JP2014021099A - Thickness profile measurement device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thickness profile measurement device that corrects an error due to a path line variation and a path angle variation, and thereby can more accurately measure a thickness profile in a width direction of a sheet-like measured object.SOLUTION: A thickness profile measurement device according to an embodiment comprises: a detector that includes an X-ray generator and a plurality of ionization chambers; and a control part that uses characteristics in which an attenuation amount of the X-ray is different depending upon a sheet thickness of a substance and a material thereof when an X-ray to be output from the X-ray generator is transmitted through the substance, and measures the sheet thickness in the width direction of the measured object from a detection result by the plurality of ionization chambers. The thickness profile measurement device is configured to include: first variation amount measurement means that calculates a path line variation amount of the measured object passing through the detector; and first correction means that, on the basis of the path line variation amount calculated by the first variation amount measurement means, calculates a sheet thickness profile in which a measurement error of the sheet thickness due to the path line variation is corrected.

Description

  Embodiments described herein relate generally to a thickness profile measuring apparatus.

  Conventionally, in a production line for various plate-like objects (here, a steel plate is taken as an example), a thickness profile measuring device for measuring a thickness profile in the width direction of the steel plate in real time has been used. In order to measure the thickness profile, a conventional thickness profile measuring apparatus includes a detection unit including an X-ray generator and a detector having a plurality of ionization chambers in the width direction of the steel plate. In the detection unit, the X-ray dose from the X-ray generator that passes through the steel plate is converted into an electrical signal by each ionization chamber, and the current is digitally converted by an integrating AD converter to obtain a current value as a control of the thickness profile measuring device. Transmitted to the department.

  In the control unit, the built-in microcomputer calculates the plate thickness using the current value, the set value and the calibration curve parameter obtained in advance by the calibration process, and outputs the plate thickness deviation. In such a thickness profile measuring apparatus, it is possible to measure the thickness profile in the width direction in real time by performing multipoint measurement using a plurality of ionization chambers.

JP 2006-170883 A

  However, when measuring the thickness profile in the width direction of the steel sheet using the thickness profile measuring apparatus as described above, the pass line fluctuation (height fluctuation from the reference position where the steel sheet should pass through the thickness profile measuring apparatus) ) And pass angle fluctuation (inclination fluctuation when the steel sheet is inclined in the width direction when passing through the thickness profile measuring device).

  When pass line fluctuations occur and the positional relationship between the X-ray generator, detector, and steel plate changes, the scattered radiation of X-rays incident on the detector changes in the above-described prior art, resulting in a thickness error. Problem arises. Further, when the pass angle variation occurs, X-rays are transmitted obliquely with respect to the steel sheet, so that the conventional technique has a problem in that different thickness errors occur depending on the positional relationship between the ionization chamber and the X-ray generator. .

  SUMMARY OF THE INVENTION Problems to be solved by the present invention are a thickness profile measuring apparatus including an X-ray generator and a detector having a plurality of ionization chambers in the width direction of a plate-like object to be measured. It is an object to provide a thickness profile measuring apparatus capable of correcting a thickness profile in the width direction of a plate-like object to be measured with higher accuracy by correcting an error due to the above.

  The thickness profile measuring apparatus according to the embodiment includes a detection unit including an X-ray generator and a detector having a plurality of ionization chambers, and when X-rays output from the X-ray generator pass through the substance, A thickness profile measuring apparatus including a control unit that measures a plate thickness in a width direction of an object to be measured from detection results obtained by a plurality of ionization chambers using characteristics in which the amount of X-ray attenuation varies depending on the plate thickness and material. In such a thickness profile measuring apparatus, the first fluctuation amount measuring means for obtaining the pass line fluctuation amount of the object passing through the detector, and the pass line fluctuation amount obtained by the first fluctuation amount measuring means, And a first correction unit for obtaining a plate thickness profile in which a plate thickness measurement error due to line fluctuation is corrected.

FIG. 1 is a schematic diagram illustrating an overall configuration of a thickness profile measuring apparatus according to an embodiment. FIG. 2 is a diagram illustrating a functional configuration related to thickness profile measurement of the control unit of the thickness profile measuring apparatus according to the embodiment. FIG. 3 is a diagram showing a change example of the laser projection image obtained by photographing the surface of the measurement object irradiated with laser from the laser oscillator with an area CCD camera. FIG. 4 is a diagram showing an example of a pass line fluctuation error correction table. FIG. 5 is a diagram for explaining the relationship among the thickness T of the object to be measured, the passage length T of X-rays passing through the object to be measured, and the thickness T ″ before correction. FIG. 6A is a diagram illustrating a detection result of the plate thickness when the pass line fluctuation error correction is performed and when it is not performed. FIG. 6B is a diagram illustrating a state in which there is a 200 mm pass line variation. FIG. 7A is a diagram illustrating a plate thickness detection result when the pass angle variation error correction is performed and when it is not performed. FIG. 7-2 is a diagram illustrating a state where there is a 5 degree path angle variation.

  First, the overall configuration of the thickness profile measuring apparatus will be described with reference to FIG. FIG. 1 is a schematic diagram illustrating an overall configuration of a thickness profile measuring apparatus according to an embodiment.

  The thickness profile measuring apparatus according to the present embodiment includes a detection unit 1 including an X-ray generator 11 and a detector 12 having a plurality of ionization chambers in the width direction of a plate-like object to be measured (such as a steel plate) 3. . When measuring the thickness profile of the object 3 to be measured, the X-ray generator 11 irradiates the object 3 passing through the detector 1 with X-rays. Then, the X-ray dose transmitted through the object to be measured 3 is converted into an electric signal by each ionization chamber of the detector 12, and the current is converted into an analog / digital signal by an integrating AD converter (not shown), and a detection signal ( Current value) to the control unit 2. The control unit 2 includes a microcomputer, and the microcomputer calculates the plate thickness using the current value received from the detection unit 1, the set value, and the calibration curve parameter obtained in advance in the calibration process. , Outputs the thickness deviation (when there is no error correction). The control unit 2 also performs various controls of the detection unit 1 such as control related to X-ray irradiation of the detection unit 1.

  The configuration and the method for calculating the plate thickness are the same as those of the conventional thickness profile measuring apparatus, but the control unit 2 of the thickness profile measuring apparatus of the present embodiment has a pass line variation measuring unit as shown in FIG. 21, a pass line fluctuation error correction unit 22, a pass angle fluctuation amount measurement unit 23, a path angle fluctuation error correction unit 24, and a pass line fluctuation error correction table 25 described later.

  The pass line fluctuation measuring unit 21 obtains the pass line fluctuation of the DUT 3. Based on the pass line fluctuation amount obtained by the pass line fluctuation amount measuring unit 21, the pass line fluctuation error correction unit 22 obtains a plate thickness profile in which a plate thickness measurement error due to the pass line fluctuation is corrected, as will be described later. The path angle variation measuring unit 23 measures the path angle variation of the DUT 3 that passes through the detection unit 1. The pass angle variation error correction unit 24 obtains a plate thickness profile in which a plate thickness measurement error due to the pass angle variation is corrected based on the pass angle variation obtained by the pass angle variation measurement unit 23 as described later.

  The control unit 2 includes a microcomputer, a storage device such as a ROM (Read Only Memory), a RAM, and a built-in HDD, an external storage device such as an HDD and a CD drive device, a display device such as a liquid crystal display device, and a keyboard. And a hardware configuration using a normal computer.

  The pass line fluctuation error correction table 25 and the control program executed by the microcomputer are stored in a storage device such as the built-in HDD or the external storage device, and the microcomputer stores the control program in a RAM as a main storage device. By loading and executing the microcomputer, the microcomputer functions as the pass line variation measuring unit 21, the pass line variation error correcting unit 22, the path angle variation measuring unit 23, and the path angle variation error correcting unit 24.

  In addition, the detection unit 1 of the thickness profile measuring apparatus of the present embodiment includes a laser oscillator 13 and an area CCD camera 14 in the width direction of the device under test 3. The pass line fluctuation measuring unit 21 and the pass angle fluctuation measuring unit 23 change a laser projection image (camera image) obtained by photographing the surface of the object 3 to be measured irradiated with laser from the laser oscillator 13 with the area CCD camera 14. From (see FIG. 3), the pass line fluctuation amount and the pass angle fluctuation amount of the DUT 3 are obtained. Or, instead of the laser oscillator 13 and the area CCD camera 14, other detectors (sensors or the like) are used to detect the pass line fluctuation amount and the pass angle fluctuation amount of the DUT 3.

  When the pass line fluctuation amount and the pass angle fluctuation amount of the device under test 3 are obtained, the following pass line fluctuation error correction and pass angle fluctuation error correction are performed.

(1) Correction of Pass Line Fluctuation Error The control unit 2 is set with a correction amount for each plate thickness and for each pass line fluctuation amount (height data from the reference position (pass line 0 mm)) as shown in FIG. The pass line fluctuation error correction table 25 is registered in advance. The pass line fluctuation error correction unit 22 of the control unit 2 uses the corresponding correction value in the pass line fluctuation error correction table 25 based on the set plate thickness and the detected pass line fluctuation amount, to correct the thickness error due to the pass line fluctuation. Make corrections.

(2) Correction of Path Angle Fluctuation Error The irradiation angle of the X-ray from the X-ray generator 11 to the object to be measured 3 varies depending on the position of each ionization chamber of the detector 12. For this reason, the pass angle correction amount is determined for each ionization chamber based on the two angles of the X-ray beam angle and the object 3 to be measured.

  As shown in FIG. 5, since the X-ray beam irradiated to the device under test 3 is not perpendicular to the device under test 3, the passage length of X-rays passing through the device under test 3 having a thickness T is not T but T '(= T / cos θ; where θ is the X-ray beam angle, and the clockwise direction is positive with respect to the vertical). For this reason, the calibration curve in the control unit 2 recognizes the thickness of the DUT 3 as T when the X-ray passage length is T ′. Here, if the measured object 3 is inclined by an angle φ (however, the counterclockwise direction is positive with respect to the horizontal direction) in the width direction due to the path angle variation, it is assumed that the X-ray passage length T ″ is before correction. The correction formula for obtaining the corrected thickness T ′ from the thickness T ″ is as follows.

  When the sign of the angle φ of the DUT 3 is the same as the X-ray beam angle θ and the clockwise direction is positive, the correction formula can be expressed by the following formula.

  When the inclination of the device under test 3 is φ, correction of the path angle variation error can be performed by correcting as described above.

(3) Labeling process A synchronization signal is input to the detection unit 1, and a pass line fluctuation amount (height), a pass angle fluctuation amount (angle), a plate obtained based on a detection result obtained in synchronization with the detection unit 1 By labeling the thickness results and performing the above-mentioned pass line fluctuation error correction and pass angle fluctuation error correction for each matching label, the correction follows the changes in the pass line fluctuation amount and the pass angle fluctuation amount in the plate. It can be performed.

  Here, FIG. 6-1 shows the detection results of the plate thickness when the pass line fluctuation error correction is performed and when it is not performed. When there is a 200 mm pass line fluctuation as shown in FIG. 6B, the above-mentioned pass line fluctuation error correction is performed on the 200 mm pass line fluctuation to reduce the plate thickness error to 0.9. % To 0.1%.

  Next, FIG. 7-1 shows the detection results of the plate thickness (T = 2 mm) when the pass angle variation error correction is performed and when it is not performed. When there is a 5 degree pass angle variation as shown in FIG. 7-2, a plate angle error (plate thickness deviation) is obtained by performing a path angle variation error correction for the 5 degree pass angle variation. The thickness was reduced from 1.97% to 0.1%.

  As described above, according to the thickness profile measuring apparatus of the above embodiment, it is possible to measure the thickness profile in the width direction of the DUT 3 with higher accuracy, in which errors due to the pass line fluctuation and the pass angle fluctuation are corrected. it can.

  As mentioned above, although embodiment of this invention was described, the said embodiment was shown as an example and is not intending limiting the range of invention. The novel embodiment can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. Further, this embodiment and its modifications are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 1 Detection part 2 Control part 3 Measured object 11 X-ray generator 12 Detector 13 Laser oscillator 14 Area CCD camera 21 Pass line fluctuation measurement part 22 Pass line fluctuation error correction part 23 Pass angle fluctuation measurement part 24 Path angle fluctuation Error correction unit 25 Pass line fluctuation error correction table

Claims (5)

A detection unit including an X-ray generator and a detector having a plurality of ionization chambers, and when X-rays output from the X-ray generator pass through the substance, In a thickness profile measuring apparatus comprising a control unit that measures the plate thickness in the width direction of a plate-like object to be measured from the detection results of the plurality of ionization chambers using characteristics with different attenuation amounts,
First fluctuation amount measuring means for obtaining a pass line fluctuation amount of an object passing through the detector;
First correction means for obtaining a plate thickness profile obtained by correcting a measurement error of the plate thickness due to pass line fluctuation based on the pass line fluctuation amount obtained by the first fluctuation amount measuring means;
A thickness profile measuring apparatus comprising:   A pass line fluctuation error correction table in which a correction amount is set for each plate thickness and for each pass line fluctuation amount, and the first correction means has the pass line fluctuation determined by the set plate thickness and the first fluctuation amount measuring means. The thickness profile measuring apparatus according to claim 1, wherein a thickness error due to the pass line fluctuation is corrected based on an amount, using a corresponding correction value in the pass line fluctuation error correction table. A second fluctuation amount measuring means for measuring a path angle fluctuation amount of the measurement object passing through the detector;
2. A second correction means for obtaining a plate thickness profile obtained by correcting a plate thickness measurement error due to the pass angle fluctuation based on the pass angle fluctuation amount obtained by the second fluctuation amount measuring means. The thickness profile measuring apparatus according to claim 2.   The first fluctuation amount measuring means and the second fluctuation amount measuring means obtain the pass line fluctuation amount and the pass angle fluctuation amount corresponding to the positions of the plurality of ionization chambers, respectively, and perform the first correction. And the second correcting means correct the plate thickness measurement error due to the pass line variation and the plate thickness measurement error due to the pass angle variation corresponding to the positions of the plurality of ionization chambers, respectively. The thickness profile measuring apparatus according to claim 3, wherein a profile is obtained.   Measurement of the pass line fluctuation amount obtained by the first fluctuation amount measurement means, the pass angle fluctuation amount obtained by the second fluctuation amount measurement means, and the plate thickness corrected by the first correction means and the second correction means. The thickness profile measuring apparatus according to claim 4, wherein the result is subjected to a labeling process.

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