Rail irregularity detection system and detection method thereof

Abstract

The application provides a rail irregularity detection system and a detection method thereof. The transmitting end of the rail irregularity detection system comprises an external cavity tunable laser, a beam splitter I, a delay optical fiber, a coupler I, a circulator, a coated optical fiber, an optical detector, a red light laser, a coupler II and a collimator. The receiving end comprises an imaging plate, a filter and an infrared camera. The signal processing end comprises a data acquisition card and a computer. The frequency-modulated continuous wave is used for distance measurement, and the infrared camera is used for tracking the position of the laser spot on the imaging plate. The distance measurement precision is high, the non-cooperative target measurement can be realized, and the anti-interference capability is strong. The infrared camera is used for positioning the position of the measurement spot, the measurement repeatability is high, and the measurement is not affected by environmental factors such as sunlight. The distance information and the spot pixel coordinates of three selected measurement positions on the rail are combined to calculate the rail height irregularity measurement value and the rail alignment irregularity measurement value, so that the rail irregularity is detected.

Description

Technical Field

[0001] This invention relates to the field of track inspection technology, and in particular to a rail irregularity detection system and method. Background Technology

[0002] High-speed railways, with their advantages of comfort, safety, convenience, speed, high carrying capacity, and low energy consumption, have become an important guarantee for my country's economic and social development. As the operating speed of high-speed trains gradually increases, the accuracy requirements for rail smoothness are also becoming increasingly stringent. Currently, the common measurement method in China is to use a track inspection vehicle combined with a track control network to precisely measure the track geometry. However, this method is costly, time-consuming, and difficult to apply to lines under construction. The chordal measurement method is another traditional method for detecting rail irregularities. It uses a smaller, more easily controlled track geometry detector to detect rail irregularities, but this method relies solely on gauge wheel contact for measurement, which can easily cause track deviation; even a small deviation in the versine can result in a large error in the curve radius. Therefore, there is an urgent need for a convenient, efficient, simple, and accurate rail irregularity detection system and method. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a rail irregularity detection system.

[0004] Another technical problem to be solved by the present invention is to provide a method for detecting rail irregularities using the above-mentioned detection system.

[0005] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows:

[0006] A rail irregularity detection system includes a transmitter (A), a receiver (B), and a signal processing unit (C), wherein,

[0007] The transmitter (A) includes an external cavity tunable laser (1), a beam splitter I (2), a delay fiber (3), a coupler I (4), a circulator (5), a coated fiber (6), a photodetector (7), a red laser (8), a coupler II (9), and a collimator (10). The coated fiber (6) is coated with a semi-transparent and semi-reflective film. The external cavity tunable laser (1), beam splitter I (2), coupler I (4), circulator (5), and photodetector (7) are connected in series via optical fibers. Meanwhile, beam splitter I (2), delay fiber (3), and coupler I (4) are connected in series via optical fibers. The circulator (5) and coupler II (9) are connected via coated fiber (6). The red laser (8) and collimator (10) are respectively connected to coupler II (9) via optical fibers.

[0008] Specifically, the external cavity tunable laser (1) emits a frequency-modulated continuous wave after being modulated by a triangular wave. The laser enters the circulator (5) after passing through the Mach-Zehnder interference optical path composed of beam splitter I (2), delay fiber (3) and coupler I (4). The frequency-modulated laser passes through the coated fiber (6) with a semi-transparent and semi-reflective film and is coupled with the visible red light emitted by the red laser (8) for indication at the coupler II (9). It is then emitted to the imaging plate (11) by the collimator (10). The return light signal carrying the target distance information is coupled with the local oscillator light through the coated fiber (6). The coupled light passes through the circulator (5) and interferes at the photodetector (7) to generate a distance measurement beat frequency signal.

[0009] The receiver (B) includes an imaging plate (11), a filter (12) and an infrared camera (13). The collimator (10) is located in front of the imaging plate (11). The imaging plate (11) is located in front of the lens of the infrared camera (13). The filter (12) is fixed on the lens of the infrared camera (13).

[0010] Specifically, the imaging plate (11) serves as a target to reflect the measurement light emitted by the transmitter (A) and also images the spot of the measurement light. The filter (12) is added in front of the infrared camera to prevent stray light in the environment from affecting the measurement process. The combination of the imaging plate (11) and the infrared camera (13) enables the tracking of the measurement light spot in a large field of view.

[0011] The signal processing terminal (C) includes a data acquisition card (14) and a computer (15). The photodetector (7) is connected to the data acquisition card (14) by lines. The data acquisition card (14) and the infrared camera (13) are respectively connected to the computer (15) by lines.

[0012] Specifically, the data acquisition card (14) records the distance measurement beat frequency signal at the photodetector (7) and transmits it to the computer (15) along with the image of the imaging plate taken by the infrared camera (13); the computer (15) combines the distance information and the measurement spot position information at different measurement points of the receiving end to complete the measurement of the rail alignment information and elevation information, and confirm whether there is rail alignment irregularity or elevation irregularity.

[0013] Preferably, in the above-mentioned rail irregularity detection system, the modulation range of the external cavity tunable laser (1) is set to 1545-1555nm, and the basic modulation rate is set to 100.08nm / s.

[0014] A method for detecting rail irregularities using the above-mentioned detection system comprises the following steps:

[0015] (1) Take the first end of the rail to be measured as measurement point S, the last end of the rail to be measured as measurement point E, and the middle point of the rail to be measured as measurement point M. Install a collimator (10) on the side of the rail to be measured near point S. Use frequency-modulated continuous wave as the measurement light source to build a frequency-modulated continuous wave measurement optical path.

[0016] (2) Install the receiver at point S, record the measurement beat frequency signal at the photodetector at the data processing end and transmit it to the signal processing end, use computer software to design a bandpass filter for software filtering, filter out the measurement signal and auxiliary signal respectively, determine the resampling point based on the peak and valley points of the auxiliary signal, perform equal optical frequency interval resampling on the measurement signal, determine the peak point of the resampled signal spectrum and solve the distance to be measured.

[0017] (3) Set the threshold to 80-130 to preprocess the images captured by the infrared camera, clear the gray values ​​of pixels with gray values ​​below the threshold to zero, eliminate the influence of ambient stray light, perform Gaussian filtering on the preprocessed image to further eliminate the influence of Gaussian noise in the environment, and determine the pixel coordinates of the measurement spot in the camera coordinate system based on the gray values ​​of each pixel.

[0018] (4) Move the receiver to point E and point M respectively, and repeat steps (2) and (3) to obtain the distance measurement value and spot position measurement value of point E and point M respectively;

[0019] (5) Based on the measurement results of points S, E and M, the lateral and longitudinal deviations of the measurement spot in the camera coordinate system caused by the rail irregularity can be determined, and then the height and direction irregularity values ​​of the rail can be calculated to complete the detection of rail irregularity.

[0020] Preferably, in the above-mentioned rail irregularity detection method, the expression I of the measurement beat frequency signal measured by the photodetector is... b (t) is:

[0021] I b (t)=2A0·{2cos[2π·(α(t)τ m t+f0τ m )]+2cos[2π·(α(t)τ r t+f0τ r )]

[0022] +cos[2π·(α(t)(τ m +τ r )t+f0(τ m +τ r ))]+cos[2π·(α(t)(τ m -τ r )t+f0(τ m -τ r))]}

[0023] Where A0 represents the amplitude of the frequency-modulated light source, f0 is the initial frequency of laser modulation, α(t) represents the real-time modulation rate of the frequency-modulated light source containing nonlinear quantities, t represents time, and τ m τ is the time delay between light emission and return caused by the optical path length of the distance to be measured. r The time delay generated by the calibrated length of the delay fiber.

[0024] Preferably, in the above-mentioned method for detecting rail irregularities, the pixel coordinates (x, y) of the measured spot in the camera coordinate system are represented as follows:

[0025]

[0026]

[0027] The resolution of the infrared camera is N×M,a ij This represents the grayscale value of the pixel in the i-th row and j-th column of the camera after preprocessing and Gaussian filtering.

[0028] Preferably, the above-mentioned rail irregularity detection method is based on the measurement results of three selected measurement points, i.e., the distance measurement result R. S R E R M and coordinate measurement results (x S ,y S ), (x E ,y E ), (x M ,y M This allows us to determine the lateral and longitudinal deviations of the measurement spot in the camera coordinate system caused by uneven rail:

[0029]

[0030]

[0031] Preferably, in the above-mentioned method for detecting rail irregularities, the vertical irregularity value f of the rail is measured. H and track irregularity value f L It is expressed as follows:

[0032] f L =β L Δx+γ L Δy

[0033] f H =β H Δx+γ H Δy

[0034] Where β L βH γ L γ H The transformation coefficients from pixel coordinates to world coordinates can be obtained by calibrating the laser tracker. Δx and Δy are the lateral and longitudinal deviations of the measurement spot in the camera coordinate system caused by the unevenness of the rail.

[0035] Beneficial effects:

[0036] The aforementioned rail irregularity detection system utilizes frequency-modulated continuous wave (FM wave) for distance measurement and simultaneously employs an infrared camera to track the position of a laser spot on an imaging plate. This results in high distance measurement accuracy, enables non-cooperative target measurement, and exhibits strong anti-interference capabilities. The infrared camera is used to locate the measurement spot, ensuring high measurement repeatability and immunity to environmental factors such as sunlight. By combining the distance information from three selected measurement locations on the rail with the laser spot pixel coordinates, the system can calculate the measured values ​​for both vertical and horizontal rail irregularities. This enables convenient, efficient, and accurate detection of rail irregularities, particularly for single rails, focusing on both vertical and horizontal irregularities. The method eliminates the need for complex data processing, offers high measurement accuracy, and features a simple, easily adjustable, efficient, and accurate measurement system with reliable results. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the overall device principle of the rail irregularity detection system in this invention;

[0038] Figure 2 This is an installation diagram of the system used in this invention to detect rail irregularities using an infrared camera and frequency-modulated continuous wave.

[0039] Figure 3 This is a schematic diagram illustrating the lateral and longitudinal deviations of the measurement spot in the camera coordinate system caused by the rail irregularity during the detection of rail irregularity using an infrared camera and frequency-modulated continuous wave in this invention.

[0040] In the diagram: 1-External cavity tunable laser; 2-Beam splitter I; 3-Delay fiber; 4-Coupler I

[0041] 5-Circulator 6-Fiber Optic 7-Photodetector 8-Red Laser 9-Coupler II

[0042] 10-Collimator 11-Imaging plate 12-Filter 13-Infrared camera

[0043] 14-Data Acquisition Card 15-Computer 16-Rail A-Transmitter B-Receiver

[0044] C-Signal Processing Terminal Detailed Implementation

[0045] The rail irregularity detection system and its detection method of the present invention will be described below with reference to the embodiments and accompanying drawings.

[0046] Example 1

[0047] like Figure 1 As shown, a rail irregularity detection system includes a transmitter A, a receiver B, and a signal processing end C. The transmitter A includes an external cavity tunable laser 1, a beam splitter I2, a delay fiber 3, a coupler I4, a circulator 5, a coated fiber 6, a photodetector 7, a red laser 8, a coupler II9, and a collimator 10. The coated fiber 6 is coated with a semi-transparent, semi-reflective film. The external cavity tunable laser 1, beam splitter I2, coupler I4, circulator 5, and photodetector 7 are connected in series via optical fibers. Simultaneously, the beam splitter I2, delay fiber 3, and coupler I4 are connected in series via optical fibers. The circulator... 5 and coupler II 9 are connected via coated optical fiber 6. The red laser 8 and collimator 10 are respectively connected to coupler II 9 via optical fiber. The receiving end B includes an imaging plate 11, a filter 12 and an infrared camera 13. The collimator 10 is set in front of the imaging plate 11. The imaging plate 11 is placed in front of the lens of the infrared camera 13. The filter 12 is fixed on the lens of the infrared camera 13. The signal processing end C includes a data acquisition card 14 and a computer 15. The photodetector 7 is connected to the data acquisition card 14 by lines. The data acquisition card 14 and the infrared camera 13 are respectively connected to the computer 15 by lines.

[0048] The external cavity tunable laser 1 in transmitter A emits a frequency-modulated continuous wave after triangular wave modulation. The laser beam passes through a Mach-Zehnder interference optical path composed of beam splitter I2, delay fiber 3, and coupler I4 before entering circulator 5. The frequency-modulated laser passes through coated fiber 6 with a semi-transparent, semi-reflective coating and couples with visible red light emitted from red laser 8 at coupler II9. This red light is then collimated by collimator 10 and emitted onto imaging plate 11. The return light signal carrying target distance information is coupled with the local oscillator light through the coated fiber. The coupled light then interferes at photodetector 7 through the circulator to generate a distance measurement beat frequency signal.

[0049] The receiver B consists of an imaging plate 11, a filter 12, and an infrared camera 13. The imaging plate 11 serves two purposes: firstly, it acts as a target to reflect the measurement light emitted from the transmitter A; secondly, it images the spot of the measurement light. The filter 12 is placed in front of the infrared camera to prevent stray light from affecting the measurement process. The combination of the imaging plate 11 and the infrared camera 13 enables tracking of the measurement light spot within a large field of view.

[0050] The PicoScope 6000E data acquisition card 14 in the signal processing terminal C records the distance measurement beat frequency signal at the photodetector 7 and transmits it along with the imaging plate spot image captured by the infrared camera 13 to the computer 15. The computer 15 combines the distance information and the measurement spot position information at different positions of the receiving end to complete the measurement of the rail alignment irregularities and elevation irregularities.

[0051] Specifically, the external cavity tunable laser 1 in the rail irregularity detection system is a LUNAPHOENIX 1400 frequency-modulated continuous wave laser, with a modulation range of 1545-1555nm and a base modulation rate of 100.08nm / s. The infrared camera is a CMLN-13S2M-CS from GrayPoint Technology, with a resolution of 1294×964, and responds to light in the 1550nm band.

[0052] Taking the frequency modulation stage of the frequency-modulated light source as an example, the instantaneous electric field E of the frequency-modulated laser emitted by the external cavity tunable laser 1 is... m (t) can be represented as:

[0053]

[0054] Where A0 represents the amplitude of the frequency-modulated light source, f0 is the initial frequency of laser modulation, α(t) represents the real-time modulation rate of the frequency-modulated light source containing nonlinear quantities, and t represents time. This represents the initial phase of the frequency-modulated continuous wave.

[0055] The distance measurement signal at the photodetector 7 is a beat frequency signal generated by the coherence of four optical signals containing different distance information. After ignoring the light intensity loss caused by the optical fiber and filtering out the DC component, the beat frequency signal I... b (t) can be represented as follows:

[0056] I b (t)=2A0·{2cos[2π·(α(t)τ m t+f0τ m )]+2cos[2π·(α(t)τ r t+f0τ r )]

[0057] +cos[2π·(α(t)(τ m +τ r )t+f0(τ m +τ r ))]+cos[2π·(α(t)(τ m -τ r )t+f0(τ m -τ r ))]}

[0058] Where A0 represents the amplitude of the frequency-modulated light source, f0 is the initial frequency of laser modulation, α(t) represents the real-time modulation rate of the frequency-modulated light source containing nonlinear quantities, t represents time, and τ m τ is the time delay between light emission and return caused by the optical path length of the distance to be measured. r The time delay generated by the calibrated length of the delay fiber.

[0059] Although the modulation rate of the frequency-modulated light source was set before the measurement, severe nonlinearity still existed due to environmental changes and mechanical vibrations. This caused significant broadening of the measurement signal spectrum, difficulty in calculating the distance information, and large measurement errors. A bandpass filter was designed using Matlab for software filtering to extract the measurement signal I. m (t) and auxiliary signal I r (t) is shown below:

[0060] I m (t)=4A0cos[2π·(α(t)τ m t+f0τ m )]

[0061] I r (t)=4A0cos[2π·(α(t)τ r t+f0τ r )]

[0062] Where A0 represents the amplitude of the frequency-modulated light source, f0 is the initial frequency of laser modulation, α(t) represents the real-time modulation rate of the frequency-modulated light source containing nonlinear quantities, t represents time, and τ m τ is the time delay between light emission and return caused by the optical path length of the distance to be measured. r The time delay generated by the calibrated length of the delay fiber.

[0063] The auxiliary signal is used as the resampling clock signal, and the extreme points of the auxiliary signal are used as resampling points. At this point, the optical frequencies corresponding to each sampling point are equally spaced. The sampling frequency F that triggers resampling... s for:

[0064] F s =2πα(t)τ r

[0065] α(t) is the instantaneous modulation rate of the frequency-modulated light source containing nonlinear quantities, τ r The time delay generated by the calibrated length of the delay fiber.

[0066] The measurement signal I is measured using the resampling points. m(t) Perform equal-frequency resampling operation, and the peak frequency f of the resulting resampled measurement signal spectrum is:

[0067]

[0068] Where τ m τ is the time delay between light emission and return caused by the optical path length of the distance to be measured. r The time delay generated by the calibrated length of the delay fiber.

[0069] At this point, the distance R to be measured can be expressed as:

[0070]

[0071] Where f is the peak frequency of the resampled measurement signal spectrum, τ r The time delay is the time delay produced by the calibrated length of the delay fiber, where c represents the speed of light and n represents the air refractive index.

[0072] The determination of the measured spot position is based on the grayscale values ​​of each pixel recorded after the infrared camera captures the imaging plate. A dynamic threshold is set according to the ambient light intensity to manually eliminate stray light interference, and Gaussian filtering is used to eliminate the influence of Gaussian noise in the environment. The pixel coordinates (x, y) of the measured spot in the camera coordinate system are expressed as follows:

[0073]

[0074]

[0075] The resolution of the infrared camera is N×M,a ij Represents the grayscale value of the pixel in the i-th row and j-th column of the camera.

[0076] Using the first end of the rail 16 to be measured as measurement point S, the last end of the rail as measurement point E, and the midpoint of the rail as measurement point M, the frequency-modulated continuous wave distance measurement results and the infrared camera spot positioning positions are recorded as follows: R S R E R M 、(x S ,y S ), (x E ,y E ), (x M ,y M The lateral deviation Δx and longitudinal deviation Δy of the measuring spot in the camera coordinate system due to the unevenness of the rail are expressed as follows:

[0077]

[0078]

[0079] Furthermore, the elevation unevenness value f of this section of rail was measured. H and track irregularity value f L It is expressed as follows:

[0080] f L =β L Δx+γ L Δy

[0081] f H =β H Δx+γ H Δy

[0082] Where β L β H γ L γ H The transformation coefficients from pixel coordinates to world coordinates can be obtained by calibrating the laser tracker. Δx and Δy are the lateral and longitudinal deviations of the measurement spot in the camera coordinate system caused by the unevenness of the rail.

[0083] This invention utilizes frequency-modulated continuous wave for distance measurement and simultaneously employs an infrared camera to track the position of a laser spot on an imaging plate, enabling convenient, efficient, and accurate detection of single-rail irregularities, i.e., rail alignment and elevation discrepancies. The specific design process includes:

[0084] Step 1: As Figure 2 To illustrate the installation of the system for detecting rail irregularities using an infrared camera and frequency-modulated continuous wave (FMCH), the first end of the rail under test (16) is designated as measurement point S, the last end as measurement point E, and the midpoint as measurement point M. A collimator (10) is installed outside the rail under test, near point S. FMCH is used as the measurement light source, with sawtooth wave modulation of the laser wavelength. The modulation range is set to 1545-1555 nm, and the basic modulation rate is set to 100.08 nm / s. An FMCH measurement optical path is then established.

[0085] Step 2: First, install receiver B at point S. The data processing unit records the measured beat frequency signal at the photodetector and transmits it to the data acquisition card. The measured beat frequency signal I... bS (t) is:

[0086] I bS (t)=2A0·{2cos[2π·(α(t)τ m t+f0τ m )]+2cos[2π·(α(t)τ r t+f0τ r )]

[0087] +cos[2π·(α(t)(τ m +τr )t+f0(τ m +τ r ))]+cos[2π·(α(t)(τ m -τ r )t+f0(τ m -τ r ))]}

[0088] Where A0 represents the amplitude of the frequency-modulated light source, f0 is the initial frequency of laser modulation, α(t) represents the real-time modulation rate of the frequency-modulated light source containing nonlinear quantities, t represents time, and τ m τ is the time delay between light emission and return caused by the optical path length of the distance to be measured. r The time delay generated by the calibrated length of the delay fiber.

[0089] Design a bandpass filter using Matlab for software filtering to extract the measured signal I. mS (t) and auxiliary signal I rS (t) is shown below:

[0090] I mS (t)=4A0cos[2π·(α(t)τ m t+f0τ m )]

[0091] I rS (t)=4A0cos[2π·(α(t)τ r t+f0τ r )]

[0092] Where A0 represents the amplitude of the frequency-modulated light source, f0 is the initial frequency of laser modulation, α(t) represents the real-time modulation rate of the frequency-modulated light source containing nonlinear quantities, t represents time, and τ m τ is the time delay between light emission and return caused by the optical path length of the distance to be measured. r The time delay generated by the calibrated length of the delay fiber.

[0093] Extracting the peak and trough points of the auxiliary signal as resampling points for the measurement signal I mS (t) Perform equal-frequency resampling operation, and obtain the peak frequency f of the spectrum of the resampled measurement signal. S for:

[0094]

[0095] Where τ m τ is the time delay between light emission and return caused by the optical path length of the distance to be measured. r The time delay generated by the calibrated length of the delay fiber.

[0096] At this time, the distance to be measured, R S It can be represented as:

[0097]

[0098] Where f is the peak frequency of the resampled measurement signal spectrum, τ r The time delay is the time delay produced by the calibrated length of the delay fiber, where c represents the speed of light and n represents the air refractive index.

[0099] Repeat the measurement five times, and take the average of the five measurements as the final distance measurement value for point S.

[0100] Step 3: Preprocess the images captured by the infrared camera by setting an appropriate threshold. Clear the grayscale values ​​of pixels with values ​​below the threshold to zero, eliminating the influence of ambient stray light. Perform Gaussian filtering on the preprocessed image to further eliminate Gaussian noise in the environment. Measure the pixel coordinates (x, y, y) of the light spot in the camera coordinate system based on the grayscale values ​​of each pixel. S ,y S The following is represented:

[0101]

[0102]

[0103] Repeat the measurement five times, and use the average of the five measurements as the final position of the light spot measured at point S by the receiver.

[0104] Step 4: Move the receiver to points E and M respectively, and repeat steps 2 and 3 to obtain the distance measurements and spot position measurements at points B and C.

[0105] Step 5: As Figure 3 This diagram illustrates the lateral and longitudinal deviations of the measurement spot in the camera coordinate system caused by rail irregularities. Based on the measurement results at points S, E, and M, the lateral deviation Δx and longitudinal deviation Δy of the measurement spot in the camera coordinate system caused by rail irregularities can be determined:

[0106] In addition, the elevation unevenness value f of the rail in this section was measured. H and track irregularity value f L It is expressed as follows:

[0107] f L =β L Δx+γ L Δy

[0108] f H=β H Δx+γ H Δy

[0109] Where β L β H γ L γ H Δx is a constant representing the transformation coefficient from pixel coordinates to world coordinates, which can be obtained by laser interferometer calibration. Δx and Δy are the lateral and longitudinal deviations of the measurement spot in the camera coordinate system caused by the unevenness of the rail.

[0110] In summary, by applying the rail irregularity detection system described in this invention, and combining the distance information of three measurement positions with the pixel coordinate information of the light spot, rail irregularities can be detected, and the measurement values ​​of rail height irregularities and rail direction irregularities can be calculated. It does not require a complex data processing process, the measurement system is simple, the measurement process is convenient, the measurement results are less affected by environmental factors, and the measurement accuracy is high.

[0111] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A rail irregularity detection system, characterized in that: It includes a transmitter (A), a receiver (B), and a signal processing unit (C), among which, The transmitter (A) includes an external cavity tunable laser (1), beam splitter I (2), delay fiber (3), coupler I (4), circulator (5), coated fiber (6), photodetector (7), red laser (8), coupler II (9), and collimator (10). The coated fiber (6) is coated with a semi-transparent and semi-reflective film. The external cavity tunable laser (1), beam splitter I (2), coupler I (4), circulator (5), and photodetector (7) are connected in series via optical fibers. Simultaneously, beam splitter I (2), delay fiber (3), and coupler I (4) are connected in series via optical fibers. The circulator (5) and coupler II (9) are connected in series via the coated fiber. The red laser (8) and collimator (10) are connected to the coupler II (9) via optical fibers. The external cavity tunable laser in the transmitter emits a frequency-modulated continuous wave after being modulated by a triangular wave. The laser enters the circulator after passing through the Mach-Zehnder interference optical path composed of beam splitter I, delay fiber and coupler I. The frequency-modulated laser passes through the coated fiber with a semi-transparent and semi-reflective film and is coupled with the visible red light emitted by the red laser for indication at the coupler II and is emitted to the image by the collimator. The return light signal carrying the target distance information is coupled with the local oscillator light through the coated fiber. The coupled light passes through the circulator and interferes at the photodetector to generate a distance measurement beat frequency signal. The receiving end (B) includes an imaging plate (11), a filter (12) and an infrared camera (13). The collimator (10) is located in front of the imaging plate (11). The imaging plate (11) is located in front of the lens of the infrared camera (13). The filter (12) is fixed on the lens of the infrared camera (13). The signal processing terminal (C) includes a data acquisition card (14) and a computer (15). The photodetector (7) is connected to the data acquisition card (14) by lines. The data acquisition card (14) and the infrared camera (13) are respectively connected to the computer (15) by lines.

2. The rail irregularity detection system according to claim 1, characterized in that: The external cavity tunable laser (1) has a modulation range of 1545-1555nm and a basic modulation rate of 100.08nm / s.

3. A method for detecting rail irregularities using the detection system described in claim 1, characterized in that: The specific steps are as follows: (1) Take the first end of the rail to be measured as measurement point S, the last end of the rail to be measured as measurement point E, and the middle point of the rail to be measured as measurement point M. Install a collimator (10) on the side of the rail to be measured near point S. Use frequency-modulated continuous wave as the measurement light source to build a frequency-modulated continuous wave measurement optical path. (2) Install the receiver at point S, record the measurement beat frequency signal at the photodetector at the data processing end and transmit it to the signal processing end, use computer software to design a bandpass filter for software filtering, filter out the measurement signal and auxiliary signal respectively, determine the resampling point according to the peak and valley points of the auxiliary signal, perform equal optical frequency interval resampling on the measurement signal, determine the peak point of the spectrum of the resampling signal and solve the distance to be measured. (3) Set the threshold to 80-130 to preprocess the images captured by the infrared camera, clear the gray values ​​of pixels with gray values ​​lower than the threshold to eliminate the influence of ambient stray light, perform Gaussian filtering on the preprocessed image to further eliminate the influence of Gaussian noise in the environment, and determine the pixel coordinates of the measurement spot in the camera coordinate system based on the gray values ​​of each pixel. (4) Move the receiver to point E and point M respectively, and repeat steps (2) and (3) to obtain the distance measurement value and spot position measurement value of point E and point M; (5) Based on the measurement results of points S, E and M, the lateral and longitudinal deviations of the measurement spot in the camera coordinate system caused by the unevenness of the rail can be determined, and then the unevenness value of the rail height and the rail direction unevenness value can be calculated to complete the detection of rail unevenness.

4. The method for detecting rail irregularities according to claim 3, characterized in that: Expression of the beat frequency signal measured by the photodetector for: ， in This indicates the amplitude of the frequency-modulated light source. It is the initial frequency of laser modulation. This represents the real-time modulation rate of a frequency-modulated light source containing nonlinear quantities. Represents time, The time delay between light emission and return caused by the optical path length of the distance to be measured. The time delay generated by the calibrated length of the delay fiber.

5. The method for detecting rail irregularities according to claim 3, characterized in that: Measure the pixel coordinates of the light spot in the camera coordinate system It is expressed as follows: ， The resolution of the infrared camera is , Represents the camera's first... after preprocessing and Gaussian filtering Line number The grayscale value of the column pixels.

6. The method for detecting rail irregularities according to claim 3, characterized in that: Based on the measurement results of the three selected measurement points, i.e., the distance measurement results , , and coordinate measurement results , , It can be determined that the lateral and longitudinal deviations of the measurement spot in the camera coordinate system are caused by the unevenness of the rail: 。 7. The method for detecting rail irregularities according to claim 3, characterized in that: Measuring the height unevenness of the rail and track irregularity value It is expressed as follows: ， in , , , The transformation coefficient from pixel coordinates to world coordinates can be obtained by calibrating a laser tracker. and The unevenness of the rails caused the lateral and longitudinal deviations of the measuring spot in the camera coordinate system.

Images