WO2021043518A1 - Procédé et dispositif de mesure destinés à mesurer un objet d'une voie ferrée - Google Patents

Procédé et dispositif de mesure destinés à mesurer un objet d'une voie ferrée Download PDF

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Publication number
WO2021043518A1
WO2021043518A1 PCT/EP2020/071946 EP2020071946W WO2021043518A1 WO 2021043518 A1 WO2021043518 A1 WO 2021043518A1 EP 2020071946 W EP2020071946 W EP 2020071946W WO 2021043518 A1 WO2021043518 A1 WO 2021043518A1
Authority
WO
WIPO (PCT)
Prior art keywords
image
scanning line
pixel
laser
series
Prior art date
Application number
PCT/EP2020/071946
Other languages
German (de)
English (en)
Inventor
Martin BÜRGER
Gerald Zauner
Original Assignee
Plasser & Theurer Export Von Bahnbaumaschinen Gesellschaft M.B.H.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Plasser & Theurer Export Von Bahnbaumaschinen Gesellschaft M.B.H. filed Critical Plasser & Theurer Export Von Bahnbaumaschinen Gesellschaft M.B.H.
Priority to EP20754195.4A priority Critical patent/EP4025868A1/fr
Publication of WO2021043518A1 publication Critical patent/WO2021043518A1/fr

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B11/00—Measuring arrangements characterised by the use of optical techniques
    • G01B11/24—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures
    • G01B11/25—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures by projecting a pattern, e.g. one or more lines, moiré fringes on the object
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T7/00—Image analysis
    • G06T7/0002—Inspection of images, e.g. flaw detection
    • G06T7/0004—Industrial image inspection
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T7/00—Image analysis
    • G06T7/50—Depth or shape recovery
    • G06T7/521—Depth or shape recovery from laser ranging, e.g. using interferometry; from the projection of structured light
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T2207/00—Indexing scheme for image analysis or image enhancement
    • G06T2207/30—Subject of image; Context of image processing
    • G06T2207/30108—Industrial image inspection
    • G06T2207/30136—Metal

Definitions

  • the invention relates to a method for measuring an object of a track by means of a laser light section sensor, a scanning line being projected onto a surface of the object by means of a laser and the surface being recorded by means of a digital image recorder.
  • the invention also relates to a measuring device for carrying out the method.
  • DE 102015 119409 A1 describes a laser light section
  • a laser projects a scanning line (laser line) onto the rail.
  • a reflection image of the scanning line is recorded using imaging optics and a high-resolution digital image sensor.
  • the output signals of the digital image sensor are evaluated in an evaluation device to determine rail deformation.
  • the invention is based on the object of improving a method of the type mentioned at the outset in such a way that disruptive influences from other light sources do not impair the measurement.
  • Another object of the invention is to specify a corresponding measuring device.
  • the scanning line is projected onto the surface with periodically varied light intensity, the image recorder recording a series of images and using corresponding image positions in the image series a detection device are jointly evaluated in order to detect an image of the scanning line. Due to the periodically varied light intensity, the projection of the scanning line can be distinguished from reflections from other light sources.
  • a correspondingly further developed laser light section sensor (3D laser profile sensor, light sectioning method) leads to increased measurement robustness when used outdoors, especially when exposed to direct sunlight.
  • the light received by the image sensor is filtered by means of a narrow-band optical filter.
  • the optical filter is matched to a central wavelength of the laser.
  • the delimitation according to the invention by evaluating the varied brightness is then only required from interfering light with the same wavelength. Light with a different wavelength does not reach the image sensor.
  • Another improvement provides that the image series is recorded at least over a period of the periodically varied light intensity of the laser. This measure simplifies the subsequent evaluation, because in the series of images the difference between the light from the laser and the light from other sources becomes clearer.
  • the subsequent evaluation is simplified if matching image positions are evaluated together in at least three images. At least five brightness values are then available for the evaluation of each pixel. It can thus be clearly determined whether the respective pixel images a surface location of the object to be measured which is illuminated by means of the laser. A joint evaluation of only two images would be too few for a detection of a periodic change in the brightness values, because no progression curve can be modeled.
  • the light intensity is varied sinusoidally, with a pixel-by-pixel Fourier transformation of an intensity signal (brightness signal) being carried out to evaluate the image series for the corresponding image positions, with an amount of a 1st harmonic of the Fourier signal for each pixel. Spectrum is determined and the amounts of the 1st harmonic are evaluated in order to detect imaging pixels of the scanning line.
  • an evaluation can be carried out with fast algorithms, whereby FPGAs (Field Programmable Gate Array) or GPUs (Graphics Processing Unit) can be used as hardware.
  • the jointly evaluated image series forms an image stack with corresponding image content, with sinusoidal brightness gradients only occurring at the points illuminated with the laser. It is therefore checked how high the absolute value of the 1st harmonic of each evaluated pixel is. Significantly increased values are present where the scanning line lies in the image stack. For the evaluation of measurement results, the image stack is merged into a common image, with the detected scanning line being highlighted.
  • a threshold value is specified for the evaluation of the 1st harmonic and if a uniform brightness value is specified for all pixels whose amount of the 1st harmonic is below the threshold value. For example, all pixels that do not image a point illuminated by the laser receive a brightness value equal to zero. Thus, in the merged image of the jointly evaluated image series, only the depicted scanning line is visible. Based on their course, the track object under consideration can be measured using optical triangulation.
  • an electronic filtering of an intensity signal is carried out pixel-by-pixel to evaluate the image series for the corresponding image positions, the filtered intensity signal of the respective pixel being evaluated for imaging pixels to detect the scanning line.
  • An electronic filter is set up in such a way that only intensity signals that are varied in accordance with the laser light can pass. In this way, those pixels are recognized that depict surface areas illuminated by the laser.
  • the laser is set up to project a scanning line with periodically varied light intensity
  • the image recorder being designed to record an image series
  • the detection device being designed to simultaneously evaluate image positions that match in the image series .
  • Such a device can comprise known components of a laser light section sensor, a modified control of the laser and evaluation logic according to the invention being implemented.
  • the laser is set up to project a scanning line with sinusoidally varied light intensity
  • the detection device being set up to generate a pixel-by-pixel Fourier transformation of an intensity signal and to determine an amount of a 1st harmonic of the respective Fourier spectrum.
  • Inexpensive and efficient components such as FPGAs or GPUs are available for implementing appropriate evaluation algorithms.
  • FIG. 3 image series with corresponding image positions.
  • FIG. 4 Fourier transformation of an intensity signal
  • FIG. 1 illustrates the measuring principle of a laser light section sensor.
  • a rail resting on a plate forms an object 1 of a track to be measured.
  • a laser 3 and a digital image recorder 4 with a common reference base 5 are directed onto a surface 2 of the object 1.
  • both components 3, 4 of the laser light section sensor are arranged in a common housing (not shown) with an alignment that is predetermined with respect to one another.
  • a scanning line 6 (laser line) is projected onto the plate and the rail by means of the laser 3. This is done, for example, by means of suitable optics such as a cylinder lens that fans out a laser beam accordingly.
  • a light plane 7 defined by the fanning out forms a first angle a with the reference base 5 and intersects the object 1 to be measured.
  • the resulting probe line 6 is interrupted several times by shadowing of the rail head and the rail foot.
  • the image recorder 4 is designed, for example, as a black-and-white digital camera and includes imaging optics and a high-resolution digital image processor. When the digital image processor is exposed, a raster graphic is created with a predetermined number of pixels 8 (picture elements). Each pixel 8 depicts a point on the object surface 2. In the case of a black-and-white recording, a brightness value W (gray value) is assigned to each pixel 8. The respective brightness value W corresponds to the amount of light which falls from the recorded location of the object surface 2 through the imaging optics onto the image processor during an exposure time. In the case of color recordings, color information is added pixel by pixel, which can also be evaluated.
  • An optical filter is advantageously arranged in front of the image processor.
  • the filter is tuned to the frequency of the laser light so that Disturbing light reflections with different frequencies are already eliminated at this point.
  • a camera axis 9 forms a second angle ⁇ with the common reference base 5.
  • the dimensions of the object 1 can be derived from the recorded probing line 6 via the known angles ⁇ , ⁇ by means of triangulation. Specifically, the height of the object 1 is deduced from a characteristic deformation of the projected scanning line 6.
  • the scanning line 6 is projected onto the surface 2 with periodically varied light intensity.
  • a control unit 10 is provided which controls the laser 3 accordingly (FIG. 2). It is advantageous if the control unit 10 outputs a sinusoidal control signal which varies the intensity of the laser light accordingly. An angle function thus determines the curve shape of a corresponding intensity signal l (z).
  • the image recorder 4 records a series 11 of images 12 during a period of the varied light intensity, which are then evaluated in a detection device 13.
  • the image recorder 4 is set up accordingly before the start of a measurement, or the image recorder 4 is controlled accordingly by means of the control unit.
  • the periodic variation of the light intensity of the laser 5 and the series recordings by the image recorder 4 are coordinated over time.
  • the present measuring device comprises, for example, an electronic circuit with FPGAs or GPUs in which the control unit 10, the Detection device 13 and optionally an evaluation device 14 for determining dimensions of the object 1 are integrated.
  • matching image positions P (x, y) are jointly evaluated in order to detect the image of the scanning line 6.
  • 3 shows such an image series 11 as an image stack with an assigned coordinate system xyz.
  • the position of a respective pixel 8 within an image 12 is determined with respect to an x-axis and a y-axis.
  • the chronological sequence of the recorded images 12 is plotted on a z-axis.
  • each image position P (x, y) is assigned an intensity signal l (z) for the course of the respective brightness value W recorded during an image series 11.
  • Corresponding image positions P (x, y) are those pixels 8 which reproduce corresponding locations of the detected object 2 in the individual images 12.
  • the image recorder 4 is advantageously aligned immovably with respect to the object 2 during the series recording.
  • the laser 3 and the image recorder 4 are supported on the object 2 during a series recording.
  • the image positions P (x, y) within an image series are stabilized before an evaluation.
  • appropriate stabilization software is set up in the detection device 13, for example.
  • optical image stabilization is provided in the imaging optics of the image recorder 4. In this way it is ensured that the images 12 of a recorded series 11 reproduce identical object locations at corresponding image positions P (x, y).
  • the starting basis for the evaluation is a respective profile of the intensity signal l (z) (brightness profile) for each image position P (x, y) of the image series 11 Signal curve over time and thus shown along the z-axis according to FIG. 3.
  • a brightness value W is determined for a corresponding pixel 8 with each image 11, and the course of the intensity signal l (z) is obtained by interpolation. A corresponding one comes into the detector device 13 Interpolation algorithm used.
  • the image recorder 6 can be set up for the pixel-by-pixel output of the intensity signal l (z).
  • the amounts of the 1st Flarmonic Fl are therefore compared over all image positions P (x, y).
  • a threshold value is expediently specified and only those pixels 8 are subsequently taken into account, the 1st Flarmonic F1 is above the threshold value.
  • Such pixels 8 reproduce those locations of the object 1 which were illuminated by the laser 3 with a sinusoidal varied light intensity. All other pixels 8 with the same or slightly changed maturity are not taken into account and are set equal to zero, for example.
  • the result of this evaluation is a merged image 17 in which only the depicted probe line 6 appears.
  • the pixel-by-pixel intensity signal l (z) is filtered by means of a digital filter.
  • the filter suppresses those signals that are outside of a narrow frequency band.
  • the frequency band is determined by the frequency with which the light intensity of the laser 3 is varied periodically. Thus, only the depicted probe line 6 appears in the merged image 17 here as well.
  • the merged image 17 is transmitted from the detection device 13 to the evaluation device 14 of the laser light section sensor.
  • the result of the evaluation are dimensions of the object 1, as described at the beginning with reference to FIG. 1.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Computer Vision & Pattern Recognition (AREA)
  • General Physics & Mathematics (AREA)
  • Theoretical Computer Science (AREA)
  • Optics & Photonics (AREA)
  • Quality & Reliability (AREA)
  • Length Measuring Devices By Optical Means (AREA)

Abstract

L'invention concerne un procédé de mesure d'un objet (1) d'une voie ferrée à l'aide de capteurs de coupe optique laser, une ligne lumineuse (6) étant projetée sur une surface (2) de l'objet (1) au moyen d'un laser (3) et la surface (2) étant enregistrée au moyen d'un appareil de prise de vues numérique (4). La ligne lumineuse (6) étant projetée avec une intensité lumineuse à variation périodique, la caméra numérique (4) enregistrant une série (11) d'images (12) et, dans la série d'images (11), des positions d'image (P(x, y)) coïncidantes étant évaluées ensemble à l'aide d'un dispositif de détection (13) afin de détecter une représentation de la ligne lumineuse (6). L'intensité lumineuse à variation périodique permet de distinguer la projection de la ligne lumineuse (6) par rapport aux réflexions d'autres sources lumineuses.
PCT/EP2020/071946 2019-09-05 2020-08-05 Procédé et dispositif de mesure destinés à mesurer un objet d'une voie ferrée WO2021043518A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
EP20754195.4A EP4025868A1 (fr) 2019-09-05 2020-08-05 Procédé et dispositif de mesure destinés à mesurer un objet d'une voie ferrée

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
ATA287/2019 2019-09-05
AT2872019 2019-09-05

Publications (1)

Publication Number Publication Date
WO2021043518A1 true WO2021043518A1 (fr) 2021-03-11

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20170059408A1 (en) * 2014-02-21 2017-03-02 Universität Stuttgart Method and Device for Generating Multispectral or Hyperspectral Light, for Hyperspectral Imaging and/or for Distance Measurement and/or 2D or 3D Profile Measurement of an Object by Means of Spectrometry
DE102015119409A1 (de) * 2015-11-11 2017-05-11 Edilon Sedra Gmbh Messverfahren zur Messung der Verformung einer Schiene
US10234278B2 (en) * 2015-09-09 2019-03-19 Faro Technologies, Inc. Aerial device having a three-dimensional measurement device

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20170059408A1 (en) * 2014-02-21 2017-03-02 Universität Stuttgart Method and Device for Generating Multispectral or Hyperspectral Light, for Hyperspectral Imaging and/or for Distance Measurement and/or 2D or 3D Profile Measurement of an Object by Means of Spectrometry
US10234278B2 (en) * 2015-09-09 2019-03-19 Faro Technologies, Inc. Aerial device having a three-dimensional measurement device
DE102015119409A1 (de) * 2015-11-11 2017-05-11 Edilon Sedra Gmbh Messverfahren zur Messung der Verformung einer Schiene

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