JP2003172699A - Method and device for discriminating material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device that discriminates the type of a plastic material with high accuracy without being affected by the properties, color, additive, etc., of the material based on spectral data in a near infrared region in which the material-specific absorption does not occur significantly, has a small size and a light weight, and causes few mechanical faults. <P>SOLUTION: The device which discriminates the type of an unknown material is provided with a light receiving mechanism section (P) which measures reflected light or transmitted light from the material to be measured and a temperature measuring section (T) which measures the surface temperature of the material. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for discriminating a material, and more particularly to a device for selecting a waste plastic.

[0002]

2. Description of the Related Art As a method for selecting waste plastics, for example, there is one disclosed in Japanese Patent Laid-Open No. 08-007113.
This is a method in which waste plastic that has been crushed in advance is put into a liquid specific gravity classifier, and light plastic and heavy plastic are separated by utilizing the difference in sedimentation speed due to the difference in specific gravity.

However, this method can select only plastics having distinctly different specific gravities. For example, the specific gravity of vinyl chloride is 1.25 to 1.45, whereas the specific gravity of polyethylene terephthalate is 1.30 to 1.40, and the two cannot be separated. Further, there is a problem in that the occupying area of the apparatus is large and the cost is high because pulverization is required in the previous process and dehydration work after selection is required.

As a device devised to solve the above problems, there is, for example, the one described in JP-A-11-287757. This is a method of irradiating plastic with near infrared light and measuring the intensity of near infrared light transmitted or reflected by the plastic. A circuit for measuring the intensity of only the absorption wavelength peculiar to the plastic to be selected is independently provided for each of the plastics to be selected, and the type is determined by comparing the measured data.

However, since the measurement wavelength is fixed in this method, the difference in molecular crystallinity, the phenomenon that the peak wavelength is subtly shifted depending on the additive, the unevenness of the surface, the color, and the thickness of the same plastic There is a problem in that the phenomenon in which the absorbance level changes cannot be followed and an erroneous determination is made. Furthermore, when a plurality of types are determined, the size of the device becomes large and there is a problem in terms of price.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems of the prior art and to provide a device which is small in size, light in weight, and has a high degree of accuracy without causing mechanical failure and which can determine the type of plastic. It is in. Also, to provide a device that accurately determines the type of plastic without being affected by the properties of the material, color, additive material, etc., based on the near-infrared spectrum data in which the absorption peculiar to the material does not appear significantly. It is in.

[0007]

The above object can be achieved by the invention described in the claims. That is, the present invention is, in an apparatus for determining a material of unknown type, a light receiving mechanism section (P) for measuring reflected light or transmitted light from an object to be measured, and a temperature measuring section for measuring the surface temperature of the material to be measured. (T) is provided.

In the above-mentioned apparatus for judging the material, the light receiving mechanism section (P) takes in the light which is transmitted or reflected by the material to be measured (P1) and the spectroscopic section (P2) which disperses the taken light. ) And a light receiving part (P3) for receiving the split light.

In the above device for judging the material, the signal information from the light receiving mechanism section and the signal information of the material registered in advance are used depending on the signal intensity from the light receiving mechanism section (P) or the signal intensity from the temperature measuring section. A determination unit (J1) that identifies the type of the unknown material may be provided by switching the determination method to either comparison or comparison between the temperature information from the temperature measurement unit and the temperature information of the material registered in advance. preferable.

In the above device for judging the material, the signal information from the light receiving mechanism (P) is compared with the signal information of the material registered in advance, and the temperature information from the temperature measuring section and the material registered in advance are compared. It is also possible to provide a determination unit (J2) that specifies the type of the unknown material based on both values of the comparison with the temperature information of.

In the above apparatus for determining a material, it is preferable that the signal information of the determination section is a wavelength spectrum.

In the above apparatus for judging the material, the light capturing section (P1), the spectroscopic section (P2) and the light receiving section (P
It is preferable that all of 3) and the temperature measuring unit (T) are of a fixed type.

In the above device for determining a material, the spectroscopic element of the spectroscopic section (P2) is preferably an echelette diffraction grating or a linear variable interference filter.

Further, the present invention is a method of judging a material of an unknown type, a step of comparing a measured wavelength spectrum with a wavelength spectrum of a material registered in advance, irradiating light to measure the temperature of the ratio measurement object. A step of measuring the temperature rise and comparing the temperature rise characteristic data with the temperature rise characteristic data of the material registered in advance, and further, when the intensity of the measured wavelength spectrum is below a certain value, it is measured. The material is determined by comparing the wavelength spectrum with the wavelength spectrum of the material registered in advance, and when the intensity of the measured wavelength spectrum is less than a certain value, the temperature rise characteristic data and the temperature registration characteristic data are registered in advance. This is a method for determining a material, characterized in that the material is determined by comparing temperature rise characteristic data of the material.

Further, in the present invention, in the method of judging a material of unknown type, the step of comparing the measured wavelength spectrum with the wavelength spectrum of the material registered in advance; And a step of comparing the temperature rise characteristic data with the temperature rise characteristic data of the material registered in advance, and, further, between the measured optical spectrum and the wavelength spectrum of the material registered in advance A method for determining a material is characterized in that the material is determined based on a total value of both comparison and comparison of the temperature increase characteristic data and the temperature increase characteristic data of the material registered in advance.

The present invention is an apparatus for determining a material having both a light receiving mechanism section (P) and a temperature measuring section (T). The light receiving mechanism section (P) has a function of measuring reflected light or transmitted light from the measured object, and the temperature measurement section (T) has a function of measuring the surface temperature of the measured object. The light receiving mechanism section (P) includes a light capturing section (P1) that captures light transmitted or reflected by a material to be measured, and a spectroscopic section (P) that disperses the captured light.
2) and a light receiving part (P3) for receiving the separated light.

Further, it is preferable that the above-mentioned respective parts do not have a mechanical operating part at the time of measurement, and instead of having no mechanical operating part, a spectroscopic part for simultaneously spectroscopically capturing light and a spectroscopic light. Light receiving part (P3)
By having, it is possible to disperse light in a short time and measure its spectrophotometric value.

Since the spectral information can be extracted in almost real time by the above method, it is possible to quickly and accurately determine the type of material. In addition, the fixed type here means
No mechanical movement during the measurement, i.e.
That is, it does not have a mechanical moving part for measurement at each part. It should be noted that light may be introduced to the light capturing section by an optical fiber or the like. Further, as the spectroscopic element of the spectroscopic section (P2), a known element can be used, but by using an Echette diffraction grating or a linear variable interference filter, the light receiving mechanism section and the spectroscopic mechanism section can be integrated, and the size of the device can be greatly reduced. Can be realized, which is preferable.

Further, it is preferable that the temperature measuring section (T) be capable of instantaneously measuring the surface temperature of the material in a non-contact manner. As the temperature measuring unit, a known method can be used as long as it can perform non-contact measurement.

In the material judging apparatus of the present invention, the judging section (J) has a spectrum generating section (S) for generating a wavelength spectrum based on a signal from the light receiving mechanism, and spectral information and materials registered in advance. It is preferable to include a spectrum discriminating unit (Js) that identifies the type of the unknown material by comparing the spectrum information with the spectrum information.

[0021]

Example 1 The present invention will be described below with reference to examples.
It should be noted that this embodiment is merely a preferable example. FIG. 1 is a schematic diagram showing an apparatus according to an embodiment of the present invention. In this device, the light collecting unit 3 (the light capturing unit (P
1)), the light distributor 11, the spectroscope 4 (the spectroscopic unit (P
2)), the light receiver 5 (corresponding to the light receiving part (P3))
And constitute a light receiving mechanism section (P).

Light including near-infrared rays is emitted from the illumination 2 to plastic of an unknown type. The light reflected by the plastic is guided from the condenser 3 to the spectroscope 4 via the light distributor 11. As illustrated in FIG. 6 or 7,
The light is split by the spectroscope 4 and guided to the photodetector 5. The light receiver 5 is composed of a light receiving element having a plurality of channels, receives light of each wavelength independently, is converted into an electric signal, and then is sent to the digital converter 6.

The digital converter 6 (corresponding to the spectrum generator (S)) converts the analog electric signal into a digital signal and generates the absorbance spectrum data corresponding to the wavelength. The generated spectrum data is sent to the histogram generator 7. In the histogram generator 7, the relative absorbance difference (Δa) between the adjacent maximum value and minimum value of the absorbance spectrum data is obtained and made into a histogram.

Further, Δa below the reference value is extracted based on the preset reference value of the histogram frequency. In the filter processor 8 in the next stage, filter processing is performed to remove the maximum and minimum values of the extracted Δa from the spectrum data, and new spectrum data is generated.

The generated histogram is sent to the binary data converter 9. In the binary data converter 9, Δa larger than the preset reference value of the histogram frequency is used.
It is converted into binary data of 1 and 0 based on the information of 1 and sent to the collator 10. In addition, in this example, the collator 10 has both a determination unit (J1) and a spectrum determination unit (Js).

One of the lights passing through the light distributor 11 is guided to the light receiver 12 and converted into an electric signal corresponding to the heat energy intensity. The converted electric signal is sent to the temperature converter 13 and converted into temperature information. The converted temperature information is sent to the collator 10.

The collator 10 stores spectral binary data of plastic of which material is clear and temperature data of plastic of which material is clear. The collator 10 is
If the sent binary data is valid, the degree of coincidence with a plurality of types of binary data stored in advance is calculated. Based on this result, the collator 10 identifies the type of plastic of which the type is unknown. If the sent binary data is invalid, the collator 10 identifies the type of plastic of which the type is unknown by collating the sent temperature data with the registered temperature data.

Specific examples carried out are shown below. Three types of plastics, polyethylene terephthalate (PET), polyvinyl chloride (PVC), and polystyrene (PS), were used for the measurement. Further, in order to confirm the practicality, four levels of samples having different morphologies were prepared (see Table 2). Although three types of plastics were targeted in the experiment, if the binary data of the wavelength spectrum and the temperature data of the material of which the type is known in advance are registered in the collator 10, the material can be specified. Therefore, the target material for selection in the present invention is not particularly limited as long as it is a substance that causes a difference in the spectrum of near infrared rays.

For the illumination 2, 100 W halogen light was used.
As the illumination, a xenon lamp, a tungsten lamp, an infrared heater, or the like can be considered as well, but any light source including light emitting infrared rays may be used and is not particularly limited. An optical fiber having a diameter of 300 μm and a numerical aperture of 0.22 was used for the light collecting unit 3. The spectroscope has a spectral wavelength band of 1100 to 1
An Echelette diffraction grating with 750 nm and a wavelength resolution of 16 nm was used. The detector 5 is 128 channels of InGa.
An As semiconductor linear image sensor was used. The arrangement of each element is shown in FIG.

In the spectrum measurement of plastics, generally, a remarkable difference in absorption occurs in the mid-infrared wavelength region, but in this case, there is a problem that the sensor is expensive and the processing circuit is complicated. On the contrary, in the measurement in the relatively short near-infrared wavelength region, the spectrum becomes broad, and the remarkable difference due to the difference in material does not occur. However, the measurement in the near infrared region has an advantage that the device is simple and inexpensive. In this embodiment, the wavelength band is set in order to demonstrate the highly accurate discrimination effect in the short near-infrared band, but the wavelength band is not particularly limited as long as it is a band in which absorption characteristics are different. There is no.

The wavelength resolution is not particularly limited as long as the shape information of the spectrum, which is a characteristic of the material described later, is not lost. 8 for the thermal energy detector 12
The surface temperature of the plastic was measured from the obtained signal using a thermopile having a detection wavelength of -12 μm.

FIG. 2 shows spectral data obtained by measuring PET, PVC and PS, and FIG. 3 shows spectral data obtained from three types of PET having different properties. Each wavelength intensity is extracted as an analog signal of 0 to 5 V as a video signal, converted into a 16-bit digital signal by the digital converter 6, and absorbance spectrum data is generated.

Next, a method for identifying the material from the spectrum data will be described with reference to FIGS. 2, 4 and 5. First, Δa of the spectrum data of FIG. 2 is obtained. next,
A histogram of Δa is obtained (FIG. 4). Next, the valley point A is obtained from the histogram (FIG. 5). In general, the measured spectrum data includes fluctuation information due to absorption peculiar to the material and fine noise information such as electric noise. These components can be easily separated by observing the distribution of the absorbance level between adjacent extreme values. Noise information in which small fluctuations randomly occur is distributed to the left of the section A in FIG. 5, and fluctuation information due to absorption peculiar to the material is distributed to the right of the section A. Therefore, the section A is a boundary point separating noise and effective information.

The value at point A is used as the binarization reference value (0.07 is determined as the binarization reference value in FIG. 4). In the embodiment, the point A is calculated by the known Otsu's discriminant analysis method and the binarization reference value is automatically calculated. However, the method is not particularly limited to this method and, for example, binarization is performed from the histogram area ratio of Δa. It is also possible to set the reference value of, or measure the noise level in advance by an experiment and input a fixed value.

Next, filter processing is performed to remove the maximum and minimum values of the spectrum corresponding to Δa smaller than point A. In the embodiment, the spectral waveform is passed through the midpoint between the maximum value and the minimum value of the removed target, and a new spectral waveform is generated so as to form a smooth curve.

Next, Δa larger than the binarization reference value is extracted from the new spectrum waveform. Set the reference value for binarization at the intermediate position between the extracted maximum ground and minimum value,
The absorbance values larger than the binarization reference value are converted into data of 1, and the other absorbance values are converted into 0.

In general, even in the case of the same material, the spectrum is often biased or has a different singularity level depending on the surface color, thickness, and surface properties as shown in FIG. Therefore, it is self-evident that a mistaken determination is often made when a material is specified by comparing the absorbance levels of specific wavelengths or by comparing the absorbance levels of a plurality of wavelengths.
The spectrum in the near infrared region that does not show a sharp absorption characteristic is not a level, and it is important to grasp the variation characteristic (pattern) of the spectrum. The present invention is extremely excellent as a means for effectively extracting only this variation characteristic. As shown in FIG. 3, even data having the same material but different spectra can generate data having substantially the same characteristics. Table 1 shows the result of converting the spectrum of FIG. 3 into coded data.

[0038]

[Table 1]

This encoded data is sent to the collator 10,
The degree of coincidence with binary data of known material is calculated. In the embodiment, the number of matches is simply counted and the normalized value is used as the matching level. Binary data of known material has 1 for each wavelength
0 or 0 is registered. The results of assaying each sample are shown in Table 2.
Shown in. It can be seen that the degree of coincidence is clearly different between the same material and other materials. Further, it can be seen that even if the color, the thickness, etc. are changed, the judgment is not affected.

[0040]

[Table 2] These series of processes are completed instantly. Unlike a general spectroscopic device having a movable part, the incident light is simultaneously separated and the separated lights are simultaneously received. Therefore, it suffices to consider only the time delay required for the charge accumulation of the light receiving element, and the material can be specified almost in real time. The processing time in the example is about 10 ms.

Although the method of measuring the spectrum of the light reflected from the sample has been described in this embodiment, in the case of a thin transmissive sample, a reflection plate made of ceramic or the like that does not absorb in the measurement wavelength band is placed on the base. It is also possible to use a method of performing measurement by measuring the light transmitted through the sample. Further, as a method for specifying the material based on the spectral information, for example, a method of directly comparing the spectrum with a known material, a method of comparing the levels of a plurality of specific wavelength absorbances to extract a difference, or differentiating the spectrum A method of processing and extracting a feature may be used and is not particularly limited.

When the object to be measured is black, the intensity of light transmitted or reflected by the object is remarkably reduced. Therefore, measurement of the absorbance spectrum may be difficult.
This phenomenon can be judged at the level of the point A section described above. Therefore, if the point A section appears below the preset reference value,
It is determined that the measurement target is black, and the determination method is switched from the spectrum comparison method to the temperature comparison method.

FIG. 8 shows the temperature rise characteristics when a black object is irradiated with far infrared rays. As can be seen from this figure, the temperature rising characteristics are different for each material. Therefore, it is possible to determine the type of the black target object by pre-storing the temperature data at the time when a certain time has passed after the infrared irradiation and comparing the temperature data with the temperature data measured under the same conditions. In this example, the object was irradiated with the spectrum measurement illumination for 5 seconds, and the surface temperature of the irradiated object was measured by a thermopile type radiation thermometer. The results are shown in Table 2 (black sample). In addition,
The degree of coincidence of the black sample is the temperature rise width of the target object after 5 seconds of light irradiation, and the temperature rise width of the known carbon kneaded black sheet (thickness 2 mm) under the same conditions for 5 seconds after light irradiation. when t _0, and the {1 - absolute value of [(t-t ₀₎ /
t]} × 100 (%). You can see that they can be identified with certainty. The longer the irradiation time of thermal energy, the more noticeable the temperature difference between the materials becomes, and the easier the discrimination.However, the irradiation time, the type of heating source, and the type and number of temperature sensors should be set according to the environment to be measured. There is no particular limitation as long as it is constructed. Further, in the above, the method of switching between the wavelength characteristic and the temperature rising characteristic is used, but it is also possible to make a comprehensive judgment from both characteristics without switching.

[0044]

Example 2 The spectroscope has a wavelength band of 1100 nm to 1900.
The same test as in Experiment 1 was performed using a linear variable interference filter that is nm. In this embodiment, the light guide section 3 is not provided, and the light reflected by the measurement material 1 is directly incident on the linear variable interference filter. Further, the green lens 11 is provided between the linear variable interference filter 4 and the light receiver 5 so that the light that has been separated and passed through the linear variable interference filter is effectively guided to the light receiver 5.
Was placed. The configuration is shown in FIG.

The results of assaying each sample are shown in Table 3. It can be seen that the same degree of coincidence is obviously different between the same material and other materials as in the first embodiment. Further, it can be seen that even if the color, the thickness, etc. are changed, the judgment is not affected. The processing speed is also about 1 ms as in the embodiment. Since the method for discriminating a black object is the same as that of the first embodiment, it is omitted.

[0046]

[Table 3]

[0047]

As described above, according to the present invention, the light transmitted or reflected by the material to be measured is simultaneously dispersed,
Let the multi-channel light receiving element simultaneously receive the split light,
A mechanism for comparing the obtained wavelength spectrum data information and the spectrum information in which the material registered in advance is known, and the temperature information in which the material registered in advance by measuring the surface temperature information of the material to be measured is By providing a mechanism for comparison, it is possible to quickly and accurately determine the material type regardless of the color of the object. In addition, excellent stability can be secured by eliminating all the mechanically movable parts of the light-trapping mechanism, the spectroscopic mechanism, and the light-receiving mechanism.

Further, by using an Echelette diffraction grating or a linear variable interference filter as the spectroscopic element of the spectroscopic mechanism, the light receiving mechanism section and the spectroscopic mechanism section can be integrated, and the size of the apparatus can be greatly reduced. As a result, for example, it becomes possible to dry-sort wastes required for recycling plastics and the like. Furthermore, since it is a portable type, it can be applied to various types of materials such as outdoors and manufacturing sites.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of a type determination device according to the present invention.

FIG. 2 is spectral data of PET, PVC, and PS in the example.

FIG. 3 is spectral data of PET having different properties in Examples.

FIG. 4 is a frequency distribution distribution of relative values between adjacent extreme values of measured spectra in Examples.

FIG. 5 is a graph in which an encoding reference value is set for the measured spectrum in the example.

FIG. 6 shows a positional relationship between a spectroscope and a light receiver in the first embodiment.

FIG. 7 shows a positional relationship between a spectroscope and a light receiver in the second embodiment.

FIG. 8 is heating characteristic data of PET, PVC, and PS in the example.

[Explanation of symbols]

1: Sample 2: Lighting 3: Light guide 4: Spectrometer 5: Detector 6: Digital converter 7: Histogram generator 8: Filter processor 9: Binary data converter 10: collator, 11: Optical distributor 12: Thermal energy detector 13: Temperature converter

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hidenori Jimbo             2-1-1 Katata, Otsu City, Shiga Prefecture Toyobo             Koki Co., Ltd. (72) Inventor Jihiro Yoshio             2-1-1 Katata, Otsu City, Shiga Prefecture Toyobo             Koki Co., Ltd. F term (reference) 2G020 AA03 CA12 CB42 CC05 CC26                 2G040 AA02 AB08 AB12 BA02 BA25                       BA29 CA02 CA23 DA05 DA12                       EA06 EB02 EC03 HA08 HA16                       ZA05                 2G059 AA05 BB08 EE01 EE02 EE12                       GG10 HH01 JJ03 JJ05 JJ17                       KK04 KK09 MM02 MM05 MM09                       MM10 NN02

Claims (9)

[Claims] 1. A device for determining a material of unknown type, a light receiving mechanism section (P) for measuring reflected light or transmitted light from an object to be measured, and a temperature measuring section (for measuring the surface temperature of the material to be measured). T) and a material discriminating device characterized by comprising: 2. The apparatus for determining a material according to claim 1, wherein a light receiving section (P1) for capturing light transmitted through or reflected by the material measured by the light receiving mechanism section (P) and a spectrum of the captured light. An apparatus for discriminating a material, comprising: a spectroscopic unit (P2) that performs light-splitting; and a light-receiving unit (P3) that receives the dispersed light. 3. The signal intensity from the light receiving mechanism (P) or the temperature intensity measuring unit (T) is used to compare the signal information from the light receiving mechanism with the signal information of the material registered in advance or the temperature. A judgment unit (J1) for specifying the unknown material type by switching the judgment method to either one of the temperature information from the measuring unit and the temperature information of the material registered in advance is provided. Item 1. The material discrimination device according to item 1 or 2. 4. A comparison between signal information from the light receiving mechanism and signal information of a material registered in advance, and a comparison of temperature information from a temperature measuring unit with temperature information of material registered in advance,
The material discriminating apparatus according to claim 1 or 2, further comprising: a discriminating unit (J2) for identifying an unknown type of material based on both of the values. 5. The material discriminating apparatus according to claim 1, wherein the signal information of the discriminating section is a wavelength spectrum. 6. A light capturing section (P1) and a spectroscopic section (P1)
2. The material discriminating apparatus according to claim 1, wherein all of 2), the light receiving section (P3) and the temperature measuring section (T) are fixed types. 7. The material discriminating apparatus according to claim 1, wherein the spectroscopic element of the spectroscopic section (P2) is an Echelette diffraction grating or a linear variable interference filter. 8. A method of determining a material of an unknown type, a step of comparing a measured wavelength spectrum with a wavelength spectrum of a material registered in advance, irradiating light to measure a temperature rise of a ratio measurement object. A step of comparing the temperature rise characteristic data with the temperature rise characteristic data of a material registered in advance, and further, if the intensity of the measured wavelength spectrum is equal to or less than a certain value, the measured wavelength The material is determined by comparing the spectrum with the wavelength spectrum of the material registered in advance, and when the intensity of the measured wavelength spectrum is less than a certain value, the temperature rise characteristic data and the material registered in advance are A method for determining a material, comprising determining the material by comparing temperature rise characteristic data. 9. A method of determining a material of an unknown type, a step of comparing a measured wavelength spectrum with a wavelength spectrum of a material registered in advance; Comparing the temperature rise characteristic data with the temperature rise characteristic data of the material registered in advance, and comparing the measured optical spectrum with the wavelength spectrum of the material registered in advance, and A method for determining a material, characterized in that the material is determined by a total of both the temperature rise characteristic data and the temperature rise characteristic data of the material registered in advance.