JP2007333562A - X-ray foreign matter detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an X-ray foreign matter detector, determining presence/absence of foreign matter mixed in food or the like with high accuracy and efficiently for determining acceptance by automatically updating a determination threshold to a value having higher accuracy, causing no erroneous determination. <P>SOLUTION: This X-ray foreign matter detector includes: an X-ray intensity signal output means for exposing an examined material conveyed on a conveying path to X-rays and outputting an X-ray intensity signal corresponding to the intensity of the transmitted X-rays; a density data generation means for generating density data from the X-ray intensity signal output from the X-ray intensity signal output means; and an acceptability determination means for determining whether to pass or fail the examined material by comparing the density data generated by the density data generation means with the threshold, wherein the detector further includes a statistic calculating means for calculating the statistic of the density data based on the density data of a predetermined number used in the acceptability determination means; and a threshold updating means for updating the threshold based on the statistic calculated by the statistic calculating means within a range not to an initialized initial threshold. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an X-ray foreign matter detection apparatus that detects the presence or absence of foreign matter such as metal or bone contained in an object to be inspected such as food and determines pass / fail.

  Conventionally, X-ray foreign object detection devices have exposed X-rays to various types of inspection objects (raw meat, fish, processed food, medicine, etc.) that are sequentially transported on a transport path such as a belt conveyor. This is a device that detects whether or not foreign matter such as metal, glass, stone, bone, etc. is mixed in the object to be inspected from the amount of X-ray transmission. In this X-ray foreign matter detection apparatus, a determination threshold value for determining the presence or absence of foreign matter is set in advance, and density data generated from the amount of X-ray transmission detected by the X-ray detector and the determination threshold value are set. In comparison, the presence / absence of foreign matter is detected to make a pass / fail decision. In the case of the pass / fail determination method using such a determination threshold, there is a risk of erroneous determination depending on how the determination threshold is set, and improvement in the accuracy of the pass / fail determination is required. Moreover, it is necessary to set and adjust the determination threshold value easily and efficiently.

  In order to improve the accuracy of the pass / fail determination, proposals have been made to facilitate adjustment of the determination threshold and improve the accuracy of the determination threshold. For example, display data on the display unit in order from the oldest of the inspections, along with the inspection process of the inspection object, selectively showing the concentration data or the average value of each inspection object, data indicating the product area, product volume, and product volume Proposals have been made so that the trend display and the inspector can confirm the tendency and variation of the inspected object at a glance, and the adjustment threshold can be easily adjusted to a more accurate determination threshold ( For example, see Patent Document 1).

JP 2004-28685 A

  However, in the adjustment method of the determination threshold value by trend display as described in Patent Document 1, the contents of the trend display while visually checking the display contents of the display for the tendency and variation of the inspection object inspected by the inspector Accordingly, a more appropriate determination threshold value must be manually set. Therefore, there is a problem that the inspection efficiency is lowered.

  Therefore, the present invention automatically updates the determination threshold value to a more accurate value, so that the presence / absence of a foreign substance mixed in food can be determined with high accuracy and efficiency, and no erroneous determination occurs. An object of the present invention is to provide an X-ray foreign object detection device.

In the X-ray foreign object detection apparatus according to claim 1 of the present invention, in order to achieve the above-mentioned object, the X-ray corresponding to the intensity of the X-ray transmitted through the X-ray exposed to the inspection object conveyed on the conveyance path. X-ray intensity signal output means for outputting an intensity signal, density data generation means for generating density data from the X-ray intensity signal output from the X-ray intensity signal output means, and the density data generation means In an X-ray foreign matter detection apparatus having a pass / fail determination unit that compares the density data with a threshold value to determine pass / fail of the object to be inspected, the density based on a predetermined number of the density data used in the pass / fail determination unit Statistical value calculating means for calculating the statistical value of the data, and threshold updating means for updating the threshold based on the statistical value calculated by the statistical value calculating means within a range not exceeding the initially set initial threshold. It is.
With this configuration, when X-rays are exposed to the inspection object, an X-ray intensity signal is output by the X-ray intensity signal output means, and the X-ray intensity signal is image-processed by the density data generation means to generate density data. Is done. The density data generated by the pass / fail determination means is compared with a threshold value, and pass / fail of the inspection object is determined. A statistical value is calculated by the statistical value calculation means based on the predetermined number of density data used by the pass / fail determination means. The threshold value is automatically updated within a range that does not exceed the initial threshold value initially set based on the statistical value by the threshold value updating means, that is, within the range between the lower limit value of the density data and the initial threshold value.

In the X-ray foreign matter detection apparatus according to claim 2 of the present invention, the threshold update unit is configured to update the threshold every time the predetermined number of the density data is generated.
With this configuration, the initial threshold value and the updated update threshold value are automatically updated every time a predetermined number of density data are generated.

In the X-ray foreign matter detection apparatus according to claim 3 of the present invention, the non-defective product density data, which is the density data of the inspected object, in which the predetermined number is determined to be non-defective by one of the initial threshold value and the updated update threshold value. Consists of only.
With this configuration, a predetermined number is counted based only on the non-defective product density data determined to be non-defective by either the initial threshold value or the updated update threshold value, and is used as a basis for calculating statistical values.

In the X-ray foreign matter detection apparatus according to claim 4 of the present invention, the statistical value calculation means is a ratio of the number of the density data exceeding the initial threshold value and the predetermined number in the predetermined number of the density data. When the value reaches a certain ratio, the density data exceeding the initial threshold value is regarded as a value having a predetermined relationship with the initial threshold value, so that the statistical value is calculated as the non-defective product density data. The
With this configuration, when the ratio between the number of density data exceeding the initial threshold and the predetermined number among the predetermined number of density data reaches a certain ratio by the statistical value calculation means, the density data exceeding the initial threshold is It is regarded as a value having a predetermined relationship with the initial threshold value, is regarded as non-defective product density data, and a statistical value is calculated. Hereinafter, the fact that the density data itself exceeds the initial threshold is expressed as “exceeded”, and the fact that the updated update threshold itself does not cross the initial threshold is expressed as “not exceeded”.

  In the X-ray foreign object detection device according to claim 1, the statistical value is calculated by the statistical value calculation means based on the predetermined number of density data used by the pass / fail determination means, and the threshold value is calculated based on the statistical value by the threshold update means. Therefore, there is an effect that a highly accurate determination according to the type and characteristics of food can be automatically and efficiently performed.

  In the X-ray foreign object detection device according to claim 2, since the threshold value is updated every time a predetermined number of density data is generated, for example, a statistical value is calculated for each batch including a series of data sets. In addition, there is an effect that it is possible to automatically and efficiently perform a highly accurate determination according to the variation of the food lot and the change of the surrounding environment.

  In the X-ray foreign matter detection apparatus according to claim 3, a predetermined number is counted based only on the non-defective product density data determined to be non-defective by either the initial threshold value or the updated update threshold value, and the statistical value is calculated. Therefore, it is possible to obtain a threshold with higher accuracy and to obtain a pass / fail judgment with high accuracy.

  In the X-ray foreign object detection device according to claim 4, when the ratio of the number of density data exceeding the initial threshold value and the predetermined number among the predetermined number of density data reaches a certain ratio by the statistical value calculation means, Since the density data exceeding the initial threshold is regarded as a value having a predetermined relationship with the initial threshold and is regarded as non-defective density data, a statistical value is calculated. For example, all the predetermined number of density data are defective. Even in this case, the calculation of the statistical value is not disabled, and the statistical value is updated within the range where the threshold does not exceed the initial threshold, that is, within the range between the lower limit value of the density data and the initial threshold. Therefore, the updated threshold value does not exceed the initial threshold value, and the threshold value can be automatically updated within a range that does not exceed the initial threshold value, and there is an effect that highly efficient inspection can be performed.

Hereinafter, an embodiment of an article inspection apparatus according to the present invention will be described with reference to the drawings.
1 to 9 show an embodiment of an X-ray foreign object detection device according to the present invention.

As shown in FIGS. 1 and 2, the X-ray foreign object detection device 1 includes a transport unit 2, an X-ray generation unit 3, an X-ray detection unit 4 as an X-ray intensity signal output unit, and a light projecting / receiving unit 5. The display unit 6, the operation unit 7, and the processing unit 8 are configured.
The X-ray foreign object detection device 1 is installed in a part of a transport line that transports a package 10 as an object to be inspected, and is mixed with metal, glass, stone, The presence / absence of a foreign substance such as a bone is detected to detect whether or not a predetermined object is present in the package 10.

  The transport unit 2 includes four pulleys 2a, 2b, 2c, and 2d and an endless transport belt 2e that is wound around these pulleys. The transport unit 2 is configured to transport various packages 10 such as packed raw meat, fish, processed food, and medicine, and the X-rays generated by the X-ray generation unit 3 are transported to the package 10 being transported. Therefore, the transport unit 2 and the X-ray generation unit 3 are arranged so as to be exposed vertically. The transport unit 2 is configured to transport the package 10 at a constant transport speed set in advance by driving of a drive motor M connected to the pulley 2a.

The X-ray generation unit 3 is disposed above the transport unit 2 at a predetermined height and is opposed to the X-ray detection unit 4 provided below the transport belt 2e.
For example, the X-ray generation unit 3 includes a cylindrical X-ray tube provided in a metal box, which is immersed in insulating oil, and irradiates an anode target with an electron beam from the cathode of the X-ray tube. A line is generated. The X-ray tube is provided in the width direction whose longitudinal direction is orthogonal to the transport direction of the package 10. The X-ray generated by the X-ray tube is directed to the lower X-ray detection unit 4 by a slit (not shown) formed on the bottom surface of the box along the longitudinal direction of the X-ray tube, and has a width orthogonal to the conveyance direction. The screen is exposed to a substantially triangular screen.

The X-ray detection unit 4 detects the transmission amount of X-rays that are exposed to and transmitted through the package 10. For the X-ray detection unit 4, for example, an array line sensor including a plurality of photodiodes arranged in a line and a scintillator provided on the photodiode is used. For example, 640 photodiodes are arranged with a pitch of 0.4 mm in the line direction (Y direction). The scintillator absorbs X-ray energy and emits fluorescence.
In the X-ray detection unit 4, X-rays are emitted from the X-ray generation unit 3 to the package 10, and X-rays transmitted through the package 10 are received by a scintillator and converted into light. Further, the light converted by the scintillator is received by a photodiode disposed under the scintillator. Each photodiode converts received light into an electrical signal and outputs it as an X-ray intensity signal 11a. The X-ray intensity signal 11 a is stored in the data memory 11 after being A / D converted by an A / D converter (not shown).

  The light projecting / receiving unit 5 includes a pair of light projecting units 5 a and a light receiving unit 5 b, and is disposed on the carry-in side of the transport unit 2. The light projecting unit 5a is located on one side of the transport belt 2e, the light receiving unit 5b is located on the other side of the transport belt 2e so as to face the light projecting unit 5a, and the package 10 is provided with the light projecting unit 5a and the light receiving unit 5b. The light receiving portion 5b is shielded from light by the package 10 when passing between the two.

The display unit 6 is connected to the bus 9 and has, for example, a display device such as a liquid crystal display shown on the left side of FIG. 3, and an X-ray fluoroscopic display 6b based on a projection view of X-rays transmitted through the numeric display unit 6a and the package 10. 4 and FIG. 5, the graph of the update threshold value K _S calculated from the initial threshold value K, the coefficient k, the average value m of the density data within a predetermined number and the standard deviation value σ, the average value m of the density data Graphs are displayed.

  The operation unit 7 is connected to a bus 9 as shown in FIG. As shown in FIG. 3, the operation unit 7 includes a switch 7a, a switch 7b, an enter key 7c, a numeric keypad 7d, a designation button 7e, a cross key 7f, and a cursor 7g displayed on the display unit 6. And are provided. When the switch 7a is depressed, the foreign object detection mode is selected, and the foreign object detection of the package 10 is executed by the CPU 19 and the mode execution program 12c. When the switch 7b is pressed down, the threshold setting mode is selected, and the threshold setting is executed by the CPU 19 and the mode execution program 12c. When the enter key 7c is pressed down, various settings input through the operation unit 7 are confirmed. The numeric keypad 7d can input numerical values in various settings, and the input numerical values are displayed on the numerical display portion 6a. The cursor 7g in the display screen of the display unit 6 can be moved by pressing the cross key 7f. In addition, the cursor 7g can be moved by a mouse (not shown) connected to the operation unit 7. When the designation button 7e is depressed, the point designated by the cursor 7g in the display screen of the display unit 6 can be designated.

  The processing unit 8 is composed of a recording medium such as a hard disk. As shown in FIG. 2, the data memory 11, the program storage unit 12, the X-ray generation unit drive circuit 16 that drives the X-ray generation unit 3, and the X-ray detection unit 4. X-ray detector drive circuit 17 for driving the motor, a motor drive circuit 18 for driving the motor M, a CPU 19 for controlling each part, and a bus 9 for connecting them.

The data memory 11 is a readable / writable semiconductor memory such as a RAM. In the data memory 11, 640 X-ray intensity signals 11a per line (Y direction) are stored at least a predetermined number of lines (for example, 480 lines) corresponding to the length in the transport direction X of the package 10 to be transported. It has become so. The data in the memory 11, the X-ray intensity signal 11a output from the X-ray intensity signal output means, setting data 11b such as set initial thresholds K and updates the threshold value K _S by the threshold setting program 12a, the density data 11c, etc. Are stored in a predetermined area.

  The program storage unit 12 includes a threshold setting program 12a, a foreign matter detection program 12b, a mode execution program 12c, a pass / fail determination program 12d as pass / fail determination means, an X-ray intensity signal output program 12e as X-ray intensity signal output means, and density data. A density data generation program 12f as a generation unit, a statistical value calculation program 12g as a statistical value calculation unit, a threshold update program 12h as a threshold update unit, and the like are stored.

  In the threshold setting program 12a, an initial threshold setting process in the threshold setting mode is performed. Specifically, an initial threshold value used in the pass / fail determination is set, and an initial threshold value K used in the pass / fail determination as to whether or not a foreign object is contained in the package 10 is set. An X-ray intensity signal 11a is obtained from the X-rays that have been exposed to and transmitted through the package 10 to be conveyed, image processing is performed, an initial threshold value K is set from the product type, characteristics, inspection conditions, etc. of the package 10, and the data memory 11 is stored as setting data 11b. The initial threshold value K is set to a value with a certain margin so that the density data 11c of the package 10 to be compared does not erroneously determine a non-defective product as a defective product due to variations in the characteristics of the package 10. That is, it is set so as to detect a foreign object that absorbs a relatively large amount of X-rays.

  In the foreign matter detection program 12b, foreign matter detection processing in the foreign matter detection mode is performed. Specifically, a pass / fail determination is made as to whether or not a foreign substance is contained in the package 10, and an inspection pass / failure process is performed.

  In the mode execution program 12c, one of the threshold setting mode by the threshold setting program 12a and the foreign object detection mode by the foreign object detection program 12b is selected and executed.

In acceptance determination program 12d, it is compared with the density data 11c of the initial threshold K or updated threshold value K _S and the package 10, foreign matter when it exceeds the updated threshold value K _S concentration data 11c is initial threshold K or update If it does not exceed the initial threshold value K or the updated update threshold value K _S , it is determined that no foreign matter is included.

  In the X-ray intensity signal output program 12e, the transmitted X-ray transmitted through the package 10 and further transmitted through the transport belt 2e is input to a scintillator provided in the X-ray detection unit 4 and converted into light, and the converted light is transmitted. It is converted into an electrical signal by a photodiode provided in the X-ray detector 4 and stored in the data memory 11 as an X-ray intensity signal 11a. The X-ray intensity signal 11a includes X-ray transmission data that transmits X-rays and X-ray absorption data that absorbs X-rays, and is used according to the purpose as appropriate.

  In the density data generation program 12f, the X-ray intensity signal 11a stored in the data memory 11 is read, and the read X-ray intensity signal 11a is converted from an analog signal to a digital signal by an A / D converter (not shown). Density data (for example, package data) that is converted and further converted into luminance information of 256 gradations from 0 to 255, subjected to image processing such as filter processing so as to emphasize a portion corresponding to a foreign object, and compared with a threshold value 10) and is stored in the data memory 11 as density data 11c. This density data 11c is used for pass / fail determination of the presence or absence of foreign matter for each package 10.

In statistical value calculating program 12g, it is read density data 11c stored in the data memory 11 as setting data 11b, for updating the initial threshold K and updates the threshold value K _S based on the read density data 11c The statistical value used for is calculated. This statistical value includes the average value m and the standard deviation value σ of the density data 11c. In the present invention, the average value m is expressed by an arithmetic average value (arithmetic average value), and the standard deviation value σ is expressed by the following equation (1).

式（１）中、ｎは自然数、ｘは検出された個々の濃度データ１１ｃを表す。

In formula (1), n represents a natural number and x represents detected individual density data 11c.

  The average value m and the standard deviation value σ of the density data 11c are calculated for each predetermined number. Here, the predetermined number means a value within a specified time or a specified number of lines. The predetermined number is, for example, p, and as shown in FIG. 6A, the number p is counted for the first time, the count is cleared for the second time, and the next 1 after the number p for the first time. The number may be a so-called batch unit in which the number p is counted after one or a plurality of pieces. Further, as shown in FIG. 6B, the number may be updated every time in units of a, in which the number p is counted for the first time and the number p is counted after the number a for the second time. a may be 1 or plural. When a is 1, the threshold value is continuously updated. When a is p, the number of batch units counted from the next one after the predetermined number p is obtained. From the viewpoint of improving the calculation efficiency, the predetermined number is preferably the number of batch units. In order to update the threshold value and obtain a more accurate threshold value, the larger the predetermined number, the better. However, the larger the number, the more complicated the calculation process. Therefore, the predetermined number is appropriately selected according to the product type, package characteristics, accumulated data, experience value, and the like. For example, 5,000 to 50 are preferable, and 1,000 to 100 are more preferable.

In principle, the predetermined number is the number of density data 11c of the package 10 determined as a non-defective product based on either the initial threshold value K or the update threshold value K _S (hereinafter referred to as “non-defective product density data 11c”). Density data 11c of the package 10 determined as a defective product (hereinafter referred to as “defective product density data 11c”) is excluded. By using only the non-defective product density data 11c as a basis for calculation, it is possible to obtain the average value m and the standard deviation value σ with higher accuracy.
However, even if it is the density data 11c of the defective product, when the ratio of the density data 11c exceeding the initial threshold value K of the density data 11c of the defective product reaches a certain ratio, the density of the defective product is reached. The data 11c that exceeds the initial threshold value K is regarded as a value having a predetermined relationship with the initial threshold value K, so that it is regarded as non-defective density data 11c, and the statistical average value m and standard deviation value σ are calculated. May be.
By treating the density data 11c of the defective product as the non-defective product density data 11c in this way, for example, all of the predetermined number of density data 11c are defective products exceeding the initial threshold value K and cannot be used as statistical value calculation data. There is an effect that it is possible to avoid that the threshold value K _S becomes 0 and to automatically set the update threshold value K _S within a range not exceeding the initial threshold value K.

The ratio between the number of defective product density data 11c exceeding the initial threshold value K and the predetermined number is the initial threshold value of the defective product density data 11c included in the predetermined number p continuously counted. NG / p is preferably from 0.5 to 1.0, where NG is the number of those exceeding K. If the ratio is less than 0.5, the average value m and the standard deviation of the density data 11c with accuracy maintained by the remaining density data 11c excluding the density data 11c of the defective product exceeding the initial threshold K. The value σ is obtained. Of density data 11c of defective products are contained within the predetermined number p, when the number and NG' but exceeds the updated threshold value _{K S,} NG' / p is a 0.5 to 1.0 Also good.

A value regarded as non-defective product density data as a value having a predetermined relationship with the initial threshold value K is a value close to the initial threshold value K that does not exceed the initial threshold value K. If a value close to the initial threshold value K is N, for example, N may be a fixed value set between the initial threshold K and 0.9K, or may be a calculated value calculated using the density data 11c of the defective product.
In the case of the calculated value, for example, when the average value of the density data 11c of defective products is F _m , the standard deviation value is σ _F , and the variable coefficient is k ′, N is the following equation, N = F _m + k calculated as'Shiguma _F, and the following equation, K ≧ N> 0.9 × K to a value having a relationship that satisfies the coefficients according to the value of the average value F _m and the standard deviation sigma _F k' Can be calculated by appropriately selecting.
However, if the average value F _m becomes larger than N, it may be set such that K ≧ N> 0.9 × K is satisfied by setting F _m = N and k ′ = 0. By setting ′ <0, K ≧ N> 0.9 × K may be satisfied.
In this way, by setting the value N close to the initial threshold value as a value having a predetermined relationship, the threshold value can be set even if a large number of defective product density data 11c are included in the predetermined number of density data 11c. It can be calculated as an effective statistical value that can be used when updating. That is, the average value m and the standard deviation value σ, which are statistical values, can be calculated as effective values based on both the value N close to the initial threshold value K calculated by the statistical value calculation program 12g and the non-defective density data 11c. it can.

In the threshold update program 12h, the initial threshold K is within a range that does not exceed the initial threshold K based on the average value m of the density data 11c calculated by the statistical value calculation program 12g and the standard deviation value σ, that is, the density data. It is updated as the update threshold value K _S within the range of the lower limit value of 11c and the initial threshold value K. Furthermore, the updated updated threshold value K _S is re-updated within a range not exceeding the initial threshold value K based average value m of the density data 11c after appropriately updated, in the standard deviation sigma. The updated and re-updated update threshold value K _S is expressed by the following equation (2), for example.

K _S = m + kσ (2)
In formula (2), k is a coefficient for determining the suitable update threshold value K _S from the average value m, for example, 2-5 are preferable and 3-4 are more preferable.
The coefficient k is input from the numeric keypad 7d of the operation unit 7 shown in FIG. 3, and the input numerical value is displayed on the numeric display unit 6a and is confirmed by pressing the enter key 7c to be used for calculating the update threshold value K _S. Can do. The coefficient k may be stored in advance in the data memory 11 as the setting data 11b based on the product type, package characteristics, accumulated data, experience values, and the like, and automatically read out for use. For example, the average value m and the update threshold value K _S used for the calculation may be displayed on the display screen of the display unit 6 as shown in FIGS.

The update threshold value K _S described above is a non-defective product when the predetermined number is only the non-defective product density data 11c and when the density data 11c of the defective product is a value having a predetermined relationship with the initial threshold value K by the statistical value calculation program 12g. When the statistical value is calculated as a value regarded as the density data 11c (value N close to the initial threshold value K), the value is within a range not exceeding the initial threshold value K.
When the predetermined number is only the density data 11c of the defective product and when the density data 11c of the defective product is included, the statistical value calculation program 12g does not correct the statistical value as the value N close to the initial threshold value K. updating threshold K _S to correct the updated threshold itself by update 12h may be a value within a range that does not exceed the initial threshold K.
As a method for correcting the update threshold value itself, a method in which the uniform update threshold value K _S is regarded as the initial threshold value K, a method by a predetermined calculation process, and the like can be cited. In the calculation method, calculation processing is performed based on both the density data 11c of the defective product and the density data 11c of the non-defective product or only the density data 11c of the defective product. For example, the coefficient k in the equation (2) K _S = m + kσ is appropriately corrected so that the update threshold value K _S satisfies the following equation, K ≧ K _S > 0.9 × K.
Since the average value m and the standard deviation value σ are positive values, the coefficient k is (K−m) / σ and (0.9K) from the equation (2) and the equation K ≧ K _S > 0.9 × K. It is corrected to be a value between -m) / σ. Thus, by correcting the coefficient k, the updated threshold value K _S can be set as a value within a range that does not exceed the initial threshold K.
As a result, even when the predetermined number of defective product density data 11c is included in a large number, the update threshold value can be calculated based on the defective product density data 11c. That is, conventionally, when the update threshold value is calculated using the density data 11c of the defective product, the calculation cannot be performed and the update threshold value cannot be obtained. However, this situation can be avoided. The threshold value can be appropriately updated continuously in succession.

  The X-ray generation unit drive circuit 16 applies a predetermined power to the X-ray detection unit 4 in response to an inspection start command from the CPU 19 so that the X-ray generation unit 3 constantly emits X-rays. X-rays emitted from the ray generator 3 are input to the X-ray detector 4.

  The X-ray detector drive circuit 17 is configured to always turn on the X-ray generator 3 in response to an inspection start command from the CPU 19 and input X-rays emitted from the X-ray generator 3.

  The motor drive circuit 18 drives the motor M by supplying predetermined power to the motor M in response to a drive start command from the CPU 19.

  The CPU 19 is a processor that controls the entire X-ray foreign object detection apparatus 1. The CPU 19 controls the X-ray generation unit drive circuit 16, the X-ray detection unit drive circuit 17, the motor drive circuit 18, and the X from the data memory 11. Reading of the line intensity signal 11a and the like, execution of the threshold setting program 12a stored in the program storage unit 12 and other various programs, transfer of other data, various calculations, temporary storage of data, and the like are performed. .

  Next, foreign substance detection execution processing in the X-ray foreign substance detection apparatus 1 according to the present invention will be described with reference to the flowcharts of FIGS.

First, the inspector places the packed package 10 such as cheese on the transport belt 2e shown in FIG. 1, and prepares for foreign object detection or threshold setting.
When the initial threshold value K is set, the inspector presses down the switch 7a shown in FIG. 3 to select the X-ray foreign matter detection mode. When the initial threshold value K is not set, the inspector presses the switch 7b. The threshold setting mode is selected by lowering (S10). When either the threshold setting mode or the foreign object detection mode is selected, the CPU 19 recognizes the selected mode (S12). When the CPU 19 recognizes the threshold setting mode, the mode execution program 12c in the program storage unit 12 reads the threshold setting program 12a and starts executing the threshold setting mode (S14). When the CPU 19 recognizes the foreign object detection mode, the mode execution program 12c in the program storage unit 12 determines whether an initial threshold is set (S30). If it is determined that the initial threshold is not set, the threshold setting program 12a is read and execution of the threshold setting mode is started (S14). If it is determined that the initial threshold is set, a foreign object is determined. The detection program 12b is read and execution of the foreign object detection mode is started (S32).

  When the execution of the threshold setting mode is started (S14), a drive command is output from the CPU 19 to the X-ray generation unit drive circuit 16, the X-ray detection unit drive circuit 17, and the motor drive circuit 18. In response to the output drive command, the motor M is driven to rotate, and the transport unit 2 starts transporting the package 10 (S16). Next, X-rays are emitted from the X-ray generator 3 (S18).

The X-ray generation unit 3 and the X-ray detection unit 4 are always in an ON state, and the X-ray is exposed from the X-ray generation unit 3 to the X-ray detection unit 4 in a substantially triangular screen shape. Yes. When the package 10 passes through the X-ray screen, the package 10 is exposed to the screen-shaped X-ray (S18). When X-rays are exposed, transmitted X-rays that have passed through the package 10 are input to a scintillator provided in the X-ray detection unit 4. When the X-ray is input to the scintillator and converted into light, the light received by the photodiode provided in the X-ray detection unit 4 is converted into an electric signal, the X-ray intensity signal output program 12e is executed, and X It is output as the line intensity signal 11 a and stored in the data memory 11. Based on the X-ray intensity signal 11a, display processing is performed and displayed on the display unit 6 as an X-ray transmission image or an X-ray absorption image. For example, it is displayed as the X-ray fluoroscopic display 6b of the package 10 (see FIG. 3). The examiner can visually observe whether or not there is a foreign substance in the package 10 with reference to the X-ray fluoroscopic display 6b.
The X-ray intensity signal 11a stored in the data memory 11 is read by the threshold setting program 12a, the X-ray intensity signal 11a is image-processed by the density data generation program 12f (S20), and an initial threshold K is set based on various conditions. Is calculated and set (S22). The initial threshold value K set by the threshold value setting program 12a is stored in the data memory 11 (S24).

  The X-ray transmission image is converted into a digital image of the X-ray transmission data of the package 10 by a line sensor such as a photodiode of the X-ray detection unit 4 and is sampled in the transport direction at a sampling pitch substantially equal to the sampling pitch on one line. The image may be displayed on the display unit 6 as an X-ray transmission image. Further, if the X-ray absorption rate of the package 10 is α and the thickness of the package 10 is t, the intensity S ′ after the X-rays having the intensity S are transmitted through the package 10 is theoretically S ′ = S · exp ( −α · t), so if the logarithm of both sides is taken and transformed, α · t = log (S) −log (S ′) can be written, and the X-ray transmission image corresponds to the two-dimensional distribution of S ′. If the logarithm is transformed, it can be converted into an X-ray absorption image showing a two-dimensional distribution of the absorption amount α · t by the package 10. Thus, you may display on the display part 6 as an X-ray absorption image.

  When the execution of the foreign object detection mode is started (S32), a drive command is output from the CPU 19 to the X-ray generation unit drive circuit 16, the X-ray detection unit drive circuit 17, and the motor drive circuit 18. In response to the output drive command, the motor M is driven to rotate, and the conveyance of the package 10 of the same type as the package 10 used in the threshold setting placed on the conveyance belt 2e is started (S34).

  When the package 10 is transported and passes between the light projecting unit 5a and the light receiving unit 5b, the emitted light from the light projecting unit 5a is blocked. Thereby, the passage of the package 10 is detected. Several seconds after the light receiving unit 5b detects light shielding, the package 10 is exposed to the package 10 by passing through the X-ray screen exposed from the X-ray generation unit 3 in a substantially triangular screen shape. Is fired (S36). In the X-ray detection unit 4, transmitted X-rays transmitted through the package 10 are input to the scintillator and converted into light. Next, light is received by the photodiode of the X-ray detector 4 and converted into an electrical signal, the X-ray intensity signal output program 12e is executed, and the X-ray intensity signal 11a is output (S38). The output X-ray intensity signal 11a is stored in the data memory 11 (S40).

  The X-ray intensity signal 11a stored in the data memory 11 is converted into luminance information of, for example, 256 gradations by the density data generation program 12f, and then subjected to image processing such as feature extraction filter processing (S42). Density data 11c is generated (S44) and stored in the data memory 11 (S46). Further, based on the density data 11c, display processing is performed to generate fluoroscopic image data, which is displayed on the display unit 6 as an X-ray fluoroscopic display 6b of the package 10 as shown in FIG.

As shown in FIG. 8, the number of stored density data 11c is counted (S50), and it is determined whether it is less than a predetermined number, for example, 100 (S52). If it is determined to be less than 100, the density data 11c of the package 10, and the current threshold value K _G is the initial threshold K or updated threshold has been updated earlier K _S is compared (S54), the previous count Is cleared (S56). If concentration data 11c exceeds the current threshold value _{K G} (S58) is an inspection failure as contains foreign substance (S60), if the density data 11c does not exceed the current threshold value _{K G} (S58) Is passed the inspection (S62) because no foreign matter is contained, the result is displayed (S94), and the display unit 6 displays, for example, necessary numbers such as NG and OK together with the serial number and lot number of the package 10. A display is made (S96). When the foreign object detection is continued (S98), (B), that is, as shown in FIG. 7, from the step S36 where the X-rays are exposed to the package 10 to the step S94 where the display process is performed are repeatedly executed. When all foreign matter detection is performed, the foreign matter detection mode ends.

If it is determined in step S52 that the number exceeds 100, the density data 11c of the defective product exceeding the initial threshold value K is counted (S70), and the ratio to the predetermined number, for example, 50/100, that is, It is determined whether it is less than 0.5 (S72). When it is determined that the ratio with respect to the predetermined number is less than 0.5 (S72), for example, when it is 0.4, the density of the remaining non-defective products excluding the density data 11c40 of the defective products from the predetermined number of 100. for data 11c60 pieces, statistical calculation program 12g is executed, statistics are calculated and executed threshold update 12h is updated threshold K _S is newly set current threshold K _G is updated (S82) . Next, the count is cleared (S84), and the density data 11c is compared with the updated update threshold K _S (S86). If concentration data 11c exceeds the updated threshold value K _S this comparison (S88) is an inspection failure as contains foreign substance (S90), if the density data 11c does not exceed the updated threshold K _S In (S88), the inspection is passed (S92) because no foreign matter is included, and the result is displayed (S94). The display unit 6 displays, for example, the package 10 reference number and lot number together with NG, OK, etc. Is displayed (S96). When the foreign object detection is continued (S98), (B), that is, as shown in FIGS. 7 to 9, the process is repeatedly executed from step S36 where the X-ray is exposed to the package 10 to step S96 where the display is made. Is done. When all foreign matter detection is performed, the foreign matter detection mode ends.

If it is determined that the ratio of the predetermined number of defective product density data 11c exceeding the initial threshold K to the predetermined number is not less than 0.5 (S72), for example, 0.8, As shown in FIG. 9, the process proceeds to C), and it is determined whether or not to correct the defective product density data 11c that exceeds the initial threshold value K (S76), and the defective product density data 11c contains the initial threshold value K. When the value exceeding the value is corrected (S76), the statistical value calculation program 12g calculates the effective statistical value as a value regarded as a value having a predetermined relationship with the initial threshold value K (S78). Then proceed to (D), and update the current threshold value _{K G} is set as updated threshold _{K S} by the threshold update 12h based on the calculated statistical value (S78). After setting the update threshold _{K S,} it executes the step S82 to step S98. When the density data 11c of the defective product is not corrected (S76), the update threshold value itself is corrected by the threshold value update program 12h. Specifically, the coefficient k in Equation (2) K _S = m + kσ is appropriately corrected so that the update threshold value K _S satisfies the following equation, K ≧ K _S > 0.9 × K (S80). The coefficient k is corrected so as to be a value between (K−m) / σ and (0.9K−m) / σ from Expression (2) and Expression K ≧ K _S > 0.9 × K. The Thus, by correcting the coefficient k, the updated threshold value K _S can be set as a value within a range that does not exceed the initial threshold K. After setting the update threshold _{K S,} it executes the step S82 to step S98.
When the foreign object detection is continued (S98), (B), that is, as shown in FIG. 7, from step S36 where X-rays are exposed to the package 10 to step S90 where display processing is performed are repeatedly executed. . When all foreign matter detection is performed, the foreign matter detection mode ends.

As described above, in the X-ray foreign object detection apparatus according to the present invention, (1) the X-ray intensity signal 11a corresponding to the intensity of X-rays that are transmitted through the package 10 conveyed on the conveyance path. It is output by the X-ray intensity signal output program 12e, image processing is performed based on the X-ray intensity signal 11a, and density data 11c is generated by the density data generation program 12f. The density data 11c is compared with any of the initial threshold K and updates the threshold value K _S, if it contains a foreign substance in the package 10 is determined by the acceptance judgment program 12d. The update threshold value K _S used for this determination is a statistical value calculated by the statistical value calculation program 12g using a predetermined number of density data 11c to be compared in the pass / fail determination program 12d, and the threshold value is based on this statistical value. The initially set initial threshold value K is updated by the update program 12h. Since the threshold value is automatically updated within a range not exceeding the initial threshold value K, it is possible to detect the presence / absence of a foreign substance with higher accuracy and to perform pass / fail determination without causing erroneous determination.

  In the X-ray foreign object detection apparatus according to the present invention, (2) the threshold value is automatically updated for each predetermined number of density data 11c of the package 10 by the threshold value update program 12h. It can be detected and a pass / fail decision can be made automatically.

In X-ray foreign material detecting apparatus according to the present invention, (3) a predetermined number of density data 11c of the package 10, only the density data 11c of the package 10 is determined to be non-defective by either of the initial threshold value K and updates the threshold value K _S Since the statistical value is calculated by the statistical value calculation program 12g based on this, the presence / absence of a foreign substance can be detected with higher accuracy, and a pass / fail determination can be made automatically.

  In the X-ray foreign object detection device according to the present invention, (4) when the ratio between the predetermined number of density data 11c exceeding the initial threshold K and the predetermined number reaches a certain ratio by the statistical value calculation program 12g, Since the density value 11c of the defective product that exceeds the initial threshold value K is regarded as a value having a predetermined relationship with the initial threshold value K, the statistical value is calculated as the non-defective product density data 11c. In other words, it is possible to detect the presence / absence of a foreign object with higher accuracy and to perform pass / fail determination without causing erroneous determination.

  As described above, according to the present invention, by automatically updating the determination threshold value to a value with higher accuracy, the presence / absence of a foreign substance mixed in food can be determined with high accuracy and efficiency. If it is an inspection device that has the effect that no determination occurs and uses the determination threshold to determine the presence or absence of foreign matter, it detects not only the X-ray foreign matter detection device but also the metal mixed in the inspection object using a magnetic field. It is also useful for metal detectors and other foreign matter inspection devices.

1 is a perspective view showing an embodiment of an X-ray foreign object detection device according to the present invention. It is a block diagram which shows one Embodiment of the X-ray foreign material detection apparatus which concerns on this invention. It is a top view which shows the operation part in one Embodiment of the X-ray foreign material detection apparatus which concerns on this invention. It is the graph displayed on the display part in one Embodiment of the X-ray foreign material detection apparatus which concerns on this invention. It is the graph displayed on the display part in one Embodiment of the X-ray foreign material detection apparatus which concerns on this invention. It is explanatory drawing which shows the predetermined number in one Embodiment of the X-ray foreign material detection apparatus which concerns on this invention. It is a flowchart which shows the foreign material detection processing procedure in one Embodiment of the X-ray foreign material detection apparatus which concerns on this invention. It is a flowchart which shows the foreign material detection processing procedure in one Embodiment of the X-ray foreign material detection apparatus which concerns on this invention. It is a flowchart which shows the foreign material detection processing procedure in one Embodiment of the X-ray foreign material detection apparatus which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 X-ray foreign material detection apparatus 2 Conveyance part 2a, 2b, 2c, 2d Pulley 2e Conveyance belt 3 X-ray generation part 4 X-ray detection part (X-ray intensity signal output means)
5 Light Emitting / Receiving Unit 5a Light Emitting Unit 5b Light Receiving Unit 6 Display Unit 6a Number Display Unit 6b X-ray Perspective Display 7 Operation Unit 7a, 7b Switch 7c Enter Key 7d Numeric Keypad 7e Designation Button 7f Cross Key 7g Cursor 8 Processing Unit 9 Bus 10 Package (Inspection)
11 Data memory 11a X-ray intensity signal 11b Setting data 11c Concentration data 12 Program storage unit 12a Threshold setting program 12b Foreign matter detection program 12c Mode execution program 12d Pass / fail judgment program (pass / fail judgment means)
12e X-ray intensity signal output program (X-ray intensity signal output means)
12f Density data generation program (density data generation means)
12g Statistical value calculation program (Statistical value calculation means)
12h Threshold update program (threshold update means)
16 X-ray generator drive circuit 17 X-ray detector drive circuit 18 Motor drive circuit 19 CPU

Claims (4)

An X-ray intensity signal output means for outputting an X-ray intensity signal corresponding to the intensity of the X-ray that has been irradiated and transmitted to the inspection object conveyed on the conveyance path, and is output from the X-ray intensity signal output means Density data generation means for generating density data from the X-ray intensity signal, and pass / fail determination means for comparing the density data generated by the density data generation means with a threshold value to determine pass / fail of the object to be inspected. In the X-ray foreign matter detection apparatus having
A statistical value calculation means for calculating a statistical value of the density data based on a predetermined number of the density data used in the pass / fail judgment means;
Threshold update means for updating the threshold based on the statistical value calculated by the statistical value calculation means within a range not exceeding the initially set initial threshold;
An X-ray foreign matter detection apparatus comprising:   The X-ray foreign object detection apparatus according to claim 1, wherein the threshold updating unit updates the threshold every time the predetermined number of the density data are generated.   3. The X-ray according to claim 2, wherein the predetermined number includes only non-defective density data that is the density data of the inspection object determined to be non-defective according to any of the initial threshold value and the updated update threshold value. Foreign object detection device.   When the ratio between the number of the density data exceeding the initial threshold and the predetermined number among the density data of the predetermined number reaches a certain ratio, the statistical value calculating means exceeds the initial threshold. 3. The X-ray foreign matter detection apparatus according to claim 2, wherein the statistical value is calculated by regarding the density data as a value having a predetermined relationship with the initial threshold value and regarding the non-defective density data.

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