Radiation detection device, radiation image acquisition system, radiation inspection system, and radiation detection method

Radiation detection device, radiation image acquisition system, radiation inspection system and radiation detection method

The invention relates to a radiation detection device, a radiation image acquisition system, a radiation inspection system and a radiation detection method.

Previously, an object that allows X-rays to pass through an object to be inspected such as food or medicine is widely used, and the presence or absence of foreign objects in the object is inspected through the X-ray image through the object. For such inspections, an X-ray image acquisition device is used, which is equipped with an X-ray source that irradiates X-rays on an object, and a linear line sensing that detects a transmission image of X-rays that irradiate the object from the X-ray source Device.

However, a linear sensor that does not have an energy discrimination function is used to detect X-ray transmission. Since it does not have an energy discrimination function, there are differences in the composition of foreign objects contained in the object (for example, bones, Differences in meat, cartilage, foreign bodies, etc.) or thickness differences, resulting in decreased detection accuracy. Therefore, it has been proposed to arrange two linear sensors that detect X-rays of different energy ranges in parallel, and obtain subtraction imaging as the differential data image from the X-ray images detected by these two linear sensors. , The detection accuracy is improved regardless of the composition or thickness of the foreign matter contained in the object (for example, refer to Patent Document 1).

<b>Prior art literature</b>

<b>Patent literature</b>

Patent Document 1 Japanese Patent Application Laid-Open No. 10-318943

<p>However, according to the research of the present inventors, when it is desired to obtain a subtraction image from an X-ray image of an object detected and generated by two linear sensors arranged side by side, it is known that there is a foreign object in the subtraction image. The edge of the image part is not clear. Therefore, only two linear sensors are used, and there are cases where it is impossible to detect foreign objects contained in the object with high accuracy.</p><p>Therefore, the present invention was made in view of the aforementioned problems, and its object is to provide a radiation detection device, a radiation image acquisition system, a radiation inspection system, and a radiation detection method that can improve the detection accuracy of foreign objects included in a target.</p>

<p>The inventors of the present invention have repeatedly and intensively studied in order to achieve the above-mentioned purpose. As a result, they have found that the reason why the edges of the image portion representing foreign objects and the like in the energy subtraction imaging are not clear is mainly caused by the clamping between the two linear sensors. Do not sense the existence of the zone. Although the insensitive area can be reduced as much as possible, the situation where different pixels are arranged on the same sheet will inevitably occur. Therefore, the inventors found that if the X-ray detection timing based on the two linear sensors is adjusted based on the width of the non-sensing zone, the detection accuracy of the foreign object inspection based on the two linear sensors can be improved. As a result, the present invention has been completed.</p><p>That is, the radiation detection device of the present invention irradiates radiation from a radiation source to an object, and detects radiation passing through a plurality of energy ranges of the object, and includes: detecting radiation passing through a first energy range of the object to generate The first detector of the first radiographic image data; the second detector that sandwiches a specific area and is arranged side by side with the first detector to detect the radiation passing through the second energy range of the object to generate the second radiographic image data ; And to make the first radiographic image data generated by the first detector and the second radiographic image data generated by the second detector correspond to each other, based on the width of the specific area, at least control the detection of the second detector The timing control part of timing.</p><p>In addition, the radiation detection method of the present invention is a radiation detection method of a radiation detection device. The radiation detection device is provided with: a radiation source for irradiating a target with radiation, a first detector for detecting radiation in a first energy range, and a clamp specific Area and arranged side by side with the first detector, a second detector that detects radiation in the second energy range, and a timing control unit that controls the timing of the radiation detection of the first detector and the second detector. The radiation detection method includes : Irradiation step in which the radiation source irradiates the object with radiation; the first detector detects the radiation that is irradiated in the irradiation step and penetrates the first energy range of the object to generate the first radiographic image data. The first detection step; the second detection The second detection step of generating the second radiation image data by detecting the radiation that is irradiated in the irradiation step and penetrating the second energy range of the object; and the timing control unit makes the first radiation image generated by the first detection step The way in which the data and the second radiographic image data generated in the second detection step correspond to each other is based on the width of the specific area, and at least the timing control step of the detection timing of the second detection step is controlled.</p><p>In the radiation detection device and the radiation detection method, the timing control unit corresponds to the radiographic image data generated by the first detector and the radiographic image data generated by the second detector, based on the width of the specific area, at least Control the detection timing of the second detector. By this, the detection timing of the second detector that has a deviation (delay, etc.) from the detection timing of the first detector due to the existence of the specific area is adjusted, so that the radiographic image data generated by the first detector and the second detection The radiographic image data generated by the device correspond to each other. In addition, in the subtraction image obtained from two radiographic image data corresponding to each other, unclear edges are reduced. As a result, the detection accuracy of foreign objects included in the object can be improved.</p><p>In addition, when generating a subtraction image, generally image processing can be used to reduce unclear edges. However, when detecting foreign objects included in objects conveyed at a high speed (for example, 80m), if you want to use image processing to reduce unclear edges, the processing speed of image processing is difficult to correspond to the high-speed conveying speed. The situation. In contrast, according to the aforementioned radiation detection device and radiation detection method, by controlling the detection timing of the radiographic image, unclear edges can be reduced from the subtraction imaging, so even if the object is conveyed at a high speed Quickly generate a subtraction image with reduced unclear edges. As a result, even in high-speed foreign object inspection, the detection accuracy of foreign objects included in the object can be improved.</p><p>The radiation image acquisition system of the present invention may also include: the aforementioned radiation detection device; and a timing calculation unit that calculates the detection timing based on the width of the specific region. The timing control unit can use the detection timing calculated by the timing calculation unit to control the detection timing of the second detector, etc., to generate a subtraction image with reduced unclear edge portions.</p><p>The radiation inspection system of the present invention irradiates radiation from a radiation source to an object, detects radiation passing through a plurality of energy ranges of the object, and inspects the object, and includes: as a radiation source, radiation is irradiated to the object. Illuminator; the first detector that detects the radiation passing through the first energy range of the object to generate the first radiographic image data; clamps a specific area and is arranged in parallel with the first detector to detect the second energy that passes through the object The second detector that generates the second radiographic image data within the range of radiation; the transport part that transports the object in a direction that intersects the radiation irradiation direction of the radiation irradiator; when the first detector and the second detector are used to detect When the radiation of the object conveyed by the conveying unit is passed through, the first radiographic image data generated by the first detector and the second radiographic image data generated by the second detector correspond to each other, based on a specific area The width and the conveying speed of the object in the conveying section at least control the detection timing of the second detector by the timing control section; the timing control sections are controlled to correspond to each other to synthesize the first radiation pattern generated by the first detector A composite image generating unit that generates a composite image from the image data and the second radiation image data generated by the second detector; and a composite image output unit that outputs the composite image generated by the composite image generation unit. According to such a radiation inspection system, it is possible to perform inspections of foreign objects contained in objects or carry-on baggage inspections with high accuracy.</p>

<p>According to the present invention, it is possible to improve the detection accuracy of foreign objects and the like contained in the object.</p>

Hereinafter, a preferred embodiment of the X-ray image acquisition system of the present invention will be described with reference to the drawings. In addition, in the description of the drawings, the same or corresponding parts are marked with the same symbols, and repeated descriptions are omitted.

Fig. 1 is a perspective view of the X-ray image acquisition system of this embodiment. In addition, FIG. 2 is a schematic configuration diagram of the X-ray image acquisition system of this embodiment. As shown in Figures 1 and 2, the X-ray image acquisition system (radiation image acquisition system, radiation inspection system) 1 irradiates X-rays (radiation) from the X-ray source (radiation source) to the object S, and the plural The energy range detects the X-ray transmission device of the irradiated X-ray through the object S. The X-ray image acquisition system 1 uses transmitted X-ray images to detect foreign objects included in the object S or carry-on baggage inspection. Such an X-ray image acquisition system 1 includes: a belt conveyor (conveying unit) 10, an X-ray irradiator (radiation irradiator) 20, a low-energy image acquisition unit 30, a high-energy image acquisition unit 40, and timing control The unit 50, the timing calculation unit 60, and the image processing device (composite image generation unit, composite image output unit) 70. The low-energy image acquisition unit 30, the high-energy image acquisition unit 40, and the timing control unit 50 constitute a dual image acquisition device (radiation detection device) 80.

As shown in FIG. 1, the belt conveyor 10 is provided with a conveyor belt portion 12 for placing or placing an object S. As shown in FIG. The belt conveyor 10 moves the conveyor belt portion 12 in the conveying direction A (from the upstream side on the left side of Fig. 1 to the downstream side on the right side of Fig. 1), thereby conveying the object S in the conveying direction A at a specific conveying speed . The conveying speed of the object S is, for example, 48 m/min. The speed of the belt conveyor 10 can be changed to, for example, a conveying speed of 24 m/min or 96 m/min by the belt conveyor control unit 14 as required. In addition, the belt conveyor control unit 14 can change the height position of the conveyor belt unit 12. By changing the height position of the conveyor belt portion 12, the distance between the X-ray irradiator 20 and the object S (equivalent to "FOD" described later) can be changed. With this change, the resolution of the X-ray transmission image acquired by the low-energy image acquisition unit 30 and the high-energy image acquisition unit 40 can be changed. In addition, as the object S to be conveyed by the belt conveyor 10, a wide range of examples include food such as meat or rubber products such as tires, which are used for security and safety inspection of luggage or cargo, and other resin products or metal products. , Minerals and other resource materials, wastes used for classification or resource recovery (reuse), electronic parts, etc.

The X-ray irradiator 20 is a device that irradiates the object S with X-rays as an X-ray source. The X-ray irradiator 20 is a point light source, which diffuses and irradiates X-rays in a specific angle range in a specific irradiation direction. The X-ray irradiator 20 is at a certain distance from the conveyor belt 12 in such a way that the X-ray irradiation direction faces the conveyor belt 12 and the diffused X-rays spread across the entire width direction of the object S (the direction crossing the conveying direction A) It is arranged above the conveyor belt portion 12. In addition, the X-ray irradiator 20 uses the specific division range in the longitudinal direction as the irradiation range in the longitudinal direction of the object S (the direction parallel to the conveying direction A), and the object S is moved toward the conveying direction by the belt conveyor 10 A is conveyed, and X-rays are irradiated to the entire length of the object S.

The low-energy image acquisition unit 30 includes a low-energy detector (first detector) 32 and a low-energy image correction unit 34.

The low-energy detector 32 detects X-rays passing through the low-energy range (first energy range) of the object S among the X-rays irradiated by the X-ray irradiator 20, and generates low-energy image data (first radiation image data) ). The low-energy detector 32 is composed of, for example, a linear linear sensor having a length equal to or greater than the width of the object S. The X-ray detection surface is opposed to the X-ray irradiator 20 and perpendicular to the conveying direction A. The method is arranged below the upstream side of the conveyor belt portion 12.

The low-energy image correction unit 34 is a part that amplifies and corrects the low-energy image data generated by the low-energy detector 32. The low-energy image correction unit 34 includes an amplifier 34a for amplifying low-energy image data, an A/D conversion unit 34b for A/D conversion of the low-energy image data amplified by the amplifier 34a, and for A/D conversion The correction circuit 34c for performing specific correction processing on the low-energy image data converted by the portion 34b, and the output interface 34d for outputting the image data corrected by the correction circuit 34c to the outside.

The high-energy image acquisition unit 40 includes a high-energy detector (second detector) 42 and a high-energy image correction unit 44.

The high-energy detector 42 detects X-rays in the high-energy range (second energy range) of the object S from the X-rays irradiated by the X-ray irradiator 20, and generates high-energy image data (second radiation image data) ). The high-energy detector 42 is composed of, for example, a linear linear sensor having a length equal to or greater than the width of the object S, and the X-ray detection surface is opposed to the X-ray irradiator 20, perpendicular to the conveying direction A The method is arranged below the downstream side of the conveyor belt portion 12. Moreover, the low-energy range detected by the low-energy detector 32 and the high-energy range detected by the high-energy detector 42 are not clearly distinguishable, and the energy ranges overlap to some extent.

The high-energy image correction unit 44 is a part that amplifies and corrects the high-energy image data generated by the high-energy detector 42. The high-energy image correction unit 44 includes: an amplifier 44a for amplifying high-energy image data, an A/D conversion unit 44b for A/D conversion of the high-energy image data amplified by the amplifier 44a, and for A/D conversion The high-energy image data converted by the section 44b is subjected to a correction circuit 44c for specific correction processing, and an output interface 44d for outputting the image data corrected by the correction circuit 44c to the outside.

Here, the low-energy detector 32 and the high-energy detector 42 will be described in detail. As shown in Figs. 1 and 3, the low-energy detector 32 is a linear sensor with a perception width of LW along the conveying direction A. In addition, the high-energy detector 42 is a linear sensor whose sensing width along the conveying direction A is HW. The perceived width LW and the perceived width HW are the same width in this embodiment, for example, 0.8 mm. In addition, the low-energy detector 32 having such a sensing width LW and the high-energy detector 42 having a sensing width HW are clamped along the conveying direction A, that is, the width direction of each detector as a linear sensor has a non-sensing bandwidth NW The non-sensing zone (specific zone) 82 is arranged side by side and fixed on the base 84 to form a dual-energy sensor 86 as a semiconductor detector.

The dual-energy sensor 86 is set to be the distance between the two detectors 32 and 42 in order to minimize the parallax between the low-energy image and the high-energy image (the difference between the X-ray incident path from the X-ray source) Be as narrow as possible. Therefore, the insensitivity bandwidth NW of the insensitivity zone 82 is set as narrow as possible to the minimum thickness that the electrons of the respective detectors 32 and 42 do not flow into other detectors. Such an insensitivity bandwidth NW in this embodiment is, for example, 0.4 mm, which is narrower than the sensing widths LW and HW (0.8 mm) of the respective detectors 32 and 42.

In addition, as the low-energy detector 32 and the high-energy detector 42 constituting the dual-energy sensor 86, for example, a filter for low-energy cut-off is arranged on the high-energy sensor and has an energy discrimination function. In addition, a scintillator that converts X-rays in the low energy range into visible light or a scintillator that converts X-rays in the high energy range into visible light can also be used, so that the two detectors 32 and 42 have different wavelength sensitivities and can detect different energies. scope. In addition, filters can also be arranged on scintillators with different wavelength sensitivities. In addition, it can also be one with energy discrimination function based on direct conversion methods such as CdTe (cadmium telluride).

The timing control unit 50 controls the X-ray detection timing of the low-energy detector 32 and the X-ray detection timing of the high-energy detector 42. The timing control unit 50 outputs to the low-energy detector 32 a control pulse for the low-energy sensor with a specific period as shown in FIG. 7(a). In addition, the timing control unit 50 outputs the high-energy sense of a pulse of the same cycle as the control pulse for the low-energy sensor by a specific time T (hereinafter referred to as "delay time T") for the high-energy detector 42 The control pulse signal for the detector. When such control pulses are input, the detectors 32 and 42 output the transmitted X-rays received by one cycle unit of each control pulse as image data at the end of each cycle.

The delay time T, when the control pulse signal of a specific period as shown in FIG. 5 is input to the low-energy detector 32 and the high-energy detector 42 at the same time, is equivalent to the low-energy image detected and generated by the low-energy detector 32 The degree of image deviation between the image data and the high-energy image data detected and generated by the high-energy detector 42. That is, the delay time T is an adjustment time determined based on the insensitivity bandwidth NW of the insensitivity region 82 of the dual energy sensor 86 and the speed of the object S passing through the insensitivity region 82 (ie, the conveying speed M).

When the timing control unit 50 generates a control pulse signal including the delay time T, it uses a PLL (Phase Locked Loop) or the like to generate the high-frequency signal for timing control shown in FIG. 7(b). As such a high-frequency signal, for example, in the energy detector 32, 42 and so on, the pixel clock required for sensor driving is driven at about 200kHz, if it is about 100 times the high frequency signal above 20MHz, it can be used. Perform fine control. When the pixel clock driven by the sensor is about 1MHz, fine control can be performed if the same signal above 100MHz is used. The higher the frequency of the high-frequency signal, the more flexibly it can respond to changes in the conveying speed M or the pixel clock, and can be finely controlled. Also, instead of the PLL, a high-frequency oscillator for the delay signal can be used to generate the delay control pulse signal.

The timing control unit 50 generates a control pulse signal including a delay time T from a high-frequency signal generated using such a PLL or the like. Then, the timing control unit 50 controls the timing of detecting transmitted X-rays by the low-energy detector 32 or the high-energy detector 42 based on the delay time T, so that the low-energy image data and the high-energy image data correspond to each other, reducing Image deviation.

The timing calculation unit 60 calculates the delay time T used by the timing control unit 50 as the detection timing. The timing calculation unit 60 calculates the delay based on the insensitivity bandwidth NW of the insensitivity region 82 of the dual energy sensor 86 and the speed of the object S passing through the insensitivity region 82 (that is, the conveying speed M) by the following formula (1) Time T. In addition, for ease of explanation in this embodiment, although the FOD (Focus Object Distance) shown in FIG. 2 and the FDD (Focus Detector Distance: The distance between the line source sensors is the same, and there is no magnification of the X-ray transmission image (ie, the magnification R is 1) as an example for description, but the magnification R is not limited to this.

T=NW/M...(1)

By formula (1), the delay time T of the detection timing of the high-energy detector 42 relative to the detection timing of the low-energy detector 32 can be calculated. In addition, the timing calculation unit 60 outputs the calculated delay time T to the timing control unit 50 as the detection timing. In addition, the insensitive bandwidth NW and the conveying speed M are input to the timing calculation unit 60 via an input unit or the like.

The image processing device 70 performs arithmetic processing to obtain the difference data between the low-energy image data detected and generated by the low-energy detector 32 and the high-energy image data detected and generated by the high-energy detector 42, and generates it as a composite A device for image energy subtraction and visualization. The detection timing of the two energy image data input to the image processing device 70 is controlled by the timing control unit 50 to make the image data correspond to each other. The image processing device 70 displays the energy subtraction display output generated by the arithmetic processing on a display or the like. With this output display, foreign objects and the like contained in the object S can be visually confirmed. In addition, it is also possible not to output the display energy subtraction imaging, but only to output the data, and to directly detect the foreign objects contained in the object S from the image data through the detection processing on the image data.

Here, the method and function of calculating the delay time T of the detection timing used by the timing control unit 50 are to obtain the transmitted X-ray image of the object S (refer to FIG. 4), and to detect the foreign object O contained in the object S The situation is explained as an example. The object S used in the description assumes that the length along the conveying direction A is 4.0mm, and the foreign object O (length OW is 0.6mm) included in a specific position. The sensing width LW and HW of each detector 32 and 42 are 0.8mm, which is to obtain the overall shape of the object S with a length of 4.0mm without being geometrically reduced. That is, the detection width of 0.8mm is used to inspect the length of 0.8mm or less For transmitted X-ray images, more than 5 segmented image data are required respectively. In addition, the conveying speed of the belt conveyor 10 is 0.8 mm/ms (48 m/min). In addition, for ease of explanation, the thickness of the object S is so thin that no blur is caused by the thickness. Also, as mentioned above, the FOD shown in Figure 2 is equal to the FDD, and the X-ray transmission image is not magnified (magnification R is 1).

First, as a comparative example, a case where a radiographic image of the object S is acquired without using the delay time T of the detection timing will be described with reference to FIGS. 5 and 6. In this case, in order to obtain an X-ray image of the object S conveyed in the conveying direction A at a conveying speed of 0.8 mm/ms, the timing control unit 50, as shown in FIG. 5, divides the low-energy detector 32 and the high-energy detector 42 The control pulses of the same period with the same detection timing are output to the low-energy detector 32 and the high-energy detector 42 at the same time, and each of the detectors 32 and 42 obtains divided image data of every 0.8 mm.

The low-energy output output by the pixel of the low-energy detector 32 corresponding to the line P of FIG. 6(a) is shown in FIG. 6(d). Similarly, the high-energy output from the pixel of the high-energy detector 42 corresponding to the line p in FIG. 6(a) is shown in FIG. 6(e). When the first division range S1 (the first 0.8mm part) located in front of the object S passes through the upper part of the detection surface as the imaging area of the low-energy detector 32, the low-energy detector 32 is One division range S1 is captured, as shown in FIG. 6(b), and first division image data S1 is generated. After that, the object S moves at a transport speed of 0.8 mm/ms. After 1 millisecond, the 0.4 mm-equivalent part of the front end of the object S is located within the imaging area of the high-energy detector 42 in the first division range S1 of the object S The upper part of the detection surface, and the remaining part equivalent to 0.4mm is located on the upper part of the non-sensitive zone 82. In this comparative example, since the X-ray detection of the two energy detectors 32 and 42 is controlled by the control pulses of the same timing, as described above, in the state where a part of the object S is located above the non-sensitive zone 82, high-energy detection The device 42 generates the first division range S1 (the first division image data S1_L) The first segmented image data S1_H. In addition, the high-energy detector 42 generates the first divided image data S1_HAt the same time, the low-energy detector 32 generates segmented image data S2 of the second segmented range S following the first segmented range S1_L。

The first segmented image data S1 generated by the low-energy detector 32_L, And the first segmented image data S1 generated by the high-energy detector 42_HIn the meantime, there is a deviation based on the insensitivity bandwidth NW of the insensitivity zone 82 and the moving speed of the object S in the insensitivity zone (that is, the conveying speed M). In addition, the low-energy detector 32 and the high-energy detector 42 controlled by the control pulse signals output at the same period at the same time continuously detect the transmitted X-rays while maintaining the deviation, and generate the remaining segmented image data. As a result, the low-energy detector 32 that detects the transmitted X-rays from the object S in the low-energy range generates the segmented image data for the low-energy image as shown in FIG. 6(b) (S1_L, S2_L, S3_L, S4_L, S5_LOf 5 segmented image data). On the other hand, the high-energy detector 42 that detects the transmitted X-rays from the object S in the high-energy range generates the segmented image data for the high-energy image as shown in FIG. 6(c) (S1_H, S2_H, S3_H, S4_H, S5_H, S6_HOf the 6 segmented image data).

Here, after comparing the divided image data shown in Fig. 6(b) with the divided image data shown in Fig. 6(c), due to the deviation of the insensitive bandwidth NW and the conveying speed M, the target object cannot be obtained. S is the correspondence between the two segmented image data on the basis. Therefore, for example, the low-energy image generated by the low-energy detector 32 is the segmented image data S4 where the data containing the most foreign matter O part is included._LIn contrast to this, the high-energy image generated by the high-energy detector 42, as shown in FIG. 6(c), spans the segmented image data S4_HWith S5_HThe 2 segmented image data. Moreover, the low energy output corresponding to the low energy image, as shown in Figure 6(d), only corresponds to the segmented image S4_LA pixel pitch causes the detection value to change significantly, showing the location of the foreign object O, which corresponds to the high-energy output of the high-energy image, as shown in Figure 6(e), which corresponds to the segmented image data S4_HWith S5_HThe 2 pixel pitch causes the detection value to slightly change (for example, the detection value for low energy output changes about half of the time), which roughly shows the location of the foreign matter O. As a result, the change in the detection value and the amount of change are different in the two energy outputs.

When the image processing device 70 wants to obtain a subtraction image based on the change of the detection value and the detection value data (refer to FIG. 6(d) and (e)) based on the change of the detection value, the change of the detection value caused by the foreign object O The position and the amount of change become unclear, and it is impossible to obtain a high-precision subtraction display of the position of the foreign object O of the object S. In addition, since the divided image data corresponding to the detection value data are respectively different, the beginning of the brightness of each edge part shown in FIG. 6(f) is also not clear. As a result, it is more difficult to obtain a high-precision subtraction display of the position of the foreign object O of the object S. In this way, if the detection timing of the low-energy detector 32 and the detection timing of the high-energy detector 42 are not controlled with high precision, the accuracy of foreign object detection may decrease due to the aforementioned deviation or blur.

Hereinafter, in order to prevent the occurrence of such deviation or blurring, for the case where the low-energy image and the high-energy image of the object S are corresponding to the low-energy image and the high-energy image of the object S are obtained by using the delay time T of the detection timing, Figure 7 and Figure are used. 8 to explain.

In this case, in order to obtain an X-ray image of the object S conveyed in the conveying direction A at a conveying speed of 0.8 mm/ms, the timing control unit 50, as shown in FIG. The detection timing of the detector 32 is delayed by a control pulse of the same period for a specific time T, and is output to the low-energy detector 32 and the high-energy detector 42, and each detector 32, 42 obtains divided image data every 0.8 mm.

That is, when the first division range S1 (the first 0.8 mm portion) in front of the object S passes through the upper part of the detection surface that is the imaging area of the low-energy detector 32, the low-energy detector 32 images the object S in the low-energy range The first division range S1, as shown in FIG. 8(b), first generates the first division image data S1_L. After that, the object S moves at a transport speed of 0.8mm/ms. After 1 millisecond, the 0.4mm-equivalent part of the front end of the first division range S1 of the object S is located as the imaging area of the high-energy detector 42 for detection On the upper part of the face, the remaining part equivalent to 0.4mm is located on the upper part of the non-sensitive zone 82. In the present embodiment using the delay time T, the object S is moved for another 0.4 mm to delay the X-ray of the high-energy detector 42 so that the specific division position in front of the object S is not located above the non-sensitive zone 82 Detection. The delay time T is 0.5 milliseconds calculated from equation (1) in the aforementioned conditions.

The high-energy detector 42 uses the control pulse signal for the high-energy sensor with a delay time T of 0.5 milliseconds, when the first division range S1 of the object S exceeds the non-sensing zone 82, that is, the first division range of the object S When all S1 reaches the upper part of the detection surface of the high-energy detector 42, the first division image data S1 corresponding to the first division range S1 of the object S is obtained_H. In addition, the first divided image data S1 is generated by the high-energy detector 42_HBefore (before the delay time T has elapsed), the low-energy detector 32 generates the first divided image data S1_LThe second division image data S2_L。

The first segmented image data S1 generated by the low-energy detector 32_L, And the first segmented image data S1 generated by the high-energy detector 42_HBetween them, there is no deviation based on the insensitive bandwidth NW of the insensitive zone 82 and the moving speed of the object S in the insensitive zone 82 (that is, the conveying speed M), as shown in Figs. 8(b) and (c). Corresponding to data. Also, consider the low-energy detector 32 and the high-energy detector 42 controlled by the control pulse signal output in the same cycle based on the delay time T of the insensitive bandwidth NW, etc., and continuously detect the transmitted X-rays in a state corresponding to the two image data, and generate The rest of the segmented image data. As a result, the low-energy detector 32 that detects the transmitted X-rays from the object S in the low-energy range generates the segmented image data for the low-energy image as shown in FIG. 8(b) (S1_L, S2_L, S3_L, S4_L, S5_L(5 segmented image data), the high-energy detector 42 that detects the transmitted X-rays from the object S in the high-energy range to generate the segmented image for the high-energy image as shown in Figure 8(c) Information (S1_H, S2_H, S3_H, S4_H, S5_HOf 5 segmented image data). In addition, the two image data respectively correspond to the image range of the object S.

Here, after comparing the divided image data shown in Fig. 8(b) with the divided image data shown in Fig. 8(c), due to the delay time T based on the insensitive bandwidth NW and the conveying speed M, the target The object S is the correspondence between the two segmented image data on the basis. Therefore, for example, where the data containing the most foreign matter O part, the low-energy image generated by the low-energy detector 32 is used as the segmented image data S4_LOne of the image data, the low-energy image produced by the high-energy detector 42 is also the segmented image data S4_HOf 1 image data. Also, the low-energy output corresponding to the low-energy image, as shown in Figure 8(d), only corresponds to the segmented image S4_LOne pixel pitch causes the detection value to change significantly, showing the location of the foreign matter O, and corresponding to the high energy output of the high energy image, as shown in Figure 8(e), which only corresponds to the segmented image data S4_HOne pixel pitch causes the detection value to change significantly, indicating the location of the foreign matter O. As a result, the change in the detection value and the amount of change are consistent with the two energy outputs. In addition, the foreign matter O does not need to be included in one divided image, as long as the divided image containing the foreign matter O of the low-energy image is consistent with the divided image containing the foreign matter O of the high-energy image.

When the image processing device 70 wants to obtain a subtraction image based on the change in the detection value and the detection value data (refer to FIG. 8(d) and (e)) that is consistent with the change in the detection value, the change in the detection value caused by the foreign object O The position and the amount of change are clear, and the position of the foreign object O of the object S can be displayed with high-precision subtraction imaging. In addition, since the divided image data corresponding to the detection value data correspond to each other, the beginning of the brightness of each edge portion shown in FIG. 8(f) is also clear. As a result, it is possible to obtain a subtracted image showing the position of the foreign object O of the object S with higher accuracy. In this way, the detection timing of the low-energy detector 32 and the detection timing of the high-energy detector 42 are controlled with high precision by the delay time T based on the non-inductive bandwidth NW and the conveying speed M, thereby preventing the deviation due to the aforementioned Or blurring causes the accuracy of foreign body detection to decrease, and foreign body detection can be carried out with high precision.

As mentioned above, in the X-ray image acquisition system 1, the timing control unit 50 uses the low-energy image data generated by the low-energy detector 32 and the high-energy image data generated by the high-energy detector 42 to correspond to each other. The method is based on the non-sensing bandwidth NW of the non-sensing zone 82 and the conveying speed M, and the control is performed so as to delay the detection timing of the high-energy detector 42 at least. Thereby, by adjusting the detection timing of the high-energy detector 42 that has a deviation (delay, etc.) relative to the detection timing of the low-energy detector 32 by the presence of the non-sensing zone 82, the low-energy image generated by the low-energy detector 32 is adjusted The image data and the high-energy image data generated by the high-energy detector 42 correspond to each other. In addition, in the subtraction image obtained from the two energy image data corresponding to each other, the change in the detection value of the foreign matter becomes clear and the unclear edge portion is reduced. As a result, the detection accuracy of foreign objects O and the like included in the object S can be improved.

In addition, in the foregoing embodiment, the timing calculation unit 60 is provided for calculating the detection timing based on the insensitivity bandwidth NW and the conveying speed M. The timing control section 50 uses the detection timing calculated by the timing calculation section 60 to control the detection timing of the low-energy detector, etc., so as to generate a subtraction image with reduced unclear edges.

The low-energy detector 32 is a linear sensor that generates low-energy image data from continuous segmented image data, and the high-energy detector 42 is a linear sensor that generates high-energy image data from continuous segmented image data. , The timing control unit 50 makes the detection range of the object S displayed by the segmented image data formed by the linear sensor of the low-energy detector 32 and the segmented image formed by the linear sensor of the high-energy detector 42 The way that the detection range of the object S shown in the data is consistent is based on at least the detection timing of the linear sensor of the high-energy detector 42 to delay control based on the non-sensing bandwidth NW and the conveying speed M. By delaying the detection timing of the linear sensor of the high-energy detector 42 in such a way that the detection range of the object S represented by the segmented image data is consistent, the detection of foreign objects can be displayed in the subtraction imaging The change in value is clear and the unclear edge is reduced.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the foregoing embodiments, and various modifications can be made. For example, in the foregoing embodiment, although the FOD and FDD shown in FIG. 2 are equal, and the transmitted X-ray image is not magnified, the present invention can also be applied to a situation where FOD and FDD are not equal to cause magnification. For example, in the case of FOD:FDD=1:2, the magnification R is 2 times, and the X-ray transmission image is also magnified by 2 times. For example, if the transport speed M is 0.4 mm/ms, the images on the detectors 32 and 42 are projected at a speed equal to 0.8 mm/ms. Considering such a magnification, the delay time T is calculated using the following formula (2) instead of the formula (1).

T=NW/(M×R)...(2)

In addition, the magnification rate R is input to the timing calculation unit 60 from a memory device (not shown) or the like of the X-ray image acquisition system 1.

In addition, in the foregoing embodiment, although the object S is described as having almost no thickness, the present invention can also be applied to a case where the object S has a specific thickness as shown in FIG. 9. In this case, the FOD is calculated based on the height of the bottom surface portion of the object S to obtain the magnification rate R, and the delay time T is calculated by equation (2) and the like. In addition, the object S is transported by the belt conveyor 10 in the same manner as in the foregoing embodiment. First, as shown in FIG. Low-energy image data. After that, the object S is moved in the conveying direction A according to the delay time T. As shown in FIG. 9(b), the high-energy detector 42 detects the high-energy image of the area R2 of the object S to generate high-energy image data . The region R1 and the region R2 are roughly the same as the irradiation bottoms R1a and R2a under the figure of the object S. The low-energy image in the region R1 and the high-energy image in the region R2, as shown in Figure 10, contain the equivalent X-ray transmission data of part of the shared area R3. The larger the common area R3 is, the smaller the deviation between the two energy images is, and the detection accuracy of the foreign matter O contained in the object S can be improved.

As such a case where the object S has a thickness, for example, the thickness of the object S is 100 mm, the distance between the X-ray irradiator 20 and the respective detectors 32 and 42 is 600 mm, and the detectors 32 and 42 and the object S (below) The distance between the X-ray irradiator 20 and the object S (top) is 490mm, the sensing width LW and HW of each detector 32 and 42 are 0.8mm, and the non-sensing bandwidth NW of the non-sensing zone 82 is 0.4mm. The situation is explained. In addition, the X-ray irradiator 20 is arranged so as to be located above the central part of the non-sensitive area 82 between the two detectors 32 and 42. In this case, the transmitted X-ray with a perception width of 0.8mm is irradiated, and the position close to 10mm from the detectors 32, 42 to the X-ray irradiator 20 side (irradiation bottom R1a, R2a) is approximately 0.787mm wide, from the detector 32 , 42 is close to 110mm from the X-ray irradiator 20 side (irradiated upper surface R1b, R2b) is about 0.653mm wide. In addition, by making the irradiation lower surface R1a and R2a of the width of about 0.787 mm coincide, the overlap of the irradiation range of the low-energy side and the high-energy side (shared area R3) is about 70%. In addition, as shown in FIG. 11, when the irradiation lower surface R1a of the region R1 and the irradiation lower surface R2a of the region R2 are not completely consistent (for example, the 0.2mm deviation in the aforementioned example), the common part R3 is greater than that shown in FIG. In rare cases, the overlap of the irradiation range on the low-energy side and the high-energy side is, for example, about 40%. In this case, the deviation between the two energy images may increase, and the detection accuracy of the foreign objects included in the object S may decrease.

In addition, in the foregoing embodiment, although the output interface 34d of the low-energy image correction unit 34 and the output interface 44d of the high-energy image correction unit 44 respectively output the low-energy image and the high-energy image to the image processing device 70, but as shown in FIG. 12, the output of the two energy images can also be output to the image processing device 70 from the common output interface 36a. In addition, in the foregoing embodiment, although the low-energy detector 32 is provided on the upstream side of the conveying direction A and the high-energy detector 42 is provided on the downstream side, the high-energy detector may be provided on the upstream side of the conveying direction A. 42. A low-energy detector 32 is provided on the downstream side. In addition, in the foregoing embodiment, although the detection timing of the high-energy detector 42 is delayed by the specific time T, the detection timing of the low-energy detector 32 may be advanced by the specific time T, or the low-energy detector 32 may be earlier. The detection timing and the detection timing of the high-energy detector 42 are delayed so that the two detection timings differ by a specific time T. In addition, in the foregoing embodiment, although the detection timing of two ranges of low energy and high energy is controlled, it is undoubtedly possible to control the detection timing of more than three ranges.

In addition, in the foregoing embodiment, although the case where the low-energy wavelength range and the high-energy wavelength range overlap to some extent has been described, the low-energy wavelength range and the high-energy wavelength range may not overlap locally. In addition, in the foregoing embodiment, although an example in which two linear sensors are provided on one sheet is described, the two detectors 32 and 42 do not necessarily have to be provided on one sheet, and two may be arranged in parallel. An independent detector increases the width of the non-sensing zone. In addition, although a point light source is used as the X-ray source in this embodiment, it is of course possible to use a linear X-ray source. In addition, in the foregoing embodiment, although the X-ray image acquisition system 1 is used for the detection of foreign objects O from the object S, the X-ray image acquisition system 1 may also be used for luggage inspection or the like.

The first detector is the first line sensor that generates the first radiographic image data from the continuous segmented image data, and the second detector is the second line of the second radiographic image data from the continuous segmented image data. Sensing sensor, the timing control unit better to make the detection range of the object of the segmented image data formed by the first line sensor and the detection of the object of the segmented image data formed by the second line sensor In the method of consistent range, at least the detection timing of the second line sensor is delayed based on the width of the specific area. By delaying and controlling the detection timing of the second linear detector in such a way that the detection range of the object shown in the segmented image data is the same, the unclear edge portion in the subtraction image can be reliably reduced.

The width of the specific area is the width along the width direction of the first detector or the second detector, and is preferably smaller than the radiation sensing width of the first detector or the second detector. Due to the narrow width of the specific area, it can prevent the geometric blur of the subtraction display based on the radiographic image generated by the first detector or the second detector.

It may also be provided with a composite image generating unit that controls and synthesizes the radiographic image data generated by the first detector and the radiographic image data generated by the second detector so that the timing control unit corresponds to each other to generate a composite image. With such a composite image generating unit, a subtracted image with reduced unclear edges can be obtained.

The timing control unit is preferably based on the distance between the radiation irradiator and the object, and the distance between the radiation irradiator and the first detector or the second detector, in addition to the width and transport speed of the specific area mentioned above. The magnification ratio of the ratio controls at least the detection timing of the second detector. By performing control including magnification, it is possible to perform inspection of foreign objects contained in the object or carry-on luggage inspection with higher accuracy.

<b>Industrial availability</b>

The present invention uses a radiation detection device, a radiation image acquisition system, a radiation inspection system, and a radiation detection method for use purposes, and can improve the detection accuracy of foreign objects included in an object.

<p>1. . . X-ray image acquisition system</p><p>10. . . Belt conveyor</p><p>20. . . X-ray irradiator</p><p>30. . . Low-energy image acquisition department</p><p>32. . . Low energy detector</p><p>34. . . Low Energy Image Correction Department</p><p>40. . . High-energy image acquisition department</p><p>42. . . High energy detector</p><p>44. . . High Energy Image Correction Department</p><p>50. . . Timing Control Department</p><p>60. . . Timing calculation unit</p><p>70. . . Image processing device</p><p>80. . . Dual image acquisition device</p><p>82. . . Uninsensitive zone</p><p>84. . . Pedestal</p><p>86. . . Dual energy sensor</p><p>A. . . Transport direction</p><p>M. . . Conveying speed</p><p>O. . . foreign body</p><p>R. . . magnification</p><p>S. . . Object</p><p>T. . . delay</p><p>HW, LW. . . Perception width</p><p>NW. . . No sense of bandwidth</p><p>R1, R2. . . Irradiated area</p><p>R3. . . Shared area</p>

Fig. 1 is a perspective view of the X-ray image acquisition system of this embodiment.

Fig. 2 is a schematic configuration diagram of the X-ray image acquisition system of this embodiment.

Figure 3 is a side view of the dual energy sensor of this embodiment.

Fig. 4 is a diagram showing an object containing foreign objects.

Fig. 5 is a diagram showing the control pulse signals of each detector of the X-ray image acquisition system of the comparative example.

Fig. 6(a)~(f) are diagrams showing the images of each energy sensor and the output of each energy generated by the X-ray image acquisition system of the comparative example.

Fig. 7 (a) is a diagram showing the control pulse signal of each detector of the X-ray image acquisition system of this embodiment, and (b) is a diagram showing the high-frequency signal used to generate the control pulse signal.

8(a)~(f) are diagrams showing the images of each energy sensor and the output of each energy generated by the X-ray image acquisition system of this embodiment.

Fig. 9 is a diagram showing the irradiation area when the object S has a thickness, (a) is a diagram showing the area detected by a low-energy detector, and (b) is a diagram showing the area detected by a high-energy detector.

FIG. 10 is a diagram showing a situation where the detection areas shown in FIG. 9 are consistent.

FIG. 11 is a diagram showing a situation where the detection areas shown in FIG. 9 are not consistent.

Fig. 12 is a diagram showing another embodiment of the energy image correction unit.