WO2016084454A1 - 放射線検出器 - Google Patents
放射線検出器 Download PDFInfo
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- WO2016084454A1 WO2016084454A1 PCT/JP2015/075308 JP2015075308W WO2016084454A1 WO 2016084454 A1 WO2016084454 A1 WO 2016084454A1 JP 2015075308 W JP2015075308 W JP 2015075308W WO 2016084454 A1 WO2016084454 A1 WO 2016084454A1
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- 230000005855 radiation Effects 0.000 title claims abstract description 142
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- 238000003384 imaging method Methods 0.000 description 44
- 230000003321 amplification Effects 0.000 description 11
- 238000010586 diagram Methods 0.000 description 11
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- 230000010354 integration Effects 0.000 description 10
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- CNQCVBJFEGMYDW-UHFFFAOYSA-N lawrencium atom Chemical compound [Lr] CNQCVBJFEGMYDW-UHFFFAOYSA-N 0.000 description 5
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- 239000010409 thin film Substances 0.000 description 3
- 230000015556 catabolic process Effects 0.000 description 2
- 238000006731 degradation reaction Methods 0.000 description 2
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- 230000007274 generation of a signal involved in cell-cell signaling Effects 0.000 description 2
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- 238000012544 monitoring process Methods 0.000 description 1
- 230000003071 parasitic effect Effects 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
- G01T1/00—Measuring X-radiation, gamma radiation, corpuscular radiation, or cosmic radiation
- G01T1/16—Measuring radiation intensity
- G01T1/20—Measuring radiation intensity with scintillation detectors
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
- H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation
- H01L27/144—Devices controlled by radiation
- H01L27/146—Imager structures
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N25/00—Circuitry of solid-state image sensors [SSIS]; Control thereof
- H04N25/30—Circuitry of solid-state image sensors [SSIS]; Control thereof for transforming X-rays into image signals
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N25/00—Circuitry of solid-state image sensors [SSIS]; Control thereof
- H04N25/60—Noise processing, e.g. detecting, correcting, reducing or removing noise
- H04N25/65—Noise processing, e.g. detecting, correcting, reducing or removing noise applied to reset noise, e.g. KTC noise related to CMOS structures by techniques other than CDS
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N25/00—Circuitry of solid-state image sensors [SSIS]; Control thereof
- H04N25/60—Noise processing, e.g. detecting, correcting, reducing or removing noise
- H04N25/67—Noise processing, e.g. detecting, correcting, reducing or removing noise applied to fixed-pattern noise, e.g. non-uniformity of response
- H04N25/671—Noise processing, e.g. detecting, correcting, reducing or removing noise applied to fixed-pattern noise, e.g. non-uniformity of response for non-uniformity detection or correction
- H04N25/673—Noise processing, e.g. detecting, correcting, reducing or removing noise applied to fixed-pattern noise, e.g. non-uniformity of response for non-uniformity detection or correction by using reference sources
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N25/00—Circuitry of solid-state image sensors [SSIS]; Control thereof
- H04N25/70—SSIS architectures; Circuits associated therewith
- H04N25/71—Charge-coupled device [CCD] sensors; Charge-transfer registers specially adapted for CCD sensors
- H04N25/75—Circuitry for providing, modifying or processing image signals from the pixel array
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N25/00—Circuitry of solid-state image sensors [SSIS]; Control thereof
- H04N25/70—SSIS architectures; Circuits associated therewith
- H04N25/76—Addressed sensors, e.g. MOS or CMOS sensors
- H04N25/78—Readout circuits for addressed sensors, e.g. output amplifiers or A/D converters
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N5/00—Details of television systems
- H04N5/30—Transforming light or analogous information into electric information
- H04N5/32—Transforming X-rays
Definitions
- the present invention relates to a radiation detector, in particular, an X-ray detector, and more particularly to a technique for realizing a radiation detection panel having a highly sensitive X-ray detection function.
- a direct conversion type that directly converts an X-ray into an electrical signal or a photoelectric conversion element that converts an X-ray into light by a scintillator
- An indirect conversion type that converts to an electrical signal is used.
- An X-ray imaging panel has been developed in which such sensor elements are provided for each pixel of a plurality of pixels arranged in a two-dimensional matrix on a substrate (panel). In such a panel, a thin film transistor element (TFT (Thin Film Transistor) element) is used to control each pixel.
- TFT Thin Film Transistor
- the one that transfers the electric signal stored in this capacitor to the amplifier outside the panel through the TFT element is called a passive pixel type, and has already been widely put into practical use as a digital X-ray imaging apparatus.
- Non-Patent Document 1 Non-Patent Document 1
- Non-Patent Document 2 the influence of thermal noise in the readout line and noise in the external readout circuit can be reduced. Also, an active pixel type that is amplified by using a TFT element as an amplifying element and transmitted to an external circuit has been developed.
- FIG. 9 is a diagram showing an example of the active pixel 101 and the readout circuit 102 provided in the conventional active pixel type radiation detector 100.
- one end of the sensor element 103 in the active pixel 101 is supplied with Vs_b which is a bias voltage of the sensor element 103.
- Vs_b is a bias voltage of the sensor element 103.
- the amplifier transistor 105 outputs a change in the gate voltage due to the generated electric signal as a current change between the drain and the source.
- the amplifier transistor 105 is a transistor that amplifies the electric signal, and its power supply voltage is Vd.
- the reset transistor 104 controls the gate electrode of the amplifier transistor 105 and the reset voltage Vd supplied from the outside of the active pixel 101 to a conductive state or a cut-off state based on a reset signal supplied via the reset signal line 109. To do.
- the read transistor 106 is a switch for outputting a current between the drain and source of the amplifier transistor 105 to the outside of the active pixel 101, and is controlled based on a read signal supplied via the read signal line 108.
- the current between the drain and source of the amplifier transistor 105 output to the outside of the active pixel 101 is connected between the integration amplifier 107 and the negative input terminal of the integration amplifier 107 and the output terminal of the integration amplifier 107.
- the read circuit 102 includes the capacitor Cf110, and the read circuit 102 outputs the output voltage Vo111.
- K. S. Karim, et al. “Readout Circuit in Active Pixel Sensors in Amorphous Silicon Technology,” IEEE Electron, Device Letters, Vol.22, No.10, October 2001.
- K.S.Karim, et.al “Amorphous Silicon Active Pixel Sensor Readout Circuit for Digital Imaging,” IEEE TRANSACTIONS ON ELECTRON DEVICES, VOL. 50, NO. 1, JANUARY 2003
- the threshold voltage and mobility of the amplifier transistor 105 vary within one active pixel 101 and between a plurality of active pixels 101.
- the initial value of the gate voltage of the amplifier transistor 105 is uniformly determined, the initial value of the current between the drain and source of the amplifier transistor 105 output to the outside of the active pixel 101 varies. For this reason, it is impossible to accurately estimate the amount of current between the drain and the source of the amplifier transistor 105 that is changed by the electrostatic capacitance in which the radiation is incident on the active pixel 101 and the electric signal generated by the sensor element 103 is accumulated.
- the dispersion of the initial current value can be corrected by measuring the initial current value between the drain and source of the amplifier transistor 105 and taking the difference from the current value after radiation incidence.
- flicker noise increases and a desired S / N ratio (Signal / Noise ratio) cannot be obtained.
- a desired S / N ratio (Signal / Noise ratio) cannot be obtained.
- an output signal (output current) may not be detected, which is a problem.
- the initial current value obtained is too small, the amplification factor of the amplifier transistor 105 is also small, which may lead to a decrease in the S / N ratio and a desired output signal may not be obtained. is there.
- the present invention has been made in view of the above problems, and an object of the present invention is to obtain an output signal that maintains a desired S / N ratio even when the threshold voltage and mobility of the amplifier transistor vary.
- An object of the present invention is to provide a radiation detector capable of performing the above.
- a radiation detector includes a sensor element that generates an electrical signal based on a dose of incident radiation, and an amplifier transistor that amplifies the electrical signal.
- a reset read circuit for reading the current value is provided, and the reset read circuit outputs an initial voltage to the gate electrode so that the current value becomes a predetermined value.
- a radiation detector that can obtain an output signal that maintains a desired S / N ratio even when the threshold voltage and mobility of the amplifier transistor vary.
- FIG. 1 It is a figure which shows schematic circuit structure of the radiation sensor which concerns on Embodiment 1 of this invention.
- (A) And (b) is a figure which shows schematic structure of the reset read-out circuit in the modification of the said radiation sensor.
- (A) And (b) is a figure which shows schematic structure of the radiation imaging device which concerns on Embodiment 2 of this invention, and schematic circuit structure in an active pixel. It is a figure which shows an example of the timing chart of the signal which drives the said radiation imaging device.
- Embodiment 1 of the present invention will be described with reference to FIG.
- the dimensions, materials, shapes, relative arrangements, processing methods, and the like of the configuration described in this embodiment are merely one embodiment, and the scope of the present invention should not be construed as being limited thereto.
- the drawings are schematic, and the ratio and shape of dimensions are different from actual ones.
- FIG. 1 is a diagram showing a schematic circuit configuration of a radiation sensor 1 according to Embodiment 1 of the present invention.
- the radiation sensor 1 (radiation detector) is a sensor that detects the presence or absence of radiation or the intensity of radiation, and includes an active pixel 2 and a reset readout circuit 10 as shown in FIG.
- the radiation sensor 1 is described as being a direct conversion type that directly converts incident radiation into an electrical signal, but is not limited thereto.
- the radiation sensor 1 may be an indirect conversion type in which incident radiation is converted into light by a scintillator or the like and then converted into an electric signal by a photoelectric conversion element.
- the active pixel 2 (pixel) outputs a current corresponding to the dose of incident radiation to the reset readout circuit 10 described later.
- a TFT Thin Film Transistor
- the active pixel 2 includes a sensor element 3, a reset transistor 4, an amplifier transistor 5, and a read transistor 6.
- the sensor element 3 is an element that directly converts radiation into an electric signal (charge or hole). In other words, the sensor element 3 generates an electrical signal corresponding to the dose of incident radiation (generates an electrical signal).
- the output terminal of the sensor element 3 is connected to the gate electrode of the amplifier transistor 5 and the drain electrode of the reset transistor 4.
- the input terminal of the sensor element 3 is connected to a bias power source (not shown).
- a bias voltage Vs_b is applied to the input terminal of the sensor element 3 from a bias power source.
- the sensor element 3 is an indirect conversion type, the light converted from the incident radiation is converted into an electric signal by a scintillator or the like.
- the reset transistor 4 controls the gate electrode of the amplifier transistor 5 and the reset voltage supplied from the outside of the active pixel 2 to a conductive state or a cut-off state based on a reset signal supplied via the reset signal line Lreset. .
- the source electrode of the reset transistor 4 is connected to the output terminal of the reset readout circuit 10.
- the gate electrode of the reset transistor 4 is connected to the reset signal line Lreset. When the reset signal from the reset signal line Lreset becomes High, the reset transistor 4 is turned on.
- the amplifier transistor 5 is a transistor that increases the electric signal generated by the sensor element 3, and outputs a voltage change of the gate voltage of the amplifier transistor 5 due to the electric signal as a current between the drain and source of the amplifier transistor 5.
- the drain electrode of the amplifier transistor 5 is connected to the source electrode of the read transistor 6.
- a source electrode of the amplifier transistor 5 is connected to a power source (not shown) of the amplifier transistor 5.
- a power supply voltage Vd is applied to the source electrode of the amplifier transistor 5 from the power supply of the amplifier transistor 5.
- the readout transistor 6 is a switch for outputting the output current of the amplifier transistor 5 to the outside of the active pixel 2.
- the drain electrode of the read transistor 6 is connected to the input terminal of a reset read circuit 10 to be described later.
- the gate electrode of the read transistor 6 is connected to the read signal line Lread. When the signal from the read signal line Lread becomes High, the read transistor 6 is turned on.
- the gate voltage applied to the gate electrode of the amplifier transistor 5 is initialized (reset) to an appropriate voltage for the following reason, and the amplifier transistor It is necessary to set the initial current value flowing between the source electrode 5 and the drain electrode 5 within an appropriate range.
- the amplifier transistor 5 is an N-type transistor
- the gate voltage is too high, the value of the current flowing between the source electrode and the drain electrode of the amplifier transistor 5 is too large, and the reset read circuit 10 to be described later reads.
- the output voltage Vo may be saturated. Also, an excessively large current may increase noise and lead to a decrease in S / N ratio.
- the gate voltage is too low, the gate voltage becomes lower than the threshold value, and current may not flow between the drain and source of the amplifier transistor 5. In addition, an excessively small current may lead to a decrease in S / N ratio due to a decrease in amplification factor.
- the appropriate initial voltage of the gate voltage of the amplifier transistor 5 (the gate voltage of the amplifier transistor 5 when the gate electrode of the amplifier transistor 5 is initialized) varies depending on the threshold value of the transistor. Therefore, even if a predetermined voltage fixed in advance is used as the initial voltage of the gate voltage, the gate voltage of the amplifier transistor 5 cannot be initialized appropriately.
- the amplification factor of the amplifier transistor 5 is a function of the output current from the amplifier transistor 5, the amplification factor of the amplifier transistor 5 can be controlled to an appropriate value by determining the output current from the amplifier transistor 5.
- the initial gate voltage of the amplifier transistor 5 is set so that the current between the drain and the source of the amplifier transistor 5 becomes a predetermined constant current value. What is necessary is just to determine a voltage.
- the reset read circuit 10 reads an output current value (a current value flowing between the source electrode and the drain electrode of the amplifier transistor 5) from the amplifier transistor 5 due to a change in the voltage of the gate electrode of the amplifier transistor 5.
- the reset readout circuit 10 outputs an initial voltage to the gate electrode of the amplifier transistor 5 so that the current value between the drain and the source becomes a predetermined constant value.
- the reset read circuit 10 includes a feedback circuit 12 and an initial value determination circuit 13. Furthermore, a terminal P1 for outputting the initial voltage and the read output voltage Vo to the gate electrode of the amplifier transistor 5 of the active pixel 2 and a terminal P2 for receiving an output current from the active pixel 2 are provided.
- the feedback circuit 12 integrates the output current value from the amplifier transistor 5 due to the change in the voltage of the gate electrode of the amplifier transistor 5.
- the output current value from the amplifier transistor 5 becomes a current value determined in advance by the reference voltage Vint_b input to the plus side input terminal of the amplifier 11 and the resistance R in the initial value determination circuit 13.
- the initial value (initial voltage) of the voltage of the gate electrode of the amplifier transistor 5 is generated using feedback control.
- the feedback circuit 12 includes an amplifier 11 and a capacitor Cf.
- the amplifier 11 has a positive input terminal connected to the reference voltage Vint_b.
- the negative input terminal of the amplifier 11 is connected to the drain electrode of the amplifier transistor 5 through the read transistor 6 of the active pixel 2 and is also connected to the initial value determination circuit 13.
- the output of the amplifier 11 is connected to the gate electrode of the amplifier transistor 5 through the reset transistor 4, and is also connected to a terminal that outputs the output voltage Vo.
- the negative input terminal and output terminal of the amplifier 11 are connected via a capacitor Cf, and constitute a feedback circuit 12.
- the output of the amplifier 11 is fed back to the negative side input terminal of the amplifier 11, and by the feedback, the initial voltage of the gate electrode voltage of the amplifier transistor 5 is output by the output of the amplifier 11. Is generated (set).
- the initial value determination circuit 13 determines the initial value of the current output from the amplifier transistor 5.
- the initial value determination circuit 13 includes a resistor R.
- the resistor R is connected to the ground.
- the initial value determination circuit 13 is connected to the drain electrode of the amplifier transistor 5 through the read transistor 6 of the active pixel 2 and to the negative input terminal of the amplifier 11.
- the radiation sensor 1 includes a sensor element 3 that generates an electric signal based on a dose of incident radiation, and an amplifier transistor 5 that amplifies the electric signal, and a voltage change of the gate electrode of the amplifier transistor 5 due to the electric signal.
- the reset readout circuit 10 outputs an initial voltage to the gate electrode so that the current value becomes a predetermined value.
- the reset readout circuit 10 sets the initial voltage of the gate electrode of the amplifier transistor 5 so that the current between the drain and source of the amplifier transistor 5 becomes a predetermined value, and the gate voltage of the amplifier transistor 5 is set. Reset (initialize). In the reset operation, the reset transistor 4 and the read transistor 6 are turned on.
- the voltage can be determined.
- the gate voltage of the amplifier transistor 5 is maintained at the initial voltage value by turning off the reset transistor 4 after initializing the gate voltage of the amplifier transistor 5 by this feedback control.
- the initial voltage of the gate voltage of the amplifier transistor 5 is set so that the current Vint_b / R flows between the drain and source of the amplifier transistor 5 by feedback of the amplifier 11.
- the initial value of the current flowing between the drain and source of the amplifier transistor 5 varies. For this reason, the amount of current between the drain and source of the amplifier transistor 5 that has fluctuated due to the electrical signal from the sensor element 3 cannot be accurately estimated.
- Variation in the initial current value can be corrected by measuring the initial current value before the radiation enters the active pixel 2 and taking the difference from the current after the radiation enters the active pixel 2.
- the initial current value is large, flicker noise increases and a desired S / N ratio may not be obtained.
- the initial current value is too small, the amplification factor of the amplifier transistor 5 is small and a desired output signal may not be obtained.
- Radio sensing operation In the radiation sensing operation, radiation enters the active pixel 2 from a state where the gate voltage of the amplifier transistor 5 is reset. In the radiation sensing operation, in FIG. 1, the reset transistor 4 and the read transistor 6 are turned off (in the case of an N-type transistor, the gate voltage is low).
- An electrical signal is generated in the sensor element 3 by the incidence of radiation, and an electrical signal corresponding to the radiation dose is accumulated in the capacitance of the active pixel 2.
- the gate voltage of the amplifier transistor 5 changes from the initial voltage value.
- An electrical signal corresponding to the radiation dose accumulated in the capacitance of the active pixel 2 is amplified by using the amplifier transistor 5 as an amplification element, and is output to the source electrode of the read transistor 6 as an output current.
- the reset read circuit 10 reads the output current value from the amplifier transistor 5.
- the reset transistor 4 is turned off and the read transistor 6 is turned on (in the case of an N-type transistor, the gate voltage is high).
- the read transistor 6 When the read transistor 6 is turned on while a current flows between the drain and source of the amplifier transistor 5, the drain and source of the read transistor 6 become conductive. As a result, the current flowing between the drain and source of the amplifier transistor 5 is output to the external reset read circuit 10.
- Vo ⁇ Ids ⁇ Ti / Cf, where Ti is the time from the start of the integration operation. Therefore it changes.
- Vo is an output voltage from the amplifier 11
- Ids is a current flowing between the drain and source of the amplifier transistor 5.
- the output voltage Vo is proportional to the current Ids.
- the change from the initial value of the output current of the amplifier transistor 5 is integrated into the capacitance Cf by the feedback circuit 12, and a voltage proportional to the change in the output current is output to the output terminal of the amplifier 11.
- the reset read circuit 10 is always connected to the active pixel 2, but the reset transistor 4 is turned off except for the reset operation, so that the voltage from the reset read circuit 10 acts on the gate voltage of the amplifier transistor 5. do not do.
- the bias of the amplifier transistor 5 is set so that a constant initial current is obtained.
- the voltage is determined and current can be output with the same gain. Therefore, it is possible to prevent the output current from the amplifier transistor 5 from being too large and saturated, or the amplification factor from being too small to detect the current. In this way, in the first embodiment, it is possible to realize both the initialization and readout operations of the active pixel 2 with one amplifier 11.
- the reset readout circuit 10 reads (1) the current value between the drain and source of the amplifier transistor 5 due to the change in the voltage of the gate electrode of the amplifier transistor 5 (read operation), and (2) the current between the drain and source.
- the initial voltage of the gate electrode voltage of the amplifier transistor 5 is set (reset operation) using feedback control so that the value becomes a predetermined constant value.
- FIG. 2 is a diagram showing a schematic configuration of a reset readout circuit 10a in a modified example of the radiation sensor 1.
- FIG. 2A shows the reset readout circuit 10a during the readout operation
- FIG. I s a reset readout circuit 10a during a reset operation.
- the reset read circuit 10a shown in FIG. 2 differs from the reset read circuit 10 in that an initial value determining circuit 13a is provided instead of the initial value determining circuit 13, and the other configurations are the same.
- the initial value determination circuit 13a includes a switch SW1 and a resistor R.
- a resistor R is connected to the negative input terminal of the amplifier 11 via a switch SW1.
- the end of the resistor R opposite to the switch SW1 is connected to the ground.
- the switch SW1 is turned off during the read operation period as shown in FIG. 2A, and is turned on during the reset operation period as shown in FIG. 2B.
- the reset read circuit 10 a includes an initial value determination circuit 13 a that determines a predetermined value of the current value including at least one resistor R, and the initial value determination circuit 13 a includes the gate electrode of the amplifier transistor 5.
- any one of at least one resistor R and the amplifier 11 are connected.
- the resistor R can be disconnected from the circuit during the read operation, so that S / N degradation due to noise generated by the resistor R can be avoided.
- the switch SW1 can be realized, for example, by controlling so that the feedback signal Fb is turned on when High and the feedback signal Fb is turned off when Low.
- the feedback signal Fb for controlling on / off of the switch SW1 is generated by, for example, a control unit (not shown) that supplies a clock signal, a start pulse signal, and the like to a control signal generation circuit (not shown) that generates a read signal and a reset signal.
- a control unit not shown
- a start pulse signal and the like
- a control signal generation circuit not shown
- the present invention is not limited to this.
- FIG. 3A is a diagram illustrating a schematic configuration of the radiation imaging apparatus 20 according to the second embodiment of the present invention.
- FIG. 3B is a diagram showing a schematic circuit configuration in the active pixel 21.
- FIG. 4 is a diagram illustrating an example of a timing chart of signals for driving the radiation imaging apparatus 20.
- FIG. 5 is a diagram showing a schematic configuration of the reset readout circuit 10 b in the radiation imaging apparatus 20.
- the radiation imaging apparatus 20 and the reset readout circuit 10b in FIG. 3A are the radiation imaging apparatus 20a and the reset readout circuit 10c in the third embodiment, and the radiation imaging apparatus 20b and the reset readout circuit 10d in the fourth embodiment. 5, the radiation imaging device 20c and the reset readout circuit 10e are read and referred to.
- the radiation imaging apparatus 20 includes a plurality of active pixels 21 in a matrix, and includes one reset readout circuit 10 b for each column of the active pixels 21 formed in a matrix.
- the other configurations are the same.
- the radiation imaging apparatus 20 (radiation detector) includes a plurality of active pixels 21, a flat panel 7, a reading integrated circuit 8, and a data processing unit 9, as shown in FIG.
- a plurality of active pixels 21 are arranged on the flat panel 7.
- the flat panel 7 includes M ⁇ N active pixels 21 (pixels) in a matrix
- FIG. 3B illustrates an example of the M ⁇ N active pixels 21.
- the circuit configuration of the active pixel 21 in the Mth row and the Nth column is shown. Note that the configuration of each active pixel 21 is the same as the configuration of the active pixel 2 described in the first embodiment, and a description thereof will be omitted.
- the read signal line Lread and the reset signal line Lreset are shared for each row of the M ⁇ N active pixels 21, and resetting is performed for each column of the M ⁇ N active pixels 21.
- the voltage line Vamp_b and the output line Iout are shared. Therefore, there are M read signal lines Lread and reset signal lines Lreset, and N reset voltage lines Vamp_b and N output lines Iout.
- the gate electrode of the reset transistor 4 is connected to the reset signal line Lreset_M in the Mth row.
- the gate electrode of the read transistor 6 is connected to the read signal line Lread_M of the Mth row.
- the reset voltage line Vamp_b_N in the Nth column is connected to the gate electrode of the amplifier transistor 5 via the reset transistor 4, and the output line Iout_N in the Nth column is connected to the amplifier transistor via the read transistor 6. 5 is connected to the drain electrode.
- the read integrated circuit 8 includes N reset read circuits 10b.
- the readout integrated circuit 8 performs the following operations (1) and (2) by N reset readout circuits 10b.
- (1) The current change between the drain and the source of the amplifier transistor 5 in each active pixel 21 is read, and N output voltages Vo_1 ⁇ Vo_2... Vo_N based on the read current are output to the data processing unit 9.
- (2) An initial voltage is output to the gate voltage of the amplifier transistor 5 in each active pixel 21.
- the read signal and the reset signal are sequentially provided in the reset period (the operation period (2)). Simultaneously generate a signal that becomes high, and in the first read period and the second read period (the operation period of (1) above), sequentially generate a signal that the read signal becomes high, and the read signal and the reset signal Switching between the operation (1) and the operation (2) is performed depending on the state.
- the data processing unit 9 can obtain an M ⁇ N resolution radiographic two-dimensional image based on M ⁇ N output voltages.
- the data processing unit 9 is supplied with N output voltages Vo_1, Vo_2,..., Vo_N output from the reset read circuit 10b at a time.
- the reset readout circuit 10 b is provided for each column of M ⁇ N active pixels 21 in the readout integrated circuit 8 as compared with the reset readout circuit 10, and The difference is that a feedback circuit 12b is provided instead of the feedback circuit 12, and the other configurations are the same.
- the reset readout circuit 10b includes a terminal Pj1 (1 ⁇ j ⁇ N) for applying an initial voltage to the gate electrode of the amplifier transistor 5 of the active pixel 21 in each column, and an active pixel 21 from each column of the radiation imaging apparatus 20. And a terminal Pj2 (1 ⁇ j ⁇ N) for receiving an output.
- the terminal Pj1 and the terminal Pj2 are connected to the above-described j-th reset voltage line Vamp_b_j (1 ⁇ j ⁇ N) and the j-th output line Iout_j (1 ⁇ j ⁇ N), respectively.
- the feedback circuit 12b is different from the feedback circuit 12 in that it further includes a switch SW2, and the other configuration is the same.
- the switch SW2 is connected in parallel with the capacitor Cf, and resets (initializes) by discharging the charge accumulated in the capacitor Cf.
- the reset readout circuit 10b integrates the current output from the active pixel 21 to obtain a current changed by the incidence of radiation. However, it is necessary to initialize the capacitance Cf when starting the integration.
- the capacitor Cf When the switch SW2 is turned on and the capacitor Cf is short-circuited, the capacitor Cf is reset and the preparation for integrating the current output from the active pixel 21 is completed.
- the capacitor Cf can be initialized to a constant output voltage state, so that the output voltage Vo as an integration result is accurately proportional to the current.
- both the output voltage Vo of the amplifier 11 before integration and the output voltage Vo of the amplifier 11 after integration are measured, and the difference between them is taken. It is also possible to obtain a measured value proportional to the output current.
- FIG. 4 is a diagram illustrating an example of a timing chart of signals for driving the radiation imaging apparatus 20.
- a period for acquiring one M ⁇ N resolution radiation-captured two-dimensional image includes, for example, a reset period, a first readout period, a radiation sensing period, 4 phases with 2 reading periods are included.
- the gate voltage of each amplifier transistor 5 of the M ⁇ N active pixels 21 is initialized (reset) sequentially for each row.
- the radiation imaging apparatus 20 performs a reset operation for each row of the active pixels 21.
- the reset signal Reset_1 and the read signal Read_1 become High, and the reset transistor 4 and the read transistor 6 in the active pixel 21 in the first row are turned on.
- the reset read circuit 10b outputs the initial voltage to the gate voltage of the amplifier transistor 5 in the active pixel 21 in the first row, and the gate voltage of the amplifier transistor 5 in the active pixel 21 in the first row is initialized.
- the reset signal Reset_1 and the read signal Read_1 become Low
- the reset signal Reset_2 and the read signal Read_2 become High
- the reset transistor 4 and the read transistor 6 in the active pixel 21 in the second row are turned on. .
- the gate voltage of the amplifier transistor 5 in the active pixel 21 in the second row is initialized.
- each amplifier transistor 5 is initialized up to the active pixels 21 belonging to the Mth row in this way.
- initial current values flowing between the source electrode and the drain electrode of each amplifier transistor 5 of the M ⁇ N initialized active pixels 21 are sequentially read out by the reset readout circuit 10b.
- the radiation imaging apparatus 20 performs a read operation before the exposure period. Reading of the current between the drain and source of each amplifier transistor 5 in the first reading period is performed for each row of the active pixels 21.
- N output voltages Vo_1, Vo_2,... Vo_N are output to the data processing unit 9 from each of the N reset read circuits 10b.
- the read signal Read_1, the read signal Read_2,..., The read signal Read_M sequentially become High, and the read transistor 6 in the active pixel 21 belonging to the corresponding i-th row (1 ⁇ i ⁇ M) is turned on. become.
- the initial current value flowing between the drain and source of each amplifier transistor 5 is read as N output voltages Vo for each row of the M ⁇ N initialized active pixels 21.
- the read N output voltages Vo are AD-converted and held as digital values in a storage element (not shown) provided in the data processing unit 9.
- the radiation sensing period Exposure period
- radiation enters the M ⁇ N active pixels 21 provided in the radiation imaging apparatus 20.
- An electrical signal generated according to the amount of radiation incident by the sensor element 3 provided in each active pixel 21 is accumulated in the capacitance of each active pixel 21.
- the current value changed by the incidence of radiation flowing between the source electrode and the drain electrode of each amplifier transistor 5 of the M ⁇ N active pixels 21 is sequentially changed by the reset readout circuit 10b.
- the radiation imaging apparatus 20 performs a read operation after the exposure period. Reading of the current between the drain and source of each amplifier transistor 5 in the second reading period is performed for each row of the active pixels 21.
- N output voltages Vo_1, Vo_2,... Vo_N are output to the data processing unit 9 from each of the N reset read circuits 10b.
- the read signal Read_1, the read signal Read_2,..., The read signal Read_M sequentially become High, and the read transistor 6 in the active pixel 21 belonging to the corresponding i-th row (1 ⁇ i ⁇ M) is turned on. Become.
- the current value flowing between the drain and source of each amplifier transistor 5 is read as N output voltages Vo by the reset read circuit 10b.
- the read N output voltages Vo can be AD-converted and acquired as digital values.
- the output voltage Vo corresponding to the initial current value held in the storage element (not shown) of the data processing unit 9 in the first reading period from the output voltage Vo acquired in the second reading period value in the data processing unit 9. By subtracting, the change in current from before the radiation is incident can be acquired as a signal.
- one frame period is composed of a reset period, a first readout period, a radiation sensing period, and a second readout period, and an example is given in which all periods are repeated for each frame.
- the reset period may be included once in several frame periods, and the reading result of the second reading period of the previous frame can be used without providing the first reading period.
- the radiation sensing period can be combined with another period without explicitly providing a radiation sensing period.
- the initial value of integration can be determined (capacitance Cf is initialized) by turning on the switch SW2 shown in FIG. 5 only for a short time at the beginning of the first readout period.
- the switch SW2 is turned off except for the first short period of the first reading period.
- the flat panel 7 may be a semiconductor substrate. In this case, each circuit can be directly formed on the semiconductor substrate.
- FIG. 6 is a diagram showing a schematic configuration of the reset readout circuit 10c in the radiation imaging apparatus 20a according to the third embodiment of the present invention.
- the radiation imaging apparatus 20a differs from the radiation imaging apparatus 20 in that a reset readout circuit 10c is provided instead of the reset readout circuit 10b, and the other configurations are the same. is there.
- the reset readout circuit 10c is different in that it includes a feedback circuit 12c instead of the feedback circuit 12b, and the other configurations are the same.
- the feedback circuit 12c is different from the feedback circuit 12b in that it includes a capacitor Cf1, a capacitor Cf2, and a switch SW3 instead of the capacitor Cf, and other configurations are the same.
- the feedback circuit 12c changes the capacitance connected between one input terminal of the amplifier 11 and the output terminal of the amplifier 11 when the reset read circuit 10c switches between the read operation and the reset operation.
- the capacitor connected to the amplifier 11 is switched from the capacitor Cf1 to the capacitor Cf1 + capacitor Cf2 by the switch SW3 in the reset period shown in FIG. 4, the first readout period, and the second readout period.
- the switch SW3 In the reset period, the switch SW3 is turned off and the switch SW2 is turned off. When the switch SW3 is off, the feedback capacitance in the feedback circuit 12c is the capacitance Cf1. In the reading period (the first reading period and the second reading period), the switch SW3 is turned on, the switch SW2 is turned on only for a short period at the beginning of the reading period, and is otherwise turned off. When the switch SW3 is on, the feedback capacitance is capacitance Cf1 + capacitance Cf2.
- the feedback capacity can be reduced as long as the feedback does not become unstable, and the feedback can be converged in a short period.
- the switch SW2 is turned on for a short time at the beginning of the readout period, so that the capacitor Cf is short-circuited, and the integrated current from the amplifier transistor 5 can be initialized.
- FIG. 7 is a diagram showing a schematic configuration of the reset readout circuit 10d in the radiation imaging apparatus 20b according to the fourth embodiment of the present invention.
- the radiation imaging apparatus 20b differs from the radiation imaging apparatus 20 in that a reset readout circuit 10d is provided instead of the reset readout circuit 10b, and the other configurations are the same. is there.
- the reset readout circuit 10d is different from the reset readout circuit 10b in that an initial value determination circuit 13d is provided instead of the initial value determination circuit 13, and the other configurations are the same.
- the initial value determination circuit 13d is different from the initial value determination circuit 13 in that a resistor R1, a resistor R2, a switch SW4, and a switch SW5 are provided instead of the resistor R, and the other configurations are the same.
- the initial value determination circuit 13d a plurality of predetermined values (initial values) of the current value flowing between the source electrode and the drain electrode of the amplifier transistor 5 are provided. The initial value of the current flowing between the source electrode and the drain electrode 5 is selected.
- the initial value determination circuit 13d selects the initial value of the target current from two of Vint_b / R1 and Vint_b / R2.
- the amplification factor of the amplifier transistor 5 decreases when the gate voltage of the amplifier transistor 5 is initialized with the same current value as that before the change over time.
- the target value is set to the above large current value even when the mobility is lowered due to a change with time.
- the number of resistors connected to the initial value determining circuit 13d that is, the number of target values of current that can be selected is not particularly limited, and can be appropriately increased in consideration of the circuit area.
- the switching of the resistor R1 and the resistor R2 may be performed by the user from the outside.
- the switching may be automatically performed by monitoring the gate voltage of the amplifier transistor 5 during the reset operation, for example, by a device provided in the radiation imaging apparatus 20b.
- a circuit for measuring the gate voltage of the amplifier transistor 5 at the time of the reset operation is built in the device, and the mobility of the amplifier transistor 5 deteriorates when the gate voltage of the amplifier transistor 5 becomes higher than a predetermined value. judge. If it is determined that the mobility has deteriorated, the circuit switches the resistance by switching SW4 and SW5, and changes the target value of the current.
- FIG. 8 is a diagram showing a schematic configuration of the reset readout circuit 10e in the radiation imaging apparatus 20c according to the fifth embodiment of the present invention.
- the radiation imaging apparatus 20c differs from the radiation imaging apparatus 20 in that a reset readout circuit 10e is provided instead of the reset readout circuit 10b, and the other configurations are the same. is there.
- the reset readout circuit 10e is different from the reset readout circuit 10b in that it further includes a holding circuit 14, and the other configurations are the same.
- the holding circuit 14 holds the voltage applied from the amplifier 11 to the reset voltage line Vamp_b_j in the capacitor Cb during the reset period (during the reset operation).
- the holding circuit 14 includes a switch SW6 and a capacitor Cb (holding capacitor) connected to the output terminal of the amplifier 11 via the switch SW6.
- the switch SW6 is turned on in the reset period, and the switch SW6 is turned off in the read period.
- the switch SW6 is turned off, so that the initial voltage is held in the capacitor Cb except during the operation of outputting the initial voltage of the gate electrode.
- the holding circuit 14 is configured to hold the voltage output from the terminal for setting the initial voltage of the gate electrode of the amplifier transistor 5 in the capacitor Cb except during the reset period. This prevents the output of the amplifier 11 from changing the voltage held in the capacitor Cb.
- a radiation detector (radiation sensor 1, radiation imaging apparatus 20, 20a, 20b, 20c) according to aspect 1 of the present invention includes a sensor element (3) that generates an electrical signal based on the dose of incident radiation, An amplifying transistor (5) for amplifying a signal, and a radiation detector for reading a current value flowing between a source electrode and a drain electrode of the amplifying transistor based on a voltage change of a gate electrode of the amplifying transistor due to the electric signal And a reset read circuit (10, 10a, 10b, 10c, 10d, 10e) that includes the amplifier (11) and reads the current value using the amplifier, and the reset read circuit has the current value An initial voltage is output to the gate electrode so as to have a predetermined value.
- the gate electrode outputs a voltage from the reset read circuit so that the current value becomes a predetermined value (reset operation).
- the reset read circuit can set the current value flowing between the source electrode and the drain electrode of the amplifier transistor to a predetermined value. Accordingly, even in the above case, the initial current value flowing between the source electrode and the drain electrode of the amplifier transistor can be set within an appropriate range, and an output signal maintaining a desired S / N ratio can be obtained.
- the radiation detector which can do is realizable.
- the radiation detector can perform a reset operation and a read operation with one amplifier. Thereby, it is possible to realize a radiation detector that can perform a reset operation and a read operation without significantly increasing the circuit area.
- the output of the amplifier (11) is connected to one input terminal of the amplifier.
- the initial voltage may be generated by feedback.
- the initial voltage is generated by feedback control of the output from the amplifier. Therefore, the reset read circuit can generate the initial voltage using, for example, a capacitor used in the read operation, and can perform the reset operation. Thereby, the reset read circuit can perform the reset operation and the read operation with one amplifier. Therefore, it is possible to realize a radiation detector that can perform a reset operation and a read operation without significantly increasing the circuit area.
- the radiation detector (radiation imaging device 20, 20a, 20b, 20c) according to aspect 3 of the present invention includes a pixel including the sensor element (3) and the amplifier transistor (5) according to aspect 1 or 2. A plurality of them may be arranged in a matrix.
- the radiation detector includes a plurality of pixels including sensor elements and amplifier transistors arranged in a matrix. For this reason, the radiation detector can obtain, for example, a radiation imaging two-dimensional image by reading out electrical signals of a plurality of pixels.
- the reset readout circuit (10c) reads the current value and the initial voltage of the gate electrode.
- the feedback capacitors capacitors Cf1 and Cf2 connected between one input terminal of the amplifier (11) and the output terminal of the amplifier may be changed.
- the operation of reading the current value and the operation of outputting the initial voltage of the gate electrode can be switched in the reset read circuit, the one input terminal of the amplifier and the output of the amplifier are switched.
- the feedback capacitance connected between the terminals is changed. That is, since the capacitance of the feedback circuit can be changed by each operation, an appropriate feedback capacitance can be set during the operation of reading the current value and during the operation of outputting the initial voltage of the gate electrode. .
- a radiation detector (radiation imaging apparatus 20b) includes a plurality of predetermined values (resistors R1 and R2) of the current value in the above aspects 1 to 4, You may select from several.
- the predetermined value of the current can be selected from a plurality. Therefore, even when the optimal initial voltage changes due to changes over time, the optimal initial voltage can be set again.
- the reset readout circuit (10e) is a storage capacitor (connected to the output terminal of the amplifier (11)).
- the capacitor Cb) is provided, and the storage capacitor holds the initial voltage.
- the initial voltage is held in the holding capacitor connected to the output terminal of the amplifier.
- a voltage close to the initial voltage is applied to the active pixel even when the initial voltage is not output.
- fluctuations in current output from the active pixel can be prevented.
- the radiation detector (radiation sensor 1) according to Aspect 7 of the present invention is the radiation detector (radiation sensor 1) according to Aspect 1, wherein the reset readout circuit (10) determines a predetermined value of the current value including at least one resistor.
- a determination circuit (13) is provided, and the initial value determination circuit may connect any one of the at least one resistor and the amplifier (11) during an operation of outputting the initial voltage of the gate electrode. .
- the initial value determination circuit that determines a predetermined value of the current value is connected to the amplifier during the operation of outputting the initial voltage of the gate electrode, and is connected to the amplifier during the operation of reading the current value. Absent. As a result, the resistor can be disconnected from the reset readout circuit during the operation of reading the current value, so that the S / N degradation due to noise generated by the resistor can be avoided.
- the present invention can be suitably used for a radiation sensor and a radiation imaging apparatus, particularly those using radiation.
- Radiation sensor (radiation detector) 3 Sensor element 5 Amplifier transistor 10, 10a, 10b, 10c, 10d, 10e Reset readout circuit 11 Amplifier 20, 20a, 20b Radiation imaging device (radiation detector) Cf1 and Cf2 capacity (feedback capacity) Cb capacity (holding capacity)
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Abstract
Description
本発明の実施形態1について、図1を参照して説明する。ただし、この実施形態に記載されている構成の寸法、材質、形状、相対配置、加工法などはあくまで一実施形態に過ぎず、これらによってこの発明の範囲が限定解釈されるべきではない。さらに図面は模式的なものであり、寸法の比率、形状は現実のものとは異なる。
図1は、本発明の実施形態1に係る放射線センサー1の概略的な回路構成を示す図である。
アクティブピクセル2(ピクセル)は、入射された放射線の線量に応じた電流を後述するリセット読出し回路10に出力する。アクティブピクセル2の制御には、TFT(Thin Film Transistor)が用いられている。アクティブピクセル2は、センサー素子3、リセットトランジスタ4、アンプトランジスタ5、および読出しトランジスタ6を備えている。
リセット読出し回路10は、アンプトランジスタ5のゲート電極の電圧の変化によるアンプトランジスタ5からの出力電流値(アンプトランジスタ5のソース電極とドレイン電極との間を流れる電流値)を読み出す。また、リセット読出し回路10は、ドレインソース間の電流値が予め定められた一定の値になるように、アンプトランジスタ5のゲート電極に初期電圧を出力する。
次に、放射線センサー1の動作について、リセット動作、放射線センシング動作、および読出し動作に分けて説明する。
リセット動作は、リセット読出し回路10が、アンプトランジスタ5のドレインソース間の電流があらかじめ定められた値となるように、アンプトランジスタ5のゲート電極の初期電圧を設定し、アンプトランジスタ5のゲート電圧をリセット(初期化)する。リセット動作おいては、リセットトランジスタ4および読出しトランジスタ6はオンされる。
放射線センシング動作は、アンプトランジスタ5のゲート電圧がリセットされた状態から、アクティブピクセル2に放射線が入射される。放射線センシング動作は、図1において、リセットトランジスタ4および読出しトランジスタ6はオフ(N型トランジスタの場合、ゲート電圧がlow)される。
読出し動作は、リセット読出し回路10がアンプトランジスタ5からの出力電流値を読み出す。読出し動作は、図1において、リセットトランジスタ4はオフ、読出しトランジスタ6はオン(N型トランジスタの場合、ゲート電圧がhigh)される。
本実施形態では、リセット読出し回路10が(1)アンプトランジスタ5のゲート電極の電圧の変化によるアンプトランジスタ5のドレインソース間の電流値を読出し(リード動作)、および(2)ドレインソース間の電流値が予め定められた一定の値になるように、フィードバック制御を用いてアンプトランジスタ5のゲート電極の電圧の初期電圧を設定する(リセット動作)を行う。
本発明の実施形態1の変形例について、図2を参照して説明する。図2は放射線センサー1の変形例におけるリセット読出し回路10aの概略的な構成を示す図であり、図2の(a)は、読出し動作中のリセット読出し回路10aであり、図2の(b)はリセット動作中のリセット読出し回路10aである。
図2に示すリセット読出し回路10aは、リセット読出し回路10と比較して、初期値決定回路13に代えて、初期値決定回路13aが設けられる点が異なり、その他の構成は同様である。
スイッチSW1は、図2の(a)に示すように、読出し動作期間にはオフされ、図2の(b)に示すように、リセット動作期間にはオンされる。言い換えると、リセット読出し回路10aは、少なくとも一つの抵抗Rを含む上記電流値の予め定められた値を決定する初期値決定回路13aを備え、初期値決定回路13aは、アンプトランジスタ5のゲート電極の初期電圧を出力する動作時には、少なくとも一つの抵抗Rのいずれか一つと増幅器11とを接続させる。これにより、読出し動作時に抵抗Rを回路から切り離すことができるので、抵抗Rが発生するノイズによるS/Nの劣化を回避できる。
本発明の実施形態2について、図3~図5を参照して説明する。図3の(a)は本発明の実施形態2に係る放射線撮像装置20の概略構成を示す図である。図3の(b)はアクティブピクセル21内の概略的な回路構成を示す図である。図4は放射線撮像装置20を駆動する信号のタイミングチャートの一例を示す図である。図5は放射線撮像装置20におけるリセット読出し回路10bの概略的な構成を示す図である。
放射線撮像装置20(放射線検出器)は、図3の(a)に示すように、複数のアクティブピクセル21、フラットパネル7、読出し用集積回路8、およびデータ処理部9を備えている。
リセット読出し回路10bは、図3および図5に示すように、リセット読出し回路10と比較して、読出し用集積回路8にM×N個のアクティブピクセル21の列毎に備えられている点、および、フィードバック回路12に代えて、フィードバック回路12bを備えている点が異なり、その他の構成は同様である。
図4は、放射線撮像装置20を駆動する信号のタイミングチャートの一例を示す図である。図4に示すように、M×N解像度の放射線撮像2次元画像を1枚取得する期間(1フレーム期間と呼ぶ)は、例えば、リセット期間と、第1読出し期間と、放射線センシング期間と、第2読出し期間との4フェーズを含む。
本発明の実施形態3について、図6を参照して説明する。図6は、本発明の実施形態3に係る放射線撮像装置20aにおけるリセット読出し回路10cの概略的な構成を示す図である。放射線撮像装置20a(図3の(a)参照)は、放射線撮像装置20と比較して、リセット読出し回路10bに代えて、リセット読出し回路10cを備えている点が異なり、その他の構成は同様である。
リセット読出し回路10cは、フィードバック回路12bに代えて、フィードバック回路12cを備えている点が異なり、その他の構成は同様である。
リセット期間では、スイッチSW3がオフ、スイッチSW2がオフされる。スイッチSW3がオフのとき、フィードバック回路12cにおいて、フィードバック容量は、容量Cf1となる。読出し期間(第1読出し期間および第2読出し期間)では、スイッチSW3はオン、スイッチSW2は読出し期間の最初に短期間のみオンされ、それ以外はオフされる。スイッチSW3がオンのとき、フィードバック容量は容量Cf1+容量Cf2となる。
本発明の実施形態4について、図7を参照して説明する。図7は本発明の実施形態4に係る放射線撮像装置20bにおけるリセット読出し回路10dの概略的な構成を示す図である。放射線撮像装置20b(図3の(a)参照)は、放射線撮像装置20と比較して、リセット読出し回路10bに代えて、リセット読出し回路10dを備えている点が異なり、その他の構成は同様である。
リセット読出し回路10dは、リセット読出し回路10bと比較して、初期値決定回路13に代えて、初期値決定回路13dを備えている点が異なり、その他の構成は同じである。
本発明の実施形態5について、図8を参照して説明する。図8は本発明の実施形態5に係る放射線撮像装置20cにおけるリセット読出し回路10eの概略的な構成を示す図である。放射線撮像装置20c(図3の(a)参照)は、放射線撮像装置20と比較して、リセット読出し回路10bに代えて、リセット読出し回路10eを備えている点が異なり、その他の構成は同様である。
リセット読出し回路10eは、リセット読出し回路10bと比較して、さらに保持回路14を備えている点が異なり、その他の構成は同じである。
保持回路14は、リセット期間(リセット動作時)において、増幅器11からリセット用電圧ラインVamp_b_jに印加されている電圧を容量Cbに保持する。
本発明の態様1に係る放射線検出器(放射線センサー1、放射線撮像装置20・20a・20b・20c)は、入射した放射線の線量に基づいた電気信号を発生させるセンサー素子(3)と、上記電気信号を増幅するアンプトランジスタ(5)と、を備え、上記電気信号による上記アンプトランジスタのゲート電極の電圧変化に基づく上記アンプトランジスタのソース電極とドレイン電極との間を流れる電流値を読み出す放射線検出器であって、増幅器(11)を含み、当該増幅器を用いて上記電流値を読み出すリセット読出し回路(10・10a・10b・10c・10d・10e)を備え、上記リセット読出し回路は、上記電流値が予め定められた値となるように、上記ゲート電極に初期電圧を出力する。
3 センサー素子
5 アンプトランジスタ
10・10a・10b・10c・10d・10e リセット読出し回路
11 増幅器
20・20a・20b 放射線撮像装置(放射線検出器)
Cf1・Cf2 容量(フィードバック容量)
Cb 容量(保持容量)
Claims (5)
- 入射した放射線の線量に基づいた電気信号を発生させるセンサー素子と、上記電気信号を増幅するアンプトランジスタと、を備え、
上記電気信号による上記アンプトランジスタのゲート電極の電圧変化に基づく上記アンプトランジスタのソース電極とドレイン電極との間を流れる電流値を読み出す放射線検出器であって、
増幅器を含み、当該増幅器を用いて上記電流値を読み出すリセット読出し回路を備え、
上記リセット読出し回路は、上記電流値が予め定められた値となるように、上記ゲート電極に初期電圧を出力することを特徴とする放射線検出器。 - 上記増幅器の出力は、上記増幅器の一方の入力端子にフィードバックされ、
上記フィードバックにより、上記初期電圧が生成されることを特徴とする請求項1に記載の放射線検出器。 - 上記センサー素子と上記アンプトランジスタとを備えたピクセルが、マトリクス状に複数個配置されていることを特徴とする請求項1または2に記載の放射線検出器。
- 上記リセット読出し回路が、上記電流値を読み出す動作と、上記ゲート電極の上記初期電圧を出力する動作とを、切り替える際には、上記増幅器の一方の入力端子と上記増幅器の出力端子との間に接続されたフィードバック容量を変更することを特徴とする請求項1から3のいずれか1項に記載の放射線検出器。
- 上記リセット読出し回路は、上記増幅器の出力端子に接続されている保持容量を備えており、
上記保持容量は上記初期電圧を保持することを特徴とする請求項1から4のいずれか1項に記載の放射線検出器。
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JP2016561428A JP6483150B2 (ja) | 2014-11-27 | 2015-09-07 | 放射線検出器 |
US15/528,108 US10180501B2 (en) | 2014-11-27 | 2015-09-07 | Radiation detector |
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JP2019220685A (ja) * | 2018-06-19 | 2019-12-26 | シャープ株式会社 | 放射線検出器 |
US11131782B2 (en) * | 2018-11-12 | 2021-09-28 | Stmicroelectronics (Crolles 2) Sas | Ionizing radiation detector |
JP7319809B2 (ja) * | 2019-03-29 | 2023-08-02 | キヤノン株式会社 | 放射線撮像装置、その制御方法及び放射線撮像システム |
CN111800094A (zh) * | 2020-07-17 | 2020-10-20 | 中山大学 | 一种传感器信号读取电路 |
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US10180501B2 (en) | 2019-01-15 |
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