CN116831629A - All-fiber ultrasonic endoscope and imaging system - Google Patents
All-fiber ultrasonic endoscope and imaging system Download PDFInfo
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- CN116831629A CN116831629A CN202310794979.3A CN202310794979A CN116831629A CN 116831629 A CN116831629 A CN 116831629A CN 202310794979 A CN202310794979 A CN 202310794979A CN 116831629 A CN116831629 A CN 116831629A
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B8/00—Diagnosis using ultrasonic, sonic or infrasonic waves
- A61B8/12—Diagnosis using ultrasonic, sonic or infrasonic waves in body cavities or body tracts, e.g. by using catheters
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B1/00—Instruments for performing medical examinations of the interior of cavities or tubes of the body by visual or photographical inspection, e.g. endoscopes; Illuminating arrangements therefor
- A61B1/06—Instruments for performing medical examinations of the interior of cavities or tubes of the body by visual or photographical inspection, e.g. endoscopes; Illuminating arrangements therefor with illuminating arrangements
- A61B1/07—Instruments for performing medical examinations of the interior of cavities or tubes of the body by visual or photographical inspection, e.g. endoscopes; Illuminating arrangements therefor with illuminating arrangements using light-conductive means, e.g. optical fibres
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- Investigating Or Analyzing Materials By The Use Of Ultrasonic Waves (AREA)
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
Technical Field
The invention belongs to the field of ultrasonic endoscopic imaging, and in particular relates to an all-fiber ultrasonic endoscope and an imaging system.
Background
The ultrasonic imaging technology utilizes the advantages of short ultrasonic wave length and strong penetrability, and has wide application in the fields of medical imaging, in particular endoscopic imaging and the like. The ultrasonic imaging technology generates ultrasonic pulses through an ultrasonic transducer with an ultrasonic excitation function, and the pulses are reflected by an object to be detected after reaching the surface of the object to be detected. The ultrasonic sensor with the ultrasonic detection function is used for detecting ultrasonic signals, so that imaging of the surface or the interior of an object to be detected is realized, and analysis of the surface and the interior structure of the object to be detected is further completed.
The optical fiber ultrasonic endoscope adopts the optical fiber as a carrier, has the advantages of small size, high flexibility and electromagnetic interference resistance, and has received extensive attention in recent years. Fiber-optic ultrasound endoscopes are typically composed of an ultrasound excitation portion and an ultrasound sensing portion. The ultrasonic excitation part is mainly based on the photoacoustic effect, and the photoacoustic material converts the energy of excitation laser into ultrasonic waves to be emitted. The usual photoacoustic materials are made of a high optical absorption material such as carbon black, graphene, carbon nanotubes, etc. mixed with a high thermal expansion coefficient elastic material such as Polydimethylsiloxane (PDMS). The ultrasonic sensing part detects ultrasonic signals mainly by measuring the change of physical parameters of the sensor caused by ultrasonic waves. At present, the ultrasonic sensing part mainly comprises a fiber bragg grating type, a micro-ring resonant cavity type and the like. The ultrasonic excitation part and the ultrasonic sensing part of the optical fiber ultrasonic endoscope are difficult to integrate together, so that the system size is difficult to further shrink, and the application of the optical fiber ultrasonic endoscope in specific scenes such as vascular endoscopic imaging is limited.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide an all-fiber ultrasonic endoscope and an imaging system, and aims to solve the technical problem that the existing fiber ultrasonic endoscope can not realize lateral ultrasonic excitation and ultrasonic sensing on one fiber at the same time.
To achieve the above object, according to one aspect of the present invention, there is provided an all-fiber ultrasonic endoscope comprising: the device comprises a guiding optical fiber, a dielectric mirror, a sensing film, a heat insulation film, an excitation film, a focusing sound reflecting mirror and a lateral guiding 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 covers the flat end face; the guide optical fiber and the focusing acoustic reflector are fixed in the lateral guide pipe with a lateral opening;
the guide optical fiber is used for guiding the transmission of excitation laser incident from the input end of the guide optical fiber, the excitation laser sequentially penetrates through the dielectric mirror, the sensing film and the heat insulation film to irradiate on the excitation film, the excitation film absorbs light energy of the excitation laser and converts the light energy into heat energy, the heat energy causes the temperature rise of the excitation film to generate thermoelastic expansion and excites ultrasonic signals, the ultrasonic signals are reflected by the focusing acoustic reflector and transmitted out of the endoscope through the lateral opening of the lateral guide pipe, and the heat insulation film blocks the conduction of the heat energy from the excitation film to the sensing film;
the guiding optical fiber is also used for guiding the transmission of the signal light incident from the input end of the guiding optical fiber, the signal light is reflected between the dielectric mirrors wrapping the sensing film and subjected to multi-beam interference, and then the signal light is reversely transmitted in the guiding optical fiber;
when the all-fiber ultrasonic endoscope detects ultrasonic waves to be detected, signal light is transmitted along the guide optical fiber and reflected by the dielectric mirror, the ultrasonic waves are transmitted into the endoscope from the lateral opening of the lateral guide pipe and reflected by the focusing sound reflecting mirror, the dielectric mirror is excited by the ultrasonic waves to be detected, the sensing film is pressed and the thickness of the sensing film is converted, and the changing frequency is equal to the frequency of the incident ultrasonic waves, so that the cavity length of a Fabry-Perot resonant cavity formed by the dielectric mirror is changed, the light power of reflected light which is reversely transmitted in the guide optical fiber and is interfered by multiple light beams is changed, and the detection of ultrasonic signals is realized by detecting the light power of the reflected light.
Preferably, the dielectric mirror is a dielectric film formed by alternately depositing two different inorganic materials with refractive indexes of 1.5-2.9, has a reflectivity of more than 95% for the wavelength of signal light, has a transmissivity of more than 80% for the wavelength of excitation laser, and has a film thickness of 1-100 mu m;
preferably, the sensing film is a polymer material with Young modulus of 100MPa to 100GPa, has transmittance of more than 90% for signal light wavelength and excitation laser wavelength, and has thermal expansion coefficient of less than 10 -4 The film thickness is 1 μm-1mm at the temperature of/DEG C;
preferably, the heat insulation film is a heat insulation material with the heat conductivity less than 0.1W/(m.K), has the transmittance of more than 95% for the excitation laser wavelength, and has the film thickness of 1-10 mu m;
preferably, the excitation film is a light absorbing material having high optical absorption in the excitation laser wavelength band, a particle size of 10nm-1 μm, and a thermal expansion coefficient of more than 10 -4 The polymer mixture composition at a temperature of 1 μm to 500 μm in film thickness.
Preferably, the guiding optical fiber is a double-cladding optical fiber, and comprises a fiber core, an inner cladding and an outer cladding which are arranged from inside to outside;
the transmission mode of the fiber core at the wavelength of the signal light is single-mode transmission, and is used for transmitting the signal light;
the transmission mode of the inner cladding at the excitation laser wavelength is multimode transmission and is used for transmitting the excitation laser;
the outer cladding is used for binding the excitation laser and the signal light;
preferably, the signal light is a narrow linewidth laser light, and the excitation laser light is pulse light or modulated continuous light;
preferably, the dielectric mirror, the guide optical fiber, the sensing film and the heat insulation film have good adsorptivity with the excitation film;
preferably, the focusing acoustic reflector is a cylindrical concave spherical reflector with the diameter of 0.2-3 mm and the focal length of 2-10mm, and the focusing acoustic reflector is made of an acoustic reflecting material with the acoustic impedance of more than 18MPa s/m;
preferably, the lateral guiding tube is a cylindrical metal tube with the diameter of 0.3mm-5mm, the metal tube laterally comprises a lateral opening with the length of 2mm-10mm and the width of 1mm-5mm, the focusing sound reflecting mirror is fixed in the lateral guiding tube relative to the guiding optical fiber, and the distance between the two is 2mm-10mm and is consistent with the focal length of the focusing sound reflecting mirror.
According to another aspect of the present invention, there is provided a fiber-optic ultrasonic endoscopic imaging system comprising an all-fiber ultrasonic endoscope as described above, further comprising: the device comprises an excitation laser, a narrow linewidth laser, an optical circulator, a feedback control device, a photoelectric detector, a data acquisition device, a double-cladding coupler and an electric displacement controller;
the output end of the excitation laser is connected with the multimode input end of the double-cladding coupler;
the first port of the optical circulator is connected with the output end of the narrow linewidth laser, the second port of the optical circulator is connected with the single-mode input end of the double-cladding coupler, and the third port of the optical circulator is connected with the input end of the photoelectric detector;
the direct current output end of the photoelectric detector is connected with the input end of the feedback control device, and the alternating current output end of the photoelectric detector is connected with the input end of the data acquisition device;
the output end of the feedback control device is connected with the control end of the narrow linewidth laser;
the output end of the double-cladding coupler is connected with the all-fiber ultrasonic endoscope, the all-fiber ultrasonic endoscope is fixed on an electric displacement table, and the electric displacement controller controls the electric displacement table to move;
the excitation laser is used for generating excitation laser, and the excitation laser is input into the multimode input end of the optical circulator; the narrow linewidth laser is used for generating narrow linewidth laser as signal light; the optical circulator is used for inputting signal light into a single-mode input end of the double-cladding coupler; the double-cladding coupler is used for coupling excitation laser input by the multimode input end with signal light input by the single-mode input end and inputting the signal light into the all-fiber ultrasonic endoscope, and is also used for reversely inputting reflected light reversely transmitted by the all-fiber ultrasonic endoscope into the single-mode input end; the optical circulator is also used for inputting reflected light reversely transmitted by the single-mode input end of the double-cladding coupler into the photoelectric detector; the photoelectric detector converts the light intensity of the reflected light into a voltage signal, the direct current component of the voltage signal is input into the feedback control device, and the alternating current component is input into the data acquisition system; the feedback control device is used for measuring the reflection spectrum of the all-fiber ultrasonic endoscope and controlling the output wavelength of the narrow linewidth laser to be positioned at the position with the maximum slope of the reflection spectrum; the data acquisition system is used for acquiring, quantifying and storing voltage signals as imaging data of the scanning point; the electric displacement controller is used for controlling the electric displacement table to move to the next scanning point after the imaging data are stored;
the operating point determination of the all-fiber ultrasonic endoscope is required before the imaging system begins an imaging scan. And the feedback control device controls the wavelength of the narrow linewidth laser which is output by the narrow linewidth laser to scan, and draws the reflection spectrum of the all-fiber ultrasonic endoscope through the direct current component of the voltage signal output by the direct current output end of the photoelectric detector. The feedback control device controls the output wavelength of the narrow linewidth laser to the position with the maximum slope of the reflection spectrum, monitors the reflection spectrum change of the all-fiber ultrasonic endoscope in real time through the direct current component of the voltage signal output by the direct current output end of the photoelectric detector in the imaging scanning process, and controls the output wavelength of the narrow linewidth laser 2 to be stabilized at the position with the maximum slope of the reflection spectrum in a real-time feedback manner.
Preferably, the multimode input end of the double-clad coupler is multimode optical fiber, the single-mode input end is single-mode optical fiber, and the output end is double-clad optical fiber; the parameters of the double-clad optical fiber at the output end of the double-clad coupler are the same as those of the double-clad optical fiber of the guide optical fiber of the all-fiber ultrasonic endoscope;
preferably, the sampling rate of the photodetector is greater than 100MHz;
preferably, the step precision of the electric displacement table controller is less than 10 mu m;
preferably, the feedback control device comprises a data acquisition card and a narrow linewidth laser controller; the data acquisition card is used for acquiring, quantifying and storing direct-current voltage signals output by the photoelectric detector; the narrow linewidth laser controller is used for controlling the wavelength of the signal light output by the narrow linewidth laser.
In general, the above technical solutions conceived by the present invention, compared with the prior art, enable the following beneficial effects to be obtained:
1. 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 all-fiber ultrasonic endoscope can simultaneously realize lateral excitation and lateral detection of the ultrasonic waves by using a single optical fiber.
2. According to the invention, the medium mirror with wavelength selective transmission is introduced into the all-fiber ultrasonic endoscope, so that excitation laser is transmitted to the excitation film through the medium mirror and absorbed by the excitation film for generating ultrasonic waves, signal light is reflected between the two medium mirrors and multi-beam interference occurs, a detected ultrasonic signal is modulated onto the light intensity of the reflected light, and ultrasonic excitation and ultrasonic detection are simultaneously realized by using one optical fiber in the all-fiber ultrasonic endoscope.
3. According to the invention, the heat insulation film is introduced into the all-fiber ultrasonic endoscope, so that the heat of the excitation film in the ultrasonic excitation process cannot be conducted to the sensing film to cause the thermal expansion of the sensing film, and the crosstalk of the ultrasonic excitation process to the ultrasonic detection process is prevented.
4. The invention adopts double-cladding optical fibers as the guiding optical fibers, and the signal light is transmitted in a single mode in the fiber core, so that the inter-mode interference of the signal light is avoided, and the noise in ultrasonic detection is reduced; the excitation light is transmitted by the inner cladding, and the characteristic that the effective area of the inner cladding is large is utilized, so that the high-energy excitation laser transmission below the damage threshold of the optical fiber is realized, and the ultrasonic intensity generated by the all-fiber ultrasonic endoscope is improved.
5. According to the invention, the sensing films are wrapped by the two dielectric mirrors to form the Fabry-Perot resonant cavity, the ultrasonic signals detected by the endoscope are modulated to the light intensity signals of the reflected light, the sensitivity of the system is greatly improved, and the ultrasonic endoscopic detection with low noise and equivalent pressure can be realized. Meanwhile, the Fabry-Perot interference type sensor is adopted, so that the imaging system is insensitive to interference such as vibration in the external environment, and the stability of the system is further improved.
6. The invention introduces a feedback control system for the narrow linewidth laser, and by carrying out real-time monitoring on the direct current component of the light intensity of the reflected light and carrying out real-time feedback control on the output wavelength of the narrow linewidth laser, the problem that the sensing sensitivity is reduced due to spectral drift of the sensing film of the all-fiber ultrasonic endoscope, which is influenced by temperature change in the external environment, is avoided, and the sensitivity stability of the system is effectively improved.
Drawings
FIG. 1 is a schematic view of an all-fiber ultrasonic endoscope in accordance with the present invention;
FIG. 2 is a schematic diagram of an all-fiber ultrasonic endoscopic imaging system of the present invention;
the same reference numbers are used throughout the drawings to reference like elements or structures, wherein: 1. exciting the laser; 2. a narrow linewidth laser; 3. an optical circulator; 4. feedback control means; 5. a photodetector; 6. a data acquisition device; 7. a double-clad coupler; 8. an electric displacement table controller; 9. an all-fiber ultrasonic endoscope; 91. guiding the optical fiber; 92. exciting laser; 93. a signal light; 94. a dielectric mirror; 95. a sensing film; 96. a heat insulating film; 97. exciting the film; 98. a focusing acoustic mirror; 99. and a lateral guiding tube.
Detailed Description
The present invention will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention. In addition, the technical features of the embodiments of the present invention described below may be combined with each other as long as they do not interfere with each other.
Fig. 1 is a schematic structural view of an all-fiber ultrasonic endoscope in the present invention. As shown in fig. 1, the present invention proposes an all-fiber ultrasonic endoscope including a guide optical fiber 91, a dielectric mirror 94, a sensing film 95, a heat insulating 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 of which is used for transmitting the excitation laser 92, and the core is used for transmitting the signal light 93. The proximal end face of the guide optical fiber 1 is polished or cut flat, and a layer of cured ultraviolet glue wrapped with a dielectric film having wavelength selective permeability is deposited on the proximal end face of the guide optical fiber 91 as the dielectric mirror 94 and the sensing film 95. The dielectric mirror 94 is used for pressing the sensing film 95 and changing the thickness thereof when being excited by the ultrasonic wave to be measured, and the changing frequency is equal to the frequency of the incident ultrasonic wave, so as to change the cavity length of the fabry-perot resonant cavity formed by the dielectric mirror 94, change the optical path length of the signal light 93, realize modulating the detected ultrasonic wave signal onto the phase of the signal light 93, and further change the optical power of the reflected light reversely transmitted in the guide optical fiber 91 by multi-beam interference. A parylene C film is deposited on the outside surface of the dielectric mirror 94 as the insulating film 96 to prevent heat from the excitation film 97 from being transferred to the sensing film 95 during ultrasonic excitation to cause thermal expansion of the sensing film, thereby preventing crosstalk of the ultrasonic excitation process to the ultrasonic detection process. A layer of a mixture of cured carbon black and Polydimethylsiloxane (PDMS) is deposited onto the surface of the insulating film 96 as the excitation film 97 for absorbing excitation laser light and generating an ultrasonic signal by excitation of the photoacoustic effect. A 45 ° cylindrical concave reflecting mirror is fixed at the front end of the guide optical fiber 91, and is used as the focusing acoustic reflecting mirror 98, for reflecting the ultrasonic signal generated by the excitation film 97 to the lateral propagation of the guide optical fiber 91, and reflecting the ultrasonic signal to be measured propagated laterally to the direction opposite to the guide optical fiber 91. An aluminum tube having a lateral opening is used as the lateral guide tube 99 for fixing the guide optical fiber 91 and the focusing acoustic mirror 98, so that a gap of 1mm exists between the excitation film 97 deposited on the proximal end surface of the guide optical fiber 91 and the focusing acoustic mirror 98, and the lateral opening direction of the lateral guide tube 99 is consistent with the reflecting direction of the focusing acoustic mirror 98, so that ultrasonic signals are input and output to and from the optical fiber ultrasonic endoscope 9 according to the fixing direction.
Specifically, the core diameter of the guiding fiber 91 is smaller than 10 micrometers, the transmission mode is single-mode transmission, and the signal light 93 is transmitted in the core. The diameter of the inner cladding of the guide fiber 91 is greater than 10 μm, the transmission mode is multimode transmission, and the excitation laser 92 is transmitted in the inner cladding. Further illustratively, the outer cladding of the guide fiber 91 is configured to bind the excitation laser 92 and the signal light 93.
Specifically, the guide fiber 91 has a core diameter of 9 microns, an inner cladding diameter of 105 microns, an outer cladding diameter of 125 microns, and the excitation laser 92 is pulsed light or modulated continuous light, and the signal light 93 is narrow linewidth laser light.
Specifically, the dielectric mirror 94 is a dielectric thin film formed by alternately depositing two different inorganic materials having refractive indexes of 1.5 to 2.9, has a transmittance of 80% or more for the wavelength of the excitation laser 92, has a reflectance of 95% or more for the wavelength of the signal light 93, has a film thickness of 1 μm to 100 μm, and has good adsorptivity with the guide optical fiber 91 and the sensing thin film 95.
Specifically, the material of the sensing film 95 is a polymer material with Young's modulus of 100MPa-100GPa, and has a transmittance of 90% or more for the wavelength of the exciting laser 92 and the signal light 93, and a thermal expansion coefficient of less than 10 -4 The film thickness is 1 μm to 1mm at/. Degree.C, and has good adsorptivity with the dielectric mirror 94.
Specifically, the heat insulating film 96 is a heat insulating material having a thermal conductivity of less than 0.1W/(mK), has a transmittance of 95% or more to the excitation laser wavelength, has a film thickness of 1 μm to 10 μm, and has good adsorptivity to the dielectric mirror 94.
Specifically, the excitation thin film 97 is a light absorbing material having an optical absorptivity of 80% or more at the wavelength of the excitation laser 92, a particle size of 10nm to 1 μm, and a thermal expansion coefficient of more than 10 -4 The polymer mixture composition at a temperature of 1 μm to 500 μm in film thickness and has good adsorptivity with the heat insulating 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, and is made of an acoustic reflecting material with an acoustic impedance of more than 18MPa s/m.
Specifically, the lateral guiding 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 is fixed in the lateral guiding tube 99 relative to the guiding optical fiber 91, and the distance between the two is 2mm-10mm, and the distance is consistent with the focal length of the focusing acoustic reflector 98.
The invention further provides a method for preparing the all-fiber ultrasonic endoscope, which comprises the following specific steps:
s1, cutting or polishing one end of the guide optical fiber 91 to be flat, and sequentially and alternately depositing multiple layers of silicon dioxide and titanium dioxide on the flat end surface of the guide optical fiber 91 by using a vacuum evaporation coating method to serve as the inner side surface of a dielectric mirror 94.
S2, immersing one end of the guide optical fiber 91 with the inner side surface of the dielectric mirror 94 into liquid ultraviolet glue, standing for 1 min, slowly lifting out the guide optical fiber 91 at a speed of 10 mu m/S, and using an ultraviolet curing lamp to irradiate the end face of the optical fiber until the ultraviolet glue adsorbed on the end face of the optical fiber is completely cured, so as to form a sensing film 95.
The time for irradiating the end face of the optical fiber by the ultraviolet curing lamp is two hours, and the optical fiber is vertically hung and placed for one circle after the film coating is finished, so that the ultraviolet glue obtains the maximum heat resistance.
S3, depositing a dielectric film which is the same as the inner side surface of the dielectric mirror 94 on the surface of the sensing film 95 by using a vacuum evaporation coating method, wherein the dielectric film is used as the outer side surface of the dielectric mirror 94.
S4, a layer of parylene C is deposited on the outer side surface of the dielectric mirror 94 by a vapor deposition coating method to serve as a heat insulation film 96.
S5, mixing carbon black and PDMS according to the following formula 1: mixing the materials according to the mass ratio of 5, uniformly stirring, putting the materials into a vacuum drying oven for two hours, and discharging bubbles in the mixture.
S6, immersing one end of the guide optical fiber 91 with the heat insulation film 96 into the mixture of carbon black and PDMS, standing for 1 min, slowly pulling out the guide optical fiber 91 at a speed of 10 μm/S, and irradiating the end face of the optical fiber with a heating lamp until the mixture adsorbed on the end face of the optical fiber is completely cured to form an excitation film 97.
The time for irradiating the end face of the optical fiber with the heating lamp was two hours, and after the end of the pulling coating, the optical fiber was hung vertically for one week to completely cure the mixture of carbon black and PDMS.
S7, fixing the guide optical fiber 91 and a cylindrical concave spherical reflector serving as a focusing sound reflector 98 in a laterally opened aluminum tube serving as a lateral guide tube 99, wherein an excitation film 97 deposited on the guide optical fiber 91 is 2mm away from a 45 DEG reflecting surface of the focusing sound reflector 98, and the lateral opening of the lateral guide tube 99 is consistent with the reflecting direction of the focusing sound reflector 98.
Further, the dielectric mirror 94 is a dielectric film formed by sequentially depositing a plurality of layers of silicon dioxide and titanium dioxide alternately, and is a periodic refractive index modulated structure capable of producing high reflectivity for light of a specific wavelength and high transmissivity for light of another specific wavelength. By designing parameters of the dielectric film, the dielectric film has high transmittance for the excitation laser 92 wavelength and high reflectance for the signal light 93 wavelength.
When the excitation laser 92 is injected into the all-fiber ultrasonic endoscope 9, the excitation laser 92 sequentially penetrates through the dielectric mirror 94, the sensing film 95 and the heat insulation film 96 along the guide optical fiber 91, and finally irradiates the excitation film 97, so that the excitation film 97 generates temperature rise and thermal elastic expansion, compresses surrounding media and generates ultrasonic waves which propagate outwards.
The ultrasonic wave generated by the all-fiber ultrasonic endoscope 9 is reflected by the focusing acoustic reflector 98 and is transmitted out of the all-fiber ultrasonic endoscope 9 from the lateral opening of the lateral guide tube 99, the ultrasonic wave reflected by the object to be tested and carrying the imaging information of the object to be tested enters the all-fiber ultrasonic endoscope 9 from the lateral opening of the lateral guide tube 99, is reflected by the focusing acoustic reflector 98 and is focused on the dielectric mirror 94 to press the sensing film 95, and the imaging information of the object to be tested carried by the ultrasonic wave is modulated on the light intensity of interference light.
When the signal light 93 is injected into the all-fiber ultrasonic endoscope 9, multi-beam interference occurs due to the function of the fabry-perot cavity formed by the dielectric mirror 94, so as to form interference light reversely transmitted along the guide optical fiber 91, and the intensity of the interference light is as follows:
wherein I is i Is the light intensity of the incident signal light 93, R is the reflectance of the single-side surface of the dielectric mirror 94 at the wavelength of the signal light 93, δ=4ρn 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 sensing film 95 material, and h is the physical length between the two side surfaces of the dielectric mirror 94.
The ultrasonic wave to be measured acts on the dielectric mirror 94 to cause the ultrasonic wave to press the sensing film 95 so as to change the optical path length of the signal light 93, and intensity modulation of interference light is realized through multi-beam interference.
Fig. 2 is a schematic diagram of a fiber optic ultrasonic endoscopic imaging system of the present invention. As shown in fig. 2, the invention also provides an imaging system of the all-fiber ultrasonic endoscope prepared based on the preparation method, which 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, an electric displacement table controller 8 and an all-fiber ultrasonic endoscope 9.
Further, the output end of the excitation laser 1 is connected to the multimode input end of the double-clad coupler 7, the output end 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 end of the double-clad coupler 7, 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, the dc output end of the photodetector 5 is connected to the input end of the feedback control device 4, the output end of the feedback control device 4 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 ultrasonic endoscope 9, and the all-fiber ultrasonic endoscope 9 is fixed on an electric displacement table controlled by the electric displacement table controller 8.
Specifically, the excitation laser 1 generates a high energy pulsed laser as the excitation laser 92 that is coupled into the multimode input of the double-clad coupler. The narrow linewidth laser 2 generates continuous narrow linewidth laser light as the signal light 93 input through the first port of the optical circulator 3 and output from the second port to the single-mode input terminal of the double-clad coupler. The excitation laser 92 and the signal light 93 are coupled by the double-clad coupler 7 and then input into the all-fiber ultrasonic endoscope 9. The signal light 93 forms interference light of reverse transmission after multi-beam interference occurs in the all-fiber ultrasonic endoscope 9, and the interference light is input to the output end of the double-cladding coupler 7, output from a single-mode input end into the second port of the optical circulator 3, and output from a third port to the input end of the photodetector 5. The photodetector 5 converts the light intensity signal received by the input end of the photodetector into an electric signal, and respectively outputs a direct current component and an alternating current component, wherein the alternating current component is output from an alternating current output end to the input end of the data acquisition device 6, and the direct current component is output from the direct current output end to the feedback control device 4. The data acquisition device 6 acquires, quantifies and stores the voltage signal input by 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, and is used for controlling the output narrow linewidth laser wavelength. 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.
Further, it is described that the operating point determination of the all-fiber ultrasonic endoscope 9 is required before the imaging system starts the imaging scan. The feedback control device 4 controls the wavelength of the narrow linewidth laser 2 to output the narrow linewidth laser for scanning, and the direct current component of the voltage signal output by the direct current output end of the photoelectric detector 5 is used for drawing the reflection spectrum of the all-fiber ultrasonic endoscope 9. The feedback control device 4 controls the output wavelength of the narrow linewidth laser 2 to the position with the maximum slope of the reflection spectrum, monitors the reflection spectrum change of the all-fiber ultrasonic endoscope 9 in real time through the direct current component of the voltage signal output by the direct current output end of the photoelectric detector 5 in the imaging scanning process, and controls the output wavelength of the narrow linewidth laser 2 to be stabilized at the position with the maximum slope of the reflection spectrum in real time.
Specifically, the wavelength of the excitation laser 92 output by the excitation laser 2 is 1064nm, and the wavelength of the signal light 93 output by the narrow linewidth laser 3 is 1550nm.
Specifically, the multimode input end of the double-clad coupler 7 is a multimode optical fiber, the single-mode input end is a single-mode optical fiber, and the output end is a double-clad optical fiber which has the same parameters as the double-clad optical fiber of the guide optical fiber 1 in the all-fiber ultrasonic endoscope 9.
Specifically, the sampling rate of the photodetector 5 is greater than 100MHz.
Specifically, the step accuracy of the electric displacement table controller 8 is less than 10 μm.
The all-fiber ultrasonic endoscope provided by the invention can be applied to ultrasonic excitation and detection in different medium environments, such as water, air and other liquid environments.
It will be readily appreciated by those skilled in the art that the foregoing description is merely a preferred embodiment of the invention and is not intended to limit the invention, but any modifications, equivalents, improvements or alternatives falling within the spirit and principles of the invention are intended to be included within the scope of the 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.
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