KR20030085291A - Width Measuring Device and Method using Laser Beam - Google Patents

Abstract

PURPOSE: A method and an apparatus for measuring a width by using laser beam is provided to continuously measure a width of a coil or a plate in a non-contact manner by using a laser triangulation method. CONSTITUTION: A width measuring apparatus includes a laser measuring device(1), an image signal obtaining section(2), a signal pre-processing section(3), a laser line recognizing section(4), a laser beam edge extracting section(5), a coordinate calculating section(6), and a control section(7). The laser measuring device(1) is installed above an object(10) to be measured in such a manner that laser beam is radiated onto edges(11,12) of the object(10). The laser measuring device(1) includes a laser radiating module for radiating laser beam onto the edges(11,12) of the object(10) and a CCD camera for detecting a reflective image.

Description

Width measuring device and method using laser beam {Width Measuring Device and Method using Laser Beam}

The present invention relates to the measurement of the width of the sheet, and more particularly, to irradiate a laser on both edges of the sheet such as coils or thick plates and to detect the reflected image data with a planar CCD camera, using the image data It relates to a width measuring apparatus and method using a laser for measuring the width of the sheet by calculating the coordinates of both ends.

In general, in the production of sheet materials such as coils or thick plates, width control rolling is performed to target the width required by the demand in the rolling process. At this time, the measured value of the width measuring system is used as the measured value, and in the correction process, the width of the final product is measured by the width measuring system and then supplied to the demand price.

Conventionally, an apparatus and method for measuring the width of an object to be measured using a laser and a line scan CCD camera are disclosed in Korean Patent Application No. 2000-49749. The prior patent application has a slit beam generator using an infrared laser as a light source to the bottom of the object to be irradiated so that the entire width is irradiated and a line scan CCD camera on the upper part of the object to be measured corresponding to the slit beam generator to install the slit Disclosed is a width measuring apparatus which scans the measured object in the width direction by using infrared rays emitted from a beam generator, and calculates the number of pixels forming a line measured continuously by the line scan CCD camera to obtain the width of the measured object. do. However, since the apparatus and method scans the laser table on the roller table carrying the object under test in full width, the installation is complicated and the installation cost increases due to the increase in cost, and since the line scan CCD camera is used, the object is measured in the width direction. There was a problem that it was cumbersome and time consuming to scan because it scans with.

In addition, the width measuring system applied to domestic and international steel or aluminum production processes makes a spot laser into a linear laser line by using a multi-facet mirror (a rotating mirror having multiple planes) and then the single laser line ( One complete laser beam is irradiated across the upper part of the object under the width direction to detect the reflected image with a line scan CCD camera, and to measure the width. It is widely used to measure the width by detecting hidden shadows, but it requires a separate installation space and is difficult to follow-up, and because the line scan CCD camera is used to scan not only the edges of the object but also the width. There was the same problem as the above patent.

In particular, the line scan CCD camera used in the width measuring apparatus in the prior art is difficult to measure because the reflection is generated when the vertical change of the measured object is severe or the position of the measured object on the laser beam scan line is severe. fell.

Therefore, in the technical field, development of a device for measuring width using a laser split scan method which is simple and easy to manage in a complicated rolling or correction process and a planar CCD camera that can be measured even when the above-mentioned diffuse reflection occurs. This has been required.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and separates and scans a laser at both edges of a coil and a sheet in motion, and detects the reflected image with a planar CCD camera. It is an object of the present invention to provide a width measuring apparatus using a laser that continuously measures the width of the coil and the sheet material in a non-contact manner after calculating coordinates of both ends using a measuring method.

1 is an overall configuration diagram of a width measuring device according to the present invention.

FIG. 2 illustrates an embodiment of an area of an object to be measured by the two laser meters of FIG. 1.

3 is a schematic diagram illustrating a Gaussian filtering process.

Figure 4 is a schematic diagram showing the internal configuration of a laser measuring instrument according to the present invention.

FIG. 5 schematically shows the arrangement of a laser oscillation module and a lens in an apparatus for converting a point point laser into a line laser.

FIG. 6 is an exemplary view of an image of both edges of an object to be detected detected by a planar CCD camera according to the present invention.

7 is an exemplary view for explaining a principle of calculating the width of the object to be measured using the coordinates (X, Y) and the coordinates of both edges of the object to be measured according to the present invention.

8 is a flowchart illustrating a width measuring method according to the present invention.

Explanation of symbols on the main parts of the drawings

1: laser measuring instrument 2: image signal acquisition unit

3: signal preprocessing unit 4: laser line recognition unit

5: laser beam edge extraction unit 6: coordinate calculation unit

7; Control unit 8: storage unit

10: measured object 11: WS side leading edge

12: DS side edge 21: DC power supply

22: planar CCD camera 23: planar window

34 laser generator 32 cylindrical lens

Width measuring apparatus according to the present invention for achieving the above object, in the width measuring apparatus using a laser for measuring the width of the coil or sheet moving in the separate irradiation of the laser and the reflected laser, at the top of the object to be measured A laser beam is installed to irradiate a linear laser beam on both end edges of the object under test, and emits a linear laser beam on both end edges of the object under test and detects an image reflected from both edges of the object under test. Measuring instrument; An image signal acquisition unit which acquires an image signal of an image detected by the laser measuring device; A signal preprocessor which removes a noise component of the video signal and extracts only a real signal; A laser line recognizing unit for recognizing an effective laser line defining an effective laser image range for the object under test from an image signal having only the real signal; A laser edge extraction unit for extracting interface information of both end edges of the object to be measured from the recognized effective laser line; A coordinate calculation unit for calculating coordinate values of both end edges of the object to be measured using triangulation principle from the extracted interface information of both end edges; And a laser measuring device, an image signal obtaining unit, a signal preprocessing unit, and a laser line recognizing unit to calculate a width between both end edges of the object to be measured using the calculated coordinate values, and to continuously measure the width of the moving object to be measured. It includes a control unit for controlling the laser edge extraction unit and the coordinate calculation unit in real time.

Here, the laser measuring device is configured by integrating a laser generating unit for generating a red laser when the DC power is supplied and a planar CCD camera for obtaining a reflected image by irradiating the generated laser. In this case, the planar CCD camera preferably acquires an image of an area having a predetermined area, and obtains an image of 157 frames per second with a resolution of 0.54 mm.

In addition, the width measuring method according to the present invention for achieving the above object, the width measuring method using a laser to measure the width of the coil or sheet in motion by using a laser measuring device for separately irradiating the laser and capturing the reflected laser image 1. The method of claim 1, further comprising: irradiating a laser to both end edges of the object to be measured by the laser meter when the object to be measured is moved to a measurement range of the laser meter; A second step of acquiring a position image of both end corners reflected from the second image and extracting an image signal from the position image; Extracting a real signal by removing noise included in the video signal; A fourth step of recognizing an effective laser image range from the extracted real signal and extracting edge boundary surface information of both ends of the object to be measured; A fifth step of calculating coordinates of both edges from the extracted edge boundary information using triangulation principles; And a sixth step of calculating a width of the object to be measured based on the respective coordinates.

Hereinafter, with reference to the accompanying drawings, preferred embodiments of the present invention will be described in detail the present invention.

1 is an overall configuration diagram of a width measuring device according to the present invention. As shown in FIG. 1, the width measuring device according to the present invention includes a laser measuring device 1, an image signal obtaining unit 2, a signal preprocessing unit 3, a laser line recognition unit 4, and a laser beam edge. A) extracting section (5), coordinate calculating section (6) and control section (7), preferably further comprising a storage section (8) for storing the calculated values.

The laser measuring device (1) irradiates a linear laser beam to the edges (11, 12) of both ends of the measurement object (10) from the top of the measurement object (plate material such as coil or thick plate) 10 And a module for irradiating a laser beam on both ends of the edges 11 and 12 of the object 10 and reflections at both edges 11 and 12 of the object 10 being moved. An area CCD camera which detects an image is integrated. Although two laser measuring apparatuses 1 are shown in the drawing, images of both edges 11 and 12 may be detected by one laser measuring apparatus using one laser measuring instrument according to the size of the object 10. It may be. Preferably, two laser measuring instruments 1 are installed to measure the images of the corner portions 11 and 12, respectively.

FIG. 2 illustrates an embodiment of an area of an object to be measured by the two laser meters of FIG. 1, wherein the laser meter 1 irradiates a linear laser to the front end of the object 10. The image reflected from the tip of the object 10 is acquired by the CCD camera on the surface. The first region and the second region each have a point P1 (X1, Y1) and a drive side (DS) of the front edge of the work side (hereinafter, referred to as WS) of the measurement target 10, respectively. The area for acquiring the image of the measurement object 10 is shown at the point P2 (X2Y2) on the side.

The laser measuring device 1 irradiates a linear laser beam to both edge portions 11 and 12 of the moving object 10 and detects the reflected image on the planar CCD camera in the laser measuring device 1. In this case, unlike the conventional line CCD camera, the planar CCD camera captures a predetermined area as an image. Therefore, in the line CCD camera, when measuring the edge of the object to be measured, the line captures the image around the edge with a line, but the CCD camera on the face captures the image by forming a constant area around the edge. In more detail, the positions of the pixels corresponding to the end points of the object 10 to be measured are P1 (X1, Y1) and P2 (X2, Y2) from the beam formed by the CCD camera. The position of is represented by one point in each reference coordinate system. The position of the pixel is correlated with the position (width, distance) of the end point of the measurement object 10 with respect to the reference coordinate system. These correlations are defined in the laser beam generating optical system of the laser measuring device 1, the geometrical arrangement of the CCD camera, the properties of the image optical system, and the like.

However, these correlations have severe nonlinearities, and therefore, the relational definition by the mathematical model is accompanied by a large error. Therefore, in the present invention, the correlation between them is obtained by an experimental method. Here, the experimental method uses a method of calculating a position of a pixel corresponding to the moving object in the width and distance directions and mathematically deriving a correlation from numerous data groups. In order to form an accurate data group, it is necessary to extract the exact position of the pixel corresponding to the end point of the actual object from the laser beam formed on the CCD camera as well as the precise alignment and experiment of the laser measuring instrument. The position of the pixel is a two-dimensional vector of the position in the horizontal direction and the position in the vertical direction on the CCD plane.

The CCD camera is set such that an image is acquired only within an effective measurement range including vibration of the object 10. Although it is actually 1300 x 1000 pixels, only the 1300 (H) x 133 (V) pixel satisfies the effective measurement range, so that the scan area is used locally. This reduces the blur effect due to the movement of the image and obtains a high quality image.

Hereinafter, a process of calculating the width of the object to be measured using the image acquired by the CCD camera will be described in more detail.

The image signal acquisition unit 2 acquires an image signal for an image acquired by the CCD camera on the surface. This is to obtain a corresponding video signal with respect to the acquired image, and extracts the video signal for the area of the portion where the laser is scanned and reflected. Then, since the image signal formed in the CCD camera varies according to the surface state of the object 10, the signal preprocessing unit 3 obtains the signal through Gaussian filtering to reduce the influence of surface characteristics and noise. The noise component contained in the received video signal is removed and only the real signal is extracted. In particular, the Gaussian filtering process in the signal preprocessing unit 3 has a net effect on the extraction of the end point that is robust to changes in color and illuminance of the object 10. 3 briefly illustrates a Gaussian filtering process according to the present invention. This indicates that the laser beam cross-sectional brightness distribution is detected based on the laser beam image of the cross-section cut point and Gaussian filtering is performed accordingly.

Subsequently, the laser line recognizing unit 4 pre-processes the signal preprocessing unit 3 to generate an effective laser line for defining an effective laser image range for the measurement object 10 from an image signal having only a real signal. Recognize. At this time, in the recognition of the effective laser line for defining the effective laser image range for the object 10, extraction of the center line of the effective laser image range is an important factor. In the present invention, the centerline is extracted to 1/20 or more pixels by the Center of Gravity. An effective laser line according to the image range of the object 10 is recognized along the center line. Subsequently, the laser beam edge extracting unit 5 extracts an interface between the edge portions 11 and 12 of both ends of the measurement object 10 from the recognized effective laser line along the extracted center line. The image of the end point of most objects including the actual measured object 10 has a characteristic that the brightness gradually decreases due to the decline of the gray level defining the brightness distribution of the image. In the present invention, the gray level distribution at the point where the laser line ends is differentiated so that the image value at which the derivative value is the maximum is taken as the end point. Usually the method has a measurement resolution of subpixel units of 1/10 or less.

Subsequently, the coordinate calculating section 6 calculates a spatial coordinate (X: horizontal direction, Y: vertical direction) from the extracted interface information of the edge portions 11, 12. The coordinate calculation is described in detail below. The controller 7 calculates the width of the measured object 10 using a triangulation principle based on the calculated spatial coordinates (X, Y) and compares it with a predetermined width to calculate a deviation, and the calculation To save, display, and print the specified width. In addition, the control unit 7 controls the laser measuring device, the image signal obtaining unit, the signal preprocessor, the laser line recognition unit, the laser edge extracting unit, and the coordinate calculating unit in real time to continuously measure the width of the measured object. In addition, the controller 7 may construct a database or the like to continuously store the width values continuously calculated for the moving object 10 to analyze the width values after completion of the work.

Figure 4 is a schematic diagram showing the internal configuration of a laser measuring instrument according to the present invention. As shown in FIG. 4, the laser measuring device 1 according to the present invention includes a DC power supply 21, a CCD camera 22, a planar window 23, a laser generator 24, and a laser driver 25. It is packaged and configured.

When the DC power supply 21 supplies the driver power to the semiconductor diode of the laser generator 24 through the laser driver 25 and the DC power is supplied to the laser generator 24 in this way, 10mW, A red laser of 660 nm is generated, which is a point laser, which is made of a linear laser having a width of 1 mm and a length of 900 nm by the cylindrical lens (shown in FIG. 5) of the device for converting the point laser into a linear laser. Preferably, the planar CCD camera has a resolution of 0.54 mm and can acquire an image of 157 frames per second.

The laser measuring device 1 separately scans the laser beams at both edge portions 11 and 12 of the object 10 to minimize the laser energy difference according to the width direction position, and responds to the change of the measurement reference height point. Use a planar CCD camera whenever possible.

FIG. 5 schematically shows the arrangement of the laser oscillation module and the lens in the apparatus for converting the point point laser into a linear laser. As shown in FIG. 5, two cylindrical lenses 32 are positioned in front of the laser oscillation module 31. As described above, the cylindrical lens 32 converts the red point laser generated by the laser oscillation module 31 into a linear laser. It should be noted that when converting a point-to-point laser into a line-like laser, the conventional width meter uses a high-speed rotating face mirror and a parabolic mirror, whereas in the present invention, only two cylindrical lenses 32 are used. In this respect, the configuration of the detector is simple and is not restricted by the installation site.

FIG. 6 is an exemplary view of an image of both edges of an object to be detected by a planar CCD camera according to the present invention. FIG. Indicates the acquired image. In FIG. 6, the left side shows an image obtained with the planar CCD camera at the corner of the WS side, and the right side shows an image obtained with the planar CCD camera at the corner of the DS side.

The image signal acquisition unit 2 acquires an image signal from the two images obtained by the planar CCD camera as described above, and removes a noise component contained in the obtained image signal by the signal preprocessor 3. Only the real signal is extracted. The laser line recognition unit 4 recognizes an effective laser line for defining an effective laser image range for the object 10 to be measured from the image signal that is the real signal. The laser beam edge extracting section 5 extracts the interface information of the edge portions 11 and 12 of both ends of the measurement object 10 from the recognized effective laser line. Subsequently, the coordinate calculating unit 6 calculates coordinates (X: horizontal direction, Y: vertical direction) of each corner by using triangulation principle from the extracted interface information of the edge portions 11, 12. The control unit 7 calculates the width of the measurement object 10 based on the calculated spatial coordinates X and Y. A method of calculating the width of the object to be measured using the coordinate calculation and the calculated coordinates will be described with reference to FIG. 7.

7 is an exemplary view for explaining the principle of calculating the width of the object to be measured using the coordinates (X, Y) and the coordinates of both edges of the object to be measured according to the present invention. FIG. 7A is a diagram for describing a process of obtaining X coordinates of both edges of an object to be measured, and FIG. 7B is a diagram for explaining a process of obtaining Y coordinates of both edges of an object to be measured. First, referring to FIG. 7A, a process of obtaining X coordinates at both edges will be described. The two laser measuring instruments 1 are installed at an upper portion of the measurement object 10 at a predetermined distance. An imaginary center line C is set at the exact center of the two laser measuring instruments 1. A reference coordinate system is formed using the virtual center line C as the Y axis and an arbitrary reference line that meets the Y axis as the X axis. At this time, the origin of the reference coordinate system is indicated by "O". As shown in FIG. 7A, the laser measuring device on the left side detects the position of the left end corner point of the object 10 with respect to the reference coordinate system, and the laser measuring instrument on the right side of the object 10 with respect to the reference coordinate system. The position of the rightmost corner point is detected. The positions of the left and right end corner points detected as described above are represented by two-dimensional vector values.

That is, if the distance from the set centerline C to the center C1 of the first area and the center C2 of the second area formed on the optical sensor surface of the laser measuring device 1 are A and B, respectively, When the position of the edge of the object to be detected 10 is viewed at the center C1 or C2 of the region, the X coordinate is A or B. However, when the position of the edge deviates from the center C1 or C2 of the region, the horizontal position of the detected edge and the center C1 or C2 of the respective region are detected by using the pixel size of the optical sensor surface. By calculating the distances (m and n in Fig. 6), the distance between the center line C and the horizontal position of the corners is calculated, and as a result, the X coordinates of both corners, that is, X1 and X2, are calculated.

Referring to Figure 7 (b) will be described the process of obtaining the Y coordinate of the corners of the object to be measured. Figure 7 (b) is a view for explaining a known triangulation principle. The Y coordinate is calculated using the triangulation principle. First, the laser irradiated to the object 10 to be measured is imaged on the optical sensor surface by the lens of the optical system inclined with respect to the laser beam axis. Since the triangulation principle is already known, a description of the principle is omitted. Using the triangulation principle, the height (Y coordinate) of the object to be measured is calculated by Equation 1 below.

[Equation 1]

Where H is the height (Y coordinate) of the object to be measured, q is the imaging position of the laser beam, m is the lens magnification, and f is the focal length of the lens.

In this way, in the image information acquired by the planar CCD camera, the vertical position information is calculated using the triangulation principle to calculate the heights H1 (Y1) and H2 (Y2) of the edges at both ends.

Accordingly, in the coordinate calculation unit 6, horizontal position coordinates X1 and X2 are calculated based on image positions of both edges of the object 10 incident on the planar CCD camera, and vertical position coordinates Y1, Y2) is calculated to calculate the coordinates (X1, Y1) and (X2, Y2) of both corners at any time. Subsequently, the controller 7 measures the width between the two points based on Equation 2 below using the calculated two coordinates, that is, (X1, Y1) and (X2, Y2).

[Formula 2]

Here, W is the width of the object 10 to be measured.

As described above, the laser measuring instrument 1 irradiates a linear laser beam to the object 10 and detects the reflected laser image by the planar CCD camera in the laser measuring instrument 1, and the image signal obtaining unit 2 ) Obtains an image signal from the detected image, removes noise included in the image signal from the signal preprocessor 3, and then the laser line recognition unit 4 detects an edge of the object 10 to be measured. Recognize the laser line and extract the laser beam edge from the laser line in the laser beam edge extraction unit 5, calculate the coordinate value of the edge (edge) in the coordinate calculation unit 6 and finally in the control unit 7 The width of the object 10 is accurately calculated using the coordinate values.

8 is a flowchart illustrating a width measuring method according to the present invention. A width measuring method will be described with reference to FIG. 8. First, each device is initialized (S10). The initialization is to perform the preparation for the operation of each component device, including the laser triangulation reference position, the planar CCD camera image data, the initialization of various parameters. Subsequently, when the measured object 10 is moved and the front end of the measured object 10 is introduced, the incoming measured object 10 is detected by a photosensor, and when the photosensor is turned on, each device operates. Initiate. Therefore, when the photosensor is turned on (S11), various data related to the width measurement are received from the host computer, such as the ID of the object to be measured, a target value for the width, and a deviation allowable threshold value (S12). The step S12 can also be entered manually. Subsequently, when it is determined that the measured object 10 has entered the measurement range of the laser meter 1 (S13), the laser meter 1 separates the laser into both edges of the measured object 10. After irradiation, the planar CCD camera in the laser meter 1 captures a laser image reflected from both edges of the measured object 10 entering the measurement field (S14). The image signal of the image is acquired from the planar CCD camera (S15), and the Gaussian filtering is performed to remove noise included in the image signal and extract the real signal (S16). Recognizing an effective laser line indicating an effective laser image range from the real signal (S17), extracting edge boundary surface information of both ends of the measurement object 10 from the effective laser line (S18), and extracting the edge boundary surface information Calculate the coordinates, (X1, Y1) and (X2, Y2) of the edges from both ends (S19). Using the coordinates, the distance between the edges of both ends, that is, the width of the object 10 is calculated (S20). Subsequently, it is determined whether the measured object 10 has passed the measurement range (S21), and if it passes, it ends, and if it passes, it repeats again from the step S14.

Here, although not shown in the drawing, the control unit 7 stores the calculated width of the measured object 10 in the storage unit 8, and the deviation between the measured width of the measured object 10 and a predetermined target value. Is calculated and stored in the storage unit (8). In addition, an alarm may be generated when the result value of the measured width exceeds the deviation limit value.

The above description and the contents of the drawings are related to a preferred embodiment of the present invention, and the configuration of the above apparatus may be substituted, changed, or modified within the scope without departing from the technical spirit of the present invention.

As described above, the present invention can accurately measure the width of the plate, such as moving or stationary coils or thick plates, and non-contact continuous measurement is possible to enhance quality control.

In addition, according to the present invention, even if the space of the laser beam line width (about 2 ~ 3mm) can be installed simply without modification or improvement of the existing process, even if the vertical position fluctuation of the measured object is severe, without measurement error The width can be measured accurately.

Furthermore, compared to the conventional lower light source installation or laser full width scanning method, the installation is simple, and the laser and the camera are modularized, so that the facility management is easy and the post management is easy.

Claims (4)

In the width measuring device using a laser to separate the irradiation of the laser and to measure the width of the moving coil or sheet using the reflected laser, The laser beam is installed to irradiate a linear laser beam on both edges of the object under the upper part of the object, and irradiate linear laser beams on both end edges of the object to be measured and reflected by both edges of the object under test. A laser meter for detecting an image; An image signal acquisition unit which acquires an image signal of an image detected by the laser measuring device; A signal preprocessor which removes a noise component of the video signal and extracts only a real signal; A laser line recognizing unit for recognizing an effective laser line defining an effective laser image range for the object under test from an image signal having only the real signal; A laser edge extraction unit for extracting interface information of both end edges of the object to be measured from the recognized effective laser line; A coordinate calculation unit for calculating coordinate values of both end edges of the object to be measured using triangulation principle from the extracted interface information of both end edges; And A laser measuring device, an image signal acquiring unit, a signal preprocessor, a laser ray recognition unit, calculates a width between both end edges of the object to be measured using the calculated coordinate values, and continuously measures the width of the object under measurement. Width measuring apparatus using a laser, characterized in that it comprises a control unit for controlling the laser edge extraction unit and the coordinate calculation unit in real time. The method of claim 1, wherein the laser measuring device, A laser generator for generating a red laser when the DC power is supplied; And A width measuring device using a laser, characterized in that the planar CCD camera for obtaining the reflected image by irradiating the generated laser is integrated. The method of claim 2, wherein the planar CCD camera, A width measuring apparatus using a laser, characterized by acquiring an image of an area having a predetermined area and acquiring an image having a resolution of 0.54 mm and 157 frames per second. In the width measuring method using a laser to measure the width of the coil or sheet in motion by using a laser measuring device for irradiating the laser and capturing the reflected laser image, A first step of irradiating a laser to both end edges of the object to be measured by the laser meter when the object to be measured is moved to a measurement range of the laser meter; A second step of acquiring a position image of both end edges reflected from both end edges of the object to be measured and extracting an image signal from the position image; Extracting a real signal by removing noise included in the video signal; A fourth step of recognizing an effective laser image range from the extracted real signal and extracting edge boundary surface information of both ends of the object to be measured; A fifth step of calculating coordinates of both edges from the extracted edge boundary information using triangulation principles; And And a sixth step of calculating the width of the object to be measured based on each of the coordinates.