected light that is reversely transmitted in the guide fiber due to multi-beam interference. By detecting the optical power of the reflected light, the ultrasonic signal is detected.

Preferably, the dielectric mirror is a dielectric film formed by alternate deposition of two different inorganic materials with a refractive index of 1.5-2.9. It has a reflectivity of more than 95% for the signal light wavelength and a transmission of more than 80% for the excitation laser wavelength. rate, film thickness is 1μm-100μm;

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

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

Preferably, the excitation film is a mixture of a light-absorbing material with high optical absorption in the excitation laser band, a particle size of 10 nm-1 μm, and a polymer with a thermal expansion coefficient greater than 10 ^-4 /°C, and a film thickness of 1 μm-500 μm. .

Preferably, the guide optical fiber is a double-clad optical fiber, including a core, an inner cladding and an outer cladding arranged from the inside out;

The transmission mode of the fiber core at the signal light wavelength is single-mode transmission, which is used for the transmission of the signal light;

The transmission mode of the inner cladding layer at the excitation laser wavelength is multi-mode transmission, which is used for the transmission of the excitation laser;

The outer cladding is used to bind the excitation laser and the signal light;

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

Preferably, the dielectric mirror, the guide optical fiber, the sensing film, the heat-insulating film, the heat-insulating film and the excitation film all have good adsorption properties;

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. The material is an acoustic reflective material with an acoustic impedance above 18MPa·s/m;

Preferably, the lateral guide tube is a cylindrical metal tube with a diameter of 0.3mm-5mm. The metal tube contains a lateral opening with a length of 2mm-10mm and a width of 1mm-5mm. The focusing acoustic reflector is facing The guide optical fiber is fixed in the lateral guide tube, with a distance of 2 mm to 10 mm and consistent with the focal length of the focusing acoustic reflector.

According to another aspect of the present invention, a fiber optic ultrasonic endoscope imaging system is provided, which includes the all-fiber ultrasonic endoscope as described above, and also includes: an excitation laser, a narrow linewidth laser, an optical circulator, and a feedback control. device, photodetector, data acquisition device, double-clad coupler and electric displacement controller;

The output end of the excitation laser is connected to the multi-mode input end of the double-cladding coupler;

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

The DC output end of the photodetector is connected to the input end of the feedback control device, and the AC output end is connected to the input end of the data acquisition device;

The output end of the feedback control device is connected to the control end of the narrow linewidth laser;

The output end of the double-clad coupler is connected to the all-fiber ultrasonic endoscope, the all-fiber ultrasonic endoscope is fixed on an electric displacement stage, and the electric displacement controller controls the movement of the electric displacement stage;

The excitation laser is used to generate excitation laser, and the excitation laser is input into the multi-mode input end of the optical circulator; the narrow linewidth laser is used to generate a narrow linewidth laser as signal light; the optical circulator is used to convert the signal Light is input into the single-mode input end of the double-cladding coupler; the double-cladding coupler is used to couple the excitation laser input from the multi-mode input end with the signal light input from the single-mode input end and input it into the all-fiber ultrasound The speculum is also used to reversely input the reflected light transmitted back by the all-fiber ultrasonic endoscope into the single-mode input end; the optical circulator is also used to reverse the single-mode input end of the double-cladding coupler. The transmitted reflected light is input to the photodetector; the photodetector converts the intensity of the reflected light into a voltage signal, the DC component of the voltage signal is input to the feedback control device, and the AC component is input 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 at the maximum slope of the reflection spectrum; the data acquisition system is used to collect, quantify and store the voltage signal as Imaging data of the scanning point; the electric displacement controller is used to control the electric displacement stage to move to the next scanning point after the imaging data is stored;

Before the imaging system starts imaging scanning, the working point of the all-fiber ultrasonic endoscope needs to be determined. The feedback control device controls the narrow linewidth laser to output the wavelength of the narrow linewidth laser for scanning, and draws the reflection spectrum of the all-fiber ultrasonic endoscope through the DC component of the voltage signal output from the DC output end of the photodetector. . The feedback control device controls the output wavelength of the narrow linewidth laser to the maximum reflection spectrum slope, and monitors the all-fiber ultrasound in real time through the DC component of the voltage signal output by the DC output end of the photodetector during the imaging scanning process. The reflection spectrum of the endoscope changes, and real-time feedback controls the output wavelength of the narrow linewidth laser 2 to stabilize at the maximum slope of the reflection spectrum.

Preferably, the multimode input end of the double-cladding coupler is a multimode optical fiber, the single-mode input end is a single-mode optical fiber, and the output end is a double-cladding optical fiber; the double-cladding optical fiber at the output end of the double-cladding coupler is The parameters of the double-clad fiber are the same as those of the all-fiber ultrasound endoscope guidance fiber;

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

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

Preferably, the feedback control device includes a data acquisition card and a narrow linewidth laser controller; the data acquisition card is used to collect, quantify and store the DC voltage signal output by the photodetector; the narrow linewidth laser controller is used to The wavelength of the signal light output by the narrow linewidth laser is controlled.

Generally speaking, compared with the prior art, the above technical solutions conceived by the present invention can achieve the following beneficial effects:

1. The present invention forms an integral structure by sequentially covering the end face of the guide fiber with a dielectric mirror, a sensing film, a heat-insulating film and an excitation film, and fixedly combines the guide fiber with a focusing acoustic reflector and a lateral guide tube. The ultrasonic waves propagating in the direction of the guided optical fiber are reflected to the side, so that the all-fiber ultrasonic endoscope can simultaneously achieve lateral excitation and lateral detection of ultrasonic waves with a single optical fiber.

2. The present invention introduces a dielectric mirror with wavelength selective transmission into the all-fiber ultrasonic endoscope, so that the excitation laser is transmitted to the excitation film through the dielectric mirror and absorbed by it to generate ultrasonic waves. The signal light is transmitted between two Multi-beam interference occurs due to reflection between dielectric mirrors, modulating the detected ultrasonic signal to the intensity of the reflected light. In an all-fiber ultrasonic endoscope, an optical fiber is used to simultaneously achieve ultrasonic excitation and ultrasonic detection.

3. The present invention introduces a heat-insulating film into the all-fiber ultrasonic endoscope, so that the heat of the excitation film during the ultrasonic excitation process cannot be conducted to the sensing film, causing thermal expansion of the sensing film, and prevents crosstalk between the ultrasonic excitation process and the ultrasonic detection process. .

4. The present invention uses double-clad fiber as the guide fiber. The signal light is transmitted in a single mode in the fiber core, which avoids the inter-mode interference of the signal light and reduces the noise in ultrasonic detection. The excitation light is transmitted through the inner cladding, using the inner cladding. The large effective area enables high-energy excitation laser transmission below the fiber damage threshold and improves the intensity of ultrasonic waves generated by the all-fiber ultrasonic endoscope.

5. The present invention wraps the sensing film with two dielectric mirrors to form a Fabry-Perot resonant cavity, modulates the ultrasonic signal detected by the endoscope to the light intensity signal of the reflected light, greatly improves the sensitivity of the system, and can realize Ultrasonic endoscopic inspection of low-noise equivalent pressure. At the same time, the Fabry-Perot interference sensor is used to make the imaging system insensitive to vibration and other interference in the external environment, further improving the stability of the system.

6. The present invention introduces a feedback control system for narrow linewidth lasers. By monitoring the DC component of the reflected light intensity in real time and performing real-time feedback control on the output wavelength of the narrow linewidth laser, it avoids the transmission of all-fiber ultrasonic endoscopes. The sensitivity of the sensing film is reduced due to spectral drift caused by temperature changes in the external environment, which effectively improves the sensitivity stability of the system.

Description of the drawings

Figure 1 is a schematic structural diagram of an all-fiber ultrasonic endoscope in the present invention;

Figure 2 is a schematic diagram of the all-fiber ultrasonic endoscopic imaging system in the present invention;

In all drawings, the same reference numerals are used to represent the same components or structures, among which: 1. Excitation laser; 2. Narrow linewidth laser; 3. Optical circulator; 4. Feedback control device; 5. Photoelectric detection 6. Data acquisition device; 7. Double-clad coupler; 8. Electric displacement stage controller; 9. All-fiber ultrasonic endoscope; 91. Guiding fiber; 92. Excitation laser; 93. Signal light; 94. Dielectric mirror; 95. Sensing film; 96. Insulating film; 97. Excitation film; 98. Focused acoustic reflector; 99. Lateral guide tube.

Detailed ways

In order to make the purpose, technical solutions and advantages of the present invention more clear, the present 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 here are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

Figure 1 is a schematic structural diagram of an all-fiber ultrasonic endoscope in the present invention. As shown in Figure 1, the present invention proposes an all-fiber ultrasonic endoscope, including a guide fiber 91, a dielectric mirror 94, a sensing film 95, a heat insulation film 96, an excitation film 97, a focusing acoustic mirror 98 and a lateral Guide tube 99. The guide fiber 91 is a double-clad fiber, the inner cladding is used to transmit the excitation laser 92 , and the core is used to transmit the signal light 93 . The proximal end surface of the guide fiber 1 is polished or cut flat, and a layer of cured UV glue wrapped with a wavelength-selective dielectric film is deposited on the proximal end surface of the guide fiber 91 to serve as the dielectric mirror. 94 and the sensing film 95. The dielectric mirror 94 is used to press the sensing film 95 and change its thickness when it is excited by the ultrasonic wave to be measured, and the change frequency is equal to the frequency of the incident ultrasonic wave, thereby changing the fabric formed by the dielectric mirror 94 The cavity length of the Li-Perot resonant cavity changes the optical path of the signal light 93, thereby modulating the detected ultrasonic signal to the phase of the signal light 93, thereby changing the direction of multi-beam interference in the guidance The optical power of the reflected light transmitted in the reverse direction in the optical 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 to prevent the heat of the excitation film 97 from being conducted to the sensing film 95 during ultrasonic excitation. Thermal expansion of the sensing film is caused to prevent crosstalk between the ultrasonic excitation process and the ultrasonic detection process. A layer of a mixture of cured carbon black and polydimethylsiloxane (PDMS) is deposited on the surface of the thermal insulation film 96 as the excitation film 97 for absorbing the excitation laser and exciting it through the photoacoustic effect. Generate ultrasonic signals. A 45° cylindrical concave reflector is fixed at the front end of the guide fiber 91 as the focused acoustic reflector 98 for reflecting the ultrasonic signal generated by the excitation film 97 to the side of the guide fiber 91 propagates, and reflects the side-propagating ultrasonic signal to be measured to the direction facing the guide optical fiber 91 . An aluminum tube with a lateral opening is used as the lateral guide tube 99 for fixing the guide fiber 91 and the focusing acoustic mirror 98 so that the excitation film 97 is deposited on the proximal end surface of the guide fiber 91 There is a 1 mm gap between the lateral guide tube 99 and the focused sound reflector 98. The lateral opening direction of the lateral guide tube 99 is consistent with the reflection direction of the focused sound reflector 98, so that the ultrasonic signal is input and output in a fixed direction. The fiber optic ultrasonic endoscope 9.

Specifically, the core diameter of the guide optical fiber 91 is less than 10 microns, the transmission mode is single-mode transmission, and the signal light 93 is transmitted within the core. The diameter of the inner cladding of the guide optical fiber 91 is greater than 10 microns, the transmission mode is multi-mode transmission, and the excitation laser 92 is transmitted in the inner cladding. To further explain, the outer cladding of the guide optical fiber 91 is used to confine the excitation laser 92 and the signal light 93 .

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

Specifically, the dielectric mirror 94 is a dielectric film formed by alternate deposition of two different inorganic materials with a refractive index of 1.5-2.9. It has a transmittance of more than 80% for the wavelength of the excitation laser 92 and a transmittance of more than 80% for the signal light. 93 wavelength has a reflectivity of more than 95%, a film thickness of 1 μm-100 μm, and good adsorption to the guide optical fiber 91 and the sensing film 95 .

Specifically, the material of the sensing film 95 is a polymer material with a Young's modulus of 100MPa-100GPa, a transmittance of more than 90% for the wavelengths of the excitation laser 92 and the signal light 93, and a thermal expansion coefficient less than 10 ^-4 /° C., the film thickness is 1 μm-1 mm, and has good adsorption with the dielectric mirror 94 .

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

Specifically, the excitation film 97 is a mixture of a light-absorbing material with a particle size of 10 nm-1 μm and a polymer with a thermal expansion coefficient greater than 10 ^-4 /°C that has an optical absorption rate of more than 80% at the wavelength of the excitation laser 92 . The film thickness is 1 μm-500 μm, and has good adsorption properties with the heat insulation film 96 .

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. The material is an acoustic reflective material with an acoustic impedance above 18MPa·s/m.

Specifically, the lateral guide tube 99 is a cylindrical metal tube with a diameter of 0.3mm-5mm. The metal tube laterally contains a lateral opening with a length of 2mm-10mm and a width of 1mm-5mm. The focusing acoustic reflector 98 The guiding optical fiber 91 is fixed in the lateral guiding tube 99 , with a distance of 2 mm to 10 mm, and is consistent with the focal length of the focusing acoustic mirror 98 .

To explain further, the present invention also proposes a method for preparing the above-mentioned all-fiber ultrasonic endoscope. The specific steps include:

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

S2, immerse the end of the guide fiber 91 with the inner surface of the dielectric mirror 94 into the liquid UV glue, let it stand for 1 minute, slowly pull out the guide fiber 91 at a speed of 10 μm/s, and use a UV curing lamp to illuminate the end face of the fiber until it is adsorbed on the fiber. The UV glue on the end surface is completely solidified to form a sensing film 95.

It should be noted that the time for irradiating the optical fiber end face with a UV curing lamp is two hours. After the pull-up coating is completed, the optical fiber is hung vertically for a week to maximize the heat resistance of the UV glue.

S3, use a vacuum evaporation coating method to deposit the same dielectric film as the inner surface of the dielectric mirror 94 onto the surface of the sensing film 95 as the outer surface of the dielectric mirror 94.

S4, use a vapor deposition coating method to deposit a layer of parylene C on the outer surface of the dielectric mirror 94 as a heat insulation film 96.

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 in the mixture.

S6, immerse the end of the guide fiber 91 with the heat-insulating film 96 into the mixture of carbon black and PDMS, let it sit for 1 minute, slowly pull out the guide fiber 91 at a speed of 10 μm/s, and use a heating lamp to illuminate the end face of the fiber until it is adsorbed. The mixture on the end face of the optical fiber is completely solidified to form an excitation film 97.

It should be noted that the heating lamp is used to illuminate the fiber end face for two hours. After the pull-up coating is completed, the fiber is hung vertically for a week to allow the mixture of carbon black and PDMS to completely solidify.

S7, fix the guide fiber 91 and the cylindrical concave spherical reflector as the focusing acoustic mirror 98 in the side-opening aluminum tube as the lateral guide tube 99, and the excitation film 97 deposited on the guide fiber 91 and the focusing acoustic mirror The 45° reflecting surfaces of 98 are 2 mm apart, and the lateral opening of the lateral guide tube 99 is consistent with the reflection direction of the focused sound mirror 98 .

To further explain, the dielectric mirror 94 is a dielectric film formed by alternately depositing multiple layers of silicon dioxide and titanium dioxide. It is a structure with periodic refractive index modulation, which can produce high reflectivity for light of a specific wavelength, and can produce high reflectivity for light of a specific wavelength. Light of a specific wavelength produces high transmittance. By designing the parameters of the dielectric film, it has high transmittance for the wavelength of the excitation laser 92 and high reflectivity for the wavelength of the signal light 93 .

When the excitation laser 92 is injected into the all-fiber ultrasonic endoscope 9 , it will sequentially pass through the dielectric mirror 94 , the sensing film 95 and the heat-insulating film 96 along the guide fiber 91 , and finally be irradiated to on the excitation film 97, causing the excitation film 97 to generate a temperature rise and undergo thermoelastic expansion, compressing the surrounding medium and generating ultrasonic waves that propagate outward.

The ultrasonic wave generated by the all-fiber ultrasonic endoscope 9 is reflected by the focused sound mirror 98 and propagates out of the all-fiber ultrasonic endoscope 9 from the lateral opening of the lateral guide tube 99, and is reflected by and mounted on the object to be measured. The ultrasonic wave after the imaging information of the object to be measured enters the all-fiber ultrasonic endoscope 9 from the lateral opening of the lateral guide tube 99, is reflected by the focusing acoustic mirror 98, and is focused on the dielectric mirror 94. The sensing film 95 modulates the imaging information of the object to be measured carried by the ultrasonic waves to the intensity of the interference light.

When the signal light 93 is injected into the all-fiber ultrasonic endoscope 9 , multi-beam interference will occur due to the Fabre-Perot cavity formed by the dielectric mirror 94 , forming interference light transmitted in the opposite direction along the guide fiber 91 , the interference light intensity is:

where I ⁱ is the light intensity of the incident signal light 93 , R is the reflectivity of the one-sided surface of the dielectric mirror 94 at the wavelength of the signal light 93 , δ=4πn ₀ h/λ is the wavelength of the signal light 93 at The optical path reflected once by the surfaces on both sides of the dielectric mirror 94 , n ₀ is the refractive index of the material of the sensing film 95 , and h is the physical length between the surfaces on both sides of the dielectric mirror 94 .

The ultrasonic wave to be measured acts on the dielectric mirror 94, causing it to press the sensing film 95, thereby changing the optical path of the signal light 93, and achieving intensity modulation of the interference light through multi-beam interference.

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

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

Specifically, the excitation laser 1 generates high-energy pulse laser, which is coupled into the multi-mode input end of the double-cladding coupler as the excitation laser 92 . The narrow linewidth laser 2 generates continuous narrow linewidth laser, as the signal light 93 is input through the first port of the optical circulator 3, and is output from the second port to the single mode of the double-cladding coupler. input terminal. The excitation laser 92 and the signal light 93 are coupled through the double-cladding 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 to form reversely transmitted interference light, which is input to the output end of the double-cladding coupler 7 and is output from the single-mode input end into the The second port of the optical circulator 3 is output from the third port to the input end of the photodetector 5 . The photodetector 5 converts the light intensity signal received at its input end into an electrical signal, and separates the DC component and the AC component into two channels, wherein the AC component is output from the AC output end to the input end of the data acquisition device 6, The DC component is output from the DC output terminal to the feedback control device 4 . The data acquisition device 6 collects, quantifies, and stores the voltage signal input from the input end as the scanning data of the imaging scanning point. The output end of the feedback control device 4 is connected to the control end of the narrow linewidth laser 2 for controlling the narrow linewidth laser wavelength output by it. The electric displacement controller 8 is used to control the scanning movement of the all-fiber ultrasonic endoscope 9 fixed on the electric displacement stage.

To further explain, before the imaging system starts to perform imaging scanning, the working point of the all-fiber ultrasonic endoscope 9 needs to be determined. The feedback control device 4 controls the narrow linewidth laser 2 to output the wavelength of the narrow linewidth laser for scanning, and draws the all-fiber ultrasonic endoscope through the DC component of the voltage signal output from the DC output end of the photodetector 5 9 reflectance spectrum. The feedback control device 4 controls the output wavelength of the narrow linewidth laser 2 to the maximum reflection spectrum slope, and monitors the DC component of the voltage signal outputted from the DC output end of the photodetector 5 in real time during the imaging scanning process. The reflection spectrum of the all-fiber ultrasonic endoscope 9 changes, and real-time feedback controls the output wavelength of the narrow linewidth laser 2 to stabilize at the maximum slope of the reflection spectrum.

Specifically, the wavelength of the excitation laser 92 output by the excitation laser 2 is 1064 nm, and the wavelength of the signal light 93 output by the narrow linewidth laser 3 is 1550 nm.

Specifically, the multi-mode input end of the double-clad coupler 7 is a multi-mode optical fiber, the single-mode input end is a single-mode optical fiber, and the output end is a double-clad optical fiber and is connected with the all-fiber ultrasonic endoscope 9 The double-clad fiber parameters of the guide fiber 1 are the same.

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

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

The all-fiber ultrasonic endoscope proposed by the present invention can be used for ultrasonic excitation and detection in different medium environments, such as water, air and other liquid environments.

It is easy for those skilled in the art to understand that the above descriptions are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements, etc., made within the spirit and principles of the present invention, All should be included in the protection scope of the present invention.

Claims (10)

1. An all-fiber ultrasonic endoscope, comprising: a guiding optical fiber (91), a dielectric mirror (94), a sensing film (95), a heat insulation film (96), an excitation film (97), a focusing sound reflecting mirror (98) and a lateral guiding tube (99);

the output end of the guide optical fiber (91) is a flat end surface, 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 surface, the guide optical fiber (91) and the focusing sound reflecting mirror (98) are fixed in the lateral guide pipe (99), and the lateral opening direction of the lateral guide pipe (99) is consistent with the reflecting direction of the focusing sound reflecting mirror (98);

when the all-fiber ultrasonic endoscope (9) is used for lateral ultrasonic excitation, excitation laser (92) is transmitted along the guide optical fiber (91), is absorbed by the excitation film (97) and excites ultrasonic signals through the dielectric mirror (94), the sensing film (95) and the heat insulation film (96), and the ultrasonic signals are reflected by the focusing acoustic reflector (98) and are laterally transmitted out of the all-fiber ultrasonic endoscope (9) along a lateral opening of the lateral guide pipe (99), so that the lateral excitation of ultrasonic waves is realized;

when the all-fiber ultrasonic endoscope (9) is used for lateral ultrasonic detection, signal light (93) is transmitted along the guide optical fiber (91), reflected by the dielectric mirror (94), ultrasonic waves to be detected are transmitted from a lateral opening of the lateral guide pipe (99) into the all-fiber ultrasonic endoscope (9) and reflected by the focusing acoustic mirror (98), focused on the dielectric mirror (94) to press the sensing film (95) to change the thickness of the sensing film, so that the optical path of the signal light (93) is changed, the dielectric mirror (94) forms a Fabry-Perot cavity, the signal light (93) generates multi-beam interference in the guide optical fiber (91), ultrasonic information is modulated onto the light intensity of interference light, and the lateral detection of the ultrasonic waves is realized by detecting the light intensity of the interference light.

2. An all-fiber ultrasonic endoscope according to claim 1, characterized in that said dielectric mirror (94) is a dielectric thin film formed by alternately depositing two different inorganic materials having refractive indexes of 1.5-2.9, having a transmittance of 80% or more for the excitation laser (92) wavelength and a reflectance of 95% or more for the signal light (93) wavelength;

two surfaces of the dielectric mirror (94) form two cavity surfaces of a Fabry-Perot cavity, so that the signal light (93) is repeatedly reflected between the two cavity surfaces and multi-beam interference occurs in the guide optical fiber (91).

3. The all-fiber ultrasonic endoscope according to claim 1, wherein said heat insulating film (96) is a heat insulating material having a thermal conductivity of less than 0.1W/(m-K), and has a transmittance of 95% or more to the wavelength of said excitation laser light (92), and a film thickness of 1 μm to 10 μm.

4. An all-fiber ultrasonic endoscope according to claim 1, characterized in that said excitation film (97) is a light absorbing material having a particle size of 10nm-1 μm and a coefficient of thermal expansion of more than 10 ^-4 A polymer blend composition of at least 80% of the excitation laser (92) wavelength, a coefficient of thermal expansion greater than 10 ^-4 The thickness is 1 μm to 500 μm at the temperature of each layer.

5. An all-fiber ultrasonic endoscope according to claim 1, characterized in that said 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 reflecting material with an acoustic impedance of 18 MPa-s/m or more.

6. An all-fiber ultrasonic endoscope according to claim 1, characterized in that said lateral guide tube (99) is a cylindrical metal tube of diameter 0.3-5 mm, laterally containing a lateral opening of length 2-10mm and width 1-5 mm, said focusing acoustic reflector (98) being fixed inside said lateral guide tube (99) with respect to said guide fiber (91) at a distance of 2-10mm and in conformity with the focal length of said focusing acoustic reflector (98).

7. An all-fiber ultrasonic endoscope according to claim 1, characterized in that the ultrasonic waves to be measured act on said dielectric mirror (99) to cause it to press said sensing film (99) to change the optical path length of said signal light (99) by multi-beam interferenceRealizes the intensity modulation of the interference light, and the intensity of the interference light is thatWherein I is ⁱ Is the light intensity of the incident signal light (93), R is the reflectivity of the single side surface of the dielectric mirror (94) at the wavelength of the signal light (93), delta=4pi n ₀ h/lambda is the optical path length of the signal light (93) reflected once on the two side surfaces of the dielectric mirror (94), n ₀ Is the refractive index of the material of the sensing film (95), and h is the physical length between the two side surfaces of the dielectric mirror (94).

8. A fiber-optic ultrasonic endoscopic imaging system comprising the all-fiber ultrasonic endoscope of any of claims 1-7, further comprising: the device comprises an excitation laser (1), a narrow linewidth laser (2), an optical circulator (3), a feedback control device (4), a photoelectric detector (5), a data acquisition device (6), a double-cladding coupler (7) and an electric displacement table controller (8);

the output end of the excitation laser (1) is connected with the multimode input end of the double-clad coupler (7), the output end of the narrow linewidth laser (2) is connected with the first port of the optical circulator (3), the second port of the optical circulator (3) is connected with the single-mode input end of the double-clad coupler (7), the third port of the optical circulator (3) is connected with the input end of the photoelectric detector (5), the alternating current output end of the photoelectric detector (5) is connected with the input end of the data acquisition device (6), the direct current output end of the photoelectric detector (5) is connected with the input end of the feedback control device (4), the output end of the feedback control device (4) is connected with the control end of the narrow linewidth laser (2), the output end of the double-clad coupler (7) is connected with the full-mode ultrasonic endoscope (9), and the full-fiber ultrasonic endoscope (9) is fixed on the displacement control platform (8) by the electric control platform;

the exciting laser (1) is used for generating pulse laser, as exciting laser (92), being coupled into the multimode input end of the double-cladding coupler, the narrow linewidth laser (2) generates continuous narrow linewidth laser, as signal light (93) being input through the first port of the optical circulator (3) and output from the second port to the single-mode input end of the double-cladding coupler, the exciting laser (92) and the signal light (93) being coupled through the double-cladding coupler (7) and then being input into the all-fiber ultrasonic endoscope (9), the signal light (93) forming interference light of reverse transmission after multi-beam interference occurs in the all-fiber ultrasonic endoscope (9), the output end of the double-cladding coupler (7) is input, the output end of the double-cladding coupler is output by a single-mode input end and enters the second port of the optical circulator (3), the output end of the single-mode input end is output to the input end of the photoelectric detector (5), the photoelectric detector (5) converts a light intensity signal received by the input end of the photoelectric detector into an electric signal, and respectively outputs a direct current component and an alternating current component, wherein the alternating current component is output from the alternating current output end to the input end of the data acquisition device (6), the direct current component is output from the direct current output end to the feedback control device (4), the data acquisition device (6) is used for acquiring, quantifying and storing a voltage signal input by the input end as scanning data of an imaging scanning point, the output end of the feedback control device (4) is connected with the control end of the narrow linewidth laser (2) and used for controlling the output narrow linewidth laser wavelength of the narrow linewidth laser, and the electric displacement controller (8) is used for controlling the scanning movement of the all-fiber ultrasonic endoscope (9) fixed on the electric displacement table.

9. The optical fiber ultrasonic endoscope imaging system according to claim 8, characterized in that the single-mode input end of the double-clad coupler (7) is a single-mode optical fiber, the multimode input end is a multimode optical fiber, and the output end is a double-clad optical fiber with the same parameters as the guiding optical fiber (91), comprising a fiber core, an inner cladding and an outer cladding arranged from inside to outside;

the fiber core diameter is 8-12 mu m, and the transmission mode at the wavelength of the signal light (93) is single-mode transmission, which is used for transmitting the signal light (93); the diameter of the inner cladding is 10-200 mu m, and the transmission mode at the wavelength of the exciting laser (92) is multimode transmission and is used for transmitting the exciting laser (92); the outer cladding is for confining the excitation laser (92) and the signal light (93).

10. A fiber-optic ultrasound endoscopic imaging system according to claim 8, characterized in that the feedback control means (4) is adapted to measure the reflection spectrum of the all-fiber-optic ultrasound endoscope (9), monitor the drift of the reflection spectrum by the direct current component of the voltage signal output by the photodetector (5) when the imaging system is scanning imaging, and control the output wavelength of the narrow linewidth laser (2) to be at the maximum slope of the reflection spectrum.