JP2002267601A - Method and apparatus for discriminating material such as plastic material or the like - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the discrimination accuracy of a plastic material and other samples. SOLUTION: Data are extracted from the absorbing spectrum of a sample (step S1) and two data among preliminarily registered reference data are read (step S2) to compare two data to judge either one of two data to which the sample spectrum data are near, to select the nearer one (step S3). Next, one of the remaining reference spectrum data is read (step S5) and the sample spectrum data is compared and judged with respect to the read data and the previously selected reference spectrum data and the nearer data among two reference spectrum data is selected (step S3). This comparing and judging operation is repeated until the remaining reference spectrum data are exhausted (step S4) and one finally selected to be near to the sample spectrum data is judged to be the material of the sample to be outputted (step S6).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for discriminating a material of a sample such as a plastic material such as a plastic bottle for beverages and a sheet-shaped plastic waste, glass, paper and the like.

[0002]

2. Description of the Related Art In order to reuse a discarded plastic material, the plastic material must be separated and collected by material. As one of the methods, a method of irradiating a plastic material with light in a near-infrared region and discriminating a material reflected or transmitted from the plastic material is being studied.

[0003] Plastic materials used as plastic bottles and sheets include PS (polystyrene), PET (polyethylene terephthalate), and PE.
(Polyethylene), PP (polypropylene), PVC
(Polyvinyl chloride). The absorption spectra in these infrared regions are different from each other as shown in FIG. However, all plastic materials are basically hydrocarbon-based polymers and therefore have similar spectra. Even if the paper is different, the difference in spectrum is even smaller.

As a method of determining the material from the reflected light or transmitted light of the plastic material, initially, it was attempted to determine the peak or bottom of the absorption spectrum, or both the position and the pattern of the magnitude of the absorption.

When three or more types of materials are determined, base data serving as a criterion is created based on the spectra of each of the known materials, and the material is determined from the similarity between the spectrum of the unknown sample and the reference database. . For example, assuming that the materials to be obtained are A, B, and C, a database serving as a criterion is created for all known spectra. However, in the method of discriminating the position of the peak and bottom of the absorption spectrum and the pattern of the magnitude of the absorption,
Since the degree of use of information is low, for example, the pattern cannot be determined if the pattern changes due to noise, the determination accuracy is originally low. For this reason, a multivariate analysis method such as principal component analysis, a neural network, or the like is used to improve the discrimination accuracy.

[0006] In the multivariate analysis method, a principal component analysis method is representative. In the principal component analysis method, it is general that a spectrum is treated as a multidimensional (number of wavelength data) vector in order to extract characteristics of each spectrum, and mathematical orthogonalization processing is performed to make the spectrum independent. . However, when the spectra of the respective materials are very similar, by orthogonalizing based on the spectra of all the materials, it is easy to expand error components such as noise, and the accuracy of the determination is reduced.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to improve the accuracy of discriminating plastic materials and other samples.

[0008]

According to the present invention, instead of comparing all the materials to be determined with a database for determination criteria to determine which material is applicable, the spectral data of the unknown sample is determined by two criteria. A method of repeatedly determining which one of the spectral data is similar is repeated, and the remaining sample is used as the material of the unknown sample.

That is, the discrimination method of the present invention prepares reference spectrum data of three or more types of materials,
(A) an initial determination step of comparing the spectrum data obtained for each sample with two of the reference spectrum data to select the closer reference spectrum data; and (B) one of the remaining reference spectrum data. And the second and subsequent determination steps of selecting the closer reference spectrum data by comparing the sample spectrum data with the reference spectrum data selected in the immediately preceding determination step, and performing 2 for each of the remaining reference spectrum data. The determination steps after the first time are sequentially executed,
When the determination step is completed for all the reference spectrum data, the material corresponding to the reference spectrum data selected last is determined to be the material of the sample. The sample whose material is to be determined is one or more of plastic, glass and paper, and the measurement light is light in the infrared region.

A sample material discriminating apparatus according to the present invention includes a measuring light irradiating section for irradiating a sample at a measuring position with measuring light, a light receiving section for receiving and detecting transmitted light or reflected light from the sample by the measuring light, A data processing unit for determining the material of the sample from the spectral characteristics of the transmitted light or reflected light detected by the unit, and the data processing unit automatically executes the material determination method according to the present invention. is there.

That is, as shown in FIG. 1, the data processing section includes a reference spectrum data storage section 40 storing reference spectrum data of three or more types of materials.
And comparing the spectrum data obtained for each sample with two of the reference spectrum data stored in the reference spectrum data storage unit 40 to select the closer reference spectrum data. One is taken out from the remaining reference spectrum data stored in 40 and is compared with the sample spectrum data together with the reference spectrum data selected in the immediately preceding comparison judgment to select a closer reference spectrum data. And a comparison / judgment unit 42 for judging that the material corresponding to the last selected reference spectrum data is the material of the sample when the comparison / judgment is completed for the reference spectrum data.

[0012]

FIG. 3 shows an embodiment of a sample material discriminating apparatus according to the present invention. A quartz glass window 2 that transmits infrared light is provided at the measurement position, and a sample 4 such as a plastic material to be measured such as a PET bottle is transported thereon by a transport mechanism (not shown) such as a belt conveyor.
Thus, as shown by an arrow, for example, 3 m /
It is transported at a flow rate of seconds.

A light receiving section 6 is arranged above the measurement position. A light source 8 for transmission measurement is arranged on the opposite side of the light receiving unit 6 with respect to the sample 4 at the measurement position, and irradiation light from the light source 8 passes through the sample 4 and enters the light receiving unit 6. A light source 10 for reflection measurement is arranged on the same side as the light receiving unit 6, and irradiation light from the light source 10 is reflected by the sample 4 and enters the light receiving unit 6. The light sources 8 and 10 are provided with an optical system as needed to constitute a measurement light irradiation unit. One or both of the transmitted light and the reflected light enter the light receiving unit 6.

The light source is a light source that generates infrared rays and may include a continuous spectrum or a discontinuous bright line spectrum. As such light sources 8, 10, a tungsten-halogen lamp or the like can be used.

The detection signal of the light receiving section 6 is taken into the detector main body 12, amplified and A / D converted (converted from an analog signal to a digital signal), sent to a personal computer for calculation 14 as a digital signal, and used for calculation. The material is determined by the personal computer 14. The data processing unit is realized by the arithmetic personal computer 14.
16 is a keyboard used for inputting data and instructions,
A monitor 18 displays the result.

FIG. 4 schematically shows the detection system in the embodiment of FIG. Transmitted light, reflected light, or both from the measurement target sample 4 enters the infrared detector 22 via the chopper mechanism 20. The chopper mechanism 20 and the infrared detector 22 are provided in the light receiving section 6. The infrared detector 22 has sensitivity in an infrared region used for measurement. Examples of such a detector include a Ge photodiode, an InGaAs photodiode, a PbS photoconductive element, a PbSe photoconductive element, and an InA
An s photovoltaic element, a pyroelectric element, or the like can be used.
The chopper mechanism 20 includes a slit plate 20a having a slit 20b, and chops light by rotating the slit plate 20a at a constant speed. In addition, the slit 20
A photo interrupter 24 is provided at a position where b is detected, and detects rotation of the slit plate 20a.

Although not shown, the infrared detector 22
A spectroscope or a filter is provided to split the infrared light incident on the light source. If a filter is used, measure 2
If performed at the wavelength, two infrared detectors 22 are arranged,
An interference filter that transmits light in a predetermined wavelength range is provided on each light incident side. Then, the light passing through the chopper mechanism 20 may be split into two light beams by a half mirror or the like and guided to the respective infrared detectors.

An amplifying circuit 26 is provided for amplifying the detection signal of the infrared detector 22. The output signal of the amplifying circuit 26 is controlled by the detection signal of the photo-interrupter 24 to synchronize with the chopping frequency of the chopper mechanism 20. An amplifier circuit 28 for taking out only the signal of. The output signal of the amplifying circuit 28 is converted into a digital signal by an A / D conversion circuit 30,
To determine the material by signal processing. The amplification circuit 26, the amplification circuit 28 and the A / D conversion circuit 30 are provided in the detector main body 12, and the microcomputer 32
Are provided in the arithmetic personal computer 14. The reference spectrum data storage unit 40 and the comparison determination unit 42 shown in FIG.

In this embodiment, only the detection signal of the signal synchronized with the chopping frequency is taken in.
Disturbance light is removed, and signal processing with a high S / N ratio can be performed.

In the case where the plastic material to be measured is distributed and measured, the same plastic material 4 is measured at a plurality of positions, for example, at spots having a diameter of 40 mm, and the material judgment results at two or more consecutive measurement positions are obtained. Only when they are the same, the data on the plastic material 4 may be treated as valid.

One embodiment of a material discriminating method using a plastic material as an example will be described with reference to FIG. PS, PET, PE,
Regarding the five types of PP and PVC, the positions and the magnitudes of the absorptions of the peaks and bottoms of the respective absorption spectra are registered in advance as reference spectrum data. When the sample 4 is transported to the material discriminating apparatus as shown in FIG. 3, the absorption spectrum of the sample is taken in, and the peak and bottom positions and the magnitude of the absorption are extracted as spectrum data from the sample absorption spectrum. (Step S1). Then, two of the reference spectrum data prepared in advance, for example, PET and PS reference spectrum data are read (step S2). The data extracted from the sample spectrum is PET and PS
Are compared with each other to determine which one is closer, and the closer reference spectrum data is selected (step S3).

Next, one of the remaining reference spectrum data is read (step S5). Then, the sample spectrum data is compared with the reference spectrum data and the reference spectrum data which has been previously determined to be close to the sample spectrum data and selected, and it is determined which one is closer. The closer one of the spectrum data is selected (step S3).

In this way, the comparison judgment between the two reference spectrum data and the sample spectrum data is repeated until the remaining reference spectrum data is exhausted (step S4), and the one which is finally selected as being close to the sample spectrum data is determined. Is determined to be the material of the sample, and the result of the determination is output (step S
6). When the next sample is sent, the comparison determination with two sets of reference spectrum data is similarly repeated to determine the material.

The spectrum data is not limited to the peak and bottom positions of the absorption spectrum and the magnitude of the absorption as described above, and other characteristics of the absorption spectrum may be used as long as the material can be determined. . The operation shown in FIG.
This is performed by the comparison / determination unit 42 of FIG.

[0025]

According to the present invention, there is provided a method for repeatedly determining whether or not the spectral data of an unknown sample is similar to two reference spectral data, and using the remaining data as the material of the unknown sample. I am taking. In this method, the reliability of the discrimination is increased as compared with the conventional method of comparing all the required materials with a database for determination criteria to determine which material is applicable.

[Brief description of the drawings]

FIG. 1 is a block diagram showing functions of a data processing unit in a sample material discriminating apparatus of the present invention.

FIG. 2 is a diagram showing infrared absorption spectra of various plastic materials.

FIG. 3 is a schematic configuration diagram showing one embodiment of a discrimination device of the present invention.

FIG. 4 is a block diagram showing an outline of a detection system in the embodiment.

FIG. 5 is a flowchart showing a material discriminating operation in one embodiment.

[Explanation of symbols]

 4 Sample to be discriminated 6 Light receiving unit 8,10 Light source 12 Detector body 14 Personal computer for calculation 40 Reference spectrum data storage unit 42 Comparison judgment unit

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Noboru 14-5 Shimogita-cho, Neyagawa-shi, Osaka Pref. Kurashiki Textile Co., Ltd. (72) Inventor Nobuyoshi Yasuda 14-5 Shimogita-cho, Neyagawa-shi, Osaka No. Kurashiki Textile Co., Ltd. Technical Research Institute F-term (reference) GG10 HH01 JJ24 KK01 KK09 MM05 MM10 NN01 PP04

Claims (3)

[Claims] 1. A method for irradiating a sample whose material is to be determined with measurement light and determining the material of the sample from the spectral characteristics of transmitted light or reflected light, wherein reference spectral data of three or more types of materials are prepared. (A) an initial determination step of comparing the spectrum data obtained for each sample with two of the reference spectrum data to select the closer reference spectrum data; and (B) the remaining reference spectrum data. A second determination step of extracting one of the data and comparing it with the sample spectrum data together with the reference spectrum data selected in the immediately preceding determination step to select a closer reference spectrum data; For each of the reference spectral data Last selected and determines the material discrimination method the material corresponding to the reference spectral data, which is the material of the sample at the time of completion of the determination step for. 2. The material discriminating method according to claim 1, wherein the sample whose material is to be discriminated is one or more of plastic, glass and paper, and the measurement light is light in an infrared region. 3. A measuring light irradiating unit that irradiates a sample at a measuring position with measuring light, a light receiving unit that receives and detects transmitted light or reflected light from the sample due to the measuring light, and the light receiving unit detects the light. A sample material discriminating apparatus comprising: a data processing unit for discriminating the material of the sample from the spectral characteristics of the transmitted light or the reflected light; wherein the data processing unit stores reference spectrum data of three or more types of materials. The spectrum data storage unit, the spectrum data obtained for each sample is compared with two of the reference spectrum data stored in the reference spectrum data storage unit and the closer reference spectrum data is selected, and then the One of the remaining reference spectrum data stored in the reference spectrum data storage unit is taken out and the reference spectrum selected in the immediately preceding comparison judgment is taken out. The reference spectrum data closer to the sample spectrum data is selected together with the vector data, and the material corresponding to the reference spectrum data selected last at the time when the comparison judgment is completed for all the reference spectrum data is selected. A sample material discriminating apparatus, comprising: a comparison judging unit for judging the material of the sample.