EP0620051A1 - Method and device for automatic sorting of products, especially of fruit or vegetables - Google Patents

Abstract

The invention relates to a method for automatic colorimetric sorting of products, such as fruit or vegetables, in which each product is illuminated by means of a beam embodying a succession of luminous streaks, the energy returned by the product in preselected wavelengths is recovered for each point of each luminous streak, the luminous intensity of each point is measured, the measured values are converted so as to form numerical data strings corresponding, for each wavelength, to the luminous intensity curves of each luminous streak, and the numerical data strings are computationally processed by comparing the values of the counterpart points in the said strings, so as to generate an exploitable colorimetric information item. <IMAGE>

Description

The invention relates to a method and an automatic sorting device for products, in particular fruit or vegetables.

Modern fruit stations are faced with the ever more pressing problem of seeking quality. In addition, modern distribution networks require perfectly homogeneous batches of fruit and vegetables, both in quality and in coloring, the quality of the fruit being assessed on the basis of conventional visual criteria established by fruit and vegetable regulations.

The consequence of such requirements is to require manual sorting personnel to make efforts which do not allow access to high calibration rates. It is indeed, for this staff, to identify, among the fruit conveyed, those which are to be downgraded, the defects justifying this downgrading being of various natures: pathology of the fruits, shocks, cuts ...

A good qualitative calibration therefore requires qualified personnel and reasonable rates much lower than the maximum rates of the packaging lines.

The solutions currently used to automate sorting and replace staff all use electronic systems based on cameras. However, these systems do not fully meet the aspirations of producers because the qualitative approach is then considered under the color aspect considering that the defects have a particular color.

Unfortunately, the physical reality of the phenomenon is quite different. Indeed and as an example, a fresh shock on an apple does not alter the color of this and yet the fruit must be downgraded. Likewise, a fruit affected by "biter pit" does not show any color change on the surface, while under the skin the fruit is rotten. Furthermore, the natural fruit cavities (pistillary and peduncle) are considered to be spots because they naturally have brown spots ("russetting"), and the detection of these cavities causes the fruit to downgrade while these areas of the fruit are subjected to a specific regulation, more flexible than for the other parts of the said fruit.

The present invention aims to overcome these drawbacks and has the main objective of providing an automatic sorting device making it possible to meet the various criteria for selecting products such as fruit and vegetables, without being influenced by the non-crippling zones of the latter.

Another objective of the invention is to provide a device capable of delivering information representative of the quality, color and volume of the products.

Another objective of the invention is to provide a device which can be installed on a conveyor with several transport lines, and ensure a great uniformity of calibration on the whole of this conveyor.

• à éclairer chaque produit au moyen d'au moins un faisceau apte à matérialiser une ligne lumineuse sur la surface dudit produit,
• à déplacer relativement la ligne lumineuse et le produit de façon à éclairer successivement le maximum de points observables de la surface dudit produit,
• à décomposer chaque ligne lumineuse en une succession de points, et pour chacun desdits points, à récupérer dans des longueurs d'onde présélectionnées, au moins une partie de l'énergie lumineuse renvoyée par le produit,
• pour chaque longueur d'onde présélectionnée, à mesurer l'intensité lumineuse de chaque point de chaque ligne lumineuse, et à délivrer des données analogiques représentatives de ladite intensité,
• pour une des longueurs d'onde présélectionnées et pour chaque point de chaque ligne lumineuse, à délivrer une information, dite de distance, représentative de la distance entre un point d'origine et une zone située à proximité immédiate du point d'impact du faisceau sur le produit,
• à convertir, pour chaque ligne lumineuse, les données analogiques représentatives de l'intensité lumineuse en une suite de valeurs numériques, chacune représentative du niveau de gris dans la longueur d'onde considérée du point correspondant de ladite ligne lumineuse, de façon que chacune des suites de valeurs corresponde à la courbe d'intensité lumineuse, dans cette longueur d'onde, de cette ligne lumineuse,
• à convertir chaque information de distance de façon à obtenir une suite de valeurs numériques représentatives du profil physique du produit aptes à permettre de discriminer d'éventuelles cavités naturelles à la surface dudit produit,
• à mémoriser les suites de données numériques correspondant à chaque longueur d'onde présélectionnée et à chaque ligne lumineuse,
• et à traiter par le calcul les suites de données numériques selon des critères programmés basés sur une comparaison des valeurs des points homologues desdites suites, de façon à générer une information colorimétrique exploitable en ne prenant en compte que les seuls points des suites numériques ne correspondant pas à une cavité.

To this end, the invention relates to a process for automatic colorimetric sorting of products, in particular fruit or vegetables, characterized in that it consists:

• to illuminate each product by means of at least one beam capable of materializing a light line on the surface of said product,
• to relatively move the light line and the product so as to successively illuminate the maximum of observable points on the surface of said product,
• to decompose each light line into a succession of points, and for each of said points, to recover, in preselected wavelengths, at least part of the light energy returned by the product,
• for each wavelength preselected, to measure the light intensity of each point of each light line, and to deliver analog data representative of said intensity,
• for one of the preselected wavelengths and for each point of each light line, to deliver information, known as distance, representative of the distance between an origin point and an area located in the immediate vicinity of the point of impact of the beam on the product,
• converting, for each light line, the analog data representative of the light intensity into a series of digital values, each representative of the gray level in the wavelength considered of the corresponding point of said light line, so that each of the series of values corresponds to the light intensity curve, in this wavelength, of this light line,
• converting each distance information so as to obtain a series of numerical values representative of the physical profile of the product capable of making it possible to discriminate possible natural cavities on the surface of said product,
• memorizing the sequences of digital data corresponding to each preselected wavelength and to each light line,
• and to process by calculation the digital data sequences according to programmed criteria based on a comparison of the values of the homologous points of said sequences, so as to generate exploitable colorimetric information by taking into account only the only points of the digital sequences that do not correspond to a cavity.

Firstly, such a method, according to which preselected wavelengths of the light energy returned by the product are used, makes it possible to improve the notion of determinism of the calibration, and thereby to increase the precision of this last.

Indeed, to each numerical value representative of a light intensity does not correspond only one fruit color, the margin of error on the determination of this color being absolutely non-existent.

By way of example, such a method makes it possible to remove the ambiguity existing between a Golden apple having a rough area and a Golden apple having a pink spot. Such ambiguity, which cannot be overcome by existing devices, is of great importance because roughness is a factor in derating, while pink spots are a factor in quality.

Likewise, and also by way of example, this method makes it possible to discriminate faults such as fresh shocks which cannot be detected with current methods.

In addition, according to this method, the colorimetric information provided is not affected by the presence of any cavities, which in particular avoids having to specifically position the products for sorting, and which therefore allows a automatic and continuous feeding of said products.

• on compare les suites de valeurs numériques correspondant aux courbes d'intensité lumineuse, de façon à délivrer une information relative à la qualité du produit, et consistant :
  • . en l'absence de discontinuité de forme concave dans toutes les courbes, en une information d'absence de défaut,
  • . en présence d'une discontinuité de forme concave dans au moins une courbe mais non dans la totalité desdites courbes, en une information d'absence de défaut,
  • . et en présence d'une discontinuité de forme concave dans une même zone de toutes les courbes, en une information de présence d'un défaut dans la zone de discontinuité,
• on effectue les calculs visant à générer l'information colorimétrique au moyen des seules valeurs des suites numériques ayant conduit à la délivrance d'une information d'absence de défaut.

According to a preferred mode of implementation:

• the sequences of numerical values corresponding to the light intensity curves are compared, so as to deliver information relating to the quality of the product, and consisting of:
  • . in the absence of discontinuity of concave shape in all the curves, in the absence of defect information,
  • . in the presence of a concave discontinuity in at least one curve but not in all of said curves, in the absence of fault information,
  • . and in the presence of a concave discontinuity in the same area of all the curves, in information of the presence of a defect in the discontinuity area,
• we carry out the calculations aiming to generate the colorimetric information by means of the only values numerical sequences having led to the delivery of information of absence of defect.

This method makes it possible to take into account, for the purpose of determining the colorimetric classification of the products, only the surfaces of this product that are healthy and free from defects, that is to say surfaces free of shocks ...

• en présence d'une discontinuité de forme concave dans toutes les courbes conduisant à la délivrance d'une information de présence d'un défaut :
  • . en l'absence de cavité, on calcule selon des critères programmés, des informations représentatives de l'état du défaut,
  • . et en présence d'au moins une cavité, on ne prend pas en considération les points concernés.

In addition, according to another characteristic:

• in the presence of a concave discontinuity in all the curves leading to the delivery of information on the presence of a fault:
  • . in the absence of a cavity, information representative of the state of the fault is calculated according to programmed criteria,
  • . and in the presence of at least one cavity, the points concerned are not taken into consideration.

This mode of implementation makes it possible to remove any ambiguity and to interpret all types of phenomena which may occur at the surface of the product.

In addition and above all, this mode of implementation makes it possible to differentiate the colorimetric aspect and the qualitative aspect, whereas at present the qualitative aspect is only approached from the colorimetric aspect, which leads numerous aberrations regarding the sorting information provided.

According to another characteristic of the invention, each product is illuminated by means of an incident beam capable of illuminating a point on the surface of said product, and said beam is moved so as to materialize a light line.

• on utilise un premier faisceau monochromatique et polarisé, et on décompose l'énergie rétrodiffusée par chaque point dans deux plans de polarisation, de façon à obtenir les profils physiques du produit,
• on éclaire simultanément le produit au moyen d'un deuxième faisceau polychromatique composé d'un nombre discret de longueurs d'onde présélectionnées, et on récupère l'énergie lumineuse renvoyée par le produit pour chacune des longueurs d'onde de ce faisceau polychromatique, de façon à obtenir les données représentatives des courbes d'intensité lumineuse.

In addition, with regard to product lighting and advantageously:

• a first monochromatic and polarized beam is used, and the energy backscattered by each point is broken down into two polarization planes, so as to obtain the physical profiles of the product,
• we simultaneously illuminate the product with means of a second polychromatic beam composed of a discrete number of preselected wavelengths, and the light energy returned by the product is recovered for each of the wavelengths of this polychromatic beam, so as to obtain the representative data light intensity curves.

In addition, the monochromatic and polychromatic beams are preferably superimposed so as to illuminate each product at a single point. This arrangement makes it possible to obtain the color coming from the same point by analyzing the energy backscattered by this point for the different wavelengths.

In addition, a polychromatic beam composed of at least three wavelengths chosen from the following colors is advantageously used: red, green, blue, yellow.

The monochromatic beam used is preferably an infrared beam.

• repérer exactement le début et la fin de chaque produit,
• obtenir par sommations successives des profils dans l'infrarouge, une information représentative du volume du produit.

The use of an infrared beam has two advantages. On the one hand, in fact, the color of the products has no influence on such a beam. In addition, the infrared beam makes it possible to obtain additional information consisting of an intensity curve in the infrared linked to the dimensions of the products and which can be used for:

• pinpoint the start and end of each product,
• obtain, by successive summation of the infrared profiles, information representative of the volume of the product.

Furthermore, polychromatic and monochromatic beams originating from laser sources are preferably used.

The use of laser sources makes it possible to use wavelengths determined to the nearest nanometer. In addition, the laser power makes it possible to detect subepidermal defects not visible to the naked eye.

According to another characteristic of the invention relates to a process in which the products are conventionally moved along a sorting line, each beam is moved, on the one hand parallel to the direction of movement of the products so as to form longitudinal light lines consisting of 'a succession of aligned points, and on the other hand, transversely, so as to cover the surface of the product by a succession of parallel light lines.

• des premiers moyens d'éclairage aptes à matérialiser une ligne lumineuse sur la surface du produit,
• des seconds moyens d'éclairage aptes à générer un faisceau monochromatique polarisé, et à matérialiser au moyen dudit faisceau une ligne lumineuse sur la surface du produit,
• des moyens de déplacement relatif des lignes lumineuses et du produit agencés pour permettre d'éclairer successivement le maximum de points observables de la surface dudit produit,
• une chaîne d'acquisition comportant des capteurs aptes à collecter l'énergie lumineuse renvoyée par le produit dans des longueurs d'onde présélectionnées, et à délivrer des signaux analogiques représentatifs, pour chaque point de chaque ligne lumineuse et dans chacune desdites longueurs d'onde, de l'intensité lumineuse dudit point,
• des moyens de séparation du faisceau incident polarisé et de l'énergie lumineuse dépolarisée renvoyée par le produit,
• un ensemble optique disposé de façon à ne recevoir que la seule énergie lumineuse renvoyée par le produit, et adapté pour délivrer un signal analogique représentatif de la distance entre ledit ensemble optique et une zone située à proximité immédiate du point d'impact du faisceau incident sur le produit,
• et une unité centrale de traitement comportant :
  • . des moyens de conversion analogique/numérique agencés pour recevoir les signaux analogiques issus des capteurs et pour délivrer, pour chaque point et dans chaque longueur d'onde, une valeur numérique représentative du niveau de gris dudit point,
  • . des moyens de conversion analogique/numérique agencés pour recevoir les signaux analogiques issus de l'ensemble optique et pour délivrer, pour chaque point d'impact du faisceau sur le produit, une valeur numérique représentative de la distance entre un point d'origine et une zone située à proximité immédiate dudit point d'impact,
  • . des moyens de mémorisation des valeurs numériques sous forme de suites de valeurs représentatives du profil physique du produit,
  • . des moyens de mémorisation des valeurs numériques sous forme de suites de valeurs représentatives, chacune, pour chaque longueur d'onde, de la courbe d'intensité lumineuse d'une ligne lumineuse,
  • . et des moyens de calcul programmés pour calculer, à partir d'une part, de critères de comparaison des valeurs numériques des points homologues des courbes d'intensité et, d'autre part, des valeurs représentatives du profil physique du produit, une information colorimétrique exploitable ne prenant en compte que les seuls points des courbes d'intensité ne correspondant pas à une cavité.

The invention extends to an automatic sorting device for products, in particular fruit or vegetables, characterized in that it comprises in combination:

• first lighting means capable of materializing a light line on the surface of the product,
• second lighting means capable of generating a polarized monochromatic beam, and of materializing by means of said beam a light line on the surface of the product,
• means of relative displacement of the light lines and of the product arranged to allow successively to illuminate the maximum of observable points on the surface of said product,
• an acquisition chain comprising sensors capable of collecting the light energy returned by the product in preselected wavelengths, and of delivering representative analog signals, for each point of each light line and in each of said wavelengths , the light intensity of said point,
• means for separating the polarized incident beam and the depolarized light energy returned by the product,
• an optical assembly arranged so as to receive only the single light energy returned by the product, and adapted to deliver an analog signal representative of the distance between said optical assembly and an area located in the immediate vicinity of the point of impact of the incident beam on the product,
• and a central processing unit comprising:
  • . analog / digital conversion means arranged to receive the analog signals from the sensors and to deliver, for each point and in each wavelength, a digital value representative of the gray level of said point,
  • . analog / digital conversion means arranged to receive the analog signals from the optical assembly and to deliver, for each point of impact of the beam on the product, a digital value representative of the distance between an origin point and a area located in the immediate vicinity of said point of impact,
  • . means for memorizing digital values in the form of sequences of values representative of the physical profile of the product,
  • . means for storing the digital values in the form of sequences of representative values, each, for each wavelength, of the light intensity curve of a light line,
  • . and calculation means programmed to calculate, on the one hand, criteria for comparing the numerical values of the homologous points of the intensity curves and, on the other hand, values representative of the physical profile of the product, colorimetric information exploitable taking into account only the only points of the intensity curves not corresponding to a cavity.

In addition, the sensors preferably comprise means for decomposing the light energy returned by the product into a discrete number of preselected wavelengths and, for each wavelength, means for collecting and focusing, and a detector arranged to receive the collected energy and to deliver an analog signal representative of said energy.

In addition, the decomposition means advantageously consist of at least one deflected blade optics selected for given wavelengths.

According to another characteristic of the invention, these decomposition means are also inserted between the two faces forming the hypotenuse of two rectangular prisms, one of said prisms being arranged so that one of its faces constitutes the entry window of said means of decomposition.

Thanks to this arrangement, and first of all, the arrangement of the various optical components forms, between the input face and that of the output, a complete optical system of the same optical index. As a result, Fresnel reflection is minimized because it takes place on the input and output faces which are as orthogonal as possible to the mean directions of the beams entering and leaving the system.

It should also be noted that, in order to further minimize these reflections, the different faces can undergo a conventional anti-reflection treatment.

Advantageously, the decomposition means can be of two types. They can thus either consist of a diffraction grating, or be made up of at least two holographic mirrors by reflection, spaced apart and selective for the predetermined wavelengths.

Furthermore, the optical assembly is advantageously adapted to deliver a second analog signal representative of the light intensity returned by the product in the wavelength of the incident beam.

• une première carte électronique, dite d'amplification, apte à amplifier les signaux analogiques délivrés par les capteurs et l'ensemble optique,
• une deuxième carte électronique, dite télémétrique, comportant des moyens de conversion analogique/numérique et agencée pour recevoir les signaux amplifiés issus de l'ensemble optique, ladite carte comportant une unité de calcul programmée pour identifier les cavités naturelles et les zones endommagées du produit, et pour calculer le volume dudit produit à partir du signal d'intensité lumineuse en défalquant du résultat obtenu les zones correspondant à des cavités,
• une troisième carte électronique, dite de traitement couleur, comportant des moyens de conversion analogique/numérique, et agencée pour recevoir les signaux amplifiés délivrés par les divers capteurs, et le signal amplifié représentatif de l'intensité lumineuse pour la longueur d'onde sélectionnée pour l'ensemble optique, ladite carte comportant une unité de calcul programmée pour réaliser un algorithme de tri colorimétrique pour les points autorisés,
• une quatrième carte, dite de traitement qualité, comportant des moyens de conversion analogique/numérique, et agencée pour recevoir les signaux amplifiés délivrés par les divers capteurs, et le signal amplifié représentatif de l'intensité lumineuse pour la longueur d'onde sélectionnée pour l'ensemble optique, ladite carte comportant une unité de calcul programmée :
  • . pour rechercher les discontinuités de forme concave dans toutes les longueurs d'onde présentes dans l'énergie diffusée par le produit, et lors de la présence d'une discontinuité dans une zone pour toutes les longueurs d'onde, pour interroger la carte de traitement télémétrique, en vue d'inhiber éventuellement les résultats du tri colorimétrique dans le cas où cette zone correspond à une cavité naturelle,
  • . pour quantifier le défaut observé dans les zones de discontinuité ne correspondant pas à des cavités,
• des moyens de communication des résultats sous forme de trois valeurs numériques représentatives de la qualité, de la couleur et du volume du produit.

According to another characteristic of the invention, the central processing unit comprises:

• a first electronic card, called an amplification card, capable of amplifying the analog signals delivered by the sensors and the optical assembly,
• a second electronic card, called telemetric, comprising analog / digital conversion means and arranged to receive the amplified signals coming from the optical assembly, said card comprising a calculation unit programmed to identify natural cavities and damaged areas of the product, and to calculate the volume of said product from the light intensity signal by deducting from the result obtained the areas corresponding to cavities,
• a third electronic card, called a color processing card, comprising analog / digital conversion means, and arranged to receive the amplified signals delivered by the various sensors, and the amplified signal representative of the light intensity for the wavelength selected for the optical assembly, said card comprising a calculation unit programmed to carry out a colorimetric sorting algorithm for the authorized points,
• a fourth card, called a quality processing card, comprising analog / digital conversion means, and arranged to receive the amplified signals delivered by the various sensors, and the amplified signal representative of the light intensity for the wavelength selected for l optical assembly, said card comprising a programmed calculation unit:
  • . to search for concave discontinuities in all wavelengths present in the energy diffused by the product, and when there is a discontinuity in an area for all wavelengths, to query the processing board telemetry, with a view to possibly inhibiting the results of colorimetric sorting in the case where this zone corresponds to a natural cavity,
  • . to quantify the defect observed in the discontinuity zones which do not correspond to cavities,
• means of communicating the results in the form of three numerical values representative of the quality, color and volume of the product.

The device of the invention can in particular allow the sorting of fruit on a conveyor comprising n transport lines. In this case, and advantageously, the first lighting means comprise a single lighting source delivering a beam divided into at least n beams transported by optical fibers at each line.

This arrangement makes it possible to illuminate the different transmission lines in a strictly identical manner, regardless of the evolution of the lighting source. As a result, any problem relating to a possible difference in brightness from one line to the next is eliminated, and perfect calibration uniformity is obtained over the whole machine.

• la figure 1 est une vue en perspective schématique d'un convoyeur de fruits à n lignes de transport, équipé d'un dispositif conforme à l'invention,
• la figure 2 est un schéma représentant un dispositif conforme à l'invention,
• la figure 3 est un schéma représentant un premier type de capteur équipant le dispositif selon l'invention,
• la figure 4 est un schéma représentant une variante de capteur pouvant équiper le dispositif selon l'invention,
• la figure 5 est un schéma représentant l'unité centrale de traitement du dispositif selon l'invention,
• les figures 6, 7, 8a à 8c illustrent des courbes d'intensité lumineuse telles que pouvant être obtenues selon le procédé de l'invention, ainsi que les courbes de traitement couleur et qualité associées à ces courbes,
• les figure 9 et 10 sont deux courbes destinées à permettre d'expliciter l'algorithme de détection des défauts conforme à l'invention.

Other characteristics, objects and advantages of the invention will emerge from the detailed description which follows, with reference to the appended drawings which represent, by way of non-limiting example, a preferred embodiment. On these drawings which form an integral part of this description:

• FIG. 1 is a schematic perspective view of a fruit conveyor with n transport lines, equipped with a device according to the invention,
• FIG. 2 is a diagram representing a device according to the invention,
• FIG. 3 is a diagram representing a first type of sensor fitted to the device according to the invention,
• FIG. 4 is a diagram showing a variant of a sensor that can be fitted to the device according to the invention,
• FIG. 5 is a diagram representing the central processing unit of the device according to the invention,
• FIGS. 6, 7, 8a to 8c illustrate curves of light intensity such as can be obtained according to the method of the invention, as well as the color and quality treatment curves associated with these curves,
• FIGS. 9 and 10 are two curves intended to make it possible to explain the algorithm of fault detection according to the invention.

The aim of the device shown in the figures is to provide a deterministic, flexible and scalable technique, making it possible to meet the various criteria for selecting fruit and vegetables without being influenced by the non-crippling zones of the latter.

Firstly, the conveyor 1 shown in FIG. 1 is a conventional conveyor comprising n parallel conveyor lines each provided, for example, with a plurality of spaced rollers between which the fruits are housed, said rollers being able to be driven in rotation around their axis of revolution to the right of the sorting device.

This device consists of n measuring heads, such as 2, each arranged above a conveyor line and resting on a gantry 3 arranged transversely above the conveyor 1.

Each of these measurement heads 2 contains an electronic rack 4 for monitoring the process, a measurement enclosure 5 containing an acquisition chain 6 capable of collecting the energy returned by the fruit, a range finder 7 and a system 8 for deflecting the beam. Each measurement head also contains the electronics 9 of the rangefinder.

Each measuring head is also connected via an optical fiber such as 10 and a multiplexer 11 for n optical fibers 10, to a cabinet 12 containing a laser assembly comprising a multi-line laser (in the red example, green, blue) and, conventionally, means for cooling said laser and an electrical cabinet.

FIG. 2 schematically represents, on the one hand, a range finder and a multi-line laser 13 inserted in accordance with the invention in an optical arrangement making it possible to superimpose the monochromatic beam coming from the range finder 7 and the polychromatic beam coming from the laser 13 and, on the other hand, a system of deflection of the beams thus superimposed.

First, the rangefinder 7 has a collimated infrared laser diode 14, the beam of which is delivered via a deflection mirror 15 to a separator 16 distinguishing the outward and return beams. This rangefinder 7 further comprises a conoscopic head 17 associated with two avalanche diodes 18, 19, and an electronic card 20 capable of calculating and delivering representative signals, on the one hand from the distance fruit / conoscopic head 17 and, d other part of the light intensity returned by the fruit in the infrared.

This rangefinder furthermore comprises two imaging lenses 21, 22 arranged on either side of the separator 16, and adapted to focus the beam respectively on the fruit and on the conoscopic head 17.

The beam from this range finder 7 and the beam from the multi-line laser 13 are delivered to a dichroic beam splitter 23 capable, as indicated above, of superimposing said beams.

This superimposed beam is itself delivered to a deflection system comprising, first of all, a rotating polygon 24 provided with facets such as 24a capable of reflecting the incident beam and of generating light lines, said polygon being associated with means of 'rotational drive (not shown).

These deflection means further comprise a mirror 25 mounted oscillating with respect to a longitudinal axis, and arranged to intercept the light line coming from a facet 24a of the polygon 24, and to project this light line towards the transport line.

This oscillating mirror 25 is also associated with rotation means (not shown) able to rotate the latter about its longitudinal axis so that the light line scans the width of the transport line.

As for the acquisition chain 6, it firstly comprises means for decomposing the light energy returned by the product into a discrete number of wavelengths corresponding to the wavelengths of the multi-line laser beam. It includes, in in addition, for each wavelength, collection and focusing means, and a detector arranged to deliver an analog signal representative of the energy returned.

Two variants of the acquisition chain are shown in Figures 3 and 4 respectively.

The acquisition chain of FIG. 3 comprises two holographic mirrors by reflection 26, 27, spaced and parallel, adapted to each deflect one of the wavelengths of the multi-line beam, and to be transparent for the third wavelength.

For each of these wavelengths, this acquisition chain comprises collection and focusing means consisting of a condenser 28, 29, 30, and detectors 31, 32, 33. In addition, an infrared filter 33a is arranged in front of the detector 33 corresponding to the third wavelength.

The acquisition chain represented in FIG. 4 comprises, for its part, a diffraction grating 34 inserted between the hypotenuse faces of two rectangular prisms 35, 36 forming a cube with said diffraction grating, said cube being arranged so that one of its faces constitutes the entry window of the acquisition chain.

This acquisition chain further comprises collection and focusing means consisting of a first common condenser 37 for two detectors 38, 39 arranged downstream of the latter, and a second condenser 40 associated with a third detector 41 and a filter. infrared 41a.

The device according to the invention also has synchronization means making it possible to create a digitization zone centered on the fruits to be examined. The latter firstly comprise means of detection, such as a cell, of the point of origin of the light line generated by the rotation of the polygon. They also include step-by-step means of measuring the progress of the fruit on the conveyor.

From this data, the triggering of a processing cycle is given by the central processing unit for each movement of one step of the product, upon reception of the signal from the detection cell.

The principle of the treatment carried out in accordance with the invention with a view to carrying out the colorimetric and qualitative analyzes is illustrated in FIGS. 6, 7, 8 which represent three intensity curves as obtained during the decomposition of the returned light energy by a light line according to the three wavelengths of the multi-line laser beam.

In the case of FIG. 6 where the curves corresponding to the three wavelengths do not have any discontinuity, the colorimetric analysis, shown diagrammatically by curve C, is carried out for all the points of the curve.

Qualitative analysis concludes that all the points analyzed are sound. It is the same when, as represented in FIG. 7, only one (or two) of the curves have (s) a discontinuity of concave shape.

By cons, when as shown in Figure 8, the three curves have a concave discontinuity in the same area, it uses the signal from the rangefinder.

In the case of FIG. 8a where the signal delivered by this rangefinder reveals the presence of a natural cavity materialized by a discontinuity of concave shape, the colorimetric analysis is carried out for the points other than those corresponding to this zone. No qualitative analysis is also carried out.

By cons, as shown in Figure 8b, if the signal from the rangefinder does not have a discontinuity, the discontinuity observed for the curves representative of the wavelengths of the laser beam, necessarily corresponds to a defect such as spot ...

In this case, the colorimetric analysis is carried out for the points other than those corresponding to the zone of the cavity. In addition, a qualitative analysis schematized by the Q curve is performed for the points in this area.

• une première carte électronique d'amplification 42, apte à amplifier les signaux analogiques délivrés par les capteurs 31-33 ou 38, 39, 41 et le télémètre 7,
• une deuxième carte électronique, dite télémétrique 43, comportant des moyens de conversion analogique/numérique et agencée pour recevoir les signaux amplifiés issus du télémètre 7, ladite carte comportant une unité de calcul programmée pour identifier les cavités naturelles et les zones endommagées du produit, et pour calculer le volume dudit produit à partir du signal d'intensité lumineuse en défalquant du résultat obtenu les zones correspondant à des cavités,
• une troisième carte électronique de traitement couleur 44, comportant des moyens de conversion analogique/numérique, et agencée pour recevoir les signaux amplifiés délivrés par les divers capteurs 31-33 ou 38, 39, 41, et le signal amplifié représentatif de l'intensité lumineuse dans l'infrarouge, ladite carte comportant une unité de calcul programmée pour réaliser un algorithme de tri colorimétrique pour les points autorisés,
• une quatrième carte de traitement qualité 45, comportant des moyens de conversion analogique/numérique, et agencée pour recevoir les signaux amplifiés délivrés par les divers capteurs 31-33 ou 38, 39, 41, et le signal amplifié représentatif de l'intensité lumineuse dans l'infrarouge, ladite carte comportant une unité de calcul programmée :
  • . pour rechercher les discontinuités de forme concave dans toutes les longueurs d'onde présentes dans l'énergie diffusée par le fruit, et lors de la présence d'une discontinuité dans une zone pour toutes les longueurs d'onde, pour interroger la carte de traitement télémétrique 43, en vue d'inhiber éventuellement les résultats du tri colorimétrique dans le cas où cette zone correspond à une cavité naturelle,
  • . pour quantifier le défaut observé dans les zones de discontinuité ne correspondant pas à des cavités,
• des interfaces 46, 47 de communication respectivement entre la carte de traitement couleur 44 et la carte de traitement qualité 45, et entre la carte de traitement télémétrique 43 et la carte de traitement qualité 45,
• des moyens (non représentés) de communication des résultats sous forme de trois valeurs numériques représentatives de la qualité, de la couleur et du volume du produit.

This processing is carried out by means of a central unit shown diagrammatically in FIG. 5 and comprising:

• a first electronic amplification card 42, capable of amplifying the analog signals delivered by the sensors 31-33 or 38, 39, 41 and the rangefinder 7,
• a second electronic card, called telemetric 43, comprising analog / digital conversion means and arranged to receive the amplified signals coming from the rangefinder 7, said card comprising a calculation unit programmed to identify the natural cavities and the damaged areas of the product, and to calculate the volume of said product from the light intensity signal by deducting from the result obtained the zones corresponding to cavities,
• a third electronic color processing card 44, comprising analog / digital conversion means, and arranged to receive the amplified signals delivered by the various sensors 31-33 or 38, 39, 41, and the amplified signal representative of the light intensity in the infrared, said card comprising a calculation unit programmed to carry out a colorimetric sorting algorithm for the authorized points,
• a fourth quality processing card 45, comprising analog / digital conversion means, and arranged to receive the amplified signals delivered by the various sensors 31-33 or 38, 39, 41, and the amplified signal representative of the light intensity in infrared, said card comprising a programmed calculation unit:
  • . to find concave discontinuities in all wavelengths present in the energy diffused by the fruit, and when there is a discontinuity in an area for all wavelengths, to interrogate the rangefinder processing card 43, with a view to possibly inhibiting the results of the colorimetric sorting in the case where this zone corresponds to a natural cavity,
  • . to quantify the defect observed in the discontinuity zones which do not correspond to cavities,
• communication interfaces 46, 47 respectively between the color processing card 44 and the quality processing card 45, and between the range measurement card 43 and the quality processing card 45,
• means (not shown) for communicating the results in the form of three numerical values representative of the quality, color and volume of the product.

The algorithm for processing faults leading to the determination of a numerical value representative of a quality score is explained below with reference to FIGS. 9 and 10.

First of all, it is advisable to locate particular points of the curve, namely the abscissae of the start points D and end F of this curve, as well as the coordinates mX, mY of the highest point of this curve (see figure 9).

The algorithm is based on the principle that for all abscissa points lower than mX, the curve must be necessarily constant or increasing.

Consequently, any point i of ordinate Yi, such that Yi is less than the ordinate Yi-1 of a previous point i-1, will be considered as stained. This appreciation can however be refined by accepting certain differences in amplitudes, that is to say by considering the stained point i only if (Yi - Yi-1) is less than a predetermined threshold.

For abscissa points greater than mX for which the curve must be normally constant or decreasing, it is enough to traverse these points in the direction of the decreasing abscissas to obtain a similar relation.

The next step is to quantify the spot, this quantification must be identical for two fruits of different shapes.

Normalization is therefore carried out by operating a projection into a normalization space in which, for a given spot and whatever its position on the fruit, the same associated gray level is obtained.

Knowing the maximum size of the fruits to be analyzed, the gray level of the stained pixel will be projected on a straight line so that the value obtained corresponds to that of a maximum size fruit.

As shown in Figure 10, a simple rule of three allows us to find the location of this projection line. Indeed, knowing D, i and mY, it is obvious to find the distance between D and the normalization line (Thales theorem). The pixel i is then projected along the axis D Ni on the projection line, to obtain the normalized gray level point Ni.norm.

• les points non tachés ont une valeur nulle,
• les points tachés ont une valeur correspondant au niveau de gris normalisé,
• les points hors du tronçon DF ont une valeur de -1.

Once this treatment has been carried out, all the points between D and F are replaced by the gray level intensity values, so as to obtain a new curve in which:

• the unstained points have a zero value,
• the stained points have a value corresponding to the normalized gray level,
• points outside the DF section have a value of -1.

• la valeur -1 aux points correspondant à des cavités naturelles,
• une valeur nulle lorsque la tache correspond à une simple tache de couleur.

This curve is then modified as a function of the results obtained by telemetry and for the other wavelengths, this modification consisting for example in assigning:

• the value -1 at points corresponding to natural cavities,
• a null value when the spot corresponds to a simple spot of color.

The curve being thus validated, the number of healthy points (zero value) and the number of points whose value is positive is memorized, which amounts to memorizing a grayscale histogram.

et entre le rouge et le vert

The color processing algorithm consists in storing, firstly, for each wavelength, the values of the gray levels (0 to 255) of all the points of the zone DF. The following steps depend on the fruit to be classified and the predominant colors of the latter, and are adaptable to each type of fruit. For example and for apples, the color spectra between green and blue are calculated for each point

and between red and green

All these values being bounded between -1 and +1, we then normalize by adding +1 to each of said values, then we multiply the latter by 16.

Finally, a 32-level histogram is established for each curve.

Claims (25)

Method for automatic colorimetric sorting of products, in particular fruit or vegetables, characterized in that it consists of: to illuminate each product by means of at least one beam capable of materializing a light line on the surface of said product, to relatively move the light line and the product so as to successively illuminate the maximum of observable points on the surface of said product, - decomposing each light line into a succession of points, and for each of said points, recovering at preselected wavelengths, at least part of the light energy returned by the product, - for each preselected wavelength, to measure the light intensity of each point of each light line, and to deliver analog data representative of said intensity, - for one of the preselected wavelengths and for each point of each light line, to deliver information, known as distance, representative of the distance between an origin point and an area located in the immediate vicinity of the impact point of the beam on the product, to convert, for each light line, the analog data representative of the light intensity into a series of digital values, each representative of the gray level in the wavelength considered of the corresponding point of said light line, so that each series of values corresponds to the light intensity curve, in this wavelength, of this light line, - to convert each distance information so as to obtain a series of numerical values representative of the physical profile of the product capable of making it possible to discriminate possible cavities natural on the surface of said product, - to memorize the digital data sequences corresponding to each preselected wavelength and to each light line, - And to process by calculation the sequences of digital data according to programmed criteria based on a comparison of the values of the homologous points of said sequences, so as to generate exploitable colorimetric information by taking into account only the only points of the corresponding digital sequences not to a cavity. Method according to claim 1, characterized in that: - the series of numerical values corresponding to the light intensity curves are compared, so as to deliver information relating to the quality of the product, and consisting of: . in the absence of discontinuity of concave shape in all the curves, in the absence of defect information, . in the presence of a concave discontinuity in at least one curve but not in all of said curves, in the absence of fault information, . and in the presence of a concave discontinuity in the same area of all the curves, in information of the presence of a defect in the discontinuity area, the calculations aiming to generate the colorimetric information are carried out using only the values of the numerical sequences which have led to the delivery of information of absence of defect. Method according to claim 2, characterized in that: - in the presence of a concave discontinuity in all the curves leading to the delivery of information on the presence of a fault: . in the absence of a cavity, information calculated according to programmed criteria representative of the state of the fault, . and in the presence of at least one cavity, the points concerned are not taken into consideration. Method according to one of claims 1 to 3, characterized in that each product is illuminated by means of an incident beam capable of illuminating a point on the surface of said product, and in that said beam is moved so as to materialize a light line. Method according to one of claims 3 or 4, characterized in that: - the product is illuminated by means of a first monochromatic and polarized beam, and the energy backscattered by each point is broken down into two polarization planes, so as to obtain the physical profiles of the product, the product is simultaneously illuminated by means of a second polychromatic beam composed of a discrete number of preselected wavelengths, and the light energy returned by the product is recovered for each of the wavelengths of this polychromatic beam, so as to obtain the data representative of the light intensity curves. Method according to claim 5, characterized in that the two beams, monochromatic and polychromatic, are superimposed so as to illuminate the product at a single point. Method according to one of claims 5 or 6, characterized in that a polychromatic beam composed of at least three wavelengths chosen from the following colors is used: red, green, blue, yellow. Method according to one of claims 5 to 7, characterized in that an infrared monochromatic beam is used. Method according to one of claims 5 to 8, characterized in that polychromatic and monochromatic beams from sources are used laser (13, 14). Method according to one of the preceding claims, in which the products are moved along a sorting chain (1), characterized in that each bundle is displaced, on the one hand parallel to the direction of movement of the products so forming longitudinal light lines consisting of a succession of aligned points, and on the other hand, transversely, so as to cover the surface of the product with a succession of parallel light lines. Automatic sorting device for products, especially fruit or vegetables, characterized in that it comprises in combination: - first lighting means (13, 24) capable of materializing a light line on the surface of the product, - second lighting means (14, 15, 23) able to generate a polarized monochromatic beam, and to materialize by means of said beam a light line on the surface of the product, means (25) of relative displacement of the light lines and of the product arranged to allow successively to illuminate the maximum of observable points on the surface of said product, - an acquisition chain (6) comprising sensors (26-33; 34-41) capable of collecting the light energy returned by the product in preselected wavelengths, and of delivering representative analog signals, for each point of each light line and in each of said wavelengths, of the light intensity of said point, - means for separating (16) the polarized incident beam and the depolarized light energy returned by the product, - an optical assembly (17-20) arranged so as to receive only the only light energy returned by the product, and adapted to deliver an analog signal representative of the distance between said optical assembly and an area located in the immediate vicinity of the point of impact of the incident beam on the product, - and a central processing unit (42-47) comprising: . analog / digital conversion means arranged to receive the analog signals from the sensors (26-33; 34-41) and to deliver, for each point and in each wavelength, a digital value representative of the gray level of said point , . analog / digital conversion means arranged to receive the analog signals from the optical assembly (17-20) and to deliver, for each point of impact of the beam on the product, a digital value representative of the distance between a point of origin and an area located in the immediate vicinity of said point of impact, . means for memorizing digital values in the form of sequences of values representative of the physical profile of the product, . means for storing the digital values in the form of sequences of representative values, each, for each wavelength, of the light intensity curve of a light line, . and calculation means programmed to calculate, on the one hand, criteria for comparing the numerical values of the homologous points of the intensity curves and, on the other hand, values representative of the physical profile of the product, colorimetric information exploitable taking into account only the only points of the intensity curves not corresponding to a cavity. Device according to claim 11, characterized in that the first lighting means comprise: - at least one laser source (13) adapted to deliver a multi-beam beam of preselected wavelengths, - means (24) for deflecting the multi-beam beam capable of generating a light line. Device according to claim 12, characterized in that the laser source consists of a multi-line laser (13). Device according to one of claims 12 or 13, characterized in that the deflection means comprise a polygon (24) provided with facets (24a) capable of reflecting the multi-line beam, and means for driving said polygon in rotation around its axis of revolution. Device according to one of Claims 13 to 15, characterized in that the means for relative displacement of the light line and of the product comprise: - a mirror (25) mounted on an oscillating axis and arranged to intercept the light line coming from the deflection means (24) along an axis parallel to its oscillating axis, and to project it onto the surface of the product, - means for rotating the oscillating axis able to pivot the mirror (25) in order to move the light line in a direction orthogonal to its longitudinal axis. Device according to one of claims 11 to 15, characterized in that the sensors (26-33; 34-41) comprise means (26, 27; 34-36) for decomposing the light energy returned by the product into a discrete number of preselected wavelengths and, for each wavelength, collection and focusing means (28-30; 37, 40), and a detector (31-33; 38, 39, 41) arranged to receive the collected energy and to deliver an analog signal representative of said energy. Device according to claim 16, characterized in that the decomposition means consist of at least one plate (26, 27; 34) with selective optical deviation for given wavelengths. Device according to claim 17, characterized in that the decomposition means (26, 27; 34) are inserted between the two faces forming the hypotenuse of two rectangular prisms (35, 36), one of said prisms being arranged so that one of its faces constitutes the window d input of the means of decomposition. Device according to one of claims 17 or 18, characterized in that the decomposition means consist of a diffraction grating (34). Device according to one of claims 17 or 18, characterized in that the decomposition means consist of at least two holographic mirrors by reflection (26, 27) spaced apart, selective for the predetermined lengths. Device according to one of claims 11 to 20, characterized in that the optical assembly (17-20) is adapted to deliver a second analog signal representative of the light intensity returned by the product in the wavelength of the beam incident. Device according to claim 21, characterized in that the second lighting means (14, 15, 23) comprise optical means (15, 23) capable of mixing the incident beams delivered by the first (13) and second means of lighting so as to obtain a single single lighting beam of the product. Device according to one of claims 21 or 22, characterized in that the central processing unit comprises: a first electronic card (42), called an amplification card, capable of amplifying the analog signals delivered by the sensors (26-33; 34-41) and the optical assembly (17-20), - A second electronic card (43), called rangefinder, comprising analog / digital conversion means and arranged to receive the amplified signals from the optical assembly (17-20), said card comprising a calculation unit programmed to identify the natural cavities and the damaged areas of the product, and to calculate the volume of said product from the light intensity signal by deducting from the result obtained the areas corresponding to cavities, - A third electronic card (44), called color processing card, comprising analog / digital conversion means, and arranged to receive the amplified signals delivered by the various sensors (26-33; 34-41), and the representative amplified signal of the light intensity for the wavelength selected for the optical assembly (17-20), said card comprising a calculation unit programmed to carry out a colorimetric sorting algorithm for the authorized points, - A fourth card (45), called quality processing card, comprising analog / digital conversion means, and arranged to receive the amplified signals delivered by the various sensors (26-33; 34-41), and the amplified signal representative of the light intensity for the wavelength selected for the optical assembly (17-20), said card comprising a programmed calculation unit: . to search for concave discontinuities in all wavelengths present in the energy diffused by the product, and when there is a discontinuity in an area for all wavelengths, to query the processing board rangefinder (43), with a view to possibly inhibiting the results of colorimetric sorting in the case where this area corresponds to a natural cavity, . to quantify the defect observed in the discontinuity zones which do not correspond to cavities, - means of communicating the results in the form of three numerical values representative of the quality, color and volume of the product. Device according to claim 14, characterized in that it comprises: - means for detecting a point, known as of origin, of the light line generated by the rotation of the polygon (24), - means of step-by-step measurement of the progress of the products on the conveyor, - the central processing unit (42-47) being programmed to trigger a processing cycle for each movement of a step of the product, upon reception of the signal from the detection means. Device according to one of claims 11 to 24 for sorting fruit, on a conveyor (1) comprising n transport lines, characterized in that the first lighting means comprise a single lighting source (12) delivering a beam divided into at least n beams transported by optical fibers (10) at each line.

Images