Method and system for determining the type of glass from which a glass element is made

Abstract

The invention relates to a method for determining the type of glass from which a glass element is made. The method comprises the steps of measuring a transmittance of the glass element using a light beam, the light beam being incident on the glass element at an angle of incidence and reflected by a reflective element outside the glass element after having passed through the entire glass element; identifying the type of glass of the glass element by comparing the measured transmittance with a set of reference transmittances, each reference transmittance of the set being associated with one type of glass, and identifying the reference transmittance closest to the measured transmittance.

Description

Description Title of the invention: Method and system for determining the type of glass making up a glass element Prior art

[0001] The present application belongs to the general field of glazing, in particular glazing for buildings (windows, facades, partitions) or even for transport. It relates more particularly to a method for determining the type of glass making up a glass element, as well as a computer program for implementing the method, a system configured to implement this method, and a sorting method implementing the method or implemented by the system. The invention finds a particularly advantageous, although in no way limiting, application in the sorting of used glass elements, so as to optimize their recycling, in particular by allowing the sorting of glass elements upstream of glass recycling channels, in particular cullet treatment, for example at deconstruction sites.

[0002] A "glass element" is, for example, a sheet of glass, for example a sheet of glass that has been used for the manufacture of flat glass glazing (e.g. single / double / triple glazing), or a piece of sheet glass. Typically, the glass element has two essentially parallel faces, as is the case with a sheet of glass or a piece of sheet glass, but not with crushed cullet.

[0003] Glass recycling is today a major issue, with the main challenges being the reduction of verifiable raw material costs and the reduction of the environmental footprint of newly manufactured products (reduction of energy consumption in the industrial manufacturing process, improvement of the carbon footprint of new products).

[0004] In a recycling problem for the manufacture of glass, particularly for flat glass, it is now necessary to separate the glass from other components, particularly non-glass components (e.g. window frames, sealants, etc.). The known processes for reusing glass, via recycling, are in fact very dependent on the composition of used glass and its homogeneity. Thus, the The presence of unwanted elements within a glass composition can, for example, destabilize a used glass remelting installation, by introducing humidity and organics into the furnace, and / or give rise to defects in the newly produced glass.

[0005] However, currently, the tonnages of glass collected and sorted, particularly for flat glass, remain low. This limitation results in particular from the significant need for labor to sort glass as well as the risk inherent in collecting glass on site.

[0006] More fundamentally, this limitation also results from the absence of an effective solution allowing the type of glass making up a glass element to be characterized precisely, while limiting the risk of error.

[0007] These cumulative disadvantages mean that in practice different types of glass elements tend to be mixed together at the time of their collection, which requires the subsequent implementation of complex processes (cleaning, drying, sieving, detection and isolation of non-glass elements, etc.), which are costly and have a high environmental footprint, and constitutes an obstacle to the development of an efficient and virtuous glass recycling sector. Statement of the invention

[0008] The present invention aims to overcome all or part of the drawbacks of the prior art, in particular those set out above, by proposing a solution which makes it possible to determine the type of glass making up a glass element in a very efficient, inexpensive manner and by minimizing the risk of error.

[0009] The solution thus proposed therefore offers effective assistance in the selective sorting of glass elements, so as to significantly improve costs and the environmental footprint, and thus promote the development of a virtuous sorting sector. To this end, and according to a first aspect, the invention relates to a method for determining the type of glass making up a glass element. The method comprises the steps of: - measurement of a transmittance value of the glass element using a light beam, the light beam being incident on the glass element at an angle of incidence and reflected by a reflective element external to the glass element after having passed through the latter in its entirety; - identification of the type of glass of the glass element by comparing the measured transmittance value to a set of reference transmittance values, each reference transmittance value in the set being associated with a type of glass, and identification of the reference transmittance value closest to the measured transmittance value.

[0010] Thus, in its general principle, the determination method according to the invention is based on a determination (characterization) of the type of glass making up the glass element by comparing a measured transmittance value of the glass element with a set of known transmittance values, each being associated with a type of glass. At the end of this comparison, the known transmittance value which is closest to the measured transmittance value of the glass element is retained, and the type of glass with which it is associated identifies the type of glass making up the glass element. The determination of the transmittance value of the glass element is carried out using a light beam which completely (in its entirety) passes through the glass element twice: a first time at the exit of a light source after having completely passed through the glass element, and a second time after having been reflected by a reflective element such as a mirror.In other words, the beam passes completely through the glass element once, and after passing through it, it is reflected and passes completely through the glass element again. The transmittance determination is therefore carried out with a light beam that has passed through the glass element twice.

[0011] This method is particularly advantageous, insofar as it allows, in correspondence with the experimental observations made by the inventors, to precisely identify the different types of glass between them and then to discriminate them. In addition, it is possible from these experimental observations to attribute scores to the identifications, scores which objectively evaluate a margin of error of the identifications.

[0012] Furthermore, the implementation of the determination method according to the invention is particularly simple and inexpensive because it does not require significant hardware investment. It typically only uses a single beam of incident light. It does not require an image acquisition device.

[0013] Finally, the determination method according to the invention offers very effective assistance in the selective sorting of glass elements. Indeed, being able to determine in a fast and efficient the type of glass making up a glass element de facto leads to increased performance in the sorting process of such a glass element. Ultimately, this results in a significant improvement in the costs and environmental footprint of the glass sorting industry. In addition, the determination method according to the invention is easily implementable in a glass sorting plant; for example, the glass to be sorted can be placed on a conveyor which includes a mirror in one place, the elements for emitting and receiving the light beam being located above the mirror to carry out the measurements. In addition, the determination method makes it possible to identify types of glass still in place (for example, the windows of a building which is going to be dismantled) since the system implementing the method can be easily placed on the glass element, in particular the reflective element can be easily fixed on faces of the glass element by any means.In general, the invention allows a system carrying out the method to have a light source configured to generate the light beam and a meter of the transmittance value of the light beam reflected by the mirror. The meter and the light source are located on the same side of the glazing. Only the mirror needs to be located on the other side. This facilitates the installation and compactness of the system since the most bulky and heavy elements are arranged on one and the same side.

[0014] By "transmittance value" (T) according to the invention, we mean, in a conventional manner, the ratio of the intensity of the transmitted light beam (I) to the intensity of the incident light beam (I o), i.e. T=I / I0. In this case, according to the invention, the transmitted light beam corresponds to the beam having passed through the glass element a first time, having been reflected by the reflecting element, and having passed through the glass element a second time.

[0015] In particular embodiments, the determination method may further comprise one or more of the following characteristics, taken individually or in all technically possible combinations.

[0016] In particular modes of implementation: - each transmittance value of the set is within a respective transmittance value range, the transmittance value range being associated with the same type of glass as the transmittance value of the set; and identifying a transmittance value of the set includes identifying of the range of transmittance values to which the determined transmittance value belongs; - each range of values comprises N sub-ranges of transmittance values, N being a positive integer greater than or equal to 1, each sub-range being associated with a score indicating an accuracy of the determination of the type of glass of the glass element; and the identification of a transmittance value of the set comprises the identification of a sub-range of transmittance values to which the determined transmittance value belongs; - the transmittance value sub-ranges cover their respective value range in its entirety, preferably each value sub-range is substantially centered around the transmittance value of the value range comprising the transmittance value sub-ranges; - each range of values comprises at least: a first sub-range of transmittance values having values deviating at most by ±X1% from the value of said each transmittance value of the set, preferably the first sub-range is associated with the best precision score for determining the type of glass of the glass element; and / or a second sub-range of transmittance values having values deviating at least by ±X1% and at most by ±X2% from the value of said each transmittance value of the set, preferably the second sub-range is associated with a precision score lower than the best precision score;and / or a third sub-range of transmittance values having values deviating by a minimum of ±X2% and a maximum of ±X3% from the value of said each transmittance value of the set, preferably the third sub-range is associated with the worst accuracy score for determining the type of glass of the glass element; more preferably X2=2*X1 and X3=2*X2 with for example Xle[l;10] or Xl=5.; - the set of transmittance values comprises at least three transmittance values including: a first transmittance value associated with a soda-lime type glass; a second transmittance value associated with a borosilicate type glass; and a third transmittance value associated with a ceramic type glass; - the transmittance values of the assembly are theoretical and / or experimental transmittance values, called ideal transmittance values, of a type of glass; and / or in which the ranges of values do not overlap, preferably the value ranges are contiguous; - each transmittance value of the set is further associated with a range of known angles of incidence, the range of known angles of incidence being between 0° and 90° limits excluded, preferably between 15° and 70° limits inclusive, more preferably between 19° and 21 limits inclusive; and wherein the identification comprises identifying a transmittance value of the set of transmittance values closest to the determined transmittance value and having the known angle of incidence closest to the angle of incidence of the light beam; - the light beam is an ultraviolet light beam, preferably having a wavelength between 250 nm and 400 nm, and / or in which the angle of incidence of the light beam is between 0° and 90° limits excluded, preferably between 15° and 70°, more preferably between 19° and 21°; - the glass element is a sheet of glass, for example a sheet of glass having been used for the manufacture of glazing, or even glazing comprising a plurality of sheets of glass, such as for example double glazing; - the reflective element is substantially parallel to the glass element so that the angle of reflection is substantially equal to the angle of incidence; - further comprising the steps of: emitting (S10) a light beam incident on the glass element at a first angle of incidence; emitting (S40) a signal representative of the type of glass determined for the glass element.

[0017] According to a second aspect, the invention relates to a computer program comprising instructions for implementing a determination method according to the invention when said computer program is executed by a computer.

[0018] This program may use any programming language, and may be in the form of source code, object code, or code intermediate between source code and object code, such as in a partially compiled form, or in any other desirable form.

[0019] According to a third aspect, the invention relates to a computer-readable information or recording medium on which a computer program according to the invention is recorded.

[0020] The information or recording medium may be any entity or device capable of storing the program. For example, the medium may include a storage medium, such as a ROM, for example a CD-ROM or a ROM of microelectronic circuit, or a magnetic recording medium, for example a hard disk.

[0021] On the other hand, the information or recording medium may be a transmissible medium such as an electrical or optical signal, which may be conveyed via an electrical or optical cable, by radio or by other means. The program according to the invention may in particular be downloaded from a network such as the Internet.

[0022] Alternatively, the information or recording medium may be an integrated circuit in which the program is incorporated, the circuit being adapted to carry out or to be used in carrying out the method in question.

[0023] According to a fourth aspect, the invention relates to a system (100) for determining the type of glass making up a glass element (10), said system comprising: a light source configured to generate the light beam; a support configured to accommodate the glass element; a reflecting element (or mirror) configured to reflect the light beam after it has passed through the glass element in its entirety, preferably the mirror reflecting between 1 and 99 percent of the light beam at the emitted wavelength of the light beam, more preferably between 10 and 90 percent, or even between 50 and 80 percent; a meter of the transmittance value (or light intensity sensor) of the light beam after having been reflected by the mirror; a visual or audible transmitter of the signal representative of the type of glass determined for the glass element;a processor coupled to a memory storing instructions which, when executed by the processor, cause the system to implement the aforementioned determining method.;

[0024] In particular embodiments, said system may further comprise one or more of the following features, taken individually or in any technically possible combination.

[0025] In particular embodiments, the mirror is arranged such that it is substantially parallel to the glass element received on the support, preferably the reflecting mirror is integral with the support, or even forms the support; and / or the light source is a light-emitting diode; and / or the meter of the transmittance value of the light beam is a photodiode; and / or a first lens for collimating the light beam at the output of the light source; and / or a second lens for converging the light beam at the input of the meter.

[0026] The system is preferably a portable system. It may be composed of a kit comprising on the one hand a reflective element, or mirror, and on the other hand a detection device comprising the light source, the transmittance value meter (or light intensity sensor). The visual or sound transmitter and / or the processor and the storage memory are preferably integrated into the detection device but may also be transferred to a terminal remote from the detection device. The detection device advantageously comprises transmission means (wired or wireless). The measured data can thus be transferred to a remote terminal, to ensure the processing and / or analysis of the data and / or the traceability of the identified glass elements.The portable system thus comprises two simple elements - the reflective element and the detection device - which can be optionally connected to a remote terminal, and which can be easily implemented by untrained personnel. In particular, the light source and the sensor are arranged in the detection device so as to form a predetermined angle of incidence with the surface of the glass element when the device is positioned on it. According to a fifth aspect, the invention relates to a method for sorting at least one glass element comprising steps of: determining the type of glass making up said at least one glass element, said determining step being implemented in accordance with an above-mentioned determination method or with the above-mentioned system, and sorting said at least one glass element according to the result of said determining step. Brief description of the drawings

[0027] Other characteristics and advantages of the present invention will emerge from the description given below, with reference to the appended drawings which illustrate an exemplary embodiment thereof without any limiting character. In the figures: [Fig. 1] schematically represents an example of the process; [Fig. 2] shows an example of reference reflectance spectra for borosilicate, soda-lime glass (SL) and glass-ceramic (GC) at an incidence angle of 0°; [Fig. 3] shows an example of transmission spectra for borosilicate, soda-lime glass (SL) and glass-ceramic (GC) at an incidence angle of 0°; [Fig. 4] represents an example of the system; [Fig. 5] represents a schematic example of the double crossing of the glass element by the light beam; [Fig. 6] shows theoretical curves of the transmittance value as a function of the angle after the light beam has passed through the glass element twice; [Fig. 7] schematically represents a computer system for carrying out the process. Description of embodiments

[0028] Figure 4 schematically represents an example of a system 100 capable of implementing the method according to the invention. An example of the method is represented in Figure 1.

[0029] The system 100 is configured to enable the determination of the type of glass making up a glass element 10.

[0030] The method can be applied to any type of glass element in order to identify its type. Providing such an indication as to the type of glass making up the glass element 10 advantageously makes it possible to facilitate and improve the sorting of said glass element 10 when the latter is used. The system 100 therefore constitutes an aid for sorting glass, in particular used glass for recycling.

[0031] The glass element 10 can therefore be a piece of used or new glass. This piece can correspond, for example, to a fragment (sample) of a sheet of glass used in the manufacture of glazing, such as for example a single / double I triple glazing, no limitation being attached to the size of such a fragment. The glass element may be an entire sheet of glass, the latter being able to be used or newly manufactured, or even a glazing comprising a plurality of sheets of glass. More generally, no limitation is attached to the nature (geometry, size, used or not, etc.) of the glass element 10.

[0032] The system 100 comprises acquisition means 110 configured to acquire measurements of light intensity transmitted through the glass element 10.

[0033] Conventionally, and as illustrated by FIG. 4, the acquisition means 110 form an acquisition chain comprising a light source 111 configured to emit light beams (the path of such a beam through the different elements forming the acquisition chain as well as the glass element 10 is represented by means of a succession of arrows 130, 132). The nature of the light beams used is described in more detail later.

[0034] Thus, in examples, the light source 111 emits S10 a light beam 130 incident on the glass element at a first angle of incidence. The light beam passes through the glass element in its entirety a first time. Then the beam is reflected by a reflecting element 20 such as, for example, a mirror; the beam is therefore reflected by an element external to the glass element after having passed through the latter in its entirety. Following the reflection, the light beam that has been reflected 132 passes through the glass element in its entirety a second time.

[0035] In examples, the angle of incidence of the light beam is between 0° and 90°, limits excluded. Preferably between 15° and 70°, more preferably between 19° and 21°. Experimental observations made by the inventors have shown that an angle of incidence between 15° and 70° gives better results for identifying the type of glass of the glass element. In a particular example, the angle of incidence is between 19° and 21°. Experimental observations have shown that this latter range offers the best results for identification, particularly when the light source emits light beams in the UV wavelengths.

[0036] Figure 5 represents the path of the light beam 130 emitted by the light source 111 configured to emit light beams through the glass element 10, before and after its reflection on the reflective element 20. The light beam 130, also called the incident beam, passes through the glass element. As shown in the figure, and depending on the angle of incidence 0i of the light beam at the surface of the glass element, a portion of the beam may be reflected on the so-called entry surface of the glass element (denoted R in FIG. 5). The non-reflected portion of the light beam on the so-called entry surface of the glass element passes through the glass element. A reflecting element such as, for example, a mirror is arranged on the surface opposite the entry surface, called the exit surface. The light beam 130 is therefore reflected by the reflecting element 20 and passes through the entire glass element 10 a second time. At the entry surface of the glass element, i.e. the interface between the glass element and the ambient medium (for example, the ambient medium comprises air), a portion of the light beam may be reflected.The remaining part 132 (i.e. not reflected at the glass element / ambient environment interface) leaves the glass element.

[0037] These light beams are intended to pass through the glass element 10 from one side to the other (in its entirety) a first time and a second time after having been reflected on the reflective element 20. Losses may occur by reflection, dependent on the angle of incidence 0i of the light beam at the surface of the glass element; at the input (R) and at the interface between the glass element and the ambient environment. It is therefore understood that these light beams intended to pass through the glass element twice from one side to the other have a sufficient light intensity value so that these light beams 132 can be acquired, for example by a measuring element, despite the losses mentioned above.

[0038] The reflective element 20 may be, but is not limited to, a mirror. In examples where the reflective element is a mirror, the mirror may reflect between 1% and 99% of the light beam, inclusive. In other examples, the reflective element reflects between 50 and 80 percent (inclusive) of the light beam at the emitted wavelength of the light beam; experimental observations have shown that a standard optical quality reflective element may be used without altering the determination of the type of the glass element.

[0039] The reflective element 20 is configured to reflect the light beam after it has passed through the glass element in its entirety. In examples, the mirror is positioned substantially parallel to the exit surface of the glass element. This configuration facilitates the adjustment of the position of the acquisition means 110 and therefore the implementation of the determination method according to the invention. It is understood that this positioning can be achieved either by configuring the position of the mirror relative to the glass element, or conversely by configuring the position of the glass element relative to the position of the mirror.

[0040] Still concerning the reflective element 20, the latter may be arranged against the glass element 10, the type of which must be determined, that is to say that there is contact between all or part of the output surface of the glass element and all or part of the reflective element. The contact between the output surface of the glass element and the reflective element may be maintained using mechanical means, for example the glass element may be accommodated by a support which may position the glass element against the reflective element. Alternatively or additionally, the reflective element may be accommodated by a support which may position the reflective element against the glass element. In another alternative, the reflective element may be fixed against the glass element, for example, using fixing means such as an adhesive, or by means of a system of magnets.

[0041] The reflective element 20 may not be disposed against the glass element 10. This does not affect the determination method despite additional losses by reflections of light beam on the output surface after being reflected by the reflective element. In this arrangement, the distance between the reflective elements 20 and glass element 10 may be maintained using mechanical means, for example those discussed previously.

[0042] Regardless of the nature of the beams themselves (type of light, wavelength), no limitation is attached to the nature of the light source 111, i.e. to the technical configuration of the source 111 for emitting light beams. For example, it may be a light-emitting diode, a laser source, a broad-spectrum lamp equipped with spectral filters, etc.

[0043] In examples, the light beam is an ultraviolet light beam. Ultraviolet light has a wavelength that is between 100 nanometers (nm) and 400 nm. Experimental observations made by the inventors have shown a wavelength of the light beam between 250 nm and 400 nm gives better results for identifying the type of glass of the glass element. In a particular example, the wavelength of the light source is between 310 and 350 nm, for example substantially around 340 nm. Experimental observations have shown that this range provides good compromise between the quality of identification results and the availability and cost of light sources in this wavelength range.

[0044] In examples of the system 100, such as for example that shown in FIG. 4, the acquisition chain 110 may also comprise optical means configured to collimate the light beams before and after the double crossing of the glass element 10. In the example of FIG. 4, and in no way limiting, said optical means correspond to a first lens 112 for collimating the light beam at the output of the light source and to a second lens 113 for converging the light beam at the input of the meter.

[0045] It is important to note that the positioning, and the maintenance in this position, of the glass element 10 between the two converging lenses 112, 113, so that the latter is crossed by collimated light beams, can be carried out by any means known per se. For example, this maintenance in position can be carried out using a mechanical arm equipped with gripping means (not shown in the figures).

[0046] As illustrated in Figure 4, the acquisition chain 110 also comprises a meter 114 of the transmittance value of the light beam. The meter (i.e. an element taking transmittance measurements) may be a sensor 114 dedicated to measuring the transmittance value resulting from the double crossing of the glass element 10. The meter may be a sensor 114 dedicated to measuring the resulting light intensity (I) of the transmitted beam 132, the transmittance value (T) then being calculated subsequently (the intensity (I o ) of the incident light beam 130 being known elsewhere).

[0047] In examples, the meter 114 is more particularly arranged at the optical path output, that is to say such that the light which reaches it is that which has passed through the glass element 10 twice. As illustrated in FIG. 4, the optical path further comprises the lenses 112, 113.

[0048] This meter 114 forms a sensitive element configured to provide a signal as a function of variations in the physical quantity with which it is associated, namely here a light transmittance. In other words, said meter 114 corresponds to an electro-optical transducer, such as for example a photodiode.

[0049] The acquisition chain 110 may also conventionally comprise other elements than those described previously, but which are nevertheless not shown in the figures for the sake of readability. Thus, for example, the acquisition chain 110 may also comprise an electronic acquisition card configured to condition the electrical signal provided by the meter 114. The conditioning implemented by the acquisition card may comprise, for example, amplification and / or filtering. Optionally, the acquisition chain 110 may also comprise, at the output, an analog / digital converter configured to digitize a conditioned electrical signal.

[0050] Generally speaking, the configuration of the acquisition means 110 for acquiring transmittance measurements through an object, such as for example said glass element 10, is well known to those skilled in the art, and is therefore not detailed here further. In particular, those skilled in the art know how to choose optical means and an appropriate sensor, for example from the catalogs of products offered by specialized manufacturers. They also know how to position these optical means and this sensor to carry out the desired measurements.

[0051] In addition to the acquisition means 110, the system 100 also comprises a processing device 120. Said processing device 120 is configured to control the light source 111, that is to say to control its operation by activating / deactivating it, but also to transmit to it commands defining the nature of the beams to be used.

[0052] The processing device 120 may further be configured to calculate, from measurements made by the sensor 114 dedicated to measuring the resulting light intensity, transmittance values. The processing device is informed of the light intensity of the light beams and can easily perform the calculation.

[0053] The processing device 120 is configured to carry out, from transmittance measurements acquired using the acquisition means 110, processing operations aimed at determining the type of the glass element 10.

[0054] In addition to the acquisition means 110 and the processing device, the system 100 may also comprise a visual or audible transmitter of a representative signal (not shown in FIG. 4). A visual transmitter sends a signal that is visible (i.e., readable) to a user of the system. For example, the visual transmitter may comprise one or more lights that light up depending on the type of the element glassworker that has been determined. A color code of the lights can also be used. The visual transmitter can include one or more lights representing a score that indicates the accuracy of the determination of the type of glass of the glass element. Here too, a color code of the lights can be used, for example green for an accurate measurement, yellow for a less accurate measurement, and red for an inaccurate measurement. The visual transmitter can be a display that indicates in the form of text or a pictogram or any other graphic representation the type of glass element that has been determined and / or the score that indicates the accuracy of the determination. An audible transmitter sends a signal that is audible to a user of the system. For example, the audible transmitter can be a loudspeaker that emits sounds indicating the type of glass element that has been determined and / or the score that indicates the accuracy of the determination.The system 100 may comprise a visual transmitter and an audible transmitter. The visual or audible transmitter may therefore emit S40 a signal representative of the type of glass determined after the identification S30 of the type of glass.

[0055] Figure 7 schematically represents an example of hardware architecture of the processing device 120 according to the invention.

[0056] As illustrated in Figure 7, the processing device 120 has the hardware architecture of a computer. Thus, such a processing device 120 comprises, in particular, a processor 1, a random access memory 2, a read-only memory 3 and a non-volatile memory 4. It also has communication means 5, for example a BUS, which connects the elements 1 to 4 of Figure 7 and allows them to communicate.

[0057] The read-only memory 3 of the processing device 120 constitutes a recording medium in accordance with the invention, readable by the processor 1 and on which is recorded a computer program PROG in accordance with the invention, comprising instructions for executing steps of the determination method according to the invention. The program PROG defines functional modules of the processing device 120, which rely on or control the hardware elements 1 to 5 of the processing device 120 mentioned above.

[0058] The communication means 5 allow the processing device 120 to transmit commands to the light source 111 but also to receive measurements carried out by the meter 114. These communication means 5 rely, in a manner known per se, on a communication interface capable of the exchange of data between the processing device 120 and the acquisition means 110. No limitation is attached to the nature of this communication interface, which can be wired or wireless, so as to allow the exchange of data according to any protocol known to those skilled in the art (Ethernet, Wifi, Bluetooth, 3G, 4G, 5G, Modbus, TCP-IP, analog, etc.).

[0059] In its general principle, the determination method according to the invention is based on a determination (characterization) of the type of glass making up the glass element 10 according to two stages: - a first measurement step S20 of a transmittance value of the glass element using a light beam, the light beam being incident on the glass element at an angle of incidence and reflected after having passed through the glass element in its entirety; - a second step of identifying (S30) the type of glass of the glass element by comparing the measured transmittance value to a set of reference transmittance values, each reference transmittance value of the set being associated with a type of glass, and identifying the reference transmittance value closest to the measured transmittance value.

[0060] The first step was discussed with reference to Figure 4 and the system. In the second step, the determination of the glass type relies on the identification of a transmittance value from a set of reference transmittance values where each reference transmittance value in the set is associated with a glass type. The identification is achieved by comparing the reference transmittance values of the set with the measured transmittance value, the comparison including the identification of the reference transmittance value of the set that is closest to the one that was measured.Closest can mean calculating the absolute difference between each transmittance value in the set and the measured transmittance value, the resulting number having the minimum absolute difference is returned as the result, i.e. the transmittance value that resulted in this number is retained as the transmittance value closest to the measured transmittance value.

[0061] The inventors conducted experimental studies and determined that the difference in intensity value of light reflection spectra for a given angle of incidence is practically zero for wavelengths ranging from UV to the far IR. This is illustrated in Figure 2, which represents an example of reflection measurements for an angle of incidence of 0° on borosilicate (B), soda-lime (SL) and glass-ceramic (CG) glasses; the ordinate of the figure expresses a percentage of reflection and the abscissa the wavelengths expressed in nanometers (nm). The curves for these three types of glass are practically the same. Reflection is in fact determined by several factors, namely the angle of incidence, the refractive indices of the two media and the state of polarization of the light, and all of these factors make it difficult to identify a type of glass based solely on reflection.

[0062] Still within the framework of these experimental studies, the inventors determined that, on the contrary, the light transmission spectrum through a glass element has a considerable advantage with a notable difference between the transmittance signals. This is for example illustrated in Figure 3 which represents an example of transmittance measurements for an angle of incidence of 0° on borosilicate (B), soda-lime (SL) and glass-ceramic (CG) glasses in the UV region; the ordinate of Figure 3 expresses a percentage of reflection and the abscissa of the wavelengths expressed in nanometers (nm). The experiments carried out on other types of glasses led the inventors to similar observations.

[0063] Based on this observation, the inventors then determined that it is possible to combine the geometry of the reflection of a light beam and the measurement of its transmittance to differentiate between types of glass. In particular, it is possible to determine one type of glass among others by measuring its transmittance after the light beam used to measure the transmittance has passed through the glass element twice. This principle is illustrated in Figure 6.

[0064] Figure 6 shows on the ordinate theoretical transmittance values (in percentages) obtained after passing twice through the glass element as a function of an angle of incidence (on the abscissa) of the light beam entering the glass element. The types of glass concerned by Figure 6 are borosilicate (B), soda-lime (SL) of the Planiclear® subtype marketed by Saint Gobain and PLANILUX® marketed by Saint Gobain, and glass-ceramic (CG). These transmittance values were obtained with a light beam emitted by a diode in the UV region; the diode has a wavelength of 340nm.

[0065] Figure 6 shows the theoretical curve of transmittance as a function of the angle of incidence under the above-mentioned experimental conditions of borosilicate 730, soda-lime PLANILUX® 720 marketed by Saint Gobain, and glass-ceramic 710. The measured values are not shown for the sake of clarity of the figure, and are close to the theoretical values.

[0066] Still in Figure 6, the dotted curves 700a and 700b represent boundaries between the types of glass: 700a between glass-ceramic and soda-lime, 700b between soda-lime and glass-ceramic. It is also important to note that these boundaries can define a band of transmittance values for each type of glass, a band which is substantially independent of the angle of incidence of the light beam. In other words, the measurement of the transmittance of a glass element crossed twice by the light beam can be considered to be independent of the angle of incidence of the light beam. It is also important to note that these boundaries define a range of transmittance values which can be associated with a type of glass.For example in Figure 6, the boundary 700a can make it possible to define a range of transmittance values (represented by the double arrow 701) associated with a transmittance value of the assembly which is in this example 702 (the theoretical transmittance value is the same as the experimental transmittance value for this type of glass in this example). The boundaries 700a and 700b can make it possible to define a range of transmittance values (represented by the double arrow 703) associated with a transmittance value of the assembly which is in this example 705. Still in Figure 6, the boundary 700b can make it possible to define a range of transmittance values (represented by the double arrow 706) associated with a transmittance value of the assembly which is in this example 707 (the theoretical transmittance value is the same as the experimental transmittance value for this type of glass).

[0067] Thus, for each transmittance value that belongs to the set of reference transmittance values in the identification step S30, it may be possible to determine a range of transmittance values to which said reference transmittance value belongs. This range of value is associated with the same type of glass as the reference transmittance value of the set. In this situation, identifying a reference transmittance value of the set comprises identifying the range of transmittance values to which the reference transmittance value determined to be closest to the measured transmittance value. Or put another way, the range of values to which the measured value belongs is identified and the type of glass associated with this range determines the type of glass.

[0068] A range of transmittance values may include discrete values or continuous values, without changing the underlying principle of identification. Since transmittance can be expressed as a percentage, a range of transmittance values may include, for example, natural numbers, each expressing a percentage of transmittance.

[0069] The value ranges do not overlap. This means that a value range can only include one reference transmittance value from the set, which ensures that only one glass type can be identified for a measured transmittance value.

[0070] In examples, the value ranges may be contiguous. In other words, any measured transmittance value is within a single value range, so that it may be possible to identify a glass type for each measurement. This is, for example, the case shown in Figure 6 with the value ranges 701, 703, and 706. Alternatively, one or more value ranges may not be contiguous. In this case, this means that the identification may not return a result (NULL), for example, in the special case where two reference transmittance values in the set would be closest to the measured transmittance value.

[0071] Returning to Figure 6, sub-bands of transmittance values are shown for each glass type. These sub-bands extend on either side of the theoretical transmittance value curve for each glass type. For example, for the theoretical transmittance curve of glass-ceramic 710, a first band 711 forms an area located ±5% of the theoretical curve and indicates the greatest accuracy of the measured value: in this area, the measured transmittance values are closely aligned with the theoretical values. A second band 712a, 712b forms an area located between ±5% and ±10% of the theoretical curve and indicates the greatest accuracy of the measured value in the second region, which is between ±5% and ±10% of the theoretical curve. The measurement accuracy is decreased compared to the first band. A third band 713a, 713b forms an area between ±10% and ±15% of the theoretical curve and indicates a lesser accuracy of the measured value in comparison with the second band 713. For curve 720, these bands are noted 721 (±5%), 722a, 722b (between ±5% and ±10%) and 723a, 723b (between ±10% and ±15%). For curve 730, these bands are noted 731 (±5%), 732a, 732b (between ±5% and ±10%) and 733a, 733b (between ±10% and ±15%). It should be noted that theoretical curves 720 and 730 concern glasses of the same type (soda-lime), which explains why the upper part (above theoretical curve 720) of bands 722 to 726 is confused with the lower part (below theoretical curve 730) of bands 732 to 736.

[0072] Based on this observation, it may be possible to subdivide a range of transmittance values into a number N of sub-ranges of transmittance values, and each sub-range may be associated with a score indicating an accuracy of the determination of the type of glass of the glass element. N is a positive integer greater than or equal to 1. For example, in Figure 6, N=3. In this situation, the identification of a reference transmittance value of the set includes the identification of the sub-range of transmittance values to which the reference transmittance value determined as being closest to the measured transmittance value belongs. Or in other words, the sub-range of values to which the measured value belongs is identified and the type of glass associated with this identified range is the one determining the type of glass. Interestingly, the determination of the type of glass may be accompanied by the score associated with the sub-range.The score is therefore equivalent to a confidence index of the determination that has been made. This indication is very useful to the user of the system, particularly because the glass elements tested may not be new, and therefore dirty, which can distort the measurement of transmittance.

[0073] In some examples, the transmittance sub-ranges may cover their respective value range in their entirety. This means that all (not each) of the transmittance sub-ranges encompass the transmittance value range. Thus, for any transmittance measurement performed, the determination of the glass type may be accompanied by a score.

[0074] In examples, each sub-range of values is substantially centered around the transmittance value of the range of values. For example, the reference transmittance values of the set are theoretical transmittance values, and for each type of glass a theoretical transmittance value is included in the set of transmittance values. Theoretical transmittance values are also called ideal transmittance values. Thus, the subranges of values may be approximately or exactly centered around the theoretical transmittance value. In another example, the reference transmittance values in the set are experimental transmittance values, also called ideal transmittance values. These two examples can be combined so that each reference transmittance value in the set is an ideal transmittance value that is either theoretical or experimental.

[0075] In examples, each range of values (for a reference transmittance value of the set) may include at least three sub-ranges. A first sub-range of transmittance values may have values deviating by a maximum of ±Xi% from the transmittance value of the set. This first sub-range may be associated with a better accuracy score for determining the glass type of the glass element. A second sub-range of transmittance values may have values deviating by a minimum of ±X1% and a maximum of ±X2% from the transmittance value of the set. This second sub-range may be associated with a lower accuracy score than the best accuracy score. The third sub-range of transmittance values may have values deviating by a minimum of ±X2% and a maximum of ±X3% from the transmittance value of the set.This third sub-range can be associated with the worst accuracy score of the glass type determination of the glass element. In these examples, the deviations Xi, X2, and X3 from the transmittance value of the set can be selected such that X2=2*Xi and X3=2*X2, with for example a value of Xi belonging to the set [1;10], or a value of Xi which is equal to 5 as in the example in the figure.

[0076] In examples, the type of glass considered in the context of the present invention may belong to the set formed by the following three types of glass: soda-lime glass SL (example: Planiclear® glass marketed by the company Saint Gobain), borosilicate glass B, ceramic glass GC. The set of reference transmittance values then comprises at least three reference transmittance values among which a first reference transmittance value associated with a soda-lime type glass, a second reference transmittance value associated with a borosilicate type glass, and a third reference transmittance value associated with a ceramic type glass.

[0077] The determination method has been described so far by considering that the determination of the type of glass of the glass element 10 was carried out by considering a single optical domain, namely the ultraviolet domain. However, the invention still covers other modes of implementation of the determination method in which it may be envisaged to consider other optical domains, for example the infrared domain.

[0078] The determination method also covers examples in which the steps for measuring a transmittance value are performed a plurality of times, so as to obtain a plurality of measured transmittance values. Therefore, on the basis of this plurality of measured values, an average or median value can be calculated intended to be the value actually used to carry out the identification. Proceeding in this way makes it possible to reinforce the robustness of the invention with respect to the transmittance values used.

[0079] Examples will be discussed in which each reference transmittance value in the set is further associated with a range of known angles of incidence. This means that the set of reference transmittance values includes at least two reference transmittance values for each type of glass, each of which is associated with an angle of incidence value. Figure 6 illustrates such an example since, for each type of glass, there are several ideal (i.e. theoretical and experimental) reference transmittance values that can belong to said set of reference transmittance values.

[0080] The identification may include identifying a transmittance value from the set of reference transmittance values that is closest to the measured transmittance value and is associated with the angle of incidence from the range of known angles of incidence that is closest to the angle of incidence of the light beam. The definition of "closest" with respect to the angle of incidence is similar to that previously presented for the transmittance values. Thus, two criteria may be used for the identification, a distance between transmittance values and a distance between angle values. In one example, the identification may include first meeting the criterion of distance between angle values and then meeting the criterion of distance between transmittance values.For example in Figure 6, if the measured transmittance value was measured with an incidence angle value 0i of the light beam which is equal to 40°, the. reference transmittance values of the set retained in a first step will be those for this incidence angle value of 40°; here 702, 705, 707. In a second step, among the reference transmittance values of the set which have been retained, the one which is closest to the measured transmittance value will be identified. Alternatively, in another example, the identification may comprise firstly the achievement of the criterion of closest value between the transmittance values and then the achievement of the criterion of distance between angle values. In these examples, the distance between the transmittance values may be associated with a greater weight than the distance between the incidence angle values, or vice versa.

[0081] In examples, the range of known incidence angles can be between 0° and 90° inclusive. Experiments have shown good results for a range of known incidence angles between 15° and 70° inclusive, and even better results for values between 19° and 21° inclusive.

[0082] It will be understood that the identification examples discussed previously apply equally in situations where each transmittance value in the array is further associated with a range of known incidence angles.

[0083] The reference transmittance values of the set may for example form at least one curve of theoretical and / or experimental transmittance values, called an ideal transmittance curve, of a type of glass for a range of known angles of incidence; for example the curves 710, 720, 730 in Figure 6. Said at least one ideal transmittance curve may comprise at least one band of transmittance values on either side of the ideal transmittance curve, said at least one band being indicative of a precision of the first determined transmittance value. This band is therefore associated with a score just as a sub-range is associated with a score. In one example, said at least one ideal transmittance curve comprises at least three bands which may be: - a first band of transmittance values having values deviating by a maximum of ±5% from the values of the ideal transmittance curve; - a second band of transmittance values having values deviating by a minimum of ±5% and a maximum of ±10% from the values of the curve of ideal transmittances; and - a third band of transmittance values having values deviating by a minimum of ±10% and a maximum of ±15% from the values of the ideal transmittance curve.

[0084] As regards the system 100 for determining the type of glass, it has been described so far by considering the means configured to implement the determination method (light source 111, lenses 112, 113, sensor 114, determination device 120) are connected to each other. That being said, nothing excludes considering that these means are disconnected in whole or in part from each other, the system 100 then taking the form of a kit. This kit is for example transportable in a case to be assembled on site (example: assembly on site or in a laboratory).

[0085] The invention however still covers other embodiments of the system 100 in which the means configured to implement the determination method are already connected to each other and integrated within a transportable device.

[0086] As mentioned previously, the invention can also be applied when the glass element is a glazing comprising a plurality of glass sheets, such as for example a double glazing comprising two glass sheets. It is then understood in this case that the reflective element 20 equipping the system for determining the type of glass is intended to be placed outside the glazing opposite a first sheet forming the latter, the acquisition means 110 configured to acquire measurements of light intensity transmitted through the glass element 10 being intended to be placed outside the glazing opposite the last sheet forming the latter. The retention of the reflective element 20 as well as the acquisition means can be carried out according to any suitable method, for example by means of a system of magnets making it possible to maintain good alignment of the optical axis, or by means of a system of suction cups.Furthermore, the determination of transmittance values can be carried out by taking into account as a parameter the type of gas separating two sheets of glazing.

[0087] Finally, the invention does not only relate to the determination method and the system configured to implement it. Indeed, and according to another aspect, the invention also relates to a method for sorting at least one glass element.

[0088] In examples, the sorting process comprises steps of: - determination G10 of the type of glass making up said at least one glass element, said determination step being implemented in accordance with a determination method according to the invention, - G20 sorting of said at least one glass element based on the result of said determination step.

[0089] The sorting step G20 may, for example, consist of placing said at least one glass element in a suitable container due to the type of glass determined.

Claims

Claims

1. Method for determining the type of glass making up a glass element (10), said method comprising the steps of: - measurement (S20) of a transmittance value of the glass element using a light beam, the light beam being incident on the glass element at an angle of incidence and reflected by a reflecting element external to the glass element after having passed through the latter in its entirety, the transmittance value (T) being defined by the ratio of the intensity (I) of the light beam transmitted through the glass element after reflection on the reflecting element to the intensity (I o ) of the incident light beam; - identification (S30) of the type of glass of the glass element by comparing the measured transmittance value to a set of reference transmittance values, each reference transmittance value of the set being associated with a type of glass, and identification of the reference transmittance value closest to the measured transmittance value.

2. The method of claim 1, wherein each reference transmittance value of the set is within a respective transmittance value range, the transmittance value range being associated with the same type of glass as the transmittance value of the set; and wherein identifying a transmittance value of the set comprises identifying the transmittance value range to which the measured transmittance value belongs.

3. The method of claim 2, wherein each range of values comprises N sub-ranges of transmittance values, N being a positive integer greater than or equal to 1, each sub-range being associated with a score indicating an accuracy of the determination of the glass type of the glass element; and wherein identifying a transmittance value of the set comprises identifying a sub-range of transmittance values to which the measured transmittance value belongs.

4. A method according to claim 3, wherein the sub-ranges of transmittance values cover their respective value range in its entirety, preferably each sub-range of values is substantially centered around the transmittance value of the range of values comprising the sub-ranges of transmittance values.

5. Method according to one of claims 3 or 4, in which each range of values comprises at least: - a first sub-range of transmittance values having values deviating by a maximum of ±Xi% from the value of said each transmittance value of the set, preferably the first sub-range is associated with the best precision score for determining the type of glass of the glass element; and / or - a second sub-range of transmittance values having values deviating by a minimum of ±Xi% and a maximum of ±X2% from the value of said each transmittance value of the set, preferably the second sub-range is associated with a precision score lower than the best precision score; and / or - a third sub-range of transmittance values having values deviating by a minimum of ±X2% and a maximum of ±X3% from the value of said each transmittance value of the set, preferably the third sub-range is associated with the worst accuracy score for determining the type of glass of the glass element; more preferably X2=2*Xi and X3=2*X2 with for example Xie[l;10] or even Xi=5.

6. A method according to any preceding claim, wherein the set of reference transmittance values comprises at least three reference transmittance values including: - a first reference transmittance value associated with a soda-lime type glass; - a second reference transmittance value associated with a borosilicate glass; and - a third reference transmittance value associated with a ceramic type glass.

7. A method according to any preceding claim, wherein the reference transmittance values of the set are theoretical and / or experimental transmittance values, called ideal transmittance values, of a type of glass; and / or whose value ranges are contiguous.

8. A method according to any preceding claim, wherein each reference transmittance value of the set is further associated with a range of known angles of incidence, the range of known angles of incidence being between 0° and 90° limits excluded, preferably between 15° and 70° limits inclusive, more preferably between 19° and 21 limits inclusive; and wherein the identifying comprises identifying a reference transmittance value of the set closest to the measured transmittance value and having the known angle of incidence closest to the angle of incidence of the light beam.

9. A method according to any one of the preceding claims, wherein the light beam is an ultraviolet light beam, preferably having a wavelength between 250 nm and 400 nm, and / or wherein the angle of incidence of the light beam is between 0° and 90°, limits excluded, preferably between 15° and 70°, more preferably between 19° and 21°.

10. Method according to any one of the preceding claims, in which the glass element is a sheet of glass, for example a sheet of glass having been used for the manufacture of a glazing unit, or else a glazing unit comprising a plurality of sheets of glass, such as for example double glazing.

11. A method according to any preceding claim, further comprising the steps of: - emission (S10) of a light beam incident on the glass element at a first angle of incidence; - emission (S40) of a signal representative of the type of glass determined for the glass element.

12. A computer program comprising instructions for implementing a determination method according to any one of claims 1 to 11 when said computer program is executed by a computer.

13. System (100) for determining the type of glass composing a glass element (10), said system comprising: a light source configured to generate the light beam; a support configured to accommodate the glass element; a mirror configured to reflect the light beam after it has passed through the glass element in its entirety, preferably the mirror reflecting between 1 and 99 percent of the light beam at the emitted wavelength of the light beam, and more preferably between 50 and 80 percent of the light beam at the emitted wavelength of the light beam; a meter of the transmittance value of the light beam after having been reflected by the mirror; a visual or audible transmitter of the signal representative of the type of glass determined for the glass element; a processor coupled to a memory storing instructions which, when executed by the processor, cause the system to implement the determination method according to claim 11.

14. System (100) according to claim 13, wherein: the mirror is arranged such that it is substantially parallel to the glass element received on the support, preferably the reflecting mirror is integral with the support; and / or the light source is a light-emitting diode; and / or the meter of the transmittance value of the light beam is a photodiode; and / or a first lens for collimating the light beam at the output of the light source; and / or a second lens for converging the light beam at the input of the meter.

15. Method for sorting at least one glass element comprising steps of: - determination (G10) of the type of glass making up said at least one glass element (10), said determination step being implemented in accordance with a determination method according to any one of claims 1 to 11 or with the system according to one of claims 13 or 14; - sorting (G20) said at least one glass element according to the result of said determination step.

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