JP2011091175A - Radiation image photographing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radiation image photographing device for reducing an effect of change of a bias voltage to be applied to respective radiation detection elements. <P>SOLUTION: The radiation image photographing device 1 includes: a substrate 4 having a plurality of radiation detection elements 7, which are two-dimensionally arrayed in respective areas r divided by mutually intersected scanning lines 5 and signal lines 6, and a plurality of bias wires 9, which are connected to the respective radiation detection elements 7, apply the bias voltage to the respective radiation detection elements 7 from a bias power supply 14, and are arranged one by one in each string of the radiation detection elements 7 among a plurality of two-dimensionally arrayed radiation detection elements 7; and wire connection 10 for bonding a plurality of bias wires 9. The bias wires 9 are connected to the respective wires Fa of a flexible printed circuit board F, respectively. The ends of the respective wires Fa on the opposite side of the ends connected to the bias wires 9 are bonded on a substrate 33 different from the substrate 4 to the wire connection 10 where a resistance value per unit length is smaller than that in each bias wire 9. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a radiographic imaging apparatus, and more particularly, to a radiographic imaging apparatus including a plurality of bias lines for applying a bias voltage to each radiation detection element and their connections.

  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, the radiation detection element is usually provided with two electrodes, and one electrode is provided with a switch element such as a thin film transistor (hereinafter referred to as TFT), so that the charge accumulated in the radiation detection element is reduced. Reading is often performed, and a bias line for applying a bias voltage (including a so-called reverse bias voltage) to the radiation detection element is often connected to the other electrode (see, for example, Patent Documents 4 and 5).

  Then, in order to apply a constant bias voltage to each radiation detection element from the bias power source, for example, as shown in each drawing of Patent Document 5, radiation arranged in a two-dimensional form (matrix form) Among the detection elements, one bias line is wired for each column of radiation detection elements, and each bias line is further tied to one connection (represented as Vs connection wiring in Patent Document 5) and biased. Often configured to connect to a power source.

JP-A-9-73144 JP 2006-058124 A JP-A-6-342099 JP 2003-325441 A Japanese Patent Laid-Open No. 2008-4920

  By the way, when a radiation image is captured by irradiating a radiation image capturing apparatus through a subject, and the charge accumulated in each radiation detection element is read, normally, an on-voltage is applied to a scanning line (also referred to as a gate line). Is applied to turn on the TFT whose gate electrode is connected to the scanning line, whereby charges (for example, electrons) accumulated from each radiation detection element are emitted to the signal line. At the same time, charges (for example, holes) are also emitted to the bias line side.

  The electric charge released to the bias line side concentrates on the connection, and a relatively large current flows through the connection. Since the connection has a resistance value, a voltage fluctuation occurs when a relatively large charge flows through the connection. For this reason, in the process of reading charges from the radiation detection elements, it is desirable that a constant bias voltage is applied to each radiation detection element in order to accurately read out the charges accumulated in each radiation detection element. Instead, the bias voltage varies.

  Further, for example, as shown in each drawing of Patent Document 5, the bias line is often configured to intersect the scanning line, and in that case, a so-called parasitic capacitance is formed between the bias line and the scanning line. appear. In the process of reading out charges from the radiation detection element, the voltage applied to each scanning line is switched between the on-voltage and the off-voltage, so that the scanning is also performed on the bias line and the connection side that intersect with it. Voltage fluctuations occur each time the voltage applied to the line is switched.

  Further, as will be described later, when radiation is irradiated with each TFT turned on, electric charges are generated in each radiation detection element, and the radiation is detected by capturing fluctuations in the current value flowing out to the bias line and the connection. The image capturing device itself can detect the start of radiation irradiation. However, in this case, since the current flowing out from each radiation detection element concentrates on the connection via each bias line, a large current flows through the connection. Therefore, also in this case, the bias voltage varies due to the resistance value of the connection.

  When the radiation imaging apparatus itself detects the start of radiation irradiation by detecting the current flowing through the connection as described above, each TFT detects the start of radiation irradiation and accumulates charges in each radiation detection element. In this case, if the bias voltage applied to each radiation detection element is fluctuated, the value of the electric charge accumulated and read out in each radiation detection element is not accurate. There is a fear.

  As described above, the radiographic imaging device is often not configured to detect the start of radiation irradiation by itself, and at the start of radiation irradiation, that is, at the start of charge accumulation in each radiation detection element. In some cases, the bias voltage does not vary as described above. However, when fluctuations occur in the bias voltage applied to each radiation detection element at the time of reading charges from each radiation detection element as described above, at the time of reading the charge accumulated from each radiation detection element, that is, image data, The value fluctuates, and there arises a problem that the image quality of the captured image composed of the finally obtained image data is deteriorated.

  The present invention has been made in view of the above points, and an object thereof is to provide a radiographic imaging apparatus capable of reducing the influence of fluctuations in bias voltage applied to each radiation detection element.

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;
A plurality of radiation detection elements arranged two-dimensionally in each region partitioned by the plurality of scanning lines and a plurality of signal lines;
A bias voltage is applied to each radiation detection element from a bias power source connected to each radiation detection element, and among each of the plurality of radiation detection elements arranged in a two-dimensional manner, for each column of the radiation detection elements A plurality of bias lines wired one by one;
A substrate comprising:
A connection for binding the plurality of bias lines;
With
The plurality of bias lines are respectively connected to the respective wirings of the flexible printed circuit board, and the end of each wiring opposite to the end connected to the bias line is on a different substrate different from the substrate. The resistance value per unit length is bundled with the connection smaller than the resistance value per unit length of each bias line.

Moreover, the radiographic imaging device of the present invention is
A plurality of scanning lines and a plurality of signal lines arranged to cross each other;
A plurality of radiation detection elements arranged two-dimensionally in each region partitioned by the plurality of scanning lines and a plurality of signal lines;
A bias voltage is applied to each radiation detection element from a bias power source connected to each radiation detection element, and among each of the plurality of radiation detection elements arranged in a two-dimensional manner, for each column of the radiation detection elements A plurality of bias lines wired one by one;
A substrate comprising:
A connection for binding the plurality of bias lines;
With
The plurality of bias lines are respectively connected to each wiring of a flexible printed circuit board, and each wiring is a resistance value per unit length of each bias line in the flexible printed circuit board. It is characterized by being bound to the smaller wire connection.

  According to the radiographic imaging apparatus of the system as in the present invention, the resistance value per unit length of the connection is formed so as to be smaller than the resistance value per unit length of each bias line. Thus, it is possible to make the fluctuation of the bias voltage based on the fluctuation of the voltage generated in (1) smaller, and even if the bias voltage fluctuates, it can be promptly restored to the original constant value. Therefore, even if fluctuations occur in the bias voltage applied to each radiation detection element via the connection, the influence of the fluctuations can be reduced, and the image quality of the captured image consisting of the finally obtained image data is reduced. Can be prevented.

It is a perspective view which shows the radiographic imaging apparatus which concerns on this 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 figure showing the connection which binds the edge part on the opposite side of each wiring on the flexible printed circuit board and PCB board | substrate with which each wiring was connected to each bias line. It is a figure showing the wiring which binds each wiring in the flexible printed circuit board and each flexible printed circuit board with which each wiring was connected to each bias line. It is a top view which shows the structure at the time of binding a bias line to a connection in the outer position of the detection part of a board | substrate. It is a block diagram showing the equivalent circuit of a radiographic imaging apparatus. It is a graph which shows transition of the electric current value output from an electric current detection means, when radiation is irradiated to the radiographic imaging apparatus. It is a top view which shows the structural example at the time of providing a bias line above a scanning line.

  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.

  FIG. 1 is an external perspective view of the radiographic image capturing apparatus according to the present embodiment, and FIG. 2 is a cross-sectional view taken along line AA in FIG. As shown in FIGS. 1 and 2, the radiation image capturing apparatus 1 according to the present embodiment is configured by housing a scintillator 3, a substrate 4, and the like in a housing 2.

  The housing 2 is formed of a material such as a carbon plate or plastic that at least the radiation incident surface R transmits 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 made up of LEDs, etc., and a battery 41 (not shown) (see FIG. 10 described later). A possible lid member 38 and the like are arranged. In the present embodiment, an antenna device 39 that is a transfer unit for transferring image data and the like wirelessly to an external device is embedded in the side surface of the lid member 38.

  It is also possible to transfer the image data or the like to an external device in a wired manner. In this case, for example, as a transfer means, a connection terminal or the like for connecting by inserting a cable or the like is used as radiation. It is provided on the side surface of the image capturing apparatus 1 or the like. The position of the antenna device 39 is not limited to the portion of the lid member 38, and is provided at an appropriate position such as a side surface of the radiographic image capturing device 1.

  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 is applied to the connected scanning line 5 by the scanning drive means 15 described later and applied to the gate electrode 8g, and is generated and accumulated in the radiation detection element 7. The charged electric charge is discharged to the signal line 6. Further, the TFT 8 is turned off when the off voltage is applied to the connected scanning line 5 and the off voltage is applied to the gate electrode 8g, and the emission of the charge from the radiation detecting element 7 to the signal line 6 is stopped. 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 made of aluminum or the like 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.

  In the present embodiment, as shown in FIG. 3, each scanning line 5, each signal line 6, and each bias line 9 are respectively connected to input / output terminals (also referred to as pads) 11 provided near the edge of the substrate 4. It is connected. As shown in FIG. 6, a COF (Chip On Film) 12 in which a chip such as an IC 12a is incorporated in each input / output terminal 11 of each scanning line 5 and each signal line 6 is an anisotropic conductive adhesive film (Anisotropic Conductive Film). It is connected via an anisotropic conductive adhesive material 13 such as a film or anisotropic conductive paste.

  The COF 12 is routed to the back surface 4b side of the substrate 4 and is 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.

  In the present embodiment, as shown in FIG. 7, each input / output terminal 11 of each bias line 9 has a flexible printed circuit board (flexible printed circuit; also referred to as a flexible circuit board or a flexible board) F copper wire or the like. As in the case of FIG. 6, each wiring Fa made of is connected via an anisotropic conductive adhesive material or the like not shown in FIG. 7.

  The flexible printed circuit board F is routed to the back surface 4b side of the substrate 4 in the same manner as the COF 12 shown in FIG. 6, and is connected to the above-described PCB substrate 33 on the back surface 4b side. In the present embodiment, as shown in FIG. 7, the end of each wiring Fa of the flexible printed circuit board F connected to each bias line 9 is opposite to the end to which the bias line 9 is connected. On the PCB substrate 33, the resistance value per unit length is bound to a connection 10 made of a copper wire or the like, which is smaller than the resistance value per unit length of each bias line 9.

  At that time, it is possible to further reduce the resistance value per unit length of the connection 10 by increasing the width of the connection 10 or forming the thickness to be thicker. Moreover, as shown in FIG. 8, it is also possible to constitute the flexible printed circuit board F so that each wiring Fa is bound to a connection 10 made of a copper wire or the like.

  7 and FIG. 8, the case where all the bias lines 9 are connected to each wiring Fa of one flexible printed board F is shown. However, each bias line 9 is divided into a plurality of flexible printed boards F. It is also possible to configure so as to be connected to each wiring Fa.

  Further, as shown in FIG. 9, the bias line 9 is configured to be bound to the connection 10 at a position outside the detection portion P of the substrate 4. For example, the width of the connection 10 on the substrate 4 is increased to increase the width of the connection 10. It can be considered that the resistance value per unit length is made smaller than the resistance value per unit length of each bias line 9.

  However, in the case of such a configuration, in order to realize the same effect as that described later of the present embodiment, the width of the connection 10 must be considerably increased. There is a practical limit to the size of the wire, and a method of reducing the resistance value per unit length by increasing the width of the connection 10 cannot be practically adopted.

  Further, for example, by forming the connection 10 on the substrate 4 to be thick, the resistance value per unit length of the connection 10 is made smaller than the resistance value per unit length of each bias line 9. However, in this case as well, in order to achieve the same effect as that described later of the present embodiment, the thickness of the connection 10 must be made considerably thick.

  However, with such a configuration, the thickness of the connection 10 is larger than the predetermined distance between the substrate 4 and the glass substrate 35 shown in FIG. 2, and the distance between the scintillator 3 and the radiation detection element 7 is It becomes larger on the side closer to 10 and smaller on the side farther from the connection 10. Therefore, the method of reducing the resistance value per unit length by forming the connection wire 10 thickly cannot be employed.

  As described above, there are special restrictions on increasing the width of the connection 10 or increasing the thickness on the PCB substrate 33 (see FIG. 6) or in the flexible printed circuit board F (see FIG. 7). Therefore, those modifications can be made as appropriate.

  Here, the circuit configuration of the radiographic image capturing apparatus 1 according to the present embodiment will be described. FIG. 10 is a block diagram showing an equivalent circuit of the radiation image capturing apparatus 1 according to this embodiment.

  As described above, each radiation detection element 7 of the detection unit P of the substrate 4 has the bias electrode 9 connected to the second electrode 78, and each bias line 9 is made of a copper wire or the like of the flexible printed circuit board F. Connected to each wiring Fa, in the present embodiment, it is bound to a connection 10 made of a copper wire or the like on the PCB substrate 33. The connection 10 is connected to a bias power supply 14.

  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 that detects the amount of current flowing through the connection 10 is provided in the connection 10 of the bias line 9.

  As described above, when the radiation image capturing apparatus 1 is irradiated with radiation at the time of capturing a radiation image, electron-hole pairs are generated in the i layer 76 (see FIG. 5) of each radiation detection element 7. At that time, for example, if the TFT 8 is turned on, one charge (electrons in the present embodiment) out of the electron-hole pairs generated in each radiation detection element 7 flows out to the signal line 6 through the TFT 8, The other charge (holes in this embodiment) flows out to the bias line 9 and a current flows through the connection 10.

  The control means 22, which will be described later, monitors the value of the current flowing through the connection 10 detected by the current detection means 43. As shown in FIG. 11, the current flowing through the connection 10 when radiation irradiation starts. Although I increases, the time T1 when the current value I reaches the predetermined value Ith is detected as the time when the irradiation of radiation is started. In addition to this, for example, it is possible to detect the time when the time differential value of the current value I becomes a predetermined threshold as the radiation irradiation start time.

  If the TFT 8 is kept in the ON state as it is, the charge (image data) generated by radiation irradiation flows out from each radiation detection element 7. Therefore, as soon as the start of radiation irradiation is detected, the control means 22 turns off each TFT 8 and accumulates charges in each radiation detection element 7. Therefore, as shown in FIG. 11, the value of the current flowing through the connection 10 via each bias line 9 gradually decreases and hardly flows through the connection 10. In the present invention, the current detection means 43 is not necessarily provided.

  As shown in FIG. 10, in the present embodiment, the bias line 9 is connected to the second electrode 78 side of the radiation detection element 7, that is, the p layer 77 side (see FIG. 5). As can be seen from this, a bias voltage lower than the voltage applied to the first electrode 74 side from the bias power supply 14 (that is, a so-called reverse bias voltage) is applied to the second electrode 78 of the radiation detection element 7 via the bias line 9. Applied.

  The first electrode 74 of each radiation detection element 7 is connected to the source electrode 8s (denoted as S in FIG. 10) of the TFT 8, and the gate electrode 8g of each TFT 8 (denoted as G in FIG. 10). Are 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 8d (denoted as D in FIG. 10) of each TFT 8 is connected to each signal line 6.

  In the present embodiment, the scanning drive unit 15 includes a power supply circuit 15a that supplies an on voltage and an off voltage to the gate driver 15b, and a voltage applied to each of the lines L1 to Lx of the scanning line 5 between the on voltage and the off voltage. A gate driver 15b that switches between the on state and the off state of each TFT 8 is provided.

  Each signal line 6 is connected to each readout circuit 17 formed in the readout IC 16. The readout circuit 17 includes an amplification circuit 18, a correlated double sampling (Correlated Double Sampling, expressed as CDS in the drawing) circuit 19, an analog multiplexer 21, and an A / D converter 20. Yes.

  For example, in radiographic imaging, radiation is applied to the radiographic imaging device 1 through the subject, and the scintillator 3 converts the radiation into electromagnetic waves of other wavelengths and irradiates the radiation detection element 7 directly below the radiation. Then, electric charges (electric signals) are generated according to the dose of radiation (the amount of electromagnetic waves) irradiated by the radiation detection element 7.

  In the process of reading charges from each radiation detection element 7, the lines L 1 to Lx of the scanning line 5 to which the on-voltage is applied from the gate driver 15 b of the scanning driving unit 15 are sequentially switched, and the scanning line 5 passes through each scanning line 5. Then, when the TFT 8 to which the ON voltage is applied to the gate electrode 8g is turned on, electric charges are discharged from the radiation detection element 7 to the signal line 6.

  Then, a voltage value is output from the amplifier circuit 18 in accordance with the amount of charge emitted from the radiation detection element 7, and is correlated double-sampled by the correlated double sampling circuit 19, and analog value image data is output to the multiplexer 21. Is done. The image data sequentially output from the multiplexer 21 is sequentially converted into digital value image data by the A / D converter 20, output to the storage means 40, and sequentially stored.

  The control means 22 includes a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), a computer having an input / output interface connected to the bus, an FPGA (Field Programmable Gate Array), and the like. ing. It may be configured by a dedicated control circuit.

  The control unit 22 controls each functional unit such as the scanning drive unit 15 and the readout circuit 17 of the radiographic imaging apparatus 1 to reset each radiation detection element 7 and accumulate charges in each radiation detection element 7. Various processes such as reading of charges from them are performed.

  The control means 22 is connected to a storage means 40 constituted by a DRAM (Dynamic RAM) or the like, and a battery 41 that supplies power to each functional unit of the radiographic image capturing apparatus 1. The battery 41 is provided with a connection terminal 42 for charging the battery 41 by supplying power to the battery 41 from a charging device (not shown) such as a cradle. Furthermore, the above-described antenna device 39 is connected to the control means 22 so that various information such as image data and various signals can be transmitted to and received from an external device.

  Next, the operation of the radiation image capturing apparatus 1 according to this embodiment will be described.

  In the conventional radiographic image capturing apparatus, as in the radiographic image capturing apparatus described in Patent Document 5 described above, the bias line 9 and the connection (Vs connection wiring in Patent Document 5) 10 are made of the same material such as aluminum, for example. It was formed on the substrate 4 by a film forming process. At that time, in order to reduce the resistance value per unit length of the connection 10, the connection 10 may be formed to have a wide width or a thick thickness.

  However, as described above, when the width of the connection 10 is increased or the thickness is increased, the size of the substrate 4 or the like is increased, or the distance between the substrate 4 and the glass substrate 35 is not uniform, There was a limit to the expansion of the width and thickness of the connection wire 10. Therefore, even if the width and thickness of the connection 10 are increased to reduce the resistance value per unit length of the connection 10, the resistance value can be reduced somewhat.

  Therefore, when the current radiation imaging apparatus is provided with the current detection means 43 as in the present embodiment, for example, as shown in FIG. Holes) concentrate on the connection 10 via the respective bias lines 9, and a large current flows in the connection 10.

  When a large current flows in the connection 10 in this way, the connection 10 has a resistance value per unit length of a certain size. Therefore, as described above, voltage fluctuation occurs in the connection 10 and each radiation detection is performed. Variations occur in the value of the bias voltage to which a constant value is to be applied to the element 7. As described above, as soon as the current value detected by the current detection means 43 increases, each TFT 8 is turned off and charge accumulation in each radiation detection element 7 starts, but the bias voltage varies. Since the TFTs 8 are turned off during the operation, there is a possibility that the charge values stored and read in the radiation detection elements 7 are not accurate values.

  Thus, when the start of radiation irradiation is detected by the current detection means 43, each TFT 8 is turned off while the bias voltage is changing. Therefore, the voltage at the connection 10 at the time when the current is turned off. The magnitude of the fluctuation affects the value of charge accumulated in each radiation detection element 7.

  Further, in the process of reading charges from each radiation detection element 7 after radiographic imaging, the charge (image data) accumulated in each radiation detection element 7 is subjected to an on-voltage from the gate driver 15b of the scanning drive means 15. While the lines L1 to Lx of the applied scanning line 5 are sequentially switched, the TFTs 8 in which the gate electrodes 8g are connected to the lines L1 to Lx of the scanning line 5 are sequentially turned on. Read out.

  At that time, the radiation detection elements 7 connected to the scanning lines 5 to which the ON voltage is applied via the TFTs 8 are several thousand, and charges (electrons) are read from the radiation detection elements 7 to the signal lines 6. At the same time, the other charge (hole) flows out to each bias line 9. Since these charges (holes) flow in the connection 10 in a concentrated manner, a relatively large current flows in the connection 10 in this case as well.

  When a relatively large current flows through the connection 10, the voltage changes in the connection 10 in the same manner as described above, and the value of the bias voltage changes during the reading of charges (electrons) from each radiation detection element 7. Therefore, there is a possibility that the value of the image data read from each radiation detection element 7 is not the original value.

  When reading out charges from each radiation detection element 7, as described above, the voltage value output from the amplification circuit 18 at the start of reading, and the amplification circuit when the charge is read out from each radiation detection element 7. The voltage value output from 18 is sampled by the correlated double sampling circuit 19 and the difference is output as image data.

  Therefore, at the time of reading out charges from each radiation detection element 7, the bias voltage that has changed due to the current flowing through the connection 10 is larger than the magnitude of the voltage fluctuation itself due to the current flowing through the connection 10 at the time of reading. Whether or not has returned to the original bias voltage at the second sampling time in the correlated double sampling circuit 19 affects the value of the charge read from each radiation detection element 7.

  In the conventional radiographic imaging apparatus, since the resistance value per unit length of the connection 10 is large, the value of the current flowing through the connection 10 increases, and the value of the bias voltage fluctuates greatly. In many cases, the original bias voltage was not restored at the second sampling time in the double sampling circuit 19. Therefore, the charge value read from each radiation detection element 7 is affected.

  On the other hand, in the radiographic image capturing apparatus 1 according to the present embodiment, each bias line 9 is connected to each wiring Fa of the flexible printed circuit board F, and the opposite end of each wiring Fa is on the PCB substrate 33 or the flexible printed circuit. The substrate F is bound to a connection 10 made of a copper wire or the like. The connection 10 is formed of a copper wire or the like, and the resistance value per unit length is formed so as to be smaller than the resistance value per unit length of each bias line 9 formed of aluminum. Yes.

  Further, as described above, the connection 10 is formed on the PCB substrate 33 (see FIG. 6) or in the flexible printed circuit board F (see FIG. 7) so that the width is increased or the thickness is increased. The value can be further reduced.

  For this reason, even when a large current flows through the connection 10 as described above at the start of radiation irradiation at the time of radiographic imaging or at the time of reading charges (image data) from each radiation detection element 7, Since the resistance value per unit length is small, the voltage fluctuation generated in the connection 10 becomes minute. In addition, since the voltage fluctuation generated in the connection 10 is very small as described above, even if the bias voltage fluctuates based on the voltage fluctuation generated in the connection 10, the bias voltage quickly recovers to the original predetermined constant value. To do.

  For this reason, as described above, the influence exerted on the charge accumulated in each radiation detection element 7 or read out from each radiation detection element 7 at the start of radiation irradiation or reading of image data is reduced.

  As described above, according to the radiographic imaging apparatus 1 according to the present embodiment, the resistance value per unit length of the connection 10 is formed to be smaller than the resistance value per unit length of each bias line 9. Therefore, it becomes possible to make the fluctuation of the bias voltage based on the fluctuation of the voltage generated in the connection 10 smaller, and even if the fluctuation of the bias voltage occurs, it can be quickly restored to the original constant value. Is possible.

  Therefore, in the radiographic image capturing apparatus 1 according to the present embodiment, even if a variation occurs in the bias voltage applied to each radiation detection element 7 via the connection 10, it is possible to reduce the influence of the variation. Therefore, it is possible to prevent the deterioration of the image quality of the photographed image made up of the image data that is obtained automatically.

  At that time, as described above, the resistance value per unit length of the connection 10 is further reduced by increasing the width of the connection 10 or by increasing the thickness of the connection 10 on the PCB substrate 33 or the flexible printed circuit board F. With this configuration, it is possible to further reduce the bias voltage fluctuation based on the voltage fluctuation generated in the connection 10, and to quickly recover the original constant value even if the bias voltage fluctuates. It becomes possible to comprise.

  Therefore, it is possible to significantly reduce the influence of fluctuations in the bias voltage applied to each radiation detection element 7 via the connection 10, and more effectively reduce the image quality of the captured image composed of the finally obtained image data. It becomes possible to prevent.

  In the radiographic image capturing apparatus 1 according to the present embodiment and the radiographic image capturing apparatuses described in Patent Documents 4 and 5, the bias line 9 is connected to the second electrode 78 of the radiation detecting element 7 as shown in FIG. Although wired so as to cross over, the bias line 9 is formed of an opaque material such as aluminum as described above. Therefore, when the wiring is performed as described above, the radiation detecting element 7 is equivalent to the bias line 9. The aperture ratio is reduced.

  And if the aperture ratio of the radiation detection element 7 falls, even if the scintillator 3 irradiates the radiation detection element 7 with the same amount of electromagnetic waves, the value of the image data obtained by the radiation detection element becomes small, and the S / N ratio deteriorates. There is a case.

  Therefore, for example, as shown in FIG. 12, the bias line 9 can be provided above the scanning line 5 and the signal line 6 (that is, on the scintillator 3 side) in parallel with them via an insulating layer.

  With this configuration, it is possible to prevent the bias line 9 from crossing at least above the radiation detection element 7, thereby improving the aperture ratio of the radiation detection element 7 and improving the S / N ratio of the radiation image. It becomes possible.

  In this case, if the bias line 9 is provided above the signal line 6, fluctuations and fluctuations in the bias voltage applied to the bias line 9 are transmitted to the signal line 6 through the insulating layer and read out via the signal line 6. The bias line 9 is preferably provided above the scanning line 5 as shown in FIG.

  In addition, it goes without saying that the present invention is not limited to this embodiment and can be changed as appropriate.

DESCRIPTION OF SYMBOLS 1 Radiographic imaging apparatus 4 Board | substrate 5 Scan line 6 Signal line 7 Radiation detection element 9 Bias line 10 Connection 14 Bias power supply 33 PCB board (another board)
F Flexible printed circuit board Fa Wiring r area

Claims (4)

A plurality of scanning lines and a plurality of signal lines arranged to cross each other;
A plurality of radiation detection elements arranged two-dimensionally in each region partitioned by the plurality of scanning lines and a plurality of signal lines;
A bias voltage is applied to each radiation detection element from a bias power source connected to each radiation detection element, and among each of the plurality of radiation detection elements arranged in a two-dimensional manner, for each column of the radiation detection elements A plurality of bias lines wired one by one;
A substrate comprising:
A connection for binding the plurality of bias lines;
With
The plurality of bias lines are respectively connected to the respective wirings of the flexible printed circuit board, and the end of each wiring opposite to the end connected to the bias line is on a different substrate different from the substrate. The radiation image capturing apparatus, wherein a resistance value per unit length is bound to the connection smaller than a resistance value per unit length of each bias line. A plurality of scanning lines and a plurality of signal lines arranged to cross each other;
A plurality of radiation detection elements arranged two-dimensionally in each region partitioned by the plurality of scanning lines and a plurality of signal lines;
A bias voltage is applied to each radiation detection element from a bias power source connected to each radiation detection element, and among each of the plurality of radiation detection elements arranged in a two-dimensional manner, for each column of the radiation detection elements A plurality of bias lines wired one by one;
A substrate comprising:
A connection for binding the plurality of bias lines;
With
The plurality of bias lines are respectively connected to each wiring of a flexible printed circuit board, and each wiring is a resistance value per unit length of each bias line in the flexible printed circuit board. A radiographic image capturing apparatus, wherein the radiographic image capturing apparatus is bound to the smaller wire connection.   The radiographic imaging apparatus according to claim 1, wherein the connection is made of a copper wire.   4. The radiographic imaging apparatus according to claim 1, wherein each wiring of the flexible printed board is formed of a copper wire. 5.

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