A laser ultrasonic testing system and method for simultaneous scanning with dual-wavelength lasers

Abstract

This invention discloses a laser ultrasonic testing system and method for simultaneous dual-wavelength laser scanning, belonging to the field of laser ultrasonic non-contact non-destructive testing technology. The system includes: a pulsed laser, a laser interferometer, an excitation / receiving dual-wavelength laser probe module, a positioning and measurement module, and a signal acquisition and control module. The pulsed laser generates an excitation laser that irradiates the material surface to excite ultrasonic waves. The laser interferometer generates a continuous probe light source to detect ultrasonic signals. The positioning and measurement module clamps the workpiece to be inspected and moves it to position it at the scanning starting point. The signal acquisition and control module acquires and displays ultrasonic signals, controls the deflection stepping of the dual-wavelength laser two-dimensional galvanometer in the excitation / receiving dual-wavelength laser probe module, and controls the excitation parameters of the pulsed laser. This invention can improve the efficiency of laser ultrasonic scanning.

Description

Technical Field

[0001] This invention belongs to the field of laser ultrasonic non-contact non-destructive testing technology, and more specifically, relates to a laser ultrasonic rapid scanning and testing system and method. Background Technology

[0002] Laser ultrasound is a novel non-destructive testing technology with advantages including high sensitivity, high spatiotemporal resolution, non-contact operation, and applicability to harsh conditions such as high temperature and high pressure. Laser ultrasound technology uses an excitation laser generated by a laser to irradiate the surface of a material, exciting various ultrasonic modes both inside and on the surface. Different types of ultrasonic waves can be used to detect different defects in the material, such as surface defects and internal defects like pores and inclusions. Furthermore, the laser-excited ultrasonic waves also contain information about the material's microstructure and properties, and have already been widely applied in detecting grain size and residual stress.

[0003] In laser ultrasonic testing, a test block and a laser are moved relative to each other to emit pulsed laser light at different locations on the test block surface and detect ultrasonic waves. The test block can be moved using a displacement platform, or a galvanometer can be used to achieve precise movement and variable focusing distance of the excitation laser on the test block surface. This method yields laser ultrasonic B-scan or C-scan images. By analyzing the ultrasonic signal defect echo characteristics in the images, internal defects in the workpiece under test can be determined.

[0004] Laser ultrasonic testing methods mainly include Time-of-Flight Diffraction (TOFD), drop-and-capture, pulse-echo, and scanning laser source methods. These methods all rely on scanning with relative movement between the sample and the laser. A common testing scheme involves fixed positions for both the detection and excitation lasers, while the sample moves with the scanner. This results in high scanner accuracy but slow speed, which is one of the main factors limiting the speed of online laser ultrasonic defect detection. Summary of the Invention

[0005] To address the aforementioned deficiencies or improvement needs of existing technologies, this invention proposes a laser ultrasonic testing system and method for simultaneous dual-wavelength laser scanning. This system abandons the slow scanning of traditional scanners and employs a galvanometer and field mirror to rapidly move the laser focal point while maintaining laser focus. Furthermore, this invention utilizes a dichroic mirror to adjust the distance between the excitation and detection lasers, enabling multiple scanning modes for laser ultrasound, including same-side coaxial and same-side heterogeneous scanning.

[0006] To achieve the above objectives, according to one aspect of the present invention, a laser ultrasonic testing system for simultaneous scanning with dual-wavelength lasers is provided, comprising: a pulsed laser, a laser interferometer, an excitation / reception dual-wavelength laser probe module, a positioning and measurement module, and a signal acquisition and control module;

[0007] The pulsed laser is used to generate an excitation laser, which irradiates the surface of the workpiece (8) to be inspected to generate ultrasonic waves;

[0008] The laser interferometer is used to generate a continuous probe light source to detect ultrasonic signals;

[0009] The positioning and measurement module is used to clamp the workpiece to be inspected and move the workpiece to be inspected to position it at the scanning start point.

[0010] The excitation / receiving dual-wavelength laser probe module is used to focus the excitation laser generated by the pulsed laser and the detection laser generated by the laser interferometer onto the surface of the workpiece to be inspected, and can change the distance between the excitation laser and the detection laser, and enable the focused excitation laser and the detection laser to scan synchronously in the x and y directions.

[0011] The signal acquisition and control module is used for the acquisition and display of ultrasonic signals, the deflection step of the dual-wavelength laser two-dimensional galvanometer in the excitation / reception dual-wavelength laser probe module, and the control of the excitation parameters of the pulsed laser, such as the pulse repetition frequency and energy.

[0012] Furthermore, the excitation / reception dual-wavelength laser probe module includes a reflector, a laser collimating lens, a dichroic mirror, a dual-wavelength laser two-dimensional galvanometer, and a dual-wavelength laser field mirror;

[0013] The reflector is positioned on the optical axis of the detection laser emitted by the interferometer to change the propagation direction of the detection laser;

[0014] The dichroic mirror is positioned at the intersection of the optical axis of the excitation laser generated by the pulsed laser and the optical axis of the detection laser after deflection.

[0015] The laser collimating lens is set in the optical path of the detection laser between the reflector and the dichroic mirror, and converts the focused beam emitted from the laser interferometer into parallel light;

[0016] The dual-wavelength laser two-dimensional galvanometer is positioned behind the dichroic mirror and simultaneously on the optical axis after reflection of the detection laser and the optical axis after reflection of the excitation laser, so as to simultaneously deflect the excitation laser and the detection laser of different wavelengths and enable both the excitation laser and the detection laser to be incident on the dual-wavelength laser field mirror.

[0017] The dual-wavelength laser field lens directs excitation lasers and detection lasers of different wavelengths onto the surface of the workpiece to be inspected at the same focusing distance.

[0018] Furthermore, in the aforementioned excitation / receiving dual-wavelength laser probe module, the dichroic mirror is fixed on the rotating shaft of the angle adjustment control motor, which can precisely adjust the rotation angle of the dichroic mirror to change the angle at which the excitation laser is incident on the dual-wavelength laser field lens, thereby precisely adjusting the bias between the excitation laser and the detection laser, realizing a coaxial detection method with a bias of 0 on the same side, or a detection method with a bias greater than 0 on the same side and different points.

[0019] Furthermore, the bias d = f·|θ g -θ d | where the angle of the laser incident field mirror is θ g The angle of the laser incident field mirror is θ. d f represents the focal length of the dual-wavelength laser field lens.

[0020] Furthermore, when the detection method is coaxial on the same side, θ g =θ d The excitation and detection lasers are focused at the same point on the surface of the workpiece to be inspected; when the detection method is same-side, different-point detection, θ g ≠θ d The excitation and detection lasers are focused on different points on the surface of the workpiece to be inspected, which are separated by a distance d.

[0021] Furthermore, the dual-wavelength laser two-dimensional galvanometer includes galvanometer sheet a and galvanometer sheet b, which respectively control the movement of the laser in the x and y directions on the surface of the workpiece to be inspected. When the deflection angle of galvanometer sheet a or b is α, the laser angle after reflection by the galvanometer sheet is rotated by 2α. The excitation laser and the detection laser will step the same distance Δx(Δy) = f·2α in the x or y direction, so as to realize the dual-wavelength laser synchronous scanning function of laser ultrasound.

[0022] Furthermore, the positioning and measurement module includes a displacement platform, a displacement platform controller, and a workpiece to be inspected; the displacement platform controller is used to control the movement of the displacement platform.

[0023] The workpiece to be inspected is fixed on the displacement platform. The displacement platform is moved to position the workpiece to be inspected and to the scanning starting point.

[0024] Furthermore, the signal acquisition and control module includes a terminal device, an acquisition card, a galvanometer controller, and a displacement platform controller;

[0025] The data acquisition card is connected to both the interferometer and the pulsed laser. Simultaneously, the pulsed laser emits an excitation laser and sends a data acquisition signal to the data acquisition card, triggering the card to acquire the ultrasonic signal received by the interferometer.

[0026] The acquisition card connects to the terminal device and sends ultrasonic data, which is then displayed on the terminal device.

[0027] The terminal device is connected to the displacement platform controller, and the terminal device program controls the stepping of the displacement platform;

[0028] The galvanometer controller is connected to the pulsed laser and the dual-wavelength laser two-dimensional galvanometer respectively to trigger the pulsed laser to generate excitation laser and to control the dual-wavelength laser two-dimensional galvanometer.

[0029] The terminal equipment is connected to the angle adjustment control motor controller to precisely adjust the angle of the dichroic mirror;

[0030] The galvanometer controller is connected to the pulsed laser and the dual-wavelength laser two-dimensional galvanometer, respectively. It generates a trigger signal to control the pulsed laser to generate excitation laser, and at the same time controls the deflection of the dual-wavelength laser two-dimensional galvanometer to achieve rapid scanning of the workpiece to be inspected.

[0031] The present invention also provides a detection method for a laser ultrasonic detection system based on dual-wavelength laser synchronous scanning as described in any one of the above claims, comprising:

[0032] Step 1: Construct a laser ultrasonic testing system, set the parameters of the pulsed laser to generate the excitation laser, including energy and pulse repetition frequency, adjust the deflection angle of the dual-wavelength laser two-dimensional galvanometer and dichroic mirror, and adjust the excitation laser and detection laser to the same side and coaxial mode.

[0033] Step 2: Set the scanning start point, inspection area, scanning method (B scan / C scan), x-direction scanning length H, y-direction scanning length W, x-direction scanning step Δx, and y-direction scanning step Δy on the terminal device, where H and W do not exceed the length L of the dual-wavelength laser field lens.

[0034] Step 3: Load the workpiece to be inspected onto the displacement platform, move the displacement platform until the excitation laser is located at the edge of the workpiece to position the workpiece, and move the displacement platform until the excitation laser (detection laser) coincides with the scanning start point;

[0035] Step 4: Finely rotate the dichroic mirror to adjust the bias, and record the current bias on the terminal device;

[0036] Step 5: Start scanning. During the scanning process, the dual-wavelength laser two-dimensional galvanometer deflects the excitation laser and the detection laser simultaneously, so that the excitation laser and the detection laser step forward a distance Δx or Δy in the x or y direction at the same time. The terminal device displays the ultrasonic signal generated by the excitation laser at the current position in real time and updates the B-scan / C-scan image.

[0037] Step 6: Scanning complete. Display B / C scan results images and save scan configuration and scan result data.

[0038] In summary, compared with the prior art, the above-described technical solutions conceived by this invention can achieve the following beneficial effects:

[0039] This invention, based on dual-wavelength laser ultrasound detection, abandons the slow scanning of traditional scanning platforms. It combines a high-speed deflecting dual-wavelength laser two-dimensional galvanometer and a dual-wavelength laser field mirror to achieve synchronous high-speed scanning of the excitation and detection lasers. By precisely controlling the rotation of the dichroic mirror, the detection mode of the excitation and detection lasers can be adjusted to either coaxial or non-coaxial detection. This system enables rapid, flexible online laser ultrasound detection with multiple scanning modes. Attached Figure Description

[0040] Figure 1 A schematic diagram of the composition and optical path propagation of a laser ultrasonic testing system for simultaneous dual-wavelength laser scanning;

[0041] Figure 2 The diagrams show the laser scanning method for adjusting a dichroic mirror and the principle of dual-wavelength laser two-dimensional galvanometer scanning. In the diagram, Figure a) shows the detection method for different points on the same side, and Figure b) shows the detection method for the same point on the same side.

[0042] Figure 3 This is a schematic diagram of a C-scan for a same-side, different-point excitation and detection method, where the steps in the x and y directions are Δx and Δy, respectively, the detection ranges in the x and y directions are H and W, respectively, and the biases of the excitation laser and the detection laser are d.

[0043] Figure 4 The timing diagram for the laser excitation and galvanometer deflection control signals is shown, where t1 is the time taken for galvanometer deflection, t2 is the set laser trigger signal delay, and t3 is the optical delay.

[0044] Figure 5 Flowchart of the operation method of a laser ultrasonic testing system for simultaneous dual-wavelength laser scanning;

[0045] Among them, 1 is a laser interferometer, 2 is a reflector, 3 is a laser collimating lens, 4 is a dichroic mirror, 5 is a pulsed laser, 6 is a dual-wavelength laser two-dimensional galvanometer, 7 is a dual-wavelength laser field mirror, 8 is the workpiece to be inspected, 9 is a displacement platform, 10 is a data acquisition card, 11 is a terminal device, 12 is a galvanometer controller, 13 is a displacement platform controller, 14 is an angle adjustment control motor, and 15 is an angle adjustment control motor controller. Detailed Implementation

[0046] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0047] like Figure 1As shown, a dual-wavelength laser synchronous scanning laser ultrasonic testing system is described. This system comprises a pulsed laser (5), a laser interferometer (1), an excitation / reception dual-wavelength laser probe module, a positioning and measurement module, and a signal acquisition and control module. The pulsed laser (5) generates an excitation laser, which irradiates the material surface to excite ultrasonic waves. The laser interferometer (1) generates a continuous probe light source to detect ultrasonic signals. The positioning and measurement module clamps the workpiece (8) to be inspected and moves it to position it at the scanning starting point. The signal acquisition and control module acquires and displays ultrasonic signals, controls the deflection step of the dual-wavelength laser two-dimensional galvanometer (6), and controls the excitation parameters of the pulsed laser (5), such as pulse repetition frequency and energy.

[0048] Preferably, the dual-wavelength laser excitation / reception probe module consists of a reflector (2), a laser collimating lens (3), a dichroic mirror (4), a dual-wavelength laser two-dimensional galvanometer (6), and a dual-wavelength laser field mirror (7). The reflector (2) is positioned on the optical axis of the detection laser emitted by the interferometer (1) to change the propagation direction of the detection laser. The laser collimating lens (3), the dichroic mirror (4), and the dual-wavelength laser two-dimensional galvanometer (6) are sequentially arranged along the propagation path of the detection laser behind the reflector (2). The detection laser becomes parallel light after passing through the laser collimating lens (3), passes through the dichroic mirror (4), and then enters the dual-wavelength laser two-dimensional galvanometer. The pulsed laser (5) is placed parallel to the interferometer (1), emitting an excitation laser that enters the dichroic mirror (4) and is reflected to the dual-wavelength laser two-dimensional galvanometer (6). The dual-wavelength laser two-dimensional galvanometer (6) reflects the excitation laser and the detection laser of different wavelengths to the dual-wavelength laser field mirror (7), focusing them on the surface of the workpiece (8) at the same working distance.

[0049] Specifically, the pulsed laser (5) emits a pulsed laser with a wavelength of 1064nm, a spot diameter of 3.5mm, and a pulse width of 10ns.

[0050] Specifically, the interferometer (1) excites a continuous, focused detection laser with a wavelength of 532 nm. The laser collimating lens (3) is a plano-concave lens, which is placed in front of the focal point of the focused 532 nm beam to convert the focused detection laser into parallel light.

[0051] Specifically, the reflector (2) reflects a detection laser with a wavelength of 532nm, the dichroic mirror (4) reflects an excitation laser with a wavelength of 1064nm, and transmits a detection laser with a wavelength of 532nm.

[0052] Specifically, the dual-wavelength laser two-dimensional galvanometer (6) includes two galvanometer pieces, galvanometer piece a and galvanometer piece b. Galvanometer pieces a and b are both broadband coated reflectors (2), which enable the galvanometer pieces to simultaneously reflect excitation lasers and detection lasers of different wavelengths. Galvanometer pieces a and b control the deflection steps of the laser in the x and y directions on the surface of the workpiece (8) to be inspected, respectively.

[0053] Specifically, such as Figure 2 As shown, in order to precisely adjust the bias between the excitation laser and the detection laser, and to achieve a coaxial detection method with a bias of 0 on the same side, or a detection method with a bias greater than 0 on the same side but different points, the angle of the dichroic mirror (4) can be adjusted. The formula for calculating the bias is: d=f·|θ g -θ d | where the angle of the laser incident field mirror is θ g The angle of the laser incident field mirror is θ. d , where f represents the focal length of the dual-wavelength laser field mirror. When the detection method is coaxial on the same side, θ g =θ d The excitation and detection lasers are focused at the same point on the surface of the workpiece (8) to be inspected; when the detection method is same-side different point, θ g ≠θ d The excitation and detection lasers are focused on different points on the surface of the workpiece (8) at a distance d apart. The angle θ of the incident laser field mirror is then used to detect the laser. d Keeping the angle constant, the angle θ of the excitation laser incident field mirror is changed by adjusting the angle of the dichroic mirror (4). g This allows the excitation laser focusing position to be moved on the workpiece (8) to be inspected, thereby adjusting the bias between the excitation laser and the detection laser.

[0054] Specifically, the dichroic mirror (4) is mounted on the angle adjustment control motor (14), and the angle adjustment control motor controller (15) is connected to the angle adjustment control motor (14) so ​​that the angle of the dichroic mirror (4) can be precisely controlled.

[0055] Specifically, the dual-wavelength laser two-dimensional galvanometer (6) includes galvanometer pieces a and b, which respectively control the movement of the laser in the x and y directions on the surface of the workpiece (8) to be inspected. When the deflection angle of galvanometer piece a or b is α, the laser angle after reflection by the galvanometer piece is rotated by 2α. The excitation laser and the detection laser will step the same distance Δx(Δy) = f·2a in the x or y direction to realize the dual-wavelength laser synchronous scanning function of laser ultrasound.

[0056] Specifically, the dual-wavelength laser field lens (7) operates simultaneously with lasers of two wavelengths, 1064nm and 532nm, and undergoes achromatic processing to ensure that the two wavelengths of light have the same working distance and are focused at the same distance from the dual-wavelength laser field lens (7).

[0057] Specifically, the positioning and measurement module includes a displacement platform (9), a displacement platform controller (13), and a workpiece to be inspected (8). The displacement platform controller (13) is used to control the movement of the displacement platform (9). The workpiece to be inspected (8) is fixed on the displacement platform (9). The displacement platform (9) is moved to position the workpiece to be inspected (8) and move the workpiece to be inspected (8) to the scanning starting point.

[0058] Specifically, the signal acquisition and control module includes a terminal device (11), a data acquisition card (10), a galvanometer controller (12), and a displacement platform controller (13). The data acquisition card (10) is connected to the interferometer (1), the pulsed laser (5), and the terminal device (11). While the pulsed laser (5) generates the excitation laser, it transmits the signal to be acquired to the data acquisition card (10). The data acquisition card (10) acquires the ultrasonic signal transmitted from the interferometer (1) and transmits it to the terminal device (11) for display and storage of the currently acquired ultrasonic signal.

[0059] Specifically, the terminal device (11) is connected to the displacement platform controller (13). The terminal device (11) program controls the moving direction and moving distance of the displacement platform (9) to accurately move the workpiece (8) to be inspected to the scanning starting point.

[0060] Specifically, the terminal device (11) is connected to the galvanometer controller (12) and controls the deflection action of the dual-wavelength laser two-dimensional galvanometer (6) through the terminal device program.

[0061] Specifically, the galvanometer controller (12) is connected to the pulsed laser (5) and the dual-wavelength laser two-dimensional galvanometer (6) to trigger the pulsed laser (5) to generate excitation laser and to control the dual-wavelength laser two-dimensional galvanometer (6). The terminal device (11) is connected to the angle adjustment control motor controller (15) to precisely adjust the angle of the dichroic mirror (4). The galvanometer controller (12) is connected to the pulsed laser (5) and the dual-wavelength laser two-dimensional galvanometer (6) to generate a trigger signal to control the pulsed laser (5) to generate excitation laser, and at the same time control the deflection of the dual-wavelength laser two-dimensional galvanometer (6) to achieve rapid scanning of the workpiece (8) to be inspected.

[0062] Specifically, the pulse repetition frequency of the pulsed laser (5) is the same as the operating frequency of the dual-wavelength laser two-dimensional galvanometer (6) to increase the scanning speed. That is, at each scanning point, the excitation laser is emitted only once and the ultrasonic signal is collected. When the operating frequency of the dual-wavelength laser two-dimensional galvanometer is reduced, and the pulse repetition frequency of the pulsed laser (5) is a multiple of the operating frequency of the dual-wavelength laser two-dimensional galvanometer (6), the laser collects signals at the same point multiple times for averaging, reducing the scanning speed and improving the quality of the collected ultrasonic signals. At the fastest scanning speed, the scanning process of the dual-wavelength laser two-dimensional galvanometer is as follows: the galvanometer controller (12) sends an instruction to control the dual-wavelength laser two-dimensional galvanometer to deflect the galvanometer mirror. After the galvanometer mirror stops deflecting, the galvanometer controller (12) generates a laser trigger signal and transmits the laser trigger signal to the pulsed laser (5) to trigger the generation of the excitation laser. At the same time as the excitation laser is generated, the pulsed laser (5) sends a trigger acquisition signal to the acquisition card (10), and the acquisition card (10) acquires the ultrasonic signal detected by the interferometer.

[0063] Specifically, as Figure 4 shown, after the laser trigger signal is transmitted, the laser is generated by the laser after a time period of t3. The set delay t2 of the excitation laser trigger signal should satisfy the condition: t1 - t3 < t2 < 10 ms - t3. Where t1 is the time taken for the galvanometer mirror to deflect, t2 is the set delay of the laser trigger signal, and t3 is the optical delay. In the terminal device program, the number of times the pulsed laser (5) emits the excitation laser can be set at each scanning point to collect the ultrasonic signal multiple times for averaging. When the pulse repetition frequency of the pulsed laser (5) generating the excitation laser is constant, the operating frequency of the dual-wavelength laser two-dimensional galvanometer (6) is reduced. When the number of acquisitions at the same scanning point increases, the quality of the collected ultrasonic signal at that position is improved after averaging.

[0064] Specifically, as Figure 3 shown, during the synchronous scanning of the dual-wavelength laser, the workpiece to be inspected (8) is fixed, and the offset d between the excitation laser and the detection laser remains unchanged. Synchronously, the same distances Δx and Δy are stepped in the x or y direction.

[0065] The usage method of the laser ultrasonic detection system for the synchronous scanning of the dual-wavelength laser is as Figure 5 shown, specifically:

[0066] 1) Construct a laser ultrasonic detection system, set the parameters of the pulsed laser (5) for emitting the excitation laser, including energy and pulse repetition frequency, adjust the deflection angles of the dual-wavelength laser two-dimensional galvanometer (6) and the dichroic mirror (4), and adjust the excitation laser and the detection laser to the same-side coaxial mode;

[0067] 2) Set the scanning starting point, the area to be inspected, the scanning method (B scan / C scan), the scanning lengths H and W in the x and y directions, and the scanning steps Δx and Δy in the x and y directions on the terminal equipment (11). Among them, H and W do not exceed the length L of the dual-wavelength laser field lens (7);

[0068] 3) Load the workpiece (8) to be inspected onto the displacement platform (9), move the displacement platform (9) until the excitation laser is located at the edge of the workpiece (8) to position the workpiece, and move the displacement platform (9) until the excitation laser (detection laser) coincides with the scanning start point;

[0069] 4) Finely rotate the dichroic mirror (4) to adjust the bias, and record the current bias on the terminal device (11);

[0070] 5) Begin scanning. The scanning process is as follows: Figure 4 As shown, during the scanning process, the dual-wavelength laser two-dimensional galvanometer (6) simultaneously deflects the excitation laser and the detection laser, so that the excitation laser and the detection laser simultaneously step a distance Δx or Δy in the x or y direction. The terminal device (11) displays the ultrasonic signal generated by the excitation laser at the current position in real time and updates the B-scan / C-scan image.

[0071] The scan is complete, displaying the B / C scan results images, and saving the scan configuration and scan result data.

[0072] It should be noted that, depending on the implementation needs, the various steps / components described in this application can be broken down into more steps / components, or two or more steps / components or parts of the operation of steps / components can be combined into new steps / components to achieve the purpose of this invention.

[0073] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A laser ultrasonic testing system with simultaneous dual-wavelength laser scanning, characterized in that, include: Pulsed laser (5), laser interferometer (1), excitation / reception dual-wavelength laser probe module, positioning and measurement module, signal acquisition and control module; The pulsed laser (5) is used to generate an excitation laser, which irradiates the surface of the workpiece (8) to be inspected and excites ultrasonic waves. The laser interferometer (1) is used to generate a continuous probe light source to detect ultrasonic signals; The positioning and measurement module is used to clamp the workpiece (8) to be inspected and move the workpiece (8) to be inspected to position it at the scanning start point; The excitation / receiving dual-wavelength laser probe module is used to focus the excitation laser generated by the pulsed laser (5) and the detection laser generated by the laser interferometer (1) onto the surface of the workpiece (8) to be inspected, and can change the distance between the excitation laser and the detection laser, and make the focused excitation laser and the detection laser scan synchronously in the x and y directions; The signal acquisition and control module is used for the acquisition and display of ultrasonic signals, the deflection step of the excitation / reception dual-wavelength laser probe module, and the control of the excitation parameters of the pulsed laser (5). The excitation / reception dual-wavelength laser probe module includes a reflector (2), a laser collimating lens (3), a dichroic mirror (4), a dual-wavelength laser two-dimensional galvanometer (6), and a dual-wavelength laser field mirror (7); The reflector (2) is positioned on the optical axis of the detection laser emitted by the interferometer (1) to change the propagation direction of the detection laser; The dichroic mirror (4) is located at the intersection of the optical axis of the excitation laser generated by the pulsed laser (5) and the optical axis of the detection laser after deflection. The laser collimating lens (3) is set in the optical path of the detection laser between the reflector (2) and the dichroic mirror (4), and converts the focused beam emitted from the laser interferometer (1) into parallel light; The dual-wavelength laser two-dimensional galvanometer (6) is positioned behind the dichroic mirror (4) and simultaneously on the optical axis after the detection laser is reflected and the optical axis after the excitation laser is reflected, so as to simultaneously deflect the excitation laser and the detection laser of different wavelengths and enable both the excitation laser and the detection laser to be incident on the dual-wavelength laser field mirror (7). The dual-wavelength laser field lens (7) directs excitation lasers and detection lasers of different wavelengths onto the surface of the workpiece (8) to be inspected at the same focusing distance; The dichroic mirror (4) is fixed on the rotating shaft of the angle adjustment control motor (14), which can adjust the rotation angle of the dichroic mirror (4) to change the angle of the excitation laser incident on the dual-wavelength laser field mirror (7), thereby adjusting the bias between the excitation laser and the detection laser, realizing the same-side coaxial detection mode with a bias of 0, or the same-side opposite-point detection mode with a bias greater than 0.

2. The laser ultrasonic testing system with simultaneous dual-wavelength laser scanning according to claim 1, characterized in that, Bias d = f·|θ g -θ d | where the angle of the laser incident field mirror is θ g The angle of the incident laser lens is θ. d f represents the focal length of the dual-wavelength laser field lens.

3. The laser ultrasonic testing system with simultaneous dual-wavelength laser scanning according to claim 2, characterized in that, When the detection method is coaxial on the same side, θ g =θ d The excitation and detection lasers are focused at the same point on the surface of the workpiece (8) to be inspected; when the detection method is same-side different point, θ g ≠θ d The excitation and detection lasers are focused on different points on the surface of the workpiece (8) to be inspected, with a distance of offset d between them.

4. The laser ultrasonic testing system with simultaneous dual-wavelength laser scanning according to claim 3, characterized in that, The dual-wavelength laser two-dimensional galvanometer (6) includes a galvanometer a and a galvanometer b, which respectively control the movement of the excitation laser and the reflected laser in the x and y directions on the surface of the workpiece (8) to be inspected; When the deflection angle of galvanometer a or galvanometer b is α, the laser angle after reflection by the galvanometer rotates by 2α. The excitation laser will step forward the same distance Δx = f·2α in the x or y direction, and the detection laser will step forward the same distance Δy = f·2α in the x or y direction, so as to realize the dual-wavelength laser synchronous scanning function of laser ultrasound.

5. The laser ultrasonic testing system with simultaneous dual-wavelength laser scanning according to claim 4, characterized in that, The positioning and measurement module includes a displacement platform (9), a displacement platform controller (13), and a workpiece to be inspected (8); The displacement platform controller (13) is used to control the movement of the displacement platform (9). The workpiece to be inspected (8) is fixed on the displacement platform (9). The displacement platform (9) is moved to position the workpiece to be inspected (8) and move the workpiece to be inspected (8) to the scanning starting point.

6. The laser ultrasonic testing system with simultaneous dual-wavelength laser scanning according to claim 5, characterized in that, The signal acquisition and control module includes a terminal device (11), an acquisition card (10), a galvanometer controller (12), and a displacement platform controller (13); The acquisition card (10) is respectively connected to an interferometer (1) and a pulsed laser (5). When the pulsed laser (5) emits excitation laser, it sends an acquisition signal to the acquisition card (10) to trigger the acquisition card (10) to acquire the ultrasonic signal received by the interferometer (1); The acquisition card (10) is connected to the terminal device (11) and sends ultrasonic data, and finally the acquired ultrasonic signal is displayed on the terminal device (11); The terminal device (11) is connected to the displacement platform controller (13), and the terminal device (11) program-controls the stepping of the displacement platform (9); The galvanometer controller (12) is respectively connected to the pulsed laser (5) and a two-wavelength laser two-dimensional galvanometer (6) to trigger the pulsed laser (5) to generate excitation laser and control the two-wavelength laser two-dimensional galvanometer (6); The terminal device (11) is connected to an angle adjustment control motor controller (15) to adjust the angle of the dichroic mirror (4); The galvanometer controller (12) is respectively connected to the pulsed laser (5) and a two-wavelength laser two-dimensional galvanometer (6), generates a trigger signal to control the pulsed laser (5) to generate excitation laser, and at the same time controls the deflection of the two-wavelength laser two-dimensional galvanometer (6) to achieve rapid scanning of the workpiece to be inspected (8).

7. The laser ultrasonic testing system with simultaneous dual-wavelength laser scanning according to claim 6, characterized in that, The set trigger signal delay t2 of the excitation laser should satisfy the condition: t1 - t3 < t2 < 10ms - t3, where t1 is the time used for galvanometer deflection, t2 is the set laser trigger signal delay, and t3 is the optical delay.

8. A detection method for a laser ultrasonic testing system based on dual-wavelength laser synchronous scanning as described in any one of claims 1 to 7, characterized in that, It includes: Set the parameters of the pulsed laser (5) to emit excitation laser, adjust the deflection angles of the two-wavelength laser two-dimensional galvanometer (6) and the dichroic mirror (4), and determine the detection method; On the terminal device (11), set the scanning starting point, the area to be detected, the scanning method, the scanning length H in the x direction, the scanning length W in the y direction, the scanning step Δx in the x direction, and the scanning step Δy in the y direction of the workpiece to be inspected (8), where both H and W do not exceed the field lens (7) amplitude length L of the two-wavelength laser; Load the workpiece to be inspected (8) on the displacement platform (9), move the displacement platform (9) until the excitation laser is at the edge of the workpiece to be inspected (8) to position the workpiece, and move the displacement platform (intentionally repeated "move the displacement platform" here as in the original), until the excitation laser or the detection laser coincides with the scanning starting point; Rotate the dichroic mirror (4) to adjust the offset, and record the current offset on the terminal device (11); The scanning begins. During the scanning process, the dual-wavelength laser two-dimensional galvanometer (6) simultaneously deflects the excitation laser and the detection laser, so that the excitation laser and the detection laser simultaneously step a distance Δx or Δy in the x or y direction. The terminal device (11) displays the ultrasonic signal generated by the excitation laser at the current position in real time and updates the B-scan / C-scan image. The scan is complete, displaying the B / C scan results images, and saving the scan configuration and scan result data.

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