A train wheel laser digital holographic detection device and detection method

Abstract

The present application relates to a kind of train wheel laser digital holography detection device and detection method, belong to nondestructive testing technical field.The present application obtains the holographic interferogram of train wheel by laser digital holography detection device, and based on holographic interferogram, three-dimensional model reconstruction is carried out to train wheel, and then relevant parameters are extracted to three-dimensional model, parameter is the data embodiment of the actual situation of train wheel, and staff determines the actual situation of train wheel by parameter;Using the detection device and detection method of the present application to carry out detection work to train wheel, can reduce the labor intensity of staff, improve detection efficiency, obtain higher accuracy detection result, improve the accuracy of judgment to the actual situation of train wheel.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of nondestructive testing, and relates to a train wheel laser digital holographic detection device and a detection method. BACKGROUND

[0002] With the rapid development of the rail transit industry, the passenger volume of high-speed railways and urban rail transit is increasing. As an important part of supporting train operation, train wheels directly affect the safety of train operation. Therefore, it is of great significance to accurately find defective train wheels in time and carry out maintenance or replacement, which is one of the important prerequisites for ensuring the safe operation of trains.

[0003] Due to the unique shape of the train wheel, the train wheel is generally detected by periodic offline manual detection. The efficiency of manual detection of train wheels is low. Considering the labor intensity and cost of manual detection, the frequency of manual detection of train wheels is limited, which increases the risk of defects of train wheels during the period between two manual detections. At present, there is also a way of detecting train wheels by using 2D images. However, 2D image detection is not intuitive, the amount of data of the detection result is limited, the accuracy of the detection result is poor, and the detection result is easily affected by foreign matter attached to the train wheel, causing detection result error.

[0004] Therefore, it is necessary to provide a train wheel laser digital holographic detection device and a detection method. The three-dimensional model of the train wheel is reconstructed for detection, the parameters that can be obtained by detection are increased, the anti-interference performance of the detection process is improved, the accuracy of the detection result is improved, the judgment of the defects of the train wheel is more accurate, manual detection is replaced, the labor intensity of the staff is reduced, and the detection frequency can be increased. SUMMARY

[0005] In order to overcome the problems in the background art, the present application provides a train wheel laser digital holographic detection device and a detection method. The train wheel is subjected to holographic interference pattern formation and image acquisition by the laser digital holographic detection device, and the three-dimensional model of the train wheel is constructed based on the holographic interference pattern by combining the detection method. Then, the relevant parameters are extracted from the three-dimensional model, and the presence of defects in the train wheel and the position and type of the defects are directly reflected by the parameters. By detecting the train wheel by the present application, the information of the holographic interference pattern not only contains the intensity information of the train wheel surface light field, but also contains the phase information of the train wheel surface light field. More information about the train wheel can be obtained, so that more parameters can be extracted to reflect the actual situation of the train wheel, thereby improving the detection result accuracy. Moreover, the detection is based on the three-dimensional model, which itself reflects the actual situation of the train wheel more comprehensively, so the anti-interference ability is stronger, and a higher precision detection result can be obtained, thereby making the judgment of the train wheel defects by the staff more accurate. Moreover, the staff only needs to place the laser digital holographic detection device at a suitable position, and the laser digital holographic detection device can form the holographic interference pattern of the train wheel and transmit the holographic interference pattern signal to the computer. The staff can perform the three-dimensional model construction and relevant parameter extraction of the train wheel by operating the computer, thereby reducing the labor intensity of the staff and increasing the frequency of detecting the train wheel according to actual needs.

[0006] In order to achieve the above-mentioned purpose, the present application provides a train wheel laser digital holographic detection device. The laser digital holographic detection device comprises a laser, a beam splitter I, a fiber coupler, a beam expander I, a lens I, a pinhole filter I, a beam expander II, a pinhole filter II, a lens IV, a beam splitter II, a lens II, a lens III, an image acquisition device, a laser filter window, and a computer. The laser emits a laser beam. The laser beam enters the beam splitter I. The beam splitter I divides the laser beam into an object beam and a reference beam.

[0007] The object beam passes through the beam expander I, the pinhole filter I, and the lens I in sequence and is incident on the train wheel to be detected. After the diffuse reflection of the train wheel to be detected, the object beam passes through the laser filter window, the lens III, and the lens II in sequence and reaches the beam splitter II. The object beam is reflected to the photoelectric conversion plane of the image acquisition device by the reflection of the beam splitter II.

[0008] The reference beam passes through the fiber coupler, the beam expander II, the pinhole filter II, and the lens IV in sequence and reaches the photoelectric conversion plane of the image acquisition device.

[0009] The object beam and the reference beam interfere with each other on the photoelectric conversion plane of the image acquisition device, forming a laser holographic interference pattern. The image acquisition device acquires the laser holographic interference pattern.

[0010] The image acquisition device is electrically connected with the computer.

[0011] Preferably, the laser digital holographic detection device is fixedly installed inside a light-proof shell, and the lens I and the laser filter window are arranged on the same side wall of the light-proof shell.

[0012] Preferably, the light-proof shell is wrapped with a rubber shockproof shell, a mobile power supply is detachably installed inside the rubber shockproof shell, the rubber shockproof shell is placed on a trolley, and the computer is placed on the top of the rubber shockproof shell.

[0013] Preferably, the splitting ratio of the beam splitter I is R:T = 90:10, wherein R is the reflected light beam intensity and T is the projected light beam intensity, the splitting ratio of the beam splitter II is R:T = 70:30, and the pinhole diameter of the pinhole filter I and the pinhole filter II is 0.5 mm. Wherein λ is the wavelength of the laser beam, f is the focal length of the corresponding beam expander, and r is the exit pupil radius of the corresponding beam expander.

[0014] Preferably, the laser is one of a He-Ne laser, a ruby laser, a CO2 laser, a Nd:YAG laser and a semiconductor laser.

[0015] Preferably, the lens I, the lens II, the lens III and the lens IV are one of a germanium lens, a silicon lens, a zinc selenide lens or a glass lens.

[0016] Preferably, the beam expander I and the beam expander II are one of a germanium lens, a silicon lens, a zinc selenide lens or a glass lens.

[0017] Preferably, the image acquisition device is one of a CCD image sensor and a CMOS image sensor.

[0018] The optical path difference between the object light beam and the reference light beam is less than the coherence length of the laser emitted by the laser.

[0019] Another aspect of the present application provides a train wheel laser digital holographic detection method, which is realized by installing noise reduction processing software, digital reproduction software, phase extraction software, phase unwrapping software, three-dimensional reconstruction software, three-dimensional image recognition software and parameter quantization extraction software in a computer.

[0020] S1: The noise reduction processing software installed in the computer sequentially performs noise reduction processing on the laser holographic interference pattern transmitted by the image acquisition device received by the computer through frequency domain filtering, Wiener filtering and gray histogram equalization.

[0021] S2: the digital reconstruction software is a secondary fast Fourier transform algorithm simulation diffraction reconstruction software written by using a Fresnel diffraction integral formula, the laser holographic interferogram after noise reduction processing in the step S1 is subjected to holographic reconstruction by using the digital reconstruction software, and the complex amplitude of the holographic reconstruction light field of the laser holographic interferogram at each distance is calculated.

[0022] S3: the phase extraction software extracts the phase of each point in the holographic reconstruction light field by performing phase extraction on the complex amplitude calculated in the step S2, and the phase distribution of each point in the holographic reconstruction light field is obtained by conversion calculation through a formula

[0023] S4: the phase unwrapping software unwraps the phase information of each point in the holographic reconstruction light field in the step S3 by using a weighted least square iterative unwrapping algorithm to obtain a continuous phase.

[0024] S5: the three-dimensional reconstruction software is written according to a formula , wherein L is the position of the point in the three-dimensional space, is the continuous phase after unwrapping processing, and λ is the wavelength of the laser.

[0025] S6: the three-dimensional image recognition software recognizes the holographic three-dimensional model of the train wheel in the step S5 to obtain the recognition result of the train wheel.

[0026] S7: the parameter quantization extraction software extracts the three-dimensional size information of the train wheel according to the recognition result in the step S6, and obtains the train wheel appearance information after calculating the three-dimensional size information, and completes the train wheel detection.

[0027] Advantages of the present application

[0028] 1. The present application applies laser digital holographic technology to carry out detection work on the train wheel, reconstructs the three-dimensional model of the train wheel, extracts parameters to represent the actual state of the train wheel, obtains more abundant parameters to judge the actual situation of the train wheel, and the three-dimensional model reacts more comprehensively to the actual situation of the train wheel, has strong anti-interference ability, can make the detection result more accurate, improve the reliability of the detection result, and improve the accuracy of judging the actual situation of the train wheel.​

[0029] 2. This invention uses a laser digital holographic detection device to collect holographic interferograms of train wheels. By using a computer to perform three-dimensional model reconstruction and parameter extraction on the holographic interferograms of train wheels acquired by the laser digital holographic detection device, the labor intensity of the staff is reduced, the detection efficiency is high, and it is also conducive to increasing the detection frequency of train wheels.

[0030] 3. By using an opaque outer shell for protection, the present invention can effectively avoid interference from ambient visible light, further reduce detection interference factors, and improve the accuracy of detection results.

[0031] 4. This invention uses a laser digital holographic detection device combined with a detection method to detect train wheels, which can obtain high-precision detection results at the micrometer level.

[0032] 5. This invention filters light through a laser filter window, ensuring that the wavelength of the light passing through the laser filter window and reaching the image acquisition device is the same as the wavelength of the laser emitted by the laser, effectively reducing interference from external stray light on the detection and reducing noise during the detection process. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the optical path of the laser digital holographic detection device of the present invention.

[0034] Figure 2 This is a three-dimensional schematic diagram of the opaque outer shell of the laser digital holographic detection device of the present invention.

[0035] Figure 3 This is a schematic diagram of the actual testing and installation of the laser digital holographic detection device of the present invention.

[0036] Figure 4 This is a schematic diagram of the portable structure of the laser digital holographic detection device of the present invention.

[0037] Figure 5 This is a flowchart of the detection method of the present invention.

[0038] Figure 6 The train wheel shape image is obtained by extracting useful information from the parameter quantization extraction software and then performing calculations.

[0039] In the diagram, 1-Laser, 2-Beam splitter I, 3-Fiber optic coupler, 4-Beam expander I, 5-Lens I, 6-Pinhole filter I, 7-Beam expander II, 8-Pinhole filter II, 9-Lens IV, 10-Beam splitter II, 11-Lens II, 12-Lens III, 13-Image acquisition device, 14-Laser filter window, 15-Computer, 16-Wheel under test, 17-Opaque housing, 18-Train rail, 19-Rubber shockproof housing, 20-Power bank, 21-Trolley. Detailed Implementation

[0040] The present invention will be further described in detail below with reference to specific embodiments.

[0041] like Figure 1 As shown, the laser digital holographic detection device includes a laser 1, a beam splitter I 2, an optical fiber coupler 3, a beam expander I 4, a lens I 5, a pinhole filter I 6, a beam expander II 7, a pinhole filter II 8, a lens IV 9, a beam splitter II 10, a lens II 11, a lens III 12, an image acquisition device 13, a laser filter window 14, and a computer 15. The laser 1 emits a laser beam, which enters the beam splitter I 2, and the beam splitter I 2 splits the laser beam into an object beam and a reference beam.

[0042] The object beam passes sequentially through beam expander I 4, pinhole filter I 6, and lens I 5 onto the wheel 16 under test. After diffuse reflection by the wheel 16, the object beam passes sequentially through laser filter window 14, lens III 12, and lens II 11 to reach beam splitter II 10. The object beam is then reflected by beam splitter II 10 onto the photoelectric conversion plane of image acquisition device 13.

[0043] The reference beam passes sequentially through fiber optic coupler 3, beam expander II 7, pinhole filter II 8, lens IV 9, and beam splitter II 10 to reach the photoelectric conversion plane of image acquisition device 13.

[0044] The object beam and the reference beam interfere with each other on the photoelectric conversion plane of the image acquisition device 13 to form a laser holographic interferogram, which is then acquired by the image acquisition device 13.

[0045] The image acquisition device 13 is connected to the computer 15.

[0046] In the above setup, the object beam and the reference beam ultimately converge on the photoelectric conversion plane of the image acquisition device 13 to generate interference. The phase and amplitude of each point on the object beam are converted into spatially varying intensity. By utilizing the contrast and spacing between the interference fringes, all the information of the object's light wave is recorded, forming a holographic interferogram. The image acquisition device 13 acquires the holographic interferogram, converts the light signal into an electrical signal, and transmits the electrical signal to the computer 15. The computer 15 receives the signal transmitted by the image acquisition device 13 and can then visualize the holographic interferogram. By operating the computer 15, the operator can perform subsequent analysis and processing on the holographic interferogram. The acquired parameters can be used to determine the actual condition of the train wheels. Furthermore, a three-dimensional model of the train wheels can be constructed during the subsequent analysis and processing of the holographic interferogram. Based on the three-dimensional model of the train wheels, the actual condition of the train wheels can be determined, resulting in more accurate detection results. This allows the operator to make more accurate judgments about defects in the train wheels. Throughout the process, the staff are mainly responsible for installing the laser digital holographic detection device in a suitable position so that the train wheels are within the field of view of the laser digital holographic detection device, and operating the computer 15 to complete the entire detection process. There is no need to measure or observe the train wheels, so the detection efficiency is high and the labor intensity is low. The staff can complete a large number of train wheel detection tasks.

[0047] The reference beam passes sequentially through fiber coupler 3, beam expander II 7, pinhole filter II 8, and lens IV 9 to complete the shaping of the reference beam, so that the reference beam illuminates the beam splitter II 10 in the form of parallel light.

[0048] The object beam passes sequentially through beam expander I 4, pinhole filter I 8, and lens I 5, causing the object beam to exhibit a certain divergence state. This allows the wheel under test 16 to diffusely reflect more of the object beam, and more object beams carrying information about the wheel under test 16 illuminate the photoelectric conversion plane of the image acquisition device 13 after diffuse reflection. This also allows the holographic interferogram acquired by the image acquisition device 13 to contain more information about the train wheel.

[0049] like Figures 2-4 As shown, the laser digital holographic detection device is fixedly installed inside the opaque housing 17, and the lens I 5 and the laser filter window 14 are located on the same side wall of the opaque housing 17. The opaque housing 17 is wrapped with a rubber shockproof housing 19, and a mobile power supply 20 is detachably installed inside the rubber shockproof housing 19. The rubber shockproof housing 19 is placed on a trolley 21, and the computer 15 is placed on top of the rubber shockproof housing 19.

[0050] In the above configuration, only one section of the object beam's optical path is located outside the opaque housing 17, while the optical paths of the reference beam and most of the object beam's optical paths are located inside the opaque housing 17. This effectively avoids interference from ambient visible light on the object beam and reference beam. In addition, the laser digital holographic detection device of the present invention can also be made into a portable device with a rubber shockproof housing 19, which can be moved by pushing the device with a trolley 21, making it convenient to transport the device to different detection points.

[0051] The beam splitter I 2 has a beam splitting ratio of R:T = 90:10, and the beam splitter II 10 has a beam splitting ratio of R:T = 70:30; the aperture of the pinhole filter I 6 and pinhole filter II 8... Where λ is the wavelength of the laser beam, f is the focal length of the corresponding beam expander, and r is the exit pupil radius of the corresponding beam expander.

[0052] In the above setup, the beam splitting ratio of the beam splitter ensures that when the object beam and the reference beam converge on the photoelectric conversion plane of the image acquisition device, the light intensity ratio is 1.2:1, with the object beam intensity slightly stronger than the reference beam. This improves the interference effect and thus enhances the holographic interferogram formation. Furthermore, the aperture size of the pinhole filter affects the quality of the object beam illuminating the wheel surface. Selecting a pinhole filter with an appropriate aperture size ensures that the object beam illuminating the wheel surface is relatively uniform and free from noise.

[0053] The laser 1 is one of the following: He-Ne laser, ruby ​​laser, CO2 laser, Nd:YAG laser, and semiconductor laser.

[0054] Lens I 5, Lens II 11, Lens III 12, and Lens IV 9 are one of germanium lenses, silicon lenses, zinc selenide lenses, or glass lenses.

[0055] The beam expander I 4 and beam expander II 7 are one of germanium lenses, silicon lenses, zinc selenide lenses or glass lenses.

[0056] The image acquisition device 13 is either a CCD image sensor or a CMOS image sensor.

[0057] In the above settings, the components can be selected according to the actual situation.

[0058] The optical path difference between the object beam and the reference beam is less than the coherence length of the laser emitted by the laser.

[0059] Example

[0060] In this embodiment, the train wheel laser digital holographic inspection device of the present invention is used to inspect the train wheel. The inspected train wheel is a defect-free wheel with a diameter of 840mm, a flange thickness of 135mm, and a bearing inner diameter of 130mm.

[0061] The laser holographic interferogram acquired by the image acquisition device 13 and received by the computer 15 is denoised using noise reduction software to obtain the denoised laser holographic interferogram.

[0062] The denoised laser holographic interferogram was holographically reproduced using digital reconstruction software, and the complex amplitude of the holographic reconstructed optical field at each distance of the laser holographic interferogram was calculated.

[0063] Phase extraction software was used to extract the phase of the complex amplitude, obtaining the phase distribution at each point in the holographic reconstructed light field. This distribution was then analyzed using the formula... The phase distribution of each point in the holographic reconstructed light field is obtained by performing conversion calculations.

[0064] Phase unwrapping software is used to unwrap the phase information of each point in the holographically reproduced light field to obtain continuous phase.

[0065] Continuous phases are converted using 3D reconstruction software, according to the formula... Write the formula, where L is the position of the point. To obtain the continuous phase after unpacking, where λ is the laser wavelength, the continuous phase distribution can be converted into a continuous position distribution, thereby converting the continuous phase information into position information in three-dimensional coordinates, and obtaining a holographic three-dimensional model of the train wheel.

[0066] Select appropriate 3D image recognition software based on actual needs to recognize the holographic 3D model of the train wheel and obtain the 3D dimension information of the train wheel.

[0067] The three-dimensional dimensional information of the train wheels is extracted using parametric quantization extraction software. Information from each region in the recognition results is selected and calculated to obtain the train wheel morphology information. For example... Figure 6 As shown.

[0068] pass Figure 6 It is clear from the visual inspection that the wheel is free of defects.

[0069] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made to it in form and detail without departing from the scope defined by the claims of the present invention.

Claims

1. A laser digital holographic detection device for train wheels, characterized in that: The laser digital holographic detection device includes a laser (1), a beam splitter I (2), an optical fiber coupler (3), a beam expander I (4), a lens I (5), a pinhole filter I (6), a beam expander II (7), a pinhole filter II (8), a lens IV (9), a beam splitter II (10), a lens II (11), a lens III (12), an image acquisition device (13), a laser filter window (14), and a computer (15). The laser (1) emits a laser beam, which enters the beam splitter I (2). The beam splitter I (2) splits the laser beam into an object beam and a reference beam. The object beam passes through beam expander I (4), pinhole filter I (6), and lens I (5) in sequence and is projected onto the wheel under test (16). After the object beam is diffusely reflected by the wheel under test (16), it passes through laser filter window (14), lens III (12), and lens II (11) in sequence to reach beam splitter II (10). Through the reflection of beam splitter II (10), the object beam is reflected onto the photoelectric conversion plane of image acquisition device (13). The reference beam passes sequentially through fiber coupler (3), beam expander II (7), pinhole filter II (8), lens IV (9), and beam splitter II (10) to reach the photoelectric conversion plane of image acquisition device (13); The object beam and the reference beam interfere with each other on the photoelectric conversion plane of the image acquisition device to form a laser holographic interferogram, and the image acquisition device (13) acquires the laser holographic interferogram; The image acquisition device (13) is electrically connected to the computer (15); The beam splitter I (2) has a beam splitting ratio of R:T=90:10, where R is the intensity of the reflected beam and T is the intensity of the projected beam; the beam splitter II (10) has a beam splitting ratio of R:T=70:30; the aperture of the pinhole filter I (6) and pinhole filter II (8) is... , where λ is the wavelength of the laser beam, f is the focal length of the corresponding beam expander, and r is the exit pupil radius of the corresponding beam expander.

2. The train wheel laser digital holographic detection device according to claim 1, characterized in that: The laser digital holographic detection device is fixedly installed inside the opaque housing (17), and the lens I (5) and the laser filter window (14) are located on the same side wall of the opaque housing (17).

3. The train wheel laser digital holographic detection device according to claim 2, characterized in that: The opaque outer shell (17) is wrapped with a rubber shockproof outer shell (19). A mobile power supply (20) is detachably installed inside the rubber shockproof outer shell (19). The rubber shockproof outer shell (19) is placed on a handcart (21). The computer (15) is placed on top of the rubber shockproof outer shell (19).

4. The train wheel laser digital holographic detection device according to claim 1, characterized in that: The laser (1) mentioned is one of He-Ne laser, ruby ​​laser, CO2 laser, Nd:YAG laser, and semiconductor laser.

5. The train wheel laser digital holographic detection device according to claim 1, characterized in that: Lens I (5), lens II (11), lens III (12), and lens IV (9) are one of germanium lenses, silicon lenses, zinc selenide lenses, or glass lenses.

6. The train wheel laser digital holographic detection device according to claim 1, characterized in that: The beam expander I (4) and beam expander II (7) are one of germanium lenses, silicon lenses, zinc selenide lenses or glass lenses.

7. The train wheel laser digital holographic detection device according to claim 1, characterized in that: The image acquisition device is either a CCD image sensor or a CMOS image sensor.

8. The train wheel laser digital holographic detection device according to claim 1, characterized in that: The optical path difference between the object beam and the reference beam is less than the coherence length of the laser emitted by the laser.

9. A method for using the detection device according to any one of claims 1-8 for train wheel detection, characterized in that: The computer (15) system is equipped with noise reduction processing software, digital reproduction software, phase extraction software, phase unwrapping software, three-dimensional reconstruction software, three-dimensional image recognition software, and parameter quantization extraction software. The detection method includes the following steps: S1: The noise reduction processing software installed in the computer (15) performs noise reduction processing on the laser holographic interferogram transmitted by the image acquisition device (13) received by the computer (15) through frequency domain filtering, Wiener filtering and grayscale histogram equalization in sequence. S2: The digital reconstruction software is a diffraction reconstruction software that uses the Fresnel diffraction integral formula to simulate the diffraction. The digital reconstruction software is used to holographically reconstruct the laser holographic interferogram after noise reduction in step S1, and the complex amplitude of the holographic reconstructed light field at each distance of the laser holographic interferogram is calculated. S3: The phase extraction software performs phase extraction on the complex amplitude calculated in step S2 to obtain the phase information of each point in the holographic reconstruction light field, and then uses the formula... The phase distribution of each point within the holographic reconstruction light field is obtained through conversion calculation, where: The phase of the point to be extracted. The magnitude of the complex amplitude at that point. for The size of the imaginary part, for The size of the real part; S4: The phase unwrapping software uses a weighted least squares iterative unwrapping algorithm to unwrap the phase information of each point in the holographic reconstructed light field in step S3 to obtain continuous phase; S5: The 3D reconstruction software follows the formula Write, in the formula This represents the position of the point in three-dimensional space. For continuous phase after unpacking, Using the laser wavelength, the continuous phase in step S4 is converted into position information in three-dimensional coordinates to obtain a holographic three-dimensional model of the train wheel. S6: The three-dimensional image recognition software recognizes the holographic three-dimensional model of the train wheel in step S5 and obtains the recognition result of the train wheel. S7: The parameter quantization extraction software extracts the three-dimensional size information of the train wheel based on the recognition results in step S6, and calculates the three-dimensional size information to obtain the shape information of the train wheel, thus completing the train wheel detection.

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