JP2001124696A - Method and device for discriminating pet from other plastics - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an easy method for discriminating a transparent PET product from other plastic products. SOLUTION: The infrared ray from a light source 2 is emitted to a matter 4 to be measured, and the light transmitted by the matter 4 to be measured is divided into two fluxes by a half mirror 10 and guided to infrared detectors 12a, 12b, respectively. An interference filter 14a for transmitting a wavelength light selected from 1640-1600 nm that is a reference wavelength for PET judgment is arranged in the optical path leading to the detector 12a. An interference filter 14b having the characteristic of transmitting a wavelength selected from 1700-1740 nm as a reference wavelength for judgment of plastics other than PET is arranged in the optical path leading to the detector 12b. The detection outputs of both the detectors 12a and 12b are inputted to the non-reverse and reverse input terminals of a comparator 16, and the output of the comparator 16 is connected to a light emitting diode 18. The light emitting diode 18 is lighted when the matter 4 to be measured is PET, and not lighted in the case of other plastics.

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 the material of a plastic, for example, from a waste plastic bottle contained in resource refuse discharged from a household or a waste plastic as an industrial waste, to a specific plastic for recycling. And a method and apparatus for identifying

[0002]

2. Description of the Related Art Materials used as plastic bottles and plastics for industrial materials include PET (polyethylene terephthalate), PS (polystyrene), and PP.
(Polypropylene), PVC (polyvinyl chloride) and PE (polyethylene) are the main ones. It is common practice to identify these materials using infrared spectra.

One method is to identify a material by measuring the absorbance at a specific wavelength specific to each material (for example, JP-A-6-3260, JP-A-6-21).
No. 0632, JP-A-9-89768, JP-A-10-24414 and the like. ). There is also a method of performing identification based on the type of differential spectrum at a measurement wavelength specific to each material (for example, see Japanese Patent Publication No. 7-111397).

[0004] As still another method, it has been proposed to perform discrimination based on the absorbance ratio at each specific wavelength (for example, JP-A-9-10703, JP-A-11-110).
See No. 156310. ). For example, JP
In the method proposed in JP-A-1-156310, PE
In order to distinguish between T and PVA, one with PET absorption
PET or PVA is identified by the ratio A ₁₆₇₀ / A ₁₇₂₀ of the absorbance A ₁₆₇₀ at 670 nm to the absorbance A _{1720 at 1720} nm, which has a characteristic absorption of PVA. .

[0005]

Of these proposed methods, Japanese Patent Application Laid-Open No. Hei 6-210632 and Japanese Patent Publication No.
The method proposed by JP 111397 is disclosed in PET, P
In order to identify various types such as S, PP, PVC, PE, etc., spectra of many specific wavelengths or continuous wavelengths are used. Therefore, it requires a spectroscope to measure spectra at many wavelengths and uses complex data analysis methods such as higher-order differentiation and neural networks.
Not only a microcomputer or a DSP (digital signal processor) is essential, but also high-speed processing is difficult and the structure becomes complicated.

[0006] In terms of the measurement wavelength, see Japanese Patent Application Laid-Open No. 9-8 / 1997.
In the method of 9768 and 10-24414,
A combination of a wavelength having a large absorption and a wavelength having little absorption of each material is used. However, in these methods, PET
In order to separate PET and non-PET, the absorption ranges of PVC, PP, and PC overlap, so even if wavelengths for identifying these can be shared, PET is also used.
Since a wavelength for identification and a wavelength for PS identification are required, 3
More than the wavelength is required. In addition, in order to make a determination based on absorbance, it is usually essential to further select a reference wavelength.

Japanese Unexamined Patent Publication No. 9-10703 discloses a method for discriminating between PET and non-PET PVC and PS by using three wavelengths. When the thickness is almost constant like an egg pack, judgment is made by absorbance. However, when the thickness is indeterminate, PET and PS cannot be distinguished by the determination based on the absorbance using the disclosed wavelength. Also, PE
Four wavelengths are required for determining T, PS, and PVC.

[0008] JP-A-11-156310 discloses PET.
/ 1670nm and 1720nm for identification of two types of PVC
It is disclosed that these two wavelengths are used. When these wavelengths are used, PE and PP can be identified as non-PET, but PS is erroneously determined to be PET. Thus, it is difficult to discriminate between PET and non-PET using only two wavelengths in the conventional method.

When the materials are separated from each other for the purpose of recycling, a function of selectively identifying only PET among PET, PS, PVC, PE, and PP is desired rather than identifying all of them. In particular, a function of detecting only transparent PET products is required for material recycling, and there is little demand for individually identifying opaque PET products and materials other than PET. It is an object of the present invention to provide a simple method for distinguishing a transparent PET product from other plastic products.

[0010]

Accordingly, the present invention limits the object to be identified to transparent PET products so that transparent PET products can be distinguished from other plastic products with a minimum of two wavelengths. . That is, in the identification method of the present invention, the light absorption by PET is greater at the first measurement wavelength than at the second measurement wavelength, and PP,
The first and second measurement wavelengths are selected so that light absorption by PE, PS and PVC is larger at the second measurement wavelength than at the first measurement wavelength, and (1) measurement is performed on the object to be measured. A light detection step of irradiating light and detecting the light intensity at the first and second measurement wavelengths in the transmitted light or reflected light,
And (2) a step of determining whether or not the object to be measured is PET based on the detected light intensities at the first and second measurement wavelengths. It is.

In the present invention, the term "infrared" has a lower limit of about 0.8 μm, which is a long wavelength end of visible light, and indicates a longer wavelength side. The range is 0.8 to 2.5 μm, which is called the outer region. By performing the identification based on the detected light intensities at the first and second two measurement wavelengths, the PET product can be distinguished from the plastic product other than the PET product simply and mechanically simply. .

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the determination step, if a determination is made by comparing the intensity ratio of detected light at two wavelengths or the magnitude comparison, a complicated signal processing circuit is not required, and inexpensive and high-speed processing can be performed. For example, if R = (first measurement wavelength light intensity) / (second measurement wavelength light intensity) (1) is smaller than 1, it is possible to judge that it is not PET and if it is more than 1, it is not PET. FIG. 1 shows infrared absorption spectra of five types of plastics at 1600 to 1850 nm to show an example of a preferable wavelength for making such a determination. The first measurement wavelength is selected from around 1640 to 1660 nm where PET has a large absorption,
The second measurement wavelength can be selected from around 1700 to 1740 nm where other plastics have large absorption. Here, the word "nearby" is used to give a range to wavelength selection. Strictly speaking, the first and second measurement wavelengths can be determined by the center wavelength, the half-value width, the measurement wavelength light intensity ratio at two wavelengths, and the determination threshold (for example, 1 in the above).

The first and second measurement wavelengths are basically determined by setting a wavelength within 1640 to 1660 nm as a reference wavelength (first measurement wavelength) for PET determination, and the PS isosbestic point at this wavelength. The above absorption wavelength is 1700 to 1740
It can be performed by selecting in the range of nm.

If a wavelength longer than 1660 nm is selected as the reference wavelength for PET determination in the wavelength region shown in FIG. 1, the probability of erroneously determining PS and PET increases.
It is possible to set the threshold value for the determination in the expression (1) to a value larger than 1, for example, 1.2, but the thickness is indeterminate.
An erroneous determination is made when the thickness of PET is small and the thickness of PS is large.

1640n as a reference wavelength for PET determination
When a wavelength shorter than m is selected, PET absorption becomes small, so that it is difficult to determine PET itself. If a wavelength shorter than 1700 nm is selected as a reference wavelength (second measurement wavelength) for plastic determination other than PET, determination of PE becomes difficult. Also, there is a possibility that PS is erroneously determined as PET.

If a wavelength longer than 1740 nm is selected as a reference wavelength for judging plastics other than PET, it becomes difficult to judge PS. Around 1640-1660 nm and 17
The wavelength range around 00 to 1740 nm is also less susceptible to scattering, dirt, or printing or labeling on the bottle surface, and is more convenient for accurate identification. In order to reduce the probability of erroneously determining that a plastic other than PET is PET when identifying it by equation (1),
The threshold of the criterion may be set to an appropriate numerical value other than 1 based on the thickness of a general PET bottle.

FIG. 2 shows infrared absorption spectra at 1050 to 1300 nm of five types of plastics for examining other measurement wavelength ranges. In this wavelength region, PET has an absorption peak near 1180 nm in addition to 1120 to 1130 nm. In this wavelength region, the first measurement wavelength for PET determination is selected from 1120 to 1130 nm, and the other second measurement wavelength for plastic determination is 1
By selecting from 200 to 1220 nm, the object of the present invention can be achieved. However, the extinction coefficient in this region is 1
1 / compared to the extinction coefficient in the range of 600 to 1800 nm.
Since it is about 10, it cannot be denied that the accuracy of the identification result becomes low.

There are various devices for realizing the identification method of the present invention. One of them is a light source that generates infrared light as measurement light, a photodetector that has sensitivity in the infrared region, and a measurement light from the light source is irradiated on the measurement target to transmit or reflect the measurement target. An optical system that causes the measured light to be incident on the photodetector, and an optical path where the measured light is incident on the object to be measured, or an optical path where the measured light is incident on the photodetector from the object to be measured. At the one measurement wavelength is greater than at the second measurement wavelength, PP, PE,
A spectroscope for selecting first and second measurement wavelengths such that light absorption by PS and PVC is greater at the second measurement wavelength than at the first measurement wavelength, and light intensity detected by the photodetector And a determination unit for determining whether or not the measurement target is PET based on the detected light intensities at the first and second measurement wavelengths. Here, it is preferable to use, for example, an interference filter as the spectroscope.

Since the material to be measured varies depending on the location, it is better to perform the measurement at two wavelengths as close as possible, rather than at a distance. The best thing is to do it in the same place. For this purpose, it is preferable that the upper optical system irradiates the measurement object with the measurement light as a single light beam, divides the measurement light from the measurement object into two light beams, and makes the two light beams incident on the photodetector. in this case,
The spectrometers for the first and second measurement wavelengths are provided for each of two light beams incident on the photodetector.

Another device for realizing the identification method of the present invention is that the light absorption by PET is greater at the first measurement wavelength than at the second measurement wavelength, and PP, PE,
Such that the light absorption by PS and PVC is greater at the second measurement wavelength than at the first measurement wavelength,
A first light-emitting element for generating light of a first measurement wavelength and a second light-emitting element.
A light source including a second light-emitting element that generates light of a measurement wavelength, a photodetector having sensitivity in the infrared region, and irradiating the measurement target with measurement light from the light source to transmit or reflect the measurement target. An optical system that causes the measured light to be incident on the photodetector, and whether or not the measurement target is PET based on the detected light intensity at the first and second measurement wavelengths based on the light intensity detected by the photodetector. And a judging unit for judging. In this case, the light source preferably uses an LED (light emitting diode) or an LD (laser diode) as a light emitting element. Since LEDs generally have a wide emission wavelength range, they are preferably used in combination with optical means for selecting a wavelength range, such as an interference filter.

In this case, in order to enable measurement at two wavelengths to be performed at the same place, the measurement light from the two light emitting elements is converted into a light flux on the same optical axis as an optical system. And irradiate the measurement light from the object to be measured into a single photodetector. The electric path from the photodetector to the determination unit is branched into two, Is a holding circuit by a digital circuit or an analog circuit,
For example, by providing a sample-and-hold circuit, sequentially turning on two light-emitting elements in the optical system, and holding the detection signal of the photodetector by light from the light-emitting element that was turned on earlier in its holding circuit, It further includes a lighting control / timing circuit for determining whether or not the object to be measured is PET based on the detection light intensity of the measurement light from the two light emitting elements turned on at different times. Is preferred.

When a common detector is used, there is an advantage that it is not necessary to consider the difference in sensitivity between the two detectors. The selection of the first and second measurement wavelengths and the identification method performed by the determination unit are the methods described in the identification method of the present invention. In addition, when the detected light intensity at both measurement wavelengths is equal to or less than a certain value, the determination unit determines that the determination is impossible or non-PET, thereby reducing a possibility that the non-PET is erroneously identified as PET. Is preferred.

The discriminating apparatus of the present invention may be used by being incorporated in a reduced volume packing or crushing machine.
It may be incorporated in a belt conveyor type separation apparatus as disclosed in Japanese Patent No. 9768. By attaching the present apparatus to these apparatuses, it becomes possible to prevent contamination other than PET and obtain high-quality recycled materials.

[0024]

FIG. 3 shows a first embodiment. Reference numeral 2 denotes a light source that generates infrared light, and the light generated from the light source 2 may include a continuous spectrum or a discontinuous bright line spectrum. As such a light source 2, a tungsten-halogen lamp or the like can be used. 4 is a plastic bottle to be measured,
A condensing optical system 6 including a lens for condensing the measurement light from the light source 2 and irradiating the measurement object 4 is disposed between the light source 2 and the measurement object 4. A light receiving optical system 8 including a lens and a half mirror 10 for dividing the measuring light condensed by the light receiving optical system 8 into two optical paths for receiving the measurement light transmitted through the measurement object 4 and guiding the measurement light to the detector. Is arranged.
Infrared detectors 12a and 12b are arranged on the optical path of the two light beams split by the half mirror 10, respectively. The detectors 12a and 12b have sensitivity in an infrared region used for measurement. Examples of such detectors include a Ge photodiode, an InGaAs photodiode, a PbS photoconductive element, a PbSe photoconductive element, and an InAs photovoltaic element. An element, a pyroelectric element, or the like can be used.

One detector 12a from the half mirror 10
, Which is a reference wavelength for PET determination, is 164.
An interference filter 14a that transmits light having a wavelength selected from 0 to 1660 nm is provided. In the optical path from the half mirror 10 to the other detector 12b, 1700 to 1740 are used as reference wavelengths for plastic determination other than PET.
An interference filter 14b having a characteristic of transmitting a wavelength selected from nm is disposed. As an example, an interference filter having a transmission center wavelength of 1655 nm and a half width of 10 nm was used as the interference filter 14a, and an interference filter 14b having a transmission wavelength of 1705 nm and a half width of 10 nm was used. The detection outputs of the two detectors 12a and 12b are input to respective non-inverting and inverting input terminals of a comparator 16 serving as a determination unit. The comparator 16 converts the measurement target 4 into PET based on the magnitude comparison of both inputs. It is determined whether there is. The output of the comparator 16 is the light emitting diode 1
8 is connected.

In this embodiment, when the measuring object 4 is PET, the light absorption at the transmission wavelength of the interference filter 14a is stronger than the light absorption at the transmission wavelength of the interference filter 14b. The detection output of 12b is the detector 12
a is weaker than the detector 12b and the comparator 1
The output of 6 becomes low level, and the light emitting diode 18 is turned on. When the measurement object 4 is a plastic other than PET, the state is opposite to the above, and the light emitting diode 18 does not light.

FIG. 4 shows a second embodiment.
Light sources including infrared LEDs of different wavelengths are provided as the light sources 22a and 22b. The light source 22a includes an LED that generates light having a wavelength within 1640 to 1660 nm as reference wavelength light for PET determination, and the light source 22b includes a PE.
1700 as a reference wavelength for plastic determination other than T
It includes an LED that generates light having a wavelength within 〜1740 nm. Since it is difficult to obtain a commercially available LED having an optimum emission wavelength and has a wide emission wavelength range, the light sources 22a and 22b are used in combination with an interference filter. As an example, as the light source 22a, L having an emission center wavelength of 1670 nm is used.
ED has a transmission center wavelength of 1655 nm and a half width of 10 nm
Are used in combination with an LED having a light emission center wavelength of 1800 nm as the light source 22b and an interference filter having a transmission center wavelength of 1705 nm and a half width of 10 nm. As such an infrared LED,
For example, a product of Telcom Devices Corp. (USA) is available.

The infrared light generated from the two light sources 22 a and 22 b is converted into a light beam on the same optical axis by the half mirror 24 and is incident on the object 4 to be measured. The infrared detector 12 is disposed at a position where the measurement light transmitted through the measurement object 4 is received. The detector 12 is the detector 12 in the embodiment of FIG.
The same as a and 12b can be used. The detection output of the detector 12 is input to the non-inverting input terminal of the comparator 16 and the sample-hold circuit 26, and the output of the sample-hold circuit 26 is input to the inverting input terminal of the comparator 16. The output terminal of the comparator 16 is shown in FIG.
The light emitting diode 18 is connected as in the embodiment.

In the embodiment shown in FIG. 4, the light sources 22a,
22b are sequentially turned on in this order, and the light source 2 turned on first
By holding the detection signal of the detector 12 by the light from the light source 2a in the sample and hold circuit 26, the comparator 16 allows the two light sources 22 to be turned on at different times.
A lighting control / timing circuit 28 is provided to enable the determination as to whether or not the measurement target 4 is PET based on the magnitude comparison of the detection light intensities of the measurement lights from the measurement lights a and 22b.

In this embodiment, the light source 22a is first turned on for the object 4 to be measured, and the detector 12 using the light is turned on.
Is held in the sample and hold circuit 26.
Next, when the light source 22b is turned on, the detection signal of the detector 12 is input to the non-inverting input terminal of the comparator 16, and the infrared light from the light source 22a detected earlier and held by the sample and hold circuit 26 is output. Is input to the inverting input terminal of the comparator 16, and the two detection signals are compared in magnitude.

In this embodiment, when the measuring object 4 is PET, the light absorption by the infrared light from the light source 22a is stronger than the light absorption by the infrared light from the light source 22b.
The input to the inverting input terminal of the comparator 16 is weaker than the input to the non-inverting input terminal, the output of the comparator 16 becomes low level, and the light emitting diode 18 is turned on. When the measurement object 4 is a plastic other than PET, the state is opposite to the above, and the light emitting diode 18 does not light.

As shown in FIGS. 3 and 4, by irradiating measurement light containing two wavelengths to the same place on the object 4 to be measured, variation in the material in place is suppressed and more accurate identification is performed. Will be able to do it. However, in the embodiment shown in FIG. 3, even if the interference filter is arranged on the incident side to the measuring object 4 and each wavelength light is incident on the measuring object 4 as a different optical axis, the optical axes are close to each other. If they do, locational effects can be avoided. FIG.
In this embodiment, even if the light from each of the light sources 22a and 22b is made to enter a different place without using the half mirror 24, if the optical axes are close to each other, the influence of the place is not affected. Can be avoided. When the number of incident optical axes is two and the detectors are arranged on the respective optical paths, the sample and hold circuit 26 and the lighting control / timing circuit 28 in FIG. 4 become unnecessary.

The optical system of the embodiment shown in FIGS. 3 and 4 is not limited to these, and may be further modified as appropriate.
In the embodiment shown in FIG. 3, a simpler structure can be obtained by using a detector in which two detection elements and two filters are combined as the infrared detector. As such a detector, for example, the detector disclosed in JP-A-7-92022 can be used. Further, if a color sensor is used as a detector, a color identification function can be added.

[0034]

According to the present invention, the light absorption by PET is the first.
Is larger than at the second measurement wavelength, and the light absorption by PP, PE, PS, and PVC is greater at the second measurement wavelength than at the first measurement wavelength. , Select a second measurement wavelength,
Since it is determined whether or not the object to be measured is PET based on the detected light intensities at these measurement wavelengths, identification can be made with a minimum of two wavelengths, and a complicated signal processing circuit is required. Inexpensive and high-speed processing can be performed without using the same.

[Brief description of the drawings]

FIG. 1 1600-1850 of five types of plastics
It is a waveform diagram which shows the infrared absorption spectrum in nm.

Fig. 2 1050-1300 of 5 kinds of plastics
It is a waveform diagram which shows the infrared absorption spectrum in nm.

FIG. 3 is a schematic configuration diagram illustrating an identification device according to an embodiment;

FIG. 4 is a schematic configuration diagram showing an identification device of another embodiment.

[Explanation of symbols]

 2 Infrared light source 4 Object to be measured 6 Condensing optical system 8 Light receiving optical system 10, 24 Half mirror 12, 12a, 12b Detector 14a, 14b Interference filter 16 Comparator 18 Light emitting diode 22a, 22b Infrared LED 26 Samp hold circuit 28 Lighting control / timing circuit

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2G020 AA03 CA02 CB04 CB23 CB27 CB42 CC26 CC27 CC47 CD05 CD11 CD13 CD22 CD31 2G059 AA02 AA10 BB08 EE01 EE11 GG01 GG02 HH01 HH06 JJ01 JJ03 JJ22 CB01 CB01 CB031 4F301 AA25 AC02 BA13 BA15 BA21 BF03 BF08 BF26

Claims (12)

[Claims] 1. The optical absorption by PET is greater at a first measurement wavelength than at a second measurement wavelength.
The first and second measurement wavelengths are selected such that light absorption by P, PE, PS and PVC is larger at the second measurement wavelength than at the first measurement wavelength. (1) Measurement object A light detection step of irradiating the measurement light to the first and second detection wavelengths of the transmitted light or the reflected light, and (2) the detection light intensity at the first and second measurement wavelengths A determination step of determining whether or not the measurement target is PET based on the above method. 2. The method according to claim 1, wherein in the determining step, if R = (first measured wavelength light intensity) / (second measured wavelength light intensity) is smaller than 1, PET is determined, and if R = (first measured wavelength light intensity) is equal to or larger than 1, it is determined not to be PET. Item 2. The identification method according to Item 1. 3. The first measurement wavelength is 1640 to 1660n.
m and the second measurement wavelength is set to 1700 to 174.
3. The identification method according to claim 1, wherein the method is selected from around 0 nm. 4. A light source that generates infrared light as measurement light; a photodetector having sensitivity in an infrared region; and a measurement light from the light source is irradiated on the measurement target to transmit or pass through the measurement target. An optical system that causes the reflected measurement light to enter the photodetector; and an optical path in which the measurement light is incident on the measurement target or an optical path in which the measurement light is incident on the photodetector from the measurement target.
Are greater at the first measurement wavelength than at the second measurement wavelength, PP, PE, PS and PV
A spectroscope for selecting the first and second measurement wavelengths such that light absorption by C is greater at the second measurement wavelength than at the first measurement wavelength, and based on the light intensity detected by the photodetector. A determination unit that determines whether or not the measurement target is PET based on the detected light intensities at the first and second measurement wavelengths. 5. The identification device according to claim 4, wherein the spectroscope is an interference filter. 6. The optical system according to claim 1, wherein the measurement system converts the measurement light into a single light beam and irradiates the measurement object with the measurement light, splits the measurement light from the measurement object into two light beams, and makes the two light beams incident on the photodetector. The identification device according to claim 4, wherein a spectroscope for each of the first and second measurement wavelengths is provided for each of two light beams incident on the photodetector. 7. The light absorption by PET at the first measurement wavelength is greater than at the second measurement wavelength, and P
A first light-emitting element for generating light of a first measurement wavelength and a second light-emitting element such that light absorption by P, PE, PS and PVC is greater at the second measurement wavelength than at the first measurement wavelength. A light source including a second light emitting element that generates light having a measurement wavelength of; a photodetector having sensitivity in an infrared region; and irradiating the measurement target with measurement light from the light source to transmit or pass through the measurement target. An optical system that causes the reflected measurement light to be incident on the photodetector; and a light object detected by the photodetector. The measurement target is PET based on the detected light intensity at the first and second measurement wavelengths. And a determining unit for determining whether or not the PET is different from other plastics. 8. The light source is an LED or L as a light emitting element.
The identification device according to claim 7, further comprising D. 9. The optical system irradiates measurement light from two light-emitting elements into a light beam on the same optical axis and irradiates the measurement object, and makes the measurement light from the measurement object incident on the single photodetector. An electric path from the photodetector to the determination unit is branched into two, and a holding circuit is provided on one of the electric paths, and the optical system sequentially connects the two light emitting elements. Lighting, by holding the detection signal of the photodetector by the light from the light emitting element that was turned on earlier in the holding circuit, the determination unit, from the two light emitting elements that were turned on at different times The object to be measured is PET based on the intensity of light detected by the measuring light.
The identification device according to claim 7, further comprising a lighting control / timing circuit configured to determine whether or not the lighting is performed. 10. The first measurement wavelength is 1640 to 1660.
nm, and the second measurement wavelength is 1700-1.
The identification device according to claim 4, wherein the identification device is selected from around 740 nm. 11. The determination unit determines that if R = (first measurement wavelength light intensity) / (second measurement wavelength light intensity) is less than 1, it is PET, and if R = (first measurement wavelength light intensity) is not less than 1, it is not PET. The identification device according to any one of claims 4 to 10, wherein 12. The apparatus according to claim 4, wherein the determination unit has a function of determining that determination is impossible or non-PET when the detected light intensity at both measurement wavelengths is equal to or less than a predetermined value.
2. The identification device according to claim 1,