An ultrasonic transmitting and detecting device and method

Abstract

The application belongs to the technical field of ultrasonic detection, and provides an ultrasonic wave emitting and detecting device and method. A pulse excitation light is irradiated to the surface of a sample to be detected through an acoustic lens, the sample to be detected absorbs the light source energy and further causes local thermal expansion, causes vibration, generates ultrasonic waves, the ultrasonic waves propagate to the inside of the sample to be detected, when encountering an interface, reflection is generated, propagates to the surface of the sample to be detected, and then propagates to the air. Since the wave surface diverges in the ultrasonic propagation process, in order to improve the sensitivity, the ultrasonic waves are focused on the film through the acoustic lens, the vibration of the film is detected by using a detection light source, and signal demodulation is performed by using a 3*3 optical fiber coupler. Since the surface of the film is smooth, the method can improve the detection sensitivity and ensure that the sample is not contaminated; the whole device is easy to integrate and miniaturize the ultrasonic emission and ultrasonic detection, and is convenient for actual use.

Description

Technical Field

[0001] This invention relates to the field of ultrasonic testing technology, and in particular to an ultrasonic emission and detection device and method. Background Technology

[0002] Ultrasonic testing equipment is widely used in medicine, industry, aerospace, and marine fields. Most of these devices use piezoelectric transducers to directly emit and detect ultrasonic signals, which are then processed to obtain the corresponding detection information. While piezoelectric transducer-based testing methods have advantages such as mature technology, simple structure, and high sensitivity, the principle of piezoelectric transducers dictates the use of an acoustic coupling medium, which limits their application in many situations. The patented "Online Ultrasonic Thickness Measurement Device" (CN207688849U) utilizes a non-contact water-immersed ultrasonic probe and employs technologies such as normal, pressure, and water pressure closed-loop control to automatically acquire the measurement normal, enabling real-time online thickness measurement. However, this measurement method requires the addition of a coupling agent, making it difficult to meet the rapid measurement requirements of industrial production lines.

[0003] To address the technical challenges of acoustic-based ultrasonic detection, various optical-based ultrasonic detection methods have been proposed, most of which are based on interferometry. When an ultrasonic signal propagates from within a sample to its surface, it causes surface vibration. These methods utilize optical interference to directly detect this vibration and process the ultrasonic signal. Compared to piezoelectric transducer-based methods, optical interferometry offers advantages such as non-contact operation and ease of device miniaturization. Optical methods do not require an acoustic coupling medium, ensuring the sample remains uncontaminated. However, they are susceptible to interference from sample surface roughness, leading to reduced interferometry sensitivity. The patent "A Fully Optical Ultrasonic Detector and Detection Method Based on Differential Interferometry" (CN115166062A) utilizes differential interference to detect photovoltage signals. The photovoltage signal is directly proportional to the square of the sound pressure, allowing for the demodulation of the ultrasonic signal. However, this measurement method is also affected by sample surface roughness. The patent "Laser Ultrasonic Optical Interference Detection Device" (CN203745385U) uses a nonlinear crystal and utilizes its dual-wavelength mixed interference effect to detect light intensity. However, this method is also affected by the roughness of the sample surface, which limits its application in many applications. Summary of the Invention

[0004] The main objective of this invention is to address the problem of interference from sample surface roughness in optical-based ultrasonic detection technology. To address the shortcomings of existing technologies, this invention provides an ultrasonic emission and detection device and method.

[0005] The technical solution of the present invention is as follows: An ultrasonic transmitting and detecting device includes an excitation light source 1, an integrated detection end 2, a detection light source 7, a 2×2 fiber optic coupler 8, a fiber optic circulator 9, a 3×3 fiber optic coupler 13, a photodetector, a high-pass filter, and a computer 20; the integrated detection end 2 is located between the excitation light source 1 and the sample to be tested 6, and includes a dichroic mirror 3, a thin film 4, and an acoustic lens 5 arranged sequentially; the excitation light source 1 is located on the side of the dichroic mirror 3 of the integrated detection end 2; the sample to be tested 6 is located on the side of the acoustic lens 5 of the integrated detection end 2; the acoustic lens 5 is hollow in the middle; the detection light source 7, the 2×2 fiber optic coupler 8, and the fiber optic circulator 9 are arranged sequentially; the fiber optic circulator 9 has three ports, namely the first port 10 of the fiber optic circulator, the second port 10 of the fiber optic circulator, and the third port 10 of the fiber optic circulator. Port 11 and the third port 12 of the fiber optic circulator; the first port 10 of the fiber optic circulator is used to receive the sample light transmitted by the 2×2 fiber optic coupler 8, and the second port 11 of the fiber optic circulator is used to output the sample light to the dichroic mirror 3 and receive the reflected light reflected from the thin film 4 back to the dichroic mirror 3; the third port 12 of the fiber optic circulator is used to output the reflected light to one end of the 3×3 fiber optic coupler 13; the 2×2 fiber optic coupler 8 transmits the reference light to one end of the 3×3 fiber optic coupler 13; the three ports at the other end of the 3×3 fiber optic coupler 13 are respectively connected to three photodetectors, and each photodetector is connected to the data acquisition card 21 in the computer 20 through a high-pass filter; the computer 20 is connected to the excitation light source 1 and controls the light intensity of the excitation light source 1 according to the information output by the data acquisition card 21.

[0006] An ultrasonic emission and detection method, based on an ultrasonic emission and detection device, includes an ultrasonic signal excitation process, an ultrasonic signal detection process, and an ultrasonic signal demodulation process;

[0007] The ultrasonic signal excitation process is as follows: the excitation light source 1 emits a laser, which passes through the dichroic mirror 3 and the thin film 4 in sequence, and then passes through the hollow acoustic lens 5 to irradiate the sample 6 to be tested; the sample 6 to be tested converts the absorbed light energy into heat energy and heats up, causing the sample 6 to expand locally and generate ultrasonic waves; the ultrasonic waves propagate into the interior of the sample 6 to be tested, and when they encounter the interface, they are reflected and propagate to the sample surface, and then propagate into the air.

[0008] The ultrasonic signal detection process is as follows: the acoustic lens 5 focuses the ultrasonic waves generated on the surface of the sample 6 onto the thin film 4, causing the thin film 4 to vibrate; the detection light source 7 emits detection light into the 2×2 fiber coupler 8, and the detection light is split into sample light and reference light; the sample light enters the fiber circulator 9 through the first port 10 of the fiber circulator, and is output from the second port 11 of the fiber circulator. After passing through the dichroic mirror 3, it illuminates the surface of the thin film 4, detecting the vibration of the thin film 4. The sample light is reflected by the thin film 4 according to the intensity of the vibration, producing reflected light with different phase changes; the reflected light reflected from the thin film 4 back to the dichroic mirror 3 enters the second port 11 of the fiber circulator and... The reference light, along with the light from the third port 12 of the fiber optic circulator, enters the 3×3 fiber optic coupler 13. The reference light and the reflected light are split into three paths by the 3×3 fiber optic coupler 13, and three signals are output respectively. The three signals enter photodetectors A14, B15, and C16 respectively. The three signals interfere with each other in the photodetectors and are converted into electrical signals. The electrical signals are filtered out by high-pass filters A17, B18, and C19 respectively before entering the computer 20. The data acquisition card 21 acquires the filtered electrical signals, and the computer 20 finally demodulates the ultrasonic signal.

[0009] The ultrasonic signal demodulation process is specifically as follows:

[0010] The three electrical signals acquired by data acquisition card 21 after passing through the high-pass filter are as follows:

[0011]

[0012] and This indicates the phase difference between the three electrical signals. D represents the phase difference between the reflected light and the reference light that cause interference. i＝1,2,3 For the DC component, A i＝1,2,3 This represents the amplitude of the interference coupling term.

[0013] From equation (1), the phase difference between the reflected light and the reference light that cause interference can be obtained.

[0014]

[0015] Parameter p i＝1,2,3 q i＝1,2,3 Specifically

[0016] Since the above parameters only relate to D i＝1,2,3 and A i＝1,2,3 The ratio is related to the ratio used, and this ratio is a constant for the 3*3 coupler, so I can be measured without exciting an ultrasonic signal. i＝1,2,3 According to Ii＝1,2,3 For D i＝1,2,3 and A i＝1,2,3 The proportions are calibrated.

[0017] Therefore, the intensity of an ultrasonic signal can be expressed as,

[0018]

[0019] λ represents the wavelength of the probe light.

[0020] When the 3×3 fiber coupler 13 uses a splitting ratio of 1:1:1, the phase difference... and They are 120° and 240° respectively.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] 1. Since it detects the vibration of the thin film surface rather than the vibration of the sample surface, it is not affected by the roughness of the sample surface, and has a wider range of applications.

[0023] 2. The acoustic lens, thin film, and dichroic mirror can be integrated into a single cavity, free from interference from the external environment. The device is easy to miniaturize and convenient for daily use.

[0024] 3. The detector and the sample do not need to be in physical contact and no acoustic coupling medium is required, thus ensuring that the sample is not contaminated.

[0025] 4. Using an acoustic lens to acquire ultrasonic signals results in a stronger signal intensity than optical methods. The ultrasonic signal focused by the acoustic lens can be amplified, thereby improving the detection sensitivity of the system.

[0026] 5. By using high-pass filtering and a 3×3 fiber optic coupler to demodulate the ultrasonic signal, the detection process is not affected by external interference and can maintain stable high sensitivity. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of an ultrasonic transmitting and detecting device.

[0028] Figure 2 This is a schematic diagram of the ultrasonic signals detected in the example.

[0029] In the diagram: 1-Excitation source, 2-Integrated detector, 3-Dichroic mirror, 4-Thin film, 5-Acoustic lens, 6-Sample to be tested, 7-Detection source, 8-2×2 fiber optic coupler, 9-Fiber optic circulator, 10-First port of fiber optic circulator, 11-Second port of fiber optic circulator, 12-Third port of fiber optic circulator, 13-3×3 fiber optic coupler, 14-Photodetector A, 15-Photodetector B, 16-Photodetector C, 17-High-pass filter A, 18-High-pass filter B, 19-High-pass filter C, 20-Computer, 21-Data acquisition card. Detailed Implementation

[0030] This invention provides an ultrasonic transmitting and detecting device, the structure of which is as follows: Figure 1 As shown, the specific working process is as follows: the pulsed excitation light passes through the acoustic lens 5 and irradiates the surface of the sample 6 to be tested. The sample 6 absorbs the energy of the light source, which causes local thermal expansion, resulting in vibration and generating ultrasonic waves. The ultrasonic waves propagate into the sample 6 and are reflected when they encounter the interface, propagating back to the surface of the sample 6 and then into the air. Since the wavefront diverges during ultrasonic propagation, the ultrasonic waves are focused onto the thin film 4 through the acoustic lens 5 to improve sensitivity. The vibration of the thin film 4 is detected by the detection light source 7, and the signal is demodulated using a 3×3 fiber coupler 13. Because the surface of the thin film 4 is smooth, the method of the present invention can improve the detection sensitivity and ensure that the sample is not contaminated. The entire device can easily integrate and miniaturize ultrasonic emission and ultrasonic detection, making it convenient for practical use. In this embodiment, the excitation light source 1 uses a 527nm pulsed laser with a pulse width of 7nm; the thin film can be a transparent thin film; the detection light source 7 uses a 1310nm semiconductor laser; and the splitting ratio of the 3×3 fiber coupler 13 in this embodiment is 1:1:1.

[0031] This invention provides a method for ultrasonic emission and detection, comprising the following steps:

[0032] The process of ultrasonic signal excitation: The excitation light source 1 emits a laser, and the excitation light enters the dichroic mirror 3 at an incident angle of 45°. Then, it passes through the thin film 4 and the hollow acoustic lens 5 and irradiates the sample 6 to be tested. The sample 6 absorbs the light energy and converts it into heat energy, causing its own temperature to rise. This leads to the local expansion of the sample 6, thus generating ultrasonic waves. The ultrasonic waves propagate into the sample. When they encounter the interface, they are reflected and propagate to the sample surface, and then propagate into the air.

[0033] The ultrasonic signal detection process: The acoustic lens 5 focuses the ultrasonic waves generated on the surface of the sample 6 onto the thin film 4, causing the thin film 4 to vibrate. The probe light emitted by the probe light source 7 enters the 2×2 fiber coupler 8 and is split into sample light and reference light. The sample light enters the fiber circulator 9 through the first port 10 of the fiber circulator, and is output from the second port 11 of the fiber circulator. After passing through the dichroic mirror 3, it illuminates the surface of the thin film 4, detecting the vibration of the thin film 4. The sample light is reflected by the thin film 4 according to the intensity of the vibration, producing different phase changes. The reflected light from the thin film 4 back to the dichroic mirror 3 enters the second port 11 of the fiber circulator and enters the 3×3 fiber coupler 13 through the third port 12 of the fiber circulator, along with the reference light. The reference light and reflected light are split into three paths by a 3×3 fiber optic coupler 13, and three signals are output respectively. The three signals enter photodetectors A14, B15 and C16 respectively, where they interfere and are converted into electrical signals. After interference is filtered out by high-pass filters A17, B18 and C19, they enter computer 20 and are acquired by data acquisition card 21. Finally, computer 20 demodulates the ultrasonic signal.

[0034] The process of ultrasonic signal demodulation:

[0035] After passing through the high-pass filter, the three electrical signals acquired by data acquisition card 21 are as follows:

[0036]

[0037] and This indicates the phase difference between the three electrical signals. D represents the phase difference between the reflected light and the reference light that cause interference. i＝1,2,3 For the DC component, A i＝1,2,3 This represents the amplitude of the interference coupling term. For a 3×3 fiber coupler with a splitting ratio of 1:1:1 in this embodiment, and They are 120° and 240° respectively.

[0038] From equation (1), the phase difference between the reflected light and the reference light that cause interference can be obtained.

[0039]

[0040] Therefore, the intensity of an ultrasonic signal can be expressed as

[0041]

[0042] The detection method in this implementation case is single-point detection, which detects a tungsten wire with a diameter of 0.4 mm. The detected ultrasonic signal is as follows: Figure 2 As shown. Figure 2 The peak value in the equation represents the maximum intensity l(t) of the ultrasonic signal.max 。

Claims

1. An ultrasonic transmitting and detecting device, characterized in that, The ultrasonic transmitting and detecting device includes an excitation source (1), an integrated detection end (2), a detection source (7), a 2×2 fiber coupler (8), a fiber optic circulator (9), a 3×3 fiber coupler (13), a photodetector, a high-pass filter, and a computer (20). The integrated detection end (2) is located between the excitation source (1) and the sample to be tested (6), and includes a dichroic mirror (3), a thin film (4), and a hollow acoustic lens (5) arranged in sequence. The excitation source (1) is located on the dichroic mirror (3) side of the integrated detection end (2). The sample to be tested (6) is located on the acoustic lens (5) side of the integrated detection end (2). The middle of the acoustic lens (5) is hollow. The detection source (7), the 2×2 fiber coupler (8), and the fiber optic circulator (9) are arranged in sequence. The fiber optic circulator (9) has three ports, namely the first port (10) of the fiber optic circulator, the first port (10) of the fiber optic circulator, and the second port (13) of the fiber optic circulator. The second port (11) and the third port (12) of the fiber optic circulator; the first port (10) of the fiber optic circulator is used to receive the sample light transmitted by the 2×2 fiber optic coupler (8), the second port (11) of the fiber optic circulator is used to output the sample light to the dichroic mirror (3) and receive the reflected light reflected from the thin film (4) back to the dichroic mirror (3); the third port (12) of the fiber optic circulator is used to output the reflected light to one end of the 3×3 fiber optic coupler (13); the 2×2 fiber optic coupler (8) transmits the reference light to one end of the fiber optic coupler (13); the three ports at the other end of the 3×3 fiber optic coupler (13) are respectively connected to three photodetectors, and each photodetector is connected to the data acquisition card (21) in the computer (20) through a high-pass filter; the computer (20) is connected to the excitation light source (1) and controls the light intensity of the excitation light source (1) according to the information output by the data acquisition card (21).

2. A method for ultrasonic emission and detection, characterized in that, Based on the ultrasonic transmitting and detecting device described in claim 1, it includes an ultrasonic signal excitation process, an ultrasonic signal detection process, and an ultrasonic signal demodulation process; The ultrasonic signal excitation process is as follows: the excitation light source (1) emits a laser, which passes through the dichroic mirror (3) and the thin film (4) in sequence, and then passes through the hollow acoustic lens (5) to irradiate the sample to be tested (6); the sample to be tested (6) converts the absorbed light energy into heat energy and heats up, causing the sample to be tested (6) to expand locally and generate ultrasonic waves; the ultrasonic waves propagate into the sample to be tested (6), and when they encounter the interface, they are reflected and propagate to the sample surface, and then propagate into the air.

3. The ultrasonic emission and detection method according to claim 2, characterized in that, The ultrasonic signal detection process is as follows: the acoustic lens (5) focuses the ultrasonic waves generated on the surface of the sample (6) onto the thin film (4), causing the thin film (4) to vibrate; the probe light emitted by the probe light source (7) enters the 2×2 fiber coupler (8), and the probe light is divided into sample light and reference light; the sample light enters the fiber circulator (9) through the first port (10) of the fiber circulator, and is output from the second port (11) of the fiber circulator. After passing through the dichroic mirror (3), it illuminates the surface of the thin film (4), detects the vibration of the thin film (4), and the sample light generates reflected light with different phase changes through the thin film (4) according to the intensity of the vibration; the reflected light is reflected by the dichroic mirror (3) and enters the second port (11) of the fiber circulator. The reference light enters the 3×3 fiber coupler (13) through the third port (12) of the fiber optic circulator. The reference light and the reflected light are split into three paths through the 3×3 fiber coupler (13) and output as three signals. The three signals enter photodetector A (14), photodetector B (15), and photodetector C (16) respectively. The three signals interfere with each other in the photodetectors and are converted into electrical signals. The electrical signals are filtered out by high-pass filter A (17), high-pass filter B (18), and high-pass filter C (19) and then enter the computer (20). The data acquisition card (21) collects the electrical signals after filtering out the interference, and finally the computer (20) demodulates the ultrasonic signal.

4. The ultrasonic emission and detection method according to claim 3, characterized in that, The ultrasonic signal demodulation process is specifically as follows: The three electrical signals acquired by the data acquisition card (21) after passing through the high-pass filter are as follows: and This indicates the phase difference between the three electrical signals. D represents the phase difference between the reflected light and the reference light that cause interference. i＝1,2,3 For the DC component, A i＝1,2,3 The amplitude of the interference coupling term; From equation (1), the phase difference between the reflected light and the reference light that cause interference is obtained. Measuring I without activating an ultrasonic signal i＝1,2,3 According to I i＝1,2,3 For D i＝1,2,3 and A i＝1,2,3 The proportions are calibrated; Therefore, the intensity of an ultrasonic signal is expressed as, λ represents the wavelength of the probe light.

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