Patent Publication Number: US-2022219205-A1

Title: Automatic metal sorting system and method using laser induced breakdown spectroscopy

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a Continuation of International Application No. PCT/KR2020/008124 filed on Jun. 24, 2020, which claims priority to and the benefit of Korean Patent Application No. 10-2019-0122274 filed in the Korean Intellectual Property Office on Oct. 2, 2019, the entire contents of which are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present disclosure relates to an automatic metal sorting system and method using laser induced breakdown spectroscopy and, more particularly, to an automatic metal sorting system and method that sorts waste metals by measuring the position and shape of waste metals and analyzing plasma that is produced when a laser is emitted. 
     Description of the Related Art 
     Waste metal resources of about a level of 4 trillion Won are made in every year in Korea and waste metals are metal resources having high economic value because it can be immediately used through only a minimal refinement process. Recycling of waste metals is promoted all over the world as a national emphasis business in terms of resource saving, but it has been known that the domestic technology of recycling waste metals and relevant industries are very poor despite the high economic value. 
     The core reason of low recycling rate of waste metal resources is because the collection route of waste metal scraps and the kinds are various, so it is impossible to sort the scraps on the basis of a unified standard and there is no technology that can accurately analyze the kinds and components of waste metals of which the collection routes are unclear. 
     It is required to develop an automated system that can sort various kinds of mixed metal scraps at a high speed in order to increase the recycling rate of waste metal resources. Existing technologies has a problem that the sorting accuracy is low because the technologies depend on the colors of metals or whether metals have magnetism. 
     Further, referring to  FIGS. 3 and 4 , when a plasma spectrum signal that a laser induced breakdown spectroscopic device collects is not corrected, a maximum of 100 mm measurement distance difference may be generated between a reference focus and plasma produced when the positions of waste metals that are input, as shown in  FIG. 3 . As a result, as shown in  FIG. 4 , when the positions of waste metals increase in the width direction from a reference point, there is a problem that the laser induced breakdown spectrum signals that are measured gradually decrease in size and a situation in which a signal is not measured even though plasma is actually produced from a laser occurs. 
     SUMMARY OF THE INVENTION 
     The present disclosure has been made in an effort to solve the problems and an objective of the present disclosure is to provide an automatic metal sorting system and method using laser induced breakdown spectroscopy. 
     The objectives of the present disclosure are not limited to those described above and other objectives may be made apparent to those skilled in the art from claims. 
     In order to achieve the objectives, an automatic metal sorting system using laser induced breakdown spectroscopy according to an embodiment of the present disclosure is disclosed. The system may include: a conveyer configured to move waste metals at a constant speed; a shape measurer configured to measure a position and a shape of at least one waste metal on the conveyer; a laser induced breakdown spectroscopic device configured to determine the kind of the waste metal by emitting a laser to the waste metal and receiving and analyzing a plasma spectrum signal generated by the emitted laser; and a discharger configured to separate and discharge the waste metal in accordance with the determined kind of the waste metal. 
     Further, according to an embodiment of the preset disclosure, the laser induced breakdown spectroscopic device may include: a laser emitter; a galvano-scanner configured to emit a laser to waste metals randomly spread on the conveyer by changing a direction of the laser emitted from the laser emitter by adjusting the angle of a mirror disposed in the galvano-scanner; and a plasma signal configured to focus plasma signals generated by the emitted laser on an optical fiber connected with a spectroscope. 
     Further, according to an embodiment of the present disclosure, the laser induced breakdown spectroscopic device may further include a focusing module configured to adjust a focal length of the laser emitted from the laser emitter in accordance with a change in position and shape of the waste metals. 
     Further, according to an embodiment of the present disclosure, the laser induced breakdown spectroscopic device may further include a collection module configured to collect plasma spectrum signals generated by emitting a laser to waste metals through the galvano-scanner. 
     Further, according to an embodiment of the present disclosure, the focusing module may include: two optical lenses; and a first variable lens inserted in the fronts of the two optical lenses. 
     Further, according to an embodiment of the present disclosure, the collection module may include: two optical lenses; and a second variable lens inserted between the two optical lenses. 
     Further, according to an embodiment of the present disclosure, the collection module may be a module that includes: two optical lenses; and a second variable lens inserted between the two optical lenses, and that adjusts a beam, which has passed through the second variable lens to become parallel light, by changing a curvature of the second variable lens, and collects adjusted plasma spectrum signals. 
     Further, according to an embodiment of the present disclosure, the first variable lens may be a liquid-state lens of which a curvature is changed when a current is applied to the first variable lens. 
     Further, according to an embodiment of the present disclosure, the second variable lens may be a liquid-state lens of which a curvature is changed when a current is applied to the second variable lens. 
     Further, according to an embodiment of the present disclosure, the discharger may be positioned at an end of the conveyer and may separate and discharge the waste metals in accordance with the determined kinds of the waste metals using air nozzles. 
     In addition, an automatic metal sorting method using laser induced breakdown spectroscopy according to an embodiment of the present disclosure is disclosed. The method may include: a shape measurement step of measuring a position and a shape of at least one of waste metals being on a conveyer that is being moved at a constant speed; a laser induced breakdown spectroscopic determination step of determining the kind of the measured waste metal by emitting a laser to the waste metal and by analyzing a plasma spectrum signal generated by the emitted laser; and a step of separating and discharging the waste metal in accordance with the kind of the waste metal determined in the laser induced breakdown spectroscopic determination step. 
     Further, according to an embodiment of the present disclosure, the laser induced breakdown spectroscopic determination step may include: a laser emission step of emitting a laser; a focusing step of adjusting a focal length of the laser emitted in the laser emission step in accordance with changes in position and shape of waste metals; a galvano-scanner step of emitting a laser to waste metals randomly spread on the conveyer by changing a direction of the laser having the adjusted focal length by adjusting a mirror disposed in a galvano-scanner; a collection step of collecting plasma spectrum signals generated by emitting a laser to the waste metals through the galvano-scanner step; and a spectrum signal obtainment step of focusing the collected plasma spectrum signals on an optical fiber connected with a spectroscope. 
     Further, according to an embodiment of the present disclosure, the focusing step may be a step of adjusting a focal length of a laser using two optical lenses and a first variable lens inserted in the fronts of the two optical lenses. 
     Further, according to an embodiment of the present disclosure, the collection step may be a step of adjusting a beam, which has passed through a second variable lens, to become parallel light by changing a curvature of the second variable lens and of collecting adjusted plasma signals by using two optical lenses and the second variable lens inserted between the two optical lenses. 
     Further, according to an embodiment of the present disclosure, the first variable lens may be a liquid-state lens of which a curvature is changed when a current is applied to the first variable lens. 
     Further, according to an embodiment of the present disclosure, the second variable lens may be a liquid-state lens of which a curvature is changed when a current is applied to the second variable lens. 
     Further, according to an embodiment of the present disclosure, the separating and discharge step may be a step that is positioned at an end of the conveyer and separates and discharges the waste metals in accordance with the determined kinds of the waste metals using air nozzles. 
     Details for achieving the objectives would be made clear by referring to the following embodiments to be described with the accompanying drawings. 
     However, the present disclosure is not limited to the embodiments disclosed hereafter and may be configured in various other ways, which is provided to complete the present disclosure and completely inform those having common knowledge in the art (hereafter, “those skilled in the art”) of the range of the present disclosure. 
     According to an embodiment of the present disclosure, it is possible to quickly perform analysis in comparison to the related art by analyzing waste metals that are moving, so it is economically excellent. 
     According to an embodiment of the present disclosure, it is possible to analyze waste metals in real time by adjusting a variable lens, so it is excellent in terms of the efficiency of sorting waste metals, whereby it is possible to increase the recycling rate of waste metals. 
     According to an embodiment of the present disclosure, the present disclosure performs analysis using laser spectroscopic analysis, thereby being able to considerably increase the economic value of waste metals by sorting non-ferrous metals having similar colors, which were impossible to sort in the related art, by accurately measuring the chemical compositions of the non-ferrous metals. 
     According to an embodiment of the present disclosure, a focal length and errors of spectrum signals are corrected using a variable lens, so it is possible to reduce determination errors due to a distance difference. 
     The effects of the present disclosure are not limited to the effects described above, and provisional effects that are expected from the technical features of the present disclosure would be clearly understood from the following description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Some of embodiments are shown in the accompanying drawings so that the characteristics of the present disclosure stated above can be understood with reference to the following detailed and more specified embodiments. Further, similar reference numerals in the drawings are given to indicate the same or similar functions in several respects. However, it should be noted that the accompanying drawings show only specific typical embodiments of the present disclosure without limiting the scope of the present disclosure and other embodiments having the same effects may be sufficiently recognized. 
         FIG. 1  is a block diagram of an automatic metal sorting system using laser induced breakdown spectroscopy according to an embodiment of the present disclosure; 
         FIG. 2  is a schematic view of the automatic metal sorting system using laser induced breakdown spectroscopy according to an embodiment of the present disclosure; 
         FIG. 3  is a view showing an existing laser induced breakdown spectroscopic device; 
         FIG. 4  is a graph showing resultant values measured by an existing laser induced breakdown spectroscopic device; 
         FIG. 5  is a view showing a laser induced breakdown spectroscopic device according to an embodiment of the present disclosure; 
         FIG. 6  is a view showing a collection module of the laser induced breakdown spectroscopic device according to an embodiment of the present disclosure; and 
         FIG. 7  is a flowchart of an automatic metal sorting method using laser induced breakdown spectroscopy according to an embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     An automatic metal sorting system using laser induced breakdown spectroscopy according to an embodiment of the present disclosure is disclosed. The system may include: a conveyer configured to move waste metals at a constant speed; a shape measurer configured to measure a position and a shape of at least one waste metal on the conveyer; a laser induced breakdown spectroscopic device configured to determine the kind of the waste metal by emitting a laser to the waste metal and receiving and analyzing a plasma spectrum signal generated by the emitted laser; and a discharger configured to separate and discharge the waste metal in accordance with the determined kind of the waste metal. 
     An automatic metal sorting method using laser induced breakdown spectroscopy according to an embodiment of the present disclosure is disclosed. The method may include: a shape measurement step of measuring a position and a shape of at least one of waste metals being on a conveyer that is being moved at a constant speed; a laser induced breakdown spectroscopic determination step of determining the kind of the measured waste metal by emitting a laser to the waste metal and by analyzing a plasma spectrum signal generated by the emitted laser; and a step of separating and discharging the waste metal in accordance with the kind of the waste metal determined in the laser induced breakdown spectroscopic determination step. 
     The present disclosure may be modified in various ways and implemented by various exemplary embodiments, so that specific exemplary embodiments are shown in the drawings and will be described in detail. 
     Various features of the present disclosure disclosed in claims will be better understood in consideration of drawings and detailed description. An apparatus, a method, a manufacturing method, and various embodiments disclosed in the specification are provided for examples. The disclosed structure and functional features are provided for those skilled in the art to be able to implement various embodiments in detail rather than limiting the scope of the present disclosure. The disclosed terms and sentences are provided to easily explain the features of the present disclosure rather than limiting the scope of the present disclosure. 
     In describing the present invention, detailed descriptions of well-known technologies will be omitted so as not to obscure the description of the present invention with unnecessary detail 
     Hereafter, an automatic metal sorting system and method using laser induced breakdown spectroscopy according to an embodiment of the present disclosure is described. 
       FIG. 1  is a block diagram of an automatic metal sorting system using laser induced breakdown spectroscopy according to an embodiment of the present disclosure and  FIG. 2  is a schematic view of the automatic metal sorting system using laser induced breakdown spectroscopy according to an embodiment of the present disclosure.  FIG. 3  is a view showing an existing laser induced breakdown spectroscopic device and  FIG. 4  is a graph showing resultant values measured by an existing laser induced breakdown spectroscopic device.  FIG. 5  is a view showing a laser induced breakdown spectroscopic device according to an embodiment of the present disclosure. 
     Referring to  FIGS. 1 to 5 , an automatic metal sorting system  10  includes a conveyer  200 , a shape measurer  300 , a laser induced breakdown spectroscopic device  400 , and a discharger  500 . 
     In an embodiment, the conveyer can move waste metals thereon at a constant speed to automatically sort the waste metals. For example, the width of the conveyer may be 500 mm in accordance with the rotation range (−20° to 20°) of a galvano-scanner  440  disposed in the laser induced breakdown spectroscopic device  400 . This example is only an example for explaining the present disclosure and the present disclosure is not limited thereto. 
     In an embodiment, the shape measurer  300  can measure the position and shape of waste metals on the conveyer that is moved at a constant speed. In more detail, the shape measurer  300  can measure the position and shape of waste metals using an optical technology when various resources and metal fragments are moved on the conveyer. The shape measurer  300  is a device that primarily measures the position and shape of waste metals on the conveyer using an optical technology to increase the sorting efficiency before the kinds of the waste metals are determined through the laser induced breakdown spectroscopic device  400 . 
     In an embodiment, the laser induced breakdown spectroscopic device  400  can determine the kinds of waste metals by emitting a laser to the waste metals measured by the shape measurer  300  and then by analyzing generated plasma spectrum signals. The laser induced breakdown spectroscopic device  400  is a device that accurately analyzes the kinds of metals by tracking waste metal spread at random positions of a conveyer belt and analyzing plasma spectrum signals generated by emitting a laser to the waste metals. 
     In more detail, the laser induced breakdown spectroscopic device  400  may include a laser emitter  410  that emits a laser, a galvano-scanner  430  that emits a laser to waste metals randomly spread on a conveyer by changing the direction of the laser emitted from the laser emitter by adjusting the angle of a mirror disposed in the galvano-scanner, and a spectrum signal obtainer  450  that focuses plasma spectrum signals generated by the emitted laser on an optical fiber connected with a spectroscope. 
     Further, the laser induced breakdown spectroscopic device  400  may further include a focusing module  420  that adjusts the focal length of the laser emitted from the laser emitter in accordance with changes in position and shape of waste metals. 
     Further, the laser induced breakdown spectroscopic device  400  may further include a collection module  440  that collects plasma spectrum signals generated by emitting a laser to waste metal through the galvano-scanner. 
     In an embodiment, the laser emitter  410  is used to analyze the kinds of waste metals of which the position and shape have been measured. For example, the laser that is emitted from the laser emitter may be a laser having output power of 90 mJ, a wavelength of 1064 nm, a pulse repetition frequency of 100 Hz, a beam diameter of 4 mm, and pulse duration of 8 ns. This example is only an example for explaining the present disclosure and the present disclosure is not limited thereto. 
     In an embodiment, the focusing module  420  may include a plurality of optical lenses and variable lenses. In more detail, the focusing lens  420  may be a module that adjusts the focal length of a laser with a first variable lens  425  inserted between the laser emitter  410  and at least one or more optical lenses. The focusing module  420  may include two optical lenses and a first variable lens inserted in the fronts of the two optical lenses. 
     Further, the focusing module  420  is positioned between the laser emitter  410  and a dichroic mirror D 1  and is composed of a double-sided concave lens  421  and a double lens  423  sequentially from the laser emitter  410 , and the first variable lens  425  may be positioned between the laser emitter  410  and the double-sided concave lens  421 . Further, the inserted first variable lens  425  is a liquid-state lens, and when a current is applied to the first variable lens  425 , the curvature may be changed. 
     Accordingly, the focusing module  420  can adjust the focal length of a laser by changing a lens curvature by applying a current to the inserted first variable lens  425 . Further, it is possible to adjust the focal length of a laser by changing the distance between the double-sided concave lens  421  and the double lens  423 . The double lens may be used to correct distortion that may be generated when a laser is focused. 
     For example, the double-sided concave lens  421  may have a focal length of 75 mm and 7.5 J/m 2 , the double lens  423  may have a focal length of 100 mm and 10 J/m 2 , and the first variable lens  425  may have 100 Hz, 2.6 J/m 2 , and −2 +2 (dpt). Further, the distance between the double-sided concave lens  421  and the double lens  423  may be 35 mm and the distance between the first variable lens  425  and the double-sided concave lens  421  may be 3 mm. This example is only an example for explaining the present disclosure and the present disclosure is not limited thereto. 
     Further, the dichroic mirror D 1 , which is a reflecting mirror composed of thin layers of substances having different refractive indexes, has a property of reflecting light of some colors and transmitting light of all the other colors. The dichroic mirror D 1  has a characteristic that a loss due to absorption is very small in comparison to a color filter and the wavelength range of light that is selectively reflected can be increased/decreased, depending on the thickness or structure of the material. For example, the dichroic mirror D 1  may have a reflection range of 380 to 850 nm and 6.5 J/m 2 . This example is only an example for explaining the present disclosure and the present disclosure is not limited thereto. 
     In an embodiment, the galvano-scanner  430  is equipment that can perform multipoint laser scanning using one laser by changing the emission direction of a laser by rotating a mirror at a predetermined speed and at a predetermined angle when it is used in cooperation with a laser. The galvano-scanner  430  can cope with real-time changes by adjusting the angle of a mirror in real time to fit to an adjusted focal length when a focal length is changed by the focusing module  420 . 
     For example, the galvano-scanner  430  may have 20°   +20°, a reflection range of 380 to 2000 nm, and 3 J/m 2 . This example is only an example for explaining the present disclosure and the present disclosure is not limited thereto. 
     In an embodiment, the collection module  440  can collect plasma spectrum signals that are generated when a laser is emitted to waste metals through the galvano-scanner  430 . The collection module  440  may include two optical lenses and a second variable lens  445  inserted between the two optical lenses. The collection module  440  may be a module that adjusts plasma spectrum signals with the second variable lens  445  inserted between two optical lenses and collects the adjusted plasma spectrum signals. 
     In more detail, the collection module  440  may be a module that has the second variable lens  445  inserted between two optical lenses, that adjusts a beam that has passed through the second variable lens  445  to become parallel light by changing the curvature of the second variable lens  445 , and that collects adjusted plasma spectrum signals. Further, the collection module  440  may be a module that is positioned over the dichroic mirror D 1  positioned between the focusing module  420  and the galvano-scanner  430 , is composed of a double lens  441  and a double lens  443 , from the bottom, and has the second variable lens  445  between these lenses. 
     Further, the inserted second variable lens  445  is a liquid-state lens, and when a current is applied to the second variable lens  445 , the curvature may be changed. Accordingly, the collection module  440  can serve to adjust the laser that has passed through the variable lens to become parallel light by changing a lens curvature by applying a current to the inserted second variable lens  445 . 
     For example, the focal length of the double lens  441  may be 150 mm, the focal length of the upper double lens  443  may be 50 mm, and the second variable lens  445  may have 100 Hz, a transmission range of 400 to 700 nm, and −1.5 to +1.5 (dpt). Further, the distance between a single lens  441  or the double lens  441  and the second variable lens  445  may be 60 mm, and the distance between the optical fiber  450  and the upper double lens  443  may be 40 mm to 50 mm. This example is only an example for explaining the present disclosure and the present disclosure is not limited thereto. 
     In an embodiment, the spectrum signal obtainer  450  is positioned over the collection module  440  and can serve to focus plasma spectrum signals collected by the collection module  440  on an optical fiber connected with a spectroscope. For example, the optical fiber may be an optical fiber of which the core has 200 μm and 0.22 NA. This example is only an example for explaining the present disclosure and the present disclosure is not limited thereto. 
     Further,  FIG. 6  is a view showing a collection module of the laser induced breakdown spectroscopic device according to an embodiment of the present disclosure. Referring to  FIG. 6 , the collection module  440  is designed using a variable lens through Zemax simulation. A collection route after an optical lens L 1  ( 441 ) is changed by the laws of refraction in accordance with a generation distance of plasma from an optical axis, which causes a change of a phase when plasma is focused on the optical fiber  450 . The system of the present disclosure is a system that additionally has the second variable lens  445  between two optical lenses L 1  and L 2  and can adjust in real time the curvature of the second variable lens  445  such that a beam coming out of the second variable lens  445  can always become parallel light in order that plasma generated at various positions in accordance with the positions of waste metal can be maximally focused on the optical fiber  450  connected to a spectroscope. The parallel light traveling into the double lens  443  is focused always in the same state, so a constant signal can be obtained at a spectroscope in this case. It can be seen that plasma spectrum signals are finally focused on the optical fiber  450  under the same condition by changing the curvature of the second variable lens in real time even if the generation position of plasma changes as the result of simulation. 
     Laser Induced Breakdown Spectroscopy (LIBS) is a chemical analysis technique that performs analysis using short laser pulses to make micro-plasma on an analysis sample. 
     The present disclosure performs analysis using laser spectroscopic analysis, thereby being able to considerably increase the economic value of waste metals by sorting non-ferrous metals having similar colors, which were impossible to sort in the related art, by accurately measuring the chemical compositions of the non-ferrous metals. 
     Further, the present disclosure corrects the focal length of a laser and corrects errors of plasma spectrum signals by inserting a variable lens when using laser induced breakdown spectroscopic analysis, thereby being able to reduce a measurement error due to a distance difference according to the positions of waste metals randomly spread. 
     In an embodiment, the discharger  500  is positioned at the end of the conveyer and can separate and discharge waste metals using air nozzles in accordance with the kinds of the waste metals. Waste metals can be automatically separated and discharged in accordance with the weight of the waste metals discharged by air sprayed from the air nozzles. 
       FIG. 7  is a flowchart of an automatic metal sorting method using laser induced breakdown spectroscopy according to an embodiment of the present disclosure. 
     Referring to  FIG. 7 , the method may include: a shape measurement step of measuring the position and the shape of at least one of waste metals being on a conveyer that is being moved at a constant speed (S 701 ); a laser induced breakdown spectroscopic determination step of determining the kind of the measured waste metal by emitting a laser to the waste metal and by analyzing a plasma spectrum signal generated by the emitted laser (S 703 ); and a step of separating and discharging the waste metal in accordance with the kind of the waste metal determined in the laser induced breakdown spectroscopic determination step (S 705 ). 
     In an embodiment, the shape measurement step S 701  is a step of measuring the shape and position of at least one of waste metals being on a conveyer that is being moved at a constant speed. 
     In more detail, the shape measurement step S 701  can measure the position and shape of waste metals using an optical technology when various resources and metal fragments are moved on the conveyer. Further, the shape measurement step S 701  is a step of primarily measuring the position and shape of waste metals on the conveyer using an optical technology to increase the sorting efficiency before the kinds of the waste metals are determined through the laser induced breakdown spectroscopic determination step S 703 . 
     In an embodiment, the laser induced breakdown spectroscopic determination step S 703  is a step of determining the kind of a measured waste metal by emitting a laser to the waste metal and analyzing a plasma spectrum signal generated by the emitted laser. Further, the laser induced breakdown spectroscopic determination step S 703  may be a step of accurately analyzing the kinds of metals by tracking waste metals spread at random positions on a conveyer belt and analyzing spectrum signals of plasma generated by emitting a laser. 
     In more detail, the laser induced breakdown spectroscopic determination step S 703  may include: a laser emission step of emitting a laser; a focusing step of adjusting the focal length of the laser emitted in the laser emission step in accordance with changes in position and shape of waste metals; a galvano-scanner step of emitting a laser to the waste metals randomly spread on a conveyer by changing the direction of the laser having the adjusted focal length by adjusting a mirror disposed in a galvano-scanner; a collection step of collecting plasma spectrum signals generated by emitting a laser to the waste metals through the galvano-scanner step; and a spectrum signal obtainment step of focusing the collected plasma spectrum signals on an optical fiber connected with a spectroscope. 
     In an embodiment, the focusing step may be a step of adjusting the focal length of a laser according to position changes of waste metals that are separated at random positions and moving on a conveyer. Further, the focusing step is a step that is performed between the laser emission step and the galvano-scanner step and may be a step of adjusting the focal length of a laser using at least one or more optical lenses. 
     In more detail, the focusing step may be a step of adjusting the focal length of a laser using two optical lenses and a first variable lens inserted in the fronts of the two optical lenses. The inserted first variable lens  425  is a liquid-state lens, and when a current is applied to the first variable lens  425 , the curvature may be changed. Further, the focusing step may be a step of adjusting the focal length of a laser by changing a lens curvature by applying a current to the inserted first variable lens  425 . 
     In an embodiment, the collection step may be a step of collecting plasma spectrum signals generated by emitting a laser to waste metals. 
     In more detail, the collection step may be a step that adjusts plasma spectrum signals with the second variable lens  445  inserted between two optical lenses and collects the adjusted plasma spectrum signals. Further, the collection step may be a step that has the second variable lens  445  inserted between two optical lenses, that adjusts a beam that has passed through the second variable lens  445  to become parallel light by changing the curvature of the second variable lens  445 , and that collects adjusted plasma spectrum signals. The inserted second variable lens  445  is a liquid-state lens, and when a current is applied to the second variable lens  445 , the curvature may be changed. Further, the collection step may be a step of adjusting the beam, which has passed through the second variable lens  445 , to become parallel light by changing a lens curvature by applying a current to the inserted second variable lens  445 . 
     In an embodiment, the separating and discharging step S 705  may be a step of separating and discharging waste metals in accordance with the kinds of the waste metals determined in the laser induced breakdown spectroscopic determination step S 703 . In more detail, the separating and discharging step S 705  is positioned at the end of the conveyer. In order to separate and discharge waste metals of which the kinds have been determined, the separating and discharging step S 705  can separate and discharge waste metals in order of heavy metals using air coming out of a discharger equipped with air nozzles. 
     The above description is only exemplary description of the spirit of the present disclosure and the present disclosure may be changed and modified by those skilled in the art in various ways without departing from the fundamental characteristics of the present disclosure. 
     Accordingly, the embodiments described herein are provided merely not to limit, but to explain the spirit of the present disclosure, and the spirit of the present disclosure is not limited by the embodiments. 
     The protection range of the present disclosure should be construed on the basis of claims and all spirits that are considered as being same or equivalent to the protection range should be construed as being included in the right range of the present disclosure.