X-ray imaging device and method for controlling the same

Abstract

Provided are an X-ray imaging device and a control method for the X-ray imaging device, which can improve the image quality for each pixel without providing a high-output X-ray source. The X-ray imaging device (100) comprises an X-ray source (4), an X-ray imaging panel (10), and a control unit (3). The control unit (3) comprises: an image processing unit that supplies a gate signal to a TFT and generates an inspection camera image based on a data signal read from the TFT; a detection control unit that detects black dot pixels from the inspection camera image; and a threshold correction unit that applies a forward shift voltage to the gate of the TFT corresponding to the black dot pixel so as to increase the gate cutoff threshold voltage of the TFT.

Description

Technical Field

[0001] The present disclosure relates to an X-ray imaging device and a control method of the X-ray imaging device. Background Art

[0002] Conventionally, an X-ray imaging device including a thin film transistor and a control method of the X-ray imaging device are known. Such an X-ray imaging device and a control method of the X-ray imaging device are disclosed in Patent Document 1, for example.

[0003] In the X-ray imaging device (solid-state X-ray detector) of the above-mentioned patent document 1, a portion of the X-ray detector is covered with a radiation shielding material. Furthermore, radiation (X-rays) of a level sufficient to reach a predetermined threshold value is irradiated to the exposed portion of the X-ray detector. The solid-state X-ray detector acquires a radiation image and determines whether there are line artifacts. The data lines determined to have line artifacts are saved to the image processor. Furthermore, the pixel values ​​of the pixels connected to the data lines determined to exhibit line artifacts are replaced with the average value of the pixel values ​​of the two data lines adjacent to the data lines. As a result, the pixel values ​​of the plurality of pixels connected to the data lines having large leakage signals of the thin-film transistors of the X-ray detector and including pixels that are prone to produce line artifacts are corrected.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application No. 2004-521721 Summary of the invention

[0007] Problem that the invention aims to solve

[0008] In the X-ray imaging device of Patent Document 1, in order to generate line artifacts, it is necessary to provide an X-ray source (a high-output X-ray source) that can irradiate stronger X-rays than the X-ray source used for ordinary X-ray imaging. In addition, in the X-ray imaging device of Patent Document 1, the pixel values ​​of all pixels connected to the data line determined to exhibit line artifacts are replaced with the average value of the pixel values ​​of the pixels connected to the two data lines adjacent to the data line. Therefore, the X-ray imaging device of Patent Document 1 has the following problem: the pixel values ​​of pixels that do not need to be corrected are also replaced (corrected).

[0009] Therefore, the present disclosure is made to solve the above-mentioned problems, and its object is to provide an X-ray imaging device and a control method of the X-ray imaging device, which can improve the image quality for each pixel without providing a high-output X-ray source.

[0010] Solutions for solving problems

[0011] In order to solve the above-mentioned problems, the first aspect of the present disclosure is an X-ray imaging device, comprising: an X-ray source; an X-ray imaging panel, which includes a scintillator that converts X-rays irradiated from the above-mentioned X-ray source into light, a photoelectric conversion element that converts light from the scintillator into an electrical signal, and a thin film transistor connected to the photoelectric conversion element; and a control unit, which controls the irradiation of X-rays by the above-mentioned X-ray source and the imaging by the above-mentioned X-ray imaging panel, and the above-mentioned control unit includes: an image processing unit, which supplies a gate signal to the above-mentioned thin film transistor, and generates an inspection imaging image based on a data signal read from the above-mentioned thin film transistor, wherein the inspection imaging image is an imaging image obtained by imaging in a state where no subject is arranged between the above-mentioned X-ray source and the above-mentioned X-ray imaging panel; a detection control unit, which detects black dot pixels from the above-mentioned inspection imaging image; and a threshold correction unit, which applies a forward shift voltage to the gate of the thin film transistor corresponding to the above-mentioned black dot pixel to increase the gate cut-off threshold voltage of the thin film transistor.

[0012] In addition, the second aspect is a control method for an X-ray imaging device, the X-ray imaging device comprising: an X-ray source; and an X-ray imaging panel, which includes a scintillator that converts X-rays irradiated from the above-mentioned X-ray source into light, a photoelectric conversion element that converts light from the scintillator into an electrical signal, and a thin film transistor connected to the photoelectric conversion element, the control method for the X-ray imaging device comprising: a step of irradiating the above-mentioned X-ray imaging panel with X-rays from the above-mentioned X-ray source; a step of supplying a gate signal to the above-mentioned thin film transistor, and obtaining an inspection camera image based on a data signal read from the above-mentioned thin film transistor, the inspection camera image being an image obtained by imaging in a state where no subject is arranged between the above-mentioned X-ray source and the above-mentioned X-ray imaging panel; a step of detecting black dot pixels from the above-mentioned inspection camera image; and a step of applying a forward shift voltage to the gate of the thin film transistor corresponding to the above-mentioned black dot pixel so as to increase the gate cut-off threshold voltage of the thin film transistor.

[0013] Effects of the Invention

[0014] According to the X-ray imaging device and control method thereof constructed as described above, since black dot pixels are detected instead of line artifacts (bright spots), thin film transistors that are prone to leakage current can be detected without providing a high-output X-ray source. Furthermore, thin film transistors whose gate cut-off threshold voltage has shifted negatively can be detected for each pixel by detecting black dot pixels. Furthermore, a positive shift voltage can be applied to the thin film transistor that has shifted negatively to increase the gate cut-off threshold voltage of the thin film transistor, thereby improving the image quality for each pixel. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram showing the X-ray imaging device in the first embodiment.

[0016] Figure 2 Schematic diagram showing a schematic structure of a photoelectric conversion panel.

[0017] Figure 3 It is the functional block diagram of the control circuit.

[0018] Figure 4 It is a diagram for explaining changes in TFT characteristics.

[0019] Figure 5 It is a diagram for explaining the gate-off voltage in the threshold correction mode.

[0020] Figure 6 FIG. 1 is a diagram showing an example of an inspection captured image.

[0021] Figure 7 : is a figure which shows the example of the coordinate information of the black dot pixel.

[0022] Figure 8 It is a diagram for explaining application of a forward shift voltage.

[0023] Fig. 9 It is a diagram for explaining the positive shift of the gate-off threshold voltage of a TFT.

[0024] Fig.10 : is a flowchart showing the control process of the X-ray imaging device.

[0025] Fig.11 This is a block diagram of an X-ray imaging device in the second embodiment.

[0026] Fig.12 This is a diagram for explaining the detection of black dot pixels in the second embodiment.

[0027] Fig.13 This is a diagram for explaining coordinate information of black dot pixels according to the second embodiment.

[0028] Fig.14 This is a diagram for explaining the forward shift of the TFT according to the second embodiment.

[0029] Fig.15 This is a block diagram of an X-ray imaging device in the third embodiment.

[0030] Fig.16A 2 is a diagram showing an example of the inspection image R1 generated using the inspection voltage value Vb1.

[0031] Fig. 16B2 is a diagram showing an example of the inspection image R2 generated using the inspection voltage value Vb2.

[0032] Fig.17 This is a diagram for explaining coordinate information of black dot pixels according to the third embodiment.

[0033] Fig.18 This is a diagram for explaining the forward shift of the TFT according to the third embodiment.

[0034] Fig.19 This is a flowchart showing the control process of the X-ray imaging device according to the third embodiment.

[0035] Description of Reference Numerals

[0036] 1…photoelectric conversion panel, 2…scintillator, 3, 203, 303…control unit, 4…X-ray source, 5…storage unit, 10…X-ray imaging panel, 13…photodiode, 33, 233, 333…control circuit, 33b…image processing unit, 33c…detection control unit, 33d…threshold correction unit, 51, 251, 351…coordinate information, 100, 200, 300…X-ray imaging device. DETAILED DESCRIPTION

[0037] Hereinafter, embodiments of the present disclosure will be described based on the accompanying drawings. In addition, the present disclosure is not limited to the following embodiments, and design changes can be appropriately made within the scope of the configuration of the present disclosure. In addition, in the following description, for parts having the same parts or the same functions, the same figure marks are used in common between different drawings, and their repeated descriptions are omitted. In addition, the various structures described in the embodiments and modifications can be appropriately combined or changed within the scope of the main purpose of the present disclosure. In addition, in order to make the description easy to understand, in the drawings referred to below, the structures are simplified or schematically shown, or a part of the components are omitted. In addition, the size ratios between the components shown in the various figures do not necessarily show the actual size ratios.

[0038] [Configuration of the First Embodiment]

[0039] Figure 1 Schematic diagram showing an X-ray imaging device 100 in the first embodiment. The X-ray imaging device 100 includes an X-ray imaging panel 10 including a photoelectric conversion panel 1 and a scintillator 2 , a control unit 3 , an X-ray source 4 , a storage unit 5 , and an operation unit 6 .

[0040] The control unit 3 includes a gate drive circuit 31, a signal readout circuit 32, and a control circuit 33. The gate drive circuit 31 and the signal readout circuit 32 are connected to the photoelectric conversion panel 1. In addition, the control circuit 33 is connected to the gate drive circuit 31, the signal readout circuit 32, and the X-ray source 4. The control circuit 33 includes a processor that executes a program stored in the storage unit 5. In addition, the control circuit 33 controls the irradiation of X-rays by the X-ray source 4 and the imaging by the X-ray imaging panel 10.

[0041] The X-ray source 4 irradiates the subject S with X-rays. The X-rays transmitted through the subject S are converted into fluorescence (hereinafter referred to as scintillation light) in the scintillator 2 disposed on the upper portion of the photoelectric conversion panel 1. The X-ray imaging device 100 images the scintillation light in the X-ray imaging panel 10, and the control unit 3 generates an X-ray imaging image.

[0042] The storage unit 5 includes, for example, a nonvolatile memory. The storage unit 5 stores programs executed by the control circuit 33 and black dot pixels B (see Figure 6 ) coordinate information 51. Regarding the black dot pixel B, refer to Figure 6 Regarding the coordinate information 51, see Figure 7 This will be described later.

[0043] The operation unit 6 includes, for example, a touch panel for accepting user operations or an operation panel provided with a plurality of operation buttons. The operation unit 6 accepts user operations for selecting either the "normal imaging mode" or the "threshold value correction mode".

[0044] Here, the “normal imaging mode” refers to a mode in which an X-ray is irradiated from the X-ray source 4 to the X-ray imaging panel 10 to generate an X-ray imaging image in a state in which a subject S is arranged between the X-ray source 4 and the X-ray imaging panel 10. The “threshold correction mode” refers to a mode in which the following series of control processes are performed: without arranging the subject S between the X-ray source 4 and the X-ray imaging panel 10, the X-ray is irradiated from the X-ray source 4 to the X-ray imaging panel 10 to generate an X-ray imaging image (inspection imaging image R), a black dot pixel B is detected, and a forward shift voltage Vh is applied to the gate of the TFT 14 corresponding to the black dot pixel B, thereby shifting (increasing) the gate cut-off threshold voltage Vth of the TFT 14 in the forward direction.

[0045] Figure 21 is a schematic diagram showing the general structure of the photoelectric conversion panel 1. The photoelectric conversion panel 1 is provided with a plurality of data lines 11 and a plurality of gate lines 12. In the area surrounded by the data lines 11 and the gate lines 12, a photodiode 13 and a thin film transistor (TFT: Thin Film Transistor) 14 are provided. This area corresponds to one pixel which is the minimum unit of an image constituting an X-ray camera image (inspection camera image R). In addition, a plurality of photodiodes 13 and a plurality of TFTs 14 are arranged in a matrix. The photodiode 13 converts the scintillation light obtained by converting the X-rays transmitted through the subject S into a charge corresponding to the amount of light. The gate lines 12 in the photoelectric conversion panel 1 are sequentially switched to a selected state by supplying a gate signal from the gate drive circuit 31, and the TFTs 14 connected to the gate lines 12 in the selected state become conductive. When the TFTs 14 become conductive, a signal corresponding to the charge converted in the photodiode 13 is output as a data signal to the signal readout circuit 32 via the data lines 11. The TFT 14 includes a semiconductor layer made of, for example, an oxide semiconductor containing indium (In), gallium (Ga), and zinc (Zn) at a predetermined ratio.

[0046] Figure 3 33 is a functional block diagram of the control circuit 33. Figure 3 As shown, the control circuit 33 functions as an irradiation control unit 33a, an image processing unit 33b, a detection control unit 33c, and a threshold correction unit 33d by executing the program stored in the storage unit 5. Figure 3 In the figure, the irradiation control unit 33a, the image processing unit 33b, the detection control unit 33c and the threshold correction unit 33d are shown as functional modules, but the control circuit can also be constructed according to each function of the image processing unit 33b, the detection control unit 33c and the threshold correction unit 33d.

[0047] The irradiation control unit 33a irradiates X-rays from the X-ray source 4 to the X-ray imaging panel 10 in the normal imaging mode when the subject S is disposed between the X-ray imaging panel 10 and the X-ray source 4. In the first embodiment, the irradiation control unit 33a irradiates X-rays from the X-ray source 4 to the X-ray imaging panel 10 in the threshold correction mode when the subject S is not disposed between the X-ray imaging panel 10 and the X-ray source 4.

[0048] The image processing unit 33b controls the gate driving circuit 31 to supply a gate signal to the TFT 14, and generates an X-ray image based on the data signal read from the TFT 14 by the signal reading circuit 32. Specifically, the image processing unit 33b sets a pixel value corresponding to the voltage value of the data signal for each pixel.

[0049] Figure 4It is a diagram for explaining the change in characteristics of TFT 14 . Figure 4 The dotted line is a curve showing the characteristics of a brand new TFT 14 that has not been irradiated with X-rays. Figure 4 The solid line is a curve showing the characteristics of the used TFT14 which has been repeatedly irradiated with X-rays. Figure 4 As shown, when TFT14 is repeatedly irradiated with X-rays, the threshold of the gate cut-off voltage is reduced (negatively shifted) from Vth1 to Vth2, for example. Therefore, when the gate cut-off threshold voltage Vth is lower than the gate cut-off voltage Va of the gate signal supplied from the gate drive circuit 31, TFT14 does not become a cut-off state (becomes a conductive state), but generates leakage current (the charge of the photodiode 13 escapes). As a result, in the X-ray image generated by the image processing unit 33b, even the pixels corresponding to the positions irradiated with X-rays are set to low pixel values ​​and become black dot pixels (black dot pixels B).

[0050] The X-ray imaging device 100 of this embodiment has a threshold correction mode in which a negative shift trend of the gate-off threshold voltage Vth is detected and the gate-off threshold voltage Vth is corrected for the TFT 14 having a negative shift in the gate-off threshold voltage Vth. Figure 5 1 is a diagram for explaining the gate cut-off voltage in the threshold correction mode. In the first embodiment, in the threshold correction mode, in order to detect the TFT 14 whose gate cut-off threshold voltage Vth is negatively shifted, a gate signal having a check voltage value Vb is supplied to the TFT 14 in a state where no subject S is arranged between the X-ray imaging panel 10 and the X-ray source 4. The check voltage value Vb is a gate cut-off voltage higher than the gate cut-off voltage Va supplied in the normal imaging mode. Here, among the TFTs 14 of the X-ray imaging panel 10, the TFTs 14 whose gate cut-off threshold voltage Vth is negatively shifted to a value lower than the check voltage value Vb are not turned off, but turned on. Thus, the TFTs 14 whose gate cut-off threshold voltage Vth is in a negative shifting trend can be detected as black dot pixels B. That is, in the threshold correction mode, black dot pixels B that do not appear at the gate cut-off voltage Va in the normal imaging mode can be detected.

[0051] Figure 6 is a diagram showing an example of an inspection camera image R. Figure 6 As shown, the image processing unit 33b generates an X-ray image for detecting black dot pixels B, that is, a test image R, based on the data signal read from the TFT 14. For example, the pixel corresponding to the TFT 14 in the negative shift trend is included in the test image R as a black dot pixel B.

[0052] Then, the detection control unit 33c detects black dot pixels B from the inspection camera image R. Specifically, the detection control unit 33c obtains the average value A of the pixel values ​​from all the pixels of the inspection camera image R, and detects the black dot pixels B based on the average value A. The detection method of the black dot pixels B based on the average value A is arbitrary, for example, a pixel having a pixel value that is smaller than the average value A by a predetermined ratio or more (for example, a pixel value that is smaller by 10% or more) is detected as a black dot pixel B. Alternatively, the detection control unit 33c may detect a pixel having a pixel value that is smaller than the average value A by a predetermined standard deviation of the average value A (for example, a pixel value that is smaller by 3σ or more) as a black dot pixel B. In addition, "σ" means standard deviation. The above two detection methods of the black dot pixels B performed by the detection control unit 33c, the size of the predetermined ratio, and the size of the predetermined standard deviation can be set arbitrarily by the user through the operation unit 6, and can also be changed according to the model of the X-ray imaging device 100. According to the above configuration, the black dot pixels B can be easily detected by comparing the average value A with the pixel value of each pixel. In addition, although the average value A is calculated from all the pixels of the inspection image R here, the average value A may be calculated from a part of the pixels.

[0053] Figure 7 5 is a diagram showing an example of coordinate information 51 of a black dot pixel B. Figure 7 As shown in FIG. 1 , the detection control unit 33 c causes the storage unit 5 to store the coordinate information 51 of the detected black dot pixel B. For example, the coordinate information 51 includes a TFT 14 (in Figure 7 "542" etc.) and which data line 11 is the TFT 14 corresponding to (in Figure 7 In addition, the coordinate information 51 is not limited to Figure 7 For example, any information that can identify the coordinates of the black dot pixel B will suffice.

[0054] Figure 8 It is a diagram for explaining application of the forward shift voltage Vh. Fig. 9 1 is a diagram for explaining the positive shift of the gate-off threshold voltage Vth of TFT14a. Figure 8 In the example, the TFT corresponding to the black pixel B is TFT14a. In addition, the data line connected to TFT14a is set to data line 11a, and the gate line connected to TFT14a is set to gate line 12a. The threshold correction unit 33d applies a positive shift voltage Vh to the gate of TFT14a based on the coordinate information 51 of TFT14a, as shown in FIG. Fig. 9As shown, the gate cut-off threshold voltage of TFT14a is increased. The gate cut-off threshold voltage is increased, for example, until it reaches the design value of TFT14. That is, the voltage value of the forward shift voltage Vh is a voltage value that can increase the gate cut-off threshold voltage Vth to the design value of TFT14. Fig. 9 As shown, the characteristic of TFT14a changes from the state of the dotted curve to the state of the solid curve. The forward shift voltage Vh has a voltage value that can increase the gate cut-off threshold voltage Vth of TFT14. This voltage value is pre-set based on the material of TFT14, etc. The forward shift voltage Vh, for example, has a voltage value higher than the gate on voltage of TFT14a. At this time, the threshold correction unit 33d applies the forward shift voltage Vh to the gate line 12a connected to TFT14a, and applies the read voltage Vd to the data line 11a connected to TFT14a, so that a potential difference is generated between the gate and the source of TFT14a. The threshold correction unit 33d can apply the forward shift voltage Vh to TFT14a once, or repeatedly. In this way, the gate cut-off threshold voltage Vth of TFT14a corresponding to the black dot pixel B can be corrected. In the case where there are multiple black dot pixels B, it is sufficient to correct the gate cut-off threshold voltage Vth of each TFT14a based on the coordinate information 51 of each of the multiple TFTs14a corresponding to the multiple black dot pixels B.

[0055] According to the above configuration, since the black pixel B is detected instead of the line artifact (bright spot), the TFT 14a whose gate-off threshold voltage Vth is negatively shifted among the TFTs 14a that are prone to leakage current can be detected for each pixel without providing a high-power X-ray source. Furthermore, a positive shift voltage Vh can be applied to the TFT 14a that is negatively shifted to increase the gate-off threshold voltage Vth of the TFT 14a, so that the image quality can be improved for each pixel without providing a high-power X-ray source.

[0056] [Control method of the first embodiment]

[0057] Next, refer to Fig.10 A method of controlling the X-ray imaging device 100 according to the first embodiment will be described. Fig.10 2 is a flowchart showing the control process of the X-ray imaging device 100. The control process (threshold value correction mode) described below is executed by the control circuit 33. In addition, the description of the control process in the normal imaging mode is omitted.

[0058] In step S1, it is determined whether the "threshold value correction mode" is selected. If the "threshold value correction mode" is selected, the process proceeds to step S2. That is, the following steps S2 to S7 are control processes executed in the "threshold value correction mode".

[0059] In step S2, the gate-off voltage is set to the inspection voltage value Vb. Then, in step S3, the X-ray source 4 irradiates the X-ray imaging panel 10 with X-rays in a state where no subject S is arranged between the X-ray source 4 and the X-ray imaging panel 10. Then, in step S4, a gate signal including the gate-off voltage of the inspection voltage value Vb is supplied to each TFT 14 to obtain a data signal, and an inspection imaging image R (X-ray imaging image) is generated based on the data signal.

[0060] Then, in step S5 , black dot pixels B are detected from the inspection camera image R. For example, pixels that are smaller than the average value A of all pixels in the inspection camera image R by a predetermined ratio of the average value A or by a predetermined standard deviation of the average value A are detected as black dot pixels B. Then, in step S6 , coordinate information 51 of the detected black dot pixels B is stored in the storage unit 5 .

[0061] Then, in step S7, based on the coordinate information 51, the forward shift voltage Vh is applied to the gate line 12a connected to the TFT 14a corresponding to the black dot pixel B, and the read voltage Vd is applied to the data line 11a connected to the TFT 14a. Fig. 9 As shown, the gate cut-off threshold voltage Vth of TFT14a shifts positively (increases). After that, the control process of the X-ray imaging device 100 (control process in the threshold correction mode) ends. According to the above control method, the image quality can be improved for each pixel without providing a high-output X-ray source. In addition, through the operation of the threshold correction mode, it is possible to detect the TFT14 whose gate cut-off threshold voltage is in a negative shift trend and correct the gate cut-off threshold voltage. In this way, it is possible to prevent the adverse effects on the captured image caused by the negative shift of the gate cut-off threshold voltage associated with the repeated use of the X-ray imaging device 100.

[0062] [Second embodiment]

[0063] Reference Figure 11 to Figure 14 The configuration of the X-ray imaging device 200 according to the second embodiment will be described. Fig.11 This is a block diagram of an X-ray imaging device 200 according to the second embodiment. Fig.12 This is a diagram for explaining the detection of black dot pixels B1 and B2 in the second embodiment. Fig.13 It is a diagram for explaining the coordinate information 251 of the black dot pixels B1 and B2. Fig.14This is a diagram for explaining the positive shift of the TFT 14 in the second embodiment. In the second embodiment, the X-ray imaging device 200 detects black dot pixels B1 and B2 having different degrees of negative shift, and applies positive shift voltages Vh1 and Vh2 corresponding to the degrees of negative shift to the TFT 14. In addition, for the same configuration as the first embodiment, the same reference numerals as those in the first embodiment are used and the description thereof is omitted.

[0064] like Fig.11 As shown in FIG. 1 , the X-ray imaging device 200 includes a control unit 203 having a control circuit 233. In addition, the storage unit 5 stores coordinate information 251 (see FIG. 1 ) of the black dot pixels B1 and B2. Fig.13 ).like Fig.12 As shown, the control circuit 233 (detection control unit) of the second embodiment calculates the average value A1 of the pixel values ​​of at least two or more pixels (for example, all pixels) of the inspection camera image R. And the control circuit 233 detects a pixel having a pixel value that is smaller than the average value A1 by a first ratio (for example, 5%) or more and smaller than a second ratio (for example, 10%) as a black dot pixel B2. And the control circuit 233 detects a pixel having a pixel value that is smaller than the average value A1 by a second ratio (for example, 10%) or more as a black dot pixel B1. Alternatively, the control circuit 233 detects a pixel having a pixel value that is smaller than the average value A1 by a first standard deviation (2σ) or more and smaller than the second standard deviation (3σ) as a black dot pixel B2. And the control circuit 233 detects a pixel having a pixel value that is smaller than the average value A1 by a second standard deviation (3σ) or more as a black dot pixel B1. Thus, it is possible to detect the black dot pixel B1 having a relatively large degree of negative shift and the black dot pixel B2 having a smaller degree of negative shift than the black dot pixel B1.

[0065] like Fig.13 As shown in FIG. 2 , the control circuit 233 stores the coordinate information 251 of the detected black dot pixels B1 and B2 in the storage unit 5. Fig.14 As shown, the control circuit 233 applies a forward shift voltage Vh1 to the gate of the TFT 14 corresponding to the black dot pixel B1, and applies a forward shift voltage Vh2 lower than the forward shift voltage Vh1 to the gate of the TFT 14 corresponding to the black dot pixel B2. The gate cut-off threshold voltage Vth of the TFT 14 corresponding to the black dot pixel B1 is shifted forward, and the gate cut-off threshold voltage Vth of the TFT 14 corresponding to the black dot pixel B2 is shifted forward. In addition, other configurations and effects are the same as those of the first embodiment.

[0066] [Third Embodiment]

[0067] Reference Figure 15 to Figure 17 The configuration of the X-ray imaging device 300 according to the third embodiment will be described. Fig.15This is a block diagram of an X-ray imaging device 300 in the third embodiment. Fig.16A 2 is a diagram showing an example of an inspection image R1 generated using the inspection voltage value Vb1. Fig. 16B 2 is a diagram showing an example of the inspection image R2 generated using the inspection voltage value Vb2. Fig.17 It is a diagram for explaining the coordinate information 351 of the black dot pixels B11 and B12. Fig.18 This is a diagram for explaining the positive shift of TFT 14 in the third embodiment. In the third embodiment, the X-ray imaging device 300 generates the inspection imaging images R1 and R2 using two-level inspection voltage values ​​Vb1 and Vb2, and detects black dot pixels B11 and B12 with different degrees of negative shift. In addition, for the same configuration as that of the first or second embodiment, the same reference numerals as those of the first or second embodiment are used and the description is omitted.

[0068] like Fig.15 As shown in FIG. 1 , the X-ray imaging device 300 includes a control unit 303 having a control circuit 333. In addition, the storage unit 5 stores coordinate information 351 (see FIG. 1 ) of the black dot pixels B11 and B12. Fig.17 ).like Fig.16A As shown, the control circuit 333 (image processing unit) of the third embodiment generates the inspection image R1 based on the data signal acquired using the gate-off voltage having the inspection voltage value Vb1 higher than the voltage value Va when the subject S is imaged. Fig. 16B As shown, the control circuit 333 (image processing unit) generates the inspection image R2 based on the data signal acquired using the gate-off voltage having the inspection voltage value Vb2 which is equal to or higher than the voltage value Va and lower than the inspection voltage value Vb1.

[0069] The control circuit 333 (detection control unit) of the third embodiment detects the pixel detected as the black dot pixel B in both the inspection camera images R1 and R2 as the black dot pixel B11 with a large negative shift. Furthermore, the control circuit 333 (detection control unit) detects the pixel detected as the black dot pixel B only in the inspection camera image R1 as the black dot pixel B12 with a relatively small negative shift. Then, as Fig.17 As shown in FIG. 3 , the control circuit 333 stores the coordinate information 351 of the detected black dot pixels B11 and B12 in the storage unit 5. Then, as shown in FIG. Fig.18As shown, the control circuit 333 applies a forward shift voltage Vh11 to the gate of the TFT14 corresponding to the black dot pixel B11, and applies a forward shift voltage Vh12 lower than the forward shift voltage Vh11 to the gate of the TFT14 corresponding to the black dot pixel B12. The gate cut-off threshold voltage Vth of the TFT14 corresponding to the black dot pixel B11 is shifted forward, and the gate cut-off threshold voltage Vth of the TFT14 corresponding to the black dot pixel B12 is shifted forward. In addition, other configurations and effects are the same as those of the first embodiment.

[0070] [Control method of the third embodiment]

[0071] Next, refer to Fig.19 A method of controlling the X-ray imaging device 300 according to the third embodiment will be described. Fig.19 3 is a flowchart showing the control process of the X-ray imaging device 300. The control process described below is executed by the control circuit 333.

[0072] In step S1, it is determined whether the "threshold correction mode" is selected. If this operation is performed, the process proceeds to step S102. In step S102, the gate cut-off voltage is set to the inspection voltage value Vb1. Then, in step S103, the X-ray source 4 irradiates the X-ray imaging panel 10 with X-rays in a state where no subject S is arranged between the X-ray source 4 and the X-ray imaging panel 10. Then, in step S104, a gate signal including the gate cut-off voltage of the inspection voltage value Vb1 is supplied to each TFT 14 to obtain a data signal, and a check imaging image R1 is generated based on the data signal.

[0073] Then, in step S105, the gate-off voltage is set to the inspection voltage value Vb2. Then, in step S106, the X-ray source 4 irradiates the X-ray imaging panel 10 with X-rays in a state where no object S is arranged between the X-ray source 4 and the X-ray imaging panel 10. Then, in step S107, a gate signal including the gate-off voltage of the inspection voltage value Vb2 is supplied to each TFT 14 to obtain a data signal, and an inspection imaging image R2 is generated based on the data signal.

[0074] In step S108, black dot pixels B11 and B12 are detected from the inspection camera images R1 and R2. For example, a pixel detected as a black dot pixel in both the inspection camera images R1 and R2 is detected as a black dot pixel B11, and a pixel detected as a black dot pixel only in the inspection camera image R1 is detected as a black dot pixel B12. Then, in step S109, the coordinate information 351 of the detected black dot pixels B11 and B12 is stored in the storage unit 5.

[0075] Then, in step S110, based on the coordinate information 351, a forward shift voltage Vh21 is applied to the gate line 12 connected to the TFT 14 corresponding to the coordinates of the black dot pixel B11, and a read voltage Vd is applied to the data line 11 connected to the TFT 14. In addition, based on the coordinate information 351, a forward shift voltage Vh22 is applied to the gate line 12 connected to the TFT 14 corresponding to the coordinates of the black dot pixel B12, and a read voltage Vd is applied to the data line 11 connected to the TFT 14. Thus, as Fig.18 As shown, the gate-off threshold voltage Vth of the TFT 14 shifts (rises) in the positive direction. Thereafter, the control process of the X-ray imaging device 300 (the control process in the threshold correction mode) ends.

[0076] Although the embodiments have been described above, the above embodiments are merely examples for implementing the present disclosure. Therefore, the present disclosure is not limited to the above embodiments, and the above embodiments can be appropriately modified and implemented within the scope of the present disclosure.

[0077] (1) In the first to third embodiments described above, the threshold correction mode is executed in accordance with the user's operation of the operation unit, but the present disclosure is not limited thereto. The threshold correction mode may be executed independently of the user's operation of the operation unit.

[0078] (2) In the first to third embodiments described above, if Fig.10 As shown, an example of performing the detection of black dot pixels and the application of the forward shift voltage to the gate of the TFT in a continuous control process is shown, but the present disclosure is not limited to this. For example, the detection of black dot pixels and the application of the forward shift voltage to the gate of the TFT can also be performed at different times. For example, the forward shift voltage can also be applied to the gate of the TFT once after the detection of the black dot pixels B is performed multiple times.

[0079] (3) In the first to third embodiments described above, an example is shown in which the inspection voltage value is set to a voltage different from the gate cut-off voltage (normal gate cut-off voltage) when the object is imaged in order to generate the inspection camera image, but the present disclosure is not limited thereto. For example, the inspection voltage value may be set to the same voltage as the gate cut-off voltage (normal gate cut-off voltage) when the object is imaged in order to generate the inspection camera image.

[0080] (4) In the first to third embodiments, the average value of all pixels in the inspection image is calculated for detecting black dot pixels, but the present disclosure is not limited thereto. For example, the average value of a portion of pixels in the inspection image may be calculated for detecting black dot pixels.

[0081] (5) In the above-mentioned first to third embodiments, an example of calculating the average value of the pixels of the inspection camera image in order to detect black dot pixels is shown, but the present disclosure is not limited to this. For example, the median value or the mode value of the pixels of the inspection camera image may be calculated in order to detect black dot pixels. In this case, the method of detecting black dot pixels based on the median value or the mode value is arbitrary. For example, when the median value is calculated, a method of detecting pixels having pixel values ​​that are smaller than the median value by a specified ratio of the median value or more may be used as black dot pixels, or a method of detecting pixels having pixel values ​​that are smaller than the median value by a specified standard deviation of the median value may be used as black dot pixels. In addition, when the mode value is calculated, a method of detecting pixels having pixel values ​​that are smaller than the mode value by a specified ratio of the mode value or more may be used as black dot pixels, or a method of detecting pixels having pixel values ​​that are smaller than the mode value by a specified standard deviation of the mode value may be used as black dot pixels.

[0082] The above-mentioned X-ray imaging device and the control method thereof can also be described as follows.

[0083] The first configuration is an X-ray imaging device comprising: an X-ray source; an X-ray imaging panel, which includes a scintillator that converts X-rays irradiated from the X-ray source into light, a photoelectric conversion element that converts light from the scintillator into an electrical signal, and a thin film transistor connected to the photoelectric conversion element; and a control unit that controls the irradiation of X-rays by the X-ray source and the imaging by the X-ray imaging panel, the control unit including: an image processing unit that supplies a gate signal to the thin film transistor and generates an inspection imaging image based on a data signal read from the thin film transistor, the inspection imaging image being an imaging image obtained by imaging in a state where no subject is arranged between the X-ray source and the X-ray imaging panel; a detection control unit that detects black dot pixels from the inspection imaging image; and a threshold correction unit that applies a forward shift voltage to the gate of the thin film transistor corresponding to the black dot pixel so as to increase the gate cut-off threshold voltage of the thin film transistor (the first configuration).

[0084] According to the first configuration, since black dot pixels are detected instead of line artifacts (bright spots), thin film transistors that are prone to leakage current can be detected without providing a high-output X-ray source. Furthermore, thin film transistors whose gate cut-off threshold voltage has shifted negatively can be detected for each pixel by detecting black dot pixels. Furthermore, a positive shift voltage can be applied to the thin film transistor that has shifted negatively to increase the gate cut-off threshold voltage of the thin film transistor, thereby improving the image quality for each pixel.

[0085] In the first configuration, the image processing unit may be configured to supply a gate signal having an inspection voltage value to the thin film transistor, and generate an inspection video image based on a data signal read from the thin film transistor, wherein the inspection voltage value is a gate cutoff voltage higher than a gate cutoff voltage supplied to the thin film transistor when photographing the subject (second configuration).

[0086] According to the second configuration, black dot pixels that do not appear at the gate-off voltage when photographing a subject (normal photographing) can be detected, so the gate-off threshold voltage of the thin film transistor can be shifted forward before the black dots appear when photographing the subject. As a result, black dots do not appear when photographing the subject, so the image quality can be improved.

[0087] The first or second configuration may further include a storage unit, the detection control unit may be configured to cause the storage unit to store information on coordinates corresponding to black dot pixels, and the threshold correction unit may be configured to apply a forward shift voltage to the gate of the thin film transistor based on the coordinate information (third configuration).

[0088] According to the third configuration, the target thin film transistor to which the forward shift voltage is to be applied can be easily determined based on the coordinate information stored in the storage unit.

[0089] In any one of the first to third configurations, the detection control unit may be configured to detect as a black dot pixel a pixel that is smaller than a specified value or more than an average value, a median value, or a mode value of pixel values ​​of two or more pixels in a captured image (the fourth configuration).

[0090] According to the fourth configuration, black dot pixels can be easily detected by comparing any one of the average value, the median value, and the mode value with the pixel value of each pixel.

[0091] The fifth configuration is a control method for an X-ray imaging device, the X-ray imaging device comprising: an X-ray source; and an X-ray imaging panel, which includes a scintillator that converts X-rays irradiated from the X-ray source into light, a photoelectric conversion element that converts light from the scintillator into an electrical signal, and a thin film transistor connected to the photoelectric conversion element, the control method for the X-ray imaging device comprising: a step of irradiating the X-ray imaging panel with X-rays from the X-ray source; a step of supplying a gate signal to the thin film transistor and acquiring an inspection imaging image based on a data signal read from the thin film transistor, the inspection imaging image being an imaging image obtained by imaging without a subject being arranged between the X-ray source and the X-ray imaging panel; a step of detecting black dot pixels from the inspection imaging image; and a step of applying a forward shift voltage to the gate of the thin film transistor corresponding to the black dot pixel so as to increase the gate cut-off threshold voltage of the thin film transistor (the fifth configuration).

[0092] According to the fifth configuration, similarly to the first configuration, the image quality can be improved for each pixel without providing a high-output X-ray source.

Claims

1. An X-ray imaging device, characterized in that: have: X-ray source; An X-ray imaging panel including a scintillator for converting X-rays irradiated from the X-ray source into light, a photoelectric conversion element for converting the light from the scintillator into an electrical signal, and a thin film transistor connected to the photoelectric conversion element; a control unit that controls the irradiation of X-rays by the X-ray source and the imaging by the X-ray imaging panel; and A gate driving circuit applies a voltage to the gate of the thin film transistor. The control unit includes: an image processing unit that supplies a gate signal to the thin film transistor and generates an inspection camera image based on a data signal read from the thin film transistor, the inspection camera image being an image obtained by imaging in a state where no object is arranged between the X-ray source and the X-ray imaging panel; a detection control unit that detects black dot pixels from the inspection camera image; as well as The threshold correction unit applies a forward shift voltage from the gate driving circuit to the gate of the thin film transistor corresponding to the black dot pixel so as to increase the gate-off threshold voltage of the thin film transistor.

2. The X-ray imaging device according to claim 1, wherein: further comprising a signal readout circuit for applying a readout voltage to a source of the thin film transistor, The threshold correction unit applies the forward shift voltage to the gate of the thin film transistor corresponding to the black dot pixel from the gate driving circuit, and applies the readout voltage to the source of the thin film transistor corresponding to the black dot pixel from the signal readout circuit.

3. An X-ray imaging device, characterized in that: have: X-ray source; An X-ray imaging panel including a scintillator for converting X-rays irradiated from the X-ray source into light, a photoelectric conversion element for converting the light from the scintillator into an electrical signal, and a thin film transistor connected to the photoelectric conversion element; and a control unit that controls the irradiation of X-rays by the X-ray source and the imaging by the X-ray imaging panel, The control unit includes: an image processing unit that supplies a gate signal to the thin film transistor and generates an inspection camera image based on a data signal read from the thin film transistor, the inspection camera image being an image obtained by imaging in a state where no object is arranged between the X-ray source and the X-ray imaging panel; a detection control unit that detects black dot pixels from the inspection camera image; as well as A threshold correction unit applies a forward shift voltage to the gate of the thin film transistor corresponding to the above-mentioned black dot pixel so as to increase the gate cut-off threshold voltage of the thin film transistor. The above-mentioned image processing unit supplies a gate signal having an inspection voltage value to the above-mentioned thin film transistor, and generates the above-mentioned inspection video image based on the data signal read out from the above-mentioned thin film transistor. The inspection voltage value is a gate cut-off voltage higher than the gate cut-off voltage supplied to the above-mentioned thin film transistor when photographing the subject.

4. The X-ray imaging device according to claim 1 or 3, wherein: The device further comprises a storage unit. The detection control unit causes the storage unit to store information on coordinates corresponding to the black dot pixels. The threshold correction unit applies the forward shift voltage to the gate of the thin film transistor based on the information of the coordinates.

5. The X-ray imaging device according to claim 1 or 3, wherein: The detection control unit detects, as the black dot pixel, a pixel that is smaller than any one of an average value, a median value, or a mode value of pixel values ​​of two or more pixels in the captured image by a predetermined value or more.

6. A method for controlling an X-ray imaging device, the X-ray imaging device comprising: X-ray source; An X-ray imaging panel including a scintillator for converting X-rays irradiated from the X-ray source into light, a photoelectric conversion element for converting the light from the scintillator into an electrical signal, and a thin film transistor connected to the photoelectric conversion element; and A gate driving circuit applies a voltage to the gate of the thin film transistor. The control method of the X-ray imaging device is characterized by comprising: irradiating the X-ray imaging panel with X-rays from the X-ray source; A step of supplying a gate signal to the thin film transistor and acquiring an inspection camera image based on a data signal read out from the thin film transistor, wherein the inspection camera image is an image obtained by photographing in a state where no object is arranged between the X-ray source and the X-ray camera panel; A step of detecting black dot pixels from the inspection camera image; and The step of applying a forward shift voltage for increasing a gate-off threshold voltage of the thin film transistor to the gate of the thin film transistor corresponding to the black dot pixel from the gate drive circuit.

7. The control method of the X-ray imaging device according to claim 6, wherein: The X-ray imaging device further comprises a signal readout circuit for applying a readout voltage to a source of the thin film transistor. The step of applying the forward shift voltage is to apply the forward shift voltage to the gate of the thin film transistor corresponding to the black dot pixel from the gate drive circuit, and to apply the readout voltage to the source of the thin film transistor corresponding to the black dot pixel from the signal readout circuit.

8. A method for controlling an X-ray imaging device, the X-ray imaging device comprising: X-ray source; and The X-ray imaging panel includes a scintillator for converting X-rays irradiated from the X-ray source into light, a photoelectric conversion element for converting the light from the scintillator into an electrical signal, and a thin film transistor connected to the photoelectric conversion element. The control method of the X-ray imaging device is characterized by comprising: irradiating the X-ray imaging panel with X-rays from the X-ray source; A step of supplying a gate signal to the thin film transistor and acquiring an inspection camera image based on a data signal read out from the thin film transistor, wherein the inspection camera image is an image obtained by photographing in a state where no object is arranged between the X-ray source and the X-ray camera panel; A step of detecting black dot pixels from the inspection camera image; and The step of applying a forward shift voltage to the gate of the thin film transistor corresponding to the black dot pixel so as to increase the gate cut-off threshold voltage of the thin film transistor, The step of acquiring the inspection camera image includes supplying a gate signal having an inspection voltage value to the thin film transistor, and generating the inspection camera image based on a data signal read out from the thin film transistor, wherein the inspection voltage value is a gate cutoff voltage higher than a gate cutoff voltage supplied to the thin film transistor when photographing the subject.

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