X-ray image acquisition device, X-ray image acquisition system, and X-ray image acquisition method

Abstract

This X-ray image acquisition device is provided with: a pixel unit having M (M is an integer of 2 or more) pixel arrays each including N (N is an integer of 2 or more) pixel sections for detecting X-rays; a control unit that controls the detection of X-rays by the pixel units; and a processing unit that generates an X-ray image of the object on the basis of the detection results of the X-rays by the pixel units. And a control unit that controls the detection of the X-rays by the pixel units so that the X-rays are sequentially detected at predetermined detection intervals in each of the N pixel units of the M pixel arrays. When a value obtained by dividing the arrangement pitch of the N pixel parts by a reference speed corresponding to the moving speed of the object is defined as a basic value, the detection interval is a value obtained by dividing the basic value by a pixel offset value, which is an integer of 2-N (inclusive).

Description

Technical Field

[0001] One aspect of this disclosure relates to an X-ray image acquisition device, an X-ray image acquisition system, and an X-ray image acquisition method. Background Technology

[0002] Patent Document 1 describes a line scan sensor comprising two pixel arrays positioned at an angle offset from each other by half a pixel. By processing the data acquired by this sensor, high-resolution images can be generated.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: U.S. Patent Application Publication No. 2022 / 0005157 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] On the other hand, for purposes such as inspecting for foreign matter contamination of objects, objects transported along a predetermined direction are sometimes irradiated with X-rays. A line-scan sensor sequentially detects the X-rays passing through the object, and a two-dimensional image of the object is generated based on the detection results. The inventors have discovered that, in such cases, there is still room for improvement in terms of the degree of freedom in image acquisition and the high resolution of the acquired image when using only the aforementioned sensor.

[0008] Therefore, one aspect of the present disclosure is to provide an X-ray image acquisition device, X-ray image acquisition system, and X-ray image acquisition method that can improve the degree of freedom in image acquisition and achieve higher resolution of acquired images.

[0009] means for solving problems

[0010] One aspect of the X-ray image acquisition apparatus disclosed herein is, [1] "An X-ray image acquisition apparatus for acquiring an X-ray image of an object moving along a first direction, comprising: a pixel unit having an M-pixel array comprising N (N is an integer greater than 2) pixel portions for detecting X-rays, the N pixel portions being arranged along the first direction, and the M-pixel arrays being arranged along a second direction intersecting the first direction; a control unit controlling the detection of the X-rays by the pixel unit; and a processing unit based on the detection of the X-rays by the pixel unit." The X-ray detection results of the pixel unit generate the X-ray image of the object. The control unit controls the detection of the X-ray by the pixel unit in such a way that the N pixel units in each of the M pixel arrays are sequentially detected at a predetermined detection interval. When the value obtained by dividing the arrangement spacing of the N pixel units in the first direction by the reference speed corresponding to the moving speed of the object along the first direction is set as the basic value, the detection interval is the value obtained by dividing the basic value by the pixel offset value, where the pixel offset value is an integer of 2 or more and N less.

[0011] In this X-ray image acquisition apparatus, X-rays are sequentially detected in each of the N pixels of an M-pixel array at a predetermined detection interval. This detection interval is set as a base value divided by a pixel offset value. The base value is the distance between the N pixels divided by a reference speed corresponding to the moving speed of the object. The pixel offset value is an integer greater than or equal to 2 and less than N. Thus, by generating an X-ray image of the object based on data detected at a detection interval shorter than the base value, the X-ray image can be made higher resolution. Furthermore, as described in Patent Document 1, while high resolution can be achieved by shifting the positions of two pixel arrays, the resolution cannot be changed, resulting in low flexibility in image acquisition. In contrast, in this X-ray image acquisition apparatus, by changing the pixel offset value, the detection interval can be changed, allowing for higher resolution X-ray images at levels corresponding to the pixel offset value. Therefore, the flexibility in image acquisition is improved. Furthermore, in X-ray image acquisition, the resolution in the direction of object movement is easily reduced due to blurring. However, in this X-ray image acquisition apparatus, by shortening the detection interval of the N pixels arranged along the first direction, the resolution in the first direction can be improved. Therefore, the acquired image can be appropriately made higher resolution. Thus, according to this X-ray image acquisition apparatus, both the degree of freedom in image acquisition and the resolution of the acquired image can be improved.

[0012] In one aspect of the X-ray image acquisition apparatus disclosed herein, it may also be, [2] "according to the X-ray image acquisition apparatus of [1], wherein the pixel offset value is selected from an integer of 2 or more and N less based on the input." In this case, the degree of freedom in image acquisition can be further improved. In addition, N may also be an integer of 3 or more.

[0013] In one aspect of the X-ray image acquisition apparatus disclosed herein, [3] "according to the X-ray image acquisition apparatus described in [1] or [2], wherein the control unit is configured to set the detection interval to the basic value." In this case, the degree of freedom in image acquisition can be further improved.

[0014] In one aspect of the X-ray image acquisition apparatus disclosed herein, it may also be, [4] "the X-ray image acquisition apparatus according to any one of [1] to [3], wherein the control unit controls the detection of the X-ray by the pixel unit in such a way that each of the N pixel units detects the X-ray within a period shorter than the basic value." In this case, the resolution of the X-ray image can be further improved.

[0015] In one aspect of the X-ray image acquisition apparatus disclosed herein, it may also be, [5] "the X-ray image acquisition apparatus according to any one of [1] to [4], wherein the control unit controls the detection of the X-ray by the pixel unit in such a manner that each of the N pixel units performs multiple detections of the X-ray only during a detection period corresponding to the basic value." In this case, it is possible to suppress the decrease in brightness of the X-ray image and to achieve a higher resolution for the X-ray image.

[0016] In one aspect of the X-ray image acquisition apparatus disclosed herein, [6] "According to any one of [1] to [5], the X-ray image acquisition apparatus generates an X-ray image having multiple pixel regions by processing the output data of the detection results of the N pixel regions in a manner that the output data of the same region of the object are superimposed on each other. When generating the X-ray image, the processing unit processes the output data in a manner that emphasizes the output data other than the output data of the pixel regions that constitute the pixel regions, where the output data of the pixel regions that constitute the pixel regions are different from the output data of the pixel regions that constitute the pixel regions adjacent to the pixel regions. The adjacent pixel regions are the pixel regions that are adjacent to the pixel regions in the detection timing front side in the direction corresponding to the first direction." In this case, the decrease in brightness of the X-ray image can be suppressed, and the X-ray image can be made more high-resolution.

[0017] In one aspect of the X-ray image acquisition system disclosed herein, [7] "an X-ray image acquisition system comprising an X-ray image acquisition device as described in any one of [1] to [6]; an X-ray source that outputs the X-rays; and a transport unit that transports the object along the first direction." Based on this X-ray image acquisition system, for the reasons stated above, it is possible to improve the degree of freedom in image acquisition and to achieve higher resolution in the acquired images.

[0018] In one aspect of the X-ray image acquisition method disclosed herein, [8] “An X-ray image acquisition method comprising: a detection step, irradiating an object moving along a first direction with X-rays, and detecting X-rays passing through the object by a pixel unit; and a processing step, generating an X-ray image of the object based on the detection result in the detection step, wherein the pixel unit has an M-pixel array comprising N (N is an integer greater than or equal to 2) pixel portions for detecting X-rays, the N pixel portions being arranged along the first direction, and the M-pixel array being arranged along a second direction intersecting the first direction, wherein in the detection step, in each of the M-pixel arrays, the N pixel portions sequentially detect the X-rays at a predetermined detection interval, and when the value obtained by dividing the arrangement spacing of the N pixel portions in the first direction by a reference speed corresponding to the moving speed of the object along the first direction is set as a base value, the detection interval is the value obtained by dividing the base value by a pixel offset value, wherein the pixel offset value is an integer greater than or equal to 2 and less than or equal to N.” Based on the above reasons, this X-ray image acquisition method can improve the degree of freedom in image acquisition and achieve higher resolution in the acquired images.

[0019] Invention Effects

[0020] According to one aspect of this disclosure, an X-ray image acquisition device, an X-ray image acquisition system, and an X-ray image acquisition method can be provided, which can improve the degree of freedom in image acquisition and achieve higher resolution of the acquired images. Attached Figure Description

[0021] Figure 1 This is a structural diagram of the X-ray image acquisition system according to the implementation method.

[0022] Figure 2 This is a structural diagram of an X-ray camera.

[0023] Figure 3 This is a flowchart illustrating the processes performed in an X-ray image acquisition device.

[0024] Figure 4 It is a diagram used to illustrate a reference speed.

[0025] Figure 5 (a) and (b) are diagrams used to illustrate typical TDI operations.

[0026] Figure 6 (a) and (b) are diagrams used to illustrate typical TDI operations.

[0027] Figure 7 This diagram illustrates the addition process in a typical TDI operation.

[0028] Figure 8 (a) and (b) are diagrams used to illustrate the action when the pixel offset value I is 4.

[0029] Figure 9 (a) and (b) are diagrams used to illustrate the action when the pixel offset value I is 4.

[0030] Figure 10 This diagram illustrates the addition process when the pixel offset value I is 4.

[0031] Figure 11 This diagram illustrates the addition process when the pixel offset value I is 4.

[0032] Figure 12 (a) and (b) are diagrams used to illustrate the action when the pixel offset value I is 3.

[0033] Figure 13 This diagram is used to illustrate the action when the pixel offset value I is 3.

[0034] Figure 14 This diagram illustrates the addition process when the pixel offset value I is 3.

[0035] Figure 15 This diagram illustrates the addition process when the pixel offset value I is 3.

[0036] Figure 16 (a) and (b) are diagrams used to illustrate the action when the pixel offset value I is 2.

[0037] Figure 17 (a) and (b) are diagrams used to illustrate the action when the pixel offset value I is 2.

[0038] Figure 18 This is a diagram illustrating the first example of addition processing when the pixel offset value I is 2.

[0039] Figure 19 This is a diagram illustrating the first example of addition processing when the pixel offset value I is 2.

[0040] Figure 20 This is a diagram illustrating the second example of addition processing when the pixel offset value I is 2.

[0041] Figure 21 This is a diagram illustrating the second example of addition processing when the pixel offset value I is 2.

[0042] Figure 22 This is a diagram showing the first example of the structure of the processing unit.

[0043] Figure 23 This is a second example of a diagram showing the structure of the processing unit.

[0044] Figure 24 This is the third example diagram showing the structure of the processing unit.

[0045] Figure 25 (a) and (b) are diagrams used to illustrate the action of the first variation.

[0046] Figure 26 (a) and (b) are diagrams used to illustrate the action of the first variation.

[0047] Figure 27 (a) and (b) are diagrams used to illustrate the action of the second variation.

[0048] Figure 28 (a) and (b) are diagrams used to illustrate the action of the second variation.

[0049] Figure 29 This diagram is used to illustrate the addition process in the second variation.

[0050] Figure 30 This diagram is used to illustrate the addition process in the second variation.

[0051] Figure 31 This diagram is used to illustrate the addition process in the second variation.

[0052] Figure 32 It is a diagram representing the objects and pixels in a hypothetical example.

[0053] Figure 33 This is a diagram used to illustrate the detection of objects in a hypothetical example.

[0054] Figure 34 This is a diagram used to illustrate the detection of objects in a hypothetical example.

[0055] Figure 35 This is a diagram used to illustrate the detection of objects in a hypothetical example.

[0056] Figure 36This is a diagram used to illustrate the detection of objects in a hypothetical example.

[0057] Figure 37 This is a diagram used to illustrate the detection of objects in a hypothetical example.

[0058] Figure 38 This is a diagram used to illustrate the detection of objects in a hypothetical example.

[0059] Figure 39 This is a diagram used to illustrate the detection of objects in a hypothetical example.

[0060] Figure 40 This is a diagram used to illustrate the results of the first simulation.

[0061] Figure 41 This is a graph used to illustrate the results of the second simulation.

[0062] Figure 42 (a) and (b) are figures used to illustrate the shortening of the exposure period.

[0063] Figure 43 This is a graph used to illustrate the results of the third simulation.

[0064] Figure 44 It is a graph used to illustrate additional simulation results.

[0065] Figure 45 This is a diagram used to illustrate a variation of shortened exposure time. Detailed Implementation

[0066] The embodiments of this disclosure will now be described in detail with reference to the accompanying drawings. In the following description, the same or equivalent elements are referred to by the same reference numerals, and repeated descriptions are omitted.

[0067] X-ray image acquisition system

[0068] Figure 1 The X-ray image acquisition system 1 shown is a system for acquiring X-ray images of an object OJ that is transported (moved) along a first direction X1. That is, the first direction X1 is the transport direction (movement direction) of the object OJ. The X-ray image acquisition system 1 includes an X-ray source 2, a transport unit 3, and an X-ray image acquisition device 4. The X-ray image acquisition device 4 includes an X-ray camera 5, a computer 6, a display unit 7, and an input unit 8.

[0069] X-ray source 2 outputs X-rays. The transport unit 3, for example, is a conveyor belt, which transports the object OJ placed on the belt along a first direction X1. The transport path of the transport unit 3 is set to pass through the irradiation range of the X-rays from X-ray source 2. As an example, the object OJ is food, and the X-ray image acquisition system 1 is used to check whether foreign objects are mixed into the object OJ.

[0070] like Figure 2 As shown, the X-ray camera 5 includes a pixel unit 10 and a circuit section 20. For example, the X-ray camera 5 converts X-rays passing through an object OJ into scintillation light via a scintillator, and the scintillation light is detected by the pixel unit 10 to acquire an X-ray image of the object OJ. In this case, the X-ray camera 5 includes a scintillator disposed above the pixel unit 10 (between the pixel unit 10 and the transport section 3). Alternatively, the pixel unit 10 may be configured as a direct conversion type detector that directly converts incident X-rays into an electrical signal instead of converting them into light. In this case, the scintillator is omitted. Examples of direct conversion type detectors include compound semiconductor detectors such as CdTe detectors and CdZnTe detectors, or direct conversion type detectors of Si.

[0071] The pixel unit 10 and the circuit section 20 are formed on a single chip and integrated with each other. The pixel unit 10 has an M-pixel array 12, each containing N (N is an integer of 2 or more) pixel sections 11 that perform photoelectric conversion. Each pixel section 11 is formed, for example, in a square shape. Alternatively, the pixel unit 10 and the circuit section 20 may be formed on different chips and these chips may be electrically connected.

[0072] N pixel units 11 are arranged in a column along a first direction X1, spaced apart by a certain interval (interval β). M pixel arrays 12 are arranged along a second direction X2, which intersects (orthogonal to) the first direction X1, spaced apart by a certain interval. The A-th pixel unit 11 (A is any integer greater than 1 and less than N) of the M pixel arrays 12 is arranged in a column along the second direction X2. That is, in the pixel unit 10, N×M pixel units 11 are arranged in a matrix. The first direction X1 and the second direction X2 are, for example, directions perpendicular to the vertical direction.

[0073] N can be an integer greater than or equal to 8, or an integer greater than or equal to 16. The following explanation uses the case where N and M are both 4 as an example, but the same applies when N and M are other values. Each pixel unit 11 is, for example, composed of a light-receiving element capable of detecting flickering light. The light-receiving element is, for example, a photodiode made of silicon, but it can also be a photodiode made of compound semiconductors such as InGaAs or CdTe. The pixel unit 10 can be, for example... Figure 2The example shown is a multiline sensor, which can also be an area sensor. Pixel unit 10 can also be composed of a SiPM (Silicon Photomultiplier). An example of a SiPM is the MPPC (Multi-Pixel Photon Counter) (registered trademark).

[0074] The circuit unit 20 includes a control unit 21 and a processing unit 22. The control unit 21 may be configured as a microcomputer mounted on a chip, or as any circuit element such as an FPGA (Field-Programmable Gate Array). The control unit 21 controls the detection of X-rays by the pixel unit 10. The processing unit 22 generates an X-ray image of the object OJ based on the detection results of the X-rays by the pixel unit 10. In other words, the processing unit 22 is an image processing unit that performs image processing. An example of the specific structure of the processing unit 22 is provided below. Figures 22-24 As will be described in detail later. The circuit section 20 (control section 21 and processing section 22) is electrically connected to each pixel section 11, for example, via wiring 15.

[0075] The circuit unit 20 is electrically connected to the computer 6. The computer 6 includes, for example, a processor such as a CPU, and storage media such as RAM and ROM. The computer 6 controls the operation of each part of the X-ray image acquisition system 1. For example, the computer 6 is electrically connected to the transport unit 3 and controls the operation of the transport unit 3. In this example, the control unit 21 controls the detection of X-rays from the pixel unit 10, but the computer 6 can also perform this control. That is, the computer 6 can also function as a control unit. In this case, the control unit 21 can be omitted. In addition, in this example, the processing unit 22 generates an X-ray image of the object OJ based on the detection result of the X-rays from the pixel unit 10, but the computer 6 can also perform this generation. That is, the computer 6 can also function as a processing unit. In this case, the processing unit 22 can be omitted. The control unit that controls the detection of X-rays from the pixel unit 10 and the processing unit that generates an X-ray image of the object OJ based on the detection result of the X-rays from the pixel unit 10 can also be composed of a common element (such as the computer 6).

[0076] Display unit 7 is, for example, a monitor connected to computer 6, which displays various information on the screen. Input unit 8 is, for example, a mouse, keyboard, etc., connected to computer 6, which receives user input. Display unit 7 and input unit 8 may also be composed of a touch screen, a smartphone, tablet, or other smart device that integrates a display unit or input unit.

[0077] [Methods for acquiring X-ray images]

[0078] In the X-ray image acquisition method of this embodiment, X-rays are irradiated from an X-ray source 2 onto an object OJ transported along a first direction X1, and the X-rays transmitted through the object OJ are detected by the pixel unit 10 (detection step). Next, the processing unit 22 generates an X-ray image of the object OJ based on the detection results from the detection step (processing step). The processing step can be performed after the detection of transmitted X-rays in the detection step is completed, or it can be performed in parallel with the detection of transmitted X-rays in the detection step.

[0079] Reference Figure 3 The following is a brief description of the processing performed in the X-ray image acquisition apparatus 4 when acquiring X-ray images. First, an input for selecting a pixel offset value I is received (step S1). In this example, the pixel offset value I is an integer greater than or equal to 1 and less than N. This input is received, for example, through the user operation input unit 8. The control unit 21 selects the pixel offset value I from the integers greater than or equal to 1 and less than N based on this input. Next, the control unit 21 sets the detection interval ΔT based on the pixel offset value I (step S2). Next, the control unit 21 sets whether to perform emphasis processing (step S3). As will be described later, emphasis processing may not be performed. Next, the control unit 21 controls the X-rays from the pixel unit 10 to be detected sequentially in each of the N pixel units 11 of the M pixel array 12 at a detection interval ΔT (step S4). Thus, the detection results of each pixel unit 11 are acquired, i.e., the output data. Next, the processing unit 22 generates an X-ray image of the object OJ based on the detection results of step S4 (step S5). Steps S1 to S4 are the processing steps for the detection step, and step S5 is the processing step for the processing step. The details of these processes will be explained below with reference to specific examples.

[0080] Figures 5-7 This diagram illustrates a typical TDI (Time Delay Integration) operation. This operation corresponds to the case where the pixel offset value I is 1. That is, when 1 is selected as the pixel offset value I in step S1, the X-ray image acquisition device 4 performs a typical TDI operation.

[0081] Figure 5 The left side of (a) shows the positional relationship between object OJ and pixel unit 10 at time T=t1. Figure 5 The right side of (a) shows the shooting timing of lines 1, 2, 3, and 4. Regarding the positional relationship between the object OJ and pixel unit 10 shown on the left and the shooting timing of lines 1-4 shown on the right, as will be discussed later... Figure 5 (b) Figure 6 , Figure 8 , Figure 9 , Figure 12 , Figure 13, Figure 16 , Figure 17 , Figures 25-28 Similarly, line 1 is a line of pixel portion 11 formed by the first pixel portion 11 of an M pixel array 12 arranged along the second direction X2, and similarly, lines 2, 3, and 4 are lines of pixel portion 11 formed by the second, third, and fourth pixel portions 11 of an M pixel array 12 arranged along the second direction X2. Hereinafter, as... Figure 5 As shown in (a), pixel array 12 is also denoted as pixel arrays a, b, c, and d respectively.

[0082] like Figure 5 As shown in (a), in a typical TDI operation, the detection interval ΔT (image interval) is set to (α + β) / (1 × V). That is, in the X-ray image acquisition method of the embodiment, the detection interval ΔT is set to (α + β) / (1 × V). In this example, since I = 1, the detection interval ΔT is set to (α + β) / (1 × V). Figure 2 As shown, α is the width of the pixel portion 11 in the first direction X1. β is the spacing between adjacent pixel portions 11 in the first direction X1. (α + β) corresponds to the arrangement spacing of the pixel portions 11 in the first direction X1 (the center-to-center distance between adjacent pixel portions 11). The spacing β can also be zero, in which case the pixel portions 11 are arranged without gaps along the first direction X1. In this case, the arrangement spacing is equal to the width α.

[0083] V is a reference velocity (determined based on the moving speed V1) corresponding to the moving speed V1 of the object OJ along the first direction X1. (Refer to...) Figure 4 The reference velocity V will be explained below. The reference velocity V can also be the moving speed V1 (transport speed) of the object OJ transported by the transport unit 3. Alternatively, the reference velocity V can also be the apparent velocity V2 on the pixel unit 10, taking into account the magnification of the X-rays from the X-ray source 2 to the X-ray camera 5. The magnification is obtained by FDD / FOD. FOD (Focus to Object Distance) is the distance from the X-ray source 2 to the object OJ. FDD (Focus to Detector Distance) is the distance from the X-ray source 2 to the X-ray camera 5. The apparent velocity V2 is obtained by (FDD / FOD) × V1. By using the apparent velocity V2, which takes into account the magnification, as the reference velocity V, image acquisition can be performed more appropriately.

[0084] Thus, in the X-ray image acquisition method of this embodiment, the detection interval ΔT is set to (α + β) / (I × V). (α + β) is the arrangement spacing of the pixel units 11, and V is the reference velocity. That is, when the value obtained by dividing the arrangement spacing (α + β) by the reference velocity V is set as the basic value, the detection interval ΔT is set to the basic value (α + β) / V divided by the pixel offset value I. Figures 5-7 In the typical TDI operation shown, since I = 1, the detection interval ΔT is set to the base value itself.

[0085] like Figure 5 As shown in (a), the detection result of line 1 during the detection period 1 from the start time T = t0 to time T = t1 is output as output data D11 from line 1. Output data Dpq represents the output data of the detection result of line p (p = 1, 2, ..., N) during frame q (q = 1, 2, ..., N) (detection period). Figure 5 As shown in (b), the detection results of each line during the detection period 2 from time T = t1 to time T = t2 are output as output data D12 from line 1 and as output data D21 from line 2. The length of frame q is equal to the basic value (α + β) / V. Figure 5 (a) and Figure 5 In (b), the portion of the object OJ corresponding to frame 1 is indicated by a shaded line. This is consistent with what will be discussed later. Figure 6 , Figure 8 , Figure 9 , Figure 12 , Figure 13 , Figure 16 , Figure 17 , Figures 25-28 Similarly. In Figure 5 In (a), the portion of the object OJ corresponding to frame 1 is located above line 1. Figure 5 In (b), the part of the object OJ corresponding to frame 1 is located above line 2, and the part of the object OJ corresponding to frame 2 is located above line 1.

[0086] like Figure 6 As shown in (a), the detection results of each line during the detection period 3 from time T = t2 to time T = t3 are output as output data D13 from line 1, output as output data D22 from line 2, and output as output data D31 from line 3. Figure 6As shown in (b), during the detection period 4 from time T = t3 to time T = t4, the detection results of each line are output as output data D14 from line 1, output as output data D23 from line 2, output as output data D32 from line 3, and output as output data D41 from line 4. Thus, in the X-ray image acquisition device 4, N pixel units 11 sequentially detect X-rays at detection intervals ΔT (step S4, detection step). This X-ray detection is performed simultaneously on each pixel array 12 (pixel arrays a to d).

[0087] Figure 7 This diagram illustrates the additive processing in a typical TDI (Total Discharge) operation. The additive processing is performed by the processing unit 22. Through this additive processing, an X-ray image of the object OJ is generated (step S5, processing step). Figure 7 As shown, in the addition process, the detection result, i.e., the output data, of the pixel unit 11 is processed by superimposing the output data of the same area of ​​the object OJ to generate an X-ray image of the object OJ.

[0088] Figure 7 The left side shows the output data (output image) from lines 1 to 4. Output data Dpqr is the output data of frame q (q = 1, 2, ...) from pixel arrays r (r = a, b, c, d) of lines p (p = 1, 2, ..., N). Furthermore, pixel array r is represented by a letter for convenience, but the number of pixels in the pixel array r can be an integer greater than 1, for example, it could be 1536 pixels, 4608 pixels, or 6144 pixels. At these points, as described later... Figure 10 , Figure 14 , Figure 18 , Figure 20 Similarly. For example... Figure 7 As shown on the right, by adding the output data from lines 1 to 4, an X-ray image of the object OJ with multiple pixel regions 30 is generated.

[0089] like Figure 7 As shown, for example, the value (pixel value) of the first pixel region 30 corresponding to pixel array a is D11a + D21a + D31a + D41a. The value of the second pixel region 30 corresponding to pixel array a is D12a + D22a + D32a + D42a. The value of the third pixel region 30 corresponding to pixel array a is D13a + D23a + D33a + D43a. The value of the fourth pixel region 30 corresponding to pixel array a is D14a + D24a + D34a + D44a. The value of the fourth pixel region 30 corresponding to pixel array d is D14d + D24d + D34d + D44d. Thus, in a typical TDI operation, an X-ray image with 4 times the brightness can be generated compared to, for example, using an output image from only one line as an X-ray image.

[0090] Figures 8-11 This diagram illustrates the operation when the pixel offset value I is 4. That is, when 4 is selected as the pixel offset value I in step S1, the X-ray image acquisition device 4 performs the following operation.

[0091] like Figure 8 As shown in (a), when the pixel offset value I is 4, the detection interval ΔT is set to (α + β) / (4 × V). Therefore, as... Figure 8 and Figure 9 As shown, detection (capturing) is performed with a shorter detection interval ΔT than in the case of a typical TDI operation (where the pixel offset value I is 1). For example, the detection results of each line during the detection period 1 from time T = t3 to time T = t4 are output as output data D11 from line 1, output as output data D21 from line 2, output as output data D31 from line 3, and output as output data D41 from line 4.

[0092] Figure 10 and Figure 11 This diagram illustrates the additive processing for a pixel offset value I of 4. In the typical TDI operation described above, the output data from lines 1 to 4 is X-ray output data from the same region of the object OJ. When the pixel offset value I is 4, as shown... Figure 10 As shown on the left, the output data from lines 1 to 4 is the output data (1 / 4 pixel offset) of the X-rays from the object OJ, which are located in a region that is offset from each other by only 1 / 4 of the width of the pixel portion 11 along the first direction X1.

[0093] like Figure 10 As shown, by adding the output data from lines 1 to 4, an X-ray image of the object OJ with multiple pixel regions 30 is generated. Figure 11 The values ​​of each pixel region 30 corresponding to pixel array a are shown. For example, the value (pixel value) of the first pixel region 30 corresponding to pixel array a is D11a + D21a + D31a + D41a. The value of the second pixel region 30 corresponding to pixel array a is D12a + D21a + D31a + D41a. The value of the third pixel region 30 corresponding to pixel array a is D12a + D22a + D31a + D41a. The value of the thirteenth pixel region 30 corresponding to pixel array a is D14a + D24a + D34a + D44a. Furthermore, as... Figure 10 and Figure 11As shown by the shaded lines, during the period from the start time T = t0 to T = t3, since it is impossible to acquire output data from all lines 1 to 4, X-ray image generation is not required for the range corresponding to this period. Similarly, for pixel arrays b to d, the output data from lines 1 to 4 are summed.

[0094] Furthermore, in the example above, the output data from lines 1 to 4 are summed together. However, when summing the output data from N lines, each output data can be filtered by a factor of 1 / N before summing the filtered output data.

[0095] Reference Figure 11 The emphasis processing (step S3) will now be explained. In step S3, if emphasis processing is not performed, as described above, the output data from lines 1 to 4 are added equally (simple addition). On the other hand, if emphasis processing is performed in step S3, specific data from the output data of lines 1 to 4 are emphasized and added together (emphasized addition) through the following emphasis processing.

[0096] exist Figure 11 In this diagram, outlier data is represented by a thick box. Outlier data is data that differs from the output data of a pixel region 30 that constitutes the pixel region 30 adjacent to it in the detection timing direction corresponding to the first direction X1. For example, in the second pixel region 30, the output data D12a differs from the output data of the adjacent first pixel region 30. In this case, for example, as a first example, the outlier data can be multiplied by n (n is a value greater than 1), and the value of the second pixel region 30 can be set as nD12a + D21a + D31a + D41a. Alternatively, as a second example, the data other than the outlier data can be multiplied by m (m is a value greater than 0 and less than 1), and the value of the second pixel region 30 can be set as D12a + mD21a + mD31a + mD41a. Furthermore, from the viewpoint of increasing the value of the pixel region 30, the first example is more preferred.

[0097] Within the third pixel region 30, the output data D22a differs from the output data of the adjacent second pixel region 30. In this case, in the first example, the value of the third pixel region 30 can be set to D12a + nD22a + D31a + D41a. In the second example, the value of the third pixel region 30 can also be set to mD12a + D22a + mD31a + mD41a. Similarly, within the first pixel region 30, in the first example, the value of the first pixel region 30 can be set to D11a + D21a + D31a + nD41a. In the second example, the value of the first pixel region 30 can also be set to mD12a + mD21a + mD31a + D41a.

[0098] Figures 12-15 This diagram illustrates the operation when the pixel offset value I is 3. That is, when 3 is selected as the pixel offset value I in step S1, the X-ray image acquisition device 4 performs the following operation.

[0099] like Figure 12 As shown in (a), when the pixel offset value I is 3, the detection interval ΔT is set to (α + β) / (3 × V). Therefore, as... Figure 12 and Figure 13 As shown, detection (imaging) is performed with a shorter detection interval ΔT than in the case of typical TDI operation (when the pixel offset value I is 1). For example, the detection results of each line during the detection period 1 from time T = t2 to time T = t3 are output as output data D11 from line 1, output as output data D21 from line 2, and output as output data D31 from line 3. When the pixel offset value I is 3, the output data from line 4 may not be used for the generation of the X-ray image. For example, the output data from line 4 may not be read out, or it may be read out but not used.

[0100] Figure 14 and Figure 15 This diagram illustrates the additive processing for a pixel offset value I of 3. In the typical TDI operation described above, the output data from lines 1 to 4 is X-ray output data from the same region of the object OJ. When the pixel offset value I is 3, as shown... Figure 14 As shown on the left, the output data from lines 1 to 3 are the output data (1 / 3 pixel offset) of X-rays from the object OJ, which are regions that are offset from each other along the first direction X1 by only 1 / 3 of the width of pixel portion 11.

[0101] like Figure 14 As shown, by adding the output data from lines 1 to 3, an X-ray image of the object OJ with multiple pixel regions 30 is generated. Figure 15 The values ​​of each pixel region 30 corresponding to pixel array a are shown. For example, the value (pixel value) of the first pixel region 30 corresponding to pixel array a is D11a + D21a + D31a. The value of the second pixel region 30 corresponding to pixel array a is D12a + D21a + D31a. The value of the tenth pixel region 30 corresponding to pixel array a is D14a + D24a + D34a. Furthermore, as... Figure 14 and Figure 15 As shown by the shaded line, during the period from the start time T = t0 to T = t2, since output data from all lines 1 to 3 cannot be acquired, no X-ray images are generated for the range corresponding to this period. Additionally, in Figure 15In the text, outlier data is represented by thick outlines. In the addition process where the pixel offset value I is 3, outlier data from the output data of lines 1 to 3 can also be highlighted and added.

[0102] Figures 16-21 This diagram illustrates the operation when the pixel offset value I is 2. That is, when 2 is selected as the pixel offset value I in step S1, the X-ray image acquisition device 4 performs the following operation.

[0103] like Figure 16 As shown in (a), when the pixel offset value I is 2, the detection interval ΔT is set to (α + β) / (2 × V). Therefore, as... Figure 16 and Figure 17 As shown, detection (capturing) is performed with a shorter detection interval ΔT than in the case of a typical TDI operation (when the pixel offset value I is 1). For example, the detection results of each line during the detection period 1 from time T = t1 to time T = t2 are output as output data D11 from line 1 and as output data D21 from line 2.

[0104] Figure 18 and Figure 19 This diagram illustrates the first example of additive processing for the case where the pixel offset value I is 2. In the typical TDI operation described above, the output data from lines 1 to 4 is X-ray output data from the same area of ​​the object OJ. When the pixel offset value I is 2, as shown... Figure 18 As shown on the left, the output data from lines 1 and 3 and the output data from lines 2 and 4 are X-ray output data (1 / 2 pixel offset) from a region in the object OJ that is offset from each other only by half the width of pixel portion 11 along the first direction X1.

[0105] like Figure 18 As shown, in the first example, an X-ray image of an object OJ with multiple pixel regions 30 is generated by adding the output data from lines 1 to 4. Figure 19 The values ​​of each pixel region 30 corresponding to pixel array a are shown. For example, the value (pixel value) of the first pixel region 30 corresponding to pixel array a is D11a + D21a + D31a + D41a. The value of the second pixel region 30 corresponding to pixel array a is D12a + D21a + D32a + D41a. The value of the seventh pixel region 30 corresponding to pixel array a is D14a + D24a + D34a + D44a. Furthermore, as... Figure 18 and Figure 19 As shown by the shaded line, during the period from the start time T = t0 to T = t1, since output data from all lines 1 to 4 cannot be acquired, X-ray images may not be generated for the range corresponding to this period. Furthermore, in Figure 19 In the diagram, special data is represented by dashed shading lines. In the addition process where the pixel offset value I is 2, special data from the output data of lines 1 to 4 can also be highlighted and added. For example, the value of the first pixel region 30 corresponding to pixel array a can also be set as D11a + nD21a + D31a + nD41a.

[0106] Figure 20 and Figure 21 This diagram illustrates a second example of additive processing for the case where the pixel offset value I is 2. In this second example, first data C1 is created by adding the output data from lines 1 and 3, which are X-ray output data from the same region of the object OJ, and second data C2 is created by adding the output data from lines 2 and 4, which are X-ray output data from the same region of the object OJ. Then, the first data C1 and the second data C2 are added to generate an X-ray image. In this case, as... Figure 21 As shown, the value of the first pixel region 30 corresponding to pixel array a is obtained by adding (D11a + D31a) of the first data C1 and (D21a + D41a) of the second data C2. In the first and second examples, the values ​​of each pixel region 30 in the generated X-ray image are the same.

[0107] [Processing Department]

[0108] Figure 22 This diagram illustrates a first example of the structure of the processing unit 22. In this first example, the processing unit 22 consists of an adder 51. The processing unit 22 includes an amplifier array 52, an ADC (Analog-to-Digital converter) array 53, an emphasis processing unit 54, and an adder memory 55. The amplifier array 52 includes M (four in this example) charge amplifiers connected to M pixel arrays 12 respectively, which convert charge signals output from the pixel section 11 of the corresponding pixel array 12 into voltage signals. The ADC array 53 includes M AD converters connected to the M charge amplifiers respectively, which perform A / D conversions to convert the voltage signals output from the corresponding charge amplifiers into digital values. The emphasis processing unit 54 is a circuit element for implementing the aforementioned emphasis processing and is connected between the ADC array 53 and the adder memory 55. The emphasis processing unit 54 can be omitted. The adder memory 55 includes multiple storage areas that store digital values ​​corresponding to the output data from each pixel section 11. With this first example of the processing unit 22, the aforementioned addition processing can be performed.

[0109] Figure 23This diagram illustrates a second example of the structure of the processing unit 22. In this second example, the processing unit 22 includes M (four in this example) adder units 51, each connected to an M pixel array 12. Each adder unit 51 includes a charge amplifier 61, an emphasis processing unit 54, a switching element 62, N AD converters 63, and an output circuit 64. The charge amplifier 61 converts the charge signal output from the pixel section 11 of the pixel array 12 into a voltage signal. The charge amplifier 61 may also be an amplifier array containing M charge amplifiers. The emphasis processing unit 54 is connected between the charge amplifier 61 and the switching element 62. The emphasis processing unit 54 may be omitted. The switching element 62 is connected between the charge amplifier 61 and the N AD converters 63, switching the connection state between the charge amplifier 61 and the N AD converters 63. The AD converters 63 convert the voltage signal output from the charge amplifier 61 connected via the switching element 62 into a digital value. The output circuit 64 outputs the signal from the AD converters 63 to the outside. With this second example of the processing unit 22, the above-described addition processing can also be performed.

[0110] Figure 24 This diagram illustrates a third example of the structure of the processing unit 22. In this third example, the processing unit 22 includes M (four in this example) adder units 51, each connected to one of the M pixel arrays 12. Each adder unit 51 includes an emphasis processing unit 54, a switching element 62, N charge amplifiers 61, an ADC array 53, and an output circuit 64. The emphasis processing unit 54 is connected between the charge amplifiers 61 and the switching element 62. The emphasis processing unit 54 can be omitted. The switching element 62 is connected between the N pixel arrays 11 and the N charge amplifiers 61, switching the connection state between the N pixel arrays 11 and the N charge amplifiers 61. The ADC array 53 includes N AD converters connected to the N charge amplifiers 61, converting the voltage signals output from the corresponding charge amplifiers 61 into digital values. The output circuit 64 outputs the signal from the ADC array 53 to the outside. This third example of the processing unit 22 can also perform the aforementioned addition processing.

[0111] [Functions and Effects]

[0112] In the X-ray image acquisition apparatus 4, in each of the M pixel arrays 12, N pixel units 11 sequentially detect X-rays at a predetermined detection interval ΔT. The detection interval ΔT is the value (α+β) / (I×V) obtained by dividing the basic value (α+β) / V by the pixel offset value I. The basic value (α+β) / V is the value obtained by dividing the arrangement spacing (α+β) of the N pixel units 11 by the reference speed V corresponding to the moving speed V1 of the object OJ. That is, the detection interval ΔT can be set based on the arrangement spacing (α+β) of the N pixel units 11, the moving speed V1 of the object OJ, and the pixel offset value I. When the pixel offset value I is an integer of 2 or more and N less, by generating an X-ray image of the object OJ based on data detected at a detection interval ΔT shorter than the basic value, the X-ray image can be made higher resolution. In addition, when the positions of the two pixel arrays are staggered as described in Patent Document 1 above, although higher resolution can be achieved, the resolution cannot be changed, and the degree of freedom (flexibility) of image acquisition is low. In contrast, in the X-ray image acquisition apparatus 4, by changing the pixel offset value I, the detection interval ΔT can be changed, and the X-ray image can be made higher resolution at a level corresponding to the pixel offset value I. Therefore, the degree of freedom in image acquisition can be improved. Moreover, in the acquisition of X-ray images, the resolution in the direction of movement of the blurred object OJ is easily reduced, but in the X-ray image acquisition apparatus 4, by shortening the detection interval ΔT of the N pixel portions 11 arranged along the first direction X1, the resolution in the first direction X1 can be improved, and therefore, the acquired image can be appropriately made higher resolution. Details of this blurring will be described later. As described above, according to the X-ray image acquisition apparatus 4, the degree of freedom in image acquisition and the acquisition image resolution can be improved.

[0113] The pixel offset value I is selected from integers above 1 and below N, based on the input. This further increases the degree of freedom in image acquisition.

[0114] The control unit 21 is configured to set the detection interval ΔT to a basic value. That is, in the example above, 1 can be selected as the pixel offset value I, and the normal TDI operation can be selected. As a result, the degree of freedom in image acquisition can be further improved.

[0115] For example, in the case of N pixel units 11, if the pixel offset value I is set to N, the resolution can be increased by N times. Compared to the normal TDI operation (N=1), since the detection interval ΔT is 1 / N, even if N sums are performed, the SNR (signal-to-noise ratio) and CNR (contrast-to-noise ratio) cannot be improved. If the pixel offset value I is set to 1, and the detection interval ΔT = (α + β) / V of the normal TDI operation is maintained, N sums are performed, thus improving the SNR, but not the resolution. By allowing the pixel offset value I to be selected from 1 to N or 2 to N, the resolution and contrast can be adjusted. For example, when high resolution is required, the pixel offset value I is set to a larger value; on the other hand, when the SNR is easily reduced due to factors such as the thickness of the object OJ, setting the pixel offset value I to a smaller value can improve both the contrast and the SNR. In addition, the pixel offset value I can be changed according to information about the object OJ, such as its type or thickness. Alternatively, the pixel offset value I can be changed based on shooting conditions such as the output of X-ray source 2, the moving speed V1 of the object OJ, and the inspection recipe. The pixel offset value I can also be set based on information obtained from shooting the object OJ. For example, a threshold for SNR or CNR can be set, and this threshold can be used to set the pixel offset value I.

[0116] As an example, with N=12, setting the pixel offset value I to 2 effectively achieves 6 levels of accumulation and 2x resolution. Setting the pixel offset value I to 3 effectively achieves 4 levels of accumulation and 3x resolution. Setting the pixel offset value I to 4 effectively achieves 3 levels of accumulation and 4x resolution. Setting the pixel offset value I to 5 effectively achieves 2 levels of accumulation and 5x resolution. In this case, there are periods where no exposure is performed or periods that are not used as data. By setting the pixel offset value I to 12 and accumulating one level at a time, 12x resolution can also be achieved.

[0117] Generally, in image sensors, pixel size (pixel size) is related to saturation charge; if the pixel size is reduced, the saturation charge decreases. That is, there is a trade-off between saturation charge and resolution. In contrast, in the X-ray image detection method of this embodiment, resolution can be improved without reducing pixel size, thus balancing saturation charge and resolution. Furthermore, in CdTe detectors, there is a tendency for pixel size to increase if energy resolution is improved. Therefore, it is difficult to ensure energy resolution while reducing pixel size. In contrast, in the X-ray image acquisition apparatus 4 of this embodiment, resolution can be improved without reducing pixel size, thus achieving a balance between the two. Additionally, while SiPMs are less prone to pixel size reduction compared to other sensors, in the X-ray image acquisition apparatus 4 of this embodiment, resolution can be improved without being limited by pixel size; therefore, even when the pixel unit 10 is composed of SiPMs, resolution can still be improved.

[0118] In the X-ray image acquisition apparatus 4, the processing unit 22 processes the detection results, i.e., the output data, from the N pixel units 11 by superimposing the output data of the same area of ​​the object OJ, thereby generating an X-ray image having multiple pixel regions 30. The processing unit 22 may also, during the generation of the X-ray image, emphasize the output data that is different from the output data constituting a pixel region 30 compared to the output data constituting a pixel region 30 adjacent to that pixel region 30 (emphasis processing). Here, the adjacent pixel region 30 is the pixel region 30 adjacent to a pixel region 30 at the detection timing forward of the direction corresponding to the first direction X1. When emphasis processing is performed, the decrease in brightness of the X-ray image can be suppressed, and the resolution of the X-ray image can be increased.

[0119] The X-ray image acquisition system 1 includes an X-ray image acquisition device 4, an X-ray source 2 that outputs X-rays, and a transport unit 3 that transports an object OJ along a first direction X1. According to the X-ray image acquisition system 1, for the reasons described above, it is possible to improve the degree of freedom in image acquisition and achieve higher resolution images.

[0120] [Variation Example]

[0121] Figure 25 and Figure 26 This diagram illustrates the operation of the first modified example. In the first modified example, the control unit 21 controls the detection of X-rays by the pixel unit 10 in such a way that each of the N pixel units 11 detects X-rays only for a period shorter than the basic value (α+β) / V. That is, in Figure 8 and Figure 9In the example shown, each pixel 11 detects X-rays across all frames, but it can also be done as follows: Figure 25 and Figure 26 As shown in the example, each pixel unit 11 detects X-rays only for half the entire frame. During the periods when X-rays are not detected, the charge generated by the pixel unit 11 can be discharged, for example, by an electronic shutter.

[0122] According to the first variation, similar to the above embodiment, it is also possible to improve the degree of freedom in image acquisition and increase the resolution of the acquired image. In addition, since each of the N pixel units 11 detects X-rays only for a period shorter than the basic value (α+β) / V, it is possible to further increase the resolution of the X-ray image.

[0123] Figure 27 and Figure 28 This diagram illustrates the operation of the second variation. In the second variation, the control unit 21 controls the detection of X-rays by the pixel unit 10 in a manner that each of the N pixel units 11 performs multiple detections of X-rays during one frame corresponding to the basic value (α+β) / V. That is, in Figure 8 and Figure 9 In the example shown, each pixel 11 detects X-rays only once during one frame, but it can also be as follows: Figure 27 and Figure 28 As shown in the example, for instance, each pixel 11 detects X-rays twice during one frame. Figure 27 and Figure 28 In the example, each pixel 11 detects X-rays twice during a first detection period and a second detection period within one frame.

[0124] Figures 29-31 This diagram illustrates the addition process for the second variation. For example, as... Figure 29 As shown, the output data during the first detection period are summed to create the first data E1, and as... Figure 30 As shown, the output data during the second detection period are summed to create the second data E2. And, as... Figure 31 As shown, an X-ray image is generated by adding the first data E1 and the second data E2. Furthermore, in Figure 29 In the figure, the "-1" label at the end of each data point is omitted, but... Figure 29 The data shown are the output data during the first detection period. Similarly, in Figure 30 In the figure, the "-2" label at the end of each data point is omitted, but... Figure 30 All the data shown are output data during the second detection period.

[0125] According to the second variation, similar to the above embodiment, it is also possible to improve the degree of freedom in image acquisition and increase the resolution of the acquired image. Furthermore, since each of the N pixel units 11 performs multiple X-ray detections between frames corresponding to the basic value (α+β) / V, it is possible to suppress the decrease in brightness of the X-ray image and increase the resolution of the X-ray image. Moreover, it is not limited to detecting X-rays twice within one frame; it is possible to detect X-rays n times (n is an integer greater than or equal to 2) within one frame. In this case, the length of the detection period can be set to 1 / n or less of the basic value.

[0126] [Additional Explanation]

[0127] Reference Figures 32-39 The X-ray image acquisition method of the embodiment will be further explained. For example... Figure 32 As shown, the scenario depicts the imaginary case where the pixel unit 11 acquires X-rays from an object OJ moving along the first direction X1. In this hypothetical example, the pixel unit 11 has a size of 0.4mm × 0.4mm, and the object OJ moves 0.4mm during the imaging of line 1.

[0128] like Figure 33 As shown, the object OJ is virtually divided into blocks A to O along the first direction X1, with units of 0.1 mm. At the start of shooting, blocks A to D are photographed. After moving 0.1 mm, blocks B to E are photographed. After moving 0.2 mm, blocks C to F are photographed. After moving 0.3 mm, blocks D to G are photographed. After moving 0.4 mm, blocks E to H are photographed. Thus, the shooting of line 1 is completed. The output data of line 1 is 0.5A + 1.5B + ​​2.5C + 3.5D + 3.5E + 2.5F + 1.5G + 0.5H. Here, for example, 0.5A means that when the data corresponding to the full length of each block is set to 1 unit, it includes half of the data from block A, which is 0.5 units. The reason why the data from block A is 0.5 units is because, due to the movement of the object OJ, only data from half of the area of ​​block A is acquired. The output data for line 2 is 0.5E+1.5F+2.5G+3.5H+3.5I+2.5J+1.5K+0.5L.

[0129] Thus, the output data of the first line includes data from a 0.8mm region of blocks A to H. As mentioned above, in the acquisition of X-ray images, the resolution in the direction of movement of the object OJ is easily reduced due to blurring, and this is the reason why. That is, the shooting range (the amount of movement of the object OJ per line) during the shooting period is determined by the moving speed of the object OJ and the width (pixel height) of the pixel section 11. Therefore, transport blurring occurs in the first direction X1, which is the direction of movement (transport direction), and the resolution in the first direction X1 is easily lower than the resolution in the second direction X2.

[0130] Consider the scenario where X-ray images are used to inspect an object (OJ) for foreign matter. For example... Figure 34 As shown, the brightness contrast is greater when there is a foreign object in block D. For example, if the transmittance (X-ray transmittance) of block D is 0% due to the presence of the foreign object, while the transmittance of other blocks is 100%, the brightness of block D with a foreign object is 78% of the brightness of the object OJ without a foreign object. That is, as mentioned above, the output data of line 1 is 0.5A + 1.5B + ​​2.5C + 3.5D + 3.5E + 2.5F + 1.5G + 0.5H. If the data corresponding to the full length of each block is set to 1 unit, it contains 16 units of data. If the contribution of block D (3.5 units) is set to 0, it contains 12.5 units of data, 12.5 / 16 ≈ 78%.

[0131] On the other hand, the contrast is lower when foreign objects are present in block G. For example, if the transmittance of block G is 0% and the transmittance of other blocks is 100%, the brightness of block G with foreign objects is 90% of the brightness of the object OJ without foreign objects (14.5 / 16≈91%). Thus, the detection result changes due to the shooting timing. Similarly, below, the brightness of the area with foreign objects will be expressed as a ratio to the brightness of the object OJ without foreign objects.

[0132] like Figure 35 As shown, when foreign objects are present in blocks B through E, the brightness is 31% (5 / 16 ≈ 31%) if considered in the same way as above. On the other hand, when foreign objects are present in blocks E through H, the brightness is 50% (8 / 16 = 50%). Thus, even when foreign objects of the same size are present, the detection result changes due to the shooting timing. More specifically, if the foreign object exists across the boundary of pixel section 11, the contrast will decrease.

[0133] In contrast, in the X-ray image acquisition method of the above embodiment, if the pixel offset value I is set to an integer of 2 or more and N or less, an X-ray image can be generated by using the output data of X-rays from a region in the object OJ that is offset from each other only by 1 / 1 of the width of the pixel portion 11 along the first direction X1, thereby increasing the contrast.

[0134] like Figure 36As shown, consider the case where the two pixel units 11 are configured with an offset of only 1 / 2 of the width of the pixel unit 11 from each other (1 / 2 pixel offset). This corresponds to the case where the pixel offset value I is 2 in the above embodiment. In this case, the output data of the first line of the first pixel unit 11 is 0.5A+1.5B+2.5C+3.5D+3.5E+2.5F+1.5G+0.5H, and the output data of the first line of the second pixel unit 11 is 0.5C+1.5D+2.5E+3.5F+3.5G+2.5H+1.5I+0.5J.

[0135] exist Figure 36 In the example, the brightness of block G with foreign objects present is 84% ​​(27 / 32≈84%). This increases the contrast compared to the 90% brightness achieved by a single pixel 11, as described above. Furthermore, in Figure 36 In the example, the brightness of blocks E to H with foreign objects present is 37.5% (12 / 32 = 37.5%). This is an increase in contrast compared to the 50% brightness achieved when captured by a single pixel 11, as described above. Therefore, by setting the pixel offset value I to an integer greater than 2 and less than N, foreign objects can be detected effectively.

[0136] like Figure 37 As shown, the exposure (detection) is not performed throughout the entire frame, but only during a portion of the frame. Figure 37 The example corresponds to the first variation mentioned above. In Figure 37 In the example, when the object OJ moves 0.4mm, exposure is performed during the 0.3mm movement period, and no exposure is performed during the remaining 0.1mm movement period. In this case, the output data of line 1 is 0.5A+1.5B+2.5C+3D+2.5E+1.5F+0.5G. The brightness of block D with foreign objects is 75%. The brightness of block G with foreign objects is 96%. The brightness of blocks B-E with foreign objects is 21%. The brightness of blocks E-H with foreign objects is 63%.

[0137] In this case, as in the X-ray image acquisition method of the above embodiment, where the pixel offset value I is set to an integer of 2 or more and N or less, an X-ray image can be generated by using output data of X-rays from a region in the object OJ that is offset from each other only by 1 / 1 of the width of the pixel portion 11 along the first direction X1, thereby increasing the contrast.

[0138] like Figure 38 As shown, with Figure 36Similarly, consider the case where the two pixel units 11 are configured with an offset of only 1 / 2 of their width from each other. In this case, the output data of the first line of the first pixel unit 11 is 0.5A+1.5B+2.5C+3D+2.5E+1.5F+0.5G, and the output data of the first line of the second pixel unit 11 is 0.5C+1.5D+2.5E+3F+2.5G+1.5H+0.5I.

[0139] exist Figure 38 In the example, the brightness of block G when there is a foreign object is 88%. This is an increase in contrast compared to the 96% brightness achieved by a single pixel 11, as described above. Furthermore, in Figure 38 In the example, the brightness of blocks E to H when foreign objects are present is 58%. This is an increase in contrast compared to the 63% brightness achieved when the image is captured by a single pixel unit 11, as described above. Therefore, by setting the pixel offset value I to an integer between 2 and N, foreign objects can be detected effectively. In particular, the contrast can be increased more effectively when exposure is performed only for a portion of a frame.

[0140] Figure 39 An example is shown where the pixel portion 11 is formed in a rectangular shape, with a length (width) of 0.6 mm in the first direction X1 and a length of 0.4 mm in the second direction X2. During the imaging of line 1, the object OJ moves 0.4 mm. In this case, the output data for line 1 is 0.5A + 1.5B + ​​2.5C + 3.5D + 4E + 4F + 3.5G + 2.5H + 1.5I + 0.5J, and the output data for line 2 is 0.5E + 1.5F + 2.5G + 3.5H + 4I + 4J + 3.5K + 2.5L + 1.5M + 0.5N. Thus, line 1 starts from block A data, and line 2 starts from block E data. When generating X-ray images by setting the pixel offset value I to an integer greater than 2 and less than N, the data for line 11 of the second pixel portion 11 preferably starts from block C. Therefore, the pixel offset is preferably set based on the amount of movement of the object OJ, rather than on the size of the pixel portion 11.

[0141] [Simulation Results]

[0142] Figure 40 This is a graph used to illustrate the results of the first simulation. In the first simulation, [the graph is used as follows]. Figure 40 The resolution chart shown on the left is the object to be analyzed. "Target" is the target image, "Original Image" is the image before reconstruction, and "Reconstructed" is the image after reconstruction. Figure 40 The diagram on the upper right side shows Figure 40The left side of the image shows the brightness value waveform (profile) along the transport direction. As shown in the brightness value waveform, in the target image, with the left end as 0 pixels, the width of the lp (line pair) (the pair of white and black lines) changes periodically every 50 pixels. Furthermore, in... Figure 40 In the chart shown in the upper right corner, a specified offset value is added to the brightness value to facilitate understanding the lower limit of the amplitude. This will be discussed later. Figure 41 , 43 The chart (grah) shown in the upper right corner also applies.

[0143] In this analysis, the aforementioned patent document 1 is used. Figure 7 A, Figure 7 The method described in B reconstructs the image. Specifically, two images, each offset by only half the pixel width, are magnified using the nearest neighbor method, their pixels are offset, and then added together to reconstruct a single image. In Patent Document 1, the image is magnified in two mutually orthogonal directions, but in this analysis, the image is magnified and added only in one direction (the transport direction). Furthermore, this analysis does not consider the effects of transport blur, scintillator blur, afterglow blur, shot noise, and readout noise.

[0144] Figure 40 The table at the bottom right shows the value obtained by dividing the amplitude of the luminance value at each lp by the amplitude of the luminance value in the target image and then normalizing the result. As shown in the table, through reconstruction, the amplitude of the original image is 0.20 within the lp range of 4 pixels, while it is 0.50 in the reconstructed image. This demonstrates that reconstructing two images obtained by offsetting each other by only half a pixel width into a single image can improve resolution.

[0145] Figure 41 This diagram illustrates the results of the second simulation. The second simulation differs from the first in that it considers transport ambiguity in its analysis. For example... Figure 41 As shown in the table on the lower right, the count value is lower when transport ambiguity is taken into account than when transport ambiguity is not taken into account, and the resolution improvement rate is reduced.

[0146] Figure 42 This is a graph used to illustrate the shortening of the exposure period. Consider: such as Figure 42 As shown in (a), the exposure is not performed across the entire frame, but rather as... Figure 42 As shown in (b), exposure occurs only for a portion of a frame. This shortening of the exposure period corresponds to the first variation described above. Figure 25 and Figure 26 )and Figure 37 Examples.

[0147] Figure 43 This graph is used to illustrate the results of the third simulation. The third simulation differs from the second simulation in that it shortens the exposure period to half. (As shown...) Figure 43 As shown in the table at the bottom right, when the exposure period is shortened to half (half exposure), the amplitude is larger than when the exposure period is not shortened (normal exposure). This demonstrates that shortening the exposure period can improve resolution.

[0148] Figure 44 This is a graph used to illustrate additional simulation results. Figure 44 The bottom of the table shows the simulation results for the case where the exposure period is shortened to 1 / 4. From Figure 44 The table shows that the shorter the exposure period, the higher the resolution.

[0149] Figure 45 This diagram is used to illustrate a variation of shortened exposure time. For example... Figure 45 As shown, in this modified example, each pixel 11 detects X-rays twice during one frame. This modified example corresponds to the second modified example described above. Figures 27-31 In this variation, similar to the second variation described above, the output data for each of the two exposure periods is added to create summed data. The two summed data are then further added to generate an X-ray image. As mentioned above, simply shortening the exposure period can suppress the effect of transport blur, but brightness may be reduced. In this variation, however, the exposure time can be substantially extended, suppressing both the decrease in brightness and the effect of transport blur.

[0150] This disclosure is not limited to the embodiments and variations described above. In the embodiments described above, the pixel offset value I can be selected from an integer of 1 or more and N or less, or it can be selected from an integer of 2 or more and N or less. In other words, 1 may not be selected as the pixel offset value I, and the normal TDI operation may also be selected. That is, the control unit 21 may not be configured to set the detection interval ΔT to a basic value. The pixel offset value I does not necessarily have to be selected from multiple values, and may also be a fixed value (e.g., N).

[0151] In the above embodiment, the M pixel arrays 12 are arranged along a second direction X2 orthogonal to the first direction X1. However, the M pixel arrays 12 can be arranged along a direction intersecting the first direction X1, or they can be arranged at an angle other than perpendicular to the first direction X1 along the direction intersecting the first direction X1. In each pixel array 12, the N pixel portions 11 can also be arranged with their positions offset from each other along the second direction X2 orthogonal to the first direction X1. In this case, not only the resolution in the first direction X1 can be improved, but the resolution in the second direction X2 can also be improved.

[0152] Explanation of reference numerals in the attached figures

[0153] 1… X-ray image acquisition system, 2… X-ray source, 10… pixel unit, 3… transport unit, 4… X-ray image acquisition device, 11… pixel unit, 12… pixel array, 21… control unit, 22… processing unit, 30… pixel area, I… pixel offset value, OJ… object, V… reference speed, V1… moving speed, X1… first direction, X2… second direction, ΔT… detection interval.

Claims

1. An X-ray image acquisition device, wherein, An X-ray image acquisition apparatus for acquiring an X-ray image of an object moving along a first direction. have: A pixel unit having M pixel arrays, each comprising N pixel portions for detecting X-rays, wherein N and M are both integers greater than 2, the N pixel portions being arranged along a first direction, and the M pixel arrays being arranged along a second direction intersecting the first direction; A control unit that controls the detection of X-rays by the pixel units; and The processing unit generates the X-ray image of the object based on the detection results of the X-rays from the pixel units. The control unit controls the detection of X-rays by the pixel units in such a way that the N pixel units in each of the M pixel arrays sequentially detect the X-rays at a predetermined detection interval. When the basic value is obtained by dividing the spacing of the N pixels in the first direction by a reference speed corresponding to the moving speed of the object along the first direction, the detection interval is the value obtained by dividing the basic value by the pixel offset value, wherein the pixel offset value is an integer of 2 or more and N less.

2. The X-ray image acquisition device according to claim 1, wherein, The pixel offset value is selected from an integer between 2 and N, based on the input.

3. The X-ray image acquisition device according to claim 1 or 2, wherein, The control unit is configured to set the detection interval to the basic value.

4. The X-ray image acquisition device according to claim 1 or 2, wherein, The control unit controls the detection of X-rays by the pixel units in such a way that each of the N pixel units detects the X-rays only for a period shorter than the basic value.

5. The X-ray image acquisition device according to claim 1 or 2, wherein, The control unit controls the detection of X-rays by the pixel unit in such a way that each of the N pixel units performs multiple detections of the X-rays during a detection period corresponding to the basic value.

6. The X-ray image acquisition device according to claim 1 or 2, wherein, The processing unit generates the X-ray image having multiple pixel regions by processing the output data, which is the detection result of the N pixel regions, in a manner that superimposes the output data of the same region of the object. When generating the X-ray image, the processing unit processes the output data in such a way that the output data that is different from the output data that constitutes the pixel region is compared with the output data other than the different output data. The adjacent pixel region is the pixel region that is adjacent to the pixel region on the detection timing front side in the direction corresponding to the first direction.

7. An X-ray image acquisition system, wherein, have: The X-ray image acquisition device according to claim 1 or 2; An X-ray source that outputs the X-rays; and A conveying unit that conveys the object along the first direction.

8. A method for acquiring X-ray images, comprising: The detection steps include irradiating an object moving along a first direction with X-rays, and detecting the X-rays transmitted through the object by pixel units; and The processing step, based on the detection results in the detection step, generates an X-ray image of the object. The pixel unit has an M pixel array, each comprising N pixel portions for detecting X-rays, wherein... N and M are both integers greater than or equal to 2. The N pixels are arranged along the first direction, and the M pixel array is arranged along a second direction that intersects the first direction. In the detection step, in each of the M pixel arrays, the N pixel units sequentially detect the X-rays at a predetermined detection interval. When the basic value is obtained by dividing the spacing of the N pixels in the first direction by a reference speed corresponding to the moving speed of the object along the first direction, the detection interval is the value obtained by dividing the basic value by the pixel offset value, wherein the pixel offset value is an integer of 2 or more and N less.

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