JP4546560B2 - Radiation imaging apparatus, driving method thereof, and radiation imaging system - Google Patents

Description

  The present invention relates to a radiation imaging apparatus suitable for use in medical diagnosis and industrial nondestructive inspection, a driving method thereof, and a radiation imaging system. In this specification, electromagnetic waves such as X-rays and γ rays, α rays, and β rays are also included in the radiation.

  Conventionally, in an X-ray imaging system installed in a hospital or the like, a film imaging system for irradiating a patient with X-rays and exposing the X-rays transmitted through the patient to a film, and an X-ray transmitted through the patient as an electrical signal There is an image processing method in which digital image processing is performed after conversion into a digital image.

  As one of image processing methods, there is a radiation imaging apparatus including a phosphor that converts X-rays into visible light and a photoelectric conversion device that converts visible light into an electrical signal. X-rays transmitted through the patient are irradiated onto the phosphor, and the in-vivo information of the patient converted into visible light by the phosphor is output as an electrical signal by the photoelectric conversion device. If the in-vivo information of the patient is converted into an electrical signal, the electrical signal is digitally converted by an AD converter, and X-ray image information for recording, display, printing, diagnosis, etc. can be handled as a digital value.

Recently, a radiation imaging apparatus using an amorphous silicon semiconductor thin film for a photoelectric conversion device has been put into practical use.
FIG. 24 is a top view of a conventional photoelectric conversion substrate configured by using an amorphous silicon semiconductor thin film as the material of the MIS type photoelectric conversion element 101 and the switch element 102, and also includes wirings for connecting them.

25 is a cross-sectional view taken along the line AB shown in FIG. In the following description, for the sake of simplicity, the MIS type photoelectric conversion element is simply referred to as a photoelectric conversion element.
As shown in FIG. 25, the photoelectric conversion element 101 and the switch element 102 (amorphous silicon TFT, hereinafter simply referred to as TFT) are formed on the same substrate 103, and the lower electrode of the photoelectric conversion element 101 is the lower part of the TFT 102. It is formed of the same first metal thin film layer 104 as the electrode (gate electrode), and the upper electrode of the photoelectric conversion element 102 is the same as the second metal of the upper electrode (source electrode, drain electrode) of the TFT 102. The thin film layer 105 is formed.

  The first and second metal thin film layers 104 and 105 are also formed in common with the gate driving wiring 106 and the matrix signal wiring 107 in the photoelectric conversion circuit portion shown in FIG. In FIG. 24, a total of 4 pixels of 2 × 2 is described as the number of pixels, and the hatched portion in the figure indicates the light receiving surface of the photoelectric conversion element 101. Reference numeral 109 denotes a power supply line for applying a bias to the photoelectric conversion element 101, and 110 denotes a contact hole for connecting the photoelectric conversion element 101 and the TFT 102.

  If the structure as shown in FIG. 24 using an amorphous silicon semiconductor as a main material is used, the photoelectric conversion element 101, the TFT 102, the gate driving wiring 106, and the matrix signal wiring 107 can be simultaneously formed on the same substrate. A large-area photoelectric conversion circuit portion can be provided easily and inexpensively.

Next, device operation of the photoelectric conversion element 101 will be described with reference to FIG.
FIGS. 26A to 26C are energy band diagrams for explaining the device operation of the photoelectric conversion element 101 shown in FIGS.

  FIGS. 26A and 26B show the operation in the refresh mode and the photoelectric conversion mode, respectively, and the horizontal axis shows the state in the film thickness direction of each layer shown in FIG. Here, M1 is a lower electrode (G electrode) formed of the first metal thin film layer 104 such as Cr. The amorphous silicon nitride (a-SiNx) insulating thin film layer 111 is an insulating layer that blocks passage of both electrons and holes, and needs to have a thickness that does not cause a tunnel effect. It is formed.

The hydrogenated amorphous silicon (a-Si: H) thin film layer 112 is a photoelectric conversion semiconductor layer formed of an intrinsic semiconductor layer (i layer) not intentionally doped with a dopant. The N ⁺ layer 113 is a single conductivity type carrier made of a non-single-crystal semiconductor such as an N-type hydrogenated amorphous silicon thin film layer formed to prevent injection of holes into the hydrogenated amorphous silicon thin film layer 112. This is an injection blocking layer. M2 is an upper electrode (D electrode) formed of the second metal thin film layer 105 such as Al.

In Figure 25, although the D electrode is the upper electrode does not completely cover the N ⁺ layer 113, the electrodes D to between the the electron transfer is freely performed between the D electrode and the N ⁺ layer 113 and the N ⁺ The layer 113 is always at the same potential, and the following description will be made on the assumption of this.
The device operation of the photoelectric conversion element 101 has two types of operation modes, a refresh mode and a photoelectric conversion mode, depending on how the voltage is applied to the D electrode and the G electrode.

In the refresh mode shown in FIG. 26 (a), a negative potential is applied to the D electrode with respect to the G electrode. Guided to the electrode. At the same time, electrons indicated by white circles in the drawing are injected into the i layer 112. At this time, some holes and electrons recombine in the N ⁺ layer 113 and the i layer 112 and disappear. If this state continues for a sufficiently long time, holes are swept out of the i layer 112.

In order to switch to the photoelectric conversion mode shown in FIG. 26A from the above state, a positive potential is applied to the D electrode with respect to the G electrode. Thereby, electrons in the i layer 112 are instantaneously guided to the D electrode. However, the holes are not guided to the i layer 112 because the N ⁺ layer 113 serves as an injection blocking layer. When light enters the i layer 112 in this state, the light is absorbed and an electron hole pair is generated. The electrons are guided to the D electrode by an electric field. On the other hand, the holes move in the i layer 112 and reach the interface between the i layer 112 and the amorphous silicon nitride (a-SiNx) insulating thin film layer 111, but cannot move into the insulating layer 111. Will stay inside. At this time, electrons move to the D electrode, and holes move to the interface of the insulating layer in the i layer, so that a current flows from the G electrode in order to maintain electrical neutrality in the photoelectric conversion element 101. Since this current corresponds to the electron-hole pair generated by light, it becomes proportional to the incident light.

  After maintaining the state of the photoelectric conversion mode shown in FIG. 26B for a certain period and then entering the state of the refresh mode of FIG. 26A again, the holes remaining in the i layer 112 are D electrodes as described above. The current corresponding to this hole flows. The amount of holes corresponds to the total amount of light incident during the photoelectric conversion mode period. At this time, a current corresponding to the amount of electrons injected into the i layer 112 also flows, but since this amount is approximately constant, it may be detected by subtracting. That is, the photoelectric conversion element 101 can output the amount of light incident at the real time and simultaneously detect the total amount of light incident during a certain period.

  However, when the period of the photoelectric conversion mode becomes longer for some reason or when the illuminance of incident light is strong, current may not flow even though light is incident. This is because, as shown in FIG. 26C, a large number of holes remain in the i layer 112, and the electric field in the i layer 112 is reduced by the holes, and the generated electrons are not guided and holes are formed in the i layer 112. This is because they are recombined. This state is referred to as a saturated state of the photoelectric conversion element 101. If the light incident state changes in this state, the current may flow in an unstable manner, but if the refresh mode is set again, the holes in the i layer 112 are swept out, so that the light is again turned on in the next photoelectric conversion mode. Proportional current flows.

In the above description, when holes in the i layer 112 are swept out in the refresh mode, it is ideal to sweep out all the holes. However, sweeping out some holes is also effective, and the current equal to that described above. There is no problem. In other words, the detection opportunity in the next photoelectric conversion mode does not have to be in the saturation state of FIG. 26C, the potential of the D electrode with respect to the G electrode in the refresh mode, the period of the refresh mode, and the N ⁺ layer 113 The characteristics of the injection blocking layer may be determined.

Further, in the refresh mode, injection of electrons into the i layer 112 is not a necessary condition, and the potential of the D electrode with respect to the G electrode is not limited to negative. This is because when many holes remain in the i layer 112, the electric field in the i layer 112 is applied in the direction leading the holes to the D electrode even if the potential of the D electrode with respect to the G electrode is a positive potential. . Similarly, the characteristics of the N ⁺ layer 113 serving as an injection blocking layer are not necessarily required to be able to inject electrons into the i layer 112.

FIG. 27 is a conventional photoelectric conversion circuit diagram for one pixel of a pixel configured to include the photoelectric conversion element 101 and the TFT 102.
In FIG. 27, the photoelectric conversion element 101 includes a capacitance component Ci composed of an i layer and a capacitance component C _SiN composed of an injection blocking layer. Further, the junction point between the i layer and the injection blocking layer (node N in FIG. 27) has no electric field when the photoelectric conversion element 101 is saturated, that is, between the D electrode and the node N (i layer). When the (small) state is reached, electrons generated by light and holes are recombined, so that hole carriers cannot be stored in the N part.

That is, the potential of the node N does not become higher than the potential of the D electrode. In order to realize the operation in the saturated state, in FIG. 27, the diode (D1) is connected in parallel to the capacitive component Ci. That is, the photoelectric conversion element 101 has three components, that is, a capacitive component Ci, a capacitive component C _SiN , and a diode D1.

  FIG. 28 is a timing chart showing an operation in the photoelectric conversion circuit for one pixel of the pixels shown in FIG. Hereinafter, the circuit operation of the pixel constituted by the photoelectric conversion element 101 and the TFT 102 will be described with reference to FIGS.

First, the refresh operation will be described.
In FIG. 27, Vs is set to 9V and Vref is set to 3V. In the refresh operation, the switch SW-A is set to Vref, the switch SW-B is set to Vg (on), and the switch SW-C is turned on. In this state, the D electrode is biased to Vref (6V), the G electrode is biased to the GND potential, and the node N is biased to the maximum Vref (6V). Here, the maximum is biased to Vref via the diode D1 when the potential of the node N has already been accumulated to a potential equal to or higher than Vref by the photoelectric conversion operation before the current refresh operation. On the other hand, when the potential of the node N is equal to or lower than Vref due to the previous photoelectric conversion operation, the refresh operation is not biased to the potential of Vref. In actual use, if a plurality of photoelectric conversion operations have been repeated in the past, it can be said that the node N is effectively biased to Vref (6 V) by this refresh operation.

  Subsequently, after the node N is biased to Vref, the switch SW-A is switched to the Vs side. As a result, the D electrode is biased to Vs (9 V). By this refresh operation, the hole carriers stored in the node N of the photoelectric conversion element 101 are swept away to the D electrode side.

Next, the X-ray irradiation period will be described.
As shown in FIG. 28, X-rays are irradiated in a pulse shape. X-rays that have passed through the detector are irradiated onto the phosphor Fl and converted into visible light. Visible light from the phosphor Fl is irradiated to the semiconductor layer (i layer) and subjected to photoelectric conversion. The hole carriers generated by the photoelectric conversion are accumulated at the node N and raise the potential. Since the TFT 102 is in an off state, the potential on the G electrode side also rises by the same amount.

  The wait period is provided between the refresh period and the X-ray irradiation period. In particular, when something is not operated, and when the characteristics of the photoelectric conversion element 101 are unstable due to dark current immediately after the refresh operation or the like, a standby period is provided so that nothing is operated until relaxation. It is. When the photoelectric conversion element 101 does not have an unstable characteristic immediately after the refresh operation, it is not necessary to provide a wait period.

Next, the transfer operation will be described.
In the transfer operation, the switch SW-B is set to the Vg (on) side and the TFT 102 is turned on. As a result, electron carriers (S _e ) corresponding to the amount of hole carriers (S _h ) stored by X-ray irradiation flow from the C ₂ side to the G electrode side via the TFT 102, and the potential of the read capacitor C ₂ is increased. Raise. At this time, the relationship between S _e and S _h is S _e = S _h × C _SiN / (C _SiN + C _i ). The potential of the read capacitor C ₂ is simultaneously amplified through an amplifier and output. The TFT 102 is turned on for a time sufficient to sufficiently transfer the signal charge, and then turned off.

Finally, the reset operation will be described.
In the reset operation, the switch SW-C is turned on to reset the read capacitor C2 to the GND potential to prepare for the next transfer operation.

FIG. 29 is a two-dimensional circuit diagram of a conventional photoelectric conversion device.
In FIG. 29, only 3 × 3 = 9 pixels are shown to simplify the description. S1-1 to S3-3 are photoelectric conversion elements, T1-1 to T3-3 are switch elements (TFTs), G1 to G3 are gate wirings for turning on / off the TFTs (T1-1 to T3-3), M1 to M3 are signal wirings, and the Vs line is a wiring for applying a storage bias or a refreshing bias to the photoelectric conversion elements S1-1 to S3-3.

The electrodes on the sides of the photoelectric conversion elements S1-1 to S3-3 that are painted black are G electrodes, and the opposite side is a D electrode. Further, although the D electrode is shared with a part of the Vs line, a thin N ⁺ layer is used as the D electrode for the convenience of light incidence. The photoelectric conversion elements S1-1 to S3-3, TFTs (T1-1 to T3-3), gate wirings G1 to G3, signal wirings M1 to M3, and Vs lines are collectively referred to as a photoelectric conversion circuit unit 100.

  The Vs line is biased by a power supply Vs or a power supply Vref, and these are switched by a VSC control signal. SR1 is a shift register that applies a driving pulse voltage to the gate wirings G1 to G3, and a voltage for turning on the TFTs (T1-1 to T3-3) is supplied from the outside. The voltage supplied at this time is determined by the power supply Vg (on).

The reading circuit unit 200 amplifies the parallel signal outputs of the signal wirings M1 to M3 in the photoelectric conversion circuit unit 100, converts the signals in series, and outputs them.
RES1 to RES3 are switches that reset the signal wirings M1 to M3, A1 to A3 are amplifiers that amplify the signals of the signal wirings M1 to M3, and CL1 to CL3 are samples that temporarily store the signals amplified by the amplifiers A1 to A3. Hold capacitors, Sn1 to Sn3 are switches for performing sample hold, B1 to B3 are buffer amplifiers, Sr1 to Sr3 are switches for serially converting parallel signals, and SR2 is a pulse for serially converting to switches Sr1 to Sr3 A shift register, Ab, is a buffer amplifier that outputs a serially converted signal.

  FIG. 30 is a timing chart illustrating the operation of the photoelectric conversion device illustrated in FIG. Hereinafter, the operation of the photoelectric conversion device in FIG. 29 will be described with reference to this timing chart.

  The control signal VSC is for applying two types of bias to the Vs line, that is, the D electrodes of the photoelectric conversion elements S1-1 to S3-3. The D electrode becomes Vref (V) when the control signal VSC is “Hi”, and becomes Vs (V) when the control signal VSC is “Lo”. The reading power source Vs (V) and the refreshing power source Vref (V) are each a DC power source.

First, the operation during the refresh period will be described.
All signals of the shift register SR1 are set to “Hi”, and the CRES signal of the reading circuit unit 200 is set to “Hi”. In this way, all the switching TFTs (T1-1 to T3-3) are turned on, and the switch elements RES1 to RES3 in the readout circuit 200 are also turned on, so that all the photoelectric conversion elements S1-1 to S3-3 are turned on. The G electrode becomes the GND potential. When the control signal VSC becomes “Hi”, the D electrodes of all the photoelectric conversion elements S1-1 to S3-3 are biased to the refresh power supply Vref (negative potential). As a result, all the photoelectric conversion elements S1-1 to S3-3 enter the refresh mode, and refresh is performed.

Next, the photoelectric conversion period will be described.
When the control signal VSC is switched to the “Lo” state, the D electrodes of all the photoelectric conversion elements S1-1 to S3-3 are biased to the reading power source Vs (positive potential). If it does in this way, photoelectric conversion element S1-1-S3-3 will be in a photoelectric conversion mode. In this state, all the signals of the shift register SR1 are set to “Lo”, and the CRES signal of the reading circuit unit 200 is set to the “Lo” state. As a result, all the switching TFTs (T1-1 to T3-3) are turned off, and the switch elements RES1 to RES3 in the readout circuit 200 are also turned off, and the G of all the photoelectric conversion elements S1-1 to S3-3 is turned off. Although the electrodes are in an open state in terms of direct current, the photoelectric conversion elements S1-1 to S3-3 also have a capacitive component as a constituent element, so that the potential is maintained.

At this point, no light is generated because no light is incident on the photoelectric conversion elements S1-1 to S3-3. That is, no current flows. In this state, when the light source is turned on in pulses, light is irradiated to the D electrodes (N ⁺ electrodes) of the respective photoelectric conversion elements S1-1 to S3-3, and so-called photocurrent flows. Although the light source is not shown in the drawing, for example, in the case of a copying machine, it is a fluorescent lamp, an LED, a halogen lamp, or the like. An X-ray imaging apparatus is literally an X-ray source. In this case, a scintillator for X-ray visible conversion may be used. In addition, the photocurrent that flows by light is accumulated as charges in each of the photoelectric conversion elements S1-1 to S3-3, and is retained even after the light source is turned off.

Next, the reading period will be described.
The reading operation is performed on the photoelectric conversion elements S1-1 to S1-3 in the first row, the photoelectric conversion elements S2-1 to S2-3 in the second row, and then the photoelectric conversion elements S3-1 in the third row. To S3-3.

  First, a gate pulse is applied from the shift register SR1 to the gate wiring G1 of the switch elements (TFT) T1-1 to T1-3 in order to read out the photoelectric conversion elements S1-1 to S1-3 in the first row. At this time, the high level of the gate pulse is the voltage V (on) supplied from the outside. Thereby, the TFTs (T1-1 to T1-3) are turned on, and the signal charges accumulated in the photoelectric conversion elements S1-1 to S1-3 are transferred to the signal wirings M1 to M3.

Although not shown in FIG. 29 in particular, a read capacitor is added to the signal wirings M1 to M3, and signal charges are transferred to the read capacitors via the TFTs (T1-1 to T1-3). become. For example, the readout capacitance added to the signal wiring M1 is the sum (three) of the inter-electrode capacitance (Cgs) between the gate and the source of each TFT (T1-1 to T3-1) connected to the signal wiring M1. Minutes) and corresponds to C ₂ in FIG. The signal charges transferred to the signal wirings M1 to M3 are amplified by the amplifiers A1 to A3. When the CRES signal is turned on, the CRES signal is transferred to the sample hold capacitors CL1 to CL3, and the CRES signal is turned off and held.

  Subsequently, by applying pulses in the order of the switches Sr1, Sr2, and Sr3 from the shift register SR2, the signals held in the sample and hold capacitors CL1 to CL3 are amplified in the order of the sample and hold capacitors CL1, CL2, and CL3. Output from Ab. As a result, photoelectric conversion signals for one row of the photoelectric conversion elements S1-1, S1-2, and S1-3 are sequentially output. The readout operation of the photoelectric conversion elements S2-1 to S2-3 in the second row is performed in the same manner as the readout operation of the photoelectric conversion elements S3-1 to S3-3 in the third row.

If the signals of the signal wirings M1 to M3 are sampled and held in the sample hold capacitors CL1 to CL3 by the SMPL signal in the first row, the signal wirings M1 to M3 are reset to the GND potential by the CRES signal, and then the gate pulse is applied to the gate wiring G2. Can be applied. That is, the signal charges of the photoelectric conversion elements S2-1 to S2-3 in the second row can be simultaneously transferred in the shift register SR1 while the signal in the first row is subjected to the serial conversion operation in the shift register SR2. it can.
With the above operation, the signal charges of all the photoelectric conversion elements S1-1 to S3-3 from the first row to the third row can be output.

  The operation of the X-ray imaging apparatus described above is an operation for acquiring a single still image by performing a refresh operation, irradiating X-rays, and performing a read operation. In addition, when acquiring continuous moving images, the timing chart shown in FIG. 30 may be repeatedly operated for the number of moving images to be acquired.

  However, when trying to obtain a moving image with an X-ray imaging apparatus having a large number of pixels, it is necessary to further improve the frame frequency. When the refresh operation of the photoelectric conversion elements is performed via the Vs line common to all the photoelectric conversion elements, it is essential to provide one refresh period for one frame. This causes a problem that the frame frequency is decreased, that is, the operation speed is decreased, particularly when a moving image is acquired.

  In general, it is said that the specs required for simple imaging of the chest are an imaging area of 40 cm square or more and a pixel pitch of 200 μm or less. If an X-ray imaging apparatus is manufactured with an imaging area of 40 cm square and a pixel pitch of 200 μm, the number of photoelectric conversion elements reaches 4 million. Refreshing the majority of these pixels at once increases the current that flows during the refresh, and therefore increases the GND and power supply line voltage fluctuations of the X-ray imaging device, thereby enabling stable imaging. I can't.

  Depending on the required image, it is necessary to provide an X-ray irradiation waiting time until these voltage fluctuations are alleviated. Although not shown in FIG. 30, the wait period in FIG. 28 corresponds to this. That is, refreshing the photoelectric conversion devices collectively requires not only one refresh period per frame but also one wait period per frame.

  The present invention has been made in view of the above-described problems. A radiation imaging apparatus capable of performing stable and high-speed moving image capturing by suppressing voltage fluctuations of the GND and the power supply line and eliminating a waiting period for each frame, It is an object to realize the driving method and the radiation imaging system.

The radiation imaging apparatus of the present invention includes a semiconductor layer between a first electrode and a second electrode and an insulating layer between the first electrode, and converts the incident radiation into an electrical signal. And a switch element connected to the first electrode for reading out the electrical signal is arranged in a plurality of rows and columns, and the control is connected to the plurality of switch elements arranged in the row direction. A plurality of wirings are arranged in the column direction, and a plurality of signal wirings connected to the plurality of switch elements arranged in the column direction are arranged in the row direction, and drive signals for conducting the switch elements are provided. A radiation imaging apparatus having a drive circuit unit for giving a row unit to a plurality of the control wirings, the refreshing unit for applying a first bias for refreshing the conversion element to the signal wirings A reset unit that applies a second bias for resetting the signal wiring to the signal wiring, and between the readout of pixels in a predetermined row and the readout of pixels in a row different from the predetermined row In addition, the refresh unit applies the first bias to the signal wiring in a state where the driving circuit unit conducts the switch elements of the pixels in the predetermined row, and the first bias is applied. The reset is performed by the reset unit applying the second bias to the signal wiring that has been completed.
In addition, the radiation imaging apparatus of the present invention has an insulating layer between the semiconductor layer between the first electrode and the second electrode and the first electrode, and converts incident radiation into an electrical signal. A plurality of pixels including a conversion element and a switch element connected to the first electrode and reading the electrical signal are arranged in a row direction and a column direction, and connected to the plurality of switch elements arranged in the row direction. A plurality of control wirings are arranged in the column direction, and a plurality of signal wirings connected to the plurality of switch elements arranged in the column direction are arranged in the row direction, and driving for conducting the switch elements Radiation having a driving circuit unit for supplying signals to the plurality of control wirings in units of rows, and a reading circuit unit connected to the plurality of signal wirings in order to read out the electrical signals in units of rows. Imaging device The reading circuit unit includes a current integration type operational amplifier in a first stage unit, and an electric power transferred from the conversion element via the switch element between an inverting terminal and an output terminal of the operational amplifier. A capacitive element for integrating the signal; and a switch for resetting the capacitive element, and a non-inverting terminal of the operational amplifier includes a first bias for refreshing the conversion element and the reset. A bias supply section for selectively supplying a second bias to be performed, and the driving circuit section between the readout of pixels in a predetermined row and the readout of pixels in a row different from the predetermined row In a state where the switch elements of the pixels in the predetermined row are conducted, the bias supply unit and the switch apply the first bias to the signal wiring, and By first bias applied to apply the second bias to the signal lines has been completed, and is characterized in that for performing the refresh.
The radiation imaging system of this invention detects the said radiation which permeate | transmitted the test subject or the test object, The radiographic imaging apparatus of any one of Claims 1-9, and the electric signal output from the said radiation imaging apparatus digitally An image processing apparatus that performs image processing after conversion, and a display device that displays an image processed by the image processing apparatus are provided.
According to the driving method of the radiation imaging apparatus of the present invention, the incident radiation having an insulating layer between the semiconductor layer between the first electrode and the second electrode and the first electrode is converted into an electrical signal. A plurality of pixels including a conversion element to be connected and a switch element connected to the first electrode for reading out the electrical signal are arranged in a row direction and a column direction, and connected to the plurality of switch elements arranged in the row direction A plurality of control wires arranged in the column direction, and a plurality of signal wires connected to the plurality of switch elements arranged in the column direction are arranged in the row direction, and the switch elements are made conductive. A drive circuit unit for supplying a drive signal to the plurality of control wirings in units of rows, a refresh unit for applying a first bias for refreshing the conversion element to the signal wirings, A reset method for applying a second bias for resetting a signal wiring, the driving method in a radiation imaging apparatus, wherein the readout of pixels in a predetermined row and the readout of pixels in a row different from the predetermined row The refresh circuit applies the first bias to the signal wiring in a state where the drive circuit unit conducts the switch elements of the pixels in the predetermined row, and the reset unit The refresh is performed by applying a second bias to the signal wiring.

  Since the present invention includes the above technical means, an electric signal from a conversion element in any one control wiring is read and transferred row by row by a driving circuit unit (shift register), and then an electric signal in the next control wiring Since it is possible to refresh the conversion elements in the control wiring for which reading has been completed for each row during the period from the transfer to reading, it is unnecessary to provide a refresh period when acquiring continuous moving images. Can do. Thereby, the frame frequency at the time of acquiring a moving image can be increased, and the speed of moving image shooting can be increased. Further, by refreshing the conversion elements for each row, the dark current (transient current) at the time of refreshing can be reduced as compared with the case where all the conversion elements are collectively refreshed. The fluctuation can be suppressed, and a waiting time for reducing the voltage fluctuation can be omitted.

  According to the present invention, since the frame frequency at the time of acquiring a moving image can be increased by sequentially refreshing the conversion elements row by row, it is possible to increase the speed of moving image shooting. In addition, the dark current (transient current) at the time of refresh can be reduced as compared with the case where all the conversion elements are collectively refreshed, and the voltage fluctuation of the GND and the power supply line can be suppressed. It is possible to eliminate the need for providing a waiting time for alleviating the problem.

  Another feature of the present invention is that the conversion element and the switch element are formed of an amorphous silicon semiconductor, so that the conversion element and the switch element can be formed on the same substrate and in the same process. Can be created. For this reason, it is possible to provide a very inexpensive X-ray imaging apparatus with good yield. Moreover, since the obtained moving image can be taken out as an electric signal subjected to photoelectric conversion, it can be easily digitized. This digital information can be performed very efficiently in terms of time and cost as compared with the case of handling analog information when, for example, recording, displaying, and the like are performed to diagnose a subject or a test object. And in the future aging society and IT society, it is possible to create a higher quality medical environment than the present.

  Next, embodiments of the radiation imaging apparatus, the driving method thereof, and the radiation imaging system of the present invention will be described with reference to the drawings. In the present embodiment, as an example of a radiation imaging apparatus, an apparatus having a substrate on which a MIS type photoelectric conversion element similar to the conventional example and a photoelectric conversion element array using an amorphous silicon semiconductor thin film as a semiconductor material of a switch element are formed. I will give you a description.

(First embodiment)
FIG. 1 is an equivalent circuit diagram for one pixel of the X-ray imaging apparatus according to the first embodiment of the present invention.
As shown in FIG. 1, the photoelectric conversion element 101 includes a capacitance component C _i composed of an i layer such as hydrogenated amorphous silicon as a semiconductor photoelectric conversion layer, and an insulating layer such as amorphous silicon nitride (injection of both conductivity type carriers). And a capacitive component C _{SiN made up of a} blocking layer. Further, the junction point between the i layer and the insulating layer (node N in FIG. 1) is that there is no electric field when the photoelectric conversion element 101 is saturated, that is, between the D electrode and the node N (i layer) ( When the (small) state is reached, holes and electrons cannot be stored in the N part because electrons and holes generated by light are recombined.

That is, the potential of the node N does not become higher than the potential of the D electrode. In order to realize the operation in the saturated state, a diode (D1) is connected in parallel to the capacitive component C _i in FIG. That is, the photoelectric conversion element 101 has three components, that is, a capacitive component Ci, a capacitive component C _SiN , and a diode D1.

The TFT 102 is a thin film transistor and is a switch element. Vs is a power source for applying a bias to the D electrode of the photoelectric conversion element 101. C ₂ is a read capacitor added to the signal wiring.

FL is a wavelength converting phosphor for converting an X-ray wavelength into a visible region wavelength, and is disposed at a position in close contact with the TFT 102 directly or indirectly. Gd ₂ O ₂ S, Gd ₂ O ₃ or the like is used for the base material of the phosphor FL, and rare earth elements such as Tb ³⁺ or Eu ³⁺ are used for the emission center. In addition, a phosphor using CsI as a base material, such as CsI: Tl or CsI: Na, is also used.

The switch SW-C is a reset switch for resetting the read capacitor C ₂ (signal wiring) to the reset bias V (reset), and the switch SW-E is used for setting the photoelectric conversion element (G electrode) to the refresh bias V (refresh). This is a switch for refreshing and is controlled by RC1 signal and RC2 signal, respectively. Vg (on) is a power source for turning on the TFT 102 and transferring signal charges to the read capacitor C ₂ , Vg (off) is a power source for turning off the TFT 102, and the switch SW-D is a power source Vg (on ) And the power source Vg (off).

  Further, when refreshing the photoelectric conversion element 101, it is necessary to turn on the switch SW-E to make the refresh bias conductive, and at the same time, set the switch SW-D to the power supply Vg (on) side.

FIG. 2 is a timing chart showing the circuit operation for one pixel of the X-ray imaging apparatus shown in FIG.
A circuit operation for one pixel of a pixel including the photoelectric conversion element 101 and the TFT 102 will be described with reference to FIGS.

First, the X-ray irradiation period will be described.
As shown in FIG. 2, X-rays are irradiated in a pulse shape. X-rays that have passed through the subject are irradiated onto the phosphor FL and converted into visible light. Visible light from the phosphor FL is irradiated onto the semiconductor layer (i layer) and subjected to photoelectric conversion. The hole carriers generated by the photoelectric conversion are accumulated at the interface between the i layer and the insulating layer (injection blocking layer), and increase the potential of the node N. Since the TFT 102 is in an off state, the potential on the G electrode side also rises by the same amount. Note that in the X-ray irradiation period, the switch SW-D is on the V (off) side, and the switches SW-C and SW-E are off.

Next, the transfer operation will be described.
In the transfer operation, the switch SW-D is set to the Vg (on) side and the TFT 102 is turned on. As a result, electron carriers (S _e ) corresponding to the amount of hole carriers (S _h ) stored by X-ray irradiation flow from the C ₂ side to the G electrode side via the TFT 102, and the potential of the read capacitor C ₂ is increased. Raise. At this time, the relationship between S _e and S _h is S _e = S _h × C _SiN / (C _SiN + C _i ).

Since the potential of the read capacitor C ₂ is mainly composed of the capacitance between the electrodes of all TFTs 102 connected to the signal wiring, it is sufficiently larger than the capacitance of the photoelectric conversion element 101. Therefore, the potential increase (ΔVC ₂ ) of the read capacitor C ₂ after charge transfer is sufficiently smaller than the potential decrease (ΔV _G ) of the G electrode. That is, the potential of the read capacitor C ₂ after the transfer is V (reset) + ΔVC ₂ , but shows a potential substantially close to V (reset). At the same time, the potential of the read capacitor C ₂ is amplified through an amplifier and output. In FIG. 1, an amplifier (AMP) is shown in the most basic form, but it functions as an amplifier circuit. Since the reset bias V (reset) is not a signal component, it is canceled separately and only a pure signal component ΔVC ₂ is treated as a signal.

Next, the refresh operation will be described.
In the timing chart of FIG. 2, in the equivalent circuit diagram shown in FIG. 1, Vs = 9 (V), Vg (reset) = 2 (V), V (refresh) = 6 (V), and the capacitance component C _i The potentials of the D electrode, the G electrode, and the node N when the capacitance component C _SiN is equal are shown.
In the refresh operation, the switch SW-C is turned off by the RC1 signal, the switch SW-E is turned on by the RC2 signal, and the switch SW-D is set to the Vg (on) side. In this way, the G electrode of the photoelectric conversion element 101 has a refresh bias V (refresh) = 6V from the potential (V (reset) + ΔVC ₂ ≈V (reset) = 2 (V)) when the signal is transferred. To rise. At the same time, the potential at the node N also rises but does not exceed Vs = 9V. By raising the potential of the node N, a part of the signal charge (hole carrier) stored in the node N is discharged to the D electrode side, and the photoelectric conversion element 101 is refreshed.

Next, the reset operation will be described.
In the reset operation, the switch SW-D is set to the Vg (on) side, the switch SW-C is turned on by the RC1 signal, and the switch SW-E is turned off by the RC2 signal. In this way, the G electrode and the signal line C ₂ of the photoelectric conversion element 101 are reset to the reset bias V (reset). At the same time, the potential of the node N is attenuated from the potential during the refresh operation (9 V in FIG. 2). The attenuation amount ΔV _N is ½ of the potential difference between V (refresh) and V (reset) when the capacitances of the capacitance component C _i and the capacitance component C _SiN are equal, and decreases by 2 V in this description. . Further, the attenuation [Delta] V _N at the node N determines the amount of hole carriers accumulated in the next photoelectric conversion operation.

Here, while the wait period is provided in FIG. 28 showing the conventional example, it is not provided in the timing chart of FIG. The reason will be described below with reference to FIGS.
FIG. 3 is an equivalent circuit diagram of the X-ray imaging apparatus according to the first embodiment. In FIG. 3, only 3 × 3 = 9 pixels are illustrated for simplifying the description of the pixels arranged two-dimensionally in the photoelectric conversion circuit unit 10.

  3, S1-1 to S3-3 are photoelectric conversion elements, T1-1 to T3-3 are switch elements (TFT), and G1 to G3 are for turning on / off the TFTs (T1-1 to T3-3). The gate wirings M1 to M3 are signal wirings, and the Vs line is a wiring for applying a storage bias to the photoelectric conversion element.

The electrodes on the sides of the photoelectric conversion elements S1-1 to S3-3 that are painted black are G electrodes, and the opposite side is a D electrode. Further, although the D electrode is shared with a part of the Vs line, a thin N ⁺ layer is used as the D electrode for the convenience of light incidence. The photoelectric conversion elements S1-1 to S3-3, TFTs (T1-1 to T3-3), gate wirings G1 to G3, signal wirings M1 to M3, and Vs lines are collectively referred to as the photoelectric conversion circuit unit 10.

  The Vs line is biased by the power supply Vs. SR1 is a shift register that applies a driving pulse voltage to the gate wirings G1 to G3. The voltage Vg (on) that turns on the TFTs (T1-1 to T3-3) and the TFTs (T1-1 to T3-3) are supplied. The voltage Vg (off) to be turned off is supplied from the outside to the driving circuit unit (shift register SR1).

The reading circuit unit 20 amplifies the parallel signal output of the signal wirings M1 to M3 in the photoelectric conversion circuit unit 10, converts the signals in series, and outputs them.
RES1 to RES3 are switches for resetting the signal wirings M1 to M3 to a reset bias V (reset). In FIG. 3, the reset bias V (reset) is represented by 0 V (GND). A1 to A3 are amplifiers for amplifying the signals of the signal wirings M1 to M3, CL1 to CL3 are sample and hold capacitors for temporarily storing the signals amplified by the amplifiers A1 to A3, and Sn1 to Sn3 are switches for sample and hold, B1 to B3 are buffer amplifiers, Sr1 to Sr3 are switches for serial conversion of parallel signals, SR2 is a shift register that provides pulses for serial conversion to the switches Sr1 to Sr3, Ab is a buffer that outputs a serially converted signal It is an amplifier.

  RES11 to RES33 are switches for refreshing the G electrode of the photoelectric conversion element 101 to the refresh bias V (refresh) via the TFTs (T1-1 to T3-3), and one side of the switches RES11 to RES33 is provided on one side. A refresh bias V (refresh) is connected.

  FIG. 4 is a timing chart showing the operation of the X-ray imaging apparatus shown in FIG. 3, and shows the operation for two frames. The operation of the photoelectric conversion device in FIG. 3 will be described with reference to this timing chart.

First, the photoelectric conversion period will be described.
The D electrodes of all the photoelectric conversion elements S1-1 to S3-3 are biased to the reading power source Vs (positive potential). All signals of the shift register SR1 are “Lo”, and all TFTs for switching (T1-1 to T3-3) are off. When the light source is turned on in a pulse state in this state, light is irradiated to the D electrodes (N ⁺ electrodes) of the respective photoelectric conversion elements S1-1 to S3-3, and the i layers of the photoelectric conversion elements S1-1 to S3-3 are irradiated. Inside, electron and hole carriers are generated. Electrons move to the D electrode by the reading power source Vs, but holes are stored at the interface between the i layer and the insulating layer in the photoelectric conversion elements S1-1 to S3-3, and are retained even after the power is turned off.

Next, the reading period will be described.
The reading operation is performed on the photoelectric conversion elements S1-1 to S1-3 in the first row, the photoelectric conversion elements S2-1 to S2-3 in the second row, and then the photoelectric conversion elements S3-1 in the third row. To S3-3.

  First, in order to read out the photoelectric conversion elements S1-1 to S1-3 in the first row, a gate pulse is applied from the shift register SR1 to the gate wiring G1 of the switch elements (TFT) T1-1 to T1-3. At this time, the high level of the gate pulse is a voltage of Vg (on) supplied from the outside. Thereby, the TFTs (T1-1 to T1-3) are turned on, and the signal charges accumulated in the photoelectric conversion elements S1-1 to S1-3 are transferred to the signal wirings M1 to M3.

Although not shown in FIG. 3 in particular, a read capacitor is added to the signal wirings M1 to M3, and the signal charges are transferred to the read capacitors via the TFTs (T1-1 to T1-3). become. For example, the readout capacitance added to the signal wiring M1 is the sum (three) of the interelectrode capacitance (Cgs) between the gate and source of each TFT (T1-1 to T3-1) connected to the signal wiring M1. Minutes) and corresponds to C ₂ in FIG. Further, the signal charges transferred to the signal wirings M1 to M3 are amplified by the operational amplifiers A1 to A3. When the SMPL signal is turned on, the SMPL signal is transferred to the sample hold capacitors CL1 to CL3, and the SMPL signal is turned off and held.

  If the signals of the signal wirings M1 to M3 are sampled and held in the sample hold capacitors CL1 to CL3 by the SMPL signal in the first row, the signals of the photoelectric conversion elements S1-1 to S1-3 are output from the photoelectric conversion circuit unit 10. It will be. Therefore, during serial conversion by the switches Sr1 to Sr3 in the readout circuit unit 20, the refresh operation of the photoelectric conversion elements S1-1 to S1-3 in the photoelectric conversion circuit unit 10 and the signal wirings M1 to M3 A reset operation can be performed.

  In the refresh operation of the photoelectric conversion elements S1-1 to S1-3, the switches RES11 to RES33 are turned on by the RC2 signal, and the voltage Vg (on) is applied to the gate wirings of the TFTs (T1-1 to T3-1). As a result, the G electrodes of the photoelectric conversion elements S1-1 to S1-3 are refreshed to the refresh bias V (refresh). After that, the transition is made to the reset operation.

  Subsequently, the reset operation is performed by turning off the switches RES11 to RES33 and turning on the switches RES1 to RES3 in a state where the voltage Vg (on) is applied to the gate wirings of the TFTs (T1-1 to T3-1). The readout capacitance of the signal wirings M1 to M3 and the G electrodes of the photoelectric conversion elements S1-1 to S1-3 are reset to a reset bias V (reset), here, the GND potential.

  After the reset operation is finished, next, a gate pulse can be applied to the gate wiring G2. That is, the signals in the first row are simultaneously refreshed in the photoelectric conversion circuit unit 10 during the serial conversion operation by the shift register SR2, and the signal wirings M1 to M3 are refreshed. By resetting, the signal charges of the photoelectric conversion elements S2-1 to S2-3 in the second row can be transferred to the signal wirings M1 to M3 by the shift register SR1. With the above operation, the signal charges of all the photoelectric conversion elements S1-1 to S3-3 from the first row to the third row can be output.

By repeating the photoelectric conversion period and the readout period, a continuous moving image can be acquired.
The difference between the timing chart shown in the present embodiment and the timing chart of FIG. 30 showing the conventional example is that no refresh period is provided, and the frame frequency for acquiring moving images is increased by the refresh period. There is an advantage that you can. In the conventional example, since all the photoelectric conversion elements are collectively refreshed, it is necessary to provide a wait period for alleviating fluctuations in GND, power supply, etc. due to dark current components during the refresh. In this embodiment, since refresh is performed in units of rows, the number of photoelectric conversion elements to be refreshed at one time is much smaller, so there is no need to provide a special wait period, and the video frame frequency is increased accordingly. Can do.

  In the X-ray imaging apparatus of the present embodiment described above, an example in which X-ray irradiation is performed in a pulse shape has been shown, but X-ray irradiation can also be performed continuously (in a direct current manner). The embodiment in this case will be described below.

FIG. 5 is a timing chart when the X-ray imaging apparatus according to the first embodiment is irradiated with X-rays continuously (in a direct current manner).
The photoelectric conversion period in this case is a period from the end of refresh to the start of transfer. In an actual medical X-ray imaging apparatus, the photoelectric conversion circuit unit is composed of a large number of pixels of N rows × M columns. For example, for the photoelectric conversion element in the first row, the readout period for N-1 rows from the second row to the Nth row excluding transfer, refresh, and reset of its own photoelectric conversion device is substantially photoelectric conversion. It becomes a period. The same applies to the photoelectric conversion elements in other rows, and the readout period for N-1 rows excluding the transfer, refresh, and reset of the own photoelectric conversion elements is the substantial photoelectric conversion period.

  For example, for the photoelectric conversion element in the 100th row, the sum of the readout period from the 101st row to the Nth row and the readout period from the 1st row to the 99th row in the next frame, that is, readout for N−1 rows. The period is a substantial photoelectric conversion period. In other words, when the X-rays are irradiated in a direct current, this photoelectric conversion period extends over two frames, but since all the photoelectric conversion periods are the same, nothing unusual occurs.

  When X-rays are irradiated continuously (in a direct current manner), the X-ray irradiation period shown in FIG. 2 or the photoelectric conversion period shown in FIG. 4 can be omitted, so that the frame rate of moving images can be further increased. There are advantages. In addition, compared to the pulse irradiation method, the intensity of X-rays can be reduced, so there is an advantage that the burden on the tube of the X-ray source can be reduced. Further, since it is not necessary to control the X-ray high-voltage power supply in a pulsed manner, there is an advantage that the burden on the X-ray power supply can be reduced.

(Second Embodiment)
FIG. 6 is an equivalent circuit diagram for one pixel of the X-ray imaging apparatus according to the second embodiment of the present invention. In the equivalent circuit diagram of the first embodiment shown in FIG. 1, the D electrode of the photoelectric conversion element 101 is biased with a constant voltage Vs, whereas in this embodiment, the voltage Vs and the voltage Vref are The switch SW-F can be switched.

  A feature of this embodiment is that it is possible to select whether to apply an applied voltage for refreshing the photoelectric conversion element 101 from the G electrode side or from the D electrode side. For example, when acquiring a single still image, a method of applying a refresh bias from the D electrode side, that is, operating with the timing chart of FIG. 28, while when acquiring a plurality of still images, the G electrode side Then, a refresh bias is applied, that is, the operation is performed according to the timing chart shown in FIG. In this embodiment, a single X-ray imaging apparatus can shoot both a conventional still image shooting mode (shooting mode or still image mode) and a moving image acquisition mode (perspective mode or moving image mode). It becomes possible.

FIG. 7 is an equivalent circuit diagram of the X-ray imaging apparatus according to the second embodiment.
7 is different from FIG. 3 in that the bias line of the sensor can be switched between the voltage Vs and the voltage Vref by the VSC control signal.
FIG. 8 is a schematic diagram of a timing chart for performing imaging by transitioning from the fluoroscopy mode (moving image mode) to the imaging mode (still image mode) of the X-ray imaging apparatus according to the second embodiment.

  FIG. 9 is a timing chart showing an operation in the fluoroscopic mode of the X-ray imaging apparatus shown in FIG. That is, the timing operation of FIG. 8 is repeated in the fluoroscopic mode. During this period, the photographer monitors the fluoroscopic image of the patient in order to determine the position and angle of the subject (patient) for photographing the still image. In general, the X-ray dose during this period is weakly irradiated. When the photographer issues an exposure request signal (intention signal for photographing a still image) to the apparatus, the mode changes from the fluoroscopic mode to the photographing mode. The operation timing in the shooting mode is shown in FIG. In addition, as shown in FIG. 8, the flow of the fluoroscopic mode and the photographing mode is not limited to the single photographing mode, and depending on the photographing composition of the subject to be photographed, the fluoroscopic mode → the photographing mode → the fluoroscopic mode → the photographing mode. May be repeated.

  FIG. 10 is a timing chart showing an example in which the timing chart in the perspective mode of FIG. 8 is different from that in FIG. The difference from FIG. 9 is that X-rays are not irradiated in pulses. Accordingly, since the reading period and the photoelectric conversion period can be performed simultaneously, there is an advantage that the operating frequency in the fluoroscopic mode can be increased. Further, since the X-ray is not operated in a pulsed manner, there is an advantage that the load on the X-ray generation source can be reduced.

  When the X-ray imaging apparatus of the present invention is applied to a fluoroscopic apparatus, in the fluoroscopic mode, a continuous image is acquired from the switch side of the readout circuit unit 20 via the TFT, and positioning is completed by fluoroscopy. When transitioning to the still image shooting mode, it is possible to obtain a still image with a high S / N ratio by refreshing from the switch SW-F. That is, in general, refreshing from the switch SW-F side has higher refresh efficiency and a better S / N ratio than refreshing from the TFT side. When taking a fluoroscopic positioning image that may have a relatively poor S / N ratio, refresh from the switch side of the readout circuit unit 20 is adopted, and a still image that requires a high image quality with a high S / N ratio. When shooting, it makes sense to employ refresh from the switch SW-F side.

(Third embodiment)
FIG. 12 is an equivalent circuit diagram for one pixel of the X-ray imaging apparatus according to the third embodiment. The same components as those in the X-ray imaging apparatus shown in FIG. 1 are denoted by the same reference numerals, and different components will be mainly described below.

  The switch SW-G shown in FIG. 12 is selectively switched to give either the reset bias V (reset) or the refresh bias V (refresh) to the non-inverting terminal (+) of the operational amplifier (AMP). Switch. Cf is a capacitive element for accumulating (integrating) the signal current from the photoelectric conversion element 101 via the TFT 102, and is connected between the inverting terminal (−) of the operational amplifier and the output terminal Vout. The switch SW-H is connected in parallel with the capacitive element Cf and is a switch for resetting the integrated signal charge or refreshing the photoelectric conversion element 101 via the TFT 102, and is controlled by the RC signal.

  Vg (on) is a power source for turning on the TFT 102 and transferring signal charges to the capacitor Cf, and Vg (off) is a power source for turning off the TFT 102. The switch SW-D is a switch for switching between the power supply Vg (on) and the power supply Vg (off).

  When the photoelectric conversion element 101 is refreshed, the switch SW-G must be set to the reset bias V (reset) side, the switch SW-E must be turned on, and the switch SW-D must be set to the power supply Vg (on) side. .

FIG. 13 is a timing chart showing the circuit operation for one pixel of the X-ray imaging apparatus shown in FIG.
A circuit operation for one pixel of a pixel including the photoelectric conversion element 101 and the TFT 102 will be described with reference to FIGS.

  First, since the operation during the X-ray irradiation period is the same as that of the first embodiment described above, description thereof is omitted. However, the switch SW-D during the X-ray irradiation period is on the V (off) side, and the switch SW. -G is on the V (reset) side, and the switch SW-H is turned off.

Next, the transfer period will be described.
In the transfer operation, the switch SW-D is set to the Vg (on) side and the TFT 102 is turned on. By this operation, electron carriers (S _e ) corresponding to the amount (S _h ) of hole carriers stored by X-ray irradiation flow from the C ₂ side to the G electrode side via the TFT 102. As a result, charges are accumulated in the capacitive element Cf, and the potential on the output terminal side of the operational amplifier changes (falls) by the amount of the signal. At this time, the relationship between S _e and S _h is S _e = S _h × C _SiN / (C _SiN + C _i ). Here, the potential of the read capacitor C ₂ does not change because it is virtually grounded by the bias of V (reset) of the non-inverting terminal (+) of the operational amplifier.

Next, the refresh operation will be described.
In the timing chart of FIG. 13, in the equivalent circuit diagram shown in FIG. 12, Vs = 9 (V), Vg (reset) = 2 (V), V (refresh) = 6 (V), and the capacitance component C _i The potentials of the D electrode, the G electrode, and the node N when the capacitance component C _SiN is equal are shown.
In the refresh operation, the switch SW-H is turned on by the RC signal, the switch SW-D is set to the Vg (on) side, and the switch SW-G is set to the V (refresh) side. By this operation, the G electrode of the photoelectric conversion element 101 rises from the potential (V (reset) = 2 (V)) when the signal is transferred to the refresh bias V (refresh) = 6V. At the same time, the potential at the node N also rises but does not exceed Vs = 9V. By raising the potential of the node N, a part of the signal charge (hole carrier) stored in the node N is discharged to the D electrode side, and the 101 refresh operation of the photoelectric conversion element is performed.

Next, the reset operation will be described.
In the reset operation, the switch SW-G is changed from the V (refresh) side to the V (reset) side while the switch SW-D is in the Vg (on) side state and the switch SW-H is in the on state. By this operation, the G electrode of the photoelectric conversion element 101 is reset to the reset bias V (reset). At the same time, the capacitive element Cf connected to the output terminal of the operational amplifier is reset to the reset bias V (reset). That is, in the reset operation in which the potential difference between both terminals of the capacitive element Cf is zero, the potential of the node N is attenuated from the potential during the refresh operation (9 V in FIG. 13). The attenuation ΔV _N is ½ of the potential difference between V (refresh) and V (reset) when the capacitances of the capacitance component C _i and the capacitance component C _SiN are equal. To do. Further, the attenuation [Delta] V _N at the node N determines the quantity of hole carriers to be stored in the next photoelectric conversion operation.

Here, while the wait period is provided in FIG. 28 showing the conventional example, it is not provided in the timing chart of FIG. The reason will be described below with reference to FIGS.
FIG. 14 is an equivalent circuit diagram of the X-ray imaging apparatus according to the third embodiment. In FIG. 14, only 3 × 3 = 9 pixels are illustrated for simplifying the description of the pixels arranged two-dimensionally in the photoelectric conversion circuit unit 10.

  The reading circuit unit 21 reads the parallel signal output from the photoelectric conversion circuit unit 10, converts it in series, and outputs it. A1 to A3 are operational amplifiers in which the signal wirings M1 to M3 and the inverting terminal (−) are respectively connected. Capacitance elements Cf1 to Cf3 are connected between the inverting terminal (−) and the output terminal, respectively. Capacitance elements Cf1 to Cf3 integrate a current based on an output signal from the photoelectric conversion element 101 when the TFT 102 is turned on, and convert it into a voltage amount. RES41 to RES43 are switches that reset the capacitive elements Cf1 to Cf3 to a reset bias V (reset), and are connected in parallel with the capacitive elements Cf1 to Cf3.

  SW-res is a switch for resetting the non-inverting terminals of the operational amplifiers A1 to A3 to a reset bias V (reset) (reset to 0 V in FIG. 14), and SW-ref is a non-inverting switch of the operational amplifiers A1 to A3. This is a switch for refreshing the terminal to a refresh bias V (refresh). These switches are controlled by a “REFRESH” signal. The “REFRESH” signal is configured such that the switch SW-ref is turned on when “Hi”, the switch SW-res is turned on when “Lo”, and the switches are not turned on at the same time.

  FIG. 15 is a timing chart showing the operation of the X-ray imaging apparatus shown in FIG. 14, and shows the operation for two frames. The operation of the photoelectric conversion device in FIG. 14 is described with reference to this timing chart.

First, the photoelectric conversion period will be described.
The D electrodes of all the photoelectric conversion elements S1-1 to S3-3 are biased to the reading power source Vs (positive potential). All signals of the shift register SR1 are “Lo”, and all TFTs for switching (T1-1 to T3-3) are off. When the light source is turned on in a pulse state in this state, light is irradiated to the D electrodes (N ⁺ electrodes) of the respective photoelectric conversion elements S1-1 to S3-3, and the i layers of the photoelectric conversion elements S1-1 to S3-3 are irradiated. Inside, electron and hole carriers are generated. Electrons move to the D electrode by the reading power source Vs, but holes are stored at the interface between the i layer and the insulating layer in the photoelectric conversion elements S1-1 to S3-3, and are held even after the X-rays are turned off.

Next, the reading period will be described.
The reading operation is performed on the photoelectric conversion elements S1-1 to S1-3 in the first row, the photoelectric conversion elements S2-1 to S2-3 in the second row, and then the photoelectric conversion elements S3-1 in the third row. To S3-3.

  First, in order to read out the photoelectric conversion elements S1-1 to S1-3 in the first row, a gate pulse is applied from the shift register SR1 to the gate wiring G1 of the switch elements (TFT) T1-1 to T1-3. At this time, the high level of the gate pulse is a voltage of Vg (on) supplied from the outside. Accordingly, the TFTs (T1-1 to T1-3) are turned on, and the signal charges accumulated in the photoelectric conversion elements S1-1 to S1-3 are passed through the TFTs (T1-1 to T1-3). Current flows, flows into the capacitive elements Cf1 to Cf3 connected to the operational amplifiers A1 to A3, and is integrated.

  Although not shown in FIG. 14 in particular, a read capacitor is added to the signal wirings M1 to M3, and the signal charges are transferred to the read capacitors via the TFTs (T1-1 to T1-3). It will be. However, since the signal wirings M1 to M3 are virtually grounded by the reset bias (GND) of the non-inverting terminals (+) of the operational amplifiers A1 to A3, there is no potential variation due to the transfer operation, and the signal wirings M1 to M3 are held in GND. It is in. That is, the signal charges described above are transferred to the capacitive elements Cf1 to Cf3.

  The output terminals of the operational amplifiers A1 to A3 change as shown in FIG. 4 according to the signal amount of the photoelectric conversion elements S1-1 to S1-3. Since the TFTs (T1-1 to T3-1) are simultaneously turned on, the outputs of the operational amplifiers A1 to A3 change simultaneously. That is, it becomes a parallel output. In this state, when the “SMPL” signal is turned on, the output signals of the operational amplifiers A1 to A3 are transferred to the sample hold capacitors CL1 to CL3, and the SMPL signal is turned off and temporarily held.

  Subsequently, by applying pulses in the order of the switches Sr1, Sr2, and Sr3 from the shift register SR2, the signals held in the sample and hold capacitors CL1 to CL3 are amplified in the order of the sample and hold capacitors CL1, CL2, and CL3. Output from Ab. As a result, photoelectric conversion signals for one row of the photoelectric conversion elements S1-1, S1-2, and S1-3 are sequentially converted in series and output. The readout operation of the photoelectric conversion elements S2-1 to S2-3 in the second row is performed in the same manner as the readout operation of the photoelectric conversion elements S3-1 to S3-3 in the third row.

  When the signals of the operational amplifiers A1 to A3 are sampled and held in the sample hold capacitors CL1 to CL3 by the SMPL signal in the first row, the signals of the photoelectric conversion elements S1-1 to S1-3 are output from the photoelectric conversion circuit unit 10. become. Therefore, during the serial conversion by the switches Sr1 to Sr3 in the readout circuit unit 21, the refresh operation of the photoelectric conversion elements S1-1 to S1-3 in the photoelectric conversion circuit unit 21 and the reset of the capacitive elements Cf1 to Cf3 The action can be performed.

  The refresh operation of the photoelectric conversion elements S1-1 to S1-3 is performed by setting the “REFRESH” signal to “Hi” to turn on the switch SW-ref, and the “RC” signal to turn on the switches RES41 to RES43. Further, this is achieved by applying a voltage Vg (on) to the gate wirings of the TFTs (T1-1 to T3-1). In other words, the G electrodes of the photoelectric conversion elements S1-1 to S1-3 are refreshed to the refresh bias V (refresh) by the refresh operation. After that, the transition is made to the reset operation.

  Subsequently, in the reset operation, the “REFRESH” signal is output while the voltage Vg (on) is applied to the gate wirings of the TFTs (T1-1 to T3-1) and the switches of the switches RES41 to RES43 are in the conductive state. Set to “Lo”. By this operation, the G electrodes of the photoelectric conversion elements S1-1 to S1-3 are reset to the reset bias reset bias V (reset) = GND, and at the same time, the signals accumulated in the capacitive elements Cf1 to Cf3 are reset.

  After the reset operation is finished, next, a gate pulse can be applied to the gate wiring G2. That is, while the signal of the first row is subjected to serial conversion operation by the shift register SR2, the photoelectric conversion elements S1-1 to S1-3 are simultaneously refreshed, the capacitance elements Cf1 to Cf3 are reset, and the second row signal is reset. The signal charges of the photoelectric conversion elements S2-1 to S2-3 can be transferred to the signal wirings M1 to M3 by the shift register SR1. With the above operation, the signal charges of all the photoelectric conversion elements S1-1 to S3-3 from the first row to the third row can be output.

By repeating the above-described photoelectric conversion period and readout period, a continuous moving image can be acquired.
The difference between the timing chart shown in the present embodiment and the timing chart of FIG. 30 showing the conventional example is that no refresh period is provided, and the frame frequency for acquiring moving images is increased by the refresh period. There is an advantage that you can. In the conventional example, since all the photoelectric conversion elements are collectively refreshed, it is necessary to provide a wait period for alleviating fluctuations in GND, power supply, etc. due to dark current components during the refresh. In this embodiment, since refresh is performed in units of rows, the number of photoelectric conversion elements to be refreshed at one time is much smaller, so there is no need to provide a special Wait period, and the video frame frequency is increased by that much. Can do.

  In the X-ray imaging apparatus of the present embodiment described above, an example in which X-ray irradiation is performed in a pulse shape has been shown, but X-ray irradiation can also be performed continuously (in a direct current manner). The embodiment in this case will be described below.

FIG. 16 is a timing chart when the X-ray imaging apparatus according to the third embodiment is irradiated with X-rays continuously (in a direct current manner).
The photoelectric conversion period in this case is a period from the end of refresh to the start of transfer. In an actual medical X-ray imaging apparatus, the photoelectric conversion circuit unit is composed of a large number of pixels of N rows × M columns. For example, for the photoelectric conversion element in the first row, the readout period for the (N−1) th row from the second row to the Nth row excluding transfer, refresh, and reset of its own photoelectric conversion device is substantially the photoelectric conversion period. It becomes. The same applies to the photoelectric conversion elements in other rows, and the readout period for N-1 rows excluding the transfer, refresh, and reset of its own photoelectric conversion elements is the actual photoelectric conversion period.

  For example, for the photoelectric conversion element in the 100th row, the sum of the readout period from the 101st row to the Nth row and the readout period from the 1st row to the 99th row in the next frame, that is, readout for N−1 rows. The period is a substantial photoelectric conversion period. In other words, when the X-rays are irradiated in a direct current, this photoelectric conversion period extends over two frames, but since all the photoelectric conversion periods are the same, nothing unusual occurs.

  When X-rays are irradiated continuously (in a direct current manner), the X-ray irradiation period shown in FIG. 2 or the photoelectric conversion period shown in FIG. 4 can be omitted, so that the frame rate of moving images can be further increased. There are advantages. In addition, compared to the pulse irradiation method, the intensity of X-rays can be reduced, so there is an advantage that the burden on the tube of the X-ray source can be reduced. Further, since it is not necessary to control the X-ray high-voltage power supply in a pulsed manner, there is an advantage that the burden on the X-ray power supply can be reduced.

(Fourth embodiment)
FIG. 17 is an equivalent circuit diagram for one pixel of the X-ray imaging apparatus according to the fourth embodiment of the present invention. In the equivalent circuit diagram of the third embodiment shown in FIG. 12, the D electrode of the photoelectric conversion element 101 is biased with a constant voltage Vs, whereas in this embodiment, the voltage Vs and the voltage Vref are The switch SW-F can be switched.

  A feature of this embodiment is that it is possible to select whether to apply an applied voltage for refreshing the photoelectric conversion element 101 from the G electrode side or from the D electrode side. For example, when a single still image is acquired, a refresh bias is applied from the D electrode side, that is, the operation is performed according to the timing chart of FIG. 28. On the other hand, when a plurality of moving image images are acquired, the G electrode side Then, the operation is performed according to the method of applying the refresh bias, that is, the timing chart shown in FIG. In this embodiment, a single X-ray imaging apparatus can shoot both a conventional still image shooting mode (shooting mode or still image mode) and a moving image acquisition mode (perspective mode or moving image mode). It becomes possible.

FIG. 18 is an equivalent circuit diagram of the X-ray imaging apparatus according to the fourth embodiment.
In the equivalent circuit diagram of FIG. 18, the difference from FIG. 14 is that the sensor bias line can be switched between the voltage Vs and the voltage Vref by the VSC control signal.
FIG. 19 is a schematic diagram of a timing chart for performing imaging by changing from the fluoroscopy mode (moving image mode) to the imaging mode (still image mode) of the X-ray imaging apparatus according to the fourth embodiment.

  FIG. 20 is a timing chart showing an operation in the fluoroscopic mode of the X-ray imaging apparatus shown in FIG. That is, in the fluoroscopic mode, the timing operation in FIG. 19 is repeated. During this period, the photographer monitors the fluoroscopic image of the patient in order to determine the position and angle of the subject (patient) for photographing the still image. In general, the X-ray dose during this period is weakly irradiated. When the photographer issues an exposure request signal (intention signal for photographing a still image) to the apparatus, the mode changes from the fluoroscopic mode to the photographing mode. The operation timing in the photographing mode is shown in FIG. In addition, as shown in FIG. 19, the flow of the fluoroscopy mode and the shooting mode is not limited to the shooting mode only once. Depending on the shooting composition of the subject to be shot, the fluoroscopy mode → the shooting mode → the fluoroscopy mode → the shooting mode ... May be repeated.

  FIG. 21 is a timing chart showing an example in which the chart in the perspective mode in FIG. 19 is different from that in FIG. The difference from FIG. 20 is that X-rays are not irradiated in pulses. Accordingly, since the reading period and the photoelectric conversion period can be performed simultaneously, there is an advantage that the operating frequency in the fluoroscopic mode can be increased. Further, since the X-ray is not operated in a pulsed manner, there is an advantage that the load on the X-ray generation source can be reduced.

  When the X-ray imaging apparatus of the present invention is applied to a fluoroscopic apparatus, in the fluoroscopic mode, a continuous image is acquired from the switch side of the readout circuit unit 21 via the TFT, and positioning is completed by fluoroscopy. When transitioning to the still image shooting mode, it is possible to obtain a still image with a high S / N ratio by refreshing from the switch SW-F. That is, in general, refreshing from the switch SW-F side has higher refresh efficiency and a better S / N ratio than refreshing from the TFT side. When taking a fluoroscopic positioning image that may have a relatively poor S / N ratio, refresh from the switch side of the readout circuit unit 21 is adopted, and a still image that requires a high image quality with a high S / N ratio. When shooting, it makes sense to employ refresh from the switch SW-F side.

(Fifth embodiment)
FIG. 23 is a schematic diagram showing an application example of the radiation imaging apparatus of the present invention to an X-ray diagnostic system.
X-rays 6060 generated by the X-ray tube 6050 pass through the chest 6062 of the patient or subject 6061 and enter a radiation imaging apparatus (image sensor) 6040. This incident X-ray includes information inside the body of the subject 6061. Corresponding to the incidence of X-rays, it is converted into visible light by a phosphor, and this is photoelectrically converted to obtain an electrical signal. This electric signal is converted into a digital signal, subjected to image processing by an image processor 6070, and observed on a display 6080 in a control room.

  Further, this image information can be transferred to a remote place by a transmission means such as a telephone line 6090, and can be displayed on a display 6081 in another place such as a doctor room or stored in a storage means such as an optical disk. It is also possible for a local doctor to make a diagnosis. The image information can also be recorded on the film 6110 by the film processor 6100.

In the above embodiment, the X-ray imaging system has been described as an example. However, the present invention can be applied to an apparatus that converts radiation such as α, β, and γ rays into light and photoelectrically converts the light.
The photoelectric conversion element array of this invention can also be used for the imaging device which detects normal visible light and infrared light. As the switch element that can be used in the present invention, a thin film transistor in which a channel region is formed using a non-single crystal semiconductor such as hydrogenated amorphous silicon is preferably used, and the form thereof is not limited to the lower gate stagger type. An upper gate stagger type, an upper gate coplanar type, or the like may be used.

  Examples of embodiments of the present invention are listed below.

[Embodiment 1] Pixels including a conversion element that converts incident radiation into an electric signal and a switch element that transfers the electric signal are two-dimensionally arranged, and a control wiring that connects the pixels in a row direction; A conversion circuit unit including a signal wiring that reads an electrical signal from the conversion element via the switch element;
A driving circuit unit for sequentially driving the plurality of control wirings;
A readout circuit unit connected to the plurality of signal wirings and reading out an electrical signal from the conversion element for each row;
The read circuit unit includes a refresh unit that applies a first bias to the conversion element that has been read and performs refresh for each row;
A radiation imaging apparatus comprising: reset means for resetting by applying a second bias to the signal wiring using at least one reset switch.

  [Embodiment 2] The read circuit unit includes an amplifying unit that amplifies the electric signal read out to the signal wiring, a storage unit that temporarily stores the amplified electric signal, and the stored electric signal. The radiation imaging apparatus according to embodiment 1, further comprising serial conversion means for serial conversion.

  [Embodiment 3] After the readout, the readout circuit unit drives the refresh means by turning on the switch element and switching the reset switch to the first bias side, and The conversion element is refreshed row by row, and then the reset switch is driven to reset the signal wiring by switching the reset switch to the second bias side. The radiation imaging apparatus according to Embodiment 1 or 2.

  [Embodiment 4] The radiation imaging apparatus according to any one of Embodiments 1 to 3, wherein the conversion element and the switch element include amorphous silicon.

  [Embodiment 5] The radiation imaging apparatus according to any one of Embodiments 1 to 4, wherein the conversion element and the switch element are formed on the same substrate by the same process.

[Embodiment 6] The conversion element includes a first metal thin film layer formed as a lower electrode on a substrate, and amorphous nitridation formed on the first metal thin film layer to prevent passage of electrons and holes. An insulating layer made of silicon, a photoelectric conversion layer made of hydrogenated amorphous silicon formed on the insulating layer, an N-type injection blocking layer formed on the photoelectric conversion layer and blocking hole injection, A transparent conductive layer formed as an upper electrode on the injection blocking layer, or a second metal thin film layer formed on a part of the injection blocking layer.
The switch element is formed on the same substrate as the conversion element, and is formed on the first metal thin film layer formed on the substrate as a lower gate electrode, and on the first metal thin film layer. A gate insulating layer made of amorphous silicon nitride, a semiconductor layer made of hydrogenated amorphous silicon formed on the gate insulating layer, an N-type ohmic contact layer formed on the semiconductor layer, and the ohmic contact layer And a transparent conductive layer or a second metal thin film layer formed as a source / drain electrode,
In the refresh mode, an electric field is applied to the conversion element in a direction in which holes are guided from the photoelectric conversion layer to the second metal thin film layer,
In the photoelectric conversion mode, an electric field is applied to the conversion element in a direction in which holes generated by radiation incident on the photoelectric conversion layer remain in the photoelectric conversion layer and electrons are guided to the second metal thin film layer. ,
Any one of Embodiments 1 to 5, wherein the holes accumulated in the photoelectric conversion layer in the photoelectric conversion mode or the electrons guided to the second metal thin film layer are detected as an optical signal. The radiation imaging apparatus according to Item.

  [Embodiment 7] The radiation imaging apparatus according to any one of Embodiments 1 to 6, further comprising a wavelength converter that performs wavelength conversion of the radiation.

EMBODIMENT 8] The wavelength converter _{is, Gd 2 O 2 S, Gd} 2 O 3, a radiation imaging apparatus according to claim 7, characterized in that a main component one of CsI.

  [Embodiment 9] The radiation imaging apparatus according to any one of Embodiments 1 to 8, further comprising a bias wiring for applying a bias to the conversion element.

[Embodiment 10] The conversion element has at least two electrodes, the switch element is connected to a first electrode, and the bias wiring is connected to a second electrode,
In the moving image mode, the photoelectric conversion element is refreshed by switching the reset switch to the first bias in the readout circuit unit and conducting the switch element.
10. The radiation imaging apparatus according to claim 9, wherein in the still image mode, the conversion element is refreshed by switching a bias with a second switch element connected to the bias wiring.

[Embodiment 11] Control is provided in which pixels including a conversion element that converts incident radiation into an electric signal and a first switch element that transfers the electric signal are two-dimensionally arranged, and the pixels are connected in a row direction. A conversion circuit unit including a wiring and a signal wiring for reading an electrical signal from the conversion element via the first switch element;
A driving circuit unit for sequentially driving the plurality of control wirings;
A readout circuit unit connected to the plurality of signal wirings and reading out an electrical signal from the conversion element for each row;
The readout circuit section includes a current integration type operational amplifier in the first stage section,
Between the inverting terminal and the output terminal of the operational amplifier, a capacitive element for integrating an electric signal transferred from the conversion element via the first switch element, and a first element for resetting the capacitive element 2 switch elements,
On the other hand, the non-inverting terminal of the operational amplifier includes bias supply means for selectively supplying at least two biases of a first bias and a second bias, the first switch element, and the second switch element. A refresh unit that applies a first bias to the conversion element that has been read out and performs refresh for each row; and a second bias that is applied to the capacitive element using the second switch element. A radiation imaging apparatus, comprising: reset means for applying and resetting.

  [Embodiment 12] The reading circuit unit includes a storage unit that temporarily stores the electrical signal read from the conversion element by the current integrating operational amplifier, and a serial conversion unit that serially converts the stored electrical signal. The radiation imaging apparatus according to embodiment 11, further comprising:

  [Embodiment 13] After the readout, the readout circuit unit conducts the first switch element, conducts the second switch element, and drives the bias supply means to operate the operational amplifier. By supplying the first bias to the non-inverting terminal, the conversion element is refreshed row by row, and then the bias supply means is driven while the second switch element is turned on. 13. The radiation imaging apparatus according to claim 11, wherein the capacitor element is reset by supplying the second bias to the non-inverting terminal.

  [Embodiment 14] The radiation imaging apparatus according to any one of Embodiments 11 to 13, wherein the conversion element and the first switch element include amorphous silicon.

  [Embodiment 15] The radiation imaging apparatus according to any one of Embodiments 11 to 14, wherein the conversion element and the first switch element are formed on the same substrate by the same process. .

[Embodiment 16] The conversion element includes a first metal thin film layer formed as a lower electrode on a substrate, and amorphous nitridation formed on the first metal thin film layer to prevent passage of electrons and holes. An insulating layer made of silicon, a photoelectric conversion layer made of hydrogenated amorphous silicon formed on the insulating layer, an N-type injection blocking layer formed on the photoelectric conversion layer and blocking hole injection, A transparent conductive layer formed as an upper electrode on the injection blocking layer, or a second metal thin film layer formed on a part of the injection blocking layer.
The first switch element is formed on the same substrate as the conversion element, and a first metal thin film layer formed as a lower gate electrode on the substrate, and on the first metal thin film layer A formed gate insulating layer made of amorphous silicon nitride, a semiconductor layer made of hydrogenated amorphous silicon formed on the gate insulating layer, an N-type ohmic contact layer formed on the semiconductor layer, and the ohmic contact A transparent conductive layer or a second metal thin film layer formed as a source / drain electrode on the contact layer;
In the refresh mode, an electric field is applied to the conversion element in a direction in which holes are guided from the photoelectric conversion layer to the second metal thin film layer,
In the photoelectric conversion mode, an electric field is applied to the conversion element in a direction in which holes generated by radiation incident on the photoelectric conversion layer remain in the photoelectric conversion layer and electrons are guided to the second metal thin film layer. ,
Any one of the embodiments 11 to 15, wherein the holes accumulated in the photoelectric conversion layer or the electrons guided to the second metal thin film layer are detected as an optical signal in the photoelectric conversion mode. The radiation imaging apparatus according to Item.

  [Embodiment 17] The radiation imaging apparatus according to any one of Embodiments 11 to 16, further comprising a wavelength converter that performs wavelength conversion of the radiation.

[Embodiment 18] The radiation imaging apparatus according to Embodiment 17, wherein the wavelength converter includes any one of Gd ₂ O ₂ S, Gd ₂ O ₃ , and CsI as a main component.

  [Embodiment 19] The radiation imaging apparatus according to any one of Embodiments 11 to 18, further comprising a bias wiring for applying a bias to the conversion element.

[Embodiment 20] The conversion element has at least two electrodes, the first switch element is connected to a first electrode, and the bias wiring is connected to a second electrode,
In the moving image mode, the refresh operation of the conversion element is performed by turning on the first switch element,
The radiation imaging apparatus according to Embodiment 19, wherein in the still image mode, the conversion element is refreshed by switching a bias connected to the bias wiring.

Embodiment 21 A radiation source for irradiating a subject or test subject with radiation,
The radiation imaging apparatus according to any one of Embodiments 1 to 20 for detecting the radiation,
An image processing apparatus for digitally converting an electrical signal output from the radiation imaging apparatus and performing image processing;
A radiation imaging system comprising: a display device that displays an image processed by the image processing device.

[Embodiment 22] Pixels including a conversion element that converts incident radiation into an electric signal and a switch element that transfers the electric signal are two-dimensionally arranged, and a control wiring that connects the pixels in a row direction; A conversion circuit unit including a signal wiring that reads an electrical signal from the conversion element via the switch element;
A driving circuit unit for sequentially driving the plurality of control wirings;
A driving method in a radiation imaging apparatus having a readout circuit unit connected to the plurality of signal wirings and reading out an electrical signal from the conversion element for each row,
A refresh process for performing refresh for each row by applying a first bias to the conversion element read by the read circuit unit;
And a reset process for resetting the signal wiring by applying a second bias to the signal wiring using at least one reset switch.

2 is an equivalent circuit diagram for one pixel of the X-ray imaging apparatus according to the first embodiment of the present invention. FIG. 3 is a timing chart showing a circuit operation for one pixel of the X-ray imaging apparatus shown in FIG. 1. 1 is an equivalent circuit diagram of an X-ray imaging apparatus in a first embodiment. 4 is a timing chart showing an operation of the X-ray imaging apparatus shown in FIG. 3. It is a timing chart at the time of irradiating X-rays continuously (in direct current) to the X-ray imaging apparatus in the first embodiment. It is an equivalent circuit diagram for 1 pixel of the X-ray imaging device in the 2nd Embodiment of this invention. It is an equivalent circuit schematic of the X-ray imaging device in 2nd Embodiment. It is a timing chart which changes to the imaging | photography mode (still image mode) from fluoroscopic mode (moving image mode) of the X-ray imaging device in 2nd Embodiment, and image | photographs. FIG. 9 is a timing chart of the fluoroscopic mode in FIG. 8. FIG. 9 is another timing chart of the fluoroscopic mode in FIG. 8. FIG. 9 is a timing chart of the shooting mode in FIG. 8. FIG. 9 is an equivalent circuit diagram for one pixel of an X-ray imaging apparatus according to a third embodiment of the present invention. 13 is a timing chart illustrating a circuit operation for one pixel of the X-ray imaging apparatus illustrated in FIG. 12. It is an equivalent circuit schematic of the X-ray imaging device in 3rd Embodiment. It is a timing chart which shows operation | movement of the X-ray imaging device shown in FIG. It is a timing chart at the time of irradiating the X-ray imaging device in 3rd Embodiment continuously (in direct current) with X-rays. It is an equivalent circuit diagram for 1 pixel of the X-ray imaging device in the 4th Embodiment of this invention. It is an equivalent circuit schematic of the X-ray imaging device in 4th Embodiment. 10 is a schematic diagram of a timing chart for performing imaging by transitioning from a fluoroscopy mode (moving image mode) to an imaging mode (still image mode) of the X-ray imaging apparatus according to the fourth embodiment. FIG. 20 is a timing chart of the perspective mode in FIG. 19. FIG. FIG. 20 is another timing chart of the perspective mode in FIG. 19. FIG. FIG. 20 is a timing chart of the shooting mode in FIG. 19. FIG. It is the schematic which showed the example of application to the X-ray diagnostic system of the radiation imaging device by this invention. It is a top view of the photoelectric conversion board | substrate which showed the prior art example and comprised using the amorphous silicon semiconductor thin film for the material of a photoelectric conversion element and a switch element. It is sectional drawing between AB of FIG. FIG. 26 is an energy band diagram for explaining the device operation of the photoelectric conversion element shown in FIGS. 24 and 25. It is a photoelectric conversion circuit diagram for 1 pixel of the pixel which shows a prior art example and is comprised including a photoelectric conversion element and TFT. 28 is a timing chart illustrating an operation in the photoelectric conversion circuit for one pixel of the pixels illustrated in FIG. 27. It is a two-dimensional circuit diagram of a conventional photoelectric conversion device. 30 is a timing chart illustrating an operation of the photoelectric conversion apparatus illustrated in FIG. 29.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10,100 Photoelectric conversion circuit part 20, 21, 200 Reading circuit part 101, S1-1 to S3-3 Photoelectric conversion element 102, T1-1 to T3-3 Switch element (TFT)
103 Insulating substrate 104 First metal thin film layer 105 Second metal thin film layer 106 Gate drive wiring 107 Matrix signal wiring 110 Contact hole portion 111 a-SiN insulating thin film layer 112 a-Si semiconductor thin film layer 113 N ⁺ layer 114 Wiring Cross section 115 Protective films A1 to A3, B1 to B3, Ab Operational amplifier FL, Fl Phosphors G1 to G3 for converting X-rays into visible light Gate drive wirings M1 to M3 Matrix signal wirings Cf1 to Cf3 Integration capacitors RES1 to RES3 and RES11 RES33, RES41 to RES43 Reset switch Sn1 to Sn3 Transfer switch Sr1 to Sr3 Read switch SR1 Shift register (for switch element)
SR2 Shift register (for readout switch)
Vref Refresh power supply Vs Bias power supply V (reset) Reset power supply V (refresh) Refresh power supply Vg (on) Power supply Vg (off) for turning on the TFT Power supply SW-A for turning off the TFT SW-B for switching the bias Switch SW-C for turning on / off TFT Switch SW-D for resetting signal wiring Switch SW-E for turning on / off TFT SW-F for refresh SW-F Switch SW-G for switching bias Switch SW-H for applying a bias to the (+) terminal of the operational amplifier Switch SW-res for resetting the capacitive element Cf Switch SW-ref for applying a reset bias Switch for applying a refresh bias

Claims (11)

A semiconductor element between the first electrode and the second electrode and an insulating layer between the first electrode and a conversion element that converts incident radiation into an electrical signal and connected to the first electrode And a plurality of pixels including a switch element for reading out the electric signal are arranged in a row direction and a column direction, and a plurality of control wirings connected to the plurality of switch elements arranged in the row direction are arranged in the column direction. And a plurality of signal lines connected to the plurality of switch elements arranged in the column direction are arranged in the row direction, and a drive signal for conducting the switch elements is provided to the plurality of control lines in a row unit. A radiation imaging apparatus having a driving circuit section for providing
A refresh unit for applying a first bias to the signal wiring for refreshing the conversion element;
A reset unit that applies a second bias for resetting the signal wiring to the signal wiring;
Have
In a state where the driving circuit unit conducts the switch element of the pixel of the predetermined row between the reading of the pixel of the predetermined row and the reading of the pixel of the row different from the predetermined row, the refresh unit The refresh is performed by applying the first bias to the signal wiring and applying the second bias to the signal wiring after the application of the first bias is completed. A radiation imaging apparatus. In order to read out the electrical signal in units of rows, it further includes a readout circuit unit connected to the plurality of signal lines,
The radiation imaging apparatus according to claim 1, wherein the readout circuit unit includes the refresh unit and the reset unit. A semiconductor element between the first electrode and the second electrode and an insulating layer between the first electrode and a conversion element that converts incident radiation into an electrical signal and connected to the first electrode And a plurality of pixels including a switch element for reading out the electric signal are arranged in a row direction and a column direction, and a plurality of control wirings connected to the plurality of switch elements arranged in the row direction are arranged in the column direction. And a plurality of signal lines connected to the plurality of switch elements arranged in the column direction are arranged in the row direction, and a drive signal for conducting the switch elements is provided to the plurality of control lines in a row unit. A radiation imaging apparatus comprising: a driving circuit unit for providing a read signal; and a readout circuit unit connected to the plurality of signal wirings in order to perform readout of the electrical signal in units of rows,
The readout circuit section includes a current integration type operational amplifier in the first stage section,
Between the inverting terminal and the output terminal of the operational amplifier, a capacitive element for integrating an electric signal transferred from the conversion element via the switch element, and a switch for resetting the capacitive element Prepared,
A non-inverting terminal of the operational amplifier is connected to a bias supply unit that selectively supplies a first bias for refreshing the conversion element and a second bias for performing the reset,
The bias supply unit in a state in which the driving circuit unit conducts the switch element of the pixel in the predetermined row between the readout of the pixel in the predetermined row and the readout of the pixel in a row different from the predetermined row. And the switch applies the first bias to the signal wiring, and applies the second bias to the signal wiring for which the application of the first bias is completed. A radiation imaging apparatus.   The readout circuit unit includes a refresh unit that supplies the first bias, a reset unit that supplies the second bias, a storage unit that temporarily stores the electrical signal, and a stored electrical signal. The radiation imaging apparatus according to claim 3, further comprising a serial conversion unit that performs serial conversion.   2. A bias wiring connected to the second electrode of the conversion element for applying a bias to the conversion element is further provided, and the conversion element and the switch element are formed including amorphous silicon. The radiation imaging apparatus of any one of -4.   The radiation imaging apparatus according to claim 1, wherein the conversion element and the switch element are formed on the same substrate by the same process. The conversion element includes a first metal thin film layer formed as the first electrode on a substrate, and amorphous silicon nitride formed on the first metal thin film layer and blocking passage of electrons and holes. The insulating layer, the semiconductor layer made of hydrogenated amorphous silicon formed on the insulating layer, an N-type injection blocking layer formed on the semiconductor layer for blocking hole injection, and the injection A transparent conductive layer formed as the second electrode on the blocking layer or a second metal thin film layer formed on a part of the injection blocking layer,
The switch element is formed on the same substrate as the conversion element, a first metal thin film layer formed as a gate electrode on the substrate, and an amorphous formed on the first metal thin film layer. A gate insulating layer made of silicon nitride, an amorphous silicon layer made of hydrogenated amorphous silicon formed on the gate insulating layer, an N-type ohmic contact layer formed on the amorphous silicon layer, and the ohmic contact layer A transparent conductive layer or a second metal thin film layer formed thereon as a source or drain electrode,
In the refresh mode, an electric field is applied to the conversion element in a direction in which holes are guided from the semiconductor layer to the second metal thin film layer,
In the photoelectric conversion mode, an electric field is applied to the conversion element in a direction in which holes generated by radiation incident on the semiconductor layer remain in the semiconductor layer and electrons are guided to the second metal thin film layer.
7. The method according to claim 1, wherein the holes accumulated in the semiconductor layer by the photoelectric conversion mode or the electrons guided to the second metal thin film layer are detected as an optical signal. The radiation imaging apparatus described in 1.   The radiation imaging apparatus according to claim 1, further comprising a wavelength converter that performs wavelength conversion of the radiation. The radiation imaging apparatus according to claim 8, wherein the wavelength converter includes, as a main component, any one of Gd ₂ O ₂ S, Gd ₂ O ₃ , and CsI. The radiation imaging apparatus according to any one of claims 1 to 9, which detects the radiation transmitted through a subject or a test object,
An image processing apparatus for digitally converting an electrical signal output from the radiation imaging apparatus and performing image processing;
A radiation imaging system comprising: a display device that displays an image processed by the image processing device. A semiconductor element between the first electrode and the second electrode and an insulating layer between the first electrode and a conversion element that converts incident radiation into an electrical signal and connected to the first electrode And a plurality of pixels including a switch element for reading out the electric signal are arranged in a row direction and a column direction, and a plurality of control wirings connected to the plurality of switch elements arranged in the row direction are arranged in the column direction. And a plurality of signal lines connected to the plurality of switch elements arranged in the column direction are arranged in the row direction, and a drive signal for conducting the switch elements is provided to the plurality of control lines in a row unit. A driving circuit section for applying the first and second biases for applying a first bias for refreshing the conversion element to the signal wiring, and a second for resetting the signal wiring to the signal wiring. A reset unit for applying a bias, a driving method in a radiation image pickup apparatus having,
Between the readout of pixels in a predetermined row and the readout of pixels in a row different from the predetermined row,
The reset unit applies the second bias after the refresh unit applies the first bias to the signal wiring in a state where the driving circuit unit conducts the switch elements of the pixels in the predetermined row. A method of driving a radiation imaging apparatus, wherein the refreshing is performed by applying the signal wiring.

Images