JP4116887B2 - Optical shape measurement method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for optically measuring the shape of a strip that runs at high speed.
[0002]
[Prior art]
In the shape measurement such as the flatness of a strip that runs at high speed, such as hot-rolled steel sheet, a number of laser displacement meters are arranged in the width direction and longitudinal direction of the steel sheet, and the C warp in the width direction of the steel sheet, or the ear in the longitudinal direction. A method of measuring a shape such as a wave or a medium stretch is known (Patent Document 1). However, even if a large number of laser displacement meters are arranged, the laser displacement meters are expensive, and there are at most several measurement points in the width direction. Further, when the plate width is changed or the plate meanders, a mechanism that follows the movement of the plate is also required.
[0003]
On the other hand, as disclosed in Patent Document 2, in the method of measuring the shape of a belt-like body by an optical cutting method that combines a linear laser light source and a delay integration type linear sensor, the shape of the belt-like body running at a high speed is set in the width direction and the longitudinal direction. It is possible to measure densely in the direction, and the obtained shape can be imaged, and shapes such as ear waves and middle stretch can be displayed in a visually clear form, and a large number of laser displacement meters are arranged. Compared with the method, it is possible to realize highly accurate shape measurement with a small number of parts and at a low cost.
[0004]
[Patent Document 1]
Japanese Patent Laid-Open No. 5-1912 “Flatness Measuring Device”
[Patent Document 2]
Japanese Patent No. 2913903 “Method for Measuring Optical Shape”
[0005]
[Problems to be solved by the invention]
However, in the actual plate passing condition of the steel plate, not only simple vertical movement, but if the shape generated on one side of the steel plate is large, the plate causes torsional vibration, and the light cut image also appears to be twisted. There was a problem that the other side, which was not bad, appeared to have a pseudo shape.
In view of such problems, the present invention has an object to provide a method for accurately measuring the shape of a strip over the entire length even when height fluctuation such as torsional vibration due to the poor shape of the strip occurs. To do.
[0006]
[Means for Solving the Problems]
The present invention, output using the linear laser light which is modulated forms a light section image by irradiating a linear laser beam in the width direction on the strip, the light cut image on the said strip while shifting One not a predetermined interval, by imaging overlapped using a linear sensor delay integration type which is disposed toward the horizontal direction in the width direction of the strip of the array of photoelectric conversion elements, of the strip thickness direction of the a shape measuring method of light section method to measure the shape, is disposed at a position separated a predetermined distance L a plurality of pairs in the longitudinal direction of the band-like body and said linear sensor and the linear laser light source, the A linear laser light source is made to emit light at a predetermined time interval, and a shape measurement value that is a height change in the width direction of the belt at each longitudinal position separated by a predetermined interval L is obtained based on the output from each linear sensor. , wherein the shape measured by each pair at the same time t The difference was calculated for each same position in the width direction of the strip for value, the said difference for each position of each width direction by integrating the time t, the height variation due to vertical vibration and the torsional vibration of the strip which moves at high speed This is an optical shape measuring method characterized in that the true shape excluding the point is densely measured over the entire surface in the width direction and the longitudinal direction of the belt-like body.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, it demonstrates with an effect | action based on the Example of this invention. FIG. 1 shows the overall configuration of an apparatus used in the present invention. Reference numeral 1 denotes a steel plate to be measured, which has a shape defect such as an ear wave or a middle elongation. Reference numeral 2 denotes a linear laser light source. When a beam 3 radiated from the fan is irradiated onto a steel plate as a measurement target, a light cut image 4 is formed along the surface shape of the measurement target. Reference numeral 5 denotes a camera having a sequential integration type linear sensor, which will be described in detail later. Reference numeral 6 denotes a measurement roll for measuring the conveyance speed of the measurement object, and reference numeral 7 denotes a rotational speed measuring device. A signal processing and control device 8 calculates the moving distance of the target object from the rotational speed signal of the rotational speed measuring device 7 and causes the linear laser light source 2 to emit light at a predetermined distance and simultaneously send it to the camera 5. The clock is controlled to obtain a predetermined video signal. This signal is processed at high speed to continuously obtain shape values. Reference numeral 9 denotes a measurement result display device.
[0008]
In the present embodiment, two pairs of the linear laser light source 2 and the special camera 5 are used, the difference in shape obtained from each pair is taken, and this is integrated to reduce the influence of the fluctuation in the height of the strip. A method of measuring the true shape that has been eliminated will be described later. This will be described in detail later. First, a method of measuring the shape using a pair of the linear laser light source 2 and the special camera 5 will be described.
[0009]
First, the special camera 5 will be described. FIG. 2 is a diagram for explaining the function of the special camera and the structure of signal processing. Reference numeral 10 denotes a photoelectric conversion charge integration transfer unit in the two-dimensional semiconductor image pickup device in the light receiving unit of the camera. The two-dimensionally arranged photoelectric conversion elements have a vertical charge transfer section for each column, and receive and integrate charges from the respective photoelectric conversion elements in the middle of the transfer. Reference numeral 11 denotes a horizontal transfer reading unit whose output has the same form as a normal linear array.
[0010]
Conventionally, when this type of sensor synchronizes the speed at which the real image to be imaged moves in the vertical direction on the photoelectric conversion surface and the transfer speed in the vertical direction, it is equivalently exposed for a long time, and the sensitivity and S / N ratio are reduced. Because it can be improved dramatically, it is used for ultra-high-speed shooting and low-light shooting.
However, in the present invention, the above elements are used in completely different forms. That is, it is not necessary to synchronize the target object and the vertical transfer speed, and transfer is performed as fast as necessary. When the laser is instantaneously emitted at an appropriate interval during this period, electric charges are accumulated at the position corresponding to the light section image. If the entire device is placed in a dark room or if an interference filter that passes only the laser beam is placed in front of the camera lens, no charge is generated in the part that is not hit by the laser. A revolutionary method that enables a much faster measurement than when using a simple TV camera so far, where the interval between cut images can be narrowed, and light cut images can be obtained continuously and continuously. It is.
[0011]
Next, an example of the real-time signal processing method will be described. This signal processing is for real-time processing utilizing the fact that the interval change of the light section image is proportional to the shape change. In FIG. 2, a preamplifier 12 amplifies the output of the sensor and simultaneously converts the impedance. A comparator 13 binarizes the analog signal and becomes 1 if there is a light section image. A shift register 14 is delayed by one line by a horizontal transfer clock. A latch 15 holds the current value and the previous value. Reference numeral 16 denotes a determiner, which outputs 1 only when the combination of the current value and the previous value is (1, 0), and determines that the next light section image has arrived in that column. Reference numeral 18 denotes an interval integration count value holding shift register, and reference numeral 17 denotes a first control circuit. The first control circuit 17 simply increments the corresponding column register while the output of the determiner 16 is 0, but when it becomes 1, the value is incremented by 1 and the value is sent to the second control circuit 19. Reference numeral 21 is a reference interval value setter, and 20 is a change integration register. When the measurement target is flat, the reference interval value is a straight line with equal intervals, and the interval value is held. The second control circuit 19 subtracts the reference value from the current interval value from the first control circuit 17 to obtain the change amount, and adds it to the value of the 20 change integral value shift register. Therefore, each data of this register represents the current height in the width direction of the measurement object, and it is possible to display a shape that changes every moment in real time. 22 is a D / A converter and 23 is a display.
[0012]
This completes the description of the method for measuring the shape using a pair of the linear laser light source 2 and the special camera 5. Next, a method for measuring the shape using two pairs of the linear laser light source 2 and the special camera 5 will be described.
The upper graph in FIG. 3 is a cross-sectional view in the width direction of a C-curved plate obtained by using a pair of a linear laser light source 2 and a special camera 5, and when the plate is tilted to the left, the plate is tilted to the right. This is an extracted display when there is no tilt and when there is no tilt. In addition, the lower graph in FIG. 3 is a plot of height changes on the left side, center portion, and right side of the plate in the longitudinal direction. As long as the change in the height of the plate in the longitudinal direction is observed, it appears that waves are also generated at the center and right side of the plate. However, when the shape of the plate was confirmed visually, an ear wave was generated on the left side of the plate, but no wave was generated on the right side from the center. The reason why the waveform appears in a pseudo manner at the central portion and the right side of the plate is that the plate is twisted due to the ear wave on the left side of the plate and the height of the plate is changed.
[0013]
Next, a method of measuring the shape by arranging two pairs of the linear laser light source 2 and the special camera 5 close to each other in the longitudinal direction at an interval L will be described. If the true shape of the plate is y = f (x) and the height variation of the plate at time t is h (t), the longitudinal position x _t -L, x by the two laser-camera pairs at time t The shape measurement values y ₁ and y _{2 at t} are approximately expressed as follows.
_{y 1 (t) = f (} x t -L) + h (t) ··· (1)
y ₂ (t) = f (x _t ) + h (t) (2)
Here, if the difference y ₂ −y ₁ of the shapes captured at the same time is calculated,
y ₂ (t) −y ₁ (t) = f (x _t ) −f (x _t −L) (3)
Thus, the common height variation measured in both pairs can be subtracted. Since the camera interval L is small, the true shape f (x) can be obtained by integrating this. If the true shape can be approximated by the sine function, even if it is integrated, it becomes a cos function, and the position is only shifted by π / 2 radians in phase. You can just calculate FIG. 4 is a diagram showing a method of calculating the true shape by integrating the difference. That is, two sets of laser that are spaced apart by a distance L - height variations of the plate in the camera pair calculates the applied shape, and then calculates the difference [Delta] y _n obtained shape at the same time, already computed The true shape y _n is calculated by adding the difference Δy _n to the data y _np that is obtained by the distance L between cameras. Usually, in a method of measuring a shape by integrating sensors such as laser displacement meters separated by a distance L and integrating a difference between measured values between two points, for example, y _0p and y separated by a distance L in FIG. Difference / integration processing can be performed only between two points of ₀ , but according to the method of the present invention, the measurement interval per camera can be taken close, so y _{1p in} addition to y _0p and y ₀ , Y _2p ,... And y ₁ , y ₂ ,... Can be subjected to difference / integration processing, and dense and highly accurate measurement is possible.
[0014]
FIG. 5 shows a recalculation of the shape in the longitudinal direction of FIG. 3 according to the method of the present invention, and the pseudo shape from the center of the plate to the right side caused by the twisting of the plate can be suppressed. The shape could be calculated accurately. FIG. 6 shows the relative plate height converted to 256-level luminance, and an image is displayed so that the higher the whiteness is, the lower the blackness is. As shown in FIG. 6, it is possible to reveal shapes that have been hidden by vibrations until now using a pair of laser-cameras, making it possible to express shapes clearly with high-precision shape measurement and imaging. Became.
[0015]
In FIG. 1, the linear laser light source 1 is described as a combination of a laser light source that can be modulated and an optical element that forms the linear beam 3. However, as shown in FIG. Two parallel laser beams may be formed between the optical element 27 to be formed via the half mirror 25 and the total reflection mirror 26, and then a linear beam may be obtained by the optical element 27.
[0016]
【The invention's effect】
According to the present invention, it is an epoch-making invention that enables continuous shape measurement of a high-speed moving object to which height fluctuation has been added, which has been difficult until now, for example, in online shape measurement in the steel industry, Compared with the conventional method, it is possible to measure the entire length of the entire surface with much higher density, and to improve the accuracy of building the product dimension and shape and to realize the complete quality assurance for the user. In terms of cost, this method can be realized with a simple device. For example, it can be installed with much lower capital investment than a method in which a large number of laser displacement meters used in hot rolling are arranged. is there.
[Brief description of the drawings]
FIG. 1 is a diagram showing an overall configuration of the present invention.
FIG. 2 is a diagram illustrating a function of a special camera and a structure of signal processing.
FIG. 3 is a diagram illustrating that a pseudo shape is generated from the center to the right side due to twisting of the plate when the shape of the left side of the plate is bad.
FIG. 4 is a diagram for explaining a method of calculating a true shape by integrating a shape difference measured by each of two sets of laser-camera pairs.
FIG. 5 is a diagram illustrating that the pseudo shape described in FIG. 3 can be suppressed by integrating the difference.
FIG. 6 is a diagram for explaining an example in which a shape hidden in vibration can be found by integrating the difference.
FIG. 7 is a diagram showing an implementation method in another form in the embodiment of the present invention.
[Explanation of symbols]
1: Object to be measured 2: Linear laser light source,
3: Linear laser beam 4: Optical cut image,
5: Special camera 6: Speed measurement roll,
7: Rotational speed measuring instrument 8: Signal processing control panel,
9: Display device 10: Photoelectric conversion charge integration transfer unit,
11: Horizontal transfer reading unit 12: Preamplifier,
13: Comparator 14: Shift register,
15: Latch 16: Judgment device
17: First control circuit 18: Shift register for holding interval integration count value,
19: Second control circuit 20: Shift register for change integration,
21: Reference interval value setting device 22: D / A converter,
23: Display 24: Laser light source,
25: Half mirror 26: Total reflection mirror,
27: Optical element for spreading into a linear beam

Claims (1)

Output using the linear laser light which is modulated forms a light section image by irradiating a linear laser beam in the width direction on the strip, not a predetermined interval the light cut image on the strip Measure the shape of the strip in the thickness direction by superimposing it using a delay integration type linear sensor arranged with the horizontal direction of the array of photoelectric conversion elements facing the width of the strip while shifting. a shape measuring method of light section method, is disposed at a position separated a predetermined distance L a plurality of pairs in the longitudinal direction of the band-like body and said linear sensor and the linear laser light source, the linear laser light source At a predetermined time interval, and based on the output from each linear sensor, a shape measurement value that is a height change in the width direction of the strip at each longitudinal position separated by the predetermined interval L is obtained, and at the same time t the shape measurement value measured by each pair Nitsu The difference was calculated for each same position in the width direction of the strip Te, the said difference for each position of each width direction by integrating the time t, the height variation due to vertical vibration and the torsional vibration of the strip which moves at high speed An optical shape measuring method, characterized in that the true shape removed is closely measured over the entire surface in the width direction and the longitudinal direction of the belt-like body.

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