A photoacoustic microscopy imaging system based on a high-speed focuser

Abstract

The present invention discloses a photoacoustic microscopy imaging system based on a high-speed focuser. The photoacoustic microscopy imaging system includes a light source component, a single-mode fiber coupling component, a high-speed focuser component, a light beam scanning component, a reflective bracket, a signal acquisition component and a computer. The present invention adopts a mobile focusing design. During the photoacoustic imaging point scanning process, the displacement of the double-cemented lens is controlled by the movement of a fast linear motor, and then the focal position of the light beam is adjusted, so that during the scanning process, the focal plane at any position always coincides with the imaging surface. The present invention establishes an imaging method for automatically adjusting the focal plane by adopting a high-speed focuser, which effectively improves the image signal-to-noise ratio and resolution, and is low in price and easy to operate. The present invention adjusts the imaging in real time according to the photoacoustic signal fed back during the scanning process, and can perform photoacoustic microscopy imaging of any unknown surface, which has broad research prospects and application value.

Description

Technical Field

[0001] The invention belongs to the field of optical medical imaging equipment, and in particular relates to a photoacoustic microscopic imaging system based on a high-speed focuser. Background Art

[0002] Optical resolution photoacoustic imaging is a new non-destructive medical imaging mode with high resolution and high contrast that has developed rapidly in the past decade. It has attracted increasing attention at home and abroad and has been successfully applied in fields such as biomedicine and clinical diagnosis.

[0003] At present, the scanning methods of photoacoustic imaging are mainly divided into two categories. One scanning method is to use a mechanical scanning photoacoustic microscopy imaging system or a target object to obtain an image of the target object. This mechanical scanning method has high requirements on the motion accuracy of the linear electric translation stage. At the same time, it is limited by the slider and screw structure of the electric translation stage, and the imaging speed of the target object is slow. The other is to use a scanning galvanometer for light scanning. This method can have a very fast imaging speed, but the optical path of light will change for different imaging points during the scanning process, so that the imaging surface and the focal plane of the light cannot perfectly coincide. In addition, traditional photoacoustic microscopy is generally used for imaging of planar objects, and it is difficult to have a good effect on imaging targets with large curvatures. Summary of the invention

[0004] 1. Technical issues to be resolved

[0005] In view of the shortcomings of the imaging method based on scanning galvanometer, the present invention proposes a photoacoustic microscopic imaging method based on a high-speed focuser, which not only retains the fast imaging speed of the light scanning method, but also makes real-time adjustments according to the gap between the focal plane and the imaging plane through a fast focusing method, so that the focal plane of light coincides with the imaging plane, thereby improving the resolution of the entire imaging plane. Through the present invention, photoacoustic microscopic imaging of any curved surface can be performed.

[0006] (II) Technical solution

[0007] In order to solve the technical problem, the present invention provides a photoacoustic microscopy imaging system based on a high-speed focuser, and the specific technical solution is as follows.

[0008] A photoacoustic microscopy imaging system based on a high-speed focuser, characterized in that the photoacoustic microscopy imaging system comprises a light source component, a single-mode optical fiber coupling component, a high-speed focuser component, a beam scanning component, a reflective bracket, a signal acquisition component and a computer;

[0009] The light source assembly includes a nanosecond pulse laser, which emits a pulse laser, which enters the high-speed focuser assembly after being collimated by the single-mode optical fiber coupling assembly, and the focused light beam enters the light beam scanning assembly;

[0010] The single-mode fiber coupling assembly includes a fiber coupling assembly, and the fiber coupling assembly includes a spatial light filter, an objective lens, a single-mode fiber coupler, a single-mode fiber, and a collimating lens;

[0011] The high-speed focuser assembly includes a fast linear motor, a double-glued lens and a first channel of a multifunctional function generator; a telescopic movable focusing design is adopted, wherein the fast linear motor is coaxially mechanically connected to the double-glued lens, and the fast linear motor is electrically connected to the multifunctional function generator; during the photoacoustic imaging point scanning process, the fast linear motor is used to move and control the displacement of the double-glued lens, thereby adjusting the focal position of the light beam, so that during the scanning process, the focal plane at any position always coincides with the imaging surface;

[0012] The beam scanning assembly includes a micro-electromechanical scanning galvanometer, a second and third channels of a multifunctional function generator for driving the micro-electromechanical scanning galvanometer, and a voltage-stabilized power supply for the micro-electromechanical scanning galvanometer;

[0013] The reflective bracket is a closed cavity filled with transparent ultrasonic coupling liquid, including a light inlet and a light outlet, the target object is arranged at the light outlet, and a light-transmitting anti-sound sheet is arranged inside the reflective bracket; wherein the center of the light inlet is collinear with the center of the light reflected by the micro-electromechanical scanning galvanometer, and the central axis of the micro-electromechanical scanning galvanometer mirror coincides with the midpoint of the line detection area of ​​the ultrasonic detector;

[0014] The signal acquisition component includes an ultrasonic detector, a high-frequency low-noise signal amplifier, a bandpass filter and a data acquisition card; wherein the ultrasonic detector, the high-frequency low-noise signal amplifier, the bandpass filter and the data acquisition card are electrically connected in sequence, the signal is detected by the ultrasonic detector, amplified by the high-frequency low-noise signal amplifier and filtered by the bandpass filter, and finally the data is collected by the data acquisition card.

[0015] More specifically, the pulse light emitted from the nanosecond pulse laser passes through the spatial light filter, objective lens, single-mode fiber coupler, single-mode fiber and collimating lens in the fiber coupling component in sequence to output a collimated light beam, passes through the high-speed focuser component, forms focused light through the double-cemented lens, enters the light beam scanning component, and enters the reflective bracket component after being reflected by the micro-electromechanical scanning galvanometer; the multifunctional function generator is controlled by the computer, and the multifunctional function generator is controlled by the same clock source, so that the signals used to drive the fast linear motor to move and the micro-electromechanical scanning galvanometer to rotate are output synchronously to ensure the correspondence between the focusing position and the scanning position; the focused light beam enters the reflective bracket through the light inlet, reacts with the target object through the light outlet to generate a photoacoustic signal and backscattered light, the generated photoacoustic signal is reflected by the light-transmitting anti-sound thin sheet to the signal acquisition component, and the photoacoustic signal is detected by the ultrasonic detector, amplified by the high-frequency low-noise signal amplifier and filtered by the bandpass filter, and finally the signal data is collected by the data acquisition card.

[0016] More specifically, for the case where the surface shape of the imaging object is known, the computer calculates the optical path difference between each scanning point of the focal plane and the image plane in advance, and converts it into a corresponding control output signal; during the scanning imaging process, the multifunctional function generator outputs the control output signal calculated in advance, and synchronously controls the micro-electromechanical scanning lens and the fast linear motor. For each scanning point, the double-cemented lens is driven by the fast linear motor to move a corresponding distance to compensate for the optical path difference between the focal plane and the imaging plane during the scanning process, thereby ensuring that the focal plane and the imaging plane coincide with each other.

[0017] More specifically, for the case where the surface shape of the imaging surface is unknown, after the scanning feedback photoacoustic signal is obtained through the signal acquisition component, the relative time information of the photoacoustic signal is collected according to the data acquisition card, the collected photoacoustic signal information is calculated in real time by the computer, and the imaging surface shape is inferred by inversion through synchronous processing to generate an adjustment control signal, and the adjustment signal is output by the multi-functional function generator to control the movement of the fast linear motor, and the focal plane is adjusted in real time to make it coincide with the imaging surface.

[0018] More specifically, the following method is used to obtain feedback signals in real time: through the reciprocating scanning method, the first B-scan scan is performed, and the micro-electromechanical scanning galvanometer is controlled by a multifunctional function generator to realize the scanning of light on a cross section of the imaging object, and the photoacoustic signal is obtained through the data acquisition component, and the A-line information of the acquired signal is analyzed by a computer to obtain the time series of the photoacoustic signal, thereby calculating the relative time from the generation to the detection of the photoacoustic signal, thereby calculating the relative distance of the signal source at that point on the imaging surface from the ultrasonic detector, obtaining the shape characteristics of the imaging target in the scanning cross section, and generating a control signal of a fast linear motor; and then through the second B-scan scan, the micro-electromechanical scanning galvanometer is controlled by a multifunctional function generator to repeatedly scan the same position, and the control signal of the fast linear motor generated by the first B-scan scan is synchronously output to the fast linear motor, so that it drives the double-cemented lens to move, and performs optical path compensation, so as to achieve the overlap of the focal plane and the image plane.

[0019] More specifically, the reflective bracket is a rectangular cavity, and the light-transmitting and sound-reflecting thin sheet forms an angle of 45° with the light outlet and the side where the ultrasonic detector is located.

[0020] More specifically, the ultrasonic detector of the signal acquisition component is placed in a reflective bracket. The photoacoustic signal generated by the sample is reflected by the light-transmitting and sound-reflecting thin film in the reflective bracket, detected by the ultrasonic detector, and transmitted to the computer through the high-frequency and low-noise signal amplifier, bandpass filter and data acquisition card for storage and processing.

[0021] More specifically, a rotating motor is used to drive the gears to rotate, thereby driving the ultrasonic detector, which greatly reduces the mass and volume compared to the previous electric linear translation stage or electric rotation stage.

[0022] More specifically, the connection relationship between the various components is as follows:

[0023] The nanosecond pulse laser is connected to the spatial optical filtering device; the filtered light is injected into the single-mode optical fiber coupler, one end of the single-mode optical fiber is fixed at the center of the coupler, and the signal trigger port of the nanosecond pulse laser is electrically connected to the multifunctional function generator and the computer respectively;

[0024] The single-mode optical fiber is connected to the lower end of the fast linear motor through a collimating lens of the corresponding wavelength, and the light is emitted from the central cavity of the fast linear motor to reach the focusing light beam of the upper stroke of the focusing double-cemented lens; the focused light is hit into the mirror surface of the micro-electromechanical scanning galvanometer, and is reflected into the reflective bracket; the ultrasonic detector is installed together in the reflective bracket, so that the central axis of the mirror surface of the micro-electromechanical scanning galvanometer coincides with the midpoint of the line detection area of ​​the ultrasonic detector, and at the same time, the laser focus of the micro-electromechanical scanning galvanometer and the line detection area of ​​the ultrasonic detector are on the same imaging end surface;

[0025] The interior of the imaging end is filled with colorless ultrasonic coupling agent and obliquely embedded with transparent inorganic polymer materials that transmit lasers and reflect ultrasonic waves. A waterproof bearing is fixed to the end of the imaging end connected to the ultrasonic detector, so that the ultrasonic detector can rotate freely inside it while ensuring that the ultrasonic coupling agent will not leak out from the connection. The target object is kept at a certain distance from the imaging end surface, and the ultrasonic coupling agent is coated between them;

[0026] The fast linear motor and the micro-electromechanical scanning galvanometer are electrically connected to the multifunctional function generator; the line-focused ultrasonic detector is driven by the rotating motor through gears; the computer controls the fast linear motor through the output signal of the multifunctional function generator; the line-focused ultrasonic detector, the radio frequency conductive slip ring, the high-frequency low-noise signal amplifier, the band-pass filter and the data acquisition card are electrically connected in sequence.

[0027] (III) Beneficial effects

[0028] Compared with the prior art, the present invention has significant positive technical effects, and its beneficial effects are at least reflected in the following aspects. (1) The existing light-focusing photoacoustic microscopy system often uses a scanning lens to correct the focal plane of light. Due to the characteristics of the scanning lens, the surface of the imaging object can only be a fixed shape, and it is difficult to achieve high-resolution imaging of an imaging surface with an arbitrary curved surface. The present invention uses a high-speed focuser and a mobile focusing design. During the scanning process of the photoacoustic imaging point, the displacement of the double-cemented lens is controlled by the movement of a fast linear motor, thereby adjusting the focal position of the light beam, which also achieves the correction of the focal plane of light and realizes a light focusing surface of an arbitrary shape, thereby achieving high-resolution photoacoustic curved surface imaging. (2) It is difficult to achieve real-time imaging of unknown imaging surfaces with the existing technology, and it is often necessary to manually focus or pre-scan an entire image in advance for imaging. The present invention uses reciprocating scanning. The first B-scan scan obtains the time series of the photoacoustic signal through the A-line information, calculates the relative distance between the signal source at that point on the imaging surface and the ultrasonic detection probe, and obtains the shape characteristics of the imaging target in the scanning section; the second B-scan scan repeats the scanning of the same position, and performs optical path compensation and automatic focusing based on the shape information obtained in the first scan. In this way, real-time imaging of unknown imaging surfaces can be achieved, and this real-time focusing method can also effectively deal with the problem of movement of the imaging surface in the vertical optical focal plane direction caused by breathing in living body imaging. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of the system structure of the present invention.

[0030] In the figure, there are nanosecond pulse laser 1, spatial light filter 2-1, objective lens 2-2, single-mode fiber coupler 2-3, single-mode fiber 2-4, collimating lens 2-5, fast linear motor 3-1, double glued lens 3-2, multifunctional function generator 3-3, micro-electromechanical scanning lens 4-1, voltage-stabilized power supply 4-2, reflective bracket 5, light-transmitting anti-sound film 5-1, ultrasonic detector 6-1, high-frequency low-noise signal amplifier 6-2, data acquisition card 6-3, and computer 7. DETAILED DESCRIPTION

[0031] In order to solve the technical problem, the present invention provides a photoacoustic microscopy system based on a high-speed focuser. The technical solution of the present invention is further described below through specific implementation methods in conjunction with the accompanying drawings of the specification.

[0032] Figure 1 The present invention provides a schematic diagram of the system structure of a photoacoustic microscopic imaging system based on a high-speed focuser, which includes a nanosecond pulse laser 1, a single-mode fiber coupling component 2, a high-speed focuser component 3, a beam scanning component 4, a reflective bracket 5, a signal acquisition component 6 and a computer 7. The computer 7 is equipped with acquisition control software and data processing software, the acquisition control software may be Labview software, and the data processing software may be Matlab software; the acquisition control software is used to control the fast focusing component 3 and the beam scanning component 4 to scan the imaging target and adjust the focus in real time, and the signal acquisition component 6 to collect the photoacoustic signal at each scanning point in the imaging area; the data processing software processes the collected signals and reconstructs the photoacoustic image of the imaging target.

[0033] The working process and principle of the present invention are as follows:

[0034] In the case of a known imaging object surface shape, the nanosecond pulse laser 1 emits a pulse laser, which enters the light inlet of the reflective bracket 5 after passing through the single-mode fiber coupling component 2, the high-speed focuser component 3 and the beam scanning component 4, and is focused to the target object surface at the light outlet of the reflective bracket 5 through the ultrasonic coupling liquid and the light-transmitting anti-sound thin film 5-1, generating a photoacoustic signal; the computer 7 controls the rotation of the micro-electromechanical scanning galvanometer 4-1 through the multifunctional function generator 3-3, so that the focused pulse laser scans along the imaging area of ​​the ultrasonic detector, and at the same time, according to the scanning trajectory of the light, drives the fast linear motor 3-1 through the multifunctional function generator 3-3, drives the double glued lens 3-2, and corrects the focal plane, so that the focal plane always coincides with the imaging surface at any scanning position. The photoacoustic signal generated at each scanning position is transmitted through the ultrasonic coupling liquid, and is reflected by the light-transmitting anti-sound thin film 5-1 inside the reflective bracket 5 to the ultrasonic detector 6-1, and is transmitted to the computer 7 through the high-frequency low-noise signal amplifier 6-2 and the data acquisition card 6-3 for storage and processing.

[0035] For the case of unknown imaging object surface shape, the overall situation is roughly the same as the above-mentioned case of known imaging object surface shape. After obtaining the scanning feedback photoacoustic signal, the imaging surface shape is inferred in real time based on the relative time information of the photoacoustic signal, and the adjustment signal is output to control the movement of the fast linear motor, and the focal plane is adjusted in real time to make it coincide with the imaging surface. The following method is used to obtain the feedback signal in real time: through the reciprocating scanning method, the first B-scan scan is performed, and the time series of the photoacoustic signal is obtained through the A-line information, so as to calculate the relative time from the generation to the detection of the photoacoustic signal, and then the relative distance from the signal source at this point on the imaging surface to the ultrasonic detection probe is calculated, and the shape characteristics of the imaging target in the scanning section are obtained; then the second B-scan scan is performed to repeatedly scan the same position, and according to the shape information obtained in the first scan, the processing method of the known imaging object surface shape is adopted to perform optical path compensation, so as to achieve the coincidence of the focal plane and the image plane.

[0036] The specific implementation cases described in this application are merely examples of the main ideas of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in similar ways, but they will not deviate from the spirit of the present invention or exceed the scope defined by the attached claims.

Claims

1. A photoacoustic microscopy imaging system based on a high-speed focuser, characterized in that: The photoacoustic microscopy imaging system includes a light source component, a single-mode optical fiber coupling component, a high-speed focusing component, a beam scanning component, a reflective bracket, a signal acquisition component and a computer; The light source assembly includes a nanosecond pulse laser, which emits a pulse laser, which enters the high-speed focuser assembly after being collimated by the single-mode optical fiber coupling assembly, and the focused light beam enters the light beam scanning assembly; The single-mode fiber coupling assembly includes a fiber coupling assembly, and the fiber coupling assembly includes a spatial light filter, an objective lens, a single-mode fiber coupler, a single-mode fiber, and a collimating lens; The high-speed focuser assembly includes a fast linear motor, a doublet lens, and a first channel of a multifunctional function generator; A telescopic mobile focusing design is adopted, in which a fast linear motor is coaxially mechanically connected to a double-glued lens, and the fast linear motor is electrically connected to a multifunctional function generator; during the photoacoustic imaging point scanning process, the fast linear motor is used to move and control the displacement of the double-glued lens, thereby adjusting the focal position of the light beam, so that during the scanning process, the focal plane at any position always coincides with the imaging surface; The beam scanning assembly includes a micro-electromechanical scanning galvanometer, a second and a third channel of a multifunctional function generator for driving the micro-electromechanical scanning galvanometer, and a voltage-stabilized power supply for the micro-electromechanical scanning galvanometer; The reflective bracket is a closed cavity filled with transparent ultrasonic coupling liquid, including a light inlet and a light outlet, the target object is arranged at the light outlet, and a light-transmitting anti-sound sheet is arranged inside the reflective bracket; wherein the center of the light inlet is collinear with the center of the light reflected by the micro-electromechanical scanning galvanometer, and the central axis of the micro-electromechanical scanning galvanometer mirror coincides with the midpoint of the line detection area of ​​the ultrasonic detector; The signal acquisition component includes an ultrasonic detector, a high-frequency low-noise signal amplifier, a bandpass filter and a data acquisition card; wherein the ultrasonic detector, the high-frequency low-noise signal amplifier, the bandpass filter and the data acquisition card are electrically connected in sequence, the signal is detected by the ultrasonic detector, amplified by the high-frequency low-noise signal amplifier and filtered by the bandpass filter, and finally the data is collected by the data acquisition card; In the case where the shape of the imaged object surface is known, the computer calculates the optical path difference between each scanning point of the focal plane and the image plane in advance, and converts it into a corresponding control output signal; during the scanning imaging process, the multifunctional function generator outputs the control output signal calculated in advance, and synchronously controls the micro-electromechanical scanning lens and the fast linear motor. For each scanning point, the fast linear motor drives the double-cemented lens to move a corresponding distance to compensate for the optical path difference between the focal plane and the imaging plane during the scanning process, thereby ensuring that the focal plane and the imaging plane coincide with each other; For the case where the surface shape of the imaging surface is unknown, after the scanning feedback photoacoustic signal is obtained through the signal acquisition component, the relative time information of the photoacoustic signal is collected according to the data acquisition card, the collected photoacoustic signal information is calculated in real time by the computer, and the imaging surface shape is inferred by inversion synchronously, and an adjustment control signal is generated. The adjustment signal is output by a multi-functional function generator to control the movement of the fast linear motor, and the focal plane is adjusted in real time to make it coincide with the imaging surface.

2. The photoacoustic microscopy imaging system based on a high-speed focuser according to claim 1, characterized in that: The pulse light emitted from the nanosecond pulse laser passes through the spatial light filter, objective lens, single-mode fiber coupler, single-mode fiber and collimating lens in the fiber coupling component in sequence, and then outputs a collimated light beam, passes through the high-speed focusing device component, forms a focused light through the double-cemented lens, enters the light beam scanning component, and enters the reflective bracket component after being reflected by the micro-electromechanical scanning galvanometer; the multi-function function generator is controlled by the computer, and the multi-channel output of the multi-function function generator is controlled by the same clock source, so that the signals used to drive the fast linear motor movement and the micro-electromechanical scanning galvanometer rotation are output synchronously, ensuring the correspondence between the focusing position and the scanning position; the focused light beam enters the reflective bracket through the light inlet, reacts with the target object through the light outlet to generate a photoacoustic signal and backscattered light, and the generated photoacoustic signal is reflected by the light-transmitting anti-sound thin sheet to the signal acquisition component, and after the photoacoustic signal is detected by the ultrasonic detector, it is amplified by the high-frequency low-noise signal amplifier and filtered by the bandpass filter, and finally the signal data is collected by the data acquisition card.

3. The photoacoustic microscopy imaging system based on a high-speed focuser according to claim 2, characterized in that: The following method is adopted to obtain feedback signals in real time: through the reciprocating scanning mode, the first B-scan scan is performed, and a multifunctional function generator is used to control a micro-electromechanical scanning galvanometer to realize the scanning of light on a cross section of the imaging object, and the photoacoustic signal is obtained through a data acquisition component, and the A-line information of the obtained signal is analyzed by a computer to obtain the time series of the photoacoustic signal, thereby calculating the relative time from the generation to the detection of the photoacoustic signal, thereby calculating the relative distance between the signal source at that point on the imaging surface and the ultrasonic detector, obtaining the shape characteristics of the imaging target in the scanning cross section, and generating a control signal of a fast linear motor; and then through a second B-scan scan, the multifunctional function generator is used to control the micro-electromechanical scanning galvanometer to repeatedly scan the same position, and synchronously output the control signal of the fast linear motor generated by the first B-scan scan to the fast linear motor, so that it drives the double-cemented lens to move, and performs optical path compensation, so as to achieve the overlap of the focal plane and the image plane.

4. The photoacoustic microscopy imaging system based on a high-speed focuser according to claim 1, characterized in that: The reflective bracket is a rectangular cavity, and the light-transmitting and sound-reflecting thin sheet is at an angle of 45° to the light outlet and the side where the ultrasonic detector is located.

5. The photoacoustic microscopy imaging system based on a high-speed focuser according to claim 1, characterized in that: The ultrasonic detector of the signal acquisition component is placed in a reflective bracket. The photoacoustic signal generated by the sample is reflected by the light-transmitting and sound-reflecting thin sheet in the reflective bracket, detected by the ultrasonic detector, and transmitted to the computer through the high-frequency and low-noise signal amplifier, bandpass filter and data acquisition card for storage and processing.

6. The photoacoustic microscopy imaging system based on a high-speed focuser according to claim 1, characterized in that: The rotating motor is used to drive the gears to rotate, thereby driving the ultrasonic detector.

7. The photoacoustic microscopy imaging system based on a high-speed focuser according to any one of claims 1 to 6, characterized in that: The connection relationship between the various components is as follows: The nanosecond pulse laser is connected to the spatial optical filtering device; the filtered light is injected into the single-mode optical fiber coupler, one end of the single-mode optical fiber is fixed at the center of the coupler, and the signal trigger port of the nanosecond pulse laser is electrically connected to the multifunctional function generator and the computer respectively; The single-mode optical fiber is connected to the lower end of the fast linear motor through a collimating lens of a corresponding wavelength. Light is emitted from the central cavity of the fast linear motor and hits the focusing double glued lens to form a focused light beam. The focused light hits the mirror surface of the micro-electromechanical scanning galvanometer and is reflected into the reflective bracket. The ultrasonic detector is installed in the reflective bracket together, so that the central axis of the mirror surface of the micro-electromechanical scanning galvanometer coincides with the midpoint of the line detection area of ​​the ultrasonic detector, and at the same time, the laser focus of the micro-electromechanical scanning galvanometer and the line detection area of ​​the ultrasonic detector are on the same imaging end surface. The interior of the imaging end is filled with colorless ultrasonic coupling agent and obliquely embedded with transparent inorganic polymer materials that transmit lasers and reflect ultrasonic waves. A waterproof bearing is fixed to the end of the imaging end connected to the ultrasonic detector, so that the ultrasonic detector can rotate freely inside it while ensuring that the ultrasonic coupling agent will not leak out from the connection. The target object is kept at a certain distance from the imaging end surface, and the ultrasonic coupling agent is coated between them; The fast linear motor and the micro-electromechanical scanning galvanometer are electrically connected to the multifunctional function generator, the line-focused ultrasonic detector is driven by the rotating motor through gears, and the computer controls the fast linear motor through the output signal of the multifunctional function generator; the line-focused ultrasonic detector, the radio frequency conductive slip ring, the high-frequency low-noise signal amplifier, the band-pass filter and the data acquisition card are electrically connected in sequence.

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