JP2013246072A - Radiation measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radiation measuring device capable of displaying a measured value of a radiation dose and information on its error without making a user feel unease.SOLUTION: In a radiation measuring device 1, a radiation sensor 21 outputs a pulse when a radiation is detected. A signal processing unit 40 calculates a radiation dose and a statistic error based on the number of pulses output from the radiation sensor 21 in a time period from start of the measurement of the radiation to the current time. A first display unit 12C displays the radiation dose calculated by the signal processing unit 40. A second display unit 12D displays a deterioration degree of the statistic error representing how the statistic error calculated by the signal processing unit 40 is deteriorated in comparison with an error limit predetermined according to the performance of the radiation sensor 21.

Description

  The present invention relates to a radiation measuring apparatus.

  Among the commercially available radiation measuring apparatuses, there are products that display radiation dose (rate) and statistical error as measurement results. For example, a radiation measuring instrument manufactured by ECOTEST (Ecotest STORA-TU RKS-01) simultaneously displays the measured radiation dose (rate), statistical error (percent display), set value, clock, and the like. The fact that the statistical error of the measured value exceeds the preset error limit is notified by blinking the error display value (see Non-Patent Document 1).

Radiation measuring instrument (Ecotest STORA-TU RKS-01) product information, [Search May 17, 2012], Internet <URL: http://www.ambient.ne.jp/product/stora.html>

  In order to perform a highly reliable measurement with a radiation measuring instrument, particularly a photodiode type measuring instrument used for a personal dosimeter, it is necessary to perform the measurement continuously for a sufficient time. In particular, in a place where the radiation dose is relatively low, the statistical error (relative error) becomes a relatively large value unless sufficient measurement time is obtained. As a result, in the radiation measuring instrument that displays the measurement accuracy together with the measurement dose as described above, the measurement accuracy is displayed very poorly, and the user's anxiety despite the fact that it is actually a safe radiation dose value. The problem of scolding occurs.

  For example, if the measurement dose is displayed as 0.01 μSv / h and the measurement error is 100% as a result of the radiation measurement, the radiation dose at the measurement location can be calculated as 0.02 μSv / h at the maximum. The dose of 0.02 μSv / h is far from the exposure dose that affects the human body, but if the measurement error is displayed as 100%, a user who does not know will be anxious.

  The present invention has been made in consideration of the above problems, and an object of the present invention is to provide a radiation measurement apparatus capable of displaying a measurement value of radiation dose and information on its error without causing the user to feel uneasy. Is to provide. Other problems and novel features will become apparent from the description of this specification and the accompanying drawings.

  In one aspect, the present invention is a radiation measurement apparatus, and includes a radiation sensor, a signal processing unit, a first display unit, and a second display unit. The radiation sensor outputs a pulse when detecting radiation. The signal processing unit calculates the radiation dose and the statistical error based on the number of pulses output from the radiation sensor from the start of radiation measurement to the current time. The first display unit displays the radiation dose calculated by the signal processing unit. The second display unit displays a degree of reduction in statistical error indicating how much the statistical error calculated by the signal processing unit has been reduced compared to a predetermined error limit according to the performance of the radiation sensor. .

Preferably, the second display unit displays a graphic representing the degree of statistical error reduction.
Preferably, the radiation measurement apparatus further includes a third display unit that displays a lower limit value and an upper limit value of the radiation dose based on the radiation dose calculated by the signal processing unit and the statistical error as a range of the measurement value at the current time. .

  Alternatively, the radiation measurement apparatus preferably displays a value representing the error limit as an absolute error and a value representing the statistical error calculated by the signal processing unit as an absolute error as a range of absolute errors at the current time. 3 display units.

  Preferably, the first to third display units are display areas defined on a common display panel.

  According to the present invention, radiation measurement values and error information can be displayed without making the user feel uneasy.

It is a block diagram which shows an example of the hardware constitutions of the mobile telephone 1 by one Embodiment. It is a block diagram which shows the functional structure of the part regarding a radiation measurement in the mobile telephone 1 of FIG. It is a figure showing the relationship between the radiation dose [microSv / h] calculated | required with respect to each measurement time, and a statistical error [%]. It is a figure which shows the example of a display of the radiation measurement result on a display panel. It is a flowchart which shows the radiation measurement procedure by the mobile telephone 1 of FIG.

  Hereinafter, embodiments will be described in detail with reference to the drawings. In the following description, an example in which a mobile phone (mobile communication terminal) such as a smartphone provided with a radiation sensor is used as a radiation measurement device will be described. However, the application target of the present invention is not limited to a mobile phone equipped with a radiation sensor, and a dedicated radiation measurement device not equipped with a communication function is also one embodiment of the present invention.

  In the following description, the same or corresponding parts are denoted by the same reference numerals, and the description thereof may not be repeated.

[Overall configuration of mobile phone (radiation measurement device)]
FIG. 1 is a block diagram illustrating an example of a hardware configuration of a mobile phone 1 according to an embodiment. A cellular phone 1 includes a central processing unit (CPU) 2, a random access memory (RAM) 3, a read only memory (ROM) 4, a nonvolatile memory 5, a communication device 6, an antenna 7, a microphone 8, and a speaker 9. , An audio signal processing circuit 10, a display unit 12, an input unit 11, a radiation detector 20, and the like.

  The CPU 2 controls the overall operation of the mobile phone 1 by executing programs stored in the ROM 4 and the nonvolatile memory 5. The RAM 3 and ROM 4 are used as the main memory of the CPU 2.

  The nonvolatile memory 5 is configured by, for example, an EEPROM (Electrically Erasable Programmable Read-Only Memory) such as a flash memory. A hard disk may be provided in place of the nonvolatile memory. The nonvolatile memory 5 stores data output from the CPU 2. In particular, in the case of this embodiment, the nonvolatile memory 5 stores data based on the output signal of the radiation detector 20.

  The communication device 6 performs wireless communication of voice signals and data signals with the wireless base station via the antenna 7 based on the command of the CPU 2.

  The audio signal processing circuit 10 performs AD (Analog-to-Digital) conversion on the audio signal detected by the microphone 8 and performs signal processing such as encoding and noise removal on the converted digital audio signal. The audio signal processing circuit 10 further performs predetermined signal processing on the digital signal to be acoustically output and outputs it to the speaker 9. Unlike the case of FIG. 1, the CPU 2 may execute the functions of the audio signal processing circuit 10 based on a program without providing the audio signal processing circuit 10.

  The display unit 12 is configured by a liquid crystal display panel or the like, and displays character information and an image based on a command from the CPU 2.

  The input unit 11 includes hardware keys for the user to perform input operations such as numbers and characters on the mobile phone 1. Alternatively, when the mobile phone 1 is a smartphone or the like, the input unit 11 may be configured to include a touch panel integrated with the display unit 12. In this case, since the user performs most of the input operation through the touch panel, only a few keys such as a power key and a volume key are provided as hardware keys, and keys for numbers and letters are not provided. Also good.

  The radiation detector 20 includes a radiation sensor that detects radiation. The detailed configuration of the radiation detector 20 will be described later with reference to FIG.

  In the case of a dedicated radiation measurement device, the communication device 6, the antenna 7, the microphone 8, the speaker 9, and the audio signal processing circuit 10 do not have to be provided.

[About radiation measurement]
FIG. 2 is a block diagram showing a functional configuration of a part related to radiation measurement in the mobile phone 1 of FIG. Referring to FIGS. 1 and 2, radiation detector 20 includes a radiation sensor 21, a signal conversion unit 22, and a counter 23.

  The radiation sensor 21 outputs a pulse signal when detecting radiation. For example, the radiation sensor 21 includes a silicon PIN photodiode to which a bias voltage is applied in the reverse direction. In this case, a pulsed current signal is generated by electron-hole pairs generated when radiation passes through the depletion layer.

  The signal conversion unit 22 includes an amplifier that amplifies the pulse signal output from the radiation sensor 21 and a comparator. When the radiation sensor is composed of a PIN photodiode, the amplifier converts the current pulse into a voltage pulse and amplifies it. The comparator compares the output voltage of the amplifier with a reference voltage and becomes a high level when the output voltage of the amplifier is equal to or higher than the reference voltage and becomes a low level when the output voltage of the amplifier is lower than the reference voltage (ie, shaping). Output pulse signal).

  The counter 23 counts the number of pulses output from the signal converter 22. The number of pulses per unit time corresponds to the radiation dose rate (also simply referred to as radiation dose in this specification).

  The CPU 2 has functions as a dose calculation unit 30 and a system control unit 31. These functions are realized by the radiation measurement program being executed by the CPU 2.

  The dose calculation unit 30 calculates the radiation dose rate [unit: μSv / h] by multiplying the number of pulses per unit time [unit: cpm (counts per minute)] based on the count result of the counter 23 by the conversion factor. Further, the dose calculation unit 30 calculates a statistical error based on the count number of the counter 23.

In general, when the total count N is detected during the measurement time t by radioactive decay, the total count N and the count per unit time (count rate) n = N / t are known to follow a Poisson distribution. For relatively large activities, the Poisson distribution can approximate a Gaussian distribution. In this case, the standard deviation (absolute error) σ ₁ of the total count N is equal to the square root of the total count N (described as “N ^1/2 ”), and the standard deviation (absolute error) σ ₂ of the count rate n is n / It is equal to the square root of t ((n / t) ^1/2 ). Therefore, the relative error, ie σ ₁ / N and σ ₂ / n, is
σ ₁ / N = σ ₂ / n = 1 / N ^1/2 (1)
It is expressed as These absolute and relative errors are called statistical errors.

  The system control unit 31 displays the radiation dose calculated by the dose calculation unit 30 in the display region 12C of the display unit (display panel) 12, and displays the calculated statistical error in the display regions 12D and 12E of the display unit 12. . However, as will be described in detail below, the system control unit 31 does not display the statistical error in the display area 12D as a percentage display (relative error display), but instead determines a predetermined error limit according to the performance of the radiation sensor. The degree of reduction of the statistical error indicating how much the statistical error has been reduced in comparison with FIG. Further, the system control unit 31 displays the measurement value range or the absolute error range in the display area 12E.

  The system control unit 31 also causes the radiation detector 20 to start measuring radiation when receiving a request for starting radiation measurement from the user via the input unit 11.

  In this specification, the signal conversion unit 22, the counter 23, and the CPU 2 in FIG. The signal processing unit 40 receives the pulse signal output from the radiation sensor 21, counts the number of output pulses, and calculates a radiation dose and a statistical error based on the counted result.

[Previous problems]
FIG. 3 is a diagram showing the relationship between the radiation dose [μSv / h] obtained for each measurement time and the statistical error [%]. FIG. 3 shows a case where the conversion factor when converting the counting rate [cpm] to the radiation dose [μSv / h] is 0.05. The measurement times are shown for 30 seconds, 1 minute, 2 minutes, and 60 minutes, respectively.

  As shown in FIG. 3, the longer the measurement time, the higher the measurement accuracy (the lower the statistical error). On the other hand, when the radiation dose is relatively high and when the radiation dose is relatively low, if the radiation dose is relatively high, sufficient measurement accuracy (sufficiently in about several minutes) Low statistical error). However, when the radiation dose is low, sufficient measurement accuracy (sufficiently low statistical error) cannot be obtained by measuring for several minutes.

  In many commercially available personal dosimeters, the measurement result is presented to the user by displaying a measurement value of radiation dose and a measurement error (statistical error) expressed as a relative error value (percentage) on a display screen. For this reason, statistical errors (relative errors) tend to be relatively large at places where the radiation dose is relatively low, and the user's anxiety despite the fact that the radiation dose is actually a safe value. There was a problem of embracing.

[Measurement accuracy display method]
FIG. 4 is a diagram illustrating a display example of the radiation measurement result on the display panel. Referring to FIG. 4, on the display surface of display unit 12, an area 12 </ b> C indicating a radiation dose value calculated from data obtained from the start of measurement to the present time, and areas 12 </ b> D and 12 </ b> E indicating statistical errors, Is provided.

  In the region 12D, the degree of reduction of the statistical error indicating how much the statistical error has been reduced as compared with a predetermined error limit according to the performance of the radiation sensor is graphically displayed. In the case of FIG. 4, a plurality (7) of star-shaped marks are displayed in a row in the region 12D. At the start of measurement, all star marks are displayed without being colored. When the statistical error reaches the error limit, all star marks are displayed in a colored state.

  In the area 12E, an error limit expressed in absolute error and a statistical error expressed in absolute error are displayed as an absolute error range. Instead of the absolute error range, the lower limit and upper limit of the measurement value calculated by the current radiation dose and the statistical error may be displayed as the measurement value range.

  For example, it is assumed that the measured value is 0.05 μSv / h, the relative error is 80%, and the error limit corresponding to the performance of the radiation sensor is 20%. In this case, 0.05 μSv / h is displayed in the area C as a measured value. In the region D, for example, a state in which three of the seven star marks from the left are colored is displayed. In the area E, 0.01 to 0.04 μSv / h is displayed as an absolute error range. Instead of the absolute error range, a range of measured values, that is, 0.01 to 0.09 μSv / h may be displayed.

  In FIG. 4, the degree of statistical error reduction is displayed with a star-shaped mark arranged in a line. However, if the display method can determine whether or not the statistical error has reached the error limit, it is displayed with another figure. It doesn't matter. For example, the statistical error reduction degree may be displayed by a method of changing the coloration of a part of an elongated rectangular figure like a thermometer.

  Other information is also displayed in other areas of the display panel. In the case of FIG. 4, it is displayed in the area 12A that radiation is being measured. In the area 12B, a warning to the user that the mobile phone is not moved during the measurement of radiation is displayed. In the regions 12F and 12G, the remaining measurement time is displayed as a graphic and a numerical value. In the areas 12H and 12I, input buttons used when canceling or ending the radiation measurement are displayed. In the case of FIG. 4, the input unit 11 in FIG. 2 is configured by a touch panel formed integrally with the display unit 12. When the user touches the area 12H or 12I on the screen with his / her finger, a command to cancel or end the measurement can be input.

[Radiation measurement procedure]
FIG. 5 is a flowchart showing a radiation measurement procedure by the mobile phone 1 of FIG. Hereinafter, with reference to FIG. 2 and FIG.

  The measurement procedure of FIG. 5 is started by an input operation of a user who requests radiation measurement (YES in step S101).

  In response to the request to start radiation measurement, the system control unit 31 causes the radiation detector 20 to start measuring radiation. While performing the radiation measurement, the dose calculation unit 30 calculates the radiation dose and the statistical error based on the radiation measurement data obtained from the measurement start time to the present time (step S103). The system control unit 31 displays the calculated radiation dose and statistical error in the regions 12C and 12D of the display unit 12 (step S104). Here, in the region 12D, a degree of reduction indicating how much the statistical error (relative error) has decreased as compared with the error limit is graphically displayed. Simultaneously with the graphical display of statistical errors, the range of measured values or the range of absolute errors is shown numerically in region 12E.

  The calculation of radiation dose and statistical error (step S103) and its display (step S104) may be performed with a predetermined time interval (for example, every fixed time such as 10 seconds).

  If the user inputs a measurement end command to the input unit 11, a predetermined measurement time has elapsed, or the calculated statistical error has reached the error limit (YES in step S105), system control The unit 31 causes the radiation detector 20 to finish measuring radiation (step S106).

[effect]
As described above, according to the mobile phone (radiation measurement apparatus) 1 of this embodiment, the measurement accuracy is not displayed as a relative error (percentage) but is displayed in a range of measured values or an absolute error. Therefore, even when the radiation dose is low, even if the measurement time is short and the statistical error is large, it can be seen at a glance that the range of the measured value is within the safe range, so that the user does not feel uneasy.

  Furthermore, in this embodiment, a statistical error reduction degree indicating how much the statistical error has been reduced as compared with a predetermined error limit according to the performance of the radiation sensor is graphically displayed. Therefore, since it becomes possible to know at a glance whether or not a more accurate measurement value can be obtained by extending the measurement time, the user can easily grasp the timing of the end of the measurement.

  Furthermore, if the range of the measured error or absolute error is displayed numerically, and the statistical error drop is displayed graphically, the measured value or absolute error range when the statistical error reaches the limit error is displayed. With this display, the user can grasp the performance limit of the sensor.

  The embodiment disclosed this time must be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  DESCRIPTION OF SYMBOLS 1 Cellular phone (radiation measurement apparatus), 2 CPU, 11 Input part, 12 Display part, 12A-12I Display area, 20 Radiation detector, 21 Radiation sensor, 22 Signal conversion part, 23 Counter, 30 Dose calculation part, 31 System Control unit, 40 signal processing unit.

Claims (5)

A radiation sensor that outputs a pulse when radiation is detected;
A signal processing unit that calculates a radiation dose and a statistical error based on the number of pulses output from the radiation sensor from the start of measurement of radiation to the current time;
A first display unit for displaying the radiation dose calculated by the signal processing unit;
A second display unit that displays a degree of reduction in statistical error indicating how much the statistical error calculated by the signal processing unit has been reduced compared to a predetermined error limit according to the performance of the radiation sensor. And a radiation measuring apparatus.   The radiation measurement apparatus according to claim 1, wherein the second display unit displays a graphic representing a degree of decrease in the statistical error.   3. The display device according to claim 1, further comprising a third display unit configured to display a lower limit value and an upper limit value of the radiation dose based on the radiation dose calculated by the signal processing unit and a statistical error as a range of measurement values at a current time. The radiation measuring apparatus described.   A third display unit for displaying the value representing the error limit as an absolute error and the value representing the statistical error calculated by the signal processing unit as an absolute error as a range of absolute errors at the current time; The radiation measuring apparatus according to claim 1.   The radiation measurement apparatus according to claim 3, wherein the first to third display units are display areas defined on a common display panel.

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