JP5466549B2 - X-ray foreign matter detector - Google Patents

Description

  The present invention relates to an X-ray foreign object detector, and more particularly to an X-ray foreign object detector capable of detecting a high-risk attention foreign object among foreign objects.

  Conventionally, it detects fresh foods such as raw meat and fish, processed foods such as bread, pharmaceuticals, industrial products, etc., or foreign substances (metal, glass, plastic, stones, bones, etc.) mixed in the package that wraps the goods. There is an X-ray foreign matter detector that can be used (for example, see Patent Document 1).

  The possibility of foreign matter being mixed into an article is that the material itself has been mixed into the material itself for some reason, and if it is intentionally mixed into the article maliciously during processing, manufacturing, packaging, etc. , Various causes can be considered, for example, when a part of the line equipment falls off and is mixed into an article during a process such as packaging.

  If a foreign substance mixed in food or medicine is, for example, a piece of metal, a piece of glass, a needle, a wire, etc., it is extremely dangerous for the human body. Is expensive.

  If the foreign body is, for example, a fine bone piece, a fine plastic piece, or a small stone, the risk to the human body may be low.

  Depending on the industrial product, for example, large items such as bolts, nuts, washers, etc., in which foreign matter mixed in the package has fallen off the line equipment, are high in risk, but small items may be low in risk.

  As described above, the risk of foreign matters mixed in an article or a package in which the article is packaged depends largely on the judgment of the manufacturer. For example, a metal foreign object may have a high risk level, a large foreign object may have a high risk level, and a linear foreign object such as a needle or wire may have a high risk level.

  If an article or package that contains a foreign object with a high degree of danger (this foreign material requires attention and is referred to as a cautioned foreign material hereinafter) is detected, the line is stopped and the cause of the contamination is detected. When a situation that must be investigated occurs or an article that contains a cautionary foreign matter is shipped by mistake, the impact on producers, consumers, etc. is immeasurable.

  Therefore, X-ray foreign object detection that can be installed especially in the production line and detects foreign substances by inspecting articles conveyed on belt conveyors or packages that wrap the articles, and distinguishing caution foreign substances from the detected foreign substances The appearance of the machine was awaited.

JP 2002-139458 A

  An object of the present invention is to detect a foreign object by inspecting a product or a package in which the product is packaged (hereinafter referred to as an object to be inspected), and having a function of discriminating a caution foreign object having a high degree of danger from the detected foreign object. It is to provide a wire foreign object detector.

  The X-ray foreign object detector of the present invention creates an X-ray transmission image based on the electrical signal output from the X-ray detector in order to determine whether the object to be inspected is a foreign object or a caution foreign object. The foreign matter and the caution foreign matter are detected by processing. It is up to the user of the X-ray foreign object detector to determine what is a foreign object and a caution foreign object.

  According to the present invention, in detecting a caution foreign matter, it is possible to detect a foreign matter having a high X-ray absorption amount such as metal, a large foreign matter, a linear foreign matter such as a needle or a wire.

  For this reason, the following four criteria are adopted as the criteria for detecting the caution foreign matter. The density of the X-ray transmission image shown below represents the degree of X-rays absorbed by the inspection object, and is determined by the product of the X-ray absorption rate α of the inspection object and the thickness t of the inspection object.

(1) Contaminant Pixel Density If there is a high-concentration foreign matter pixel in the X-ray transmission image, a cautionary foreign matter may be mixed. In particular, metals mixed in food are extremely dangerous. Since metal has a higher X-ray absorption rate than glass or plastic, the pixel density is increased.

  Therefore, it is effective for a user who regards a metal as a caution foreign object to use the pixel density as a detection reference when the metal is to be detected reliably.

(2) Number of pixels of foreign matter When a foreign matter pixel exceeds a predetermined density level (threshold) in an X-ray transmission image and a large area occupied by adjacent foreign matter pixels is large, a large foreign matter Can be considered. Here, “large” means that it is large in the X-ray transmission direction. Although it depends on the arrangement state of the inspection object irradiated with X-rays, the fact that the area is large when viewed in the X-ray transmission direction is highly likely to be a large foreign object.

  Therefore, it is effective for a user who regards a large foreign object as a caution foreign object to use the number of foreign pixels as a detection criterion.

(3) Accumulated value of foreign object pixel density As described above, depending on the arrangement state of the inspection object, the number of foreign object pixels exceeding a predetermined density level may be small despite being a large foreign object. For example, when coins (coins) are positioned in parallel in the X-ray transmission direction, the X-ray transmission image becomes a long and narrow image, and it is not detected that the foreign object is large only by calculating the number of foreign object pixels.

  However, when paying attention to the density distribution of the X-ray transmission image, the density of the central portion of the image is high, and the density is lowered toward the end portion of the image. This indicates that the central portion of the inspection object has a large thickness, and the thickness decreases as it goes to the end portion of the inspection object.

  In such a case, the accumulated pixel density value obtained by accumulating the densities of a plurality of continuous foreign matter pixels becomes large. This can be presumed to be a large foreign substance because the inspection object has a thickness.

  Therefore, in order to reliably detect a large foreign matter, it is effective to use the accumulated pixel density value of the foreign matter pixel as a detection reference in addition to the number of foreign matter pixels.

(4) Linear foreign matter Linear foreign matters such as needles and wires are extremely dangerous for foods. If it is detected from the X-ray transmission image that the foreign matter is a linear foreign matter, the caution foreign matter can be identified. Therefore, it is effective to use whether or not it is a linear foreign object as a detection criterion.

  The X-ray foreign object detector of the present invention can be configured using at least one of the four detection standards (1) to (4).

  The present invention has been made based on the above concept. Therefore, the present invention is an X-ray foreign matter detector for detecting a caution foreign matter from foreign matters mixed in an inspection object, an X-ray generator for generating X-rays to irradiate the inspection object, and an inspection target An X-ray detector that converts X-rays that have passed through an object into an electrical signal, and an image processing device that performs image processing based on the electrical signal output from the X-ray detector. A transmission image forming unit that forms a line transmission image, an image processing of the formed X-ray transmission image, a foreign object detection unit that detects the presence or absence of a foreign material, and an image processing of the formed X-ray transmission image, There is a caution foreign matter detection unit that detects foreign matter, and a caution foreign matter determination unit that determines the presence or absence of a caution foreign matter based on the detection result of the caution foreign matter detection unit. Number of pixels, accumulated value of foreign pixel density, and linear foreign matter And detecting the attention foreign object based on at least one Chino.

  According to the X-ray foreign object detector of the present invention, the X-ray foreign object detector has an output unit that outputs the presence / absence result of the foreign object detected by the foreign object detection unit and the presence / absence result of the warning foreign object determined by the foreign object determination unit. It is preferable that an alarm is output when there is a foreign object.

In addition, the foreign matter detection unit extracts foreign matter pixels having a predetermined density level or more from the X-ray transmission image to form a foreign matter image to detect the presence or absence of foreign matter, and the caution foreign matter detection unit performs image processing on the foreign matter image, It includes a pixel density detection unit that extracts pixels that have a warning density level that is greater than the predetermined density level and that is detected as a warning foreign substance when there is a pixel that is higher than the warning density level. It is preferable to configure so as to determine that there is a caution foreign object when detecting the error.
The image processing apparatus further includes a pixel number calculation unit that performs image processing on the foreign object image and calculates the number of pixels having a predetermined predetermined density level or higher. The attention foreign object detection unit is a pixel number calculation unit. When the calculated number of pixels is equal to or greater than the predetermined number, the image processing apparatus further includes a pixel number detection unit that detects as a caution foreign matter, and the caution foreign matter determination unit includes at least one of the pixel density detection unit and the pixel number detection unit. It is preferable to configure so as to determine that there is a caution foreign matter when a foreign matter is detected.
The image processing apparatus further includes a pixel density accumulating unit that performs image processing on the foreign object image and accumulates the densities of a plurality of continuous pixels, and the caution foreign object detecting unit includes the density obtained by the pixel density accumulating unit. It further includes a pixel density cumulative value detection unit that detects as a caution foreign substance when the cumulative value is equal to or greater than a predetermined value, and the caution foreign substance determination unit includes a pixel density detection unit, a pixel number detection unit, and a pixel density cumulative value detection unit. It is preferable that at least one of them is configured to determine that there is a caution foreign material when the caution foreign material is detected.

  The caution foreign matter detection unit further includes a linear foreign matter detection unit that performs image processing on the foreign matter image to detect a linear foreign matter, and the caution foreign matter determination unit includes a pixel density detection unit, a pixel number detection unit, and a pixel density. It is preferable that at least one of the cumulative value detection unit and the linear foreign matter detection unit is configured to determine that there is a caution foreign matter when the caution foreign matter is detected.

  ADVANTAGE OF THE INVENTION According to this invention, the X-ray foreign material detector which can test | inspect a to-be-inspected object and can detect a caution foreign material from the foreign materials mixed in the to-be-inspected object can be provided.

  By installing such an X-ray foreign matter detector in the production line and detecting the inspected object conveyed by a belt conveyor, etc., not only products that contain foreign matter are excluded from the production line system, but also the caution. If there is an article or package that contains foreign matter, you can stop the line and investigate the cause, or you can prevent shipment of goods or packages that contain foreign matter. Serious effects can be avoided.

It is a figure which shows the basic composition of one Embodiment of the X-ray foreign material detector of this invention. It is a functional block diagram of the image processing apparatus of FIG. It is a figure which shows a X-ray transmissive image. It is a figure which shows the X-ray transmissive image by which the filter process was carried out. It is a figure which shows a foreign material image. It is the figure which expanded the foreign material of Fig.5 (a). It is a figure which shows the density | concentration gradation of each pixel of the foreign material image of FIG. It is a figure which shows the image of a caution foreign material. It is a figure which shows the image of a linear foreign material.

  Hereinafter, an embodiment of an X-ray foreign matter detector according to the present invention will be described.

(Basic configuration of X-ray foreign matter detector)
As shown in FIG. 1, the X-ray foreign object detector includes an X-ray generator 10, an X-ray detector 12, and an image processing device 14. The X-ray generator 10 is disposed above the belt conveyor 18 that conveys the inspection object 16 in the production line, and the X-ray detector 12 is below the belt conveyor 18 and corresponds to the X-ray generator 10. It is arranged at the position.

  In the X-ray generator 10, for example, a cylindrical X-ray tube provided inside a metal box is immersed in an insulating oil, and the anode target is irradiated with an electron beam from the cathode of the X-ray tube to generate an X A line is generated. The dose of the generated X-ray is adjusted by a current flowing through the X-ray tube.

  The X-ray tube is provided in the width direction (Y direction) whose longitudinal direction is orthogonal to the product conveyance direction (X direction). The X-rays 20 generated by the X-ray tube are irradiated toward the lower X-ray detector 12 in the form of a substantially triangular screen in the direction orthogonal to the transport direction by the slit.

  On the other hand, the X-ray detector 12 is, for example, an arrayed line sensor including a plurality of photodiodes arranged in a line and a scintillator provided on the photodiode. The scintillator absorbs X-ray energy and converts it into light. The light converted by the scintillator is converted into an electric signal representing the concentration by the photodiode.

  The X-ray detector 12 receives the X-rays irradiated and transmitted to the inspection object 16 and outputs an electric signal representing the concentration. As shown in FIG. 2, the electric signal is converted into a digital density signal by the A / D converter 22. In the case of 8 bits, this digital density signal displays a density of 256 gradations. Although not shown, the A / D converter 22 may be built in the X-ray detector 12 or may be built in the image processing apparatus 14.

  The image processing device 14 creates an X-ray transmission image having a density gradation representing the degree of X-rays absorbed by the object to be inspected from the digital signal indicating the density, performs image processing on the X-ray transmission image, Attention Basically has a function to detect foreign matter.

(Configuration of Image Processing Device 14)
As shown in FIG. 2, the image processing apparatus 14 includes a personal computer having an input unit 24, an output unit 26, and an image processing unit 28.

  The input unit 24 inputs an instruction to the image processing unit 28, and is configured by a keyboard, for example.

  The output unit 26 has functions such as displaying the presence / absence of foreign matter and the presence / absence of a caution foreign matter, outputting an NG signal to the outside, and outputting an alarm based on the output of the image processing unit 28.

  The image processing unit 28 is a central processing unit of a personal computer, and executes various processes by software. Functionally, as shown in FIG. 2, a storage unit 30, an X-ray transmission image forming unit 32, a filter processing unit 34, a foreign matter detection unit 36, a pixel number calculation unit 38, and a pixel density accumulation unit 40. And a caution foreign matter detection unit 42 and a caution foreign matter determination unit 44.

  The storage unit 30 stores the converted density signal. For example, it is composed of a RAM.

  The X-ray transmission image forming unit 32 reads the density signal from the storage unit 30 and forms an X-ray transmission image.

  The X-ray transmission image is composed of, for example, 480 lines (X direction) and 640 pixels on one line. Therefore, the X-ray transmission image is composed of 640 × 480 pixels. The density of one pixel is expressed by the light and shade of 256 gradations (0: white, 255: black).

  The filter processing unit 34 filters the X-ray transmission image and extracts only foreign matters. By performing such preprocessing, the accuracy of foreign object detection in postprocessing can be increased.

  The foreign matter detection unit 36 extracts foreign matter pixels having a predetermined density level (threshold value) or more from the filtered X-ray transmission image, forms a foreign matter image, and detects the presence or absence of foreign matter depending on whether or not the foreign matter has been extracted.

  The predetermined density level is set such that a caution foreign substance to be detected is included in the formed foreign substance image. Since what determines the caution foreign matter is determined by the user using the X-ray foreign matter detector, the predetermined density level is determined by the user.

  For example, even if the foreign matter image has a low density, when it is desired to detect a large foreign matter pixel, that is, a large foreign matter as a caution foreign matter, a predetermined density level is set so that, for example, metal, glass, and plastic can be detected as foreign matter. It will be set low.

  The pixel number calculation unit 38 performs image processing on the foreign object image, and calculates the number of continuous pixels (the number of foreign object pixels). For example, a labeling process is performed on the foreign object image, and the number of pixels is calculated for each continuous pixel block.

  The pixel density accumulation unit 40 performs image processing on the foreign object image, accumulates each density of continuous pixels, and calculates a pixel density accumulation value. For example, a labeling process is performed on the foreign object image, and the pixel density is accumulated and calculated for each continuous pixel block.

  The attention foreign matter detection unit 42 includes the following four detection units, that is, a pixel density detection unit 46, a pixel number detection unit 48, a pixel density cumulative value detection unit 50, and a linear foreign matter detection unit 52. . Each detection unit detects a caution foreign matter from the formed foreign matter image based on the foreign matter pixel density, the number of foreign matter pixels, the foreign matter pixel density cumulative value, and the linear foreign matter detection criterion. The detection result is sent to the caution foreign matter determination unit 44.

  The pixel density detection unit 46 performs image processing on the foreign substance image input from the foreign substance detection unit 36, and detects a pixel that is equal to or higher than a caution density level (threshold value) that is a value larger than a predetermined density level. If a pixel of the attention density level or higher is detected, it is determined that there is a caution foreign material. For example, the foreign object image is binarized at the attention density level to detect the attention foreign object, and the image of the attention foreign object is obtained from the binarized image and the X-ray transmission image. Since attention is paid only to the pixel density of the foreign matter, the caution foreign matter may be detected directly from the filtered X-ray transmission image.

  The pixel number detection unit 48 detects whether the number of pixels calculated by the pixel number calculation unit 38 is equal to or greater than a predetermined number (threshold value). When a predetermined number of pixels or more are detected, it is determined that there is a caution foreign object.

  The pixel density accumulation value detection unit 50 detects whether the pixel density accumulation value accumulated by the pixel density accumulation unit 40 is equal to or greater than a predetermined value (threshold value). If a cumulative density value greater than or equal to a predetermined value is detected, it is determined that there is a caution foreign object.

  The linear foreign matter detection unit 52 performs image processing on the foreign matter image output from the foreign matter detection unit 36 and detects a linear foreign matter. If a linear foreign object is detected, it is determined that there is a caution foreign object.

  An example of a linear foreign object detection method is a value obtained by calculating the number of pixels obtained by calculating the number of continuous pixels and the peripheral length of an area composed of continuous pixels in the foreign object image, and dividing the peripheral length by the number of pixels. Is larger than a predetermined value, it is regarded as a caution foreign object such as a needle or a wire.

  The detection method of the linear foreign matter is not limited to this, and any method such as a method of performing image processing on the foreign matter image using a linear foreign matter filter may be used.

  The caution foreign matter determination unit 44 detects that at least one of the pixel density detection unit 46, the pixel number detection unit 48, the pixel density cumulative value detection unit 50, and the linear foreign matter detection unit 52 has a caution foreign matter. Is output, it is determined that there is no caution foreign matter, and if all detection units output a detection result indicating no caution foreign matter, it is determined that there is no caution foreign matter.

(Operation of X-ray foreign object detector)
The operation of the X-ray foreign object detector will be described with reference to FIGS. At the start of the operation of the X-ray foreign object detector, the user inputs each threshold value from the input unit 24 to the foreign object detection unit 36 and the caution foreign object detection unit 42 and sets them.

  In FIG. 1, the X-ray generator 10 irradiates the inspection object 16 conveyed by the belt conveyor 18 from the X-ray generator 10 and the X-ray detector 12 receives the X-ray transmitted through the inspection object 16.

  The X-ray detector 12 converts X-rays into electrical signals and outputs them. The electrical signal is converted into a digital density signal by the A / D converter 22 and sent to the X-ray transmission image forming unit 32.

  The X-ray transmission image forming unit 32 forms an X-ray transmission image. FIG. 3A shows an example of the formed X-ray transmission image. The X-ray transmission image is composed of 640 × 480 pixels, and the density of one pixel is expressed by the shade of 256 gradations (0: white, 255: black). In this X-ray transmission image, a package and two foreign matters mixed in the package are displayed. FIG. 3B shows the density distribution on one line in the Y direction. As shown in the figure, it is assumed that there are differences in density between the two foreign objects. Such an X-ray transmission image is sent to the filter processing unit 34.

  The filter processing unit 34 filters the X-ray transmission image and extracts only foreign matters. The filtered X-ray transmission image is shown in FIG. FIG. 4B shows the density distribution on one line in the Y direction. The package is not shown and only two foreign objects are shown. The filtered X-ray transmission image is sent to the foreign object detection unit 36.

  The foreign matter detection unit 36 extracts pixels having a predetermined density level (threshold value) or more from the filtered X-ray transmission image, forms a foreign matter image, and detects the presence or absence of foreign matter depending on whether or not the foreign matter has been extracted. The formed foreign matter image is shown in FIG. FIG. 5B shows the density distribution on one line in the Y direction. Only one foreign object above the threshold level is shown. The foreign object image is sent to the pixel number calculation unit 38 and the pixel density accumulation unit 40. On the other hand, it is also sent to the pixel density detection unit 46 and the linear foreign matter detection unit 52. The foreign object detection result is sent to the output unit 26.

  The pixel number calculation unit 38 performs image processing on the foreign object image and calculates the number of continuous pixels. FIG. 6 is an enlarged view of the foreign matter in FIG. One grid represents one pixel. Since the foreign object is displayed as one lump, the number of continuous pixels is calculated. The calculated number of pixels, that is, the number of foreign pixels is sent to the pixel number detection unit 48.

  On the other hand, the pixel density accumulation unit 40 performs image processing on the foreign object image, accumulates the densities of successive pixels, and calculates a pixel density accumulation value. FIG. 7 is a view similar to FIG. 6, but the density gradation of each pixel is indicated by a number. The pixel density accumulation value is calculated by accumulating the density of each pixel of such a foreign object image. The calculated pixel density cumulative value is sent to the pixel density cumulative value detection unit 50.

  Next, the operation of each detection unit constituting the caution foreign matter detection unit 42 will be described.

  When the foreign substance image shown in FIG. 5A is input, the pixel density detection unit 46 performs image processing on the foreign substance image and detects a pixel having a warning density level (threshold value) or higher that is greater than a predetermined density level. If a pixel with a warning density level or higher is detected, it is regarded as a warning foreign object. Such a caution foreign material is often a metal. FIG. 8A shows an image of a caution foreign object, and FIG. 8B shows a density distribution on one line in the Y direction. The detection result is sent to the caution foreign matter determination unit 44.

  The pixel number detection unit 48 detects whether the number of pixels input from the pixel number calculation unit 38 is equal to or greater than a predetermined number (threshold value). If a predetermined number of pixels or more are detected, it is determined as a large foreign matter and a caution foreign matter. The detection result is sent to the caution foreign matter determination unit 44.

  The pixel density cumulative value detection unit 48 detects whether the input pixel density cumulative value is equal to or greater than a predetermined value (threshold value). If a cumulative concentration value equal to or greater than a predetermined value is detected, it is regarded as a large foreign matter and is regarded as a caution foreign matter. The detection result is sent to the caution foreign matter determination unit 44.

  The linear foreign matter detection unit 52 performs image processing on the foreign matter image input from the foreign matter detection unit 36 and detects a linear foreign matter. FIG. 9 shows an example of an image of a linear foreign object.

  As an example of a method for detecting a linear foreign object, in a foreign object image, a value obtained by calculating the number of pixels obtained by calculating the number of continuous pixels and a peripheral length of an area composed of continuous pixels, and dividing the peripheral length by the number of pixels. Is larger than a predetermined value, it is regarded as a caution foreign object such as a needle or a wire. The detection result is sent to the caution foreign matter determination unit 44.

  The caution foreign matter determination unit 44 refers to the detection result of the caution foreign matter from the pixel density detection unit 46, the pixel number detection unit 48, the pixel density cumulative value detection unit 50, and the linear foreign matter detection unit 52, and at least one detection unit If the detection result indicating that there is a caution foreign matter is output, it is determined that there is a caution foreign matter. If all the detection units output the detection result indicating that there is no caution foreign matter, it is determined that there is no caution foreign matter. The determination result is sent to the output unit 26.

  The output unit 26 displays the presence / absence of a foreign substance and the presence / absence of a caution foreign substance. At this time, the reason why it is determined to be a caution foreign substance, that is, whether the caution foreign substance may be a metal due to the pixel density, whether the caution foreign substance is a large foreign substance due to the number of pixels or the accumulated pixel density, or is a linear foreign substance. It is also possible to display information on whether there is any at the same time.

  Further, the output unit 26 outputs a foreign object NG signal and a caution foreign object NG signal for excluding articles including foreign objects and caution foreign objects. As a result, it is possible to exclude articles mixed with foreign substances and articles mixed with caution foreign substances into separate NG boxes placed outside the production line. Furthermore, by setting from the input unit 24 by the user at the start of operation, it is possible to output an alarm for notifying the outside that there is a caution foreign material, and to stop the belt conveyor.

  The X-ray foreign matter detector according to the present invention is installed in a production line, and a cautionary foreign matter is contained in a processed food, pharmaceutical product, industrial product, or other package that is conveyed by a belt conveyor or the like. It can be used to detect whether or not.

10 X-ray generator 12 X-ray detector
DESCRIPTION OF SYMBOLS 14 Image processing apparatus 16 Inspected object 18 Belt conveyor 24 Input part 26 Output part 28 Image processing part 30 Storage part 32 X-ray transmission image formation part 34 Filter processing part 36 Foreign material detection part 38 Pixel number calculation part 40 Pixel density accumulation part 42 Caution foreign matter detection unit 44 Caution foreign matter determination unit 46 Pixel density detection unit 48 Pixel number detection unit 50 Pixel density cumulative value detection unit 52 Linear foreign matter detection unit

Claims (6)

An X-ray foreign matter detector for detecting a caution foreign matter from foreign matter mixed in an inspection object,
An X-ray generator for generating X-rays to irradiate the inspection object;
An X-ray detector for converting X-rays transmitted through the inspection object into electrical signals;
An image processing device that performs image processing based on an electrical signal output from the X-ray detector,
The image processing apparatus includes:
A transmission image forming unit that forms an X-ray transmission image by the electrical signal;
A foreign matter detection unit that performs image processing on the formed X-ray transmission image and detects the presence or absence of foreign matter;
An image processing of the formed X-ray transmission image and a caution foreign object detection unit for detecting a caution foreign object,
A caution foreign matter determination unit for determining the presence or absence of a caution foreign matter based on the detection result of the caution foreign matter detection unit;
An X-ray foreign object detector that detects an attention foreign object based on at least one of the density of the foreign object pixel, the number of foreign object pixels, the accumulated value of the foreign object pixel density, and the linear foreign object. .   It has an output unit for outputting the presence / absence result of foreign matter detected by the foreign matter detection unit and the presence / absence result of attention foreign matter determined by the caution foreign matter determination unit, and the output unit outputs an alarm when there is a caution foreign matter The X-ray foreign material detector according to claim 1. The foreign matter detection unit extracts foreign matter pixels having a predetermined density level or more from the X-ray transmission image to form a foreign matter image to detect the presence or absence of foreign matter,
The caution foreign matter detection unit performs image processing on the foreign matter image, extracts pixels having a caution density level higher than the predetermined density level, and detects pixel density detection when there is a pixel having a caution density level or higher. Part
The X-ray foreign matter detector according to claim 1, wherein the caution foreign matter determination unit determines that there is a caution foreign matter when the pixel density detection unit detects the caution foreign matter. The image processing apparatus further includes a pixel number calculation unit that performs image processing on the foreign object image and calculates the number of pixels having a predetermined density level or higher.
The caution foreign object detection unit further includes a pixel number detection unit that detects a caution foreign material when the number of pixels calculated by the pixel number calculation unit is a predetermined number or more,
The X-ray foreign object detector according to claim 3, wherein at least one of the pixel density detection unit and the pixel number detection unit determines that there is a caution foreign material when the caution foreign material is detected. . The image processing apparatus further includes a pixel density accumulation unit that performs image processing on the foreign object image and accumulates each density of a plurality of continuous pixels,
The caution foreign matter detection unit further includes a pixel density cumulative value detection unit that detects a caution foreign matter when the density cumulative value obtained by the pixel density accumulation unit is a predetermined value or more,
The caution foreign matter determination unit determines that there is a caution foreign matter when at least one of the pixel density detection unit, the pixel number detection unit, and the pixel density cumulative value detection unit detects a caution foreign matter. 4. The X-ray foreign object detector according to 4. The caution foreign matter detection unit further includes a linear foreign matter detection unit that performs image processing on the foreign matter image to detect a linear foreign matter,
The caution foreign matter determination unit has a caution foreign matter when at least one of the pixel density detection unit, the pixel number detection unit, the pixel density cumulative value detection unit, and the linear foreign matter detection unit detects the caution foreign matter. The X-ray foreign material detector according to claim 5, which is determined as follows.

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