JP2011041075A - Radioactive image photographing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radioactive image photographing apparatus which performs dark read processing in a practical time while maintaining accuracy of an offset correction. <P>SOLUTION: The radioactive image photographing apparatus 1,100 includes: a plurality of radioactive detecting elements 7; switch means 8; a current detecting means 43 detecting a current flowing in a device by the irradiation of radioactive rays; and a control means 22 detecting the start of the irradiation of at least radioactive rays on the basis of the value of the detected current. The control means 22 applies an off voltage Voff to each switch means 8 before radioactive image photographing and stores dark charges in each radioactive detecting element 7, applies an on voltage Von to each switch means 8 and applies the off voltage Voff to each switch means 8 again when detecting the start of the irradiation of the radioactive rays. The control means 22 applies the on voltage Von to each switch means 8 at the same time interval as the applying time T2-T1 of the on voltage Von to each switch means 8 at radioactive image photographing for dark reading processing, and conducts the dark reading processing. T1 represents the time bringing each switch means 8 to an on state and T2 the irradiation start time of radioactive rays. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a radiographic image capturing apparatus, and more particularly to a radiographic image capturing apparatus capable of detecting the start of radiation irradiation and the like by the apparatus itself.

  A so-called direct type radiographic imaging device that generates electric charges by a detection element in accordance with the dose of irradiated radiation such as X-rays and converts it into an electrical signal, or other radiation such as visible light with a scintillator or the like. Various so-called indirect radiographic imaging devices have been developed that convert charges to electromagnetic waves after being converted into electrical signals by generating electric charges with photoelectric conversion elements such as photodiodes in accordance with the energy of the converted and irradiated electromagnetic waves. Yes. In the present invention, the detection element in the direct type radiographic imaging apparatus and the photoelectric conversion element in the indirect type radiographic imaging apparatus are collectively referred to as a radiation detection element.

  This type of radiographic imaging apparatus is known as an FPD (Flat Panel Detector), and conventionally formed integrally with a support base (or a bucky apparatus) (see, for example, Patent Document 1). A portable radiographic imaging device in which an element or the like is housed in a housing has been developed and put into practical use (see, for example, Patent Documents 2 and 3).

  By the way, in these radiographic imaging apparatuses, particularly portable radiographic imaging apparatuses, information on the start and end of radiation irradiation is transmitted to the radiographic imaging apparatus from an external device such as a computer that manages the radiation irradiation apparatus and system. Accordingly, the radiation image capturing apparatus may be configured to read image data from each radiation detection element after the radiation irradiation ends.

  However, for that purpose, an interface between the radiation irradiating apparatus and the computer and the radiation imaging apparatus must be established, and a control configuration must be constructed in the entire system including the radiation irradiating apparatus and the computer. The configuration for recognizing the start and end of irradiation is large. For this reason, it is desirable that the radiation imaging apparatus itself can detect the start and end of radiation irradiation.

  In order to detect the start of radiation irradiation by the radiographic imaging apparatus itself, a sensor or the like is provided in the radiographic imaging apparatus so that the sensor can detect the start or end of radiation irradiation. Although it is possible, a space for arranging the sensor in the radiographic image capturing apparatus is required, and the apparatus becomes large. Further, when the sensor is provided, there is a problem that a large amount of electric power is consumed for driving the sensor, and in particular, a portable radiographic imaging apparatus consumes a built-in battery.

  Therefore, as shown in FIG. 7 to be described later, for example, it is configured to detect a bias line 9 for applying a bias voltage from the bias electrode 14 to each radiation detection element 7 and a current flowing through the connection 10 to detect radiation. Is used to detect the start and end of radiation irradiation by increasing or decreasing the current value by utilizing the fact that an electron-hole pair is generated in each radiation detection element 7 and a current flows in the bias line 9. Has been proposed (see Patent Document 4).

JP-A-9-73144 JP 2006-058124 A JP-A-6-342099 US Pat. No. 7,211,803

  By the way, when detecting the current flowing through the bias line 9 and the connection 10 as described above and detecting the start or end of radiation irradiation by increasing or decreasing the current value, the switch means connected to each radiation detection element 7 is used. When each TFT 8 (Thin Film Transistor; see FIG. 7 and the like) is in an ON state and the gate of each TFT 8 is in an open state, a current flowing through the bias line 9 and the connection line 10 flows with radiation. easy. Further, in each radiation detection element 7, so-called dark charges are generated by thermal excitation or the like due to the heat of each radiation detection element 7 itself, but by turning each TFT 8 on before radiation irradiation as described above, It is also possible to remove dark charges generated in each radiation detection element 7 from each radiation detection element 7.

  Thus, since it becomes easy to detect the increase / decrease in the current for detecting the start of radiation irradiation, and since the dark charge generated in the radiation detection element 7 can be removed, when detecting the start of radiation irradiation, As shown at time T1 in the timing chart shown in FIG. 16, the on-voltage Von is applied to the lines L1 to Lx of the scanning line 5 from the gate driver 15b (see FIG. 7) of the scanning driving means 15 to turn on the TFTs 8. Often configured to keep

If the TFT 8 is kept on even after the start of radiation irradiation, the charge generated in each radiation detection element 7 due to the radiation irradiation flows out without being accumulated in the radiation detection element 7. When the start of radiation irradiation is detected at T2, the voltage applied to each TFT 8 from the gate driver 15b of the scanning drive means 15 via each line L1 to Lx of the scanning line 5 is switched to the off voltage Voff, and each TFT 8 is turned on. Switched off. Then, after the irradiation with radiation, in order to read out the electric charge accumulated in each radiation detection element 7, the on-voltage Von is applied to each line L 1 to Lx of the scanning line 5 while being sequentially switched (time T 3 _{1 to} T 3 _x Reference), electric charge (image data) is read from each radiation detection element 7.

As described above, dark charges are accumulated in the radiation detection elements 7 during the periods ΔT _{1 to} ΔT _x in which the TFTs 8 are turned off, and are read together with the charges (image data). Since it is superimposed on the image data as a so-called offset, each TFT 8 is normally turned on / off in the same manner as in the radiographic image capture after the radiographic image is not irradiated, and dark charges are applied to the radiation detection elements 7. A so-called dark reading process is performed in which the data is stored and read out. The offset is calculated based on the so-called dark reading value obtained by this dark reading process, and offset correction is performed to obtain true image data by subtracting it from the image data on which the offset is superimposed. Is called.

  In order to accumulate dark charges and read out as dark reading values under the same conditions as in radiographic imaging as much as possible, in the dark reading process, the time interval T5-T4 (see FIG. 16) for turning on each TFT 8 is normally It is adjusted so as to be the same time interval as the time interval T2-T1 in which each TFT 8 is turned on in radiographic imaging.

  However, when the time interval T2-T1 from when the TFTs 8 are turned on at the time T1 to the start of radiation irradiation takes longer, for example, several tens of seconds during radiographic image capture, The time interval T5-T4 for turning on the TFT 8 must be several tens of seconds. However, this takes too much time for the dark reading process and is not realistic (hereinafter referred to as problem 1).

  On the other hand, the time interval T2-T1 in which each TFT 8 is turned on at the time of radiographic imaging takes several tens of seconds as described above, but the time interval T5-T4 in which each TFT 8 is turned on in the dark reading process. If, for example, the time is shortened to about 1 second, at the time T2, each TFT 8 is turned off from the state where the dark charge is sufficiently removed from the inside of each radiation detection element 7 at the time of radiographic imaging, and the accumulation of dark charge starts. On the other hand, in the dark reading process, the time interval T5-T4 at which each TFT 8 is turned on is short, and each TFT 8 is turned off before dark charges are sufficiently removed, and accumulation of dark charges is started. It becomes like this.

  Therefore, even if the offset is calculated based on the dark reading value obtained in this way, the calculated offset is not necessarily the offset due to the dark charge accumulated in each radiation detection element 7 at the time of radiographic image capturing. It will not be the same value. For this reason, even if the offset obtained by the dark reading process is subtracted from the image data, true image data cannot always be obtained, and the accuracy of the offset correction is reduced (hereinafter, this is a problem). It is called point 2.)

  The present invention has been made in view of the above-described problems, and provides a radiographic imaging device capable of performing dark reading processing within a realistic time while maintaining the accuracy of offset correction. For the purpose.

In order to solve the above-described problem, the radiographic imaging device of the present invention includes:
A plurality of scanning lines and a plurality of signal lines arranged to cross each other, and the plurality of the plurality of radiation detecting elements arranged two-dimensionally in each area partitioned by the scanning lines and a plurality of signal lines ,
Are arranged for each said radiation detecting element, through the connected the scan lines holding the charge generated in the radiation detection element off voltage is applied, and the ON voltage is applied from the radiation detection element Switch means for releasing the charge;
Scanning drive means for switching between the on-voltage and the off-voltage applied to the scanning line;
Current detection means for detecting a current flowing in the apparatus by irradiation of radiation;
Control means for detecting at least the start of radiation irradiation based on the value of the current detected by the current detection means;
With
The control means includes
Before the radiation is emitted by the radiation image capturing, after the off-state voltage is applied to to accumulate dark charges in said each of the radiation detection element to the respective switching means via the respective scan lines from said scan driver means , Applying the ON voltage to each of the switch means,
When the start of radiation irradiation is detected, the off-voltage is applied again to the switch means,
Dark During the reading process, the said radiation image capturing the same amount time intervals each switching means and the time interval until the application of the off voltage again by applying the on voltage to each switch means upon A dark reading process is performed after an on voltage is applied and the voltage applied to each of the switch means is switched to the off voltage.

Moreover, the radiographic imaging device of the present invention is
A plurality of scanning lines and a plurality of signal lines arranged so as to intersect with each other; a plurality of radiation detecting elements arranged in a two-dimensional manner in each region partitioned by the plurality of scanning lines and the plurality of signal lines; ,
When an off voltage is applied via the connected scanning line, the charge generated in the radiation detection element is retained for each radiation detection element, and when the on voltage is applied, the radiation detection element Switch means for releasing the charge;
Scanning drive means for switching between the on-voltage and the off-voltage applied to the scanning line;
Current detection means for detecting a current flowing in the apparatus by irradiation of radiation;
Control means for detecting at least the start of radiation irradiation based on the value of the current detected by the current detection means;
With
The control means includes
Before radiation is emitted in radiographic imaging, the voltage applied from the scanning drive means to the switch means via the scan lines is alternately repeated between the on voltage and the off voltage,
When the start of radiation irradiation is detected in a state where the on-voltage is applied to each switch means, the off-voltage is applied to each switch means,
In the dark reading process, the switch means is applied for the same time interval as the time interval from the last application of the on-voltage to the switch means during the radiographic image capture to the application of the off-voltage again. A dark reading process is performed after applying the ON voltage to the switching means and switching the voltage applied to each switch means to the OFF voltage.

Moreover, the radiographic imaging device of the present invention is
A plurality of scanning lines and a plurality of signal lines arranged so as to intersect with each other; a plurality of radiation detecting elements arranged in a two-dimensional manner in each region partitioned by the plurality of scanning lines and the plurality of signal lines; ,
When an off voltage is applied via the connected scanning line, the charge generated in the radiation detection element is retained for each radiation detection element, and when the on voltage is applied, the radiation detection element Switch means for releasing the charge;
Scanning drive means for switching between the on-voltage and the off-voltage applied to the scanning line;
Current detection means for detecting a current flowing in the apparatus by irradiation of radiation;
Control means for detecting at least the start of radiation irradiation based on the value of the current detected by the current detection means;
An input means for inputting information to irradiate radiation when irradiated with radiation;
With
The control means includes
When the on-voltage is applied to the switch means via the scanning lines from the scanning drive means before radiation is emitted in radiographic imaging, and the information is input from the input means, When the voltage applied to the switch means is switched to the off voltage and dark charges are accumulated in the radiation detecting elements, the voltage applied to the switch means is switched to the on voltage and the start of radiation irradiation is detected. , Applying the off-voltage again to each switch means,
In the dark reading process, the radio frequency image is captured by the switch means at the same time interval from when the on voltage is applied to the switch means until the off voltage is applied again. A dark reading process is performed after an on voltage is applied and the voltage applied to each of the switch means is switched to the off voltage.

  According to the radiographic imaging apparatus of the system as in the present invention, in the reset process of each radiation detection element before radiographic imaging, the voltage applied to each switch means is temporarily applied while the on-voltage is applied to each switch means. Is switched to an off voltage to bring each radiation detection element into a charge accumulation state, and then an on voltage is applied again to wait for the start of radiation irradiation.

  Therefore, each radiation detection element is configured to periodically apply an on-voltage to each switch means in a reset process before radiographic imaging, or switch the voltage applied to each switch means to an off-voltage based on a signal from the input means. In the charge accumulation state, it is possible to shorten the time interval from the last application of the on-voltage to each switch means until the start of radiation irradiation is detected and the off-voltage is applied again.

  In the reset process of each radiation detection element before the dark reading process, the on-voltage is applied to each switch unit for the same time interval as the time interval at which each switch unit was turned on in the reset process before the radiographic image capturing and reset. Since the processing is configured to be performed, it is possible to accurately prevent the time required for the dark reading process including the reset process before the dark reading process from being increased, and the dark reading process can be performed within a realistic time. It becomes possible. In the present invention, it is possible to solve the above-mentioned problem 1.

  In addition, since the voltage applied to each switch means is temporarily switched to the off voltage in the reset process before radiographic image capturing and each radiation detection element is set in the charge accumulation state, as described in Problem 2 described above, Unlike the case where the dark charge in each radiation detection element is sufficiently removed by turning each switch means on, the amount of residual charge such as dark charge remaining on each radiation detection element at the start of radiation irradiation and Thus, it is possible to make the amount of residual charge remaining in each radiation detection element at the same level at the end of the reset process before the dark reading process.

  Therefore, if the offset is calculated based on the dark reading value obtained in the dark reading process, the calculated offset is almost the same value as the offset due to the dark charge accumulated in each radiation detection element at the time of radiographic image capturing. Therefore, true image data can be obtained accurately by subtracting the offset obtained by the dark reading process from the image data, and the accuracy of offset correction can be maintained and improved. In the present invention, it is possible to solve the above-mentioned problem 2.

It is a perspective view which shows the radiographic imaging apparatus which concerns on 1st Embodiment. It is sectional drawing which follows the AA line in FIG. It is a top view which shows the structure of the board | substrate of a radiographic imaging apparatus. It is an enlarged view which shows the structure of the radiation detection element, TFT, etc. which were formed in the small area | region on the board | substrate of FIG. It is sectional drawing which follows the XX line in FIG. It is a side view explaining the board | substrate with which COF, a PCB board | substrate, etc. were attached. It is a block diagram showing the equivalent circuit of a radiographic imaging apparatus. It is a block diagram showing the equivalent circuit about 1 pixel which comprises a detection part. It is an equivalent circuit diagram showing the structure of a current detection means. It is a graph showing the change of the voltage value etc. in a correlated double sampling circuit. It is a figure showing the timing chart in the reset process before radiographic imaging of 1st Embodiment. It is a graph showing the example of the voltage value corresponded to the electric current detected by an electric current detection means, (A) is the state where irradiation of radiation was started and TFT was turned off, (B) is the irradiation end of radiation. Represents the state. It is a figure showing the timing chart in the reset process before a radiographic image photography, a read-out process, the reset process before a dark reading process, and a dark reading process. It is a perspective view which shows the radiographic imaging apparatus which concerns on 2nd Embodiment. It is a figure showing the timing chart in the reset process before radiographic imaging of 2nd Embodiment. It is a figure showing the timing chart in the reset process before a radiographic image imaging | photography with the conventional radiographic imaging apparatus, a reading process, the reset process before a dark reading process, and a dark reading process.

  Embodiments of a radiographic image capturing apparatus according to the present invention will be described below with reference to the drawings.

  In the following description, the radiographic imaging device is a so-called indirect radiographic imaging device that includes a scintillator or the like and converts the irradiated radiation into electromagnetic waves of other wavelengths such as visible light to obtain an electrical signal. As will be described, the present invention can also be applied to a direct radiographic imaging apparatus. Although the case where the radiographic image capturing apparatus is portable will be described, the present invention is also applicable to a radiographic image capturing apparatus formed integrally with a support base or the like.

[First Embodiment]
FIG. 1 is an external perspective view of a radiographic imaging apparatus according to the first embodiment of the present invention, and FIG. 2 is a cross-sectional view taken along line AA of FIG. As shown in FIGS. 1 and 2, the radiographic imaging apparatus 1 according to the present embodiment is configured as a portable (cassette type) apparatus in which a scintillator 3, a substrate 4, and the like are housed in a housing 2. .

  The housing 2 is formed of a material such as a carbon plate or plastic that transmits radiation at least on a surface R (hereinafter referred to as a radiation incident surface R) that receives radiation. 1 and 2 show a case in which the housing 2 is a so-called lunch box type formed by the frame plate 2A and the back plate 2B. However, the housing 2 is integrally formed in a rectangular tube shape. It is also possible to use a so-called monocoque type.

  As shown in FIG. 1, the side surface of the housing 2 is opened and closed for replacement of a power switch 36, an indicator 37 composed of LEDs and the like, and a battery 41 (not shown) (see FIG. 7 described later). A possible lid member 38 and the like are arranged. In the present embodiment, an antenna device 39 that is a communication means for wirelessly communicating with an external device (not shown) is embedded in the side surface of the lid member 38.

  As shown in FIG. 2, a base 31 is disposed inside the housing 2 via a thin lead plate or the like (not shown) on the lower side of the substrate 4. The disposed PCB substrate 33, the buffer member 34, and the like are attached. In the present embodiment, a glass substrate 35 for protecting the substrate 4 and the radiation incident surface R of the scintillator 3 is disposed.

  The scintillator 3 is attached to a detection unit P, which will be described later, of the substrate 4. As the scintillator 3, for example, a scintillator 3 that has a phosphor as a main component and converts it into an electromagnetic wave having a wavelength of 300 to 800 nm, that is, an electromagnetic wave centered on visible light when it receives incident radiation, is used.

  In the present embodiment, the substrate 4 is formed of a glass substrate. As shown in FIG. 3, a plurality of scanning lines 5 and a plurality of signal lines are provided on a surface 4 a of the substrate 4 facing the scintillator 3. 6 are arranged so as to cross each other. In each small region r defined by the plurality of scanning lines 5 and the plurality of signal lines 6 on the surface 4 a of the substrate 4, radiation detection elements 7 are respectively provided.

  Thus, the entire region r in which a plurality of radiation detection elements 7 arranged in a two-dimensional manner are provided in each small region r partitioned by the scanning line 5 and the signal line 6, that is, shown by a one-dot chain line in FIG. The region is a detection unit P.

  In the present embodiment, a photodiode is used as the radiation detection element 7, but other than this, for example, a phototransistor or the like can also be used. Each radiation detection element 7 is connected to the source electrode 8s of the TFT 8 serving as a switch means, as shown in the enlarged views of FIGS. The drain electrode 8 d of the TFT 8 is connected to the signal line 6.

  The TFT 8 is turned on when a turn-on voltage Von is applied to the connected scanning line 5 by the scan driving means 15 described later, and is applied to the gate electrode 8g, and is generated in the radiation detection element 7. Then, the accumulated electric charge is discharged to the signal line 6. The TFT 8 is turned off when the off voltage Voff is applied to the connected scanning line 5 and the off voltage Voff is applied to the gate electrode 8g, and the emission of the charge from the radiation detection element 7 to the signal line 6 is stopped. Thus, the charges generated in the radiation detection element 7 are held and accumulated in the radiation detection element 7.

  Here, the structure of the radiation detection element 7 and the TFT 8 in this embodiment will be briefly described with reference to the cross-sectional view shown in FIG. FIG. 5 is a sectional view taken along line XX in FIG.

A gate electrode 8g of a TFT 8 made of Al, Cr or the like is formed on the surface 4a of the substrate 4 so as to be integrally laminated with the scanning line 5, and silicon nitride (laminated on the gate electrode 8g and the surface 4a). The first electrode 74 of the radiation detecting element 7 is connected to the upper portion of the gate electrode 8g on the gate insulating layer 81 made of SiN _x ) or the like via the semiconductor layer 82 made of hydrogenated amorphous silicon (a-Si) or the like. The formed source electrode 8s and the drain electrode 8d formed integrally with the signal line 6 are laminated.

The source electrode 8s and the drain electrode 8d are divided by a first passivation layer 83 made of silicon nitride (SiN _x ) or the like, and the first passivation layer 83 covers both electrodes 8s and 8d from above. In addition, ohmic contact layers 84a and 84b formed in an n-type by doping hydrogenated amorphous silicon with a group VI element are stacked between the semiconductor layer 82 and the source electrode 8s and the drain electrode 8d, respectively. The TFT 8 is formed as described above.

  In the radiation detecting element 7, an auxiliary electrode 72 is formed by laminating Al, Cr, or the like on the insulating layer 71 formed integrally with the gate insulating layer 81 on the surface 4 a of the substrate 4. A first electrode 74 made of Al, Cr, Mo or the like is laminated on the auxiliary electrode 72 with an insulating layer 73 formed integrally with the first passivation layer 83 interposed therebetween. The first electrode 74 is connected to the source electrode 8 s of the TFT 8 through the hole H formed in the first passivation layer 83.

  On the first electrode 74, an n layer 75 formed in an n-type by doping a hydrogenated amorphous silicon with a group VI element, an i layer 76 which is a conversion layer formed of hydrogenated amorphous silicon, and a hydrogenated amorphous A p layer 77 formed by doping a group III element into silicon and forming a p-type layer is formed by laminating sequentially from below.

  When radiation enters from the radiation incident surface R of the housing 2 of the radiographic imaging apparatus 1 and is converted into an electromagnetic wave such as visible light by the scintillator 3, and the converted electromagnetic wave is irradiated from above in the figure, the electromagnetic wave is detected by radiation. The electron hole pair is generated in the i layer 76 by reaching the i layer 76 of the element 7. In this way, the radiation detection element 7 converts the electromagnetic waves irradiated from the scintillator 3 into electric charges.

  On the p layer 77, a second electrode 78 made of a transparent electrode such as ITO is laminated and formed so that the irradiated electromagnetic wave reaches the i layer 76 and the like. In the present embodiment, the radiation detection element 7 is formed as described above. The order of stacking the p layer 77, the i layer 76, and the n layer 75 may be reversed. Further, in the present embodiment, a case where a so-called pin-type radiation detection element formed by sequentially stacking the p layer 77, the i layer 76, and the n layer 75 as described above is used as the radiation detection element 7. However, it is not limited to this.

A bias line 9 for applying a bias voltage to the radiation detection element 7 is connected to the upper surface of the second electrode 78 of the radiation detection element 7 via the second electrode 78. The second electrode 78 and the bias line 9 of the radiation detection element 7, the first electrode 74 extended to the TFT 8 side, the first passivation layer 83 of the TFT 8, that is, the upper surfaces of the radiation detection element 7 and the TFT 8 are A second passivation layer 79 made of silicon nitride (SiN _x ) or the like is covered from above.

  As shown in FIGS. 3 and 4, in this embodiment, one bias line 9 is connected to a plurality of radiation detection elements 7 arranged in rows, and each bias line 9 is connected to a signal line 6. Are arranged in parallel with each other. Further, each bias line 9 is bound to the connection 10 at a position outside the detection portion P of the substrate 4.

  In this embodiment, as shown in FIG. 3, each scanning line 5, each signal line 6, and connection 10 of the bias line 9 are input / output terminals (also referred to as pads) provided near the edge of the substrate 4. 11 is connected. As shown in FIG. 6, a COF (Chip On Film) 12 in which a chip such as a gate IC 12a constituting a gate driver 15b of the scanning drive means 15 described later is incorporated in each input / output terminal 11 is anisotropically conductively bonded. They are connected via an anisotropic conductive adhesive material 13 such as a film (Anisotropic Conductive Film) or an anisotropic conductive paste (Anisotropic Conductive Paste).

  The COF 12 is routed to the back surface 4b side of the substrate 4 and connected to the PCB substrate 33 described above on the back surface 4b side. Thus, the board | substrate 4 part of the radiographic imaging apparatus 1 is formed. In FIG. 6, illustration of the electronic component 32 and the like is omitted.

  Here, the circuit configuration of the radiation image capturing apparatus 1 will be described. FIG. 7 is a block diagram showing an equivalent circuit of the radiographic imaging apparatus 1 according to the present embodiment, and FIG. 8 is a block diagram showing an equivalent circuit for one pixel constituting the detection unit P.

  As described above, each radiation detection element 7 of the detection unit P of the substrate 4 has the bias line 9 connected to the second electrode 78, and each bias line 9 is bound to the connection 10 to the bias power supply 14. It is connected. The bias power supply 14 applies a bias voltage to the second electrode 78 of each radiation detection element 7 via the connection 10 and each bias line 9. The bias power source 14 is connected to a control unit 22 described later, and the control unit 22 controls a bias voltage applied to each radiation detection element 7 from the bias power source 14.

  In the present embodiment, the current detection means 43 for detecting the amount of current flowing through the connection 10 (bias line 9) is provided in the connection 10 of the bias line 9, and the increase / decrease in the current flowing through the connection 10 is detected. The start and end of radiation irradiation can be detected.

  7 and FIG. 8 and FIG. 3 described above show the case where each bias line 9 is bound to one connection 10. In this case, the current detection means 43 is connected to one connection 10. However, there are cases where each bias line 9 is configured to be bound to a plurality of connections 10. In that case, the current detection means 43 can be provided in each connection 10, or the current detection means 43 can be provided in some of the plurality of connections 10. Is possible.

  In the present embodiment and the second embodiment to be described later, the current detection means 43 is provided in the bias line 9 and the connection 10, and the current flowing through the bias line 9 and the connection 10 due to radiation irradiation to the radiographic imaging apparatus 1 is detected. Although the case where it is comprised so that it may detect is demonstrated, the electric current detection means 43 should just be what can detect the electric current which flows through an apparatus by irradiation of a radiation, and is provided in the bias line 9 and its connection 10 It is not limited to the case.

  Here, the configuration of the current detection means 43 will be described. In the present embodiment, the current detection means 43 is provided at a connection portion between the connection 10 of the bias line 9 and the bias power supply 14 and flows between the bias power supply 14 and the radiation detection element 7 with the start of radiation irradiation. The current is detected.

  Specifically, as shown in FIG. 9, the current detection unit 43 is a resistor having a predetermined resistance value connected in series to the connection 10 of the bias wiring 9 that connects the bias power supply 14 and each radiation detection element 7. 43 a, a diode 43 b connected in parallel thereto, and a differential amplifier 43 c that measures the voltage V between both terminals of the resistor 43 a and outputs the voltage V to the control means 22.

  Thus, in this embodiment, the current detection means 43 measures the voltage V between both terminals of the resistor 43a by the differential amplifier 43c, and flows the current flowing through the resistor 43a, that is, the connection 10 of the bias line 9. The current is converted into a voltage value V, detected, and output to the control means 22.

  As the resistor 43a provided in the current detection means 43, a resistor having a resistance value capable of converting the current flowing through the connection 10 into an appropriate voltage value V is used. Moreover, the detection accuracy in the case of a low dose is improved by connecting the diode 42d in parallel with the resistor 43a. It is also possible to connect only the resistor 43a or the diode 43b in series to the wiring and measure the voltage V between both terminals with the differential amplifier 43c.

  Further, in cases other than the case where the start or end of radiation irradiation is detected, it is not necessary for the current detection means 43 to detect the current flowing between the bias power supply 14 and each radiation detection element 7. Since the resistor 43a obstructs the application of a bias voltage from the bias power supply 14 to each radiation detection element 7, the current detection means 43 requires a gap between both terminals of the resistor 43a when current detection is not required. Accordingly, a switch 43d for short-circuiting is provided.

  The differential amplifier 43c is supplied with power from the power supply means 44. When the current detection means 43 detects current, the power is supplied from the power supply means 44 to the differential amplifier 43c. When the short circuit of the switch 43d is released and the current detection means 43 is put into operation and no current is detected, both terminals of the resistor 43a are short-circuited by the switch 43d and the power supply means 44 to the differential amplifier 43c. The power supply is stopped and the operation of the current detection means 43 is stopped.

  As shown in FIGS. 7 and 8, in this embodiment, it can be seen that the bias line 9 is connected via the second electrode 78 to the p-layer 77 side (see FIG. 5) of the radiation detection element 7. In addition, the bias power supply 14 supplies a voltage equal to or lower than a voltage applied to the second electrode 78 of the radiation detection element 7 via the bias line 9 as a bias voltage on the first electrode 74 side of the radiation detection element 7 (that is, a so-called reverse bias voltage). Is applied.

  The first electrode 74 of each radiation detection element 7 is connected to the source electrode 8s of the TFT 8 (indicated as S in FIGS. 7 and 8), and the gate electrode 8g of each TFT 8 (FIGS. 7 and 8). Are respectively connected to the lines L1 to Lx of the scanning line 5 extending from the gate driver 15b of the scanning driving means 15 to be described later. Further, the drain electrode 8 d (denoted as D in FIGS. 7 and 8) of each TFT 8 is connected to each signal line 6.

  In this embodiment, the scanning drive unit 15 includes a power supply circuit 15a and a gate driver 15b. In this embodiment, the gate driver 15b is formed by arranging a plurality of the gate ICs 12a described above in parallel. Further, the scanning drive means 15 controls the voltage applied to the gate electrode 8g of the TFT 8 via the lines L1 to Lx of the scanning line 5 connected to the gate driver 15b, and the voltage is set to the above-described on voltage Von. Switching between the off voltage Voff is made.

  Specifically, the power supply circuit 15a of the scanning drive unit 15 sets each voltage value of the on voltage Von and the off voltage Voff applied to each scanning line 5 from the gate driver 15b to a predetermined voltage value, and sets the gate driver 15b is supplied. Further, the gate driver 15b of the scanning driving unit 15 selectively switches between the on voltage Von and the off voltage Voff supplied from the power supply circuit 15a, and applies the on voltage Von or the off voltage Voff to each scanning line 5. ing. The gate driver 15b can modulate the pulse width of the on-voltage Von of the pulse waveform applied to each line L1 to Lx of the scanning line 5.

  Each signal line 6 is connected to each readout circuit 17 formed in the readout IC 16. Note that a predetermined number of readout circuits 17 are provided in the readout IC 16, and by providing a plurality of readout ICs 16, readout circuits 17 corresponding to the number of signal lines 6 are provided.

  The readout circuit 17 includes an amplifier circuit 18, a correlated double sampling circuit 19, an analog multiplexer 21, and an A / D converter 20. 7 and FIG. 8 and FIG. 10 described later, the correlated double sampling circuit 19 is expressed as CDS. In FIG. 8, the analog multiplexer 21 is omitted.

  In the present embodiment, the amplifier circuit 18 is configured by a charge amplifier circuit, and is configured by connecting a capacitor 18b and a charge reset switch 18c in parallel to the operational amplifier 18a and the operational amplifier 18a. In addition, a power supply unit 18 d for supplying power to the amplifier circuit 18 is connected to the amplifier circuit 18.

Further, the signal line 6 is connected to the inverting input terminal on the input side of the operational amplifier 18 a of the amplifier circuit 18, and the reference potential V ₀ is applied to the non-inverting input terminal on the input side of the amplifier circuit 18. ing. Note that the reference potential V ₀ is set to an appropriate value, and in this embodiment, for example, 0 [V] is applied.

  The charge reset switch 18c of the amplifier circuit 18 is connected to the control means 22 described later, and is controlled to be turned on / off by the control means 22. When the charge reset switch 18c is off and the TFT 8 of the radiation detection element 7 is turned on (that is, when the on voltage Von is applied to the gate electrode 8g of the TFT 8 via the scanning line 5), The electric charge discharged from the radiation detecting element 7 flows into the capacitor 18b and is accumulated, and a voltage value corresponding to the accumulated electric charge is output from the output side of the operational amplifier 18a.

  In this way, the amplifier circuit 18 outputs a voltage value in accordance with the amount of charge output from each radiation detection element 7 to perform charge voltage conversion and amplify. When the charge reset switch 18c is turned on, the input side and the output side of the amplifier circuit 18 are short-circuited, and the charge accumulated in the capacitor 18b is discharged to reset the amplifier circuit 18. ing. Note that the amplifier circuit 18 may be configured to output a current in accordance with the charge output from the radiation detection element 7.

  A correlated double sampling circuit (CDS) 19 is connected to the output side of the amplifier circuit 18. In this embodiment, the correlated double sampling circuit 19 has a sample and hold function. The sample and hold function in the correlated double sampling circuit 19 is turned on / off by a pulse signal transmitted from the control means 22. To be controlled.

  That is, in the reading process of image data from each radiation detection element 7 after radiographic imaging, the control means 22 first controls the charge reset switch 18c of the amplification circuit 18 of each readout circuit 17 to turn it off. To do. At that time, so-called kTC noise occurs at the moment when the charge reset switch 18c is turned off, and the charge q caused by the kTC noise accumulates in the capacitor 18b of the amplifier circuit 18.

As described above, in the amplifier circuit 18, a voltage value corresponding to the amount of charge accumulated in the capacitor 18 b is output from the output terminal of the operational amplifier 18 a of the amplifier circuit 18, but as described above, the charge q caused by kTC noise. 10 is accumulated in the capacitor 18b, the voltage value output from the output terminal of the operational amplifier 18a at the moment when the charge reset switch 18c is turned off (indicated as “18coff” in FIG. 10), as shown in FIG. , the reference potential V ₀ which as described above, instantaneously changes by the amount of charge q due to kTC noise varies with the voltage value Vin.

  At this stage (indicated as “CDS hold” (left side) in FIG. 10), the control means 22 transmits the first pulse signal Sp1 to the correlated double sampling circuit 19 and is output from the amplifier circuit 18 at that time. The voltage value Vin being held is held.

  Subsequently, when the control means 22 applies the ON voltage Von from the scanning drive circuit 15 to one scanning line 5 and turns on the TFT 8 having the gate electrode 8g connected to the scanning line 5 (in FIG. 10). The charge accumulated from each radiation detection element 7 connected to these TFTs 8 flows into the capacitor 18b of the amplifier circuit 18 via each signal line 6 and is accumulated, as shown in FIG. In addition, the voltage value output from the output side of the operational amplifier 18a increases in accordance with the amount of charge accumulated in the capacitor 18b.

  Then, after a predetermined time has elapsed, the control means 22 switches the on voltage Von applied to the scanning line 5 from the scanning drive circuit 15 to the off voltage Voff, and the gate electrode 8g is connected to the scanning line 5. The TFT 8 is turned off (displayed as “TFToff” in FIG. 10), and at this stage, the second pulse signal Sp2 is transmitted to each correlated double sampling circuit 19 and output from the amplifier circuit 18 at that time. The voltage value Vfi is held (displayed as “CDS hold” (right side) in FIG. 10).

  When each correlated double sampling circuit 19 holds the voltage value Vfi with the second pulse signal Sp2, the difference Vfi−Vin between the voltage values is calculated, and the calculated difference Vfi−Vin is output to the downstream side as image data. It has become.

  The image data of each radiation detection element 7 output from the correlated double sampling circuit 19 is transmitted to the analog multiplexer 21 (see FIG. 7), and is sequentially transmitted from the analog multiplexer 21 to the A / D converter 20. Then, the A / D converter 20 sequentially converts the image data into digital values, which are output to the storage means 40 and sequentially stored.

  The control means 22 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), an input / output interface connected to the bus, an FPGA (Field Programmable Gate Array), or the like (not shown). It is configured. It may be configured by a dedicated control circuit. And the control means 22 controls operation | movement etc. of each member of the radiographic imaging apparatus 1. The control means 22 is connected to a storage means 40 composed of a DRAM (Dynamic RAM) or the like.

  In the present embodiment, the above-described antenna device 39 is connected to the control unit 22, and each member such as the detection unit P, the scanning drive unit 15, the readout circuit 17, the storage unit 40, the bias power supply 14, and the like. A battery 41 for supplying electric power is connected. In addition, a connection terminal 42 for charging the battery 41 by supplying power from the external device to the battery 41 is attached to the battery 41.

  As described above, the control means 22 controls the bias power supply 14 to set a bias voltage to be applied to each radiation detection element 7 from the bias power supply 14, or the charge reset switch 18 c of the amplification circuit 18 of the readout circuit 17. Various processes such as on / off control and transmission of a pulse signal to the correlated double sampling circuit 19 to control on / off of the sample hold function are executed.

  Further, the control means 22 performs scanning from the scanning driving means 15 to the scanning driving means 15 at the time of reset processing of each radiation detecting element 7 or reading of image data from each radiation detecting element 7 after radiographic imaging. A pulse signal for switching the voltage applied to the gate electrode 8g of each TFT 8 between the on voltage Von and the off voltage Voff via the line 5 is transmitted.

  Hereinafter, reset processing of each radiation detection element 7, detection of radiation irradiation start based on the voltage value V corresponding to the current detected by the current detection means 43, read processing of image data, reset processing before dark reading processing, The dark reading process will be described.

  The control means 22 performs a reset process of each radiation detection element 7 before the radiation image capturing apparatus 1 is irradiated with radiation in the radiation image capturing, and once applies the off voltage Voff to the gate electrodes 8g of the TFTs 8 at once. When applied, the gate of each TFT 8 is closed, and a charge accumulation operation for accumulating dark charges in each radiation detection element 7 is performed. Then, after ensuring a predetermined charge accumulation time in this way, the ON voltage Von is applied simultaneously to the gate electrodes 8g of the TFTs 8 and the start of radiation irradiation is waited in a state where the gates of the TFTs 8 are opened. Has been.

  In the present embodiment, in order to realize this, the control means 22 scans the drive means as shown in FIG. 11 at the stage of the reset process of each radiation detection element 7 before the radiation image is irradiated. The voltage applied simultaneously to the gate electrodes 8g of the TFTs 8 from the line 15 to the scanning lines 5 through the lines L1 to Lx is alternately repeated between the on-voltage Von and the off-voltage Voff, thereby resetting each radiation detection element 7. Is to be repeated.

  Specifically, when the radiographic imaging device 1 is turned on or receives a signal from an external device via the antenna device 39, the control unit 22 transmits a pulse signal to the scanning drive unit 15. Equally, the voltage applied simultaneously to the gate electrodes 8g of the TFTs 8 is switched between the on voltage Von and the off voltage Voff at a predetermined time interval.

  During the reset process of each radiation detection element 7, the control unit 22 causes the differential amplifier 43c of the current detection unit 43 to supply power from the power supply unit 44 to release the short circuit of the switch 43d and thereby detect the current. 43 is in an operating state, and control is performed so that the current flowing through the bias line 9 and the connection 10 can be detected by the current detection means 43.

  In addition, when the TFT 8 is in the on state, that is, when the gate of the TFT 8 is open, the electron-hole pair generated in each radiation detection element 7 due to radiation irradiation is more than that when the TFT 8 is in the off state. It becomes easy to flow out to the bias line 9 and the connection 10, and it becomes easy to detect an increase in current due to the start of radiation irradiation.

  For this reason, in this embodiment, an operator such as a radiologist starts radiation irradiation when each TFT 8 is in an on state, that is, starts radiation irradiation when each TFT 8 is in an off state. In order to prevent this, the control means 22 turns on the indicator 37 (see FIG. 1) when the voltage applied to the gate electrode 8g of each TFT 8 is the off-voltage Voff, so that the TFT 8 is turned off to the operator. It is supposed to notify that there is.

  That is, in the present embodiment, the indicator 37 serves as a notification unit, and the operator does not irradiate the radiation image capturing apparatus 1 while the indicator 37 is lit. Note that the notification means does not need to be the indicator 37, and can be configured to transmit a signal via the antenna device 39 to light the lamp of the operation room, and the gate of each TFT 8 As long as it can notify that the voltage applied to the electrode 8g is the off voltage Voff, in addition to the notification by lighting the light, it can also be configured to notify by sounding, for example. It is.

  In the present embodiment, in this way, a charge accumulation operation for accumulating dark charges in each radiation detection element 7 by periodically switching the voltage applied to the gate electrodes 8g of the TFTs 8 to the off voltage Voff in a regular manner is performed. While ensuring a predetermined charge accumulation time (see ΔTa in FIG. 11 and FIG. 13 described later), the voltage applied to the gate electrodes 8g of the TFTs 8g is switched to the on voltage Von and the gates of the TFTs 8 are opened. Waiting for the start of irradiation in the state.

  Then, as shown at time T1 in FIG. 11, when radiation irradiation is started on the radiographic imaging apparatus 1 with the on-voltage Von applied to the gate electrodes 8g of the TFTs 8 at the same time (in addition, this As shown in FIG. 12A, the voltage value V corresponding to the current output from the differential amplifier 43c of the current detection means 43 rapidly increases as shown in FIG. 12A. .

  Therefore, in the present embodiment, the control unit 22 increases the voltage value V output from the current detection unit 43. For example, when the voltage value V exceeds a preset threshold value, the increase rate of the voltage value V is set in advance. When the threshold value is exceeded, it is detected that radiation irradiation has started.

  Further, if the TFT 8 is left in the ON state as described above, all the charges generated in each radiation detection element 7 flow out, and no charges (image data) are accumulated in each radiation detection element 7. Therefore, the control means 22 is turned off from the scanning drive means 15 to each of the lines L1 to Lx of the scanning line 5 at a time point (time T2) when it is detected that the voltage value V is increased and radiation irradiation is started. The voltage Voff is applied all at once, and the off voltage Voff is applied all at once to the gate electrodes 8g of the TFTs 8 so that all the TFTs 8 are turned off.

  In FIG. 12A and FIG. 12B, which will be described later, the time interval between time t1 and time T2 is enlarged to make it easier to see the graph. Compared to the time interval when the voltages applied simultaneously to the gate electrodes 8g of the TFTs 8 are switched between the on voltage Von and the off voltage Voff, the time interval between the times t1 and T2 is very short. Seen from the time interval, it is almost simultaneous.

  When the off voltage Voff is applied simultaneously to the gate electrodes 8g of the TFTs 8 so that all the TFTs 8 are turned off (time T2), the voltage value V corresponding to the current output from the current detection means 43 is rapidly reduced.

  On the other hand, even if each TFT 8 is turned off, as long as radiation irradiation continues, a current flows through the bias line 9 and the connection line 10 although they are weak, and the current detection means 43 may detect the current.

  The reason why the current flows through the bias line 9 even when each TFT 8 is in the OFF state is that, for example, when the TFT 8 is in the OFF state in FIG. 8, it closes from the scanning line 5 to the bias power supply 14 via the TFT 8 and the radiation detection element 7. A loop is formed, and it can be considered that the TFT 8 and the radiation detection element 7 each having a predetermined parasitic capacitance are arranged in a capacitor shape. Then, when electron-hole pairs are generated and accumulated in the i layer 76 (see FIG. 5) of the radiation detection element 7 due to the irradiation of radiation, the second electrode 78 to which a predetermined bias voltage is applied in the radiation detection element 7. The potential of the first electrode 74 with respect to (this potential is equal to the potential on the source electrode 8s side of the TFT 8) is lowered. Therefore, the amount of charge accumulated in the first and second electrodes 74 and 78 of the radiation detection element 7 and the gate electrode 8g and the source electrode 8s of the TFT 8 changes, so that the bias line 9 and the radiation detection element 7 are compensated for this. A current flows through the wiring between the TFTs 8 and the scanning line 5.

  As described above, when the current flowing through the bias line 8 or the connection line 10 (or the voltage value V corresponding thereto) can be detected even after each TFT 8 is turned off, the output from the current detection means 43 is completed when radiation irradiation is completed. As shown in FIG. 12B, the voltage value V corresponding to the applied current further decreases at the time point t2 when the radiation irradiation is completed. Therefore, it is possible to detect that the voltage value V, which has been reduced when all the TFTs 8 are turned off, further decreases, and the control means 22 detects the end of radiation irradiation.

  However, as shown in FIG. 9, when the current flowing through the bias line 9 and the connection line 10 is passed through the resistor 43a of the current detection means 43 and the current is detected as the voltage V between the two terminals, the current is supplied from the bias power supply 14. The bias voltage having a predetermined voltage value fluctuates by the voltage V between both terminals of the resistor 43 a, and the fluctuating bias voltage is applied to the second electrode 78 of each radiation detection element 7. In addition, noise with respect to the bias voltage generated by the current detection unit 43 may affect the amount of charge (image data) generated and accumulated in the radiation detection element 7 due to radiation irradiation.

  Thus, after detecting the start of radiation irradiation at time T2, as shown in FIG. 12 (A), in order to eliminate the adverse effect of keeping the current detection means 43 in an operating state even after the start of radiation irradiation. The operation of the current detection unit 43 is stopped, the switch 43d is short-circuited, and the bias voltage applied to the radiation detection element 7 can be controlled so as not to adversely affect the current detection unit 43.

  In this case, the end of radiation irradiation cannot be detected based on the voltage value V corresponding to the current output from the current detection means 43. In this case, the time T2 at which the start of radiation irradiation is detected. It is possible to configure so that the subsequent processing is performed assuming that the irradiation of the radiation has been completed when a predetermined time set in advance has elapsed.

  In the case where it is configured to detect the end of radiation irradiation (see time point t2 in FIG. 12B) based on the current value (or the corresponding voltage value V) output from the current detection means 43. In other words, the control means 22 stops the operation of the current detection means 43 when it detects the end of radiation irradiation, and short-circuits the switch 43d.

  When the control means 22 detects that the irradiation of radiation has ended (or determines that the irradiation of radiation has ended after a predetermined time has elapsed from the start of irradiation of radiation (time T2)), each radiation detection is subsequently performed. A process for reading image data from the element 7 is performed.

As shown in the timing chart of FIG. 13, the control means 22 detects that radiation irradiation has started at time T2, and indicates that radiation irradiation has ended at time t2, not shown in FIG. Upon detection, a pulse signal is transmitted to the scanning drive means 15, and the ON voltage Von is sequentially applied to the gate electrode 8g of each TFT 8 while sequentially switching the lines L1 to Lx of the scanning line 5 to which the ON voltage Von for signal reading is applied. When applied (see times T3 _{1 to} T3 _{x in} FIG. 13), the charge is read from each radiation detection element 7 as described above.

  In FIG. 13, the pulse width of the on-voltage Von for signal reading is shown to be long in order to make the timing chart easier to see, but actually, compared to the application time of the on-voltage Von between times T1 and T2. The pulse width of the ON voltage Von for signal readout is very short.

  Then, the charge read from each radiation detection element 7 is subjected to charge-voltage conversion by the amplifier circuit 18, and image data is cut out from the output value converted into the voltage value by the correlated double sampling circuit 19 and output from the correlated double sampling circuit 19. The processed image data is sequentially transmitted to the A / D converter 20 via the analog multiplexer 21. Then, the image data sequentially converted into digital values by the A / D converter 20 is output to the storage means 40 and sequentially stored.

  Subsequently, the control means 22 performs a reset process before the dark reading process. In the reset process before the dark reading process, as shown in FIG. 13, the control means 22 applies the ON voltage Von to the gate electrodes 8g of the TFTs 8 at the same time at time T4, and then at the time T1 at the time of radiographic imaging. Further, the ON voltage Von is applied to the gate electrode 8g of each TFT 8 for the same time interval as the time interval T2-T1 from when the ON voltage Von is last applied to the gate electrode 8g of each TFT8 to when the OFF voltage Voff is applied again at time T2. After the voltage is continuously applied, the voltage applied to the gate electrode 8g of each TFT 8 is simultaneously switched to the off voltage Voff at time T5 (T5 = T4 + T2-T1).

  Therefore, at the time of radiographic imaging, the control means 22 starts counting time from the time T1 when the ON voltage Von is finally applied to the gate electrodes 8g of the TFTs 8 at the same time, and applies the gate electrodes 8g of the TFTs 8 at time T2. The time interval T2-T1 until the ON voltage Von is applied all at once is stored in a memory such as a RAM.

  Subsequently, the control means 22 performs a dark reading process. In the dark reading process, after the reset process before the dark reading process is completed, the control unit 22 leaves the radiographic image capturing apparatus 1 in a state where no radiation is irradiated, and generates dark charges generated in each radiation detection element 7. It accumulates in each radiation detection element 7.

Time interval [Delta] T _n for each scan line 5 to leave the radiation image capturing apparatus 1, the radiation image time interval [Delta] T n which has a respective TFT8 turned off during _shooting, that is, each line of the scanning lines 5 in terms of the 13 The time interval is set to be the same as the time interval ΔT _n (= T3 _n −T2) from time T2 to time T3 _n for each of L1 to Lx.

Then, the control means 22 performs the time for each line L1 to Lx of the scanning line 5 from the time T5 when the reset process before the dark reading process is completed and the voltage applied to the gate electrode 8g of the TFT 8 is switched to the off voltage Voff. After leaving for the interval ΔT _n, the dark reading value corresponding to the dark charge accumulated from each radiation detection element 7 is read out by the same procedure as the reading processing of the image data.

  Note that it is possible to perform a periodic reset process as shown in FIG. 11 about once or twice before the reset process before the dark reading process at times T4 to T5.

  Further, the offset correction for calculating the offset from the dark reading value of each radiation detection element 7 acquired as described above, and subtracting the offset from the image data of each radiation detection element 7 to obtain true image data, The radiographic imaging apparatus 1 may be configured to perform the process, or the image data and the dark reading value may be transmitted to the external apparatus via the antenna apparatus 39, for example, and the external apparatus may be configured to perform the offset correction. Is possible.

  As described above, according to the radiographic image capturing apparatus 1 according to the present embodiment, the voltage to be applied to the gate electrodes 8g of the TFTs 8 before the radiographic image capturing is periodically performed between the on voltage Von and the off voltage Voff. In the reset process before the dark reading process, the time interval T2-T1 is the same as the time interval T2-T1 from the last application of the ON voltage Von to the detection of the start of radiation irradiation and the application of the OFF voltage Voff again. After the ON voltage Von was applied to the gate electrode 8g of each TFT 8, it was configured to simultaneously switch to the OFF voltage Voff.

  Therefore, if the application time (pulse width) of the on-voltage Von periodically applied in the reset process before radiographic imaging is appropriately adjusted to a short time of about 1 second, for example, the last time the on-voltage Von is applied. The time interval T2-T1 from the detection of the start of radiation irradiation to the application of the OFF voltage Voff again can be set to at least a shorter time interval.

  Since the time interval T5-T4 required for the reset process before the dark reading process is set to the same time interval as the time interval T2-T1, the time required for the dark reading process including the reset process before the dark reading process becomes longer. This can be accurately prevented, and the dark reading process can be performed within a realistic time. In the radiographic image capturing apparatus 1 according to the present embodiment, the above-described problem 1 is solved.

  Further, in order to periodically perform the reset process before radiographic imaging, a predetermined charge accumulation time (FIG. 11) for accumulating dark charges in each radiation detection element 7 before the last reset process before the start of radiation irradiation. And ΔTa in FIG. 13) are secured. Therefore, as described in the above-described problem 2, unlike the case where each TFT 8 is turned on continuously for a long time and the dark charge in each radiation detection element 7 is sufficiently removed, the radiation irradiation start point ( The amount of residual charges such as dark charges remaining in each radiation detection element 7 at time T2) and the amount of residual charges remaining in each radiation detection element 7 at the end of reset processing before dark reading processing (time T5). Can be made comparable.

  Therefore, if the offset is calculated based on the dark reading value obtained in the dark reading process, the calculated offset is almost the same as the offset due to the dark charge accumulated in each radiation detection element 7 at the time of radiographic image capturing. Value. Therefore, true image data can be accurately obtained by subtracting the offset obtained by the dark reading process from the image data, and the accuracy of offset correction can be maintained and improved. In the radiation image capturing apparatus 1 according to the present embodiment, the above-described problem 2 is solved.

[Second Embodiment]
In the first embodiment, a case has been described in which the reset processing of each radiation detection element 7 before radiographic imaging is performed by periodically switching between the on voltage Von and the off voltage Voff as shown in FIG. However, the present invention can also be applied to the case where the ON voltage Von is continuously applied to the gate electrode 8g of each TFT 8 for a long time. The second embodiment configured as described above will be described below.

  However, in this case, when the start of radiation irradiation is detected while the on-voltage Von is continuously applied to the gate electrode 8g of each TFT 8 for a long time, the dark charge in each radiation detection element 7 is reduced as described above. Since it is sufficiently removed, the amount of residual charges such as dark charge remaining in each radiation detection element 7 at the radiation irradiation start time (time T2) and the end time of reset processing before dark reading processing (time T5) As a result, the amount of residual charge remaining in each radiation detection element 7 becomes a significantly different value, leading to a decrease in the accuracy of offset correction (that is, problem 2 described above cannot be solved).

  Therefore, also in the second embodiment, the applied voltage is temporarily switched to the off voltage Voff from the state in which the on voltage Von is applied to the gate electrode 8g of each TFT 8 continuously for a long time in the reset process before radiographic imaging. Thus, a predetermined charge accumulation time ΔTa for accumulating dark charges in each radiation detection element 7 is secured, and then the voltage applied simultaneously to the gate electrodes 8g of the TFTs 8 is switched again to the on-voltage Von to turn on the gates of the TFTs 8. It is necessary to configure to wait for the start of radiation irradiation in a state in which is opened.

  For this purpose, a signal indicating that preparation for radiation irradiation has been completed is received from a radiation irradiation device or the like, and the ON voltage Von applied to the gate electrode 8g of each TFT 8 based on the received signal is converted to the OFF voltage Voff. It is also possible to switch to the on-voltage Von again, but there is a practical problem such as the fact that the manufacturer of the radiation imaging apparatus is different from that of the radiation imaging apparatus. It is not always easy to interface with the image capturing device.

  Therefore, in the radiographic imaging device 100 according to the present embodiment, as shown in FIG. 14, the cord 50 is extended from the side surface portion of the housing 2 provided with the antenna device 39, and a push button type is provided at the tip thereof. An input unit 51 is provided, and information indicating that the radiation image capturing apparatus 100 is irradiated with radiation is input by the operator pressing the button unit 52 of the input unit 51 immediately before the radiation is irradiated. It has become.

  The configuration other than the configuration of the input unit 51 and the like of the radiographic image capturing apparatus 100 is the same as the configuration of the radiographic image capturing apparatus 1 according to the first embodiment, and each functional unit is denoted by the same reference numeral and described. To do.

  The input unit 51 is not limited to the push button type input unit including the code 50 as described above, and can input information indicating that the radiation imaging apparatus 100 is irradiated with radiation when the radiation is irradiated. Anything is possible. Therefore, for example, an operator can operate the external device to input information from the external device via the antenna device 39. In this case, the antenna device 39 is an input unit. Become. Further, the power switch 36 or a switch (not shown) provided separately from the power switch 36 may be used as input means, and the above information may be input by operating the input means.

  In the present embodiment, in the reset process of each radiation detection element 7 before radiographic image capturing, the control unit 22 first converts the lines L1 to Lx of the scanning line 5 from the scanning driving unit 15 as shown in FIG. Thus, the ON voltage Von is applied to the gate electrodes 8g of the TFTs 8 at the same time, and the state is maintained.

  When information indicating that radiation is irradiated is input via the input unit 51, the voltage applied to the gate electrodes 8 g of the TFTs 8 is simultaneously switched to the off voltage Voff, and dark charges are generated in the radiation detection elements 7. After securing a predetermined charge accumulation time ΔTa for accumulation, the voltages applied to the gate electrodes 8g of the TFTs 8 are simultaneously switched to the on voltage Von at time T1.

  In the subsequent processing, as in the case of the radiographic imaging apparatus 1 according to the first embodiment, as shown in FIG. 13, the control unit 22 performs the current value detected by the current detection unit 43 (or When the start of radiation irradiation is detected at time T2 based on the corresponding voltage value V), the off voltage Voff is simultaneously applied again to the gate electrodes 8g of the TFTs 8, and when the radiation irradiation is completed, the applied on voltage Von. The image data is read from each radiation detection element 7 while switching for each of the lines L1 to Lx of the scanning line 5.

  In the reset process of each radiation detection element 7 before the dark reading process, the on-voltage Von is applied to the gate electrode 8g of each TFT 8 at time T1 and the off-voltage Voff is applied at time T2 at the time of radiographic imaging. The ON voltage Von is applied simultaneously to the gate electrodes 8g of the TFTs 8 for the same time interval T5-T4 as the time intervals T2-T1 until the voltage applied to the gate electrodes 8g of the TFTs 8 is simultaneously switched to the OFF voltage Voff. After that, dark reading processing is performed.

  As described above, the radiographic image capturing apparatus 100 according to the present embodiment can achieve the same effect as the radiographic image capturing apparatus 1 according to the first embodiment, and maintain the accuracy of offset correction. It is possible to perform the dark reading process within a realistic time while improving.

  In particular, in the present embodiment, in the reset process of each radiation detection element 7 before radiographic imaging, each TFT 8 is turned on continuously for a long time, so that dark charges in each radiation detection element 7 are sufficiently removed. After that, when information indicating that radiation is irradiated is input via the input means 51, the voltages applied to the gate electrodes 8g of the TFTs 8 are once switched to the off voltage Voff at a time. After securing the charge accumulation time ΔTa for accumulating dark charges in the pixel 7, the voltages applied to the gate electrodes 8g of the TFTs 8 are simultaneously switched to the on voltage Von at time T1, and the start of radiation irradiation is awaited.

  Therefore, the amount of residual charges such as dark charge remaining in each radiation detection element 7 at the radiation irradiation start time (time T2) is equal to each radiation detection element 7 at the end of reset processing before the dark reading process (time T5). As in the case of the first embodiment, it is possible to maintain and improve the accuracy of offset correction.

  In addition, the current detection means 43 in the radiographic imaging apparatuses 1 and 100 according to the first and second embodiments can detect a current flowing in the apparatus such as the bias line 9 and its connection 10 by irradiation of radiation. Any configuration may be used, and the configuration is not limited to the configuration in each of the above embodiments including the resistor 43a, the diode 43b, the differential amplifier 43c, the switch 43d, and the like as illustrated in FIG.

DESCRIPTION OF SYMBOLS 1,100 Radiation imaging device 5 Scan line 6 Signal line 7 Radiation detection element 8 TFT (switch means)
15 Scanning drive means 22 Control means 37 Indicator (notification means)
43 Current detection means 51 Input means r Region T2-T1 Time interval T5-T4 Time interval V Voltage value corresponding to current (current value)
Voff OFF voltage Von ON voltage

Claims (4)

A plurality of scanning lines and a plurality of signal lines arranged so as to intersect with each other; a plurality of radiation detecting elements arranged in a two-dimensional manner in each region partitioned by the plurality of scanning lines and the plurality of signal lines; ,
When an off voltage is applied via the connected scanning line, the charge generated in the radiation detection element is retained for each radiation detection element, and when the on voltage is applied, the radiation detection element Switch means for releasing the charge;
Scanning drive means for switching between the on-voltage and the off-voltage applied to the scanning line;
Current detection means for detecting a current flowing in the apparatus by irradiation of radiation;
Control means for detecting at least the start of radiation irradiation based on the value of the current detected by the current detection means;
With
The control means includes
Before applying radiation in radiographic imaging, after applying the off voltage to the switch means via the scanning lines from the scanning drive means to accumulate dark charges in the radiation detecting elements. , Applying the ON voltage to each of the switch means,
When the start of radiation irradiation is detected, the off-voltage is applied again to the switch means,
In the dark reading process, the radio frequency image is captured by the switch means at the same time interval from when the on voltage is applied to the switch means until the off voltage is applied again. A radiographic imaging apparatus, wherein dark reading processing is performed after an on voltage is applied and a voltage applied to each of the switch means is switched to the off voltage. A plurality of scanning lines and a plurality of signal lines arranged so as to intersect with each other; a plurality of radiation detecting elements arranged in a two-dimensional manner in each region partitioned by the plurality of scanning lines and the plurality of signal lines; ,
When an off voltage is applied via the connected scanning line, the charge generated in the radiation detection element is retained for each radiation detection element, and when the on voltage is applied, the radiation detection element Switch means for releasing the charge;
Scanning drive means for switching between the on-voltage and the off-voltage applied to the scanning line;
Current detection means for detecting a current flowing in the apparatus by irradiation of radiation;
Control means for detecting at least the start of radiation irradiation based on the value of the current detected by the current detection means;
With
The control means includes
Before radiation is emitted in radiographic imaging, the voltage applied from the scanning drive means to each switch means via each scanning line is alternately repeated between the on-voltage and the off-voltage,
When the start of radiation irradiation is detected in a state where the on voltage is applied to each switch means, the off voltage is applied to each switch means,
In the dark reading process, the switch means is applied for the same time interval as the time interval from the last application of the on-voltage to the switch means during the radiographic image capture to the application of the off-voltage again. A radiographic image capturing apparatus, wherein dark reading processing is performed after applying the ON voltage to the switching means and switching the voltage applied to each switch means to the OFF voltage.   The radiographic image capturing apparatus according to claim 2, further comprising a notification unit configured to notify that a voltage applied to each of the switch units is the off-voltage when performing radiographic image capturing. A plurality of scanning lines and a plurality of signal lines arranged so as to intersect with each other; a plurality of radiation detecting elements arranged in a two-dimensional manner in each region partitioned by the plurality of scanning lines and the plurality of signal lines; ,
When an off voltage is applied via the connected scanning line, the charge generated in the radiation detection element is retained for each radiation detection element, and when the on voltage is applied, the radiation detection element Switch means for releasing the charge;
Scanning drive means for switching between the on-voltage and the off-voltage applied to the scanning line;
Current detection means for detecting a current flowing in the apparatus by irradiation of radiation;
Control means for detecting at least the start of radiation irradiation based on the value of the current detected by the current detection means;
An input means for inputting information to irradiate radiation when irradiated with radiation;
With
The control means includes
When the on-voltage is applied to the switch means via the scanning lines from the scanning drive means before radiation is emitted in radiographic imaging, and the information is input from the input means, When the voltage applied to the switch means is switched to the off voltage and dark charges are accumulated in the radiation detecting elements, the voltage applied to the switch means is switched to the on voltage and the start of radiation irradiation is detected. , Applying the off-voltage again to each switch means,
In the dark reading process, the radio frequency image is captured by the switch means at the same time interval from when the on voltage is applied to the switch means until the off voltage is applied again. A radiographic imaging apparatus, wherein dark reading processing is performed after an on voltage is applied and a voltage applied to each of the switch means is switched to the off voltage.

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