EP1889038A2 - Device and method for optical characterisation of translucent and opaque bodies - Google Patents

Abstract

The invention relates to a device for optical characterisation of translucent and opaque bodies (2), comprising illumination means (3) with a light source (S), for emission of a light flux towards the body (2), a detection and analysis system (4) for the light flux transmitted or diffused (f<SUB>t/d</SUB>) by the body (2), device calibration means (10), comprising an optically neutral element (11) to be put in place of the body (2) in the light path such as to define a new measuring scale between a first level, corresponding to the optical signature for the optically neutral element (11) and a second level, corresponding to the optical signature of a completely opaque body. Optical characterisation devices.

Description

 DEVICE AND METHOD FOR OPTICAL CHARACTERIZATION OF TRANSLUCENT AND / OR OPAQUE BODIES

TECHNICAL AREA

The present invention relates to the general technical field of devices for optical characterization of bodies, and in particular of solid or fluid bodies. In particular, the present invention relates to the field of devices for optical characterization of objects or materials, intended for example to control the reproducibility of an industrial process.

The present invention relates more particularly to a device for optical characterization of a translucent and / or opaque body.

PRIOR ART

Devices are known to characterize optically transparent bodies, that is to say, in the sense of the invention, bodies that let the light and clearly distinguish the objects behind them. In particular, a perfectly transparent body is characterized by a zero optical density D. Thus, if the opacity O of the body is defined by the ratio of the incident luminous flux φj and the transmitted luminous flux φt (O = φi / φ _t ), then the optical density D is defined by the decimal logarithm of the opacity (D = log (O)). In the case of a perfectly transparent body, for which the transmitted flux φt is equal to the incident flux φj, the optical density D is zero (log (φj / φ _t ) = log 1 = 0). In the same way, there are known devices for optically characterizing opaque bodies. In the sense of the invention, an opaque body opposes the passage of light. In particular, a perfectly opaque body is characterized by an infinite optical density D.

Existing optical characterization devices generally employ a wide spectrum light source and are designed to perform spectral measurements of the scattered light either by reflection on the surface of the body, when the latter is opaque, or by transmission through the body, when the latter is transparent.

In particular, to measure the color of the opaque objects, colorimetric spectrophotometers with a diffuse geometry (using an integrating sphere) or with a directional geometry are generally used.

Such devices also make it possible to optically characterize transparent objects, by replacing the measurement in reflection used to characterize the opaque objects by a measurement in transmission. Hazemeters are also known which make it possible to characterize transparent objects by means of a measurement in transmission.

The known devices implement computer means that make it possible to present the results of the measurements in the form of spectral response curves. In particular, known devices use detectors and electronic processing units, including in particular digital analog converters.

The spectral response curves are the representation of a set of integrated data in a mathematical and physical model allowing the precise characterization of bodies, and in particular mixtures composed of pigments, particles and binders. The determination of these curves of Spectral response is particularly interesting on the industrial level, especially in the context of a process of manufacture of paint or auto body repair, in order to reproduce identically the pigment composition of the paint for example.

These known devices, if they can optically characterize reliably opaque or transparent objects, do not, however, reliably characterize translucent bodies.

In the sense of the invention, a translucent body is permeable to light, allows it to pass, but does not clearly distinguish the objects (including the contours of objects) placed behind him, and this in contrast to a transparent body.

The known devices have in fact insufficient sensitivity to discriminate the translucent bodies, and this for lack of sensitivity.

The known optical characterization devices use analog digital converters with a dynamic of 16 bits. This dynamic is sufficient to characterize transparent bodies, whose transparency varies between 100% and about 0.2%. In particular, only the first 9 bits are needed to encode the transparent bodies.

On the other hand, the optical signature of the translucent bodies generally corresponds to a transparency less than 0.1%, or even often less than 0.01%. The set of bits, and especially the last five, is therefore necessary to characterize the translucent bodies. However, the known devices offer a resolution of 0.01% maximum, this resolution corresponding to the eleventh bit approximately so that the twelfth, thirteenth, fourteenth, fifteenth and sixteenth bits are not used. It is therefore not possible, with the known devices, to characterize the translucent bodies, and in particular to determine the color of translucent bodies with high opacity.

Moreover, the known devices, in particular certain spectrophotometers, require, for the same transparent body to be characterized, to take two successive measurements of the sample to be analyzed and to characterize on the optical plane, for example a first measurement of the light energy. transmitted, then a second measurement of the reflected light energy, and while requiring a displacement of the sample to bring it and position it on the measuring device at the exact location for each measurement.

Such devices, not only are limited in their use to transparent bodies, but still, do not meet imperfectly conventional industrial constraints of efficiency, time saving and reliability. In addition, such devices require two successive and separate calibrations. The known devices require in fact a large number of manipulations and suffer from a significant risk of errors related in particular to the number of necessary manipulations.

SUMMARY OF THE INVENTION

The objects assigned to the invention therefore aim to remedy the drawbacks enumerated above and to propose a new device for optical characterization of translucent and / or opaque bodies making it possible to easily determine, with high precision and sensitivity, the optical characteristics of translucent and / or opaque bodies and in particular their color, their transparency, their optical density or any other optical characteristic well known to those skilled in the art. Another object of the invention is to propose a new device for optical characterization of translucent bodies, to accurately characterize such bodies, even when they have a high opacity.

Another object of the invention is to propose a new device for optical characterization of translucent bodies requiring, for its implementation, only standard components.

Another object of the invention is to propose a novel device for optical characterization of translucent and / or opaque bodies that is particularly simple and quick to use.

Another object of the invention is to propose a novel device for optical characterization of translucent and / or opaque bodies capable of presenting a broad spectrum of use.

Another object of the invention is to propose a new device for optical characterization of translucent bodies making it possible, using the same device, to measure different optical characteristics.

The objects assigned to the invention also aim at proposing a new method of optical characterization of translucent and / or opaque bodies which is particularly simple to implement and makes it possible to obtain directly usable results with great sensitivity.

Another object of the invention is to propose a new method of optical characterization of translucent and / or opaque bodies which make it possible to obtain several measurement values of the optical properties of the bodies without significantly lengthening the measurement time, nor complicating the measure itself. The objects assigned to the invention are achieved by means of an optical characterization device of a body 2, in particular a translucent and / or opaque body comprising: lighting means 3 comprising a light source S , able to emit a light flux φ _e towards the body 2, a detection and analysis system 4 of the light flux transmitted and / or scattered φt / d by the body 2,

means 10 for calibrating the device, comprising an optically neutral element 11 of known optical density D, which is finite and non-zero, intended to be positioned in place of the body 2 in the light path so as to define, by calibration of the device 1 on the base of said optically neutral element 11, a new measurement scale between a first level, corresponding to the optical signature of the optically neutral element 11, and a second level, corresponding to the optical signature of a perfectly opaque body .

The objects assigned to the invention are also achieved by means of a process for optical characterization of a body 2, in particular of a translucent and / or opaque body comprising: a step of measuring the optical characteristics of the body 2 during which the body 2 is illuminated by means of illumination 3 and the light energy transmitted and / or diffused by the body 2 is detected and analyzed,

a calibration step, preceding the measurement step, during which an optically neutral element 11 of known optical density, finite and non-zero, is interposed on the light path in the place of the body 2 and defined a new measurement scale between a first level, corresponding to the optical signature of the optically neutral element 11, and a second level, corresponding to the optical signature of a perfectly opaque body.

SUMMARY DESCRIPTION OF THE DRAWINGS

Other objects and advantages of the invention will appear in more detail on reading the description which follows, and with the aid of the accompanying drawings, given purely by way of non-limiting illustration, among which:

FIG. 1 illustrates a schematic diagram of the optical characterization device according to the invention.

FIG. 2 illustrates a detailed block diagram of an alternative embodiment of an optical characterization device according to the invention, said diagram showing in particular the means necessary for the optical characterization of the translucent bodies.

FIG. 3 illustrates a detailed block diagram of an alternative embodiment of an optical characterization device of a body according to the invention, said diagram showing in particular the technical means allowing the simultaneous optical characterization of the translucent bodies and or opaque.

BEST MODE OF REALIZING THE INVENTION

Figures 1 to 3 illustrate a device 1 for optical characterization of a translucent body and / or opaque 2 according to the invention. The term "optical characterization" refers to the measurement of the optical characteristics of the body, including its color, transparency, reflection, its optical density or any other optical characteristic well known to those skilled in the art.

Preferably, the device 1 according to the invention constitutes a device for characterizing the color of the body 2, and, even more preferably, a spectrophotocolorimeter.

In the sense of the invention, and as has been described above, a translucent body is a body permeable to light, which allows it to pass, but which does not clearly distinguish the objects placed behind it. In particular, a translucent body has a very high opacity and a non-zero optical density and relatively high, especially greater than 2.5 and for example between 2.5 and 6.

By the term "body" is meant here a solid material substance, liquid or gaseous. A translucent body may be in the form of an object or material having a pigment and / or particulate composition but not necessarily. For example, pure water, which has no composition neither pigmentary nor particulate, changes from a transparent state to a translucent state by simple change of physical state.

By way of illustrative and non-limiting example, frosted glass, plastics, paper, textiles, blinds, curtains and curtains, films or screens constitute, according to their composition, more translucent bodies. or less diffusing.

As illustrated in FIGS. 1 and 2, the device 1 according to the invention comprises lighting means 3, illustrated in full lines in FIG. 1 and in dotted lines in FIG. 2, comprising a light source S, capable of emitting a luminous flux, said emitted luminous flux φ _e , in the direction of the body 2, thus defining a light path. Ways lighting 3 advantageously have an extended spectrum and comprise a lamp L, preferably of spectrophotometric quality, formed for example by a xenon lamp, xenon flash or a halogen lamp. The lamp L thus advantageously forms a primary light source, the light source S, illuminated by the lamp L, then forming a secondary light source.

According to the invention, the optical characterization device is able to detect and analyze the light flux transmitted and / or diffused and / or reflected by different body types, and in particular the translucent and / or opaque bodies. For this purpose, it comprises the necessary means of detection and analysis of the luminous flux, whether the body 2 or the sample to be analyzed is a body or an object having optical transmission and / or reflection properties.

To this end, according to the invention, the device 1 comprises a system 4 for detecting and analyzing the light flux transmitted and / or scattered φ _{t / d} by the body 2 if the latter is at least partially translucent. The detection and analysis system 4 is illustrated in full lines in FIG. 1 and in dashed lines in FIG.

To this end, the device according to the invention may also comprise a detection and analysis system 4 'of the reflected light flux φ _r by the body 2 if the latter is at least partially opaque.

Thus, according to an alternative embodiment, the device for optical characterization of a body 2 according to the invention may be capable of providing an optical characterization of translucent and / or opaque bodies making it possible to characterize, substantially simultaneously, and by a single measurement and without moving the sample: on the one hand, the optical properties of the translucent materials by transmission by means of the device 4 for detecting and analyzing the luminous flux transmitted and / or diffused by a translucent body,

on the other hand, the optical properties of the translucent bodies and the opaque bodies by reflection by means of the detection and analysis system 4 'of the luminous flux reflected by the body 2 when the latter is to possess reflection properties, more or not, transmission and / or broadcast properties.

The device according to the invention therefore has the technical means necessary to analyze at one time a double beam whether it is a light beam transmitted and / or scattered on the one hand, and / or a reflected light beam of light. on the other hand (Fig. 3) on the other hand.

In particular, the detection and analysis system 4 of the transmitted and / or _scattered light flux φ _Vd advantageously comprises: an input optical device 5, formed for example by a suitable lens and situated in the extension of the light path, one or more sensors C1, C2 capable of reading the light energy and preferably comprising photocells, and an electronic processing unit 30 comprising in particular a CAN digital analog converter advantageously having a dynamic of 16 bits.

According to an essential characteristic of the invention, the device 1 comprises calibration means 10 of the device 1, designed to increase the sensitivity of the device 1 vis-à-vis the optical characterization of the translucent bodies. According to the invention, the calibration means 10 comprise an optically neutral element 11 of known optical density D, finite and not null, intended to be positioned in place of the body 2 in the light path extending between the light source S and the detection and analysis system 4 of the transmitted and / or scattered light flux φt _{/ d} so as to define, by calibrating the device 1 on the basis of the optically neutral element 11, a new measurement scale comprised between a first level, corresponding to the optical signature of the optically neutral element, and a second level, corresponding to the optical signature of a perfectly opaque body. Thus, compared to known devices whose measurement scale is between a so-called "white" level, corresponding to the optical signature of a perfectly transparent body, and a so-called "black" level, corresponding to the optical signature of a perfectly opaque body, the calibration means 10 and in particular the optically neutral element 11 make it possible to shift the scale of measurement, and in particular to shift the white level of the latter to a first level called "gray level" which then constitutes a new reference zero for the measurement.

The term "gray level" here simply means an intermediate level between the "white" level, corresponding to the optical signature of a perfectly transparent body and the "black" level, corresponding to the optical signature of a perfectly opaque body.

On the other hand, the term "optically neutral" refers to the fact that the optically neutral element 11 does not alter the spectral characteristics of the luminous flux, but merely has the effect of reducing the luminous intensity. It is indeed a filter reducing the luminous flux.

Thus, by knowing the optical characteristics of the optically neutral element 11, it is possible to reset the device 1, and in particular the detection and analysis system 4 of the transmitted and / or scattered light flux φ _{t / d} so that for the measure, the latter takes as a reference "zero" neither the "white" level, but the first level (or gray level) corresponding to the optical signature of the optically neutral element 11.

Advantageously, the optically neutral element 11 is formed by a filter 12 of neutral optical density (or neutral filter). The device 1 according to the invention preferably comprises a set of several neutral filters 12, of different optical densities D, so as to allow the user to select, according to the body 2 to be analyzed, the neutral filter 12 the most adapted.

According to a preferred embodiment, the calibration means 10 comprise a set of neutral filters of different optical densities which are arranged in a mobile charger, preferably motorized, such as a carousel, so as to allow the user to select easily the optically neutral element most suitable for the body 2 to be characterized.

Thus, when the optically neutral element 11 is positioned in place of the body 2, during calibration, it is in the path of the luminous flux while said body 2 is located outside said path. In particular, it is conceivable that the optically neutral element 11 and the body 2 may each occupy a distinct location in the path of the luminous flux, or, conversely, that they share alternately a same location.

Preferably, the light source S is collimated, preferably on a diameter of 0.1 mm to 40 mm and even more preferably on a diameter of 25 mm. The use of a collimated source S thus makes it possible to increase the light energy received by the body 2 and / or the optically neutral element 11 without modifying and in particular without increasing the power of the lamp L so as to avoid heating the lamp. device 1 and in particular heating the body 2 so as not to modify its optical characteristics. The collimated source S thus illuminates the body 2 or the optically neutral element 11 by means of a collimated light beam F which extends rectilinearly between the light source S and the input E of the detection system. analysis 4 of the transmitted and / or scattered light flux φ _{t / d} , materialized by the input optical device 5.

Preferably, the device 1 is configured such that the body 2 and / or the optically neutral element 11 is arranged so that its main extension plane is substantially perpendicular to the collimated light beam F.

Advantageously, the device 1 comprises a support 13 adapted to receive the body 2 to be characterized (FIGS. 1 and 2). Where appropriate, the support 13 may be arranged so as to alternatively receive the body 2 or the optically neutral element 11 of reference. The support 13 is advantageously arranged between the light source S and the detection and analysis system 4 of the transmitted and / or scattered light flux φ _{t / d} , at a distance X from the light source S and at a distance X 'from the light source S. detection and analysis system 4 of the transmitted and / or scattered light flux φ _{t / d} . The distances X and X 'are advantageously variable so as to allow the determination of several distinct optical characteristics of the body 2, in particular its color, or the energy transmitted or diffused by the body 2.

For this purpose, the support 13 is preferably mounted movable in translation between the light source S and the detection and analysis system 4 of the transmitted and / or scattered light flux φ _{t / d} so as to allow, depending on its position , the determination of distinct optical characteristics of the body 2. The support 13 may thus advantageously be secured to a carriage (not shown) capable of sliding between the light source S and the detection and analysis system 4 of the transmitted and / or scattered light flux φyd.

In order to measure the diffusion, it will thus be possible to bring the support 13 closer to the light source S, so that it occupies, for example, the position (I) illustrated in FIG. 1, the distance X being then less than half the sum of the distances X and X '(X <(X + X') / 2).

Conversely, for a measurement of the transmission, the support 13 of the detection and analysis system 4 will be brought closer to the transmitted and / or scattered light flux φ _{t / d} so that it occupies, for example, the position ( II) illustrated in FIG. 1, the distance X 'then being less than half the sum of the distances X and X' (X '<(X + X72).

Preferably, the distance d between the light source and the input E of the detection and analysis system 4 of the transmitted and / or scattered light flux φ _{t / d} is between 0 mm and 250 mm, and preferably from the order of 100 mm to allow a good optical characterization of translucent bodies. The light source S, the body 2 and / or the optically neutral element 11 and the optical input device 5 are advantageously aligned along the light beam F.

Advantageously, the electronic processing unit 30 includes software for automatically calibrating the device 1 on the basis of the measurement of the light energy effected with the optically neutral element 11.

In a particularly advantageous manner, the optical characterization device 1 is designed to take into account, as far as possible, the variations of light intensity of the lighting means 3 and in particular of the lamp L. The device 1 is thus configured so as to substantially simultaneously characterize the luminous flux emitted by the lighting means 3, in particular by the lamp L and the flux transmitted light and / or scattered φy _d by the body 2. The lighting means 3 and comprise a first and a second optical devices 6, 7 to respectively generate a first light beam F1, directed to the detection and analysis system 4 of the light flux transmitted and / or scattered φt / _d and whose light path passes through the body 2 and / or the optically neutral element 11, and a second light beam F2, directed to the detection and analysis system 4 of the light flux transmitted and / or scattered φ _{t / d} and whose light path is carried out without crossing, that is to say without encountering on its way, the body 2 and / or the optically neutral element 11.

According to a particularly advantageous characteristic of the invention, the detection and analysis system 4 of the transmitted and / or scattered light flux φt _{/ d} is designed to optically substantially simultaneously characterize the first and second beams F1, F2 and comprises effect first and second sensors C1, C2 respectively for detecting the first and second beams F1, F2. In particular, the first sensor C1 is designed and arranged to read the light energy transmitted and / or scattered by the body 2, the second sensor C2 being designed and arranged to read the light energy emitted by the means d 3, and in particular by the lamp L. Since the sensors C1, C2 are coupled to the digital analog converter CAN, it is possible to take into account, at each measurement, the possible variations in the intensity of the lamp L so as to take account of them. account in the result. This two-sensor configuration is particularly interesting compared to a conventional single-sensor configuration in that it allows the measurement in real time, that is to say without temporal shift, of the variations The first and second sensors C1, C2 advantageously make it possible to read spectra extending from 290 to 785 nanometers, from 310 to 1100 nanometers and from 190 to 720 nanometers, thus covering the entire spectral range. ranging from ultraviolet radiation to infrared radiation, through visible radiation.

According to another particularly advantageous characteristic of the invention, the device 1 takes into account, at each measurement, the specific noise of the detection and analysis system 4 of the transmitted and / or scattered light flux φ _{t / d} , and in particular the electronic variations of C1, C2 sensors.

For this purpose, the device 1 comprises a simultaneous switching device 20 of the first and second light beams F1, F2 so as to measure the own noise of the detection and analysis system 4 of the transmitted and / or scattered light flux φ _{t / d} , and in particular the noise of the sensors C1, C2.

Advantageously, the electronic processing unit 30, integrating the CAN digital analog converter, is operatively connected to the cut-off member 20 to control its actuation. In particular, the electronic processing unit 30 uses software that allows, before each measurement of the optical characteristics of the body 2, to automatically control the actuation of the cut-off device 20 so as to measure the noise of the detection system and The electronic processing unit 30 also makes it possible, using the aforementioned software, to perform the calibration of the device 1 according to the optical characteristics of the optically neutral element 11, and to calculate the curves. spectral corresponding to the body 2, taking into account the noise.

Preferably, the cutoff member 20 is formed by an opaque screen 21, or "shutter"("shutter" in English), mounted movably between a first position (i), shown in dashed lines in FIG. 2, in which it allows the passage of the two light beams F1, F2 and a second position (ii), shown in full lines in FIG. 2, in which it is opposes simultaneously with the passage of the two light beams F1, F2.

In the second position (ii) illustrated in FIG. 2, the opaque screen 21 is located simultaneously on the light paths of the two light beams F1, F2. In this second position (ii), the detection and analysis system 4 no longer detects the light energy emitted by the lamp L so that the detected quantity corresponds to its own noise. The clean noise can then be deduced from each measurement which makes it possible to significantly increase the accuracy of the device 1.

Particularly advantageously, the device 1 is placed in an opaque and closed enclosure coated inside an optical black, and this in order to avoid the disturbance of the measurements by the ambient light.

FIG. 3 illustrates a preferred variant of the invention corresponding to a polyvalent device for optical characterization of a body 2, in particular of translucent and / or opaque bodies, making it possible to characterize the optical properties of a translucent and / or opaque body simultaneously by a single measurement and without having to move the sample.

For this purpose, the device illustrated in FIG. 3 contains all the elements and functionalities illustrated in particular in FIG. 2 and previously described, a set of elements to which the flow detection and analysis system 4 'has been added. reflected light φ _r .

The detection and analysis system 4 'of the reflected light flux is functionally associated with the detection and analysis system 4 of the light flux transmitted and / or diffused so as to be able to characterize in one only operation the optical transmission and reflection properties of the body 2 to be characterized.

Thus, the hardware configuration described in Examples 1 and 2 above, all of whose functionalities are retained, is completed by an additional sensor C3 associated with a corresponding optics. The detection and analysis system 4 'of the reflected light flux φ _r thus comprises an optical device 5' for receiving the reflected light flux mounted on the support 13 adapted to receive the body 2 to be characterized, said optical device 5 'being connected by at least one sensor C3 for reading the reflected light energy, at the electronic processing unit 30 integrating the digital analog converter CAN. The latter is as for the previous examples, operatively connected to the cutoff 20 to control its actuation and ensure the associated function.

According to a particularly advantageous characteristic, the optical device 5 'for receiving the reflected light flux is positioned facing the sample, that is to say facing the body 2 to be characterized, so as to receive the reflected flux φ _r according to an inclined angle α (Figure 3) between approximately 43 to 47 ° of the incident normal of the body 2 to be characterized. In practice, the axis of the optical sensor included in the optical device 5 'is thus inclined by about 45 ° plus or minus 2 ° relative to the normal incident of the main face of the sample to be characterized.

The device thus formed and connected to the previously described electronic processing unit 30 thus forms a spectrophotometer with directional geometry 0745 °, double beam, adapted to the spectrophotometric measurements of the bodies by reflection in addition to the spectrophotometric measurements of the bodies by transmission. In general, the optical characterization device according to the invention may also comprise in addition to the various optical devices described above, a diffuse light measurement unit, of the hazemeter type (not shown in the figures). In such a case, the diffuse light measurement unit is advantageously positioned behind the body 2 to be characterized at a low angle of incidence, of the order of, for example, 4 °. Of course, the diffuse light measurement unit is, like the detection and analysis systems 4, 4 ', provided with suitable optical devices, which are connected to the electronic processing unit 30.

The set of detection and analysis systems 4, 4 'and possibly the diffuse light measuring unit are integrated in the device according to the invention so as to operate with the cut-off device 20 and the sensor C2. in order to measure the inherent noise of the detection and analysis system 4, 4 'or the diffuse light measuring unit.

The present invention also relates to a method for the optical characterization of a body 2, in particular of a translucent and opaque body 2 comprising: a step of measuring the optical characteristics of the body (2) during which the light is illuminated, using lighting means (3), the body (2) and detecting and analyzing the light energy transmitted and / or scattered by the body (2), a calibration step, preceding the measuring step, during which an optically neutral element (11) of known optical density, finite and non-zero, is interposed in the light path in the place of the body (2), and a new measurement scale between a first corresponding to the optical signature of the optically neutral element (11), and a second level, corresponding to the optical signature of a perfectly opaque body.

Thus, the measurement step is carried out on the basis of the new measurement scale thus defined, from the first level, which then constitutes the new reference, which makes it possible to increase the sensitivity of the device 1 and in particular of the system of measurement. detection and analysis 4 of the transmitted and / or scattered light flux φ _{t / d} with respect to known devices.

Advantageously, during the measuring step, the luminous flux emitted by the light-transmitting and / or scattered light sources φt / _d is characterized substantially simultaneously by means of the detection and analysis system 4 of the transmitted and / or scattered light flux. lighting 3, and the light flux transmitted and / or scattered φ _{t / d} by the body 2 so as to take into account, to the extent, the variations in light intensity of the lighting means 3. With this method, it is possible to controls at each measurement the variations of luminous intensity. lighting means 3 and in particular the lamp L so as to correct the measurement as a function of the variations and the drift thereof.

Advantageously, the simultaneous characterization of the emitted light flux and of the transmitted and / or scattered light flux φ _t / d takes place via a two-beam configuration comprising a first light beam F1, whose light path passes through the body 2 and / or the optically neutral element 11 before joining the detection and analysis system 4, and a second light beam F2, whose light path preferably directly joins the detection and analysis system 4 of the transmitted light flux and / or scattered φt _{/ d} , without passing through the body 2 and / or the optically neutral element 11. In a particularly advantageous manner, the method comprises, before the measurement step, a noise evaluation step of the detection and analysis system 4 of the transmitted and / or scattered light flux φ _{t / d} , during which one substantially cuts simultaneously, with the aid of a cut-off device 20, such as a shutter, the first and second light beams F1, F2 so as to isolate and evaluate the system's own noise. of detection and analysis 4 of the transmitted and / or scattered light flux φt _{/ d} - In particular, this step aims to evaluate the noise of the two sensors C1 and C2.

The device for optical characterization of a body 2 illustrated in FIG. 3 can also implement a method of optical characterization of a particularly interesting body 2.

This is a method of optical characterization of a body 2, in particular of a translucent and / or opaque body comprising, in accordance with the optical characterization method previously described and further comprising a measurement step in reflection during from which is detected and analyzed the light energy reflected by the body (2) and a calibration step, preceding the measurement step in reflection, during which is interposed, in the light path, instead body (2) standards, preferably white and black, calibration by reflection.

Preferably, the luminous energy transmitted and / or diffused, and / or, on the other hand, reflected during a same step of measuring the optical characteristics of the body 2 is analyzed and detected substantially simultaneously.

Calibration standards for reflection measurement and transmission are interposed successively and immediately one after the other. The two operations are therefore successive and in any order if one prefers to perform the reflection calibration first. Preferably, the reflection calibration and the transmission / diffusion calibration during which an optically neutral element 11 is interposed in the light path and a new measurement scale are defined in one and the same calibration step.

The presence in the device of the two detection and analysis systems 4, 4 'advantageously makes it possible to characterize substantially simultaneously, by a single measurement and without moving the sample, the optical properties of translucent materials by transmission on the one hand and the optical properties of the translucent bodies and opaque bodies by reflection by means of the directional geometry 0745 ° previously described and corresponding to the use of the detection and analysis system 4 'of the reflected light flux on the other hand.

The method therefore makes it possible to characterize the optical transmission and / or reflection properties of the body 2 in a single operation without moving said body.

Particularly advantageously, the luminous flux reflected from the body 2 is measured at an incidence angle of between approximately 43 and 47 °, preferably approximately 45 °, with respect to the normal direction of the surface of the body 2.

The method may also comprise a step during which the diffuse light is measured in addition, simultaneously or not, with the transmission and reflection measurements.

In such a case, the diffuse light measurement is performed at a low angle of incidence, of the order of, for example, about 4 °. During the step of measuring the luminous flux, the luminous flux emitted by the lighting means 3, and the transmitted luminous flux are characterized substantially simultaneously by means of the detection and analysis systems 4, 4 '. and / or scattered (φ _t / _d ) and / or reflected by the body 2 so as to take into account in the measurement, the variations in light intensity of the lighting means.

According to the method, the simultaneous characterization of the emitted light flux and the transmitted and / or scattered light flux (φ _{t / d} ) and / or reflected is effected by means of a two-beam configuration similar to that described above, the reflected light flux (φ _r ) being generated by reflection of all or part of the first beam F1 on the body 2 while the second light beam F2 joins the detection and analysis system 4, 4 'without passing through the body 2.

Finally, the method comprises, before the measuring step, a step of evaluating the noise of the detection and analysis systems 4,4 ', during which a substantially cut-off device is cut off simultaneously. 20, the first and second light beams F1, F2, so as to isolate and evaluate the noise of the specific detection and analysis systems 4,4 '.

Finally, after the calibration operations of the transmission geometry of the luminous flux on the one hand and the directional geometry of the luminous flux on the other hand, each measurement on a sample or a body 2 can simultaneously give the results of the optical properties of the body in transmission and reflection.

In a particularly preferred manner, the characterization method according to the invention will constitute a method for determining the color of the body 2. In particular, the measurement step (s) may be repeated for a plurality of wavelengths to form one or more spectral response curves.

The modes of operation and use of an alternative embodiment of the device 1 according to the invention will now be described with reference to FIGS. 1 and 2.

In order to characterize, using the device 1, a translucent body 2, for example an object or a translucent material, the operator first determines the optical density of the neutral filter 12 that is the most suitable and the closest to the optical characteristics of the translucent body 2 to analyze. For this purpose, the operator has, within the device 1, a set of optically neutral elements 11 of variable optical densities.

The operator then determines the distances X, X 'separating the support 13 from the light source S and the detection and analysis system 4 enabling it to better evaluate the optical characteristics and for example the color and / or the density optical translucent body 2 to characterize.

Once the optically neutral element 11 is arranged on the light path, the operator can proceed to the calibration of the device 1 using the software associated with the electronic processing unit 30. Thanks to this calibration, the operator defines a new measurement scale with a new "zero", offset from the white level corresponding to the optical signature of perfectly transparent bodies.

Once the calibration step has been completed, the operator replaces the optically neutral element 11 with the translucent body 2 to be analyzed, without changing the positioning of the support 13 in order to measure the optical characteristics of the translucent body 2, based on the new reference "zero" above-mentioned.

Before each measurement, the device 1 automatically proceeds to a noise evaluation step of the detection and analysis system 4 in order to take it into account in the calculations of the optical characteristics of the translucent body 2.

If the sensitivity obtained with the neutral filter 12 initially selected is not sufficient, the operator can proceed to a new measurement sequence, using a neutral filter 12 of higher optical density, closer to the optical characteristics of the translucent body 2 to analyze.

The optical characterization device 1 according to the invention therefore makes it possible to analyze with high sensitivity translucent and / or opaque bodies having a high opacity and in a simple, automatic and reproducible manner.

POSSIBILITY OF INDUSTRIAL APPLICATION

The invention finds its industrial application in the production of optical characterization machines of translucent and / or opaque bodies, and in particular in the determination of the color of parts or paint compositions.

Claims

- Device for optical characterization of a body (2), in particular a translucent and / or opaque body comprising: lighting means (3) comprising a light source (S), able to emit a luminous flux (φ _e ) in the direction of the body (2), a detection and analysis system (4) of the transmitted and / or diffused light flux (φ _t / _d ) by the body (2), calibration means (10) of the device, comprising an optically neutral element (11), of known optical density (D), finite and non-zero, intended to be positioned in place of the body (2) in the light path so as to define, by calibration of the device ( 1) on the basis of said optically neutral element (11), a new measurement scale between a first level, corresponding to the optical signature of the optically neutral element (11), and a second level, corresponding to the optical signature of a perfectly opaque body.

- Device according to claim 1 characterized in that the optically neutral element (11) is formed by a filter (12) of neutral optical density.

- Device according to claim 1 or 2 characterized in that the light source (S) is collimated.

- Device according to claim 1, 2 or 3 characterized in that the light source (S) is collimated over a diameter of 0.1 mm to 40 mm, preferably on a diameter of 25 mm. - Device according to one of the preceding claims characterized in that the lighting means (3) comprise a first and a second optical devices (6, 7) for respectively generating a first light beam (F1), whose light path passes through the body (2) before joining the detection and analysis system (4) and a second light beam (F2) whose light path joins the detection and analysis system (4) of the transmitted light flux and / or diffused (φ _{t / d} ) without passing through the body (2).

- Device according to claim 5 characterized in that the system for detecting and analyzing (4) the transmitted and / or diffused light flux (φ _{t /} d) is designed to optically substantially simultaneously characterize the first and second light beams ( F1, F2).

- Device according to one of claims 5 to 9 characterized in that the detection system and analysis (4) of the transmitted and / or diffused light flux (φ _{t / d} ) comprises a first and a second sensors (C1, C2), respectively for detecting the first and second beams (F 1, F 2).

- Device according to one of claims 1 to 7 characterized in that it comprises a support (13) adapted to receive the body (2), said support (13) being movably mounted in translation between the light source (S) and the detection and analysis system (4) of the transmitted and / or scattered light flux (φ _{t / d} ) so as to allow, according to its position, the determination of distinct optical characteristics of the body (2).

- Device according to one of the preceding claims characterized in that the distance (d) between the light source (S) and the input (E) of the detection and analysis system (4) of the transmitted light flux and / or diffused (φ _{t / d} ) is between 0 mm and 250 mm, and preferably of the order of 100 mm.

- Device according to one of the preceding claims characterized in that the detection system and analysis (4) of the transmitted and / or diffused light flux (ψt / _d ) comprises an analog digital converter (CAN) having a dynamic of 16 bits.

-Dispositif according to one of the preceding claims characterized in that the lighting means (3) have an extended spectrum and comprise a lamp (L) of spectrophotometric quality, for example a Xenon lamp, Xenon flash or a halogen lamp.

- Device according to one of the preceding claims characterized in that it further comprises a detection and analysis system (4 ') of the reflected light flux (φ _r ) by the body (2), the calibration means ( 10) of the device comprising the necessary standards, preferably white and black, calibration by reflection.

-Dispositif according to claim 12 characterized in that the detection and analysis system (4 ') of the reflected light flux (φ _r ) is functionally associated with the detection and analysis system (4) of the transmitted light flux and / or diffused (φ _{t / d} ) so as to be able to characterize in a single operation the optical transmission and reflection properties of the body (2) to be characterized.

- Device according to claim 12 or 13 characterized in that the detection and analysis system (4 ') of the reflected light flux (φ _r ) comprises an optical device (5') for receiving the reflected light flux mounted on a support (13) adapted to receive the body (2) to be characterized, said optical device (5 ') being connected by at least one sensor (C3) for reading the reflected light energy to an electronic processing unit (30).

- Device according to claim 14 characterized in that the optical device (5 ') for receiving the reflected light flux is positioned to receive said reflected light flux at an inclined angle between about 43 and 47 ° of the normal incident of the body (2) to characterize.

- Device according to claim 5 and one of claims 12 to 15 characterized in that the reflected light flux (φ _r ) is generated by reflection of all or part of the first beam (F1) on the body (2).

- Device according to one of claims 5 to 7 and / or according to claim 16 characterized in that it comprises a switching member (20) simultaneously the first and second light beams (F1, F2) so as to measure the noise own of the detection and analysis system (s) (4,4 ').

- Device according to claim 17 characterized in that it comprises an electronic processing unit (30), operably connected to the cut-off member (20) to control its actuation.

- Device according to claim 17 or 18 characterized in that the cutoff member (20) is formed by an opaque screen (21) movably mounted between a first position (i), in which it allows the passage of the two light beams ( F1, F2) and a second position (ii), in which it simultaneously opposes the passage of the two light beams F1, F2. - Device according to one of the preceding claims characterized in that it further comprises a diffuse light measuring unit, the kind of hazemeter.

- Device according to claim 20 characterized in that the diffuse light measuring unit is positioned behind the body (2) to be characterized at a low angle of incidence, of the order of eg 4 °.

- Device according to one of the preceding claims characterized in that the calibration means (10) comprise a set of neutral filters of different optical densities, said filters being arranged in a mobile charger, such as a carousel, so as to allow the user to select the optically neutral element most suitable for the body (2) to be analyzed.

- Device according to one of the preceding claims characterized in that it constitutes a device for optical characterization of the body color (2) spectrophotocolorimeter type.

Optical characterization method for a body (2), in particular a translucent and / or opaque body comprising: a step of measuring the optical characteristics of the body (2) during which light is illuminated, with the aid of lighting means (3), the body (2) and the light energy transmitted and / or diffused by the body (2) is detected and analyzed, a calibration step, preceding the measurement step, during the which is placed in the light path, in place of the body (2), an optically neutral element (11) of known optical density, finite and non-zero, and defines a new scale of measurement between a first level, corresponding to the optical signature of the optically neutral element (11), and a second level, corresponding to the optical signature of a perfectly opaque body.

- Method according to claim 24 characterized in that during the measuring step is characterized substantially simultaneously, with the aid of a detection system and analysis (4) of the light flux transmitted and / or broadcast (φ _{t / d} ), the luminous flux emitted by the lighting means (3), and the light flux transmitted and / or diffused (φ _{t / d} ) by the body (2) so as to take into account in the measurement, the variations in light intensity of the lighting means (3).

- Method according to claim 25, characterized in that the simultaneous characterization of the emitted light flux and of the transmitted and / or scattered light flux (φ _t / d) takes place via a two-beam configuration comprising a first light beam (F1), whose light path passes through the body (2) before joining the detection and analysis system (4) of the transmitted and / or scattered light flux (φ _{t / d} ) and a second light beam (F2) whose light path joins the detection and analysis system (4) of the transmitted and / or scattered light flux (φ _{t / d} ) without passing through the body.

- Method according to one of claims 24 to 26 characterized in that it further comprises a reflection measurement step during which is detected and analyzed the light energy reflected by the body (2) and a calibration step, preceding the measurement step in reflection, during which is interposed, in the light path, instead of the body (2) standards, preferably white and black, calibration by reflection. - Method according to claim 27 characterized in that characterizes the optical properties of transmission and reflection of the body (2) in a single operation without displacement of said body.

- Method according to claim 27 or 28, characterized in that the light flux reflected from the body (2) is measured at an incidence angle of between approximately 43 and 47 °, preferably approximately 45 °, with respect to the normal direction of the body surface (2).

- Method according to claim 29 characterized in that further measured, simultaneously or not with the transmission and reflection measurements, diffuse light.

- Method according to claim 30 characterized in that the diffuse light measurement is performed at a low angle of incidence, of the order for example about 4 °.

- Method according to one of claims 27 to 31 characterized in that during the measurement step in reflection, is characterized substantially simultaneously, using the detection and analysis system (4 ') of the flow reflected light (φ _r ), the luminous flux emitted by the lighting means (3), and the reflected luminous flux (φ _r ) by the body (2) so as to take into account in the measurement, the variations of luminous intensity of the lighting means (3).

- Process according to claims 26 and 32 characterized in that the simultaneous characterization of the _. emitted luminous flux and the reflected luminous flux is effected by means of a two-beam configuration, the reflected luminous flux (φ _r ) being generated by reflection of all or part of the first beam (F1) on the body (2) while the second beam light (F2) joins the detection and analysis system (4, 4 ') without passing through the body (2).

-Procédé according to claim 26 and / or claim 33 characterized in that it comprises, before the step or steps of measurement, a step of evaluating the noise of the detection or analysis system (4, 4 '), during which the first and second light beams (F1, F2) are cut substantially simultaneously with a cut-off member (20) so as to isolate and evaluate the noise of the detection and analysis systems (4, 4 ').

- Method according to one of claims 24 to 34 characterized in that it constitutes a method for determining the color of the body 2.

- Method according to one of claims 24 to 35 characterized in that the one or more measurement steps are repeated for a plurality of wavelengths to form one or more spectral response curves.