dosimeter

Abstract

A dosimeter (1) comprises a radiation detection unit (2) a first amplification unit (3) a capacitor (11), an A / D converter, and a first comparator. The radiation detection unit (2) outputs a current signal of a magnitude corresponding to the intensity of an incident radiation pulse RP each time the radiation pulse RP is incident. The first amplification unit (3) converts the current signal into a voltage signal. The first amplification unit (3) includes a first amplifier (31) and a first reset switch (34). The first comparator is connected to the first amplification unit (3) via the capacitor (11), and outputs a first comparison result signal indicating the result of a comparison between the voltage signal and a first threshold. The A / D converter is connected to the first amplification unit (3) via the capacitor (11), and generates a digital signal indicating the magnitude of the voltage signal. The A / D converter starts a conversion operation on the basis of the first comparison result signal indicating that the voltage signal exceeds the first threshold.

Description

Dosimeter

[0001] This disclosure relates to a dosimeter. This application claims priority under Japanese application No. 2024-187684, filed on 24 October 2024, and incorporates all the provisions contained herein.

[0002] Patent Document 1 discloses a dosimeter. This dosimeter is a personal alarm dosimeter carried by workers working in radiation controlled areas to measure the radiation exposure of those workers, or an environmental dosimeter to measure the radiation level of the environment. This dosimeter measures radiation levels at regular intervals, stores the measurement data in its internal memory, and outputs the measurement data in response to external requests.

[0003] Japanese Patent Publication No. 2000-171561

[0004] In dosimeters, counting the number of incident radiation pulses is an effective method for measuring minute radiation doses. This method converts the incident radiation pulses into electrical signals and amplifies those signals. However, if electrical signals are generated at a high frequency, such as when approaching a radiation source, the amplification circuit may saturate, leading to the loss of some radiation pulses. This can result in problems such as a decrease in the measured value despite approaching a radiation source. In addition, dosimeters are required to reduce power consumption. Portable dosimeters, in particular, are often required to operate for long periods on batteries, making power consumption reduction desirable.

[0005] This disclosure aims to provide a dosimeter that can reduce the number of missed radiation pulses and lower power consumption.

[0006] [1] A dosimeter according to one aspect of the present disclosure comprises a radiation detection unit, a first amplification unit, a capacitor, a first comparator, an A / D converter, a signal recording unit, and a control circuit. The radiation detection unit outputs an electrical signal of a magnitude corresponding to the intensity of the incident radiation pulse each time a radiation pulse is incident. The first amplification unit is connected to the radiation detection unit and generates a voltage signal based on the electrical signal. The capacitor is connected to the first amplification unit. The first comparator is connected to the first amplification unit via the capacitor and outputs a first comparison result signal indicating the result of comparing the voltage signal with a first threshold. The A / D converter is connected to the first amplification unit via the capacitor and generates a digital signal indicating the magnitude of the voltage signal. The signal recording unit is connected to the A / D converter and records a plurality of digital signals, each of which is a digital signal and corresponds to a plurality of incident radiation pulses. The control circuit controls the reading of the plurality of digital signals from the signal recording unit. The first amplification unit includes a first amplifier and a first reset switch, which are connected in series with the radiation detection unit and in parallel with each other. The A / D converter starts the conversion operation based on the first comparison result signal indicating that the voltage signal has exceeded a first threshold. When the number of multiple digital signals recorded in the signal recording unit reaches a predetermined number, the control circuit reads out at least two of the multiple digital signals from the signal recording unit together.

[0007] In the dosimeter described in [1] above, a first reset switch is provided in the first amplifier. By periodically turning on the first reset switch (connected state), saturation of the first amplifier is avoided. Therefore, even if an electrical signal is output from the radiation detection unit at a high frequency, for example, due to approaching a radiation source, saturation of the first amplifier is suppressed, and the number of missed radiation pulses can be reduced. In addition, in the dosimeter described in [1] above, the A / D converter starts its conversion operation based on the first comparison result signal indicating that the voltage signal has exceeded a first threshold. In this way, by having the A / D converter perform the conversion operation only when a radiation pulse of a countable magnitude is incident, power consumption can be reduced compared to when the A / D converter always performs the conversion operation. In addition, in the dosimeter described in [1] above, the control circuit reads out at least two digital signals from the signal recording unit together when the number of multiple digital signals recorded in the signal recording unit reaches a predetermined number. Instead of acquiring a digital signal each time a digital signal is output from the A / D converter, power consumption can be further reduced by recording multiple digital signals in the signal recording unit and reading out at least two digital signals from the signal recording unit together. In addition, in the dosimeter described in [1] above, a capacitance is provided between the first amplifier and the first comparator. This capacitance functions as a coupling capacitor. That is, even if an offset voltage caused by dark current or the like is superimposed on the voltage signal, the offset voltage can be removed from the voltage signal, reducing fluctuations in the level of the voltage signal input to the A / D converter and the first comparator. Therefore, measurement accuracy can be improved.

[0008] [2] In the dosimeter described in [1] above, the first reset switch may be turned ON in conjunction with the completion of the output of the digital signal in the A / D converter. By resetting the first amplifier by turning ON in conjunction with the timing when the operation of the A / D converter is completed, the saturation of the first amplifier can be suppressed more reliably, and the number of radiation pulses that are missed can be further reduced.

[0009] [3] In the dosimeter described in [1] or [2] above, the first amplification unit may further include a first resistor connected in series with the radiation detection unit and in parallel with the first amplifier and the first reset switch. In this case, saturation of the first amplifier can be suppressed between the time the first reset switch is turned off and when it is turned on.

[0010] [4] The dosimeters described in [1] to [3] above may further include a second comparator connected to a node between the first amplifier and the capacitor, which outputs a second comparison result signal indicating the result of comparing the voltage signal with a second threshold. In this case, the saturation state of the first amplifier can be detected based on the second comparison result signal.

[0011] [5] The dosimeters described in [1] to [4] above may further include a second amplification unit. The second amplification unit may be connected between the capacitor and both the first comparator and the A / D converter, and may amplify the voltage signal. In this case, the voltage signal can be further amplified. Therefore, the need to reduce the voltage resolution of the A / D converter can be reduced. In addition, the number of bits required for the D / A converter used to correct the first threshold in the first comparator can be reduced, making it easier to adjust the first threshold.

[0012] [6] In the dosimeter described in [5] above, the second amplification section may include a second amplifier and a second reset switch. The second amplifier and the second reset switch may be connected in series with the capacitor and both the first comparator and the A / D converter, and may also be connected in parallel with each other. When the first reset switch switches from the ON state to the OFF state, the voltage signal output from the first amplification section fluctuates. If the second reset switch is not provided, the fluctuation of the voltage signal is further amplified by the second amplification section. Therefore, the period (dead time) during which radiation pulses cannot be measured immediately after the first reset switch is switched becomes longer. To address this problem, by providing a second reset switch in parallel with the second amplifier and turning the second reset switch ON when the first reset switch is switched, it is possible to prevent further amplification of the voltage signal fluctuation and reduce the fluctuation of the voltage signal transmitted to the first comparator. Therefore, the dead time can be shortened.

[0013] [7] In the dosimeter described in [6] above, the second amplifier may further include a second resistor. The second resistor may be connected in series with the capacitor and both the first comparator and the A / D converter, and in parallel with the second amplifier and the second reset switch. In this case, fluctuations in the voltage signal that occur when switching the second reset switch from the ON state to the OFF state can be reduced.

[0014] [8] In the dosimeter described in [6] or [7] above, the second reset switch may be turned off after the first reset switch has been turned off. In this case, the fluctuation of the voltage signal is prevented from being further amplified by the second amplification unit, and the fluctuation of the voltage signal transmitted to the first comparator can be reduced. Therefore, the dead time can be shortened.

[0015] [9] The dosimeters described in [1] to [8] above may further include a buffer amplifier connected between the capacitance and the A / D converter. Normally, the input capacitance of the A / D converter is large, so when the A / D converter is driven directly, the current consumption must be increased in order to speed up settling. In contrast, by providing a buffer amplifier in front of the A / D converter, settling can be accelerated while suppressing an increase in power consumption. The buffer amplifier may be configured to be switchable between an operating state and a non-operating state. The buffer amplifier may be activated based on the first comparison result signal indicating that the voltage signal has exceeded a first threshold. In this case, the buffer amplifier operates only when a radiation pulse of a countable magnitude is incident, so power consumption can be reduced compared to when the buffer amplifier is always operating.

[0016]

[10] The dosimeters described in [1] to [9] above may further include a sample-and-hold circuit connected between the capacitor and the A / D converter. The sample-and-hold circuit may hold the voltage signal at a predetermined time after a first comparison result signal indicates that the voltage signal has exceeded a first threshold. At the time when the voltage signal exceeds the first threshold, the voltage value of the voltage signal is often still rising and has not yet reached its peak. As described in

[10] above, by holding the voltage signal at a predetermined time after a predetermined time has elapsed after the first comparison result signal indicates that the voltage signal has exceeded the first threshold, the voltage value of the voltage signal that is at its peak (or close to its peak) can be input to the A / D converter.

[0017]

[11] In the dosimeters described in [1] to

[10] above, the control circuit may read at least two digital signals from the signal recording unit when it determines that the A / D converter has generated a predetermined number of digital signals. In this case, the reading operation only needs to be performed when the digital signals have been generated a predetermined number of times, thus reducing the power consumption of the control circuit.

[0018]

[12] In the dosimeter described in

[11] above, the control circuit may read out the digital signal from the signal recording unit at predetermined intervals. In this case, the measurement results can be read out periodically even if the incidence of radiation pulses of a countable magnitude is low.

[0019]

[13] The dosimeters described in [1] to

[12] above may further include a gain amplifier. The gain amplifier may be connected between the capacitor and both the first comparator and the A / D converter to amplify the voltage signal. In this case, the need to reduce the voltage resolution of the A / D converter can be reduced. In addition, the number of bits required for the D / A converter used to correct the first threshold in the first comparator can be reduced, making it easier to adjust the first threshold.

[0020]

[14] The dosimeters described in [1] to

[13] above may further include a bandpass filter connected between the capacitor and the first comparator. In this case, the noise contained in the voltage signal is reduced by the bandpass filter. The first comparator compares the voltage signal containing noise with the first threshold, so if the noise contained in the voltage signal is large, the first threshold needs to be increased by the amount of noise. According to the dosimeter described in

[14] above, the noise is reduced by the bandpass filter, so the first threshold can be made smaller, and the voltage signal value required for the A / D converter to start its conversion operation can be made smaller.

[0021]

[15] In the dosimeters described in [1] to

[14] above, the A / D converter may be a successive approximation type. Successive approximation type A / D converters consume less power during conversion compared to other types, such as flash type, pipeline type, or delta-sigma type. In addition, since successive approximation type A / D converters are mainly composed of digital circuits, their power consumption in standby mode (when conversion is possible) is extremely low. Therefore, the power consumption of the dosimeter can be further reduced.

[0022]

[16] In the dosimeters described in [1] to

[15] above, the control circuit may calculate the radiation dose value based on the at least two digital signals read out together from the signal recording unit. If the radiation dose value is calculated each time a digital signal is read out, the power supply of the large integrated circuit that performs the calculation must be turned on each time, which increases power consumption. By calculating the radiation dose value based on at least two digital signals, power consumption can be reduced.

[0023] The dosimeter described in this disclosure can provide a dosimeter that reduces the number of missed radiation pulses and also reduces power consumption.

[0024] Figure 1 is a circuit diagram showing a part of the configuration of a dosimeter according to one embodiment of the present disclosure. Figure 2 is a circuit diagram showing the remaining configuration of the dosimeter. Figure 3 is a timing chart showing the operation of the internal signals of the dosimeter. Figure 4 is a timing chart when radiation pulses are incident at a high frequency within one cycle. Figure 5 is a graph for explaining paralysis-type operation. Figure 6 is a timing chart showing the effect of capacitance. Figure 7 is a timing chart showing the effect of the first resistor. Figure 8 is a timing chart for explaining the effect of the operation of the control circuit. Figure 9 is a timing chart for explaining the effect of the operation of the first reset switch and the second reset switch. Figure 10 is a timing chart for explaining the effect obtained by the operation of the buffer amplifier.

[0025] Specific examples of the present disclosure will be described below with reference to the drawings. The present invention is not limited to these examples, but is intended to be included in the claims, and all modifications within the meaning and scope of the claims are intended to be included. In the following description, the same elements in the description of the drawings are denoted by the same reference numerals, and redundant descriptions are omitted.

[0026] Figure 1 is a circuit diagram showing a part of the configuration of a dosimeter 1 according to one embodiment of the present disclosure. Figure 2 is a circuit diagram showing the remaining configuration of the dosimeter 1. As shown in these figures, the dosimeter 1 of this embodiment comprises a radiation detection unit 2, a first amplification unit 3, a second amplification unit 4, a sample-and-hold circuit 5, and a control circuit 6. The dosimeter 1 further comprises a capacitor 11, a gain amplifier 12, a buffer amplifier 13, an A / D converter 14, a delay circuit 15, a bandpass filter 16, a first comparator 17, a signal recording unit 18, a second comparator 19, and a switch 71.

[0027] The radiation detection unit 2 generates a pulsed current signal J of a magnitude corresponding to the intensity of the incident radiation pulse RP. ＰＤAn electrical signal is output each time a radiation pulse RP is incident. The radiation detection unit 2 includes, for example, a photodiode. The photodiode is sensitive to radiation such as X-rays, gamma rays, or beta rays. The figure shows an equivalent circuit of the photodiode, and the radiation detection unit 2 includes a photodiode 21, a parasitic capacitance 22 of the photodiode, and an internal resistance 23 of the photodiode. The radiation detection unit 2 has a bias voltage V ＢＩＡＳ A light is applied. The photodiode may be sensitive to light with a wavelength longer than that of radiation. In that case, a scintillator is provided on the photodiode, and light converted from radiation by the scintillator is incident on the photodiode.

[0028] The first amplification unit 3 is connected to the output side of the radiation detection unit 2 and receives a current signal J from the radiation detection unit 2. ＰＤ The input is the current signal J. The first amplification unit 3 receives the current signal J. ＰＤ Convert current to voltage to obtain a voltage signal V ＯＵＴ１ Generates a voltage signal V ＯＵＴ１ The first amplifier 3 is, for example, a transimpedance amplifier (TIA). The first amplifier 3 is connected in series with the radiation detection unit 2. In the illustrated example, the first amplifier 3 includes a first amplifier 31, a first capacitor 32, a first resistor 33, and a first reset switch 34. The first amplifier 31, the first capacitor 32, the first resistor 33, and the first reset switch 34 are connected in parallel with each other. The first amplifier 31 is, for example, an operational amplifier. The first reset switch 34 is, for example, a transistor. The on / off state of the first reset switch 34 is controlled by a first reset signal S from the control circuit 6. ＲＥＳＥＴ１ It is controlled by [something].

[0029] Capacitor 11 is connected to the output side of the first amplifier 3. Capacitor 11 is a coupling capacitor and controls the voltage signal V ＯＵＴ１ It blocks the DC component and allows the AC component to pass through.

[0030] The second amplifier 4 is connected between the capacitor 11 and both the first comparator 17 and the A / D converter 14. The second amplifier 4 is connected to the output side of the first amplifier 3 via the capacitor 11, and receives a voltage signal V from the first amplifier 3.ＯＵＴ１ is input. The second amplification unit 4 amplifies the voltage signal V ＯＵＴ１ to generate a voltage signal V ＯＵＴ２ and outputs the voltage signal V ＯＵＴ２ . The second amplification unit 4 is, for example, a TIA. The second amplification unit 4 is connected in series with the first amplification unit 3. In the illustrated example, the second amplification unit 4 includes a second amplifier 41, a second capacitor 42, a second resistor 43, and a second reset switch 44. The second amplifier 41, the second capacitor 42, the second resistor 43, and the second reset switch 44 are connected in parallel with each other. The second amplifier 41 is, for example, an operational amplifier. The second reset switch 44 is, for example, a transistor. The on / off of the second reset switch 44 is controlled by a second reset signal S ＲＥＳＥＴ２ from the control circuit 6.

[0031] The gain amplifier 12 is connected between the first comparator 17 and the capacitor 11. In the illustrated example, the gain amplifier 12 is connected to the output side of the second amplification unit 4 and receives the voltage signal V ＯＵＴ２ from the second amplification unit 4. The gain amplifier 12 amplifies the voltage signal V ＯＵＴ２ to generate a voltage signal V ＯＵＴ３ and outputs the voltage signal V ＯＵＴ３ .

[0032] The sample and hold circuit 5 is connected between the capacitor 11 and the A / D converter 14. In the illustrated example, the sample and hold circuit 5 is connected to the output side of the gain amplifier 12 and receives the voltage signal V ＯＵＴ３ from the gain amplifier 12. The sample and hold circuit 5 has a switch 51 and a capacitor 52. The switch 51 is connected in series with the capacitor 11 and the gain amplifier 12. The on / off of the switch 51 is controlled by a control signal S ＤＥＬＡＹ from the delay circuit 15. The delay circuit 15 generates the control signal S ＤＥＬＡＹ by delaying the control signal from the control circuit 6 by a predetermined time. The capacitor 52 is connected in series between the end of the switch 51 on the side opposite to the capacitor 11 and the gain amplifier 12 and the reference potential line. When the switch 51 is in the on state, the charge due to the voltage signal V ＯＵＴ３ is stored in the capacitor 52, and the voltage across both ends of the capacitor 52 becomes the voltage signal VＯＵＴ３ This matches. Subsequently, when switch 51 is turned off, the voltage signal V at the time switch 51 was turned off is obtained. ＯＵＴ３ The voltage value of the voltage signal V Ｓ／Ｈ It is held by a capacity of 52.

[0033] The buffer amplifier 13 is connected between the capacitor 11 and the A / D converter 14. In the illustrated example, the buffer amplifier 13 is connected to the output side of the sample-and-hold circuit 5, and receives a voltage signal V from the sample-and-hold circuit 5. Ｓ／Ｈ The input is sent to the A / D converter 14 as a voltage signal V Ｓ／Ｈ (Voltage signal V) ＢＵＦ ) outputs. Normally, the input capacitance of the A / D converter 14 is large, so when the A / D converter 14 is driven directly, the current consumption needs to be increased in order to speed up settling. In contrast, by providing a buffer amplifier 13 in front of the A / D converter 14, the input capacitance of the A / D converter 14 is charged in a short time, and settling can be sped up (i.e., the operation of the A / D converter 14 is accelerated) while suppressing an increase in power consumption. The buffer amplifier 13 has control terminals for switching between an operating state and a non-operating state. The control terminals are connected to a reference potential line via a switch 71. When the switch 71 is in either the ON state or the OFF state, the buffer amplifier 13 is in the operating state. When the switch 71 is in either the ON state or the OFF state, the buffer amplifier 13 is in the non-operating state. The ON / OFF of the switch 71 is controlled by a switch control signal S from the control circuit 6. ＳＷ２ It is controlled by [something].

[0034] The A / D converter 14 is connected to the first amplifier 3 via the capacitor 11. In the illustrated example, the A / D converter 14 is connected to the output side of the buffer amplifier 13. The A / D converter 14 receives a voltage signal V from the buffer amplifier 13. Ｓ／Ｈ Input a voltage signal V Ｓ／Ｈ Performs analog / digital conversion and outputs a voltage signal V Ｓ／Ｈ A digital signal D indicating the magnitude is generated. The start and end of the conversion operation of the A / D converter 14 are controlled by a control signal S from the control circuit 6. ＣＮＶIt is controlled by the control signal S. The A / D converter 14 in this embodiment is a successive approximation register (SAR) type. The successive approximation A / D converter 14 always maintains a convertible state (standby state) and is controlled by the control signal S. ＣＮＶ A / D conversion starts immediately after input.

[0035] The first comparator 17 is connected to the first amplifier 3 via the capacitor 11. The bandpass filter 16 is connected between the capacitor 11 and the first comparator 17. In the illustrated example, the first comparator 17 is connected to node N2 between the gain amplifier 12 and the sample-and-hold circuit 5 via the bandpass filter 16. The bandpass filter 16 receives a voltage signal V ＯＵＴ３ The first comparator 17 removes the high-frequency and low-frequency components of the signal V from the gain amplifier 12 via the bandpass filter 16. ＯＵＴ３ The first comparator 17 receives the voltage signal V. ＯＵＴ３ and the first threshold V ＲＥＦ１ First comparison result signal S, which shows the comparison result with [the other signal]. ＣＭＰ１ It outputs the following. The first comparator 17 is, for example, an LLD (Lower Limit Discriminator).

[0036] The signal recording unit 18 is connected to the A / D converter 14 via the control circuit 6. The signal recording unit 18 records multiple digital signals D corresponding to multiple incidents of radiation pulse RP. If multiple radiation pulses RP are incident in a short period of time and the waveforms of multiple pulses overlap, a single voltage signal V is recorded for those multiple radiation pulses RP. Ｓ／Ｈ Sometimes, all of these signals are held by the capacity 52, and only one digital signal D is generated. This phenomenon is called pile-up. Such a digital signal D is included among the multiple digital signals D that the signal recording unit 18 records, each corresponding to multiple incidents of the radiation pulse RP. The signal recording unit 18 is either a volatile memory or a non-volatile memory. Alternatively, the signal recording unit 18 may be a data recording device such as a hard disk.

[0037] The control circuit 6 includes a digital circuit section 61 and a large-scale integrated circuit section 62. The digital circuit section 61 receives the first reset signal S mentioned above. ＲＥＳＥＴ１ , second reset signal S ＲＥＳＥＴ２ , control signal to delay circuit 15, switch control signal S ＳＷ２ , and control signal S ＣＮＶ The digital circuit unit 61 receives the aforementioned digital signal D from the A / D converter 14 and the aforementioned first comparison result signal S ＣＭＰ１ The first comparator 17 inputs this signal. The control circuit 6 receives the first comparison result signal S. ＣＭＰ１ Based on this, the A / D converter 14 receives a digital signal D and records the digital signal D in the signal recording unit 18. The control circuit 6 receives the first comparison result signal S ＣＭＰ１ Based on this, a control signal to the delay circuit 15 and a switch control signal S are issued. ＳＷ２ , and control signal S ＣＮＶ Generates.

[0038] The large-scale integrated circuit unit 62 is, for example, an MPU (Micro Processor Unit), an MCU (Micro Controller Unit), or an FPGA (Field Programmable Gate Array). The large-scale integrated circuit unit 62 receives control signals S from the signal recording unit 18. ＲＥＡＤ The system outputs a signal and reads the digital signal D from the signal recording unit 18. At this time, the large-scale integrated circuit unit 62 reads at least two digital signals D from the signal recording unit 18 together, performs a predetermined calculation based on the at least two digital signals D, and calculates a radiation dose value. In this embodiment, a predetermined calculation is performed based on at least two digital signals D to calculate a single radiation dose value. In other words, the radiation dose value can be said to be the radiation dose value accumulated over a certain period of time. A timestamp is assigned to each calculated radiation dose value, and the time of measurement is associated with each radiation dose value. With this configuration, a history (time-series data) of radiation dose values ​​can be easily created.

[0039] The large-scale integrated circuit unit 62 outputs the calculated radiation dose value data Dout to the display device of the dosimeter 1, or transmits it to an external device via wireless communication or the like. The dosimeter 1 has a recording unit (external memory) separate from the signal recording unit 18, and the data Dout related to the radiation dose value calculated by the large-scale integrated circuit unit 62 is output to the separate recording unit. The separate recording unit outputs, for example, data Dout related to multiple radiation dose values ​​to an external device (server, etc.) via wireless communication or the like every other day. Based on the data Dout related to multiple radiation dose values ​​recorded in the separate recording unit, the dose value accumulated over a certain period may be displayed on the display device of the dosimeter 1. The large-scale integrated circuit unit 62 may output at least two digital signals D in place of, or together with, the data Dout.

[0040] The timing at which the large-scale integrated circuit unit 62 reads the digital signal D from the signal recording unit 18 is determined by the control signal S from the digital circuit unit 61. ＦＬＡＧ It is controlled by the following. The digital circuit unit 61 determines whether the generation of the digital signal D has been performed a predetermined number of times in the A / D converter 14, and when the number of digital signals D recorded in the signal recording unit 18 reaches a predetermined number, it issues a control signal S ＦＬＡＧ The large-scale integrated circuit unit 62 outputs the control signal S. ＦＬＡＧ Each time it receives a signal, it reads out the digital signal D. In addition, the large-scale integrated circuit unit 62 reads out the digital signal D from the signal recording unit 18 at predetermined intervals, regardless of whether or not the A / D converter 14 has generated the digital signal D. The digital circuit unit 61 reads out the control signal S at predetermined intervals. ＦＬＡＧThe output may be a predetermined period of two cycles or more. For example, the predetermined number of times the digital signal D is generated is set to five, and the predetermined period is set to ten minutes. In this case, if the digital signal D is generated five times in less than ten minutes, the large-scale integrated circuit unit 62 reads out five digital signals D at the time of the fifth generation. If only one digital signal D has been generated after ten minutes have elapsed, the large-scale integrated circuit unit 62 reads out one digital signal D at that time. Even if no digital signals D have been generated at all after ten minutes have elapsed, the large-scale integrated circuit unit 62 performs a digital signal D readout operation at that time.

[0041] In the above description, at least two digital signals D are read together from the signal recording unit 18 to the large-scale integrated circuit unit 62, but the configuration is not limited to this. For example, at least two digital signals D may be read together from the signal recording unit 18 to the control circuit (large-scale integrated circuit, etc.) of the dosimeter 1, which is located outside the housing of the dosimeter 1, and the at least two digital signals D may be output together outside the housing.

[0042] The second comparator 19 (see Figure 1) is connected to node N1 between the first amplifier 3 and the capacitor 11. The second comparator 19 processes the voltage signal V ＯＵＴ１ and the second threshold V ＲＥＦ２ The second comparison result signal S shows the comparison result with the previous one. ＣＭＰ２ The second comparator 19 outputs the control signal S. ＡＣＴ It operates in response to this. The second comparator 19 is, for example, an LLD.

[0043] Figure 3 is a timing chart showing the operation of the internal signals of the dosimeter 1. Figure 3 shows the timing chart for one cycle. The dosimeter 1 repeats the operation shown in Figure 3 over multiple cycles. In Figure 3, from top to bottom, are the first reset signal S ＲＥＳＥＴ１ , second reset signal S ＲＥＳＥＴ２ , current signal J ＰＤ Voltage signal V ＯＵＴ３ , first comparison result signal S ＣＭＰ１ Control signal S ＤＥＬＡＹ Voltage signal V Ｓ／Ｈ, and control signal S ＣＮＶ This is shown.

[0044] When a cycle begins, the digital circuit section 61 first receives the first reset signal S ＲＥＳＥＴ１ and the second reset signal S ＲＥＳＥＴ２ The first reset switch 34 and the second reset switch 44 are turned ON (timing T1 in the figure). This turns ON the first reset switch 34 and the second reset switch 44. In other words, the input terminal and the output terminal of the first amplifier 3 and the second amplifier 4 are short-circuited to each other, and the first amplifier 31 and the first capacitor 32, and the second amplifier 41 and the second capacitor 42 are reset.

[0045] Next, at a predetermined time, the digital circuit unit 61 receives the first reset signal S ＲＥＳＥＴ１ The first reset switch 34 is turned off (timing T2 in the figure). As a result, the first reset switch 34 is turned off, and the first amplifier unit 3 starts the current-voltage conversion operation. After a predetermined time interval, the digital circuit unit 61 receives the second reset signal S ＲＥＳＥＴ２ The second reset switch 44 is turned off (timing T3 in the diagram). As a result, the second amplifier unit 4 starts its amplification operation.

[0046] Next, at timing T4, which is after timing T3, a radiation pulse RP is incident, and a pulsed current signal J is generated from the radiation detection unit 2. ＰＤ Assume that the following is output. At this time, the pulsed voltage signal V is generated by the continuous operation of the first amplification unit 3, the second amplification unit 4, and the gain amplifier 12. ＯＵＴ３ A voltage signal V is generated. ＯＵＴ３ The voltage value is the first threshold V ＲＥＦ１ At a timing T5 exceeding this, the first comparison result signal S ＣＭＰ１ However, the voltage signal V ＯＵＴ３ The voltage value is the first threshold V ＲＥＦ１ The value changes to one that indicates it has exceeded the limit. The digital circuit section 61 receives the first comparison result signal S ＣＭＰ１ In response to the change, a control signal is output to control the on / off state of switch 51. This control signal is delayed by a predetermined time by the delay circuit 15, and the control signal S ＤＥＬＡＹto control the switch 51 (timing T6 in the figure). As a result, after a predetermined time has elapsed since the first comparison result signal S ＯＵＴ３ indicates that the voltage signal V ＲＥＦ１ has exceeded the first threshold value V ＣＭＰ１ , the sample hold circuit 5 holds the voltage signal V ＯＵＴ３ . Then, a constant voltage is output from the sample hold circuit 5 as the voltage signal V Ｓ／Ｈ . In response to the change in the first comparison result signal S ＣＭＰ１ , the digital circuit section 61 outputs a switch control signal S ＳＷ２ and activates the buffer amplifier 13.

[0047] Next, at timing T7 after a predetermined time has elapsed since the change in the first comparison result signal S ＣＭＰ１ , the digital circuit section 61 outputs a control signal S ＣＮＶ to start the conversion operation of the A / D converter 14. That is, the A / D converter 14 starts the conversion operation based on the fact that the first comparison result signal S ＯＵＴ３ indicates that the voltage signal V ＲＥＦ１ has exceeded the first threshold value V ＣＭＰ１ . Then, when the output of the digital signal D in the A / D converter 14 is completed, the digital circuit section 61 terminates the conversion operation of the A / D converter 14 in accordance with the completion, deactivates the buffer amplifier 13, and turns on the first reset signal S ＲＥＳＥＴ１ and the second reset signal S ＲＥＳＥＴ２ (timing T8 in the figure). As a result, the first reset switch 34 and the second reset switch 44 are turned on in accordance with the completion of the output of the digital signal D in the A / D converter 14. Thereafter, the next cycle starts.

[0048] The effects obtained by the dosimeter 1 according to the present embodiment described above will be described. FIG. 4 is a timing chart when radiation pulses RP are incident at a high frequency within one cycle. The broken line in the figure shows, as a comparative example, the case where the first amplifier section 3 does not have the first reset switch 34. In this comparative example, the current signal J ＰＤSince this is input to the first amplification unit 3, the first amplifier 31 and the first capacitor 32 become saturated, and the voltage signal V ＯＵＴ１ The voltage signal V remains fixed at a low voltage value (when the first amplifier 3 is an inverting amplifier type; when the first amplifier 3 is a non-inverting amplifier type, it is a high voltage value). Therefore, even when a radiation pulse RP is incident, the voltage signal V ＯＵＴ３ The voltage value remains constant, resulting in counting errors of the radiation pulse RP. This type of operation is called "paralytic operation." Figure 5 is a graph illustrating paralytic operation. In Figure 5, the horizontal axis represents the true counting rate, and the vertical axis represents the observed counting rate, which is the actual counting rate. Ideally, as shown by the straight line G1 in Figure 5, it is desirable for the observed counting rate to be proportional to the true counting rate. However, in reality, as the true counting rate increases, the counting errors of the radiation pulse RP increase, and the growth of the observed counting rate slows down. Nevertheless, if the observed counting rate continues to increase monotonically with respect to the true counting rate, as shown by the curve G2 in Figure 5, measurement is still possible. This state is called "non-paralytic operation." In contrast, in paralytic operation, as shown by the curve G3 in Figure 5, when the true counting rate exceeds a certain value, the observed counting rate decreases as the true counting rate increases. In this state, the measurable incidence frequency of radiation pulse RP is severely limited.

[0049] To address this "paralysis-type operation" problem, in this embodiment, a first reset switch 34 is provided in the first amplification unit 3. As shown by the solid line in the figure, the first reset switch 34 is turned ON (connected) at some point during each cycle, thereby preventing the first amplifier 31 from becoming saturated. Therefore, for example, when approaching a radiation source, the radiation detection unit 2 frequently receives a current signal J ＰＤ Even if a signal is output, the saturation of the first amplifier 31 is suppressed, and the counting loss of radiation pulses RP can be reduced. Therefore, the dosimeter 1 can be operated in "non-paralytic mode" by avoiding the "paralytic mode" described above.

[0050] In the dosimeter 1 of the present embodiment, a capacitor 11, which is a coupling capacitor, is provided between the first amplifier section 3 and the node N2. FIG. 6 is a timing chart showing the effect of the capacitor 11. The broken line in the figure shows, as a comparative example, the case where the capacitor 11 is not provided. In this comparative example, due to the offset current (dark current, etc.) included in the current signal J ＰＤ the steady voltage value of the voltage signal V ＯＵＴ３ does not stabilize and fluctuates. As a result, the offset level of the A / D converter 14 fluctuates, and the measurement accuracy decreases. On the other hand, as in the present embodiment, by providing the capacitor 11 between the first amplifier section 3 and the node N2, even when the current signal J ＰＤ includes an offset current (dark current, etc.), the fluctuation of the steady voltage value of the voltage signal V ＯＵＴ３ can be suppressed, and the measurement accuracy can be improved. More specifically, even if the offset current included in the current signal J ＰＤ fluctuates, the fluctuation of the level of the voltage signal V ＯＵＴ３ as shown by the broken line in FIG. 6 can be suppressed, and the level of the voltage signal V ＯＵＴ３ shown by the solid line in FIG. 6 can be maintained. When the capacitor 11 is arranged between the first amplifier section 3 and the radiation detection section 2, even if the first amplifier section 3 is provided with the first reset switch 34, the radiation detection section 2 may enter a saturated state, and the dead time may increase. By arranging the capacitor 11 between the first amplifier section 3 and the first comparator 17 as in the present embodiment, an increase in the dead time can be prevented.

[0051] In the dosimeter 1 of the present embodiment, the first amplifier section 3 includes a first resistor 33 connected in parallel with the first amplifier 31. FIG. 7 is a timing chart showing the effect of the first resistor 33. The broken line in the figure shows, as a comparative example, the case where the first resistor 33 is not provided. In this comparative example, immediately after the first reset switch 34 is turned off, the first amplifier 31 gradually approaches a saturated state and finally saturates (timing T9 in the figure). And after this timing T9, the voltage signal V ＯＵＴ１ is based on the current signal J ＰＤ until the first reset switch 34 is turned on again.It does not react to changes in the A / D converter 14. Therefore, this leads to an increase in the output error and dead time of the A / D converter 14. To address this problem, in this embodiment, the first amplification unit 3 includes a first resistor 33 connected in parallel with the first amplifier 31. This suppresses the saturation of the first amplifier 31 between the time the first reset switch 34 is turned off and when it is turned on, as shown by the solid line in the figure. Therefore, the increase in the output error and dead time of the A / D converter 14 can be suppressed, and the measurement accuracy can be improved.

[0052] In the dosimeter 1 of this embodiment, when the number of digital signals D recorded in the signal recording unit 18 reaches a predetermined number, the control circuit 6 reads out at least two digital signals D from the signal recording unit 18 together. Figure 8 is a timing chart to explain the effect of this operation of the control circuit 6. Unlike the figures described above, Figure 8 shows a timing chart for four cycles. As shown in Figure 8, in the dosimeter 1, when a radiation pulse RP is incident, a pulsed current signal J is generated. ＰＤ Each time this occurs, the control circuit 6 controls the signal S ＣＮＶ The A / D converter 14 generates a digital signal D. The dashed line in the figure shows a comparative example in which the large-scale integrated circuit unit 62 acquires the digital signal D from the A / D converter 14 each time the A / D converter 14 generates the digital signal D. In this comparative example, since it is unknown when the digital signal D will be generated in the A / D converter 14, the large-scale integrated circuit unit 62 must be constantly operating, which increases the power consumption of the large-scale integrated circuit unit 62 required to acquire the digital signal D. In contrast, in this embodiment, instead of the large-scale integrated circuit unit 62 acquiring the digital signal D each time the A / D converter 14 outputs the digital signal D, multiple digital signals D are recorded in the signal recording unit 18, and the large-scale integrated circuit unit 62 acquires at least two digital signals D from the signal recording unit 18 together (solid line in the figure). As a result, the large-scale integrated circuit unit 62 acquires the control signal S ＦＬＡＧSince it only needs to operate when it receives a signal, the power consumption of the dosimeter 1 can be reduced. In addition, each time multiple digital signals D are recorded in the signal recording unit 18, the digital signals D are read out from the signal recording unit 18 and the digital signals D recorded in the signal recording unit 18 are erased, thereby keeping the amount of data recorded in the signal recording unit 18 small and reducing the recording capacity of the signal recording unit 18.

[0053] In the dosimeter 1 of this embodiment, the second reset switch 44 turns off at timing T3, which follows timing T2, when the first reset switch 34 turns off. Figure 9 is a timing chart to explain the effect of this operation of the first reset switch 34 and the second reset switch 44. The dashed line in the figure shows the operation when the second reset switch 44 turns off before the first reset switch 34, as a comparative example. In this comparative example, the voltage fluctuation P that occurs instantaneously when the first reset switch 34 changes from the ON state to the OFF state is amplified by the already operating second amplifier 4, and the voltage signal V ＯＵＴ３ It is superimposed on the voltage signal V. Therefore, in order to prevent voltage fluctuations P from causing false detections, the voltage signal V ＯＵＴ３ This necessitates a longer period for stabilization (settling). As a result, the period during which the radiation pulse RP cannot be measured (dead time) becomes longer, and the measurement accuracy decreases. In contrast, as in this embodiment, the first reset switch 34 turns off before the second reset switch 44, thereby reducing the voltage signal V ＯＵＴ１ This prevents the voltage fluctuation P from being further amplified by the second amplification unit 4, and the voltage signal V transmitted to the first comparator 17. ＯＵＴ３ This prevents voltage fluctuations P from being superimposed. Therefore, the dead time can be shortened and the measurement accuracy can be improved.

[0054] In the dosimeter 1 of this embodiment, the voltage signal V ＯＵＴ３ The first threshold V ＲＥＦ１ The first comparison result signal S exceeds this value. ＣＭＰ１Based on what was indicated, the A / D converter 14 starts the conversion operation. In addition, the buffer amplifier 13 is configured to be switchable between operating and non-operating states. Then, the voltage signal V ＯＵＴ３ The first threshold V ＲＥＦ１ The first comparison result signal S exceeds this value. ＣＭＰ１ Based on the above, the buffer amplifier 13 enters an operating state. Figure 10 is a timing chart to explain the effects obtained by these operations. As shown in Figure 10, the buffer amplifier 13 operates only when a radiation pulse RP of a countable magnitude is incident (area A1 shown by halftones in the figure), so the operating time of the buffer amplifier 13 can be shortened compared to when the buffer amplifier 13 is always operating, and the power consumption of the dosimeter 1 can be reduced. In addition, the A / D converter 14 performs conversion operations only when a radiation pulse RP of a countable magnitude is incident (area A2 shown by halftones in the figure), so the operating time of the A / D converter 14 can be shortened compared to when the A / D converter 14 performs conversion operations constantly, and the power consumption of the dosimeter 1 can be reduced. These reductions in power consumption enable a long lifespan, such as being usable for more than one year even when using a button cell battery, as a portable miniature dosimeter.

[0055] As in this embodiment, the first reset switch 34 may be turned ON in conjunction with the completion of the output of the digital signal D in the A / D converter 14. By resetting the first amplifier 31 by turning ON the first reset switch 34 in conjunction with the timing of the completion of the operation of the A / D converter 14, the saturation of the first amplifier 31 can be suppressed more reliably, and the counting loss of radiation pulses RP can be further reduced.

[0056] As in this embodiment, the dosimeter 1 may also include a second comparator 19. The second comparator 19 is connected to node N1 between the first amplifier 3 and the capacitor 11, and receives the voltage signal V ＯＵＴ１ and the second threshold V ＲＥＦ２ The second comparison result signal S shows the comparison result with the previous one. ＣＭＰ２ The output may also be the second comparison result signal S. ＣＭＰ２Based on this, the saturation state of the first amplifier 31 can be detected. Specifically, when the first amplifier 31 is not saturated, the second comparison result signal S ＣＭＰ２ If the device is turned off and a large current flows that causes the first amplifier 31 to saturate, the second comparison result signal S ＣＭＰ２ The second threshold V is set to the ON state. ＲＥＦ２ This sets the second comparison result signal S. ＣＭＰ２ Based on the fact that it is in the ON state, it can be determined that the first amplifier 31 is in a saturated state. Second comparison result signal S ＣＭＰ２ When it is in the ON state, the voltage signal V ＯＵＴ３ Since it is not output, the first comparison result signal S ＣＭＰ１ It remains in the off state. Therefore, the first comparison result signal S ＣＭＰ１ and the second comparison result signal S ＣＭＰ２ By comparing these, the saturation state of the first amplifier 31 can be detected more reliably.

[0057] As in this embodiment, the dosimeter 1 may also include a second amplification unit 4. The second amplification unit 4 is connected between the capacitor 11 and both the first comparator 17 and the A / D converter 14, and the voltage signal V ＯＵＴ１ The voltage signal V may be amplified. ＯＵＴ３ This can be further amplified. Therefore, the need to reduce the voltage resolution of the A / D converter 14 can be reduced. In addition, the first comparator 17 has a first threshold voltage V ＲＥＦ１ Since the number of bits in the D / A converter required to correct this is small, the first threshold V ＲＥＦ１ This makes adjustment easier.

[0058] As in this embodiment, the second amplification unit 4 may include a second amplifier 41 and a second reset switch 44. The second amplifier 41 and the second reset switch 44 may be connected in series with the capacitor 11 and both the first comparator 17 and the A / D converter 14, and also connected in parallel with each other. When the first reset switch 34 switches from the ON state to the OFF state, the voltage signal V output from the first amplification unit 3 ＯＵＴ１ The voltage V fluctuates. If the second reset switch 44 is not provided, the voltage signal V is generated by the second amplifier 4. ＯＵＴ１The fluctuations are further amplified. Therefore, the period (dead time) during which the radiation pulse RP cannot be measured immediately after switching the first reset switch 34 becomes longer. To address this problem, a second reset switch 44 is provided in parallel with the second amplifier 41, and the second reset switch 44 is turned ON when the first reset switch 34 is switched, thereby reducing the voltage signal V ＯＵＴ１ This prevents the fluctuations from being further amplified, and the voltage signal V transmitted to the first comparator 17 ＯＵＴ３ This reduces fluctuations. Therefore, it shortens dead time.

[0059] As in this embodiment, the second amplification unit 4 may include a second resistor 43. The second resistor 43 may be connected in series with the capacitor 11 and both the first comparator 17 and the A / D converter 14, and in parallel with the second amplifier 41 and the second reset switch 44. In this case, the voltage signal V generated when the second reset switch 44 switches from the ON state to the OFF state is ＯＵＴ２ This can reduce voltage fluctuations.

[0060] As in this embodiment, the dosimeter 1 may include a sample-and-hold circuit 5. Then, the voltage signal V ＯＵＴ３ The first threshold V ＲＥＦ１ The first comparison result signal S exceeds this value. ＣＭＰ１ At a predetermined time after the signal V is shown, the sample-and-hold circuit 5 receives the voltage signal V ＯＵＴ３ The voltage signal V may be held. ＯＵＴ３ The first threshold V ＲＥＦ１ At timings exceeding this, the voltage signal V ＯＵＴ３ The voltage value is often still rising and has not yet reached its peak. As in this embodiment, the voltage signal V ＯＵＴ３ The first threshold V ＲＥＦ１ The first comparison result signal S exceeds this value. ＣＭＰ１ At a predetermined time after the indicator is shown, the voltage signal V ＯＵＴ３ By holding the peak (or near-peak) voltage signal V ＯＵＴ３ The voltage value can be input to the A / D converter 14.

[0061] As in this embodiment, the control circuit 6 may read at least two digital signals D from the signal recording unit 18 when it determines that the A / D converter 14 has generated a predetermined number of digital signals D. In this case, the large-scale integrated circuit unit 62 only needs to perform a read operation when the generation of digital signals D has occurred a predetermined number of times. Therefore, the power consumption of the control circuit 6 can be reduced.

[0062] As in this embodiment, the control circuit 6 may further read the digital signal D from the signal recording unit 18 at predetermined intervals. In this case, even if the incidence frequency of radiation pulses RP of a countable magnitude is low, the measurement results can be output periodically.

[0063] As in this embodiment, the dosimeter 1 may also include a gain amplifier 12. The gain amplifier 12 is connected between the capacitor 11 and the first comparator 17, and receives the voltage signal V ＯＵＴ２ The first threshold V may be amplified. In this case, the first comparator 17 has a first threshold V ＲＥＦ１ Since the number of bits in the D / A converter required to correct this is small, the first threshold V ＲＥＦ１ This makes adjustment easier.

[0064] As in this embodiment, the dosimeter 1 may include a bandpass filter 16 connected between the capacitor 11 and the first comparator 17. In this case, the voltage signal V ＯＵＴ３ The noise contained in the signal is reduced by the bandpass filter 16. The first comparator 17 processes the voltage signal V containing noise. ＯＵＴ３ and the first threshold V ＲＥＦ１ Since we are comparing it with the voltage signal V ＯＵＴ３ If the noise contained is large, the first threshold V ＲＥＦ１ It is necessary to increase the value by the amount of noise. According to this embodiment, since the noise is reduced by the bandpass filter 16, the first threshold V ＲＥＦ１ This reduces the voltage signal V required for the A / D converter 14 to start its conversion operation. ＯＵＴ３ The value can be made smaller.

[0065] As in this embodiment, the A / D converter 14 may be a successive approximation type. Compared to other types of A / D converters other than the successive approximation type, such as flash type, pipeline type, or delta-sigma type, the successive approximation type A / D converter 14 consumes less power during conversion operation. In addition, since the successive approximation type A / D converter 14 is mainly composed of digital circuits, the power consumption in the standby state (the state in which conversion operation is possible) is extremely low. Therefore, the power consumption of the dosimeter can be further reduced.

[0066] As in this embodiment, the control circuit 6 may calculate the radiation dose value based on at least two digital signals D read together from the signal recording unit 18. If the radiation dose value is calculated each time a digital signal D is read, the power supply of the large integrated circuit that performs the calculation must be turned on each time, increasing power consumption. By calculating the radiation dose value based on at least two digital signals D, power consumption can be reduced.

[0067] The dosimeter according to this disclosure is not limited to the embodiments described above, and various other modifications are possible. For example, some of the components described above may be omitted from the dosimeter 1 as needed. Some of the circuits constituting the dosimeter 1 of this disclosure may be provided outside the housing of the dosimeter 1. In the embodiments described above, the first amplification unit 3 and the second amplification unit 4 were exemplified as TIAs including resistors and capacitors connected in parallel with the amplifier, but the configuration of the first amplification unit 3 and the second amplification unit 4 is not limited to TIAs. Resistors or capacitors may be omitted in the first amplification unit 3 and the second amplification unit 4. The delay circuit 15 may be included in the digital circuit unit 61. The control circuit 6 may be provided as an integrated unit without being divided into the digital circuit unit 61 and the large-scale integrated circuit unit 62. In the embodiments described above, the signal recording unit 18 is provided separately from the control circuit 6, but the signal recording unit 18 may be included in the control circuit 6. A current-voltage conversion circuit may be further provided between the radiation detection unit 2 and the first amplification unit 3, and the first amplification unit 3 may amplify the voltage signal. The A / D converter 14 does not have to be a successive approximation type. The A / D converter 14 may be, for example, a flash type, a pipeline type, a delta-sigma type, or a combination thereof. In that case, a switch is provided at the power terminal of the A / D converter 14, and the voltage signal V ＯＵＴ３ The first threshold V ＲＥＦ１ The first comparison result signal S exceeds this value. ＣＭＰ１ Based on what has been indicated, the switch may be turned ON and power may be supplied to the A / D converter 14. Then, after a predetermined time has elapsed since the start of power supply to the A / D converter 14, or simultaneously with the start of power supply to the A / D converter 14, the control signal S ＣＮＶ You may also input this information to start the conversion operation of the A / D converter 14.

[0068] While the principles of the present invention have been illustrated and described in preferred embodiments, it will be recognized by those skilled in the art that the present invention can be modified in arrangement and detail without departing from such principles. The present invention is not limited to the specific configurations disclosed in these embodiments. Accordingly, all modifications and changes arising from the scope of the claims and their spirit are claimed.

[0069] 1... Dosimeter, 2... Radiation detection unit, 3... First amplification unit, 4... Second amplification unit, 5... Sample-and-hold circuit, 6... Control circuit, 11, 52... Capacitor, 12... Gain amplifier, 13... Buffer amplifier, 14... A / D converter, 15... Delay circuit, 16... Bandpass filter, 17... First comparator, 18... Signal recording unit, 19... Second comparator, 21... Photodiode, 22... Parasitic capacitance, 23... Internal resistance, 31... First amplifier, 32... First capacitance, 33... First resistor, 34... First reset switch, 41... Second amplifier, 42... Second capacitance, 43... Second resistor, 44... Second reset switch, 51, 71... Switch, 61... Digital circuit unit, 62... Large-scale integrated circuit unit, D... Digital signal, G1... Linear, G2, G3... Curved, J ＰＤ ...current signal, N1, N2...nodes, P...voltage fluctuation, RP...radiation pulse, S ＡＣＴ , S ＣＮＶ , S ＤＥＬＡＹ , S ＦＬＡＧ , S ＲＥＡＤ ...control signal, S ＣＭＰ１ ...first comparison result signal, S ＣＭＰ２ ...Second comparison result signal, S ＲＥＳＥＴ１ ...First reset signal, S ＲＥＳＥＴ２ ...Second reset signal, S ＳＷ２ ...Switch control signals, T1-T9...Timing, V ＢＩＡＳ ...Bias voltage, V ＯＵＴ１ , V ＯＵＴ２ , V ＯＵＴ３ , V Ｓ／Ｈ ...voltage signal, V ＲＥＦ１ ...First threshold, V ＲＥＦ２ ...Second threshold.

Claims

1. A radiation detection unit that outputs an electrical signal of a magnitude corresponding to the intensity of an incident radiation pulse each time the radiation pulse is incident; a first amplification unit connected to the radiation detection unit and generating a voltage signal based on the electrical signal; a capacitor connected to the first amplification unit; a first comparator connected to the first amplification unit via the capacitor and outputting a first comparison result signal indicating the result of comparing the voltage signal with a first threshold; an A / D converter connected to the first amplification unit via the capacitor and generating a digital signal indicating the magnitude of the voltage signal; a signal recording unit connected to the A / D converter and recording a plurality of digital signals, each of which is the digital signal and corresponds to multiple incidents of the radiation pulse; and a control circuit that controls the reading of the plurality of digital signals from the signal recording unit, wherein the first amplification unit includes a first amplifier and a first reset switch connected in series with the radiation detection unit and connected in parallel with each other, and the A / D converter starts a conversion operation based on the first comparison result signal indicating that the voltage signal has exceeded the first threshold. The control circuit reads out at least two of the multiple digital signals from the signal recording unit when the number of the multiple digital signals recorded in the signal recording unit reaches a predetermined number, thereby providing a dosimeter.

2. The dosimeter according to claim 1, wherein the first reset switch is turned ON in conjunction with the completion of the output of the digital signal in the A / D converter.

3. The dosimeter according to claim 1 or 2, wherein the first amplification unit further includes a first resistor connected in series with the radiation detection unit and in parallel with the first amplifier and the first reset switch.

4. The dosimeter according to any one of claims 1 to 3, further comprising a second comparator connected to a node between the first amplification unit and the capacitor, which outputs a second comparison result signal indicating the result of comparing the voltage signal with a second threshold.

5. The dosimeter according to any one of claims 1 to 4, further comprising a second amplification unit connected between the capacitance and both the first comparator and the A / D converter for amplifying the voltage signal.

6. The dosimeter according to claim 5, wherein the second amplification section includes the capacitor, and a second amplifier and a second reset switch connected in series with both the first comparator and the A / D converter and connected in parallel with each other.

7. The dosimeter according to claim 6, wherein the second amplification section further includes the capacitor and a second resistor connected in series with both the first comparator and the A / D converter and in parallel with the second amplifier and the second reset switch.

8. The dosimeter according to claim 6 or 7, wherein the second reset switch turns off after the first reset switch turns off.

9. The dosimeter according to any one of claims 1 to 8, further comprising a buffer amplifier connected between the capacitor and the A / D converter, wherein the buffer amplifier is configured to be switchable between an operating state and a non-operating state, and the buffer amplifier enters an operating state based on the first comparison result signal indicating that the voltage signal exceeds a first threshold.

10. The dosimeter according to any one of claims 1 to 9, further comprising a sample-and-hold circuit connected between the capacitor and the A / D converter, wherein the sample-and-hold circuit holds the voltage signal at a predetermined time after a first comparison result signal indicates that the voltage signal has exceeded the first threshold.

11. The dosimeter according to any one of claims 1 to 10, wherein the control circuit reads out at least two digital signals from the signal recording unit when it determines that the A / D converter has generated the digital signals a predetermined number of times.

12. The dosimeter according to claim 11, wherein the control circuit further reads the digital signal from the signal recording unit at predetermined intervals.

13. The dosimeter according to any one of claims 1 to 12, further comprising a gain amplifier connected between the capacitance and both the first comparator and the A / D converter for amplifying the voltage signal.

14. The dosimeter according to any one of claims 1 to 13, further comprising a bandpass filter connected between the capacitance and the first comparator.

15. The dosimeter according to any one of claims 1 to 14, wherein the A / D converter is of the successive approximation type.

16. The dosimeter according to any one of claims 1 to 15, wherein the control circuit calculates a radiation dose value based on the at least two digital signals read out together from the signal recording unit.

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