A high-power optical fiber endoscopic scanning laser vibration measuring device and a working method thereof

Abstract

The application discloses a kind of high-power optical fiber endoscopic scanning laser vibration measuring device and working method thereof, including double optical fiber output laser, interference optical path body and endoscopic scanning probe;Laser includes two optical fiber outputs, one is as reference light output to interference optical path body, the other is as measurement light output to endoscopic scanning probe;Interference optical path body is used to complete the light splitting of reference laser, frequency shift, transmission, and the light receiving and coherent beam combination of measurement laser, endoscopic scanning probe is used to introduce measurement light into narrow space detection area, and the measured object is scanned and detected quickly in non-contact mode, and light receiving signal is received to interference optical path body.The application adopts double optical fiber output high-power narrow linewidth laser, and reference light and measurement light are branched output, wherein high-power measurement light is used for target detection, and low-power reference light is used for heterodyne interference, to ensure that in weak light scene, while improving total laser power, reference laser power remains constant.

Description

Technical Field

[0001] This invention relates to the fields of laser interferometric vibration measurement and fiber optic endoscopy, and particularly to a high-power fiber optic endoscopic scanning laser vibration measurement device and its working method suitable for non-contact scanning vibration measurement in confined spaces, deep cavities and complex internal structures. Background Technology

[0002] Laser vibration measurement technology is a non-contact vibration measurement technology based on the principle of optical interference. It has advantages such as high sensitivity, wide bandwidth, high spatial resolution and no introduction of additional mass, and has been widely used in fields such as structural vibration testing, ultrasonic signal detection, non-destructive testing and equipment condition monitoring.

[0003] Existing laser vibration measurement devices mostly employ a free-space optical path structure, typically integrating components such as the laser, interferometric optical path, scanning galvanometer, and detector into the instrument body. Vibration measurement is achieved by illuminating the surface of the object under test with measuring light and receiving the reflected light signal, which is then interfered with a reference light. While such devices are suitable for open spaces or external surface measurement scenarios, in confined spaces, enclosed areas, deep cavities, and complex internal structures, limitations in instrument size, optical path arrangement, incident angle, and field of view make it difficult to effectively introduce the measuring light into the target area and conduct scanning detection.

[0004] To improve application flexibility, fiber optic laser vibration measurement solutions exist in existing technologies, but they are mostly based on single-point measurements. The probes typically only have beam transmission, collimation, or backlight reception functions, making it difficult to achieve two-dimensional scanning measurements in confined spaces. For scenarios requiring vibration distribution, ultrasonic propagation characteristics, or defect imaging results, external mechanical motion mechanisms are often needed for point-by-point scanning, which suffers from low scanning efficiency, path limitations, and significant positioning errors.

[0005] Furthermore, in endoscopic vibration measurement scenarios, the reflectivity, curvature, and orientation of the measured surface vary significantly, resulting in weak reflected light signals that can easily lead to a decrease in the signal-to-noise ratio of the interference signal. Existing fixed-focal-length probes have limited adaptability to changes in working distance and complex curved surfaces, making it difficult to maintain stable focusing and efficient light collection during scanning, thus affecting vibration measurement stability and imaging quality.

[0006] Therefore, existing free-space laser vibration measurement devices are difficult to enter narrow, enclosed and complex internal areas, existing fiber-optic laser vibration measurement devices are difficult to achieve scanning measurement of internal areas, and there are technical problems such as insufficient signal-to-noise ratio of vibration measurement signals under weak backlight conditions and difficulty in quickly focusing point by point during scanning of complex curved surfaces. Summary of the Invention

[0007] Purpose of the invention: The purpose of this invention is to provide a high-power fiber optic endoscopic scanning laser vibration measurement device and its working method suitable for detecting confined spaces and complex internal structures.

[0008] Technical solution: The present invention includes a dual-fiber output laser, an interference optical path body, and an endoscopic scanning probe for introducing measurement light into a narrow detection area; the laser is a dual-fiber output laser of the same source, the two output lights are coherent, one of which is output as a reference light to the interference optical path body, and the other is output as a measurement light to the endoscopic scanning probe, and the output power of the measurement light is greater than the output power of the reference light;

[0009] The measuring light passes through a polarizing beam splitter, a liquid focusing lens, a quarter-wave plate, and a miniature scanning mirror in sequence before illuminating the surface of the object under test. The light reflected back from the object under test passes through the miniature scanning mirror, a quarter-wave plate, a liquid focusing lens, a polarizing beam splitter, and a sixth reflecting mirror in sequence before being input into the interference light path body to interfere with the reference light.

[0010] The reference light is guided by the first reflecting mirror to the acousto-optic modulator for frequency shifting, then reflected by the second reflecting mirror, and subsequently split by the beam splitter. The measurement light is received by the endoscopic scanning probe and returns to the interference optical path body. It then coherently combines with the frequency-shifted reference light at the beam splitter. After being reflected by the third and fourth reflecting mirrors, it is received by the balanced photodetector, forming a heterodyne interference signal containing the vibration information of the measured object.

[0011] The laser outputs dual optical fibers with unequal power. One fiber outputs a reference light with a fixed power of less than 5mW and is connected to the interference optical path body; the other fiber outputs a measurement light with a power of more than 1W and adjustable power and is connected to the endoscopic scanning probe.

[0012] The beam splitter has a splitting ratio of 50:50, which is used to enable two complementary interference beams to be incident on a balanced photodetector with equal power.

[0013] The maximum outer diameter of the endoscopic scanning probe is no more than 15 mm to meet the detection needs of confined spaces, deep cavity structures and complex internal areas.

[0014] The sixth reflecting mirror is located directly below the polarizing beam splitter and is closely connected to the polarizing beam splitter. It is used to reflect the return measurement light separated by the polarizing beam splitter to the return transmission fiber.

[0015] The geometric centers of the polarizing beam splitter, liquid focusing lens, quarter-wave plate, and miniature scanning mirror are located on the same horizontal line to ensure that the measurement light is stably transmitted along the preset optical axis inside the probe.

[0016] The measurement light is output from the side of the miniature scanning galvanometer.

[0017] The liquid focusing lens is driven by current to change the curvature of the focusing lens, thereby achieving continuous zoom of the measurement light. This is used to compensate for defocusing problems caused by changes in the curvature of the surface of the object being measured, fluctuations in working distance, or changes in probe posture during the scanning process.

[0018] The miniature scanning galvanometer is based on the electromagnetic drive principle. A single lens can achieve two-dimensional beam deflection, which is used to perform rapid scanning measurements on different positions on the surface of the object being measured.

[0019] The present invention also provides the working process of a high-power fiber optic endoscopic scanning laser vibrometer, comprising:

[0020] Turn on the laser so that it outputs two laser beams simultaneously: one is a low-power reference beam that enters the interference optical path body; the other is a high-power measurement beam that enters the endoscopic scanning probe.

[0021] The reference light is incident on the acousto-optic modulator through the first reflecting mirror. The acousto-optic modulator frequency-shifts the reference light. The frequency-shifted reference light is then guided into the beam splitter by the second reflecting mirror.

[0022] After the measuring light enters the endoscopic scanning probe, it passes sequentially through a polarizing beam splitter, a liquid focusing lens, a quarter-wave plate, and a miniature scanning mirror. After being reflected by the miniature scanning mirror, it illuminates the surface of the object being measured. The measuring light returning from the surface of the object being measured returns along the original path, passes through the miniature scanning mirror, the quarter-wave plate, and the liquid focusing lens, and then reaches the polarizing beam splitter. The returning measuring light separates from the incident light at the polarizing beam splitter and, after being reflected by the sixth reflecting mirror, enters the interference light path body.

[0023] The returning measurement light and the frequency-shifted reference light are coherently combined at the beam splitter to form two complementary interference light signals. The two complementary interference lights are incident on the balanced light detector through the third and fourth reflecting mirrors, respectively. The balanced light detector outputs a heterodyne interference electrical signal. After subsequent signal acquisition and demodulation processing, the vibration information at different scanning positions on the surface of the measured object can be obtained.

[0024] Beneficial effects: This invention has the following advantages:

[0025] (1) The present invention uses a high-power narrow-linewidth laser with dual fiber output to output the reference light and the measurement light separately. The high-power measurement light is used for target detection, and the low-power reference light is used for heterodyne interference. This ensures that in weak backlight scenarios, while increasing the total laser power, the reference laser power remains constant, thereby avoiding the problem of saturation of the balanced photodetector due to excessive reference light.

[0026] (2) The present invention introduces the measurement light into the endoscopic scanning probe through the optical fiber, and realizes the side light output and back light reception through the miniaturized probe, so that the laser vibration measurement device can enter or approach the narrow, closed, deep cavity and complex internal area, and overcomes the problem that the traditional free space laser vibration measurement device is limited by the size and optical path arrangement and is difficult to perform internal structure detection.

[0027] (3) The present invention integrates a micro scanning galvanometer in the endoscopic scanning probe, which can realize two-dimensional deflection of the measurement light and regional scanning while the probe position remains basically unchanged, avoiding complete reliance on external mechanical motion mechanism to move the probe point by point, thus improving the efficiency and flexibility of scanning measurement of complex internal regions.

[0028] (4) The present invention provides a liquid focusing lens in the endoscopic scanning probe, which can quickly compensate for the defocusing problem caused by surface undulation, working distance change or probe posture error during the scanning process, and improve the focusing consistency, light return collection efficiency and vibration signal stability at different scanning positions.

[0029] (5) The integrated vibration measurement link constructed by the present invention can realize non-contact scanning vibration measurement in narrow spaces and complex internal structures, providing a new technical solution for vibration testing, laser ultrasonic testing and non-destructive imaging of complex equipment internal structures. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the overall structure of the present invention. Detailed Implementation

[0031] The invention will now be further described with reference to the accompanying drawings.

[0032] Example 1

[0033] like Figure 1 As shown, the high-power fiber optic endoscopic scanning laser vibrometer device of this embodiment includes a laser, an interference optical path body, and an endoscopic scanning probe. The laser is a high-power narrow-linewidth laser 1, which provides a stable and highly coherent laser source for the entire device. The high-power narrow-linewidth laser 1 is a 1550 nm wavelength semiconductor continuous laser with a total output power greater than 1 W and a linewidth less than 5 kHz. The high-power narrow-linewidth laser 1 has two fiber optic outputs. One outputs a low-power reference light with a fixed output power of no more than 5 mW, and is connected to the interference optical path body. The other outputs a high-power measurement light with an adjustable output power greater than 1 W, and is connected to the endoscopic scanning probe via a second fiber optic cable 11. Both fiber optic outputs can be equipped with fiber collimators to convert the fiber output light into a collimated spatial beam.

[0034] In this embodiment, the reference light and the measurement light employ different power outputs. The reference light uses a lower and fixed power, primarily for the heterodyne interferometer reference arm, to prevent excessive reference light power from saturating the balanced photodetector 9. The measurement light uses a higher and adjustable power, primarily for entering the endoscopic scanning probe and illuminating the object under test 17, to compensate for the light power loss caused by the low reflectivity of the object under test 17's surface, thereby improving the intensity of the returned measurement light and the signal-to-noise ratio of the interference signal. The output power of the measurement light can be adjusted according to the surface reflectivity of the object under test 17, the working distance, and the intensity of the returned light. When the surface reflectivity is low, the measurement distance is far, or the returned light is weak, the measurement light power can be appropriately increased; when the returned light is strong or the balanced photodetector 9 is close to saturation, the measurement light power can be reduced to ensure that the heterodyne interferometer signal is within a suitable dynamic range.

[0035] The interference optical path body is used to perform beam splitting, frequency shifting, and transmission of the reference light, as well as the reception and coherent beam combining of the measurement return light, and to convert the vibration information of the surface of the measured object into a detectable heterodyne interference signal. It includes a first reflecting mirror 2, an acousto-optic modulator 3, a second reflecting mirror 4, a third reflecting mirror 5, a beam splitter prism 6, a fifth reflecting mirror 7, a fourth reflecting mirror 8, a balanced photodetector 9, and a first optical fiber 10. After entering the interference optical path body, the reference light first changes its propagation direction via the first reflecting mirror 2 and then enters the acousto-optic modulator 3. The acousto-optic modulator 3 is used to frequency shift the reference light, giving it a preset frequency offset relative to the measurement light. The frequency-shifted reference light is then adjusted in direction by the second reflecting mirror 4 and enters the beam splitter prism 6. The beam splitter prism 6 is preferably a 50:50 beam splitter prism, used to ensure that the two complementary optical signals after interference are output to the two detection ends of the balanced photodetector 9 with equal power.

[0036] The maximum outer diameter of the endoscopic scanning probe does not exceed 15 mm to accommodate the testing requirements of confined spaces, deep cavities, complex chambers, and internal curved surfaces. The endoscopic scanning probe includes a polarizing beam splitter 12, a sixth reflecting mirror 13, a liquid focusing lens 14, a quarter-wave plate 15, and a miniature scanning galvanometer 16. The sixth reflecting mirror 13 is located directly below and closely fitted to the polarizing beam splitter 12, reflecting the returned measurement light separated by the polarizing beam splitter 12 back to the return transmission fiber. The geometric centers of the polarizing beam splitter 12, the liquid focusing lens 14, the quarter-wave plate 15, and the miniature scanning galvanometer 16 are located on the same horizontal line to ensure stable transmission of the measurement light along a preset optical axis inside the probe. This compact optical path arrangement enables lateral light emission, dynamic focusing, and two-dimensional scanning within a relatively small probe outer diameter.

[0037] The measurement light is output from the high-power output end of a high-power, narrow-linewidth laser 1 and transmitted to the endoscopic scanning probe via a second optical fiber 11. After exiting the second optical fiber 11, the measurement light enters a polarization beam splitter 12, which separates the incident and returning measurement light. After passing through the polarization beam splitter 12, the incident measurement light passes sequentially through a liquid focusing lens 14 and a quarter-wave plate 15 before reaching a miniature scanning galvanometer 16. By controlling the two-dimensional deflection angle of the miniature scanning galvanometer 16, the measurement light can form a two-dimensional scanning trajectory on the surface of the object under test 17, thereby achieving non-contact scanning vibration measurement at different positions in the target area of ​​the object under test 17.

[0038] After the measurement light shines on the surface of the object under test 17, the vibration of the surface of the object under test 17 will cause a phase change in the returned measurement light. The returned measurement light returns along the original optical path, passing sequentially through the miniature scanning galvanometer 16, the quarter-wave plate 15, and the liquid focusing lens 14 before entering the polarization beam splitter 12. Because the polarization state of the returned measurement light changes relative to the incident measurement light after passing through the quarter-wave plate 15, the returned measurement light is separated and its propagation direction is changed at the polarization beam splitter 12. Subsequently, the returned measurement light is reflected by the sixth reflecting mirror 13 and coupled into the first optical fiber 10, and then transmitted to the interference optical path body by the first optical fiber 10.

[0039] The measurement light returning to the main body of the interference optical path and the reference light after frequency shifting by the acousto-optic modulator 3 are coherently combined at the beam splitter prism 6. The two complementary interference beams after beam combining are adjusted in propagation direction by the third reflecting mirror 5 and the fourth reflecting mirror 8, respectively, and then incident on the balanced photodetector 9. The balanced photodetector 9 performs photoelectric conversion on the two complementary interference beam signals and outputs a differential electrical signal.

[0040] Because the beam splitter prism 6 employs a 50:50 splitting ratio, the average power of the two complementary interference beams is essentially equal. The balanced photodetector 9 effectively cancels out the DC light intensity component, laser intensity noise, and some environmental common-mode disturbances, while simultaneously enhancing the interference modulation signal caused by the vibration of the object under test 17, thus improving the signal-to-noise ratio of the vibration measurement signal. The differential electrical signal output by the balanced photodetector 9 is a heterodyne interference signal, which contains phase modulation information caused by the surface vibration of the object under test 17. By demodulating this heterodyne interference signal, the vibration displacement, velocity, and acceleration response information at the corresponding scanning position on the surface of the object under test 17 can be obtained.

[0041] In this embodiment, the first optical fiber 10 is a single-mode polarization-maintaining fiber, and its length is set according to the optical path difference between the measuring arm and the reference arm. By adjusting the length of the first optical fiber 10, optical path compensation can be performed on the measuring arm and the reference arm, so that the optical path difference between the returned measuring light and the reference light meets the coherence length requirements and heterodyne interferometry detection requirements of the high-power narrow-linewidth laser 1. Through this optical path compensation method, the coherent beam combining effect of the returned measuring light and the reference light can be improved, the visibility of the interference signal can be enhanced, and the phase noise caused by light source frequency fluctuations and environmental disturbances can be reduced.

[0042] A liquid focusing lens 14 is positioned between the polarizing beam splitter 12 and the quarter-wave plate 15 to adjust the focusing state of the measurement light. The liquid focusing lens 14 can achieve continuous zoom by changing the curvature of its internal liquid lens using an electric current. The liquid focusing lens 14 can complete focal length adjustment within microseconds, compensating for defocusing problems caused by changes in the working distance between the probe and the object 17 during scanning, as well as probe attitude errors.

[0043] The liquid focusing lens 14 can be controlled in either an open-loop or closed-loop manner. In the open-loop control mode, the corresponding driving current can be applied to the liquid focusing lens 14 according to the scanning position based on the pre-calibrated correspondence between the probe working distance and the driving current. In the closed-loop control mode, the driving current of the liquid focusing lens 14 can be adjusted in real time according to the backlight intensity, interference signal amplitude, or other optical feedback signals, so that the system maintains high backlight efficiency and good signal quality during scanning.

[0044] A quarter-wave plate 15 is positioned between the liquid focusing lens 14 and the miniature scanning mirror 16 to adjust the polarization state of the measurement light. The measurement light passes through the quarter-wave plate 15 and then enters the miniature scanning mirror 16. The miniature scanning mirror 16 is preferably positioned at a 45° angle, so that the measurement light is converted from axial transmission of the probe to lateral output and illuminates the surface of the object 17 being measured.

[0045] The miniature scanning galvanometer 16 is based on the principle of electromagnetic drive, and a single lens can achieve two-dimensional beam deflection. The scanning mode of the miniature scanning galvanometer 16 can be set to point-by-point grid scanning, line scanning, or other preset trajectory scanning according to the detection requirements. When the beam is deflected by the miniature scanning galvanometer 16, the endoscopic scanning probe body can remain basically fixed, thereby reducing the dependence on external mechanical displacement mechanisms and improving scanning efficiency in confined spaces and complex internal areas.

[0046] When the miniature scanning galvanometer 16 operates in a two-dimensional grid scanning mode, it first deflects point by point along the first direction to complete one scan line, and then deflects along the second direction to the next scan line, repeating the above process until the entire target area is scanned. Each scanning position corresponds to a set of heterodyne interference signals. By demodulating and spatially reconstructing multiple sets of heterodyne interference signals, the vibration distribution or ultrasonic response distribution of the target area on the surface of the object under test 17 can be obtained.

[0047] The high-power fiber optic endoscopic scanning laser vibrometer provided in this embodiment uses a dual-fiber high-power narrow-linewidth laser 1 to provide low-power reference light and high-power measurement light respectively. The interference optical path body achieves reference light frequency shifting, backlight reception, and heterodyne interferometry detection. The endoscopic scanning probe enables dynamic focusing, lateral light emission, and two-dimensional scanning of the measurement light. This device can achieve non-contact scanning vibrometer measurement in confined, enclosed, deep cavity, and complex internal regions, solving the problems of traditional free-space laser vibrometers' difficulty in entering complex internal regions, traditional fiber optic vibrometers' difficulty in performing regional scanning, and insufficient signal-to-noise ratio of the vibration measurement signal under weak backlight conditions.

[0048] Example 2

[0049] The working process of the high-power fiber optic endoscopic scanning laser vibrometer in this embodiment includes:

[0050] Turn on the high-power, narrow-linewidth laser 1 to output two laser beams simultaneously. One beam is a low-power reference beam that enters the interference optical path body; the other beam is a high-power measurement beam that enters the endoscopic scanning probe via the second optical fiber 11.

[0051] The reference light is incident on the acousto-optic modulator 3 via the first reflecting mirror 2. The acousto-optic modulator 3 frequency-shifts the reference light to form a reference light with a preset frequency offset. The frequency-shifted reference light is then guided by the second reflecting mirror 4 and enters the beam splitter prism 6.

[0052] After the high-power measurement light enters the endoscopic scanning probe, it passes sequentially through the polarizing beam splitter 12, the liquid focusing lens 14, the quarter-wave plate 15, and the miniature scanning galvanometer 16. The light is then reflected by the miniature scanning galvanometer 16 and emitted laterally onto the surface of the object 17 being measured. The miniature scanning galvanometer 16 is controlled to deflect in two dimensions according to a preset trajectory, allowing the measurement light to sequentially illuminate different locations within the measured area.

[0053] During the scanning process, the liquid focusing lens 14 adjusts the focus according to changes in the distance to the surface of the object 17, changes in the intensity of the reflected light, or preset focus control commands, so that the measurement light maintains a good focused state at different scanning positions. For the object 17 with curvature changes or surface undulations, the liquid focusing lens 14 can quickly compensate for defocus, improve the intensity of the returned measurement light and the stability of the vibration measurement signal.

[0054] The measurement light returning from the surface of the object under test 17 returns along the original path, passing through the miniature scanning galvanometer 16, the quarter-wave plate 15, and the liquid focusing lens 14 before reaching the polarizing beam splitter 12. The returning measurement light is separated from the incident light at the polarizing beam splitter 12, reflected by the sixth reflecting mirror 13, coupled into the first optical fiber 10, and then returns to the interference optical path body through the first optical fiber 10.

[0055] The returning measurement light and the frequency-shifted reference light are coherently combined at beam splitter prism 6 to form two complementary interference light signals. The two complementary interference lights are incident on balanced photodetector 9 through third mirror 5 and fourth mirror 8, respectively. Balanced photodetector 9 outputs heterodyne interference electrical signals, which, after subsequent signal acquisition and demodulation processing, provide vibration information at different scanning positions on the surface of the measured object 17.

Claims

1. A high-power fiber endoscopic scanning laser vibrometer device, characterized by, It includes a dual-fiber output laser, an interference optical path body, and an endoscopic scanning probe for introducing measurement light into a narrow detection area; the laser is a dual-fiber output laser with coherent output of the two beams, one of which is output as a reference beam to the interference optical path body, and the other is output as a measurement beam to the endoscopic scanning probe, and the output power of the measurement beam is greater than that of the reference beam. The measuring light passes through a polarizing beam splitter, a liquid focusing lens, a quarter-wave plate, and a miniature scanning mirror in sequence before illuminating the surface of the object under test. The light reflected back from the object under test passes through the miniature scanning mirror, a quarter-wave plate, a liquid focusing lens, a polarizing beam splitter, and a sixth reflecting mirror in sequence before being input into the interference light path body to interfere with the reference light. The reference light is guided by the first reflecting mirror to the acousto-optic modulator for frequency shifting, then reflected by the second reflecting mirror, and subsequently split by the beam splitter. The measurement light is received by the endoscopic scanning probe and returns to the interference optical path body. It then coherently combines with the frequency-shifted reference light at the beam splitter. After being reflected by the third and fourth reflecting mirrors, it is received by the balanced photodetector, forming a heterodyne interference signal containing the vibration information of the measured object.

2. The high-power fiber endoscopic swept laser vibrometer apparatus of claim 1, wherein, The laser outputs dual optical fibers with unequal power. One fiber outputs a reference light with a fixed power of less than 5mW and is connected to the interference optical path body; the other fiber outputs a measurement light with a power of more than 1W and adjustable power and is connected to the endoscopic scanning probe.

3. The high power fibered endoscopic swept laser vibrometer device according to claim 1, wherein, The beam splitter has a beam splitting ratio of 50:

50.

4. The high power fibered endoscopic swept laser vibrometer according to claim 1, wherein, The maximum outer diameter of the endoscopic scanning probe does not exceed 15 mm.

5. The high power fibered endoscopic swept laser vibrometer device according to claim 1, wherein, The sixth reflecting mirror is located directly below the polarizing beam splitter and is closely connected to the polarizing beam splitter.

6. The high power fibered endoscopic swept laser vibrometer device according to claim 1, wherein, The geometric centers of the polarizing beam splitter, liquid focusing lens, quarter-wave plate, and miniature scanning mirror are located on the same horizontal line.

7. The high power fibered endoscopic swept laser vibrometer device according to claim 1, wherein, The measurement light is output from the side of the miniature scanning galvanometer.

8. The high power fibered endoscopic swept laser vibrometer device according to claim 1, wherein, The liquid focusing lens changes the curvature of the focusing lens based on current driving.

9. The high-power fiber optic endoscopic scanning laser vibrometer according to claim 1, characterized in that, The miniature scanning galvanometer is based on the principle of electromagnetic drive, and a single lens can achieve two-dimensional beam deflection.

10. A working process applicable to the high-power fiber optic endoscopic scanning laser vibrometer device according to any one of claims 1 to 9, characterized in that, include: Turn on the laser so that it outputs two laser beams simultaneously: one is a low-power reference beam that enters the interference optical path body; the other is a high-power measurement beam that enters the endoscopic scanning probe. The reference light is incident on the acousto-optic modulator through the first reflecting mirror. The acousto-optic modulator frequency-shifts the reference light. The frequency-shifted reference light is then guided into the beam splitter by the second reflecting mirror. After the measuring light enters the endoscopic scanning probe, it passes sequentially through a polarizing beam splitter, a liquid focusing lens, a quarter-wave plate, and a miniature scanning mirror. After being reflected by the miniature scanning mirror, it illuminates the surface of the object being measured. The measuring light returning from the surface of the object being measured returns along the original path, passes through the miniature scanning mirror, the quarter-wave plate, and the liquid focusing lens, and then reaches the polarizing beam splitter. The returning measuring light separates from the incident light at the polarizing beam splitter and, after being reflected by the sixth reflecting mirror, enters the interference light path body. The returning measurement light and the frequency-shifted reference light are coherently combined at the beam splitter to form two complementary interference light signals. The two complementary interference lights are incident on the balanced light detector through the third and fourth reflecting mirrors, respectively. The balanced light detector outputs a heterodyne interference electrical signal. After subsequent signal acquisition and demodulation processing, the vibration information at different scanning positions on the surface of the measured object can be obtained.

Images