JP6542005B2 - Thickness measuring device - Google Patents

Description

  Embodiments of the present invention relate to a thickness measuring device.

  Conventionally, in a rolling process of a metal plate, a thickness measuring device is used which irradiates radiation to the rolled metal plate and measures the thickness of the metal plate from the attenuation of the radiation transmitted through the metal plate. .

JP, 2008-128756, A

  However, in the prior art, when the thickness of the metal plate is measured, in the case where the pass angle fluctuation occurs in the metal plate (the metal plate is inclined), an error occurs when the thickness of the metal plate is measured. Was likely to occur.

  One embodiment of the present invention is made in view of the above, and proposes a thickness measurement device that suppresses thickness measurement error even when a pass angle variation occurs in a metal plate.

ｔは、測定対象物のパスアングル変動が生じていない場合の測定対象物の厚さであり、
ｔ _２ 、ｔ _３ 、およびｔ _４ は、測定対象物のパスアングル変動が生じている場合に、複数の放射線検出部の各々によって測定された測定対象物の厚みであり、
φは、複数の放射線検出部の相互の傾きの角度であり、
Ａ＝ａ／（−ｄ）、Ｂ＝ｂ／（−ｄ）、Ｃ＝ｃ／（−ｄ）、Ｄ＝ｄ／（−ｄ）＝−１であり、
θは、測定対象物のパスアングル変動が生じている場合の測定対象物の傾きの角度である。 The thickness measurement device of the embodiment includes a radiation source, a plurality of radiation detection units, and a control unit. The radiation source irradiates radiation to the measurement object. The plurality of radiation detection units are disposed at positions facing the radiation source via the measurement object, and detect radiation transmitted through the measurement object. When the measurement object passes between the radiation source and each of the plurality of radiation detection units , the control unit outputs the output of the plurality of radiation detection units when the path angle variation of the measurement object occurs. Based on the result, the thickness of the measurement object in the case where no change in the path angle of the measurement object occurs and the angle of inclination of the measurement object due to the change in the path angle are calculated. Each of the plurality of radiation detection units is installed at a predetermined angle with respect to an axis indicating a vertical direction from the surface of the measurement object when no pass angle variation occurs. Further, the control unit calculates the thickness of the object to be measured in the case where no path angle variation occurs by the equations (1) and (2), and the case where the path angle variation occurs by the equation (3) Calculate the angle of inclination of the measurement object of

t is the thickness of the measurement object when no change in the path angle of the measurement object occurs;
t ₂ , t ₃ , and t ₄ are thicknesses of the measurement object measured by each of the plurality of radiation detection units when the path angle variation of the measurement object occurs.
φ is the angle of mutual inclination of the plurality of radiation detection units,
A = a / (− d), B = b / (− d), C = c / (− d), D = d / (− d) = − 1,
θ is the angle of inclination of the measurement object when the path angle variation of the measurement object occurs.

FIG. 1 is a block diagram illustrating the configuration of the X-ray thickness measurement apparatus according to the embodiment. FIG. 2 is a block diagram illustrating a software configuration implemented by the control unit of the embodiment. FIG. 3 is a diagram illustrating the positional relationship between the measurement object of the embodiment and a plurality of ionization chambers. FIG. 4 is a diagram illustrating the interrelationship of measurement values of a plurality of ionization chambers according to the embodiment. FIG. 5 is a flowchart showing the procedure of thickness calculation processing of the measurement object in the control unit of the thickness measurement device of the embodiment. FIG. 6 is a flowchart showing the procedure of the thickness calculation procedure in the first ionization chamber processing unit of the embodiment.

  Next, the thickness measuring device of the embodiment will be described with reference to the drawings.

  FIG. 1 is a block diagram illustrating the configuration of the X-ray thickness measurement apparatus of the present embodiment. As shown in FIG. 1, the X-ray thickness measurement apparatus 1 of this embodiment includes an X-ray source 101, four ionization chambers 121 to 124, four AD converters 131 to 134, and a control unit. And 100.

  The X-ray source 101 has an X-ray tube 111 that irradiates X-rays to the measurement object 150.

  A plurality of four ionization chambers 121 to 124 are disposed at positions facing the X-ray source 101 via the measurement object 150. The four ionization chambers 121 to 124 detect X-rays transmitted through the measurement object 150, and output analog signals indicating the X-ray detection results.

  The ionization chamber is a cylindrical, gas-filled device sandwiched between two electrodes. When radiation enters the ionization chambers 121 to 124, energization occurs. Thereby, the ionization chambers 121 to 124 can detect X-rays (radiation).

  Moreover, although X-rays (radiation) cause attenuation when passing through the measurement object 150, the attenuation rate differs depending on the thickness. Therefore, in the present embodiment, the thickness is measured based on the amount of attenuation detected when the X-ray passes through the measurement object 150.

  Moreover, although the example using an ionization chamber is demonstrated as a radiation detection part in this embodiment, you may use another radiation detection part.

  The four AD converters 131 to 134 are converters provided to correspond to each of the four ionization chambers 121 to 124, and are analog signals indicating X-ray detection results from the ionization chambers 121 to 124. Is converted into a digital signal indicating the X-ray detection result, and is output to the control unit 100.

  The control unit 100 controls the entire X-ray thickness measurement apparatus 1. For example, the control unit 100 controls the X-ray irradiation by the X-ray source 101.

  Further, the control unit 100 calculates the thickness of the measurement target 150 based on the digital signals input from the AD converters 131 to 134.

  Conventionally, the attenuation factor of X-rays was calculated based on the X detection result detected in one ionization chamber, and the thickness of the measurement object was derived from the attenuation factor. However, in the method, when the pass angle fluctuation occurs in the measurement object, the thickness of the measurement object in the state in which the pass angle fluctuation occurs, in other words, the inclined state is to be calculated. . In such a case, measurement errors occur because X-rays are transmitted obliquely to the object to be measured.

  Therefore, in the X-ray thickness measurement apparatus 1 of the present embodiment, four ionization chambers 121 to 124 are provided. Then, from the thickness derived from each of the four ionization chambers 121 to 124, the thickness of the measurement object 150 in the case where the path angle fluctuation (the inclination with respect to the movement direction of the measurement object 150) does not occur is derived. In the present embodiment, the case of four ionization chambers will be described, but a plurality of ionization chambers may be provided, and for example, three or five or more may be provided.

  FIG. 2 is a block diagram exemplifying a software configuration realized by the control unit 100 of the present embodiment. As shown in FIG. 2, the control unit 100 of the present embodiment includes an input unit 201, a first ionization chamber processing unit 211, a second ionization chamber processing unit 212, and a third ionization chamber processing unit 213. , A fourth ionization chamber processing unit 214, a selection unit 205, a corrected thickness calculation unit 206, and an output unit 207.

  When the measurement object 150 passes between the X-ray source 101 and each of the plurality of ionization chambers 121 to 124, the control unit 100 of the present embodiment causes a change in the path angle of the measurement object 150. In this case, based on the output results of the plurality of ionization chambers 121 to 124, the thickness of the measurement object 150 in the case where the path angle variation of the measurement object 150 does not occur is calculated. Next, a specific configuration of the control unit 100 will be described.

  The input unit 201 outputs a digital signal indicating the X-ray detection result input from the four ionization chambers 121 to 124 via the AD converters 131 to 134 to the ionization chamber processing unit 211 corresponding to the ionization chamber. Do.

  The first ionization chamber processing unit 211 includes a first current detection unit 202A, a first thickness calculation unit 203A, and a first correction unit 204A, and the measurement result of the first ionization chamber 121 is obtained. The thickness of the measurement object 150 based on the calculation is calculated.

  The first current detection unit 202A detects the current value output from the first ionization chamber 121 from the digital signal indicating the X-ray detection result by the first ionization chamber 121 from the input unit 201. In the present embodiment, an example in which the current value is detected will be described, but there may be a voltage value or the like.

  The first thickness calculator 203A calculates the thickness of the measurement object 150 in the direction of the first ionization chamber 121 from the X-ray source 101 based on the current value detected by the first current detector 202A. Do.

  The first correction unit 204A corrects the thickness of the measurement object 150 calculated by the first thickness calculation unit 203A. For example, the thickness of the measurement object 150 may change depending on the temperature or the material. Thus, the first correction unit 204A of the present embodiment performs thickness correction based on current conditions such as temperature and material.

  Further, in the present embodiment, the first ionization chamber 121 is installed so as to be tilted from the vertical direction from the surface of the measurement object 150 when no path angle variation occurs. Therefore, the first correction unit 204A performs correction according to the inclination of the ionization chamber 121. The specific correction will be described later. Then, the thickness corrected by the first correction unit 204A is output to the selection unit 205.

  The second ionization chamber processing unit 212 includes a second current detection unit 202B, a second thickness calculation unit 203B, and a second correction unit 204B, and the measurement results of the second ionization chamber 122 The thickness of the measurement object 150 based on the calculation is calculated. The second current detection unit 202B, the second thickness calculation unit 203B, and the second correction unit 204B set the thickness of the measurement object 150 in the direction from the X-ray source 101 to the second ionization chamber 122. Descriptions will be omitted, assuming that processing similar to that of the first current detection unit 202A, the first thickness calculation unit 203A, and the first correction unit 204A is performed except calculation.

  The third ionization chamber processing unit 213 includes a third current detection unit 202C, a third thickness calculation unit 203C, and a third correction unit 204C, and the measurement results of the third ionization chamber 123 The thickness of the measurement object 150 based on the calculation is calculated. The third current detection unit 202C, the third thickness calculation unit 203C, and the third correction unit 204C determine the thickness of the measurement object 150 in the direction from the X-ray source 101 to the third ionization chamber 123. Descriptions will be omitted, assuming that processing similar to that of the first current detection unit 202A, the first thickness calculation unit 203A, and the first correction unit 204A is performed except calculation.

  The fourth ionization chamber processing unit 214 includes a fourth current detection unit 202D, a fourth thickness calculation unit 203D, and a fourth correction unit 204D, and the measurement results of the fourth ionization chamber 124 The thickness of the measurement object 150 based on the calculation is calculated. The fourth current detection unit 202D, the fourth thickness calculation unit 203D, and the fourth correction unit 204D determine the thickness of the measurement object 150 in the direction from the X-ray source 101 to the fourth ionization chamber 124. Descriptions will be omitted, assuming that processing similar to that of the first current detection unit 202A, the first thickness calculation unit 203A, and the first correction unit 204A is performed except calculation.

  The selection unit 205 selects any three of the four thicknesses (the first ionization chamber 121 to the fourth ionization chamber 124). For example, if the four thicknesses include a thickness considered to be an outlier, the selection unit 205 selects three thicknesses excluding the thickness considered to be an outlier. In the present embodiment, the selection unit 205 holds a threshold for determining an abnormal value. And the selection part 205 considers the said thickness as an abnormal value, when arbitrary thickness exceeds the said threshold value. Then, the selecting unit 205 selects three pieces excluding the thickness regarded as the abnormal value.

  In the present embodiment, the thickness in the case where the pass angle of the measurement object 150 is not generated (not inclined) is calculated from the three thicknesses. In the present embodiment, since four ionization chambers are provided, even when one ionization chamber outputs an abnormal value, the thickness can be accurately calculated.

  The corrected thickness calculation unit 206 calculates the thickness of the measurement object 150 when the measurement object 150 is not inclined, from the three thicknesses.

  FIG. 3 is a diagram illustrating the positional relationship between the measurement object 150 of the present embodiment and the ionization chambers 121 and 123. As shown in FIG. 3, the angle θ in the present embodiment indicates the path angle (tilt angle) of the measurement object 150 with respect to the moving direction 201 of the measurement object 150.

  Further, in the present embodiment, the inclination of each ionization chamber with respect to the vertical axis (Z axis) is taken as an angle 。. Then, when the inclination between the ionization chambers is an angle φ, tan (Φ) = √2 · tan (φ) holds. However, (0 <φ <π / 2). The vertical axis (Z-axis) is taken as an axis showing a vertical direction from the surface (plane) of the plate-like object to be measured 150 when no path angle is generated.

  In the present embodiment, each ionization chamber is installed at an angle Φ from the vertical axis as shown in FIG. Therefore, in the ionization chambers 121 to 124, the thickness of the measurement object 150 according to the inclination is measured. However, in the present embodiment, the correction units 204A to 204D correct so that they can be treated as having no angle Φ. That is, when a 1.0 mm plate having a pass angle of 0 degrees is measured, in the present embodiment, the first ionization chamber processing unit 211 to the fourth ionization chamber processing unit are output so as to output a thickness of 1.0 mm as a calculation result. The correction units 204A to 204D of 214 correct.

  FIG. 4: is the figure which illustrated the correlation of the measured value of the ionization chamber 121-124 of this embodiment. In the example illustrated in FIG. 4, an intersection point of a vertical straight line from the X-ray focal point by the X-ray source 101 and the plate-like measurement object 150 is set as an origin. The plate length direction is taken as an X axis, the plate width direction as a Y axis, and the plate thickness direction (vertical direction) as a Z axis.

The thickness t ₁ is to be measured by the first ionization chamber 121. The thickness t ₂ is to be measured by the second ionization chamber 122. The thickness t ₃ is to be measured in the third ionization chamber 123. The thickness t ₄ is the measurement object of the first ionization chamber 124.

  The present embodiment assumes that the surface of the measurement object 150 is a plane. In that case, when the upper surface (on the ionization chamber side) of the measurement object 150 is the surface P, if the equation of the plane with respect to the origin (coordinate 0) can be obtained, the origin, in other words, the measurement object 150 The distance from the point on the bottom surface (of the X-ray source 101) to the plane P, that is, the thickness of the measurement object 150 can be determined. Then, next, the equation of the plane P will be described.

  The vectors of the axes between the focal point of the X-ray source 101 to each of the ionization chambers 121 to 124 and the point of intersection of the measurement object 150 (from the point of intersection of the bottom to the point of intersection of the top) are Become.

  In the calculation results by the first ionization chamber processing unit 211 to the fourth ionization chamber processing unit 214 of the present embodiment, the correction corresponding to the installation angle of each ionization chamber 121 to 124 is performed. For this reason, Formula (5)-Formula (8) can be derived | led-out.

  The equations (9) to (12) can be derived by applying the equations (5) to (8) to the general form a.x + b.y + c.z + d = 0 of the equation of plane.

  A = a / (− d), B = b / (− d), C = c / (− d), D = d / (− d) = − for the formulas (9) to (12) By setting it as 1, Formula (13)-Formula (16) can be derived | led-out.

  Expression (17) can be expressed by matrixing the variables A, B, and C shown in the expressions (13) to (16) as unknowns.

  Because there are three unknowns, any three of the equations (13) to (16) may be used. So, in this embodiment, the matrix M can be represented as Formula (18) by using Formula (14)-Formula (16).

Then, the determinant det M of the matrix M can be expressed as Expression (19). As a matter of course, t ₂ ≠ 0, t _{3 、} 0, and t ₄ t 0 hold. Then, equation (20) can be derived.

  Then, equation (21) can be derived from equation (17) and equation (20).

  As described above, the thickness of the measurement object 150 corresponds to the distance between the general form a · x + b · y + c · z + d = 0 of the equation and the origin O (0, 0, 0). Therefore, the thickness t can be expressed by equation (22).

  Then, the thickness t can be derived by substituting the value represented by the equation (21) into the equation represented by the equation (22).

  The inclination of the plane of the measurement object 150 is the angle between the normal vector (a, b, c) of the plane and the z-axis vector (0, 0, 1). Therefore, the angle θ which is a pass angle (inclination angle) can be derived from the equation (23).

The corrected thickness calculation unit 206 according to the present embodiment calculates the thickness when no pass angle is generated based on the input thicknesses t ₂ , t ₃ , t ₄ , and the equations (21) and (22). Calculate t and an angle θ which is a path angle (inclination angle).

  The output unit 207 outputs, to an external device, the thickness t when no pass angle is generated and the angle θ that is a pass angle (inclination angle). Alternatively, the output unit 207 outputs the thickness t and the angle θ to a display device (not shown) provided in the X-ray thickness measurement device 1 of the present embodiment. Thus, the monitor can grasp the accurate thickness t of the measurement object 150.

  Next, thickness calculation processing of the measurement object 150 in the thickness measurement device 1 of the present embodiment will be described. FIG. 5 is a flowchart showing the procedure of the above-described processing in the control unit 100 of the thickness measuring device 1 of the present embodiment.

  First, the input unit 201 inputs an X-ray detection signal (digital signal indicating the X-ray detection result) from the four ionization chambers 121 to 124 via the AD converters 131 to 134 (S501).

Next, from the X-ray detection signal (digital signal indicating the X-ray detection result) input from the first ionization chamber 121, the first ionization chamber processing unit 211 detects the detection result from the first ionization chamber 121. calculating a certain thickness t ₁ (S502).

The thickness t which is the detection result by the second ionization chamber 122 from the X-ray detection signal (digital signal indicating the X-ray detection result) input from the second ionization chamber 122 by the second ionization chamber processing unit 212 ₂ is calculated (S503).

The thickness t which is the detection result by the third ionization chamber 123 from the X-ray detection signal (digital signal indicating the X-ray detection result) input from the third ionization chamber 123 by the third ionization chamber processing unit 213 ₃ is calculated (S504).

The thickness t which is the detection result by the fourth ionization chamber 124 from the X-ray detection signal (digital signal indicating the X-ray detection result) input from the fourth ionization chamber 124 by the fourth ionization chamber processing unit 214 ₄ is calculated (S505). Note that the present embodiment does not limit the order of processing, and for example, S502 to S504 may be performed in any order. Moreover, S502 to S504 may perform parallel processing.

Selecting unit 205, based on a threshold, of the four thicknesses t ₁ ~t ₄ calculated, excluding the thickness of the abnormal value (S506). When there is no abnormal value is passed four thicknesses t ₁ ~t ₄ to the next process. Further, if the thickness t ₁ ~t ₄ is removed more than starts from measurement by ionization chamber 121-124 again.

Next, when receiving _four thicknesses t _{1 to} t ₄ as thicknesses considered to be normal, the selection unit 205 selects any three of the thicknesses t ₁ to t ₄ considered to be normal (S507) ). When the three thicknesses are received as the thickness considered to be normal in S506, the selection unit 205 passes these three thicknesses to the next processing.

  Then, the corrected thickness calculation unit 206 calculates the thickness t of the object to be measured 150 in a state in which no pass angle variation occurs, based on the three received thicknesses (S508). Further, the corrected thickness calculation unit 206 also calculates an angle θ which is a pass angle. In addition, since the calculation method is mentioned above, description is abbreviate | omitted.

  The output unit 207 outputs the thickness t of the measurement object 150 and the angle θ to be the pass angle to an external device or a display device in a state where no pass angle variation occurs (S509).

  By the above-described processing procedure, it is possible to confirm the thickness t of the measurement object 150 in the case where no path angle variation occurs.

Next, the calculation procedure of the thickness t1 in the _first ionization chamber processing unit 211 shown in S502 will be described. FIG. 6 is a flowchart showing the procedure of the above-described processing in the first ionization chamber processing unit 211 of the present embodiment.

  First, the first current detection unit 202A detects the current value from the first ionization chamber 121 (S601).

  Next, the first thickness calculation unit 203A calculates the thickness of the measurement object 150 in the direction from the X-ray source 101 to the first ionization chamber 121 from the detected current value (S602).

The first correction unit 204A, to the thickness t ₁ calculated makes various corrections including correction according to the inclination of the ionization chamber 121 (S603).

The processing procedure described above, derives the thickness t ₁ in which the correction is performed in accordance with the inclination of the ionization chamber 121. In the flowchart shown in FIG. 6, although the case of the first ionization chamber processing unit 211 has been described, it is assumed that the second ionization chamber processing unit 212 to the fourth ionization chamber processing unit 214 perform the same processing as well. Omit.

  The X-ray thickness measurement apparatus 1 according to this embodiment of the present embodiment includes the above-described configuration, so that no pass angle variation occurs regardless of whether the pass angle variation occurs in the measurement object 150 or not. The thickness of the measurement object 150 in the state can be calculated. Thereby, the measurement accuracy of thickness can be improved.

  Moreover, although the case where thickness is measured using X-rays is described in this embodiment, it is not limited to thickness measurement using X-rays, and thickness measurement using radiation may be used. For example, the thickness may be measured using gamma rays.

  Furthermore, in the present embodiment, by using any three of the four thicknesses calculated from the four ionization chambers, it is possible to measure the thickness in a state in which no path angle variation occurs. This enables accurate thickness measurement even when an abnormality occurs in one of the four ionization chambers.

  The present embodiment is not limited to the example of measuring the thickness by using the above-described arithmetic expression, and calculation of the thickness in the case where the pass angle variation does not occur from the plurality of thicknesses based on the measurement results of the plurality of ionization chambers Any arithmetic expression may be used as long as it is a method.

  While certain embodiments of the present invention have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and the gist of the invention, and are included in the invention described in the claims and the equivalent scope thereof.

  DESCRIPTION OF SYMBOLS 1 ... X-ray thickness measurement apparatus, 100 ... Control part, 101 ... X-ray source, 111 ... X-ray tube, 121 ... 1st ionization chamber, 122 ... 2nd ionization chamber, 123 ... 3rd ionization chamber, 124: fourth ionization chamber, 131 to 134: AD converter, 150: measurement object, 201: input unit, 202A: first current detection unit, 202B: second current detection unit, 202C: third Current detection unit, 202D: fourth current detection unit, 203A: first thickness operation unit, 203B: second thickness operation unit, 203C: third thickness operation unit, 203D: fourth thickness Calculation unit 204A: first correction unit 204B: second correction unit 204C: third correction unit 204D: fourth correction unit 205: selection unit 206: corrected thickness calculation unit 207 ... output unit, 211 ... first ionization chamber processing unit, 212 ... second ionization chamber processing unit, 213 ... Ionization chamber processing unit of 3, 214 ... fourth of the ionization chamber processing unit.

Claims (5)

A radiation source for irradiating the object to be measured with radiation;
Through the object to be measured, a plurality arranged in a position opposed to the radiation source, for detecting radiation transmitted through the object to be measured, and the radiation detecting portion of the multiple,
And the radiation source, wherein when the with each of the plurality of radiation detection units, said measurement object between the passes, if the path angle variation of the measurement object has occurred, the plurality of radiation detector output And a control unit that calculates the thickness of the measurement object in the case where no change in the path angle of the measurement object occurs and the angle of inclination of the measurement object due to the change in the path angle based on the result .
Each of the plurality of radiation detection units is installed at a predetermined angle with respect to an axis indicating a direction perpendicular to the surface of the measurement object when no path angle variation occurs.
The control unit calculates the thickness of the object to be measured in the case where no path angle variation occurs by the equations (1) and (2), and the path angle variation occurs by the equation (3) Calculate the angle of inclination of the measurement object of
Thickness measuring device.

t is the thickness of the measurement object when no change in the path angle of the measurement object occurs;
t ₂ , t ₃ , and t ₄ are thicknesses of the measurement object measured by each of the plurality of radiation detection units, when a path angle variation of the measurement object occurs.
φ is an angle of mutual inclination of the plurality of radiation detection units,
A = a / (− d), B = b / (− d), C = c / (− d), D = d / (− d) = − 1,
θ is the angle of inclination of the measurement object when the path angle variation of the measurement object occurs. Provided with three or more of the radiation detection units ,
The thickness measuring device according to claim 1. Provided with four or more of the radiation detection units ;
The control unit is configured to adjust the path angle of the measurement object when the measurement object passes between the radiation source and each of the four or more radiation detection units. The thickness of the measurement object in the case where no change in the path angle of the measurement object occurs is calculated based on the output result of any three of the four or more radiation detection units .
Thickness measuring apparatus according to claim 2. The control unit is configured such that, among the output results of the four or more radiation detection units , the path angle fluctuation of the measurement object does not occur based on the output result satisfying the threshold value for determining whether or not it is an abnormal value. Calculate the thickness of the measurement object of
Thickness measuring apparatus according to claim 3. The radiation emitted by the radiation source is X-rays or γ-rays,
The thickness measuring device according to any one of claims 1 to 4 .

Images