Radiation imaging apparatus, control method, and storage medium

Abstract

To provide a radiation imaging apparatus capable of improving the quality of a captured image, and a method of controlling the same.SOLUTION: A conversion element that converts radiation or light into an electric charge, a switch element that includes a control terminal, a first terminal, and a second terminal, the first terminal being connected to the conversion element, a drive circuit that supplies a drive voltage to the control terminal of the switch element to control the switch element, and a control unit that controls the drive circuit by outputting a control signal to the drive circuit, the radiation imaging apparatus is configured to restore the lowered threshold voltage of the switch element.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The technology disclosed in this specification relates to a radiation imaging apparatus, a control method, and a program. [Background technology]

[0002] Conventionally, radiation imaging devices equipped with thin film transistors are known (see, for example, Patent Document 1). This radiation imaging device includes a detection substrate on which pixels, each having a photoelectric conversion element and a switching element such as a thin film transistor (TFT), are arranged in a two-dimensional matrix (array), a drive circuit, and a readout circuit. It is known that when this imaging device is used for a long period of time and radiation is continuously irradiated onto the TFT, the threshold voltage of the TFT shifts to a lower value. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 06-252393 Summary of the Invention [Problem to be solved by the invention]

[0004] As a method for restoring a fluctuated threshold voltage, Patent Document 1 discloses applying a DC stress voltage via a switch between the gate terminal and the drain terminal of a MOS transistor when exposed to high levels of radiation. However, with the method disclosed in Patent Document 1, the threshold voltage may not be sufficiently restored or may take a long time to recover, which may result in a deterioration in the quality of captured images.

[0005] The present technology has been made in view of the above-mentioned problems, and has an object to provide a radiation imaging apparatus and a control method thereof that can improve the quality of captured images. [Means for solving the problem]

[0006] This specification discloses a radiation imaging apparatus, a control method thereof, and a program described in the following items.

[0007] [Configuration 1] a conversion element that converts radiation or light into an electric charge; a switch element having a control terminal, a first terminal, and a second terminal, the first terminal being connected to the conversion element; a drive circuit that supplies a drive voltage to the control terminal of the switch element to control the switch element; a control unit that controls the drive circuit by outputting a control signal to the drive circuit; Equipped with The control unit is configured to restore a decreased threshold voltage of the switch element by causing the drive circuit to supply an AC voltage as the drive voltage to the control terminal. Radiography equipment.

[0008] [Configuration 2] The AC voltage satisfies at least one of the conditions that an on-duty ratio is 30% or more and an AC frequency is 10 mHz or more. The radiation imaging apparatus according to configuration 1 above.

[0009] [Configuration 3] a plurality of the conversion elements and the switch elements are arranged in a matrix; The control unit Controlling the drive circuit to supply a non-conducting voltage for bringing the first terminal and the second terminal of the switch element into a non-conducting state, thereby storing an electric signal in the conversion element; a control for reading out the electrical signals from the conversion elements by causing the drive circuit to sequentially supply a conductive voltage to each row to bring the first terminal and the second terminal of the switch element into a conductive state; is configured to run The high-level voltage of the AC voltage is configured to be set to a potential higher than the conducting voltage. 3. The radiation imaging apparatus according to configuration 1 or 2.

[0010] [Configuration 4] a plurality of the conversion elements and the switch elements are arranged in a matrix; The control unit Controlling the drive circuit to supply a non-conducting voltage for bringing the first terminal and the second terminal of the switch element into a non-conducting state, thereby storing an electric signal in the conversion element; a control for reading out the electrical signals from the conversion elements by causing the drive circuit to sequentially supply a conductive voltage to each row to bring the first terminal and the second terminal of the switch element into a conductive state; is configured to run The waveform of the AC voltage is configured to be an inverted AC waveform obtained by inverting an AC waveform obtained by superimposing the conduction voltages supplied to each row in sequence. 4. The radiation imaging apparatus according to any one of the above configurations 1 to 3.

[0011] [Configuration 5] a conversion element that converts radiation or light into an electric charge; a switch element having a control terminal, a first terminal, and a second terminal, the first terminal being connected to the conversion element; a drive circuit that supplies a drive voltage to the control terminal of the switch element to control the switch element; a control unit that controls the drive circuit by outputting a control signal to the drive circuit; A method for controlling a radiation imaging apparatus comprising: A control method comprising the step of restoring a decreased threshold voltage of the switch element by causing the drive circuit to supply an AC voltage as the drive voltage to the control terminal.

[0012] [Configuration 6] The AC voltage is controlled so as to satisfy at least one of the conditions of an on-duty of 30% or more and an AC frequency of 10 mHz or more. 6. The control method according to configuration 5 above.

[0013] [Configuration 7] In the radiation imaging device, a plurality of the conversion elements and the switch elements are arranged in a matrix, The control method includes: causing the drive circuit to supply a non-conducting voltage for bringing the first terminal and the second terminal of the switch element into a non-conducting state, thereby storing an electric signal in the conversion element; reading out the electrical signals from the conversion elements by causing the drive circuit to sequentially supply a conductive voltage to each row to bring the first terminal and the second terminal of the switch element into a conductive state; Including, The high level voltage of the AC voltage is controlled to be set to a potential higher than the conducting voltage. 7. The control method according to configuration 5 or 6 above.

[0014] [Configuration 8] In the radiation imaging device, a plurality of the conversion elements and the switch elements are arranged in a matrix, The control method includes: causing the drive circuit to supply a non-conducting voltage for bringing the first terminal and the second terminal of the switch element into a non-conducting state, thereby storing an electric signal in the conversion element; reading out the electrical signals from the conversion elements by causing the drive circuit to sequentially supply a conductive voltage to each row to bring the first terminal and the second terminal of the switch element into a conductive state; Including, The waveform of the AC voltage is controlled to be an inverted AC waveform obtained by inverting an AC waveform obtained by superimposing the conduction voltages supplied to each row in sequence. The control method according to any one of the above configurations 5 to 7.

[0015] [Configuration 9] A program for causing a computer to execute each step of the method for controlling a radiation imaging apparatus according to any one of the above configurations 5 to 8. [Effects of the Invention]

[0016] According to an embodiment of the present invention, it is possible to provide an active matrix substrate with an improved contact structure between a pixel electrode and a TFT. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a schematic diagram showing the configuration of an X-ray imaging apparatus according to an embodiment. [Figure 2] FIG. 2 is a schematic diagram of an equivalent circuit of an X-ray imaging device according to an embodiment. [Figure 3] FIG. 3 is a diagram illustrating a control method for an X-ray imaging apparatus according to a reference example. [Figure 4] FIG. 4 is a schematic diagram of an equivalent circuit of an X-ray imaging device according to a reference example. [Figure 5] FIG. 5 is a schematic diagram illustrating the relationship between the X-ray irradiation time and the change in gate threshold voltage according to the reference example. [Figure 6] FIG. 6 is a diagram illustrating a control method for AC-driven X-ray imaging apparatus according to an embodiment. [Figure 7] FIG. 7 is a schematic diagram illustrating the relationship between the X-ray irradiation time and the recovery of the gate threshold voltage during AC driving according to one embodiment. [Figure 8] FIG. 8 is a diagram illustrating a control method during normal driving of an X-ray imaging apparatus according to an embodiment. [Figure 9] FIG. 9 is a schematic diagram illustrating the relationship between the X-ray irradiation time and the recovery of the gate threshold voltage during normal driving according to one embodiment. [Figure 10] FIG. 10 is a diagram illustrating a control method when an X-ray imaging apparatus according to another embodiment is driven by AC. [Figure 11] FIG. 11 is a diagram illustrating a control method when an X-ray imaging apparatus according to another embodiment is driven by AC. [Figure 12] FIG. 12 is a diagram for explaining a control method when an X-ray imaging apparatus according to another reference example is driven by DC. [Figure 13]FIG. 13 is a schematic diagram illustrating the relationship between the X-ray irradiation time and the recovery of the gate threshold voltage during DC driving according to another reference example. DETAILED DESCRIPTION OF THE INVENTION

[0018] A radiation imaging apparatus, a control method thereof, and a control program therefor according to an embodiment will be described below with reference to the accompanying drawings. While a radiation imaging apparatus for medical use will be exemplified as an embodiment of the radiation imaging apparatus, the present technology is not limited thereto and may be used for other purposes such as electronic component inspection or piping inspection.

[0019] FIG. 1 is a schematic diagram showing a configuration of an X-ray imaging system 100 as an example of a radiation imaging system according to the present technology. The X-ray imaging system 100 generally includes an X-ray imaging device 1 and an X-ray generating device 2 (an example of a radiation generating device). The X-ray imaging device 1 includes a control unit 5. The control unit 5 may be, for example, a component of the X-ray imaging device 1, or may be provided separately from the X-ray imaging device 1. The control unit 5 is, for example, connected to the X-ray generating device 2 and the X-ray imaging device 1 via a wired or wireless connection. Although FIG. 1 illustrates one each of the X-ray generating device 2, the X-ray imaging device 1, and the control unit 5, one X-ray imaging system 100 may include one or more of each of the X-ray generating device 2, the X-ray imaging device 1, and the control unit 5.

[0020] 1, in the X-ray imaging system 100, an object to be inspected (subject M) is placed between an X-ray imaging device 1 and an X-ray generating device 2, and X-rays (an example of radiation) are emitted from the X-ray generating device 2 toward the X-ray imaging device 1. The X-ray imaging device 1 receives, for example, X-rays that have passed through the subject M, and generates a digital image signal based on the received X-rays. The X-ray imaging device 1 outputs the generated digital image signal to, for example, a control unit 5.

[0021] The control unit 5 controls, for example, the operation of the entire X-ray imaging system. The control unit 5 optionally includes, for example, a processor such as a central processing unit (CPU) that executes digital signal processing and various programs, a storage device (memory) such as a ROM (read only memory) that stores the programs executed by the CPU and a RAM (random access memory) used as a working area for expanding the programs, and an input / output unit (IF) that exchanges various signals with the X-ray generator 2, the detection board 10, etc. The control unit 5 is, for example, a computer. The control unit 5 may also include an input device for receiving various instructions and an output device such as a monitor or display, which are not shown.

[0022] The control unit 5 includes, for example, a radiation control unit 51, a drive unit 52, an amplifier unit 53, a signal processing unit 54, etc. For example, a storage device of the control unit 5 stores programs such as functional modules that function as the radiation control unit 51, the drive unit 52, the amplifier unit 53, the signal processing unit 54, etc. Each of these functional elements of the control unit 5 is realized by a processor executing the programs stored in the storage device. However, the radiation control unit 51, the drive unit 52, the amplifier unit 53, and the signal processing unit 54 may be realized by a circuit, or may be realized by combining a circuit with a functional module.

[0023] The radiation control unit 51 controls the operation of the X-ray generation device 2. For example, the radiation control unit 51 supplies the X-ray generation device 2 with a supply signal for a voltage required for generating X-rays and a signal for controlling the generation and stopping of X-rays. The drive unit 52 controls the drive of the detection board 10, which will be described later. The drive unit 52 also recovers a shift in the threshold of the switch element 13 of the detection board 10. The amplifier unit 53 controls the operation of each component of the readout circuit 15, which will be described later. The signal processing unit 54 generates an X-ray captured image, for example, based on the digital image signal from each pixel P.

[0024] The X-ray imaging device 1 typically includes a detection board 10 and a scintillator 20 that is arranged on the X-ray generator 2 side of the detection board 10 and overlaps the detection board 10. The detection board 10 includes a detection circuit 12 (see FIG. 2) that will be described later. In this X-ray imaging device 1, first, the scintillator 20 converts X-rays that have passed through the subject M into lower energy light (scintillation light), and the detection circuit 12 on the detection board 10 acquires the scintillation light as a digital image signal (sensor signal).

[0025] Each part of the X-ray imaging device 1 will be described below. First, the scintillator 20 will be described. The scintillator 20 is an optional component of the X-ray imaging device 1. The scintillator 20 converts the energy (wavelength) of radiation such as X-rays and gamma rays. For example, the scintillator 20 converts radiation into low-energy light in the ultraviolet to visible light range. Compared to a direct conversion method that does not use the scintillator 20, the use of the scintillator 20 eliminates the need to apply a bias voltage, thereby reducing the power consumption of the entire X-ray imaging device 1, and also reduces the radiation dose due to its high radiation absorption rate.

[0026] The material constituting the scintillator 20 can be appropriately selected depending on, for example, the nuclide used, and examples thereof include cesium iodide (CsI), thallium-activated cesium iodide (CsI:Tl), thallium-activated sodium iodide NaI(Tl), gadolinium (Gd), and terbium-activated gadolinium sulfate (Gd2O2S:Tb). CsI:Tl is a suitable material for the scintillator 20 of the X-ray imaging device 1. The scintillator 20 can be formed by adhering a film made of the material constituting the scintillator 20 to the detection substrate 10, or by directly growing a crystalline film made of the material constituting the scintillator 20 on the detection substrate 10 by vacuum deposition or the like. The scintillator 20 is preferably formed of columnar crystals formed by crystal growth of the material in a direction substantially perpendicular to the surface (input surface) of the detection substrate 10.

[0027] Next, the detection substrate 10 will be described. 2 is a schematic diagram of an equivalent circuit of the X-ray imaging device 1. The X-ray imaging device 1 includes, for example, a detection circuit 12, a drive circuit 14, a readout circuit 15, a buffer amplifier 36, and an analog-to-digital (A / D) converter 37. As described above, the detection circuit 12 is provided on the detection substrate 10. The drive circuit 14 and the readout circuit 15 may each be configured as an integrated circuit (IC) on the same substrate 11 as the detection substrate 10 or on another substrate, or may be formed monolithically (integrally with the substrate 11). For example, the drive circuit 14 is provided on the detection substrate 10, and the readout circuit 15 is disposed on a substrate different from the detection substrate 10, and each is connected to the detection circuit 12 via, for example, wiring or a flexible printed circuit board.

[0028] The detection substrate 10 has a plurality of pixels P arranged in a matrix for detecting X-rays (an example of radiation). The detection substrate 10 includes a substrate 11 and a detection circuit 12 arranged on the substrate 11. The detection circuit 12 includes drive lines 14a and signal lines 15a. The substrate 11 is provided with a plurality of drive lines 14a (gate wiring) arranged in the row direction. One end of each drive line 14a is connected to the drive circuit 14. The substrate 11 is provided with a plurality of signal lines (source wiring) 15a arranged in the column direction. One end of each signal line 15a is connected to the readout circuit 15. Each pixel P is surrounded by a pair of adjacent drive lines 14a and a pair of adjacent signal lines 15a. For simplicity, FIG. 2 shows only a portion of the pixels P, but an actual detection substrate includes many more pixels, for example, an array of approximately 3000 rows and 3000 columns of pixels.

[0029] The detection circuit 12 includes a conversion element 16 (sensor) for each pixel, and a switch element 13 for reading out a signal (sensor signal) from the conversion element 16. The conversion element 16 may be, for example, a photoelectric conversion element that converts light (including scintillation light and radiation) into an electric charge. An example of the photoelectric conversion element is a photodiode. In this embodiment, a PIN-type photodiode is used as the conversion element 16. Alternatively, the conversion element 16 may be, for example, a magnetic image sensor that uses a magnetic element whose resistance value changes in response to the strength of a magnetic field.

[0030] The switch element 13 in this embodiment may be, for example, a field-effect transistor such as a thin film transistor (TFT). The TFT has a gate electrode, a source electrode, a drain electrode, and a channel layer. The gate electrode of the TFT corresponds to the control terminal 13a of the switch element 13. The drain electrode or source electrode of the TFT corresponds to the first terminal 13b or the second terminal 13c of the two main terminals of the switch element 13. The gate electrode is made of, for example, a metal layer. The channel layer is made of an oxide semiconductor layer. The source electrode and the drain electrode are made of, for example, a conductive layer (e.g., sheet resistance: 200 Ω / □ or less) formed by performing resistance reduction treatment on one end and the other end of the oxide semiconductor layer, which is the same as the channel layer. An insulating material layer is provided between the metal layer constituting the gate electrode and the oxide semiconductor layer. From the viewpoint of increasing the speed and resolution of the radiation imaging device, the oxide semiconductor layer may be made of In-Ga-Zn oxide (IGZO), indium zinc oxide (IZO), or the like.

[0031] A control terminal 13a (gate electrode) of the switch element 13 is electrically connected to a corresponding drive line 14a. A first terminal 13b (drain electrode or source electrode) of the switch element 13 is electrically connected to an output terminal of the conversion element 16. A second terminal 13c (source electrode or drain electrode) of the switch element 13 is electrically connected to a corresponding signal line 15a. The drive unit 52 switches the switch element 13 between a conductive state and a non-conductive state by supplying a gate control signal to the control terminal 13a of the switch element 13 via the drive line 14a.

[0032] In the present embodiment, the switch element 13 receives a non-conducting voltage V as a gate control signal from the drive circuit 14 to the control terminal 13a. OFF is supplied, the first terminal 13b and the second terminal 13c are in a non-conductive state (OFF state). Also, the drive circuit 14 supplies the control terminal 13a with a conductive voltage V ON is supplied, the first terminal 13b and the second terminal 13c are in a conductive state (ON state) where electrical continuity is established between them. The switch element 13 operates as a so-called normally-off transistor. OFF is usually the threshold voltage V of the transistor included in the switch element 13. TH is set lower than the conduction voltage V ON is the threshold voltage V TH is set higher than

[0033] Conduction voltage V ON and non-conduction voltage V OFF The value of V depends on the configuration of the switching element 13 and cannot be generalized. However, in the case of an N-type channel TFT using an oxide semiconductor as an active layer, for example, ON = 5 to 25V, and V OFF = -15 to -5 V. In the case of a P-type channel TFT, for example, V ON = -15 to -5V, and V OFF =5 to 25 V. However, the present technology is not limited to this example.

[0034] In the detection substrate 10, when scintillation light that has passed through the scintillator 20 enters the conversion elements 16, the scintillation light is converted into electric charges by the conversion elements 16. An amount of electric charge corresponding to the amount of light irradiated is accumulated in the conversion elements 16. When the driver 52 supplies a gate control signal (Gn) to the drive line 14a for each row, the multiple switch elements 13 connected to the drive line 14a are turned on, and the electric charge accumulated in the conversion elements 16 of that row is sent from the drain electrode to the source electrode. This electric charge is supplied as a sensor signal corresponding to the amount of electric charge from the source electrode to the signal line 15a of each column and output to the readout circuit 15. Each of the multiple pixels P in the same row is provided with a corresponding signal line 15a, and the sensor signal is sent in parallel for each pixel P to the readout circuit 15. When the driver 52 supplies a gate control signal (G1, G2, ...) for each row, the sensor signals of the pixels P of each column are transmitted to the readout circuit 15 row by row in sequence.

[0035] The readout circuit 15 is provided with an amplifier circuit 30 for each signal line 15a. The amplifier circuit 30 amplifies the sensor signal output from each pixel P of the detection substrate 10. The amplifier circuit 30 includes, for example, an integral amplifier 31, a variable amplifier 32, a sample-and-hold circuit 33, and a buffer amplifier 34, which are connected in series in this order.

[0036] The integral amplifier 31 includes, for example, an operational amplifier, an integral capacitor, and a reset switch. The inverting input terminal of the operational amplifier is connected to the signal line 15a, and the non-inverting input terminal is electrically connected to the reference power supply 111. The integral capacitor is disposed between the inverting input terminal and the output terminal of the operational amplifier. The reset switch is disposed in parallel with the integral capacitor. When a reference potential Vref is input to the non-inverting input terminal and a sensor signal is input to the inverting input terminal, an amplified electrical signal is output from the output terminal. At this time, the amplification factor of the sensor signal by the integral amplifier 31 can be changed by changing the capacitance value Cf of the integral capacitor.

[0037] The variable amplifier 32 amplifies the signal amplified by the integrating amplifier 31 with a variable gain. The sample-and-hold circuit 33 includes a sampling switch and a sampling capacitor. The sample-and-hold circuit 33 samples and holds the signal amplified by the variable amplifier 32. The readout circuit 15 further includes a multiplexer 35 that sequentially outputs the electrical signals read out in parallel from each amplifier circuit 30 as a serial image signal, and a buffer amplifier 36 that performs impedance conversion on the image signal and outputs it. The image signal Vout, which is an analog electrical signal output from the buffer amplifier 36, is converted into digital image data by an A / D converter 37 and output to the signal processing unit 54 of the control unit 5.

[0038] The drive circuit 14 receives a conduction voltage V from the drive power supply 110 to turn on the switch element. ON and the non-conduction voltage V OFF to each drive line 14a. The drive circuit 14 is configured to be able to supply a reference potential Vref from a reference power supply 111 to the non-inverting input terminal of the operational amplifier. For convenience of explanation, the case where the drive power supply 110 and the reference power supply 111 are provided separately is described here, but these power supplies may also be provided together.

[0039] The drive unit 52 of the control unit 5 drives the switch elements of each pixel by, for example, outputting control signals to the drive circuit 14. The control signals include, for example, a gate shift clock signal (GCK), a gate start pulse signal (GSP), and a gate output enable signal (GOE) (in the case of a line-sequential scanning method). The gate start pulse signal GSP is a signal that notifies the drive circuit 14 of the start of scanning of the drive line that transmits the gate control signal. The gate start pulse signal GSP is a signal that is output by switching between low level, high level, and low level in accordance with, for example, image capture. The gate clock signal GCK is a signal whose voltage level switches between low level and high level at regular intervals. One cycle of the gate clock signal GCK corresponds, for example, to the period (one line period, here one horizontal scanning period) during which sensor signals are sent from the pixels P of one row. The gate output enable signal GOE controls the output of the gate signal. In this embodiment, the gate out enable signal GOE functions as a control signal that enables the output of each gate signal when the voltage level is Low, for example.

[0040] The amplifier unit 53 of the control unit 5 controls the operation of each component of the readout circuit 15, for example, by supplying control signals RC, SH, and CLK to the readout circuit 15. The control signal RC controls the operation of the reset switch of the integral amplifier 31. The control signal SH controls the operation of the sample-and-hold circuit 33. The control signal CLK controls the operation of the multiplexer 35.

[0041] (Reference example 1) FIG. 3 is an example of a timing diagram showing the control signals and the on / off timing of the switch element 13 in the reference example. The drive unit 52 of the control unit 5 outputs, for example, a gate clock signal GCK, a gate start pulse signal GSP, and a gate out enable signal GOE as control signals to the drive circuit 14. For example, when a pulse of the gate start pulse signal GSP is provided, the drive circuit 14 selects the destination drive line 14a of the gate control signal (G1, G2, ...) in order from the first row to the Nth row while shifting the destination for the gate control signal (G1, G2, ...) for each period of the gate clock signal GCK. The drive circuit 14 functions, for example, to output each pulse of the gate control signal (G1, G2, ...) when the gate out enable signal GOE is at a high level. For example, the drive circuit 14 supplies gate control signals (G1, G2, ...) of a predetermined duration to all drive lines 14a for each row at a predetermined timing. This allows the switch elements 13 of all pixels P to be driven, and sensor signals of all pixels P arranged in a matrix, i.e., sensor signals for one frame, to be output to the readout circuit 15 for each matrix. When the next pulse of the gate start pulse signal GSP is given, the drive circuit 14 repeats the above operation.

[0042] FIG. 4 is a schematic diagram of an equivalent circuit of the detection board of the X-ray imaging device 1 according to the reference example. For example, as shown in FIG. 4, the conventional detection substrate disclosed in Patent Document 1 is provided with a DC stress power supply 112, and the DC stress power supply 112 and the second terminal (terminal on the signal line 15a side) of the switch element 13 of each pixel P are connected to each other by a switch S ON ,S st1 ,S st2 The power supply 100 is electrically connectable via the power supply 100.

[0043] If the patient is exposed to X-rays above the allowable level, these switches S st1 ,S st2 is turned on, and a DC stress voltage Vd is applied between the control terminal and the second terminal for all pixels P. This compensates for the positive fixed charges generated in the gate oxide film by X-rays by hot electron injection, and restores the lowered threshold voltage.5 In the case of a transistor whose threshold voltage has been lowered (shifted in the negative direction) from 0.5 V to 0.2 V due to X-ray irradiation at 10 rad, a DC stress voltage Vd of 6.5 V is applied at approximately 10 4 It is said that applying the radiation for 10 seconds (approximately 2.8 hours) can restore the lowered threshold to almost the value before irradiation.

[0044] In contrast, the present inventor has found that when the radiation exposure dose exceeds a certain level, even if the stress voltage is applied, it may take a long time for the threshold voltage to recover, or the threshold voltage may not be able to recover at all.

[0045] 5 is a schematic diagram illustrating the relationship between the X-ray irradiation time and the change in gate threshold voltage according to the reference example. The horizontal axis of the graph in the figure represents the X-ray irradiation time (cumulative) in the X-ray imaging device 1, and the vertical axis represents the threshold voltage V of the TFT serving as a switching element. TH The amount of fluctuation is shown.

[0046] When the detection substrate in the X-ray imaging device 1 is irradiated with X-rays, the threshold voltage V TH As the X-ray irradiation time increases, the threshold voltage V TH In such a case, for example, applying a DC stress voltage Vd to the detection substrate for about 10 minutes reduces the threshold voltage V TH However, if the detection substrate 10 is irradiated with X-rays for two hours, the threshold voltage V TH When the voltage Vd is reduced by 3.2V, even if a DC stress voltage Vd is applied to the detection board for a long time, for example, the threshold voltage V TH can only recover 2.8V, and the threshold voltage V TH may remain shifted by -0.8V.

[0047] [Embodiment 1] In this technology, in order to recover the decreased threshold voltage of the switch element 13, a positive AC voltage is applied between the control terminal 13a and the second terminal 13c of the switch element 13. By varying the potential between the control terminal 13a and the second terminal 13c, it is possible to assist in the release of charges trapped in the gate oxide film of the switch element 13 and promote the recovery of the decreased threshold voltage.

[0048] Fig. 6 is a diagram illustrating a control method for the X-ray imaging device 1 during AC driving according to an embodiment. Fig. 7 is a schematic diagram illustrating the relationship between X-ray irradiation time and the recovery of the gate threshold voltage during AC driving according to an embodiment. Fig. 8 is a diagram illustrating a control method for the X-ray imaging device 1 during normal driving according to an embodiment. Fig. 9 is a schematic diagram illustrating the relationship between X-ray irradiation time and the recovery of the gate threshold voltage during normal driving according to an embodiment.

[0049] During threshold voltage recovery, the driver 52 outputs a control signal to the driver circuit 14 that differs from that during X-ray imaging. The driver 52 outputs, for example, a gate clock signal GCK, a gate start pulse signal GSP, and a gate out enable signal GOE, each having a waveform as shown in FIG. 6 , as control signals to the driver circuit 14. As the gate clock signal GCK, the driver 52 outputs, for example, a signal whose voltage level switches between low and high at regular intervals, similar to a normal drive signal. As the gate start pulse signal GSP, the driver 52 outputs a signal to notify the driver circuit 14 of the start of the threshold voltage recovery operation. The driver 52 outputs the gate start pulse signal GSP, for example, when the threshold voltage shift amount reaches a predetermined reference value or when the X-ray irradiation time reaches a predetermined reference time. As the gate out enable signal GOE, the driver 52 outputs, for example, a signal that starts at low level and switches between low and high levels in synchronization with the gate clock signal GCK.

[0050] Whether the shift amount of the threshold voltage has reached a predetermined standard can be determined, for example, by measuring the threshold voltage of the switch element 13 periodically or at some timing. The threshold voltage can be determined, for example, by setting a control signal for turning on the switch element 13 to a signal level V ON The switch element 13 is driven while shifting the potential by a predetermined potential (for example, in units of 1 V), and the signal level V ON The value of V TH Alternatively, for example, a threshold voltage V may be set based on the rate of change of the sensor signal. TH or by other known methods. TH may be calculated.

[0051] Furthermore, whether the X-ray irradiation time has reached a predetermined reference time can be evaluated by measuring (accumulating) the X-ray irradiation time since the first or previous threshold voltage shift recovery operation was performed. The X-ray irradiation time since the first or previous threshold voltage shift recovery operation was performed can be stored in, for example, a storage device. Note that the threshold voltage shift recovery operation may be performed periodically (for example, once a month, once a year, etc.) or at an appropriate timing, such as when calibrating the X-ray imaging device.

[0052] In this embodiment, the gate start pulse signal GSP is adjusted to have a waveform that rises from low to high at the start of the recovery operation and maintains that high level throughout the recovery operation. The gate out enable signal GOE generally maintains a low potential and switches to high for a predetermined time interval in synchronization with the gate clock signal GCK. Based on these control signals, the drive circuit 14 outputs, to all of the multiple drive lines 14a, AC signals whose potential switches between high and low levels throughout the recovery operation. Hereinafter, this type of recovery operation may be referred to as "AC drive."

[0053] In the example of FIG. 6, after the gate start pulse signal GSP is supplied, when the gate out enable signal GOE is in an enable (low level) state, the drive circuit 14 outputs, for example, a conduction voltage V ON , and turns on the switch element 13. After the gate start pulse signal GSP is supplied, when the gate out enable signal GOE is in a disabled (High level) state, the drive circuit 14 outputs, for example, a non-conducting voltage V as the gate control signal (G1, G2, ...). OFF to turn off the switch element 13. In other words, the drive circuit 14 functions to output pulses of the gate control signals (G1, G2, . . . ) when the gate out enable signal GOE is at a low level, for example.

[0054] FIG. 7 shows a schematic diagram of the recovery effect of the threshold voltage when AC driving of such a detection substrate 10 is performed under the following conditions. 1 horizontal scan period (1H): 200 μs High level voltage period: 199 μs High level voltage: 22V Low level voltage: -10V AC frequency: 5kHz TFT on duty: 99.5%

[0055] In this way, by performing the threshold voltage recovery operation with AC drive, the threshold voltage V TH This is expected to be due to the fact that charges tightly trapped in the gate oxide film of the switch element 13 are vibrated in the direction of applied voltage during AC driving, and are released from the traps. According to FIG. 7, it can be estimated that the threshold voltage drop can be recovered by approximately 1 V by performing AC driving according to the present technology for, for example, one hour. This can speed up the recovery speed of the threshold voltage drop.

[0056] Furthermore, AC driving of the detection board 10 can be achieved by outputting a control signal, for example, as shown in FIG. 6, from the drive unit 52 to the drive circuit 14. Therefore, for example, there is no need to provide a DC stress power supply 112 as in the reference example. In other words, the drop in threshold voltage can be recovered simply by operating the control signal without changing the configuration of the detection circuit 12 itself.

[0057] In the AC drive of this embodiment, the on-duty is set to a high condition value of 99.5%. A higher on-duty is preferable in that it enhances the effect of securing trapped positive charge. However, the on-duty may be any condition that exerts an effect of assisting the release of trapped charge. Although not limited thereto, the on-duty may be, for example, 30% or more, or 50% or more, or even 70% or more, 80% or more, 90% or more, 95% or more, 99% or more, etc.

[0058] In addition, in the AC drive of this embodiment, the AC frequency is set to a relatively high condition value of 5 kHz. A higher AC frequency is preferable because it increases the amount of potential fluctuation per unit time and can provide a stronger impact on trapped charges. However, the AC frequency may be any condition that supports the release of trapped charges. While not limited thereto, the AC frequency may be, for example, 10 mHz or higher, or may be 100 mHz or higher, or may be, for example, 1 Hz or higher. Note that excessively increasing the AC frequency does not provide an effect commensurate with the increase in frequency. Therefore, the AC frequency may typically be 100 kHz or lower, 50 kHz or lower, for example, 10 kHz or lower.

[0059] For reference, during X-ray imaging, the driver 52 can output, as control signals, a gate clock signal GCK, a gate start pulse signal GSP, and a gate out enable signal GOE, as shown in FIG. 8 , to the driver circuit 14. For example, the driver 52 outputs, as the gate clock signal GCK, a signal whose voltage level switches between low and high at regular intervals, similar to a normal drive signal. For example, the driver 52 outputs, as the gate start pulse signal GSP, a signal whose voltage level switches from low to high and back to low to notify the driver circuit 14 of the start of a threshold voltage recovery operation. The driver 52 outputs the gate start pulse signal GSP in synchronization with, for example, the timing of imaging. For example, the driver 52 outputs, as the gate out enable signal GOE, a signal whose voltage level starts at high and switches between high and low.

[0060] In the example of FIG. 8, when a pulse of the gate start pulse signal GSP is given to the drive circuit 14, the drive circuit 14 moves the destination of the gate control signals (G1, G2, ...) for each period of the gate clock signal GCK and sequentially selects the destination drive lines 14a from the first row to the Nth row. For example, when the gate out enable signal GOE is at a low level, the drive circuit 14 functions to output each pulse of the gate control signals (G1, G2, ...). For example, the drive circuit 14 supplies gate control signals (G1, G2, ...) of a predetermined duration to all drive lines 14a at a predetermined timing for each row.

[0061] FIG. 9 shows a schematic diagram of the recovery effect of the threshold voltage when an imaging operation (normal driving) of such a detection board 10 is performed under the following conditions. 1 frame period: 630 ms 1 horizontal scan period (1H): 200 μs High level voltage period: 50 μs High level voltage: 22V Low level voltage: -10V AC frequency: approx. 1.6Hz On Duty: 0.008%

[0062] In this way, in the case of normal driving, the TFT is only turned on once per frame (for example, on duty 0.008%), and it is estimated that the effect of releasing the charge trapped in the gate oxide film is small. Therefore, in the normal driving for imaging, the lowered threshold voltage V TH It turns out that it is not possible to recover.

[0063] [Configuration and Effects of Embodiment 1] The X-ray imaging device 1 (an example of a radiation imaging device) in this embodiment includes a conversion element 16 that converts radiation or light into an electric charge, a switch element 13 that has a control terminal 13a, a first terminal 13b, and a second terminal 13c, with the first terminal 13b connected to the conversion element 16, a drive circuit 14 that controls the switch element 13 by supplying a drive voltage to the control terminal 13a of the switch element 13, and a control unit 5 that controls the drive circuit 14 by outputting a control signal to the drive circuit 14. The control unit 5 is configured to cause the drive circuit 14 to supply an AC voltage as a drive voltage to the control terminal 13a, thereby restoring a lowered threshold voltage of the switch element 13. In this way, by performing the threshold voltage restoration operation by AC drive, the threshold voltage V TH can be suitably restored in a short time.

[0064] In the X-ray imaging device 1 of this embodiment, the AC voltage is configured to satisfy at least one of the conditions that the on-duty is 30% or more and the AC frequency is 10 mHz or more. By setting the waveform of the AC voltage in this way, the threshold voltage V TH This is preferable because it allows for more efficient recovery.

[0065] Note that the control signals in this embodiment are merely examples, and the combination and timing of the control signals are not limited to these examples. Furthermore, in the present technology, "alternating current" refers to a waveform in which the potential alternates between positive and negative, and the potential does not necessarily have to fluctuate constantly. The AC waveform according to the present technology can include, for example, a square wave, a triangular wave, a sawtooth wave, a sine wave, etc., and is preferably a square wave as shown in FIG. 6, etc.

[0066] [Embodiment 2] The X-ray imaging device of the second embodiment has a lowered threshold voltage V TH This embodiment differs from the first embodiment in that the waveform of the AC potential applied between the control terminal and the second terminal of the switch element is different in AC drive for restoring the capacitor. The other points may be the same as those of the first embodiment, and a description of the common configuration, effects, etc. will be omitted.

[0067] 10 is a diagram illustrating a control method during AC driving of the X-ray imaging apparatus according to embodiment 2. Although not specifically shown, for example, the driver 52 outputs signals having the same waveforms as those in normal driving as the gate clock signal GCK and the gate out enable signal GOE to the driver circuit 14. Then, as the gate start pulse signal GSP, the driver 52 outputs a signal having a waveform that rises from a low level to a high level at the timing when the recovery operation starts and remains at the high level throughout the recovery operation, as in embodiment 1, to the driver circuit 14.

[0068] As a result, as shown in FIG. 10, the drive circuit 14 outputs the gate control signals (G1, G2, ...) during AC drive as an inverted AC waveform Gall-inv, which is obtained by inverting the AC waveform Gall, which is formed by superimposing all of the gate control signals G1, G2, ... applied to each row during normal drive, between High and Low levels. In other words, the drive circuit 14 outputs, as the gate control signals (G1, G2, ...) during AC drive, a signal having a waveform obtained by inverting the gate out enable signal GOE between High and Low voltages. The AC waveform Gall (an inverted signal of the GOE signal) and the inverted AC waveform Gall-inv have the same one horizontal scanning period (1H), High and Low voltages, and AC frequency. Furthermore, the High and Low voltage periods of the AC waveform Gall are the same as the Low and High voltage periods of the inverted AC waveform Gall-inv, respectively. The ON duty of the AC waveform Gall and the inverted AC waveform Gall-inv adds up to 100%.

[0069] AC driving using such a waveform can also perform the recovery operation of the downward shift of the threshold voltage. Note that such a waveform (inverted AC waveform Gall-inv) can be easily output by, for example, providing an inversion circuit in the drive circuit 14. Therefore, AC driving using such a waveform is also preferable in that it does not require a special timing instruction signal or complicated circuitry for AC driving.

[0070] [Configuration and Effects of Embodiment 2] In the radiation imaging apparatus of the second embodiment, a plurality of conversion elements 16 and a plurality of switch elements 13 are arranged in a matrix. The control unit 5 also controls the drive circuit 14 to apply a non-conducting voltage V OFF , and a control for storing an electric signal in the conversion element 16 by supplying a voltage V ONis supplied to each row in turn, thereby controlling the reading out of an electrical signal from the conversion element 16. The waveform of the AC voltage is configured to be an inverted AC waveform Gall-inv obtained by inverting the AC waveform Gall obtained by superimposing the conducting voltages supplied to each row in turn. This configuration allows the threshold voltage V TH This is preferable in that it can recover the

[0071] [Embodiment 3] The X-ray imaging device of the third embodiment has a lowered threshold voltage V TH This embodiment differs from the first and second embodiments in that the waveform of the AC potential applied between the control terminal and the second terminal of the switch element is different in AC drive for restoring the capacitor. In other respects, this embodiment may be the same as the first or second embodiment, and a description of the common configuration, effects, etc. will be omitted.

[0072] FIG. 11 is a diagram illustrating a control method when an X-ray imaging apparatus according to another embodiment is driven by AC. The drive circuit 14 outputs the gate control signals (G1, G2, ...) during AC drive so that the potential difference between the High level and the Low level is larger than the potential difference between the High level and the Low level of the gate control signals (G1, G2, ...) during normal drive. The gate control signals shown in Fig. 11 can be easily formed by, for example, increasing the High level voltage and / or decreasing the Low level voltage of the gate control signals during AC drive such as in embodiment 1.

[0073] In order to facilitate the injection of hot carriers into the gate oxide film, it is desirable to make the High level voltage of the gate control signal during AC driving higher than the High level voltage of the gate control signal during normal driving. It is considered effective to make the High level voltage of the gate control signal during AC driving, for example, even slightly higher than the High level voltage of the gate control signal during normal driving, and the voltage can be increased by, for example, 0.1% to 20%, or 1% to 15%.

[0074] [Configuration and Effects of Embodiment 3] In the radiation imaging apparatus of the third embodiment, a plurality of conversion elements 16 and a plurality of switch elements 13 are arranged in a matrix. The control unit 5 also controls the drive circuit 14 to apply a non-conducting voltage V OFF , and a control for storing an electric signal in the conversion element 16 by supplying a voltage V ON is supplied to each row in turn, thereby controlling the reading of electrical signals from the conversion elements 16. The high level voltage of the AC voltage is a conduction voltage V ON With this configuration, the threshold voltage V TH This is preferable because it allows for more efficient recovery.

[0075] (Reference example 2) Note that the second reference example discloses an example in which the DC stress voltage Vd similar to that of the first reference example is applied between the control terminal and the second terminal only by operation using a control signal, without using the DC stress power supply 112. Fig. 12 is a diagram illustrating a control method for DC-driven X-ray imaging apparatus according to another reference example. Fig. 13 is a schematic diagram illustrating the relationship between X-ray irradiation time and gate threshold voltage recovery during DC drive according to another reference example.

[0076] In the X-ray imaging apparatus of Reference Example 2, the driver 52 outputs, for example, a gate clock signal GCK, a gate start pulse signal GSP, and a gate out enable signal GOE having waveforms such as those shown in Fig. 12 as control signals to the driver circuit 14. The driver 52 outputs, for example, a signal having the same waveform as that of normal driving as the gate clock signal GCK to the driver circuit 14. The driver 52 also outputs, for example, signals having waveforms that rise from a low level to a high level at the start of a recovery operation and maintain the high level throughout the recovery operation, similar to the GSP signal of Embodiment 1, as the gate start pulse signal GSP and the gate out enable signal GOE to the driver circuit 14.

[0077] As a result, the drive circuit 14 outputs DC waveform signals as gate control signals (G1, G2, ...) to all drive lines 14a. Even when the detection substrate 10 is driven by such a DC waveform, the downward shift of the threshold voltage can be recovered, as shown in Reference Example 1. However, as shown in FIG. 13, for example, the recovery speed is about 0.1 V per hour, which is 1 / 10 of that in Embodiment 1. It can be seen that when the detection substrate 10 is driven by a DC voltage, the recovery efficiency of the downward shift of the threshold voltage is poor, and the recovery speed may be slow.

[0078] Although the embodiments have been described above, the above-described embodiments are merely examples for implementing the present disclosure. Therefore, the present disclosure is not limited to the above-described embodiments, and can be implemented by appropriately modifying the above-described embodiments within the scope of the present disclosure.

[0079] [Radiation imaging device] In the above embodiment, a case has been described in which X-rays are used as an example of radiation in a radiation imaging device, but radiation is not limited to X-rays. The radiation according to the present technology may include particle radiation such as α-rays, β-rays, neutron beams, proton beams, heavy ion beams, and meson beams, which are beams formed by particles (including photons) emitted by radioactive decay, as well as electromagnetic radiation such as X-rays and γ-rays.

[0080] Furthermore, in the above embodiment, an example of an indirect conversion type detection substrate 10 in which radiation is converted into low-energy light and then detected has been shown, but the detection substrate 10 may be configured as a direct conversion type in which radiation is directly converted into an electrical signal. In this case, instead of the combination of the scintillator 20 and the photoelectric conversion element (an example of the conversion element 16), an X-ray conversion film can be used as the conversion element 16. As the X-ray conversion film, for example, a film made of amorphous selenium or cadmium telluride (CdTe) can be used.

[0081] [About TFT] As described above, the TFT is disposed for each pixel P on the substrate 11. The TFT is configured by stacking, from the bottom closest to the substrate, for example, a gate electrode (control terminal) and drive line 14a, a gate insulating layer, an oxide semiconductor layer, a first interlayer insulating layer, a source electrode (second terminal) layer, a second interlayer insulating layer, a drain electrode (first terminal) layer, and an organic insulating film. The oxide semiconductor layer includes a channel region facing the gate electrode via the gate insulating layer, and a source region and a drain region located on both sides of the channel region. The source region and the drain region of the oxide semiconductor layer are made conductive by, for example, a resistance reduction treatment. The source region of the oxide semiconductor layer and the source electrode layer are electrically connected via a source contact hole formed through the first interlayer insulating layer. The drain region of the oxide semiconductor layer and the drain electrode layer are electrically connected via a drain contact hole formed through the first interlayer insulating layer and the second interlayer insulating layer.

[0082] In such a TFT, the thickness of the gate metal layer constituting the gate electrode (control terminal) and drive line is, for example, 100 nm to 500 nm. The thickness of the gate insulating layer is, for example, 150 nm to 400 nm. The thickness of the oxide semiconductor layer is, for example, 10 nm to 200 nm. The thickness of the first interlayer insulating layer is, for example, 200 nm to 700 nm. The thickness of the source metal layer is, for example, 200 nm to 700 nm. The thickness of the second interlayer insulating layer is, for example, 100 nm to 600 nm. The thickness of the connection electrode is, for example, 30 nm to 100 nm. The thickness of the planarizing layer is, for example, approximately 2.5 μm to 5.0 μm.

[0083] [About oxide semiconductors] The oxide semiconductor contained in the oxide semiconductor layer may be an amorphous oxide semiconductor or a crystalline oxide semiconductor having a crystalline portion. Examples of the crystalline oxide semiconductor include a polycrystalline oxide semiconductor, a microcrystalline oxide semiconductor, and a crystalline oxide semiconductor whose c-axis is oriented substantially perpendicular to the layer surface.

[0084] The oxide semiconductor layer may have a stacked structure of two or more layers. The oxide semiconductor layer having a stacked structure may include an amorphous oxide semiconductor layer and a crystalline oxide semiconductor layer, or may include a plurality of crystalline oxide semiconductor layers with different crystal structures. Furthermore, the oxide semiconductor layer having a stacked structure may include a plurality of amorphous oxide semiconductor layers. When the oxide semiconductor layer has a stacked structure, the energy gaps of the layers may be different from each other.

[0085] The materials, structures, film formation methods, and configurations of oxide semiconductor layers having a stacked structure of the amorphous oxide semiconductor and the above-mentioned crystalline oxide semiconductors are described, for example, in JP 2014-007399 A. The entire disclosure of JP 2014-007399 A is incorporated herein by reference.

[0086] The oxide semiconductor layer may contain at least one metal element selected from the group consisting of In, Ga, and Zn. In the above-described embodiment, the oxide semiconductor layer contains, for example, an In-Ga-Zn-based oxide semiconductor (e.g., indium gallium zinc oxide). The In-Ga-Zn-based oxide semiconductor is a ternary oxide of In (indium), Ga (gallium), and Zn (zinc). The ratio (composition ratio) of In, Ga, and Zn is not particularly limited, and may be, for example, In:Ga:Zn=2:2:1, In:Ga:Zn=1:1:1, In:Ga:Zn=1:1:2, or In:Ga:Zn=1:3:5. Such an oxide semiconductor layer can be formed from an oxide semiconductor film containing an In-Ga-Zn-based oxide semiconductor. The In-Ga-Zn-based oxide semiconductor may be amorphous or crystalline. The crystalline In-Ga-Zn-based oxide semiconductor may be, for example, a c-axis-oriented In-Ga-Zn-based oxide semiconductor, in which the c-axis is aligned perpendicular to the substrate 11.

[0087] The crystal structure of crystalline In-Ga-Zn-based oxide semiconductors is disclosed in, for example, the aforementioned Japanese Patent Application Laid-Open Nos. 2014-007399, 2012-134475, and 2014-209727. For reference, the entire disclosures of Japanese Patent Application Laid-Open Nos. 2012-134475 and 2014-209727 are incorporated herein by reference. TFTs containing In-Ga-Zn-based oxide semiconductors have high mobility (more than 20 times that of a-Si TFTs) and low leakage current (less than one-hundredth that of a-Si TFTs), making them suitable for use as pixel TFTs (TFTs provided in pixels) and driver TFTs (e.g., TFTs included in driver circuits provided on the substrate 11).

[0088] The oxide semiconductor layer may contain other oxide semiconductors instead of the In-Ga-Zn-based oxide semiconductor. The oxide semiconductor layer may contain, for example, an In-Sn-Zn-based oxide semiconductor (e.g., In2O3-SnO2-ZnO; InSnZnO). The In-Sn-Zn-based oxide semiconductor is a ternary oxide of In (indium), Sn (tin), and Zn (zinc). Alternatively, the oxide semiconductor layer may contain an In-Al-Zn-based oxide semiconductor, an In-Al-Sn-Zn-based oxide semiconductor, a Zn-based oxide semiconductor, an In-Zn-based oxide semiconductor, a Zn-Ti-based oxide semiconductor, a Cd-Ge-based oxide semiconductor, a Cd-Pb-based oxide semiconductor, a Cd-Zn-based oxide semiconductor, CdO (cadmium oxide), an Mg-Zn-based oxide semiconductor, an In-Ga-Sn-based oxide semiconductor, an In-Ga-based oxide semiconductor, a Zr-In-Zn-based oxide semiconductor, an Hf-In-Zn-based oxide semiconductor, an Al-Ga-Zn-based oxide semiconductor, a Ga-Zn-based oxide semiconductor, an In-Ga-Zn-Sn-based oxide semiconductor, or the like. [Explanation of symbols]

[0089] 1...X-ray imaging device, 2...X-ray generator, 5...control unit, 51...radiation control unit, 52...drive unit, 53...amplification unit, 54...signal processing unit, 10...detection board, 12...detection circuit, 13...switch element, 13a...control terminal, 13b...first terminal, 13c...second terminal, 14...drive circuit, 14a...drive line, 15...readout circuit, 15a...signal line, 16...conversion element, 20...scintillator, 30...amplification circuit, 100...X-ray imaging system

Claims

1. a conversion element that converts radiation or light into an electric charge; a switch element having a control terminal, a first terminal, and a second terminal, the first terminal being connected to the conversion element; a drive circuit that supplies a drive voltage to the control terminal of the switch element to control the switch element; a control unit that controls the drive circuit by outputting a control signal to the drive circuit; Equipped with The control unit is configured to restore a decreased threshold voltage of the switch element by causing the drive circuit to supply an AC voltage as the drive voltage to the control terminal. Radiography equipment.

2. The AC voltage satisfies at least one of the conditions that an on-duty ratio is 30% or more and an AC frequency is 10 mHz or more. The radiation imaging apparatus according to claim 1 .

3. a plurality of the conversion elements and the switch elements are arranged in a matrix; The control unit a control for storing an electric signal in the conversion element by causing the drive circuit to supply a non-conducting voltage for bringing the first terminal and the second terminal of the switch element into a non-conducting state; a control for reading out the electrical signals from the conversion elements by causing the drive circuit to sequentially supply a conductive voltage to each row to bring the first terminal and the second terminal of the switch element into a conductive state; is configured to run a high-level voltage of the AC voltage is configured to be set to a potential higher than the conduction voltage; The radiation imaging apparatus according to claim 1 .

4. a plurality of the conversion elements and the switch elements are arranged in a matrix; The control unit a control for storing an electric signal in the conversion element by causing the drive circuit to supply a non-conducting voltage for bringing the first terminal and the second terminal of the switch element into a non-conducting state; a control for reading out the electrical signals from the conversion elements by causing the drive circuit to sequentially supply a conductive voltage to each row to bring the first terminal and the second terminal of the switch element into a conductive state; is configured to run The waveform of the AC voltage is configured to be an inverted AC waveform obtained by inverting an AC waveform obtained by superimposing the conduction voltages supplied to each row in sequence. The radiation imaging apparatus according to claim 1 .

5. a conversion element that converts radiation or light into an electric charge; a switch element having a control terminal, a first terminal, and a second terminal, the first terminal being connected to the conversion element; a drive circuit that supplies a drive voltage to the control terminal of the switch element to control the switch element; a control unit that controls the drive circuit by outputting a control signal to the drive circuit; A method for controlling a radiation imaging apparatus comprising: A control method comprising the step of restoring a decreased threshold voltage of the switch element by causing the drive circuit to supply an AC voltage as the drive voltage to the control terminal.

6. The AC voltage is controlled so as to satisfy at least one of the conditions that an on-duty ratio is 30% or more and an AC frequency is 10 mHz or more. The control method according to claim 5 .

7. In the radiation imaging device, a plurality of the conversion elements and the switch elements are arranged in a matrix, The control method includes: causing the drive circuit to supply a non-conducting voltage for bringing the first terminal and the second terminal of the switch element into a non-conducting state, thereby storing an electric signal in the conversion element; a step of reading out the electrical signals from the conversion elements by causing the drive circuit to sequentially supply a conductive voltage to each row to bring the first terminal and the second terminal of the switch element into a conductive state; Including, The high-level voltage of the AC voltage is controlled to be set to a potential higher than the conduction voltage. The control method according to claim 5 .

8. In the radiation imaging device, a plurality of the conversion elements and the switch elements are arranged in a matrix, The control method includes: causing the drive circuit to supply a non-conducting voltage for bringing the first terminal and the second terminal of the switch element into a non-conducting state, thereby storing an electric signal in the conversion element; a step of reading out the electrical signals from the conversion elements by causing the drive circuit to sequentially supply a conductive voltage to each row to bring the first terminal and the second terminal of the switch element into a conductive state; Including, The waveform of the AC voltage is controlled to be an inverted AC waveform obtained by inverting an AC waveform obtained by superimposing the conduction voltages supplied to each row in sequence. The control method according to claim 5 .

9. A program for causing a computer to execute each step of the method for controlling a radiation imaging apparatus according to any one of claims 5 to 8.

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