EP1660866A1 - Measuring system for the optical characterization of materials and method for the implementation thereof by said system - Google Patents

Measuring system for the optical characterization of materials and method for the implementation thereof by said system

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Publication number
EP1660866A1
EP1660866A1 EP04767900A EP04767900A EP1660866A1 EP 1660866 A1 EP1660866 A1 EP 1660866A1 EP 04767900 A EP04767900 A EP 04767900A EP 04767900 A EP04767900 A EP 04767900A EP 1660866 A1 EP1660866 A1 EP 1660866A1
Authority
EP
European Patent Office
Prior art keywords
sample
optical
measuring
measurement
fibers
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP04767900A
Other languages
German (de)
French (fr)
Inventor
Stéphane Perquis
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
ColorDimensions
Original Assignee
ColorDimensions
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Filing date
Publication date
Application filed by ColorDimensions filed Critical ColorDimensions
Publication of EP1660866A1 publication Critical patent/EP1660866A1/en
Withdrawn legal-status Critical Current

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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
    • G01N21/55—Specular reflectivity
    • G01N21/57—Measuring gloss
    • 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
    • G01J3/46—Measurement of colour; Colour measuring devices, e.g. colorimeters
    • 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
    • G01N21/47—Scattering, i.e. diffuse reflection
    • G01N21/4738—Diffuse reflection, e.g. also for testing fluids, fibrous materials
    • G01N21/474—Details of optical heads therefor, e.g. using optical fibres
    • 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
    • G01N21/84—Systems specially adapted for particular applications
    • G01N21/88—Investigating the presence of flaws or contamination
    • G01N21/8806—Specially adapted optical and illumination features

Definitions

  • the invention relates to a measurement system for the optical characterization of materials and to a measurement method implemented by the system.
  • optical characterization of the materials means the measurement of the visual and optical properties of the materials such as the gloss - the surface condition, the transparency, the color effects (pigment color, pearlescent effect, metallic effect) so that the results are expressed as close as possible to the sensations of human vision and the most applicable for manufacturers controlling materials.
  • the production of materials has strongly evolved in recent years because to attract the eye of consumers and replace the traditional, uniform colors, designers use all the possibilities of finishing (glossy, matte and satin ...), of juxtaposition of colors ( speckled, printed effects ...), texture (veined, granita %) and pigment effect (metallic or pearly) at their disposal.
  • spectrophotometer manufacturers have manufactured multi-angle instruments that allow spectral analysis of paints with metallic and / or pearlescent effects from 3 to 7 angles. The measurements are not complete enough (too little angular information and no axial information) and the associated software does not allow satisfactory operation due to the insufficient number of measurement angles.
  • profilometers also called diffusometers. These instruments are very complete since they are capable of illuminating and measuring a point on a material in all directions. But they are not suitable for industrialists in a manufacturing process because: they are too slow (up to
  • the subject of the invention is a measurement system for the characterization of materials, that is to say the determination of their optical properties such as gloss, surface appearance, transparency, color (pigments and dyes).
  • the invention more particularly relates to a characterization system for measuring optics of a sample material comprising a sample illumination optical device, an optical device, for measuring the light reflected by the sample for treatment by a spectral decomposition device (diffraction grating or ' of a filter system) mainly characterized in that it comprises: - a mechanical structure supporting the optical measurement device placed above the sample, the optical measurement device comprising an optical system for simultaneously forming a measurement point, of the sample from several angles, comprising n optical fibers (102), n being strictly greater than two, these fibers being provided at their ends of a microlens (101), and being positioned at equal distance above the sample so as to be oriented in the direction of the sample to capture the light reflected by the sample.
  • a spectral decomposition device diffiffraction grating or ' of a filter system
  • the number n of fibers is advantageously equal to a few tens. In the embodiment described n is equal to 10.
  • the fibers are distributed at a predetermined distance above the sample in order to define the different measurement angles.
  • the illumination optic comprises a light source and an optical fiber provided at its end with a microlens transporting the light emitted by the source, this fiber being supported by the mechanical structure.
  • the illumination optic comprises a light source placed above the sample to be analyzed, provided with a focusing lens on the sample and being supported by the mechanical structure.
  • the measurement optic further comprises an optical fiber provided at its end with a microlens used for calibrating the system and a fiber provided at its end with a microlens used for controlling the illumination fiber, these two fibers being arranged. in a sector not occupied by the measuring fibers on the mechanical structure.
  • the measurement fibers and the control fibers are brought together and aligned in a mechanical system so that all of the fibers are positioned facing the slit (s) or points input of a spectral decomposition device.
  • the support of the optical device comprises a system for moving the illumination fiber above the sample at an angle ranging from 0 ° to -90 °.
  • the mechanical support structure of the optical measurement device comprises at least one hoop.
  • the sample holder has a turntable mounted on a sliding and tilting assembly for raising and lowering the sample and tilting it.
  • the system includes analysis and processing means.
  • the processing means comprise means for automatically controlling the mechanical structure.
  • the analysis means comprise a spectral decomposition device and a matrix sensor of the scientific video camera type.
  • the subject of the invention is also a method of measuring optical characterization implemented by the system which has just been described, consisting of: - illuminating the sample at a given angle, - acquiring a first series of measurements at by means of optical fibers simultaneously conveying the light reflected by the sample at angles defined by their respective positions relative to the sample, - acquiring several other series of measurements by rotating the sample or the optical measuring device with respect to to a measurement axis passing through the central measurement point of the sample up to one complete rotation with a predetermined increment of value, the method thus making it possible to obtain the measurement of the information of the colored reflection in all directions predetermined and taking into account the effects of matter.
  • FIG. 1 represents a diagram of a general view of the system according to the invention
  • FIG. 2A represents a partial diagram of the arch 301
  • FIG. 2B represents an alternative embodiment for the visualization optics
  • Figure 3 shows a perspective diagram of the system of the system according to the invention
  • Figure 4 shows a diagram of the illumination device and measuring according to a first embodiment
  • Figure 5 shows a diagram of the device of illumination and measurement according to a second embodiment
  • - Figure 6 shows a diagram illustrating the flow of light transported by the fibers arriving on the entry slit of a spectral decomposition device.
  • the system according to the invention comprises two functional assemblies for the actual measurement and a functional assembly for signal processing - and possibly the control of the assembly, this control also being able to be manual.
  • the system comprises: 1) - an optical device 100 comprising a measurement lens 101, 102, a sample illumination lens 103, a calibration device 104, 106 and a device for controlling the illumination optics 105, 107. 2) - a mechanical support structure 300 comprising , a support for the optical device 301 and a sample support 320: 302-305. 3) - means of analysis 400, 600 and processing 500 of the information extracted from the light flows transported by the optical device.
  • the optical measuring device comprises a set of microlenses 101 and optical fibers 102 for measuring.
  • Each microlens 101 is coupled to a fiber 102 so as to analyze the reflection of the sample from a very precise angle without the reflections from other angles disturbing the analysis.
  • the use of n fibers provided with microlenses allows n simultaneous angular measurements.
  • the fibers 102 have the function of simultaneously transporting the light reflected by the sample from several angles towards a spectral decomposition device.
  • the optical measurement device is composed of 28 optical fibers, 2 calibration fibers for the measurement in transmission and, lateral diffusion and a brightness measurement fiber 107 placed in the axis of illumination.
  • the illumination device comprises two fibers 103,
  • the illumination of the sample is ensured for example by • the fiber 103 serving for the transport of the light supplied by a source 110, coupled to the other end to a microlens 108.
  • This fiber and the associated microlens may be identical to of measuring fibers.
  • the light transport fiber is placed vertically above the sample and can be moved from 0 to -90 ° above the sample.
  • the second fiber 104 is used for calibrating the system and transports the light from the source through a fiber and a microlens 106 identical to the measurement fibers.
  • the microlens of this fiber is placed outside the measurement chamber and illuminates a white and diffusing calibration tile.
  • the third fiber 105 is used 'to directly control the state of the illumination source simultaneously with the measurements. It is this value which is used to calibrate all the measurements.
  • the measurement fibers and the illumination fiber 105 are gathered in a cable 120 connected by a connector 410 to a spectral decomposition device which is connected to a matrix sensor of the scientific video camera type 600 so that the captured light is analyzed and processed by the processing unit 500 to which is connected to the matrix sensor of the scientific video camera type.
  • the illumination device can, in a variant of embodiment illustrated in FIG.
  • optical support device is produced by a curved arch 301 pierced with n holes, ie 28 holes for the measurement fibers in the example given.
  • the arch is bent over 255mm and is 550mm high and 300mm wide, it is fixed on the basis of "the mechanical structure and is removable.
  • the arch 301 is designed to so as to ensure a pointing of the microlenses at the end of the fibers on the measured location of the sample 1.
  • the dimensions and the bending of the arch are chosen according to the samples and of the desired angular resolution.
  • the engine is controlled by integrated electronics 306, to the support, advantageously controlled by the processing and control unit 500.
  • the sample support comprises a rotating plate
  • the control of the movements of the plate is programmed to have, for example, an accuracy of 0.01mm relative to the optical part and to have a rapid triggering of the angular measurements every n degrees of axis.
  • Turntable 303 is driven by a belt
  • the mechanical device 305, 308, 309 under the plate is designed to compensate for the thickness and the inclination of the samples of variable shape and size and to allow the measurement point to be placed exactly under the optical device, at the point of convergence of the measurement beams and illumination beam.
  • the mechanical device comprises a mechanism for leveling the sample comprising two support axes 315 on which the plate slides during the ups and downs of the plate and motor assembly, for example manually driven by a pulley 310.
  • the mechanical device under the tray further comprises two bananas' 305 on which the tray, motor, raising / lowering mechanism which is moved over ⁇ 10 ° by a crank 311 rests. This set allows samples to swing by ⁇ 10 ° relative to the measuring point.
  • the mechanical structure 300 also comprises a base 302 which supports the mechanism for positioning the samples 320 and the arch, the bending of which begins above the measurement level 'zero' of the plate. In the practical embodiment, the base has a robustness making it possible to avoid any dimensional variation and supporting samples of more than 20kg.
  • the mechanical structure 300 is striated with grooves under the plate every 1 ° of axis and coupled to a detection optic situated under the plate making it possible to synchronize the axial position of the sample with the light source and a scientific video camera type matrix sensor.
  • the use of its ridges allows the use of a continuous motor while allowing synchronization of the axial positioning.
  • the processing unit is for example made " by a PC type computer or by processing electronics placed after the matrix sensor of the scientific video camera type, comprising a program implementing the sequence of movements, this program being able to include parameters selected by the operator according to the nature of the sample to be characterized and the desired precision of the movements of the sample holder.
  • the arch 301 is produced in one piece as is the case in the diagrams of Figures 1 and 3.
  • this arch comprises a measurement side 301 and an illumination side 201.
  • Figure 4 - illustrates this configuration.
  • the roll bar measures on the same axis as the illumination, providing better results for colorimetry than those obtained with conventional systems.
  • Another solution illustrated by the diagram in FIG. 5 can consist in making a mechanical support for the optical device in two distinct parts in which, the illumination part 201 is not on the arch as the part measures 301 (axis Z). This makes it possible to position the illumination in any direction and to measure the variations in color of the materials as a function of the position of the lighting.
  • the measurement part is organized in the same way as on the hoop which was previously described but is amputated of the lighting part: the arch only forms a half-arch.
  • the lighting part can be placed either below or above the measurement part.
  • the illumination part is connected to the measurement part above the center of the plate and functions in the same way as the illumination part represented in FIG. 4 since the source moves from 0 to -90 ° in moving along the hoop.
  • the illumination part is positionable in all axes and in combination with the angular movement of the source and allows to illuminate practically all directions.
  • the sample to be analyzed is placed in the center of the plate which is adjusted in height and inclination so that its surface is positioned horizontally exactly at the point of convergence of the measurement beams and the illumination beam.
  • the positioning adjustment can be done either manually or assisted by an optical system and automatically managed by the computer to allow perfect repeatability of repositioning of the samples.
  • the intensity and the value are measured source spectral thanks to the source measurement fibers and after processing by the spectral decomposition device and acquisition by the matrix sensor of the scientific video camera type.
  • This spectral value of the source is the reference for the calculation of the fluxes reflected by the sample towards the different optics, under the predefined angles.
  • a control calibration is carried out simultaneously to check for possible processing errors.
  • the processing unit controls the calibration and measurement sequence.
  • the calibration sequence is performed on a metal standard
  • the optical lenses are positioned on the arch at equidistance and for example at 25 cm from the sample every 3 ° of angle with an angular precision greater than - k - 2 minutes of angle (0.06 mm). It is possible to increase the accuracy of the system by positioning the optics on a larger arch. In this case, an identical spacing between the micro-lenses allows angular measurements to be made at all degrees of angle.
  • the light reflected by the sample is routed simultaneously by the 24 measuring optical fibers which point in front of the entry slit of a spectral decomposition device.
  • the connection between the fibers and the spectral decomposition device is ensured by a connector 410 for positioning on the frame of the spectral decomposition device 400.
  • the measurement and control information arrives simultaneously on the slot as illustrated in the diagram of the
  • a high quality image contains all the angular spectral information of the measured sample.
  • the measurement time is very short (from 3. to 0.1 seconds) and the processing is almost instantaneous.
  • the image is converted into spectra (bottom right, a section of the image at 550nm), saved as a function of the absolute axis and the calculated axis of the positioning of the sample.
  • a complete measurement is carried out after rotation of the plate.
  • the multispectral data file obtained following this complete measurement then contains all the spectral values of the sample, from all the angles measured and along all the axes.
  • the system which has just been described makes it possible to define the color quality of the material (existing values and new functions and indices), the brightness (the representation of the specular) and to translate the texture effects into information of variation in tone and of shine.
  • the illumination angle, rotation and inclination of the sample information is collected to highlight variations in hue and reflection of the material measured with great precision and perfect repeatability.
  • this measurement geometry is similar to a point illumination at 0 ° and a diffuse measurement (in the upper half sphere only). The sum of the measured spectral values makes it possible to find a value close to the spectral measurement values in normalized geometry 0 ° / Diffuse.
  • the angular offset of the source By shifting the illumination point from 0 ° to -10 ° every n degrees, the angular offset of the source generates different measurement angles relative to the axis of the specular (axis of reflection of the brightness), which increases the number of measurement references and the angular resolution.
  • a complete measurement with an angular resolution of one degree and a measurement every degree axis may take 30 to 90 seconds.
  • the multispectral values thus acquired provide all the brightness, surface texture and color information that is needed depending on the angle observation.
  • acquisitions will be made in several passes to refine the measurement resolution in certain axes and angles. For the measurements to be reliable and fast, we will only retain the significant values for calculations and graphical representations.

Abstract

The invention relates to a measuring system for the characterization of materials i.e. determination of the optical properties thereof such as brightness, surface aspect, transparency, color (pigments and colorants) and color effects (pearly or metallic). According to the invention, said system comprises an optical sample illumination device (110, 103, 108), an optical device (100) for measuring the light reflected by the sample for treatment by a spectral decomposition device, and a mechanical support structure (300) for the optical measuring device placed above the sample. The optical measuring device (101, 102) comprises a lens formed by several simultaneous measuring points at several angles of the sample.

Description

SYSTEME DE MESURE DE LA CARACTERISATION OPTIQUE DES MATERIAUX ET PROCEDE MIS EN ŒUVRE PAR LEDIT SYSTEME. SYSTEM FOR MEASURING THE OPTICAL CHARACTERIZATION OF MATERIALS AND METHOD IMPLEMENTED THEREWITH.
L'invention concerne un système de mesure pour la caractérisation optique des matériaux et un procédé de mesure mis en œuvre par le système. On entend par caractérisation optique des matériaux, la mesure des propriétés visuelles et optiques des matériaux telles que la brillance- l'état de surface, la transparence, les effets de couleur (couleur pigmentaire, effet nacré, effet métallisé) de telle sorte que les résultats soient exprimés de la manière la plus proche possible des sensations de la vision humaine et la plus applicable pour les industriels contrôlant les matériaux. La production des matériaux à fortement évolué ces dernières années car pour attirer l'œil des consommateurs et remplacer les traditionnelles couleurs , uniformes, les designers utilisent toutes les possibilités de finition (brillantes, mattes et satinées...) , de juxtaposition de teintes (les effets mouchetés, imprimés...), de texture (veiné, granité..) et d'effet pigmentaire (métallisé 'ou nacré) à leur disposition. Les industriels de la couleur qui englobent toutes les étapes de fabrication (de la conception au contrôle de l'aspect final du produit en passant par la fabrication des pigments et la préparation des matériaux aux étapes intermédiaires) rencontrent de réels problèmes de contrôle, de suivi et de communication avec les matériaux modernes qu'ils doivent reproduire en utilisant las appareils de mesure de la couleur existants . s En effet, ces professionnels utilisent les spectrophotomètres, car ces appareils utilisent des géométries de mesure recommandées et acceptées par la Commission Internationale de l'Eclairage (norme NF X 08-012) il y a vingt ans. Les conditions d'illumination et de mesure des échantillons utilisées par les spectrophotomètres définissent les conditions de mesure pour des échantillons plans, lisses, opaques et de couleur unie. Ces conditions de mesure ne sont plus adaptées aux contraintes des matériaux d'a jourd'hui. Les résultats colorimétriques sont calculés à partir d'une unique mesure monodirec ionnelle insuffisante qui ne permet ni la mesure uniquement de l'information colorée ni la prise en compte des effets de matière. Depuis 1990 et sous la pression des fabricants de peintures automobiles, les constructeurs de spectrophotomètres ont fabriqué des instruments multiangles qui permettent une analyse spectrale des peintures à effets métallisés et/ou nacrés sous 3 à 7 angles. Les mesures ne sont pas assez complètes (trop peu d'informations angulaires et aucune information axiale) et les logiciels associés n'en permettent pas une exploitation satisfaisante en raison du nombre d'angle de mesure insuffisant . Depuis quelques années, il existe également des instruments permettant de mesurer l'enveloppe de diffusion d'un matériau, ce sont des profilomètres également appelés des diffusomètres . Ces instruments sont très complets puisqu'ils sont capables d' illuminer et de mesurer un point sur un matériau dans toutes les directions. Mais ils ne conviennent pas aux industriels dans - un processus de fabrication car : ils sont trop__ lents (jusqu'àThe invention relates to a measurement system for the optical characterization of materials and to a measurement method implemented by the system. The term optical characterization of the materials means the measurement of the visual and optical properties of the materials such as the gloss - the surface condition, the transparency, the color effects (pigment color, pearlescent effect, metallic effect) so that the results are expressed as close as possible to the sensations of human vision and the most applicable for manufacturers controlling materials. The production of materials has strongly evolved in recent years because to attract the eye of consumers and replace the traditional, uniform colors, designers use all the possibilities of finishing (glossy, matte and satin ...), of juxtaposition of colors ( speckled, printed effects ...), texture (veined, granita ...) and pigment effect (metallic or pearly) at their disposal. Color manufacturers who include all stages of production (from design to control of the final appearance of the product, including the manufacture of pigments and the preparation of materials at intermediate stages) encounter real problems of control, monitoring and communication with modern materials that they have to reproduce using existing color measurement devices. s Indeed, these professionals use spectrophotometers, because these devices use recommended and accepted measurement geometries by the International Lighting Commission (standard NF X 08-012) twenty years ago. The conditions of illumination and measurement of the samples used by the spectrophotometers define the conditions of measurement for flat, smooth, opaque and solid color samples. These measurement conditions are no longer adapted to the constraints of today's materials. The colorimetric results are calculated from a single insufficient monodirectional measurement which neither allows the measurement only of the colored information nor the taking into account of the effects of matter. Since 1990 and under pressure from automobile paint manufacturers, spectrophotometer manufacturers have manufactured multi-angle instruments that allow spectral analysis of paints with metallic and / or pearlescent effects from 3 to 7 angles. The measurements are not complete enough (too little angular information and no axial information) and the associated software does not allow satisfactory operation due to the insufficient number of measurement angles. In recent years, there have also been instruments for measuring the diffusion envelope of a material, these are profilometers also called diffusometers. These instruments are very complete since they are capable of illuminating and measuring a point on a material in all directions. But they are not suitable for industrialists in a manufacturing process because: they are too slow (up to
30 minutes par mesure) , ils ne permettent de mesurer qu'un seul point sur des échantillons plans et ils ne sont pas associés à des logiciels adaptés à l'industrie de la colorimétrie moderne permettant de faire la synthèse de toutes les caractéristiques visuelles des matériaux. Ils sont par contre parfaitement adaptés pour l'industrie de l'image, la simulation des matériaux et la représentation d'objets de réalité virtuelle grâce à la mesure très précise de l'enveloppe, diffuse : la BRDF des matériaux (Bidirectional Réflectance Distribution Function : fonction de distribution de la réflexion d'un faisceau lumineux provenant de n' importe quelle direction sur un échantillon et analysé sous n'importe quel angle.) La présente invention a pour but' de remédier aux inconvénients de l'état- de la technique. L'invention a pour objet un système de mesure pour la caractérisation des matériaux c'est-à-dire la ' détermination de leurs propriétés optiques telles que la brillance, l'aspect de surface, la transparence, la couleur (pigments et colorants) et les effets de couleur (nacrés ou métallisés) . L'invention a plus particulièrement pour objet un système de mesure de caractérisation' optique d'un échantillon de matériau , comprenant un dispositif optique d'illumination de l'échantillon, un dispositif Optique , de' mesure de la lumière réfléchie par l'échantillon pour traitement par un dispositif de décomposition spectrale (réseau de diffraction ou ' d'un système de filtres) principalement caractérisé en ce qu'il comporte : - une structure _ mécanique support du dispositif de mesure optique placée au-dessus de l'échantillon, le dispositif optique de mesure comportant une optique de .formation simultanée d'un point de mesure, de l'échantillon sous plusieurs angles, comprenant n fibres optiques (102) , n étant strictement supérieur à deux, ces fibres étant munies en leur e trémité d'une microlentille (101), et étant positionnées à égale distance au-dessus de l'échantillon de manière à être orientées en direction de l'échantillon pour capter la lumière réfléchie par 1' échantillon. Le nombre n de fibre est avantageusement égal à quelques dizaines. Dans l'exemple de réalisation décrit n est égal à 10. Selon une autre caractéristique, les fibres sont réparties à une distance prédéterminée au dessus de l'échantillon afin de définir les différents angles de mesure . Selon une autre caractéristique, l'optique d'illumination comprend une source de lumière et une fibre optique munie en son extrémité d'une microlentille transportant la lumière émise par la source, cette fibre étant supportée par la structure mécanique. Selon une alternative à ce mode de , réalisation, l'optique d'illumination comprend une source de lumière placée au dessus de l'échantillon à analyser, munie d'une lentille de focalisation sur l'échantillon et étant supportée par la structure mécanique. L'optique de mesure comprend en outre une fibre optique munie en son extrémité d'une microlentille servant- au calibrage du système et une fibre munie en son extrémité d'une microlentille servant au contrôle de la fibre d'illumination ces deux fibres étant disposées dans un secteur non occupé par les fibres de mesure sur la structure mécanique . Selon une autre caractéristique, les fibres de mesure et les fibres de contrôle (calibrage et illumination) sont réunies et alignées dans un système mécanique de telle sorte que l'ensemble des fibres soit positionné face à la ou les fente (s) ou points d'entrée d'un dispositif de décomposition spectrale. Le support du dispositif optique comporte un système pour déplacer la fibre d'illumination au dessus de l'échantillon sous un angle allant de 0° à -90°. Selon une autre structure, la structure mécanique support du dispositif optique de mesure comporte au moins un arceau. Le support d'échantillon comporte un plateau rotatif monté sur un ensemble coulissant et basculant permettant de monter et descendre l'échantillon et de l'incliner. Selon une autre caractéristique, le système comprend des moyens d'analyse et de traitement. Avantageusement, les moyens de traitement comportent des moyens de pilotage automatique de la structure mécanique . Selon une autre caractéristique, les moyens d'analyse comportent un dispositif de décomposition spectrale et un capteur matriciel de type caméra vidéo scientifique. L'invention a également pour objet, un procédé 'de mesure de caractérisation optique mis en œuvre par le système qui vient d'être décrit consistant : - à illuminer l'échantillon sous un angle donné, - à acquérir une première série de mesure au moyen des fibres optiques acheminant simultanément la lumière réfléchie par l'échantillon sous des angles définis par leurs positions respectives par rapport à l'échantillon, - à acquérir plusieurs autres séries de mesures en faisant tourner l'échantillon ou le dispositif optique de mesure par rapport à un axe de mesure passant par le point central de mesure de l'échantillon jusqu'à une rotation complète avec un incrément de valeur prédéterminé, le procédé permettant ainsi d'obtenir la mesure de l'information de la réflexion colorée dans toutes les directions prédéterminées et la prise en compte des effets de matière.30 minutes per measurement), they only allow one point to be measured on flat samples and they are not associated with software suitable for the modern colorimetry allowing the synthesis of all the visual characteristics of the materials. On the other hand, they are perfectly suited for the image industry, the simulation of materials and the representation of virtual reality objects thanks to the very precise measurement of the diffuse envelope: the BRDF of materials (Bidirectional Reflectance Distribution Function : distribution function of the reflection of a light beam from n. any direction on a sample and analyzed from any angle) the present invention is intended 'to overcome the drawbacks of the Main the technical. The subject of the invention is a measurement system for the characterization of materials, that is to say the determination of their optical properties such as gloss, surface appearance, transparency, color (pigments and dyes). and color effects (pearlescent or metallic). The invention more particularly relates to a characterization system for measuring optics of a sample material comprising a sample illumination optical device, an optical device, for measuring the light reflected by the sample for treatment by a spectral decomposition device (diffraction grating or ' of a filter system) mainly characterized in that it comprises: - a mechanical structure supporting the optical measurement device placed above the sample, the optical measurement device comprising an optical system for simultaneously forming a measurement point, of the sample from several angles, comprising n optical fibers (102), n being strictly greater than two, these fibers being provided at their ends of a microlens (101), and being positioned at equal distance above the sample so as to be oriented in the direction of the sample to capture the light reflected by the sample. The number n of fibers is advantageously equal to a few tens. In the embodiment described n is equal to 10. According to another characteristic, the fibers are distributed at a predetermined distance above the sample in order to define the different measurement angles. According to another characteristic, the illumination optic comprises a light source and an optical fiber provided at its end with a microlens transporting the light emitted by the source, this fiber being supported by the mechanical structure. According to an alternative to this embodiment, the illumination optic comprises a light source placed above the sample to be analyzed, provided with a focusing lens on the sample and being supported by the mechanical structure. The measurement optic further comprises an optical fiber provided at its end with a microlens used for calibrating the system and a fiber provided at its end with a microlens used for controlling the illumination fiber, these two fibers being arranged. in a sector not occupied by the measuring fibers on the mechanical structure. According to another characteristic, the measurement fibers and the control fibers (calibration and illumination) are brought together and aligned in a mechanical system so that all of the fibers are positioned facing the slit (s) or points input of a spectral decomposition device. The support of the optical device comprises a system for moving the illumination fiber above the sample at an angle ranging from 0 ° to -90 °. According to another structure, the mechanical support structure of the optical measurement device comprises at least one hoop. The sample holder has a turntable mounted on a sliding and tilting assembly for raising and lowering the sample and tilting it. According to another characteristic, the system includes analysis and processing means. Advantageously, the processing means comprise means for automatically controlling the mechanical structure. According to another characteristic, the analysis means comprise a spectral decomposition device and a matrix sensor of the scientific video camera type. The subject of the invention is also a method of measuring optical characterization implemented by the system which has just been described, consisting of: - illuminating the sample at a given angle, - acquiring a first series of measurements at by means of optical fibers simultaneously conveying the light reflected by the sample at angles defined by their respective positions relative to the sample, - acquiring several other series of measurements by rotating the sample or the optical measuring device with respect to to a measurement axis passing through the central measurement point of the sample up to one complete rotation with a predetermined increment of value, the method thus making it possible to obtain the measurement of the information of the colored reflection in all directions predetermined and taking into account the effects of matter.
D'autres particularités et avantages de l'invention apparaîtront clairement à la lecture de "la description suivante qui est donnée à titre d'exemple non limitatif et en regard des dessins sur lesquels : la figure 1, représente un schéma d'une vue générale du système selon l'invention, la figure 2A, représente un schéma partiel de l'arceau 301, - la figure 2B, représente une variante de réalisation pour l'optique de visualisation, la figure 3, représente un schéma en perspective du système du système selon l'invention, la figure 4, représente un schéma du dispositif d'illumination et de' mesure selon un premier mode de réalisation, la figure 5, représente un schéma du dispositif d'illumination et de mesure selon un deuxième mode de réalisation, - la figure 6, représente un schéma illustrant le flux de lumière transportée par les fibres arrivant sur la fente d'entrée d'un dispositif de décomposition spectrale . Le système selon l'invention comprend deux ensembles fonctionnels pour la mesure proprement dite et un ensemble fonctionnel pour les traitements de signaux - et éventuellement le pilotage de l'ensemble, ce pilotage pouvant également être manuel . Comme cela est illustré par le schéma de la Figure 1, le système comprend : 1) - un dispositif optique 100 comprenant une optique de mesure 101, 102, une optique d'illumination de l'échantillon 103, un dispositif de calibrage 104, 106 et un dispositif de contrôle de l'optique d'illumination 105, 107. 2)- une structure mécanique support 300 comportant, un support du dispositif optique 301 et un support d'échantillon 320 : 302-305. 3)- des moyens d'analyse 400, 600 et de traitement 500 des informations extraites des flux de lumière transportés par le dispositif optique. On va maintenant détailler chacun de ces ensembles. On pourra se reporter indifféremment aux schémas des Figures 1, 2, 2B et 3 pour mieux comprendre.Other features and advantages of the invention will appear clearly on reading "the following description which is given by way of non-limiting example and with reference to the drawings in which: FIG. 1 represents a diagram of a general view of the system according to the invention, FIG. 2A represents a partial diagram of the arch 301, FIG. 2B represents an alternative embodiment for the visualization optics, Figure 3 shows a perspective diagram of the system of the system according to the invention, Figure 4 shows a diagram of the illumination device and measuring according to a first embodiment, Figure 5 shows a diagram of the device of illumination and measurement according to a second embodiment, - Figure 6, shows a diagram illustrating the flow of light transported by the fibers arriving on the entry slit of a spectral decomposition device. The system according to the invention comprises two functional assemblies for the actual measurement and a functional assembly for signal processing - and possibly the control of the assembly, this control also being able to be manual. As illustrated by the diagram in FIG. 1, the system comprises: 1) - an optical device 100 comprising a measurement lens 101, 102, a sample illumination lens 103, a calibration device 104, 106 and a device for controlling the illumination optics 105, 107. 2) - a mechanical support structure 300 comprising , a support for the optical device 301 and a sample support 320: 302-305. 3) - means of analysis 400, 600 and processing 500 of the information extracted from the light flows transported by the optical device. We will now detail each of these sets. Reference may be made to the diagrams in Figures 1, 2, 2B and 3 for better understanding.
Le dispositif optique- de mesure comporte un ensemble de microlentilles 101 et de fibres optiques 102 de mesures. Chaque microlentille 101 est couplée à une fibre 102 de manière à analyser la réflexion de l'échantillon sous un angle très précis sans que les réflexions pa asites provenant d'autres angles ne viennent troubler l'analyse. L'utilisation de n fibres munies de microlentilles permet n mesures angulaires simultanées. Les fibres 102 ont pour fonction le transport simultané de la lumière réfléchie par l'échantillon sous plusieurs angles vers un dispositif de décomposition spectrale. Dans l'exemple de réalisation donné le dispositif optique de mesure est composé de 28 fibres optiques, de 2 fibres de calibrage de la mesure en transmission et de , la diffusion latérale et d'une fibre de mesure de la brillance 107 placée dans l'axe d'illumination. Le dispositif d'illumination comporte deux fibres 103,The optical measuring device comprises a set of microlenses 101 and optical fibers 102 for measuring. Each microlens 101 is coupled to a fiber 102 so as to analyze the reflection of the sample from a very precise angle without the reflections from other angles disturbing the analysis. The use of n fibers provided with microlenses allows n simultaneous angular measurements. The fibers 102 have the function of simultaneously transporting the light reflected by the sample from several angles towards a spectral decomposition device. In the exemplary embodiment given, the optical measurement device is composed of 28 optical fibers, 2 calibration fibers for the measurement in transmission and, lateral diffusion and a brightness measurement fiber 107 placed in the axis of illumination. The illumination device comprises two fibers 103,
104, munies d'une lentille en extrémité 106, 108 et une- fibre 105. L'illumination de l'échantillon est assurée par exemple par • la fibre 103 servant au transport de la lumière fournie par une source 110, couplée à l'autre extrémité à une microlentille 108. Cette fibre et la microlentille associée peuvent être identiques aux fibres de' mesure. La fibre de transport de lumière est placée à la verticale au dessus de l'échantillon et peut être déplacée de 0 à -90° au dessus de ce dernier. La deuxième fibre 104 sert au calibrage du système et transporte la lumière de la source au travers d'une fibre et d'une microlentille 106 identiques aux fibres de mesure. La microlentille de cette fibre est placée en dehors de l'enceinte de mesure et illumine un carreau de calibrage blanc et diffusant. Ces fibres sont au-dessus d'un étalon de calibrage 2 placé sur un support 3. La troisième fibre 105 est utilisée' pour contrôler directement l'état de la source d'illumination simultanément aux mesures. C'est cette valeur qui est utilisée pour calibrer l'ensemble des mesures. Les fibres de mesure et la fibre d'illumination 105 sont rassemblées dans un câble 120 connecté par un connecteur 410 à un dispositif de décomposition spectrale lequel est relié à un capteur matriciel de type caméra vidéo scientifique 600 afin que la lumière captée soit analysée et traitée par l'unité de traitement 500 à laquelle est reliée au capteur matriciel de type caméra vidéo scientifique. Le dispositif d'illumination peut dans une variante.de réalisation illustrée par la Figure 2B, être réalisé par un système optique comprenant une source d'illumination 111, un ensemble optique de convection 112 du faisceau lumineux vers l'échantillon e un miroir 113 permettant de mesurer simultanément la qualité de la source (fibre 105) et la lumière réfléchie par l'échantillon (fibre 104). Une telle variante permet une illumination plus importante de l'échantillon avec une source moins puissante. Ce système peut être monté directement sur la structure support comme illustré sur la figure 2B. La structure mécanique 300 permet d'assurer une fonction support de l'ensemble mais aussi, des mouvements en particulier le mouvement du support d'échantillon. Dans un exemple de réalisation, le dispositif support de l'optique est réalisé par un arceau 301 cintré percé de n trous soit 28 trous pour les fibres de mesure dans l'exemple donné. Il comporte également plusieurs trous 200 pour la fibre d'illumination dont un trou principal 200 dans l'axe principal d'illumination Y qui permet le déplacement de la source de 0° à -10° tous les 1° comme on peut le voir sur le détail de la Figure 2A. Dans l'exemple particulier de réalisation qui est donné, l'arceau est cintré sur 255mm et fait 550mm de haut et 300mm de large, il est fixé sur la base de" la structure mécanique et est démontable. L'arceau 301 est conçu de manière à assurer un pointage des microlentilles en extrémité des fibres sur l'emplacement mesuré de l'échantillon 1. Les dimensions et le cintrage de l'arceau sont choisis selon les échantillons et de la résolution angulaire souhaitée. Le support d'échantillon 300 est motorisé, le pilotage du moteur est réalisé par une électronique 306 intégrée , au support, avantageusement commandée par l'unité de traitement et de commande 500. Le support d'échantillon comporte un plateau rotatif104, provided with a lens at the end 106, 108 and a fiber 105. The illumination of the sample is ensured for example by • the fiber 103 serving for the transport of the light supplied by a source 110, coupled to the other end to a microlens 108. This fiber and the associated microlens may be identical to of measuring fibers. The light transport fiber is placed vertically above the sample and can be moved from 0 to -90 ° above the sample. The second fiber 104 is used for calibrating the system and transports the light from the source through a fiber and a microlens 106 identical to the measurement fibers. The microlens of this fiber is placed outside the measurement chamber and illuminates a white and diffusing calibration tile. These fibers are above a calibration standard 2 placed on a support 3. The third fiber 105 is used 'to directly control the state of the illumination source simultaneously with the measurements. It is this value which is used to calibrate all the measurements. The measurement fibers and the illumination fiber 105 are gathered in a cable 120 connected by a connector 410 to a spectral decomposition device which is connected to a matrix sensor of the scientific video camera type 600 so that the captured light is analyzed and processed by the processing unit 500 to which is connected to the matrix sensor of the scientific video camera type. The illumination device can, in a variant of embodiment illustrated in FIG. 2B, be produced by an optical system comprising an illumination source 111, an optical assembly for convection 112 of the light beam towards the sample and a mirror 113 allowing to simultaneously measure the quality of the source (fiber 105) and the light reflected by the sample (fiber 104). Such a variant allows greater illumination of the sample with a less powerful source. This system can be mounted directly on the support structure as illustrated in Figure 2B. The mechanical structure 300 makes it possible to provide a support function for the assembly, but also movements, in particular the movement of the sample support. In an exemplary embodiment, the optical support device is produced by a curved arch 301 pierced with n holes, ie 28 holes for the measurement fibers in the example given. It also has several holes 200 for the illumination fiber including a main hole 200 in the main illumination axis Y which allows the movement of the source from 0 ° to -10 ° every 1 ° as can be seen on the detail of Figure 2A. In the particular embodiment which is given, the arch is bent over 255mm and is 550mm high and 300mm wide, it is fixed on the basis of "the mechanical structure and is removable. The arch 301 is designed to so as to ensure a pointing of the microlenses at the end of the fibers on the measured location of the sample 1. The dimensions and the bending of the arch are chosen according to the samples and of the desired angular resolution. motorized, the engine is controlled by integrated electronics 306, to the support, advantageously controlled by the processing and control unit 500. The sample support comprises a rotating plate
303. Le pilotage des mouvements du plateau est programmé pour avoir par exemple une précision de 0.01mm par rapport à la partie optique et pour avoir un déclenchement rapide des mesures angulaire tous les n degrés d'axe. Le plateau tournant 303 est entraîné par une courroie303. The control of the movements of the plate is programmed to have, for example, an accuracy of 0.01mm relative to the optical part and to have a rapid triggering of the angular measurements every n degrees of axis. Turntable 303 is driven by a belt
304 reliée à un moteur 307. Les échantillons plans ou ayant toujours la même forme sont positionnés sur un gabarit placé sur le plateau rotatif pour que leur surface soit horizontale et positionné au point de convergence des faisceaux de mesure et du faisceau d' illumination. Le dispositif mécanique 305, 308, 309 sous le plateau est conçu pour rattraper l'épaisseur et l'inclinaison des échantillons de forme et de dimension variables et pour permettre de placer le point de mesure exactement sous le dispositif optique, au point de convergence des faisceaux de mesure et du faisceau d'illumination. Le dispositif mécanique comporte un mécanisme de mise à niveau de l'échantillon comprenant deux axes de soutien 315 sur lesquels le plateau coulisse lors des montées et descentes de l'ensemble plateau et moteur, entraîne par exemple manuellement par une poulie 310. Le dispositif mécanique sous le plateau comporte en outre deux bananes' 305 sur lesquelles repose l'ensemble plateau, moteur, mécanisme de montée/descente qui est mu sur ±10° par une manivelle 311. Cet ensemble permet d'obtenir un balancement des échantillons de ±10° par rapport au point de mesure . La structure mécanique 300 comporte également une base 302 qui supporte le mécanisme de positionnement des échantillons 320 et l'arceau dont le cintrage commence au- dessus du niveau de mesure 'zéro' du plateau. Dans l'exemple de réalisation pratique, la base présente une robustesse permettant d'éviter toute variation dimensionnelle et supportant des échantillons de plus de 20kg. Dans l'exemple de réalisation pratique, la structure mécanique 300 est striée de rainures sous le plateau tous les 1° d'axe et couplée à une^optique de détection située sous le plateau permettant de synchroniser la position axiale de l'échantillon avec la source d'éclairage et un capteur matriciel de type caméra vidéo scientifique. L'utilisation des ses striures permet l'utilisation d'un moteur continu tout en permettant la synchronisation du positionnement axial. L'unité de traitement est par exemple réalisée" par un ordinateur de type PC ou par une électronique de traitement placée après le capteur matriciel de type caméra vidéo scientifique, comprenant un programme mettant en œuvre la séquence des mouvements, ce. programme pouvant comporter des paramètres sélectionnés par l'opérateur selon- la nature de l'échantillon à caractériser et la précision désirée des déplacements du support d'échantillon.304 connected to a 307 motor. Flat samples or samples that always have the same shape are positioned on a template placed on the turntable so that their surface is horizontal and positioned at the point of convergence of the measurement beams and the illumination beam. The mechanical device 305, 308, 309 under the plate is designed to compensate for the thickness and the inclination of the samples of variable shape and size and to allow the measurement point to be placed exactly under the optical device, at the point of convergence of the measurement beams and illumination beam. The mechanical device comprises a mechanism for leveling the sample comprising two support axes 315 on which the plate slides during the ups and downs of the plate and motor assembly, for example manually driven by a pulley 310. The mechanical device under the tray further comprises two bananas' 305 on which the tray, motor, raising / lowering mechanism which is moved over ± 10 ° by a crank 311 rests. This set allows samples to swing by ± 10 ° relative to the measuring point. The mechanical structure 300 also comprises a base 302 which supports the mechanism for positioning the samples 320 and the arch, the bending of which begins above the measurement level 'zero' of the plate. In the practical embodiment, the base has a robustness making it possible to avoid any dimensional variation and supporting samples of more than 20kg. In the practical embodiment, the mechanical structure 300 is striated with grooves under the plate every 1 ° of axis and coupled to a detection optic situated under the plate making it possible to synchronize the axial position of the sample with the light source and a scientific video camera type matrix sensor. The use of its ridges allows the use of a continuous motor while allowing synchronization of the axial positioning. The processing unit is for example made " by a PC type computer or by processing electronics placed after the matrix sensor of the scientific video camera type, comprising a program implementing the sequence of movements, this program being able to include parameters selected by the operator according to the nature of the sample to be characterized and the desired precision of the movements of the sample holder.
Selon un exemple de réalisation conduisant à réduire les coûts du système, l'arceau 301 est réalisé d'une seule pièce comme c'est le cas sur les schémas des Figures 1 et 3. Dans ce cas cet arceau comporte un côté mesure 301 et un côté illumination 201. La Figure 4 -illustre cette configuration. L'arceau effectue les mesures sur le même axe que l'illumination procurant de meilleurs 'résultats pour la colorimétrie que ceux obtenus avec les systèmes classiques.According to an exemplary embodiment leading to reducing the costs of the system, the arch 301 is produced in one piece as is the case in the diagrams of Figures 1 and 3. In this case this arch comprises a measurement side 301 and an illumination side 201. Figure 4 - illustrates this configuration. The roll bar measures on the same axis as the illumination, providing better results for colorimetry than those obtained with conventional systems.
Une autre solution illustrée par le schéma de la Figure 5 peut consister à réaliser une mécanique support du dispositif optique en deux parties distinctes dans laquelle, la partie illumination 201 n'est pas sur le arceau que la partie mesure 301 (axe Z) . Cela permet de positionner l'illumination dans n'importe quelle direction et de mesurer les variations de teinte des matériaux en fonction de la position de l'éclairage. La partie mesure est organisée de la même manière que sur l'arceau qui a été précédemment décrit mais est amputée de la partie illumination : l'arceau ne forme plus qu'un demi-arceau. La partie illumination peut être placée indifféremment en dessous ou au dessus de la partie mesure. Dans l'exemple de réalisation pratique, la partie illumination est reliée à la partie mesure au-dessus du centre du plateau et fonctionne de la même manière que la partie illumination représenté sur la figure 4 puisque la source bouge de 0 à -90° en bougeant le long de -l'arceau. La partie illumination est positionnable dans tous les axes et la combinaison avec le mouvement angulaire de la source et permet d'illuminer pratiquement toutes les directions. Dans un exemple de réalisation préféré on a choisi des lentilles montées en bout de fibres ayant une précision de visée de 0.1mm. Cela signifie que tout faisceau de lumière arrivant sur la microlentille avec un angle supérieur à 0.1° n'est pas pris en compte. Grâce à cette particularité, il est possible de mesurer des objets courbes sans que les différentes parties de l'objet ou une réverbération parasite influent sur la mesure .Another solution illustrated by the diagram in FIG. 5 can consist in making a mechanical support for the optical device in two distinct parts in which, the illumination part 201 is not on the arch as the part measures 301 (axis Z). This makes it possible to position the illumination in any direction and to measure the variations in color of the materials as a function of the position of the lighting. The measurement part is organized in the same way as on the hoop which was previously described but is amputated of the lighting part: the arch only forms a half-arch. The lighting part can be placed either below or above the measurement part. In the practical embodiment, the illumination part is connected to the measurement part above the center of the plate and functions in the same way as the illumination part represented in FIG. 4 since the source moves from 0 to -90 ° in moving along the hoop. The illumination part is positionable in all axes and in combination with the angular movement of the source and allows to illuminate practically all directions. In a preferred embodiment, we chose lenses mounted at the end of fibers having an aiming precision of 0.1mm. This means that any beam of light arriving on the microlens with an angle greater than 0.1 ° is not taken into account. Thanks to this feature, it is possible to measure curved objects without the different parts of the object or parasitic reverberation affecting the measurement.
On va maintenant détailler le fonctionnement du système de mesure selon la présente invention. L'échantillon à analyser est placé au centre du plateau qui est réglé en hauteur et en inclinaison pour que sa surface soit positionnée horizontalement exactement au point de convergence des faisceaux de mesure et du faisceau d'illumination. Le réglage du positionnement 'peut être fait soit manuellement soit de façon assistée par un système optique et- géré automatiquement par l'ordinateur pour permettre une parfaite répétabilité de repositionnement des échantillons . Lors de chaque acquisition, et -simultanément aux mesures angulaires, sont mesurées l'intensité et la valeur spectrale de la source grâce aux fibres de mesures de la source et après traitement par le dispositif de décomposition spectrale et acquisition par le capteur matriciel de type caméra vidéo scientifique. Cette valeur spectrale de la source est la référence pour le calcul des flux réfléchis par l'échantillon vers les différentes optiques, sous les angles prédéfinis. Un calibrage de contrôle est réalisé simultanément pour vérifier les erreurs de traitement possibles. L'unité de traitement pilote la séquence de calibrage et de mesures. La séquence de calibrage est réalisée sur un étalon métalliqueWe will now detail the operation of the measurement system according to the present invention. The sample to be analyzed is placed in the center of the plate which is adjusted in height and inclination so that its surface is positioned horizontally exactly at the point of convergence of the measurement beams and the illumination beam. The positioning adjustment can be done either manually or assisted by an optical system and automatically managed by the computer to allow perfect repeatability of repositioning of the samples. During each acquisition, and -simultaneously to the angular measurements, the intensity and the value are measured source spectral thanks to the source measurement fibers and after processing by the spectral decomposition device and acquisition by the matrix sensor of the scientific video camera type. This spectral value of the source is the reference for the calculation of the fluxes reflected by the sample towards the different optics, under the predefined angles. A control calibration is carried out simultaneously to check for possible processing errors. The processing unit controls the calibration and measurement sequence. The calibration sequence is performed on a metal standard
2, prévu à cet effet. Les lentilles optiques sont positionnées sur l'arceau à équidistance et par exemple à 25cm de' l'échantillon tous les 3° d'angle avec une précision angulaire supérieure à-k- 2 minutes d'angle (0.06mm). Il est possible d'augmenter la précision du système en positionnant les optiques sur un arceau plus grand. .Dans ce cas, un espacement identique entre les micrόlentilles permet de réaliser des mesures angulaires tous les degrés d'angle. Lors de chaque acquisition, la lumière réfléchie par l'échantillon est acheminée simultanément par les 24 fibres optiques de mesure qui pointent devant la fente d'entrée d'un dispositif de décomposition spectrale. La connexion entre les fibres et le dispositif ' de décomposition spectrale est assurée par un connecteur 410 de positionnement sur la monture du dispositif de décomposition spectrale 400. Les informations de mesure et de contrôle arrivent simultanément sur la fente comme l'illustre le schéma de la2, provided for this purpose. The optical lenses are positioned on the arch at equidistance and for example at 25 cm from the sample every 3 ° of angle with an angular precision greater than - k - 2 minutes of angle (0.06 mm). It is possible to increase the accuracy of the system by positioning the optics on a larger arch. In this case, an identical spacing between the micro-lenses allows angular measurements to be made at all degrees of angle. During each acquisition, the light reflected by the sample is routed simultaneously by the 24 measuring optical fibers which point in front of the entry slit of a spectral decomposition device. The connection between the fibers and the spectral decomposition device is ensured by a connector 410 for positioning on the frame of the spectral decomposition device 400. The measurement and control information arrives simultaneously on the slot as illustrated in the diagram of the
Figure 6. Une image de grande qualité contient toutes les informations spectrales angulaires de l'échantillon mesuré.Figure 6. A high quality image contains all the angular spectral information of the measured sample.
Le temps d'une mesure est très court (de 3.,à 0,1 secondes) et le traitement est presque instantané. L'image est convertie en spectres (à droite en bas, une coupe de l'image à 550nm) , sauvegardés en fonction de l'axe absolu et de l'axe calculé du positionnement de l'échantillon. Une mesure complète est réalisée après rotation co pète du plateau. Le fichier de données multispectrales obtenu à la suite de cette mesure complète contient alors toutes les valeurs spectrales de l'échantillon, sous tous les angles mesurés et suivant tous les axes.The measurement time is very short (from 3. to 0.1 seconds) and the processing is almost instantaneous. The image is converted into spectra (bottom right, a section of the image at 550nm), saved as a function of the absolute axis and the calculated axis of the positioning of the sample. A complete measurement is carried out after rotation of the plate. The multispectral data file obtained following this complete measurement then contains all the spectral values of the sample, from all the angles measured and along all the axes.
Le système qui vient d'être décrit permet de définir la qualité colori étrique du matériau (valeurs existantes et nouvelles fonctions et indices) , la brillance (la représentation du spéculaire) et de traduire les effets de texture en des informations de variation de tonalité et de brillance . Avec une gestion motorisée et contrôlée par l'ordinateur de l'angle d'illumination, de la rotation et de l'inclinaison de l'échantillon, on récupère des informations permettant de mettre en évidence les variations de teinte et de réflexion du matériau mesuré avec une grande précision et une parfaite répétabilité . Lorsque l'illumination s'effectue à 0° à la perpendiculaire de l'échantillon, cette géométrie de me-sure s'apparente à une illumination ponctuelle à 0° et à une mesure diffuse (dans la demi sphère supérieure seulement) . La somme des valeurs spectrales mesurées permet de retrouver une valeur proche des valeurs de mesure spectrales en géométrie normalisée 0°/Diffus. En décalant le point d'illumination de 0° à -10° tous les n degrés, le décalage angulaire de la source génère des angles de mesure différents par rapport à l'axe du spéculaire (axe de réflexion de la brillance) , ce qui permet d'augmenter le nombre de références de mesure et la résolution angulaire. Une mesure complète avec 'une résolution angulaire d'un degré et une mesure tous les degrés d'axe peut prendre 30 à 90 secondes. Après traitement par le dispositif de décomposition spectrale par le capteur matriciel de type caméra vidéo scientifique et par un ordinateur de type PC ou par une électronique de traitement placée après le capteur matriciel, les valeurs multispectrales ainsi acquises fournissent toutes les informations de brillance, d'état de surface et de couleur dont on a besoin en fonction de l'angle d'observation. Lorsque la structure de la surface ou la texture des échantillons le demande, on réalisera les acquisitions en plusieurs passes pour affiner la résolution de mesure dans certains axes et certains angles. Pour que les mesures soient fiables et rapides, on ne retiendra que les valeurs significatives pour les calculs et les représentations graphiques. The system which has just been described makes it possible to define the color quality of the material (existing values and new functions and indices), the brightness (the representation of the specular) and to translate the texture effects into information of variation in tone and of shine. With motorized and computer-controlled management of the illumination angle, rotation and inclination of the sample, information is collected to highlight variations in hue and reflection of the material measured with great precision and perfect repeatability. When the illumination is carried out at 0 ° perpendicular to the sample, this measurement geometry is similar to a point illumination at 0 ° and a diffuse measurement (in the upper half sphere only). The sum of the measured spectral values makes it possible to find a value close to the spectral measurement values in normalized geometry 0 ° / Diffuse. By shifting the illumination point from 0 ° to -10 ° every n degrees, the angular offset of the source generates different measurement angles relative to the axis of the specular (axis of reflection of the brightness), which increases the number of measurement references and the angular resolution. A complete measurement with an angular resolution of one degree and a measurement every degree axis may take 30 to 90 seconds. After processing by the spectral decomposition device by the matrix sensor of the video camera type scientific and by a PC-type computer or by a processing electronics placed after the matrix sensor, the multispectral values thus acquired provide all the brightness, surface texture and color information that is needed depending on the angle observation. When the surface structure or texture of the samples so requires, acquisitions will be made in several passes to refine the measurement resolution in certain axes and angles. For the measurements to be reliable and fast, we will only retain the significant values for calculations and graphical representations.

Claims

REVENDICATIONS
1. Système de mesure de caractérisation optique d'un échantillon de matériau comprenant un dispositif optique d'illumination de l'échantillon, un dispositif optique de mesure de la lumière réfléchie par l'échantillon pour traitement par un dispositif de décomposition spectrale, caractérisé en ce qu' il comporte : - une structure mécanique support (300) du dispositif- de mesure optique placée au-dessus de l'échantillon, - et en ce que le dispositif optique de mesure (10,0) comporte une optique (101, 102) de formation de plusieurs points de mesure spectrale simultanée sous plusieurs angles de l'échantillon (1) comprenant n^ fibres optiques (102), n étant strictement supérieur à deux, ces fibres étant munies en leur extrémité d'une microlentille (101), et étant positionnées à égale distance au-dessus de "l' échantillon de manière à être orientées en direction de l'échantillon pour capter la lumière réfléchie par l'échantillon.1. A system for measuring the optical characterization of a sample of material comprising an optical device for illuminating the sample, an optical device for measuring the light reflected by the sample for treatment by a spectral decomposition device, characterized in what it comprises: - a mechanical support structure (300) of the optical measurement device placed above the sample, - and in that the optical measurement device (10,0) includes an optic (101, 102) of forming several simultaneous spectral measurement points from several angles of the sample (1) comprising n ^ optical fibers (102), n being strictly greater than two, these fibers being provided at their end with a microlens (101 ), and being positioned equidistant above the sample so as to be oriented towards the sample to capture the light reflected by the sample.
2. Système de mesure de caractérisation optique d-'un échantillon selon la revendication 1, caractérisé en ce que n est égal à quelques dizaines, les fibres étant réparties a une distance prédéterminée au dessus de l'échantillon (1) sur un secteur d'ouverture α prédéterminée afin de définir les différents angles de mesure.2. Measuring system for optical characterization of a sample according to claim 1, characterized in that n is equal to a few tens, the fibers being distributed at a predetermined distance above the sample (1) over a sector d aperture α predetermined in order to define the different measurement angles.
3. Système de mesure de caractérisation optique d'un échantillon selon l'une quelconque des revendications précédentes, caractérisé en ce que l'optique d'illumination (110 ou 111) comprend une source de lumière (110) placée au t dessus de l'échantillon (1) et éventuellement si nécessaire d'une fibre optique (103) munie en son extrémité d'une microlentille (108) transportant la lumière émise par la source, cette fibre étant supportée par la structure mécanique . 3. A system for measuring the optical characterization of a sample according to any one of the preceding claims, characterized in that the illumination optics (110 or 111) comprises a light source (110) placed above t 'sample (1) and possibly if necessary an optical fiber (103) provided at its end with a microlens (108) transporting the light emitted by the source, this fiber being supported by the mechanical structure.
4. Système de mesure de caractérisation ' optique d'un échantillon selon les revendications précédentes, caractérisé en ce que l'optique de mesure (100) comprend en outre une fibre optique (104) munie en son extrémité d'une microlentille servant au calibrage du système et disposée dans un secteur non occupé par les fibres de mesure sur la structure mécanique et une fibre (105) servant au contrôle de la source d'illumination et assemblée en son extrémité aux fibres de mesure dans un câble 120 connecté à un système de diffraction.4. Characterization measuring system optics of a sample according to the preceding claims, characterized in that the optical measurement apparatus (100) further comprises an optical fiber (104) provided at its end with a microlens used for calibration of the system and arranged in a sector not occupied by the measurement fibers on the mechanical structure and a fiber (105) used for controlling the source of illumination and assembled at its end to the measurement fibers in a cable 120 connected to a system diffraction.
5. Système de mesure de caractérisation optique d'un échantillon selon la revendication- précédente, caractérisé en ce que la structure support (300) comporte des. moyens (200 ou 201) pour permettre le déplacement de l'optique d'illumination au dessus de l' échantillon ..sous un angle allant de 0° à -90° .5. A system for measuring the optical characterization of a sample according to the preceding claim, characterized in that the support structure (300) comprises. means (200 or 201) to allow the displacement of the illumination optics above the sample. . at an angle from 0 ° to -90 °.
6. Système de mesure de caractérisation optique d'un échantillon selon l'une quelconque des revendications précédentes, caractérisé en ce que la -structure mécanique support du dispositif optique de mesure comporte au moins un arceau (301) .6. Measuring system for optical characterization of a sample according to any one of the preceding claims, characterized in that the mechanical support structure of the optical measuring device comprises at least one hoop (301).
7. Système de mesure de caractérisation optique d'un échantillon selon l'une quelconque des- revendications précédentes, caractérisé en ce que le support d'échantillon comporte un plateau rotatif ((303) monté sur un ensemble coulissant et basculant (315, 305, 308, 309)) permettant de monter et descendre l'échantillon et de l'incliner.7. A system for measuring the optical characterization of a sample according to any one of the preceding claims, characterized in that the sample holder comprises a rotary plate ((303) mounted on a sliding and tilting assembly (315, 305 , 308, 309)) to raise and lower the sample and tilt it.
8. Système de mesure de caractérisation' optique d'un échantillon selon l'une quelconque des revendications précédentes, caractérisé en ce qu'il comprend des moyens d'analyse et de traitement (400, 500, 600).8. A system for measuring the optical characterization of a sample according to any one of the claims. above, characterized in that it comprises analysis and processing means (400, 500, 600).
9. Système de mesure de caractérisation optique d'un échantillon selon la revendication 7, caractérisé en ce que les moyens de traitement (500) comportent des moyens de pilotage automatique de la structure mécanique.9. A system for measuring the optical characterization of a sample according to claim 7, characterized in that the processing means (500) comprise means for automatically controlling the mechanical structure.
10. Système de mesure de caractérisation optique d'un échantillon selon 7, caractérisé en ce que les moyens d'analyse comportent un dispositif de décomposition spectrale (400) et un capteur matriciel de type caméra vidéo scientifique (600) . 10. A system for measuring the optical characterization of a sample according to 7, characterized in that the analysis means comprise a spectral decomposition device (400) and a matrix sensor of the scientific video camera type (600).
11. Procédé de mesure de caractérisation optique selon l'une quelconque des revendications précédentes caractérisé en ce qu'il consiste : - à illuminer l'échantillon sous un angle donné,. - à acquérir une première série de mesure au moyen des fibres optiques acheminant simultanément la lumière réfléchie par l'échantillon sous un angle défini par leur position respectives par rapport à l'échantillon, à acquérir plusieurs autres séries de mesures en faisant tourner l'échantillon ou le dispositif optique de mesure jusqu'à une rotation complète avec un incrément' de valeur prédéterminé. 11. Optical characterization measurement method according to any one of the preceding claims, characterized in that it consists in: - illuminating the sample at a given angle ,. - to acquire a first series of measurements by means of optical fibers simultaneously transporting the light reflected by the sample at an angle defined by their respective position relative to the sample, to acquire several other series of measurements by rotating the sample or the optical measuring device up to one complete rotation with an increment of predetermined value.
EP04767900A 2003-07-31 2004-07-15 Measuring system for the optical characterization of materials and method for the implementation thereof by said system Withdrawn EP1660866A1 (en)

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FR0309449A FR2858412B1 (en) 2003-07-31 2003-07-31 SYSTEM AND METHOD FOR MEASURING THE VISUAL ASPECT OF MATERIALS.
PCT/FR2004/050339 WO2005012883A1 (en) 2003-07-31 2004-07-15 Measuring system for the optical characterization of materials and method for the implementation thereof by said system

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JP6384183B2 (en) * 2014-08-05 2018-09-05 株式会社リコー Sample measuring apparatus and sample measuring program
US10564096B2 (en) * 2015-09-14 2020-02-18 University Of Florida Research Foundation, Incorporated Method for measuring bi-directional reflectance distribution function (BRDF) and associated device
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US20060274316A1 (en) 2006-12-07

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