JP2008070253A - Electromagnetic wave detector and radiation imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electromagnetic wave detector for suppressing a residual image and reducing an intensity difference, and a radiation imaging apparatus using it. <P>SOLUTION: A flat panel X-ray detector includes: a semiconductor layer for converting X rays into a charge; a plurality of divided electrodes for collecting the charge converted by the semiconductor layer as a detection signal; a switching element for reading the collected detection signal; two amplifier array circuits for processing the read detection signal; and a light irradiating section for irradiating the divided electrodes in the semiconductor layer with a light. The light irradiating section is turned off during an accumulating period, and turned on during a reading period. A residual output can be prevented from being generated, and the afterimage can be suppressed during the reading period. A crosstalk between a leakage current and a signal line can be suppressed, and the intensity difference can be reduced in an image during the accumulating period. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to electromagnetic fields (radiation such as X-rays, visible light, ultraviolet rays, infrared rays, etc.) used in the medical field, industrial fields such as non-destructive inspection, RI (Radio Isotope) inspection, and optical inspection, and nuclear power field. And an radiation imaging apparatus using the same.

  Conventional electromagnetic wave detectors for detecting electromagnetic waves are, in order from the incident side of electromagnetic waves, a semiconductor layer that converts electromagnetic waves into electric charges, an active matrix substrate that collects and reads out electric charges generated in the semiconductor layers as detection signals, A light irradiating unit that irradiates light toward one surface where the divided electrodes are provided. An active matrix substrate is configured by forming a plurality of divided electrodes for collecting charges on an insulating substrate, switching elements provided for each divided electrode, and the like. The electromagnetic wave detector further processes a detection signal read out in cooperation with a gate driver that drives the switching element, a drive control circuit that operates the gate driver to control reading of the detection signal, and the drive control circuit. And an amplifier array circuit. Two amplifier array circuits are provided on both sides of the switching element group. Then, the switching element group is divided into two substantially at the center, and each switching element belonging to one side is connected to an amplifier array circuit arranged on the side thereof.

  FIG. 9 is a timing chart of the electromagnetic wave detector according to the conventional example. Light irradiation by the light irradiation unit is started before the detection operation for detecting the electromagnetic wave to be detected is started, and is continued for a predetermined time after the detection operation is ended. During the period in which the light irradiating part irradiates light, a state in which charges are accumulated is always maintained in the space between the divided electrodes of the semiconductor layer. The detection operation is divided into an accumulation operation for accumulating a detection signal collected according to an electromagnetic wave to be detected and a read operation for reading out the detection signal.

  Specifically, the drive control circuit and the gate driver sequentially drive the switching elements in synchronization with the vertical and horizontal synchronization signals. Detection signals are sequentially read from the driven switching elements. Such a reading operation ends when a detection signal for one image is read, and the operation proceeds to an accumulation operation. The accumulation operation is continued until the timing of the next vertical synchronization signal, and the read operation is started again.

According to the electromagnetic wave detector according to the conventional example configured as described above, since the light irradiation unit is provided, the charge corresponding to the electromagnetic wave to be detected does not accumulate in the space between the divided electrodes. Does not happen. In addition, the residual output is not generated because the electric charge accumulated in the space between the divided electrodes is not swept out regardless of whether or not the electromagnetic wave to be detected is incident. Therefore, it is possible to prevent an afterimage from occurring in an image obtained by processing the detection signal by the amplifier array circuit (see, for example, Patent Document 1).
JP 2004-146769 A

However, the conventional example having such a configuration has the following problems.
In the conventional example, the switching element group is divided into two, and the detection signal is processed by each separate amplifier array circuit. Therefore, there is a disadvantage that a luminance difference occurs between regions corresponding to each amplifier array circuit in the image. is there. This luminance difference is promoted when strong X-rays are incident only on one of the two divided switching element groups.

  This invention is made in view of such a situation, Comprising: It aims at providing the electromagnetic wave detector which can reduce a brightness | luminance difference, and a radiography apparatus using the same, suppressing an afterimage. To do.

In order to achieve such an object, the present invention has the following configuration.
That is, according to the first aspect of the present invention, in the electromagnetic wave detector for detecting the electromagnetic wave, the semiconductor layer for converting the electromagnetic wave into electric charge and the one side of the semiconductor layer are provided, and the converted electric charge is collected as a detection signal. A plurality of divided electrodes, a switching element provided for each of the divided electrodes, for reading a detection signal, and a separate element group provided for each element group in which all switching elements are divided into two or more, and corresponding element groups A plurality of amplifier array circuits for processing detection signals read from the switching elements, drive control means for controlling the reading of the detection signals by driving the switching elements, and one surface on which the divided electrodes of the semiconductor layer are provided The detection signal is read from any switching element in cooperation with the light irradiation means for irradiating light toward the A light control means for controlling the light irradiating means so as to irradiate the light with a light intensity smaller than that of the reading period in which the detection signal is read from any of the switching elements in the storage period that is not emitted. It is characterized by this.

  [Operation / Effect] According to the invention described in claim 1, since the light control means irradiates the light irradiating means with a relatively large intensity light during the readout period, the residual output when reading the detection signal from each switching element. Can be prevented. Thereby, an afterimage can be suppressed in an image obtained based on the read detection signal.

  Further, since the light control unit irradiates light having a relatively low intensity from the light irradiation unit during the accumulation period, it is possible to suppress leakage current and crosstalk between the signal lines during the accumulation period. Thereby, in the image obtained based on the detection signal, it is possible to reduce the luminance difference between the regions corresponding to each element group.

  According to a second aspect of the present invention, in the electromagnetic wave detector for detecting an electromagnetic wave, the semiconductor layer for converting the electromagnetic wave into an electric charge and the one side of the semiconductor layer are provided, and the converted electric charge is collected as a detection signal. A plurality of divided electrodes, a switching element provided for each of the divided electrodes, for reading a detection signal, and a separate element group provided for each element group in which all switching elements are divided into two or more, and corresponding element groups A plurality of amplifier array circuits for processing detection signals read from the switching elements, drive control means for controlling the reading of the detection signals by driving the switching elements, and one surface on which the divided electrodes of the semiconductor layer are provided The detection signal is read from any switching element in cooperation with the light irradiating means for irradiating the light toward and the drive control means. And a light control means for turning on the light irradiation means during a readout period in which the light irradiation means is turned off during the non-accumulation period and a detection signal is read out from any of the switching elements. .

  [Operation / Effect] According to the invention described in claim 2, since the light control means turns on the light irradiation means during the readout period, it prevents the occurrence of residual output when reading the detection signal from each switching element. be able to. Thereby, an afterimage can be suppressed in an image obtained based on the read detection signal.

  Further, since the light control unit turns off the light irradiation unit during the accumulation period, it is possible to suppress leakage current and crosstalk between the signal lines during the accumulation period. Thereby, in an image obtained based on the detection signal, it is possible to reduce a luminance difference between regions corresponding to each element group.

  According to a third aspect of the present invention, there is provided a radiation imaging apparatus for imaging a subject, a radiation source for irradiating the subject with radiation, a conversion means for converting the radiation transmitted through the subject into charges, and the conversion A plurality of divided electrodes provided on one side of the means for collecting the converted charges as detection signals, a switching element provided for each of the divided electrodes for reading out the detection signals, and all switching elements A plurality of amplifier array circuits which are provided separately for each of the element groups divided as described above and process detection signals read from the switching elements of the corresponding element groups, and the switching elements are driven so that the radiation generation source Drive control means for reading out a detection signal in a non-irradiation period in which no irradiation is performed, and a split electrode of the semiconductor layer are provided In the light irradiation means for irradiating light toward the direction, and at least in the irradiation period in which the radiation generation source irradiates the radiation, the intensity is smaller than that in the readout period in which the detection signal is read from one of the switching elements. And a light control means for controlling the light irradiation means so as to irradiate with light.

  [Operation / Effect] According to the invention described in claim 3, since the light control means irradiates light having a relatively high intensity from the light irradiating means in the readout period, the residual output when reading the detection signal from each switching element. Can be prevented. Thereby, an afterimage can be suppressed in an image obtained based on the read detection signal.

  In addition, since the light control unit irradiates light having a relatively low intensity from the light irradiation unit at least during the irradiation period, it is possible to suppress leakage current and crosstalk between signal lines due to incident radiation. Thereby, in an image obtained based on the detection signal, it is possible to reduce a luminance difference between regions corresponding to each element group.

  According to a fourth aspect of the present invention, there is provided a radiation imaging apparatus for imaging a subject, a radiation source for irradiating the subject with radiation, a conversion means for converting the radiation transmitted through the subject into electric charge, and the conversion A plurality of divided electrodes provided on one side of the means for collecting the converted charges as detection signals, a switching element provided for each of the divided electrodes for reading out the detection signals, and all switching elements A plurality of amplifier array circuits which are provided separately for each of the element groups divided as described above and process detection signals read from the switching elements of the corresponding element groups, and the switching elements are driven so that the radiation generation source Drive control means for reading out a detection signal in a non-irradiation period in which no irradiation is performed, and a split electrode of the semiconductor layer are provided A light irradiating means for irradiating light toward the direction, and a reading period in which at least the light irradiating means is extinguished and the detection signal is read from any of the switching elements during the irradiation period in which the radiation generation source is irradiating And a light control means for turning on at least the light irradiation means.

  [Operation / Effect] According to the invention described in claim 4, since the light control means turns on the light irradiation means in the readout period, it is possible to prevent a residual output from being generated when the detection signal is read out from each switching element. be able to. Thereby, an afterimage can be suppressed in an image obtained based on the read detection signal.

  In addition, since the light control unit turns off the light irradiation unit at least during the irradiation period, leakage current and crosstalk between signal lines due to incident radiation can be suppressed. Thereby, in an image obtained based on the detection signal, it is possible to reduce a luminance difference between regions corresponding to each element group.

  The invention according to claim 5 is a radiation imaging apparatus for imaging a subject, a radiation generation source for irradiating the subject with radiation, a conversion means for converting the radiation transmitted through the subject into charges, and the conversion A plurality of divided electrodes provided on one side of the means for collecting the converted charges as detection signals, a switching element provided for each of the divided electrodes for reading out the detection signals, and all switching elements A plurality of amplifier array circuits that are provided separately for each of the element groups divided as described above and process detection signals read from the switching elements of the corresponding element groups, and drive the switching elements to control reading of the detection signals Drive control means, light irradiation means for irradiating light toward one surface where the divided electrodes of the semiconductor layer are provided, and the radiation generation source A light control means for controlling the light irradiating means so as to irradiate with a light having a smaller intensity compared to a non-irradiation period in which the radiation generating source is not irradiating in the irradiation period in which radiation is irradiated; It is characterized by having.

  [Operation and Effect] According to the invention described in claim 5, since the light control means irradiates light having a relatively high intensity from the light irradiation means in the non-irradiation period, it is possible to prevent the generation of residual output. Thereby, an afterimage can be suppressed in an image obtained based on the read detection signal.

  Further, since the light control unit irradiates light with relatively low intensity from the light irradiation unit during the irradiation period, it is possible to suppress leakage current and crosstalk between the signal lines due to incident radiation. Thereby, in an image obtained based on the detection signal, it is possible to reduce a luminance difference between regions corresponding to each element group.

  According to a sixth aspect of the present invention, there is provided a radiation imaging apparatus for imaging a subject, a radiation generation source for irradiating the subject with radiation, conversion means for converting the radiation transmitted through the subject into electric charges, and the conversion A plurality of divided electrodes provided on one side of the unit means for collecting the converted charges as detection signals, a switching element provided for each of the divided electrodes, for reading the detection signals, and all switching elements. Provided separately for each element group divided into two or more, a plurality of amplifier array circuits for processing detection signals read from the switching elements of the corresponding element group, and driving the switching elements to control reading of the detection signals Drive control means for irradiating, light irradiating means for irradiating light toward one surface of the semiconductor layer where the divided electrodes are provided, and radiation generation A light control unit that turns off the light irradiation unit during the irradiation period during which the radiation source is irradiated, and turns on the light irradiation unit during the non-irradiation period when the radiation generation source does not emit the radiation. It is characterized by.

  [Operation / Effect] According to the invention described in claim 6, since the light control means turns on the light irradiation means in the non-irradiation period, it is possible to prevent the generation of the residual output. Thereby, an afterimage can be suppressed in an image obtained based on the read detection signal.

  In addition, since the light control unit turns off the light irradiation unit during the irradiation period, it is possible to suppress leakage current and crosstalk between the signal lines due to incident radiation. Thereby, in an image obtained based on the detection signal, it is possible to reduce a luminance difference between regions corresponding to each element group.

  The present specification also discloses an invention relating to the following electromagnetic wave detector and a radiation imaging apparatus using the same.

  (1) In the electromagnetic wave detector according to (1), the light control means is at least between regions corresponding to each element group in an image obtained based on a result of processing a detection signal by each amplifier array circuit. An electromagnetic wave detector characterized in that the intensity of light in the accumulation period is reduced to such an extent that a luminance difference cannot be visually recognized.

  According to the invention as described in said (1), a brightness | luminance difference can be reduced suitably.

  (2) In the electromagnetic wave detector according to claim 1 or 2, the light control means is such that at least an afterimage cannot be visually recognized in an image obtained based on a result of processing the detection signal by each amplifier array circuit. Until now, the intensity of light in the readout period is increased.

  According to the invention as described in said (2), an afterimage can be suppressed suitably.

  (3) In the radiation imaging apparatus according to claim 3 or 4, the light control unit increases the light intensity in the readout period as the intensity of the radiation emitted from the radiation source increases. A characteristic radiographic apparatus.

  According to the invention as described in said (3), an afterimage can be suppressed suitably.

  (4) In the radiation imaging apparatus according to any one of claims 3 to 6, the light control unit decreases the intensity of light during the irradiation period as the intensity of radiation irradiated from the radiation source decreases. A radiation imaging apparatus characterized by:

  According to the invention as described in said (4), a brightness | luminance difference can be reduced suitably.

  (5) In the radiographic apparatus according to claim 3 or 4, the light control means is such that at least an afterimage cannot be visually recognized in an image obtained based on a result of processing the detection signal by each amplifier array circuit. The radiation imaging apparatus characterized by increasing the light intensity in the readout period.

  According to the invention as described in said (5), an afterimage can be suppressed suitably.

  (6) In the radiation imaging apparatus according to claim 3 or 5, the light control unit corresponds to at least each element group in an image obtained based on a result of processing a detection signal by each amplifier array circuit. The radiation imaging apparatus is characterized in that the intensity of light in the irradiation period is reduced to such an extent that a luminance difference cannot be visually recognized between the areas.

  According to the invention as described in said (6), a brightness | luminance difference can be reduced suitably.

  (7) In the radiographic apparatus according to claim 5 or 6, the light control means is such that at least an afterimage cannot be visually recognized in an image obtained based on a result of processing a detection signal by each amplifier array circuit. The radiation imaging apparatus characterized by increasing the intensity of light during the non-irradiation period.

  According to the invention as described in said (7), an afterimage can be suppressed suitably.

According to the electromagnetic wave detector of the present invention, since the light control means irradiates light having a relatively high intensity from the light irradiation means in the readout period, it is possible to generate a residual output when reading the detection signal from each switching element. Can be prevented. Thereby, an afterimage can be suppressed in an image obtained based on the read detection signal. Further, since the light control means irradiates light having a relatively low intensity from the light irradiation means during the accumulation period, leakage current and crosstalk between the signal lines can be suppressed during the accumulation period. Thereby, in an image obtained based on the detection signal, it is possible to reduce a luminance difference between regions corresponding to each element group.
can do.

Embodiment 1 of the present invention will be described below with reference to the drawings.
1 and 2 are a cross-sectional view and a plan view showing a schematic configuration of the flat panel X-ray detector according to the first embodiment.

  The flat panel X-ray detector (hereinafter simply referred to as FPD as appropriate) 1 according to the first embodiment is intended to detect X-rays. As shown in the figure, an application electrode 3 for applying a bias voltage, a semiconductor layer 5 for converting X-rays into electric charges, an active matrix substrate 11 having divided electrodes 7, switching elements s, and the like, in order from the X-ray incident side. Are stacked. The divided electrode 7 collects the charges converted by the semiconductor layer 5 as a detection signal. The switching element s reads the collected detection signals by shifting to the ON state. Examples of the semiconductor layer 5 include amorphous and selenium.

  On the back surface (surface opposite to the surface on which the semiconductor layer 5 is provided) of the active matrix substrate 11, a light irradiation unit 13 that irradiates light toward one surface of the semiconductor layer 5 on which the divided electrodes 7 are provided. Is provided. In FIG. 1, light is schematically shown by a one-dot chain line. Furthermore, the gate driver 15 that drives each switching element s, the drive control circuit 21 that controls the reading of the detection signal by operating the gate driver 15, and the detection signal that is read out in cooperation with the drive control circuit 21 are processed. Two amplifier array circuits 23 and 24, and a light control unit 25 that controls the light irradiation unit 13 in cooperation with the drive control circuit 21. The FPD 1 corresponds to the electromagnetic wave detector in the present invention. The gate driver 15 and the drive control circuit 21 correspond to drive control means in the present invention.

  The active matrix substrate 11 will be described. In the active matrix substrate 11, the divided electrode 7, the capacitor Ca, the switching element s, the scanning line 33, the signal line 35, and the like are formed on a transparent glass substrate 31 having electrical insulation. There are a large number of divided electrodes 7, which are arranged in a state of being separated from each other along rows and columns that are biaxially intersecting on the lower surface side of the semiconductor layer 5. Each divided electrode 7 is connected to a capacitor Ca for storing the collected detection signals. A switching element s is connected to each pair of the divided electrode 7 and the capacitor Ca. Examples of the switching element s include thin film transistors.

  The set of divided electrodes 7, the capacitor Ca, and the switching element s constitute one detection element d together with the semiconductor layer 5 and the application electrode 3 in a region corresponding thereto. Therefore, when the detection surface of the FPD 1 is viewed in plan, it can be seen that a large number of detection elements d are arranged in a matrix as shown in FIG.

  Further, the scanning line 33 is formed for each row of the detection elements d, and is commonly connected to the gates of the switching elements s in each row. Two signal lines 35 are formed for each column, and extend from the approximate center to both sides. Then, approximately half of the switching elements s in each column are commonly connected to the signal line 35. It should be noted that the rows and columns are merely used for convenience to distinguish the directions, and it may be considered that the scanning lines 33 are provided for each column and the signal lines 35 are provided for each row.

  The gate driver 15 is connected to one end side of each scanning line 33. Then, a gate pulse for driving on / off the switching elements s in each row is output via each scanning line 33. The amplifier array circuits 23 and 24 are separately provided on both sides of the detection element d group, and signal lines 35 drawn from the detection element d group are respectively connected thereto. Accordingly, all the switching elements s are divided into two element groups G1 and G2 corresponding to the amplifier array circuits 23 and 24, and each of the amplifier array circuits 23 and 24 has a corresponding element group G1 and G2 respectively. The detection signal read from the switching element s included in is processed. The drive control circuit 21 comprehensively controls the gate driver 15 and the amplifier array circuits 23 and 24 described above based on the vertical synchronization signal and the horizontal synchronization signal.

  The light irradiation unit 13 includes a planar light guide unit 41 and a light emitting unit 43. The planar light guide portion 41 is a plate-like object that is formed of a light-transmitting plate-like object such as acrylic or glass and has an active matrix substrate 11 side as a light emitting surface. The light emitting unit 43 emits light to the end surface of the planar light guide unit 41. Examples of the light emitting unit 43 include a light emitting diode and a cold cathode tube.

  The light control unit 25 controls switching on / off of the light irradiation unit 13 in cooperation with the drive control circuit 21 described above. Specifically, it is realized by a current limiting circuit, a switching circuit, a booster circuit using an inverter, or the like according to the type of the light emitting unit 43.

  Next, the operation of the FPD according to the first embodiment will be described with reference to the drawings. FIG. 3 is a timing chart illustrating an operation example of the FPD according to the first embodiment. FIG. 3 schematically shows a detection operation, a vertical synchronization signal, a horizontal synchronization signal, a switching element, and light irradiation.

  In the detection period (time t1 to time t6) in which the detection operation is performed, the semiconductor layer 5 is applied with a bias voltage by the application electrode 3, and converts incident X-rays into electric charges. The converted charge is collected by any one of the divided electrodes 7.

  During this detection period, under the control of the drive control circuit 21, a read operation for reading the collected charges (time t2 to time t3 and time t4 to time t5) and an accumulation operation for storing charges (time t1 to time t2). And time t3 to time t4 and time t5 to time t6) are alternately performed. Each will be described below.

<Read operation>
The drive control circuit 21 operates the gate driver 15 based on the vertical synchronization signal and the horizontal synchronization signal. Thereby, the gate driver 15 sequentially outputs a gate pulse to each scanning line 33 in synchronization with the horizontal synchronizing signal to drive the switching element s (time t2 to time t3 and time t4 to time t5). Therefore, the period from time t2 to time t3 and the period from time t4 to time t5 correspond to a “reading period” in which the detection signal is read from any switching element s. In the timing chart of the switching element s in FIG. 3, a period in which any switching element s is driven and is turned on is indicated as “On”. Note that the period of the vertical synchronization signal is, for example, 33.3 msec.

  Further, the light control unit 25 turns on the light irradiation unit 13 during the readout period in cooperation with the drive control circuit 21. The light irradiation unit 13 irradiates light through the active matrix substrate 11 toward one surface where the divided electrodes 7 of the semiconductor layer 5 are formed. Thereby, the electric charge according to the irradiated light is stored in the space between the divided electrodes 7 without being swept out. Here, the intensity of the light emitted by the light irradiation unit 13 is large enough that at least an afterimage cannot be visually recognized in an image obtained based on the result of detection signals being processed by the amplifier array circuits 23 and 24. preferable.

  The switching elements s sequentially shift to the on state in units of one row connected to the scanning line 33, and the detection signals are sequentially read out via the switching elements s in the on state. The detection signal read from the switching element s in the element group G1 is sent to the amplifier array circuit 23, and the detection signal read from the switching element s in the element group G2 is sent to the amplifier array circuit 24. The amplifier array circuits 23 and 24 perform processing such as amplifying the detection signal in cooperation with the drive control circuit 21. Then, an image is generated for each detection signal obtained in each readout period.

<Accumulation operation>
By the operation by the drive control circuit 21, the gate driver 15 does not drive any switching element s. Therefore, the period from time t1 to time t2, the period from time t3 to time t4, and the period from time t5 to time t6 correspond to an “accumulation period” in which no detection signal is read from any switching element s. To do. In FIG. 3, a period in which all the switching elements s are in the off state is indicated as “Off”. The light control unit 25 cooperates with the drive control circuit 21 to turn off the light irradiation unit 13 during the accumulation period.

  As described above, according to the FPD 1 according to the first embodiment, the light control unit 25 turns on the light irradiation unit 13 in the readout period, so that a residual output is prevented from being generated when the detection signal is read from each switching element s. can do. Thereby, it is possible to suppress the occurrence of an afterimage in an image obtained based on the read detection signal.

  Further, since the light control unit 25 turns off the light irradiation unit 13 during the accumulation period, it is possible to suppress the occurrence of leakage current and crosstalk between signal lines during the accumulation period. Thereby, in an image obtained based on the detection signal, a luminance difference can be reduced between regions corresponding to the element groups G1 and G2.

  In addition, afterimages can be suitably suppressed by irradiating light of sufficiently large intensity from the light irradiation unit 13 during the readout period.

Embodiment 2 of the present invention will be described below with reference to the drawings.
FIG. 4 is a cross-sectional view illustrating a schematic configuration of the X-ray imaging apparatus according to the second embodiment. In addition, about the same structure as Example 1, detailed description is abbreviate | omitted by attaching | subjecting the same code | symbol.

  An X-ray imaging apparatus according to the present embodiment includes an X-ray tube 51 that irradiates an X-ray toward a subject (not shown), and a flat panel X-ray detector (hereinafter referred to as an X-ray detector that detects X-rays transmitted through the subject). And a high voltage generator 55 that controls the tube voltage, tube current, and irradiation time of the X-ray tube 51. The X-ray tube 51 corresponds to the radiation source in this invention. The semiconductor layer 5 corresponds to the conversion means in this invention.

  The drive control circuit 22 provided in the FPD 53 cooperates with the high voltage generator 55 to control the detection signal to be read out during the non-irradiation period in which the X-ray tube 51 is not irradiated with X-rays. Here, the gate driver 15 and the drive control circuit 22 correspond to drive control means in the present invention.

  The light control unit 26 provided in the FPD 53 variably controls the intensity of light emitted from the light irradiation unit 13 in cooperation with the drive control circuit 22. Illuminance (lx) is exemplified as the light intensity. The light control unit 26 is realized by a current limiting circuit, a booster circuit using an inverter, or the like according to the type of light emitter provided in the light emitting unit 43.

  Next, the operation of the X-ray imaging apparatus according to the second embodiment will be described with reference to the drawings. FIG. 5 is a timing chart illustrating an operation example of the X-ray imaging apparatus according to the second embodiment. FIG. 5 schematically shows the detection operation, X-ray irradiation, vertical synchronization signal, horizontal synchronization signal, switching element, and light intensity.

  During the detection period (time t1 to time t10) in which the detection operation is performed, a bias voltage is applied to the semiconductor layer 5 by the application electrode 3. During this detection period, the X-ray tube 51 emits X-rays during the period from time t2 to time t3 and during the period from time t6 to time t7 under the control of the high voltage generator 55. Hereinafter, the period during which this X-ray is irradiated is referred to as an irradiation period, and the period during which no X-ray is irradiated (time t1 to time t2, time t3 to time t6, time t7 to time t10) is referred to as a non-irradiation period. . The semiconductor layer 5 detects X-rays irradiated from the X-ray tube 51 and transmitted through a subject (not shown), and converts them into electric charges.

  The drive control circuit 22 cooperates with the high voltage generator 55 to perform a reading operation within the non-irradiation period and control so that X-ray irradiation is performed within the period during which the accumulation operation is performed. Specifically, the readout period is controlled from time t4 to time t5 and from time t8 to time t9 so that the readout period is included in the non-irradiation period. Note that the period other than the reading period is an accumulation period.

  In addition, the light control unit 26 controls the light irradiation unit 13 in cooperation with the drive control circuit 22 so that the intensity of light is smaller in the irradiation period than in the non-irradiation period. In the present embodiment, as shown in FIG. 5, the light control unit 26 switches the intensity of the irradiated light in two stages, “high” and “small”, and sets the light intensity to “low” during the irradiation period. In the non-irradiation period, the light intensity is controlled to be “high”. Here, it is preferable that the light intensity “high” is large enough that at least an afterimage cannot be visually recognized in the image obtained based on the result of processing the detection signal by the amplifier array circuits 23 and 24. The light intensity “low” is a difference in luminance between at least the regions corresponding to the element groups G1 and G2 in the image obtained based on the result of processing the detection signals by the amplifier array circuits 23 and 24. It is preferable to be small to the extent that it cannot be visually recognized.

  Thus, according to the X-ray imaging apparatus according to the second embodiment, in conjunction with the high voltage generator 55, the drive control circuit 22 that controls the readout of the detection signal within the non-irradiation period, and the irradiation period And a light control unit 25 that controls the light irradiation unit 13 so as to irradiate light having a relatively small intensity and emit light having a relatively large intensity in a non-irradiation period including a readout period. It is possible to prevent the residual output from being generated. Thereby, it is possible to suppress the occurrence of an afterimage. In addition, leakage current and occurrence of crosstalk between signal lines can be suppressed during the irradiation period. Thereby, in an image obtained based on the detection signal, a luminance difference can be reduced between regions corresponding to the element groups G1 and G2.

  In addition, afterimages can be suitably suppressed by irradiating light with sufficiently large intensity from the light irradiation unit 13 during the non-irradiation period. In addition, the luminance difference can be suitably reduced by irradiating light with sufficiently small intensity from the light irradiation unit 13 during the irradiation period.

  The present invention is not limited to the above-described embodiment, and can be modified as follows.

  (1) In each of the first and second embodiments described above, the detection target of FPD1 or FPD53 is X-rays, but is not limited to this, and includes radiation other than X-rays (including neutron rays, γ rays, and β rays). ) May be changed as appropriate. In this case, the semiconductor layer 5 that converts X-rays into charges may be appropriately changed to a semiconductor layer that converts radiation into charges.

  (2) In each of the first and second embodiments described above, the direct conversion type FPD1 or FPD53 that directly converts X-rays into electric charges is used. However, the indirect conversion type X-ray detector may be appropriately changed. Good. Please refer to FIG. FIG. 6 is a cross-sectional view showing a schematic configuration of an X-ray detector according to a modification. As shown in the figure, a scintillator 4 that converts X-rays into light, a semiconductor layer 6 that converts light into charges, and an active matrix substrate 11 are stacked in this order from the X-ray incident side. Examples of the semiconductor layer 6 include a photodiode. In addition, about the same structure as Example 1, detailed description is abbreviate | omitted by attaching | subjecting the same code | symbol. Even the indirect conversion type X-ray detector and the X-ray imaging apparatus using the indirect conversion type X-ray detector configured as described above can suitably implement the present invention. The scintillator 4 and the semiconductor layer 6 correspond to the conversion means in this invention. The indirect type X-ray detector corresponds to the electromagnetic wave detector in the present invention.

  (3) As described in each of the first and second embodiments and the modifications described above, the semiconductor layer 5 can be appropriately selected and changed so as to convert radiation or light into electric charge. The semiconductor layer may be selectively changed so as to be converted. That is, the semiconductor layer can be appropriately configured to convert electromagnetic waves into electric charges.

  (4) In the above-described first embodiment, the light control unit 25 switches and controls the blinking of the light irradiation unit 13, but is not limited thereto. Like the light control unit 26 described in the second embodiment, the light control unit may be changed so that the intensity of light emitted from the light irradiation unit 13 can be varied in two stages. In this case, the accumulation period may be configured to control the light intensity smaller than the reading period. Further, the light control unit may be changed so that the light can be varied to an arbitrary intensity without being limited to two steps.

  (5) In Example 2 mentioned above, although the light control part 26 was comprised so that the intensity | strength of the light irradiated from the light irradiation part 13 could be varied in two steps, it is not restricted to this. For example, as described in the first embodiment, the light irradiation unit 13 may be changed to control the blinking. In this case, it may be controlled to turn off the irradiation period and turn on the non-irradiation period.

  (6) In the above-described second embodiment, the light control unit 26 controls the irradiation period to emit light having a lower intensity than that in the non-irradiation period, but the present invention is not limited to this. The irradiation period can be appropriately changed in design as long as light having a smaller intensity than that of the readout period is irradiated. Hereinafter, two operation examples are illustrated.

  Please refer to FIG. FIG. 7 is a timing chart showing an operation example of the X-ray imaging apparatus according to the modification. As shown in the figure, the light control unit 26 may control to irradiate light having a relatively large intensity during the readout period, and irradiate the accumulation period with a light intensity smaller than that of the readout period. With such a configuration, it is possible to prevent the residual output from occurring in the reading operation and to suppress the afterimage. In addition, leakage current and crosstalk between signal lines can be suppressed during the accumulation period, and a luminance difference can be reduced.

  Please refer to FIG. FIG. 8 is a timing chart showing an operation example of the X-ray imaging apparatus according to the modification. As shown in the drawing, if it is within the accumulation period under the control of the light control unit 26, it is compared with the readout period at a time (t7) prior to the time (time t2, time t8) at which the irradiation period starts. You may control to change to the light of small intensity | strength. Similarly, within the accumulation period, irradiation is performed with light having a lower intensity than the readout period until time (time t4, time t10) after the end time (time t3, time t9) of the irradiation period. You may control to. Further, when it is not the irradiation period, irradiation may be performed with light having a higher intensity than that in the readout period even within the accumulation period (for example, around time t4, time t7, and time t10). As shown in the drawing, the intensity does not have to be constant during the irradiation period. Further, the light intensity in the reading period is also constant in FIG. 8, but may not be constant.

  (7) In the above-described second embodiment, the light control unit 26 may vary the intensity of light emitted from the light irradiation unit 13 according to the intensity of X-rays emitted from the X-ray tube 51. . Specifically, based on the control of the high voltage generator 55 (tube voltage, tube current, X-ray irradiation time), the intensity of the X-rays emitted from the X-ray tube 51 increases, so that the light control unit 26 You may control to increase the intensity | strength of the light irradiated in a read-out period. According to this, an afterimage can be suppressed more suitably. Alternatively, based on the control of the high voltage generator 55, the light control unit 26 performs control so that the intensity of the light irradiated in the accumulation period is decreased as the intensity of the X-ray irradiated from the X-ray tube 51 is weaker. May be. According to this, it is possible to more suitably reduce the luminance difference.

  (8) The FPD 1 described in the first embodiment is further provided with a radiation generation source that irradiates the subject with radiation such as X-rays, and the semiconductor layer 5 provided on the FPD 1 charges the radiation transmitted through the subject. You may comprise the radiography apparatus converted into. The drive control circuit 21 of the FPD 1 is configured to control the gate driver 15 and cooperate with the amplifier array circuits 23 and 24 and the light control unit 25 independently of the operation of the radiation generation source. Even with this configuration, the present invention can be implemented.

  (9) In each of the first and second embodiments described above, all switching elements s are divided into two element groups G1 and G2, and two amplifier array circuits 23 and 24 are provided corresponding to each element group G1 and G2. However, the present invention is not limited to this. For example, three or more amplifier array circuits may be provided corresponding to three or more element groups.

  (10) The electromagnetic wave detector and the radiation imaging apparatus using the electromagnetic wave detector may be configured by appropriately combining each of the first and second embodiments and the modifications described above.

  (11) In each of the first and second embodiments described above, the use of the FPD 1 or the X-ray imaging apparatus is not specified, but may be applied to, for example, an X-ray imaging apparatus used in the medical field. The present invention can also be applied to X-ray imaging apparatuses used in industrial fields such as nondestructive inspection and RI (Radio Isotope) inspection.

1 is a cross-sectional view illustrating a schematic configuration of a flat panel X-ray detector according to Embodiment 1. FIG. 1 is a plan view showing a schematic configuration of a flat panel X-ray detector according to Embodiment 1. FIG. 3 is a timing chart illustrating an operation example of the FPD according to the first embodiment. 3 is a cross-sectional view illustrating a schematic configuration of an X-ray imaging apparatus according to Embodiment 2. FIG. 6 is a timing chart illustrating an operation example of the X-ray imaging apparatus according to the second embodiment. FIG. 6 is a cross-sectional view showing a schematic configuration of an X-ray detector according to a modification. It is a timing chart which shows the operation example of the X-ray imaging apparatus which concerns on a modification. It is a timing chart which shows the operation example of the X-ray imaging apparatus which concerns on a modification. It is a timing chart of the electromagnetic wave detector which concerns on a prior art example.

Explanation of symbols

1, 53 ... Flat panel X-ray detector (FPD)
DESCRIPTION OF SYMBOLS 4 ... Scintillator 5, 6 ... Semiconductor layer 7 ... Divided electrode s ... Switching element 11 ... Active matrix substrate 13 ... Light irradiation part 15 ... Gate driver 23, 24 ... Amplifier array circuit 21, 22 ... Drive control circuit 25, 26 ... Light Control unit G1, G2 ... Element group 51 ... X-ray tube 55 ... High voltage generator

Claims (6)

  In an electromagnetic wave detector for detecting electromagnetic waves, a semiconductor layer that converts electromagnetic waves into electric charges, a plurality of divided electrodes that are provided on one side of the semiconductor layer and collect the converted electric charges as detection signals, and the divided electrodes Provided separately for each switching element for reading out the detection signal and for each element group obtained by dividing all switching elements into two or more, and processing detection signals read from the switching elements of the corresponding element group A plurality of amplifier array circuits; drive control means for driving the switching elements to control reading of detection signals; and light irradiating means for irradiating light toward one surface where the divided electrodes of the semiconductor layer are provided. In the accumulation period in which the detection signal is not read from any switching element in cooperation with the drive control means, An electromagnetic wave detector comprising: a light control unit that controls the light irradiation unit so that the light irradiation unit emits light with a light intensity smaller than a readout period in which a detection signal is read from any one of the switching elements. .   In an electromagnetic wave detector for detecting electromagnetic waves, a semiconductor layer that converts electromagnetic waves into electric charges, a plurality of divided electrodes that are provided on one side of the semiconductor layer and collect the converted electric charges as detection signals, and the divided electrodes Provided separately for each switching element for reading out the detection signal and for each element group obtained by dividing all switching elements into two or more, and processing detection signals read from the switching elements of the corresponding element group A plurality of amplifier array circuits; drive control means for driving the switching elements to control reading of detection signals; and light irradiating means for irradiating light toward one surface where the divided electrodes of the semiconductor layer are provided. In conjunction with the drive control means, during the accumulation period when no detection signal is read from any switching element, the light irradiation means It is turned off, any of the electromagnetic wave detector readout period in which reading the detection signal from the switching element is characterized in that it comprises a light control means for turning on the light irradiation means.   In a radiographic apparatus for imaging a subject, a radiation generation source that irradiates the subject with radiation, a conversion unit that converts the radiation that has passed through the subject into charges, and one surface side of the conversion unit are provided and converted. A plurality of divided electrodes that collect collected charges as detection signals, a switching element for each of the divided electrodes, and a switching element for reading out the detection signal, and a separate element group for each of the switching elements divided into two or more And a plurality of amplifier array circuits that process detection signals read from the switching elements of the corresponding element group, and the switching elements are driven to detect within the non-irradiation period in which the radiation source is not irradiated with radiation. Drive control means for reading signals, and light irradiation for irradiating light toward one surface where the divided electrodes of the semiconductor layer are provided And at least in the irradiation period in which the radiation generating source is irradiating the light, the light irradiating means irradiates with light having a smaller intensity than the readout period in which the detection signal is read from any of the switching elements. A radiation imaging apparatus comprising: a light control means for controlling the light.   In a radiographic apparatus for imaging a subject, a radiation generation source that irradiates the subject with radiation, a conversion unit that converts the radiation that has passed through the subject into charges, and one surface side of the conversion unit are provided and converted. A plurality of divided electrodes that collect collected charges as detection signals, a switching element for each of the divided electrodes, and a switching element for reading out the detection signal, and a separate element group for each of the switching elements divided into two or more And a plurality of amplifier array circuits that process detection signals read from the switching elements of the corresponding element group, and the switching elements are driven to detect within the non-irradiation period in which the radiation source is not irradiated with radiation. Drive control means for reading signals, and light irradiation for irradiating light toward one surface where the divided electrodes of the semiconductor layer are provided And a light control means for turning off at least the light irradiating means during the irradiation period in which the radiation source is irradiating, and at least turning on the light irradiating means during the reading period in which the detection signal is read from any of the switching elements. And a radiation imaging apparatus.   In a radiographic apparatus for imaging a subject, a radiation generation source that irradiates the subject with radiation, a conversion unit that converts the radiation that has passed through the subject into charges, and one surface side of the conversion unit are provided and converted. A plurality of divided electrodes that collect collected charges as detection signals, a switching element for each of the divided electrodes, and a switching element for reading out the detection signal, and a separate element group for each of the switching elements divided into two or more A plurality of amplifier array circuits for processing detection signals read from the switching elements of the corresponding element group, drive control means for controlling the reading of the detection signals by driving the switching elements, and the divided electrodes of the semiconductor layer A light irradiating means for irradiating light toward the one surface where the radiation source is provided, and an irradiation period in which the radiation generating source irradiates the radiation And a light control means for controlling the light irradiating means so as to irradiate the light with a light having a smaller intensity than a non-irradiation period in which the radiation generating source is not irradiating radiation. Radiography equipment.   In a radiographic apparatus for imaging a subject, a radiation source that irradiates the subject with radiation, a conversion unit that converts the radiation that has passed through the subject into charges, and a conversion unit provided on one surface side of the conversion unit A plurality of divided electrodes for collecting the detected charges as detection signals; a switching element provided for each of the divided electrodes; and a switching element for reading out the detection signal; and an element group in which all switching elements are divided into two or more. A plurality of amplifier array circuits that process detection signals read from the switching elements of the corresponding element group; drive control means for driving the switching elements to control reading of the detection signals; and division of the semiconductor layer A light irradiating means for irradiating light toward the one surface on which the electrodes are provided, and an irradiation period in which the radiation generating source irradiates the radiation The light irradiation unit is turned off, the radiation source a radiation imaging apparatus, wherein a non-irradiation period that is not irradiated with radiation is provided with a light control means for lighting said light irradiating means.

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