EP0620051B1 - 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 a automatic sorting device for products, especially fruits or vegetables.

Modern fruit stations are faced with the ever more pressing problem of search for quality. In addition, the networks of modern distribution require lots of fruits and vegetables perfectly homogeneous, both in quality and coloring, the quality of the fruit being appreciated from classic visual criteria established by the regulations fruits and vegetables.

The consequence of such requirements is ask the manual sorting staff for efforts don't not allowing access to calibration rates high. It is indeed, for this staff, to identify, among the conveyed fruits, those to be downgraded, defects justifying this downgrade being of various natures: pathology of fruits, shocks, cuts ...

A good qualitative calibration therefore requires a qualified staff and clearly reasonable rates lower than the maximum rates of the chains of conditioning.

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

Unfortunately, the physical reality of phenomenon is quite different. Indeed and by way of example, a fresh shock on an apple does not alter its color and yet the fruit must be downgraded. Likewise, a fruit affected by "biter pit" shows no deterioration colored on the surface, while under the skin the fruit is rotten. In addition, the natural fruit cavities (pistillary and peduncle) are considered to be spots because naturally containing brown spots ("russetting"), and the detection of these cavities causes the fruit downgrade while these areas of the fruit are subject to specific regulations, more flexible than for the other parts of the said fruit.

Another technique described in the patent GB-2 167 180 consists in lighting the products by means a light source with a complex spectrum, and measure the light energy reflected in ranges of wavelengths given, the fruit being animated by a rotational movement during its inspection, and a scanning of the surface of said fruit being carried out during this inspection. Such a technique seems a priori more reliable than the one described above: However, it appears to be of questionable reliability when examining fruits such as apples. In addition, such as the previous, such a technique does not allow to discern the natural fruit cavities, which are therefore considered tasks that could lead to unjustified downgrading of said fruit.

In order to overcome this drawback, a other technique described in patent NL 90 00565 a consisted in using two sensors arranged so as to intercept the reflected light energy when the part lit fruit consists of a cavity or tail said fruit, and to inhibit the measurement values when these sensors are activated. However, such a technique turns out to be very random. Indeed, and in the first place, the position of the sensors is fixed, and the latter are ineffective for fruits of different sizes of those for whom this position was determined. Moreover, fruits, such as apples in particular, level of the pistillary and peduncle cavities, a surface absorbing light, so these cavities cannot be detected by the aforementioned sensors.

The present invention aims to overcome these disadvantages and has as main objective to provide a automatic sorting device to respond to various product selection criteria such as fruits and vegetables, without being influenced by areas not prohibitive of these.

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

Another object of the invention is to provide a device that can be installed on a conveyor to several transport lines, and ensure great uniformity of calibration across 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 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 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.

First, such a process, according to which one uses preselected wavelengths of the light energy returned by the product allows to improve the notion of determinism of calibration, and by itself to increase the accuracy of the latter.

Indeed, with each numerical value representative of a light intensity does not match only one fruit color, the margin of error on the determination of this color being absolutely nonexistent.

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

Likewise, and also by way of example, this process makes it possible to discriminate faults such as fresh shocks not detectable with current processes.

In addition, according to this process, the information colorimetric provided is not affected by the presence possible cavities, which in particular avoids having to specifically position products for their sorting, which therefore allows automatic feeding and continuous 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,
• the calculations are carried out aimed at generating the colorimetric information using only the values of the numerical sequences which have led to the delivery of information of absence of defect.

This method allows to take into account, in view of the determination of the color classification of products, only healthy surfaces of this product and flawless, i.e. surfaces free from 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 allows lifting all ambiguity and to interpret all types of phenomena which may appear at the surface of the product.

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

According to another characteristic of the invention, each product is illuminated by means of a 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,
• 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.

In addition, we preferentially superimpose the monochromatic and polychromatic beams so as to illuminate each product at a single point. This arrangement allows to obtain the color from the same point by analyzing the energy backscattered by this point for different wavelengths.

In addition, a polychromatic beam composed of at least three lengths wave selected from the following colors: red, green, blue, yellow.

The monochromatic beam used is for its part 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.

In addition, we use preferential polychromatic beams and monochromatic from laser sources.

The use of laser sources allows to use wavelengths determined in nanometers near. 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 directed to a process in which the products are conventionally moved along a sorting chain, we moves each beam, on the one hand parallel to the direction moving products to form lines longitudinal lights made up of a succession of points aligned, and on the other hand, transversely, so to cover the surface of the product with 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 chaíne 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 able to collect the light energy returned by the product in preselected wavelengths, and to deliver 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 include preferentially means of energy decomposition light returned by the product in a discreet number of preselected wavelengths and, for each length wave, collection and focusing means, and a detector arranged to receive the collected energy and for deliver an analog signal representative of said energy.

In addition, the means of decomposition are advantageously made up of at least one deflection blade optics selected for given wavelengths.

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

Thanks to this arrangement, and first place, the arrangement of the different optical components forms, between the entry face and the exit face, a complete optical system with the same optical index. Thereby, Fresnel reflection is minimized because it takes place on input and output faces which are the most orthogonal possible to the mean directions of beams entering and leaving the system.

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

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

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

• 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 a telemetric card, 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 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 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 sorting of fruit on a conveyor with n transport lines. In this case, and advantageously, the first lighting means include a source single lighting delivering a beam divided into at least n beams transported by optical fibers at each line.

This arrangement allows to illuminate strictly identical the different lines of transport, whatever the evolution of the source lighting. Therefore, any problem relating to a possible difference in brightness from one line to the next is discarded, and we get a perfect uniformity of calibration on 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 for detecting faults according to the invention.

The device shown in the figures has for purpose of providing a deterministic, flexible and scalable, allowing to meet the various criteria of selection of fruits and vegetables without being influenced by the non-crippling zones of the latter.

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

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

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

Each measuring head is additionally connected through an optical fiber such as 10 and a multiplexer 11 for n optical fibers 10, at one cabinet 12 containing a laser assembly comprising a laser multi-lines (in the example red, green, blue) and, so conventional means for cooling said laser and a electrical cabinet.

FIG. 2 schematically represents, on the one hand, a rangefinder and a multi-line laser 13 inserted according to the invention in an optical arrangement allowing to superimpose the monochromatic beam from rangefinder 7 and the polychromatic beam from laser 13 and, on the other hand, a system for deflecting beams thus superimposed.

First, the rangefinder 7 has a collimated infrared laser diode 14 whose beam is delivered via a deflection mirror 15 towards a separator 16 distinguishing the outgoing beams and return. This rangefinder 7 further comprises a head conoscopic 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 on the other hand the intensity luminous reflected by the fruit in the infrared.

This rangefinder also has 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 rangefinder 7 and the beam from the multi-line laser 13 are delivered to a dichroic beam splitter 23 suitable, as shown above, superimposing said beams.

This superimposed beam is itself delivered towards a diversion system comprising, first of all, a rotating polygon 24 with facets such as 24a able to reflect the incident beam and generate light lines, said polygon being associated with rotary drive means (not shown).

These means of diversion include in addition to a mirror 25 mounted oscillating with respect to an axis longitudinal, and arranged to intercept the light line from a facet 24a of polygon 24, and to project this light line to the transmission line.

This oscillating mirror 25 is also associated to rotation means (not shown) capable of making rotate the latter around its longitudinal axis so that the light line sweeps across the width of the line of transport.

The acquisition chain 6 comprises as for it, first of all, means of decomposition of the light energy returned by the product in a number discrete wavelengths corresponding to the lengths of multi-line laser beam waves. It includes, in in addition, for each wavelength, means of collection and focusing, and a detector arranged for 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 Figure 3 comprises two holographic mirrors by reflection 26, 27, spaced and parallel, adapted to deflect each 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 includes means of collection and focus consisting of a condenser 28, 29, 30, and detectors 31, 32, 33. In in addition, an infrared filter 33a is disposed in front of the detector 33 corresponding to the third wavelength.

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

This acquisition chain includes besides means of collection and focusing 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 to an infrared filter 41a.

The device according to the invention presents in in addition to synchronization means making it possible to create a digitization area centered on the fruits to be examined. These include first of all means of detection, such as a cell, of the point of origin of the light line generated by the rotation of the polygon. They further include step by step measurement means advancement of fruit on the conveyor.

From this data, the trigger of a treatment cycle is given by the central processing unit processing for each step of the product, when receiving the signal from the detection.

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

In the case of Figure 6 where the curves corresponding to the three wavelengths do not exhibit of discontinuity, the colorimetric analysis, schematized by curve C, is made for all the points of the curve.

Qualitative analysis to conclude that all the points analyzed are healthy. It is the same when, as shown in Figure 7, only one (or two) curves have a discontinuity in shape concave.

However, when as shown in the figure 8, the three curves show a discontinuity of concave shape in the same area, it uses signal from the rangefinder.

In the case of Figure 8a where the signal issued by this rangefinder reveals the presence of a cavity natural materialized by a discontinuity of form concave, colorimetric analysis is performed for points other than those corresponding to this zone. Any qualitative analysis is also not performed.

However, as shown in Figure 8b, if the signal from the rangefinder does not have of discontinuity, the discontinuity noted for representative curves of the beam wavelengths laser, must correspond to a defect such as task...

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

• 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 search for 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 query the treatment card rangefinder 43, 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,
• 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 fault processing algorithm leading to the determination of a numerical value representative of a quality score is explained below with reference to Figures 9 and 10.

First, it is important to identify particular points of the curve, namely the abscissas start points D and end F of this curve, as well that 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 constant or increasing.

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

For abscissa points greater than mX for which the curve must be normally constant or decreasing, just browse these points in the sense of decreasing abscissa to obtain a relation similar.

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

Normalization is therefore carried out in operating in a normalization space in which, for a given task and whatever its position on the fruit, we get the same gray level associated.

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

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 right of projection, to obtain the gray level point Ni.norm standardized.

• 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, we memorize the number of healthy points (zero value) and the number of points whose value is positive, which amounts to memorize a grayscale histogram.

The color processing algorithm consists in memorizing, at first, for each wavelength, the values of the levels of gray (0 to 255) of all points in the DF area. Steps following are a function of the fruit to be classified and the colors predominant of the latter, and are adaptable to each type of fruit. For example and for apples, we calculates for each point, the color spectra between green and blue NiV - NiB / NiV + NiB, and between red and green NiR - NiV / NiR + NiV.

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

Finally, we establish for each curve a 32-level histogram.

Claims (25)

1. A method for the automatic colorimetric sorting of articles, especially pieces of fruit or vegetable, characterized in that it comprises:

   illuminating each article by means of at least one beam able to materialize an illumination line on the surface of said article;

   moving the illumination line in relation to the article in order to successively illuminate the maximum number of visible points on the surface of the article;

   splitting each illumination line into a series of points and for each of said points, retrieving at least part of the light energy returned by the article, at preselected wavelengths;

   for each preselected wavelength, measuring the intensity of the light from each point on each illumination line, and outputting analog data representative of said intensity;

   for one of the preselected wavelengths and for each point on each illumination line, outputting a so-called distance information, representative of the distance between a point of origin and a region close to the point of impingement of the beam on the article;

   converting, for each illumination line, the analog data representative of the intensity of the light into a series of digital values, each representative of the level of grey in the considered wavelength from the corresponding point on said illumination line, so that each of the series of values corresponds to the light intensity curve, at this wavelength, of this illumination line;

   converting each distance information for obtaining a series of digital values representative of the physical profile of the article, said digital values allowing a discrimination of possible natural cavities at the surface of said article;

   storing the series of digital data corresponding to each preselected wavelength and to each illumination line; and

   processing the series of digital data by means of a computation according to programmed criteria based on a comparison of the values of the homologous points of said series, for generating a workable colorimetric information while only taking into account such points in the digital series which are not related to a cavity.
2. The method according to claim 1, characterized in that:

   the series of digital values corresponding to the light intensity curves are compared so as to output an article quality information which consists of:

   in the case of the absence of concave shaped discontinuity in all curves, an information of absence of a default;

   in the case of the presence of a concave shaped discontinuity in at least one curve, although not in all curves, an information of absence of a default; and

   in the case of the presence of a concave shaped discontinuity in one same region in all curves, an information of presence of a default in the region of discontinuity;

   the computations for generating the colorimetric information are performed solely by means of the values of the digital series which resulted in the output of an information of absence of a default.
3. The method according to claim 2, characterized in that:

   in the case of the presence of a concave shaped discontinuity in all curves, resulting in the output of an information of presence of a default:

   in the case of the absence of a cavity, an information representative of the condition of the default is computed according to programmed criteria; and

   in the case of the presence of at least one cavity, the related points are not considered.
4. The method according to one of the claims 1 to 3, characterized in that each article is illuminated by means of an incident beam able to illuminate a point on the surface of said article, and in that said beam is moved so as to materialize an illumination line.
5. The method according to one of the claims 3 or 4, characterized in that:

   the article is illuminated by means of a first monochromatic, polarized beam, and the retrodiffused energy from each point is splitted into two polarization planes for obtaining the physical profiles of the article;

   the article is simultaneously illuminated by means of a second polychromatic beam comprised of a discrete number of preselected wavelengths, and the light energy which is returned by the article is retrieved for each of the wavelengths of this polychromatic beam, for obtaining the data representative of the light intensity curves.
6. The method according to claim 5, characterized in that both monochromatic and polychromatic beams are superposed so as to illuminate the article on one single point.
7. The method according to one of the claims 5 or 6, characterized in that a polychromatic beam is used, which is composed of at least three wavelengths selected from the following colours red, green, blue, yellow.
8. The method according to one of the claims 5 to 7, characterized in that an infrared monochromatic beam is used.
9. The method according to one of the claims 5 to 8, characterized in that polychromatic and monochromatic beams are used, which are delevered by laser sources (13, 14).
10. The method according to one of the preceding claims, wherein the articles are conveyed along a sorting line (1), characterized in that each beam is moved both parallel to the direction of conveyance of the articles, for forming longitudinal illumination lines consisting of a series of aligned points, and transversally for covering the surface of the article with a series of parallel illumination lines.
11. A device for the automatic sorting of articles, especially pieces of fruit or vegetable, characterized in that it comprises in combination:

    first illumination means (13, 24) able to materialize an illumination line on the surface of the article;

    second illumination means (14, 15) able to generate a polarized monochromatic beam and to materialize an illumination line on the surface of the article by means of said beam;

    means (25) for moving the illumination lines in relation to the article, for successively illuminating the maximum number of visible points on the surface of said article;

    an acquisition line (6) comprising sensors (26-33; 34-41) able to collect the light energy returned by the article at preselected wavelengths, and to output, for each point on each illumination line and at each of said wavelengths, analog signals representative of the light intensity from said point;

    means (16) for separating the polarized incident beam and the depolarized light energy returned by the article;

    an optical unit (17-20) arranged to receive only the light energy returned by the article, and adapted to output an analog signal representative of the distance between said optical unit and a region close to the point of impingement of the incident beam on the article; and

    a central processing unit (42-47) comprising:

    analog/digital conversion means arranged to receive the analog signals delivered by the sensors (26-33; 34-41) and to output, for each point and in each wavelength, a digital value representative of the level of grey of said point;

    analog/digital conversion means arranged to receive the analog signals delivered by the optical unit (17-20) and to output, for each point of impingement of the beam on the article, a digital value representative of the distance between a point of origin and a region close to said point of impingement;

    means for storing the digital values as series of values representative of the physical profile of the article;

    means for storing the digital values as series of values each representative, for each wavelength, of the light intensity curve of an illumination line; and

    computation means which are programmed for computing a workable colorimetric information, both from comparison criteria of the digital values of the homologous points of the intensity curves and from values representative of the physical profile of the article, while only taking into account the points on the intensity curves which are not related to a cavity.
12. The device according to claim 11, characterized in that the first illumination means comprise:

    at least one laser source (13) adapted to output a multiline beam with preselected wavelengths;

    means (24) for deflecting the multiline beam, said means being able to generate an illumination line.
13. The device according to claim 12, characterized in that the laser source consists of a multiline laser (13).
14. The device according to one of the claims 12 or 13, characterized in that the deflection means comprise a polygon (24) provided with facets (24a) able to reflect the multiline beam, and means for rotating said polygon about the axis of revolution thereof.
15. The device according to one of the claims 13 and 14, characterized in that the means for moving the illumination line in relation to the article comprise:

    a mirror (25) mounted on an oscillating axis and arranged to intercept the illumination line delivered by the deflection means (24) along an axis which is parallel to the oscillating axis thereof, and to project it on the surface of the article;

    means for rotating the oscillating axis, said means being able to pivot the mirror (25) in order to move the illumination line along a direction which is orthogonal to the longitudinal axis thereof.
16. The device according to one of the claims 11 to 15, characterized in that the sensors (26-33; 34-41) comprise means (26, 27; 34-36) for splitting the light energy returned by the article into a discrete number of preselected wavelengths and, for each wavelength, collecting and focusing means (28-30; 37, 40) and a detector (31-33; 38, 39, 41) arranged to receive the collected energy and to output an analog signal representative of said energy.
17. The device according to claim 16, characterized in that the splitting means consist of at least one selective optical deflection strip (26, 27; 34) for selected wavelengths.
18. The device according to claim 17, characterized in that the splitting means (26, 27; 34) are inserted between the two faces which form the hypotenuse of two right prisms (35, 36), one of said prisms being so positioned that one of the faces thereof forms the entrance window of the splitting means.
19. The device according to one of the claims 17 or 18, characterized in that the splitting means consist of a diffraction grid (34).
20. The device according to one of the claims 17 or 18, characterized in that the splitting means are constituted by at least two spaced apart holographic reflection mirrors (26, 27) which are selective for the predetermined wavelengths.
21. The device according to one of the claims 11 to 20, characterized in that the optical unit (17-20) is adapted to output a second analog signal representative of the light intensity returned by the article at the wavelength of the incident beam.
22. The device according to claim 21, characterized in that the second illumination means (14, 15, 23) comprise optical means (15, 23) able to blend the incident beams outputted by the first (13) and second illumination means, so as to obtain one single beam illuminating the article.
23. The device according to one of the claims 21 or 22, characterized in that the central processing unit comprises:

    a first so-called amplifying electronic circuit board (42), able to amplify the analog signal outputted by the sensors (26-33; 34-41) and the optical unit (17-20);

    a second so-called telemetry electronic circuit board (43), comprising analog/digital conversion means and arranged to receive the amplified signal delivered by the optical unit (17-20), said circuit board comprising a computation unit which is programmed to identify the natural cavities and the damaged regions on the article and compute the volume of said article based on the light intensity signal, by means of substracting the regions associated with cavities from the obtained result;

    a third so-called colour processing electronic circuit board (44), comprising analog/digital conversion means, and arranged to receive the amplified signals from the various sensors (26-33; 34-41) and the amplified signal representative of the light intensity for the wavelength which was selected for the optical unit (17-20), said circuit board comprising a computation unit which is programmed to perform a colorimetric sorting algorithm for the authorized points;

    a fourth so-called quality processing circuit board (45), comprising analog/digital conversion means and arranged to receive the amplified signals outputted by the various sensors (26-33; 34-41) and the amplified signal representative of the light intensity for the wavelength which was selected for the optical unit (17-20), said circuit board comprising a computation unit which is programmed to:

    scan the concave shaped discontinuities in all wavelengths present in the energy which is diffused by the article, and in the case of the presence of a discontinuity in one region for all the wavelengths, ask the telemetric processing circuit board (43) as to whether the results of the colorimetric sorting should be suppressed in the case where such region is related to a natural cavity;

    quantify the observed default in the discontinuity regions which are not related to cavities;

    means for transmitting the results as three digital values representative of the quality, the colour and the shape of the article.
24. The device according to claim 14, characterized in that it comprises:

    means for detecting a so-called point of origin of the illumination line generated by means of the rotation of the polygon (24),

    means for measuring step by step the feeding of the articles on the conveyor,

    the central processing unit (42-47) being programmed to activate a processing cycle for each feeding step of an article upon reception of the signal delivered by the detection means.
25. The device according to one of the claims 11 to 24, for the sorting of pieces of fruit on a conveyor (1) comprising n conveying lines, characterized in that the first illumination means comprise one single illumination source (12) outputting a beam which is divided in at least n beams directed to each line by means of optical fibers (10).

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