JP2017067681A - Radiation image imaging apparatus - Google Patents

Abstract

An object of the present invention is to provide a radiographic imaging apparatus that suppresses the generation of noise, improves characteristics such as contrast, resolution, and detection resolution, and enables lower exposure doses. SOLUTION: A substrate 2, a plurality of optical sensor sections 4A disposed on the substrate 2, and a plurality of scintillator sections 51 disposed one by one to face each optical sensor section 4A. , and the scintillator section 51 is characterized in that it is surrounded by a reflective surface (inner surface) 52A having a condensing property that reflects light toward the optical sensor section 4A. [Selection diagram] Figure 1

Description

  The present invention relates to a radiographic imaging apparatus that detects radiation and outputs an electrical signal corresponding to the intensity distribution of the radiation.

  A radiation image capturing apparatus 100 as shown in FIG. 5 is known. The radiographic image capturing apparatus 100 captures a subject using X-rays R that have passed through a subject (not shown). The radiographic image capturing apparatus 100 includes a substrate 101, a thin film transistor (hereinafter referred to as TFT) circuit unit 102 provided on the substrate 101, a photodiode array 103, and a scintillator array 104 disposed on the photodiode array 103. And.

  The photodiode array 103 includes a large number of photodiodes arranged for each pixel. FIG. 5 shows three photodiodes S101 to S103 arranged adjacent to each other. The scintillator array 104 includes a plurality of scintillators 104A partitioned by partition walls 105 for each pixel. A reflective film 106 is formed on the surface on which the X-rays are incident. Each scintillator 104 </ b> A has a function of converting X-rays incident through the reflective film 106 into light (visible light). As such a prior art, for example, one described in Patent Document 1 is known.

JP 2014-29314 A

  As shown in FIG. 5, for example, when the X-ray R is incident on the scintillator 104A located above the photodiode S102, the X-ray R is converted into light at the light emitting point L inside the scintillator section 104A. The light emitted from the light emitting point L diffuses in all directions. In this radiographic imaging device 100, since the partition wall 105 and the reflective film 106 exist, it is possible to prevent light as indicated by reference numerals F1 and F2 from leaking to the adjacent pixel side. Therefore, as shown in FIG. 5, the detection intensities A3 and A4 as shown in the detection coordinates corresponding to the photodiode S101 and the photodiode S103 are not detected.

  However, when the number of reflections is increased by repeating the reflection at the partition wall 105 or the reflection film 106, there arises a problem that the optical path length of the diffused light becomes longer and the light is attenuated. In particular, as shown in FIG. 5, since the scintillator portion 104A is sandwiched between partition walls 105 that are parallel to each other, the number of reflections of light increases. Therefore, as shown in FIG. 5, the detection intensity A1 of the light (converted light) actually incident on the photodiode S102 immediately below the light emitting point L is higher than the detection intensity A2 assumed when the diffused light is collected. Significantly smaller. For this reason, the detection intensity in the photodiode S102 is lowered, and characteristics such as the contrast, resolution, and detection resolution of the captured image are deteriorated. If the irradiation output of the X-ray generation source is increased in order to increase the detection intensity, there arises a problem that the exposure dose during imaging increases.

  The present invention has been made in view of the above-described problems, and improves the characteristics of a captured image, such as contrast, resolution, and detection resolution, and enables a radiation image to reduce the radiation exposure dose during imaging. An object is to provide a photographing apparatus.

  In order to solve the above-described problems and achieve the object, an aspect of the radiographic imaging apparatus according to the present invention includes a substrate, a plurality of photosensor units disposed on the substrate, and each photosensor unit. A plurality of scintillator portions arranged so as to face each other, and the scintillator portion is surrounded by a reflecting surface having a light collecting property to reflect light toward the optical sensor portion. Features.

  As said aspect, it is preferable that a reflective surface is an inner surface of the reflecting film formed so that the surface other than the surface which opposes the optical sensor part in a scintillator part may be covered.

  As said aspect, it is preferable that the cross-sectional shape cut | disconnected in the direction orthogonal to the said board | substrate of a scintillator part is either a convex lens shape, a hemispherical shape, a semi-ellipsoid shape, a semi-polygon shape, and the shape containing these shapes. .

  As said aspect, it is preferable that the said reflective surface does not have a pair of planes mutually parallel.

  As said aspect, it is preferable that the scintillator part is arrange | positioned in the recessed part formed in the reflecting film.

  As the above aspect, the reflection surface is an interface between the scintillator portion and the material film formed so as to cover the scintillator portion other than the surface facing the optical sensor portion, and the light refractive index of the material film is that of the scintillator portion. It is good also as a structure smaller than the optical refractive index of a constituent material.

  According to the radiographic image capturing apparatus of the present invention, it is possible to improve characteristics such as contrast, resolution, and detection resolution of a captured image, and to reduce the radiation exposure dose during imaging.

FIG. 1 is an explanatory cross-sectional view of a main part of a radiographic image capturing apparatus according to a first embodiment of the present invention. FIG. 2 is an enlarged cross-sectional view of a main part of the radiographic image capturing apparatus according to the first embodiment of the present invention. FIG. 3 is an explanatory cross-sectional view of a main part of a radiographic image capturing apparatus according to the second embodiment of the present invention. FIG. 4-1 is a cross-sectional view illustrating Modification Example 1 of the scintillator unit of the radiographic image capturing apparatus according to the first embodiment of the present invention. FIG. 4-2 is a cross-sectional view illustrating Modification Example 2 of the scintillator unit of the radiographic image capturing apparatus according to the first embodiment of the present invention. 4-3 is sectional drawing which shows the modification 3 of the scintillator part of the radiographic imaging apparatus which concerns on the 1st Embodiment of this invention. FIG. 5 is an explanatory cross-sectional view showing a conventional radiographic image capturing apparatus.

  Below, the detail of the radiographic imaging apparatus which concerns on embodiment of this invention is demonstrated based on drawing. However, it should be noted that the drawings are schematic, and the dimensions, ratios and shapes of the members are different from actual ones. In addition, the drawings include portions having different dimensional relationships, ratios, and shapes.

[First Embodiment]
Hereinafter, the configuration of the radiographic image capturing apparatus 1 according to the present embodiment will be described with reference to FIGS. 1 and 2. As shown in FIG. 1, the radiographic image capturing apparatus 1 includes a glass substrate 2 as a substrate, a TFT circuit unit 3 formed on the surface of the glass substrate 2, and an optical sensor formed on the TFT circuit unit 3. An array 4 and a scintillator array 5 formed on the photosensor array 4 are provided.

(TFT circuit part)
As shown in FIG. 2, the TFT circuit unit 3 includes a TFT 31 as a switching element for each pixel. That is, these TFTs 31 are arranged in a matrix on the surface of the glass substrate 2. In addition, the TFT circuit section 3 includes a charge storage capacitor, a gate line, a data line, and the like (not shown).

  The TFT 31 includes a gate electrode 32 formed on the surface of the glass substrate 2, a gate insulating film 33 covering the gate electrode 32 and the surface of the glass substrate 2, a semiconductor layer 34 formed to face the gate electrode 32, A source electrode 35 disposed so as to be joined to one side of the semiconductor layer 34 across the gate electrode 32; and a drain electrode 36 disposed so as to be joined to the other side of the semiconductor layer 34 across the gate electrode 32. . An interlayer insulating film 37 is formed on the TFT 31 and the gate insulating film 33.

(Optical sensor array)
The optical sensor array 4 includes a large number of optical sensor units 4A. As shown in FIG. 2, the optical sensor array 4 includes a large number of pixel electrodes 41 patterned for each pixel region on the interlayer insulating film 37, and the entire imaging region on the pixel electrodes 41 and the interlayer insulating film 37. The photoelectric conversion layer 42 formed over the transparent electrode 43 formed on the photoelectric conversion layer 42 is provided.

  In the present embodiment, the pixel electrode 41 is formed of a conductive material such as metal. The transparent electrode 43 is formed over the entire imaging region as a common electrode of the photosensor array 4. As shown in FIGS. 1 and 2, the optical sensor unit 4 </ b> A includes a pixel electrode 41, a photoelectric conversion layer 42, and a transparent electrode 43 in a region facing the pixel electrode 41. Each pixel electrode 41 is connected to the drain electrode 36 of the TFT 31 formed in the corresponding pixel region via the extraction electrode 38 embedded in the contact hole formed in the interlayer insulating film 37.

(Scintillator array)
As shown in FIG. 1, the scintillator array 5 includes a large number of scintillator units 51 arranged corresponding to the optical sensor units 4A. As shown in FIG. 2, the scintillator array 5 is formed on the transparent electrode 43. The scintillator unit 51 in the radiographic image capturing apparatus 1 according to the present embodiment has a semi-ellipsoidal shape in which an ellipsoid is cut in half so as to be perpendicular to the major axis in the vicinity of the center of the major axis. That is, the shape cut by the plane including the major axis of the scintillator portion 51 is a semi-elliptical shape. As shown in FIG. 2, the scintillator portion 51 includes a bottom surface portion 51A that is a surface that is in close contact with the transparent electrode 43, and a curved surface portion 51B that spreads from the top of the scintillator portion 51 toward the periphery of the bottom surface portion 51A. .

In the present embodiment, the scintillator material constituting the scintillator array 5 can be selected from CsI: Tl, Gd ₂ O ₂ S: Tb, LaBr ₃ : Ce, and the like.

  As shown in FIGS. 1 and 2, the scintillator array 5 includes a reflective film 52. The reflective film 52 includes a reflective layer 53 and a condensing shape layer 54. The reflective layer 53 is formed so as to be in close contact with and cover the surface of the scintillator portion 51. As a material constituting the reflective layer 53, Al, Ag, Ni, Au, or the like can be selected. The reflective layer 53 covers the surface of the scintillator 51 in a state of being in close contact with the surface. The condensing shape layer 54 is formed on the scintillator portion 5 </ b> A on which the reflective layer 53 is formed and the optical sensor array 4. The condensing shape layer 54 can be formed of, for example, a synthetic resin. The reflection surface of the reflection film 52 of the radiographic imaging apparatus 1 according to the present embodiment, that is, the inner side surface 53A of the reflection layer 53 does not have a pair of planes parallel to each other. The inner side surface 53A of the reflective layer 53 that covers the scintillator unit 51 has a light condensing property that directs the light diffused in the scintillator unit 51 to the optical sensor unit 4A.

(Operation and effect of the first embodiment)
Next, the operation and effect of the radiation image capturing apparatus 1 will be described. FIG. 1 shows a case where X-rays R are incident on the scintillator unit 51 located above the optical sensor unit 4A (S2) in the radiographic imaging apparatus 1. The X-ray R passes through the reflective film 52 and enters the scintillator unit 51. This X-ray R is converted into light at a light emitting point L located at the upper part of the scintillator unit 51. The light emitted from the light emitting point L diffuses in all directions.

  In FIG. 1, the light directing from the light emitting point L to the optical sensor unit 4A is F12, the light going to the optical sensor units 4A (S1), 4A (S3) on both sides is F11, F14, and the light going above the light emitting point L is shown. This is indicated by F13. Here, the light F11, F13, and F14 traveling toward the pixel region adjacent to the optical sensor unit 4A (S2) immediately below the light emitting point L is reflected by the inner side surface 53A of the reflective layer 53 and is irradiated with the light F15, F16, and F19. To the optical sensor unit 4A (S2). That is, these lights F11, F13, and F14 reach the optical sensor unit 4A (S2) through a single reflection.

  As described above, since the inner side surface 53A is a curved surface that spreads from the upper part toward the lower part (on the optical sensor unit side), the light incident on the inner side surface 53A does not repeat reflection and goes to the lower optical sensor unit 4A. Directed. For this reason, the optical path length until the light diffused from the light emitting point L reaches the optical sensor unit 4A is shortened. For this reason, attenuation of light diffusing from the light emitting point L is suppressed.

  In the radiographic imaging device 1, the light is reflected by the inner side surface 53A, so that it is possible to prevent the light F11, F13, F14 and the like diffusing toward the adjacent pixels from leaking to the adjacent pixel region. For this reason, in this radiographic imaging device 1, generation | occurrence | production of crosstalk can be suppressed and the fall of characteristics, such as the contrast of a captured image, resolution, and detection resolution, can be prevented.

  In this radiographic imaging device 1, the light diffused in the scintillator unit 51 can reach the optical sensor unit 4A (S2) with a small number of reflections. Therefore, the radiation image capturing apparatus 1 can suppress attenuation of diffused light. As shown in FIG. 1, in the optical sensor unit 4A (S2), high detection intensity can be secured by suppressing the occurrence of the crosstalk and suppressing the attenuation of the diffused light. A detection intensity B4 shown in FIG. 1 indicates a calculated detection intensity obtained by adding light leaking to an adjacent pixel region in a state where the diffused light is not attenuated. In this radiographic imaging device 1, a detection intensity B5 that approximates the detection intensity B4 is detected. In the radiographic imaging device 1, it is not necessary to increase the dose of X-ray R at the time of imaging due to the effect of suppressing crosstalk and the effect of suppressing attenuation of diffused light, and an increase in exposure dose can be suppressed. .

[Second Embodiment]
Next, a radiographic imaging device 60 according to the second exemplary embodiment of the present invention will be described using FIG. This radiographic imaging device 60 is a configuration example in which X-rays R are incident from the back surface (upper surface in FIG. 3) side of the glass substrate 61.

  As shown in FIG. 3, the radiographic image capturing device 60 includes a glass substrate 61, a TFT circuit unit 62 formed on the surface of the glass substrate 61, a photosensor array 63, and a scintillator array 65. . The optical sensor array 63 includes a large number of optical sensor units 63A. The scintillator array 65 includes a large number of scintillator portions 66 disposed so as to respectively correspond to the optical sensor portions 63 </ b> A, and a reflective film 67 that covers the large number of scintillator portions 66. The reflective film 67 has an inner side surface 67 </ b> A that closely contacts the scintillator portion 66.

  In the radiation image capturing apparatus 60, the X-ray R passes through the TFT circuit unit 62 and enters the scintillator unit 66. The scintillator unit 66 of the radiographic image capturing apparatus 60 according to the present embodiment has the same shape as the scintillator unit 51 in the radiographic image capturing apparatus 1 according to the first embodiment described above.

(Operation and effect of the second embodiment)
The X-ray R passes through the TFT circuit unit 62 and the optical sensor unit 63A, enters the scintillator unit 66, and is converted into light. The light converted by each scintillator section 66 of the scintillator array 65 is reflected by the inner surface 67A of the reflective film 67 and enters the photosensor array 63 side, so that the light collecting function is high and the optical path length can be shortened. . For this reason, the contrast of the captured image can be improved. The other actions and effects of the radiographic image capturing apparatus 60 according to the present embodiment are the same as those of the radiographic image capturing apparatus 1 according to the first embodiment.

[Other embodiments]
Although the first and second embodiments have been described above, it should not be understood that the description and the drawings, which form part of the disclosure of these embodiments, limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

  For example, as the scintillators 51 and 66 in the radiographic imaging apparatuses 1 and 60 according to the first and second embodiments described above, those having a semi-ellipsoidal shape are used, but the modification shown in FIG. As shown in FIG. The scintillator portion 55 includes a bottom surface portion 55A and a curved surface portion 55B, and the light diffused in the scintillator portion 55 by the reflection layer 52 (not shown) and the reflection film 67 that covers the curved surface portion 55B is collected on the optical sensor portion 4A side (not shown). Has the effect of light.

  FIG. 4B shows a scintillator unit 56 as a second modification of the scintillator units 51 and 66 in the radiation image capturing apparatuses 1 and 60 according to the first and second embodiments described above. The cross-sectional shape of the scintillator portion 56 is a semi-polygon shape. The scintillator portion 56 includes a bottom surface portion 56A and a plurality of flat surface portions 56B that form a peripheral surface of a polygonal column. The reflection layer 53 (not shown) and the reflection film 67 that cover the plurality of flat portions 56B in close contact with each other have a function of condensing the light diffused in the scintillator portion 56 toward the photosensor unit 4A (not shown).

  FIG. 4-3 shows a scintillator 57 as a third modification of the scintillators 51 and 66 in the radiographic imaging apparatuses 1 and 60 according to the first and second embodiments described above. The scintillator portion 57 includes a bottom surface portion 57A and three curved surface portions 57B, 57C, and 57D having a condensing function. The reflection layer 53 (not shown) and the reflection film 67 that cover these three curved surface portions 57B, 57C, 57D in close contact with each other have a function of condensing light diffused in the scintillator portion 57 to the optical sensor portion 4A (not shown).

  As the structure of the scintillator, in addition to this, a convex lens shape such as a biconvex lens, a plano-convex lens, and a convex meniscus lens, a hemispherical shape, a semi-polygonal shape, and a cylindrical lens-shaped structure are cut along a plane parallel to the axis. A shape or the like may be adopted.

  In the radiographic imaging apparatuses 1 and 60 according to the first and second embodiments described above, the scintillator sections 51 and 66 are configured to be covered with the reflective films 52 and 67 such as metal, but such reflection is performed. Instead of the layer 53 and the reflective film 67, the scintillator portions 51, 66 are covered and covered with a material film (not shown) having a light refractive index smaller than that of the constituent materials of the scintillator portions 51, 66. Also good. In this case, when X-rays are converted into light and diffused in the scintillator units 51 and 66, light is reflected in the scintillator units 51 and 66 at the interface between the scintillator units 51 and 66 and the optical sensor unit. Can be reflected to the side.

  In the radiographic imaging apparatuses 1 and 60 according to the first and second embodiments described above, the optical sensor arrays 4 and 63 are configured using photodiodes, but various types of light such as a CCD sensor and a CMOS sensor are used. A detection element may be applied.

1,60 Radiation imaging device 2,6 Glass substrate (substrate)
3,62 TFT circuit portion 4,64 Photo sensor array 4A, 63A Photo sensor portion 5,65 Scintillator array 51, 55, 56, 57, 66 Scintillator portion 52, 67 Reflective film 53 Reflective layer 54 Condensing shape layer 53A, 67A Inner surface

Claims (6)

A substrate,
A plurality of optical sensor units disposed on the substrate;
A plurality of scintillator units arranged to face each of the photosensor units one by one;
With
The scintillator section is surrounded by a reflecting surface having a light collecting property for reflecting light toward the optical sensor section. The radiographic image capturing apparatus according to claim 1, wherein the reflection surface is an inner surface of a reflection film formed so as to cover a surface of the scintillator unit other than the surface facing the optical sensor unit. The cross-sectional shape of the scintillator section cut in a direction perpendicular to the substrate is any one of a convex lens shape, a hemispherical shape, a semi-ellipsoidal shape, a semi-polygonal shape, and a shape including these shapes. The radiographic imaging apparatus of Claim 1 or Claim 2. The radiographic imaging apparatus according to claim 1, wherein the reflection surface does not have a pair of planes parallel to each other. The radiographic imaging apparatus according to any one of claims 2 to 4, wherein the scintillator section is disposed in a recess formed in the reflective film. The reflective surface is an interface between the scintillator portion and a material film formed so as to cover other than the surface of the scintillator portion facing the optical sensor portion,
The radiographic imaging apparatus according to claim 1, wherein a light refractive index of the material film is smaller than a light refractive index of a constituent material of the scintillator portion.

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