JP5262563B2 - Radiation image detection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radiographic image detecting device that has improved graininess of a radiographic image since electric power supplied from a power source includes power supply noise in a radiographic image detecting device using a TFT read system and then noise is included even in a readout signal output from a scan driving circuit to a TFT switch element and flows out as a noise signal to a signal line to be added to electric charge read out by a readout circuit, so that graininess of a radiographic image is made worse. <P>SOLUTION: A switch SW1 is prepared between a TFT switch element and a predetermined OFF voltage source 302 which supplies a predetermined OFF voltage to the TFT switch element, and is turned off while a signal converter 671 performs at least CDS so that the noise generated at the OFF voltage source 302 is blocked. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to an FPD (Flat Panel Detector) that is a radiation image detection apparatus that detects radiation transmitted through a subject, and more particularly to an FPD with improved image quality.

  Conventionally, in the medical field and the like, various radiological image detection apparatuses that record radiation images related to a subject upon receiving radiation transmitted through the subject and detect an image signal corresponding to the recorded radiation image have been proposed and put into practical use. ing.

  As the radiation image detection device, for example, there is a radiation image detection device using a semiconductor material that generates a charge upon irradiation of radiation, and a so-called TFT reading type is proposed as such a radiation image detection device. .

  As a radiographic image detection apparatus of a TFT reading system, for example, a light emitting layer that emits light upon irradiation with radiation, a detection element that converts emitted light into electric charge and accumulates, and conduction control for reading out the accumulated electric charge A device including an imaging unit having a TFT switch element as a means has been proposed.

  The detection elements are arranged two-dimensionally in the orthogonal direction. Further, the imaging unit includes a large number of signal lines provided in parallel for each column of detection elements, and a large number of scanning lines provided in parallel for each row of detection elements orthogonal to the signal lines. It has.

  When a radiographic image is recorded using the radiographic image detection apparatus configured as described above and a radiographic image is read, a readout signal is selectively output from the scanning drive circuit to the scanning line, In response to the readout signal, the TFT switch element connected to the scanning line is turned on, and the electric charge flowing out from the capacitor as a power storage unit provided in the detection element to the signal line is amplified in the readout circuit connected to the signal line ( For example, it is detected as an image signal by a charge amplifier or the like, and a radiation image is read. The readout signal output from the scan drive circuit to the TFT switch element is based on the power from the power source input to the scan drive circuit.

  Here, in the radiation image detection apparatus as described above, since the scanning line and the signal line are provided orthogonally via the insulating layer, a parasitic capacitance is formed in the vicinity of the intersection of the scanning line and the signal line. The

  Since the power supplied from the power supply includes power supply noise, the readout signal output from the scanning drive circuit to the TFT switch element also includes power supply noise. This power supply noise flows out to the signal line as a noise signal, and this noise signal is added to the electric charge flowing out from the power storage unit of the detection element.

In order to solve this problem, for example, in Patent Document 1, after the charge accumulated in the power storage unit is once read, noise is canceled by inputting a read signal with reversed polarity to the scanning line. Technology has been proposed.
JP 2006-101396 A

  With the technique described in Patent Document 1, it is possible to reduce noise generated in an offset manner by inverting the polarity, but it is not possible to remove randomly generated noise. Therefore, noise in the readout signal cannot be removed, and the granularity of the obtained radiographic image is deteriorated.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a radiographic image detection apparatus that improves the granularity of a radiographic image.

  The above object is achieved by the invention described below.

1. An imaging panel in which a plurality of detection elements for converting irradiated radiation into electric charges are two-dimensionally arranged;
Holding and outputting the electric charge converted by the detection element, and conduction control means arranged for each detection element;
A scanning line to which the conduction control means is connected for each row;
An ON voltage source for supplying an ON voltage for controlling the conduction control means to the conduction control means through the scanning line so as to output the electric charge converted by the detection element;
An OFF voltage source for supplying an OFF voltage for controlling the conduction control means to the conduction control means through the scanning line so as to hold the electric charge converted by the detection element;
A scanning drive circuit comprising switching means for selecting one of the ON voltage source or the OFF voltage source and connecting to the conduction control means corresponding to each scanning line;
Switch means disposed in a path between the OFF voltage source and the conduction control means;
A charge storage means having one end connected to the path between the switch means and the conduction control means and the other end virtually grounded;
Charge-voltage conversion means for converting the charge output from the detection element into a voltage;
Difference means for calculating a difference between the first voltage and the second voltage converted by the charge voltage conversion means;
In the state where the switching means is switched to apply the OFF voltage to the conduction control means, the first voltage is acquired by the charge voltage conversion means, and then the ON voltage is applied to the conduction control means. After switching the switching means and outputting the charge held in the detection element, the charge voltage conversion means obtains the second voltage, and the difference means determines the difference between the first voltage and the second voltage. A control unit that calculates radiation image data based on the calculation result;
Have
When acquiring the first voltage, the control unit turns off the switch unit corresponding to at least one scanning line, and corresponds to the one scanning line until the second voltage is acquired. A radiological image detection apparatus characterized in that an OFF state of a switch means is continued.

  2. 2. The radiological image detection according to claim 1, wherein the control unit also turns off the switch unit corresponding to another scan line while the switch unit is turned off with respect to the one scan line. apparatus.

3. An imaging panel in which a plurality of detection elements for converting irradiated radiation into electric charges are two-dimensionally arranged;
Holding and outputting the electric charge converted by the detection element, and conduction control means arranged for each detection element;
A plurality of scanning lines to which the conduction control means is connected for each row;
An ON voltage source for supplying an ON voltage for controlling the conduction control means to the conduction control means through the scanning line so as to output the electric charge converted by the detection element;
An OFF voltage source for supplying an OFF voltage for controlling the conduction control means to the conduction control means through the scanning line so as to hold the electric charge converted by the detection element;
A scanning drive circuit comprising switching means for selecting one of the ON voltage source or the OFF voltage source and connecting to the conduction control means corresponding to each scanning line;
Have
The OFF voltage source includes a plurality of OFF voltage sources,
The radiation image detecting apparatus , wherein an OFF voltage source having random noise independent of each other is connected to at least one of the plurality of scanning lines.

  In the radiological image detection apparatus, the power supply noise generated in the OFF voltage source that supplies the OFF voltage to the conduction control unit is cut off or canceled, or the power supply noise is canceled out to superimpose the power supply noise on the image signal. Therefore, a radiographic image with good graininess can be obtained.

  Although the present invention will be described based on an embodiment, the present invention is not limited to the embodiment. A radiographic image detection apparatus according to this embodiment will be described with reference to FIGS. FIG. 1 is a diagram showing a schematic configuration of a radiographic image capturing system 1 in the present embodiment.

  As shown in FIG. 1, the radiographic imaging system 1 includes an imaging operation device 4 that performs operations related to radiographic imaging, an access point 5 that performs wireless communication, for example, via a wireless LAN (Local Area Network), and a radiographic image detection device. 6 (hereinafter simply referred to as FPD 6) is connected to a console 7 for performing image processing on a radiation image signal generated through a network N. Although not shown here, the radiographic imaging system 1 includes a HIS (Hospital Information System) that centrally manages patient diagnosis information and accounting information, and an RIS (Radiology Information System) that manages radiological information and a network N. Connected through. The network N may be a communication line dedicated to the system, but is preferably an existing line such as Ethernet (registered trademark) because the degree of freedom of the system configuration is low.

  Reference numeral 100 denotes a photographing room. The imaging room 100 includes a radiation irradiation device 3, an imaging operation device 4, an access point 5 that performs wireless communication, and a router 9 that is connected to the access point.

  The radiation irradiation device 3 is configured to irradiate a patient 12 as a subject lying on the supine imaging stand 11, and a detection device in which the FPD 6 is mounted below the supine imaging stand 11. A mounting opening 11a is provided. The radiation irradiation device 3 is controlled by the imaging operation device 4 to perform radiation imaging under predetermined imaging conditions. Note that the synchronization of the imaging timing between the radiation irradiation device 3 and the FPD 6 attached to the detection device attachment port 11a may be performed by wireless communication via the access point 5 between them.

  The access point 5 has a function of relaying these communications when the FPD 6 and the console 7 communicate wirelessly within a predetermined area of the imaging room provided with the radiation irradiation device 3. Note that an example in which wireless communication is performed by a wireless LAN (for example, a communication method compliant with IEEE802.11a / b / n) will be described. However, the present invention is not limited to this. In addition to using radio waves (spatial waves), infrared or visible Wireless communication may be performed by optical wireless communication (for example, IrDA) using light beams or the like (laser or the like), or acoustic communication using sound waves or ultrasonic waves.

  In the description of FIG. 1, an example in which communication is performed by wireless communication via the access point 5 has been described. However, the present invention is not limited to this, and a communication connector for connecting to the network N is provided in the detection device mounting port 11a. You may make it carry out wired communication with the network N by mounting | wearing with the said detection apparatus mounting port 11a.

[Block Diagram]
Next, the principal part structure of FPD6 and the console 7 is demonstrated using FIG. 2 which is a block diagram. The FPD 6 includes an imaging unit 6A, a control unit 60, an image storage unit 660, a power supply unit 300, a transmission / reception unit 65, and the like. The imaging unit 6A has a function of acquiring a radiation image signal. Details will be described later. The control unit 60 has a function of comprehensively controlling each unit of the FPD 6, a ROM that stores a control program, data, and the like, a CPU that executes control of the control unit 60 according to the control program, and a RAM that the CPU uses as a work area , Etc. The image storage unit 660 includes a RAM, a hard disk, a flash memory, and the like that store image signals captured by the imaging unit 6A. The transmission / reception unit 65 communicates with the console 7 and the like. The power supply unit 300 supplies power to an electric circuit constituting the FPD 6, for example, a TFT switch element that is a conduction control unit of the present invention.

  The console 7 includes a console control unit 70, a transmission / reception unit 75, a display unit 77, an input operation unit 78, and an image storage unit 760. The console control unit 70 has a function of comprehensively controlling each part of the console, a ROM that stores a control program, data, and the like, a CPU that executes control of the console control unit 70 according to the control program, and a CPU that is used as a work area And the like.

  The display unit 77 is configured to include, for example, a CRT (Cathode Ray Tube), an LCD (Liquid Crystal Display), and the like, and in accordance with an instruction of a display signal sent from the console control unit 70, an image signal captured by the FPD 6 and an imaging condition Various screens such as information, patient list, various messages and images are displayed.

  The input operation unit 78 includes, for example, a keyboard, a mouse, and the like, and outputs a key press signal pressed by the keyboard and an operation signal from the mouse to the console control unit 70 as input signals. The input operation unit 78 outputs position information input by touching a transparent sheet panel covering the display screen of the display unit 77 with a fingertip or a dedicated stylus pen to the console control unit 70 as an input signal. It may be constituted by a so-called touch panel. Then, information on photographing conditions is input by the input operation unit 78. The imaging condition information here refers to radiation dose, radiation detection sensitivity information, and the like. For example, the radiation dose irradiated from the radiation irradiation device 3 varies depending on the imaging region and the patient's condition. The radiation detection sensitivity information corresponds to the FPD 6 used for imaging, and has different radiation detection sensitivities depending on the type (such as GOS and CSI described later) of the light emitting layer 64 used in the FPD 6 and the performance of the detection element 620. become.

  The image storage unit 760 includes a hard disk, a flash memory, or the like that stores an image signal captured by the imaging unit 6A, an image signal obtained by processing by the console 7, and the like. The transmission / reception unit 75 performs communication with the FPD 6 and the like.

[FPD6]
The FPD 6 acquires a radiation image signal (hereinafter simply referred to as an image signal), and is a portable cassette FPD device in which an imaging panel is accommodated in a cassette.

  Hereinafter, the configuration of the FPD 6 will be described with reference to FIGS. 3 and 4. FIG. 3 is a perspective view of the FPD 6. FIG. 4 is a circuit configuration diagram of the imaging unit 6 </ b> A of the FPD 6.

  As shown in FIG. 3, the FPD 6 includes a casing 61 that protects the inside, and is configured to be transportable as a cassette, that is, to be transportable. A light emitting layer 64 that emits light with a light intensity corresponding to the intensity of incident radiation is provided inside the housing 61. An imaging panel 62 that converts light emitted from the light emitting layer 64 into an electric signal is formed in layers. Further, the overall size of the imaging panel corresponds to a shooting size such as a large angle, half cut, or six cut. A direct imaging panel that directly converts incident radiation into an electrical signal may be used.

  The light emitting layer 64 is generally called a scintillator layer. For example, a phosphor is a main component, and based on incident radiation, an electromagnetic wave having a wavelength of 300 nm to 800 nm, that is, an ultraviolet ray to an infrared ray centered on a visible ray. Outputs electromagnetic waves (light) over light.

The phosphor used in the light emitting layer 64 is, for example, a material having CaWO ₄ or the like as a base, or a luminescent center substance activated in the base such as CsI: Tl, Gd ₂ O ₂ S: Tb, or ZnS: Ag. Things can be used. Further, when the rare earth element is M, a phosphor represented by a general formula of (Gd, M, Eu) ₂ O ₃ can be used. In particular, cesium iodide CsI: Tl (hereinafter referred to as CSI) and gadolinium oxysulfide Gd ₂ O ₂ S: Tb (hereinafter referred to as GOS) are preferable because of high radiation absorption and luminous efficiency, and these are used. Thus, a high-quality image with low noise can be obtained.

  Moreover, the radiation detection sensitivity with respect to the radiation dose irradiated to FPD6 changes with the luminous efficiency of these fluorescent substance. The radiation detection sensitivity information is managed by a console 7 to be described later based on identification information given to each FPD 6.

  The imaging panel 62 is provided on the surface of the light emitting layer opposite to the surface on which the radiation is irradiated, converts electromagnetic waves (light) output from the light emitting layer into electrical energy, accumulates them, and stores the accumulated electricity Detection elements that output image signals based on energy are arranged in a matrix.

  The connection terminal 69 is a terminal for connecting to a cradle terminal (not shown), and charges the power supply unit 300 by connecting to the cradle terminal.

  Reference numerals 60 and 65 denote a control unit and a transmission / reception unit, respectively. Reference numeral 609 denotes a scanning drive circuit, and 608 denotes a readout circuit.

[Imaging unit 6A]
As shown in FIG. 4, which is a circuit configuration diagram of the imaging unit 6A, the imaging unit 6A includes an imaging panel 62, a scanning drive circuit 609, a readout circuit 608, a control unit 60, a power supply unit 300, an image storage unit 660, and the like. . In the imaging panel 62, a plurality of light receiving elements (hereinafter referred to as detection elements) 620 for converting light into an electrical signal are two-dimensionally arranged, and one detection element 620 corresponds to one pixel of a radiation image. These pixels are arranged at a density of, for example, 100 to 600 dpi (dots per inch) over the size of the imaging region of the subject.

  Further, scanning lines (horizontal lines) 623 and signal lines (vertical lines) 624 are arranged between the detection elements 620, and in the same figure, they are arranged in a lattice shape so that they are orthogonal to each other. Here, assuming that one section surrounded by the scanning line 623 and the signal line 624 is one pixel, the number of pixels of the imaging panel 62 is, for example, m in one direction and n in the other direction. In this case, it is composed of m × n pixels. The imaging panel 62 includes photodiodes 621- (1,1) to 621- (m, n) corresponding to the number of m × n pixels and a TFT 622- (1, 1) to 622- (m, n) are arranged, and between the pixels, the scanning lines 623-1 to 623-m and the signal lines 624-1 to 624-n are arranged to be orthogonal to each other. .

  For example, in the first light receiving element, a TFT 622-(1, 1) which is a conduction control unit made of a silicon laminated structure or an organic semiconductor is connected to the photodiode 621-(1, 1). As the TFT 622-(1, 1), for example, a TFT (Thin Film Transistor) is used. The drain electrode or the source electrode of the TFT 622- (1, 1) is connected to the detection element 620- (1, 1), and the gate electrode is connected to the scanning line 623-m. When the drain electrode is connected to the detection element 620- (1,1), the source electrode is connected to the signal line 624-1, and when the source electrode is connected to the detection element 620- (1,1), the drain electrode is a signal. Connect to line 624-1. In addition, the detection element 620, the photodiode 621, and the TFT 622 in the other pixels are similarly connected to the scanning line 623 and the signal line 624.

  The imaging panel 62 converts the radiation image into an image signal through these circuits. That is, the control unit 60 supplies the readout signal RS to each of the scanning lines 623-1 to 623-m via the scanning drive circuit 609 to perform image scanning, capture an image signal for each scanning line, and capture a radiation image. Convert to digital image signal.

[First power noise removal process]
A first process for removing power supply noise when the radiation image is converted into an image signal in the imaging panel 62 will be described.

  The scan driving circuit 609 mainly controls the ON / OFF operation of the TFT 622. To turn on the TFT 622, an ON voltage is supplied from the scanning drive circuit 609 to the gate terminal of the TFT 622 via the scanning line 623, and to turn off the TFT 622, the scanning drive circuit 609 to the gate terminal of the TFT 622 via the scanning line 623. Supply OFF voltage. When a TFT is employed as the switch element, the ON power supply voltage is set to 15 V, for example. The voltage of the OFF power supply is set to -10V, for example. An ON voltage source 301 is used to supply the ON voltage, and an OFF voltage source 302 is used to supply the OFF voltage. A switching circuit 303, which will be described later, is used as switching means of the present invention that selects supply of ON voltage and OFF voltage and connects to each scanning line. Since the switching circuit that selects either one of the two inputs as one output is a generally known technique, a description thereof is omitted here.

  The scanning lines 623-1 to 623-m of the imaging panel 62 are connected to the scanning drive circuit 609 as shown in FIG. 4. When the ON voltage as the readout signal RS is supplied from the scanning drive circuit 609 to any scanning line 623-p (p is any value from 1 to m) among the scanning lines 623-1 to 623-m, The TFTs 622- (p, 1) to 622- (p, n) connected to the scanning line 623-p are turned on (having an ON resistance but conducting), and the photodiode 621- (p, 1) The charges accumulated between .about.621- (p, n) and TFT 622- (p, 1) .about.622- (p, n) are output onto the signal lines 624-1.about.624-n.

  The signal lines 624-1 to 624-n are connected to signal converters 671-1 to 671-n of the readout circuit 608. The signal converter functions as the charge voltage conversion means of the present invention. The signal converters 671-1 to 671-n are configured by a circuit using so-called correlated double sampling (also referred to as CDS) (details will be described later). The output result of the signal converter 671 is supplied to the multiplexer 672.

  The signal converter 671 in the reading circuit 608 will be described with reference to FIGS. FIG. 5 is a diagram showing a partial circuit configuration of the signal converter 671 from the two voltage sources of the ON voltage source 301 and the OFF voltage source 302 until the pixel signal is converted into an analog voltage value. FIG. 6 is a time chart showing the operation in the circuit configuration.

  A part of the circuit configuration of the signal converter 671 shown in FIG. Selection of the ON voltage source 301 and the OFF voltage source 302 which are voltage sources for performing the switching operation of the TFT 622 is performed using a switching circuit 303 provided in the scan driving circuit 609. The switching operation of the switching circuit 303 is controlled by an instruction from the control unit 60. Between the OFF voltage source 302 and the switching circuit 303, a switch SW1 which is a switch means is provided in series. Connected between the switching circuit 303 and the switch SW1 is the other end of the capacitor C1, which is a charge storage means having one end virtually grounded. The output switched by the switching circuit 303 is connected to the gate of the TFT 622. A photodiode 621 supplied with power to the power source 304 is connected to the source side of the TFT. The charge accumulated in the photodiode 621 is output from the drain side by the switching operation of the TFT 622. The drain of the TFT 622 is connected to the input terminal of the amplifier 305. A capacitor C2 is arranged in parallel at the input / output terminal of the amplifier 305, and a potential difference is generated by the electric charge accumulated in the capacitor C2. CV converter) 307 operates. A reset switch 306 is disposed in parallel with the capacitor C2.

  To the output terminal of the amplifier 305, SW2 and the capacitor C3 are connected as holding means for holding the output voltage, and in parallel, SW3 and the capacitor C4 are also connected as holding means.

  A differential amplifier (308), which is a differential circuit (difference means), amplifies the difference in potential generated between the capacitors by holding the voltage by the electric charges accumulated in the capacitors C3 and C4, and AD through a multiplexer 608 (not shown) in the subsequent stage. Output to a converter (not shown). The switches SW1, SW2, and SW3 are controlled by the control unit 60.

  Next, the operation of this circuit configuration will be described with reference to FIG. First, before the reset switch 306 is turned on and the charge accumulated in the photodiode 621 is received, the charge remaining in the capacitor C2 in the CV converter 307 is extinguished. Next, the reset switch 306 is turned off to prepare for the step of converting the charge accumulated in the photodiode 621 into a voltage using the amplifier 305.

  Next, the switch SW1 disposed between the TFT 622 as the conduction control means and the OFF power source 302 is turned off. Here, the order of resetting the reset switch 306 may be switched, or at the same time. By turning off the switch SW1, the OFF voltage obtained by adding the noise voltage of the OFF voltage source 302 at that moment is held at both ends of the capacitor C1.

  Next, before the electric charge accumulated in the photodiode 621 is accumulated in the capacitor C2, the switch SW2 is switched from OFF to ON for a predetermined time. The output voltage of the amplifier 305 in the CV converter is held as an initial voltage in the capacitor C3 as holding means. As the initial voltage, the noise of the OFF voltage source and the KTC noise that is the thermal noise of the capacitor C2 are held. The KTC noise is noise generated when the reset switch 306 is turned off and both ends of the capacitor C2 are opened. The noise voltage generated in the capacitor C2 due to the KTC noise is held as a noise voltage in the capacitor C3 by turning on the switch SW2.

  Next, the switching circuit 303 is switched to connect the ON voltage source 301 to the scanning line 623, supply the ON voltage to the gate voltage of the TFT 622, and turn on the TFT 622. When the TFT 622 is turned on, the electric charge accumulated by imaging is output to the CV converter 307 via the signal line, and is converted into a voltage by the CV converter 307.

  Next, after the electric charge accumulated by imaging is output via the TFT 622 and the signal line, the switching circuit 303 is switched and connected to the OFF voltage source 302 side, and the TFT 622 is turned OFF.

  Next, by turning on the switch SW3, the voltage output from the CV converter is held by the capacitor C4 as the second holding means. The capacitor C4 holds a voltage corresponding to the radiation dose at the time of imaging, a noise voltage of an OFF voltage source when the switch SW1 is turned off, and a KTC noise voltage. The same amount of noise voltage of the OFF voltage source when the switch SW1 is turned off is superimposed on the capacitors C3 and C4. Accordingly, the noise of the OFF voltage source and the KTC noise are offset in the output of the differential amplifier 308, and a pixel signal corresponding to the radiation dose at the time of imaging is output.

  As described above, CDS is a method for canceling KTC noise by holding voltages in capacitors C3 and C4. And by the structure of this invention, not only KTC noise but the noise of an OFF voltage source can be canceled.

  In order to simplify the description, the configuration of a general CDS operation principle is used, but the output of the amplifier 305 is a differential amplifier that is a difference circuit without the switch SW3 and the capacitor C4 as the second holding means. It is directly connected to the input of 308, and the difference calculation may be performed at the timing when SW3 is turned from ON to OFF, and is not limited.

  As described above, when charges are read from the photodiodes 621- (1,1) to 621- (1, n) on the scanning line 623-1, the switches SW1-2 to SW1-m in FIG. As shown in the time chart of FIG. 7 or FIG. 7, the switches SW1-2 related to the other scanning lines are connected so that the power supply noise from the OFF voltage source 302 via the other scanning lines does not affect the image signal. SW1-m is preferably turned off.

  In this manner, noise superimposed on the OFF voltage of the OFF voltage source 322 can be reduced (removed).

  The operation in the reading circuit 608 is performed according to an instruction from the control unit 60. The multiplexer 672 sequentially selects the voltage signal supplied from the signal converter 671, and the selected voltage signal is converted into, for example, a 12-bit digital image signal by an A / D (analog / digital) converter 673. The

  As described above, according to the first process of removing the power supply noise, at least the initial voltage after turning off SW1 is held by the capacitor C3 that is the holding means, and the accumulated charge is converted into a voltage to be different from the initial voltage. By continuing to turn off SW1 until calculating and outputting, voltage noise superimposed on the OFF power source can be reduced (removed), and a radiation image with good granularity can be obtained.

  SW1 and the capacitor C1 are arranged on the OFF voltage source side from the scanning drive circuit 609. However, as shown in FIG. 5B, only the capacitor C1 may be arranged between the scanning drive circuit 609 and the TFT 622. In addition, as shown in FIG. 5C, SW1 and capacitor C1 may be arranged between the scanning drive circuit 609 and the TFT 622. In these cases, SW1 of the scanning line for reading out charges is not turned off at least. The control of the present invention is performed for a scanning line from which no charge is read.

  Although the noise reduction effect is small, some scanning lines may be selected to control the present invention. For example, the scanning drive circuit may be composed of a plurality of groups, SW1 and C1 may be configured for each group, and a group of only scanning lines that are not turned on may be controlled.

  In the above-described embodiment, an example in which the control of the present invention is performed on the scanning line from which reading is performed has been described. However, the control of the present invention is not necessarily performed on the scanning line from which reading is performed. . For example, when reading the first row, the control of the present invention may be performed for at least one other row without performing the control of the present invention for the first row.

  In order to simplify the description, one ON power source is configured. However, a configuration in which a plurality of ON power sources are switched by a switching unit is not limited.

[Second processing for removing power supply noise]
Hereinafter, a description will be given with reference to FIGS. FIG. 8 is a schematic diagram of a detailed circuit configuration of the power supply unit 300 of the imaging panel 62, and FIG. 9 is a schematic explanatory diagram of an output voltage.

  In the second process of removing power supply noise, the scan drive circuit 609 is divided into at least two scan drive circuits 609a and 609b, and voltage fluctuations generated in the output voltage of the OFF voltage source 302a connected to the scan drive circuit 609a. A voltage having a voltage fluctuation opposite to that is generated and supplied to the scanning drive circuit 609b as the OFF voltage source 302b, thereby canceling out the noise and reducing the deterioration of the image quality.

  In FIG. 8, a switching circuit 303-1 to a switching circuit 303 -x, which are means for switching the voltage source, are provided in the scanning drive circuit 609 a, and a switching circuit 303 -x + 1 to a switching circuit 303 -m are provided in the scanning drive circuit 609 b. And provide. The switching circuit 303-1 to the switching circuit 303-x are circuits that select either the ON voltage of the ON voltage source 301 or the first OFF voltage from the OFF voltage source 302 a. The switching circuit 303- (x + 1) to the switching circuit 303-m are circuits for selecting either the ON voltage of the ON voltage source 301 or the second OFF voltage from the OFF voltage source 302a. The switching circuit 303-1 to the switching circuit 303-m are switched by an instruction from the control unit 60.

  The switching circuit 303-1 to the switching circuit 303-m are provided corresponding to each scanning line. In the scanning drive circuit 609, the switching circuit 303-x is connected to the scanning line 623-x, for example. Noise riding on the OFF voltage source 302a and the OFF voltage source 302b is transmitted to the readout circuit 608 via the scanning line and affects the image signal.

  In general, the output voltage of a voltage source is loaded with random noise caused by various factors. In addition, ripple noise is added to the output voltage in the voltage source created using the DC / DC converter. In the circuit configuration shown in FIG. 8, these noises are canceled without being superimposed on the image signal. This will be described below.

  In FIG. 8, the output of the OFF voltage source 302a is divided into two systems of a route 703 and a route 704 in parallel. A voltage VA that is an output of the OFF voltage source 302a is applied to one route 703, which is connected to the scan driving circuit 609a and to the adder 702. The other route 704 is provided with a capacitor C5, a multiplier 701 that inverts the polarity of the input voltage and doubles the amplitude, and an adder 702. In the adder 702, the output of the OFF voltage source 302a and the output of the multiplier 701 are added. The added output is connected to the scan driving circuit 609b. Here, it is preferable that the value of the capacitor C5 is determined so that a frequency band corresponding to a spatial frequency at which a decrease in the graininess of the image is visually recognized passes, and it is preferable to determine the value from the size of the pixel and the processing speed.

  As shown in FIG. 9A, the voltage VA in the route 703 is in a state where noise generated by various factors in the OFF voltage source 302a is superimposed on a predetermined output voltage value V0. The output voltage value refers to a voltage set by the user as the output voltage of the OFF voltage source 302a.

  The voltage VB in the route 704 has only a noise component as shown in FIG. 9B because only the AC component is output when the voltage VA is input to the capacitor C5. As shown in FIG. 9C, the voltage VC is output by the multiplier 701 with the polarity of the voltage VB inverted and the amplitude doubled. The adder 702 adds the voltage VA and the voltage VC and outputs a voltage VD as shown in FIG. The voltage VD has the same voltage value VO as the voltage VA, and is in a state where noise is inverted, that is, a reverse noise is on. The scan drive circuit 609a is supplied with the OFF voltage from the OFF voltage source 302a, and the scan drive circuit 609b is supplied with the OFF voltage from the OFF voltage source 302b. Therefore, noises having opposite voltages cancel each other, so that noise generated by the OFF voltage source 302a does not affect the image signal in the imaging panel 6A. The capacitor C5, the multiplier 701, and the adder 702 function as a negative phase waveform generation unit of the present invention.

  An example of a circuit that generates a voltage having reverse noise is not limited to the above.

  If the numbers of the OFF voltage sources 302a and the OFF voltage sources 302b are different, the influence on the image signal is biased, and the influence of noise remains. Therefore, the switching circuits 303-1 to 303-x and the switching circuit 303- (x + 1) ) To 303-m are preferably the same number.

  As described above, according to the second process of removing the power supply noise, a voltage that changes in reverse to the noise generated in the OFF voltage source 302a is generated by detecting the voltage variation of the OFF voltage source 302a, and the scan driving circuit 609a. In addition, the radiation is transmitted to the scanning lines 303-1 to 303-m via the scanning driving circuit 609b to cancel the noise and reduce the influence on the reading circuit 608, whereby a radiographic image with good graininess can be obtained.

[Third process of power supply noise elimination]
In the third process of power supply noise removal, by providing a plurality of OFF voltage sources 302 having random noises independent from each other, the random noise generated by each voltage source is added to reduce the influence. Hereinafter, a description will be given with reference to FIG. FIG. 10 is a diagram for explaining a method of adding and subtracting random noise.

  First, a method for removing random noise will be described with reference to FIG. In the figure, V1 and V2 are random noises, and V3 is a voltage when V1 and V2 are added. The horizontal axis represents time, and the vertical axis represents voltage amplitude. Assuming that some noise parts of V1 and V2 have the same amplitude value and are inverted in polarity, V3 obtained by adding V1 and V2 has the same amplitude value and the part of which polarity is inverted. They will be erased. As a result of canceling random noises in this way, noise can be reduced.

Since the phase of random noise in the output voltage of the voltage source is different, if statistical processing is performed, the noise that reaches the readout circuit 608 is reduced to a value divided by n ^1/2 . Here, n is the number of OFF voltage sources 302. Therefore, the effect of reducing noise increases as the number of sources of random noise increases.

  FIG. 10B shows a part of the imaging unit 6A having the power supply unit 300 in which the same number of OFF voltage sources as random noise generation sources as the number of scanning lines are prepared. For example, an OFF voltage source 302a is connected to the switching circuit 303-1, an OFF voltage source 302b is connected to the switching circuit 303-2, and an OFF voltage source 302c is connected to the switching circuit 303-3. Thus, a plurality of OFF voltage sources 302 that generate different random noises are provided, and as a result, the influence of random noises is reduced.

  In a power supply with ripple noise superimposed using a DC / DC converter, the operation frequency of the DC / DC converter is made to be different from each other, or the timing (phase) at which the ripple noise is superimposed even if the operating frequency is the same. ) Are configured to operate so as to deviate from each other, image quality degradation can be improved even with respect to ripple noise.

  As described above, according to the third process of power supply noise removal, by using different OFF voltage sources 302, random noises having different phases generated in the respective OFF voltage sources 302 are generated and transmitted to the scanning drive circuit 609. In addition, by reducing the influence on the readout circuit 608, a radiation image with good graininess can be obtained.

1 is a diagram illustrating a schematic configuration of a radiographic image capturing system 1. FIG. FIG. 3 is a block diagram of a main part configuration of an FPD 6 and a console 7. It is a perspective view of FPD6. It is a circuit block diagram of the imaging part 6A of FPD6. It is a figure which shows the circuit structure until it converts a pixel signal into an analog voltage value from two voltage sources, ON voltage source 301 and OFF voltage source 302. FIG. It is a time chart which shows the operation | movement in a circuit structure. 3 is a schematic diagram of a power supply unit 300 and a scanning drive circuit 609 of the imaging panel 62. FIG. 3 is a schematic diagram of a circuit configuration of a power supply unit 300 of an imaging panel 62. FIG. 6 is a schematic explanatory diagram of an output voltage of a power supply unit 300 of the imaging panel 62. FIG. It is a figure explaining the method and circuit structure which add and reduce random noise.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Radiographic imaging system 3 Radiation irradiation apparatus 4 Imaging operation apparatus 5 Access point 6 Radiographic image detection apparatus 7 Console 9 Router 11a Detection apparatus installation port 11 Supine photography stand 12 Patient 60 Control part 61 Case 62 Imaging panel 64 Light emitting layer 65 , 75 Transmission / reception unit 70 Console control unit 77 Display unit 78 Input operation unit 100 Shooting room 300 Power supply unit 301 ON voltage source 302 OFF voltage source 303 Switching circuit 304 Power source 305 Amplifier 306 Differential amplifier 306 Reset switch 307 CV converter 608 Reading circuit 609 Scanning drive circuit 620 Detector element 623 Scan line 624 Signal line 660 Image storage unit 671 Signal converter 672 Multiplexer 673 A / D converter 701 Multiplier 702 Adder 703, 704 Route 760 Image storage unit 6A Image panel C1, C2, C3, C4 capacitor

Claims (3)

An imaging panel in which a plurality of detection elements for converting irradiated radiation into electric charges are two-dimensionally arranged;
Holding and outputting the electric charge converted by the detection element, and conduction control means arranged for each detection element;
A scanning line to which the conduction control means is connected for each row;
An ON voltage source for supplying an ON voltage for controlling the conduction control means to the conduction control means through the scanning line so as to output the electric charge converted by the detection element;
An OFF voltage source for supplying an OFF voltage for controlling the conduction control means to the conduction control means through the scanning line so as to hold the electric charge converted by the detection element;
A scanning drive circuit comprising switching means for selecting one of the ON voltage source or the OFF voltage source and connecting to the conduction control means corresponding to each scanning line;
Switch means disposed in a path between the OFF voltage source and the conduction control means;
A charge storage means having one end connected to the path between the switch means and the conduction control means and the other end virtually grounded;
Charge-voltage conversion means for converting the charge output from the detection element into a voltage;
Difference means for calculating a difference between the first voltage and the second voltage converted by the charge voltage conversion means;
In the state where the switching means is switched to apply the OFF voltage to the conduction control means, the first voltage is acquired by the charge voltage conversion means, and then the ON voltage is applied to the conduction control means. After switching the switching means and outputting the charge held in the detection element, the charge voltage conversion means obtains the second voltage, and the difference means determines the difference between the first voltage and the second voltage. A control unit that calculates radiation image data based on the calculation result;
Have
When acquiring the first voltage, the control unit turns off the switch unit corresponding to at least one scanning line, and corresponds to the one scanning line until the second voltage is acquired. A radiological image detection apparatus characterized in that an OFF state of a switch means is continued. The radiographic image according to claim 1, wherein the control unit also turns off the switch unit corresponding to another scan line while the switch unit is turned off with respect to the one scan line. Detection device. An imaging panel in which a plurality of detection elements for converting irradiated radiation into electric charges are two-dimensionally arranged;
Holding and outputting the electric charge converted by the detection element, and conduction control means arranged for each detection element;
A plurality of scanning lines to which the conduction control means is connected for each row;
An ON voltage source for supplying an ON voltage for controlling the conduction control means to the conduction control means through the scanning line so as to output the electric charge converted by the detection element;
An OFF voltage source for supplying an OFF voltage for controlling the conduction control means to the conduction control means through the scanning line so as to hold the electric charge converted by the detection element;
A scanning drive circuit comprising switching means for selecting one of the ON voltage source or the OFF voltage source and connecting to the conduction control means corresponding to each scanning line;
Have
The OFF voltage source includes a plurality of OFF voltage sources,
The radiation image detecting apparatus , wherein an OFF voltage source having random noise independent of each other is connected to at least one of the plurality of scanning lines.

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