JP2022035706A - Material discrimination device - Google Patents

Abstract

To provide a material discrimination device that can discriminate a material of an inspection target object by comparing a detection spectrum obtained by transmitting an X-ray through the inspection target object and a reference spectrum stored in advance obtained by transmitting an X-ray through a specific material.SOLUTION: The material discrimination device includes: an X-ray source 1 for irradiating an inspection target object 2 with an X-ray; a detection unit 10 for detecting a spectrum in a predetermined band of the X-ray having gone through the inspection target object 2; and a control unit 20 for receiving the detected spectrum obtained by the detection unit 10 and performing an operation. The control unit 20 has a comparison unit 22 for comparing the detection spectrum with a reference spectrum as an X-ray transmission spectrum of a known material stored in advance, and estimates the material of the inspection target object 2 by the consistency between the detection spectrum and the reference spectrum.SELECTED DRAWING: Figure 1

Description

The present invention discriminates the material of an inspected object by comparing the detection spectrum obtained by transmitting X-rays through the inspected object with a pre-stored reference spectrum obtained by transmitting X-rays through a specific material. Regarding the material discrimination device to be used.

In household waste and business waste treatment facilities, fire accidents that occur during crushing due to the inclusion of flammable hazardous materials have become a problem. Therefore, there is an increasing need for a discrimination device that can automatically discriminate flammable dangerous substances mixed in household waste and business waste. Flammable hazardous materials include, for example, disposable writer (liquefied butane gas), lithium ion (Li-ion) battery, nickel-metal hydride (Ni-MH) battery, alkaline dry battery, spray can (liquefied flammable gas), and the like. Refers to those that have a risk of ignition or explosion due to impact.

Household waste and business waste are a mixture of various shapes and sizes and made of various materials, and it is not easy to find flammable dangerous substances from them. At present, workers are squeezing out the dust that has spread on the flat ground and visually inspecting the presence of ignitable dangerous substances. Many of the garbage is wrapped in plastic bags, and it is necessary to unpack and check each of them, which takes a lot of time and effort.

On the other hand, if an X-ray inspection machine is used, it is possible to see through the inside of the plastic bag and take a picture, so that there is a possibility that an incendiary dangerous substance can be found.

Document 1 describes an X-ray inspection machine that transmits X-rays to an object to be inspected and receives the transmitted light to obtain an X-ray image. In an X-ray image, a portion having a low transmittance of X-rays is photographed lightly, and a portion having a high transmittance of X-rays is photographed darkly. The transmittance of X-rays is determined by the material and thickness of the object to be inspected. If there is a part of the X-ray image taken darker than the surroundings, this may be a foreign substance such as an ignitable dangerous substance.

Document 2 describes an X-ray inspection apparatus that determines whether or not a material (foreign substance) that should not be originally present is mixed in an object to be inspected by elemental analysis using X-rays. In this X-ray inspection device, a multi-energy sensor having an X-ray wavelength resolution is used to acquire a spectrum of X-rays transmitted through an object to be inspected, and an attempt is made to identify a specific material (foreign substance) based on this spectrum. It is a thing.

Japanese Unexamined Patent Publication No. 11-194104 Japanese Unexamined Patent Publication No. 2018-155643

The X-ray inspection apparatus described in Document 1 detects a foreign substance from the shading of an X-ray image. However, for example, a lithium-ion battery for a mobile phone may produce an image with the same density as a relatively thick plastic. Therefore, it may not be possible to distinguish between the lithium ion battery and the plastic only by the shading of the X-ray image, and automatic discrimination is difficult.

In the X-ray inspection apparatus described in Document 2, the spectra of each pixel of the X-ray image are compared with each other to discriminate the pixels of foreign substances in the X-ray image. However, when various materials such as household waste are mixed and overlapped, it is difficult to distinguish between a plurality of types of ignitable dangerous substances.

Therefore, the present invention is obtained by transmitting X-rays through the inspected object by providing an analysis method capable of estimating the material of the inspected object with high accuracy by using an X-ray multi-energy sensor capable of element analysis. It is an object of the present invention to provide a material discrimination apparatus for discriminating the material of an inspected object by comparing the detected detection spectrum with a pre-stored reference spectrum obtained by transmitting X-rays through a specific material.

When the object to be inspected is irradiated with X-rays, the elements contained in the object to be inspected absorb X-rays having a specific wavelength, and the transmittance differs depending on the wavelength. When the X-rays transmitted in this way are received by the multi-energy sensor, a unique spectrum corresponding to the elements constituting the inspected object can be obtained.

Therefore, the material discrimination apparatus according to the first invention is
An X-ray source that irradiates the object to be inspected with X-rays,
A detector that detects the spectrum of a predetermined band of X-rays that have passed through the object to be inspected,
A control unit that sends and calculates the detection spectrum obtained by the detection unit,
Equipped with
The control unit has a comparison unit that compares the detection spectrum with a reference spectrum which is an X-ray transmission spectrum of a known material stored in advance, and is inspected by the identity between the detection spectrum and the reference spectrum. It is characterized by estimating the material of an object.

The material discrimination apparatus according to the second invention is the material discrimination apparatus according to the first invention.
The reference spectrum is characterized in that at least one or more thereof is stored in advance in the comparison unit.

The material discrimination apparatus according to the third invention is the material discrimination apparatus according to the first or second invention.
The control unit is characterized in that the detection spectrum and the reference spectrum are subjected to a logarithmic function to determine the identity.

The material discrimination apparatus according to the fourth invention is the material discrimination apparatus according to the first, second or third invention.
The control unit is characterized in that the identity is determined by using the transmittances at at least two wavelengths in the detection spectrum and the reference spectrum.

The material discriminating device according to the fifth invention is the material discriminating device according to any one of the first to fourth inventions.
The control unit is characterized in that, when the difference between the detection spectrum and the reference spectrum is within a predetermined reference, it is determined that each spectrum has the sameness.

The material discriminating device according to the sixth invention is the material discriminating device according to any one of the first to fourth inventions.
The control unit is characterized in that it determines that the detection spectrum and the reference spectrum having the smallest difference from the detection spectrum among the plurality of reference spectra stored in advance have the sameness. be.

The material discrimination apparatus according to the seventh invention is the material discrimination apparatus according to the fifth or sixth invention.
The control unit is characterized in that the ratio of the reference spectrum and the detection spectrum at each wavelength is obtained, and the maximum value of each ratio is the difference.

The material discrimination apparatus according to the eighth invention is the material discrimination apparatus according to the fifth or sixth invention.
The control unit is characterized in that the ratio of the reference spectrum and the detection spectrum at each wavelength is obtained, and the ratio of the maximum value of each ratio to a predetermined reference value is set as the difference. be.

The material discrimination apparatus according to the ninth invention is the material discrimination apparatus according to the fifth or sixth invention.
The control unit is characterized in that the difference between the reference spectrum and the detection spectrum at each wavelength is obtained, and the total of the differences at each wavelength is the difference.

The material discrimination apparatus according to the tenth invention is the material discrimination apparatus according to the fifth or sixth invention.
The control unit is characterized in that the difference between the reference spectrum and the detection spectrum at each wavelength is obtained, and the difference of the total difference at each wavelength with respect to a predetermined reference value is used as the difference. ..

In the present invention, for example, the X-ray transmission spectrum for each material such as a Li-ion battery, an alkaline dry battery, or a spray can, which are flammable dangerous substances, is stored in advance as a reference spectrum, and these are compared with the detection spectrum. This is characterized by estimating the material of the object to be inspected.

According to the invention, the material of the inspected object is obtained by comparing the detection spectrum obtained by transmitting X-rays through the inspected object with the pre-stored reference spectrum obtained by transmitting X-rays through the specific material. A material discriminating device for discriminating can be provided.

That is, according to the invention, in elemental analysis using a multi-energy sensor, reference spectra of various materials such as lithium ion batteries, alkaline batteries, and spray cans are stored in advance, and the cover of an unknown material is covered. By comparing the detection spectrum obtained by X-ray photography of the inspected object with the reference spectrum, it is possible to discriminate the material of the inspected object.

Explanatory drawing of material discriminating apparatus of embodiment Explanatory drawing of control part of material discriminator Explanatory drawing of comparison part of material discrimination apparatus Example of reference spectrum (aluminum (thickness 5 mm, 10 mm)) Example of applying a logarithmic function to the reference spectrum (aluminum (thickness 5 mm, 10 mm)) Example of comparison / judgment between the detection spectrum and the reference spectrum (reference spectrum: aluminum (thickness 5 mm), detection spectrum: aluminum) Example of comparison / judgment between the detection spectrum and the reference spectrum (reference spectrum: resin material, detection spectrum: aluminum)

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

The material discrimination device according to the embodiment of the present invention is a material discrimination device that estimates the material of household waste, business waste, etc. (for example, plastic container, PET bottle, paper, food, etc.) as an inspected object.

[Structure of material discrimination device]
FIG. 1 is an explanatory diagram of a material discrimination device according to an embodiment.

As shown in FIG. 1, this material discrimination apparatus detects an X-ray source 1 that irradiates an inspected object 2 with X-rays and a detection spectrum that is a spectrum of a predetermined band of X-rays that have passed through the inspected object 2. It is provided with a detection unit 10. The detection unit 10 has a light receiving unit 11 and a memory 12. The light receiving unit 11 is a multi-energy sensor capable of detecting X-rays in a predetermined band separately for each wavelength.

The light receiving unit 11 (multi-energy sensor) has a wavelength resolution in the X-ray wavelength band. For example, the multi-energy sensor of "Detection Technology" has a wavelength resolution of 128 divisions from 20 keV to 160 keV at equal intervals. When the inspected object 2 is irradiated with X-rays containing various wavelengths, X-rays having a partial wavelength are absorbed by the inspected object 2 by the constituent elements of the inspected object 2. At this time, the unabsorbed X-rays pass through the inspected object 2 and are received by the light receiving unit 11, and a detection spectrum peculiar to the inspected object 2 is obtained. The light receiving unit 11 can be adopted regardless of the number or arrangement of sensors, such as an area camera in which sensor elements are arranged two-dimensionally or a licensor camera in which sensor elements are arranged one-dimensionally.

As the X-ray source 1, since the detection spectrum of the object 2 to be inspected is acquired in a wide wavelength band, a source 1 that emits X-rays having various wavelengths is used. In view of the light receiving wavelength of the light receiving unit 11 (multi-energy sensor), it is preferable to select an X-ray source having a tube voltage of 80 kV or more.

When the light receiving unit 11 receives X-rays, the detection unit 10 stores the light receiving data in the memory 12 and outputs the light receiving data to the control unit 20. The control unit 20 has a calculation unit 21 that calculates the transmitted detection spectrum, and a comparison unit 22 to which the calculation result of the calculation unit 21 is sent. The comparison unit 22 compares the detection spectrum sent from the calculation unit 21 with the reference spectrum which is the X-ray transmission spectrum of the known material stored in advance. At least one reference spectrum is stored in advance in the comparison unit 22. As will be described later, the control unit 20 estimates the material of the inspected object 2 based on the comparison result in the comparison unit 22 based on the identity between the detection spectrum and the reference spectrum.

Further, this material discrimination device includes a transport unit 3 for transporting the object to be inspected 2. The transport unit 3 places the object to be inspected 2 on the endless conveyor belt 5 spanned between the pair of conveyor rollers 4a and 4b, and rotates the one conveyor roller 4a to rotate the conveyor 4a to load the object 2 to be inspected. It is configured as a conveyor to carry. The transport unit 3 moves (conveys) the object to be inspected 2 with respect to the detection unit 10. The detection spectrum is acquired by the detection unit 10 while the inspected object 2 is moving. In order to efficiently discriminate a large amount of household waste, the transport unit 3 is suitable in the form of a conveyor, but various transport methods such as a free roller and a slope may be adopted.

In this material discrimination device, in a state where X-rays are irradiated from the X-ray source 1, the X-ray transmitted through the inspected object 2 is transmitted by the conveying unit 3 while the X-rays transmitted through the inspected object 2 are transmitted by the light receiving unit 11 of the detecting unit 10. Receives light by. The received information (detection spectrum) is converted into digital data and transferred to the calculation unit 21 of the control unit 20 via the memory 12. The calculation unit 21 compares the detection spectrum of the inspected object 2 with the existing reference spectrum to estimate the material of the inspected object 2.

FIG. 2 is an explanatory diagram of a control unit of a material discrimination device.

The control unit 20 is mainly composed of a computer, and as shown in FIG. 2, the X-ray source 1, the transport unit 3, and the detection unit 10 are connected, and these X-ray source 1, the transport unit 3, and the detection unit 10 are connected. Is controlled, and the output from the detection unit 10 is input. Further, the display monitor 50 and the output unit 51 to the downstream device are connected to the control unit 20 to control the display monitor 50 and output to the downstream device.

The estimation result of the material of the inspected object 2 is displayed on the display monitor 50, and the operator is notified of the material of the inspected object 2. Further, the output unit 51 to the downstream device conveys the discrimination result to the distribution device downstream of the transport unit 3, and sorting into various materials is performed based on the discrimination result.

FIG. 3 is an explanatory diagram of a comparison unit of the material discrimination device.

As shown in FIG. 3, the control unit 20 stores the reference spectra of various materials acquired in advance in the memory 31 of the comparison unit 22. For example, the reference spectrum 31a of the lithium ion battery is stored, the reference spectrum 31b of the alkaline dry battery is stored, the reference spectrum 31c of the spray can is stored, and so on.

In the comparison unit 22, the determination 32 for specifying the material of the inspected object 2 is derived from the result of comparing the detection spectrum 30 of the inspected object 2 with the reference spectra 31a, 31b, 31c ... Of various materials.

[Preparation]
Next, the signal processing in the arithmetic unit 21 will be specifically shown.

First, in order to obtain the detection spectrum of the object 2 to be inspected by the light receiving unit 11, it is necessary to obtain two correction values in advance.

The first correction value is to store the output value from the light receiving unit 11 in a state where the X-ray is not irradiated. Since there is no X-ray incident on the light receiving unit 11 in the state where the X-ray is not irradiated, the amount of light received is zero in any wavelength band. However, when the light receiving unit 11 is energized, the output from the light receiving unit 11 does not become zero due to the flow of a weak current, electronic noise, and the like. Therefore, the output value from the light receiving unit 11 is read in a state where the X _- ray is not irradiated, and this is set as the reference value IB.

The second correction value is to store the output value from the light receiving unit 11 when the X-ray is irradiated in a state where the object 2 to be inspected is not transmitted. At this time, the imaging conditions of the object 2 to be inspected include the X-ray tube voltage and tube current, the distance between the X-ray source 1 and the light receiving unit 11, the presence or absence of the endless transport belt 5, and the exposure time of the light receiving unit 11. Is the same as. X-rays containing various wavelengths from the X-ray source 1 do not have a constant amount of photons for each wavelength. Further, since X-rays may be absorbed by the endless transport belt 5 or the cover covering the light receiving unit 11, it is necessary to check the output value from the light receiving unit 11 in advance for each wavelength. Let the output value from the light receiving unit 11 obtained here be _IL . Since _IL includes the offset of the previous IB, the actual output value is _{IL - IB} excluding _IB .

[Calculation of detection spectrum of the object to be inspected]
The object 2 to be inspected is irradiated with X-rays to acquire the output value _Iobj of the sensor. Since I _obj includes the offset of IB described above, the actual output value is _{obj - IB} excluding _IB .

The ratio of the amount of X-ray light I _{obj -} IB that has passed through the object 2 to be inspected and the amount of X _- ray light I _L -IB that does not pass through the object 2 to be inspected is as follows [Equation 1]. Will be shown.

This [Equation 1] indicates to what extent the photons reach the light receiving unit 11 without being absorbed by the inspected object 2 with respect to the amount of the irradiated X-ray photons. It should be noted that [Equation 1] can be realized by an offset circuit and a gain circuit in terms of electronic circuits.

FIG. 4 is an example of a reference spectrum (aluminum (thickness 5 mm, 10 mm)).
As an example of receiving X-rays transmitted through the object 2 to be inspected by the light receiving unit 11 and calculating from the data using [Equation 1], FIG. 4 shows reference spectra of aluminum having a thickness of 5 mm and 10 mm, respectively. .. In each graph, the shape is convex upward, and the value of about 60 keV is the peak. The reason why the graph is lower overall with a thickness of 10 mm than with a thickness of 5 mm is that the amount of X-rays absorbed increases and the amount of light received by the light receiving unit 11 decreases because the thickness is doubled. Responsible.

On the other hand, the relational expression of the intensity I when the X-ray of the intensity I ₀ advances d cm in the substance having the linear attenuation coefficient μ, which is a value peculiar to the substance, is defined as the following [Equation 2]. ln is the natural logarithm. That is, the control unit 20 applies a logarithmic function to the detection spectrum and the reference spectrum to determine the identity.

The term in parentheses on the right side of [Equation 2] is the total thickness of the material dcm (if there is a space between them, the thickness excluding it) with the line attenuation coefficient μ with respect to the original X-ray intensity. Hereinafter, the thickness has the same meaning as [Equation 1] because it represents the ratio with the intensity of X-rays when passing through the object 2 to be inspected (meaning the distance excluding space). The sum of [Equation 1] and [Equation 2] is as follows.

FIG. 5 shows an example (aluminum (thickness 5 mm, 10 mm)) in which a logarithmic function is applied to a reference spectrum.
When the right side of [Equation 3] is calculated (a logarithmic function is applied), the graph of FIG. 4 becomes as shown in FIG. At 50 keV, the vertical axis is 0.43 for an aluminum thickness of 5 mm and 0.86 for an aluminum thickness of 10 mm, which is almost twice the thickness of 5 mm. Similarly, at 60 keV, when the thickness is 10 mm, the thickness is about twice that of 5 mm. Since d is constant unless the material of the object 2 to be inspected changes, the fact that FIG. 5 draws a curve depending on the wavelength means that the line attenuation coefficient μ changes depending on the wavelength.

[Memory of reference spectra of various materials]
Lithium-ion batteries, alkaline batteries, button batteries, spray cans, lighters, and other ordinary waste such as plastic and aluminum cans, which are classified as flammable hazardous materials, and other reference spectra have been obtained in advance and shown in FIG. As described above, it is stored in the memory 31 of the comparison unit 22. At this time, the calculation result on the right _side of [Equation 3] may be stored, the calculation result of [Equation 1] may be stored, or each _obj , _IB , or IL may be stored. Further, if the thickness d of the object to be inspected 2 is known, the value obtained by dividing the right side of [Equation 3] by d may be used.

[Comparison method between the detection spectrum of the object to be inspected, which is an unknown material, and the reference spectrum of the material stored in advance]

Regarding [Equation 3], if the linear attenuation coefficient of the material stored in advance is μ _ref , the thickness is d _ref , and the calculation result on the right side is N _ref , it becomes as shown in [Equation 4].

Regarding [Equation 3], if the line attenuation coefficient of the object 2 to be inspected, which is an unknown material, is μ _obj , the thickness is _dobbj , and the calculation result on the right side is Nobj, it becomes as shown in [ _Equation 5].

When [Equation 4] is used as the denominator and [Equation 5] is used as the numerator, [Equation 6] is obtained.

According to [Equation 6], if the same material is used, the linear attenuation coefficient μ _obj = μ _ref , and [Equation 7] can be obtained.

According to [Equation 7], since the left side does not have a term of the line attenuation coefficient μ that changes depending on the wavelength, the right side and the left side of [Equation 7] show constant values regardless of the wavelength. That is, _Nobj / N _ref is constant (= ratio of thickness). On the contrary, if the line attenuation coefficient μ _obj ≠ μ _ref of [Equation 6], it means that _Nobj / N _ref changes depending on the wavelength.

FIG. 6 is an example of comparison / determination between the detection spectrum and the reference spectrum (reference spectrum: aluminum (thickness 5 mm), detection spectrum: aluminum).

As an example of detection / calculation / comparison of _Nobj / _Nref , FIG. 6 shows a detection spectrum of an inspected object 2 which is an unknown material, using aluminum having a thickness of 5 mm as a known material. Here, it can be seen that the unknown material is aluminum having a thickness of 10 mm, and since it is the same material, it shows a substantially constant value regardless of the wavelength band. Moreover, since the thickness is doubled, the value is about twice the value of a known material.

FIG. 7 is an example of comparison / determination between the detection spectrum and the reference spectrum (reference spectrum: resin material, detection spectrum: aluminum).

On the other hand, FIG. 7 shows a reference spectrum using a known material as a resin. It can be seen that it does not show a constant value depending on the wavelength.

[First form]
The control unit 20 can determine the identity by using the transmittances at at least two wavelengths in the detection spectrum and the reference spectrum. Further, the control unit 20 can determine that each spectrum has the sameness when the difference between the detection spectrum and the reference spectrum is within the predetermined reference. Then, the control unit 20 obtains the difference between the reference spectrum and the detection spectrum at each wavelength, and the difference between the total difference at each wavelength and the predetermined reference value can be used as the difference.

In order to evaluate the difference between FIGS. 6 and 7 numerically, the maximum deviation value is used as the difference with respect to the value at the predetermined wavelength. For example, in FIG. 6, the value of 40 keV is 2.01, but the largest difference from the value of 30 keV is 1.75, and the difference is 0.26. On the other hand, in FIG. 7, the value of 40 keV is 0.78, and the difference is 0.47 at 60 keV, which is the largest difference from the value, and the difference is 0.31. That is, it can be judged that aluminum is a closer material than resin. At this time, the reference value of the default wavelength may be the average value of the values in all wavelength bands.

[Second form]
The control unit 20 obtains the ratio of the reference spectrum and the detection spectrum at each wavelength, and the ratio of the maximum value of each ratio to the predetermined reference value can be used as a difference. Further, the control unit 20 may obtain the ratio of the reference spectrum and the detection spectrum at each wavelength, and may use the maximum value of each ratio as the difference.

In FIG. 6, a value (ratio) obtained by dividing 1.75 of 30 keV, which has the largest difference from 2.01 of 40 keV as a reference, may be used as a difference of 1.75 / 2.01 = 0.87. In this case, it is judged that the closer to 1 the smaller the difference. The value in FIG. 7 is 0.47 / 0.78 = 0.6. At this time, the reference value of the default wavelength may be the average value of the values in all wavelength bands.

[Third form]
The control unit 20 can obtain the difference between the reference spectrum and the detection spectrum at each wavelength, and can use the total of the differences at each wavelength as the difference.

A default reference value may be set for _obj / N _ref , and when the total absolute value of the difference is small, it may be determined that the material is close to a known material. For example, it may be the sum of the absolute values of the deviations, or it may be the sum of least squares.

[Fourth form]
In the second embodiment, it is also possible to set a reference value and determine that the closer the value obtained by dividing the total absolute value of the differences by the number of wavelengths is to 1, the closer to the known material. The calculation of the sum may be, for example, the sum of the absolute values of the deviations or the sum of the least squares.

In the first to fourth forms, a predetermined threshold value may be set, and if the difference is within the threshold value, it may be determined that the material is a known material.

As described above, the control unit 20 can determine that the detection spectrum and the reference spectrum having the smallest difference from the detection spectrum among the plurality of reference spectra stored in advance have the sameness. Further, the control unit 20 can determine that the detection spectrum and the reference spectrum have the sameness by using various discrimination methods described above in combination. In this case, it may be determined that there is identity when there is one or more discrimination methods that are determined to have identity, and it is determined that there is identity when there are multiple discrimination methods that are determined to have identity. You may judge.

1 X-ray source 2 Inspected object 3 Conveyor unit (conveyor)
4 Conveyor roller 5 Endless transfer belt 10 Detection unit 11 Light receiving unit 12 Memory 20 Control unit 21 Calculation unit 22 Comparison unit 30 Wavelength spectrum of the object to be inspected 31 Memory 31a Reference spectrum of known material 31b Reference spectrum of known material 31c Known Reference spectrum of material 32 Judgment result 50 Display monitor 51 Output to the device on the downstream side

Claims (10)

An X-ray source that irradiates the object to be inspected with X-rays,
A detector that detects the spectrum of a predetermined band of X-rays that have passed through the object to be inspected,
A control unit that sends and calculates the detection spectrum obtained by the detection unit,
Equipped with
The control unit has a comparison unit for comparing the detection spectrum with a reference spectrum which is an X-ray transmission spectrum of a known material stored in advance, and the inspection is performed based on the identity between the detection spectrum and the reference spectrum. A material discrimination device characterized by estimating the material of an object. The material discrimination apparatus according to claim 1, wherein at least one of the reference spectra is stored in advance in the comparison unit. The material discrimination apparatus according to claim 1 or 2, wherein the control unit applies a logarithmic function to the detection spectrum and the reference spectrum to determine the identity. The material discrimination apparatus according to claim 1, 2 or 3, wherein the control unit determines the identity by using the transmittances at at least two wavelengths in the detection spectrum and the reference spectrum. The control unit according to any one of claims 1 to 4, wherein when the difference between the detection spectrum and the reference spectrum is within a predetermined reference, the control unit determines that each spectrum has the sameness. Material discrimination device. The claim is characterized in that the control unit determines that the detection spectrum and the reference spectrum having the smallest difference from the detection spectrum among the plurality of reference spectra stored in advance have the sameness. The material discrimination apparatus according to any one of 1 to 4. The material discrimination apparatus according to claim 5 or 6, wherein the control unit obtains a ratio of the reference spectrum and the detection spectrum at each wavelength, and sets the maximum value of each ratio as the difference. The claim is characterized in that the control unit obtains a ratio of the reference spectrum and the detection spectrum at each wavelength, and sets the ratio of the maximum value of each ratio to a predetermined reference value as the difference. The material discrimination apparatus according to 5 or 6. The material discrimination apparatus according to claim 5 or 6, wherein the control unit obtains a difference between the reference spectrum and the detection spectrum at each wavelength, and sets the total of the differences at each wavelength as the difference. 5. The control unit obtains a difference between the reference spectrum and the detection spectrum at each wavelength, and makes the difference of the total difference at each wavelength with respect to a predetermined reference value as the difference. Or the material discrimination apparatus according to 6.

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