JP2013195193A - Portable electronic equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress an increase in detection errors of a radiation dose, which are caused by vibration.SOLUTION: In portable electronic equipment, a counter provided on a radiation detector 20 detects the number of pulses included in a signal from a radiation sensor. An evaluation value calculation part 32 detects displacement caused by vibration of own equipment, by an acceleration sensor 14, and calculates an evaluation value representing a degree of strength and the number of the vibration from the detected displacement. A radiation dose calculation part 31 calculates a final radiation dose by correcting a provisional radiation dose corresponding to the number of pulses detected by the counter, by the evaluation value.

Description

  The present invention relates to a portable electronic device equipped with a radiation sensor, and is suitably used for, for example, a mobile phone equipped with a radiation sensor or PDA (Personal Digital Assistants).

  In a portable electronic device equipped with a radiation sensor, erroneous detection of radiation due to vibration shock becomes a problem. For this reason, a mechanism for suppressing an increase in radiation detection error due to vibration shock is required.

  For example, a radiation measuring instrument disclosed in Japanese Patent Application Laid-Open No. 2007-285914 (Patent Document 1) includes a noise sensor that detects electromagnetic noise and an impact sensor that detects impact. The signal processing unit prevents erroneous detection due to noise by disabling the signal output from the radiation sensor when either the noise detection signal or the impact detection signal is valid.

JP 2007-285914 A

  One application of a portable electronic device equipped with a radiation sensor is an application as a personal dosimeter for knowing an individual's cumulative exposure dose. Since it is necessary to always wear a personal dosimeter, how to suppress radiation detection errors caused by vibration is an important issue.

  As a method for reducing detection error due to vibration, the output signal of the radiation sensor when vibration is detected is treated as invalid, as in the radiation measuring instrument described in Japanese Patent Application Laid-Open No. 2007-285914 (Patent Document 1). Can be considered. However, when a radiation detector is always worn as a personal dosimeter, vibrations occur intermittently. Therefore, it is difficult to detect the radiation amount by taking too much time in the method described in the above document. It is thought that it may become.

  The present invention has been made in consideration of the above problems, and an object thereof is to suppress an increase in radiation dose detection error caused by vibration in a portable electronic device equipped with a radiation sensor. .

  A portable electronic device according to an embodiment of the present invention includes a radiation sensor, an acceleration sensor, a counter, an evaluation value calculation unit, and a radiation dose calculation unit. The counter detects the number of pulses included in the signal from the radiation sensor. The evaluation value calculation unit detects a displacement due to the vibration of the own device using an acceleration sensor, and calculates an evaluation value representing the strength of the vibration and the degree of the number of vibrations from the detected displacement. The radiation dose calculation unit calculates a final radiation dose by correcting the provisional radiation dose corresponding to the number of pulses detected by the counter with the evaluation value.

  Preferably, the portable electronic device further includes a correction table storage unit that stores a table representing a correspondence relationship between the correction coefficient for correcting the provisional radiation dose and the evaluation value. In this case, the radiation dose calculation unit reads the correction coefficient corresponding to the evaluation value from the correction table storage unit, and corrects the provisional radiation dose with the read correction coefficient to calculate the final radiation dose.

  Preferably, the evaluation value calculation unit calculates the evaluation value by integrating the magnitude of displacement due to vibration of the own device.

  Preferably, the evaluation value calculation unit calculates the evaluation value by integrating the maximum value of the magnitude of displacement due to the vibration of the own device.

  Preferably, the evaluation value calculation unit evaluates by quantizing the maximum value of the displacement due to the vibration of the own device with a numerical value of N stages (N is an integer of 2 or more) and integrating the quantized maximum values. Calculate the value.

  Preferably, the counter detects the number of pulses for each detection period that is continuously repeated. The evaluation value calculation unit calculates an evaluation value for each detection period. The radiation dose calculation unit calculates a final radiation dose based on the number of pulses detected by the counter for each detection period and the evaluation value calculated by the evaluation value calculation unit.

  Preferably, the detection period is updated every time a predetermined time elapses. Alternatively, the detection period is updated every time the number of pulses detected by the counter reaches a predetermined value.

  Preferably, the portable electronic device is a portable terminal having a telephone function.

  According to the above-described embodiment, an increase in radiation dose detection error due to vibration can be suppressed.

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 hardware constitutions of the radiation detector 20 of FIG. 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 for demonstrating the calculation method of the evaluation value by the evaluation value calculation part 32 of FIG. 5 is a flowchart illustrating a procedure for calculating an evaluation value within a detection period DT in the example illustrated in FIG. 4. It is a figure which shows the specific example of the radiation dose calculation by the radiation dose calculation part 31 of FIG. It is a figure which shows an example of the correction table 33 of FIG. It is a flowchart which shows the procedure which measures a radiation with the mobile telephone 1 with a radiation detector of this Embodiment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following description, a mobile phone (mobile communication terminal) such as a smartphone provided with a radiation sensor will be described as an example. Since a mobile phone is often worn and used at all times, it is suitable for being easily used as a personal dosimeter by mounting a radiation sensor.

  However, the application target of the present invention is not limited to a mobile phone. A radiation sensor can be mounted on a PDA or the like not equipped with a communication function, and a device in which an acceleration sensor is mounted on a portable radiation measuring instrument is 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.

[Hardware configuration of mobile phone]
FIG. 1 is a block diagram illustrating an example of a hardware configuration of a mobile phone 1 according to an embodiment. The cellular phone 1 includes a central processing unit (CPU) 2, a random access memory (RAM) 3, a read only memory (ROM) 4, a memory 5, a communication device 6, an antenna 7, a microphone 8, a speaker 9, and audio. A signal processing circuit 10, a display unit 12, an input unit 11, an acceleration sensor 14, and a radiation detector 20 are included.

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

  The memory 5 is configured by an EEPROM (Electrically Erasable Programmable Read-Only Memory) such as a flash memory or a hard disk. The memory 5 stores data output from the CPU 2. Particularly in this embodiment, the memory 5 stores data based on the output signal of the acceleration sensor 14 and data based on the output signal of the radiation detector 20.

  The communication device 6 performs wireless communication of an audio signal and a data signal via the antenna 7 based on a command from 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 via the touch panel, only a small number of keys such as a power key and a volume key are provided as hardware keys, and keys for numbers and characters are not provided.

  The acceleration sensor 14 is a sensor that detects acceleration. For example, the acceleration sensor 14 has a weight supported by a beam structure, and detects and outputs the amount of displacement of the weight as a change in capacitance or piezoresistance. The displacement amount of the weight body is proportional to the acceleration acting on the acceleration sensor 14. Usually, a mobile phone such as a smartphone is provided with a triaxial acceleration sensor for detecting the attitude of the mobile phone.

  The output of the acceleration sensor 14 is obtained by adding displacement due to vibration and displacement due to gravitational acceleration. Since displacement due to gravity acceleration changes more slowly than displacement due to vibration, displacement due to gravity acceleration is eliminated by removing the average value of output within a predetermined period (equivalent to passing through a low-frequency cutoff filter). can do. As a result, the displacement amount due to the vibration of the mobile phone 1 can be detected by the acceleration sensor 14. For example, in the case of a three-axis acceleration sensor, displacements Δx, Δy, and Δz due to vibrations in three directions can be obtained.

[Configuration of radiation detector]
FIG. 2 is a block diagram showing a hardware configuration of the radiation detector 20 of FIG. Referring to FIG. 2, radiation detector 20 includes a radiation sensor 21, an analog front end 23, a noise canceller 24, a counter 25, and a memory 26 such as an EEPROM. In the case of FIG. 2, the analog front end 23, the noise canceller 24, and the counter 25 are configured as an ASIC (Application Specific Integrated Circuit), and operate in accordance with a control signal from the CPU 2 in FIG.

  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 analog front end 23 amplifies the pulse signal output from the radiation sensor 21. The noise canceller 24 performs AD conversion on the output of the analog front end 23 and then removes noise. The counter 25 counts the number of pulses of the pulse signal. The output of the counter is stored in the memory 26.

[Problems and solutions for radiation detectors]
The radiation detector 20 configured as described above is characterized by being easily affected by impacts and vibrations. For example, a pseudo pulse is generated when the stray capacitance of an amplifier provided in the analog front end 23 changes due to vibration. If this pseudo pulse is erroneously detected as a pulse by radiation, an error is caused in the measurement result of radiation.

  When the displacement due to the vibration of the own device is monitored by the acceleration sensor 14 as in the present embodiment, it can be detected to some extent whether or not a pseudo pulse is generated. However, the output signal of the acceleration sensor 14 and the output signal of the analog front end 23 are not necessarily proportional. In particular, when a pulse due to radiation and a pseudo pulse due to vibration overlap, it is difficult to separate them.

  To deal with such a problem, the output of the radiation sensor 21 is invalidated when the vibration of the own device is detected by the acceleration sensor 14 as described in Japanese Patent Application Laid-Open No. 2007-285914 (Patent Document 1). It is possible. However, when a mobile phone with a radiation detector is always worn as a personal dosimeter, vibrations occur intermittently. Therefore, in the method described in the above document, it takes too much time to detect radiation or the value of radiation dose. It may be difficult to obtain the product itself.

  As will be described in detail below, in this embodiment, even when vibration is intermittently generated by always wearing the mobile phone 1 with a radiation detector, data with as little error as possible can be obtained. Provide technology that can. Specifically, an evaluation value representing the intensity of vibration and the number of times of vibration within the detection period for detecting the radiation dose is calculated, and the evaluation value is used to detect the radiation detector 20 within the detection period. The radiation dose corresponding to the number of pulses is corrected.

[Calculation of evaluation value]
FIG. 3 is a block diagram showing a functional configuration of a part related to radiation measurement in the mobile phone 1 of FIG.

  1 and 3, the CPU 2 has functions as an evaluation value calculation unit 32 and a radiation dose calculation unit 31. These functions are realized when a program for radiation measurement is executed by the CPU 2.

  Based on the output signal of the acceleration sensor 14, the evaluation value calculation unit 32 calculates an evaluation value that represents the strength of vibration of the own device and the degree of vibration. In the case of the present embodiment, the evaluation value calculation unit 32 quantizes the maximum value of the displacement due to the vibration of the own device with a numerical value of N stages (N is an integer of 2 or more), and calculates the maximum value after quantization. The evaluation value is calculated by accumulating.

  Here, the magnitude of the displacement is given as an absolute value of the detected displacement amount in the case of a uniaxial acceleration line sensor. Since a positive displacement and a negative displacement are generated to the same extent in the displacement due to vibration, only the positive displacement may be taken out as a representative value to be the magnitude of the displacement. In the case of a triaxial acceleration sensor, if Δx, Δy, and Δz are obtained as displacements in three directions, the magnitude of the displacement is given as the square root of the sum of squares of Δx, Δy, and Δz. Alternatively, the maximum value of the absolute values of Δx, Δy, and Δz may be set as the magnitude of the displacement.

  FIG. 4 is a diagram for explaining a method of calculating an evaluation value by the evaluation value calculation unit 32 in FIG. For the sake of simplicity, FIG. 4 shows the change over time of the displacement due to the vibration detected by the uniaxial acceleration sensor. It is assumed that the displacement due to gravitational acceleration has been removed. The period from time t1 to time t2 is one detection period DT, and the evaluation value is calculated and the radiation dose is measured for each detection period that is continuously repeated.

  FIG. 5 is a flowchart showing a procedure for calculating an evaluation value within the detection period DT in the example shown in FIG. In the case of the examples shown in FIGS. 4 and 5, the maximum value of displacement is quantized with five-stage numerical values (0 to 4), and the evaluation value is calculated by integrating the quantized maximum values.

  First, the evaluation value calculation unit 32 in FIG. 3 initializes the evaluation value to 0 at the start of the detection period (step S101) (step S102).

  When the evaluation value calculation unit 32 detects a maximum point of displacement (step S103), the evaluation value calculation unit 32 quantizes the maximum value in four stages, and corrects the evaluation value based on the maximum value after quantization. Specifically, the evaluation value calculation unit 32 does not change the evaluation value when the maximum value is less than the reference value “1” (NO in step S104). When the maximum value is not less than “1” and less than “2” (NO in step S105), the evaluation value calculating unit 32 adds “1” to the evaluation value (step S108). When the maximum value is not less than “2” and less than “3” (NO in step S106), the evaluation value calculating unit 32 adds “2” to the evaluation value (step S109). When the maximum value is not less than “3” and less than “4” (NO in step S107), the evaluation value calculating unit 32 adds “3” to the evaluation value (step S110). When the maximum value is “4” or more (YES in step S107), the evaluation value calculation unit 32 adds “4” to the evaluation value (step S111).

  The evaluation value calculation unit 32 may quantize the maximum points in each interval sampled within the detection period DT for a certain period, and correct the evaluation values based on the quantized maximum points.

  The above steps are repeatedly executed until the detection period ends. When the detection period ends (YES in step S <b> 112), the evaluation value calculation unit 32 outputs the obtained evaluation value to the radiation dose calculation unit 31.

  As a simpler method than the above, the evaluation value may be calculated by quantizing the maximum value in two steps. That is, the evaluation value in this case is equal to the number of local maximum points that are equal to or greater than the reference value within the detection period. As a more precise method, an integrated value obtained by integrating the magnitude of displacement due to vibration within the detection period in a predetermined time step may be used as the evaluation value.

[About calculation of radiation dose]
Referring to FIG. 3 again, the radiation dose calculation unit 31 calculates a provisional radiation dose corresponding to the number of pulses output from the radiation detector 20. Since the pulse counted by the counter 25 in FIG. 2 includes a pseudo pulse caused by vibration in addition to a new pulse due to radiation, the provisional radiation dose includes a considerably large error. In order to reduce this error, the radiation dose calculation unit 31 corrects the provisional radiation dose based on the evaluation value calculated by the evaluation value calculation unit 32. The final radiation dose obtained by the correction is stored in the memory 5 (radiation dose storage unit 34).

  In order to correct the provisional radiation dose, a correction table 33 is stored in the memory 5 in advance. The correction table 33 represents the correspondence between the correction coefficient for correcting the provisional correction amount and the evaluation value. The radiation dose calculation unit 31 reads a correction coefficient corresponding to the evaluation value from the correction table 33, and calculates the final radiation dose by correcting the provisional correction amount with the read correction coefficient. The correction coefficient is experimentally determined so that the radiation dose after correction by the evaluation value is as equal as possible to the radiation dose detected when there is no vibration.

  It is difficult to accurately determine whether each pulse signal detected by the radiation detector 20 is due to vibration. However, within a certain detection period, it is considered that the total number of pseudo pulses caused by vibration correlates with an evaluation value representing the intensity and number of vibrations. Therefore, in the case of the present embodiment, the final radiation dose is calculated by correcting the provisional radiation dose using the evaluation value calculated for each detection period.

  FIG. 6 is a diagram illustrating a specific example of radiation dose calculation by the radiation dose calculation unit 31 in FIG. 3. In FIG. 6, each detection period is numbered starting from 1. For each detection period, the provisional radiation dose [μSv / h] corresponding to the number of pulses detected by the counter 25 in FIG. 2 and the evaluation value calculation in FIG. 3 are calculated. The evaluation value calculated by the unit 32 and the corrected radiation dose [μSv / h] are shown.

  FIG. 7 is a diagram illustrating an example of the correction table 33 of FIG. In the correction table 33 of FIG. 7, correction coefficients are defined corresponding to the ranges of evaluation values. The procedure for calculating the radiation dose will be specifically described below with reference to FIGS.

  In the detection period 1, the provisional radiation dose is 0.1 and the evaluation value is 26. The radiation dose calculation unit 31 determines a correction coefficient (0.8) corresponding to the evaluation value (26) based on the correction table shown in FIG. The radiation dose calculation unit 31 multiplies the provisional radiation dose (0.1) by the determined correction coefficient (0.8) to obtain 0.08 [μSv / h] as the final radiation dose.

  In the detection period 2, the provisional radiation dose is 0.3 and the evaluation value is 18. The radiation dose calculation unit 31 determines a correction coefficient (0.9) corresponding to the evaluation value (18) based on the correction table shown in FIG. The radiation dose calculation unit 31 multiplies the determined correction coefficient (0.9) by the provisional radiation dose (0.3) to obtain 0.27 [μSv / h] as the final radiation dose. Similarly, in the detection period 3 and after, the final radiation dose is determined from the provisional correction amount and the evaluation value.

[Radiation measurement procedure]
FIG. 8 is a flowchart showing a procedure for measuring radiation by the mobile phone 1 with the radiation detector of the present embodiment.

  The mobile phone 1 according to the present embodiment has a continuous measurement mode in which the radiation dose is continuously measured repeatedly as a radiation measurement mode and a fixed point measurement mode in which the radiation dose is measured only once. As described above, the continuous measurement mode is a mode that is selected when measuring radiation while correcting the influence of vibration on the premise of being carried by the user. The fixed point measurement mode is a mode that is selected when an accurate radiation dose is measured only once with the cellular phone 1 fixed. The measurement procedure of FIG. 8 is started when the continuous measurement mode is selected by the user (YES in step S201).

  When the continuous measurement mode is started, the CPU 2 in FIG. 1 turns on the acceleration sensor 14 and the radiation detector 20. In the case of a smartphone or the like, the acceleration sensor is often always on.

  The CPU 2 further initializes the counter 25 of FIG. 2 used for counting the number of pulses (sets the count number to 0) (step S204), and initializes the evaluation value indicating the degree of vibration to 0 (step S204). S205).

  The counter 25 after initialization counts the number of pulses based on the output signal of the radiation sensor 21 (step S206). The evaluation value calculation unit 32 (CPU 2) in FIG. 3 calculates an evaluation value representing the degree of vibration according to the output of the acceleration sensor 14. Specifically, in the case of FIGS. 4 and 5, an evaluation value is obtained by integrating the maximum values of the magnitude of displacement due to vibration. The counting of the number of pulses and the integration of the maximum value are repeatedly performed until a predetermined detection time has elapsed (YES in step S209).

  When a predetermined detection time elapses (that is, when the detection period ends), the radiation dose calculation unit 31 (CPU 2) in FIG. 3 calculates a provisional radiation dose corresponding to the count number of the counter 25 (step S209), and provisional The radiation dose is corrected by the calculated evaluation value (step S210). The corrected radiation dose is stored in the memory 5 in FIG. 1 (radiation dose storage unit 34 in FIG. 3) and displayed on the display unit 12.

  When the predetermined detection time has elapsed, the CPU 2 further initializes the counter 25 (step S206) and initializes the evaluation value to 0 (step S207), and starts radiation measurement in the next detection period. The radiation measurement is repeatedly performed until the user selects the end of the continuous measurement mode (YES in step S212).

[Modification]
In the radiation measurement procedure shown in FIG. 8, every time a predetermined measurement time elapses (YES in step S208), the counter 25 is reset and the evaluation value is initialized to zero. That is, the radiation detection period is updated each time a predetermined time (for example, 1 to 10 minutes) elapses.

  Alternatively, the radiation detection period may be updated each time the count number of the counter 25 reaches a predetermined value. When the radiation dose is relatively small, the measurement accuracy can be improved by measuring for a longer time, and when the radiation dose is relatively large, the measurement can be completed in a short time.

  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 Mobile phone, 2 CPU, 14 Acceleration sensor, 20 Radiation detector, 21 Radiation sensor, 31 Radiation dose calculation part, 32 Evaluation value calculation part, 33 Correction table.

Claims (9)

A radiation sensor;
An acceleration sensor;
A counter for detecting the number of pulses included in the signal from the radiation sensor;
An evaluation value calculation unit that detects displacement due to vibration of the own device by the acceleration sensor and calculates an evaluation value that represents the degree of vibration strength and the number of vibrations from the detected displacement;
A portable electronic device comprising: a radiation dose calculator that calculates a final radiation dose by correcting a provisional radiation dose corresponding to the number of pulses detected by the counter with the evaluation value. The portable electronic device further includes a correction table storage unit that stores a table representing a correspondence relationship between a correction coefficient for correcting the provisional radiation dose and the evaluation value,
The radiation dose calculation unit reads a correction coefficient corresponding to the evaluation value from the correction table storage unit, and calculates the final radiation dose by correcting the provisional radiation dose with the read correction coefficient. The portable electronic device described in 1.   The portable electronic device according to claim 1, wherein the evaluation value calculation unit calculates the evaluation value by integrating the magnitude of displacement due to vibration of the own device.   The portable electronic device according to claim 1, wherein the evaluation value calculation unit calculates the evaluation value by integrating a maximum value of the magnitude of displacement due to vibration of the own device.   The evaluation value calculation unit quantizes a maximum value of the magnitude of displacement due to vibration of the own device with a numerical value in N stages (N is an integer of 2 or more), and integrates the maximum value after quantization to obtain the evaluation value The portable electronic device according to claim 1, wherein the portable electronic device is calculated. The counter detects the number of pulses for each detection period that is continuously repeated,
The evaluation value calculation unit calculates the evaluation value for each detection period,
The radiation dose calculation unit calculates a final radiation dose based on the number of pulses detected by the counter for each detection period and the evaluation value calculated by the evaluation value calculation unit. 6. The portable electronic device according to any one of 5 above.   The portable electronic device according to claim 6, wherein the detection period is updated every time a predetermined time elapses.   The portable electronic device according to claim 6, wherein the detection period is updated every time the number of pulses detected by the counter reaches a predetermined value.   The portable electronic device according to claim 1, wherein the portable electronic device is a portable terminal having a telephone function.

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