JP2014081316A - Radiation imaging device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain a radiation imaging device that can make a thickness of a radiation conversion film of a radiation imaging device thin, and acquire a highly precise radiation photographing image.SOLUTION: A radiation imaging device (1000) has: a first imaging panel (1); and a second imaging panel (2), and respective imaging panels have a plurality of pixels (15 and 16) arranged. Each pixel of the second imaging panel (2) is caused to correspond to each pixel of the first imaging panel (1). The pixel of the second imaging panel (2) is respectively arranged on a straight line connecting a radiation source LS and a central point of a corresponding pixel of the first imaging panel (1). An imaging signal is captured by the pixels of the first imaging panel (1) and the second imaging panel (2), and thereby the highly precise radiation photographing image can be acquired.

Description

  The present invention relates to radiation imaging technology.

  2. Description of the Related Art A radiation imaging apparatus that captures a radiation image (for example, an X-ray image) with a sensor array that includes a plurality of pixels arranged in a grid pattern on a flat substrate is known. In such a radiation imaging apparatus, radiation is converted into electric charges by a radiation conversion film (for example, an X-ray conversion film using amorphous selenium). Then, the converted charges are collected in a storage capacitor (charge collecting electrode) of the sensor array, and the collected charges are sequentially read out to acquire a radiation image.

  In a conventional radiation imaging apparatus, a dotted line source is often used as a radiation source, and it is difficult to acquire a highly accurate radiation image. Therefore, for example, in the technique disclosed in Patent Document 1, two solid-state sensors are provided with two conductive layers having different radiation energy absorption characteristics, and the charges accumulated in the two conductive layers are sequentially read out to obtain two A radiographic image is acquired, and the acquired two radiographic images are combined to acquire a high-accuracy radiographic image (for example, a subtraction image).

JP 2001-249182 A

  However, in the above prior art, it is necessary to provide the solid sensor with two conductive layers (a plurality of conductive layers) having different radiation energy absorption characteristics. Further, if it is attempted to obtain a highly accurate radiation image, radiation conversion is required. It is considered necessary to increase the thickness of the film.

  On the other hand, when a radiation imaging apparatus is configured using one type of radiation conversion film, the thickness of the radiation conversion film is set to about several hundred to several thousand μm in order to sufficiently capture radiation (for example, X-rays). There is a need. For this reason, in the case of a radiation imaging apparatus using a point source, the radiation image acquired by the peripheral pixels away from the point source is blurred. This will be described with reference to FIG.

  FIG. 10 is a diagram schematically illustrating a cross section of a common electrode, a radiation conversion film, and a pixel electrode portion in a radiation imaging apparatus using a point source. In FIG. 10, the thickness of the radiation conversion film is set to 300 μm in order to sufficiently capture radiation (for example, X-rays). Further, the incident angle of radiation at point A in FIG.

  As shown in FIG. 10, when the thickness of the radiation conversion film is 300 μm, the radiation incident on the point A travels in the horizontal direction (thickness in the cross section) while traveling 300 μm in the thickness direction (vertical direction) of the radiation conversion film. In the orthogonal direction), it proceeds 300 × tan θ [μm]. For example, in the case of tan θ = 18/70 (for example, the distance from the radiation source (point source) to the common electrode surface is 70 cm, and from the intersection of the perpendicular drawn from the radiation source to the common electrode surface and the common electrode surface) When the distance to the point A is 18 cm), the radiation incident on the point A is about 77 μm (= 300 × 18/70 [= 300 × 18/70 [horizontal direction] while traveling 300 μm in the thickness direction (vertical direction) of the radiation conversion film. μm]). Assuming that the pixel pitch (interval between pixel electrodes) is 50 μm, as shown in FIG. 10, the charges generated in the radiation conversion film by the radiation incident on the point A are accumulated in the storage capacitor (charge collection) of the adjacent pixel (pixel P1). Electrode). That is, as the pixel is arranged farther from the radiation source (point source) (incident angle θ becomes larger), interference with adjacent pixels becomes stronger. As a result, the peripheral image region (image region formed by the image signal acquired by the pixels arranged far from the radiation source (point source)) of the captured image to be acquired is blurred.

  In view of the above problems, an object of the present invention is to realize a radiation imaging apparatus capable of reducing the thickness of the radiation conversion film of the radiation imaging panel and acquiring a highly accurate radiation imaging image.

  In order to solve the above-described problem, a radiation imaging apparatus having a first configuration is a radiation imaging apparatus that acquires a radiation image based on radiation irradiated to a subject from a radiation source that is a point source, and the first radiation conversion apparatus Unit, a first pixel unit, a second radiation conversion unit, a second pixel unit, and an image processing unit.

  The first radiation conversion unit includes a first radiation conversion film that converts radiation into a predetermined physical quantity.

  The first pixel unit has a plurality of pixels, acquires a signal corresponding to the physical quantity converted by the first radiation conversion unit for each pixel, and outputs the acquired signal as a first image signal.

  The second radiation conversion unit includes a second radiation conversion film that is disposed at a position farther from the position where the first radiation conversion film is disposed when the radiation source is used as a reference, and converts the radiation into a predetermined physical quantity.

  The second pixel unit has a plurality of pixels, acquires a signal corresponding to the physical quantity converted by the second radiation conversion unit for each pixel, and outputs the acquired signal as a second image signal.

  The image processing unit acquires a final image signal based on the first image signal and the second image signal.

  Each pixel of the second pixel unit is associated with each pixel of the first pixel unit. The pixels of the second pixel portion are each arranged on a straight line connecting the radiation source and the center point of the corresponding pixel of the first pixel portion.

  ADVANTAGE OF THE INVENTION According to this invention, the thickness of the radiation conversion film of a radiation imaging panel can be made thin, and the radiation imaging device which can acquire a highly accurate radiation imaging image is realizable.

1 is a schematic configuration diagram of a radiation imaging apparatus 1000 according to a first embodiment. FIG. 3 is a partial cross-sectional view of the first imaging panel 1 and the second imaging panel 2 of the radiation imaging apparatus 1000 according to the first embodiment. FIG. 3 is a diagram illustrating an example of a schematic configuration of a first imaging panel 1, a first gate control unit 11, and a first charge reading unit 12 of the radiation imaging apparatus 1000 according to the first embodiment. FIG. 3 is a diagram illustrating an example of a schematic configuration of a second imaging panel 2, a second gate control unit 21, and a second charge reading unit 22 of the radiation imaging apparatus 1000 according to the first embodiment. An example of arrangement | positioning of the pixel electrode of the 1st pixel electrode layer 15 of the 1st imaging panel 1 of the radiation imaging device 1000 which concerns on 1st Embodiment, and the pixel electrode of the 2nd pixel electrode layer of the 2nd imaging panel 2 is shown typically. Perspective view. The figure which shows typically light source LS, pixel electrode E1 (x1, y1) of the 1st pixel electrode layer 15, and pixel electrode E2 (x1, y1) of the 2nd pixel electrode layer 25. The figure for demonstrating the interference to an adjacent pixel. The figure for demonstrating pixel arrangement | positioning. FIG. 3 is a diagram showing a schematic configuration of a first common electrode 13, a first radiation conversion film 14, a first pixel electrode layer 15, a first pixel circuit unit 16, a pixel electrode 151, and a pixel circuit 161. The figure which shows typically the cross section of the common electrode, radiation conversion film, and pixel electrode part in the radiation imaging device using a point source.

[First Embodiment]
The first embodiment will be described below with reference to the drawings.

<1.1: Configuration of radiation imaging apparatus>
First, the configuration of the radiation imaging apparatus will be described.

  FIG. 1 is a schematic configuration diagram of a radiation imaging apparatus 1000 according to the first embodiment.

  FIG. 2 is a partial cross-sectional view of the first imaging panel 1 and the second imaging panel 2 of the radiation imaging apparatus 1000 according to the first embodiment.

  FIG. 3 is a diagram illustrating an example of a schematic configuration of the first imaging panel 1, the first gate control unit 11, and the first charge reading unit 12 of the radiation imaging apparatus 1000 according to the first embodiment.

  FIG. 4 is a diagram illustrating an example of a schematic configuration of the second imaging panel 2, the second gate control unit 21, and the second charge reading unit 22 of the radiation imaging apparatus 1000 according to the first embodiment.

  FIG. 5 shows an example of the arrangement of the pixel electrodes of the first pixel electrode layer 15 of the first imaging panel 1 and the pixel electrodes of the second pixel electrode layer of the second imaging panel 2 of the first imaging panel 1 of the radiation imaging apparatus 1000 according to the first embodiment. It is a perspective view showing typically. In FIG. 5, for convenience of explanation, pixel electrodes respectively corresponding to a total of 16 pixels of 4 pixels × 4 pixels of the first imaging panel 1 and a total of 4 pixels × 4 pixels of the second imaging panel 2. Pixel electrodes respectively corresponding to 16 pixels are illustrated. Naturally, in the radiation imaging apparatus 1000, the number of pixels of the first imaging panel 1 and the second imaging panel 2 may be any number of pixels (M pixels × N pixels (M, N: natural number)).

  As shown in FIG. 1, the radiation imaging apparatus 1000 includes a first imaging panel 1, a second imaging panel 2, a first gate control unit 11, a first charge reading unit 12, and a second gate control unit 21. The second charge reading unit 22, the control unit 3, and the image processing unit 4. In the radiation imaging apparatus 1000, as shown in FIG. 1, radiation emitted from a radiation source (point source) LS and transmitted through a subject B is imaged by the first imaging panel 1 and the second imaging panel 2, thereby generating radiation. An image is acquired (details will be described later).

  The first imaging panel 1 has a flat plate shape and is substantially the same shape as the second imaging panel 2 in plan view. The first imaging panel 1 is disposed on the second imaging panel 2. That is, as shown in FIG. 1, the first imaging panel 1 and the second imaging panel 2 are arranged in this order from the side closer to the radiation source LS.

  The first imaging panel 1 has, for example, a plurality of pixels arranged in a lattice shape in a plan view, accumulates charges according to the intensity of irradiated radiation for each pixel, and stores the accumulated charges. Based on this, an image signal is acquired.

  As shown in FIG. 2, the first imaging panel 1 includes a first common electrode 13, a first radiation conversion film 14, a first pixel electrode layer 15, a first pixel circuit unit 16, and a first substrate 17. . As shown in FIG. 2, the first imaging panel 1 includes a first common electrode 13, a first radiation conversion film 14, a first pixel electrode layer 15, a first pixel circuit unit 16, One substrate 17 is arranged in this order.

  The first common electrode 13 has a flat plate shape and is formed so as to cover the entire region where a plurality of pixels (a plurality of pixels of the first imaging panel 1) are arranged in a plan view. The first common electrode 13 is formed of a conductor and applies a voltage between the first common electrode 13 disposed with the first radiation conversion film 14 interposed therebetween and the pixel electrode of the first pixel electrode layer 15. Electrode.

  The first radiation conversion film 14 has a flat plate shape and is formed so as to cover the entire region where a plurality of pixels are arranged in plan view. As shown in FIG. 2, the first radiation conversion film 14 is disposed so as to be sandwiched between the first common electrode 13 and the first pixel electrode layer 15 in a cross-sectional view. When the first radiation converting film 14 is irradiated with radiation, the first radiation converting film 14 generates a charge corresponding to the intensity of the irradiated radiation. The first radiation conversion film 14 can be formed using amorphous selenium (amorphous selenium), for example.

  The first pixel electrode layer 15 includes a plurality of pixel electrodes provided for each pixel. The pixel electrodes included in the first pixel electrode layer 15 are arranged (arranged), for example, in a lattice shape in a plan view, and are set in the pixel circuit (the first pixel circuit unit 16) immediately below each pixel. Pixel circuit for each pixel).

  The first pixel circuit unit 16 includes a plurality of pixel circuits provided for each pixel. Each pixel circuit is electrically connected to the pixel electrode of the first pixel electrode layer 15 disposed at substantially the same position in plan view. As shown in FIG. 3, each pixel circuit of the first pixel circuit unit 16 includes a switching element SW (for example, (thin film transistor (TFT))) and a charge storage capacitor Cs. In each pixel circuit, the gate terminal (control terminal) of the switching element is connected to the gate line. The switching element SW is turned on or off when the first gate controller 11 sets the gate lines (gate lines G0 to G3 in FIG. 3) to a predetermined voltage. A source terminal of the switching element SW (one terminal through which current flows when the switching element SW is ON) is connected to the charge storage capacitor Cs and the pixel electrode Ex of the first pixel electrode layer 15. Further, the drain terminal of the switching element SW (the other terminal through which a current flows when the switching element SW is ON) is connected to the first charge reading unit 12 by a data line (D0 to D3 in FIG. 3). The charge storage capacitor Cs is connected to the switching element SW and a predetermined potential Vd (for example, ground potential).

  In FIG. 3, for example, the source terminal of the pixel circuit of the pixel P <b> 1 (0, 0) (one terminal through which a current flows when the switching element SW is ON) is the pixel of the charge storage capacitor Cs and the first pixel electrode layer 15. It is connected to the electrode E1 (0, 0). The pixels connected to the gate line Gx (x: integer, 0 ≦ x ≦ 3) and the data line Dy (y: integer, 0 ≦ y ≦ 3) of the first imaging panel 1 are designated as “P1 (x, y ) ”, And the pixel electrode Ex of the first pixel electrode layer 15 connected to the pixel P1 (x, y) is expressed as“ E1 (x, y) ”(the same applies hereinafter).

  As shown in FIG. 2, the second imaging panel 2 includes a second common electrode 23, a second radiation conversion film 24, a second pixel electrode layer 25, a second pixel circuit unit 26, and a second substrate 27. . As shown in FIG. 2, the second imaging panel 2 includes the second common electrode 23, the second radiation conversion film 24, the second pixel electrode layer 25, the second pixel circuit unit 26, The substrates 27 are arranged in this order.

  The second common electrode 23 has a flat plate shape and is formed so as to cover the entire region where a plurality of pixels (a plurality of pixels of the second imaging panel 2) are arranged in a plan view. The second common electrode 23 is formed of a conductor, and is an electrode for applying a voltage between the second common electrode 23 and the second pixel electrode layer 25 disposed with the second radiation conversion film 24 interposed therebetween. is there.

  The second radiation conversion film 24 has a flat plate shape and is formed so as to cover the entire region where a plurality of pixels are arranged in a plan view. As shown in FIG. 2, the second radiation conversion film 24 is disposed so as to be sandwiched between the second common electrode 23 and the second pixel electrode layer 25 in a cross-sectional view. When the second radiation converting film 24 is irradiated with radiation, the second radiation converting film 24 generates a charge corresponding to the intensity of the irradiated radiation. The second radiation conversion film 24 can be formed using, for example, amorphous selenium (amorphous selenium). The second radiation conversion film 24 preferably has a thickness equal to or greater than the thickness of the first radiation conversion film 14.

  The second pixel electrode layer 25 includes a plurality of pixel electrodes provided for each pixel. The pixel electrodes included in the second pixel electrode layer 25 are arranged (arranged), for example, in a lattice shape in a plan view, and are set in the pixel circuit (second pixel circuit unit 26) immediately below each pixel. Pixel circuit for each pixel). The pixel electrode of the second pixel electrode layer 25 is provided at a position corresponding to the pixel electrode of the first pixel electrode layer 15 for each pixel, as shown in FIGS. Specifically, the pixel electrode of the second pixel electrode layer 25 includes, for each pixel, a radiation source LS and a pixel electrode of the first pixel electrode layer 15 (a pixel electrode of the first pixel electrode layer 15 corresponding to each pixel). It is provided at a position including the intersection of the straight line connecting the center point and the second pixel electrode layer 25 (plane). For example, as shown in FIGS. 2 and 5, in the first imaging panel 1, the second imaging is performed by using the pixel electrode E <b> 1 (xa, ya) of the first pixel electrode layer 15 arranged in the xa-th column and the ya-th row. In the panel 2, when the pixel electrode E2 (xa, ya) of the second pixel electrode layer 25 arranged in the xa column and the ya row is connected, the radiation source LS and the center point of the pixel electrode E1 (xa, ya) are connected. The pixel electrode of the second pixel electrode layer 25 is arranged so that the center point of the pixel electrode E2 (xa, ya) is located on the straight line.

That is, the position of the radiation source LS is LS, the center point of the pixel electrode E1 (xa, ya) of the first pixel electrode layer 15 is E1c (xa, ya), and the pixel electrode E2 (xa) of the second pixel electrode layer 25 is , Ya) is E2c (xa, ya).
Vec (LS, E2c (xa, ya)) = k × Vec (LS, E2c (xa, ya))
k: The pixel electrode of the second pixel electrode layer 25 is arranged so as to be a constant. Vec (α, β) indicates a vector from the point α to the point β. The operator “x” indicates multiplication.

  Here, the position of the pixel electrode of the second pixel electrode layer 25 will be described with reference to FIGS.

  FIG. 6 is a diagram similar to FIG. 5, in which the light source LS, the pixel electrode E1 (x1, y1) of the first pixel electrode layer 15, and the pixel electrode E2 (x1, y1) of the second pixel electrode layer 25 are illustrated. FIG.

  In FIG. 6, a point N <b> 1 includes a perpendicular line drawn from the radiation source LS to the first pixel electrode layer 15 (a plane including the first pixel electrode layer 15), and a first pixel electrode layer 15 (including the first pixel electrode layer 15). (Plane). Point N2 is an intersection with the second pixel electrode layer 25 (a plane including the second pixel electrode layer 25).

  FIG. 7 is a diagram for explaining interference with adjacent pixels. Specifically, the left diagram in FIG. 7 is a cross-sectional view of a plane including the point LS (radiation source LS), the point N1, and the point E1c (x1, y1) in FIG. The right diagram in FIG. 7 is a diagram for comparison, and is a cross-sectional view in the case where an imaging panel (radiation conversion film) is configured by one.

  As shown in FIG. 7, when radiation is incident on the radiation conversion film obliquely, the radiation incident on the left pixel is incident on the right pixel (pixel adjacent to the right). The region that receives the interference is the portion shown in gray in FIG.

Conversion efficiency (conversion efficiency when converting radiation into electric charge) equivalent to that of a radiation imaging device configured using a radiation conversion film (one imaging panel) having a thickness t is converted into a plurality of radiation conversion films (a plurality of imaging panels). In the case of realizing the radiation imaging apparatus 1000 using the above, the total thickness of each radiation conversion film may be made equal to t. That is, in the case of FIG. 7, in the radiation imaging apparatus 1000 (the left diagram in FIG. 7), when trying to achieve the same conversion efficiency as the radiation conversion film in the right diagram in FIG. 7,
t = t1 + t2
t1: The thickness of the first radiation conversion film 14 t2: The thickness of the second radiation conversion film 24 may be used.

  That is, in the radiation imaging apparatus 1000, if the thickness t1 of the first radiation conversion film and the thickness t2 of the second radiation conversion film are set so as to satisfy the above formula, it is equivalent to the radiation conversion film having the thickness t of the radiation conversion film. Conversion efficiency can be realized. However, the radiation conversion amount (conversion amount to electric charge) decreases exponentially according to the distance that has passed through the radiation conversion film, and is larger as it is closer to the incident surface. It is preferable to reduce the thickness. That is, in the case of FIG. 7, it is preferable that t1 <t2.

  Charges generated in the radiation conversion film (for example, electrons indicated by “−” and holes indicated by “+” in FIG. 9) are generated along the electric field generated by the common electrode and the pixel electrode, for example, as shown in FIG. Since it moves to the electrode substantially vertically, a radiation passage (for example, an arrow line R1 in FIG. 7) passing through the position of the common electrode (for example, the point Px in FIG. 7) immediately adjacent to the boundary between adjacent pixels is adjacent. It becomes a boundary that interferes with the pixel. As can be seen from FIG. 7, when the radiation conversion film is divided into two, the interference area (area shown in gray in FIG. 7) is smaller than in the case of one radiation conversion film. Therefore, as shown in the left diagram of FIG. 7, when a radiation conversion film having a thickness t is used by adopting a configuration in which t = t1 + t2 and the radiation conversion film is divided into two. The amount of interference with adjacent pixels can be reduced while realizing the same conversion efficiency.

  Furthermore, as shown in FIG. 8, the amount of interference with the adjacent pixel can be further reduced by disposing the pixel electrode (pixel) outside the boundary that receives interference with the adjacent pixel. FIG. 8 shows a radiation source LS, a perpendicular line drawn from the radiation source LS to the first pixel electrode layer 15 (a plane including the first pixel electrode layer 15), and the first pixel electrode layer 15 (first pixel electrode layer 15). Of the first imaging panel 1 and the second imaging panel 2 on the plane including the intersection point N1 with the center plane E1c (x1, y1) of the pixel electrode E1 (x1, y1) of the first pixel electrode layer 15. It is the figure which showed the cross section typically. For convenience of explanation, the x-axis and the y-axis are taken as shown in FIG.

As shown in FIG. 8, on the first common electrode 13 of the first imaging panel 1, a point corresponding to the right end (end point in the positive x-axis direction) of the pixel P1 (x0, y0) is defined as a point S00, and the pixel P1 ( The point corresponding to the right end of (x1, y1) (end point in the positive x-axis direction) is point S01, the radiation incident angle at point S00 is θ0, the radiation incident angle at point S01 is θ1, and the first common electrode 13 The distance from the upper surface of the first pixel electrode layer 15 to the upper surface of the first pixel electrode layer 15 is L1, the distance from the upper surface of the first common electrode 13 to the upper surface of the second pixel electrode layer 25 is L2, and the pixel electrode E1 (x1, y1) The leftmost point (the point where the value of x is minimum) is E1L (x1, y), and the rightmost point (the point where the value of x is maximum) of the pixel electrode E1 (x1, y1) is E1R (x1, y ) And the leftmost point of the pixel electrode E2 (x1, y1) (the value of x is the smallest) E2L (x1, y) and the rightmost point of the pixel electrode E2 (x1, y1) (the point where the value of x is maximum) is E2R (x1, y).
x_pos (E1L (x1, y1)) ≧ x_pos (S00) + L1 × tan θ0
x_pos (E1R (x1, y1)) ≦ x_pos (S01) + L1 × tan θ1
x_pos (E2L (x1, y1)) ≧ x_pos (S00) + L2 × tan θ0
x_pos (E2R (x1, y1)) ≦ x_pos (S01) + L2 × tan θ1
It is preferable to arrange the pixel electrode E1 (x1, y1) of the first pixel electrode layer 15 and the pixel electrode E2 (x1, y1) of the second pixel electrode layer 25 so that the above holds. The same applies to the other pixel electrodes. Note that x_pos (A) is a function for obtaining the value of x at point A (the position on the x coordinate in FIG. 8).

  By disposing the pixel electrode at the above position, it is possible to efficiently reduce interference (crosstalk) between adjacent pixels.

  As described above, by arranging the pixel electrodes of the second pixel electrode layer 25, the radiation imaging apparatus 1000 can efficiently reduce the amount of interference with adjacent pixels.

Further, in the radiation imaging apparatus 1000 having a plurality of radiation conversions, the area of the pixel electrode of the imaging panel in a plan view is arranged far from the radiation source LS while satisfying the above-described conditions that can reduce the amount of interference with adjacent pixels. As the area of the pixel electrode increases, the area may be increased. For example, in the case of FIGS. 6 and 8, assuming that the area of the pixel electrode E1 (xa, ya) in plan view is Area (E1 (xa, ya)),
Area (E1 (xa, ya)) ≦ Area (E2 (xa, ya))
The shape of the pixel electrode of the first pixel electrode layer 15 and the pixel electrode of the second pixel electrode layer 25, the area in plan view, and the like may be determined.

  The second pixel circuit unit 26 includes a plurality of pixel circuits provided for each pixel. Each pixel circuit is electrically connected to the pixel electrode of the second pixel electrode layer 25 disposed at substantially the same position in plan view. As shown in FIG. 4, each pixel circuit of the second pixel circuit unit 26 includes a switching element SW (for example, (thin film transistor (TFT))) and a charge storage capacitor Cs. In each pixel circuit, the gate terminal (control terminal) of the switching element is connected to the gate line. The switching element SW is turned on or off when the second gate control unit 21 sets the gate lines (gate lines G0 to G3 in FIG. 4) to a predetermined voltage. The source terminal of the switching element SW (one terminal through which current flows when the switching element SW is ON) is connected to the charge storage capacitor Cs and the pixel electrode Ex. Further, the drain terminal of the switching element SW (the other terminal through which a current flows when the switching element SW is ON) is connected to the second charge reading unit 22 by a data line (D0 to D3 in FIG. 4). The charge storage capacitor Cs is connected to the switching element SW and a predetermined potential Vd (for example, ground potential).

  In FIG. 4, for example, the source terminal of the pixel circuit of the pixel P2 (0, 0) (one terminal through which current flows when the switching element SW is ON) is the charge storage capacitor Cs and the pixel electrode E2 (0, 0). It is connected to the. Note that pixels connected to the gate line Gx (x: integer, 0 ≦ x ≦ 3) and the data line Dy (y: integer, 0 ≦ y ≦ 3) of the second imaging panel 2 are designated as “P2 (x, y ) ”, And the pixel electrode Ex connected to the pixel P2 (x, y) is represented as“ E2 (x, y) ”(the same applies hereinafter).

  Note that the “first pixel unit” includes, for example, the first common electrode 13, a plurality of pixel electrodes included in the first pixel electrode layer 15, and a plurality of pixel circuits included in the first pixel circuit unit 16. That function is realized. In addition, the “second pixel unit” includes, for example, a second common electrode 23, a plurality of pixel electrodes included in the second pixel electrode layer 25, and a plurality of pixel circuits included in the second pixel circuit unit 26. That function is realized.

<1.2: Operation of radiation imaging apparatus>
The operation of the radiation imaging apparatus 1000 configured as described above will be described below.

  As shown in FIG. 1, radiation is emitted from the radiation source LS to the subject B, the first imaging panel 1 and the second imaging panel 2. The irradiated radiation passes through the subject B or directly enters the first imaging panel 1 and the second imaging panel 2.

  In the radiation imaging apparatus 1000, a predetermined voltage is applied to each pixel electrode of the first common electrode 13 and the first pixel electrode layer 15 in the first imaging panel 1. In the radiation imaging apparatus 1000, a predetermined voltage is applied to each pixel electrode of the second common electrode 23 and the second pixel electrode layer 25 in the second imaging panel 2.

  In the radiation conversion film of the first imaging panel 1, an electric charge corresponding to the intensity of the passed radiation is generated. The generated charges are collected in the pixel electrode according to the generation position by the electric field between the first common electrode 13 and each pixel electrode of the first pixel electrode layer 15 and connected to the pixel electrode. The charge is stored in the charge storage capacitor Cs of the pixel circuit (pixel circuit of the first pixel circuit unit 16).

  The charge stored in the charge storage capacitor Cs of the pixel circuit of the first pixel circuit unit 16 is first transmitted through the data line at a predetermined timing in accordance with a control signal output from the first gate control unit 11 through the gate line. Read by the charge reading unit 12. The charge read by the first charge reading unit 12 is subjected to predetermined processing by the first charge reading unit 12 and then output to the image processing unit 4 as the first image signal Din1.

  Further, in the radiation conversion film of the second imaging panel 2, an electric charge corresponding to the intensity of the radiation that has passed is generated. The generated charges are collected by the pixel electrode according to the generation position by the electric field between the second common electrode 23 and each pixel electrode of the second pixel electrode layer 25, and are connected to the pixel electrode. The charge is stored in the charge storage capacitor Cs of the pixel circuit (the pixel circuit of the second pixel circuit unit 26).

  The charge stored in the charge storage capacitor Cs of the pixel circuit of the second pixel circuit unit 26 is secondly transmitted through the data line at a predetermined timing in accordance with a control signal output from the second gate control unit 21 through the gate line. Read by the charge reading unit 22. The charge read by the second charge reading unit 22 is subjected to predetermined processing by the second charge reading unit 22 and then output to the image processing unit 4 as the second image signal Din2.

  Note that, as described above, each pixel electrode of the second pixel electrode layer 25 is arranged at a position where it is difficult to receive interference with adjacent pixels, and thus is acquired from the charge acquired in the second imaging panel 2. The second image signal Din2 is a high-quality signal that is not subject to interference with adjacent pixels (low crosstalk).

  The image processing unit 4 obtains the image signal Dout by combining the first image signal Din1 output from the first charge reading unit 12 and the second image signal Din2 output from the second charge reading unit 22. The The acquired image signal Dout is output from the image processing unit 4.

Note that the method of synthesizing the first image signal Din1 and the second image signal Din2 in the image processing unit 4 is, for example, the signal value of the first image signal Din1 and the second image signal Din2 for each corresponding pixel. The signal value may be added to obtain the signal value of the image signal Dout of the pixel. Further, the image signal Dout may be acquired by performing predetermined weighting. That is, in the pixel (x, y), the signal value of the first image signal Din1 is Din1 (x, y), the signal value of the second image signal Din2 is Din2 (x, y), and the signal value of the image signal Dout Let Dout (x, y) be
Dout (x, y) = k1 × Din1 (x, y) + k2 × Din2 (x, y)
k1, k2: The image signal Dout may be acquired by combining the weighting coefficients.

  Note that the weighting coefficients k1 and k2 may be adjusted in accordance with, for example, the non-uniformity of irradiation of the second imaging panel 2 generated by the first imaging panel 1 in advance. Good. At this time, the weighting coefficients k1 and k2 may change according to the pixel position (the position of the pixel electrode). In the above synthesis process, a predetermined clip process, normalization process, or the like may be performed.

  As described above, since the image signal Dout acquired by the radiation imaging apparatus 1000 is acquired using a plurality of imaging panels, the conversion efficiency for converting radiation into electric charge is maintained at a certain level or more, and the adjacent pixels are converted. The signal is based on the charge acquired with the interference amount (crosstalk) suppressed. That is, in the radiation imaging apparatus 1000, since the thickness t1 of the first radiation conversion film 14 of the first imaging panel 1 and the thickness t2 of the second radiation conversion film 24 of the second imaging panel 2 are set, the thickness is (t1 + t2). Radiation-charge conversion efficiency equivalent to that of a single radiation conversion film can be realized. Furthermore, in the radiation imaging apparatus 1000, the arrangement of the pixel electrodes of each layer (each imaging panel) is arranged so as to reduce interference with adjacent pixels in consideration of the radiation irradiation path (the lower the pixel, the lower the pixel). Since the electrodes (pixels) are arranged so as to be sparse, the image signal acquired by the radiation imaging apparatus 1000 is a signal with reduced interference (crosstalk) between adjacent pixels.

  As described above, the radiation imaging apparatus 1000 can acquire a high-quality image signal (imaging signal) while maintaining high radiation-charge conversion efficiency and reducing interference (crosstalk) between adjacent pixels. That is, in the radiation imaging apparatus 1000, the thickness of the radiation conversion film of the radiation imaging panel can be reduced, and a highly accurate radiation imaging image can be acquired.

[Other Embodiments]
In the above embodiment, the case of two layers, that is, the case where the radiation imaging apparatus is configured using two imaging panels has been described. However, the present invention is not limited to this, and the radiation imaging apparatus may be configured using more multilayers, that is, three or more imaging panels. Even in this case, the total thickness of the plurality of radiation conversion films is made to coincide with t (the thickness t of the radiation conversion film when a single radiation conversion film is used) by the same concept as the above embodiment. The radiation-to-charge conversion efficiency equivalent to that of the radiation conversion film having the thickness t can be realized.

  In the case of multiple layers, the radiation conversion film disposed in the lower layer (the radiation conversion film disposed at a position away from the radiation source LS) is thickened. As a result, it is possible to maintain high radiation-charge conversion efficiency while making it difficult to receive interference from adjacent pixels (particularly in the upper layer).

  Even in the case of multiple layers, the position, shape, and area of the pixel electrode of each layer (each imaging panel) are determined in consideration of the radiation emission path by the same concept as described in the above embodiment. That's fine.

  Even in the case of multiple layers, in consideration of the non-uniformity of irradiation caused by radiation irradiation (passage of radiation) of the layers above the own layer in each layer based on the same concept as described in the above embodiment. The image signal to be finally output may be acquired by combining (for example, combining by weighted addition) the image signals acquired by the respective layers (each imaging panel).

  Moreover, although the case where an image signal was acquired by what is called a direct conversion system was demonstrated in the said embodiment, it is not limited to this, For example, a radiation is converted into light using a scintillator etc. The present invention may be applied to a method). Even in this case, the arrangement, shape, area, and the like of the pixels of each imaging panel may be determined so as to reduce interference with adjacent pixels using a plurality of imaging panels.

  In addition, part or all of the radiation imaging apparatus of the above embodiment may be realized as an integrated circuit (for example, an LSI, a system LSI, or the like).

  Part or all of the processing of each functional block in the above embodiment may be realized by a program. A part or all of the processing of each functional block in the above embodiment is performed by a central processing unit (CPU) in the computer. In addition, a program for performing each processing is stored in a storage device such as a hard disk or a ROM, and is read out and executed in the ROM or the RAM.

  Each processing of the above embodiment may be realized by hardware, or may be realized by software (including a case where the processing is realized together with an OS (Operating System), middleware, or a predetermined library). Further, it may be realized by mixed processing of software and hardware.

  Moreover, the execution order of the processing method in the said embodiment is not necessarily restricted to description of the said embodiment, The execution order can be changed in the range which does not deviate from the summary of invention.

  A computer program that causes a computer to execute the above-described method and a computer-readable recording medium that records the program are included in the scope of the present invention. Here, examples of the computer-readable recording medium include a flexible disk, a hard disk, a CD-ROM, an MO, a DVD, a DVD-ROM, a DVD-RAM, a BD (Blu-ray Disc), and a semiconductor memory. .

  The computer program is not limited to the one recorded on the recording medium, and may be transmitted via a telecommunication line, a wireless or wired communication line, a network represented by the Internet, or the like.

  The specific configuration of the present invention is not limited to the above-described embodiment, and various changes and modifications can be made without departing from the scope of the invention.

[Appendix]
The present invention can also be expressed as follows.

  A first configuration is a radiation imaging apparatus that acquires a radiation image based on radiation irradiated to a subject from a radiation source that is a point source, and includes a first radiation conversion unit, a first pixel unit, and a second radiation. A conversion unit, a second pixel unit, and an image processing unit are provided.

  The first radiation conversion unit includes a first radiation conversion film that converts radiation into a predetermined physical quantity.

  The first pixel unit has a plurality of pixels, acquires a signal corresponding to the physical quantity converted by the first radiation conversion unit for each pixel, and outputs the acquired signal as a first image signal.

  The second radiation conversion unit includes a second radiation conversion film that is disposed at a position farther from the position where the first radiation conversion film is disposed when the radiation source is used as a reference, and converts the radiation into a predetermined physical quantity.

  The second pixel unit has a plurality of pixels, acquires a signal corresponding to the physical quantity converted by the second radiation conversion unit for each pixel, and outputs the acquired signal as a second image signal.

  The image processing unit acquires a final image signal based on the first image signal and the second image signal.

  Each pixel of the second pixel unit is associated with each pixel of the first pixel unit. The pixels of the second pixel portion are each arranged on a straight line connecting the radiation source and the center point of the corresponding pixel of the first pixel portion.

  In this radiation imaging apparatus, the pixels of the second pixel unit are each arranged on a straight line connecting the radiation source and the center point of the corresponding pixel of the first pixel unit, and therefore interference (crosstalk) between adjacent pixels. Can be effectively suppressed. In this radiation imaging apparatus, since the radiation conversion film is divided into a plurality of layers, the radiation conversion film of each layer can be made thin. Therefore, in this radiation imaging apparatus, the radiation conversion film of each layer (each radiation imaging panel) can be made thin, and a highly accurate radiation imaging image in which the influence of adjacent pixel interference (crosstalk) is effectively suppressed. It is possible to realize a radiation imaging apparatus that can acquire the above.

  The “pixel” is a concept including a “pixel electrode” in the case of the direct conversion method, that is, when the radiation conversion film directly converts the radiation into the electric charge. In addition, in the case of an indirect conversion method, that is, when the radiation conversion film converts radiation into light, the “pixel” is a photoelectric conversion element (for example, a photodiode) that converts light into an electric signal, or the photoelectric conversion element It is a concept including a pixel having

  Further, the number of layers is not limited to two, that is, two radiation conversion films, but may be three layers or more, that is, three or more radiation conversion films. Also in this case, the pixels of each layer are arranged on a straight line connecting the radiation source and the center point of the corresponding pixel of the first pixel unit.

  The center point of the pixel of the second pixel unit may be arranged on a straight line connecting the radiation source and the center point of the corresponding pixel of the first pixel unit.

  The “predetermined physical quantity” is, for example, an amount of charge or a light amount.

  The second configuration is the first configuration, wherein the thickness of the second radiation conversion film is equal to or greater than the thickness of the first radiation conversion film.

  In this radiation imaging apparatus, since the thickness of the first radiation conversion film can be reduced, the conversion efficiency of the first radiation conversion film can be increased. Furthermore, in this radiation imaging apparatus, since the thickness of the first radiation conversion film can be reduced, the range that receives interference from adjacent pixels is reduced, and as a result, the pixels can be closely arranged. In this radiation imaging apparatus, since the thickness of the second radiation conversion film can be increased, the conversion efficiency in the second radiation conversion film can be maintained in a high state.

  According to a third configuration, in the first or second configuration, the pixel of the second pixel unit has a larger pixel area as the pixel is located farther from the radiation source.

  In this radiation imaging apparatus, since the pixels of the second pixel unit arranged farther from the radiation source have a larger pixel area, the physical quantities converted by the second radiation conversion film can be efficiently collected. Note that the pixels of the second pixel portion are preferably arranged so as to have as large an area as possible in a region (or a region in consideration of a predetermined margin) excluding a region that receives interference from adjacent pixels.

  According to a fourth configuration, in any one of the first to third configurations, the image processing unit is based on non-uniformity of irradiation caused by radiation passing through the first radiation conversion film, which occurs in the second radiation conversion film. Thus, the final image signal is obtained by combining the first image signal and the second image signal.

  Thereby, in this radiation imaging device, it is possible to perform correction in consideration of non-uniformity of irradiation, and it is possible to acquire a highly accurate image signal (radiation imaging image).

  The radiation imaging apparatus according to the present invention can reduce the thickness of the radiation conversion film of the radiation imaging panel and can acquire a highly accurate radiation imaging image. Can be implemented in the field.

1000 Radiation Imaging Device 1 First Imaging Panel 11 First Gate Control Unit 12 First Charge Reading Unit 13 First Common Electrode 14 First Radiation Conversion Film 15 First Pixel Electrode Layer 16 First Pixel Circuit Unit 17 First Substrate 2 First 2 imaging panel 21 second gate control unit 22 second charge reading unit 23 second common electrode 24 second radiation conversion film 25 second pixel electrode layer 26 second pixel circuit unit 27 second substrate

Claims (4)

A radiation imaging apparatus that acquires a radiation image based on radiation irradiated to a subject from a radiation source that is a point source,
A first radiation conversion unit having a first radiation conversion film for converting radiation into a predetermined physical quantity;
A first pixel unit that has a plurality of pixels, acquires a signal corresponding to the physical quantity converted by the first radiation conversion unit for each pixel, and outputs the acquired signal as a first image signal;
A second radiation conversion unit having a second radiation conversion film disposed at a position far from the position at which the first radiation conversion film is disposed when the radiation source is used as a reference and converting the radiation into a predetermined physical quantity; ,
A second pixel unit that has a plurality of pixels, acquires a signal corresponding to the physical quantity converted by the second radiation conversion unit for each pixel, and outputs the acquired signal as a second image signal;
An image processing unit for obtaining a final image signal based on the first image signal and the second image signal;
With
Each pixel of the second pixel unit is associated with each pixel of the first pixel unit,
The pixels of the second pixel portion are respectively arranged on a straight line connecting the radiation source and the center point of the corresponding pixel of the first pixel portion.
Radiation imaging device. The thickness of the second radiation conversion film is equal to or greater than the thickness of the first radiation conversion film.
The radiation imaging apparatus according to claim 1. The pixels of the second pixel portion have a larger pixel area as the pixels arranged at positions farther from the radiation source.
The radiation imaging apparatus according to claim 1 or 2. The image processing unit generates the first image signal and the second image signal based on non-uniformity of irradiation caused by the radiation passing through the first radiation conversion film, which occurs in the second radiation conversion film. By combining, the final image signal is acquired.
The radiation imaging apparatus according to claim 1.