Article inspection device

Abstract

To provide an article inspection device with which it is possible to reliably converge a temporal change of X-ray detection characteristic in a necessary and sufficient time, and to achieve sufficient inspection accuracy while using an X-ray detector of direct conversion type.SOLUTION: Provided is an article inspection device comprising: an image data generation unit 41 for generating image data Di on the basis of the output Lx of an X-ray detector 23, and an inspection control unit 40A capable of switching an X-ray source 21 and the X-ray detector 23 between an operating state and a non-operating state for starting or stopping, and executing inspection control for inspecting an article P by using the image data Di and determination criteria during the operating state. The inspection control unit 40A includes: steady state detection means 49 for detecting the steady state of outputs of the X-ray source 21 and the X-ray detector 23 after these have started operating; and a storage control unit 42 for storing the X-ray image data Di generated by the image data generation unit 41 on the basis of the output of sensor element on condition that a steady state is detected, in an image memory 42a which is usable for inspection control.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an article inspection apparatus, and more particularly to an article inspection apparatus that irradiates an object to be inspected with X-rays and generates X-ray image data based on the scan output from an X-ray detector. [Background technology]

[0002] In an object inspection device that uses X-rays (electromagnetic waves that pass through an object), generally, X-rays are irradiated onto the object to be inspected within the inspection area, and the X-rays that pass through the inspection area are incident on an X-ray detector and detected, causing the X-ray detector to output an image detection signal, and image data of the X-ray transmission image is generated based on this output signal.

[0003] Such object inspection devices often use X-ray detectors with a flat array of sensor elements. In such cases, even if the thickness of the conveyor belt or the object being inspected is constant, the amount of X-rays detected by each sensor element tends to decrease at both ends of the X-ray detector depending on the material penetration distance and incident angle of the X-rays incident on each sensor element of the X-ray detector.

[0004] Therefore, conventionally, before inspecting an object, a calibration process is performed in which the sensitivity of the output level of the X-ray detector is corrected so that the image density level of the inspection image based on the output of each element of the X-ray detector becomes a constant value, thereby suppressing variations in the inspection image relative to the reference image density and suppressing blurring and unnecessary gradations in the X-ray transmission image.

[0005] Known examples of this type of item inspection device include those that set appropriate correction values ​​so that the output level of each element of the X-ray detector remains constant when the object to be inspected is not being transported or during the transport section, and then perform sensitivity correction of the output level of the X-ray detector before inspection based on these correction values ​​(see, for example, Patent Documents 1 and 2).

[0006] In recent years, X-ray detectors that use a direct conversion method to convert incident X-rays into an output signal proportional to the dose have become increasingly popular. Unlike conventional indirect conversion methods, these direct conversion X-ray detectors do not use a scintillator, but instead allow X-rays to be incident on and absorbed by an X-ray sensor element made of a compound semiconductor, generating an electric charge proportional to the amount of energy, thereby enabling the generation of an output signal with high detection accuracy.

[0007] An example of an object inspection device equipped with this type of X-ray detector is one that generates calibration data based on the output signals of multiple sensor elements of the X-ray detector when a calibration member is interposed between the conveying belt surface and the X-ray irradiation unit, and the output signals of multiple sensor elements of the X-ray detector when no calibration member is interposed, so that calibration conditions suitable for the object to be inspected can be set in a timely manner from the image data of the corresponding X-ray images, thereby improving the calibration accuracy of the output signals of the X-ray detector (see, for example, Patent Document 3).

[0008] Alternatively, there is also known an X-ray detector that provides an incident condition changing means for changing the X-ray incident conditions for the multiple sensor elements of the X-ray detector to two or more types, and creates the necessary calibration data for each incident condition so that the density of the image generated based on the output signals from the multiple sensor elements of the X-ray detector is uniform (see, for example, Patent Document 4). [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-91016 [Patent Document 2] Japanese Patent Application Laid-Open No. 2006-300888 [Patent Document 3] Japanese Patent Publication No. 2022-109774 [Patent Document 4] JP 2019-12011 A Summary of the Invention [Problem to be solved by the invention]

[0010] In conventional article inspection devices such as those described above, the quality of the X-rays emitted from the anode portion of the X-ray tube varies depending on the longitudinal position of the X-ray tube due to the so-called heel effect, and the dose and spectrum of the X-rays emitted from the X-ray source change over time due to factors such as drift in the focal position caused by thermal expansion of the anode portion of the X-ray tube.As a result, there is concern that the accuracy of article inspection during operation of the article inspection device, such as the accuracy of foreign object detection, will decrease based on image data of the article being inspected.

[0011] In response to this, it is possible to set a predetermined waiting time after the start of operation of the X-ray source, and start the inspection after the fluctuations in the detection signal of the X-ray detector immediately before the inspection have converged as much as possible.

[0012] However, in the case of a direct conversion type X-ray detector, the high bias voltage applied to the semiconductor layer that converts incident X-rays into a signal changes over time, so even if the amount of X-rays from the X-ray source does not change over time, the imaging data based on the output signal of the X-ray detector may change.

[0013] Furthermore, because direct conversion X-ray detectors are constructed by joining the required number of sensor element modules in the scan line direction or by arranging multiple sensor element modules in multiple rows so that the scan lines are parallel, brightness gaps occur due to differences in the X-ray incidence conditions on adjacent sensor elements in adjacent parts of the sensor element modules, combined with differences in readout circuit characteristics, and differences occur in the detection characteristics of the X-ray detector and their changes over time depending on the combination of multiple sensor element modules.For this reason, simply setting a fixed fluctuation convergence time has not made it easy to sufficiently suppress output fluctuations in the X-ray detector while reducing the waiting time before the start of inspection and ensuring the required inspection accuracy.

[0014] Therefore, the present invention aims to provide an object inspection device that can reliably converge the detection characteristics of an X-ray detector and the changes in those characteristics over time in a sufficient amount of time, thereby achieving sufficient inspection accuracy when using a direct conversion X-ray detector. [Means for solving the problem]

[0015] (1) To achieve the above object, an article inspection device according to the present invention includes an X-ray source that irradiates an inspection area into which an object to be inspected is carried with X-rays; an X-ray detector that detects X-rays that pass through the inspection area using a plurality of sensor elements adjacent in a predetermined scanning direction and outputs brightness detection signals corresponding to a plurality of detection positions in the predetermined scanning direction; an image data generation unit that generates X-ray image data corresponding to a distribution of X-ray transmission amounts within the inspection area within a predetermined brightness value range based on the outputs of the plurality of sensor elements of the X-ray detector; and an image data generation unit that is switchable between an operating state in which the X-ray source and the X-ray detector are operated and an operating stop state in which the operation of the X-ray source and the X-ray detector is stopped, and and an inspection control unit that executes inspection control to inspect the object to be inspected using X-ray image data generated by a stable state detection unit and a preset judgment criterion, wherein the inspection control unit has a stable state detection unit that detects a stable state in which the outputs of the X-ray source and the X-ray detector are stable after the X-ray source and the X-ray detector start operating and are in the operating state, and a storage control unit that stores the X-ray image data generated by the image data generation unit based on the outputs of the plurality of sensor elements in a memory that can be used for the inspection control, on the condition that the stable state detection unit has detected the stable state in the outputs of the X-ray source and the X-ray detector.

[0016] With this configuration, in the present invention, the storage control means stores the X-ray image data generated by the image data generation unit based on the outputs of the multiple sensor elements in a memory that can be used for inspection control, on the condition that the stable state of the outputs of the X-ray source and X-ray detector are detected by the stable state detection means after the X-ray source and X-ray detector start operating, putting the device into operation. Therefore, the X-ray image data used for inspection control is data obtained after the X-ray detector fluctuations have converged, and the detection characteristics of the X-ray detector and any changes over time in those characteristics are reliably suppressed for a necessary and sufficient time, thereby achieving the required inspection accuracy of an article inspection device that uses a direct conversion X-ray detector.

[0017] (2) In a preferred embodiment of the present invention, the X-ray detector further comprises a sensitivity correction means for setting a sensitivity correction coefficient for each of the plurality of sensor elements of the X-ray detector so that output signals of the plurality of sensor elements of the X-ray detector are aligned to the maximum luminance of the X-ray image data in a pre-load state where the object to be inspected is not within the inspection area, and the sensitivity correction means can be configured to set the sensitivity correction coefficient for the plurality of sensor elements using luminance values ​​of X-ray image data generated by the image data generation unit based on outputs of the plurality of sensor elements of the X-ray detector.

[0018] In this case, before the object to be inspected is carried into the inspection area, the sensitivity correction means uses the brightness values ​​of the X-ray image data generated by the image data generation unit based on the outputs of the plurality of sensor elements of the X-ray detector to set the sensitivity correction coefficients of each sensor element so that the output signals of the plurality of sensor elements of the X-ray detector are aligned to the maximum brightness (minimum or maximum value of the grayscale image density) of the X-ray image data. Therefore, the brightness detection values ​​of the X-rays that have passed through the object to be inspected in the inspection area and are incident on the plurality of sensor elements of the X-ray detector can be displayed as multi-grayscale image density, and the setting accuracy of the sensitivity correction coefficients is improved.

[0019] (3) In a preferred embodiment of the present invention, the sensitivity correction means executes a first sensitivity correction for setting the sensitivity correction coefficients for the plurality of sensor elements of the X-ray detector during the period from when the X-ray source and the X-ray detector start operating until the stable state of the output of the X-ray detector is detected by the stable state detection means, and a second sensitivity correction for resetting the sensitivity correction coefficients for the plurality of sensor elements of the X-ray detector on the condition that the stable state of the output of the X-ray detector is detected by the stable state detection means, and the memory control means can be configured to store the sensitivity correction coefficients after the second sensitivity correction in a correction coefficient memory that can be used for the inspection control.

[0020] In this case, the sensitivity correction coefficients set for the multiple sensor elements of the X-ray detector in the second sensitivity correction, which is performed after a stable state of the output of the X-ray detector is detected, are stored in a correction coefficient memory that can be used for inspection control, thereby increasing the reliability of the sensitivity correction coefficients.

[0021] (4) In a preferred embodiment of the present invention, the sensitivity correction means may be configured to perform the first sensitivity correction multiple times during an adjustment period after the X-ray source and the X-ray detector start operating and before the inspection control starts, and to perform the second sensitivity correction once after the multiple first sensitivity corrections.

[0022] In this case, the sensitivity correction means performs the first sensitivity correction multiple times during an adjustment period before the start of inspection control, and then performs the second sensitivity correction once. Therefore, for differences in output depending on the positions of the multiple sensor elements that are unrelated to output fluctuations of the X-ray detector, an effective sensitivity correction coefficient can be set in the first of the multiple first sensitivity corrections, and for variations in the luminance detection signals of the multiple sensor elements that are affected by output fluctuations, an accurate sensitivity correction coefficient can be set in the next of the first sensitivity corrections according to the range of such variations. After the output fluctuations have converged, a sensitivity correction coefficient effective for the immediately following inspection control can be determined as a result of the second sensitivity correction.

[0023] (5) In a preferred embodiment of the present invention, the inspection control unit has an inspection condition variable setting means that can change the inspection control conditions in accordance with the type of the object to be inspected while the power is on, and the sensitivity correction means can be configured to, on condition that the inspection control conditions have been changed by the inspection condition variable setting means, perform the first sensitivity correction again during the period from when the X-ray source and the X-ray detector start operating after the condition change until when the inspection control after the condition change starts, under the same power-on state as when the condition change was made.

[0024] In this case, the influence of changes in the output of the X-ray source, etc., can be regarded as being in a stable state during the short period until the start of inspection control after the condition change, regardless of the detection result of the stable state detection means, and the first sensitivity correction can be performed to reset the sensitivity correction coefficient that is effective against drift, etc.

[0025] (6) In a preferred embodiment of the present invention, the sensitivity correction means can be configured to maintain the latest sensitivity correction coefficient set by the second sensitivity correction or the first sensitivity correction from the initial start of operation of the X-ray source and the X-ray detector to the start of the inspection control immediately thereafter, until the end of a period during which the same power-on state and the same operating state continue without the conditions of the inspection control being changed by the inspection condition variable setting means.

[0026] In this case, the influence of changes in the output of the X-ray source, etc., can be considered to be stable during the short period until the interrupted inspection control is resumed, regardless of the detection result of the stable state detection means, and the latest sensitivity correction coefficient can be maintained.

[0027] (7) In a preferred embodiment of the present invention, the stable state detection means may be configured to detect the stable state when it is determined that fluctuations in the average output values ​​of the plurality of sensor elements of the X-ray detector have converged.

[0028] In this case, the sensitivity correction coefficient for inspection control is set after the fluctuations in the average output values ​​of the multiple sensor elements have converged, making it possible to perform sensitivity correction that can effectively correct the variations in the brightness detection signals of the multiple sensor elements.

[0029] (8) In a preferred embodiment of the present invention, the X-ray detector is composed of a plurality of sensor element modules, each having a predetermined number of sensor element groups, and the stable state detection means may detect the stable state when it determines that the fluctuations in inter-module brightness gaps, which are different between the plurality of sensor element modules, have converged in the average output values ​​of the sensor element groups of each sensor element module.

[0030] In this case, the sensitivity correction coefficient for inspection control is set after the fluctuations in the average output values ​​of the multiple sensor elements of the X-ray detector have converged, making it possible to perform sensitivity correction that can effectively correct variations in the average background luminance values ​​between multiple sensor element modules, etc.

[0031] (9) In a preferred embodiment of the present invention, the stable state detection means may be configured to detect the stable state by determining that the stable state has been achieved when a predetermined stabilization time has elapsed since the X-ray source and the X-ray detector started operating.

[0032] In this case, the time taken for fluctuations due to various factors to converge and stabilize can be measured and used, so that the sensitivity correction coefficient for inspection control is set after the fluctuations have converged, making it possible to perform effective sensitivity correction. [Effects of the Invention]

[0033] According to the present invention, it is possible to provide an object inspection device that can reliably converge the detection characteristics of an X-ray detector and the changes in those characteristics over time in a sufficient amount of time, thereby achieving sufficient inspection accuracy when using a direct conversion X-ray detector. [Brief explanation of the drawings]

[0034] [Figure 1] 1 is a schematic configuration diagram of an X-ray inspection type article inspection device according to an embodiment of the present invention. [Figure 2] This is a schematic cross-sectional view of the general configuration of an X-ray detector in an object inspection device according to one embodiment of the present invention, cut at a predetermined transport position of the transport belt after the calibration member has been introduced, showing the arrangement of multiple sensor element modules M1 to Mk and the arrangement of multiple sensor elements e1 to en within any one of the sensor element modules M(i). [Figure 3] 1A is a plan view of an example of a calibration member used in an article inspection device according to an embodiment of the present invention, and FIG. 1B is a side view of the same example of the calibration member. [Figure 4] 1 is a graph showing, by a characteristic curve, the characteristics in which the detection brightness output Lx of each sensor element of an X-ray detector in an object inspection device according to one embodiment of the present invention changes depending on the magnitude of the incident X-ray dose to each sensor element (the magnitude of the X-ray transmittance by an object in the X-ray irradiation path), in which the vertical axis indicates the magnitude of the output Lx of the sensor element and the magnitude of the correction target value Ct, and the horizontal axis indicates the incident X-ray dose of each sensor element or the magnitude of the X-ray transmittance of an object in the X-ray irradiation path. [Figure 5] This graph shows the state before the calibration member is introduced and the first and second states after the introduction, with the detection brightness output Lx of multiple sensor element modules in an item inspection device according to one embodiment of the present invention correlated with the position in the line scanning direction of multiple sensor elements of the multiple sensor element modules. The vertical axis shows the magnitude of the output Lx of the sensor element and the magnitude of the correction target value Ct, and the horizontal axis shows the increasing element number on one side of the line scanning direction of the multiple sensor elements. [Figure 6] 1 is a timing chart of sensitivity correction showing whether or not an operating state in which the X-ray source and X-ray detector are activated from power-on in an article inspection device according to one embodiment of the present invention has started, and whether or not sensitivity correction has been performed. [Figure 7] This is a graph showing the detected brightness output Lx of multiple sensor element modules relative to the line scanning direction position of multiple sensor elements of the multiple sensor element modules when a sensitivity correction equivalent to a zero point correction of the X-ray detector is performed once in an item inspection device according to one embodiment of the present invention before the calibration member is introduced, where the vertical axis indicates the magnitude of the output Lx of the sensor element, and the horizontal axis indicates the arrangement position of each of the multiple sensor elements in the line scanning direction while dividing the multiple sensor element modules. [Figure 8]This graph shows the time change in the average brightness value AvD(i) for each sensor element module of the X-ray detector in the pre-load state in an item inspection device according to one embodiment of the present invention, based on the output Lx of multiple sensor elements in each sensor element module, with solid lines indicating cases where the value converges to an increasing side and dashed lines indicating cases where the value converges to a decreasing side. The vertical axis indicates the average brightness value AvD(i), and the horizontal axis indicates the time after the X-ray source and X-ray detector start operating. [Figure 9] This is a graph showing the time change in the detection brightness gap gp(i) between adjacent sensor element modules based on the detection brightness output Lx of multiple sensor element modules in a pre-load state in an item inspection device according to one embodiment of the present invention, with solid lines indicating cases where the gap converges to an increasing side and dashed lines indicating cases where the gap converges to a decreasing side, where the vertical axis indicates the absolute value of the brightness gap gp(i) and the horizontal axis indicates the time after the X-ray source and X-ray detector start operating. [Figure 10] 1 is a flowchart illustrating an example of an outline of a processing procedure for inspection control in an article inspection device according to an embodiment of the present invention. [Figure 11] 1 is a flowchart illustrating an outline of a processing procedure of Example 1 regarding sensitivity correction before inspection control in an article inspection device according to an embodiment of the present invention. [Figure 12] 10 is a flowchart illustrating an outline of a processing procedure of Example 2 regarding sensitivity correction before inspection control in an article inspection device according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0035] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0036] 1 to 12 are diagrams for explaining an X-ray inspection type article inspection device according to one embodiment of the present invention, with Fig. 1 showing a schematic configuration of the device and Fig. 2 showing a schematic configuration of the main parts of the X-ray detector. First, the configuration of this embodiment will be described.

[0037] As shown in Figures 1 and 2, the item inspection device 1 of this embodiment comprises a conveying unit 10 that conveys the item P to be inspected, an inspection unit 20 that performs X-ray inspection of the item P while being conveyed, a control unit 40 that controls the conveying unit 10 and the inspection unit 20, and a display and operation unit 50 that is signal-connected to the control unit 40 and is arranged near the inspection unit 20 to allow manual operation input.

[0038] This article inspection device 1 irradiates an article P (inspection object) conveyed by a conveying unit 10 with X-rays using an inspection unit 20 while detecting brightness, generates line image data Di corresponding to the transmitted X-ray dose distribution and image data Dpx of the X-ray image of the article P, and inspects the quality state of the article P based on the image data Dpx. Note that the quality state referred to here refers to whether the article P meets the quality and physical quantities required for a product, such as the presence or absence of contaminants, the presence or absence of missing parts, the pass / fail of the shape, size, and storage state of the contents, and the distribution of density, thickness, volume, or mass. Furthermore, X-rays may be replaced by other electromagnetic waves such as gamma rays.

[0039] The conveying unit 10 is a conveyor that can sequentially convey items P through an inspection area Zx on the conveying belt 11 in a predetermined conveying direction (hereinafter also referred to as conveying direction d1) indicated by arrow d1 in Figure 1, for example, by winding a loop-shaped conveying belt 11 around multiple conveying rollers 12 and 13, and is supported by a housing not shown.

[0040] The inspection unit 20 is composed of an X-ray generator 21 (X-ray source) with an X-ray tube 22 built in, and a line sensor-shaped X-ray detector 23 arranged at a predetermined position in the conveying direction so that X-rays emitted from the X-ray generator 21 and transmitted through the inspection area Zx are incident thereon, and is an imaging unit that can image the item P in the inspection area Zx using X-rays.

[0041] The X-ray generator 21 includes a power supply necessary for driving the X-ray tube 22 as an X-ray source, cooling means for the X-ray tube 22, X-ray shielding means, etc., and is configured to enable the X-ray tube 22 to generate X-rays with a wavelength and intensity according to its tube current and tube voltage.

[0042] The X-ray generator 21 is also configured to irradiate the articles P in the inspection zone Zx on the conveyor belt 11 with, for example, fan-beam-shaped X-rays Xfb that spread in a line scanning direction d2 perpendicular to the conveying direction d1 of the conveyor unit 10 (see FIG. 2) through an X-ray window portion of an enclosure (details of which are not shown). However, the X-ray generator 21 is not limited to an X-ray irradiation direction that passes through the conveyor belt 11, and may be installed in a manner that passes through the articles P on the conveyor belt 11 in a substantially horizontal direction. The X-ray beam may also be deflected.

[0043] The X-rays generated by the X-ray generator 21 include a plurality of different wavelength regions, and the energy of the X-rays needs to be set within a range suitable for inspecting the article P. Here, the tube voltage and tube current applied to the X-ray tube 22 can be variably controlled by the control unit 40. Furthermore, the X-rays emitted from the X-ray generator 21 or detected by the X-ray detector 23 are assumed to have a certain radiation quality (energy, wavelength) specified according to the quality of the article W, but it is also possible to generate so-called dual-energy or multi-energy X-ray images by using a plurality of different types of X-ray radiation qualities.

[0044] 2, the X-ray detection unit 23 includes a plurality of sensor elements e1 to en, each of which receives an X-ray and converts it into an electrical signal, and these sensor elements e1 to en are arranged in a line in adjacent rows in the line scanning direction d2 so that X-rays that have passed through the article P can be incident on the corresponding X-ray irradiation paths. Here, n is a natural number (positive integer) that is sufficiently larger than 1.

[0045] Specifically, the X-ray detection unit 23 has a configuration in which a required number (k in the figure) of sensor element modules M1 to Mk (k is a natural number greater than 1) are joined together and arranged in a row in the scanning line direction, and each of the sensor element modules M1 to Mk has a plurality of sensor elements e1 to en, as exemplified by any one sensor element module M(i) in the figure (hereinafter also referred to as each sensor element module M(i)). Note that the sensor element modules M1 to Mk may be arranged in parallel in a plurality of rows so that a plurality of scanning lines are arranged in parallel.

[0046] As shown in the enlarged partial view at the bottom of Figure 2, each sensor element module M(i) has a direct conversion type semiconductor element 32 in its X-ray conversion section, formed, for example, from a flat layer of cadmium telluride (CdTe), and is provided with opposing electrodes on both sides, one of which serves as a bias electrode 31 and the other of which serves as an arrangement layer 33 of multiple pixel electrodes corresponding to multiple sensor elements e1 to en. When X-rays that have passed through the article P are incident on the semiconductor element 32 of each sensor element module M(i), electrons and holes corresponding to the energy of the incident X-rays (photons) are generated, generating a voltage detection signal between the opposing electrodes 31, 33 corresponding to the incident X-ray dose, and the signal can be output to a readout circuit 34 composed of an ASIC (application-specific integrated circuit) or the like.

[0047] The control unit 40 has a conveyance control function that controls the conveying speed Vc and conveying interval of the articles W by the conveyor belt 11 in the conveying unit 10, and an inspection control function that controls the X-ray irradiation intensity and irradiation period in the inspection unit 20, and controls the X-ray detection cycle and detection period of each article P in the X-ray detector 23 according to the belt width of the conveyor belt 11 and the conveying speed Vc of the articles W. However, since the configuration of the conveyance control function unit is similar to that of a known unit, detailed illustration and description thereof will be omitted.

[0048] The control unit 40 is composed of hardware including, for example, a microcomputer having a CPU, ROM, RAM, and I / O interface (not shown), an auxiliary storage device that readably stores control programs for performing image processing functions, inspection and judgment functions, and their control functions in cooperation with the ROM, and a timer circuit, etc., and the CPU executes predetermined arithmetic processing while exchanging data with the RAM, etc., in accordance with software such as the control programs stored in the ROM, etc., and also executes the control programs.

[0049] (Inspection Control Unit) Specifically, the control unit 40 includes an inspection control unit 40A having control processing functions for X-ray inspection, an image data generation unit 41, an image data storage unit 42, an image processing unit 43, a pass / fail judgment unit 44, and an operating condition setting unit 45.

[0050] The image data generating unit 41 sequentially receives image detection signals (brightness detection signals) Lx from the X-ray detector 23 at predetermined intervals, and generates image data Di of an X-ray image corresponding to the transmission amount distribution of X-rays transmitted through the examination region Zx. For example, the image data generating unit 41 A / D converts the detection brightness outputs Lx (image detection signals) from the plurality of detecting elements e1-en in each sensor element module M(i) of the X-ray detector 23, and performs an operation (hereinafter referred to as line scanning) of writing, for each predetermined unit transport time corresponding to the detecting element size of the X-ray detector 23, data on the cumulative transmission amount within that unit time for all detecting element regions having the number N=n×k of detecting elements (e.g., 256×8), into the image data storage unit 42 as digital data of density levels (brightness) representing, for example, 1024 gradations from 0 to 1023.

[0051] The image data storage unit 42 accumulates and stores the image data Di of the X-ray image from the image data generation unit 41 during a predetermined inspection period corresponding to the length of the item P in the conveying direction, and generates and stores image data of the X-ray transmission image of the item P. This image data storage unit 42 has a data processing program and a working memory area that perform the function of generating image data Dpx of the X-ray photographed image corresponding to the dose distribution of the X-rays that have passed through the item P, based on the detection data Di of the line scan image that is written sequentially while the line scan by the X-ray detector 23 is repeated a predetermined number of times corresponding to the inspection period of the item P, and outputting the image data Dpx to the image processing unit 43 as imaging data of the item P.

[0052] The image processing unit 43 is configured to perform predetermined filter processing (including pre-processing) capable of extracting image features by importing image data of the X-ray transmission image of the article P from the image data storage unit 42, and image analysis processing such as feature measurement for determining the feature amount of the extracted image features. In this image processing unit 43, a predetermined inspection algorithm combining image processing filters, etc. is set and stored in advance in order to perform a predetermined article inspection based on the image data Dpx imported from the image data generation unit 41.

[0053] The image processing filter included in the inspection algorithm of the image processing unit 43 is a processing program for extracting image features required for a predetermined item inspection based on image data Dpx, which is a captured image of the item P. If the inspection algorithm includes a filter for foreign object detection, it may have a feature extraction filter that performs edge detection processing to emphasize the outline of a foreign object in the item P, and may perform differential processing or the like on an area near a pixel of interest to emphasize the edge of the foreign object. Also, the feature measurement of image features executed by the image processing unit 43 is a process of measuring feature quantities required for judgment processing in the pass / fail judgment unit 44 by performing calculations, for example, on shading features, color features, shape features, etc., on an image that has been subjected to necessary pre-processing and image processing on the image data Dpx of the item P imported from the image data generation unit 41.

[0054] The pass / fail judgment unit 44 is configured to perform judgment processing to judge whether or not the item P has a predetermined quality state based on the feature data extracted by the image processing unit 43, such as judgment processing to determine whether or not there is any foreign matter mixed in, whether or not there is a missing part, and whether or not the shape, size, or storage state of the contents are pass / fail. Based on the feature amounts extracted and measured by the image processing unit 43, the pass / fail judgment unit 44 detects characteristic shapes, foreign matter, etc. detected in the item P, and compares the feature amounts such as the area, contour length, and density sum of the detected object with predetermined judgment reference values ​​(hereinafter referred to as predetermined judgment reference) to perform judgment processing to determine whether or not the item P contains a local characteristic shape, etc. corresponding to a foreign matter or a defective part that satisfies the judgment conditions.

[0055] In this way, the item inspection device 1 of this embodiment is configured so that the control unit 40 irradiates the inspection area Zx where the item P is brought in with X-rays Xfb from the X-ray irradiation unit 21 of the inspection unit 20, detects the X-rays that pass through the inspection area Zx with an X-ray detector 23 having multiple sensor elements e1 to en, generates image data Di of the X-ray line image and image data Dpx of the X-ray image of the item P from an image detection signal based on the output Lx of the multiple sensor elements e1 to en, and performs inspection control to inspect the item P using the image data Dpx and the predetermined judgment criteria that have been set in advance.

[0056] (X-ray detector sensor sensitivity correction) The control unit 40 is configured to include an operating condition setting unit 45, a correction coefficient calculation unit 46, and a correction coefficient memory 47 in order to perform a sensitivity correction process for correcting the sensitivity of the X-ray detector 23 and a calibration process (details of which will be described later) for calibrating the image data Di (measurement values) generated by the image data generation unit 41 based on the brightness detection signal Lx from the X-ray detector 23.

[0057] Here, if each of the multiple sensor elements e1 to en in any one of the multiple sensor element modules M1 to Mk, M(i), is designated as each sensor element e(i, j), the image detection signal Lx of the X-ray detector 23 is the output (voltage signal) of N sensor elements output in the order of line scanning from the first sensor element e1 of the sensor element module M1 on the line scanning start side to the last sensor element en of the sensor element module Mk on the line scanning end side, and is quantized by the image data generation unit 41 into N line image data (hereinafter also referred to as N image data Di(i, j)) corresponding to the voltage signals, each of which has a brightness value that is image density information with a predetermined number of gradations.

[0058] As shown in FIG. 4, the output Lx(i, j) of each sensor element e(i, j) constituting the image detection signal Lx (output from N sensor elements) exhibits a change characteristic that increases as the amount of X-rays incident on each sensor element e(i, j) increases, and this change characteristic can be grasped as a characteristic curve that can be expressed using a quadratic function, an exponential function, or the like.

[0059] Therefore, the control unit 40 stores in advance in the correction coefficient calculation unit 46, for each sensor element e(i, j) of the X-ray detector 23, a characteristic calculation formula corresponding to a characteristic curve of a preferable change characteristic of the sensor element output Lx with respect to the incident X-ray dose.

[0060] The control unit 40 measures the output Lx values ​​of the multiple sensor elements e1 to en of the multiple sensor element modules M1 to Mk over the entire area of ​​the line scanning direction d2 of the X-ray detector 23 when there are no objects such as the object P or the calibration member Sp on the conveyor belt 11 in the inspection area Zx and only X-rays that have passed through the conveyor belt 11 are incident on the X-ray detector 23 (hereinafter referred to as the pre-loading state), and also measures the output Lx values ​​of the multiple sensor elements e1 to en of the multiple sensor element modules M1 to Mk over the entire area of ​​the line scanning direction d2 of the X-ray detector 23 when a first calibration member Sp1 of the calibration members Sp with a transmittance Trm1 [%] is loaded onto the conveyor belt 11 in the inspection area Zx and is being X-ray imaged (hereinafter referred to as the first post-loading state).

[0061] As a result, the control unit 40 determines the shape parameters of the characteristic curves stored in the correction coefficient calculation unit 46 based on the measurement value Lx1(i,j) in the pre-load state and the measurement value Lx2(i,j) in the first post-load state for each sensor element e(i,j). This allows the control unit 40 to set a reference characteristic curve Lxa(i,j) capable of correcting the detection sensitivity of each sensor element e(i,j) in each sensor element module M(i) of the X-ray detector 23 to a sensitivity correction value that is valid across the entire gradation density range, as well as first and second sensitivity correction coefficients C1 and C2, which will be described later. Note that FIG. 4 also shows the respective maximum, minimum, and average values ​​Lxa1(i,j) and Lxa2(i,j). The same applies to the measurement value Lx3(i,j), which will be described later.

[0062] The control unit 40 further measures values ​​of output signals Lx of the plurality of sensor elements e1 to en of the plurality of sensor element modules M1 to Mk across the entire area in the line scanning direction d2 of the X-ray detector 23 in a state where a second calibration member Sp2 having a transmittance Trm2 [%] of the calibration members Sp is loaded onto the conveyor belt 11 within the inspection region Zx and is being X-ray imaged (hereinafter referred to as a second post-loading state). As a result, for each sensor element e(i, j), based on the measurement value Lx1(i, j) in the pre-loading state and the measurement value Lx2(i, j) in the first post-loading state, the control unit 40 determines shape parameters of the characteristic curve stored in the correction coefficient calculation unit 46, and then determines whether the set characteristic curve is appropriate or not by determining whether the measurement value Lx3(i, j) in the second post-loading state is within the allowable error range of the set characteristic curve, or adjusts the shape parameters, thereby improving the setting accuracy of the detection sensitivity of each sensor element e(i, j) in each sensor element module M(i) of the X-ray detector 23.

[0063] The sensitivity correction referred to here includes both sensitivity correction for correcting variations in the detected brightness of the plurality of sensor elements e1 to en resulting from differences in the position of each sensor element e(i, j) in the line scanning direction and the amount of incident X-rays, and sensitivity correction for correcting variations in the detected brightness Lx(i, j) of the plurality of sensor elements e1 to en resulting from variations in the detectability of each sensor element e(i, j).

[0064] In this embodiment, the former sensitivity correction and the latter sensitivity correction are performed in stages, thereby simplifying and increasing the accuracy of the sensitivity correction process. The former sensitivity correction process is a process in which, as shown in FIG. 5, for example, the sensitivity of N sensor elements is corrected so that the measurement value Lx1 in the pre-carry-in state, the measurement value Lx2 in the first post-carry-in state, and the measurement value Lx3 in the second post-carry-in state are aligned with the respective sensitivity correction target values ​​La0, Laf, and Las.

[0065] In the latter sensitivity correction process, for example, as shown in FIG. 4, the change characteristic in which the detection brightness output Lx(i,j) of each sensor element e(i,j) of each sensor element module M(i) increases in response to an increase in the amount of X-rays incident on that sensor element e(i,j) is preset as a preferred characteristic curve whose curve shape can be finely adjusted using a shape parameter, and then the measurement value Lx1(i,j) in the pre-carry-in state, the measurement value Lx2(i,j) in the first post-carry-in state, and the measurement value Lx3(i,j) in the second post-carry-in state are measured, thereby determining the characteristic curve in the same figure corresponding to each sensor element e(i,j).

[0066] Next, the measurement values ​​Lx1(i,j), Lx2(i,j), and Lx3(i,j) are obtained for each of the N sensor elements e(i,j), and their respective characteristic curves are determined. Among these, the characteristic curve with the maximum output value Lx for the same incident X-ray dose and the characteristic curve with the minimum output value Lx for the same incident X-ray dose are identified, and the characteristic curve taking the intermediate or average value of these is set as the reference characteristic curve Lxa(i,j), and the reference characteristic curve Lxa that serves as the basis for sensitivity correction corresponding to each sensor element e(i,j) is determined.

[0067] In other words, by using this reference characteristic curve Lxa to sensitivity-correct the detection brightness output Lx(i,j) on the characteristic curve of each sensor element e(i,j) to the output value on the corresponding reference characteristic curve Lxa, the detection sensitivity can be corrected to uniform detection characteristics for all N sensor elements e(i,j).

[0068] The device configuration related to the sensitivity correction of such an X-ray detector will be described in detail below.

[0069] 3, the calibration member Sp is formed integrally with a first calibration member Sp1 with a plate thickness Tf1 arranged on one side of the conveyor belt 11 in the item conveying direction d1, and a second calibration member Sp2 with a plate thickness Tf2 (>Tf1) arranged on the other side of the conveyor belt 11 in the item conveying direction d1. When this calibration member Sp is arranged on the conveyor belt 11 with the direction of length Wt close to the belt width of the conveyor belt 11 facing the line scanning direction d2, the first calibration member Sp1 and the second calibration member Sp2 extend over substantially the entire belt width of the conveyor belt 11 and have constant widths W1 and W2 in the item conveying direction d1 and constant thicknesses Tf1 and Tf2 in the X-ray irradiation direction d3.

[0070] 5, in the pre-load state where the article P is not in the inspection region Zx, the correction coefficient calculation unit 46 of the control unit 40 sets the luminance value of the background image as a zero-point correction target value La0, which is the sensitivity correction target value for each sensor element e(i,j), and sets the zero-point correction coefficient Ct0(i,j) = La0 / Lx1(i,j) for each sensor element e(i,j) so that N image data Di(i,j) based on the detected luminance output Lx1 of the X-ray detector 23 matches the background image density that is the maximum luminance among the image data Dpx of the X-ray image. Furthermore, the correction coefficient calculation unit 46 stores and saves the first and second sensitivity correction coefficients C1 and C2, which are the zero-point correction coefficients Ct0(i,j) for each sensor element e(i,j) in the pre-load state and the post-load state, in the correction coefficient memory 47.

[0071] As a result, the correction coefficient calculation unit 46 and the correction coefficient memory 47 function as sensitivity correction means that can set zero point correction coefficients Ct0(i,j) for N sensor elements e(i,j) based on the brightness value detection signal Lx of the X-ray detector 23 in the pre-loading state and the zero point correction target value La0 so as to align the N detection brightness outputs Lx(i,j) of the N X-ray image data Di(i,j) generated by the image data generation unit 41 in the pre-loading state with the zero point correction target value La0.

[0072] Returning to FIG. 1, the control unit 40 further includes a mode switching unit 48 that can switch between a normal inspection mode and a calibration mode, and a stable state detection means 49 that detects that the operating state of the imaging unit, the X-ray generator 21 and the X-ray detector 23, has stabilized after the start of operation.

[0073] Before the control unit 40 controls the inspection, the correction coefficient calculation unit 46 and the correction coefficient memory 47 first perform a first sensitivity correction P1 in which the zero point correction coefficients Ct0(i, j) before output stabilization are set as first sensitivity correction coefficients C1 for the plurality of sensor elements e1 to en in each sensor element module M1 to Mk of the X-ray detector 23 from the start of operation of the X-ray generator 21 and the X-ray detector 23 until the stable state of the output of the X-ray detector is detected by the stable state detection means 49.

[0074] Furthermore, on condition that the stable state of the output of the X-ray detector 23 is detected by the stable state detection means 49, the correction coefficient calculation unit 46 and the correction coefficient memory 47 execute a second sensitivity correction P2 to reset the zero point correction coefficient Ct0(i, j) as a second sensitivity correction coefficient C2 that can be used for inspection control after the output has stabilized for the multiple sensor elements e1 to en in each sensor element module M1 to Mk of the X-ray detector 23.

[0075] The first sensitivity correction coefficient C1 and the sensitivity correction coefficient C2 after the second sensitivity correction are stored and saved by the storage control unit 42 in a correction coefficient memory 47 (memory) that can be used for inspection control so that they can be read out sequentially.

[0076] The control unit 40 configured in this manner can calculate the detection sensitivity of the multiple sensor elements e1 to en in each sensor element module M(i) of the X-ray detector 23, and the detection sensitivity of each sensor element module M(i) as a whole (average detection sensitivity, maximum and minimum detection sensitivity), and can also correct the detection sensitivity of each sensor element e1 to en.

[0077] 6, the correction coefficient calculation unit 46 and the correction coefficient memory 47 as sensitivity correction means first perform the first sensitivity correction P1 once during the adjustment period Tp after the X-ray generator 21 and the X-ray detector 23 start operating and before the control unit 40 starts inspection control. Then, the correction coefficient calculation unit 46 detects stabilization times Ts1(i) and Ts2(i) described below and performs the second sensitivity correction P2 once. Alternatively, the second sensitivity correction P2 is performed once after the stabilization time Ts has elapsed. The stabilization time Ts is determined by measuring the stabilization times Ts1(i) and Ts2(i) in advance and corresponding the measured time lapse to the adjustment period Tp immediately after power-on. The stable state is detected by determining that the stable state has been reached after the stabilization time Ts has elapsed. Alternatively, the sensitivity correction may be repeated multiple times until the stabilization time Ts has elapsed, and the sensitivity correction performed after the stabilization time Ts has elapsed (or the last of a predetermined number of repetitions) may be treated as the second sensitivity correction P2, and the adjustment period Tp may be terminated. In this case, for example, the first sensitivity correction may be performed three times, and after these multiple times, the second sensitivity correction P2 may be performed once.

[0078] Furthermore, the inspection control unit 40A of the control unit 40 has an operating condition setting unit 45 as an inspection condition variable setting means that can change the inspection control conditions according to the type of object to be inspected when the power is on, and the sensitivity correction means 49 is configured to execute the first sensitivity correction P1 again during the relatively short period Tpr from the start of operation of the X-ray generator 21 and X-ray detector 23 after the conditions have been changed to the start of inspection control after the conditions have been changed, under the same power-on state as when the conditions were changed.

[0079] The second sensitivity correction P2 is performed during the adjustment period Tp immediately after power-on. However, as shown in FIG. 6, if the first sensitivity correction P1 is performed again after a predetermined time Tsw has elapsed since the second sensitivity correction P2 was performed, the second sensitivity correction P2 may be similarly performed again. For example, this makes it possible to set a stable sensitivity correction coefficient even in the event of fluctuations caused by a change in the surrounding environment without powering on again.

[0080] On the other hand, while the same power-on state and the same operating state continue without the operating condition setting unit 45 changing the conditions of the inspection control, for example, during the period Tw from the start time t4 of the operating state to the end time t8 of the next inspection control in FIG. 6, the correction coefficient calculation unit 46 and the correction coefficient memory 47 as sensitivity correction means are configured to maintain the latest sensitivity correction coefficient C2 or C1 set by the second sensitivity correction P2 or the first sensitivity correction P1 between the start time t4 of the first operation of the X-ray generator 21 and the X-ray detector 23 and the start time t5 of the next inspection control until the end time t8 of the period Tw.

[0081] The mode switching unit 48, in cooperation with the display operation unit 50 or in cooperation with the article detection sensor 24 of the inspection unit 20 and the calibration member detection processing unit 43a of the image processing unit 43, determines at predetermined intervals whether there is a request to switch to the calibration mode, and, depending on the result, can switch between a normal inspection mode in which the article P is inspected and a calibration mode in which the output signals Lx(i,j) of the plurality of sensor elements e1-en are calibrated using the calibration member Sp. The control unit 40 is configured to switch from the inspection mode to the calibration mode, for example, when a predetermined mode switching request is input from the display operation unit 50, or when, instead of that input, the insertion of the calibration member Sp is detected by the detection signal of the article detection sensor 24 and predetermined calibration member detection processing in the image processing unit 43, assuming that there has been a request to switch to the calibration mode.

[0082] The stable state detection means 49 is configured to detect a state in which the outputs of the X-ray generator 21 and the X-ray detector 23 satisfy predetermined stable conditions (hereinafter referred to as stable state) after the start of operation of the X-ray generator 21 and the X-ray detector 23, which are the operating state of the article inspection apparatus 1. Then, on the condition that the stable state detection means 49 has detected the stable state of the outputs of the X-ray generator 21 and the X-ray detector 23, the memory control unit 42 (memory control means) is configured to sequentially readably store the X-ray image data Di generated by the image data generation unit 41 based on the outputs of the sensor elements e1 to en of the plurality of sensor element modules M1 to Mk in an image memory 42a that can be used for inspection control.

[0083] 8, the stable state detection means 49 is configured to detect a stable state when it is determined that fluctuations have converged in the output average value AvD(j) of a plurality of sensor element modules M1 to Mk (here, k sets of sensor elements e1 to en) in the X-ray detector 23. The solid line in the figure indicates a case where the output average value AvD(i) of each sensor element module M(i) increases over time, and the dotted line in the figure indicates a case where the output average value AvD(i) decreases over time, and both tend to converge after a predetermined stabilization time Ts1(i) has passed.

[0084] In this embodiment, since the X-ray detector 23 is composed of a plurality of sensor element modules M1 to Mk, each having a predetermined number of sensor elements e1 to en (sensor element group), the stable state detection means 49 is further configured to detect a stable state when it is determined that the fluctuations in the inter-module luminance gap, in which the output average values ​​of the plurality of sensor elements e1 to en of each sensor element module M(i) differ among the plurality of sensor element modules M1 to Mk, for example, the inter-module luminance gap gp(i) between any of the sensor element modules M(i) and the sensor element module M(i+1) with the next module number shown in Figure 7, have converged.

[0085] Specifically, as shown in FIG. 9, the absolute value |gp(i)| of the inter-module luminance gap gp(i) tends to gradually decrease and converge to a constant value until a predetermined stabilization time Ts2(i) has elapsed.

[0086] Note that signal G1 from the inspection unit 20 to the control unit 40 shown in FIG. 1 indicates detection signal inputs such as an object detection signal from the inspection unit 20, an encoder pulse for the transport motor, and the tube voltage of the X-ray tube 22, and signal G2 from the control unit 40 to the inspection unit 20 indicates a control signal output for controlling a speed control signal for the transport motor of the transport unit 10 and the tube voltage of the X-ray tube 22, etc.

[0087] The material and thickness of the calibration member Sp can be selected and set according to the type of item P to be inspected. For example, the control unit 40 may select the material and thickness of the calibration member Sp suitable for calibration based on the type information of the item P selected as the inspection object, and display and output it on the display operation unit 50.

[0088] Furthermore, as the material for the calibration member Sp, if the item P is, for example, meat, polyacetal resin, polyethylene terephthalate, acrylic resin, or a container of such a resin filled with water or the like can be used, and if the item P contains a lot of fat, polyethylene or a container of such a resin filled with oil or the like can be used. Furthermore, if the item P contains bone or salt, the calibration member Sp can be made of aluminum, polyvinyl chloride, or the like.

[0089] Furthermore, in this embodiment, the calibration member Sp has thicknesses Tf1, Tf2 that are uniform over the entire area in the line scanning direction d2 and that change stepwise depending on the position in the article conveying direction, but the calibration member Sp may have a constant thickness Tf in the X-ray irradiation direction relative to the inspection region Zx over the entire area in the line scanning direction d2, which is the direction in which the sensor elements of the X-ray detector 23 are arranged, or the thickness may change gradually depending on the position in the conveying direction. Alternatively, if the X-ray detector 23 has a sensor element arrangement in which multiple rows are arranged side by side in the article conveying direction, for example, a calibration member Sp may be used whose X-ray transmittance changes depending on the incident position and incident angle of each row (each scanning line).

[0090] Furthermore, calculation of correction coefficients for correcting the sensor sensitivity may be performed by acquiring image detection signals of the calibration member Sp without driving the transport unit 10. Furthermore, if the calibration member Sp cannot cover the plurality of sensor element modules M1 to Mk of the X-ray detection unit 23, image detection signals of the calibration member Sp that covers a predetermined number of the sensor element modules M1 to Mk may be collected multiple times to generate calibration data.

[0091] (Calibration of measurement data) On the other hand, the image processing unit 43 has a calibration processing unit 43b (calibration processing means) that imports calibration data Dhs(i,j) including the second or first sensitivity correction coefficient C2 or C1, etc., associated with the position (i,j) of each sensor element e(i,j) from the correction coefficient memory 47, and also acquires image data Dpx from the image memory 42a of the storage control unit 42 and performs a predetermined calibration process.

[0092] The zero-point correction target value La0, the low transmittance side correction target value Laf, and the intermediate transmittance region correction target value Las are each set prior to calibration processing by the image processing unit 43 and stored in the sensitivity correction coefficient memory 47. As described above, the control unit 40 sets the shape parameters of the characteristic curve for each sensor element e(i, j) based on the pre-load state measurement value Lx1(i, j) and the first and second post-load state measurement values ​​Lx2(i, j) and Lx3(i, j), and has already set a reference characteristic curve Lxa(i, j) and second and / or first sensitivity correction coefficients C2 and / or C1 that can correct the detection sensitivity of each sensor element e(i, j) in each sensor element module M(i) of the X-ray detector 23 over the entire gradation density range.

[0093] The image processing unit 43 performs the function of a calibration processing means using the calibration processing unit 43b to perform calibration processing on the image data Dpx of the X-ray image of each item P, using n pieces of image data Di(i,j) for each line scanning period as a unit, depending on the line scanning order and pixel position, and performs calibration processing to calculate the detected luminance A(i,j) of the multiple sensor elements e1 to en in each of the multiple sensor element modules M1 to Mk so that the set standard characteristic curve Lxa(i,j) is applied to the output Lx(i,j) of each sensor element e(i,j) during the first line scanning of the item P to be inspected, and then sequentially performs calibration processing to calculate the detected luminance A(i,j) of the multiple sensor elements e1 to en in each of the multiple sensor element modules M1 to Mk by applying the set standard characteristic curve Lxa(i,j) to the output Lx(i,j) of each sensor element e(i,j) during the next line scanning.

[0094] The inspection unit 20, which is an imaging unit, can adjust the tube voltage or X-ray irradiation intensity of the X-ray tube 22 in multiple stages, and the setting means 45a of the operating condition setting unit 45 can set multiple correction target values ​​(zero-point correction target value La0, correction target value Laf on the low transmittance side, and correction target value Las in the intermediate transmittance range) according to the tube voltage or X-ray irradiation intensity of each stage among the multiple stages.

[0095] In addition, the operating condition setting unit 45 may set the operating conditions so that when the X-ray generator 21 of the inspection unit 20 or the X-ray detector 23 is replaced, the correction coefficient calculation unit 46 is activated and the generation of the calibration data Dhs is performed again.

[0096] The procedure for the calibration process can be roughly the same as that exemplified in Patent Document 2.

[0097] For example, the correction coefficient calculation unit 46 pre-calculates the second and first sensitivity correction coefficients C2 and / or C1 required to ensure that the image data obtained by the image data generation unit 41 has a uniform density for each incident condition, and stores these in the correction coefficient memory 47. When calculating each sensitivity correction coefficient C1, C2, the conveying unit 10 is driven, and image data in which fluctuations in the image data due to the thickness of the belt and seams have been averaged is used, thereby preventing a decrease in accuracy.

[0098] In addition, the calibration data Dhs, which includes the second and first sensitivity correction coefficients C2 and / or C1, may include an element Ha for compensating for changes in the incident intensity of X-rays depending on the distance from the X-ray generator 21 to each sensor element e(i, j), particularly the material penetration distance, an element Hb for compensating for sensitivity differences due to differences in the incident direction and incident position of the X-rays on the item P to be inspected, an element Hc for compensating for sensitivity differences to X-rays for each sensor element module M(i), an element Hd for compensating for sensitivity differences for each sensor element within each sensor element module M(i), an element He for compensating for noise generated at the boundary between adjacent sensor element modules, and an element Hf for compensating for sensitivity differences due to other X-ray transparent members (for example, the belt support member of the conveying section 10 or the exit port cover material of the X-ray generator 21).

[0099] Of these compensation elements, Ha and Hb depend on the material and thickness of the substance through which the X-rays pass, so the calibration error can be reduced by using a material for the calibration member Sp that has a transmittance and thickness close to that of the inspected item P. Ideally, it would be possible to use a portion of the contents of the inspected item P that is made of a uniform material and has a constant thickness as the calibration member Sp.

[0100] For example, if the density of the image obtained from the output of the jth sensor element e(i,j) of any (ith) sensor element module M(i) under the first incident condition (for example, incident on a background image area with a transmittance close to 100%) before the sensor element is loaded is A1(i,j), the ideal density of the image is R1(i,j), and the compensation term according to the incident condition is H(i,j), then: A1(i,j)=R1(i,j)+H(i,j) ···(1) H(i,j)=Ha(i,j)+Hb(i,j)+Hc(i,j)+Hd(i,j)+He(i,j)+Hf(i,j) ···(2) This becomes:

[0101] Furthermore, if the density of the image obtained from the output under the second incident condition (for example, transmittance 30%), which is the state after delivery, is A2(i,j), and the ideal density of the image is R2(i,j), then: A2(i,j)=R2(i,j)+H(i,j) ···(3) In the above formula (3), the density obtained by image processing is expressed as the sum of the ideal density R2(i,j) and the compensation term H(i,j), but it can also be expressed as the product of the ideal density and the compensation term.

[0102] In this way, in this embodiment, from a plurality of different transmittances and the image densities (detected luminance) obtained for each transmittance, it is possible to grasp the characteristics and perform correction calculations for each sensor element e(i, j) using a characteristic curve of transmittance versus image density as shown in Fig. 4. The characteristic diagram in the same figure shows, as measurement points, detected luminance under three different incident conditions: an X-ray transmittance of 100%, which is the state before the calibration member Sp is transported, and X-ray transmittances of 30% and 50%, which are the first and second states after the calibration member Sp is transported. This characteristic diagram is a characteristic curve that sufficiently accurately represents the output characteristics of the sensor element e(i, j) in the low transmittance region, and as mentioned above, can be approximated by a quadratic function, exponential function, etc.

[0103] Here, if we assume that H(i,j) ≈ 0 for the detected luminance output Lx2(i,j) of each sensor element e(i,j) at a predetermined low transmittance, for example a transmittance of 30%, i.e., that the detected luminance obtained from the output of sensor element e(i,j) is an image density close to the ideal value, then it is possible to calculate a characteristic curve of transmittance versus image density that is close to the ideal value from the detected luminance outputs Lx1(i,j) and Lx2(i,j) at transmittances of 100% and 30%, respectively, and as mentioned above, it is possible to determine the suitability of the set characteristic curve based on whether the detected luminance output Lx3(i,j) at a transmittance of 50% is within the allowable error range of the set characteristic curve.

[0104] Here, the transmittance of interest is set to three levels: 100%, 30%, and 50%. However, the transmittance may be changed to 100%, 60%, and 30%, or the transmittance may be set to two levels: high and low. Alternatively, the standard may be set by focusing on two or more types of transmittance excluding 100%.

[0105] As described above, it is possible to change the incidence conditions not only by changing the incidence conditions using the calibration member Sp but also by changing the tube current or tube voltage of the X-ray tube 22 of the X-ray generator 21. By changing the tube current or tube voltage, it is possible to adjust the incidence conditions of X-rays for each sensor element e(i, j), but it is also possible to combine changing the transmittance using the calibration member Sp (for example, 100% and 30%), changing the tube voltage, or changing the tube current. Furthermore, calibration data can also be obtained for each energy of X-rays incident on the X-ray detector 23.

[0106] Next, the operation will be described.

[0107] (Inspection control and sensor sensitivity correction) In the inspection mode, the control unit 40 acquires an X-ray transmission image of the article P conveyed by the conveying unit 10, and executes inspection control to determine whether the article P is good or bad by determining the presence or absence of foreign matter.

[0108] Specifically, the control unit 40 executes the process of the inspection mode as shown in FIG. 10, and also executes the sensor sensitivity correction.

[0109] When inspection control is started, first, it is determined whether there is a request to change the currently set inspection conditions (step S11). If there is no change in the inspection conditions, no sensitivity correction is required, and the start of the inspection is requested (NO in step S11), the transport unit 10 and the X-ray generator 21 are started up. On the other hand, if sensitivity correction is required (YES in step S11), the sensitivity correction operation described below is executed (step S13).

[0110] Once the transport unit 10 and the X-ray generator 21 are started or the sensitivity correction operation is completed, the pass / fail judgment unit 44 executes a judgment process (step S14), and then determines whether the inspection is complete (step S15). The pass / fail judgment unit 44 executes the judgment process again until the inspection is complete, and if the inspection is complete, the current process ends.

[0111] (Example 1 of sensitivity correction) In the sensitivity correction operation, as in Example 1 shown in FIG. 11, first, the X-ray generator 21 is started (step S21), and then a first sensitivity correction P1 is performed to set a first sensitivity correction coefficient C1 that can correct output variations due to the positions of multiple sets of sensor elements e1 to e even before the output of the X-ray detector 23 stabilizes (step S22).

[0112] Next, it is determined whether the conditions for implementing the second sensitivity correction P2 are met (step S23), and if the conditions are met (YES in step S23), the stabilization time is allowed to elapse (YES in step S24), and then the second sensitivity correction P2 is executed (step S25), setting a second sensitivity correction coefficient C2 that can be used for inspection control after the output has stabilized.

[0113] On the other hand, if the conditions for performing the second sensitivity correction P2 are not met (NO in step S24), then the transport unit 10 is activated, conveyance by the conveyor is started, and the current processing ends.

[0114] (Example 2 of sensitivity correction) Alternatively, as in Example 2 shown in FIG. 12, first, the X-ray generator 21 is started (step S31), and then the first sensitivity correction P1 is performed from the first time up to a certain number of times, and thereafter the second sensitivity correction P2 is performed (step S32).

[0115] Next, it is determined whether the conditions for performing the second sensitivity correction P2 are met (step S33), and if the conditions are met (YES in step S33), the first sensitivity correction P1 or the subsequent second sensitivity correction P2 is performed within a certain number of times from the first time until the stabilization time has elapsed or the number of times the first sensitivity correction P1 has been performed reaches a predetermined number corresponding to the stabilization time (NO in step S34) (step S32).

[0116] On the other hand, if the conditions for performing the second sensitivity correction P2 are not met (NO in step S33), then the transport unit 10 is activated and conveyor transport begins (step S35), and the current process ends.

[0117] Next, the operation will be described.

[0118] In the object inspection device 1 of this embodiment configured as described above, when the stable state detection means 49 detects a stable state of the outputs of the X-ray generator 21 and the X-ray detector 23 after the X-ray generator 21 and the X-ray detector 23 enter the operating state of the device after the start of operation in the inspection control unit 40A, the memory control unit 42 stores the X-ray image data D1 generated by the image data generation unit 41 based on the outputs Lx of each of the multiple sensor elements e1 to en of the multiple sensor element modules M1 to Mk in an image memory 42a that can be used for inspection control.

[0119] Therefore, the X-ray image data Dpx used for inspection control is obtained after the fluctuations in the brightness detection signal Lx of the X-ray detector 23 have converged, and the detection characteristics of the X-ray detector 23 and their changes over time are reliably suppressed for a sufficient period of time, thereby achieving the required inspection accuracy of the item inspection device 1 using the direct conversion type X-ray detector 23.

[0120] In addition, in this embodiment, a correction coefficient calculation unit 46 and a correction coefficient memory 47 are provided as sensitivity correction means for setting sensitivity correction coefficients C1, C2 for each sensor element e(i, j) so that the output signals Lx of the multiple sensor elements e1 to en of the X-ray detector 23 are aligned to the maximum brightness of the X-ray image data D1 in the pre-load state when the item P is not within the inspection area Zx, and the sensitivity correction coefficients for the multiple sensor elements e1 to en (hereinafter simply referred to as N sensor elements e(i, j)) of each sensor element module M(i) are set using the brightness values ​​of the X-ray image data Di generated by the image data generation unit 41 based on the output signals Lx of the multiple sensor elements e1 to en of each sensor element module M(i) of the X-ray detector 23.

[0121] Therefore, before the article P is carried into the inspection area Zx, the sensitivity correction coefficients C1 and C2 of each sensor element e(i,j) are set using the brightness values ​​of the X-ray image data Di generated by the image data generation unit 41 based on the outputs Lx(i,j) of the N sensor elements e(i,j) of the X-ray detector 23 so that the output signals Lx(i,j) of the N sensor elements e(i,j) of the X-ray detector 23 are aligned to the maximum brightness (minimum or maximum value of grayscale image density, for example, background image density) of the X-ray image data Dpx. Therefore, the brightness detection values ​​of the X-rays that have passed through the article P in the inspection area Zx and are incident on the N sensor elements e(i,j) of the X-ray detector 23 can be displayed as multi-level grayscale image density, improving the accuracy of setting the sensitivity correction coefficients.

[0122] Furthermore, in this embodiment, the correction coefficient calculation unit 46 and the correction coefficient memory 47 serving as sensitivity correction means execute a first sensitivity correction P1 that sets a first sensitivity correction coefficient C1 for the N sensor elements e(i, j) of the X-ray detector 23 during the period from when the X-ray generator 21 and the X-ray detector 23 start operating until the stable state of the output of the X-ray detector 23 is detected by the stable state detection means 49, and a second sensitivity correction that resets a second sensitivity correction coefficient C2 for the N sensor elements e(i, j) of the X-ray detector 23 on the condition that the stable state of the output of the X-ray detector 23 is detected by the stable state detection means 49, and the memory control unit 42 stores the sensitivity correction coefficient C2 after the second sensitivity correction P2 in the correction coefficient memory 47, which can be used for inspection control.

[0123] Therefore, the sensitivity correction coefficients C1 and C2 set for the multiple sets of sensor elements e1 to en of the multiple sensor element modules M1 to Mk of the X-ray detector 23 in the second sensitivity correction P2, which is executed after a stable state of the output of the X-ray detector 23 is detected, are stored in a correction coefficient memory 47 that can be used for inspection control by the memory control unit 42 via the correction coefficient calculation unit 46, thereby increasing the reliability of the sensitivity correction coefficients.

[0124] In addition, in this embodiment, the correction coefficient calculation unit 46 and the correction coefficient memory 47 as sensitivity correction means perform the first sensitivity correction P1 multiple times during the adjustment period Tp (see Figure 6) after the X-ray generator 21 and the X-ray detector 23 start operating and before the start of inspection control, and after performing the first sensitivity correction P1 multiple times, perform the second sensitivity correction P2 once.

[0125] Therefore, for differences in output depending on the positions (module position and element position) of multiple sets of sensor elements e1 to en that are unrelated to the output fluctuations of the luminance detection signal Lx of the X-ray detector 23, an effective sensitivity correction coefficient C1 can be set in the first or first half of the multiple first sensitivity corrections P1, and for variations in the luminance detection signals of multiple sets of sensor elements e1 to en that are affected by output fluctuations, an accurate sensitivity correction coefficient C2 can be set in accordance with the range of variation in the remaining sensitivity corrections in the second half of the first sensitivity correction P1, and after the output fluctuations have converged, a sensitivity correction coefficient C2 that is effective for the immediate inspection control can be determined as a result of the second sensitivity correction P2.

[0126] In addition, in this embodiment, the inspection control unit 40A has a setting means 45a (inspection condition variable setting means) that can change the inspection control conditions according to the type of item P when the power is on, and the correction coefficient calculation unit 46 and correction coefficient memory 47, which serve as sensitivity correction means, perform the first sensitivity correction P1 again when the conditions are changed, for example, under the same power-on state as when the conditions are changed, t4 (or t9), from the time when the X-ray generator 21 and X-ray detector 23 start operating after the condition change to the time when the inspection control starts t5 (or t10) after the condition change, provided that the inspection control conditions have been changed by the setting means 45a.

[0127] Therefore, regardless of the detection result of the stable state detection means 49, the influence of the change in output of the X-ray generator 21, etc., can be considered to be in a stable state during the short period until the start of inspection control after the condition change, and the first sensitivity correction P1 can be executed to reset the sensitivity correction coefficient that is effective against drift, etc.

[0128] Furthermore, in this embodiment, during a period Tw in which the same power-on state and the same operating state continue without the setting means 45a changing the inspection control conditions, the correction coefficient calculation unit 46 and the correction coefficient memory 47 as sensitivity correction means maintain the latest sensitivity correction coefficient C1 set by the first sensitivity correction P1 between the time t4 when the X-ray generator 21 and the X-ray detector 23 first start operation and the time t5 (or t2) when the inspection control starts immediately thereafter until the end of the period Tw. Similarly, during a period Tp in which the same power-on state and the same operating state continue without the setting means 45a changing the inspection control conditions, the correction coefficient calculation unit 46 and the correction coefficient memory 47 as sensitivity correction means maintain the latest sensitivity correction coefficient C2 set by the second sensitivity correction P2 between the time t1 when the X-ray generator 21 and the X-ray detector 23 first start operation and the time t2 when the inspection control starts immediately thereafter until the end of the period Tp.

[0129] Therefore, during the short period until the interrupted inspection control is resumed, regardless of the detection result of the stable state detection means 49, the influence of changes in the output of the X-ray generator 21, etc., can be considered to be in a stable state, and the latest sensitivity correction coefficients C2 and / or C1 can be maintained.

[0130] Furthermore, in this embodiment, the stable state detection means 49 detects a stable state when it determines that the fluctuations in the output average value AvD(i) of the multiple sensor elements e1 to en of each sensor element module M(i) of the X-ray detector 23 have converged. Therefore, the sensitivity correction coefficients C1 and C2 for inspection control are set after the fluctuations in the output average value AvD(i) of the multiple sensor elements e1 to en of each sensor element module M(i) have converged, making it possible to perform sensitivity correction that can effectively correct the variations in the brightness detection signals of the multiple sensor element modules M(i) and each of the multiple sensor elements e1 to en.

[0131] Furthermore, in this embodiment, the X-ray detector 23 is composed of a plurality of sensor element modules M1 to Mk, each having a predetermined number of sensor elements e1 to en (sensor element group), and the stable state detection means 49 detects the stable state when it determines that the output average value AvD(i) of the plurality of sensor elements e1 to en of each sensor element module M(i) has converged due to the fluctuation of the inter-module brightness gap gp(i) that differs among the plurality of sensor element modules M1 to Mk.

[0132] Therefore, the sensitivity correction coefficients C1 and C2 for inspection control are set after the fluctuations in the output average values ​​AvD(i) of the multiple sensor elements e1 to en in each sensor element module M(i) of the X-ray detector 23 have converged, making it possible to perform sensitivity correction that can effectively correct variations in the average background luminance values ​​among the multiple sensor element modules M1 to Mk.

[0133] Thus, according to this embodiment, it is possible to provide an object inspection device 1 that can reliably converge the detection characteristics of the X-ray detector 23 and the changes in those characteristics over time in a necessary and sufficient time, thereby achieving sufficient inspection accuracy when using a direct conversion type X-ray detector 23.

[0134] As a means for changing the incidence conditions from the X-ray generator 21 to the X-ray detector 23, at least one of the following can be used: a method for changing the incidence conditions of X-rays to the X-ray detector 23 by moving the calibration member Sp back and forth in a direction intersecting the X-ray passage path or changing its posture; and a method for changing the incidence conditions of X-rays for the sensor elements e1 to en of each sensor element module M(i) of the X-ray detector 23 by changing the tube voltage or tube current supplied to the X-ray tube 22 of the X-ray generator 21.

[0135] Therefore, the calibration member Sp may be, for example, a flat plate made of a uniform material with an almost uniform transmittance of X-rays passing from the top surface to the bottom surface that is less than 100% (for example, 50%), a plurality of plates made of a uniform material with a constant thickness stacked on top of each other, a plate made of a constant material with a thickness that varies between the front and rear ends and with an X-ray transmittance that varies, for example, from 50 to 20%, or a plate made of different materials stacked on top of each other to form a plate with a constant thickness (for example, one with an X-ray transmittance of 50 to 20% and the other with an X-ray transmittance of 70 to 90%).

[0136] Furthermore, for a single calibration member Sp, two incidence conditions can be set: a position where X-rays pass from the top surface to the bottom surface (X-ray transmittance 50%), and a position where X-rays pass through without intersecting (X-ray transmittance 100%).In addition, three incidence conditions can be set: a position where X-rays pass through from the top row to the bottom surface (X-ray transmittance 25%), a position where X-rays pass through from the middle row to the bottom surface (X-ray transmittance 50%), and a position where X-rays pass through without intersecting (X-ray transmittance 100%).

[0137] In the above-described embodiment, as a direct conversion type X-ray detector, when X-rays that have passed through the article P are incident on the semiconductor element 32 of each sensor element module Mi, electrons and holes (charges) are generated according to the energy of the incident X-rays (photons), thereby generating a detection signal of a voltage corresponding to the incident dose of X-rays between the opposing electrodes 31, 33, and outputting the signal to a readout circuit 34 composed of an ASIC or the like. However, since the X-rays from the X-ray generator 21 have large photon energy (short wavelength) and are not constant, it goes without saying that, rather than being limited to charge-voltage conversion by charge accumulation, a pulse signal of a peak value corresponding to the energy of the photon can be output each time an X-ray photon is incident on each sensor element, and the peak value can be measured by a photon-counting type readout circuit 34. In this case, the predetermined energy range from the X-ray generator 21 is divided into a plurality of energy (wavelength) ranges by the peak value of the pulse signal, and the number of pulse signals incident per unit time for each pixel electrode in the pixel electrode arrangement layer 33 in the energy range effective for inspection is counted, and the counted value can be made to correspond to the image density or brightness for each pixel of the X-ray image.

[0138] As described above, the present invention can provide an article inspection device that can reliably converge the detection characteristics of an X-ray detector and the time variations in those characteristics in a necessary and sufficient time, thereby achieving sufficient inspection accuracy when using a direct conversion X-ray detector. The present invention is useful for all article inspection devices that irradiate an inspection object with X-rays and generate X-ray image data based on the scan output from the X-ray detector. [Explanation of symbols]

[0139] 1. Item inspection equipment 10 Conveying section 11 Conveyor belt 12,13 Conveyor roller 20 Inspection unit (imaging unit) 21 X-ray generator (X-ray source, X-ray irradiation source) 22 X-ray tube 23 X-ray detector 24 Item detection sensor 31 Bias electrode (one of the opposing electrodes) 32 Semiconductor elements 33 Alignment layer (alignment layer of multiple pixel electrodes; the other electrode of the opposing electrode) 34 Readout circuit 40 Control Unit 40A Inspection control unit 41 Image data generation unit 42 Memory control unit (memory control means) 42a Image memory (memory) 43 Image processing section 43a Calibration member detection processing unit 43b Calibration processing unit (calibration processing means) 44 Good / bad judgment unit (inspection control unit) 45 Operating condition setting section 45a Setting means (inspection condition variable setting means, operating condition variable setting means) 45b Operating condition adjustment means 46 Correction coefficient calculation unit (sensitivity correction means) 47 Correction coefficient memory (sensitivity correction means) 48 Mode switching unit (mode switching means) 49 Steady state detection means 50 Display operation section Ct correction target value Ct0, Ctf, Cts Correction target value (brightness detection value of correction target) d1 Conveying direction d2 Line scan direction d3 X-ray irradiation direction Dhs calibration data Di1 image data (image data before output stabilization) Di2 image data (image data after output stabilization) e1~en Sensor element (multiple sensor elements) G1 signal (detection signal input) G2 signal (control signal output) La0, Laf, Las Sensitivity correction target value Lx Luminance detection signal (image detection signal, sensor element output) Lx(i,j) Sensor element output (detected brightness) Lx1, Lx2, Lx3 measurement values ​​(output, detected brightness output) Lx1(i,j) Measurement value before loading (output, detector output) Lx1(i,j)max Maximum measured value before loading (output, detector output) Lx1(i,j)min Maximum measured value before loading (output, detector output) Lx2(i,j) Measurement value of the first post-load state (output, detector output) Lx2(i,j)max Maximum measured value of the first post-load state (output, detector output) Lx2(i,j)min Maximum measured value of the first post-load state (output, detector output) Lx3(i,j) Second measurement value after loading (output, detector output) Lx3(i,j)max Maximum measured value of the second post-load state (output, detector output) Lx3(i,j)min Maximum measured value of the second post-load state (output, detector output) Lxa(i,j) Reference characteristic curve (reference output characteristic of any sensor element) Lxa1(i,j), Lxa2(i,j), Lxa3(i,j) average value (median value) M1~Mk Sensor element module (multiple sensor element modules) M(i) Sensor element module (any one sensor element module) P Article (object to be inspected) Trm1, Trm2 transmittance (incident X-ray dose)

Claims

1. an X-ray source (21) for irradiating an inspection area (Zx) into which an object to be inspected (P) is carried with X-rays; an X-ray detector (23) that detects X-rays transmitted through the inspection area by a plurality of sensor elements adjacent to each other in a predetermined scanning direction and outputs luminance detection signals (Lx) corresponding to a plurality of detection positions in the predetermined scanning direction; an image data generating unit (41) that generates X-ray image data (Di) corresponding to a distribution of X-ray transmission amounts within the examination area within a predetermined brightness value range based on outputs from the plurality of sensor elements of the X-ray detector; an inspection control unit (40A) that is switchable between an operating state in which the X-ray source and the X-ray detector are operated and an operating stop state in which the operation of the X-ray source and the X-ray detector is stopped, and that, in the operating state, executes inspection control to inspect the object to be inspected using X-ray image data generated by the image data generation unit and preset criteria, The inspection control unit a stable state detection means (49) for detecting a stable state in which outputs of the X-ray source and the X-ray detector are stable after the X-ray source and the X-ray detector are put into the operating state and start operating; and a storage control means (42) for storing the X-ray image data generated by the image data generation unit based on the output of the plurality of sensor elements in a memory (42a) that can be used for inspection control, on the condition that the stable state of the outputs of the X-ray source and the X-ray detector has been detected by the stable state detection means.

2. a sensitivity correction unit (46, 47) for setting a sensitivity correction coefficient (Ct(j)) of each of the sensor elements of the X-ray detector so that output signals of the plurality of sensor elements of the X-ray detector are aligned to a maximum luminance of the X-ray image data in a pre-load state when the object to be inspected is not within the inspection area; 2. The object inspection device according to claim 1, wherein the sensitivity correction means sets the sensitivity correction coefficients for the plurality of sensor elements using brightness values ​​of X-ray image data generated by the image data generation unit based on the outputs of the plurality of sensor elements of the X-ray detector.

3. the sensitivity correction means executes a first sensitivity correction (P1) for setting the sensitivity correction coefficients for the plurality of sensor elements of the X-ray detector during a period from when the X-ray source and the X-ray detector start operating until the stable state of the output of the X-ray detector is detected by the stable state detection means, and a second sensitivity correction (P2) for resetting the sensitivity correction coefficients for the plurality of sensor elements of the X-ray detector on the condition that the stable state of the output of the X-ray detector is detected by the stable state detection means; 3. An object inspection device according to claim 2, wherein the memory control means stores the sensitivity correction coefficients after the second sensitivity correction in a correction coefficient memory (47) that can be used for the inspection control.

4. The object inspection device described in claim 3, characterized in that the sensitivity correction means performs the first sensitivity correction multiple times during an adjustment period (Tp) after the X-ray source and the X-ray detector start operating and before the inspection control starts, and performs the second sensitivity correction once after the multiple first sensitivity corrections.

5. the inspection control unit has an inspection condition variable setting means (45) that can change the conditions of the inspection control in accordance with the type of the object to be inspected under a power-on state, The object inspection device described in claim 3, characterized in that the sensitivity correction means, on the condition that the inspection control conditions have been changed by the inspection condition variable setting means, performs the first sensitivity correction again under the same power-on state as when the conditions were changed (t4), between the start of operation of the X-ray source and the X-ray detector after the conditions have been changed and the start of inspection control after the conditions have been changed (Tpr).

6. The object inspection device described in claim 5, characterized in that during a period (Tw) in which the same power-on state and the same operating state continue without the inspection control conditions being changed by the inspection condition variable setting means, the sensitivity correction means maintains the latest sensitivity correction coefficient (C1) set by the second sensitivity correction or the first sensitivity correction (P1) between the initial start of operation (t4) of the X-ray source and the X-ray detector and the start of inspection control immediately thereafter (t5) until the end of the period (t8) of the period.

7. 5. An object inspection device according to claim 2, wherein the stable state detection means detects the stable state when it determines that fluctuations in the average output values ​​of the plurality of sensor elements of the X-ray detector have converged.

8. the X-ray detector is composed of a plurality of sensor element modules (M1 to Mk), each having a predetermined number of sensor element groups (e1 to en), The object inspection device described in any one of claims 2 to 4, characterized in that the stable state detection means detects the stable state when it determines that the fluctuation in inter-module brightness gap, in which the output average value of the sensor element group of each sensor element module (M(i)) differs among the plurality of sensor element modules, has converged.

9. 5. An object inspection device according to claim 2, wherein the stable state detection means detects the stable state by determining that the stable state has been achieved when a predetermined stabilization time (Ts) has elapsed since the X-ray source and the X-ray detector started operating.

Images