Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
  • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
  • G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
  • G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
  • G01N21/35—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light
  • G01N21/3577—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light for analysing liquids, e.g. polluted water
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
  • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
  • G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
  • G01N21/27—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands using photo-electric detection ; circuits for computing concentration
  • G01N21/274—Calibration, base line adjustment, drift correction
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
  • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
  • G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
  • G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
  • G01N21/35—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light
  • G01N21/3504—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light for analysing gases, e.g. multi-gas analysis
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
  • G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
  • G01J3/02—Details
  • G01J3/10—Arrangements of light sources specially adapted for spectrometry or colorimetry
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
  • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
  • G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
  • G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
  • G01N21/314—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry with comparison of measurements at specific and non-specific wavelengths
  • G01N2021/3181—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry with comparison of measurements at specific and non-specific wavelengths using LEDs
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
  • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
  • G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
  • G01N21/27—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands using photo-electric detection ; circuits for computing concentration
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N2201/00—Features of devices classified in G01N21/00
  • G01N2201/06—Illumination; Optics
  • G01N2201/062—LED's
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N2201/00—Features of devices classified in G01N21/00
  • G01N2201/06—Illumination; Optics
  • G01N2201/062—LED's
  • G01N2201/0624—Compensating variation in output of LED source
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N2201/00—Features of devices classified in G01N21/00
  • G01N2201/12—Circuits of general importance; Signal processing
  • G01N2201/121—Correction signals
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N2201/00—Features of devices classified in G01N21/00
  • G01N2201/12—Circuits of general importance; Signal processing
  • G01N2201/121—Correction signals
  • G01N2201/1211—Correction signals for temperature
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N2201/00—Features of devices classified in G01N21/00
  • G01N2201/12—Circuits of general importance; Signal processing
  • G01N2201/124—Sensitivity
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N2201/00—Features of devices classified in G01N21/00
  • G01N2201/12—Circuits of general importance; Signal processing
  • G01N2201/124—Sensitivity
  • G01N2201/1242—Validating, e.g. range invalidation, suspending operation
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N2201/00—Features of devices classified in G01N21/00
  • G01N2201/12—Circuits of general importance; Signal processing
  • G01N2201/124—Sensitivity
  • G01N2201/1247—Thresholding
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N2201/00—Features of devices classified in G01N21/00
  • G01N2201/12—Circuits of general importance; Signal processing
  • G01N2201/127—Calibration; base line adjustment; drift compensation
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N2201/00—Features of devices classified in G01N21/00
  • G01N2201/12—Circuits of general importance; Signal processing
  • G01N2201/127—Calibration; base line adjustment; drift compensation
  • G01N2201/12723—Self check capacity; automatic, periodic step of checking

Definitions

• the present invention relates to the analysis of fluids by spectrometry.
• the present invention applies in particular but not exclusively to the analysis of fluids in a heat engine, and in particular to the analysis of hydrocarbons used as fuel for such an engine.
• This analysis concerns all thermal engines, whether used in land, sea and air transport, military engines or stationary engines.
• near infrared spectrometry 700 to 2500 nm
• a sensor based on the principle of spectrometry, especially in the near infrared generally comprises a spectrometer and a data processing computer for transforming the gross output signals (gross spectrum) of the spectrometer into qualitative information on the product to be measured.
• the spectrometer comprises a light source which covers at least one wavelength band in which the analysis is to be performed, a measuring cell in which the light produced by the light source and the product to be analyzed interact, and a sensor that provides a spectrum of light output from the measuring cell.
• the spectrometer can measure the spectrum of the product to be analyzed in transmission, reflection or absorbance of a beam of light emitted by the light source.
• a spectrometer is mainly characterized by its range of spectral analysis (width and position of the generated spectrum), its analytical fineness or the number of measurement points constituting the generated spectrum, and its measurement precision.
• LEDs light-emitting diodes
• the measured spectrum which is characteristic of the quality and / or the composition of the product to be analyzed, is affected by external factors, such as temperature, as well as by the characteristics of the spectrum of the light beam. interacting with the product to be analyzed.
• the LEDs are aging, so that their emission spectrum varies over time as stated in the LED article "LED lighting Life Prediction" by Jianzhong Jiao, Ph.D., Director of Regulatory & Emerging Technologies, Osram Opto Semiconductors, Inc., Oct. 2009.
• near-infrared spectrometry in general is sensitive to temperature (as exposed for example in the publication "On-line monitoring "Zinc-Ping Chen, Julian Morris, Antonia Borissova, Shahid Khan, Tariq Mahmud,””Chemometrics and Intelligent Laboratory Systems 96” (2009) 49-58, "Bombardment of crystallization of organic compounds using ATR-FTIR spectroscopy coupled with an advanced calibration method". Rado Penchev, Kevin J. Roberts). Near-infrared spectrometry using an LED-based light source is therefore particularly sensitive to temperature.
• a sensor associated with a heat engine, embedded in particular in a vehicle must be able to operate in a very wide temperature range (depending on the application, current standards require a temperature range from -40 ° C to + 105 ° C, or up to + 150 ° C).
• embedded sensors are expected to guarantee a long life (depending on the application, current standards require a few thousand hours to several tens of thousands of hours). It is therefore crucial to ensure the proper functioning of the spectrometer to be able to manage in real time the influence of the temperature and the aging of the light source to ensure a qualitative determination of the product to be analyzed which is precise and robust.
• Embodiments relate to a method of controlling a product analysis spectrometer, the spectrometer comprising a light source having a plurality of light-emitting diodes having respective emission spectra covering in combination a analysis wavelengths, the method comprising the steps of: supplying a supply current to at least one of the light-emitting diodes to turn it on, and measuring a light intensity emitted by the light source by measuring a current at a terminal of at least one other of the light-emitting diodes kept off, determining, as a function of each light intensity measurement, a set value of the supply current of each lit diode, and regulating the supply current of each lit diode to match the set point.
• the method comprises steps of successively igniting groups of at least one light-emitting diode, the diodes of a group having substantially identical emission spectra, while other light-emitting diodes are kept off. measuring a luminous intensity by each of the other light-emitting diodes kept extinguished, and adjusting, as a function of each measurement of light intensity obtained, of the supply current setpoint value of the lit diode.
• the method comprises the steps of: determining, as a function of the light intensity measurements, a value of integration time of photosensitive cells of a sensor of the spectrometer, arranged on a path of a light beam emitted by the light source and having interacted with a product to be analyzed, and if the integration time value and / or the supply current setpoint of each lighted diode is between threshold values, provide to each diode illuminates a regulated supply current as a function of the value of the supply setpoint current, adjust the integration time of each photosensitive cell to the determined value of integration time, and acquire by means of each sensor cell light intensity measurements making it possible to form a spectrum.
• new supply current setpoint values of each lit diode and / or integration duration of each cell are determined and a supply current corresponding to the determined current set point value.
• power supply is provided to each light-emitting diode lit, as long as the value determined integration time is not between the threshold values.
• the supply current setpoint of each light-emitting diode on is also adjusted as a function of a light intensity measurement provided by a photodiode of the light source, and / or a measurement of the temperature of the light source, and / or a measurement of current or supply voltage of each diode illuminated.
• the method includes self-diagnostic test steps comprising at least one of the following comparisons: comparisons to determine whether light intensity measurements, and / or power current measurements provided to the illuminated diode, and / or temperature measurements of the light source are coherent with each other and with each light-emitting diode supply current set point on, comparisons of the power supply setpoint value supplied to each light-emitting diode lit at minimum and maximum values, and if any of the comparisons reveals a fault, the spectrometer has entered a degraded or faulty operating mode.
• the method comprises a step of correcting light intensity measurements taking into account a difference in the temperature of the product to be analyzed and / or the temperature of the sensor with a reference temperature, so as to obtain corrected light intensity measurements resulting from measurements at the reference temperature, corrected measurements forming a corrected spectrum).
• the method comprises steps for obtaining a corrected spectrum for each light emitting diode, and for summing the corrected spectra obtained by applying weighting coefficients, in order to obtain a resulting spectrum), and possibly calculating an average of several of the resulting spectra the number of averaged spectra that may depend on a mode of operation, normal or degraded, of the spectrometer.
• the method comprises a calibration of the spectrometer, comprising: steps for determining minimum and maximum values of correspondence of light intensity measurements a luminous flux produced by each light-emitting diode, with supply current setpoint values of each of the light-emitting diodes, and / or with the temperature of the light source, and / or steps of determining minimum and maximum values a reference current for supplying the light source, and / or steps for determining minimum and maximum values for the integration time of the photosensitive cells of the sensor, and / or steps performed in the presence of one or more reference products determining a function providing an optimal integration time of a photosensitive cell of the sensor as a function of light intensity measurements of the luminous flux produced by each light-emitting diode, and / or steps performed in the presence of one or more several reference products, during which the temperature of the light source and / or the temperature of the sensor are independently varied. and / or the temperature of the reference product, light intensity measurements provided by the sensor, diode power supply setpoint values
• Embodiments may also relate to a spectrometer comprising a light source emitting a light beam and comprising a plurality of light emitting diodes having respective emission spectrums covering in combination an analysis wavelength band, a sensor comprising cells photosensitive objects arranged on a path of the light beam after interacting with an analyte, and a control device adjusting light-emitting diode power supply setpoint values of the light source, and an integration time of the photosensitive cells, the control device being configured to implement the method as previously defined.
• the spectrometer is configured to ignite a single light-emitting diode of the light source at a time, and to collect a light intensity measurement by measuring a current at a terminal of each of the light emitting diodes extinguished from the light source.
• the light source is configured to supply the control device with voltages and / or supply currents of the light-emitting diodes.
• the light-emitting diodes are integrated in the same electronic component, possibly with the photodiode and / or a temperature sensor.
• the spectrometer comprises a temperature sensor providing measurements of the temperature of the light source, and / or a temperature sensor providing measurements of the temperature of the sensor, and / or a temperature sensor providing measurements. the temperature of the product to be analyzed.
• the spectrometer comprises a measuring cell in which an analyte interacts with the light beam, an optical element for shaping the beam at the output of the light source and transmitting it to the measuring cell, a filter of wavelength configured to spatially spread the different wavelengths of the light beam at the output of the measuring cell and transmit them to different photosensitive cells of the sensor, the light source, the optical element, the measuring cell, the filter and the sensor being assembled so as to form no air zone capable of being traversed by the light beam between the light source and the sensor.
• FIG. 1 schematically represents a spectrometer according to an embodiment
• FIG. 2 diagrammatically represents an electronic control circuit of a light source of the spectrometer, according to one embodiment
• FIGS. 3A and 3B show emission spectra of LEDs, in the form of light intensity variation curves emitted as a function of the wavelength
• FIG. 4 represents sensitivity spectra of the LED diodes, in the form of curves of variation of intensity of electric current generated as a function of the wavelength
• FIG. 5 schematically represents an electronic control circuit of a light source of the spectrometer, according to another embodiment
• FIG. 6 represents a sequence of steps executed by a regulation processor of the spectrometer
• FIG. 7 represents a graph defining areas of operation of the spectrometer.
• FIG. 1 represents a spectrometer designed in particular to respond to the specific constraints of an on-board sensor on a vehicle or a heat engine.
• the spectrometer includes:
• a wavelength filter WFL for spatially spreading the different wavelengths of the beam LB at the output of the FLC cell
• an OPS sensor which provides measurements making it possible to constitute a light spectrum at the output of the WFL filter.
• the LS light source covers at least one so-called "analysis" wavelength band in which the spectrum measurements are to be performed.
• the optical element CLS transforms the geometry of the beam LB and introduces it into the measuring cell FLC.
• the optical element CLS may for example comprise a collimating lens which makes the beam LB parallel to the beam.
• the FLC cell includes an OPW output window transmitting to the OPS sensor the light that interacted with the product to be analyzed.
• the OPS sensor includes several photosensitive cells (n cells) and receives the light transmitted by the OPW window through the WFL filter.
• the WFL filter distributes the wavelengths composing the light transmitted by the FLC measuring cell onto the photosensitive cells of the OPS sensor, so that each cell of the OPS sensor receives only a reduced wavelength range belonging to the OPS sensor. to the wavelength band corresponding to the spectrum to be generated.
• the WFL filter can for example be of the Fabry-Perot type, or of variable linear type and generate a spatial dispersion of the wavelengths of the order of 20 to 50 nm / mm.
• the OPS sensor may be of the CCD or CMOS type, and comprise a strip of 20 to 200 photosensitive cells.
• the light source LS comprises one or more LEDs (p LED diodes), which can be integrated in a single electronic component associated with a single LLD lens concentrating the light rays emitted by the diodes into a weak solid angle beam.
• the supply current, or the direct voltage of each of the LEDs, can be measured electronically by conventional means known to those skilled in the art.
• the light source LS may be fixed to the optical element CLS via an optical block OB through which the light beam LB emitted by the source LS is passed, so as not to trap air in the zone traversed by the beam.
• OB optical block is transparent to the wavelengths to be analyzed and can be full or hollow and filled with an inert fluid.
• the lateral faces of the OB block, not crossed by the light beam from the source SL, may be covered with an opaque coating to prevent light leakage through these faces.
• the filter WFL is fixed on the window OPW, so as not to trap air, directly or via an optical block having the same characteristics as those of the OB optical block mentioned above. Similarly, the filter WFL is fixed on an input window of the OPS sensor so as not to trap air, directly or via an optical unit that can have the same characteristics as those of the optical block OB mentioned previously.
• the spectrometer can be monoblock, which makes it easy to store and manipulate industrially.
• the alignment of the various optical elements composing the spectrometer can thus be adjusted once and for all during the manufacture of the spectrometer.
• the absence of air in the zone crossed by the light beam LB between the source LS and the OPS sensor also makes it possible to overcome any risk of condensation of water vapor in this zone, the presence of water droplets. in the path of the beam LB can indeed disrupt the analysis of the product in the measuring cell FLC.
• the spectrometer is controlled by a RPRC control and regulation device which regulates the LCx supply current (x being an integer between 1 and p) of each LED of the light source LS, integrating ITy (where y is an integer between 1 and n) of each photosensitive cell y of the OPS sensor, according to different parameters comprising at least one of the following parameters: LFLx intensities of luminous flux emitted by the LED diodes of the light source LS, the temperature TPL of the source LS, the temperature TPP of the product to be analyzed, and the temperature TPS of the OPS sensor.
• the integration time ITy of a photosensitive cell corresponds to the time during which a potential well of the photosensitive cell is left under charge under the effect of a luminous flux.
• the intensity LFLx of the luminous flux emitted by each LED of the source is measured by LED diodes of the source LS kept off (receiving a zero supply current), only one or more of the LEDs of the source LS being lit at a given moment.
• the LEDs of the source are lit successively by a group of at least one LED, while each of at least a portion of the LED diodes kept off of the source LS, is used in photodiode for measure the light intensity emitted by the LS source.
• a spectrum is measured using the photosensitive cells of the OPS sensor.
• the RPRC regulator performs loop mode regulation of both the LCx supply current of the LEDs of the source LS and the integration time ITy of the photosensitive cells of the OPS sensor.
• the integration time ITy has reached a limit value, without a satisfactory signal (between two limit values) being obtained at the output of the OPS sensor, the intensity or the voltage of the supply current LCx of the light source is adjusted.
• This regulation aims to stabilize the signal received by each of the photosensitive cells of the sensor, and thus to minimize the impact of factors external to the product to be analyzed itself, such as variations in ambient temperature or the aging of the source LEDs.
• LS This regulation aims to allow the spectrometer to operate in a very wide range of temperatures, while maintaining a signal / noise ratio relatively constant over time and homogeneous as a function of the wavelength, and therefore a substantially constant measurement sensitivity.
• the integration time of the OPS sensor can be adjusted individually for each photosensitive cell of the OPS sensor, or globally for all the photosensitive cells, for example by choosing as the overall integration time, the minimum value of the integration times ITy determined for each of the cells there.
• the RPCR control device receives a measurement of light intensity MSy for each cell y of the OPS sensor, and can provide corrected MSCy measurements according to various parameters such as the TPP temperature of the product to be analyzed and / or the TPS temperature of the OPS sensor. .
• FIG. 2 represents an electronic control circuit LSCC of the light source LS, according to one embodiment.
• the LSCC circuit is connected to the LS source and is connected to the RPRC control device via a CVM conversion module comprising several analog / digital converters and several digital / analog converters.
• the LS light source comprises several LEDs LD1, LD2, LD3, LD4.
• the circuit LSCC comprises current regulation circuits REG1, REG2, REG3, REG4, adjustable gain amplifiers A1 1, A12, A13, A14, A21, A22, A23, A24, switches CM1, CM2, CM3, CM4 and resistors R1, R2, R3, R4.
• the cathode of each diode LD1 to LD4 is connected to ground.
• each diode LD1 to LD4 is connected via a respective switch CM1 to CM4, to the input of one of the amplifiers A21 to A24 and to the output of one of the amplifiers A1 1 to A14.
• the output of each of the amplifiers A21 to A24 is connected to the input of an analog / digital converter of the CVM conversion module, which transmits to the RPRC device digital values of light intensity measurements LFL1, LFL2, LFL3, LFL4 provided. by the diodes LD1 to LD4.
• Each amplifier A1 1 to A14 is connected to a source of AV supply voltage via one of the resistors R1 to R4.
• Each amplifier A1 1 to A14 receives on a gain control input a current control signal AC1 to AC4 emitted by one of the regulators REG1 to REG4.
• Each regulator REG1 to REG4 performs a measurement of the supply current 11 to 14 of the diode LD1 to LD4 to which it is connected.
• Each regulator REG1 to REG4 receives a set current value LC1 to LC4 provided in digital form by the RPRC controller and converted by a digital-to-analog converter of the CVM module.
• Each regulator REG1 to REG4 regulates one of the current control signals AC1 to AC4 as a function of the value of the reference current LC1 to LC4 that it receives and as a function of the intensity of the current 11 to 14 that it measures. at the output of the amplifier A1 to A4 which it controls the gain, so that the current 11 to 14 measured corresponds to the value of the target current LC1 to LC4.
• the LSCC circuit or the LS light source may comprise a TSS temperature sensor for measuring the temperature of the LS source.
• the temperature sensor TSS is then connected to an analog digital converter of the CVM module, which supplies the device RPRC with digital values of temperature measurements TPL of the source LS.
• Each regulator REG1 to REG4 can transmit the current measurement 11 to 14 to an analog / digital converter of the CVM module, which in turn transmits a corresponding digital value to the RPRC device.
• the anode of each diode LD1 to LD4 may also be connected to an analog digital converter of the CVM module, which supplies the RPRC device with a digital value representative of the voltage V1 to V4 of the anode of the diode.
• the diodes LD1 to LD4 can be formed on the same semiconductor substrate and integrated in the same component.
• the RPRC device may comprise a connector for connecting by means of a serial or parallel DTB bus to a computer and for transmitting measurement spectra MR (1 ..n) and an operating state OMD, and possibly other signals for example relating to the measurements made on the spectrometer.
• the LS light source comprises four LEDs. Each LED can emit light having a spectrum of the shape of an asymmetrical Gauss curve.
• FIG. 3A represents emission spectra of the diodes LD1 to LD4, in the form of curves C1 to C4 of variation of luminous intensity emitted as a function of the wavelength.
• the curves C1 to C4 of FIG. 3A were obtained at constant and identical supply current for all the diodes LD1 to LD4.
• the luminous intensity values indicated on the ordinate axis are normalized values.
• the curve C1 of the spectrum of the diode LD1 has a maximum intensity of 1 at a wavelength equal to about 850 nm.
• Curve C2 of the LD2 diode spectrum has a maximum intensity at about 0.92 at a wavelength of about 890 nm.
• Curve C3 of the spectrum of the LD3 diode has a maximum intensity at about 0.41 at a wavelength of about 940 nm.
• Curve C4 of the spectrum of the LD4 diode has a maximum intensity at about 0.22 at a wavelength of about 970 nm. It can be noted in FIG. 3A that the longer the wavelength of the maximum light intensity emitted by the diode LD1 to LD4, the lower this intensity is.
• FIG. 3B represents, in the form of curves C1 'to C4' of variation of luminous intensity emitted as a function of the wavelength, the emission spectra of the diodes LD1 to LD4 after adjustment of the supply current LC1 to LC4; of each diode LD1 to LD4 by the regulator RPRC.
• the curves C1 'to C4' all have a maximum normalized intensity value of 1.
• FIG. 3B also shows in the form of a CR curve, a combined emission spectrum emitted when the diodes LD1 to LD4 are lit at the same time, with their LC1 to LC4 power supply adjusted.
• FIG. 3B represents, in the form of curves C1 'to C4' of variation of luminous intensity emitted as a function of the wavelength, the emission spectra of the diodes LD1 to LD4 after adjustment of the supply current LC1 to LC4; of each diode LD1 to LD4 by the regulator
• the combined emission spectrum of the light source is approximately 840 to 980 nm. It should be noted that the numerical values appearing in FIGS. 3A and 3B are given by way of example and may vary in particular as a function of the manufacturing conditions of the diodes.
• FIG. 4 shows sensitivity spectra of the LD1 diodes to
• LD4 in the form of curves C1 1 to C14 of variation of current intensity generated as a function of the wavelength. These spectra were obtained by measuring the intensity of the current generated by each diode LD1 to LD4 when the light-emitting surface thereof is subjected to a luminous flux of 1 mW / cm 2 and in the absence of a supply current. According to FIG. 4, the current generated by the diodes LD1 to LD4 reaches a few tenths of ⁇ when the diode is subjected to a luminous flux of 1 mW / cm 2 .
• the switches CM1 to CM4 are controlled so that only one of the diodes LD1 to LD4 is lit at a time, the other diodes being off (not receiving power supply) to operate in as photodiodes.
• the off LEDs each provide a LFL1 measurement to LFL4 (three four possible measurements) of the light intensity generated by the lit diode in their respective sensitivity spectrum.
• the circuit LSCC can be simplified by keeping only one of the regulators REG1 to REG4, and only one of the amplifiers A1 1 to A14.
• Each of the switches CM1 to CM4 then comprises a terminal connected to the output of the amplifier A1 1 to A14 remaining, a terminal connected to the anode of a diode LD1 to LD4 and a terminal connected to the input of one of the amplifiers A21 to A24.
• Switches CM1 to CM4 may be omitted if the regulators
• REG1 -REG4 (or the remaining regulator) sets their current input 11 to 14 to a floating potential and the amplifiers A1 1 to A13 (or the remaining amplifier) set their amplified current output to a floating potential.
• the resulting emission spectrum may not be fully covered by the combined sensitivity spectrum of the LD1 to LD4 diodes. It can then be expected to use a photodiode measuring the light intensity emitted directly by each lit diode. This photodiode may for example be integrated in the source LS.
• FIG. 5 represents an electronic control circuit LSC1 of a light source LS1, according to one embodiment.
• the light source LS1 differs from the light source LS in that it comprises a PHD photodiode.
• the circuit LSC1 differs from the LSCC circuit in that it comprises an additional amplifier A20 receiving the output signal of the photodiode PHD and supplying an electrical signal for measuring light intensity LFL0 to an analog / digital converter of the conversion module CVM.
• the digital value of the measurement LFL0 is used with the digital values of the measurements LFL1 to LFL4, by the regulator RPRC to regulate the luminous intensity provided by the source LS1.
• An example of a photodiode sensitivity spectrum is shown in FIG. 4.
• FIG. 4 An example of a photodiode sensitivity spectrum is shown in FIG. 4.
• the curve CP is substantially constant. (varies between 0.5 and 0.6) in the analysis wavelength band, approximately between 840 and 980 nm.
• Fig. 6 shows a sequence of steps that can be executed by the RPRC controller.
• the sequence of steps comprises steps S1 to S18.
• the device RPRC adjusts to a set value LCx the supply current (intensity or voltage) of a diode LDx of the light source LS (x being successively equal to 1, 2, 3 and 4 in the example of Figure 2).
• the value LCx is that of a predefined initial value or a value previously applied to the LDx diode.
• the RPRC device receives light intensity measurements LFLz (z being different from x) from the unlit LD1 -LD4 diodes, and optionally, a light intensity measurement LFL0 from a photodiode and a temperature measurement TPL from the TSS sensor.
• the RPRC determines by comparison whether the received light intensity measurements LFLz and temperature TPL are coherent with each other and with the current LCx supplied to the diode LDx.
• steps S4 and S5 make it possible to perform a self-diagnosis of the spectrometer in step S6.
• the spectrometer switches to a degraded OMD operating mode DG.
• the comparisons made in steps S4 and S5 reveal a malfunction and the spectrometer is in a degraded operating state DG, the spectrometer proceeds to step S18 in a fault mode DF in which it can no longer function. If the comparisons made in steps S4 and S5 do not reveal a malfunction, the RPRC performs the following steps S7 and S8.
• step S7 the RPRC device determines an optimum integration time ITy of each photosensitive cell y of the OPS sensor by means of a function f1 applied to the luminous intensities LFLz measured at the step S2.
• the function f1 can be determined by graphs giving the optimum integration time of each cell y of the OPS sensor, as a function of measurements of intensity of the emitted light LFLz provided by each diode operating in photodiode.
• step S8 the RPRC device compares for each cell y, the integration time ITy obtained at minimum values ITmy and maximum ITMy determined for the cell y. If the integration time ITy is between the minimum and maximum values ITmy, ITMy for each cell y, the device RPRC executes the steps S15 to S17 and then returns to the step S1 to execute a new regulation phase, otherwise it executes step S9.
• step S9 the RPRC device compares the optimum integration time ITy with the minimum integration time ITmy for each cell y for which the test at step S8 has not been verified. If the integration time ITy is less than the integration time ITmy for all or part of the cells y of the OPS sensor, the module RPRC executes the step S10, then the step S12, otherwise (case where the integration time ITy is greater than the maximum integration time ITMy for all or some of the cells y) it executes the steps S1 1 and S12. In step S10, the RPRC device decreases by one step STP the LCx supply current of the LED diode LDx.
• step S1 the RPRC device increments the LCx feed current of the LDx diode STP step.
• the RPRC device determines whether the new LCx supply current obtained in step S10 or S1 1 is between the minimum values LCmx and maximum LCMx determined for the LDx diode. If this is the case, the RPRC device returns to step S1 to execute a new regulation phase. In the opposite case, the device RPRC executes step S13 where it tests the OMD mode of operation of the spectrometer. If the OMD mode is normal NL, the RPRC device performs step S14 where the OMD operating mode switches to DG degraded mode. If in step S13, the OMD mode is degraded DG, the RPRC device performs step S18, where the OMD mode fails DF.
• steps S10 and S1 1 if the optimal integration time ITy determined for at least one photosensitive cell is outside the minimum and maximum thresholds ITmy and ITMy, the LDx diode LED LCx is added to the supply current LCx , a pitch STP of a certain amplitude, positive or negative (positive if the optimal integration time ITy is greater than the maximum threshold ITMy, and negative if this integration time is less than the minimum threshold ITmy).
• a new optimal integration time ITy is then again determined in steps S1 to S7 as a function of the new current LCx.
• the execution of steps S1 to S12 is repeated as long as the optimal integration time ITy is outside the thresholds ITmy and ITMy and as long as the current LCx is between the thresholds LCmx and LCMx.
• step S15 the RPRC device sets the integration time of each cell y of the OPS sensor to its optimum integration time ITy determined in step S7.
• step S16 the RPRC device acquires an MSxy measurement supplied by each cell y with the diode LDx on, as well as optionally, a measurement of the temperature TP of the product to be analyzed in the cell. FLC (TPP) and / or OPS sensor temperature measurement (TPS) and / or LS (TPL) source temperature measurement.
• step S17 the RPRC applies a correction to each measurement MSxy using a function f2 and provides a corrected measure MSCxy for each cell y. Function f2 is applied to the measured temperature TP (or measured temperatures) in step S16.
• the sequence of steps S1 to S18 thus makes it possible to obtain a corrected spectrum MSCx (1 ..n) for each LDx diode.
• the sequence of steps S1 to S15 is thus executed for each LDx diode of the source LS in order to obtain at least one MSCx spectrum (L.n) for each LDx diode.
• a resulting spectrum MR (1 ..n) is calculated by adding the spectra obtained with each diode LDx on, with a weighting coefficient Pxy specified for each diode LDx and each cell y of the sensor OPS:
• the weighting coefficients Pxy can be adjusted to give more importance to the useful signal in the resulting spectrum.
• the signals of the cells therein measuring the highest raw signals, and therefore providing the most reliable information (high signal-to-noise ratio) are associated with a higher weighting coefficient Pxy.
• the weighting coefficients Pxy are determined during the calibration phase and depend on the temperature TPL of the source LS.
• the resultant spectrum MR (1 ..n) obtained can also be averaged with several other successive spectra obtained, in order to obtain a spectrum that can be used by a device for regulating the operating parameters of a device. thermal motor.
• the number of MR spectra (1 ..n) used for this averaging can be increased by changing from the normal OMD operating mode NL to the degraded mode DG.
• Number of spectra obtained to average in normal mode can be of the order of 5 to 20, and in degraded mode, of the order of 100.
• the integration time ITy of all the photosensitive cells y of the OPS sensor can, in step S15, be set globally to the smallest integration time determined in step S7 for each cell y.
• the RPRC device performs a self-diagnosis of the spectrometer by distinguishing three modes of OMD operation of the spectrometer: the normal operating mode NL in which the spectrometer produces actionable measurements, the degraded DG operating mode in which the spectrometer always produces actionable measurements, but in abnormal conditions, and a fault mode DF in which the spectrometer is considered faulty and can no longer provide a usable measurement.
• the normal operating mode NL in which the spectrometer produces actionable measurements
• the degraded DG operating mode in which the spectrometer always produces actionable measurements, but in abnormal conditions
• a fault mode DF in which the spectrometer is considered faulty and can no longer provide a usable measurement.
• the time to provide a measurement is greatly increased or the degree of confidence in the measurements provided decreases (may be at the discretion of the user).
• the RPRC device may output a self-diagnostic signal indicating the OMD operating mode of the spectrometer. This signal can be transmitted for example to an on-board computer of the vehicle in which the spectrometer is embedded.
• FIG. 7 represents a graph of the LCx setpoint current supplied to an LED LDx of the source LS (ordinate axis) as a function of light intensity measurements LFLz or of the temperature TPL of the source LS (abscissa axis).
• This graph presents four lines D1, D2, D3, D4 passing through the origin O of the graph.
• the lines D1 and D2 delimit between them an operating zone 1 corresponding to the normal operating mode NL in which the LCx current supplied to an LED LDx of the source LS, the source temperature TPL and / or the measured luminous intensities LFLz have normal values (neither too low nor too high).
• the ordinate axis and the line D3 delimit between them an area 3a.
• Zones 3a and 3b correspond to fault mode DF in which the LCx current supplied to an LDx diode of the light source is strong and the light intensity supplied by the source is abnormally low, or in which the current supplied to the diode LDx is low and the temperature of the source TPL is abnormally high. Between zone 1 and zones 3a and 3b are zones 2a and 2b corresponding to the degraded operating mode DG.
• the minimum values LCmx and maximum LCMx of the supply current of each LDx diode result from tests carried out during a calibration phase to determine the ideal operating range of each of the light emitting diodes of the source LS.
• the maximum value LCMx is determined so as not to accelerate the aging of the diode.
• the minimum value LCmx may be chosen so as to ensure repeatability and stability of the luminous flux emitted by the diode.
• the minimum values ITmy and maximum ITMy of each cell y of the OPS sensor are also determined during the calibration phase by tests making it possible to determine an ideal operating range of the photosensitive cells y of the OPS sensor, considered independently or as a whole.
• the maximum value ITMy is determined in order to avoid saturation of the photosensitive cell y.
• the minimum value ITmy is determined so as to obtain a stable and repeatable signal, while respecting a minimum target value of signal / noise ratio, previously defined.
• the functions f1 and f2 used in steps S7 and S17 can be determined during the calibration phase.
• the function f1 giving the optimal integration time ITy of each cell y of the OPS sensor as a function of the light intensities LFLz measured by the unlit diodes LD1 -LD4 can be determined using one or more reference products, fluids or solid, with which a series of tests is carried out. For each of the reference products and each LED LDx, the supply current reference value LCx of the diode LDx is varied, and the luminous intensities LFLz measured by the diodes LD1 -LD4 extinguished and the possible photodiode PHD are stored. .
• an optimal integration time ITy is sought which makes it possible to obtain a luminous flux measured by the y-cell, stable and constant, that is to say substantially independent.
• the intensity of the luminous flux emitted by the source LS is to say substantially independent.
• the temperature of the TPL source if available, is also collected, as well as the product temperature TPP and the corresponding LCx current setpoint.
• the variations of the luminous intensities LFLz measured by each diode LD1 -LD4 extinguished and / or by the possible photodiode PHD, are such that for a part of the measurements carried out, the optimal integration time ITy is outside the predefined threshold values ITmy , ITMy.
• ITmy ITmy
• minimum and maximum values of correspondence between the light intensity measurements LFLz and the temperature TPL of the source LS (if it is available) are determined, and between the measurements of luminous intensity.
• the function f2 making it possible to correct the measurement of the luminous intensity MSxy supplied by each cell y as a function of the temperature TP, can be determined by a series of tests during which the temperature TPL of the source LS is independently varied, the TPS temperature of the OPS sensor and the TPP temperature of the product to be analyzed. These temperatures range from -40 to + 105 ° C, or ideally from -50 to + 150 ° C with at least one fluid or solid reference product. For each test, the MSxy intensity measurement values, LCx setpoint current and temperature are collected.
• the abacuses obtained make it possible to determine a corrected measure of luminous intensity MSCxy at the reference temperature as a function of the measurement of luminous intensity MSxy measured at ambient temperature by each photosensitive cell y, as a function of the temperatures TPL, TPP, TPS of the source LS, of the product in the measuring cell FLC and the OPS sensor, and as a function of the integration time ITy and the current LCx power supply of the LDx LED diode.
• the spectrometer that has just been described can thus function in a very wide range of temperatures, including with very large temperature differences between the product to be analyzed and the LS light source. It should be noted that this arrangement is obtained without using a complex reference channel requiring a second sensor which directly receives the light emitted by the source, as proposed in the patent application FR 2 940 447, but only with intensity measurements. luminous LFL0-LFL4 carried out directly on the luminous flux emitted by the LD1 -LD4 diodes, therefore at a lower cost and without increasing the size of the spectrometer.
• the regulation carried out by the sequence of steps S1 to S18 can be carried out on the basis of the temperature of the source TPL and / or the product to be analyzed TPP, or on the basis of the voltages Vx or Ix currents (x being between 1 and 4 in the example of Figure 2) measured in the circuit of Figure 2.
• the LFL1 -LFL4 light intensity measurements provided by the off diodes, the TPL temperature and / or the Vx voltages and / or the Ix currents can be used to check the correct operation of the PHD photodiode and the TSS temperature sensor. .
• control method is not limited to the use of light-emitting diodes as a light source.
• control method described above can be applied to any light source, whose emitted light intensity can be adjusted by the power supply of the light source.
• control method can be applied to other spectrometers than that described with reference to FIG. It is simply important that the integration time of the spectrometer sensor be adjusted, and that the spectrometer can provide measurements representative of the operation of the light source.
• the correction step of the spectral measurements obtained is also not necessary. It may indeed be considered to place the spectrometer in an enclosure whose temperature is kept constant, or to make a spectrum measurement only when the temperature of the spectrometer has reached a set temperature.
• the light source may comprise several groups of several light-emitting diodes having identical or substantially identical emission spectra, that is to say the drifts of manufacture. As a result, several diodes, i.e. all the diodes in each group can be lit at the same time.

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