JP2013096796A - Radiation measuring apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve a radiation measuring apparatus capable of, in an entire width measurement using a line sensor, performing real-time correction for a central part and a peripheral part and a medium-and-long term correction.SOLUTION: The radiation measuring apparatus irradiates radiation on a measuring object having a predetermined width from a radiation source, and measures intensity of the radiation transmitted through the measuring object by a line sensor, thereby measuring a thickness or basis weight of the measuring object by referring to predetermined transmitted radiation intensity characteristics measured on a plurality of reference objects of the same material as the measuring object and with known thicknesses. The radiation measuring apparatus includes: calibration sample moving means for moving a calibration sample along a detection part of the line sensor, the calibration sample being arranged between the radiation source and the measuring object and having known basis weight or thickness determined by another measurement; and calibration processing means for calculating a correction value based on a transmitted radiation intensity signal obtained by the line sensor at a moved position of the calibration sample and correcting the transmitted radiation intensity characteristics.

Description

  The present invention irradiates a measurement object having a predetermined width from a radiation source, measures the intensity of the radiation transmitted through the measurement object in the width direction by a line sensor, and uses the same material as the measurement object. The present invention relates to a radiation measuring apparatus that measures the thickness or basis weight of the object to be measured with reference to transmission radiation intensity characteristics obtained in advance by measuring a plurality of reference objects with known thicknesses.

  As a radiation source used in the radiation measuring apparatus of the present invention, an X-ray source, a radiation source containing β-rays, and the like are options. However, in the following description and drawing notation, an example using a general X-ray source is used. Will be explained.

  FIG. 10 is a functional block diagram showing a configuration example of a conventional X-ray measurement apparatus disclosed in Patent Document 1. As shown in FIG. The X-ray source 10 irradiates X-rays from the X-ray source 10 in the orthogonal direction to the DUT 20 having a predetermined width and transported in the direction of the arrow P, and the line sensor 30 Measure in the width direction.

  The measured value Xi of the line sensor 30 is input to the basis weight calculation means 40. The basis weight calculating means 40 holds a transmission X-ray intensity characteristic obtained in advance by measurement of a plurality of reference objects having the same material as the object to be measured 20 and a known thickness based on the measurement value Xi in a table or an approximate function. The basis weight Wi with respect to the measured value Xi is acquired with reference to the line intensity characteristic holding unit 50, and passed to the external output unit 60.

  A calibration sample 70 whose basis weight Ws is known in advance by another measurement is fixedly arranged in the vicinity of the X-ray irradiation position on the object to be measured. The calibration sample 70 is irradiated with X-rays from the X-ray source 10, and a measured value Xi ′ obtained by measuring the transmitted X-ray intensity with the line sensor 30 is input to the transmitted X-ray intensity correcting means 80.

  The transmitted X-ray intensity correction means 80 calculates a correction value M such that the reference value Wi ′ by the transmitted X-ray intensity characteristic holding means 50 for the measured value Xi ′ matches the basis weight Ws of the calibration sample 70 and transmits the correction value M ′. The characteristic data held in the X-ray intensity characteristic holding means 50 is corrected.

JP 2003-329430 A

  In the X-ray measuring apparatus having the conventional configuration, the calibration sample 70 is placed beside the object to be measured 20 (in the vicinity of the X-ray irradiation position) for correction. However, the transmission intensity of the calibration sample at one end of the line sensor 30 is corrected. In this method, the entire measurement system is corrected by the measured value.

  According to this method, correction in the vicinity where the calibration sample 70 is placed (around the end of the line sensor 30) and short-term source fluctuation can be accurately corrected. On the other hand, it is unclear whether the same correction result can be reliably obtained in the periphery and the center of the line sensor 30, and it is not possible to guarantee the identity between the measurement around the edge and the measurement at the center.

FIG. 11 is a perspective view showing the relative relationship between the X-ray source, the line sensor, and the object to be measured. The distance from the X-ray source 10 to the object to be measured 20 is different between the central portion distance L1 and the peripheral end portion L2 distance. In addition, since the distance to the line sensor 30 and the irradiation angle are different, the projected area of X-rays is also different between S1 and S2. Depending on the area ratio, the X-ray transmission intensity differs between the central portion and the peripheral portion. Moreover, it is affected by the atmosphere (temperature, humidity, atmospheric pressure, etc.) by changing the irradiation distance.
(0000)
Further, the peripheral edge is affected by beam hardening. Furthermore, since the peripheral edge portion passes through the inspection object (sheet) 20 obliquely, the output of the line sensor 30 is reduced in the post-transmission dose depending on the incident angle of the flux even if the measurement object 20 has the same thickness. . For example, assuming a case where the full width measurement of the inspection object 20 is performed with a fan-shaped beam whose measurement range is 45 ° left and right from the radiation source, cos 45 ° = 0.707, which is nearly 30%.
(0000)
Since the measurement accuracy of the basis weight measurement is generally expected to be about a few percent, even if the calibration can be performed temporarily accurately without the inspection object 20, the periphery and center are initially in the middle and long term. It cannot be guaranteed that the state is maintained.

  An object of the present invention is to realize a radiation measurement apparatus that enables real-time correction and mid-long-term correction of the central portion and the peripheral end portion in full width measurement using a line sensor.

In order to achieve such a subject, the present invention has the following configuration.
(1) Radiation is applied to a measurement object having a predetermined width from a radiation source, the intensity of the radiation transmitted through the measurement object is measured in the width direction by a line sensor, and the thickness is the same as that of the measurement object. In a radiation measuring apparatus that measures the thickness or basis weight of the object to be measured with reference to transmission radiation intensity characteristics obtained in advance by measurement of a plurality of reference objects whose lengths are known,
Calibration sample moving means for moving a calibration sample whose basis weight or thickness interposed between the radiation source and the object to be measured is known in advance by another measurement along the detection unit of the line sensor;
Calibration processing means for calculating a correction value based on a transmission radiation intensity signal by the line sensor at the movement position of the calibration sample, and correcting the transmission radiation intensity characteristics;
A radiation measurement apparatus comprising:

(2) The calibration processing means corrects the transmission radiation intensity characteristic in real time based on instantaneous information of a transmission radiation intensity measurement signal from the line sensor at the movement position of the calibration sample. The radiation measuring apparatus described.

(3) The calibration processing means calculates and corrects the medium- to long-term characteristic of the transmitted radiation intensity characteristic based on trend information of the transmitted radiation intensity measurement signal by the line sensor at the movement position of the calibration sample. The radiation measuring apparatus according to (1), wherein:

(4) The calibration processing means calculates the medium-long-term characteristic by moving average calculation or operation cycle fluctuation calculation of the trend information, and corrects the peripheral transmission radiation intensity characteristic according to (3) Radiation measurement device.

(5) The calibration processing means, based on a signal obtained by measuring the transmitted radiation intensity from the calibration sample with the line sensor in the state where the measurement object is not interposed at the moving position end of the calibration sample, The radiation measuring apparatus according to any one of (1) to (4), wherein the characteristic is corrected.

(6) The radiation measuring apparatus according to any one of (1) to (5), further comprising display means for displaying movement position information of the calibration sample and correction information by the calibration processing means.

(7) The radiation according to any one of (1) to (6), wherein the calibration sample is made of a material having the same material as that of the object to be measured or having an atomic number equivalent to that of the object to be measured. measuring device.

(8) The calibration sample has a basis weight or thickness that is several times larger than that of the object to be measured, and in the case of the same material as the object to be measured, a plurality of stacked samples, the object to be measured And the atomic number is the same, the radiation measuring apparatus according to (7), wherein the basis weight or thickness is several times larger.

(9) The calibration sample is sufficiently smaller than the object to be measured, and a region overlapping with the object to be measured due to the movement thereof is a sufficiently narrow range with respect to the size of the object to be measured. The radiation measuring apparatus according to any one of (8).

According to the present invention, the following effects can be expected.
(1) The same measurement accuracy can be obtained at the center portion and the peripheral end portion of the line sensor.
(2) It is possible to correct the operation cycle (production lot unit cycle, morning / night daily cycle fluctuation, etc.).
(3) The influence of the measurement environment (temperature, humidity, atmospheric pressure, etc.) can be corrected.
(4) By displaying the measurement value of the calibration sample in real time in the operator window, the measurement accuracy can always be clearly shown to the operator.
(5) Trend management of the measured values of the calibration sample enables collection of maintenance information such as dose reduction and detector sensitivity stability.
(6) Periodic calibration with only the calibration sample in the area where there is no object to be measured eliminates the need for a long-term (several months) and complicated guarantee work for pulling out the entire apparatus and verifying the calibration sample.

It is a functional block diagram which shows one Example of the X-ray measuring apparatus to which this invention is applied. It is a perspective view which shows the relative relationship of a X-ray source, a line sensor, a to-be-measured object, and a calibration sample. It is a longitudinal cross-sectional view which shows the relative relationship of a X-ray source, a line sensor, a to-be-measured object, and a calibration sample. It is an output characteristic figure of a line sensor. It is a characteristic view explaining the correction | amendment method of a X-ray transmission intensity characteristic. It is a screen block diagram of a display means. It is a schematic diagram explaining the scanning locus of a calibration sample and a non-measurable region. It is a functional block diagram which shows the other Example of the X-ray measuring apparatus to which this invention is applied. It is a perspective view which shows the structural example of a calibration sample holder. It is a functional block diagram which shows the structural example of the conventional X-ray measuring apparatus. It is a perspective view which shows the relative relationship of a X-ray source, a line sensor, and a to-be-measured object.

  Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a functional block diagram showing an embodiment of an X-ray measuring apparatus to which the present invention is applied. FIG. 2 is a perspective view showing the relative relationship of the X-ray source, line sensor, object to be measured, and calibration sample in FIG. FIG. 3 is a longitudinal sectional view showing a relative relationship among the X-ray source, the line sensor, the object to be measured, and the calibration sample. 1, 2, and 3, the same components as those in the conventional configuration described in FIGS. 10 and 11 are denoted by the same reference numerals, and the description thereof is omitted.

  The configurations of the X-ray source 10, the DUT 20, and the line sensor 30 are the same as those in FIGS. 10 and 11. The line sensor 30 is installed facing the X-ray source 10. It is placed at a position away from the line sensor 30 and in the vicinity of the line sensor 30.

  If the measurement object 20 is moved in a direction substantially perpendicular to the X-ray irradiation direction (horizontal direction in FIG. 2) and measured by the line sensor 30, the full width of the measurement object can be measured. In addition to this configuration, a beam shaping collimator may be provided immediately below the X-ray source 10.

  Calibration sample moving means 200 that can move (scan) over the entire detection range of the line sensor 30 is provided above the line sensor 30 and slightly above the object 20 to be measured. The calibration sample moving means 200 is provided with a holder 201 that holds the calibration sample 100, can move the calibration sample 100 in parallel with the line sensor 300, and can continuously and repeatedly move back at the end of the movement range. It has a configuration.

  The calibration sample 100 is moved and scanned across the object to be measured 20 during the measurement of the object to be measured 20, and the transmitted dose transmitted through the calibration sample 100 and the object to be inspected 20 continuously is measured by the line sensor 30. The movement form of the calibration sample 100 includes intermittent movement and temporary stop in addition to the above-mentioned continuous repeated movement.

  As a general calibration sample, it can be realized by an aluminum plate or a resin plate accurately cut into a known area in advance, and a sample having a known basis weight by accurately measuring the weight with an electronic balance is used.

  In the present invention, this general calibration sample may be used, but optimally, the same material as the object to be measured 20 (or a composite material with coating) may be used. What was cut out and measured accurately with an electronic balance is more preferable. A plurality of (3 to 7) calibration samples are stacked and set on the holder 201.

  Since the X-ray source 10 must be arranged at a distance from the line sensor 30, a high energy band (15 to 25 KeV) is used so that the energy intensity of the X-ray source 10 is relatively unaffected by air.

  When the object to be measured 20 is a thin resin sheet, metal foil, battery electrode sheet, etc., 10 to 15 KeV is appropriate for the measurement, but if a high energy band (15 to 25 KeV) is used, the object to be measured 20 is measured. In addition, there is a sufficient transmission power, and it is possible to transmit a plurality of sheets.

  FIG. 4 is an output characteristic diagram of the line sensor 30 and shows measured values of the line sensor 30 in the width direction of the DUT 20. The basis weight calculation means 300 that inputs the measurement value Xi of the line sensor 30 except the overlapping portion W through which the calibration sample 100 passes refers to the transmission direction X-ray intensity characteristic holding means 50 to obtain the basis weight profile Wi in the width direction. Calculate and pass to the external output means 60. This basis weight calculation method is the same as the conventional configuration.

  The calibration processing means 400 that inputs the measurement value Xi ′ of the line sensor 30 in the overlapping portion W calculates the correction value M from this measurement value and outputs it to the transmission X-ray intensity characteristic holding means 50, so that the calibration sample 100 passes. The transmitted X-ray intensity characteristics of all regions except the inner region are corrected.

  The calibration processing unit 400 includes an instantaneous correction value calculating unit 401 that calculates a real-time correction value, a trend data holding unit 402, and a medium to long-term correction value calculating unit 403 that calculates a medium to long-term correction value based on trend information.

  The medium / long-term correction value calculation means 403 calculates the medium / long-term correction value M by executing the moving average calculation or the operation cycle fluctuation calculation of the trend information for a predetermined period, and outputs it to the transmission X-ray intensity characteristic holding means 50 for transmission X-ray. Correct the intensity characteristics. As an analysis method based on trend information, for each passing position of the calibration sample 100, a trend analysis based on past data and current data is executed in consideration of the passing position.

  The correction value M is obtained by converting the correction amount in accordance with the ratio of the number of calibration samples 100 to the number of calibration samples 100. However, it is not certain whether the basis weight of the object to be measured 20 has actually become heavy or whether a change has occurred due to a disturbance. Therefore, it is not directly corrected by the difference, and specifically, it is performed as follows.

  The effect on the measurement accuracy when the number of calibration samples is four is the sum of the transmission attenuation of one sheet (object to be measured) whose basis weight is unknown at the overlapping part and the transmission attenuation of four known basis weights. It becomes. If the basis weight of the object to be measured is 200g / m2 and 2% (= 4g / m2) heavier than the specified value, the overlap will be 4 / (200+ (200 × 4)) = 0.4g / m2 change. The measured value of becomes higher.

  Although it is not immediately known whether the cause of this change is the fact that the basis weight of the object to be measured has become heavy or a 2% change has occurred due to disturbance, the medium- to long-term correction value calculation means 403 moving average calculation By combining with, it is possible to infer whether there has been a change in the short term or a long term.

  In the operation according to the present invention, for short-term fluctuations, basically, correction is not performed or only slight correction is performed, and the amount of change or operation cycle (production lot unit) that matches the cycle of the calibration sample scan. ) And those that coincide with the daily fluctuation of the morning and evening, etc.) will be positively corrected.

  The scanning cycle of the calibration sample 100 is several seconds to 10 seconds, and correction value data is created from moving average information several times to several tens of times. For example, if the moving average value is 16 times (about 1 minute), the variation is 1 / √16 = 1/4, and the above 0.4 g / m2 is a stable correction value up to 0.1 g / m2, and the object to be measured However, a correction value M sufficient to correct the disturbance value can be obtained.

  FIG. 5 is a characteristic diagram for explaining a method for correcting the X-ray transmission intensity characteristic. Similar to the conventional method described with reference to FIG. 10, the transmission X-ray intensity characteristic F1 obtained in advance by measurement of a plurality of reference objects having the same material as the object to be measured 20 and a known thickness is used as a basic data in a table or approximate function. Hold. This basic data can also be obtained by measuring a plurality of calibration samples having different thicknesses in a stable state in which fluctuations in the radiation source are sufficiently suppressed.

  A characteristic obtained by correcting the basic data of the transmission X-ray intensity characteristic F1 with the medium-to-long-term correction value M based on the actually measured value measured by moving the correction sample 100 on the object to be measured is indicated by F2. The basis weight Wi1 based on the characteristic F1 based on the uncorrected basic data at the measurement value Xi is corrected to the basis weight Wi2 based on the corrected characteristic, and the measurement accuracy is improved.

  When there is no change between the measurement value of the previous measurement cycle and the current measurement value in the central part of the line sensor 30 and a change is recognized only in the periphery, the correction limited to the area of the line sensor 30 can be executed.

  The scanned calibration sample 100 always displays the measured value within the standard value as a correction result excluding instantaneous fluctuations, so that it is sufficient for the difference between the center portion and the peripheral end portion of the line sensor 30 and the change with time. It is possible to clearly indicate to the operator that a high measurement accuracy is maintained.

  FIG. 6 is a screen configuration diagram of the display means 500. The basis weight of the calibration sample 100 is calculated in real time from the measured value of the overlapped portion, and the basis weight of the calibration sample 100 is calculated, passed to the display means 500 as correction information, and displayed on the operating window. It may be displayed together with the position movement position information P of the calibration sample 100.

  The measured value is updated with time in the central measuring unit, and the old data disappears upward. The trajectory through which the calibration sample has passed is displayed in black because it is thicker than the measurement part, and as a result, is displayed as a zigzag line. At the tip of the line, the measured value of the calibration sample is displayed in basis weight and is updated every moment. It is clearly indicated that the calibration process is normally executed when the basis weight measurement value of the calibration sample is a known regulation value.

  The average value of the measurement unit is also displayed near the lower right corner of the screen. When thick coating occurs, the measurement result is displayed at a color-coded or gray scale level, and is graphed as surface information and can be recognized by the operator.

  The screen flows from moment to moment, but logs remain so that past data analysis can be performed in chronological order by collecting data. The trajectory through which the calibration sample has passed is shown as a continuous zigzag, but it can also be measured and displayed from time to time in a form that crosses every few minutes or hours.

  FIG. 7 is a schematic diagram for explaining the scanning trajectory of the calibration sample and the unmeasurable region. The scanning trajectory of the calibration sample 100 is displayed as a zigzag line as the object to be measured 20 moves. A section that does not overlap the object to be measured 20 is provided at both ends where the calibration sample 100 is folded back. In this section, the basis weight of only the calibration sample 100 is measured, and the transmitted X-ray intensity characteristics are corrected based on the measured value. Can do.

  FIG. 8 is a functional block diagram showing another embodiment of the X-ray measuring apparatus to which the present invention is applied. The difference from FIG. 1 is a configuration in which X-rays from the X-ray source 10 pass only through the calibration sample 100 and are directly input to the line sensor 20 without passing through the DUT 20.

  In this way, by incorporating a mechanism for periodically measuring only the calibration sample 100 that does not include the object to be measured 20, long-term (several months) and complicated guarantee work for drawing out the entire apparatus and verifying the calibration sample is unnecessary. become.

  FIG. 9 is a perspective view illustrating a configuration example of the calibration sample holder 201. As shown in FIG. 9A, the area that cannot be measured can be reduced by narrowing or eliminating the rib that supports the calibration sample 100.

  As shown in FIG. 9B, if the end face of the calibration sample 100 can be accurately overlapped by the configuration in which the calibration sample 100 is cantilevered, even when the calibration sample is passing as shown in FIG. It is possible to reduce or eliminate areas that cannot be measured.

DESCRIPTION OF SYMBOLS 10 X-ray source 20 Measured object 30 Line sensor 50 Transmission X-ray intensity characteristic holding means 60 External output means 100 Calibration sample 200 Calibration sample moving means 201 Holder 300 Basis weight calculation means 400 Calibration processing means 401 Instantaneous correction value calculation means 402 Trend information holding means 403 Medium to long-term correction value calculating means 500 Display means

Claims (9)

Radiation is irradiated from a radiation source to an object to be measured having a predetermined width, the intensity of the radiation transmitted through the object to be measured is measured in the width direction by a line sensor, and the thickness is known with the same material as the object to be measured. In the radiation measurement apparatus for measuring the thickness or basis weight of the object to be measured with reference to the transmitted radiation intensity characteristics obtained in advance in the measurement of the plurality of reference objects,
A calibration sample moving means for moving a calibration sample whose basis weight or thickness is known in advance by another measurement, interposed between the radiation source and the object to be measured, along the detection unit of the line sensor;
Calibration processing means for calculating a correction value based on a transmission radiation intensity signal by the line sensor at the movement position of the calibration sample, and correcting the transmission radiation intensity characteristics;
A radiation measurement apparatus comprising:   2. The radiation according to claim 1, wherein the calibration processing unit corrects the transmitted radiation intensity characteristic in real time based on instantaneous information of a transmitted radiation intensity measurement signal by the line sensor at a movement position of the calibration sample. measuring device.   The calibration processing means calculates and corrects the medium- to long-term characteristic of the transmitted radiation intensity characteristic based on trend information of the transmitted radiation intensity measurement signal by the line sensor at the movement position of the calibration sample. The radiation measuring apparatus according to claim 1, wherein   The radiation measurement apparatus according to claim 3, wherein the calibration processing unit calculates the medium-long-term characteristic by moving average calculation or operation cycle variation calculation of the trend information to correct the circumferential transmission radiation intensity characteristic. .   The calibration processing unit corrects the transmitted radiation intensity characteristic based on a signal obtained by measuring the transmitted radiation intensity from the calibration sample with the line sensor in a state where the measurement object is not interposed at the moving position end of the calibration sample. The radiation measuring apparatus according to claim 1, wherein   6. The radiation measuring apparatus according to claim 1, further comprising display means for displaying movement position information of the calibration sample and correction information by the calibration processing means.   The radiation measurement apparatus according to claim 1, wherein the calibration sample is made of a material having the same material as that of the object to be measured or having an atomic number equivalent to that of the object to be measured.   The calibration sample is one whose basis weight or thickness is several times larger than the object to be measured, and in the case of the same material as the object to be measured, a plurality of stacked ones, the object to be measured and the atomic number 8. The radiation measuring apparatus according to claim 7, wherein when the same material is used, the basis weight or thickness is several times larger.   9. The calibration sample according to claim 1, wherein the calibration sample is sufficiently smaller than the object to be measured, and a region overlapping the object to be measured by the movement thereof is a sufficiently narrow range with respect to the size of the object to be measured. A radiation measuring apparatus according to claim 1.