Method and system for non-contact measurement of the temperature of a portion of an object, by absorption of a luminescent material

Abstract

The present invention relates to a system and method for non-contact temperature measurement of a portion (3') of an object (3) coated with a layer of a luminescent material from the zinc oxide family. Using a light source (1) emitting in a wavelength range covering at least partially a range between 360 and 480 nm, and means for measuring light intensity as a function of wavelength (5) covering at least part of the range of the light source (1), the light intensity is measured as a function of the wavelength of radiation scattered by the portion of the object. Then, from the measurement of the light intensity as a function of wavelength, a value of at least one parameter is determined, and the temperature of the portion (3') of the object (3) is determined from the value of the parameter and a predetermined lookup table. Figure 2 to be published

Description

Title of the invention: Method and system for non-contact measurement of the temperature of a portion of an object, by absorption of a luminescent material. Technical field

[0001] The present invention relates to the field of measuring the temperature of an object, without direct contact with that object, by means of luminescent materials. The present invention is particularly relevant in the case of a rotating object.

[0002] Many technical applications require non-contact temperature measurement. This is the case for moving parts (e.g., turbine blades), for which the ability to take the measurement at a precise point on the surface of interest is an additional requirement, or for traction elements (e.g., power electronics), where direct contact with the measurement point poses technical problems. In the specific case of developing a permanent magnet electric motor, it is essential to know the temperature of the magnets in order to approach the performance limits without risk of demagnetization, and thus ensure continuous performance. Temperature monitoring near critical areas must therefore be carried out without any electromagnetic, thermal, or mechanical interference on a rotor rotating at high speed. Previous technique

[0003] Phosphorus thermometry is a widely used approach for non-contact temperature measurement in laboratories or under specific conditions. The principle is based on the excitation of certain specific materials, generally called "phosphors," and relating the light re-emitted by the phosphors to the temperature. This allows for an accurate temperature estimation while avoiding any direct contact. However, this approach relies on a light source that must be powerful (generally lasers) and, in principle, in the deep UV range to obtain usable light emissions from the phosphor.

[0004] A different approach, called thermochromy, is also known, where the temperature of the target object is deduced from the light absorbed by a temperature-sensitive substance. This approach allows the use of lower-intensity light sources. In particular, utility model CN202307819U is known, which relates to an in-situ temperature measurement device. This device comprises a broad-spectrum light source located under a substrate, a broad-spectrum signal acquisition unit, and a signal analysis unit. broad spectrum. Thus in this device, the temperature is deduced by the absorption of light, but in this configuration, the heat-sensitive substance is located between the light source and the light sensor (i.e., the transmitted radiation is exploited), which can make the device bulky.

[0005] We also know of application DE102014218284A1, which relates to a monitoring device for automatically monitoring the temperature of a machine component comprising a thermochromic coating. More specifically, in this application, the thermochromic coating is placed directly on the object for which it is sought to detect whether a threshold temperature has been exceeded. The spectrum of the scattered light, affected by the absorption properties, is then observed. However, this document uses light sources with a wide range of wavelengths, from X-rays to infrared. Furthermore, no specific thermochromic material is mentioned.

[0006] The present invention aims to overcome these drawbacks. Thus, the present invention relates to a system and a method for measuring, without contact, the temperature of a portion of an object by absorption of a luminescent material. More specifically, the present invention uses a luminescent material from the zinc oxide family. This material, resistant to high temperatures (up to 900 K), allows for temperature monitoring of machines operating under harsh conditions. Furthermore, the luminescent material according to the invention allows the use of light sources and detectors within a limited wavelength range, from 360 to 480 nm.This aspect is particularly important because it allows for implementation with inexpensive components (e.g., LEDs and photodiodes), as well as temperature measurement through liquid films, which tend to be transparent in this range for most working / cooling fluids. Furthermore, the invention exploits the fact that when the phosphor material according to the invention is illuminated with a source whose wavelength is at least partially between 360 and 480 nm, some of the light is scattered and some is absorbed, the spectrum of absorbed light varying with temperature. It is therefore possible to exploit the temperature-sensitive properties of the phosphor material using low-power, low-cost, and compact light sources and sensors.Finally, the use of a material from the ZnO family makes it possible to obtain a light response on the nanosecond scale, which allows the temperature of a moving object to be determined with good spatial resolution. Summary of the invention

[0007] The present invention relates to a method for non-contact measurement of the temperature of a portion of an object, by means of at least one light source and means for measuring light intensity as a function of wavelength, said light source being capable of emitting radiation in a wavelength range covering at least partially a wavelength range between 360 and 480 nm and said means for measuring light intensity being capable of measuring the intensity of radiation in at least a part of said wavelength range of said light source, said portion of said object being coated with a layer of a luminescent material from the zinc oxide family, the method according to the invention comprising at least the following steps:

[0008] A) by means of said at least one light source, at least one radiation is emitted in said wavelength range of said at least one light source, and, by means of said means of measuring a light intensity as a function of wavelength, at least one light intensity is measured as a function of the wavelength of a radiation scattered by said portion of said object coated by said layer of said luminophore material when said portion of said object coated by said layer of said luminophore material is illuminated by said at least one radiation emitted by said at least one light source;

[0009] B) from said at least one measurement of said light intensity as a function of the wavelength of said at least one scattered radiation, a value of at least one parameter is determined;

[0010] C) the temperature of the portion of the object coated with the luminophore coating is determined from the value of the at least one determined parameter and a predetermined lookup table, the lookup table allowing a correspondence between values ​​of the at least one parameter and values ​​of the temperature.

[0011] According to one embodiment of the invention, said lookup table can be constructed in the following manner: said temperature of said portion of said object is varied between a minimum temperature and a maximum temperature with a predefined temperature step, steps A) and B) are applied for each temperature step, and a value of said at least one parameter determined at the end of step B) as well as said temperature of the portion of the object for each of said temperature steps is recorded in said lookup table.

[0012] According to one embodiment of the invention, said parameter can be determined from at least a part of at least one intensity spectrum or at least one absorption spectrum, said intensity spectrum and absorption spectrum being determined from said at least one measurement of said light intensity as a function of wavelength.

[0013] According to one embodiment of the invention, said method can be implemented using a single light source and a spectrometer, and said parameter can be determined from an integral of said intensity spectrum or said absorption spectrum over at least a part of said wavelength range of the light source.

[0014] According to one embodiment of the invention, said method can be implemented using a single light source and a spectrometer, and said parameter can be determined by a ratio between, on the one hand, an integral of said intensity spectrum or said absorption spectrum over a first part of the wavelength range of the light source and, on the other hand, an integral of said intensity spectrum or said absorption spectrum over a second part of the wavelength range of the light source.

[0015] According to one embodiment of the invention, said method can be implemented by means of a single light source and a first and a second photodiodes, and said parameter can be determined by a ratio between, on the one hand, an integral of said intensity spectrum or of said absorption spectrum over a range of wavelengths of said first photodiode and, on the other hand, an integral of said intensity spectrum or of said absorption spectrum over a range of wavelengths of said second photodiode, or vice versa.

[0016] According to one embodiment of the invention, said method can be implemented by means of a first and a second light source, and a photodiode, and said parameter can be determined by a ratio between, on the one hand, an integral of said intensity spectrum or of said absorption spectrum over a range of wavelengths of said first light source, and, on the other hand, an integral of said intensity spectrum or of said absorption spectrum over a range of wavelengths of said second light source, or vice versa.

[0017] According to one embodiment of the invention, said method can be implemented by means of a light source having a bandwidth between 5 and 15 nm and a photodiode, and said parameter can be determined by a value of the intensity at the central wavelength of said bandwidth, optionally referred to a reference intensity measured on a surface of the object not coated by said luminophore material.

[0018] The invention further relates to a system for non-contact temperature measurement of at least a portion of an object, said system being configured for implementing the method as described above, said system comprising at least said light source capable of emitting radiation in a wavelength range covering at least partially a wavelength range between 360 and 480 nm and said means for measuring light intensity capable of a measurement of the intensity of radiation in at least a part of said wavelength range of said light source.

[0019] According to one embodiment of the invention, said system may further comprise a paint of said luminophore, or a white sticker and said paint of said luminophore intended to be applied to said white sticker, or a sticker having said luminophore on its non-adhesive surface.

[0020] The invention further relates to a system for non-contact temperature measurement of at least a portion of an object, said portion of said object being coated with a layer of a luminescent material from the zinc oxide family, said system comprising:

[0021] - at least one light source capable of emitting radiation in a range of wavelengths covering at least partially a range of wavelengths between 360 and 480 nm;

[0022] - means for measuring light intensity as a function of wavelength capable of measuring the intensity of radiation in at least a part of said wavelength range of said at least one source;

[0023] - means for analyzing said light intensity as a function of length of wavelength, said analytical means being configured to determine at least one parameter from said light intensity measured as a function of wavelength, as well as said temperature of said portion of said object coated by said layer of said luminophore coating from said at least one parameter and a predetermined lookup table, said lookup table allowing a correspondence between values ​​of said at least one parameter and values ​​of said temperature.

[0024] According to one embodiment of the invention, said system may further comprise a paint of said luminophore, or a white sticker and said paint of said luminophore to be applied to the non-adhesive part of said sticker, or a sticker having said luminophore on its non-adhesive surface.

[0025] According to one embodiment of the invention, said system may include a support in which are integrated said at least one light source and said means for measuring a light intensity as a function of wavelength.

[0026] According to one embodiment of the invention, said analysis means may include computer means such as a computer, a processor or a calculator.

[0027] Other features and advantages of the system and method according to the invention will become apparent from the following description of non-limiting examples of embodiments, with reference to the figures attached and described below. List of figures [Fig 1]

[0028] Fig. 1 schematically illustrates an example of implementation of the system according to the invention. [Fig 2]

[0029] Figure 2 shows examples of intensity spectra recorded by a spectrometer for different temperatures of the portion of an object. [Fig 3]

[0030] Fig. 3 illustrates an intensity spectrum of two LED lamps suitable for implementing the second variant of the invention. [Fig 4]

[0031] Figure 4 illustrates an example of the evolution as a function of temperature of the parameter defined for the third variant according to the invention. [Fig 5]

[0032] Figure 5 illustrates an example of a system design according to the invention, comprising a central LED integrated on a circular support and two photodiodes having distinct bandwidths distributed around the central LED. [Figure 6]

[0033] Fig. 6 illustrates another example of the system design according to the invention, comprising a circular support, a central LED, and nine photodiodes having three distinct bandwidths distributed around the central LED. Description of the implementation methods

[0034] According to a first aspect, the invention relates to a method for a non-contact measurement of the temperature of at least a portion of an object, by means of at least one light source and means for measuring a light intensity as a function of wavelength.

[0035] According to a second aspect, the invention relates to a system for a non-contact measurement of the temperature of at least a portion of an object, for the implementation of the method according to the invention.

[0036] According to a third aspect, the invention relates to a system for a non-contact measurement of the temperature of at least a portion of an object.

[0037] By "non-contact temperature measurement of a portion of an object", we mean the measurement of the temperature of the portion of an object without direct application of a temperature measuring instrument to the portion of the object in question.

[0038] According to the invention, the portion of the object is coated with a layer of a luminescent (also called "phosphorescent") material from the zinc oxide (ZnO) family. ZnO phosphors are characterized by an absorption spectrum that starts in the deep UV (100 to 200 nm) and extends into the visible range. After numerous Laboratory tests have shown that the Applicant has observed that the intensity spectrum of ZnO is strongly temperature-dependent in the range between 360 and 480 nm (also referred to hereafter as the characteristic wavelength range of the luminophore material according to the invention), and is even more temperature-sensitive in the 380-420 nm range. Consequently, compared to other luminophore materials, the use of a luminophore material from the ZnO family allows the system and method according to the invention to be implemented using light sources and means for measuring light intensity in the visible range, as described below.It is clear that the phosphor layer according to the invention is in thermal contact with the portion of the object whose temperature is to be measured, which implies that the phosphor layer is (approximately) at the same temperature as the portion of the object whose temperature is to be measured. By "portion of the object coated with a phosphor layer," it is understood that the phosphor layer is in direct contact with the portion of the object or that the phosphor layer is in contact with the portion of the object via an intermediate material (for example, glue). According to one embodiment of the invention, the phosphor material can be attached to the portion of the object by glue, or by any mechanical or adhesive means. Furthermore, the phosphor material may include, in addition to the phosphor components, components that ensure the cohesion of the layer.

[0039] According to one embodiment of the invention, the layer of luminescent material according to the invention has a thickness of between 5 µm and 100 µm. Indeed, such a thickness is sufficient to allow diffusion of light radiation emitted by a source according to the invention, without having a thermal impact on the object. The layer of luminescent material according to the invention may have been previously applied to the portion of the object under study, or may be applied in a prior step of the process according to the invention.

[0040] According to one embodiment of the invention, the layer of luminescent material according to the invention can be of any shape, but advantageously its surface can at least cover a disk with a surface area of ​​10 mm². Indeed, such a dimension is sufficient to allow diffusion of light radiation emitted by a source according to the invention.

[0041] The method and system can be implemented for a static or mobile object.

[0042] According to one embodiment of the invention, the object may be a component of a rotating machine, such as a turbine blade or the rotor of an electric machine. In the case of a moving object, the measurement can either be averaged over the entire surface of the portion of the object coated with the phosphor material and illuminated by the light source, or limited to a specific region. Depending on one implementation of The invention provides a synchronization system that can link the acquisition to the position of the target surface.

[0043] According to one embodiment of the invention, the object may be a component of a static machine such as the inner surface of the cylinder of a reciprocating combustion engine.

[0044] The system according to the invention comprises at least:

[0045] - a light source capable of emitting radiation in a wavelength range of waves covering at least partially a wavelength range between 360 and 480 nm;

[0046] - means for measuring light intensity as a function of wavelength capable of measuring the intensity of radiation in at least a part of said wavelength range of said light source.

[0047] It is clear that the light source according to the invention can cover a narrower or a wider range than the characteristic wavelength range of the phosphor material according to the invention. Similarly, it is clear that the means for measuring the light intensity as a function of the wavelength of the system according to the invention can cover a narrower range than the wavelength range of the light source according to the invention.

[0048] The method according to the invention can advantageously be implemented using the system according to the invention. However, the method according to the invention can be implemented using any light source capable of emitting radiation in a wavelength range covering at least partially the characteristic wavelength range of the phosphor material according to the invention (i.e., in a wavelength range between 360 and 480 nm) and means for measuring light intensity as a function of wavelength capable of measuring the intensity of radiation in at least a portion of the wavelength range of the light source according to the invention. Preferably, the full width at half maximum (FWHM) of the spectrum of the light source is at least 5 nm, preferably 10 nm.

[0049] Advantageously, the light source according to the invention can be capable of emitting radiation in a wavelength range of at most between 360 and 480 nm. A light source in this range is indeed sufficient for implementing the method according to the invention.

[0050] According to one embodiment of the invention, the light source may be an LED (Light Emissive Diode) or a xenon lamp emitting at least in a portion of the characteristic wavelength range of the phosphor material according to the invention. The advantage of using an LED lamp is that lamps of this type consume little energy and can be focused on a particular wavelength range, in this case a portion of the range of characteristic wavelength of the phosphor material according to the invention. The advantage of using a Xenon lamp is that its light radiation has a wide range, not requiring any special adaptation (in particular a filter), and is more intense than that emitted by LED lamps.

[0051] According to one embodiment of the invention, the means for measuring light intensity as a function of wavelength can correspond to a spectrometer. It is clear that a spectrometer covers a range of wavelengths including by default at least a portion of the wavelength range of the light source according to the invention.

[0052] Alternatively, the means for measuring light intensity as a function of wavelength according to the invention may be formed by a photodiode covering at least a portion of the wavelength range of the light source according to the invention. Photodiodes are compact and inexpensive means for measuring light intensity as a function of wavelength.

[0053] Preferably, the means for measuring light intensity as a function of wavelength according to the invention can be formed by at least two photodiodes, each of the photodiodes covering at least a part of the wavelength range of the light source according to the invention, preferably without overlap.

[0054] According to one embodiment of the invention, the luminescent material according to the invention is a zinc oxide doped with gallium or zinc. Indeed, the Applicant has observed that these particular zinc oxides have a thermochromic response in the visible range, allow for good measurement accuracy, are robust, and are relatively inexpensive.

[0055] The method and system according to the invention exploit the temperature-changing optical properties of a particular phosphorescent material. To this end, the surface of interest, which has been previously coated with the phosphorescent material according to the invention, is illuminated by a light source whose spectral characteristics correspond to those of phosphorus; that is, the light source emits in the range of wavelengths in which phosphorus absorbs. Since phosphorus absorbs a fraction of the light in a manner that depends on its temperature, the intensity of the remaining scattered light is measured, and from its spectral characteristics, the surface temperature can be determined using a lookup table.

[0056] According to one embodiment of the invention, the system according to the invention may include means for analyzing light intensity as a function of wavelength, the analysis means being configured to determine at least one parameter from a light intensity as a function of wavelength, as well as the The temperature of the portion of the object coated with the phosphor coating is determined from a parameter and a predetermined lookup table, the lookup table allowing a correspondence between parameter values ​​and temperature values. The analysis methods may include computing resources such as a computer, a processor, or a calculator.

[0057] Figure 1 schematically illustrates an example of an embodiment of the system according to the invention. More specifically, the system according to this embodiment comprises a light source 1 (for example, an LED). The radiation emitted 2 by the light source 1 illuminates at least a portion 3' of an object 3 coated with a luminescent material according to the invention. A spectrometer 5 is arranged in an optical path suitable for measuring radiation emitted 2 by the light source 2 and scattered 4 by the portion 3' of the object 3.

[0058] The method according to the invention comprises at least the following steps

[0059] 1) Emission of radiation and measurement of light intensity

[0060] 2) Determination of at least one parameter

[0061] 3) Determination of the temperature

[0062] The steps of the process according to the invention are detailed below.

[0063] 1) Emission of radiation and measurement of light intensity

[0064] During this step, by means of said at least one light source, one emits at least one radiation in the said wavelength range from said at least one light source, and, by means of said means of measuring a luminous intensity as a function of wavelength, at least one luminous intensity is measured as a function of the wavelength of a radiation scattered by said portion of said object coated by said layer of said luminophore material when said portion of said object coated by said layer of said luminophore material is illuminated by said at least one radiation emitted by said at least one light source.

[0065] In other words, during this step, at least one radiation is emitted by means of at least one light source which illuminates at least the portion of the object coated by the layer of luminophore material, and simultaneously, by means of the means for measuring a light intensity as a function of wavelength, at least one light intensity is measured as a function of the wavelength of at least one radiation scattered by the portion of the object coated by the layer of luminophore material.

[0066] According to one embodiment of the invention, at least one light source and means for measuring light intensity can be arranged so as to receive the radiation scattered by the portion of the object coated with the phosphor material when it is illuminated by the light source. In this so-called direct configuration, the light source and the means for measuring light intensity may have substantially the same position (the emitted and scattered radiation are then parallel to each other and perpendicular to the surface of the portion of the object coated by the luminophore material) or may be distant (there is then an angle between the emitted and scattered radiation at the surface of the portion 3' of the object 3 coated by the luminophore material).

[0067] Alternatively, optical elements can be interposed between the radiation emitted by at least one of the light sources and the radiation scattered by the portion of the object coated with the luminophore material when it is illuminated by the light source and measured by means of measuring light intensity, such as optical fibers, lenses, beam splitters or mirrors.

[0068] According to a first embodiment, the method and / or system are implemented using a single light source and a spectrometer as means for measuring light intensity as a function of wavelength. Such a configuration makes it possible to measure the intensity for the entire wavelength range of the light source.

[0069] According to a second embodiment, the method and / or system are implemented using a single light source and two photodiodes, each photodiode covering at least a portion of the wavelength range of the light source, preferably without overlap. Advantageously, this embodiment can be implemented using LED lamps, which are inexpensive. An LED can emit in various wavelength ranges, from narrow wavelength ranges (+ / - 5 nm) to wider ranges (+ / - 40 nm) and having varying center wavelengths. Advantageously, an LED lamp is used whose wavelength range is consistent with the temperature range to be explored. For example, for a temperature range between 20 and 300°C, an LED with a center wavelength of 395 nm and a full width at half maximum (FWHM) of + / - 10 nm can be used.If the process and / or system are implemented using a Xenon arc source or an LED source, both photodiodes may include a filter adapted to the targeted measurement range.

[0070] According to a third embodiment, the method and system are implemented using two light sources, emitting in non-overlapping wavelength ranges (although up to 60% overlap is possible), preferably LED lamps, and a photodiode. In this embodiment, each lamp can be capable of emitting radiation in at least a portion of the characteristic wavelength range of the phosphor material, and the photodiode can be capable of measuring light intensity as a function of wavelength in at least each of the lamp wavelength ranges. This embodiment is particularly advantageous, especially compared to the second This variant is because LED lamps are less expensive than photodiodes. When the method according to the invention is implemented using this variant of the system according to the invention, it may include a repetition of step A) of the method according to the invention for each of the light sources. In other words, the two LED lamps are switched on one after the other, at two different times (or, in other words, the lamps flash alternately, for example, every 100 to 200 ns), and the light intensity is measured as a function of wavelength for each of the beams emitted by each of the LED lamps and scattered by the portion of the object coated with the phosphor material.

[0071] According to a fourth embodiment, the method and system are implemented using an LED light source and a photodiode, the LED and the photodiode having a bandpass filter whose wavelength range is a function of a target temperature. In other words, for this configuration, the wavelength range of the light source and the means for measuring the light intensity can be narrow, for example, with a full width at half maximum (FWHM) of 10 nm (the limiting width of current LED lamps). This embodiment can be implemented, in particular, when it is necessary to detect whether the object under study has reached a critical temperature beyond which operational risks are increased. 2) Determination of at least one parameter

[0072] During this step, from said at least one measurement of said light intensity as a function of the wavelength of said at least one scattered radiation, a value of at least one parameter is determined.

[0073] According to one embodiment of the invention, the parameter can be determined from at least a part of at least one measured intensity spectrum or from at least a part of at least one absorption spectrum which can be determined from the measurement of the light intensity as a function of the wavelength of at least one scattered radiation.

[0074] The intensity spectrum corresponds to the evolution of the intensity as a function of the wavelength.

[0075] Conventionally, an absorption spectrum (evolution of absorbance as a function of wavelength) is determined from a measured light intensity and a reference light intensity according to the following formula:

[0076]

[0077] where A is the absorbance, X is the wavelength, Is(A) is the luminous intensity as a function of the wavelength of the measured radiation, and / 0(^) is the luminous intensity as a function of the wavelength of the measured radiation for a reference. In this case, the reference light intensity can be measured on any surface not containing luminophore material.

[0078] According to one embodiment of the invention, the parameter may be an absolute parameter or a relative parameter, determined by taking into account a reference intensity measurement, carried out, for example, at the beginning of the implementation of the process according to the invention or periodically. A relative parameter may be advantageous for compensating for variations in the light source and / or soiling of the portion of the object considered. Thus, a reference intensity spectrum could be measured on a surface of the object considered (or any other object) not coated by the layer of phosphor material.

[0079] When the method and / or system are implemented according to the first variant described above (a single light source and measurement of light intensity by a spectrometer), the parameter can be determined from the integral of the intensity spectrum (or absorption spectrum) over the entire wavelength range of the light source (since means for measuring light intensity in the form of a spectrometer necessarily cover the entire wavelength range of the light source). Alternatively, the parameter can be determined as a ratio between the integral of the intensity spectrum (or absorption spectrum) over a first part of the wavelength range of the light source and the integral of the intensity spectrum (or absorption spectrum) over a second part of the wavelength range of the light source.In other words, in this latter approach, a ratio is calculated for the measured light intensity (or absorbance) across two windows with different wavelengths. Figure 2 shows examples of intensity spectra (the evolution of intensity I as a function of wavelength L) recorded by a spectrometer for different temperatures T of a portion of an object, with the temperature increasing in the direction of the arrow (between 23°C and 304°C). This figure shows that the intensity varies significantly with the temperature of the object portion. The figure also presents two zones, Z1 and Z2, corresponding to two parts of the wavelength range of the light source (from 350 to 480 nm), for the purpose of determining a parameter in the form of a ratio as described in the alternative above.It is quite clear from this figure that the ratio thus defined has different values ​​depending on the temperature of the portion of the object.

[0080] When the method and / or system are implemented according to the second variant described above (a single light source and two photodiodes), the parameter can be determined in the form of a ratio between the integral (of at least a part) of the intensity spectrum (or absorption spectrum) over the wavelength range of the first photodiode and the integral of the intensity spectrum (or absorption spectrum) on the wavelength range of the second photodiode (or vice versa equivalently).

[0081] When the method and / or system are implemented according to the third variant described above, the parameter can correspond to a ratio between the integral of the intensity (or absorption) spectrum measured for the first LED source and the integral of the intensity (or absorption) spectrum measured for the second LED source (or vice versa equivalently).

[0082] Figure 3 illustrates the evolution of the intensity I as a function of the wavelength L of two LED lamps suitable for implementing the second embodiment of the invention, one centered on a wavelength of 395 nm and the other centered on a wavelength of 415 nm. In this particular case, the spectra II, 12 of the two LED lamps partially overlap. Figure 4 illustrates an example of the evolution as a function of temperature T of the parameter defined for the third embodiment according to the invention, in the form of a ratio R. It can be observed that the parameter defined for this embodiment is indeed discriminating with respect to temperature T: a single value of the ratio R corresponds to a single value of temperature T (monotonous curve).

[0083] When the method and / or system are implemented according to the fourth variant described above (narrow bandwidth light source), the parameter can correspond to an absolute value of the measured intensity (maximum value or average value over the width of the wavelength range of the LED for example) or to a relative value of the measured intensity (for example a ratio between the measured light intensity and a reference intensity, measured on a reference surface not containing luminophore material).

[0084] 3) Determination of the temperature from the parameter

[0085] During this step, the temperature of the portion of the object coated by the layer of the luminophore coating is determined from the value of the parameter determined and from a predetermined correspondence table between values ​​of the temperature according to the ratio, the correspondence table allowing a correspondence between values ​​of the parameter and values ​​of the temperature.

[0086] It is therefore necessary, starting from the value of the parameter determined in the previous step, to determine which temperature corresponds to this parameter value in a predetermined correspondence table.

[0087] According to one embodiment of the invention, in a step prior to step 3), the correspondence table between parameter values ​​and temperature values ​​can be determined. This can be done as follows: the temperature of the object under study is varied between a minimum temperature and a maximum temperature with a predefined temperature step, and steps 1) and 2) of the method according to the invention for each temperature step, and the value of the parameter determined at the end of step 2) as well as the temperature of the object for each temperature step are recorded in the lookup table. According to one embodiment of the invention, the temperature of the object can be varied in 10°C increments. According to one embodiment of the invention, the temperature of the object can be controlled by means of a temperature sensor such as a thermocouple.

[0088] According to one embodiment of the invention, the system comprises a support in which at least one light source and means for measuring light intensity as a function of wavelength are integrated. The support may, for example, be circular in shape. The support may, for example, be made of metal, such as stainless steel. Each photodetector and the light source may be equipped with a collimating lens (lens array) to increase the efficiency of light collection.

[0089] According to this design, in the case of a single light source, the light source can be at the center of the support and the photodiodes distributed around the light source.

[0090] Figure 5 illustrates an example of this design, comprising a circular support 10, a central LED 20, and two photodiodes 30, 31 having distinct bandwidths, distributed around the LED 20. This design example is particularly suitable for implementing the second variant described above.

[0091] Figure 6 illustrates another example of this design, comprising a circular support 10, a central LED 20, and nine photodiodes 30, 31, 33 having three distinct bandwidths, distributed around the LED 20. The presence of several photodiodes with the same bandwidth allows for measurement redundancy and thus improves measurement uncertainties and / or enables an alternative measurement in case of failure of one of the components. Compared to the second variant described above, the addition of at least one photodiode with a bandwidth distinct from the others allows for an alternative measurement in case of failure of one of the components. Examples

[0092] The characteristics and advantages of the method and system according to the invention will become clearer upon reading the application example below.

[0093] More specifically, the method according to the invention has been implemented for non-contact temperature measurement of a permanent magnet in a rotor. A layer of the phosphor material according to the invention has been applied to the permanent magnet. The method according to the invention is implemented by means of a sensor as described in [Fig. 5], comprising a central LED integrated on a circular support and two photodiodes having distinct bandwidths distributed around the LED. central. Using a synchronization system, the LED emits a flash of light simultaneously with the passage of the measurement target (the portion coated with the phosphor material). The scattered light emissions are collected simultaneously by the two photodiodes. From the ratio of the light intensities collected by the two photodiodes and a lookup table, the temperature of the rotor's permanent magnet is then determined.

[0094] Thus, the present invention, based on the use of a phosphor material from the ZnO family, enables temperature monitoring of objects that can reach temperatures of at least 300°C. Furthermore, the use of this particular phosphor material allows for implementation with light sources and detectors within a limited wavelength range, at a low cost. Finally, the use of a ZnO family material enables a very rapid light response (on the order of nanoseconds), and therefore real-time monitoring.

Claims

Demands

1. A method for non-contact temperature measurement of a portion (3') of an object (3), using at least one light source (1) and means for measuring light intensity as a function of wavelength (5), said light source (1) being capable of emitting radiation (2) in a wavelength range covering at most a wavelength range between 360 and 480 nm and said means for measuring light intensity (5) being capable of measuring the intensity of radiation in at least a portion of said wavelength range of said light source (1), characterized in that said portion (3') of said object (3) is coated with a layer of a luminescent material of the zinc oxide family and in that it comprises at least the following steps: A) using said at least one light source (1), at least one radiation (2) is emitted in said wavelength range of said at least one light source (1),and, by means of said means for measuring luminous intensity as a function of wavelength (5), at least one luminous intensity is measured as a function of the wavelength of a scattered radiation (4) by said portion (3') of said object (3) coated with said layer of said luminophoretic material when said portion (3') of said object (3) coated with said layer of said luminophoretic material is illuminated by said at least one radiation (2) emitted by said at least one light source (1); B) from said at least one measurement of said luminous intensity as a function of the wavelength of said at least one scattered radiation (4), a value of at least one parameter is determined; C) said temperature of said portion (3') of said object (3) coated with said luminophoretic coating is determined from said value of said at least one determined parameter and a predetermined lookup table,said lookup table allowing a correspondence between values ​​of said at least one parameter and values ​​of said temperature.

2. A method according to claim 1, wherein said lookup table is constructed in the following manner: said temperature of said portion of said object between a minimum temperature and a maximum temperature with a predefined temperature step, steps A) and B) are applied for each temperature step, and a value of said at least one parameter determined at the end of step B) is recorded as well as said temperature of the portion of the object for each of said temperature steps in said lookup table.

3. A method according to any one of the preceding claims, wherein said parameter is determined from at least a part of at least one intensity spectrum or at least one absorption spectrum, said intensity spectrum and absorption spectrum being determined from said at least one measurement of said light intensity as a function of wavelength.

4. A method according to claim 3, wherein said method is carried out by means of a single light source (1) and a spectrometer, and wherein said parameter is determined from an integral of said intensity spectrum or said absorption spectrum over at least a part of said wavelength range of the light source (1).

5. A method according to claim 3, wherein said method is implemented by means of a single light source (1) and a spectrometer, and wherein said parameter is determined by a ratio between, on the one hand, an integral of said intensity spectrum or of said absorption spectrum over a first part of the wavelength range of the light source (1) and, on the other hand, an integral of said intensity spectrum or of said absorption spectrum over a second part of the wavelength range of the light source (1).

6. A method according to claim 3, wherein said method is implemented by means of a single light source (1) and a first and a second photodiode, and wherein said parameter is determined by a ratio between, on the one hand, an integral of said intensity spectrum or of said absorption spectrum over a range of wavelengths of said first photodiode and, on the other hand, an integral of said intensity spectrum or of said absorption spectrum over a range of wavelengths of said second photodiode, or vice versa.

7. A method according to claim 3, wherein said method is implemented by means of a first and a second light source (1), and a photodiode, and wherein said parameter is determined by a ratio between, on the one hand, an integral of said intensity spectrum or of said absorption spectrum over a range of wavelengths of said first light source, and, on the other hand, an integral of said intensity spectrum or of said absorption spectrum over a range of wavelengths of said second light source, or vice versa.

8. A method according to claim 3, wherein said method is implemented by means of a light source (1) having a bandwidth between 5 and 15 nm and a photodiode, and wherein said parameter is determined by a value of the intensity at the central wavelength of said bandwidth, optionally referred to a reference intensity measured on a surface of the object (3) not coated by said luminophore material.

9. System for non-contact measurement of the temperature of at least a portion (3') of an object (3), said system being configured for carrying out the method according to any one of the preceding claims, said system comprising at least said light source (1) capable of emitting radiation in a wavelength range covering at most a wavelength range between 360 and 480 nm and said means for measuring light intensity (5) capable of measuring the intensity of radiation in at least a part of said wavelength range of said light source (1).

10. System according to claim 9, wherein said system further comprises a paint of said phosphor, or a white sticker and said paint of said phosphor intended to be applied to said white sticker, or a sticker having said phosphor on its non-adhesive surface.

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